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11862732 | DETAILED DESCRIPTION The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the performance of a first process before a second process in the description that follows may include embodiments in which the second process is performed immediately after the first process, and may also include embodiments in which additional processes may be performed between the first and second processes. Various features may be arbitrarily drawn in different scales for the sake of simplicity and clarity. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In some embodiments, the present disclosure may repeat reference numerals and/or letters in some various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between some various embodiments and/or configurations discussed. Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. Some embodiments of the disclosure are described. Additional operations can be provided before, during, and/or after the stages described in these embodiments. Some of the stages that are described can be replaced or eliminated for different embodiments. Additional features can be added to the semiconductor device structure. Some of the features described below can be replaced or eliminated for different embodiments. Although some embodiments are discussed with operations performed in a particular order, these operations may be performed in another logical order. The gate all around (GAA) transistor structures may be patterned using any suitable method. For example, the structures may be patterned using one or more photolithography processes, including double-patterning or multi-patterning processes. Generally, double-patterning or multi-patterning processes combine photolithography and self-aligned processes, allowing patterns to be created that have, for example, pitches smaller than what is otherwise obtainable using a single, direct photolithography process. For example, in one embodiment, a sacrificial layer is formed over a substrate and patterned using a photolithography process. Spacers are formed alongside the patterned sacrificial layer using a self-aligned process. The sacrificial layer is then removed, and the remaining spacers may then be used to pattern the GAA structure. FIGS.1A-1Pare cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. As shown inFIG.1A, a semiconductor substrate102is received or provided, in accordance with some embodiments. In some embodiments, the semiconductor substrate102is a bulk semiconductor substrate, such as a semiconductor wafer. For example, the semiconductor substrate102is a silicon wafer. The semiconductor substrate102may include silicon or another elementary semiconductor material such as germanium. In some other embodiments, the semiconductor substrate102includes a compound semiconductor. The compound semiconductor may include gallium arsenide, silicon carbide, indium arsenide, indium phosphide, another suitable material, or a combination thereof. In some embodiments, the semiconductor substrate102includes a semiconductor-on-insulator (SOI) substrate. The SOI substrate may be fabricated using a separation by implantation of oxygen (SIMOX) process, a wafer bonding process, another applicable method, or a combination thereof. In some embodiments, the semiconductor substrate102is an un-doped substrate. However, in some other embodiments, the semiconductor substrate102is a doped substrate such as a P-type substrate or an N-type substrate. In some embodiments, the semiconductor substrate102includes various doped regions (not shown) depending on design requirements of the semiconductor device. The doped regions include, for example, p-type wells and/or n-type wells. In some embodiments, the doped regions are doped with p-type dopants. For example, the doped regions are doped with boron or BF2. In some embodiments, the doped regions are doped with n-type dopants. For example, the doped regions are doped with phosphor or arsenic. In some embodiments, some of the doped regions are p-type doped, and the other doped regions are n-type doped. Still referring toFIG.1A, a stacked-layer structure104is formed over the semiconductor substrate102, in accordance with some embodiments. As shown inFIG.1A, the stacked-layer structure104includes one or more of the first semiconductor material layers106and one or more of the second semiconductor material layers108alternately stacked vertically over the semiconductor substrate102, in accordance with some embodiments. Although the stacked-layer structure104shown inFIG.1Aincludes four second semiconductor material layers108and four first semiconductor material layers106, the embodiments of the present disclosure are not limited thereto. In some other embodiments, the stacked-layer structure104includes one first semiconductor material layers106and one second semiconductor material layers108vertically stacked over the semiconductor substrate102. In some embodiments, the second semiconductor material layer108and the first semiconductor material layer106are independently made of silicon, silicon germanium, germanium tin, silicon germanium tin, gallium arsenide, indium gallium arsenide, indium arsenide, another suitable material, or a combination thereof. In some embodiments, the material of second semiconductor material layer108is different than the material of first semiconductor material layer106. In some embodiments, the second semiconductor material layer108is made of silicon germanium, whereas the first semiconductor material layer106is made of silicon, and the semiconductor substrate102is made of silicon. In some embodiments, the second semiconductor material layer108is made of indium gallium arsenide, whereas the first semiconductor material layer106is made of gallium arsenide, and the semiconductor substrate102is made of gallium arsenide. In some embodiments, the first semiconductor material layers106and the second semiconductor material layers108are formed using an epitaxial growth process. Each of the first semiconductor material layers106and the second semiconductor material layers108may be formed using a selective epitaxial growth (SEG) process, a chemical vapor deposition (CVD) process (e.g., a vapor-phase epitaxy (VPE) process, a low-pressure CVD (LPCVD) process, and/or an ultra-high vacuum CVD (UHV-CVD) process), a molecular beam epitaxy process, another applicable process, or a combination thereof. In some embodiments, the first semiconductor material layers106and the second semiconductor material layers108are grown in-situ in the same process chamber. Afterwards, as shown inFIG.1B, multiple recesses (or trenches)110are formed to pattern the first semiconductor material layers106, the second semiconductor material layers108, and the upper portion of the semiconductor substrate102, in accordance with some embodiments. In some embodiments, multiple photolithography processes and etching processes are performed to form the recesses110. The recess110may be used to separate two neighboring field effect transistors (FETs). As a result, the patterned semiconductor substrate102includes a base portion112, a first fin portion114over the base portion112and a second fin portion116over the base portion112and adjacent to each other, in accordance with some embodiments. As shown inFIG.1B, the first fin portion114and the second fin portion116are between the recesses110, in accordance with some embodiments. As shown inFIG.1B, the patterned first semiconductor material layers106and the patterned second semiconductor material layers108form the first semiconductor layers118and the second semiconductor layers120respectively, in accordance with some embodiments. In some embodiments, the first semiconductor layers118and the second semiconductor layers120form two stack structures122over the first fin portion114and the second fin portion116respectively. As shown inFIG.1B, the first semiconductor layers118and the second semiconductor layers120of the stack structure122vertically stacked over the first fin portion114and/or the second fin portion116, in accordance with some embodiments. In some embodiments, the second semiconductor layer120and the first semiconductor layer118are independently made of silicon, silicon germanium, germanium tin, silicon germanium tin, gallium arsenide, indium gallium arsenide, indium arsenide, another suitable material, or a combination thereof. In some embodiments, the material of second semiconductor layer120is different than the material of first semiconductor layer118. In some embodiments, the second semiconductor layer120is made of silicon germanium, whereas the first semiconductor layer118is made of silicon, and the semiconductor substrate102is made of silicon. In some embodiments, the second semiconductor layer120is made of indium gallium arsenide, whereas the first semiconductor layer118is made of gallium arsenide, and the semiconductor substrate102is made of gallium arsenide. In some embodiments, the thickness of the second semiconductor layer120is substantially equal to the thickness of the first semiconductor layer118. As shown inFIG.1B, one or more isolation structures including an isolation structure124are formed over the semiconductor substrate102and formed in the recesses110to surround the first fin portion114and the second fin portion116, in accordance with some embodiments. The isolation structure124is adjacent to the first fin portion114and the second fin portion116. In some embodiments, the isolation structure124continuously surrounds the first fin portion114and the second fin portion116. The isolation structure124is used to define and electrically isolate various device elements formed in and/or over the semiconductor substrate102. In some embodiments, the isolation structure124includes a shallow trench isolation (STI) feature, a local oxidation of silicon (LOCOS) feature, another suitable isolation structure, or a combination thereof. In some embodiments, the isolation structure124has a multi-layer structure. In some embodiments, the isolation structure124is made of a dielectric material. The dielectric material may include silicon oxide, silicon nitride, silicon oxynitride, fluoride-doped silicate glass (FSG), low-K dielectric material, another suitable material, or a combination thereof. In some embodiments, a first STI liner126and a second STI liner128are formed to reduce crystalline defects at the interface between the semiconductor substrate102and the isolation structure124. In some embodiments of the present disclosure, the first STI liner126is formed over the sidewalls of the first fin portion114and the second fin portion116and over the base portion112, and the second STI liner128is formed over the first STI liner126. The first STI liner126and the second STI liner128may also be used to reduce crystalline defects at the interface between the fin portions106and the isolation structure124. In some embodiments, two STI liner material layers and a dielectric layer is deposited to cover the semiconductor substrate102and the stack structure122using a chemical vapor deposition (CVD) process, a spin-on process, another applicable process, or a combination thereof. The chemical vapor deposition may include, but is not limited to, low pressure chemical vapor deposition (LPCVD), low temperature chemical vapor deposition (LTCVD), rapid thermal chemical vapor deposition (RTCVD), plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), or any other suitable method. The dielectric layer covers the first fin portion114and the second fin portion116and fills the recesses110between the fin portions106. Afterwards, in some embodiments, a planarization process is performed to thin down the two STI liner material layers and the dielectric layer. For example, the dielectric layer is thinned until the stack structure122is exposed. The planarization process may include a chemical mechanical polishing (CMP) process, a grinding process, a dry polishing process, an etching process, another applicable process, or a combination thereof. Afterwards, the two STI liner material layers and the dielectric layer are etched back to be below the top of the stack structure122. As a result, the first STI liner126, the second STI liner128and the isolation structure124are formed. Afterwards, as shown inFIG.1C, a dummy gate dielectric layer130is deposited covering the stack structure122and the isolation structure124, in accordance with some embodiments. In some embodiments, the dummy gate dielectric layer130is made of silicon oxide, silicon nitride, silicon oxynitride, the high-k material, another suitable dielectric material, or a combination thereof. In some embodiments, the high-k material may include, but is not limited to, metal oxide, metal nitride, metal silicide, transition metal oxide, transition metal nitride, transition metal silicide, transition metal oxynitride, metal aluminate, zirconium silicate, zirconium aluminate. For example, the material of the high-k material may include, but is not limited to, LaO, AlO, ZrO, TiO, Ta2O5, Y2O3, SrTiO3(STO), BaTiO3(BTO), BaZrO, HfO2, HfO3, HfZrO, HfLaO, HfSiO, HfSiON, LaSiO, AlSiO, HfTaO, HfTiO, HfTaTiO, HfAlON, (Ba,Sr)TiO3(BST), Al2O3, another suitable high-k dielectric material, or a combination thereof. In some embodiments, the applicable deposition methods for depositing the dummy gate dielectric layer130include a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, a thermal oxidation process, a spin-on coating process, other applicable processes, and combinations thereof. Afterwards, as shown inFIG.1D, a dummy gate electrode132is formed over the dummy gate dielectric layer130, in accordance with some embodiments. In some embodiments, the dummy gate electrode132is made of polysilicon, a metal material, another suitable conductive material, or a combination thereof. In some embodiments, the metal material may include, but is not limited to, copper, aluminum, tungsten, molybdenum, titanium, tantalum, platinum, or hafnium. In some embodiments, the dummy gate electrode132will be replaced with another conductive material such as a metal material in subsequent processes. Still referring toFIG.1D, a mask element136is formed over the dummy gate electrode132, in accordance with some embodiments. In some embodiments, the mask element136is made of silicon oxide, silicon nitride, silicon oxynitride or another suitable material. In some embodiments of the present disclosure, a gate electrode material layer (not shown) is deposited over the dummy gate dielectric layer130. In some embodiments the gate electrode material layer is deposited by using applicable deposition methods. In some embodiments, the applicable deposition methods for depositing the gate electrode material layer include a chemical vapor deposition (CVD) process, a physical vapor deposition (PVD) process, and other applicable methods. Afterwards, according to some embodiments of the present disclosure, the mask element136is formed over the dummy gate electrode132, in accordance with some embodiments. In some embodiments, the applicable deposition methods for depositing the mask element136include a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, a thermal oxidation process, a spin-on coating process, other applicable processes, and combinations thereof. Afterwards, according to some embodiments of the present disclosure, by using the mask element136as an etching mask, the gate electrode material layer is patterned to form the dummy gate electrode132. As shown inFIG.1D, the dummy gate dielectric layer130and the dummy gate electrode132form a dummy gate structure134, in accordance with some embodiments. As shown inFIG.1D, the dummy gate structure134covers a portion of the stack structure122, in accordance with some embodiments. As shown inFIG.1D, the dummy gate structure134exposes another portion of the stack structure122, in accordance with some embodiments. In some embodiments, a spacer layer138is deposited over the semiconductor substrate102, the stack structure122, the dummy gate structure134and the mask element136. In some embodiments, the spacer layer138is made of silicon nitride, silicon oxynitride, silicon carbide, another suitable material, or a combination thereof. The spacer layer138may be deposited using a CVD process, a PVD process, a spin-on coating process, another applicable process, or a combination thereof. Afterwards, as shown inFIG.1E, an etching process, such as an anisotropic etching process, is performed to partially remove the spacer layer138. As a result, the remaining portions of the spacer layer138over the sidewalls of the dummy gate structure134form the spacer elements140. As shown inFIG.1E, the spacer elements140are formed over sidewalls of the dummy gate structure134, in accordance with some embodiments. In some embodiments, the spacer elements140are made of silicon nitride, silicon oxynitride, silicon carbide, another suitable material, or a combination thereof. Still referring toFIG.1E, the first fin portion114and the second fin portion116has channel regions142and source/drain regions144, in accordance with some embodiments. As shown inFIG.1E, the channel regions142are the regions covered by the dummy gate structure134and the spacer elements140, in accordance with some embodiments. As shown inFIG.1E, the source/drain regions144are the regions exposed by the dummy gate structure134and the spacer elements140, in accordance with some embodiments. In some embodiments of the present disclosure, the spacer elements140expose the stack structures122in the source/drain regions144, in accordance with some embodiments. Afterwards, as shown inFIG.1F, a mask element146is formed over the dummy gate structure134, the spacer elements140, the mask element136and the stack structures122which are over the first fin portion114, in accordance with some embodiments. As shown inFIG.1F, the mask element146exposes the stack structures122over the second fin portion116, in accordance with some embodiments. Afterwards, as shown inFIG.1F, an etching process, such as an anisotropic etching process, is performed to remove the second semiconductor layers120over the second fin portion116in the source/drain regions144and form spaces between the first semiconductor layers118, in accordance with some embodiments. As shown inFIG.1F, the second semiconductor layers120over the second fin portion116in the channel regions142remain, in accordance with some embodiments. Afterwards, as shown inFIG.1F, source/drain portions148are formed in the stack structure122in the source/drain region144over the second fin portion116, in accordance with some embodiments. As shown inFIG.1F, the source/drain portions148are between the second semiconductor layers120in the channel regions142, in accordance with some embodiments. As shown inFIG.1F, the source/drain portions148are adjacent to the second semiconductor layers120in the channel regions142, in accordance with some embodiments. In some embodiments, the source/drain portions148are an n-type semiconductor material. The source/drain portions148may include epitaxially grown silicon, epitaxially grown silicon phosphide (SiP), or another applicable epitaxially grown semiconductor material. The source/drain portions148are not limited to being an n-type semiconductor material. In some other embodiments, the source/drain portions148are made of a p-type semiconductor material. For example, the source/drain portions148may include epitaxially grown silicon germanium. In some embodiments, a semiconductor material is epitaxially grown in the space between the first semiconductor layers118to form the source/drain portions148over the second fin portion116. In some embodiments, the source/drain portions148are formed by using a selective epitaxial growth (SEG) process, a CVD process (e.g., a vapor-phase epitaxy (VPE) process, a low pressure chemical vapor deposition (LPCVD) process, and/or an ultra-high vacuum CVD (UHV-CVD) process), a molecular beam epitaxy process, another applicable process, or a combination thereof. Afterwards, the mask element146is removed, in accordance with some embodiments. Afterwards, other source/drain portions150are formed over the first fin portion114by a process that is similar to the one mentioned above, in accordance with some embodiments. It should be noted that the source/drain portions150are not shown inFIG.1F, but are shown inFIG.4A. As shown inFIG.4A, source/drain portions150are formed in the stack structure122in the source/drain region144over the first fin portion114, in accordance with some embodiments. As shown inFIG.4A, the source/drain portions150are between the first semiconductor layers118in the channel regions142, in accordance with some embodiments. As shown inFIG.4A, the source/drain portions150are adjacent to the first semiconductor layers118in the channel regions142, in accordance with some embodiments. In some embodiments, the source/drain portions150are an n-type semiconductor material. The source/drain portions150may include epitaxially grown silicon, epitaxially grown silicon phosphide (SiP), or another applicable epitaxially grown semiconductor material. The source/drain portions150are not limited to being an n-type semiconductor material. In some other embodiments, the source/drain portions150are made of a p-type semiconductor material. For example, the source/drain portions150may include epitaxially grown silicon germanium. In some embodiments, a mask element (not shown) is formed to cover the stack structures122over the second fin portion116and to expose the stack structures122over the first fin portion114, in accordance with some embodiments. Afterwards, an etching process, such as an anisotropic etching process, is performed to remove the first semiconductor layers118over the first fin portion114in the source/drain regions144and to form spaces between the second semiconductor layers120, in accordance with some embodiments. Afterwards, in some embodiments, a semiconductor material is epitaxially grown in the space between the second semiconductor layers120to form the source/drain portions150over the first fin portion114. In some embodiments, the source/drain portions150are formed by using a selective epitaxial growth (SEG) process, a CVD process (e.g., a vapor-phase epitaxy (VPE) process, a low pressure chemical vapor deposition (LPCVD) process, and/or an ultra-high vacuum CVD (UHV-CVD) process), a molecular beam epitaxy process, another applicable process, or a combination thereof. Afterwards, as shown inFIG.1G, an etch stop layer152is conformally deposited over the dummy gate structure134, the spacer elements140, the mask element136and the stack structures122, in accordance with some embodiments. In some embodiments, the etch stop layer152is made of silicon nitride, silicon oxynitride, silicon carbide, another suitable material, or a combination thereof. In some embodiments, the applicable deposition methods for depositing the etch stop layer152includes a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, a spin-on coating process, other applicable processes, and combinations thereof. Afterwards, as shown inFIG.1H, an interlayer dielectric layer154is subsequently formed over the etch stop layer152, in accordance with some embodiments. In some embodiments, the interlayer dielectric layer154is made of silicon oxide, silicon oxynitride, borosilicate glass (BSG), phosphoric silicate glass (PSG), borophosphosilicate glass (BPSG), fluorinated silicate glass (FSG), low-k material, porous dielectric material, another suitable material, or a combination thereof. In some embodiments, the interlayer dielectric layer154is deposited using a CVD process, an ALD process, a spin-on process, a spray coating process, another applicable process, or a combination thereof. In some embodiments, a dielectric layer is deposited over the etch stop layer152using a chemical vapor deposition (CVD) process, a spin-on process, another applicable process, or a combination thereof. In some embodiments, a planarization process is performed to thin down the dielectric layer. For example, the dielectric layer is thinned until the dummy gate electrode132is exposed. The planarization process may include a chemical mechanical polishing (CMP) process, a grinding process, a dry polishing process, an etching process, another applicable process, or a combination thereof. As a result, the interlayer dielectric layer154and the structure shown inFIG.1Hare formed. Afterwards, one or more first nanowires and one or more second nanowires are formed, in accordance with some embodiments. As shown inFIGS.2A and4A, the dummy gate structure134in the channel regions shown inFIG.1Eis removed, in accordance with some embodiments. As shown inFIGS.2A and4A, the first semiconductor layers118and the second semiconductor layers120of the stack structure122in the channel regions are exposed, in accordance with some embodiments. Afterwards, as shown inFIGS.2B and4B, a mask element156is formed to cover the stack structure122over the second fin portion116, in accordance with some embodiments. As shown inFIGS.2B and4B, the mask element156exposes the stack structure122over the first fin portion114, in accordance with some embodiments. Afterwards, as shown inFIGS.2B and4B, an etching process, such as an anisotropic etching process, is performed to remove the second semiconductor layers120over the first fin portion114in the channel regions, in accordance with some embodiments. As shown inFIGS.2B and4B, the remaining portion of the first semiconductor layers118over the first fin portion114in the channel regions form semiconductor material wires158, in accordance with some embodiments. Afterwards, as shown inFIGS.2C and4C, a cladding layer160is formed to surround the semiconductor material wire158to form a first nanowire162, in accordance with some embodiments. In some embodiments of the present disclosure, the cladding layer160is made of silicon, silicon germanium, germanium tin, silicon germanium tin, gallium arsenide, indium gallium arsenide, indium arsenide, another suitable material, or a combination thereof. In some embodiments of the present disclosure, the material of the cladding layer160is the same as the material of the semiconductor material wire158. In some embodiments of the present disclosure, In some embodiments, the cladding layer160is formed using an epitaxial growth process. The cladding layer160may be formed using a selective epitaxial growth (SEG) process, a chemical vapor deposition (CVD) process (e.g., a vapor-phase epitaxy (VPE) process, a low-pressure CVD (LPCVD) process, and/or an ultra-high vacuum CVD (UHV-CVD) process), a molecular beam epitaxy process, another applicable process, or a combination thereof. As shown inFIG.4C, the first nanowire162includes two first edge portions164adjacent to the two source/drain portions150respectively, in accordance with some embodiments. As shown inFIG.4C, the first nanowire162includes one first central portion166between the two first edge portions164, in accordance with some embodiments. As shown inFIG.4C, the first nanowire162is adjacent to the source/drain portions150, in accordance with some embodiments. FIG.2Dis an enlarged view of the first nanowire162in accordance with some embodiments of the present disclosure,FIG.2Eis a cross-sectional view of the first edge portions164of the first nanowire162in accordance with some embodiments of the present disclosure, andFIG.2Fis a cross-sectional view of the first central portion166of the first nanowire162in accordance with some embodiments of the present disclosure. As shown inFIGS.2E and2F, the first nanowire162has a polygonal cross-section, in accordance with some embodiments. Specifically, as shown inFIG.2E, the two first edge portions164have a hexagonal cross-section, in accordance with some embodiments. As shown inFIG.2F, the first central portion166has a quadrilateral cross-section, in accordance with some embodiments. In some embodiments of the present disclosure, since the first nanowire162includes the semiconductor material wire158and the cladding layer160, rather than only including the semiconductor material wire158, the cross-sectional area of the first nanowire162is increased. Therefore, in some embodiments of the present disclosure, the current flowing through the first nanowire162under a given voltage is increased, and the drain-induced barrier lowering issue is reduced, compared to the nanowire with a circular cross-section or the FinFET transistor. As shown inFIGS.2E and2F, the first nanowires162vertically arranged over the first fin portion114, and two adjacent first nanowires162are spaced apart from each other. However, the embodiments of the present disclosure are not limited thereto. In some other embodiments, two adjacent first nanowires162contact each other. Still referring toFIGS.2C to2F, the cross-sectional area of the first nanowire162vary from the edge portion164to the central portion166, in accordance with some embodiments. As shown inFIGS.2C to2F, the edge portion164of the first nanowire162has a first cross-sectional area, and the central portion166of the first nanowire162has a second cross-sectional area, in accordance with some embodiments. In some embodiments of the present disclosure, the first cross-sectional area is greater than the second cross-sectional area. Afterwards, the mask element156is removed, in accordance with some embodiments. Afterwards, as shown inFIG.1I, similar processes are performed to form second nanowires168over the second fin portion116, in accordance with some embodiments. In some embodiments, the material of second nanowires168is different than the material of first nanowire162. In some embodiments of the present disclosure, the second nanowires168are made of silicon, silicon germanium, germanium tin, silicon germanium tin, gallium arsenide, indium gallium arsenide, indium arsenide, another suitable material, or a combination thereof. In some embodiments of the present disclosure, the second nanowires168are made of silicon germanium, and the first nanowires162are made of silicon. In some embodiments of the present disclosure, two second source/drain portions148are adjacent to the second nanowire168. In some embodiments of the present disclosure, the second nanowires168have the same or similar cross-section or shape as that of the first nanowire162.FIGS.3A and3Bare cross-sectional views of the edge portion of the second nanowires168in accordance with some embodiments of the present disclosure.FIG.3Aalso shows the subsequently formed gate dielectric layer and the gate electrode surrounding the second nanowires168in accordance with some embodiments of the present disclosure. As shown inFIG.3A, the second nanowires168also includes a semiconductor material wire168A and a cladding layer168B surrounding the semiconductor material wire168A. As shown inFIG.3A, two adjacent second nanowires168contact each other. However, the embodiments of the present disclosure are not limited thereto. In some other embodiments, two adjacent second nanowires168are spaced apart from each other. As shown inFIG.3B, the direction A1is the direction parallel to the top surface of the first fin portion114, the second fin portion116or the base portion112, in accordance with some embodiments. As shown inFIG.3B, the sides S1and S3are the slanted sides of the second nanowires168, and the side S2is the vertical side of the second nanowires168, in accordance with some embodiments. In some embodiments of the present disclosure, the side S1has <111> crystal plane. In some embodiments of the present disclosure, the side S2has <110> crystal plane. In some embodiments of the present disclosure, the first nanowires162have the same or similar crystal plane as that of the second nanowires168. As shown inFIG.3B, the side S3and the direction A1intersect at an acute angle θ. In some embodiments of the present disclosure, the acute angle θ is in a range from about 40 degrees to about 70 degrees, for example from about 50 degrees to about 60 degrees, or about 54.74 degrees. The term “about” typically means +/−20% of the stated value, more typically +/−10% of the stated value, more typically +/−5% of the stated value, more typically +/−3% of the stated value, more typically +/−2% of the stated value, more typically +/−1% of the stated value and even more typically +/−0.5% of the stated value. The stated value of the present disclosure is an approximate value. When there is no specific description, the stated value includes the meaning of “about”. Afterwards, as shown inFIG.1I, a gate dielectric layer170, a work function layer172and a gate electrode layer174are sequentially formed to surround the first nanowire162and the second nanowires168, in accordance with some embodiments. In some embodiments of the present disclosure, the gate dielectric layer170, the work function layer172and the gate electrode layer174form the gate structure176surrounding the first nanowire162and the second nanowires168. As shown inFIG.1I, the work function layer172surrounds the gate dielectric layer170, and the gate electrode layer174surrounds the work function layer172, in accordance with some embodiments. As shown inFIG.1I, a gate dielectric layer170surrounds the first nanowire162and the second nanowires168, in accordance with some embodiments. In some embodiments, the gate dielectric layer170is made of metal oxide, metal nitride, metal silicide, transition metal oxide, transition metal nitride, transition metal silicide, transition metal oxynitride, metal aluminate, zirconium silicate, zirconium aluminate. For example, the material of the gate dielectric layer170may include, but is not limited to, LaO, AlO, ZrO, TiO, Ta2O5, Y2O3, SrTiO3(STO), BaTiO3(BTO), BaZrO, HfO2, HfO3, HfZrO, HfLaO, HfSiO, HfSiON, LaSiO, AlSiO, HfTaO, HfTiO, HfTaTiO, HfAlON, (Ba,Sr)TiO3(BST), Al2O3, any other suitable high-k dielectric material, or a combination thereof. In some embodiments, applicable deposition methods for depositing the gate dielectric layer170include a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, a thermal oxidation process, a spin-on coating process, other applicable processes, and combinations thereof. In some embodiments of the present disclosure, the work function layer172provides the desired work function for transistors to enhance device performance, including improved threshold voltage. In the embodiments of forming an NMOS transistor, the work function layer172can be an N-type metal capable of providing a work function value suitable for the device. The work function value is, for example, equal to or less than about 4.5 eV. The n-type metal may include metal, metal carbide, metal nitride, or a combination thereof. For example, the N-type metal includes tantalum, tantalum nitride, or a combination thereof. In some embodiments, the gate electrode164includes the N-type metal. On the other hand, in the embodiments of forming a PMOS transistor, the work function layer172can be a P-type metal capable of providing a work function value suitable for the device. The work function value is, for example, equal to or greater than about 4.8 eV. The P-type metal may include metal, metal carbide, metal nitride, other suitable materials, or a combination thereof. For example, the P-type metal includes titanium, titanium nitride, other suitable materials, or a combination thereof. In some embodiments, the gate electrode164includes the P-type metal. The work function layer172may also be made of hafnium, zirconium, titanium, tantalum, aluminum, metal carbides (e.g., hafnium carbide, zirconium carbide, titanium carbide, aluminum carbide), aluminides, ruthenium, palladium, platinum, cobalt, nickel, conductive metal oxides, or a combination thereof. In some embodiments, the work function layer172(such as an N-type metal) are deposited using an applicable deposition process. Examples of an applicable deposition process include a PVD process, a plating process, a CVD process, other applicable processes, and combinations thereof. In some embodiments, the gate electrode layer174is made of a suitable metal material. The suitable metal material may include aluminum, tungsten, gold, platinum, cobalt, other suitable metal materials, an alloy thereof, or a combination thereof. In some embodiments of the present disclosure, the gate electrode layer174is deposited over the work function layer172by using, for example, a PVD process, a plating process, a CVD process, or the like. Afterwards, as shown inFIG.1J, top portions of the work function layer172and the gate electrode layer174are removed, in accordance with some embodiments. Afterwards, as shown inFIG.1J, a sacrificial layer178is formed over the work function layer172and the gate electrode layer174. In some embodiments of the present disclosure, the sacrificial layer178is made of silicon nitride, silicon oxide, silicon oxynitride, another suitable dielectric material, or a combination thereof. Afterwards, as shown inFIG.1K, the interlayer dielectric layer154is removed, in accordance with some embodiments. Afterwards, as shown inFIG.1L, a patterned dummy material layer180is formed to cover a portion of the etch stop layer152, the spacer elements140and the sacrificial layer178, in accordance with some embodiments. As shown inFIG.1L, the patterned dummy material layer180has an opening182exposing another portion of the etch stop layer152, the spacer elements140and the sacrificial layer178, in accordance with some embodiments. Afterwards, as shown inFIG.1M, an interlayer dielectric layer184is formed in the opening182, in accordance with some embodiments. In some embodiments, the interlayer dielectric layer184is made of silicon oxide, silicon oxynitride, borosilicate glass (BSG), phosphoric silicate glass (PSG), borophosphosilicate glass (BPSG), fluorinated silicate glass (FSG), low-k material, porous dielectric material, another suitable material, or a combination thereof. In some embodiments, the interlayer dielectric layer184is deposited using a CVD process, an ALD process, a spin-on process, a spray coating process, another applicable process, or a combination thereof. In some embodiments, a dielectric layer is deposited over the patterned dummy material layer180and filled into the opening182using a chemical vapor deposition (CVD) process, a spin-on process, another applicable process, or a combination thereof. In some embodiments, a planarization process is performed to thin down the dielectric layer. For example, the dielectric layer is thinned until the patterned dummy material layer180is exposed. The planarization process may include a chemical mechanical polishing (CMP) process, a grinding process, a dry polishing process, an etching process, another applicable process, or a combination thereof. As a result, the interlayer dielectric layer184and the structure shown inFIG.1Mare formed. Afterwards, as shown inFIG.1N, the patterned dummy material layer180and the portion of the etch stop layer152not covered by the interlayer dielectric layer184are removed, in accordance with some embodiments. Afterwards, as shown inFIG.1O, a barrier layer186is conformally deposited over the interlayer dielectric layer184, the spacer elements140, the source/drain portions148and150, and the sacrificial layer178, in accordance with some embodiments. In some embodiments of the present disclosure, the barrier layer186is made of titanium nitride, titanium, another suitable material, or a combination thereof. As shown inFIG.1O, recesses188are formed over the source/drain portions148and150, in accordance with some embodiments. Afterwards, as shown inFIG.1P, a contact plug190is formed in the recesses188, in accordance with some embodiments. In some embodiments of the present disclosure, the contact plug190is made of a single layer or multiple layers of cobalt, copper, aluminum, tungsten, gold, chromium, nickel, platinum, titanium, iridium, rhodium, an alloy thereof, a combination thereof, or another conductive material. In some embodiments of the present disclosure, a contact material layer (not shown in this figure) is deposited over the barrier layer186and filled into the recesses188. In some embodiments, the applicable deposition methods for depositing the contact material layer include a chemical vapor deposition (CVD) process, a physical vapor deposition (PVD) process, and other applicable methods. Afterwards, in some embodiments, a planarization process is performed to thin down the contact material layer and the barrier layer186. For example, the contact material layer and the barrier layer186are thinned until the sacrificial layer178is exposed. The planarization process may include a chemical mechanical polishing (CMP) process, a grinding process, a dry polishing process, an etching process, another applicable process, or a combination thereof. As a result, the contact plug190and the semiconductor device structure100shown inFIG.1Pare formed. In some embodiments of the present disclosure, the contact plugs190are electrically connected to the source/drain portion148and/or the source/drain portion150. It should be noted that the exemplary embodiment set forth inFIGS.1A-1Pis merely for the purpose of illustration. In addition to the embodiment set forth inFIGS.1A-1P, the nanowire may be formed by another method as shown inFIGS.5A-5B. This will be described in more detail in the following description. Therefore, the present disclosure is not limited to the exemplary embodiment shown inFIGS.1A-1P. Note that the same or similar elements or layers corresponding to those of the semiconductor device are denoted by like reference numerals. In some embodiments, the same or similar elements or layers denoted by like reference numerals have the same meaning and will not be repeated for the sake of brevity. As shown inFIG.5A, after the semiconductor material wires, such as the semiconductor material wires158, are formed, and before forming the cladding layer160, an outer portion of the semiconductor material wire158is removed by an etching process, such as an anisotropic etching process, in accordance with some embodiments. As shown inFIG.5A, a portion of the semiconductor material wire158remains, in accordance with some embodiments. As shown inFIG.5B, after the semiconductor material wire158is partially etched and partially removed, the cladding layer160is formed to surround the remaining portion of the semiconductor material wire158to form the first nanowire162, in accordance with some embodiments. As shown inFIG.5B, a portion of the semiconductor material wire158has a thickness that is less than that of the first source/drain portion148. FIG.6Ais a top view of a semiconductor device structure600A in accordance with some cases. In some cases, the semiconductor device structure600A includes a P-type FET604A and an N-type FET606A. In some cases, the P-type FET604A includes three or more fin structures608A which use a portion of the fin structures608A or a nanowire with a circular cross-section as a channel. In some cases, the N-type FET606A includes three or more fin structures610A which use a portion of the fin structures610A or a nanowire with a circular cross-section as a channel. In addition, a dielectric layer612is positioned between the P-type FET604A and the N-type FET606A. In addition, one or more gate structures602traverse through the fin structures608A and610A. FIG.6Bis a top view of a semiconductor device structure600B in accordance with some embodiments. In some embodiments, the semiconductor device structure600B includes a P-type FET604B and an N-type FET606B. In some embodiments, the P-type FET604B includes two fin structures608B which use a nanowire with a polygonal cross-section as a channel. In some embodiments, the N-type FET606B includes two fin structures610B which use a nanowire with a polygonal cross-section as a channel. Since the nanowire in the embodiments of the present disclosure has a polygonal cross-section, the current flowing through the nanowire in the embodiments of the present disclosure under a given voltage is increased, and the drain-induced barrier lowering issue is reduced, compared to the device using nanowire with a circular cross-section or the FinFET transistor. Therefore, the P-type FET604B and the N-type FET606B may use fewer fin structures606B and608B and fewer tracks compared to the device using nanowire with a circular cross-section or the FinFET transistor. FIG.6Cis a top view of a semiconductor device structure600C in accordance with some embodiments. In some embodiments, the semiconductor device structure600C includes a P-type FET604C and an N-type FET606C. In some embodiments, the P-type FET604C includes one fin structure608C which uses a nanowire with a polygonal cross-section as a channel. In some embodiments, the N-type FET606C includes one fin structure610C which uses a nanowire with a polygonal cross-section as a channel. Since the nanowire in the embodiments of the present disclosure has a polygonal cross-section, the current flowing through the nanowire in the embodiments of the present disclosure under a given voltage is increased, and the drain-induced barrier lowering issue is reduced, compared to the device using nanowire with a circular cross-section or the FinFET transistor. Therefore, the P-type FET604C and the N-type FET606C may use fewer fin structures606C and608C and fewer tracks compared to the device using nanowire with a circular cross-section or the FinFET transistor. Embodiments of the disclosure use nanowire with a polygonal cross-section. Therefore, the current flowing through the nanowire in the embodiments of the present disclosure under a given voltage is increased, and the drain-induced barrier lowering issue is reduced, compared to the device using nanowire with a circular cross-section or the FinFET transistor. Embodiments of the disclosure are not limited and may be applied to fabrication processes for any suitable technology generation. Various technology generations include a 20 nm node, a 16 nm node, a 10 nm node, or another suitable node. In accordance with some embodiments, a semiconductor device structure is provided. The semiconductor device structure includes a substrate including a first fin portion, a first nanostructure over the first fin portion. The first nanostructure has a dumbbell shape. The first nanostructure includes a semiconductor material layer over the first fin portion, and a cladding layer surrounding the semiconductor material layer. The semiconductor material layer has a rectangular shape, and the cladding layer has a hexagonal or quadrilateral shape. The semiconductor device structure includes a first gate structure surrounding the first nanostructure. In accordance with some embodiments, a semiconductor device structure is provided. The semiconductor device structure includes a first nanostructure formed over a substrate, and the first nanostructure comprises a first edge portion and a central portion. The first edge portion has a first height along a first direction, and the first direction is vertical to a top surface of the substrate, the central portion has a second height along the first direction, and the first height is greater than the second height. The semiconductor device structure includes a first gate structure surrounding the first nanostructure. In accordance with some embodiments, a method for forming a semiconductor device structure is provided. The method includes providing a substrate having a first fin, and the first fin has a channel region and a source/drain region. The method includes forming a stack structure over the first fin, and the stack structure comprises a first semiconductor layer and a second semiconductor layer vertically stacked over the fin. The method also includes removing a portion of the second semiconductor layer in the channel region, and a portion of the first semiconductor layer is remaining in the channel region. The method further includes forming a cladding layer over the remaining first semiconductor material layer in the channel region to form a nanostructure, wherein the nanostructure has a dumbbell shape. The method includes forming a gate structure surrounding the nanostructure. In accordance with some embodiments, a method for forming a semiconductor device structure is provided. The method includes providing a substrate having a first fin and a second fin, and forming a plurality of first nanostructures over the first fin, wherein two adjacent first nanostructures are spaced apart from each other. The method also includes forming a plurality of second nanostructures over the second fin, and the second nanostructures and the first nanostructures are made of different materials, and each of the second nanostructures has a second cladding layer, and two adjacent second cladding layer contact each other. In accordance with some embodiments, a method for forming a semiconductor device structure is provided. The method includes forming a first fin, and the first fin has a channel region and a source/drain (S/D) region. The method also includes forming a stack structure over the first fin, and the stack structure includes a first semiconductor layer and a second semiconductor layer vertically stacked over the first fin. The method includes removing a portion of the second semiconductor layer in the channel region, and a portion of the first semiconductor layer is remaining in the channel region. The method includes forming a cladding layer over the remaining first semiconductor material layer in the channel region to form a first nanostructure. The first nanostructure includes a central portion and an edge portion, and the central portion and the edge portion have different shapes. The method includes forming a gate dielectric layer surrounding the first nanostructure, and a portion of the gate dielectric layer has a hexagonal shape, and a portion of the gate dielectric layer has a quadrilateral shape. The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. | 52,486 |
11862733 | DETAILED DESCRIPTION Hereinafter, example embodiments will be described with reference to the accompanying drawings. FIG.1is a top view of a semiconductor device according to example embodiments. FIG.2is a cross-sectional view of a semiconductor device according to example embodiments.FIG.2illustrates cross sections taken along lines I-I′, II-II′, and III-III′ of the semiconductor device ofFIG.1. For brevity of description, only main components of the semiconductor device are illustrated inFIGS.1and2. Referring toFIGS.1and2, a semiconductor device100may include a substrate101, active regions105on the substrate101, channel structures140, each including a plurality of channel layers141,142, and143disposed on the active regions105to be vertically spaced apart from each other, source/drain regions150in contact with the plurality of channel layers141,142, and143, gate structures160extended to intersect the active region105, and/or contact plugs180connected to the source/drain regions150. The semiconductor device100may further include isolation layers110, internal spacer layers130, and/or an interlayer insulation layer190. The gate structure160may include a gate dielectric layer162, a gate electrode165, spacer layers164, and/or a gate capping layer166. In the semiconductor device100, the active regions105may have a fin structure, and the gate electrode165may be disposed between the active region105and the channel structure140and between the plurality of channel layers141,142, and143of the channel structures140. Accordingly, the semiconductor device100may include a MBCFET™ (Multi Bridge Channel FET) formed by the channel structures140, the source/drain regions150, and the gate structures160. The substrate101may have an upper surface extending in an x direction and a y direction. The substrate101may include a semiconductor material such as a group IV semiconductor, a group III-V compound semiconductor, or a group II-VI compound semiconductor. For example, the group IV semiconductor may include silicon, germanium or silicon germanium. The substrate101may be provided as a bulk wafer, an epitaxial layer, a silicon on insulator (SOI) layer, a semiconductor on insulator (SeOI) layer, or the like. The active region105may be defined in the substrate101by the isolation layers110and may be disposed to extend in a first direction, for example, the x direction. The active region105may have an active fin structure protruding from the substrate101. The active region105may be disposed such that an upper end thereof protrudes from top surfaces of the isolation layers110by a predetermined height. The active region105may include a portion of the substrate101, or may include an epitaxial layer grown from the substrate101. A portion of the active region105on the substrate101may be recessed on opposite sides adjacent to the gate structure160, and the source/drain region150may be disposed on the recessed portion of the active region105. Accordingly, the active region105may have a relatively greater height below the channel structure140and the gate structure160, as illustrated inFIG.2. In some embodiments, the active region105may include impurities, and at least portions of the active regions105may include impurities having conductivity types opposite to each other, but an example embodiment of the active regions105is not limited thereto. The isolation layer110may define the active region105on the substrate101. The isolation layer110may be formed by, for example, a shallow trench isolation (STI) process. The isolation layer110may be formed to expose upper sidewalls of the active regions105. In some embodiments, the isolation layer110may include a region extending deeper to a lower portion of the substrate101between the active regions105. The isolation layer110may have a curved top surface having a level becoming higher in a direction to the active region105, but a shape of the top surface of the isolation layer110is not limited thereto. The isolation layer110may be formed of an insulating material. The isolation layer110may be, for example, an oxide, a nitride, or a combination thereof. As illustrated inFIG.2, the isolation layer110may have different heights of the top surface below and outside of the gate structure160. Such variation in shape is formed depending on the manufacturing process, and the height difference of the top surface may be changed according to example embodiments. The channel structure140includes first to third channel layers141,142, and143, a plurality of channel layers, disposed on the active region105to be spaced apart from each other in a direction perpendicular to the top surface of the active region105, for example, a z direction. The first to third channel layers141,142, and143may be spaced apart from the top surface of the active region105while being connected to the source/drain regions150. Each of the first to third channel layers141,142, and143may have a width equal or similar to a width of the active region105in a y direction, and may have a width equal or similar to a width of the gate structure160in the x direction. However, in some embodiments, the first to third channel layers141,142, and143may have decreased widths such that side surfaces thereof are disposed below the gate structure160in the x direction. Each of the first to third channel layers141,142, and143may be formed of a semiconductor material and may include at least one of silicon (Si), silicon germanium (SiGe), and germanium (Ge). The first to third channel layers141,142, and143may be formed of, for example, the same material as that of the substrate101. The number and shape of the channel layers141,142, and143, constituting a single channel structure140, may be variously changed according to example embodiments. The source/drain regions150may be disposed on active regions105at opposite sides adjacent to the gate structure160. The source/drain regions150may be provided as a source region or a drain region of a transistor. Each of the source/drain regions150may be disposed such that an upper surface thereof is higher than an uppermost surface of the channel structure140, and may be an elevated source/drain disposed to be higher than a bottom surface of the gate electrode165on the channel structure140. The source/drain regions150may be disposed on a region in which a portion of the active region105is recessed between the channel structures140and the gate structures160adjacent to each other in the x direction. The source/drain regions150may extend from a sidewall of the active region105to be inclined with respect to an upper surface of the substrate101at opposite sides adjacent to the gate structure160, as illustrated in a cross-section view taken in the y direction. The source/drain regions150may have a major width in the y direction in a region disposed adjacent to the first channel layer141, a lowermost layer adjacent to the active region105among the plurality of channel layers141,142, and143, for example, a region, disposed adjacent to the first channel layer141in the direction, having a height corresponding to a height of the first channel layer141. The source/drain regions150may have relatively decreased widths in regions disposed adjacent to the overlying first and second channel layers142and143, for example, regions, disposed adjacent to the second and third channel layers142and143, each having a height corresponding to a height at which the second and third channel layers142and143are disposed. In the source/drain regions150, an inclined surface, extending from the sidewall of the active region105, may be a facet provided along a crystal plane, for example, a <111> facet. Shapes of the source/drain regions150will be described in further detail later with reference to FIGS.3A to5. The source/drain regions150may be formed of a semiconductor material. For example, the source/drain regions150may include at least one of silicon germanium (SiGe), silicon (Si), silicon arsenic (SiAs), silicon phosphide (SiP), and silicon carbide (SiC). Specifically, the source/drain regions150may be formed of an epitaxial layer. For example, the source/drain regions150may include n-type doped silicon (Si) and/or p-type doped silicon germanium (SiGe). In example embodiments, the source/drain regions150may include a plurality of regions including elements having different concentrations, and/or doping elements. In addition, in example embodiments, the source/drain regions150are connected to each other on two or more active regions105disposed adjacent to each other, or may be merged to form a single source/drain region150. The gate structure160may be disposed to intersect the active regions105and the channel structures140above the active regions105and the channel structures140to extend in one direction, for example, the y direction. Channel region of transistors may be formed in the active regions105and the channel structures140intersecting the gate structure160. The gate structure160includes a gate electrode165, a gate dielectric layer162between the gate electrode165and the plurality of channel layers141,142, and143, spacer layers164on side surfaces of the gate electrode165, and a gate capping layer166on a top surface of the gate electrode165. The gate dielectric layer162may be disposed between the active region105and the gate electrode165and between the channel structure140and the gate electrode165, and may be disposed to cover at least a portion of a surface of the gate electrode165. For example, the gate dielectric layer162may be disposed to surround all surfaces except for an uppermost surface of the gate electrode165. The gate dielectric layer162may extend between the gate electrode165and the spacer layers164, but extension of the gate dielectric layer162is not limited thereto. The gate dielectric layer162may include an oxide, a nitride, or a high-k material. The high-k material may refer to a dielectric material having a dielectric constant higher than a dielectric constant of silicon oxide (SiO2). The high-k material may include one of, for example, aluminum oxide (Al2O3), tantalum oxide (Ta2O3), titanium oxide (TiO2), yttrium oxide (Y2O3), zirconium oxide (ZrO2), zirconium silicon oxide (ZrSixOy), hafnium oxide (HfO2), hafnium silicon oxide (HfSixOy), lanthanum oxide (La2O3), lanthanum aluminum oxide (LaAlxOy), lanthanum hafnium oxide (LaHfxOy), hafnium aluminum oxide (HfAlxOy), and praseodymium oxide (Pr2O3). The gate electrode165may be disposed over the active region105to extend to an upper portion of the channel structure140while filling spaces between the plurality of channel layers141,142, and143. The gate electrode165may be spaced apart from the plurality of channel layers141,142, and143by the gate dielectric layer162. The gate electrode165may include a conductive material, and may include a metal nitride such as titanium nitride (TiN), tantalum nitride (TaN), or a tungsten nitride (WN), and/or a metal material such as aluminum (Al), tungsten (W), or molybdenum (Mo), or a semiconductor material such as doped polysilicon. The gate electrode165may have a multilayer structure including two or more layers. The gate electrode165may be divided between at least some of adjacent transistors by an additional division portion, depending on the configuration of the semiconductor device100. The spacer layers164may be disposed on both side surfaces of the gate electrode165on the channel structure140. The spacer layers164may insulate the source/drain regions150and the gate electrodes165from each other, together with internal spacer layers130. In some embodiments, the spacer layers164may have a multilayer structure. The spacer layers164may include an oxide, a nitride, and oxynitrides. Specifically, the spacer layers164may include a low-k dielectric layer. Active spacer layers164F may be formed simultaneously in the same process as the spacer layers164, and thus, may include the same material as the spacer layers164. The active spacer layers164F may be disposed on the upper sidewalls of the active regions105exposed by the isolation layers110at opposite sides adjacent to the gate structure160. The gate capping layer166may be disposed on an uppermost surface of the gate electrode165, and a lower surface and side surfaces thereof may be surrounded by the gate electrode165and the spacer layers164, respectively. The gate capping layer166may include an oxides, a nitrides, and an oxynitride. The internal spacer layers130may be disposed parallel to the gate electrode165between spaces of the channel structure140. Below the third channel layer143, the gate electrode165may be spaced apart from the source/drain regions150by the internal spacer layers130to be electrically insulated from the source/drain regions150. The internal spacer layers130may have a shape in which a side surface, facing the gate electrode165, is convexly rounded inwardly toward the gate electrode165, but a shape of the internal spacer layers is not limited thereto. The internal spacer layers130may include an oxide, a nitride, and an oxynitride. Specifically, the internal spacer layers130may include a low-k dielectric layer. In some embodiments, the internal spacer layers130may be omitted. In this case, the gate electrode165may be disposed to extend between the spaces of the channel structure140, and a side surface of the gate electrode165along the x direction may be disposed to be vertically parallel to a side surface of the channel structure140. The interlayer insulation layer190may be disposed to cover top surfaces of the source/drain regions150, the gate structures160, and the isolation layers110. The interlayer insulation layer190may include at least one of, for example, an oxide, a nitride, and an oxynitride, and may include a low-k dielectric material. The contact plug180may be connected to the source/drain region150to apply an electrical signal to the source/drain region150. The contact plug180may penetrate through the interlayer insulation layer190to vertically extend. The contact plug180may be disposed on the source/drain region150, as illustrated inFIG.1. In some embodiments, the contact plug180may be disposed to have a length greater than a length of the source/drain region150in the y direction. The contact plug180may have an inclined side surface, having a lower portion narrower than an upper portion, depending on an aspect ratio, but a shape of the contact plug180is not limited thereto. The contact plug180may be disposed to recess the source/drain region150to a predetermined depth. The contact plug180may extend to, for example, a portion lower than the third channel layer143. The contact plug180may be recessed to, for example, an upper surface of the second channel layer142, but recessing of the contact plug180is not limited thereto. In example embodiments, the contact plug180may be disposed to be in contact with the source/drain region150along the top surface of the source/drain region150without recessing the source/drain region150. FIGS.3A and3Bare a top view and a cross-sectional views of a semiconductor device according to example embodiments, respectively.FIGS.3A and3Billustrate an enlarged version of region ‘A’ ofFIG.1and an enlarged version of region ‘B’ ofFIG.2, respectively. Referring toFIGS.3A and3B, the source/drain region150may extend further than the active region105, to opposite sides adjacent to the gate structure160in the y direction and may include a plurality of regions, each having a width greater than a width of the active region105. The source/drain region150has a first region including a first point P1having a first major width W1from a lower portion thereof, a second region including a second point P2having a second major width W2less than the first major width W1, and a third region P3having a third major width W3less than the first major width W1. The first major width W1of the first point P1may be a major width of the first region in the y direction and may be a major width of the entire source/drain region150in the y direction. The source/drain region150may have a width greater than the active region105at least in the first to third points P1, P2, and P3, and thus, may have a curvature. The shape of the source/drain region150may result from the fact that a lower portion of the source/drain region150is grown from the sidewall of the active region105and an upper portion of the source/drain region150has regions in which growth of the source/drain region150is limited due to the internal spacer layers130described with reference toFIGS.1and2. The first point P1may be a point in which the source/drain region150is grown from the top surface and the sidewalls of the active region105and grown from the side surface of the first channel layer141in the x direction to have a major width. Specifically, the source/drain region150may be grown from the sidewall of the active region105to the first point P1while forming a facet provided along a crystal plane. Accordingly, in the source/drain region150, a side surface extending to the first point P1may form a specific angle θ depending on a crystal plane. For example, when forming a [111] facet, the angle θ may be about 54.7 degrees. A side surface of an upper portion of the first point P1may also be a facet depending on a crystal plane. Accordingly, side surfaces of upper and lower portions on the basis of the first point P1may be facets, and the source/drain region150may have the major width on a boundary between the facets. The first point P1may be disposed at a height between the first channel layer141and the active region105, but a detailed height may be variously changed in example embodiments. For example, the first point P1may be disposed at a height between an upper surface of the first channel layer141and an upper surface of the active region105. For example, the first point P1may be disposed at a height between a lower surface of the first channel layer141and an upper surface of the active region105. The location of the first point P1may be controlled by a first length L1, at which the sidewall of the active region105is exposed by active spacer layers164F, and a second length L2, a length between the top surface of the active region105and a lower surface of the first channel layer141. The second length L2may be controlled by a depth at which the active region105is recessed in the source/drain region150during a manufacturing process. When a length from a point, in which the active region105is exposed, to a height of a middle of the first and second channel layers141and142is defined as a third length L3, a fourth length L4, at which the first point P1protrudes from an extension line of a side surface of the first channel layer141or the active region105in the y direction, may be approximately calculated by (L3/2)/tan θ. Accordingly, the fourth length L4may be increased as a first length L1, at which the sidewall of the active region105is exposed by the active spacer layers164F, and a second length L2between the top surface of the active region105and the lower surface of the first channel layer141are increased. In example embodiments, the fourth length L4may range from about 7 nm to 20 nm. When a length, at which the second point P2protrudes from an extension line of a side surface of the second channel layer142or the active region105in the y direction, is defined as a fifth length L5, the length L5may also be calculated in a manner similar to the calculation manner of the fourth length L4. In example embodiments, a ratio of the fifth length L5to the fourth length L4(L5/L4) may range from about 0.4 to about 0.7. The range may be controlled by changing thicknesses and a spacing distance of the first and second channel layers141and142and the first and second lengths L1and L2. The second point P2and the third point P3may be disposed at heights corresponding to the second channel layer142and the third channel layer143, respectively. As illustrated inFIG.3A, the second point P2and the third point P3may be disposed in substantially the same position on a plane. For example, the second major width W2and the third major width W3may be substantially the same, but are not limited thereto. According to embodiments, the third major width W3may be less than the second major width W2. In this case, the first point P1, the second point P2, and the third point P3may be sequentially disposed from outside of the source/drain region150in the y direction on a plane. The source/drain region150may include regions, each having a decreased width, between the first to third points P1, P2, and P3. For example, the source/drain region150may include regions, each having a decreased width between the first point P1and the second point P2and between the second point P2and the third point P3and regions, each having a local minimum width. The minimum width may be proximate to, for example, the width of the active region105, but is not limited thereto. The regions, each locally having a minimum width, may be disposed at a height corresponding to, for example, a height at which the internal spacer layers130are disposed. Accordingly, the source/drain region150may have a curvature corresponding to dispositions of the plurality of channel layers141,142, and143and internal spacer layers130, and may have a gently curved top surface above the third point P3. As illustrated inFIG.3B, the source/drain region150may have an external side surface having facets in at least one region between the first to third points P1, P2, and P3. FIG.4is a cross-sectional view of a semiconductor device according to example embodiments.FIG.4illustrates an enlarged version of a region corresponding to the region ‘B’ ofFIG.2. Referring toFIG.4, various types of contact plugs180,180a, and180baccording to example embodiments are illustrated together with a source/drain region150and a contact plug180to describe a disposing relationship between the source/drain region150and the contact plug180. The contact plugs180,180a, and180bmay be disposed to recess an upper portion of the source/drain region150to a predetermined depth RD from an upper surface thereof. The recessed depth RD may be a height substantially corresponding to an upper surface of a second channel layer142. However, the recessed depth RD is not limited thereto and may be variously changed in example embodiments. A person having ordinary skill the art would know when the recessed depth RD is relatively large, the source/drain region150may be decreased in volume to insufficiently perform electrical functions. When the recessed depth RD is relatively small, the source/drain region150and the contact plugs180,180a, and180bmay not be electrically connected to each other due to a process variation. The contact plugs180,180a, and180baccording to example embodiments may have different widths, which are sequentially increased in the y direction. Similarly to the contact plug180b, when the contact plug180bhas a width greater than a width of the source/drain region150in contact with the contact plug180b, an upper portion of the source/drain region150is removed at opposite sides adjacent to a gate structure160by the recessed depth RD. Accordingly, in an ultimate structure of a semiconductor device, a shape of the source/drain region150may also be different depending on widths of the contact plugs180,180a, and180b. FIGS.5A to5Care cross-sectional views of a semiconductor device according to example embodiments.FIGS.5A to5Cillustrate enlarged versions of a region corresponding to the region ‘B’ ofFIG.2, respectively. Referring toFIG.5A, a source/drain region150amay have a shape in which facets are generally alleviated while including first to third points P1, P2, and P3, each having a locally large width, and including the first point P1having a major width, as illustrated inFIG.3A. For example, the source/drain region150amay have a curvature corresponding to a plurality of channel layers141,142, and143. Such a shape may be controlled depending on a material of the source/drain region150a. For example, when the source/drain region150aincludes impurities occupying an interstitial site, the source/drain region150amay be grown to have such a curved external surface. In this case, the source/drain region150amay be formed of, for example, silicon phosphide (SiP). Referring toFIG.5B, a source/drain region150bmay have a box-shaped upper portion which does not include a third point P3while including first and points P1and P2, each having a locally large width, and including the first point P1having a major width, as illustrated inFIG.3A. The source/drain region150bmay have a fourth width W4, smaller than a first width W1of the first point P1, at a height corresponding to a third channel layer143. The fourth width W4may be smaller than a second width W2aof the second point P2, or may be similar to the second width W2a. Even in this case, the source/drain region150bmay have an inclined surface up to the first point P1having a major width. Referring toFIG.5C, a source/drain region150cmay be disposed such that a portion of the source/drain region150cis grown onto active spacer layers164F from a lower end thereof to contact the active spacer layers164F. Accordingly, the source/drain region150cmay have a shape, in which a surface extending from a sidewall of an active region105to a first point P1includes a plurality of surfaces or curved surfaces rather than a single facet, while including the first point P1having a major width. Such a shape of the source/drain region150cmay appear when a lower end portion thereof is not grown along a crystal plane under growth conditions of the source/drain region150c. An upper portion of the source/drain region150cis provided with second and third points P2and P3, each having a locally large width, but the source/drain region150cmay have a box shape, as illustrated inFIG.5B, in some embodiments. FIG.6is a cross-sectional view of a semiconductor device according to example embodiments.FIG.6illustrates a region corresponding to a cross section taken along line II-II′ ofFIG.1. Referring toFIG.6, a semiconductor device100amay include an active region105aand a channel structure140ahaving widths different from those in the example embodiment ofFIG.2. The active region105aand the channel structure140amay have relatively smaller widths, such that a plurality of channel layers141a,142a, and143aof the channel structure140amay each have a circular shape or an elliptical shape, in which a difference between lengths of a major axis and a minor axis is relatively small, on a cross section in a y direction. For example, in the example embodiment ofFIG.2, each of the plurality of channel layers141,142, and143may have a width of about 20 nm to 50 nm in the y direction and, in this embodiment, each of the plurality of channel layers141a,142a, and143amay have a width of about 3 nm to 12 nm in the y direction. As described above, in example embodiments, widths and shapes of the active region105aand the channel structure140amay be variously changed. FIGS.7A to7Jare cross-sectional views illustrating a method of manufacturing a semiconductor device according to example embodiments. InFIGS.7A to7J, an example embodiment of a method of manufacturing the semiconductor device ofFIGS.1and2will be described and cross sections corresponding toFIG.2are illustrated. Referring toFIG.7A, sacrificial layers120and channel layers141,142, and143may be alternately stacked on a substrate101. The sacrificial layers120may be layers replaced with a gate dielectric layer162and a gate electrode165in a subsequent process, as illustrated inFIG.2. The sacrificial layers120may be formed of a material having an etching selectivity with respect to the channel layers141,142, and143. The channel layers141,142, and143may include a material different from a material of the sacrificial layers120. The sacrificial layers120and channel layers141,142and143include a semiconductor material including at least one of silicon (Si), silicon germanium (SiGe), and germanium (Ge) and may include different materials. The sacrificial layers120and channel layers141,142and143may or may not include impurities. For example, the sacrificial layers120may include silicon germanium (SiGe), and the channel layers141,142and143may include silicon (Si). The sacrificial layers120and the channel layers141,142, and143may be formed by performing an epitaxial growth process using the substrate101as a seed. Each of the sacrificial layers120and channel layers141,142, and143may have a thickness ranging from about 1 Å to 100 nm. The number of the channel layers141,142, and143, stacked alternately with the sacrificial layer120, may be variously changed in example embodiments. Referring toFIG.7B, a stacked structure of the sacrificial layers120and the channel layers141,142, and143and a portion of the substrate101may be removed to form active structures. The active structure may include sacrificial layers120and channel layers141,142, and143alternately stacked with each other. The active structure may further include active regions105formed by removing a portion of the substrate101to protrude to an upper surfaced of the substrate101. The active structures may be formed in a linear shape extending in one direction, for example, the x direction inFIG.1, and may be spaced apart from each other in the y direction. In a region in which a portion of the substrate101is removed, isolation layers110may be formed by filling the region with an insulating material and recessing the insulating material such that the active regions105protrude. Top surfaces of the isolation layers110may be formed to be lower than top surface of the active regions105. Referring toFIG.7C, sacrificial gate structures170and spacer layers164may be formed on the active structures. Each of the sacrificial gate structures170may be a sacrificial structure formed in a region, in which a gate dielectric layer162and a gate electrode165are disposed above the channel structures140, in a substrate process, as illustrated inFIG.2. The sacrificial gate structure170may include first and second sacrificial gate layers172and175, and a mask pattern layer176, which are sequentially stacked. The first and second sacrificial gate layers172and175may be patterned using a mask pattern layer176. The first and second sacrificial gate layers172and175may be respectively an insulating layer and a conductive layer, but are not limited thereto. The first and second sacrificial gate layers172and175may be provided as a single layer. For example, the first sacrificial gate layer172may include a silicon oxide and the second sacrificial gate layer175may include polysilicon. The mask pattern layer176may include a silicon oxide and/or a silicon nitride. The sacrificial gate structures170may have a linear shape extending in one direction while intersecting the active structures. The sacrificial gate structures170may extend, for example, in the y direction ofFIG.1and be spaced apart from each other in the x direction. The spacer layers164may be formed on both sidewalls of the sacrificial gate structures170. With the spacer layers164, active spacer layers164F may also be formed on both sidewalls of the active structures exposed from the sacrificial gate structures170. The spacer layers164and the active spacer layers164F may be formed by forming a layer having a uniform thickness along top and side surfaces of the sacrificial gate structures170and the active structures and anisotropically etching the layer having a uniform thickness. The spacer layers164and the active spacer layers164F may be formed of the same material. The spacer layers164and the active spacer layers164F may be formed of a low-k dielectric material and may include at least one of, for example, SiO, SiN, SiCN, SiOC, SiON, and SiOCN. Referring toFIG.7D, the sacrificial layers120and channel layers141,142, and143exposed between sacrificial gate structures170may be removed to form channel structures140. The exposed sacrificial layers120and the exposed channel layers141,142, and143may be removed using the sacrificial gate structures170and spacer layers164as masks. Accordingly, the channel layers141,142, and143each may have a limited length in the x direction and constitute the channel structure140. In example embodiments, portions of the sacrificial layers120and a portion of the channel structure140may be removed from side surfaces thereof below the sacrificial gate structures170, such that both sides thereof may be disposed below the sacrificial gate structures170and the spacer layers164. In this process, portions of the active regions105may also be recessed and removed from top surfaces thereof. In addition, portions of the active spacer layers164F, disposed on both sidewalls of the active structures, are removed while the sacrificial layers120and channel layers141,142, and143are removed, and portions thereof may be further removed during a process of recessing the active regions105. The active spacer layers164F are controlled to remain by changing conditions of the processes such that upper sidewalls of the active regions105are exposed by a predetermined length L1, as illustrated in the drawing. According to embodiments, the length L1may be varied within a range of exposing the upper sidewalls of the active regions105. According to embodiments, in this process, portions of the spacer layers164on both sidewalls of the sacrificial gate structures170may also be removed from upper portions thereof to a predetermined depth. In example embodiments, the active spacer layers164F may be removed through an additional process to be formed in such a manner. Referring toFIG.7E, portions of the exposed sacrificial layers120may be removed from side surfaces thereof. The sacrificial layers120may be etched selectively with respect to the channel structures140by, for example, a wet etching process, to be removed from the side surfaces thereof to a predetermined depth in the x-direction. The sacrificial layers120may have inwardly recessed side surfaces due to such side etching. However, shapes of the side surfaces of the sacrificial layers120are not limited to those illustrated in the drawing. Referring toFIG.7F, internal spacer layers130may be formed in regions in which the sacrificial layers120are removed. The internal spacer layers130may be formed by filling the regions, in which the sacrificial layers120are removed, with an insulating material and removing the insulating material deposited on outside of the channel structures140. The internal spacer layers130may be formed of the same material as the spacer layers164, but a material of the internal spacer layers130is not limited thereto. For example, the internal spacer layers130may include at least one of SiN, SiCN, SiOCN, SiBCN, and SiBN. When the active spacer layers164F are formed to be higher than the upper sidewalls of the active regions105, rather than being formed to expose the upper sidewall of the active regions105in the above process referring toFIG.7D, a material of the internal spacer layers130may remain between the active spacer layers164F and the active region105in this process. In this case, growth of the source/drain regions150may be hampered and the volume of the source/drain regions150may be decreased in a subsequent process to degrade electrical characteristics of the semiconductor device. However, according to example embodiments, since the active spacer layers164F are formed to expose the upper sidewalls of the active regions105, the material of the internal spacer layers130does not remain in regions, in which the source/drain regions150are to be formed, in this process. Therefore, the growth of the source/drain regions150may not be hampered. Referring toFIG.7G, source/drain regions150may be formed on active regions105at opposite sides adjacent to the sacrificial gate structures170. The source/drain regions150may be formed by performing a selective epitaxial growth process using the active regions105and the channel structures140as seeds. The source/drain regions150may be connected to the channel layers141,142, and143of the channel structures140through side surfaces thereof and may be in contact with the internal spacer layers130between the channel layers141,142, and143. Since the source/drain regions150are grown from the sidewalls of the active regions105on a cross section in a y direction, each of the source/drain regions150may be grown with a facet provided along a crystal plane in an epitaxial growth process. For example, the source/drain regions150may be grown to form a side surface inclined with respect to an upper surface of the active regions105while being grown on a (100) plane, the top surface of the active regions105, at a relatively high speed in a direction perpendicular to the top surface. Thus, the source/drain regions150may include a region having a major width, disposed between the source/drain regions150and the first channel layer141. The source/drain regions150may include impurities doped during the growth process or after the growth process. Referring toFIG.7H, an interlayer insulation layer190may be formed, and the sacrificial layers120and the sacrificial gate structures170may be removed. The interlayer insulation layer190may be formed by forming an insulating layer to cover the sacrificial gate structures170and the source/drain regions150and performing a planarization process. The sacrificial layers120and the sacrificial gate structures170may be selectively removed with respect to the spacer layers164, the interlayer insulation layer190, and the channel structures140. After the sacrificial gate structures170are removed to form upper gap regions UR, the sacrificial layers120, exposed through the upper gap regions UR, may be removed to form lower gap regions LR. For example, when the sacrificial layers120includes silicon germanium (SiGe) and the channel structures140includes silicon (Si), the sacrificial layers120may be selectively removed by performing a wet etching process using a peracetic acid as an etchant. During the removal process, the source/drain regions150may be protected by an interlayer insulation layer190and the internal spacer layers130. Referring toFIG.7I, gate dielectric layers162may be formed in the upper gap regions UR and the lower gap regions LR. The gate dielectric layers162may be formed to conformally cover internal surfaces of the upper gap regions UR and the lower gap regions LR. Referring toFIG.7J, gate electrodes165may be formed to fill the upper and lower gap regions UR and LR, and a gate capping layer166may be formed on the gate electrodes165. After the gate electrodes165are formed to completely fill the upper gap regions UR and the lower gap regions LR, they may be removed from upper portion thereof in the upper gap regions UR to a predetermined depth. The gate capping layer166may be formed in the region in which the gate electrodes165are removed in the upper gap regions UR. Thus, gate structures160, including the gate dielectric layer162, the gate electrode165, the spacer layers164, and the gate capping layer166, may be formed. Next, referring toFIG.2, contact plugs180may be formed. First, the interlayer insulation layer190may be patterned to form contact holes, and a conductive material may fill the contact holes to form the contact plugs180. The contact holes may be formed by removing the interlayer insulation layer190at opposite sides adjacent to the gate structure160using an additional mask layer such as a photoresist pattern. Bottom surfaces of the contact holes may be recessed into the source/drain regions150or may have a curvature along the top surface of the source/drain regions150. In example embodiments, shapes and dispositions of the contact plugs180may be variously changed. As described above, a structure and a shape of a source/drain region may be controlled to provide a semiconductor device having improved electrical characteristics. While example embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present inventive concept as defined by the appended claims. | 40,444 |
11862734 | DETAILED DESCRIPTION The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. Still further, when a number or a range of numbers is described with “about,” “approximate,” and the like, the term is intended to encompass numbers that are within +/−10% of the number described, unless otherwise specified. For example, the term “about 5 nm” encompasses the dimension range from 4.5 nm to 5.5 nm. The present disclosure is generally related to semiconductor devices and fabrication methods, and more particularly to fabricating gate-all-around (GAA) transistors with self-aligned inner-spacers. It is also noted that the present disclosure presents embodiments in the form of multi-gate transistors. Multi-gate transistors include those transistors whose gate structures are formed on at least two-sides of a channel region. These multi-gate devices may include a p-type metal-oxide-semiconductor device or an n-type metal-oxide-semiconductor device. Specific examples may be presented and referred to herein as FINFET, on account of their fin-like structure. Also presented herein are embodiments of a type of multi-gate transistor referred to as a gate-all-around (GAA) device. A GAA device includes any device that has its gate structure, or portion thereof, formed on 4-sides of a channel region (e.g., surrounding a portion of a channel region). Devices presented herein also include embodiments that have channel regions disposed in nanowire channel(s), bar-shaped channel(s), and/or other suitable channel configuration. Presented herein are embodiments of devices that may have one or more channel regions (e.g., nanowires) associated with a single, contiguous gate structure. However, one of ordinary skill would recognize that the teaching can apply to a single channel (e.g., single nanowire) or any number of channels. One of ordinary skill may recognize other examples of semiconductor devices that may benefit from aspects of the present disclosure. As scales of the fin width in fin field effect transistors (FinFET) decreases, channel width variations could cause undesirable variability and mobility loss. GAA transistors, such as nanosheet transistors are being studied as an alternative to fin field effect transistors. In a nanosheet transistor, the gate of the transistor is made all around the channel (e.g., a nanowire channel or a bar-shaped channel) such that the channel is surrounded or encapsulated by the gate. Such a transistor has the advantage of improving the electrostatic control of the channel by the gate, which also mitigates leakage currents. A nanosheet transistor includes an inner spacer and a sidewall spacer (also termed as an outer spacer), among others. An inner spacer is typically formed by an additional process to the sidewall spacer. For example, after making a sidewall spacer and epitaxially growing source/drain (S/D) features, a space for the inner spacer is made by wet or vapor etch removal. Then, the inner spacer is formed by dielectric material deposition. However, a fine control of the space for inner spacer may be challenging during a wet or vapor etch removal, such as due to loading effects. Consequently, the resulting inner spacer may have non-uniform dimensions across different layers of the nanosheets, further causing channel length variation. An object of the present disclosure is to devise a self-aligned inner spacer formation method so as to accurately control dimensions and positions of the inner spacer and to improved channel length uniformity across different layers of the nanosheets. Illustrated inFIGS.1A and1Bis a method100of semiconductor fabrication including fabrication of multi-gate devices. As used herein, the term “multi-gate device” is used to describe a device (e.g., a semiconductor transistor) that has at least some gate material disposed on multiple sides of at least one channel of the device. In some examples, the multi-gate device may be referred to as a GAA device or a nanosheet device having gate material disposed on at least four sides of at least one channel of the device. The channel region may be referred to as a “nanowire,” which as used herein includes channel regions of various geometries (e.g., cylindrical, bar-shaped) and various dimensions. FIGS.2,3,4,5,6,7,8A,9A,10A,11A,12A, and13Aare perspective views of an embodiment of a semiconductor device200according to various stages of the method100ofFIGS.1A and1B.FIGS.8B,9B,10B,11B,12B, and13Bare corresponding cross-sectional views of an embodiment of the semiconductor device200along a first cut (e.g., cut B-B inFIG.8A), which is along a lengthwise direction of the channel and perpendicular to a top surface of the substrate;FIGS.8C,9C,10C,11C,12C, and13Care corresponding cross-sectional views of an embodiment of the semiconductor device200along a second cut (e.g., cut C-C inFIG.8A), which is in the gate region and perpendicular to the lengthwise direction of the channel;FIGS.8D,9D,10D,11D,12D, and13Dare corresponding cross-sectional views of an embodiment of a semiconductor device200along a third cut (e.g., cut D-D inFIG.8A), which is along the lengthwise direction of the channel and parallel to the top surface of the substrate. As with the other method embodiments and exemplary devices discussed herein, it is understood that parts of the semiconductor device200may be fabricated by a CMOS technology process flow, and thus some processes are only briefly described herein. Further, the exemplary semiconductor devices may include various other devices and features, such as other types of devices such as additional transistors, bipolar junction transistors, resistors, capacitors, inductors, diodes, fuses, static random access memory (SRAM) and/or other logic circuits, etc., but is simplified for a better understanding of the inventive concepts of the present disclosure. In some embodiments, the exemplary devices include a plurality of semiconductor devices (e.g., transistors), including PFETs, NFETs, etc., which may be interconnected. Moreover, it is noted that the process steps of method100, including any descriptions given with reference toFIGS.2-13D, as with the remainder of the method and exemplary figures provided in this disclosure, are merely exemplary and are not intended to be limiting beyond what is specifically recited in the claims that follow. Referring toFIG.1A, the method100begins at step102where a substrate is provided. Referring to the example ofFIG.2, in an embodiment of step102, a substrate202is provided. In some embodiments, the substrate202may be a semiconductor substrate such as a silicon substrate. The substrate202may include various layers, including conductive or insulating layers formed on a semiconductor substrate. The substrate202may include various doping configurations depending on design requirements as is known in the art. For example, different doping profiles (e.g., n-wells, p-wells) may be formed on the substrate202in regions designed for different device types (e.g., n-type field effect transistors (NFET), p-type field effect transistors (PFET)). The suitable doping may include ion implantation of dopants and/or diffusion processes. The substrate202may have isolation features (e.g., shallow trench isolation (STI) features) interposing the regions providing different device types. The substrate202may also include other semiconductors such as germanium, silicon carbide (SiC), silicon germanium (SiGe), or diamond. Alternatively, the substrate202may include a compound semiconductor and/or an alloy semiconductor. Further, the substrate202may optionally include an epitaxial layer (epi-layer), may be strained for performance enhancement, may include a silicon-on-insulator (SOI) structure, and/or may have other suitable enhancement features. In an embodiment of the method100, in step102, an anti-punch through (APT) implant is performed. The APT implant may be performed in a region underlying the channel region of a device for example, to prevent punch-through or unwanted diffusion. Returning toFIG.1A, the method100then proceeds to step104where one or more epitaxial layers are grown on the substrate. With reference to the example of FIG.2, in an embodiment of step104, an epitaxial stack204is formed over the substrate202. The epitaxial stack204includes epitaxial layers206of a first composition interposed by epitaxial layers208of a second composition. The first and second composition can be different. In an embodiment, the epitaxial layers206are SiGe and the epitaxial layers208are silicon (Si). However, other embodiments are possible including those that provide for a first composition and a second composition having different oxidation rates and/or etch selectivity. In some embodiments, the epitaxial layers206include SiGe and where the epitaxial layers208include Si, the Si oxidation rate of the epitaxial layers208is less than the SiGe oxidation rate of the epitaxial layers206. The epitaxial layers208or portions thereof may form nanosheet channel(s) of the multi-gate device200. The term nanosheet is used herein to designate any material portion with nanoscale, or even microscale dimensions, and having an elongate shape, regardless of the cross-sectional shape of this portion. Thus, this term designates both circular and substantially circular cross-section elongate material portions, and beam or bar-shaped material portions including for example a cylindrical in shape or substantially rectangular cross-section. The use of the epitaxial layers208to define a channel or channels of a device is further discussed below. It is noted that seven (7) layers of the epitaxial layers206and six (6) layers of the epitaxial layers208are alternately arranged as illustrated inFIG.2, which is for illustrative purposes only and not intended to be limiting beyond what is specifically recited in the claims. It can be appreciated that any number of epitaxial layers can be formed in the epitaxial stack204; the number of layers depending on the desired number of channels regions for the device200. In some embodiments, the number of epitaxial layers208is between 2 and 10. In some embodiments, each epitaxial layer206has a thickness ranging from about 2 nanometers (nm) to about 6 nm. The epitaxial layers206may be substantially uniform in thickness. Yet in the illustrated embodiment, the top epitaxial layer206is thinner (e.g., half the thickness) than other epitaxial layers206thereunder. The top epitaxial layer206functions as a capping layer providing protections to other epitaxial layers in subsequent processes. In some embodiments, each epitaxial layer208has a thickness ranging from about 6 nm to about 12 nm. In some embodiments, the epitaxial layers208of the stack are substantially uniform in thickness. As described in more detail below, the epitaxial layers208may serve as channel region(s) for a subsequently-formed multi-gate device and the thickness is chosen based on device performance considerations. The epitaxial layers206in channel regions(s) may eventually be removed and serve to define a vertical distance between adjacent channel region(s) for a subsequently-formed multi-gate device and the thickness is chosen based on device performance considerations. Accordingly, the epitaxial layers206may also be referred to as sacrificial layers, and epitaxial layers208may also be referred to as channel layers. By way of example, epitaxial growth of the layers of the stack204may be performed by a molecular beam epitaxy (MBE) process, a metalorganic chemical vapor deposition (MOCVD) process, and/or other suitable epitaxial growth processes. In some embodiments, the epitaxially grown layers such as, the epitaxial layers208include the same material as the substrate202. In some embodiments, the epitaxially grown layers206and208include a different material than the substrate202. As stated above, in at least some examples, the epitaxial layers206include an epitaxially grown silicon germanium (SiGe) layer and the epitaxial layers208include an epitaxially grown silicon (Si) layer. Alternatively, in some embodiments, either of the epitaxial layers206and208may include other materials such as germanium, a compound semiconductor such as silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide, an alloy semiconductor such as SiGe, GaAsP, AlInAs, AlGaAs, InGaAs, GaInP, and/or GaInAsP, or combinations thereof. As discussed, the materials of the epitaxial layers206and208may be chosen based on providing differing oxidation, etching selectivity properties. In some embodiments, the epitaxial layers206and208are substantially dopant-free (i.e., having an extrinsic dopant concentration from about 0 cm−3to about 1×1017cm−3), where for example, no intentional doping is performed during the epitaxial growth process. The method100then proceeds to step106where fin elements (referred to as fins) are formed by patterning. With reference to the example ofFIG.3, in an embodiment of block106, a plurality of fins210extending from the substrate202are formed. In various embodiments, each of the fins210includes a substrate portion formed from the substrate202and portions of each of the epitaxial layers of the epitaxial stack including epitaxial layers206and208. The fins210may be fabricated using suitable processes including double-patterning or multi-patterning processes. Generally, double-patterning or multi-patterning processes combine photolithography and self-aligned processes, allowing patterns to be created that have, for example, pitches smaller than what is otherwise obtainable using a single, direct photolithography process. For example, in one embodiment, a sacrificial layer is formed over a substrate and patterned using a photolithography process. Spacers are formed alongside the patterned sacrificial layer using a self-aligned process. The sacrificial layer is then removed, and the remaining spacers, or mandrels, may then be used to pattern the fins210by etching initial epitaxial stack204. The etching process can include dry etching, wet etching, reactive ion etching (RIE), and/or other suitable processes. In the illustrated embodiment, a hard mask (HM) layer212is formed over the epitaxial stack204prior to patterning the fins210. In some embodiments, the HM layer212includes an oxide layer214(e.g., a pad oxide layer that may include SiO2) and a nitride layer216(e.g., a pad nitride layer that may include Si3N4) formed over the oxide layer214. The oxide layer214may act as an adhesion layer between the epitaxial stack204and the nitride layer216and may act as an etch stop layer for etching the nitride layer216. In some examples, the HM layer212includes thermally grown oxide, chemical vapor deposition (CVD)-deposited oxide, and/or atomic layer deposition (ALD)-deposited oxide. In some embodiments, the HM layer212includes a nitride layer deposited by CVD and/or other suitable technique. The fins210may subsequently be fabricated using suitable processes including photolithography and etch processes. The photolithography process may include forming a photoresist layer (not shown) over the HM layer212, exposing the resist to a pattern, performing post-exposure bake processes, and developing the resist to form a masking element including the resist. In some embodiments, patterning the resist to form the masking element may be performed using an electron beam (e-beam) lithography process. The masking element may then be used to protect regions of the substrate202, and layers formed thereupon, while an etch process forms trenches218in unprotected regions through the HM layer212, through the epitaxial stack204, and into the substrate202, thereby leaving the plurality of extending fins210. The trenches218may be etched using a dry etch (e.g., reactive ion etching), a wet etch, and/or combination thereof. Numerous other embodiments of methods to form the fins on the substrate may also be used including, for example, defining the fin region (e.g., by mask or isolation regions) and epitaxially growing the epitaxial stack204in the form of the fin210. In some embodiments, forming the fins210may include a trim process to decrease the width of the fins210. The trim process may include wet and/or dry etching processes. Referring toFIGS.1A and4, method100proceeds to step108by forming shallow trench isolation (STI) features220interposing the fins210. By way of example, in some embodiments, a dielectric layer is first deposited over the substrate202, filling the trenches218with the dielectric material. In some embodiments, the dielectric layer may include silicon oxide, silicon nitride, silicon oxynitride, fluorine-doped silicate glass (FSG), a low-k dielectric, combinations thereof, and/or other suitable materials. In various examples, the dielectric layer may be deposited by a CVD process, a subatmospheric CVD (SACVD) process, a flowable CVD process, an ALD process, a physical vapor deposition (PVD) process, and/or other suitable process. In some embodiments, after deposition of the dielectric layer, the device200may be annealed, for example, to improve the quality of the dielectric layer. In some embodiments, the dielectric layer (and subsequently formed STI features220) may include a multi-layer structure, for example, having one or more liner layers. In some embodiments of forming the isolation (STI) features, after deposition of the dielectric layer, the deposited dielectric material is thinned and planarized, for example by a chemical mechanical polishing (CMP) process. In some embodiments, the HM layer212(FIG.3) functions as a CMP stop layer. The STI features220interposing the fins210are recessed. Referring to the example ofFIG.4, the STI features220are recessed providing the fins210extending above the STI features220. In some embodiments, the recessing process may include a dry etching process, a wet etching process, and/or a combination thereof. The HM layer212may also be removed before, during, and/or after the recessing of the STI features220. The HM layer212may be removed, for example, by a wet etching process using H3PO4or other suitable etchants. In some embodiments, the HM layer212is removed by the same etchant used to recess the STI features220. In some embodiments, a recessing depth is controlled (e.g., by controlling an etching time) so as to result in a desired height of the exposed upper portion of the fins210. In the illustrated embodiment, the desired height exposes each of the layers of the epitaxial stack204. The method100then proceeds to step110where sacrificial layers/features are formed and in particular, a dummy gate structure. While the present discussion is directed to a replacement gate process whereby a dummy gate structure is formed and subsequently replaced, other configurations may be possible. With reference toFIG.5, a gate stack222is formed. In an embodiment, the gate stack222is a dummy (sacrificial) gate stack that is subsequently removed (with reference to step118). Thus, in some embodiments using a gate-last process, the gate stack222is a dummy gate stack and will be replaced by the final gate stack at a subsequent processing stage of the device200. In particular, the dummy gate stack222may be replaced at a later processing stage by a high-K dielectric layer (HK) and metal gate electrode (MG) as discussed below. In some embodiments, the dummy gate stack222is formed over the substrate202and is at least partially disposed over the fins210. The portion of the fins210underlying the dummy gate stack222may be referred to as the channel region. The dummy gate stack222may also define a source/drain (S/D) region of the fins210, for example, the regions of the fin210adjacent and on opposing sides of the channel region. In the illustrated embodiment, step110first forms a dummy dielectric layer224over the fins210. In some embodiments, the dummy dielectric layer224may include SiO2, silicon nitride, a high-K dielectric material and/or other suitable material. In various examples, the dummy dielectric layer224may be deposited by a CVD process, a subatmospheric CVD (SACVD) process, a flowable CVD process, an ALD process, a PVD process, or other suitable process. By way of example, the dummy dielectric layer224may be used to prevent damages to the fins210by subsequent processes (e.g., subsequent formation of the dummy gate stack). Subsequently, step110forms other portions of the dummy gate stack222, including a dummy electrode layer226and a hard mask228which may include multiple layers230and232(e.g., an oxide layer230and a nitride layer232). In some embodiments, the dummy gate stack222is formed by various process steps such as layer deposition, patterning, etching, as well as other suitable processing steps. Exemplary layer deposition processes include CVD (including both low-pressure CVD and plasma-enhanced CVD), PVD, ALD, thermal oxidation, e-beam evaporation, or other suitable deposition techniques, or combinations thereof. In forming the gate stack for example, the patterning process includes a lithography process (e.g., photolithography or e-beam lithography) which may further include photoresist coating (e.g., spin-on coating), soft baking, mask aligning, exposure, post-exposure baking, photoresist developing, rinsing, drying (e.g., spin-drying and/or hard baking), other suitable lithography techniques, and/or combinations thereof. In some embodiments, the etching process may include dry etching (e.g., RIE etching), wet etching, and/or other etching methods. In some embodiments, the electrode layer226may include polycrystalline silicon (polysilicon). In some embodiments, the hard mask228includes an oxide layer230such as a pad oxide layer that may include SiO2. In some embodiments, hard mask228includes the nitride layer232such as a pad nitride layer that may include Si3N4, silicon oxynitride and/or silicon carbide. Still referring toFIG.5, in some embodiments, after formation of the dummy gate stack222, the dummy dielectric layer224is removed from the S/D regions of the fins210. The etch process may include a wet etch, a dry etch, and/or a combination thereof. The etch process is chosen to selectively etch the dummy dielectric layer224without substantially etching the fins210, the hard mask228, and the dummy electrode layer226. Referring toFIGS.1A and6, the method100then proceeds to step112where a spacer material layer is deposited on the substrate. The spacer material layer may be a conformal layer that is subsequently etched back to form sidewall spacers. In the illustrated embodiment, a spacer material layer234is disposed conformally on top and sidewalls of the dummy gate stack222. The term “conformally” may be used herein for ease of description upon a layer having substantial same thickness over various regions. The spacer material layer234may include a dielectric material such as silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, SiCN films, silicon oxycarbide, SiOCN films, and/or combinations thereof. In some embodiments, the spacer material layer234includes multiple layers, such as main spacer walls, liner layers, and the like. By way of example, the spacer material layer234may be formed by depositing a dielectric material over the gate stack304using processes such as, CVD process, a subatmospheric CVD (SACVD) process, a flowable CVD process, an ALD process, a PVD process, or other suitable process. It is noted that in the illustrated embodiment the spacer material layer234also conformally covers sidewalls of the fins210in the exposed S/D regions, for example, in an ALD process, and partially fills the space between adjacent fins210. If there are gaps remained between adjacent fins210after filling the spacer material layer234, the block112may further deposit other dielectric material, for example, the dielectric material layer236, to fill up the gaps between adjacent fins210in the S/D regions. The dielectric material layer236may include silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, SiCN films, silicon oxycarbide, SiOCN films, and/or combinations thereof. In various embodiments, the spacer material layer234and dielectric material layer236include different material compositions, such as the spacer material layer234includes silicon nitride and the dielectric material layer236includes silicon carbide. The step112may subsequently perform an anisotropic etching process to expose portions of the fins210adjacent to and not covered by the dummy gate stack222(e.g., in source/drain regions). Portions of the spacer material layer directly above the dummy gate stack222may be completely removed by this anisotropic etching process. Portions of the spacer material layer on sidewalls of the dummy gate stack222may remain, forming sidewall spacers, which is denoted as the sidewall spacers234, for the sake of simplicity. Still referring toFIGS.1A and6, the method100then proceeds to step114where epitaxial S/D features238are formed on the substrate. The epi features238may be formed by performing an epitaxial growth process that provides an epitaxial material on the fin210in the source/drain region. During the epitaxial growth process, the dummy gates222and sidewall spacers234limit the epitaxial S/D features238to the S/D regions. Suitable epitaxial processes include CVD deposition techniques (e.g., vapor-phase epitaxy (VPE) and/or ultra-high vacuum CVD (UHV-CVD)), molecular beam epitaxy, and/or other suitable processes. The epitaxial growth process may use gaseous and/or liquid precursors, which interact with the composition of the substrate102. In some embodiments, the epitaxial S/D features238grown on adjacent semiconductor fins210are spaced from each other. In some embodiments, epitaxial S/D features238are grown in a way that they are merged, such as illustrated inFIG.6. In the illustrated embodiment, the height of the fins210in the source/drain regions is also recessed before expitaxially growing the epitaxial S/D features238. As an example, the fins210in the source/drain regions may become equal to or lower than the top surface of the STI features220, and epitaxial S/D features238extend upwardly from the top surfaces of the fins210to a height above the STI features220. In various embodiments, the epitaxial S/D features238may include Ge, Si, GaAs, AlGaAs, SiGe, GaAsP, SiP, or other suitable material. The epitaxial S/D features238may be in-situ doped during the epitaxial process by introducing doping species including: p-type dopants, such as boron or BF2; n-type dopants, such as phosphorus or arsenic; and/or other suitable dopants including combinations thereof. If the epitaxial S/D features238are not in-situ doped, an implantation process (i.e., a junction implant process) is performed to dope the epitaxial S/D features238. In an exemplary embodiment, the epitaxial S/D features238in an NMOS device include SiP, while those in a PMOS device include GeSnB and/or SiGeSnB. Furthermore, silicidation or germano-silicidation may be formed on the epitaxial S/D features238. For example, silicidation, such as nickel silicide, may be formed by depositing a metal layer over the epitaxial S/D features238, annealing the metal layer such that the metal layer reacts with silicon in the epitaxial S/D features238to form the metal silicidation, and thereafter removing the non-reacted metal layer. Referring toFIGS.1A and7, the method100then proceeds to step116where an inter-layer dielectric (ILD) layer240is formed on the substrate. In some embodiments, a contact etch stop layer (CESL)242is also formed prior to forming the ILD layer240. In some examples, the CESL includes a silicon nitride layer, silicon oxide layer, a silicon oxynitride layer, and/or other materials known in the art. The CESL may be formed by plasma-enhanced chemical vapor deposition (PECVD) process and/or other suitable deposition or oxidation processes. In some embodiments, the ILD layer240includes materials such as tetraethylorthosilicate (TEOS) oxide, un-doped silicate glass, or doped silicon oxide such as borophosphosilicate glass (BPSG), fused silica glass (FSG), phosphosilicate glass (PSG), boron doped silicon glass (BSG), and/or other suitable dielectric materials. The ILD layer240may be deposited by a PECVD process or other suitable deposition technique. In some embodiments, after formation of the ILD layer240, the semiconductor device200may be subject to a high thermal budget process to anneal the ILD layer. In some examples, after depositing the ILD layer, a planarization process may be performed to remove excessive dielectric materials. For example, a planarization process includes a chemical mechanical planarization (CMP) process which removes portions of the ILD layer240(and CESL layer, if present) overlying the gate stack222and planarizes a top surface of the semiconductor device200. In some embodiments, the CMP process also removes hard mask228(FIG.6) and exposes the gate electrode layer226. The method100then proceeds to step118(FIG.1B) by removing the dummy gate stack222to form a gate trench246in the channel region. The resultant structure200is shown inFIGS.8A-8D, whereinFIG.8Ais a perspective view of the device200,FIG.8Brefers to a cross-sectional view taken along a lengthwise direction of the channel (e.g., along the B-B line),FIG.8Crefers to a cross-sectional view taken in the channel region and perpendicular to the lengthwise direction of the channel (e.g., along the C-C line), andFIG.8Drefers to a cross-sectional view taken though one of the epitaxial layer206and parallel to a top view (e.g., along the D-D line). A final gate structure (e.g., including a high-K dielectric layer and metal gate electrode) may be subsequently formed in the gate trench246, as will be described below. The step118may include one or more etching processes that are selective to the material in the dummy gate stack222. For example, the removal of the dummy gate stack222may be performed using a selective etch process such as a selective wet etch, a selective dry etch, or a combination thereof. The epitaxial layers206and208of the fin210are exposed in the gate trench246. The opposing sidewalls S234of the sidewall spacers234are also exposed in the gate trench246. The method100then proceeds to step120(FIG.1B) by removing the epitaxial layers206from the fin210in the gate trench246. The resultant structure200is shown inFIGS.9A-9D, which are perspective view and cross-sectional views along the B-B, C-C, D-D lines of the device200, respectively. In an embodiment, the epitaxial layers206are removed by a selective wet etching process. In an embodiment, the epitaxial layers206are SiGe and the second epitaxial layers208are silicon allowing for the selective removal of the epitaxial layers206. In some embodiments, the selective wet etching includes an APM etch (e.g., ammonia hydroxide-hydrogen peroxide-water mixture). In some embodiments, the selective removal includes SiGe oxidation followed by a SiGeOx removal. For example, the oxidation may be provided by O3clean and then SiGeOx removed by an etchant such as NH4OH. It is noted that as illustrated in the accompanying figures the second epitaxial layers208(e.g., nanowires) have a substantially rounded shape (e.g., cylindrical) due to removal process of the epitaxial layers206. It is noted that during the interim processing stage of step120, gaps248are provided between the adjacent nanowires in the channel region (e.g., gaps248between epitaxial layers208). The gaps248may be filled with the ambient environment conditions (e.g., air, nitrogen). The method100then proceeds to step122(FIG.1B) by depositing a dielectric material layer252in the gate trench246. As will be shown in further details below, the dielectric material layer252is etched and formed into inner spacer features. Therefore, the dielectric material layer252is also referred to as the inner spacer material layer252. The resultant structure200is shown inFIGS.10A-10D, which are perspective view and cross-sectional views along the B-B, C-C, D-D lines of the device200, respectively. The inner spacer material layer252is deposited on opposing sidewalls S234of the sidewall spacers234and over the substrate202. The inner spacer material layer252also wraps over each of the epitaxial layers208in the channel region. The inner-spacer layer840may fill the gaps248provided by the removal of the epitaxial layers206described in step120above. The inner spacer material layer252may include a dielectric material, such as SiN, SiOC, SiOCN, SiCN, SiO2, and/or other suitable material. In various embodiments, the sidewall spacers234and the inner spacer material layer252include different material compositions, such as the sidewall spacer layer234includes SiN and the inner spacer material layer252includes SiOC. It is noted that in the illustrated embodiment the inner spacer material layer252is conformally deposited on sidewalls S234of the sidewall spacers234and on each of the nanowires of the fins210in the channel region, for example, by an ALD process. The method100then proceeds to step124(FIG.1B) where a treatment process260is performed. In various embodiments, the treatment process260is through the gate trench246, using the sidewall spacers234as a treatment mask. The resultant structure200is shown inFIGS.11A-11D, which are perspective view and cross-sectional views along the B-B, C-C, D-D lines of the device200, respectively. A middle portion of the inner spacer material layer252between two opposing sidewalls S234of the sidewall spacers234(denoted as portion252a) receives the treatment process260, resulting in a material composition change, such that an etch selectivity exhibits compared to other parts of the inner spacer material layer252(denoted as portion252b). In some embodiments, the treatment process260includes an oxygen (O2) ashing, such as a plasma oxygen ashing. During the plasma oxygen ashing, the oxygen radicals react with components, for example, C, H, S, and N, in the middle portion252ato afford their respective oxides which are volatile. In a specific example, the inner spacer material layer252includes SiCN. During the plasma oxygen ashing, carbon and nitrogen are released from the middle portion252ain the form of carbon oxide and nitrogen oxide, while silicon is oxidized and remains in the middle portion252ain the form of silicon oxide. As a comparison, in portions252b, which is covered by the sidewall spacers234from receiving the treatment process260, SiCN substantially remains. Therefore, etch selectivity exists between portions252aand252b. As will be explained in further details below, portion252awill subsequently be removed in a selective etching process, and portion252bwill remain as inner spacers. In some embodiments, the plasma oxygen ashing includes a gaseous combination of C2F6and O2in a first ashing step and then follow with a pure O2in a second ashing step. The gaseous combination of C2F6and O2is more effective than a pure O2to remove ions from a dielectric material layer if there is any. Similarly, the plasma oxygen ashing may include a gaseous combination of CF4and O2in a first plasma ash step and pure O2plasma is then used in a second step to complete the ashing process. In some embodiments, the treatment process260includes a nitrogen treatment, such as a nitrogen plasma treatment. During the nitrogen plasma treatment, oxygen in the middle portion252ais released and oxide component is converted to nitride component. In a specific example, the inner spacer material layer252includes silicon oxide, which releases oxygen and is converted to silicon nitride after the nitrogen plasma treatment. The nitrogen plasma treatment may use a pure nitrogen plasma source or a N2and O2mixture source with a volumetric ratio of N2to O2from about 60:1 to about 90:1. The nitrogen plasma treatment includes exposure to the plasma source at a vacuum of between about 4 to 8 Torr at a temperature of between about 350° C. to about 450° C., at a power of between about 180 to about 220 watts for about 10 to 50 seconds. In some embodiments, the treatment process260includes an annealing process. The annealing process may weaken bonds within molecular structure or even create dangling bonds, which facilitate the release of components such as C, N, S, H, and O. In at least some embodiments, the device200is exposed to a temperature range of about 500° C. to about 800° C., and for a time from about 0.5 to about 2 hours. If the annealing process is below 500° C., the release of components may be insufficient in some examples. If the annealing process is above 800° C., the device performance deviation may increase due to dopant diffusion in some examples. The annealing process may further include a water vapor or steam as an oxidant, at a pressure of about 1 Atmosphere. In a specific example, the inner spacer material layer252includes SiOC, where the annealing process weakens the bonding of C and further releases C in form of carbon oxide. After the annealing process, the middle portion252aincludes mainly silicon oxide, while SiOC in portion252bsubstantially remains. Referring toFIG.11B, a region264along the cut of B-B line, which comprises an interface between the portions252aand252b, is enlarged for details. The portion252amay expand to a region directly under the sidewall spacer234, such as due to diffusion during the treatment process260. Therefore, the interface between the portions252aand252balong the cut of B-B line may have a curvature shape. The portion252amay expand into portion252bfor a distance d1of about 0.5 nm to about 5 nm in some embodiments. Referring toFIG.11D, a region266along the cut of D-D line, which comprises the interface between the portions252aand252b, is enlarged for details. Similarly, the portion252amay expand beyond sidewall surface S234of the sidewall spacer234along the Y-direction for a distance d2of about 0.5 nm to about 5 nm in some embodiments, such as due to diffusion. The inventors of the present disclosure have observed that from a top view the diffusion is easier to occur in areas closer to the sidewall spacer234. Therefore, the interface between the portions252aand252balong the cut of D-D line may have two curvature segments intersecting at an apex approximately at middle of a width of the portion252b(width along the X-direction). In some embodiments, the distance d1is equal to the distance d2. The method100then proceeds to step126(FIG.1B) where the middle portion252aof the inner spacer material layer252is selectively removed. The resultant structure200is shown inFIGS.12A-12D, which are perspective view and cross-sectional views along the B-B, C-C, D-D lines of the device200, respectively. In various embodiments the middle portion252ais removed in an etching process that is tuned to be selective to the middle portion252aand does not substantially etch the portion252b. The etching process may include wet etching, dry etching, reactive ion etching, or other suitable etching methods. For example, a dry etching process may implement an oxygen-containing gas, a fluorine-containing gas (e.g., CF4, SF6, CH2F2, CHF3, and/or C2F6), a chlorine-containing gas (e.g., Cl2, CHCl3, CCl4, and/or BCl3), a bromine-containing gas (e.g., HBr and/or CHBR3), an iodine-containing gas, other suitable gases and/or plasmas, and/or combinations thereof. For example, a wet etching process may comprise etching in diluted hydrofluoric acid (DHF), potassium hydroxide (KOH) solution, ammonia, a solution containing hydrofluoric acid (HF), nitric acid (HNO3), and/or acetic acid (CH3COOH), or other suitable wet etchants. In a specific example, the middle portion252aincludes nitride and the etching process is a wet etching process using H3PO4or other suitable etchants. After removing the middle portion252a, gaps248appear between the adjacent nanowires (i.e., epitaxial layers208) in the channel region. Along the Y direction, one end of the portion252babuts the epitaxial S/D features238, and another end of the portion252bfaces the gate trench246and gaps248. As will be shown in further details below, a high-K metal gate (HK MG) will be form in the gate trench246, abutting the portion252b. The portion252btherefore provides isolation between the HK MG and the epitaxial S/D features238. Thus, the portion252bis also referred to as the inner spacers252b. The enlarged region264is illustrated inFIG.12B. After removing the middle portion252a, the inner spacers252bhas a concave surface facing the gate trench246and the gaps248along the cut of B-B line. The concave surface extends inwardly towards the epitaxial S/D features238. In some embodiments, the concave surface has a depth d1of about 0.5 nm to about 5 nm. Similarly, the enlarged region266is illustrated inFIG.12D. After removing the middle portion252a, the inner spacers252bhas a convex surface facing the gate trench246and the gaps248along the cut of D-D line. The convex surface comprises two curvature segments intersecting at an apex268, which is approximately at middle of a width of the portion252b(width along the X-direction). The apex268extends outwardly towards the gate trench246and the gaps248. The two curvature segments on both sides of the apex268bend inwardly away from the gate trench246and the gaps248. In some embodiments, the convex surface has a height d2of about 0.5 nm to about 5 nm. In some embodiments, the distance d1is equal to the distance d2. A thickness d3of the portion252bis defined as a distance from the apex268to the epitaxial S/D features238along the Y-direction. In some embodiments, the thickness d3is substantially the same as a thickness of the sidewall spacers234. The thickness d3may be between approximately 5 nm and approximately 12 nm. Since dimensions of the inner spacers252bis mainly defined by the sidewall spacers234, which covers the inner spacers252bfrom receiving the prior treatment260, each of the inner spacers252bhas substantially the same dimensions from the top layers to the bottom layers, due to the conformal thickness of the sidewall spacers234. Compared with conventional etching process in forming inner spacers252b, the inner spacers252bat lower layers (e.g., closer to the substrate202) may become larger than those in upper layers, such as due to loading effects in an etching process. The inner spacers252bwith substantially same dimensions in the illustrated embodiment improves uniformity of the device, such as uniform gate lengths for the HK MG to be formed in the gate trench246in subsequent steps. The method100then proceeds to step128(FIG.1B) where a gate structure is formed. The resultant structure is shown inFIGS.13A-13D, which are perspective view and cross-sectional views along the B-B, C-C, D-D lines of the device200, respectively. The gate structure may be the gate of a multi-gate transistor. The gate structure may be a high-K/metal gate (HK MG) stack, however other compositions are possible. In some embodiments, the gate structure forms the gate associated with the multi-channels provided by the plurality of nanowires (now having gaps therebetween) in the channel region. In an embodiment of step128, a HK MG stack280is formed within the trench of the device200provided by the removal of the middle portions (i.e., middle portions252a) of inner spacer material layer252and/or release of nanowires208, described above with reference to prior step126. In various embodiments, the HK MG stack280includes an interfacial layer282, a high-K gate dielectric layer284formed over the interfacial layer, and/or a gate electrode layer286formed over the high-K gate dielectric layer284. High-K gate dielectrics, as used and described herein, include dielectric materials having a high dielectric constant, for example, greater than that of thermal silicon oxide (˜3.9). The gate electrode layer used within HK MG stack may include a metal, metal alloy, or metal silicide. Additionally, the formation of the HK MG stack may include depositions to form various gate materials, one or more liner layers, and one or more CMP processes to remove excessive gate materials and thereby planarize a top surface of the semiconductor device200. Interposing the HK MG stack280and the epitaxial S/D features238is the inner spacers252b, providing isolation. Due to the uniformity of dimensions of the inner spacers252bfrom top to bottom of the device200, the uniformity of the gate length is herein improved. In some embodiments, the interfacial layer282of the HK MG stack280may include a dielectric material such as silicon oxide (SiO2), HfSiO, or silicon oxynitride (SiON). The interfacial layer282may be formed by chemical oxidation, thermal oxidation, atomic layer deposition (ALD), chemical vapor deposition (CVD), and/or other suitable method. The high-K gate dielectric layer284of the high-K/metal gate stack280may include a high-K dielectric layer284such as hafnium oxide (HfO2). Alternatively, the high-K gate dielectric layer284of the gate stack1002may include other high-K dielectrics, such as TiO2, HfZrO, Ta2O3, HfSiO4, ZrO2, ZrSiO2, LaO, AlO, ZrO, TiO, Ta2O5, Y2O3, SrTiO3(STO), BaTiO3(BTO), BaZrO, HfZrO, HfLaO, HfSiO, LaSiO, AlSiO, HfTaO, HfTiO, (Ba,Sr)TiO3(BST), Al2O3, Si3N4, oxynitrides (SiON), combinations thereof, or other suitable material. The high-K gate dielectric layer284may be formed by ALD, physical vapor deposition (PVD), CVD, oxidation, and/or other suitable methods. As illustrated inFIG.13D, in some embodiments, the high-K gate dielectric layer284is deposited conformally on sidewalls of the inner spacer252band sidewall spacers234. Accordingly, the high-k dielectric layer284may also have a convex surface with an apex extending outwardly towards the gate electrode layer286. The gate electrode layer286of the HK MG stack280may include a single layer or alternatively a multi-layer structure, such as various combinations of a metal layer with a selected work function to enhance the device performance (work function metal layer), a liner layer, a wetting layer, an adhesion layer, a metal alloy or a metal silicide. By way of example, the gate electrode layer286of HK MG stack280may include Ti, Ag, Al, TiAlN, TaC, TaCN, TaSiN, Mn, Zr, TiN, TaN, Ru, Mo, Al, WN, Cu, W, Re, Ir, Co, Ni, other suitable metal materials or a combination thereof. In various embodiments, the gate electrode layer284of the HK MG stack280may be formed by ALD, PVD, CVD, e-beam evaporation, or other suitable process. Further, the gate electrode layer284may be formed separately for N-FET and P-FET transistors which may use different metal layers (e.g., for providing an N-type or P-type work function). In various embodiments, a CMP process may be performed to remove excessive metal from the gate electrode layer284of the HK MG stack280, and thereby provide a substantially planar top surface of the HK MG stack280. The HK MG stack280includes portions that interpose each of the epitaxial layers (nanowires)208, which form channels of the multi-gate device200. The semiconductor device200may undergo further processing to form various features and regions known in the art. For example, subsequent processing may form contact openings, contact metal, as well as various contacts/vias/lines and multilayers interconnect features (e.g., metal layers and interlayer dielectrics) on the substrate202, configured to connect the various features to form a functional circuit that may include one or more multi-gate devices. In furtherance of the example, a multilayer interconnection may include vertical interconnects, such as vias or contacts, and horizontal interconnects, such as metal lines. The various interconnection features may employ various conductive materials including copper, tungsten, and/or silicide. In one example, a damascene and/or dual damascene process is used to form a copper related multilayer interconnection structure. Moreover, additional process steps may be implemented before, during, and after the method100, and some process steps described above may be replaced or eliminated in accordance with various embodiments of the method100. Referring now toFIGS.14A and14B, illustrated is a method1400of fabricating a multi-gate device. The method1400is substantially similar to the method100in many aspects and the description of the method100above also applies to the method1400. An embodiment of the method1400additionally starts with a bottom sacrificial layer thicker than other sacrificial layers thereabove, which will be replaced by an inner sidewall material layer to provide better isolation between a gate stack and S/D features, as well as between substrate and S/D features, as will be discussed in further detail below. FIGS.15,16,17,18,19,20,21A,22A,23A,24A,25A, and26Aare perspective views of an embodiment of a semiconductor device201according to various stages of the method1400ofFIGS.14A and14B.FIGS.21B,22B,23B,24B,25B, and26Bare corresponding cross-sectional views of an embodiment of the semiconductor device201along a first cut (e.g., cut B-B inFIG.21A), which is along a lengthwise direction of the channel and perpendicular to a top surface of the substrate;FIGS.21C,22C,23C,24C,25C, and26Care corresponding cross-sectional views of an embodiment of the semiconductor device201along a second cut (e.g., cut C-C inFIG.21A), which is in the gate region and perpendicular to the lengthwise direction of the channel;FIGS.21D,22D,23D,24D,25D, and26Dare corresponding cross-sectional views of an embodiment of a semiconductor device201along a third cut (e.g., cut D-D inFIG.21A), which is along the lengthwise direction of the channel and parallel to the top surface of the substrate. Many aspects of the semiconductor device201are substantially similar to those of the semiconductor device200. For the sake of convenience, reference numerals are repeated for ease of understanding. Some differences are discussed below. The method1400begins at step1402where a substrate is provided. Step1402may be substantially similar to step102, discussed above with reference to the method100ofFIG.1A. Referring toFIG.15, a substrate202is provided as discussed above. The method1400proceeds to step1404where an epitaxial stack is provided. Step1404may be substantially similar to Step104, discussed above with reference to the method100ofFIG.1A. Referring toFIG.15, an epitaxial stack204is grown. The various material compositions of interleaved epitaxial layers206and208are similar to what have been discussed above with reference to the epitaxial stack204inFIG.2. One difference is that the bottom epitaxial layer206has a thickness larger than other epitaxial layers206thereabove in the stack, such as about 1 nm to about 5 nm thicker. For example, other epitaxial layer206thereabove may have a uniform thickness about 5 nm, while the bottom epitaxial layer206may have a thickness from about 6 nm to about 10 nm. As a comparison, the epitaxial layers208of the stack are substantially uniform in thickness, such as from about 6 nm to about 12 nm. As will be shown, the bottom epitaxial layer206acts as a space holder for an inner sidewall material layer to replace which extends below S/D features, and the relatively larger thickness of the bottom epitaxial layer206facilitates filling in dielectric materials besides other benefits such as better gate to S/D isolation and better leakage suppression. The method1400proceeds to step1406where one or more fins are patterned and formed. Step1406may be substantially similar to step106, discussed above with reference to the method100ofFIG.1A. Referring to the example ofFIG.16, one or more fins210are provided as discussed above. The method1400proceeds to step1408where STI features are formed. Step1408may be substantially similar to step108, discussed above with reference to the method100ofFIG.1A. Referring to the example ofFIG.17, STI features220is deposited interposing the fins210and then recessed to expose the stack204as discussed above. The method1400proceeds to step1410where a dummy gate structure is formed. Step1410may be substantially similar to step110, discussed above with reference to the method100ofFIG.1A. Referring to the example ofFIG.18, a dummy gate structure222is disposed over a channel region of the fins210as discussed above. The method1400proceeds to step1412where sidewall spacers are formed. Step1410may be substantially similar to step112, discussed above with reference to the method100ofFIG.1A. Referring to the example ofFIG.19, sidewall spacers234is conformally deposited then anisotropically etched to cover sidewalls of the dummy gate structure222as discussed above. The method1400proceeds to step1414where epitaxial S/D features238are formed in source/drain regions of the device201. Forming the epitaxial S/D features238may include recessing fins210in S/D regions prior to epitaxially growing S/D features238, similar to step114discussed above with reference to the method100ofFIG.1A. One difference is that during the recessing of the fins210, the bottom epitaxial layer206of the stack204substantially remains, separating the epitaxial S/D features238from the substrate. For example, the alternating fashion between the different semiconductor materials of the epitaxial layers206and208allows an end mode etching to stop at the bottom epitaxial layer206. Alternatively, a time mode etching may be applied to time the etching process to stop at the bottom epitaxial layer206. The relatively larger thickness of the bottom epitaxial layer206also helps this layer to survive a time mode etching process. In some embodiments, in S/D regions, a top portion of the bottom epitaxial layer206may be recessed during the etching process (as shown inFIG.21B). The method1400proceeds to step1416where an inter-layer dielectric layer is formed. Step1416may be substantially similar to step116, discussed above with reference to the method100ofFIG.1A. Referring to the example ofFIG.20, an ILD layer240is formed as discussed above. A CESL layer242may be formed prior to the forming of the ILD layer240. The method1400proceeds to step1418where a dummy gate removal is performed. Step1418may be substantially similar to step118, discussed above with reference to the method100ofFIG.1B. Referring to the example ofFIGS.21A-21D, the dummy gate structure222is removed to form a gate trench246between two opposing sidewalls S234of the sidewall spacers234as discussed above. The method1400proceeds to step1420where the sacrificial epitaxial layers are removed. Step1420may be substantially similar to step120, discussed above with reference to the method100ofFIG.1B. Referring to the example ofFIGS.22A-22D, epitaxial layers206in the channel region are removed in an etching process, including the bottom layer. The removal process “releases” the nanowires in the channel region (e.g., epitaxial layers208) as discussed above. Furthermore, the bottom layer206in the S/D region is also removed, forming a cavity under the S/D features238continuously extending from one S/D region to opposing S/D region. The method1400proceeds to step1422where an inner spacer material layer is conformally deposited in the gate trench. Step1422may be substantially similar to step122, discussed above with reference to the method100ofFIG.1B. Referring to the example ofFIGS.23A-23D, the inner spacer material layer252is conformally deposited on opposing sidewalls S234of the sidewall spacers234and over the substrate202. The inner spacer material layer252also wraps over each of the epitaxial layers208in the channel region. Furthermore, the inner spacer material layer252also fills the cavities directly under the S/D features238. To be noticed, due to the relatively larger gap between the bottom epitaxial layer208and the substrate202(due to the thicker bottom epitaxial layer206described above), a void298may remain in the channel region between the bottom epitaxial layer208and the substrate202. In some alternative embodiments, the region of the otherwise void298is filled up with the inner spacer material layer252(not shown). The method1400proceeds to step1424where a treatment process is performed towards the inner spacer material layer. Step1424may be similar to step124, discussed above with reference to the method100ofFIG.1B. Referring to the example ofFIGS.24A-24D, the treatment process may be an oxygen ashing process, a nitridation process, or an annealing process using the sidewall spacers234as a treatment mask. A middle portion of the inner spacer material layer252between two opposing sidewalls S234of the sidewall spacers234(denoted as portion252a) receives the treatment process260, resulting in a material composition change, such that an etch selectivity exhibits compared to other parts of the inner spacer material layer252(denoted as portion252b). As illustrated inFIG.24B, the middle portion252abetween the bottom epitaxial layer208and the substrate202has larger width than other portions252aabove, due to its larger correctional area and therefore wider lateral diffusion. In some embodiment, in the Y-direction, the middle portion252abetween the bottom epitaxial layer208and the substrate202has an extra width d4on each side for about 0.5 nm to about 5 nm. The method1400proceeds to step1426where the middle portion of the inner spacer material layer receiving the treatment process is selectively removed. Step1426may be similar to step126, discussed above with reference to the method100ofFIG.1B. Referring to the example ofFIGS.25A-25D, portions252bof the inner spacer material layer252remains as inner spacers. The inner spacers provide isolation between the epitaxial S/D features238and the high-K/metal gate to be formed in the gate trench246. Furthermore, portions252balso remain vertically between the epitaxial S/D features238and the substrate202to provide isolation therebetween. The method1400proceeds to step1428where a gate structure (e.g., replacement gate structure, HK MG structure) is formed. Step1428may be substantially similar to step128, discussed above with reference to the method100ofFIG.1B. Referring to the example ofFIGS.26A-26D, a gate structure280is formed including an interfacial layer282, a high-K gate dielectric layer284, and a gate electrode layer286. In an embodiment, portion of the gate structure280between the bottom epitaxial layer208and the substrate202is laterally wider than other portions thereabove, such as about 0.5 nm to about 5 nm wider on each end (d4). The inner spacers252bprovide isolation between the epitaxial S/D features238and the HK MG stack280, as well as between the epitaxial S/D features238and the substrate202. Although not intended to be limiting, one or more embodiments of the present disclosure provide many benefits to a semiconductor device and the formation thereof. For example, embodiments of the present disclosure provide a self-aligned inner spacer formation method so as to accurately control uniformity of the inner spacers. As a bench mark of uniformity, the overall thickness variation (from top to bottom) of the inner spacers may be within ±5% in some embodiments (also termed as substantially uniform thickness). The uniformity of the inner spacers helps to improve channel length uniformity across different layers of the nanosheets in a multi-gate semiconductor device (e.g., GAA device). The inner spacers may also provide isolation between S/D regions and the gate stack, and also between S/D regions and the substrate. Furthermore, the inner spacer formation method can be easily integrated into existing semiconductor fabrication processes. In one exemplary aspect, the present disclosure is directed to a method. The method includes forming a fin extruding from a substrate, the fin having a plurality of sacrificial layers and a plurality of channel layers, wherein the sacrificial layers and the channel layers are alternately arranged; removing a portion of the sacrificial layers from a channel region of the fin; depositing a spacer material in areas from which the portion of the sacrificial layers have been removed; removing a portion of the spacer material, thereby exposing the channel layers in the channel region of the fin, wherein other portions of the spacer material remain as a spacer feature; and forming a gate structure engaging the exposed channel layers. In some embodiments, the method further includes prior to the removing of the portion of the spacer material, performing a treatment process to the portion of the spacer material, such that the portion of the spacer material has an etching selectivity compared to the other portions of the spacer material. In some embodiments, the treatment process includes an oxygen ashing process or a nitridation process. In some embodiments, the treatment process includes an annealing process. In some embodiments, the method further includes prior to the removing of the portion of the sacrificial layers, forming an outer spacer layer, wherein the spacer material is in physical contact with the outer spacer layer, and wherein the spacer feature has a thickness approximately equal to that of the outer spacer layer. In some embodiments, a sidewall surface of the spacer feature has a convex shape in a plane parallel to a top surface of the substrate, the convex shape having an apex extending towards the gate structure. In some embodiments, a sidewall surface of the spacer feature has a concave shape in a plane perpendicular to a top surface of the substrate and along a lengthwise direction of the fin, the concave shape bending away from the gate structure. In some embodiments, the method further includes forming a source/drain (S/D) feature, wherein the spacer feature interposes the S/D feature and the gate structure. In some embodiments, the S/D feature is formed on a bottommost one of the plurality of sacrificial layers. In some embodiments, the bottommost one of the plurality of sacrificial layers has a greater thickness than any other sacrificial layers. In some embodiments, the plurality of sacrificial layers includes silicon germanium and the plurality of channel layers includes silicon. In another exemplary aspect, the present disclosure is directed to a method of fabricating a semiconductor device. The method includes forming a stack of a first type and a second type epitaxial layers on a semiconductor substrate, the first type and second type epitaxial layers having different material compositions and the first type and second type epitaxial layers being alternatingly disposed in a vertical direction; forming a dummy gate covering a portion of the stack in a channel region; forming an outer spacer layer covering sidewalls of the dummy gate; removing the dummy gate to from a gate trench, wherein the gate trench exposes opposing sidewalls of the outer spacer layer; etching the second type epitaxial layers in the gate trench; depositing a dielectric layer in the gate trench along the opposing sidewalls of the outer spacer layer and wrapping around the first type epitaxial layers; performing a treatment process to a portion of the dielectric layer between the opposing sidewalls of the outer spacer layer, wherein the treatment process uses the outer spacer layer as a treatment mask; removing the portion of the dielectric layer, thereby forming an inner spacer layer; and forming a gate stack in the gate trench and wrapping around the first type epitaxial layers. In some embodiments, the treatment process includes an oxidization treatment or a nitridation treatment. In some embodiments, the treatment process includes an annealing process. In some embodiments, the dielectric layer is deposited conformally in the gate trench. In some embodiments, after the depositing of the dielectric layer, a void remains under a bottom first type epitaxial layer. In some embodiments, the outer spacer layer and the inner spacer layer include different dielectric materials. In yet another exemplary aspect, the present disclosure is directed to a multi-gate semiconductor device. The multi-gate semiconductor device includes a fin element extending upwardly from a substrate; a gate structure over the fin element; an epitaxial source/drain (S/D) feature adjacent the fin element; and a dielectric spacer interposing the gate structure and the epitaxial S/D feature, wherein a sidewall surface of the dielectric spacer facing the gate structure has a convex shape in a plane parallel to a top surface of the substrate, the convex shape having an apex extending towards the gate structure. In some embodiments, the multi-gate semiconductor device further includes a gate spacer covering sidewalls of the gate structure, wherein the dielectric spacer has a thickness substantially equal to that of the gate spacer. In some embodiments, the dielectric spacer has a substantially uniform thickness. The foregoing outlines features of several embodiments so that those of ordinary skill in the art may better understand the aspects of the present disclosure. Those of ordinary skill in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those of ordinary skill in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. | 67,328 |
11862735 | DESCRIPTION The embodiments of the present disclosure generally relate to semiconductor devices. More particularly, the embodiments relate to providing ESD protection devices in semiconductor devices. Such ESD protection devices may, for example, be incorporated into integrated circuits (ICs). The semiconductor devices or ICs may be used with apparatuses such as, but not limited to, consumer electronic products. Existing methods for integrating ESD protection devices into the semiconductor devices require multiple etching masks and large footprints. Some embodiments relate to ESD protection devices that have a smaller footprint and that may be integrated into semiconductor devices with a reduced number of etching masks in the manufacturing process. Aspects of the present invention and certain features, advantages, and details thereof, are explained more fully below with reference to the non-limiting examples illustrated in the accompanying drawings. Descriptions of well-known materials, fabrication tools, processing techniques, etc., are omitted so as not to unnecessarily obscure the invention in detail. It should be understood, however, that the detailed description and the specific examples, while indicating aspects of the invention, are given by way of illustration only, and are not by way of limitation. Various substitutions, modifications, additions, and/or arrangements, within the spirit and/or scope of the underlying inventive concepts will be apparent to those skilled in the art from this disclosure. Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “approximately”, “about,” is not limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Further, a direction is modified by a term or terms, such as “substantially” to mean that the direction is to be applied within normal tolerances of the semiconductor industry. For example, “substantially parallel” means largely extending in the same direction within normal tolerances of the semiconductor industry and “substantially perpendicular” means at an angle of ninety degrees plus or minus a normal tolerance of the semiconductor industry. The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include (and any form of include, such as “includes” and “including”), and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a method or device that “comprises,” “has,” “includes” or “contains” one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more steps or elements. Likewise, a step of a method or an element of a device that “comprises,” “has,” “includes” or “contains” one or more features possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed. As used herein, the term “connected,” when used to refer to two physical elements, means a direct connection between the two physical elements. The term “coupled,” however, can mean a direct connection or a connection through one or more intermediary elements. As used herein, the terms “may” and “may be” indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of “may” and “may be” indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while considering that in some circumstances the modified term may sometimes not be appropriate, capable or suitable. For example, in some circumstances, an event or capacity can be expected, while in other circumstances the event or capacity cannot occur—this distinction is captured by the terms “may” and “may be.” FIG.1shows a simplified cross-sectional view of a bi-directional bi-polar ESD device according to various non-limiting embodiments. FIG.2shows a simplified schematic view of a bi-directional bi-polar ESD device ofFIG.1according to various non-limiting embodiments. Referring toFIG.1, an ESD device according to various non-limiting embodiments of the present disclosure may include a symmetrical bi-directional bi-polar transistor structure with two emitter/collector portions. The emitter/collector portions may each include a highly doped terminal region of a second conductivity type130,134(e.g., N+ region or P+ region) within a medium-voltage well region of the second conductivity type108,110(e.g., MV Well or MV PWell). The highly doped terminal regions130,134are connected to conductive terminals160,162(e.g., formed in a metal layer over the substrate). In the center between the emitter/collector portions, there is a highly doped floating region (i.e., not connected to any terminal) of the second conductivity type132(e.g., N+ region or P+ region) which is within and surrounded by a low-voltage well region of the first conductivity type120(e.g., LV PWell or LV NWell) and a drift region of the first conductivity type122(e.g. P-Drift or N-Drift). The highly doped floating center island region132is isolated from both the highly doped terminal regions by a blocking or insulating layer159formed on the surface of the substrate. The insulating layer159may be formed between the conductive terminals and over at least a surface of the low-voltage well region with drift region120,122which within the substrate separates the two emitter/collector portions including the emitter/collector terminals from the floating center island region). The insulating layer159may be a silicide blocking layer150(e.g., SAB) or polysilicon blocking layer151a,151b, but not a shallow trench isolation (STI) structure. The bi-directional bi-polar transistor structure is arranged within a high-voltage well of a first conductivity type106(e.g., HV PWell or HV NWell) that is isolated from a bulk substrate region of a first conductivity type102(e.g., P-Sub or N-Sub). A substrate isolation region103separates the high-voltage well of the first conductivity type106(e.g., HV PWell or HV NWell) from the bulk substrate region of the first conductivity type102(e.g., P-Sub or N-Sub). The substrate isolation region103may be an epitaxial doped region having a second conductivity type (e.g., N-epi or P-epi) or a buried oxide region. The low-voltage well and drift region of the first conductivity type120,122(e.g., P-type region or N-type region) may also compensate a part of the medium-voltage well of a second conductivity type108,110(e.g., MV NWell or MV PWell) at a top portion (e.g., towards a surface of the substrate101opposite the bulk substrate layer102) to make the top portion of the medium-voltage well into a region of the first conductivity type. That is, the low-voltage well with drift region120,122(e.g., P-type region or N-type region) compensates a part of the medium-voltage well (e.g., MV NWell) at the top as the base of the bi-polar transistor structure (NPN or PNP). In particular, in this region the total doping concentration of the low-voltage well with drift region120,122(e.g., LV PWell and P-Drift or LV NWell and N-Drift) is higher than the doping concentration of the medium-voltage well region108,110(e.g., MV NWell or MV PWell) causing the net doping concentration in a portion of the medium-voltage well region108,110near the terminals160,162to become a first conductivity type (e.g. P-type or N-type). Referring toFIG.1, in some non-limiting embodiments, in the plurality of doped regions of a first conductivity type (102,106,120,122) and a second conductivity type (103,108,110,130,132,134), the first conductivity type is a P-type and the second conductivity type is an N-type. Alternatively, in other non-limiting embodiments, in the plurality of doped regions of a first conductivity type (102,106,120,122) and a second conductivity type (103,108,110,130,132,134), the first conductivity type is an N-type and the second conductivity type is a P-type. The ESD protection device100may include a substrate101. In various non-limiting embodiments, the substrate101may include any silicon-containing substrate including, but not limited to, silicon (Si), single crystal silicon, polycrystalline Si, amorphous Si, silicon-on-sapphire (SOS), silicon-on-insulator (SOI) or silicon-on-replacement insulator (SRI) or silicon germanium substrates and the like. Substrate102may in addition include various isolations, dopings and/or device features. The substrate102may include other suitable elementary semiconductors, such as, for example, germanium (Ge) in crystal, a compound semiconductor, such as silicon carbide (SiC), gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide (InP), indium arsenide (InAs), and/or indium antimonide (InSb) or combinations thereof; an alloy semiconductor including GaAsP, AlInAs, GaInAs, GaInP, GaInAsP, or combinations thereof. In various non-limiting embodiments, the substrate101may have a bulk or substrate region102arranged within substrate101. The substrate region102may have a first conductivity type. For example, the substrate region102may have a first conductivity type that is a P type. In such case, the substrate region102may contain P type dopants. The doping concentration of the substrate region102may range from about 1E15 cm−3to 5E15 cm−3. Accordingly, the substrate region102may include a P type substrate region (e.g., P-Sub). However, in alternative non-limiting embodiments, the substrate101may have a substrate region102of a first conductivity type that is an N type. Accordingly, the substrate region102may include an N type substrate region (e.g., N-Sub). In such case, the substrate region102may contain N type dopants with a similar doping concentration as with P type dopants. The substrate101of the ESD protection device100may further include a substrate isolation region103arranged within substrate101and at least partially over the substrate region102. The substrate isolation region103may be an epitaxial region104. The epitaxial region104may have a second conductivity type different from the first conductivity type of substrate region102. The epitaxial region104may have a higher doping concentration than the substrate region102. For example, the epitaxial region104may have a doping concentration ranging from about 5E15 cm−3to 1E16 cm−3. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the epitaxial region104may include N type dopants. Accordingly, the epitaxial region104may include an N-epitaxial region. However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the epitaxial region104may include P type dopants. Accordingly, the epitaxial region104may include a P-epitaxial region (e.g., P-Epi). Alternatively, the substrate isolation region103may include a deep well region instead of an epitaxial region. For example, in some embodiments, a deep Well (or deep PWell) may be used instead of an N-epitaxial region (or P-epitaxial region, respectively). The substrate101of the ESD protection device100may further include a first conductivity region106arranged within substrate101and at least partially over both the substrate isolation region103(e.g., epitaxial region104) and the substrate region102. The first conductivity region106may have a first conductivity type similar to substrate region102. The first conductivity region106may have a higher doping concentration than the doping concentration of the substrate region102and the substrate isolation region103. The first conductivity region106may be a high-voltage well region. For example, the first conductivity region106may have a doping concentration ranging from about 1E16 cm−3to 5E16 cm−3. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the first conductivity region106may include P type dopants. Accordingly, the first conductivity region106may include a high-voltage P type well (e.g., HV PWell). However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the first conductivity region106may include N type dopants. Accordingly, the first conductivity region106may include a high-voltage N type well (e.g., HV N-Well). The substrate101of the ESD protection device100may further include a first terminal portion including a second conductivity region108and a second terminal portion including a third conductivity region110, the first and second terminal portions are arranged within substrate101and at least partially over the first conductivity region106. The second and third conductivity regions108,110may be arranged to be spaced apart from each other. At least a portion of the second conductivity region108and the third conductivity region110may each be arranged immediately below a top surface of substrate101. The top surface of substrate101being opposite the substrate region102. The second conductivity region108and the third conductivity region110may each be a medium-voltage well. The second and third conductivity regions108,110may have a second conductivity type same as epitaxial region104or deep well region of the substrate isolation region103. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the second conductivity region108and the third conductivity region110may include N type dopants. Accordingly, the second and third conductivity regions108,110may each include a medium-voltage N type well region (e.g., MV Well). However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the second and third conductivity regions108,110may include P type dopants. Accordingly, the second and third conductivity regions108,110may each include a medium-voltage P type well region (e.g., MV PWell). The second and third conductivity regions (medium-voltage well regions) may have a higher doping concentration than the first conductivity region106. For example, the second and third conductivity regions may have a doping concentration ranging from about 1E17 cm−3to 5E17 cm−3. The first and second terminal portions may each further include respective terminal regions. A first terminal region130may be arranged at least partially within the second conductivity region108. The first terminal region130may be configured for connection to a first external voltage. A second terminal region134may be arranged at least partially within the third conductivity region110. The second terminal region134may be configured for connection to a second external voltage. The first and second terminal regions130,134may have the second conductivity type same as the conductivity type of the second and third conductivity regions108,110. The first terminal region130and the second terminal region134may each include highly doped regions. That is, the doping concentration of the first and second terminal regions130,134is higher than the doping concentration of the second and third conductivity regions108,110. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the first and second terminal regions130,134may include N type dopants. Accordingly, the first and second terminal regions130,134may each be an N+ region. However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the first and second terminal regions130,134may include P type dopants. Accordingly, the first and second terminal regions130,134may each be a P+ region. Referring to an exemplary non-limiting embodiment as shown inFIG.1, the first terminal region130and second terminal region134may be arranged immediately below a top surface of substrate101. The first terminal region130may be connected to a first external terminal160to which the first external voltage may be applied and the second terminal region134may be connected to a second external terminal162to which the second external voltage may be applied. Further, the first and second terminal regions130,134, and the second and third conductivity regions108,110may be isolated from the substrate region102via the first conductivity region106and the substrate isolation region103(e.g., epitaxial region104). The substrate101of the ESD protection device100may further include a fourth conductivity region120arranged within the substrate101and at least partially over the first conductivity region106. At least a portion of the fourth conductivity region120may be arranged immediately below a top surface of substrate101. At least a portion of the fourth conductivity region120may further abut (i.e., directly contact) a portion of the first conductivity region106. The fourth conductivity region120may further be arranged centrally (e.g., equidistant) between the second conductivity region108and the third conductivity region110of the first and second terminal portions. The fourth conductivity region120may also abut (i.e., directly contact) the second and third conductivity regions108,110. A first sidewall111of the fourth conductivity region120may abut the second conductivity region108and a second side wall113(opposite the first sidewall) of the fourth conductivity region120may abut the third conductivity region110. The fourth conductivity region120is separated from the first and second terminal regions130,134by at least a portion of the second and third conductivity regions. Additionally, in some embodiments, a portion of the fourth conductivity region120may further overlap a portion of the second conductivity region108and another portion of the fourth conductivity region120may further overlap a portion of the third conductivity region110. The overlap may provide better performance of the ESD protection device. The fourth conductivity region120may be a low-voltage well region having a first conductivity type. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the fourth conductivity region120may include P type dopants. Accordingly, the fourth conductivity region120may include a low-voltage P type well (e.g., LV PWell). However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the fourth conductivity region120may include N type dopants. Accordingly, the fourth conductivity region120may include a low-voltage N type well (e.g., LV NWell). Referring to an exemplary non-limiting embodiment as shown inFIG.1, the fourth conductivity region may be arranged immediately below a top surface of substrate101. Further, the fourth conductivity region120may be separated from the substrate region102via the first conductivity region106and the substrate isolation region103(e.g., epitaxial region104). The fourth conductivity region120may further include a floating (or unconnected) center island region132. The floating region132may be a highly doped region arranged within the fourth conductivity region120. The floating region132may be arranged at a center of the fourth conductivity region120so that the floating region132is equidistant from the first sidewall111and the second sidewall113of the fourth conductivity region120. The floating region132may be arranged a distance L away from the first and second sidewalls111and113of the fourth conductivity region120. The distance L tunes the bi-directional bi-polar ESD protection device for different voltage application. The breakdown voltage and holding voltage may change based on the distance L. For example, a bi-directional NPN (or PNP) device with a longer distance L between the floating region and the sidewalls has a higher breakdown voltage and higher holding voltage than one with a shorter distance L. A bi-directional NPN (or PNP) device with a shorter distance L between the floating region and the sidewalls has a lower breakdown voltage and lower holding voltage than one with a longer distance L. The floating region132has a second conductivity type same as the first and the second terminal regions130,134. However, the floating region132is not configured for connection to an external voltage. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the floating region132may include N type dopants. Accordingly, the floating region132may include a N+ region. However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the floating region132may include P type dopants. Accordingly, the floating region132may include a P+ region. Referring to an exemplary non-limiting embodiment as shown inFIG.1, the floating region132may be centrally arranged immediately below a top surface of substrate101within the fourth conductivity region120. Further, the floating region132may be isolated from the substrate region102via the first conductivity region106and the substrate isolation region103(e.g., epitaxial region104). A depth of the fourth conductivity region120may be less than or substantially the same as a depth of the second conductivity region108and third conductivity region110. Referring to an exemplary non-limiting embodiment as shown inFIG.1, a depth of the fourth conductivity region120may less than a depth of the second conductivity region108and third conductivity region110. However, the depths of the second conductivity region108, the third conductivity region110and the fourth conductivity region120may be substantially the same in alternative non-limiting embodiments. The second conductivity region108and the third conductivity region110may have approximately equal doping concentrations. Further, the doping concentrations of the second and third conductivity regions108,110may be higher than the doping concentration of the first conductivity region106. The first terminal region130and the second terminal region134may have higher doping concentrations than the second and third conductivity regions108,110, respectively. For example, the second conductivity region108may have a doping concentration ranging from about 1E17 cm−3to 5E17 cm−3; the third conductivity region110may also have a doping concentration ranging from about 1E17 cm−3to 5E17 cm−3; the first terminal region130may have a doping concentration ranging from about 5E19 cm−3to 5E20 cm−3, and the second terminal region134may have a doping concentration ranging from about 5E19 cm−3to 5E20 cm−3. The second and third conductivity regions108,110and the first and second terminal regions130,134may have a same conductivity type as the epitaxial region104. That is, they may have the second conductivity type. In exemplary non-limiting embodiments where the first conductivity type may be P type and the second conductivity type may be N type, the second and third conductivity regions108,110may be N type wells and the first and second terminal regions130,134may be N+ regions. The fourth conductivity region120may have a doping concentration ranging from about 5E17 cm−3to 1E18 cm−3. Further, the doping concentration of the fourth conductivity region120may be higher than the doping concentration of the epitaxial region104. The fourth conductivity region120may have a higher doping concentration than the first conductivity region106. The fourth conductivity region120may have a higher doping concentration than the second and third conductivity regions108,110. Providing a fourth conductivity region120having a higher doping concentration than the second and third conductivity regions108,110may help to achieve a holding voltage high enough to provide latch-up immunity. The highly doped floating region132may have the same doping concentration as the highly doped first terminal region130and the second terminal region134. In the plurality of doped regions, the substrate region102has the lowest doping concentration. When the substrate isolation region104is an epitaxial region103or a deep well region it has a higher doping concentration than the substrate region102. The first conductivity region106has a higher doping concentration than the substrate isolation region104and/or substrate region102. The second and third conductivity regions108,110have the same doping concentration and is higher than the doping concentration of the first conductivity region106. The fourth conductivity region120has a higher doping concentration than the second and third conductivity regions108,110. The first terminal region130, floating region132, and second terminal region134have the same doping concentration and is also the highest doping concentration relative to the other regions. In some exemplary non-limiting embodiments, the fourth conductivity region120may further include a drift region122(e.g., P-drift for an LV PWell or an N-drift for an LV NWell) along the boundaries (e.g., along sidewalls111and113of the fourth conductivity region120) with the second and third conductivity regions108,110. The drift region122may have a doping concentration ranging from about 5E16 cm−3to 1E17 cm−3. The drift regions may help to increase the breakdown voltage of the ESD protection device100. The ESD protection device100may also include a blocking or an insulating layer159arranged over a top surface of the substrate101. As shown inFIG.1, the insulating layer159may be a silicide blocking layer150arranged to extend between the second conductivity region108and the third conductivity region110, overlapping at least a part of these conductivity regions108,110and the fourth conductivity region120. In various non-limiting embodiments, the silicide blocking layer150may prevent silicide interaction or processing on (or in other words, block silicide, that may be deposited during fabrication of the ESD protection device100, from interacting with) the first terminal region130, the second terminal region134, and the floating region132. The insulating layer159is used to electrically insulate the floating region132from the terminal regions130,134. The silicide blocking layer150may be formed of any silicide blocking material known to those skilled in the art, such as, but not limited to, nitride. An insulation layer159is needed because silicide material may be generated in any exposed or uncovered regions of the surface of the substrate101. Electrically, the silicide material acts like a metal and would make the floating region132and the terminal regions130,134short together. The silicide blocking material (e.g. nitride) prevents silicide generation in a covered region thus preventing shorts. The ESD protection device100may further include a first isolation element140and a second isolation element142. The first isolation element140may be configured to isolate the second conductivity region108and first terminal region130. The second isolation element142may be configured to isolate the third conductivity region110and the second terminal region134. The first isolation element140is arranged immediately below a top surface of substrate101on a side of the first terminal region130and second conductivity region108facing away from the floating terminal region132and the fourth conductivity region120. The second isolation element142is arranged immediately below a top surface of substrate101on a side of the second terminal region134and third conductivity region110facing away from the floating terminal region132and the fourth conductivity region120. That is, the first and second isolation elements140,142are arranged at the ends of the ESD protection device100. For example, the first and second isolation elements140,142may be shallow trench isolation (STI) blocks. When the ESD protection device100is in use, the ESD protection device100may be further configured to connect to an apparatus (not shown inFIG.1), such as, but not limited to a consumer electronic product, that is to be protected by the ESD protection device100. In use, the apparatus to be protected is connected to the first and second terminals160,162of the ESD protection device100. The voltage between these terminals160,162may be referred to as the ESD voltage. The first and second terminals160,162may be an emitter or collector depending on the ESD voltage. That is, one of the first and second terminals160,162may be an emitter and the other one of the first and second terminals160,162may be a collector depending on the direction of the voltage difference of the ESD voltage. When the ESD voltage is below a predefined level, negligible current flows through the ESD protection device100. However, when the ESD voltage exceeds the predefined level, the ESD protection device100turns on to conduct current away from the apparatus, hence protecting the apparatus from damage. In particular, to protect the apparatus from damage due to overly high ESD voltages between the terminals160,162, the ESD protection device100may be configured such that when a difference between the first external voltage and the second external voltage exceeds a predetermined threshold, at least one discharge current may pass through the ESD protection device100. Referring toFIGS.1and2, the apparatus may be configured to connect to the first terminal region130and the second terminal region134, for example, via the terminals160,162. When the first external voltage is higher than the second external voltage, the p-n (or n-p) junction at the first sidewall111between the fourth conductivity region220and the second conductivity region108may be reverse biased. Accordingly, when a difference between the first external voltage and the second external voltage exceeds a first predetermined threshold, the p-n junction at the first sidewall111may break down, and a first npn (or pnp) transistor may turn on, which may include the second conductivity region108as the collector, the fourth conductivity region120as the base and the third conductivity region110as the emitter. A first discharge current may then pass from the emitter through the base to the collector of the first npn transistor. In other words, the first discharge current may pass through the fourth conductivity region120between the second conductivity region108and the third conductivity region110. The first discharge current may then turn on a second npn (or pnp) transistor which may include the third conductivity region110as the emitter, the first conductivity region106as the base, and the epitaxial region104as the collector. A second discharge current may then pass from the emitter through the base to the collector of this second npn (or pnp) transistor. In other words, the first discharge current may cause the second discharge current to pass through the first conductivity region106between the epitaxial region104and the third conductivity region110. When the second external voltage is higher than the first external voltage, the p-n junction at the second sidewall113between the fourth conductivity region120and the third conductivity region110, may also be reverse biased. Accordingly, when a difference between the first external voltage and the second external voltage exceeds the first predetermined threshold, the p-n (or n-p) junction at the second sidewall113may break down and a first npn (or pnp) transistor may turn on, which may include the third conductivity region110as the collector, the fourth conductivity region120as the base and the second conductivity region108as the emitter. A first discharge current may then pass from the emitter through the base to the collector of the first npn (or pnp) transistor. In other words, the first discharge current may pass through the fourth conductivity region120between the second conductivity region108and the third conductivity region110. The first discharge current may then turn on a second npn (or pnp) transistor which may include the second conductivity region108as the emitter, the first conductivity region106as the base and the epitaxial region104as the collector. A second discharge current may then pass from the emitter through the base to the collector of this second npn transistor. In other words, the first discharge current may cause the second discharge current to pass through the first conductivity region106between the epitaxial region104and the second conductivity region108. Accordingly, as shown inFIG.2, in various non-limiting embodiments, an equivalent circuit of the ESD protection device100may include a transistor having the second conductivity region108as the emitter (when the second external voltage is higher than the first external voltage) and the third conductivity region110as the emitter (when the first external voltage is higher than the second external voltage). The first conductivity region106may act as the base regardless of the direction of the current flow through the ESD protection device. It is understood that the direction of the currents described above may be reversed if the conductivity types in the depicted embodiment ofFIG.2are reversed. Providing the substrate isolation region103(e.g., epitaxial region104) and the first conductivity region106and setting these regions103,106to float may allow the substrate isolation region103to act as a collector of the second npn (or pnp) transistor and the first conductivity region106to act as a base of the first and second npn (or pnp) transistors, regardless of the polarity of the voltage between the first and second terminal portions108/130,110/134(in other words, regardless which of the first and second external voltages is higher). Therefore, the ESD protection device100may be capable of supporting bi-directional high voltage bias and providing bi-directional ESD current conduction. In various non-limiting embodiments where the first external voltage may be higher than the second external voltage, the first external voltage may be a general power supply voltage (e.g., VDD) and the second external voltage may be ground (e.g., GND), or the first external voltage may be positive and the second external voltage may be negative. In alternative non-limiting embodiments where the first external voltage may be lower than the second external voltage, the second external voltage may be a general power supply voltage (e.g., VDD), and the first external voltage may be ground. Or the first external voltage may be negative, and the second external voltage may be positive. Further, both the first discharge currents and the second discharge currents through the ESD protection device100as described above may help to conduct current away from the apparatus in various non-limiting embodiments. This may allow the ESD protection device100to have improved ESD current conduction capability. In various non-limiting embodiments, the ESD protection device100may be compact, and may have good clamping ability (i.e., minimize the change to the on-resistance) and a high holding voltage to provide latch-up immunity.FIG.3illustrates TCAD simulated TLP-like I-V curves of the invented Bi-NPN structures with different base lengths.FIG.3illustrates the performance of the ESD protection device100when a base length of the ESD protection device100is set as 0.8 um (301) and 1.2 um (311) and when the first external voltage is greater than the second external voltage. However, due to the symmetry of the structure of the ESD protection device100, the results obtained when the second external voltage is greater than the first external voltage may be substantially the same as those shown inFIG.3. In particular, graph300are plots of transmission line pulse (TLP) current against transmission line pulse (TLP) voltage. Graph300shows results obtained from simulating the device100with technology computer aided design (TCAD). Referring to graph300, the results indicate that the device100with a base length of 0.8 um may have a holding voltage (Vh) of about 12.0V (at303), a triggering voltage (Vt1) of about 13.0V (at305), a second breakdown voltage (Vt2) of about 23.5V (at307), and a second breakdown current (It2) of about 3.5 mA/um (at307). Additionally, the results indicate that the device100with a base length of 1.2 um may have a holding voltage (Vh) of about 14.0V (at313), a triggering voltage (Vt1) of about 16.0V (at315), a second breakdown voltage (Vt2) of about 27.5V (at317), and a second breakdown current (It2) of about 3.4 mA/um (at317). As shown inFIG.3, each of plots301and311show a high holding voltage and a small snapback to provide a latch-up immune ESD protection. For example, a holding voltage must be larger than the power supply voltage (e.g., VDD) to avoid latch-up and should be high to minimize the difference between the trigger voltage and the holding voltage (i.e., a small snapback). The plots do not exhibit a bending behavior common in uni-directional NPN devices. There is no bending behavior due to more uniform current flow. The bending behavior is undesirable because that would mean a large increase of turn-on resistance. FIGS.4A-4Bshow current density graphs of a portion of the ESD protection device100obtained from simulating the ESD protection device100using TCAD.FIG.4Aillustrates a current density graph for a discharge current of about 0.2 mA/um.FIG.4Billustrates a current density graph for a discharge current of about 2 mA/um. In the simulation, the first voltage (left terminal) is higher than the second voltage (right terminal). As shown inFIG.4A, at a lower discharge current, a higher current density flows from the second conductivity region108through the first conductivity region106as compared to through the fourth conductivity region120to the third conductivity region110. As shown inFIG.4B, at a higher discharge current, a higher current density flows from the second conductivity region108through the fourth conductivity region120to the third conductivity region110as compared to through the first conductivity region208. In other words, the current density graph indicates that the first discharge current may be higher than the second discharge current for high discharge currents. This shows that the ESD device100is initially triggered at the bottom. But as the discharge current increases, the floating region132assists collecting a lot of current at higher current levels. In various non-limiting embodiments, the implant material for the substrate region102, epitaxial region104, first to fourth conductivity regions106,108,110,120; the terminal regions130,134; and the floating region132may be the same implant material, for example, an epitaxial silicon material in a non-limiting embodiment. The P type material may be or include, but is not limited to, epitaxial silicon germanium, and/or the N type material may be or include, but is not limited to, doped silicon material including N type dopants. P type dopants can for example, include but are not limited to, boron (B), aluminium (Al), indium (In), or a combination thereof, while N type dopants can include carbon (C), phosphorus (P), arsenic (As), antimony (Sb), or a combination thereof. Other types of implant materials and dopants as known to those skilled in the art may also be useful for forming the regions102,104,106,108,110,120; the terminal regions130,134; and the floating region132. FIG.5shows a simplified cross-sectional view of an ESD protection device500according to alternative non-limiting embodiments. The ESD protection device500is similar to the ESD protection device100and hence, the common features are labeled with the same reference numerals and need not be discussed. As shown inFIG.5, the fourth conductivity region120′ is similar to the fourth conductivity region120of the ESD protection device100, except that the fourth conductivity region120′ of the ESD protection device500does not overlap the second and third conductivity regions108,110. Additionally, the substrate portions of ESD protection device500may be further isolated from other devices in the substrate by vertical isolation elements (e.g., trenches)170,172. The vertical isolation elements170,172may be deep trench isolation (e.g., DTI) structures that extend from the top surface of the substrate101to within the substrate region102of the substrate101(i.e., bulk substrate). For example, the vertical isolation elements170,172may be arranged at the ends of the ESD protection device500adjacent to the first and second isolation elements140,142, respectively. FIG.6shows a simplified cross-sectional view of an ESD protection device600according to alternative non-limiting embodiments. The ESD protection device600is a bi-directional bi-polar ESD protection device with poly bounded junctions. The ESD protection device600is similar to the ESD protection device100and hence, the common features are labeled with the same reference numerals and need not be discussed. As shown inFIG.6, the blocking or insulation layer159of the ESD protection device600may include two poly bounded junctions (e.g., polyblocks)151a,151binstead of a silicide blocking layer150. A polyblock151a,151bmay include a gate oxide region156a,156b, polysilicon158a,158b, and spacers154a,154bfor the polysilicon. A first poly block151amay insulate the floating region132from the first terminal region130. A second poly block151bmay insulate the floating region132from the second terminal region134. FIG.7shows a simplified cross-sectional view of an ESD protection device700according to alternative non-limiting embodiments. The ESD protection device700is a bi-directional bi-polar ESD protection device formed using a Silicon-on-Insulator (SOI) structure. The ESD protection device700is similar to the ESD protection device100and hence, the common features are labeled with the same reference numerals and need not be discussed. As shown inFIG.7, the substrate isolation region103may include a buried oxide region105rather than an epitaxial region103. The buried oxide region105may be provided between the substrate region102and the first conductivity region106, instead of an epitaxial region or deep well region of the ESD protection device100. A buried oxide region105may facilitate a thinner substrate. An oxide material is a kind of insulator material that hardly conducts current electrically. The oxide material may be used to fully isolate the bi-directional bi-polar device from the substrate. The buried oxide layer105may provide much better isolation performance. FIG.8shows a simplified cross-sectional view of an ESD protection device800according to alternative non-limiting embodiments.FIG.8illustrates ESD protection devices arranged in a stack for higher voltage applications. The ESD protection device800may include stacking two or more of the ESD protection devices100to facilitate greater current conduction. For example, as shown inFIG.8, ESD protection device800may include a first ESD protection device100aand a second ESD protection device100barranged adjacent to each other in the substrate101. The first and second ESD protection devices100a,100bmay each be an ESD protection device ofFIG.1. The common features are labeled with the same reference numerals and need not be discussed. Referring toFIG.8, the substrate portions of the first and second ESD protection devices100a,100bmay be isolated from each other by vertical isolation elements (e.g. trenches)170,172,174. Vertical isolation elements170,172,174may be deep trench isolation (e.g., DTI) structures that extend from the top surface of the substrate101to within the substrate region102of the substrate101(i.e., bulk substrate). The vertical isolation elements may be arranged between each of the two or more adjacent ESD protection devices (e.g., between the first and second ESD protection devices100a,100b) and at the ends of the ESD protection devices configured as the terminal ends (e.g., at the ends of the first and second ESD protection devices100a,100b). Referring toFIG.8, a first terminal region130aof the first ESD protection device100amay be configured for connection to a first external voltage via a first external terminal160′ and a second terminal region134bof the second ESD protection device100bmay be configured for connection to a second external voltage via a second external terminal162′. The second terminal region134aof the first ESD protection device100amay be connected to a first terminal region130bof the second ESD protection device100bvia terminal connector165. The terminal connector165may be formed in the same layer as the external terminals160′ and162′ (e.g., metal layer over the substrate). For even higher voltage ESD protection, additional ESD protection devices100may be arranged adjacent to each other in the substrate and their terminals connected in series. For example, a first terminal region of the first ESD protection device may be configured for connection to a first external voltage via a first external terminal and a second terminal region of the last ESD protection device may be configured for connection to a second external voltage via a second external terminal. Each intervening ESD protection device may be daisy chained. For example, the first terminal region of an intervening ESD protection device may be connected to a second terminal region of a preceding ESD protection device and a second terminal region of an intervening ESD protection device may be connected to a first terminal region of a subsequent ESD protection device. Alternatively, the ESD protection devices100a,100bmay also be one of the ESD protection devices500,600, or700. FIG.9Ashows a simplified cross-sectional view of an ESD protection device900according to alternative non-limiting embodiments.FIG.9Aillustrates an ESD protection device configured for multiple terminal protection. In particular,FIG.9Aillustrates an ESD protection device900for a three terminal structure where each terminal (160,162,164) is isolated from the other two terminals. For example, the three terminals may be a supply terminal (e.g., VDD), an input/output terminal (e.g., TO), and a ground terminal (e.g., GND). The ESD protection device900can provide dual polarity ESD current conduction for both a VDD to I/O path and an I/O to ground path within one structure. Portions of the ESD protection device900are similar to the ESD protection device100and hence, the common features are labeled with the same reference numerals and need not be discussed.FIG.9Bshows a simplified schematic view of the ESD protection device900according to various aspects of the present disclosure. As shown inFIG.9B, the ESD protection device900may be connected to and/or integrated with another semiconductor device901(e.g., a consumer electronic apparatus) to provide ESD protection to the semiconductor device901. As shown inFIG.9A, the ESD protection device900may further include a third terminal portion. The third terminal portion may include a fifth conductivity region112, a third terminal region138, and a third external terminal164. The fifth conductivity region112may be arranged within substrate101and at least partially over the first conductivity region106. The fifth conductivity region112is similar to the second and third conductivity regions108,110. That is, the doping concentration is similar to and the conductivity type is the same as the second and third conductivity regions108,110. Further, the second, third, and fifth conductivity regions108,110,112may be arranged to be spaced apart from each other within the first conductivity region106. At least a portion of the fifth conductivity region112may also be arranged immediately below a top surface of substrate101. The fifth conductivity region112may also be a medium-voltage well. The fifth conductivity region112may also have a second conductivity type same as the second and third conductivity regions108,110. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the fifth conductivity region112may also include N type dopants. Accordingly, the fifth conductivity region112may also include a medium-voltage N type well region (e.g., MV However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the fifth conductivity region111may include P type dopants. Accordingly, the fifth conductivity region112may include a medium-voltage P type well region (e.g., MV PWell). Similarly, the fifth conductivity region112may also further include a respective terminal region. A third terminal region138may be arranged at least partially within the fifth conductivity region112. The third terminal region138may be configured for connection to a third external voltage. For example, a first terminal region130may be configured for connection to a power supply line (e.g., VDD), a second terminal region134may be configured for connection to an input/output line, and a third terminal region138may be configured for connection to ground. The third terminal region138may also have the second conductivity type same as the conductivity type of the fifth conductivity region112. The third terminal region138may be similar to the first and second terminal regions130,134. That is, the doping concentration is similar and the conductivity type is the same. The third terminal region138may also include a highly doped region. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the third terminal region138may also include N type dopants. Accordingly, the third terminal region138may also be an N+ region like the first and second terminal regions. However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the third terminal region138may include P type dopants. Accordingly, the third terminal region138may also be a P+ region like the first and second terminal regions. Referring to an exemplary non-limiting embodiment as shown inFIG.9A, the third terminal region138may also be arranged immediately below a top surface of substrate101. The third terminal region138may be connected to a third external terminal164to which the third external voltage may be applied. Further, the third terminal region138and the fifth conductivity region112may be isolated from the substrate region102via the first conductivity region106and the substrate isolation region103(e.g., epitaxial region104). The substrate101of the ESD protection device900may further include a sixth conductivity region124arranged within the substrate101and at least partially over the first conductivity region106. At least a portion of the sixth conductivity region124may abut (i.e., directly contact) a portion of the first conductivity region106. The sixth conductivity region124may further be arranged centrally (e.g., equidistant) between the third conductivity region110and the fifth conductivity region112. The sixth conductivity region124may abut (i.e., directly contact) the third and fifth conductivity regions110,112. A first sidewall115of the sixth conductivity region124may abut the third conductivity region110and a second sidewall117(opposite the first sidewall) of the sixth conductivity region124may abut the fifth conductivity region112. The sixth conductivity region124is separated from the second and third terminal regions134,138by at least a portion of the third and fifth conductivity regions. Additionally, in some embodiments, a portion of the sixth conductivity region124may further overlap a portion of the third conductivity region110and another portion of the sixth conductivity region124may further overlap a portion of the fifth conductivity region112. The overlap may provide better performance of the ESD protection device. The sixth conductivity region124is similar to the fourth conductivity region120. That is, the doping concentration is similar and the conductivity type is the same. The sixth conductivity region124may also be a low-voltage well region having a first conductivity type. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the sixth conductivity region124may include P type dopants. Accordingly, the sixth conductivity region124may include a low-voltage P type well (e.g., LV PWell). However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the sixth conductivity region124may include N type dopants. Accordingly, the sixth conductivity region124may include a low-voltage N type well (e.g., LV NWell). Referring to an exemplary non-limiting embodiment as shown inFIG.9A, the sixth conductivity region124may be arranged immediately below a top surface of substrate101. Further, the sixth conductivity region124may be separated from the substrate region102via the first conductivity region106and the substrate isolation region103(e.g., epitaxial region104). The sixth conductivity region124may further include a second highly doped floating (or unconnected) region136. The second floating region136may be arranged within the sixth conductivity region124. The second floating region136may be arranged at a center of the sixth conductivity region124so that the second floating region136is equidistant from the first sidewall115and the second sidewall117of the sixth conductivity region124. The second floating region136is similar to the floating region132. In some exemplary non-limiting embodiments, the first conductivity type may be P type and the second conductivity type may be N type. In such case, the first and second floating regions132,136may include N type dopants. Accordingly, the first and second floating regions132,136may also include a N+ region. However, in alternative non-limiting embodiments, the first conductivity type may be N type and the second conductivity type may be P type. In such case, the first and second floating regions132,136may include P type dopants. Accordingly, the first and second floating regions132,136may include a P+ region. Referring to an exemplary non-limiting embodiment as shown inFIG.9A, the second floating region136may be arranged immediately below a top surface of substrate101. Further, the second floating region136may be isolated from the substrate region102via the first conductivity region106and the substrate isolation region103(e.g., epitaxial region104). In some exemplary non-limiting embodiments, the sixth conductivity region124may further include a drift region126(e.g., P-drift for an LV PWell or N-Drift for an LV NWell) (not shown in the figures) along the boundaries (e.g., along sidewalls115and117of the sixth conductivity region124) with the third and fifth conductivity regions110,112. The drift regions may help to increase the breakdown voltage of the ESD protection device900. The ESD protection device900may also include a second blocking or insulating layer159′ arranged over a top surface of the substrate101. As shown inFIG.9A, the second insulating layer159′ may be a second silicide blocking layer152arranged to extend between the third conductivity region110and the fifth conductivity region112, overlapping at least a part of these conductivity regions110,112and the sixth conductivity region124. The second insulating layer159′, like the insulating layer159, prevents silicide interaction or processing on (or in other words, block silicide, that may be deposited during fabrication of the ESD protection device900, from interacting with) the second terminal region134, the third terminal region138, and the second floating region136. The insulating layer159′ is used to electrically insulate the second floating region136from the terminal regions134,138. The ESD protection device900may further include a first isolation element140′ and a second isolation element142′. The first isolation element140′ may be configured to isolate the second conductivity region108and first terminal region130. The second isolation element142′ may be configured to isolate the fifth conductivity region112and the third terminal region138. The first isolation element140′ is arranged immediately below a top surface of substrate101on a side of the first terminal region130and second conductivity region108facing away from the floating terminal region132and the fourth conductivity region120. The second isolation element142′ is arranged immediately below a top surface of substrate101on a side of the third terminal region138and fifth conductivity region112facing away from the second floating terminal region136and the sixth conductivity region124. That is, the first and second isolation elements140′,142′ are arranged at the ends of the ESD protection device900. For example, the first and second isolation elements140′,142′ may be shallow trench isolation (STI) blocks. Additionally, the substrate portions of ESD protection device900may be further isolated from other devices in the substrate by vertical isolation elements (e.g., trenches)170′,172′. FIGS.10A and10Bshow a flow chart of a method1000for forming the ESD protection device according to various non-limiting embodiments. As shown inFIG.10A, the method1000may begin (at1002) by providing the substrate101. The method1000may include forming (at1004) the substrate region102for a first conductivity type within the substrate101. The method1000may include forming (at1006) the substrate isolation region103(e.g., epitaxial region104of a second conductivity type or a buried oxide layer105) within the substrate101and at least partially over the substrate region102. The method1000may include forming (at1008) the first conductivity region106of the first conductivity type within substrate101and at least partially over the epitaxial region104. The method1000may include forming (at1010) the second and third conductivity regions108,110of the second conductivity type within substrate101and at least partially over the first conductivity region106. The second and third conductivity regions108,110spaced apart from each other. The method1000may include forming (at1012) the fourth conductivity region120within substrate101and at least partially over the first conductivity region106and between the second and third conductivity regions108,110. In some alternative non-limiting embodiments, the fourth conductivity region120may further be formed partially over portions of the second and third conductivity regions108,110. The substrate region102, epitaxial region104, buried oxide region105, first, second, third and fourth conductivity regions106,108,110,120may be formed using any method as known to those skilled in the art. In a non-limiting example, each of these regions102,104,106,108,110,120may be formed by using a mask to expose a portion of the substrate101intended for the respective regions102,104,106,108,110,120and doping the exposed portion with the appropriate dopants (e.g. either P type or N type dopants). In a non-limiting example, the buried oxide region105may be formed by using a mask to expose a portion of the substrate101intended for the respective regions102,104,106,108,110,120and implanting the exposed portion with oxygen. Next, the method1000may include forming and configuring (at1016) the terminal regions130,134and the floating region132. For example, at1016, the method1000may include forming the first terminal region130at least partially within the second conductivity region108, the second terminal region134at least partially within the third conductivity region110, the floating region132at least partially within the fourth conductivity region120, and configuring the first terminal region130and the second terminal region134for connection to the first external voltage and the second external voltage respectively. In various non-limiting embodiments, the terminal regions130,134and the floating region120may be formed by injecting dopants into the respective portions of the substrate101. The injection of the dopants may be performed by any method known to those skilled in the art, such as, but not limited to ion injection. The method1000may further include forming (at1018) a blocking or insulation layer159(e.g., silicide blocking layer150or polysilicon blocks151a,151b) over the substrate101to at least cover the fourth conductivity region120and at least partially cover the second conductivity region108and the third conductivity region110. A silicide blocking layer150may further completely cover the floating region132and the fourth conductivity region120and at least partially cover the first terminal region130, the second conductivity region108, the second terminal region134, and the third conductivity region110. The silicide blocking layer150and polysilicon blocks151a,151bmay be formed using any method as known to those skilled in the art. For instance, in a non-limiting example, the silicide blocking layer150may be formed by depositing a silicide blocking material over a top surface of the substrate101, and etching the silicide blocking material. The method1000may then include forming (at1020) the isolation elements140,142, (e.g., shallow trench isolation (STI) blocks). In various non-limiting embodiments, the isolation elements140,142may be formed by any method as known to those skilled in the art. For instance, a mask may be arranged over the substrate101to expose portions of the substrate101intended for the isolation elements140,142, the exposed portions may then be etched to form trenches, and the trenches may be filled with isolation material. The method1000may then include forming (at1003) the deep isolation elements170,172,174(e.g., deep trench isolation (DTI) blocks) prior to forming the substrate region. In various non-limiting embodiments, the deep isolation elements170,172may be formed by any method as known to those skilled in the art. For instance, a mask may be arranged over the substrate101to expose portions of the substrate101intended for the deep isolation elements170,172, the exposed portions may then be etched to form deep trenches, and the trenches may be filled with isolation material. The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments, therefore, are to be considered in all respects illustrative rather than limiting the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein. | 64,375 |
11862736 | DETAILED DESCRIPTION In the following paragraphs, embodiments will be described in detail by way of example with reference to the accompanying drawings, which are not drawn to scale, and the illustrated components are not necessarily drawn proportionately to one another. Throughout this description, the embodiments and examples shown should be considered as exemplars, rather than as limitations of the present disclosure. As used herein, the “present disclosure” refers to any one of the embodiments described herein, and any equivalents. Furthermore, reference to various aspects of the disclosure throughout this document does not mean that all claimed embodiments or methods must include the referenced aspects. Reference to materials, configurations, directions, and other parameters should be considered as representative and illustrative of the capabilities of exemplary embodiments, and embodiments can operate with a wide variety of such parameters. It should be noted that the figures do not show every piece of equipment, nor the materials, configurations, and directions of the various circuits and communications systems. Referring toFIGS.1-4, exemplary embodiments of monolithic multi-dimensional integrated circuits will first be described. Exemplary ICs are built on both sides of an electronic board and have a multi-dimensional integration utilizing all if the IC package's planes for semiconductor circuitry. Thus, the IC architecture may be comprised of wafers located on any and all planes of a rectangular or square package for maximum area utilization. This type of structure enables multi-dimensional utilization of integrated circuits for all manufacturing processes. An exemplary monolithic multi-dimensional integrated circuit10comprises an electronic board12and one or more semiconductor wafers14. The semiconductor wafers14may be any shape or may be of several different shapes. As discussed in more detail herein, in exemplary embodiments the multiple planes or the wafers have a honeycomb or beehive shape. As best seen inFIG.1, the electronic board12has two opposite sides16a,16b, and IC10and wafers14are mounted on both sides16a,16bof the board12.FIG.1shows a multi-dimensional integrated circuit cross-section mounted on electronic board. The multi-dimensional integrated circuit is located on both sides of an electronic board. The semiconductor wafers14may be mounted on one or more of the planes20of the electronic package18and may be mounted on all its planes. In exemplary embodiments, multiple ICs are constructed on one or more planes of the electronic package18. A multi-dimensional electronic package18is provided and is comprised of multiple planes20a-20d, best seen inFIG.4. Advantageously, any type of circuit could be placed on any plane of the multi-dimensional integrated circuit. This electronic circuitry could be designed hierarchically in layers. A plurality of layered integrated circuits could be placed on a single semiconductor wafer. As best seen inFIG.2, a multi-dimensional integrated circuit10may contain semiconductor wafers14on multiple sides or on all sides.FIG.3demonstrates different wafer sizes. As shown inFIG.4, an exemplary multi-dimensional IC10is comprised of a plurality of tiers or planes utilized for the electronic circuitry area, where the IC layout is designed to be electronically connected taking multi-dimensional planes into consideration. Each tier or plane may have electronic circuits, and a plurality of monolithic multi-dimensional wafers and circuits could be located on all planes, enabling efficient silicon area for maximum utilization. An internal, silicon based, heat-sink mechanism may provide advanced temperature control for the entire integrated circuit.FIG.4shows the inner horizontal and vertical connectivity. Multiple monolithic IC units10are provided which are active and reconfigurable for different uses. One or more vertical crossbars24couple the circuitry units and allow communication between the units. Multi-directional crossbars26may be associated with a first tier of a plurality of tiers or planes. In exemplary embodiments, the multi-directional crossbars26couple a plurality of electronic circuitry units within a single tier to vertical crossbars24. The crossbars may be centrally located in between the planes according to connectivity necessities. In exemplary embodiments, the multi-directional crossbars26support a shuffle architecture. The ICs may be connected to IO pads via internal metal wires that are routed in multi-dimensional planes. More particularly, the IC structure may include interconnects die side-side wire bars to connect between the silicon's internal connections and the IO PADs. In exemplary embodiments, the multi-dimensional electronic circuitry has crossed over power supplies to provide power to all integrated circuits on the wafer, in all planes. As discussed above, improved interconnection is provided by an internal architecture comprised of horizontal, vertical and/or angled VIAs and cavities.FIG.2shows connected VIAs24running vertically from top to bottom. The internal connections described may support an in/out architecture. Metal crossbars22,24,26may cross side-to-side and top-down in order to perform the electronic connections that are necessary for the IC's circuitry. The multi-dimensional layout structure typically comprises vertical and horizontal connectivity on the order of microns long. In exemplary embodiments, at least one horizontal crossbar22communicates signals within a horizontal plane20. A horizontal crossbar22may be provided for power supplies within a first tier or horizontal plane. One or more vertical crossbars24may be provided to provide communication between electronic circuitry units. As best seen inFIG.4, in exemplary embodiments one or more multi-directional crossbars26communicate signals between one or more electronic circuitry units in a single plane to at least one vertical crossbar24. In exemplary embodiments, at least one tier or plane comprises all-directions signals routings. In exemplary embodiments, each electronic circuitry unit is connected to the second tier that may be on any plane of the package, but the circuitry could be connected to any tier on any plane. In exemplary embodiments, the integrated circuits are connected via multi-dimensional VIAs at all planes' levels. These “through-silicon VIAs” (TSVs) pass through the silicon substrate(s) between active layers and/or between an active layer and an external bond pad. The large numbers of vertical VIAs between the layers advantageously allows construction of wide bandwidth routing buses between functional blocks in different layers. A typical example would be a microcontroller and memory multi-dimensional stack, with the cache memory stacked on top of the processor. This arrangement allows a bus much wider than the typical 128 or 256 bits between the cache and microcontroller. Wide buses in turn alleviate the memory wall problem. Disclosed embodiments provide methods of fabricating or manufacturing multi-dimensional or 3D integrated circuits and IC packaging. An exemplary method of forming a multi-dimensional circuitry structure in an IC includes positioning a first electronic circuit unit on a first tier or plane of a multi-dimensional IC and positioning a second electronic circuitry unit on a second tier or plane of the multi-dimensional IC. Third, fourth, and additional electronic circuitry units could be positioned on respective tiers or planes of the IC. The first electronic circuitry unit may be coupled to the second electronic circuitry unit with vertical crossbars. In exemplary embodiments, one or more multi-directional crossbars are provided within one of the electronic circuit's units at all planes. Control logic may be provided and configured to determine which, if any, electronic circuits within the first and second electronic circuit units are active and to reconfigure usage of the units based on such determination by deactivating those units that are not active. In exemplary embodiments, monolithic multi-dimensional ICs are built in layers on a single semiconductor wafer, which is then diced into many sub-ICs. The semiconductor wafers can be cut into one more dies having a geometric shape. Advantageously, the fabrication can be done with only one substrate, eliminating the need for aligning, thinning, bonding, or through-silicon VIAs. Process temperature limitations may be addressed by partitioning the transistor fabrication to two phases. A high temperature phase can be done before layer transfer followed by a layer transfer use ion-cut, also known as layer transfer. Multiple thin (e.g., 10s-100s nanometer scale) layers of virtually defect-free silicon can be created by utilizing low temperature (<400° C.) bond and cleave techniques and placed on top of active transistor circuitry. This would be followed by finalizing the transistors using etch and deposition processes. This monolithic multi-directional IC technology can be done as a three-dimensional IC but on all the package's planes. In this way sub-wafers can be placed on the top, bottom, left and right of the package's planes and it therefore maximizes the area utilization of the IC's. The manufacturing of the multi-dimensional IC may be done utilizing Die-to-Die, Die-to-Wafer or Wafer-to-Water methods, depending on the needs and goals of the manufacturer and based on the knowledge of the skilled artisan. Each manufacturing methodology has its advantages and disadvantages according to the design process and node's size. In the Die-to-Die method the electronic components are built on multiple dies, which are then aligned and bonded. Thinning and TSV creation may be done before or after bonding. One advantage of die-to-die is that each component die can be tested first, so that one bad die does not ruin an entire stack. Moreover, each die in the 3D IC can be binned beforehand, so that they can be mixed and matched to optimize power consumption and performance (e.g., matching multiple dice from the low power process corner for a mobile application). In Die-to-Wafer the electronic components are built on two semiconductor wafers. One wafer is diced; the singulated dice are aligned and bonded onto die sites of the second wafer. As in the wafer-on-wafer method, thinning and TSV creation are performed either before or after bonding. Additional dies may be added to the stacks before dicing. In the multi-dimensional IC, the same technique is used but for multiple sub-wafers that are located on all the package's planes. In the Wafer-to-Wafer manufacturing technique the electronic components are built on two or more semiconductor wafers, which are then aligned, bonded, and diced into the multi-dimensional ICs. Each wafer may be thinned before or after bonding. Vertical connections are either built into the wafers before bonding or created in the stack after bonding. These “through-silicon VIAs” (TSVs) pass through the silicon substrate(s) between active layers and/or between an active layer and an external bond pad. Wafer-to-wafer bonding can reduce yields, since if any 1 of N chips in a multi-dimensional IC are defective, the entire 3D IC will be defective. Moreover, the wafers must be the same size, but many exotic materials (e.g. III-Vs) are manufactured on much smaller wafers than CMOS logic or DRAM (typically 300 mm and below), complicating heterogeneous integration. The sub-wafer's layers can be built with different processes, or even on different types of wafers. This means that components can be optimized to a much greater degree than if they were built together on a single wafer. Moreover, components with incompatible manufacturing could be combined in a single multi-dimensional IC. An exemplary method of manufacturing a multi-dimensional IC packaging comprises first forming an outer circuit having a top side and a bottom side and mounting an IC aside of the bottom side. Then device connectors are attached to the IC. An encapsulation is formed which has an encapsulation top side and an encapsulation bottom side so the encapsulation bottom side is partially exposed and the encapsulation is directly on the device connector and over the IC. Exemplary methods further include the step of forming a vertical interconnect through the encapsulation so the vertical interconnect has an interconnect bottom side directly on the outer circuit side and an interconnect top side exposed from the encapsulation. Forming the encapsulation may include forming it so it has an encapsulation plane on the bottom, top, left and right sides directly and connect them all via routing. In exemplary embodiments, forming the encapsulation includes forming an encapsulation cavity with the outer contact pad within the encapsulation cavity. Then an external connector may be attached on a side of the outer circuit opposite the outer circuit top side with the vertical interconnect directly thereon. In exemplary embodiments, manufacturing methods include providing a package substrate having a substrate top side with the IC thereover so the substrate top side is coplanar with the outer pad top side. The method may include forming left- and right-side circuits that connect to all other circuitry on all planes. All circuits of the IC on all planes may include inner connections to the IO PADS. Turning toFIGS.5-11, exemplary embodiments of a monolithic multi-dimensional memory architecture will now be described. Monolithic multi-dimensional memory architecture110generally is comprised of a multi-dimensional, multiple plane memory crossbar architecture with tight-pitched vertical, horizontal and angled monolithic inter-tier vias (MIVs)114for inter-unit routing and multiplexers at each tier for block access are used to shorten overall conductor length and reduce resistive-capacitive (RC) delay. More particularly, exemplary embodiments have one or more tiers or planes112and monolithic inter-tier vias114spanning the tiers. As shown inFIG.5, memory cells may be placed on a honeycomb structure. Silicon sub-dies can be placed on all honeycomb planes and connected via crossbars or other electrical conductors. In exemplary embodiments, there is at least one memory cell116in each tier or plane112and the memory cell116may be located within a client memory unit117. At least one tier memory unit may lie in planes perpendicular to the other memory units and/or in planes parallel to the other memory units and/or in planes at any angle to the other memory units. A basic structure would have at least one horizontal crossbar for memory cells116within tiers112. In exemplary embodiments, a stack of memory integrated circuit memory chips, each containing memory circuitry, are located on multi-planar structure and connected via vertical, horizontal and angled crossbars. The memory cells116may have random access memory (RAM), and the RAM may comprise static RAM (SRAM). In exemplary embodiments, one or more of the memory cells116could have a three-dimensional mask-programmed read-only memory (3D-MPROM) or a three-dimensional electrically-programmable read-only memory (3D-EPROM). FIGS.6-8illustrate multi-planar structures for memory cells allocation.FIG.6shows one plane within a honeycomb structure125.FIG.7shows an exemplary structure comprised of multiple planes112and monolithic inter-tier vias114spanning the planes112. Silicon sub-dies may be glued/mounted to these planes enabling significantly higher surface area for memory cells allocation. Another planar structure for memory cells allocations is shown inFIG.8, also having multiple planes112and monolithic inter-tier vias114spanning the planes112. Silicon sub-dies are glued/mounted on each plane, significantly enhancing the surface area for memory cells allocation. Exemplary crossbar architecture uses multiple plane, horizontal, vertical and/or angled structures, in some instances, bee hive or honeycomb structure125shape. The MIVs114may be minimized to small run-length, in all directions, and connect circuits on multiple planes and therefore can work without the need for repeaters. The plurality of MIVs114may be configured to act as crossbars in all directions for the memory structure and may comprise a vertical, horizontal or angled length on the order of microns long. In exemplary embodiments, a vertical, horizontal or angled crossbar is associated with a first tier, and the vertical, horizontal or angled crossbar couples a plurality of client memory units within a single tier to the vertical, horizontal, or angled crossbar. The honeycomb/bee hive structure, illustrated inFIGS.9and10advantageously enables shorter, more efficient MIV structure. Silicon sub-dies can be placed on the honeycomb planes. Implementation of this type of structural design for memory silicon dies significantly increases the surface area for memory cells implementation. The multi-plane, multi-dimensional memory layout surface design advantageously enables significantly larger capacity to implement more memory cells on the same area than current industry standard structures. InFIG.11, surface division for memory cells allocation is illustrated with a cube and sub-cube structure. The main cube140is constructed of many sub-cubes142. On each sub-cube's plane112, memory cells can be placed. The sub-cubes' planes112are covered with memory cells sub-dies. All sub dies are connected via crossbars or any other conductor technology. In exemplary embodiments, as shown inFIG.12, a multiplexer118is disposed in one of the tiers or in multiple tiers. The multiplexer118is communicatively coupled to the memory cell116in the respective tier112. In exemplary embodiments, a second multiplexer118ais disposed in a second tier or plane among a plurality of tiers and coupled to a second respective memory cell116awithin the second tier. Control logic120may be used to configure the memory banks based on use. More particularly, control logic may be used to determine whether the memory cells116are active and which memory cells116are active and to control usage of the memory cells116based on such determinations. In exemplary embodiments, the control logic is configured to reconfigure usage of memory cells deactivates unused memory cells so that power is conserved. With reference toFIGS.12and13, multi-dimensional memory structures can be incorporated into multi-dimensional ICs. As discussed above, such memory structure has a plurality of planes112, and each plane has at least one memory cell116. Monolithic intertier vias (MIVs)114span the planes112. A first multiplexer118amay be disposed in a first plane112aand coupled to at least a respective memory cell116awithin the first plane, and a second multiplexer118bmay be disposed in a second plane112band coupled to at least a second respective memory cell116bwithin the second plane. Control logic120, as discussed above, may be coupled to at least one of the MIVs114. In exemplary embodiments, the stack of memory units is located on multiple planes in multiple dimensions. As discussed above, a series of memory units may be arranged in a bee hive or honeycomb structure and connected via vertical, horizontal or angled crossbars, creating a memory structure having multiple planes in multiple dimensions. The series of memory units may be held together by glue or another adhesive to make one memory microchip. The IC may be comprised of silicon sub-dies of memory cells, each glued/mounted on a different plane and connected via crossbars or any other electrical conductor. The silicon sub-dies may be on different planes and can be on different manufacturing process nodes and connected via crossbars or any other electrical conductor. In exemplary embodiments, the series of memory units is structurally integrated to a microprocessor chip to constitute a microprocessor and a memory module. Exemplary multi-dimensional, multi-planar memory ICs may incorporate different types of memory. For example, the IC may have a multi-dimensional read-only memory (ROM) or a multiple-dimensional random-access memory (RAM). In exemplary embodiments, the IC has a multi-dimensional Flash memory. An IC may have one or more of a memristor, a resistive random-access memory (RRAM or ReRAM), a phase-change memory (PCM), a programmable metallization cell (PMC), and a conductive-bridging random-access memory (CBRAM). Exemplary methods of manufacturing and forming a multi-dimensional memory integrated circuit (IC) memory structure will now be described. In exemplary embodiments, a first step is positioning a first client memory unit117aon a first plane112aof a multi-dimensional memory integrated circuit10. Next, a second client memory unit117bis positioned on a second plane112bof the multi-dimensional memory integrated circuit. At least one vertical, horizontal or angled crossbar22,24,26,114may be provided within one of the client memory units117. Subsequent steps include coupling the first client memory unit117ato the second client memory unit117bwith a vertical, horizontal or angled crossbar22,24,26,114and providing control logic120. As discussed above, the control logic120is configured to determine which, if any, memory cells116within the first and second client memory units117are active and reconfigure usage of the client memory units117based on such determination by deactivating client memory units which are not active. As mentioned above, dies are used in manufacturing disclosed multi-dimensional ICs and packages, and the multi-dimensional die and said intermediate-circuit dies may be located in a memory package, a memory module, a memory card or a solid-state drive. Turning toFIGS.14-18, monolithic multi-dimensional integrated circuits incorporating solar cells will now be described. Generally, solar cells and/or MEMS can be mounted on or incorporated into the multiple-planes wafers described above for purposes of charging various devices. Advantageously, as the number of surfaces increases the battery power time is significantly higher. The solar cells can be produced as MEMS or on-chip solar cells based on nanotechnology research and development.FIG.14illustrates an exemplary multi-dimensional integrated circuit having multiple planes20suitable for on-chip solar cells. As shown inFIG.15, wafers14of the integrated circuit10may include solar cells28. More particularly, the semiconductor wafers14may be mounted on all planes20of the electronic package18and comprise non-silicon substrate on-chip solar cells28. As best seen inFIGS.16and17, in exemplary embodiments the semiconductor wafers14are mounted on selected planes20of the multi-dimensional structure and comprise silicon on-chip solar cells28.FIG.18shows a multi-dimensional die and on-chip solar microcells structure. The semiconductor wafers could be mounted on all planes of the electronic package and comprise silicon MEMS and/or on-chip solar cells structure. The solar cells may be fully integrated within the integrated circuit structure for power harvesting. In exemplary embodiments, photo diodes, electrically connected, are used as on-chip micro solar cells. With reference toFIGS.19-26, exemplary embodiments of multi-dimensional photonic integrated circuits210will now be described. As illustrated inFIGS.19-21, a photonic integrated circuit (PIC)209is a chip that contains photonic or optical components215, i.e., components that work with light (photons). Whereas conventional integrated circuits work by conducting electricity or allowing electrons to flow through the circuit, PICs utilize photons, massless fundamental particles representing a quantum of light, instead of electrons. In a photonic chip, photons pass through optical components such as waveguides (equivalent to electrical wires), lasers (equivalent to transistors), and similar. PICs typically use a laser source to inject light that drives the components, like turning on/off a typical electron-based CMOS transistor. In a CMOS transistor, electrons are injected to drive electronic components as in PICs light is used instead of electrons. Photonic integrated circuits are typically fabricated with a wafer-scale technology using lithography on silicon related materials substrates. An exemplary multi-dimensional photonic integrated circuit (MD PIC)210is comprised of a photonic integrated circuit209including a substrate212having two sides216a,216band a multi-dimensional package218with planes220that extend in multiple dimensions. The planes220may have horizontal sides213aand vertical sides213b. Optical components215such as waveguides or lasers are mounted on or otherwise connected to one or both sides216a,216bof the package218as well as being mounted on the package's multi-dimensional planes220on the horizontal213aand/or vertical sides213b. In exemplary embodiments, at least one of the optical components215is mounted on at least one of the horizontal sides213a, and another optical component215is mounted on at least one of the vertical sides213b. The optical components215may be mounted on all the planes220of the package218. As best seen inFIGS.19and22, the optical components215of a PIC209include a laser215aand one or more optical waveguides215b. A laser injects light into the PIC209to drive the other optical components215, and the waveguides guide the light, restricting the spatial region where the photons can propagate. This enables the PIC209to operate using the photons of light. The optical components215may be connected by optical fiber217that runs throughout the PIC209. As shown inFIGS.23-26, the multi-dimensional planes220of the package218can be of various structures such as hexahedron, dodecahedron, icosahedron, and can have a honeycomb/beehive structure219. This advantageously enables shorter, more efficient MIV structure. The optical components215can be placed on the honeycomb planes. Implementation of this type of structural design significantly increases the surface area for memory cells implementation. The multi-planar, multi-dimensional memory layout surface design advantageously enables significantly larger capacity to implement more memory cells on the same area. Turning toFIG.27, it can be seen that exemplary multi-dimensional photonic integrated circuits210incorporate solar cells. On-chip solar cells and/or MEMS can be mounted on or incorporated into the multiple-planes described above. The solar cells228may be mounted on all planes220of the package218and comprise silicon or non-silicon substrate on-chip solar cells. The solar cells228may be fully integrated within the photonic circuit structure for power harvesting. With reference toFIGS.28-31, the multi-dimensional photonic integrated circuit210can include multi-dimensional memory architecture310, which is comprised of a multi-dimensional, multiple plane memory crossbar architecture with tight-pitched vertical, horizontal, and angled monolithic inter-tier vias (MIVs)314for inter-unit routing. There may be multiplexers at each tier for block access used to shorten overall conductor length and reduce resistive-capacitive (RC) delay. Exemplary embodiments have one or more tiers or planes312and monolithic inter-tier vias314spanning the tiers. In exemplary embodiments, there is at least one memory cell316in each tier or plane312and the memory cell316may be located within a client memory unit. At least one tier memory unit may lie in planes perpendicular to the other memory units and/or in planes parallel to the other memory units and/or in planes at any angle to the other memory units. A basic structure would have at least one horizontal crossbar for memory cells316within tiers312. The memory cells316may have random access memory (RAM), and the RAM may comprise static RAM (SRAM). In exemplary embodiments, one or more of the memory cells316could have a three-dimensional mask-programmed read-only memory (3D-MPROM) or a three-dimensional electrically-programmable read-only memory (3D-EPROM). With reference toFIGS.32and33, a hybrid system202of conventional multi-dimensional integrated circuits10and multi-dimensional photonic integrated circuits210is provided. The multi-dimensional integrated circuit10communicates with the multi-dimensional photonic integrated circuit210by electrical communication and/or photonic communication. In exemplary embodiments, the conventional 3D, MP circuitries/chip10communicates with the photonic circuitries/chip210via optical based wiring connections. For example, microfiber optics may function as light-based-wires. Another option is light conducting wires that are like fiber optics in structure but embedded into the silicon substrate. It should be noted that any type of light conducting material that functions as wire and can be implemented within a microchip could be used. The signals are transmitted using a light source such as a laser215a, high intensity LEDs, or any other similar light source. It should be noted that one advantage of the multi-dimensional photonic integrated circuits210is that fiber optics or any other light oriented medium that is functioning as wire can be bent according to the 3D, MP shape and enable electrical connectivity. These and other modifications could be done during fabrication of a multi-dimension PIC, a stage of which is shown inFIG.34. Dedicated circuitries are made to produce the light-based communication between circuits and can transmit the signals in different frequencies. This feature enables multiplexing capabilities, meaning transmitting different data on the same light wire as a frequency dependent. For example, on one light-based wire using one frequency specific data can be transmitted and using different frequency will transmit another data. The light pulses can alternate and transmit many data to many circuitries or components on the same line, very similar to transmitting data signals over high power lines for example. As described in detail above, multi-dimensional integrated circuit10comprises an electronic board12and one or more semiconductor wafers14. The electronic board12has two opposite sides16a,16b, and IC10and wafers14are mounted on both sides16a,16bof the board12. The semiconductor wafers14may be mounted on one or more of the planes20of the electronic package18and may be mounted on all its planes. In exemplary embodiments, multiple ICs are constructed on one or more planes of the electronic package18. A multi-dimensional electronic package18is provided and is comprised of multiple planes20a-20d. Also described above, multi-dimensional PIC210has a substrate212with two sides216a,216band a multi-dimensional package218with planes220that extend in multiple dimensions. Optical components215are mounted on one or both sides216a,216bof the package218as well as being mounted on the package's multi-dimensional planes220. A hybrid system is advantageous for many applications, including in the telecommunications industry where high-speed information is transmitted along fiber optic waveguides. The information must ultimately be converted into digital signals for common electronic devices to process since common data networks and power infrastructures exist on electrical structures and not photonic ones. As optical systems are more power efficient than electrical systems, PICs will likely continue replacing conventional ICs within a wide range of applications. The silicon photonics market is projected to rapidly grow in the next few years. Therefore, it is likely that more photonic integrated circuits will replace conventional electric circuits in a wide range of industries including IoT, autonomous machines, data centers, high-performance computing, telecommunications, and medical applications. Disclosed embodiments include and enable larger PICs, with higher performance and less energy/heat loss. These chips increase the traffic speed and bandwidth of data centers, reduce power consumption/heat, lowering cost, and ultimately helping create a “greener world”. Embodiments of the present disclosure encapsulate the next generation of high performance, bandwidth, and efficiency of PICs, making them a vital part of the high-speed technology of the future. Thus, it is seen that monolithic multi-dimensional integrated and photonic circuits and memory architectures are provided. It should be understood that any of the foregoing configurations and specialized components or connections may be interchangeably used with any of the systems of the preceding embodiments. Although illustrative embodiments are described hereinabove, it will be evident to one skilled in the art that various changes and modifications may be made therein without departing from the scope of the disclosure. It is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the present disclosure. | 33,004 |
11862738 | Identical, similar or equivalent parts of the various figures described below bear the same numerical references so as to facilitate passing from one figure to another. The various parts shown on the figures are not necessarily shown to a uniform scale, to make the figures more legible. The various possibilities (variants and embodiments) must be understood not to be exclusive of one another and may be combined with one another. DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS A photovoltaic cell100according to a first embodiment is described below in relation toFIG.1. In this example, the cell100is a heterojunction cell. The cell100includes at least one p-n junction including an absorber formed by a crystalline semiconductor substrate102doped according to a first conductivity type. In the example embodiment described here, the substrate102includes n-doped crystalline silicon. The cell100includes a first charge-collecting layer104configured for extracting and collecting charges of the first conductivity type (electrons in the example described here). According to an example embodiment, the first charge-collecting layer104includes amorphous semiconductor (hydrogenated amorphous silicon in this example), doped according to the first conductivity type (n-doped in this example). The cell100also includes a first passivation layer106covering a first main face of the substrate102so that the first passivation layer106is disposed between this first main face of the substrate102and the first charge-collecting layer104. In this example embodiment, the first passivation layer106includes amorphous semiconductor (hydrogenated amorphous silicon in this example), not intentionally doped. The cell100also includes a second charge-collecting layer108configured for extracting and collecting charges of the second conductivity type (holes in the example described here). According to an example embodiment, the second charge-collecting layer108includes amorphous semiconductor (hydrogenated amorphous silicon in this example) doped according to the second conductivity type (p doped in this example). The cell100also includes a second passivation layer110covering a second main face of the substrate102so that the second passivation layer110is disposed between this second main face of the substrate102and the second charge-collecting layer108. In this example embodiment, the second passivation layer110includes amorphous semiconductor (hydrogenated amorphous silicon in this example) not intentionally doped. The layers104,106,108and110each have for example a thickness of between 2 nm and 20 nm, and advantageously less than 15 nm. The substrate102and the layers104,106,108and110form an assembly provided with a first main face112disposed on the same side as the first main face of the substrate102and a second main face112opposite and disposed on the same side as the second main face of the substrate102. In the example embodiment described here, the first and second main faces112,114are formed respectively by the surfaces of the first and second charge-collecting layers104,108opposite to those in contact with the first and second passivation layers106,110. According to an example embodiment of the cell100, the first passivation layer106and the first charge-collecting layer104are first of all disposed on the same side as the first main face of the substrate102. Use of these deposits gives rise to a deposit of portions of these first layers104,106against at least a part of the lateral faces116of the substrate102. The second passivation layer110and the second charge-collecting layer110are next deposited on the second main face of the substrate102, opposite to the first main face of the substrate102. Use of these deposits gives rise to a deposit of portions of the second layers108,110against any parts of the lateral faces116of the substrate102not covered by the first layers104,106, and optionally against a part of the portions of the first layers104,106located against the lateral faces116of the substrate102. The layers104,106,108and110are for example deposited by PECVD (plasma enhanced chemical vapour deposition) or HWCVD (hot wire chemical vapour deposition). The cell100also includes a first layer of conductive transparent oxide (TCO)118disposed against a part of the first main face112. Furthermore, the form of the first layer of TCO118is such that the edges120of the first main face112are not covered by the first layer of TCO118. This non-covering of the edges120of the first main face112by the first layer of TCO118is for example obtained by using a deposit of the first layer of TCO118through an element masking the edges120. This masking element corresponds for example to the support on which the cell100is disposed when the first layer of TCO118is deposited. In the example embodiment described here, the edges120of the first main face112form, in a plane parallel to the first main face112, a contour with a width (the dimension referenced “a” onFIG.1) less than or equal to 500 μm, and for example between 100 μm and 500 μm. The cell100also includes a second layer of TCO122covering the whole of the second main face114and also covering at least first parts of the first charge-collecting layer104and/or of the second charge-collecting layer108disposed on the lateral faces116of the substrate102. In the example inFIG.1, the second layer of TCO122covers the whole of the second main face114as well as some of the portions of the second charge-collecting layer108disposed on the lateral faces116of the substrate102. Advantageously, the TCO of the layers118,122corresponds to indium tin oxide (ITO). Furthermore, the material of the first layer of TCO118may be identical to or different from the material of the second layer of TCO122. The thickness of each of the layers of TCO118,122is for example between 5 nm and 100 nm. This thickness of each of the layers of TCO118,122is advantageously constant. The layers of TCO118,122are for example deposited by cathodic sputtering or by PVD (physical vapour deposition), or by PLD (pulsed laser deposition). The cell100also includes first electrically conductive contacts124disposed against the first layer of TCO118and second electrically conductive contacts126disposed against the second layer of TCO122. These electrically conductive contacts124,126advantageously include at least one metallic material such as silver, copper or aluminium. These electrically conductive contacts124,126correspond to the metallisation fingers of the cell100and to the busbars of the cell100(onFIG.1, only the metallisation fingers are shown). By way of example, the width (bearing the reference “b” onFIG.1) of each of these metallisation fingers is for example between 30 μm and 50 μm, and the thickness thereof is for example of the order of 8 μm. Finally, the cell100includes a non-reflective coating128covering at least second parts of the first charge-collecting layer104and/or of the second charge-collecting layer108disposed against the side of the lateral faces116of the substrate102and not covered by the second layer of TCO122, and also covering the edges120of the first main face112. In the first embodiment described in relation toFIG.1, the coating122also covers:the first layer of TCO118and the first electrically conductive contacts124disposed against the first layer of TCO118, andthe second layer of TCO122and the second electrically conductive contacts126disposed against the second layer of TCO122. In this first embodiment, the non-reflective coating128forms an envelope surrounding the whole of the various elements of the cell100. Thus the non-reflective coating128also forms a moisture-barrier layer. The thickness of the non-reflective coating128is for example between 5 nm and 100 nm. Because, in this first embodiment, the non-reflective coating128is in contact with the first and second charge-collecting layers104,108and with the second layer of TCO122, the material of the non-reflective coating128is dielectric. The non-reflective coating128includes for example silicon nitride, for example in the form of SiN or in another stoichiometric form, and/or silicon oxide, for example in the form of SiO2or in another stoichiometric form. Furthermore, so that the non-reflective coating128has good optical properties, the material of the coating128can be selected so that it has a refractive index the value of which is between that of the refractive index of the first layer of TCO118and that of a material encapsulating the cell100, not visible onFIG.1, covering the coating128. In this first embodiment, the non-reflective coating128is for example deposited by ALD (“Atomic Layer Deposition”), which makes it possible to deposit the coating128on all the sides of the cell100. A photovoltaic cell100according to a second embodiment is described below in relation toFIG.2. Compared with the first embodiment previously described, the non-reflective coating128does not form an envelope surrounding all the various elements of the cell100. This is because, in this second embodiment, the non-reflective coating128covers:the second parts of the first charge-collecting layer104and/or of the second charge-collecting layer108disposed on the same side as the lateral faces116of the substrate102and not covered by the second layer of TCO122, andthe edges120of the first main face112, andthe first layer of TCO118and the first electrically conductive contacts124. Because, in this second embodiment, the non-reflective coating128is in contact with the first and second charge-collecting layers104,108and with the second layer of TCO122, the material of the non-reflective coating128is dielectric. In this second embodiment, the non-reflective coating128is for example deposited by PECVD (plasma enhanced chemical vapour deposition) or PVD (physical vapour deposition), with the cell100disposed on a support so that the second layer of TCO122is located on the same side as this support. A photovoltaic cell100according to a third embodiment is described below in relation toFIG.3. As in the second embodiment described above, the non-reflective coating128does not form an envelope surrounding all the various elements of the cell100. On the contrary, in this third embodiment, the non-reflective coating128covers only:the second parts of the first charge-collecting layer104disposed on the same side as the lateral faces116of the substrate102and the edges120of the first main face112, andthe first layer of TCO118and the first electrically conductive contacts124disposed against the first layer of TCO118. In this third embodiment, the non-reflective coating128is not in contact with the second layer of TCO122. The material of the non-reflective coating128can therefore be dielectric or electrically conductive. Such an electrically conductive material able to serve as a non-reflective coating128corresponds for example to a TCO such as ITO or to ZnO:Al (aluminium doped zinc oxide, or AZO). In this third embodiment, the non-reflective coating128is for example deposited by PECVD (plasma enhanced chemical vapour deposition) or PVD (physical vapour deposition), with the cell100disposed on a support so that the second layer of TCO122is located on the same side as this support, and by masking the second parts of the second charge-collecting layer108disposed on the same side as the lateral faces116of the substrate102and which are not covered by the second layer of TCO122. A photovoltaic cell100according to a fourth embodiment is described below in relation toFIG.4. As in the second and third embodiments described above, the non-reflective coating128does not form an envelope surrounding all the various elements of the cell100. On the contrary, in this fourth embodiment, the non-reflective coating128covers:the second parts of the first and second charge-collecting layers104,108disposed on the same side as the lateral faces116of the substrate102and not covered by the second layer of TCO122, andthe edges120of the first main face112. In this fourth embodiment, it is possible for the non-reflective coating128to be in contact with the second layer of TCO122. Thus, to avoid any risk of short-circuit, the material of the non-reflective coating128is preferably dielectric. In this fourth embodiment, the non-reflective coating128is for example deposited by PECVD (plasma enhanced chemical vapour deposition) or PVD (physical vapour deposition), with the cell100disposed on a support so that the second layer of TCO122is located on the same side as the support, and using an element masking, during this deposition, the first layer of TCO118. A photovoltaic cell100according to a fifth embodiment is described below in relation toFIG.5. In this fifth embodiment, the non-reflective coating128does not form an envelope surrounding all the various elements of the cell100, and covers only the parts of the first charge-collecting layer104disposed on the same side as the lateral faces116of the substrate102and the edges120of the first main face112. In this fifth embodiment, the non-reflective coating128is for example deposited by PECVD (plasma enhanced chemical vapour deposition) or PVD (physical vapour deposition), with the cell100disposed on a support so that the second layer of TCO122is located on the same side as this support, and using an element masking, during the deposition, the first layer of TCO118and the parts of the portions of the second charge-collecting layer108disposed on the same side as the lateral faces116of the substrate102and which are not covered by the second layer of TCO122. As in the third embodiment, the material of the non-reflective coating128may be dielectric or electrically conductive. A photovoltaic cell100according to a sixth embodiment is described below in relation toFIG.6. In this sixth embodiment, the non-reflective coating128does not form an envelope surrounding all the various elements of the cell100, and covers:the second parts of the first and second charge-collecting layers104,108disposed on the same side as the lateral faces116of the substrate102and the edges120of the first main face112, andthe second layer of TCO122and the second electrically conductive contacts126disposed against the second layer of TCO122. In this sixth embodiment, the non-reflective coating128is for example deposited by PECVD (plasma enhanced chemical vapour deposition) or PVD (physical vapour deposition). It is for example possible to deposit first of all the non-reflective coating128on the same side as the first main face112so that it covers only the parts of the first and second charge-collecting layers104,108disposed on the same side as the lateral faces116of the substrate102and the edges120of the first main face112, and then by implementing a second deposition on the same side as the second main face114in order to result in the configuration shown onFIG.6. Variants of the various embodiments described above can be envisaged. For example, considering the fourth embodiment described above it is possible for the non-reflective coating128to partially cover the first layer of TCO118and optionally some of the first electrically conductive contacts124. In the various example embodiments described above, the substrate102and the first charge-collecting layer104include n-doped semiconductor, and the second charge-collecting layer108includes p-doped semiconductor. In a variant, for the various embodiments described above, it is possible for the substrate102and the first charge-collecting layer104to include p-doped semiconductor, and for the second charge-collecting layer108to include n-doped semiconductor. In the various example embodiments described above, the passivation layers106,110and the charge-collecting layers104,108include amorphous semiconductor. In a variant, it is possible for these layers104,106,108and110to include microcrystalline or nanocrystalline semiconductor. In the various example embodiments described above, the cells100are of the inverse emitter type, i.e. the emitters of the cells (corresponding to the second charge-collecting layer108) are formed on the side of the cells100that is not intended to directly receive light radiation. In a variant, it is possible for the cells100to be of the standard emitter type, i.e. such that the emitters of the cells are formed on the side of the cells100intended to receive direct light radiation. In the various example embodiments described above, the cell100corresponds to a heterojunction cell formed by means of a crystalline semiconductor substrate and thin layers of amorphous (or microcrystalline or nanocrystalline) silicon deposited on this substrate. In a variant of all the embodiments described above, the cell100may correspond to a cell of the TOPCon type. In this case, the passivation layers106,110correspond to tunnel oxide layers comprising for example SixOyand the thickness of which is for example between 1 nm and 5 nm. In such a TOPCon cell, the first and second charge-collecting layers104,108include doped polycrystalline semiconductor (for example silicon) (first charge-collecting layer104n-doped and second charge-collecting layer p-doped108when the substrate102includes n-doped semiconductor). FIG.7shows another embodiment of the photovoltaic cell100. In this other embodiment, the cell100is of the tandem on semiconductor type, and advantageously with a perovskite on silicon (PK/Si) structure. The cell100according to this other embodiment includes the substrate102, the first and second passivation layers106,110and the first and second charge-collecting layers104,108that form a bottom cell130. The characteristics of the substrate102and the layers104,106,108and110(materials, thicknesses, deposition techniques used for producing them, etc.) are for example similar to those described above for a heterojunction cell100. The cell100according to this other embodiment also includes a top cell132disposed on a recombination layer134formed in advance on the bottom cell130. The recombination layer134includes for example TCO (ITO, AZO). The top cell132includes a layer of material with a perovskite structure136including for example CsxFA1-xPb(IyBr1-y)3, and the thickness of which is for example between 200 nm and 1 μm. The layer136is disposed between a first charge-collecting layer138, which includes for example an autoassembled monolayer 2PACz, MeO-2PACz or Me-4PACz as described in the document WO 2019/207029 A1, and the thickness of which is between 0.1 nm and 3 nm, and a second charge-collecting layer140including for example fullerene (═C60) and SnO2and the thickness of which is for example between 0.1 nm and 30 nm. The layers134,136,138and140are for example produced by the successive implementation of deposition steps on the bottom cell130. Other details of embodiment of such a cell are indicated in the document “Co-Evaporated Formamidinium Lead Iodide Based Perovskites with 1000 h Constant Stability for Fully Textured Monolithic Perovskite/Silicon Tandem Solar Cells” of Marcel Roß et al., Advanced Energy Materials, vol. 11, Issue 35, 2021. In the structure thus obtained, a main face of the bottom cell130(the one located on the side opposite to the top cell132) forms the second main face114, and a main face of the top cell132(the one located on the side opposite to the bottom cell130) forms the first main face112. As in the example embodiments described above, the cell100includes the first layer of TCO118disposed against a part of the first main face112(without covering the edges120), and the second layer of TCO122covering the whole of the second main face114and also covering at least first parts of the first and second charge-collecting layers104,108disposed on the lateral faces116of the substrate102. The cell100also includes the first electrically conductive contacts124disposed against the first layer of TCO118and the second electrically conductive contacts126disposed against the second layer of TCO122. Finally, the cell100includes a non-reflective coating128covering at least second parts of the first charge-collecting layer104and/or of the second charge-collecting layer108disposed against the side of the lateral faces116of the substrate102and not covered by the second layer of TCO122, and also covering the edges120of the first main face112. In the example embodiment shown onFIG.7, the coating128also covers:the first layer of TCO118and the first electrically conductive contacts124disposed against the first layer of TCO118, andthe second layer of TCO122and the second electrically conductive contacts126disposed against the second layer of TCO122. However, all the configurations described above in relation toFIGS.1to6can apply to the cell100of the tandem on semiconductor type. The various steps implemented for producing the cell100can be implemented collectively to simultaneously produce a plurality of photovoltaic cells. In the example embodiments described above, the non-reflective coating128is deposited on the cell100before the latter is electrically connected to other photovoltaic cells. In a variant, it is possible for the non-reflective coating128to be deposited on a plurality of photovoltaic cells100that are already electrically connected to one another. | 21,342 |
11862739 | DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS Hereinafter, a light-receiving device according to an embodiment of the present disclosure will be described. First Embodiment First, a light-receiving device according to a first embodiment of the present disclosure will be described with reference toFIGS.1A and1B. Additionally,FIG.1Billustrates a cross-section taken along a line a-a′ ofFIG.1A. This light-receiving device includes a plurality of light-receiving elements102which are arranged in a row on a main surface of a substrate101and a first reflection surface103and a second reflection surface104which extend in the arrangement direction with the row of the plurality of light-receiving elements102interposed therebetween and are formed on the substrate101. Further, an antireflective film105is formed on the back surface of the substrate101. Each light-receiving element102includes a first semiconductor layer121which is formed on the substrate101and is formed from a first conductive type semiconductor, a light absorbing layer122which is formed on the first semiconductor layer121and is formed from a semiconductor, and a second semiconductor layer123which is formed on the light absorbing layer122and is formed from a second conductive type semiconductor. Further, the light-receiving element102includes a first electrode124which is connected to the second semiconductor layer123and a second electrode125which is connected to the first semiconductor layer121. Further, in the light-receiving element102, a reflection layer formed by the first electrode124formed from a metal is disposed on the second semiconductor layer123. Further, the first electrode124may be formed on the second semiconductor layer123with a dielectric layer (not illustrated) interposed therebetween and the reflection layer can include these layers. The light-receiving element102is a so-called back-incident photodiode. For example, the substrate101is formed from InP, the first semiconductor layer121is formed from n-type InP, the light absorbing layer122is formed from InGaAs, and the second semiconductor layer123is formed from p-type InGaAs. In these cases, the first conductive type is n-type and the second conductive type is p-type. The light absorbing layer122and the second semiconductor layer123are patterned into a desired shape, a portion of the first semiconductor layer121is exposed in the planar direction, and the second electrode125is formed in the exposed region. For example, the light absorbing layer122and the second semiconductor layer123are formed into a cylindrical shape having a diameter of about 22 μm. Further, the first semiconductor layer121is formed into a cylindrical shape having a diameter of about 25 μm. Further, although not illustrated in the drawings, a lead-out wire is connected to each of the first electrode124and the second electrode125. Further, each of the first reflection surface103and the second reflection surface104includes an inclined surface forming one flat surface formed from the main surface of the substrate101on which the light-receiving element102is formed to the back surface side of the substrate101. Further, an angle formed between the main surface of the substrate101in the region where the light-receiving element102is formed and each of the first reflection surface103and the second reflection surface104is an obtuse angle. For example, this inclined surface can be used as the first reflection surface103by forming a V-groove106extending in the arrangement direction of the plurality of light-receiving elements102in the substrate101. Similarly, this inclined surface can be used as the second reflection surface104by forming a V-groove107extending in the arrangement direction of the plurality of light-receiving elements102in the substrate101. The V-groove106and the V-groove107are formed in parallel in the arrangement direction with the plurality of arranged light-receiving elements102interposed therebetween. For example, the substrate101is formed from InP, and a surface orientation of the main surface is (001) or is equivalent thereto, thereby the V-groove can be formed. First, a resist pattern having a rectangular opening in a plan view at positions where the V-groove106and the V-groove107of the substrate101are formed is formed on the substrate101by a known photolithography technique. Next, this resist pattern is used as a mask, and wet etching is performed using an etching solution such as a mixture of bromine and methanol. This etching is so-called crystal anisotropic etching, and a surface on the (111)A plane, which is hard to be etched, appears as the etching progresses, so that an inclined surface is formed. An angle of this inclined surface is about 54.7 with respect to the main surface of the substrate101on the (001) plane. Each of the first reflection surface103and the second reflection surface104formed in this way has an angle of about 125.3 with respect to the main surface of the substrate101in a region where the light-receiving element102is formed. For example, the above-described processing may be performed so that the extension direction of the V-groove106and the V-groove107is parallel to the orientation flat of the substrate101formed from InP. Signal light151which passes through the antireflective film105and is incident from the back surface of the substrate101is reflected by the first reflection surface103, passes through the light absorbing layer122, and is reflected by the reflection layer formed by the first electrode124. The signal light151which is reflected by this reflection layer passes through the light absorbing layer122again. Thus, in the first embodiment, for example, when signal light having a wavelength of 1.55 μm is incident on the light absorbing layer122having a thickness of 400 nm, the coupling efficiency which is ideally about 40% in the case of the vertical incidence can be improved to about 80%. Additionally, because the coupling efficiency is less than 100%, the signal light151which cannot be absorbed is emitted from the light absorbing layer122to the outside. The light which is not absorbed by the light absorbing layer122but passes therethrough is reflected by the second reflection surface104and is emitted from the back surface of the substrate101to pass through the antireflective film105. In this way, according to the first embodiment, because the light which is not absorbed by the light absorbing layer122but passes through the light absorbing layer122is emitted from the substrate back surface, the light is not incident on the other light-receiving elements102and does not cause crosstalk. The light-receiving device according to the first embodiment and an optical component that emits light incident from the side of the substrate101toward the first reflection surface103are assembled and used as a light receiver. The optical component is disposed at a position other than an optical path of light which is incident from the side of the substrate101toward the first reflection surface103, is reflected by the first reflection surface103, passes through the light absorbing layer122, is reflected by the reflection layer, passes through the light absorbing layer122again, is then reflected by the second reflection surface104, and is emitted from the side of the substrate101. In the light receiver, for example, as illustrated inFIG.2, a planar silica optical waveguide202which is an optical component fixed onto a pedestal201, an optical system203which is an optical component formed by a lens array, and the like are assembled to the light-receiving device according to the first embodiment. The signal light151which is emitted from the planar silica optical waveguide202, passes through the optical system203, and is incident from the side of the substrate101toward the first reflection surface103is received by the light-receiving device. The signal light151is incident from the back surface side of the substrate101. The signal light151which is received by the light-receiving element102and is not absorbed thereto is emitted from the back surface side of the substrate101. In such a light receiver, the light-receiving device including the substrate101on which the plurality of light-receiving elements102are formed is, for example, flip-chip mounted on a subcarrier (not illustrated), so that a photodiode chip on carrier (PDCoC) is formed. The planar silica optical waveguide202and the optical system203which are optical components are not arranged on an optical path of light152emitted from the light-receiving device. Incidentally, when light is reflected by the first reflection surface103and is incident on the light absorbing layer122at an angle with respect to the flat surface of the substrate101, the light receiving sensitivity varies according to the ratio of the TM mode component and the TE mode component of the signal light151. In the case where the sensitivity is a quality determination criterion, the yield may be reduced. However, in the case of light emitted from a waveguide type optical filter such as that described in Non Patent Literature 1, the ratio of the modes of the polarization components described above can be controlled by the structure of the exit end of the waveguide type optical filter and thus the above-described problems do not arise. As described above, according to the first embodiment, because the first reflection surface103and the second reflection surface104are formed on the substrate101to extend in the arrangement direction with the row of the plurality of light-receiving elements102interposed therebetween, crosstalk between the arranged light-receiving elements102can be suppressed. Second Embodiment Next, a light-receiving device according to a second embodiment of the present disclosure will be described with reference toFIGS.3A,3B, and3C.FIG.3Billustrates a cross-section taken along a line b-b′ ofFIG.3AandFIG.3Cillustrates a cross-section taken along a line c-c′ ofFIG.3A. This light-receiving device includes a plurality of light-receiving elements102which are arranged in a row on a main surface of a substrate301, a reflection surface303, and a reverse mesa groove307. The reflection surface ss303extends in the arrangement direction of the row of the plurality of light-receiving elements102and is formed on the substrate301. Each reverse mesa groove307is formed in the substrate301between the plurality of light-receiving elements102which are adjacent to each other in the arrangement direction. The light-receiving element102is the same as that of the first embodiment. Further, an antireflective film105is formed on a back surface of the substrate301as in the first embodiment. For example, the substrate301is formed from InP as in the first embodiment. Further, the reflection surface303includes an inclined surface forming one flat surface formed from the main surface of the substrate301where the light-receiving element102is formed to the back surface side of the substrate301. Further, an angle formed between the main surface of the substrate301in a region where the light-receiving element102is formed and the reflection surface303is an obtuse angle. For example, this inclined surface can be used as the reflection surface303by forming a V-groove306extending in the arrangement direction of the plurality of light-receiving elements102in the substrate301. The V-groove306is formed in parallel to the arrangement direction of the plurality of light-receiving elements102. A method of forming the V-groove306is the same as those of the V-groove106and the V-groove107of the first embodiment described above. Further, a cross-section perpendicular to the arrangement direction of the reverse mesa groove307has a shape that becomes wider toward a bottom surface of the reverse mesa groove307. The reverse mesa grooves307and the V-groove306can be formed simultaneously. A side surface304of the reverse mesa groove307extends in a direction perpendicular to the arrangement direction of the plurality of light-receiving elements102. Thus, the extension direction of the side surface304is orthogonal to the extension direction of the reflection surface303. Further, an angle formed between the main surface of the substrate101in a region where the light-receiving element102is formed and the side surface304adjacent to the light-receiving element102is an acute angle. For example, the substrate301is formed from InP, and a surface orientation of a main surface is (001) or is equivalent thereto, thereby the V-groove306is formed as in the first embodiment, and the reverse mesa groove307can be formed simultaneously. For example, a resist pattern having a rectangular opening in a plan view at positions where the V-groove106and the reverse mesa grooves307of the substrate301are formed is formed on the substrate301by a known photolithography technique. Next, this resist pattern is used as a mask, and wet etching is performed using an etching solution such as a mixture of bromine and methanol. This etching is crystalline anisotropic etching and a surface on the (111)A plane, which is hard to be etched, appears as the etching progresses, so that an inclined surface is formed. An angle of this inclined surface is about 54.7 with respect to the main surface of the substrate101on the (001) plane. An angle formed between the first reflection surface103formed in this way and the main surface of the substrate101in a region where the light-receiving element102is formed is about 125.3. An angle formed between the side surface304and the main surface of the substrate101in a region where adjacent light-receiving element102is formed is about 54.7. For example, the above-described processing may be performed so that the extension direction of the V-groove106is parallel to the orientation flat of the substrate101formed from InP and the extension direction of the reverse mesa groove307is perpendicular. Because the reverse mesa grooves307and the V-groove106can be simultaneously formed under the same conditions, and a new process is not required for forming the reverse mesa grooves307, the cost does not increase. In the second embodiment, the signal light151which passes through the antireflective film105and is incident from the back surface of the substrate301is reflected by the reflection surface303, passes through the light absorbing layer122, and is reflected by the reflection layer formed by the first electrode124. The signal light151which is reflected by this reflection layer passes through the light absorbing layer122again. Thus, also in the second embodiment, for example, when signal light having a wavelength of 1.55 μm is incident on the light absorbing layer122having a thickness of 400 nm, the coupling efficiency which is ideally about 40% in the case of vertical incidence can be improved to about 80%. Further, because the coupling efficiency is less than 100%, the signal light151which is not absorbed is emitted from the light absorbing layer122to the outside. The light which is not absorbed by the light absorbing layer122but passes therethrough is emitted from an end surface301aof the substrate301formed in parallel to the arrangement direction of the plurality of light-receiving elements102. The end surface301acan include, for example, a side surface formed by cutting the substrate301. The light emitted from the end surface301ais not incident on the other light-receiving elements102and does not cause crosstalk. Here, a part of the signal light151reaching the end surface301adoes not pass through the end surface301abut is reflected thereby. There is a probability that this reflected signal light151will be incident on the other light-receiving elements102and cause crosstalk. In contrast, because each reverse mesa groove307is provided in the second embodiment, signal light which is reflected by the end surface301aand is directed toward the other light-receiving elements102is reflected by the side surface304and is emitted from the back surface of the substrate301. Therefore, the signal light is not incident on the other light-receiving elements102and does not cause crosstalk. As described above, according to the second embodiment, the reflection surface303is formed on the substrate301to extend in the arrangement direction of the row of the plurality of light-receiving elements102, and each reverse mesa groove307is formed in the substrate301between the light-receiving elements102adjacent to each other in the arrangement direction. Thus, it is possible to suppress crosstalk between the arranged light-receiving elements102. The light-receiving device according to the present disclosure and the optical component can be assembled and used as a light receiver as illustrated inFIG.4. In the light receiver, the signal light151which is emitted from the planar silica optical waveguide202fixed onto the pedestal201and passes through the optical system203aformed on the back surface of the substrate101is received by the light-receiving device. In this example, the optical system203acan include a lens shape formed on the back surface of the substrate101. In this case, the optical system203acan be regarded as a part of the light-receiving device and can be regarded as an optical component assembled to the light-receiving device. In this case, the optical component is also disposed at a position other than an optical path of the light152emitted from the light-receiving device. Further, the light-receiving element102can include a well-known avalanche photodiode. As described above, according to the present disclosure, because the reflection surfaces which extend in the arrangement direction of the plurality of light-receiving elements are formed on the substrate, it is possible to suppress crosstalk between the arranged light-receiving elements. The present disclosure is not limited to the embodiments described above, and it is obvious that many modifications and combinations can be implemented by a person having ordinary knowledge in the field within the technical spirit of the present disclosure. REFERENCE SIGNS LIST 101Substrate102Light-receiving element103First reflection surface104Second reflection surface105Antireflective film106V-groove107V-groove151Signal light. | 18,314 |
11862740 | DETAILED DESCRIPTION OF THE EMBODIMENTS Preferred embodiments of the present invention are specifically described in detail with the accompanying drawings below. <Illuminance Sensor A1> FIG.1shows an illuminance sensor according to a first embodiment of the present invention, that is, an illuminance sensor A1. The illuminance sensor A1includes a first light receiving portion11, a second light receiving portion12, an optical region30, and a difference detecting portion60. The first light receiving portion11and the second light receiving portion12are, for example, photodiodes manufactured and incorporated into the same integrated circuit (IC), and are located in a same plane serving as the main surface of the IC100. The optical region30is disposed opposite to the first light receiving portion11and the second light receiving portion12. The optical region30has a first optical region30A disposed corresponding to the first light receiving portion11, and a second optical region30B disposed corresponding to the second light receiving portion12. The optical region30(the first optical region30A and the second optical region includes a first linear polarization plate31, a first quarter-wave plate32, a second quarter-wave plate33, and a second linear polarization plate34. The first linear polarization plate31, the first quarter-wave plate32, the second quarter-wave plate33, and the second linear polarization plate34are disposed sequentially in an order that the first linear polarization plate31is farthest from the first light receiving portion11and the second light receiving portion12. The first linear polarization plate31, the first quarter-wave plate32, the second quarter-wave plate33, and the second linear polarization plate34may be closely deposited on one another, or may be interposed with an air layer or a simple transparent layer. In this embodiment, a color filter layer20in, for example, red, green or blue, is interposed between the first light receiving portion11and the second light receiving portion12and the second linear polarization plate34. Both the first linear polarization plate31and the second linear polarization plate34are similarly disposed throughout the first optical region30A and the second optical region30B (a region corresponding to the first light receiving portion11and a region corresponding to the second light receiving portion12). In this embodiment, a polarization direction (a first polarization direction) of the first linear polarization plate31is the same with a polarization direction (a second polarization direction) of the second linear polarization plate34, and is represented by slant shading lines of the same direction inFIG.1. Further, at least any one of the first linear polarization plate31and second linear polarization plate34is implemented by a polarization plate in which an ineffective band includes at least a portion of an infrared band. Herein, an ineffective band refers to a light wavelength band that does not effectively perform polarization. That is to say, at least any one of the first linear polarization plate31and second linear polarization plate34is implemented by, for example, a polarization plate of the following characteristics: the polarization plate has a polarization function for an entire visible band, and does not polarize but allows passing through of an entire infrared band. For example, a polarization plate “MCPR-4” sold by MeCan Imaging Inc. may be used as a linear polarization plate of the foregoing characteristics. Further, a boundary between an effective band and the ineffective band of the ineffective band of the polarization function of the linear polarization plate in which the ineffective band includes at least a portion of an infrared band does not necessarily coincide with a boundary between a visible band and an infrared band, and may be closer to the side of the visible band or the infrared band. The foregoing feature also applies to the description below. The first quarter-wave plate32is located closely to a lower layer of the first linear polarization plate31. In the entire of the first optical region30A and the second optical region30B (a region corresponding to the first light receiving portion11and a region corresponding to the second light receiving portion12), a slow axis of the first quarter-wave plate32has a relation of +45° or −45° in regard to a polarization direction (a first polarization direction) of the first linear polarization plate31. In this embodiment, the slow axis of the first quarter-wave plate32has a relation of +45° in regard to the first polarization direction, and is denoted by “+45°” inFIG.1. The second quarter-wave plate33is located closely to a lower layer of the first quarter-wave plate32. The second quarter-wave plate33has a first portion331in the first optical region30A and a second portion332in the second optical region30B. The relation of a slow axis of the first portion331in regard a polarization direction (a second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45° or −45°. In this embodiment, the polarization direction (the first polarization direction) of the first linear polarization plate33is the same with the polarization direction (the second polarization direction) of the second linear polarization plate34, and thus the slow axis of the first portion331also has a relation of +45° in regard to the first polarization direction, is denoted as “+45°” inFIG.1. On the other hand, a relation of a slow axis of the second portion332in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. In this embodiment, the slow axis of the second portion332has a relation of −45° in regard to the second polarization direction. Further, in this embodiment, the polarization direction (the first polarization direction) of the first linear polarization plate31is the same with the polarization direction (the second polarization direction) of the second linear polarization plate34, and thus the slow axis of the second portion332also has a relation of −45° in regard to the first polarization direction, and is denoted by “−45°” inFIG.1. The difference detecting portion60obtains a difference between an output of the first light receiving portion11and an output of the second light receiving portion12. The different detecting portion60may be implemented by, for example, a differential amplifier such as an operational amplifier. Next, the functions of the illuminance sensor A1shown inFIG.1are described individually below, for when the ineffective bands of both the first linear polarization plate31and the second linear polarization plate34include the infrared band, when the ineffective band of only the first linear polarization plate31between the first linear polarization plate31and the second linear polarization plate34includes the infrared band, and when the ineffective band of only the second linear polarization plate34between the first linear polarization plate31and the second linear polarization plate34includes the infrared band. [When the Ineffective Bands of Both the First Linear Polarization Plate31and the Second Linear Polarization Plate34Include the Infrared Band] Neither of the first linear polarization plate31and the second linear polarization plate34has a polarization function for infrared light, and thus both of the first light receiving portion11and the second light receiving portion12are capable of receiving infrared light. On the other hand, regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331)(+45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate)(+45°. As described above, the relation of the slow axis of the second portion332)(−45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A1is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. [When the Ineffective Band of Only the First Linear Polarization Plate31Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the first linear polarization plate31does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. Infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the first linear polarization plate31likewise does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. The infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the second light receiving portion12. That is to say, regarding infrared light, the first light receiving portion11and the second light receiving portion12similarly receive the infrared light. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331)(+45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate)(+45°. As described above, the relation of the slow axis of the second portion332)(−45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A1is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. [When the Ineffective Band of Only the Second Linear Polarization Plate34Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the infrared light is polarized at the first linear polarization plate31, and the direction of the polarized light changes by 90° in a period of passing through the first quarter-wave plate32and the second quarter-wave plate33(the first portion331). The second linear polarization plate34does not have a polarization function for infrared light, and thus the polarized light changed by 90° in direction directly arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the infrared light is also polarized at the first linear polarization plate31, and arrives at the second linear polarization plate34in a manner that the polarization direction thereof is not changed at timings of passing through the first quarter-wave plate32and the second quarter-wave plate33(the second portion332). The second linear polarization plate34does not have a polarization function for infrared light, and thus the polarized light generated by the first linear polarization plate31directly arrives at the second light receiving portion12. That is to say, regarding infrared light, the first light receiving portion11and the second light receiving portion12receive the infrared light by the same light amount for polarized light of a phase difference of 90°. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331)(+45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the second portion332)(−45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A1is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. <Illuminance Sensor A2> FIG.2shows an illuminance sensor A2as a variation example of the illuminance sensor A1. In the illuminance sensor A2, the arrangements and configurations of the first quarter-wave plate32and the second quarter-wave plate33are different from those in the illuminance sensor A1inFIG.1, and the remaining configuration details are identical to those in the illuminance sensor A1inFIG.1. That is to say, in the illuminance sensor A1inFIG.1, the first quarter-wave plate32is set to “+45°” in the entire of the first optical region30A and the second optical region30B (the region corresponding to the first light receiving portion11and the region corresponding to the second light receiving portion12). Regarding the second quarter-wave plate33, the first portion331in the first optical region30A is set to “+45°”, and the second portion332in the second optical region30B is set to “−45°”. On the other hand, in the illuminance sensor A2inFIG.2, the second quarter-wave plate33is set to “+45°” in the entire of the first optical region30A and the second optical region30B. Regarding the first quarter-wave plate32, the first portion321in the first optical region30A is set to “+45°”, and the second portion322in the second optical region30B is set to “−45°”. That is to say, the slow axis of the first portion321of the first quarter-wave plate32has a relation of +45° in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, and the relation of the slow axis of the second portion322of the first quarter-wave plate32to the first polarization direction is −45° that is opposite in sign to the relation of the first portion321. The relation of the slow axis of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first portion321in regard to the first polarization direction, that is, +45°. On the other hand, the relation of the slow axis of the second quarter-wave plate33in regard to the second polarization direction is +45° that is opposite in sign to the relation of the slow axis of the second portion322in regard to the first polarization relation)(−45°. Further, the functions of the illuminance sensor A2shown inFIG.2are described individually below, for when the ineffective bands of both the first linear polarization plate31and the second linear polarization plate34include the infrared band, when the ineffective band of only the first linear polarization plate31between the first linear polarization plate31and the second linear polarization plate34includes the infrared band, and when the ineffective band of only the second linear polarization plate34between the first linear polarization plate31and the second linear polarization plate34includes the infrared band. [When the Ineffective Bands of Both the First Linear Polarization Plate31and the Second Linear Polarization Plate34Include the Infrared Band] Neither of the first linear polarization plate31and the second linear polarization plate34has a polarization function for infrared light, and thus both of the first light receiving portion11and the second light receiving portion12are capable of receiving infrared light. On the other hand, regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first portion321)(+45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first portion321in regard to the first polarization direction, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first portion321of the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving region12), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the second portion322)(−45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the second polarization direction is +45° that is opposite in sign to the relation of the slow axis of the second portion322in regard to the first polarization direction)(−45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the second portion322of the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A2is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. [When the Ineffective Band of Only the First Linear Polarization Plate31Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the first linear polarization plate31does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. Infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the first linear polarization plate31likewise does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. The infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the second light receiving portion12. Regarding infrared light, the first light receiving portion11and the second light receiving portion12similarly receive the infrared light. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first portion321)(+45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first portion321in regard to the first polarization direction, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first portion321of the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving region12), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the second portion322)(−45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the second polarization direction is +45° that is opposite in sign to the relation of the slow axis of the second portion322in regard to the first polarization direction)(−45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the second portion322of the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A2is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. [When the Ineffective Band of Only the Second Linear Polarization Plate34Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the infrared light is polarized at the first linear polarization plate31, and the polarization direction thereof changes by 90° in a period of passing through the first quarter-wave plate32(the first portion321) and the second quarter-wave plate33. The second linear polarization plate34does not have a polarization function for infrared light, and thus the polarized light changed by 90° in direction directly arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the infrared light is polarized at the first linear polarization plate31, and arrives the second linear polarization plate34without changing in direction at timings of passing through the first quarter-wave plate32(the second portion322) and the second quarter-wave plate33. The second linear polarization plate34does not have a polarization function for infrared light, and thus the polarized light generated by the first linear polarization plate31directly arrives at the second light receiving portion12. That is to say, regarding infrared light, the first light receiving portion11and the second light receiving portion12receive the infrared light by the same light amount for polarized light of a phase difference of 90°. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first portion321)(+45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first portion321in regard to the first polarization direction, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first portion321of the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the second portion322)(−45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the second polarization direction is +45° that is opposite in sign to the relation of the slow axis of the second portion322in regard to the first polarization direction)(−45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the second portion322of the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A2is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. <Illuminance Sensor A3> FIG.3shows an illuminance sensor A3as an illuminance sensor according to a second embodiment of the present invention. Compared to the illuminance sensor A1inFIG.1, the illuminance sensor A3differs in terms of the relation of the polarization directions of the first linear polarization plate31and the second linear polarization plate34, and the arrangements and configurations of the first quarter-wave plate32and the second quarter-wave plate33, and the remaining configuration details are identical to those in the illuminance sensor A1inFIG.1. That is to say, in the illuminance sensor A3inFIG.3, the polarization direction (the first polarization direction) of the first linear polarization plate31differs from the polarization direction (the second polarization direction) of the second linear polarization plate34by 90°. InFIG.3, slant shading lines in different directions are used for representation. The first quarter-wave plate32is set to “+45°” in the entire of the first optical region30A and the second optical region30B (the region corresponding to the first light receiving region11and the region corresponding to the second light receiving region12). Regarding the second quarter-wave plate33, the first portion331in the first optical region30A is set to “−45°”, and the second portion332in the second optical region30B is set to “+45°”. That is to say, the slow axis of the first quarter-wave plate32has a relation of +45° in regard to the polarization direction (the first polarization) of the first linear polarization plate32. The slow axis of the first portion331of the second quarter-wave plate33has a relation of −45° in regard to the first polarization direction. In this embodiment, the polarization direction (the first polarization direction) of the first linear polarization plate31differs from the polarization direction (the second polarization direction) of the second linear polarization plate34by 90°, and hence the slow axis of the first portion331of the second quarter-wave plate33has a relation of +45° in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34. Therefore, the relation of the slow axis of the first portion331in regard to the polarization (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45°. On the other hand, the slow axis of the second portion332of the second quarter-wave plate33has a relation of +45° in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. The polarization direction (the first polarization direction) of the first linear polarization plate31differs from the polarization direction (the second polarization direction) of the second linear polarization direction34by 90°, and hence the slow axis of the second portion332of the second quarter-wave plate33has a relation of −45° in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34. Therefore, the relation of the slow axis of the first portion331in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Next, functions of the illuminance sensor A3shown inFIG.3are described individually below, for when the ineffective bands of both the first linear polarization plate31and the second linear polarization plate34include the infrared band, when the ineffective band of only the first linear polarization plate31between the first linear polarization plate31and the second linear polarization plate34includes the infrared band, and when the ineffective band of only the second linear polarization plate34between the first linear polarization plate31and the second linear polarization plate34includes the infrared band. [When the Ineffective Bands of Both the First Linear Polarization Plate31and the Second Linear Polarization Plate34Include the Infrared Band] Neither of the first linear polarization plate31and the second linear polarization plate34has a polarization function for infrared light, and thus both of the first light receiving portion11and the second light receiving portion12are capable of receiving infrared light. On the other hand, regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), linearly polarized light passing through the first polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the second portion332of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A3is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. [When the Ineffective Band of Only the First Linear Polarization Plate31Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the first linear polarization plate31does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. Infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the first linear polarization plate31likewise does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. The infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the second light receiving portion12. Regarding infrared light, the first light receiving portion11and the second light receiving portion12similarly receive the infrared light. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the second portion332of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A3is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. [When the Ineffective Band of Only the Second Linear Polarization Plate34Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the infrared light is polarized at the first linear polarization plate31, and arrives at the second linear polarization plate34in a manner that the polarization direction thereof is not changed at timings of passing through the first quarter-wave plate32and the second quarter-wave plate33(the first portion331). The second polarization plate34does not have a polarization function for infrared light, and thus polarized light generated by the first linear polarization plate31directly arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the infrared light is polarized at the first linear polarization plate31, and the polarization direction thereof changes by 90° at timings in a period of passing through the first quarter-wave plate32and the second quarter-wave plate33(the second portion332). The second polarization plate34does not have a polarization function for infrared light, and thus the foregoing polarized light changed by 90° directly arrives at the second light receiving portion12. That is to say, regarding infrared light, the first light receiving portion11and the second light receiving portion12receive the infrared light by the same light amount for polarized light of a phase difference of 90°. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate)(+45°. As described above, the relation of the slow axis of the second portion332of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A3is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. <Illuminance Sensor A4> FIG.4shows an illuminance sensor A4as a variation example of the illuminance sensor A3. In the illuminance sensor A4, the arrangements and configurations of the first quarter-wave plate32and the second quarter-wave plate33are different from those in the illuminance sensor A3inFIG.3, and the remaining configuration details are identical to those in the illuminance sensor A3inFIG.3. That is to say, in the illuminance sensor A3inFIG.3, the first quarter-wave plate32is set as “+45°” in the entire of the first optical region30A and the optical region30B (a region corresponding to the first receiving portion11and a region corresponding to the second light receiving portion12). Regarding the second quarter-wave plate33, the first portion331in the first optical region30A is set to “−45°”, and the second portion332in the second optical region30B is set to “+45°”. On the other hand, in the illuminance sensor A4inFIG.4, the second quarter-wave plate33is set to “+45°” in the entire of the first optical region30A and the second optical region30B. Regarding the first quarter-wave plate32, the first portion321in the first optical region30A is set to “−45°”, and the second portion322in the second optical region30B is set to “+45°”. That is to say, the slow axis of the first portion321of the first quarter-wave plate32has a relation of −45° in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, and the relation of the slow axis of the second portion322of the first quarter-wave plate32in regard to the first polarization direction is +45° that is opposite in sign to the relation of the first portion321. The slow axis of the second quarter-plate33has a relation of +45° in regard to the first polarization direction. In this embodiment, similar to the illuminance sensor A3inFIG.3, the polarization direction (the first polarization direction) of the first linear polarization plate31differs from the polarization direction (the second polarization direction) of the second linear polarization plate34by 90°, and thus the slow axis of the second quarter-wave plate33has a relation of −45° in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34. Therefore, the relation of the slow axis of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first portion321of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, −45°. On the other hand, the relation of the slow axis of the second quarter-wave plate33in regard to the second polarization direction is −45° that is opposite in sign to the relation)(+45° of the slow axis of the second portion322of the first quarter-wave plate32in regard to the first polarization direction. Next, the functions of the illuminance sensor A4shown inFIG.4are described individually below, for when the ineffective bands of both the first linear polarization plate31and the second linear polarization plate34include the infrared band, when the ineffective band of only the first linear polarization plate31between the first linear polarization plate31and the second linear polarization plate34includes the infrared band, and when the ineffective band of only the second linear polarization plate34between the first linear polarization plate31and the second linear polarization plate34includes the infrared band. [When the Ineffective Bands of Both the First Linear Polarization Plate31and the Second Linear Polarization Plate34Include the Infrared Band] Neither of the first linear polarization plate31and the second linear polarization plate34has a polarization function for infrared light, and thus both of the first light receiving portion11and the second light receiving portion12are capable of receiving infrared light. On the other hand, regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first portion321)(−45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first portion321in regard to the first polarization direction, that is, −45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first portion321of the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the second portion322)(+45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the second polarization direction is −45° that is opposite in sign to the relation)(+45° of the slow axis of the second portion322in regard to the first polarization direction. Therefore, the circularly polarized light formed by the first linear polarization plate31and the second portion322of the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A4is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. [When the Ineffective Band of Only the First Linear Polarization Plate31Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the first linear polarization plate31does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. Infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the first linear polarization plate31likewise does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. The infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the second light receiving portion12. Regarding infrared light, the first light receiving portion11and the second light receiving portion12similarly receive the infrared light. On the other hand, regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first portion321)(−45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first portion321in regard to the first polarization direction, that is, −45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first portion321of the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the second portion322)(+45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the second polarization direction is −45° that is opposite in sign to the relation)(+45° of the slow axis of the second portion322in regard to the first polarization direction. Therefore, the circularly polarized light formed by the first linear polarization plate31and the second portion322of the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A4is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. [When the Ineffective Band of Only the Second Linear Polarization Plate34Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the infrared light is polarized at the first linear polarization plate31, and arrives at the second linear polarization plate34in a manner that the polarization direction thereof is not changed at timings of passing through the first quarter-wave plate32(the first portion321) and the second quarter-wave plate33. The second polarization plate34does not have a polarization function for infrared light, and thus polarized light generated by the first linear polarization plate31directly arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the infrared light is polarized at the first linear polarization plate31, and the polarization direction thereof changes by 90° in a period of passing through the first quarter-wave plate32(the second portion322) and the second quarter-wave plate33. The second polarization plate34does not have a polarization function for infrared light, and thus the foregoing polarized light changed by 90° directly arrives at the second light receiving portion12. That is to say, regarding infrared light, the first light receiving portion11and the second light receiving portion12receive the infrared light by the same light amount for polarized light of a phase difference of 90°. On the other hand, regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first portion321)(−45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first portion321in regard to the first polarization direction, that is, −45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first portion321of the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11receives only infrared light. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the second portion322)(+45° of the first quarter-wave plate32. As described above, the relation of the slow axis of the second quarter-wave plate33in regard to the second polarization direction is −45° that is opposite in sign to the relation)(+45° of the slow axis of the second portion322in regard to the first polarization direction. Therefore, the circularly polarized light formed by the first linear polarization plate31and the second portion322of the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives both infrared light and visible light. The difference detecting portion60eliminates infrared light components from light receiving amounts of the first light receiving portion11and the second light receiving portion12according to the difference between the outputs of the two light receiving portions11and12, and outputs a light receiving amount of visible light as a signal. Therefore, the illuminance sensor A4is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. <Illuminance Sensor A5> FIG.5shows an illuminance sensor according to a third embodiment of the present invention. The illuminance sensor A5shown in the drawing primary differs from the illuminance sensors A1to A4by the configurations of the first light receiving portion11and the second light receiving portion12and the configuration of the color filter layer20. Further, inFIG.5, only the second linear polarization plate34in the optical region30(the first optical region30A and the second optical region30B) is depicted, and the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33are omitted. In the illuminance sensor A5of this embodiment, the first light receiving portion11and the second light receiving portion12includes a plurality of light receiving elements, respectively. More specifically, the first light receiving portion11includes a first light receiving element111, a second light receiving element112and a third light receiving element113. The second light receiving portion12includes a first light receiving element121, a second light receiving element122and a third light receiving element123. In this embodiment, a protective film19is formed on an IC100, and the color filter layer20is formed on the protective film19. The color filter layer20includes a first filter portion20A disposed corresponding to the first light receiving portion11, and a second filter portion20B disposed corresponding to the second light receiving portion12. The first filter portion20A includes a first red light filter21r, a first green light filter20gand a first blue light filter21b. The second filter portion20B includes a second red filter22r, a second green filter22gand a second blue filter22b. The first red filter21rand the second red filter22rselectively attenuate light in wavelength regions of blue light and green light of a visible band, such that light in wavelength regions of red light and infrared light selectively pass through. The first red filter21rcovers the first light receiving element111in a direction (to be referred to as a z direction) orthogonal to light receiving surfaces of the first to third light receiving elements111to113or the first to third light receiving elements121to123. The second red filter22rcovers the first light receiving element121in the z direction. In the drawings, the first red filter21rand the second red filter22rare denoted by the letter “R”. The first green filter21band the second green filter22gselectively attenuate light in wavelength regions of red light and blue light of a visible band, such that light in wavelength regions of green light and infrared light selectively pass through. The first green filter21gcovers the second light receiving element112in the z direction. The second green filter22gcovers the second light receiving element122in the z direction. In the drawings, the first green filter21gand the second green filter22gare denoted by the letter “G”. The first blue filter21band the second blue filter22bselectively attenuate light in wavelength regions of red light and green light of a visible band, such that light in wavelength regions of blue light and infrared light selectively pass through. The first blue filter21bcovers the third light receiving element113in the z direction. The second blue filter22bcovers the third light receiving element123in the z direction. In the drawings, the first blue filter21band the second blue filter22bare denoted by the letter “B”. The filters21r,21g,21b,22r,22gand22bof the different colors may consist of, for example, color resist or gelatin films with pigments as a base. Further, inFIG.5, thicknesses of the filters21r,21g,21b,22r,22gand22bof the different colors are substantially even. However, transmittances are different depending on different pigments of the filters of the different colors, and thus the thicknesses of the filters21r,21g,21b,22r,22gand22bof the different colors may be designed to be different according to characteristics of the filters of the different colors. In this embodiment, the color filter layer20includes a protective film23. The protective film23is disposed on the entire of the first filter portion20A and the second filter portion20B, the first filter portion20A covers the entire of the first red filter21r, the first green filter20gand the first blue filter21b, and the second filter portion20B covers the entire of the second red filter22r, the second green filter22gand the second blue filter22b. The protective film23includes, for example, a transparent resin such as titanium oxide (TiO2). The illuminance sensor A5of this embodiment includes three difference detecting portions60. One of the difference detecting portions60obtains a difference between outputs of the first light receiving portion111and the first light receiving element121. Another of the difference detecting portions60obtains a difference between outputs of the second light receiving portion112and the second light receiving element122. The remaining one of the difference detecting portions60obtains a difference between outputs of the third light receiving portion113and the third light receiving element123. Further, inFIG.5, regarding the optical region30(the first optical region30A and the second optical region30B), description other than the second linear polarization plate34is omitted. The configurations of the first optical region30A and the second optical region30B (the first linear polarization plate31, the first quarter-wave plate32, the second quarter-wave plate33and the second linear polarization plate34) may also be implemented by the configurations of those in any one of the illuminance sensors A1to A4. Regardless of by which of the configurations of the illuminance sensors A1to A4the first optical region30A and the second optical region30B are implemented, the first light receiving portion11(the first light receiving element111, the second light receiving element112and the third light receiving element113) receives only infrared light, and the second light receiving portion12(the first light receiving element121, the second light receiving element122and the third light receiving element123) receives both infrared light and visible light. The difference detecting portion60eliminates the infrared components from the light receiving amounts of the first light receiving portion11and the second light receiving portion12by means of obtaining the difference between the two light receiving portions11and12, and outputs the light receiving amount of visible light as a signal. Further, in this embodiment, the first light receiving element111, the second light receiving element112and the third light receiving element113of the first light receiving portion11are covered by the first red filter21r, the first green filter21gand the first blue filter21b, respectively. Further, the first light receiving element121, the second light receiving element122and the third light receiving element123of the second light receiving portion12are covered by the second red filter22r, the second green filter22gand the second blue filter22b, respectively. Thus, the first light receiving portion11and the second light receiving portion12are capable of receiving a visible band in a manner of splitting the light into wavelength regions into red, green, and blue. Therefore, the illuminance sensor A5of this embodiment is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light, and performing illuminance detection of each of red, green and blue. <Illuminance Sensor A6> FIG.6andFIG.7show an illuminance sensor according to a fourth embodiment of the present invention. The illuminance sensor A6shown in the drawings includes a plurality of first light receiving portions11and a plurality of second light receiving portions12, a plurality of first filter portions20A and a plurality of second filter portions20B, a plurality of first optical regions30A and a plurality of second optical regions30B, and a difference detecting portion60(omitted from the drawings). Although associated details are omitted, each first light receiving portion11, each second light receiving portion12, each first filter portion20A, each second filter portion20B, each first optical region30A and each second optical region30B of this embodiment have identical configurations as the first light receiving portion11, the second light receiving portion12, the first filter portion20A, the second filter portion20B, the first optical region30A and the second optical region30B of the illuminance sensor A5, respectively. That is to say, in this embodiment, each first light receiving portion11includes the first light receiving element111, the second light receiving element112and the third light receiving element113, and each second light receiving portion12includes the first light receiving element121, the second light receiving element122and the third light receiving element123. Further, each first filter portion20A includes the first red filter21rcovering the first light receiving element111, the first green filter21gcovering the second light receiving element112, and the first blue filter21bcovering the third light receiving element113. Each second filter portion20B includes the second red filter22rcovering the first light receiving element121, the second green filter22gcovering the second light receiving element122, and the second blue filter22bcovering the third light receiving element123. In this embodiment, it is understood according toFIG.6andFIG.7that, the first light receiving portion11and the second light receiving portion12, the first filter portion20A and the second filter portion20B of the color filter layer20, and the first optical region30A and the second optical region30B are alternately disposed in a matrix in an x direction (a first direction) and a y direction (a second direction) that are orthogonal to each other. In the examples shown, 8 first light receiving portions11and 8 second light receiving portions12totaling up to 16 first light receiving portions11and second light receiving portions12are disposed in a matrix of four rows and four columns in the x direction and the y direction. The first light receiving portion11and the second light receiving portion12are disposed alternately in any one of the x direction and the y direction. Further, 8 first filter portions20A and 8 second filter portions20B totaling up to 16 first filter portions20A and second filter portions20B are disposed in a matrix of four rows and four columns in the x direction and the y direction. The first filter portion20A and the second filter portion20B are disposed alternately in any of the x direction and the y direction. Similarly, 8 first optical regions30A and 8 second optical regions30B totaling up to 16 first optical regions30A and second optical regions30B are arranged in a matrix of four rows and four columns in the x direction and the y direction. The first optical region30A and the second optical region30B are disposed alternately in any of the x direction and the y direction. Further, as shown inFIG.6, the 16 first filter portions20A and the second filter portions20B disposed in a matrix in a plane in the x direction and y direction to form a filter disposing region2. As shown inFIG.6, in this embodiment, each first filter portion20A and each second filter portion20B are divided into two portions in the x direction and the y direction, respectively, into a total of four portions. In the first filter portion20A, the first red filter21r, the first green filter21gand the first blue filter21bare disposed in any one of the four divided portions. Similarly, in the second filter portion20B, the second red filter22r, the second green filter22gand the second blue filter22bare disposed in any one of the four divided portions. InFIG.6, zones of the first red filter21rand the second red filter22rare denoted by the letter “R”, zones of the first green filter21gand the second green filter22gare denoted by the letter “G”, and zones of the first blue filter21band the second blue filter22bare denoted by the letter “B”. Further, in the drawings, zones not denoted with any letter and zones denoted by the letter “C” are not disposed with any filters of the different colors. As shown inFIG.7, the first light receiving portion11and the second light receiving portion12of this embodiment include light receiving elements for transparency118and128, and the first filter portion20A and the second filter portion20B in zones denoted by the letter “C” are at positions corresponding to the light receiving elements for transparency118and128. As shown inFIG.6, in the adjacent first filter portion20A and second filter portion20B, focusing on the first red filter21rand the second red filter22r, the first red filter21rand the second red filter22rare disposed adjacently in at least one of the x direction and the y direction. Similarly, in the adjacent first filter portion20A and second filter portion focusing on the first green filter21gand the second green filter22g, the first green filter21gand the second green filter22gare disposed adjacently in at least one of the x direction and the y direction. Similarly, further, in the adjacent first filter portion20A and second filter portion20B, focusing on the first blue filter21band the second blue filter22b, the first blue filter21band the second blue filter22bare disposed adjacently in at least one of the x direction and the y direction. As shown inFIG.6, in this embodiment, in the filter disposing region2disposed with a plurality of first filter portions20A and a plurality of second filter portions20B, all the first red filters21rand the second red filters22rare disposed as being dot symmetric relative to the center C2of the filter disposing region2as the center of symmetry. Similarly, all the first green filters21gand second green filters22g, and all the first blue filter21band second blue filters22bare disposed as being dot symmetric relative to the center point C2of the filter disposing region2as the center of symmetry. Omitting detailed description on the drawings, in this embodiment, one difference detecting portion60obtains the difference between the outputs of the first light receiving element111and the first light receiving element121of the adjacent first light receiving portion11and second light receiving portion12. Another difference detecting portion60obtains the difference between the outputs of the second light receiving element112and the second light receiving element122of the adjacent first light receiving portion11and second light receiving portion12. Similarly, another difference detecting portion60obtains the difference between the outputs of the third light receiving element113and the third light receiving element123of the adjacent first light receiving portion11and second light receiving portion12. Another difference detecting portion60obtains the difference between the outputs of the first light receiving element for transparency118and the second light receiving element for transparency128of the adjacent first light receiving portion11and second light receiving portion12. As such, the difference detecting portions60are disposed in a manner of obtaining the differences between the outputs of the corresponding light element receiving pair in the adjacent first light receiving portion11and second light receiving portion12. Further, inFIG.7, regarding the optical region30(the first optical region30A and the second optical region30B), description other than the second linear polarization plate34is omitted. The configurations of the first optical region30A and the second optical region30B (the first linear polarization plate31, the first quarter-wave plate32, the second quarter-wave plate33and the second linear polarization plate34) may also be implemented by the configurations of those in any one of the illuminance sensors A1to A4. Regardless of by which of the configurations of the illuminance sensors A1to A4the first optical region30A and the second optical region30B are implemented, the first light receiving portion11(the first light receiving element111, the second light receiving element112, the third light receiving element113and the light receiving element for transparency118) receives only infrared light, and the second light receiving portion12(the first light receiving element121, the second light receiving element122, the third light receiving element113and the light receiving element for transparency128) receives both infrared light and visible light. The difference detecting portion60eliminates the infrared components from the light receiving amounts of the plurality of first light receiving portions11and the plurality of second light receiving portions12by means of obtaining the difference in the two light receiving portions11and12, and outputs the light receiving amount of visible light as a signal. Further, in this embodiment, the first light receiving element111, the second light receiving element112and the third light receiving element113of each first light receiving portion11are covered by the first red filter21r, the first green filter21gand the first blue filter21b, respectively. Further, the first light receiving element121, the second light receiving element122and the third light receiving element123of each second light receiving portion12are covered by the second red filter22r, the second green filter22gand the second blue filter22b, respectively. Thus, the plurality of first light receiving portions11and the plurality of second light receiving portions12are capable of receiving a visible band in a manner of splitting the light into wavelength regions into red, green, and blue. Therefore, the illuminance sensor A5of this embodiment is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light, and performing illuminance detection of each of red, green and blue. Further, in this embodiment, in the adjacent first filter portion20A and second filter portion20B, the first red filter21rand the second red filter22r, the first green filter21gand the second green filter22g, and the first blue filter21band the second blue filter22bare disposed adjacently in at least one of the x direction and they direction, respectively. According to such configuration, light receiving element pairs obtaining the differences in the outputs so as to detect the illuminances of the components of red, green and blue are adjacent, hence enhancing illuminance detection accuracy for the colors. Further, in the filter disposing region2disposed with a plurality of first filter portions20A and a plurality of second filter portions20B in a matrix, all the first red filters21rand the second red filters22r, all the first green filters21gand second green filters22g, and all the first blue filters21band second blue filters22bare disposed as being dot symmetric relative to the center C2of the filter disposing region2as the center of symmetry. According to such configuration, influences of non-uniform light amounts at different positions of an illuminance detection range, that is, the filter disposing region2, of the illuminance sensor A6may be suppressed, hence enhancing the illuminance detection accuracy each of red, green and blue. <Illuminance Sensor A7> FIG.8shows an illuminance sensor according to a fifth embodiment of the present invention. The illuminance sensor A7shown in the drawing primary differs from the illuminance sensors A1to A4by the configurations of the first light receiving portion11and the second light receiving portion12, and the configuration of the optical region30(the first optical region30A and the second optical region30B). Further, inFIG.8, only the second linear polarization plate34in the optical region30(the first optical region30A and the second optical region30B) is depicted, and the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33are omitted. In the description above, a situation below is illustrated: in the illuminance sensors A1to A4of the embodiments, at least any one of the first linear polarization plate31and the second linear polarization plate34has characteristics of providing a polarization function for an entire visible band, and not polarizing but allowing passing through of an entire infrared band. In contrast, in this embodiment, at least any one of the first linear polarization plate31and the second linear polarization plate34has the following characteristics: providing a polarization function for an entire visible band, providing a polarization function for a portion of an infrared band, and not polarizing but allowing passing through of the remaining band of the infrared band. In this case, if a difference between outputs of the first light receiving portion11and the second light receiving portion12is received, a portion of infrared components is included as noise. In the illuminance sensor A7of this embodiment, the first light receiving portion11and the second light receiving portion12include a plurality of light receiving elements, respectively. The first light receiving portion11includes a light receiving element for visible light116having a sensing peak in a visible band, and a light receiving element for infrared light117having a sensing peak in an infrared band. The second light receiving portion12includes a light receiving element for visible light126having a sensing peak in a visible band, and a light receiving element for infrared light127having a sensing peak in an infrared band. Further, in this embodiment, different from the foregoing embodiments, the color filter layer20is not included. The illuminance sensor A7of this embodiment includes two difference detecting portions60. One of the difference detecting portions60obtains a difference between outputs of the light receiving element for visible light116and the light receiving element for visible light126. The other of the difference detecting portions60obtains a difference between outputs of the light receiving element for infrared light117and the light receiving element for infrared light127. Further, inFIG.8, regarding the optical region30(the first optical region30A and the second optical region30B), description other than the second linear polarization plate34is omitted. The configurations of the first optical region30A and the second optical region30B (the first linear polarization plate31, the first quarter-wave plate32, the second quarter-wave plate33and the second linear polarization plate34) may also be implemented by the configurations of those in any one of the illuminance sensors A1to A4. Regardless of by which of the configurations of the illuminance sensors A1to A4the first optical region30A and the second optical region30B are implemented, the first light receiving portion11(the light receiving element for visible light116and the light receiving element for infrared light117) receives only a portion of infrared light (an ineffective band), and the second light receiving portion12(the light receiving element for visible light126and the light receiving element for infrared light127) receives both infrared light and visible light. The difference detecting portion60obtains a difference between the first light receiving portion11and the second light receiving portion12(the light receiving element for visible light116and the light receiving element for infrared light117, and the light receiving element for visible light126and the light receiving element for infrared light127), and outputs the light receiving amount of the visible band and the light receiving amount of a portion of infrared components as a signal. Therefore, the illuminance sensor A7according this embodiment is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. <Illuminance Sensor A8> FIG.9andFIG.10show an illuminance sensor according to a sixth embodiment of the present invention. The illuminance sensor A8shown in the drawings includes a plurality of first light receiving portions11and a plurality of second light receiving portions12, a plurality of first optical regions30A and a plurality of second optical regions30B, and a difference detecting portion60(omitted from the drawings). Although associated details are omitted, each first light receiving portions11, each second light receiving portion12, each first optical region30A and each second optical region30B of this embodiment have identical configurations as the first light receiving portion11, the second light receiving portion12, the first optical region30A and the second optical region30B of the illuminance sensor A5, respectively. That is to say, each first light receiving portion11includes the light receiving element for visible light116and the light receiving element for infrared light117, and each second light receiving portion12includes the light receiving element for visible light126and the light receiving element for infrared light127. In this embodiment, it is understood according toFIG.9andFIG.10that, the first light receiving portion11and the second light receiving portion12, and the first optical region30A and the second optical region30B are alternately disposed in a matrix in the x direction (the first direction) and the y direction (the second direction) that are orthogonal to each other. In the examples shown, 8 first light receiving portions11and 8 second light receiving portions12totaling up to 16 first light receiving portions11and second light receiving portions12are disposed in a matrix of four rows and fourth columns in the x direction and the y direction. The first light receiving portion11and the second light receiving portion12are disposed alternately in any one of the x direction and the y direction. Similarly, 8 first optical regions30A and 8 second optical regions30B totaling up to 16 first optical regions30A and second optical regions30B are arranged in a matrix of four rows and four columns in the x direction and the y direction. The first optical region30A and the second optical region30B are disposed alternately in any of the x direction and the y direction. Further, as shown inFIG.9, the 16 first light receiving portions11and second light receiving portions12disposed in a matrix in a plane in the x direction and y direction form a light receiving portion disposing region1. Further, inFIG.9andFIG.10, the light receiving element for visible light116and light receiving element for visible light126are denoted by the letter “V”, and the light receiving element for infrared light117and the light receiving element for infrared light127are denoted by the letter “I”. As shown inFIG.9, in the first light receiving portion11and the second light receiving portion12adjacent to each other, focusing on the light receiving element for visible light116and light receiving element for visible light126, the light receiving element for visible light116and light receiving element for visible light126are disposed adjacently in at least any one of the x direction and the y direction. Similarly, in the first light receiving portion11and the second light receiving portion12adjacent to each other, focusing on the light receiving element for infrared light117and light receiving element for infrared light127, the light receiving element for infrared light117and light receiving element for infrared light127are disposed adjacently in at least any one of the x direction and the y direction. As shown inFIG.9, in this embodiment, in the filter disposing region1disposed with a plurality of first light receiving portions11and a plurality of second light receiving portions12in a matrix, all light receiving elements for visible light116and light receiving elements for visible light126are disposed as being dot symmetric relative to the center C1of the light receiving portion disposing region1as the center of symmetry. Similarly, all the light receiving elements for infrared light117and the light receiving elements for infrared light127are disposed as being dot symmetric relative to the center C1of the light receiving portion disposing region1as the center of symmetry. Omitting detailed description on the drawings, in this embodiment, one difference detecting portion60obtains the difference in the outputs of the light receiving element for visible light116and light receiving element for visible light126of the adjacent first light receiving portion11and second light receiving portion12. The other difference detecting portion60obtains the difference in the outputs of the light receiving element for infrared light117and the light receiving element for infrared light127of the adjacent first light receiving portion11and second light receiving portion12. As such, the difference detecting portions60are disposed in a manner of obtaining the differences between the outputs of the corresponding light element receiving pair in the adjacent first light receiving portion11and second light receiving portion12. Further, inFIG.10, regarding the optical region30(the first optical region30A and the second optical region30B), description other than the second linear polarization plate34is omitted. The configurations of the first optical region30A and the second optical region30B (the first linear polarization plate31, the first quarter-wave plate32, the second quarter-wave plate33and the second linear polarization plate34) may also be implemented by the configurations of those in any one of the illuminance sensors A1to A4. Regardless of by which of the configurations of the illuminance sensors A1to A4the first optical region30A and the second optical region30B are implemented, the first light receiving portion11(the light receiving element for visible light116and the light receiving element for infrared light117) receives only a portion of infrared light (an ineffective band), and the second light receiving portion12(the light receiving element for visible light126and the light receiving element for infrared light127) receives both infrared light and visible light. The difference detecting portion60receives the difference between the plurality of first light receiving portions11and the plurality of second light receiving portions12, and outputs the light receiving amount of the visible band and the light receiving amount of a portion of the band of the infrared components as a signal. Therefore, the illuminance sensor A7according this embodiment is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light and performing illuminance detection. Further, in this embodiment, in the first light receiving portion11and the second light receiving portion12adjacent to each other, the light receiving element for visible light116of the first light receiving portion11and the light receiving portion for visible light126of the second light receiving portion12, and the light receiving portion for infrared light117for the first light receiving portion11and the light receiving portion for infrared light127of the second light receiving portion are disposed adjacently at least any one of the x direction and the y direction. According to such configuration, the light receiving element pairs obtaining the differences in outputs so as to perform illuminance detection are adjacent, hence enhancing illuminance detection accuracy. Further, in the light receiving portion disposing region1disposed with a plurality of first light receiving portions11and a plurality of second light receiving portions12in a matrix, all light receiving elements for visible light116and light receiving elements for visible light126, and all the light receiving elements for infrared light117and light receiving elements for infrared light127are disposed as being dot symmetric relative to the center C1of the light receiving portion disposing region1as the center of symmetry. According to such configuration, influences of non-uniform light receiving amounts at different positions of an illuminance detection range, that is, the light receiving portion disposing region1, of the illuminance sensor A8may be suppressed, thereby enhancing the illuminance detection accuracy. <Two-Dimensional (2D) Image Sensor70> FIG.11shows a 2D image sensor70using the configuration of the illuminance sensor A1. Further, the configuration of the illuminance sensor used by the 2D image sensor may be any of the configurations of the illuminance sensors A1to A4, A5and A7. The 2D image sensor70uses the configuration inFIG.1as one unit, and disposes a plurality of such unit into a plurality columns and a plurality of rows inside a transparent optical window50. The 2D image sensor70may be a contact-type or a non-contact type. When the 2D image sensor70is a non-contact type, a 2D image is projected to the optical window by an optical lens (not shown). The functions of the illuminance sensor A1forming the pixel units are as described with reference toFIG.1, that is, eliminating or mitigating noise produced by infrared light in pixel information under detection. <Electronic Machine1> FIG.12shows an electronic machine B1as an electronic machine according to the first embodiment of the present invention. The electronic machine B1includes an OLED the first light receiving portion11, the second light receiving portion12, the optical region30and the difference detecting portion60. The first light receiving portion11and the second light receiving portion12are disposed on the side of a back surface of the OLED40, for example, manufactured and incorporated into a photodiode of the same IC100and located in the same plane serving as the main surface of the IC100. The optical region30is disposed opposite to the first light receiving portion11and the second light receiving portion12. The optical region30has a first optical region30A disposed corresponding to the first light receiving portion11, and a second optical region30B disposed corresponding to the second light receiving portion12. The optical region30(the first optical region30A and the second optical region30B) includes a first linear polarization plate31, a first quarter-wave plate32, a second quarter-wave plate33, and a second linear polarization plate34. In this embodiment, the first quarter-wave plate32and the first linear polarization plate31are sequentially disposed on the side of the observe surface of the OLED40, and the second quarter-wave plate33and the second linear polarization plate34are sequentially disposed at the back surface of the OLED40. In this embodiment, the optical window50serving as the electronic machine B1consists of the first linear polarization plate31and the first quarter-wave plate32deposited on the side of the back surface of the transparent window material. The first linear polarization plate31is similarly disposed in the entire of the first optical region30A and the second optical region30B (the regions corresponding to the first light receiving portion11and the region corresponding to the second light receiving portion12). In the entire of the first optical region30A and the second optical region30B (the regions corresponding to the first light receiving portion11and the region corresponding to the second light receiving portion12), the slow axis of the first quarter-wave plate has a relation of +45° or −45° in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. In this embodiment, the slow axis of the first quarter-wave plate32has a relation of +45° in regard to the first polarization direction, and is denoted by “+45°” inFIG.12. The first light receiving portion11and the second light receiving portion12are located in the same plane parallel to the OLED40. In this embodiment, further, the second quarter-wave plate33and the second linear polarization plate34are used as an integral body manufactured and incorporated with the first light receiving portion11and the second light receiving portion12, and is deposited and formed on the main surface of the OLED40. Further, in this embodiment, the color filter layer20of such as red, green or blue is interposed between the first light receiving portion11and the second light receiving portion12and the second linear polarization plate34. The second linear polarization plate34is similarly disposed in the entire of the first optical region30A and the second optical region30B (the regions corresponding to the first light receiving portion11and the region corresponding to the second light receiving portion12). In this embodiment, the polarization direction (the first polarization direction) of the first linear polarization plate31is the same with the polarization direction (the second polarization direction) of the second linear polarization plate34, and is represented by slant shading lines in the same direction inFIG.12. Further, at least any one of the first linear polarization plate31and the second linear polarization plate34is implemented by a polarization plate in which an ineffective band includes at least a portion of an infrared band. Herein, an ineffective band refers to a wavelength band of light that does not effectively perform polarization. That is to say, at least any one of the first linear polarization plate31and second linear polarization plate34is implemented by, for example, a polarization plate of the following characteristics: the polarization plate has a polarization function for an entire visible band, and does not polarize but allows passing through of an entire infrared band. For example, a polarization plate “MCPR-4” sold by MeCan Imaging Inc. may be used as a linear polarization plate of the foregoing characteristics. The second quarter-wave plate33has a first portion331in the first optical region30A and a second portion332in the second optical region30B. The relation of a slow axis of the first portion331in regard a polarization direction (a second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45° or −45°. In this embodiment, the polarization direction (the first polarization direction) of the first linear polarization plate33is the same with the polarization direction (the second polarization direction) of the second linear polarization plate34, and thus the slow axis of the first portion331also has a relation of +45° in regard to the first polarization direction, is denoted as “+45°” inFIG.12. On the hand, a relation of a slow axis of the second portion332in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. In this embodiment, the slow axis of the second portion332has a relation of −45° in regard to the second polarization direction. Further, in this embodiment, the polarization direction (the first polarization direction) of the first linear polarization plate31is the same with the polarization direction (the second polarization direction) of the second linear polarization plate34, and thus the slow axis of the second portion332also has a relation of −45° in regard to the first polarization direction, is denoted by “−45°” inFIG.12. The difference detecting portion60obtains a difference between an output of the first light receiving portion11and an output of the second light receiving portion12. The different detecting portion60may be implemented by, for example, a differential amplifier such as an operational amplifier. Further, the electronic machine in which a display portion consists of the OLED disposed inside the foregoing optical window50is, for example, a portable information terminal such as a smartphone, a television, or a personal computer display. Next, the functions of the electronic machine B1shown inFIG.12are described individually below, for when the ineffective bands of both the first linear polarization plate31and the second linear polarization plate34include the infrared band, when the ineffective band of only the first linear polarization plate31between the first linear polarization plate31and the second linear polarization plate34includes the infrared band, and when the ineffective band of only the second linear polarization plate34between the first linear polarization plate31and the second linear polarization plate34includes the infrared band. [When the Ineffective Bands of Both the First Linear Polarization Plate31and the Second Linear Polarization Plate34Include the Infrared Band] In external light (visible light) entering from the optical window50, regarding reflected light formed by an electrode (omitted from the drawing) of the OLED40, circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is reflected by the electrode (omitted from the drawing) of the OLED40to become reversely turned circularly polarized light, and again enters the first quarter-wave plate32from the back surface. The reversely turned circularly polarized light becomes, when passing through the first quarter-wave plate32from the side of the back surface, polarized light differing by 90° in regard to the polarization direction of the first linear polarization plate31. Therefore, the polarized light is incapable of passing through the first linear polarization plate31, and is incapable of exiting from the optical window50. That is to say, the light reflected by the electrode in the OLED40in the external light (visible light) entering from the optical window50is prohibited or suppressed from exiting to the exterior of the optical window50. A portion of the light emitted from the OLED40faces the second quarter-wave plate33from the side of the back surface of the OLED40. The exiting light from the side of the back surface of the OLED40passes through the first portion331of the second quarter-wave plate33in the first optical region30A (the region corresponding to the first light receiving portion11), is polarized by the second linear polarization plate34and arrives at the first light receiving portion11. Similarly for the second optical region30B (the region corresponding to the second light receiving portion12), the exiting light from the side of the back surface of the OLED40passes through the second portion332of the second quarter-wave plate33, is polarized by the second linear polarization plate34and arrives at the second light receiving portion12. Neither of the first linear polarization plate31and the second linear polarization plate34has a polarization function for infrared light, and thus neither of the first light receiving portion11and the second light receiving portion12is capable of receiving infrared light. On the other hand, regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331)(+45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11does not receive visible light from the exterior, but receives infrared light and light from the OLED40. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate)(+45°. As described, the relation of the slow axis of the second portion332)(−45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives infrared light, visible light from the exterior, and light from the OLED40. The difference detecting portion60eliminates the infrared components from the light receiving amounts and the components of light from the OLED40of the first light receiving portion11and the second light receiving portion12by means of obtaining the difference between the two light receiving portions11and12, and outputs the light receiving amount of visible light from the exterior as a signal. Therefore, the electronic machine B1is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light or light from the OLED40, and performing illuminance detection. [When the Ineffective Band of Only the First Linear Polarization Plate31Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] In terms of prohibiting or suppressing the light reflected by the electrode of the OLED40in the external light (visible light) entering from the optical window50from exiting the optical window50, associated details are the same with the description given for when effective bands of both the first linear polarization plate31and the second linear polarization34include the visible band. The exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the first portion331) in the first optical region30A (the region corresponding to the first light receiving portion11), is polarized by the second linear polarization plate34and arrives at the first light receiving portion11. Similarly for the second optical region30B (the region corresponding to the second light receiving portion12), the exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the second portion332), is polarized by the second linear polarization plate34and arrives at the second light receiving portion12. Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the first linear polarization plate31does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. Infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the first linear polarization plate31likewise does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. The infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the second light receiving portion12. Regarding infrared light, the first light receiving portion11and the second light receiving portion12similarly receive the infrared light. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331)(+45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11does not receive visible light from the exterior, but receives infrared light and light from the OLED40. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate)(+45°. As described, the relation of the slow axis of the second portion332)(−45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives infrared light, visible light from the exterior, and light from the OLED40. The difference detecting portion60eliminates the infrared components from the light receiving amounts and the components of light from the OLED40of the first light receiving portion11and the second light receiving portion12by means of obtaining the difference between the two light receiving portions11and12, and outputs the light receiving amount of visible light from the exterior as a signal. Therefore, the electronic machine B1is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light or light from the OLED40, and performing illuminance detection. [When the Ineffective Band of Only the Second Linear Polarization Plate34Between the First Linear Polarization Plate31and the Second Linear Polarization Plate31Includes the Infrared Band] In terms of prohibiting or suppressing the light reflected by the electrode of the OLED40in the external light (visible light) entering from the optical window50from exiting the optical window50, associated details are the same with the description given for when effective bands of both the first linear polarization plate31and the second linear polarization34include the visible band. The exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the first portion331) in the first optical region30A (the region corresponding to the first light receiving portion11), is polarized by the second linear polarization plate34and arrives at the first light receiving portion11. Similarly for the second optical region30B (the region corresponding to the second light receiving portion12), the exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the second portion332), is polarized by the second linear polarization plate34and arrives at the second light receiving portion12. Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the infrared light is polarized at the first linear polarization plate31, and the direction of the polarized light changes by 90° in a period of passing through the first quarter-wave plate32and the second quarter-wave plate33(the first portion331). The second linear polarization plate34does not have a polarization function for infrared light, and thus the polarized light changed by 90° in direction directly arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the infrared light is also polarized at the first linear polarization plate31, and arrives at the second linear polarization plate34in a manner that the polarization direction thereof is not changed at timings of passing through the first quarter-wave plate32and the second quarter-wave plate33(the second portion332). The second linear polarization plate34does not have a polarization function for infrared light, and thus the polarized light generated by the first linear polarization plate31directly arrives at the second light receiving portion12. That is to say, regarding infrared light, the first light receiving portion11and the second light receiving portion12receive the infrared light by the same light amount for polarized light of a phase difference of 90°. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331)(+45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11does not receive visible light from the exterior, but receives infrared light and light from the OLED40. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate)(+45°. As described, the relation of the slow axis of the second portion332)(−45° of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives infrared light, visible light from the exterior, and light from the OLED40. The difference detecting portion60eliminates the infrared components from the light receiving amounts and the components of light from the OLED40of the first light receiving portion11and the second light receiving portion12by means of obtaining the difference between the two light receiving portions11and12, and outputs the light receiving amount of visible light from the exterior as a signal. Therefore, the electronic machine B1is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light or light from the OLED40, and performing illuminance detection. <Electronic Machine B2> FIG.13shows an electronic machine B2as an electronic machine according to the second embodiment of the present invention. Comparing to the electronic machine B1inFIG.12, the electronic machine B2differs by the relations of the polarization directions of the first linear polarization plate31and the second linear polarization plate34, and the configurations of the first quarter-wave plate32and the second quarter-wave plate33, and the remaining configuration details are the same with those in the electronic machine B1inFIG.12. That is to say, in the electronic machine B2inFIG.13, the polarization direction (the first polarization direction) of the first linear polarization plate31differs from the polarization direction (the second polarization direction) of the second linear polarization plate34by 90°. InFIG.13, such is represented by slant shading lines in different directions. The first quarter-wave plate32is set to “+45°” in the entire of the first optical region30A and the second optical region30B (the region corresponding to the first receiving portion11and the region corresponding to the second light receiving portion12). Regarding the second quarter-wave plate33, the first portion331in the first optical region30A is set to “—45°”, and the second portion332in the second optical region30B is set to “+45°”. That is to say, the slow axis of the first quarter-wave plate32has a relation of +45° in regard to the polarization direction (the first polarization) of the first linear polarization plate32. The slow axis of the first portion331of the second quarter-wave plate33has a relation of −45° in regard to the first polarization direction. In this embodiment, the polarization direction (the first polarization direction) of the first linear polarization plate31differs from the polarization direction (the second polarization direction) of the second linear polarization plate34by 90°, and hence the slow axis of the first portion331of the second quarter-wave plate33has a relation of +45° in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34. Therefore, the relation of the slow axis of the first portion331in regard to the polarization (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45°. On the other hand, the slow axis of the second portion332of the second quarter-wave plate33has a relation of +45° in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. The polarization direction (the first polarization direction) of the first linear polarization plate31differs from the polarization direction (the second polarization direction) of the second linear polarization direction34by 90°, and hence the slow axis of the second portion332of the second quarter-wave plate33has a relation of −45° in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34. Therefore, the relation of the slow axis of the first portion331in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Next, the functions of the electronic machine B1shown inFIG.13are described individually below, for when the ineffective bands of both the first linear polarization plate31and the second linear polarization plate34include the infrared band, when the ineffective band of only the first linear polarization plate31between the first linear polarization plate31and the second linear polarization plate34includes the infrared band, and when the ineffective band of only the second linear polarization plate34between the first linear polarization plate31and the second linear polarization plate34includes the infrared band. [When the Ineffective Bands of Both the First Linear Polarization Plate31and the Second Linear Polarization Plate34Include the Infrared Band] In terms of prohibiting or suppressing the light reflected by the electrode of the OLED40in the external light (visible light) entering from the optical window50from exiting the optical window50, associated details are the same with the description given for the electronic machine B1inFIG.12. The exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the first portion331) in the first optical region30A (the region corresponding to the first light receiving portion11), is polarized by the second linear polarization plate34and arrives at the first light receiving portion11. Similarly for the second optical region30B (the region corresponding to the second light receiving portion12), the exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the second portion332), is polarized by the second linear polarization plate34and arrives at the second light receiving portion12. Neither of the first linear polarization plate31and the second linear polarization plate34has a polarization function for infrared light, and thus both of the first light receiving portion11and the second light receiving portion12are capable of receiving infrared light. On the other hand, regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11does not receive visible light from the exterior, but receives infrared light and light from the OLED40. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate)(+45°. As described above, the relation of the slow axis of the second portion332of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives infrared light, visible light from the exterior, and light from the OLED40. The difference detecting portion60eliminates the infrared components from the light receiving amounts and the components of light from the OLED40of the first light receiving portion11and the second light receiving portion12by means of obtaining the difference between the two light receiving portions11and12, and outputs the light receiving amount of visible light from the exterior as a signal. Therefore, the electronic machine B1is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light or light from the OLED40, and performing illuminance detection. [When the Ineffective Band of Only the First Linear Polarization Plate31Between the First Linear Polarization Plate31and the Second Linear Polarization Plate34Includes the Infrared Band] In terms of prohibiting or suppressing the light reflected by the electrode of the OLED40in the external light (visible light) entering from the optical window50from exiting the optical window50, associated details are the same with the description given for the electronic machine B1inFIG.12. The exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the first portion331) in the first optical region30A (the region corresponding to the first light receiving portion11), is polarized by the second linear polarization plate34and arrives at the first light receiving portion11. Similarly for the second optical region30B (the region corresponding to the second light receiving portion12), the exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the second portion332), is polarized by the second linear polarization plate34and arrives at the second light receiving portion12. Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the first linear polarization plate31does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. Infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the first linear polarization plate31likewise does not have a polarization function, and thus the infrared light directly passes through the first linear polarization plate31, the first quarter-wave plate32and the second quarter-wave plate33. The infrared light arriving at the second linear polarization plate34is polarized by the second linear polarization plate34, and arrives at the second light receiving portion12. Regarding infrared light, the first light receiving portion11and the second light receiving portion12similarly receive the infrared light. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11does not receive visible light from the exterior, but receives infrared light and light from the OLED40. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate)(+45°. As described above, the relation of the slow axis of the second portion332of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives infrared light, visible light from the exterior, and light from the OLED40. The difference detecting portion60eliminates the infrared components from the light receiving amounts and the components of light from the OLED40of the first light receiving portion11and the second light receiving portion12by means of obtaining the difference between the two light receiving portions11and12, and outputs the light receiving amount of visible light from the exterior as a signal. Therefore, the electronic machine B1is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light or light from the OLED40, and performing illuminance detection. [When the Ineffective Band of Only the Second Linear Polarization Plate34Between the First Linear Polarization Plate31and the Second Linear Polarization Plate31Includes the Infrared Band] In terms of prohibiting or suppressing the light reflected by the electrode of the OLED40in the external light (visible light) entering from the optical window50from exiting the optical window50, associated details are the same with the description given for the electronic machine B1inFIG.12. The exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the first portion331) in the first optical region30A (the region corresponding to the first light receiving portion11), is polarized by the second linear polarization plate34and arrives at the first light receiving portion11. Similarly for the second optical region30B (the region corresponding to the second light receiving portion12), the exiting light from the side of the back surface of the OLED40passes through the second quarter-wave plate33(the second portion332), is polarized by the second linear polarization plate34and arrives at the second light receiving portion12. Regarding infrared light, in the first optical region30A (the region corresponding to the first light receiving portion11), the infrared light is polarized at the first linear polarization plate31, and arrives at the second linear polarization plate34in a manner that the polarization direction thereof is not changed at timings of passing through the first quarter-wave plate32and the second quarter-wave plate33(the first portion331). The second polarization plate34does not have a polarization function for infrared light, and thus polarized light generated by the first linear polarization plate31directly arrives at the first light receiving portion11. Regarding infrared light, in the second optical region30B (the region corresponding to the second light receiving portion12), the infrared light is polarized at the first linear polarization plate31, and the polarization direction thereof changes by 90° at timings in a period of passing through the first quarter-wave plate32and the second quarter-wave plate33(the second portion332). The second polarization plate34does not have a polarization function for infrared light, and thus the foregoing polarized light changed by 90° directly arrives at the second light receiving portion12. That is to say, regarding infrared light, the first light receiving portion11and the second light receiving portion12receive the infrared light by the same light amount for polarized light of a phase difference of 90°. Regarding visible light, in the first optical region30A (the region corresponding to the first light receiving portion11), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate32)(+45°. As described above, the relation of the slow axis of the first portion331of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is the same with the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31, that is, +45°. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is incapable of passing through the second linear polarization plate34. That is to say, the first light receiving portion11does not receive visible light from the exterior, but receives infrared light and light from the OLED40. Regarding visible light, in the second optical region30B (the region corresponding to the second light receiving portion12), the linearly polarized light passing through the first linear polarization plate31becomes circularly polarized light by the first quarter-wave plate)(+45°. As described above, the relation of the slow axis of the second portion332of the second quarter-wave plate33in regard to the polarization direction (the second polarization direction) of the second linear polarization plate34is −45° that is opposite in sign to the relation of the slow axis of the first quarter-wave plate32in regard to the polarization direction (the first polarization direction) of the first linear polarization plate31. Therefore, the circularly polarized light formed by the first linear polarization plate31and the first quarter-wave plate32is capable of passing through the second linear polarization plate34and arriving at the second light receiving portion12. That is to say, the second light receiving portion12receives infrared light, visible light from the exterior, and light from the OLED40. The difference detecting portion60eliminates the infrared components from the light receiving amounts and the components of light from the OLED40of the first light receiving portion11and the second light receiving portion12by means of obtaining the difference between the two light receiving portions11and12, and outputs the light receiving amount of visible light from the exterior as a signal. Therefore, the electronic machine B1is capable of eliminating or mitigating undesirable influences such as noise caused by infrared light or light from the OLED40, and performing illuminance detection. Further, in the electronic machines B1and B2, the configurations of the first light receiving portion11, the second light receiving portion12, the color filter layer20, the first optical region30A and the second optical region30B may be implemented by the configurations of any of the illuminance sensors A5to A8described with reference toFIG.5toFIG.10. In this case, the illuminance sensors A5to A8produce the same effects as above. It should be noted that, the scope of the present invention is not limited to the embodiments described, and all variations made within the scope of the items stated in the claims are to be encompassed within the scope of the invention. For example, regarding the first quarter-wave plate32and the second quarter-wave plate33, a wave plate having a function indicated as “+45°” may be modified to a wave plate having a function indicated as “−45°”, and a wave plate having a function indicated as “−45°” may be modified to a wave plate having a function indicated as “+45°”. Further, inFIG.1,FIG.2andFIG.12, examples in which the polarization direction (the first polarization direction) of the first linear polarization plate31is the same with the polarization direction (the second polarization direction) of the second linear polarization plate34are described; inFIG.3,FIG.4andFIG.14, examples in which the polarization direction (the first polarization direction) of the first linear polarization plate31differs from the polarization direction (the second polarization direction) of the second linear polarization plate34by 90° are described. However, the relations of the first polarization direction of the first linear polarization plate31and the second polarization direction of the second linear polarization plate34are not limited to these examples. That is to say, given that the relation of the slow axis of the first quarter-wave plate32in regard to the first polarization plate direction and the relation of the slow axis of the second quarter-wave plate33in regard to the second polarization plate direction satisfy the relations specified above, any phase difference between the first polarization direction of the first linear polarization plate31and the second polarization direction of the second linear polarization plate34may be applied. The present invention includes the configurations associated with the addenda below. [Addendum 1] An illuminance sensor, including: a first light receiving portion and a second light receiving portion;a first optical region and a second optical region, disposed corresponding to the first light receiving portion and the second light receiving portion, respectively;a difference detecting portion, obtaining a difference between outputs of the first light receiving portion and the second light receiving portion;wherein, the first optical region and the second optical region comprise a first linear polarization plate, a first quarter-wave plate, a second quarter-wave plate and a second linear polarization plate corresponding to both the first light receiving portion and the second light receiving portion, and disposed sequentially in an order that the first linear polarization plate is farthest from the first light receiving portion and the second light receiving portion,an ineffective band of either one or both of the first and second linear polarization plates comprises a least a portion of an infrared band,a slow axis of the first quarter-wave plate comprises a relation of +45° or −45° in regard to a first polarization direction that is a polarization direction of the first linear polarization plate,the second quarter-wave plate comprises a first portion and a second portion, wherein the first portion is in the first optical region and the second portion is in the second optical region,a slow axis of the first portion comprises a relation of +45° or −45° in regard to a second polarization direction that is a polarization direction of the second linear polarization plate, wherein the relation of the slow axis of the first portion in regard to the second polarization direction is the same with the relation of the slow axis of the first quarter plate in regard to the first polarization direction, anda relation of a slow axis of the second portion in regard to the second polarization direction is −45° or +45° that is opposite in sign to the relation of the slow axis of the first quarter plate in regard to the first polarization direction. [Addendum 2] An illuminance sensor, including:a first light receiving portion and a second light receiving portion;a first optical region and a second optical region, disposed corresponding to the first light receiving portion and the second light receiving portion, respectively;a difference detecting portion, obtaining a difference between outputs of the first light receiving portion and the second light receiving portion;wherein, the first optical region and the second optical region comprise a first linear polarization plate, a first quarter-wave plate, a second quarter-wave plate and a second linear polarization plate corresponding to both the first light receiving portion and the second light receiving portion, and disposed sequentially in an order that the first linear polarization plate is farthest from the first light receiving portion and the second light receiving portion,an ineffective band of either one or both of the first and second linear polarization plates comprises a least a portion of an infrared band,the first quarter-wave plate comprises a first portion and a second portion, wherein the first portion is in the first optical region and the second portion is in the second optical region,a slow axis of the first portion comprises a relation of +45° or −45° in regard to a first polarization direction that is a polarization direction of the first linear polarization plate,a relation of a slow axis of the second portion in regard to the first polarization direction is −45° or +45° that is opposite in sign to the relation of the slow axis of the first portion in regard to the first polarization direction, anda slow axis of the second quarter-wave plate comprises a relation of +45° or −45° in regard to a second polarization direction that is a polarization direction of the second linear polarization plate, wherein the relation of the slow axis of the second quarter-wave plate in regard to the second polarization direction is the same with the relation of the slow axis of the first portion in regard to the first polarization direction. [Addendum 3] The illuminance sensor according to addendum 1 or 2, wherein the first light receiving portion and the second light receiving portion are manufactured and incorporated into the same integrated circuit (IC). [Addendum 4] The illuminance sensor according to any one of addenda 1 to 3, including a color filter layer interposed between the first light receiving portion and the second light receiving portion and the second linear polarization plate. [Addendum 5] The illuminance sensor according to addendum 4, wherein:the color filter layer includes a first filter portion corresponding to the first light receiving portion, and a second filter portion corresponding to the second light receiving portion,the first light receiving portion and the second light receiving portion comprise a plurality of light receiving elements, respectively,the plurality of light receiving elements comprise a first light receiving element, a second light receiving element and a third light receiving element,the first filter portion and the second filter portion comprise: a first red filter and a second red filter, covering the first light receiving element so that blue light and green light are selectively attenuated; a first green filter and a second green filter, covering the second light receiving element so that red light and the blue light are selectively attenuated; and a first blue filter and a second blue filter, covering the third light receiving element so that the red light and the green light are selectively attenuated. [Addendum 6] The illuminance sensor according to addendum 5, wherein:the first optical region and the second optical region, the first filter portion and the second filter portion of the color filter layer, and the first light receiving portion and the second light receiving portion are alternately arranged in a matrix in a first direction and a second direction orthogonal to each other, respectively; andin the first filter portion and the second filter portion that are adjacent, the first red filter, the first green filter and the first blue filter are disposed adjacent to the second red filter, the second green filter and the second blue filter in at least any one of the first direction and the second direction. [Addendum 7] The illuminance sensor according to addendum 6, wherein:in a filter disposing region formed by disposing a plurality of first filter portions and a plurality of second filter portions, all the first red filters and the second red filters, all the first green filters and second green filters, and all the first blue filters and second blue filters are disposed as being dot symmetric relative to the center of the filter disposing region as a center of symmetry. [Addendum 8] The illuminance sensor according to any one of addenda 1 to 3, wherein:the first light receiving portion and the second light receiving portion include a plurality of light receiving elements, respectively; andthe plurality of light receiving elements include a light receiving element for visible light having a sensing peak in a visible band, and a light receiving element for infrared light having a sensing peak in an infrared band. [Addendum 9] The illuminance sensor according to addendum 8, wherein:the first optical region and the second optical region, and the first light receiving portion and the second light receiving portion are alternately arranged in a matrix in a first direction and a second direction orthogonal to each other, respectively; andin the first light receiving portion and the second light receiving portion adjacent to each other, the light receiving element for visible light and the light receiving element for infrared light of the first light receiving portion are disposed adjacently in at least any one of the first direction and the second direction, respectively. [Addendum 10] The illuminance sensor according to addendum 9, wherein:all the light receiving elements for visible light and all the light receiving elements for infrared light are disposed as being dot symmetric relative to a center of a light receiving portion disposing region as a center of symmetry, and the light receiving portion disposing region is formed by a plurality of first light receiving portions and a plurality of second light receiving portions in a matrix. [Addendum 11] An electronic machine, including the illuminance sensor of any one of the addenda 1 to 10. [Addendum 12] A two-dimensional (2D) image sensor, disposed with a plurality of the illuminance sensor according to any one of addenda 1 to 5 and 8 in a same plane. [Addendum 13] The 2D image sensor according to addendum 12, wherein the illuminance sensor is disposed in a plurality of rows and a plurality of columns. [Addendum 14] An electronic machine, including:the illuminance sensor according to any one of addenda 1 to 10; andan organic light-emitting diode (OLED), disposed between the first quarter-wave plate and the second quarter-wave plate, having a display surface thereof facing the side of the first quarter-wave plate;wherein, the first light receiving portion and the second light receiving portion are disposed in a plane parallel to the OLED on a side of a back surface of the OLED. Details and technical contents of the present invention are given with the accompanying drawings below. It should be noted that the accompanying drawings are for illustration purposes and are not to be construed as limitations to the present invention. | 150,292 |
11862741 | DETAILED DESCRIPTION As can be seen from the background technology, the prior art has a problem that the contact resistance of the solar cell is relatively large. The analysis found that one of the factors for the large contact resistance of the solar cell is that, in the existing process, the textured structure on the rear surface of the solar cell is generally polished after the solar cell is textured, so as to improve the back reflection of long-wavelength light and the uniformity of film layer subsequently formed on the rear surface, which is beneficial to reduce the recombination rate of carrier on the rear surface and improve the utilization rate of light. However, after the rear surface is polished, it is difficult to match between the subsequently formed doped conductive layer and the rear metal electrode, that is, a good ohmic contact cannot be formed. Therefore, the contact resistivity of the doped conductive layer is relatively large, and the contact resistance between the rear electrode and the doped conducive layer is relatively large, which affects the efficiency improvement of the solar cell. A solar cell is provided according to an embodiment of the present disclosure. The rear surface of the substrate of the solar cell includes the textured region and the flat region adjacent to the textured region, a doped surface field is formed on a surface of the textured region of the substrate, there are doping elements in the doped surface field, and a part of the bottom surface of the rear electrode is in contact with the doped surface field, that is, the rear electrode is in direct contact with the doped surface field, so that the doped conductive layer forms a good ohmic contact with the rear electrode, which is beneficial to reduce the contact resistivity on the rear surface of the solar cell and overall improve the efficiency of the solar cell. The doped surface field has doping elements, which can be used as carriers to improve the mobility of carriers and further reduce the contact resistivity of the rear surface of the solar cell. The substrate located at the flat region is a non-textured structure. A conventional tunneling dielectric layer and a doped conductive layer are formed in the flat region of the substrate. The rear electrode is in direct contact with the doped conductive layer, which has a good passivation effect while reducing the recombination rate of carriers on the rear surface and increasing the utilization rate of light, so that the photoelectric conversion efficiency of the solar cell is improved. The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that, in each embodiment of the present disclosure, many technical details are provided for readers to better understand the present disclosure. However, the technical solutions claimed in the present disclosure can be realized even without these technical details and various changes and modifications based on the following embodiments. FIG.1is a schematic structural view of a solar cell according to an embodiment of the present disclosure. Referring toFIG.1, an aspect of the embodiments of the present disclosure provides a solar cell, including: a substrate100, where the substrate100has a front surface101and a rear surface102that opposite to each other, the rear surface102includes a textured region A and a flat region B adjacent to the textured region A, a doped surface field120is formed in the textured region A of the substrate100, there are doping elements in the doped surface field120, and the doping elements are N-type doping elements or P-type doping elements. The solar cell further includes a tunneling dielectric layer131, where the tunneling dielectric layer131is located on the flat region B on the rear surface102of the substrate100. The solar cell further includes a doped conductive layer132, where the doped conductive layer132is located on a surface of the tunnelling dielectric layer131away from the rear surface102of the substrate100, the doped conductive layer132has doping elements, and the doping elements in the doped conductive layer132are of the same type as the doping elements in the doped surface field120. The solar cell further includes a rear electrode141, where a part of a bottom surface of the rear electrode141is located on the doped conductive layer132and the part of the bottom surface of the rear electrode141is in contact with the doped surface field120. In some embodiments, the solar cell is a tunnel oxide passivated contact, TOPCon, cell, which may include a double-sided tunnel oxide passivation contact cell or a single-sided tunnel oxide passivation contact cell. Exemplarily, the solar cell is a single-sided tunnel oxide passivation contact cell, and the rear surface of the solar cell has a tunnelling oxide passivation layer. The substrate100is a region that absorbs incident photons to generate photo-generated carriers. In some embodiments, the substrate100is a silicon substrate100, which may include one or more of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. In other embodiments, the substrate100may be made of silicon carbide, organic material, or multi-component compound. The multicomponent compound may include, but is not limited to, perovskite, gallium arsenide, cadmium telluride, copper indium selenide etc. Exemplarily, the substrate100in the present disclosure is a single crystal silicon substrate. In some embodiments, the front surface101of the substrate100is a light-receiving surface to absorb incident light, and the rear surface102of the substrate100is a backlight surface. The substrate100has doping elements, the doping elements are N-type doping elements or P-type doping elements, and the N-type doping element may be group V element, such as phosphorus, P, element, bismuth, Bi, element, stibium, Sb, element, or arsenic, As, element. The P-type element may be a group III element, such as boron, B, element, aluminum, Al, element, gallium, Ga, element, or indium, In, element. For example, in a case that the substrate100is a P-type substrate, its internal doping element is P-type element. For another example, in a case that the substrate100is an N-type substrate, its internal doping element is N-type element. In some embodiments, the type of doping element in doped surface field120is the same as the type of doping element in substrate100. For example, in a case that the substrate100is a P-type substrate, the doping element in the doped surface field120is P-type element. For another example, in a case that the substrate100is an N-type substrate, the doping element in the doped surface field120is N-type element. The textured region A is a region of the rear surface102of the substrate100that has a textured structure, and the flat region B is a region of the rear surface102of the substrate100that is processed by a rear surface polishing process. In some embodiments, along an arrangement direction X of the rear electrode141, a ratio of a width of the textured region A of the substrate100and a width of the substrate100located at the flat region B ranges from 1:3 to 1:1. Specifically, the ratio may be 1:2.8, 1:2.3, 1:1.9, 1:1.3 or 1:1. Preferably, the ratio of the width of the textured region A of the substrate100and the width of the substrate100located at the flat region B is 1:2. In this way, the area of the flat region B can be ensured to be larger, and the film integrity of the tunneling dielectric layer131and the doped conductive layer132on the substrate100located at the flat region B is better, and the passivation effect of the solar cell and the anti-PDI effect are desirable. In addition, the recombination rate of carriers on the rear surface is reduced, the utilization rate of light is improved, and the photoelectric conversion efficiency of the solar cell is improved. Further, the width of the textured region A of the substrate100ranges from 10 μm to 30 μm, such as 10.3 μm, 13 μm, 15 μm, 23 μm or 29 μm. In some embodiments, along the arrangement direction X of the rear electrode141, the width of the textured region A of the substrate100is smaller than the width of the rear electrode141. Excessive width of the textured region A of the substrate100may affect the integrity and uniformity of the film in the flat region B, reduce the internal reflection of light, so as to be unfavorable for improving the surface recombination rate of carriers and the photoelectric conversion efficiency of the solar cell. In addition, the interface passivation effect of the passivation contact structure constructed by the tunneling dielectric layer131and the doped conductive layer132is affected, resulting in a high Jo load current and a decrease in the surface recombination rate of carriers. In some embodiments, an extension direction of the textured region A is the same as that of the rear electrode, and an extension length of the textured region A corresponds to an extension length of the rear electrode141, so that the doped surface field120located at the textured region A can increase the lateral transmission of the solar cell, reduce the lateral transmission loss of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell. In other embodiments, the rear surface102includes multiple textured regions A arranged along the extending direction of the rear electrode141. A space between two adjacent textured regions A ranges from 10 mm to 20 mm, which reduces the recombination rate of carriers, and the area for collecting the carriers is enhanced, and the passivation effect of the formed passivation contact structure is better, which is beneficial to improve the open circuit voltage, Voc, and the filling factor, FF. Specifically, the space between two adjacent textured regions A may be 10.3 mm, 13 mm, 15.1 mm, 17 mm, or 19 mm. For the same rear electrode141, multiple textured regions A are formed on the rear surface102along the arrangement direction X of the rear electrode141. A space between two adjacent textured regions A ranges from 5 μm to 20 μm. Specifically, the space between two adjacent textured regions A may be 5.3 μm, 7 μm, 13 μm, 15 μm or 18.3 μm. In some embodiments, for the same rear electrode141, a ratio of an area of a contact surface between the doped surface field120and the rear electrode141and an area of a contact surface between the doped conductive layer132and the rear electrode141ranges from 1:2 to 2:1, specifically the ratio may be 1.3:2, 1.6:2, 1:1.2, 2:1.8, or 2:1.3. Preferably, the ratio of the area of the contact surface between the doped surface field120and the rear electrode141and the area of the contact surface between the doped conductive layer132and the rear electrode141ranges from 1:1.2 to 1.2:1, specifically the ratio may be 1:1.15, 1:1.1, 1:1 or 1.13:1. In this way, the rear electrode141is ensured to be in contact with the doped surface field120or be regarded that the rear electrode141is in direct contact with the substrate100, so that the rear electrode and the substrate form a good ohmic contact, which reduces the contact resistance of the rear electrode141. Moreover, the integrity of film of the tunneling dielectric layer131and the doped conductive layer132on the substrate100located at the flat region B is desirable. The rear electrode141is in direct contact with the doped conductive layer132, so that the passivation effect is desirable. In addition, the recombination rate of carriers on the rear surface is reduced, and the utilization of light is improved, so that the photoelectric conversion efficiency of the solar cell is improved. In some embodiments, for the same rear electrode141, along the arrangement direction X of the rear electrode141, a ratio of a cross-sectional width of a contact surface between the doped surface field120and the rear electrode141and a width of the rear electrode141ranges from 1:4 to 1:2, specifically, the ratio may be 1:3.8, 1:3.3, 1:2.9, 1:2.3 or 1:2. Preferably, the ratio of the cross-sectional width of the contact surface between the doped surface field120and the rear electrode141and the width of the rear electrode141ranges from1:2.5to1:3.2, specifically, the ratio may be 1:2.6, 1:2.9, 1:3 or 1:3.2. The rear electrode141has a width of40um is taken as a reference, the cross-sectional width of the contact surface between the doped surface field120and the rear electrode141may range from 5 μm to 20 μm, specifically may be 6 μm, 8 μm, 12 μm, 15 μm or 19 μm. In some embodiments, along a direction from the rear surface102to the front surface101, the doped surface field120includes a first doped region121and a second doped region122, and a doping concentration of the first doped region121is greater than that of the second doped region122. The rear electrode141is in contact with a surface of the first doped region121, and the doping concentration of the first doped region121is relatively larger, which is conducive to improve the transport efficiency of carriers, improve the open circuit and the current transmission efficiency, thereby being beneficial to improve the photoelectric conversion efficiency of the solar cell. The doping concentration of the first doped region121ranges from 2×1020cm−3to 2×1021cm−3. In some embodiments, the doping concentration of the first doped region121is greater than or equal to the doping concentration of the doped conductive layer132. In this way, the recombination loss between the tunneling dielectric layer131and the doped surface field120and between the doped surface field120and the doped conductive layer132can be reduced, which is beneficial to improve the transport efficiency of carriers, improve the open circuit voltage and current transmission efficiency, thereby being beneficial to improve the photoelectric conversion efficiency of the solar cell. In addition, the doping concentration of the doped surface field120is greater than the doping concentration of the doped conductive layer132, which can further reduce the contact resistance of the rear electrode141, so as to improve the photoelectric conversion efficiency. In some embodiments, a ratio of a depth of the first doped region121and a height of the doped surface field120ranges from 1.5% to 4%. Preferably, the depth of the first doped region ranges from 90 nm to 200 nm, specifically 130 nm, 160 nm, 178 nm or 193 nm. A doping depth of the first doped region121can avoid the tunneling effect caused by the high doping of the first doped region121, that is, the doping elements of the first doped region121will not diffuse into the substrate100, a surface in contact with an emitter110, and the emitter110, so that the open circuit voltage of the solar cell is increased, which is beneficial to improve the photoelectric conversion efficiency of the solar cell. In some embodiments, the doped surface field120includes at least one protruding structure. A height difference between the top of the protruding structure and the rear surface102of the substrate100ranges from 2 μm to 10 μm. Due to the light trapping effect of the protruding structure and the height difference between the top of the protruding structure and the rear surface102of the substrate100, the light is incident on a slope of a surface of protruding structure, and the light is then reflected to a slope of another protruding structure to form multiple absorptions. Under multiple reflections, the advancing direction of the incident light in the solar cell is changed, which not only prolongs the optical path, but also increases the absorption of long-wavelength photons. In other embodiments, the number of protruding structures is at least two. A space between two adjacent protruding structures ranges from 2 μm to 4 μm, and the space between two adjacent protruding structures can ensure that the incident light is reflected by multiple times between two adjacent protruding structures to extend the optical path of incident light, thereby facilitating the absorption of long-wavelength photons. In some embodiments, the protruding structure includes a pyramid-shaped structure, and the textured surface formed by the pyramid-shaped structure has a better antireflection effect, that is, the reflectivity of light is reduced, and the short-circuit current, Isc, is increased, thereby improving the photoelectric conversion efficiency of the solar cell. In other embodiments, the protruding structure includes pyramid-shaped structure or other pyramidal structures with a slope. In some embodiments, the tunneling dielectric layer131may be made of, but is not limited to, aluminum oxide, silicon oxide, silicon nitride, silicon oxynitride, intrinsic amorphous silicon, intrinsic polysilicon, and other dielectric materials with tunneling function. The thickness of the tunneling dielectric layer131ranges from 0.5 nm to 2.5 nm. Optionally, the thickness of the tunneling dielectric layer131ranges from 0.5 nm to 2 nm. Further, the thickness of the tunneling dielectric layer131ranges from 0.5 nm to 1.2 nm. The doped conductive layer132may be made of at least one of polycrystalline semiconductor, amorphous semiconductor, or microcrystalline semiconductor. Preferably, the doped conductive layer132is made of at least one of polycrystalline silicon, amorphous silicon, or microcrystalline silicon. The thickness of the doped conductive layer132ranges from 40 nm to 150 nm. Optionally, the thickness of the doped conductive layer132ranges from 60 nm to 90 nm. The thickness of the doped conductive layer132can ensure that the optical loss of the doped conductive layer132is relatively small, and the interface passivation effect of the tunneling dielectric layer131is better, thereby improving the efficiency of the solar cell. Exemplarily, in the present disclosure, the doped conductive layer132is made of polysilicon, and the thickness of the doped conductive layer132is 80 nm. In some embodiments, a passivation layer133is located on a surface of the doped conductive layer132, and the passivation layer133can be regarded as a rear passivation layer. The passivation layer133may be a single-layer structure or a laminated structure, and the passivation layer133may be made of one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbonitride, titanium oxide, hafnium oxide, or aluminum oxide etc. The rear electrode141is the grid line of the solar cell for collecting the current of the solar cell. The rear electrode141can be sintered from a fire-through type paste. The rear electrode141may be made of one or more of aluminum, silver, gold, nickel, molybdenum, or copper. In some embodiments, the rear electrode141refers to a thin grid line or a finger-shaped grid line to be distinguished from a main grid line or a bus bar. In some embodiments, the solar cell further includes: a first passivation layer113, the first passivation layer113is located on a surface of the emitter110away from the substrate100, the first passivation layer113is regarded as a front passivation layer. Multiple electrodes142are arranged in a spaced manner, and the electrodes142penetrate the first passivation layer113to be in contact with the emitter110. In some embodiments, the first passivation layer113may be a single-layer structure or a laminated structure, and the first passivation layer113may be made of one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbonitride, titanium oxide, hafnium oxide or aluminum oxide. Each of the multiple electrodes142may be sintered from a fire-through type paste. The contact between the electrodes142and the emitter110may be a localized contact or a complete contact. The electrodes142may be made of one or more of aluminum, silver, nickel, gold, molybdenum, or copper. In some embodiments, each of the electrodes142is an upper electrode or a front surface electrode. In some cases, each of the electrodes142refer to a thin grid line or a finger-like grid line to be distinguished from a main grid line or a bus bar. In the solar cell provided according to an embodiment of the present disclosure, the rear surface of the substrate of the solar cell includes the textured region and the flat region adjacent to the textured region, a doped surface field is formed on a surface of the textured region of the substrate, there are doping elements in the doped surface field, and a part of the bottom surface of the rear electrode is in contact with the doped surface field, that is, the rear electrode is in direct contact with the doped surface field, so that the doped conductive layer forms a good ohmic contact with the rear electrode, which is beneficial to reduce the contact resistivity on the rear surface of the solar cell and overall improve the efficiency of the solar cell. The doped surface field has doping elements, which can be used as carriers to improve the mobility of carriers and further reduce the contact resistivity of the rear surface of the solar cell. The substrate located at the flat region is a non-textured structure. A conventional tunneling dielectric layer and a doped conductive layer are formed in the flat region of the substrate. The rear electrode is in direct contact with the doped conductive layer, which has a good passivation effect while reducing the recombination rate of carriers on the rear surface and increasing the utilization rate of light, so that the photoelectric conversion efficiency of the solar cell is improved. FIG.2is a schematic structural view of a photovoltaic module provided according to an embodiment of the present disclosure. Correspondingly, referring toFIG.2, another embodiment of the present disclosure further provides a photovoltaic module, which is configured to convert received light energy into electrical energy and transmit it to an external load. The photovoltaic module includes: at least one cell string, where the cell string is formed by connecting multiple solar cells10with each other, each of the multiple solar cells10being a solar cell10according to any one above (e.g., as described inFIG.1); a package film21configured to cover a surface of the cell string; a cover plate22configured to cover a surface of the package film21facing away from the cell string. The package film21may be embodied as an organic package film, such as ethyl vinyl acetate, EVA, or polyolefin elastomer, POE. The package film21is configured to cover a surface of the cell string to seal and protect the cell string. In some embodiments, the package film21includes an upper layer package film and a lower layer package film respectively covering both sides of the surface of the solar cell string. The cover plate22may be embodied as a cover plate such as a glass cover plate or a plastic cover plate for protecting the cell string, and the cover plate22is configured to cover the surface of the package film21away from the cell string. In some embodiments, a light trapping structure is arranged on the cover plate22to increase the utilization rate of incident light. The photovoltaic module has high current collection capability and low recombination rate of carriers, which can achieve high photoelectric conversion efficiency. In some embodiments, the cover plate22includes an upper cover plate and a lower cover plate located on both sides of the cell string. Correspondingly, another aspect of the embodiments of the present disclosure provides a method for preparing a solar cell, which is executed to prepare the solar cell provided in the above embodiment (FIG.1). Details of the same or similar contents or elements as the descriptions given in the above embodiments will not be repeated, and only descriptions that are different from the above descriptions will be described in detail.FIG.3is a schematic structural view of providing a substrate in a method for preparing a solar cell provided according to an embodiment of the present disclosure;FIG.4is a schematic structural view of forming an emitter in a method for preparing a solar cell provided according to an embodiment of the present disclosure;FIG.5is a schematic structural view of a rear surface of a substrate of a solar cell provided according to an embodiment of the present disclosure;FIG.6is another schematic structural view of a rear surface of a substrate of a solar cell provided according to an embodiment of the present disclosure;FIG.7is yet another structural schematic view of a rear surface of a substrate of a solar cell provided according to an embodiment of the present disclosure;FIG.8is yet another schematic structural view of a rear surface of a substrate of a solar cell provided according to an embodiment of the present disclosure;FIG.9is a schematic structural view of forming an initial textured structure in a method for preparing a solar cell provided according to an embodiment of the present disclosure;FIG.10is a schematic structural view of forming a conductive film in a method for preparing a solar cell provided according to an embodiment of the present disclosure;FIG.11is a schematic structural view of etching a conductive film in a method for preparing a solar cell provided according to an embodiment of the present disclosure;FIG.12is a schematic structural view of forming a doped surface field in a method for preparing a solar cell provided according to an embodiment of the present disclosure;FIG.13is a schematic structural view of forming a passivation layer in a method for preparing a solar cell provided according to an embodiment of the present disclosure; andFIG.14is a schematic structural view of forming a rear electrode in a method for preparing a solar cell provided according to an embodiment of the present disclosure. Referring toFIG.3, a substrate100is provided. The substrate100has a front surface101and a rear surface102opposite to each other, and the front surface101and the rear surface102of the substrate100have a textured structure. In some embodiments, the textured structure can be prepared by a solution texturing method, and the textured structure can increase the number of refractions of light on the surface of the solar cell, which is beneficial to the absorption of light by the solar cell, so as to maximize the utilization rate of solar energy value of the solar cell. Specifically, the substrate100is made of monocrystalline silicon, and the surface of the substrate100is subjected to a texturing process by using a mixed solution of an alkaline solution and an alcohol solution. It will be appreciated that an initial substrate can be regarded as the substrate100, and the initial substrate also has a front surface and a rear surface opposite to each other. In some embodiments, the substrate100has doping elements, and the doping elements are N-type doping elements or P-type elements. Referring toFIG.4, the emitter110is formed on the front surface101of the substrate100, and the rear surface102of the substrate100is polished to form a textured region A and a flat region B adjacent to the textured region A. In some embodiments, an alkaline solution or an acid solution can be used for polishing, and the rear surface102of the substrate100is a polished surface, which can increase the internal reflection of light, reduce the surface recombination rate of carriers, and improve the photoelectric conversion efficiency of the solar cell. The rear surface of the initial substrate includes a textured region and a flat region adjacent to the textured region. In some embodiments, along an arrangement direction X of the rear electrode141, a ratio of a width of the textured region A of the substrate100and a width of the substrate100located at the flat region B ranges from 1:3 to 1:1, specifically, the ratio may be 1:2.8, 1:2.3, 1:1.9, 1:1.3 or 1:1. Preferably, the ratio of the width of the textured region A of the substrate100and the width of the substrate100located at the flat region B is 1:2. Further, the width of the textured region A of the substrate100ranges from 10 μm to 30 μm. Referring toFIG.5, the extension direction of the texture region A is the same as the extension direction Y of the rear electrode141formed subsequently, and the extension length of the textured region A corresponds to an extension length of the rear electrode141, so that the doped surface field120located at the textured region A can increase the lateral transmission of the solar cell, reduce the lateral transmission loss of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell. In other embodiments, the rear surface102includes multiple textured regions A arranged along the extending direction of the rear electrode141. A space between two adjacent textured regions A ranges from 10 mm to 20 mm, which reduces the recombination rate of carriers, and the area for collecting the carriers is enhanced, and the passivation effect of the formed passivation contact structure is better, which is beneficial to improve the open circuit voltage, Voc, and the filling factor, FF. In yet other embodiments, in the same area where the rear electrode141is subsequently formed, the rear surface102includes multiple textured regions A arranged along the arrangement direction X of the rear electrode141. A space between two adjacent textured regions A ranges from 5 μm to 20 μm. In yet other embodiments, in the same area where the rear electrode141is subsequently formed, the rear surface102includes multiple textured regions A arranged along the arrangement direction X of the rear electrode141, and the multiple textured regions are arranged along the extension direction Y of the rear electrode141. Referring toFIG.9toFIG.12, the doped surface field120is formed. The doped surface field120is formed on the textured region A of the substrate100, and the doped surface field120has doping elements, and the doping elements are N-type doping elements or P-type doping elements. The tunneling dielectric layer131is formed, and the tunneling dielectric layer131is located on the flat region B of the rear surface102of the substrate100. The doped conductive layer132is formed, and the doped conductive layer132is located on the surface of the tunneling dielectric layer131away from the rear surface102of the substrate100, and the doped conductive layer132has doping elements, and the doping elements in the doped conductive layer132are of the same type as the doping elements in the doped surface field130. In some embodiments, along the direction from the rear surface102to the front surface101, the doped surface field120includes the first doped region121and the second doped region122, and the doping concentration of the first doped region121is greater than that of the second doped region122. The doping concentration of the first doped region121is greater than or equal to the doping concentration of the doped conductive layer132. Specifically, the doping concentration of the first doped region121ranges from 2×1020cm−3to 2×1021cm−3. In some embodiments, a ratio of the depth of the first doped region121and a height of the doped surface field120ranges from 1.5% to 4%. Preferably, the depth of the first doped region ranges from 90 nm to 200 nm, specifically 130 nm, 160 nm, 178 nm or 193 nm. Specifically, referring toFIG.9, the rear surface of the initial substrate located at the textured region A is subjected to a texturing process to form an initial textured structure103. In some embodiments, the texturing process is a laser process, and parameters of the laser process include: laser wavelength ranges from 355 nm to 460 nm, laser pulse width ranges from 20 ps to 80 ps, laser power ranges from 30 W to 100 W, size of a laser spot ranges from 15 μm to 50 μm, laser frequency ranges from 200 kHz to 2 MHz, and laser line speed ranges from 20 m/s to 40 m/s. Preferably, the parameters of the laser process include: the laser wavelength ranges from 355 nm to 400 nm, the laser pulse width ranges from 20 ps to 50 ps, the laser power ranges from 50 W to 80 W, the size of the laser spot ranges from 10% to 30% of the size of the required laser area, the laser frequency ranges from 300 kHz to 800 kHz, and the laser line speed ranges from 20 m/s to 30 m/s. In some embodiments, the initial textured structure103includes at least one protruding structure. The height difference between the top of the protruding structure and the rear surface102of the substrate100ranges from 2 μm to 10 μm, and the protruding structure includes a pyramid-shaped structure. In other embodiments, the number of protruding structures is at least two, the space between two adjacent protruding structures ranges from 2 μm to 4 μm, and the protruding structures include pyramid-shaped structures or other protruding structures with a slope. Referring toFIG.10, the tunneling dielectric film104and the conductive film105are formed on the flat region B located on the rear surface of the initial substrate and the surface of the initial textured structure103. Referring toFIG.11, the tunneling dielectric film104and the conductive film105on the surface of the initial textured structure130are removed, so that the top surface of the conductive film105away from the substrate100is slightly lower than the highest end of the initial textured structure103. Preferably, a height difference between the top surface of the conductive film105away from the substrate100and the highest end of the initial textured structure130ranges from 1 nm to 4 nm, so that the top surface of the initial textured structure103is exposed and the area the first doped region formed after the subsequent doping treatment is avoided to be smaller. Referring toFIG.12, the initial textured structure103(referring toFIG.11) and the conductive film105(referring toFIG.11) are doped to form the doped surface field120, the remaining tunneling dielectric film104(referring toFIG.11) serves as the tunneling dielectric layer131, and the remaining conductive film105(referring toFIG.11) serves as the doped conductive layer132. In some embodiments, a borosilicate glass BSG layer is first formed on the initial textured structure103(referring toFIG.11) and the conductive film105(referring toFIG.11), and then a laser process is adopted for doping treatment, and finally the remaining BSG layer is removed. In other embodiments, the doping process is performed using an ion implantation process. Referring toFIG.13, the passivation layer133and the first passivation layer113are formed on the surface of the doped conductive layer132, and the passivation layer133can be regarded as a rear passivation layer. The first passivation layer113is located at a surface of the emitter110away from the substrate100, and the first passivation layer113is regarded as a front passivation layer. Referring toFIG.14, the rear electrode141is formed, and a part of the bottom surface of the rear electrode141is located in the doped conductive layer131and the part of the bottom surface of the rear electrode141is in contact with the doped surface field120. The rear electrode141is in contact with the surface of the first doped region121of the doped surface field120. In some embodiments, along the arrangement direction X of the rear electrode141, the width of the textured region A of the substrate100is smaller than the width of the rear electrode141. In some embodiments, for the same rear electrode141, the ratio of the area of the contact surface between the doped surface field120and the rear electrode141and the area of the contact surface between the doped conductive layer132and the rear electrode141ranges from 1:2 to 2:1, specifically the ratio may be 1.3:2, 1.6:2, 1:1.2, 2:1.8, or 2:1.3. Preferably, the ratio of the area of the contact surface between the doped surface field120and the rear electrode141and the area of the contact surface between the doped conductive layer132and the rear electrode141ranges from 1:1.2 to 1.2:1, specifically the ratio may be 1:1.15, 1:1.1, 1:1 or 1.13:1. For the same rear electrode141, along the arrangement direction X of the rear electrode141, the ratio of the cross-sectional width of the contact surface between the doped surface field120and the rear electrode141and the width of the rear electrode141ranges from 1:4 to 1:2, specifically, the ratio may be 1:3.8, 1:3.3, 1:2.9, 1:2.3 or 1:2. Preferably, the ratio of the cross-sectional width of the contact surface between the doped surface field120and the rear electrode141and the width of the rear electrode141ranges from1:2.5to1:3.2, specifically, the ratio may be 1:2.6, 1:2.9, 1:3 or 1:3.2. Reference is made back toFIG.14, the electrodes142are formed, and the electrodes142penetrate the first passivation layer113to be in contact with the emitter110. Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present disclosure. In practice, various changes can be made in form and details without departing from the spirit and scope of the present disclosure. Any person skilled in the art can make changes and amendments without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure should be subject to the scope defined by the claims. | 37,494 |
11862742 | DETAILED DESCRIPTION OF THE INVENTION The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. For simplicity, most of the embodiments discussed herein disclose colloidal MnO-based quantum dots (or nanostructures) that are used in a photodetector as an example that these quantum dots can be applicable for devices. However, many other devices may take advantage of these quantum dots (nanostructures), as for example, transistors, diodes, spin transistor, etc. Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. According to an embodiment, a WBGS-based p-n junction DUV device is introduced that uses p-type manganese oxide WBGS quantum dots (MnO QDs) (or nanostructure). Highly crystalline MnO QDs may be synthesized via a femtosecond-laser ablation method in liquid and their p-type stability is demonstrated by Kelvin probe and field effect transistor measurements. In one application, the composition of the p-type WBGS MnO QDs is 81.5% MnO, 12.0% MnOOH, and 6.5% Mn2O3. However, variations of these numbers in a range of +/−15%, as discussed later, still achieve the properties noted above. Self-powered and solar-blind photodetectors capable of detecting DUV wavelengths below 300 nm under ambient conditions, based on the novel MnO QDs, confirm the carrier (hole) generation and UV transparency. This novel material is now discussed in more detail. The MnO QDs may be manufactured based on a femtosecond laser ablation in liquid (FLAL) method as developed by the present inventors [1] and [2]. The FLAL method uses ultrashort laser pulses that can be performed in atmospheric conditions. In one application, a titanium-sapphire femtosecond (fs) laser device102, as shown inFIG.1, sends a plurality of laser beam pulses104ito a target106provided in a liquid108. The laser device102may be used with operating conditions of 150 fs pulse width and 76 MHz pulse repetition rate at 800 nm wavelength. The laser beam pulses104iare directed to the target106, which is submerged in the solvent108, which is contained in a vessel110. The target106may be a manganese oxide material. As this technique is free from ablation damage to the manganese oxide target, it would be minimizing the formation of undesired components consisting of complex stoichiometric compositions (e.g., MnxO1-x) during the fabrication process. Interaction of the laser beam pulses104iwith the target106expels nanosized chunks of material from the target106, and these chunks of material form the desired MnO nanoparticles112, also called colloidal MnO based quantum dots (MnO QDs). High-resolution transmission electron microscopy (HR-TEM) measurements were performed to examine the structural properties of the FLAL-synthesized colloidal MnO QDs112. Electron energy-loss spectroscopy (EELS) by the TEM system was conducted to confirm the material composition.FIGS.2A-2Cillustrate the crystallographic and dimensional properties of the MnO QDs synthesized via the FLAL technique. More specifically,FIG.2Ashows the MnO QDs112on a TEM grid200, whereby a mean diameter of the MnO QDs was calculated to be 4.8±0.2 nm, as indicated by the distribution graph presented inFIG.2B. Note that a MnO QD is considered herein to have a diameter of 10 nm or less andFIG.2Bshows that all the MnO QD are less than 10 nm. The HR-TEM image shown inFIG.2Cdemonstrates the atomic distribution of the MnO QDs112with good crystallinity. The inter-planar spacing210was measured to be about 2.22 Å, which is a good match to the inter-plannar spacing of (200) and (111) planes of MnO. The atomic compositions were confirmed by electron energy loss spectroscopy (EELS) mapping. The EELS shown the presence of Mn, O, and C atoms, confirming that the Mn and O atoms are homogeneously distributed within a single MnO QD112. Similar evidence for the presence of both Mn and O atoms in the structure was provided by energy-dispersive X-ray (EDX) spectroscopy measurements. FIG.3Ashows the XPS spectra of the Mn 2p core level from MnO QDs, indicating that the MnO QDs are mostly in the MnO phase, with a small contribution of MnOOH (MnO QDs having —OH termination) and Mn2O3phases.FIG.3Bshows that the Mn 3s multiple splitting is 5.8 eV, which is very close to the value pertaining to the MnO. The inventors believe that this unique and novel mix composition of MnO, Mn2O3and MnO phase passivated by OH is the reason of the unique electrical and optical characteristic of the MnO QDs. For simplicity, herein, this novel material that includes quantum dots having a chemical composition of 85% or less of MnO, between 10 and 15% MnO2H, and less than 10% Mn2O3is called the colloidal MnO QDs. The name colloidal MnO QDs is used herein interchangeably with the term MnO QDs. Such compound has been found to have a bandgap that exceeds 4.1 ev in the DUV range, as illustrated inFIG.4, which shows the absorption spectra of the colloidal MnO QDs in ethanol versus the wavelength and the energy. The p-type nature of the MnO QDs manufactured as discussed above is now explored by using the Kelvin probe measurement (KPSs) and the field effect transistor (FET) measurements. KPMs are typically conducted to determine the Fermi level position for a particular material, which is represented by its work function. In preparation for the KPM, colloidal MnO QDs solution was spray-coated on a gold-plated glass, which was placed on a KPM stage inside a Faraday cage in which the measurements were carried out. When performing KPM, a vibrating metal tip (gold tip) is placed in the vicinity of the sample surface. An electron flow is maintained until the Fermi level is aligned between the two materials. This results in a potential buildup that can be nullified by an external feedback loop. Before carrying out the KPM scanning measurements on the MnO QDs sample, the system was calibrated using a pure gold-plated sample. Based on the repeated scans of a 100 μm2area, the average work function was found to be 4.87±0.02 eV, which is consistent with a p-type material. To estimate the electrical properties of the synthesized colloidal MnO QDs, an interdigitated electrode (IDE) for a top contact was constructed on a 200 nm thick silicon dioxide (p-type SiO2) substrate using a shadow mask. Then, the MnO QDs were spray-coated onto the IDE/SiO2substrate using a N2blowing gun. An FET based on the coated MnO QDs film (which is illustrated later inFIG.7B) exhibited the p-type electrical characteristics due to the holes being the majority carriers, as shown inFIG.5, where the source-drain transfer characteristic is plotted as a function of the gate voltage. However, a high source-drain voltage (>10 V) was used to activate a hole conducting channel due to a large channel length of 50 μm and the porous morphology of the MnO QDs film. Then, the accumulation of hole carriers properly occurred in the range of the negative gate voltage. Having confirmed that the novel colloidal MnO QDs discussed above exhibit p-type conduction, the photo-carrier generation of such material under DUV illumination is investigated, followed by the description of various optoelectronic devices that are built based on such material. For the photo-carrier generation of the p-type colloidal MnO QDs under DUV illumination, the colloidal p-type MnO QDs112were spray-coated at a constant temperature and stable nitrogen gas flow on a (Ti—Ti) IDE602having a 30 μm channel length L, as shown inFIG.6A. The IDE602includes a first set of electrodes603and a second set of electrodes605separated by the channel607.FIG.6Bshows the dark photocurrent620, the photocurrent622when the laser is off, and the photocurrent624when the laser is on under DUV illumination. For this experiment, a 244 nm laser emission was used and the current-voltage (I-V) relationship was established based on a source meter604measurements. It is noted that, when the photodetector600was fabricated with the asymmetric IDE configuration (Ti—Au), a photocurrent was produced even at 0V bias, as shown inFIG.6C, indicating that this device can work as a self-powered device. In the dark state620, the MnO QDs based device exhibits the Ohmic-like current (e.g., 3 nA at 0.1 V), although a small variation in the voltage of the electrically open state was noted owing to the randomly sprayed MnO QDs between the IDEs, as shown inFIG.6A. The relative responsivity of the photodetector device versus the wavelength of the incident light is plotted inFIG.6Dand it shows a very high responsivity in the DUV range.FIG.6Eshows the transient UV detection behavior of the MnO QDs device under various power densities (10, 42, 98, and 185 mW/cm2) when illuminated by the 244 nm laser. To achieve a high-quality DUV photodetector, the absorption and photo-response in the visible and UV-A range need to be negligibly small or limited, which is typically denoted as a “solar blind” device, which is typical for space communications and missile sensors. Therefore, the wavelength-dependent photo-response of the photodetector600was measured to demonstrate its solar blind nature, which resulted in the relative responsivities depending on the exposed wavelength of light, as shown inFIG.6D. The figure shows that the relative responsivity is very high in the 200-250 nm range, declining rapidly at wavelengths above 300 nm (UV-A) to reach 0, demonstrating the solar blind characteristics of the novel material. Therefore, the rejection ratio compared to the UV-A range is very high and it is even higher when compared to the visible spectrum. High-performance DUV photodetectors should have a very low-base current and a high photocurrent, which is shown by the transient photo-response under different illumination power densities inFIG.6E. The voltage applied during these measurements never exceeded 2 V. The graph inFIG.6Eindicates that throughout the experiment, the base current remained extremely low (<50 nA), whereas a high photocurrent generation was observed even at 0.5 V applied bias. At the same time, this device is capable of detecting a very low illumination (10 mW/cm2at 244 nm). Another photodetector700is now discussed with regard toFIGS.7A to7E. The photodetector700is based on a heterojunction formed by coating p-type MnO QDs onto a 2D-MoS2layer (or any 2D material) as now discussed. A photodetector based on 2D materials coated by MnO QDs are characterized by a significantly lower dark current and increased photocurrent compared to that uncoated pristine 2D materials. The contact between (1) the MnO QDs as a p-type material (with holes as the majority carriers) and (2) the 2D-MoS2as an n-type material (whereby electrons are the majority carriers) creates a heterojunction, theoretically resulting in a charge transfer at the interface between the two materials due to the difference in their work functions. FIG.7Ashows the schematic of the heterojunction MnO QDs-MoS2based photodetector700having interdigited electrodes704and706formed on a substrate702, which can be SiO2. The electrodes can be made of Au or Ti, or a combination of these materials. The 2D-MoS2layer710may be transferred onto the 200 nm thick silicon dioxide (SiO2)/Si (a heavily doped p-type) substrate702using a taping method. The MnO QDs712are placed directly onto the 2D-MoS2layer710. The 2D-MoS2layer710coated with the MnO QDs712is placed in a channel708defined by the electrodes704and706, as illustrated inFIG.7B. The electrical contact between the electrodes and the MnO QDs coated MoS22D layer was established via 100 nm thick Au interdigitated electrodes, and the channel708has a channel length and width of 5 μm and 640 μm, respectively. A cross-section through the MnO QDs-MoS2photodetector700is shown inFIG.7B. In one application, a third electrode713can be added to the back of the substrate702, to face the MnO QDs-MoS2layers710and712, and this electrode can be used as a gate, so that the entire device700becomes a transistor. In one embodiment, the transistor may be an optical transistor, where the properties of the gate are modified by DUV illumination so that an electron or hole flow is controlled. The dynamic photo-responses of both the bare MoS2photodetector (not shown) and the MnO QDs-MoS2heterojunction based photodetector700upon illumination cycles of 5 s ON and 10 s OFF are shown inFIG.7C. At 0.2 V, both devices were exposed to light724having different power density Pden values (100, 40, 25, 15, 10, and 1 mW/cm2), which were modulated using neutral-density (ND) filters722placed beneath the output window of the solar simulator720. As the Pden increased, the MnO QDs-MoS2photodetector700produced higher photocurrents compared to the bare MoS2photodetector due to the heterojunction710/712, as shown inFIG.7C. When the two materials MnO QDs and MoS2are merged as schematically depicted inFIGS.7D and7E, their respective Fermi energies Efare aligned, whereby the electrons in the MoS2material are transferred to the MnO QDs, decreasing the electron conductivity. As the valence band (VB) of the MnO QDs has an energy below the VB of the MoS2, accordingly a cusp discontinuity730can be created at the VB interface. Under illumination, three absorption paths (denoted as λ1, λ2, and λ3) can be activated to generate the electron-hole pairs. The paths indicated by λ1 and λ2 are the main photogeneration paths corresponding to intrinsic bandgap energies of MoS2and MnO QDs, respectively. Here, two preconditions are assumed: (i) multiple and complex absorption processes theoretically occurring in such a multi-layered MoS2can be described simply by λ1; and (ii) the MnO QDs dispersed on the MoS2surface form a complete film with electrical paths. The frequency of photogeneration through the λ2 path is high enough due to a sufficient hole density around the VB of the MnO QDs material. Then, the photogenerated electrons in the conduction band (CB) of the MnO QDs material can be favorably supplied into the MoS2material owing to the high-potential difference, increasing the electron density in the CB of the MoS2material. However, another absorption path, denoted as λ3, can be established, as shown inFIG.7E, because the recombination process is prone to occur around the VB cusp with many trap sites. Based on the band diagram shown inFIG.7E, as well as the spectroscopic data, it is believed that this heterojunction contributes to the dark current decrement, while increasing the photocurrent of the MnO QDs-MoS2devices. Another photodetector is now discussed with regard toFIGS.8A to9C.FIG.8Ashows a device800that has a substrate (e.g., SiO2substrate)802on which plural nanowires804were grown. The nanowires804extend along an axis X, which is perpendicular to the plane of the substrate802. The nanowires may be made of any known material and they may be grown by the MBE technique. However, in this embodiment, the nanowires (NW) are made of GaN. The colloidal MnO QDs material was drop-casted on the GaN NWs804to form MnO QDs812, which are randomly attached to the GaN NWs804, as shown inFIG.8A. The inventors have found that the emission of the GaN NWs804is significantly enhanced after drop-casting the MnO QDs812. These experiments were carried out repeatedly, yielding similar results, i.e., the photoluminescence spectrum820of the GaN NWs without the MnO QDs812is much smaller than the photoluminescence spectrum822of the GaN NWs804with the MnO QDs812. This enhancement can be due to the hole carriers injected to the GaN, increasing the electron-hole recombination events. This process can increase the carrier density that recombined, resulting in a greater radiative recombination rate. FIGS.9A to9Cillustrate variations of the device800that are configured to work as photodetectors. The photodetector900shown inFIG.9Ahas a substrate902on which the GaN NWs904were grown perpendicular to the surface of the substrate. A transparent contact layer920is formed on the free end of the GaN NWs904, as shown inFIG.9A. A first electrode930is formed on the transparent contact layer920and a second electrode932is formed on the substrate902. FIG.9Billustrates a variation of the above photodetector900, in which the photodetector940includes a substrate942, which is an n-type UV wide bandgap semiconductor, for example, an epilayer or a layer including quantum wells. A layer944of p-type MnO QDs is formed on top the substrate942and a contact transparent layer946is formed over the layer944. Electrodes947and948are formed over the transparent layer946and the substrate942, respectively.FIG.9Cillustrates another photodetector960in which the substrate962is made of SiO2. An n-type UV wide bandgap semiconductor layer964is formed over the substrate and the layer964may include plural NWs904as inFIG.9A. P-type MnO QDs912are randomly distributed only on the top of the NWs904, and a transparent contact layer946is formed over the MnO QDs912, as shown inFIG.9C. Electrodes947and948are formed over the layers962and946similar to those inFIG.9A. Those skilled in the art will understand that other variations of the photodetectors900,940, and960may be implemented based on the teachings from this application. A UV and DUV optoelectronic device1000that uses a p-type layer of MnO QDs is now discussed with regard toFIG.10. As commercial emitting devices, including white LED, DUV (UV-C) LEDs, and laser diodes are based on p-n junctions, the p-type MnO QDs112can act as a p-type layer for such devices. The p-type DUV semiconductors need to be configured to not absorb the light coming from the active layer in such devices. For example, Al-rich III-N materials, and AlGaN in particular, are the most suitable for DUV LED operating at 260-275 nm (4.5-4.78 eV). However, obtaining DUV LEDs with a high external quantum efficiency (EQE) remains a significant challenge for the industry and scientific community. The device1000ofFIG.10achieves a high internal efficiency AlGaN (or any wide bandgap semiconductor) DUV LED structure (<280 nm) on AlN substrate1002, with no TDs and with a high IQE (>83%).FIG.10shows the novel DUV LED that uses the MnO QDs based layer1010that can be transparent for even UV-C light emitted by the active layer1006. The active layer1006is sandwiched between an n-type contact layer1004, made for example, of AlGaN having a thickness of 1.8 micrometers, and an AlGaN electron blocking layer1008having a thickness of about 30 nm. An advantage of the MnO QDs layer1010is that such a layer does not need to be lattice matched as it can be deposited on the device1000by drop-casting, spin coating or spray-coating, which are simple and cost effective methods. In addition, the preparation of the MnO QDs112is very cost-effective. The disclosed embodiments provide a p-type colloidal MnO QDs based optoelectronic device that shows a very good responsivity in the DUV range as well as transparent electronic devices such as high-power devices, e.g., high-electron-mobility transistor (HEMT), that work in a harsh environment based on DUV wide bandgap semiconductor (e.g., AlGaN). It should be understood that this description is not intended to limit the invention. On the contrary, the embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details. Although the features and elements of the present embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein. This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims. REFERENCES [1] Mitra, S., Aravindh A. Das G., Pak Y., Ajia I., Loganathan K. Fabrizio D. E., Rogan S. I.,Nano Energy48, 551 (2018).[2] International Patent Application Publication No. WO 2018/215893, entitled “Method and Apparatus for Fabricating High Performance Optoelectronic Devices,” assigned to the assignee of this application. | 21,442 |
11862743 | DETAILED DESCRIPTION Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the example embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. Hereinafter, example embodiments will be described in detail with reference to the accompanying drawings. In the following drawings, the same reference numerals refer to the same components, and sizes of respective components in the drawings may be exaggerated for the sake of clear and convenient description. The embodiments described below are merely examples, and various modifications may be made from the embodiments. Hereinafter, terms “upper portion” or “on” may include not only members that are directly above in contact therewith, but also members that are above not in contact therewith. Terms such as first and second may be used to describe various elements but are used only for the purpose of distinguishing one element from another element. The terms are not intended to limit differences in materials or structures of components. A singular expression includes plural expressions unless the context clearly indicates otherwise. In addition, when a portion “includes” a certain component, this means that other components may be further included rather than excluding other components unless specifically stated to the contrary. The use of a term “above-described” and instruction terms similar thereto may correspond to both the singular and the plural. Unless explicitly stated or contradicted to the order of steps constituting the method, the steps may be performed in an appropriate order and are not limited to the described order. In addition, terms such as “ . . . portion” and “module” mean units that process at least one function or operation, which may be implemented as hardware or software, or a combination of hardware and software. Connections or connecting members of lines between components shown in the drawings are illustrative representations of functional connections and/or physical or circuit connections and may be represented as alternative or additional various functional connections, physical connections, or circuit connections, in an actual device. All examples or example terms are used to merely describe the technical idea in detail and the scope is not limited by the examples or example terms unless limited by the claims. Most image sensors have a structure of an array of photodiodes using a silicon process. However, other materials have to be used in the near infrared (about 750 nm to about 2,500 nm) due to the of light absorption limitation due to a band gap energy of silicon. A quantum dot is a semiconductor material and changes in light-absorption wavelength depending on sizes, and for example, an InAs quantum dot absorbs light more easily than silicon at a wavelength of 1,100 nm or more and is expected to be used without environmental issues in the near infrared band. When quantum dots are placed on an image sensor or an optical sensor to form a device, the degree of light absorption may be changed into a voltage or a current by using characteristics of a diode or a transistor of a silicon substrate. In addition, when a3T or4T (here, T represents a transistor) circuit is formed on a silicon substrate, a drive circuit suitable for an image sensor may be provided. FIG.1is a cross-sectional view schematically showing a structure of an opto-electronic device100according to an example embodiment.FIG.2shows an example of a plan view ofFIG.1. Referring toFIGS.1and2, the opto-electronic device100according to the embodiment includes a base portion, first and second electrodes31and35formed to be apart from each other on an upper surface of the base portion, a quantum dot layer50between the first electrode31and the second electrode35on the base portion, and a bank structure40formed to cover at least a partial region of the first and second electrodes31and35limiting (e.g., defining) a region where the quantum dot layer50is formed and formed of an inorganic material. In other words, the bank structure40may cover a first partial region of the first electrode31and a second partial region of the second electrode35. In the opto-electronic device100according to the example embodiment, the base portion includes a first semiconductor layer10doped with a first conductivity type (e.g., a first conductivity), and a second semiconductor layer20that is arranged on an upper surface of the first semiconductor layer10and doped with a second conductivity type (e.g., a second conductivity) different from the first conductivity type. In this case, an upper surface of the base portion may correspond to an upper surface of the second semiconductor layer20, and the first and second electrodes31and35may be electrically connected to the second semiconductor layer20. In addition, the quantum dot layer50may be formed on the second semiconductor layer20to be positioned between the first electrode31and the second electrode35. In addition, the base portion may further include first and second doped regions21and25that are apart from each other on the second semiconductor layer20and doped with a concentration different from that of the second semiconductor layer20, and the first and second electrodes31and35may be electrically connected to the first and second doped regions21and25as shown inFIG.1. One of the first and second doped regions21and25may be a source region and the other may be a drain region, and among the first and second electrodes31and35, an electrode electrically connected to the source region may be a source electrode, and an electrode electrically connected to the drain region may be a drain electrode. The first semiconductor layer10may be formed of, for example, a semiconductor material doped with a p+-type of a high concentration. For example, the first semiconductor layer10may be formed of silicon (Si), germanium (Ge), or a compound semiconductor material, and may be doped with the p+-type. The second semiconductor layer20may be formed of, for example, a semiconductor material doped with an n−-type. For example, the second semiconductor layer20may be formed of a semiconductor material and may be doped with the n−-type opposite to the first semiconductor layer10at a lower concentration than that of the first semiconductor layer10. The second semiconductor layer20may be formed of the same type of semiconductor material as that of the first semiconductor layer10and may be doped with a conductive type that is electrically opposite to that of the first semiconductor layer10. Accordingly, the first semiconductor layer10and the second semiconductor layer20may form a pn junction. In an example embodiment, the second semiconductor layer20may be formed on the first semiconductor layer10to have a step difference from the first semiconductor layer10. For example, the second semiconductor layer20may be formed only on a partial region of the first semiconductor layer10, thereby having a step difference from the first semiconductor layer10. For example, the first semiconductor layer10and the second semiconductor layer20may be formed on a substrate such as a semiconductor substrate through a doping process or a deposition process, and in this case, a region corresponding to the second semiconductor layer20may be patterned such that the second semiconductor layer20is positioned only on a partial region of the first semiconductor layer10, and thus, the second semiconductor layer20may have a step difference from the first semiconductor layer10. As another example, the first semiconductor layer10may be formed by doping a region of a semiconductor substrate corresponding to the first semiconductor layer10, and the second semiconductor layer20may be formed by being deposited on a partial region of the first semiconductor layer10. The first and second doped regions21and25may be formed to be apart from each other in the second semiconductor layer20by doping with a different concentration from the second semiconductor layer20. For example, the first and second doped regions21and25may be formed by doping partial regions of the second semiconductor layer20with an n+-type. The first and second electrodes31and35may be formed to be electrically connected to the first and second doped regions21and25, respectively. The first and second electrodes31and35may be formed of a metal material such as Al, AlN, Ti, TiN, Mo, Pt, Au, Cr, Ni, or Cu. The first and second electrodes31and35may include various metallic materials used as electrode materials. The bank structure40may be formed to cover at least partial regions of the first and second electrodes31and35so that a region where the quantum dot layer50is formed is limited. In addition, the bank structure40may be formed to have an uppermost surface higher than an upper surface of a light-receiving region including the quantum dot layer50to limit the region where the quantum dot layer50is formed. By applying the bank structure40in which the uppermost surface thereof is higher than the upper surface of the light-receiving region including the quantum dot layer50, when a plurality of quantum dots51of the quantum dot layer50, for example, colloidal quantum dots (CQDs) mixed with an organic material such as a solvent are spin-coated or ink-jet-sprayed, a layer in which the plurality of quantum dots51are evenly arranged may be obtained, and thus, a more uniform quantum dot layer50may be formed. The bank structure40may be formed in a split type so that stripes are positioned on both sides of the quantum dot layer50or may be formed in a ring structure surrounding the quantum dot layer50. In the split type of the bank structure40, a first stripe of the bank structure40may be formed on a first side of the quantum dot layer50and a second stripe of the bank structure40may be formed on a second side of the quantum dot layer50opposite to the first side. For example, the bank structure40may be formed in a rectangular ring structure.FIG.2shows an example of the bank structure40formed in a rectangular ring structure. In addition, in an example embodiment, the bank structure40may be formed to be in contact with an upper surface of the second semiconductor layer20in a region between the first and second doped regions21and25to block an electrical connection between the quantum dot layer50and the first and second doped regions21and25. For example, the bank structure40may be formed over partial regions of upper surfaces of the first and second electrodes31and35, side surfaces of the first and second electrodes31and35that are close to the quantum dot layer50, and an upper surface of the second semiconductor layer20between the first and second doped regions21and25, and thus, the bank structure40may have a stair structure. To block the electrical connection, the bank structure40may be formed of an insulator, for example, of inorganic oxide. The bank structure40may be formed of, for example, any one of SiO2, Si3N4, Al2O3, and HfO2. As such, when the bank structure40is formed to block the electrical connection between the quantum dot layer50and the first and second doped regions21and25, photo carriers generated by light absorption in the quantum dot layer50are not directly transferred to the first and second doped regions21and25and may be transferred thereto through the second semiconductor layer20forming a channel. In addition, an insulating layer30may be further formed over the first semiconductor layer10and the second semiconductor layer20. The insulating layer30may be formed on the stepped portion of the first semiconductor layer10and the second semiconductor layer20and up to a portion of the second semiconductor layer20reaching the first and second doped regions21and25on the second semiconductor layer20, and the first and second electrodes31and35may be formed to be positioned on the insulating layer30and on the first and second doped regions21and25, respectively, to be electrically connected to the first and second doped regions21and25. The insulating layer30may be formed of, for example, any one of SiO2, Si3N4, Al2O3, and HfO2. As such, when the insulating layer30is further provided over the first semiconductor layer10and the second semiconductor layer20, due to the presence of the insulating layer30, the first electrode31and the second electrode35may form a stepped structure, and the bank structure40may be formed to cover stepped portions of the first and second electrodes31and35. As such, the first and second electrodes31and35may be apart from each other and formed in the stepped structure so as to be electrically connected to the first and second doped regions21and25, respectively, on an upper surface of the base portion, and the bank structure40may be formed to be in contact with an upper surface of the second semiconductor layer20and cover the stepped portions of the first and second electrodes31and35, thereby blocking an electrical connection between the quantum dot layer50and the first and second doped regions21and25in the upper surface of the base portion. FIG.3is a schematic cross-sectional view of a structure of an opto-electronic device200according to an example embodiment.FIG.4shows an example of a plan view ofFIG.3. The example embodiments ofFIGS.3and4differ from the example embodiments ofFIGS.1and2in that a protective layer60is further provided on an uppermost portion of a light-receiving region. The protective layer60may be formed over the quantum dot layer50and the bank structure40. The protective layer60may stably protect the quantum dot layer50by preventing penetration of oxygen (O2), moisture (H2O), foreign materials, and so on. For example, the protective layer60may be formed of any one of insulating materials such as Al2O3, HfO2, and ZrO2. The protective layer60may be formed by, for example, an atomic layer deposition (ALD) method. The protective layer60may also be formed of a material such as SiO2. The opto-electronic devices100and200according to the example embodiments shown inFIGS.1to4may be formed, for example, by applying an n-channel epi-wafer on a p+ substrate. FIG.5is a schematic cross-sectional view of a structure of an opto-electronic device300according to an example embodiment. The example embodiment ofFIG.5differs from the example embodiment ofFIG.1in which the second semiconductor layer20is formed by doping a partial region of the semiconductor substrate in which the first semiconductor layer10is formed with a second conductivity type, instead of forming the second semiconductor layer20to be stepped from the first semiconductor layer10. FIG.6is a schematic cross-sectional view of a structure of an opto-electronic device400according to an example embodiment. The example embodiment ofFIG.6differs from the example embodiment ofFIG.5in that a protective layer60is further provided on an uppermost portion of a light-receiving region. The protective layer60may be formed over the quantum dot layer50and the bank structure40. The protective layer60prevents penetration of oxygen O2, moisture H2O, foreign materials, and so on and may be formed of, for example, any one of Al2O3, HfO2, and ZrO2. Referring toFIGS.5and6, the first and second semiconductor layers10and20may be formed such that uppermost surfaces thereof are at the same height. As such, when the second semiconductor layer20is formed by doping with a second conductivity type opposite to a partial region of the first semiconductor layer10doped with the first conductivity type, the first and second doped regions21and25may be formed by doping on the second semiconductor layer20to be apart from each other at a different doping concentration from that of the second semiconductor layer20. In addition, the first electrode31and the second electrode35may be formed on the second semiconductor layer20to be electrically connected to the first and second doped regions21and25. The bank structure40may be formed over partial regions of the first and second electrodes31and35and side surfaces of the first and second electrodes31and35close to the quantum dot layer50and may be formed to contact an upper surface of the second semiconductor layer20in a region between the first and second doped regions21and25, and thus the bank structure40may block an electrical connection between the quantum dot layer50and the first and second doped regions21and25. In addition, as shown inFIGS.5and6, even when the first and second semiconductor layers10and20are formed to have uppermost surfaces at the same level, an insulating layer30may be further provided on the upper surface of the first semiconductor layer10, the upper surface of the second semiconductor layer20and on portions of upper surfaces of the first and second doped regions21and25. In this case, the first and second electrodes31and35may be formed on the insulating layer30to be electrically connected to the first and second doped regions21and25, respectively. As such, when the insulating layer30is further provided over the first semiconductor layer10and the second semiconductor layer20, due to the presence of the insulating layer30, the first electrode31and the second electrode35may form a stepped structure, and the bank structure40may be formed to cover a stepped portion of the first and second electrodes31and35. The opto-electronic devices100,200,300, and400ofFIGS.1to6may include the base portion formed to have a pn junction between the first semiconductor layer10doped with a first conductivity type and the second semiconductor layer20doped with a second conductivity type, thereby having a structure of a junction field-effect transistor (JFET). In this case, the first semiconductor layer10serves as a gate, and the second semiconductor layer20may correspond to a channel. In the opto-electronic devices100,200,300, and400according to the example embodiments shown inFIGS.1to6, when the first semiconductor layer10serving as a gate is doped with, for example, a p+-type and the second semiconductor layer20serving as a channel is doped with an n−-type, a current flows between the first doped region21and the second doped region25through the second semiconductor layer20while a gate voltage is not applied to the first semiconductor layer10. However, when a reverse voltage, that is, a negative voltage, is applied to the first semiconductor layer10, a depletion region is widened in the second semiconductor layer20, and thus, the current flowing between the first doped region21and the second doped region25is reduced. In addition, when a reverse voltage higher than or equal to a certain intensity is applied to the first semiconductor layer10, the second semiconductor layer20is filled with a depletion region, and thus, no current flows between the first doped region21and the second doped region25. Accordingly, the opto-electronic devices100,200,300, and400turn on when a voltage is not applied to the first semiconductor layer10and turn off when a reverse voltage higher than or equal to a threshold voltage is applied to the first semiconductor layer10. In addition, in the opto-electronic devices100,200,300, and400according to various example embodiments shown inFIGS.1to6, the quantum dot layer50may be an absorption layer for performing photoelectric conversion by absorbing incident light and may be provided between the first and second electrodes31and35on an upper surface of the base portion. That is, the quantum dot layer50may be provided between the first and second electrodes31and35on the upper surface of the second semiconductor layer20of the base portion. The quantum dot layer50may include a plurality of quantum dots51. The quantum dot layer50may be formed of only a plurality of quantum dots51. In addition, the quantum dot layer50may further include an oxide layer55on at least one side thereof. That is, the quantum dot layer50may be provided where the plurality of quantum dots51are arranged to be in contact with an upper surface of the base portion, that is, an upper surface of the second semiconductor layer20, and the oxide layer55may be provided to cover the plurality of quantum dots51. As another example, the quantum dot layer50may be provided where the plurality of quantum dots51are in contact with the upper surface of the quantum dot layer50, and the oxide layer55may be provided between the plurality of quantum dots51and the upper surface of the base portion, that is, the upper surface of the second semiconductor layer20. As another example, the quantum dot layer50may be provided in a form in which the plurality of quantum dots51are surrounded by the oxide layer55. That is, the oxide layer55may be provided between the plurality of quantum dots51and the upper surface of the base portion, that is, the upper surface of the second semiconductor layer20, and the oxide layer55may also be provided above the plurality of quantum dots51on an upper surface of the quantum dot layer50. The plurality of quantum dots51may be arranged to form a layer. That is, the quantum dot layer50may have a structure that includes a layer in which the plurality of quantum dots51are arranged and the oxide layer55formed between the layer and an upper surface of the base portion, that is, an upper surface of the second semiconductor layer20, on an upper portion of the layer, or both sides of the layer. As another example, the plurality of quantum dots51may also be dispersed and distributed in the oxide layer55constituting the quantum dot layer50. As such, the plurality of quantum dots51may be arranged in various ways within the quantum dot layer50. FIGS.7A to7Dshow examples of various arrangements of the plurality of quantum dots51in the quantum dot layer50. Referring toFIG.7A, a plurality of quantum dots51may be arranged on a two-dimensional plane as a single layer structure. A planar layer in which the plurality of quantum dots51are arranged may be parallel to an upper surface of the second semiconductor layer20.FIG.7Ashows that the plurality of quantum dots51are densely arranged to be in contact with each other, but embodiment are not limited thereto. The plurality of quantum dots51may be scattered and distributed and spaced apart from each other in a planar layer in which the plurality of quantum dots51are arranged. However, when the number of quantum dots51is too small, it is difficult to obtain an amplification effect, and thus, a sufficient number of quantum dots may be arranged. For example, a ratio of an area occupied by the plurality of quantum dots51to an area of the two-dimensional plane of the layer in which the plurality of quantum dots51are arranged may be greater than or equal to 0.1. In the example shown inFIG.7A, the plurality of quantum dots51are buried in the oxide layer55. Accordingly, surfaces of the plurality of quantum dots51may be completely surrounded by the oxide layer55. In addition, the plurality of quantum dots51may be not in contact with an upper surface of the second semiconductor layer20and an upper surface of the quantum dot layer50. However, embodiment are not limited thereto. In addition, referring toFIG.7B, the plurality of quantum dots51may also be arranged in a stack structure of a plurality of two-dimensional layers. In this case, the number of quantum dots51may increase, and thus, an amplification effect may be further enhanced. However, when the number of layers in which the plurality of quantum dots51are stacked is excessively increased, incident light may not reach the bottom. Accordingly, to obtain highest efficiency, the number of layers in which the plurality of quantum dots51are stacked may be appropriately selected. For example, the plurality of quantum dots51may be stacked in 30 or fewer layers. Alternatively, the plurality of quantum dots51may be stacked in 10 or fewer layers. Alternatively, the plurality of quantum dots51may be stacked in three or fewer layers. FIG.7Bshows that, when the plurality of quantum dots51are arranged in a stack structure of a plurality of two-dimensional layers, the plurality of quantum dots51are stacked without gaps between the layers in which the plurality of quantum dots51are arranged, but embodiment are not limited thereto. Referring toFIG.7C, there may be a gap between adjacent two-dimensional layers in which the plurality of quantum dots51are arranged. In this case, gaps between the layers in which the plurality of quantum dots51are arranged may be filled with the oxide layer55. In addition, referring toFIG.7D, the plurality of quantum dots51may also be irregularly distributed and arranged within the oxide layer55. Accordingly, gaps between the plurality of quantum dots51may not be constant. FIGS.8A and8Bshow examples of different arrangements of the plurality of quantum dots51in the quantum dot layer50. Referring toFIG.8A, the plurality of quantum dots51may be arranged on an upper surface of the second semiconductor layer20. In this case, lower portions of the plurality of quantum dot51may be in contact with the upper surface of the second semiconductor layer20. The oxide layer55may be provided on the second semiconductor layer20to cover the plurality of quantum dots51. The oxide layer55may be in contact with side surfaces and upper portions of the plurality of quantum dots51and may not be in contact with lower portions of the plurality of quantum dots51that are in contact with the second semiconductor layer20. In addition, referring toFIG.8B, the plurality of quantum dots51may be arranged on an upper surface of the oxide layer55. In this case, only the lower portions of the plurality of quantum dots51may be in contact with the upper surface of the oxide layer55. FIGS.1,3,5, and6and drawings of following embodiments show examples in which the quantum dot layer50includes a layer in which the plurality of quantum dots51are arranged, and the oxide layer55surrounding the layer, but the examples are illustrative, and the arrangements of the plurality of quantum dots51in the quantum dot layer50may be variously modified as described above. In the opto-electronic devices100,200,300, and400according to various embodiments, the oxide layer55and the plurality of quantum dots51included in the quantum dot layer50serve to amplify a photocurrent generated by photons incident on the opto-electronic devices100,200,300, and400. The quantum dot51may be a particle of a certain size having a quantum confinement effect. For example, the quantum dot51may be formed of a compound such as CdSe, CdTe, InP, InAs, InSb, PbSe, PbS, PbTe, AlAs, ZnS, ZnSe, or ZnTe. When light is incident on the quantum dot51, the quantum dot51absorbs the light to generate a photocarrier, that is, a pair of a movable electron and hole. When the photocarrier generated by the quantum dot51moves to the second semiconductor layer20, which is a channel, a photocurrent flows between the first doped region21and the second doped region25. For example, when the second semiconductor layer20serving as a channel has an n−-type conductivity, electrons serving as a photocarrier may move to the second semiconductor layer20. A wavelength of light absorbed by the quantum dot51may change according to a band gap of the quantum dot51. The band gap of the quantum dot51may be mainly determined by a diameter of the quantum dot51. For example, the quantum dot51may have a diameter of about 1 nm to about 10 nm. Accordingly, the diameter of the quantum dot51may change according to the wavelength of light to be sensed by the opto-electronic devices100,200,300, and400. When the opto-electronic device100,200,300, or400is configured to detect light of a wide wavelength band, the plurality of quantum dots51may have various diameters. In addition, when the opto-electronic device100,200,300, or400is configured to detect light of a specific wavelength band, the plurality of quantum dots51may have the same diameter. The oxide layer55may serve to transfer efficiently the photocarrier generated by the quantum dot51to the second semiconductor layer20. In particular, the oxide layer55may efficiently separate electrons and holes generated by the quantum dots51and may transfer the separated electrons or holes to the second semiconductor layer20. To this end, the oxide layer55may be formed to be in contact with each of the plurality of quantum dots51. In addition, the oxide layer55may be formed of a material that is transparent to a wavelength band of light to be detected by the opto-electronic devices100,200,300, and400so that incident light may be transferred to the quantum dots51. The oxide layer55may be formed of a transparent oxide semiconductor material. For example, the oxide layer55may be formed of a transparent oxide semiconductor material such as silicon indium zinc oxide (SIZO), silicon zinc tin oxide (SZTO), gallium indium zinc oxide (GIZO), indium zinc oxide (IZO), zinc tin oxide (ZTO), indium tin oxide (ITO), CuAlO2, CuG2O2, SrCu2O2, or SnO2. The oxide layer55may be formed to have a thin thickness. For example, a thickness of the oxide layer55may be about 1 nm to about 100 nm. Alternatively, the thickness of the oxide layer55may be about 1 nm to about 50 nm. Alternatively, the thickness of the oxide layer55may be about 1 nm to about 30 nm. Because the oxide layer55is formed to have a thin thickness, the opto-electronic devices100,200,300, and400may have a sufficiently thin thickness. In the above description, a configuration is described and shown in which the quantum dot layer50includes the plurality of quantum dots51and the oxide layer55in contact with the plurality of quantum dots51on at least one side, but embodiments are not limited thereto. For example, in the opto-electronic device100,200,300, or400according to the example embodiment, the quantum dot layer50may include only an arrangement of the plurality of quantum dots51without including the oxide layer55. In addition, in the opto-electronic devices100,200,300and400according to various example embodiments, the plurality of quantum dots51may be arranged in the form of a thin film by spin-coating or ink-jet-spraying, for example, colloidal quantum dots (CQDs) made by mixing the quantum dots51with an organic material such as a solvent. In this case, a layer in which the plurality of quantum dots51are uniformly arranged may be obtained by the bank structure40that limits a region where the quantum dot layer50is formed. For example, when the quantum dot layer50includes an arrangement of the plurality of quantum dots51and the oxide layer55, the oxide layer55may be deposited by using a method such as sputtering, and the arrangement of the plurality of quantum dots51may be formed by applying CQDs by using a spin coating method or an ink jet spraying method. For example, when the quantum dot layer50has a sandwich stack structure of a two- or three-dimensional arrangement of a plurality of quantum dots51sandwiched between two different portions of the oxide layer55, as shown in FIGS.7A and7B, a lower portion of the oxide layer55may be deposited on an upper surface of the second semiconductor layer20which corresponds to a light-receiving region of the second semiconductor layer20and is surrounded by the bank structure40by using a method such as sputtering and a two-dimensional arrangement of the plurality of quantum dots51may be formed by applying a CQD on the lower portion of the oxide layer55by using a spin coating method or an ink jet spraying method. As such, the two-dimensional arrangement of a plurality of quantum dots51is formed, and then an upper portion of the oxide layer55may be deposited to cover the plurality of quantum dots51by using a method such as sputtering, and thus, the quantum dot layer50may be formed in a shape in which the plurality of quantum dots51are surrounded by the oxide layer55. In addition, when the quantum dot layer50has a structure in which the plurality of quantum dots51are located at a plurality of heights and the oxide layer55is between quantum dots located at different heights as shown inFIGS.7C and7D, the quantum dot layer50may be formed by alternately performing a process of applying the quantum dots51and a process of depositing the oxide layer55. In addition, when the quantum dot layer50is formed so that the plurality of quantum dots51are in contact with an upper surface of the base portion, that is, an upper surface of the second semiconductor layer20, and the oxide layer55covers the plurality of quantum dots51, as shown inFIG.8A, the quantum dot layer may be formed by forming an arrangement of the plurality of quantum dots51through a process of applying the quantum dots51and depositing the oxide layer55on the arrangement. In addition, when the quantum dot layer50is formed to have a structure in which the plurality of quantum dots51are arranged at the uppermost surface of the quantum dot layer50, as shown inFIG.8B, the quantum dot layer may be formed by depositing the oxide layer55on the upper surface of the base portion, that is, the upper surface of the second semiconductor layer20, and by applying the plurality of quantum dots51on the oxide layer55to form an arrangement of the plurality of quantum dots51. In addition, when the quantum dot layer50includes only a two-dimensional arrangement of the plurality of quantum dots51, an arrangement of the plurality of quantum dots51may be formed by applying the plurality of quantum dots51on the upper surface of the base portion, that is, the upper surface of the second semiconductor layer20. In the opto-electronic devices100,200,300, and400having a structure of a junction-type field effect transistor described above, a current flowing between the first doped region21and the second doped region25may be controlled by adjusting a voltage applied to the first semiconductor layer10to adjust an area of a depletion region in the second semiconductor layer20. Accordingly, dark noise generated by a current flowing between the first doped region21and the second doped region25when no light is incident on the opto-electronic device100,200,300, or400may be prevented or reduced. Accordingly, signal-to-noise ratios of the opto-electronic devices100,200,300, and400may be improved. In addition, the opto-electronic devices100,200,300, and400may be easily turned on or turned off by adjusting a voltage applied to the first semiconductor layer10, and thus, a switching operation of outputting a photocurrent from the opto-electronic device100,200,300, or400may be performed by turning the opto-electronic device100,200,300, or400on only when a signal output is required. In addition, more photocarriers than photons incident on the opto-electronic devices100,200,300, and400per unit time may be generated by using the plurality of quantum dots51and the oxide layer55arranged on the second semiconductor layer20serving as a channel, and thus, the opto-electronic devices100,200,300, and400may obtain a gain greater than 1. Accordingly, an amplification effect of an output signal is obtained by the oxide layer55and the plurality of quantum dots51, and thus, signal-to-noise ratios of the opto-electronic devices100,200,300, and400may be further increased. Accordingly, when the opto-electronic devices100,200,300, and400according to the present example embodiment are used, a clear image may be obtained even with weak incident light. The example embodiments described with reference toFIGS.1to6describe and show that the first semiconductor layer10is doped with a p+-type and the second semiconductor layer20is doped with an n−-type, but embodiments are not limited thereto. For example, in the opto-electronic device100,200,300, or400according to the example embodiment, the first semiconductor layer10may be doped with an n+-type of a high concentration, and the second semiconductor layer20may be doped with a p−-type of a low concentration. In this case, because the second semiconductor layer20serving as a channel has a p−-type conductivity, when light is incident on the plurality of quantum dots51, holes serving as photocarriers may move from the plurality of quantum dots51to the second semiconductor layer20. As such, in the opto-electronic devices100,200,300, and400according to the example embodiments, the first semiconductor layer10and the second semiconductor layer20may be doped with an opposite conductivity type, thereby forming a pn junction. The first semiconductor layer10may have a p-type conductivity and the second semiconductor layer20may have an n-type conductivity, or the first semiconductor layer10may have an n-type conductivity and the second semiconductor layer20may have a p-type conductivity. In addition, the first semiconductor layer10serving as a gate may be doped with a high concentration, and the second semiconductor layer20serving as a channel may be doped with a low concentration. However, when the second semiconductor layer20serving as a channel has an n-type conductivity, charge carriers of the channel are electrons, and when the second semiconductor layer20serving as a channel has a p-type conductivity, charge carriers of the channel are holes. Because mobility of electrons is higher than mobility of holes, the performance of the opto-electronic device100,200,300, or400may be higher in an n-type channel than in a p-type channel. In addition, although example embodiments of the opto-electronic devices100,200,300, and400having a JFET structure are described and shown above, embodiments are not limited thereto. For example, the opto-electronic devices according to the embodiments may also be formed to have field effect transistor structures shown inFIGS.9A and9BandFIGS.10A and10B. FIG.9Ais a schematic cross-sectional view showing a structure of an opto-electronic device500according to an example embodiment, andFIG.9Bshows an example of a plan view ofFIG.9A. Referring toFIGS.9A and9B, the opto-electronic device500according to the example embodiment is a field effect transistor (FET) type and may include a base portion, first and second electrodes531and535formed on the base portion to be apart from each other, a quantum dot layer50between the first electrode531and the second electrode535on the base portion, and a bank structure540which is formed to cover at least partial regions of the first and second electrodes531and535, limits a region where the quantum dot layer50is formed, and is formed of an inorganic material. In an example embodiment, the base portion may include a substrate501, a gate510formed on the substrate501to have a certain width, and an insulating layer530formed on the substrate501. The substrate501may include various substrates such as a glass substrate, an Si substrate, a Ge substrate, and a compound semiconductor substrate. The gate510may be positioned below and between the first electrode and the second electrode, The gate510may be formed of a metal material such as Al, AlN, Ti, TiN, Mo, Pt, Au, Cr, Ni, or Cu. The insulating layer530may be formed of, for example, any one of SiO2, Si3N4, Al2O3, and HfO2. The first and second electrodes531and535may be formed on the insulating layer530to be electrically connected to the quantum dot layer50. The first electrode531and the second electrode535may be formed on the insulating layer530to be apart from each other and to extend to both sides of the gate510with the quantum dot layer50therebetween. In other words, the first electrode531may extend on a first side of the gate510and the second electrode535may extend on a second side of the gate510opposite to the first side. For example, the first and second electrodes531and535may be formed of a metal material such as Al, AlN, Ti, TiN, Mo, Pt, Au, Cr, Ni, or Cu. Between the first electrode531and the second electrode535, one may be a source electrode and the other may be a drain electrode. The bank structure540may be formed to limit a region of the quantum dot layer50on the first and second electrodes531and535. The bank structure540may be formed to cover at least partial regions of the first and second electrodes531and535to limit the region where the quantum dot layer50is formed. In addition, the bank structure540may be formed to limit the region where the quantum dot layer50is formed by forming an uppermost surface to be higher than an upper surface of a light-receiving region including the quantum dot layer50. The bank structure540may be an insulator and may be formed of, for example, inorganic oxide. The bank structure540may be formed of, for example, any one of SiO2, Si3N4, Al2O3, and HfO2. As described above, the bank structure540may be formed in a split type so that stripes are on both sides of the quantum dot layer50or may be formed in a ring structure surrounding the quantum dot layer50. For example, the bank structure540may be formed in a rectangular ring structure.FIG.9Bshows an example in which the bank structure540is formed in a rectangular ring structure. The quantum dot layer50may be formed at a position corresponding to the gate510between the first electrode531and the second electrode535. The quantum dot layer50may include a plurality of quantum dots51. The quantum dot layer50may also be formed of only the plurality of quantum dots51. In addition, the quantum dot layer50may further include an oxide layer55on at least one side of the plurality of quantum dots51. That is, the quantum dot layer50may be provided where the plurality of quantum dots51are arranged to be in contact with an upper surface of the base portion, that is, an upper surface of the second semiconductor layer20, and the oxide layer55covers the plurality of quantum dots51. As another example, the quantum dot layer50may be provided where the plurality of quantum dots51are in contact with the upper surface of the quantum dot layer50, and the oxide layer55is provided between the plurality of quantum dots51and the upper surface of the base portion, that is, the upper surface of the second semiconductor layer20. As another example, the quantum dot layer50may be provided in a form in which the plurality of quantum dots51are surrounded by the oxide layer55. That is, the oxide layer55may be provided between the plurality of quantum dots51and the upper surface of the base portion, that is, the upper surface of the second semiconductor layer20, and the oxide layer55may also be provided on an upper end of the quantum dot layer50. Various configurations of the quantum dot layer50and a method of forming the quantum dot layer50may be the same as described above, and repetitive descriptions thereon are omitted. FIG.10Ais a schematic cross-sectional view of a structure of an opto-electronic device600according to an example embodiment.FIG.10Bis an example of a plan view ofFIG.10A. Example embodiments ofFIGS.10A and10Bdiffer from the example embodiments ofFIGS.9A and9Bin that a protective layer560is further provided on an uppermost portion of the light-receiving region. The protective layer560may be formed over the quantum dot layer50and the bank structure540. The protective layer560may stably protect the quantum dot layer50by preventing penetration of oxygen (O2), moisture (H2O), foreign materials, and so on. For example, the protective layer560may be formed of any one of insulating materials such as Al2O3, HfO2, and ZrO2. The protective layer560may be formed by, for example, an ALD method. The protective layer560may also be formed of a material such as SiO2. Hereinafter, examples of various samples in which the opto-electronic device according to the example embodiment is formed to have a JFET structure will be described. FIG.11Aa schematic top view of an opto-electronic device to which a split-type bank structure is applied, andFIG.11Bis an enlarged view of a main portion ofFIG.11A.FIG.12Ashows a schematic top view of an opto-electronic device to which a rectangular ring-shaped bank structure is applied, andFIG.12Bis an enlarged view of a main portion ofFIG.12A.FIGS.11A and11B, andFIGS.12A and12Bshow examples in which an effective quantum dot layer is formed to have a size of about 10×50 μm. InFIGS.11A and11BandFIGS.12A and12B, a size of 10×50 μm of an effective quantum dot layer may correspond to a size of a channel region. FIGS.11A and11B, and12A and12Bshow examples in which an SiO2layer is formed as an insulating layer, patterns for a channel and electrodes are formed on the SiO2layer, and then first and second electrodes are formed, and then a bank structure pattern is formed by using Si3N4so that the first and second electrodes are not in direct contact with a quantum dot layer, and then a quantum dot layer (oxide-quantum dot-oxide: OQO) having a stack structure of an arrangement of a plurality of quantum dots sandwiched between oxide layers is formed on the bank structure pattern. Not only an Si3N4material but also an insulator such as SiO2may be used to form a bank structure. The quantum dot layer (OQO) may be formed, for example, by depositing an oxide layer and spin-coating a CQD, and then performing lift-off or etching. As can be seen from a comparison betweenFIGS.11A and11BandFIGS.12A and12B, uniformity of the quantum dot layer (OQO) provided on an upper portion of a central channel region is better in an applied structure of rectangular bank surrounding the quantum dot layer (OQO) (OQO-surrounded rectangular bank) than in a split bank structure between first and second doped regions, that is, a source and a drain. FIGS.13A and13B,14A and14Bshow a difference between the split bank structure between the source and the drain and the OQO-surrounded square bank-applied structure and show examples in which a size of an effective quantum dot layer, that is, a channel region is about 5×25 μm, compared toFIGS.11A and11BandFIGS.12A and12B. As can be seen from a comparison betweenFIGS.13A and13BandFIGS.14A and14B, even when a size of a channel region is about 5×25 μm, uniformity of a quantum dot layer (OQO) provided on an upper portion of a central channel layer is better in the OQO-surrounded rectangular bank-applied structure than in a split bank structure between a source and a drain. FIGS.15A and15BandFIGS.16A and16Bshow a difference between a split bank structure between a source and a drain and an OQO-surrounded square bank-applied structure and show examples in which an effective quantum dot layer, that is, a channel region has an approximately square shape with a size of about 10×10 μm, compared toFIGS.11A and11BandFIGS.12A and12B. In addition,FIGS.17A and17BandFIGS.18A and18Bshow a difference between a split bank structure between a source and a drain and an OQO-surrounded square bank-applied structure and show examples in which an effective quantum dot layer, that is, a channel region has an approximately square shape with a size of about 5×5 μm, compared toFIGS.11A and11BandFIGS.12A and12B. As can be seen from a comparison betweenFIGS.15A and15BandFIGS.16A and16B, and a comparison betweenFIGS.17A and17BandFIGS.18A and18B, even when the channel regions are formed to have square shapes with sizes of about 10×10 μm and 5×5 μm, respectively, uniformity of a quantum dot layer (OQO) provided on an upper portion of a central channel layer is better in the OQO-surrounded square bank-applied structure than in the split bank structure between the source and the drain. FIGS.19A to19Dshow portions of quantum dot layers remained after an unnecessary portion of quantum dot layer (OQO) of an outer periphery is etched as a subsequent process for the OQO-surrounded rectangular bank-applied structures ofFIGS.12B,14B,16B, and18B, respectively. InFIGS.19A to19D, portions denoted by dotted lines are the portions of the quantum dot layers remaining after the unnecessary quantum dot layer (OQO) of the outer periphery is etched as a subsequent process and corresponds to an effective light-receiving region. FIGS.20A and20Bshow I-V characteristics of an opto-electronic device sample according to an example embodiment in a dark state, which includes a channel region having a size of about 50×50 μm and has a JFET (junction field-effect transistor) structure.21A and21B show I-V characteristics of an opto-electronic device sample according to an example embodiment in a dark state, which includes a channel region having a size of about 2×2 μm and has a JFET structure.FIGS.20A and21Ashow I-V characteristics of an opto-electronic device according to a gate voltage which is applied thereto, andFIGS.20B and21Bshow changes in source/drain current of the opto-electronic device for the gate voltage. As can be seen fromFIGS.20A and20B, andFIGS.21A and21B, when a reverse bias voltage less than or equal to a certain value is applied as the gate voltage, the source/drain current converges to zero, and thus, dark noise is almost zero. FIG.22shows graphs of characteristics of an n-channel JFET. InFIG.22, the left graph shows a relationship between a gate voltage VGS and a source/drain current IDS, and the right graph shows I-V characteristics according to the applied gate voltage. FIG.23show I-V characteristics of an opto-electronic device sample according to an example embodiment in a dark state, which includes a channel region having a size of about 50×50 μm and has a JFET structure. InFIG.23, the left graph shows a relationship between the gate voltage VGS and the source/drain current IDS, and the right graph shows I-V characteristics according to the applied gate voltage. As can be seen from a comparison betweenFIG.22andFIG.23, when the opto-electronic device according to the example embodiment is formed to have a JFET structure, characteristics of the JFET are exhibited. In the opto-electronic devices100,200,300,400,500, and600according to the example embodiments described above, dark noise may be reduced by including the quantum dot layer50limited by the bank structure40, and by using a plurality of quantum dots51, more photocarriers than photons incident on the opto-electronic device per unit time may be generated, and thus, a gain greater than 1 may be obtained and light-receiving efficiency may be increased. The opto-electronic devices100,200,300,400,500, and600described above may be used alone as a light-receiving element or may be arranged in a two-dimensional array to constitute an image sensor. FIG.24is a cross-sectional view schematically showing a structure of an image sensor1000to which a plurality of opto-electronic devices100,200,300,400,500, or600according to an example embodiment are applied.FIG.24shows an example of a case in which the opto-electronic device300described with reference toFIG.5is applied to the image sensor1000. The opto-electronic devices100,200,300,400,500, and600according to various example embodiments described above may be applied to the image sensor1000. Referring toFIG.24, the image sensor1000includes an array of a plurality of opto-electronic devices100,200,300,400,500, or600formed on a substrate1001and a plurality of drive circuits1100for outputting signals from each of the plurality of the opto-electronic devices100,200,300,400,500, or600.FIG.24shows only two opto-electronic devices300and two drive circuits1100for convenience, but in practice, many opto-electronic devices and drive circuits may be arranged in the form of a two-dimensional array. The above-described opto-electronic devices100,200,300,400,500, and600have low dark noise and high sensitivity, and thus, the image sensor1000may obtain a clear image even with weak incident light. In addition, sizes of pixels included in the image sensor1000may be further reduced, and thus, a resolution of the image sensor may be further increased. The image sensor1000may be implemented, for example, as a CMOS image sensor. In addition, by changing sizes of the plurality of quantum dots in the above-described opto-electronic devices100,200,300,400,500, and600to correspond to a wavelength range to be detected, an image sensor or a quantum dot image sensor may be implemented, or various optical sensors such as an optical device, an infrared sensor, and an infrared image sensor, which detect light in a desired wavelength range, may be implemented. The opto-electronic devices100,200,300,400,500, and600, including the quantum dot layers50limited by the above-described bank structures40and540, and the image sensor1000including the opto-electronic device are described with reference to the embodiments shown in the drawings, but the embodiments are only examples, and those skilled in the art will understand that various modifications and equivalent other embodiments may be made therefrom. Therefore, the disclosed embodiments should be considered from an illustrative point of view rather than a limiting point of view. The scope of rights is represented in the claims rather than the above description, and all differences within the same scope should be construed as being included in the scope of rights. According to an opto-electronic device and an image sensor including the same of the example embodiments, a plurality of quantum dots are used as a light-absorbing material, and thus, low dark noise and a high signal-to-noise ratio may be achieved. In addition, a quantum dot layer is formed by using a bank structure in which an uppermost surface is higher than an upper surface of a light-receiving region including the quantum dot layer, and thus, a layer in which a plurality of quantum dots are evenly arranged may be obtained and a more uniform quantum dot layer may be formed. It should be understood that example embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While example embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims. | 54,717 |
11862744 | DETAILED DESCRIPTION It is known from the background technology that the photovoltaic module in the background technology is prone to crack or fragment of the solar cell sheet, which leads to low yield and high manufacturing cost of the photovoltaic module. A photovoltaic module is provided according to an embodiment of the present disclosure. In the process of using multiple full back-contact solar cells to construct a cell string, after multiple full back-contact solar cell sheets are disposed in order, the welding strip composed of multiple bending portions arranged continuously is used to connect the adjacent solar cell sheets, the multiple bending portions are used as buffer joints to fully release the stress in the process of connecting the solar cell sheets with the welding strips, so that warping of the solar cell sheets is avoided, the reliability and yield of the cell string are improved. In the process of connecting adjacent solar cell sheets by using the welding strips, along the second direction, the orthographic projection of the central line of each of the multiple welding strips on a back surface of the solar cell sheet is aligned with the orthographic projection of the central line of the corresponding bus bar on the back surface of the solar cell sheet and/or the orthographic projection of the central line of each of the multiple bonding pads on the corresponding bus bar on the back surface of the solar cell sheet, so that the orthographic projection of the central line of each of the multiple welding strips on the back surface of the solar cell sheet coincides with the orthographic projection of the central line of the corresponding bus bar on the back surface of the solar cell sheet and/or the orthographic projection of the central line of each of the multiple bonding pads on the corresponding bus bar on the back surface of the solar cell sheet. After that, the welding strip is in electrical contact with the corresponding bus bar to complete the production of the cell string. By aligning the orthographic projection of the central line of each of the multiple welding strips on the back surface of the solar cell sheet with the orthographic projection of the central line of the corresponding bus bar on the back surface of the solar cell sheet and/or the orthographic projection of the central line of each of the multiple bonding pads on the corresponding bus bar on the back surface of the solar cell sheet, the aesthetic degree and connection effect when using the welding strips to connect the solar cell sheets are guaranteed, and the rise of contact resistance caused by the deviation of the welding strip from the bus bar area is avoided, so that the efficiency of the cell string can be prevented from being affected. The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art shall understand that, in each embodiment of the present disclosure, many technical details are provided for readers to better understand the present disclosure. However, the technical solutions claimed in the present disclosure can be realized even without these technical details and various changes and modifications based on the following embodiments. Reference is made toFIG.1toFIG.4, whereFIG.1is a schematic structural view of a cell string101provided according to an embodiment of the present disclosure,FIG.2is a schematic structural view of grid lines of a solar cell sheet102provided according to an embodiment of the present disclosure,FIG.3is a schematic structural view of a welding strip103provided according to an embodiment of the present disclosure, andFIG.4is a schematic structural view of the solar cell sheet102provided according to an embodiment of the present disclosure. The photovoltaic module includes: at least one cell string101, where each of the at least one cell string101includes multiple solar cell sheets102, and each of the multiple solar cell sheets102includes a substrate1021, and the substrate1021has a front surface, a back surface opposite to the front surface, a first passivation layer1022disposed on the front surface of the substrate1021, and a second passivation layer1023disposed on the back surface of the substrate1021. The photovoltaic module further includes multiple bus bars1024disposed on a surface of the second passivation layer1023, where the multiple bus bars1024are disposed at intervals along a first direction and extend along a second direction, and each of the multiple bus bars1024includes multiple bonding pads1025disposed at intervals along the second direction and a bus bar connecting line801. The photovoltaic module further includes multiple welding strips103, where two adjacent solar cell sheets102in the multiple solar cell sheets102are connected to each other by one of the multiple welding strips103, and each of the multiple welding strips103is in electrical contact with a corresponding bus bar1024, and each of the multiple welding strips103includes multiple bending portions arranged continuously along the second direction, and along the second direction, an orthographic projection of a central line of each of the multiple welding strips103on a back surface of the solar cell sheet102coincides with an orthographic projection of a central line of the corresponding bus bar1024on the back surface of the solar cell sheet102and/or an orthographic projection of a central line of each of the multiple bonding pads1025on the corresponding bus bar1024on the back surface of the solar cell sheet102. The photovoltaic module further includes at least one package layer120and at least one cover plate130, where after the at least one package layer120is disposed on a surface of the at least one cell string101, and the at least one cover plate130is disposed on a surface of the at least one package layer120away from the at least one cell string101, the at least one package layer120and the at least one cover plate130are laminated. In Figures, the first direction is shown as X direction, and the second direction is shown as Y direction. It should be understood that an exemplary example of the electrical contact between the welding strip103and the bus bar1024is shown in the above embodiment. In specific disclosures, the possible deviation of each of the multiple bonding pads1025during the manufacturing of the bus bar1024and the difficulty of fully aligning the central lines are considered, in response to aligning the orthographic projection of the central line of each of the multiple welding strips103on the back surface of the solar cell sheet102with the orthographic projection of the central line of the corresponding bus bar1024on the back surface of the solar cell sheet102and/or the orthographic projection of the central line of each of the multiple bonding pads1025on the corresponding bus bar1024on the back surface of the solar cell sheet102, a certain coincidence deviation is allowed between the central lines. For example, along a direction perpendicular to the second direction, there is allowed to be a 10% or 20% deviation between the central lines, that is, a coincidence area of the central lines ranges from 80% to 90% of the total area of the central lines, so that the disclosure difficulty of the scheme is reduced while ensuring the electrical contact effect as much as possible. In the process of using multiple full back-contact solar cells, in which multiple bus bars1024are all disposed on the second passivation layer1023on the back surface of the solar cell sheet102, to construct the cell string101, the welding strip103composed of multiple bending portions arranged continuously is used to connect the adjacent solar cell sheets102, so that when welding each of the multiple bonding bands103to a corresponding bus bar1024to realize electrical contact, multiple bending portions of the welding strip103are used as buffer joints to fully release the stress caused by different welding stresses respectively formed in the welding strip103and the solar cell sheet102due to the welding strip103and the solar cell sheet102have different thermal expansion coefficient, to ensure the welding quality of adjacent solar cell sheet102done by the welding strip103, avoid warping of the solar cell sheets102, and improve the reliability and yield of the cell string101. In the process of electrical contacting the welding strip103with the corresponding bus bar1024, along the second direction, the orthographic projection of the central line of each of the multiple welding strips103on a back surface of the solar cell sheet102is aligned with the orthographic projection of the central line of the corresponding bus bar1024on the back surface of the solar cell sheet102and/or the orthographic projection of the central line of each of the multiple bonding pads1025on the corresponding bus bar1024on the back surface of the solar cell sheet102. After the orthographic projection of the central line of each of the multiple welding strips103on the back surface of the solar cell sheet102coincides with the orthographic projection of the central line of the corresponding bus bar1024on the back surface of the solar cell sheet102and/or the orthographic projection of the central line of each of the multiple bonding pads1025on the corresponding bus bar1024on the back surface of the solar cell sheet102, each of the multiple welding strip103is in electrical contact with the corresponding bus bar1024by electrical connection process, such as welding, to connect adjacent solar cell sheets102together to form the cell string101. By aligning the orthographic projection of the central line of each of the multiple welding strips103on the back surface of the solar cell sheet102with the orthographic projection of the central line of the corresponding bus bar1024on the back surface of the solar cell sheet102and/or the orthographic projection of the central line of each of the multiple bonding pads1025on the corresponding bus bar1024on the back surface of the solar cell sheet102, the aesthetic degree and connection effect when using the welding strips103to connect the solar cell sheets102are guaranteed, and the rise of contact resistance caused by the deviation of the welding strip103from the area where the bus bar1024is located is avoided, so that the efficiency of the cell string101can be prevented from being affected. The substrate1021is configured to receive incident light and generate photogenerated carriers. In some embodiments, the substrate1021may be embodied as a silicon substrate, and the silicon substrate is made of at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. In other embodiments, the substrate1021may also be made of silicon carbide, organic material, or multi-component compound. The multi-component compound includes, but is not limited to, perovskite, gallium arsenide, cadmium telluride, copper indium selenium and other materials. In addition, the first direction and the second direction are perpendicular to each other, or there may be an included angle of less than 90 degrees between the first direction and the second direction, for example, 60 degrees, 45 degrees, 30 degrees, as long as the first direction and the second direction are different directions. For the convenience of explanation and understanding, an embodiment in which the first direction and the second direction are perpendicular to each other is taken as an example. In specific disclosures, the included angle between the first direction and the second direction can be adjusted according to actual needs and disclosure scenarios, which will not be limited thereto. In some embodiments, the bending portion is in a shape of an arc, a zigzag or a broken line. Reference is made toFIG.2andFIG.5, whereFIG.5a schematic structural view of a variety of welding strips103formed by different bending portions, such as arc bending portions501, zigzag bending portions502, and broken line bending portions503, provided according to an embodiment of the present disclosure. In the process of shaping the welding strip103, the shape of the bending portion formed by shaping can be set according to the needs of the disclosure scenarios. For example, in response to a difference between a thermal expansion coefficient of each of the multiple solar cell sheets102and a thermal expansion coefficient of each of the multiple welding strips103being big, in order to improve the stress release capacity of each bending portion on the welding strip103as much as possible, in response to the bending degree is consistent, that is, in response to a distance between each bending vertex farthest from the central line of each of the multiple welding strip103and the central line of each of the multiple welding strip103being consistent along the second direction, the bending portions can be in the shape of arc or zigzag. In this way, a ratio of the length of each of the multiple bending portions in a bending direction to the length of each of the multiple bending portions along the first direction is raised as much as possible, to improve the stress release capacity of the multiple bending portions. In response to the difference between the thermal expansion coefficient of each of the multiple solar cell sheets102and the thermal expansion coefficient of each of the multiple welding strips103being small, and other conditions such as bending degree are consistent, in order to reduce the coverage area of the welding strip103on the back surface of the solar cell sheet102as much as possible, the bending portions can be in a shape of broken line, such as triangle, rectangle or trapezoid, so that short circuit caused by the contact between the welding strip103and the finger on the back surface of the solar cell sheet102is avoided, to ensure the insulation of cell string101. In response to other conditions being consistent, and reducing the coverage area of the welding strip103on the back surface of the solar cell sheet102while ensuring the stress release capacity of the welding strip103, the bending portion can be in a shape an arc, in which the welding strip103occupies a relative smaller area of the back surface of the solar cell sheet102. In response to improving the stress release capacity of the welding strip103as much as possible, the bending portion can be in a shape of a zigzag, in which the welding strip103occupies a relative larger area of the back surface of the solar cell sheet102. According to the disclosure scenarios and requirements, the welding strip103is formed by shaping the multiple bending portions to an appropriate shape selected from the above shapes, to ensure the adaptability of the welding strip103to different disclosure scenarios and requirements. It should be understood that the arc shape in the above shapes of the multiple bending portions may be an arc, an elliptical arc or an irregular arc formed by multiple arcs. The broken line shape may be a triangle, rectangle, trapezoid or other figure composed of multiple broken lines. The zigzag shape may be a smooth figure composed of multiple arcs, or a figure composed of multiple broken lines and multiple arcs, or a figure similar to a normal distribution curve. The specific structure of the multiple bend portions with different shapes is not limited thereto. In some embodiments, the bending directions of adjacent bending portions are the same or opposite along the second direction. Reference is made toFIG.6, which is a schematic structural view of another variety of welding strips103formed by different bending portions, in which along the second direction, adjacent bending portions in the arc shape are bent in the same direction or opposite directions, adjacent bending portion in the zigzag shape are bent in the same direction or opposite directions, provided according to an embodiment of the present disclosure. In the process of shaping the welding strip103, a relationship between the bending directions of adjacent bending portions can be adjusted as needed. In response to other conditions such as the bending degree and the width of the welding strip103being consistent, in order to minimize the coverage area of the welding strip103on the back surface of the solar cell sheet102, two adjacent bending portions can be bent in the same bending direction in the process of shaping the welding strip103, so that the coverage area of the welding strip103on the back surface of the solar cell sheet102is reduced, and the contact between the welding strip103and the finger on the back surface of the solar cell sheet102is minimized, so as to avoid short circuit on the solar cell sheet102. In order to make the welding strip103have a desirable stress release effect, in the process of shaping the welding strip103, the two adjacent bending portions can be bent in opposite bending directions. Since bending portions with different bending directions in each of the multiple welding strips103are alternately arranged, the multiple bending portions in each of the multiple welding strips103have a desirable stress release effect in more directions, and the overall shape of the welding strip103will be as smooth and beautiful as possible. Therefore, the bending directions of adjacent bending portions in the weld strip103can be set to be the same or opposite to adapt to different disclosure scenarios and requirements. It should be understood that, in order to facilitate understanding, the embodiments of the present disclosure, in which the relationship between bending directions of adjacent bending portions are consistent, are taken as examples to perform illustration. However, in specific disclosures, along the second direction, the relationship between the bending directions of adjacent bending portions in the welding strip103may be consistent, that is, the bending directions of adjacent bending portions are the same or opposite. The relationship between the bending directions of adjacent bending portions may also be inconsistent, that is, the bending directions of some adjacent bending portions are the same, while the bending directions of some adjacent bending portions are opposite, which are not limited thereto. In some embodiments, each bonding pad1025is electrically contacted with two adjacent bending portions on the welding strip103. Referring toFIG.2andFIG.7, the welding strip103is composed of adjacent arc bending portions501with opposite bending directions. Each bonding pad1025contacts two adjacent bending portions on the welding strip103. Along the first direction, intersection line of the two adjacent arc bending portions501coincides with the central line of the bonding pad1025. That is to say, before the welding strip103is electrical contacted with the bus bar1024, after the orthographic projection of the central line of the welding strip103on the back surface of the solar cell sheet102is aligned with the orthographic projection of the central line of the corresponding bus bar1024on the back surface of the solar cell sheet102and/or the orthographic projection of the central line of each of the multiple bonding pads1025on the corresponding bus bar1024on the back surface of the solar cell sheet102along the second direction, the intersection line between the adjacent bending portions connected with the bonding pad1025is aligned with the central line of the bonding pad1025along the direction perpendicular to the second direction. Subsequently, the bonding pad1025is electrical contacted with the two adjacent bending portions by the electrical connection process to complete the electrical contact between the welding strip103and the corresponding bus bar1024. Since the bonding pad1025is electrically contacted with both two adjacent bending portions, in response to the welding strip103and the solar cell sheet102having different shrinkage due to the difference in thermal expansion coefficient, the bonding pad1025can directly release the stress generated by the different shrinkage of the welding strip103and the solar cell sheet102through the two adjacent bending portions electrically in contact with the bonding pad1025to improve the capacity and effect of stress release. It should be understood that in the above embodiment, only a schematic structural view of electrical contact between the bonding pad1025and the welding strip103is given. In the process of electrical contact between bonding pad1025and two adjacent bending portions in welding strip103, the difficulty of implementation, mechanical error and other factors are taken into consideration. Along the direction perpendicular to the second direction, not only the intersection line between bending portions is aligned with the central line of bonding pad1025, but also the position relationship between the intersection line between bending portions and the central line of the bonding pad1025is set to be not completely coincident with each other or apart from each other. For example, the coincidence area of the central line of the bonding pad1025and the intersection line of adjacent bending portion occupies 90%, 80% or 50% of the total area, or along the second direction, a distance between the intersection line of the adjacent bending portions and the central line is 10%, 20% or 45% of the maximum length of the bonding pad1025. On the basis of ensuring the effect of stress release, the difficulty of implementing electrical contact between the welding strip103and the bonding pad1025is reduced. In this embodiment, in response to the bonding pad1025being electrical contacted with two adjacent bending portions on the welding strip103, the specific position relationship between the intersection line between the bending portions and the central line of the bonding pad1025along the second direction is not limited. In addition, referring toFIG.2andFIG.8, the bus bar1024includes a bus bar connecting line801and the bonding pad1025. In order to avoid the electrical contact between the finger on the back surface of the solar cell sheet102and a heteropolarity bus bar1024with opposite polarity to the finger, or between the finger and the welding strip103corresponding to the heteropolarity bus bar1024with opposite polarity to the finger, the bus bar1024on the back surface of each solar cell sheet102can also be solder resisted in advance before the connection of the solar cell sheets102is performed. With each bonding pad1025on the bus bar1024as a partition, the bus bar connecting line801is divided into multiple solder resist areas802arranged along the second direction, and the multiple solder resist areas802are processed by printing or dispensing with solder resist ink, such as insulating glue. During the solder resist processing, solder resist ink can be used to completely cover each of the multiple solder resist areas802, or multiple solder resist sub areas803can be divided in each of the multiple solder resist areas802. Each of the multiple solder resist sub areas803is completely covered, and the position of each of the multiple solder resist sub areas803corresponds to the position of a heteropolarity finger with opposite polarity to the bus bar1024, to avoid contact between the welding strip103and the bus bar1024, and between the welding strip103and the finger with opposite polarity to the bus bar1024. In the process of solder resist processing, the size of solder resist ink should be 15 μm or above higher than the height of solder resist area802or solder resist sub area803, and be 50 μm or above wider than the width of solder resist area802or solder resist sub area803, which will not be limited thereto. Reference is made toFIG.2andFIG.9, where the third direction is the Z direction. In some embodiments, each of the multiple bending portions includes a first bending portion901in electrical contact with the bonding pad1025and a second bending portion902not in electrical contact with the bonding pad1025. Along the third direction, the size of the first bending portion901is larger than that of the second bending portion902, and the third direction is perpendicular to the bending direction of the multiple bending portions. The welding strip103is mainly configured to connect adjacent solar cell sheets102, and transmit the current collected on the bus bar1024in electrical contact with the welding strip103to a component end connected with the cell string101. The current transmission capability of the welding strip103is related to its own resistance and the contact resistance between the welding strip103and the bus bar1024. In response to the welding strip103being in electrical contact with the bus bar1024by each of the multiple bonding pads1025on the bus bar1024, the contact resistance between the welding strip103and the bus bar1024is related to the contact area between the welding strip103and the bonding pad1025. Therefore, in the process of shaping the welding strip103to form bending portions, the welding strip103is shaped into multiple bending portions arranged continuously along the second direction, and the welding strip103is aligned with the corresponding bus bar1024to determine the first bending portion901in electrical contact with the bonding pad1025and the second bending portion902not in electrical contact with the bonding pad1025in the welding strip103. Along the third direction, the sizes of the first bending portion901and the second bending portion902refer to their widths along the third direction, respectively. Therefore, the third direction is a direction parallel to the back surface of the solar cell sheet102and perpendicular to the second direction. In response to an original width of the welding strip103before shaping along a direction perpendicular to the extension direction being relatively small, the first bending portion901is stretched along the third direction perpendicular to the bending direction, so that the size of the first bending portion901is larger than the size of the second bending portion902along the third direction of the welding strip103. In response to the original width of the welding strip103before shaping along the direction perpendicular to the extension direction being relatively large, the second bending portion902is compressed along the third direction perpendicular to the bending direction, so that the size of the first bending portion901is larger than the size of the second bending portion902along the third direction. The first bending portion901or the second bending portion902in the welding strip103are reshaped for the second time, so that the size of the first bending portion901is larger than the size of the second bending portion902along the third direction perpendicular to the bending direction, and the adjacent first bending portions901are connected to the corresponding bonding pad1025to complete the electrical contact between the welding strip103and the corresponding bus bar1024. Along the third direction perpendicular to the bending direction, in the welding strip103, the size of the first bending portion901in electrical contact with the bonding pad1025is set to be larger, so that the electrical contact area between the welding strip103and the bonding pad1025is enhanced, which reduces the contact resistance between the welding strip103and the bonding pad1025, thereby improving the current transmission capability of the welding strip103and ensuring the working efficiency of the cell string101. Referring toFIG.2andFIG.10, the fourth direction is the F direction. In some embodiments, along the fourth direction, a distance between a bending vertex1001of the bending portion away from the bus bar1024and the bus bar1024ranges from 0.1 mm to 0.3 mm, and the fourth direction is perpendicular to the second direction. InFIG.10, the welding strip103is composed of arc bending portions, in which adjacent bending portions are bent in opposite bending directions. Along the fourth direction, the distance between the bending vertex1001of the bending portion and the bus bar1024is the minimum distance between the orthographic projection of the bending vertex1001on the solar cell sheet102and the central line of the orthographic projection of the bus bar1024on the back surface of the solar cell sheet102, that is, the fourth direction is a direction parallel to the back surface of the solar cell sheet102and perpendicular to the second direction. Along the fourth direction, in response to the distance between the bending vertex1001and the bus bar1024being too small, the bending degree of the bending portion is low, which will reduce the capability of the bending portion to release the stress generated between the welding strip103and the solar cell sheet102, and it is easy to cause the solar cell sheet102to warp or even break due to the ineffective release of the stress, thereby affecting the yield and production cost of the cell string101. In response to the distance between the bending vertex1001and bus bar1024being excessive, the bending degree of the bending portion is also excessive, and the capability of the bending portion to release the stress generated between the welding strip103and the solar cell sheet102exceeds the demand. In addition, the overall length of the welding strip103is too excessive, which reduces the current transmission capability of the welding strip103. In response to the bending degree being excessive, the welding strip103is easy to be in electrical contact with the heteropolarity finger with opposite polarity to the bus bar1024, on the back surface of the solar cell sheet102, which affects the insulation of the solar cell sheet102. Therefore, along the fourth direction, in the welding strip103, the distance between the bending vertex1001away from the bus bar1024and the bus bar1024is set to range from to 0.3 mm, such as 0.15 mm, 0.2 mm or 0.25 mm, so that the bending portion can effectively release the stress generated between the welding strip103and the solar cell sheet102to improve the yield of the cell string101, while ensuring the current transmission capability of the welding strip103and the insulation of the solar cell sheet102. In some embodiments, the ratio of the length of the bending portion along the bending direction to the length of the bending portion along the second direction ranges from 1.05 to 1.25. The core function of the bending portion is to release the stress generated between the welding strip103and the solar cell sheet102as a buffer. The stress release capacity of the bending portion is not only related to the bending degree of the bending portion itself, but also to the ratio of the length of the bending portion along the bending direction to the length of the bending portion along the extension direction, that is, to the ratio of the length of the bending portion along the bending direction to the length of the bending portion along the second direction. In response to other conditions being consistent, and the ratio of the length of the bending portion along the bending direction to the length of the bending portion along the second direction being too small, the stress that the bending portion can release will be quite limited, which limits the capability of the bending portion to release the stress generated between the welding strip103and the solar cell sheet102, resulting in limited stress release effect, and the solar cell sheet102is still prone to warp or even crack, the yield and production cost of cell string101is affected. In response to the ratio of the length of the bending portion along the bending direction to the length of the bending portion along the second direction being excessive, the bending portion can release a large amount of stress, and the capability of the bending portion to release the stress generated between the welding strip103and the solar cell sheet102exceeds the demand. In addition, the overall length of the welding strip103is excessive, which reduces the current transmission capability of the welding strip103, and increases the production cost of the cell string101. Therefore, in the welding strip103, the ratio of the length of the bending portion along the bending direction to the length of the bending portion along the second direction is set to range from 1.05 to 1.25, such as 1.10, 1.15 or 1.20, so that the bending portion can effectively release the stress generated between the welding strip103and the solar cell sheet102to improve the yield of the cell string101, while ensuring the current transmission capability of the welding strip103, and avoiding the problem of high production cost of the cell string101. In some embodiments, multiple bending portions have the same length along the second direction. As described in the above embodiments, the core function of the bending portion is to release the stress generated between the welding strip103and the solar cell sheet102as a buffer joint. The bus bar1024on the solar cell sheet102is generally made of the same material. In response to the welding strip103being in electrical contact with the bus bar1024, the stress to be released at each contact position is basically the same. Therefore, the length of each bending portion along the second direction can be consistent, the regular distribution and the same specification of the bending portion are also conducive to the shaping and production of the welding strip103while ensuring the stress release effect and the aesthetic degree, wo that the shaping difficulty of the welding strip103is reduced, thereby improving the shaping and production efficiency. It should be understood that in response to the solar cell sheet102having a special structure or requirement, the length of a specific part of the bending portion along the second direction can also be set separately according to the requirements of the disclosure scenario. In addition, the production efficiency, and the difficulty and accuracy of actual production are taken into consideration, there may be a certain deviation between the length of each bending portion along the second direction and a preset standard length, for example, the deviation between the actual length and the standard length may be 5%, 10%, 15%, which will not be limited thereto. In some embodiments, the plane of each welding strip103is parallel to the back surface of the solar cell sheet102. In the process of shaping the welding strip103, on the plane parallel to the back surface of the solar cell sheet102, multiple bending portions continuously arranged along the extension direction are formed. In the process of connecting the solar cell sheets102with the welding strip103, the plane of each bending portion of the welding strip103are placed parallel to the back surface of the solar cell sheet102, and the welding strip103is in electrical contact with the bus bar1024by the electrical connection process. The plane of the welding strip103is placed parallel to the back surface of the solar cell sheet102, so that a protrusion or a recess portion on the welding strip103in the direction perpendicular to the back surface of the solar cell sheet102is avoided, and the problem of the maximum height of the cell string101rising caused by the protrusion is avoided, which reduces the accommodation volume of the cell string101, and thus reducing the volume of the photovoltaic module. In addition, the problem that the welding strip103is easy to scratch the solar cell sheet102and the bus bar1024caused by the recess portion is avoided, and the integrity of the grid line of the solar cell sheet102and the overall photoelectric conversion efficiency of the solar cell sheet102are guaranteed. Correspondingly, a method for preparing the photovoltaic module is further provided according to another embodiment of the disclosure, to prepare the photovoltaic module provided according above embodiments of the present disclosure. The specific process of the method can refer toFIG.11, and includes the following operations. Referring toFIG.2andFIG.4, at least one cell string101is provided. Each of the at least one cell string101includes solar cell sheets102, and each of the multiple solar cell sheets102includes a substrate1021, the substrate1021has a front surface and a back surface opposite to the front surface. The solar cell sheet102further includes a first passivation layer1022disposed on the front surface of the substrate1021, a second passivation layer1023disposed on the back surface of the substrate1021, multiple bus bars1024disposed on a surface of the second passivation layer1023. The multiple bus bars1024are disposed at intervals along the first direction and extend along the second direction, and each of the multiple bus bars1024includes multiple bonding pads1025disposed at intervals along the second direction. Referring toFIG.2, multiple bus bars1024are provided. The multiple bus bars1024are disposed on a surface of the second passivation layer1023, and the multiple bus bars1024are disposed at intervals along the first direction and extend along the second direction, and each of the multiple bus bars1024includes multiple bonding pads1025disposed at intervals along the second direction and the bus bar connecting line801. Referring toFIG.3, multiple welding strips103are provided, and the multiple welding strips103are continuously shaped by the shaping process to form the bending portions arranged continuously along the extension direction. In the process of shaping the welding strip103to form the bending portion, since the continuous shaping method is adopted, it is unnecessary to consider how to space the bending portions and the distance between adjacent bending portions. Therefore, the shaping process is simpler and the yield of the shaped welding strip103is higher. In addition, since the welding strip103is composed of bending portions arranged continuously, the appearance of the welding strip103is smoother and aesthetic. In some embodiments, the shaping process includes pressing, bending, forging, or stamping. Referring toFIG.1toFIG.3, the placement position of the welding strip103is determined, and the electrical connection process is performed to form the cell string101. Along the second direction, the orthographic projection of the central line of each welding strip103on the back surface of the solar cell sheet102is aligned with the orthographic projection of the central line of the corresponding bus bar1024on the back surface of the solar cell sheet102and/or the orthographic projection of the central line of each of the multiple bonding pads1025on the corresponding bus bar1024on the back surface of the solar cell sheet102. After that, the electrical connection process is adopted to electrically contact each welding strip103with the corresponding bus bar1024to form the cell string101, in which two adjacent solar cell sheets102are connected to each other by the welding strip103. Referring toFIG.12, at least one package layer120and at least one cover plate130are provided. After the at least one package layer120is placed on a surface of the at least one cell string101and the at least one cover plate130is placed on a surface of the at least one package layer120away from the at least one cell string101, the at least one package layer120and the at least one cover plate are laminated. The photovoltaic module formed ultimately includes: the at least one cell string101formed by multiple solar cell sheets102, and each of the at least one cell string101is the cell string101provided according to above embodiments. Each of the at least one package layer120is configured to cover the surface of the solar cell sheet102. Each of the at least one cover plate130is configured to cover the surface of the at least one package layer120away from the solar cell sheet102, and the multiple solar cell sheets102are electrically connected in series and/or parallel. Specifically, in some embodiments, the multiple solar cell sheets102are electrically connected by the welding strips103. The package layer120is configured to cover the front surface and the back surface of the solar cell sheet102. Specifically, the package layer120may be an organic packaging adhesive film, such as an ethylene vinyl acetate copolymer (EVA) adhesive film, a polyethylene octene copolymer (POE) adhesive film, or a polyethylene terephthalate (PET) adhesive film. In some embodiments, the cover plate130may be a glass cover plate, a plastic cover plate or the like with a light transmission function. Specifically, the surface of the cover plate130toward the package layer120can be a surface with protrusions and recesses, thereby increasing the utilization rate of incident light. Although the present disclosure is disclosed above with preferred embodiments, it is not used to limit the claims. Any person skilled in the art can make some possible changes and modifications without departing from the concept of the present disclosure. The scope of protection shall be subject to the scope defined by the claims of the present disclosure. Those of ordinary skill in the art can understand that the above embodiments are specific examples for realizing the present disclosure, and in actual disclosures, various changes may be made in shape and details without departing from the spirit and range of the present disclosure. Any person skilled in the art can make their own changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the scope defined by the claims. | 41,802 |
11862745 | DETAILED DESCRIPTION The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Any implementation described herein as exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. This specification includes references to “one embodiment” or “an embodiment.” The appearances of the phrases “in one embodiment” or “in an embodiment” do not necessarily refer to the same embodiment. Particular features, structures, or characteristics may be combined in any suitable manner consistent with this disclosure. Terminology. The following paragraphs provide definitions and/or context for terms found in this disclosure (including the appended claims): “Comprising.” This term is open-ended. As used in the appended claims, this term does not foreclose additional structure or steps. “Configured To.” Various units or components may be described or claimed as “configured to” perform a task or tasks. In such contexts, “configured to” is used to connote structure by indicating that the units/components include structure that performs those task or tasks during operation. As such, the unit/component can be said to be configured to perform the task even when the specified unit/component is not currently operational (e.g., is not on/active). Reciting that a unit/circuit/component is “configured to” perform one or more tasks is expressly intended not to invoke 35 U.S.C. § 112, sixth paragraph, for that unit/component. “First,” “Second,” etc. As used herein, these terms are used as labels for nouns that they precede, and do not imply any type of ordering (e.g., spatial, temporal, logical, etc.). For example, reference to a “first” solar cell does not necessarily imply that this solar cell is the first solar cell in a sequence; instead the term “first” is used to differentiate this solar cell from another solar cell (e.g., a “second” solar cell). “Coupled”—The following description refers to elements or nodes or features being “coupled” together. As used herein, unless expressly stated otherwise, “coupled” means that one element/node/feature is directly or indirectly joined to (or directly or indirectly communicates with) another element/node/feature, and not necessarily mechanically. In addition, certain terminology may also be used in the following description for the purpose of reference only, and thus are not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, “side”, “outboard”, and “inboard” describe the orientation and/or location of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. “Inhibit”—As used herein, inhibit is used to describe a reducing or minimizing effect. When a component or feature is described as inhibiting an action, motion, or condition it may completely prevent the result or outcome or future state completely. Additionally, “inhibit” can also refer to a reduction or lessening of the outcome, performance, and/or effect which might otherwise occur. Accordingly, when a component, element, or feature is referred to as inhibiting a result or state, it need not completely prevent or eliminate the result or state. Approaches for fabricating one-dimensional metallization for solar cells, and the resulting solar cells, are described herein. In the following description, numerous specific details are set forth, such as specific paste compositions and process flow operations, in order to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to one skilled in the art that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known fabrication techniques, such as lithography and patterning techniques, are not described in detail in order to not unnecessarily obscure embodiments of the present disclosure. Furthermore, it is to be understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale. Disclosed herein are solar cells. In one embodiment, a solar cell includes a substrate having a back surface and an opposing light-receiving surface. A plurality of alternating N-type and P-type semiconductor regions is disposed in or above the back surface of the substrate and parallel along a first direction to form a one-dimensional layout of emitter regions for the solar cell. A conductive contact structure is disposed on the plurality of alternating N-type and P-type semiconductor regions. The conductive contact structure includes a plurality of metal lines corresponding to the plurality of alternating N-type and P-type semiconductor regions. The plurality of metal lines is parallel along the first direction to form a one-dimensional layout of a metallization layer for the solar cell. Also disclosed herein are photovoltaic assemblies. In one embodiment, a photovoltaic assembly includes first and second solar cells. Each of the first and second solar cells includes a substrate having a back surface and an opposing light-receiving surface. Each of the first and second solar cells also includes a plurality of alternating N-type and P-type semiconductor regions disposed in or above the back surface of the substrate and parallel along a first direction to form a one-dimensional layout of emitter regions for the solar cell. Each of the first and second solar cells also includes a conductive contact structure disposed on the plurality of alternating N-type and P-type semiconductor regions, the conductive contact structure including a plurality of metal lines corresponding to the plurality of alternating N-type and P-type semiconductor regions parallel along the first direction to form a one-dimensional layout of a metallization layer for the solar cell. Each of the plurality of metal lines terminates in a staggered fashion at first and second ends of the substrate. The photovoltaic assembly also includes an interconnect structure electrically coupling the first and second solar cells between the second end of the substrate of the first solar cell and the first end of the substrate of the second solar cell. The interconnect structure is disposed over and electrically contacts first alternating ones of the plurality of metal lines of the first solar cell. However, the interconnect structure is not disposed over second alternating ones of the plurality of metal lines of the first solar cell. The interconnect structure is also disposed over and electrically contacts first alternating ones of the plurality of metal lines of the second solar cell. However, the interconnect structure is not disposed over second alternating ones of the plurality of metal lines of the second solar cell. In another embodiment, a photovoltaic assembly includes first and second solar cells. Each of the first and second solar cells includes a substrate having a back surface and an opposing light-receiving surface. Each of the first and second solar cells also includes a plurality of alternating N-type and P-type semiconductor regions disposed in or above the back surface of the substrate and parallel along a first direction to form a one-dimensional layout of emitter regions for the solar cell. Each of the first and second solar cells includes a conductive contact structure disposed on the plurality of alternating N-type and P-type semiconductor regions. The conductive contact structure includes a plurality of metal lines corresponding to the plurality of alternating N-type and P-type semiconductor regions parallel along the first direction to form a one-dimensional layout of a metallization layer for the solar cell. Each of the plurality of metal lines terminates in a parallel fashion at first and second ends of the substrate. The photovoltaic assembly also includes an interconnect structure electrically coupling the first and second solar cells between the second end of the substrate of the first solar cell and the first end of the substrate of the second solar cell. The interconnect structure is disposed over and electrically contacts first alternating ones of the plurality of metal lines of each of the first and second solar cells. The interconnect structure is also disposed over, but is not electrically contacting, second alternating ones of the plurality of metal lines of each of the first and second solar cells. One or more embodiments described herein are directed to one dimensional cell metallization and interconnection structures. In an embodiment, an on-cell metallization pattern includes multiple parallel lines that are not connected together at the edges of the cell. Such a pattern may be referred to as “busless and padless” or “one-dimensional.” In an embodiment, when implementing such a pattern, photocurrent collection losses associated with pad and bus areas of the cell can be eliminated. This can lead to increased conversion efficiency of the cell. Furthermore, in an embodiment, due to its elegant simplicity in design, a one-dimensional finger pattern enables certain cost effective and high throughput patterning methods for both emitter formation and on-cell metallization. Specific implementations that may benefit include those based on in-situ patterning with ion-implantation. Described in greater detail below are cell interconnect designs. Such one-dimensional on-cell metallization has the potential for higher efficiency, cost savings and improved reliability. To provide context, in order to achieve ultimate cell conversion efficiencies, loss mechanisms must be minimized. One or more embodiments described herein involve approaches for minimizing photocurrent collection losses otherwise due to busbars and pads by moving the busbar function to an interconnect structure. The interconnect pads are distributed across all fingers such that each pad is, in effect, the same width as an individual finger. Such arrangements mitigate, or altogether eliminate, a compromise to cell performance otherwise associated with state-of-the-art solar cell configurations. To provide further context, state-of-the-art approaches for metallizing a one-dimensional emitter include printing a patterned polyimide layer under a plating seed layer, in conjunction with a two-dimensional patterned plating mask which defines pads and bus bars on the cell. The polyimide layer prevents shorts as busbars and pads cross the opposite polarity emitters. However, it is not yet well understood if a polyimide based approach (e.g., polyimide as an inter-layer dielectric) will necessarily be compatible with next generation metal bonding methods (e.g., bonding methods based on thermo-compression bonding (TCB) and/or laser welding). The high temperature used in TCB (e.g., approximately 450 degrees Celsius) may degrade the polyimide significantly and create unacceptable outgas sing. Additionally, the topology introduced by the polyimide may hinder the application of uniform bonding pressure between a metal foil and an underlying wafer during TCB. For laser bonding, although it may not be necessary to laser weld a metal foil directly on top of the polyimide layer, the topology introduced by the polyimide layer may create additional challenges. Furthermore, if a polyimide print operation is avoidable by using a interconnect busbar, then an overall processing flow may be simplified. In accordance with one or more embodiments of the present disclosure, a one-dimensional finger pattern is implemented for emitter formation. Such a one-dimensional finger pattern may be preferred since the arrangement can make use of a stationary mask/travelling wafer patterning scheme based on ion implantation. It is to be appreciated that a one-dimensional finger pattern may be the only way of effectively patterning with ion implantation. Accordingly, cell architectures described herein involve a cell metallization and interconnect fabrication approach compatible with a one-dimensional emitter. Additional embodiments include the use of one dimensional finger patterning as a preferential approach for laser patterning operations, such as metallization patterning. For example, a one-dimensional finger pattern may be patterned via multiple beam-splitters and a one dimensional scanner system for higher throughput. One dimensional finger patterning may be implemented to enable a fabrication approach based on epoxy mask removal during etching. Furthermore, by providing a large number of distributed bond points, the failure of any single bond may have a minimal impact on the cell performance and current distribution. By contrast, in state-of-the-art interconnect approaches based on three bond points for each polarity, the failure of a single bond causes a significant redistribution of current in the cell and can lead to hot spots and cell failure. As examples of one dimensional on-cell metallization patterns,FIGS.1A and1Billustrate plan views of the back side of solar cells, in accordance with an embodiment of the present disclosure. Referring toFIGS.1A and1B, a solar cell100A or100B, respectively, includes a substrate102having a back surface104and an opposing light-receiving surface (not shown). A plurality of alternating N-type and P-type semiconductor regions106is disposed in or above the back surface104of the substrate102and parallel along a first direction150to form a one-dimensional layout of emitter regions for the solar cell100A or100B. The plurality of alternating N-type and P-type semiconductor regions may be referred to herein as fingers of alternating polarity. A conductive contact structure108is disposed on the plurality of alternating N-type and P-type semiconductor regions106. The conductive contact structure108includes a plurality of metal lines corresponding to the plurality of alternating N-type and P-type semiconductor regions106(the conductive contact structure108and the plurality of alternating N-type and P-type semiconductor regions106are shown collectively as lines106/108inFIGS.1A and1B). The plurality of metal lines108is parallel along the first direction150to form a one-dimensional layout of a metallization layer for the solar cell100A or100B. With reference only toFIG.1A, in an embodiment, each of the plurality of metal lines108terminates in a staggered fashion at first120and second122ends of the substrate102. With reference only toFIG.1B, in another embodiment, each of the plurality of metal lines108terminates in a parallel fashion at first124and second126ends of the substrate102. In an embodiment, with reference again to bothFIGS.1A and1B, the conductive contact structure108further includes a metal seed layer disposed between the plurality of alternating N-type and P-type semiconductor regions106and the plurality of metal lines108. In an embodiment, the substrate102is a monocrystalline silicon substrate, and the plurality of alternating N-type and P-type semiconductor regions106is a plurality of N-type and P-type diffusion regions formed in the silicon substrate102. In another embodiment, however, the plurality of alternating N-type and P-type semiconductor regions106is a plurality of N-type and P-type polycrystalline silicon regions formed above the back surface104of the substrate102(e.g., as polycrystalline silicon emitter regions formed on a dielectric layer formed on the back surface104of the substrate102). With reference again toFIG.1A, in an embodiment, the staggered arrangement provides for one polarity (e.g., N-type or P-type) of fingers as slightly shortened. As described in greater detail below in association withFIGS.2and3, this arrangement ofFIG.1Acan be implemented such that one polarity of fingers not extend under an overlying interconnect formed thereon. In a specific embodiment, as described in greater detail below, the second polarity of fingers stops approximately one millimeter from the substrate102edge to provide clearance at the edge for a cloaking layer. With reference again toFIG.1B, in an embodiment, the parallel terminating arrangement can be accommodated in other photovoltaic architectures, as is described in greater detail below in association withFIG.4. In a first implementation of the solar cells of the type ofFIG.1A, and as described in greater detail in association withFIG.2below, a cell interconnection geometry can be referred to as inter-layer dielectric free, “ILD free.” On each side of the cell, one polarity of fingers is slightly shortened such that it does not extend under an overlying interconnect. Since the fingers need to be shortened, metal 1 (M1; e.g., seed layer) and metal 2 (M2; e.g., foil or electroplated conductive layer) patterning may involve some complexity. The overlying interconnect (M3; e.g., an overlying aluminum or copper sheet or the like) extends the full width of the cell, and is bonded to each finger of a same polarity. The opposite side of the interconnect is bonded to each finger of the opposite polarity on the next cell. By bonding the interconnect individually to each finger, on-cell bussing or pads may be omitted. It is to be appreciated that such an approach can require high accuracy of bonding points between the interconnect (M3) and the on-cell metallization M2. Specifically, bond points must be aligned with the M2 fingers. In an embodiment, such a level of accuracy is achieved using laser welding. The placement accuracy of the interconnect itself, however, is relaxed somewhat in comparison with other approaches since there is no ILD pattern on the interconnect that must be aligned with the M2 fingers. In an embodiment, such an approach relies on a bottom anti-reflective coating (BARC) layer and a physical gap to insulate between the M3 and the opposite polarity emitter (assuming the emitter is continuous to the edge of the wafer). In one such embodiment, the approach is workable since the M3 does not penetrate into any underlying pinholes. As an example,FIG.2illustrates a plan view and corresponding cross-sectional views of a photovoltaic assembly based on solar cells of the type ofFIG.1A, in accordance with an embodiment of the present disclosure. Referring toFIG.2, a photovoltaic assembly200includes first202and second204solar cells. Each of the first202and second204solar cells includes a substrate206having a back surface207and an opposing light-receiving surface208. Each of the first202and second204solar cells also includes a plurality of alternating N-type and P-type semiconductor regions210disposed in or above the back surface207of the substrate206and parallel along a first direction250to form a one-dimensional layout of emitter regions for the solar cell202or204. Each of the first202and second204solar cells also includes a conductive contact structure disposed on the plurality of alternating N-type and P-type semiconductor regions210. The conductive contact structure includes a plurality of metal lines212corresponding to the plurality of alternating N-type and P-type semiconductor regions210parallel along the first direction250to form a one-dimensional layout of a metallization layer for the solar cell. Each of the plurality of metal lines212terminates in a staggered fashion at first214and second ends216of the substrate206. The photovoltaic assembly also200includes an interconnect structure220electrically coupling the first202and second204solar cells between the second end216of the substrate206of the first solar cell204and the first end214of the substrate206of the second solar cell204. The interconnect structure220is disposed over and electrically contacts first alternating ones of the plurality of metal lines212of the first solar cell202. However, the interconnect structure is not disposed over second alternating ones of the plurality of metal lines212of the first solar cell202. The interconnect structure220is also disposed over and electrically contacts first alternating ones of the plurality of metal lines212of the second solar cell204. However, the interconnect structure220is not disposed over second alternating ones of the plurality of metal lines212of the second solar cell204. As is depicted inFIG.2, in an embodiment, the interconnect structure220includes one or more stress relief cuts222formed therein. As is also depicted inFIG.2, in an embodiment, the interconnect structure220is bonded (e.g., soldered, welded, joined, glued, etc.) to each of the first alternating ones of the plurality of metal lines212of the first solar cell202and to each of the first alternating ones of the plurality of metal lines212of the second solar cell204(e.g., as is depicted by bond points224). In a second implementation of the solar cells of the type ofFIG.1A, and as described in greater detail in association withFIG.3below, a cell interconnection geometry can be referred to as “ILD free” with cloaking. As an example,FIG.3illustrates a plan view and corresponding cross-sectional views of a photovoltaic assembly based on solar cells of the type ofFIG.1A, in accordance with another embodiment of the present disclosure. Referring toFIG.3, a photovoltaic assembly300includes first302and second304solar cells. Each of the first302and second304solar cells includes a substrate306having a back surface307and an opposing light-receiving surface308. Each of the first302and second304solar cells also includes a plurality of alternating N-type and P-type semiconductor regions310disposed in or above the back surface307of the substrate306and parallel along a first direction350to form a one-dimensional layout of emitter regions for the solar cell302or304. Each of the first302and second304solar cells also includes a conductive contact structure disposed on the plurality of alternating N-type and P-type semiconductor regions310. The conductive contact structure includes a plurality of metal lines312corresponding to the plurality of alternating N-type and P-type semiconductor regions310parallel along the first direction350to form a one-dimensional layout of a metallization layer for the solar cell. Each of the plurality of metal lines312terminates in a staggered fashion at first314and second ends316of the substrate306. The photovoltaic assembly also300includes an interconnect structure320electrically coupling the first302and second304solar cells between the second end316of the substrate306of the first solar cell304and the first end314of the substrate306of the second solar cell304. The interconnect structure320is disposed over and electrically contacts first alternating ones of the plurality of metal lines312of the first solar cell302. However, the interconnect structure is not disposed over second alternating ones of the plurality of metal lines312of the first solar cell302. The interconnect structure320is also disposed over and electrically contacts first alternating ones of the plurality of metal lines312of the second solar cell304. However, the interconnect structure320is not disposed over second alternating ones of the plurality of metal lines312of the second solar cell304. In an embodiment, from a perspective taken from the light-receiving surface308, portions of the interconnect structure320exposed between the first302and second304solar cells are covered with a cloaking layer399. The cloaking layer399may be a black polymer material which matches the color of the cells and the black backsheet to provide a uniform black appearance to the finished module. Alternatively, a white backsheet and white cloaking layer can be used to give a uniform white appearance around the perimeter of the cell. As is depicted inFIG.3, in an embodiment, the interconnect structure320includes one or more stress relief cuts322formed therein. As is also depicted inFIG.3, in an embodiment, the interconnect structure320is bonded (e.g., soldered, welded, joined, glued, etc.) to each of the first alternating ones of the plurality of metal lines312of the first solar cell302and to each of the first alternating ones of the plurality of metal lines312of the second solar cell304(e.g., as is depicted by bond points324). In an implementation of the solar cells of the type ofFIG.1B, and as described in greater detail in association withFIG.4below, a cell interconnection geometry can be referred to as a cell interconnection geometry with inter-layer dielectric, “with ILD.” In such an approach, a plurality of solar cells such as the solar cell ofFIG.1Bwhere fingers may extend as far to the edge of the substrate as needed, are coupled together with a cell interconnect. It is to be appreciated that although there may be a limit imposed by the emitter or BARC coverage at the extreme edges of the substrate, the interconnect extends the full width of the cell, and is bonded on to each finger of the same polarity. The opposite side of the interconnect is bonded to each finger of the opposite polarity on the next cell. By bonding the interconnect individually to each finger, on-cell bussing or pads may be omitted. In an embodiment, the M3 interconnect is fabricated such that a patterned insulating layer prevents shorting. The insulator layer may also be colored so that the interconnect tab is not visible from the front of the module, thus serving two functions. It is also to be appreciated that such an approach may require high accuracy of bonding points between the interconnect (M3) and the on-cell M2, where bond points must be aligned with the M2 fingers. Such a level of accuracy may be achieved using laser welding. In an embodiment, the interconnect is placed and held during bonding with sufficient accuracy such that the exposed bond areas on the interconnect line up with the fingers. The bond points on in the interconnect may need to be pressed (coined) such that they can make intimate contact with the M2 layer on the cell. However, the need for such approaches may depend on the ability of the bond method to bridge gaps or fit-up into gaps. As an example,FIG.4illustrates a plan view and corresponding cross-sectional views of a photovoltaic assembly based on solar cells of the type ofFIG.1B, in accordance with an embodiment of the present disclosure. Referring toFIG.4, a photovoltaic assembly400includes first402and second404solar cells. Each of the first402and second404solar cells includes a substrate406having a back surface407and an opposing light-receiving surface408. Each of the first402and second404solar cells also includes a plurality of alternating N-type and P-type semiconductor regions410disposed in or above the back surface407of the substrate406and parallel along a first direction450to form a one-dimensional layout of emitter regions for the solar cell402or404. Each of the first402and second404solar cells includes a conductive contact structure disposed on the plurality of alternating N-type and P-type semiconductor regions410. The conductive contact structure includes a plurality of metal lines412corresponding to the plurality of alternating N-type and P-type semiconductor regions410, and parallel along the first direction450to form a one-dimensional layout of a metallization layer for the solar cell402or404. Each of the plurality of metal lines412terminates in a parallel fashion at first414and second416ends of the substrate. The photovoltaic assembly400also includes an interconnect structure420electrically coupling the first402and second404solar cells between the second end416of the substrate406of the first solar cell402and the first end414of the substrate406of the second solar cell404. The interconnect structure420is disposed over and electrically contacts first alternating ones of the plurality of metal lines412of each of the first402and second404solar cells. The interconnect structure420is also disposed over, but is not electrically contacting, second alternating ones of the plurality of metal lines412of each of the first402and second404solar cells. Referring again toFIG.4, in an embodiment, an insulating layer499blocks electrical contact of the interconnect structure420to the second alternating ones of the plurality of metal lines412of each of the first402and second404solar cells. In a particular such embodiment, from a perspective taken from the light-receiving surface408, portions of the interconnect structure420exposed between the first402and second404solar cells are cloaked by the insulating layer499, as is depicted inFIG.4. In an embodiment, the interconnect structure420includes one or more stress relief cuts422formed therein. In an embodiment, the interconnect structure420is bonded (e.g., soldered, welded, joined, glued, etc.) to each of the first alternating ones of the plurality of metal lines412of each of the first402and second404solar cells (e.g., as is depicted by bond points424). It is to be appreciated that the appearance of an interconnect structure when viewed from a light-receiving surface of a photo-voltaic module can vary depending on the implementation. In a first example,FIG.5Aillustrates a plan view from a light-receiving surface of a photovoltaic assembly of the type ofFIG.3, in accordance with an embodiment of the present disclosure. Referring toFIG.5A, an interconnect structure500includes metal interconnect portions502for bonding to adjacent solar cells. An insulating layer and/or cloaking layer504masks exposure of the portion of the interconnect structure500between the adjacent solar cells. In a second example,FIG.5Billustrates a plan view from a light-receiving surface of a photovoltaic assembly of the type ofFIG.4, in accordance with an embodiment of the present disclosure. Referring toFIG.5B, an interconnect structure550includes metal interconnect portions552for bonding to adjacent solar cells. An insulating layer and/or cloaking layer554masks exposure of the portion of the interconnect structure550between the adjacent solar cells. In an embodiment, alternating N-type and P-type semiconductor regions described herein are formed from polycrystalline silicon. In one such embodiment, the N-type polycrystalline silicon emitter regions are doped with an N-type impurity, such as phosphorus. The P-type polycrystalline silicon emitter regions are doped with a P-type impurity, such as boron. The alternating N-type and P-type semiconductor regions may have trenches formed there between, the trenches extending partially into the substrate. Additionally, although not depicted, in one embodiment, a bottom anti-reflective coating (BARC) material or other protective layer (such as a layer amorphous silicon) may be formed on the alternating N-type and P-type semiconductor regions. The alternating N-type and P-type semiconductor regions may be formed on a thin dielectric tunneling layer formed on the back surface of the substrate. In an embodiment, a light receiving surface of a solar cell described herein may be a texturized light-receiving surface. In one embodiment, a hydroxide-based wet etchant is employed to texturize the light receiving surface of the substrate. In an embodiment, a texturized surface may be one which has a regular or an irregular shaped surface for scattering incoming light, decreasing the amount of light reflected off of the light receiving surface of the solar cell. Additional embodiments can include formation of a passivation and/or anti-reflective coating (ARC) layers on the light-receiving surface. In an embodiment, an M1 layer, if included, is a plurality of metal seed material regions. In a particular such embodiment, the metal seed material regions are aluminum regions each having a thickness approximately in the range of 0.3 to 20 microns and composed of aluminum in an amount greater than approximately 97% and silicon in an amount approximately in the range of 0-2%. In an embodiment, an M2 layer as described herein is a conductive layer formed through electroplating or electroless plating. In another embodiment, an M2 layer as described herein is a metal foil layer. In one such embodiment, the metal foil is an aluminum (Al) foil having a thickness approximately in the range of 5-100 microns and, preferably, a thickness approximately in the range of 30-100 microns. In one embodiment, the Al foil is an aluminum alloy foil including aluminum and second element such as, but not limited to, copper, manganese, silicon, magnesium, zinc, tin, lithium, or combinations thereof. In one embodiment, the Al foil is a temper grade foil such as, but not limited to, F-grade (as fabricated), O-grade (full soft), H-grade (strain hardened) or T-grade (heat treated). In another embodiment, a copper foil, or a copper layer supported on a carrier, is used the “metal foil.” In some embodiments, a protective layer such as a zincate layer is included on one or both sides of the metal foil. Although certain materials are described specifically with reference to above described embodiments, some materials may be readily substituted with others with other such embodiments remaining within the spirit and scope of embodiments of the present disclosure. For example, in an embodiment, a different material substrate, such as a group III-V material substrate, can be used instead of a silicon substrate. Additionally, although reference is made significantly to back contact solar cell arrangements, it is to be appreciated that approaches described herein may have application to front contact solar cells as well. In other embodiments, the above described approaches can be applicable to manufacturing of other than solar cells. For example, manufacturing of light emitting diode (LEDs) may benefit from approaches described herein. Thus, approaches for fabricating one-dimensional metallization for solar cells, and the resulting solar cells, have been disclosed. Although specific embodiments have been described above, these embodiments are not intended to limit the scope of the present disclosure, even where only a single embodiment is described with respect to a particular feature. Examples of features provided in the disclosure are intended to be illustrative rather than restrictive unless stated otherwise. The above description is intended to cover such alternatives, modifications, and equivalents as would be apparent to a person skilled in the art having the benefit of this disclosure. The scope of the present disclosure includes any feature or combination of features disclosed herein (either explicitly or implicitly), or any generalization thereof, whether or not it mitigates any or all of the problems addressed herein. Accordingly, new claims may be formulated during prosecution of this application (or an application claiming priority thereto) to any such combination of features. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in the specific combinations enumerated in the appended claims. | 35,750 |
11862746 | DETAILED DESCRIPTION OF THE INVENTION Referring to the figures, wherein like numeral refer to like parts throughout, there is seen inFIG.1a process10according to the present for directly forming the metallo-dielectric waveguide arrays over a solar cell surface12between the front contacts of the solar cell. Process10begins with the casting of a resin formulation14comprises a two component blend over solar cell surface12. Resin14is irradiated by an array of blue LED beams16, which facilitates the phase separation of the two component blend to form a core-cladding architecture, as well as concurrent photoreduction of the AgSbF6into Ag. The result is the formation of a vast array of periodically spaced cylindrical waveguides16located over the solar cell, which can be positioned to be between the front contacts18or over contacts18. With waveguide arrays16directly processed over solar cell surface12, there is no deleterious effect from the reflective contacts on the fabrication process, for example, back reflection of LED light, scattering, etc. In addition, waveguides16do not have to be produced over contacts18, i.e., they are misaligned, so that any effect of the contacts18is very local, thereby allowing for vast, well-ordered waveguide arrays to be produced. This result of the present invention is critical, as it ensures the quality of the processed coatings and ensures optimal functionality in the collection of light. The directly processing and formation of vertically aligned waveguide arrays directly over a solar cell surface12according to the present invention is an advancement over the lamination of pre-made thin-films over the solar cell. Based on the alignment position of the mask, waveguides16can be formed over the contacts18, if desired, or aligned so that the contacts lie in the spacing between waveguides16. Referring toFIG.2, Raman volume maps reveal the spatial location of the nanoparticles in the waveguide arrays. These 3D volume images were created by mapping a Raman intensity signal for crystalline silver (peak) over x, y, z space. Higher intensities reveal regions with higher concentration of silver nanoparticles, owing to Raman peaks concentration dependence. Notably, the silver nanoparticles are located solely in the waveguide cores, as expected owing to these being the regions of high illumination by the optical beams. The distribution of the nanoparticles appears uniform over the length of the cylindrical cores, and the concentration slightly tapers at the peripheries in accordance with the drop in intensity of light which is confined to the self-written and formed waveguide during the fabrication process. Furthermore, there is no observation of phase separation of the nanoparticles in to the interstitial space (i.e., the waveguide common cladding surroundings). This is most likely due to the silver nanoparticles forming in conditions in which the NOA is highly crosslinked, and thus it cannot easily diffuse outside of the courses, yet the Ag salt precursor can diffuse from the dark regions into the bright to facilitate their consumption and continued growth of the particles Referring toFIG.3, the present invention has ability to capture and transmitted optical energy incident over a wide range of incident angles along the waveguide axes. Preservation of the optical intensity located at the exit points of the individual waveguides is clearly observed. This is in contrast to the optical intensity for a uniform resin which shows increasingly dimmer intensity with increased incidence angle. The concept then is that a major of the optical energy retains a quasi-normally incident nature in terms of its angular direction upon which it impinges the underlying cell. Notably, the preservation of the optical intensity is visually enhanced for the silver nanoparticle metallo-dielectric waveguides as compared to the undoped waveguide arrays. Previous work on the photo-reduction of noble metal nanoparticles places their size at around 10-50 nm, such that the plasmon absorbance peak of the silver nanoparticles is in the UV range, beyond the operation range of the nanoparticles, and thus the main mechanism by which the nanoparticles effect the waveguides is through scattering and refractive index volume averaging.FIG.4(a)shows transmission spectra of the waveguide array structures as a function of the different doping weight percent of AgSbF6. Highly transparent samples in the visible and NIR region are produced.FIG.4(b)shows refractive index measurements of uniformly cured slabs of NOA65 with the sample relative doping concentrations, as a means to measure in bulk the expected refractive index of the waveguide core as a function of the quantity of silver nanoparticles. There is a drop in the refractive index of the polymer core, owing to the slight decrease in conversion of the polymer with increase silver precursor concentration, and this conversion to higher molecular weight is what causes the higher refractive index of the polymer. This acceptance range (Δθ) of a waveguide is determined by the refractive index values of the core (n1) and cladding (n2) according to the relation derived based on total internal reflection for light entrant from surrounding air: sin(Δθ/2)=√{square root over (n12−n22)}. Based on the refractive index values of the polymers (NOA:, PDMS:), a maximum acceptance range 30° should be achievable. However, the drop in refractive index is with increased weight percent of AgSbF6is quite small (0.003) such that the theoretical acceptance angle range is essentially based on the refractive index difference between the core and cladding. All of the cured samples were transparent, indicating the formation of metallic particles in nanometer range size, was has been confirmed previously for TEM size analysis of samples (10-50 nm) photocured at the same intensity (as well as similar salt, AgSbF6, and photoinitator concentrations, 1-5% and 2% respectively). Optical microscopy (FIG.1) also indicates that the nanoparticles are well dispersed on the core (which is corroborated by Raman mapping), with no significant, macroscopic agglomerates. The small sizes also place the surface plasmon resonance of the silver nanoparticles to ˜400 nm, at the edge boundary of the operational window of the silicon solar cells, and hence it is not disruptive to the efficiency (vide infra), as the operate more so as lossless scattering centers. The solar cell performances of the metal-dielectric waveguides were compared relative to the waveguide with no silver nanoparticles, which have been established as widening the acceptance range relative to a uniform encapsulant.FIG.5shows external quantum efficiency measurements of encapsulated solar cells for the range of Ag doping concentrations explored for the laminated and directly processes films. The first observation is the abated of the drop of the EQE when employing metallo-dielectric waveguides relative to a regular waveguide arrays, especially for wide incident angles θinc>40°. The EQE drops the least with increased incident angle for the sample with 0.5 wt % silver doping (FIG.5(c)), and this drop is less than for a uniform encapsulant (FIG.5(a)). For directly processed resins, two key observations are notable. The first at that the drop in the EQE for a regular waveguide array is less than for that produced through lamination, indicating that overall lamination could provide better efficiency performance as compared to lamination. This might be explained by the interface between the resin and the silicone priming layer used to planarize the silicon solar cell surface, which can cause additional back reflection of light which is lost from the cell. The second observation that that there is an reduction in the abatement in EQE when using metallo-dielectric waveguides; however, the difference among samples are smaller, yet the sample with 0.5 wt % silver still shows, nominally, the greatest abatement in the drop in EQE, specifically as assessed within the visible region of the spectra (λ˜725 nm) FIG.6shows the average EQE value as a function of incident angle for all encapsulants explored in this work. In the case of laminated films, the Ag doping concentrations from 0.1-2.0 wt % abate the drop in EQE with increased incident angle, as seen inFIG.7(a). The greatest abatement is observed from 0.5 wt %. The total EQEs overall are greater for solar cells with directly processed encapsulants, as seen inFIG.7(b), including a regular waveguide array (0 wt %). Because the EQE values all higher, the abatement is less pronounced, yet there is an enhancement in EQE when metallo-dielectric waveguides are employed. FIG.7shows I-V curves for the encapsulated solar cells as a function of incident angle over the range of silver concentrations explored. All plots show a monotonic decrease in the short circuit currents with increase incident angle, which is a natural trend, owing to increase shading loss from the great apparent coverage of the contacts on the surface. While EQE spectra show enhancements to the conversion efficiency in encapsulated cells, the electrical output, specifically the short circuit current density (JSC), reveals more complex interactions. Specific Ag concentrations lead to increases in JSCat particular incident angles. For example, waveguide arrays with 0.5 wt % AgSbF6increase JSC, with respect to undoped samples, nominally by 3.5 mA/cm2at 0° and by ˜1 mA/cm2at 60 and 70°; however, JSCis less or equal to an undoped waveguide array for intermediate angles. Waveguide arrays with 2 and 3 wt % AgSbF6increase JSCby ˜0.5 mA/cm2(max) in the angular ranges of 0-30°. All other concentrations appear to provide no enhancement to the current density, despite their apparent increases in efficiency for particular angular ranges shown inFIG.6b. The variations in the EQE performance of the cells can be explained by the interactions of the waveguide and the nanoparticle scattering. At low incident angles, the waveguide properties are suitable for collecting light, and the nanoparticles as diffuse scatterers, scatters light out of the waveguide, which is not optimal lead to reduced efficiency. With increasing angle, beyond the collection range of the waveguide guides, scattering because beneficial, as it possess a redirecting effect, steering light otherwise outside of the collection range of the waveguides into the acceptance range, allowing for greater light collection. At even greater angles these collection effects can be sustained, particularly for lower doping concentrations, thereby provide enhancement at ultrawide angles. However, at greater concentrations, the scattering effect might over dominate, leading to reduced efficiency. It is also likely that the silver nanoparticles enables scattering of light beyond the loss cone of the solar cell. Similar measurements were performed on solar cells that were covered in pre-cured waveguide array thin-films. Overall, the efficiency and current density were more stable and better performance was observed for solar cells with encapsulants directly processed over it. Arrays of metallodielectric waveguides were fabrication in thin-films consisting of a binary component blend of polymers and a silver salt as the metal source. The structures were tested as encapsulant materials for silicon solar cells for their wide-angle collection properties. Increases in both the conversion efficiency and the current output over a wide range of incident angles are observed, with a specific weight fraction of silver dopant attaining the maximum conversion efficiency and current output. The present invention is thus a promising approach for solar cell encapsulants that can increase solar cell output over the course of the day and across seasons. Thus, the present invention comprises metallo-dielectric waveguide array structures that are produced by combining light-induce self-writing in a two-component photopolymerizable blend with concurrent in situ synthesis of silver nanoparticles via photoreduction of a silver salt (AgSbF6). The waveguide array structures are processed directly over the silicon solar cell via casting the precursor resin and then irradiating the resin from above an array of microscale UV optical beams, making the process compatible with the processing of modules. Irradiation with an array of UV beams creates periodic waveguide architectures with the waveguide cores consisting of a homogenous distribution of silver nanoparticles. The present invention includes a waveguide array structure that provides a baseline structure for a wider acceptance window, and the nanoparticles impart optical functionality—through light scattering—to the resulting waveguide array structure, thereby enhancing the collection range through a combination of waveguide and scattering of light in the waveguide cores. This enables transformation of wide incident angle light rays into quasi-normally incident light, thereby mitigation shadow losses and increasing light collection and conversion. As described above, the present invention was tested by systematically varying the AgSbF6to produce waveguide cores with different silver nanoparticle concentrations. The results show an increase in the external quantum efficiency over the angular range (0-70°) and a nominal increase in the current density of 1 mA/cm2. Advantageously, preparing the structures from a single photocurable formulation aligns with the imperative to maintain the approach as straightforward and easily integrated into manufacturing photovoltaic modules. The combination of light self-trapping and the intensity-dependent photo-reduction of the silver salt enables the nanoparticle formation specifically in the desired high index regions of the structure. EXAMPLE Following are the specific details for the experiments described above: Materials. Norland Optical Adhesive 65 (hereon referred to as NOA65) was purchase from Norland Products Inc. and an epoxide-terminated PDMS oligomer and Silver hexafluoroantimonate(V) (AgSbF6) from Sigma-Aldrich. The free-radical photoinitiator camphorquinone (CQ) was purchased from Sigma-Aldrich and cationic initiator (4-octyloxyphenyl) phenyliodonium hexafluoroantimonate (OPPI) from Hampford Research Inc. All chemicals were used as received. Preparation of Photopolymerizable Media. Polymer blends were prepared by mixing PDMS and NOA65 in a 1:1 by weight fraction with OPPI (1.5 wt % of total mixture) and different weight fractions of AgSbF6(0.1-3.0 wt % of total mixture). The vial containing the mixture was protected from ambient light, placed on a magnetic stirrer, and mixed for ˜24 hours prior to use. The mixture was poured into a circular well fabricated from a Teflon ring placed over a transparent plastic substrate. Relative weight fractions of PDMS and NOA65 are expressed herein as a ratio of PDMS/NOA65 (wt %/wt %). Photopolymerization of the blends. The mixture was irradiated with collimated UV light generated from a Xenon lamp source (˜30 mW/cm2). The light was first passed through an optical mask consisting of an array (of square or hexagonal symmetry) of apertures of diameter 40 μm and spacing of 200 μm. Two approached for encapsulation of the solar cells were explored. In the first approach, the encapsulation was synthesized separately, as previously reported, and then laminated on the solar cell, which was first planarized with a thin layer of silicone (Sylgard 184). This approach is hereon referred as a lamination. In the second approach, the resin was casted over the solar cell, and irradiated with the array of optical beams from above. This approach is hereon referred to a direct processing. Refractive Index Measurements. Refractive index values for photocured NOA65—Silver formations were measured with an Abbe refractometer (Atago, NAR-1T SOLID). Raman volume mapping. Raman spectra of the processed encapsulants were acquired with a confocal Raman microscope (Renishaw, InVia) using a 785 nm continuous wave (CW) diode laser. The system combined the Raman spectrometer and a Leica DM2700P microscope. Raman volume images were created by collecting spectra at spacing intervals of 10 μm in x, y, and z directions. The phase separation is revealed by 3D mapping of the ratio of the C═O peak of NOA65 to the Si—CH3peak of the PDMS to identify NOA-rich regions. Solar Cell Measurements. A quantum efficiency system (IQE 200B, Newport) with wavelength range of 300-1100 nm was used to measure the external quantum efficiency (EQE) of a planar multi-crystalline Silicon screen-printed solar cell with dimensions 5 cm×5 cm×0.5 mm, and a measured short circuit current density of 35.5 mA/cm2. The EQE measurement setup includes a 300-watt xenon arc lamp whose emitted light is modulated by a chopper at 80 Hz and dispersed by a monochromator consist of sorting filters to produce the light output. The output light was focused on the photopolymerized sample placed over the solar cell, which was first coated with a thin “priming” layer (˜0.12 mm) of PDMS (Sylgard). EQE measurements at different angles were achieved by placing the encapsulated solar cell on machined, ramp-shaped blocks of different inclination angles. External quantum efficiency measurements were carried out according to the ASTM standard (E1021-15). The beam cross-section was circular with a diameter of ˜1 cm. All measurements were conducted in the same region of the solar cell. The total EQE was determined based on the spectral response of the encapsulated cell to the AM 1.5 G solar reference spectrum and the EQE(λ) data, calculated according to the equation: ∫ϕ(λ)·EQE(λ)dλ∫ϕ(λ)dλ×100%(1) Where ϕ (λ) is the photon flux of AM 1.5 G at a wavelength, λ. Equation 1 expresses the total EQE as a weighted average across the wavelength range investigated. Current-Voltage Measurements. Current-voltage (I-V) curves of the encapsulated solar cells were collected under irradiation (AM 1.5 G) using an ABB class solar simulator (Newport 94021A) at an intensity of 1 Sun (100 mW/cm2). In another embodiment of the invention, irradiation may be provided at an angle to the mask used to define the waveguide array so that the resulting waveguides 16 are positioned at an angle to normal relative to surface12. Several arrays of columns of waveguides16can be produced to provide a wide angular window of collection. As seen inFIG.10, a wide variety of angles may be produced. In addition, multiple irradiation sources may be used to simultaneously form waveguides16form an intersecting lattice, as seen inFIG.9. For example, lattices of waveguides16may be formed in binary component polymer blends using irradiation (˜1 hour) using a multi-beam configuration that comprises several collimated LED sources (5-10 mW/cm2). The light sources are transmitted through a common mask, as seen inFIG.12, to concurrently generate multiple intersecting arrays of optical beams, all of which will produce a waveguide having a lattice structure, as seen inFIG.13. The symmetry of the arrangement may be changed by varying the number of beams and their respective orientations, as seen inFIG.14A through14D. The self-writing of each beam occurs independently of any other propagating or intersecting filaments. Different orientation configurations are possible, which may be expressed as sets of angular orientations of the core axes with respect to the normal of the air-film interface. For example, the combinations shown inFIGS.14A through14Dare (−15, 15°), (−30, 0 ,30°), (−15, 0, 15°), and (−15, 15°), respectively. Within the diameter range of the core that supports broadband light (i.e., D>10 μm), smaller core sizes can accommodate smaller spacing (S), which increases the overall waveguide density, yet over dense arrays may result in cross-talk and less light confinement. Using a high refractive index commercial acrylate (Norland Optics, NOA65) and a low refractive index epoxide terminated polydimethyl siloxane (PDMS). Refractive index values (both in their cured state) of 1.653 and 1.412, respectively, yield a maximum possible refractive index difference (Δn) between waveguide core and cladding of approximately 0.241, which can provide an acceptance range from approximately −30 to +30°. PDMS provides elastomeric properties to the thin-films and is beneficial for handling the mechanical and thermal stresses in applications. Based on this refractive index difference, three waveguide lattices oriented so that their acceptance windows are adjacent should be sufficient to cover the angular range of light of interest. The boundaries of the acceptance window change as the waveguide core becomes more slanted with respect to the air-film interface. The overlap of adjacent waveguide collection ranges are expected to provide greater changes to the propagation direction of incident light; hence, a range of 3-lattice configurations over a range waveguide orientation combinations: e.g., (−30, 0, 30°), (−20, 0, 20°), (−15, 0, 15°) may be manufactured to determine optimal configurations. Common to these arrangements is the “primary” waveguide lattice oriented at 0°. Additionally, 4-lattice configurations, e.g., (−30, −15, 15, 30°), i.e., no primary waveguide lattice, may also be synthesized, as normally incident light can still be collected by either the −15° or +15° lattice. Waveguides16of this embodiment may be made with or without the nanoparticles described above, as the angling of waveguides16can provide the desired ultra-wide collection angle in the absence of the nanoparticles. | 21,668 |
11862747 | MODES FOR CARRYING OUT INVENTION Embodiment 1 A semiconductor light-receiving element50of Embodiment 1 will be described with reference to the drawings. For the same or equivalent configuration elements herein, the same reference numerals will be given, so that repetitive description thereof will be omitted as the case may be.FIG.1is a sectional view showing a schematic configuration of a first semiconductor light-receiving element according to Embodiment 1.FIG.2is a diagram showing calculation results of breakdown voltages and reach-through voltages of the semiconductor light-receiving element ofFIG.1, andFIG.3is a graph showing current characteristics of the semiconductor light-receiving element ofFIG.1,FIG.4is a sectional view showing a schematic configuration of a semiconductor light-receiving element as a comparative example, andFIG.5is a graph showing current characteristics of the semiconductor light-receiving element ofFIG.4.FIG.6andFIG.7are diagrams illustrating diffusion steps for forming a p-type region inFIG.1.FIG.8is a sectional view showing a schematic configuration of a second semiconductor light-receiving element according to Embodiment 1, andFIG.9is a sectional view showing a schematic configuration of a third semiconductor light-receiving element according to Embodiment 1.FIG.10is a sectional view showing a schematic configuration of a fourth semiconductor light-receiving element according to Embodiment 1. On the surface of a semiconductor substrate1provided as an n-type InP substrate, an n-type AlInAs multiplication layer2containing Al (aluminum), a p-type InP electric-field control layer3, an n-type InGaAs light absorption layer4and an n-type InP window layer5are stacked sequentially. A p-type region6is formed partly in the window layer5, and a vertical structure region including the p-type region6is provided as a light receiving region22. InFIG.1, the light receiving region22is a region from a broken line21ato a broken line21e, and the surface shape of the p-type region6is a circular shape, for example. On the surface of the window layer5(a surface on the opposite side from the semiconductor substrate1), a passivation film8of SiN, SiO2or the like is formed, and on the surface of the p-type region6, an anode electrode7is formed. The p-type region6and the anode electrode7are electrically connected to each other. On the back surface of the semiconductor substrate1, a cathode electrode9and an anti-reflection film10are formed. The back surface of the semiconductor substrate1and the cathode electrode9are electrically connected to each other. A shape of the cathode electrode9viewed from the back side of the semiconductor light-receiving element50(back surface shape) is, for example, an oblong shape; a circular opening20is created in that electrode; and the anti-reflection film10is formed on the back surface of the semiconductor substrate1inside the opening20. The back surface shape of the anti-reflection film10is a circular shape. InFIG.1, a case is shown where the outer periphery of the p-type region6in a radial direction about a central axis21ccoincides with the outer periphery of the anti-reflection film10in the radial direction. The semiconductor light-receiving element50shown inFIG.1is an avalanche photodiode of a back-surface incident type on which light is incident from the back side of the semiconductor substrate1. The multiplication layer2, the electric-field control layer3, the light absorption layer4and the window layer5are each an epitaxial layer formed using an MOCVD (Metal Organic Chemical Vapor Deposition) apparatus, an MBE (Molecular Beam Epitaxy) apparatus or the like. The passivation film8is formed using a photolithographic technique and an etching technique, after film deposition by use of a vapor deposition apparatus, a sputtering apparatus, a CVD (Chemical Vapor Deposition) apparatus or the like. The anode electrode7and the cathode electrode9are each formed using a photolithographic technique and an etching technique, after film deposition by use of a vapor deposition apparatus, a sputtering apparatus or the like. The anti-reflection film10is formed using a sputtering apparatus, a vapor deposition apparatus, a CVD apparatus, an MBE apparatus or the like. The p-type region6is formed in a part above the interface between the light absorption layer4and the window layer5, namely it is formed in an inner part of the window layer5to be spaced apart from the interface. The p-type region6has: a first p-type portion14whose depth in the stacked direction of the epitaxial layers is shallow; and a second p-type portion15whose depth in the stacked direction of the epitaxial layers is deeper than that of the first p-type portion14. The second p-type portion15extends toward the semiconductor substrate1further than the first p-type portion14. Further, the second p-type portion15is formed as an outermost peripheral portion of the p-type region6in the radial direction. The diffusion fronts of the first p-type portion14and the second p-type portion15are each located above the interface between the light absorption layer4and the window layer5, and are thus created as inner parts of the window layer5spaced apart from the interface between the light absorption layer4and the window layer5. Note that the “diffusion front” shall be indicative of a depth-direction boundary between a dopant diffused portion and a dopant non-diffused portion that are provided when dopants are diffused from the surface of the epitaxial layers (a surface through which diffusion sources containing the dopants may enter). The surface shape of the first p-type portion14is a circular shape, and the surface shape of the second p-type portion15is a ring shape that surrounds the outer periphery of the first p-type portion14. The diffusion front of the second p-type portion15is deepest at positions indicated by broken lines21b,21d. A broken line21cindicates the central axis of the p-type region6and also the central axis of the light receiving region22. The central axis21cis perpendicular to the semiconductor substrate1, and light will be incident on the semiconductor light-receiving element50in a direction, for example, parallel to the central axis21c. A diffusion-front difference d1that is a distance between the diffusion front of the first p-type portion14and the diffusion front of the second p-type portion15may be any difference, and is, for example, not less than 1 nm but less than 100 nm. The carrier concentration (impurity concentration) of the p-type region6is, for example, about 5×1017cm−3. It can also be said that the diffusion-front difference d1is a differential distance in the direction of the central axis21cbetween an end portion in the first p-type portion14that is closest to the semiconductor substrate1and an end portion in the second p-type portion15that is closest to the semiconductor substrate1. When the diffusion front of the second p-type portion15is made deeper than the diffusion front of the central portion of the p-type region6including the central axis21c, namely, the first p-type portion14, it is possible to make differences between breakdown voltages (Vbr) as well as reach-through voltages (Vre) of the APD at the central portion and the outer peripheral portion of the p-type region6, namely at a central portion and an outer peripheral portion in the light receiving region22. UsingFIG.2andFIG.3, characteristics of the first p-type portion14and the second p-type portion15will be described. InFIG.2, calculation results of breakdown voltages (Vbr), reach-through voltages (Vre) and multiplication factors are shown. InFIG.3, current characteristics of the semiconductor light-receiving element50are shown schematically. InFIG.3, the abscissa and the ordinate represent a voltage and a current, respectively. As shown inFIG.2, the breakdown voltage (Vbr), the reach-through voltage (Vre) and the multiplication factor at the first p-type portion14are 35.16 V, 15.78 V and 6.7, respectively. The breakdown voltage (Vbr), the reach-through voltage (Vre) and the multiplication factor at the second p-type portion15are 33.46 V, 14.60 V and 9.6, respectively. The multiplication factor due to light incidence is the ratio between a current I0before the occurrence of avalanche multi-plication and a current I1under the occurrence of avalanche multiplication, and is represented as I1/I0. The values of the multiplication factors shown inFIG.2are values when a reverse bias of 30 V is applied between the anode electrode7and the cathode electrode9. The symbol shown inFIG.3is the operation voltage of the semiconductor light-receiving element50, which is 30 V, for example. A current characteristic25inFIG.3is a current characteristic at a central portion of the first p-type portion14, and a current characteristic26inFIG.3is a current characteristic of the second p-type portion15. As shown inFIG.3, the central portion in the light receiving region22and the outer peripheral portion in the light receiving region22have different current-voltage characteristics and also have different multiplication factors at the time of application of the same voltage. Thus, according to the semiconductor light-receiving element50of Embodiment 1, it is possible to make a difference between the multiplication factors of the central portion in the light receiving region22and the outer peripheral portion in the light receiving region22, even at the same application voltage between the anode electrode7and the cathode electrode9. Specifically, when a constant application voltage is applied between the anode electrode7and the cathode electrode9, a condition is provided in which the multiplication factor of the central portion in the light receiving region22, namely, the first p-type portion14, is lower than that of the outer peripheral portion in the light receiving region22, namely, the second p-type portion15. As mentioned above, the multiplication factor indicates a rate of increase due to the current generated by input light, namely, how many times larger the number of carriers to be outputted becomes. This means that the larger the multiplication factor is, the larger the flowing photo-electric current becomes even at the same input light. As described previously in general, the positions of the optical fiber for propagating light and the APD are adjusted so that the density of light incident on the light receiving region22in the APD is highest in the central portion in the light receiving region22. Accordingly, at the time light is inputted, the light density is high in the central portion in the light receiving region22, in particular, at the center indicated by the broken line21c, so that many carriers are generated in the central portion in the light receiving region22and, as the result, the current flowing through the central portion in the light receiving region22becomes larger. This phenomenon is significant particularly at the center indicated by the broken line21c. Thus, when light is inputted excessively, the photo-electric current flowing through the central portion in the light receiving region22increases, so that a case may arise that heat is generated with the increase of the photo-electric current to cause the deterioration in characteristics. However, according to the semiconductor light-receiving element50of Embodiment 1, the multiplication factor of the central portion in the light receiving region22, namely the first p-type portion14, is lower than that of the outer peripheral portion in the light receiving region22, namely the second p-type portion15. Thus, the photo-electric current flowing through the second p-type portion15in the light receiving region22increases and the photo-electric current flowing through the first p-type portion14in the light receiving region22decreases, so that, if an excessive current is generated, the photo-electric current is less likely to concentrate in the first p-type portion14in the light receiving region22, and this makes it possible to suppress the deterioration in characteristics due to generated heat. Description will be made about current characteristics of a semiconductor light-receiving element60as a comparative example in which a guard ring64is formed. The semiconductor light-receiving element60shown inFIG.4differs from the semiconductor light-receiving element50ofFIG.1in that the electric-field control layer3is formed on the surface of the light absorption layer4, a multiplication layer62and the window layer5are formed on the surface of the electric-field control layer3, and the guard ring64is formed on the outer periphery of the first p-type portion14. The back side of the first p-type portion14(its side facing toward the semiconductor substrate1) is in contact with the n-type multiplication layer62. The diffusion front of the guard ring64is deepest at the positions indicated by the broken lines21b,21d. In the semiconductor light-receiving element60of the comparative example, the multiplication layer62is made of InP, and the impurity concentration of the guard ring64is lower than that of the first p-type portion14. According to the semiconductor light-receiving element60of the comparative example, when light is incident thereon, no avalanche multiplication occurs beneath the guard ring64, so that it operates as a PD which does not cause avalanche multiplication beneath the guard ring64. InFIG.5, current characteristics of the semiconductor light-receiving element60of the comparative example are shown schematically. InFIG.5, the abscissa and the ordinate represent a voltage and a current, respectively. A current characteristic27inFIG.5is a current characteristic at a central portion of the first p-type portion14, and a current characteristic28inFIG.5is a current characteristic of the guard ring64. As shown inFIG.5, the semiconductor light-receiving element60of the comparative example is structured so that the photo-electric current in the guard ring64as an outer peripheral portion in the light receiving region22is less than the photo-electric current in the central portion in the light receiving region22, and thus the multiplication factor of the guard ring64as the outer peripheral portion in the light receiving region22is lower than the multiplication factor of the central portion in the light receiving region22. Note that, since no avalanche multiplication occurs beneath the guard ring64, the multiplication factor of the outer peripheral portion in the light receiving region22is 1. Therefore, distributions according to the current characteristics of the central portion and the outer peripheral portion in the light receiving region22in the semiconductor light-receiving element60of the comparative example, are in inverse relation to those according to the current characteristics of the central portion and the outer peripheral portion in the light receiving region22in the semiconductor light-receiving element50of Embodiment 1. In this manner, the guard ring64in the semiconductor light-receiving element60of the comparative example in which the multiplication layer62is made of InP, differs in function from the second p-type portion15as the outer peripheral portion in the light receiving region22in the semiconductor light-receiving element50of Embodiment 1. Thus, the semiconductor light-receiving element60of the comparative example does not achieve an effect according to the semiconductor light-receiving element50of Embodiment 1, namely, an effect in which, even when high-intensity light is incident on the light receiving region22and an excessive current is generated therein, because a photo-electric current flowing through the second p-type portion15in the light receiving region22increases relative to a photo-electric current flowing through the first p-type portion14in the light receiving region22, the excessive photo-electric current is less likely to concentrate in the first p-type portion14in the light receiving region22, so that the deterioration in characteristics due to generated heat can be suppressed. Unlike the semiconductor light-receiving element50of Embodiment 1, according to the semiconductor light-receiving element60of the comparative example, when high-intensity light is incident on the light receiving region22and an excessive current is generated therein, the photo-electric current will concentrate in the first p-type portion14in the light receiving region22, so that a case may arise that heat is generated with the increase of the photo-electric current to cause the deterioration in characteristics. For the semiconductor light-receiving element60of the comparative example, it is required to make the driving voltage lower than that of the semiconductor light-receiving element50of Embodiment 1, or to reduce the intensity of incident light. According to the semiconductor light-receiving element50of Embodiment 1, it is possible to make the multiplication factor of the high light-density central portion (first p-type portion14) in the light receiving region22, lower than that of the outer peripheral portion (second p-type portion15) in the light receiving region22, to thereby suppress excessive multiplication in the central portion (first, p-type portion14) in the light receiving region22at the time light is inputted excessively; so that the deterioration in characteristics due to generated heat can be suppressed. According to the semiconductor light-receiving element50of Embodiment 1, its characteristics are not deteriorated even when high-intensity light is incident on the light receiving region22and an excessive current is generated therein, namely, its resistance to excessive current or its resistance to excessively inputted light is high, so that its lifetime is longer than that of the semiconductor light-receiving element60of the comparative example. Further, since the resistance to excessive current or the resistance to excessively inputted light is high, the semiconductor light-receiving element50of Embodiment 1 can be operated with a higher degree of sensitivity by setting its operation voltage V1higher than that of the semiconductor light-receiving element60of the comparative example. It is noted that, by lowering the operation voltage V1to decrease the multiplication factor as a whole, it is also possible to suppress the deterioration in characteristics due to generated heat. In this case, however, the photo-electric current decreases in the entire light receiving region22, thus causing a problem that the receiving sensitivity is degraded. In contrast, according to the semiconductor light-receiving element50of Embodiment 1, since the multiplication factor of the outer peripheral portion in the light receiving region22is high, even if the operation voltage V1is lowered, a total amount of photo-electric current flowing through the entire light receiving region22is not decreased too much, so that such characteristic degradation due to the decrease of the photo-electric current is less likely to occur. Namely, when the operation voltage V1is lowered, unlike the semiconductor light-receiving element60of the comparative example, the semiconductor light-receiving element50of Embodiment 1 can suppress characteristic degradation due to the decrease of the photo-electric current. An example of the method of forming the p-type region6will be described usingFIG.6andFIG.7. The p-type region6is formed, for example, by two diffusion steps. The p-type region6is a region in which p-type dopants such as Zn (zinc), Be (beryllium) or the like are diffused. The p-type dopant used for the p-type region6may be other than Zn and Be. However, as the p-type dopant used for the p-type region6, Zn is preferable. When the p-type dopant is Zn, the carrier concentration (impurity concentration) of the p-type region6can be easily increased and the diffusion front is easily controllable and thus, this dopant is well-suited for forming the structure of the p-type region6according to Embodiment 1, namely, the structure in which the diffusion front of the second p-type portion15is deeper than the diffusion front of the first p-type portion14. When the p-type dopant is Zn (zinc), the p-type region6is a Zn(zinc)-diffused region. FIG.6shows a state in which, after the formation of a layered body by sequentially stacking the multi-plication layer2, the electric-field control layer3, the light absorption layer4and the InP window layer5on the semiconductor substrate1(after a layered-body formation step), a diffusion prevention mask24has been formed and the p-type dopants have been diffused through an opening29of the diffusion prevention mask24to thereby form the second p-type portion15. The opening29of the diffusion prevention mask24is formed into a ring shape. After the second p-type region15is formed in the window layer5, the diffusion prevention mask24shown inFIG.6is removed and then a diffusion prevention mask24is newly formed as shown inFIG.7. The diffusion prevention mask24shown inFIG.7is formed so that its opening29is conformed with the outer periphery of the second p-type portion15. The p-type dopants are diffused through the opening29of the diffusion prevention mask24to thereby form the first p-type portion14.FIG.6shows a second p-type portion formation step of forming the second p-type portion15of the p-type region, andFIG.7shows a first p-type portion formation step of forming the first p-type portion14of the p-type region6after the second p-type portion formation step. Note that a p-type dopant concentration of the second p-type portion15is higher on its surface side than on the other side. It is noted that, in each of the figures illustrated with cross sections, illustration of how the second p-type portion15is spread in the horizontal direction (in a direction parallel to the semiconductor substrate1) by diffusion, is omitted. Also, inFIG.4, illustration of how the guard ring64is spread in the horizontal direction (in a direction parallel to the semiconductor substrate1) by diffusion, is omitted. As shown inFIG.8, a contact layer18for lowering a contact resistance, made of AlGaInAs, InOaAsP, InGaAs or the like or any combination thereof, may be interposed between the p-type region6and the anode electrode7. Further, at interface portions between the respective epitaxial layers, in order to relax the band discontinuity band-discontinuity relaxation layers17a,17b,17cand17d, each using InGaAsP, AlGaAs or the like, may be interposed. The band-discontinuity relaxation layer17ais formed between the semiconductor substrate1and the multiplication layer2, and the band-discontinuity relaxation layer17bis formed between the multiplication layer2and the electric-field control layer3. The band-discontinuity relaxation layer17cis formed between the electric-field control layer3and the light absorption layer4, and the band-discontinuity relaxation layer17dis formed between the light absorption layer4and the window layer5. As shown inFIG.9, similarly to the anode electrode7, the cathode electrode9may be located, not on the back surface of the semiconductor substrate1, but on the surface side of the window layer5. The third semiconductor light-receiving element50of Embodiment 1 shown inFIG.9is provided with: a trench portion13that penetrates the window layer5, the light absorption layer4, the electric-field control layer3and the multiplication layer2, to reach the semiconductor substrate1: the cathode electrode9connected to the semiconductor substrate1; and an insulating film12that insulates the cathode electrode9from the respective layers of the window layer5, the light absorption layer4, the electric-field control layer3and the multiplication layer2. InFIG.9, a case is shown where the anti-reflection film10is not formed on a back surface of semiconductor substrate1corresponding to the light receiving region22, and the passivation film8is not formed on an area of the window layer5which is outside the light receiving region22and on which the cathode electrode9is not formed. Also, the semiconductor light-receiving element50in eitherFIG.1orFIG.8may not have the passivation film8and the anti-reflection film10. Note that the semiconductor light-receiving element50may have a passivation film.8that is formed on a side surface of the epitaxial layers. The semiconductor light-receiving element50is not limited to the back-surface incident type, and may instead be an avalanche photodiode of a front-surface incident type as shown inFIG.10. The fourth semiconductor light-receiving element50of Embodiment 1 shown inFIG.10differs from the first semiconductor light-receiving element50of Embodiment 1 shown inFIG.1, in the following points. In the fourth semiconductor light-receiving element50, the cathode electrode9is formed on the back surface of the semiconductor substrate1, the anode electrode7has a ring shape, and an anti-reflection film16is formed on a surface area of the window region5on which the anode electrode7is not formed. In the fourth semiconductor light-receiving element50, a region corresponding to an opening30of the anode electrode7, namely, an open region, is provided as a light receiving region22. InFIG.10, the light receiving region22ranges from a broken line23ato a broken line23b. Because the fourth semiconductor light-receiving element50has the p-type region6whose structure is similar to that of the first semiconductor light-receiving element50, it achieves an effect similar to that of the first semiconductor light-receiving element50. It is noted that, although a case has been described where the carrier concentration (impurity concentration) of the p-type region6is about 5×1017cm−3, it is preferable that the carrier concentration (impurity concentration) of the p-type region6be 1×1018cm−3or more. The carrier concentration of the light absorption layer4is usually 1×1010cm−3or less, so that, when the carrier concentration of the p-type region6is low, the depletion layer width becomes unstable and thus a difference between the multi-plication factor of the second p-type portion15and the multiplication factor of the first p-type portion14cannot be established accurately. However, when the carrier concentration (impurity concentration) of the p-type region6is about 5×1017cm−3, a difference between the multiplication factor of the second p-type portion15and the multiplication factor of the first p-type portion14can be established accurately. Further, when the carrier concentration (impurity concentration) of the p-type region6is 1×1018cm−3or more, a difference between the multiplication factor of the second p-type portion15and the multiplication factor of the first, p-type portion14can be established more accurately. According to the semiconductor light-receiving elements50of Embodiment 1, since the carrier concentration (impurity concentration) of the p-type region6is about 5×1017cm−3, it is possible to accurately determine the depletion layer width to be achieved when a bias is applied, so that the effect according to the first semiconductor light-receiving element50will be obtained stably. Further, according to the semiconductor light-receiving elements50of Embodiment 1, when the carrier concentration (impurity concentration) of the p-type region6is 1×1018cm−3or more, it is possible to more accurately determine the depletion layer width to be achieved when the bias is applied, so that the effect according to the first semiconductor light-receiving element50will be obtained more stably. Although a case has been described where the p-type region6is formed by two diffusion steps, these steps may instead be one step. For example, the first p-type portion14may be formed concurrently with the second p-type portion15, in such a manner that a central portion of the diffusion prevention mask24inFIG.6, namely, a portion thereof under which the formation of the first p-type portion14is prevented, is replaced with a diffusion control mask in which the diffusion rate of the p-type dopant is low. It is noted that the material of the light absorption layer4is not limited to InGaAs so long as it is a material that produces carriers when light is incident, namely, that has a small bandgap for the incident light, and thus may lie InGaAsP, InGaAsSb or the like, or the combination thereof. The window layer5may use any material so long as it produces no carrier when light is incident, namely that has a large bandgap for the incident, light, such as, AlInAs, AlGaInAs, InGaAsP or the like, or any combination thereof. The electric-field control layer3is not limited to being formed of InP and may be formed using AlInAs. Further, any type of material may be used for each of the epitaxial layers so long as a characteristic necessary for an operation as an APD is achieved thereby, and thus, the materials of the respective epitaxial layers are not limited to the materials that were used for the description. As described above, the semiconductor light-receiving element50of Embodiment 1 is a semiconductor light-receiving element in which the multiplication layer2, the electric-field control layer3, the light absorption layer4and the window layer5are sequentially formed on the semiconductor substrate1, and the p-type region6is formed in the window layer5. The p-type region6has the first p-type portion14and the second p-type portion15whose current multiplication factor due to light incidence is larger than that of the first p-type portion14. The first p-type portion14is formed as a central portion of the p-type region6, said central portion including the central axis21cperpendicular to the semiconductor substrate1, and the second p-type portion15is formed on the outer periphery of the central portion in a radial direction about the central axis21c. Because the p-type region6has the first p-type portion14formed as the central portion, and the second p-type portion15on the outer periphery of the central portion, whose current multiplication factor due to light incidence is larger than that of the first p-type portion14, the semiconductor light-receiving element50of Embodiment 1 can suppress the deterioration in characteristics if excessive light is incident on the p-type region6formed in the light receiving region22subject to incident light. A semiconductor light-receiving element manufacturing method of Embodiment 1 is a semiconductor light-receiving element manufacturing method of manufacturing the semiconductor light-receiving element50which comprises the semiconductor substrate1, the multiplication layer2, the electric-field control layer3, the light absorption layer4and the window layer5, and in which the p-type region6is formed in the window layer5, said p-type region having the first p-type portion14and the second p-type portion15whose current multiplication factor due to light incidence is larger than that of the first p-type portion14. The semiconductor light-receiving element manufacturing method of Embodiment 1 comprises: a step of forming the multiplication layer2, the electric-field control layer3, the light absorption layer4and the window layer5, sequentially on the semiconductor substrate1; a second p-type portion formation step of forming the second p-type portion15of the p-type region6; and a first p-type portion formation step of forming, after the second first p-type portion formation step, the first p-type portion14of the p-type region6. According to the semiconductor light-receiving element manufacturing method of Embodiment 1, it is possible to manufacture the semiconductor light-receiving element50in which the p-type region6has the first p-type portion14formed as the central portion, and the second p-type portion15on the outer periphery of the central portion, whose current multiplication factor due to light incidence is larger than that of the first p-type portion14. Thus, it is possible to manufacture the semiconductor light-receiving element50which can suppress the deterioration in characteristics if excessive light is incident on the p-type region6formed in the light receiving region22subject to incident light. In another aspect, a semiconductor light-receiving element manufacturing method of Embodiment 1 comprises: a step of stacking the multiplication layer2, the electric-field control layer3, the light absorption layer4and the window layer5, sequentially on the semiconductor substrate1, to thereby form a layered body; a second p-type portion formation step of forming the second p-type portion15of the p-type region6; and a first p-type portion formation step of forming, after the second p-type portion formation step, the first p-type portion14of the p-type region6. According to the semiconductor light-receiving element manufacturing method of Embodiment 1, it is possible to manufacture the semiconductor light-receiving element50in which the p-type region6has the first p-type portion14formed as the central portion, and the second p-type portion15on the outer periphery of the central portion, whose current multiplication factor due to light incidence is larger than that of the first p-type portion14. Thus, it is possible to manufacture the semiconductor light-receiving element50which can suppress the deterioration in characteristics if excessive light is incident on the p-type region6formed in the light receiving region22subject to incident light. Embodiment 2 FIG.11is a sectional view showing a schematic configuration of a semiconductor light-receiving element according to Embodiment 2, andFIG.12is a sectional view showing a schematic configuration of another semiconductor light-receiving element according to Embodiment 2. Each semiconductor light-receiving element50of Embodiment 2 differs from the semiconductor light-receiving element50of Embodiment 1 in that the diffusion front of the second p-type portion15of the p-type region6is formed in the light absorption layer4, namely, the second p-type portion15is formed to extend into the light absorption layer4. The structure other than the above is similar to that in the semiconductor light-receiving element50of Embodiment 1. In the semiconductor light-receiving element50of Embodiment 2, like in the semiconductor light-receiving element50of Embodiment 1, the diffusion front of the first p-type portion14of the p-type region6is formed in the window layer5to be spaced apart from the interface between the light absorption layer4and the window layer5. The semiconductor light-receiving element50shown inFIG.11is an avalanche photodiode of a back-surface incident type, and the semiconductor light-receiving element50shown inFIG.12is an avalanche photodiode of a front-surface incident type. In the semiconductor light-receiving element50of Embodiment 2, like in the semiconductor light-receiving element50of Embodiment 1, there is a difference in bandgap between the light absorption layer4and the window layer5, so that, when a reverse bias is applied between the anode electrode7and the cathode electrode9, such a difference in bandgap functions as a barrier for holes generated in the light absorption layer4. Namely, because of the difference in bandgap between the light absorption layer4and the window layer5, the holes generated in the light absorption layer4will be less likely to flow to the first p-type portion14. When the second p-type portion15is formed up to the inner side of the light absorption layer4beyond the interface between the light absorption layer4and the window layer5, in a region where the second p-type portion15and the light absorption layer4are connected to each other, there is no connection portion between the light absorption layer4and the window layer5, so that a bandgap between the second p-type portion15and the light absorption layer4is lower than a bandgap between portions of the light absorption layer4and the window layer5that are placed under the first p-type portion14. In this case, because of such a lower barrier, it is easier for the holes generated in the light absorption layer4to move, after traveling in the light absorption layer4, to the second p-type portion15in which holes are provided as majority carriers, than to move to the window layer5from the light absorption layer4. Thus, the holes generated in the light absorption layer4are likely to flow to the second p-type portion15that is formed up to a position in the light absorption layer4and thus has the lower barrier. Namely, the holes generated in the light absorption layer4tend to flow through the second p-type portion15of the p-type region6. This means that the photo-electric current flowing through the first p-type portion14in the light receiving region22is reduced, namely that the photo-electric current flowing through the central portion in the light receiving region22is reduced. Because the second p-type portion15of the p-type region6is formed up to the inner side of the light absorption layer4beyond the interface between the light absorption layer4and the window layer5, if excessive light is incident on the p-type region6formed in the light receiving region22, the semiconductor light-receiving element50of Embodiment 2 can suppress the deterioration in characteristics more significantly than the semiconductor light-receiving element50of Embodiment 1 does. More detailed description will be given below. According to the semiconductor light-receiving element50of Embodiment 2, when light is incident on the p-type region6formed in the light receiving region22, a photo-electric current always flows through the second p-type portion15that is larger than that flowing through the first p-type portion14. Thus, if excessive light is incident on the p-type region6, the photo-electric current flowing through the second p-type portion15in the light receiving region22will increase accordingly so that if an excessive current is generated, the photo-electric current is less likely to concentrate in the first p-type portion14in the light receiving region22and thus the deterioration in characteristics due to generated heat can be suppressed, more significantly than in the case of the semiconductor light receiving element50of Embodiment 1. As described above, like the semiconductor light-receiving element50of Embodiment 1, the semiconductor light-receiving element50of Embodiment 2 is provided with the p-type region6which has the first p-type portion14and the second p-type portion15whose diffusion front is deeper than that of the first p-type portion14, and thus it achieves an effect similar to that of the semiconductor light-receiving element50of Embodiment 1. Further, according to the semiconductor light-receiving element50of Embodiment 2, because the second p-type portion15of the p-type region6is formed up to the inner side of the light absorption layer4beyond the interface between the light absorption layer4and the window layer5, if an excessive current is generated, the photo-electric current is less likely to concentrate in the first p-type portion14in the light receiving region22and thus the deterioration in characteristics due to generated heat can be suppressed, more significantly than in the case of the semiconductor light receiving element50of Embodiment 1. Embodiment 3 FIG.13is a sectional view showing a schematic configuration of a semiconductor light-receiving element according to Embodiment 3, andFIG.14is a sectional view showing a schematic configuration of another semiconductor light-receiving element according to Embodiment 3. Each semiconductor light-receiving element50of Embodiment 3 differs from the semiconductor light-receiving element50of Embodiment 1 in that the second p-type portion15of the p-type region6is formed into a ring shape interposed between an outer periphery of the p-type region6in the radial direction and the center thereof (central axis21c). Further, according to the semiconductor light-receiving element50of Embodiment 3, it can be said that another first p-type portion14is further formed on an outer periphery of the second p-type portion15in the radial direction and, it can also be said that the second p-type portion15is formed to be displaced toward the central axis21cfrom the outermost peripheral portion of the p-type region6in the radial direction. The structure other than the above is similar to that in the semiconductor light-receiving element50of Embodiment 1. The outer periphery of the p-type region6is a portion along which a broken line21apasses and also a portion along which a broken line21epasses, and the center of the p-type region6is a portion along which a broken line21cpasses. The semiconductor light-receiving element50shown inFIG.13is an avalanche photodiode of a back-surface incident type, and the semiconductor light-receiving element50shown inFIG.14is an avalanche photodiode of a front-surface incident type. Like the semiconductor light-receiving element50of Embodiment 1, the semiconductor light-receiving element50of Embodiment 3 is provided with the p-type region6which has the first p-type portion14and the second p-type portion15whose diffusion front is deeper than that of the first p-type portion14, and thus it achieves an effect similar to that of the semiconductor light-receiving element50of Embodiment 1. Further, according to the semiconductor light-receiving element50of Embodiment 3, an outer periphery of the first p-type portion14that is the outer periphery of the p-type region6, is apart from the periphery of the second p-type portion15, and a deepest-portion distance11, that is a distance between the broken line21athat passes along the outer periphery of the p-type region6and a broken line21bthat passes through a deepest diffusion front of the second p-type portion15, is longer than that of the semiconductor light-receiving element50of Embodiment 1. Likewise, according to the semiconductor light-receiving element50of Embodiment 3, another deepest-portion distance I1, that is a distance between the broken line21ethat passes along the outer periphery of the p-type region6and a broken line21dthat passes through a deepest diffusion front of the second p-type portion15, is longer than that of the semiconductor light-receiving element50of Embodiment 1. According to the semiconductor light-receiving element50of Embodiment 3, because the deepest-portion distance I1is longer than that of the semiconductor light-receiving element50of Embodiment 1, it is possible to make the shape of an outer peripheral portion of the p-type region6, namely the shape of either a region from the broken line21ato the broken line21band a region from the broken line21dto the broken line21e, more moderate than in the case of the semiconductor light-receiving element50of Embodiment 1, so that electric-field concentration in the outer peripheral portion of the p-type region6can be reduced more significantly than in the case of the semiconductor light-receiving element50of Embodiment 1. When focusing on the curvature of the shape of an outer peripheral portion of the p-type region6, the semiconductor light-receiving element50of Embodiment 3 can make the curvature of the outer periphery portion of the p-type region6, smaller than in the case of the semiconductor light-receiving element50of Embodiment 1. Because the shape of the outer peripheral portion of the p-type region6is more moderate than in the case of the semiconductor light-receiving element50of Embodiment 1, the semiconductor light-receiving element50of Embodiment 3 can suppress edge breakdown at an edge portion of the light receiving region22, more significantly than the semiconductor light-receiving element50of Embodiment 1 does. Embodiment 4 FIG.15is a sectional view showing a schematic configuration of a semiconductor light-receiving element according to Embodiment 4, andFIG.16is a sectional view showing a schematic configuration of another semiconductor light-receiving element according to Embodiment 4. Each semiconductor light-receiving element50of Embodiment 4 differs from the semiconductor light-receiving element50of Embodiment 3 in that the diffusion front of the second p-type portion15of the p-type region6is formed in the light absorption layer4. The structure other than the above is similar to that in the semiconductor light-receiving element50of Embodiment 3. The semiconductor light-receiving element50shown inFIG.15is an avalanche photodiode of a back-surface incident type, and the semiconductor light-receiving element50shown inFIG.16is an avalanche photodiode of a front-surface incident type. Note that the semiconductor light-receiving element50of Embodiment 4 results from combining the structure of the semiconductor light-receiving element50of Embodiment 3 and the structure of the semiconductor light-receiving element50of Embodiment 2. Like the semiconductor light-receiving element50of Embodiment 1, the semiconductor light-receiving element50of Embodiment 4 is provided with the p-type region6which has the first p-type portion14and the second p-type portion15whose diffusion front is deeper than that of the first p-type portion14, and thus it achieves an effect, similar to that of the semiconductor light-receiving element50of Embodiment 1. Further, according to the semiconductor light-receiving element50of Embodiment 4, like in the semiconductor light-receiving element50of Embodiment 3, an outer periphery of the first p-type portion14that is the outer periphery of the p-type region6, is apart from the periphery of the second p-type portion15, and the deepest-portion distance11is longer than that of the semiconductor light-receiving element50of Embodiment 1. Thus, it is possible to make the shape of an outer peripheral portion of the p-type region6, more moderate than in the case of the semiconductor light-receiving element50of Embodiment 1, so that electric-field concentration in the outer peripheral portion of the p-type region6can be reduced more significantly than in the case of the semiconductor light-receiving element50of Embodiment 1. Furthermore, according to the semiconductor light-receiving element50of Embodiment 4, like in the semiconductor light receiving element50of Embodiment 2, the diffusion front of the second p-type portion15of the p-type region6is formed in the light absorption layer4. Thus, a path through which a photo-electric current easily flows can be formed at other than the central portion in the light receiving region22. Therefore, according to the semiconductor light-receiving element50of Embodiment 4, the multiplication factor of the central portion (the first p-type portion14placed inwardly from the second p-type portion15) in the light receiving region22decreases more significantly than in the case of the semiconductor light-receiving element50of Embodiment 3, so that, if an excessive current is generated, the photo-electric current is less likely to concentrate in the first p-type portion14in the light receiving region22and thus the deterioration in characteristics due to generated heat can be suppressed, more significantly than in the case of the semiconductor light receiving element50of Embodiment 3. According to the semiconductor light-receiving element50of Embodiment 4, because it results from combining the structure of the semiconductor light-receiving element50of Embodiment 3 and the structure of the semiconductor light-receiving element50of Embodiment 2, if excessive light is incident on the p-type region6, it is possible to suppress edge breakdown at an edge portion of the light receiving region22, while suppressing the deterioration in characteristics due to generated heat. Embodiment 5 FIG.17is a sectional view showing a schematic configuration of a semiconductor light-receiving element according to Embodiment 5, andFIG.18is a sectional view showing a schematic configuration of another semiconductor light-receiving element according to Embodiment 5. Each semiconductor light-receiving element50of Embodiment 5 differs from the semiconductor light-receiving element50of Embodiment 1 in that the diffusion-front difference that is a distance between the diffusion front of the first p-type portion14and the diffusion front of the second p-type portion15, is a diffusion-front difference d2of 100 nm or more. The structure other than the above is similar to that in the semiconductor light-receiving element50of Embodiment 1. The semiconductor light-receiving element50shown inFIG.17is an avalanche photodiode of a back-surface incident type, and the semiconductor light-receiving element50shown inFIG.18is an avalanche photodiode of a front-surface incident type. According to one exemplary calculation, when the diffusion-front difference as a distance between the diffusion front of the first p-type portion14and the diffusion front of the second p-type portion15is 100 nm or more, the multiplication factor of the central portion (the first p-type portion14placed inwardly from the second p-type portion15) in the light receiving region22can be lowered from 9.6 to 6.7, so that the photo-electric current flowing through the central portion in the light receiving region22can be reduced by about 30%. According to the semiconductor light-receiving element50of Embodiment 5, because the diffusion-front difference as a distance between the diffusion front of the first p-type portion14and the diffusion front of the second p-type portion15is 100 nm or more, the difference between the multiplication factor of the central portion in the light receiving region22and the multiplication factor of the outer peripheral portion therein, can be established more stably than in the case of the semiconductor light-receiving element50of Embodiment 1. When the structure in which the diffusion-front difference as a distance between the diffusion front of the first p-type portion14and the diffusion front of the second p-type portion15is 100 nm or more, is applied to the semiconductor light-receiving element50of Embodiment 3, the difference between the multiplication factor of the central portion in the light receiving region22and the multiplication factor of the outer peripheral portion therein, can be established more stably than in the case of the semiconductor fight-receiving element50of Embodiment 3. Further, the structure in which the diffusion-front difference as a distance between the diffusion front of the first p-type portion14and the diffusion front of the second p-type portion15is 100 nm or more, may be applied to the semiconductor light-receiving element50of Embodiment 2 or the semiconductor light-receiving element50of Embodiment 4. If this is the case, the difference between the multiplication factor of the central portion in the light receiving region22and the multiplication factor of the outer peripheral portion therein can be stably established as well. Like the semiconductor light-receiving element50of Embodiment 1, the semiconductor light-receiving element50of Embodiment 5 is provided with the p-type region6which has the first p-type portion14and the second p-type portion15whose diffusion front is deeper than that of the first p-type portion14, and thus it achieves an effect similar to that of the semiconductor light-receiving element50of Embodiment 1. Furthermore, according to the semiconductor light-receiving element50of Embodiment 5, because the diffusion-front difference as a distance between the diffusion front of the first p-type portion14and the diffusion front of the second p-type portion15is 100 nm or more, the difference between the multiplication factor of the central portion in the light receiving region22and the multiplication factor of the outer peripheral portion therein, can be established more stably than in the case of the semiconductor light-receiving element50of Embodiment 1. It is noted that, in this application, a variety of exemplary embodiments and examples are described; however, every characteristic, configuration or function that is described in one or more embodiments, is not limited to being applied to a specific embodiment, and may be applied singularly or in any of various combinations thereof to another embodiment. Accordingly, an infinite number of modified examples that are not exemplified here are supposed within the technical scope disclosed in the present description. For example, such cases shall be included where at least one configuration element is modified; where any configuration element is added or omitted; and furthermore, where at least one configuration element is extracted and combined with a configuration element of another embodiment. DESCRIPTION OF REFERENCE NUMERALS AND SIGNS 1: semiconductor substrate,2: multiplication layer,3: electric-field control layer,4: light absorption layer,5: window layer,6: p-type region,14: first p-type portion,15: second p-type portion,21c: broken line (central axis),50: semiconductor light-receiving element, d1: diffusion-front difference (differential distance), d2: diffusion-front difference (differential distance). | 53,185 |
11862748 | The foregoing summary, as well as the following detailed description of certain techniques of the present application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustration, certain techniques are shown in the drawings. It should be understood, however, that the claims are not limited to the arrangements and instrumentality shown in the attached drawings. DETAILED DESCRIPTION Certain inventive techniques discussed herein describe a cytometer that uses an avalanche photodiode (“APD”) with a lower cost implementation instead of a PMT to obtain low-level fluorescence detection, such that bull sperm chromosomal content can be determined or differentiated. The advantageous techniques may also enable the use of an APD in other cytometer sensing applications. An APD has substantial advantages over a PMT, including, for example, lower cost, no “warm-up” period, smaller and more efficient active area, improved control over the detection component, lower bias voltage (hundreds of volts vs. thousands of volts for a PMT), and no need for a light-blocking shutter when not in use. With regard to the active area, a PMT may have a relatively large active area (in one example, approximately 13.7 mm×3.9 mm) whereas an exemplary APD may have a substantially smaller and more symmetrical active area (in one example, a circular area having a 1 mm diameter). This may result in an improved fill factor for the sensor (for example, one order of magnitude or greater). By improving fill factor, it is easier to align the APD (versus the PMT) with the laser beam cross-sectional area, which makes the optical alignment relatively easier when constructing a system. With regard to improved control over the APD (versus the PMT), certain inventive techniques described herein allow for improved compensation and biasing, for example, by incorporating the APD into the cytometer in a manner that leverages the APDs quantum efficiency combined with the sensor optical gain. The quantum efficiency of the APD is related to the cytometer through a chosen dye and optical excitation wavelength. The optical gain factor of the APD may combine with the quantum efficiency, which is cell-stain (dye) dependent to produce the sensor output signal. According to certain inventive techniques, the APD is configured as an element of the voltage supply output filter network. Furthermore, the cytometer may include temperature compensation circuitry. APD optical gain may vary with temperature. If the temperature change is known, the bias voltage on the APD may be adjusted to compensate for the temperature change (to keep gain substantially constant). Alternatively, a heater that keeps the APD at constant temperature, or a relatively giant thermal mass, or a thermal electric cooler could also be used to stabilize the APD temperature (and thus keep the APD optical gain substantially constant). According to certain inventive techniques, APD conditioning circuitry may employ a two-stage feedback network to achieve relatively low noise performance. The first stage may be an analog stage controlled by a resistive feedback circuit to a flyback converter in a high-voltage power supply that reverse-biases the APD. The resistive feedback circuit in the power supply may have a digital-to-analog converter connected through circuitry that provides the ability to change the output voltage of the flyback converter. The second stage may allow the APD to become a part of an output filter network of the high-voltage power supply. The second stage may be designed to take into consideration that the flyback converter feedback may not accurately represent the voltage at the APD due to relatively large output filtering used to achieve low noise performance. The second stage feedback network may measure the output voltage after the first output filter stage and digitize it, becoming a digital feedback element in the control loop. This configuration may combine both analog and digital feedback elements in a hybridized implementation. By using the second stage feedback network, relatively large values in the output filtering, such as relatively large pole compensation generating relatively large resistor and capacitor combinations, may be able to be used for improved noise filtering through the use of both the analog and digital feedback mechanisms. The second stage feedback network may operate by sensing the voltage after a first output filter stage of the high-voltage power supply. This may take into consideration the voltage substantially near or at the APD. The sensed voltage may be digitized and processed by a processor (for example, a single processor or a plurality of processors or processing elements working together) in a substantially real-time manner. The processor may evaluate the sensed voltage proximate the APD (after the first output filter) as well as, optionally, other parameters such as the APD temperature and characteristics particular to a given APD (for example, APD reverse voltage VR or breakdown voltage VBR). The processor then may output a value that is converted into an analog signal. This signal may be used to influence the voltage at the feedback node of the flyback converter. As will be further described, the second stage feedback may be generated using an attenuated output voltage read back through an analog-to-digital converter (for example, 16-bit). This same analog-to-digital converter (or a separate analog-to-digital converter) may also be used to read in temperature data from the APD operating environment. FIG.1shows a flow cytometer100, according to certain inventive techniques. A stream of sperm cells104may pass through a flow chamber102, such that they may be single-file in certain strategic locations. The flow chamber may direct a fluid stream including the sperm cells104(sample particles) through a particle interrogation location. The sperm cells104may have been previously stained with a dye, such as a DNA-intercalating dye. Such a dye may fluoresce (or cause fluorescence) as it generates responsive light in response to being exposed to a light (or electromagnetic radiation) source. As the dyed sperm cells104pass one-by-one, they may be exposed to a beam of electromagnetic radiation (for example, light of a given wavelength) generated by a laser and emitted along a beam path (and optionally associated optics106) to the particle interrogation location. Such associated optics may include lenses, filters, or the like. The exposure of the dye to the laser light may cause the dye to emit fluorescently generated light. The amount of fluorescently generated light may vary by a detectable degree, depending on whether the sperm cell104carries XX chromosomes or XY chromosomes. The fluorescently generated light may be received by optics108(for example, lenses, filters, or the like), and it may be focused onto an active area of a photodetector112. According to certain inventive techniques, the photodetector112may include an APD. The photodetector112may generate an output signal that corresponds (varies linearly or non-linearly) to the amount of electromagnetic radiation (for example, light of a given wavelength) that it receives from the interrogation location. The photodetector output signal may include a time-varying analog signal indicative of an intensity of the received electromagnetic radiation. This photodetector output signal may ultimately be communicated to a processor114(which may include one processor or a plurality of processors that control a portion of the operation or the entire operation of the flow cytometer100). The photodetector output signal may be amplified by at least one amplifier (or two or more amplifiers in series) before it is communicated to the processor114. Furthermore, the photodetector output signal (for example, as amplified) may be digitized before being communicated to the processor114. A temperature sensor116may generate an output signal that corresponds (varies linearly or non-linearly) to the sensed temperature. As such, the temperature signal may encode temperature data that corresponds to a given sensed temperature. This temperature signal may ultimately be communicated to the processor114(for example, after amplification). The processor114may also receive a signal corresponding to the bias voltage (for example, the reverse-bias voltage) of the photodetector112generated by the power supply110and filtered by the output filter120. It should be understood that the photodetector signal, the temperature signal, and the bias voltage signal may be conditioned and/or digitized before they are received by the processor114—that is, they need not be directly connected such that the exact voltages output by the sensors112,116or the output filter120are delivered to the processor114. Instead, the system need only be designed such that the information generated by the sensors112,116and the bias voltage is communicated to the processor114. In this sense, these signals are communicated to the processor114. Depending on the temperature signal, the bias voltage signal, and/or known photodetector112characteristics, the processor114may influence the voltage of the power supply110that conditions (for example, reverse-biases) the photodetector112. Such known photodetector112characteristics may include an APD reverse voltage VR or breakdown voltage VBR. These characteristics may be stored in memory (not shown) which may be accessed by the processor114for computations. Such a memory may include a single memory or a plurality of memories separately addressable. The memory may be within a package with the processor or may be in a package external to the processor package. The memory may be non-volatile (for example, EEPROM or flash memory). The memory may also store relevant curves (for example, curves defining the input-output relationships of the photodetector112or the temperature sensor116, or other characteristics within the flow cytometer100). The processor114may make a decision as to whether the sperm cell104carries XX or XY chromosomes (that is, female or male gendered sperm cells104, respectively). If a sperm cell104does not carry the desired set of chromosomes, the processor114may control the kill/segregation componentry118to kill or segregate the unwanted sperm cell104. In this manner, a substantially high-purity population of gender-specific sperm cells104may be generated. FIG.2shows a block diagram200for circuitry capable of detecting the chromosomal content of sperm cells using an avalanche photodiode (“APD”), according to certain inventive techniques. The block diagram200may generally correspond to elements110,112,114,116, and120depicted inFIG.1and discussed above. Furthermore,FIGS.6A-6Xdepict circuit schematics (just one exemplary embodiment of many possibilities) that correspond to block diagram200, according to certain inventive techniques. Linear drop-out (“LDO”) regulator circuitry202(for example, including an integrated circuit, such as Linear Technology's LT1764) may receive an input DC voltage and convert it to a regulated low voltage (e.g., substantially 5 VDC). This block provides pre-regulation for the high voltage that will be created downstream. This initial stage of regulation may improve system noise by removing a substantial amount of the switching residue from the upstream voltage supply. The regulated low voltage output from the LDO circuitry202is received by high-voltage generator circuitry204, which generates a relatively high voltage. Such circuitry204may include an integrated circuit (such as Linear Technology's LT3580). The output of the high-voltage generator circuitry204may be provided to the transformer206. The transformer206may step the voltage up, for example, by a factor of 10. Schottky diode(s) (one or more in series) may receive the output of the transformer206. The resulting voltage may be fed back to the high-voltage generator circuitry204through feedback circuitry214(for example, one or more resistors in series). The high-voltage generator circuitry204, the transformer206, and the feedback circuitry214may form a power supply, such as a DC/DC boost switching power supply. The power supply may be a boost configuration that implements a resistive feedback circuit and the digital-to-analog converter220to generate the output voltage (as will be further explained). Overall, the power supply may include input circuitry (for example, including the high-voltage generator circuitry204), the transformer206, and output circuitry (for example, including one or more Schottky diodes in series between the output of the transformer206and the first filter208, or other suitable components). A feedback loop may communicate what the voltage is after the output circuitry to a feedback node arranged as an input to the high-voltage generator circuitry204. A first filter208may be located at the output of the power supply. The first filter208may include a network of one or more capacitor(s) and/or resistor(s). For example, the first filter208may be an RC-type filter. The first filter208may remove a degree of relatively high-frequency noise (for example, switching noise). The output of the first filter208may be provided to APD circuitry210. The filtered voltage from the first filter208may be used to reverse-bias the APD, which may be included in the APD circuitry210. The APD may include a Hamamatsu S8664 series APD. A second filter212may also be provided as part of the output filter network to the switching power supply. Altogether, the output filter network may include an RC-type filter (an example of the first filter208) followed by the APD circuitry210, and an additional output capacitor used to provide additional device stabilization (an example of the second filter212). Because the impedance of the APD mimics that of a capacitor, it may be built into the output filter network and act as a component in the device output filter circuitry. The output filter circuitry may use relatively large values that are typically too large for commercially-practical power supply circuits. However, because the APD requires relatively low bias currents, the output filter network can use these otherwise impractical components to aid in achieving advantageously low noise levels. For example, output voltage noise measured in a 20 MHz bandwidth has been shown to be below 150 microvolts (VRMS). The APD circuitry210may output a current signal when it receives light in a given frequency range. The current signal may be converted and/or amplifiers by one or more amplifiers. The amplifier(s) may include a first amplifier216and optionally a second amplifier218. The first amplifier216may convert the current signal to a voltage signal. The second amplifier218may provide additional gain if/as needed by amplifying the output provided by the first amplifier216. The second amplifier218may also invert the signal to mimic a PMT voltage output signal. Although not shown, the output of the second amplifier may be a voltage signal which may be digitized (for example, by A-to-D converter230) and communicated to a processor (such as processor222). A different processor (not shown) and/or another A-to-D converter (not shown) may be used for digitization/processing of the output signal. In addition to the feedback loop in the power supply, a second feedback loop may be included in the circuitry represented by block diagram200. This second feedback loop may include voltage adjustment circuitry, which is configured to adjust a voltage on the first feedback loop based at least in part on a voltage measured between the first filter208and the APD circuitry210. This second feedback loop (including the voltage adjustment circuitry) may include readback circuitry228, multiplexer226, A-to-D converter230, processor222, D-to-A converter224, and circuitry220. The second feedback loop may influence the voltage at the feedback node in the DC boost switching power supply to adjust its output based potentially a variety of factors, including the substantially real-time voltage at or proximate the APD. The particular techniques disclosed for the second feedback loop including voltage adjustment circuitry are just one of many different possible techniques that can influence the voltage at the feedback node of the power supply according to a voltage measured between the first filter208and the APD circuitry210. The readback circuitry228may receive the voltage between the first filter208and APD circuitry210. The readback circuitry228may include an amplifier to amplify the received voltage. The output of the readback circuitry228may be provided to multiplexer226. The multiplexer226may be an analog multiplexer, and it may receive a plurality of input signals. Such signals may include the output of the readback circuitry228, the output of a temperature sensor amplifier232, and/or the output of the amplifier network that conditions the output signal from the APD circuitry210(not shown). The processor222may provide a select signal to the multiplexer226to determine which of these (or other) signals will be output from the multiplexer226. The output of the multiplexer226is provided to the A-to-D converter230(for example, 16-bit). The digitized output of the A-to-D converter230may be provided to the processor222. Thus, the digital signal encodes the measured voltage between the first filter208and the APD circuitry210. The processor222may execute an equation or algorithm (through processing) to generate a digital output signal. The equation or algorithm may account for different input variables, including the voltage between the first filter208and the APD circuitry210, the temperature at or near the APD, and/or APD device characteristics (for example, APD reverse voltage VR or breakdown voltage VBR). The output signal from the processor may be provided to the D-to-A converter224(for example, 16-bit), and the analog output (an adjustment voltage) of the converter224may be received by circuitry220. Circuitry220may condition the signal (for example, filter/amplify the output of the converter224). The output of the circuitry220may influence or cause the voltage at the feedback input (or node) to the high-voltage generator circuitry204to change. The feedback node voltage is influenced by the electrical signal summation of the digital-to-analog converter224voltage output and the output voltage of the DC-DC converter. The feedback voltage generated from the output of the DC-DC converter combines with the digital-to-analog converter224output to generate the power supply output voltage. The temperature sensor234(for example a TI LM35 series sensor) may provide a temperature reading with a minimum of 0.25° C. linearity. The temperature sensor234output may be amplified by temperature sensor amplifier232before it is provided to multiplexer226. The temperature may be measured at periodic intervals for changes from when the last user adjustment from an operator occurred. Based on the change in temperature, the processor222may either increase or decrease the APD reverse-bias voltage. A slope calculation from the configuration step of the APD may be used to adjust the voltage bias by a fixed amount for every 0.25° C. change at the temperature sensor (near or at the APD). For example, each 0.25° C. temperature change may be converted into a number of digital counts based on the slope of the output voltage. It is then determined how many digital counts are needed need to generate ‘X’ voltage value. The slope value is generated for each power supply by setting the power supply's digital-to-analog converter224, measuring the output voltage of the power supply, setting the digital-to-analog converter224to a different value, and measuring the output voltage. This results in an equation: (voltage2−voltage1)/(DAC_value2−DAC_value1)=slope. The slope informs how much voltage the output will change per digital-to-analog converter224count value. It may be known that for every single degree C. change, the device will need to adjust by, for example, 0.78V. So for every 0.25° C., it may be known that the output will need to be adjusted by 0.78V/4, or 0.195V at the output. The slope determines how many digital counts are needed to effect the proper change (either up or down depending on if temperature is increasing or decreasing). For example, if the slope is 0.0076, and the temperature changes by 0.25° C., the digital-to-analog converter224may need to be adjusted by 0.195V/0.0076, which equals 26 digital counts. Consider the following illustrative example for the operation of circuitry illustrated by block diagram200. Each APD may have a different operating voltage bias and breakdown voltage. The APD reverse voltage (VR) and breakdown voltage (VBR) may be specified by the APD manufacturer. These characteristics of a particular APD may be stored in memory (for example, non-volatile memory) readable by the processor (for example, integrated EEPROM). Thus, each cytometer may be individualized for a given APD. Supply output voltage values may also be measured (for example, using an external NIST traceable voltmeter) as part of a one-time configuration process for each cytometer, and these calibration values for the output voltage may then be stored in memory (along with the other unique variables for the APD as discussed above). For each given system, the VREF value may control the APD's voltage bias. For example, a value of 0.5V at VREF may correspond to an optical gain of M=50 for the APD and moving the value from 0.1V to 1V may adjust the gain of the APD by increasing the bias voltage. Protection algorithms may be built into the processor222such that an unreasonably high VREF may not allow the APD to reach breakdown voltage, and therefore the APD may be protected. Under certain conditions, because VREF adjusts the optical gain at the APD, this does not mean that the supply simply adjusts the output voltage in the same increments for each device for a given VREF. This is because from VREF=0.1 to 1V, the algorithm used to control the flyback converter supply may treat the VREF signal as an optical gain parameter, and not a voltage adjustment parameter. This may mean that a VREF of 0.5V may produce a different voltage value which is unique for the given APD installed in the system. If an APD has a VR of 403.3V for M=50, and a separate APD has a VR value of 390.8V for M=50, the VREF input of 0.5V may still be selected to produce the exact same optical gain of M=50. This means that the output voltage adjustment through VREF may actually be a function of the desired optical gain, which may be unique to the APD device itself, and is not a uniformly applicable output voltage adjustment. These customized values corresponding to the characteristics may be programed into each system at startup, and the customized characteristics may enable uniform “black box” performance across all similarly configured systems. Because the flyback power supply may utilize a hybrid analog and digital feedback from different nodes, the output voltage to achieve the M=50 may be obtained by comparing the high voltage read back signal of the actual APD itself, and the processor222may generate an error term from the flyback's analog control generated value. The second feedback loop value may be converted into a digital count based on the slope of a linear curve fit performed at the initial startup configuration. When a user sets VREF at ostensibly 0.5V, the processor222may recognize that based on the values entered, the particular APD installed needs a reverse-bias voltage of 403.3V, and sets the precise VREF to be something potentially different from 0.5V. The digital-to-analog converter224may be sent a value determined from the initial configuration at startup, and, if the APD was not present in the output filter, it may have the correct output voltage. However, because the first filter208may use relatively large value resistor component(s), the feedback network of the supply may “think” it is providing the correct voltage when really it is offset because the system now has an APD present in the output filter network. The second feedback node, which may be a digitized value of the actual output voltage at or proximate the APD (for example, a voltage at a location between the first filter208and the APD circuitry210), may then be used to solve an internal slope compensation equation (or other suitable algorithm) in the processor222that sets the correct output voltage for a desired optical gain. This algorithm may then be used to adjust the D-to-A converter224value sent to the flyback converter's feedback node. Temperature compensation may also be implemented. Once the optical gain is set for M=50, the processor may measure the temperature, and for example, for any changes in 0.5° C. (or other suitable increment), the output voltage that was used for M=50 may be adjusted to a new value, for example, based on the breakdown coefficient of the APD to keep the gain set at M=50. This means that temperature compensation may be invoked after an interval of time has passed since VREF has changed. This may allow for temperature once a user has set VREF (because not all systems will want M=50, some may be at M=55, M=60, or other suitable optical gains depending on the desired mode of operation). FIG.3illustrates a flowchart300for a method, according to certain inventive techniques. The method may be performed by systems100or200. The certain steps in the flowchart300may be performed at times overlapping other steps or substantially simultaneously with other steps. Certain steps could be performed in a different order, and there is no implication by the flow of flowchart300that steps must be performed in any particular order. At step302, an input voltage may be received at input circuitry (for example, high-voltage generator circuitry204) of a power supply, such as a DC/DC boost switching power supply. At step304, a transformer (for example, transformer206) transforms a voltage supplied by the input circuitry into a transformed voltage. At step306, output circuitry (for example, one or more Schottky diodes in series between the transformer206and the first filter208) of the power supply receives the transformed voltage. At step308, the output circuitry generates an output voltage. At step310, a voltage corresponding to the output voltage is fed back to the input circuitry. At step312, the output voltage is received at a filter (for example, first filter208), and a filtered voltage is generated by the filter. At step314, the filtered voltage is received at APD circuitry (for example, APD circuitry210), which includes an APD. At step316, the filtered voltage is received at voltage adjustment circuitry (for example, readback circuitry228). This circuitry may be part of the second feedback loop, as discussed above. At step318, the feedback voltage may be adjusted by the voltage adjustment circuitry according to at least the output voltage. At step320, a temperature sensor (for example, temperature sensor234) may generate a temperature signal corresponding to a measured temperature (that is, a sensed temperature). Furthermore, step318may further include adjusting the feedback voltage by the voltage adjustment circuitry according to at least the filtered voltage and the measured temperature. Additionally, step318may further adjusting the feedback voltage by the voltage adjustment circuitry according to at least the filtered voltage, the measured temperature, and at least one value corresponding to a characteristic of the avalanche photodiode. Also, step318may further include adjusting the feedback voltage by the voltage adjustment circuitry according to at least the filtered voltage and at least one value corresponding to a characteristic of the avalanche photodiode. According to one technique, step318further includes: converting, with an analog-to-digital converter (for example, analog-to-digital converter230), the filtered voltage into a digital measured signal encoding filtered voltage data; processing, with a processor (for example, processor222), at least the filtered voltage data to generate a digital adjustment signal; converting, by a digital-to-analog converter (for example, digital-to-analog converter224), the digital adjustment signal to an adjustment voltage; and adjusting the feedback voltage according to the adjustment voltage. According to another technique, said processing at least the output voltage data may further include processing at least temperature data and the filtered voltage data to generate the digital adjustment signal. According to another technique, said processing at least the output voltage data further comprises processing at least data corresponding to at least one characteristic of the avalanche photodiode, temperature data, and the filtered voltage data to generate the digital adjustment signal. According to another technique, the at least one characteristic of the avalanche photodiode comprises at least one of a breakdown voltage and a reverse bias voltage corresponding to a predetermined optical gain. At step322, a first amplifier (for example, first amplifier216) may amplify a voltage at an anode of the avalanche photodiode to form a first amplified voltage. At step324, a second amplifier (for example, second amplifier218) may amplify the first amplified voltage to generate a second amplified voltage. FIG.4illustrates a flowchart400for a method, according to certain inventive techniques. The method may be performed by systems100or200. The certain steps in the flowchart400may be performed at times overlapping other steps or substantially simultaneously with other steps. Certain steps could be performed in a different order, and there is no implication by the flow of flowchart400that steps must be performed in any particular order. At step402, electromagnetic radiation (for example, light of a given wavelength) is emitted from a laser (for example, laser106). At step404, a fluid stream and sperm cells contained therein are illuminated with the electromagnetic radiation. At step406, an APD (for example, photodetector112) detects electromagnetic radiation emitted from the sperm cells. This emitted radiation (for example, light of a given wavelength) may be generated by a fluorescing dye (for example, stained on sperm chromosomes) that generates responsive radiation in response to received radiation. At step408, the APD generates a time-varying analog signal indicative of an intensity of the detected electromagnetic radiation. At step410, an analog-to-digital converter (for example, converter230) converts the time-varying analog signal into a corresponding digital signal. The time-varying signal may be processed before digitization (for example, by read back circuitry228). At step412, a processor (for example, processor222) analyzes the digital signal to determine characteristics of the sperm cells in the fluid stream. FIG.5illustrates a flowchart500for a method, according to certain inventive techniques. The method may be performed by systems100or200. The certain steps in the flowchart500may be performed at times overlapping other steps or substantially simultaneously with other steps. Certain steps could be performed in a different order, and there is no implication by the flow of flowchart500that steps must be performed in any particular order. At step502, DNA within a nucleus of a sperm cell (for example, sperm cell104) is stained, for example, with a DNA-intercalating, fluorescing dye. At step504, the stained DNA within the nucleus of the sperm cell is irradiated (for example, by laser106). At step506, fluorescent light emitted from the irradiated and stained DNA within the nucleus of the sperm cell is detected with an avalanche photodiode (for example, photodetector112). At step508, a sex of a sperm cell is determined using the detected amount of DNA within the nucleus of the sperm cell. For example, a sperm cell with XX chromosomes may have 3% more DNA than a sperm cell with XY chromosomes. This may lead to a corresponding increase (linear or non-linear increase) of light emission from the stained DNA. Due to the inventive techniques disclosed herein, it may be possible to measure this difference with an avalanche photodiode, thereby determining the “sex” of a sperm cell. At step510, a plurality of sperm cells are differentiated based upon said sex determination. The cells may be sorted (creating two or more populations; for example, an X-chromosome population and a non-X-chromosome population), or cells within the population can be selected for deactivation (for example, by laser ablation). At step512, a given sperm cell may be deactivated based upon the determined amount of DNA within the nucleus of the given sperm cell. For example, processor114may control operation of kill/segregation componentry118to deactivate (separate, degrade, or destroy) the sperm cell so it may not be useful for fertilization based on the result of step510. One technique of deactivation is illustrated generally by steps514,516,518, and520. At step514, a plurality of droplets may be formed for entraining a corresponding plurality of the sperm cells. At step516, each of the plurality of droplets may be differentially charged based upon the sex differentiation characteristic of the corresponding entrained sperm cells. At step518, each of the plurality of droplets may be deflected. At step520, each of the droplets may be differentially collected based upon the sex differentiation characteristic of the plurality of sperm cells entrained in the corresponding plurality of droplets. For example, one approach for sexing is laser-kill in which anything that is not an X-chromosome-bearing sperm cell may be ablated via laser pulse. Such techniques are described in U.S. Pat. Nos. 8,933,395, 9,000,357, 9,140,690, and 9,335,295, the entireties of which are herein incorporated by reference. As another example, charge/deflection techniques are also used in the sexing industry. Such techniques are described in U.S. Pat. No. 9,145,590, the entirety of which is herein incorporated by reference. Other conceivable approaches include the use of optical traps and/or laser steering, as described in U.S. Pat. Nos. 8,149,416 and 8,158,927, the entireties of which are herein incorporated by reference. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the novel techniques disclosed in this application. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the novel techniques without departing from its scope. Therefore, it is intended that the novel techniques not be limited to the particular techniques disclosed, but that they will include all techniques falling within the scope of the appended claims. | 35,156 |
11862749 | DETAILED DESCRIPTION OF EMBODIMENTS Reference will now be made in detail to particular embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be readily apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, processes, components, structures, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention. Some portions of the detailed descriptions which follow are presented in terms of processes, procedures, logic blocks, functional blocks, processing, schematic symbols, and/or other symbolic representations of operations on data streams, signals, or waveforms within a computer, processor, controller, device, and/or memory. These descriptions and representations are generally used by those skilled in the data processing arts to effectively convey the substance of their work to others skilled in the art. Usually, though not necessarily, quantities being manipulated take the form of electrical, magnetic, optical, or quantum signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer or data processing system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, waves, waveforms, streams, values, elements, symbols, characters, terms, numbers, or the like. Referring now toFIG.1, shown is an example application using the module assembly, in accordance with embodiments of the present invention. In example100, a redistribution layer (RDL) as used in wafer level chip scale packaging (WLCSP) is shown. WLCSP refers to the technology of packaging an integrated circuit at a wafer level, resulting in a device that is practically the same size as the die. While the name implies devices would be packaged, the bare die can actually be modified to add environmental protection layers and solder balls that are then used as the direct connection to the package carrier or substrate. WLCSP technology can allow devices to be integrated in the design by using the smallest possible form factor, and WLCSP devices may require no additional process steps on surface mount assembly lines. In WLCSP, the bare die can be processed to have solder balls attached directly to the device, which may remove the need for external casing and wiring in some cases. In this particular example, silicon die112can be covered with a nitride passivation layer (e.g.,110), except for pad openings (e.g.,114) in some cases. For example, RDL108can be used to route between pad114and a region for external connectivity. A polymer dielectric (e.g.,106) can then be added, followed by deposition of under bump metallization (UBM), such as104. A solder ball (e.g.,102) can then be attached to each UBM pad. After processing, the device can be a die with an array pattern of solder balls, which may then be attached at a pitch that is comparable to traditional circuit board (e.g., printed-circuit board [PCB]) assembly processes. In this way, there may be no need for external packaging material in order to protect the chip. In particular embodiments, optical transceivers and/or optical receivers can be implemented in WLCSP technology, and then may be connected to a corresponding PCB to form a full integrated module assembly. Referring now toFIG.2, shown is an example WLCSP device (top view), in accordance with embodiments of the present invention. Example200is one particular example of an optical module in WLCSP device implementation. In addition to optical module implementation, such technology may be used in supporting analog and digital circuitry. In this particular example, optical transmitter206-T and optical receiver206-R can be on opposite sides at the edges of the WLCSP/die204. This arrangement allows multiple rows of blocking balls (e.g.,102) and vias to be placed between the optical transmitter and receiver. Balls102can be near the edge of the die, but not exactly where the optical transmitter/receiver are located. Lenses202can be in alignment with the corresponding optical device206. In one embodiment, an integrated module assembly can include: (i) an optical integrated circuit having first and second optical devices; (ii) a PCB having first and second holes therein, where the optical integrated circuit is coupled upside down to a first side of the PCB; and (iii) first and second lenses coupled to a second side of the PCB, where the first and second sides of the PCB are opposite thereto; and (iv) where the first lens is in alignment with the first hole and the first optical device, and the second lens is in alignment with the second hole and the second optical device. In one embodiment, an integrated module assembly can include: (i) an optical integrated circuit comprising first and second optical devices; (ii) a PCB having first and second clear regions therein, where the optical integrated circuit is coupled upside down to a first side of the PCB; (iii) first and second lenses coupled to the first side of the PCB; and (iv) where the first lens is in alignment with the first clear region and the first optical device, and the second lens is in alignment with the second clear region and the second optical device. In one embodiment, a method of making an integrated module assembly can include: (i) forming an optical integrated circuit comprising first and second optical devices; (ii) forming a PCB having first and second clear regions therein; (iii) arranging the optical integrated circuit upside down on the PCB; (iv) forming first and second lenses on the PCB; and (v) aligning the first lens with the first clear region and the first optical device, and aligning the second lens with the second clear region and the second optical device. In particular embodiments, by using an optically clear PCB, the PCB may no longer block light to and from the active surface of the die that includes optical devices. In some cases, the PCB may be used directly as the optical sensor window in the housing of the final product. As an example of an application using this assembly technology, an optical distance detector can include an integrated circuit having an optical transmitter (e.g., light-emitting diode [LED], vertical-cavity surface-emitting laser [VCSEL], etc.) and one or more optical receivers (e.g., PIN diodes, etc.), in addition to analog and digital circuitry. A VCSEL is a type of semiconductor laser diode with laser beam emission perpendicular from the top surface, as opposed to edge-emitting semiconductor lasers or in-plane lasers that emit from surfaces formed by cleaving the individual chip out of a wafer. VCSELs are used in various laser products, including computer mice, fiber optic communications, laser printers, Face ID, and smart glasses. A PIN diode is a diode with a wide, undoped intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region. The p-type and n-type regions are typically heavily doped because they are used for ohmic contacts. The wide intrinsic region makes this device particularly suitable for attenuators, fast switches, photodetectors, and high voltage power electronics applications. The LED may alternatively be a separate die or “chiplet” made in a different process technology than the rest of the circuit, as LEDs are typically made in a technology that is difficult to integrate with standard CMOS devices. The LED transmitter may thus be a separate die from the rest of the circuit, or it may be a chiplet that is mounted of the surface of the main die. The optical receiver (e.g., phototransistor, PIN diode, etc.) may be integrated on the main die, or this may be a chiplet or separate die as well. An “optical device” as described herein can be an optical transmitter or an optical receiver. WLCSP assembly can include layers of copper (e.g., RDL) and insulators. The materials used for insulation are transparent for most wavelengths, including infrared (IR). One of the materials that can be used for repassivation is a polyimide (e.g., Kapton, which is transparent in infrared). This material typically blocks blue and green light, but for WLCSP, the layers are so thin that the material may be partially transparent also for green and blue. In certain embodiments, one or more optical devices can be integrated with, or otherwise attached thereto, the WLCSP assembly. An “optical integrated circuit” as described herein can include, e.g., the WLCSP assembly/structure that includes one or more optical devices. Referring now toFIG.3, shown is an example individual lens device, in accordance with embodiments of the present invention. For a WLCSP device, the optical sensors (e.g., light receivers) can be mounted upside down toward the PCB. For example, “holes” or otherwise clear regions can be formed in the PCB for the optical sensor to see the outside world. In particular embodiments, actual holes can be formed in the PCB, and/or optically clear regions can be formed in the PCB. In addition, the light transmitters (e.g., LED, VCSEL, etc.) can also be mounted downward toward the PCB in alignment with holes/clear regions therein. Further, lenses can be included that are attached to the PCB, and/or are formed within the PCB itself in some cases. In example300, the WLCSP can include silicon die308with optical receiver306-R and optical transmitter306-T, as well as repassivation layer(s) and polyimide (e.g., Kapton)310, UBM318, and solder balls304. The PCB can include PCB traces/pads312, PCB solder mask314, and PCB core316. In addition, via322can be included in PCB core316in order to form connections PCB traces and pads312. In example300, the lenses302may be individual lenses (e.g., one for the optical transmitter and one for the optical receiver), and light beams320can be as shown emanating from optical transmitter306-T, and coming into optical receiver306-R. Depending on which particular WLCSP technology is used,318may be just the under bump metallization, or can be both the UBM and RDL, as this particular example does not differentiate between the two. Also, UBM may or may not be a separate layer, depending on the particular WLCSP technology used. In1, the UBM is shown as a separate layer. In some WLCSP technologies, bumps may be placed directly on die pads, but usually a UBM layer is still used. RIM, may be utilized when the bumps need to be in a different physical location than the pads (see, e.g.,FIG.2). RDL is typically a single layer on the die, but multi-layer RDL can also be used in some cases. In particular embodiments, any suitable WLCSP technology may be employed in order to implement the optical integrated circuit. In this particular case, a 2-layer PCB is shown; however, a multi-layer PCB or even a single-layer PCB can be utilized in certain embodiments. Referring now toFIG.4, shown is an example multiple lens device, in accordance with embodiments of the present invention. In example400, a cast module that includes multiple lenses can be utilized can be utilized instead of individual lenses for each optical device. In example400, the WLCSP can include silicon die308with optical receiver306-R and optical transmitter306-T, as well as repassivation layer(s)/polyimide310, UBM318, and solder balls304. The PCB can include PCB traces/pads312, PCB solder mask314, and via322in PCB core316to connect PCB traces and pads312. As shown, light beams320can be transmitted from optical transmitter306-T, and light beams can be received by optical receiver306-R. In example400, lenses402may be a cast module that includes multiple lenses with curved lens shapes corresponding to each optical device, as well as a common flat surface that mounts to the bottom of the PCB. Referring now toFIG.5, shown is an example device with lenses using PCB holes for alignment, in accordance with embodiments of the present invention. In example500, the WLCSP can similarly include silicon die308with optical receiver306-R and optical transmitter306-T, as well as repassivation layer(s)/polyimide310, UBM318, and solder balls304. The PCB can include PCB traces/pads312, PCB solder mask314, and PCB core316, and via322in PCB core316to connect PCB traces and pads312. As shown, light beams320can be transmitted from optical transmitter, and light beams can be received by optical receiver306-R. In example500, lenses502can use the holes in the PCB for alignment. As such, lenses502can be partially within the PCB holes and partially outside of the holes. Lenses502can have curved surfaces that fit within the corresponding holes on one side, and another curved surface on the other side. This arrangement may allow for improved alignment between the lens, hole, and corresponding optical device306. Referring now toFIG.6, shown is an example device with spherical ball lenses that fit in the PCB hole, in accordance with embodiments of the present invention. In example600, the WLCSP can similarly include silicon die308with optical receiver306-R and optical transmitter306-T, as well as repassivation layer(s)/polyimide310, UBM318, and solder balls304. The PCB can include PCB traces/pads312, PCB solder mask314, and PCB core316, and via322can be included in PCB core316to connect PCB traces and pads312. As shown, light beams320can be transmitted from/to optical transmitter306-T and optical receiver306-R. In example600, lenses602can be spherical ball lenses that fit in the PCB hole. As such, lenses602can be partially within the PCB holes and partially outside of the holes, while maintaining the spherical ball shape. Lenses602can be perfect spheres, or may be more elliptical in some cases. The particular type of lenses utilized in certain embodiments can depend on the optical requirements of the given application. Referring now toFIG.7, shown is a first example clear PCB device, in accordance with embodiments of the present invention. This particular example utilizes a clear and flat PCB. In example700, the WLCSP can include silicon die308with optical receiver306-R and optical transmitter306-T, as well as repassivation layer(s)/polyimide310, UBM318, and solder balls304. The PCB can include PCB traces/pads312, PCB solder mask314, and PCB core704, and via322can be included in PCB core704to connect between PCB traces and pads312. As shown, light beams720can be transmitted from optical transmitter306-T, and light beams may be received by optical receiver306-R. For example, PCB core704can be an optically clear material, and in particular may have clear regions corresponding to the optical devices and lenses, such as in place of holes in the PCB. In particular embodiments, a clear PCB can be employed as shown, and such a clear PCB may also shield the surface of the die from the outside environment. Thus, the clear regions as described herein can include substantial portions of the PCB, but designated clear regions/holes may be aligned with optical transceiver306-T and optical receiver306-R. The clear PCB in this case can also serve as the external window of the optical structure, thereby reducing both cost and size of the final module. In example700, lenses702can be spherical ball lenses on one side and flat surfaces on the other, and that may at least partially fit in, or are otherwise aligned with, the PCB hole. Further, lenses702in this example can be arranged between the WLCSP and the PCB, as opposed to being located on the bottom of the PCB. Referring now toFIG.8, shown is a second example clear PCB device, in accordance with embodiments of the present invention. In example800, a clear PCB that is flat is shown. In example800, the WLCSP can similarly include silicon die308with optical receiver306-R and optical transmitter306-T, as well as repassivation layer(s)/polyimide310, UBM318, and solder balls304. The PCB can include PCB traces/pads312, PCB solder mask314, and PCB core704, and vias322formed in PCB core704to connect between PCB traces and pads312. As shown, light beams720can be transmitted from optical transmitter306-T. In addition, light beams can be received by optical receiver306-R. In example800, lenses702can be spherical ball lenses on one side and flat surfaces on the other, and that may at least partially fit in, or are otherwise aligned with, the PCB hole. In this example, the optical transmitter306-T and optical receiver306-R are placed father apart in order to substantially avoid optical interference. Multiple solder balls304and vias322can further block such interference between the optical devices306. Referring now toFIG.9, shown is a third example clear PCB device, in accordance with embodiments of the present invention. In example900, the clear PCB may be shaped to act as a lens itself (e.g.,902) for the transmitted and received light beams920. In example900, the WLCSP can include silicon die308with optical receiver306-R and optical transmitter306-T, as well as repassivation layer(s)/polyimide310, UBM318, and solder balls304. The PCB can include PCB traces/pads312, PCB solder mask314, and PCB core904, and vias322formed in PCB core704to connect PCB traces and pads312. As shown, light beams920can be transmitted from optical transmitter306-T, and light beams can be received by optical receiver306-R. In example900, additional lenses702can be shaped within the PCB hole itself between the WLCSP and the PCB, and/or lenses may be formed as a curved shape902within PCB core904. In some cases, curved lens902can be the only lens utilized for each optical device, while in other cases both of lenses702and902can be utilized in alignment with the corresponding optical device. Any suitable curved shape902for forming an optical lens can be employed in certain embodiments. In addition, the optical transmitter306-T and optical receiver306-R can similarly be placed father apart and with multiple solder balls and vias322therebetween in order to substantially avoid optical interference. Referring now toFIG.10, shown is a flow diagram of an example method of making an integrated module assembly, in accordance with embodiments of the present invention. In example1000, the method can include formation of an optical integrated circuit including first and second optical devices at1002. For example, this optical integrated circuit can be implemented using WLCSP technology, and may be fully integrated and/or may utilize one or more chiplets. At1004, a PCB having first and second clear regions (e.g., holes or optically transparent regions) therein can be formed. At1006, the optical integrated circuit may be arranged upside down on the PCB. At1008, first and second lenses can be formed on the PCB. For example, the lenses can be separate lenses (see, e.g.,FIG.3), multiple lenses in a cast module (see, e.g.,FIG.4, and/or the lenses may be integrated within a clear PCB (see, e.g.,FIG.9). At1010, the first lens can be aligned with the first clear region and the first optical device, and the second lens can be aligned with the second clear region and the second optical device. The alignment can be facilitated by utilizing the PCB holes themselves in some cases, such as in the examples ofFIGS.5and6. Of course, the ordering of the various steps shown inFIG.10represent but one possible ordering, and any suitable ordering of these particular steps, as well as numbers of steps or sub-steps, can be supported in certain embodiments. In particular embodiments, various alternatives can be utilized in order to reduce optical reflections between the optical transmitter and the optical receiver. For example, the clear PCB may only need to be clear at proximate locations or regions corresponding to and in alignment with the transmitter and receiver. In this case, the rest of the area can be covered by traces, (matte) black silk screen, or any other suitable material in order to block optical reflections. For example, in very low cost applications, printed traces and glue may be utilized instead of copper traces and solder. Alternatively, a glass/ITO process, as found in liquid crystal display (LCD) panels, can be utilized. In that case, the traces may be clear, and the silk screen can do the blocking of light reflections. Indium tin oxide (ITO) is a ternary composition of indium, tin, and oxygen in varying proportions. As shown in various examples, one or more solder bumps can be placed directly between the optical transmitter and the optical receiver in order to block the direct light path therebetween. Even though this direct path may be blocked, solder bumps tend to be shiny, and the amount of light coming in through secondary light reflections may actually increase as a result. To help alleviate this potential problem, and/or if the PCB itself becomes an unwanted optical path between transmitter and receiver, one or more vias (e.g.,322) can be placed within the PCB in order to break that unwanted path. Referring now toFIG.11, shown is a fourth example clear PCB device, in accordance with embodiments of the present invention. In example1100, if the air gap between the WLCSP/die and the PCB represents another potential problem, an optically clear underfill material1102(e.g., clear silicone, clear epoxy, etc.) can be utilized in that air gap. With an appropriate material choice, there may essentially be two fewer interfaces on each side where the refractive index changes. For example, by selectively only placing the underfill material1102at the locations of the transmitter306-T and receiver306-R (e.g., one small drop in each location), problems related to air bubbles in the underfill can substantially be avoided, and the optical coupling between the two may accordingly be reduced. Further, the solder balls304can generally provide suitable mechanical strength in pairing the WLCSP and the PCB with appropriate dimensions. As another example, in addition to the clear underfill1102that lies in the desired optical path, a regular opaque underfill can be added to fill that air gap for the rest of the die. Such an opaque underfill can block additional light, while also increasing mechanical strength, if required. As shown inFIGS.8and9, e.g., the optical transmitter and optical receiver can be on opposite sides at the edges of the WLCSP/die. This arrangement allows multiple rows of blocking balls (e.g.,304) and vias (e.g.,322) to be placed between the optical transmitter and receiver. Balls can still be near the edge of the die, but not exactly where the optical transmitter/receiver are located. Having the optical transmitter and receiver at the edge may also facilitate the dispensing of a small drop of clear underfill corresponding to each optical device, as discussed above. If lenses are to be added to a clear PCB, there are multiple options supported in certain embodiments. For a glass PCB, these may be separate lenses (see, e.g.,FIGS.7and8). For a plastic material, and in some cases for a glass material, the lenses may be molded as part of the PCB, e.g., as shown inFIG.9. In addition, while only one side of the PCB is shown as molded inFIG.9, one or both sides of the PCB may be so molded form lenses in certain embodiments. Particular embodiments may be applicable to an optical distance measurement circuit using infrared light, but can also be used for any other optical circuit using wavelengths where the materials in the optical path are sufficiently transparent, such as (e.g., infrared) image sensors. Certain embodiments can also be extended to a wider optical wavelength range by using different (optically clear) materials (e.g., polyimide materials) as the insulator on top of the WLCSP, which is effectively between the WLCSP and the PCB. Particular embodiments may be especially suitable for manufacturers of systems that need robotic vision, proximity sensing, and/or distance measurement. The drawings herein primarily show a single optical element (e.g., lens, molded transparent PCB, etc.) in the light path. However, an even more sophisticated optical system can be implemented in certain embodiments by having more than a single optical element, such as by combining the molded PCB shown inFIG.9with the external lenses as shown inFIG.3. This is also exemplified inFIG.9with lenses702and molded curved lenses902in the optical path. In addition, any suitable optical devices can be used in certain embodiments. For example, the optical transmitter may be a LED for a low cost, short range applications, but a VCSEL may provide a more cost-effective in some cases. While the above examples include circuit, operational, and structural implementations of certain memory cells and programmable impedance devices, one skilled in the art will recognize that other technologies and/or cell structures can be used in accordance with embodiments. Further, one skilled in the art will recognize that other device circuit arrangements, architectures, elements, and the like, may also be used in accordance with embodiments. Further, the resistance levels, operating conditions, and the like, may be dependent on the retention, endurance, switching speed, and variation requirements of a programmable impedance element. The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents. | 26,619 |
11862750 | Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention. The optoelectronic device components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT According to one aspect, the invention resides in an optoelectronic device comprising a semiconductor structure. In preferred embodiments, the semiconductor structure is constructed by growth, for example, epitaxial layer growth, along a predetermined growth direction. The semiconductor structure is comprised solely of one or more superlattices. For example, where the semiconductor structure comprises more than one superlattice, the superlattices are formed atop one another in a contiguous stack. In preferred embodiments, the one or more superlattices are short period superlattices. Each of the one or more superlattices is comprised of a plurality of unit cells, and each of the plurality of unit cells comprises at least two distinct substantially single crystal layers. In preferred embodiments, one or more of the at least two distinct substantially single crystal layers are distinct single crystal semiconductor layers, and more preferably all of the at least two distinct substantially single crystal layers are distinct single crystal semiconductor layers. However, in some embodiments, one or more of the at least two distinct substantially single crystal layers are metal layers. For example, the metal layers can be formed of aluminium (Al). The semiconductor structure includes a p-type active region and an n-type active region. The p-type active region of the semiconductor structure provides p-type conductivity and an n-type active region provides n-type conductivity. In preferred embodiments, the semiconductor structure includes an i-type active region between the n-type active region and the p-type active region to form a p-i-n device. In some embodiments, each region of the semiconductor structure is a separate superlattice. However, in some alternative embodiments, the n-type active region, the p-type active region and/or the i-type active region are regions of a single superlattice. In other alternative embodiments, the active region, the p-type active region and/or the i-type active region each comprise one or more superlattices. In preferred embodiments, the optoelectronic device is a light emitting diode or a laser and/or emits ultra violet light, preferably, in the wavelength range of 150 nm to 280 nm, and more preferably in the wavelength range of 210 nm to 240 nm. However, in alternative embodiments, the optoelectronic device emits ultra violet light, preferably, in the wavelength range of 240 nm to 300 nm, and more preferably in the wavelength range of 260 nm to 290 nm. When the optoelectronic device is configured as a light emitting device, the optical energy is generated by recombination of electrically active holes and electrons supplied by the p-type active region and the n-type active region. The recombination of holes and electrons occurs in a region substantially between the p-type active region and the n-type active region, for example, in the i-type active region or around an interface of the p-type active region and n-type active region when an i-type active region is omitted. Each layer in each unit cell in the one or more superlattices has a thickness that can be selected to control electronic and optical properties of the optoelectronic device by controlling quantized energy states and spatial wavefunctions for electrons and holes in the electronic band structure of the superlattice. From this selection a desired electronic and optical energy can be achieved. In preferred embodiments, an average thickness in the growth direction of each of the plurality of unit cells is constant within at least one of the one or more superlattices. In some embodiments, the unit cells in two or more of the n-type active region, the p-type active region and the i-type active region have a different average thickness. In some embodiments, one of the at least two layers of each of the plurality of unit cells within at least a portion of the one or more superlattices comprises 1 to 10 monolayers of atoms along the growth direction and the other one or more layers in each of the respective unit cells comprise a total of 1 to 10 monolayers of atoms along the growth direction. In some embodiments, all or a majority of the distinct substantially single crystal layers of each unit cell within each superlattice have a thickness of 1 monolayer to 10 monolayers of atoms along a growth direction. In some embodiments, at least two layers in each of the plurality of unit cells each have a thickness of less than or equal to 6 monolayers of a material of which the respective layer is composed along the growth direction. In some embodiments, the thickness of each unit cell is chosen based on the composition of the unit cell. An average alloy content of each of the plurality of unit cells can be constant or non-constant along the growth direction within at least one of the one or more superlattices. Maintaining a constant average alloy content enables lattice matching of the effective in-plane lattice constant of the unit cells of dissimilar superlattices. In preferred embodiments, throughout the semiconductor structure, unit cells that are adjacent one another have substantially the same average alloy content. In some embodiments, the average alloy content of each of the plurality of unit cells is constant in a substantial portion of the semiconductor structure. In some embodiments, the average alloy content of each of the plurality of unit cells varies periodically and/or aperiodically along the growth direction within a portion of at least one of the one or more superlattices. In some embodiments, the average alloy content of each of the plurality of unit cells varies periodically and aperiodically along the epitaxial growth direction in distinct regions of at least one of the one or more superlattices. In preferred embodiments, the at least two distinct substantially single crystal layers of each unit cell have a wurtzite crystal symmetry and have a crystal polarity in the growth direction that is either a metal-polar polarity or nitrogen-polar polarity. In some embodiments, the crystal polarity is spatially varied along the growth direction, the crystal polarity being alternately flipped between the nitrogen-polar polarity and the metal-polar polarity. Preferably, each of the at least two distinct substantially single crystal layers of each unit cell in each superlattice comprises at least one of the following compositions: a binary composition single crystal semiconductor material (AxNy), where 0<x≤1 and 0<y≤1; a ternary composition single crystal semiconductor material (AuB1-uNy), where 0≤u≤1 and 0<y≤1; a quaternary composition single crystal semiconductor material (ApBqC1-p-qNy), where 0≤p≤1, 0≤q≤1 and 0<y≤1. Here A, B and C are distinct metal atoms selected from group II and/or group III elements and N are cations selected from at least one of a nitrogen, oxygen, arsenic, phosphorus, antimony, and fluorine. More preferably, each of the at least two distinct substantially single crystal layers of each unit cell in each superlattice comprises at least one of the following compositions: a group III metal nitride material (MxNy); a group III metal arsenide material (MxAsy); a group III metal phosphide material (MxPy); a group III metal antimonide material (MxSby); a group II metal oxide material (MxOy); a group II metal fluoride material (MxFy). Here 0<x≤3 and 0<y≤4, and where M is a metal. In some embodiments, the metal M is selected from one or more group II, group III or group IV elements. For example, each of the at least two distinct substantially single crystal layers of each unit cell in each superlattice comprises at least one of the following compositions: aluminium nitride (AlN); aluminium gallium nitride (AlxGa1-xN) where 0≤x<1; aluminium indium nitride (AlxIn1-xN) where 0≤x<1; aluminium gallium indium nitride (AlxGayIn1-x-yN) where 0≤x<1, 0≤y≤1 and 0<(x+y)<1. In some embodiments, one of the at least two distinct substantially single crystal layers comprises a narrower band gap material and another of the at least two distinct substantially single crystal layers comprises a wider bandgap material. In some embodiments, one or more of the at least two distinct substantially single crystal layers of each unit cell is formed of a metal. For example, each unit cell can comprise an aluminium (Al) layer and an aluminium nitride (AlN) layer. In some embodiments, one or more layers of each unit cell of the one or more superlattices is not intentionally doped with an impurity species, for example, in the n-type active region, the p-type active region and/or the i-type active region. Alternatively or additionally, one or more layers of each unit cell of the one or more superlattices of the n-type active region and/or the p-type active region is intentionally doped with one or more impurity species or formed with one or more impurity species. For example, the one or more impurity species in the n-type active region are selected from: silicon (Si); germanium (Ge); silicon-germanium (SixGe1-x), where 0<x<1; crystalline silicon-nitride (SixNy), where 0<x<3 and 0<y<4; crystalline germanium-nitride (GexNy), where 0<x<3 and 0<y<4; crystalline silicon-aluminium-gallium-nitride (Siu[AlxGa1-y]zNv) where u>0, x>0, 0<y<1 and v>0; or crystalline germanium-aluminium-gallium-nitride (Geu[AlxGa1-y]zNv) where u>0, x>0, 0<y<1 and v>0. For example, the one or more impurity species in the p-type active region are selected from: magnesium (Mg); zinc (Zn); magnesium-zinc (MgxZn1-x), where 0≤x≤1; crystalline magnesium-nitride (MgxNy), where 0<x≤3 and 0<y≤2; or magnesium-aluminium-gallium-nitride (Mgu[AlxGa1-y]zNv), where u>0, x>0, 0<y<1 and v>0. The one or more impurity species in the n-type active region or the p-type active region can also be selected from: hydrogen (H); oxygen (O); carbon (C); or fluorine (F). At least a portion of the at least one of the one or more superlattices can include a uniaxial strain, a biaxial strain or a triaxial strain to modify a level of activated impurity doping. That is, by the action of crystal deformation in at least one crystal direction, the induced strain can deform advantageously the energy band structure of the materials in the layers of the one or more superlattices. The resulting energy shift of the conduction or valence band edges can then be used to reduce the activation energy of a given impurity dopant relative to the superlattice. For example, a group III nitride material such as p-type Mg-doped GaN with a wurtzite lattice structure can be subjected to an elastic tensile strain substantially parallel to the c-plane and perpendicular to the growth direction. The resulting shift in energy of the valence band edges results in a reduced energy separation between the said valence band edge and the Mg impurity level. This energy separation is known as the activation energy for holes and is temperature dependent. Therefore, reducing the activation energy of a specific carrier due to an impurity dopant via the application of a strain dramatically improves the activated carrier density of the doped material. This built-in strain can be selected during an epitaxial material formation step during the formation of the superlattice. For example, a GaN epilayer can be formed to include a tensile in-plane strain if deposited directly upon a single crystal AlN layer. If, for example, in the p-type active region, the AlN and Mg doped GaN layers are each limited in thickness to 1 to 7 monolayers, then they will both elastically deform without the creation of deleterious crystal defects, such as interfacial dislocations. Here the AlN layer will undergo an in-plane compressive stress, whereas the Mg-doped GaN layer will undergo in-plane tensile stress. Therefore, strain can enhance the activation energy of one or more of the intentionally doped regions that contain the impurity species. This improves an electron or hole carrier concentration in the one or more of the intentionally doped regions. FIG.1is a diagram showing a sectional view of a stack100for an optoelectronic device according to some embodiments of the present invention. In one embodiment, the optoelectronic device is a Light Emitting Diode (LED). However, it should be appreciated that the present invention may also be adapted to fabricate superluminescent LEDs and lasing devices with the positioning of suitable reflective layers or mirrors in the optoelectronic device. The stack100comprises a crystalline substrate110. A buffer region112is grown first on the substrate110followed by a semiconductor structure114. The buffer region112and the semiconductor structure114are formed or grown in a growth direction indicated by arrow101. The buffer region112includes a buffer layer120and one or more superlattices130. In preferred embodiments, the buffer region acts as a strain control mechanism providing a predetermined in-plane lattice constant. The semiconductor structure114comprises, in growth order, an n-type active region140, an i-type active region150and a p-type active region160. A p-type contact layer170is optionally formed on the p-type active region160. A first contact layer180is formed on the p-type contact layer170or the p-type active region160if the p-type contact layer is not present. In preferred embodiments, at least one region of the semiconductor structure is substantially transparent to an optical energy emitted by the optoelectronic device. For example, the p-type active region and/or the n-type active region are transparent to the emitted optical energy. In preferred embodiments, the substrate110has a thickness of between 300 μm and 1,000 μm. The thickness of the substrate110can be chosen based on a diameter of the substrate110. For example, a substrate having a diameter of two inches (25.4 mm) and made of c-plane sapphire may have a thickness of about 400 μm and a substrate having a diameter of six inches may have a thickness of about 1 mm. The substrate110can be a native substrate made of a native material that is native to the n-type active region or a non-native substrate made from a non-native material that is non-native to the n-type active region. For example, if the n-type active region comprises one or more group III metal nitride materials, the substrate110can be made of a similar group III metal nitride material, such as AlN or GaN, or from a non-native material, such as Al2O3or Si(111). However, a person skilled in the art will realise that the substrate110may be made from many other materials which are compatible with a layer formed above the substrate110. For example, the substrate can be made of a crystalline metal oxide material, such as magnesium oxide (MgO) or zinc-oxide (ZnO), silicon-carbide (SiC), Calcium Fluoride (CaF2), a crystalline thin film semiconductor on amorphous glass, or a crystalline thin film semiconductor on a metal. The buffer region112functions as a transition region between the substrate110and semiconductor structure114. For example, the buffer region112provides a better match in lattice structure between the substrate110and the semiconductor structure114. For example, the buffer region112may comprise a bulk like buffer layer followed by at least one superlattice designed to achieve a desired in-plane lattice constant suitable for depositing the one or more superlattices of the semiconductor structure of the device. In preferred embodiments, the buffer layer120in the buffer region112has a thickness of between 50 nm and several micrometres, and preferably, between 100 nm and 500 nm. The buffer layer120can be made from any material that is suitable for matching the lattice structure of the substrate110to the lattice structure of a lowest layer of the one or more superlattices. For example, if the lowest layer of the one or more superlattices is made of a group III metal nitride material, such as AlN, the buffer layer120can be made of AlN. In alternative embodiments, the buffer layer120can be omitted. The one or more superlattices130in the buffer region112and the one or more superlattices in the semiconductor structure114can be considered to comprise a plurality of unit cells. For example, the unit cells132in the buffer region112, the unit cells142in the n-type active region140, the unit cells152in the i-type active region150, and the unit cells162of the p-type active region160. Each of the plurality of unit cells comprises two distinct substantially single crystal layers. A first layer in each unit cell is labelled “A” and a second layer in each unit cell is labelled “B”. In different regions of the semiconductor structure, the first layer and/or the second layer in each unit cell can have the same or a different composition, and/or the same or a different thickness. For example,FIG.1shows the first layers and the second layers having a greater thickness in the i-type active region150than in the n-type active region140and the p-type active region160. The n-type active region140provides n-type conductivity. In preferred embodiments, one or both of the first layer142A and the second layer142B in each unit cell142in the n-type active region140is doped with, or formed of, a dopant material, such as the materials described above. In some embodiments, the dopant material is different in the first layer and the second layer of each unit cell. The i-type active region150is the main active region of the optoelectronic device. In preferred embodiments, the i-type active region is designed to optimize the spatial electron and hole recombination to a selected emission energy or wavelength. In preferred embodiments, the first layer152A and the second layer152B in each unit cell152of the i-type active region150have a thickness that is adjusted to control the quantum mechanical allowed energies within the unit cell or the i-type active region150. As the thickness of each layer of the unit cells is 1 to 10 monolayers in some embodiments, a quantum description and treatment of the superlattice structure is necessary to determine the electronic and optical configuration. If group III metal nitride materials having a wurtzite crystal symmetry and further having a polar nature are used to form the layers, there are many internal electric fields across each heterojunction of the unit cell and the one or more superlattices. These built in electric fields form due to spontaneous and piezoelectric charges that occur at each heterojunction. The complex spatial band structure along the growth direction creates a non-trivial potential variation in the conduction and valence bands which is modulated by the spatial variation in composition between the layers of the unit cells. This spatial variation is of the order of the deBroglie wavelength of the respective carriers within the conduction and valence bands, and thus requires a quantum treatment of the resulting confined energy levels and spatial probability distribution (defined herein as the carrier wavefunction) within the one or more superlattices. Furthermore, a crystal polarity of the semiconductor structure is preferably selected from either a metal-polar or a nitrogen-polar growth along the growth direction101, for example, for one or more superlattices formed of group III metal nitride materials. Depending on the crystal polarity of the semiconductor structure, at least a portion of the i-type active region150can be further selected to optimize the optical emission. For example, a metal-polar oriented growth along the growth direction101, can be used to form a superlattice in the i-type active region of an n-i-p stack comprising alternating layers of GaN and AlN. As the n-type active region in an n-i-p stack is formed closest to the substrate, the i-type active region will have a linearly increasing depletion field across it spanning the distance between the n-type active region and the p-type active region (for example, seeFIGS.9,15and21). The i-type active region superlattice will then be subjected to yet a further electric field due to the built-in depletion field of the n-i-p stack. Alternatively, the built-in depletion field across the i-type active region can be generated in other configurations. For example, the stack can be a p-i-n stack with the p-type active region160closest to the substrate and/or grown using nitrogen-polar crystal growth orientation along101. The said depletion field across the depletion region of a p-n stack or the i-type active region150of a p-i-n stack can also partially set an optical emission energy and emission wavelength of the optoelectronic device. In preferred embodiments, one or both of the first layer152A and the second layer152B in each unit cell in the i-type active region is un-doped or not intentionally doped. In some embodiments, the i-type active region150has a thickness of less than or equal to 100 nm and a thickness of greater than or equal to 1 nm. The i-type active region has a lateral width selected from the range of 1 nm to approximately 10 μm. The total width of the i-type active region150can be selected to further tune the depletion field strength across the i-type active region150between the p-type active region160and the n-type active region140. Depending upon the crystal growth polarity, the width and the effective electron and hole carrier concentrations of the n-type active region140and the p-type active region160, the depletion field strength will provide either a blue-shift or a red-shift in the emission energy or wavelength of the light emitted from the i-type active region. The p-type active region160provides p-type conductivity. In preferred embodiments, one or both of the first layer162A and the second layer162B in each unit cell162in the p-type active region is doped with, or formed of, a dopant material, such as the materials described above. In preferred embodiments, the first layer and the second layer of each of the plurality of unit cells in each of the one or more superlattices in the semiconductor structure are composed of group III metal nitride materials. For example, the first layers can be composed of aluminium nitride (AlN), and the second layers can be composed of gallium nitride (GaN). However, it should be appreciated that the first and second layers in each of the one or more superlattices can be composed of any of the materials specified above. In preferred embodiments, the average alloy content, for example Al and/or Ga where the first layers consist essentially of AlN and the second layers consist essentially of GaN, of the one or more superlattices is constant. In alterative embodiments, the average alloy content of one or more of the one or more superlattices is non-constant. In some embodiments, the average alloy content of the unit cells is the same in all superlattices of the semiconductor structure114and/or stack100, but the period is changed between superlattices and/or within superlattices. Maintaining a constant average alloy content enables lattice matching of dissimilar superlattices. Such lattice matched growth of each unit cell enables large numbers of periods to be formed without an accumulation of strain. For example, using a specific period of the superlattice for an n-type active region140would make the n-type active region140more transparent to a wavelength of the emitted light. In another example, using a different period for the i-type active region150, would cause the light to be emitted vertically i.e. in a same plane as the growth direction101. In another embodiment, the one or more superlattices have constant average alloy content and an optical emission that is substantially perpendicular to the plane of the superlattice layers. For example, a vertically emitting device is formed by using superlattices with layers of AlN and AlGaN with the Al percentage of the AlGaN layers less than 60%. In yet another preferred embodiment, a plurality of or all of the one or more the superlattices are constructed from unit cells comprising AlN and GaN thereby enabling an improved growth process that is optimized at a single growth temperature for only two materials. Doping may be incorporated into the n-type active region and/or p-type active region of the one or more superlattices in several ways. In some embodiments, doping is introduced into just one of the first layer and the second layer in each unit cell. For example, Si can be introduced into GaN in the second layer of the unit cell to create an n-type material or Mg can be introduced into GaN in the second layer of the unit cell to create a p-type material. In alternative embodiments, doping can be introduced into more than one layer/material in each unit cell and the dopant material can be different in each layer of the unit cell. In some embodiments, the one or more superlattices include a uniaxial strain or a biaxial strain to modify a level of activated doping. In preferred embodiments, the one or more superlattices of the semiconductor structure comprise a wurtzite lattice structure, preferably grown along the c-axis (0001). Where the one or more superlattices have a wurtzite lattice structure, a monolayer is defined as half a thickness of the “c” dimension of the hexagonal unit cell of the lattice. In some embodiments, the one or more superlattices of the semiconductor structure comprise a zinc-blend lattice structure, preferably grown along (001)-axis. Where the one or more superlattices have a zinc-blend lattice structure, one monolayer is defined as half a thickness of the “a” dimension of the cubic unit cell of the lattice. While a single superlattice is shown inFIG.1for each region of the semiconductor structure, it should be appreciated that each region may include more than one superlattice stacked atop one another. For example, the n-type active layer140can include a first superlattice wherein respective layers in each unit cell have a first material composition and a second superlattice grown on the first super lattice wherein the respective layers in each unit cell have a second material composition. In some embodiments, the stack100can comprise a single superlattice comprising one or more of the buffer region130, the n-type active region140, the i-type active region150and the p-type active region160. In some embodiments, at least one of the one or more superlattices is periodic, meaning that each unit cell of the respective superlattice has the same structure. For example, each unit cell of the respective superlattice has the same number of layers, the same layer thicknesses and the same material compositions in respective layers. In some embodiments, at least one of the one or more superlattices is aperiodic meaning that one of more of the unit cells have a different structure. The differences can be in materials chosen for each of the layers, the thicknesses of the layers, the number of layers in each unit cell, or a combination thereof. Each of the superlattices may have a different structure to achieve different electronic and optical properties. Thus, one superlattice could be periodic, while the others could be aperiodic. In addition, all of the superlattices in a stack100can be periodic, or all of the superlattices can be aperiodic. In yet another embodiment, one or more superlattices can be periodic, while one or more superlattices are aperiodic. For example, a superlattice in the buffer region130can be aperiodic to assist in lattice matching. The p-type contact layer170also known as a hole injection layer is formed on top of the p-type active region of the one or more superlattices. A first contact layer180is formed on the p-type contact layer170, such that the p-type contact layer170is formed between the first contact layer180and the p-type active region160. In preferred embodiments, the first contact layer180is a metal contact layer. The p-type contact layer170aids an electrical ohmic contact between the p-type active region160and the first contact layer180. In preferred embodiments, the p-type contact layer170is made from p-type GaN and has a thickness of between 5 nm and 200 nm, and preferably, between 10 nm and 25 nm. The thickness of the p-type contact layer170can be optimized to reduce the optical absorption at a specific optical wavelength and/or to make the p-type contact layer170optically reflective to an emission wavelength of the stack100. The first contact layer180enables the stack100to be connected to a positive terminal of a voltage source. In preferred embodiments, the first contact layer180has a thickness of between 10 nm and several 1000 nm, and preferably, between 50 nm and 500 nm. A second contact layer (not shown) is formed on the n-type active region140to connect to a negative terminal of a voltage source. In preferred embodiments, the second contact layer has a thickness of between 10 nm and several 1000 nm, and preferably, between 50 nm and 500 nm. The first contact layer180and the second contact layer may be made from any suitable metal. In preferred embodiments, the first contact layer180is made from a high work function metal to aid in the formation of a low ohmic contact between the p-type active region160and the first contact layer180. If the work function of the first contact layer180is sufficiently high, then the optional p-type contact layer170may not be required. For example, if the substrate is transparent and insulating, the light emitted by the semiconductor structure is directed substantially out through the substrate and the p-type active region160is disposed further from the substrate than the n-type active region140, then the first contact layer180should ideally have the property of high optical reflectance at the operating wavelength, so as to retroreflect a portion of the emitted light back through the substrate. For example, the first contact layer180can be made from metals selected from Aluminium (Al), Nickel (Ni), Osmium (Os), Platinum (Pt), Palladium (Pd), Iridium (Jr), and Tungsten (W). Especially, for deep ultraviolet (DUV) operation in which the stack100emits DUV light, the first contact layer180may not in general fulfil the dual specification of low p-type ohmic contact and high optical reflectance. High work function p-type contact metals for group III metal nitrides are generally poor DUV wavelength reflectors. Platinum (Pt), Iridium (Ir), Palladium (Pd) and Osmium (Os) are an ideal high work function p-type contact metals to high Al % group III metal nitride compositions and superlattices. In preference, Osmium is a superior low ohmic contact metal to p-type regions comprising group III metal nitrides. However, for ultraviolet and DUV operation of the stack100, aluminium is the most preferred of all metals, as it has the highest optical reflectance over a large wavelength range spanning from 150 to 500 nm. In general, metals are preferred as DUV optical reflectors due to the low penetration depth and low loss of light into the metal. This enables optical microcavity structures to be formed. Conversely, relatively low work function metals, such as Aluminium (Al), Titanium (Ti) and Titanium Nitride (TiN) can be utilized to form low ohmic metal contacts to n-type group III metal nitride compositions and superlattices. It should be appreciated that the stack100shown inFIG.1is an exemplary stack for an optoelectronic device, and that the stack100may be made in many other ways. For example, the n-type active layer140and the p-type active layer160may be reversed such that the p-type layer160is grown first. However, a reason for growing the n-type active layer140first is that it is generally less challenging to grow a low defect density n-type superlattice using group III metal nitride compositions on a substrate or buffer layer than a p-type superlattice. It should also be noted that the buffer layer120and/or the buffer region130are optional layers, and the one or more superlattices can be grown directly on the substrate110. However it is generally easier to grow the one or more superlattices on the buffer layer120and/or buffer region130, as the surfaces of such layers/regions are generally oriented in the c-plane of the crystal. In some embodiments, the buffer region and the adjacent p-type or n-type active region are part of the same superlattice with the only difference between the buffer region and the p-type or n-type active region being the incorporation of an impurity dopant in the p-type or n-type active region. In some embodiments, a first superlattice is grown upon the substrate with a sufficient thickness to render the superlattice in a substantially relaxed or free standing state with a low defect density and a preselected in-plane lattice constant. In another embodiment, the stack100may be fabricated without an i-type active layer150such that the stack forms a p-n junction rather than the p-i-n junction ofFIG.1. Furthermore, it should be appreciated that p-type contact layer170is optional, and the first contact layer180may be grown directly on the p-type active region160of the one or more superlattices. However, it is more difficult to fabricate the first contact layer180directly on the p-type active region160using conventional ex-situ fabrication techniques. For example a thin but heavily doped p-type contact layer170enables easier and more consistent post epitaxial process for metallization to achieve an ohmic contact. However, an in-situ metallization process directly onto a final epitaxial surface of the p-type active region160that is free of contamination provides an alternate means for formation of the first contact layer180. In preferred embodiments, the one or more superlattices are grown sequentially during at least one deposition cycle. That is dopants are introduced during epitaxy via a process of co-deposition. An alternative method is to physically grow at least a portion of the one or more superlattices without a dopant and then, post-growth, introduce the desired dopant. For example, experiments have found that n-type group III metal nitride materials are typically superior in crystal structure quality to p-type group III metal nitride materials. Therefore, in some embodiments, p-type materials are deposited as the final sequence of the fabrication of the stack. A post growth method for incorporating dopant introduced from a surface can then be used. For example, ion-implantation, and diffusion (e.g., via a spin-on dopant) followed by activation thermal anneals. The semiconductor structure114can be grown with a polar, non-polar or semi-polar crystal polarity oriented along the growth direction101. For example, a wurtzite lattice structure can be grown which is oriented with the hexagonal symmetry of the c-plane being substantially perpendicular to the growth direction. The plane of so formed unit cell layers are then said to be oriented upon a c-plane. Ionic wurtzite crystals such as the group III metal nitrides, further form polar crystals (that is, crystals that lack a centre of inversion symmetry). These polar crystals can be metal-polar or nitrogen polar along a crystal direction perpendicular to the c-plane. Other growth plane orientations can also be achieved resulting in semi-polar and even non-polar crystal growth along the growth direction101. A semiconductor structure formed of group III metal nitrides in a non-polar orientation can be via growth of a cubic and/or zinc-blend lattice structure. However, when the semiconductor structure is formed with such lattice structures it is typically less stable than when the semiconductor structure is formed with a wurtzite lattice structure. For example, group III metal nitrides can be grown with a semi-polar crystal polarity on an r-plane sapphire substrate, resulting in one or more a-plane oriented superlattices. Reducing the crystal polarity from a polar to a semi-polar crystal along a growth direction is advantageous for the reduction of the spontaneous and piezoelectric charges that are created at each and every heterojunction. While such semi-polar and non-polar crystal polarities have some advantages, it is found that the highest crystalline quality superlattices are formed using wurtzite crystal structures having a single crystal polarity oriented along a growth direction. The internal polarization charges can be managed advantageously by keeping the effective alloy content constant in each unit cell of the one or more superlattices. Once the average alloy content in any one unit cell or superlattice varies from another, a net polarization charge is accumulated. This can be used advantageously to control the band edge energy position in the one or more superlattices relative to the Fermi energy. For example, a wurtzite lattice can have charge polarization at the interface between layers of the unit cells when the first layers and second layers are composed of GaN and AlN respectively. By using one or more superlattices for the n-type active region, the i-type active region and the p-type active region, varying the period to tune the optoelectronic device and keeping an average Al content in each unit cell constant, the charge polarisation at the interfaces in the optoelectronic stack100can be reduced. In a further embodiment, a single superlattice structure is used for n-type active region140, the i-type active region150, and the p-type active region160and the superlattice is strained via biaxial and or uniaxial stresses to further affect the desired optical and/or electronic tuning. In some embodiments, the n-type active region140comprises a total thickness from 50 to 5000 nm, or from 200 to 1000 nm, or from 300 to 500 nm, and a total number of unit cells142from 10 to 5000, or from 100 to 500, or from 150 to 350. The unit cells142contain two distinct substantially single crystal layers142A and142B, one of which can be a barrier (e.g., AlN) and one of which can be a well (e.g., GaN). The barriers (e.g., AlN) in the unit cells142can be from 1 to 20 monolayer (ML), or from 2 to 12 ML, or from 4 to 8 ML thick. The wells (e.g., GaN) in the unit cells142can be from 1 to 10 ML, or from 0.1 to 3 ML, or from 0.2 to 1.5 ML thick. In some embodiments, the i-type active region150comprises a total thickness from 10 to 2000 nm, or from 10 to 100 nm, or from 40 to 60 nm, and a total number of unit cells152from 1 to 5000, or from 25 to 400, or from 10 to 100, or from 20 to 30. The unit cells152contain two distinct substantially single crystal layers152A and152B, one of which can be a barrier (e.g., AlN) and one of which can be a well (e.g., GaN). The barriers (e.g., AlN) in the unit cells152can be from 1 to 20 ML, or from 2 to 20 ML, or from 5 to 10 ML thick. The wells (e.g., GaN) in the unit cells152can be from 1 to 10 ML, or from 0.1 to 2 ML, or from 0.2 to 1.5 ML thick. In some embodiments, the p-type active region160comprises a superlattice with an approximately constant average composition, and comprises a total thickness from 20 to 5000 nm, or from 10 to 100 nm, or from 30 to 50 nm, and a total number of unit cells162from 1 to 5000, or from 1 to 100, or from 1 to 10. The unit cells162can contain two distinct substantially single crystal layers162A and162B, one of which can be a barrier (e.g., AlN) and one of which can be a well (e.g., GaN). The barriers (e.g., AlN) in the unit cells162can be from 0 to 20 ML, or from 1 to 20 ML, or from 0 to 12 monolayers (ML), or from 4 to 8 ML thick. The wells (e.g., GaN) in the unit cells162can be from 1 to 10 ML, or from 0.5 to 6 ML, or from 0.2 to 1.5 ML thick. In some cases, the unit cells162can contain only one distinct substantially single crystal layer, which is a well (e.g., GaN), and can be from 100 to 300 ML, or from 100 to 200 ML thick. In some embodiments, the p-type active region160comprises a superlattice with an average composition that changes through the thickness of the superlattice, and the p-type active region160comprises a total thickness from 10 to 100 nm, or from 10 to 30 nm, and a total number of unit cells162from 1 to 50, or from 1 to 20, or from 5 to 15. The unit cells162contain two distinct substantially single crystal layers162A and162B, one of which can be a barrier (e.g., AlN) and one of which can be a well (e.g., GaN). In the embodiments where the average composition changes through the thickness of the superlattice, the starting and ending thickness of the barriers and/or the wells in unit cells162can be different. In such cases, the starting thickness of the barriers (e.g., AlN) in the unit cells162can be from 2 to 8 monolayers (ML), or from 3 to 5 ML thick; the starting thickness of the wells (e.g., GaN) in the unit cells162can be from 0.0 to 2 ML, or from 0.2 to 0.3 ML thick; the ending thickness of the barriers (e.g., AlN) in the unit cells162can be from 0 to 8 monolayers (ML), or from 3 to 5 ML thick; and the ending thickness of the wells (e.g., GaN) in the unit cells162can be from 4 to 20 ML, or from 5 to 10 ML thick. Some of the preceding ranges contain layers with thicknesses of 0 ML. These cases describe situations where the starting and/or ending thickness of the barriers and/or wells is 0 ML, meaning that the unit cell at the start or the end of the superlattice contains only one layer, either a barrier or a well. FIG.2is a diagram showing a sectional view of a stack200for an optoelectronic device according to a second embodiment of the present invention. The stack200is similar to the stack100ofFIG.1except that the buffer region112does not comprise the one or more superlattices130. FIG.3is a diagram showing a sectional view of an optoelectronic device300according to a third embodiment of the present invention. Similar to the stacks100and200ofFIGS.1and2, the optoelectronic device300comprises a substrate110on which a buffer layer120and a semiconductor structure114are formed. The semiconductor structure114comprises, in growth order, an n-type active region140, an i-type active region150and a p-type active region160. A p-type contact layer170is formed on the p-type active region160and a first contact layer180is formed on the p-type contact layer170. In the embodiment shown inFIG.3, the i-type active region150, the p-type active region160, p-type contact layer170and the first contact layer180form a mesa on the n-type active region140. The mesa shown inFIG.3has straight sidewalls. However, in alternative embodiments, the mesa can have angled side walls. The device300further comprises a second contact layer382formed on the n-type active region140. In preferred embodiments, the second contact layer382forms a ring or loop around the mesa. The second contact layer382enables a negative terminal of a voltage source to be connected to the n-type active region140. The device300further comprises a passivation layer390that covers the exposed or physically etched layers of the one or more superlattices. The passivation layer390is preferably made of a material having a wider band gap than the exposed or physically etched layers that it covers. The passivation layer390reduces current leakage between the layers of the one or more superlattices. The device300can be operated as a vertically emissive device or a waveguide device. For example, in some embodiments, the optoelectronic device300can behave as a vertically emissive device with light out coupled from the interior of an electron-hole recombination region of the i-type active region150through the n-type active region140and the substrate110. In preferred embodiments, light propagating upwards (in the growth direction) in the optoelectronic device300is also retroreflected, for example, from the first contact layer180. FIG.4is a diagram showing a sectional view of an optoelectronic device400according to a fourth embodiment of the present invention. The optoelectronic device400is similar to the optoelectronic device300ofFIG.3. However, the optoelectronic device comprises a first lateral contact486and a second lateral contact484. The first lateral contact486extends partially into the p-type active region160from the first contact layer180. In preferred embodiments, the first lateral contact486is an annular shaped protrusion extending from the first contact layer180into in the p-type active region160and (where applicable) the p-type contact layer170. In some embodiments, the first lateral contact486is made from the same material as the first contact layer180. The second lateral contact484extends partially into the n-type active region140from the second contact layer482formed on a surface of the n-type active region140. In preferred embodiments, the second lateral contact484is an annular shaped protrusion extending into in the n-type active region140from the second contact layer382. In some embodiments, the second lateral contact484is made from the same material as the second contact layer382to improve electrical conduction between the n-type active region140and the second contact layer382. In preferred embodiments, the first lateral contact486and the second lateral contact484contact a plurality of narrower bandgap layers of the one or more superlattices in the semiconductor structure114, and therefore couple efficiently for both vertical transport of charge carriers perpendicular to the plane of the layers and parallel transport of charge carriers parallel to the plane of the layers. In general, carrier transport in the plane of the layers achieves higher mobility than carrier transport perpendicular to the plane of the layers. However, efficient transport perpendicular to the plane of the layers is achieved by using thin wider bandgap layers to promote quantum mechanical tunnelling. For example, in a superlattice comprising alternating layers of AlN and GaN, it is found that electron tunnelling between adjacent allowed energy states in each GaN layer is enhanced when the interposing AlN layers have a thickness of less than or equal to 4 monolayers. Holes on the other hand, and in particular the heavy-holes, have a tendency to remain confined in their respective GaN layers and be effectively uncoupled by tunnelling through the AlN layers, which act as barriers, when the AlN layers have thicknesses of 2 monolayers or greater. In preferred embodiments, the first lateral contact486, and the second lateral contact484improve electrical conductivity between the first contact layer180and the p-type active region160, and between the second contact layer482and the n-type active region140, respectively, by making use of a superior in-plane carrier transport compared to a vertical transport across the layer band discontinuities of the superlattice. The second lateral contact484and the first lateral contact486can be formed using post growth patterning and production of 3D electrical impurity regions to discrete depths. FIG.5is a diagram showing a sectional view of an optoelectronic device500according to a fifth embodiment of the present invention. The optoelectronic device500is similar to the optoelectronic device400ofFIG.4, except that the optoelectronic device500does not include a p-type contact layer170and the first lateral contact486is surrounded by an enhancement layer588, such as a layer of p-type GaN, between the first lateral contact486and the p-type active region160. The enhancement layer588can improve an Ohmic connection between the p-type active region160and the first contact layer180. The enhancement layer588can be created by selective area regrowth upon a patterned surface of the p-type active region160. FIG.6is diagram showing a sectional view of an optoelectronic device600according to a sixth embodiment of the present invention. The optoelectronic device600is similar to the optoelectronic device500ofFIG.5. However, the first contact layer680is annular shaped and a reflector layer692is provided to improve the out coupling of the optical energy generated within the semiconductor structure. The reflector layer692is positioned atop the optoelectronic device600to substantially retroreflect emitted light from the interior of the optoelectronic device600. In preferred embodiments, the passivation layer390is also provided within the annulus formed by the first contact layer680, and the reflector692is formed atop of the passivation layer390. In alternative embodiments, the reflector692may be formed on top of the p-type active region160, or, if present, the p-type contact layer170. FIG.7is a diagram showing a perspective view of an optoelectronic device700according to a seventh embodiment of the present invention. The optoelectronic device700is similar to the optoelectronic device600ofFIG.6. However, the optoelectronic device700comprises a buffer region130and the passivation layer390is not shown. The first contact layer680and the reflector layer692are shown above the p-type active region160on the mesa. The second contact layer382is formed on the buffer region130as a ring around the mesa. FIG.8is a diagram showing a sectional view of an optoelectronic device800according to an eighth embodiment of the present invention. The optoelectronic device800is similar to the optoelectronic device600ofFIG.6. However, the optoelectronic device does not comprise the enhancement layer588. As shown inFIG.8, upon application of an external voltage and current source between the first contact layer680and the second contact layer382, holes802are injected into the p-type active region and combine, for example at point808, with electrons804generated in the n-type active region140. The injected electrons804and holes802recombine advantageously in the electron-hole recombination (EHR) region809that is substantially confined spatially within the i-type active region150. The EHR region809generates photons via electron-hole recombination with an energy and optical polarization of the photons dictated by the energy-momentum band structure of the one or more superlattices. As illustrated inFIG.8, the EHR emits photons806A,806B,806C,806D, in directions that can be classified as substantially in the plane of the layers or vertically parallel to the growth direction. Light can also propagate in other directions and can propagate in a non-trivial way within the structure. In general, light generated with a propagation vector that is substantially vertical and within an escape cone (determined by the angle of total internal reflection and thus the refractive index of the material) will be the major source of photons that can be out coupled vertically through the transparent substrate110. Photons806A are emitted in a generally vertical direction and in the same direction as the growth direction101shown inFIG.1. Photons806B are emitted in a generally vertical direction and in an opposite direction to the growth direction101. Photons806C,806D are emitted in a generally horizontal direction, parallel to the layers of the device, for example, parallel to the plane of the layers of the i-type active region150. In the embodiment shown inFIG.8, some of the photons806A are reflected off the optical reflector692and exit the light emitting device800through the substrate110. It should be appreciated that with the addition of suitable mirrors (not shown) or an advantageous optical cavity and refractive index discontinuity between the substrate and i-type active region the device may therefore be modified to produce a microcavity LED or laser or a superluminescent LED. Superluminescence is found to improve the extraction efficiency of light by limiting the number of optical modes available for the generated light to couple into. This effective optical phase space compression improves selectivity of the device for advantageous vertical emission. An optical cavity can be formed using the total optical thickness formed by the buffer layer120, the n-type active region140, the i-type active region150and the p-type active region160. If the optical cavity is formed between the reflector692and the substrate110and the thickness of the optical cavity along the growth direction is less than or equal to one wavelength of the emission wavelength, then the cavity is a microcavity. Such a microcavity possesses the properties necessary to create superluminescence and stable wavelength operation imposed by the optical cavity mode wavelength. In some embodiments of the present invention, an emission wavelength from the EHR region809is equal to the lowest order wavelength cavity mode of the microcavity and superluminescence is achieved. A second optical reflector can also be included within the buffer region112. For example, a reflector comprising a superlattice having unit cells comprising elemental Al and AlN layers termed herein a metal-dielectric superlattice. In some embodiments, a transparent region is provided adjacent to the buffer layer120and the substrate110, and the buffer layer120is transparent to optical energy emitted from the device. The optical energy is coupled externally through the transparent region, the buffer layer120and the substrate110. Photons806C,806D are emitted in a generally horizontal direction, parallel to the layers of the device, for example, parallel to the plane of the layers of the p-type active region160. In some embodiments, the optoelectronic device emits light having a substantially transverse magnetic optical polarization with respect to the growth direction. The optoelectronic device operates as an optical waveguide with light spatially generated and confined along a direction substantially parallel to the plane of the one or more layers of the unit cells of the one or more superlattices of the semiconductor structure. In some embodiments, the optoelectronic device emits light having a substantially transverse electric optical polarization with respect to the growth direction. The optoelectronic device operates as a vertically emitting cavity device with light spatially generated and confined along a direction substantially perpendicular to the plane of the one or more layers of the unit cells of the one or more superlattices of the semiconductor structure. The vertically emitting cavity device has a vertical cavity disposed substantially along the growth direction and formed using metallic reflectors spatially disposed along one or more portions of the semiconductor structure. The reflectors can be made from a high optical reflectance metal. The cavity is defined by the optical length between the reflectors being less than or equal to a wavelength of the light emitted by the device. The emission wavelength of the optoelectronic device is determined by the optical emission energy of the one or more superlattices comprising the semiconductor structure and optical cavity modes determined by the vertical cavity FIG.9is a graph900of spatial energy levels in the conduction band and the valence band with respect to a distance along the growth direction z for an optoelectronic device, according to an embodiment of the present invention. In this embodiment, a single superlattice comprises the n-type active region140, the i-type active region150and the p-type active region160of the optoelectronic device. Each unit cell of the superlattice comprises a first layer formed of two monolayers of AlN and a second layer formed of one monolayer of GaN. The superlattice comprises 25 unit cells in each of the n-type active region140, the i-type active region150and the p-type active region160. The superlattice is deposited on a c-plane with a metal-polar crystal growth oriented parallel to the growth direction. A p-type contact layer made of p-GaN is deposited on the p-type active region160. A first contact layer made of an idealized ohmic metal M is located on the p-GaN contact layer and a second contact layer made of an idealized ohmic metal M is located on the n-type active region140. The y-axis ofFIG.9is the energy level in eV relative to the Fermi energy, and the x-axis is the distance in nanometres (nm) along the growth direction101from the base of the substrate. The positions of the n-type active region140, the i-type active region150and the p-type active region160and other regions/layers of the device are shown above the x-axis. Trace910is the zone centre (i.e., k=0) energy in the conduction band; the troughs are due to GaN, and the peaks are due to AlN. Graph900shows in trace910that the conduction band energy Eck=0(z) is close to the Fermi energy in the n-type active region140with the troughs of the conduction band energy Eck=0(z) below the Fermi energy. This provides a highly activated n-type active region. Trace920is energy in the valence band; the troughs are due to AlN, and peaks are due to GaN. Graph900shows in trace920that the valence band energy EHHk=0(z) is close to the Fermi energy in the p-type active region160with the peaks of the valence band energy EHHk=0(z) above the Fermi energy. This provides a highly activated p-type active region. The metal polar oriented growth results in the pyroelectric and piezoelectric charges at each AlN/GaN and GaN/AlN heterojunction. A spatial wavefunction is a probability amplitude in quantum mechanics that describes the quantum state of a particle and how it behaves.FIG.10is a graph1000showing the quantized lowest energy electron spatial wavefunctions Ψcn=1(i,z) with respect to a distance z along the growth direction for the optoelectronic device described with reference toFIG.9. The index i represents the distinct wavefunctions. Each quantized wavefunction is plotted at the corresponding allowed quantized eigenenergy within the energy band structure. A non-zero wavefunction probability above the respective quantized energy level indicates a finite probability of localizing an electron in the associated spatial region. The conduction band edge energy Eck=0(z) is shown for reference. It is evident from graph1000that the electron wavefunctions are delocalized over a large number of unit cells. This is indicative of high coupled GaN potential wells. The thin AlN barriers (2 monolayers) allow efficient quantum mechanical tunnelling and thus form energy manifolds spatially confined within the n-type and p-type active regions. An electron injected into the n-type active region would be efficiently transported along the growth direction toward the i-type active region. The allowed lowest energy wavefunctions within the i-type active region are more confined than within the n-type or p-type active regions, as is evidenced by the more localized wavefunctions in the i-type active region. The small thickness of the unit cells forces the quantized energy levels to be relatively close to the AlN conduction band edge and thus under the influence of a large depletion electric field generated across the i-type active region breaks the coupling between adjacent neighbouring GaN potential minima. As a result the electron wavefunctions in the i-type active region are not strongly confined to their respective GaN potential minima. FIG.11is a graph1100showing the quantized lowest energy heavy hole spatial wavefunctions ΨHHn=1(j,z) with respect to a distance along the growth direction for the optoelectronic device described with reference toFIG.9. The heavy hole zone centre valence band energy EHHk=0(z) is shown for reference. The group III metal nitride materials have a unique valence band structure comprising an energy momentum dispersion that has three distinct bands, namely, the heavy-hole (HH), light-hole (LH) and crystal field split (CF) bands. At zone centre, the superlattice has the heavy-hole band which is the lowest energy of the three, that is, EHHk=0<ELHk=0<ECHk=0. For optical processes of interest herein it is sufficient to describe the HH band only. In the graph1100, it is evident that there is substantial spatial delocalization of heavy-hole wavefunctions ΨHHn=1(j,z) within the p-type active region, whereas they are tightly confined to the GaN potential minima within the i-type active region. Again the built-in depletion electric field within the device breaks the coupling within the i-type active region. FIG.12is a graph1200showing the spatial overlap integral of the conduction and HH wavefunctions. The overlap integral is essentially the product of the electron spatial wavefunctions Ψcn=1(i,z) ofFIG.10with each of the heavy hole spatial wavefunctions ΨHHn=1(j,z) ofFIG.11with respect to a distance along the growth direction for the optoelectronic device described with reference toFIG.9. It can be seen from graph1200that the probability that an electron and a hole are present at the same location is higher in the i-type active region150than the n-type active region140and the p-type active region160. Hence emission is more likely to occur from the i-type active region150than the n-type active region140and the p-type active region160of the optoelectronic device. FIG.13is a graph1300showing the overlap integral of the electron spatial wavefunctions Ψcn=1(i,z) and the heavy hole spatial wavefunctions ΨHHn=1(j,z) with respect to a combined transition energy between the corresponding electron and hole quantized energy levels for the optoelectronic device described with reference toFIG.9. The discrete plot ofFIG.13shows the energy spectrum of allowed optical transitions between the lowest n=1 quantized electron states and the n=1 HH states within the entire semiconductor structure. The graph1300therefore shows the device is capable of emitting with a lowest energy optical emission of about 5.3 eV. The width of the emission spectrum inFIG.13is indicative of the miniband widths of quantized energy levels throughout the device. FIG.14is a graph1400showing an emitted luminance versus wavelength for the optoelectronic device described with reference toFIG.9. The discrete overlap integrals ofFIG.13are homogeneously broadened in energy to simulate thermal variations anticipated at room temperature. The sum of individual oscillator strength contributions are plotted as a function of wavelength for two choices of broadening parameters. The longest wavelength and sharpest transition is attributed to the lowest energy heavy-hole exciton experimentally observable. As shown inFIG.14, the wavelength of maximum intensity is at approximately 230 nm corresponding to the lowest energy transition between the n=1 quantized electron and hole wavefunctions. Reference toFIG.12indicates that a substantial portion of the light generated will be from a region near the i-type active region and p-type active region interface. The shaded region ofFIG.14shows the spectral region populated by the p-type and n-type active regions which will have states occupied and thus not available for optical recombination process. Furthermore, the actual emission energy is due to the lowest order exciton annihilation. An exciton is an intermediate particle comprising a bound electron-hole pair that is spatially confined to enhance the electrostatic binding energy. The n=1 exciton binding energy (EXn=1) in an AlN/GaN superlattice is of the order of 50-60 meV and is due to the electrostatic attraction of the n=1 electron and n=1 HH wavefunctions. In general, the emission energy of a photon, emitted from the n=1 exciton Eγn=1, is given by Eγn=1=ECn=1−EHHn=1−EXn=1, where the exciton binding energy reduces the observed emission energy. FIG.15is a graph1500of spatial energy levels in the conduction band and the valence band with respect to a distance along the growth direction z for an optoelectronic device, according to another embodiment of the present invention. In this embodiment, superlattice forming the n-type active region140and the p-type active region160of the device are the same as for the optoelectronic device ofFIG.9. However, in the i-type active region150the first layer in each unit cell is formed of 4 monolayers of AlN and the second layer in each unit cell is formed of 2 monolayers of GaN. The p-type and n-type regions are formed using impurity doped superlattices with a first layer formed of 2 monolayers of AlN and a second layer formed of 1 monolayer of GaN. The doped regions are therefore transparent to the n=1 exciton formed in the intrinsic region. While the period or thickness of the unit cells changes between the n-type and p-type active regions and the i-type active region, the unit cells in each region have the same average alloy content. That is, the Al fraction in the unit cells is constant. There are 25 repetitions of the unit cell in each region. It is found that a higher number of unit cell repetitions can also be used. The average alloy content of a simple unit cell comprising two compositions, such as, a GaN layer of thickness tGaNand AlN layer of thickness tAlN, is given by xave=tAlN/(tAlN+tGaN), where the xaverepresents the effective Al fraction of the pair in the unit cell. In alternative embodiments, the unit cells can comprise three or more AlGaN compositions and in such embodiments the effective alloy content can be similarly determined. The average alloy content of other layer compositions comprising binary, ternary and quaternary materials can be defined according to one or more elemental constituents. For example, the Al fraction in a tri-layered unit cell comprising the triple layers of AlN/AlxGa-1xN/GaN or AlN/AlxGa1-xN/AlyInzGa1-y-zN can be determined. An optional p-type GaN Ohmic contact layer is included on the p-type active region. Ohmic metal contacts provided on the n-type active region and the optional p-type GaN Ohmic contact layer. The energy band structure is shown with zero external electrical bias applied between the Ohmic metal contacts. The y-axis ofFIG.15is the energy level in eV relative to the Fermi energy, and the x-axis is distance in nanometres (nm) along the growth direction from the base of the substrate. The positions of the n-type active region140, the i-type active region150and the p-type active region160of the device are shown above the x-axis. Trace1510is energy in the conduction band; the troughs are due to GaN, and the peaks are due to AlN. The AlN layer and GaN layer in the unit cells forms a type-I superlattice, wherein the GaN conduction band is lower in energy than the AlN conduction band edge and the GaN valence band is higher in energy than the AlN valence band edge. That is, the AlN layer presents a potential barrier for both electrons and holes in the GaN layer. Trace1520is energy in the valence band; the troughs are due to AlN, and peaks are due to GaN. In particular, the heavy-hole valence band edge is shown.FIG.15shows that the period and amplitude of the peaks and troughs in traces1510and1520has increased in the i-type active region150. The larger layer thicknesses of both the GaN and AlN layers in the unit cells in the i-type active region generates a larger built-in electric field across each due to the spontaneous and piezoelectric fields of the metal-polar heterointerfaces. This effect is particularly unique to polar wurtzite crystals. Again, the device ofFIG.15is contacted by ideal metal contacts M and a p-GaN contact layer connects the p-type active region160to one of the metal contacts. Flat band conditions are shown, that is, zero external applied bias between both contacts, and thus the Fermi energy is continuous throughout the structure along the growth direction. FIG.16is a graph1600showing the quantized lowest energy (nSL=1) electron spatial wavefunctions Ψcn=1(i,z) with respect to a distance z along the growth direction for the optoelectronic device described with reference toFIG.15. The conduction band edge energy Eck=0(z) is shown for reference. The electron wavefunctions are clearly spread out across a large number of adjacent and neighbouring unit cells due to the thin AlN tunnel barriers in both the n-type and p-type active region. The larger unit cell period of the i-type active region shows a pronounced localization of the electron wavefunctions to at most a nearest neighbour penetration. There are no leaky wavefunctions outside of the superlattice within the forbidden gap of the i-type active region as was observed in the structure ofFIG.10. Therefore, the electrons injected from the n-type active region would undergo efficient transport through the n-type active region miniband and into the i-type active region. Electrons that are captured in the lowest energy quantized wavefunctions in the i-type active region are then available for recombination with a spatially coincident nSL=1 heavy-hole in the valence band. FIG.17is a graph1700showing the quantized lowest energy heavy hole spatial wavefunctions ΨHHn=1(j,z) with respect to a distance along the growth direction for the optoelectronic device described with reference toFIG.15. The heavy hole valence band energy edge EHHk=0(z) is shown for reference. Once again, as observed inFIG.11, the heavy hole wavefunctions are substantially delocalized across several unit cells in the n-type and p-type active regions. The i-type active region has a larger unit cell period than the n-type and p-type active regions, and the same average Al fraction within the unit cell as the p-type and n-type superlattice regions. Again, the GaN potential minima generate the lowest energy valence states as belonging to heavy hole states. FIG.18is a graph1800showing the spatial overlap integral between the lowest energy quantized electron and heavy hole valence wavefunction states. The overlap integral is substantially the product of the quantized electron spatial wavefunctions Ψcn=1(i,z) ofFIG.16and the heavy hole spatial wavefunctions ΨHHn=1(j,z) ofFIG.17with respect to a distance along the growth direction for the optoelectronic device described with reference toFIG.15. The strength of the overlap integral is proportional to the oscillator strength of the specific transition. In general, if the electron and hole wavefunction probabilities coincide spatially, then there is a finite probability for an electron-hole recombination event. The energy width of the allowed optical transitions is indicative of quantum mechanical tunnelling between GaN layers through a thin AlN barrier layer. The intrinsic region has thicker AlN barriers and thus reduced conduction band tunnelling. The oscillator strength of the intrinsic region is shown to be stronger compared to the n-type and p-type regions. It can be seen from graph1800that the probability that an electron and a hole are present at the same location is higher in the i-type active region150than the n-type active region140and the p-type active region160. Hence optical emission due to electron and heavy hole recombination is more likely to occur from the i-type active region150than the n-type active region140and the p-type active region160of the optoelectronic device. Graph1800also shows that probability of emission from the i-type active region150is higher for the optoelectronic device described with reference toFIG.15than for the optoelectronic device described with reference toFIG.9. FIG.19is a graph1900showing the overlap integral of the electron spatial wavefunction Ψcn=1(i,z) and the heavy hole spatial wavefunction ΨHHn=1(j,z) with respect to a combined transition energy of the corresponding lowest energy quantized electrons and heavy holes for the optoelectronic device described with reference toFIG.15. The lowest energy optical transition due to the n=1 exciton is therefore due to recombination originating in the i-type active region which has a larger period than both the p-type and n-type active regions. The emission energy of the i-type active region is therefore selected to be at a longer wavelength than the lowest energy absorption of both the n-type and p-type active regions. This enables the generated photons within the i-type active region to propagate without absorption (and thus loss) within the cladding regions, i.e. the p-type and n-type active regions, and furthermore enables the light to be extracted from the interior of the device. This represents a preferred implementation of the present invention wherein the emission and absorption properties of the regions of the semiconductor structure or the device are controlled by selection of the respective superlattice unit cell periods. Furthermore, the average alloy content is kept constant throughout the superlattice regions and thus the in-plane lattice constant of each unit cell is matched and no accumulation of strain energy is witnessed as a function of growth direction. This enables high crystal quality superlattice stacks to be realized. Furthermore, there is no discontinuity in the built-in electric fields due to polarization charges within the structure, enabling the stack to be polarization stabilized. FIG.20is a graph2000showing an emitted luminance versus wavelength for the optoelectronic device described with reference toFIG.15. The discrete overlap integrals ofFIG.19are homogeneously broadened in energy to simulate thermal variations anticipated at room temperature. The sum of individual oscillator strength contributions are plotted as a function of wavelength for two choices of broadening parameters. The longest wavelength and sharpest transition is attributed to the lowest energy n=1 heavy-hole exciton and is spatially confined in the intrinsic region. As shown inFIG.20, the wavelength of maximum intensity is at approximately 247 nm, which is longer than the wavelength of maximum intensity inFIG.14for the optoelectronic device described with reference toFIG.9. The optoelectronic devices ofFIGS.9and15differ only in the choice of period for the one or more superlattices in the i-type active region. All the unit cells of all the one or more superlattices in the semiconductor structure are selected for these examples to have a fixed average alloy content. The average alloy content is selected to be defined as the Al fraction of the unit cell. For example, a unit cell comprising 1 monolayer of GaN and 2 monolayers of AlN has an Al fraction xave=⅔, and for a unit cell with 2 monolayers of GaN and 4 monolayers of AlN equally has an Al fraction xave= 4/6=⅔. Again, for simplicity only, 25 unit cell repetitions are used in each region. That is, not only does the average Al fraction of the unit cell determine an equivalent ordered ternary alloy composition of the form of AlxaveGa1-xaveN, but the period defines an optical emission energy for the said unit cell. FIG.21is a graph2100of the spatially dependent energy levels in the conduction band and the valence band with respect to a distance along the growth direction for a optoelectronic device, according to another embodiment of the present invention. It is understood that reference to the zone centre (k=0) conduction and heavy hole valence bands are sufficient to describe the device operation. In this embodiment, one or more superlattices forming the n-type active region, the i-type active region and the p-type active region are similarly composed of bilayered unit cells having an AlN layer and a GaN layer as in the case of the optoelectronic devices described with reference toFIGS.9and15. The effective Al fraction in the case ofFIG.21is however selected to have a lower Al fraction of xave=0.5. In the i-type active region150, the first layer in each unit cell is formed of 3 monolayers of AlN and the second layer in each unit cell is formed of 3 monolayers of GaN. Both the n-type and p-type active regions are selected to also have xave=0.5 but designed to have a larger optical energy at the onset of absorption to render them substantially transparent to the optical emission energy generated by the i-type active region. The p-type and n-type active regions are selected to have unit cells comprising only 2 monolayers of GaN and 2 monolayers of AlN. The thinner layers of GaN results in an increase in the energy separation between the lowest quantized energy levels in the conduction and valence bands. The p-type and n-type regions are formed using impurity doped superlattices. The y-axis ofFIG.21is the energy level band diagram (in units of electron volts, eV) relative to the Fermi energy, and the x-axis is distance in nanometres (nm) along the growth direction from the base of the substrate. The spatial positions and extent of the n-type active region140, the i-type active region150and the p-type active region160of the optoelectronic device are shown above the x-axis. Trace2110is the zone centre (or minimum) energy in the conduction band; the troughs are due to GaN, and the peaks are due to AlN. Careful inspection shows that the built-in pyroelectric and piezoelectric fields for the metal polar structure are different in the i-type active region to both the n-type and p-type active regions. This is due to the larger layer thicknesses of GaN and AlN in the i-type active region. Trace2120is spatial energy modulation in the valence band; the troughs are due to AlN, and peaks are due to GaN.FIG.21shows that the period of the unit cell (shown as the peaks and troughs) in the i-type active region150in traces2110and2120is roughly the same as the unit cell period shown in traces1510and1520shown inFIG.15. However, the duty cycle (i.e. the relative GaN and AlN layer thickness within the unit cell) has changed. Again, the device is selected to have p-type and n-type active regions which are substantially transparent to the emission wavelength of the i-type active region. FIG.22is a graph2200showing the lowest energy quantized electron spatial wavefunctions Ψcn=1(i,z) with respect to a distance along the growth direction for the optoelectronic device described with reference toFIG.21. The zone centre (k=0) conduction band energy Eck=0(z) is shown for reference. The n-type and p-type spatial regions exhibit highly coupled wavefunctions and form an n=1 superlattice miniband. The intrinsic region shows electron wavefunctions coupled across only nearest neighbour potential wells by virtue of the built-in depletion field and the thicker AlN barriers. FIG.23is a graph2300showing lowest energy quantized heavy hole spatial wavefunctions ΨHHn=1(j,z) with respect to a distance along the growth direction for the optoelectronic device described with reference toFIG.21. The zone centre (k=0) heavy hole valence band energy EHHk=0(z) is shown for reference. The heavy-hole wavefunctions in the p-type and n-type regions are delocalized over a large number of neighbouring potential wells. Conversely, the heavy-hole wavefunctions in the i-type active region are highly localized to their respective potential well by virtue of the larger AlN barrier width and built-in depletion field. FIG.24is a graph2400showing the spatial overlap integral of the electron and heavy hole wavefunctions. The overlap integral is substantially the product of the electron spatial wavefunctions Ψcn=1(i,z) ofFIG.22and the heavy hole spatial wavefunctions ΨHHn=1(j,z) ofFIG.23with respect to a distance along the growth direction for the optoelectronic device described with reference toFIG.21. The overlap integral represents the oscillator strength for the respective direct electron & heavy-hole transition. The energy width of the allowed optical transitions is indicative of quantum mechanical tunnelling between GaN layers through an AlN barrier layer. The i-type active region has thicker AlN barriers and thus reduced conduction band tunnelling. The oscillator strength of the i-type active region is shown to be stronger compared to the n-type and p-type active regions. It can be seen from graph2400that the probability that an electron and a hole are present at the same spatial location is higher in the i-type active region150than both the n-type active region140and the p-type active region160. Hence emission is more likely to occur from the i-type active region150than the n-type active region140and the p-type active region160of the optoelectronic device. Graph2400also shows that probability of emission from the n-type active region140and the p-type active region160is lower for the optoelectronic device described with reference toFIG.21than for the optoelectronic devices described with reference toFIGS.9and15. FIG.25is a graph2500showing the overlap integral of the electron spatial wavefunctions Ψcn=1(i,z) and the heavy hole spatial wavefunctions ΨHHn=1(j,z) with respect to a combined transition energy of the corresponding lowest energy quantized electrons and holes for the optoelectronic device described with reference toFIG.21. A stronger oscillator strength of the lowest energy transitions in the i-type active region compared to the n-type and p-type active regions is due to electron and heavy-hole recombination in the i-type active region. FIG.26is a graph2600showing an emitted luminance versus wavelength for the optoelectronic device described with reference toFIG.21. The discrete overlap integrals ofFIG.25are homogeneously broadened in energy to simulate thermal variations anticipated at room temperature. The sum of individual oscillator strength contributions are plotted as a function of wavelength for two choices of broadening parameters. The longest wavelength and sharpest transition is attributed to the lowest energy n=1 heavy-hole exciton and is spatially confined in the i-type active region As shown inFIG.26, the wavelength of maximum intensity is at approximately 262 nm, which is substantially longer than the wavelengths of maximum intensity inFIGS.14and20for the optoelectronic devices described with reference toFIGS.9and15respectively. The tuning of the emission wavelength and the other aspects of the device is discussed in further detail below. The present invention utilizes a semiconductor structure that is preferably crystalline and more preferably formed as a single crystal atomic structure. In a preferred embodiment, for emission of ultraviolet and deep ultraviolet light, the semiconductor structure has a wurtzite crystal structure composed of ionic bonds and formed from one or more semiconductors, such as, group III metal nitride (III-N) semiconductors or group II metal oxide (II-VI) semiconductors. FIG.27Ashows a wurtzite crystal structure2700for a group III metal nitride semiconductor. The wurtzite crystal structure includes metal crystal sites2715and nitrogen atom sites2720. The polarity of the crystal bonds along the miller notation [h k i l]=[0 0 0 1] direction2750is shown to be of a nitrogen-polar crystal orientation having a nitrogen polar bond2725. The structure can be inverted by mirror reflection about2760and becomes a metal-polar oriented crystal. If the crystal axis2750is taken as the growth direction [0 0 0 1] then the c-plane (0 0 0 1) is identified as the plane labelled2730. The horizontal crystal axis2760is one of the high symmetry slices through the wurtzite crystal having [1 1 −2 0] direction. FIG.27Bshows a view of the c-plane2730with the metal atoms terminating the surface. Nitrogen atom surface terminations of the c-plane are also possible. The crystal directions2760and2780represent in miller notation the [1 1 −2 0] and [0 0 1 −1] directions, respectively. Abrupt surface terminations are further subject to surface reconstructions of lower symmetry bond patterns. These surface reconstructions minimize the growing surface energy, but ultimately form substantially idealized crystal structure within the bulk of the layer when the reconstructed surface is then overgrown with further material in the wurtzite crystal structure. The ideal metal terminated surface exhibits the hexagonal c-plane crystal cell identified as the hexagon2785having equal sides of in-plane lattice constant2790. The crystal fundamental repeating unit is then characterized by a wurtzite cell parameterized as the lattice constant a, labelled as2790, and the hexagonal column of height c, labelled as2705or2710inFIG.27A. For example, a strain free AlN epilayer would have a=4.982 Å and c=5.185 Å. One monolayer (1 ML) is defined herein as equal to 1 ML=c/2, for film deposited upon a c-plane. FIG.27Cshows perspective view of an AlN wurtzite crystal2770oriented along the c-axis2750and further exposing an Al atom surface. The Al terminated surface lies wholly in the c-plane2730with the wurtzite crystal unit cell defined by the hexagon2760. The vertical thickness along the direction2750shows four monolayers of AlN material and the associated crystal orientations. For example, in some embodiments, a c-plane oriented epitaxial deposition upon a substrate cam include depositing with high uniformity a plurality of monolayered films which extend laterally in directions2760and2780, spanning the substrate surface area. FIG.28is a chart2800showing the preferred range of layered thicknesses for an example superlattice. The unit cells of the superlattice comprise two layers formed exclusively of binary compositions of GaN and AlN, respectively. For example, the superlattice is formed of wurtzite GaN and AlN films deposited upon a c-plane as shown schematically for an idealized spatial portion inFIG.27C. The chart2800ofFIG.28shows the columns tabulated in terms AlN thickness as a whole number of monolayers N along a c-axis, and the physical thickness in units of Angstroms (n.b., 1 Å=0.1 nm). Similarly, the rows tabulate in terms of whole monolayers M of GaN with the table entries calculating the unit cell period thickness: ΛSL=M·(1 ML GaN)+N·(1 ML AlN)=M·cGaN/2+N·cAlN/2. A superlattice having a unit cell which repeats Nptimes and has a constant Al fraction along a growth direction can be defined as a GaN and AlN pair having M and N monolayers, written for convenience herein as M:N. FIG.29shows a crystal lattice structure of one unit cell of a 4:4 superlattice wherein the 4 monolayers of GaN2940are deposited epitaxially upon 4 monolayers of AlN2930along a c-axis2750which defines a growth direction. The Al atoms sites are shown as the large white spheres2905, the Ga atom sites are depicted as the large grey spheres2920and the nitrogen atom sites are shown as the small black spheres2915and2925. The AlN/GaN heterointerface2935can be abrupt having purely Ga or Al metal terminations or can be an intermixed interface having random distribution of Ga and Al atoms in the plane2935. The vertical height of the GaN epilayer2940is larger than the lower AlN epilayer2930by virtue of elastic deformation of the crystal unit cells. A free standing superlattice unit cell2900would ideally exhibit no interfacial dislocations (namely, misfit dislocations) and would have the AlN layer in state of in-plane tensile strain and the GaN epilayer in a state of in-plane compressive strain. The elastically deformed dissimilar epilayers are ideally deposited with a thickness along a c-axis2750that is below the critical layer thickness (CLT). The CLT is the maximum thickness that a lattice mismatched material can be deposited upon an underlying crystal without forming misfit dislocations. All of the M:N combinations disclosed in chart2800ofFIG.28are representative of such superlattice unit cells which are deposited below the CLT of each material. Note, the CLT can be theoretically calculated and experimentally determined. For example, direct in-situ measurements using reflection high energy electron diffraction (RHEED) during heteroepitaxy in MBE can determine the CLT with great accuracy. FIG.30is a chart3000showing further possible implementations of unit cells formed by using on GaN and AlN materials deposited along a c-axis as defined herein. Chart3000defines fractional monolayer pairs of M:N with table entries showing the unit cell thickness ΛSL. These unit cell thicknesses can be applied to deep ultraviolet emitters using group III metal nitride semiconductors. It is also found that other material compositions can be used and more than two compositions comprising a superlattice unit cell are applicable. FIGS.28and30show examples of layers of GaN and AlN making up the unit cells of a superlattice (e.g., in the i-type region) with combined thickness of the two layers from 2.5 Angstroms to 35.6 Angstroms. FIG.31shows a graph3100of an equilibrium in-plane lattice constant a∥SLof a superlattice, constructed with unit cells having only a GaN and an AlN layer. The graph3100shows the calculated in plane lattice constant a∥SLfor a given selection of M monolayers of GaN and N monolayers of AlN in each unit cell. Each curve is parameterized by a distinct choice of N monolayers of AlN. The curves of graph3100can be used directly to design a superlattice LED comprising different unit cell M:N pairs and is discussed hereafter. FIG.32shows schematically the atomic forces present in a structure3200comprising two unit cells3270and3280. Each unit cell comprises two layers and each of the two layers is formed of a dissimilar material, for example, first layers3230and3250can be GaN layers and second layers3240and3260can be AlN layers. The layers are formed by epitaxial deposition of crystals, which are elastically deformed due to the dissimilar crystal lattice constants in each adjacent layer. If the structure is deposited upon a c-plane, then the GaN layers3230and3250are subject to compressive in-plane stress3220and the AlN layers3240and3260have an induced tensile in-plane strain3210. Such a superlattice formed using lattice mismatched materials with each layer of each unit cell being formed with thickness below the CLT can achieve high crystalline perfection when formed with a sufficient number of periods. For example, using GaN and AlN materials only, a superlattice according to the teaching of the present invention is formed on a bulk-like c-plane AlN surface, a (0001)-oriented Sapphire surface, or another suitable surface. After approximately 10 to 100 periods of superlattice growth the final unit cells attain idealized free-standing in-plane lattice constants a∥SL. This is one example method of forming a superlattice buffer130as discussed in relation toFIG.1. In some embodiments of the present invention, each superlattice in the semiconductor structure has a distinct configuration that achieves a selected optical and electronic specification. Experiments show that keeping an average alloy content in each unit cell constant along the superlattice is equivalent to keeping the average in-plane lattice constant of the unit cell a∥SLconstant. Experiments also show that the thickness of the unit cell can then be selected to achieve a desired optical and electrical specification. This enables a plurality of distinct superlattices to have a common effective in-plane unit cell lattice constant and thus enables the advantageous management of strain along a growth direction. FIGS.33and34show graphs3300and3400of the equilibrium in-plane lattice constant a∥SLof a superlattice, constructed with unit cells having only a GaN and an AlN layer. The graphs3300and3400show the calculated in plane lattice constant a∥SLfor a given selection of M monolayers of GaN and N monolayers of AlN in each unit cell. Each curve is parameterized by a distinct choice of N monolayers of AlN. Black dots are provided in each graph to show unit cell configurations having the same average alloy content. The black dots shown in the graph3300ofFIG.33include M:N combinations where M=N and thus an effective Al fraction of xaveSL=½ is achieved. The black dots in graph3400inFIG.34include M:N combinations where N=2M and thus a xaveSL=⅔. Graphs3300and3400show examples of equilibrium in-plane lattice constants of the GaN and AlN layers in a superlattice (e.g., in the i-type region) from 3.11 Angstroms to 3.19 Angstroms. The graphs ofFIGS.33and34can be particularly useful for designing semiconductor structures having superlattices with unit cells exclusively built from GaN and AlN material combinations deposited along a c-axis and having wurtzite crystal structure. FIG.35shows a graph3500of a calculated portion of the energy band structure of a Np=100 period superlattice comprising a M:N=5:5 unit cell that is repeated along a growth direction z. The spatial variation of the conduction band edge3520and heavy hole valence band edge3550are shown along with the quantized energy and spatially confined carrier wavefunctions3510and3560. GaN and AlN layers are selected from thicknesses which preserve the CLT of each of the respective layers, as shown inFIG.30.FIG.35shows that the electron wavefunctions3510exhibit a strong tendency for quantum mechanical tunnelling3570through the AlN barriers, whereas the heavy hole wavefunctions3560are tightly localized within their respective GaN potential minima. FIG.36shows a superlattice3600used to simulate a semi-infinite number of periods of a superlattice of constant unit cell length and composition. In the superlattice, the unit cells have a constant length and composition. However, the first GaN layer3605is split in half and added to the end3610of the superlattice. Applying periodic boundary conditions for the wavefunctions thus simulates a semi-infinite number of periods, while investigating the interacting property of the base99unit cells3620. Using a finite element method and full k.p theory the wavefunctions are calculated along with the quantized energies of the lowest lying superlattice states. As described earlier, the optical emission spectrum is calculated from the overlap integrals and energy separation between the lowest energy (n=1) conduction band states and the n=1 heavy hole states. FIGS.37,38,39,40and41show graphs of the transverse electric (TE) optical emission spectra of superlattices having xaveSL=⅔ and M:N configurations of 1:2, 2:4, 3:6, 4:8 and 5:10, respectively. Each of the graphs shows four curves corresponding to the total emission and emission due to a particular valence band type (namely, HH, LH or CH) with an allowed conduction state. As discussed previously, a desired lowest energy emission is for a transition between an allowed conduction band state and a heavy-hole state, which satisfies the criteria for vertical emission parallel to c-axis and or growth direction. FIG.37shows a graph3700of the emission spectrum of a 1:2 superlattice for the lowest energy transition of the n=1 conduction states and the n=1 heavy hole states (ECn=1−EHHn=1)3705, the lowest energy transition of the n=1 conduction states and the n=1 crystal field split states (ECn=1−ECHn=1)3710, and the lowest energy transition of the n=1 conduction states and the n=1 light hole states (ECn=1−ELHn=1)3715. Curve3720shows the total spectrum that is observable. The large energy width of the emission peaks is fundamentally due to the large coupling between nearest neighbour GaN potential minima and thus the formation of wide energy width minibands in both the conduction and respective valence bands. FIG.38shows a graph3800of the emission spectrum of a 2:4 superlattice for the lowest energy transition of the n=1 conduction states and the n=1 heavy hole states (ECn=1−EHHn=1)3805, the lowest energy transition of the n=1 conduction states and the n=1 crystal field split states (ECn=1−ECHn=1)3810, and the lowest energy transition of the n=1 conduction states and the n=1 light hole states (ECn=1−ELHn=1)3815. Curve3820shows the total spectrum that is observable. The smaller energy width of the emission peaks compared toFIG.37is due to the smaller coupling between nearest neighbour GaN potential minima and thus the formation of narrower energy width minibands in both the conduction and respective valence bands. FIG.39shows a graph3900of the emission spectrum of a 3:6 superlattice for the lowest energy transition of the n=1 conduction states and the n=1 heavy hole states (ECn=1−EHHn=1)3905, the lowest energy transition of the n=1 conduction states and the n=1 crystal field split states (ECn=1−ECHn=1)3910, and the lowest energy transition of the n=1 conduction states and the n=1 light hole states (ECn=1−ELHn=1)3915. Curve3920shows the total spectrum that is observable. FIG.40shows a graph4000of the emission spectrum of a 4:8 superlattice for the lowest energy transition of the n=1 conduction states and the n=1 heavy hole states (ECn=1−EHHn=1)4005, the lowest energy transition of the n=1 conduction states and the n=1 crystal field split states (ECn=1−ECHn=1)4010, and the lowest energy transition of the n=1 conduction states and the n=1 light hole states (ECn=1−ELHn=1)4015. Curve4020shows the total spectrum that is observable. FIG.41shows a graph4100of the emission spectrum of a 5:10 superlattice for the lowest energy transition of the n=1 conduction states and the n=1 heavy hole states (ECn=1−EHHn=1)4105, the lowest energy transition of the n=1 conduction states and the n=1 crystal field split states (ECn=1−ECHn=1)4110, and the lowest energy transition of the n=1 conduction states and the n=1 light hole states (ECn=1−ELHn=1)4115. Curve4120shows the total spectrum that is observable. Of particular importance is the achievement of (ECn=1−EHHn=1) optical transitions that are always the lowest energy emission and thus enable efficient vertically emissive devices of the form shown inFIG.7. FIG.42shows a graph4200of the optical emission spectra for the heavy hole transition for each M:N pair plotted inFIGS.37to41. In general larger GaN layer thicknesses result in quantized energy levels that are closer to the GaN band edges and thus result in longer emission wavelengths. Conversely, thinner GaN layers improve the overlap of the lowest energy quantized conduction and valence band states and thus improve the oscillator strength and emission intensity. It is found that for GaN epilayers in excess of 8 to 10 monolayers the overlap integral is severely degraded and poor optical emission results. For application to ultraviolet and deep ultraviolet devices, the M:N configurations ofFIG.42are found to be optimal and or desired. Shorter emission wavelengths are possible using superlattice unit cells comprising AlN and AlxGa1-xN compositions. To preserve the TE character of the emission it is found that AlxGa1-xN where x is less than or equal to about 0.5 is preferred. The above can be used to design semiconductor structures, such as the semiconductor structure ofFIGS.1to8. For example, the M:N configuration of the unit cells of the i-type active region, the n-type active region and the p-type active region can be selected to produce an emission wavelength from the i-type active region that is longer than the absorption edge of the n-type active region and the p-type active region. Further, embodiments of the invention can be designed with a constant average alloy fraction throughout the semiconductor structure which further improves the crystal quality of the resulting structure. FIGS.43and44show graphs of the calculated optical emission wavelength of the lowest energy transition between the allowed superlattice conduction band states and the heavy hole states for unit cells comprising exclusively AlN and GaN epilayers.FIG.43discloses the emission wavelength for N=2M superlattices having xaveSL=⅔=0.667, whereasFIG.44discloses the emission wavelength for N=M superlattice and xaveSL=½=0.50. The curves4300and4400show the variation in the lowest energy optical emission wavelength as a function of the unit cell period ΛSLwhich has a corresponding M:N configuration. From the graphs it can be seen that the optical emission can be tuned over a wide and desirable optical range spanning from about 230 nm to less than 300 nm. In one example, a semiconductor structure is formed of distinct superlattice regions. The unit cells of each superlattice have an Al fraction xaveSL=⅔ and are formed exclusively of a GaN and an AlN layer. The desired design wavelength for a light emitting device comprising the semiconductor structure is, for example, λe=265 nm. Thus, referring toFIG.43, an M:N=3:6 unit cell is selected of the i-type active region. The device comprises an n-type active region formed atop a transparent substrate using a superlattice unit cell that is substantially transparent to the desired design wavelength λe. Similarly, the device comprises a p-type active region that substantially transparent to the desired design wavelength λe. The superlattice in the n-type active region can therefore be selected to have M:N=1:2 unit cells and the superlative in the p-type active region can be selected to have M:N=2:4 unit cells. This will improve the activated heavy hole concentration and provide an improved hole wavefunction injection into a portion of the M:N=3:6 unit cells of the superlattice in the i-type active region. The i-type active region can be partitioned into two distinct superlattices, being a first superlattice with M:N=2:4 unit cells and a second superlattice with M:N=3:6 unit cells. The first superlattice is positioned between the n-type active region and the second superlattice. The second superlattice is positioned between the first superlattice and the p-type active region. The first superlattice acts as an electron energy filter for injecting preferred electrons into the electron-hole recombination region (EHR) defined by the second superlattice. This configuration therefore provides improved carrier transport of electrons and holes throughout the semiconductor structure. The EHR of the second superlattice is positioned close to the hole reservoir due to the inherently low hole mobility in the group III metal nitrides. Therefore, a light emitting device can be produced having a semiconductor structure having [n-type 1:2/i-type 2:4/i-type 3:6/p-type 2:4] superlattice regions. The total thickness of the i-type active region can also be optimized. FIGS.45and46show graphs of a conduction band edge4510and4610and a heavy hole valence band edge4505and4605in electron volts (eV) along the growth direction z for semiconductor structures comprising 100 periods of n-type M:N=1:2 unit cells in the n-type active region and 100 periods of p-type M:N=1:2 unit cells in the p-type active region. The unit cells are exclusively constructed from c-plane oriented GaN and AlN monolayered films with a constant Al fraction of xaveSL=⅔. The i-type active region similarly has a constant Al fraction of xaveSL=⅔ but has a large period in order to tune the emission wavelength to a longer wavelength.FIG.45shows a graph for a semiconductor structure that has 25 periods of 2:4 unit cells in the i-type active region4530, whereasFIG.46shows a graph for a semiconductor structure that has 100 periods of 2:4 unit cells in the i-type active region4630. The built-in depletion region electric field Ed(z)4520, due to the p-type and n-type active regions, inFIG.45is larger than the built-in depletion region electric field Ed(z)4620inFIG.46. The built-in depletion region electric field Ed(z) is affected by the total thickness of the i-type active region superlattice and places yet another Stark shifting potential across the superlattice confined states. It is found that this quantum confined superlattice Stark effect (QC-SL-SE) can be used to further tune the optical properties of the device. FIG.47shows the graphs ofFIGS.45and46on a single graph for comparison. An optional p-GaN contact layer that is inserted above the p-type active region pins the Fermi level via an induced two-dimensional hole gas (2DHG). The devices have a metal polar growth orientation along the growth direction z. FIG.48shows a graph of the calculated lowest energy quantized electron wavefunctions4800within the i-type active region of the semiconductor structure referred to inFIG.45under the influence of the built-in depletion electric field. Compared to the semiconductor structure with no depletion electric field, the wavefunctions are observed to be blue shifted and there is a reduction of the resonant tunnelling between nearest neighbours. The conduction band edge4510is plotted as a reference. FIG.49shows a graph of the calculated quantized lowest energy heavy hole wavefunctions4900within the i-type active region of the semiconductor structure referred to inFIG.46under the influence of the built-in depletion electric field. The heavy hole band edge4605is plotted as a reference. FIGS.50A and50Bshow graphs of the emission spectra from the i-type active regions of the devices referred to inFIGS.45and46, respectively.FIG.50Ashows the emission spectra for the optical transitions between the lowest energy n=1 conduction band states and their respective HH5005, LH5010and CH5015valence bands and the total TE emission spectrum5020in the device ofFIG.45.FIG.50Bshows the emission spectra for the optical transitions between the lowest energy n=1 conduction band states and their respective HH5025, LH5035and CH5030valence bands and the total TE emission spectrum5040in the device ofFIG.46. The device ofFIG.45has a larger built-in electric field than the device ofFIG.46due to the thinner i-type active region. This larger built-in electric field breaks the coupling between adjacent unit cells in the i-type active region, produces a small blue shift in the emission energy and reduces the emission spectral line width. ComparingFIG.50AtoFIG.50B, it can be seen that there is a reduction in the full width at half maximum (FWHM) of the low energy side of the peak emission and a blue shift of the low energy emission edge due to the larger built-in electric field.FIG.50Bshows a larger integrated luminescence thanFIG.50Adue to the large number of periods in i-type active region of the device ofFIG.46. FIG.51schematically describes the influence of the built-in depletion field5130having potential energy5135along a distance5140that is parallel to a growth direction5110. The superlattice band diagram without a built-in depletion field is shown as the spatial conduction band edge5115and the vertical axis5105represents energy. The delocalized electron wavefunction5120is coupled between adjacent GaN regions by virtue of quantum mechanical tunnelling through the high potential energy AlN barriers. The internal pyroelectric and piezoelectric fields are also shown and representative of a metal polar oriented growth. The tunnelling of the wavefunctions5120results in an energy miniband5125for the allowed quantized conduction states. Application of a linearly increasing potential5130such as occurs with the built-in depletion field, results in spatial band structure5160. The resulting wavefunctions of the superlattice with application of the depletion field5130generates the wavefunctions5145and5155which are no longer resonantly coupled to their nearest neighbour GaN potential minima. The quantized allowed energy states of the band structure5160now has discrete energy states5165and5170that are higher in energy compared to the miniband energy states5125. This effect can be modified by application of a depletion electric field across a nitrogen-polar oriented growth, with a resulting lowering of the energy of Stark split states. This is particularly useful for example, for a nitrogen polar p-i-n superlattice device composed of only one unit cell type, such as an M:N=3:6 unit cell having a GaN layer and an AlN layer. The built-in depletion field across the superlattice having M:N=3:6 unit cells cause an emission energy to be stark shifted to longer wavelengths (i.e., red-shifted) and will not be substantially absorbed in surrounding p-type and n-type active regions having M:N=3:6 unit cells. In general, a metal polar oriented growth produces blue shift in the emission spectrum of the i-type active region or i-type active region of a n-i-p device due to a p-up epilayer stack. That is, for a depletion electric field as shown for a device formed in the order: substrate, n-type active region, i-type active region, p-type active region [SUB/n-i-p]. Conversely, a redshift is observed in the emission spectrum of the i-type active region for a p-i-n device formed as a p-down epilayer stack, that is, [SUB/p-i-n]. Conversely, a nitrogen polar oriented growth produces a blue shift in the emission spectrum of the i-type active region of a n-i-p device due to the depletion electric field, and a redshift in the emission spectrum of the i-type active region of a p-i-n device due to the depletion electric field. The present invention provides many benefits over the prior art, including improved light emission, especially at UV and Deep UV (DUV) wavelengths. For example, the use of ultrathin layered superlattices enables photons to be emitted vertically, i.e. perpendicular to the layers of the device, as well as horizontally, i.e. parallel with the layers. Furthermore, the present invention provides spatial overlap between the electron and hole wavefunctions enabling improved recombination of electrons and holes. In particular, for the application of ultra-violet devices, GaN proves extremely beneficial for the narrower band gap material and AlN for the wider bandgap material. GaN is inherently a vertically emissive material when deposited on c-plane surfaces, whereas AlN emits substantially with TM optical polarizations, i.e. in the plane of the sub-layers. The thickness of the first layer and second layer of the unit cells can be used to select the quantisation energy of electrons and holes and the coupling of electrons in the conduction band. For example, the thickness of layers of GaN can be used to select the quantization energy of electrons and holes and the thickness of layers of AlN can control the coupling of electrons in conduction band. The ratio of thickness of the layers of GaN to the layers of AlN can be used to select the average in-plane lattice constant of the superlattice. Hence, the optical transition energy of a given superlattice can be altered by choice of both the average unit cell composition and the thickness of the each layer of each unit cell. Further advantages of the present invention include: simpler manufacturing and deposition processes; customisable electronic and optical properties (such as the wavelength of the emitted light) suitable for high efficiency light emission; optimised optical emission polarisation for vertically emissive devices when deposited on c-plane oriented surfaces; improved impurity dopant activation for n-type and p-type conductivity regions; and strain managed monolayers enabling optically thick superlattices to be formed without excessive strain accumulation. For example, aperiodic superlattices can be used to prevent strain propagation and enhance optical extraction. Furthermore, spreading out the electron and or hole carrier spatial wavefunctions within the electron-hole recombination regions improves both the carrier capture probability by virtue of increase volume of material, and also improves the electron and hole spatial wavefunction overlap and thus improves the recombination efficiency of the device over prior art. In this specification, the term “superlattice” refers to a layered structure comprising a plurality of repeating unit cells including two or more layers, where the thickness of the layers in the unit cells is small enough that there is significant wavefunction penetration between corresponding layers of adjacent unit cells such that quantum tunnelling of electrons and/or holes can readily occur. In this patent specification, adjectives such as first and second, left and right, front and back, top and bottom, etc., are used solely to define one element from another element without necessarily requiring a specific relative position or sequence that is described by the adjectives. Words such as “comprises” or “includes” are not used to define an exclusive set of elements or method steps. Rather, such words merely define a minimum set of elements or method steps included in a particular embodiment of the present invention. It will be appreciated that the invention may be implemented in a variety of ways, and that this description is given by way of example only. The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. Accordingly, this patent specification is intended to embrace all alternatives, modifications and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in Australia or elsewhere. | 113,903 |
11862751 | DETAILED DESCRIPTION OF THE EMBODIMENTS To better and concisely explain the disclosure, the same name or the same reference number given or appeared in different paragraphs or figures along the specification should has the same or equivalent meanings while it is once defined anywhere of the disclosure. FIG.1shows an LED manufacturing method in accordance with an embodiment of the present application.FIG.2shows a cross-sectional view of an LED wafer100which is composed by a plurality of LEDs1formed on the substrate10after the step S1and the step S2are completed. Referring toFIG.1andFIG.2, first, an epitaxy growth is performed in the step S1to form a semiconductor stack12on an upper surface10aof a substrate10. The semiconductor stack12includes a first semiconductor layer121, an active region123and a second semiconductor layer122. Next, a chip manufacturing process is performed in the step S2. A transparent conductive layer18is formed on the semiconductor stack12. The semiconductor stack12is then separated into a plurality of LEDs1on the substrate10by an isolation region ISO. An insulating layer50, a first electrode20and a second electrode30are sequentially formed on the semiconductor stack12. In one embodiment, the plurality of LEDs1is arranged on the substrate10in an array. The plurality of LEDs1is isolated from each other by the isolation region ISO. The insulating layer50covers the isolation regions ISO, the semiconductor stacks12and the transparent conductive layers18. The insulating layer50comprises an opening501exposing the first semiconductor layer121and another opening502exposing the transparent conductive layer18. The first electrode20is formed on the insulating layer50and electrically connected to the first semiconductor layer121through the opening501. The second electrode30is formed on the insulating layer50and electrically connected to the second semiconductor layer122through the opening502. Substrate The substrate10can be a growth substrate, including a GaP substrate or a GaAs substrate for growing AlGaInP thereon, or a sapphire substrate, a GaN substrate or a SiC substrate for growing InGaN or AlGaN thereon. The substrate10includes the upper surface10a. In one embodiment, the upper surface10ais a flat surface. In another embodiment, the substrate10includes a patterned substrate; that is, the substrate10includes a patterned structure (not shown) on the upper surface10a. The patterned structure includes a plurality of protrusions or a plurality of recesses. In an embodiment, the light emitted from the semiconductor stack12can be refracted by the patterned structure of the substrate10, thereby improving the brightness of the LED. In addition, the patterned structure lessens or suppresses the dislocation caused by lattice mismatch between the substrate10and the semiconductor stack12, thereby improving the epitaxy quality of the semiconductor stack12. Semiconductor Stack In an embodiment of the present application, the semiconductor stack12is formed on the substrate10by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor epitaxy (HVPE) or ion plating such as sputtering or evaporating. A buffer structure (not shown), a first semiconductor layer121, an active region123, and a second semiconductor layer122are sequentially formed on the substrate10. The semiconductor stack12includes the buffer structure, the first semiconductor layer121, the active region123, and the second semiconductor layer122. The buffer structure reduces the lattice mismatch and suppresses dislocation so as to improve the epitaxy quality. The material of the buffer structure includes GaN, AlGaN, or AlN. In an embodiment, the buffer structure includes a plurality of sub-layers (not shown) having the same material or different materials. In one embodiment, the buffer structure includes a first sub-layer and a second sub-layer. The first sub-layer is grown by sputtering or MOCVD and the second sub-layer thereof is grown by MOCVD. In another embodiment, the buffer structure further includes a third sub-layer. The third sub-layer is grown by MOCVD, and the growth temperature of the second sub-layer is higher or lower than the growth temperature of the third sub-layer. In an embodiment, the first, second, and third sub-layers include the same material, such as AlN. In an embodiment, the first semiconductor layer121and the second semiconductor layer122are, for example, cladding layer or confinement layer. The first semiconductor layer121and the second semiconductor layer122have different conductivity types, different electrical properties, different polarities or different dopants for providing electrons or holes. For example, the first semiconductor layer121is an n-type semiconductor and the second semiconductor layer122is a p-type semiconductor. The active region123is formed between the first semiconductor layer121and the second semiconductor layer122. Driven by a current, electrons and holes are combined in the active region123to convert electrical energy into optical energy for illumination. The wavelength of the light generated by the semiconductor stack12can be adjusted by changing the physical properties and chemical composition of one or more layers in the semiconductor stack12. The material of the semiconductor stack12includes III-V semiconductor with AlxInyGa(1-x-y)N or AlxInyGa(1-x-y)P, where 0≤x, y≤1; x+y≤1. When the material of the active region of the semiconductor stack12includes AlInGaP, the semiconductor stack12emits red light having a wavelength between 610 nm and 650 nm or yellow light having a wavelength between 550 nm and 570 nm. When the material of the active region of the semiconductor stack12includes InGaN, the semiconductor stack12emits blue light or deep blue light having a wavelength between 400 nm and 490 nm or green light having a wavelength between 490 nm and 550 nm. When the material of the active region of the semiconductor stack12includes AlGaN, the semiconductor stack12emits UV light having a wavelength between 250 nm and 400 nm. The active region123can be a single hetero-structure (SH), a double hetero-structure (DH), a double-side double hetero-structure (DDH), or a multi-quantum well (MQW). The material of the active region123can be i-type, p-type or n-type. Transparent Conductive Layer The transparent conductive layer18covers the upper surface of the second semiconductor layer122of each LED1and electrically connects with the second semiconductor layer122. The transparent conductive layer18can be metal or transparent conductive material. The metal material can form a thin metal layer having light transparency. The transparent conductive material is transparent to the light emitted by the active region123, such as grapheme, indium tin oxide (ITO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), zinc oxide (ZnO) or indium zinc oxide (IZO). In another embodiment, the LED1does not include the transparent conductive layer18and the opening502exposes the second semiconductor layer122. Insulating Layer The insulating layer50is transparent to the light emitted from the semiconductor stack12, and can be a layer composed of a single insulating material or a stack composed of multiple layers of different insulating materials. In one embodiment, the insulating layer50is formed by alternately stacking a pair or a plurality of pairs of insulating materials with different refractive indices. The insulating material includes silicon oxide, silicon nitride, silicon oxynitride, niobium oxide, hafnium oxide, titanium oxide, magnesium fluoride, aluminum oxide, etc. In one embodiment, by selecting insulating materials with different refractive indices and the thickness thereof, the insulating layer50functions as a reflective structure such as distributed Bragg reflector. The reflective structure selectively reflects the light within a specific wavelength range. The insulating layer50can be formed by atomic layer deposition (ALD), sputtering, evaporation, spin-coating, etc. In another embodiment, the insulating layer50includes a stack of multiple layers of the same insulating material formed by different methods or different insulating materials formed by different methods. Electrode The electrodes include a first electrode20and a second electrode30. The material of the electrode includes metals, such as Cr, Ti, Au, Al, Cu, Sn, Ni, Rh, W, Pt, an alloy or a laminated stack composed by the above materials. In this embodiment, the size of the LED1has a diagonal length less than 150 μm, and the distance between the first electrode20and the second electrode30is less than 30 μm. In another embodiment, the size of the LED1has a diagonal length less than 100 μm, and the distance between the first electrode20and the second electrode30is less than or equal to 25 μm. After completing the step S2, the plurality of LEDs1are tested in the step S3. In order to test the LEDs, a testing circuit is formed on the wafer100. First, as shown inFIG.3, the wafer100is divided into a plurality of zones such as a first zone Z1to a fourth zone Z4. Each of the first zone Z1, the second zone Z2, the third zone Z3and the fourth zone Z4includes N LEDs1arranged in an array and the N LEDs1in one zone are defined as an LED group G1. The testing circuit is formed in each zone. The testing circuit is formed on the upper surface10aof the substrate10, including on the isolation region ISO. In the present application, the number N of the LEDs1in each zone, the arrangement of the LEDs1, the allocations of the zones, the area of each zone and the quantity of the zones can have different designs in accordance with the requirements of use and testing. FIGS.4A,4B,4C and4Dshow a testing circuit in a single zone in accordance with different embodiments of the present application, respectively. The following embodiments only show the testing circuit in one zone on the substrate, and the testing circuit in the other zones on the substrate can be selected from any of the same testing circuit or different testing circuits in the following embodiments. As shown inFIG.4A, the N LEDs1are arranged into an array with K rows and M columns. The testing circuit includes a first testing pad60a, a second testing pad60b, a first wire40a, a second wire40b, a first branch wire401aand a second branch wire401b. Each of the first branch wires401ais connected to the first electrode20of each LED1, and is electrically connected to the first testing pad60avia the first wire40a. Each of the second branch wire401bis connected to the second electrode30of each LED1, and is electrically connected to the second testing pad60bvia the second wire40b. In this way, the LED group G1in the zone forms a parallel circuit. The photoelectric characteristics of the LED group G1in the zone can be obtained by using the probes to touch the testing pad such as the first testing pad60aand the second testing pad60band inputting a current into the LED group G1. In another embodiment (not shown), the testing circuit includes a plurality of first testing pad60aand/or a plurality of second testing pad60b. For example, the N LEDs1are arranged in K rows, the first electrodes20of the LEDs1in the same row is connected to the same first testing pad60a, and the second electrodes30of the LEDs1in the same row is connected to the same second testing pad60b. The LEDs1in the same row are electrically connected in parallel. In the zone, the testing circuit includes K first testing pad60aand K second testing pad60b. In this way, the LEDs1of each row in the LED group1can be tested respectively. FIG.4Bshows the testing circuit in a single zone in accordance with another embodiments of the present application. The N LEDs1are arranged in K rows and M columns. In the embodiment, the first electrodes20of the plurality of LEDs1located in the same row (row1, row2, . . . row K) are electrically connected to the first testing pads60-1a,60-2a, and60-3aon both sides of the row via the first wires40aand the first branch wires401a. For example, the first electrodes20of the plurality of LEDs1located in the first row (row1) are electrically connected to the first testing pads60-1aon both sides of the first row (row1) via the first wire40aand the first branch wires401a. The second electrodes30of the plurality of LEDs1located in the same column (column1, column2, . . . column M) are electrically connected to the second testing pads60-1b,60-2b, and60-3bon both sides of the column via the second wires40band the second branch wires401b. The first wire40aand the first branch wire401aconnected to the first electrode20are electrically insulated from the second wire40band the second branch wire401bconnected to the second electrode30. In one embodiment, the second wire40band/or the second branch wire401bare formed on the first wire40aand/or the first branch wire401ain a bridge manner, and an insulating layer (not shown) is formed between the overlapping portions between the two. In one embodiment, the insulating layer can be formed on the entire surface of the LEDs1, the first wire40aand the first branch wire401a. The insulating layer includes openings (not shown) to expose the second electrodes30, and then the second branch wires401band the second wires40bthat are connected to the second electrode30are formed thereon. The second branch wires401band the second wires40bare electrically insulated from the first wires40aand the first branch wires401aby the insulating layer. In this embodiment, selective testing can be performed. The N LEDs1are arranged into a two-dimensional array of K rows and M columns. For example, by using probes to contact the first testing pad60-2aand the second testing pad60-2band inputting a testing current, the photoelectric characteristics of the LED1at the second column and the second row can be obtained. For example, by using probes to contact the first testing pad60-1aand the second testing pad60-3band inputting a testing current, the photoelectric characteristics of the LED1at the Mthcolumn and the first row can be obtained. FIG.4Cshows a testing circuit in a single zone in accordance with another embodiment of the present application. As shown inFIG.4C, the LEDs1in the single zone are further divided into sub-groups. The LEDs in adjacent rows in the sub-group are connected to a common first testing pad and the LEDs in adjacent columns in the sub-group are connected to a common second testing pad. For example, the second wires40bwhich are connected to the LEDs in the first column to the third column are connected to a common second testing pad60-1band the first wires40awhich are connected to the LEDs in the first row to the third row are connected to a common first testing pad60-1a. By using probes to touch the first testing pad60-1aand the second testing pad60-1band inputting a testing current, the photoelectric characteristics of nine LEDs1in the sub-group located in the first column to the third column and in the first row to the third row can be obtained. By using probes to contact the first testing pad60-1aand the second testing pad60-2band inputting a testing current, the photoelectric characteristics of the plurality of LEDs1located in the fourth column to the Mthcolumn and in the first row to the third row (i.e. the LEDs1in the sub-group enclosed by the dash line shown inFIG.4C) can be obtained. In this manner, a selective testing for the sub-group can be further performed in the LED group G1. The formation of the insulating layer between the first wire40a(first branch wire401a) and the second wire40b(second branch wire401b) is similar to the embodiment ofFIG.4B, and will not be repeated. In another embodiment (not shown), the first wires40aof each row shown inFIG.4BorFIG.4Care connected to the same first testing pad, and the second wires40bof each column are connected to the same second testing pad. In this way, all the LEDs1in the zone can be tested at the same time. In addition, compared to the embodiment shown inFIG.4Athat the LEDs1in the same row are electrically connected in parallel and the wires40aand40bare arranged in the same direction (e.g., horizontal direction), the wires40aand40bof the present embodiment are arranged in different directions; that is, the first wires40aare arranged horizontally and the second wires40bare arranged vertically. The area occupied by the wires can be reduced. Therefore, in the present embodiment, more LEDs1can be formed in a unit area on the wafer and more LEDs1can be tested at the same time. FIG.4Dshows a testing circuit in a single zone in accordance with another embodiment of the present application. The electrical connection in the present embodiment is similar with that ofFIG.4A. The difference is that, in this embodiment, the first electrodes20of one LED1is adjacent to the first electrode20of an adjacent LED1in the same column. The second electrode30of the one LED1is adjacent to the second electrode30of another adjacent LED1in the same column. In this way, the first electrodes20of two adjacent LEDs1in the same column connect to the same first wire40aand the second electrodes30of two adjacent LEDs1in the same column connect to the same second wire40b. The number of the wires40aand40bin this embodiment is less than that in the previous embodiment, and the area on the wafer occupied by the wires can be reduced. Therefore, in the present embodiment, more LEDs1can be formed in a unit area on the wafer and more LEDs1can be tested at the same time. In one embodiment, the LEDs1are subsequently transferred to a target carrier such as a carrier of an end-product or a carrier of an LED module in groups. The arrangement and the grouping of the LEDs1on the substrate10, such as the numbers of the rows and the columns, or the distance between adjacent LEDs, depend on the arrangement of the LEDs1on the target carrier or the module carrier. While the arrangement of the LEDs1on the target carrier or the module carrier has high density and small pitch, the LEDs1on the substrate10has the corresponding arrangement. Otherwise, the arrangement of the LEDs may cause the upper surface of the wafer100does not have sufficient space for disposing the testing circuit, then testing the LEDs1on the wafer100would be difficult. In accordance with the layouts of the testing circuits shown in the embodiments of the present application, the space on the upper surface of the substrate10can be effectively used to form the testing circuit and performing LED1testing. Testing Circuit The testing circuit includes the first testing pads60a,60-1a,60-2aand60-3a, the second testing pads60b,60-1b,60-2band60-3b, first wire40a, second wire40b, the first branch wire401aand the second branch wire401b. When testing the LED group in a single zone, the forward voltage of each of the plurality of parallel-connected LEDs1are substantially equal; for example, the starting voltage and the operating voltage of each LED measured at a specific current are substantially equal. This ensures that the photoelectric characteristics measured from each LED1in a single group are correct based on the same operating voltage. Taking the embodiment shown inFIG.4Aas an example, each of the second wires40bbetween any two adjacent columns can be regarded as a node. The difference between the operating voltage (or the starting voltage) of the LED measured from the first testing pad60aand the first node and the operating voltage (or the starting voltage) of the LED measured from the first testing pad60aand the second testing pad60bis less than 5 mV. The material of the testing circuit includes metals, such as Cr, Ti, Au, Al, Cu, Sn, Ni, Rh, W, In, Pt or an alloy or a laminated stack of the above materials. The selection of the above metal materials for forming the testing circuit depends on user's requirement. The user's requirement includes, for example, the space of the substrate10that can be used to form the testing circuit, the layout of the testing circuit, etc. Metal materials with suitable resistance and length can be selected for forming the testing circuit to meet the requirement that the forward voltages of each of the plurality of parallel-connected LEDs1are substantially equal. Preferably, the material of the testing circuit is different from the material of a top layer of the first electrode20and the second electrode30. After the LED testing is completed, the testing circuit is removed by, for example, wet etching or dry etching. In the embodiment of removing the testing circuit by wet etching, the etchant has the characteristic of removing the testing circuit but not damaging the top layer of the first electrode20and the second electrode30. In one embodiment, the photoelectric characteristics of the LEDs1obtained in the testing methods in accordance with the embodiments can be presented in images. The image can be used to identify if the photoelectric characteristics of each of the LEDs1are substantially consistent or if any LEDs1is damaged, failed, or whose photoelectrical characteristics does not meet the specification. In the present application, the damaged LED, the failed LED, and the LED whose photoelectrical characteristics does not meet the specification are defined as a defective LED. In one embodiment, the photoelectric characteristics of the LEDs1obtained by the testing method in accordance with the embodiments can be presented in a gray scale image or RGB color image. The brightness of all LEDs1in a zone can be distinguished by the shade of the image. In one embodiment, a luminance meter, spectroradiometer, near-field measurement system, photoluminescence (PL) measurement system can be used to test the LEDs1and obtain the gray scale image or the RGB color image.FIG.5shows a near-field image of the LED group G1lit in one zone on the wafer. The measured photoelectric characteristic of the LEDs1in the testing method which is presented in an image form has the following characteristics: 1) Near-field measurement or photoluminescence (PL) measurement can be used to determine the brightness of the LEDs by intensity; 2) The wavelength spectrum of each LED can be obtained; and 3) A current of 1 pA to 100 μA is inputted into the LEDs to slightly light up the LEDs. Defective LEDs with abnormal reverse current can be picked out based on the dim brightness of the LEDs. In the present application, the wafer100is divided into a plurality of zones and the testing circuit formed in each zone is used for testing the LEDs, which solves the problem that the electrodes of the small-sized LED are too small to perform conventional testing for each LED. The LEDs in a single zone are tested at a time and the photoelectric characteristics of the LED group can be obtained through the division of the wafer. In one embodiment, the field of view of the optical lens of the testing system covers whole single zone or a plurality of zones at a time, and a plurality of probes can be placed on the plurality of testing pads for testing the LEDs in one zone or in the plurality of zones at a time. In one embodiment, if the LEDs1in any one of the plurality zone on the wafer100is damaged or failed, the LEDs1in other zones can still be selectively turned on to measure the photoelectric characteristics of the LEDs in these zones. For example, if any of the LEDs1in the first zone Z1are damaged or failed, the LEDs1in the second zone Z2to the fourth zone Z4can be selectively tested. As a result, the efficiency of the LED testing can be improved. In addition, if a part of the LEDs1in one zone on the wafer100are damaged or failed, the other LEDs1in the present zone can still be selectively turned on, and the photoelectric characteristics of the other LEDs1can be measured. For example, when the overall yield of the LEDs1in the first zone Z1meets user's specifications and the first zone Z1is identified as a compliant zone, even a part of the LEDs1in the first zone Z1are damaged or failed, the other LEDs1in the first zone Z1can still be tested. In addition, the testing circuit in the present application has the functions of regional testing and selective testing. During the testing process, the location of the LEDs1can be obtained through the testing apparatus. As described in the above embodiments, the wafer100is divided into a plurality of zones such as the first zone Z1to the fourth zone Z4. Through the optical lens of the testing system, the position such as the coordinate of each LED1in each zone and the coordinates of each zone in the wafer100can be obtained. In any of the first zone Z1to the fourth zone Z4, the testing system can perform luminance measurement, spectroradiometer measurement, near-field measurement, or photoluminescence (PL) measurement. Through the optical lens of the testing system, each LED1can be identified and its location can be defined. The measurement result can be represented by the coordinates. For example, during testing the LEDs1the first zone Z1to the fourth zone Z4by probes at a time, when an LED1in the second zone Z2is identified as a defective LED according to the obtained image, the coordinates of the second zone Z2on the wafer100and the coordinates of the defective LED1in the second zone Z2can be obtained by the testing system. The position such as the coordinates of the LED1can be used for the following process. In one embodiment, the defective LED is removed and then the other LEDs are transferred. In another embodiment, during the process of transferring the LEDs1to a temporary carrier and removing the substrate10, the defective LED can be removed together with the substrate10. In another embodiment, during the process of transferring the LEDs1to the temporary carrier, the defective LED is not transferred to the temporary carrier and the other LEDs are transferred to the temporary carrier. In another embodiment, the defective LED can be repaired after the process of transferring the LEDs1is completed. The transferring process described above includes transferring the LEDs to the temporary carrier, to the target carrier or to the module carrier. In one embodiment, the repairing method includes removing the defective LED from the target carrier or the module carrier, and placing a good LED as a substitute at the position of the defective LED. In another embodiment, the repairing method includes providing a backup circuit on the target carrier or the module carrier. A good LED is placed on the vicinity of the defective LED, connected and driven by the backup circuit while the defective LED is not removed from the target carrier or the module carrier. In another embodiment, if the defective LED is removed from the substrate before the process of transferring or is not transferred, the corresponding position thereof on the temporary carrier, the target carrier or the module carrier is vacant. A good LED can be placed on the vacant position of the defective LED as a substitute. Next, in the step S4after the step S3of testing the plurality of LEDs1, the testing circuit on the wafer100is removed, the wafer100is joined to another substrate, such as a temporary carrier101, and the substrate10is removed. As shown inFIG.6, the wafer100is joined to the temporary carrier101with a bonding layer16, and then the substrate10is removed by, for example, a laser lift-off or chemical lift-off method, to expose the semiconductor stack12. In one embodiment, the temporary carrier101includes glass, sapphire substrate, or polymer materials such as acrylic and polycarbonate (PC). In one embodiment, after removing the testing circuit, the wafer100can be cut into a plurality of sub-wafers100′ as shown inFIG.7corresponding to the first zone Z1to the fourth zone Z4, and the plurality of sub-wafers100′ are joined to the temporary carrier101, and then the substrates10in each of the sub-wafers100′ is removed to expose the semiconductor stack12. After removing the substrate10, the LEDs1are tested in an optional step S5to measure the characteristics, such as photoelectric characteristics, of the LEDs that are transferred to the temporary carrier101. A testing circuit is formed on and around the LEDs1like the testing circuit formed in the step S3, but being different from the testing circuit formed in the step S3, any of the testing circuits described in the aforementioned embodiments is formed on the surface of the temporary carrier101as shown inFIG.6.FIG.6shows an example of the first branch wire401a′ and the second branch wire401b′ of the testing circuit. When joining the wafer100and the temporary carrier101, the first electrode20and the second electrode30of the LED1are respectively connected to the first branch wire401a′ and the second branch wire401b′ through a conductive adhesive layer32so that the LED1and the testing circuit on the temporary carrier101are electrically connected. In one embodiment, the conductive adhesive layer32includes metal, such as solder, Au—Sn eutectic, or other metal (gold, indium) bonding techniques. The details of the testing method in the step S5is the same as the aforementioned step S3and is not be repeated here. AlthoughFIG.6does not show the whole testing circuit on the temporary carrier101, people having ordinary skill in the art can understand that the testing circuit on the temporary carrier101can include the wiring layouts shown inFIGS.4A-4D, a parallel connection, and a series-parallel connection. In this step, the testing pad (not shown inFIG.6) on the temporary carrier101can be used to perform regional testing on the LEDs1. Similar to the embodiment inFIG.3, the temporary carrier101is divided into a plurality of zones and the testing circuit is formed in each zone. The LED group G1can be tested in each zone. In another embodiment, the testing step S5is not performed. In this case, the temporary carrier101does not have the testing circuit and the conductive adhesive layer32formed thereon. In one embodiment, the temporary carrier101includes one zone or a plurality of zones of the LED groups G1. When the one zone or any one of the plurality of zones includes a defective LED, the position of the defective LED can be defined and recorded by the testing method in accordance with aforementioned step S3and/or the step S5. Next, in the step S6, the LEDs1on the temporary carrier101are transferred. For example, the LEDs1are transferred from the temporary carrier101to the target carrier or the module carrier by group, and then an end-product manufacturing process or a module manufacturing process is performed, as shown in the step S7inFIG.1. For example, a wavelength conversion material, such as a phosphor material or a quantum dot material, is formed on the LEDs1that have been transferred and an encapsulation material is coated to form a packaging module, and then a display panel is assembled in subsequent processes. In one embodiment, the target carrier includes a display backplane. In one embodiment, the LEDs1are taken up from the temporary carrier101by picking or sucking, and then placed on the target carrier or the module carrier. In one embodiment, the LED groups in the plurality of zones on the temporary carrier101can be classified according to the photoelectric characteristics thereof. The plurality of LED groups with the same photoelectric characteristic, that is, the plurality of LED groups in the same classification, can be placed on a carrier board (not shown). The same photoelectric characteristic can be the same wavelength. In one embodiment, the average wavelength of each of the LED groups can be measured. Then, the plurality of LED groups with the same average wavelength which is included in one classification is joined to the same carrier board. The plurality of LED groups of different classifications can be respectively joined to different regions on the same carrier board or to different carrier boards according to user's requirement. Next, the LEDs are taken up from the carrier board by picking or sucking, and then placed on the target carrier or the module carrier. In another embodiment, the temporary carrier101can be divided into a plurality of individual sections according to the plurality of zones, and then the LED groups on the individual sections are classified according to the photoelectric characteristics thereof. The subsequent processes such as joining to the carrier board and transferring to the target carrier or the module carrier are the same as described above. After removing the substrate10, the testing process is performed to inspect whether any defective LEDs exist after the substrate10is removed. In one embodiment, the defective LEDs can be removed in accordance with the coordinates thereof, and then the other LEDs are transferred to the target carrier or the module carrier. In another embodiment, the defective LED is not transferred to the target carrier or the module carrier and only the other the other LEDs are transferred. In another embodiment, the defective LED can be repaired on the target carrier or the module carrier after being transferred. In another embodiment, if the defective LED is removed from the substrate before the process of transferring or is not transferred to the temporary carrier, the corresponding position thereof on the target carrier or the module carrier is vacant after transferring. A good LED can be placed on the vacant position of the defective LED as a substitute. In another embodiment, similar to the embodiments mentioned above, the difference is that after the step S3is completed, only part of the process in the step S4is then performed; that is, the testing circuit on the wafer100is removed after testing, but the processes of joining the wafer100to the temporary carrier101and removing the substrate10are not performed. In one embodiment, the wafer100is divided into a plurality of sub-wafers100′ as shown inFIG.7corresponding to first zone Z1to the fourth zone Z4after removing the testing circuit. In another embodiment, after the step S3is completed, the step S6is subsequently preformed and the steps S4and S5are skipped. The LEDs1on the substrate10are transferred to the target carrier or the module carrier by group after removing the testing circuit, and then an end-product manufacturing process or a module manufacturing process as shown in the step S7inFIG.1is performed. It will be apparent to those having ordinary skill in the art that various modifications and variations can be made to the devices in accordance with the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure covers modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents. | 34,916 |
11862752 | DETAILED DESCRIPTION Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics. Referring toFIG.1, an embodiment of a method of manufacturing at least one light-emitting diode (LED), for instance, a gallium nitride (GaN)-based LED, according to the disclosure includes the following steps. First, in step (a), referring toFIG.2, a substrate100is provided. The substrate100has an upper surface S11, a lower surface S12that is opposite to the upper surface S11, and a side surface S13that interconnects the upper surface S11and the lower surface S12. The substrate100may be a growth substrate, or a non-growth substrate. Examples of the substrate may include, but are not limited to, a plain sapphire substrate, a patterned sapphire substrate, a silicon substrate, a silicon carbide substrate, a GaN substrate, and a glass substrate. In this embodiment, the substrate100is a patterned sapphire substrate. Then, in step (b), a distributed Bragg reflector (DBR) structure110is formed on the upper surface S11of the substrate100. The configuration and composition of the DBR structure110according to this disclosure will be described later. Afterwards, in step (c), a semiconductor layered structure130is formed on the DBR structure110opposite to the substrate100by e.g., metal-organic chemical vapor deposition (MOCVD). The semiconductor layered structure130may include an n-type semiconductor layer, an active layer and a p-type semiconductor layer that are sequentially disposed on the DBR structure110. The semiconductor layered structure130is configured to emit a light having a first wavelength. The first wavelength may range from 400 nm to 800 nm, for instance, blue light, cyan light, and green light. The DBR structure110may have a reflectance of not greater than 30% for the light emitted from the semiconductor layered structure130, and a reflectance of not smaller than 50% for another light having a second wavelength which is different from the first wavelength (i.e., not emitted from the semiconductor layered structure130). In certain embodiments, the another light may be a laser beam suitable for used in a dicing process in the subsequent steps. In this embodiment, before step (c), the method further includes a step of forming a buffer layer120on the DBR structure110opposite to the substrate100by, e.g. physical vapor deposition (PVD). The buffer layer120may be made of an AlN-based material. The buffer layer120may have a thickness ranging from 10 nm to 100 nm. The semiconductor layered structure130is then formed on the buffer layer120opposite to the DBR structure110in step (c). Alternatively, for step (c), in certain embodiments of the method, the semiconductor layered structure130which is first epitaxially grown and formed on another substrate (such as a GaAs growth substrate) is transferred to the substrate100through a transparent bonding layer formed on the the DBR structure110, followed by removal of the another substrate. That is, the semiconductor layered structure130is bonded to the DBR structure110opposite to the substrate100through the transparent bonding layer. The dicing process which includes the following steps (d) and (e) may be further conducted to cut the product obtained in step (c). Referring toFIGS.3and4, in step (d), laser scribing is performed on the semiconductor layered structure130using a first laser beam. The reflectance of the DBR structure110for the first laser beam having the second wavelength is not smaller than 50%. For example, the second wavelength of the first laser beam used in laser scribing may be 365135 nm. Specifically, in this embodiment, step (d) is conducted by laser scanning a top surface of the semiconductor layered structure130opposite to the substrate110along a first direction (A) and a second direction (B) which traverses (e.g., perpendicular to) the first direction, so as to form scribe trenches200in a network form as shown inFIG.3. Each of the scribe trenches200may have a depth ranging from 5 μm to 10 μm, and may extend through the semiconductor layered structure130and the buffer layer120to expose the substrate100. The scribe trenches200may be further subjected to an etching process using a chemical etching solution, such that the semiconductor layered structure130is tapered inwardly toward the DBP structure110. The buffer layer120may also be tapered inwardly toward the DBR structure110through an etching process. Referring toFIG.5, in step (e), stealth dicing is performed from the lower surface S12of the substrate100using a second laser beam different from the first laser beam. The reflectance of the DBR structure110for the second laser beam is not smaller than 50% (such as not smaller than 60%, or not smaller than 90%). For example, the second wavelength of the second laser beam used in stealth dicing may be 1064±100 nm. Specifically, during stealth dicing, the second laser beam which is focused on interior parts of the substrate100is scanned along dicing lanes corresponding in position to the scribe trenches200. The scans of the second laser beam may be conducted multiple times depending on a thickness of the substrate100, where the second laser beam is focused at different depths of the substrate100, so as to obtain a plurality of inscribed features101. For example, when the substrate100has a thickness of 100 μm to 150 μm, the scans of the second laser beam are scanned at least three times to obtain at least 3 inscribed features101at different depths of the substrate100. When the substrate100has a thickness of 150 μm to 200 μm, at least 4 inscribed features101are formed by performing laser scans at least four times. When the substrate100has a thickness greater than 200 μm, at least 5 inscribed features101are formed by performing laser scans at least five times. That is, the inscribed features101may be formed in a predetermined pattern. For example, one of the inscribed features101that is most adjacent to the upper surface S11of the substrate100may be spaced apart therefrom by a distance less than 20 μm (e.g., 1 μm to 10 μm), or even less than 5 nm. Each of the immediately adjacent inscribed features101may be spaced part from each other by 10 μm to 30 μm. Referring toFIG.6, after step (d), the semiconductor layered structure130is subjected to a photolithographic process using a photoresist mask, such that the n-type semiconductor layer of the semiconductor layered structure is partially exposed. A p-type electrode141is disposed on the p-type semiconductor layer, and an n-type electrode142is disposed on the exposed n-type semiconductor layer. Then, the substrate100may be further subjected to a grinding process, and a breaking process is conducted along the scribe trenches200and the inscribed features101, so as to obtain a plurality of the LEDs of this disclosure. For each of the LEDs thus obtained, the side surface S13of the substrate100may have the inscribed features101of stealth dicing. The inscribed features101may be evenly distributed throughout the side surface S13or may be present in a predetermined pattern, as described above, on the side surface S13. It should be noted that the abovementioned method for manufacturing the at least one LED does not require the adoption of both laser scribing and stealth dicing. In certain embodiments, only the stealth dicing may be performed to form the inscribed features101in the substrate100, followed by the breaking process to form individual LEDs. According to this disclosure, an embodiment of the light-emitting diode (LED) manufactured by the abovementioned method is provided and includes the substrate100, the DBR structure110, and the semiconductor layered structure130(seeFIG.6). The DBR structure110is disposed on the upper surface S11of the substrate100and is configured to highly reflect a laser beam used in the desired dicing process, and minimally reflect the light emitted from the semiconductor layered structure130. In this embodiment, the DBR structure110has a reflectance of not greater than 30% (such as not greater than 20% or not greater than 10%) for the light which is emitted by the semiconductor layered structure130and which has the first wavelength ranging from 400 nm to 800 nm. The DBR structure110has a reflectance of not smaller than 50% (such as not smaller than 60% or about 90%) for the laser beam which may be the one used for the abovementioned dicing process, e.g., laser scribing or stealth dicing. For example, the second wavelength of the laser beam may be 365±35 nm (used for laser scribing) and 1064±100 nm (used for stealth dicing). Specifically, the DBR structure110may include a first layered unit which includes a plurality of pairs of layers, and each pair includes a first high refractive index layer and a first low refractive index layer. The first high refractive index layers and the first low refractive index layers in the first layered unit are alternately stacked. Each of the first high refractive index layers may be made of a material including, but not limited to TiO2, Nb2O5, Ta2O5, HfO2, ZrO2, ZnO, LaTiO3, and combinations thereof. Each of the first low refractive index layers may be made of a material including, but not limited to SiO2, MgF2, Al2O5, SiON, and combinations thereof. Each of the first high refractive index layers and the first low refractive index layers may have an optical thickness of (¼)×k1×λ1, wherein 1000 nm<λ1<1200 nm, and k1is an odd number. In certain embodiments, the first layered unit of the DBK structure110may include n pairs of layers, and n≥3 (such as 3, 5, 7, 10, etc.). The reflectance of the DBR structure110for the laser beam may be determined by the composition and configuration of the first layered unit. Fox example, when n is 3, in which each of the first high refractive index layers is made of HfO2and has a thickness of about 126 nm, and each of the first low refractive index layers is made of SiO2and has a thickness of about 182 nm, the DBR structure110may exhibit a reflectance of about 70% for the laser beam having a wavelength of 1064±100 nm. When n=5, the DBR structure110may exhibit a reflectance of about 90% for the laser beam having a wavelength of 1064-100 nm. When n=7 or more, the DBF structure110may exhibit a reflectance of greater than 90% for the laser beam having a wavelength of 1064±100 nm. While the DBR structure110including more pairs of layers may increase reflectance for the laser beam used for laser cutting, such DBR structure110may be too thick to be further processed. Thus, in certain embodiments, the DBR structure110includes 5 to 18 of the pairs of layers. In certain embodiments, the DBR structure110may further include a second layered unit disposed on the first layered unit opposite to the substrate100. The second layered unit includes a plurality of pairs of layers, each pair including a second high refractive index layer and a second low refractive index layer and the second high refractive index layers and the second low refractive index layers in the second layered unit being alternately stacked. Each of the second high refractive index layers has an optical thickness different from that of each of the first high refractive index layers, and each of the second low refractive index layers has an optical thickness different from that of each of the first low refractive index layers. Each of the second high refractive index layers and the second low refractive index layers may have an optical thickness of (¼)×k2×λ2, wherein 350 nm<λ2<380 nm, and k2is an odd number. Examples of a material for making each of the second high refractive index layers may include, but are not limited to TiO2, Nb2O5, Ta2O5, HfO2, ZrO2, ZnO, LaTiO3, and combinations thereof. Examples of a material for making each of the second low refractive index layers may include, but are not limited to, SiO2, MgF2, Al2O5, SiON, and combinations thereof. In certain embodiments, the first and second layered units of the DBR structure110may respectively include n and m pairs of layers, where n≥3 and m≥2. In the following examples, different DBR structures110with different configuration (i.e., different pairs of layers) are prepared and analyzed to determine the reflectance thereof for light with various wavelengths. Examples 1 and 2 (E1 and E2) In each of E1 and E2, the DBR structure110includes the first layered unit which includes n pairs (n is 3 for E1 and n is 5 for E2) of the first high refractive index layers and the first low refractive index layers. Each of the first high refractive index layers is made of HfO2(with a refractive index of 2.1) and has a thickness of 126.19 nm (corresponding optical thickness is 265 nm), and each of the first low refractive index layers is made of SiO2(with a refractive index of 1.46) and has a thickness of 182.80 nm (corresponding optical thickness is 266.89 nm). The results of the spectral reflectance of the DBR structure for E1 and E2 are shown inFIGS.7and8, and are also summarized in Table 1, where for E1 and E2, R1 represents reflectance for 400 nm to 800 nm, R2 represents reflectance for 1000 nm to 1100 nm, and R3 represents reflectance for 350±20 nm. Examples 3 and 4 (E3 and E4) The DBR structures110of E3 and E4 are generally similar to those of E1 and E2, respectively, except that in E3 and E4, the first layered unit of the DBR structure110includes m pairs of layers (m is 3 for E3 and m is 5 for E4), and each of the first high refractive index layers and the first low refractive index layers has an optical thickness of (¼)×k×λ, wherein 350 nm<λ<380 nm, and k is an odd number. Specifically, each of the first high refractive index layers has a thickness of 42.26 nm (corresponding optical thickness is 88.75 nm), and each of the first low refractive index layers has a thickness of 60.79 nm (corresponding optical thickness is 88.75 nm). The results of the spectral reflectance of the DBR structure for E3 and E4 are shown inFIGS.9and10, and are also summarized in Table 1, where for E3 and E4, R1 represents reflectance for 435 nm to 700 nm, R2 represents reflectance for 1000 nm to 1100 nm, and R3 represents reflectance for 350120 nm. Examples 5 to 9 (E5 to E9) The DBR structures110of E5 to E9 are generally similar to that of E1, except that in E5 to E9, the DBR structure110further includes the second layered unit. That is, in the DBR structures110of E5 to E9, the first layered unit includes n pairs of layers and the second layered unit includes m pairs of layers, and the n and m values for each example are shown in Table 1. In addition, each of the first high refractive index layers is made of HfO2and has a thickness of 126.19 nm (corresponding optical thickness is 265.00 nm), and each of the first low refractive index layers is made of SiO2and has a thickness of 182.80 nm (corresponding optical thickness is 266.89 nm). Each of the second high refractive index layers is made of HfO2and has a thickness of 42.26 nm (corresponding optical thickness is 88.75 nm), and each of the second low refractive index layers is made of SiO2, and has a thickness of 60.79 nm (corresponding optical thickness is 88.75 nm). The results of the spectral reflectance of the DBR structure for E5 to E9 are shown inFIGS.11to15, and are also summarized in Table 1, where for E5 to E9, R1 represents reflectance for 435 nm to 700 nm, R2 represents reflectance for 1000 nm to 1100 nm, and R3 represents reflectance for 350120 nm. TABLE 1nmR1 (%)R2 (%)R3 (%)E1FIG. 73—<10~7050 to 70E2FIG. 85—<20~9060 to 90E3FIG. 9—3<30<1060 to 70E4FIG. 10—5<30<1080 to 90E5FIG. 1132<3055 to 7080 to 90E6FIG. 1253<30>9080 to 95E7FIG. 1377<30>95>95E8FIG. 141010<25~99~99E9FIG. 151515<30~99~99Note:“—” indicates not applicable. As shown in Table 1, each of the DBR structures110of E1 to E9 exhibits a reflectance of not greater than 30% (such as less than 20% or even 10% in E1 and E2) for light having wavelength of about 400 nm to about 800 nm, indicating the DBR structure110of the LED according to this disclosure is capable of allowing passage of a majority of the light emitted from the semiconductor layered structure130(e.g., blue light, cyan light, green light). In addition, each of the DBR structures110of E1 to E9 exhibits a reflectance of not lower than 50% (such as not lower than 60%, even 80% or about 90%) for light having wavelength of 350±20 nm, indicating that the DBR structure110of the LED structure is capable of effectively reflecting a laser beam used for laser scribing (365±35 nm) on the semiconductor layered structure130, so as to prevent the laser beam from damaging the upper surface S1lof the substrate100during the manufacturing processes thereof. Additionally the DBR structures110of E1, E2 and E5 to E9 even exhibit a reflectance of greater than 50%, such as approximately 70%, or even approximately 90%, for light having a wavelength of 1000 nm to 1100 nm, which is highly conducive to preventing the laser beam used in stealth dicing from damaging the semiconductor layered structure130. Therefore, during the stealth dicing process of the LED of this disclosure, the laser beam can be focused at a location more adjacent to the semiconductor layered structure130, and may scan the substrate110more times without causing damage to the semiconductor layered structure130due to the presence of the DBR structure100, such that the side surface S13of the substrate100can have an improved roughness, so as to increase the light extraction efficiency of the LED of this disclosure. Furthermore, it can be inferred from the results of E5 to E9 that when n≥5 and m≥3, the DBR structures110exhibit R1, R2, R3 values that are at a good compromise, each of the values having satisfactory reflectance at different wavelengths. To conclude, by including the DBR structure110having a reflectance of not greater than 30% for the light emitted from the semiconductor layered structure130, and a reflectance of not smaller than 50% for a laser beam used for desired dicing process (with a wavelength different from the light emitted from the semiconductor layered structure130), the LED according to the disclosure can be manufactured by adopting different laser dicing process without damaging the substrate100and the semiconductor layered structure130. In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure. While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. | 20,034 |
11862753 | DETAILED DESCRIPTION Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics. Referring toFIG.1, a light-emitting diode (LED) structure in accordance with an embodiment of the disclosure includes a substrate10, a first type semiconductor layer20, a stress relief layer30, an active layer40, a second type semiconductor layer50, a first electrode61, and a second electrode62. The first type semiconductor layer20is disposed on the substrate10. The stress relief layer30is disposed, on the first type semi conductor layer20opposite to the substrate10, and includes at least one first repeating unit. The first repeating unit contains a first well layer31and a first barrier layer32that are alternately stacked. The active layer40is disposed on the stress relief layer30opposite to the first type semiconductor layer20, and includes one second repeating unit. The second repeating unit contains a second well layer41and a second barrier layer42that are alternately stacked. The second type semiconductor layer50is disposed on the active layer40opposite to the stress relief layer30. The first electrode61is electrically connected to the first type semiconductor layer20. The second electrode62is electrically connected to the second type semiconductor layer50. The first well layer31is made of a material including In. The second well layer41is made of a material including In. The second barrier layer42is formed with multiple sub-layers, each of which is made of a material including Al. The substrate10is selected from the group consisting of sapphire (Al2O3), SiC, GaAs, GaN, ZnO, Si, GaP, InP, Ge, and combinations thereof. Preferably, the substrate10is made of sapphire, such as a plane sapphire substrate or a patterned sapphire substrate (PSS, not shown), but is not limited thereto. A multi-layered semiconductor, which is layer-by-layer disposed on one of a surface of the substrate10such as c-plane of PSS, includes the first type semiconductor layer20doped with n-type dopants, the second type semiconductor layer50doped with p-type dopants, and the active layer40for emitting light. That is, the first type semiconductor layer20is an n-type semiconductor layer, and the second type semiconductor layer50is a p-type semiconductor layer. The multi-layered semiconductor may be made of group III-V nitride-based materials, such as GaN, InN, AlN, InGaN, AlGaN and/or AlInGaN, etc., but are not limited thereto. Examples of n-type dopants may be Si, Ge, Sn, Te, O, C, etc., and examples of p-type dopants may be Mg, Zn, Be, Ca, etc., but are not limited thereto. Referring toFIG.2, a structure of the stress relief layer30and the active layer40in accordance with the embodiment of the disclosure is illustrated. The active layer40is a region where electron-hole recombination occurs and energy of electron-hole recombination emerges as photons of light. In some embodiments, the active layer40includes a multi-quantum well structure. The active layer40is formed as a superlattice structure having the second well layer41and the second barrier layer42that are periodically and alternately stacked. In some embodiments, the active layer40has at least two repeating units, and the second well layers41and the second barrier layers42of the repeating units are alternately stacked on one another. The number of the repeating units can be reduced by increasing a thickness of the second well layer41or the second barrier layer42. In some embodiments, the second well layer41is made of a material including In. The second well layer41may be formed as a single-layer structure or a multi-layered structure having multiple sub-layers. In the case that the second well layer41has a multi-layered structure, the In contents of the sub-layers of the multi-layered structure of the second well layer41may be different from one another, e.g., adjusting the In contents of the sub-layers to be varied in certain sequence or adjusting a thickness of each of the sub-layers, so that the energy bandgaps of the sub-layers of the multi-layered structure of the second well layer41may be different and adjustable. The second barrier layer42is made of a material including Al, and may be formed as a multi-layered structure having multiple sub-layers, each of which is made of a material including Al. Similarly, the Al contents of the sub-layers of the multi-layered structure of the second barrier layer42may be different from one another, e.g., adjusting the Al contents of the sub-layers of the second barrier layer42to be varied in certain sequence or adjusting a thickness of each of the sub-layers of the second barrier layer42, so that the energy bandgaps of the sub-layers of the multi-layered structure of the second, barrier layer42may be different and adjustable. Conventionally, the active layer40is directly disposed on the first type semiconductor layer20(i.e., the n-doped semiconductor layer). However, a mismatch of lattice constant and coefficient of thermal expansion between the active layer40and the first type semiconductor layer20would induce stress, thus generating a lot of cracks and defects in materials, resulting in a leakage current path in multiple semiconductor layers thus formed. In addition, the lattice mismatch would also lead to piezoelectric polarisation which induces bending of an energy band structure of the active layer40, resulting in internal quantum efficiency droop, which is the so-called quantum confined Stark effect. Therefore, in this embodiment, the stress relief layer30is disposed between the active layer10and the first type semiconductor layer20(i.e., the n-doped semiconductor layer) to lower a defect density and reduce the stress of multi-quantum well in the active layer40to obtain a higher luminous intensity. The stress relief layer30is formed as a superlattice structure having the first well layer31and the first barrier layer32that are periodically and alternately stacked. In sortie embodiments, the stress relief layer30has at least two repeating units, and the first well layers31and the first barrier layers32of the repeating units of the stress relief layer30are alternately stacked on one another. The number of the repeating units of the stress relief layer30can be reduced by increasing a thickness of the first well layer31or that of the first barrier layer32. In some embodiments, the first well layer31is made of a material including In, and may be formed as a single-layer structure or a multi-layered structure having multiple sub-layers. In the case that the first well layer31has a multi-layered structure, the In contents of the sub-layers of the multi-layered structure of the first well layer31may be different from one another, e.g., adjusting the In contents of the sub-layers to be varied in certain sequence or adjusting a thickness of each of the sub-layers, so that the energy bandgaps of the sub-layers of the multi-layered structure of the first well layer31may be different and adjustable. The first barrier layer32is made of an Al-containing or an Al-free material, and may be formed as a single-layer structure or a multi-layered structure having multiple sub-layers. In some embodiments, the energy bandgap(s) of the sub-layer(s) of the first barrier layer32is adjustable by changing the Al content or a thickness of the sub-layer(s) of the first barrier layer32. In some embodiments, the material for making the first well layer31is represented by a chemical formula of Inx1Ga(1-x1)N, and the material for making the first barrier layer32is represented by a chemical formula of Aly1Inz1Ga(1-y1-z1)N, where 0<x1≤1, 0≤y1≤1, and 0≤z1≤1. The material for snaking the second well layer41is represented by a chemical formula of Inx2Ga(1-x2)N, and the material for making the second barrier layer42is represented by a chemical formula of Aly2Inx2Ga(1-y2-z2)N, where 0<x2≤1, 0≤y21, and 0≤z2<1. In certain embodiments, the first well layer31is made of InGaN, the first barrier layer32is made of GaN, the second well layer41is made of InGaN, and the second barrier layer42is made of AlGaN, where x1 ranges from 0.02 to 0.2, x2 ranges from 0.15 to 0.35 and y2 ranges from 0.15 to 0.35. In some embodiments, when x2 ranges from 0.15 to 0.25, the LED is configured to emit blue light, and when x2 ranges from 0.15 to 0.35, the LED is configured to emit green right. An energy bandgap of a group III-V compound semiconductor will be varied according to its alloy composition. Hence, the energy bandgap of a semiconductor material can be altered by controlling the alloy composition of the same to meet desired corresponding properties. In this disclosure, the stress relief layer30has an average energy bandgap that is smaller than an average energy bandgap of the active layer40. In some embodiments, the first well layer31has an energy bandgap that is greater than an energy bandgap of the second well layer41by adjusting the In contents of the same, and the first barrier layer32has an energy bandgap that is smaller than an energy bandgap of the second barrier layer42by adjusting the Al contents of the same. Therefore, the first well layer31has an In content that is smaller than that or the second well layer41. By adjusting the alloy composition, the quality of epitaxial growth of the active layer40can be further improved. A conventional LED faces a technical dilemma between a reduction in efficiency droop and an improvement in the quality of epitaxial growth of a barrier layer with quantum wells. The conventional LED is prone to have efficiency droop induced by piezoelectric polarization under high current density. One conventional approach to improve efficiency droop is to make the barrier layer with quantum wells in an active layer thinner, however, such approach would result in a lower epitaxial growth quality of the barrier layer which affects the quality of the active layer. Conventionally, an active layer that is thick tends to guarantee a good quality of quantum wells. In comparison to the conventional active layer having a thicker barrier layer to achieve a better epitaxial growth quality of multi-quantum well, which leads to higher light attenuation, in this disclosure, a thinner barrier layer with quantum wells (i.e., the second barrier layer42) under the premise of maintaining a nigh quality epitaxial growth of the active layer40can be achieved by adjusting the Al content (y2) in each of the sub-layers of the multi-layered structure of the second barrier layer42. Referring toFIG.1, in some embodiments, the first electrode61is disposed on an electrode contact region of the first type semiconductor layer20, which is an upper surface of the first type semiconductor layer20spaced apart from the stress relief layer30, and the second electrode62is disposed on the first type semiconductor layer50, so as to form a horizontal LED structure. In some embodiments, the first type semiconductor layer20is formed as a multi-layered structure having multiple sub-layers. The sub-layer in the electrode contact region farthest away from the substrate10is doped with n-type dopant, such as Si, Ge, Sn, Te, O, C, etc., but are not limited thereto, and this sub-layer of the electrode contact region in contact with the first electrode61has a doping concentration that is greater than 8×1018cm−3. The electrode contact region is formed by an etching process to remove from top to down, portions of the second type semiconductor layer50, the active layer40, the stress relief layer30and the first type semiconductor layer20, and then the etching process is stopped at the first type semiconductor layer20, so that an upper surface of the first type semiconductor layer20which is relatively far away from the substrate10is exposed. The etching process is selected from dry etching with plasma or wet etching with corrosion using a mixed acid solution. The LED further includes a buffer layer21disposed on the first type semiconductor layer20opposite to the stress relief layer30so as to alleviate a lattice mismatch between the substrate10and the first type semiconductor layer20. A material of the buffer layer21includes undoped GaN (uGaN) or AlN, etc., but is not limited thereto. Mobility of electrons, which are a major carrier in the first type semiconductor layer20, is higher than mobility of holes, which are a major carrier in the second type semiconductor layer50. Hence, the electrons tend to overflow to the second type semiconductor layer50, which reduces luminous efficiency of the LED. Therefore, in some embodiments, the LED further includes an electron blocking layer70disposed between the second type semiconductor layer50and the active layer40for blocking the electron overflow. A material of the electron blocking layer70includes AlGaN, but is not limited thereto. The electron blocking layer70has a much higher energy bandgap than that of the active layer40and the first type semiconductor layer20, so that the electron blocking layer70functions as a buffer or a barrier to electrons, and further increases luminous efficiency, reduces forward voltage of the LED chip, reduces energy consumption and extends lifetime of LED. The LED further includes a current spreading layer90disposed be tureen the second type semiconductor layer50and the second electrode62. In the absence of the current spreading layer90, due to doping concentration of p-type dopant in the second type semiconductor layer50being lower than that of n-type dopant in the first type semiconductor layer20, a good ohmic contact could not be formed between the second electrode62(i.e., P-type electrode) and the second type semiconductor layer50(i.e., p-type semiconductor layer). Hence, the current spreading layer90aims to reduce the contact resistance of the contacting surface between the second type semiconductor layer50and the second electrode62. Examples of the material suitable for forming the current spreading layer90include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), nickel oxide (NiO), cadmium tin oxide (CTO), ZnO:Al, ZnGa2O4, SnO2:Sb, Ga3O:Sn, AgInO2:Sn, In2O3:Zn, CuAlO2, LaCuOS, CuGaO2, SrCu2O2, and combinations thereof, but are not limited thereto. Preferably, the current spreading layer90is made of ITO owing to excellent transparency of ITO. The LED further includes a current blocking layer80disposed between the second type semiconductor layer50and the current spreading layer90. In the conventional LED, a current flow tends to choose the shortest path from the second electrode62to the first electrode61. Hence, the current tends to accumulate below the second electrode62, and flows vertically through the second type semiconductor layer50and the active layer40. That is, the current only flows through a central region of the second type semiconductor layer50and the active layer40, and not through a surrounding region of the second type semiconductor layer50and the active layer40, i.e., a phenomenon known as current crowding effect. Hence, electrons and holes in the surrounding region of the second type semiconductor layer50and the active layer20can not be activated, and electron-hole recombination only occurs in the central region of the second type semiconductor layer50and the active layer25where the energy of electron-hole recombination emerges as photons of light. In order to improve the phenomenon of current-crowding effect below the second electrode62, the current blocking layer80is disposed on the second type semiconductor layer50(i.e., p-type semiconductor layer). The current blocking layer80has a projected image on the substrate10the same with that of the second electrode62(i.e., P-type electrode), i.e., the current blocking layer30has a top-down correspondence relationship with the second electrode62. The current blocking layer80is generally formed of insulators without conductivity, so that the current injected from the second electrode62tends to first flow horizontally along a surface of the current blocking layer50, and then is vertically injected into the second type semiconductor layer50(i.e., P-type semiconductor layer) rather than flowing vertically through the current blocking layer80directly. Thus, the phenomenon of current crowding effect below the second electrode62(i.e., P-type electrode) is improved. In this embodiment, the current blocking layer80only has a top-down correspondence relationship with the second electrode62, that is, the current blocking layer80only partially covers the second type semiconductor layer50. Evidently, if the current blocking layer80entirely covers the second type semiconductor layer50, the LED will be inefficient in emitting light. Hence, in some embodiments, the current spreading layer90is disposed on the remaining region of the second type semiconductor layer50which is not covered by the current blocking layer80to facilitate current spreading. The LED further includes a contact resistance reducing layer51disposed between the second type semiconductor layer50and the second electrode62. In some embodiments, the contact resistance reducing layer51is disposed between the second type semiconductor layer50and the current spreading layer90to reduce the contact resistance of the contacting surface between the second type semiconductor layer50and the current spreading layer90. The first electrode €1and the second electrode62are both formed as metal electrodes, and are independently formed as a multi-layered structure having multiple metal sub-layers made of multiple materials. Examples of the material suitable for forming the first electrode61and the second electrode62include nickel (Ni), palladium (Pd), platinum. (Pt), chromium (Cr), gold (Au), titanium (Ti), silver (Ag), aluminum (Ax), germanium (Ge), tungsten (W), tungsten silicide (SiW), Tantalum (Ta), Au—Zn alloy (AuZn), Au—Be alloy (AuBe), Au—Ge alloy (AuGe), Au—Ge—Ni alloy (AuGeNi), and combinations thereof, but are not limited thereto. In some embodiments, a metal sub-layer of the second electrode62closest to the substrate10and in contact with the current spreading layer30is made of a metal (e.g., Au) that has a good adhesion, a low contact resistance and a high conductivity. An embodiment of a method for making an LED of the disclosure includes the steps of preparing a substrate IQ, forming a first type semiconductor layer20on a surface of the substrate10, forming a stress relief layer30on an upper surface of the first type semiconductor layer20opposite to the substrate10, forming an active layer40the stress relief layer30opposite to the first type semiconductor layer20, forming a second type semiconductor layer50on the active layer40opposite to the stress relief layer30, electrically connecting a first electrode61to the first type semiconductor layer20, and electrically connecting a second electrode62to the second type semiconductor layer50. The step of electrically connecting the first electrode61to the first type semiconductor layer20further includes an etching process implemented by etching away from top to down, portions of the second type semiconductor layer50, the active layer40, the stress relief layer30and the first type semi conductor layer20, and then stopping at the first type semiconductor layer20to expose an electrode contact region for forming the first electrode61. In this embodiment, the first well layer31is made of the material including In, the second well layer41is made of the material including In, the first barrier layer32is made of an Al-containing or an Al-free material, and the second barrier layer42is formed as a multi-layered structure having multiple sub-layers, each of which is made of a material including Al. The energy bandgap of the stress relief layer30and the active layer40can be adjusted by changing material species, dopant concentrations or thickness of the stress relief layer30and the active layer40. In summary, by disposing the stress relief layer30between the active layer40and the first type semiconductor layer20, the stress of multi-quantum well in the active layer40can be reduced to achieve a high quality epitaxial growth of the active layer40. In addition, since the stress relief layer30has an average energy bandgap that is smaller than that of the active layer40, the first well layer31has an energy bandgap greater than that of the second well layer41, and the first barrier layer32has an energy bandgap smaller than that of the second barrier layer42, the quality of epitaxial growth of the active layer40can be further improved. Furthermore, by forming the second barrier layer42in the active layer10as a multi-layered structure having multiple sub-layers that are made of a material including Al, and by adjusting the composition of Al in each of the sub-layers, the second barrier layer42can be made thinner while maintaining a high quality epitaxial growth of the active layer40, in comparison to a conventional active layer with thicker barrier layers, so as to alleviate light attenuation. In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment(s). It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure. While the disclosure has been described in connection with what is (are) considered the exemplary embodiment (s), it is understood that this embodiment(s) is not intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. | 22,720 |
11862754 | DETAILED DESCRIPTION Referring toFIGS.2A-2E, a first step in a method for fabricating light emitting diode (LED) dice includes the steps of providing a substrate30(FIG.2A) and forming a plurality of die sized semiconductor structures32(FIG.2E) on the substrate30. In an illustrative embodiment, the substrate30comprises a sapphire wafer and the semiconductor structures32have a die size and include different layers of compound semiconductor materials formed on the substrate30. The die sized semiconductor structures32can be formed using conventional semiconductor fabrication techniques and physically separated by etching a pattern of criss cross openings38(FIG.2B) to the surface of the substrate30. However, the exact construction of the semiconductor structures32will depend on the type of (LED) dice being fabricated. The GaN layer34(FIG.2E) can be hetero-epitaxially grown on the substrate30(FIG.2E) using techniques that are known in the art. Please note that following the etching process, there is no GaN material in the openings38. To facilitate GaN crystal growth, an initial GaN layer can be deposited at a relatively low temperature, less than 800° C., causing the initial GaN layer to contain a high density of various defects due to a large lattice mismatch. Crystal defects, such as dislocations, nanopipes and inversion domains, elevate surface energy which results in higher absorption of the laser beam. During a subsequent laser-lift off (LLO) step, GaN will quickly decompose to gallium metal vapor and nitrogen gas resulting in explosive force acting on the semiconductor structures32and the substrate30. The die sized semiconductor structures32are much smaller in weight as well as size, compared to the substrate30, such that each semiconductor structure32will have a large force acting on it. In the illustrative embodiment, the semiconductor structures32are measured in microns and the substrate30is measured in millimeters. As also shown inFIG.2E, a laser beam40used for the subsequent laser lift-off (LLO) step has an outline that is larger than the footprint of the die sized semiconductor structures32that one desires to lift off (LLO). In addition, one can lift off more than one die sized semiconductor structure at a time by changing the size of the laser beam40as shown inFIGS.9A-9B. Referring toFIG.3, the method for fabricating light emitting diode (LED) dice also includes the step of providing a receiving plate42coated with an elastomeric polymer layer44. A preferred material for the receiving plate comprises quartz. Exemplary materials for the elastomeric polymer layer44include silicone, siloxane, rubber, or other elastomeric based material. As shown inFIG.3, the receiving plate42can have a size and shape that corresponds to, but is slightly larger than, the size and shape of the substrate30. For example, if the substrate30comprises a circular wafer, the receiving plate42can comprise a circular plate that is slightly larger than the circular wafer. Referring toFIG.4, the method for fabricating light emitting diode (LED) dice also includes the step of placing the substrate30and the receiving plate42in physical contact with an adhesive force applied by the elastomeric polymer layer44. As shown inFIG.4, the semiconductor structures32can have the configuration of vertical light emitting diode (VLED) dice, such that the pad electrodes36provide a spacing of Z1between the semiconductor structures32and the elastomeric polymer layer44. In addition, an adhesive force F is applied to the pad electrodes36by the elastomeric polymer layer44. The die sized semiconductor structure32is still physically connected to the substrate30but physically separated from the adjacent semiconductor structures. Example 1. Referring toFIGS.5and6, an exemplary placing step uses a four inch diameter circular substrate30and a six inch square receiving plate42S. In this example, the elastomeric polymer layer44comprises a curable silicone pressure sensitive adhesive configured to apply the adhesive force. Other suitable materials for the elastomeric polymer layer44include sorbothane and neoprene. One suitable adhesive is disclosed in Japanese Patent Application No. 2020-016200 filed on Feb. 3, 2020, entitled “Addition Curable Silicone Pressure-Sensitive Adhesive Composition and Cured Product Thereof”, which is incorporated by reference. As shown inFIG.5, the placing step can include a first step of placing the substrate30and the receiving plate42S in physical contact, a second step of applying a weight48and curing the elastomeric polymer layer44using the weight48, and a third step of removing the weight48. By way of example, the elastomeric polymer layer44can have an adhesive force of more than 0.08 MPa, <70 type A hardness, and a tensile strength of >0.01 MPa. Table 1 identifies some characteristics of a spin on elastomeric polymer layer44made of silicone. TABLE 1MaterialsSilicone SampleViscosity (Pa-s)3.0-7Spin coating condition2500 RPM × 60 - 180 sec(Target thickness = 20 μm)Standard curing condition150° C.; 30 min - 2 hrHardness (Type A)5-70Tensile strength (MPa)0.5-5Elongation at break (%)90-250Specific gravity (g/cm3)1.03-1.1Sticky force at 200 mm/min (MPa)0.05-0.5 Referring toFIGS.7and8, the method for fabricating light emitting diode (LED) dice also includes the step of performing a laser lift-off (LLO) process. During the laser lift-off process, a uniform laser beam40is directed through the substrate30onto an interfacial semiconductor layer50at the interface with the substrate30to lift off the die sized semiconductor structures32onto the receiving plate42. During the laser lift-off (LLO) process each semiconductor structure32is individually pushed towards the receiving plate42by decomposition of the interfacial semiconductor layer50. For example, with the interfacial semiconductor layer50comprised of GaN, decomposition will be to gallium (G) and nitrogen (N2) in gaseous form. InFIG.7, this explosive force is represented by explosive force arrows52that pass through the semiconductor structure32and are absorbed by the elastomeric polymer layer44on the receiving plate42. The elastomeric polymer layer44acts as a soft cushion or shock absorber to absorb the kinetic energy from the semiconductor structure32via momentum energy transfer. The semiconductor structure32comes to rest on the elastomeric polymer layer44undamaged and stays in the desired position on the receiving plate42. Example 2. An exemplary laser lift-off (LLO) process uses a 248 nm laser beam40, such as a KrF excimer laser with wavelength of λ=248 nm and pulse width of 25 ns. The laser output energy can be varied from 10 nJ to 50 mJ. The laser beam is reshaped and homogenized using a special optical system to form an uniform beam profile, preferably less than 10% RMS. The LLO processing beam passed through a projection system and then focuses onto the wafer/sample with a spot size such as 0.9×0.9 mm2. Other laser beam sizes and shapes can be used. The excimer laser is not limited to KrF (248 nm). For example, the excimer laser can be from a F2 excimer laser (155 nm), to an ArF excimer laser (198 nm). An excimer laser typically uses a combination of a noble gas (argon, krypton, or xenon) and a reactive gas (fluorine or chlorine). The receiving plate42is preferably larger than the substrate30. In addition, the receiving plate42is preferably flat with a TTV (total thickness variation) of less than <5 μm, but more preferably less than <2 um, for preventing flipping, titling, rotating and cracking of the semiconductor structures32after the laser lift-off (LLO) process. In addition, the receiving plate42can include one or more alignment marks for aligning the semiconductor structures32on the substrate30. Proper alignment also ensures proper placement of the semiconductor structure32on the receiving plate42following the laser lift-off (LLO) process (i.e., desired coordinate on the receiving plate42). In addition, the receiving plate42can include one or more notches or flats for pre-alignment. Example 3. Referring toFIGS.9A and9B, in this example, the receiving plate42includes a spin-on elastomeric polymer layer44comprised of a curable silicone pressure-sensitive adhesive composition. Also in this example, the substrate30comprises a four inch diameter wafer, and the receiving plate42comprises a six inch diameter circular plate. Further, the receiving plate42has a TTV (total thickness variation) of <5 μm. For forming the elastomeric polymer layer44the elastomer can be dispensed on the center of the receiving plate42using a spin coater to provide a selected thickness T (e.g., −20 μm). For a spin-on process, the thickness T of the elastomeric polymer layer44will be the function of spin speed, the spin-on liquid viscosity and other factors. Normally the thickness T is radially dependent. To provide optimum thickness uniformity, one would use a larger diameter receiving plate42. Rather than spin coating, the elastomeric polymer layer44can also be applied by vapor deposition, doctor blade, or screen printing. As shown inFIG.9A, a laser lift off area54can be selectively located by appropriate focusing of the laser beam40to lift selected semiconductor structures32onto the receiving plate42. Using the receiving plate42, one could selectively remove certain semiconductor structures32without performing laser lift-off (LLO) on the entire substrate30as with the prior art secondary substrate24(FIG.1C). Following the laser lift-off (LLO) step, the method can also include the step of cleaning and or etching the surface of the semiconductor structure32on the receiving plate42. The semiconductor structure32on receiving plate42can be etched to create rough surface improving its performance such as light extraction, output, handling. With the die sized semiconductor structure32resting on the surface of the elastomeric polymer layer44of the receiving plate42, the method can also include the step of removing the semiconductor structures32from the receiving plate42. This step can be performed using a conventional technique such as a pick and place mechanism for semiconductor dice. Referring toFIG.10, a completed semiconductor structure that has been separated from the receiving plate42comprises a flip chip light emitting diode (FCLED) die32FCLED. The flip chip light emitting diode (LED) die32FCLED includes an epitaxial stack57comprised of a p-type confinement layer (P-layer)64, an n-type confinement layer (N-layer)60, an active layer (multiple quantum well (MQW) layer)62between the confinement layers configured to emit light, P-metal layers66making contact to the p-type confinement layer (P-layer)64, a mirror layer68, an isolation layer72, and an N-electrode70making contact to the n-type confinement layer (N-layer)60. While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and subcombinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope. | 11,266 |
11862755 | DETAILED DESCRIPTION Referring toFIGS.2A-2E, a first step in a method for fabricating light emitting diode (LED) dice includes the steps of providing a substrate30(FIG.2A) and forming a plurality of die sized semiconductor structures32(FIG.2E) on the substrate30. In an illustrative embodiment, the substrate30comprises a sapphire wafer and the semiconductor structures32have a die size and include different layers of compound semiconductor materials formed on the substrate30. The die sized semiconductor structures32can be formed using conventional semiconductor fabrication techniques and physically separated by etching a pattern of criss cross openings38(FIG.2B) to the surface of the substrate30. However, the exact construction of the semiconductor structures32will depend on the type of (LED) dice being fabricated. The GaN layer34(FIG.2E) can be hetero-epitaxially grown on the substrate30(FIG.2E) using techniques that are known in the art. Please note that following the etching process, there is no GaN material in the openings38. To facilitate GaN crystal growth, an initial GaN layer can be deposited at a relatively low temperature, less than 800° C., causing the initial GaN layer to contain a high density of various defects due to a large lattice mismatch. Crystal defects, such as dislocations, nanopipes and inversion domains, elevate surface energy which results in higher absorption of the laser beam. During a subsequent laser-lift off (LLO) step, GaN will quickly decompose to gallium metal vapor and nitrogen gas resulting in explosive force acting on the semiconductor structures32and the substrate30. The die sized semiconductor structures32are much smaller in weight as well as size, compared to the substrate30, such that each semiconductor structure32will have a large force acting on it. In the illustrative embodiment, the semiconductor structures32are measured in microns and the substrate30is measured in millimeters. As also shown inFIG.2E, a laser beam40used for the subsequent laser lift-off (LLO) step has an outline that is larger than the footprint of the die sized semiconductor structures32that one desires to lift off (LLO). In addition, one can lift off more than one die sized semiconductor structure at a time by changing the size of the laser beam40as shown inFIGS.9A-9B. Referring toFIG.3, the method for fabricating light emitting diode (LED) dice also includes the step of providing a receiving plate42coated with an elastomeric polymer layer44. A preferred material for the receiving plate comprises quartz. Exemplary materials for the elastomeric polymer layer44include silicone, siloxane, rubber, or other elastomeric based material. As shown inFIG.3, the receiving plate42can have a size and shape that corresponds to, but is slightly larger than, the size and shape of the substrate30. For example, if the substrate30comprises a circular wafer, the receiving plate42can comprise a circular plate that is slightly larger than the circular wafer. Referring toFIG.4, the method for fabricating light emitting diode (LED) dice also includes the step of placing the substrate30and the receiving plate42in physical contact with an adhesive force applied by the elastomeric polymer layer44. As shown inFIG.4, the semiconductor structures32can have the configuration of vertical light emitting diode (VLED) dice, such that the pad electrodes36provide a spacing of Z1 between the semiconductor structures32and the elastomeric polymer layer44. In addition, an adhesive force F is applied to the pad electrodes36by the elastomeric polymer layer44. The die sized semiconductor structure32is still physically connected to the substrate30but physically separated from the adjacent semiconductor structures. Example 1 Referring toFIGS.5and6, an exemplary placing step uses a four inch diameter circular substrate30and a six inch square receiving plate42S. In this example, the elastomeric polymer layer44comprises a curable silicone pressure sensitive adhesive configured to apply the adhesive force. Other suitable materials for the elastomeric polymer layer44include sorbothane and neoprene. One suitable adhesive is disclosed in Japanese Patent Application No. 2020-016200 filed on Feb. 3, 2020, entitled “Addition Curable Silicone Pressure-Sensitive Adhesive Composition and Cured Product Thereof”, which is incorporated by reference. As shown inFIG.5, the placing step can include a first step of placing the substrate30and the receiving plate42S in physical contact, a second step of applying a weight48and curing the elastomeric polymer layer44using the weight48, and a third step of removing the weight48. By way of example, the elastomeric polymer layer44can have an adhesive force of more than 0.08 MPa, <70 type A hardness, and a tensile strength of >0.01 MPa. Table 1 identifies some characteristics of a spin on elastomeric polymer layer44made of silicone. TABLE 1MaterialsSilicone SampleViscosity (Pa · s)3.0-7Spin coating condition2500 RPM × 60-180 sec(Target thickness = 20 μm)Standard curing condition150° C.; 30 min-2 hrHardness (Type A)5-70Tensile strength (MPa)0.5-5Elongation at break (%)90-250Specific gravity (g/cm3)1.03-1.1Sticky force at 200 mm/min (MPa)0.05-0.5 Referring toFIGS.7and8, the method for fabricating light emitting diode (LED) dice also includes the step of performing a laser lift-off (LLO) process. During the laser lift-off process, a uniform laser beam40is directed through the substrate30onto an interfacial semiconductor layer50at the interface with the substrate30to lift off the die sized semiconductor structures32onto the receiving plate42. During the laser lift-off (LLO) process each semiconductor structure32is individually pushed towards the receiving plate42by decomposition of the interfacial semiconductor layer50. For example, with the interfacial semiconductor layer50comprised of GaN, decomposition will be to gallium (G) and nitrogen (N2) in gaseous form. InFIG.7, this explosive force is represented by explosive force arrows52that pass through the semiconductor structure32and are absorbed by the elastomeric polymer layer44on the receiving plate42. The elastomeric polymer layer44acts as a soft cushion or shock absorber to absorb the kinetic energy from the semiconductor structure32via momentum energy transfer. The semiconductor structure32comes to rest on the elastomeric polymer layer44undamaged and stays in the desired position on the receiving plate42. Example 2 An exemplary laser lift-off (LLO) process uses a 248 nm laser beam40, such as a KrF excimer laser with wavelength of λ=248 nm and pulse width of 25 ns. The laser output energy can be varied from 10 nJ to 50 mJ. The laser beam is reshaped and homogenized using a special optical system to form an uniform beam profile, preferably less than 10% RMS. The LLO processing beam passed through a projection system and then focuses onto the wafer/sample with a spot size such as 0.9×0.9 mm2. Other laser beam sizes and shapes can be used. The excimer laser is not limited to KrF (248 nm). For example, the excimer laser can be from a F2 excimer laser (155 nm), to an ArF excimer laser (198 nm). An excimer laser typically uses a combination of a noble gas (argon, krypton, or xenon) and a reactive gas (fluorine or chlorine). The receiving plate42is preferably larger than the substrate30. In addition, the receiving plate42is preferably flat with a TTV (total thickness variation) of less than <5 μm, but more preferably less than <2 μm, for preventing flipping, titling, rotating and cracking of the semiconductor structures32after the laser lift-off (LLO) process. In addition, the receiving plate42can include one or more alignment marks for aligning the semiconductor structures32on the substrate30. Proper alignment also ensures proper placement of the semiconductor structure32on the receiving plate42following the laser lift-off (LLO) process (i.e., desired coordinate on the receiving plate42). In addition, the receiving plate42can include one or more notches or flats for pre-alignment. Example 3 Referring toFIGS.9A and9B, in this example, the receiving plate42includes a spin-on elastomeric polymer layer44comprised of a curable silicone pressure-sensitive adhesive composition. Also in this example, the substrate30comprises a four inch diameter wafer, and the receiving plate42comprises a six inch diameter circular plate. Further, the receiving plate42has a TTV (total thickness variation) of <5 μm. For forming the elastomeric polymer layer44the elastomer can be dispensed on the center of the receiving plate42using a spin coater to provide a selected thickness T (e.g., −20 μm). For a spin-on process, the thickness T of the elastomeric polymer layer44will be the function of spin speed, the spin-on liquid viscosity and other factors. Normally the thickness T is radially dependent. To provide optimum thickness uniformity, one would use a larger diameter receiving plate42. Rather than spin coating, the elastomeric polymer layer44can also be applied by vapor deposition, doctor blade, or screen printing. As shown inFIG.9A, a laser lift off area54can be selectively located by appropriate focusing of the laser beam40to lift selected semiconductor structures32onto the receiving plate42. Using the receiving plate42, one could selectively remove certain semiconductor structures32without performing laser lift-off (LLO) on the entire substrate30as with the prior art secondary substrate24(FIG.1C). Following the laser lift-off (LLO) step, the method can also include the step of cleaning and or etching the surface of the semiconductor structure32on the receiving plate42. The semiconductor structure32on receiving plate42can be etched to create rough surface improving its performance such as light extraction, output, handling. With the die sized semiconductor structure32resting on the surface of the elastomeric polymer layer44of the receiving plate42, the method can also include the step of removing the semiconductor structures32from the receiving plate42. This step can be performed using a conventional technique such as a pick and place mechanism for semiconductor dice. Referring toFIG.10, a completed semiconductor structure that has been separated from the receiving plate42comprises a flip chip light emitting diode (FCLED) die32FCLED. The flip chip light emitting diode (LED) die32FCLED includes an epitaxial stack57comprised of a p-type confinement layer (P-layer)64, an n-type confinement layer (N-layer)60, an active layer (multiple quantum well (MQW) layer)62between the confinement layers configured to emit light, P-metal layers66making contact to the p-type confinement layer (P-layer)64, a mirror layer68, an isolation layer72, and an N-electrode70making contact to the n-type confinement layer (N-layer)60. While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and subcombinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope. | 11,265 |
11862756 | DETAILED DESCRIPTION Specific details of several embodiments of representative SST dies and associated methods of manufacturing SST dies are described below. The term “SST” generally refers to a solid-state transducer that includes a semiconductor material as an active medium to convert electrical energy into electromagnetic radiation in the visible, ultraviolet, infrared, and/or other spectra. For example, SST dies include solid-state light emitters (e.g., LED dies, laser diodes, etc.) and/or sources of emission other than conventional electrical filaments, plasmas, or gases. LEDs include semiconductor LEDs, PLEDs (polymer light emitting diodes), OLEDs (organic light emitting diodes), and/or other types of solid state devices that convert electrical energy into electromagnetic radiation in a desired spectrum. In some embodiments, SST dies can include solid-state devices that convert electromagnetic radiation into electricity. A person skilled in the relevant art will also understand that the technology may have additional embodiments, and that the technology may be practiced without several of the details of the embodiments described below with reference toFIGS.4A-6. Briefly described, several embodiments of SST dies and devices having SST dies disclosed below improve the emitting efficiency compared to the conventional devices described above with reference toFIGS.1A-3C. When energized, the active material of the SST emits light, but a portion of the light refracts or reflects back toward the SST die from either the converter material or the interface between the lens and air. The electrical contacts on the conventional SST dies absorb the returned light, which reduces the light output and creates an appearance of undesirable dark areas on the surface of the SST die. To resolve this problem, several embodiments of the present technology have a reflective material over, covering, or otherwise proximate to at least a portion of selected electrical contacts to reflect the returned light away from the electrical contacts. For example, depending on the orientation of the die, the reflective material can be on, above (upward facing dies), below (downward facing dies), and/or around the selected electrical contacts. This reduces absorption of the light by the contacts and concomitantly increases the efficiency and enhances the visual appearance of the SST die. FIG.4Aillustrates an SST die100ain accordance with embodiments of the presently disclosed technology. The SST die100acan have a support substrate120and an SST130attached to the support substrate120using a bond material122. The SST130can have a transduction structure131that includes an active material135(e.g., gallium nitride/indium gallium nitride (GaN/InGaN) having multiple quantum wells) between a first semiconductor material133(e.g., P-type GaN) defining a back side132aof the transduction structure131and a second semiconductor material137(e.g., N-type GaN) defining a front side132bof the transduction structure131. In general, the front side132bfaces in the direction E that light or other radiation passes from and/or to the SST130, while the back side132afaces toward the support substrate120. The SST130can further include a first connector141(e.g., P-type connector) at the back side132aof the transduction structure131and one or more second connectors142(e.g., N-type connectors) at the front side132bof the transduction structure131. The second connectors142can be, for example, elongated rails or distributed dots disposed over the front side132bof the SST130. The layout and shape of the second connectors142is selected to distribute electrical current flow through the transduction structure131. The bond material122can be a stack of Ni and Sn materials. Other bond materials are also possible. The illustrated support substrate120has the same width as the SST130, i.e., the sides of the support substrate120are aligned with the sides of the SST130, but the support substrate120can also be wider and deeper than the outline of the SST130. The second connectors142can include a base material143on the second semiconductor material137and a current spreading material144on the base material143. The second connectors142can further include a reflective material146over (e.g., on, covering, around and/or otherwise proximate to) the base material143and the current-spreading metal144. In some embodiments of the SST die100a, the second connectors142do not include the current spreading material144such that the reflective material146directly contacts the base material. The reflective material146can be deposited over the base material143and/or over the current-spreading material144using vacuum evaporation, sputtering, or chemical vapor deposition or other suitable processes known in the art. The base material143and/or the current spreading material144of the second connectors142can have a first reflectivity. The base material143, for example, can be a titanium-aluminum alloy, other alloys of aluminum, aluminum, and/or other suitable conductive materials. The current spreading material144should have good electrical conductivity and avoid adverse interaction with the base material143and the reflective material146. The current spreading material144, for example, can be gold. The reflective material146can have a second reflectivity greater than the first reflectivity of the base material143and/or the current spreading material144. The reflective material146, for example, can be silver, a silver alloy, aluminum, polished metals, or other materials having high a reflectivity. The first connector141, which can be a P-type connector, should also have a high reflectivity to reflect the emitted and the returned light away from the first connector141. The first connector141, for example, can also be silver or a silver alloy. FIG.4Billustrates a packaged SST device100bthat includes the SST die100a, a converter material160over the SST die100a, and a lens180over the converter material160. In operation, a portion of the light scattered/reflected from the converter material160and/or the lens180returns toward the SST130and impinges either on the reflective material146or the active material130. The reflective material146reflects most of the light away from the front side132bof the transduction structure130such that the additional reflected light increases the overall efficiency of the SST die100acompared to conventional devices without the reflective material146. Furthermore, the second connectors142do not appear as dark compared to the connectors in conventional configurations without the reflective material146. FIG.5Aillustrates an SST die200ain accordance with another embodiment of the presently disclosed technology. The SST die200ais similar to the embodiments described in conjunction withFIGS.4A-4B, but the SST die200ahas a buried contact. In the illustrated embodiment, the SST die200ahas an SST230with a transduction structure231including an active material235between a first semiconductor material233and a second semiconductor material237. The first semiconductor material233may be a P-type GaN and the second semiconductor material237may be an N-type GaN, or alternatively the first semiconductor material233may be an N-type GaN and the second semiconductor material237may be a P-type GaN. The SST230also has a first connector241at a back side232aof the transduction structure231and a second connector242buried in the transduction structure231under a front side232bof the transduction structure231. The first connector241can be a P-type connector electrically coupled to the P-type first semiconductor material233, and the second connector242can be an N-type connector electrically coupled to the second semiconductor material237. The second connector242can include a conductive base material243having a first reflectivity and a reflective material246having a second reflectivity over (e.g., on, covering and/or at least proximate to) at least a portion of the base material243that faces the front side232bof the SST230. The second reflectivity of the reflective material246is greater than the first reflectivity of the base material243. The SST230further includes an insulation material240electrically separating the base material243of the second connector242from the active material235, the first semiconductor material233, and the first connector241. Suitable insulation materials include, for example, ceramics, oxides, polymers, epoxies, and other dielectric materials know to persons skilled in the art. The SST230, which includes the transduction structure231, the first connector241, the second connector242, and the insulation material240, can be bonded to a support substrate220by a bond material222. The support substrate220and the bond material222can be similar to those described in reference toFIGS.4A-4B. In operation, an electrical current flowing through the first and the second connectors241and242causes the transduction structure231to emit light. A portion of the emitted light refracts/reflects back toward the reflective material246, which in turn reflects this light away from the SST230. The SST230with the reflective cover246accordingly improves the output efficiency and reduces dark areas compared to configurations without the reflective material246. FIG.5Billustrates an SST die200bin accordance with another embodiment of the presently disclosed technology. Here, the reflective material246completely covers the portion of the second connector242in electrical contact with the second semiconductor material237. For example, the side and top surfaces of the upper portion of the second connector242can be coated by the reflective materials246. The increased coverage of the second connector242by the reflective material246can further increase the amount of light emitted by the device. FIG.6illustrates an SST device300having the SST die200aofFIG.5A, a converter material360, and a lens380. In operation, a portion of the light emitted from the active material235can scatter from the converter material60or reflect from the edge of the lens80. The scattered/reflected light reflects from the reflective material246, and as described above, the higher reflectivity of the reflective material246increases the amount of light that is emitted by the SST device300. From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. For example, different materials can be used for SST devices and/or the substrates in further embodiments. Furthermore, the structures of the devices may differ from those shown in the Figures. For example, several SST dies can be combined into one SST device and/or one package. The reflective material can be used to at least partially cover the substrate carrier to further increase overall amount of the light reflected outside of the SST die. In at least some embodiments, the insulation material facing toward outside of the SST die can be partially covered with the reflective material, while preserving the function of the insulation material. Moreover, while various advantages and features associated with certain embodiments have been described above in the context of those embodiments, other embodiments may also exhibit such advantages and/or features, and not all embodiments need necessarily exhibit such advantages and/or features to fall within the scope of the technology. Accordingly, the disclosure can encompass other embodiments not expressly shown or described herein. | 11,668 |
11862757 | DETAILED DESCRIPTION Like features have been designated by like references in the various figures. In particular, the structural and/or functional features that are common among the various embodiments may have the same references and may dispose identical structural, dimensional and material properties. For the sake of clarity, only the steps and elements that are useful for an understanding of the embodiments described herein have been illustrated and described in detail. In particular, the applications of the device located in the package will not be detailed. Unless indicated otherwise, when reference is made to two elements connected together, this signifies a direct connection without any intermediate elements other than conductors, and when reference is made to two elements coupled together, this signifies that these two elements can be connected or they can be coupled via one or more other elements. In the following disclosure, unless otherwise specified, when reference is made to absolute positional qualifiers, such as the terms “front”, “back”, “top”, “bottom”, “left”, “right”, etc., or to relative positional qualifiers, such as the terms “above”, “below”, “upper”, “lower”, etc., or to qualifiers of orientation, such as “horizontal”, “vertical”, etc., reference is made to the orientation shown in the figures. Unless specified otherwise, the expressions “around”, “approximately”, “substantially” and “in the order of” signify within 10%, and, in some embodiments, within 5%. FIG.1Ais a perspective view of an embodiment of a package10comprising an optoelectronic device12.FIG.1Bis a cross-section view of the embodiment ofFIG.1Ain plane B ofFIG.1A. In alternative embodiments, the optoelectronic device12may instead be replaced with a die, an electronic component, or some other type of electronic device. In some embodiments, device12is an optoelectronic device. In some embodiments, device12is a device receiving or emitting light radiations. In some embodiments, the device12is a device receiving or emitting light rations via an upper surface12a. Device12is, for example, an image sensor, which may be, for example, a video camera. Package10comprises a support14. Support14forms the lower surface or plate of the package. In some embodiments, device12rests on support14. Support14comprises conductive elements16enabling to electrically connect the upper surface of support14to the lower surface of support14. In some embodiments, support14is made of an insulating material having the conductive elements located therein. For example, conductive elements16are conductive tracks. For example support14comprises levels of conductive tracks16electrically coupled to one another by conductive vias, not shown. In some embodiments, support14comprises conductive tracks16aflush with the upper surface of support14and allowing electric connections with device12, for example, by electric wires17, not shown inFIG.1A. Support14further comprises tracks16b, or pads16b, flush with the lower surface of support14. Solder balls18are for example located on tracks16b. Package10may thus be soldered to another device, not shown, by solder balls18. As a variant, solder balls18may be replaced with other metal elements enabling to solder package10to the other device. Thus, a metal land grid array (LGA) or a solder paste may be formed on the lower surface of support14, to replace balls18. Electric connections may thus be formed between the device12located in package10and the other device via wires17, tracks16, and solder elements, for example, balls18or lands. Package10further comprises a wall20. Wall20is for example made of plastic, of resin, of ceramic, or of an organic material. In some embodiments, wall20is made of resin. The wall may be referred to as a layer, which may be made, for example, of plastic, of resin (e.g., molding compound or encapsulant), of ceramic, of an organic material, or some other suitable type of material. Wall20forms the lateral contour of package10. Wall20thus forms the lateral surfaces of package10. Wall20rests on support14. Wall20extends from package10. Thus, wall20extends on the periphery of the upper surface of support14. Wall20extends around device12. In some embodiments, wall20is separated from device12by a gap24a, for example, filled with air. The gap24amay be a portion of cavity24. Gap24aextends from wall20to sidewalls of device12. In some embodiments, wall20is a continuous wall. In some embodiments, wall20is at least as tall as device12based on the orientation as shown inFIG.1B. Thus, in some embodiments, the upper surface of wall20is located above device12based on the orientation as shown inFIG.1B. A plate22is bonded to wall20. The plate22thus forms the upper surface of package10. Plate22includes a first surface23that faces towards the device12, the support14, and the wall20. Package10thus comprises support14, wall20, and plate22. Support14, wall20, and plate22form an inner cavity24having device12located therein. Support14, wall20, and plate delimit inner cavity24in which device12is located therein. In some embodiments, cavity24is filled with air, which surrounds device12. Plate22is rigid, that is, the shape of the plate22is not modified during its placing on wall20. In particular, plate22does not stretch in the cavity24of package10. In particular, in some embodiments, plate22comprises planar upper and lower surfaces parallel to each other. Thus, in some embodiments, plate22is not in contact with device12. In some embodiments, plate22is separated from device12by a gap24b, which is in some embodiments filled with air. Gab24bbeing a portion of cavity24, and gap24bextends from upper surface of device12to lower surface24bof plate22. In some embodiments, plate22is made of a transparent material. In particular, if device12is an optoelectronic device, plate22is made of a material transparent to the wavelengths emitted and/or received by device12. For example, if device12is a video camera, plate22is transparent to visible wavelengths. In some embodiments, plate22is made of glass. Package10further comprises a bonding layer26, bonding plate22to wall20. Package10further comprises a region28between plate22and wall20. In some embodiments, layer26is a glue layer. Layer26rests on top of and in contact with the upper surface of wall20. Plate22rests on top of and in contact with layer26. Layer26extends on the upper surface of wall20, continuously around cavity24, except for the location of region28. Thus, in some embodiments, layer26extends over the entire upper surface of wall20except for the location of region28. In other words, layer26comprises an opening totally filled with the material of region28. Thus, region28and layer26form a continuous ring surrounding cavity24. Region28is thus in contact with layer26. The inner layer24of package10, and thus device12, is thus totally surrounded with package10. Plate22is thus separated from wall20by layer26or region28. Region28extends from the inner cavity24of package10, that is, the inside of package10, to the outside of package10. Thus, region28is not separated from the inner cavity24of package10and is not separated from the outside of package10. In particular, region28is not separated from the inner cavity24of package10and from the outside of package10by layer26. The inner cavity24of package10is thus directly separated from the outside of package10by region28. Region28for example has a parallelepipedal shape. Region28for example comprises:a surface, which is in some embodiments a lateral surface, is in contact with the inside of package10. In some embodiments, the surface is in contact with the air contained in the inner cavity24of package10;a surface, which is in some embodiments a lateral surface, is in contact with the outside of package10. In some embodiments, the surface is in contact with the air located outside of package10;a surface, which is in some embodiments an upper surface, is in contact with plate22;a surface, which is in some embodiments a lower surface, is in contact with wall20; andtwo surfaces, which are in some embodiments lateral surfaces. In some embodiments, the two surfaces are opposite to each other, and are in contact with layer26. Package10thus comprises an assembly of plate22on an assembly comprising wall20and support14. In some embodiments, the plate22is separated from wall20by two distinct materials, which are in some embodiments only two materials, that is, the material for bonding layer26and the material of region28. Package10may be submitted, after its forming, for example, after the steps described in relation withFIGS.2A to2E, to a cleaning or rinsing step. The cleaning or rinsing step is for example carried out with a liquid, for example, with water. During this rinsing step, package10is tight, that is, the liquid dos not penetrate into the inner cavity24of package10. In other words, the material of bonding layer26and the material of region28are tight, that is, they are such that the bonding between plate22and wall20is tight. In other words, a seal is formed between the material of bonding layer26, the material of region28, and the plate such that liquid does not penetrate into the inner cavity24of package10. There thus is no opening between plate22and wall20during this step. After the cleaning or rinsing step, package10may be stored for a long time, for example, for several days, or even several weeks, before being fastened, for example, by balls18or by another solder element, to another device. The fastening step corresponds to a step of soldering, for example, of balls18, in other words to a step of melting of the solder elements located on the lower surface of support14, for example, balls18, on the other device. Package10is thus heated up to a temperature, for example, greater than 150° C. During the storage period, humidity may propagate in the inner cavity24of package10, for example, via support14, or wall20. During the step of melting of the solder elements, for example, balls18, the humidity in the inner cavity24of package10turns into vapor and increases the pressure in the inner cavity24of package10. The material of region28is selected in such a way that region28degrades under the pressure of the water vapor during this melting step and forms an opening. Region28thus forms an exhaust valve for package10. The melting temperature of the solder elements, for example balls18, depends on the material of the solder elements, for example, balls18. The solder elements are made of metal and in some embodiments have a melting temperature greater than 150° C., in some embodiments have a melting temperature greater than 200° C., and in some embodiments have a melting temperature greater than 250° C. Thus, the material of region28is selected to form an opening between the outside of package10and the inner cavity24of package10at the melting temperature of the solder elements, that is, in some embodiments at a temperature greater than 150° C., in some embodiments greater than 200° C., and in some embodiments greater than 250° C. The opening extends from the inner cavity24to an external environment outside of package10. In some embodiments, region28is configured to form an opening when the pressure in the inner cavity24of package10reaches a value greater than 1 atmosphere. However, in some embodiments, the pressure in the inner cavity24of the package10reaches a value greater than 1.5 atmosphere. Region28thus forms a vent in package10during the step of melting of the solder elements. Region28thus enables to degas the inner cavity24of package10. For example, the region is made of a material which is flexible, stretchable, and/or deformable in such a way that during the melting step, at least a portion of the surface of region28located closest to the inner cavity24of package10displaces to end up outside of package10. For example, the region is made of a material flexible, stretchable, and/or deformable in such a way that during the melting step, an air bubble forms in region28and bursts outside of cavity24. In some embodiments, material of region28remains after the forming of the opening. For example, the material of region28has an adherence to the material of plate22, of layer26, and/or of wall20such that, during the step of melting of the solder elements, the pressure causes the separation of region28and of plate22, of layer26, and/or of wall20, which enables air to flow outside of package10. In other words, the pressure generated during the melting step may cause the delamination of the material of region28. For example, the material of region28is a porous material, capable of being crossed by air but not by water. For example, the material of region28is a viscous material, for example, a gel enabling, under the pressure generated during the melting step, to allow the passage of air. In some embodiments, the material of region28is a silicone. In some embodiments, the material of region28is a silicone gel. The opening formed in region28may then close back after the passage of air. In some embodiments, the opening formed in region28is definitive. In other words, material28, in some embodiments, does not recover its original shape after the melting step. In other words, the opening is permanent once formed. It could have been chosen not to form a region28. Bonding layer26would then form a continuous ring surrounding the inner cavity24of package10and making the cavity tight. During the storage period, the cavity24of package10might accumulate enough humidity for the pressure formed in cavity24during the melting of the solder elements to damage package10, in particular to damage wall20, support14, or plate22. The generated damage would then be in unexpected locations and might disadvantageously modify the structure of package10. FIGS.2A to2Eshow the result of steps, which are in some embodiments successive, of an example of a method of manufacturing the embodiment ofFIGS.1A and1B.FIGS.2A to2Eare cross-section views in the plane ofFIG.1B. More particularly,FIGS.2A to2Eshow steps of forming of three packages10, each comprising a device12. More generally, the manufacturing steps described in relation withFIGS.2A to2Eare, for example, carried out from a plate40enabling to form a plurality of packages10. FIG.2Ashows the result of a step of manufacturing of the embodiment ofFIGS.1A and1B. During this step, the support14of each package10is formed. In particular, tracks16are formed to form supports14. In some embodiment the tracks16are formed in an insulating material. In other words, plate40, in some embodiments, comprises a plurality of supports14, is formed.FIG.2Ashows three supports14, each surrounded with dotted lines, in plate40. The tracks16of supports14will not be detailed in the following drawings. FIG.2Bshows the result of a step of manufacturing the embodiment ofFIGS.1A and1B. During this step, a mold42is placed on plate40. Mold42is located in contact with the surface of plate40having the walls20of the different packages10located thereon. Mold40comprises cavities44at the locations of walls20. Cavities44are located on the side of plate40. Certain cavities44may correspond to the walls20of a plurality of neighboring packages10. Thus,FIG.2Bshows cavities44ahaving dimensions substantially corresponding to two walls20side by side. The two walls will be separated afterwards, during the individualization of packages10. Mold42further comprises openings, not shown, providing access to cavities44when the mold is in contact with plate40. More particularly, said openings, not shown, are openings intended to be used to place the material of walls20in the cavities44of mold42. FIG.2Cshows the result of a step of manufacturing the embodiment ofFIGS.1A and1B. During this step, the material of walls20is placed in cavities44by the openings, not shown. For example, the material of walls20is a resin. The resin is for example heated to become liquid. The liquid resin is then sent into cavities44via openings, not shown. The resin is then cooled to take a solid state. Devices12are then placed on plate40. Each device12is placed to be surrounded with a wall20. More generally, this step comprises the forming of the various elements located in the inner cavity24of each package10. This step thus comprises, for example, the forming of electric wires, not shown, coupling a device12to tracks16. FIG.2Dshows the result of a step of manufacturing of the embodiment ofFIGS.1A and1B. During this step, a bonding layer corresponding to the bonding layers26of packages10is formed on walls20, particularly on the upper surface of walls20. The bonding layer is not located at the locations of regions28. The locations of regions28are thus kept empty. During this step, the plates22of each package10are placed on the layer26of the corresponding package10. In some embodiments, layers26have been placed in such a way that when plates22rest on layers26, the material of layers26does not overflow into the locations of regions28. Bonding layers26are then, for example, heated, for example, at a temperature in the range from 80° C. to 200° C. and/or placed under UV (Ultraviolet) light, to solidify the material of layers26and to bond plates22to walls20. In some embodiments, the only openings in the rings formed by layers26are located at the locations of regions28. FIG.2Eshows the result of a step of manufacturing the embodiment ofFIGS.1A and1B. During this step, the locations of regions28are filled with the material of regions28. During this step, packages10are individualized. In other words, plate40, walls20a, and layers26are cut to separate the different packages10. In other words, plate40is separated into a plurality of supports14, walls20aare separated into a plurality of walls20, and layers26are separated to form the layers26of the different packages10. In some embodiments, plates22are placed to be sufficiently separated from one another to enable to individualize packages10, in other words to enable to separate walls20aand supports14between plates22. During this step, balls18are bonded to tracks on the lower surface of each support14. As a variant, balls18or, more generally the solder elements, may be formed later on, for example before the step of soldering package10to another device, for example, after the rinsing step. The filling of regions28, the individualization of packages10, and the placing of balls18may be performed in a different order. As a variant, the steps illustrated byFIGS.2B and2Cmay be replaced with steps during which: a mesh network corresponding to the walls20corresponding to the supports14of plate40is formed separately from plate40; and said mesh network is bonded to plate40by a bonding layer, which is in some embodiments a glue layer. The bonding between wall20and support14is, in this embodiment, tight. The placing of devices12is performed as described in relation withFIG.2C. The next steps are then for example carried out as described in relation withFIGS.2D and2E. FIG.3shows a variant of the embodiment ofFIGS.1A and1B. More particularly,FIG.3is a cross-section view of a variant of the embodiment ofFIGS.1A and1B.FIG.3comprises the elements ofFIGS.1A and1B, which will not be described again. The embodiment ofFIG.3differs from the embodiment ofFIGS.1A and1Bin that region28is separated from layer26by portions46. Portions46extend from the upper surface of wall20. Portions46extend all the way to plate22. Portions46are thus in contact, by an upper surface, with plate22and, by a lower surface, with wall20. In some embodiments, each portion46extends from the outside of package10to inner cavity24. In some embodiments, portions46are made of the material of wall20. The portions46may be integral with the wall20such that portions46and wall20are made of a continuous and unitary material. The portions46may be extension or protrusions that extend outward from lateral wall20. In the example ofFIG.3, package10comprises two portions46only. Each of the two portions is located between a lateral surface of region28and layer26. Region28is thus not in contact with layer26. The region delimited by the two portions46, plate22, and by wall20is totally (e.g., entirely) filled with region28. Region28is thus in contact with portions46. Similarly, layer26is in contact with portions46, and, in some embodiments, with all portions46. The method of manufacturing the embodiment ofFIG.3differs from the method described in relation withFIGS.2A to2Eby the shape of mold42. Indeed, mold42in a method of manufacturing the embodiment ofFIG.3comprises cavities44having the shape of wall20and of portions46. Portions46are thus formed during the forming of wall20, by injection of the material of wall20into cavities44. Afterwards, layer26is deposited all over the upper surface of wall20outside of the location of region28. In some embodiments, the thickness of layer26is selected in such a way that the upper surface of layer26, after the bonding of plate22, is substantially coplanar with the upper surfaces of portions46. An advantage of the embodiment ofFIG.3is that it is possible to better control the dimensions of region28. Indeed, layer26cannot overflow on the location of region28, the material of layer26being blocked by portions46. As shown inFIG.3, wall20includes a second surface43and a third surface45separated from each other by the portions46. Layer26is on the second surface43and region28of material is on the third surface45. Layer26includes a first dimension D1that extends from the second surface43to plate22, and region28of material includes a second dimension D2that extends from the third surface45to the plate22. In this embodiment, the first dimension D1is substantially equal to or equal to the second dimension D2. In some embodiments, the first dimension D1may be greater than the first dimension D2such that the third surface45is closer to plate22as compared to the second surface43. FIG.4shows another variant of the embodiment ofFIGS.1A and1B. More particularly,FIG.4is a cross-section view of a variant of the embodiment ofFIGS.1A and1B.FIG.4comprises the elements ofFIGS.1A and1Band the elements ofFIG.3, which will not be described again. The embodiment ofFIG.4differs from the embodiment ofFIG.3in that layer26is separated into a plurality of portions26′ by portions48. Portions48extend from the upper surface of wall20. Portions48extend all the way to plate22. Portions48are thus in contact, by an upper surface, with plate22, and by a lower portion with wall20. Portions48are made of the material of wall20. In some embodiments, each portion48extends from the outside of package10to inner cavity24. As a variant, portions48may have a different shape. For example, portions48may not extend from the outside of package10to inner cavity24, but only over a portion of the dimension, from the outside of package10to inner cavity24. The portions48may be integral with the wall20such that portions48and wall20are made of a continuous and unitary material. The portions48may be extension or protrusions that extend outward from lateral wall20. In the embodiment ofFIG.4, package10comprises three portions48. Each portion48is located on a side of package10. More particularly, in the embodiment ofFIG.4, layer26comprises four portions substantially rectangular in top view, each portion being separated, for example, substantially in the middle, by a portion48or by portions46and region28. In other words, layer26comprises four portions, located on the angles of the upper surface of wall20, each portion being separated from the neighboring portion by a portion48or by portions46and region48. More generally, package10may comprise at least one portion48, preferably located opposite region46, to keep plate22horizontal. Preferably, package10comprises at least two portions48. Preferably, the at least two portions48are located on different sides of package10to hold plate22. Plate22is preferably separated from wall20by two distinct materials, preferably two materials only, other than the materials of wall20, that is, the bonding material of layer26and the material of region28. As a variant, at least one of portions48may be replaced with a region28. Said region28may for example be surrounded with portions46. FIG.5shows another variant of the embodiment ofFIGS.1A and1B. The embodiment ofFIG.5comprises a package50which differs from the package10ofFIGS.1A and1Bin that wall20is bonded to support14by a bonding layer52and that region28is located between wall20and support14. As the package10ofFIGS.1A and1B, package50comprises support14, the solder elements, for example, balls18, wall20, and plate22. Plate22is bonded to wall20by layer26. Layer26totally surrounds the inner cavity24of package50. Thus, the upper surface of wall20is, in some embodiments, totally covered to bond plate22to wall20. Plate22is thus separated from wall20by a single material, the bonding material. The bonding between wall20and plate22is then tight. In other words, the bonding between wall20and plate22, in some embodiments, does not allow the passage of liquid. Wall20is, in this embodiment, formed separately from support14, as described as a variant of the manufacturing method ofFIGS.2A to2E. Wall20is thus bonded to support14by bonding layer52. Region28is, in this embodiment, located between wall20and support14, in the same way as region28is located between plate22and wall20in the embodiment ofFIGS.1A and1B. Wall20and support14are thus separated by layer52and region28. The method of manufacturing package50for example comprises:the forming of support14, for example, the forming of a plurality of supports14in a same plate;the forming of a mesh network of walls20separated from supports14, as previously described;the deposition of layers52and of the material of regions28on supports14;the placing of the mesh network on supports14and its bonding, for example, by heating;the placing of the elements contained in the packages;the forming of insulating layer26; andthe individualization of packages50. As a variant, the forming of region28may be performed after the individualization of packages50. An advantage of the described embodiments is that they avoid damage to wall20, to support14, and to plate22during the melting of balls18. Another advantage of the described embodiments is that the package is tight during the cleaning or rinsing step. Another advantage of the described embodiments is that the package comprises, in a way, an air vent valve during the step of melting of balls18. Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants may be combined, and other variants will occur to those skilled in the art. Finally, the practical implementation of the described embodiments and variations is within the abilities of those skilled in the art based on the functional indications given hereabove. Package (10) for an electronic device (12), the package may be summarized as including a plate (14,22) and a lateral wall (20), separated by a layer made of a bonding material and at least one region (28) made of a material configured to form in the region (28) an opening between the inside and the outside of the package when the package is heated. Method of manufacturing a package (10) for an electronic device (12), the package may include a plate (14,22) and a lateral wall (20), the method may be summarized as including the forming of a layer made of a bonding material and at least one region (28), separating the plate and the wall, the region being made of a material configured to form in the region (28) an opening between the inside and the outside of the package when the package is heated. The region (28) may be configured to form the opening when the package (10) is heated up to a temperature greater than 150° C. The lateral wall (20) may be made of resin. The plate (22) may be made of glass. Said region (28) may be located between the wall (20) and the plate (22). The device (12) located in the package (12) may be an optoelectronic device, and, in some embodiments, the optoelectronic device is a camera. The device (12) and the wall (20) may rest on a support (14), the support including conductive elements (16) coupling the device (12) to solder elements (18) located under the support (14). The plate may be the support (14). The opening may be configured to form during a step of soldering of the solder elements (18). The package (10) may be configured to be tight before the solder step. The package (10) may be cleaned or rinsed with a liquid before the solder step. Method may include the deposition of a mold (42) on the support (14) and the injection of resin into the mold to form the wall (20). Method may include the forming of the wall (20) separately from the support (14) and the bonding of the wall to the support with a bonding layer (52). The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure. | 29,651 |
11862758 | DETAILED DESCRIPTION Example embodiments will now be described more fully with reference to the accompanying drawings. Phosphor ceramics are currently employed in LED lighting, mostly based on Ce-doped garnets and are deployed in fixtures requiring high incident blue LED flux, but they lack sufficient red emission mainly at 630 nm to provide warm white light efficiently. To produce white light with a spectrum comparable to incandescent bulbs, while maximizing electrical efficiency, a red phosphor is needed with narrow band emission near 630 nm. Low flux LED packages typically employ powdered phosphors in a polymer matrix, sometimes including a combination of Ce-doped garnet powders and K2SiF6:Mn4+(KSF) phosphor powder. The powder phosphors' performance is limited by the poor thermal conductivity, droop, and imperfect environmental stability of powders. The co-inventors of the present disclosure have found that the K2SiF6:Mn4+(KSF) phosphor may be consolidated into ceramic form, and that multicomponent phosphor ceramics including KSF with garnets may be fabricated with good transparency or translucency into the KSF portion of the phosphor body.FIG.1shows one embodiment of a phosphor ceramic structure10being used to create a phosphor converted white light LED component12. The white light LED component12makes use of a blue LED14and three phosphors arranged in distinct layers, which are formed into an integrated ceramic structure: a red phosphor, for example KSF:Mn (K2SiF6:Mn4+) 16, a green/yellow phosphor18, for example a Ce-doped garnet), and a cyan phosphor20such as BaSi2O2N2:Eu (BSON). The phosphor ceramic structure10thus forms a “multicomponent” phosphor ceramic structure. To produce white light22, some blue light24from the blue LED14is absorbed by each of the three phosphors16,18and20which are arranged in a layered structure, and a small amount of the blue light24passes through unabsorbed. Another example of an LED component100employing a phosphor ceramic structure102is shown inFIG.2. The LED component100in this example likewise employs a blue LED excitation source104that generates blue light106. The phosphor ceramic structure102in this example is likewise formed as an integrated ceramic structure with Ce-doped garnets, combined with KSF:Mn and a cyan phosphor (e.g., BSON), all mixed together as a homogenous mixture. The phosphor ceramic structure102, which thus also forms a multicomponent phosphor structure, can provide a high CRI (e.g., >90), as well as high efficacy (>120 lm/W). The blue light106emitted from the blue LED excitation source104is absorbed by the phosphor ceramic structure102, which absorbs a majority of the blue light to produce a white light108. A small amount of the blue light106(e.g., typically about 10%-20%) passes through the phosphor ceramic structure102unabsorbed. Minimally, the phosphor composite invention contains the KSF ceramic with a green/yellow phosphor either in the form of a powder incorporated into the ceramic or applied to or near the surface of the KSF ceramic, or as an additional ceramic arranged as sequential horizontal layers traversed by the blue diode light or as dispersed phosphors in a KSF-based matrix separately encountering the blue light. Ce-doped garnets are the most common green phosphor although there are additional possibilities under development. FIG.3depicts one geometry for pumping the transparent (or translucent) KSF phosphor ceramic structure102with blue light106from blue laser diodes104(LDs) rather than the far more conventional LEDs. Because laser output can be focused much more tightly than LEDs, for example it is possible to pump the laser light into the narrow peripheral side102aof a phosphor disk rather than the larger face102b. In the example shown inFIG.3, the phosphor ceramic structure102includes Ce:YAG particles102c. The phosphor ceramic structure may also include a reflective metal coating such as aluminum102dand be supported on a heat sink103. Transparent ceramics such as the phosphor ceramic structures10and102shown inFIGS.1and2, may be formed via a number of suitable methods including, but not limited to, vacuum sintering, controlled atmosphere sintering, hot-pressing, spark plasma sintering, 3D printing, among other methods, all of which are contemplated as feasible methods of manufacturing the various embodiments described herein. One process methodology for producing the phosphor ceramic structures10and102is shown inFIG.4in which the fluoride phosphor powder110is consolidated into a ceramic by heating at a temperature above room temperature and below the melting or decomposition temperature of the fluoride phosphor. InFIG.4, KSF:Mn powder110is pressed in a hot pressing operation112at pressures of preferably about 1000-20,000 psi, and temperatures of preferably about 150-400° C. to achieve transparency.FIG.4also shows the resulting KSF phosphor ceramic114excited by blue LED lights116, and emitting red light118. The thickness of the ceramic needed for a particular LED package is determined by the activator doping level and the absorption cross section of the phosphor ceramic at the LED emission wavelength. In most instances, however, it is anticipated that the thickness will be in the range of about 0.1 mm to 1 mm, but it will be appreciated that this range may vary considerably based on the design of a particular LED package. Use of thicker ceramics with lower Mn4+doping throughout a volume offers advantages of a lower temperature rise (if assumed to be heat-sunk) and also reduces excited state density which is likely to minimize the amount of “droop”. The resulting KSF phosphor ceramic114exhibits comparable absorption (with optimized doping and thickness) and emission properties to the powdered KSF phosphor, as shown inFIGS.5-7, with good transparency and conversion of blue light from blue light LEDs116into red light118.FIG.5shows photos of KSF:Mn ceramics with Mn doping ranging from 0.045-1% along top row120; under 254 nm excitation in darkness in the middle row122; and under 365 nm excitation in room lights in the lower row124.FIG.6shows graphs126a-126eillustrating the absorption spectra of the KSF:Mn ceramics ofFIG.5for the different percentages shown inFIG.5. The graph128ofFIG.7shows that the emission spectra of KSF:Mn phosphor ceramic changes in intensity but not in spectral features. Furthermore, its intensity tracks the absorption, shown in the inset graph128aby emission curve128a1and absorbance curve128a2(and also that the emission occurs in the desirable red region of 610-650 nm). In particular, note inFIG.7that the emission occurs in the desirable red region of 600-650 nm, which enables high CRI (“whiteness”) and sufficient R9 (i.e., red component) to be achieved. In addition to the single phosphor KSF:Mn ceramic shown inFIG.5, the fluoride phosphor matrix ceramic approach described herein may be extended to development of multicomponent phosphor ceramics or “white emitting” ceramics, such as shown inFIGS.1-3. By controlling the relative amounts of one or more phosphor powders in the manufactured multicomponent ceramic, the color point or “correlated color temperature” (CCT) may be tuned for different fields of use. FIG.8shows an example of a multicomponent phosphor ceramic132(inset) that was fabricated by mixing 0.74 grams of KSF:0.045 wt % Mn powder with 0.06 grams of YAG:1 wt % Ce powder, followed by hot pressing to translucency with a controlled amount of scatter afforded by the particles.FIG.8shows the appearance of the mixed phosphor ceramic132backlit with 450 nm blue light excitation (inset picture). The multicomponent phosphor ceramic132(i.e., mixed K2SiF6:Mn and Y3Al6O12:Ce phosphors) provides luminescence minimally altered from the constituent powder phosphors, but embedded within an inert fluoride matrix. In particular, inFIG.8it can be seen that the multicomponent phosphor ceramic132emits desirable warm white light138under the blue LED138aexcitation, as indicated by curve135a. Curve135bcompares a sensitivity of the human eye at this color temperature, and curve135ccompares a blackbody curve at this color temperature. The multicomponent phosphor ceramic10,102,114or132described ceramic herein may have a density >80% of the single-crystal's full density of the phosphor, and more preferably reach >90% of the full density, and even more preferably being consolidated to >99% of the full density. Most generally, the invention comprises a Manganese-doped fluoride ceramic as the red-emitting component. The fluoride phosphor powder used to form the multicomponent phosphor ceramics10and102described herein preferably has a cubic structure, and more preferably the K2PtCl6cubic structure type. The specific phosphor selected may have the chemical formula M2M′F6, where M is at least one monovalent ion, and M′ is at least one tetravalent ion, and wherein the selected monovalent and tetravalent ions form a stable compound. The phosphor and phosphor matrix selected may, for example, be comprised of M=Li, Na, K, Rb, Cs or mixtures thereof, and M′ being comprised of Si, Ge, Sn, Ti, Zr, Hf or mixtures thereof. In various implementations of the phosphor ceramic structures10or102, one or more of the following ceramics are used: Li2SiF6, Na2SiF6, K2SiF6, Rb2SiF6, Cs2SiF6, Li2GeF6, Na2GeF6, K2GeF6, Rb2GeF6, CS2GeF6, Li2SnF6, Na2SnF6, K2SnF6, Rb2SnF6, Cs2SnF6, Li2ZrF6, Na2ZrF6, K2ZrF6, Rb2ZrF6, Cs2ZrF6, Li2HfF6, Na2HfF6, K2HfF6, Rb2HfF6, Cs2HfF6, Li2TiF6, Na2TiF6, K2TiF6, Rb2TiF6, and Cs2TiF6, and in some implementations two or more mixtures or solid solutions thereof are used. In one example the selected phosphor is doped with Mn4+. In one example the Me doping level is between 0.01% to 30%, and more preferably being between 0.01% to 5%. As noted above, the ceramic structures10and102and114may be comprised of a doped or undoped transparent or translucent ceramic matrix, with one or more additional phosphors dispersed in the matrix. If one or more additional phosphors are used, they may be consolidated into a single ceramic structure as distinct particles which form within the fluoride phosphor comprising the ceramic structure. Each one of the differing phosphors may emit at wavelengths which differ from one another. One or more of the additional phosphors may be selected from among the colors cyan, green, yellow, or further orange or red emission. One or more of the additional phosphors may comprise an oxide garnet, such as Ce-doped (Lu,Gd,Y)3(Al,Ga)5O12compounds, or a nitride phosphor, or an oxynitride phosphor or a sulfide phosphor, or a selenide phosphor. FIG.9illustrates the improved thermal conductivity of phosphor ceramics as compared to powders. Graph134illustrates the falloff in intensity as a function of temperature for KSF:1% ceramic, while graph136shows the intensity vs. temperature falloff for KSF:1% Mn powder. The improved thermal conductivity of phosphor ceramics mitigates the temperature rise due to “nonradiative decay” pathways that are active at high pump powers, and from the unavoidable “Stokes loss” derived from the energy deposited into phonons when the blue LED light is absorbed by the phosphor and then converted into longer wavelength light. This is seen particularly well in the graph134ofFIG.9. Single or multicomponent phosphor ceramics fabricated by consolidating one or more phosphor powders within an undoped fluoride matrix improves the thermal conductivity by about one or more orders of magnitude, compared to powders dispersed in a silicone or other organic polymer. If the phosphor ceramic is configured with a heat sink to keep the ceramic temperature low, it can permit the use of higher excitation flux than is possible for phosphor powders. For example, Ce:YAG powder embedded in polymer has thermal conductivity of k<1 W/m-K while a dense Ce:YAG ceramic has a much higher k of ˜10 W/m-K. We have measured the KSF ceramics thermal conductivity at ˜1 W/m-K, and may presume that the thermal conductivity of powdered KSF phosphor in silicone is about 10× lower (i.e. 0.1), similar to the garnet case. The use of higher flux, in turn, can reduce the number of LEDs needed per lumen of white light. The ceramic phosphor can therefore be used with a higher blue light pump flux, since heat generated may be efficiently conducted away (most efficiently if held in a heat sink structure), thus minimizing thermal quenching at high power.FIG.9shows the mitigated thermal quenching of a KSF ceramic compared to KSF powder for temperatures above 475° K (about 200° Celsius). InFIG.9, the graph136shows emission as a function of temperature, acquired with 450 nm excitation for K2SiF6:Mn powder (open square symbols), while graph134shows the performance of K2SiF6:Mn ceramic (red triangle symbols) over the same temperature range. Significant luminescence quenching is observed in graph136for the powder phosphor at >475° K, limiting the incident excitation flux that may be used. For the KSF ceramic performance shown in graph134, emission at temperatures >500° K does not exhibit quenching. This is believed to be due to improved thermal conductivity of the ceramic as well as the reduced light intensity in the KSF phosphor. While nearly all oxide phosphors are stable in the ambient for expected device lifetimes of >30 years, fluorides and nitrides exhibit degradation in humid environments. Fluoride ceramics are more stable in ambient humidity compared to powders. Since the K2SiF6:Mn4+phosphor is known to be susceptible to degradation due to reaction with water, this may be an important advantage afforded by KSF ceramics versus KSF powders. Water reacting with Mn4+can turn the phosphor black, likely due to leaching of Mn out of the KSF structure and its conversion into MnO2(a dark brown substance). To address this issue, commercial K2SiF6:Mn4+phosphor powder is often synthesized with a shell of undoped K2SiF6on the surface of particles, to prevent water from reacting with Mn4+and darkening the body color of the phosphor. Even more preferably, phosphor ceramics of K2SiF6:Mn4+can be fabricated encapsulated in a shell of undoped KSF, a polymer, glass or other material with resistance to water diffusion, for example using a >100 micron thick layer, thus providing a protective coating of even greater durability for the ceramic. While many fluoride hosts may be considered as phosphor ceramic matrix, KSF offers a particularly low refractive index of 1.34 (at 589 nm), resulting in improved light extraction compared to other polymer and ceramic host candidates due to a reduction in the amount of total internal reflection. This low refractive index permits luminescence from any phosphor suspended within it to more readily escape from the front surface of the phosphor ceramic and reduces the photon “flight path” length prior to escape. For the KSF phosphor, use in the form of a KSF ceramic permits lower Mn doping, since the excitation volume in a transparent or translucent ceramic can be significantly larger (e.g., >1 mm3, compared to <0.05 mm3in a powder). Lower Mn doping reduces concentration quenching (by Auger upconversion and cross-relaxation), and thereby mitigates thermal quenching arising from these deactivation pathways. Physical clustering of Mn when doping levels are high is likely the basis for degraded emission properties with high Mn doping, and can be nearly entirely avoided by use of lower Mn concentrations, as is enabled by employment of KSF in ceramic form. Experimentally, the advantage of a transparent (or translucent) phosphor ceramic over the usual incorporation of particles in a polymer relates to larger excitation volume for more transparent phosphor ceramics, as described above, where the blue pump (i.e., excitation) light excites a larger volume (e.g., blue LED excitation light). InFIGS.10aand10b, the “droop” performance of two KSF:Mn ceramics were tested as a function of the blue light power level.FIG.10ashows the “droop” performance via graph140of KSF:Mn ceramic doped with 0.045 percent weight of Mn, whileFIG.10bshows the droop performance via graph142of KSF:Mn ceramic doped with 0.25 percent weight of Mn. It is apparent from graph142inFIG.10bthat the higher Mn-doped ceramic exhibits a stronger down-turn at the highest power level. It will be appreciated that the use of lower Mn doping in KSF is only useful in a transparent or translucent ceramic, not in an opaque powder. A key aspect of this effect is that the thermal conductivity of a KSF:Mn ceramic structure constructed in accordance with the present disclosure may be expected to be at least about, or greater than, 5× higher than the typical polymer film. The teachings presented herein enable single phosphor or multicomponent phosphor powders to be consolidated into single component or multicomponent ceramic structures. The single and multicomponent phosphor ceramic structures described herein enable a tunable light emission (e.g., tunable white light emission) to be achieved from a blue pump light excitation source, with an effective low refractive index for more efficient light extraction. The embodiments of the phosphor ceramic structures described herein offer significantly improved thermal stability and thermal conductivity as compared to powdered phosphors contained in a binder. The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The color description such as “red” or “green” are not intended to be restrictive such that “red” may be interpreted as “orange” or “orange/red” and for example “green” may be “yellow/green”. | 22,230 |
11862759 | DETAILED DESCRIPTION Embodiments of the invention include wavelength-converting materials or luminescent materials such as phosphors that emit near-infrared (NIR) radiation. For economy of language, infrared radiation may be referred to herein as “light.” The NIR phosphors may be used, for example, in phosphor-converted LEDs. The NIR phosphors may emit light having a peak wavelength of at least 700 nm in some embodiments and no more than 1100 nm in some embodiments. The NIR phosphors may have a distributed emission intensity within the 700-1100 nm range; for example, in some embodiments, the NIR phosphors may have a full width at half maximum of at least 1700 cm−1in some embodiments and no more than 4000 cm−1in some embodiments. The NIR phosphors may be excited, for example, by light in the visible spectral range, meaning that they absorb visible light, and in response, emit NIR light. The NIR phosphors may be wide band gap materials. Use of wide band gap host lattices may limit luminescence quenching at elevated temperatures due to photoionization. The band gap of the NIR phosphors may be at least 4.8 eV in some embodiments, greater than 5 eV in some embodiments, and less than 7 eV in some embodiments. In some embodiments, the NIR phosphors are electrically insulating materials. One benefit of electrically insulating materials may be higher band gap, as electrical conductivity is related to band gap. The higher the band gap, the lower the electrical conductivity. In addition, semiconductors often show increased conductivity at higher temperatures, while an insulator such as diamond (band gap 5.5 eV, comparable with the band gap of NIR phosphors according to some embodiments) remains insulating even at increased temperature. Wavelength converting materials such as phosphors typically include a host lattice and at least one dopant species. The atoms of the dopant species function as light emitting centers. In some embodiments, the NIR phosphors include trivalent cations such as Cr(III) (Cr(III) is the same as Cr3+) as emitting centers. In some embodiments, in addition to or instead of trivalent cations, the NIR phosphors include tetravalent cations as emitting centers. In some embodiments, the host lattice includes a tetravalent cation such as Si4+with an effective ionic radius for fourfold coordination that is 38% smaller than the effective ionic radius of Cr4+. The small tetravalent host lattice cation size may suppress the formation of unwanted Cr(IV), which may improve the stability of the NIR phosphors and may increase the luminescence conversion efficiency of the NIR phosphors at elevated temperatures. In some embodiments, the NIR phosphors contain less than 10% Cr(IV), relative to the total chromium content in the NIR phosphor, to reduce or eliminate self-absorption losses, where emitted light is reabsorbed in the phosphor material. Self-absorption loss may occur because of the overlap of the Cr(III) emission band and the Cr(IV) absorption band. Most of the emission energy is transferred into heat, which may reduce efficiency. For example, Cr(IV) is less than 10% (of total Cr content) in some embodiments, less than 5% in some embodiments, less than 1% in some embodiments, and 0% in some embodiments. The low concentrations of Cr(IV) required in some embodiments cannot be easily reached in other phosphors, such as La3Ga5GeO14:Cr, which do not include a small radius tetravalent cation in the host lattice, because the larger sized Ge4+cation has the same size as Cr4+within 5%, thus the Cr4+is stabilized in the structure. In such phosphors, expensive workarounds like reductive firing under elevated pressures are needed to suppress e.g. gallium loss. NIR phosphors according to some embodiments include Si4+, which is much smaller than Ge4+and Cr4+. Accordingly, techniques such as the above-described reductive firing are not required to prevent Cr4+incorporation on the Si+site. In addition, the inclusion of Cr(IV) in, for example, La3Ga5GeO14:Cr also leads to pronounced afterglow (a low intensity, persistent emission that is undesirable in applications where short light pulses with constant spectral power distributions are needed), and a shift of the emission spectrum towards longer wavelengths if Cr(IV) is directly excited with red light. The afterglow phenomenon can be enhanced by doping the La3Ga5GeO14:Cr material further with divalent cations, which may stabilize Cr(IV) in the structure. NIR phosphors according to some embodiments do not include divalent cations, such as, for example, Mg2+as dopants. NIR phosphors according to some embodiments do not include tetravalent cations in the host lattice that undesirably stabilize Cr(IV), such as, for example, Ge4+. In some embodiments, the NIR phosphor has a host lattice belonging to the calcium gallogermanate structure family crystallizing in the polar space group P321. The host lattice may crystallize in a trigonal calcium gallogermanate structure type. Suitable calcium gallogermanate materials may have a compositional range RE3Ga5−x−yAxSiO14:Cry(RE=La, Nd, Gd, Yb, Tm; A=Al, Sc), where 0≤x≤1 and 0.005≤y≤0.1. In some embodiments, the NIR phosphor has a calcium gallogermanate, garnet, or colquiirite crystal structure host lattice including a quantity of divalent trace metals like Mg, Ca, Yb, Sr, Eu, Ba, Zn, Cd. The concentration of divalent trace metals is kept low, less than 400 ppm in some embodiments and less than 100 ppm in some embodiments. Small divalent trace metals, such as Mg, Zn, and Cd, may substitute for gallium in the RE3Ga5−x−yAxSiO14:Crymaterial described above. In some embodiments, the NIR phosphor is La3Ga5−ySiO14:Cry, also known as Langasite, which shows an optical band gap at 5.1 eV. In some embodiments, the NIR phosphor is one or more gallogermanate compounds of composition RE3Ga5−x−yAxSiO14:Cry, which show optical band gaps larger than 4.6 eV. In some embodiments, the optical band gap of a gallogermanate material may be increased by partial substitution of Ga by Al and/or Sc, and/or by replacing part of the La by the smaller rare earth elements Nd, Gd, and Yb. The replacement of Ga by Al and/or Sc may further improve the efficiency of the phosphor material, especially at higher temperatures. Nd3+and Yb3+show additional emission in the 950-1070 nm wavelength range which can be beneficial for certain applications. In some embodiments, the NIR phosphor RE3Ga5−x−yAxSiO14:Cry(RE=La, Nd, Gd, Yb, Tm; A=Al, Sc) is combined with a second, wide band gap, NIR phosphor material such as one or more chromium doped garnets of composition Gd3−xRExSc2−y−zLnyGa3−wAlwO12:Crz(Ln=Lu, Y, Yb, Tm; RE=La, Nd), where 0≤x≤3; 0≤y≤1.5; 0≤z≤0.3; and 0≤w≤2, and/or one or more chromium doped colquiirite materials of composition AAEM1−xF6:Crx(A=Li, Cu; AE=Sr, Ca; M=Al, Ga, Sc) where 0.005≤x≤0.2, and/or one or more chromium doped tungstate materials of composition A2−x(WO4)3:Crx(A=Al, Ga, Sc, Lu, Yb) where 0.003≤x≤0.5. In some embodiments, the NIR phosphor may have a compositional range (La,Gd)3Ga5−x−yAlxSiO14:Cry, where 0≤x≤1 and 0.02≤y≤0.08. In some embodiments, the NIR phosphor (La,Gd)3Ga5−x−yAlxSiO14:Cryis combined with a second, wide band gap, NIR phosphor material such as one or more chromium doped garnets of composition Gd3−x1Sc2−x2−yLux1+x2Ga3O12:Cry, where 0.02≤x1≤0.25, 0.05≤x2≤0.3 and 0.04≤y≤0.12. FIG.1illustrates the emission spectra of two NIR phosphor powders according to some embodiments. The materials inFIG.1are chromium doped garnets. Curve A is the emission spectrum of Gd2.8La0.2Sc1.7Lu0.2Ga3O12:Cr0.1when excited by 440 nm light. Curve B is the emission spectrum of Gd2.4La0.6Sc1.5Lu0.4Ga3O12:Cr0.1when excited by 440 nm light. The synthesis of these materials is described below in the Examples. The NIR phosphors according to some embodiments may have advantages over known phosphor systems such as, for example, higher absorption and increased quantum efficiency at elevated temperatures (for example, greater than 25° C. and no more than 85° C. in some embodiments), especially in the wavelength range >800 nm. The NIR phosphor materials described above can be manufactured, for example, in powder form, in ceramic form, or in any other suitable form. The NIR phosphor materials may be formed into a structure that is formed separately from and can be handled separately from the light source, such as a prefabricated glass or ceramic tile, or may be formed into a structure that is formed in situ with the light source, such as a conformal or other coating formed on or above the light source. In some embodiments, the NIR phosphors described above may be powders that are dispersed for example in a transparent matrix, a glass matrix, a ceramic matrix, or any other suitable material or structure. The NIR phosphor dispersed in a matrix may be, for example, singulated or otherwise formed into a tile that is disposed over a light source. The glass matrix may be for example a low melting glass with a softening point below 1000° C., or any other suitable glass or other transparent material. In some embodiments, the low melting glass belongs to the family of zinc bismuth borate glasses with a softening point below 600° C. and a refractive index larger than 1.75. In some embodiments, the low melting glass may further comprise barium and/or sodium, a softening point below 500° C. and a refractive index larger than 1.8. The ceramic matrix material can be for example a fluoride salt such as CaF2or any other suitable material. The NIR phosphors described above may be used in powder form, for example by mixing the powder phosphor with a transparent material such as silicone and dispensing or otherwise disposing the mixture in a path of light from the light source. In powder form, the average particle size (for example, particle diameter) of the NIR phosphors may be at least 1 μm in some embodiments, no more than 50 μm in some embodiments, at least 5 μm in some embodiments, and no more than 20 μm in some embodiments. Individual NIR phosphor particles, or NIR powder phosphor layers, may be coated with one or more materials such as a silicate, a phosphate, and/or one or more oxides in some embodiments, for example to improve absorption and luminescence properties and/or to increase the material's functional lifetime. The NIR phosphors described above may be used, for example, in a light source including a light emitting diode (LED). Light emitted by the light emitting diode is absorbed by the phosphor according to embodiments of the invention and emitted at a different wavelength.FIG.2illustrates one example of a suitable light emitting diode, a III-nitride LED that emits blue light. Though in the example below the semiconductor light emitting device is a III-nitride LED that emits blue or UV light, semiconductor light emitting devices besides LEDs such as laser diodes and semiconductor light emitting devices made from other materials systems such as other III-V materials, III-phosphide, III-arsenide, II-VI materials, ZnO, or Si-based materials may be used. In particular, the NIR phosphors described above may be pumped by, for example, light sources such as LEDs emitting either in the blue (420-470 nm) or in the red (600-670 nm) wavelength range. FIG.2illustrates a III-nitride LED1that may be used in embodiments of the present invention. Any suitable semiconductor light emitting device may be used and embodiments of the invention are not limited to the device illustrated inFIG.2. The device ofFIG.2is formed by growing a III-nitride semiconductor structure on a growth substrate10as is known in the art. The growth substrate is often sapphire but may be any suitable substrate such as, for example, SiC, Si, GaN, or a composite substrate. A surface of the growth substrate on which the III-nitride semiconductor structure is grown may be patterned, roughened, or textured before growth, which may improve light extraction from the device. A surface of the growth substrate opposite the growth surface (i.e. the surface through which a majority of light is extracted in a flip chip configuration) may be patterned, roughened or textured before or after growth, which may improve light extraction from the device. The semiconductor structure includes a light emitting or active region sandwiched between n- and p-type regions. An n-type region16may be grown first and may include multiple layers of different compositions and dopant concentration including, for example, preparation layers such as buffer layers or nucleation layers, and/or layers designed to facilitate removal of the growth substrate, which may be n-type or not intentionally doped, and n- or even p-type device layers designed for particular optical, material, or electrical properties desirable for the light emitting region to efficiently emit light. A light emitting or active region18is grown over the n-type region. Examples of suitable light emitting regions include a single thick or thin light emitting layer, or a multiple quantum well light emitting region including multiple thin or thick light emitting layers separated by barrier layers. A p-type region20may then be grown over the light emitting region. Like the n-type region, the p-type region may include multiple layers of different composition, thickness, and dopant concentration, including layers that are not intentionally doped, or n-type layers. After growth, a p-contact is formed on the surface of the p-type region. The p-contact21often includes multiple conductive layers such as a reflective metal and a guard metal which may prevent or reduce electromigration of the reflective metal. The reflective metal is often silver but any suitable material or materials may be used. After forming the p-contact21, a portion of the p-contact21, the p-type region20, and the active region18is removed to expose a portion of the n-type region16on which an n-contact22is formed. The n- and p-contacts22and21are electrically isolated from each other by a gap25which may be filled with a dielectric such as an oxide of silicon or any other suitable material. Multiple n-contact vias may be formed; the n- and p-contacts22and21are not limited to the arrangement illustrated inFIG.2. The n- and p-contacts may be redistributed to form bond pads with a dielectric/metal stack, as is known in the art. In order to form electrical connections to the LED1, one or more interconnects26and28are formed on or electrically connected to the n- and p-contacts22and21. Interconnect26is electrically connected to n-contact22inFIG.5. Interconnect28is electrically connected to p-contact21. Interconnects26and28are electrically isolated from the n- and p-contacts22and21and from each other by dielectric layer24and gap27. Interconnects26and28may be, for example, solder, stud bumps, gold layers, or any other suitable structure. The substrate10may be thinned or entirely removed. In some embodiments, the surface of substrate10exposed by thinning is patterned, textured, or roughened to improve light extraction. Any suitable light emitting device may be used in light sources according to embodiments of the invention. The invention is not limited to the particular LED illustrated inFIG.2. The light source, such as, for example, the LED illustrated inFIG.2, is illustrated in the following figures by block1. FIGS.3,4, and5illustrate devices that combine an LED1and a wavelength converting structure30. The wavelength converting structure30may include one or more NIR phosphors, according to the embodiments and examples described above. InFIG.3, the wavelength converting structure30is directly connected to the LED1. For example, the wavelength converting structure may be directly connected to the substrate10illustrated inFIG.2, or to the semiconductor structure, if the substrate10is removed. InFIG.4, the wavelength converting structure30is disposed in close proximity to LED1, but not directly connected to the LED1. For example, the wavelength converting structure30may be separated from LED1by an adhesive layer32, a small air gap, or any other suitable structure. The spacing between LED1and the wavelength converting structure30may be, for example, less than 500 μm in some embodiments. InFIG.5, the wavelength converting structure30is spaced apart from LED1. The spacing between LED1and the wavelength converting structure30may be, for example, on the order of millimeters in some embodiments. Such a device may be referred to as a “remote phosphor” device. The wavelength converting structure30may be square, rectangular, polygonal, hexagonal, circular, or any other suitable shape. The wavelength converting structure may be the same size as LED1, larger than LED1, or smaller than LED1. Multiple wavelength converting materials and multiple wavelength converting structures can be used in a single device. Examples of wavelength converting structures include luminescent ceramic tiles; powder phosphors that are disposed in transparent material such as silicone or glass that is rolled, cast, or otherwise formed into a sheet, then singulated into individual wavelength converting structures; wavelength converting materials such as powder phosphors that are disposed in a transparent material such as silicone that is formed into a flexible sheet, which may be laminated or otherwise disposed over an LED1, wavelength converting materials such as powder phosphors that are mixed with a transparent material such as silicone and dispensed, screen printed, stenciled, molded, or otherwise disposed over LED1; and wavelength converting materials that are coated on LED1or another structure by electrophoretic, vapor, or any other suitable type of deposition. A device may also include other wavelength converting materials in addition to the NIR phosphors described above, such as, for example, conventional phosphors, organic phosphors, quantum dots, organic semiconductors, II-VI or III-V semiconductors, II-VI or III-V semiconductor quantum dots or nanocrystals, dyes, polymers, or other materials that luminesce. The wavelength converting materials absorb light emitted by the LED and emit light of one or more different wavelengths. Unconverted light emitted by the LED is often part of the final spectrum of light extracted from the structure, though it need not be. Wavelength converting materials emitting different wavelengths of light may be included to tailor the spectrum of light extracted from the structure as desired or required for a particular application. Multiple wavelength converting materials may be mixed together or formed as separate structures. In some embodiments, other materials may be added to the wavelength converting structure or the device, such as, for example, materials that improve optical performance, materials that encourage scattering, and/or materials that improve thermal performance. EXAMPLES 1. Synthesis of La3Ga4.98SiO14:Cr0.02. The starting materials 4.805 g lanthanum oxide (Auer Remy, 4N), 4.589 g gallium oxide (Alfa, 5N), 0.0149 g chromium (III) oxide (Alfa, 99%), 0.591 g fumed silica (Evonik) and 0.1 g boric acid (Aldrich) are mixed in ethanol, dried at 100° C. and fired under carbon monoxide at 1300° C. for 4 hrs. After ball milling, the powder is washed with water, dried and sieved. Single phase La3Ga4.98SiO14:Cr0.02is obtained.FIG.6is an X-ray diffraction (XRD) pattern of the synthesized La3Ga4.98SiO14:Cr0.02, crystallizing in the calcium gallogermanate structure with a0=8.163 Å and c0=5.087 Å. 2. Synthesis of La3Ga4.48Al0.5SiO14:Cr0.02. The starting materials 9.8182 g lanthanum oxide (Auer Remy, 4N), 8.4354 g gallium oxide (Molycorp, UHP grade), 0.0314 g chromium (III) oxide (Alfa, 99%), 1.208 g fumed silica (Evonik), 0.5136 g alumina (Baikowski) and 0.2005 g boric acid (Aldrich) are mixed in ethanol, dried at 100° C. and fired under carbon monoxide at 1320° C. for 4 hrs. and under forming gas at 1000° C. for another 4 hrs. After ball milling, the powder is washed with water, dried and sieved.FIG.7is an XRD pattern of the synthesized La3Ga4.48Al0.5SiO14:Cr0.02, crystallizing in the calcium gallogermanate structure with a0=8.146 Å and c0=5.075 Å. 2.1. Synthesis of La2.98Gd0.02Ga4.76Al0.2SiO14:Cr0.04. The starting materials 59.262 g lanthanum oxide (Auer Remy, 4N), 54.769 g gallium oxide (Molycorp, UHP grade), 0.369 g chromium (III) oxide (Materion, 2N5), 7.6 g fumed silica (Evonik), 1.24 g aluminum oxide (Baikowski, SP-DBM) and 0.52 g gadolinium fluoride (Materion, >2N) are mixed in ethanol by ball milling, dried at 100° C. and fired under flowing nitrogen at 1320° C. for 8 hrs. (heating and cooling rampls: 200 K/h). After ball milling, the powder is washed with water, dried and sieved.FIG.14is an X-ray diffraction (XRD) pattern of the synthesized La2.89Gd0.02Ga4.76Al0.2SiO14:Cr0.04, crystallizing in the calcium gallogermanate structure with a0=8.1595 Å and c0=5.0871 Å. 3. Synthesis of Gd2.8La0.2Sc1.7Lu0.2Ga3O12:Cr0.1. The starting materials 5.148 g gadolinium oxide (Rhodia, superamic grade), 1.189 g scandium oxide (Alfa Aesar, 4N), 0.404 g luthetium oxide (Rhodia), 2.852 g gallium oxide (Alfa Aesar, 4N), 0.0771 g chromium (III) oxide (Alfa, 99%), 0.3305 g lanthanum oxide (Auer Remy, 4N) and 0.2 g barium fluoride (Alfa Aesar) are mixed and fired at 1500° C. for 4 h in air atmosphere. After crushing and ball milling, the powder is washed in hot water, dried and sieved.FIG.8is an XRD pattern of the synthesized Gd2.8La0.2Sc1.7Lu0.2Ga3O12:Cr0.1, crystallizing in the garnet structure with a0=12.440 Å. 4. Synthesis of Gd2.4La0.6Sc1.5Lu0.4Ga3O12:Cr0.1. The starting materials 4.330 g gadolinium oxide (Rhodia, superamic grade), 1.103 g scandium oxide (Alfa Aesar, 4N), 0.792 g luthetium oxide (Rhodia), 2.799 g gallium oxide (Alfa Aesar, 4N), 0.0757 g chromium (III) oxide (Alfa, 99%), 0.9730 g lanthanum oxide (Auer Remy, 4N) and 0.2 g barium fluoride (Alfa Aesar) are mixed and fired at 1550° C. for 4 h in air atmosphere. After milling the powder is fired again for 4 hrs. at 1400° C. in a carbon monoxide atmosphere. After crushing and ball milling, the powder is washed in hot water, dried and sieved.FIG.9is an XRD pattern of the synthesized Gd2.4La0.6Sc1.5Lu0.4Ga3O12:Cr0.1, crystallizing in the garnet structure with a0=12.604 Å. 4.1. Synthesis of Gd2.85Sc1.75Lu0.3Ga3O12:Cr0.1. The starting materials 61.404 g gadolinium oxide (Treibacher, >3N8), 14.888 g scandium oxide (Treibacher, 4N), 7.291 g luthetium oxide (Solvay, 4N), 34.638 g gallium oxide (Dowa, 4N) 0.925 g chromium (III) oxide (Materion, >2N5) and 1.956 g gadolinium fluoride (Materion, >2N) are mixed by means of ball milling, and fired twice at 1550° C. and 1520° C. with intermediate milling for 8 hrs. After crushing, milling and washing with water, the powders are dried and sieved.FIG.15is an XRD pattern of the synthesized Gd2.85Sc1.75Lu0.3Ga3O12:Cr0.1, crystallizing in the garnet structure with a0=12.503 Å. 5. Synthesis of SrLiAl0.995F6:Cr0.005. The starting materials AlF3(99.99%, anhydrous), LiF (99.999%), SrF2(99.99%, dry) and CrF3(99.98%, anhydrous) are mixed under argon and transferred in a platinum crucible. After firing at 600° C. for 4 hrs. under argon atmosphere, the resulting powder cake is milled under ethanol and dried. 6. Phosphor mixtures. For infrared illumination applications like NIR spectroscopy it is often preferable to have a broad, continuous emission intensity distribution. Accordingly, in some embodiments, one or more longer wavelength emitting materials, for example from the class of Cr doped calcium gallogermanate type phosphors illustrated by e.g. examples 1), 2), and 2.1), is combined with one or more shorter wavelength emitting materials, for example from the class of Cr doped garnets illustrated by e.g. examples 3), 4), and 4.1), and/or with materials from the class of Cr doped colquiirite materials illustrated by e.g. example 5). FIGS.10and11show examples of emission spectra obtained from such phosphor mixtures when excited with 445 nm light. InFIG.10, curve A is the emission spectrum of a mixture of La3Ga4.98SiO14:Cr0.02and Gd2.8La0.2Sc1.7Lu0.2Ga3O12:Cr0.01mixed at a ratio of 5:1 (weight/weight). Curve B is the emission spectrum of a mixture of La3Ga4.98SiO14:Cr0.02and Gd2.8La0.2Sc1.7Lu0.2Ga3O12:Cr0.01mixed at a ratio of 2:1 (weight/weight).FIG.11illustrates the emission spectrum of a mixture of La3Ga4.98SiO14:Cr0.02and SrLiAl0.995F6:Cr0.005.mixed at a ratio of 4:1 (weight/weight). The combination of at least two different phosphor systems may enable a broad composed emission spectrum in the 700-1100 nm range with superior conversion efficiency compared to a single phosphor system spectrum, especially at elevated temperatures 7. LED evaluation. The phosphor powder of example 1) with a density of 5.52 g/cm3and example 3) with a density of 6.80 g/cm3were suspended, in weight ratios of 90:10 and 95:5, in silicone (Dow Corning OE-7662). The suspension was dispensed with a needle dispenser into a package equipped with 450 nm emitting blue InGaN pump LEDs. After curing the silicone, the phosphor-converted LEDs were measured at different temperatures, as illustrated inFIGS.12and13. For a pulse current of e.g. 350 mA, a total radiant flux >50 mW was obtained for the 600-1050 nm range. FIG.12illustrates the emission spectra of a phosphor converted LED including a mixture of 5 wt % Gd2.8La0.2Sc1.7Lu0.2Ga3O12:Cr0.01and 95 wt % La3Ga4.98SiO14:Cr0.02dispensed in a package with a 450 nm blue pump LED for I=350 mA, 20 ms pulse length. Curve A is the emission spectrum at 25° C. (LED board temperature), where the device emits a total radiant flux of 53 mW for the 600-1050 nm range. Curve B is the emission spectrum at 55° C., where the device emits a total radiant flux of 39 mW for the 600-1050 nm range. Curve C is the emission spectrum at 85° C., where the device emits a total radiant flux of 28 mW for the 600-1050 nm range. FIG.13illustrates the emission spectra of a phosphor converted LED including a mixture of 10 wt % Gd2.8La0.2Sc1.7Lu0.2Ga3O12:Cr0.1and 90 wt % La3Ga4.98SiO14:Cr0.02dispensed in a package with a 450 nm blue pump LED for I=350 mA, 20 ms pulse length. Curve A is the emission spectrum at 25° C. (LED board temperature), where the device emits a total radiant flux of 64 mW for the 600-1050 nm range. Curve B is the emission spectrum at 55° C., where the device emits a total radiant flux of 49 mW for the 600-1050 nm range. Curve C is the emission spectrum at 85° C., where the device emits a total radiant flux of 38 mW for the 600-1050 nm range. The phosphor powder of example 2.1) with a density of 5.752 g/cm3and example 3) with a density of 6.803 g/cm3were suspended, in a weight ratio of 88:12, in silicone (24.7 vol % phosphor load). The suspension was dispensed with a needle dispenser into a package equipped with 450 nm emitting blue InGaN pump LEDs. After curing the silicone, the phosphor-converted LEDs were measured at room temperature, as illustrated inFIG.16. For a pulse current of e.g. 350 mA, a total radiant flux >50 mW was obtained for the 600-1100 nm range. FIG.16illustrates the emission spectra of a phosphor converted LED including a mixture of 12 wt % Gd2.85Sc1.75Lu0.3Ga3O12:Cr0.01and 88 wt % La2.98Gd0.02Ga4.76Al0.2SiO14:Cr0.04dispensed in a package with a 450 nm blue pump LED for I=350 mA, 20 ms pulse length at 25° C. (LED board temperature), where the device emits a total radiant flux of 57 mW for the 600-1100 nm range. Having described the invention in detail, those skilled in the art will appreciate that, given the present disclosure, modifications may be made to the invention without departing from the spirit of the inventive concept described herein. Therefore, it is not intended that the scope of the invention be limited to the specific embodiments illustrated and described. | 27,920 |
11862760 | DETAILED DESCRIPTION A light emitting device according to an embodiment includes: a substrate; a light emitting element that is provided on the substrate and emits first light; a wavelength conversion layer that is provided on the light emitting element and converts a wavelength of a part of the first light to emit second light; and a wall that includes a light reflective material, surrounds the wavelength conversion layer, and is provided with an opening portion exposing at least a part of a top surface of the wavelength conversion layer. In the light emitting device, a surface of the wall includes a top surface provided at a higher position than the top surface of the wavelength conversion layer, and an inner surface forming the opening portion. The wall includes a first portion surrounding the wavelength conversion layer, and a second portion provided over the first portion and surrounding the first portion. The opening portion is hollow. An angle of a corner portion between the top surface and the inner surface of the wall is in a range of 90 degrees or greater and less than 180 degrees. A method of manufacturing a light emitting device according to an embodiment includes: disposing a light emitting element on a substrate; disposing a wavelength conversion layer on the light emitting element; placing a mold member on the wavelength conversion layer; providing a light reflecting material that is uncured so as to surround the wavelength conversion layer and the mold member such that a top surface of the light reflecting material after being cured protrudes toward a direction from the substrate to the top surface of the light reflecting material or is parallel to a top surface of the substrate; forming a wall by curing the light reflecting material, and removing the mold member to form a hollow opening portion in the wall, the hollow opening portion exposing at least a part of a top surface of the wavelength conversion layer. Next, a specific configuration of a light emitting device according to certain embodiments will be described. Hereinafter, in the present specification, an XYZ Cartesian coordinate system is employed for convenience of description. As illustrated inFIGS.1and2, a direction from a substrate110toward a light emitting element120is referred to as a “Z direction”. The Z direction is also referred to as an “upward direction”. A direction opposite to the Z direction is also referred to as a “downward direction”. One direction orthogonal to the Z direction is referred to as an “X direction”. A direction orthogonal to the Z direction and the X direction is referred to as a “Y direction”. Furthermore, a direction orthogonal to the Z direction, such as the X direction and the Y direction, is also referred to as a “lateral direction”. First Embodiment First, a light emitting device100according to a first embodiment will be described. FIG.1is a schematic top view illustrating the light emitting device100according to the present embodiment. FIG.2is a schematic end view taken along line II-II inFIG.1. As illustrated inFIGS.1and2, the light emitting device100includes the substrate110, the light emitting element120, a wavelength conversion layer130, and a wall140. As illustrated inFIG.2, the light emitting element120is provided on the substrate110and emits a first light L1. The wavelength conversion layer130is provided on the light emitting element120and converts a wavelength of a part of the first light L1to emit a second light L2. The wall140contains a light reflective material. The wall140surrounds the wavelength conversion layer130and forms an opening portion140kexposing at least a part of a top surface130aof the wavelength conversion layer130. The surface of the wall140includes a top surface140aprovided at a higher position than the top surface130aof the wavelength conversion layer130, and an inner surface140bthat forms the opening portion140k. The wall140includes a first portion141surrounding the wavelength conversion layer130, and a second portion142provided over the first portion141and around the first portion141. The opening portion140kis hollow. The “opening portion140k” refers to a portion located above the top surface130aof the wavelength conversion layer130and surrounded by the inner surface140b. An angle θ of a corner portion c defined by the top surface140aand the inner surface140bof the wall140is in a range of 90 degrees or greater and less than 180 degrees. Each component of the light emitting device100will be described in detail below. The substrate110is, for example, a wiring substrate in which wiring for the light emitting element120is disposed in a base material formed from a resin material. However, the base material of the substrate110is not limited thereto, and ceramics or the like can be used. The surface of the substrate110includes a top surface110aand a bottom surface110b, as illustrated inFIG.2. The top surface110aand the bottom surface110bare flat surfaces and are substantially parallel in the X direction and the Y direction. As illustrated inFIG.1, the shape of the substrate110in a top view is rectangular. However, the shape of the substrate110in top view is not limited thereto. Three of the light emitting elements120are mounted on the top surface110aof the substrate110. The three light emitting elements120are arranged along the X direction. However, the number of the light emitting elements120provided on the substrate110is not particularly limited as long as the number is one or more. If a plurality of the light emitting elements120are provided in the light emitting device100, the plurality of light emitting elements120can be arranged not only in the X direction, but also in the Y direction. The shape of each of the light emitting elements120in a top view is quadrangular. However, the shape of the light emitting element120is not limited thereto. As illustrated inFIG.2, in the present embodiment, the light emitting element120is a light emitting diode (LED) in which a front surface side of a semiconductor layer on a growth substrate of the light emitting element120is mounted on the substrate110by face-down mounting. A conductive joint member150is provided between each of the light emitting elements120and the substrate110. Each of the light emitting elements120is joined to the substrate110by using the joint member150. The light emitting element120emits blue light as the first light L1. However, the color of the first light L1is not limited to blue. A light shielding layer160is provided between each of the light emitting elements120and the substrate110. The light shielding layer160includes a base material formed of a resin material, and a plurality of fillers dispersed in the base material. A thermosetting resin such as a silicone resin or an epoxy resin can be used as the resin material. A light reflective material such as titanium oxide (TiO2) can be used as the filler. However, the light shielding layer160need not necessarily be provided between each of the light emitting elements120and the substrate110. FIG.3is an enlarged schematic end view illustrating a part of the light emitting element and a part of the wavelength conversion layer illustrated inFIG.2. The wavelength conversion layer130is provided on the top surface of each of the light emitting elements120. The wavelength conversion layer130contains a plurality of wavelength conversion particles131. The top surface130aof the wavelength conversion layer130has protrusions and recesses resulting from the plurality of wavelength conversion particles131. A yellow phosphor that absorbs the blue first light L1and emits the yellow second light L2can be used for the wavelength conversion particles131. The wavelength conversion layer130emits the second light L2and transmits a part of the first light L1. Therefore, the light emitting device100emits white light in which the first light L1and the second light L2are mixed. However, the wavelength conversion particles131are not limited to the yellow phosphor. A red phosphor that converts the wavelength of the first light L1to emit red light, or a green phosphor that converts the wavelength of the first light L1to emit green light can be used as the wavelength conversion particles131. In this case, the light emitting device100can emit white light by mixing the red color of the light emitted by the red phosphor, the green color of the light emitted by the green phosphor, and the blue color of the first light L1. The light emitting device100can also emit single color light other than white light. Each of the wavelength conversion particles131is covered by a glass layer132. The glass layer132is formed of silica (SiO2). The glass layer132holds the wavelength conversion particles131in the wavelength conversion layer130by allowing the wavelength conversion particles131to be bonded to each other and allowing the light emitting element120and the wavelength conversion particles131to be bonded to each other. The glass layer132protects the wavelength conversion particles131from moisture in the air and other substances. An air layer130k(a gap) is formed between the wavelength conversion particles131and between the light emitting element120and the wavelength conversion particles131. Next, an example of the dimensions of each of the components will be described. The thickness of the wavelength conversion layer130is in a range from 20 μm to 200 μm, for example. The diameter of each of the wavelength conversion particles131is, for example, in a range from 2 μm to 23 μm, or in a range from 5 to 15 μm. The thickness of the glass layer132is in a range from 1 μm to 5 μm, for example. The configuration of the wavelength conversion layer130is not limited to the configuration described above. For example, each of the wavelength conversion particles131needs not necessarily be covered by the glass layer132. In this case, the wavelength conversion particles131can be held in the wavelength conversion layer130by using a binder formed of a resin material such as silicone resin to bond the wavelength conversion particles131to each other and bond the light emitting element120and the wavelength conversion particles131. The wavelength conversion particles131can be held in the wavelength conversion layer130by adhering the wavelength conversion particles131to each other and adhering the light emitting element120and the wavelength conversion particles131through electrostatic adhesion, without using a binder, for example. The top surface130aof the wavelength conversion layer130can be a flat surface. For example, the wavelength conversion layer130can be formed of a light transmissive plate in which the plurality of wavelength conversion particles131are dispersed. As illustrated inFIG.1, the wavelength conversion layer130is surrounded by the wall140. The wall140has a tubular shape. That is, the wall140forms the opening portion140kexposing at least a part of the top surface130aof the wavelength conversion layer130. The wall140includes the first portion141and the second portion142, as illustrated inFIG.2. Each of the first portion141and the second portion142includes a base material formed of a resin material, and a plurality of particles of filler formed of a light reflective material. A thermosetting resin such as a silicone resin or an epoxy resin can be used as the resin material of the wall140. Silicon oxide (SiO2), titanium oxide (TiO2), aluminum (Al), silver (Ag), or the like can be used as the light reflective material of the wall140. The density of the filler in the first portion141and the density of the filler in the second portion142are different from each other. The “density of the filler” means the mass of the filler contained in the unit volume of each of the first and second portions141and142. In the present embodiment, the first portion141surrounds both the light emitting element120and the wavelength conversion layer130. The surface of the first portion141includes an inner surface141a, an outer surface141b, and a bottom surface141c. The inner surface141asurrounds the light emitting element120and the wavelength conversion layer130, and is in contact with a lateral surface of the light emitting element120and an end portion of the wavelength conversion layer130in the lateral direction. An upper end141tlocated at the uppermost position in the inner surface141ais located at a position higher than the top surface130aof the wavelength conversion layer130. A first region141slocated between the upper end141tand the top surface130aof the wavelength conversion layer130in the inner surface141ais perpendicular to the top surface110aof the substrate110. The term “perpendicular” can include variations in the manufacturing process and can mean not only “exactly perpendicular” but also “substantially perpendicular”. The outer surface141bsurrounds the inner surface141aand is in contact with the inner surface141aand the bottom surface141c. The outer surface141bextends so as to become farther from the inner surface141aas advancing in a downward direction. However, a top surface of the first portion141can be located between the inner surface141aand the outer surface141b. In this case, the outer surface141bcan be perpendicular to the top surface110aof the substrate110. The bottom surface141cis in contact with the top surface110aof the substrate110. The second portion142is provided over the first portion141and surrounds the first portion141. The density of the filler contained in the first portion141is higher than the density of the filler contained in the second portion142. Thus, the light reflectance of the first portion141is higher than the light reflectance of the second portion142. The surface of the second portion142includes a top surface142a, an inner surface142b, an outer surface142c, and a bottom surface142d. In the present embodiment, the top surface142ais a flat surface parallel to the top surface110aof the substrate110. The term “parallel” can include variations in the manufacturing process and can mean not only “exactly parallel” but also “substantially parallel”. An upper end142tlocated at the uppermost position in the inner surface142bis located above the upper end141tof the first portion141. The inner surface142bincludes a second region142s1located between the upper end141tand the upper end142t, and a third region142s2located between the upper end141tand the bottom surface142d. The second region142s1is in contact with the top surface142a. The second region142s1is perpendicular to the top surface110aof the substrate110. The second region142s1is flush with the first region141sof the first portion141. The third region142s2is in contact with the outer surface141bof the first portion141. The outer surface142csurrounds the top surface142aand is in contact with the top surface142aand the bottom surface142d. The outer surface142cis perpendicular to the top surface110aof the substrate110. However, the outer surface142ccan be inclined with respect to the top surface110aof the substrate110. The bottom surface142dis in contact with the top surface110aof the substrate110. Thus, the top surface140aof the entire wall140includes the top surface142aof the second portion142. The inner surface140bof the entire wall140includes the inner surface141aof the first portion141and the second region142s1of the second portion142. An outer surface140cof the entire wall140includes the outer surface142cof the second portion142. A bottom surface140dof the entire wall140includes the bottom surface141cof the first portion141and the bottom surface142dof the second portion142. Thus, the top surface140ais located above the top surface130aof the wavelength conversion layer130. The distance between the top surface130aof the wavelength conversion layer130and the top surface140aof the wall140is preferably in a range from 50 μm to 2000 μm. “The distance between the top surface130aof the wavelength conversion layer130and the top surface140aof the wall140” refers to the shortest distance in the Z direction between the top surface130aof the wavelength conversion layer130and the top surface140aof the wall140. The angle θ of the corner portion c between the top surface140aand the inner surface140bis in a range of 90 degrees or greater and less than 180 degrees. In particular, in the present embodiment, the top surface140ais parallel to the top surface110aof the substrate110, and a region (e.g., the second region142s1) of the inner surface140bthat includes the upper end142tis perpendicular to the top surface110aof the substrate110. Thus, the angle θ is 90 degrees. Next, operation of the light emitting device100according to the present embodiment will be described. FIG.4Ais a schematic diagram illustrating an example of a path of light at an end surface taken along the line II-II ofFIG.1. FIG.4Bis an enlarged schematic end view illustrating an example of a path of light at a corner portion he of a light emitting device100haccording to a reference example. The wall140surrounds the light emitting element120and the wavelength conversion layer130. Thus, when the light emitting element120is illuminated, a portion of the first light L1emitted from the light emitting element120and a portion of the second light L2emitted from the wavelength conversion layer130are reflected by the wall140. In particular, on the inner surface140bof the wall140, the luminance of the incident second light L2is higher in a region closer to a region adjacent to the wavelength conversion layer130. Thus, the second light L2easily propagates in a portion of the wall140adjacent to the wavelength conversion layer130. In the present embodiment, the reflectance of the first portion141adjacent to the wavelength conversion layer130is higher than the reflectance of the second portion142. Therefore, as illustrated inFIG.4A, the second light L2can be suppressed from propagating into the first portion141adjacent to the wavelength conversion layer130. Further, in the present embodiment, the top surface140aof the wall140is located above the top surface130aof the wavelength conversion layer130. Thus, even if the second light L2propagates in the first portion141, the propagated second light L2is attenuated in the wall140, and emission of the second light L2from the top surface140aof the wall140can be suppressed. As a result, the second light L2propagating in the wall140can be suppressed from leaking from the top surface140aof the wall140. Further, in the present embodiment, the angle θ of the corner portion c is in the range from 90 degrees or greater to less than 180 degrees. Thus, a thickness t of the corner portion c (the distance between the top surface140aand the inner surface140bin the vicinity of the corner portion c) can be increased. As a result, even if the second light L2propagates into the wall140from a region of the inner surface140bof the wall140near the corner portion c, the propagated second light L2is attenuated in the wall140, and the second light L2can be suppressed from leaking from the top surface140a. On the other hand, as in the light emitting device100haccording to the reference example, if an angle hθ of the corner portion hc between a top surface140haand an inner surface140hbof a wall140his less than 90 degrees, a thickness ht of the corner portion hc is small. Thus, if the second light L2propagates into the wall140hfrom a region of the inner surface140hbof the wall140hnear the corner portion hc, the propagated second light L2leaks more easily from the top surface140hacompared to the present embodiment. Accordingly suppression of light leakage from the top surface140aof the wall140can suppress that a peripheral region S2surrounding a region S1directly above the light emitting element120and the wavelength conversion layer130becomes brighter. Thus, the contrast between the peripheral region S2and the region S1directly above the light emitting element120and the wavelength conversion layer130can be increased. Further, in the present embodiment, a region (the second region142s1) of the wall140including the upper end142tis perpendicular to the top surface110aof the substrate110. Therefore, the light distribution angle can be a narrow angle, and thus, the luminance of the light emitting device100can be enhanced. The opening portion140kis hollow. Thus, the light extraction efficiency of the light emitting device100can be improved. FIG.4Cis a schematic diagram illustrating an example of a path of light at an end surface in which a part of the light emitting element and a part of the wavelength conversion layer inFIG.2are illustrated in an enlarged manner. In the present embodiment, the wavelength conversion particles131are covered by the glass layer132. Therefore, when the first light L1emitted from the light emitting element120and the second light L2emitted from the wavelength conversion layer130are incident on the glass layer132from the air layer130kin the wavelength conversion layer130, the first light L1and the second light L2are likely to be reflected at a boundary surface between the air layer130kand the glass layer132. Thus, propagation of light in the lateral direction is blocked in the wavelength conversion layer130, and the light is emitted from the region S1directly above the light emitting element120and the wavelength conversion layer130. Thus, the contrast between the peripheral region S2and the region S1directly above the light emitting element120and the wavelength conversion layer130can be increased. Next, a method of manufacturing the light emitting device100according to the present embodiment will be described. FIGS.5A to5Fare schematic diagrams illustrating a method of manufacturing the light emitting device100according to the present embodiment. As illustrated inFIG.5A, the light emitting element120is mounted on the substrate110. In the present embodiment, the light emitting element120is joined to the substrate110with the conductive joint member150. In the present embodiment, the light shielding layer160is provided between the light emitting element120and the substrate110. Subsequently, as illustrated inFIG.5B, the wavelength conversion layer130is arranged on the light emitting element120. The wavelength conversion layer130is provided by spraying a slurry material containing the plurality of wavelength conversion particles131. Specifically, a mask material is provided so as to surround the light emitting element120, the slurry material is sprayed onto the light emitting element120, and the mask material is removed. The slurry material contains polysilazane, the plurality of wavelength conversion particles131, and an organic solvent. Heptane or dibutyl ether, for example, is used as the organic solvent. A slurry material not containing an organic solvent can be used. The slurry material contains no resin material. Subsequently, the base onto which the slurry material is sprayed is heated or left at room temperature to convert the polysilazane into silica. Thus, the wavelength conversion particles131are covered with the glass layer132containing the silica and the air layer130kis formed between the wavelength conversion particles131. Thus, the wavelength conversion layer130is formed on the light emitting element120. The method of disposing the wavelength conversion layer is not limited to the method described above. For example, the slurry material to be sprayed need not contain polysilazane and can contain a binder including a resin material such as a silicone resin. The wavelength conversion layer can be provided by electrostatically adhering the wavelength conversion particles to each other and electrostatically adhering the wavelength conversion particles and the light emitting element. The wavelength conversion layer130formed by the light transmissive plate in which the plurality of wavelength conversion particles are dispersed can be disposed on the top surface of the light emitting element120. Subsequently, as illustrated inFIG.5C, a mold member170is placed on the wavelength conversion layer130. The mold member170is held by a holding tool171, for example. The mold member170is a plate member. The surface of the mold member170includes a top surface170a, a bottom surface170b, and a lateral surface170c. The top surface170aand the bottom surface170bare flat surfaces. The bottom surface170bis located on a side opposite to the top surface170aand faces the wavelength conversion layer130. The lateral surface170cis in contact with the top surface170aand the bottom surface170b, and is perpendicular to the top surface170aand the bottom surface170b. The mold member170is arranged such that the top surface170aand the bottom surface170bare parallel to the top surface110aof the substrate110. The mold member170is disposed at a position overlapping three light emitting elements120in a top view. The mold member170is preferably formed of a light transmissive material, and is formed of glass or a Teflon (registered trademark) sheet, for example. In the case in which the mold member170is formed of a light transmissive material, the light emitting element120and the wavelength conversion layer130can be visually recognized from above the mold member170in a state where the mold member170is placed on the wavelength conversion layer130. Thus, when placing the mold member170, the mold member170can be easily positioned with respect to the light emitting element120and the wavelength conversion layer130. However, the mold member170can also be formed of a metal material. Subsequently, as illustrated inFIGS.5D and5E, an uncured light reflecting material140F is provided so as to surround the wavelength conversion layer130and the mold member170. At this time, the uncured light reflecting material140F is provided such that the top surface140aof the light reflecting material140F after curing, which is illustrated inFIG.5F, is parallel to the top surface110aof the substrate110. The uncured light reflecting material140F includes a base material formed of an uncured resin material, and a filler formed of a light reflective material. A thermosetting resin such as a silicone resin or an epoxy resin can be used as the resin material of the light reflecting material140F. Silicon oxide (SiO2), titanium oxide (TiO2), aluminum (Al), silver (Ag), or the like can be used as the light reflective material of the light reflecting material140F. The light reflecting material140F can contain a thickening agent. The term “uncured” means that the light reflecting material140F is at least not completely cured and is flexible enough to be deformed to match the shape of the mold member170. The “light reflecting material140F after curing” means the light reflecting material140F which is completely cured and corresponds to the wall140. Next, a step of providing the uncured light reflecting material140F will be described in detail, using an example where the uncured light reflecting material140F includes a first member141F and a second member142F. The first member141F and the second member142F each include a base material formed of an uncured resin material and a filler formed of a light reflective material, and differ from each other in terms of concentration of the filler. After the first member141F is cured, the first member141F forms the first portion141of the wall140. After the second member142F is cured, the second member142F forms the second portion142of the wall140. First, as illustrated inFIG.5D, the first member141F is provided so as to surround the wavelength conversion layer130and a lower region of the lateral surface170cof the mold member170and in contact with the lower region of the lateral surface170cof the mold member170. The uncured first member141F preferably has a viscosity such that after being provided to surround the wavelength conversion layer130and the mold member170, the first member141F does not flow into the wavelength conversion layer130. For example, the viscosity of the uncured first member141F is preferably in a range from 450 Pa s to 1000 Pa s. This may make it possible to prevent the first member141F from flowing into the wavelength conversion layer130while bringing an inner surface141Fb of the uncured first member141F into contact with the lower region of the lateral surface170cof the mold member170. A region between the top surface130aof the wavelength conversion layer130and an upper end141Ft located at the uppermost position in the inner surface141Fb of the uncured first member141F is in contact with the lower region of the lateral surface170cof the mold member170. Thus, the first region141sperpendicular to the top surface110aof the substrate110is formed in the first portion141which is the first member141F after curing, as illustrated inFIG.2. Subsequently, the first member141F is semi-cured. The first member141F need not necessarily be semi-cured. Subsequently, as illustrated inFIG.5E, the second member142F is provided over the first member141F and surround the first member141F. The viscosity of the uncured second member142F is lower than the viscosity of the uncured first member141F. A method of decreasing the viscosity of the second member142F than the viscosity of the first member141F is not particularly limited. Examples of the method include a method of decreasing the concentration of a filler contained in the second member142F than the concentration of a filler contained in the first member141F, and a method of decreasing the amount of a thickening agent added to the second member142F than the amount of a thickening agent added to the first member141F. The uncured second member142F preferably has a viscosity such that the second member142F can be fluidal along the shape of the lateral surface170cof the mold member170. For example, the viscosity of the second member142F is preferably in a range from 5 Pa s to 250 Pa s. When disposing the second member142F, a frame member180that surrounds the mold member170and the first member141F can be provided with a distance from the mold member170and the first member141F, and the second member142F can be disposed between the mold member170and the frame member180. In the present embodiment, the second member142F is provided such that the cured top surface140ais parallel to the top surface110aof the substrate110. For example, if a top surface142Fa of the uncured second member142F is located below the top surface170aof the mold member170and a top surface180aof the frame member180, the second member142F spreads onto the top surface170aof the mold member170and the top surface180aof the frame member180due to surface tension, and thus, the top surface142Fa of the uncured second member142F is recessed in a direction approaching the substrate110. On the other hand, in the present embodiment, the uncured second member142F is provided such that the top surface142Fa of the uncured second member142F is flush with the top surfaces170aand180a. Thus, the top surface142Fa of the uncured second member142F is parallel to the top surface110aof the substrate110. With this configuration, the top surface140aafter curing is parallel to the top surface110aof the substrate110. As a result, the angle θ of the corner portion c of the light reflecting material140F after curing (i.e., the wall140) can be 90 degrees. When it is expected that the top surface140aof the cured second member142F is located lower than the top surface142Fa of the uncured second member142F and is recessed in the direction approaching the substrate110, the uncured second member142F can be provided such that the top surface142Fa of the uncured second member142F protrudes in the direction from the top surface110aof the substrate110to the top surface140aof the light reflecting material140F. In this case, the top surface142Fa can be flattened by polishing or the like after the second member142F is cured. As described above, the first member141F is in contact with the lower region of the lateral surface170cof the mold member170and surrounds the wavelength conversion layer130. Therefore, the second member142F can be made to flow along the shape of the lateral surface170cof the mold member170while being suppressed from flowing into the wavelength conversion layer130by the first member141F. Subsequently, the light reflecting material140F is cured. If the base material of the light reflecting material140F is a thermosetting resin, the light reflecting material140F is cured by being heated. The heating temperature is in a range from 150° C. to 200° C., for example. However, the curing method can be appropriately selected according to the material of the light reflecting material140F. For example, the resin in the light reflecting material140F can be formed of an ultraviolet curable resin and cured by ultraviolet rays. Subsequently, as illustrated inFIG.5F, the mold member170and the frame member180are removed from the substrate110. Specifically, the mold member170is detached from the cured light reflecting material140F by applying a force in a direction in which the mold member170is pulled apart from the cured light reflecting material140F. Thus, the light emitting device100is formed with the angle θ of the corner portion c of the wall140in the range from 90 degrees to less than 180 degrees. Next, an effect of the present embodiment will be described. In the light emitting device100according to the present embodiment, the top surface140aof the wall140is positioned higher than the position of the top surface130aof the wavelength conversion layer130. Furthermore, the angle θ of the corner portion c between the top surface140aand the inner surface140bof the wall140is in the range from 90 degrees to less than 180 degrees. Thus, even if the second light L2propagates into the wall140, emission of the propagated second light L2from the top surface140acan be suppressed. Therefore, a light emitting device100in which light can be suppressed from leaking from the top surface140aof the wall140can be provided. Also with this configuration, the contrast between the peripheral region S2and the region S1directly above the light emitting element120and the wavelength conversion layer130can be increased. The opening portion140kis hollow. Thus, the light extraction efficiency of the light emitting device100can be improved. The wall140includes a base material formed of a resin material, and a filler that is dispersed in the base material and formed of a light reflective material. The density of the filler contained in the first portion141is higher than the density of the filler contained in the second portion142. Thus, the reflectance of the first portion141can be set higher than the reflectance of the second portion142. As a result, the second light L2is less likely to propagate into the first portion141adjacent to the wavelength conversion layer130. In such a configuration, the viscosity of the uncured first member141F is higher than the viscosity of the uncured second member142F during manufacturing. Thus, the second member142F can be easily caused to flow along the shape of the lateral surface170cof the mold member170while being suppressed from flowing into the wavelength conversion layer130by the first member141F. A region (e.g., the second region142s1) of the inner surface140bof the wall140, the region includes the upper end142tis perpendicular to the top surface110aof the substrate110. Thus, the contrast between the peripheral region S2and the region S1directly above the light emitting element120and the wavelength conversion layer130can be further increased. The distance between the top surface130aof the wavelength conversion layer130and the top surface140aof the wall140is in a range from 50 μm to 2000 μm. There may be a case in which the second light L2propagates into the wall140from a region of the inner surface140bof the wall140, the region being adjacent to the wavelength conversion layer130. Even in this case, the propagated second light L2is attenuated and the second light L2can be suppressed from leaking from the top surface140aof the wall140by allowing the top surface130aof the wavelength conversion layer130and the top surface140aof the wall140to be sufficiently separated. The top surface140aof the wall140is parallel to the top surface110aof the substrate110. Therefore, the thickness t of the corner portion c can be increased further than in a case in which the top surface140aof the wall140is recessed in the direction approaching the top surface110aof the substrate110. Thus, light leakage from the top surface140aof the wall140can be suppressed. The wavelength conversion layer130contains the plurality of wavelength conversion particles131, and the top surface130aof the wavelength conversion layer130has protrusions and recesses resulting from the plurality of wavelength conversion particles131. With this configuration, the light distribution angle can be a narrow angle, and thus the luminance of the light emitting device100can be enhanced. The wavelength conversion layer130further includes the glass layer132that covers the surface of the wavelength conversion particles131. The wavelength conversion particles131are bonded to each other via the glass layer132, and the air layer130kis formed between the wavelength conversion particles131covered by the glass layer132. Thus, the contrast between the peripheral region S2and the region S1directly above the light emitting element120and the wavelength conversion layer130can be further increased. In the method of manufacturing the light emitting device100according to the present embodiment, first, the light emitting element120is mounted on the substrate110. Subsequently, the wavelength conversion layer130is disposed on the light emitting element120. Then, the mold member170is placed on the wavelength conversion layer130. Subsequently, the uncured light reflecting material140F is disposed surrounding the wavelength conversion layer130and the mold member170such that the top surface140aof the cured light reflecting material140F is parallel to the top surface110aof the substrate110. Then, the light reflecting material140F is cured to form the wall140. Subsequently, the mold member170is removed to form, in the wall140, the hollow opening portion140kthat exposes at least a part of the top surface130aof the wavelength conversion layer130. According to this method of manufacturing, the light emitting device100, in which light leakage from the top surface140aof the wall140can be suppressed, can be manufactured. The light reflecting material140F includes the first member141F and the second member142F, and the step of providing the light reflecting material140F includes a step of providing the first member141F so as to surround the wavelength conversion layer130, and a step of providing the second member142F over the first member141F and surrounding the first member141F. The viscosity of the second member142F is lower than the viscosity of the first member141F. Thus, the second member142F can be easily caused to flow along the shape of the lateral surface170cof the mold member170while the second member142F is suppressed from flowing into the wavelength conversion layer130by the first member141F. If the mold member170is formed of a light transmissive material, positioning and disposition of the mold member170can be easily performed with respect to the light emitting element120and the wavelength conversion layer130. Second Embodiment Next, a second embodiment will be described. FIG.6is a schematic end view illustrating a light emitting device200according to the present embodiment. The light emitting device200according to the present embodiment differs from the light emitting device100according to the first embodiment in that a top surface242aof a second portion242of a wall240is not parallel to the top surface110aof the substrate110. In the following description, in general, only differences from the first embodiment will be described. The second embodiment is the same as or a similar to the first embodiment, except for the points described below. The wall240includes a first portion241and the second portion242. The configuration of the first portion241is substantially the same as the configuration of the first portion141in the first embodiment, and thus, description of the first portion241will be omitted. The configuration of the second portion242is substantially the same as the configuration of the second portion142in the first embodiment, except for the shape of the top surface242a. The top surface242aof the second portion242is a curved surface that protrudes toward the direction from the top surface110aof the substrate110to the top surface242aof the second portion242. A top surface240aof the entire wall240includes the top surface242aof the second portion242. Thus, the angle θ of the corner portion c between the top surface240aand an inner surface240bof the wall240is in a range of 90 degrees or greater and less than 180 degrees. Here, the angle θ is an angle formed by the inner surface240band a tangent line L of the top surface242apassing through an upper end242tof the inner surface240b. Thus, the angle θ can be greater than 90 degrees. In this case, the thickness t of the corner portion c can be further increased. Thus, even if the second light L2propagates into the wall240from a region of the inner surface240bof the wall240near the corner portion c, the propagated second light L2is attenuated, and the second light L2can be suppressed from leaking from the top surface240a. Next, a method of manufacturing the light emitting device200according to the present embodiment will be described. FIG.7is a schematic diagram illustrating the method of manufacturing the light emitting device200according to the present embodiment. The method of manufacturing according to the present embodiment is different from the method of manufacturing of the light emitting device100according to the first embodiment in terms of a step of providing a second member242F included in a light reflecting material240F. The light reflecting material240F includes a first member241F and the second member242F. Each of the first member241F and the second member242F contains a base material formed of an uncured resin material, and a filler formed of a light reflective material. After the first member241F is cured, the first member241F forms the first portion241of the wall240. After the second member242F is cured, the second member242F forms the second portion242of the wall240. The process until the step of providing the first member241F is the same as or a similar to the process until the step of providing the first member141F in the method of manufacturing the light emitting device100according to the first embodiment, and thus, description of this process will be omitted. After the first member241F is provided, the second member242F is provided such that the cured top surface240aprotrudes in the direction from the top surface110aof the substrate110to the top surface240aof the wall240, as illustrated inFIG.7. Specifically, the uncured second member242F is provided such that a top surface242Fa protrudes in the direction from the top surface110aof the substrate110to the top surface240aof the wall240due to surface tension. Thus, the top surface242aof the cured second member242F protrudes in the direction from the top surface110aof the substrate110to the top surface240aof the wall240. The subsequent procedure is the same as or a similar to the first embodiment. Next, an effect of the present embodiment will be described. In the present embodiment, the top surface242aof the wall240protrudes toward the direction from the substrate110to the top surface240aof the wall240. Thus, the thickness t of the corner portion c can be further increased. Therefore, even if the second light L2propagates into the wall240from a region of the inner surface240bof the wall240near the corner portion c, the propagated second light L2is attenuated, and the second light L2can be suppressed from leaking from the top surface242a. Third Embodiment Next, a third embodiment will be described. FIG.8is a schematic end view illustrating a light emitting device300according to the present embodiment. The light emitting device300according to the present embodiment differs from the light emitting device100according to the first embodiment in terms of the configuration of a wall340. The wall340includes a first portion341, a second portion342, and a filler portion343. The configuration of the first portion341is the same as or a similar to the configuration of the first portion141in the first embodiment, and thus, description of the first portion341will be omitted. The configuration of the second portion342is the same as or similar to the configuration of the second portion142in the first embodiment, except for the shape of a top surface342a. The top surface342aof the second portion342is recessed in the direction approaching the substrate110. The filler portion343is provided in the recess in the top surface342aof the second portion342. The filler portion343contains a base material formed of a resin material, and a filler dispersed in the base material. A thermosetting resin such as a silicone resin or an epoxy resin can be used as the resin material. A light reflective material such as silicon oxide (SiO2), titanium oxide (TiO2), aluminum (Al), and silver (Ag), or a light absorbing material such as carbon particles formed of carbon powder can be used as the filler. A top surface343aof the filler portion343is parallel to the top surface110aof the substrate110. However, the filler portion343can protrude in the direction from the substrate110to the top surface343aof the filler portion343. A top surface340aof the entire wall340includes the top surface343aof the filler portion343. Thus, the angle θ of the corner portion c between the top surface340aand an inner surface340bof the wall340can be in a range of 90 degrees or greater and less than 180 degrees. If the filler in the filler portion343is formed of a light reflective material, the density of the filler included in the filler portion343is preferably higher than the density of the filler included in the second portion342. With this configuration, the second light L2that has propagated into the wall340can be further suppressed from leaking from the top surface343a. If the filler in the filler portion343is formed of a light absorbing material, the filler in the filler portion343can absorb the second light L2that has propagated into the wall340. With this configuration, the second light L2that has propagated into the wall340can be further suppressed from leaking from the top surface343a. Fourth Embodiment Next, a fourth embodiment will be described. FIG.9is a schematic end view illustrating a light emitting device400according to the present embodiment. The light emitting device400according to the present embodiment differs from the light emitting device100according to the first embodiment in terms of the configuration of a wall440. The wall440includes a first portion441, a second portion442, and a third portion443. The first portion441is provided to surround the light emitting element120and the wavelength conversion layer130. The second portion442is provided over the first portion441and surrounds the first portion441. The third portion443is provided over the second portion442and surrounds the second portion442. Each of the first portion441, the second portion442, and the third portion443contains a base material formed of a resin material, and a filler formed of a light reflective material. The density of the filler contained in the first portion441is higher than the density of the filler contained in the second portion442. The density of the filler contained in the second portion442is higher than the density of the filler contained in the third portion443. Thus, the light reflectance of the first portion441is higher than the light reflectance of the second portion442, and the light reflectance of the second portion442is higher than the light reflectance of the third portion443. The surface of the first portion441includes an inner surface441a, an outer surface441b, and a bottom surface441c. The inner surface441asurrounds the light emitting element120and the wavelength conversion layer130, and is in contact with a lateral surface of the light emitting element120and an end portion of the wavelength conversion layer130in the lateral direction. An upper end441tlocated at the uppermost position in the inner surface441ais located above the top surface130aof the wavelength conversion layer130. A first region441slocated between the upper end441tand the top surface130aof the wavelength conversion layer130in the inner surface441ais perpendicular to the top surface110aof the substrate110. The outer surface441bsurrounds the inner surface441aand is in contact with the inner surface441aand the bottom surface441c. The outer surface441bextends so as to become farther from the inner surface441aas advancing in the downward direction. However, the top surface of the first portion441can be located between the inner surface441aand the outer surface441b. In this case, the outer surface441bcan be perpendicular to the top surface110aof the substrate110. The bottom surface441cis in contact with the top surface110aof the substrate110. The surface of the second portion442includes an inner surface442a, an outer surface442b, and a bottom surface442c. The inner surface442asurrounds the first portion441. An upper end442tlocated at the uppermost position in the inner surface442ais located above the upper end441tof the first portion441. The inner surface442aincludes a second region442s1located between the upper end442tand the upper end441tof the first portion441, and a third region442s2located between the upper end441tand the bottom surface442c. The second region442s1is perpendicular to the top surface110aof the substrate110and flush with the inner surface441aof the first portion441. The outer surface442bis provided to surround the inner surface442aand contacts the inner surface442aand the bottom surface442c. A portion of the top surface110acan exist between the inner surface442aand the outer surface442b. The bottom surface442ccontacts the top surface110aof the substrate110. The third portion443is provided over the second portion442and surrounds the second portion442. The surface of the third portion443includes a top surface443a, an inner surface443b, an outer surface443c, and a bottom surface443d. The top surface443ais parallel to the top surface110aof the substrate110. However, the top surface443acan protrude in the direction from the substrate110to the top surface443aof the third portion443. An upper end443tlocated at the uppermost position in the inner surface443bis located above the upper end442tof the second portion442. The inner surface443bincludes a fourth region443s1located between the upper end443tand the upper end442t, and a fifth region443s2located between the upper end442tand the bottom surface443d. The fourth region443s1is in contact with the top surface443a. The fourth region443s1is perpendicular to the top surface110aof the substrate110. The fourth region443s1is flush with the second region442s1of the second portion442. The fifth region443s2is in contact with the outer surface442bof the second portion442. The outer surface443cis provided to surround the top surface443aand is in contact with the top surface443aand the bottom surface443d. The outer surface443cis perpendicular to the top surface110aof the substrate110. However, the outer surface443ccan be inclined with respect to the top surface110aof the substrate110. The bottom surface443dis in contact with the top surface110aof the substrate110. Thus, a top surface440aof the entire wall440includes the top surface443aof the third portion443. An inner surface440bof the entire wall440includes the inner surface441aof the first portion441, the second region442s1of the second portion442, and the second region443s1of the third portion443. An outer surface440cof the entire wall440includes the outer surface443cof the third portion443. A bottom surface440dof the entire wall440includes the bottom surface441cof the first portion441, the bottom surface442cof the second portion442, and the outer surface443cof the third portion443. The angle θ of the corner portion c between the top surface440aand the inner surface440bof the wall440is in a range of 90 degrees or greater and less than 180 degrees. Next, a method of manufacturing the light emitting device400according to the present embodiment will be described. FIGS.10A to10Care schematic diagrams illustrating the method of manufacturing the light emitting device400according to the present embodiment. The method of manufacturing according to the present embodiment is different from the method of manufacturing the light emitting device100according to the first embodiment in terms of a step of providing a light reflecting material440F. The light reflecting material440F includes a first member441F, a second member442F, and a third member443F. The first member441F, the second member442F, and the third member443F each contain a base material formed of an uncured resin material and a filler formed of a light reflective material, and differ from each other in terms of concentration of the filler. After the first member441F is cured, the first member441F forms the first portion441of the wall440. After the second member442F is cured, the second member442F forms the second portion442of the wall440. After the third member443F is cured, the third member443F forms the third portion443of the wall440. A method of providing the light reflecting material440F will be described in detail below. As illustrated inFIG.10A, similar to the first embodiment, the first member441F is provided so as to surround the wavelength conversion layer130and a lower region of the lateral surface170cof the mold member170, and be in contact with the lower region of the lateral surface170cof the mold member170. Subsequently, the first member441F is semi-cured. Semi-cure of the first member441F need not necessarily be performed. Subsequently, as illustrated inFIG.10B, the second member442F is provided over the first member441F and surrounding the first member441F. The viscosity of the uncured second member442F is lower than the viscosity of the uncured first member441F. Therefore, the second member442F can be sufficiently brought into contact with the lateral surface170cof the mold member170while being suppressed from flowing into the wavelength conversion layer130by the first member441F. Subsequently, the second member442F is semi-cured. The semi-cure of the second member442F need not necessarily be performed. Subsequently, as illustrated inFIG.10C, the third member443F is provided over the second member442F and surrounding the second member442F. At this time, the third member443F is provided such that the cured top surface440ais parallel to the top surface110aof the substrate110. The third member443F can be provided such that the cured top surface440aprotrudes in the direction from the top surface110aof the substrate110to the top surface440aof the wall440. The viscosity of the uncured third member443F is lower than the viscosity of the uncured second member442F. Thus, the third member443F flows along the shape of the lateral surface170cof the mold member170. As described above, before the third member443F is provided, the first member441F and the second member442F contact the lateral surface170cof the mold member170and cover the wavelength conversion layer130. Therefore, the third member443F can be deformed along the shape of the lateral surface170cof the mold member170while being suppressed from flowing into the wavelength conversion layer130by both the first member441F and the second member442F. Subsequently, the first member441F, the second member442F, and the third member443F are cured. The subsequent procedure is the same as or a similar to the first embodiment. Next, an effect of the present embodiment will be described. In the light emitting device400according to the present embodiment, the wall440further includes the third portion443provided over the second portion442and surrounding the second portion442. The density of the filler contained in the third portion443is lower than the density of the filler contained in the second portion442. Thus, the reflectance of the second portion442can be made higher than the reflectance of the third portion443. Therefore, propagation of the second light L2in the wall440can be further suppressed. The viscosity of the uncured second member442F during manufacturing is higher than the viscosity of the uncured third member443F. Therefore, the third member443F can be deformed along the shape of the lateral surface170cof the mold member170while being suppressed from flowing into the wavelength conversion layer130by both the first member441F and the second member442F. In the embodiment described above, an example is described in which the wall440includes the three portions441,442, and443having different filler densities. However, the wall440can include four or more portions having different filler densities. Fifth Embodiment Next, a fifth embodiment will be described. FIG.11is a schematic end view illustrating a light emitting device500according to the present embodiment. The light emitting device500according to the present embodiment differs from the light emitting device100according to the first embodiment in that a light emitting element520is an LED that is mounted on the substrate110such that a growth substrate side of the light emitting element520faces the substrate110(i.e., face-up mounting). The light emitting element520is mounted on the substrate110. An electrode on a top surface of the light emitting element520is connected to one end of a wire550. The other end of the wire550is connected to an electrode on the substrate110(not illustrated). A light shielding layer560is provided around the light emitting element520. The light shielding layer560is in contact with the top surface110aof the substrate110. The light shielding layer560includes a base material formed of a resin material, and a filler dispersed in the base material. A thermosetting resin such as a silicone resin or an epoxy resin can be used as the base material of the light shielding layer560. A light reflective material such as titanium oxide (TiO2) can be used as the filler of the light shielding layer560. A wall540is provided on the light shielding layer560, and a part of the wire550is embedded in the wall540. The wall540includes a first portion541and a second portion542. The configuration of the first portion541and the second portion542is the same as or a similar to the configuration of the first portion141and the second portion142in the first embodiment except that the first portion541and the second portion542are in contact with the light shielding layer560. Thus, the light emitting element520can be mounted face up. The wall540is only required to surround at least the wavelength conversion layer130and need not necessarily surround the light emitting element520. Sixth Embodiment Next, a sixth embodiment will be described. FIG.12is a schematic diagram illustrating a method of manufacturing the light emitting device100according to the present embodiment. The method of manufacturing the light emitting device100according to the present embodiment differs from the method of manufacturing the light emitting device100according to the first embodiment in that a film671is disposed on the lateral surface170cof the mold member170. Before the light reflecting material140F is provided, the film671is disposed on the lateral surface170cof the mold member170. The film671includes a mold release agent that assists in removing the mold member170from the cured light reflecting material140F. A fluorine-based coating agent or a silicone-based coating agent can be used as the mold release agent. However, the film671can be a gold-plated film. Resin and gold do not tend to strongly adhere to each other. Thus, if the film671is a gold-plated film, the mold member170can be easily removed from the cured light reflecting material140F. Next, as illustrated inFIG.12, the light reflecting material140F is provided in a similar manner as in the first embodiment. The subsequent procedure is the same as or a similar to the first embodiment. Seventh Embodiment Next, a seventh embodiment will be described. FIG.13is a schematic diagram illustrating a method of manufacturing the light emitting device100according to the present embodiment. The method of manufacturing the light emitting device100according to the present embodiment differs from the method of manufacturing the light emitting device100according to the first embodiment in that a mold member770is not a plate like member. The mold member770can be a tubular member. The shape of the mold member770is a hollow rectangular parallelepiped. The mold member770can be formed of a resin material or a metal material. A mold release agent or gold plating can be provided on a lateral surface of the mold member770. Similar to the mold member170in the first embodiment, the mold member770is removed after the light reflecting material140F is cured. Eighth Embodiment Next, an eighth embodiment will be described. FIGS.14A to14Dare schematic diagrams illustrating a method of manufacturing a light emitting device800according to the present embodiment. The method of manufacturing the light emitting device800according to the present embodiment differs from the method of manufacturing the light emitting device100according to the first embodiment in that the mold member170is made to temporarily adhere to the wavelength conversion layer130. As illustrated inFIG.14A, in the step of disposing the mold member170, an adhesive agent880is provided between the mold member170and the wavelength conversion layer130such that the mold member170and the wavelength conversion layer130temporarily adhere to each other. The term “temporarily adhere” means that, when a force separating the mold member170and the wavelength conversion layer130is applied after the light reflecting material140F is cured, the mold member170and the wavelength conversion layer130adhere to each other with an adhesive force having a strength at which adhesion between the mold member170and the wavelength conversion layer130can be released without damaging the mold member170and the wavelength conversion layer130. A phenyl-based adhesive agent can be used as the adhesive agent880. In the case in which the adhesive agent880is formed of the phenyl-based adhesive agent, the mold member170and the wavelength conversion layer130can be easily detached. However, the adhesive agent880can also be a water soluble adhesive agent. Next, as illustrated inFIG.14B, the first member141F of the light reflecting material140F is provided. Then, as illustrated inFIG.14C, the second member142F of the light reflecting material140F is provided. In these steps, the mold member170is caused to temporarily adhere to the wavelength conversion layer130. Thus, when providing the light reflecting material140F, displacement of the mold member170relative to the light emitting element120and the wavelength conversion layer130can be suppressed. Next, the light reflecting material140F is cured. Then, as illustrated inFIG.14D, the mold member170is removed. Thus, the light emitting device800is formed. InFIG.14D, after the mold member170is removed, the adhesive agent880remains on an upper portion of the wavelength conversion layer130. However, when the adhesive agent880adheres to the mold member170at a strength higher than to the wavelength conversion layer130, the adhesive agent880is removed together with the mold member170. When the adhesive agent880is a water soluble adhesive agent, the adhesive agent880can be dissolved in water or an aqueous solution and removed after the step of removing the mold member170. Next, an effect of the present embodiment will be described. In the method of manufacturing the light emitting device800according to the present embodiment, in the step of disposing the mold member170, the adhesive agent880is provided between the mold member170and the wavelength conversion layer130such that the mold member170temporarily adheres to the wavelength conversion layer130. Therefore, displacement of the mold member170when the light reflecting material140F is provided can be suppressed. In the method of manufacturing the light emitting device800according to the present embodiment, the adhesive agent880is water soluble, and after the step of removing the mold member170, the adhesive agent880is dissolved in water or an aqueous solution and removed. Therefore, the adhesive agent880can be suppressed from remaining on the wavelength conversion layer130. Thus, the light extraction efficiency of the light emitting device800can be improved. Ninth Embodiment Next, a ninth embodiment will be described. FIGS.15A to15Care schematic diagrams illustrating a method of manufacturing the light emitting device800according to a modification of the present embodiment. The method of manufacturing the light emitting device800according to the present embodiment differs from the method of manufacturing the light emitting device800according to the eighth embodiment in that, after the mold member170is caused to temporarily adhere to the wavelength conversion layer130, the mold member170is temporarily detached from the wavelength conversion layer130. As illustrated inFIG.15A, in the step of disposing the mold member170, the adhesive agent880is provided between the mold member170and the wavelength conversion layer130such that the mold member170temporarily adheres to the wavelength conversion layer130. Next, as illustrated inFIG.15B, the mold member170is temporarily detached from the wavelength conversion layer130. Then, as illustrated inFIG.15C, the mold member170and the wavelength conversion layer130temporarily adhere to each other again. With this configuration, the adhesive force between the mold member170and the wavelength conversion layer130can be reduced. The subsequent procedure is the same as or a similar to the eighth embodiment. Next, an effect of the present embodiment will be described. In the method of manufacturing the light emitting device800according to the present embodiment, in the step of disposing the mold member170, the adhesive agent880is provided between the mold member170and the wavelength conversion layer130such that the mold member170and the wavelength conversion layer130temporarily adhere to each other. Subsequently, the mold member170is temporarily detached from the wavelength conversion layer130. Then, the mold member170and the wavelength conversion layer130are caused to temporarily adhere to each other again. With this configuration, the adhesive force between the mold member170and the wavelength conversion layer130can be reduced. Therefore, the mold member170can be easily removed after the light reflecting material140F is cured. In the plurality of embodiments described above, an example is described in which the mold member is removed by detaching the mold member. However, the mold member can be formed of a material that sublimates by being heated such that the mold member is removed by being heated. If the light reflecting material is cured by being heated, a step of sublimating the mold member is preferably performed simultaneously with the step of heating and curing the light reflecting material. The mold member preferably sublimates in a range from 150° C. to 200° C., for example. Embodiments of the present disclosure can be utilized in various types of light sources for illumination, in-vehicle light sources, and the like. | 68,166 |
11862761 | DETAILED DESCRIPTION Multiple embodiments are described in the present disclosure, but the description is exemplary rather than restrictive, and there may be more embodiments and implementation solutions within the scope of the embodiments described in the present disclosure. Although many possible feature combinations are shown in the drawings and discussed in specific implementation modes, the disclosed features may also be combined in many other manners. Unless specifically restricted, any feature or element of any embodiment may be combined with any other feature or element in any other embodiment for use, or may take place of any other feature or element in any other embodiment. When a representative embodiment is described, a method and/or process may have been presented as a specific sequence of steps in the specification. However, to an extent that the method or the process does not depend on the specific sequence of the steps described herein, the method or the process should not be limited to the steps in the specific sequence described. As understood by those of ordinary skills in the art, another sequence of steps is also possible. Therefore, the specific sequence of steps described in the specification should not be explained as a limit to the claims. In addition, claims with respect to the method and/or process should not be limited to execute their steps according to a written sequence. A person skilled in the art may easily understand that these sequences may change, and are still maintained in the spirit and scope of the embodiments of the present disclosure. Unless otherwise defined, technical terms or scientific terms used in the embodiments of the present disclosure shall have common meanings as construed by those of ordinary skills in the art to which the present disclosure pertains. “First”, “second”, and similar terms used in the embodiments of the present disclosure do not represent any sequence, quantity, or significance but are only adopted to distinguish different components. “Include”, “contain”, or a similar word means that an element or object appearing before the word covers an element or object and equivalent thereof listed after the word and does not exclude other elements or objects. “Connect”, “interconnect”, or a similar word is not limited to physical or mechanical connection but may include electrical connection, either direct or indirect. In the embodiments of the present disclosure, “about” means that a limit is not strictly limited, and a value within a range of process and measurement error is allowed. A conventional backlight module often includes the following parts: a substrate and a related drive circuit, an LED light source, an LED encapsulation layer, a quantum dots (QD) film, a first diffusion sheet, a prism sheet with two-layer orthogonal structures, and a second diffusion sheet. Among them, on one hand, a multi-layer diffusion sheet is often needed to uniformize light in order to achieve uniformity of exited light, so that an overall thickness of a backlight module is relatively increased and an overall efficiency of light exiting is greatly affected adversely. On the other hand, a conventional LED chip is based on upward light emission, and a coverage area of a single lamp is limited, more chips are needed to ensure a light coverage of a light-exit surface, which leads to a significant increase in a backlight cost of a large-size display device, and affects adversely an overall control for a volume and a cost. A Mini-LED light source has smaller chip size and broad application prospects, it is used in a backlight module, because of high operability of each chip and high fineness of a coverage area, operations such as regional lighting may be achieved and controllability of the backlight module may be improved. However, in a straight down type backlight module, a larger quantity of light sources are usually needed, more film layer structures and a larger optical distance are needed to achieve a uniform light effect with a high light uniformity, which will cause a Mini-LED straight down type backlight module to be relatively thicker. This limits a Mini-LED light source as a backlight module application to be thinner and lighter in design, and will bring about a problem of a higher cost. FIG.1Ais a schematic diagram of light emission of a Lambertian light source. As shown inFIG.1A, an LED light source (e.g., a Mini-LED light source) is usually a Lambertian light source (solid line inFIG.1), and its energy distribution is shown in Formula (1). Iθ=I0cosθFormula(1) As shown inFIG.1, since the LED light source is encapsulated in a light-emitting module, for this light-exit characteristic of the LED light source, only energy within a radiation angle range of +/−40 degrees can be utilized and light beams beyond +/−40 degrees are limited in an LED structure due to total reflection. In addition, an outgoing light within the radiation angle range of +/−40 degrees concentrates about 61% of light energy of the LED light source. FIG.1Bis a schematic diagram of coverage of light emitted upwards by a Mini-LED light source. As shown inFIG.1B, in a light-exit range of a Mini-LED, after passing through an optical medium with a thickness of t, a width (or diameter) L1of an area that can be radiated by the Mini-LED light source may be shown in the following Formula (2). L1=2×D+l=2×t×tanθ+lFormula(2) In Formula (2), θ indicates a total reflection angle of the optical medium to Mini-LED light, l indicates a chip length of the Mini-LED light source, D indicates a coverage range of Mini-LED edge light within a range of the total reflection angle, and L1indicates a coverage diameter of light emitted on a surface of the optical medium when a Mini-LED chip emits light upwards (i.e. the width of the area that can be radiated by the Mini-LED light source). Taking an optical medium as glass with a thickness of 0.5 mm and a refractive index of 1.52, and a chip length of a Mini-LED light source is 100 μm as an example, in an available range of a Mini-LED radiation light, when a light emitted by a Mini-LED is transmitted through the glass and coupled out of the glass to the air, L1=0.969 mm (i.e., a spot coverage of about 1 mm in diameter) may be calculated through the above Formula (2). In order to achieve backlight uniformity, a Mini-LED chip arrangement design is needed to be carried out for a conventional backlight module based on this. For a large-size display apparatus, such as a 65-inch display (wherein a size of an AA area is 1430 mm×840 mm), at least 1.28 million Mini-LED chips are needed to achieve uniformity of exited light and brightness, which causes a problem of a higher cost. In addition, in order to improve the uniformity of exited light, a diffusion sheet with a certain thickness is also used for the conventional backlight module. For example, a diffusion sheet with a thickness of 2 mm is used for a Mini-LED backlight module used in some 65-inch 4K displays to achieve uniformity of backlight, which makes a thickness of the backlight module reach about 3.85 mm. It may be seen that the use of this thick diffusion sheet greatly affects adversely thinning of a display device, and this thick diffusion sheet cannot be applied to thin and light display devices. An embodiment of the present disclosure provides a light-emitting module capable of achieving higher light uniformity, a higher light effect, a smaller optical distance (OD), a lower thickness, and a lower quantity of light-emitting elements, which may be widely applied to a backlight module in a design of a display device with a large size and a lower requirement for thickness. In an exemplary embodiment, the light-emitting module may include a substrate, at least one light-emitting element located at one side of the substrate, and a first light-uniformizing component and a reflective layer disposed at a light-exit side of the light-emitting element; wherein, the first light-uniformizing component is configured to make light emitted by the light-emitting element uniformly incident on the reflective layer; and the reflective layer is configured to reflect the light incident on the reflective layer toward a direction away from the light-exit side of the light-emitting element. In this way, the light-emitting element emits light downwards and the light is reflected by the reflection layer disposed at one side of the first light-uniformizing component, so that a thickness of the substrate may be effectively utilized to achieve a light-uniformizing optical path, a structure of a diffusion sheet in the light-emitting module may be omitted, a thickness as well as a cost of the light-emitting module can be reduced. By using a first light-uniformizing component to disperse light and using a reflective layer of the first light-uniformizing component to undermine a total reflection waveguide effect, a light-exiting effect with high uniformity can be achieved, an effect of increasing a light-taking amount can be achieved, and a light-taking efficiency of a light-emitting module may be improved. In an exemplary embodiment, the light-emitting module may further include an encapsulation layer, wherein the encapsulation layer and the substrate are respectively located at two sides of the light-emitting element. In this way, by using a thickness of the substrate and a light source encapsulation structure as a light-uniformizing optical path, a structure of a diffusion sheet in the light-emitting module may be omitted, a thickness of the light-emitting module can be reduced more effectively and a cost can be reduced. By using a first light-uniformizing component to disperse light and using a reflective layer of the first light-uniformizing component to undermine a total reflection waveguide effect, a light-exiting effect with high uniformity can be achieved, an effect of increasing a light-taking amount can be achieved, and a light-taking efficiency of a light-emitting module may be improved. For example, when an encapsulation layer is located on a light-exit side of a light-emitting element and a substrate is located on a side away from the light-exit side of the light-emitting element, a reflective layer is configured to reflect light incident on the reflective layer toward a direction away from the light-exit side (i.e., toward a direction close to the substrate) and exit from the substrate. Or, when a substrate is located on a light-exit side of a light-emitting element and an encapsulation layer is located on a side away from the light-exit side of the light-emitting element, a reflective layer is configured to reflect light incident on the reflective layer toward a direction away from the light-exit side (i.e., toward a direction close to the encapsulation layer) and exit from the encapsulation layer. In an exemplary embodiment, the light-emitting module may further include a second light-uniformizing component disposed on a side away from a light-exit side of a light-emitting element, configured to uniformize light emitted from a substrate when the substrate is located on a side away from the light-exit side of the light-emitting element, or configured to uniformize light emitted from a encapsulation layer when the encapsulation layer is located on a side away from the light-exit side of the light-emitting element. In an exemplary embodiment, the light-emitting module may further include a transflective film disposed on a side of the second light-uniformizing component away from the light-emitting element. In an exemplary embodiment, the light-emitting module may further include a metal wiring layer disposed between the substrate and the light-emitting element, wherein the metal wiring layer includes multiple transflective control areas, and each transflective control area includes multiple concentrically disposed areas with different transmittances. Next, a light-emitting module will be described below by taking an example where an encapsulation layer is located on a light-exit side of a light-emitting element and a substrate is located on a non-light-exit side of the light-emitting element (i.e., the substrate is located on a side away from the light-exit side of the light-emitting element). FIG.2is a schematic diagram of a first structure of a light-emitting module according to an embodiment of the present disclosure. As shown inFIG.2, the light-emitting module may include a light-emitting element10, a substrate11, an encapsulation layer12, a first light-uniformizing component13, and a reflective layer14disposed on a side of the first light-uniformizing component13away from the light-emitting element10. The encapsulation layer12is located on a light-exit side of the light-emitting element10. The substrate11is located on a non-light-exit side of the light-emitting element10, and a side of the substrate11away from the light-emitting element10is a light-exit surface of the light-emitting module. The first light-uniformizing component13is located on the light-exit side of the light-emitting element10(that is, on a side of the encapsulation layer12away from the light-emitting element10), and is configured to transmit light emitted by the light-emitting element10, so that the light emitted by the light-emitting element10is uniformly incident on the reflective layer14; and the first light-uniformizing component13is further configured to transmit light reflected by the reflective layer14, so that the reflected light is uniformly incident on the encapsulation layer12. The reflective layer14is configured to reflect light incident on the reflective layer14in a direction close to the substrate11(i.e., toward a direction away from the light-exit side of the light-emitting element) when the substrate11is located on the non-light-exit side of the light-emitting element10, and the light is uniformly emitted from the side of the substrate11away from the light-emitting element10. In this way, when the substrate is located on the non-light-exit side of the light-emitting element and the encapsulation layer is located on the light-exit side of the light-emitting element, the light-emitting element emits light downwards in a form of a Lambertian light source (that is, emits light toward a direction close to the encapsulation layer). Light emitted by the light-emitting element enters the encapsulation layer, and then enters the first light-uniformizing component after being transmitted through the encapsulation layer. The first light-uniformizing component transmits and uniformizes the light emitted by the light-emitting element. After the light is uniformized by the first light-uniformizing component, it is reflected by the reflective layer provided on a lower surface (i.e., a side of the first light-uniformizing component away from the light-emitting element) of the first light-uniformizing component. The light reflected by the reflective layer enters the encapsulation layer after being transmitted by the first light-uniformizing component, and then enters the substrate after being transmitted by the encapsulation layer. After being transmitted by the substrate, the light exits from a light-exit surface of the substrate. In this way, thicknesses of the encapsulation layer and the substrate may be effectively used to increase an optical path by using the light-emitting element to emit light downwards. Therefore, compared with a conventional backlight module, a structure of a diffusion sheet in a light-emitting module may be omitted, a thickness as well as a cost of the light-emitting module can be reduced, and an overall light-exit efficiency is improved. Furthermore, the light emitted by the light-emitting element is scattered by the first light-uniformizing component, so that the light emitted by the light-emitting element may be uniformized, which can improve uniformity of light emitted from the light-exit surface, increase utilization of light energy of the light-emitting element, and enhance luminous efficiency. In an exemplary embodiment, the light-emitting element may be a Mini-LED light source, an LED light source, and the like. FIG.3is a schematic diagram of coverage of light emitted downwards by a Mini-LED light source. As shown inFIG.3, in a light-exit range of a Mini-LED, after passing through an optical medium with a thickness of t, a width (or diameter) L2of an area that can be radiated by the Mini-LED light source may be shown in the following Formula (3). L2=4×D+l=4×t×tanθ+lFormula(3) In Formula (3), θ indicates a total reflection angle of the optical medium to Mini-LED light, l indicates a chip length of the Mini-LED light source, D indicates a coverage range of Mini-LED edge light within the total reflection angle range, and L2indicates a coverage diameter of light emitted on a surface of the optical medium when a Mini-LED chip emits light downwards (i.e. the width of the area that can be radiated by the Mini-LED light source). According to Formula (3), in the light-emitting module provided in the embodiment of the present disclosure, by using a design solution of inverted light emission of a Mini-LED chip, since light emitted by the Mini-LED is returned in a substrate or an encapsulation layer, an optical path may be expanded, and a coverage area of each LED chip on an upper surface has been expanded to a certain extent. Because of expansion of a coverage area of a single Mini-LED bright spot, a quantity of Mini-LED chips in a whole light-emitting module may be directly decreased, thus reducing a cost of the light-emitting module. As may be seen from the above, in the light-emitting module in the embodiment of the present disclosure, a substrate and a light source encapsulation structure are used as a light-uniformizing optical path, a structure of a diffusion sheet in a light-emitting module may be omitted, and a thickness as well as a cost of the light-emitting module can be reduced. By using a first light-uniformizing component to disperse light and using a reflective layer of the first light-uniformizing component to undermine a total reflection waveguide effect, a light-exiting effect with high uniformity can be achieved, an effect of increasing a light-taking amount can be achieved, and a light-taking efficiency of a light-emitting module may be improved. By using a solution that a light-emitting element emits light downwards, an optical path may be enlarged, and a coverage area of emitted light of each light-emitting element is enlarged to a certain extent, so that a quantity of chips of light-emitting elements in an entire light-emitting module may be decreased, thereby reducing a cost of the light-emitting module. In an exemplary embodiment, as shown inFIG.4, the light-emitting module may further include a second light-uniformizing component15; the second light-uniformizing component15is disposed on a side of a substrate11away from a light-emitting element10(that is, on a non-light-exit side of the light-emitting element10), and is configured to uniformize light emitted from the substrate11when the substrate11is located on the non-light-exit side of the light-emitting element10. In this way, when the substrate is located on the non-light-exit side of the light-emitting element, light emitted from the substrate is scattered by the second light-uniformizing component disposed on an upper surface of the substrate (i.e., a side of the substrate away from the light-emitting element), so that a reflection/diffraction angle may be increased, and most of the emitted light may be transmitted repeatedly in oscillation in the substrate. Therefore, a quantity of light-emitting elements used is further reduced, light-uniformizing exiting in a larger area is achieved, and a light-uniformizing effect and a light efficiency are further improved, therefore, power consumption of the light-emitting module is reduced accordingly. In an exemplary embodiment, as still shown inFIG.4, the light-emitting module may further include a transflective film16disposed on a side of the second light equalizing module15away from the light-emitting element10(at this time, that is, on a side of the substrate11away from the light-emitting element10). In this way, since the substrate is located on a non-light-exit side of the light-emitting element, light emitted from the substrate is scattered by the second light-uniformizing component and the transflective film disposed on an upper surface of the substrate (i.e., a side of the substrate away from the light-emitting element) together, so that a reflection/diffraction angle can be better increased, and most of the emitted light may be transmitted repeatedly in oscillation in the substrate. Therefore, a quantity of light-emitting elements used is reduced, light-uniformizing exiting in a larger area is better achieved, and a light-uniformizing effect and a light efficiency are greatly improved, therefore, power consumption of the light-emitting module is reduced accordingly. Next, a light-emitting module will be described below by taking an example where a substrate is located on a light-exit side of a light-emitting element and an encapsulation layer is located on a non-light-exit side of the light-emitting element (i.e., the encapsulation layer is located on a side away from the light-exit side of the light-emitting element). FIG.5is a schematic diagram of a third structure of a light-emitting module according to an embodiment of the present disclosure. As shown inFIG.5, the light-emitting module may include a light-emitting element10, a substrate11, an encapsulation layer12, a first light-uniformizing component13, and a reflective layer14disposed on a side of the first light-uniformizing component13away from the light-emitting element10. The substrate11is located on a light-exit side of the light-emitting element10. The encapsulation layer12is located on a non-light-exit side of the light-emitting element10, and a side of the encapsulation layer12away from the light-emitting element10is a light-exit surface of the light-emitting module. The first light-uniformizing component13is located on the light-exit side of the light-emitting element10(that is, on a side of the substrate11away from the light-emitting element10), and is configured to transmit light emitted by the light-emitting element10, so that the light emitted by the light-emitting element10is uniformly incident on the reflective layer14; and the first light-uniformizing component13is also configured to transmit light reflected by the reflective layer14, so that the reflected light is uniformly incident on the substrate11. The reflective layer14is configured to reflect light incident on the reflective layer14in a direction close to the encapsulation layer12(i.e., toward a direction away from the light-exit side of the light-emitting element) when the substrate11is located on the light-exit side of the light-emitting element10, and the light is uniformly emitted from the encapsulation layer12. In this way, when the substrate is located on the light-exit side of the light-emitting element and the encapsulation layer is located on the non-light-exit side of the light-emitting element, the light-emitting element emits light downwards in a form of a Lambertian light source. Light emitted by the light-emitting element enters the substrate, and then enters the first light-uniformizing component after being transmitted through the substrate. The first light-uniformizing component transmits and uniformizes the light emitted by the light-emitting element. After the light is uniformized by the first light-uniformizing component, it is reflected by the reflective layer provided on a lower surface of the first light-uniformizing component. The light reflected by the reflective layer enters the substrate after being transmitted by the first light-uniformizing component, and then enters the encapsulation layer after being transmitted by the substrate. After being transmitted by the encapsulation layer, the light exits from a light-exit surface of the encapsulation layer. In this way, thicknesses of the encapsulation layer and the substrate may be effectively used to increase an optical path by using the light-emitting element to emit light downwards. Therefore, compared with a conventional backlight module, a structure of a diffusion sheet in the light-emitting module may be omitted, a thickness as well as a cost of the light-emitting module can be reduced, and an overall light-exit efficiency can be improved. Furthermore, the light emitted by the light-emitting element is scattered by the first light-uniformizing component, so that the light emitted by the light-emitting element may be uniformized, which can improve uniformity of light emitted from a light-exit surface, increase utilization of light energy of the light-emitting element, and enhance a luminous efficiency. As may be seen from the above, in the light-emitting module in the embodiment of the present disclosure, a substrate and a light source encapsulation structure are used as a light-uniformizing optical path; a structure of a diffusion sheet may be omitted, and a thickness as well as a cost of the light-emitting module can be reduced. By using a first light-uniformizing component to disperse light in combination with a reflective layer of the first light-uniformizing component to change a total reflection waveguide effect, a light-exiting effect with high uniformity can be achieved, an effect of increasing a light-taking amount can be achieved, and a light-taking efficiency of a light-emitting module may be improved, and a backlight efficiency is increased. By using a solution that a light-emitting element emits light downwards, an optical path may be enlarged, and a coverage area of emitted light of each light-emitting element is enlarged to a certain extent, so that a quantity of chips of light-emitting elements are used in an entire light-emitting module may be decreased, thereby reducing ae cost of the light-emitting module. In an exemplary embodiment, as shown inFIG.6, the light-emitting module may further include a second light-uniformizing component15; the second light-uniformizing component15is disposed on a side of the encapsulation layer12away from the light-emitting element10(i.e., on a non-light-exit side of the light-emitting element10), and is configured to uniformize light emitted from the encapsulation layer12when the substrate11is located on the non-light-exit side of the light-emitting element10(i.e., the encapsulation layer12is on the non-light-exit side of the light-emitting element10). In this way, when the encapsulation layer is located on the non-light-exit side of the light-emitting element, the light emitted from the encapsulation layer may be scattered by the second light-uniformizing component disposed on an upper surface of the encapsulation layer (i.e., a side of the encapsulation layer away from the light-emitting element), so that a reflection/diffraction angle may be increased, and most of the emitted light may be transmitted repeatedly in oscillation in the encapsulation layer. Therefore, a quantity of light-emitting elements used may be further reduced, light-uniformizing exiting in a larger area may be achieved, and a light-uniformizing effect and a light efficiency are further improved, thus power consumption of the light-emitting module will be reduced accordingly. In an exemplary embodiment, as still shown inFIG.6, the light-emitting module may further include a transflective film16disposed on a side of the second light equalizing module15away from the light-emitting element10(at this time, that is, on a side of the encapsulation layer12away from the light-emitting element10). In this way, since the encapsulation layer is located on the non-light-exit side of the light-emitting element, light emitted from the encapsulation layer is scattered by the second light-uniformizing component and the transflective film disposed on an upper surface of the substrate (i.e., a side of the encapsulation layer away from the light-emitting element) together, so that a reflection/diffraction angle may be better increased, and most of the emitted light may be transmitted repeatedly in oscillation in the substrate. Therefore, a quantity of light-emitting elements used may be reduced, light-uniformizing exiting in a larger area is better achieved, and a light-uniformizing effect and a light efficiency are greatly improved, thus power consumption of the light-emitting module will be reduced accordingly. In an exemplary embodiment, as shown inFIG.2,FIG.4,FIG.5, andFIG.6, the light-emitting module may further include a metal wiring layer17disposed on a side of the light-emitting element10away from the encapsulation layer12. The metal wiring layer includes multiple transflective control areas (not shown inFIG.2,FIG.4,FIG.5, orFIG.6), and each transflective control area includes multiple concentrically disposed areas with different transmittances. Here, “concentric” may mean that multiple areas have a same geometric center. In this way, the metal wiring layer is located between the substrate and the encapsulation layer. Through a transflective control area design of the metal wiring layer, a transflective distribution design of a light-exit surface of the substrate or the encapsulation layer is achieved, and a light energy intensively emitted by light-emitting elements is redistributed to reduce transmitted light and increase reflected light entering a next transmission process, thus achieving an energy distribution and a light-uniformizing design of the emitted light. In this way, a light-uniformizing exiting effect may be achieved on one hand, on the other hand, a quantity of light-emitting elements can be greatly reduced, and a cost can be reduced. In an exemplary embodiment, each light-emitting element may correspond to one transflective control area. In an exemplary embodiment, taking an example where each light-emitting element corresponds to one transflective control area, a geometric center of each light-emitting element may be configured corresponding to a geometric center of its corresponding transflective control area. In a practical application, a quantity of divided areas included in each transflective control area depends on a distance of chips of light-emitting elements and a designed surface transmittance. For example, a transflective control area may include three areas. Of course, a quantity of divided areas may also be other. For example, under a condition of a large distance between chips of light-emitting elements or under a condition of a low requirement for an overall transmittance, more divided areas may be designed, such as 4 and 5. Here, the embodiments of the present disclosure are not limited here. The following description takes a transflective control area including three areas as an example. Taking a 3-area energy distribution design where a substrate is located on a non-light-exit side of a light-emitting element, an encapsulation layer is located on a light-exit side of the light-emitting element, and a LED light source emits light downwards into the encapsulation layer as an example, as shown inFIG.7, a geometric center of the LED light source corresponds to a geometric center of Area1, light emitted by the LED light source propagates in the encapsulation layer, a main light-exit area is Area1, and a second exit area where light reaches an upper surface after being reflected by upper and lower surfaces of the encapsulation layer is Area2, and Area3 may be divided in the same way. Next, a transmittance of Area1 is set to 40.0%, a transmittance of Area2 to 66.7%, and a transmittance of Area3 to 100%. Area3 is considered as a superposition part of optical paths of two LED light sources. In this way, according to LED luminous characteristics, a regional transmittance distribution design may ensure overall luminous uniformity under a condition of increasing a distance between two lamps. In an exemplary embodiment, since a metal wiring layer is mainly of a metal wiring structure, a duty ratio (or aperture ratio) of the metal wiring layer may be controlled by any one or more of a wiring thickness and a wiring line width. In this way, by controlling the duty ratio (or aperture ratio) of the metal wiring layer, a regional transmittance control of light energy on a surface of each area in a transflective control area and energy regulation may be achieved, thus a light-uniformizing exiting effect on a light-exit surface is obtained. For example, taking an example where a metal wiring layer is made of Cu (copper), a transmittance of Area1 is set to 40.0%, a transmittance of Area2 is set to 66.7%, and a transmittance of Area3 is set to 100%, and a duty ratio of the metal wiring layer is controlled by a wiring thickness, then according to a relationship between the thickness of the metal wiring layer and the duty ratio as shown inFIG.8, a thickness of the wiring layer in Area1 may be set to 1.9 μm, a thickness of the wiring layer in Area2 may be set to 4.8 μm, and a thickness of the wiring layer in Area3 may be set to be without wiring. In an exemplary embodiment, multiple areas are any one of a circular ring area and a rectangular annular area. For example, taking a transflective control area including three areas as an example, as shown inFIG.9A, the transflective control area may be concentrically disposed annular areas with different transmittances. As shown inFIG.9B, the transflective control area may be a concentrically disposed rectangular annular area with different transmittances. In an exemplary embodiment, there is an overlapping area between adjacent transflective control areas. For example, light-emitting elements are concentric square annular areas as shown inFIG.9B, and according to a distribution design of a transflective control area as shown inFIG.7, an outermost area (e.g., Area3) in the transflective control area belong to an overlapping part of two adjacent chips of light-emitting elements. In this way, due to use of an overlapping design of light-exit areas of light-emitting elements, light transmitted many times in an encapsulation layer or a substrate is superimposed to maintain a higher far-end brightness in a case of increasing a distance between adjacent chips of light-emitting elements, thereby ensuring light-exit uniformity of an entire light-emitting module. Therefore, according to the light-emitting module provided by the embodiment of the present disclosure, a quantity of chips of light-emitting elements required by the entire light-emitting module may be greatly reduced, and a cost is greatly optimized. For example, taking an example where light-emitting elements are divided into areas in a mode of concentric squares as shown inFIG.9Baccording to a distribution design of a transflective control area as shown inFIG.7, for a design of a light-emitting module for a 65-inch 4K display, a horizontal distance and a vertical distance of the Mini-LED array may all be designed to be 4.445 mm, and a size of an AA area in the 65-inch 4K display is 1430 mm*840 mm. Therefore, 61,000 Mini-LEDs may be used to achieve a light-emitting module with an OD of 0 mm, which is less than a demand of 100,000 Mini-LEDs for a conventional light-emitting module, and a cost is greatly optimized. Furthermore, according to an experiment of the present disclosure, a backlight uniformity of the light-emitting module with the OD of 0 mm achieved by 61,000 Mini-LEDs in the embodiment of the present disclosure is about 91.8%, which is far greater than a backlight uniformity of the conventional light-emitting module. Hereinafter, taking a design solution of a transflective control area as shown inFIG.7as an example, how to determine a radius value or a side length value of each area in the transflective control area to determine coverage of the transflective control area will be described. For a concentric ring area as shown inFIG.9A, a radius value Rnof each area in a transflective control area may satisfy the following Formula (4). Rn=0.5l+(2n-1)t×tanθFormula(4) In Formula (4), Rnrepresents a radius value of the n-th level area, t represents a thickness of an encapsulation layer or a substrate, n represents a level of a divided area, θ represents a total reflection angle of light in the encapsulation layer or substrate, and l represents a side length of a chip of a light-emitting element. At this time, a distance L between adjacent light-emitting elements may satisfy the following Formula (5). L=l+2×2(N-1)t×tanθFormula(5) In Formula (5), L represents a distance between adjacent light-emitting elements, l represents a side length of a chip of a light-emitting element, N represents a quantity of divided areas, t represents a thickness of an encapsulation layer or that of a substrate, θ represents a total reflection angle of light in the encapsulation layer or the substrate. For a concentric square annular area as shown inFIG.9B, a side length of each square in a transflective control area is the same as a diameter of each concentric circle in a transflective control area in a circular ring area as shown inFIG.9A, which may satisfy the following Formula (6). dn=2RnFormula(6) In Formula (6), dnrepresents a side length of the n-th level area, and Rnrepresents a radius value of the n-th level area. In order to achieve the highest utilization rate of light energy, 61% of energy in Area1 needs to be divided equally into each area. Therefore, a quantity N of divided areas of a transflective control area is related to a light efficiency of a final light-exit surface. If the quantity of divided areas increases, energy allocated to each area is relatively lower. A transmittance of each area in the transflective control area may be calculated through the following Formula (7). Tn=22×(N-n)+1Formula(7) In Formula (7), n represents a level of a divided area; N represents a quantity of divided areas, and Tnrepresents a transmittance of the n-th level area. Furthermore, a transmittance of an outermost area in the transflective control area is 100%. For example, taking an energy distribution in three areas as an example, if a transflective control area is a circular ring area as shown inFIG.8A, according to the above Formula (4), radius values from Area1 to Area3 may be calculated as 0.919 mm, 1.788 mm, and 2.657 mm. If a transflective control area is a rectangular annular area as shown inFIG.9B, according to the above Formula (6), side length values from Area1 to Area3 may be calculated as 1.838 mm, 3.576 mm, and 5.314 mm. According to the above Formula (5), a distance between adjacent light-emitting elements may be calculated as 4.445 mm. According to the above Formula (7), a transmittance of Area1 may be set to 40.0%, and a transmittance of Area2 may be set to 66.7%, and a transmittance of Area3 may be set to 100%. Of course, in addition to energy distribution design solutions listed above, other calculation rules may be used to design an energy distribution of each area in a transflective control area, which also generates a light-uniformizing effect. For example, an entire surface energy may be set as 25% of a central energy for an energy distribution design. In an exemplary embodiment, a metal wiring layer has a first surface close to a light-emitting element and a second surface away from the light-emitting element disposed oppositely, and at least one of the first surface and the second surface is provided with a reflective film. In this way, a reflective film with low absorption loss is correspondingly designed on at least one of the first surface and the second surface that are oppositely disposed on the metal wiring layer, so that absorption loss caused by the metal wiring layer in an optical path may be reduced, and a light efficiency of a light-emitting module may be improved. For example, taking a first light-uniformizing component being a microlens array, and microlenses in the microlens array being convex microlenses, and curved surfaces of the microlenses being convex in a direction away from light-emitting elements, as an example, as shown inFIGS.10A,10B, and10C, the light-emitting module may further include a reflective film19. As shown inFIG.10A, the reflective film19may be disposed on the first surface of the metal wiring layer17close to the light-emitting element10. Or, as shown inFIG.10B, the reflective film19may be disposed on the second surface of the metal wiring layer17away from the light-emitting element10. Or, as shown inFIG.10C, the reflective film19may be disposed on the first surface of the metal wiring layer17close to the light-emitting element10and the second surface of the metal wiring layer17away from the light-emitting element10. Here, the reflective film may cover only wirings in the metal wiring layer. For example, reflective films provided on the first surface and the second surface of the metal wiring layer may be of an ITO/Ag/ITO composite structure, or may be high reflectivity material layers (such as white oil layers). Here, the metal wiring layer is connected with a light-emitting element and may be used as a drive circuit layer of the light-emitting element to drive the light-emitting element to emit light. In an exemplary embodiment, a material of the metal wiring layer may be Al (aluminum) material or Ag (silver) material and other materials that cannot absorb light. In this way, light reaching the metal wiring layer (for example, as a drive circuit layer of a light-emitting element) can be efficiently reflected or completely transmitted rather than being absorbed or lost, so that a light efficiency of a light-emitting module can be improved. In addition, in order to prevent Ag oxidation, a thin ITO (indium tin oxide) layer needs to be deposited on a surface of an Ag layer for protection, so the metal wiring layer may be of an ITO/Ag/ITO or ITO/Ag/Al/Ag/ITO composite structure. Each structure in a light-emitting module will be described in detail below. In an exemplary embodiment, a material of a substrate may be a Printed Circuit Board (PCB) material, or may be a transparent material. For example, taking a material of a substrate as a transparent material as an example, considering requirements for an optical path and an ultra-thin device structure, a transmittance of the substrate may be as high as possible, so the material of the substrate may be a glass material. For example, the substrate may be a glass substrate with a refractive index of 1.52. For example, a thickness of the glass substrate may be 0.5 mm, 0.7 mm, etc. Of course, it may be others, and the embodiments of the present disclosure are not limited here. In an exemplary embodiment, a refractive index of an encapsulation layer is less than or equal to a refractive index of a substrate. Therefore, it is ensured that light may exit from the substrate or the encapsulation layer. For example, the substrate may be a glass substrate with a refractive index of 1.52, and the encapsulation layer may be made of a PCB material with a refractive index of 1.5. For example, a thickness of an encapsulation layer may be 0.2 mm, 0.5 mm, etc. Of course, it may be others, and the embodiments of the present disclosure are not limited here. In an exemplary embodiment, the first light-uniformizing component may include any one of a microlens array and an uneven microstructure. Of course, it may be others, and the embodiments of the present disclosure are not limited here. In an exemplary embodiment, the second light-uniformizing component may include any one of a microlens array and an uneven microstructure. Here, the embodiments of the present disclosure are not limited here. Here, a microlens array is one of important micro-optical elements, which can achieve modulation functions of shaping, uniformizing, diffusing, and focusing an incident light by designing parameters such as a shape, a radius of curvature, an arrangement, and a thickness of a microlens. In this embodiment of the present disclosure, a first light-uniformizing component is achieved by a microlens array using a light-uniformizing effect of the microlens array on light. The microlens array is superimposed under a substrate (i.e., a side away from a light-emitting element) when the substrate is located on a light-exit side of the light-emitting element, or under an encapsulation layer (i.e., a side away from the light-emitting element) when the encapsulation layer is located on the light-exit side of the light-emitting element, and a reflective layer (for example, a total reflection film) is added to a curved surface of the microlens array, which can solve a problem of a deficiency in light uniformity due to an energy distribution of a Lambertian light type LED light source. In addition, in a practical application, the microlens array may be disposed below the substrate or the encapsulation layer by using a process with a low influence on performance, such as dispensing, or by bonding, without a further processing on the substrate or the encapsulation layer, which will not affect stability of devices in the light-emitting module. Moreover, the micro-lens array has stronger processing controllability and a relatively higher design degree, which can ensure stability of performance of the light-emitting module and high product yield. In an exemplary embodiment, a microlens array includes multiple convex or concave microlenses disposed in an array, wherein a curved surface of a microlens is a part of a spherical surface. For example, the curved surface of the microlens is hemispherical. In an exemplary embodiment, taking a microlens array including multiple convex microlenses disposed in an array as an example, as shown inFIG.11A, a surface of a microlens in a microlens array18close to a light-emitting element10may be a curved surface convex toward a direction close to the light-emitting element10. In another exemplary embodiment, as shown inFIG.11B, a surface of a microlens in a microlens array18away from a light-emitting element may be a curved surface convex toward a direction away from the light-emitting element10. In an exemplary embodiment, taking a microlens array including multiple concave microlenses disposed in an array as an example, as shown inFIG.11C, a surface of a microlens in a microlens array18close to a light-emitting element10may be a curved surface concave toward a direction away from the light-emitting element10. In another exemplary embodiment, as shown inFIG.11D, a surface of a microlens in a microlens array18away from a light-emitting element may be a curved surface concave toward a direction close to the light-emitting element10. In an exemplary embodiment, a curved surface of a microlens array may face a light-exit surface of a light-emitting module (that is, a solution with a curved surface of a microlens array facing upwards). Or, a curved surface of a microlens array may face a non-light-exit surface of a light-emitting module (that is, a solution with a curved surface of a microlens array facing downwards). For example, as shown inFIG.11A, taking a curved surface of a microlens array18as a convex curved surface as an example, when an encapsulation layer12is located on a light-exit side of a light-emitting element10, the curved surface of the microlens array18may be attached below the encapsulation layer12(that is, a side of the encapsulation layer12away from the light-emitting element10), and at this time, the curved surface of the microlens array18faces a light-exit surface of a light-emitting module (that is, the curved surface of the microlens array18faces upwards). For example, as shown inFIG.11C, taking a curved surface of a microlens array18as a concave curved surface as an example, when an encapsulation layer12is located on a light-exit side of a light-emitting element10, the curved surface of the microlens array18may be attached below the encapsulation layer12(that is, a side of the encapsulation layer12away from the light-emitting element10), and at this time, the curved surface of the microlens array18faces a non-light-exit surface of a light-emitting module (that is, the curved surface of the microlens array18faces downwards). In an exemplary embodiment, structural parameters of a microlens array may include any one or more of the following parameters: a diameter Lens_D of a single microlens may be less than 20 μm (for example, a diameter of a single microlens may be 2 μm, 4 μm, 6 μm, 8 μm, 9 μm, and 16 μm), where a diameter of a microlens may be a diameter of a spherical surface where a curved surface of the microlens is located; a ratio of the diameter Lens_D of the single microlens to a pitch Lens_Pitch between adjacent microlenses in either a row direction or a column direction of the microlens array (recorded as a duty ratio of the microlens array) may be greater than or equal to 2 (for example, Lens_D:Lens_Pitch=2:1). Here, when curved surfaces of microlenses are convex, a pitch between adjacent microlenses may be a pitch between vertices of convex surfaces of two adjacent microlenses, and when curved surfaces of microlenses are concave, a pitch between adjacent microlenses may be a pitch between lowest points of concave surfaces of two adjacent microlenses. In this way, small-angle light incident on a surface of a microlens array (small-angle light with concentrated LED main energy) is reflected at a slightly larger angle to avoid absorption loss of an upper LED chip; large-angle light incident on the surface of the microlens array (for example, large-angle light with an angle larger than a total reflection angle of a substrate) is reflected under a condition smaller than the total reflection angle, a quantity of rays limited in the substrate is reduced, the maximum light energy can be obtained, an light-taking amount of a light-emitting module may be improved, and a higher light efficiency may be obtained. Here, a pitch between adjacent microlenses (or may be referred to as an arrangement period of microlenses) can characterize a degree of close contact of adjacent microlenses. In an exemplary embodiment, according to a difference in a ratio of a diameter Lens_D of a microlens to a pitch Lens_Pitch between adjacent microlenses, as shown inFIG.12, adjacent microlenses have three difference states: spaced, overlapping, and in contact with each other. When the ratio of the diameter Lens_D of the microlens to the pitch Lens_Pitch between adjacent microlenses is less than 1, the adjacent microlenses are in a spaced state. When the ratio of the diameter Lens_D of the microlens to the pitch Lens_Pitch between adjacent microlenses is greater than 1, the adjacent microlenses are in an overlapping state. When the ratio of the diameter Lens_D of the microlens to the pitch Lens_Pitch between adjacent microlenses is equal to 1, the adjacent microlenses are in contact with each other. For example,FIG.12is a diagram of light-uniformizing effects of a microlens array with different duty ratios. InFIG.12, taking a diameter of microlens Lens_D=2 μm as an example, from top to bottom, a diagram of light-uniformizing effects is provided when the ratio of the diameter Lens_D of the microlens to the pitch Lens_Pitch between adjacent microlenses may be none (i.e., no microlens array), 1:2 (at this time, the Lens_Pitch between adjacent microlenses is 4 μm), 1:1.5 (at this time, the Lens_Pitch between adjacent microlenses is 3 μm), 1:1 (at this time, the Lens_Pitch between adjacent microlenses is 2 μm), 1:0.75 (at this time, the Lens_Pitch between adjacent microlenses is 1.5 μm), and 1:0.5 (at this time, the Lens_Pitch between adjacent microlenses is 1 μm), and schematic diagrams of adjacent microlenses corresponding to different ratios are given. As shown inFIG.12, when Lens_D:Lens_Pitch=1:0.5 (i.e., Lens_D:Lens_Pitch=2:1) for both of solutions of curved surfaces of microlenses facing upwards and curved surfaces of microlenses facing downwards in the microlens array, a better light-uniformizing effect can be obtained. That is to say, when adjacent microlenses are closely tightly disposed in a way of Lens_D:Lens_Pitch=1:0.5, a better light-uniformizing effect can be obtained. For example, a diameter of a microlens Lens_D=2 μm, and multiple microlenses are disposed in a two-dimensional array with Lens_Pitch=1 μm as a period. Here, a curved surface of a microlens facing upwards means that a surface of the microlens close to a light-emitting element is curved, and a curved surface of a microlens facing downwards means that a surface of the microlens away from a light-emitting element is a curved. In an exemplary embodiment, a microlens in a microlens array may be made of polymethyl methacrylate (PMMA) or Printed Circuit Board (PCB), and of course, it may be made of another material, such as a material with a refractive index similar to that of an encapsulation layer or a substrate, which is not limited in the embodiments of the present disclosure. In an exemplary embodiment, a difference between a refractive index of a microlens and that of at least one of a substrate and an encapsulation layer may be 0 to 1 (i.e., the refractive index of the microlens is similar to that of at least one of the substrate and the encapsulation layer). For example, the microlens may be made of a PMMA material with a refractive index of 1.49, the substrate may be made of a glass material with a refractive index of 1.52, and the encapsulation layer may be made of an encapsulation glue material with a refractive index of 1.5. In an exemplary embodiment, a reflective layer may be disposed on a curved surface of a microlens array. In an exemplary embodiment, a microstructure may include multiple convex areas or multiple concave areas, wherein the multiple concave areas are areas other than the multiple convex areas in the microstructure, and the multiple convex areas and the multiple concave areas include any one or more of a part of a sphere and a part of a pyramid. A shape of a convex or concave structure is any one or more of prism frustum, truncated frustum, ellipsoid, hemisphere, pyramid-shape, pyramid, cone, and V-shape. For example, taking multiple convex areas and multiple concave areas including a part of a pyramid as an example, as shown inFIG.13A, a microstructure may include: pyramid protrusions or depressions; or, as shown inFIG.13B, a microstructure may be multiple pyramid structures disposed in an array (for example, for a microstructure including pyramid structures, nano-imprinting may be used for preparation); or, as shown inFIG.13C, a microstructure may be a combination of multiple protrusions or depressions in a prism frustum and a pyramid. In an exemplary example, taking an example where a microstructure is multiple pyramid structures disposed in an array, a side length of each pyramid structure may be 50 μm, and a distance between adjacent pyramid structures may be 50 μm. Here, a distance between adjacent pyramid structures may refer to a distance between center points of two adjacent pyramid structures. In an exemplary embodiment, a microstructure may be achieved by wet etching, electrochemical texturing, reactive ion etching texturing, laser texturing, mask texturing, mechanical texturing, etc. Here, the embodiments of the present disclosure are not limited here. In an exemplary embodiment, a reflective layer may be of a single-layer structure or a multi-layer structure, for example, a reflective layer may be of a single-layer structure of a material with high reflectivity, such as Ag (silver) film, white reflective material film, and white oil. For example, a reflective film may be of a multi-layer structure of materials with high reflectivity such as ITO/Ag/ITO. In this way, light incident on a reflective layer and scattered by a first light-uniformizing component may be reflected and emitted through an encapsulation layer or a substrate to obtain a light-exiting effect with high-uniformity. In an exemplary embodiment, a thin film deposition technique may be used to deposit a reflective layer on a side of a first light-uniformizing component away from a light-emitting element. In an exemplary embodiment, light-emitting elements may include multiple Mini-LED light sources. In an exemplary embodiment, taking light-emitting elements including multiple Mini-LED light sources as an example, as shown inFIG.14A, the multiple Mini-LED light sources may be disposed in a quadrilateral distribution manner. InFIG.14A, a Mini-LED light source is illustrated by a small black square. In this way, a light-exit surface may be utilized as high as possible, and a difficulty of wiring of a chip drive circuit can be reduced. In another exemplary embodiment, taking light-emitting elements including multiple Mini-LED light sources as an example, as shown inFIG.14B, the multiple Mini-LED light sources may be disposed in a regular triangle distribution manner. A Mini-LED light source is illustrated by a small white square inFIG.14B. In this way, a light-exit area of each Mini-LED chip may be utilized most efficiently, so that a light-emitting module can achieve a backlight effect with a low thickness and high uniformity. Of course, an arrangement of the light-emitting elements in the light-emitting module in the embodiment of the present disclosure may be other than the two arrangements listed above. Here, the embodiments of the present disclosure are not limited here. In a practical application, a distance of Mini-LED light sources may be determined according to a design of divided areas, that is, an overlapping design of light-exit control ranges. For example, if Mini-LED light sources are disposed in a regular quadrangle, a distance between every two Mini-LED chips is the same in transverse and longitudinal directions, which may all be 4.445 mm (millimeter). When Mini-LED light sources are disposed in a regular triangle, a distance in a transverse direction may be 4.445 mm, and a distance in a longitudinal direction may be 3.849 mm. In an exemplary embodiment, a size of a Mini-LED light source is 100 μm*100 μm. In an exemplary embodiment, a first light-uniformizing component and a reflective layer may be of an integrated structure, which is a diffuse reflective material layer with bubbles. For example, as shown inFIG.15, a first light-uniformizing component and a reflective layer may be achieved by a foamed white reflective film. Here, the foamed white reflective film is formed by adding foaming agent (for example, titanium dioxide (TiO2)) or inert gas in a process of extruding a resin material (for example, polyethylene terephthalate (PET)) of a white reflective film to build small bubbles. In this way, the bubbles in the foamed white reflective film may achieve diffuse reflection. In an exemplary embodiment, a transflective film may be achieved by a thin film made of Ni—Cr (nickel-chromium) alloy, or may be achieved by an Al (aluminum) thin film, or may be displayed by a multi-layer film alternately constructed by SiO2/TiO2 materials. Of course, it may be others, and the embodiments of the present disclosure are not limited here. Based on the foregoing embodiments, the embodiment of the present disclosure provides a light-emitting module, taking the light-emitting element being a Mini-LED light source and a first light-uniformizing component being a microlens array as an example. In an exemplary embodiment, as shown inFIGS.11A,11B,11C, and11D, the light-emitting module may include multiple light-emitting elements10(Mini-LED light sources); a metal wiring layer17located on a non-light-exit side of the multiple light-emitting elements10(Mini-LED light sources); a substrate11located on a side of the metal wiring layer17away from multiple light-emitting elements10(Mini-LED light sources); an encapsulation layer12located on a light-exit side of the multiple light-emitting elements10(Mini-LED light sources); a microlens array18located on a side of the encapsulation layer12away from the multiple light-emitting elements10(Mini-LED light sources); and a reflective layer14located on a curved surface of the microlens array18. Next, the structure of the light-emitting module will be explained with a preparation process. In the embodiments of the present disclosure, “film” and “layer” may be interchanged. For example, sometimes “reflective layer” may be replaced with “reflective film”. A “patterning process” mentioned in the embodiments of the present disclosure includes processes such as deposition of a film layer, coating of a photoresist, mask exposure, development, etching, and stripping of photoresist, and are mature manufacturing processes in the art. Deposition may be performed by using a known process such as sputtering, evaporation, chemical vapor deposition, and the like, coating may be performed by using a known coating process, and etching may be performed by using a known approach, which is not limited here. In description of the embodiments of the present disclosure, it should be understood that a “thin film” refers to a layer of thin film made of a material by using deposition or another process on a base substrate. If the “thin film” does not need a patterning process during a whole manufacturing process, the “thin film” may be called a “layer”. If the “thin film” further needs a patterning process during the whole manufacturing process, it is called a “thin film” before the patterning process and a “layer” after the patterning process. The “layer” subsequent to the patterning process contains at least one “pattern”. For example, a glass substrate may be selected to be a substrate in a process, and a Mini-LED encapsulation layer may be used as a transmission structure of light emitted by a Mini-LED chip, which simplifies a whole process into a single-sided process, reduces a process difficulty in bonding, and increases a utilization rate of light energy. Copper may be selected as a material of a metal wiring layer. On one hand, an ITO/Ag/ITO reflective film corresponding to a structure of a copper wiring layer (i.e., a metal wiring layer) may be prepared on a lower surface of a glass substrate (i.e., a surface of a substrate close to a light-emitting element, that is, a surface of the metal wiring layer away from the light-emitting element) through a patterning process, so that the ITO/Ag/ITO reflective film covers a copper wiring, thus absorption loss of reflected light caused by the copper wiring layer (i.e., the metal wiring layer) in an optical path can be reduced. On the other hand, a white PR glue (Photoresist) layer corresponding to a structure of a copper wiring layer (i.e., a metal wiring layer) may be prepared on a lower surface (i.e., a surface of the metal wiring layer away from a light-emitting element) of the copper wiring layer through a patterning process, so that the copper wiring layer (i.e., the metal wiring layer) may construct a designed transflective control area with its aperture ratio. A white reflective material layer may be selected to be a reflective layer, and a microlens array board with the white reflective material layer is attached to a lower surface of an encapsulation layer (that is, a surface of the encapsulation layer away from the light-emitting element). In addition, for preparation of a microlens array, a size of the microlens array involved in a light-emitting module provided by the embodiment of the present disclosure is relatively small (for example, a diameter of a microlens may be less than 20 μm, and a pitch between adjacent microlenses may be half of the diameter of the microlens), so an overall structure is simple and has strong uniformity. Based on this feature, a microlens array may be prepared using a spraying and dispensing technology. The microlens array with a cell size of less than 20 μm may be obtained by accurately positioning, dispensing, and then curing on an encapsulation layer. Corresponding to a process capability, a diameter of a microlens ranges from 4 μm to 16 μm, and improvement effects of uniformity are almost the same, all of which may achieve an improvement effect of about 10%. Simulation software is used for modeling and simulation in the present disclosure. It may be seen from simulation results that in a backlight structure provided in the embodiments of the present disclosure, light-emitting elements are divided into concentric squares as shown inFIG.9B. According to a distribution design of a transflective control area shown inFIG.7, taking light-emitting modules shown inFIG.11A,FIG.11B,FIG.11C, andFIG.11Das examples, for a design of a light-emitting module of a 65-inch 4K display, a horizontal distance and a vertical distance of a Mini-LED array may all be designed to be 4.445 mm, and a size of an AA area in the 65-inch 4K display is 1430 mm*840 mm. Therefore, 61,000 Mini-LEDs may be used to achieve the light-emitting module with an OD of 0 mm, which is less than a demand of 100,000 Mini-LEDs in a conventional light-emitting module, and a cost is greatly optimized from one dimension. In addition, backlight uniformity of the light-emitting module with the OD of 0 mm achieved by using 61,000 Mini-LEDs in the embodiment of the present disclosure is about 91.8% or more, which is far greater than backlight uniformity of a conventional light-emitting module, and a light-uniformizing effect with high uniformity is achieved. In addition, in the light-emitting module in the embodiment of the present disclosure a diffusion sheet structure in an existing light-emitting module is omitted, and an overall thickness of the light-emitting module is reduced from 3.85 mm to 1.18 mm, thus reducing a cost of the light-emitting module from another dimension. Based on the foregoing embodiments, an embodiment of the present disclosure provides a light-emitting module, in which a light-emitting element is a Mini-LED light source, a lower surface of a substrate is provided with a first light-uniformizing component and a reflective layer, and the encapsulation layer is provided with a second light-uniformizing component and a transflective film. The light-emitting module in the embodiment of the present disclosure will be described by taking both the first uniformizing component and the second uniformizing component being microstructures as an example. Then, in an exemplary embodiment, the light-emitting module may include multiple Mini-LED light sources; a metal wiring layer located on a light-exit side of the multiple Mini-LED light sources; a substrate located on a side of the metal wiring layer away from the multiple Mini-LED light sources; a first microstructure located on a side of the substrate away from the multiple Mini-LED light sources, a reflective layer located on a side of the first microstructure away from the multiple Mini-LED light sources, an encapsulation layer located on a non-light-exit side of the multiple Mini-LED light sources; a second microstructure located on a side of the encapsulation layer away from the multiple Mini-LED light sources; and a transflective film located on a side of the second microstructure away from the multiple Mini-LED light sources. In this way, Mini-LED chips are inversely mounted on the substrate and disposed at a certain distance. A Mini-LED array emits light downwards in a form of a Lambertian light source; then, the substrate is used as a transmission layer to transmit the light emitted downwards by the Mini-LED array to increase an optical path and reduce a thickness of the light-emitting module. In addition, the light is scattered and reflected upwards by the first microstructure and the reflective layer disposed on the lower surface of the substrate (a side away from the light-emitting element), so that the reflected light may be effectively transmitted by the substrate, and the optical path is increased again. The thickness of the light-emitting module and a cost can be reduced, an overall light-exit efficiency can be improved as well as uniformity of light emitted from a light-exit surface, utilization of light energy of the light-emitting element can be increased, and a backlight light efficiency can be improved. Then, the encapsulation layer is used as a transmission layer to continuously transmit the reflected light, which increases the optical path again and reduces the thickness of the light-emitting module. Moreover, through the second microstructure and the transflective film disposed on the upper surface of the encapsulation layer, the emitted light is further scattered, a reflection angle and a diffraction angle are increased, most of the emitted light is made oscillate and transmit repeatedly in the encapsulation layer, thereby reducing a quantity of Mini-LEDs used, achieving uniform light exiting in a larger area while reducing power consumption. Therefore, a light-exiting effect with high uniformity on a surface of the light-emitting module can be achieved, a light-taking efficiency of the light-emitting module can be improved, the thickness and the cost of the light-emitting module can be reduced, and an overall light-exit efficiency of the light-emitting module can be increased. For example, taking a first microstructure as that shown inFIG.13C, light emitted by a Mini-LED reaching a lower surface of a substrate may be further scattered, so that small-angle light (e.g., 0 to 10 degrees) which concentrates most of energy may be scattered into reflected light of other angles, thus preventing the small-angle light from being reflected at a small angle again and affecting a uniform distribution effect of the energy. In addition, light with a large angle larger than a total reflection angle (for example, 41 degrees) of the substrate can be scattered and converted into light with a small angle within a range of the total reflection angle, so that light-taking of the substrate can be maximized and a backlight light efficiency can be improved. Simulation software is used for modeling and simulation in the present disclosure. It may be seen from simulation results that according to the light-emitting module provided by the embodiment of the present disclosure, a light-exit uniformity greater than 80% (where local uniformity is greater than 81%, and overall uniformity is greater than 93%) can be obtained at a zero optical distance on a surface of the light-emitting module. In addition, a light efficiency of the light-emitting module can reach 78%. In this way, a light-uniformizing effect with a high light-uniformizing degree can be achieved at the zero optical distance of zero of the light-emitting module. An embodiment of the present disclosure further provides a display module, which includes a display panel and the light-emitting module in one or more of the above embodiments, wherein the display panel is disposed on a side away from a light-exit side of a light-emitting element. In an exemplary embodiment, the display module may be any product or component with a display function such as a mobile phone, a tablet computer, a television, a display, a laptop computer, a digital photo frame, and a navigator. Although the embodiments disclosed in the present disclosure are described as above, the contents described are merely embodiments used to facilitate understanding of the present disclosure and are not used to limit the present disclosure. Those skilled in the art may make any modifications and variations to implementation forms and details without departing from the spirit and scope disclosed by the present disclosure. However, the patent protection scope of the present disclosure should also be subject to the scope defined by the appended claims. | 72,198 |
11862762 | DETAILED DESCRIPTION OF THE INVENTION The configuration of a prismatic secondary battery20according to an embodiment will be described below. It is to be noted that the present disclosure is not limited to the following embodiment. As illustrated inFIGS.1to5, the prismatic secondary battery20includes a prismatic outer body1having an opening, and a sealing plate2that seals the opening. The prismatic outer body1and the sealing plate2constitute a battery case. The prismatic outer body1and the sealing plate2are each preferably made of metal, and for instance, may be made of aluminum or aluminum alloy. The prismatic outer body1has a bottom1a, a pair of large-area side walls1b, and a pair of small-area side walls1c. The prismatic outer body1is a bottomed tubular prismatic outer body which has an opening at a position opposed to the bottom. Flat-shaped winding electrode bodies3, in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween (those components are not illustrated), are housed in the prismatic outer body1together with an electrolyte. In the positive electrode plate, a positive electrode active material layer including a positive electrode active material is formed on a positive electrode metal core. A positive electrode core exposed portion4b, where the positive electrode core is exposed, is formed at a widthwise end of the positive electrode plate. It is to be noted that aluminum foil or aluminum alloy foil is preferably used for the positive electrode core. In the negative electrode plate, a negative electrode active material layer including a negative electrode active material is formed on a negative electrode metal core. A negative electrode core exposed portion5b, where the negative electrode core is exposed, is formed at a widthwise end of the negative electrode plate. It is to be noted that copper foil or copper alloy foil is preferably used for the negative electrode core. In the prismatic secondary battery20, the positive electrode core exposed portion4bconstitutes a positive electrode tab portion4c, and the negative electrode core exposed portion5bconstitutes a negative electrode tab portion5c. As illustrated inFIGS.2to4, in the prismatic outer body1, two flat-shaped winding electrode bodies3are disposed so that the direction in which the winding axis extends is perpendicular to the sealing plate2. The positive electrode core exposed portion4band the negative electrode core exposed portion5bof each winding electrode body3are located on one end of the winding electrode body3closer to the sealing plate2than the other end. The positive electrode core exposed portions4bof the winding electrode bodies3are located on the same side (the upper side ofFIG.2), and the negative electrode core exposed portions5bof the winding electrode bodies3are located on the same side (the lower side ofFIG.2). One end side of each winding electrode body3in the direction in which the winding axis extends is provided with the stacked positive electrode core exposed portions4band the stacked negative electrode core exposed portions5b. A positive electrode current collector6is welded to the stacked positive electrode core exposed portions4b, and a welding spot30is formed. A positive electrode terminal7is electrically connected to the positive electrode current collector6. A negative electrode current collector8is welded to the stacked negative electrode core exposed portions5b, and a welding spot30is formed. A negative electrode terminal9is electrically connected to the negative electrode current collector8. The positive electrode terminal7and the positive electrode current collector6are each fixed to the sealing plate2via an insulating member10and a gasket11. The negative electrode terminal9and the negative electrode current collector8are each fixed to the sealing plate2via an insulating member12and a gasket13. The gaskets11,13are disposed between the sealing plate2and the terminals7,9, respectively. The insulating members10,12are disposed between the sealing plate2and the current collectors6,8, respectively. It is to be noted that the gasket and the insulating member are preferably composed of an insulating resin member. Each winding electrode body3is housed in the prismatic outer body1with covered by an insulating sheet14which is bent in a box shape. The insulating sheet14covers the winding electrode body3and is disposed between the winding electrode body3and the prismatic outer body1. The sealing plate2is weld-connected to an opening edge of the prismatic outer body1by laser welding or the like. The sealing plate2has an electrolytic solution injection hole15, which is sealed by a sealing plug16after injection. In the sealing plate2, a gas exhaust valve17is formed for exhausting gas when the pressure inside the battery increases. The dimensions of the prismatic secondary battery20may be, for instance, such that the width (the length in perpendicular direction to the sealing plate2, the length in the crosswise direction inFIG.1) is 18 cm, the thickness (the depth direction inFIG.1) is 3 cm, and the height (the length in parallel to the sealing plate2and perpendicular to the thickness direction of the prismatic secondary battery20, the length in the vertical direction inFIG.1) is 9 cm. The present disclosure is particularly effective when the ratio of the width to the height of the prismatic secondary battery is greater than or equal to 2. The present disclosure is particularly effective when the height of the prismatic secondary battery is 10 cm or less and the width of the prismatic secondary battery is 17 cm or greater. In addition, the present disclosure is particularly effective when the battery capacity is 30 Ah or higher. It is to be noted that the value of battery capacity may be a designed capacity, that is, the value of the nominal capacity specified by a manufacturer of batteries. Next, a method of manufacturing the prismatic secondary battery20will be described. [Production of Positive Electrode Plate] Positive electrode slurry including lithium cobalt oxide as a positive electrode active material polyvinylidene fluoride (PVdF) as a binder, a carbon material as a conductive material, and N-methylpyrrolidone (NMP) is produced. The positive electrode slurry is applied to both sides of a 15 μm-thick rectangular aluminum foil which is the positive electrode core. By drying the positive electrode slurry, the N-methylpyrrolidone in the positive electrode slurry is removed, and a positive electrode active material layer is formed on the positive electrode core. Subsequently, compression processing is performed so that the positive electrode active material layer has a predetermined thickness. The positive electrode plate thus obtained is cut so that the positive electrode core exposed portions with a predetermined width are formed with predetermined intervals at one widthwise end of the positive electrode plate. As illustrated inFIG.6, in the positive electrode plate4thus obtained, a positive electrode active material layer4ais formed on the positive electrode core. At one widthwise end of the positive electrode plate4, positive electrode core exposed portions4bwith a predetermined width are formed with predetermined intervals. It is to be noted that the positive electrode core exposed portions4bconstitute the positive electrode tab portions4c. Here, width W1of each positive electrode tab portion4cto 40 mm. Also, interval W2between adjacent positive electrode tab portions4cis 120 mm. It is to be noted that the width W1of the positive electrode tab portions4cis the width in the longitudinal direction of the positive electrode plate. [Production of Negative Electrode Plate] A negative electrode slurry including black lead as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickening agent, and water is produced. The negative electrode slurry is applied to both sides of a 8 μm-thick rectangular copper foil which is the negative electrode core. By drying the negative electrode slurry, the water in the negative electrode slurry is removed, and a negative electrode active material layer is formed on the negative electrode core. Subsequently, compression processing is performed so that the negative electrode active material layer has a predetermined thickness. The negative electrode plate thus obtained is cut so that the negative electrode core exposed portions with a predetermined width are formed with predetermined intervals at one widthwise end of the negative electrode plate. As illustrated inFIG.7, in the negative electrode plate5thus obtained, a negative electrode active material layer5ais formed on the negative electrode core. At one widthwise end of the negative electrode plate5, negative electrode core exposed portions5bwith a predetermined width are formed with predetermined intervals. It is to be noted that the negative electrode core exposed portions5bconstitute negative electrode tab portions5c. The negative electrode core exposed portion5bare also formed at the other widthwise end of the negative electrode plate5. Here, width W3of each negative electrode tab portion5cis 40 mm. Also, interval W4between adjacent negative electrode tab portions5cis 120 mm. It is to be noted that the width W3of each negative electrode tab is the width in the longitudinal direction of the negative electrode plate5. It is preferable that the relationship of W1+W2>2L be satisfied between the width W1of each positive electrode tab portion4c, the interval W2between adjacent positive electrode tab portions4c, length L of a linear portion of the winding electrode body3, and radius R of a curved portion of the winding electrode body3. When W1+2πR<L and the start position for rolling the positive electrode plate is 0°, it is preferable that the start position for rolling the negative electrode plate be 180 to 270°. It is preferable that the relationship of W3+W4>2L be satisfied between the width W2of each negative electrode tab portion5c, the interval W4between adjacent negative electrode tab portions5c, length L of a linear portion of the winding electrode body3, and radius R of a curved portion of the winding electrode body3. [Winding Electrode Body] The positive electrode plate4and the negative electrode plate5obtained by the above-described method are slid so that no overlap occurs between the positive electrode tab portions4cand the negative electrode tab portions5c, and a porous separator made of polyethylene is interposed between the positive electrode plate4and the negative electrode plate5, which are stacked, wound, and pressed, thereby forming the flat-shaped winding electrode body3. FIG.8is a view illustrating the surface on which the positive electrode tab portions4cand the negative electrode tab portions5care formed. As illustrated inFIG.8, the positive electrode tab portions4cand the negative electrode tab portions5care disposed on one end side of the winding electrode body3in the direction in which the winding axis extends. The positive electrode tab portions4care stacked on one side of the winding electrode body3in the width direction (the direction perpendicular to the direction in which the winding axis of the winding electrode body3extends, and perpendicular to the thickness direction of the winding electrode body3), and the negative electrode tab portions5care stacked on the other side of the winding electrode body3. The positive electrode tab portions4cand the negative electrode tab portions5ceach have a linear portion31disposed on the linear portion (flat portion) of the winding electrode body3, and a curve portion32disposed on a curved portion (bent portion) of the winding electrode body3. In addition, the positive electrode tab portions4care disposed and stacked to be displaced sequentially by a small distance from the winding start to the winding end. The negative electrode tab portions5care also disposed and stacked to be displaced sequentially by a small distance from the winding start to the winding end. Therefore, a stepped portion33, which is constituted by the ends of the positive electrode tab portions4c, is formed in the stacked positive electrode tab portions4c. In addition, a stepped portion33, which is constituted by the ends of the negative electrode tab portions5c, is formed in the stacked negative electrode tab portions5c. Two winding electrode bodies3thus produced are prepared and bundled securely by an insulating tape so that the positive electrode tab portions4cand the negative electrode tab portions5cof each winding electrode body3are disposed on the same side. It is to be noted that at least two winding electrode bodies3may be used and the number of winding electrode bodies3to be used is not particularly limited. Although a plurality of winding electrode bodies3is not necessarily fixed, the winding electrode bodies3are preferably bundled securely. The bundling method is not particularly limited, and the winding electrode bodies3may be secured by an insulating tape or bundled by being disposed in an insulating sheet which is molded in a bag shape or a box shape. [Assembly of Sealing Plate, Current Collector, and Terminal] As illustrated inFIGS.1and2, on one end side of the sealing plate2in the longitudinal direction, the gasket11is disposed on the outer side of the sealing plate2and the insulating member10is disposed on the inner side of the sealing plate2. The positive electrode terminal7has a flange portion7aand an insert portion7b. The positive electrode terminal7is disposed on the gasket11, and the positive electrode current collector6is disposed on the undersurface of the insulating member10. A through hole is formed in each of the gasket11, the sealing plate2, the insulating member10, and the positive electrode current collector6, and the positive electrode terminal7is inserted in each through hole and the distal end of the positive electrode terminal7is swaged, and thus the positive electrode terminal7, the gasket11, the sealing plate2, the insulating member10, and the positive electrode current collector6are integrally secured. It is preferable that the swaged portion of the positive electrode terminal7and the positive electrode current collector6be welded by laser welding or the like. On the other end side of the sealing plate2in the longitudinal direction, the gasket13is disposed on the outer side of the sealing plate2and the insulating member12is disposed on the inner side of the sealing plate2. The negative electrode terminal9has a flange portion9aand an insert portion9b. The negative electrode terminal9is disposed on the gasket13, and the negative electrode current collector8is disposed on the undersurface of the insulating member12. A through hole is formed in each of the gasket13, the sealing plate2, the insulating member12, and the negative electrode current collector8, and the negative electrode terminal9is inserted in each through hole and the distal end of the negative electrode terminal9is swaged, and thus the negative electrode terminal9, the gasket13, the sealing plate2, the insulating member12, and the negative electrode current collector8are integrally secured. It is preferable that the swaged portion of the negative electrode terminal9and the negative electrode current collector8be welded by laser welding or the like. The positive electrode current collector6and the negative electrode current collector8illustrated inFIG.9are used. The positive electrode current collector6will be described as an example. The positive electrode current collector6has a base portion6ato be connected to the positive electrode terminal7, and a connecting portion6bthat extends from an end of the base portion6ain the direction to the winding electrode body3. A through hole6cis formed in the base portion6a. The positive electrode terminal7is inserted in the through hole6c, and the distal end of the positive electrode terminal7is swaged on the base portion6a, thereby connecting the positive electrode terminal7and the positive electrode current collector6. The connecting portion6bis provided in both ends (the end on the near side and the end on the far side inFIG.9) of the base portion6ain the thickness direction of the battery. A projection34is formed in each connecting portion6b. Also, a slit35is formed in the connecting portion6b. The negative electrode current collector8may also have the same shape as that of the positive electrode current collector6. The positive electrode current collector6and the negative electrode current collector8are preferably formed by bending a plate-like metal member. [Connection of Current Collector and Winding Electrode Body] FIG.10is a view illustrating a process of connecting a tab portion and a current collector, and is a sectional view corresponding toFIG.2andFIG.3. As illustrated inFIG.10, in each of one surface side and the other surface side, the positive electrode tab portions4care disposed which are stacked on the projection34formed in the connecting portion6bof the positive electrode current collector6. With the stacked positive electrode tab portions4cand the positive electrode current collector6interposed between a pair of resistance welding electrodes40, a resistance welding current is fed and resistance welding is performed. Thus, the stacked positive electrode tab portions4cand the positive electrode current collector6are weld-connected. For the negative electrode side also, the negative electrode tab portions5cand the negative electrode current collector8are weld-connected in the same manner. When the positive electrode current collector6or the negative electrode current collector8illustrated inFIG.9is used, welding connection is first performed on the portions where the projection34is formed on the near left side and on the far side ofFIG.9, by the method illustrated inFIG.10. Subsequently, welding connection is performed on the portions where the projection34is formed on the near right side and on the far side ofFIG.9, by the method illustrated inFIG.10. At this point, since the slit35is formed in each connecting portion6bas illustrated inFIG.9, when resistance welding is performed on the second spot, generation of reactive current (a current which is not involved in the resistance welding) passing through the first welding spot which has undergone resistance welding may be avoided. It is to be noted that with regard to the order of performing resistance welding, either the left side or the right side inFIG.9may be the first spot, or both sides may be the first spot at the same time. The same method may also be applied to the negative electrode side. As illustrated inFIG.11, the positive electrode current collector6may be weld-connected to the stepped portion33of the positive electrode tab portions4c. This allows the positive electrode current collector6to be more securely connected to not only the positive electrode tab portions4clocated on the outermost circumference of the winding electrode body3, but also the positive electrode tab portions4clocated on the inner circumferential side of the winding electrode body3. In addition, not only the positive electrode tab portions4clocated on the outermost circumference of the winding electrode body3, but also the positive electrode tab portions4clocated on the inner circumferential side of the winding electrode body3are welded at positions near the positive electrode current collector6. Therefore, current may be collected more uniformly. The same method may also be applied to the negative electrode side. Next, the winding electrode body3connected to the positive electrode current collector6and the negative electrode current collector8is inserted in the prismatic outer body1with installed in the insulating sheet14bent in a box shape. The joint portion between the sealing plate2and the prismatic outer body1is then welded by laser welding, and the opening of the prismatic outer body1is sealed. Subsequently, a nonaqueous electrolyte is injected from the electrolysis solution injection hole15provided in the sealing plate2, and the electrolysis solution injection hole15is sealed by the sealing plug16, thereby producing the prismatic secondary battery20. In the prismatic secondary battery20, the positive electrode tab portions4cand the negative electrode tab portions5care each disposed on one end of the winding electrode body3closer to the sealing plate2than the other end in the winding electrode body3. Therefore, space for disposing members not involved in power generation may be reduced in the prismatic outer body1, and thus a prismatic secondary battery having a high volume energy density is achieved. In addition, in the prismatic secondary battery20, the sealing plate2is disposed on the face with the smallest area, which is one of six faces of the battery case constituted by the prismatic outer body1and the sealing plate2. In other words, the sealing plate2and the bottom1aof the prismatic outer body1have an area smaller than the area of each of four side walls (a pair of large-area side walls1band a pair of small-area side walls1c) of the prismatic outer body1. Consequently, space for disposing members not involved in power generation may be reduced, and a prismatic secondary battery having a higher volume energy density is achieved. Furthermore, in the prismatic secondary battery20, a plurality of flat-shaped winding electrode bodies3is housed in the prismatic outer body1. When a prismatic secondary battery with a larger capacity (for instance, a battery capacity of 30 Ah or higher) is produced, if a single winding electrode body is housed in the prismatic outer body1, the winding electrode body has a large number of winding and an increased thickness as illustrated inFIG.12. In such a winding electrode body, position alignment of the positive electrode tab portions4cand of the negative electrode tab portions5cis difficult, and it is also difficult to increase the width of each positive electrode tab portion4cand negative electrode tab portion5c. In addition, there is a possibility that the positive electrode tab portions4cand the negative electrode tab portions5care likely to come into contact with each other. Furthermore, connection between the positive electrode tab portions4cand the positive electrode current collector6, and connection between the negative electrode tab portions5cand the negative electrode current collector8are difficult to make. In contrast to this, housing a plurality of flat-shaped winding electrode bodies3in the prismatic outer body1makes it easy to perform position alignment of the positive electrode tab portions4cand of the negative electrode tab portions5c. Also, contact between the positive electrode tab portions4cand the negative electrode tab portions5cmay be easily prevented by increasing the width of each positive electrode tab portion4cand negative electrode tab portion5c(seeFIG.13). Therefore, dividing the electrode body to be housed in the prismatic outer body1into multiple pieces as in the prismatic secondary battery20allows the width of each positive electrode tab portion4cand negative electrode tab portion5cto be increased while preventing contact between the positive electrode tab portions4cand the negative electrode tab portions5c, thereby improving the current collection efficiency. Furthermore, it is possible to protect the positive electrode tab portions4cand the negative electrode tab portions5cagainst damage and fracture due to vibration. Consequently, a highly reliable prismatic secondary battery having a superior current collection efficiency is obtained. <First Modification> FIG.14illustrates a current collector according to a first modification. In the positive electrode current collector6(the negative electrode current collector8), the projection34provided in each connecting portion6b(8b) may be a linear projection that extends in a horizontal direction. With this configuration, the positional displacement of the resistance welding electrodes40with respect to the projection34at the time of welding may be allowed. Thus, a current collection structure having a higher productivity and a superior welding quality is achieved. <Second Modification> FIG.15illustrates a current collector according to a second modification. In the positive electrode current collector6(the negative electrode current collector8), a portion where a welding spot is formed may be provided on each of the near side and the far side. Also, the projection34may also be punctiform (such as square, circular, hemispherical). Also, the base portion6a(8a) has a wide-width portion6a1(8a1) which has a large width in the thickness direction of the prismatic secondary battery20, and a narrow-width portion6a2(8a2) which has a smaller width than the wide-width portion6a1(8a1) in the thickness direction of the prismatic secondary battery20. The positive electrode terminal7(the negative electrode terminal9) is connected to the wide-width portion6a1(8a1). The connecting portions6b(8b) are formed at ends of the narrow-width portion6a2(8a2). With this configuration, the area of the portion in the base portion6a(8a), connected to the positive electrode terminal7(the negative electrode terminal9) can be enlarged, and thus workability of connecting the positive electrode terminal7(the negative electrode terminal9) to the base portion6a(8a) improves. Since the area with both ends including a pair of connecting portions6b(8b) can be small in the base portion6a(8a), deformation of the base portion6a(8a) may be reduced when the positive electrode current collector6(the negative electrode current collector8) is interposed between a pair of resistance welding electrodes at the time of resistance welding. <Third Modification> FIG.16illustrates a current collector according to a third modification. As illustrated, the narrow-width portions6a2(8a2) may be provided at both sides of the wide-width portion6a1(8a1). Also, each of both sides of one narrow-width portions6a2(8a2) may be provided with the connecting portions6b(8b), and each of both sides of the other narrow-width portion6a2(8a2) may be provided with the connecting portions6b(8b). <Fourth Modification> FIG.17illustrates a current collector according to a fourth modification. The positive electrode terminal7(the negative electrode terminal9) may be connected to the base portion6a(8a) by welding or the like in advance. When such a current collector is used, the positive electrode terminal7(the negative electrode terminal9) is inserted in a through hole of the sealing plate2from the inner side of the battery, and the positive electrode terminal7(the negative electrode terminal9) is fixedly swaged to an external conductive member disposed on the outer side of the battery. <Fifth Modification> FIG.18illustrates a process of connecting the positive electrode current collector6and the positive electrode tab portions4cin a prismatic secondary battery according to a fifth modification. As illustrated inFIG.18, a current collector receiving component41may be disposed on an outer surface of stacked positive electrode tab portions4c, the outer surface being on the opposite side to the side where the connecting portion6bof the positive electrode current collector6is disposed. The current collector receiving component41has a first area41adisposed along the positive electrode tab portions4c, and a bent portion41bwhich is formed at an end of the first area41a, the end being closer to the winding electrode body3than the other end. When the bent portion41bis formed, even if sputtering occurs at the time of resistance welding, scattering of sputtered material toward a power generation unit (portion where the positive electrode plate4and the negative electrode plate5are stacked) of the winding electrode body3and damage to the power generation unit may be avoided. <Sixth Modification> FIG.19illustrates a process of connecting the positive electrode current collector6and the positive electrode tab portions4cin a prismatic secondary battery according to a fifth modification. In the positive electrode current collector6, a spacer42may be disposed between the connecting portion6bon one side and the connecting portion6bon the other side. Thus, when the stacked positive electrode tab portions4cand the connecting portions6bof the positive electrode current collector6are interposed between the pair of resistance welding electrodes40, deformation of the positive electrode current collector6may be reduced. It is to be noted that the spacer42may be composed of a metal member or a resin member. The spacer42is preferably an insulating resin member. Also, the spacer42may be plate-shaped, block-shaped, or pillar-shaped. The details of the embodiment and modifications described above are applicable to each of the positive electrode side and the negative electrode side. In the embodiment and modifications described above, an example has been illustrated in which connection between the positive electrode tab portions and the positive electrode current collector and connection between the negative electrode tab portions and the negative electrode current collector are made by resistance welding. However, the connection may also be made by another method. For instance, instead of the resistance welding, ultrasonic welding or welding by high energy rays such as a laser may be used. <Seventh Modification> The following configuration may be adopted to a winding electrode body according to a modification.FIG.20is a plan view of the positive electrode plate54(the negative electrode plate55). In the positive electrode plate54(the negative electrode plate55), a positive electrode active material layer54a(55a) is formed on the positive electrode core (the negative electrode core). Positive electrode core exposed portions54b(negative electrode core exposed portions55b) are formed at both ends of the positive electrode plate54(the negative electrode plate55) in the longitudinal direction. A positive electrode tab56(a negative electrode tab57) is connected by welding to each of the positive electrode core exposed portions54b(the negative electrode core exposed portions55b). The positive electrode tab56(the negative electrode tab57) is preferably a metal plate having a thickness greater than that of the positive electrode core (the negative electrode core). The positive electrode plate54and the negative electrode plate55like this are wound with a separator interposed therebetween, and a flat-shaped winding electrode body60is formed in which each of the positive electrode tabs56and the negative electrode tabs57projects from one end in the axial direction of flat-shaped winding (FIG.21). Then using a plurality of such flat-shaped winding electrode bodies60, it is possible to produce a prismatic secondary battery. For instance, the flat-shaped winding electrode bodies60are stacked and used in the orientation ofFIG.21. In this case, it is preferable that four or more flat-shaped winding electrode bodies60be used. By using four or more flat-shaped winding electrode bodies60like this, a prismatic secondary battery, which avoids the reduction in current collection performance and yet has a high volume energy density, is achieved. It is to be noted that the widths X2and X3of the positive electrode tab56and the negative electrode tab57are each preferably ¼ the width X1of the flat-shaped winding electrode body60or greater. This enables the reduction of internal resistance and a prismatic secondary battery having an improved vibration resistance is achieved. In order to achieve a prismatic secondary battery having a further improved vibration resistance, it is preferable that the positive electrode tab56(negative electrode tab57) be disposed from one end E1to the other end E2crossing a center line C in the width direction of the positive electrode plate54(the negative electrode plate55) as illustrated inFIG.20. This enables the winding electrode body60to be securely connected to the sealing plate via the positive electrode tabs56and the negative electrode tabs57. <Current Cutoff Mechanism> Either one of a conductive path between the positive electrode plate and the positive electrode terminal and a conductive path between the negative electrode plate and the negative electrode terminal may be provided with a current cut-off mechanism that operates with increasing internal pressure of the battery and blocks the conductive path between the positive electrode plate and the positive electrode terminal or the conductive path between the negative electrode plate and the negative electrode terminal to cut off the current. In this case, the operating pressure of a gas exhaust valve preferably has a value greater than the operating pressure of the current cut-off mechanism. The current cut-off mechanism preferably includes a deformation plate that deforms with increasing internal pressure of the battery, and a breaking portion that breaks due to deformation of the deformation plate. The breaking portion is preferably formed in the positive electrode current collector. In this case, for instance, the positive electrode current collector may be the positive electrode current collector6illustrated inFIG.15. In the positive electrode current collector6, a thin-walled portion or a notched portion is formed as the breaking portion in the periphery of the through hole6c. A deformation plate is disposed above the base portion6aof the positive electrode current collector6. The periphery of the through hole6cis then weld-connected to the lower surface of the deformation plate by laser welding or the like. Thus, when the deformation plate is deformed upward with increasing internal pressure of the battery, the thin-walled portion or the notched portion provided in the base portion6abreaks and a conductive path is cut off. In such a case, connection between the positive electrode tab portions4cand the positive electrode current collector6is preferably made by resistance welding. Thus, in contrast to the case where the positive electrode tab portions4cand the positive electrode current collector6are ultrasonic-welded, adverse effect of vibration on the breaking portion may be reduced. Also, in contrast to the case where the positive electrode tab portions4cand the positive electrode current collector6are laser-welded, adverse effect of sputtering on the breaking portion may be reduced. In addition, due to the formation of the wide-width portion6a1(8a1), a breaking portion may be easily formed. When an insulating member is disposed between the deformation plate and the base portion6a, and the insulating member and the base portion6aare fixed, the wide-width portion6a1(8a1) allows easy fixing. As a method for this, for instance, a through hole or a notch is provided in the wide-width portion6a1(8a1), and a projection formed in the insulating member may be fitted into the through hole or the notch. Also, a portion in the base portion, where the connecting portion6bis formed, is the narrow-width portion6a2, and so when the positive electrode tab portions4care connected to the connecting portion6b, deformation of the base portion6ais reduced, and thus the degree of damage on the breaking portion may be reduced. FIG.22illustrates a sectional view of a prismatic secondary battery having the current cut-off mechanism. It is to be noted that the sectional view corresponds to the enlarged view of the positive electrode terminal and its periphery inFIG.2. A cup-shaped conductive member60having a tubular portion is disposed on the lower surface of the insulating member10. Near the insulating member10, the conductive member60has a through hole, in which the positive electrode terminal7is inserted, and the conductive member60is connected to the positive electrode terminal7. The conductive member60has an opening on the inner side of the battery. The deformation plate61is disposed so as to block the opening. The peripheral edge of the deformation plate61is weld-connected to the conductive member60, and the opening is sealed by the deformation plate61. The positive electrode current collector6is connected to the surface, on the inner side of the battery, of the deformation plate61. The positive electrode current collector6has a through hole63, the edge of which is weld-connected to the deformation plate61. In the periphery of a portion which is weld-connected, a thin-walled portion64is formed. A circular groove65is formed in the thin-walled portion64. When the pressure inside the battery increases, a central portion of the deformation plate61is deformed so as to move upward toward the sealing plate2. In conjunction with this, the connecting portion between the deformation plate61and the positive electrode current collector6is pulled toward the sealing plate2and the circular groove65breaks. Thus, the conductive path between the positive electrode plate and the positive electrode terminal7is cut off and charging current is blocked. This enables the protection against further development of overcharge. It is to be noted that an insulating plate62made of resin is disposed between the deformation plate61and the positive electrode current collector6. The insulating plate62is latched and fixed to an insulating plate10(not illustrated). The insulating plate62has a projection67for fixation, and the projection67is inserted in a through hole66for fixation formed in the positive electrode current collector6, and the diameter of the end of the projection67is expanded. Thus, the insulating plate62and the base portion6aof the positive electrode current collector6are connected and fixed. FIG.23is a perspective view of the positive electrode current collector6used for the current cut-off mechanism. It is to be noted thatFIG.22corresponds to a sectional view taken along line XXII-XXII ofFIG.23. The positive electrode current collector6has the base portion6aand the connecting portions6bthat extend from the base portion6atoward the electrode body. The base portion6ahas a wide-width portion6a1which has a large width in the thickness direction (the direction of the shorter side of the sealing plate) of the prismatic secondary battery, and a narrow-width portion6a2which has a smaller width than the wide-width portion6a1in the thickness direction of the prismatic secondary battery. In the wide-width portion6a1, the base portion6ais connected to the deformation plate61. Also, in the wide-width portion6a1, the base portion6ais fixed to the insulating plate62. The connecting portions6bare provided in the narrow-width portion6a2. With the current cut-off mechanism thus formed, when the positive electrode tab portions4care weld-connected to the connecting portions6bof the positive electrode current collector6, adverse effect on a fragile portion (expected breaking portion) provided in the base portion6a, and the connecting portion between the deformation plate61and the base portion6amay be reduced. For instance, scattering of sputtered material to the fragile portion or the connecting portion may be reduced, the sputtered material being generated at the time of welding the connecting portions6band the positive electrode tab portions4c. Or deformation of the periphery of the fragile portion and the connecting portion in the base portion6ais reduced due to stress at the time of welding the connecting portions6band the positive electrode tab portions4c. It is preferable that the relationship of W1/W2≥3/2 be satisfied between the width W1of the wide-width portion6a1and the width W2of the narrow-width portion6a2. It is to be noted that the current cut-off mechanism in this configuration is effective even when a single winding electrode body is housed in the prismatic outer body. In addition, the current cut-off mechanism in this configuration is effective even when stacked electrode bodies are housed in the prismatic outer body. The following configuration may be adopted for an assembled battery using a plurality of prismatic secondary batteries20. As illustrated inFIG.24, in an assembled battery50, a plurality of prismatic secondary batteries20is stacked between a pair of end plates51in an orientation in which respective large-area side walls are parallel. The pair of end plates51are connected by a bind bar52. It is to be noted that the end plates and a bus bar are connected using a bolt or a rivet or by welding. An insulating separator53is disposed between the prismatic secondary batteries20, and the separator53is preferably composed of a resin. In the assembled battery50, the positive electrode terminal7and the negative electrode terminal9of each prismatic secondary battery20are disposed on one lateral face (the lateral face on the near side inFIG.24). Terminals of adjacent prismatic secondary batteries20are connected by a bus bar54. The bottom of each prismatic secondary battery20is disposed on the other lateral face (the lateral face on the far side inFIG.24). The small-area side walls of each prismatic secondary battery20are disposed on the upper surface and the lower surface of the assembled battery50. By adopting this configuration, a low-height assembled battery having an extremely high volume energy density is achieved. The assembled battery50thus constructed is mounted in a vehicle in the orientation illustrated inFIG.24, thereby achieving significantly improved occupant comfort in the vehicle. It is to be noted that a cooling plate55, in which a cooling medium flows, is disposed in the bottom surface of the assembled battery50, and each prismatic secondary battery20is preferably cooled by the cooling plate. It is to be noted that the cooling medium may be a gas or a liquid. While detailed embodiments have been used to illustrate the present invention, to those skilled in the art, however, it will be apparent from the foregoing disclosure that various changes and modifications can be made therein without departing from the spirit and scope of the invention. Furthermore, the foregoing description of the embodiments according to the present invention is provided for illustration only, and is not intended to limit the invention. | 42,463 |
11862763 | DETAILED DESCRIPTION The present invention is generally directed to a system for supplying power to a portable battery pack including a wearable and replaceable pouch or skin with one or more batteries enclosed in the pouch or skin using at least one solar panel for military, law enforcement, aviation, personal survival, hiking, sports, recreation, hunting, land surveying, expedition, watersports, and camping applications. In one embodiment, the present invention provides a system for supplying power to a portable battery pack using at least one foldable solar panel including a portable battery pack including one or more batteries enclosed in a wearable pouch and at least one foldable solar panel, wherein the one or more batteries include at least one battery element, a battery cover including one or more channels to accommodate wires of one or more flexible omnidirectional leads and a compartment sized to receive the at least one battery element, a battery back plate attached to the battery cover, and the one or more flexible omnidirectional leads including a connector portion and a wiring portion, wherein a flexible spring is provided around the wiring portion, wherein the wiring portion and the flexible spring are held securely in the one or more channels in the battery cover such that a portion of the flexible spring is positioned inside the battery cover and a portion of the flexible spring is positioned outside the battery cover, wherein the wearable pouch includes a closeable opening through which the one or more batteries are operable to be removed from the wearable pouch, and one or more openings through which the one or more flexible omnidirectional leads from the one or more batteries can be accessed, wherein the at least one foldable solar panel includes at least two solar modules electrically connected to one another and to at least one output connector, and wherein the at least one foldable solar panel is operable to supply power to the one or more batteries. In another embodiment, the present invention provides a system for supplying power to a portable battery pack using at least one foldable solar panel including a portable battery pack including one or more batteries enclosed in a wearable pouch and at least one foldable solar panel, wherein the one or more batteries are rechargeable and include at least one battery element, a battery cover including one or more channels to accommodate wires of one or more flexible omnidirectional leads and a compartment sized to receive the at least one battery element, a battery back plate attached to the battery cover, and the one or more flexible omnidirectional leads including a connector portion and a wiring portion, wherein a flexible spring is provided around the wiring portion, wherein the wiring portion and the flexible spring are held securely in the one or more channels in the battery cover such that a portion of the flexible spring is positioned inside the battery cover and a portion of the flexible spring is positioned outside the battery cover, wherein the wearable pouch includes a closeable opening through which the one or more batteries are operable to be removed from the wearable pouch, and one or more openings through which the one or more flexible omnidirectional leads from the one or more batteries can be accessed, wherein the one or more flexible omnidirectional leads are operable to charge at least one of the one or more batteries, wherein the at least one foldable solar panel includes at least two solar modules electrically connected to one another and to at least one output connector, wherein the at least one foldable solar panel is operable to supply power to the one or more batteries, and wherein the one or more flexible omnidirectional leads are operable to supply power to a power consuming device. In yet another embodiment, the present invention provides a system for supplying power to a portable battery pack using at least one foldable solar panel including a portable battery pack including one or more batteries enclosed in a wearable pouch and at least one foldable solar panel, wherein the one or more batteries include at least one battery element, a battery cover including one or more channels to accommodate wires of one or more flexible omnidirectional leads and a compartment sized to receive the at least one battery element, a battery back plate attached to the battery cover, and the one or more flexible omnidirectional leads including a connector portion and a wiring portion, wherein a flexible spring is provided around the wiring portion, wherein the wiring portion and the flexible spring are held securely in the one or more channels in the battery cover such that a portion of the flexible spring is positioned inside the battery cover and a portion of the flexible spring is positioned outside the battery cover, wherein the wearable pouch includes a closeable opening through which the one or more batteries are operable to be removed from the wearable pouch and one or more openings through which the one or more flexible omnidirectional leads from the one or more batteries can be accessed, wherein the wearable pouch and/or the at least one foldable solar panel includes a pouch attachment ladder system (PALS) operable to attach the wearable pouch and/or the at least one foldable solar panel to a load-bearing platform, wherein the at least one foldable solar panel includes at least two solar modules electrically connected to one another and to at least one output connector, and wherein the at least one foldable solar panel is operable to supply power to the one or more batteries. None of the prior art discloses a system for supplying power to a portable battery including one or more batteries enclosed in a wearable pouch using at least one solar panel, wherein the one or more batteries include at least one battery element, a battery cover, a battery back plate, and one or more flexible omnidirectional leads that include a connector portion and a wiring portion, wherein a flexible spring is provided around the wiring portion such that a portion of the flexible spring is positioned inside the battery cover and a portion of the flexible spring is positioned outside the battery cover. Referring now to the drawings in general, the illustrations are for the purpose of describing one or more preferred embodiments of the invention and are not intended to limit the invention thereto. Portable Battery Pack In some embodiments, the present invention provides a portable battery pack including a battery enclosed by, e.g., inside of, a wearable and replaceable pouch or skin, wherein the pouch or skin can be provided in different colors and/or patterns. Namely, a set of multiple interchangeable pouches or skins can be provided with one battery unit. This feature is particularly beneficial when it is required that the portable battery pack blend into different environments, such as in military applications. In one example, if the portable battery pack is used in a jungle or wilderness environment, the battery can be placed inside a camouflage pouch or skin. In another example, if the portable battery pack is used in an arctic environment, the battery can be placed inside a white-colored pouch or skin. In yet another example, if the portable battery pack is used in a desert environment, the battery can be placed inside a sand-colored pouch or skin. Representative camouflages include, but are not limited to, Universal Camouflage Pattern (UCP), also known as ACUPAT or ARPAT or Army Combat Uniform; MULTICAM®, also known as Operation Enduring Freedom Camouflage Pattern (OCP); Universal Camouflage Pattern-Delta (UCP-Delta); Airman Battle Uniform (ABU); Navy Working Uniform (NWU), including variants, such as, blue-grey, desert (Type II), and woodland (Type III); MARPAT, also known as Marine Corps Combat Utility Uniform, including woodland, desert, and winter/snow variants; Disruptive Overwhite Snow Digital Camouflage, Urban Digital Camouflage, and Tactical Assault Camouflage (TACAM). Therefore, an aspect of the portable battery pack is that it provides a battery in combination with one or more wearable and replaceable pouches or skins, wherein the one or more pouches or skins can be different colors and/or patterns. Another aspect of the portable battery pack is that the battery has one or more leads that can be flexed repeatedly in any direction without breaking or failing. This means the portable battery pack is operable to deliver energy from the battery to power consuming devices located in different areas of the load bearing equipment. Similarly, the portable battery pack is operable to receive energy from charging devices located in different areas of the load bearing equipment to the battery. Yet another aspect of the portable battery pack is that the battery and pouch or skin are lightweight and contoured for comfortable wearing or ease of fastening to other equipment, such as a backpack or body armor, while still maintaining the lowest possible profile. Advantageously, this low profile prevents the portable battery pack from interfering with the wearer while in motion or seated. Still another aspect of the portable battery pack is that the pouch or skin can be MOLLE-compatible. “MOLLE” means Modular Lightweight Load-carrying Equipment, which is the current generation of load-bearing equipment and backpacks utilized by a number of NATO armed forces. The portable battery pack can also be made to affix to other equipment (e.g., chair or seat, boat or kayak, helmet) or a user's body (e.g., back region, chest region, abdominal region, arm, leg) using straps, snaps, hook and loop tape, snaps, ties, buckles, and/or clips for other applications. FIGS.1-3are perspective views of an example of the portable battery pack100that includes a battery enclosed by a wearable pouch or skin. For example, portable battery pack100includes a pouch110for holding a battery150. The pouch110is a wearable pouch or skin that can be sized in any manner that substantially corresponds to a size of the battery150. In one example, the pouch110is sized to hold a battery150that is about 9.75 inches long, about 8.6 inches wide, and about 1 inch thick. In a preferred embodiment, the pouch110is formed of a flexible, durable, and waterproof or at least water-resistant material. For example, the pouch110is formed of polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, or polycotton canvas. In one embodiment, the pouch110is formed of a material that is laminated to or treated with a waterproofing or water repellant material (e.g., rubber, PVC, polyurethane, silicone elastomer, fluoropolymers, wax, thermoplastic elastomer). Additionally or alternatively, the pouch110is treated with a UV coating to increase UV resistance. The exterior finish of the pouch110can be any color, such as white, brown, green, orange (e.g., international orange), yellow, black, or blue, or any pattern, such as camouflage, as provided herein, or any other camouflage in use by the military, law enforcement, or hunters. For example, inFIGS.1-3, the pouch110is shown to have a camouflage pattern. In one embodiment, the exterior of the pouch110includes a reflective tape (e.g., infrared reflective tape), fabric, or material. Advantageously, the reflective tape, fabric, or material improves visibility of the user in low-light conditions. The pouch110has a first side112and a second side114. The pouch110also includes a pouch opening116, which is the opening through which the battery150is fitted into the pouch110. In the example shown inFIGS.1-3, the pouch opening116is opened and closed using a zipper, as the pouch110includes a zipper tab118. Other mechanisms, however, can be used for holding the pouch opening116of the pouch110open or closed, such as, a hook and loop system (e.g., VELCRO®), buttons, snaps, hooks, ties, clips, buckles, and the like. Further, a lead opening120(seeFIG.2,FIG.3,FIG.5) is provided on the end of the pouch110that is opposite the pouch opening116. For example, the lead opening120can be a 0.5-inch long slit or a 0.75-inch long slit in the edge of the pouch110. In one embodiment, the lead opening120is finished or reinforced with stitching. In another embodiment, the lead opening120is laser cut. The battery150includes at least one lead. In one example, the battery150is a rechargeable battery with two leads152(e.g., a first lead152aand a second lead152b) as shown inFIGS.2-3. Each lead152can be used for both the charging function and the power supply function. In other words, the leads152a,152bare not dedicated to the charging function only or the power supply function only, both leads152a,152bcan be used for either function at any time or both at the same time. In one example, the first lead152acan be used for charging the battery150while the second lead152bcan be used simultaneously for powering equipment, or both leads152can be used for powering equipment, or both leads152can be used for charging the battery150. Each lead is preferably operable to charge and discharge at the same time. In one example, a Y-splitter with a first connector and a second connector is attached to a lead. The Y-splitter allows the lead to supply power to equipment via the first connector and charge the battery via the second connector at the same time. Thus, the leads are operable to allow power to flow in and out of the battery simultaneously. In another embodiment, each lead is operable to charge or discharge, but not operable to charge and discharge simultaneously. In one embodiment, the battery includes at least one sensor operable to determine if a lead is connected to a load or a power supply. If the at least one sensor determines that a lead is connected to a load, the discharging function is enabled and the charging function is disabled. If the at least one sensor determines that a lead is connected to a power supply, the charging function is enabled and the discharging function is disabled. In a preferred embodiment, a dust cap is used to cover a corresponding lead. Advantageously, the dust cap protects the connector from dust and other environmental contaminants that may cause battery failure in the field. The dust cap is preferably permanently attached to the corresponding lead. Alternatively, the dust cap is removably attachable to the corresponding lead. The battery is operable to be charged using at least one charging device. In a preferred embodiment, the at least one charging device is an alternating current (AC) adapter, a solar panel, a generator, a wind turbine, a portable power case, a fuel cell, a vehicle battery, a rechargeable battery, and/or a non-rechargeable battery. Examples of a portable power case are disclosed in U.S. Publication No. 20170229692 and U.S. application Ser. Nos. 15/664,776 and 15/836,299, each of which is incorporated herein by reference in its entirety. In one embodiment, the battery is connected to the at least one charging device through a direct current-direct current (DC-DC) converter cable. In another embodiment, the battery is operable to be charged via inductive charging. In one embodiment, the battery is operable to be charged using an inductive charging mat. In an alternative embodiment, the battery is operable to be charged using an inductive puck worn in a pocket, on the back of a helmet, or in a rucksack. In one embodiment, the inductive puck is powered using a DC power source. Advantageously, this reduces the number of cables required for a user, which prevents users from accidentally disconnecting cables (e.g., when getting in and out of spaces like vehicles). Additionally, this allows a user to use proximity charging, which allows the user to focus on the task at hand instead of spending a few seconds connecting the battery to a charging device, which may be located behind the user in a rucksack. Further, this embodiment eliminates the possibility of reverse polarity and arcing between connectors caused by the electrical potential. The inductive puck is operable to charge additional power consuming devices carried by a user (e.g., a smartphone, a tablet). In one embodiment, the battery is operable to be charged by harvesting ambient radiofrequency (RF) waves. Alternatively, the battery is operable to be charged by capturing exothermic body reactions (e.g., heat, sweat). In one embodiment, the battery is operable to be charged using thermoelectric generators, which use temperature differences between the body and the external environment to generate energy. In another embodiment, the battery is operable to be charged using sweat (e.g., using lactate). In an alternative embodiment, the battery is operable to be charged using friction (e.g., triboelectric effect) or kinetic energy. In yet another example, the battery is operable to be charged by a pedal power generator. In one embodiment, the battery is connected to the pedal power generator through a direct current-direct current (DC-DC) converter cable. The battery is also operable to be charged using energy generated from running water and wind energy. In one embodiment, the wind energy is generated using an unmanned aerial system or drone on a tether. In an alternative embodiment, the wind energy is generated using a drive along turbine. In yet another embodiment, the wind energy is generated using a statically mounted turbine (e.g., ground mounted, tower mounted). With respect to using the battery150with pouch110, first the user unzips the pouch opening116, then the user inserts one end of the battery150that has, for example, the second lead152bthrough the pouch opening116and into the compartment inside the pouch110. At the same time, the user guides the end of the second lead152bthrough the lead opening120, which allows the housing of the battery150to fit entirely inside of the pouch110, as shown inFIG.1. The first lead152ais left protruding out of the unzipped portion of the pouch opening116. Then the user zips the pouch opening116closed, leaving the zipper tab118snugged up against the first lead152a, as shown inFIG.2andFIG.3.FIG.2shows the portable battery pack100with the first side112of the pouch110up, whereasFIG.3shows the portable battery pack100with the second side114of the pouch110up. As previously described, the battery has at least one lead. In one embodiment, the pouch has an opening for each corresponding lead. In one example, the battery has four leads and the pouch has four openings corresponding to the four leads. Alternatively, the pouch utilizes the zippered pouch opening to secure one lead and has an opening for each remaining lead. In one example, the battery has four leads and the pouch has three openings for three of the four leads. The remaining lead is secured by the zipper. In another embodiment, the pouch has a seal around an opening for a corresponding lead. The seal is tight around the lead, which prevents water from entering the pouch through the opening. In one embodiment, the seal is formed of a rubber (e.g., neoprene). In a preferred embodiment, the pouch of the portable battery pack is MOLLE-compatible. In one embodiment, the pouch incorporates a pouch attachment ladder system (PALS), which is a grid of webbing used to attach smaller equipment onto load-bearing platforms, such as vests and backpacks. For example, the PALS grid consists of horizontal rows of 1-inch (2.5 cm) webbing, spaced about one inch apart, and reattached to the backing at 1.5-inch (3.8 cm) intervals. In one embodiment, the webbing is formed of nylon (e.g., cordura nylon webbing, MIL-W-43668 Type III nylon webbing). Accordingly, a set of straps122(e.g., four straps122) are provided on one edge of the pouch110as shown inFIGS.2-3. Further, rows of webbing124(e.g., four rows124) are provided on the first side112of the pouch110, as shown inFIG.2. Additionally, rows of slots or slits126(e.g., seven rows of slots or slits126) are provided on the second side114of the pouch110, as shown inFIG.3. In a preferred embodiment, the set of straps122, the rows of webbing124, and the rows of slots or slits126replicate and duplicate the MOLLE underneath the portable battery pack on the load bearing equipment. Advantageously, this allows for minimal disruption to the user because the user can place additional gear pouches or gear (e.g., water bottle, antenna pouch) on the MOLLE of the portable battery pack in an equivalent location. In other embodiments, the portable battery pack is made to affix to other equipment (e.g., chair or seat, boat or kayak, helmet) or a user's body (e.g., back region, chest region, abdominal region, arm, leg) using straps, snaps, hook and loop tape, snaps, buckles, ties, and/or clips. In one example, the portable battery pack is made to affix to a seat of a kayak using at least one strap and at least one side-release buckle. In another example, the portable battery pack is made to affix to a user's body using two shoulder straps. In yet another example, the portable battery pack includes two shoulder straps, a chest strap, and a side-release buckle for the chest strap. FIGS.4-6are perspective views of an example of the pouch110of the portable battery pack100.FIG.4shows details of the first side112of the pouch110and of the edge of the pouch110that includes the pouch opening116.FIG.4shows the pouch opening116in the zipper closed state. Again, four rows of webbing124are provided on the first side112of the pouch110.FIG.5also shows details of the first side112of the pouch110and shows the edge of the pouch110that includes the lead opening120.FIG.6shows details of the second side114of the pouch110and shows the edge of the pouch110that includes the pouch opening116.FIG.6shows the pouch opening116in the zipped closed state. Again, seven rows of slots or slits126are provided on the second side114of the pouch110. In another embodiment, the portable battery pack is made to affix to a plate carrier, body armor, or a vest with at least one single width of zipper tape sewn on the front panel or the back panel (e.g., JPC 2.0™ by Crye Precision) as shown inFIGS.7A-7B.FIG.7Ashows details of the first side112of the pouch110including a single width of zipper tape190aand a zipper slider192a. The single width of zipper tape190amates with a corresponding single width of zipper tape on the plate carrier, the body armor, or the vest.FIG.7Bshows details of the second side114of the pouch110including a single width of zipper tape190band a zipper slider192b. The single width of zipper tape190bmates with a corresponding single width of zipper tape on the plate carrier, the body armor, or the vest. FIG.8shows a side perspective view of the portable battery pack100affixed to a vest600using zippers. A first single width of zipper tape190ais shown mated with a corresponding first single width of zipper tape194aon a right side of the vest600using a first zipper slider192a, thereby attaching the portable battery pack100to the vest600. Similarly, a second single width of zipper tape (not shown) is mated with a second corresponding single width of zipper tape (not shown) on a left side of the vest600using a second zipper slider (not shown). Advantageously, this allows cables to extend out of the pouch through an opening in the second side of the pouch because the rows of slots or slits are not required to the secure the pouch to the vest. FIGS.9A-9Eillustrate various other views of the pouch110of the portable battery pack100.FIG.9Ashows a view (i.e., “PLAN-A”) of the first side112of the pouch110.FIG.9Bshows a side view of the pouch110.FIG.9Cshows a view (i.e., “PLAN-B”) of the second side114of the pouch110.FIG.9Dshows an end view (i.e., “END-A”) of the non-strap end of the pouch110.FIG.9Eshows an end view (i.e., “END-B”) of the strap122-end of the pouch110.FIG.10is an exploded view of an example of the battery150of the portable battery pack100. The battery150includes a battery element164that is housed between a battery cover154and a back plate162. The battery element164supplies the first lead152aand the second lead152b. The battery element164is formed of a plurality of sealed battery cells or individually contained battery cells, i.e. batteries with their own cases, removably disposed therein. In a preferred embodiment, the battery cells are electrochemical battery cells, and more preferably, include lithium ion rechargeable batteries. In one embodiment, the battery cells are lithium metal or lithium ferrous phosphate cells. In an alternative embodiment, the battery cells are all-solid-state cells (e.g., using glass electrolytes and alkaline metal anodes), such as those disclosed in U.S. Publication Nos. 20160368777 and 20160365602, each of which is incorporated by reference in its entirety. In another embodiment, the battery is formed using at least one metal-organic framework. In one embodiment, the battery cells are 18350, 14430, 14500, 18500, 16650, 18650, 21700, or 26650 cylindrical cells. The plurality of battery cells may be constructed and configured in parallel, series, or a combination. The plurality of battery cells may be in one group or more than one group. Advantageously, subdividing the plurality of battery cells into more than one group allows a larger quantity of lithium ion batteries to arrive by air that otherwise could not be transported due to regulations. In one example, the output of the battery element164can be from about 5 volts DC to about 90 volts DC at from about 0.25 amps to about 10 amps. The plurality of battery cells is preferably connected to the leads via a battery management system. The battery management system protects the battery from operating outside of a safe operating area by including at least one safety cutoff. The at least one safety cutoff relates to voltage, temperature, state of charge, state of health, and/or current. In another embodiment, the battery management system calculates a charge current limit, a discharge current limit, an energy delivered since last charge, a charge delivered, a charge stored, a total energy delivered since first use, a total operating time since first use, and/or a total number of cycles. In one embodiment, the plurality of battery cells is removably disposed within the battery cover and the back plate. For example, the plurality of battery cells can be replaced if they no longer hold a sufficient charge. In one embodiment, the plurality of battery cells is removably disposed within the battery cover and the back plate as a battery cartridge. In a preferred embodiment, the battery cartridge slides into an opening in the battery cover or the back plate through a battery access panel. In one embodiment, the battery cartridge is a spring-loaded cartridge. Additionally or alternatively, the battery cartridge has flat contacts and pins. The battery cartridge preferably has features that allow the battery cartridge to matingly fit with features in the opening. In another embodiment, the plurality of battery cells is removably disposed within the battery cover and the back plate using a battery holder or a snap connector. In one embodiment, the battery holder or the snap connector is electrically connected to the battery management system via a mating connector (e.g., a rectangular connector), such as those available from MOLEX® or POWERPOLE® by Anderson Power. The battery access panel is preferably accessed within the battery cover or the back plate via a door on hinges, which allows the door to stay anchored to the device. Alternatively, the door is secured to the battery cover or the back plate by screws. The battery access panel preferably contains a gasket that provides a water tight seal when the door is secured to the battery cover or the back plate. Alternatively, the plurality of battery cells is sealed within the battery cover and the back plate. In one embodiment, the plurality of battery cells is sealed using an adhesive and/or at least one mechanical fastener (e.g., screws, rivets, pins). In another embodiment, the plurality of battery cells is sealed within the battery cover and the back plate via bonding (e.g., solvent bonding, fusion bonding) and/or welding (e.g., vibration welding, ultrasonic welding). The battery cover154includes a compartment156that is sized to receive at least one battery element164. In a preferred embodiment, the compartment156is substantially rectangular in shape with a top hat style rim158provided around the perimeter of the compartment156. The battery cover154incudes at least one channel formed in the battery cover154to accommodate a wire of a corresponding lead. The example inFIG.10shows two channels160(e.g., channels160a,160b) formed in the battery cover154(one on each side) to accommodate the wires of the first lead152aand the second lead152bpassing therethrough. More details of the leads152and the battery cover154are shown and described herein below with reference toFIG.16. The battery cover154and the back plate162is formed of plastic using, for example, a thermoform process or an injection molding. The back plate162can be mechanically attached to the rim158of the battery cover154via, for example, an ultrasonic spot welding process or an adhesive. Advantageously, the top hat style rim158provides a footprint for the ultrasonic spot welding process and provides structural integrity for the battery. In one embodiment, a water barrier material (e.g., silicone) is applied to the mating surfaces of the rim158and the back plate162. In another embodiment, the battery cover154, the back plate162, and/or the battery element164has a slight curvature or contour for conforming to, for example, the user's vest, backpack, or body armor. In one example, the curvature of the portable battery pack is engineered to match the outward curve of body armor. Advantageously, this means that the portable battery pack does not jostle as the operator moves, which results in less caloric energy expenditure when the operator moves. Alternatively, the battery cover154, the back plate162, and/or the battery element164can have a slight outward curvature or contour for conforming to a user's body (e.g., back region, chest region, abdominal region, arm, leg). In yet another embodiment, the battery cover154, the back plate162, and/or the battery element164can have a slight outward curvature or contour for conforming to a user's helmet or hat. More details of the battery cover154are shown and described herein below with reference toFIG.13andFIGS.14A-14D. More details of the back plate162are shown and described herein below with reference toFIGS.15A-15C. As previously described, the housing of the at least one battery includes a battery cover and a back plate. In one embodiment, the battery includes more than one battery element encased in the housing. The output voltages of the more than one battery element may be the same or different. In one example, a first battery element has an output voltage of 16.8V and a second battery element has an output voltage of 16.8V. In another example, a first battery element has an output voltage of 16.8V and a second battery element has an output voltage of 5V. Advantageously, including more than one battery element encased in the housing allows a larger quantity of lithium ion batteries to arrive by air that otherwise could not be transported due to regulations. FIGS.11-12are perspective views of the battery150of the portable battery pack100when fully assembled.FIG.11shows a view of the battery cover154-side of the battery150, whileFIG.12shows a view of the back plate162-side of the battery150. FIG.13is a perspective view of the side of the battery cover154that faces the battery element164.FIGS.14A-14Dshows various other views of the battery cover154of the battery150of the portable battery pack100, including example dimensions of the battery cover154.FIG.14Aillustrates a top perspective view of the battery cover of the portable battery pack.FIG.14Billustrates a cross-section view of the battery cover of the portable battery pack.FIG.14Cillustrates another cross-section view of the battery cover of the portable battery pack.FIG.14Dillustrates yet another cross-section view of the battery cover of the portable battery pack. FIGS.15A-15Cillustrate various views of the back plate162of the battery150and show the contour and example dimensions of the back plate162.FIG.15Aillustrates a cross-section view of the back plate of the battery of the portable battery pack.FIG.15Billustrates a view of the back plate of the battery of the portable battery pack.FIG.15Cillustrates another view of the back plate of the battery of the portable battery pack. In one example, the back plate162is about 9.75 inches long, about 8.6 inches wide, and about 0.4 inches thick. FIG.16is a cutaway view of a portion of the battery150, which shows more details of the flexible omnidirectional battery leads152. Each lead152has a connector portion170and a wiring portion172. The wiring portion172is electrically connected to the battery element164. In one embodiment, the wiring portion172is formed of a saltwater resistant cable. The connector portion170can be any type or style of connector needed to mate to the equipment to be used with the battery150of the portable battery pack100. In a preferred embodiment, the connector portion170is a female circular type of connector (e.g., TAJIMI™ part number R04-P5f). In an alternative embodiment, at least one connector portion170is a male universal serial bus (USB), micro USB, lightning, and/or Firewire connector. In another embodiment, the at least one connector portion170is a 360° mating connector (e.g., LP360 by FISHER®). In yet another embodiment, the connector portion170has an Ingress Protection (IP) rating of IP2X, IP3X, IP4X, IP5X, IP6X, IPX1, IPX2, IPX3, IPX4, IPX5, IPX6, IPX7, or IPX8. More preferably, the connector portion170has an IP rating of IPX6, IPX7, or IPX8. IP ratings are described in IEC standard 60529, ed. 2.2 (May 2015), published by the International Electrotechnical Commission, which is incorporated herein by reference in its entirety. In one embodiment, the connector portion meets standards described in Department of Defense documents MIL-STD-202E, MIL-STD-202F published February 1998, MIL-STD-202G published 18 Jul. 2003, and/or MIL-STD-202H published 18 Apr. 2015, each of which is incorporated herein by reference in its entirety. The wiring portion172is fitted into a channel160formed in the battery cover154such that the connector portion170extends away from the battery cover154. A spring174is provided around the wiring portion172, such that a portion of the spring174is inside the battery cover154and a portion of the spring174is outside the battery cover154. In one example, the spring174is a steel spring that is from about 0.25 inches to about 1.5 inches long. The wiring portion172of the lead152and the spring174are held securely in the channel160of the battery cover154via a clamping mechanism176. Alternatively, the wiring portion of the lead and the spring are held securely in the channel of the battery cover using an adhesive, a retention pin, a hex nut, a hook anchor, and/or a zip tie. The presence of the spring174around the wiring portion172of the lead152allows the lead152to be flexed in any direction for convenient connection to equipment from any angle. The presence of the spring174around the wiring portion172of the lead152also allows the lead152to be flexed repeatedly without breaking or failing. The design of the leads152provides benefit over conventional leads and/or connectors of portable battery packs that are rigid, wherein conventional rigid leads allow connection from one angle only and are prone to breakage if bumped. In one embodiment, a layer of heat shrink tubing is placed around the wiring portion before the spring is placed around the wiring portion. The heat shrink tubing is preferably flexible. Advantageously, the heat shrink tubing provides additional waterproofing for the battery. In one embodiment, the battery includes at least one step up voltage converter and/or at least one step down voltage converter. In one example, the battery includes a step up voltage converter from 16.8V to 29.4V. In another example, the battery includes a step down voltage converter from 16.8V to 5V. Advantageously, this allows the portable battery pack to power devices (e.g., smartphones) with a charging voltage of 5V. This also reduces the bulk outside the portable battery pack because the step down voltage converter is housed within the battery element and a separate external voltage converter is not required. In one embodiment, the wearable pouch includes a material for dissipating heat. Additionally or alternatively, the battery of the wearable battery pack includes at least one layer of a material for dissipating heat. Examples of a material for dissipating heat are disclosed in U.S. Publication Nos. 20170229692 and 20160112004 and U.S. application Ser. No. 15/664,776, each of which is incorporated herein by reference in its entirety. FIGS.17A-17Dare cross-sectional views of examples of structures that include a material for dissipating heat from electronic devices and/or clothing. The heat-dissipating material can be used in combination with, for example, one or two substrates. For example,FIG.17Ashows a structure1500that includes a heat-dissipating layer1520. The heat-dissipating layer1520can be sandwiched between a first substrate1525and a second substrate1530. The heat-dissipating layer1520can be any material that is suitable for dissipating heat from electronic devices and/or clothing. The heat-dissipating layer1520can be from about 20 μm thick to about 350 μm thick in one example. In particular embodiments, the heat-dissipating layer1520can have a thickness ranging from about 1 mil to about 6 mil, including, but not limited to, 1, 2, 3, 4, 5, and 6 mil, or about 25 μm to about 150 μm, including, but not limited to, 25, 50, 75, 100, 125, and 150 μm. Examples of the heat-dissipating layer1520include anti-static, anti-radio frequency (RF), and/or anti-electromagnetic interference (EMI) materials, such as copper shielding plastic or copper particles bonded in a polymer matrix, as well as anti-tarnish and anti-corrosion materials. A specific example of the heat-dissipating layer1520is the anti-corrosive material used in Corrosion Intercept Pouches, catalog number 034-2024-10, available from University Products Inc. (Holyoke, Mass.). The anti-corrosive material is described in U.S. Pat. No. 4,944,916 to Franey, which is incorporated by reference herein in its entirety. Such materials can be formed of copper shielded or copper impregnated polymers including, but not limited to, polyethylene, low-density polyethylene, high-density polyethylene, polypropylene, and polystyrene. In another embodiment, the heat shielding or blocking and/or heat-dissipating layer is a polymer with aluminum and/or copper particles incorporated therein. In particular, the surface area of the polymer with aluminum and/or copper particles incorporated therein preferably includes a large percent by area of copper and/or aluminum. By way of example and not limitation, the surface area of the heat-dissipating layer includes about 25% by area copper and/or aluminum, 50% by area copper and/or aluminum, 75% by area copper and/or aluminum, or 90% by area copper and/or aluminum. In one embodiment, the heat shielding or blocking and/or heat-dissipating layer is substantially smooth and not bumpy. In another embodiment, the heat shielding or blocking and/or heat-dissipating layer is not flat but includes folds and/or bumps to increase the surface area of the layer. Alternatively, the heat-shielding or blocking and/or heat-dissipating layer1520includes a fabric having at least one metal incorporated therein or thereon. The fabric further includes a synthetic component, such as by way of example and not limitation, a nylon, a polyester, or an acetate component. Preferably, the at least one metal is selected from the group consisting of copper, nickel, aluminum, gold, silver, tin, zinc, and tungsten. The first substrate1525and the second substrate1530can be any flexible or rigid substrate material. An example of a flexible substrate is any type of fabric. Examples of rigid substrates include, but are not limited to, glass, plastic, and metal. A rigid substrate may be, for example, the housing of any device. In one example, both the first substrate1525and the second substrate1530are flexible substrates. In another example, both the first substrate1525and the second substrate1530are rigid substrates. In yet another example, the first substrate1525is a flexible substrate and the second substrate1530is a rigid substrate. In still another example, the first substrate1525is a rigid substrate and the second substrate1530is a flexible substrate. Further, the first substrate1525and the second substrate1530can be single-layer or multi-layer structures. In structure1500ofFIG.17A, the heat-shielding or blocking and/or heat-dissipating layer1520, the first substrate1525, and the second substrate1530are bonded or otherwise attached together, by way of example and not limitation, by adhesive, laminating, stitching, or hook-and-loop fastener system. In another example and referring now toFIG.17B, in a structure1505, the first substrate1525is bonded to one side of the heat shielding or blocking and/or heat-dissipating layer1520, whereas the second substrate1530is not bonded or otherwise attached to the other side of the heat shielding or blocking and/or heat-dissipating layer1520. In yet another example and referring now toFIG.17C, in a structure1510, the first substrate1525is provided loosely against one side of the heat shielding or blocking and/or heat-dissipating layer1520and the second substrate1530is provided loosely against the other side of the heat-dissipating layer1520. The first substrate1525and the second substrate1530are not bonded or otherwise attached to the heat shielding or blocking and/or heat-dissipating layer1520. In still another example and referring now toFIG.17D, in a structure1515, the heat shielding or blocking and/or heat-dissipating layer1520is provided in combination with the first substrate1525only, either bonded or loosely arranged. InFIG.17D, if the two layers are loosely arranged, the heat-dissipating layer1520is not bonded or otherwise attached to the first substrate1525. The material for dissipating heat is not limited to the structures1500,1505,1510,1515. These structures are exemplary only. In one embodiment, the pouch includes at least one layer of a material to dissipate heat on the first side and/or the second side. In one embodiment, the first substrate is an interior layer of the pouch and the second substrate is an exterior layer of the pouch. In an alternative embodiment, a structure (e.g., the structure1515ofFIG.17D) is formed separately and then inserted into the pouch. Advantageously, this provides for retrofitting the pouch with heat protection from the heat-shielding or blocking and/or heat-dissipating material layer or coating. In a preferred embodiment, the battery includes at least one layer of a material to dissipate heat.FIG.18illustrates an exploded view of an example of a battery150of the portable battery pack100into which the heat dissipating material is installed. The battery150includes a battery element164that is housed between a battery cover154and a back plate162. A first heat-dissipating layer180is between the battery cover154and the battery element164. The first heat-dissipating layer180protects the battery from external heat sources (e.g., a hot vehicle). A second heat-dissipating layer182is between the battery element164and the back plate162. The second heat-dissipating layer182protects the user from heat given off by the battery element164. In another embodiment, the battery150includes only the first heat-dissipating layer180. In yet another embodiment, the battery150includes only the second heat-dissipating layer182. In another embodiment, the pouch includes at least one layer of a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles. In one embodiment, the at least one layer of a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is formed from an aramid (e.g., KEVLAR®, TWARON®), an ultra-high-molecular-weight polyethylene fiber (UHMWPE) (e.g., SPECTRA®, DYNEEMA®), a polycarbonate (e.g., LEXAN®), a carbon fiber composite material, ceramic, steel, boron nitride, a boron nitride composite material, and/or a metal (e.g., titanium). In one embodiment, the pouch is sized to fit the battery and the at least one layer of a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles. In another embodiment, the at least one layer of a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is incorporated into the pouch itself. In yet another embodiment, the at least one layer of a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is housed in a built-in pocket inside of the pouch or permanently affixed (e.g., laminated, stitched, adhered) to the pouch. In a preferred embodiment, the at least one layer of a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is on the first side (i.e., the exterior facing side) of the pouch. Advantageously, this layer protects the battery as well as the user. In one embodiment, the at least one layer of a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles has a slight curvature or contour for conforming to the battery cover. Additionally or alternatively, the at least one layer of a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is on the second side (i.e., the user facing side) of the pouch. In one embodiment, the at least one layer of a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles has a slight curvature or contour for conforming to the back plate. Advantageously, this layer provides additional protection to the user. In another embodiment, the battery includes a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles. In one embodiment, the material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is incorporated into the battery cover and/or back plate. In an alternative embodiment, the material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is between the battery cover and the battery element. Advantageously, this layer protects the plurality of battery cells housed in the battery as well as the user. Additionally or alternatively, the material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is between the battery element and the back plate. Advantageously, this layer provides additional protection to the user. As previously described, the pouch is preferably formed of a flexible, durable, and waterproof and/or water-resistant material. In one embodiment, seams of the pouch are sewn with an anti-wick or non-wicking thread. In one example, the anti-wick or non-wicking polyester thread is a bonded polyester thread with wax coating (e.g., DABOND®). The wax coating on the thread plugs stitch holes to waterproof seams. Alternatively, seams are joined together using ultrasonic welding. In one embodiment, the pouch includes drainage holes to remove water from the pouch. The drainage holes are formed of a mesh fabric. Alternatively, the drainage holes are formed using holes with grommets in the waterproof and/or water-resistant material. In another embodiment, the pouch incudes at least one desiccant to remove moisture from the pouch. In one embodiment, the at least one desiccant includes silica. Alternatively, the at least one desiccant includes activated charcoal, calcium sulfate, calcium chloride, and/or molecular sieves (e.g., zeolites). The portable battery pack includes leads having a connector portion. As previously described, the connector portion can be any type or style of connector needed to mate to equipment to be used with the battery of the portable battery pack. In one embodiment, a cord connector is used to protect a mated connection between the connector portion and the equipment. Examples of a cord connector include U.S. Pat. Nos. 5,336,106, 5,505,634, and 5,772,462, each of which is incorporated herein by reference in its entirety. Alternatively, a piece of heat shrink tubing is positioned to cover a mated connection between the connector portion and the equipment. In a preferred embodiment, the heat shrink tubing is sized to cover at least 0.25 inch of cabling on either side of the mated connection. Heat is then applied using a heat gun or hair dryer to shrink the tubing and seal the mated connection. In one embodiment, the portable battery pack includes at least one processor. The at least one processor is preferably housed in the battery. In another embodiment, the at least one processor is incorporated into control electronics used to determine the state of charge (SOC) of the portable battery pack. Examples of state of charge indicators are disclosed in U.S. Publication Nos. 20170269162 and 20150198670, each of which is incorporated herein by reference in its entirety. FIG.19illustrates a block diagram of one embodiment of the control electronics for a state of charge indicator incorporated into the portable battery pack. In this example, the control electronics2430includes a voltage sensing circuit2432, an analog-to-digital converter (ADC)2434, a processor2436, the indicator2440, and optionally a driver2442. The voltage sensing circuit2432can be any standard voltage sensing circuit, such as those found in volt meters. An input voltage VIN is supplied via the power BUS. In one embodiment, the voltage sensing circuit2432is designed to sense any direct current (DC) voltage in the range of from about 0 volts DC to about 50 volts DC. In one embodiment, the voltage sensing circuit2432includes standard amplification or de-amplification functions for generating an analog voltage that correlates to the amplitude of the input voltage VIN that is present. The ADC2434receives the analog voltage from the voltage sensing circuit2432and performs a standard analog-to-digital conversion. The processor2436manages the overall operations of the SOC indicator. The processor2436is any controller, microcontroller, or microprocessor that is capable of processing program instructions. The indicator2440is any visual, audible, or tactile mechanism for indicating the state of charge of the portable battery pack. A preferred embodiment of a visual indicator is at least one 5-bar liquid crystal display (LCD), wherein five bars flashing or five bars indicates greatest charge and one bar or one bar flashing indicates least charge. Another example of a visual indicator is at least one seven-segment numeric LCD, wherein the number 5 flashing or the number 5 indicates greatest charge and the number 1 or the number 1 flashing indicates least charge. Alternatively, the at least one LCD displays the voltage of the portable battery pack as measured by the control electronics. The at least one LCD is preferably covered with a transparent material. In a preferred embodiment, the cover is formed of a clear plastic (e.g., poly(methyl methacrylate)). This provides an extra layer of protection for the at least one LCD, much like a screen protector provides an extra layer of protection for a smartphone. This increases the durability of the at least one LCD. In one embodiment, the at least one LCD is on the housing of the battery. In a preferred embodiment, the housing of the battery includes a waterproof sealant (e.g., silicone) around the cover. Alternatively, a visual indicator is at least one LED. One preferred embodiment of a visual indicator is a set of light-emitting diodes (LEDs) (e.g., 5 LEDs), wherein five lit LEDs flashing or five lit LEDs indicates greatest charge and one lit LED or one lit LED flashing indicates least charge. In one embodiment, the LEDs are red, yellow, and/or green. In one example, two of the LEDs are green to indicate a mostly full charge on the portable battery pack, two of the LEDs are yellow to indicate that charging will soon be required for the portable battery pack, and one LED is red to indicate that the portable battery pack is almost drained. In a preferred embodiment, at least three bars, lights, or numbers are used to indicate the state of charge. In one embodiment, the at least one LED is preferably covered with a transparent material. In a preferred embodiment, the cover is formed of a clear plastic (e.g., poly(methyl methacrylate)). This provides an extra layer of protection for the at least one LED. This increases the durability of the at least one LED. In one embodiment, the at least one LED is on the housing of the battery. In a preferred embodiment, the housing of the battery includes a waterproof sealant (e.g., silicone) around the cover. One example of an audible indicator is any sounds via an audio speaker or a headset, such as beeping sounds, wherein five beeps indicates greatest charge and one beep indicates least charge. Another example of an audible indicator is vibration sounds via any vibration mechanism (e.g., vibration motor used in mobile phones), wherein five vibration sounds indicates greatest charge and one vibration sound indicates least charge. One example of a tactile indicator is any vibration mechanism (e.g., vibration motor used in mobile phones), wherein five vibrations indicate greatest charge and one vibration indicate least charge. Another example of a tactile indicator is a set of pins that rise up and down to be felt in Braille-like fashion, wherein five raised pins indicates greatest charge and one raised pin indicates least charge. In one example, the processor2436is able to drive indicator2440directly. In one embodiment, the processor2436is able to drive directly a 5-bar LCD or a seven-segment numeric LCD. In another example, however, the processor2436is not able to drive indicator2440directly. In this case, the driver2442is provided, wherein the driver2442is specific to the type of indicator2440used in the control electronics2430. Additionally, the processor2436includes internal programmable functions for programming the expected range of the input voltage VIN and the correlation of the value the input voltage VIN to what is indicated at the indicator2440. In other words, the discharge curve of the portable battery pack can be correlated to what is indicated at indicator2440. In one embodiment, the processor2436is programmed based on a percent discharged or on an absolute value present at the input voltage VIN. In one embodiment, the processor is programmed with the purpose of intentionally giving a lower state of charge than actually available. In this embodiment, the battery will last longer because it will not reach a completely discharged state as frequently. Advantageously, this embodiment encourages the user to recharge the battery before it runs down. Further, this embodiment extends the overall life of the battery and increases performance of the battery. In another embodiment, the processor is programmed to not take a voltage reading when the load is a maximum load. In one example, the battery is powering a radio, and the processor is programmed to not take a voltage reading when the radio is transmitting or receiving. Alternatively, the processor is programmed to take a voltage reading when the load is minimized. In one embodiment, the control electronics includes at least one antenna, which allows the portable battery pack to send information (e.g., state of charge information) to at least one remote device (e.g., smartphone, tablet, laptop computer, satellite phone) and/or receive information (e.g., software updates, activation of kill switch) from at least one remote device. The at least one antenna provides wireless communication, standards-based or non-standards-based, by way of example and not limitation, radiofrequency, BLUETOOTH®, ZIGBEE®, Near Field Communication, or similar commercially used standards. FIG.20Aillustrates a block diagram of an example of an SOC system2500that includes a mobile application for use with a portable battery pack. The SOC system2500includes a battery150having a communications interface2510. The communications interface2510is any wired and/or wireless communication interface for connecting to a network and by which information may be exchanged with other devices connected to the network. Examples of wired communication interfaces include, but are not limited to, System Management Bus (SMBus), USB ports, RS232 connectors, RJ45 connectors, Ethernet, and any combinations thereof. Examples of wireless communication interfaces include, but are not limited to, an Intranet connection, Internet, ISM, BLUETOOH® technology, WI-FI®, WIMAX®, IEEE 802.11 technology, radio frequency (RF), Near Field Communication (NFC), ZIGBEE®, Infrared Data Association (IrDA) compatible protocols, Local Area Networks (LAN), Wide Area Networks (WAN), Shared Wireless Access Protocol (SWAP), any combinations thereof, and other types of wireless networking protocols. The communications interface2510is used to communicate, preferably wirelessly, with at least one remote device, such as but not limited to, a mobile phone2130or a tablet2132. The mobile phone2130can be any mobile phone that (1) is capable of running mobile applications and (2) is capable of communicating with the portable battery pack. The mobile phone2130can be, for example, an ANDROID™ phone, an APPLE® IPHONE®, or a SAMSUNG® GALAXY® phone. Likewise, the tablet2132can be any tablet that (1) is capable of running mobile applications and (2) is capable of communicating with the portable battery pack. The tablet2132can be, for example, the 3G or 4G version of the APPLE® WAD®. Further, in the SOC system2500, the mobile phone2130and/or the tablet2132is in communication with a cellular network2516and/or a network2514. The network2514can be any network for providing wired or wireless connection to the Internet, such as a local area network (LAN) or a wide area network (WAN). An SOC mobile application2512is installed and running at the mobile phone2130and/or the tablet2132. The SOC mobile application2512is implemented according to the type (i.e., the operating system) of mobile phone2130and/or tablet2132on which it is running. The SOC mobile application2512is designed to receive SOC information from the portable battery pack. The SOC mobile application2512indicates graphically, audibly, and/or tactilely, the state of charge to the user (not shown). FIG.20Billustrates a block diagram of an example of an SOC system2520of the portable battery pack that is capable of communicating with the SOC mobile application2512. In this example, the SOC system2520includes an SOC portion2522and a communications portion2524. The SOC portion2522is substantially the same as the control electronics2430shown inFIG.19. The communications portion2524handles the communication of the SOC information to the SOC mobile application2512at, for example, the mobile phone2130and/or the tablet2132. The communications portion2524includes a processor2526that is communicatively connected to the communications interface2510. The digital output of the ADC2434of the SOC portion2522, which is the SOC information, feeds an input to the processor2526. The processor2526can be any controller, microcontroller, or microprocessor that is capable of processing program instructions. One or more batteries2528provide power to the processor2526and the communications interface2510. The one or more batteries2528can be any standard cylindrical battery, such as quadruple-A, triple-A, or double-A, or a battery from the family of button cell and coin cell batteries. A specific example of a battery2528is the CR2032 coin cell 3-volt battery. In SOC system2520, the SOC portion2522and the communications portion2524operate substantially independent of one another. Namely, the communications portion2524is powered separately from the SOC portion2522so that the communications portion2524is not dependent on the presence of the input voltage VIN at the SOC portion2522for power. Therefore, in this example, the communications portion2524is operable to transmit information to the SOC mobile application2512at any time. However, in order to conserve battery life, in one embodiment the processor2526is programmed to be in sleep mode when no voltage is detected at the input voltage VIN at the SOC portion2522and to wake up when an input voltage VIN is detected. Alternatively, the processor2526is programmed to periodically measure the SOC and send SOC information to the SOC mobile application2512on the at least one remote device periodically, such as every hour, regardless of the state of input voltage VIN. FIG.20Cillustrates a block diagram of another example of control electronics2530of the portable battery pack that is capable of communicating with the SOC mobile application2512. In this example, the operation of the communications interface2510is dependent on the presence of a voltage at input voltage VIN. This is because, in control electronics2530, the communications interface2510is powered from the output of voltage sensing circuit2432. Further, the processor2436provides the input (i.e., the SOC information) to the communications interface2510. A drawback of the control electronics2530ofFIG.20Cas compared with the SOC system2520ofFIG.20B, is that it is operable to transmit SOC information to the SOC mobile application2512only when the portable battery pack has a charge. Alternatively, the SOC of the battery of the portable battery pack is determined by a pluggable state of charge indicator. An example of a pluggable state of charge indicator is disclosed in U.S. Publication Nos. 20170269162 and 20150198670, each of which is incorporated herein by reference in its entirety. Advantageously, intermittently measuring the SOC of the battery extends the run time of the battery. In another preferred embodiment, the portable battery pack includes a battery enclosed by a wearable pouch or skin sized to hold the battery and additional devices or components as shown inFIGS.21-22. In this example, the pouch110is a wearable pouch or skin that can be sized in any manner that substantially corresponds to a size of at least one battery, at least one radio, at least one power and/or data hub, at least one GPS system, and/or other gear. In a preferred embodiment, the pouch110is formed of a flexible, durable, and waterproof or at least water-resistant material. For example, the pouch110is formed of polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, or polycotton canvas. In one embodiment, the pouch110is formed of a material that is laminated to or treated with a waterproofing or water repellant material (e.g., rubber, PVC, polyurethane, silicone elastomer, fluoropolymers, wax, thermoplastic elastomer). Additionally or alternatively, the pouch110is treated with a UV coating to increase UV resistance. The exterior finish of the pouch110can be any color, such as white, brown, green, orange (e.g., international orange), yellow, black, or blue, or any pattern, such as camouflage, as provided herein, or any other camouflage in use by the military, law enforcement, or hunters. For example, inFIGS.21-22, the pouch110is shown to have a camouflage pattern. In one embodiment, the exterior of the pouch110includes a reflective tape (e.g., infrared reflective tape), fabric, or material. Advantageously, the reflective tape, fabric, or material improves visibility of the user in low-light conditions. The pouch110has a first side112and a second side114. The pouch110also includes a pouch opening116, which is the opening through which a battery is fitted into the pouch110. In the example shown inFIGS.21-22, the pouch opening116is opened and closed using a zipper, as the pouch110includes a zipper tab118. Other mechanisms, however, can be used for holding the pouch opening116of the pouch110open or closed, such as, a hook and loop system (e.g., VELCRO®), buttons, snaps, hooks, ties, clips, buckles, and the like. In a preferred embodiment, the pouch110has at least one opening for a corresponding lead. In the example shown inFIGS.21-22, the pouch110has a first lead opening120afor a first lead152aand a second lead opening120bfor a second lead152b. For example, the first lead opening120aand/or the second lead opening120bcan be a 0.5-inch long slit or a 0.75-inch long slit in the edge of the pouch110. In one embodiment, the first lead opening120aand/or the second lead opening120bis finished or reinforced with stitching. In another embodiment, the first lead opening120aand/or the second lead opening120bis laser cut. In a preferred embodiment, the pouch110of the portable battery pack100is MOLLE-compatible. In one embodiment, the pouch110incorporates a pouch attachment ladder system (PALS), which is a grid of webbing used to attach smaller equipment onto load-bearing platforms, such as vests and backpacks. For example, the PALS grid consists of horizontal rows of 1-inch (2.5 cm) webbing, spaced about one inch apart, and reattached to the backing at 1.5-inch (3.8 cm) intervals. In one embodiment, the webbing is formed of nylon (e.g., cordura nylon webbing, MIL-W-43668 Type III nylon webbing). Accordingly, a set of straps122(e.g., four straps122) are provided on one edge of the pouch110as shown. Further, rows of webbing124(e.g., seven rows124) are provided on the first side112of the pouch110, as shown inFIG.21. Additionally, rows of slots or slits126(e.g., eleven rows of slots or slits126) are provided on the second side114of the pouch110, as shown inFIG.22. In a preferred embodiment, the set of straps122, the rows of webbing124, and the rows of slots or slits126replicate and duplicate the MOLLE underneath the portable battery pack on the load bearing equipment. Advantageously, this allows for minimal disruption to the user because the user can place additional gear pouches or gear (e.g., water bottle, antenna pouch) on the MOLLE of the portable battery pack in an equivalent location. In the embodiment shown inFIGS.21-22, the portable battery pack is made to affix to a plate carrier, body armor, or a vest with at least one single width of zipper tape sewn on the front panel or the back panel (e.g., JPC 2.0™ by Crye Precision).FIGS.21-22show details of the first side112of the pouch110including a first single width of zipper tape190aand a first zipper slider192aand a second single width of zipper tape190band a second zipper slider192b. The first single width of zipper tape190amates with a corresponding single width of zipper tape on the plate carrier, the body armor, or the vest. The second single width of zipper tape190balso mates with a corresponding single width of zipper tape on the plate carrier, the body armor, or the vest. In one embodiment, at least one lead of the battery of the portable battery pack is used to power at least one device enclosed in the pouch of the portable battery pack. In the example shown inFIGS.23-24, the battery of the portable battery pack has a first lead152aand a second lead (not shown). The first lead152aexits the pouch110through a lead opening120. The second lead is used to power at least one device enclosed in the pouch110of the portable battery pack. The portable battery pack is operable to supply power to a power distribution and data hub. The power distribution and data hub is operable to supply power to at least one peripheral device (e.g., tablet, smartphone, computer, radio, rangefinder, GPS system). The power distribution and data hub is also operable to transfer data between at least two of the peripheral devices. Additionally, the power distribution and data hub is operable to transfer data between the battery and the at least one peripheral device when the battery includes at least one processor. In a preferred embodiment, the power distribution and data hub is enclosed in the pouch of the portable battery pack. Alternatively, the power distribution and data hub is not enclosed in the pouch of the portable battery pack. FIG.25illustrates a block diagram of one example of a power distribution and data hub (e.g., STAR-PAN™ by Glenair). The power distribution and data hub2100is connected to the battery150of the portable battery pack. The battery150supplies power to the power distribution and data hub2100. In the example shown inFIG.25, the power distribution and data hub2100provides power to an end user device (EUD)2102. The end user device2102is a tablet, a smartphone, or a computer (e.g., laptop computer). The power distribution and data hub2100is operable to provide power to a first peripheral device2104, a second peripheral device2106, a third peripheral device2108, and a fourth peripheral device2110through a personal area network (PAN). In one embodiment, the first peripheral device2104, the second peripheral device2106, the third peripheral device2108, and/or the fourth peripheral device2110is a radio, a rangefinder (e.g., Pocket Laser Range Finder (PLRF)), a laser designator (e.g., Special Operations Forces Laser Acquisition Marker (SOFLAM), Type 163 Laser Target Designator), a targeting system (e.g., FIRESTORM™), a GPS device (e.g., Defense Advanced GPS Receiver (DAGR)), night vision goggles, an electronic jamming system (e.g., AN/PLT-4, AN/PLT-5 (Thor II) by Sierra Nevada Corporation, Thor III), a mine detector, a metal detector, a camera (e.g., body camera), a thermal imaging device (e.g., camera, binoculars), a short wave infrared (SWIR) device, a satellite phone, an antenna, a lighting system (e.g., portable runway lights, infrared strobe lights), an environmental sensor (e.g., radiation, airborne chemicals, pressure, temperature, humidity), an amplifier, and/or a receiver (e.g., Tactical Net ROVER™ Intelligence, Surveillance, and Reconnaissance (ISR), Multi-Band Digital Video Receiver Enhanced (MVR VIE), Multi-Band Video Receiver (MVR W), Soldier Intelligence Receiver (SIR), STRIKEHAWK™ Video Downlink Receiver). The power distribution and data hub2100is operable to supply power to peripheral devices that require 5V charging via a USB adapter. The power distribution and data hub2100is operable to supply power to a first radio2112and a second radio2114. In a preferred embodiment, the first radio2112and/or the second radio2114is a PRC-152, a PRC-154, a PRC-117G, a PRC-161, a persistent wave relay, a PRC-148 MBITR, a PRC-148 JEM, a PRC-6809 MBITR Clear, a RT-1922 SADL, a RF-7850M-HH, a ROVER® (e.g., ROVER® 6× Transceiver by L3 Communication Systems), a push-to-talk radio, and/or a PNR-1000. Alternative radios are compatible with the present invention. In another embodiment, the first peripheral device2104, the second peripheral device2106, the third peripheral device2108, and/or the fourth peripheral device2110is a fish finder and/or a chartplotter, an aerator or a live bait well, a camera (e.g., an underwater camera), a temperature and/or a depth sensor, a stereo, a drone, and/or a lighting system. In one embodiment, the lighting system includes at least one LED. The power distribution and data hub is operable to recharge at least one battery. For example, the power distribution and data hub is operable to recharge a battery for a drone and/or a robot. The power distribution and data hub is also operable to recharge CR123 batteries, which are often used in devices, such as camera and lighting systems. Advantageously, this allows the power distribution and data hub to recharge batteries in remote locations without access to a power grid, a generator, and/or a vehicle battery. The power distribution and data hub2100is operable to transfer data between the end user device2102, the first peripheral device2104, the second peripheral device2106, the third peripheral device2108, the fourth peripheral device2110, the first radio2112, the second radio2114, and/or the battery150when the battery150includes at least one processor. The power distribution and data hub2100has a port to obtain power from an auxiliary power source2116. In one embodiment, the auxiliary power source2116is an alternating current (AC) adapter, a solar panel, a generator, a portable power case, a fuel cell, a vehicle battery, a rechargeable battery, and/or a non-rechargeable battery. Alternatively, the auxiliary power source2116is an inductive charger. In another embodiment, the auxiliary power source2116is operable to supply power to the power distribution and data hub2100by harvesting ambient radiofrequency (RF) waves, capturing exothermic body reactions (e.g., heat, sweat), using friction (e.g., triboelectric effect) or kinetic energy, or harvesting energy from running water or wind energy. In yet another embodiment, the auxiliary power source2116is a pedal power generator. The auxiliary power source2116is preferably operable to recharge the battery150. FIG.26illustrates a block diagram of another example of a power distribution and data hub (e.g., APEX™ by Black Diamond Advanced Technology). The power distribution and data hub2200is connected to the battery150of the portable battery pack. The battery150supplies power to the power distribution and data hub2200. In the example shown inFIG.26, the power distribution and data hub2200provides power to an end user device2102. The end user device2102is a tablet, a smartphone, or a computer (e.g., laptop computer). The power distribution and data hub2200is operable to provide power to a first peripheral device2104, a second peripheral device2106, a third peripheral device2108, and a fourth peripheral device2110. In one embodiment, the first peripheral device2104, the second peripheral device2106, the third peripheral device2108, and/or the fourth peripheral device2110is a radio, a rangefinder (e.g., Pocket Laser Range Finder (PLRF)), a laser designator (e.g., Special Operations Forces Laser Acquisition Marker (SOFLAM), Type 163 Laser Target Designator), a targeting system (e.g., FIRESTORM™), a GPS device (e.g., Defense Advanced GPS Receiver (DAGR)), night vision goggles, an electronic jamming system (e.g., AN/PLT-4, AN/PLT-5 (Thor II) by Sierra Nevada Corporation, Thor III), a mine detector, a metal detector, a camera (e.g., body camera), a thermal imaging device (e.g., camera, binoculars), a short wave infrared (SWIR) device, a satellite phone, an antenna, a lighting system (e.g., portable runway lights, infrared strobe lights), an environmental sensor (e.g., radiation, airborne chemicals, pressure, temperature, humidity), an amplifier, and/or a receiver (e.g., Tactical Net ROVER™ Intelligence, Surveillance, and Reconnaissance (ISR), Multi-Band Digital Video Receiver Enhanced (MVR VIE), Multi-Band Video Receiver (MVR IV), Soldier Intelligence Receiver (SIR), STRIKEHAWK™ Video Downlink Receiver). In a preferred embodiment, the radio is a PRC-152, a PRC-154, a PRC-117G, a PRC-161, a persistent wave relay, a PRC-148 MBITR, a PRC-148 JEM, a PRC-6809 MBITR Clear, a RT-1922 SADL, a RF-7850M-HH, a ROVER® (e.g., ROVER® 6× Transceiver by L3 Communication Systems), a push-to-talk radio, and/or a PNR-1000. Alternative radios are compatible with the present invention. The power distribution and data hub2200is operable to transfer data between the end user device2102, the first peripheral device2104, the second peripheral device2106, the third peripheral device2108, the fourth peripheral device2110, and/or the battery150when the battery150includes at least one processor. In one embodiment, the power distribution and data hub includes at least one step up voltage converter and/or at least one step down voltage converter. In one example, the power distribution and data hub is powered by a 16.8V battery and includes a step up voltage converter to 29.4V. In another example, the power distribution and data hub is powered by a 16.8V battery and includes a step down voltage converter to 5V. Advantageously, this allows the portable battery pack to power devices (e.g., smartphones) with a charging voltage of 5V. This also reduces the bulk outside the power distribution and data hub because the step down voltage converter is housed within the power distribution and data hub and a separate external voltage converter is not required. In another embodiment, the power distribution and data hub is operable to prioritize a supply of power to the at least one peripheral device. In one example, the power distribution and data hub is connected to a first peripheral device and a second peripheral device. The power distribution and data hub will stop supplying power to the second peripheral device when the available power in the battery and/or auxiliary power source is lower than a designated threshold. In another example, the power distribution and data hub is connected to a first peripheral device, a second peripheral device, a third peripheral device, and a fourth peripheral device. The power distribution and data hub will stop supplying power to the fourth peripheral device when the available power in the battery and/or auxiliary power source is lower than a first designated threshold, the power distribution and data hub will stop supplying power to the third peripheral device when the available power in the battery and/or auxiliary power source is lower than a second designated threshold, and the power distribution and data hub will stop supplying power to the second peripheral device when the available power in the battery and/or auxiliary power source is lower than a third designated threshold. In one embodiment, the power distribution and data hub provides power in an order of priority of the attached peripheral device and automatically cuts out devices of lower mission priority in order to preserve remaining power for higher priority devices. In one example, a radio has a first (i.e., top) priority, a tablet has a second priority, a mobile phone has a third priority, and a laser designator (e.g., Special Operations Forces Laser Acquisition Marker (SOFLAM)) has a fourth priority. In one embodiment, the power distribution and data hub prioritizes at least one peripheral device by using at least one smart cable. The at least one smart cable stores information including, but not limited to, a unique identifier (e.g., MAC address) for the at least one peripheral device, power requirements of the at least one peripheral device, a type of device for the at least one peripheral device, and/or a priority ranking for the at least one peripheral device. FIG.27illustrates an interior perspective view of an example of the portable battery pack that includes a battery150and a power distribution and data hub2100enclosed by a wearable pouch or skin. The first side112of the pouch110has an interior of the first side2301. The second side114of the pouch110has an interior of the second side2302. The first side112has a first side gusset2303and the second side114has a second side gusset2304. The first side gusset2303and the second side gusset2304are attached at a top position of a fabric stop2306and a bottom position of the fabric stop2306. A zipper2308with a zipper pull2310is attached to the first side gusset2303and the second side gusset2304. Advantageously, this configuration allows the pouch110to lie flat when opened. In a preferred embodiment, an interior of the pouch includes at least one integrated pocket. In the example shown inFIG.27, the interior of the first side2301has an integrated pocket2312. The integrated pocket2312is formed of polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, polycotton canvas, and/or a mesh fabric. In a preferred embodiment, the integrated pocket2312is formed of a clear vinyl fabric. Advantageously, this allows a user to see the contents of the integrated pocket2312. In one example, the user stores a map or instructions in the integrated pocket2312. The integrated pocket2312closes using a piece of elastic2314. Alternatively, the integrated pocket2312closes using a zipper, a hook and loop system, one or more buttons, one or more snaps, one or more ties, one or more buckles, one or more clips, and/or one or more hooks. The interior of the second side2302holds a battery150, a power distribution and data hub2100, a first radio2112, and a second radio2114. In a preferred embodiment, the battery150is held in place by at least one strap2318. The at least one strap2318is preferably made of an elastic material. Alternatively, the at least one strap2318is made of a non-elastic material. In other embodiments, the at least one strap2318includes hook-and-loop tape. A first spring174aof a first lead (not shown) extends out of the pouch110through a lead opening120. A second spring174bsurrounds wiring that is electrically connected to a connector portion170b. The connector170bis electrically connected to a mating connector2320that is attached to a battery cable2322, which connects to the power distribution and data hub2100. In a preferred embodiment, the power distribution and data hub2100is held in place by at least one strap2324. The at least one strap2324is preferably made of an elastic material. Alternatively, the at least one strap2324is made of a non-elastic material. In other embodiments, the at least one strap2324includes hook-and-loop tape. The power distribution and data hub2100is connected to an end user device2102(e.g., tablet, smartphone, computer) via an end user device cable2326. The end user device cable2326extends out of the pouch110through an end user device cable opening2328. The power distribution and data hub2100is connected to the first radio2112via a first radio cable2332. The first radio2112is held in place by at least one strap2330. The at least one strap2330is preferably made of an elastic material. Alternatively, the at least one strap2330is made of a non-elastic material. In other embodiments, the at least one strap2330includes hook-and-loop tape. In one embodiment, the first radio2112has an antenna2334that extends out of the pouch110through a first radio antenna opening2336in the second side gusset2304. The power distribution and data hub2100is connected to the second radio2114via a second radio cable2340. The second radio2114is held in place by at least one strap2338. The at least one strap2338is preferably made of an elastic material. Alternatively, the at least one strap2338is made of a non-elastic material. In other embodiments, the at least one strap2338includes hook-and-loop tape. The second radio2114has an antenna2342that extends out of the pouch110through a second radio antenna opening2344in the second side gusset2304. AlthoughFIG.27illustrates the power distribution and data hub2100in an orientation above the battery150, it is equally possible for the battery150to be in an orientation above the power distribution and data hub2100. In one embodiment, the orientation of the power distribution and data hub2100relative to the battery150is selected by the user based on multiple factors, including accessibility to equipment and weight distribution. FIG.28is a detail view of the interior perspective view of the example of the portable battery pack shown inFIG.27. The power distribution and data hub2100is operable to provide power to a first peripheral device2104, a second peripheral device2106, a third peripheral device2108, and a fourth peripheral device2110through a personal area network (PAN). The power distribution and data hub2100is connected to the first peripheral device2104via a first peripheral device cable2346. The first peripheral device cable2346extends out of the pouch110through a first peripheral device cable opening2348in the second side gusset2304. Alternatively, the first peripheral device cable2346extends out of the pouch110through an opening in the second side114of the pouch110. The power distribution and data hub2100is connected to the second peripheral device2106via a second peripheral device cable2354. The second peripheral device cable2354extends out of the pouch110through a second peripheral device cable opening2356in the second side114of the pouch110. Alternatively, the second peripheral device cable2354extends out of the pouch110through an opening in the second side gusset2304. The power distribution and data hub2100is connected to the third peripheral device2108via a third peripheral device cable2350. The third peripheral device cable2350extends out of the pouch110through a third peripheral device cable opening2352in the second side gusset2304. Alternatively, the third peripheral device cable2350extends out of the pouch110through an opening in the second side114of the pouch110. The power distribution and data hub2100is connected to the fourth peripheral device2110via a fourth peripheral device cable2358. The fourth peripheral device cable2358extends out of the pouch110through a fourth peripheral device cable opening2360in the second side114of the pouch110. Alternatively, the fourth peripheral device cable2358extends out of the pouch110through an opening in the second side gusset2304. In other embodiments, at least one of the first peripheral device2104, the second peripheral device2106, the third peripheral device2108, and/or the fourth peripheral device2110is stored in the pouch110. The power distribution and data hub2100is operable to obtain power from an auxiliary power source2116. The power distribution and data hub2100is connected to the auxiliary power source2116via an auxiliary power source cable2364. The auxiliary power source cable2364extends out of the pouch110through an auxiliary power source cable opening2364in the second side gusset2304. Alternatively, the auxiliary power source cable2364extends out of the pouch110through an opening in the second side114of the pouch110. In another embodiment, the auxiliary power source2116(e.g., a non-rechargeable battery) is stored in the pouch110. In one embodiment, the auxiliary power source2116is an alternating current (AC) adapter, a solar panel, a generator, a portable power case, a fuel cell, a vehicle battery, a rechargeable battery, and/or a non-rechargeable battery. Alternatively, the auxiliary power source2116is an inductive charger. In another embodiment, the auxiliary power source2116is operable to supply power to the power distribution and data hub2100by harvesting ambient radiofrequency (RF) waves, capturing exothermic body reactions (e.g., heat, sweat), using friction (e.g., triboelectric effect) or kinetic energy, or harvesting energy from running water or wind energy. In yet another embodiment, the auxiliary power source2116is a pedal power generator. The auxiliary power source2116is preferably operable to recharge the battery150. FIG.29Aillustrates an interior perspective view of an example of the portable battery pack that includes an object retention system in the wearable pouch or skin. The pouch110has an interior of a first side2301and an interior of a second side2302. In a preferred embodiment, the interior of the first side2301and/or the interior of the second side2302contains an object retention system (e.g., GRID-IT® by Cocoon Innovations) as described in U.S. Publication Nos. 20090039122, 20130214119, and 20130256498, each of which is incorporated herein by reference in its entirety. The object retention system is formed of a weave of a plurality of rubberized elastic bands. The plurality of rubberized elastic bands is preferably formed of a first set of straps2902and a second set of straps2904. The first set of straps2902is preferably oriented substantially perpendicular to the second set of straps2904. Additionally, each strap in the first set of straps2902is preferably oriented substantially parallel to other straps in the first set of straps2902. Further, each strap in the second set of straps2904is preferably oriented substantially parallel to other straps in the second set of straps2904. In the example shown inFIG.29A, the first set of straps2902is shown in a substantially vertical direction and the second set of straps2904is shown in a substantially horizontal direction. In the example shown inFIG.29A, the interior of the first side2301has an object retention system. The object retention system is shown holding a state of charge indicator2906. An example of a state of charge indicator2906is disclosed in U.S. Publication Nos. 20170269162 and 20150198670, each of which is incorporated herein by reference in its entirety. The object retention system is also shown holding a universal DC power adaptor2908. An example of a universal DC power adaptor2908is disclosed in U.S. Pat. No. 9,240,651, which is incorporated herein by reference in its entirety. The object retention system is shown holding a first half of an AC adapter2910and a second half of an AC adapter2912. The interior of the second side2302holds a battery150. A first wiring portion172aof a first lead (not shown) extends out of the pouch110through a first lead opening120a. A second wiring portion172bof a second lead152bextends out of the pouch110through a second lead opening120b. A first spring174ais provided around the first wiring portion172a, such that a portion of the first spring174ais inside the battery cover and a portion of the first spring174ais outside the battery cover. The presence of the first spring174aaround the first wiring portion172aof the first lead (not shown) allows the first lead to be flexed in any direction for convenient connection to equipment from any angle. The presence of the first spring174aaround the first wiring portion172aof the first lead also allows the first lead to be flexed repeatedly without breaking or failing. A second spring174bis provided around the second wiring portion172b, such that a portion of the second spring174bis inside the battery cover and a portion of the second spring174bis outside the battery cover. The presence of the second spring174baround the second wiring portion172bof the second lead152ballows the second lead152bto be flexed in any direction for convenient connection to equipment from any angle. The presence of the second spring174baround the second wiring portion172bof the second lead152balso allows the second lead152bto be flexed repeatedly without breaking or failing. In one example, the first spring174aand/or the second spring174bis a steel spring that is from about 0.25 inches to about 1.5 inches long. FIG.29Billustrates an interior perspective view of another example of the portable battery pack that includes an object retention system in the wearable pouch or skin. In the example shown inFIG.29B, the interior of the second side2302holds a battery150and a power distribution and data hub2200. In a preferred embodiment, the battery150is held in place by a battery pocket2950. The battery pocket2950is formed of polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, polycotton canvas, and/or a mesh fabric. In one embodiment, the battery pocket2950closes using a piece of elastic2952. In another embodiment, the battery pocket2950includes at least one layer of a material for dissipating heat. Alternatively, the battery pocket2950closes using a zipper, a hook and loop system, one or more buttons, one or more snaps, one or more ties, one or more buckles, one or more clips, and/or one or more hooks. A first spring174aof a first lead (not shown) extends out of the battery pocket2950through a first battery pocket opening2954. A first wiring portion172aof the first lead extends out of the pouch110through a first lead opening120a. A second spring174bof a second lead extends out of the battery pocket2950through a second battery pocket opening2956. The second spring174bsurrounds wiring that is electrically connected to a connector portion170b. The connector170bis electrically connected to a mating connector2320that is attached to a battery cable2322, which connects to the power distribution and data hub2200. In a preferred embodiment, the power distribution and data hub2200is held in place by at least one strap2324. The at least one strap2324is preferably made of an elastic material. Alternatively, the at least one strap2324is made of a non-elastic material. In other embodiments, the at least one strap2324includes hook-and-loop tape. In another embodiment, the power distribution and data hub2200is held in place by a hub pocket. The hub pocket is formed of polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, polycotton canvas, and/or a mesh fabric. In one embodiment, the hub pocket closes using a piece of elastic. In another embodiment, the hub pocket includes at least one layer of a material for dissipating heat. The power distribution and data hub2200is connected to an end user device2102(e.g., tablet, smartphone, computer) via an end user device cable2326. The end user device cable2326extends out of the pouch110through an end user device cable opening2328. The power distribution and data hub2200is connected to a first peripheral device via a first peripheral device cable2346. The first peripheral device cable2346extends out of the pouch110through a first peripheral device cable opening2348. Alternatively, the first peripheral device cable2346extends out of the pouch110through an opening in the second side114of the pouch110. In the example shown inFIG.29B, the first peripheral device is a first radio (not shown). The first radio is connected to a first antenna relocator2962. The first antenna relocator2962extends out of the pouch110through a first antenna relocator opening2964in the second side114of the pouch110. The first antenna relocator2962is connected to the first radio via a first antenna relocator cable2966that extends out of the pouch110through a first antenna relocator cable opening2968. The power distribution and data hub2200is connected to the second peripheral device2106via a second peripheral device cable2354. In the example shown inFIG.29B, the second peripheral device2106is a GPS device (e.g., GPS puck). The second peripheral device2106is held in place by a GPS device pocket2970. The GPS device pocket2970is formed of polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, polycotton canvas, and/or a mesh fabric. In one embodiment, the GPS device pocket2970closes using a piece of elastic2972. Alternatively, the GPS device pocket2970closes using a zipper, a hook and loop system, one or more buttons, one or more snaps, one or more ties, one or more buckles, one or more clips, and/or one or more hooks. In another embodiment, the GPS device pocket2970includes at least one layer of a material for dissipating heat. The power distribution and data hub2200is connected to the third peripheral device2108via a third peripheral device cable2350. The third peripheral device cable2350extends out of the pouch110through a third peripheral device cable opening2352in the second side gusset2304. Alternatively, the third peripheral device cable2350extends out of the pouch110through an opening in the second side114of the pouch110. The power distribution and data hub2200is connected to the fourth peripheral device2110via a fourth peripheral device cable2358. The fourth peripheral device cable2358extends out of the pouch110through a fourth peripheral device cable opening2360. Alternatively, the fourth peripheral device cable2358extends out of the pouch110through an opening in the second side114of the pouch110. In the example shown inFIG.29B, the fourth peripheral device2110is a second radio. The second radio is connected to a second antenna relocator2974. The second antenna relocator2974extends out of the pouch110through a second antenna relocator opening2976in the second side114of the pouch110. The second antenna relocator2974is connected to the second radio via a second antenna relocator cable2978that extends out of the pouch110through a second antenna relocator cable opening2980. FIG.30is an exploded view of an example of a battery and a power distribution and data hub housed in the same enclosure3000. The enclosure3000includes a battery element164and a power distribution and data hub3002that is housed between a cover3054and a back plate3062. The battery element164supplies the first lead152aand the second lead152b. The battery element164is formed of a plurality of sealed battery cells or individually contained battery cells, i.e. batteries with their own cases, removably disposed therein. The power distribution and data hub3002is connected to the battery element164via a cable3070. The power distribution and data hub3002includes at least one connector3072. The at least one connector3072is panel mounted or an omnidirectional flexible lead (e.g.,FIG.16). In one embodiment, the at least one connector3072includes a dust cap (not shown) to cover a corresponding lead. Advantageously, the dust cap protects the at least one connector from dust and other environmental contaminants that may cause battery failure in the field. The cover3054includes a battery compartment3056that is sized to receive at least one battery element164. The cover3054includes a hub compartment3064that is sized to receive the power distribution and data hub3002. In a preferred embodiment, the battery compartment3056is substantially rectangular in shape. In one embodiment, the hub compartment3064is substantially rectangular in shape. The battery compartment3056is connected to the hub compartment3064via a channel3066sized to receive the cable3070. A top hat style rim3058is provided around a perimeter of the battery compartment3056and the hub compartment3064. The cover3054incudes at least one channel formed in the cover3054to accommodate a wire of a corresponding lead. The example inFIG.30shows two channels3060(e.g., channels3060a,3060b) formed in the cover3054(one on each side) to accommodate the wires of the first lead152aand the second lead152bpassing therethrough. The cover3054includes at least one channel formed in the cover3054to accommodate the at least one connector3072. The cover3054and the back plate3062are formed of plastic using, for example, a thermoform process or an injection molding. The back plate3062can be mechanically attached to the rim3058of the cover3054via, for example, an ultrasonic spot welding process or an adhesive. Advantageously, the top hat style rim3058provides a footprint for the ultrasonic spot welding process and provides structural integrity for the battery and the power distribution and data hub housed in the same enclosure. In one embodiment, a water barrier material (e.g., silicone) is applied to the mating surfaces of the rim3058and the back plate3062. In another embodiment, the cover3054, the back plate3062, the power distribution and data hub3002, and/or the battery element164has a slight curvature or contour for conforming to, for example, the user's vest, backpack, or body armor. In one example, the curvature of the portable battery pack is engineered to match the outward curve of body armor. Advantageously, this means that the portable battery pack does not jostle as the operator moves, which results in less caloric energy expenditure when the operator moves. Alternatively, the cover3054, the back plate3062, the power distribution and data hub3002, and/or the battery element164can have a slight outward curvature or contour for conforming to a user's body (e.g., back region, chest region, abdominal region, arm, leg). In yet another embodiment, the cover3054, the back plate3062, the power distribution and data hub3002, and/or the battery element164can have a slight outward curvature or contour for conforming to a user's helmet or hat. FIG.31illustrates an interior perspective view of an example of the portable battery pack that includes a battery and a power distribution and data hub housed in the same enclosure3000. The first side112of the pouch110has an interior of the first side2301. The second side114of the pouch110has an interior of the second side2302. The first side112has a first side gusset2303and the second side114has a second side gusset2304. The first side gusset2303and the second side gusset2304are attached at a top position of a fabric stop2306and a bottom position of the fabric stop2306. A zipper2308with a zipper pull2310is attached to the first side gusset2303and the second side gusset2304. Advantageously, this configuration allows the pouch110to lie flat when opened. In the example shown inFIG.31, the interior of the first side2301has an object retention system. The object retention system is shown holding a state of charge indicator2906. An example of a state of charge indicator2906is disclosed in U.S. Publication Nos. 20170269162 and 20150198670, each of which is incorporated herein by reference in its entirety. The object retention system is also shown holding a universal DC power adaptor2908. An example of a universal DC power adaptor2908is disclosed in U.S. Pat. No. 9,240,651, which is incorporated herein by reference in its entirety. The object retention system is shown holding a first half of an AC adapter2910and a second half of an AC adapter2912. The interior of the second side2302holds a battery and a power distribution and data hub housed in the same enclosure3000. In a preferred embodiment, the battery and the power distribution and data hub housed in the same enclosure3000is held in place by at least one strap3102. The at least one strap3102is preferably made of an elastic material. Alternatively, the at least one strap3102is made of a non-elastic material. In other embodiments, the at least one strap3102includes hook-and-loop tape. A first wiring portion172aof a first lead (not shown) extends out of the pouch110through a first lead opening120a. A second wiring portion172bof a second lead152bextends out of the pouch110through a second lead opening120b. A first spring174ais provided around the first wiring portion172a, such that a portion of the first spring174ais inside the battery cover and a portion of the first spring174ais outside the battery cover. The presence of the first spring174aaround the first wiring portion172aof the first lead (not shown) allows the first lead to be flexed in any direction for convenient connection to equipment from any angle. The presence of the first spring174aaround the first wiring portion172aof the first lead also allows the first lead to be flexed repeatedly without breaking or failing. A second spring174bis provided around the second wiring portion172b, such that a portion of the second spring174bis inside the battery cover and a portion of the second spring174bis outside the battery cover. The presence of the second spring174baround the second wiring portion172bof the second lead152ballows the second lead152bto be flexed in any direction for convenient connection to equipment from any angle. The presence of the second spring174baround the second wiring portion172bof the second lead152balso allows the second lead152bto be flexed repeatedly without breaking or failing. In one example, the first spring174aand/or the second spring174bis a steel spring that is from about 0.25 inches to about 1.5 inches long. FIG.32is a detail view of the interior perspective view of the example of the portable battery pack shown inFIG.31. As previously mentioned, the cover of the battery and the power distribution and data hub housed in the same enclosure3000includes a channel3066sized to receive a cable to connect the battery element and the power distribution and data hub. The power distribution and data hub of the battery and the power distribution and data hub housed in the same enclosure3000is connected to an end user device2102(e.g., tablet, smartphone, computer) via an end user device cable2326connected to a second panel mount connector3218. The end user device cable2326extends out of the pouch110through an end user device cable opening2328. The power distribution and data hub of the battery and the power distribution and data hub housed in the same enclosure3000is operable to provide power to a first peripheral device2104, a second peripheral device2106, a third peripheral device2108, and a fourth peripheral device2110through a personal area network (PAN). In the example shown inFIG.32, the first peripheral device2104is a first radio. The first peripheral device2104is held in place by at least one strap3202. The at least one strap3202is preferably made of an elastic material. Alternatively, the at least one strap3202is made of a non-elastic material. In other embodiments, the at least one strap3202includes hook-and-loop tape. In one embodiment, the first peripheral device2104has an antenna3204that extends out of the pouch110through a first antenna opening3206in the second side gusset2304. The power distribution and data hub is connected to the first peripheral device2104via a first peripheral device cable3208with a connector3210that mates to a first flexible omnidirectional lead3212of the power distribution and data hub. The first flexible omnidirectional lead3212of the power distribution and data hub extends out of the cover of the battery and the power distribution and data hub housed in the same enclosure3000via a first channel3214in the cover. A first spring3215is provided around the wiring portion of the first flexible omnidirectional lead3212, such that a portion of the first spring3215is inside the cover of the battery and the power distribution and data hub housed in the same enclosure3000and a portion of the first spring3215is outside the cover of the battery and the power distribution and data hub housed in the same enclosure3000. In one example, the first spring3215is a steel spring that is from about 0.25 inches to about 1.5 inches long. In another example, the first spring3215is a steel spring that is from about 0.25 inches to about 8 inches long. The wiring portion of the first flexible omnidirectional lead3212and the first spring3215are held securely in the first channel3214via a clamping mechanism. Alternatively, the wiring portion of the lead and the spring are held securely in the first channel using an adhesive, a retention pin, a hex nut, a hook anchor, and/or a zip tie. The presence of the first spring3215around the wiring portion of the first flexible omnidirectional lead3212allows the first flexible omnidirectional lead3212to be flexed in any direction for convenient connection to equipment from any angle. The presence of the first spring3215around the wiring portion of the first flexible omnidirectional lead3212also allows the first flexible omnidirectional lead3212to be flexed repeatedly without breaking or failing. The power distribution and data hub is connected to the second peripheral device2106via a second peripheral device cable2354connected to a first panel mount connector3216. The second peripheral device cable2354extends out of the pouch110through a second peripheral device cable opening2356in the second side gusset2304. Alternatively, the second peripheral device cable2354extends out of the pouch110through an opening in the second side114of the pouch110. The power distribution and data hub is connected to the third peripheral device2108via a third peripheral device cable2350connected to a third panel mount connector3220. The third peripheral device cable2350extends out of the pouch110through a third peripheral device cable opening2352in the second side gusset2304. Alternatively, the third peripheral device cable2350extends out of the pouch110through an opening in the second side114of the pouch110. In the example shown inFIG.32, the fourth peripheral device2110is a second radio. The first peripheral device2104is held in place by at least one strap3222. The at least one strap3222is preferably made of an elastic material. Alternatively, the at least one strap3222is made of a non-elastic material. In other embodiments, the at least one strap3222includes hook-and-loop tape. In one embodiment, the fourth peripheral device2110has an antenna3224that extends out of the pouch110through a second antenna opening3226in the second side gusset2304. The power distribution and data hub is connected to the fourth peripheral device2110via a fourth peripheral device cable3228with a connector3230that mates to a second flexible omnidirectional lead3232of the power distribution and data hub. The second flexible omnidirectional lead3232of the power distribution and data hub extends out of the cover of the battery and the power distribution and data hub housed in the same enclosure3000via a second channel3234in the cover. A second spring3235is provided around the wiring portion of the second flexible omnidirectional lead3232, such that a portion of the second spring3235is inside the cover of the battery and the power distribution and data hub housed in the same enclosure3000and a portion of the second spring3235is outside the cover of the battery and the power distribution and data hub housed in the same enclosure3000. In one example, the second spring3235is a steel spring that is from about 0.25 inches to about 1.5 inches long. In another example, the second spring3235is a steel spring that is from about 0.25 inches to about 8 inches long. The wiring portion of the second flexible omnidirectional lead3232and the second spring3235are held securely in the second channel3234via a clamping mechanism. Alternatively, the wiring portion of the lead and the spring are held securely in the first channel using an adhesive, a retention pin, a hex nut, a hook anchor, and/or a zip tie. The presence of the second spring3235around the wiring portion of the second flexible omnidirectional lead3232allows the second flexible omnidirectional lead3232to be flexed in any direction for convenient connection to equipment from any angle. The presence of the second spring3235around the wiring portion of the second flexible omnidirectional lead3232also allows the second flexible omnidirectional lead3232to be flexed repeatedly without breaking or failing. As previously described, the power distribution and data hub includes at least one flexible omnidirectional lead in one embodiment. The flexible omnidirectional lead of the power distribution and data hub is preferably formed using a spring that is about 0.25 inches to about 8 inches long. In one embodiment, the spring of the power distribution and data hub extends out of the pouch through an opening in the second side gusset. In one embodiment, the opening includes a grommet. In another embodiment, the pouch has a seal around an opening for a corresponding lead of the power distribution and data hub. The seal is tight around the lead, which prevents water from entering the pouch through the opening. In one embodiment, the seal is formed of a rubber (e.g., neoprene). In one embodiment, the power distribution and data hub includes at least one processor and at least one memory. Advantageously, this allows the power distribution and data hub to run software. In one embodiment, the end user device is a screen (e.g., touch screen). An additional advantage of running software off of the power distribution and data hub is that if the screen breaks, a user can leave the screen behind without a risk of confidential information being exposed. In another embodiment, the power distribution and data hub includes at least one data port. Advantageously, this allows the power distribution and data hub to receive information from another computing device (e.g., laptop, desktop computer). In another embodiment, the power distribution and data hub includes at least one layer of a material to dissipate heat. In one embodiment, the at least one layer of a material to dissipate heat is housed within the power distribution and data hub. In one embodiment, at least one layer of a material to dissipate heat is housed within the power distribution and data hub on an external facing side. Advantageously, this protects the power distribution and data hub from external heat sources (e.g., a hot vehicle). In another embodiment, at least one layer of a material to dissipate heat is housed within the power distribution and data hub on a side of the power distribution and data hub facing the wearer. Advantageously, this protects the wearer from heat given off by the power distribution and data hub. In yet another embodiment, the at least one layer of a material to dissipate heat is between the cover and the power distribution and data hub of the battery and the power distribution and data hub housed in the same enclosure. Advantageously, this protects the power distribution and data hub from external heat sources (e.g., a hot vehicle). In another embodiment, the at least one layer of a material to dissipate heat is between the back plate and the power distribution and data hub of the battery and the power distribution and data hub housed in the same enclosure. Advantageously, this protects the wearer from heat given off by the power distribution and data hub. In one embodiment, the battery management system of the battery of the portable battery pack is housed in the power distribution and data hub. Advantageously, this separates heat generated by the battery management system from the plurality of electrochemical cells. In this embodiment, the power distribution and data hub preferably includes at least one layer of a material to dissipate heat. This embodiment may also provide additional benefits for distributing weight within the pouch. In another embodiment, the power distribution and data hub includes a material to provide resistance to bullets, knives, shrapnel, and/or other projectiles. In one embodiment, the material to provide resistant to bullets, knives, shrapnel, and/or other projectiles is incorporated into a housing of the power distribution and data hub. In an alternative embodiment, the material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is housed within the power distribution and data hub on an external facing side. Advantageously, this layer protects the electronics housed in the power distribution and data hub as well as the user. Additionally or alternatively, the material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is housed within the power distribution and data hub on a side of the power distribution and data hub facing the wearer. Advantageously, this layer provides additional protection to the user. In another embodiment, the material to provide resistance to bullets, knives, shrapnel, and/or other projectiles is incorporated into the cover and/or back plate of the battery and the power distribution and data hub housed in the same enclosure. FIG.33illustrates a side perspective view of another example of a portable battery pack100affixed to a vest600using zippers. In the example shown inFIG.33, the pouch of the portable battery pack100is sized to hold the battery and additional devices or components. A first single width of zipper tape190ais shown mated with a corresponding first single width of zipper tape194aon a right side of the vest600using a first zipper slider192a, thereby attaching the portable battery pack100to the vest600. Similarly, a second single width of zipper tape (not shown) is mated with a corresponding second single width of zipper tape (not shown) on a left side of the vest600using a second zipper slider (not shown). Solar Panel FIGS.34-35illustrate an example of a solar panel3100. The solar panel3100is a multilayer structure that includes at least one solar module3102mounted on a substrate, wherein the substrate with the at least one solar module3102is sandwiched between two layers of fabric. In one embodiment, openings, e.g., windows, are formed in at least one of the two layers of fabric for exposing the at least one solar module3102. In a preferred embodiment, the two layers of fabric are waterproof or water resistant. The outer two layers of fabric can be any color or pattern. In the example shown inFIG.34andFIG.35, the outer two layers of fabric have a camouflage pattern thereon. Representative camouflages include, but are not limited to, Universal Camouflage Pattern (UCP), also known as ACUPAT or ARPAT or Army Combat Uniform; MULTICAM®, also known as Operation Enduring Freedom Camouflage Pattern (OCP); Universal Camouflage Pattern-Delta (UCP-Delta); Airman Battle Uniform (ABU); Navy Working Uniform (NWU), including variants, such as, blue-grey, desert (Type II), and woodland (Type III); MARPAT, also known as Marine Corps Combat Utility Uniform, including woodland, desert, and winter/snow variants; Disruptive Overwhite Snow Digital Camouflage, Urban Digital Camouflage, and Tactical Assault Camouflage (TACAM). A hem3104is provided around a perimeter of the solar panel3100in one embodiment. The output of any arrangement of the at least solar module3102in the solar panel3100is a direct current (DC) voltage. Accordingly, the solar panel3100includes at least one output connector3106(e.g., male FISCHER® SOV 105 A087 connectors, TAJIMI™ Electronics part number R04-P5m, FISCHER® LP360) that is wired to the arrangement of the at least one solar module3102. The at least one output connector3106is used for connecting any type of DC load to the solar panel3100. In one example, the solar panel3100is used for supplying power to a device, such as a DC-powered radio. In another example, the solar panel3100is used for charging a battery. In yet another example, the solar panel3100is used for charging the battery of a portable battery pack. FIG.36illustrates an exploded view of one example of the solar panel3100, wherein the solar panel3100comprises a multilayer structure. Namely, the solar panel3100includes a solar panel assembly3108that is sandwiched between a first fabric layer3110and a second fabric layer3112. The solar panel assembly3108of the solar panel3100includes the at least one solar module3102mounted on a substrate3114. Materials for forming the at least one solar module3102include, but are not limited to, amorphous silicon, an anti-reflection coating, cadmium telluride (CdTe), a carbon fullerene, copper indium gallium (di)selenide (CIGS), copper phthalocyanine, copper zinc tin sulfide (CZTS), copper zinc tin selenide (CZTSe), copper zinc tin sulfide/selenide (CZTSSe), dye-sensitized solar cells (DSSCs), fullerene derivatives (e.g., phenyl-C61-butyric acid methyl ester (PCBM)), gallium arsenide (GaAs), gallium indium phosphide (GaInP), germanium, graphene, Gratzel cells, kesterite, lanthanide-doped materials (e.g., Er3+, Yb3+, Ho3+), monocrystalline silicon, multicrystalline silicon, multijunction solar cells, organic solar cells, perovskite solar cells, polycrystalline silicon on glass, polymer solar cells, polyphenylene vinylene, quantum dot solar cells, silicon nitride, thin film solar cells, and/or titanium dioxide. In a preferred embodiment, the at least one solar module and/or the solar cells have camouflage, an image (e.g., logo), text, and/or other patterns printed on or within the at least one solar module and/or the solar cells. In another embodiment, the solar panel includes at least one blocking diode and/or at least one bypass diode. The size of the at least one solar module3102can be, for example, from about 1 inch to about 48 inches on a side. In one example, the at least one solar module3102is about 3 inches by about 6 inches. In another example, the at least one solar module3102is about 4 inches by about 8 inches. In a preferred embodiment, the first fabric layer3110, the solar panel assembly3108, and the second fabric layer3112are intimately adhered together using a hook-and-loop system and/or stitching. In one embodiment, stitching passes through all of the layers of the solar panel3100(i.e., through the first fabric layer3110, the substrate3114, and the second fabric layer3112). In another embodiment, a hook-and-loop system is used to secure an edge of the first fabric layer3110around a corresponding edge of the at least one solar module3102. In one embodiment, the substrate3114is secured to the second fabric layer3112using a hook-and-loop system and/or stitching. In yet another embodiment, the first fabric layer3110, the solar panel assembly3108, and the second fabric layer3112are intimately adhered together using an adhesive, a glue, or an epoxy. Advantageously, this increases the water resistance of the solar panel. The first fabric layer3110and the second fabric layer3112can be formed of any flexible, durable, and waterproof or water-resistant material, such as but not limited to, polyester, PVC-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, and polycotton canvas. The first fabric layer3110and the second fabric layer3112can be any color or pattern, such as the camouflage pattern shown inFIG.36. Additionally, the first fabric layer3110and the second fabric layer3112can be the same color or pattern or can be different colors or patterns. In a preferred embodiment, at least one window or opening3116is provided in the first fabric layer3110for exposing a face of the at least one solar module3102. The size and position of the at least one window or opening3116in the first fabric layer3110substantially correspond to the size and position of the at least one solar module3102on the substrate3114. The substrate3114is preferably formed of a material that is lightweight, flexible (i.e., foldable or rollable), and waterproof or water resistant. In one embodiment, the substrate3114is formed of polyethylene, for example, a flashspun high-density polyethylene such as DUPONT′ TYVEK® material. A flashspun high-density polyethylene substrate is flexible, such that it can be folded and stowed for storage, and tear resistant. The solar modules3102can be mounted on the substrate3114using, for example, an adhesive, hook and loop tape, or rivets. When the solar panel3100is assembled, the solar panel assembly3108is substantially hidden from view between the first fabric layer3110and the second fabric layer3112, except for the face of the at least one solar module3102showing through the at least one window or opening3116. Wherein flashspun high-density polyethylene is conventionally used as a vapor barrier material in weatherization systems in buildings, one aspect of the presently disclosed solar panel3100is the use of flashspun high-density polyethylene material as a substrate for electronics in a flexible panel. A pattern of wiring traces3118for electrically connecting any configuration of the at least one solar module3102is easily printed on the flashspun high-density polyethylene substrate using, for example, electrically conductive ink, while at the same time the flashspun high-density polyethylene substrate is flexible such that it can be folded and provides a layer of water barrier to protect the at least one solar module3102. One end of a cable or wire3120is electrically connected to the wiring traces3118, while the at least one output connector3106is on an opposite end of the cable or wire3120. The at least one output connector3106can be any type or style of connector needed to mate to the equipment to be used with the solar panel3100. The solar panel assembly3108is not limited to one connector or to one type or style of connector. Examples of connectors used with the solar panel assembly3108include circular connectors, barrel connectors, Molex connectors, IEC connectors, fiber optic connectors, rectangular connectors, RF connectors, power connectors (e.g., NEMA sockets and/or plugs), USB, micro USB, mini USB, HDMI, firewire, and lightning. Additionally, a plurality of connectors (of the same type or different types) can be connected to the cable or wire3120. In this way, the solar panel3100can be used to supply multiple devices at the same time, albeit the multiple devices must have substantially the same power requirements. For example, by providing a plurality of connectors, the solar panel3100can be used to charge multiple batteries at the same time or to power multiple pieces of equipment at the same time. In one embodiment, a solar converter is placed on the at least one output cable to step up or step down the voltage of the solar panel. Advantageously, this allows the solar panel to charge batteries of different voltages. In a preferred embodiment, a battery includes an integrated battery management system that allows the battery to be charged by the solar panel without the use of a solar converter. Advantageously, this reduces the weight and complexity of the system for an end user. In other embodiments, instead of printing the wiring traces on the substrate, a discrete flexible wiring harness (not shown) is provided for electrically connecting the at least one solar module and the at least one output connector. When the solar panel is assembled, the wiring harness is substantially hidden from view between the first fabric layer and the second fabric layer, except for the at least one output connector extending outward from one edge. The solar panel3100is modular and configurable to provide any output voltage. WhileFIGS.34-36show six solar modules3102in the solar panel3100, this is exemplary only. The solar panel3100can include any number of solar modules3102configured in series, configured in parallel, or configured in any combination of series and parallel arrangements. In particular, the configuration of the at least one solar module3102in the solar panel3100can be tailored in any way to provide a certain output voltage and current. More details of the solar panel3100are shown and described herein below with reference toFIGS.37-39. Additionally, example configurations of the at least one solar module3102are shown and described herein below with reference toFIGS.40-43. In one embodiment, at least two solar modules of solar module are changed from working in parallel to working in series via a voltage sensing circuit. Alternatively, the at least two solar modules are wired to a connector that includes separate pins for parallel and series output. In one example, parallel output is wired to pins 1-2 of a 7-pin connector and series output is wired to pins 6-7 of the 7-pin connector. Advantageously, this allows the voltage output of the solar panel to be selected based on usage requirements. In a preferred embodiment, the substrate of the solar panel is printable (e.g., DUPONT™ TYVEK®), allowing manufacturing assembly instructions and/or any other markings to be printed thereon for assisting the assembly of the solar modules on the substrate. For example,FIG.37illustrates a plan view of the substrate3114of the solar panel3100. In this example,FIG.37shows wiring traces3118printed on the substrate3114using, for example, electrically conductive ink.FIG.37also shows a set of alignment features3122that mark the corners of each of the at least one solar module3102. Additionally, each position of the at least one solar module3102may have certain text3124printed thereon, such as PNL #1, PNL #2, PNL #3, PNL #4, PNL #5, and PNL #6, and polarity indicators (+ and −). Further, step-by-step assembly instructions3126can be printed in any available space on the substrate3114. The alignment features3122, the text3124, and the manufacturing assembly instructions3126can be printed using standard permanent ink. Standard printing processes can be used for both the electrically conductive ink and the permanent ink. FIG.38AandFIG.38Billustrate side views of a portion of the solar panel assembly3108, showing two example methods of electrically connecting a solar module3102to the substrate3114. In one example,FIG.38Ashows an output pad3128of a solar module3102in close proximity to a wiring trace3118on the substrate3114. A conductor3130, such as a flexible conductor, is used to electrically connect the output pad3128of the solar module3102to the wiring trace3118. For example, a first end of the conductor3130is soldered to the output pad3128of the solar module3102and a second end of the conductor3130opposite of the first end of the conductor3130is soldered to the wiring trace3118. In this example, to replace the solar module3102, the conductor3130is desoldered and removed, the solar module3102is removed from the substrate3114, a replacement solar module is mounted on the substrate3114, and the conductor3130is soldered to the output pad3128of the replacement solar module and the wiring trace3118. In another example,FIG.38Bshows a connector3132installed along the length of the conductor3130. In this example, to replace the solar module3102, the connector3132is disconnected, the solar module3102is removed from the substrate3114, a replacement solar module is mounted on the substrate3114, and the connector3132is reconnected. Advantageously, the connector method simplifies field repair of the solar panel. FIG.39illustrates a portion of the solar panel3100showing a hook-and-loop system for securing at least one edge of the first fabric layer3110around at least one edge of the at least one solar module3102. By way of example,FIG.39shows one window or opening3116in the first fabric layer3110and one solar module3102of the solar panel assembly3108. An arrangement of hook strips3150is provided on the first fabric layer3110around the edges of the window or opening3116and an opposing arrangement of loop strips3152is provided on the substrate3114around the edges of solar module3102. In another embodiment, the loop strips3152are on the first fabric layer3110and the hook strips3150are on the substrate3114. The hook strips3150and the loop strips3152are, for example, components of a VELCRO® hook-and-loop fastening system. In yet another embodiment, instead of using a hook-and-loop fastening system, stitching is provided around the windows or openings3116, wherein the stitching passes through all of the layers of the solar panel3100(i.e., through the first fabric layer3110, the substrate3114, and the second fabric layer3112). In this example, however, it must be ensured that the stitching not interfere with any wiring traces on the substrate3114. FIGS.40-43show schematic views of examples of configuring the at least one solar module3102in the solar panel3100. Again,FIGS.40-43show six solar modules3102, but this is exemplary only. The solar panel3100can include any number of solar modules3102. Namely,FIG.40,FIG.41,FIG.42, andFIG.43show a first configuration3700, a second configuration3800, a third configuration3900, and a fourth configuration4000, respectively, wherein each of the configurations includes six solar modules3102. Namely, the configurations3700,3800,3900, and4000each include the solar modules3102a,3102b,3102c,3102d,3102e, and3102f. Additionally, each of the solar modules3102a,3102b,3102c,3102d,3102e, and3102fprovides substantially the same output voltage (VSM). In the first configuration3700, the solar modules3102a,3102b,3102c,3102d,3102e, and3102fare connected in parallel. Therefore, using the first configuration3700, the output voltage (VOUT) of the solar panel3100is VSM×1. In one example, if VSM=3 volts, then VOUTof the solar panel3100=3 volts. In the second configuration3800, the solar modules3102a,3102b,3102c,3102d,3102e, and3102fare connected in series. Therefore, using the second configuration3800, the output voltage (VOUT) of the solar panel3100is VSM×6. In one example, if VSM=3 volts, then VOUTof the solar panel3100=18 volts. In the third configuration3900, the solar modules3102aand3102bare connected in series, the solar modules3102cand3102dare connected in series, and the solar modules3102eand3102fare connected in series. Therefore, each series-connected pair of solar modules3102provides an output voltage of VSM×2. Then, the three series-connected pairs of solar modules3102are connected in parallel with each other. Namely, the series-connected pair of solar modules3102aand3102b, the series-connected pair of solar modules3102cand3102d, and the series-connected pair of solar modules3102eand3102fare connected in parallel with each other. Therefore, using the third configuration3900, the output voltage (VOUT) of the solar panel3100is VSM×2. In one example, if VSM=3 volts, then VOUTof the solar panel3100=6 volts. In the fourth configuration4000, the solar modules3102a,3102c, and3102eare connected in series and the solar modules3102b,3102d, and3102fare connected in series. Therefore, each series-connected arrangement of solar modules3102provides an output voltage of VSM×3. Then, the two series-connected arrangements of solar modules3102are connected in parallel with each other. Namely, the series-connected arrangement of solar modules3102a,3102c, and3102eand the series-connected arrangement of solar modules3102b,3102d, and3102fare connected in parallel with each other. Therefore, using the fourth configuration4000, the output voltage (VOUT) of the solar panel3100is VSM×3. In one example, if VSM=3 volts, then VOUTof the solar panel3100=9 volts. In the event of failure of one or more solar modules3102in the solar panel3100, one skilled in the art will recognize that parallel arrangements of the solar modules3102provide certain advantages over series arrangements of the solar modules3102. For example, if one or more solar modules3102fail in the first configuration3700ofFIG.40, the output voltage (VOUT) of the solar panel3100is not changed, albeit the current capacity is reduced. By contrast, if one solar module3102fails in the second configuration3800ofFIG.41, the output voltage (VOUT) of the solar panel3100is reduced by an amount equal to the VSMof the failing solar module. In one embodiment, at least one bypass diode is installed across at least one solar cell. The at least one bypass diode provides a current path around shaded cells to prevent the shaded cells from overheating or burning out. In one example, a solar module contains 36 solar cells and two bypass diodes. In a preferred embodiment, the solar panel is MOLLE-compatible. In one embodiment, the solar panel incorporates a pouch attachment ladder system (PALS), which is a grid of webbing used to attach smaller equipment onto load-bearing platforms, such as vests and backpacks. For example, the PALS grid consists of horizontal rows of 1-inch (2.5 cm) webbing, spaced about one inch apart, and attached to the backing at 1.5-inch (3.8 cm) intervals. In one embodiment, the webbing is formed of nylon (e.g., cordura nylon webbing, MIL-W-43668 Type III nylon webbing). Accordingly, a set of straps3160(e.g., four straps3160) are provided on one edge of the solar panel3100as shown inFIGS.44-45. Additionally, rows of slots or slits3162(e.g., eleven rows of slots or slits3162) are provided on the back side of the solar panel3100, as shown inFIG.45. In a preferred embodiment, the set of straps3160and the rows of slots or slits3162attach to the MOLLE underneath the solar panel3100on the load bearing equipment (e.g., vest, backpack, rucksack, body armor). FIG.46illustrates a side perspective view of an example of a solar panel3100affixed to a portable battery pack100. The solar panel3100has at least one output connector3106electrically connected to the at least one solar module3102(e.g., four solar modules3102) via a cable or wire3120. A connector portion170of the battery of the portable battery pack100is shown mated to the at least one output connector3106of the solar panel3100. In the example shown inFIG.46, the pouch of the portable battery pack100is sized to hold a battery and additional devices or components (e.g., signal marker panel, state of charge indicator, AC adapter, power distribution and data hub, GPS). The portable battery pack100is affixed to a vest600using zippers. A first single width of zipper tape190ais shown mated with a corresponding first single width of zipper tape194aon a right side of the vest600using a first zipper slider192a, thereby attaching the portable battery pack100to the vest600. Similarly, a second single width of zipper tape (not shown) is mated with a corresponding second single width of zipper tape (not shown) on a left side of the vest600using a second zipper slider (not shown). Alternatively, an exterior surface of the pouch of the portable battery pack includes the solar panel. In a preferred embodiment, the at least one solar module is formed of microsystem enabled photovoltaic (MEPV) material, such as that disclosed in U.S. Pat. Nos. 8,736,108, 9,029,681, 9,093,586, 9,143,053, 9,141,413, 9,496,448, 9,508,881, 9,531,322, 9,548,411, and 9,559,219 and U.S. Publication Nos. 20150114444 and 20150114451, each of which is incorporated herein by reference in its entirety. In another preferred embodiment, the at least one solar module is formed of SUNPOWER™ MAXEON™ Gen III solar cells. In one embodiment, the solar cells are formed of monocrystalline silicon. The solar cells preferably have an antireflection coating. The solar cells have a tin-coated, copper metal grid backing. SUNPOWER™ MAXEON™ Gen III solar cells are described in an article entitled “Generation III High Efficiency Lower Cost Technology: Transition to full scale Manufacturing” by authors Smith, et al., published in Photovoltaic Specialists Conference (PVSC), 2012 38thIEEE, doi: 10.11009/PVSC.2012.6317899, which is incorporated herein by reference in its entirety. FIG.47illustrates another example of a solar module3102used with the solar panel. The solar module3102includes a layer of ethylene tetrafluoroethylene (ETFE)4402, a first layer of ethylene-vinyl acetate (EVA)4404, a layer containing at least one solar cell4406, a second layer of EVA4408, and a layer of fiberglass4410. In a preferred embodiment, the at least one solar module is less than about 0.04 inches thick. In a preferred embodiment, the at least one solar module weighs less than about 1 oz. In one embodiment, the at least one solar module has dimensions of about 4 inches by about 8 inches. The at least one solar module is preferably flexible. In one embodiment, the at least one solar module produces about 1 W of power. In one embodiment, the at least one solar module produces a voltage of about 6 V. In one embodiment, the at least one solar module produces a current of about 160 mA. Advantageously, the at least one solar module is operable to extend the life/run time of a rechargeable battery using this lower current (e.g., about 160 mA) in a constant-voltage phase while the battery is over 85% charged and the battery is in its state of highest internal resistance. In yet another preferred embodiment, the solar panel is made of glass free, flexible thin film solar modules. The solar modules are formed of amorphous silicon with triple junction cell architecture. Alternatively, the solar modules are formed of multicrystalline silicon. These solar modules continue to deliver power when damaged or perforated. Additionally, these panels provide higher production and a higher output in overcast conditions than comparable glass panels. These panels also provide better performance at a non-ideal angle of incidence. FIG.48illustrates a solar panel3100made with glass free, thin film solar modules. The solar panel3100includes at least one solar module3102mounted on a substrate3114. WhileFIG.48shows eighteen solar modules3102in the solar panel3100, this is exemplary only. The solar panel3100can include any number of solar modules3102configured in series, configured in parallel, or configured in any combination of series and parallel arrangements. In particular, the configuration of solar modules3102in the solar panel3100can be tailored in any way to provide a certain output voltage and current. The output of any arrangement of solar modules3102in the solar panel3100is a direct current (DC) voltage. Accordingly, the solar panel3100includes at least one output connector3106that is electrically connected to the arrangement of solar modules3102via a cable or wire3120. The at least one output connector3106is used for connecting any type of DC load to the solar panel3100. In one embodiment, the cable or wire3120of the at least one output connector3106includes a blocking diode to prevent power from running back into the solar panel3100. In a preferred embodiment, the at least one output connector3106is a circular connector (e.g., male FISCHER® SOV 105 A087 connector, FISCHER® LP360). In one example, the solar panel is used for supplying power to a device, such as a DC-powered radio. In another example, the solar panel is used for charging a battery. In yet another example, the solar panel is used for charging the battery of a portable battery pack. In one embodiment, the at least one connector includes one or more connectors that allow a first solar panel to connect to a second solar panel in series or in parallel. This allows a plurality of solar panels3100to be connected together in series, in parallel, or any combination of series and parallel arrangements. Advantageously, connecting a plurality of panels together allows the output current and/or output voltage to be raised. The solar panel3100is preferably foldable. Prior art solar panels that are rollable require a tube to roll the solar panel. The solar panel3100of the present invention does not require a tube, which provides a weight and volume savings advantage over prior art. The weight and dimensions of the solar panel is important because it must be easily transported by a human. Soldiers often carry 60-100 lbs. of gear, including equipment (e.g., radios, solar panels, batteries) in their rucksack or attached to their vest. Additional weight slows soldiers down and also makes it more likely that they will suffer injuries to their body (e.g., injuries to the back, shoulders, hips, knees, ankles, and feet). Additional volume also impedes the movement of the soldiers. The solar panel3100includes clips (female clip3170shown) to secure the solar panel3100when not in use in one embodiment. The female clip3170is attached to the solar panel3100via top webbing3172. The solar panel3100includes eyelets3174, which allows the solar panel to be secured to the ground or another surface. WhileFIG.48shows a total of four eyelets3174(one in each corner), this is exemplary only. The solar panel3100can include any number of eyelets3174. The solar panel3100has a vertical fold axis3176, a top horizontal fold axis3178, and a plurality of horizontal fold axes3180. In one embodiment, the solar panel3100includes eighteen solar modules3102as shown inFIG.48. In one embodiment, the solar modules are formed of amorphous silicon. The maximum power is about 118 W in one embodiment. The voltage at maximum power is about 28.8V in one embodiment. The current at maximum power is about 4.1 A in one embodiment. The dimensions of the solar panel3100are about 8 feet by about 3 feet when deployed in one embodiment. The weight of the solar panel3100is preferably less than about 10 pounds. The solar panel3100weighs about 9 pounds in one embodiment. The dimensions of the solar panel3100are about 10 inches by about 15 inches by about 2 inches when folded. In a preferred embodiment, the solar panel includes 6 solar modules. In one embodiment, the solar modules are formed of multicrystalline silicon. The maximum power is 102 W in one embodiment. The voltage at maximum power is about 30.8V in one embodiment. The current at maximum power is about 3.3 A in one embodiment. The dimensions of the solar panel are about 3 feet by about 2.5 feet when deployed in one embodiment. The weight of the solar panel is preferably less than about 8 pounds. The solar panel weighs about 6.5 pounds in one embodiment. The dimensions of the solar panel are about 15 inches by about 12 inches by about 1 inch when folded. FIG.49shows a front perspective view of the solar panel3100while folded. The solar panel3100includes a handle3182. The solar panel3100also includes clips (e.g., female clip3170, male clip3184) to secure the solar panel3100when not in use in one embodiment. The female clips3170are attached to a front flap3186via top webbing3172. The male clips3184are attached to bottom webbing3188. The front flap3186partially covers a back side of the substrate3114in one embodiment. The bottom webbing3188is in two pieces that are secured by hook-and-loop tape in one embodiment. FIG.50shows a back perspective view of one embodiment of the solar panel3100while folded. In one embodiment, the integrated pocket3190is used to store the at least one output connector (not shown) and/or a signal marker panel when not in use. The integrated pocket3190has an opening3192. The opening3192of the integrated pocket3190is preferably closed using a hook-and-loop fastener system. Alternatively, the opening3192of the integrated pocket3190is closed using ties, an arrangement of buttons or snaps, or a zipper. FIG.51illustrates a top perspective view of one embodiment of the solar panel3100while unfolded. The front flap3186is connected to the female clips3170via top webbing3172. The front flap3186is connected to a top section3194. The handle3182is attached to the top section3194. The top section3194is also connected to a back flap3196. The back flap3196contains the integrated pocket (not shown). In a preferred embodiment, the integrated pocket is on the reverse side of the back flap3196such that the integrated pocket is not exterior facing when the solar panel3100is folded. This protects the contents of the integrated pocket from accidentally spilling out. This also protects the cable or wire electrically connecting the at least one connector to the solar modules from getting caught on other gear, vehicle components, etc. The back flap3196is also connected to the male clips3184via bottom webbing3188. FIG.52illustrates another portion of a solar panel3100. The cable or wire3120is electrically connected to the at least one solar module (not shown) via a junction box3198. The at least one output connector (not shown) is secured in the integrated pocket3190. In the embodiment shown inFIG.52, the back side of the substrate3114is shown in a camouflage pattern. Alternatively, the substrate is a solid color (e.g., black, blue, brown, tan, green, white). In a preferred embodiment, the front flap, the top section, and the back flap are made of a canvas or nylon material. The front flap, the top section, and the back flap are formed of a camouflage pattern or a solid color (e.g., black, blue, brown, tan, green, white). Representative camouflages include, but are not limited to, Universal Camouflage Pattern (UCP), also known as ACUPAT or ARPAT or Army Combat Uniform; MULTICAM®, also known as Operation Enduring Freedom Camouflage Pattern (OCP); Universal Camouflage Pattern-Delta (UCP-Delta); Airman Battle Uniform (ABU); Navy Working Uniform (NWU), including variants, such as, blue-grey, desert (Type II), and woodland (Type III); MARPAT, also known as Marine Corps Combat Utility Uniform, including woodland, desert, and winter/snow variants; Disruptive Overwhite Snow Digital Camouflage, Urban Digital Camouflage, and Tactical Assault Camouflage (TACAM). In yet another embodiment, the solar panel3100is foldable and includes 4 solar modules3102as shown inFIG.53A. The solar modules3102are mounted on a substrate3114. The solar panel3100includes a vertical fold axis3176and a horizontal fold axis3180. A cable or wire (not shown) is electrically connected to the solar modules3102via a junction box3198(back of junction box shown). The junction box3198is mounted to a junction box substrate3197. The junction box is electrically connected to an output connector (not shown) that is preferably operable to connect to the portable battery pack. Alternatively, the output connector is operable to connect to a portable power case. In one embodiment, the output connector is a male FISCHER® SOV 105 A087 connector, a TAJIMI™ Electronics part number R04-P5m connector, or a TAJIMI™ Electronics part number TR05 R5m connector. The solar panel3100is shown resting on a strap3181including a piece of hook tape3177that attaches to a piece of loop tape (not shown). The piece of hook tape3197and the piece of loop tape are adhered, e.g., glued, sewn, or otherwise attached to the strap3181. In one embodiment, the strap is formed of webbing, polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, or polycotton canvas. Alternatively, the strap is fully or partially formed of an elastomeric material. In another embodiment, the solar panel is secured in a folded configuration using an elastomeric closure, a zipper, an arrangement of buttons or snaps, ties, and/or a hook-and-loop fastener system. In a preferred embodiment, the solar panel has maximum dimensions of 27.94 cm (11 inches) by 35.56 cm (14 inches). The solar panel preferably has maximum dimensions of 13.97 cm (5.5 inches) by 17.78 cm (7 inches) when folded. In one embodiment, the solar panel has a output voltage of about 17V and an output current of about 1.5 A. In another embodiment, the solar panel has an output voltage of between about 12V and about 23V. In yet another embodiment, the solar panel has an output voltage of about 30V. In still another embodiment, the solar panel has an output voltage of between about 25V and about 30V. FIG.53Bshows the solar panel3100ofFIG.53Aafter the solar panel3100is folded along the horizontal axis3180. FIG.53Cshows the solar panel3100ofFIG.53Bafter the solar panel3100is folded along the vertical axis3176. FIG.53Dshows the reverse side of the solar panel3100shown inFIG.53C. A front side of the junction box3198is shown. The strap3181includes the piece of hook tape3177and the piece of loop tape3181. A junction box substrate cover3199is shown covering the junction box substrate. In one embodiment, the junction box substrate cover is formed of polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, or polycotton canvas. In the example shown inFIG.53D, the strap3181is secured between the junction box substrate and the junction box substrate cover3199. The junction box substrate and the junction box substrate cover3199are adhered, e.g., glued, sewn, or otherwise attached to each other. In one embodiment, the solar panel3100is foldable and includes 2 solar modules3102as shown inFIG.53E. The solar modules3102are mounted on a substrate3114. The solar panel3100includes eyelets3174, which allows the solar panel to be secured to the ground or another surface. WhileFIG.53Eshows a total of four eyelets3174(one in each corner), this is exemplary only. The solar panel3100can include any number of eyelets3174. The solar panel3100includes a vertical fold axis3176. A cable or wire3120is electrically connected to the solar modules3102via a junction box3198. The cable or wire3120is electrically connected to an output connector3106that is preferably operable to connect to the portable battery pack. Alternatively, the output connector is operable to connect to a portable power case. In another preferred embodiment, the solar panel has maximum dimensions of 31.75 cm (12.5 inches) by 24.13 cm (9.5 inches). The solar panel preferably has maximum dimensions of 15.88 cm (6.25 inches) by 24.13 cm (9.5 inches) when folded. In one embodiment, the solar panel has an output voltage of about 17V and an output current of about 750 mA. In another embodiment, the solar panel has an output voltage of between about 12V and 23V. The solar panel preferably is secured in a folded configuration using an elastomeric closure, a zipper, an arrangement of buttons or snaps, ties, and/or a hook-and-loop fastener system. In one embodiment, the solar panel has a lower output voltage than a corresponding at least one battery to be charged by the solar panel. By reducing the output voltage of the solar panel below what would otherwise be considered optimal, the size, weight, open footprint, and/or cost of the solar panel is reduced. Additionally, this allows for charging of the at least one battery to continue indefinitely. In one embodiment, the at least one solar panel includes at least one layer of a material for dissipating heat.FIG.54is an exploded view of an example of a solar panel3100into which a heat-shielding or blocking and/or heat-dissipating layer1520is installed. In this example, the heat-dissipating layer1520is incorporated into the layers of fabric that form the solar panel3100, in similar fashion to the structure1500ofFIG.17A. Namely, the heat-dissipating layer1520is provided at the back of solar modules3102, between the substrate3114and the second fabric layer3112. In this example, the first fabric layer3110, the substrate3114, the heat-dissipating layer1520, and the second fabric layer3112are held together by stitching and/or by a hook-and-loop fastener system. In this example, the heat-shielding or blocking and/or heat-dissipating layer1520protects the user from heat from the back of the solar panel3100, the heat-shielding or blocking and/or heat-dissipating layer1520protects the back of the solar panel3100from any external heat source (not shown), and the heat-dissipating layer1520reduces the heat profile of the solar panel3100. Combination Solar Panel and Signal Marker Panel Conventional signal marker panels and solar panels typically are provided separately and used independently of one another. In contrast, the present invention includes a combination signal marker panel and solar panel. Namely, in the combination signal marker panel and solar panel, a signal marker panel is detachably secured to a flexible solar panel. The combination signal marker panel and solar panel is lightweight, flexible (i.e., foldable or rollable), and waterproof or water resistant. As a result, the combination signal marker panel and solar panel is well-suited for portability and for use in adverse conditions. An aspect of the combination signal marker panel and solar panel is that both the signal marker panel and the solar panel fulfill their traditional functions unhindered. The signal marker panel and the solar panel can be used simultaneously, or the signal marker panel can be used alone, or the solar panel can be used alone. Yet another aspect of the combination signal marker panel and solar panel is that the solar panel is modular and configurable to provide any output voltage. The solar panel can include any number of solar modules configured in series, configured in parallel, or configured in any combination of series and parallel arrangements. In one embodiment of the present invention, the signal marker panel can be positioned to provide secondary protection to the solar panel, and solar modules thereof, when folded up and stowed. Another aspect of the combination signal marker panel and solar panel is that the output voltage of the solar panel is provided in an unregulated state. As a result, the complexity of the solar panel is reduced as compared with conventional solar panels because it does not include voltage conditioning circuitry at its output. FIG.55andFIG.56illustrate front and rear perspective views, respectively, of an example of a combination signal marker panel and solar panel4700that is lightweight, foldable, waterproof or water resistant, and well-suited for portability. The combination signal marker panel and solar panel4700includes a signal marker panel4710that is detachably secured to a solar panel3100. In one embodiment, the solar panel3100of the combination signal marker panel and solar panel4700is a multilayer structure that includes a plurality, e.g., one or more, of solar modules3102mounted on a substrate, wherein the substrate with the plurality of solar modules3102is sandwiched between two layers of waterproof or water-resistant fabric. In one embodiment, openings, e.g., windows, are formed in at least one of the two layers of fabric for exposing the solar modules3102. The outer two layers of fabric can be any color or pattern. In the example shown inFIG.55andFIG.56, the outer two layers of fabric have a camouflage pattern thereon. One of ordinary skill in the art would recognize that the two layers of fabric can have any camouflage pattern including, but not limited to, Universal Camouflage Pattern (UCP), also known as ACUPAT or ARPAT or Army Combat Uniform; MULTICAM®, also known as Operation Enduring Freedom Camouflage Pattern (OCP); Universal Camouflage Pattern-Delta (UCP-Delta); Airman Battle Uniform (ABU); Navy Working Uniform (NWU), including variants, such as, blue-grey, desert (Type II), and woodland (Type III); MARPAT, also known as Marine Corps Combat Utility Uniform, including woodland, desert, and winter/snow variants; Disruptive Overwhite Snow Digital Camouflage, Urban Digital Camouflage, and Tactical Assault Camouflage (TACAM). A hem3104is provided around the perimeter of the solar panel3100in one embodiment. The output of any arrangement of solar modules3102in the solar panel3100is a direct current (DC) voltage. Accordingly, the solar panel3100includes at least one output connector3106that is wired to the arrangement of solar modules3102. The at least one output connector3106is used for connecting any type of DC load to the solar panel3100. In one example, the solar panel3100is used for supplying power to a device, such as a DC-powered radio. In another example, the solar panel3100is used for charging a battery. In yet another example, the solar panel3100is used for charging the battery of a portable battery pack. In one embodiment, the at least one connector3106includes one or more connectors that allow a first solar panel to connect to a second solar panel in series or in parallel. This allows a plurality of solar panels3100of multiple combination signal marker panel and solar panels4700to be connected together in series, parallel, or any combination of series and parallel arrangements. The signal marker panel4710of the combination signal marker panel and solar panel4700is preferably formed of any flexible, durable, and waterproof or water-resistant material used in conventional signal marker panels. For example, the signal marker panel4710can be formed of polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, or polycotton canvas. The signal marker panel4710can be any color suitable for signaling, such as, but not limited to, red, orange, yellow, pink, and white. In one embodiment, the signal marker panel4710includes a U.S. Coast Guard-approved distress signal (e.g., a black square and circle) on a top surface and/or a bottom surface of the signal marker panel4710. In another embodiment, the signal marker panel4710incorporates reflective material and/or thermal identification material on the top surface and/or the bottom surface. A hem4712is provided around a perimeter of the signal marker panel4710in this embodiment of the present invention. In one embodiment, the solar panel and/or the signal marker panel include tie straps, loops, eyelets, and/or grommets. The tie straps, loops, eyelets, and/or grommets allow the solar panel and/or the signal marker panel to attach to different surfaces (e.g., the ground, trees, or a backpack). In one embodiment, tie straps are made of the same material as the signal marker panel, nylon, elastic, or parachute cord. The solar panel and/or the signal marker panel are operable to attach to the ground with stakes through the eyelets, grommets, and/or loops. The length of the signal marker panel can be about the same or can be different than the width. The footprint of the signal marker panel can be, for example, square or rectangular. The length and width of the signal marker panel can be, for example, from about 8 inches to about 48 inches. In one example, the signal marker panel is about 36 inches by about 36 inches. Similarly, the length of the solar panel can be about the same or can be different than the width. The footprint of the solar panel can be, for example, square or rectangular. The length and width of the solar panel can be, for example, from about 8 inches to about 48 inches. In one example, the solar panel is about 36 inches by about 36 inches. The signal marker panel4710and the solar panel3100can be substantially the same size or can be different sizes and still be joined together. For example,FIG.55,FIG.56, andFIG.57Ashow an example of the combination signal marker panel and solar panel4700wherein the signal marker panel4710and the solar panel3100are substantially the same size.FIG.57B, however, shows an example of the combination signal marker panel and solar panel4700wherein a smaller signal marker panel4710is joined to a larger solar panel4700. Further,FIG.57Cshows an example of the combination signal marker panel and solar panel4700wherein a larger signal marker panel4710is joined to a smaller solar panel3100. In one embodiment of the combination signal marker panel and solar panel, one edge of the signal marker panel is sewed, adhered, or otherwise fastened to one edge of the solar panel in a substantially permanent fashion. In another embodiment, however, the signal marker panel is detachable from the solar panel. For example, one edge of the signal marker panel is fastened to one edge of the solar panel using a zipper, an arrangement of buttons or snaps, ties, and/or a hook-and-loop fastener system. In a preferred embodiment, the hook-and-loop fastener system is a first strip including hooks and a second strip including loops. The first strip and the second strip are adhered, e.g., glued, sewn, or otherwise attached, to opposing surfaces to be fastened. For example, in some embodiments, the first strip including hooks is attached to the signal marker panel and the second strip including loops is attached to the solar panel. In other embodiments, the first strip including hooks is attached to the solar panel and the second strip including loops is attached to the signal marker panel. When the first strip and the second strip are pressed together, the hooks catch in the loops and the two strips reversibly bind or fasten. The two strips can be separated by pulling apart. The hook-and-loop fastener system can be made of any appropriate material known in the art including, but not limited to, nylon, polyester, TEFLON®, and the like. VELCRO® is an example of a hook-and-loop fabric fastener system. The signal marker panel is preferably a single layer of lightweight fabric, which reduces the overall weight of the combination signal marker panel and solar panel. In an alternative embodiment, the signal marker panel has two layers. One layer can be any color suitable for signaling, such as, but not limited to, red, orange, yellow, pink, and white. The other layer can be a different color or a pattern (e.g., camouflage). FIG.58illustrates one embodiment of a signal marker panel4710. The signal marker panel4710is preferably rectangular or square in shape. In a preferred embodiment, the signal marker panel4710is fluorescent orange (or “international orange”) on a first side and cerise on a second side. In a preferred embodiment, the signal marker panel4710is formed of ripstop nylon. In the example shown inFIG.58, the signal marker panel4710includes tie straps4712, which allows the signal marker panel4710to attach to different surfaces (e.g., the ground, trees, a backpack). In one embodiment, the tie straps4712are made out of the same material as the signal marker panel4710, nylon, elastic, hook-and-loop tape, or parachute cord. In one embodiment, the signal marker panel4710includes snaps, which allows multiple signal marker panels4710to be connected together. The snaps include sockets4714(cap shown) and studs4716. In a preferred embodiment, the signal marker panel includes a cerise side and an international orange side. In one embodiment, the signal marker panel includes grommets on two opposing ends. The signal marker panel preferably includes at least one piece of hook tape and at least one piece of loop tape on both sides of the signal marker panel (i.e., on both the cerise and international orange sides). In an alternative embodiment, the signal marker panel includes at least one piece of hook tape and at least one piece of loop tape on only one side. The signal marker panel includes at least one piece of hook tape and/or at least one piece of loop tape on two opposing ends of at least one side of the signal marker panel in another embodiment. In one embodiment, the signal marker panel is about 3 feet wide and about 3 feet long. FIGS.59A-59Billustrate another embodiment of a signal marker panel4710.FIG.59Aillustrates a first side4730of the signal marker panel4710. In the example shown inFIG.59A, the first side4730is cerise. The signal marker panel4710includes grommets4718on two opposing ends. The first side4730includes a first piece of hook tape4732and a first piece of loop tape4734. In the embodiment shown inFIG.59A, the first piece of hook tape4732is shown above the first piece of loop tape4734. In an alternative embodiment, the first piece of hook tape4732is below the first piece of loop tape4734. FIG.59Billustrates a second side4740of the signal marker panel4710. In the example shown inFIG.59B, the second side4740is international orange. The second side4740includes a second piece of loop tape4742and a second piece of hook tape4744. In the embodiment shown inFIG.59B, the first piece of loop tape4742is shown above the first piece of hook tape4744. In an alternative embodiment, the first piece of loop tape4742is below the first piece of hook tape4744. Advantageously, the dual hook and loop configuration (i.e.,4strips of hook and loop tape with a piece of hook tape and a piece of loop tape on each side) shown inFIGS.59A-59Bfacilitates installation of the signal marker panel into any pocket that closes with hook and loop tape. Further, the dual hook and loop configuration allows the pocket to maintain its closing operability. Examples of pockets that close with hook and loop tape include a base of a plate carrier, a long pocket in a vest, and the opening of the integrated pocket of the solar panel. The combination signal marker panel and solar panel can include other features. In one embodiment, the combination signal marker panel and solar panel includes an elastic band or strap (not shown) that is used for wrapping around the combination signal marker panel and solar panel when folded or rolled. Alternatively, the combination signal marker panel and solar panel includes side release buckles, backpack clips, toggle clips, friction buckles, tongue buckles, quick connect buckles, and/or magnetic closures to secure the combination signal marker panel and solar panel when folded or rolled. In one example application—a military application, the combination signal marker panel and solar panel provides the following advantages over using separate signal marker panels and solar panels: 1) The combination signal marker panel and solar panel can be used to harvest solar energy while simultaneously marking the user's position to friendlies in the battle space, both on the ground and in the air. 2) The combination signal marker panel and solar panel has a small footprint that allows it to be draped over the user's backpack or rucksack, which allows the solar panel portion to be used while on the move. 3) The small footprint of the combination signal marker panel and solar panel facilitates stationary charging in tight spaces, and makes the overall folded or rolled dimension light enough and small enough to be carried by the user instead of the user carrying additional batteries. Advantageously, this allows device use in austere environments over longer periods of time when resupply is not possible (e.g., due to weather, natural disaster, battle). In summary and referring now toFIG.1throughFIG.59B, the present invention provides a system for supplying power to a portable battery pack including one or more batteries enclosed in a wearable pouch using at least one solar panel, wherein the one or more batteries include at least one battery element, a battery cover, a battery back plate, and one or more flexible omnidirectional leads that include a connector portion and a wiring portion, wherein a flexible spring is provided around the wiring portion such that a portion of the flexible spring is positioned inside the battery cover and a portion of the flexible spring is positioned outside the battery cover. In other embodiments, the present invention provides a portable battery pack including a wearable pouch and one or more batteries enclosed in the wearable pouch, wherein the pouch has a first side and an opposite second side, a closable opening through which the one or more batteries can be fitted into the pouch, one or more openings through which one or more leads from the one or more batteries can be accessed, and wherein the pouch includes a pouch attachment ladder system (PALS) adapted to attach the pouch to a load-bearing platform. In some embodiments, the pouch is formed of a flexible, durable, and waterproof and/or water-resistant material. In particular embodiments, the material forming the pouch is selected from the group consisting of polyester, polyvinyl chloride (PVC)-coated polyester, vinyl-coated polyester, nylon, canvas, PVC-coated canvas, and polycotton canvas. In yet more particular embodiments, the pouch has an exterior finish with a camouflage pattern. In representative embodiments, the camouflage pattern is selected from the group consisting of Universal Camouflage Pattern (UCP), also known as ACUPAT or ARPAT or Army Combat Uniform; MULTICAM®, also known as Operation Enduring Freedom Camouflage Pattern (OCP); Universal Camouflage Pattern-Delta (UCP-Delta); Airman Battle Uniform (ABU); Navy Working Uniform (NWU), including variants, such as, blue-grey, desert (Type II), and woodland (Type III); MARPAT, also known as Marine Corps Combat Utility Uniform, including woodland, desert, and winter/snow variants; Disruptive Overwhite Snow Digital Camouflage, Urban Digital Camouflage, and Tactical Assault Camouflage (TACAM). In some embodiments, the closable opening can be closed by a mechanism selected from the group consisting of a zipper, a hook and loop system, one or more buttons, one or more snaps, one or more ties, one or more buckles, one or more clips, and one or more hooks. In particular embodiments, the load-bearing platform is selected from the group consisting of a vest (e.g., bulletproof vest, Rhodesian vest), a backpack, body armor, a belt (e.g., tactical belt), a chair, a seat, a boat, a kayak, a canoe, a body of a user (e.g., back region, chest region, abdominal region, arm, leg), a vehicle (e.g., truck, high mobility multipurpose wheeled vehicle (Humvee), all-terrain vehicle (ATV), sport utility vehicle (SUV)), a cargo rack, a helmet, or a hat. In certain embodiments, the portable battery pack is Modular Lightweight Load-carrying Equipment (MOLLE)-compatible. In yet more certain embodiments, the pouch attachment ladder system is formed of a plurality of straps, a plurality of horizontal rows of webbing, a plurality of slits, and combinations thereof. In some embodiments, the one or more batteries include a battery element, a battery cover, and a battery back plate. In particular embodiments, one or more of the battery element, battery cover, and battery back plate have a curvature or contour adapted to conform to a curvature or contour of the load-bearing platform. In further embodiments, the one or more batteries includes one or more flexible omnidirectional leads, wherein each lead includes a connector portion and a wiring portion, and wherein at least a portion of the wiring portion is encompassed by a flexible spring. In certain embodiments, the battery has a length having a range from about 12 inches to about 8 inches, a width having a range from about 10 inches to about 7 inches, and a thickness having a range from about 2 inches to about 0.5 inches. The above-mentioned examples are provided to serve the purpose of clarifying the aspects of the invention, and it will be apparent to one skilled in the art that they do not serve to limit the scope of the invention. By way of example, the battery may include more than two flexible omnidirectional leads. Also by way of example, the pouch may have different dimensions than those listed. By nature, this invention is highly adjustable, customizable and adaptable. The above-mentioned examples are just some of the many configurations that the mentioned components can take on. All modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the present invention. | 173,923 |
11862764 | DETAILED DESCRIPTION OF THE INVENTION Terms or words used in the specification and the claims should not be interpreted as being limited to typical or dictionary meanings and should be interpreted with a meaning and a concept that are consistent with the technical spirit of the present disclosure. In the present disclosure, the term “comprise”, “include”, or “have” is intended to indicate the presence of the characteristic, number, step, constituent element, or any combination thereof implemented, and should be understood to mean that the possibility of the presence or addition of one or more other characteristics or numbers, steps, constituent elements, or any combination thereof is not precluded. Further, in the description of “the carbon number a to b” in the present specification, “a” and “b” mean the number of carbon atoms included in a specific functional group. That is, the functional group may include “a” to “b” carbon atoms. For example, the “alkylene group having 1 to 5 carbon atoms” means an alkylene including carbon atoms with the number of carbon atoms 1 to 5, that is, —CH2—, —CH2CH2—, —CH2CH2CH2—, —CH2(CH2)3CH2—, —CH(CH3)CH2—, —CH(CH3)CH2CH2—, and the like. In addition, in the present specification, the alkyl group or the alkylene group may be substituted or unsubstituted on otherwise defined. The “substitution” means that at least one hydrogen bonded to carbon is substituted with an element other than hydrogen, and means being substituted with an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a cycloalkenyl group having 3 to 12 carbon atoms, a heterocycloalkyl group having 3 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a halogen atom, a fluoroalkyl group having 1 to 20 carbon atoms, a nitro group, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 2 to 20 carbon atoms, a haloaryl group having 6 to 20 carbon atoms, and the like. Hereinafter, the present disclosure will be described in more detail. Non-Aqueous Electrolyte A non-aqueous electrolyte according to an exemplary embodiment of the present disclosure includes a compound represented by the following Chemical Formula 1. A secondary battery including the non-aqueous electrolyte of the present disclosure may have excellent high temperature cycle characteristics and excellent high temperature storage characteristics because the degradation caused by an interfacial reaction at high temperature is suppressed. In Chemical Formula 1, R1to R5may each independently be any one selected from the group consisting of H, an alkyl group having 1 to 10 carbon atoms, and an alkoxy group having 1 to 10 carbon atoms, preferably any one selected from the group consisting of H, an alkyl group having 1 to 5 carbon atoms and an alkoxy group having 1 to 5 carbon atoms, and most preferably H. In Chemical Formula 1, R may be an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms, or —OR′ (R′ is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms). Preferably, R may be an aliphatic unsaturated hydrocarbon group having 2 to 5 carbon atoms, or —OR′ (R′ is an aliphatic unsaturated hydrocarbon group having 2 to 5 carbon atoms). By additionally including an aliphatic unsaturated hydrocarbon in the coumarin structure, a dense film may be formed on the electrode, whereby there is an effect of suppressing the degradation caused by an interfacial reaction at high temperature. In Chemical Formula 1, the aliphatic unsaturated hydrocarbon group may include a triple bond. When R of Chemical Formula 1 includes a triple bond, a dense film may be formed on the electrode, whereby there is an effect of suppressing the degradation caused by an interfacial reaction at high temperature. Further, in Chemical Formula 1, R may be an alkenyl group or alkynyl group having 2 to 5 carbon atoms. Specifically, the compound represented by Chemical Formula 1 of the present disclosure may be a compound represented by the following Chemical Formula 1-1. In Chemical Formula 1-1, R may be an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms, or —OR′ (R′ is an aliphatic unsaturated hydrocarbon group having 2 to 10 carbon atoms). Preferably, R may be an aliphatic unsaturated hydrocarbon group having 2 to 5 carbon atoms, or —OR′ (R′ is an aliphatic unsaturated hydrocarbon group having 2 to 5 carbon atoms). By additionally including an aliphatic unsaturated hydrocarbon in the coumarin structure, a dense film may be formed on the electrode, whereby there is an effect of suppressing the degradation caused by an interfacial reaction at high temperature. In Chemical Formula 1-1, the aliphatic unsaturated hydrocarbon group may include a triple bond. When R of Chemical Formula 1-1 includes a triple bond, a dense film may be formed on the electrode, whereby there is an effect of suppressing the degradation caused by an interfacial reaction at high temperature. In addition, in Chemical Formula 1-1, R may be an alkenyl group or alkynyl group having 2 to 5 carbon atoms. Specifically, the compound represented by Chemical Formula 1 of the present disclosure may be any one of the compounds represented by the following Chemical Formulae 2-1 to 2-8. In the present disclosure, the additive for a non-aqueous electrolyte may be included in a content of 0.01 parts by weight to 5 parts by weight, preferably 0.1 parts by weight to 1 part by weight, and more preferably 0.1 parts by weight to 0.5 parts by weight, based on 100 parts by weight of the non-aqueous electrolyte. When the content of the compound represented by Chemical Formula 1 is less than the above range, the effect of suppressing degradation is not sufficiently exhibited, and when the content of the compound represented by Chemical Formula 1 exceeds the above range, a hydrocarbon group including an unsaturated bond increases the resistance of the secondary battery too much, and thus there is a problem in that life characteristics deteriorate. When the content of the compound represented by Chemical Formula 1 is less than 0.01 parts by weight, an effect of forming the positive/negative electrode film becomes insignificant as the driving time increases, so the electrode interface protection effect may be reduced. Furthermore, when the content of the compound represented by Chemical Formula 1 exceeds 5 parts by weight, the viscosity of the electrolyte may be increased by an excessive amount of additive, and rate characteristics or life characteristics during storage at high temperature may deteriorate because the mobility of ions in the battery is adversely affected by a reduction in ion conductivity caused by an increase in viscosity. In addition, excessive decomposition of additives may increase battery resistance and cause side reactions and by-products. The non-aqueous electrolyte according to the present disclosure may further include a lithium salt, an organic solvent and optionally other electrolyte additives. The lithium salt is used as an electrolyte salt in a lithium secondary battery, and is used as a medium for transferring ions. Typically, the lithium salt includes, for example, Li+as a cation, and may include at least any one selected from the group consisting of F−, Cl−, Br−, I−, NO3−, N(CN)2−, BF4−, ClO4−, B10Cl10−, AlCl4−, AlO2−, PF6−, CF3SO3−, CH3CO2−, CF3CO2−, AsF6−, SbF6−, CH3SO3−, (CF3CF2SO2)2N−, (CF3SO2)2N−, (FSO2)2N−, BF2C2O4−, BC4O8−, PF4C2O4−, PF2C4O8−, (CF3)2PF4−, (CF3)3PF3−, (CF3)4PF2−, (CF3)5PF−, (CF3)6P−, C4F9SO3−, CF3CF2SO3−, CF3CF2(CF3)2CO−, (CF3SO2)2CH−, CF3(CF2)7SO3−and SCN−. Specifically, the lithium salt may include a single material or a mixture of two or more thereof selected from the group consisting of LiCl, LiBr, LiI, LiBF4, LiClO4, LiB10Cl10, LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2(lithium bis(fluorosulfonyl)imide; LiFSI), LiN(SO2CF2CF3)2(lithium bis(perfluoroethanesulfonyl)imide; LiBETI) and LIN(SO2CF3)2(lithium bis(trifluoromethanesulfonyl)imide; LiTFSI). In addition to these, lithium salts typically used in an electrolyte for a lithium secondary battery may be used without limitation. Although the lithium salt may be appropriately changed within a range that can be typically used, the lithium salt may be included at a concentration of 0.5 M to 5.0 M, preferably 0.8 M to 2.5 M, and more preferably 1.0 M to 2.0 M in order to obtain an optimum effect of forming a corrosion-preventing film on the electrode surface. When the concentration of the lithium salt is less than 0.5 M, a condition under which lithium is excessively deficient is created, so the capacity and cycle characteristics may deteriorate, and when the concentration exceeds 5.0 M, electrolyte impregnability deteriorates as the viscosity of the non-aqueous electrolyte is increased excessively, and performance deterioration caused by an increase in battery resistance may occur. The non-aqueous organic solvent may include at least one or more organic solvents selected from the group consisting of a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent and a cyclic ester-based organic solvent. Specifically, the organic solvent may include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent or a mixed organic solvent thereof. The cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant, and thus can dissociate the lithium salt in the electrolyte well, and may include at least one or more organic solvents selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and vinylene carbonate as specific examples thereof, and may include ethylene carbonate among them. Further, the linear carbonate-based organic solvent is an organic solvent having low viscosity and a low dielectric constant, it is possible to use at least one or more organic solvents selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate as representative examples thereof, and specifically, the linear carbonate-based organic solvent may include ethyl methyl carbonate (EMC). In addition, the organic solvent may additionally include at least one or more ester-based organic solvents selected from the group consisting of a linear ester-based organic solvent and a cyclic ester-based organic solvent in at least one or more carbonate-based organic solvents selected from the group consisting of the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent in order to prepare an electrolyte having high ion conductivity. Specific examples of the linear ester-based organic solvent include at least one or more organic solvents selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate. Furthermore, examples of the cyclic ester-based organic solvent include γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone. Meanwhile, as the organic solvent, an organic solvent typically used for a non-aqueous electrolyte may be added without limitation, if necessary. For example, the organic solvent may additionally include at least one or more organic solvents of an ether-based organic solvent, a glyme-based solvent and a nitrile-based organic solvent. As the ether-based solvent, it is possible to use any one or a mixture of two or more thereof selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, ethylpropyl ether, 1,3-dioxolane (DOL) and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), but the ether-based solvent is not limited thereto. The glyme-based solvent is a solvent that has a higher dielectric constant and lower surface tension, and is less reactive with a metal than the linear carbonate-based organic solvent, and may include at least one or more selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, triglyme, and tetraglyme (TEGDME). The nitrile-based solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto. Further, the non-aqueous electrolyte of the present disclosure may additionally include known electrolyte additives in the non-aqueous electrolyte, if necessary, in order to prevent the induction of collapse of an electrode due to the decomposition of the non-aqueous electrolyte in a high voltage environment, or to further improve low-temperature high-rate discharge characteristics, high temperature stability, the prevention of overcharge, a battery expansion suppression effect at high temperature, and the like. Representative examples of these other electrolyte additives may include at least one or more additives for forming an SEI film selected from the group consisting of cyclic carbonate-based compounds, halogen-substituted carbonate-based compounds, sultone-based compounds, sulfate-based compounds, phosphate-based compounds, borate-based compounds, nitrile-based compounds, benzene-based compounds, amine-based compounds, silane-based compounds and lithium salt-based compounds. Examples of the cyclic carbonate-based compound include vinylene carbonate (VC) or vinylethylene carbonate. Examples of the halogen-substituted carbonate-based compound include fluoroethylene carbonate (FEC). Examples of the sultone-based compound include at least one or more compounds selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone and 1-methyl-1,3-propene sultone. Examples of the sulfate-based compound include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS). Examples of the phosphate-based compound include one or more compounds selected from lithium difluoro (bisoxalato)phosphate, lithium difluorophosphate, tetramethyl trimethyl silyl phosphate, trimethyl silyl phosphite, tris(2,2,2-trifluoroethyl)phosphate, or tris(trifluoroethyl)phosphite. Examples of the borate-based compound include tetraphenylborate, lithium oxalyldifluoroborate (LiODFB), and lithium bisoxalatoborate (LiB(C2O4)2, LiBOB). Examples of the nitrile-based compound include at least one or more compounds selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile. Examples of the benzene-based compound include fluorobenzene, examples of the amine-based include triethanolamine, ethylene diamine, or the like, and examples of the silane-based compound include tetravinylsilane. The lithium salt-based compound is a compound different from the lithium salt included in the non-aqueous electrolyte, and examples thereof include lithium difluorophosphate (LiDFP), LiPO2F2, or the like. When a combination of vinylene carbonate (VC), 1,3-propane sultone (PS), ethylene sulfate (Esa), and lithium difluorophosphate (LiDFP) is additionally included in these other electrolyte additives, during the initial activation process of the secondary battery, a more solid SEI film may be formed on the surface of the negative electrode, and the high temperature stability of the secondary battery may be improved by suppressing the generation of gas which may be produced by the decomposition of the electrolyte at high temperature. Meanwhile, the other electrolyte additives may be used in mixtures of two or more thereof, and may be included in an amount of 0.01 to 20 wt %, specifically 0.01 to 10 wt %, and preferably 0.05 to 5 wt %, based on the total weight of the non-aqueous electrolyte. When the content of the other electrolyte additives is less than 0.01 wt %, the effect of improving the high temperature storage characteristics and high temperature life characteristics of the battery is insignificant, and when the content of the other electrolyte additives exceeds 20 wt %, side reactions in the electrolyte may occur excessively during charging and discharging of the battery. In particular, when the other electrolyte additives are added in an excessive amount, the additives are not sufficiently decomposed at high temperature, and thus may be present while being unreacted or precipitated in the electrolyte at room temperature. Accordingly, side reactions, in which the life or resistance characteristics of the secondary battery deteriorate, may occur. Lithium Secondary Battery The present disclosure also provides a lithium secondary battery including the non-aqueous electrolyte. Specifically, the lithium secondary battery includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and the above-described non-aqueous electrolyte. In this case, the lithium secondary battery of the present disclosure may be manufactured by a typical method known in the art. For example, after a positive electrode, a negative electrode and a separator between the positive electrode and the negative electrode are sequentially stacked to form an electrode assembly, the lithium secondary battery may be manufactured by inserting the electrode assembly into a battery case and injecting the non-aqueous electrolyte according to the present disclosure into the resultant. (1) Positive Electrode The positive electrode may be manufactured by coating a positive electrode current collector with a positive electrode including a positive electrode active material, a binder, a conductive material, a solvent, and the like. The positive electrode current collector is not particularly limited as long as the collector has conductivity without causing a chemical change to the battery, and for example, it is possible to use stainless steel; aluminum; nickel; titanium; calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, and the like. The positive electrode active material is a compound enabling reversible intercalation and deintercalation of lithium, and specifically, the positive electrode active material may include a lithium metal oxide including lithium and one or more metals such as cobalt, manganese, nickel or aluminum. More specifically, examples of the lithium metal oxide include a lithium-manganese-based oxide (for example, LiMnO2, LiMn2O4, and the like), a lithium-cobalt-based oxide (for example, LiCoO2, and the like), a lithium-nickel-based oxide (for example, LiNiO2, and the like), a lithium-nickel-manganese-based oxide (for example, LiNi1-YMnYO2(here, 0<Y<1), LiMn2-zNizO4(here, 0<Z<2), and the like), a lithium-nickel-cobalt-based oxide (for example, LiNi1-Y1CoY1O2(here, 0<Y1<1) and the like), a lithium-manganese-cobalt-based oxide (for example, LiCo1-Y2MnY2O2(here, 0<Y2<1), LiMn2−z1Coz1O4(here, 0<Z1<2), and the like), a lithium-nickel-manganese-cobalt-based oxide (for example, Li(NipCoqMnr1)O2(here, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Nip1Coq1Mnr2)O4(here, 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), and the like), or a lithium-nickel-cobalt-transition metal (M) oxide (for example, Li(Nip2Coq2Mnr3MS2)O2(here, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, p2, q2, r3, and s2 are each an atomic fraction of an independent element, and 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, and p2+q2+r3+s2=1), and the like), and the like, and among them, any one or two or more compounds may be included. Among them, in view of enhancing the capacity characteristics and stability of a battery, the lithium metal oxide may be LiCoO2, LiMnO2, LiNiO2, a lithium nickel manganese cobalt oxide (for example, Li(Ni1/3Mn1/3Co1/3)O2, Li(Ni0.6Mn0.2Co0.2)O2, Li(Ni0.5Mn0.3Co0.2)O2, Li(Ni0.7Mn0.15Co0.15)O2, Li(Ni0.5Mn0.1Co0.1)O2, and the like), a lithium nickel cobalt aluminum oxide (for example, Li(Ni0.5Co0.15Al0.05)O2, and the like), and the like, and in consideration of remarkable improvement effects caused by controlling the type and content ratio of constituent elements forming a lithium composite metal oxide, the lithium composite metal oxide may be Li(Ni0.6Mn0.2Co0.2)O2, Li(Ni0.5Mn0.3Co0.2)O2, Li(Ni0.7Mn0.15Co0.15)O2, Li(Ni0.5Mn0.1Co0.1)O2, and the like, and among them, any one or a mixture of two or more may be used. Among them, a positive electrode active material having a nickel content of 80 atm % or more among a total transition metal content may be used in that the capacity characteristics of the battery may be most enhanced. For example, the positive electrode active material may include a lithium transition metal oxide represented by the following [Chemical Formula 3]. LixNiaCobM1cM2dO2[Chemical Formula 3] In Chemical Formula 3, M1is one or more selected from Mn or Al, and may be preferably Mn or a combination of Mn and Al. M2may be one or more selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P and S. x represents an atomic fraction of lithium in the lithium transition metal oxide, and may be 0.90≤x≤1.1, preferably 0.95≤x≤1.08, and more preferably 1.0≤x≤1.08. a represents an atomic fraction of nickel among the metal elements except for lithium in the lithium transition metal oxide, and may be 0.80≤a<1.0, preferably 0.80≤a≤0.95, and more preferably 0.80≤a≤0.90. When the nickel content satisfies the above range, high capacity characteristics may be implemented. b represents an atomic fraction of cobalt among the metal elements except for lithium in the lithium transition metal oxide, and may be 0<b<0.2, 0<b≤0.15, or 0.01≤b≤0.10. c represents an atomic fraction of M1among the metal elements except for lithium in the lithium transition metal oxide, and may be 0<c<0.2, 0<c≤0.15, or 0.01≤c≤0.10. d represents an atomic fraction of M2among the metal elements except for lithium in the lithium transition metal oxide, and may be 0≤d≤0.1, or 0≤d≤0.05. The positive electrode active material may be included in an amount of 60 to 99 wt %, preferably 70 to 99 wt %, and more preferably 80 to 98 wt %, based on the total weight of the solid content in the positive electrode mixture slurry. The binder is a component that assists in the binding between the active material and the conductive material, and the like and the binding to the current collector. Examples of such a binder include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene, sulfonated ethylene-propylene-diene, styrene-butadiene rubber, fluororubber, various copolymers thereof, and the like. Typically, the binder may be included in an amount of 1 to 20 wt %, preferably 1 to 15 wt %, and more preferably 1 to 10 wt %, based on the total weight of the solid content in the positive electrode mixture slurry. The conductive material is a component for further improving the conductivity of the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change to the battery, and it is possible to use, for example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite; conductive fibers such as carbon fibers, carbon nanotubes, or metal fibers; carbon fluoride powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, or the like. Typically, the conductive material may be included in an amount of 1 to 20 wt %, preferably 1 to 15 wt %, and more preferably 1 to 10 wt %, based on the total weight of the solid content in the positive electrode mixture slurry. The solvent may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount to obtain a preferred viscosity when including the positive electrode active material, and selectively, a binder, a conductive material, and the like. For example, the solvent may be included such that the concentration of the solid content including the positive electrode active material, and optionally the binder and the conductive material is 50 to 95 wt %, preferably 70 to 90 wt %, and more preferably 70 to 90 wt %. (2) Negative Electrode The negative electrode may be manufactured, for example, by coating a negative electrode current collector with a negative electrode mixture slurry including a negative electrode active material, a binder, a conductive material, a solvent, and the like, or a graphite electrode made of carbon (C) or a metal itself may be used as a negative electrode. For example, when a negative electrode is manufactured by coating the negative electrode current collector with a negative electrode mixture slurry, the negative electrode current collector generally has a thickness of 3 to 500 μm. The negative electrode current collector is not particularly limited as long as the negative electrode current collector has high conductivity without causing a chemical change to the battery, and for example, it is possible to use copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, and the like, an aluminum-cadmium alloy, and the like. In addition, similar to the positive electrode collector, the adhesion of a negative electrode active material may also be increased by forming fine irregularities on a surface of the negative electrode collector and the collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foaming body, and a nonwoven body. Furthermore, the negative electrode active material may include at least one or more selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating/deintercalating lithium ions, metals or alloys of these metals and lithium, metal composite oxides, a material capable of doping and dedoping lithium, and transition metal oxides. As the carbon material capable of reversibly intercalating/deintercalating lithium ions, any carbon-based negative electrode active material generally used in lithium ion secondary batteries may be used without particular limitation, and as a representative example thereof, crystalline carbon, amorphous carbon or a combination thereof may be used. Examples of the crystalline carbon include graphite such as amorphous, plate, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low temperature calcined carbon), hard carbon, mesophase pitch carbide, calcined coke, and the like. As the metals or alloys of these metals and lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn or an alloy of these metals and lithium may be used. As the metal composite oxide, it is possible to use those selected from the group consisting of PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, LixFe2O3(0≤x≤1), LixWO2(0≤x≤1) and SnxMe1-xMe′yOz(Me: Mn, Fe, Pb, Ge; Me′: Al, B, P, Si, Group 1, Group 2 and Group 3 elements of the Periodic Table, and a halogen; 0≤x≤1; 1≤y≤3; and 1≤z≤8). Examples of the material capable of doping and dedoping lithium include Si, SiOx(0<x≤2), a Si—Y alloy (Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements and combinations thereof, and is not Si), Sn, SnO2, Sn—Y (Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements and combinations thereof, and is not Sn) and the like, and at least one of them and SiO2may also be mixed and used. The element Y may be selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, dubnium (Db), Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po and a combination thereof. Examples of the transition metal oxide include a lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, and the like. The negative electrode active material may be included in an amount of 60 to 99 wt %, preferably 70 to 99 wt %, and more preferably 80 to 98 wt %, based on the total weight of the solid content in the negative electrode mixture slurry. The binder is a component that assists in the binding among the active material, the active material, and the current collector. Examples of such a binder include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, an ethylene-propylene-diene monomer, a sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, various copolymers thereof, and the like. Typically, the binder may be included in an amount of 1 to 20 wt %, preferably 1 to 15 wt %, and more preferably 1 to 10 wt %, based on the total weight of the solid content in the negative electrode mixture slurry. The conductive material is a component that further improves the conductivity of the negative electrode active material, and is not particularly limited as long as it has conductivity without causing a chemical change to the battery, and it is possible to use, for example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite; conductive fibers such as carbon fibers, carbon nanotubes, or metal fibers; carbon fluoride powder; conductive powders such as aluminum powder and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, or the like. The conductive material may be included in an amount of 1 to 20 wt %, preferably 1 to 15 wt %, and more preferably 1 to 10 wt %, based on the total weight of the solid content in the negative electrode mixture slurry. The solvent may include water or an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount to obtain a preferred viscosity when including the negative electrode active material, and selectively, a binder, a conductive material, and the like. For example, the solvent may be included such that the concentration of the solid content including the negative electrode active material and optionally the binder and the conductive material is 50 wt % to 95 wt %, preferably 70 wt % to 90 wt %. When a metal itself is used as the negative electrode, the negative electrode may be manufactured by a method of physically bonding, rolling or depositing the metal on a metal thin film itself or the negative electrode current collector. As the deposition method, an electrical deposition method or chemical vapor deposition method for metal may be used. For example, the metal bonded/rolled/deposited on the metal thin film itself or the negative electrode current collector may include one metal or an alloy of two metals selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu) and indium (In). (3) Separator Further, as a separator, a typical porous polymer film used as a separator in the related art, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer and an ethylene/methacrylate copolymer may be used either alone or a laminate thereof can be used, or a typical porous nonwoven fabric, for example, a nonwoven fabric made of high-melting point glass fiber, polyethylene terephthalate fiber, and the like may be used, but the separator is not limited thereto. Furthermore, a coated separator including a ceramic component or a polymeric material may be used to secure heat resistance or mechanical strength and may be optionally used in a single-layered or multi-layered structure. The external shape of the lithium secondary battery of the present disclosure is not particularly limited, but may be a cylindrical type using a can, a prismatic type, a pouch type, or a coin type. Hereinafter, the present disclosure will be described in more detail through specific Examples. However, the following Examples are merely examples for facilitating the understanding of the present disclosure, and do not limit the scope of the present disclosure. Of course, it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and technical spirit of the present disclosure, and such changes and modifications also fall within the scope of the appended claims. EXAMPLES Example 1 (Preparation of Non-Aqueous Electrolyte) A non-aqueous solvent was prepared by dissolving LiPF6, vinylene carbonate (VC), 1,3-propane sultone (PS), ethylene sulfate (Esa) and lithium difluorophosphate (LiDFP) in an organic solvent (volume ratio of ethylene carbonate (EC):ethyl methyl carbonate (EMC)=3:7) such that LiPF6, vinylene carbonate (VC), 1,3-propane sultone (PS), ethylene sulfate (Esa) and lithium difluorophosphate (LiDFP) were 1.0 M, 0.5 wt %, 0.5 wt %, 1.0 wt % and 0.8 wt %, respectively, and a non-aqueous electrolyte was prepared by putting 0.1 g of 7-ethynylcoumarin (compound of Chemical Formula 2-1) into 99.9 g of the non-aqueous solvent. (Manufacture of Lithium Secondary Battery) A positive electrode mixture slurry (75.5 wt % solid content) was prepared by adding a positive electrode active material (LiNi0.85Co0.05Mn0.07Al0.03O2), a conductive material (carbon nanotubes) and a binder (polyvinylidene fluoride) at a weight ratio of 98.0:0.7:1.3 to N-methyl-2-pyrrolidone (NMP) which is a solvent. A positive electrode was manufactured by applying the positive electrode mixture slurry to one surface of a positive electrode current collector having a thickness of 12 m and drying and roll-pressing the resultant. A negative electrode mixture slurry (50 wt % solid content) was prepared by adding a negative electrode active material (artificial graphite), a conductive material (carbon black) and a binder (styrene-butadiene rubber) at a weight ratio of 96.5:1.5:2.0 to distilled water which is a solvent. A negative electrode was manufactured by applying the negative electrode mixture slurry to one surface of a negative electrode current collector (Cu thin film) having a thickness of 8 m and drying and roll-pressing the resultant. After a polyethylene porous film separator was interposed between the positive electrode and the negative electrode prepared above in a dry room, a secondary battery was manufactured by injecting the prepared non-aqueous electrolyte. Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by putting 0.3 g of 7-ethynylcoumarin (compound of Chemical Formula 2-1) into 99.7 g of the non-aqueous solvent prepared in Example 1. Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by putting 0.5 g of 7-ethynylcoumarin (compound of Chemical Formula 2-1) into 99.5 g of the non-aqueous solvent prepared in Example 1. Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared by putting 1.0 g of 7-ethynylcoumarin (compound of Chemical Formula 2-1) into 99.0 g of the non-aqueous solvent prepared in Example 1. Example 5 A secondary battery was manufactured in the same manner as in Example 2, except that a non-aqueous electrolyte was prepared by putting 0.3 g of 7-(Propargyloxy)coumarin (compound of Chemical Formula 2-6) instead of 0.3 g of 7-ethynylcoumarin (compound of Chemical Formula 2-1) into 99.7 g of the non-aqueous solvent prepared in Example 2. Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that a non-aqueous electrolyte was prepared using 100 g of the non-aqueous solvent prepared in Example 1. Experimental Example 1—Evaluation of High Temperature Cycle Characteristics For each of the secondary batteries manufactured in Examples 1 to 5 and Comparative Example 1, cycle characteristics were evaluated. Specifically, after 100 cycles of charging and discharging were performed by setting the charging and discharging of each of the batteries manufactured in Examples 1 to 5 and Comparative Example 1 to 4.2 V at a constant current of 0.33 C and to 3.0 V at a constant current of 0.33 C, respectively, at 45° C. as 1 cycle, a capacity retention rate compared to the initial capacity after 100 cycles was measured. The results are shown in the following Table 1. TABLE 1Capacity retention rate (%)Example 194.2Example 293.8Example 393.1Example 489.7Example 595.3Comparative87.8Example 1 As shown in Table 1, it could be confirmed that Examples 1 to 5 using the additive for a non-aqueous electrolyte of the present disclosure had excellent life characteristics due to a high capacity retention rate compared to Comparative Example 1 not using the additive. Experimental Example 2—Evaluation of High Temperature Storage Characteristics For each of the secondary batteries manufactured in Examples 1 to 5 and Comparative Example 1, high temperature storage characteristics were evaluated. Specifically, each of the secondary batteries in Examples 1 to 5 and Comparative Example 1 was fully charged to 4.2 V, and then stored at 60° C. for 8 weeks. Before the secondary battery was stored, the thickness of the cell body portion of the fully charged secondary battery was measured using a flat plate measuring device and set as a thickness of the initial secondary battery. After 8 weeks, a thickness increased during the storage period of 8 weeks was calculated by again measuring the thickness of the cell body portion for the stored secondary battery using a flat plate measuring device. A rate of increase in thickness after 8 weeks was derived by calculating a percentage ratio of increase in thickness to the initial thickness of the secondary battery. The results are shown in the following Table 2. TABLE 2Rate of increase in thickness (%)Example 125.0Example 222.1Example 319.6Example 417.3Example 525.2Comparative32.7Example 1 As shown in Table 2, it could be confirmed that the secondary batteries of Examples 1 to 5 had a smaller rate of increase in thickness, and thus less gas generation at high temperature after 4 weeks than the secondary battery of Comparative Example 1. The compound represented by Chemical Formula 1 provided as the additive for a non-aqueous electrolyte of the present disclosure is a compound based on a coumarin structure, and can form a stable solid electrolyte interphase (SEI) film on the surface of the negative electrode while being rapidly reduced and decomposed during charging and discharging. Therefore, the degradation of the negative electrode can be prevented by suppressing a reduction in the passivation ability of SEI at high temperature. Further, a reactive oxygen compound generated at a positive electrode including a high-nickel positive electrode active material and the coumarin structure contained in the compound represented by Chemical Formula 1 are bonded to each other to have an effect of suppressing the decomposition of the electrolyte and the generation of gas. In addition, the compound represented by Chemical Formula 1 provided as the additive for a non-aqueous electrolyte of the present disclosure can form a dense film on the electrode by additionally including an aliphatic unsaturated hydrocarbon in the coumarin structure. This has an effect of suppressing the degradation caused by an interfacial reaction at high temperature. Therefore, since an electrode-electrolyte interface, which is stable and has low resistance even at high temperature, is formed when the non-aqueous electrolyte of the present disclosure including the compound of Chemical Formula 1 is used, high temperature cycle characteristics and high temperature storage characteristics are improved, and thus a lithium secondary battery with improved overall performance can be implemented. | 42,045 |
11862765 | DESCRIPTION OF EMBODIMENTS The invention will be specifically described hereinbelow. The electrolyte solution of the invention contains a fluorinated ether represented by the following formula (1): R11—(OR12)n11—O—R13 wherein R11and R13are the same as or different from each other, and are each an alkyl group optionally containing a fluorine atom, with at least one of R11or R13containing a fluorine atom; R12is an alkylene group optionally containing a fluorine atom; and n11 is 0, 1, or 2. Preferably, n11 is 0. The alkyl group is preferably a C1-C10 alkyl group, more preferably a C1-C5 alkyl group, still more preferably includes at least one selected from the group consisting of —CH3, —C2H5, —C3H7, —C4H9, —CF2CF2H, —CH2CF3, —CF2CF3, —CH2CF2CF2H, —CH2CF2CF3, —CF2CHFCF3, and —CF2CF2CF3. The alkyl group may be linear or branched. The alkylene group is preferably a C1-C3 alkylene group, more preferably includes at least one selected from the group consisting of —CH2CH2— and —CF2CF2—. When n11 is 2, the two alkylene groups for R12s may be the same as or different from each other. The alkylene group may be linear or branched. The fluorinated ether preferably includes at least one selected from the group consisting of HCF2CF2CH2OCF2CHFCF3, HCF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CHFCF3, CF3CF2CH2OCF2CF2H, HCF2CF2OC2H5, HCF2CF2OC3H7, HCF2CF2OC4H9, CF3CHFCF2OC2H5, and CF3CH2OCH2CH2OCH3. In order to achieve much better cycle performance and a much lower overvoltage, the electrolyte solution preferably contains the fluorinated ether in an amount of 0.001 to 60% by mass relative to the electrolyte solution. The amount of the fluorinated ether is more preferably 5% by mass or more, still more preferably 10% by mass or more, particularly preferably 20% by mass or more, while more preferably 50% by mass or less, still more preferably 40% by mass or less. In order to achieve much better cycle performance and a much lower overvoltage, the electrolyte solution preferably further contains at least one selected from the group consisting of a fluorinated saturated cyclic carbonate, a fluorinated acyclic carbonate, and a fluorinated ester. In order to achieve much better cycle performance and a much lower overvoltage, the electrolyte solution preferably contains at least one selected from the group consisting of a fluorinated saturated cyclic carbonate, a fluorinated acyclic carbonate, and a fluorinated ester in an amount of 0.001 to 99.999% by mass relative to the electrolyte solution. The amount thereof is more preferably 30% by mass or more, still more preferably 40% by mass or more, particularly preferably 50% by mass or more, while more preferably 95% by mass or less, still more preferably 90% by mass or less, particularly preferably 80% by mass or less, most preferably 60% by mass or less. The fluorinated saturated cyclic carbonate is preferably one represented by the following formula (2): wherein R21to R24are the same as or different from each other, and are each —H, —CH3, —F, a fluorinated alkyl group optionally containing an ether bond, or a fluorinated alkoxy group optionally containing an ether bond, with at least one of R21to R24being —F, a fluorinated alkyl group optionally containing an ether bond, or a fluorinated alkoxy group optionally containing an ether bond. The “ether bond” as used herein means a bond represented by —O—. The fluorinated alkyl group is preferably one containing 1 to 10 carbon atoms, more preferably one containing 1 to 6 carbon atoms, still more preferably one containing 1 to 4 carbon atoms. The fluorinated alkyl group may be linear or branched. The fluorinated alkoxy group is preferably one containing 1 to 10 carbon atoms, more preferably one containing 1 to 6 carbon atoms, still more preferably one containing 1 to 4 carbon atoms. The fluorinated alkoxy group may be linear or branched. R21to R24are the same as or different from each other, and preferably include at least one selected from the group consisting of —H, —CH3, —F, —CF3, —C4F9, —CHF2, —CH2F, —CH2CF2CF3, —CH2—CF(CF3)2, —CH2—O—CH2CHF2F2H, —CH2CF3, and —CF2CF3. In this case, at least one of R21to R24includes at least one selected from the group consisting of —F, —CF3, —C4F9, —CHF2, —CH2F, —CH2CF2CF3, —CH2—CF(CF3)2, —CH2—O—CH2CHF2F2H, —CH2CF3, and —CF2CF3. The fluorinated saturated cyclic carbonate preferably includes at least one selected from the group consisting of the following compounds. The fluorinated acyclic carbonate is preferably one represented by the following formula (3): wherein R31and R32are the same as or different from each other, and are each an alkyl group optionally containing an ether bond and optionally containing a fluorine atom, with at least one of R31or R32containing a fluorine atom. The alkyl group is preferably one containing 1 to 10 carbon atoms, more preferably one containing 1 to 6 carbon atoms, still more preferably one containing 1 to 4 carbon atoms. The alkyl group may be linear or branched. R31and R32are the same as or different from each other, and preferably include at least one selected from the group consisting of —CH3, —CF3, —CHF2, —CH2F, —C2H5, —CH2CF3, —CH2CHF2, and —CH2CF2CF2H. In this case, at least one of R31or R32includes at least one selected from the group consisting of —CF3, —CHF2, —CH2F, —CH2CHF2, —CH2CF3, and —CH2CF2CF2H. The fluorinated acyclic carbonate preferably includes at least one selected from the group consisting of the following compounds. The fluorinated ester is preferably one represented by the following formula (4): wherein R41and R42are the same as or different from each other, are each an alkyl group optionally containing an ether bond and optionally containing a fluorine atom, and optionally bind to each other to form a ring, with at least one of R41or R42containing a fluorine atom. The alkyl group is preferably one containing 1 to 10 carbon atoms, more preferably one containing 1 to 6 carbon atoms, still more preferably one containing 1 to 4 carbon atoms. The alkyl group may be linear or branched. R41and R42are the same as or different from each other, and preferably include at least one selected from the group consisting of —CH3, —C2H5, —CHF2, —CH2F, —CH(CF3)2, —CHFCF3, —CF3, and —CH2CF3. In this case, at least one of R41or R42includes at least one selected from the group consisting of —CHF2, —CH(CF3)2, —CHFCF3, —CF3, and —CH2CF3. The expression “R41and R42bind to each other to form a ring” means that R41and R42form a ring together with the carbon atom and the oxygen atom to which R41and R42respectively bind, and R41and R42constitute parts of the ring as fluorinated alkylene groups. When R41and R42bind to each other to form a ring, R4′and R42preferably include at least one selected from the group consisting of —CH2CH2CH(CH2CF3)—, —CH(CF3) CH2CH2—, —CHFCH2CH2—, —CH2CH2CHF—, and —CH2CH2CH(CF3)—. The fluorinated ester preferably includes at least one selected from the group consisting of the following compounds. The electrolyte solution may further contain any of a non-fluorinated ether, a non-fluorinated saturated cyclic carbonate, a non-fluorinated acyclic carbonate, a non-fluorinated acyclic ester, a non-fluorinated cyclic ester, an unsaturated cyclic carbonate, polyethylene oxide, an overcharge inhibitor, an aid, a nitrogen-containing compound, a boron-containing compound, an organosilicon-containing compound, a fireproofing agent (a flame retarder), a surfactant, an additive for giving high dielectricity, a cycle performance improver, a rate performance improver, and an ion conductive compound. Examples of the non-fluorinated ether include 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and 4-methyl-1,3-dioxolane. Examples of the non-fluorinated saturated cyclic carbonate include ethylene carbonate, propylene carbonate, and butylene carbonate. Examples of the non-fluorinated acyclic carbonate include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate, isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, and t-butyl ethyl carbonate. In order to achieve much better cycle performance and a much lower overvoltage, the electrolyte solution preferably contains the fluorinated ether and at least one selected from the group consisting of the fluorinated saturated cyclic carbonate, the fluorinated acyclic carbonate, and the fluorinated ester in an amount of 75% by mass or more in total relative to the electrolyte solution. The amount thereof is more preferably 80% by mass or more, still more preferably 85% by mass or more. The upper limit thereof may be 100% by mass. The electrolyte solution is preferably a non-aqueous electrolyte solution. The electrolyte solution preferably further contains an electrolyte salt. The electrolyte salt to be used may be any of those to be used for the electrolyte solution, such as a lithium salt, an ammonium salt, and a metal salt as well as a liquid salt (ionic liquid), an inorganic polymer form salt, and an organic polymer form salt. The electrolyte salt is preferably a lithium salt. Any lithium salt may be used. Specific examples thereof include the following:inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, LiTaF6, and LiWF7;lithium tungstates such as LiWOF5;lithium carboxylates such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, and CF3CF2CF2CF2CO2Li;lithium sulfonates such as FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, CF3SO3Li, CF3CF2SO3Li, CF3CF2CF2SO3Li, and CF3CF2CF2CF2SO3Li;lithium imide salts such as LiN(FCO)2, LiN(FCO) (FSO2), LiN(FSO2)2, LiN(FSO2) (CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, and LiN(CF3SO2) (C4F9SO2);lithium methide salts such as LiC(FSO2)3, LiC(CF3SO2)3, and LiC(C2F5SO2)3;lithium oxalatoborates such as lithium difluorooxalatoborate and lithium bis(oxalato)borate;lithium oxalatophosphates such as lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)phosphate, and lithium tris(oxalato)phosphate; andfluorine-containing organic lithium salts such as salts represented by the formula: LiPFa(CnF2n+1)6-a(wherein a is an integer of 0 to 5; and n is an integer of 1 to 6) (e.g., LiPF4(CF3)2, LiPF4(C2F5)2), LiPF4(CF3SO2)2, LiPO2F2, LiPF4(C2F5SO2)2, LiBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2. Preferred among these are LiPF6, LiBF4, LiSbF6, LiTaF6, FSO3Li, CF3SO3Li, LiN(FSO2)2, LiN(FSO2) (CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropanedisulfonylimide, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate, lithium difluorobis(oxalato)phosphate, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, and LiPF3(C2F5)3. More preferred is at least one selected from the group consisting of LiPF6, LiBF4, LiN(CF3SO2)2and LiN(C2F5SO2)2. The electrolyte salt in the electrolyte solution may have any concentration that does not impair the effects of the invention. In order to make the electric conductivity of the electrolyte solution within a favorable range and to ensure good battery performance, the lithium in the electrolyte solution preferably has a total mole concentration of 0.3 mol/L or higher, more preferably 0.4 mol/L or higher, still more preferably 0.5 mol/L or higher, while preferably 4 mol/L or lower, more preferably 2.5 mol/L or lower, still more preferably 1.5 mol/L or lower. The electrolyte solution of the invention is an electrolyte solution for an alkali metal-sulfur-based secondary battery that includes a positive electrode containing a carbon composite material that contains a carbon material and a sulfur-containing positive electrode active material. Examples of the positive electrode active material include those containing a sulfur atom. Preferred is at least one selected from the group consisting of simple sulfur, a metal sulfide, a metal polysulfide, an organic polysulfide, and an organosulfur compound. More preferred is simple sulfur. An example of a sulfur-based metal sulfide is Li2Sx(wherein 0<x≤8). An example of a sulfur-based metal polysulfide is MSx(wherein M=Ni, Cu, or Fe, 0<x≤2). Examples of the organosulfur compound include an organic polysulfide, an organic disulfide compound, and a carbon sulfide compound. In order to achieve much better cycle performance and a much lower overvoltage, the amount of the sulfur contained in the positive electrode active material in the carbon composite material is preferably 40 to 99% by mass, more preferably 50% by mass or more, still more preferably 60% by mass or more, while more preferably 90% by mass or less, still more preferably 85% by mass or less, relative to the carbon composite material. In the case of using simple sulfur as the positive electrode active material, the amount of the sulfur contained in the positive electrode active material is equal to the amount of the simple sulfur. The amount of the sulfur can be determined by measuring the weight change under heating from room temperature to 600° C. at a temperature-increasing rate of 10° C./m in a helium atmosphere. In order to achieve much better cycle performance and a much lower overvoltage, the amount of the carbon material in the carbon composite material is preferably 1 to 60% by mass, more preferably 10% by mass or more, still more preferably 15% by mass or more, while more preferably 45% by mass or less, still more preferably 40% by mass or less, relative to the positive electrode active material. The carbon material includes pores. The “pores” as used herein include micropores, mesopores, and macropores. The micropores mean pores having a diameter of 0.1 nm or greater and smaller than 2 nm. The mesopores mean pores having a diameter of greater than 2 nm and 50 nm or smaller. The macropores mean pores having a diameter of greater than 50 nm. The carbon material particularly used in the invention is a carbon material having a pore volume ratio (micropores/mesopores) of 1.5 or higher, the pore volume ratio being the ratio of the pore volume of the micropores to the pore volume of the mesopores. The pore volume ratio is more preferably 2.0 or higher. The upper limit of the pore volume ratio may be, but is not limited to, 3.0 or lower. The presence of the pores in the carbon material is presumed to greatly reduce dissolution of the positive electrode active material. The pore volume does not take the macropore volume into account. The BET specific surface area, the average pore diameter, and the pore volume in the invention can be determined using a nitrogen adsorption isotherm obtained by allowing a sample (carbon material, carbon composite material) to adsorb nitrogen gas at the liquid nitrogen temperature. Specifically, the nitrogen adsorption isotherm may be used to determine the BET specific surface area of the sample by the Brenauer-Emmet-Telle (BET) method, and to determine the average pore diameter and pore volume of the sample by the quenched solid density functional theory (QSDFT). For example, these values may be measured using as a measurement device a specific surface area/pore distribution measurement device (Autosorb) available from Quantachrome Instruments. In order to achieve much better cycle performance and a much lower overvoltage, the positive electrode active material is preferably contained in the pores of the carbon material in the carbon composite material. The presence of the positive electrode active material in the pores is presumed to greatly reduce dissolution of the positive electrode active material. The presence of the positive electrode active material in the pores can be confirmed by measuring the BET specific surface area of the carbon composite material. The presence of the positive electrode active material in the pores causes the BET specific surface area of the carbon composite material to be smaller than the BET specific surface area of the carbon material alone. The carbon material is preferably a porous carbon including macropores and mesopores. In order to achieve much better cycle performance and a much lower overvoltage, the carbon material preferably has a BET specific surface area of 500 to 2500 m2/g. The BET specific surface area is more preferably 700 m2/g or larger and 2000 m2/g or smaller. In order to achieve much better cycle performance and a much lower overvoltage, the carbon material preferably has an average particle size of 1 to 50 nm. The average particle size is more preferably 2 nm or greater and 30 nm or smaller. The carbon material may be produced by any production method, such as a method in which a composite of a readily degradable polymer and a not readily degradable (thermosetting) organic component is formed, and then the readily degradable polymer is removed from the composite. For example, the carbon material may be produced by preparing a regularly nanostructured polymer utilizing an organic-organic interaction between a phenol resin and a thermally degradable polymer, and then carbonizing the regularly nanostructured polymer. The carbon composite material may be produced by any production method, such as a method in which the positive electrode active material is vaporized and allowed to deposit on the carbon material. The deposits may be heated at about 150° C., so that an excessive portion of the positive electrode active material may be removed. The positive electrode may further contain any other components such as a binding agent, a thickening agent, and a conductive aid. The binding agent may be any material that is stable against the electrolyte solution and a solvent used in electrode production. Examples of the binding agent include resin-type polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, chitosan, alginic acid, polyacrylic acid, polyimide, cellulose, and nitrocellulose; rubber-type polymers such as styrene-butadiene rubber (SBR), isoprene rubber, butadiene rubber, fluoroelastomers, acrylonitrile-butadiene rubber (NBR), and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers and hydrogenated products thereof; thermoplastic elastomer-type polymers such as ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-butadiene-styrene copolymers, styrene-isoprene-styrene block copolymers, and hydrogenated products thereof; soft resin-type polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride copolymers, polyvinylidene fluoride, and tetrafluoroethylene-ethylene copolymers; and polymer compositions having an ion conductivity for an alkali metal ion (especially a lithium ion). These may be used alone or may be used in any combination of two or more at any ratio. Examples of the thickening agent include carboxymethyl cellulose, methyl cellulose, and polyvinylpyrrolidone. Examples of the conductive aid include particulate carbon, fibrous carbon, graphite, activated carbon, metal, metal compounds such as cobalt oxyhydroxide, and carbon-metal composites. Examples of the particulate carbon include carbon black, graphite, expanded graphite, porous carbon, carbon nanotube, carbon nanohorn, and Ketjenblack. The positive electrode may further include a positive electrode current collector. The positive electrode current collector may be produced from any material. Any known material may be used. Specific examples thereof include metal materials such as aluminum, stainless steel, nickel-plated metal, titanium, and tantalum; and carbon materials such as carbon cloth and carbon paper. Preferred among these are metal materials, in particular aluminum. In the case of a metal material, the current collector may be in the form of metal foil, metal cylinder, metal coil, metal plate, metal film, expanded metal, punched metal, or metal foam, for example. In the case of a carbon material, the current collector may be in the form of carbon plate, carbon film, or carbon cylinder, for example. The positive electrode may be produced by forming, on the positive electrode current collector, a positive electrode active material layer containing the carbon composite material and optionally other components. The positive electrode active material layer may be formed by, for example, a method in which the carbon composite material and optionally components such as a binding agent and a thickening agent are mixed in a dry manner to provide a sheet, and this sheet is press-bonded to the positive electrode current collector, or a method in which these components are dissolved or dispersed in a liquid medium to provide slurry, and this slurry is applied to the positive electrode current collector and then dried. A solvent to form the slurry may be any solvent that can dissolve or disperse the carbon composite material and other materials. Either an aqueous medium or an organic medium may be used. Examples of the aqueous medium include water and a solvent mixture of an alcohol and water. Examples of the organic medium include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methyl naphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethyl formamide, and dimethyl acetamide; and aprotic polar solvents such as hexamethylphosphoramide and dimethyl sulfoxide. The amount of the carbon composite material in the positive electrode active material layer is preferably 40 to 99.5% by mass, more preferably 60% by mass or more, still more preferably 80% by mass or more, while more preferably 98% by mass or less, still more preferably 97% by mass or less, relative to the positive electrode active material layer. The amount of the positive electrode active material in the positive electrode active material layer is preferably 20 to 90% by mass, more preferably 30% by mass or more, still more preferably 40% by mass or more, while more preferably 87% by mass or less, still more preferably 85% by mass or less, relative to the positive electrode active material layer. The positive electrode current collector and the positive electrode active material layer may have any thickness ratio, and the ratio (thickness of positive electrode active material layer on one side before injection of electrolyte solution)/(thickness of current collector) is preferably 20 or lower, more preferably 15 or lower, most preferably 10 or lower. The lower limit thereof is preferably 0.5 or higher, more preferably 0.8 or higher, most preferably 1 or higher. A ratio exceeding this range may cause the current collector to generate heat due to Joule's heat during high-current-density charge and discharge. A ratio below this range may cause an increase in the volume ratio of the positive electrode current collector to the positive electrode active material, reducing the capacity of the battery. The alkali metal-sulfur-based secondary battery may further include a negative electrode. The invention also relates to an alkali metal-sulfur-based secondary battery including the positive electrode, the negative electrode, and the electrolyte solution. The alkali metal-sulfur-based secondary battery preferably exhibits a single main discharge plateau on and after the second cycle, and a reaction accompanied by Li2S8represents 5% or less of all discharge reactions. The number of discharge plateaux can be confirmed by a discharge curve on and after the second cycle obtained using the alkali metal-sulfur-based secondary battery. Each cycle is composed of charge at 25° C. at a constant current corresponding to 0.1 C until 3.0 V and discharge at a constant current of 0.1 C until 1.0 V. The proportion of discharge owing to the reaction accompanied by Li2S8can be determined by the following formula based on the capacity (1) in a discharge plateau region generated around 2.2 V owing to the reaction accompanied by Li2S8and the capacity (2) in a discharge plateau region generated at and below 2.0 V owing to the other reactions in the second cycle discharge curve. Li2S8discharge proportion (%)=capacity (1)/(capacity(1)+capacity(2))×100 The negative electrode may contain a negative electrode active material. Examples of the negative electrode active material include a carbonaceous material, an alloyed material, and a lithium-containing metal composite oxide material. The alloyed material to be used as the negative electrode active material may be any of those capable of occluding and releasing lithium, without limitation, including simple lithium, a simple metal and an alloy constituting a lithium alloy, and compounds such as oxides, carbides, nitrides, silicides, sulfides, and phosphides thereof. The simple metal and alloy constituting a lithium alloy are preferably materials containing a metal or semimetal element (i.e., excluding carbon) of the Group 13 or 14, more preferably a simple metal of aluminum, silicon, or tin (hereinafter, also abbreviated as a “specific metal element”) or an alloy or compound containing any of these atoms. These may be used alone, or may be used in any combination of two or more at any ratio. The negative electrode may further include a negative electrode current collector. The negative electrode current collector may be produced from any material. Any known material may be used. Specific examples thereof include metal materials such as aluminum, copper, titanium, nickel, stainless steel, and nickel-plated steel. In the case of a metal material, the negative electrode current collector may be in the form of metal foil, metal cylinder, metal coil, metal plate, metal film, expanded metal, punched metal, or metal foam, for example. The negative electrode may be produced by forming, on the negative electrode current collector, a negative electrode active material layer containing the negative electrode active material and optionally other components. The negative electrode may be formed by, for example, mixing the negative electrode active material with materials such as a binding agent, a solvent, a thickening agent, a conductive material, and filler to provide slurry, applying this slurry to the negative electrode current collector, and then drying and pressing the workpiece. In the case of an alloyed material, vapor deposition, sputtering, plating, or the like may be used to form a film layer containing the negative electrode active material (negative electrode active material layer). The negative electrode active material layer having a predetermined shape (e.g., a rectangular or circular shape) may also be punched from lithium foil. The negative electrode current collector and the negative electrode active material layer may have any thickness ratio, and the ratio (thickness of negative electrode active material layer on one side before injection of electrolyte solution)/(thickness of current collector) is preferably 150 or lower, still more preferably 20 or lower, particularly preferably 10 or lower, while preferably 0.1 or higher, still more preferably 0.4 or higher, particularly preferably 1 or higher. A ratio of the thicknesses between the negative electrode current collector and the negative electrode active material layer exceeding the above range may cause the current collector to generate heat due to Joule's heat during high-current-density charge and discharge. A ratio below the above range may cause an increase in the volume ratio of the negative electrode current collector to the negative electrode active material, reducing the capacity of the battery. The alkali metal-sulfur-based secondary battery may further include a separator. A separator is usually placed between the positive electrode and the negative electrode to prevent a short circuit. In this case, this separator is impregnated with the electrolyte solution. The separator may be formed from any material and may have any shape. Any known material and shape may be applicable as long as they do not significantly impair the effects of the invention. Particularly used is resin, glass fiber, an inorganic substance, or the like formed from a material stable against the electrolyte solution. Preferred is one in the form of porous sheet or nonwoven fabric having excellent liquid retention. Examples of materials of a resin or glass fiber separator include polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and glass filters. Preferred among these are glass filters and polyolefins, still more preferred are polyolefins. These materials may be used alone, or may be used in any combination of two or more at any ratio. The separator may have any thickness that is usually 1 μm or greater, preferably 5 μm or greater, still more preferably 8 μm or greater, while usually 50 μm or smaller, preferably 40 μm or smaller, still more preferably 30 μm or smaller. The separator having a thickness very smaller than the above range may cause reduced insulation and mechanical strength. The separator having a thickness very greater than the above range may cause not only reduced battery performance such as rate performance, but also a reduced energy density of the battery. In the case of using porous one such as a porous sheet or nonwoven fabric as the separator, the separator may have any porosity that is usually 20% or higher, preferably 35% or higher, still more preferably 45% or higher, while usually 90% or lower, preferably 85% or lower, still more preferably 75% or lower. A porosity very lower than the above range tends to cause a high membrane resistance, resulting in poor rate performance. A porosity very higher than the above range tends to cause reduced mechanical strength of the separator, resulting in poor insulation. The separator may also have any average pore size that is usually 0.5 μm or smaller, preferably 0.2 μm or smaller, while usually 0.05 μm or greater. An average pore size exceeding the above range may easily cause a short circuit. An average pore size below the above range may cause a high membrane resistance, resulting in poor rate performance. Examples of the inorganic material used include oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate. Those in the form of particles or fibers may be used. The separator may be one having a thin film shape such as nonwoven fabric, woven fabric, or a fine porous film. The thin film-shaped separator to be preferably used has a pore size of 0.01 to 1 μm and a thickness of 5 to 50 μm. In addition to the above discrete thin film shaped one, a binding agent formed from resin may be used to form a separator that includes a composite porous layer containing particles of the inorganic substance on the outer layer(s) of the positive electrode and/or the negative electrode. For example, a fluororesin may be used as a binding agent to form porous layers from alumina particles having a 90% particle size of smaller than 1 μm on both surfaces of the positive electrode. The alkali metal-sulfur-based secondary battery may further include an external housing. The alkali metal-sulfur-based secondary battery usually has a structure in which the aforementioned components such as the electrolyte solution, the negative electrode, the positive electrode, and the separator are accommodated in the external housing. This external housing may be any of known housings as long as it does not significantly impair the effects of the invention. Specifically, the external housing may be formed from any material, and is usually formed from nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like. The external housing may have any shape such as a cylindrical shape, a square shape, a laminate shape, a coin shape, or a large-scale shape. The shapes and structures of the positive electrode, the negative electrode, and the separator may be modified in accordance with the shape of the battery. A module including the aforementioned alkali metal-sulfur-based secondary battery is also one aspect of the invention. EXAMPLES The invention is described with reference to examples, but the examples are not intended to limit the invention. Examples and Comparative Examples (Preparation of Electrolyte Solution) The components were mixed at the proportions shown in Table 1 or Table 2. A lithium salt was added thereto so as to have a concentration of 1.0 mol/L. Thereby, a non-aqueous electrolyte solution was obtained. (Production of Coin-Shaped Alkali Metal-Sulfur-Based Secondary Battery) A carbon composite material (sulfur content: 65% by mass) containing a carbon material (whose pore volume ratio is shown in Table 1 or Table 2) and a predetermined sulfur serving as a positive electrode active material, carbon black serving as a conductive material, carboxymethyl cellulose (CMC) dispersed in pure water, and styrene-butadiene rubber were mixed at a solid content ratio of 90/5/2.5/2.5 (mass % ratio). Thereby, positive electrode mixture slurry was prepared. The resulting positive electrode mixture slurry was uniformly applied to an aluminum foil current collector having a thickness of 20 μm, and then dried and compression molded using a press. Thereby, a positive electrode was formed. This positive electrode laminate was punched using a punch, whereby a circular positive electrode having a diameter of 1.6 cm was produced. Separately, a circular lithium foil piece punched to have a diameter of 1.6 cm was used as a negative electrode. The positive electrode and the negative electrode were placed so as to face each other with a 20-μm-thick fine porous polyethylene film (separator) in between. The non-aqueous electrolyte solution obtained above was injected and the electrolyte solution was made to sufficiently infiltrate into the components such as the separator. Then, the workpiece was sealed, pre-charged, and aged. Thereby, a coin-shaped alkali metal-sulfur-based secondary battery was produced. (Measurement of Battery Performance) For the resulting coin-shaped alkali metal-sulfur-based secondary battery, the cycle performance and the proportion of the Li2S8discharge plateau were examined as follows. (Cycle Test) The secondary battery produced above was charged at 25° C. at a constant current corresponding to 0.1 C until 3.0 V, and then discharged at a constant current of 0.1 C until 1.0 V. These charge and discharge constitute one cycle. The initial discharge capacity was determined from the discharge capacity of the first cycle. Here, 1 C means the current value at which the reference capacity of the battery is discharged over one hour. For example, 0.1 C means 1/10 of this current value. The cycle was repeated, and the discharge capacity after the 50th cycle was taken as the capacity after the cycles. The ratio of the discharge capacity after the 50th cycle to the initial discharge capacity was determined, and this value was taken as the cycle capacity retention (%). Cycle capacity retention (%)=(discharge capacity after 50th cycle)/(initial discharge capacity)×100 (Pore Volume Ratio (Micropores/Mesopores)) The nitrogen adsorption isotherm of the carbon material contained in the carbon composite material was obtained using a specific surface area/pore distribution measurement device (Autosorb) available from Quantachrome Instruments. The pore volume ratio of the micropores to the mesopores was determined from the nitrogen adsorption isotherm by the quenched solid density functional theory (QSDFT). (Proportion of Discharge Plateau Owing to Reaction Accompanied by Li2S8) In the discharge curve of the second cycle in the cycle test, the plateau generated around 2.2 V was defined as the discharge owing to the reaction accompanied by Li2S8and the plateaux generated at and below 2.0 V were defined as the discharge plateaux owing to the other reactions. The proportion of the discharge owing to the reaction accompanied by Li2S8was calculated from the whole discharge capacity. Proportion of Li2S8discharge (%)=(capacity of Li2S8discharge plateau region)/((capacity of Li2S8discharge plateau region)+(capacity of other discharge plateau regions))×100 The items in Table 1 and Table 2 represent the following compounds. Other Components EC: ethylene carbonate EMC: ethyl methyl carbonate DME: 1,2-dimethoxyethane DOL: 1,3-dioxolane Lithium Salt TABLE 1ComparativeComparativeExample 1Example 1Example 2Pore volume ratio2.12.11.4(micropores/mesopores)Component (I)(I)-1(I)-16060Component (II)(II)-1(II)-1(II)-1403040Other componentsDME40DOL30Lithium saltLiTFSILiTFSILiTFSILi2S8discharge0.113.817.1proportion (%)Cycle capacity441518retention (%) TABLE 2Exam-Exam-Exam-Exam-Exam-Exam-Exam-Exam-Exam-Exam-Exam-ple 2ple 3ple 4ple 5ple 6ple 7ple 8ple 8ple 10ple 11ple 12Pore volume ratio2.111.621.512.112.112.112.112.112.112.112.11Component (I)(I)-1(I)-1(I)-1(I)-2(I)-3(I)-2(I)-2(I)-2(I)-2(I)-2(I)-25050505050301555404040Component (II)(II)-1(II)-1(II)-1(II)-1(II)-1(II)-1(II)-1(II)-2(II)-1(II)-1(II)-15050505050505045202020(II)-5(II)-5(II)-3(II)-4(II)-52020404040Other componentsDME15Lithium saltLiTFSILiTFSILiTFSILiTFSILiTFSILiTFSILiTFSILiTFSILiTFSILiPF6LiPF6Li2S8discharge0.41.21.40.50.80.21.11.82.12.22.1proportion (%)Cycle capacity4645434446484039424140retention (%)Compara-Compara-Compara-Compara-Compara-Exam-Exam-Exam-Exam-Exam-Exam-Exam-tive Ex-tive Ex-tive Ex-tive Ex-tive Ex-ple 13ple 14ple 15ple 16ple 17ple 18ple 19ample 3ample 4ample 5ample 6ample 7Pore volume ratio2.112.112.112.112.112.112.111.41.12.112.112.11Component (I)(I)-2(I)-2(I)-2(I)-1(I)-1(I)-1(I)-2(I)-1(I)-240404030202086060Component (II)(II)-6(II)-1(II)-1(II)-2(II)-1(II)-1(II)-1(II)-1(II)-1(II)-1(II)-1(II)-1602020402020204040505020(II)-7(II)-8(II)-3(II)-3(II)-3(II)-3(II)-740401030305080Other componentsDOLEMCECECDME3050301220EMCDOL3030Lithium saltLiPF6LiPF6LiPF6LiTFSILiPF6LiPF6LiTFSILiTFSILiTFSILiTFSILiPF6LiTFSILi2S8discharge1.83.12.84.44.84.94.717.135201821proportion (%)Cycle capacity413938363332281835119retention (%) | 39,026 |
11862766 | EMBODIMENTS The invention relates to a battery comprising electrodes, which act as a capacitor, and electrolytic solution, and a coolant for hot conditions. The principle of the battery with electrodes shaped according to the invention is that the inductive device generates a magnetic field through an inductor coil, which rapidly changes direction and charges capacitor power between the electrodes. FIG.1shows a battery10according to at least one embodiment of the present invention. The battery10may also be referred to as an energy storage device, battery cell or an accumulator. The battery10comprises of an inductor coil27, a tube28, packing rings33, a coolant25and electrode cones22which are surrounded by electrolytic solution26. The packing rings33, storage vessel30and tubes28jointly form a space where all the elements are. The inductor coil27, which is located in the tube28, can also be referred to as an electrical conductor or inductor and is designed as an inductor or inductance and may also be carried out with a core of, for example, ferrite. According to one embodiment, the inductor coil27is arranged so that it is enclosed in the battery10or in the electrode22between the heat sink31and the cathode23as a spiral inductor coil27. The electrolytic solution26is in liquid or gel form is illustrated inFIG.1by dashing. The electrolytic solution26is preferably an organic compound and with ion molecules, particularly various heavy metal molecular compounds. The battery has multiple electrode cones22. The embodiment illustrated inFIG.1shows three electrode pairs, but there may be more of fewer number of electrode pairs. The first electrode is illustrated in more detail inFIGS.3and4, the identical second and third electrodes are illustrated in more detail inFIGS.5and6and the fourth electrode is illustrated in more detail inFIGS.7and8. The size of the battery can be increased or decreased by adding or removing electrode cones similar to the second or third electrode. Also, when the size of the battery is increased or decreased, the size of the inductor coil27, heat sink31and storage vessel30and the amount of coolant25and electrolytic solution26have to be changed accordingly. The tube28may have a coil-shaped or spiral-shaped electric conductor. The inductor coil27is preferably formed of an electrically conductive metal, such as copper with lacquer on the surface or other metal with good conductivity. Further, the inductor coil27is electrically insulated with an insulating casing. According to one embodiment, the battery10has a storage vessel30that further comprises of a lid, a bottom and packing rings33. The storage vessel holds all the components of the battery10inside of itself. The coolant liquid25is located outside of the storage vessel30. The coolant25and electrolytic solution are divided by the packing rings33. The storage vessel30may have a Faraday cage which captures the magnetic flow. When charging the battery10, the voltage source100will be connected to the inductor coil27. An electric circuit will generate a magnetic field with varying flow direction in the battery10and thus in the electrolytic solution26. The electrical circuit is connected to the outputs101,102of the voltage source100. Outputs101and102have electrical performance, where an alternating current voltage is fed from output101. The voltage source100is carried out with three outputs101,102and103. Output101connects to the second connector27bof the inductor coil27. The output103connects to the anode side of first electrode cone22. This reduces the light metal, which has a dense ion flow, with a dense direct current when the surface of the anode is small. The output102connects to the first connector27aon the inductor coil27as well as to cathode side of the electrode22. This increases the energy of molecules in the electrolytic solution26with alternating current to higher energy position and gives more electrons out of the molecule with direct current. The same process goes through all electrodes when charging and vice versa, when discharging. Preferably, an AC source is utilized which, with a diode circuit or other rectifying circuit, creates a voltage which is half-wave rectified, full wave rectified, and/or with other pulse forms for charging. With a high duty cycle as an output voltage AC current creates a dynamically varying magnetic field in the electrolytic solution26. As an electric alternating current has passed the inductor coil27, a magnetic field is induced in the electrolytic solution26, which brings the electrolytic solution26into a moving position and to a higher energy level when the electrons can be more easily released in the charging mode. The energy storage is charged by the charging voltage. Outputs102and103are connected to pole connection plus200and pole connection minus300respectively. Since outputs102and103have different electrical potential, the direction of current will change when zero is passed, where the voltage source100gives the current change through the inductor coil27and will generate a swinging AC circuit. The electrical conductor, inductor coil27, at the first connection27aof the inductor coil27, connects to the cathode side of the bottom electrode22. Further, the second connection27bof the inductor coil27connects to output101. A first pole connection comes from output102to plus200arranged to the cathode side of the bottom electrode22and the first connection27aof the inductor coil. A second pole connection comes from output103to minus300which is arranged to the anode side of the top electrode22. The first pole connection plus200and the second pole connection minus300are used to connect the battery to a charger and when the battery is connected to a load. FIG.2shows the geometrical shape of the electrode22. r describes the radius of the smaller circle which appears at the top of the truncated electrode cone22. R indicates the radius of the larger circle which appears at the bottom of the truncated electrode cone22. s indicates thickness of the mantle of the truncated electrode cone22. h indicates the height of the truncated electrode cone22. In an example of a design of an electrode22R is between 50 mm and 300 mm, r between 10 mm and 30 mm, s between 0.05 mm and 0.15 mm, h between 40 mm and 300 mm. The cone angle α is preferably 45° but the angle can also be different. The size of the cone and the thickness can be varied according to the areas of use of the battery. Electrodes22are preferably carried out in the form of a truncated cone where the top of the cone is removed and insulated. The electrodes22can also be carried out in other forms, not necessarily conical, but they can also have a spherically rounded shape. The electrodes22need not have circular symmetry but can be, for example, elliptical, or pyramid shaped. The cone is made, for example, by casting or made of a sheet which is curved, and/or made of screen. The thickness of the sheet and the screen wires are in the order of 0.05 mm but can also be either thicker or thinner. Furthermore, both the anode24and the cathode23are preferably coated with a chloride layer or nitride layer or with another coating, or the coating can be left out. However, the shape of the anode24, heat sink31, and cathode23and method of manufacturing are not limited by the above examples. FIG.3shows a detailed enlargement of the outer part of the top electrode in accordance with at least some embodiments of the present invention. The top part of the electrode comprises of a heat sink31, which is coated with a layer of plastic or lacquer. The packing ring33is located below the heat sink31. There is a storage vessel30on top of the heat sink31. FIG.4shows a detailed enlargement of the inner part of the top electrode in accordance with at least some embodiments of the present invention. The electrode22is comprised of an anode24, and heat sink31. The side of the electrode22that is in contact with the tube28is insulated with insulation29. On top of the heat sink31is the top part of the storage vessel30. Below the heat sink31can be coated with a plastic of lacquer. FIG.5shows a detailed enlargement of the outer part of a middle electrode in accordance with at least some embodiments of the present invention. The upper side of the middle electrodes comprise a cathode23. The cathode is in contact with the electrolytic solution26. The lower side of the electrode is coated with a layer of plastic or lacquer. In between the cathode23and the coating there is located a heat sink31. FIG.6shows a detailed enlargement of the inner part of a middle electrode in accordance with at least some embodiments of the present invention. The middle electrodes comprise of an anode24, a heat sink31and a cathode23. Similarly toFIG.4, the side of the electrode22that is in contact with the tube28is insulated with insulation29. Below the heat sink31can be coated with a plastic of lacquer. Both the anode24and the cathode23are in contact with an electrolytic solution26. The anode24is in contact with the electrolytic solution26located on the top side of the electrode22and the cathode23is in contact with the electrolytic solution26below the electrode22. FIG.7shows a detailed enlargement of the outer part of the bottom electrode in accordance with at least some embodiments of the present invention. The bottom electrode22comprises a cathode23, a heat sink31and the bottom storage vessel30. The storage vessel goes up to the tube28and forms a bottom wall which forms a closed space for the electrolytic solution26. Packing rings33separate the electrodes22. The packing rings33are located at the bottom of the truncated electrode22cone. The packing rings33may be glued to all the electrodes22or fastened by another method. The packing rings33are made of electrically insulating material. FIG.8shows a detailed enlargement of the inner part of the bottom electrode in accordance with at least some embodiments of the present invention. The bottom electrode comprises a cathode23and a heat sink31. Similarly toFIGS.4and6the side of the electrode22that is in contact with the tube28is insulated with insulation29. The cathode23is in contact with the electrolytic solution26. The bottom storage vessel30is located below the heat sink31. The bottom layer30is made of suitable plastic and together with the tube28forms a tight vessel which can comprise an electrolytic solution26. As seen fromFIGS.3,5and7, the heat sink31is not limited only to the packing rings, but continues “over” them. This creates a thermal pathway along the length of the electrode which is not in contact with the electrolytic solution. As illustrated, the heat sink may be separated from the electrolytic solution via a coating. The bottom and the top electrodes22are provided with a bottom and a lid of the storage vessel30and together with the storage vessel walls seen inFIG.1the whole vessel encloses all the components of the battery. The coolant25in the outer part of the storage vessel30may be glycol water mixture or any other coolant. Alternatively the circulation of the coolant25can be arranged to different cooling elements, outside the storage vessel30. The storage vessel30may be made from electrically insulating material such as rubber, teflon, or other plastics, such as thermoset or thermoplastic materials. As mentioned above, the battery10is charged by an external voltage source100with three outputs101,102and103. The output101feeds the inductive circuit with an alternating voltage or a square pulse or other electrical signal with current changing over time by connecting to the second connection27bof the inductor coil27. The magnetic flux change generates a magnetic field, which changes the energy state of the electrode cones22. The magnetic field induces ion electrolytes in the electrolytic solution26, which brings dense electric current to the surface of the anode24from the cathode and a dense ion flow from or to electrolytic solution26when charging and discharging respectively. This induces a reduction reaction to the anode23and charging can be done with a higher voltage. This enables fast charging and as a higher capacitor voltage in the battery10. The voltage source100may be equipped with an adjustable frequency inverter/frequency converter which provides adjustable voltage in alternating current at a certain frequency and at different rates, adjustable voltage and adjustable direct current for charging. In certain embodiments there can be several electrode cones on top of each other separated by packing rings33. The electrode cones can partly be coated and partly uncoated. Each cathode surface has insulation29over that part of the surface which is arranged closest to the central tube28. The thickness of this insulated part may be approximately 0.04-0.005% of the thickness of the mantle of the electrode22, but also other size or thickness of insulation is possible and the invention is not limited by this. The insulation29may be a rubber seal or a rubber “collar”, which may be comprised of plastic, thermoplastic or other insulator material. The anode24and heat sink31are preferably made of light metal or aluminum or other suitable alloy. The cathode23is preferably made of heavy metal or stainless steel AISI 304, or a screen of acid-resistant steel AISI 316 or another alloy including substances and metals. In the electrodes22the heat sink31and the cathode23are preferably joined together by laser welding. According to one embodiment, the material of the anode24and heat sink31of the battery10may be selected from metals in the group 1, 2 or 13 of the periodic table, especially any of the metals lithium, sodium, potassium, beryllium, magnesium, calcium, boron, aluminum, gallium, indium and/or thallium or alloys comprising any of the following materials: lithium, sodium, potassium, beryllium, magnesium, calcium, boron, aluminum, gallium, indium and/or thallium. The anode24and the heat sink31are preferably coated with chlorides or some other coating. Preferably, the battery10, anode24and heat sink31electrode are made of high purity aluminum or made of a suitable alloy, for example an aluminum alloy. The anode electrode can be produced, for example, by casting. According to one embodiment, the material of the cathode23is selected from the group of heavy metals, for example any of the following materials: nickel, cobalt, iron, manganese, chrome, molybdenum, or stainless or acid-resistant alloys comprising any of the following materials: nickel, cobalt, iron, manganese, chrome, molybdenum, or steel alloys, preferably coated with nitride or some other coating or from finished alloys of stainless steel or acid-resistant steel Aisi 304-316, possibly with a nitride coating, or other substances. Examples of materials in the electrodes are various forms of chlorides and nitrides. In addition to various forms of nitrides, the surface of the electrode may also be provided with a chloride and nitride coating in order to further improve its properties. Industrial chloriding and nitriding processes for coating surfaces are usually carried out with gas techniques, plasma supported techniques, or chloriding with salt bath techniques. The electrolytic solution26may comprise nitride, ammonium, chloride and oxide molecules which comprises molecules which comprise basic elements in an organic solvent. According to one embodiment, the electrolytic solution comprises AlCl3, manganese ions or iron ions, and an organic solvent. The anode24part of the electrode22can have a very small surface in the scale of mm2. The cathode23part of the electrode22can have a very large surface in the scale of cm2or m2. The surfaces may vary in size and are not tied to any exact size. The difference between the surface size of the anode24and the cathode23may be in the scale of 1M mm2. According to one embodiment the ratio between the surface areas of the cathode and anode is in the range of 100-100 000. The anode24and the cathode23are not arranged against each other; instead they are at an angle next to each other. Both are in contact with the electrolytic solution26and the top of the large cathode23is insulated with and insulator29. One advantage of this invention is that when the battery is charged there is a capacitor voltage constantly in the battery10from the cathode23and heat sink31to the anode24through the electrolytic solution26. The same voltage prevails in all electrodes22when there is still charge in the battery. According to one embodiment, the charging and discharging of the battery10generates a dense ion flow and dense electrical current to the top of the electrode22to the anode24. The anode then reduces ion molecules from the cathode23to metal. According to one embodiment, the battery10comprises of conically shaped electrodes22having an inner opening. Insulation29is arranged close to the inner opening of the electrodes22. The bottom opening of the electrodes22are separated with packing rings33. The electrodes comprise a heat sink31that is made of aluminum and an anode that has a coating of an aluminum chloride on its surface. The elements of the battery10act as a capacitor having a voltage between the electrodes22. The heat sink31is coated with plastic or lacquer. The battery10is an inductive device and has a minus pole300and a plus pole200. The battery10is charged with direct current from the voltage source100for 0.5 s. For another 0.5 s, the electrical conductor is driven with alternating current. The inductor coil27creates a varying magnetic field to the battery10and the electrolytic solution26. Output102of the voltage source100is attached to the plus pole connection200of the battery. As the half-wave rectified signal from the voltage source100is changed to alternating current, the current will flow in varying direction directly from the output101of the voltage source100through the inductor coil27to the output102of the voltage source100and back at a rate of 50 kHz/s. This causes the magnetic field in the circuit to change dynamically, which activates, or induces, energy and causes the electrons of the metal compounds in the electrolytic solution to move to a higher energy level, and the electrons can then be easily released. At the energy charging rate of 0.5/s, to inductive power, of electrolyte molecules which move to a higher energy state, at the same time, the ion function is good at higher heat states between anode24and cathode23. The voltage source100has current of 10-100 A/cm2and voltage of 7.5-10 V. The battery is a 230-360 V inductive device. This can be regulated and such a battery can be produced for all needs and purposes. A high duty cycle indicates that a high percentage of the signal from output101of the voltage source100is active. Preferably, the duty cycle is >90% for signal101. Because the output voltage from output101goes through zero passes, the current changes direction which, in turn, creates a changing magnetic field in the inductor coil27. The frequency, current, pulse shape and voltage vary depending on the design of the battery10but can be in the output voltage range of 2-7.5 V/pair of inductive device 230-360 V or greater, and current of 0.1-100 A/s per pair, preferably 3-100 A/s per pair, such as 10 100 A/s per pair and the frequency of the output voltage between 1-50 kHz. The rate between direct current, alternating current and back can be different, for example from 0.1/s to 1.0/s. The inductive device current to the inductor coil27and the voltage are approximately 1-3 A and 230-360 V. Capacitor and charging voltage in one pair or with several pairs can be from 10 V in one pair to several pairs in the range of 230-360 V or more. It works with the voltage/couple used and the current when charging from 0.1-100 A, preferably 1.0-10 A, such as 1.0-100 A or more, depending on the size of the storage vessel30and which substances are used in the electrolytic solution26. In an embodiment of the present invention the charging voltage is 2 V/pair and current 125 mA/g. In the current invention the voltage is 10 V and inductive device with 230-360 V, discharge voltage 1.8 V with 305 mAh/g. In the current invention another possible voltage is 7.5 V inductive device 230-360 V, and double current. The voltage in the battery10is higher and the current is high when charging or discharging with 10-7.5 V inductive device 230-360 V. In an embodiment of the present invention, in the battery10there is a discharge reaction where aluminum is chlorinated and oxidized, and the V2O5and MnO2in the electrolytic solution decrease to lower oxidation, which can be increased when charging to Mn7+, and Fe 3+ to Fe6+, which gives more current and higher voltage. Reduction of aluminum is powerful and efficient because the cone top has a smaller surface area at aluminum anode24and in the electrolytic solution26. As a result the ion flow is denser at the anode24. The battery10functions as a conventional energy storage or battery construction, but differs regarding high voltage which increases the energy amount with an inductive device and capacitor voltage, which are good in cold climate. It can be used with different molecules in the electrolytic solutions, with organic electrolyte, with different voltage and current in different chargeable batteries or energy storages. When charging, it is an advantage of the battery10that the anode24has a small surface and the cathode23has a large surface. The cathode23and the molecules in the electrolytic solution26are charged with high-voltage, 10-360 V. The anode24receives alkali or light metal ions with a dense current, which reduces the ions. The charging current varies and temporarily becomes zero and goes through zero passes, possibly after a certain variable time delay. The inductive device generates an increased magnetic field in the inductor coil27, which changes the state of energy in the electrolytic solution26and increases the magnetic flux in heavy metal cathode molecules to a higher energy state when electrons are delivered to the cathode23. Another advantage is that the battery10with electrodes22have a voltage between the electrodes22when charging and discharging, more precisely the voltage is between cathode23and heat sink31. When the dense ion flow at anode23passes through the electrolytic solution, the electrons in the molecules change shell and emits electrons to the cathode23. According to one embodiment, the electrodes22act as a capacitor. More precisely the cathode23and the heat sink31act as a capacitor. The electrolytic solution26is comprised of atoms and molecules. Although these are outwardly electrically neutral, they comprise protons (positive charge) and electrons (negative charge). In addition, the insulating29material may also comprise a small amount of free charge carriers (electrons or ions). When such a substance is exposed to an external electric field, the electrical equilibrium is disturbed. The positively charged particles move slightly in the direction of the field and the negatively charged particles move in the opposite direction. When the direction of the external electric field is reversed, a corresponding displacement occurs in the other direction. The faster the direction of the field is reversed, and the stronger the electric field is, the faster and larger these changes are. Due to this vibration of the charges inside the substance, it becomes hot. Energy is transferred from the electric field to the material that is supposed to increase energy to the atom and the electron as the molecule is simultaneously heated. Energy transfer depends not only on the frequency and field strength used, but also on the substance itself. This is illustrated by εr·tan δ. These factors depend not only on the material to be heated, but also on the frequency used. The battery10operates in four modes, a first mode when the energy storage is charged and a second mode when the energy storage is discharged and a third mode when the battery or energy storage is not used, and a fourth mode when the battery or energy storage has no current or the voltage is 0. In the first mode, charging, the external voltage source100is used to supply electrical energy to the electrolytic solution26between the cathode23and the anode24. Charging takes place partly through a conventional electrochemically reversible reaction and partly by an inductive method where the magnetic field generated by the inductor coil27changes the energy state of the electrolytic solution26. In other words, partly by heating the electrolytic solution26, and partly because molecules comprised in the electrolytic solution26change energy states by the electrons in the molecules changing shells and electrons moving to the current. In the second mode, discharging can also be take place through the voltage source100, which changes the direct current to an adjustable alternating current that goes to a load. In the third mode, in rest, there is no current in the battery10, but the capacitor voltage works all the time and keeps the energy storage ready to start. The battery is in good balance. In the fourth mode, the battery10is totally empty of current voltage and no capacitor voltage is present in the battery either. The electrolytic solution26comprises both an anolyte and a catholyte, as well as organic liquids, gels or masses in solid form. The electrolytic solution26can partly comprise nitride, ammonium, chloride and oxide molecules, which comprise molecules comprising basic elements. The catholyte molecules of the electrolytic solution26may comprise different forms of metal compounds including a number of electrons which can be excited to higher energy levels with a varying magnetic field and direct current. The anolyte molecules of the electrolytic solution26may comprise different metal compounds or other molecules suitable for the purpose. The anolyte molecules can be ionized with a varying magnetic field and direct current. The voltage source100is designed to generate an output voltage of outputs101,102and103, which can be adjusted based on existing needs. For example, the pulse shape, rise time, frequency, voltage, pulse length and additional capacities can be varied in method inductor coil27with inductive device. The voltage source100can also be utilized to heat and lift the molecules of the battery10to higher energy level in order to improve the capacity of the battery, for example in cold climate. In this case, the voltage source100is arranged to supply an alternating voltage of a slightly higher frequency, to generate a magnetic field which heats the electrolytic solution26. For example, frequencies in the order of some kHz can be used, but also higher as well as lower frequencies of the voltage source100can be used to heat the electrolytic solution26and lift the molecules in the electrolytic solution26to a higher energy level. The electrons can then be more easily released during charging and thus improve the charging capacity and charging time. The battery10according to one embodiment of the present invention is preferably in the order of 80 kg or 60 liters, but other sizes are also applicable. The battery10is preferably used in vehicles such as cars, boats, aircraft and other purposes, with room for one or more batteries or battery cells or large energy storages. The battery10is adapted for 230-360 V and is preferably built of a number of electrodes22where each electrode has a charge/discharge voltage of at least approximately 7.5-15, V, preferably 10-15 V inductive device with high voltage of 230-360 V and discharge voltage of 7.5-15, preferably 10-15 V per electrode pair, and a charge/discharge current of approximately 0.2-10 A/cm2, preferably 3-10 A/cm2. The charging time to reach 80% energy level is about 2-4 hours but the time interval may also be different depending on the design of the energy storage and the materials used. The energy capacity of the battery10is possibly in the order of approximately 1.0-5.0 kWh/kg or approximately 2.0-5.6 kWh/liter, depending on the materials used. The power capacity of the battery10is in the order of approximately 125-500 Ah/kg or approximately 175-1000 Ah/litre. Depending on which chemicals are used in the electrolytic solution26. The number of charge cycles for the battery10may exceed 3,000-10,000, but the number of charge cycles can be extended by servicing the battery, for example by changing electrodes, electrolytic solution or other components in the battery. Examples The electrolytic solution used was 1-ethyl-3-methylimidazolium chloride ([EMim]Cl) with aluminum chloride (AlCl3). Charging takes place with direct current and alternating current from current bridge V100which gets its power from a power station. The cathode is, to Aisi 316 steel cathode1), MnO2, to Mn7+2) Fe2O3, to Fe6+which takes electrons from the electrolytic solution26, which is charged with organic electrolyte and ionic substances1) AlCl3, ion reduction to aluminum anode which only starts operating above 8.0 volts/pair of voltage, with 2) AlCl3, MgCl2. Charging takes place with a drive voltage of 10-15 volts/pair of minimum, the same voltage in the capacitor, in both variations and inductive device 230 volts, 50,000 Hz alternating current with 1-3 A in the inductor coil27, which produces magnetic power in the electrolytic solution26that is charged in the largest possible energy position, the voltage decreases when discharging with 7.5 volts/pair and capacitor 7.5 volts/pair, inductive device 230 volts in inductor coil27, drive voltage from +acid-resistant cathode23which is partly coated, and anode24/heat sink31poles, discharging renders current with high voltage from cathode23and anode24. The energy capacity of the battery10is possibly in the order of approximately 1.0-3.0 kWh/kg or approximately 2.0-5.6 kWh/litre, with different heavy metal compounds. The battery10has the same or better minimum energy density of (270-310 mAhr/g, at least about 260 mAhr/g) than the invention of the Cornell University in New York, with the same organic electrolyte and in its aluminum ion battery WO 2013/049097 A1, without its nanowire invention. The finished test results agree well with those described in the patent application WO 2013/049097 A1, that is, in minimum function for battery10, when using the same electrolyte substances and mass as in the described patent application by Cornell University NY, US. A test result, it is in the minimum function for storage vessel30with the battery10and the chemical substances of triflate in PC/THF and 1-Ethyl-3-methylimidozolium chloride+AlCl3, and possibly (TMPAC) ionic liquid and mass of MnO2. The battery has the charging voltage of 10.0 V inductive device 360-230 V, current is 125 mA/g minimum and a discharge voltage of 1.8 V. For example −7.5—inductive device 230-360 V, current 305 mAh/g. The capacitor voltage used is 10 V. This with charging and discharging higher voltage 10-7.5, inductive device with higher voltage 230-360 V and high current A in the battery10. In the battery10the capacitor voltage at discharge is the one used in charging with an inductive device, and using the previously explained current and voltage. It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting. Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below. The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality. INDUSTRIAL APPLICABILITY The invention can be used in batteries for cars, boats or aircrafts, or other subjects that use one or more batteries. Acronyms List DC Direct current REFERENCE SIGNS LIST 10Battery22Electrode cone23Cathode24Anode25Coolant26Electrolytic solution27Inductor coil27aFirst connection of inductor coil27bSecond connection of inductor coil28Tube29Insulation30Storage vessel31Heat sink33Packing ring100Voltage source101Output102Output103Output200Plus pole300Minus pole CITATION LIST Patent Literature WO 2013/049097US 2012/0082904 Non Patent Literature “An ultrafast rechargeable aluminum-ion battery”, Meng-Chang et. al., Nature, #520, p. 324-328, published in April 2015E. Menthe, K. T. Rie, J. W. Schultze and S. Simson, “Surface and Coatings Technology”, vol. 74-75 (1995) 412-416 | 35,510 |
11862767 | The energy storage module according to the invention and method according to the invention for producing an energy storage module of this kind are described in greater detail below with reference to the illustrations inFIGS.1through5. Identical or equivalent elements and functions are provided with the same or similar reference characters. With the continuously increasing number of electric energy consuming units and the development of vehicles2000in the direction of electric vehicles and/or hybrid vehicles, there is an increasing demand for energy storage systems with a relatively high power density which can furthermore be produced quickly and at low cost. However, it is furthermore equally conceivable to use the energy storage module100according to the invention in sectors in which a relatively high power density of the energy storage module100and of the energy storage system1000, combined with a small installation volume and low prices, is required. In the text which follows, “side-by-side” means at least substantially in a horizontal direction and “one above the other” means at least substantially in a vertical direction. FIG.1shows a schematic representation of a vehicle2000, which has at least one energy storage system1000. The energy storage system1000furthermore has at least one energy storage module100according to the invention with a multiplicity of energy storage cells10. In this case, the energy storage system1000can be arranged in a region of the vehicle2000which is at the front in the direction of travel, in a rear region of the vehicle2000and/or in a region underneath the seats, in particular underneath the driver's seat. The vehicle2000can be an aircraft or a watercraft, a rail vehicle, an all-terrain vehicle, or preferably a road vehicle, wherein a road vehicle can mean a passenger vehicle, a truck, a bus, or a motor home. The vehicle2000is driven by a drive unit. The drive unit can comprise an internal combustion engine, an electric motor or a combination thereof. A vehicle2000which is driven exclusively by an electric motor is referred to as an electric vehicle. A vehicle2000which has both an electric motor and an internal combustion engine is referred to as a hybrid vehicle. Hybrid vehicles can furthermore be subdivided into microhybrid vehicles, mild hybrid vehicles, full hybrid vehicles and/or plug-in hybrid vehicles. Here, plug-in hybrid vehicles can be taken to mean any hybrid vehicle which is not only charged by means of the internal combustion engine but can likewise be charged by means of the power grid. Full hybrid vehicles means vehicles which can be driven exclusively by means of the electric motor. Microhybrid vehicles have a start-stop functionality and preferably also have a stop-in-motion functionality. Moreover, microhybrid vehicles can charge the energy storage system1000by “brake energy recovery”. Mild hybrid vehicles can furthermore have a boost function, which is used to assist the internal combustion engine to increase power. FIG.2shows a schematic exploded representation of an energy storage module100according to the present invention. Accordingly, the energy storage module100has a multiplicity of energy storage cells10, which are connected electrically in series. Furthermore, the energy storage module100has a housing20which is produced from plastic, at least in some region or regions, preferably completely. A barrier layer is furthermore provided between the housing20and the multiplicity of energy storage cells10, at least in some region or regions, in particularly completely. In the course of this application, the barrier layer means a layer which prevents gases and/or liquids from being able to enter the housing20of the energy storage module100from the environment or prevents gases and/or liquids from being able to escape from the housing20into the environment. In particular, the “barrier layer” means a layer which is impermeable to gases in the ambient air, to gases which are formed during the operation of the energy storage module100and to liquid in the environment. In this context, the barrier layer can be constructed from metal, metal oxide and/or silicates. A barrier layer made from ethylene-vinyl alcohol copolymer is also conceivable. Active barrier layers can furthermore also be used. These are taken to mean barrier layers which can (chemically) bind the gases and/or liquids. The metal can be or comprise a light metal, in particular aluminum and/or an aluminum alloy or magnesium and/or a magnesium alloy. In particular, any layer which prevents the passage of gas and liquid through the plastic without changing the electrochemical properties of the cell is suitable as a barrier layer. The barrier layer can be connected materially, at least in some region or regions, to inner surfaces of the housing, in particular to inner surfaces of the lower housing shell20band of the upper housing shell20a, it being possible, in particular, for the barrier layer to be vapor-deposited on the inner surfaces of the housing20. This is preferably accomplished by chemical vapor deposition or physical vapor deposition. It is likewise possible for the barrier layer to be formed, at least in some region or regions, in particular completely, as a foil which is connected to the inner surfaces of the housing, in particular of the lower housing shell20band the upper housing shell20a. This is preferably a metal foil, which is connected materially to the inner surfaces of the housing20. FIG.2furthermore indicates that each energy storage cell10can have a connecting element11a,11bon each of two opposing sides. In this case, a first connecting element11acan correspond to a positive contact of the energy storage cell10and a second connecting element11bcan correspond to a negative contact of the energy storage cell10. Furthermore, the connecting elements11a,11bcan be formed from a metal foil, in particular a copper foil or an aluminum foil Moreover, two directly adjacent energy storage cells10can each be connected to one another by a connecting element11a,11bof these energy storage cells10. The connection between two directly adjacent energy storage cells10is preferably accomplished by welding in each case one connecting element11a,11bof the energy storage cells10to be connected. In this case, the connecting elements11a,11bof the two directly adjacent energy storage cells10form a region of overlap, in which welding takes place. At the same time, it should be noted that the connection between two directly adjacent energy storage cells10is performed in each case by means of a connecting element11a,11bof the energy storage cells10in such a way that a flexible and/or bendable connection point is formed. Connecting a multiplicity of energy storage cells10by means of the connecting elements11a,11bthereof advantageously eliminates the need to provide a busbar. Furthermore, at least one plastic film30can be provided. Here, the plastic film30is arranged between the multiplicity of energy storage cells10and the housing20or the lower housing shell20band the upper housing shell20a. The plastic film30can furthermore be pre-shaped, in particular pre-shaped plastically and preferably thermoformed, more specifically in such a way that the plastic film30has a multiplicity of recesses, which are each designed to receive one energy storage cell10. A lower plastic film30b, which is arranged between the lower housing shell20band the multiplicity of energy storage cells10, and an upper plastic film30a, which is arranged between the upper housing shell20aand the multiplicity of energy storage systems1000, are preferably provided. Here, the at least one film30can be produced, for example, from acrylonitrile butadiene styrene, a polycarbonate, a polyamide, polyvinyl chloride, polyethylene terephthalate, polyoxymethylene, a polyolefin, e.g. polypropylene and/or polyethylene, or a copolymer thereof. In regions in which the connecting elements11a,11bof the energy cells10are arranged, the at least one plastic film30can furthermore have apertures. These apertures are used, on the one hand, to enable further production steps, e.g. the connection of two directly adjacent energy storage cells10by means of the connecting elements11a,11bthereof, to be carried out more easily and, on the other hand, to enable the monitoring of the individual cells to be simplified by contacting the connecting elements11a,11bto a measurement line40. A measurement line40can furthermore be provided in an energy storage module100. This measurement line40can be integrated into the plastic film30, for example, in particular into the upper plastic film30a, or into the housing20, in particular into the upper housing shell20a. In this arrangement, the measurement line40can determine a state of an energy storage cell10, of a plurality of energy storage cells10and/or of all the multiplicity of energy storage cells10. In particular, the measurement line40can determine a voltage and/or a current flow and/or a capacity thereof. The energy storage module100which is shown schematically inFIG.2has four energy storage cells10. However, it should be noted that the number of energy storage cells10of an energy storage module100depends on the desired power density of the energy storage module100. Thus, an energy storage module100with more or fewer energy storage cells10can also be conceivable. FIG.3shows a schematic representation of an energy storage module100, which is designed as a cell stack100′. For this purpose, the energy storage module100, which is initially aligned substantially horizontally, that is to say that the individual energy storage cells10are situated substantially horizontally side-by-side, is bent by way of the connecting elements11a,11bof the energy storage cells10in such a way that the energy storage cells10of the cell stack100′ are arranged substantially vertically one above the other. Here, the connecting elements11a,11bof two connected energy storage cells10preferably form an at least substantially 180° bend. This bend is likewise formed by the housing20and, where applicable, by the at least one plastic film30, more specifically at points at which the connecting elements11a,11bof the energy storage cells10are accommodated. FIG.4shows a schematic representation of an energy storage system1000, which has a system housing1200and an energy storage module100formed as a cell stack100′. For the sake of clarity, a lid has not been illustrated here. The lid, which is not illustrated, has a positive and a negative connection element, which can each be connected by means of a contacting element to a connecting element11a,11bof the cell stack100′. It is furthermore conceivable for a multiplicity of energy storage modules100formed as a cell stack100′ to be arranged in the system housing1200. Here, the number of energy storage modules100depends on the desired total capacity of the energy storage system1000. Even if this is not explicitly emphasized in the figures, each energy storage cell10can have at least one filling and/or venting hole. It is advantageous if the filling and/or venting hole is designed in such a way that it can be re-closed, preferably hermetically closed, by means of a plug. It is also conceivable to re-close the filling and/or venting hole by means of a diaphragm, which is preferably designed as a bursting diaphragm. Such a diaphragm is distinguished especially by the fact that it is impermeable to gases and/or liquids and provides protection to the extent that it bursts when an internal pressure of the energy storage cell exceeds a predetermined or predeterminable value. FIG.5shows a schematic illustration of the method for producing an energy storage module100, which is a continuous method. Here, a magazine10′ containing a multiplicity of energy storage cells10is illustrated. Also illustrated is a roller20′, onto which a supply of the housing20is wound, in particular a roller20b′, onto which a lower housing shell20bis wound as an endless strip, and a roller20a′, onto which an upper housing shell20ais wound as an endless strip. The housing20or the lower housing shell20band the upper housing shell20ais/are preferably already pre-shaped, more specifically in such a way that the housing20or the lower housing shell20band the upper housing shell20ahas/have a multiplicity of recesses, each of which is designed to receive an energy storage cell10. As a particular preference, a barrier layer is arranged on the housing20or on the lower housing shell20bor the upper housing shell20a, namely on a surface of the housing or of the lower housing shell20bor of the upper housing shell20a, more specifically in the direction of the multiplicity of energy storage cells10. Here, the production direction is indicated by the arrow F. Here, the barrier layer prevents gases and/or liquids from being able to penetrate into the energy storage module100via the housing20and prevents gases and/or liquids from emerging via the housing20. In this context, the barrier layer can be constructed from metal, metal oxide and/or silicates. A barrier layer made from ethylene-vinyl alcohol copolymer is also conceivable. Active barrier layers can furthermore also be used. These are taken to mean barrier layers which can (chemically) bind the gases and/or liquids. The metal can be or comprise a light metal, in particular aluminum and/or an aluminum alloy or magnesium and/or a magnesium alloy. The barrier layer can be connected materially, at least in some region or regions, to inner surfaces of the housing, in particular to inner surfaces of the lower housing shell20band of the upper housing shell20a, it being possible, in particular, for the inner surfaces of the housing20to be damped. This is preferably accomplished by chemical vapor deposition or physical vapor deposition. It is likewise possible for the barrier layer to be formed, at least in some region or regions, in particular completely, as a foil which is connected to the inner surfaces of the housing, in particular of the lower housing shell20band the upper housing shell20a. This is preferably a metal foil, which is connected materially to the inner surfaces of the housing20. Furthermore, at least one roller30′ can be provided with a supply of plastic film as an endless strip. First of all, the lower plastic film30bis unrolled from the roller30b′ carrying the lower plastic film30band is pre-shaped in a first step (S1b). The pre-shaping of the lower plastic film30bis, in particular, plastic pre-shaping, with the pre-shaping preferably being accomplished by means of a thermoforming step. During this process, the lower plastic film30bis pre-shaped in such a way that a multiplicity of recesses is introduced. One energy storage cell10in each case is then supplied from the magazine10′ of energy storage cells10in a feed direction L in such a way that one energy storage cell10is arranged in each recess of the lower plastic film30b. Here, the feed direction of the energy storage cells10is indicated by the arrow L. An upper plastic film30ais then supplied from a roller30a′ containing a supply of film and is pre-shaped (S1a) in a manner corresponding to the lower plastic film30b. The pre-shaped film30acan then be arranged on the multiplicity of energy storage cells10in such a way that one energy storage cell10is arranged in each recess of the upper plastic film30a. Connecting elements11a,11bof two directly adjacent energy storage cells10are then connected to one another (S2) through apertures in the upper and lower plastic film30a,30b. This is preferably accomplished by means of a welding process. Care should be taken here to ensure that a flexible and/or bendable connection point is formed. The lower housing shell20bis then supplied as an endless strip from the roller20b′ containing the lower housing shell supply and, at the same time, the upper housing shell20ais also supplied as an endless strip from the roller20a′ containing the upper housing shell supply, more specifically in such a way that the lower housing shell20band the upper housing shell20asurround the lower plastic film30band the upper plastic film30aas well as the multiplicity of energy storage cells10. As a particular preference in this case, a barrier layer is already provided on the lower or upper housing shell20a,20b, and this barrier layer is also already pre-shaped. The upper and the lower housing shell20a,20bare fed in in such a way that recesses in the lower and the upper housing shell20a,20breceive the recesses in the lower and the upper plastic film30a,30band the energy storage cells10. In a further step, the endless arrangement of energy storage cells10with the housing20and the at least one plastic film30is cut into individual energy storage modules100comprising a predetermined or predeterminable number of energy storage cells10by means of a cutting operation. In a further step, an energy storage module100can be bent. This is performed in such a way that an energy storage module100which was previously arranged substantially horizontally is bent in such a way that a cell stack100′ is formed, in which the energy storage cells10are stacked substantially vertically one above the other. However, it is equally conceivable that the multiplicity of energy storage cells10is not arranged on a plastic film30but directly in the housing. For this purpose, the individual energy storage cells10are each formed with a cell housing. In this case, the energy storage cells10from the magazine are first of all placed on a conveyor belt and, on the latter, are connected to one another by means of the connecting elements11a,11bof two adjacent energy storage cells10. The connected energy storage cells10are then arranged in the housing20or in the lower housing shell20band the upper housing shell20aand subsequently divided into energy storage modules100by means of a cutting operation. Even if this is not illustrated explicitly in the figures, a measurement line40can be integrated into the upper or into the lower plastic film30a,30b, for example. Such a measurement line40can likewise be integrated into the upper or into the lower housing shell20a,20b. At this point it should be noted that all the parts described above, viewed on their own or in any combination, in particular the details shown in the drawings, are claimed as essential to the invention. Amendments thereof are familiar to the person skilled in the art. REFERENCE CHARACTER LIST 10energy storage cell10′ energy storage cell magazine11a,11bconnecting element20housing20a,20blower/upper housing shell20a′,20b′ roller containing housing supply for lower/upper housing shell30at least one plastic film30a,30blower/upper plastic film30a′,30b′ lower/upper supply of film40measurement line100energy storage module100′ cell stack1000energy storage system1200system housing2000vehicleL feed direction of the energy storage cellsF production directionS1thermoforming stepS2joining stepS3cutting step | 19,078 |
11862768 | In the accompanying drawings, the accompanying drawings are not drawn to actual scale.Mark descriptions:1000-vehicle;100-battery;10-box;11-first box body portion;12-second box body portion;20-battery cell;21-box body;22-end cover assembly;23-electrode assembly;231-positive electrode plate;2311-positive tab;2312-positive body;23121-first positive winding end portion;23121a-positive active material layer of first positive winding end portion;23122-positive winding middle section;23122a-positive active material layer of positive winding middle section;23121b-start end of positive winding starting section;23121c-tail end of positive winding starting section;23121d-tail end of positive winding ending section;23121e-start end of positive winding ending section;23121f-positive current collector of first positive winding end portion;23123-second positive winding end portion;23123a-positive active material layer of second positive winding end portion;23123b-positive current collector of second positive winding end portion;23124-insulating layer;23124a-insulating layer of first positive winding end portion;23124b-insulating layer of positive winding middle section;23124c-insulating layer of second positive winding end portion;232-negative electrode plate;2321-negative tab;2321a-first side face;2321b-negative active material layer of negative tab;2321c-second side face;2322-negative body;23221-first portion;23221a-negative active material layer of first portion;23221b-negative current collector of first portion;23221c-connection surface;23221d-start end of first portion;23221e-tail end of first portion;23222-second portion;23222a-negative active material layer of second portion;23222b-negative current collector of second portion;23223-third portion;23223a-negative active material layer of third portion;23223b-start end of third portion;23223c-tail end of third portion;23223d-combining face;23223e-negative current collector of third portion;23224-first extending portion;23225-second extending portion;233-separator film;200-controller;300-motor; A-winding direction; B-winding axial direction; C-width direction; I-straight area; II-bent area;400-device for manufacturing electrode assembly;410-first providing apparatus;420-second providing apparatus; and430-assembling apparatus. DESCRIPTION OF EMBODIMENTS To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly describes the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application the described embodiments are some rather than all of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application. Unless otherwise defined, all technical and scientific terms used in the present application have the same meanings as those commonly understood by those who belong to the technical field of the present application. In the present application, the terms used in the specification of the present application are merely for the purpose of describing specific embodiments, and are not intended to limit the present application. The terms “including” and “having” and any variations thereof in the specification and claims of the present application and the above accompanying drawings are intended to cover non-exclusive inclusion. The terms “first”, “second”, etc. in the specification and claims of the present application or the above accompanying drawings are used to distinguish different objects, but not to describe a specific order or primary and secondary relationship. Reference to an “embodiment” in the present application means that a specific feature, structure or characteristic described in conjunction with an embodiment may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. In the description of the present application, it should be noted that, unless otherwise explicitly specified and defined, the terms “mounting”, “connecting”, “connection” and “attachment” should be understood in a broad sense, for example, they may be a fixed connection, a detachable connection, or an integrated connection; and may be a direct connection, or an indirect connection via an intermediate medium, or communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application could be understood according to specific circumstances. In the embodiments of the present application, the same reference numerals refer to same parts, and for the sake of brevity, detailed descriptions of the same parts are omitted in different embodiments. It should be understood that a thickness, a length, a width and other dimensions of various parts and an overall thickness, length, width and other dimensions of an integrated device shown in the accompanying drawings in the embodiments of the present application are merely exemplary, and should not constitute any limitation on the present application. The term “a plurality of” in the present application means two or more. In the present application, battery cells may include a lithium ion secondary battery, a lithium ion primary battery, a lithium-sulfur battery, a sodium lithium-ion battery, a sodium ion battery, a magnesium ion battery, etc., which is not limited by the embodiments of the present application. The battery cell may be cylindrical, flat, cuboid or in other shapes, which is not limited by the embodiments of the present application. Generally, the battery cells are divided into three types according to a packaging mode: cylindrical battery cells, square battery cells and pouch battery cells, which is not limited by the embodiments of the present application. A battery mentioned in the embodiment of the present application refers to a single physical module which includes one or a plurality of battery cells and therefore provides a higher voltage and capacity. For example, the battery mentioned in the present application may include a battery module, a battery pack, etc. Generally, the battery includes a box body for packaging one or a plurality of battery cells. The box body may prevent other foreign matter from affecting charging or discharging of the battery cell. The battery cell includes an electrode assembly and an electrolyte solution, where the electrode assembly consists of a positive electrode plate, a negative electrode plate and a separator film. The battery cell works mainly depending on movement of metal ions between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive current collector and a positive active material layer, the positive active material layer coating a surface of the positive current collector. A lithium ion battery is taken as an example, the positive current collector may be made from aluminum, and a positive active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganate, etc. The negative electrode plate includes a negative current collector and a negative active material layer, the negative active material layer coating a surface of the negative current collector. The negative current collector may be made from copper, and a negative active material may be carbon, silicon, etc. In order to guarantee that fusing does not occur during large current flow, there are a plurality of positive tabs, the plurality of positive tabs are stacked together, there are a plurality of negative tabs, and the plurality of negative tabs are stacked together. The separator film may be made from PP (polypropylene), PE (polyethylene), etc. In addition, in the present application, the electrode assembly is of a winding type structure. For development of a battery technology, various design factors should be considered at the same time, such as energy density, cycle life, discharge capacity, charge-discharge rates and other performance parameters. In addition, safety of the battery needs to be further considered. Lithium plating is one of the main factors affecting electrical performance and safety performance of the battery. Once the lithium plating occurs, it may reduce the electrical performance of the battery, and may be likely to form dendrites with accumulation of the lithium plating, which may puncture the separator film and cause short circuit in the battery, resulting in potential safety hazards. There are many reasons for the lithium plating. The applicant finds that there is a problem of the lithium plating at a winding start end and a winding tail end of the electrode assembly. After analysis, it is found that the reason that a size of a part, exceeding the positive active material layer of the positive electrode plate in a winding axial direction, of the negative active material layer of the negative electrode plate does not meet a design requirement is one of the main reasons for the lithium plating. Further studies indicate that several reasons why the size of the part, exceeding the positive active material layer of the positive electrode plate in the winding axial direction, of the negative active material layer of the negative electrode plate does not meet the design requirement are as follows: As for a head of the electrode assembly (the winding start end of the electrode assembly), due to an inaccurate feeding position, feeding and drawing out a wound winding type electrode assembly from a winding needle, a structural error of a winding device, or no binding of a head of the positive electrode plate and a head of the negative electrode plate, it is likely to cause relative deviation between the head of the positive electrode plate and the head of the negative electrode plate, resulting in that a size of a part, exceeding the positive electrode plate in the winding axial direction, of the negative electrode plate does not meet the design requirement. As for a tail of the electrode assembly (the winding tail end of the electrode assembly), the negative electrode plate may be cut off when winding is about to finish, so there is no tension at the tail of the cut negative electrode plate, and a tail of the negative electrode plate is likely to deviate from a tail of the positive electrode plate when the winding is finished. In addition, after the winding is completed, the electrode assembly needs to transfer hot pressing, which is likely to cause relative deviation between the tail of the positive electrode plate and the tail of the negative electrode plate in a transfer process, thus causing the size of the part, exceeding the positive electrode plate in the winding axial direction, of the negative electrode plate to be incapable of meeting the design requirement. In view of this, the embodiments of the present application provide a technical solution, and a maximum width difference between a negative active material layer of the negative electrode plate at the head or tail and a positive active material layer of the positive electrode plate is larger than a maximum width difference between a negative active material layer of a middle section and the positive active material layer of the positive electrode plate, so that the risk of the lithium plating caused by the reason that the size of the part, exceeding the positive active material layer of the positive electrode plate in the winding axial direction, of the negative active material layer of the negative electrode plate does not meet the design requirement is reduced. The technical solution described in the embodiment of the present application is applicable to a battery and a power consumption device using the battery. The power consumption device may be a vehicle, a mobile phone, a portable apparatus, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool, etc. The vehicles may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid electric vehicle, an extended-range vehicle, etc. The spacecraft includes an aircraft, a rocket, a space shuttle, a spaceship, etc. The electric toy includes fixed or mobile electric toys, such as a game machine, an electric car toy, an electric boat toy and an electric airplane toy. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator and an electric planer. The embodiment of the present application does not make special restrictions on the above power consumption device. In the following embodiments, a vehicle1000is taken as an example of the power consumption device for the convenience of description. With reference toFIG.1,FIG.1is a structural schematic diagram of the vehicle1000provided by some embodiments of the present application. A battery100is arranged inside the vehicle1000, and the battery100may be arranged at a bottom, a head or a tail of the vehicle1000. The battery100may be configured to supply power to the vehicle1000, for example, the battery100may be configured to an operating power source of the vehicle1000. The vehicle1000may further include a controller200and a motor300, where the controller200is configured to control the battery100to supply power to the motor300, for example, for working power requirements during starting, navigating and driving the vehicle1000. In some embodiments of the present application, the battery100may not only be used as an operating power source for the vehicle1000, but serve as a driving power source for the vehicle1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle1000. As shown inFIG.2, the battery100includes a box body10and a battery cell20, where the battery cell20is accommodated in the box body10, the box body10provides an accommodating space for the battery cell20, the box body10includes a first box body portion11and a second box body portion12, and the first box body portion11and the second box body portion12are configured to jointly define the accommodating space for accommodating the battery cell20. In the battery100, there may be one or more battery cells20. If there are a plurality of battery cells20, the plurality of battery cells20may be connected to one another in series, in parallel or in hybrid, the hybrid connection means that the plurality of battery cells20are connected in both series and parallel. The plurality of battery cells20may be directly connected in series, in parallel or in hybrid, and then a whole formed by the plurality of battery cells20can be accommodated in the box body10. Of course, the plurality of battery cells20may be connected in series, in parallel or in hybrid to form a battery module firstly, and then a plurality of battery modules are connected in series, in parallel or in hybrid to form a whole to be accommodated in the box body10. The battery cell20may be cylindrical, flat, or in other shapes. In some embodiments, the battery100may further include a bus component (not shown in the figure), and a plurality of battery cells20may be electrically connected to one another by means of the bus component, so as to realize series connection, parallel connection or parallel-series connection of the plurality of the battery cells20. With reference toFIG.3,FIG.3shows an exploded view of the battery cell20provided by some embodiments of the present application. The battery cell20includes a housing21, an end cover assembly22and an electrode assembly23, where the housing21is provided with an opening, the electrode assembly23is accommodated in the housing21, and the end cover assembly22is used to cover the opening. The housing21may be in various shapes, such as a cylinder and a flat shape. A shape of the housing21may be determined according to a specific shape of the electrode assembly23. For example, if the electrode assembly23is of a cylinder structure, the housing21may be selected to be of a cylinder structure. If the electrode assembly23is of a flat structure, the housing21may be selected to be of a cuboid structure. The housing21may be made from various materials, such as copper, iron, aluminum, stainless steel and aluminum alloy, which is not specifically limited in the embodiment of the present application. There may be one or more electrode assemblies23of the battery cell20.FIG.3shows the battery cell20with the rectangular housing21and the two flat electrode assemblies23as an example. InFIG.3, the two electrode assemblies23are arranged side by side. With reference toFIGS.4and5,FIG.4is a structural schematic diagram of a winding type electrode assembly23provided by some embodiments of the present application, andFIG.5is a cutaway view of a P0-P0direction inFIG.4. The electrode assembly23includes the positive electrode plate231, the negative electrode plate232and the separator film233, and the positive electrode plate231, the negative electrode plate232and the separator film233are arranged in a stacking mode and wound in a winding direction A to form the electrode assembly23. The separator film233is configured to separate the positive electrode plate231from the negative electrode plate232, thus avoiding the short circuit in the battery100or the battery cell20. The positive electrode plate231includes the positive tab2311and a positive body2312, the positive body2312of the positive tab231includes a first positive winding end portion23121and a positive winding middle section23122connected to each other, and the positive tab2311protrudes out of the positive body2312in the winding axial direction B; and the negative electrode plate232includes a negative body2322and the negative tab2321, the negative body2322of the negative electrode plate232includes a first portion23221and a second portion23222connected to each other, and the negative tab2321protrudes out of the negative body2322in the winding axial direction B. In a thickness direction of the positive electrode plate231, the positive tab2311may protrude out of the positive body2312and may not protrude out of the positive body2312, for example, if the positive tab2311is welded to one end of the positive body2312in the winding axial direction B, the positive tab2311may protrude out of the positive body2312in the thickness direction; and if the positive tab2311is formed by die cutting the positive current collector, the positive tab2311may not protrude out of the positive body2312. In a thickness direction of the negative electrode plate232, the negative tab2321may protrude out of the negative body2322and may not protrude out of the negative body2322, for example, if the negative tab2321is welded to one end of the negative body2322in the winding axial direction B, the negative tab2321may protrude out of the negative body2322in the thickness direction; and if the negative tab2321is formed by die cutting the negative current collector, the negative tab2321may not protrude out of the negative body2322. When the electrode assembly is in a winding state, the thickness direction of the positive electrode plate231is perpendicular to the winding axial direction B of the electrode assembly23, and the thickness direction of the negative electrode plate232is perpendicular to the winding axial direction B of the electrode assembly23. The first portion23221is arranged opposite to the first positive winding end portion23121, and the second portion23222is arranged opposite to the positive winding middle section23122; and in the winding axial direction B of the winding type electrode assembly23, the negative active material layer of the negative electrode plate232exceeds the positive active material layer of the positive electrode plate231, a maximum width of a negative active material layer23221aof the first portion is H1, a minimum width of a positive active material layer23121aof the first positive winding end portion is L1, a maximum width of a negative active material layer23222aof the second portion is H2, a minimum width of a positive active material layer23122aof the positive winding middle section is L2, and H1−L1>H2−L2. A width difference between the maximum width of the negative active material layer23221aof the first portion and the minimum width of the positive active material layer23121aof the first positive winding end portion is set to be larger than a width difference between the maximum width of the negative active material layer23222aof the second portion and the minimum width of the positive active material layer23122aof the positive winding middle section, that is, a maximum width difference between the positive active material layer23121aof the first positive winding end portion and the negative active material layer23221aof the first portion is larger than a maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section, so that the risk of the lithium plating caused by the reason that the size of the part, exceeding the positive active material layer of the positive electrode plate231in the winding axial direction B, of the negative active material layer of the negative electrode plate232does not meet the design requirement is reduced. It should be noted that a width of a positive active material of the positive electrode plate231and a width of a negative active material of the negative electrode plate232both refers to sizes of the winding type electrode assembly23in the winding axial direction B. The maximum width of the negative active material layer23221aof the first portion refers to a maximum size of the negative active material layer23221aof the first portion in the winding axial direction B; the minimum width of the positive active material layer23121aof the first positive winding end portion refers to a minimum size of the positive active material layer23121aof the first positive winding end portion in the winding axial direction B; the maximum width of the negative active material layer23222aof the second portion refers to a maximum size of the negative active material layer23222aof the second portion in the winding axial direction B; and the minimum width of the positive active material layer23122aof the positive winding middle section refers to a minimum size of the positive active material layer23122aof the positive winding middle section in the winding axial direction B. The maximum width difference refers to a difference between the maximum width and the minimum width, and the maximum width difference between the positive active material layer23121aof the first positive winding end portion and the negative active material layer23221aof the first portion refers to H1-L1; and the maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section refers to H2-L2. In some embodiments, with reference toFIGS.4and5, the first positive winding end portion23121is a positive winding starting section, the first positive winding end portion23121is the positive body2312wound for a certain distance from a start end23121bof the positive winding starting section in the winding direction A of the winding type electrode assembly23, and the positive winding middle section23122is the positive body2312connected to the tail end of the first positive winding end portion23121(a tail end23121cof the positive winding starting section) and wound in the winding direction A of the winding type electrode assembly23for a certain distance. A part with a large line width shown in the present application is a part with an increased width of the negative active material layer of the negative electrode plate232, which does not mean that a thickness of the part with the large line width of the negative electrode plate232is larger than that of a part with a small line width of the negative electrode plate232, and when the electrode assembly is in the winding state, the thickness direction of the negative electrode plate232is perpendicular to the winding axial direction B of the electrode assembly23. The first portion23221is arranged opposite to the first positive winding end portion23121, that is, the first portion23221is arranged opposite to the positive winding starting section, which is further described as that a start end23221dof the first portion corresponds to the start end23121bof the positive winding starting section, and a tail end23221eof the first portion corresponds to the tail end23121cof the positive winding starting section. When the first positive winding end portion23121is the positive winding starting section, a positive active material layer of the positive winding starting section and the negative active material layer23221aof the first portion meet a condition that H1−L1>H2−L2, so that a possibility that due to the inaccurate feeding position, feeding and drawing out the wound winding type electrode assembly from the winding needle, the structural error of the winding device, or no binding of the positive winding starting section and the first portion23221, thus causing relative deviation between the positive winding starting section and the first portion23221, resulting in that the size of the part, exceeding the positive electrode plate231in the winding axial direction B, of the negative electrode plate232does not meet the design requirement may be reduced. In some embodiments, as shown inFIG.6, the first positive winding end portion23121is a positive winding ending section, the first positive winding end portion23121is the positive body2312wound for a certain distance from a tail end23121dof the positive winding ending section in a direction opposite to the winding direction A of the winding type electrode assembly23, and the positive winding middle section23122is the positive body2312connected to a start end of the first positive winding end portion23121(a start end23121eof the positive winding ending section) and wound in the direction opposite to the winding direction A of the winding type electrode assembly23for a certain distance. The first portion23221is arranged opposite to the first positive winding end portion23121, that is, the first portion23221is arranged opposite to the positive winding ending section, which is further described as that a tail end23221eof the first portion corresponds to the tail end23121dof the positive winding ending section, and the start end23221dof the first portion corresponds to the start end23121eof the positive winding ending section. A positive active material layer of the positive winding ending section and the negative active material layer23221aof the first portion meet the condition that H1−L1>H2−L2, so that a possibility that when the winding is about to finish, there is no tension at the first portion23221after the negative electrode plate232is cut, and after the winding is completed, the electrode assembly23needs to transfer hot pressing, which is likely to cause relative deviation between the first portion23221and the positive winding ending section in the transfer process, thus causing the size of the part, exceeding the positive electrode plate231in the winding axial direction B, of the negative electrode plate232to be incapable of meeting the design requirement may be reduced. In the winding direction A, each position on the positive active material layer23121aof the first positive winding end portion has a corresponding position of the negative active material layer23221aof the first portion. In some embodiments, a maximum width position of the negative active material layer23221aof the first portion and a minimum width position of the positive active material layer23121aof the first positive winding end portion are staggered. For example, inFIG.7, M1 is the maximum width position of the negative active material layer23221aof the first portion, N1 is the minimum width position of the positive active material layer23121aof the first positive winding end portion, and M1 and N1 are staggered in the winding direction A. InFIG.7, a dotted line except a dotted line representing the separator film233is only used to clarify a relative positional relation between M1 and N1. In some embodiments, the maximum width position of the negative active material layer23221aof the first portion corresponds to a minimum width position of the first positive winding end portion23121. For example, inFIG.8, M2 is the maximum width position of the negative active material layer23221aof the first portion, N2 is the minimum width position of the positive active material layer23121aof the first positive winding end portion, and M2 corresponds to N2. InFIG.8, a dotted line except the dotted line representing the separator film233is only used to clarify a relative positional relation between M2 and N2. In order to realize the purpose that the maximum width difference between the positive active material layer23121aof the first positive winding end portion and the negative active material layer23221aof the first portion is larger than the maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section, improvement may be made to the negative electrode plate232or the positive electrode plate231or the positive electrode plate231and the negative electrode plate232. In some embodiments, a structure of the negative electrode plate232is improved so as to enable the maximum width difference between the positive active material layer23121aof the first positive winding end portion and the negative active material layer23221aof the first portion to be larger than the maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section. In some embodiments, with reference toFIG.9,FIG.9is a structural schematic diagram of the negative electrode plate232provided by some embodiments of the present application. In the winding axial direction B (consistent with a shown width direction C), the negative active material layer23221aof the first portion and the negative active material layer23222aof the second portion have a width difference, that is, H1>H2, which means that a width of the negative active material layer23221aof the first portion is increased compared with the negative active material layer23222aof the second portion, so that on the premise of guaranteeing the energy density, the risk of the lithium plating caused by the reason that the size of the part, exceeding the positive active material layer of the positive electrode plate231in the winding axial direction B, of the negative active material layer of the negative electrode plate232does not meet the design requirement may be reduced. In some embodiments, a minimum width of the negative active material layer23221aof the first portion is H3, where H3≥H2. The maximum width of the negative active material layer23221aof the first portion is larger than the maximum width of the negative active material layer23222aof the second portion, and the minimum width of the negative active material layer23221aof the first portion is not less than the maximum width of the negative active material layer23222aof the second portion, so that a possibility of the lithium plating caused by the reason that a size of a part, exceeding the positive active material layer23121aof the first positive winding end portion in the winding axial direction B, of the negative active material layer23221aof the first portion does not meet the design requirement due to relative deviation between the first positive winding end portion23121and the first portion23221may be reduced. When a width of the first portion23221is too large, it is possible that the width exceeds a width of the separator film233and the first portion further interferes with an end cover assembly22(as shown inFIG.3), increasing the short circuit risk; and if the width of the first portion23221is two small, the first portion is likely affected by a tolerance of a winding device and cannot cover the first positive winding end portion23121. In some embodiments, 0.3 mm≤H1−H2≤3 mm may guarantee use safety of the winding type electrode assembly23, may enable the first portion23221of the negative electrode plate232to cover the first positive winding end portion23121, and reduces the possibility that the size of the part, exceeding the positive active material layer of the positive electrode plate231in the winding axial direction B, of the negative active material layer of the negative electrode plate232does not meet the design requirement. In some embodiments, 0.3 mm≤H1−H2≤1.5 mm. In some embodiments, with further reference toFIG.9, the negative active material layer23221aof the first portion is of an equal-width structure, that is, the negative active material layer23221aof the first portion is consistent in width, and H1=H3. In some embodiments, as shown inFIG.9, in the winding axial direction B (consistent with the shown width direction C), two ends of the negative active material layer23221aof the first portion exceed two ends of the negative active material layer23222aof the second portion correspondingly. A dotted line inFIG.9is only used to distinguish the first portion23221from the second portion23222, and does not affect the structure of the negative electrode plate232. In some embodiments, as shown inFIG.10, in the winding axial direction B (consistent with the shown width direction C), one end of the negative active material layer23221aof the first portion exceeds a corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative active material layer23221aof the first portion is flush with the other end of the negative active material layer23222aof the second portion. A dotted line inFIG.10is only used to distinguish the first portion23221from the second portion23222, and does not affect the structure of the negative electrode plate232. The fact that the end of the negative active material layer23221aof the first portion exceeds the corresponding end of the negative active material layer23222aof the second portion means that in the winding axial direction, the end of the negative active material layer23221aof the first portion exceeds one end of the negative active material layer23222aof the second portion closest to the negative active material layer23221aof the first portion in the winding axial direction B. In some embodiments, with further reference toFIG.10, in the winding axial direction B (consistent with the shown width direction C), the negative tab2321is located at one end of the negative electrode plate232, one end of the negative active material layer23221aof the first portion close to the negative tab2321exceeds a corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative active material layer23221aof the first portion is flush with the other end of the negative active material layer23222aof the second portion, which means that the other end of the negative active material layer23221aof the first portion and the other end of the negative active material layer23222aof the second portion are coplanar. In the winding axial direction B, one end of the negative active material layer23221aof the first portion close to the negative tab2321completely exceeds the corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative active material layer23221aof the first portion is flush with the other end of the negative active material layer23222aof the second portion. As shown inFIG.11, the negative electrode plate232is generally formed by applying a negative active material layer consistent in width to the negative current collector and then forming the negative tab2321on two sides of the negative current collector in the width direction C through die cutting. The two negative electrode plates232with the negative tabs2321on single sides are formed on a middle position in the width direction C through cutting, that is, the two negative electrode plates232are formed in a dotted line direction inFIG.11through die cutting. One end of the negative active material layer23221aof the first portion close to the negative tab2321exceeds the corresponding end of the negative active material layer23222aof the second portion, so that in a process of forming the negative tab2321through the die cutting, the negative electrode plate232with a width difference between the negative active material layer23221aof the first portion and the negative active material layer23222aof the second portion may be formed, that is, the negative electrode plate with the width difference between the negative active material layer23221aof the first portion and the negative active material layer23222aof the second portion may be formed by using an original forming process of the negative electrode plate232. It should be noted that after the electrode assembly is formed through winding, the width direction C of the negative current collector is consistent with the winding axial direction B of the electrode assembly. In some embodiments, as shown inFIG.12, in the winding axial direction B (consistent with the shown width direction C), it may also be one end of the negative active material layer23221aof the first portion away from the negative tab2321that at least partially exceeds a corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative active material layer23221aof the first portion is flush with the other end of the negative active material layer23222aof the second portion. A dotted line inFIG.12is only used to distinguish the first portion23221from the second portion23222, and does not affect the structure of the negative electrode plate232. In some embodiments, the negative active material layer23221aof the first portion is of a variable-width structure, that is, the negative active material layer23221aof the first portion is inconsistent in width. The negative active material layer23221aof the first portion which is of the variable-width structure has various structural forms. With reference toFIG.13, the width of the negative active material layer23221aof the first portion gradually increases in a direction away from the second portion23222, and a width of any position of the negative active material layer23221aof the first portion is larger than the maximum width of the negative active material layer23222aof the second portion. A dotted line inFIG.13is only used to distinguish the first portion23221from the second portion23222, and does not affect the structure of the negative electrode plate232. As shown inFIG.14, a width of a part of the negative active material layer23221aof the first portion is smaller than a width of the other part of the negative active material layer23221aof the first portion, and inFIG.14, widths of negative active material layers on two sides of the negative tab2321protruding out of the first portion23221are larger than a width of a negative active material layer at a connection position between the first portion23221and the negative tab2321. When H3=H2, one end of the negative active material layer23221aof the first portion close to the negative tab2321at least partially exceeds the negative active material layer23222aof the second portion, and when H3>H2, one end of the negative active material layer23221aof the first portion close to the negative tab2321completely exceeds the negative active material layer23222aof the second portion. A dotted line inFIG.14is only used to distinguish the first portion23221from the second portion23222, and does not affect the structure of the negative electrode plate232. As long as the maximum width of the negative active material layer23221aof the first portion is larger than the maximum width of the negative active material layer23222aof the second portion and the minimum width of the negative active material layer23221aof the first portion is not less than the maximum width of the negative active material layer23222aof the second portion, the possibility of the lithium plating may be reduced. In this way, in the winding axial direction B, a width of the negative current collector23221bof the first portion and a width of the negative current collector23222bof the second portion may be consistent or not. In some embodiments, with further reference toFIG.15, in the winding axial direction B (consistent with the shown width direction C), the negative current collector23221bof the first portion and the negative current collector23222bof the second portion are consistent in width, one end of the negative active material layer23221aof the first portion close to the negative tab2321is flush with a corresponding end of the negative current collector23221bof the first portion, and the other end of the negative active material layer23221aof the first portion is flush with a corresponding end of the negative current collector23221bof the first portion; one end of the negative current collector23222bof the second portion close to the negative tab2321exceeds a corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative current collector23222bof the second portion is flush with a corresponding end of the negative active material layer23222aof the second portion; and one end of the negative active material layer23221aof the first portion close to the negative tab2321exceeds a corresponding end of the negative active material layer23222aof the second portion. In some embodiments, as shown inFIG.16, in the winding axial direction B (consistent with the shown width direction C), one end of the negative current collector23221bof the first portion away from the negative tab2321exceeds a corresponding end of the negative active material layer23221aof the first portion, and the other end of the negative current collector23221bof the first portion is flush with a corresponding end of the negative active material layer23221aof the first portion; one end of the negative current collector23222baway from the negative tab2321of the second portion exceeds a corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative current collector23222bof the second portion is flush with the corresponding end of the negative active material layer23222aof the second portion; and one end of the negative current collector23221bof the first portion away from the negative tab2321is flush with one end of the negative current collector23222bof the second portion away from the negative tab2321; and one end of the negative active material layer23221aof the first portion away from the negative tab2321is flush with a corresponding end of the negative active material layer23222aof the second portion, and one end of the negative active material layer23221aof the first portion close to the negative tab2321exceeds the corresponding end of the negative active material layer23222aof the second portion. In some embodiments, as shown inFIG.17, in the winding axial direction B (consistent with the shown width direction C), one end of the first portion23221close to the negative tab2321exceeds a corresponding end of the second portion23222, and the other end of the first portion23221is flush with the other end of the second portion23222. It may be understood that one end of the negative current collector23221bof the first portion close to the negative tab2321exceeds a corresponding end of the negative current collector23222bof the second portion, and the other end of the negative current collector23221bof the first portion is flush with the other end of the negative current collector23222bof the second portion; one end of the negative active material layer23221aof the first portion close to the negative tab2321exceeds the corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative active material layer23221aof the first portion is flush with the other end of the negative active material layer23222aof the second portion; one end of the negative current collector23221bof the first portion close to the negative tab2321is flush with one end of the negative active material layer23221aof the first portion close to the negative tab2321, and the other end of the negative current collector23221bof the first portion is flush with the other end of the negative active material layer23221aof the first portion; and one end of the negative current collector23222bof the second portion close to the negative tab2321is flush with one end of the negative active material layer23222aof the second portion close to the negative tab2321, and the other end of the negative current collector23222bof the second portion is flush with the other end of the negative active material layer23222aof the second portion. The negative electrode plate232not only facilitates coating of the negative active material layer, but also may form the negative electrode plate232with a width difference between the first portion23221and the second portion23222in the process of forming the negative tab2321through the die cutting, that is, the negative electrode plate with the width difference between the first portion23221and the second portion23222may be formed by using the original forming process of the negative electrode plate232. In some embodiments, with further reference toFIG.17, in the winding direction A, the first portion23221is provided with a connection surface23221cconnected to the second portion23222; and negative tabs2321are multiple in quantity, one negative tab2321of the multiple negative tabs2321protrudes out of the first portion23221in the winding axial direction B and is provided with a first side face2321aclose to the second portion23222, and the first side face2321aand the connection surface23221care coplanar. The connection surface23221cconnecting the first portion23221and the second portion23222is coplanar with one side face of the negative tab2321, so that a situation that the connection surface23221cwarps due to no binding and then punctures the separator film233during and after winding may be avoided. In some embodiments, with further reference toFIG.17, in the winding axial direction B (consistent with the shown width direction C), an extending direction of the first side face2321ais consistent with the winding axial direction B, and the connection surface23221cis a flat face parallel to the first side face2321a, that is, an extending direction of the connection surface23221cis consistent with the winding axial direction B. In some embodiments, as shown inFIG.18, the first side face2321ais an inclined face which gradually inclines to the second portion23222from top to bottom in the figure, the connection surface23221cis also an inclined face, and in the winding axial direction B, the connection surface23221cgradually inclines to the second portion23222from one end close to the negative tab2321. In some embodiments, as shown inFIG.19, the connection surface23221cmay also be located between the two adjacent negative tabs2321and not coplanar with a side face of any negative tab2321. In some embodiments, there may be one negative tab2321, and the first side face2321aof the negative tab2321is coplanar or not coplanar with the connection surface23221c. In some embodiments, as shown inFIG.20, in the winding axial direction B (consistent with the shown width direction C), the negative tab2321protruding out of the first portion23221is provided with a negative active material layer, and the negative active material layer2321bon the negative tab protruding out of the first portion23221is connected to the negative active material layer23221aof the first portion. The negative active material layer on the negative tab2321may further cover the positive electrode plate231, which means that a width of a negative active material layer of part of the first portion23221is further increased, so that the risk of the lithium plating caused by the reason that the size of the part, exceeding the positive active material layer of the positive electrode plate231in the winding axial direction B, of the negative active material layer of the negative electrode plate232does not meet the design requirement may be further reduced. In some embodiments, with reference toFIG.21, the winding type electrode assembly23includes a straight area I and two bent areas II, and the two bent areas II are connected to two ends of the straight area I respectively. The first portion23221passes through the straight area I at least two times. In fact, after the first portion23221passes through the straight area I two times, a winding length is close to a length of a circle, when the next circle of winding is started, a certain binding effect is made on the start end23121bof the positive winding starting section and a start end of the negative electrode plate232, and a possibility of relative deviation between the first positive winding end portion23121and the first portion23221is small, so the first portion23221passes through the straight area I at least two times, which may reduce the possibility of the lithium plating caused by the reason that the size of the part, exceeding the negative active material layer23221aof the first portion in the winding axial direction B, of the positive active material layer23121aof the first positive winding end portion does not meet the design requirement due to relative deviation between the first positive winding end portion23121and the first portion23221as much as possible. An inner side and an outer side of the positive current collector of the positive electrode plate231are both coated with positive active material layers, widths of the positive active material layers on the inner side and the outer side of the positive current collector of the positive electrode plate231may be consistent or not, an inner side and an outer side of the negative current collector of the negative electrode plate232are both coated with negative active material layers, and widths of the negative active material layers on the inner side and the outer side of the negative current collector of the negative electrode plate232may be consistent or not. In some embodiments, comparison between the width of the negative active material layer23221aof the first portion and a width of the positive active material layer23121aof the first positive winding end portion may be made by comparing only a width of a negative active material layer of the first portion23221facing the first positive winding end portion23121and a width of a positive active material layer of the first positive winding end portion23121facing the first portion23221, so that only the width of the negative active material layer of the first portion23221facing the first positive winding end portion23121may be increased so as to meet H1−L1>H2−L2. It should be noted that the inner sides and the outer sides of the positive current collector of the positive electrode plate231and the negative current collector of the negative electrode plate232are defined with respect to a winding axis, one side of the positive current collector of the positive electrode plate231close to winding axis is the inner side of the positive current collector of the positive electrode plate231, one side of the positive electrode plate231away from the winding axis is the outer side of the positive current collector of the positive electrode plate231, one side of the negative current collector of the negative electrode plate232close to the winding axis is the inner side of the negative current collector of the negative electrode plate232, and one side of the negative current collector of the negative electrode plate232away from the winding axis is the outer side of the negative current collector of the negative electrode plate232. In some embodiments, as shown inFIGS.21and22, the first portion23221passes through the straight area I two times, the first positive winding end portion23121passes through the straight area I two times. The negative active material layers on the outer sides of the negative current collector23221bof the first portion in the two straight areas I face a positive active material on an inner side of a positive current collector23121fof the first positive winding end portion, so that only the negative active material layers on the outer sides of the negative current collector23221bof the first portion in the two straight areas I may be widened so as to meet H1−L1>H2−L2. In some embodiments, as shown inFIGS.23and24, the first portion23221passes through the straight area I three times, which is divided into a straight area for first time, a straight area for second time and a straight area for third time according to a passing sequence (first→later). If the first positive winding end portion23121passes through the straight area I two times, a negative active material layer on an inner side of the negative current collector23221bof the first portion in the straight area for third time faces a positive active material layer on an outer side of a part of the positive current collector23121fof the first positive winding end portion in the straight area for first time, and negative active material layers on outer sides of parts of the negative current collector23221bof the first portion in the straight area for the first time and the straight area for second time face a positive active material layer on an inner side of the positive current collector23121fof the first positive winding end portion, so that in the winding axial direction B, only the negative active material layers on the outer sides of the negative current collector23221bof the first portion in the straight area for the first time and the straight area for second time and the negative active material layer on the inner side of the part of the negative current collector23221bof the first portion in the straight area for third time may be widened so as to meet H1−L1>H2−L2. As shown inFIG.25, if the first positive winding end portion23121passes through the straight area I three times, negative active material layers on the inner and outer sides of the part of the negative current collector23221bof the first portion in the straight area for third time face a positive active material layer on an outer side of a part of the positive current collector23121fof the first positive winding end portion in the straight area for first time and a positive active material layer on an inner side of a part of the positive current collector23121fof the first positive winding end portion in the straight area for third time respectively. The negative active material layers on the outer sides of the parts of the negative current collector23221bof the first portion in the straight area for the first time and the straight area for second time face positive active material layers on inner sides of the positive current collector23121fof the first positive winding end portion in the straight area for the first time and the straight area for second time, so that in the winding axial direction, only the negative active material layers on the outer sides of the parts of the negative current collector23221bof the first portion in the straight area for the first time and the straight area for second time and the negative active material layers on the inner and outer sides of the part of the negative current collector23221bof the first portion in the straight area for third time may be widened so as to meet H1−L1>H2−L2. In some embodiments, the winding type electrode assembly23is the cylindrical electrode assembly23, and the first portion23221is wound at least one circle. As shown inFIG.26, in order to guarantee that the negative electrode plate232is capable of completely covering the positive electrode plate231in the winding direction A, the negative body2322further includes a first extending portion23224. In the winding direction A, the first extending portion23224is connected to one end of the first portion23221away from the second portion23222, and the first extending portion23224exceeds the start end (the start end23121bof the positive winding starting section) of the first positive winding end portion23121in the direction opposite to the winding direction A. A width of a negative active material layer of the first extending portion23224in the winding axial direction B may be increased or not increased compared with that of the negative active material layer23222aof the second portion. The negative active material layer of the first extending portion23224is widened compared with the negative active material layer23222aof the second portion (with reference toFIG.23). As shown inFIG.26, the negative active material layer of the first extending portion23224is not widened compared with that of the negative active material layer23222aof the second portion. In some embodiments, as shown inFIG.27, the first extending portion23224is provided with the negative tab2321in a protruding mode, and in the winding direction A, negative active material layers of the first extending portion23224at two sides of the negative tab2321are widened compared with the negative active material layer23222aof the second portion. In some embodiments, in the winding direction A, in the negative active material layers of the first extending portion23224at the two sides of the negative tab2321, only one side of the negative active material layer is widened compared with the negative active material layer23222aof the second portion. In some embodiments, as shown inFIG.28, the positive body2312of the positive electrode plate231further includes a second positive winding end portion23123, and the first positive winding end portion23121and the second positive winding end portion23123are connected to two ends of the positive winding middle section23122respectively. The negative body2322of the negative electrode plate232further includes a third portion23223, the first portion23221and the third portion23223are connected to two ends of the second portion23222respectively, and the third portion23223is arranged opposite to the second positive winding end portion23123; and a maximum width of a negative active material layer23223aof the third portion is H4, a minimum width of a positive active material layer23123aof the second positive winding end portion is L3, and H4−L3>H2−L2. In some embodiments, the first positive winding end portion23121is the positive winding starting section, and the second positive winding end portion23123is the positive winding ending section. The first positive winding end portion23121is the positive body2312wound for a certain distance from the start end23121bof the positive winding starting section in the winding direction A of the winding type electrode assembly23, and the positive winding middle section23122is the positive body2312connected to the tail end of the first positive winding end portion23121(the tail end23121cof the positive winding starting section) and wound in the winding direction A of the winding type electrode assembly23for a certain distance. The second positive winding end portion23123is a positive body2312wound for a certain distance from a tail end23121d(a tail end of the second positive winding end portion23123) of the positive winding ending section in the direction opposite to the winding direction A of the winding type electrode assembly23, and the positive winding middle section23122is a positive body2312connected to a start end of the second positive winding end portion23123(the start end23121eof the positive winding ending section) and wound in the direction opposite to the winding direction A of the winding type electrode assembly23for a certain distance. The third portion23223is arranged opposite to the second positive winding end portion23123, that is, the third portion23223is arranged opposite to the positive winding ending section, which is further described as that a start end23223bof the third portion corresponds to the start end of the second positive winding end portion23123(the start end23121eof the positive winding ending section), and a tail end23223cof the third portion corresponds to the tail end of the second positive winding end portion23123(the tail end23121dof the positive winding ending section). The maximum width difference between the positive active material layer23121aof the first positive winding end portion and the negative active material layer23221aof the first portion is larger than the maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section, and the maximum width difference between the positive active material layer23123aof the second positive winding end portion and the negative active material layer23223aof the third portion is larger than a maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section, so that the risk of the lithium plating caused by the reason that the size of the part, exceeding the positive active material layer of the positive electrode plate231in the winding axial direction, of the negative active material layer of the negative electrode plate232does not meet the design requirement due to relative deviation between the head of the positive electrode plate231and the head of the negative electrode plate232and between the tail of positive electrode plate231and the tail of the negative electrode plate232may be reduced. In some embodiments, as shown inFIGS.28and29, H4>H2. Due to the fact that the third portion23223is arranged opposite to the second positive winding end portion23123and the second portion23222is arranged opposite to the positive winding middle section23122, the maximum width of the negative active material layer23223aof the third portion is larger than the maximum width of the negative active material layer23222aof the second portion, which means that the negative active material layer23223aof the third portion is widened compared with the negative active material layer23222aof the second portion, so that on the premise of guaranteeing the energy density, the risk of the lithium plating caused by the reason that the size of the part, exceeding the positive active material layer of the positive electrode plate231in the winding axial direction B, of the negative active material layer of the negative electrode plate232does not meet the design requirement may be reduced. In some embodiments, a minimum width of the negative active material layer23223aof the third portion is H5, and H5≥H2. The minimum width of the negative active material layer23223aof the third portion is not less than the maximum width of the negative active material layer23222aof the second portion, so that the risk of the lithium plating caused by the reason that a size of a part, exceeding the positive active material layer23123aof the second positive winding end portion in the winding axial direction B, of the negative active material layer23223aof the third portion does not meet the design requirement is reduced. A structure of the third portion23223may refer to that of the first portion23221, a structural relation between the third portion23223and the second portion23222may refer to that between the first portion23221and the second portion23222, a structure of the second positive winding end portion23123may refer to that of the first positive winding end portion23121, and a relative relation between the second positive winding end portion23123and the third portion23223may refer to that between the first positive winding end portion23121and the first portion23221, which will not be described in detail herein. With further reference toFIG.29, in the winding axial direction B (consistent with the shown width direction C), the negative tab2321is located at one end of the negative electrode plate232, one end of the negative active material layer23223aof the third portion close to the negative tab2321exceeds a corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative active material layer23223aof the third portion is flush with the other end of the negative active material layer23222aof the second portion. In the winding axial direction B, the end of the negative active material layer23223aof the third portion close to the negative tab2321completely exceeds the corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative active material layer23223aof the third portion is flush with the other end of the negative active material layer23222aof the second portion. One end of the third portion23223close to the negative tab2321exceeds a corresponding end of the second portion23222, and the other end of the third portion23223is flush with the other end of the second portion23222. It may be understood that one end of a negative current collector23223eof the third portion close to the negative tab2321exceeds a corresponding end of the negative current collector23222bof the second portion, and the other end of the negative current collector23223eof the third portion is flush with the other end of the negative current collector23222bof the second portion; one end of the negative active material layer23223aof the third portion close to the negative tab2321exceeds the corresponding end of the negative active material layer23222aof the second portion, and the other end of the negative active material layer23223aof the third portion is flush with the other end of the negative active material layer23222aof the second portion; one end of the negative current collector23223eof the third portion close to the negative tab2321is flush with one end of the negative active material layer23223aof the third portion close to the negative tab2321, and the other end of the negative current collector23223eof the third portion is flush with the other end of the negative active material layer23221aof the first portion; and one end of the negative current collector23222bof the second portion close to the negative tab2321is flush with one end of the negative active material layer23222aof the second portion close to the negative tab2321, and the other end of the negative current collector23222bof the second portion is flush with the other end of the negative active material layer23222aof the second portion. The negative electrode plate232not only facilitates coating of the negative active material layer, but also may form the negative electrode plate232with a width difference between the third portion23223in the process of forming the negative tab2321through the die cutting, that is, the negative electrode plate with the width difference between the third portion23223and the second portion23222may be formed by using the original forming process of the negative electrode plate232. The third portion23223is provided with a combining face23223dconnected to the second portion23222; and negative tabs2321are multiple in quantity, one negative tab2321of the multiple negative tabs2321protrudes out of the third portion23223in the winding axial direction B and is provided with a second side face2321cclose to the second portion23222, and the second side face2321cand the combining face23223dare coplanar. The combining face23223dand one side face of the negative tab2321are coplanar, so that a situation that the combining face23223dwarps due to no binding and then punctures the separator film233during and after winding may be avoided. The third portion23223passes through the straight area I at least one time. In some embodiments, as shown inFIGS.28and30, the third portion23223passes through the straight area I one time, the second positive winding end portion23123passes through the straight area I one time, and a negative active material layer on an inner side of the negative current collector23223eof the third portion faces a positive active material layer on an outer side of a positive current collector23123bof the second positive winding end portion, so that only the negative active material layer on the inner side of the negative current collector23223eof the third portion may be widened so as to meet H4−L3>H2−L2. In some embodiments, if an outer diameter of the winding needle for forming the electrode assembly23through winding is small, the number of times of passing through the straight area I by the third portion may be appropriately increased. In some embodiments, as shown inFIGS.31and32, the third portion23223passes through the straight area I two times, and negative active material layers on inner sides of parts of the negative current collector23223eof the third portion in the two straight areas I face a positive active material layer on an outer side of the positive current collector23123bof the second positive winding end portion, so that only the negative active material layers on the inner sides of the parts of the negative current collector23223eof the third portion in the two straight areas I may be widened so as to meet H4−L3>H2−L2. In some embodiments, as shown inFIGS.33and34, in the winding direction A, the third portion23223passes through the straight area I three times, the second positive winding end portion23123passes through the straight area I three times, which is divided into a straight area for first time, a straight area for second time and a straight area for third time according to a passing sequence (first→later). Negative active material layers on inner and outer sides of a part of the negative current collector23223eof the third portion in the straight area for first time face a positive active material layer on an outer side of a part of the positive current collector23123bof the second positive winding end portion in the straight area for first time and a positive active material layer on an inner side of a part of the positive current collector23123bof the second positive winding end portion in the straight area for third time respectively, and negative active material layers on inner sides of parts of the negative current collector23222bof the second portion in the straight area for second time and the straight area for third time face positive active material layers on outer sides of parts of the positive current collector23123bof the second positive winding end portion in the straight area for second time and the straight area for third time, so that in the winding axial direction B, only the negative active material layers on the inner and outer sides of the part of the negative current collector23223eof the third portion in the straight area for first time and the negative active material layers on the inner sides of the parts of the negative current collector23222bof the second portion in the straight area for second time and the straight area for third time may be widened so as to meet H4−L3>H2−L2. As shown inFIG.35, if the third portion23223passes through the straight area I three times, the second positive winding end portion23123passes through the straight area I two times, positive active material layers on inner and outer sides of a part of the positive current collector23123bof the second positive winding end portion in the straight area for second time face a negative active material layer on an outer side of a part of the negative current collector23223eof the third portion in the straight area for first time and a negative active material layer on an inner side of a part of the negative current collector23223eof the third portion in the straight area for third time respectively, and a positive active material layer on an outer side of a part of the positive current collector23123bof the second positive winding end portion in the straight area for first time faces a negative active material layer on an inner side of a part of the negative current collector23223eof the third portion in the straight area for second time. In the winding axial direction B, only the negative active material layer on the outer side of the part of the negative current collector23223eof the third portion in the straight area for first time and negative active material layers on inner sides of parts of the negative current collector23223eof the third portion in the straight area for second time and the straight area for third time may be widened so as to meet H4−L3>H2−L2. In order to guarantee that the negative electrode plate232is capable of completely covering the positive electrode plate231in the winding direction A, the negative body2322further includes a second extending portion23225. In the winding direction A, the second extending portion23225is connected to one end of the third portion23223away from the second portion23222, and the second extending portion23225exceeds the tail end of the second positive winding end portion23123in the winding direction A. The second extending portion23225may be widened or not widened compared with the second portion23222. InFIG.33, the second extending portion23225is widened compared with the second portion23222, and inFIG.36, a negative active material layer of the second extending portion23225is not widened compared with the negative active material layer23222aof the second portion. In some embodiments, the third portion23223may also be wound a circle. For example, when the winding type electrode assembly23is of a cylindrical structure, the third portion23223is wound at least one circle. In some embodiments, a structure of the positive electrode plate231is improved so as to enable the maximum width difference between the positive active material layer23121aof the first positive winding end portion and the negative active material layer23221aof the first portion to be larger than the maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section. In some embodiments, as shown inFIG.37, in the winding axial direction B (consistent with the shown width direction C), a maximum width of the positive active material layer23121aof the first positive winding end portion is L4, a maximum width of the positive active material layer23122aof the positive winding middle section is L5, and L4<L5, so that a maximum width difference between the first positive winding end portion23121and the first portion23221is larger than a maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section, and by changing a width of the first positive winding end portion23121of the positive electrode plate231, the risk that the size of the part, exceeding the positive active material layer of the positive electrode plate231in the winding axial direction B, of the negative active material layer of the negative electrode plate232does not meet the design requirement due to the relative deviation between the positive electrode plate231and the negative electrode plate232is reduced. In some embodiments, with further reference toFIG.37, a maximum width of the positive active material layer23123aof the second positive winding end portion is L6, the maximum width of the positive active material layer23122aof the positive winding middle section is L5, and L6<L5, so that a maximum width difference between the positive active material layer23121aof the first positive winding end portion and the negative active material layer23221aof the first portion is larger than a maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section, a maximum width difference between the positive active material layer23123aof the second positive winding end portion and the negative active material layer23223aof the third portion is larger than a maximum width difference between the negative active material layer23222aof the second portion and the positive active material layer23122aof the positive winding middle section, and the risk that the size of the part, exceeding the positive active material layer of the positive electrode plate231in the winding axial direction B, of the negative active material layer of the negative electrode plate232does not meet the design requirement due to the relative deviation between the head and the tail of the negative electrode plate232during winding is reduced. The maximum width difference between the positive active material layer23123aof the second positive winding end portion and the negative active material layer23223aof the third portion is H4−L3. In some embodiments, the positive active material layer23121aof the first positive winding end portion may be of an equal-width structure, and L1=L4. Or, the positive active material layer23121aof the first positive winding end portion may be of a variable-width structure, and L1<L4. In some embodiments, the positive active material layer23122aof the positive winding middle section may be of an equal-width structure, and L2=L5. Or, the positive active material layer23122aof the positive winding middle section may be of a variable-width structure, and L2<L5. In some embodiments, the positive active material layer23123aof the second positive winding end portion may be of an equal-width structure, and L6=L3. Or, the positive active material layer23123aof the second positive winding end portion may be of a variable-width structure, and L3<L6. In some embodiments, in the winding axial direction B, one end of the positive active material layer23122aof the positive winding middle section at least partially exceeds the corresponding end of the positive active material layer23121aof the first positive winding end portion, and the other end of the positive active material layer23122aof the positive winding middle section is flush with the other end of the positive active material layer23121aof the first positive winding end portion. In this way, the width of the first positive winding end portion23121is reduced from one side in the winding axial direction B relative to the positive winding middle section23122, so that a forming mode of the positive electrode plate231is simple and processing difficulty is reduced. In some embodiments, in the winding axial direction B, the positive tab2311is located at one end of the positive electrode plate231, and one end of the positive active material layer23122aof the positive winding middle section close to the positive tab2311exceeds the corresponding end of the positive active material layer23121aof the first positive winding end portion. One end of the positive active material layer23122aof the positive winding middle section close to the positive tab2311exceeds the corresponding end of the positive active material layer23123aof the second positive winding end portion. In this way, in a process of forming the positive tab2311through the die cutting or in a process of arranging an insulating layer23124, the positive electrode plate231with a width difference between the positive active material layer23121aof the first positive winding end portion as well as the positive active material layer23123aof the second positive winding end portion and the positive active material layer23122aof the positive winding middle section may be formed, thus reducing the processing difficulty. Generally, the positive electrode plate231further includes the insulating layer23124, and the insulating layer23124is configured to separate burrs at one end of the positive body2312in the winding axial direction B from the negative body2322(shown inFIG.18) to reduce the short circuit risk. In the winding axial direction B, the insulating layer23124is arranged between the positive tab2311and the positive active material layer on the positive body2312, and the insulating layer23124is coated in the positive current collector of the positive body2312, so that the larger a width occupied by the insulating layer23124, the smaller a width of the positive active material layer with a corresponding position capable of being subjected to coating, otherwise, the smaller the width occupied by the insulating layer23124, the larger the width of the positive active material layer with the corresponding position capable of being subjected to coating. Therefore, a minimum width of an insulating layer23124aof the first positive winding end portion is larger than a maximum width of an insulating layer23124bof the positive winding middle section. A minimum width of an insulating layer23124cof the second positive winding end portion is larger than the maximum width of the insulating layer23124bof the positive winding middle section. The insulating layer23124includes an inorganic filler and an adhesive. The inorganic filler includes one or more of boehmite, alumina, magnesia, titania, zirconia, silica, silicon carbide, boron carbide, calcium carbonate, aluminum silicate, calcium silicate, potassium titanate and barium sulfate. The adhesive includes one or more of polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, polyacrylate, polyacrylic acid-acrylate, polyacrylonitrile-acrylic acid and polyacrylonitrile-acrylate. In some embodiments, in the winding axial direction B, the widths of the first positive winding end portion23121, the positive winding middle section23122and the positive active material layer23123aof the second positive winding end portion are consistent, the insulating layer23124is coated in one sides of the first positive winding end portion23121close to the positive tab2311, the positive winding middle section23122and the positive active material layer23123aof the second positive winding end portion, and the insulating layer23124is applied to the positive active material layer, so that the insulating layer23124overlaps with the positive active material layer, and the positive active material layer not covered by the insulating layer23124is an effective active material layer of the positive body2312. The maximum widths of the insulating layer23124aof the first positive winding end portion and the insulating layer23124cof the second positive winding end portion are both larger than the maximum width of the insulating layer23124bof the positive winding middle section, so that maximum widths of an effective active material layer of the first positive winding end portion23121and an effective active material layer of the second positive winding end portion23123are both smaller than a maximum width of an effective positive active material layer of the positive winding middle section23122. In some embodiments, as shown inFIG.38, in the winding axial direction B (consistent with the width direction C), it may also be one end of the positive active material layer23122aof the positive winding middle section away from the positive tab2311that exceeds a corresponding end of the positive active material layer23121aof the first positive winding end portion. One end of the positive active material layer23122aof the positive winding middle section away from the positive tab2311exceeds the corresponding end of the positive active material layer23123aof the second positive winding end portion. In some embodiments, as shown inFIG.39, in the winding axial direction B (consistent with the width direction C), it may also be two ends of the positive active material layer23122aof the positive winding middle section that exceed two ends of the positive active material layer23121aof the first positive winding end portion correspondingly. The two ends of the positive active material layer23122aof the positive winding middle section exceeds the two end of the positive active material layer23123aof the second positive winding end portion correspondingly. In some embodiments, the structures of the positive electrode plate231and the negative electrode plate232are improved to meet H1−L1>H2−L2 and H4−L3>H2−L2. Under the condition that part or all of the width of the negative active material layer23221aof the first portion is partially or completely increased, part or all of the width of the positive active material layer23121aof the first positive winding end portion is decreased. Under the condition that part or all of the width of the negative active material layer23223aof the third portion is increased, the part or all of width of the positive active material layer23123aof the second positive winding end portion is decreased. In some embodiments, the negative active material layer23223aof the third portion is not widened compared with the negative active material layer23222aof the second portion, and by increasing a size of the negative active material layer23221aof the first portion in the winding axial direction B and decreasing a size of the positive active material layer23123aof the second positive winding end portion in the winding axial direction B, H1−L1>H2−L2 and H4−L3>H2−L2 are met. In some embodiments, the negative active material layer23221aof the first portion is not widened compared with the negative active material layer23222aof the second portion, and by decreasing a size of the positive active material layer23121aof the first positive winding end portion in the winding axial direction B and increasing a size of the negative active material layer23223aof the third portion in the winding axial direction B, H1−L1>H2−L2 and H4−L3>H2−L2 are met. The embodiments of the present application further provide the method for manufacturing a winding type electrode assembly23, and as shown inFIG.40, the method for manufacturing a winding type electrode assembly23includes thatS100: providing a positive electrode plate231, the positive electrode plate231including a first positive winding end portion23121and a positive winding middle section23122connected to each other;S200: providing a negative electrode plate232, the negative electrode plate232including a first portion23221and a second portion23222connected to each other; andS300: winding the positive electrode plate231and the negative electrode plate232to form the winding type electrode assembly23, so that the first portion23221is arranged opposite to the first positive winding end portion23121, and the second portion23222is arranged opposite to the positive winding middle section23122; and in a winding axial direction B of the winding type electrode assembly23, a negative active material layer of the negative electrode plate232exceeds a positive active material layer of the positive electrode plate231, a maximum width of a negative active material layer23221aof the first portion is H1, a minimum width of a positive active material layer23121aof the first positive winding end portion is L1, a maximum width of a negative active material layer23222aof the second portion is H2, a minimum width of a positive active material layer23122aof the positive winding middle section is L2, and H1−L1>H2−L2. In the present application, an execution sequence of all the steps of the method for manufacturing a winding type electrode assembly23is not limited, as long as the electrode assembly23is manufactured. The embodiments of the present application provide the apparatus400for manufacturing a winding type electrode assembly. As shown inFIG.41, the apparatus400for manufacturing a winding type electrode assembly includes a first providing apparatus410, a second providing apparatus420and an assembling apparatus430, where the first providing apparatus410is configured to provide a positive electrode plate231, the positive electrode plate231including a first positive winding end portion23121and a positive winding middle section23122connected to each other; the second providing apparatus420is configured to provide a negative electrode plate232, the negative electrode plate232including a first portion23221and a second portion23222connected to each other; and the assembling apparatus430is configured to wind the positive electrode plate231and the negative electrode plate232, so as to enable the first portion23221to be arranged opposite to the first positive winding end portion23121, and enable the second portion23222to be arranged opposite to the positive winding middle section23122, in a winding axial direction B of the winding type electrode assembly23, a negative active material layer of the negative electrode plate232exceeds a positive active material layer of the positive electrode plate231, a maximum width of a negative active material layer23221aof the first portion is H1, a minimum width of a positive active material layer23121aof the first positive winding end portion is L1, a maximum width of a negative active material layer23222aof the second portion is H2, a minimum width of a positive active material layer23122aof the positive winding middle section is L2, and H1−L1>H2−L2. The positive electrode plate231and the negative electrode plate232provided by the first providing apparatus410and the second providing apparatus420may overcome a defect that the part, exceeding the positive active material layer of the positive electrode plate231, of the negative active material layer of the negative electrode plate232is not enough due to the relative deviation of the positive electrode plate231and the negative electrode plate232at the head or tail caused by a structural tolerance and a winding error of the assembling apparatus430in a process of forming the winding type electrode assembly23through winding. Although the present application has been described with reference to preferred embodiments, various modifications may be made and equivalents may be substituted for parts thereof without departing from the scope of the present application. Especially, as long as there is no structural conflict, the technical features mentioned in the embodiments may be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims. | 91,546 |
11862769 | DETAILED DESCRIPTION The inventive separator includes a porous membrane (such as a microporous membrane having pores less than about 5 microns, preferably having pores less than about 1 micron, mesoporous membrane, or a macroporous membrane having pores greater than about 5 microns) made of natural or synthetic materials, such as polyolefin, polyethylene, polypropylene, phenolic resin, PVC, rubber, synthetic wood pulp (SWP), glass fibers, cellulosic fibers, or combinations thereof, more preferably a microporous membrane made from thermoplastic polymers. The preferred microporous membranes may have average pore size within the range of 0.05 to 0.5 μm, preferably 0.1 to 0.2 μm, and/or pore diameters of about 0.1 micron (100 nanometers), and/or porosities of about 20 to 80%, preferably about 60%. The thermoplastic polymers may, in principle, include all acid-resistant thermoplastic materials suitable for use in lead acid batteries. The preferred thermoplastic polymers include polyvinyls and polyolefins. The polyvinyls include, for example, polyvinyl chloride (PVC). The polyolefins include, for example, polyethylene, such as ultrahigh molecular weight polyethylene (UHMWPE), and polypropylene. One preferred embodiment may include a mixture of filler (for example, silica) and UHMWPE. The porous membrane layer can include a polyolefin, such as polypropylene, ethylene-butene copolymer, and preferably polyethylene, more preferably high molecular weight polyethylene, i.e. polyethylene having a molecular weight of at least 600,000, even more preferably ultra high molecular weight polyethylene, i.e. polyethylene having a molecular weight of at least 1,000,000, in particular more than 4,000,000, and most preferably 5,000,000 to 8,000,000 (measured by viscosimetry and calculated by Margolie's equation), a standard load melt index of substantially 0 (measured as specified in ASTM D 1238 (Condition E) using a standard load of 2,160 g) and a viscosity number of not less than 600 ml/g, preferably not less than 1,000 ml/g, more preferably not less than 2,000 ml/g, and most preferably not less than 3,000 ml/g (determined in a solution of 0.02 g of polyolefin in 100 g of decalin at 130° C.). In accordance with at least one embodiment, the porous membrane can include an ultrahigh molecular weight polyethylene (UHMWPE) mixed with a processing oil and precipitated silica. In accordance with at least one embodiment, the microporous membrane can include an ultrahigh molecular weight polyethylene (UHMWPE) mixed with a processing oil, additive and precipitated silica. The mixture may also include minor amounts of other additives or agents as is common in the separator arts (such as wetting agents, colorants, antistatic additives, and/or the like). The microporous polymer layer can be a homogeneous mixture of 8 to 100 vol. % of polyolefin, 0 to 40 vol. % of a plasticizer and 0 to 92 vol. % of inert filler material. The filler can be dry, finely divided silica. The preferred plasticizer is petroleum oil. Since the plasticizer is the component which is easiest to remove from the polymer-filler-plasticizer composition, it is useful in imparting porosity to the battery separator. In some embodiments, the porous membrane may be made by mixing, in an extruder, about 30% by weight silica with about 10% by weight UHMWPE, and about 60% processing oil. The microporous membrane can be made by passing the ingredients through a heated extruder, passing the extrudate generated by the extruder through a die and into the nip formed by two heated calender rolls to form a continuous web, extracting a substantial amount of the processing oil from the web by use of a solvent, drying the extracted web, slitting the web into lanes of predetermined width, and winding the lanes into rolls. The heated calender rolls may be engraved with various groove patterns to impart ribs to the membrane. Alternatively, or additionally, ribs may be imparted to the porous membrane by passing the extruded membrane through additional appropriately grooved embossing rolls, calender rolls or presses. The microporous polymer layer can have an average pore size of less than 1 μm in diameter. Preferably more than 50% of the pores are 0.5 μm or less in diameter. It is especially preferred that at least 90% of the pores have a diameter of less than 0.5 μm. The microporous polymer layer preferably has an average pore size within the range of 0.05 to 0.5 μm, preferably 0.1 to 0.2 μm. In some embodiments, the additive includes a surfactant. Suitable surfactants include surfactants such as salts of alkyl sulfates; alkylarylsulfonate salts; alkylphenol-alkylene oxide addition products; soaps; alkyl-naphthalene-sulfonate salts; dialkyl esters of sulfo-succinate salts; quaternary amines; block copolymers of ethylene oxide and propylene oxide; and salts of mono and dialkyl phosphate esters. The additive can be a non-ionic surfactant such as polyol fatty acid esters, polyethoxylated esters, polyethoxylated alcohols, alkyl polysaccharides such as alkyl polyglycosides and blends thereof, amine ethoxylates, sorbitan fatty acid ester ethoxylates, organosilicone based surfactants, ethylene vinyl acetate terpolymers, ethoxylated alkyl aryl phosphate esters and sucrose esters of fatty acids. In certain embodiments, the additive can be represented by a compound of Formula (I) R(OR1)n(COOMx+1/x)m(I) in whichR is a non-aromatic hydrocarbon radical with 10 to 4200 carbon atoms, preferably 13 to 4200, which can be interrupted by oxygen atoms,R1is H, —(CH2)kCOOMx+1/xor —(CH2)k—SO3Mx+1/x, preferably H, where k is 1 or 2,M is an alkali metal or alkaline-earth metal ion, H+or NH4+, where not all the variables M simultaneously have the meaning H+,n is 0 or 1,m is 0 or an integer from 10 to 1400 andx is 1 or 2,the ratio of oxygen atoms to carbon atoms in the compound according to Formula (I) being in the range from 1:1.5 to 1:30 and m and n not being able to simultaneously be 0. However, preferably only one of the variables n and m is different from 0. By non-aromatic hydrocarbon radicals is meant radicals which contain no aromatic groups or which themselves represent one. The hydrocarbon radicals can be interrupted by oxygen atoms, i.e. contain one or more ether groups. R is preferably a straight-chain or branched aliphatic hydrocarbon radical which can be interrupted by oxygen atoms. Saturated, uncross-linked hydrocarbon radicals are quite particularly preferred. Surprisingly it was found that through the use of the compounds of Formula (I) for the production of battery separators, they can be effectively protected against oxidative destruction. Battery separators are preferred which contain a compound according to Formula (I) in whichR is a hydrocarbon radical with 10 to 180, preferably 12 to 75 and quite particularly preferably 14 to 40 carbon atoms, which can be interrupted by 1 to 60, preferably 1 to 20 and quite particularly preferably 1 to 8 oxygen atoms, particularly preferably a hydrocarbon radical of formula R2—[(OC2H4)p(OC3H6)q]—, in whichR2is an alkyl radical with 10 to 30 carbon atoms, preferably 12 to 25, particularly preferably 14 to 20 carbon atoms,P is an integer from 0 to 30, preferably 0 to 10, particularly preferably 0 to 4 andq is an integer from 0 to 30, preferably 0 to 10, particularly preferably 0 to 4,compounds being particularly preferred in which the sum of p and q is 0 to 10, in particular 0 to 4,n is 1 andm is 0. Formula R2—[(OC2H4)p(OC3H6)q]— is to be understood as also including those compounds in which the sequence of the groups in square brackets differs from that shown. For example according to the invention compounds are suitable in which the radical in brackets is formed by alternating (OC2H4) and (OC3H6) groups. Additives in which R2is a straight-chain or branched alkyl radical with 10 to 20, preferably 14 to 18 carbon atoms have proved to be particularly advantageous. OC2H4preferably stands for OCH2CH2, OC3H6for OCH(CH3)CH2and/or OCH2CH(CH3). As preferred additives there may be mentioned in particular alcohols (p=q=0; m=0) primary alcohols being particularly preferred, fatty alcohol ethoxylates (p=1 to 4, q=0), fatty alcohol propoxylates (p=0; q=1 to 4) and fatty alcohol alkoxylates (p=1 to 2; q=1 to 4) ethoxylates of primary alcohols being preferred. The fatty alcohol alkoxylates are for example accessible through reaction of the corresponding alcohols with ethylene oxide or propylene oxide. Additives of the type m=0 which are not, or only difficulty, soluble in water and sulphuric acid have proved to be particularly advantageous. Also preferred are additives which contain a compound according to Formula (I), in whichR is an alkane radical with 20 to 4200, preferably 50 to 750 and quite particularly preferably 80 to 225 carbon atoms,M is an alkali metal or alkaline-earth metal ion, H+or NH4+, in particular an alkali metal ion such as Li+, Na+and K+or H+, where not all the variables M simultaneously have the meaning H+,n is 0,m is an integer from 10 to 1400 andx is 1 or 2. As suitable additives there may be mentioned here in particular polyacrylic acids, polymethacrylic acids and acrylic acid-methacrylic acid copolymers, whose acid groups are at least partly, i.e. preferably 40%, particularly preferably 80%, neutralized. The percentage refers to the number of acid groups. Quite particularly preferred are poly(meth)acrylic acids which are present entirely in the salt form. By poly(meth)acrylic acids are meant polyacrylic acids, polymethacrylic acids and acrylic acid-methacrylic acid copolymers. Poly(meth)acrylic acids are preferred and in particular polyacrylic acids with an average molar mass Mwof 1,000 to 100,000 g/mol, particularly preferably 1,000 to 15,000 g/mol and quite particularly preferably 1,000 to 4,000 g/mol. The molecular weight of the poly(meth)acrylic acid polymers and copolymers is ascertained by measuring the viscosity of a 1% aqueous solution, neutralized with sodium hydroxide solution, of the polymer (Fikentscher's constant). Also suitable are copolymers of (meth)acrylic acid, in particular copolymers which, besides (meth)acrylic acid contain ethylene, maleic acid, methyl acrylate, ethyl acrylate, butyl acrylate and/or ethylhexyl acrylate as comonomer. Copolymers are preferred which contain at least 40 wt.-%, preferably at least 80 wt.-% (meth)acrylic acid monomer, the percentages being based on the acid form of the monomers or polymers. To neutralize the polyacrylic acid polymers and copolymers, alkali metal and alkaline-earth metal hydroxides such as potassium hydroxide and in particular sodium hydroxide are particularly suitable. The porous membrane can be provided in various ways with the additives, agents, and/or fillers, and/or can be coated with the additives. For example, the additive be applied to the porous membrane when it is finished (i.e. after the extraction) and/or added to the mixture used to produce the membrane. According to a preferred embodiment, the additive or a solution of the additive is applied to the surface of the porous membrane. This variant is suitable in particular for the application of non-thermostable additives and additives which are soluble in the solvent used for the subsequent extraction. Particularly suitable as solvents for the additives according to the invention are low-molecular-weight alcohols, such as methanol and ethanol, as well as mixtures of these alcohols with water. The application can take place on the side facing the negative electrode, the side facing the positive electrode or on both sides of the microporous membrane. The application may also take place by dipping the microporous membrane in the additive or a solution of the additive and subsequently optionally removing the solvent, e.g. by drying. In this way the application of the additive can be combined for example with the oil extraction often applied during separator production. Another preferred option is to mix the additive or additives into the mixture of thermoplastic polymer and optionally fillers and other additives which is used to produce the porous membrane. The additive-containing homogeneous mixture is then formed into a web-shaped material. The additive can be present at a density of at least about 0.5 g/m2, 1.0 g/m2, 1.5 g/m2, 2.0 g/m2, 2.5 g/m2, 3.0 g/m2, 3.5 g/m2, 4.0 g/m2, 4.5 g/m2, 5.0 g/m2, 5.5 g/m2, 6.0 g/m2, 6.5 g/m2, 7.0 g/m2, 7.5 g/m2, 8.0 g/m2, 8.5 g/m2, 9.0 g/m2, 9.5 g/m2or 10.0 g/m2. The additive can be present on the separator at a density between about 0.5-10 g/m2, 1.0-10.0 g/m2, 1.5-10.0 g/m2, 2.0-10.0 g/m2, 2.5-10.0 g/m2, 3.0-10.0 g/m2, 3.5-10.0 g/m2, 4.0-10.0 g/m2, 4.5-10.0 g/m2, 5.0-10.0 g/m2, 5.5-10.0 g/m2, 6.0-10.0 g/m2, 6.5-10.0 g/m2, 7.0-10.0 g/m2, 7.5-10.0 g/m2, 5.0-10.5 g/m2, 5.0-11.0 g/m2, 5.0-12.0 g/m2, or 5.0-15.0 g/m2. The additive can be present on the microporous membrane at a density of about 6.0-10.0 g/m2, 6.5-9.5 g/m2, 6.5-9.0 g/m2, 6.5-8.5 g/m2, 6.5-8.0 g/m2, or 7.0-8.0 g/m2. In some embodiments, the additive is present at a density of about 7.5 g/m2. In certain selected embodiments, the porous membrane may further contain one or more PIMS material. A PIMS mineral derived from fish bone (such as commercial, lab ground fish meal) has been shown to have greatest affinity for metal ions. The fish bone powder can be extruded via pilot operation into a typical battery separator format at several loading concentrations. In accordance with at least certain embodiments, it is preferred that the fish bone powder be added to substitute for a portion of the silica at substitution levels of about 1% to 20% of the silica, more preferably about 2% to 10%, and most preferably at about 2% to 5%. In accordance with at least other certain embodiments, it is preferred that the ground fish bone powder (ground fish meal) be added to substitute for a portion of the silica at substitution levels of about 1% to 50% or more of the silica, more preferably about 5% to 30%, and most preferably at about 10% to 20%. In accordance with at least another object of the present invention, there is provided a microporous membrane with ribs. The microporous membrane can have transverse cross-ribs on the opposite face of the membrane as the longitudinal ribs. The cross-rib can be parallel to the longitudinal ribs, or can be disposed at an angle thereto. For instance, the cross ribs can be oriented about 90°, 80°, 75°, 60°, 50°, 45°, 35°, 25°, 15° or 5° relative to the longitudinal ribs. The cross-ribs can be oriented about 90-60°, 60-30°, 60-45°, 45-30°, or 30-0° relative to the longitudinal ribs. Typically the cross ribs are on the face of the membrane facing the negative electrode. In some embodiments of the present invention, the ribbed membrane can have a transverse cross-rib height of at least about 0.005 mm, 0.01 mm, 0.025 mm, 0.05 mm, 0.075 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1.0 mm. In some embodiments of the present invention, the ribbed membrane can have a transverse cross-rib height of no greater than about 1.0 mm, 0.5 mm, 0.25 mm, 0.20 mm, 0.15 mm, 0.10 mm or 0.05 mm. The ribbed membrane can have a transverse cross-rib height between about 0.005-1.0 mm, 0.01-0.5 mm, 0.025-0.25 mm, 0.05-0.25 mm, 0.075-0.25 mm, 0.075-0.20 mm, 0.075-0.15 mm, 0.10-0.25 mm, 0.1-0.20, 0.10-0.15 mm, or 0.10-0.125 mm. In some embodiments of the present invention, the ribbed membrane can have a transverse cross-rib width of at least about 0.005 mm, 0.01 mm, 0.025 mm, 0.05 mm, 0.075 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1.0 mm. In some embodiments of the present invention, the ribbed membrane can have a transverse cross-rib width of no greater than about 1.0 mm, 0.5 mm, 0.25 mm, 0.20 mm, 0.15 mm, 0.10 mm or 0.05 mm. The ribbed membrane can have a transverse cross-rib width between about 0.005-1.0 mm, 0.01-0.5 mm, 0.025-0.25 mm, 0.05-0.25 mm, 0.075-0.25 mm, 0.075-0.20 mm, 0.075-0.15 mm, 0.10-0.25 mm, 0.1-0.20, 0.10-0.15 mm, or 0.10-0.125 mm. The spacing between the transverse cross-ribs (pitch-to-pitch width) can be from about 0.10-1.0 mm, 0.2-1.0 mm, 0.3-1.0 mm, 0.4-0.9 mm, 0.4-0.8 mm, 0.5-0.8 mm, 0.5-0.7 mm, or 0.6-0.7 mm. In some embodiments of the present invention, the ribbed membrane can have longitudinal rib height of at least about 0.005 mm, 0.01 mm, 0.025 mm, 0.05 mm, 0.075 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, or 1.5 mm. The ribbed membrane can have a longitudinal rib height between about 0.005-1.5 mm, 0.01-1.0 mm, 0.025-1.0 mm, 0.05-1.0 mm, 0.075-1.0 mm, 0.1-1.0 mm, 0.2-1.0 mm, 0.3-1.0 mm, 0.4-1.0 mm, 0.5-1.0 mm, 0.4-0.8 mm or 0.4-0.6 mm. The ribbed membrane can have a longitudinal rib height from about 0.01-0.2 mm, 0.05-0.2 mm, 0.05-0.15 mm, 0.075-0.15 mm, 0.1-0.15 mm, or 0.1 to 0.125 mm. In some embodiments of the present invention, the ribbed membrane can have longitudinal rib width of at least about 0.005 mm, 0.01 mm, 0.025 mm, 0.05 mm, 0.075 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, or 1.5 mm. The ribbed membrane can have a longitudinal rib width between about 0.005-1.5 mm, 0.01-1.0 mm, 0.025-1.0 mm, 0.05-1.0 mm, 0.075-1.0 mm, 0.1-1.0 mm, 0.2-1.0 mm, 0.3-1.0 mm, 0.4-1.0 mm, 0.5-1.0 mm, 0.4-0.8 mm or 0.4-0.6 mm. The ribbed membrane can have a longitudinal rib width from about 0.01-0.2 mm, 0.05-0.2 mm, 0.05-0.15 mm, 0.075-0.15 mm, 0.1-0.15 mm, or 0.1 to 0.125 mm. The spacing between the longitudinal ribs (pitch-to-pitch width) can be from about 0.10-1.0 mm, 0.2-1.0 mm, 0.3-1.0 mm, 0.4-0.1 mm, 0.5-1.0 mm, 0.5-0.9 mm, 0.6-0.9 mm, 0.6-0.8 mm, or 0.7-0.8 mm. The longitudinal ribs can be present in a “U” shape, semicircular or rectangular. In some embodiments, the rib height of the longitudinal ribs can be greater than the height of the cross ribs and the rib spacing of the longitudinal ribs can be greater than the spacing of the cross ribs. In certain selected embodiments the porous membrane can have a transverse cross-rib (negative cross ribs, transverse mini-ribs) height of about 0.10-0.15 mm, and a longitudinal rib height of about 0.1-0.15 mm or greater. In some embodiments, the porous membrane can have a transverse cross-rib height of about 0.10-0.125 mm, a longitudinal rib height of about 0.1-0.125 mm, a transverse cross rib width of about 0.5-0.7 mm and a longitudinal rib width of about 0.6-0.9 mm. The microporous membrane can have a backweb thickness that is at least 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1.0 mm. The ribbed separator can have a backweb thickness that is no more than about 1.0 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm, 0.4 mm, 0.3 mm, 0.2 mm or 0.1 mm. In some embodiments, the microporous membrane can have a backweb thickness between about 0.1-1.0 mm, 0.1-0.8 mm, 0.1-0.5 mm, 0.2-0.5 mm, 0.2-0.4 mm, 0.25-0.35 mm. In some embodiments, the microporous membrane can have a backweb thickness of about 0.3 mm. In certain selected embodiments the porous membrane can have a transverse cross-rib height of about 0.10-0.15 mm, a longitudinal rib height of about 0.10-0.15 mm, and a backweb thickness of about 0.25-0.35 mm. In some embodiments, the porous membrane can have a transverse cross-rib height of about 0.10-0.125 mm, a longitudinal rib height of about 0.10-0.125 mm, and a backweb thickness of about 0.3 mm. In some embodiments, the porous membrane can have a total thickness (i.e., rib tip to rib tip) from about 0.2-0.8 mm, 0.3-0.7 mm, or 0.4-0.6 mm. In some embodiments, the total thickness can be about 0.5-0.55 mm. In some selected embodiments, the separator also contains one of more fibrous layers. In certain embodiments, the side of the microporous membrane facing the positive electrode has a fibrous layer, while in other embodiments, the side of the microporous membrane facing the negative electrode has a fibrous layer. In some preferred embodiments, a fibrous layer is present on both sides of the microporous membrane. The fibrous layers can be made of glass fibers, polymeric fibers or a mixture of glass fibers and polymeric fibers. Suitable mats made of polymer fibers which may be used as fibrous layers in the present invention are disclosed in U.S. Pat. No. 5,962,161, the disclosure of which is incorporated herein by reference. The preferred fibrous material is glass. Generally all glass fiber materials known in the art for producing glass mats or absorptive glass mat (AGM) separators may be used for forming the fibrous layers of the present invention. A preferred fibrous material are absorptive microfiber glass fleeces without organic components like binder or polymeric fibers. It is preferred that the fibers have a diameter ranging from 0.1 to 10 μm, more preferably from 0.1 to 5 μm. The fibers are preferably blends of acid resistant glass fibers of various diameter, usually extremely thin fibers with an average fiber diameter below 1 μm, referred to as microfibers, and “coarse” fibers with an average diameter of approx. 3 μm. The microfibers increase the internal surface, improve the tensile strength and decrease the pore diameter but significantly increase the product cost. The larger fibers facilitate the battery filling by creating larger pores with faster acid pick-up, often referred to as wicking rate. In some embodiments, the fibrous glass layers can comprise 20 to 40% by weight of glass microfibers having an average diameter of less than 1 μm and 60 to 80% by weight of coarse glass fibers having an average diameter of about 3 μm, for instance 30% by weight microfibers and 70% by weight coarse fibers. In certain embodiments, the fibers can have higher diameters, for instance about 5-25 μm, 5-15 μm, 10-15 μm, 10-25 μm, 10-20 μm or 15-20 μm. Blends of such fibers can also be employed, for instance blends of 10-15 μm fibers and 15-20 μm fibers. In some embodiments, fibers having a length of about 0.5-2.0 mm, 0.5-1.5 mm, or 1.0-1.5 mm can be employed. Suitable glass fiber mats and the preparation thereof are well known to a person skilled in the art (see for instance Böhnstedt W., in Handbook of Battery Materials, Editor Besenhard J. O., Wiley-VCH, Weinheim 1999, pages 245 to 292 and literature cited therein). Preferred fibrous layers made of polymer fibers comprises a nonwoven web, mat or fleece of fibers of a diameter of 0.1 to 10 μm, preferably 0.1 to 5 μm. It is preferred that more than 10% by weight of the fibers, more preferably more than 15% by weight of the fibers and most preferably 20 to 40% by weight of the fibers have a diameter smaller than 1 μm, preferably about 0.1 μm, and it is further preferred that at least 60% by weight of the fibers have diameters of less than 5 μm. The fibers are made of a thermoplastic polymer, which is preferably selected from the group consisting of polyolefins, polystyrenes, polyamides, polyesters, halogenated polymers, and the respective copolymers, more preferably polyolefins and in particular polyethylenes and polypropylenes. To render the fibrous layer wettable, a suitable surface active agent is added to the polymer prior to extrusion or hydrophilic groups are covalently bonded to the surface of the fibers after formation. Suitable treatments are described in U.S. Pat. No. 5,962,161, the disclosure of which is incorporated herein by reference. Nonwoven mats of this type can be manufactured by extrusion and blowing processes. One preferred way is described in U.S. Pat. No. 6,114,017, which comprises melting a polymer by polymer heating and extrusion means, extruding said polymer at flow rates of less than 1 g/min/hole through polymer orifices arranged in one or more spaced apart cross directional rows on one or more modular dies heated by a heating unit, wherein the diameters of said orifices may be equal to each other or may differ from row to row to obtain a web comprising fibers of essentially uniform or varying diameter, blowing said polymer extrudate using heated air of at least 95° C. from two or more constant or variable cross-section air jets per polymer orifice, preferably variable cross-section air jets being converging-diverging nozzles capable of producing supersonic drawing velocities, or tempered air between 10° C. and 375° C. of two or more continuous converging-diverging nozzle slots placed adjacent and essentially parallel to said polymer orifice exits to attenuate said filaments and to produce essentially continuous polymer filaments, and depositing said fiberized polymer on a collecting means to form a self-bonded web consisting of as many layers of disbursed continuous polymer filaments as the number of rows of said polymer orifices in said die. U.S. Pat. No. 5,679,379 discloses modular die units suitable for the production of the above nonwoven mats. The disclosure of both U.S. Pat. Nos. 6,114,017 and 5,679,379 is incorporated herein by reference. The self-bonded webs produced in the above process may also be thermally bonded to provide even greater strength by using conventional hot calendering techniques where the calender rolls may pattern engraved or flat. The nonwoven webs, mats or fleeces have low average diameters, improved uniformity, a narrow range of fiber diameters, and significantly higher unbonded strength than a typical meltblown web. When the material is thermally bonded it is similar in strength to spunbonded nonwovens of the same polymer and basis weight. When a mixture of glass fibers and polymeric fibers is used, the different fibers are preferably used in such proportions that the sheet has an absorbency with respect to the electrolyte of from 75 to 95% in the absence of a surfactant. Preferably the glass and polymeric fibers defined above are used. Fibrous sheets of this type may be prepared by the methods disclosed in U.S. Pat. No. 4,908,282, the disclosure of which is incorporated herein by reference. The fibrous layers can be present on the microporous membrane at a thickness of at least about 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm or 1.5 mm. In some embodiments, the fibrous layers can be present on the microporous membrane at a thickness from about 0.1-1.5 mm, 0.5-1.5 mm, 0.75-1.5 mm, 0.75-1.25 mm or 1.0-1.25 mm. In certain selected embodiments the porous membrane can have a transverse cross-rib height of about 0.10-0.15 mm, a longitudinal rib height of about 0.10-0.15 mm, a backweb thickness of about 0.25-0.35 mm, and fibrous layers present on both faces of the membrane having a thickness of about 0.75-1.25 mm. In certain embodiments, it is preferred that the fibrous layer is only on the side of the porous membrane that faces the positive electrode. In some embodiments, the porous membrane can have a transverse cross-rib height of about 0.10-0.125 mm, a longitudinal rib height of about 0.10-0.125 mm, a backweb thickness of about 0.3 mm, and fibrous layers present on both faces of the membrane having a thickness of about 0.75-1.25 mm. The separators of the present invention can be provided either in sheet form or in the form of an envelope. In some embodiments, a microporous membrane, covered on at least one side with at least one fibrous layer, is provided as a pocket or envelope. In such embodiments, it is preferred that the microporous membrane has a larger surface area than the fibrous layers. Thus, when combining the microporous membrane and the fibrous layers, the fibrous layers do not completely cover the microporous layer. It is preferred that at least two opposing edge regions of the membrane layer remain uncovered to provide edges for heat sealing which facilitates the formation of pockets or envelope. The separators can be processed to form hybrid envelopes. The hybrid envelope can be formed by forming one or more slits or openings before, during or after, folding the separator sheet in half and bonding edges of the separator sheet together so as to form an envelope. The slits are preferably in or near the bottom fold of the pocket or envelope. The sides are bonded together using welds or mechanical seals to form seams that bring one side of the separator sheet into contact with another side of the separator sheet. Welds can be accomplished, for instance, using heat or ultrasonic processes. This process results in an envelope shape having a bottom folded edge and two lateral edges. The fibrous layer can be present on the inner face or the envelope, the outer face or the envelope, or both faces of the envelope. Separators disclosed herein in the form of an envelope may have one or more slits or openings along the folded or sealed creases of the envelope. The length of the openings can at least 1/50th, 1/25th, 1/20th, 1/15th, 1/10th, ⅛th, ⅕th, ¼th, or ⅓rdthe length of the entire edge. The length of the openings can be 1/50thto ⅓rd, 1/25thto ⅓rd, 1/20thto ⅓rd, 1/20thto ¼th, 1/15thto ¼th, 1/15thto ⅕thor 1/10thto ⅕ththe length of the entire edge. The hybrid envelope can have 1-5, 1-4, 2-4, 2-3 or 2 openings, which may or may not be equally disposed along the length of the bottom edge. It is preferred that no opening is in the corner of the envelope. The slits may be cut after the separator has been folded and sealed to give an envelope, or the slits may be formed prior to shaping the porous membrane into the envelop. EXAMPLE 1 Details of Test Battery A Battery Type: 12V, 100 AhPlates per Cell: 15 (7 pos.+8 neg.)Grid Antimony Content: Selenium alloy grids with 2.5% Sb in the positive grids, and 1.60% Sb in the negative gridsGrid Thickness: 2.2 mm thick positive grids, and 1.7 mm thick negative gridsPlate Thickness: 2.4 mm thick positive plates, and 1.9 mm thick negative platesPaste Density: 4.20 g/cc on the positive plates, and 4.45 g/cc on the negative plates Details of Separators Standard PE Separator: Profile: Standard RibbedBack Web: 250 μmOverall Thickness: 1.8 mm (1.0 mm thick PE Separator+0.8 mm thick Glassmat)Separator Form: Positive plate enveloping New Separator:Profile: Special profile with ribs on both sides, longitudinal ribs parallel to the machine direction on the positive side (the side adapted to face the positive plate in the battery) and cross ribs orthogonal to the machine direction on the negative side (the side adapted to face the negative plate in the battery) (seeFIG.20).Back Web: 300 μmOverall Thickness: 1.6 mm (0.50 mm thick New Separator+1.1 mm thick Glassmat)Coating Density: 7.5 g/m2Separator Form: Hybrid envelope, enveloping the negative plate With reference toFIGS.11-14, comparison data between batteries equipped with the two separators described above are illustrated. As can be seen, the batteries equipped with the exemplary inventive separator yield less water loss and a lower end of charge current during the first 50 cycles. EXAMPLE 2 Details of Test Battery B Battery Type: 12V, 100 AhPlates per Cell: 15 (7 pos.+8 neg.)Grid Antimony Content: Selenium alloy grids with 2.5% Sb in the positive grids, and 1.60% Sb in the negative grids.Grid Thickness: 2.1 mm thick positive grids, and 1.85 mm thick negative gridsPlate Thickness: 2.3 mm thick positive plates, and 2.05 mm thick negative platesPaste Density: 4.25 g/cc on the positive plates, and 4.55 g/cc on the negative plates Details of Separators Standard Fiber Based Separator: Profile: Standard RibbedMaterial: Fiber basedOverall Thickness: 1.6 mm (1.0 mm thick PE Separator+0.6 mm thick Glassmat)Separator Form: Negative plate enveloping New Separator:Profile: Special profile with ribs on both sides, longitudinal ribs parallel to the machine direction on the positive side (the side adapted to face the positive plate in the battery) and cross ribs orthogonal to the machine direction on the negative side (the side adapted to face the negative plate in the battery) (seeFIG.20).Back Web Thickness: 300 μmOverall Thickness: 1.6 mm (0.50 mm thick New Separator+1.1 mm thick Glassmat)Coating Density: 7.5 g/m2Separator Form: Hybrid envelope, enveloping the negative plate With reference toFIGS.15-18, comparison data between batteries equipped with the two separators described above are illustrated. As can be seen, the batteries equipped with the exemplary inventive separator yield less water loss and a lower end of charge current during the first 25 cycles. EXAMPLE 3 Details of Test Battery C Battery Type: 12V, 100 AhPlates per Cell: 15 (7 pos.+8 neg.)Grid Antimony Content: Selenium alloy grids with 1.7% Sb in the positive grids, and 0.11% Ca in the negative gridsGrid Thickness: 2.1 mm thick positive grids, and 1.6 mm thick negative gridsPlate Thickness: 2.3 mm thick positive plates, and 1.8 mm negative platesPaste Density: 4.20 g/cc on the positive plates, and 4.45 g/cc on the negative plates Details of Separators Standard PE Separator: Profile: No ribs on the pos. side, mini ribs on the negative side.Back Web: 250 μmOverall Thickness: 1.4 mm (0.40 mm thick PE Separator+1.0 mm thick Glassmat)Separator Form: Negative plate enveloping New Separator:Profile: Special profile with ribs on both sides, longitudinal ribs parallel to the machine direction on the positive side (the side adapted to face the positive plate in the battery) and cross ribs orthogonal to the machine direction on the negative side (the side adapted to face the negative plate in the battery) (seeFIG.20).Back web: 300 μmOverall Thickness: 1.5 mm (0.50 mm thick New Separator+1.0 mm thick Glassmat)Coating Density: 7.5 g/m2Separator Form: Hybrid envelope, enveloping the negative plate With reference toFIG.19, comparison data between batteries equipped with the two separators described above are illustrated. As can be seen, the batteries equipped with the exemplary inventive separator yield less water loss and a lower end of charge current. On average, batteries equipped with an exemplary inventive separator as described herein yield approximately 47% less water loss as compared to batteries tested with standard control separators. This reduction in water loss, in addition to a lower end of charge current, helps reduce positive grid corrosion and has been observed to yield approximately 25% less grid corrosion. The relatively small overall thickness of the exemplary separators allow for a relatively thicker glass mat. In addition, the negative cross ribs on the negative side of the separator help to reduce stratification and therefore support rechargeability. Besides lowering water loss and leading to extended battery life, preferred separators are also designed to bring other benefits. With regard to assembly, the separators have the negative cross rib design to maximize bending stiffness and ensure highest manufacturing productivity. To prevent shorts during high speed assembly and later in life, the separators have superior puncture and oxidation resistance when compared to standard PE separators. Disclosed herein are novel or improved separators, battery separators, lead battery separators, batteries, cells, and/or methods of manufacture and/or use of such separators, battery separators, lead battery separators, cells, and/or batteries. In accordance with at least certain embodiments, aspects or objects, the present disclosure or invention is directed to novel or improved battery separators for lead acid batteries. In addition, disclosed herein are methods, systems and battery separators for enhancing battery life, reducing active material shedding, reducing grid and spine corrosion, reducing failure rate reducing acid stratification and/or improving uniformity in at least lead acid batteries, in particular batteries for electric rickshaws. In accordance with at least particular embodiments, the present disclosure or invention is directed to an improved separator for lead acid batteries wherein the separator includes improved membrane profiles, improved coatings, improved configurations, and/or the like. In accordance with at least certain embodiments, aspects or objects, the present disclosure or invention is directed to or provides an improved separator for use in a battery for an electric rickshaw comprising: a porous membrane comprisingan additive at a density from about 4.0-10.0 g/m2;cross ribs having a height from about 0.075-0.15 mm;longitudinal ribs having a height from about 0.075-0.15 mm;a backweb thickness of about 0.20-0.35 mm; and optionally a fibrous layer on at least one face of the porous membrane, the separator having a total thickness of about 0.425-3.0 mm, the separator or membrane being a piece, sleeve, wrap, pocket, or envelope, and/or the separator or membrane having one or more slits or openings. The above separator, wherein the porous membrane is a microporous membrane, wherein the membrane comprises polyethylene, wherein the membrane comprises ultrahigh molecular weight polyethylene, wherein the additive is a surfactant, wherein the additive is a non-ionic surfactant, wherein the additive is present at a density of about 7.5 g/m2, wherein the cross ribs have a rib height of about 0.075-0.125 mm, wherein the longitudinal ribs have a rib height of about 0.075-0.125 mm, wherein the fibrous layer comprises glass fibers, wherein the fibrous layer is present on both sides of the porous membrane, wherein the fibrous layer is from about 0.75-1.25 mm thick, wherein the porous membrane is in the shape of an envelope or pocket, wherein the envelope comprises at least one slit, wherein the separator having a total thickness of about 1.5-2.7 mm, wherein the backweb thickness is about 0.30 mm, wherein the additive is a surfactant coating, wherein the additive is a component of the polymer mixture, or combinations thereof. An improved separator for use in a battery adapted for an electric rickshaw comprising: a porous membrane comprisingcross ribs having a height from about 0.075-0.15 mm;longitudinal ribs having a height from about 0.075-0.15 mm; anda backweb thickness of about 0.20-0.35 mm; and an additive at a density from about 4.0-10.0 g/m2; and optionally a fibrous layer on at least one face of the porous membrane, the separator having a total thickness of about 0.425-3.0 mm, the separator or membrane being a piece, sleeve, wrap, pocket, or envelope, and/or the separator or membrane having one or more slits or openings. A lead acid battery characterized by at least one of the following: reduced active material shedding; reduced grid and spine corrosion; reduced failure rate; wherein the battery comprises the above separator. An improved electric rickshaw, comprising at least one of the above batteries. A method of reducing failure in a lead acid battery for an electric rickshaw, wherein the method comprises providing the above separator. Novel or improved separators, battery separators, lead battery separators, batteries, cells, and/or methods of manufacture and/or use of such separators, battery separators, lead battery separators, cells, and/or batteries; novel or improved battery separators for lead acid batteries; novel or improved lead acid batteries; novel or improved e-rickshaws; methods, systems and battery separators for enhancing battery life, reducing active material shedding, reducing grid and spine corrosion, reducing failure rate reducing acid stratification and/or improving uniformity in at least lead acid batteries, in particular batteries for electric rickshaws; improved separator for lead acid batteries wherein the separator includes improved membrane profiles, improved coatings, improved configurations, and/or the like; and/or combinations thereof as shown or described herein. The present invention may be embodied in other forms without departing from the spirit and the essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention. The foregoing written description of structures and methods has been presented for purposes of illustration only. Examples are used to disclose exemplary embodiments, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. These examples are not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible. The patentable scope of the invention is defined by the appended claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. The compositions and methods of the appended claims are not limited in scope by the specific compositions and methods described herein, which are intended as illustrations of a few aspects of the claims. Any compositions and methods that are functionally equivalent are intended to fall within the scope of the claims. Various modifications of the compositions and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative compositions and method steps disclosed herein are specifically described, other combinations of the compositions and method steps also are intended to fall within the scope of the appended claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein or less, however, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated. As used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. Throughout the description and claims of this specification, the word “comprise” and variations of the word, such as “comprising” and “comprises,” means “including but not limited to,” and is not intended to exclude, for example, other additives, components, integers, or steps. The terms “consisting essentially of” and “consisting of” can be used in place of “comprising” and “including” to provide for more specific embodiments of the invention and are also disclosed. “Exemplary” means “an example of” and is not intended to convey an indication of a preferred or ideal embodiment. “Such as” is not used in a restrictive sense, but for explanatory or exemplary purposes. Other than where noted, all numbers expressing geometries, dimensions, and so forth used in the specification and claims are to be understood at the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, to be construed in light of the number of significant digits and ordinary rounding approaches. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed invention belongs. Publications cited herein and the materials for which they are cited are specifically incorporated by reference. Additionally, the invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not specifically disclosed herein. | 44,716 |
11862770 | When practical, similar reference numbers denote similar structures, features, or elements. DESCRIPTION Metal batteries, such as lithium (Li) batteries, are susceptible to internal shorts, which can lead to hazardous thermal runaway and combustion. For example, the charging and discharging of a metal battery can give rise to metal dendrites. These metal dendrites can penetrate the porous separator between the anode and the cathode of the metal battery, thereby causing an internal short. Solid state electrolytes (SSEs) are not porous and are thought to be less prone to being penetrated by metal dendrites. Nevertheless, metal dendrites may still penetrate the structural defects, such as pinholes and cracks, that are inevitably present in solid state electrolytes. Thus, a metal battery formed with solid state electrolytes may still succumb to an internal short, particularly after the metal battery is subjected to a large number of charge and discharge cycles. As such, in some implementations of the current subject matter, a battery cell having a solid state electrolyte may further include an electrical barrier against internal shorts. For example, this enhanced solid state battery cell can include a resistive layer configured to regulate internal current flow in the event of an internal short caused by a breach of the solid state electrolyte. FIG.1depicts a schematic diagram illustrating a battery cell100consistent with some implementations of the current subject matter. Referring toFIG.1A, the battery cell100can include a solid state electrolyte layer110, a polymer electrolyte layer120, a base film layer130, a first electrode140A, and a second electrode140B. In some implementations of the current subject matter, the first electrode140A can be the negative electrode (e.g., anode) of the battery cell100. Meanwhile, the second electrode MOB can be the positive electrode (e.g., cathode) of the battery cell100. However, it should be appreciated that the battery cell100can also be configured with an opposite electrical polarity. The solid state electrolyte layer110can be interposed between the polymer electrolyte layer120and the base film layer130. Furthermore, as shown inFIG.1A, the polymer electrolyte layer120can be interposed between the solid state electrolyte layer110and the first electrode140A while the base film layer130can be interposed between the solid state electrolyte layer110and the second electrode140B. It should be appreciated that the solid state electrolyte layer110may be formed from solid state electrolytes that tend to be fragile and highly reactive. For example, the solid state electrolyte layer110can decompose and/or breakdown during production of the battery cell100due to reaction with common environmental elements such as water and/or oxygen. The solid state electrolyte layer110can also decompose and/or breakdown during operation of the battery cell100by reacting with the first electrode140A and the second electrode140B of the battery cell100upon contact. Thus, in some implementations of the current subject matter, the polymer electrolyte layer120and the base film layer130can be configured to isolate the solid state electrolyte layer110from environmental elements as well as both the first electrode140A and the second electrode140B, thereby preventing a decomposition and/or breakdown of the solid state electrolyte layer110during both the production and operation of the battery cell100. Furthermore, the polymer electrolyte layer120and/or the base film layer130can also mitigate the high contact impedance between the solid state electrolyte layer110and the first electrode140A and/or between the first solid state electrolyte layer110and the second electrode140B. As noted earlier, the solid state electrolyte layer110can include physical defects (e.g., pinholes, cracks) that render the solid state electrolyte layer110susceptible to being penetrated by metal dendrites, especially after the battery cell100is subjected to a large number of charge and discharge cycles. For example, metal dendrites forming on the first electrode140A and/or the second electrode140B can penetrate the solid state electrolyte layer110, the polymer electrolyte layer120, and the base film layer130to form an internal short circuit160between the first electrode140A and the second electrode140B.FIG.1Bdepicts a schematic diagram illustrating the internal short circuit160consistent with some implementations of the current subject matter. This internal short circuit160provides an alternative path that is less resistive than a path through an electric load150of the battery cell170. Thus, the bulk of the current170is diverted from the electric load150to the internal short circuit160. The resulting short circuit current165flowing through the battery cell100(e.g., from the second electrode140B to the first electrode140A) can be much greater than the current170still flowing through the electric load150. This short circuit current165can generate a large quantity of heat (e.g., thermal runaway) within the battery cell100that can lead to combustion of the battery cell100. No existing mechanisms are available to mitigate the effects of the internal short circuit160caused by the penetration of the solid state electrolyte layer110. FIG.2Adepicts a schematic diagram illustrating a battery cell200consistent with implementations of the current subject matter. Referring toFIG.2A, the battery cell200can include a solid state electrolyte layer210, a polymer electrolyte layer220, a base film layer230, a resistive layer240, a first electrode250A, and a second electrode250B. In some implementations of the current subject matter, the first electrode250A can be the negative electrode (e.g., anode) of the battery cell200. Meanwhile, the second electrode250B can be the positive electrode (e.g., cathode) of the battery cell200. The solid state electrolyte layer210can be interposed between the polymer electrolyte layer220and the base film layer230and/or the resistive layer240. For example, as shown inFIG.2A, the solid state electrolyte layer210can be interposed between the polymer electrolyte layer220and the base film layer230while the polymer electrolyte layer220is interposed between the first electrode250A and the solid state electrolyte layer210. Furthermore, the polymer electrolyte layer220can be interposed between the solid state electrolyte layer210and the first electrode250A. Meanwhile the base film layer230and/or the resistive layer240can be interposed between the solid state electrolyte layer210and the second electrode250B. However, it should be appreciated that the base film layer230can be optional. In the absence of the base film layer230, the solid state electrolyte layer210can also be interposed directly between the polymer electrolyte layer220and the resistive layer240. Furthermore, the positions of the various layers of the battery cell200shown inFIG.2Aare interchangeable. For example, the respective positions of the polymer electrolyte layer220and the base film layer230can be swapped such that the base film layer230is interposed between the first electrode250A and the solid state electrolyte layer210instead of the polymer electrolyte layer220. Alternately and/or additionally, the respective positions of the base film layer230and the resistive layer240can be swapped such that the base film layer230is interposed between the resistive layer240and the second electrode250B instead of the resistive layer240being interposed between the base layer230and the second electrode250B. It should be appreciated that the solid state electrolyte layer210may be formed from solid state electrolytes that tend to be fragile and highly reactive. For example, the solid state electrolyte layer210can decompose and/or breakdown during production of the battery cell200due to reaction with common environmental elements such as water and/or oxygen. The solid state electrolyte layer210can also decompose and/or breakdown during operation of the battery cell200by reacting with the first electrode250A and the second electrode250B of the battery cell200upon contact. Thus, in some implementations of the current subject matter, the polymer electrolyte layer220, the base film layer230, and/or the resistive layer240can be configured to isolate the solid state electrolyte layer210from environmental elements as well as both the first electrode250A and the second electrode250B, thereby preventing a decomposition and/or breakdown of the solid state electrolyte layer210during both the production and operation of the battery cell200. Furthermore, the polymer electrolyte layer220, the base film layer230, and/or the resistive layer240can also mitigate the high contact impedance between the solid state electrolyte layer210and the electrode250A and/or between the first solid state electrolyte layer210and the second electrode250B. As noted earlier, the solid state electrolyte layer210can include physical defects (e.g., pinholes, cracks) that render the solid state electrolyte layer210susceptible to being penetrated by metal dendrites, especially after the battery cell200is subjected to a large number of charge and discharge cycles. For example, metal dendrites forming on the first electrode250A and/or the second electrode250B can penetrate the solid state electrolyte layer210, the polymer electrolyte layer220, the base film layer230, and the resistive layer240to form an internal short circuit270between the first electrode250A and the second electrode250B. FIG.2Bdepicts a schematic diagram illustrating the internal short circuit270consistent with implementations of the current subject matter. According to some implementations of the current subject matter, the resistive layer240can be configured to regulate a short circuit current275between the second electrode250B and the first electrode250A, in the event of a breach of the solid state electrolyte layer210and the formation of the internal short circuit20. The resistive layer240can be ionically conductive, electrically conductive, and/or electrochemically active. The short circuit current275that results from the internal short circuit270within the battery cell200can be controlled via the electrical conductivity and/or electrochemical activity of the resistive layer240. As shown inFIG.2B, the resistive layer240can provide an electric resistance292. A rate (e.g., amperage) of the short circuit current275can be dependent upon the electric resistance292, which may be directly proportional to a quantity of electrically conductive material and/or electrochemically active material in the resistive layer240. Meanwhile, the resistive layer240will not interfere with the normal operation of the battery cell200because the resistive layer240is ionically conductive and/or electrochemically active, and will therefore not impede the transfer of charged particles and/or ions between the first electrode250A and the second electrode250B. However, it should be appreciated that the resistive layer240can impose some ionic resistance294. Thus, the power of the battery cell200can be dependent upon the ionic conductivity and/or the electrochemical activity of the resistive layer240. For instance, the power of the battery cell200can be directly proportional to a quantity of ionically conductive material and/or electrochemically active in the resistive layer240. In some implementations of the current subject matter, the resistive layer240can be formed from a polymer binder such as, for example, polyvinylidene fluoride (PVDF), styrene-butadiene (SBR), carboxymethyl cellulose (CMC), polyimide, polyamide, polyethylene, and/or the like. The resistive layer240can include one or more electrically conductive additives such as, for example, carbon black, carbon nano tubes, graphene, a conductive polymer, a conductive inorganic compound, and/or the like. The resistive layer240can further include one or more ionically conductive additives such as, for example, a polymer electrolyte, a polymer gel electrolyte, a solid state electrolyte, and/or the like. Alternately and/or additionally, the resistive layer240can include nano-particle fillers such as, for example, calcium carbonate (CaCO3), silicon titanium oxide (SiTiO3), aluminum oxide (Al2O3), fumed silica, and/or the like. The resistive layer240can also be formed from one or more electrochemically active materials (e.g., lithium nickel cobalt (NCM), lithium iron fluorine oxide (LiFeFO2), lithium nickel manganese cobalt oxide (NMC), iron fluoride (FeFx/C)) and/or compounds having a negative thermal expansion coefficient. It should be appreciated that the resistive layer240can have a thickness between 0.1 to 30 microns (μm) or preferably between 1 to 10 microns. Furthermore, heat generated from electrochemical activity within the resistive layer240can provide an indication of the presence of the internal short circuit270and/or trigger one or more safety mechanisms. It should be appreciated that the battery cell200can be any type of metal battery including, for example, a lithium (Li) battery, a sodium (Na) battery, a potassium (K) battery, and/or the like. The first electrode240A and/or the second electrode240B of the battery cell200can be formed from any material. For instance, the positive second electrode240B can be formed from lithium nickel cobalt (NCM), lithium iron fluorine oxide (LiFeFO2), lithium nickel manganese cobalt oxide (NMC), and/or the like. The solid state electrolyte layer210can be formed from one or more type of solid state electrolytes including, for example, sulfide-based solid state electrolytes (e.g., Li2S—SiS2—P2S5, Li7P3S11, Li4.34Ge0.73Ga0.24S4), garnet-type lithium ion-conducting oxides (e.g., Li5+xLa3(Zrx, A2-x)O12where 1.4<x<2), ceramic ion conductors (e.g., LISICON) containing the frame work structure SiO4, PO4, and ZnO4, and/or the like. Meanwhile, the base film layer230can be formed from any combinations of one or more solid state electrolytes, silicon oxides, alumina oxides, lithium salts, organic binders, inorganic binders, and/or the like. The base film layer230can be a separator or any combination of separators including, for example, a polyethylene separator (e.g., Asahi® D420), a tri-layer polyolefin separator (e.g., Celgard® 2300), a fiber separator, a non-woven fabric separator, a glass fiber separator, a ceramic separator, and/or the like. In some implementations of the current subject matter, the polymer electrolyte layer220can be formed a polymers and/or a polymer composite. For example, the polymer electrolyte layer220can be formed from a crosslinked polymer (e.g., containing crosslinking agents such as polyethylene oxide, poly-(bis((methoxyethoxy)ethoxy)phosphazene) (MEEP), single ionic conductor (e.g., lithium (Li) replaced Nafion®), polyhedral oligomeric silsesquioxane (POSS), carboxymethyl cellulose (CMC), methacrylate, and/or the like), a non-crosslinked polymer, a stiff polymer (e.g., polyamide imide (PAI)), a block polymer, a composite of different polymers, and/or the like. Alternately and/or additionally, the protective layer120may be formed from a composite of one or more polymers and at least one additive including, for example, conductive and/or nonconductive ceramic particles, lithium salt particles (e.g., lithium fluoroborate (LiBF4and/or LiPF6), lithium nitrate (LiNO3), lithium bis(fluorosulfonyl)imide, lithium bis(perfluoroethanesulfonyl)imide), lithium metal stabilizers (e.g., vinyl carbonate), ether solvents, and/or the like. FIG.3depicts a schematic diagram illustrating a battery cell300consistent with some implementations of the current subject matter. Referring toFIG.3, the battery cell300can include a first electrode350A, a second electrode350B, a solid state electrolyte layer310, a base film layer330, and a resistive layer340. The first electrode350A can be the negative electrode (e.g., anode) of the battery cell300while the second electrode350B can be the positive electrode (e.g., cathode) of the battery cell300. However, it should be appreciated that the battery cell300can also be configured with an opposite electrical polarity. In some implementations of the current subject matter, the battery cell300can include more than one polymer electrolyte layers configured to mitigate the high contact impedance with respect to the first electrode350A and/or the second electrode350B. For example, the battery cell300can include a first polymer electrolyte layer320A that is interposed between the first electrode350A and the solid state electrolyte layer310. The battery cell300can also include a second polymer electrolyte layer320B that is interposed between the second electrode350B and the resistive layer340. It should be appreciated that one or both of the first polymer electrolyte320A and the second polymer electrolyte320B may be optional. In some implementations of the current subject matter, the resistive layer340can be configured to regulate a short circuit current flowing through the battery cell300in the event that metal dendrites formed at the first electrode350A and/or the second electrode350B penetrates the first polymer electrolyte layer320A, the second polymer electrolyte layer320B, the solid state electrolyte layer310, and the base film layer330to form an internal short circuit within the battery cell300. The resistive layer340can be formed from one or more materials that are ionically conductive, electrically conductive, and/or electrochemically active. As such, the short circuit current resulting from the internal short circuit within the battery cell300can be controlled by the electrically conductive and/or electrochemically active material within the resistive layer340. Meanwhile, the resistive layer340will not interfere with the normal operation of the battery cell300because the resistive layer340is ionically conductive and/or electrochemically active, and will therefore not impede the transfer of charged particles and/or ions between the first electrode350A and the second electrode350B. However, it should be appreciated that the resistive layer340can impose some ionic resistance. Therefore, the power of the battery cell300can be dependent upon the ionic conductivity of the resistive layer340including, for example, the ionically conductive and/or electrochemically active material within the resistive layer340. FIG.4depicts a flowchart illustrating a process400for manufacturing a battery cell consistent with implementations of the current subject matter. Referring toFIGS.1A-Band4, the process400can be performed to manufacture a battery cell such as, for example, the battery cell100. At402, a solid state electrolyte layer can be formed. For example, the solid state electrolyte layer110of the battery cell100can be formed, for example, by vapor deposition and/or plasma deposition. In some implementations of the subject matter, forming the solid state electrolyte layer110can include dissolving, using a high speed mixer, 5 grams of polyethylene oxide (PEO) with 1,000,000 molecular weight into approximately 100 grams of deionized water, thereby forming a polyethylene oxide aqueous solution. Furthermore, 1 gram of lithium nitrate can be mixed into the polyethylene oxide aqueous solution followed by 20 grams of Li7La3Zr2O12(LLZO). The resulting slurry can be coated onto the base film layer130. The base film layer130can be a separator such as, for example, Celgard® 2300 and/or the like. Here, an automatic coating machine can be used to deposit an approximately 20 microns thick coating of the slurry onto the separator at 0.1 meter per minute. The coating of slurry can further be dried using the automatic coating machine with a first heating zone set to 60° C. and a second heating zone set to 80° C. At404, a polymer electrolyte layer can be formed. For example, the polymer electrolyte layer120of the battery cell100can be formed. In some implementations of the current subject matter, forming the polymer electrolyte layer120can include dissolving, using a high speed mixer, 5 grams of polyethylene oxide (PEO) with 500,000 molecular weight into approximately 50 grams of deionized water, thereby forming a polyethylene oxide aqueous solution. Furthermore, 1 gram of lithium nitrate can be mixed into the polyethylene oxide aqueous solution. The solution can be coated onto the solid state electrolyte layer110formed at operation402. For instance, the coating can be performed using an automatic coating machine at 0.1 meter per minute. The coating can further be dried using the automatic coating machine with a first heating zone set to 60° C. and a second heating zone set to 80° C. It should be appreciated that the resulting polymer electrolyte layer120will interface directly with the negative first electrode140A (e.g., anode) of the battery cell100. At406, a positive electrode can be formed. For example, the second electrode140B of the battery cell100can be formed. In some implementations of the current subject matter, forming the second electrode140B can include dissolving 10.5 grams of polyvinylidene fluoride (PVDF) into 120 grams of N-methylpyrrolidone (NMP). Furthermore, 9 grams of carbon black can be added to the mixture and mixed for 15 minutes at 6500 revolutions per minute (rpm). A flowable slurry can subsequently be formed by adding 280 grams of LiNi0.5Mn0.3Co0.2O2(NMC) (280 g) to the mixture and mixing for 30 minutes at 6500 revolutions per minute. Additional N-methylpyrrolidone (NMP) can be added to adjust the viscosity of the slurry. The resulting slurry can be coated onto a 15 micron thick layer of aluminum foil using an automatic coating machine. The coating of slurry can further be dried using the automatic coating machine with a first heat zone set to approximately 80° C. and a second heat zone set to approximately 130° C. It should be appreciated that subjecting the slurry to heat can evaporate the N-methylpyrrolidone (NMP) in the slurry. The final dried second electrode140B can have a loading of approximately 15.55 milligrams per square centimeter (mg/cm2). The second electrode140B can further be compressed to a thickness of approximately 117 microns. At408, a battery cell can be prepared. For example, the battery cell100can be formed. In some implementations of the current subject matter, forming the battery cell100can include using an electrode tab to punch out the pieces forming the first electrode140A and/or the second electrode140B. The second electrode140B (e.g., positive electrode) can be dried at 125° C. for 10 hours. Furthermore, the first electrode140A and the second electrode140B can be laminated, in a dry room, with the solid state electrolyte layer110interposed between the first electrode140A, the polymer electrolyte layer120, the base film layer130, and the second electrode140B. It should be appreciated that in the resulting jelly-flat, the polymer electrolyte layer120will directly interface with the first electrode140A while the base film layer130will interface directly with the second electrode140B. This jelly-flat can be inserted into an aluminum (Al) composite bag, which is subsequently filled with a limited quantity of a liquid electrolyte such as, for example, a LiPF6based organic carbonate electrolyte. The aluminum composite bag can be sealed at 190° C. to form the battery cell100. The battery cell100can be aged at 45° C. for 5 hours before being subject to an initial charge and discharge cycle. For instance, the sealed battery cell100can be first charged to 4.2V at a C/20 rate for 5 hours and then to 4.2V at 0.2 C rate for 5 hours before the battery cell100is rested for 20 minutes. The rested battery cell100can subsequently be discharged to 2.8V at 0.2 C rate. In addition, the battery cell100can be punctured, while under vacuum, to release any gases before the battery cell100is resealed. At this point, the battery cell100is ready for operation and/or evaluation. FIG.5depicts a flowchart illustrating a process500for manufacturing a battery cell consistent with implementations of the current subject matter. Referring toFIGS.2A-Band5, the process500can be performed to manufacture a battery cell such as, for example, the battery cell200. At502, a solid state electrolyte layer can be formed. For example, the solid state electrolyte layer210of the battery cell200can be formed, for example, by vapor deposition and/or plasma deposition. In some implementations of the subject matter, forming the solid state electrolyte layer110can include dissolving, using a high speed mixer, 5 grams of polyethylene oxide (PEO) with 1,000,000 molecular weight into approximately 100 grams of deionized water, thereby forming a polyethylene oxide aqueous solution. Furthermore, 1 gram of lithium nitrate can be mixed into the polyethylene oxide aqueous solution followed by 20 grams of Li7La3Zr2O12(LLZO). The resulting slurry can be coated onto the base film layer230. The base film layer230can be a separator such as, for example, Celgard® 2300 and/or the like. Here, an automatic coating machine can be used to deposit an approximately 20 microns thick coating of the slurry onto the separator at 0.1 meter per minute. The coating of slurry can further be dried using the automatic coating machine with a first heating zone set to 60° C. and a second heating zone set to 80° C. At504, a resistive layer can be formed on top of a base film. For example, the resistive layer240can be formed on top of the base film layer230. In some implementations of the current subject matter, forming the resistive layer240can include dissolving 10 grams of polyvinylidene fluoride (PVDF) LBG-1 into 100 grams of acetone and 20 grams of N-methylpyrrolidone (NMP). Furthermore, 0.5 grams of carbon black can be added to the mixture and mixed for 15 minutes at 6500 revolutions per minute. A flowable slurry can be formed by adding 1 grams of a lithium salt (e.g., lithium imide) and mixing for 30 minutes at 6500 revolutions per minute. Additional N-methylpyrrolidone (NMP) may be added to adjust the viscosity of the flowable slurry. This resulting slurry can be coated, using an automatic coating machine, onto one side of the base film layer230(e.g., Celgard® 2300) with the solid state electrolyte layer210being disposed on the opposite side of the base film layer230. The automatic coating machine can further be used to dry the slurry with a first heat zone set to approximately 60° C. and a second heat zone set to approximately 80° C. It should be appreciated that the slurry is subjected to heat in order to evaporate off the acetone and the N-methylpyrrolidone (NMP) in the slurry. The final dried resistive layer240can have a loading of approximately 2 milligrams per square centimeter. At506, a polymer electrolyte layer can be formed. For example, the polymer electrolyte layer220of the battery cell200can be formed. In some implementations of the current subject matter, forming the polymer electrolyte layer220can include dissolving, using a high speed mixer, 5 grams of polyethylene oxide (PEO) with 500,000 molecular weight into approximately 50 grams of deionized water, thereby forming a polyethylene oxide aqueous solution. Furthermore, 1 gram of lithium nitrate can be mixed into the polyethylene oxide aqueous solution. The solution can be coated onto the solid state electrolyte layer210formed at operation502. For instance, the coating can be performed using an automatic coating machine at 0.1 meter per minute. The coating can further be dried using the automatic coating machine with a first heating zone set to 60° C. and a second heating zone set to 80° C. It should be appreciated that the resulting polymer electrolyte layer220will interface directly with the negative first electrode250A (e.g., anode) of the battery cell200. At508, a positive electrode can be formed. For example, the second electrode250B of the battery cell200can be formed. In some implementations of the current subject matter, forming the second electrode250B can include dissolving 10.5 grams of polyvinylidene fluoride (PVDF) into 120 grams of N-methylpyrrolidone (NMP). Furthermore, 9 grams of carbon black can be added to the mixture and mixed for 15 minutes at 6500 revolutions per minute (rpm). A flowable slurry can subsequently be formed by adding 280 grams of LiNi0.5Mn0.3Co0.2O2(NMC) (280 g) to the mixture and mixing for 30 minutes at 6500 revolutions per minute. Additional N-methylpyrrolidone (NMP) can be added to adjust the viscosity of the slurry. The resulting slurry can be coated onto a 15 micron thick layer of aluminum foil using an automatic coating machine. This coating of slurry can further be dried using the automatic coating machine with a first heat zone set to approximately 80° C. and a second heat zone set to approximately 130° C. It should be appreciated that subjecting the slurry to heat can evaporate the N-methylpyrrolidone (NMP) in the slurry. The final dried second electrode250B can have a loading of approximately 15.55 milligrams per square centimeter (mg/cm2). The second electrode250B can further be compressed to a thickness of approximately 117 microns. At510, a battery cell can be prepared. For example, the battery cell200can be formed. In some implementations of the current subject matter, forming the battery cell200can include using an electrode tab to punch out the pieces forming the first electrode250A and/or the second electrode250B. The second electrode250B (e.g., positive electrode) can be dried at 125° C. for 10 hours. Furthermore, the first electrode250A and the second electrode250B can be laminated, in a dry room, with the solid state electrolyte layer210interposed between the first electrode250A, the polymer electrolyte layer220, the base film layer230, the resistive layer240, and the second electrode250B. It should be appreciated that in the resulting jelly-flat, the polymer electrolyte layer220will directly interface with the first electrode250A while the resistive layer240will interface directly with the second electrode250B. This jelly-flat can be inserted into an aluminum (Al) composite bag, which is subsequently filled with a limited quantity of a liquid electrolyte such as, for example, a LiPF6based organic carbonate electrolyte. The aluminum composite bag can be sealed at 190° C. to form the battery cell200. The battery cell200can be aged at 45° C. for 5 hours before being subject to an initial charge and discharge cycle. For instance, the sealed battery cell200can be first charged to 4.2V at a C/20 rate for 5 hours and then to 4.2V at 0.2 C rate for 5 hours before the battery cell200is rested for 20 minutes. The rested battery cell200can subsequently be discharged to 2.8V at 0.2 C rate. In addition, the battery cell200can be punctured, while under vacuum, to release any gases before the battery cell200is resealed. At this point, the battery cell200is ready for operation and/or evaluation. FIG.6depicts a flowchart illustrating a process600for manufacturing a battery cell consistent with implementations of the current subject matter. Referring toFIGS.2A-Band6, the process600can be performed to manufacture a battery cell such as, for example, the battery cell200. At602, a solid state electrolyte layer can be formed. For example, the solid state electrolyte layer210of the battery cell200can be formed, for example, by vapor deposition and/or plasma deposition. In some implementations of the subject matter, forming the solid state electrolyte layer110can include dissolving, using a high speed mixer, 5 grams of polyethylene oxide (PEO) with 1,000,000 molecular weight into approximately 100 grams of deionized water, thereby forming a polyethylene oxide aqueous solution. Furthermore, 1 gram of lithium nitrate can be mixed into the polyethylene oxide aqueous solution followed by 20 grams of Li7La3Zr2O12(LLZO). The resulting slurry can be coated onto the base film layer230. The base film layer230can be a separator such as, for example, Celgard® 2300 and/or the like. Here, an automatic coating machine can be used to deposit an approximately 20 microns thick coating of the slurry onto the separator at 0.1 meter per minute. The coating of slurry can further be dried using the automatic coating machine with a first heating zone set to 60° C. and a second heating zone set to 80° C. At604, a polymer electrolyte layer can be formed. For example, the polymer electrolyte layer220of the battery cell200can be formed. In some implementations of the current subject matter, forming the polymer electrolyte layer220can include dissolving, using a high speed mixer, 5 grams of polyethylene oxide (PEO) with 500,000 molecular weight into approximately 50 grams of deionized water, thereby forming a polyethylene oxide aqueous solution. Furthermore, 1 gram of lithium nitrate can be mixed into the polyethylene oxide aqueous solution. The solution can be coated onto the solid state electrolyte layer210formed at operation502. For instance, the coating can be performed using an automatic coating machine at 0.1 meter per minute. The coating can further be dried using the automatic coating machine with a first heating zone set to 60° C. and a second heating zone set to 80° C. It should be appreciated that the resulting polymer electrolyte layer220will interface directly with the negative first electrode250A (e.g., anode) of the battery cell200. At606, a positive electrode can be formed. For example, the second electrode250B of the battery cell200can be formed. In some implementations of the current subject matter, forming the second electrode250B can include dissolving 10.5 grams of polyvinylidene fluoride (PVDF) into 120 grams of N-methylpyrrolidone (NMP). Furthermore, 9 grams of carbon black can be added to the mixture and mixed for 15 minutes at 6500 revolutions per minute (rpm). A flowable slurry can subsequently be formed by adding 280 grams of LiNi0.5Mn0.3Co0.2O2(NMC) (280 g) to the mixture and mixing for 30 minutes at 6500 revolutions per minute. Additional N-methylpyrrolidone (NMP) can be added to adjust the viscosity of the slurry. The resulting slurry can be coated onto a 15 micron thick layer of aluminum foil using an automatic coating machine. This coating of slurry can further be dried using the automatic coating machine with a first heat zone set to approximately 80° C. and a second heat zone set to approximately 130° C. It should be appreciated that subjecting the slurry to heat can evaporate the N-methylpyrrolidone (NMP) in the slurry. The final dried second electrode250B can have a loading of approximately 15.55 milligrams per square centimeter (mg/cm2). The second electrode250B can further be compressed to a thickness of approximately 117 microns. At608, a resistive layer can be formed on top of the positive electrode. For example, the resistive layer240can be formed on top of the positive second electrode250B instead of the base film layer230as in process500. In some implementations of the current subject matter, forming the resistive layer240can include dissolving 10 grams of polyvinylidene fluoride (PVDF) LBG-1 into 100 grams of acetone and 20 grams of N-methylpyrrolidone (NMP). Furthermore, 0.5 grams of carbon black can be added to the mixture and mixed for 15 minutes at 6500 revolutions per minute. A flowable slurry can be formed by adding 1 grams of a lithium salt (e.g., lithium imide) and mixing for 30 minutes at 6500 revolutions per minute. Additional N-methylpyrrolidone (NMP) may be added to adjust the viscosity of the flowable slurry. This resulting slurry can be coated, using an automatic coating machine, onto one side of the second electrode250B (e.g., Celgard® 2300) formed at operation606. The automatic coating machine can further be used to dry this coating of slurry with a first heat zone set to approximately 60° C. and a second heat zone set to approximately 80° C. It should be appreciated that the slurry is subjected to heat in order to evaporate off the acetone and the N-methylpyrrolidone (NMP) in the slurry. The final dried resistive layer240can have a loading of approximately 2 milligrams per square centimeter. At610, a battery cell can be prepared. For example, the battery cell200can be formed. In some implementations of the current subject matter, forming the battery cell200can include using an electrode tab to punch out the pieces forming the first electrode250A and/or the second electrode250B. The second electrode250B (e.g., positive electrode) can be dried at 125° C. for 10 hours. Furthermore, the first electrode250A and the second electrode250B can be laminated, in a dry room, with the solid state electrolyte layer210interposed between the first electrode250A, the polymer electrolyte layer220, the base film layer230, the resistive layer240, and the second electrode240B. It should be appreciated that in the resulting jelly-flat, the polymer electrolyte layer220will directly interface with the first electrode250A while the resistive layer240will interface directly with the second electrode250B. This jelly-flat can be inserted into an aluminum (Al) composite bag, which is subsequently filled with a limited quantity of a liquid electrolyte such as, for example, a LiPF6based organic carbonate electrolyte. The aluminum composite bag can be sealed at 190° C. to form the battery cell200. The battery cell200can be aged at 45° C. for 5 hours before being subject to an initial charge and discharge cycle. For instance, the sealed battery cell200can be first charged to 4.2V at a C/20 rate for 5 hours and then to 4.2V at 0.2 C rate for 5 hours before the battery cell200is rested for 20 minutes. The rested battery cell200can subsequently be discharged to 2.8V at 0.2 C rate. In addition, the battery cell200can be punctured, while under vacuum, to release any gases before the battery cell200is resealed. At this point, the battery cell200is ready for operation and/or evaluation. FIG.7depicts a flowchart illustrating a process700for manufacturing a battery cell consistent with implementations of the current subject matter. Referring toFIGS.3and7, the process700can be performed to manufacture a battery cell such as, for example, the battery cell300. At702, a solid state electrolyte layer can be formed. For example, the solid state electrolyte layer310of the battery cell300can be formed, for example, by vapor deposition and/or plasma deposition. In some implementations of the subject matter, forming the solid state electrolyte layer310can include dissolving, using a high speed mixer, 5 grams of polyethylene oxide (PEO) with 1,000,000 molecular weight into approximately 100 grams of deionized water, thereby forming a polyethylene oxide aqueous solution. Furthermore, 1 gram of lithium nitrate can be mixed into the polyethylene oxide aqueous solution followed by 20 grams of Li7La3Zr2O12(LLZO). The resulting slurry can be coated onto the base film layer330. The base film layer330can be a separator such as, for example, Celgard® 2300 and/or the like. Here, an automatic coating machine can be used to deposit an approximately 20 microns thick coating of the slurry onto the separator at 0.1 meter per minute. The coating of slurry can further be dried using the automatic coating machine with a first heating zone set to 60° C. and a second heating zone set to 80° C. At704, a first polymer electrolyte layer can be formed. For example, the first polymer electrolyte layer320A of the battery cell300can be formed. In some implementations of the current subject matter, forming the first polymer electrolyte layer320can include dissolving, using a high speed mixer, 5 grams of polyethylene oxide (PEO) with 500,000 molecular weight into approximately 50 grams of deionized water, thereby forming a polyethylene oxide aqueous solution. Furthermore, 1 gram of lithium nitrate can be mixed into the polyethylene oxide aqueous solution. The solution can be coated onto the solid state electrolyte layer310formed at operation702. For instance, the coating can be performed using an automatic coating machine at 0.1 meter per minute. This coating of slurry can further be dried using the automatic coating machine with a first heating zone set to 60° C. and a second heating zone set to 80° C. It should be appreciated that the resulting first polymer electrolyte layer320A will interface directly with the negative first electrode350A (e.g., anode) of the battery cell300. At706, a resistive layer can be formed on top of a base film layer. For example, the resistive layer340can be formed on top of the base film layer330. In some implementations of the current subject matter, forming the resistive layer340can include dissolving 10 grams of polyvinylidene fluoride (PVDF) LBG-1 into 100 grams of acetone and 20 grams of N-methylpyrrolidone (NMP). Furthermore, 0.5 grams of carbon black can be added to the mixture and mixed for 15 minutes at 6500 revolutions per minute. A flowable slurry can be formed by adding 1 grams of a lithium salt (e.g., lithium imide) and mixing for 30 minutes at 6500 revolutions per minute. Additional N-methylpyrrolidone (NMP) may be added to adjust the viscosity of the flowable slurry. This resulting slurry can be coated, using an automatic coating machine, onto one side of the base film layer330(e.g., Celgard® 2300) with the solid state electrolyte layer310being disposed on the opposite side of the base film layer330. The automatic coating machine can further be used to dry this coating of slurry with a first heat zone set to approximately 60° C. and a second heat zone set to approximately 80° C. It should be appreciated that the slurry is subjected to heat in order to evaporate off the acetone and the N-methylpyrrolidone (NMP) in the slurry. The final dried resistive layer340can have a loading of approximately 2 milligrams per square centimeter. At708, a second polymer electrolyte layer can be formed on top of the resistive layer. For example, the second polymer electrolyte layer320B of the battery cell300can be formed on top of the resistive layer340. In some implementations of the current subject matter, forming the second polymer electrolyte layer320B can include dissolving, using a high speed mixer, 5 grams of polyethylene oxide (PEO) with 500,000 molecular weight into approximately 50 grams of deionized water, thereby forming a polyethylene oxide aqueous solution. Furthermore, 1 gram of lithium nitrate can be mixed into the polyethylene oxide aqueous solution. The solution can be coated onto one side of the resistive layer340formed at operation706, opposite from the base film layer330. For instance, the coating can be performed using an automatic coating machine at 0.1 meter per minute. This coating of slurry can further be dried using the automatic coating machine with a first heating zone set to 60° C. and a second heating zone set to 80° C. It should be appreciated that the resulting second polymer electrolyte layer320B will interface directly with the positive second electrode350B (e.g., cathode) of the battery cell300. At710, a positive electrode can be formed. For example, the second electrode350B of the battery cell300can be formed. In some implementations of the current subject matter, forming the second electrode250B can include dissolving 10.5 grams of polyvinylidene fluoride (PVDF) into 120 grams of N-methylpyrrolidone (NMP). Furthermore, 9 grams of carbon black can be added to the mixture and mixed for 15 minutes at 6500 revolutions per minute (rpm). A flowable slurry can subsequently be formed by adding 280 grams of LiNi0.5Mn0.3Co0.2O2(NMC) (280 g) to the mixture and mixing for 30 minutes at 6500 revolutions per minute. Additional N-methylpyrrolidone (NMP) can be added to adjust the viscosity of the slurry. The resulting slurry can be coated onto a 15 micron thick layer of aluminum foil using an automatic coating machine. This coating of slurry can further be dried using the automatic coating machine with a first heat zone set to approximately 80° C. and a second heat zone set to approximately 130° C. It should be appreciated that subjecting the slurry to heat can evaporate the N-methylpyrrolidone (NMP) in the slurry. The final dried second electrode350B can have a loading of approximately 15.55 milligrams per square centimeter (mg/cm2). The second electrode350B can further be compressed to a thickness of approximately 117 microns. At712, a battery cell can be prepared. For example, the battery cell300can be formed. In some implementations of the current subject matter, forming the battery cell300can include using an electrode tab to punch out the pieces forming the first electrode350A and/or the second electrode350B. The second electrode350B (e.g., positive electrode) can be dried at 125° C. for 10 hours. Furthermore, the first electrode350A and the second electrode350B can be laminated, in a dry room, with the solid state electrolyte layer310interposed between the first electrode350A, the first polymer electrolyte layer320A, the base film layer330, the resistive layer340, the second polymer electrolyte layer320B, and the second electrode350B. It should be appreciated that in the resulting jelly-flat, the first polymer electrolyte layer320A will directly interface with the first electrode350A while the second polymer electrolyte layer320B will interface directly with the second electrode350B. Meanwhile, the base film layer330is interposed between the solid state electrolyte layer310and the resistive layer340. This jelly-flat can be inserted into an aluminum (Al) composite bag, which is subsequently filled with a limited quantity of a liquid electrolyte such as, for example, a LiPF6based organic carbonate electrolyte. The aluminum composite bag can be sealed at 190° C. to form the battery cell300. The battery cell300can be aged at 45° C. for 5 hours before being subject to an initial charge and discharge cycle. For instance, the sealed battery cell300can be first charged to 4.2V at a C/20 rate for 5 hours and then to 4.2V at 0.2 C rate for 5 hours before the battery cell300is rested for 20 minutes. The rested battery cell300can subsequently be discharged to 2.8V at 0.2 C rate. In addition, the battery cell300can be punctured, while under vacuum, to release any gases before the battery cell300is resealed. At this point, the battery cell300is ready for operation and/or evaluation. Implementations of the current subject matter can include, but are not limited to, articles of manufacture (e.g. apparatuses, systems, etc.), methods of making or use, compositions of matter, or the like consistent with the descriptions provided herein. In the descriptions above and in the claims, phrases such as “at least one of” or “one or more of” may occur followed by a conjunctive list of elements or features. The term “and/or” may also occur in a list of two or more elements or features. Unless otherwise implicitly or explicitly contradicted by the context in which it used, such a phrase is intended to mean any of the listed elements or features individually or any of the recited elements or features in combination with any of the other recited elements or features. For example, the phrases “at least one of A and B;” “one or more of A and B;” and “A and/or B” are each intended to mean “A alone, B alone, or A and B together.” A similar interpretation is also intended for lists including three or more items. For example, the phrases “at least one of A, B, and C;” “one or more of A, B, and C;” and “A, B, and/or C” are each intended to mean “A alone, B alone, C alone, A and B together, A and C together, B and C together, or A and B and C together.” Use of the term “based on,” above and in the claims is intended to mean, “based at least in part on,” such that an unrecited feature or element is also permissible. The subject matter described herein can be embodied in systems, apparatus, methods, and/or articles depending on the desired configuration. The implementations set forth in the foregoing description do not represent all implementations consistent with the subject matter described herein. Instead, they are merely some examples consistent with aspects related to the described subject matter. Although a few variations have been described in detail above, other modifications or additions are possible. In particular, further features and/or variations can be provided in addition to those set forth herein. For example, the implementations described above can be directed to various combinations and subcombinations of the disclosed features and/or combinations and subcombinations of several further features disclosed above. In addition, the processes depicted in the accompanying figures and/or described herein do not necessarily require the operations to be performed in the order shown, or in any sequential order, in order to achieve desirable results. For example, one or more operations from these processes may be repeated and/or omitted. Other implementations may be within the scope of the following claim. | 49,179 |
11862771 | An overview of the features, functions and/or configurations of the components depicted in the various figures will now be presented. It should be appreciated that not all of the features of the components of the figures are necessarily described. Some of these non-discussed features, such as various couplers, etc., as well as discussed features are inherent from the figures themselves. Other non-discussed features may be inherent in component geometry and/or configuration. DETAILED DESCRIPTION For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of this disclosure is thereby intended. In the present disclosure, the term “about” can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range. In the present disclosure, the term “substantially” can allow for a degree of variability in a value or range, for example, within 90%, within 95%, or within 99% of a stated value or of a stated limit of a range. A device, system, and a method are presented in the present disclosure that can reduce unwanted power consumption of a contactor when the contactor is energized. The following disclosure is provided in view of the content ofFIG.1andFIG.2, which show a battery124having a plurality of cells50, a generic battery management system, a contactor106, and a load122, as referenced in further detail herein. The general disclosure ofFIG.1andFIG.2provides context and is related to the disclosure provided herein. An exemplary battery management system (BMS) according to the present disclosure is shown inFIG.3A. As shown inFIG.3A, an exemplary BMS (system100) includes a microcontroller unit (MCU, also referred to herein as a microcontroller)102having a general-purpose output (GPO)101, a switching mechanism104coupled to the microcontroller102and to a contactor106having a coil107with inductance (L). A contactor106, as provided in further detail herein, can be a relay including a coil107that when energized closes (or causes a coupling mechanism121in communication with contactor106and/or coil107) contacts disposed between the battery124and the load122thereby coupling the load122to the battery124. The microcontroller102(e.g., ST MICROELECTRONICS STM32F105RCT7) can also be a suitable processor, as known to a person having ordinary skill in the art. In at least one embodiment, the switching mechanism104is a low-side driver disposed between the contactor106and the ground108. The low-side driver (an exemplary switching mechanism104), in at least one embodiment, includes a resistive network110, including a first resistor112(R1) and a second resistor114(R2), and also includes a switch116(of switching mechanism104) that is configured to couple the contactor106to ground108. The switch116can be a semiconductor device, for example. In one embodiment, the switch116can be an N-channel field effect transistor (e.g., an ON SEMICONDUCTOR NCV8406ADTRKG), identified as Q1. In another embodiment, such as shown inFIG.3B, the switching mechanism104can be via a high-side driver disposed between the high side voltage source120and the contactor106. The high-side driver includes a resistive network110, and includes a switch116that is configured to couple the contactor106to the high side voltage120. The switch116can be a semiconductor device. In one embodiment, the switch116can be an N-channel field effect transistor with the appropriate boost circuitry for driving the transistor with the appropriate resistive network110, known to a person having ordinary skill in the art. In another embodiment, the switch116can be a P-channel field effect transistor with the appropriate resistive network110, known to a person having ordinary skill in the art. In order to reduce the power consumption of the contactor106, the microcontroller102is configured to provide an on/off signal to the switching mechanism104with a selective frequency and pulse width modulation (PWM) provided by either componentry of the switching mechanism104or a pulse width modulator103in communication with the switching mechanism104(or otherwise associated with the switching mechanism). The frequency is selective between about 1 KHz to 20 KHz and the duty cycle of the PWM can be between about 50% to 100%, for example. Initially, the microcontroller102may provide a 100% duty cycle, and after a predetermined amount of time or based on inputs received from a downstream circuitry (not shown), the microcontroller102changes the duty cycle from 100% to a number smaller than 100%. The exact number for the duty cycle is determined based on several factors, such as the equivalent capacitance of the load122connected to the contactor106, the equivalent of the inductance of the load122connected to the contactor106, the resistance of the load122connected to the contactor106, the temperature of the contactor106, the condition of the cells in the battery124, the health of the switch (Q1)116of switching mechanism,104, for example, as well as other sensory input as known to a person having ordinary skill in the art. “The microcontroller102is coupled to the switching mechanism104at a general-purpose output (identified as GPO)101. When the GPO output is at 0V (i.e., off), the switch Q1(116) is off and the inductor (L) of the contactor coil107is disconnected from ground108, and therefore no current runs through the inductor (L) (i.e., the output identified as GPO_out109is at the high voltage). In this state the contactor106is open (i.e., load122is disconnected from the battery124in a high-side contactor arrangement as shown inFIG.2orFIG.3Bor the load122is disconnected from the ground108in a low-side contactor arrangement, as shown inFIG.2ofFIG.3A). Conversely, when the GPO output is at a high voltage (e.g., 3.3 V, i.e., on), the switch Q1(116) turns on, allowing current to pass through the inductor (L) of coil107, causing the GPO_out109to be at about zero volts (i.e., near ground). In this state the contactor106closes (i.e., the load122is connected to the battery124in a high-side contactor arrangement or the load122is connected to the ground108in a low-side contactor arrangement).” Referring toFIG.4, a plot of voltages and current at various positions are shown. In particular, the top trace indicates the current running through coil107with inductance L (in the embodiment tested the coil107had an inductance of about 20 mH, however, the inductance according to the present disclosure can range from 5 mH to 250 mH). The middle trace represents GPO_out109which is the output of the switching mechanism104and is connected to the contactor106. The lower trace represents the output of the microcontroller102(GPO101). The three traces shown inFIG.4are obtained at 100% duty cycle for a PWM signal output at GPO101. In this configuration, the current provided to the coil107of the contactor106is about 954 mA (the equivalent of a direct current as typically implemented in the prior art approaches). At this level and at 12 V high side voltage, the power consumption is about 11.4 Watts (representing a coil resistance of about 12.6 ohms). Referring toFIG.5, the same series of traces are shown by instead of a 100% duty cycle, the microcontroller102provides about 90% duty cycle at the same frequency (about 1 kHz). In this case, the average current drops to about 434 mA (representing a 5.2 W power consumption, a reduction of power consumption of about 54% as compared to the direct current approach, as seen in the prior art). It should be noted that the contactor106remains closed at 90% duty cycle, therefore no adverse impact (i.e., momentary disconnection of the load122) is realized as a result of cycling the coil107of the contactor106. The disconnection of the relay coil107generates a transient voltage peak, which is only limited by the parasitic inductivity and capacity of the electrical system. According to one embodiment, one protection method for the driver includes connecting a diode (not shown) in parallel to the relay coil107. According to one embodiment the optimum duty cycle is determined according to testing performed apriori and provided to the system100of the present disclosure as a predetermined value. However, in another embodiment the optimum duty cycle can be measured for a selective frequency. Each system and characteristics associated therewith (i.e., contactor106, high side voltage, etc.) are different. In one embodiment, the microcontroller102may be configured to upon initialization determine the optimum duty cycle by measuring voltage or current at the connectivity to the load122(seeFIG.3A, for example). By reducing duty cycle, at some point the contactor may momentarily open. A margin-of-safety away from that duty cycle can represent the optimum duty cycle. While various embodiments of devices and systems for reducing unwanted power consumption of a contactor and methods for the same have been described in considerable detail herein, the embodiments are merely offered as non-limiting examples of the disclosure described herein. It will therefore be understood that various changes and modifications may be made, and equivalents may be substituted for elements thereof, without departing from the scope of the present disclosure. The present disclosure is not intended to be exhaustive or limiting with respect to the content thereof. Further, in describing representative embodiments, the present disclosure may have presented a method and/or a process as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth therein, the method or process should not be limited to the particular sequence of steps described, as other sequences of steps may be possible. Therefore, the particular order of the steps disclosed herein should not be construed as limitations of the present disclosure. In addition, disclosure directed to a method and/or process should not be limited to the performance of their steps in the order written. Such sequences may be varied and still remain within the scope of the present disclosure. | 10,406 |
11862772 | DETAILED DESCRIPTION The present invention will now be described in more detail with reference to exemplary embodiments as shown in the accompanying drawings. While the present invention is described herein with reference to the exemplary embodiments, it should be understood that the present invention is not limited to such exemplary embodiments. Those possessing ordinary skill in the art and having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other applications for use of the invention, which are fully contemplated herein as within the scope of the present invention as disclosed and claimed herein, and with respect to which the present invention could be of significant utility. As background, the figures that will be described relate to two different embodiments, and methods of operation thereof, of a battery recharging device for a mobile phone. As will be described in more detail and is apparent to those skilled in the art, the battery recharging device may take different forms and be used with various battery powered devices. Embodiments FIG.1shows a first embodiment of a battery recharging device100. The device comprises a mobile phone105, a switch box110, a first connector115connecting a power port120of the mobile phone105with an output port125of the switch box110, and a second connector130adapted to connect an input port135of the switch box110with a standard electrical outlet (approximately 120 volts, 60 hertz). Preferably, the first connector115attaches to the output port125via a Universal Serial Bus (“USB”) connection. The first connector115attaches to the mobile phone105based upon a connector specified by the mobile phone manufacturer for that particular model mobile phone. Again referring toFIG.1, the mobile phone105comprises a software module140, a battery145, and an electronics module150interposed between the battery145and the power port120. The battery145is connected to the power port120through a third connector155, the electronics module150, and a fourth connector160. The battery145may be any type of rechargeable battery and, illustratively, is a lithium-ion battery. The software module140comprises a user interface module165and a charge profile generator170which are able to communicate with each other through a fifth connector175. The software module140is also connected via a communications bus180to a memory185of mobile phone105, a microprocessor190of mobile phone105, and a user input means195of the mobile phone105as shown. The user input means195may be any means for a user to interact with the mobile phone105including but not limited to touchscreens and mechanical keyboards. The software module140may be an application, also referred to as an “app.” FIG.2shows a second embodiment of a battery recharging device200. The components of battery recharging device200are essentially the same as the components of battery recharging device100ofFIG.1expect that the function of the switch box110is moved inside a mobile phone205. More specifically, the device comprises the mobile phone205, a first connector215connecting a power port220of the mobile phone205with a standard electrical outlet (approximately 120 volts, 60 hertz). Preferably, the first connector215attaches to a standard electrical plug216adapted to fit into a standard electrical outlet via a USB connection. The first connector215attaches to the mobile phone205based upon a connector specified by the mobile phone manufacturer for that particular model mobile phone. Again referring toFIG.2, the mobile phone205comprises a software module240, a battery245, and an electronics module250interposed between the battery245and the power port220. The electronics module also comprises a switch252. The battery245is connected to the power port220through a third connector255, the electronics module250(including the switch252), and a fourth connector260. The battery245may be any type of rechargeable battery and, illustratively, is a lithium-ion battery. The software module240comprises a user interface module265and a charge profile generator270which are able to communicate with each other through a fifth connector275. The software module240is also connected via a communications bus280to a memory285of mobile phone205, a microprocessor290of mobile phone205, and a user input means295of the mobile phone205as shown. The user input means295may be any means for a user to interact with the mobile phone205including but not limited to touchscreens and mechanical keyboards. The software module240may be an application, also referred to as an “app.” Two elements are said to be “connected” if they are directly connected, indirectly connected, adapted to be directly connected, adapted to be indirectly connected, in direct electrical communication, in indirect electrical communication, and/or adapted to be in direct and/or indirect electrical communication. For example, referring toFIG.2, the power port220and switch252are shown as being directly connected by fourth connector260. This connection need not be a direct connection. Similarly, referring toFIG.1, the power port120is shown to be directly connected to the output port125of the switch box110. Thus, inFIG.1, a switch (not shown) inside the switch box110is considered “connected” to the power port120even though the connection is indirect and/or even though the direct and/or indirect connection may only when the mobile phone105is recharging. Experimental Results and Method of Operation In various portions of the remainder of this detailed description, when describing particular steps and referring to structures in bothFIGS.1and2, a shorthand shall be used wherein a slash (“/”) is used between various structures ofFIGS.1and2. For example, the phrase “mobile phone105/205” refers to mobile phone105and/or mobile phone205ofFIGS.1and2, respectively. Similarly, the phrase “software module140/240” refers to software module140and/or software module240ofFIGS.1and2, respectively. FIG.3shows a graph300of temperature over time for two recharging techniques, namely a first technique and a second technique, used on a mobile phone. Graph305, based on the first technique, shows the temperature of a model HTC 10 mobile phone while it was connected directly to a standard outlet and charging from ten percent battery capacity to 100 percent battery capacity. Graph310, based on the second technique, shows the temperature of the same phone when it was recharged according to a charge profile400ofFIG.4. Graph310also charged the HTC mobile phone from ten percent battery capacity to 100 percent battery capacity. The temperature for both graphs represents the temperature of the model HTC 10 mobile phone. It is apparent that the higher the temperature of the model HTC 10 mobile phone, the higher the temperature of the battery (and other components) inside the model HTC 10 phone will be. The temperature was recorded using the temperature monitoring component of Cooling Master-Phone Cooler on the Google Play Store. Again referring toFIG.3, graph305was generated in 150 minutes. Likewise, graph310was generated in 150 minutes. As seen from graph300, the temperature of the HTC 10 mobile phone (and thus other components such as the battery), was almost identical for the first 27.54 minutes of each experiment, with the temperature being about one degree higher for about the last half of this first time period315, represented by the time period between T0and T1, when the second technique was used. The time period T1to T2shall be referred to as the second time period320. The first time period315and the second time period320are 27.54 minutes and 122.46 minutes, respectively. The HTC 10 mobile phone (and thus other components such as the battery) was cooler throughout the second time period320when the second technique was used. From T0through T2, the inventors estimate that the areas under the graph310and graph305are 4733.1 and 5137.55, respectively. Thus, the area under graph305is approximately 7.6% more than the area under graph310. In sum, for the vast majority of the 150 minutes, the second technique kept the HTC 10 mobile phone (and thus other components such as the battery) cooler, outperforming the first technique and thus, increasing battery life. The results shown inFIG.3may be improved upon by modifying the second technique to reduce the peak heat of graph310between times T0and T1. To accomplish this, one could divide a time sub-period (“TSP”) such as TSP1420ofFIG.4into multiple shorter time intervals, at least some of which will be time intervals during which no current is applied. This could reduce the peak heat of graph310because the battery145/245will heat up less during a shorter time interval, and it will cool during the time interval(s) during which no current is applied. In the first embodiment of battery recharging device100, the switch box110and other components play an important role in reducing the temperature to which the battery145is exposed, leading to longer battery145life. Similarly, in the second embodiment of battery recharging device200, the switch252and other components play an important role in reducing the temperature to which the battery245is exposed, leading to longer battery245life. By way of example, unlike prior techniques that use a “slow charge” (such as described in U.S. Pat. No. 8,922,329) which result in constant current being applied during a recharging period, the switch252of battery recharging device200does not allow current to continually be applied to the battery245during the recharging period. Instead, the switch252, working in unison with other components of the battery recharging device200, allowing a current to be applied to battery245based upon a charge profile generated by charge profile generator270. Similarly, the switch box110of battery recharging device100does not allow current to continually be applied to the battery145during the recharging period. Instead, the switch box110, working in unison with other components of the battery recharging device100, allowing a current to be applied to battery145based upon a charge profile generated by charge profile generator170. FIG.4discloses a charge profile400represented by a graph of temperature over time. The charge profile400has a user-defined time period405of 150 minutes (from T0to T8). The user-defined time period405has a start time410and an end time415represented by T0and T8, respectively. The start time410is the time prior to which recharging does not occur based upon a user input. The end time415is the time after which recharging does not occur and is also based upon a user input. The user-defined time period405comprises eight distinct time sub-periods, namely TSP1420, TSP2425, TSP3430, TSP4435, TSP5440, TSP6445, TSP7450, and TSP8455representing the time from T0to T1, T1to T2, T2to T3, T3to T4, T4to T5, T5to T6, T6to T7, and T7to T8, respectively wherein T0, T1, T2, T3, T4, T5, T6, T7, and T8are times 0, 20, 40, 60, 80, 100, 120, 140, and 150 minutes, respectively. Again referring toFIG.4, the charge profile400shows whether a recharging current is to be applied to battery145/245during TSP1420, TSP3430, TSP5440, TSP7450, and TSP8455. Further, the charge profile400called for three portions of time during which the battery145/245had no recharging current applied to it. These three portions are TSP2425, TSP4,435, and TSP6445. Thus, in this example, the charge profile400is associated with a set of charges (i.e., the charges applied to battery145/245during TSP1420through TSP7455) that will be applied to the battery during the user-defined time period (i.e., from T0[0 minutes] through T8[150 minutes]) wherein the set of charges comprises a first charge (e.g., the charge applied during TSP2425which is equal to zero) applied to the battery after the start time (i.e., T0) and prior to the end time (i.e., T8) during which the battery does not recharge. This example also shows that the set of charges is associated with an additional set of time portions (i.e., TSP4435and TSP6445) within the user-defined time period during which the battery does not recharge. Thus, the charge profile400comprises at least one portion of time (e.g., TSP2425) after the start time410and prior to the end time415during which the current applied to the battery is zero. During TSP1420, TSP3430, TSP5440, TSP7450, and TSP8455, the current applied to the battery145/245was supplied by a 5V/2.5 A, 9V/1.7 A, 12V/1.25 A standard HTC 10 charger. A graph460is the graph of temperature over time as explained with respect toFIG.3. Thus, use of charge profile400helps keep the battery temperature lower as compared to slow charging. The manner in which the charge profile400is generated and the manner in which the charge profile400is used to apply zero current to the battery for, e.g., multiple portions of the user-defined time period405is described more fully with respect toFIG.5and the remainder of the specification. FIG.5shows a flowchart500detailing a method of recharging a battery in accordance with the present invention and applies to methods of recharging with respect to bothFIGS.1and2. The description assumes all connections to a standard outlet are already complete. More specifically, with respect toFIG.1, the description assumes the switch box110is connected to both the power port120of mobile phone105and a standard electrical outlet (not shown) using the first connector115the second connector130as shown inFIG.1. Likewise, with respect toFIG.2, the description assumes that the mobile phone205is connected to a standard electrical outlet (not shown) using the first connector215as shown inFIG.2. Again referring toFIG.5, the flowchart500comprises a first step505of launching a recharging app, a second step510of receiving a user input due to a user entering information via the user input means195/295, a third step515of determining the charge profile400via the profile charge generator170/270, and a fourth step520of recharging the battery based upon the charge profile400, an example of which is shown inFIG.4. In the first step505, the recharging app may be launched by clicking on an icon. The recharging app may also be launched when the mobile phone105/205senses that the first connector115/215is plugged into the power port120/220. Next, in the second step510, the recharging app will prompt the user for input via the user input means195/295. In this example, the user input means195/295uses touchscreen technology well known in the art. Prior to providing additional description of the third step515and the fourth step520, additional description of the first step505and second step510is provided with reference toFIG.6. FIG.6shows a mobile phone105/205wherein the recharging app has been activated, causing the user input means195/295to display a screen600requesting recharging information. As shown on the screen600, the user is prompted to enter a user-defined time period405. More specifically, the user is prompted to enter “start recharging” time in space605, an “end recharging” time in space610, and a “desired final charge state” in space615. The phrases “desired final charge state” and “desired state of charge” are used interchangeably throughout this document. When the user provides entries in spaces605and610, the user has provided a user-defined time period405. Space605and space610also have A.M./P.M. selectors620and625, respectively. Alternatively, the A.M./P.M. selectors620and625, respectively, may be omitted if military time is used. The information input by the user is space605,610, and615is session-specific to an upcoming recharging event in that, e.g., it does not rely upon historical user usage. In other words, it will be used in the upcoming recharging event for battery145/245and will not be used again absent: (1) the user entering identical information for future recharging event; and/or (2) the user “saving” the information input (in, e.g., memory185/285) as, e.g., a “favorite” to use in a future recharging event wherein the user input into the user input means195/295would enable the user to retrieve and designate (via, e.g., another space or set of spaces—not shown) the “favorite” stored input information as being the information to use in a future recharging event. Again referring toFIG.6, in other embodiments, the user-defined time period405is provided with a single entry in space610. For example, the recharging app may be programmed such that it defaults to assume that the “start recharging” time is the time at which user makes the last input into the user input means195/295. Thus, continuing with this example, if the user input means195/295only requests an “end recharging” time in space610and a “desired final charge state” in space615, the “start recharging” time will default to use the time at which the last space (e.g., space615) was populated by the user. Alternatively, the recharging app may be programmed such that it defaults to assume the “start recharging” time is the time at which the recharging app is activated. In the event that the charge profile generator170/270would not determine that charging should begin immediately, this alternative method neglects any negligible recharging that may occur between activation of the recharging app and the time at which the charge profile generator170/270would determine recharging should begin. In the case wherein the user-defined time period405is provided via a single entry in space610, the recharging app would not prompt the user to make an entry in space605and instead would be programmed to, e.g., automatically populate space605with the current time and/or not display space605. While this is advantageous in that it only requires the user to provide a single entry to provide a user-defined time period405, it does not allow a cost-conscious user to specify that recharging occur when electrical rates may be the low. Thus, in this example, even though the user makes a time entry only in space610, the user is considered to have input a “user-defined time period.” Yet again referring toFIG.6, in preferred embodiments, the user is prompted to enter a desired final charge state for the battery145/245in space615. The desired final charge state is a percentage to which the user would like to charge the battery145/245. For example, the user may elect to only charge the battery145/245to 80% or 90% of the total charge the battery145/245is capable of holding. This is because charging the battery145/245to less than 100% is recommended to help increase the lifetime of the battery145/245. Also, charging the battery145/245to less than 100% is also recommended for storage by some organizations. For example, Section 6.13 of the document available at https://www.riscauthority.co.uk/about/latest-news detail.new-document-release-rc61-recommendations-for-the-storage-handling-and-use-of-batteries.html states “nickel and lithium based batteries should be stored at about 40% of their full charge.” Due to this, preferably, charge profile generator170/270may generate a charge profile400that serves to keep the battery at about a 40% charge for as long as possible while still serving to have the battery reach the user's desired final charge state. Returning now toFIG.5, the third step515and the fourth step520will now be described in more detail with reference to Appendix A. Appendix A is source code (with comments) for one embodiment of the charge profile generator170/270. The source code in Appendix A is written in the C computing language and is capable of running on an Arduino Beetle microcontroller. As denoted in Appendix A, the source code for charge profile generator170/270has three modules. A first module A100is a module that obtains the “start recharging” time, “end recharging” time, and a “desired final charge state” from the user input means195/295. The first module A100contains code lines 50 to 72, inclusive. Once the user input means195/295passes the user input entered via screen600to the charge profile generator170/270via fifth connector175/275, the charge profile generator170/270uses a second module A200to determine the charge profile400based upon information received from the first module A100. The second module A200contains code lines 73 to 164, inclusive. A third module A300communicates with switch box110ofFIG.1via various connections shown inFIG.1(or switch252ofFIG.2via various connections shown inFIG.2) to enable current to flow to the battery145/245based upon the charge profile400. The third module A300contains code lines 165 to 180. Lines 1 through 49 set up the use of the first module A100, the second module A200, and the third module A300. It should be noted that in Appendix A the “start recharging” time is the time at which the charge profile generator170/270is initiated. The second module A200of Appendix A shows code for the third step515ofFIG.5. More specifically, the second module A200shows that part of the code used to determine the charge profile400is shown in, e.g., code line 95 which calculates a charge slope to be used in determining the charge profile400. The third module A300of Appendix A shows code for the fourth step520ofFIG.5. More specifically, the third module A300shows the actual code used to recharge the battery145in accordance with the charge profile400. Also, the manner in which the charge profile400is used in the operation of switch box110ofFIG.1to enable current to flow to the battery145is also shown. The charge profile400is used in the fourth step520to change the state of the switch box110(first embodiment) and/or the switch252(second embodiment) such that during the user-defined time period405the battery145/245will recharge to the desired final charge state previously entered in space620while also having a portion of time after the start time previously entered in space605and the end time previously entered in space610during which the battery145/245is not recharging. As noted previously, in some embodiments, there need not be a start time entered due to the use of default values. Also, as used herein, start time and end time are synonymous with, e.g., the “start recharging” time and “end recharging” time entered in space605and610, respectively. One may use many known techniques in the switch box110to ensure this occurs, including, e.g., a relay switch. Also as well know, one may use various components, such as a set of one or more transistors, to create switch252. More generally, those skilled in the art realize that there are many ways to enable current to flow to the battery245ofFIG.2using switch252which may be comprised of hardware (such as a transistor and/or other electronics), software, firmware or a combination thereof. Those skilled in the art will realize that the charge profile400shown inFIG.4and discussed in this detailed description was for the HTC 10 mobile phone recharging with a user-defined time period of 150 minutes and that other charge profiles for the HTC 10 mobile phone may vary due to a change to any or all of the user inputs (e.g., there may be a larger or smaller user-defined time period and/or a different desired final charge state). Those skilled in the art will also realize that other charge profiles may differ due to the battery being recharged being in a device other such as a laptop and/or portable computer, a personal digital assistant, a tablet, a camcorder, a power tool, an automobile, and/or another vehicle, or any other device using a rechargeable battery and that this invention may be used with any such device. Additionally, while various embodiments of the present invention have been shown and described, various modifications to those embodiments may be made. These modifications include, but are not limited to: 1) the battery145/245being any other type of rechargeable battery, not only a lithium-ion battery; 2) the communication paths and connections being implemented using various technologies and topologies such as a communication bus; 3) the memory185/285being any type of memory including Random Access Memory (RAM), flash memory, Read Only Memory (ROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, hard disk, or any other form of storage medium known in the art; 4) the microprocessor being any type of processor including a processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, e.g., a combination of a Digital Signal Processor (DSP) and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration; 5) the software module140/240being implemented software, hardware, firmware or any combination thereof. Further, to the extent implemented in anything other than hardware, the software module may be stored in any type of memory device including but not limited to those identified in (3) above; 6) the user input means being voice activated and one wherein the user is able to enter user inputs via voice; 7) the charging of the battery being performed wirelessly; 8) the charging of the battery being performed in accordance with any USB protocol including but not limited to those referenced at http://www.usb.org/developers/powerdelivery/; 9) the user input being able to be overridden by the user. This may occur, for example, if after the recharging begins, the user must shorten or lengthen the user-defined time period due to a change in plans; 10) the switch box110having multiple ports (e.g., USB ports) enabling the user to recharge batteries on multiple devices simultaneously by using a single recharging app; and/or 11) any combination of features such as, e.g., the microprocessor, memory, and software module, may reside in an Application Specific Integrated Circuit (ASIC). Those skilled in the art will realize and appreciate many other variations and modifications may be made to the invention that are within the claims. Thus, the previously described embodiments are provided to enable any person skilled in the art to make or use the present invention. Various modifications to these exemplary embodiments will be readily apparent to those skilled in the art and may be applied in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the broadest scope consistent with the claims. | 26,646 |
11862773 | DESCRIPTION OF EMBODIMENTS The following clearly describes the technical solutions in the embodiments of the present disclosure with reference to the accompanying drawings in the embodiments of the present disclosure. Though terminals develop rapidly and hardware technologies are upgraded quickly, terminal battery technologies do not make much progress in recent years, and a battery electricity quantity restricts use of terminals (for example, a smartphone). Emergence of fast charging technologies provides a new approach to resolve a terminal charging problem. Although the fast charging technologies can effectively resolve a problem about along charging time, excessively frequent fast charging causes irreversible damages to a battery, and reduces a battery life. In principle, battery damages are basically caused by two aspects. On one hand, when a battery is charged, the cathode and anode of the battery shrink with release of ions; and when a battery discharges, the cathode and anode of the battery expand with absorption of the ions. Frequent fast charging may damage chemical substances in the battery, shortening the battery life. On the other hand, during fast charging, a current is relatively high, and a thermal effect of the current is intensified. Therefore, the battery is at a high temperature, and the high temperature may cause a sharp drop in a capacity and permanent damages to a battery. In a normal charging state (generally, charging with a power less than 10 W, such as 5V1 A or 5V1.5 A, is deemed as normal charging), a charging current is relatively low, and damages to the battery are slight. However, in a fast charging state, a charging current is several times of a normal charging current, and an excessively high current during the charging intensifies a chemical reaction in the battery, and doubles damages to a battery electrode material and to an electrode structure, shortening a battery service life. The present disclosure provides a charging method and a terminal. The terminal can automatically learn historical data by using a machine learning algorithm, to establish a habit model of a user, and may determine a current charging intention of the user according to a current time and the usage habit model of the user, so as to determine a charging mode according to the charging intention. By means of the technical solutions, a charging requirement of a user can be effectively identified, and on-demand charging can be implemented. This improves user experience while avoiding a battery life decrease caused by frequent fast charging. As shown inFIG.1,FIG.1is a terminal10. The terminal10includes an obtaining unit110, a matching unit120, a determining unit130, a charging unit140, and a training unit150. The terminal10may be an electronic device such as a mobile phone, a tablet computer, or an intelligent wearable device. It can be understood that, the terminal10trains historical data within a preset time period according to a machine learning algorithm to obtain a usage habit model of a user. It can be understood that more historical data is beneficial to training for the usage habit model of the user. The historical data in the terminal10includes but is not limited to a time period for which the user uses the terminal10, a location at which the user uses the terminal10, an activity type of the user corresponding to the time and the location, an environmental status corresponding to the time period and the location, a time period of peak power consumption, and an application program used at a frequency greater than a third preset threshold. For example, a user X continuously uses a mobile phone at 9:00 to 11:00 every night at home, an activity type of the user corresponding to the time period and the location is entertainment, an environment status corresponding to the time period and the location is quiet with dark light, and a time period of peak power consumption is 9:00 to 11:00. It should be noted that, for example, an application program that runs longer than 20 minutes per day can be considered as an application program used at a frequency greater than the third preset threshold. That is, more than the third preset threshold is a service time of more than 20 minutes. No limitation is imposed herein on the third preset threshold. The third preset threshold may be a default setting of the terminal, or may be set by a user. For another example, an application program that runs for more than three times per day can be considered as an application program used at a frequency greater than the third preset threshold. That is, the third preset threshold is three running times. A common application program used at a frequency greater than the third preset threshold may be a game application program, or may be a social application program, or even may be a news application program. There are many methods for obtaining the historical data, which can be obtained directly from a storage medium or a database of the terminal, or can be obtained from a cloud data center connected to the terminal. For example, the terminal10stores, by using various types of sensors (such as a temperature sensor, a gyroscope, a camera, an acceleration sensor, and a location sensor), a process of using the terminal10by the user in a log. For example, the log may record in chronological order what application programs the user uses today, and how long each application program is used. In this way, an application program used at a frequency greater than the third preset threshold may be determined based on the log. For example, the log may record how many times the user charges the terminal each day, how long the terminal is charged each time, and whether the user uses the terminal each time when the terminal is being charged. In this way, a fixed charging time period of the user and a electricity quantity consumption rate of the terminal may be determined according to the log. For example, the log may also record a location at which the terminal10is located today and duration for which the terminal10stays at each location. In this way, a main activity place of the user may be determined according to the log. For example, an area where the terminal10stays for more than eight hours (the area may be a building, a community, a company, or the like) is considered as a home or an office by default. For example, the log may also record a time period in which a power consumption rate of the terminal10is relatively high. In conclusion, the terminal10may obtain a large amount of data information by using various sensors, for example, obtain an ambient temperature by using a temperature sensor, obtain an ambient humidity by using a humidity sensor, obtain a current altitude by using an altitude sensor, locate a current location by using a GPS system, and obtain a current light intensity by using a light sensor. Then the terminal may store the obtained information in the log. The machine learning algorithm includes but is not limited to a classification algorithm, a clustering algorithm, a regression algorithm, an enhanced learning algorithm, a migration learning algorithm, and a deep learning algorithm. The obtaining unit10is configured to obtain historical data stored by the terminal10. For example, the historical data may be historical data obtained from the log. The training unit150is configured to train, according to at least one machine learning algorithm, the historical data obtained by the obtaining unit10to obtain the usage habit model of the user. The training unit150may analyze the historical data by using the at least one machine learning algorithm, correct an analysis result, and set the corrected analysis result to the usage habit model of the user. In an embodiment of the present disclosure, the terminal further includes a detection unit160. The detection unit160is configured to detect whether a connection is established between the terminal10and a charger. When the detection unit160detects that a connection is established between the terminal10and the charger, the detection unit160sends an instruction to the obtaining unit110. The obtaining unit110is configured to obtain a current time and the usage habit model of the user according to the instruction. The obtaining unit110may obtain the current time by using a clock of the terminal. The matching unit120is configured to: when the obtaining unit110successfully obtains the usage habit model of the user, match the current time with the usage habit model of the user to obtain a charging intention of the user. It should be noted that the charging intention includes but is not limited to 2-hour full charge, 8-hour full charge, fast charging, and any-time full charge. For example, a user B is an office worker who works for five days and rests for two days at weekend every week, and has regular routines and habits. Based on historical use data of using an intelligent terminal by the user in a time period of one month, usage habits of using the intelligent terminal by the user are obtained as follows: LocationActivityChargingTime periodof a usertypeUsage habitintention0:00 to 8:00HomeSleepingNo use/PowerFull chargeoff/Silencecompletedbefore8:008:00 to 19:00Office,WorkingUse as neededFastfor workingvehicle, orchargingdaysbusiness trip19:00 to 24:00HomeHomeFrequent use forFastfor workingentertainmententertainmentchargingdaysand socialcommunication8:00 to 20:00Outdoors,OutdoorExtremely lowFastfor weekendsmall, orrecreationpowerchargingself-driving20:00 to 21:00HomeReadingNormal useNormalfor weekendsnewscharging Optionally, the obtaining unit110is further configured to obtain the location of the terminal10. It can be understood that the location of the terminal may be located by using a GPS. Common locations include but are not limited to a home, a workplace, a bar, a library, a restaurant, and the like. The terminal10may be connected to sensors by using the obtaining unit110, and may be connected directly to the sensors by using a bus. When the obtaining unit110successfully obtains the usage habit model of the user, the obtaining unit110sends a matching instruction to the matching unit120. The matching unit120is configured to match the current time and the location of the terminal10with the usage habit model of the user according to the matching instruction sent by the obtaining unit110, to obtain the charging intention of the user. It can be understood that, the charging intention of the user may be more accurately determined by inputting the current time and the location of the terminal to the usage habit model of the user. Optionally, the obtaining unit110is further configured to obtain information about an environment in which the terminal10is located. It can be understood that, the obtaining unit110may obtain, by using a temperature sensor, a temperature of the environment in which the terminal10is located; may also obtain, by using a humidity sensor, a humidity of the environment in which the terminal10is located; may also obtain, by using an altitude sensor, an altitude of the location of the terminal10; may also obtain, by using a light sensor, a light intensity of the environment in which the terminal10is located; may also obtain, by using a microphone, sound information of the environment in which the terminal10is located; may also obtain a motion state of the user by using an acceleration sensor; and may also obtain a status of the terminal10by using a level instrument. An activity of the user may be determined with reference to the humidity, the temperature, the altitude, the light intensity, and the sound that are of the environment in which the terminal10is located, and the motion state of the user. For example, if the environment is quiet with bright light, and the user is not in a motion state, the user may work in office. For another example, if the environment is noisy, the humidity is high, and the user is in a rapid motion state, the user may be in a car. For another example, if the environment is quiet with no light, the user is in a motionless state, and a time period is from 1:00 a.m. to 5:00 a.m., the user may be in a sleeping state. For another example, if an altitude is high, a humidity is high, a temperature is low, and the user is in a motion state, the user may be climbing a mountain outdoors or the like. When the obtaining unit110successfully obtains the usage habit model of the user, the obtaining unit110sends a matching instruction to the matching unit120. The matching unit120is configured to match, according to the matching instruction sent by the obtaining unit110, the current time, the location of the terminal10, and the environment in which the terminal10is located with the usage habit model of the user to obtain the charging intention of the user. It can be understood that, the charging intention of the user may be more accurately determined by inputting the current time, the location of the terminal, and the information about the environment in which the terminal is located to the usage habit model of the user. The matching unit120is further configured to send the charging intention to the determining unit130. The determining unit130is configured to determine a charging mode according to the charging intention. A correspondence between the charging intention and the charging mode may be stored in the terminal in advance. Alternatively, a charging solution may be determined according to the charging intention. If there are multiple charging solutions, one charging solution meeting the usage habit of the user is selected from the multiple charging solutions. It should be pointed out that, the charging solution may include one charging mode, or may include multiple charging modes (for example, a combination mode of fast charging and slow charging). There are many fast charging modes, and no limitation is imposed herein on the fast charging mode (such as open-loop fast charging, closed-loop fast charging, or the like). For example, when the user considers that charging may be completed between 1:00 a.m. and 7:00 a.m., in this period, fast charging may be selected, or the combination mode of fast charging and slow charging may be selected, or even slow charging may be selected. It should be noted that, if time permits, long-time slow charging or short-time fast charging is selected preferably. For another example, if it is determined that, according to the time period and the usage habit model of the user, the user may be playing a game in the current time period, fast charging is selected preferably. Optionally, the terminal10further includes a prompting unit170and a receiving unit180. After the charging mode is determined, the prompting unit170is configured to prompt the user whether charging is performed according to the charging mode. The prompting unit170is configured to send a charging mode confirmation request to the user. The charging mode confirmation request is used to ask the user whether charging is performed according to the charging mode. When the receiving unit180receives an instruction that the user confirms that charging is performed according to the charging mode, the charging unit140charges the terminal according to the charging mode. It should be noted that the prompting unit170has many prompting manners, including but not limited to word prompting and voice prompting manners. As shown inFIG.2,FIG.2shows a specific prompting manner.FIG.2shows a prompting interface. On the interface, a charging mode, whether the terminal is in a machine learning state (an auto-learning state), and optional charging modes are displayed. Optionally, the prompting unit170is further configured to: when a charging mode change instruction entered by the user is received, prompt the user to select a new charging mode. The receiving unit180is further configured to receive the user-selected charging mode; and the charging unit140is configured to perform charging according to the user-selected charging mode. Further, the terminal10further includes a correction unit190. The correction unit190is configured to correct the usage habit model of the user according to the user-selected charging mode. For example, the correction unit190determines a time period to which the current time belongs; determines a corresponding charging mode in the usage habit model of the user that is in the time period; and changes the corresponding charging mode in the usage habit model of the user that is in the time period to the user-selected charging mode. The current time is 3:00 a.m., belonging to a time period from 1:00 a.m. to 6:00 a.m., and correspondingly, a charging mode in the usage habit model of the user is slow charging. When the user changes the charging mode to fast charging, the correction unit190changes the charging mode that corresponds to the time period from 1:00 a.m. to 6:00 a.m. in the usage habit model of the user to fast charging. It can be understood that, after the charging mode is determined according to the charging intention, the user is prompted to determine whether the charging mode meets a requirement of the user, and the usage habit model of the user is corrected according to feedback information of the user. It should be noted that, the user may set whether a prompting option is shown. If the user considers that, after several previous corrections, a subsequent charging intention or a charging mode corresponding to a charging intention can meet the requirement of the user, it may be considered that the usage habit model of the user is an accurate model, and the user may set an option “Confirmation of a charging mode is not prompted” on a setting page. When the determining unit130determines the charging mode, the charging unit140performs charging according to the charging mode. A battery in the terminal10includes but is not limited to, a lithium battery, a lithium-ion battery, an air battery, a lead-acid battery, and a super capacitor. The charging unit140is further configured to obtain a battery status parameter such as a battery voltage, a current, an internal resistance, a battery capacity, a battery temperature, or a battery internal pressure, so as to adjust the charging mode according to the battery status parameter. For example, when a battery temperature is greater than a temperature threshold (40° C.) or a battery voltage is greater than a voltage threshold (4.0V), a charging mode cannot be or is not recommended to be switched to the fast charging mode. When a battery capacity is less than a capacity threshold (20%) or a battery voltage is less than a voltage threshold (3.3V), the fast charging mode is preferably selected or it is recommended that the charging mode be switched to the fast charging mode. It can be understood that, thresholds of the battery status parameters are related to a battery type. The thresholds may be set by default before delivery, or may be user-defined. Safety performance of switching a battery charging mode may be further determined by setting the battery status parameter thresholds. It can be understood that the present disclosure provides a charging method and a terminal. The terminal can automatically learn historical data by using a machine learning algorithm, to establish a habit model of a user, and may determine a current charging intention of the user according to a current time and the usage habit model of the user, so as to determine a charging mode according to the charging intention. By means of the technical solutions, the charging requirement of a user can be effectively identified, and on-demand charging can be implemented. This improves user experience while avoiding a battery life decrease caused by frequent fast charging. As shown inFIG.3, based on the foregoing embodiment, in another embodiment of the present disclosure, the terminal10further includes a judging unit210and a calculation unit220. The detection unit160is configured to detect whether a connection is established between the terminal10and a charger. The obtaining unit110is configured to obtain a current time and a usage habit model of a user when the detection unit210detects that a connection is established between the terminal10and the charger. The judging unit210is configured to: when the obtaining unit220fails to obtain the usage habit model of the user, determine whether the current time is in a preset sleep time period. The calculation unit220is configured to calculate a length of time available for charging according to the current time and the preset sleep time period when the current time is in the preset sleep time period. For example, if the current time is 1:00 a.m., and the preset sleep time period is from 0:00 a.m. to 6:00 a.m., the current time is in the preset sleep time period. Further, it can be calculated that a length of time available for charging is five hours. The determining unit130is further configured to determine a charging mode according to the time length. For example, if a current electricity quantity of the terminal is 40%, and a preset value of an electricity quantity is 90% (which may be a default value of the terminal, or may be set by the user), that is, a charging requirement of the terminal10is to charge 50% within five hours. With respect to this requirement, there may be multiple charging manners. In slow charging, the terminal can be charged 10% per hour, and in fast charging, the terminal can be charged 40% per hour. Solution 1: Slow charging for five consecutive hours. Solution 2: Fast charging for one hour and slow charging for two hours. Solution 3: Fast charging for one and a half hours. However, from a perspective of meeting a usage requirement of the user to the maximum extent and from a perspective of prolonging a battery service life, the charging mode may be determined as a slow charging mode because the user basically does not use the terminal10in the sleep time period. The charging unit140performs charging according to the charging mode. As shown inFIG.1, in another embodiment of the present disclosure, if obtaining the habit model of the user fails because the terminal10does not yet obtain the usage habit model of the user by means of training or a storage medium is faulty, a current electricity quantity and whether a charging condition is satisfied need to be considered. Details are as follows: The obtaining unit110is further configured to obtain a remaining electricity quantity and a current location of the terminal when obtaining the usage habit model of the user fails. The determining unit130is configured to: when the remaining electricity quantity is less than a first preset threshold and the current location does not belong to a preset location set, determine that the charging mode is a fast charging mode. It should be noted that, the first preset threshold may be a default value of the terminal, or may be set by the user. The preset location set may be understood as a place where a long-time charging is allowed, for example, a home or an office. For example, the first preset threshold is 20%, and the preset location set is home and office. When the terminal10is connected to the charger, if it is determined that a location of the terminal10is a shop, and an electricity quantity of the terminal10is 15%, a charging mode is determined as a fast charging mode. For another example, when the terminal10is connected to the charger, it is determined that a location of the terminal10is home, and an electricity quantity of the terminal10is 30%, the user is prompted whether fast charging is performed. If time permits, the user may select slow charging; or if the time does not permit, the user may select fast charging. As shown inFIG.1, in another embodiment of the present disclosure, if obtaining the habit model of the user fails because the terminal10does not yet obtain the usage habit model of the user by means of training or a storage medium is faulty, a current electricity quantity and a current usage status of the terminal10need to be considered. Details are as follows: The obtaining unit110is further configured to obtain a remaining electricity quantity of the terminal when obtaining the usage habit model of the user fails. The detection unit160is configured to: when obtaining the usage habit model of the user fails, detect whether there is a running application program in the terminal. The determining unit130is configured to: when the remaining electricity quantity is less than a second preset threshold and there is a running application program, determine that the charging mode is a fast charging mode. It should be noted that, the second preset threshold may be a default value of the terminal, or may be set by the user. For example, the second preset threshold is 30%. When the terminal10is connected to the charger, and a running application program is detected in the terminal10, it indicates that the user needs to use the terminal10, and the terminal should be charged fast to meet the requirement of the user. As shown inFIG.1, in another embodiment of the present disclosure, if obtaining the habit model of the user fails because the terminal10does not yet obtain the usage habit model of the user by means of training or a storage medium is faulty, a current electricity quantity, a current usage status of the terminal10, and whether a charging condition is satisfied at the place where the terminal10is currently located need be considered. When the current electricity quantity is less than a second preset threshold, the terminal is in the state of running multiple application programs, and a charging condition is satisfied, the terminal10is charged according to a fast charging mode. In another embodiment of the present disclosure, it can be understood that, user habits can be obtained by analyzing a relationship between a common activity of a user, such as entertainment, sport, or sleeping, and use of an intelligent terminal. For example, if a terminal is suddenly out of power when a user is using the terminal for entertainment, it may be determined that a charging intention of the user is fast charging, and an entertainment activity may continue even without full charge. If the user likes to run outdoors and records sport data, and an intelligent terminal is out of power when the user is running, it may be determined that the user needs fast charging. If the user has a regular sleeping habit, for sleeping at night, it may be determined that the user does not need to use the intelligent terminal, and in this case, slow charging is selected preferably. For a lunch break, it may be determined that the user needs to increase the electricity quantity of the intelligent terminal, a charging rate may be determined according to a length of the lunch break of the user. The terminal provided in this embodiment of the present disclosure can establish a usage habit model of a user by means of auto-learning (by using a machine learning algorithm and historical data), so as to match a current time, a location of the terminal, and an environment in which the terminal is located with the usage habit model of the user to determine a charging intention of the user; and determine a charging mode according to the charging intention. By means of the technical solutions, a fast charging requirement of a user can be effectively identified, and on-demand fast charging can be implemented. This improves user experience while avoiding a battery life decrease caused by unnecessary frequent fast charging. As shown inFIG.4, in another embodiment of the present disclosure, a terminal30is provided. The terminal30includes a CPU310(Central Processing Unit, central processing unit), a memory320, a display330, and a bus340. The CPU310is configured to run code stored in the memory320to start a charging program. A charging process includes:obtaining a current time and a usage habit model of a user when it is detected that a connection is established between the terminal30and a charger;matching the current time with the usage habit model of the user to obtain a charging intention of the user;determining a charging mode corresponding to the charging intention; andcharging the terminal according to the determined charging mode. It should be noted that, before the obtaining a usage habit model of a user, the executed process further includes:training, by using a preset machine learning algorithm, historical data that the user uses the terminal, to obtain the usage habit model of the user, where it should be noted that, the machine learning algorithm and the historical data may be stored in the memory320in advance. It should be noted that, before the training, by using a preset machine learning algorithm, historical data that the user uses the terminal, the executed process further includes:obtaining the historical data that the user uses the terminal within a preset time period, where the historical data includes but is not limited to a time period for which the user uses the terminal, a location at which the user uses the terminal, an activity type of the user corresponding to the time and the location, an environmental status corresponding to the time period and the location, a time period of peak power consumption, and an application program used at a frequency greater than a third preset threshold. The training, by using a preset machine learning algorithm, historical data that the user uses the terminal includes:analyzing the historical data by using the preset machine learning algorithm; andcorrecting an analysis result, and setting the corrected analysis result to the usage habit model of the user. As shown inFIG.5, the terminal30further includes a temperature sensor410, a humidity sensor420, a light sensor430, a location sensor440, a camera450, a gyroscope460, an acceleration sensor470, or the like. The terminal30obtains user data by using the foregoing sensors, and stores the data in the memory320. The stored data may be considered as the historical data. Optionally, before the matching the current time with the usage habit model of the user to obtain a charging intention of the user, the executed process further includes:obtaining a location of the terminal; andthe matching the current time with the usage habit model of the user to obtain a charging intention of the user includes:determining the charging intention of the user according to the current time, the location of the terminal, and the usage habit model of the user. Optionally, before the matching the current time with the usage habit model of the user to obtain a charging intention of the user, the executed process further includes:obtaining information about an environment in which the terminal is located; andthe matching the current time with the usage habit model of the user to obtain a charging intention of the user includes:determining the charging intention of the user according to the current time, the location of the terminal, the information about the environment in which the terminal is located, and the usage habit model of the user. Optionally, after the determining a charging mode of the user according to the charging intention, the executed process further includes:prompting the user whether charging is performed according to the charging mode; andcharging the terminal according to the charging mode when an instruction that the user confirms that charging is performed according to the charging mode is received. Optionally, the executed process further includes:when a charging mode change instruction entered by the user is received, prompting the user to select a new charging mode; andreceiving the user-selected charging mode, performing charging according to the user-selected charging mode, and correcting the usage habit pattern of the user according to the user-selected charging mode. Optionally, the executed process further includes:when obtaining the usage habit model of the user fails, determining whether the current time is in a preset sleep time period;when the current time is within a preset sleep time period, calculating, according to the current time and the preset sleep time period, a terminal charging time length required to make the electricity quantity of the terminal reach a preset value; anddetermining the charging mode according to the time length. Optionally, the executed process further includes:when obtaining the usage habit model of the user fails, obtaining a remaining electricity quantity and a current location of the terminal; andwhen the remaining electricity quantity is less than a first preset threshold and the current location does not belong to a preset location set, determining that the charging mode is a fast charging mode. Optionally, the executed process further includes:when obtaining the usage habit model of the user fails, obtaining a remaining electricity quantity of the terminal, and detecting whether there is a running application program in the terminal; andwhen the remaining electricity quantity is less than a second preset threshold and there is a running application program, determining that the charging mode is a fast charging mode. As shown inFIG.6, the present disclosure provides a charging method, and the charging method includes the following steps. S501: Obtain a current time and a usage habit model of a user when it is detected that a connection is established between a terminal and a charger. The method is performed by the terminal, and the terminal may be an electronic device such as a mobile phone, a tablet computer, or an intelligent wearable device. It can be understood that, before obtaining a usage habit model of a user, the terminal trains, by using a preset machine learning algorithm, historical data that the user uses the terminal, to obtain the usage habit model of the user. The machine learning algorithm includes but is not limited to a classification algorithm, a clustering algorithm, a regression algorithm, an enhanced learning algorithm, a migration learning algorithm, and a deep learning algorithm. The terminal obtains the historical data about the terminal from a database, a storage medium, or a cloud, then analyzes the historical data by using the preset machine learning algorithm to obtain an analysis result, and then performs generalization, convergence, and correction on the analysis result so as to obtain the usage habit model of the user. The historical data includes but is not limited to a time period for which the user uses the terminal, a location at which the user uses the terminal (for example, may be located by using a GPS), an activity type of the user corresponding to the time period and the location (for example, sleeping, working, entertainment, outdoor sports, or the like), an environmental status corresponding to the time period and the location (for example, a temperature, a humidity, a light intensity, and an altitude), a time period of peak power consumption, and an application program used at a frequency greater than a third preset threshold (for example, an application program that runs for at least 20 minutes each day or an application program that runs for at least three times each day). S502: Match the current time with the usage habit model of the user to obtain a charging intention of the user. Optionally, to more accurately understand the charging intention of the user, the following may be considered: obtaining a location of the terminal, and inputting the current time and the location of the terminal as parameters into the usage habit model of the user to determine the charging intention of the user. Optionally, to more accurately understand the charging intention of the user, the following may be considered: obtaining a location of the terminal, and inputting the current time and the location of the terminal as parameters into the usage habit model of the user to determine the charging intention of the user. Optionally, to more accurately understand the charging intention of the user, the following may be considered: obtaining information about an environment in which the terminal is located, and inputting the current time and the information about the environment in which the terminal is located as parameters into the usage habit model of the user to determine the charging intention of the user. Optionally, to more accurately understand the charging intention of the user, the following may be considered: obtaining information about an environment in which the terminal is located and a location of the terminal, and inputting the current time, the location of the terminal, and the information about the environment in which the terminal is located as parameters into the usage habit model of the user to determine the charging intention of the user. S503: Determine a charging mode corresponding to the charging intention. Common modes include fast charging, slow charging, standard charging or a combination of fast charging and slow charging (for example, first fast charging and then slow charging or first slow charging and then fast charging). S504: Charge the terminal according to the determined charging mode. It should be noted that, before the charging the terminal according to the charging mode, the determined charging mode may also be displayed on a screen for confirmation by the user; and charging the terminal according to the charging mode when an instruction that the user confirms that charging is performed according to the charging mode is received. When a charging mode change instruction entered by the user is received, the user is prompted to select a new charging mode, the user-selected charging mode is received, the charging is performed according to the user-selected charging mode, and the usage habit pattern of the user is corrected according to the user-selected charging mode. In addition, it should be noted that, there is also a possibility that the usage habit model of the user fails to be obtained. For example, the terminal does not yet obtain the usage habit model of the user by means of training, or a storage medium is damaged, and the terminal cannot obtain the usage habit model from the medium. In this case, there are several methods to determine a charging mode. Optionally, when obtaining the usage habit model of the user fails, whether the current time is in a preset sleep time period is determined; and when the current time is within the preset sleep time period, to make the electricity quantity of the terminal reach a preset value, a required terminal charging time length is calculated according to the current time and the preset sleep time period; and the charging mode is determined according to the time length. Optionally, when obtaining the usage habit model of the user fails, a remaining electricity quantity and a current location of the terminal are obtained. When the remaining electricity quantity is less than a first preset threshold and the current location does not belong to a preset location set, the charging mode is determined as a fast charging mode. Optionally, when obtaining the usage habit model of the user fails, a remaining electricity quantity is obtained, and whether there is a running application program in the terminal is detected. When the remaining electricity quantity is less than a second preset threshold and there is a running application program in the terminal, the charging mode is determined as a fast charging mode. It can be learnt from the foregoing that the present disclosure provides a charging method for a terminal. The terminal can automatically learn historical data by using a machine learning algorithm, to establish a habit model of a user, and may determine a current charging intention of the user according to a current time and the usage habit model of the user, so as to determine a charging mode according to the charging intention. By means of the technical solutions, a charging requirement of a user can be effectively identified, and on-demand charging can be implemented. This improves user experience while avoiding a battery life decrease caused by frequent fast charging. A person of ordinary skill in the art may be aware that, in combination with the examples described in the embodiments disclosed in this specification, units and algorithm steps may be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed by hardware or software depends on particular applications and design constraint conditions of the technical solutions. A person skilled in the art may use different methods to implement the described functions for each particular application, but it should not be considered that the implementation goes beyond the scope of the present disclosure. It may be clearly understood by a person skilled in the art that, for the purpose of convenient and brief description, for a detailed working process of the foregoing system, apparatus, and unit, reference may be made to a corresponding process in the foregoing method embodiments, and details are not described herein again. In the several embodiments provided in this application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described apparatus embodiment is merely an example. For example, the unit division is merely logical function division and may be other division in actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms. The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments. In addition, functional units in the embodiments of the present disclosure may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit. When the functions are implemented in the form of a software functional unit and sold or used as an independent product, the functions may be stored in a computer-readable storage medium. Based on such an understanding, the technical solutions of the present disclosure essentially, or the part contributing to the prior art, or some of the technical solutions may be implemented in a form of a software product. The software product is stored in a storage medium, and includes several instructions for instructing a computer device (which may be a personal computer, a server, or a network device) to perform all or some of the steps of the methods described in the embodiments of the present disclosure. The foregoing storage medium includes: any medium that can store program code, such as a USB flash drive, a removable hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk, or an optical disc. The foregoing descriptions are merely specific implementation manners of the present disclosure, but are not intended to limit the protection scope of the present disclosure. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in the present disclosure shall fall within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims. | 44,238 |
11862774 | DETAILED DESCRIPTION The following description is of various exemplary embodiments only, and is not intended to limit the scope, applicability or configuration of the present disclosure in any way. Rather, the following description is intended to provide a convenient illustration for implementing various embodiments including the best mode. As will become apparent, various changes may be made in the function and arrangement of the elements described in these embodiments without departing from the scope of the appended claims. For the sake of brevity, conventional techniques for battery pack construction, configuration, and use, as well as conventional techniques for wiring, interconnecting, operation, measurement, optimization, and/or control of battery cells, may not be described in detail herein. Furthermore, the connecting lines shown in various figures contained herein are intended to represent exemplary functional relationships, electrical connections/relationships, and/or physical couplings between various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system or related methods of use, for example an interconnect assembly for a battery pack for an electric vehicle. Various shortcomings of prior battery interconnect systems can be addressed by utilizing battery packs, interconnect components, and related components configured in accordance with principles of the present disclosure. For example, prior interconnect systems typically involve connecting metal strips or wires to each cell. This approach is time consuming in manufacturing, and can introduce an unacceptable level of variability in the manufacturing process. Moreover, prior connection systems typically make use of wire harnesses for voltage and temperature measurement as well as cell balancing; manufacturing and assembly of such harnesses often introduces a higher failure rate, lowering overall reliability and longevity of the system. In contrast, exemplary systems and methods disclosed herein enable improved battery cell interconnection in a battery pack by use of an interconnect assembly. The interconnect assembly may have a plurality of conductive layers, for example a first interconnect layer and a second interconnect layer oriented in parallel with the first interconnect layer. The two interconnect layers may be electrically isolated from each other at various points (for example, via one or more insulating layers), and electrically coupled to one another at various points, and may be overmolded to form a package. The interconnect layers may comprise a plurality of segments, which may be configured in an at least partially overlapping manner (for example, in a manner similar to a “running bond” style of overlapping bricks). The interconnect assembly is placed over a plurality of cells and tabs of the interconnect assembly are connected, respectively, to the positive and negative terminals of each cell. In some exemplary embodiments, the interconnect assembly is described as an overmolded package. In other exemplary embodiments, the interconnect assembly is described as a stack of current carrying plates (configured without overmolding). Additionally, exemplary systems and methods disclosed herein hold and correctly locate battery cells in place (both prior to collection and thereafter) at the same end as the electrical connections on the cell. Moreover, the interconnect assembly, in an example embodiment, comprises a trace for sensing various conditions associated with the battery pack (e.g., thermal, voltage, and/or current sensing), and reporting sensed information to a battery management system. Moreover, the tabs may be configured to function as fuses to protect the cell and/or battery pack as a whole. Yet further, the interconnect assembly can provide electrical connections suitable for parallel cell balancing. An interconnect system in accordance with principles of the present disclosure may be configured with any suitable components, structures, and/or elements in order to provide desired dimensional, mechanical, electrical, chemical, and/or thermal properties. A “battery pack” as used herein describes a set of any number of battery cells, interconnected in series or parallel or a combination of series and parallel, to provide energy storage and/or electric power to a system as a single integrated unit. An example of a battery pack would be an electric vehicle lithium-ion battery pack, which can consist of thousands of cylindrical lithium ion battery cells. A “battery cell” (or “cell”) as used herein describes an electrochemical cell that is capable of generating electrical energy from a chemical reaction. Some battery cells can be rechargeable by introducing a current through the cell. Battery cells come in different types, such as lead-acid, nickel cadmium, nickel hydrogen, nickel metal hydride, lithium ion, or sodium nickel chloride (a.k.a. “zebra”), based on the chemical reaction used to generate the electric current. Because battery cells produce electricity based on a chemical reaction, the temperature of the cell can influence the efficiency at which the electricity is produced. Battery cells can also be fuel cells, such as hydrogen-oxide proton exchange membrane cells, phosphoric acid cells, or solid acid cells. Principles of the present disclosure may desirably be applied to a wide variety of battery cell types, and are not limited to a particular battery cell chemistry, size, or configuration. Each battery cell may comprise a positive terminal and a negative terminal. In an example embodiment, the positive and negative terminals are located in close proximity to each other. For example, the positive terminal and negative terminal may be located on the same end (i.e., an end proximal to an interconnect assembly) of a battery cell. In one example embodiment, the positive pole (positive electrode or positive terminal) may be located at the top center of a cylindrical battery cell, and the negative pole (negative electrode or negative terminal) may be located on the top outside edge of the cell (also known as the “shoulder” of the cell) or outside “can” of the cell. Moreover, any suitable arrangement of the positive and negative terminals at or near the proximal end of the battery cell is contemplated in this disclosure. With reference now toFIG.1, in various example embodiments, an electrical system100comprises a battery pack110and an interconnect assembly120. Interconnect assembly120may be located primarily on one side of, and is electrically coupled to, battery pack110. In some exemplary embodiments, interconnect assembly120may also be configured to structurally support and/or retain the cells of battery pack110in-place, relative to interconnect assembly120and/or relative to one another. Electrical system100may further comprise and/or be coupled to a load190. Load190may, for example, be an electric motor or other electric components in a vehicle. Moreover, load190can be any suitable electric component. Interconnect assembly120may be selectively electrically coupled to load190via a power connector135that is configured to pass power from battery pack110to load190(or vice versa). Moreover, it will be appreciated that, in various exemplary embodiments, in electrical system100, any suitable number of battery packs110and corresponding interconnect assemblies120may be utilized in serial and/or parallel arrangements, for example in order to achieve a desired level of energy storage, continuous current supplied at a particular voltage, and/or the like. Accordingly, electrical system100may be configured with various bus bars, terminals, and/or the like, configured to route electrical power from and/or to one or more battery packs110via corresponding interconnect assemblies120. Electrical system100may further comprise and/or be coupled to a power source170. Power source170may comprise, for example, a plug-in charger for a vehicle, a fuel cell, or any other suitable source of power. In an example embodiment, power source170is connected to interconnect assembly120and/or load190via power connector135. Interconnect assembly120may further be configured to pass power from power source170to the cells in battery pack110. It is noted that in various embodiments, an electric motor may be used as a brake and thus may generate power to charge the cells of battery pack110. The foregoing are only example configurations, and interconnect assembly120may be electrically connected to loads and/or sources of power in any suitable manner and using any suitable switching, connecting, and control devices. Electrical system100may further comprise (and/or be coupled to) a battery management system (“BMS”)140. Interconnect assembly120may be in signal communication with BMS140. BMS140may be configured to control, manage, monitor, and/or otherwise govern operation and behavior of battery pack110, such as controlling the charging, discharging, balancing, and so forth for the cells in battery pack110. Moreover, BMS140may control any suitable aspects of the charging, storing, and discharging of battery pack110and the use of power in electrical system100. BMS140may be integrated with interconnect assembly120; alternatively, BMS140may be coupled to interconnect assembly120via a connector cable or other suitable electrical connection. In an example embodiment, interconnect assembly120comprises a first layer121and a second layer122. In other example embodiments, interconnect assembly120further comprises an optional sensing layer123. In accordance with various example embodiments, first layer121, second layer122, and/or sensing layer123(described in more detail below) are primarily located in planes that are parallel to each other and at least partially over-lapping perpendicular to each other. As described in further detail herein, first layer121and second layer122are connected to the terminals of various cells of battery pack110. Thus, the first layer121and second layer122are configured to be electrically connected to terminals of cells of battery pack110and to conduct current from and to these cells. In an example embodiment, first layer121may comprise a first current carrying plate151and a first interconnect plate152. First current carrying plate151is oriented parallel to, and at least partially overlapping first interconnect plate152. First current carrying plate151is electrically connected to first interconnect plate152. For example, these two plates151,152may be connected along at least a portion of their overlapping surfaces. In one example embodiment, the overlap is coincident such that the two plates151,152touch along their overlapping, facing surfaces, and are thus electrically connected along the bulk of their overlapping, facing surfaces. First current carrying plate151and first interconnect plate152may be coupled together via any suitable method, for example cladding, welding, soldering, and/or the like. Similarly, second layer122may comprise a second current carrying plate161and a second interconnect plate162that are oriented and in electrical contact as described with respect to first layer121. In an example embodiment, first and second current carrying plates151,161, are generally thicker than first and second interconnect plates152,162, respectively. For example, first and second current carrying plates151,161, may be thick enough to carry a maximum desired current associated with operation of battery pack110without excessive resistive losses, overheating, or constraining the power input or output of the cells comprising battery pack110. However, it will be appreciated that first and second current carrying plates151,161, may also be thinner than (or configured with a similar thickness to) first and second interconnect plates152,162. Moreover, in some embodiments, one or more of first and second current carrying plates151,161, or first and second interconnect plates152,162are formed of multiple layers of material. Additionally, in some exemplary embodiments, first current carrying plate151and first interconnect plate152may comprise a single, monolithic plate; a similar structure may be utilized for second current carrying plate161and second interconnect plate162. It will be appreciated that other example embodiments, as described in additional detail below, may be configured absent “thinner” interconnect plates, but instead comprise one or more current carrying plates having thin tabs. In some exemplary embodiments, first and second current carrying plates151,161, are configured with a thickness of between about 0.3 millimeters (mm) and about 2.0 mm. Moreover, any suitable thicknesses may be used for the current carrying plates151,161, to carry a desired amount of current without generating excess heat. Moreover, first and second interconnect plates152,162, may be configured with a thickness of between about 0.05 (mm) and about 0.3 mm. Moreover, any suitable thicknesses may be used, for example in order to provide a desired current carrying capacity, ease of interconnection, to facilitate connection of the tabs to the cell (e.g., laser welding, spot welding, wire bonding, use of conductive adhesives) and/or the like. In an example embodiment, first and second interconnect plates152,162, may be configured to be thin enough to enable typical electrical connections (i.e., between the battery cells of battery pack110and the first and second interconnect plates152,162). For example, first and second interconnect plates152,162may be thin enough to enable electrical connections made by brazing, cladding, soldering, spot welding, ultrasonic welding, laser welding, wire bonding, use of conductive adhesives, and/or the like. In an example embodiment, first current carrying plate151is thicker than first interconnect plate152. Similarly, in this exemplary embodiment, second current carrying plate161is thicker than the second interconnect plate162. In other exemplary embodiments, plate thicknesses may vary as noted above. In various exemplary embodiments, and as discussed further below in connection withFIGS.10D, and11A-11B, first interconnect plate152may be integrally formed with first current carrying plate151. In other exemplary embodiments, first interconnect plate152is formed apart from first current carrying plate151and then coupled thereto. First current carrying plate151and/or first interconnect plate152may comprise any suitable electrically conductive material, for example copper, aluminum, nickel, and/or the like, or combinations and/or alloys thereof. In some exemplary embodiments, first current carrying plate151comprises aluminum, and first interconnect plate152comprises nickel. In this manner, first interconnect plate152may comprise a material configured to facilitate electrical connections with cells in battery pack110, while first current carrying plate151comprises a material configured to facilitate bulk transmission of electrical current with minimal losses. Similar approaches may be utilized for plates161,162. Moreover, in an example embodiment, the thickness of the first and second current carrying plates151,161is not dependent on the thickness limitations associated with connecting the interconnect layers to the cells of battery pack110, whereas if the first layer121were not made of two layers (i.e., plates151,152, for example), and instead of just one layer, this may not be true. Stated another way, the first and second layers121,122are configured so that the total current capacity for each of these layers is not dependent on the thickness (and/or current-carrying capacity) of the tabs, which is associated with method of connecting the tabs to the battery terminals. In addition, in an example embodiment, the first layer121and second layer122each comprise two layers of selected thickness to reduce or eliminate any need for cooling due to heat generated in the first and/or second layers121,122due to resistive heating effects in these layers. Moreover, electrical system100may comprise any other suitable components configured to support, guide, modify, and/or otherwise manage and/or control operation of electrical system100and/or components thereof. Interconnect assembly120may be utilized to make a solid electrical contact with the cells of battery pack110, to provide flexibility in combining the cells in various parallel/series configurations, to hold the battery cells in place, to sense characteristics of battery pack110, and/or the like. FIG.2Aillustrates an isometric view of an interconnect assembly220(with the overmolding not shown) and battery pack210. Battery pack210comprises a plurality of cells211. For example, the illustrated battery pack210comprises 300 cells211, though battery pack210may comprise any suitable number of cells211. In an example embodiment, each cell211is a cylindrical cell with terminals located at the proximal end of cell211(i.e., the end proximate interconnect assembly220). Cell211can be any other suitable shape, as desired. Interconnect assembly220may further comprise a positive tab228and a negative tab229. These power tabs electrically connect interconnect assembly220to the power connector135, the load190, and/or the power source170. FIG.2Billustrates an isometric exploded view of an exemplary interconnect assembly220and battery pack210. In this exploded view, first layer121is illustrated as an ‘upper layer’ having an ‘upper thick’ first current carrying plate151and an ‘upper thin’ first interconnect plate152. Similarly, second layer122is illustrated as a ‘lower layer’ having a ‘lower thick’ second current carrying plate161and a ‘lower thin’ second interconnect plate162. As stated above, interconnect assembly220may further comprise a sensing layer123. In an example embodiment, sensing layer123comprises a lead frame. In another example embodiment, sensing layer123comprises a printed circuit board. In another example embodiment, sensing layer123comprises a flexible printed circuit board. Moreover, sensing layer123may comprise any structure suitable for running signal wires or traces124in at least partially a substantially planar manner to various locations on interconnect assembly220. Sensing layer123may comprise sensors, and/or be configured to connect to sensors for communicating sensed information (e.g., data) from sensors sensing current, voltage, temperature, and/or other useful parameters associated with the battery and/or operation of the same. Sensing layer123may, for example, carry signal from thermistors located near one or more cells211to a communications connector125. Similarly, sensing layer123may provide connections to first layer121and second layer122at various locations, for example to allow for measuring the voltage of a group (or groups) of parallel cells211in battery pack210, cell211balancing, and/or the like. The communications connector125may be configured to facilitate communication with BMS140and/or other components of electrical system100. Sensing layer123may be disposed generally parallel to first layer121and second layer122. Moreover, sensing layer123(or portions thereof) may be located above, between, and/or below first layer121and second layer122. FIGS.2C,2D,2E, and2Frespectively illustrate an isometric view of the first current carrying plate151, first interconnect plate152, second current carrying plate161, and second interconnect plate162. InFIG.2C, first current carrying plate151comprises more than one current carrying plate segment. First current carrying plate151may comprise any suitable number of current carrying plate segments. For example, first current carrying plate151may comprise six current carrying plate segments151A,151B,151C,151D,151E,151F. First current carrying plate151segments may be structurally separate components of first current carrying plate151. As described in greater detail herein, first current carrying plate151segments may be electrically connected in series, parallel, and/or interwoven with segments of second current carrying plate161. In an example embodiment, current carrying plate segment151A has a negative connection point229and current carrying plate segment151F has a positive connection point228. These connection points may be configured as tabs or other structures suitable for connecting interconnect assembly120to other electrical components of electrical system100. When interconnect assembly120is coupled to battery pack110, first current carrying plate segment151A has the greatest negative potential, and current carrying plate segment151F has the greatest positive potential. First current carrying plate151is configured to be in electrical communication with first interconnect plate152, for transmitting power between cells211and the connection points228/229. First current carrying plate151comprises a plurality of windows. The windows may be free of obstruction permitting, through the windows, access to objects below the windows of the first current carrying plate151. InFIG.2D, first interconnect plate152comprises more than one interconnect plate segment. First interconnect plate152may comprise any suitable number of interconnect plate segments. For example, first interconnect plate152may comprise six interconnect plate segments152A,152B,152C,152D,152E,152F. The interconnect plate segments may be structurally separate components of first interconnect plate152. First interconnect plate152segments may be electrically connected to corresponding current carrying plate segments of first current carrying plate151. First interconnect plate152further comprises tabs that are bent, angled, and/or oriented to form leads suitable for connecting to either the positive or negative terminal of cells211. First interconnect plate152comprises a plurality of windows. A first subset of those windows may be free of obstruction permitting access to objects below the windows of the first interconnect plate152through the windows. A second subset of those windows may comprise the tabs. In an example embodiment, the plurality of windows comprise pairs of windows, where each pair corresponds to a cell211. The selection of which window of the pair of windows comprises the tab will determine whether the tab is connected to the positive terminal or the negative terminal of the cell211. In an example embodiment, for any one of the first interconnect plate152segments, all of the tabs contact the same polarity terminal of cell211. However, in other example embodiments, a single interconnect plate152segment may have a first group of tabs in contact with negative terminals and a second group of tabs in contact with positive terminals of cells211. In other exemplary embodiments, the plurality of windows include a single window per cell211; in these exemplary embodiments, each window includes both a portion free of obstruction permitting access to objects below the window, as well as a tab or tabs for connecting to a cell211. With reference now toFIG.2E, in various exemplary embodiments second current carrying plate161comprises more than one current carrying plate segment. Second current carrying plate161may comprise any suitable number of current carrying plate segments. For example, second current carrying plate161may comprise five current carrying plate segments161A,161B,161C,161D,161E. The current carrying plate segments may be structurally separate components of second current carrying plate161. As described in greater detail herein, the current carrying plate segments comprising second current carrying plate161may be electrically connected in series, parallel, interleaved with, and/or combinations of the same, with the current carrying plate segments comprising first current carrying plate151. Second current carrying plate161is configured to be in electrical communication with second interconnect plate162, for transmitting power between the cells and the second current carrying plate161. The second current carrying plate161comprises a plurality of windows. The windows may be free of obstruction permitting access to objects below the windows of the second current carrying plate161through the windows, and permitting the tabs from the first interconnect plate152to pass through the second current carrying plate161to contact cells211. It is noted that in some instances, the current carrying plate segments of the second layer122overlap exactly with the current carrying plate segments of the first layer121. However, in other embodiments, a plate segment from the first layer121overlaps two or more plate segments from the second layer122, or vice versa. For example, current carrying plate segment161A overlaps portions of151A and151B, current carrying plate segment161B overlaps portions of151B and151C, current carrying plate segment161C overlaps portions of151C and151D, current carrying plate segment161D overlaps portions of151D and151E, and current carrying plate segment161E overlaps portions of151E and151F. With reference now toFIG.2F, second interconnect plate162comprises more than one interconnect plate segment. Second interconnect plate162may comprise any suitable number of interconnect plate segments. For example, second interconnect plate162may comprise five interconnect plate segments162A,162B,162C,162D,162E. The interconnect plate segments may be structurally separate components of second interconnect plate162. The interconnect plate segments may be electrically connected to corresponding current carrying plate segments of second current carrying plate161. The second interconnect plate162further comprises tabs that are bent to form leads suitable for connecting to either the positive or negative terminal of cell211. The second interconnect plate162comprises a plurality of windows. A first subset of those windows may be free of obstruction permitting access to objects below the windows of the second interconnect plate162through the windows. A second subset of those windows may comprise the tabs. In an example embodiment, the plurality of windows comprise pairs of windows, where each pair corresponds to a cell211. The selection of which window of the pair of windows comprises the tab will determine whether the tab is connected to the positive terminal or the negative terminal of the cell211. In an example embodiment, for any one of the interconnect plate segments, all of the tabs contact the same polarity terminal of cell211. However, in other example embodiments, a single interconnect plate segment may have a first group of tabs in contact with negative terminals and a second group of tabs in contact with positive terminals of cell211. Moreover, for each pair of windows in first interconnect plate152, there is an opposite pair of windows in second interconnect plate162, such that each pair only has one window with a tab, the tabs locations are opposite each other to not interfere with each other, and one of the two plates is connected by such tab to the positive terminal of a cell and the other of the two plates is connected by its tab to the negative terminal. With momentary reference toFIG.3H, it will be appreciated that, while windows are discussed hereinabove as being in “pairs”, configurations where a single window covers the area of a “pair” of windows may likewise be utilized; moreover, combinations of paired windows and single windows may also be utilized. In an example embodiment, there are two power connections to interconnect assembly120, a positive connection and a negative connection. The two connections can both be located on a first end of the interconnect assembly, for example as shown inFIGS.2C and4B. In other embodiments, a positive connection is located on one end and a negative connection is located on the other end, for example in interconnect assembly120as shown inFIG.4C(individual layers of which are shown inFIGS.4D,4E,4F, and4G). In an example embodiment, the positive and negative connections can both be on the first current carrying plate151or the second current carrying plate161. However, in other embodiments, the positive connection can be on one of the two current carrying layers and the negative connection can be on the other. Moreover, additional power and/or voltage sensing connections may be provided within interconnect assembly120, for example connections configured to allow monitoring, charging, discharging, and so forth for a subset of cells211in battery back110. Within one ‘stack’ of windows, the windows in the first and second layers121,122may all be approximately the same size, though variation may be possible if the tabs can pass through and access to make the connections. The open windows in the lower layers are configured to permit the tab from the upper thin layer to extend through the lower layers to the battery below the lower layer. The open windows are configured to permit access from above, through the upper layer and the lower layer to connect/couple the tabs in the upper thin layer and lower thin layer to the respective cell terminals. With reference now toFIG.6, in connection with various exemplary embodiments,FIG.6illustrates a cut-away side view of a portion of interconnect assembly120and battery pack110, with a thermistor612located between two adjacent cells211. In an example embodiment, interconnect assembly120comprises sensing layer123and trace124located generally above the first and second layers121,122. A thermistor612is located in proximity to a first cell211of battery pack110. In an example embodiment, the thermistor612is connected to the trace124through a thermistor lead624. In an example embodiment, the thermistor lead624passes through a via to connect with trace124, however, any suitable routing or method (such as rivets, pins, tabs that can be soldered or welded in place, etc.) may be used to connect thermistor612with trace124. In another example embodiment, thermistor612is embedded, or partially embedded in an overmold (discussed further herein). In this example embodiment, the thermistor612is integral with the interconnect assembly120. Interconnect assembly120may comprise any suitable number of thermistor(s)612. In this example embodiment, placing interconnect assembly120over battery pack110simultaneously accurately positions the thermistor(s)612to sense the temperatures of the cells211. Thus, this device and method of assembly avoids separate manual processes for attaching sensors to or near battery cells. With reference now toFIG.3A, in accordance with various example embodiments, interconnect assembly120further comprises an overmold material. The overmold material can comprise a plastic, injection molded plastic, a ceramic material, a polymer, and/or the like. In various embodiments, the polymer may comprise a liquid crystal polymer (LCP), polyphenylene pulfide (PPS), polyether ether ketone (PEEK), a thermoplastic polymer, a thermoset polymer, and/or the like. Thus, the overmold material may comprise any suitable material for casting, injection molding, or otherwise overmolding the leadframe(s) as described herein. Furthermore, overmold material380may comprise any material that can electrically and/or thermally insulate first layer121, second layer122and/or sensing layer123from each other, that can provide structural support for the components (e.g.,121,122,123, and so forth) of interconnect assembly120, and/or that can structurally hold and position cells211of battery pack110. FIGS.3A and3Billustrate cross-sectional, partial, isometric views of the interconnect assembly120and the battery pack110, with a close up of the positive tab163, in accordance with exemplary embodiments. In an example embodiment, the overmold material380covers the top surface of the interconnect assembly120, is located between the first layer121and second layer122, and/or is located under the second layer122, with windows and/or apertures in the overmold material380that are aligned with the windows in the first layer121, second layer122, and/or sensing layer123. The interconnect assembly120may further comprise (and/or be coupled to) retaining structure381. In an example embodiment, retaining structure381is located below the second layer122. Stated another way, retaining structure381is located on the side of second layer122opposite the first layer121. In an example embodiment, retaining structure381is made of the overmold material380. Moreover, retaining structure381may comprise any suitable electrically insulating material suitable for holding and/or supporting cells211in a desired position. The retaining structure381may be configured as a ring like structure, as circles in an otherwise continuous structure, or the like. In other embodiments, the retaining structure381may comprise posts (not shown). The retaining structure381may be configured to contact the cells211, for example on the side and/or top of the cell211, or near the top of the cell211. The contact can be continuous or discontinuous. The contact may prevent or restrain relative movement of the top portion of the cells211relative to each other and/or relative to interconnect assembly120. The contact may further assist with alignment of the tabs153,163to the cells211. The contact may further create a seal around the top of cell211to prevent gases or fluids from being communicated between a space390between the cells211and the environment on the other side of interconnect assembly120. Moreover, the retaining structure381may comprise any suitable structure for holding cells211in place. Additionally, in these exemplary embodiments, interconnect assembly120may function to at least partially retain, secure, and/or align battery cells211with respect to one another, reducing and/or eliminating the need for other cell211retention and/or alignment components. In an example embodiment, a positive tab163extends from second interconnect plate162and is aligned with the top center212of cell211, which is generally the positive terminal in a typical cylindrical battery. Similarly, a negative tab153extends from the first interconnect plate152and is aligned with the top edge213of cell211, which is generally the negative terminal in a typical cylindrical battery. The tabs are each bent, curved, and/or angled to reach down through the window to the proximal end of the cell211. FIG.3Billustrates that overmold material380surrounds layers121,122and insulates the layers, including on the inside of the windows. It will be appreciated that, whileFIGS.3A and3Bshow windows configured in pairs, with momentary reference toFIG.3H, single-window configurations may also be utilized. FIGS.3C and3Dillustrate a cross-sectional, partial, isometric views of the interconnect assembly120and the battery pack110with a close up of a negative tab153, in accordance with exemplary embodiments. With momentary reference toFIGS.3A through3I, it will be appreciated that a negative tab153and positive tab163may be coupled to a corresponding cell211via any suitable method and/or materials, for example welding (laser, ultrasonic, etc.) brazing, soldering, and/or the like. FIG.3Eillustrates a cross-sectional, partial, isometric view of interconnect assembly120showing a repeating pattern of positive and negative tabs153,163, in accordance with exemplary embodiments. Positive tab163is located proximate negative tab153. For example, the window associated with positive tab163may be side by side with the window associated with negative tab153. In one example embodiment, first layer121is connected to the positive terminal of cell211and second layer122is connected to the negative terminal of cell211. However, in another example embodiment, first layer121is connected to the negative terminal of cell211and second layer122is connected to the positive terminal of cell211. Moreover, in an example embodiment, all of the connections to cells for a particular plate segment are the same, such that a plate segment may be considered a “positive” plate segment or a “negative” plate segment. However, in various exemplary embodiments, some of the connections to cells211on a particular plate segment are positive and other connections are negative. For example, with momentary reference toFIG.4A, in various exemplary embodiments a plate segment is configured with a positive connection to a selected number of cells211, and a negative connection to an identical number of other cells211. In this manner, cells211are configured to function as electrical routing paths between plate segments. FIG.3Fillustrates an exploded, partial, isometric view of a second current carrying plate162aligned with a second interconnect plate161. Alignment holes364,365(disposed in plates161,162, respectively) permit alignment and coupling of these and other components of interconnect assembly120. FIG.3Gillustrates a partial top view of interconnect assembly120, in accordance with exemplary embodiments. In this example embodiment, interconnect assembly120has been overmolded. Thus, interconnect assembly120forms a package that is convenient for mounting to battery pack110. FIG.3Hillustrates a partial top view of the interconnect assembly120with cells211partially visible through windows and/or apertures in interconnect assembly120, in accordance with exemplary embodiments. In this view, the positive tab163and negative tab153and portions of the top of cells211are visible through windows in the overmold material and first and second layers. In an example embodiment, interconnect assembly120comprises an array of pairs of windows388, with each pair388comprising a positive window and a negative window. Associated with the positive window is a positive tab163connected (or for connecting) to the positive terminal at the proximal end of the cell211near the center of the battery. Associated with the negative window is a negative tab153connected (or for connecting) to the negative terminal at the proximal end of the cell211near the edge of the battery. Each window has sufficient size to facilitate electrically connecting the corresponding tab(s) to the cell211. As discussed elsewhere, in place of pairs388, a single common window389may be utilized, as desired. FIG.3Iillustrates a partial bottom view of interconnect assembly120, in accordance with exemplary embodiments. The illustration shows certain cells211removed, so the corresponding positive tab163and negative tab153, and associated windows, are visible through the overmold material380. In this example embodiment, the retaining structure381is in the shape of a plane of overmold material380configured with circular holes therethrough. The interconnect assembly120is configured with a plurality of apertures to accept portions of a plurality of cells211therein. The interconnect assembly120facilitates close packing of the plurality of cells211. The cells211may be disposed less than 1 mm from one another. A cell211in the plurality of battery cells has a first end and a second end distal from the first end, the first end and second end having a length therebetween. With reference now toFIG.4A, in various exemplary embodiments, interconnect assembly120is configured to create a desired combination of parallel and series arrangements for cells211in battery pack110. For example, a combination of interconnect assembly120and battery pack110may result in a “10s, 30p” arrangement (a serial arrangement of 10 groups, each group comprising 30 cells211in parallel). Moreover, any suitable arrangement may be implemented, for example “5s, 60p”, “20s, 20p”, “10s, 40p”, and/or the like, as desired, in order to achieve desired current and voltage levels in electrical system100. For example, with momentary reference toFIGS.2C through2F and4B, in one exemplary embodiment, when an exemplary battery pack110comprising 300 cells211is coupled to interconnect assembly120, an electrical path traverses the following components in order: negative terminal229→151A→161A→151B→161B→151C→161C→151D→161D→151E→161E→151F→positive terminal228, in order to form a “10s, 30p” arrangement. However, any suitable routing and/or wiring path may be utilized, as desired. Moreover, it will be appreciated that interconnect assembly120may be sized and/or scaled to any appropriate voltage, current, and/or size, for example by use of a suitable number of segments in first current carrying plate151and second current carrying plate161. In certain exemplary embodiments interconnect assembly120also serves as a lid to a vapor chamber within which cells211are at least partially located and/or disposed. In this example embodiment, interconnect assembly120is configured with various seals, retaining mechanisms, sealants, potting materials, and/or the like, so that interconnect assembly120may receive a portion of multiple cells211while preventing and/or reducing leakage and/or evaporation of a working fluid from within a vapor chamber. For example, in one exemplary embodiment interconnect assembly120comprises a rigid primary material overmolded with an elastomer, in order to provide a compressible seal at the interface where each cell211is inserted into interconnect assembly120. In other exemplary embodiments, o-rings or other mechanical sealing approaches may be utilized. Moreover, a suitable potting material may be utilized in order to seal the joints between cells211and interconnect assembly120. For example, in various exemplary embodiments the joints between cells211and interconnect assembly120may be sealed via a flexible or semi-flexible potting material, adhesive, sealant, epoxy, or hot melt; the sealing material may be silicone, urethane, polyurethane, polyester, or polyamide based and/or may comprise any other suitable sealing and/or adhesive materials or compounds. In some exemplary embodiments, retaining structure381has any suitable shape, for example, a ring structure, with contiguous surface contact or intermittent surface contact with cells211. Moreover, shapes other than circular can be used, especially if cells211are not cylindrical (for example, rectangular cells). Contact rings can be formed from straight wall segments, or be smoothly circular with no corners. In various exemplary embodiments, retaining structure381is configured as a plurality of post-like structures. Posts are formed from retaining structure381in a three-sided post shape. Posts can include indents or other shapes to fit securely to the shape of cells211. However, any suitable shape for posts may be utilized. In an example embodiment, the post is made of the overmold material380. Moreover, any suitable number of posts may be utilized as retaining structure381. For example, each cell211may be in contact with at least one post, or at least two posts, or at least three posts, or at least four posts. In some exemplary embodiments, the posts are configured with a length of about 5 mm. Additionally, certain posts (and/or all posts) may extend from an inner surface of interconnect assembly120all the way to a corresponding inner surface on the opposite side near the distal end of cell211. The posts may be sized and/or configured to fit entirely into spaces that exist between cells211when cells211are packed as close as geometrically possible. The posts may extend from interconnect assembly120in a direction generally parallel to the cylindrical axis of the cells211, or along the length of a particular cell211. In an exemplary embodiment, a method for interconnecting a battery pack comprising a plurality of cells comprises placing the interconnect assembly over the cells, and connecting the tabs of the interconnect assembly to the terminals of the cells. In some embodiments, a retaining structure is coupled to the cells in order to align them prior to coupling the interconnect assembly. The interconnect assembly may be located and/or positioned with respect to the retaining structure in order to align for proper connection with the cells. FIGS.5A and5Billustrate various fuse designs for tabs, in accordance with example embodiments. In a first example embodiment, a tab163is configured with a hole164in the tab. In another example embodiment, a tab153has a narrow neck154(for example, a trench-like structure) in the tab. The hole164or the narrow neck154in the tab may be located anywhere that an open on the tab would isolate the connected cell211from the other cells and the rest of the electrical circuit of interconnect assembly120. For example, the hole164or neck154may be located between the point of connection to the cell211and the main body of the interconnect plate152,162. The hole164has a diameter, and the narrow neck154has a portion that is narrower than the rest of the tab. The dimensions of the diameter or thickness are designed such that the tab functions as a fuse by reducing the total cross sectional area to the point that a particular amperage for a long enough time will melt or vaporize the tab at that location. Thus, if there is a short or other high amperage situation with respect to that cell211, it will be fused out of the circuit and protect the rest of battery pack110and electrical system100. It will be appreciated that other suitable structures and methods may be used to create a fuse in the tabs. With reference now toFIGS.7A,7B, and7C, in various exemplary embodiments, portions of interconnect assembly120may be configured to be compatible with and/or optimized for creation via “pick and place” component assembly systems, for example surface mount technology placement robots commonly utilized in the electronics assembly industry. For example, a portion of layer121and/or layer122may comprise a set of tab assemblies173. Each tab assembly173is configured with a plurality of plate connection points174, which may comprise flanges, extensions, and/or the like. Moreover, tab assembly173is configured with a cell tab175. Cell tab175is configured to couple to a cell211(for example, to form a negative tab153or a positive tab163). Tab assembly173may also be configured with a frangible link176, which may be severed as desired, for example when cell tab175is bent, pressed, and/or otherwise brought into contact with a cell211, when tab assembly173is placed into contact with a first current carrying plate151(or second current carrying plate161), or the like. In various exemplary embodiments, a plurality of tab assemblies173may be coupled to a current carrying plate (for example first current carrying plate151), in lieu of (and/or to serve a similar purpose to) an interconnect plate (for example, first interconnect plate152). For example, a tab assembly173may be placed in a window of a window pair388in order to facilitate a connection with a corresponding cell211. Moreover, any suitable number of tab assemblies173may be coupled to a particular current carrying plate in any suitable configuration, as desired, in order to facilitate interconnection with a desired number and configuration of cells211. With reference now toFIG.7C, in various exemplary embodiments a first or second current carrying plate151,161may be configured with a series of solder pads184. Solder pads184are configured to corresponding to plate connection points174on tab assemblies173. Solder pads184may be formed via any suitable process, for example stencil printing in connection with a mask. Once solder pads184are formed, tab assemblies173are picked and placed into contact with solder pads184. The resulting assembly is then heated to reflow the solder and thereby couple tab assemblies173to first and/or second current carrying plate151,161. Turning now toFIGS.8A and8B, in various exemplary embodiments interconnect assembly120comprises (and/or is configured to couple to) one or more socket bus bars191. For example, a first socket bus bar191may function as (and/or take the place of) a positive tab228, and a second socket bus bar191may function as (and/or take the place of) a negative tab229. However, socket bus bars191may be located in any suitable location within interconnect assembly120. Socket bus bar191comprises a material configured to effectively conduct electrical current, and is configured with one or more holes192. Holes192are configured to act as receptacles for electrical connections, for example as “female” connector portions corresponding to “male” connector portions (e.g., “banana” style connectors and/or the like). In this manner, interconnect assembly120may be electrically connected to other components of electrical system100(and/or to external components) without the use of fasteners, enabling “plug and play” operation. With reference now toFIG.9, in various exemplary embodiments portions of interconnect assembly120, for example first layer121and/or second layer122, may be implemented via a printed circuit board (PCB) assembly and/or components or materials thereof. For example, in an interconnect assembly120, a first current carrying layer151may comprise a metal layer of a metal-backed and/or metal-core PCB. Stated another way, in interconnect assembly120, metal PCB layers that, in other applications, were typically utilized for structural and/or thermal purposes (rather than electrical connections), may be utilized to carry current between cells211. Other PCB layers, for example FR-4 glass reinforced epoxy material, may be used to form portions of first layer121and/or second layer122and/or selectively insulate them from one another. In this exemplary interconnect assembly120, second current carrying layer161may comprise a different metal layer of the same PCB incorporating first current carrying layer151; alternatively, second current carrying layer161may comprise a metal layer of a second PCB. Moreover, sensing layer123may be embodied in the traces of the various PCBs. First layer121and/or second layer122may be coupled together, coated with overmold material380, coupled to a series of tab assemblies173, and/or the like, as suitable, in order to form interconnect assembly120. With reference now toFIGS.10A through17F, in various exemplary embodiments, an interconnect assembly120may be configured with various conductive plates128to form conductive layers121,122; conductive plates128may be sized and configured such that a conductive plate128may serve a similar function to (and/or be utilized in lieu of) both a current carrying plate151and an interconnect plate152as seen in other exemplary embodiments above. Stated another way, in some exemplary embodiments interconnect assembly120, rather than being configured with some plates whose primary function is connection with cells211and other plates whose primary function is to pass current between cells211, is instead configured with plates that serve to provide connective functions and current carrying functions simultaneously. Moreover, interconnect assembly120may be configured with conductive plates128forming one or more conductive layers121,122in a manner which distributes, splits, allocates, or otherwise at least partially divides current from cells211within battery pack110among the conductive plates128, thus reducing heating and/or resistive losses associated with a particular conductive plate128and/or permitting the use of lower cost and/or higher resistivity materials. Additionally, interconnect assembly120may be configured with features which facilitate automated handling and/or processing of portions thereof, for example automated stamping, stacking, welding, and/or other coupling, linking, or joining of conductive plates128. Moreover, interconnect assembly120may be configured with various insulating layers and/or other components such that overmolding of interconnect assembly120may be optional, thus reducing the volume and/or weight of interconnect assembly120. Additionally, interconnect assembly120may be configured to “float” atop a corresponding battery pack110(in other words, interconnect assembly120may be coupled to battery pack110only at the anodes and cathodes of cells211within battery pack110, rather than also being coupled to mechanical portions of battery pack110or an enclosure thereof); in this manner, interconnect assembly120may be made more vibration and/or shock resistant, thus improving the longevity of electrical connections between interconnect assembly120and cells211. Furthermore, in various embodiments, voltage may be sensed directly from the conductive layers without a separate sensing layer. However, in other embodiments, a discrete sensing layer can be utilized. With reference now toFIGS.10A and10B, in various exemplary embodiments an interconnect assembly120comprises a number of conductive layers, for example a first conductive layer121and a second conductive layer122. Moreover, any suitable number of conductive layers may be utilized, for example three conductive layers, four conductive layers, and so forth. In these exemplary embodiments, interconnect assembly120and/or layers thereof are not configured with a “thin” layer (i.e., interconnect plate152) and a “thick layer” (i.e., current carrying plate151), as described in connection with various prior example embodiments, but rather with components that provide connective and current carrying capabilities simultaneously. An insulating layer126may be disposed between conductive layer121and conductive layer122. Additionally, an insulating layer126may be disposed atop conductive layer121and/or below conductive layer122(or vice versa); stated generally, an insulating layer or layers126may be disposed at any location in interconnect assembly120wherein electrical insulating properties are desired. The various insulating layers126are shaped, positioned, and/or otherwise configured to reduce and/or prevent undesired electrical connections and/or shorts in interconnect assembly120. In various exemplary embodiments, insulating layer126comprises a dielectric material such as plastic, polypropylene, polyimide, polycarbonate, glass-reinforced epoxy laminate (e.g., FR-4), and any other electrically insulating material. Insulating layer126may comprise a single layer structure; alternatively, insulating layer126may comprise multiple layers of a common material or differing materials. Turning toFIGS.10C and10D, in various exemplary embodiments interconnect assembly120is configured with tabs153,163for coupling to cells211. A particular tab163is positioned and shaped to be coupled to the cathode of a cell211(i.e., the positive terminal); another tab153is positioned and shaped to be coupled to the anode of that cell211(i.e., the negative terminal). In some exemplary embodiments, with reference toFIGS.11C,11D, and11E, tabs153,163may be initially formed in a conductive plate128via the same process utilized to form the bulk of conductive plate128, for example by die stamping, laser cutting, waterjet cutting, plasma cutting, electrical discharge machining, and/or the like. In various exemplary embodiments, conductive plate128comprises a planar material, and thus tabs153,163, as initially formed, may be co-planar with the rest of conductive plate128(for example, as seen inFIGS.11C and11D). Tabs153,163may be bent, stretched, stamped, pressed, and/or otherwise formed or configured to extend at least partially out of, away from, or below the main body of interconnect assembly120; in this manner, tabs153,163may be extended for easier coupling to cells211, for example via spot welding or other suitable process. This deformation and/or extension of tabs153,163at least partially out of the plane of the remainder of conductive plate128may occur at the same or similar time as the initial formation of conductive plate128; alternatively, it may occur in a later processing step. It will be appreciated that, by extending tabs153,163, space is created between conductive plate128and cells211, allowing electrically insulating, thermally insulating, and/or motion damping materials to be placed therebetween. In some exemplary embodiments, tabs153,163are stamped, pressed, bent, and/or otherwise processed to extend away from the main body of conductive plate128. Via this or any other suitable manufacturing process, tabs153,163may be increased in area and/or made somewhat thinner as compared to the thickness of the main body of conductive plate128(for example, as illustrated inFIG.10D). Moreover, tabs153,163may be trimmed, cut, or otherwise further shaped or formed after bending, in order to obtain a desired size and/or shape of tabs153,163. A view of tabs153,163after processing can be seen inFIG.11EandFIG.10D, showing the post-processing size of tabs153,163as well as deformation at least partially out of the plane occupied by the main body of conductive plate128. In one example embodiment, the tab is locally formed down to about 0.5 mm while the main body of conductive plate128is about 1.0 mm thick. The thin tab can be welded using any suitable method (e.g., laser) while still maintaining the same current carrying thickness required for the application. In various exemplary embodiments, conductive plate128comprises one or more of aluminum, nickel, copper, or any other suitable conductive alloy. In an example embodiment, tabs153,163, after deformation, have a thickness of about half of the thickness of conductive plate128. However, any suitable thicknesses of the conductive plate and tabs may be used. With reference now toFIGS.10E through10H, in various exemplary embodiments conductive layer121and conductive layer122are each comprised of a set of conductive plates128having windows127therein. Windows127are configured with corresponding shapes such that when conductive layer121and conductive layer122are disposed atop one another, windows127partially and/or fully align to form a common path (for example a vertical path, i.e., a path generally perpendicular to the plane of interconnect assembly120) through interconnect assembly120. A window127may have a tab153and/or163extending thereinto; moreover, a window127may be configured absent any tab153or163and thus be “empty”. In this manner, in interconnect assembly120tabs153,163may extend without obstruction to be coupled to corresponding cells211. Turning now toFIG.10I, in various exemplary embodiments conductive layer121and/or conductive layer122comprises one or more conductive plates128. A conductive plate128may be configured with a plurality of windows127therein, including windows127configured with either tab153or tab163. Additionally, conductive plate128may be configured with one or more tabs153on one end of conductive plate128, and/or configured with one or more tabs163on an opposing end of conductive plate128; in this manner, multiple conductive plates128may be placed adjacent to one another while preserving a desired pattern of windows127, tabs153, and tabs163. In these configurations, it will be appreciated that gaps or spaces between adjacent conductive plates128may serve the function of windows127; stated another way, conductive plates128may be shaped such that, when two conductive plates128are brought adjacent to one another, voids or spaces similar in size and/or shape to windows127are left unobstructed and tabs153,163extend into the window-like spaces. With reference now toFIG.10J, in various exemplary embodiments, in interconnect assembly120, conductive layer121and conductive layer122may be separated by an insulating layer or layers126. Insulating layer126may extend the length and/or width of interconnect assembly120. Moreover, multiple insulating layers126or sections thereof may be utilized, as desired, in order to electrically isolate conductive layer121from conductive layer122. Additionally, insulating layer126may be configured with windows127such that when conductive layer121, insulating layer126, and conductive layer122are stacked atop one another, windows127partially and or fully align with one another to form pathways through interconnect assembly120. With reference again toFIGS.10C,10E through10H,11C through11E, and11G, in various exemplary embodiments windows127are configured as “vision windows” that enable automated handling, coupling, and/or processing of interconnect assembly120and/or components thereof, for example in connection with machine vision. In an example embodiment, the vision windows are shaped to maximize the amount of conductive material present in conductive plate128and thus minimize resistive heating in the conductive plate128, while also providing proper vision capabilities for use in connection with an attachment device (e.g., a laser welding device, a wire bonding apparatus, a dispensing apparatus for conductive adhesive, and/or the like). For example, in various exemplary embodiments, in interconnect assembly120, windows127may be configured in two shapes, a first shape for windows127associated with positive tabs163, and a second shape for windows127associated with negative tabs153. In another example embodiment, a single shape for a window127may be utilized for both positive and negative tabs. In an example embodiment, when interconnect assembly120is aligned with a battery pack110comprising cells211, positive tabs163are laser welded to the positive terminals (e.g. the cathodes of cells211) and negative tabs153are laser welded to the negative terminals (e.g., the anodes of cells211), the anodes and cathodes both located on a common end of each cell211. In an example embodiment, the positive terminal of each cell211is located at the center top portion of the cell211, and the negative terminal of the cell211is located near the top shoulder of the cell211. Although various embodiments are described herein as utilizing laser welding, it will be appreciated that any suitable coupling technique may be used. In an example embodiment, tabs153,163are spot welded to the respective terminals of the cell. During integration of interconnect assembly120with battery pack110, a laser welder may, in an example embodiment, be located in a position above the battery pack110and the interconnect assembly120to provide a vertical or approximately vertical laser to generate the welds. Any suitable laser welder may be used to generate the spot welds, for example gas lasers, solid state lasers, fiber type lasers, or any other suitable laser. In connection with the laser welder or other coupling apparatus, a machine vision system may facilitate alignment of the laser welding beam (or other coupling mechanism) based on the location of tabs153,163and/or cells211. In an example embodiment, the machine vision system is angled at about 20 degrees, or about 15 degrees, or about 10 degrees, or about 5 degrees from vertical (i.e., between about 5 degrees and about 20 degrees away from perpendicular to the plane of interconnect assembly120), although any suitable angle can be used. In an example embodiment, the machine vision system comprises a high resolution digital camera configured with a suitable imaging algorithm; however, any suitable machine vision system may be used. In accordance with an example embodiment, conductive plates128and/or insulating layers126in interconnect assembly120comprise windows127configured as vision windows. In an example embodiment, the vision windows127are shaped, sized, and/or otherwise configured to permit the machine vision system to view at least a portion of a particular individual cell211to improve alignment of the laser welding or other coupling associated therewith. Each vision window127may be configured, for example, to provide an opening through which the machine vision system can observe the location of at least a portion of a cell211and/or observe the location of a tab153and/or163to be welded thereto. In an example embodiment, the vision window127may be considered or described as a “cutout” in the various insulating and conductive layers comprising interconnect assembly120. In an example embodiment, each cutout is shaped to provide space around the positive tab163and the negative tab153, and to provide the machine vision system with a view of a portion of the cell211. In one example embodiment, window127possesses a geometry that is concentric with a cylindrical cell211and reveals at least a portion of the negative shoulder of the cell211for the machine vision system to “see.” In another example embodiment, the shape of window127includes “wings” that increase the amount of cell211shoulder visible to the machine vision system (for example, as illustrated inFIG.11E). In an example embodiment, each window127exposes or permits to be visible, through the interconnect assembly120, a portion of the shoulder and/or circumference of a corresponding cell211. In various exemplary embodiments, windows127may be configured such that the portion of the cell211visible to the machine vision system may comprise more than, for a particular cell211: ½ of the circumference, ⅜thof the circumference, 5/16thof the circumference, ¼thof the circumference, 3/16thof the circumference, ⅛thof the circumference, or 1/12thof the circumference. In an example embodiment, a window127exposes between 7% and 40% of the circumference of a cell211. Moreover, in another exemplary embodiment a window127exposes a distance along the circumference of cell211of at least one inch, or at least ½ inch. The portion of cell211visible through window127may comprise a first portion of the cell211circumference on a first side of a tab, for example tab163, and a second portion of the cell211circumference on a second side of the tab. In one example embodiment, at least 60 degrees of the outside diameter of the cell may be exposed. Moreover, the more of a cell211that is exposed through a vision window127, the more accurate and fast the machine vision system may be, but the more of cell211that is exposed, correspondingly, a reduced amount of material in conductive plate128is available for conducting current to and from cells211. In an example embodiment, windows127are configured with a first shape for windows127containing or associated with a positive tab163, and a second shape for windows127containing or associated with a negative tab153, as illustrated inFIGS.10E through10HandFIG.11E. In another example embodiment, not shown, the same shape may be used for a window127that contains or is associated with a positive tab163as for a window127that contains or is associated with a negative tab153. Moreover, shapes of windows127can vary from plate to plate and/or layer to layer in interconnect assembly120; alternatively, shapes of windows127can remain constant throughout interconnect assembly120. In an example embodiment, the shape, orientation, layout and dimensions of the windows127are configured to provide sufficient vision for proper coupling and to provide sufficient cross sectional area for current flow in the conductive material without excessive heating. In particular, in applications where windows127cannot be made smaller but the power loads arising in connection with operation of cells211are still generating too much heat, conductive plates128can be split into multiple layers. It will be appreciated that, although cells211are described herein primarily as cylindrical cells, the machine vision system, in connection with windows127, can expose a portion of any type of cell211to enable a machine vision assisted alignment of the laser welding of the positive and/or negative tabs to that cell211. With reference now toFIGS.12A,12B, and12C, in various exemplary embodiments a conductive plate128is configured to make contact with the anodes and/or cathodes of a particular parallel group of cells211in battery pack110. Moreover, a conductive plate128can also form a series connection by making contact with the opposite terminals on another (for example, adjacent) group of parallel cells211in battery pack110. Moreover, conductive plates128may be configured such that multiple conductive plates128may be stacked atop one another, allowing the connections associated with a particular parallel group of cells211to be split among the conductive plates128comprising the stack. Stated another way, in some exemplary embodiments a conductive plate128may be considered to be formed of multiple sub-plates in a stacked arrangement. In interconnect assembly120, in various exemplary embodiments, a conductive plate128may be configured for coupling to a group or groups of cells211. With reference now toFIG.12A, a particular conductive plate128is configured with tabs153for connecting to the positive terminals of a parallel group of cells211. As seen inFIG.12B, another conductive plate128is configured with tabs163for connecting to the negative terminals of a parallel group of cells211. Additionally, as seen inFIG.12C, yet another conductive plate128is configured with tabs163for connecting to the negative terminals of a first parallel group of cells211and with tabs153for connecting to the positive terminals of a second parallel group of cells211, thus making a series connection therebetween. In various exemplary embodiments, in interconnect assembly120, multiple conductive plates128may be utilized to link (i.e., make a series connection between) a first parallel group of cells211and a second parallel group of cells211. In this manner, current between the first parallel group of cells211and the second parallel group of cells211may be divided among the multiple conductive plates128. This arrangement can result in reduced resistive losses and consequent heat generation in conductive plates128. With reference now toFIG.13A, a particular conductive plate128-A is configured with tabs153and163present, collectively, in half of the windows127of conductive plate128-A, with the remaining windows127being empty. Tabs153and163may be arranged, for example, in stripes, bands, or other groupings within conductive plate128-A, separated by stripes or bands of empty windows127. In addition to stripes or bands, any suitable arrangements of tabs153and163may be utilized, for example a checkerboard or other interleaved pattern. Due to the presence of tabs153and163, conductive plate128-A makes a series connection between a first subset of a first parallel group of cells211and a first subset of a second parallel group of cells211. It will be appreciated that, while the number of tabs163and the number of tabs153is often equal, that is not required; a particular conductive plate128may have all tabs163, or all tabs153, or both tabs153and163but an unequal number thereof. Turning now toFIG.13B, a particular conductive plate128-B is configured with tabs153and163present, collectively, in half of the windows127of conductive plate128-B; however, where conductive plate128-A had empty windows127, conductive plate128-B has tabs153and/or163, and vice versa. Thus, conductive plate128-B makes a series connection between a second subset of the first parallel group of cells211and a second subset of the second parallel group of cells211. It will be appreciated that the first subset and the second subset are non-overlapping; stated another way, a particular battery cell211is a member of only one subset. In interconnect assembly120, conductive plate128-A and conductive plate128-B may be stacked atop one another, and the resulting double-layer stack provides a series connection between the entire first parallel group of cells211and the entire second parallel group of cells211(for example, similar to the single conductive plate illustrated inFIG.12C). In this configuration, conductive plate128-A and conductive plate128-B each carry approximately half of the electrical current passing in series between the first parallel group of cells211and the second parallel group of cells211. With reference now toFIGS.13C,13D, and13E, in some exemplary embodiments a triple-layer stack may be utilized; conductive plates128-C,128-D, and128-E each are configured with tabs153and163present in one-third of their windows127, and with the remaining windows127empty. When conductive plates128-C,128-D, and128-E are stacked atop one another, the resulting triple-layer stack provides a series connection between the entire first parallel group of cells211and the entire second parallel group of cells211(again, similar to the single conductive plate illustrated inFIG.12C). In this configuration, conductive plates128-C,128-D, and128-E each carry approximately one-third of the electrical current passing in series between the first parallel group of cells211and the second parallel group of cells211. By stacking conductive plates128, each plate conductive plate128may be made thinner and/or lighter due to the reduced current carrying capacity required. Additionally, each conductive plate128may be made of lower cost and/or higher resistivity materials. In one exemplary embodiment, a conductive plate128comprises copper, aluminum, nickel, any alloy variants, and/or the like. The ability to split layers, thereby reducing current through each layer, facilitates reducing the thickness of each layer and thus opens more manufacturing methods for interconnect assembly120(for example, traditional multi layered PCB automated processing methods). In an example embodiment, an interconnect assembly120is configured to form a 10s 30p (10 series and 30 parallel) combination of cells211. In one example embodiment, each conductive plate128that makes a series connection between parallel groups of cells211is configured with a size of about 570 mm×230 mm. Each parallel group may comprise 30 cells, which can be split across 2, 3, 4, 5 or 6 subgroups (i.e., layers in conductive plate128), depending on power loads. In this example embodiment, there are300windows127corresponding to 300 battery cells211, where the windows are counted as 1 window per cell211and not 1 window127per cell211per layer). In this example embodiment, there are 600 total tabs, one for each positive and negative terminal for each cell211. Thus, each conductive plate128may have 60 tabs, corresponding to 30 parallel cells. That conductive plate128may then be split into any suitable number of layers to split the current and reduce resistive heating due to the current running through those layers. In this example, if 3 layers are used, each layer within a group of parallel cells will have 10 cells connected in parallel, and 20 tabs connected to that plate (corresponding to 10 cells). This is just one example embodiment, and the number of layers, number of cells, dimensions, and parallel series combinations will vary significantly depending on cell layout, module size, series and parallel requirements, and so forth. With reference now toFIGS.14A,14B, and14C, it will be appreciated that in various exemplary embodiments, interconnect assembly120may be configured with connections between groups of parallel cells211via any suitable number of, and/or stack thicknesses of, conductive plates128. As seen inFIG.14A, a single-layer arrangement of conductive plates128may be utilized; in this arrangement, all the current between a first group of parallel cells211and a second group of parallel cells211flows through a single conductive plate128having a first thickness. As seen inFIG.14B, a double-layer arrangement of conductive plates128may be utilized; in this arrangement, each conductive plate128in the stack has half as many tabs153,163as the single-layer conductive plate depicted inFIG.14A, and each conductive plate128carries approximately half the current between a first group of parallel cells211and a second group of parallel cells211. In these exemplary embodiments, each conductive plate128is typically thinner than the conductive plate128ofFIG.14A. Moreover, as seen inFIG.14C, a triple-layer arrangement of conductive plates128may be utilized; in this arrangement, each conductive plate128in the stack has one-third as many tabs153,163as the single-layer conductive plate depicted inFIG.14A, and each conductive plate128carries approximately one-third the current between a first group of parallel cells211and a second group of parallel cells211. In these exemplary embodiments, each conductive plate128is typically thinner than the conductive plates128ofFIG.14B. Any suitable stack thickness and consequent division of tabs153,163may be utilized, as desired. Moreover, conductive plates128in a stack may have a common thickness; alternatively, conductive plates128in a stack may differ in thickness from one another. Turning now toFIGS.15A through15D, in various exemplary embodiments interconnect assembly120is configured with multiple current carrying layers, for example a first conductive layer121and a second conductive layer122. Each of conductive layers121,122may be formed from stacks of conductive plates128. For example, as seen in the exploded view ofFIG.15A, first conductive layer121is formed from a double stack of conductive plates128, and second conductive layer122is likewise formed from a double stack of conductive plates128.FIG.15Billustrates first conductive layer121disposed atop cells211in battery pack110;FIG.15Cillustrates second conductive layer122disposed atop cells211in battery pack110; andFIG.15Dillustrates both first conductive layer121and second conductive layer122disposed atop cells211in battery pack110. First conductive layer121and second conductive layer122are complementary in regards to having either a tab153or a tab163for each cell211. When configured as seen inFIG.15D, first conductive layer121and second conductive layer122form connections resulting in a desired configuration of parallel and series groupings of cells211, for example in a manner similar to that discussed above with respect toFIG.4A. In the embodiment illustrated inFIGS.15A through15D, moving from left to right an electrical path traverses the following components in order: positive terminal228→121A→122A→121B→122B→121C→122C→121D→122D→121E→122E→121F→negative terminal229, in order to form a “10s, 30p” arrangement of cells211. FIGS.16A through16Cfurther illustrate exemplary complementary arrangements of windows127, tabs153, and tabs163for conductive plates128utilized in a double-layer stack to form a conductive layer in interconnect assembly120, for example conductive layer121. With reference toFIGS.17A through17C, each conductive plate128disposed at the most positive end of interconnect assembly120is configured with a connective feature133for electrically connecting that conductive plate128to a load (or a bus bar or other current collecting component). When multiple stacked conductive plates128are utilized, the connective feature133may be offset from plate to plate, allowing for multiple connection points to the stack as seen inFIG.17Cand thus preventing excessive current from accumulating at any particular connection point. Likewise, with reference now toFIGS.17D through17F, each conductive plate128disposed at the most negative end of interconnect assembly120is configured with a connective feature133for electrically connecting that conductive plate128to a load (or a bus bar or other current collecting component). When multiple stacked conductive plates128are utilized, the connective feature133may be offset from plate to plate, allowing for multiple connection points to the stack as seen inFIG.17Fand thus preventing excessive current from accumulating at any particular connection point. Returning toFIGS.17A through17B, in various exemplary embodiments conductive plates128may be configured with assembly, sensing, and/or management features, for example flanges129, through holes130, and/or the like. These features may be utilized as desired, for example for handling of conductive plates128during assembly, for linking stacks of conductive plates128together, and so forth. Through holes130disposed in a common position between conductive plates128may be utilized for a rivet or other mechanical connection to retain all conductive plates128in a stack. Alternatively, conductive plates128may be welded, soldered, brazed, or otherwise coupled together. Additionally, flanges129may be utilized as electrical connection points for use in connection with cell211balancing and battery management system voltage readings. In various exemplary embodiments, interconnect assembly120may be coupled to and/or utilized with other components for control and/or management of a battery pack110, for example temperature sensors, current sensors, voltage sensors, battery management systems, and/or the like. In this manner, interconnect assembly120can facilitate improved performance, operational lifetime, and/or reliability of battery pack110. With reference now toFIGS.18A and18B, in various exemplary embodiments interconnect assembly120may include (and/or be coupled to) a voltage sensing board141. Voltage sensing board141is configured with a number of electrical leads142, and each lead142is intended for coupling to a conductive plate128in interconnect assembly121. Leads142may be routed and/or aggregated together in voltage sending board141, for example into a male/female socket connector143, in order to facilitate single-cable coupling of voltage sensing board141to other control electronics associated with system100. Voltage sensing board141is thus configured to facilitate monitoring (for example, in connection with operation of BMS140) the voltage of each trace/group of parallel cells211. In accordance with various example aspects, this approach eliminates use of wiring harnesses. The voltage sensing board141may comprise, for example, a printed circuit board with leads142for connecting to the conductive plates128comprising first and second layers121,122. In an example embodiment, voltage sensing board141connects (for example, via rivet or nut/bolt) to 4-12 separate conductive plates128in the first layer121. Similarly, voltage sensing board141may connect to 4-12 separate conductive plates in the second layer122. Moreover, any suitable number of connections may be made between locations in interconnect assembly120and voltage sensing board141. Turning now toFIGS.19A and19B, in various exemplary embodiments, interconnect assembly120may be coupled to (and/or work in tandem with) a temperature sense ribbon145for monitoring the temperature of one or more cells211in a battery pack110. The temperature sense ribbon145, in an example embodiment, comprises a flexible PCB ribbon having a surface mount thermistor or thermistors147thereon. Temperature sense ribbon145may further comprise a nonconductive housing146, for example to facilitate coupling to other components of a battery pack110. In various exemplary embodiments, temperature sense ribbon145extends through and between cells211, for example in a serpentine manner. Temperature sense ribbon145may be configured such that thermistors147make contact with associated cells211at a level between the top and the bottom of the cells211(for example, at a location within +/−20% of the halfway point of the cell211height). By locating thermistors147in these positions, temperature sense ribbon145is able to provide an improved measurement of the temperature of cells211, particularly in instances where cells211are cooled primarily from one end and thus experience a temperature gradient along the height of the cells211. Use of temperature sense ribbon145provides the capability to measure the temperature of cells211throughout the cell211structure comprising battery pack110. In particular, temperature sense ribbon145provides the capability to sense the temperature of middle/interior cells211in battery pack110. Moreover, temperature sense ribbon145facilitates measuring the temperature of individual cells211, or at least a small number of cells211in a particular location of battery pack110, as opposed to measuring the average temperature of all of the cells211comprising battery pack110. In various exemplary embodiments, when constructing battery pack110, temperature sense ribbons145may first be placed a and/or positioned, and thereafter cells211may be placed into battery pack110. In this manner, automated assembly of battery pack110is facilitated, as thermistors147are thus pre-placed with respect to corresponding cells211rather than needing to be separately placed and/or coupled thereto. Alternatively, temperature sense ribbons145may be inserted after cells211are positioned in battery pack110. In accordance with principles of the present disclosure, an exemplary electrical system100(and/or battery pack110and/or interconnect assembly120) may desirably be utilized in connection with an electric vehicle or item of mobile industrial equipment, for example an automobile, tractor, truck, trolley, train, van, quad, golf cart, scooter, boat, airplane, drone, forklift, telehandler, backhoe, and/or the like. In an example embodiment, interconnect assembly120replaces wire harnesses, and increases the reliability and speed of assembly for connecting a battery pack with hundreds of cells into an electrical system100. Principles of the present disclosure may be combined with principles of thermal management of battery systems, for example as disclosed in U.S. patent application Ser. No. 15/815,975 entitled “SYSTEMS AND METHODS FOR BATTERY THERMAL MANAGEMENT UTILIZING A VAPOR CHAMBER” and filed on Nov. 17, 2017, the entire contents of which are hereby incorporated by reference for all purposes. In an exemplary embodiment, an electrical system comprises: an interconnect assembly comprising a first plate and a second plate, wherein the first plate comprises a first plate segment and a second plate segment, and wherein the second plate comprises a third plate segment and a fourth plate segment; and a battery pack comprising a plurality of cells comprising a first group of cells, a second group of cells, and a third group of cells, wherein the interconnect assembly is connected to a top portion of the plurality of cells, wherein each cell of the plurality of cells comprises a first terminal of a first polarity and a second terminal of a second polarity. In an exemplary embodiment, a battery interconnect assembly for electrically connecting a plurality of cells of a battery pack comprises: a first plate comprising: a first window; a first tab associated with the first window, the first tab configured to connect the first plate to a first terminal of a cell of the plurality of cells of the battery pack; and a second plate parallel to and at least partially overlapping the first plate, the second plate comprising: a second window aligned with the first window, wherein the first tab extends through the second window; a second tab associated with the second window, the second tab configured to connect the second plate to a second terminal of the cell; wherein the first plate is physically separated from the second plate, wherein the first plate is electrically connected to the second plate through the cell, wherein the first terminal has a first polarity, and wherein the second terminal has a second polarity. the first plate may comprise: a first current carrying plate; and a first interconnect plate electrically connected to the first current carrying plate along a first side of the first current carrying plate, wherein the first tab is a portion of the first interconnect plate; and the second plate comprises: a second current carrying plate; and a second interconnect plate electrically connected to the second current carrying plate along a first side of the second current carrying plate, wherein the second tab is a portion of the second interconnect plate. The first current carrying plate may be thicker than the first interconnect plate; and the second current carrying plate may be thicker than the second interconnect plate. The first current carrying plate may comprise a first conductive material, the first interconnect plate may comprise a second conductive material the second current carrying plate may comprise a third conductive material, and the second interconnect plate may comprises a fourth conductive material. The interconnect assembly may further comprise an overmold material, wherein the overmold material forms a package assembly holding the first plate and the second plate in fixed location relative to each other, wherein the overmold material is electrically non-conductive, and wherein the overmold material forms an overall shape of the interconnect assembly, including the first window, the second window, the third window, and the fourth window. The overmold material may comprise an opening that is shaped to conform to a shape of a top portion of the cell for receiving and holding the cell in a fixed position relative to the first plate and the second plate. The cell may be a cylindrical cell, and the overmold material may comprise a circular opening for receiving a top portion of the cylindrical cell, and the circular opening may be aligned with the first and second tabs. The battery interconnect assembly may further comprise a retaining structure formed of the overmold material and comprising a plurality of post structures for holding the cell in a fixed position relative to the battery interconnect assembly. The battery interconnect assembly may further comprise a sensing layer overmolded in the battery interconnect assembly, the sensing layer comprising a trace for communicating sensed signals to a communications connector, wherein the sensed signals represent at least one of a sensed voltage associated with the battery pack attached to the battery interconnect assembly, and a temperature associated with a thermistor sensing the temperature at a location in the battery pack. An exemplary embodiment comprises an electronic system comprising a battery interconnect assembly as disclosed above, the electronic system further comprising: a first group of cells and a second group of cells, each having each having a first polarity terminal and a second polarity terminal; wherein the first plate comprises a first segment and a second segment; wherein the second plate comprises a third segment and a fourth segment; wherein the first segment is electrically connected to the third segment through the first group of cells; wherein the first segment is connected to the first polarity terminals of the first group of cells; wherein the third segment is connected to the second polarity terminals of the first group of cells; wherein the third segment is electrically connected to the second segment through the second group of cells; wherein the third segment is connected to the first polarity terminals of the second group of cells; and wherein the second segment is connected to the second polarity terminals of the second group of cells. In the battery interconnect assembly, the first plate may comprise a first segment and a second segment, and the second plate may comprise a third segment and a fourth segment; the third segment aligns with the first segment and a portion of the second segment, and the second segment aligns with a portion of the third segment and a portion of the fourth segment. In the battery interconnect assembly, the first plate comprises a first segment and a second segment, and the second plate comprises a third segment and a fourth segment; the third segment aligns with the first segment and a portion of the second segment, and the second segment aligns with a portion of the third segment and a portion of the fourth segment; the first segment and a portion of the third segment, when connected to the battery pack, are configured to align with a first group of cells, the first segment is configured to connect to terminals of the first polarity of the first group of cells, and a portion of the third segment is configured to connect to terminals of a second polarity of the first group of cells; and a portion of the second segment and a portion of the third segment, when connected to the battery pack, are configured to align with a second group of cells, a portion of the second segment is configured to connect to terminals of the second polarity of the first group of cells, and a portion of the third segment is configured to connect to terminals of the first polarity of the first group of cells. In the battery interconnect assembly, the first plate comprises a first segment and a second segment, the second plate comprises a third segment and a fourth segment, and an electrical flow path from the most negative to most positive proceeds from first segment to third segment, from third segment to second segment, and from second segment to fourth segment through various attached cells. The first tab may comprise a fuse structure isolating the cell, from the rest of the plurality of cells, in the event that current through the first tab exceeds a threshold for a predetermined amount of time. The battery interconnect assembly may further comprise a negative power connection point and a positive power connection point that are located on the same end of the battery interconnect assembly. The battery interconnect assembly may further comprise a negative power connection point and a positive power connection point that are located on the battery interconnect assembly. In an exemplary embodiment, an interconnect assembly for electrically connecting a plurality of cells of a battery pack comprises: a first plate comprising: a first window; a first tab associated with the first window, the first tab configured to connect the first plate to a first terminal of a cell of the plurality of cells of the battery pack; a second window; and a second plate parallel to and at least partially overlapping the first plate, the second plate comprising: a third window aligned with the first window, wherein the first tab extends through the third window; a fourth window aligned with the second window; and a second tab associated with the fourth window, the second tab configured to connect the second plate to a second terminal of the cell. The overmold material comprises an opening that is shaped to conform to the shape of a top portion of the cell for receiving and holding the cell in a fixed position relative to the first plate and the second plate. In another exemplary embodiment, an electrical system comprises: an interconnect assembly comprising a first plate and a second plate that is stacked on the first plate, wherein the first plate and the second plate comprise weld tabs; and a battery pack comprising a plurality of cells comprising a first group of cells, a second group of cells, and a third group of cells, wherein the interconnect assembly is connected to a top portion of the plurality of cells, wherein each cell of the plurality of cells comprises a first terminal of a first polarity and a second terminal of a second polarity; and wherein the weld tabs on the interconnect assembly serve as the only mechanical connection from the interconnect assembly to the battery pack; and wherein the interconnect assembly is a floating interconnect assembly. Another exemplary embodiment comprises an interconnect assembly for electrically connecting a plurality of cells of a battery pack, the plurality of cells comprising a first group of cells, a second group of cells, and a third group of cells, the interconnect assembly comprising: a first plate; and a second plate; wherein the first plate forms a series connection between the first group of cells and the second group of cells; wherein the second plate forms a series connection between the second group of cells and the third group of cells; and wherein the first plate and the second plate are electrically connected to the plurality of cells via tabs extending into windows in the respective plates. The first plate may further comprise a first tab, and further comprise a vision window, wherein the vision window is shaped to include a positive terminal tab and a negative terminal tab, in addition to exposing a portion of the shoulder of a cell of one of the first group of cells. The first plate may be formed from a stack of plates, and wherein each plate in the stack is configured to individually carry a portion of the total current flowing through the first plate. Each plate of the stacked plates may comprise positive tabs and/or negative tabs; wherein the tabs from each plate extend out of the plane of the first plate towards respective cells of the first group of cells or the second group of cells. The interconnect assembly may only be supported or connected to components (other than via the weld tabs) via sensor wires, power connections, and other data communication connections. The interconnect assembly may be a floating interconnect assembly. The battery pack may comprise a temperature sense ribbon comprising a ribbon with surface mount thermistors, wherein the temperature sense ribbon extends through and between cells, of at least one of the first group of cells, the second group of cells, and the third group of cells, at a level between the top and the bottom of the cells, and passes alongside more than two cells, of at least one of the first group of cells, the second group of cells, and the third group of cells; and wherein the temperature sense ribbon is configured to sense the temperature of middle cells in the battery pack. While the principles of this disclosure have been shown in various embodiments, many modifications of structure, arrangements, proportions, the elements, materials and components, used in practice, which are particularly adapted for a specific environment and operating requirements may be used without departing from the principles and scope of this disclosure. These and other changes or modifications are intended to be included within the scope of the present disclosure and may be expressed in the following claims. The present disclosure has been described with reference to various embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present disclosure. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure. Likewise, benefits, other advantages, and solutions to problems have been described above with regard to various embodiments. However, benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims. As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Also, as used herein, the terms “coupled,” “coupling,” or any other variation thereof, are intended to cover a physical connection, an electrical connection, a magnetic connection, an optical connection, a communicative connection, a functional connection, a thermal connection, and/or any other connection. When language similar to “at least one of A, B, or C” or “at least one of A, B, and C” is used in the specification or claims, the phrase is intended to mean any of the following: (1) at least one of A; (2) at least one of B; (3) at least one of C; (4) at least one of A and at least one of B; (5) at least one of B and at least one of C; (6) at least one of A and at least one of C; or (7) at least one of A, at least one of B, and at least one of C. | 99,874 |
11862775 | DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention provide a system and method optimizing electrochemical cell manufacturing by reducing commercialization costs, including reduction of electrolyte costs used in their manufacturing. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein. Definitions Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this general inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. The following definitions apply to some of the aspects described with respect to certain embodiments of the invention. These definitions may likewise be expanded upon herein. As used herein, the term “or” includes “and/or” and the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. As used herein, the singular terms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an object can include multiple objects unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. As used herein, the term “set” refers to a collection of one or more objects. Thus, for example, a set of objects can include a single object or multiple objects. Objects of a set also can be referred to as members of the set. Objects of a set can be the same or different. In some instances, objects of a set can share one or more common properties. As used herein, the term “adjacent” refers to being near or adjoining. Adjacent objects can be spaced apart from one another or can be in actual or direct contact with one another. In some instances, adjacent objects can be coupled to one another or can be formed integrally with one another. As used herein, the terms “connect,” “connected,” and “connecting” refer to a direct attachment or link. Connected objects have no or no substantial intermediary object or set of objects, as the context indicates. As used herein, the terms “couple,” “coupled,” and “coupling” refer to an operational connection or linking. Coupled objects can be directly connected to one another or can be indirectly connected to one another, such as via an intermediary set of objects. The use of the term “about” applies to all numeric values, whether or not explicitly indicated. This term generally refers to a range of numbers that one of ordinary skill in the art would consider as a reasonable amount of deviation to the recited numeric values (i.e., having the equivalent function or result). For example, this term can be construed as including a deviation of ±10 percent of the given numeric value provided such a deviation does not alter the end function or result of the value. Therefore, a value of about 1% can be construed to be a range from 0.9% to 1.1%. As used herein, the terms “substantially” and “substantial” refer to a considerable degree or extent. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation, such as accounting for typical tolerance levels or variability of the embodiments described herein. As used herein, the terms “optional” and “optionally” mean that the subsequently described event or circumstance may or may not occur and that the description includes instances where the event or circumstance occurs and instances in which it does not. As used herein, the term “size” refers to a characteristic dimension of an object. Thus, for example, a size of an object that is spherical can refer to a diameter of the object. In the case of an object that is non-spherical, a size of the non-spherical object can refer to a diameter of a corresponding spherical object, where the corresponding spherical object exhibits or has a particular set of derivable or measurable properties that are substantially the same as those of the non-spherical object. Thus, for example, a size of a non-spherical object can refer to a diameter of a corresponding spherical object that exhibits light scattering or other properties that are substantially the same as those of the non-spherical object. Alternatively, or in conjunction, a size of a non-spherical object can refer to an average of various orthogonal dimensions of the object. Thus, for example, a size of an object that is a spheroidal can refer to an average of a major axis and a minor axis of the object. When referring to a set of objects as having a particular size, it is contemplated that the objects can have a distribution of sizes around the particular size. Thus, as used herein, a size of a set of objects can refer to a typical size of a distribution of sizes, such as an average size, a median size, or a peak size. As used herein, the term “residual water content” of a coordination compound, particularly a TMCCC material, refers to a total water content of the TMCCC. Residual water content includes a total water mass divided by a total dry mass of the TMCCC material (the mass of the metals, CN groups, and any other chemical species such as chelating species). For example, in the case of a TMCCC with a dry mass of 100 g and a total water content of 10 g, then the residual water content is calculated as 10 g water/100 g dry mass=10%. As used herein, a water content of a class of coordination compound materials is a complex topic and refers to a hybrid residual water state which identifies a coordinated water content (e.g., coordinated water) and a non-coordinated water content (e.g., non-coordinated water). Non-coordinated water may be present in various ways, primarily as interstitial water and/or water bound to surfaces of particles of the coordination compound materials and/or water present in any pores or micropores within a TMCCC particle. As used herein, “coordinated water” is meant as an abbreviated term for “transition metal-coordinated water” and, as such, specifically describes water molecules that coordinate to transition metal atoms, and not to alkali metal ions. While the interaction between water and alkali metal ions could generally also be understood as “coordinated”, water molecules that interact with alkali ions and not with transition metal atoms are considered herein, due to their relatively weak interaction, as belonging to the category of non-coordinated water. Coordinated water molecules are strongly bound to transition metal atoms that are deficient in cyanide ligands; therefore, coordinated water is considered essential for stabilizing TMCCC materials. Non-coordinated water above a threshold included in an optimally selected residual water content would be considered an undesired impurity that degrades the desired electrochemical properties. However, removing all non-coordinated water may result in poor alkali cation mobility in the TMCCC material, leading to diminished cell energy available for high-power discharge, with only marginal improvement of cycle or calendar life of the cell. Therefore, in addition to coordinated water, a certain amount of non-coordinated water is also necessary and desired. As discussed herein, absent sufficient care, water management processes (e.g., drying) may not sufficiently distinguish between coordinated and non-coordinated water in a compound coordination material. Coordination compound materials discussed herein may be used in a system including a water-containing electrolyte which may influence the water content of the coordination compound material after assembly or during use. A coordination compound having its residual water adjusted to a desired non-degrading water content range is referred to herein as a water mediated coordination compound material. Similarly, a coordination compound having its residual water outside this range is referred to herein as a water non-mediated coordination compound material. As used herein, the term “aqueous” in the context of an electrolyte for an electrochemical cell means an electrolyte including water as a solvent and one or more dissolved materials with the water solvent having a concentration greater than 5%. As used herein, the term “non-aqueous” in the context of an electrolyte for an electrochemical cell means an electrolyte including a solvent other than water, with either no water being present or water having a concentration less than 5%. As used herein, the term “anhydrous” in the context of an electrolyte for an electrochemical cell means an electrolyte including a solvent other than water, water as a trace impurity having a concentration less than 0.01%. As used herein, the term “drying” in the context of removal of water from a material, refers to removal of water to the greatest degree possible consistent with the drying process leaving water as a trace impurity at a concentration limited by the drying process actually used. Drying changes a material to an anhydrous state (therefore a dried material is an anhydrous material). As used herein, the term “dehydrating” in the context of modifying a concentration of water in a material, refers to controllably reducing the water content to a desired level greater than a trace impurity. In contrast to drying, dehydrating contemplates retaining water as necessary desirable component of the material, for example, retaining all coordinated water and retaining a certain residual content of non-coordinated water. As used herein, the term “hydrating” in the context of modifying a concentration of water in a material, refers to controllably increasing the water content to a desired level greater than a trace impurity, within target ranges needed for optimal performance and calendar life of an electrochemical cell. As used herein, the term “mediating” in the context of modifying a concentration of water content in a coordination compound such as a TMCCC material includes dehydrating or hydrating the material to achieve a desired coordinated water concentration that enables the desired electrochemical properties. One way to consider water content quantity mediation is consideration of a mass fraction of water of a TMCCC material, including non-coordinated and coordinated water, both before and after mediation. Described herein is a new class of battery cell that is based on electrodes that contain transition metal cyanide coordination compound (TMCCC) materials as electrochemically active materials. These TMCCC materials naturally contain water. Some of the water they contain is tightly bound to transition metal atoms within the crystal structure of the material, whereas non-coordinated water is less strongly bound as it resides in interstitial sites, or at the surface of the TMCCC material. Some of the non-coordinated water may reversibly move in and out of the electrode as it is charged and discharged. Water that leaves the TMCCC material may then undergo chemical or electrochemical reactions with other cell components and thereby cause degradation of cell performance. One would therefore expect that continued removal of non-coordinated water from the TMCCC material would continue to enhance electrode and cell performance by eliminating these undesirable reactions. However, we found that dehydration is beneficial only to a certain extent, beyond which it degrades the performance of the material. Embodiments of the present invention set the water content to a preferred level that retains not only all of the coordinated water, but also a substantial content of non-coordinated water. An alternative to electrochemical cells as described herein, and methods for their assembly and use, predetermine desired levels of water in the components. Water impurities in electrolytes for battery cells can be eliminated by minimizing the water content of electrolyte components, and minimizing the exposure of these components to ambient humidity during the process steps of mixing electrolyte solutions, storage, transport, and filling battery cells with electrolyte. A disadvantage of this alternative includes use of additional process steps such as vacuum-drying of electrolyte salts, drying electrolyte solvents over desiccants, regenerating the desiccant and avoiding impurities introduced by the contact between solvent and desiccant, are costly and may require additional downstream process modifications, such as handling dried salts and solvents in gloveboxes or dry rooms that are expensive to operate. Further, the purchase of materials that have been processed this way require a premium charge over purchase of materials that offer less rigorous manufacturing, handling, and end-use requirements. In contrast, use of an embodiment of the present invention may allow for a reduction of production cost through the consolidation of separate dehydration processes for battery electrodes, electrolyte salts and electrolyte solvents into one or two process steps in which only the battery electrodes are dehydrated. This may be of particular advantage in using electrolytes made with organic solvents such as acetonitrile as solvent, because the manufacture of acetonitrile uses water as a process medium to isolate acetonitrile from its mixture with acrylonitrile, and further processing is needed to subsequently remove water from thus obtained acetonitrile. Furthermore, strict environmental humidity control is typically only needed during cell stacking operations and not in the upstream process steps. Some of the content described herein is generally related to U.S. patent application Ser. No. 16/708,213, the contents of which are hereby expressly incorporated by reference thereto in its entirety for all purposes. One embodiment of an electrochemical cell of concern includes a TMCCC anode and a TMCCC cathode, and a liquid electrolyte electrically communicated to the electrodes. This liquid electrolyte is made with one or more organic solvents and at least one alkali metal salt, and may or may not contain additives. Preferred examples of solvents include acetonitrile, propionitrile, and butyronitrile for example. Preferred examples of alkali metal salts include suitable salts containing an alkali metal cation and an anion, wherein the alkali metal cation is sodium, potassium, rubidium or cesium, and anions include, but are not limited to, perchlorate, tetrafluoroborate, hexafluorophosphate, difluoro-oxalatoborate, triflate, bis(trifluoromethanesulfonyl)imide, bis(fluorosulfonyl)imide, dicyanamide, tricyanomethanide, and mixtures thereof. Preferred examples of sodium salts include sodium salts such as, but not limited to, sodium perchlorate, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium difluoro-oxalatoborate, sodium triflate, sodium bis(trifluoromethanesulfonyl)imide, sodium dicyanamide, and sodium tricyanomethanide, and mixtures thereof. A preferred sodium salt includes sodium bis(trifluoromethanesulfonyl)imide. Examples of additives include malonitrile, succinonitrile, glutaronitrile, and adiponitrile with a mass ratio between solvent and additive between 99:1 and 70:30. FIG.1illustrates a representative secondary electrochemical cell100schematic having one or more TMCCC electrodes disposed in contact with a cosolvent electrolyte as described herein. Cell100includes a negative electrode105, a positive electrode110and an electrolyte115electrically communicated to the electrodes. FIG.2illustrates a unit cell of the cubic Prussian Blue crystal structure, one example of a TMCCC structure. Transition metal cations are linked in a face-centered cubic framework by cyanide bridging ligands. The large, interstitial A sites can contain water and/or inserted alkali ions. FIG.3illustrates a process sequence300for cell optimization by use of one or more water absorbing TMCCC electrodes including steps305-315. In step305, desired components of an electrochemical cell are obtained, such as through manufacture or purchase. For simplifying the discussions, two components of a cell stack for a secondary electrochemical cell including TMCCC active materials are described in process305. These components include an electrode and an electrolyte. Further, this example scenario includes a chemical manufacturer synthesizing TMCCC active materials for the electrode and a third-party manufacturer producing an electrolyte to be used with the electrode and other components such as additional electrodes, binders, separators, additives, and the like. The TMCCC active material to be included in this electrode includes an “as synthesized” quantity of water that may be present in various forms, e.g., coordinated, interstitial, and surface. The electrolyte used with such an electrode will include, for this example, a combination of solvents, one of which is water which exceeds a quantity more than a “trace” or “impurity” quantity as discussed herein. Step310includes pre-assembly processing of one or more components of the electrochemical (that is, before the electrodes are communicated to the electrolyte and other assembly of the final electrochemical cell are produced). In this example, the electrode is pre-processed to remove some of the as-synthesized water. In some cases, the water concentration of the electrode may be set or determined to a desired/acceptable level during synthesis so that a separate distinct step of adjusting the water concentration is not required. Step315assembles the electrochemical cell from the components, including those that have been pre-processed. Some or all of the components of the cell have different water concentrations post-assembly from their pre-assembly water concentrations. For this example, water from the electrolyte is transferred to the water-reduced TMCCC electrode. This transfer results in the water concentration of the electrolyte decreasing and the water concentration in the electrode increasing during step315. FIG.4-FIG.6illustrate a result of the process300in the context of one electrode and a simple electrolyte and that other implementations are possible as described herein.FIG.4illustrates a concept view of select components of an electrochemical cell400in an “as synthesized” state for water concentrations for an electrode and an electrolyte. These components include a TMCCC electrode405and a quantity of electrolyte410. The small circles represent water that is present in the components. FIG.5illustrates the concept view ofFIG.4with a pre-assembly system500including a pre-assembly processing of electrode405ofFIG.4to adjust it so that it is a water-adjusted (reduced) electrode505wherein the water concentration of electrode405is reduced from its as synthesized state. The fewer number of visualized small circles in electrode505ofFIG.5represent this decreased water concentration for electrode505as compared to electrode405ofFIG.4. FIG.6illustrates the concept view ofFIG.5with a post-assembly system600including a post-assembly change in water concentrations of a post-assembly electrode605and a post-assembly electrolyte610. As illustrated by the change in the number of small circles in electrode605, a water concentration of electrode605is greater than pre-assembly electrode505(and may be more, less, or the same as the water concentration of as-synthesized electrode405). Similarly, a water concentration of post-assembly electrolyte610is less than the water concentration of electrolyte410which in this example was obtained from a third party. These changes of water concentrations in system600include a transfer of water from electrolyte410to electrode505to produce the concentrations represented byFIG.6. TMCCC anodes and TMCCC cathodes used in a secondary electrochemical cell may be made in a precipitation reaction by mixing precursor solutions in water of transition metal salts, alkali metal salts, and either alkali cyanide or hexacyanometallate salts; examples of said precipitation reaction can be found in US 2020/0071175 A1, expressly incorporated by reference thereto in its entirety. The as-synthesized materials typically contain substantial amounts of water that exists in three different forms: (i) water molecules physisorbed to the surface of TMCCC particles, (ii) water molecules in interstitial spaces of a regular TMCCC crystal lattice, and (iii) water molecules coordinated to transition metal sites with an incomplete coordination environment due to an adjacent hexacyanometallate vacancy. For each hexacyanometallate vacancy present in the TMCCC lattice, the six neighboring transition metal sites each lack one of six cyanide ligands; each of these transition metal sites then coordinates to one water molecule, thus maintaining a sixfold coordination environment. In the following, these three forms of water in (i)-(iii) may be referred to as (i) surface water, (ii) interstitial water, and (iii) coordinated water. Typical non-coordinated water contents of TMCCC materials in their as-synthesized form can range from about zero to about 45% by anhydrous weight. The water content of synthesized TMCCC electrodes in an example electrochemical cell may be reduced by vacuum drying; however, the vacuum drying process is intentionally carried out in such a way that a still substantial amount of non-coordinated water is retained in the electrode materials, which typically is within a range from 1% to 12%. It is important to note there are several differences between compositions of matter disclosed in incorporated references US 2019/0190006 A1 and U.S. Pat. No. 9,099,718 B2, and the electrode compositions of matter described herein. In references US 2019/0190006 A1 and [2], cathode electrodes are dehydrated to the extent that all of their initial water content is removed with the exception of coordinated water, for example. By contrast, the residual water content in the TMCCC electrodes described herein is not limited to coordinated water, but a substantial amount of interstitial water is also retained. Typical partially dehydrated anodes in the battery cell described herein contain only between 0.7% to 5% residual water content as coordinated water, whereas the remaining portion, typically the majority, is in the form of interstitial water. Likewise, typical partially dehydrated cathodes described herein contain only between 4% and 6% (wt.) residual water content in the form of coordinated water, and an additional 0.5% to 5% of interstitial water is still present. The true amount of interstitial water can be expected to be even larger than the aforementioned values when the total water content is underreported by a Karl Fischer titration, whose accuracy relies on all of the water content being released upon heating. Heat-induced reactions that consume water, such as formation of metal oxides and hydrogen gas, are not uncommon in measurements of water content in solid materials, and lead to artificially lower readings in a Karl Fischer titration. Furthermore, reference [2] describes a TMCCC cathode material AxMn[Fe(CN)6]y·zH2O in which the removal of interstitial water has caused the material to form a rhombohedral crystal structure, with Mn2+/3+and Fe2+/3+having the same reduction/oxidation potential. By contrast, our invention includes TMCCC materials having the same crystal structure in their as-synthesized and in their partially dehydrated forms, and it also includes TMCCC cathode materials having a cubic crystal structure and having three different oxidation-reduction potentials for nitrogen-coordinated Fe2+/3+, carbon-coordinated Fe2+/3+, and nitrogen-coordinated Mn2+/3+. As an example,FIG.7shows a charge-discharge potential profile of a sodium iron manganese hexacyanoferrate electrode having a cubic crystal structure, which was dehydrated from an as-synthesized water content of 17% to a residual water content of 7.3%. Three distinct oxidation/reduction potentials are found at 2.95 V, 3.37 V and 3.6 V, respectively.FIG.8shows the differential capacity plot that is derived from the potential profile inFIG.7. In comparing the composition of matter with the specific capacity at each of the three oxidation/reduction potentials, we found that the capacity measurements are in perfect agreement with an assignment the three redox potentials as nitrogen-coordinated Fe2+/3+(2.95 V), carbon-coordinated Fe2+/3+(3.37 V) and nitrogen-coordinated Mn2+/3+(3.6 V). An advantage of this composition of matter over a fully anhydrous sodium iron manganese hexacyanoferrate electrode having the same composition of matter except for its water content is that the presence of interstitial water not only prevents the formation of the rhombohedral structure, but it also maintains the cubic crystal structure of the electrode material throughout its entire range of sodium intercalation/deintercalation. One skilled in the art will recognize the advantages of an electrode material exhibiting solid-solution intercalation mechanism instead of a phase-change mechanism, where the former mechanism typically results in higher rate capability and longer cycle life. Furthermore, the presence of multiple reactions is desirable because it allows for differential coulometry techniques that enable more precise state of charge and state of health monitoring. These partially dehydrated TMCCC electrodes may act as strong desiccants with substantial water absorption capacity when in contact with organic-solvent-based electrolytes that contain water as an impurity. Other materials systems that are known to intercalate water, such as zeolitic metal oxides, reach an equilibrium between interstitial water and ambient water in an electrolyte. That equilibrium can be described with a Langmuir isotherm or, if a distribution of absorption energies into non-equivalent sites is present, a convolution of several different Langmuir isotherms, similar to what has been reported for the water absorption of zeolite materials (R. Lin, A. Ladshaw, Y. Nan, J. Liu, S. Yiacoumi, C. Tsouris, D. W. DePaoli, and L. L. Tavlarides, Ind. Eng. Chem. Res. 2015, 54, 42, 10442-10448). Generally, the distribution of water between its states of being dissolved in the electrolyte and being absorbed in the anode and/or cathode active material can be described with a mass-balance equation: mH2Ocell=x0mE+y0mC+z0mA=x1mE+y1mC+z1mA(I) wherein mH2Ocellis the total water content of all cell components, mE, mCand mAare the masses of electrolyte, cathode active material and anode active material, respectively, xi, yiand ziare the mass fractions of water in the electrolyte, the cathode active material and the anode active material, respectively, and the indices 0 and 1 refer to the initial and final distribution of water, such that index 0 describes a distribution in which an electrolyte with a higher water content x0is filled into a cell containing a stack of cathode and anode electrodes, wherein the cathode electrodes have been partially dehydrated to an initial residual water content y0and the anode electrodes have been partially dehydrated to an initial residual water content z0. Upon equilibration between the cell components, water is redistributed, resulting in the distributions of x1, y1and z1. This equilibrium is spontaneously reached under a standard cell filling procedure in which electrolyte is added to the electrode stack, after which the cell pouch is heat-sealed and stored for a duration of hours. Upon said redistribution of water from the cell electrolyte to the electrode active materials, the electrolyte water content is diminished by Δx=x1-x0=-ΔymC+ΔzmAmE(II) In a typical cell design, the electrolyte volume is optimized in such a way that the porous structure of the cell stack is wetted, and pore volume and electrolyte volume are optimized to achieve high power, high energy density and long cycle life. Generally, the masses of active materials and electrolyte can be expected to be of the same or very similar order of magnitude. Since TMCCC electrodes can contain several percent by weight of interstitial water at equilibrium with electrolyte containing only trace impurities of water, very large values of Ax can be achieved. A preferred multi-layer pouch cell design with 4.5 Ah capacity contains approximately 62 g (by anhydrous mass) TMCCC anode active material, between 61 g and 70 g (by anhydrous mass) TMCCC cathode active material, and approximately 59 g liquid electrolyte. The electrolyte in said preferred cell design may contain up to 1000 ppm water by weight as an impurity (x0); such water impurity may be introduced with one or more of the electrolyte components (electrolyte salt, solvents, additives) and/or with the process conditions of mixing the electrolyte, during which electrolyte salts, solvents, additives and/or their mixture may be exposed to a humid atmosphere. In said cell design with a cathode active material to electrolyte weight ratio between 1.05 and 1.2, the water content of electrolyte initially containing up to 1000 ppm water is diminished to 20 ppm or less upon contact with the cathode (x1), with 20 ppm being the detection limit for water using Karl Fischer titration, whereas the water content of the cathode active material increases by no more than 800 ppm (Δy). Since the preferred total residual water content of an active material (y1or z1) is between 6% and 9%, and the addition of less than 0.1% has no measurable effect on cell performance or cycle life, such a wide range of water impurities in the electrolyte as from 0 ppm up to 1000 ppm can be tolerated without needing to adjust the process conditions for dehydration of anode or cathode electrodes. This principle may be further extended to include an initial electrolyte water concentration x0of greater than 1000 ppm, and in some embodiments, of approximately 50,000 ppm, while still achieving a preferred final water distribution x1, y1, z1. The said function of TMCCC electrode materials as a desiccant is not limited to one particular composition of matter of a TMCCC material, but it can be achieved with any TMCCC cathode or anode material that has a substantial affinity towards absorption of interstitial water. Preferred examples of such interstitially hydrated TMCCC materials include hexacyanoferrates including but not limited to sodium manganese iron hexacyanoferrates, sodium iron hexacyanoferrates, sodium manganese hexacyanoferrates, sodium copper hexacyanoferrates, sodium nickel hexacyanoferrates, potassium nickel hexacyanoferrates, hexacyanomanganates including but not limited to sodium manganese hexacyanomanganates and sodium zinc hexacyanomanganates, and hexacyanochromates including but not limited to sodium manganese hexacyanochromate. Particularly preferred cathode TMCCC materials are sodium manganese iron hexacyanoferrates with a composition Na2−s−p−(4−s)qMnII1−pFeIIp[FeII+s(CN)6]1−q(H2O)6q+r, wherein 0≤p≤1, 0≤q≤0.5, r≥0, and 0≤s≤1. Particularly preferred anode TMCCC materials are sodium manganese hexacyanomanganates with a composition Na2−4qMn[Mn(CN)6]1−q(H2O)6q+r, wherein 0≤q≤0.5 and r≥0. In another preferred cell design, an electrolyte with even higher water content on the order of several percent can be used, when the dehydration process for the electrodes is adjusted accordingly to avoid higher than preferred total water content of the cell. In this case, one or both of the anode and cathode electrodes is initially dehydrated to a residual water content that is intentionally lower than the water content that is targeted for optimal cell performance. Said optimum water concentrations in the electrode active materials are then gained back upon exposure of the “over-dried” electrode stack to the electrolyte. In one preferred cell design, a TMCCC cathode is used and the optimum residual water content in said TMCCC cathode is 6.4%, of which 4.8% water is present as coordinated water and 1.6% is present as interstitial water, the anode in this cell design is dehydrated to an optimum residual water content of 7.5%, the TMCCC cathode is over-dried to 5.3% residual water content and electrolyte with an initial water content of 12,000 ppm is used. In another preferred cell design, the TMCCC cathode is used and dehydrated to its optimum residual water content of 6.4%, and a TMCCC anode, containing 2.2% coordinated water and, for optimum cell performance and cycle life, 5.4% interstitial water, is dehydrated to 3.1% residual water content, and the resulting cell is filled with electrolyte containing 42,000 ppm water. Many other variations of this type of cell design can be practiced, in which electrolytes with substantial initial water content, ranging up to 50,000 ppm, can be effectively desiccated when appropriate TMCCC electrode materials with low initial water content and large water absorption capacity are employed. In addition, variations of this type of cell design could incorporate one or electrodes each of which comprising a combination of one or more TMCCC materials and another electrochemically active electrode material. In such a variation, said one or more TMCCC materials could be introduced as a component to the electrode in a concentration of 1% to 10% or more, and said electrodes may contain another electrochemically active electrode material including but not limited to carbons such as graphite or hard carbon, metallic and intermetallics such as sulfur and silicon, or ceramics such as transition metal oxides or phosphates, including but not limited to lithium transition metal oxides such as lithium cobalt oxide, lithium manganese oxide, or lithium nickel cobalt manganese oxide, or lithium transition metal phosphates such as lithium iron phosphate, and including but not limited to sodium transition metal oxides or phosphates, including but not limited to sodium titanium phosphate and oxides containing sodium, nickel, and optionally one or more other transition metals. In such as variation, the TMCCC component of said electrode would absorb water from the electrolyte as described herein, enhancing the performance of the cell or said another electrochemically active electrode material. Example 1: Karl Fischer Titration of Electrolytes Before and After Contact with TMCCC Cathode Three electrolytes with a concentration of 0.88 M NaTFSI in acetonitrile and with a systematic variation of water content were made, referred to hereafter as electrolytes a, b and c. Electrolyte a was taken from a stock solution made with high-purity acetonitrile and NaTFSI salt, whereas electrolytes b and c were made by intentionally adding small amounts of water to aliquots taken from electrolyte a, in order to obtain target water concentrations of 500 ppm and 1000 ppm in electrolytes b and c, respectively. Each of the electrolytes a, b and c was exposed to a partially dehydrated TMCCC cathode. For this purpose, cathode electrodes made with hydrated sodium manganese iron hexacyanoferrate as the active material, with an active material mass loading of approximately 15.3 mg/cm2by anhydrous active material weight, an area of approximately 385 cm2, calendared to a porosity of approximately 35%, were vacuum-dried to a residual water content of 7.2%±0.1% by active material weight. For each electrolyte exposure test, one of the said cathode electrodes was placed inside a laminated aluminum pouch, and a volume of electrolyte twice as large as the pore volume of the electrode was added. The pouches were then heat-sealed and stored overnight, after which they were cut open and the excess electrolyte volume collected for Karl Fischer titration. Table 1 illustrates the measured water content in electrolytes a, b and c before and after exposure to partially dehydrated cathode electrodes. Illustrated is a desiccant effect of sodium manganese iron hexacyanoferrate cathodes in contact with 0.88 M NaTFSI/acetonitrile electrolytes with different initial water concentrations. Electrolyte H2O concentrations before and after exposure are measured by Karl Fischer titration; the H2O absorption of the cathode samples is calculated from the H2O concentration change in the electrolyte. In each of the three electrolyte samples, regardless of their initial water content, the water content after exposure was diminished to the detection limit of the Karl Fischer titration. TABLE 1Desiccant effectCalculatedH2O beforeH2O aftercathode H2Oexposure toexposure toabsorptionElectrolytecathode (ppm)cathode (ppm)(% wt. of active)a59160.005b491230.05c1009220.09 Example 2: Karl Fischer Titration of Electrolytes Before and After Contact with TMCCC Anode Three electrolytes with a concentration of 0.88 M NaTFSI in acetonitrile and with a systematic variation of water content were made, referred to hereafter as electrolytes d, e and f. The electrolytes were made using the same procedure as for electrolyte a in Example 1, followed by additions of small amounts of water in order to reach target water concentrations of 100 ppm, 1000 ppm and 10000 ppm, respectively. Each of the electrolytes d, e and f was exposed to a partially dehydrated TMCCC anode. In addition to electrolyte exposure to partially dehydrated anodes directly obtained from the vacuum-drying process, the effect of anode SOC was also tested. Anode electrodes made with hydrated sodium manganese hexacyanomanganate as the active material, with an active material mass loading of approximately 14.8 mg/cm2, an area of approximately 385 cm2, calendared to a porosity of approximately 28%, were vacuum-dried to a residual water content of 7.5%. Three anodes with an SOC of 0% were directly obtained from the vacuum-drying process and exposed to electrolytes d, e, and f using the same procedure as in Example 1. Additional anodes from the same drying batch were built into multilayer pouch cells using sodium manganese iron hexacyanoferrate cathodes with 6.8% cathode residual water content. These cells underwent1C-1C charge-discharge cycles and were stopped at appropriate voltages to obtain anode SOCs of 50%, 80% and 100%, respectively. The thus prepared anodes were harvested from their cells and subjected to the same soaking protocol as the 0% SOC anodes. Table 2 illustrates an electrolyte water content in electrolytes d, e and f before and after exposure to partially dehydrated anodes at four different anode states of charge. At the given initial residual water content of 7.5% in the anode, the corresponding equilibrium water concentration in the electrolyte is 128 ppm. While this indicates a lower affinity of the anode material towards water absorption, we still observe substantial removal of water from electrolytes with higher initial concentrations of 1017 and 9983 ppm. It is noteworthy that the anode in this example has a much higher initial concentration of interstitial water (6.5%) prior to electrolyte exposure than the cathode in Example 1 (2.4%), and still exhibits substantial absorption capacity. An additional benefit can be seen in Table 2, which illustrates that the state of charge of this electrode material does not significantly affect its water absorption capacity, allowing the cell to be assembled at any state of charge while still retaining the ability to capture water from an electrolyte. Described is a desiccant effect of sodium manganese hexacyanomanganate anodes at different SOCs in contact with 0.88 M NaTFSI/acetonitrile electrolytes with initial water concentrations. Electrolyte H2O concentrations before and after exposure are measured by Karl Fischer titration; the H2O absorption of the anode samples is calculated from the H2O concentration change in the electrolyte. TABLE 2Desiccant effectAnodeH2O beforeH2O afterCalculated anodeElec-SOCexposure toexposure toH2O absorptiontrolyte(%)anode (ppm)anode (ppm)(% wt. of active)d0128980.003d501281280.000d801281300.000d1001281280.000e010171340.09e5010171720.07e8010172130.07e10010172360.07f0998317300.72f50998314290.75f80998319190.70f100998318760.71 Example 3: Cell Design with Electrolytes Containing Different Water Impurity Levels Cathode electrodes made with hydrated sodium manganese iron hexacyanoferrate were partially dehydrated to a residual water content of 7.1%±0.1% using the same vacuum drying process as in example 1. Anode electrodes made with hydrated sodium manganese hexacyanomanganate as the active material, with an active material mass loading of approximately 14.8 mg/cm2and an electrode porosity of approximately 28%, were vacuum-dried for 70 minutes at 80° C. to a residual water content of 7.8%±0.1%. Anode and cathode electrodes were stacked and formed into multi-layer pouch cells. Three different groups A, B and C of cells were made with different electrolytes. The electrolytes used in cell groups A, B and C had the same compositions as the electrolytes a, b and c in example 1, respectively. All three groups of cells were subjected to an accelerated cycle age test at 45° C., during which they were continuously floated at a maximum voltage of 1.81 V and fully discharged at a 2.2 C rate once daily. FIG.9illustrates the initial1C-1C voltage profiles of cells from groups A, B and C. FIG.10illustrates the cell energy versus time for cells from groups A, B, and C, measured during the accelerated cycle age test at 45° C. FIG.11illustrates the cell capacity versus time for cells from groups A, B, and C, measured during the accelerated cycle age test at 45° C. No differences were observed between the initial1C-1C voltage profiles of cells with varied electrolyte water content, and during 3 months of accelerated cycle-aging the performance of the three different groups was indistinguishable in terms of energy fade and capacity fade. These observations are consistent with the desiccant property of the cathode material demonstrated in Example 1. The added water in the 491 ppm and 1009 ppm groups is entirely absorbed by the cathode, and the differences in resulting cathode water introduced with the electrolyte are less than 0.09% between the groups; these differences are within typical process variations of electrode vacuum drying and their effect on cell performance or cell life are negligible. REFERENCES—EXPRESSLY INCORPORATED HEREIN BY REFERENCE THERETO Reference [1]—Imhof, R. In Situ Investigation of the Electrochemical Reduction of Carbonate Electrolyte Solutions at Graphite Electrodes. J. Electrochem. Soc., 145, 1081-1087 (1998)Reference [2]—U.S. Pat. No. 9,099,718 B2 (Lu '718)Reference [3]—Wu, J, et al, J. Am. Chem. Soc., 139, 18358-18364 (2017), The system and methods above have been described in general terms as an aid to understanding details of preferred embodiments of the present invention. In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the present invention. Some features and benefits of the present invention are realized in such modes and are not required in every case. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention. Reference throughout this specification to “one embodiment”, “an embodiment”, or “a specific embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention and not necessarily in all embodiments. Thus, respective appearances of the phrases “in one embodiment”, “in an embodiment”, or “in a specific embodiment” in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any specific embodiment of the present invention may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments of the present invention described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the present invention. It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. Additionally, any signal arrows in the drawings/Figures should be considered only as exemplary, and not limiting, unless otherwise specifically noted. Combinations of components or steps will also be considered as being noted, where terminology is foreseen as rendering the ability to separate or combine is unclear. The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention. Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the invention is not limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include any and all embodiments and equivalents falling within the scope of the appended claims. Thus, the scope of the invention is to be determined solely by the appended claims. | 48,290 |
11862776 | In the accompany drawings, the accompany drawings are not drawn to actual scale. DESCRIPTION OF EMBODIMENTS Implementation manners of the present application will be further described below in detail with reference to the accompanying drawings and embodiments. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate principles of the present application, but cannot be used to limit the scope of the present invention, that is, the present application is not limited to the described embodiments. In the depiction of the present application, it is noted that unless otherwise defined, all technological and scientific terms used have the same meanings as those commonly understood by those skilled in the art to which the present application belongs. The terms used are merely for the purpose of describing specific embodiments, but are not intended to limit the present application. The terms “including” and “having” and any variations thereof in the specification and the claims of the present application as well as the brief description of the drawings described above are intended to cover non-exclusive inclusion. “A plurality of” means more than two; and orientations or positional relationships indicated by terms such as “up”, “down”, “left”, “right”, “inside”, and “outside” are merely for convenience of describing the present application and for simplifying the description, rather than for indicating or implying that an apparatus or element indicated must have a specific orientation, and must be constructed and operated in a specific orientation, which thus may not be understood as a limitation the present application. In addition, the terms “first”, “second”, and “third” are only intended for the purpose of description, and shall not be understood as an indication or implication of relative importance. “Vertical” is not strictly vertical, but within an allowable range of error. “Parallel” is not strictly parallel, but within an allowable range of error. The phrase “embodiments” referred to in the present application means that the descriptions of specific features, structures, and characteristics in combination with the embodiments are included in at least an embodiment of the present application. The phrase at various locations in the specification does not necessarily refer to the same embodiment, or an independent or alternative embodiment exclusive of another embodiment. Those skilled in the art understand, in explicit and implicit manners, that the embodiments described in the present application may be combined with other embodiments. The terms representing directions in the following description are all directions shown in the drawings, and do not limit the specific structure of the present application. In the description of the present application, it should be further noted that unless otherwise explicitly specified and defined, the terms “mounting”, “connecting” and “connection” should be understood in a broad sense; for example, they may be a fixed connection, a detachable connection, or an integrated connection; may be a direct connection and may also be an indirect connection through an intermediate medium, or may be communication between the interiors of two elements. Those of ordinary skill in the art may appreciate the specific meanings of the foregoing terms in the present application according to specific circumstances. In the present application, the term “and/or” is only an association relation describing associated objects, which means that there may be three relations. For example, A and/or B may represent three situations: A exists alone, both A and B exist, and B exists alone. In addition, the character “/” in the present application generally indicates that the associated objects before and after the character are in an “or” relation. In the present application, battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium/lithium-ion batteries, sodium-ion batteries or magnesium-ion batteries, etc., which are not limited by the embodiments of the present application. The battery cells may be cylindrical, flat, cuboid or in another shape, which is not limited by the embodiments of the present application. The battery cells are generally divided into three types according to the way of packaging: cylindrical battery cells, prismatic battery cells and pouch battery cells, which are not limited by the embodiments of the present application. The battery mentioned in the embodiment of the present application refers to a single physical module that includes one or more battery cells to provide a higher voltage and capacity. For example, the battery mentioned in the present application may include a battery pack, etc. The battery generally includes a box body for enclosing one or more battery cells. The box body may prevent liquid or other foreign matters from affecting the charging or discharging of the battery cell. The battery cell includes an electrode assembly and an electrolytic solution, and the electrode assembly is composed of a positive electrode sheet, a negative electrode sheet and a separator. Operations of the battery cell mainly rely on movements of metal ions between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive active material layer. The positive active material layer is coated on a surface of the positive current collector, and the current collector that is not coated with the positive active material layer protrudes from the current collector coated with the positive active material layer and is used as a positive tab. In an example of a lithium-ion battery, the material of the positive current collector may be aluminum, and the positive active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganate, or the like. The negative sheet includes a negative current collector and a negative active material layer. The negative active material layer is coated on a surface of the negative current collector, and the current collector that is not coated with the negative active material layer protrudes from the current collector coated with the negative active material layer and is used as a negative tab. A material of the negative current collector may be copper, and a material of the negative active material may be carbon, silicon, or the like. In order to ensure that no fusing occurs when a large current passes through, there are a plurality of positive tabs which are stacked together, and there are a plurality of negative tabs which are stacked together. A material of the separator may be polypropylene (PP) or polyethylene (PE), and the like. In addition, the electrode assembly may be a winding structure or a laminated structure, and the embodiments of the present application are not limited thereto. In order to meet different power demands, the battery may include a plurality of battery cells, where the plurality of battery cells may be series-connected, parallel-connected or series-parallel connected. The series-parallel connection refers to a combination of series connection and parallel connection. Optionally, a plurality of battery cells may be firstly series-connected, parallel-connected or series-parallel connected to form a battery module, and then a plurality of battery modules are series-connected, parallel-connected or series-parallel connected to form a battery. That is, the plurality of battery cells may directly form a battery, or may firstly form battery modules, and then the battery modules form a battery. The battery is further provided in a power consumption device to provide electrical energy for the power consumption device. The development of the battery technology is necessary to take into account design factors in multiple aspects simultaneously, such as energy density, cycle life, discharge capacity, C-rate, safety, etc. Among them, when an internal space of the battery is fixed, improving the utilization rate of the internal space of the battery is an effective measure to improve the energy density of the battery. However, while improving the utilization rate of the internal space of the battery, other parameters of the battery, such as thermal management, are also needed to be considered. In view of this, embodiments of the present application provide a technical solution, in the battery, the thermal management component is provided to be connected to the first wall that has the largest surface area of each battery cell among a column of the plurality of battery cells arranged along the first direction, where the thermal management component includes a pair of heat conducting plates that are oppositely arranged along a second direction of the first wall and a flow passage between the pair of heat conducting plates, and in the second direction, the thickness D of the heat conducting plate and the size H of the flow passage satisfy: 0.01≤D/H≤25. In this way, there is no need to provide beams and other structures in the middle of the box body of the battery, which can maximize the space utilization rate inside the battery, thereby improving the energy density of the battery; besides, the use of the above thermal management component can also ensure the thermal management in the battery. Thus, technical solutions of the embodiments of the present application could ensure the thermal management in the battery while improving the energy density of the battery, thereby improving the performance of the battery. The technical solutions described in the embodiments of the present application are all applicable to various apparatuses using batteries, such as mobile phones, portable apparatus, notebook computers, electromobiles, electronic toys, electric tools, electric vehicles, ships and spacecrafts. For example, the spacecrafts include airplanes, rockets, space shuttles and spaceships, and the like. It should be understood that the technical solutions described in the embodiments of the present application are not only applicable to the apparatus described above, but to all apparatus using batteries. However, for brief description, the following embodiments are all described by an example of an electric vehicle. For example, as shown inFIG.1,FIG.1is a schematic structural diagram of the vehicle1according to an embodiment of the present application. The vehicle1may be a fuel-powered vehicle, a gas-powered vehicle or a new energy vehicle, and the new energy vehicle may be a battery electric vehicle, a hybrid vehicle, an extended-range vehicle, or the like. The vehicle1may be internally provided with a motor40, a controller30and a battery10, and the controller30is configured to control the battery10to supply power to the motor40. For example, the battery10may be provided at the bottom or the head or the tail of the vehicle1. The battery10may be configured to supply power to the vehicle1. For example, the battery10may be used as an operation power supply of the vehicle1for a circuit system of the vehicle1, for example, for a working power demand of the vehicle1during startup, navigation and operation. In another embodiment of the present application, the battery10may be used not only as an operating power source for the vehicle1but a driving power source for the vehicle1, replacing or partially replacing the fuel or natural gas to provide driving power for the vehicle1. In order to satisfy different power demands, the battery10may include a plurality of battery cells. For example, as shown inFIG.2, it is a schematic structural diagram of the battery10according to an embodiment of the present application. The battery10may include a plurality of battery cells20. The battery10may further include a box body11with a hollow structure inside, and the plurality of battery cells20are accommodated in the box body11. For example, the plurality of battery cells20are connected in series or in parallel or in a hybrid and are then placed in the box body11. Optionally, the battery10may also include other structures, which will not be described in detail herein. For example, the battery10may also include a busbar component. The busbar component is configured to implement electric connection among the plurality of battery cells20, such as parallel connection, series connection or series-parallel connection. Specifically, the busbar component may implement an electrical connection between the battery cells20by connecting electrode terminals of the battery cells20. Further, the busbar component may be fixed to the electrode terminals of the battery cells20by means of welding. Electric energy of the plurality of battery cells20may be further led out through an electrically conductive mechanism passing through the case. Optionally, electrically conductive mechanism may also belong to the busbar component. According to different power requirements, the number of the battery cells20may be set to any value. The plurality of battery cells20may be series-connected, parallel-connected or series-parallel connected to implement larger capacity or power. Since there may be many battery cells20included in each battery10, the battery cells20may be provided in groups for convenience of installation, and each group of battery cells20constitutes a battery module. The number of the battery cells20included in the battery module is not limited and may be set as required. The battery may include a plurality of battery modules, and these battery modules may be series-connected, parallel-connected or series-parallel connected. FIG.3is a schematic structural diagram of the battery cell20according to an embodiment of the present application. The battery cell20includes one or more electrode assemblies22, a housing211and a cover plate212. The housing211and the cover plate212form a shell or a battery case21. A wall of the housing211and the cover plate212are both referred to as a wall of the battery cell20, where for a cuboid battery cell20, the walls of the housing211includes a bottom wall and four side walls. The housing211is shaped according to a shape of one or more electrode assemblies22after combination. For example, the housing211may be a hollow cuboid, cube or cylinder, and one surface of the housing211has an opening such that one or more electrode assemblies22may be placed in the housing211. For example, when the housing211is a hollow cuboid or cube, one plane of the housing211is an opening surface, i.e., the plane does not have a wall, so that the inside and outside of the housing211are in communication with each other. When the housing211is a hollow cylinder, an end face of the housing211is an opening surface, i.e., the end surface does not have a wall, so that the inside and outside of the housing211are in communication with each other. The cover plate212covers the opening and is connected to the housing211to form a closed cavity in which the electrode assembly22is placed. The housing211is filled with an electrolyte, such as an electrolytic solution. The battery cell20may further include two electrode terminals214, and the two electrode terminals214may be provided on the cover plate212. The cover plate212is generally in the shape of a flat plate, and the two electrode terminals214are fixed on a flat plate surface of the cover plate212. The two electrode terminals214are a positive electrode terminal214aand a negative electrode terminal214b, respectively. Each electrode terminal214is correspondingly provided with a connection member23, or also referred to as a current collection member23, which is located between the cover plate212and the electrode assembly22and configured to electrically connect the electrode assembly22to the electrode terminal214. As shown inFIG.3, each electrode assembly22has a first tab221aand a second tab222a. The first tab221aand the second tab222ahave opposite polarities. For example, when the first tab221ais a positive tab, the second tab222ais a negative tab. The first tab221aof the one or more electrode assemblies22is connected to an electrode terminal through a connection member23, and the second tab222aof the one or more electrode assemblies22is connected to the other electrode terminal through the other connection member23. For example, the positive electrode terminal214ais connected to the positive tab via a connection member23, and the negative electrode terminal214bis connected to the negative tab via the other connection member23. In the battery cell20, according to actual usage requirements, there may be a single or a plurality of electrode assemblies22. As shown inFIG.3, there are four independent electrode assemblies22in the battery cell20. A pressure relief mechanism213may also be provided on the battery cell20. The pressure relief mechanism213is configured to be actuated when an internal pressure or temperature of the battery cell20reaches a threshold, to relieve the internal pressure or temperature. The pressure relief mechanism213may be in various possible pressure relief structures, which is not limited in the embodiments of the present application. For example, the pressure relief mechanism213may be a temperature-sensitive pressure relief mechanism, the temperature-sensitive pressure relief mechanism is configured to be capable of being melted when the internal temperature of the battery cell20provided with the pressure relief mechanism213reaches a threshold; and/or the pressure relief mechanism213may be a pressure-sensitive pressure relief mechanism, and the pressure-sensitive pressure relief mechanism is configured to be capable of being fractured when an internal gas pressure of the battery cell20provided with the pressure relief mechanism213reaches a threshold. FIG.4shows a schematic structural diagram of the battery10according to an embodiment of the present application. The battery10includes a plurality of battery cells20arranged along a first direction x and a thermal management component101. The first direction x is the arrangement direction of a column of battery cells20in the battery10. That is, the column of battery cells20in the battery10are arranged along the direction x. FIG.5shows an exploded diagram of the column of battery cells20and thermal management components101;FIG.6is a planar schematic diagram of the column of battery cells20and thermal management components101;FIG.7is a sectional schematic view taken along A-A inFIG.6; andFIG.8is an enlarged view of the part B inFIG.7. The thermal management component101extends along the first direction x and is connected to a first wall2111of each battery cell20among the plurality of battery cells20, and the first wall2111is a wall of the battery cell20that has the largest surface area. The battery cell20may include a plurality of walls, and the first wall2111that has the largest surface area of the battery cell20is connected to the thermal management component101. That is, the first wall2111of the battery cell20faces the thermal management component101, i.e., the first wall2111of the battery cell20are parallel to the first direction x. As shown inFIG.7andFIG.8, the thermal management component101includes a pair of heat conducting plates1011that are oppositely arranged along a second direction y and a flow passage1012located between the pair of heat conducting plates1011, the flow passage1012is configured to accommodate a fluid to adjust a temperature of the battery cell20, and the second direction y is vertical to the first wall2111. The thermal management component101is configured to accommodate a fluid to adjust temperatures of the plurality of battery cells20. The fluid may be a liquid or a gas, and the temperature adjustment means heating or cooling the plurality of battery cells20. In a case of cooling or lowering the temperature of the battery cells20, the flow passage1012is configured to accommodate a cooling medium to adjust the temperatures of the plurality of battery cells20. In this case, the thermal management component101may also be called a cooling component or a cooling plate, or the like. The fluid accommodated in the flow passage1012may also be referred to as a cooling medium or a cooling fluid, and more specifically, may be referred to as a cooling liquid or a cooling gas. In addition, the thermal management component101may also be used for heating, which is not limited in the embodiments of the present application. Optionally, the fluid may flow in a circulating manner to achieve a better temperature adjustment effect. Optionally, the fluid may be water, a mixture of water and ethylene glycol, refrigerant, air, or the like. Optionally, the thermal management component101is provided with a current collector102and a pipe103at both ends in the first direction x, the pipe103is used for conveying the fluid, and the current collector102is used for collecting the fluid. In the second direction y, a thickness D of the heat conducting plate1011and a size H of the flow passage1012satisfy: 0.01≤D/H≤25. In an embodiment of the present application, in the battery10, the thermal management component101is provided to be connected to the first wall2111that has the largest surface area of each battery cell20among a column of the plurality of battery cells20arranged along the first direction x. In this way, there is no need to provide beams and other structures in the middle of the box body11of the battery10, which can maximize the space utilization rate inside the battery, thereby improving the energy density of the battery10. Correspondingly, in order to ensure the performance of the battery10, the thermal management component101needs to take into account the requirements of strength and thermal management performance. In an embodiment of the present application, in the second direction y, when the thickness D of the heat conducting plate1011and the size H of the flow passage1012satisfy: 0.01≤D/H≤25, both the strength and the thermal management performance requirements can be taken into account. Specifically, when the size H of the flow passage1012is large, a flow resistance of the fluid in the flow passage1012is low, which can improve a heat exchange amount per unit time of the thermal management component101; when the thickness D of the heat conduction plate1011is relatively large, the thermal management component101has high strength. When D/H is less than 0.01, the size H of the flow passage1012is big enough, but takes up too much space; or under the given space of the thermal management component101, the thickness D of the heat conducting plate1011may be too thin, resulting in insufficient strength, for example, vibration and shock requirements of the battery10cannot be met, and even the thermal management component101is crushed when the battery is firstly assembled. When D/H≥25, the thickness D of the heat conducting plate1011is thick enough, but under the given space of the thermal management component101, it may result in that the size H of the flow passage1012is too small, and the flow resistance of the fluid in the flow passage1012increases, and a heat exchange performance is deteriorated or the flow passage1012is blocked during use. Besides, since the thickness of the wall of the heat conducting plate1011is too large, a force generated by the expansion of the battery cell20cannot satisfy the crushing force on the thermal management component101corresponding to the expansion space required by the battery cell20, that is, the thermal management component101cannot release the expansion space required by the battery cell20in time, which will accelerate the capacity reduction of the battery cell20. Therefore, the thickness D of the heat conducting plate1011and the size H of the flow passage1012satisfy: 0.01≤D/H≤25, both the strength and the thermal management performance requirements can be taken into account simultaneously to ensure the performance of the battery10. In an embodiment of the present application, in the battery10, the thermal management component101is provided to be connected to the first wall2111that has the largest surface area of each battery cell20among a column of the plurality of battery cells20arranged in the first direction x, where the thermal management component101includes a pair of heat conducting plates1011that are oppositely arranged along a second direction y of the first wall2111and a flow passage1012between the pair of heat conducting plates1011, and in the second direction y, the thickness D of the heat conducting plate1011and the size H of the flow passage1012satisfy: 0.01≤D/H≤25. In this way, there is no need to provide beams and other structures in the middle of the box body11of the battery10, which can maximize the space utilization rate inside the battery10, thereby improving the energy density of the battery10; besides, the use of the above thermal management component101can also ensure the thermal management in the battery10. Thus, technical solutions of the embodiments of the present application could ensure the thermal management in the battery10while improving the energy density of the battery10, thereby improving the performance of the battery10. Optionally, when 0.01≤D/H≤0.1, the fluid may be a solid-liquid phase change material or a liquid working substance, an outer layer of the thermal management component101may be made of a film-like material as a skin, and the interior can be filled with a skeleton structure for reinforcement. This solution can be used in the case where the requirement of strength is relatively low or the compressibility of the thermal management component101is relatively high. Optionally, in the range of 0.01≤D/H≤0.1, convection heat exchange using a fluid working substance or vapor-liquid phase change cooling scheme can be adopted inside the thermal management component101, and the liquid working substance is used as the heat exchange medium to ensure the heat transfer performance of the thermal management component101. Optionally, when 0.01≤D/H≤25, the thermal management component101may use a vapor-liquid phase change cooling scheme, and the overall pressure may be increased by adjusting an interior gap to ensure that the working medium exists in the form of liquid inside the thermal management component101so as to prevent coexistence of the two states of vapor and liquid caused by pressure loss, and provide the heat exchange performance Besides, the thickness D of the heat conducting plate1011is thick enough to prevent the thermal management component101from breaking due to vaporization of the internal working medium and the increase of pressure during being heated. Optionally, in an embodiment of the present application, the thickness D of the heat conducting plate1011and the size H of the flow passage1012satisfy: 0.05≤D/H≤15, and further satisfy 0.1≤D/H≤1, so as to better take into account space, strength and thermal management, thereby further improving the performance of the battery10. Optionally, in an embodiment of the present application, a size W of the thermal management component101in the second direction y is 0.3 to 100 mm. W is the total thickness of the thermal management component101, that is, W=2*D+H. If W is too large, the thermal management component101will take up too much space, and if W is too small, it will result in too low strength or too narrow flow passage and affect the thermal management performance. Therefore, when the total thickness W of the thermal management component101is 0.3 to 100 mm, the thermal management component101can take into account the space, the strength and the thermal management to ensure the performance of the battery10. Optionally, in an embodiment of the present application, the thickness d of the heat conducting plate is 0.1 to 25 mm. If the thickness D of the heat conducting plate1011is too large, the heat conducting plate1011will take up too much space and the thermal management component101will not be able to give up the expansion space required by the battery cell20, and if the D is too small, it will result in low strength. Therefore, when the thickness D of the heat conducting plate1011is 0.1 to 25 mm, the thermal management component101may take into account the space, the strength and the expansion requirements of the battery cell20to ensure the performance of the battery10. Optionally, in an embodiment of the present application, the size H of the flow passage1012is 0.1 to 50 mm. Specifically, the size H of the flow passage1012needs to be at least larger than the particle size of impurities that may appear inside, so as to prevent blockage during application, and if the size H of the flow passage1012is too small, the flow resistance of the fluid in the flow passage1012increases, and the heat exchange performance is deteriorated, so the size H of the flow passage1012is not less than 0.1 mm. If the size H of the flow passage1012is too large, it will take up too much space or not have enough strength. Therefore, when the size H of the flow passage1012is 0.1 to 50 mm, the space, the strength and the thermal management performance can be taken into account to ensure the performance of the battery10. Optionally, in an embodiment of the present application, the size W of the thermal management component101in the second direction y and an area A of the first wall2111satisfy: 0.03 mm−1≤W/A*1000≤2 mm−1. If W and A satisfy the above conditions, and the heat exchange performance requirements and the size and space requirements of the battery cell20can be met. Specifically, when the area A of the first wall2111of the battery cell20is relatively large, the cooling area is relatively large, which can reduce the heat transfer resistance from the thermal management component101to the surface of the battery cell20; and when the total thickness of the thermal management component101is relatively large, the strength can be increased. If W/A*1000 is less than 0.03 mm−1, the area A of the first wall2111of the battery cell20is large enough, but the thermal management component101is too thin, resulting in insufficient strength, and the thermal management component101may have problems, such as damage or crack during use. If W/A*1000 is greater than 2, the thermal management component101is thick enough, but the area A of the first wall2111of the battery cell20is too small, and the cooling surface that the thermal management component101may supply to the battery cell20is insufficient, having the risk that the cooling needs of the battery cell20cannot be met. Therefore, when the total thickness W of the thermal management component101and the area A of the first wall2111satisfy 0.03 mm−1≤W/A*1000≤2 mm−1, the strength and thermal management performance requirements can be taken into account to ensure the performance of the battery10. Optionally, in an embodiment of the present application, as shown inFIG.8, the thermal management component101may further include a rib1013provided between the pair of heat conducting plates1011, and the rib1013and the pair of heat conducting plates1011form the flow passage1012. The rib1013can also increase the strength of the thermal management component101. The number of the rib1013may be set according to the requirements of the flow passage1012and the strength. As shown inFIG.8, the rib1013may be vertical to the heat conducting plate1011, in this case, the thermal management component101may bear a greater pressure. Optionally, the rib1013can be a special shape, such as a C shape, a wave shape or a cross shape, etc., which can effectively absorb expansion, and can also increase turbulence and enhance a heat exchange effect. Optionally, in an embodiment of the present application, an angle formed of the rib1013and the heat conducting plate1011may be an acute angle. That is to say, the rib1013are not vertical to the heat conducting plate1011. In this case, in the second direction y, the thermal management component101can have a relatively large space for compression, thereby providing a relatively larger space for the expansion of the battery cell20. Optionally, in an embodiment of the present application, a thickness X of the rib1013is not less than (−0.0005*F+0.4738)mm, where F is a tensile strength of a material of the rib1013, in MPa. That is, the thickness X of the ribs1013may be at least (−0.0005*F+0.4738)mm. The thickness X of the rib1013is related to the tensile strength of the material of the rib1013. According to the above relational expression, in order to meet stress requirements of the thermal management component101, materials with higher strength are selected, and the thickness X of the internal rib1013can be thinner, thereby saving the space and improving the energy density. Optionally, the thickness X of the rib1013may be 0.2 mm to 1 mm. Optionally, in an embodiment of the present application, the battery cell20includes two first walls2111that are oppositely arranged in the second direction y and two second walls2112that are oppositely arranged in the first direction x, where in the first direction x, the second walls2112of two adjacent battery cells20are opposite. That is, for the prismatic battery cell20, the large side thereof, i.e., the first wall2111, is connected to the thermal management component101, and the small side thereof, i.e., the second wall2112, is connected to the second wall2112of the adjacent battery cell20, so that the battery cells20are arranged in a column in the first direction x. In this way, a first wall2111with a large area is used to connect with the thermal management component101, which is beneficial to the heat exchange of the battery cells20and ensures the performance of the battery10. Optionally, in an embodiment of the present application, the battery10includes a plurality of columns of the plurality of battery cells20arranged in the first direction x and the plurality of thermal management components101, where the plurality of columns of battery cells20and the plurality of thermal management components101are alternately arranged in the second direction y. That is, the plurality of columns of battery cells20and the plurality of thermal management components101may be arranged in the order of a thermal management components101, a column of battery cells20, a thermal management components101. . . , or, a column of battery cells20, a thermal management components101, a column of battery cells20. . . , in this way, the plurality columns of battery cells20and the plurality of thermal management components101are connected to each other to form as a whole that is accommodated in the box body11, which can not only perform effectively thermal management of each column of battery cells20, but ensure the overall structural strength of the battery10, thereby improving the performance of the battery10. Optionally, in an embodiment of the present application, the battery10may include a plurality of battery modules. The battery module includes at least one column of the plurality of battery cells20arranged along the first direction x and at least one thermal management component101, and the at least one column of battery cells20and the at least one of thermal management component101are alternately arranged in the second direction y. That is, for each battery module, the column of battery cells20and the thermal management component101are alternately arranged in the second direction y, and the plurality of battery modules are accommodated in the box body11to form the battery10. Optionally, the plurality of battery modules are arranged along the second direction y, and there is a gap between adjacent battery modules. Optionally, in an embodiment of the present application, the thermal management component101is bonded to the first wall2111. That is, the thermal management component101and the battery cell20may be fixedly connected by bonding, such as boding by the structural glue, but this is not limited by the embodiments of the present application. Optionally, the battery cell20may be bonded and fixed to the box body11. Optionally, adjacent battery cells20in each column of battery cells20may also be bonded, for example, the second walls2112of adjacent battery cells20are bonded by the structural glue, but this is not limited by the embodiments of the present application. The fixing effect of the battery cells20may be further enhanced by bonding and fixing adjacent battery cells20in each column of battery cells20. It should be understood that relevant parts in each embodiment of the present application may be referred to each other, and for the sake of brevity, details are not described herein again. An embodiment of the present application further provides a power consumption device, which may include the battery10in the above-mentioned embodiments. Optionally, the power consumption device may be a vehicle1, a ship or a spacecraft, etc., but this is not limited by the embodiments of the present application. The battery10and the power consumption device of the embodiments of the present application are described above, and a method and device for producing a battery of the embodiments of the present application will be described below. For the parts that are not described in detail, reference is made to the foregoing embodiments. FIG.9shows a schematic flowchart of a method300for producing a battery according to an embodiment of the present application. As shown inFIG.9, the method300may include: 310, providing a plurality of battery cells20arranged along a first direction x; 320, providing a thermal management component101, the thermal management component101extending along the first direction x and being connected to a first wall2111of each battery cell20among the plurality of battery cells20, the first wall2111being a wall that has the largest surface area of the battery cell20, the thermal management component101including a pair of heat conducting plates1011that are oppositely arranged along a second direction y and a flow passage1012located between the pair of heat conducting plates1011, the flow passage1012being configured to accommodate a fluid to adjust temperatures of the battery cells20, and the second direction y being vertical to the first wall2111, where in the second direction y, a thickness D of the heat conducting plate1011and a size H of the flow passage1012satisfy: 0.01≤D/H≤25. FIG.10is a schematic block diagram of a device400for producing a battery according to an embodiment of the present application. As shown inFIG.10, the device400for producing a battery may including: a first provision module410, configured to provide a plurality of battery cells20arranged along the first direction x; a second provision module420configured to provide a thermal management component101, the thermal management component101extending along the first direction x and being connected to a first wall2111of each battery cell20among the plurality of battery cells20, the first wall2111being a wall that has the largest surface area of the battery cell20, the thermal management component101including a pair of heat conducting plates1011that are oppositely arranged along a second direction y and a flow passage1012located between the pair of heat conducting plates1011, the flow passage1012being configured to accommodate a fluid to adjust temperatures of the battery cells20, and the second direction y being vertical to the first wall2111, where in the second direction y, a thickness D of the heat conducting plate1011and a size H of the flow passage1012satisfy: 0.01≤D/H≤25. Hereinafter, embodiments of the present application are illustrated. The embodiments described below are exemplary, only used to explain the present application, and should not be construed as a limitation to the present application. If no specific technique or condition is indicated in the embodiments, the technique or condition described in the literature in the art or the product specification is used. Simulation tests on heating rate and deformation force of the thermal management component101are carried out using the battery cell20and the thermal management component101shown in the accompanying drawings, and the test results are shown in Table 1. L2 in Table 1 is the size of the battery cell20in the first direction x, L3 is the size of the battery cell20in the second direction y, L1 is the size of the first wall2111of the battery cell20in the third direction z, and the third direction is vertical to the first direction x and the second direction y. TABLE 1HeatingL1L2L3WDHW/A*1000RateDeformationmmmmmmmmmmmmD/Hmm−1° C./minForce N71100026.541.950.119.50.056338028<0.5>10000010096026.541.80.44.50.041666667<0.5>1000007112026.552.450.124.50.58685446<0.5>1000007112026.58321.50.938967136<0.5>10000085.912012.531.450.114.50.291036088<0.5>1000009114826.531.450.114.50.222750223<0.5>100000112.514885.852.250.54.50.3003003<0.5>100000951485252.250.54.50.355618777<0.5>100000851734241.750.53.50.272016321<0.5[10000,100000]199.7173.653.541.750.53.50.115380444<0.5[10000,100000]201.7173.628.612280.250.342709093[0.5,[10000,1.6]100000]199.7173.653.5101.570.2142857140.28845111[0.5,[10000,1.6]100000]97.514828.530.520.250.207900208[0.5,[10000,1.6]100000]102.851487930.42.20.1818181820.197085759[0.5,[10000,1.6]100000]971487930.42.20.1818181820.208971858[0.5,[10000,1.6]100000]199.7173.671.254120.50.115380444[0.5,[10000,1.6]100000]302001020.6250.750.8333333330.333333333[0.5,[10000,1.6]100000]555513.550.540.1251.652892562[0.5,[10000,1.6]100000]63.470356140.251.351960342[0.5,[10000,1.6]100000]112.52034460.255.50.0454545450.26272578[0.5,<100001.6]112.52038860.255.50.0454545450.26272578[0.5,<100001.6]9114826.50.30.10.110.022275022<0.5<10000112.51944840.23.60.0555555560.18327606<0.5<10000112.519470.740.23.60.0555555560.18327606<0.5<1000020020085.8605500.11.5[0.5,>1000001.6] Although the present application is already described with reference to the preferred embodiments, various improvements may be made to the present application and the components therein may be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, various technical features mentioned in the various embodiments may be combined in any manner. The present application is not limited to the specific embodiments disclosed herein, and includes all technical solutions falling within the scope of the claims. | 42,708 |
11862777 | DETAILED DESCRIPTION Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but should be interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the configurations described in the following description with reference the accompanying drawings do not represent all technical concepts or ideas of the present disclosure but should be considered to be exemplary embodiments of the present disclosure. It should be understood that various modifications and equivalents of the embodiments may be devised within the scope of the present invention at the time of the filing of the application. Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same elements are denoted by the same reference numerals as much as possible. Furthermore, detailed descriptions related to well-known functions or configurations may be omitted in order not to unnecessarily obscure subject matters of the present disclosure. For the same reason, some of the elements in the accompanying drawings are exaggerated, omitted, or shown schematically, and the size of each element may not entirely reflect the actual size. FIG.1is a perspective view schematically illustrating a battery module100according to an embodiment of the present disclosure,FIG.2is an exploded perspective view illustrating the battery module100shown inFIG.1, andFIG.3is an enlarged perspective view illustrating a battery cell10shown inFIG.2. In addition,FIG.4is a cross-sectional view taken along line I-I′ ofFIG.1,FIG.5is an exploded view ofFIG.4, andFIGS.6A and6Bare enlarged views illustrating a portion A and a portion B ofFIG.4. Referring toFIGS.1to6, the battery module100of the present embodiment may have an approximately hexahedral shape and may include a plurality of battery cells10, circuit units70configured to electrically connect the battery cells10, and a case30configured to protect the battery cells10from external environments. The battery cells10may be arranged side by side in a layered manner, and electrode leads15may protrude outwardly from bodies of the battery cells10. The battery cells10may be, for example, pouch-type secondary batteries. Each of the battery cells10may be formed by placing an electrode assembly (not shown) in a pouch11. The electrode assembly includes a plurality of electrode plates and a plurality of electrode tabs and is accommodated in the pouch11. Here, the electrode plates may include a positive electrode plate and a negative electrode plate, and the electrode assembly may be formed by stacking the positive and negative electrode plates with a separator being therebetween and wide surfaces of the positive and negative electrode plates facing each other. Each of the positive and negative electrode plates may be formed by applying an active material slurry to a current collector, and in general, the active material slurry may be prepared by stirring materials such as a granular active material, an auxiliary conductor, a binder, and a plasticizer in a solvent. In addition, the electrode assembly may be formed by vertically stacking a plurality of positive electrode plates and a plurality of negative electrode plates. In this case, the positive electrode plates and the negative electrode plates may respectively include electrode tabs, and electrode tabs of the same polarity may be brought into contact with each other and connected to the same electrode lead15(refer toFIG.3). In the present embodiment, two electrode leads15are arranged to face opposite directions. The pouch11is formed in a container shape and provides an internal space in which the electrode assembly and an electrolyte (not shown) are accommodated. In this case, portions of the electrode leads15of the electrode assembly are exposed to the outside of the pouch11. The pouch11may be divided into sealing portions202and an accommodation portion204. The accommodation portion204is formed in a container shape to provide a rectangular internal space. The electrode assembly and the electrolyte are accommodated in the inner space of the accommodation portion204. The sealing portions202are formed in a flange shape extending outwardly from the accommodation portion204formed in a container shape. Therefore, the sealing portions202are arranged in a rim shape along the outer periphery of the accommodation portion204. The sealing portions202may be joined by a thermal fusing method. However, the sealing portions202are not limited thereto. Furthermore, in the present embodiment, the sealing portions202may include first sealing portions2021on which the electrode leads15are arranged, and a second sealing portion2022on which the electrode leads15are not arranged. In the present embodiment, the pouch11is manufactured using a sheet of casing material through a forming process. That is, the pouch11is manufactured by forming two receiving portions on the casing material through a forming process, and then the casing material is folded such that the two receiving portions may form a single space. In the present embodiment, the accommodation portion204has a rectangular shape. However, since it is not required to form a sealing portion on a lower side S1of the battery cell10, the sealing portions202are formed around the accommodation portion204only on three sides of the accommodation portion204. In the present embodiment, the electrode leads15are arranged to face opposite directions. That is, two electrode leads15are arranged on sealing portions202formed on different sides. Therefore, the sealing portions202provided on three sides of the accommodation portion204include: two first sealing portions2021on which the electrode leads15are arranged; and a single second sealing portion2022on which the electrode leads15are not arranged. Furthermore, in the battery cell10of the present embodiment, the sealing portions202are folded at least once so as to increase joining reliability of the sealing portions202and minimize the areas of the sealing portions202. More specifically, in the present embodiment, the second sealing portion2022of the sealing portions202on which the electrode leads15are not arranged is folded twice and is then fixed. For example, the second sealing portion2022may be folded by 180 degrees along a first folding line C1shown inFIG.3, and may then be folded by 180 degrees along a second folding line C2shown inFIG.3. The battery cells10configured as described above may be rechargeable nickel metal hydride (Ni-MH) batteries or rechargeable lithium ion (Li-ion) batteries capable of generating current. In addition, the battery cells10are vertically stood in the case30(described later) and stacked in a left-right direction or a horizontal direction. Referring toFIGS.6A and6B, each of battery cells has a lower side S1secured to the lower plate52of the first plate50, an upper side S2, opposite said lower side S1, in contact with the second plate40, and opposite lateral sides in the first direction, the stacking direction of the battery cells. Although not shown, at least one buffer pad may be placed between the battery cells10arranged in a stack. The buffer pad may be provided to prevent an increase in the total volume of the battery cells10when a particular battery cell10swells. The buffer pad may be formed of polyurethane foam, but is not limited thereto. The case30defines the outer shape of the battery module100and is arranged outside the battery cells10to protect the battery cells10from external environments. In the present embodiment, along therewith, the case30also functions as a cooling member of the battery module100. The case30of the present embodiment includes a first plate50coupled to lower portions of the battery cells10, a second plate40coupled to upper portions of the battery cells10, and covers60coupled to sides of the battery cells10on which the electrode leads15of the battery cells10are arranged. Among the first plate, the second plate40, and the covers60, the first plate50and the second plate40function as cooling members of the battery module100. The first plate50may include: a lower plate52placed on the lower portions of the battery cells10and supporting the lower sides S1of the battery cells10; and side plates58supporting sides of the battery cells10on which the accommodation portions204of the battery cells10are located. However, in some cases, the side plates58and the lower plate52may be provided as separate elements. Portions of a seating surface of the lower plate52on which the battery cells10are placed in contact with the lower plate52may be curved such that the lower side S1of the battery cells10may be more securely supported. Accordingly, the lower side S1of the battery cells10may be in contact with the lower plate52with a large contact area, and thus heat transfer to the lower plate52may effectively occur. In the present embodiment, the pouches11of each of the battery cells10is formed by folding a sheet of the casing material, and thus lower end portions of the first sealing portions2021(refer toFIG.6B) may protrude downward from the accommodation portion204of each of the battery cells10. Thus, insertion grooves54are formed in the seating surface of the lower plate52to receive the first sealing portions2021. The insertion grooves54have a width and depth for the first sealing portions2021to be easily inserted into the insertion grooves54. The side plates58extend from both sides of the lower plate52and are arranged along sides of the battery cells10stacked in the left-right direction such that the accommodation portions204of the battery cells10may be supported by the side plates58. The side plates58may be in contact with the accommodation portions204of the battery cells10to securely support the battery cells10. However, this is a non-limiting example. That is, various modifications may be made, and for example, members such as heat-dissipating pads or buffer members may be placed between the side plates58and the accommodation portions204. The first plate50configured as described above is formed of a material having high thermal conductivity such as a metal. For example, the first plate50may be formed of an aluminum material. However, this is a non-limiting example. That is, the first plate50may be formed of any other material having strength and thermal conductivity similar to those of a metal. The second plate40is arranged on the upper portions of the battery cells10and is coupled to the upper sides s2of the battery cells10. In addition, the second plate40is fastened to upper ends of the side plates58of the first plate50. Therefore, after the second plate40is fastened to the first plate50, the second plate40and the first plate50have the shape of a tubular member having a hollow interior. Portions of a lower side of the second plate40which make contact with the battery cells10may be curved such that the contact between the second plate40and the battery cells10may be securely maintained. Therefore, the upper sides s2of the battery cells10may be in contact with the second plate40with a large contact area, and thus heat may be effectively dissipated. In addition, since the battery cells10are vertically stood and stacked in the left-right direction, the second sealing portions2022are located on the upper sides s2of the battery cells10. Therefore, the accommodation grooves42are formed in the lower side of the second plate40to accommodate the second sealing portions2022. The accommodation grooves42have a width and depth for the second sealing portions2022to be easily inserted into the accommodation grooves42. Since the second sealing portions2022are folded at least once, the accommodation grooves42have a width and depth greater than those of the insertion grooves54. Furthermore, in the accommodation grooves42, the second sealing portions2022are spaced apart from the second plate40. In this case, the second sealing portions2022may be shaken in the accommodation grooves42, or heat released from the second sealing portions2022may not easily transfer to the second plate40. Therefore, in the present embodiment, a heat transfer material90is disposed in the accommodation grooves42. The heat transfer material90may be prepared based on a silicon material or an epoxy material, but is not limited thereto. The heat transfer material90may be filled in the accommodation grooves42in a liquid or gel state and may then be cured. Then, the second sealing portions2022may be firmly fixed in the accommodation grooves42, and heat released through the second sealing portions2022may rapidly transfer to the second plate40through the heat transfer material90. In addition, the heat transfer material90of the present embodiment may be highly insulative and may have dielectric strength, for example, within the range of 10 KV/mm to 30 KV/mm. Therefore, in the battery module100of the present embodiment, even if the second sealing portions2022arranged in the accommodation grooves42partially undergo a dielectric breakdown, electrical insulation between the second sealing portions2022and the second plate40may be maintained owing to the heat transfer material90provided around the second sealing portions2022. Furthermore, in the present embodiment, the casein the heat transfer material90is filled only in the accommodation grooves42is described as an example. However, the present disclosure is not limited thereto, and in some cases, the heat transfer material90may be filled in the insertion grooves54. Like the first plate50, the second plate40is formed of a material having high thermal conductivity such as a metal. The second plate40may be formed of an aluminum material. However, this is a non-limiting example. That is, the second plate40may be formed of any other material having strength and thermal conductivity similar to those of a metal. The first plate50and the second plate40may be joined together by a method such as welding. However, this is a non-limiting example, and the first plate50and the second plate40may be joined together by various other methods such as a sliding coupling method or a method of using fixing members such as bolts or screws. The covers60are coupled to sides of the battery cells10on which the electrode leads15are arranged. The covers60are coupled to the first plate50and the second plate40to complete the outer shape of the battery module100together with the first plate50and the second plate40. The covers60may be formed of an insulative material such as a resin and may include through-holes62to expose connection terminals72of the circuit units70as described later. The covers60may be coupled to the first plate50and the second plate40using fixing members such as screws or bolts. However, this is a non-limiting example. The circuit units70may be placed between the covers60and the battery cells10. The circuit units70are connected to the electrode leads15of the battery cells10and include the connection terminals72for connection with an external device. Therefore, the battery cells10may be electrically connected to an external device through the circuit units70. The connection terminals72of the circuit units70are exposed to the outside through the through-holes62formed in the covers60. Therefore, the through-holes62of the covers60are sized according to the size and shape of the connection terminals72. Each of the circuit units70may include a circuit board (for example, a printed circuit board (PCB)) and a plurality of electronic devices (not shown) mounted on the circuit board, and may have a function of sensing the voltage of the battery cells10. In the battery module100of the present embodiment, the first plate50and the second plate40arranged on the upper sides S2and lower side S1of the battery cells10are in contact with the battery cells10with a large area. Therefore, heat generated in the battery cells10may be dissipated through the upper sides S2and lower sides S1of the battery cells10. In addition, since the heat transfer material90is placed in a space between the second sealing portions2022and the second plate40, heat dissipation may occur more effective than in the related art. In addition, since the second sealing portions2022are fixed by the heat transfer material90, upper end portions of the battery cells10may be securely fixed to the second plate40, and thus the battery cells10may not be shaken due to external vibrations or impacts. The present disclosure is not limited to the above-described embodiments, and various modifications may be made in the embodiments. FIG.7is a cross-sectional view schematically illustrating a battery module according to another embodiment of the present disclosure. Referring toFIG.7, the battery module of the present embodiment includes the battery module of the previous embodiment, and a cooling device20is coupled to the lower side of the first plate50and the upper side of the second plate40. In the present embodiment, a water-cooling-type cooling device may be used as the cooling devices20. InFIG.7, cooling plates of the water-cooling-type cooling device which include cooling pipes or cooling passages are partially shown as the cooling device20. However, the present disclosure is not limited thereto. For example, an air-cooling-type cooling device may be used. When the cooling device20is provided on an outer side of the case30as described above, cooling efficiency may be further increased. Although not shown, a thermal pad may be arranged between the cooling device20and the first plate50or the second plate40for effective heat transfer. While exemplary embodiments have been shown and described above, the scope of the present invention is not limited thereto, and it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present invention as defined by the appended claims. For example, although each of the battery cells10includes three sealing portions202in the above-described embodiments, each of the battery cells10may include four sealing portions in other embodiments. In this case, the insertion grooves54may have a size equal to or similar to the size of the accommodation grooves42, and the heat transfer material90may also be placed in the insertion grooves54. In addition, although the first plate50and the second plate40are used as the case30of the battery module100in the above-described embodiments, the first plate50and second plate40may be used only as cooling members, and an additional case may be provided outside the first plate50and the second plate. That is, various modifications may be made. According to the embodiments of the present disclosure, heat generated in the battery cells10of the battery module100may be dissipated through the upper sides S2and lower sides S1of the battery cells10, and owing to the heat transfer material90placed between the sealing portions202and the case30, heat may be dissipated more effectively than in the related. In addition, since the heat transfer material90fixes the sealing portions202, the battery cells10may be securely fixed to the case30without being shaken by external vibrations or impacts. | 19,596 |
11862778 | DETAILED DESCRIPTION In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. In the present specification, an overlapped description for the same components will be omitted. Further, in the present specification, it is to be understood that when one component is referred to as being ‘connected to’ another component, it may be connected directly to another component or be connected to another component with the other component interposed therebetween. On the other hand, in the present specification, it is to be understood that when one component is referred to as being ‘directly connected to’ another component, it may be connected to another component without the other component interposed therebetween. In addition, terms used in the present specification are used only in order to describe specific exemplary embodiments rather than limiting the present invention. Further, in the present specification, singular forms are intended to include plural forms unless the context clearly indicates otherwise. It should be further understood that terms “include” or “have” used in the present specification specify the presence of features, numerals, steps, operations, components, parts mentioned in the present specification, or combinations thereof, but do not preclude the presence or addition of one or more other features, numerals, steps, operations, components, parts, or combinations thereof. Further, in the present specification, a term ‘and/or’ includes a combination of a plurality of stated items or any one of the plurality of stated items. In the present specification, ‘A or B’ may include ‘A’, ‘B’, or ‘both of A and B’. FIG.1illustrates a battery module1000according to an exemplary embodiment of the present invention andFIG.2illustrates a view illustrating a receiving part220illustrated inFIG.1. As illustrated inFIGS.1and2, the battery module1000according to an exemplary embodiment of the present invention includes a cell stack100in which a plurality of unit cells110are aligned in a first direction X and including an insulation member112around (or surrounding) the plurality of unit cells110, and a module housing200in which a plurality of receiving parts220into which the cell stack100is inserted are provided, wherein the receiving part220includes a fixed wall250around (or surrounding) the cell stack100and having at least a portion which is in contact with the cell stack100. The cell stack100includes the plurality of unit cells110aligned in the first direction X. The unit cell100may include an electrode assembly, correspond to one secondary battery including a terminal part, and include a case of various shapes such as a rectangular shape, a cylindrical shape, or the like. FIGS.1and2illustrates the unit cell110having a case having a rectangular pillar shape, but the unit cell110is not necessarily limited thereto, and the unit cell110having the case of the rectangular shape illustrated inFIGS.1and2will hereinafter be described for convenience of explanation. The plurality of unit cells110are aligned in the cell stack100, and an alignment direction of the unit cells110may be various, but the unit cells110may be preferably aligned in a direction in which wide side surfaces of side surfaces of the unit cells110face each other, as illustrated inFIGS.1and2. The alignment direction of the unit cells110will hereinafter be defined as the first direction X. The unit cells110may be disposed or the end supports120may be disposed at both ends of the cell stack100in the first direction X. The number of unit cells110configuring the cell stack100may be various as necessary. The unit cells110included in one cell stack100may be electrically connected with each other by using a bus bar, which can be provided in various shapes, and the like. In the meantime, the cell stack100includes the insulation member112around (or surrounding) the plurality of unit cells110. The insulation member112is formed of an insulating material, such as rubber and plastic, and surrounds the plurality of unit cells110. In one or more embodiments, the insulation member112may also be provided so as to surround end supports120disposed at both ends of the cell stack100in the first direction X together with the plurality of unit cells110, and may surround only the plurality of unit cells110, except for the end supports120, and the end supports120may also be separately disposed at both ends of the cell stack100. The insulation member112may be provided in the form of a film, or a plurality of configurations shaped like a plate having hardness may be provided in the insulation member112. The insulation member112may be provided in the form around (or surrounding) all of the four lateral surfaces of the cell stack100or may be disposed at some of the four lateral surfaces, and may also be provided so as to surround both an upper surface and a lower surface of the cell stack100. However, the insulation member112disposed on the upper surface of the cell stack100may be provided so as to expose the terminal unit of each unit cell110. FIG.1illustrates the state where the insulation member112is prepared in the form of an insulation film to surround the lateral surfaces of the plurality of unit cells110, except for the end supports120, in the cell stack100according to one exemplary embodiment of the present invention. In the module housing200, a plurality of receiving parts220, into and/or onto which the cell stacks100are inserted, is provided.FIG.1illustrates the state where four receiving parts220are formed in the module housing200, and inFIG.2, two receiving parts220are separately illustrated in the module housing200illustrated inFIG.1. The number of receiving parts220provided in the module housing200may be changed as desired. In the module housing200, an outer wall210, which protrudes from a floor surface260in an upper direction and surrounds the floor surface260, is present, and an internal space is formed at an inner side of the outer wall210. The plurality of receiving parts220may be provided in the internal space. A shape of the module housing200may be various, and the module housing200according to one exemplary embodiment of the present invention may be provided so as to have the floor surface260having an approximately quadrangular shape as illustrated inFIGS.1and2. The module housing200may be provided in the form in which an upper portion of the module housing200is opened, and thus, the receiving part220provided in the module housing200may also be provided in the form in which an upper portion of the receiving part220is opened. A module cover may be coupled to the opened upper surface of the module housing200, so that the module housing200may be sealed, and when the module cover is coupled with the module housing200, the module cover corresponds to the upper surface of the receiving part220. The module cover may include a bus bar holder for covering the cell stack100, and bus bars arranged in the bus bar holder to electrically connect the unit cells110constituting the cell stack100. Additionally,FIGS.1and2illustrate the receiving part220according to one exemplary embodiment of the present invention. The receiving part220includes the fixed wall250which surrounds the cell stack100and of which at least a part is in contact with the cell stack100. FIG.1illustrates the state where the portion of the receiving part220into which the cell stack100is inserted, and the portion of the receiving part220into which the cell stack100is not inserted, are disposed in parallel. The fixed wall250corresponds to a boundary wall around (or surrounding) an area of the receiving part220, and the cell stack100inserted into the receiving part220stably maintains a fixed state surrounded by the fixed wall250in four directions. The fixed wall250may be variously disposed according to the form of the cell stack100, but as illustrated inFIG.1, the fixed wall250may have four surfaces, which support four-directional lateral surfaces of the cell stack100while facing the four-directional lateral surfaces, respectively, and be disposed so as to surround the cell stack100. At least a part of the fixed wall250of the receiving part220is in direct contact with the cell stack100. For example, any one surface of the fixed wall250positioned in the first direction X may also be in direct contact with the cell stack100, and any one surface of the fixed wall250positioned in a second direction Y perpendicular to the first direction X may also be in direct contact with the lateral surfaces of the plurality of unit cells110, for example, the insulation member112. The second direction Y may be defined as a direction perpendicular to the first direction X on the same plane as that of the first direction X, and may be defined as a width direction of the unit cell110as illustrated inFIG.1. As described above, in one exemplary embodiment of the present invention, the cell stack100may maintain the shape by the fixed wall250even without a separate component, and may maintain a state pressed in the first direction X. In a case of a related art general battery module, not the battery module1000of the present disclosure, a module frame is coupled to one cell stack and one cell stack, which is coupled with the module frame and is treated as a unit configuration, forms one module. The generally treated cell stack may be coupled with a module frame for a performance aspect, such as energy density, and treatment easiness, and the module frame may be formed of end blocks pressing both ends of the cell stack, side plates extended alongside surfaces of the cell stack, and the like, and the end blocks and the side plates may be coupled with each other in the state where the cell stack is pressed to maintain the structure of the cell stack. In a related art general battery module, the cell stack coupled with the module frame is inserted and the module housing is fastened to the module frame, and the general battery module becomes a battery module having the power amount provided by one cell stack. In the case of the related art general battery module, a plurality of battery modules needs to be provided so as to meet higher power demanded than that of one cell stack, and thus, a module frame fastening the cell units into a unit body and a plurality of components configuring a module itself are additionally required. Therefore, in the related art, a process for manufacturing the battery module may be increased, the consumption for the components may be increased, a weight of the battery module may be increased, and the time and cost required for manufacturing the battery module may be increased. However, in the battery module1000according to one exemplary embodiment of the present invention, the plurality of cell stacks100is mounted to one module, unlike the related art general battery module, which is thus advantageous to meet the high power demanded, and the cell stack100is fixed by the fixed wall250of the receiving part220, of which at least a part is separate from the outer wall210of the module housing200, so that a component, such as a module frame, for fixing the cell stack100, is not separately required. That is, as shown inFIG.1andFIG.2, in one exemplary embodiment of the present disclosure, a plurality of receiving parts220exists in one module housing200, and the fixed wall250around the receiving part220is provided to fix each cell stack100while surrounding the same, unlike the outer wall210of the module housing200. Additionally, as shown inFIG.1toFIG.2, the module housing200according to one exemplary embodiment of the present disclosure may further include end walls240that extend in the second direction Y and may be disposed at both ends of each of the plurality of receiving parts220in the first direction X to each engage (e.g., press or pressurize) the end surfaces of both sides of the cell stack100, and the end wall240may correspond to a part of the fixed wall250. In one exemplary embodiment, the side surfaces of both ends of the cell stack100in the first direction X are defined as the end surfaces, respectively. According to one exemplary embodiment of the present disclosure, the end surface may correspond to the insulation member112or one surface of the end support120. FIGS.1and2illustrate a figure in which the end walls240are disposed at both sides of the cell stack100in the first direction X. A plurality of end walls240may exist in the module housing200and may correspond to both sides of the fixed wall250of the receiving part220in the first direction X. The end wall240may be distinguished from the outer wall210of the module housing200. For example, the end wall240has a shape protruding from the floor surface260in the inner space of the module housing200and extends in the second direction Y, and a plurality of end walls240may be disposed so as to be spaced apart from the outer wall210facing one surface or the other end wall240facing each other. FIG.1illustrates a figure in which a plurality of receiving parts220, for example a total of four receiving parts220are provided with two in the first direction X and two in the second direction Y, and one separation wall230that crosses a portion of the inner space of the module housing200in the first direction X and four end walls240extending in the second direction Y are provided. The separation wall230is shared by the receiving parts220disposed at both sides in the second direction Y, and the end walls240are not shared at both sides in the length direction and the respective end walls240are disposed to be spaced apart from each other (e.g., by a gap) and with surfaces of the two receiving parts220facing each other in the first direction X. That is, the end wall240may be disposed in a way that one side of the end wall240contacts the end surface of the cell stack100that is inserted into the corresponding receiving part220and the other side thereof is disposed apart from an outer wall210that faces thereto or an end wall240of another receiving part220that is disposed in parallel in the first direction X. At least a part of each of the pair of end walls240disposed at both sides of the receiving part220in the first direction X is in direct contact with the facing end surface of the cell stack100, for example, one surface of the end support120. Further, the end wall240may be disposed to press the cell stack100in the first direction X. As described above, in one exemplary embodiment of the present disclosure, the cell stack100inserted into the receiving part220is not fastened with a module frame, such as an end block or a side plate, but is provided in the form of which the lateral surfaces may be surrounded by the insulation member112in the state where the plurality of unit cells110is simply arranged, and in the battery module1000, the end wall240may serve to press and fix the cell stack100in the first direction X. The cell stack100is pressed in the first direction X to provide higher power under the same volume, and may be maintained in a structurally stable state. The cell stack100may be inserted between the fixed walls250of the receiving part220, such as between the pair of end walls240provided at both sides in the first direction X in the state of pressing the end surfaces and being pressed through a zig inserted into the receiving part220, and may maintain a pressed state by the pair of end walls240. FIG.3illustrates a cross section of the module housing200according to an exemplary embodiment of the present invention, and illustrates a figure in which a cooling channel300having a flowing space310in which a coolant flows is formed below the floor surface260.FIG.4illustrates a bottom view of the cooling channel300. As shown inFIG.3, in the battery module1000according to an exemplary embodiment of the present disclosure, the cooling channel300through which the coolant (e.g., coolant water) flows may be formed below the floor surface260of the module housing200. In addition, a plurality of guide protrusions350extending in a flow direction of the coolant and guiding the flow of the coolant may be provided on a lower surface of the floor surface260as illustrated inFIG.4. The flowing space310of the cooling channel300may be formed across the entirety of the floor surface260, or may also be formed to correspond to a cross sectional area of the inner space of the module housing200in which the receiving parts220are formed. For example, in one or more embodiments, the flowing space310of the cooling channel300may not exist below the first impact absorbing space215. The coolant flows through the cooling channel300, and various refrigerants such as air instead of the coolant may also be used. The unit cells110constituting the cell stack100correspond to heating elements that dissipate heat during discharge, and in a case in which the temperature of the unit cells rises excessively, swelling may be induced or a thermal runaway phenomenon may occur where heat is rapidly increased due to abrupt chemical reaction and fire or the like occurs. In addition, in a case in which the cell stack100in which the plurality of unit cells110are aligned is used as in an exemplary embodiment of the present disclosure, when the thermal runaway phenomenon occurs in any one of the unit cells110, a thermal runaway diffusion phenomenon, which affects other peripheral unit cells110, may also occur. As described above, when the plurality of unit cells110are disposed, it is important to adequately cool the heat generated in the cell stack100, and accordingly, the battery module1000according to an exemplary embodiment of the present disclosure efficiently implements the cooling of the entirety of the plurality of cell stacks100by forming the cooling channel300below the bottom surface260of the module housing200. In addition, in an exemplary embodiment of the present disclosure, the maintenance and management of the cooling channel300may be more easily performed by forming the cooling channel300below the bottom surface260of the module housing200rather than the inside of the module housing200, that is, the inner space and the partitioned space of the module housing200. For example, in an exemplary embodiment of the present disclosure, even when a module cover of the module housing200is assembled, the maintenance and management of the cooling channel300from a lower portion of the module housing200can be performed. Additionally, in the battery module1000according to the exemplary embodiment of the present disclosure, the lateral wall320of the cooling channel300protrudes from the floor surface260in the down direction, is extended along a border of the floor surface260and is formed to surround the floor surface260, and the channel cover330is coupled to a lower end of the lateral wall320to seal the cooling channel300. Further, the lateral wall320of the cooling channel300may be integrally formed with the floor surface260of the module housing200through a casting process, and the channel cover330may be welded and coupled to the lateral wall320of the cooling channel300. FIG.3illustrates the state where the lateral wall320of the cooling channel300extends along the border of the floor surface260of the module housing200to surround the floor surface260, and protrudes from the floor surface260in the down direction. In the exemplary embodiment of the present disclosure, the lateral wall320of the cooling channel300is integrally formed with the floor surface260of the module housing200through the cast process, so that a coupling region between the lateral wall320and the floor surface260does not exist, and thus, it is possible to prevent the coolant from unintentionally leaking into the module housing200. The channel cover330sealing the cooling channel300may be coupled to the lateral wall320of the cooling channel300by a method, such as welding, and a border of the channel cover330may be coupled to the lower end of the lateral wall320. The coupling method may be various, but a gasket may be provided or welded for preventing leakage of the coolant, andFIG.13illustrates the cooling channel300viewed from the bottom side in the state where the channel cover330is removed. In an exemplary embodiment of the present disclosure, since lateral walls320of the cooling channel300protrude downward from the floor surface260of the module housing320and an opened lower part of the cooling channel300is coupled with the channel cover330such that the cooling channel300is closed and sealed, the cooling channel300is formed outside the module housing200and thus a risk in operation of the cell stack100due to a leakage of coolant in the cooling channel300can be effectively reduced. In addition, all of the outer wall210and the floor surface260of the module housing200and the lateral wall320of the cooling channel300are integrally formed through the cast process, so that a water leakage possible region does not exist, and further, the cooling channel300is provided in the lower portion of the floor surface260of the module housing200, that is, the outside of the internal space of the module housing200, so that even if the coolant unintentionally leaks from the cooling channel300, it is possible to prevent the coolant from flowing into the internal space of the module housing200, in which the cell stack100is present. As a result, in the exemplary embodiment of the present disclosure, the plurality of cell stacks100is inserted to simplify an assembling process and components and effectively satisfy high power demanded, it is possible to effectively cool the plurality of cell stacks100through the cooling channel300, and further, it is possible to effectively protect the plurality of cell stacks100from the coolant leakage phenomenon in the cooling channel300. Meanwhile,FIG.5illustrates a figure in which a plurality of battery modules according to an exemplary embodiment of the present disclosure are provided and are interconnected. That is,FIG.5illustrates a figure in which the large modules of a battery are coupled to each other to form a large pack. As illustrated inFIG.5, the battery module according to an exemplary embodiment of the present disclosure may further include a coupling part400provided in the module housing200and coupled to the adjacent module housing1001. In the module housing200of the present invention the plurality of receiving parts220are provided to provide the plurality of cell stacks100, thereby effectively achieving high output. In some cases, required power required by an electrical energy consuming device may exceed an output that can be provided by the battery module1000according to the exemplary embodiment of the present invention. The battery modules1000may be coupled to each other to meet the required power, thereby making it possible to realize a large pack structure, andFIG.5illustrates a figure in which the coupling parts400between the corresponding module housing200and the adjacent module housing1001are coupled to each other. The coupling part400may be provided in various types and shapes, andFIG.5illustrates fastening parts410fastened to each other through the fastening member, guide parts420aligning positions of the respective fastening parts410of the corresponding battery module and the adjacent battery module, and connection parts430, which are connection passages of a bus bar436for electrical connection with the adjacent module housing1001according to an exemplary embodiment of the present invention. Additionally, inFIG.6, a coolant line360coupled to the plurality of module housings200is illustrated. As shown inFIG.6, the battery module1000according to the exemplary embodiment of the present invention may further include a coolant line that is connected together with each cooling channel of neighboring module housings200. The coolant line360is provided in the form or a pipe or a tube through which coolant flows, and may supply the coolant to the cooling channel300that is provided below the module housing200or receive the coolant discharged from the cooling channel300. The cooling channel300connected to the coolant line360may cool the plurality of receiving parts240that are disposed above while the coolant flows through the cooling channel300. The coolant line360may be connected to the cooling channel of the corresponding module housing200and cooling channels300of neighboring module housings200. Thus, even when the battery module1000according to the exemplary embodiment of the present invention is provided as a large pack in which a plurality of battery modules1000are coupled to each other, the respective cooling channels300of the plurality of module housings200can be cooled through one coolant line360. The coolant line360may be connected with the respective cooling channel300of the plurality of module housings200through various methods. The coolant line360may be a serial type in which coolant is supplied to one cooling channel300and coolant discharged from the cooling channel300is supplied to the adjacent cooling channel300, and in one or more embodiments the coolant line360may be a parallel type in which any one of the coolant lines360supplies the coolant to the plurality of cooling channels300and the coolant discharged from the plurality of cooling channels300flows in the other coolant line360. Additionally, as shown inFIG.6, in an exemplary embodiment of the present disclosure, the module housing200is coupled to the neighboring module housing200in a second direction Y that is perpendicular to the first direction X, and the coolant line360extends in the second direction Y, and may include a plurality of port connection holes370that are disposed apart from each other along a length direction and coupled to the cooling channel300. Since the module housing200is provided with a plurality of cell stacks100, each in which a plurality of unit cells110are aligned, the module housing200may have a rectangular shape that extends in the first direction X in which the unit cells110are aligned, and the module housing200may include a coupling part400so as to be coupled with the neighboring module housing200in the second direction Y. In addition, the coolant line360may have the plurality of port connection holes370that extend in the second direction Y and are disposed apart from each other so as to be connected to the respective cooling channels300of the plurality of module housings200that are aligned in the second direction Y as described above. In the large pack, the respective port connection holes370may be connected with cooling channels300of different module housings200. InFIG.6, the coolant line360provided with the plurality of port connection holes370is illustrated, andFIG.7illustrates that different port connection holes370are connected to connection ports325that are respectively provided in the cooling channels300. One coolant line360extends in the second direction Y and is connected with a plurality of cooling channels300that are aligned in the second direction Y. That is, the coolant line360according to the exemplary embodiment of the present invention has a parallel form in which coolant is supplied to the plurality of cooling channels300or coolant discharged from the plurality of cooling channels300is recovered. That is, in the exemplary embodiment of the present invention, the coolant line360extends in the second direction Y and thus simultaneously connected to the respective cooling channels300of the plurality of module housings200such that the coolant can be supplied to or recovered from the plurality of cooling channels300, thereby improving structural safety and at the same time improving cooling efficiency. Additionally, as illustrated inFIG.5, in the battery module1000according to an exemplary embodiment of the present disclosure, the coupling parts400may be provided on a first wall211and a second wall212positioned in the second direction Y among the outer wall210of the module housing200, and the coupling part400provided on the second wall212of the module housing200may be coupled to the coupling part400provided on the first wall211of the adjacent module housing1001. The coupling parts400may be disposed in the module housing200, and as shown inFIG.5, may be disposed on the outer wall210of the module housing200. The coupling parts400may be respectively provided in every two sides that face each other among four sides of the outer wall210such that the plurality of battery modules can be coupled to each other. In one or more embodiments, in the battery module1000according to an exemplary embodiment of the present disclosure, since the plurality of cell stacks100are inserted therein and the cell stacks100include the plurality of unit cells110aligned in the first direction X, the module housing200may have a cross section of a rectangular shape having a longer length in the first direction X. Accordingly, even when the plurality of module housings200are aligned in one line or coupled to each other through the coupling parts400, the coupling parts400may be disposed on the first wall211and the second wall212positioned in the second direction Y among the outer wall210of the module housing200so that an entire length of the plurality of module housings200may be reduced. However, a cross-section shape of the module housing200or a location of the coupling part400on the outer wall210may not be limited to the above-stated description. Accordingly, the coupling part400disposed on the first wall211of any one of the module housings200may be coupled to the coupling part400disposed on the second wall212of the other of the module housings facing the first wall211, and the coupling part400disposed on the second wall212of any one of the module housings200may be coupled to the coupling part400disposed on the first wall211of the other of the module housings1001facing the second wall212. Additionally, the coupling part400disposed in the first wall211in the outer wall210of the module housing200is inserted into the coupling part400of the neighboring module housing1001such that the corresponding module housing200and the neighboring module housing1001can be coupled to each other. For example, although it is not illustrated inFIG.5, a fastening part410, a guide pin of a guide part420, and a tunnel insertion part of a connection part430may be disposed in the first wall211. In addition, the coupling part400disposed in the second wall212may be inserted into the coupling part400of the neighboring module housing1001such that the corresponding module housing200and the adjacent module housing1001may be coupled to each other. For example, as shown inFIG.5, a fastening part410, a guide pin of a guide part420, and a connection tunnel of a connection part430may be disposed in the second wall212. However, an insertion relationship and each constituent element of the coupling parts400disposed in the first wall211and the second wall212, respectively, are not limited thereto. FIG.12illustrates a figure in which a plurality of battery modules according to another exemplary embodiment of the present disclosure are provided and are interconnected. That is,FIG.12illustrates a figure in which the battery modules are coupled to each other to form a large pack (e.g., a battery pack). As shown inFIG.12, the coupling parts400are formed on the upper surface (or module cover) and the bottom surface of the battery module, and the coupling parts400between the battery modules adjacent to each other are coupled to each other. Accordingly, the plurality of battery modules may be stacked in the vertical direction (directions perpendicular to the first direction X and the second direction Y) through the coupling parts400. For example, the connection part430disposed on the upper surface of the battery module1000may be inserted into the connection part430disposed on the bottom surface of the adjacent battery module1001. In addition, the connection parts430may be connection passages of the bus bar for electrical connection with the adjacent battery modules. Additionally, as shown inFIG.6, in the battery module1000according to an exemplary embodiment of the present disclosure, the coolant line360includes an inflow line362through which coolant is supplied to the cooling channel300and an outflow line364through which coolant is supplied from the cooling channel300, and the inflow line372is connected to one side of the cooling channel300in the first direction X and the outflow line364is connected to the other side of the cooling channel300in the first direction X. The coolant line360may be formed of the inflow line362and the outflow line362, and the inflow line362transmits coolant supplied to a water source to the cooling channel300and the outflow line362transmits coolant discharged from the cooling channel300back to the water source. The water source stores or supplies coolant, and may be provided in various types and methods, and a cooling system may be provided to re-cool the coolant recovered from the cooling channel300. As shown inFIG.6, the inflow line362and the outflow line364may be extended in the second direction Y, and each may be connected to the entire cooling channels300. As shown inFIG.5andFIG.6, in one exemplary embodiment of the present disclosure, the plurality of module housings200may be aligned along the second direction Y, and the coupling part400may be disposed in the first wall211and the second wall212of the second direction Y among the outer walls210of the module housing200. That is, when the plurality of module housing200are coupled to each other, each module housing200may be coupled with a module housing1001of which first and second walls211and212of the respective module housings are neighbored with each other, and accordingly, the coolant line260may be connected to the lateral wall320that is disposed on the first direction X of the cooling channel300. In one embodiment, the inflow line362may be connected on one lateral wall disposed on the first direction X among lateral walls320of the cooling channel300, and the outflow line364may be connected on the other lateral wall, that is, the opposite lateral wall disposed in the first direction X among the lateral walls of the cooling channel300. In the cooling channel300, the inflow line362and the outflow line362are disposed opposite to each other, and accordingly, in one exemplary embodiment of the present disclosure, the coolant can flow along the first direction X without consuming additional power in the cooling channel300. In addition, since the plurality of cooling channels300receive the coolant in a parallel manner, the plurality of cooling channels300substantially receive the cooing water having the same water temperature, thereby improving cooling performance. Meanwhile,FIG.8illustrates the connection portion325where the port connection hole370is engaged. In the drawing, the port connection hole370shown inFIG.7is omitted. In an exemplary embodiment of the present disclosure, at least one of the plurality of port connection holes370may have a different diameter from the rest. In one exemplary embodiment of the present disclosure, the coolant line360is extended in the second direction Y and enables supplying coolant to the plurality of cooling channels300that are aligned in the second direction Y. However, the number of receiving parts240formed in the module housing200may be different as desired as described above, and when each of the plurality of module housings200that are coupled to each other has a different number of receiving parts240, the amount of coolant required for each module housing200may be different from one another. In one or more embodiments, the amount of coolant supplied to the plurality of cooling channels300connected to one coolant line360may be different from each other depending on a distance from a water source. Accordingly, in the exemplary embodiment of the present invention, at least one of the plurality of port connection holes370provided in the coolant line360is different in diameter from the rest so as to set a flow amount of coolant differently for each cooling channel300. The port connection hole370may be provided in a form that can be coupled to or separated from the coolant line360, and accordingly, when a diameter of one port connection hole370is changed, the corresponding port connection hole370can be removed and a port connection hole370having a different diameter may be coupled to the corresponding location to thereby adjust a diameter. The connection port325shown inFIG.8may be integrally formed with the cooling channel300, or may be manufactured as a separate injection product and coupled to an opening of the cooling channel300. The connection port325may be provided with a predetermined diameter range so that a plurality of port connection holes370of which diameters are included in the range can be coupled to the connection port325, or may be exchangeable with another connection port325having a diameter that corresponding to a diameter of the corresponding port connection hole370. Additionally, referring back toFIG.1andFIG.2, in the battery module1000according to an exemplary embodiment of the present disclosure, the module housing200may further include the separation wall230that extends in the first direction X, and partitions the inner space surrounded by the outer wall210to contribute to form the plurality of receiving parts220, and the separation wall230may configure a portion of the fixed walls250of the two receiving parts220disposed at both sides along the second direction Y, and may be in contact with the side surfaces of the cell stack100inserted into each of the two receiving parts220. The side surfaces refer to both side surfaces extending in the first direction X among the side surfaces of the cell stack, and as described above, since the cell stack100according to the present invention does not include the separate module frame, the side surfaces may correspond to the insulation member112around (or surrounding) the side surfaces of the plurality of unit cells110. The separation wall230may be provided to protrude upwardly from a floor surface260of the module housing200, and may be provided to divide the inner space of the module housing200while extending along the first direction X. That is, the separation wall230may correspond to a portion of the fixed wall250around (or surrounding) the receiving part220, that is, one surface thereof. Referring toFIGS.1and2, the receiving parts220are formed at both sides of the separation wall230, and the separation wall230becomes the fixed wall250for the two receiving parts220formed at both sides thereof. Referring toFIG.2, the separation wall230faces the side surfaces of the cell stack100inserted into the receiving part220, and accordingly, the separation wall230corresponding to a portion of the fixed wall250is in direct contact with at least a portion of the side surfaces of the cell stack100inserted into the receiving part220to thereby support the cell stack100in the second direction Y. Additionally, inFIG.2, a part of the plurality of end walls240is provided at a distance from the outer wall210of the module housing200, andFIG.9shows the end wall240spaced by a distance from the outer wall210, viewed from the top side. In an exemplary embodiment of the present disclosure, the end wall240among the end walls240, which is disposed so that one surface faces the outer wall210of the module housing200, may be spaced apart from the outer wall210in the first direction X and form the first impact absorption space215between the end wall240and the outer wall210. In an exemplary embodiment of the present disclosure, the plurality of end walls240may be provided as illustrated inFIGS.1and2, the end wall240facing the outer wall210among the plurality of end walls240may be spaced apart from the facing outer wall210of the module housing200in the first direction X and form the first impact absorption space215between the end wall240and the outer wall210as illustrated inFIG.2andFIG.9. FIG.9illustrates the end wall240among the end walls240facing the outer wall210of the module housing200configuring the fixed wall250of the receiving part220, and illustrates the first impact absorption space215formed between the end wall240and the outer wall210. The module housing200needs to safely protect the cell stack100inserted into the receiving part220against the impact transferred from the outside, and in an exemplary embodiment of the present among the end walls240, the end wall240, which is in direct contact with the end surface of the cell stack100and supports and presses the cell stack100, is spaced apart from the outer wall210, thereby preventing the impact transferred to the outer wall210from being directly transferred to the end wall240. Further, the safety of the battery can be improved because the impact transmitted from outside the module housing200by the first impact absorption space215is transmitted to the end wall240and the cell stack100in a reduced state. Further, it is important to appropriately cool the unit cell110heating during use process, and the first impact absorption space215itself may advantageously serve as a heat radiating space, in which heat of the cell stack100is dispersed. Additionally, in an exemplary embodiment of the present disclosure, as illustrated inFIGS.1and2, the plurality of receiving parts220is disposed in the internal space of the module housing200in the first direction X, and in two receiving parts220adjacent in the first direction X, the end walls240disposed on surfaces facing in the first direction X are spaced apart from each other to form the second impact absorption space216between the end walls240. InFIG.1, the module housing200where four receiving parts220are formed depending on the exemplary embodiment of the present invention is illustrated, and every two receiving parts220are aligned along the first direction X. However, the number of receiving parts220aligned along the first direction X may be different in one or more other embodiments. In each of the two receiving parts220adjacent to each other in the first direction X, one surface, in which the fixed wall250of one receiving part220faces the fixed wall250of the other receiving part220, the two receiving parts220have different end walls240facing each other. That is, the receiving parts220arranged in the first direction X do not share the end wall240. Referring toFIG.2, it is illustrated the case where in the two receiving parts220arranged in the first direction X, the end walls240facing each other are spaced apart from each other, and the second impact absorption space216is formed between the end walls240. The second impact absorption space216protects the cell stack100inserted into the corresponding receiving part220from the impact transferred from the outside of the receiving part220, like the first impact absorption space215. For example, the first impact absorption space215may suppress the impact transferred form the outer wall210of the module housing200from being transferred to the internal space of the module housing200, and the second impact absorption space216may suppress the impact transferred to any one receiving part220from being transferred to the other receiving part220adjacent in the first direction X. Additionally,FIG.9illustrates that the end support120is disposed at an outer side of the outermost cell of the cell stack100, andFIG.11shows an end surface of the end support120. As illustrated inFIGS.9and11, in the battery module1000according to an exemplary embodiment of the present disclosure, the cell stack100may further include one pair of end supports120, which is disposed at both end portions in the first direction X and of which an outer surface corresponds to the end surface. In an exemplary embodiment of the present disclosure, the plurality of unit cells110is provided in the form of which at least the lateral surface is surrounded by the insulation member112, and the end supports120may be disposed in the form in which the inner surface of each of the end supports120is in surface contact with the insulation member112, at both ends of the cell stack100in the first direction X. However, a positional relationship between the insulation member112and the end support120are not essentially limited thereto. The end supports120are disposed at both ends of the cell stack100in the first direction X, and the outer surfaces of the end supports120may correspond to the end surfaces. The end support120may serve to absorb impact between the end wall240and the plurality of unit cells110, and may serve to uniformly transfer pressing force of the end wall240to the outermost cell among the plurality of unit cells110. The outermost cell means the unit cell100positioned at the outermost side in the first direction X among the plurality of unit cells110configuring the cell stack100, and in an exemplary embodiment of the present disclosure, the outermost cell is disposed at each of both ends in the first direction X among the plurality of unit cells110. Even though the end wall240does not press the end support120with the entire surface thereof because the end wall240has the bent shape and the like, the end support120may press the insulation member112and the outer surface of the outermost cell with the entire surface thereof. Additionally,FIG.9illustrates the end wall240, which is bent so that the center portion is further from the end surface, andFIG.10illustrates the inner surface looking at the end surface of the cell stack100in the bent end wall240. As shown inFIGS.9and10, in the battery module according to an exemplary embodiment of the present disclosure, the end wall240is bent to the outside so that the center portion of the end wall240is further from the facing end surface, so that a swelling space217may be formed between the end wall240and the end surface. The end wall240may be formed in the shape bent so that the center portion of the end wall240is further from the end surface that faces in the cell stack100inserted into the receiving part220. Only the center portion may be concavely indented based in the second direction Y and the height direction, but the end wall240may be provided in the form bent so that the cross-section of the end wall240is curved, as illustrated inFIG.9. The end wall240has the bent shape, so that a space is formed at least the center portion between the end wall240and the end surface of the cell stack100, and the corresponding space corresponds to the swelling space217in an exemplary embodiment of the present disclosure. In the unit cell110of the cell stack100, a swelling phenomenon, in which gas is generated from the internal electrode assembly and is expanded, may be generated according to deterioration of durability by the use and a peripheral situation, and the implementation of the structure, which is capable of appropriately treating the swelling, is beneficial in the structure, in which the plurality of unit cells110is arranged. For example, when swelling occurs in any one of unit cells110, other unit cells110of the cell stack100that includes the corresponding unit cell110may possibly experience the swelling, and when the swelling occurs in one unit cell110among the entire unit cells110and thus a thickness is increased, the entire length of the cell stack110may be greatly affected. Further, the length change of the cell stack100may affect the end wall240that presses the cell stack100in the first direction X such that a damage and the like may be caused. When the swelling phenomenon occurs, the unit cells110have a large amount of expansion of the central portion on the side surface positioned in the first direction X due to structural characteristics thereof, and accordingly, in an exemplary embodiment of the present disclosure, the swelling space217is formed between the end wall240and the end surface so as to accommodate a volume expansion of the cell stack100due to the swelling when the swelling phenomenon of the cell stack100occurs. Additionally, as described above, the cell stack100may be pressed or pressurized in the first direction X in terms of efficiency such as energy density and the like, and in an exemplary embodiment of the present invention, even though the central portion of the end wall240pressurizing the end surface is bent to be recessed, since at least the both end sides of the end wall240maintain a pressed or pressurized state of the end surface, the cell stack100is advantageously operated. Furthermore, as shown inFIG.9andFIG.11, the end surface may be concavely indented such that a center portion of the end surface may be away from the facing end wall240. That is, the end wall240may have a shape in which a center portion of the end surface is concave. In an embodiment in which the end support120is provided, the end surface corresponding to the outer surface of the end support120may have the shape, in which the center portion of the end surface is indented, so that a space is formed in at least the center portion between the end surface and the end wall240similar to the end wall240having the bent shape, and thus the swelling space217may be formed in at least the center portion between the end support120and the end wall240. For example, if swelling occurs in at least one of the plurality of unit cells110and thus a center portion of the unit cell110is expanded, a center portion of the end support120is pressed toward the end wall240due to the expansion of the center portion of the plurality of unit cells110. However, the center portion of the end surface of the end support120is inwardly concave such that even when the center portion of the end support120is pressed to the outside or deformed, deformation or damage to the end wall240can be suppressed or prevented by the swelling space217formed between the end support120and the end wall240. Additionally, as shown inFIG.2andFIG.9, a plurality of first ribs242may be formed in the end wall240according to the exemplary embodiment of the present invention. Particularly, the end wall240may include the plurality of first ribs242on the outer surface based on the first direction X. In one or more embodiments, the end wall240is strong against impact from the outside while pressing the end surface of the cell stack100, and further, even when the swelling space217is formed, the end wall240has mechanical strength, by which the end wall240is prevented from being damaged. Accordingly, in an exemplary embodiment of the present disclosure, as illustrated inFIGS.2and9, the plurality of first ribs242may be provided in the outer surface of the end wall240, that is, one surface facing the outer wall210or a surface opposite to the cell stack100. The first rib242is formed on the outer surface of the end wall240for protecting the cell stack100. The outer surface of the end wall240means a surface facing the opposite side of the end support120. The first rib242may be separately manufactured and be coupled to the end wall240, and the first rib242may be integrally formed with the end wall240by a cast process. As illustrated inFIGS.2and9, the plurality of first ribs242may be extended in the height direction of the end wall240, and may be spaced apart from each other in the second direction Y. The first rib242may be provided in the form extended in the height direction of the end wall240, that is, may be extended toward the top side from the bottom side260of the module housing200. Accordingly, the first rib242may effectively improve strength of the end wall240and may be integrally formed with the end wall240in a cast process using an upper mold and a lower mold. Further, the plurality of first ribs242is spaced apart from each other in the second direction Y, thereby achieving uniformly and stably improving strength for the entire end wall240.FIG.9illustrates a cross-section of the plurality of first ribs242spaced apart from each other in the second direction Y. Additionally,FIG.11illustrates the end support120in which the plurality of second ribs122is formed on the end surface. As shown inFIG.11, in an exemplary embodiment of the present disclosure, the end support120may include the plurality of second ribs122that protrude toward the end wall240in the end surface. Swelling force transferred from the plurality of unit cells110is applied to the end support120at the time of the generation of swelling and the end support120responds to expansion of the unit cells110, and therefore in one or more embodiments the end support120is strong again transformation and damage due to the swelling phenomenon. Accordingly, the second rib122is formed on the end surface of the end support120to improve strength of the end support120. That is, an inner surface of the end support120, that is, the surface opposite to the end surface, is in surface contact with the outermost cell of the cell stack100or the insulation member112to uniformly secure pressing performance, and the second ribs122are formed on the end surface of the end support120. Further, as illustrated inFIG.5, in n exemplary embodiment of the present disclosure, the second ribs122may be spaced apart from each other in the second direction Y and the height direction of the end support120so as to form a lattice shape. Referring toFIG.11, in an exemplary embodiment of the present disclosure, the second ribs122may be formed to approximately cross the entirety of the end surface in the extension direction, and some of the plurality of second ribs122are extended in the second direction Y and the remaining second ribs122are extended in the height direction of the end support120, so that the plurality of second ribs122may be disposed to form a lattice form. That is, the plurality of second ribs122may be disposed to be spaced apart from each other in the second direction Y and the height direction of the end support120to form a lattice shape, and accordingly, robustness of the end support120can be effectively improved. That is, in the end support120, quadrangular recesses may be approximately disposed in the lattice shape on the end surface, and the second rib122may be separately manufactured and be coupled to the end surface of the end support120or be integrally formed with the end support120when the end support120is manufactured. Additionally, in an exemplary embodiment of the present disclosure, the fixed wall250of any one receiving part220may be defined to include the separation wall230, one pair of end walls240, and a part of the outer wall210, and the separation wall230and the end walls240may be integrally formed through a cast process or the like. Further, as illustrated inFIG.2, in an exemplary embodiment of the present disclosure, one surface among the four surfaces of the fixed wall250corresponds to the separation wall230, two other surfaces correspond to the end walls, respectively, and one remaining surface may be formed of the outer wall210of the module housing200. In the battery module1000according to n exemplary embodiment of the present disclosure, the end walls240, the separation wall230, and the outer wall210may be integrally formed with the floor surface260of the module housing200by a cast process. That is, in an exemplary embodiment of the present disclosure, the end walls240and the separation walls230may be integrally formed with the module housing200, and when a mold is manufacturing for the cast process, intaglio (i.e., an engraving) of the end walls240and the separation wall230may be integrally formed in the mold. Further, in an exemplary embodiment of the present disclosure, the end walls240and the separation wall230may also be integrally formed with the outer wall210of the module housing200. In this case, in the module housing200, all of the outer wall210, the separation wall230, the end walls240, and the floor surface260may be integrally formed. As described, in the module housing200to which the end wall240and the separation wall230are integrally formed, an additional manufacturing process for including the end wall240and the separation wall230are components can be omitted, and as previously described, even when a module frame is omitted by the end wall240and the separation wall230, the cell stack100can be stably fixed while the plurality of unit cells110are in a pressed stated in the receiving parts220. While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Description of symbols100: cell stack110: unit cell120: end support122: second rib200: module housing210: outer wall of module housing211: first wall212: second wall215: first impact absorption space216: second impact absorptionspace220: receiving part230: separation wall240: end wall242: first rib250: fixed wall260: floor surface of module housing300: cooling channel310: flowing space320: lateral wall of cooling channel325: connection port330: channel cover350: guide protrusion360: coolant line362: inflow line364: outflow line370: port connection hole400: coupling part410: fastening part420: guide part430: connection part1000: battery module | 58,109 |
11862779 | DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS The various cooling systems disclosed herein include arrangements in which certain electronic components can be cooled using separate cooling loops for improved efficiency. For example, in order to reduce the chiller energy consumption to improve system efficiency, the batteries can have a separate coolant loop than the motor/generator and power electronics during higher ambient conditions. With reference toFIG.1, there is illustrated a schematic depiction an exemplary cooling system100including coolant reservoir120providing coolant to an outer coolant loop111, and a fan124operable to provide cooling air to low temperature radiator122. Low temperature radiator122lowers the temperature of the coolant in outer coolant loop111and, in certain operating conditions, of the coolant in an inner coolant loop113. Outer coolant loop111provides the lower temperature coolant from low temperature radiator122to power electronics110and to a motor/generator112downstream from power electronics110. The heat from power electronics110and motor/generator112is transferred to the coolant in outer coolant loop111and provided to pump132downstream from motor generator112for circulation through low temperature radiator122to lower the coolant temperature. Inner coolant loop113is flow connected with outer coolant loop111via a first three-way valve134and a second three-way valve136. In certain lower ambient temperature conditions, coolant from low temperature radiator122is provided to inner coolant loop113from outer coolant loop111through first three-way valve134for circulation through coolant chiller126and battery cold plate118, and then the coolant that is heated by the battery114is returned to outer loop111through second three-way valve136. Although the discussion herein references a battery specifically, any suitable energy storage device for an electrified powertrain is contemplated as may be known in the art. Inner loop113can be flow isolated from outer coolant loop111in high ambient temperature conditions using three-way valves134,136and the coolant is circulated within the closed inner loop113using the second coolant pump130. The coolant chiller126is connected with the cabin A/C refrigerant loop140, which is fluidly isolated from but in thermal communication with the coolant in inner coolant loop113within coolant chiller126. Inner coolant loop113provides coolant to battery cold plate118downstream from coolant chiller126that is cooled by the A/C refrigerant loop140during higher temperature ambient conditions. The battery cold plate118may be thermally coupled to battery114with an electric heater116therebetween, although any suitable battery arrangement is contemplated. With reference toFIG.2, there is illustrated a schematic depiction of certain portions of another embodiment cooling system200that is similar to cooling system100except that the low temperature radiator122is replaced with a waste heat recovery system (WHR)220. WHR system220includes a WHR working fluid236that is circulated through a WHR heat exchanger222and WHR boiler234downstream from WHR heat exchanger222. The working fluid236is isolated from but in thermal communication with the coolant in the outer coolant loop111inside of WHR heat exchanger222. The WHR heat exchanger222receives the heat from the coolant in outer coolant loop111and, in certain low ambient temperature operating conditions, the inner coolant loop213to provide a lower temperature coolant for circulation through power electronics110and motor/generator112and battery114. WHR heat exchanger222does not provide lower temperature coolant to inner coolant loop113during higher ambient temperature conditions. Rather, the coolant in inner loop113is flow isolated from outer loop111as discussed above, and the coolant is circulated within inner loop113and cooled with cabin A/C refrigerant circulated through coolant chiller126 With reference toFIG.3, there is illustrated another embodiment cooling system300that is similar to cooling system200except that a second coolant loop313is provided as a separate cooling system302that does not share coolant with outer coolant loop111under any operating conditions. The cooling system302includes a first coolant reservoir310providing coolant to second coolant loop313. The second coolant loop313is provided with coolant from second coolant reservoir310. Second coolant loop313provides coolant to battery cold plate318. Battery cold plate318is thermally coupled to battery314with electric heater316therebetween. Second coolant loop313then provides coolant heated from the battery314to a second pump330downstream from battery cold plate318. Second pump330circulates the heated coolant to coolant chiller326downstream from second pump330. Cabin A/C refrigerant140is provided to coolant chiller326through cabin A/C refrigerant loop117to cool the heated coolant before it is circulated back to the battery cold plate318. In this embodiment, the cabin A/C refrigerant provides all the cooling for battery314, whereas in the embodiments ofFIGS.1and2the cabin A/C refrigerant only provides cooling of the battery during higher temperature ambient conditions. With reference toFIG.4, there is illustrated a schematic depiction of another embodiment cooling system400including WHR refrigerant417feeding coolant to a first coolant loop411. The first coolant loop411provides coolant for cooling of power electronics410and motor/generator412, and the heated coolant is circulated through WHR heat exchanger422. The heated working fluid from WHR heat exchanger422is circulated WHR boiler415. Cooling system400also includes a second coolant loop413. Second coolant loop413includes a pump430that circulates coolant heated by battery414for cooling by coolant WHR heat exchanger422during lower temperature ambient conditions. Second coolant loop413circulates coolant from WHR heat exchanger422to coolant chiller426and then to battery cold plate418which is thermally coupled to battery414with electric heater416therebetween. Depending on the position of three-way valve436, pump430circulates coolant to either coolant WHR heat exchanger422during a low temperature ambient condition, or for recirculation within second coolant loop413(bypassing WHR exchanger422) during high temperature ambient conditions. During lower temperature ambient conditions, the coolant in second coolant loop413is circulated through coolant WHR heat exchanger422to lower the temperature of the coolant. During the high temperature ambient conditions, the cabin A/C refrigerant140is provided to coolant chiller426via the cabin A/C refrigerant loop117, which is isolated from second coolant loop413, in order to cool the coolant in the second coolant loop413. With reference toFIG.5, there is illustrated another embodiment cooling system500including WHR refrigerant534provided from, for example, a feed-pump (not shown). The WHR refrigerant534is provided to WHR refrigerant loop515, which provides refrigerant to refrigerant heat exchanger532to exchange heat with the coolant from coolant chiller526during certain operating conditions. Refrigerant coolant loop515then provides refrigerant to coolant heat exchanger530downstream from refrigerant heat exchanger532. Refrigerant loop515then provides refrigerant to WHR system536downstream from coolant heat exchanger530. In one embodiment, the WHR system536, and the WHR systems ofFIGS.2-4, is an Organic Rankine Cycle WHR system. Coolant reservoir524provides coolant to first coolant loop511. First coolant loop511includes a first pump528which circulates coolant through coolant heat exchanger530, power electronics510, and motor/generator512. The coolant in first coolant loop511is isolated from but in thermal communication with the WHR refrigerant in refrigerant loop515within coolant heat exchanger530. First coolant loop511also provides coolant to three-way valve535that is located between a first portion513aand a second portion513bof a second coolant loop513downstream from coolant heat exchanger530. As discussed below, the positioning of three-way valve535can be used to control whether the coolant from first loop511is circulated in second coolant loop513to receive heat from the battery514and returned to first coolant loop511, or is circulated in a closed loop within second coolant loop513formed in part by second portion513bfor a heat exchange with refrigerant circulated in a third coolant loop519. The third coolant loop519provides a coolant flow path from coolant chiller526to refrigerant heat exchanger532under certain operating conditions. For example, as shown inFIG.6, the modified cooling system500′ is shown with active flow paths during a hot or higher temperature ambient temperature condition. In cooling system500′ the three-way valve535and two-way valve520are positioned so that a first coolant or refrigerant is circulated through third coolant loop519and coolant chiller526, and that the coolant from first loop511is recirculated through coolant chiller526with pump538in a closed loop formed by second portion513aof the second coolant loop513. The first coolant loop511is thus isolated from the third coolant loop519from providing coolant for cooling the battery514, which may include cold plate516and heater518. The refrigerant or coolant in third coolant loop519receives the heat from the battery514via a heat exchange in coolant chiller526, and can be compressed with compressor522in a vapor compression cycle before being returned to refrigerant heat exchanger532. With reference toFIG.7, there is illustrated the active coolant flow paths of the cooling system500during a lower ambient temperature operation, as indicated by cooling system500″. InFIG.7the two-way valve520is closed to prevent circulation through third coolant loop519, and the three-way valve535is positioned so that coolant from first coolant loop511is circulated through coolant chiller526and to receive heat from battery514and back into first coolant loop511. The heat from battery514is transferred to the coolant and returned to coolant heat exchanger530during this operating condition, rather than being returned to the refrigerant heat exchanger532through the refrigerant in third loop519as occurs in theFIG.6operation. With reference to the embodiments inFIGS.1and2the chiller energy consumption may be improved by flow isolating the second or inner coolant loop113for the batteries from the first or outer coolant loop111for the motor/generator112and power electronics114during higher temperature ambient conditions. The inner coolant loop113is isolated by utilizing the three-way valves134,136and pump130to segregate the cooling of battery114during warmer ambient temperature conditions. In theFIG.3embodiment, a separate second low temperature (lower coolant temperature for cooling) loop313for the battery314cooling is utilized with a separate first high temperature (higher coolant temperature for cooling) loop111for power electronics110and motor/generator112. This embodiment may have the benefit of reducing the overall coolant chiller326load from the high temperature loop111, but relies exclusively on the coolant chiller326for the low temperature loop313even during cooler ambient conditions. FIGS.2,3,4, and5illustrate embodiments with the usage of a WHR system. The WHR working fluid236,417,534out of the WHR heat exchanger provides a near ambient temperature heat sink within coolant WHR heat exchanger222,422,532that can be utilized without the need to integrate a separate low temperature radiator. With reference to the embodiments ofFIGS.1,2,3,4the cabin A/C refrigerant140is utilized to cool the areas requiring lower temperature cooling, like the batteries114,314,414. These embodiments may be modified to include a separate vapor compression cycle like cooling system500to transfer heat from the battery cooling loop to another cooling loop which is either a WHR working fluid loop or a refrigerant coolant loop, particularly when the ambient temperature is too high for direct cooling with the WHR working fluid534or low temperature coolant. According to one aspect of the present disclosure, a cooling system for an electrified vehicle includes a first cooling loop and a second cooling loop. The first cooling loop circulates coolant for cooling at least one of power electronics and a motor/generator of the vehicle. The first cooling loop includes a heat exchanger for exchanging heat with the coolant in the first cooling loop. The second cooling loop circulates coolant for cooling an energy storage device of the vehicle. The second cooling loop includes a coolant chiller connected to a refrigeration system of the vehicle for exchanging heat in the coolant received from the energy storage device with the refrigeration system of the vehicle. In one embodiment, the heat exchanger is a radiator. In one embodiment, at least one of the first and second cooling loops includes a pump for circulating coolant. In one embodiment, each of the first and second cooling loops includes a pump for circulating coolant. In one embodiment, the refrigeration system is part of a cabin refrigeration system for the vehicle. In one embodiment, the heat exchanger is part of a WHR system of the vehicle. In one embodiment, the second cooling loop is connected to the first cooling loop with a flow control valve, and the flow control valve is positionable to isolate the coolant in the second cooling loop in response to a first ambient temperature condition, and the flow control valve is positionable to allow coolant flow from the second cooling loop to the first cooling loop in response to a second ambient temperature condition. In one embodiment, the second cooling loop is completely separate from the first cooling loop. In one embodiment, the coolant in the first cooling loop is in thermal communication with a WHR refrigerant from the WHR system. In one embodiment, the refrigeration system is part of the WHR system and includes a refrigerant heat exchanger and the coolant chiller is connected to the refrigerant heat exchanger with a third cooling loop. In one embodiment, the third cooling loop includes a compressor for compressing refrigerant from the coolant chiller. In one embodiment, the third cooling loop includes a flow control valve to selectively allow circulation of refrigerant in the third cooling loop in response to an ambient temperature condition greater than a threshold. In one embodiment, the second cooling loop is connected to the first cooling loop with a second flow control valve, and the second flow control valve is positionable to isolate the coolant in the second cooling loop in response to the ambient temperature condition being greater than the threshold for recirculation of the coolant in the second cooling loop, and the second flow control valve is positionable to allow coolant flow from the first cooling loop, through the second cooling loop and the coolant chiller, and back to the first cooling loop in response to the ambient temperature condition being less than the threshold. According to another aspect, a method for operating an electrified vehicle cooling system includes: circulating coolant in a first cooling loop to cool at least one of power electronics and a motor/generator of the vehicle, where the first cooling loop includes a heat exchanger for exchanging heat with the coolant in the first cooling loop; and circulating coolant in a second cooling loop to cool an energy storage device of the vehicle, where the second cooling loop includes a coolant chiller connected to a refrigeration system of the vehicle for exchanging heat in the coolant received from the energy storage device with the refrigeration system of the vehicle. In one embodiment, the method includes positioning a flow control valve that connects the second cooling loop to the first cooling loop to isolate the coolant in the second cooling loop in response to a first ambient temperature condition; and positioning the flow control valve to allow coolant flow from the second cooling loop to the first cooling loop in response to a second ambient temperature condition. In one embodiment, the second cooling loop is completely separate from the first cooling loop, and the coolant in the first cooling loop is in thermal communication with a WHR refrigerant from a WHR system of the vehicle. In one embodiment, the refrigeration system is part of the WHR system and includes a refrigerant heat exchanger and the coolant chiller is connected to the refrigerant heat exchanger with a third cooling loop. In one embodiment, the third cooling loop includes a compressor for compressing refrigerant from the coolant chiller and a flow control valve to selectively allow circulation of refrigerant in the third cooling loop in response to an ambient temperature condition greater than a threshold. In one embodiment, the method includes positioning a second flow control valve connecting the second cooling loop to the first cooling loop to isolate the coolant in the second cooling loop in response to the ambient temperature condition being greater than the threshold for recirculation of the coolant in the second cooling loop. The method further includes positioning the second flow control valve to allow coolant flow from the first cooling loop, through the second cooling loop and the coolant chiller, and back to the first cooling loop in response to the ambient temperature condition being less than the threshold. In one embodiment, the refrigeration system is part of a cabin refrigeration system for the vehicle. The present disclosure further contemplates that an electronic control apparatus can be employed for operating the systems and/or for performing the methods disclosed herein. While illustrative embodiments of the disclosure have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain exemplary embodiments have been shown and described and that all changes and modifications that come within the spirit of the claimed inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary. Non-limiting examples of what may be claimed in one or more non-provisional applications claiming priority to the present application include the following. | 19,237 |
11862780 | DETAILED DESCRIPTION In the following detailed description, reference will be made to the accompanying drawing(s), in which identical functional elements are designated with like numerals. The aforementioned accompanying drawings show by way of illustration, and not by way of limitation, specific embodiments and implementations consistent with principles of the present invention. These implementations are described in sufficient detail to enable those skilled in the art to practice the invention and it is to be understood that other implementations may be utilized and that structural changes and/or substitutions of various elements may be made without departing from the scope and spirit of present invention. The following detailed description is, therefore, not to be construed in a limited sense. Below, we propose a novel, alternative hybrid system100for integrating a fuel cell stack and a battery that eliminates the need for both the DC/DC power converter between the battery112and the fuel cell stack (e.g., fuel cell system200), and the boost converter between the battery112and the propulsion inverter. The propulsion inverter is configured to convert alternating current to direct current for actuating motors in electrical communication with the motors. This system results in substantial savings in cost, weight, and power losses compared to state of the art. Specifically, our novel system100consists of the fuel cell stack (e.g., fuel cell system200) and the battery112connected substantially in series, with individual disconnects104,108a,108b, and with bypass diodes116a,116b,116callowing the power flow even when the battery112or the fuel cell system200is removed from the circuit by the disconnect108a,108b. High quality bypass diodes116a,116b,116care inexpensive and light, and at typical 250V fuel cell stack (e.g., fuel cell system200)/battery112voltage levels, the bypass diodes116a,116b,116cmay result in only 0.3-0.5% losses in the system, compared to the state of the art system losses of up to 10%, with corresponding improvement in the complexity and weight of the cooling systems for such a powertrain. The system100may include an output control system130. Furthermore, the system100also contains an output voltage sensor106, a voltage regulating disconnect104(e.g., a field effect transistor (FET)), and an electronic voltage limiting device102that work together with the output control system130to prevent overvoltage on the output of the hybrid system100. An electronic voltage limiting device102, for example, may include a calibrated load/power resistor that is designed to load the output if the voltage exceeds a predetermined value. For example, the voltage sensor106may detect a voltage and the voltage regulating disconnect104may open above a source-drain voltage of about 790V and switch in the voltage limiting device102(e.g., the calibrated load) to provide sufficient load on the fuel cell to avoid overvoltage of the output supply, sufficient to manage most transient conditions (e.g., sudden load drop, before the fuel cell output control system130is able to reduce the fuel cell stack200and/or battery112output). Due to the typical characteristics of fuel cells, a relatively small load (1% of the max power rating) will result in a very significant voltage drop relative to the open circuit voltage. The dissipated power can be used for useful purposes (heating of the passenger compartment, battery recharge, etc). Finally, the output control system130reads the sensors, conducts necessary calculations, and produces commands delivered to the fuel cell system200, disconnects108a,108b,104, and the electronic voltage limiting device102. In one or more embodiments, the proposed connection approach for the battery112and fuel cell stack (e.g., fuel cell system200) results in the output voltage high enough to operate the propulsive system without an intermediate booster, yet without a possibility of overvoltage. In one or more embodiments, the output control system130connects the battery112to the circuit only when the peak/high power is required. An example of a perfect application is an aircraft powertrain, where peak power is needed only on takeoff, while in cruise, only 50-70% of the peak power is required. In the case of such a power profile, the output control system130connects the battery112into the circuit only for the takeoff and initial climb, producing full output voltage and power. Once the initial climb is complete, the system disconnects the battery and the powertrain operates on just a fuel cell stack (e.g., fuel cell system200) at a steady output equivalent to 50-70% of the max system power rating. In one or more embodiments, the battery112can be optionally recharged from the fuel cell stack (e.g., fuel cell system200) via an isolated DC/DC converter. Such DC/DC converter would require a much lower power rating than the original booster converter and therefore would be significantly cheaper and lighter. The overall system weight optimization can be achieved through balancing of the battery112capacity (and therefore weight) and the converter power rating. Below, the Hydrogen fuel cell cathode air compressor118can be powered solely off of battery power will be described. In one or more embodiments, before hydrogen and oxygen are supplied to the anode and cathode of the hydrogen fuel cell stack (e.g., fuel cell system200), we can power up the cathode air compressor118to bring up the hydrogen fuel cell voltage before closing the system #2fuel cell disconnect108b. SeeFIG.1. Below, the Hydrogen fuel cell cathode air compressor118can be powered solely of the hydrogen fuel cell power while the system load is driven off of the battery112and fuel cell (e.g., fuel cell system200) in series will be described. In one or more embodiments, to reduce the energy required from the rechargeable battery system we can bypass the battery112with a single pole double throw relay122on the positive end of the cathode air compressor118. Bypassing the battery112in this manner allows us to extend the power reserves of our system as much as possible. SeeFIG.1. Below, the Hydrogen fuel cell cathode air compressor118which can be powered off the hydrogen fuel cell (e.g., fuel cell system200) and the rechargeable battery112in series will be described. In one or more embodiments, to run the cathode air compressor118as efficiently and at full power we can drive the cathode air compressor118on the combined battery112and fuel cell voltage (e.g., fuel cell system200) using the system100detailed inFIG.1. By closing both the battery and fuel cell disconnects108a,108band not bypassing the battery112with the double pole single throw relay122, we can supply the combined voltage to the cathode air compressor118. SeeFIG.1. Below, the hydrogen fuel cell cathode air compressor118can be started off of the rechargeable battery112and transition to run off of both the rechargeable battery112and fuel cell (e.g., fuel cell system200) in series. In one or more embodiments, the system can start with the fuel cell disconnect108aopen effectively removing the fuel cell (e.g., fuel cell system200) from the circuit, and allowing current to pass through the fuel cell bypass diode116a. Power is applied to the cathode air compressor118, voltage is then present across the fuel cell (e.g., fuel cell system200), and then the fuel cell disconnect108ais closed to bring the system to the full combined stack voltage. SeeFIG.1. Below, the hydrogen fuel cell can charge the rechargeable battery via an isolated DC to DC converter110will be described. In one or more embodiments, when excess power is available from the (e.g., fuel cell system200) it is possible using an isolated DC to DC converter110to charge the battery112to extend the range of the system100. This is desirable because hydrogen has a significant energy density advantage over the currently available battery technologies. SeeFIG.1. Below, a voltage limiting device102is used such that the combined battery112and fuel cell (e.g., fuel cell system200) output voltage cannot exceed a specified high voltage limit will be described. In one or more embodiments, a power resistor and a FET opening above 790V source-drain voltage to provide sufficient load on the fuel cell to avoid overvoltage of the output supply—sufficient to manage most transient situations (e.g., sudden load drop, before the fuel cell output control system130is able to reduce the fuel cell output). Below, the system100provides a method to remove the battery can be removed if its no longer desirable will be described. In one or more embodiments, if the battery is depleted or no longer desired it can be taken out of the circuit by opening the battery system disconnect108a,108b. SeeFIG.1. The system power will then flow through the battery bypass diode keeping the system powered. Reasons to remove the battery include safety. FIG.1illustrates an electrical system diagram—The Hybrid Energy generation system consists of the following items: Fuel Cell: Combines Hydrogen and Oxygen to produce power; Battery: Electrochemical energy storage system; Isolated DC/DC converter: Charges battery from fuel cell, with excess power from fuel cell; Cathode Air Compressor118: Compresses air containing oxygen to supply the cathode of the hydrogen fuel cell. The cathode air compressor118consists of an inverter driving an electric motor which drives a turbine to compress air; Voltage Limiting Device: Prevents the system output voltage from exceeding the voltage limits of the cathode air compressor118; and Voltage sensor106: provides feedback to voltage limiting device, FIG.2illustrates a Fuel Cell diagram. Specific components that can be used in a 200 kw power generation system: To build a 250KW capable system we can use the following components: Diodes116a,116b,116c—APTDF400U120G. This diode is capable of running in systems up to 1200V and is capable of operating at 400A continuously with 750A surges. Isolated DC to DC converter110—Isolated DC/DC Converter 27kW—300-400V to 500-700V Reversible. This isolated DC to DC converter110can convert the optimal 300V fuel cell to a 700 combined stack voltage if connected as an additive DC to DC converter. Disconnects—KILOVAC LEV200 Series Contactor With 1 Form X Contacts Rated 500+ Amps, 12-900Vd—This contactor is capable of running in systems up to 900V and is capable of operating at 500A continuously with 1000A surges. Single Pole Double Throw Relay—GIGAVAC 15 kV SPDT HV Relay—This relay is capable of running in systems up to 15 KV and is capable of operating at 45A continuously. This is capable of conducting the power needed to supply 27KW at 600V, easily supplying a sub 20KW cathode air compressor118. Fuel cell cathode air compressor118—EMTC-120 k Air—This compressor has been configured to supply air to a 120 KW fuel cell system200, running optimally at 17 KW. Finally, it should be understood that processes and techniques described herein are not inherently related to any particular apparatus and may be implemented by any suitable combination of components. Further, various types of general purpose devices may be used in accordance with the teachings described herein. It may also prove advantageous to construct specialized apparatus to perform the method steps described herein. The present invention has been described in relation to particular examples, which are intended in all respects to be illustrative rather than restrictive. Moreover, other implementations of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. Various aspects and/or components of the described embodiments may be used singly or in any combination in aircraft power plants. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims. | 12,040 |
11862781 | DETAILED DESCRIPTION A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. Referring now toFIG.1, illustrated is a schematic of an embodiment of a hydrogen-fueled power system10. Hydrogen fuel12is stored in liquid phase in a hydrogen tank14at, for example, a temperature of 20 degrees Kelvin or less. The hydrogen fuel12flows from the hydrogen tank14, and a first fuel portion12ais directed through a heat exchanger16where it is warmed via thermal energy exchange with a heat transfer fluid18from a heat source. The heated first fuel portion12ais then directed to a thermal engine20as gaseous hydrogen. A second fuel portion12b, which as liquid hydrogen is much colder than the first fuel portion12a, is injected into the thermal engine20from the hydrogen tank14. The liquid hydrogen second fuel portion12bis rapidly expanded at the thermal engine20and is exhausted as gaseous hydrogen fuel12from the thermal engine20at, for example, 300 degrees Kelvin or more. The gaseous hydrogen fuel12is then utilized for power generation at, for example, a fuel cell22. While a fuel cell is discussed and shown inFIG.1, one skilled in the art will readily appreciate that alternative power generation means, such as combustion, may be utilized. Further, in some embodiments and intermediate working fluid, such as gaseous hydrogen or nitrogen, may be utilized to transfer thermal energy between the first fuel portion12aand the second fuel portion12b. Referring now toFIG.2, the thermal energy at the heat exchanger16may be utilized in several ways. In the embodiment ofFIG.2, before flowing to the thermal engine20, the heated first fuel portion12ais flowed from the heat exchanger16through a turbine24to drive rotation of the turbine24and expand the heated first fuel portion12a. From the turbine24, the heated first fuel portion12ais flowed to the thermal engine20. In some embodiments, a fluid separator60is located between the heat exchanger16and the turbine24to remove any condensate or liquid in the first fuel portion12abefore it reaches the turbine24. The turbine24is connected to an electrical generator26and drives the generator26to generate electrical power, which may be utilized to power various components28connected to the generator26either directly or via a power storage unit such as a battery30. The generator26has a volume of lubricant such as oil to lubricate the generator26. This flow of oil32is directed to the heat exchanger16via pump34, where the flow of oil32exchanges thermal energy with the first fuel portion12ato expand the first fuel portion12aand cool the flow of oil32before the flow of oil32is returned to the generator26. In another embodiment, illustrated inFIG.3, the system10includes a compressor64connected to the generator26, which may also be operated as a motor to drive the compressor64, which may be the compressor for the environmental control system (ECS) of the vehicle or aircraft. The compressor64compresses an airflow36from an air source, for example, ambient, and directs the compressed airflow36to the ECS38. Referring now toFIG.4, a cooling loop40using non-freezing working fluids such as Helium, Neon, or Hydrogen is connected to the heat exchanger16from one or more other vehicle components such as motors, electronics, oil system or the ECS38, The cooling loop40provides cooling to the one or more vehicle components, and at the heat exchanger16exchanges thermal energy with the first fuel portion12ato heat the first fuel portion2abefore the first fuel portion12ais directed to the thermal engine20. Referring now toFIG.5, the heat exchanger16may be operated as a distiller42. The distiller utilizes the first flow of fuel12aand a flow of air44to provide oxygen enriched air46and nitrogen enriched exhaust48as will as the heated first fuel portion12a. The gaseous heated first fuel portion12ais directed to the thermal engine20, which in systems10where the power generation means is combustion, the oxygen enriched air46is flowed to a combustor for combustion with the flow of fuel12. Referring now toFIG.6, illustrated is an embodiment of a hydrogen tank14. The hydrogen tank14surrounds the hydrogen fuel12with one or more thermal insulating layers. In one embodiment, such as illustrated inFIG.6, the one or more insulating layers includes two vacuum insulating layers52, with a methane insulating layer54between the vacuum insulating layers52. The methane insulating layer54has a boiling point of 116 degrees Kelvin, and may be utilized for combustion if needed. As shown inFIG.7, in some embodiments the insulating layer54is also a liquid fuel, which may be combusted with the hydrogen fuel12stored in the hydrogen tank. The insulating layer54is for example, methane or a renewable fuel having a low boiling temperature. This insulating layer54may be processed similar to the hydrogen fuel12as inFIGS.2and/or3. For example, as shown inFIG.7a first insulating layer portion54athrough the heat exchanger16where it is warmed via thermal energy exchange with the heat transfer fluid18from a heat source. The heated first insulating layer portion54ais then directed to a thermal engine20as gaseous hydrogen. A second insulting layer portion54b, which as liquid insulating layer material is much colder than the first insulating layer portion54a, is injected into the thermal engine20from the hydrogen tank14. The liquid second insulating layer portion54bis rapidly expanded at the thermal engine20and is exhausted as gaseous insulating layer material54bfrom the thermal engine20at, for example, 300 degrees Kelvin or more. The insulating layer material54bis then utilized for power generation at, for example, a fuel cell22a. While a fuel cell is discussed and shown inFIG.7, one skilled in the art will readily appreciate that alternative power generation means, such as combustion, may be utilized. Utilization of the thermal energy of the hydrogen fuel12when heating the first fuel portion12acan provide an additional onboard power supply, reducing overall power consumption and improve hydrogen-powered vehicle efficiency. The cooling capacity of the liquid hydrogen fuel provides either in cooling to either in flight ECS or Oxygen/Nitrogen enrichment of air for combustion. The use of enriched airflow for combustion may increase combustion efficiency by up to 15%. The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims. | 8,080 |
11862782 | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may properly define the concept of the terms in order to best describe its invention. The terms and words should be construed as meaning and concept consistent with the technical idea of the present invention. In the present invention, “coating end” means not only the case of terminating the electrode slurry coating, but also the case of temporarily stopping the slurry coating. Specifically, it includes the case of terminating or temporarily stopping the operation of the electrode slurry coating apparatus, for example, the case of repeating the progress and interruption of slurry coating to form a patterned active material layer, and the case of stopping the slurry coating. In the present invention, “coating start” is meant to encompass not only the case of starting electrode slurry coating, but also the case of resuming the temporarily stopped slurry coating. Specifically, it includes the case of starting the operation of the electrode slurry coating apparatus or restarting the operation that has been temporarily stopped, for example, the case of repeating the progress and interruption of slurry coating to form a patterned active material layer, and the case of performing the slurry coating. In addition, in the present invention, the “correspondence” of two specific points is meant to encompass cases where the two points are located on the same line or within a similar range thereof. The fact that the two points are located on the same line includes not only the case that they are physically located on the same line, but also a case that they exist within an error range of facility or measurement equipment or a range including a buffer area of a certain level. In general, in manufacturing an electrode, slurry including an active material, a conductive material, and a binder is prepared, discharged onto a current collector to form a slurry layer, and finally, an active material layer (electrode layer) is formed through a drying process. The present invention relates to an electrode slurry coating apparatus and a coating method for manufacturing an electrode having a double-layer active material layer. First, the present invention relates to an electrode slurry coating apparatus130composed of a lower plate131, a middle plate132, and an upper plate133, including: a first discharge port110formed between the lower plate131and the middle plate132and for discharging the slurry forming a lower slurry layer onto a current collector; a second discharge port120formed between the middle plate132and the upper plate133, positioned to be spaced apart from the first discharge port in the downstream direction in the coating direction, and for discharging the slurry forming an upper slurry layer onto the lower slurry layer on the current collector; and a movement controller for moving the coating apparatus in a direction opposite to the discharge direction. Characteristically, in the present invention, the ends of the lower plate, the middle plate, and the upper plate are located on the same straight line. In one embodiment, the movement controller moves the electrode slurry coating apparatus so that the shortest distance H1 between the end of the coating apparatus and the current collector satisfies the following condition. [Condition] When a certain time elapses after forming the lower slurry layer, the coating apparatus is moved in the opposite direction to the discharge direction to form the upper slurry layer on the lower slurry layer. At this time, the moved distance H1Tis in the range of 60 to 140% of the average thickness of the upper slurry layer. Preferably, the H1Tis in the range of 60 to 120% or 60 to 100% of the average thickness of the upper slurry layer. The H1Tprovides a space in which the upper slurry layer is formed. If the above range is less than 60%, compared to the amount of liquid discharged, the space where the slurry stays to be coated, that is, the total area between the end of the coating apparatus and the lower slurry layer, is insufficient, so that the supplied slurry cannot be coated and leaks back. On the other hand, in the case of more than 140%, compared to the supplied slurry, the coating area is too large, so that the coating may not be evenly coated, or only the lower layer may be coated and the upper layer may not be coated. Accordingly, in the electrode slurry coating apparatus according to the present invention, the lower and upper slurry layers are not mixed, and the lower and upper slurry layers are then dried to stably form a two-layer structure composed of lower and upper active material layers. In the present invention, the average thickness of the upper slurry layer is preferably 40 to 200 μm, more preferably 50 to 180 μm, and the average thickness of the lower slurry layer is 40 to 200 μm, more preferably 50 to 180 μm. Typically, the average particle diameter of the secondary battery active material is around 10 μm, but since the particle diameter follows a normal distribution, d(90) or d(max) is generally greater than 10 μm. In order to achieve good coating, in the present invention, the coating apparatus is moved in the opposite direction to the discharge direction to form the upper slurry layer. At this time, when the average thickness of the upper slurry layer is less than 40 μm, the moving distance H1Tis a value between 24 μm and 56 μm. In this case, as the moving distance H1Tbecomes closer to d (max), when the upper active material is coated, the moving distance H1Twith the active material having the maximum particle diameter becomes close, and when the active material contained in the slurry is coated, there may be a phenomenon in which it is not possible to pass a height that is as high as H1T. It is because this may cause defects in the coating surface, for example, a situation that a line is formed on the coating surface because a large active material is caught, and it is caught between the moving current collector and the coating end and damages the current collector, thereby causing a rupture phenomenon of the current collector. In addition, if the thickness of the slurry layer is 200 μm or more, it may be advantageous, but there is a problem that it is difficult to achieve realistically to exceed 200 μm coating amount actually used for the secondary battery. In addition, the time point at which the coating apparatus moves in the direction opposite to the discharge direction can be calculated by, for example, Formula 1 below. Movement switching point(TdS,sec)=(thickness(a) of middle plate (mm)+thickness (b) of first discharge port (mm))/moving speed (mm/sec) of current collector in the moving direction(MD). [Formula 1] In the electrode slurry coating apparatus according to the present invention, the height H1, which is the shortest distance between the end of the coating apparatus and the current collector, is changed from H1Sto H1Tafter the position (movement) change time calculated by Formula 1 above. Here, the shortest distance between the end of the coating apparatus and the current collector means the length from the straightened ends of the upper, middle and lower plates of the coating apparatus to a vertical tangent to the current collector. This is to stably form an upper slurry layer on the lower slurry layer formed after the lower slurry layer is formed first. In one example, the shortest distance (H1S) between the current collector and the end of the coating apparatus before starting electrode slurry coating is controlled in the range of 60 to 140% of the average thickness of the lower slurry layer, preferably 80 to 120%, and more preferably 80 to 100%. If the above range is less than 60%, compared to the amount of liquid discharged, the space where the slurry stays to be coated, that is, the total area between the end of the coating apparatus and the current collector, is insufficient, so that the supplied slurry cannot be coated and leaks back. On the other hand, when it exceeds 140%, compared to the supplied slurry, the coating area becomes too large, resulting in a phenomenon in which coating is not evenly performed. Meanwhile, the slurry is discharged from the first discharge port to form a lower slurry layer, and the slurry is again discharged from the second discharge port on the formed lower slurry layer to form an upper slurry layer. In the present invention, the slurry discharged from the second discharge port is designed to pressurize the lower slurry layer to a certain level. Through this, interlayer interfacial bonding properties are improved, and air bubbles or the like are prevented from being formed at the interface. In the present invention, the lower plate, the middle plate, and the ends of the upper plate are characterized in that they are located on the same straight line. In the present invention, the lower slurry layer is first formed through the first discharge port, and then the coating apparatus is moved in the opposite direction to the discharge direction after a certain time has elapsed, so that a space in which the upper slurry layer is formed is secured through the second discharge port. In another example, an electrode slurry coating apparatus according to the present invention further includes: a first valve for opening and closing the discharge of the first discharge port; a second valve for opening and closing the discharge of the second discharge port; and a valve controller for controlling opening and closing of the first and second valves. In addition, the valve controller opens the first valve when the electrode slurry coating starts, and opens the second valve when the coating apparatus moves in a direction opposite to the discharge direction. This is to first form a lower slurry layer by opening the first valve. When the formed lower slurry layer reaches the position of the second discharge port by the movement of the conveyor that moves the current collector, the second valve is opened at that time to stably form the upper slurry layer on the lower slurry layer. In addition, by controlling the opening timing of the first and second valves, the coating start points of the lower and upper slurry layers correspond to each other, and the area of the surplus portion discarded through this may be minimized. In another example, for example, when the electrode slurry coating ends, the valve controller sets the closing time of the second valve to be delayed by a closing delay time according to Formula 2 below from the closing time of the first valve. Upper slurry discharge closing delay time (sec)=(thickness(a) of middle plate (mm)+thickness(b) of first discharge port (mm))/moving speed (mm/sec) of current collector in the moving direction(MD). [Formula 2] The closing delay time according to Formula 2 above is to minimize the area of the surplus portion at the end time point of coating within a range that does not impede the stable formation of the two-layered active material layer. Through the valve closing delay as described above, the distance difference between the surplus portion, that is, the coating end point of the upper slurry layer and the coating end point of the lower slurry layer, is adjusted to be within 3 mm. This is because if the length of the surplus portion exceeds 3 mm as described above, the area to be discarded increases, which is not economical. In another embodiment, the ratio of the average thickness (D1) of the lower slurry layer formed by the slurry discharged through the first discharge port and the average thickness (D2) of the upper slurry layer formed by the slurry discharged through the second discharge port is in the range of 1:3 to 3:1 (D1:D2). The thickness ratio is a relative average value of the length of each layer in the thickness direction. The thickness of the slurry layer as described above can be seen as the pressure of the immediately supplied slurry. In the case that the pressure of the upper slurry layer is supplied in excess of 3 times the pressure of the lower slurry layer so that the thickness ratio of the lower slurry layer and the upper slurry layer is 1:3 or more, since the upper layer has stronger pressure than the lower layer, the lower layer slurry is pushed back in the opposite direction to the coating direction, thereby increasing the possibility of leakage, and the lower slurry may not be supplied properly due to the strong pressure of the upper slurry. In addition, due to the high pressure of the upper slurry, the supply of the slurry to the lower slurry layer is not uniform, so that it is difficult to form the lower slurry layer uniformly. On the other hand, when the pressure of the lower slurry layer is supplied in excess of 3 times the pressure of the upper slurry layer so that the thickness ratio of the lower slurry layer and the upper slurry layer is 3:1 or more, there is a problem that the supply of the upper slurry layer may become difficult, or the coating of the upper slurry layer may be pushed in the coating direction, and the surface of the coating liquid may be uneven. The present invention also provides an electrode slurry coating method using the apparatus described above. In the detailed description mentioned in the description of the apparatus or the specific numerical range limitation, the overlapping portion will be omitted in the description of the electrode slurry coating method below. The method of coating an electrode slurry according to the present invention includes: forming a lower slurry layer by discharging a slurry through a first discharge port on a current collector moving in a coating direction (MD) by using an apparatus130for coating an electrode slurry, composed of a lower plate131, a middle plate132and a upper plate133; moving the apparatus in a direction opposite to the discharge direction; and forming an upper slurry layer by discharging a slurry through a first discharge port and a second discharge port positioned to be spaced from a downstream side in a coating direction, on a lower slurry layer. In the present invention, the ends of the lower plate, the middle plate, and the upper plate are located on the same straight line. In one example, in the electrode slurry coating method, the height (H1), which is the shortest distance between the end of the coating apparatus and the current collector, is changed from H1Sto H1Tat a point in time after a certain time elapses after the start of electrode slurry coating, and the H1Tprovides a space in which an upper slurry layer is formed. Accordingly, in the electrode slurry coating method according to the present invention, the lower and upper slurry layers are not mixed, and a two-layer structure composed of the lower and upper slurry layers is stably formed. For example, the time point at which the coating apparatus moves in a direction opposite to the discharge direction can be calculated by the following Formula. Movement switching point(TdS,sec)=(thickness(a) of middle plate (mm)+thickness (b) of first discharge port (mm))/moving speed (mm/sec) of current collector in the moving direction(MD). [Formula 1] In the electrode slurry coating method according to the present invention, the height (H1) is changed from H1Sto H1Tafter the movement conversion point calculated by Formula 1 above. This is to stably form an upper slurry layer on the lower slurry layer formed after the lower slurry layer is formed first. In one example, the electrode slurry coating method according to the present invention starts discharging the slurry through the first discharge port when coating the electrode slurry, and when the coating apparatus moves in a direction opposite to the discharge direction, slurry discharge is started through the second discharge port. Through this, when the formed lower slurry layer reaches the position of the second discharge port by the movement of the conveyor that moves the current collector, the second valve is opened at that time to stably form the upper slurry layer on the lower slurry layer. In addition, by controlling the opening timing of the first and second valves like the above, the coating start points of the lower and upper slurry layers correspond to each other, and the area of the surplus portion discarded through this may be minimized. In another example, in one example, the shortest distance (H1S) between the current collector and the end of the coating apparatus before starting electrode slurry coating is controlled in the range of 60 to 140% of the average thickness of the lower slurry layer, preferably 80 to 120%, and more preferably 80 to 100%. If the above range is less than 60%, compared to the amount of liquid discharged, the space where the slurry stays to be coated, that is, the total area between the end of the coating apparatus and the current collector, is insufficient, so that the supplied slurry cannot be coated and leaks back. On the other hand, in the case of more than 140%, compared to the supplied slurry, the coating area is too large, so that the coating may not be evenly performed, or only the lower layer may be coated and the upper layer may not be coated. Here, the shortest distance between the end of the coating apparatus and the current collector means the length from the straightened ends of the upper, middle and lower plates of the coating apparatus to a vertical tangent to the current collector. The slurry is discharged from the first discharge port to form a lower slurry layer, and the slurry is again discharged from the second discharge port on the formed lower slurry layer to form an upper slurry layer. In the present invention, the slurry discharged from the second discharge port is designed to pressurize the lower slurry layer to a certain level. Through this, interlayer interfacial bonding properties are improved, and air bubbles or the like are prevented from being formed at the interface. In another example, the electrode slurry coating method according to the present invention is characterized in that, at the end of the electrode slurry coating, the discharge stop time of the slurry forming the upper slurry layer is delayed by the valve closing delay time according to Formula 2 below than the discharge stop time of the slurry forming the lower slurry layer. Upper slurry discharge closing delay time (sec)=(thickness(a) of middle plate (mm)+thickness(b) of first discharge port (mm))/moving speed (mm/sec) of current collector in the moving direction(MD). [Formula 2] The closing delay time according to Formula 2 above is to minimize the area of the surplus portion at the end time point of coating within a range that does not impede the stable formation of the two-layered active material layer. The surplus portion as described above is referred to as the loading off section, which means a section from the point at which the thickness of the slurry layer is reduced by stopping the discharge of the slurry, to the end of the discharged slurry. Through this, it is possible to show an effect of reducing the surplus portion that is discarded as the loading off section is caused. This leads to an increase in process efficiency and a decrease in manufacturing cost. The loading off section means a section from the point at which the thickness of the slurry layer is reduced by stopping the discharge of the slurry, to the most end (end portion) of the discharged slurry. In general, when the discharge closing is not delayed or is delayed too much, it is common that a loading off section of 5.5 mm or more occurs. Through the slurry discharge delay in the upper slurry layer as described above, the distance difference between the surplus portion, that is, the coating end point of the upper slurry layer and the coating end point of the lower slurry layer, is adjusted to be within 3 mm. This is because if the length of the surplus portion exceeds 3 mm as described above, the area to be discarded increases, which is not economical. FIG.3shows a case in which the lower slurry layer111and the upper slurry layer121are sequentially coated on a current collector moving in the coating direction MD by a conveyor and are terminated. By delaying the discharge of the slurry from the upper slurry layer as described above, the distance difference between the coating end point (E bottom) of the lower slurry layer111and the coating end point (E top) of the upper slurry layer121can be reduced. In addition, it is possible to reduce the length of the surplus portion compared to the prior art by delaying the discharge of the slurry in the upper slurry layer as described above. Here, the loading off section means the total distance from the portion where the thickness of the slurry layer starts to decrease (E terminal) to the end (E top) of the slurry. In the present invention, while the E bottom and E top coincide, the length of the loading off section is reduced at the same time. In another embodiment, the ratio of the average thickness (D1) of the lower slurry layer formed by the slurry discharged through the first discharge port and the average thickness (D2) of the upper slurry layer formed by the slurry discharged through the second discharge port is in the range of 1:3 to 3:1 (D1:D2). The thickness ratio is a relative average value of the length of each layer in the thickness direction. Hereinafter, the present invention will be described in more detail through drawings and examples. FIGS.1and2are schematic diagrams showing an active material slurry coating process using an electrode slurry coating apparatus according to an embodiment of the present invention. Referring toFIG.1, the electrode slurry coating apparatus includes a lower plate131and an upper plate133, and a middle plate132is interposed between the lower plate131and the upper plate133. A slurry including an active material, a conductive material, and a binder fluidly moves along a flow path between the lower plate and the middle plate131and132, and the slurry forming the lower slurry layer111is discharged through the first discharge port110. A slurry including an active material, a conductive material, and a binder fluidly moves along the flow path between the middle plate and the upper plates132and133, and the slurry forming the upper slurry layer121is discharged through the second discharge port120. In addition, a conveyor (not shown) for moving the current collector101in the coating direction MD is located spaced apart from the first and second discharge ports110and120by a predetermined distance. At this time, the ends of the lower plate, the middle plate and the upper plate of the coating apparatus are located on the same straight line. In addition, referring toFIG.2, in the coating apparatus, the ends of the apparatus, that is, the ends of the lower plate, the middle plate, and the upper plate are spaced apart from the current collector101by a predetermined distance. Herein, it is spaced apart before the start of coating by the shortest distance H1Sbetween the end of the coating apparatus and the current collector. The slurry discharged through the first discharge port110forms a lower slurry layer111having an average thickness D1on the current collector101and makes the coating apparatus to be separated from the current collector by a predetermined distance through a movement controller (not shown) that moves the coating apparatus in a direction opposite to the discharge direction. Thereafter, the slurry discharged through the second discharge port120forms an upper slurry layer121having an average thickness D2on the lower slurry layer111. First Embodiment A positive electrode for a lithium secondary battery was manufactured through the electrode slurry coating apparatus and method shown inFIG.1. Specifically, when starting electrode slurry coating, the shortest distance H1Sbetween the surface of the current collector101moving along the conveyor and the end of the coating apparatus is 80 μm. The slurry is discharged from the first discharge port110to form a lower slurry layer. Then, the height H1of the coating apparatus is moved in the opposite direction to the discharge direction by H1Sto H1Tas shown inFIG.2. The time point at which the coating apparatus moves is calculated by Formula 1 below. Specifically, the moving speed of the current collector101by the conveyor was 50 m/min, the thickness (a) of the middle plate was 1 mm, and the thickness (b) of the first discharge port was also 1 mm. Applying this to Formula 1 is as follows. Movement switching point(TdS,sec)=(thickness of middle plate (mm)+thickness of first discharge port (mm))/moving speed (mm/sec) of current collector in the moving direction (MD). [Formula 1] The sum of the thickness of the middle plate and the thickness of the first discharge port is 2 mm. In addition, moving speed (mm/sec) of the current collector101in the moving direction (MD) by the conveyor is 50 (m/min), that is, 83.3 (mm/sec). If calculated according to Formula 1, the travel time (TdT) is 2.4×10−3(sec), that is, 2.4 ms (milliseconds). H1T, which is the distance the coating apparatus was moved in the direction opposite to the discharge direction during the above time, was 60 μm. The overall average thickness (DT) of the slurry double layer coated by the electrode slurry coating apparatus is about 150 μm. Among them, the average thickness of the lower slurry layer D1 is 90 μm, and the average thickness of the upper slurry layer D2 is 60 μm. Second Embodiment A positive electrode for a lithium secondary battery was prepared using the electrode slurry coating apparatus shown inFIG.1. A detailed description of the electrode slurry coating method is omitted since it overlaps with the first embodiment. However, H1T, the distance by which the coating apparatus was moved in the opposite direction to discharge direction, which was the starting distance, was 90 μm. The overall average thickness (DT) of the slurry double layer coated by the electrode slurry coating apparatus is about 180 μm. Among them, the average thickness of the lower slurry layer D1 is 90 μm, and the average thickness of the upper slurry layer D2 is 90 μm. Third Embodiment A positive electrode for a lithium secondary battery was prepared using the electrode slurry coating apparatus shown inFIG.1. A detailed description of the electrode slurry coating method is omitted since it overlaps with the first embodiment. However, at the end of the electrode slurry coating, the closing time of the second valve was delayed by the closing delay time according to Formula 2 below from the closing time of the first valve. Specifically, the moving speed of the current collector101by the conveyor was 50 m/min, the thickness (a) of the middle plate was 1 mm, and the thickness (b) of the first discharge port was also 1 mm. Applying this to Formula 2 is as follows. Upper slurry discharge closing delay time (sec)=(thickness(a) of middle plate (mm)+thickness(b) of first discharge port (mm))/moving speed (mm/sec) of current collector in the moving direction(MD). [Formula 2] The sum of the thickness of the middle plate and the thickness of the first discharge port is 2 mm. In addition, moving speed (mm/sec) of the current collector101in the moving direction (MD) by the conveyor is 50 (m/min), that is, 83.3 (mm/sec). If calculated according to Formula 2, the valve closing delay time is 2.4×10−3(sec) or 2.4 ms (milliseconds). Therefore, at the end of the electrode slurry coating, the closing time of the second valve was delayed by 2.4 ms from the closing time of the first valve. In this case, in the manufactured electrode, the coating end points of the lower and upper slurry layers111and121were identical (E top=E bottom), and as a result of measuring the loading off length, which is the distance from the portion (E terminal) where the thicknesses of the upper and lower slurry layers are reduced to the end portion (E top, E bottom) where the coating is finished, it was formed as 4.5 mm. In general, the loading off length is formed to be 5.5 mm or more, and in the case of manufacturing according to the third embodiment, a portion to be discarded is saved by reducing the length of the surplus portion, thereby increasing the efficiency of the process. In the above, the present invention has been described in more detail through the drawings and examples. Accordingly, the embodiments described in the specification and the configurations described in the drawings are only the most preferred embodiments of the present invention, and do not represent all of the technical ideas of the present invention. It is to be understood that there may be various equivalents and variations in place of them at the time of filing the present application. DESCRIPTION OF REFERENCE NUMERALS 101: current collector110: first discharge port111: lower slurry layer120: second discharge port121: upper slurry layer131: lower plate of coating apparatus132: middle plate of coating apparatus133: upper plate of coating apparatusa: thickness of the middle plateb: thickness of the first discharge port | 29,480 |
11862783 | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Atomic layer deposition (ALD) is a modified form of chemical vapor deposition (CVD) that uses the self-limiting nature of specific precursors to deposit films in a layer-by-layer fashion. ALD is particularly well-suited for coating electrode surfaces in that a conformal coating can be applied with precise control of thickness and composition. Previous studies on ALD-coated electrodes have primarily focused on metal oxides such as Al2O3, TiO2, LiAlO2, and LiTaO3because the ALD chemistry of these oxides is well known. Metal fluoride growth by ALD is complex and challenging, mainly due to the lack of suitable fluorine precursors. For example, HF, a highly aggressive chemical etching agent, has been used to deposit CaF2, ZnF2, and SrF2. More recently, alternative ALD chemistries have been developed such as MgF2and LiF ALD using either TaF5or TiF4as the fluorine precursor for optical applications. However, the substrate temperatures in these cases were 300-400° C.; high enough to degrade battery electrode laminates containing polymeric binders. Another potential limitation of AlF3for Li-Ion batteries is that it is a wide-bandgap dielectric and hence electrically insulating. Although still promising as a coating, methods to enhance the material's conductivity while maintaining its superb resistance to chemical attack could be advantageous. U.S. Pat. No. 8,921,799 and pending application published as U.S. Pat. App. Pub. No. 2012/0187305 describe a general method and materials from the method relating to atomic layer deposition of a composite coating. Described herein is a method for and composition and product having ultrathin, amorphous, composite aluminum-tungsten-fluoride (AlWxFy) films on, in one embodiment, LiCoO2electrodes via ALD using, in one embodiment, trimethyaluminum (TMA) and tungsten hexafluoride (WF6), at 50° C. to 300° C. preferably at 200° C. Such films are created with metal fluoride and do not utilize a metal oxide. There is no oxidant step involved in TMA-WF6process; TMA reduces tungsten terminated surface in various embodiments, AlWxFyCzis formed where x and y are any non-zero positive number and wherein z can be zero (no carbide), or any positive number. These films are highly conducting, but incorporate AlF3in the composite. Although LiCoO2is the most commercially successful cathode material for Li-ion batteries, the practical use of LiCoO2is limited, in part, to surface reactions involving cobalt dissolution, electrolyte oxidation, as well as structural transformations occurring at potentials higher than ˜4.3 V (vs. Li/Li+). As such, LiCoO2might be considered as a model system for surface studies on Li-ion cathodes. Ultrathin AlWxFycoatings (˜1 nm) on LiCoO2are shown to significantly increase stability relative to bare LiCoO2when cycled up to 4.4 V. These results reveal new possibilities for designing ultrathin and electrochemically robust coatings of metal fluorides via ALD, and potentially other techniques, to enhance the stability of Li-ion electrodes. Using high vapor pressure precursors are beneficial when implemented in role-to-role ALD or spatial ALD. ALD of AlWxFywas accomplished using alternating exposures of WF6and TMA. In-situ quartz crystal microbalance (QCM) measurements recorded during alternating, 1 second WF6and TMA exposures at 200° C. showed a staircase pattern comprised of 160 ng/cm2steps consistent with layer-by-layer growth (FIG.1A). Substrate temperature below 2000 is desirable when ALD is applied to electrode laminates composed of active material, carbon, and polymeric binder. Additional QCM measurements verified that each of the precursor exposures was self-limiting under these conditions.FIG.7illustrates the self-limiting growth of TMA-WF6ALD. Ellipsometric measurements indicated a growth rate of 2.56 Å/cycle, and combined with the QCM data yield a film density of 6.5 g/cm3. The resulting films appear amorphous by X-ray diffraction are highly conducting; four-point probe measurements give a resistivity of 3.5×10−2Ωcm. The growth rate of the film, deposited by alternating cycles of TMA-WF6, is relatively high compared to that of typical oxides (˜1-1.5 Å/cycle) and is due in part to tungsten and/or tungsten carbide byproducts that have growth rates of 2.5 Å/cycle. X-ray photoelectron spectroscopy (XPS) survey scans, performed during depth-profiling of these films deposited on silicon, revealed that they are comprised of W, C, Al, and F. Higher resolution XPS analysis demonstrated that the Al and F are bound as AlF3, and that the W may be present as both metallic W and tungsten carbide (WCx) (SeeFIG.5). For brevity, in this application these films are referred to as AlWxFyor AlWxFyCzwhere z may equal zero to reflect that carbide may or may not be included. High resolution transmission electron microscopy (HRTEM) and nano-beam diffraction (NBD) measurements, taken from cross-sections of an AlWxFyfilm deposited on Al2O3-coated silicon (FIG.1B), confirmed the amorphous nature of the films. These measurements also revealed that the AlWxFyexists as a nanocomposite of ˜1 nm particles in a matrix of lower density. It is believed that the darker particles inFIG.1Bare W and WCx, while the surrounding matrix of lower density material is AlF3. In one embodiment, particles are uniformly dispersed in the matrix from TEM, but can be controlled by ALD sequence; WF6-WF6 pulsing might generate localized nanoparticles. It is believed that TMA pulse on WF6 terminated surface reduces tungsten to form metallic or carbide form while fluorine create stable bonding with Al. To evaluate the electrochemical properties of the AlWxFycoating, 5 ALD cycles of TMA-N2—WF6—N2(˜1 nm) were applied on laminates of LiCoO2. XPS survey scan of coated LiCoO2confirmed that the AlWxFyfilms are deposited on the laminates (FIG.6).FIG.8illustrates characterization of a ALD coated ALWxFyCzlayer.FIG.2Ashows first-cycle voltage profiles of two Li+/LiCoO2cells, with and without AlWxFycoatings, between 4.4-2.5 V at 20 mA/g. Uncoated LiCoO2exhibited first-cycle capacities of ˜170 mAh/g compared to ˜165 mAh/g of the coated sample. This difference, though fairly negligible, might be attributed to the inactive nature of the coating layer resulting in slightly higher first-cycle impedance. The polarization on charging, however, disappeared after the first cycle indicating possible changes, such as a lithiated phase in the film, allowing diffusion of lithium ions and similar lithium extraction/insertion voltages as the uncoated electrode (insetFIG.2A). Recent molecular dynamics (MD) calculations on Al2O3coating suggests that the Al2O3coating layer absorbs lithium until it reaches the thermodynamically stable composition during the lithiation process. The characteristic hexagonal to monoclinic transformation of LiCoO2occurring at ˜4.1 V is observed for both cells, though slightly less pronounced for the coated electrode. This is an indication that the ALD coating process did not drastically alter the bulk characteristics of the material; similar to previous coating studies on LiCoO2. The discharge capacity of the uncoated LiCoO2continuously decreased while the coated electrode showed excellent capacity retention over the course of cycling between 4.4-2.5 V. The bare LiCoO2retained only 85% of its initial capacity, while the 1 nm AlWxFycoating enabled a 99% capacity retention after 50 charge-discharge cycles as shownFIG.2B. The capacity loss of the bare material is attributed to parasitic, interfacial reactions as previously reported. It should be noted that thicker (˜10 nm) AlWxFycoatings on LiCoO2 showed discharge capacities of just ˜10 mAh/g, revealing a limitation in practical thicknesses. There is a trade-off between protection capability and facile diffusion of lithium ion. A 1 nm thick AlWxFyallows diffusion of lithium and protect underlying electrodes. FIGS.3A and3Bshow voltage profiles and corresponding differential capacity (dQ/dV) plots of bare and coated samples on cycles 5, 25, and 50. Voltage profiles of the uncoated LiCoO2clearly showed increased polarization on charge and discharge with continued cycling accompanied by a broadening and shifting of the dQ/dV peaks; typical of increasing impedance and structural degradation. On the other hand, voltage profiles and dQ/dV plots of the AlWxFy-coated material showed little change upon cycling. This data reveals that the phase transition associated with lithium ordering at ˜4.1 V is a relatively “soft” transition and a significant fraction of the lithium can be repeatedly, and reversibly, extracted without significant damage to the bulk of the structure. Furthermore, it is clear that surface damage, mitigated here by the AlWxFyfilm, is a much greater factor in the degradation of LiCoO2under these cycling conditions. XPS studies were employed on AlWxFy-coated materials to probe the chemical composition of the surface before/after the electrochemical cycling.FIG.3Cshows Al 2p3/2spectra of pristine, coated LiCoO2and after 50 cycles. The binding energy of the pristine and cycled samples was fitted to 74.9 eV and 75.0 eV, respectively, indicating only marginal change in the binding energy after electrochemical cycling and a stable AlWxFycoating under insertion/extraction of lithium. The fitted value is higher than those of Al2O3(74.2 eV) and LiAlO2(73.4 eV), and is closer to O—Al—F bonding as reported earlier. FIG.4compares the rate capability up to 400 mA/g for the coated and uncoated LiCoO2. AlWxFy-coated LiCoO2exhibited superior rate capability at all current rates compared to the uncoated material, but the most dramatic improvements occurred at the highest rates (200-400 m A/g). Discharge capacities at a current of 400 mA/g were 51% and 92% of the first-cycle capacities for bare and AlWxFymaterials respectively. It is well known that reactions at electrode/electrolyte interfaces result in surface films that greatly increase cathode electrode impedances, thereby, causing capacity fade and poor power performance. Furthermore, it has been shown, in agreement with our results inFIG.3B, that mitigating reactions at the surface of LiCoO2results in more stable bulk processes. As such, the data herein clearly demonstrate the improved surface stability of AlWxFy-coated LiCoO2, resulting in excellent electrochemical performance. FIG.9illustrates the interactions of the layers in one embodiment demonstrating the resistance to diffusion of lithium. The AlWxFyCz coating resists HF and transition metal dissolution from the cathode. Various cycles and supercycle arrangements can be utilized.FIG.10is a graph illustrating the sequence of cycles in one embodiment where a 3:1 cycle sequence is applied.FIG.11illustrates a graph of the number of supercycles for various ratios demonstrating a similar thickness with different compositions resultant from the differing ratios. Generally, the ALD supercycle comprises (a[TMA-H2O]*bWF6)×n=total number. In that supercycle, a and b can be, for example, 3:1, 2:1, 1:1, 4:2. The total thickness may be the same for different compositions by varying the a:b ratio. For example, (3:1)×3, (2:1)×4, (1:1)×6, (4:2)×2˜ similar thickness with different compositions. In summary, a novel ALD process allowing the deposition of metal fluoride materials has been developed for surface protection of Li-ion battery electrodes. A ˜1 nm AlWxFyfilm deposited on LiCoO2electrodes has been shown to dramatically enhance cycle life and rate capability of Li+/LiCoO2cells. These AlWxFythin film composites appear to combine the chemical inertness of AlF3with the high electrical conductivity of a metal. This study suggests new opportunities for ALD and the design of advanced surface structures enabling high capacity lithium ion batteries. Moreover, adjusting the composition of the ALD composites may yield further improvements in performance. Atomic Layer Deposition: Aluminum fluoride-based composite films were deposited via sequential pulsing of trimethylalumium (TMA) (97%, Sigma Aldrich) and tungsten hexafluoride (WF6) (99.8%, Sigma Aldrich). The deposition was performed at 200° C. in a hot-walled viscous flow ALD reactor. TMA and WF6precursors were maintained at room temperature and ultrahigh purity N2was used as a carrier gas with 300 sccm. The base pressure of the ALD reaction chamber was maintained at ˜1.0 Torr. TMA and WF6were alternatively pulsed into the 15 sccm of N2carrier flow with the following time sequence: 1 s WF6dose—5 s purge—1 s TMA dose—5 s purge. An in situ QCM study was performed to study the nature of the deposition. The QCM measurements typically used longer N2purge times of 10 s to allow the QCM signal to stabilize after each precursor exposure. The thicknesses of AlWxFycoating layers were determined by ex situ spectroscopic ellipsometry using a Cauchy model (Alpha-SE, J. A. Woollam Co.). The resistance of the film deposited on fused silica was determined by performing current-voltage (I-V) measurements using a four point probe measurement (Keithley Model 6487 current voltage source). X-ray photoelectron spectroscopy of AlWxFyfilms deposited on silicon was performed by Evans Analytical Group. Transmission electron microscopy: Microstructure and crystallinity of AlWxFyfilms deposited on silicon wafer were analyzed using TEM. TEM analysis was performed by Evans Analytical Group (Sunnyvale, CA). Cross-section TEM samples were prepared using the in-situ focused ion beam (FIB) lift out technique on an FEI Strata Dual Beam FIB/SEM. The samples were capped with a protective layer of carbon prior to FIB milling, and were imaged with a FEI Tecnai TF-20 FEG/TEM operated at 200 kV in bright-field (BF) TEM mode, high-resolution (HR) TEM mode, and nano-beam diffraction (NBD) mode. Electrochemical measurements: The LiCoO2electrodes were prepared by mixing a slurry of commercial LiCoO2powder (Sigma-Aldrich), Super-P carbon, and polyvinylidenedifluoride (PVDF) with a mass ratio of 84:8:8 in N-methyl pyrrolidone (NMP). The mixed slurry was caste on an aluminum foil current collector. AlWxFyfilms were deposited via ALD on the finished electrode laminates with thicknesses of ˜1 nm. 2032-type coin cells were assembled in an Ar-filled glovebox (water and oxygen ≤1 ppm) with metallic lithium anodes. The electrolyte consisted of a 1.2M LiPF6solution in ethylene carbonate and ethylmethyl carbonate (3:7 mixture). Charge-discharge measurements were recorded on a MACCOR potentiostat at room temperature under a current rate of 20 mA/g between 2.5 V and 4.4 V. Rate capability experiments were conducted with a constant charge rate of 20 mA/g and discharge rates of 20, 100, 200, and 400 mA/g. X-ray photoelectron spectroscopy: The chemical state of aluminum before and after electrochemical cycling was analyzed by XPS (Sigma Probe: Thermo VG Scientific) with monochromatic Al Kα radiation (1486.6 eV). The cycled 2032 coin cells were disassembled and washed with dimethyl carbonate (DMC), and transferred directly to XPS to eliminate air-exposure during sample transport. The foregoing description of illustrative embodiments has been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents. | 15,607 |
11862784 | GENERAL REMARKS The following precursors were used: A precursor was made by precipitating a mixed Ni—Co—Mn carbonate from a solution containing nickel sulfate/cobalt sulfate/manganese sulfate in a molar ratio of 23:12:65 followed by drying under air at 200° C. Precipitating agent was aqueous sodium carbonate solution in aqueous ammonia solution. Average particle diameter (D50): 10.2 μm. Nl: liters at “normal conditions”: 20° C./one atmosphere. I. Manufacture of Cathode Active Materials I.1: Manufacture of Oxide MO.1 Step (a.1): The following equipment is used: in a roller hearth kiln, a saggar filled with an intimate mixture of precursor and Li2CO3so the molar ratio of lithium to the sum of transition metals is 1.42:1. Said mixture is heated to 800° C. in a forced stream of air. When a temperature of 800° C. is reached, heating is continued at 800° C. over a period of time of 4 hours. The formation of metal oxide (MO.1) is observed, formula 0.42Li2MnO3.0.58Li(Ni0.4Co0.2Mn0.4)O2. This corresponds to a formula of Li1.17TM0.83O2. Step (b.1): in the same roller hearth kiln, the saggar is moved on and allowed to cool down to 120° C. within two hours in dry oxygen (30% by vol) in Ar. Step (c.1): The air supply is shut down and replaced by O2/Ar/SO3mixture in a ratio of 30:70:0.5 by volume. Over 30 minutes, metal oxide (MO.1) is exposed to a gas stream of O2/Ar/SO3. Since the SO3has been made in parallel by a one-stage SO2-oxidation at a V2O5-catalyst the SO3contains some SO2(maximum 30% by mole). After said treatment according to step (c.1), the material so obtained was cooled down to ambient temperature, step (d.1). MO.1 was obtained. I.2: Manufacture of Oxide MO.2 Step (a.1) is repeated as above. Step (b.2): in the same roller hearth kiln, the saggar is moved on and allowed to cool down to 200° C. within two hours in dry oxygen (30% by vol) in Ar. Step (c.2): The air supply is shut down and replaced by O2/Ar/SO3mixture in a ratio of 30:70:0.5 by volume. Over one hour, metal oxide (MO.1) is exposed to a gas stream of O2/Ar/503. Since the SO3has been made in parallel by a one-stage SO2-oxidation at a V2O5-catalyst the SO3contains about 5% by vol. of SO2. After said treatment according to step (c.2), the material so obtained is cooled down to ambient temperature, step (d.2). MO.2 is obtained. MO.2 has a sulfur content of 0.9% by weight, determined by combustion analysis (“CHNS”). Compared to C-MO.3, the difference is 0.6% by weight. I.3: Manufacture of Comparative Oxide C-MO.3 (No SO3Treatment) Step (a.1): The following equipment is used: in a roller hearth kiln, a saggar filled with an intimate mixture of precursor and Li2CO3so the molar ratio of lithium to the sum of transition metals is 1.42:1. Said mixture is heated to 800° C. in a forced stream of air. The formation of metal oxide (MO.1) is observed, formula 0.42Li2MnO30.58Li(Ni0.4Co0.2Mn0.4)O2. Then, the material so obtained is cooled down to ambient temperature, step (d.3). C-MO.3 was obtained. The residual sulfur content was 0.3% by weight, determined by CHNS. The sulfate most likely stems from sulfate adsorbed during the precipitation process. I.4: Manufacture of MO.4: Step (a.1) was repeated as above. Step (b.4): in the same roller hearth kiln, the saggar was moved on and allowed to cool down to 400° C. within two hours in pure nitrogen. Step (c.4-1): The N2supply was shut down and replaced by N2/SO2mixture in a ratio of 98:2 by volume. Over 2 hours, metal oxide (MO.1) was exposed to a flow of N2/SO2, 6 cm3/min. No impurities of the SO3were detectable. After said treatment according to step (c.4-1), the material so obtained was cooled down to ambient temperature, step (d.4). MO.4-1 was obtained. In MO.4-1 the resulting ratio of sulfur to the sum of transition metals, S/(Ni+Mn+Co) was 0.47% by weight, determined Inductively Coupled Plasma (“ICP”). From the S 2p peak of XPS spectra the amounts of sulfates were estimated as follows: 16% sulfates of transition metals [i.e., MnSO4, NiSO4, and CoSO4,] and 84% of Li2SO4. Step (c.4-1) was repeated with fresh samples from (b.4), but the treatments with N2/SO2had durations of 60 or 30 minutes, respectively. MO.4-2 and MO.4-3 were obtained. TABLE 1Storage of cathode active materialsstorage conditionsTest productMO.1Inert atmosphereMO.1*MO.2Inert atmosphereMO.2*MO.4-1Inert atmosphereMO.4-1*MO.1Ambient conditionsMO.1**MO.2Ambient conditionsMO.2**MO.4Ambient conditionsMO.4-1**C-MO.3Inert atmosphereC-MO.3*C-MO.3Ambient conditionsC-MO.3**“Inert atmosphere”: Ar-filled glovebox (25° C., <0.1 ppm H2O and CO2)“Ambient conditions”: 1 week, 25° C., 100% relative humidity, atmospheric CO2 I.5: Manufacture of MO.5-1 and MO.5-2 A precursor was made by precipitating a mixed Ni—Co—Mn carbonate from a solution containing nickel sulfate/cobalt sulfate/manganese sulfate in a molar ratio of 85:10:05 followed by drying under air at 120° C. and sieving. Precipitating agent was aqueous sodium hydroxide solution in aqueous ammonia solution. Average particle diameter (D50): 11.0 μm. Step (a.5): The following equipment is used: in a roller hearth kiln, a saggar was filled with an intimate mixture of the above precursor and LiOH monohydrate so the molar ratio of lithium to the sum of transition metals was 1.03:1. Said mixture was heated to 760° C. in a forced stream of a mixture of N2:O240:60 in volume %. When a temperature of 760° C. is reached, heating is continued at 760° C. over a period of time of 10 hours. The formation of metal oxide (MO.5) was observed, formula Li1.02(Ni0.85Co0.10Mn0.05)O2.02. Step (b.5): in the same roller hearth kiln, the saggar was moved on and allowed to cool down to 400° C. within two hours in pure nitrogen. Step (c.5-1): The N2supply was shut down and replaced by N2/SO2mixture in a ratio of 98:2 by volume. Over 5 minutes, metal oxide (MO.5-1) was exposed to a flow of N2/SO2, 6 cm3/min. No impurities of the SO2were detectable. Step (c.5-2): The N2supply was shut down and replaced by N2/SO2mixture in a ratio of 98:2 by volume. Over 20 minutes, metal oxide (MO.5-2) was exposed to a flow of N2/SO2, 6 cm3/min. No impurities of the SO2were detectable. After said treatment according to step (c.5-1) or (c.5-2, the materials so obtained were cooled down to ambient temperature, step (d.5). MO.5-1 and (MO.5-2) were obtained. II. Testing of Cathode Active Materials To produce a cathode, the following ingredients are blended under stirring with one another under inert conditions: 46.25 g of active material, 1.75 g polyvinylidene difluoride, (“PVdF”), commercially available as Kynar Flex® 2801 from Arkema Group, 2 g carbon black, BET surface area of 62 m2/g, commercially available as “Super C 65L” from Timcal. While stirring, a sufficient amount of N-methylpyrrolidone (NMP) is added in several steps and the mixture is stirred with a planetary orbital mixer (Thinky) until a stiff, lump-free paste has been obtained. Cathodes are prepared as follows: On an 18 μm thick aluminum foil, the above paste is applied with a 100 μm four-edge-blade. The loading after drying is 1.5 mAh/cm2. Disc-shaped cathodes with a diameter of 14 mm are punched out of the foil and compressed at 2.5 t for 20 seconds. The cathode discs are then weighed, dried for 14 hours in a vacuum oven at 120° C. and introduced into an argon glove box without exposure to ambient air. Then, cells with the cathodes are assembled. Electrochemical testing was conducted in “CR2032” coin type cells. The electrolyte used was 80 μl of a 1 M solution of LiPF6in fluoroethylene carbonate/diethyl carbonate/fluorinated ether K2 (volume ratio 64:12:24). Alternatively, electrochemical testing was conducted in coin cells of 2325-type fabricated with Li-metal counter electrodes, two Celgard 2500 polypropylene separators, and electrolyte solution (LP57, BASF) comprising ethylene carbonate-ethyl methyl carbonate (3:7), and 1M LiPF6. Anode: lithium foil, thickness 0.45 mm, separated from the cathode by two glass-fiber separators, thickness 0.025 mm each TABLE 2Cycling conditions of inventive cells and comparative cellsPotential rangeC-rateC-rateSegment[V vs. Li+/Li]ChargeDischargeCycles1Activation4.8-2.0C/15 (CC)C/15 (CC)12Slow cycling4.7-2.0C/10 (CC)C/10 (CC)33DCIR pulse(40% SOC)-2.0C/10 (CC)C/10 (CC)14Fast cycling4.7-2.0C/2 (CCCV)3C (CC)35Standard cycling4.7-2.0C/2 (CCCV)1C (CC)33 Segments 2 to 5 are looped. C-rate referenced to 250 mAh/gHE-NCM; CC (constant current), CCCV (constant current constant voltage with C/10 lower current limit), DCIR (direct current internal resistance) measurement at 40% SOC (state of charge). TABLE 3Specific discharge capacities at ambient temperature.Specific discharge capacity [mAh/gHE-NMC] at cycle number40 (1 C)80 (1 C)120 (1 C)160 (1 C)200 (1 C)240 (1 C)44 (0.1 C)84 (0.1 C)124 (0.1 C)164 (0.1 C)204 (0.1 C)244 (0.1 C)samplerate48 (3 C)88 (3 C)128 (3 C)168 (3 C)208 (3 C)248 (3 C)C-MO. 3*1C221 ± 1214 ± 1210 ± 1207 ± 2195 ± 2201 ± 20.1C251 ± 0245 ± 4249 ± 0248 ± 0200 ± 47245 ± 03C174 ± 3167 ± 4163 ± 4157 ± 4149 ± 6142 ± 6MO. 1*1C224 ± 1218 ± 1215 ± 1213 ± 1210 ± 1207 ± 10.1250 ± 0249 ± 0249 ± 0248 ± 0247 ± 1246 ± 03C185 ± 1179 ± 1174 ± 3169 ± 4164 ± 4154 ± 6 Average and maximum deviation of two cells per sample TABLE 3aSpecific capacities of first activation at 30° C.1st C [mA · h/g]1st D [mA · h/g]1st C. E. [%]C-MO.3332.5 ± 1281.2 ± 384.5%MO.4-1336.1 ± 2294.8 ± 387.7% TABLE 3bSpecific discharge capacities at 30° C.[mA · h/g]0.1 C0.33 C0.8 C1 C2 C4 C1 C/0.1 CC-MO. 3249 ± 2236 ± 3221 ± 3214.7 ± 3190 ± 5136 ± 1886.0%MO. 4-1263 ± 3257 ± 2241 ± 5238 ± 2220 ± 2178 ± 990.5% TABLE 4Specific discharge capacities during cycling at C/3 at 30° C.1st10th50th80thQ80/Q1[mA · h/g][mA · h/g][mA · h/g][mA · h/g][%]C-MO.3226 ± 3221 ± 3207 ± 4188 ± 683.2%MO.4-1253 ± 1.6249 ± 1.4236 ± 3220 ± 787.0% Average and maximum deviation of three cells per sample TABLE 5CO2evolution from 1.03 g cathode active materials mixed with 240μl of 1.5M LiClO4in ethylene carbonate at 60° C.CO2[μmol]CO2[μmol]CO2[μmol]after 3 hafter 7 hafter 12 hC-MO.3*789C-MO.3**202630MO.1**111315 The CO2evolution is measured by On-line Electrochemical Mass Spectrometry (OEMS) Alternative cycling conditions of inventive cells and comparative cells for coin cells based upon MO.5: The first two cycles were performed at C/10 rate, charging to 4.3V and discharged to 3V with a 30 min constant voltage step at 4.3 V. The C rate is defined as 185 mAh/g. All subsequent cycles were charged at C/2 rate and discharged at different rates namely 0.2 C, 0.5 C, 1 C, 2 C, 3 C, 5 C and 0.2 C rate for two cycles each and continued to cycling at 1 C rate up to 125 Cycles. The specific capacities obtained initially and at various rates and cycling are shown in Tables 5-7. TABLE 6Specific discharge capacities during cycling at 1 C at 25° C.Cycling1st10th30th50th100thQ50/Q1Q100/Q1SamplemAh/gmAh/gmAh/gmAh/gmAh/g%%MO. 5187.8185.2178.7172.4157.891.884.0MO. 5-1189.4188.2185.1181.1170.395.689.9MO. 5-2179.8179.6176.9174.3165.196.991.8 average of 3 cells per sample | 11,093 |
11862785 | DESCRIPTION OF EMBODIMENTS FIG.1is a longitudinal section showing an all-solid-state secondary battery1in accordance with one preferable preferred embodiment of the present invention. The all-solid-state secondary battery1has a positive electrode11, a lithium ion conductive material layer13which is a solid electrolyte or includes a solid electrolyte, and a negative electrode12in this order from the upper side. Specifically, the lithium ion conductive material layer13is positioned between the positive electrode11and the negative electrode12. The positive electrode11includes a current collector111and a positive electrode layer112including a positive electrode active material. The negative electrode12includes a current collector121and a negative electrode layer122. The negative electrode layer122is formed of a material including a negative electrode active material. The positive electrode active material of the positive electrode layer112is preferably a lithium composite oxide having a layered rock salt structure. More preferably, the lithium composite oxide having a layered rock salt structure is lithium cobalt oxide (LiCoO2). The lithium composite oxide is preferably a sintered body. Preferably, the negative electrode layer122includes Ti, and a lithium ion is insertable therein and removable therefrom at 0.4 V or more with the Li/Li+equilibrium potential as the reference. In other words, the lithium ion is insertable and removable at a potential higher than the Li/Li+equilibrium potential by 0.4 V or more. Specific examples of such a material are lithium titanate (Li4Ti5O12), niobium titanium composite oxide (Nb2TiO7), and titanium oxide (TiO2). The respective compositions and materials of the positive electrode11and the negative electrode12in the all-solid-state secondary battery1are not limited to those described above, but other various compositions and materials may be adopted. In an exemplary manufacture of the all-solid-state secondary battery1, prepared are the positive electrode11obtained by forming the current collector111on the positive electrode layer112and the negative electrode12obtained by forming the current collector121on the negative electrode layer122. Then, while the positive electrode layer112and the negative electrode layer122face the lithium ion conductive material, the lithium ion conductive material is sandwiched between the positive electrode11and the negative electrode12and heated, or the like, and the lithium ion conductive material thereby becomes the lithium ion conductive material layer13and thus the all-solid-state secondary battery1is manufactured. The positive electrode11, the lithium ion conductive material layer13, and the negative electrode12may be connected by any other method. Further, the lithium ion conductive material layer13may be formed by adding another material to the lithium ion conductive material. In other words, the lithium ion conductive material layer13is a layer including the lithium ion conductive material. Next, Experimental Examples on the lithium ion conductive material will be described. Experimental Example 1 As raw materials, prepared are LiOH (having a purity of 98.0% or more) and LiBr (having a purity of 99.9% or more) which are commercially available. In a glove box under an Ar gas atmosphere whose dew point temperature is −50° C. or lower, these raw materials are weighed and mixed so that LiOH:LiBr should be 1.0:1.0 (molar ratio). The mixed powder obtained thus is put into an alumina crucible (having a purity of 99.7%) and then into a quartz tube, and the quartz tube is sealed by a flange. This quartz tube is set in a tube furnace, and a heat treatment is performed at 350° C. for 30 minutes while Ar gas whose dew point temperature is −50° C. or lower is carried from a gas introduction port of the flange and exhausted from a gas exhaust port and the mixed powder is stirred. After cooling, the gas introduction port and the gas exhaust port are closed, and the crucible is taken out again in the glove box under the Ar gas atmosphere whose dew point temperature is −50° C. or lower. The compound is taken out from the crucible and ground in a mortar, and powder of the lithium ion conductive material is thereby obtained. Further, the heating temperature and the heating time under the Ar gas atmosphere may be changed as appropriate, and generally the heating temperature has only to be not lower than 250° C. and not higher than 600° C. and the heating time has only to be 0.1 hours or more. Experimental Example 2 As the raw materials, prepared are LiOH (having a purity of 98.0% or more), LiBr (having a purity of 99.9% or more), and LiF (having a purity of 99.9%) which are commercially available. These raw materials are weighed so that LiOH:LiBr:LiF should be 0.95:1.0:0.05 (molar ratio), and the same processing as performed in Experimental Example 1 is performed, to thereby obtain the powder of the lithium ion conductive material. Experimental Example 3 The same processing as performed in Experimental Example 2 is performed, except that these raw materials are weighed so that LiOH:LiBr:LiF should be 0.9:1.0:0.1 (molar ratio), to thereby obtain the powder of the lithium ion conductive material. Experimental Example 4 The same processing as performed in Experimental Example 2 is performed, except that these raw materials are weighed so that LiOH:LiBr:LiF should be 0.85:1.0:0.15 (molar ratio), to thereby obtain the powder of the lithium ion conductive material. Experimental Example 5 The same processing as performed in Experimental Example 2 is performed, except that these raw materials are weighed so that LiOH:LiBr:LiF should be 0.99:1.0:0.01 (molar ratio), to thereby obtain the powder of the lithium ion conductive material. Experimental Example 6 The same processing as performed in Experimental Example 2 is performed, except that these raw materials are weighed so that LiOH:LiBr:LiF should be 0.87:1.0:0.13 (molar ratio), to thereby obtain the powder of the lithium ion conductive material. Experimental Example 7 The same processing as performed in Experimental Example 2 is performed, except that these raw materials are weighed so that LiOH:LiBr:LiF should be 1.0:1.0:0.11 (molar ratio), to thereby obtain the powder of the lithium ion conductive material. <Crystal Structure Analysis> A crystal structure analysis is performed on the powder of the lithium ion conductive material obtained in each of above-described Experimental Examples. First, in the glove box, the powder of the lithium ion conductive material is ground in the mortar, put into a hermetic holder, and measured while not being exposed to air. The crystal phase thereof is identified by the X-ray diffractometry using Cu-Kα ray in an X-ray diffraction apparatus. Under the measurement conditions of 40 kV, 40 mA, and 2θ=10−70°, a sealed-tube X-ray diffraction apparatus (D8 ADVANCE manufactured by Bruker Corporation) is used. The step width of the measurement is 0.02°.FIG.2shows the X-ray diffraction spectrum in Experimental Example 3. In the X-ray diffraction spectrum of the powder of the lithium ion conductive material in each of Experimental Examples, a peak is detected at the same position as the position of a peak of antiperovskite-type Li2(OH)Br of ICCD No. 035-0241 having the most intense peak in the vicinity of 2θ=31.2°. Since respective ionic radii of OH and F are 1.37 Å and 1.33 Å and it is thought that almost no peak shift occurs due to replacement, it is estimated that the lithium ion conductive material includes a crystal phase of antiperovskite-type Li2(OH)1-xFxBr (where 0≤x≤1) or a crystal phase having a structure similar thereto. The word “antiperovskite-type” means that “the material has an antiperovskite-type crystal structure”. In the diffraction spectra of Experimental Examples 2 to 6, a peak is detected at the same position as the position of a peak of layered antiperovskite-type Li5(OH)2Br3of ICCD No. 072-6895 having the most intense peak in the vicinity of 2θ=30.2°. As described above, since it is thought that almost no peak shift occurs due to replacement between OH and F, it is estimated that the lithium ion conductive material includes a crystal phase of layered antiperovskite-type Li5(OH)2-xFxBr3(where 0≤x≤2) or a crystal phase having a structure similar thereto. The word “layered antiperovskite-type” means that “the material has a layered antiperovskite-type crystal structure”. Herein, in order to relatively compare the content percentages of the layered antiperovskite-type substance, the peak intensity ratio in the X-ray diffraction spectra of the antiperovskite-type substance and the layered antiperovskite-type substance is calculated by the following method. Assuming that the peak intensity of the X-ray diffraction spectrum in the vicinity of 2θ=31.2°, which is thought to correspond to the antiperovskite-type substance, is A and the peak intensity of the X-ray diffraction spectrum in the vicinity of 2θ=30.2°, which is thought to correspond to the layered antiperovskite-type substance, is B, a value of B/(A+B) is obtained as the peak intensity ratio. Further, for this calculation, used is JADE 7 manufactured by MDI (Materials Data, Inc.), which is a commercially-available software. The peak search conditions of JADE 7 are as follows. The filter type is a parabolic filter and the peak position definition is a peak top, and as to threshold values and ranges, the threshold value σ=3.0, the peak intensity cutoff (%)=0.1%, the range of BG determination=1.0, the number of points in BG averaging=7, and the angle range=10.0 to 70.0°. Further, the variable filter length (data point) is ON, elimination of Kα2 peak is ON, and elimination of existing peak list is ON. <Composition Analysis> A composition analysis is performed on the powder of the lithium ion conductive material obtained in each of above-described Experimental Examples. 1 g of the lithium ion conductive material is dissolved in 100 cc of ion exchange water, to thereby form an aqueous solution. The aqueous solution is diluted as appropriate, and a quantitative analysis is performed by the calibration curve method, specifically, by using ion chromatography (IC) on F and Br which are halogens and using ICP (inductively coupled plasma) atomic emission spectroscopy (ICP-AES) on Li. As to the OH group which cannot be directly analyzed, the molar amounts of F, Br, and Li are calculated from respective analysis values thereof, the numbers of moles thereof expressed to two decimal places are multiplied by respective valencies assuming that F has a valency of −1, Br has a valency of −1, and Li has a valency of +1, and the number of moles of OH is calculated so that the total of electric charges respectively multiplied by the numbers of moles of F, Br, Li, and OH should be 0.00 assuming that OH has a valency of −1. <Measurement of Lithium Ionic Conductivity> In order to measure the lithium ionic conductivity of the lithium ion conductive material which is obtained in each of above-described Experimental Examples, a SUS cell is manufactured. First, 0.05 g of ceramic spacer is mixed into 1 g of the powder of the lithium ion conductive material and this is mixed lightly in the mortar. Then, 0.02 g of the obtained powder of the lithium ion conductive material with the ceramic spacer mixed therein is so laid down as to be spread entirely on a stainless steel plate having a diameter of 15.5 mm and a thickness of 0.3 mm, which has been subjected to Au sputtering of 500 Å. Further, on the powder of the lithium ion conductive material, another stainless steel plate having a diameter of 15.5 mm and a thickness of 0.3 mm, which has been subjected to Au sputtering of 500 Å, is placed so that an Au sputtered surface thereof should be in contact with the powder of the lithium ion conductive material, to thereby form a layered body, and a weight is placed thereon. The layered body is put into an electric furnace in the glove box, and a heat treatment is performed at 400° C. for 45 minutes, to thereby melt the powder of the lithium ion conductive material. Then, the molten lithium ion conductive material is cooled at 100° C./h, to thereby form the lithium ion conductive material layer, and the SUS cell is thereby obtained. When the thickness of the SUS cell is measured and the sum of the thicknesses of the upper and lower stainless steel plates each having a thickness of 0.3 mm and the Au sputtering thickness is subtracted from the thickness of the SUS cell, the thickness of the lithium ion conductive material layer in each of Experimental Examples is calculated to be 30 μm. The lithium ionic conductivity of the SUS cell is measured by the AC (alternating current) impedance measurement in a range from 0.3 MHz to 0.1 Hz. The AC impedance measurement is performed with measuring terminals connected to respective surfaces of the two SUS plates which are surfaces of opposite side to the lithium ion conductive material layer. Table 1 shows respective results of the composition analysis, the measurement of the lithium ionic conductivity, and the peak intensity ratio in the X-ray diffraction spectrum. TABLE 1Raw Material RatioSynthesisAnalysis ValuesValues ofPeakLiBrLiOHLiFConditionsICP-AESICComposition FormulaIntensity1XYTemp.TimeLiFBrLia(OH)bFcBrConductivityRatioUnitmolmolmol° C.hrmol/gmol/gmol/gab = a − c − 1cS/cmB/(A + B)Experimental1103500.51.87E−040.00E+009.39E−051.990.990.008.0E−070Example 1Experimental10.950.053500.51.87E−044.26E−068.89E−052.101.050.051.1E−060.02Example 2*Experimental10.90.13500.51.73E−048.42E−068.64E−052.000.900.101.9E−060.13Example 3*Experimental10.850.153500.51.73E−041.05E−059.01E−051.920.800.124.6E−070.24Example 4Experimental10.990.013500.51.70E−041.10E−069.01E−051.890.880.018.5E−070.005Example 5*Experimental10.870.133500.51.89E−041.02E−058.90E−052.121.010.111.2E−060.2Example 6*Experimental110.113500.51.98E−049.97E−068.91E−052.221.110.111.1E−060Example 7* In Table 1, Experimental Examples 2, 3, 5 to 7 with the mark “*” are embodiments in which the lithium ionic conductivity is high. The other Experimental Examples are comparative examples. From these Experimental Examples, it is thought that when the molar ratio of LiBr, LiOH, and LiF which are the raw materials is 1:X:Y where 0.87≤X≤1 and 0.01≤Y≤0.13, it is possible to achieve a new lithium ion conductive material having relatively high lithium ionic conductivity. Further, it is found that the lithium ionic conductivity can be increased by including LiF even just a little bit in the raw materials. Though detailed reason is not known, it is thought that the lithium ionic conductivity can be increased as a result of complicatedly relating whether Li5(OH)2-xFxBr3(where 0≤x≤2) which is a subphase is formed or not and existence of some unreacted raw materials to each other, from the above condition about X and Y. In this case, assuming that the composition formula is Lia(OH)bFcBr, the value of “c” is not less than 0.01 and not more than 0.11, where b=a−c−1 and the value of “a” has a range not less than 1.8 and not more than 2.3 depending on variations in the weighing process or the analysis process. More preferably, the value of “c” is not less than 0.05 and not more than 0.11. The above-described peak intensity ratio (B/(A+B)) in the X-ray diffraction spectrum is not less than 0 and not more than 0.2. More preferably, the peak intensity ratio (B/(A+B)) is not less than 0.02 and not more than 0.2. The above-described lithium ion conductive material, all-solid-state secondary battery, and manufacturing method thereof are not limited to those described above but may be modified in various manners. For example, the lithium ion conductive material may be used for any use other than the all-solid-state secondary battery. The manufacturing condition of the lithium ion conductive material may be changed as appropriate. Further, the raw materials used for manufacturing the lithium ion conductive material may include any other material. As described earlier, the composition and the manufacturing method of the all-solid-state secondary battery1may be changed as appropriate. The positive electrode11and the negative electrode12described above are each only one example. In the all-solid-state secondary battery1, instead of individually manufacturing the positive electrode11and the negative electrode12in advance, heating and pressurizing may be performed in a state where the current collector111, the positive electrode layer112, the lithium ion conductive material, the negative electrode layer122, and the current collector121are layered. Even when the same heat treatment as performed to obtain the above-described SUS cell is performed while using a plate of positive electrode layer, e.g., a plate of lithium cobalt oxide instead of one stainless steel plate and a plate of negative electrode layer, e.g., a plate including Ti, in which a lithium ion is insertable and removable at 0.4 V or more with the Li/Li+equilibrium potential as the reference instead of the other stainless steel plate in the manufacture of the above-described SUS cell, the all-solid-state secondary battery can be manufactured. The configurations in the above-discussed preferred embodiment and variations may be combined as appropriate only if those do not conflict with one another. While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention. REFERENCE SIGNS LIST 1All-solid-state secondary battery11Positive electrode12Negative electrode13Lithium ion conductive material layer | 17,847 |
11862786 | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in more detail below with reference to the drawings and in connection with embodiments. It should be understood that, the exemplary embodiments and description thereof of the invention are used for illustrating the present invention and are not intended to limit the invention Referring toFIG.1andFIG.2, a neural electrode in a preferred embodiment of the present invention includes a current generation device1, a first electrode3and a second electrode4. The current generation device1is connected to the first electrode3and the second electrode4through a conductive metal wire2respectively. At least one of the first electrode3and the second electrode4is a graphene electrode. The second electrode4is a graphene electrode in this embodiment. The graphene electrode has a disc or a strip shape. To increase a specific surface area and improve a charge injection rate and stability, the graphene electrode4is a three-dimensional porous graphene electrode. To avoid potential safety hazards, an insulating protective sleeve5is disposed outside the conductive metal wire2. Preferably, the protective sleeve5is silica gel or polyurethane, and the thickness of the protective sleeve5is between 0.5 mm and 3 mm. Preferably, the conductive metal wire2is a silver wire or a copper wire, and is preferably a silver wire. Preferably, the conductive metal wire2is connected to the three-dimensional porous graphene electrode by a conductive adhesive, and is preferably a silver adhesive. To support the three-dimensional porous graphene electrode4and protect the conductive connecting surface of the conductive metal wire2, the silver adhesive and the three-dimensional porous graphene electrode4, a protective substrate6is disposed on one surface of the three-dimensional porous graphene electrode4. The other surface of electrode is unprotected and the graphene is exposed. The conductive connecting surface is connected with and supported by the protective substrate6. Preferably, the protective substrate6is formed of a polymer material. The polymer material is polydimethylsiloxane (PDMS), polyurethane or a polyacrylic acid copolymer, and is preferably PDMS. Preferably, the thickness of the protective substrate6is 0.1 mm to 2 mm. If the thickness of protective substrate in the three-dimensional porous graphene electrode4is excessively large, the three-dimensional porous graphene electrode4is not soft enough and heavy and thus has poor usability. If the protective substrate6is thin, the three-dimensional porous graphene electrode4is not firm and cannot completely prevent the graphene electrode4from contacting with a tissue. If the protective substrate6fully covered onto the graphene foam material, making the graphene material insulated with the tissues and organs. The electrode4cannot work properly. Therefore, a thickness ratio of the three-dimensional porous graphene electrode4to the protective substrate6is 1:0.25 to 4. Embodiment 1 Preparation of a neural electrode based on a three-dimensional porous graphene material includes the following steps:(1) A three-dimensional porous graphene electrode4was bonded to a silver wire by a silver adhesive, and then was heated to 70° C. such that the silver adhesive was completely cured, wherein the thickness of the three-dimensional porous graphene electrode4is 0.5 mm.(2) A connecting portion of the silver wire and the three-dimensional porous graphene electrode4was immersed in a PDMS solution, vacuuming was performed to remove bubbles from the solution, and the temperature was kept at 70° C. for 6 h to cure PDMS, then a protective substrate6with a thickness of 2 mm was prepared. Around 0.2 mm of graphene foam material was exposed and 0.3 mm (0.5−0.2=0.3 mm) of graphene foam material was protected with PDMS.(3) The three-dimensional porous graphene electrode4with the protective substrate6and a metal titanium electrode were connected to a current generation device1through a silver wire respectively, and then a neural electrode was obtained. Embodiment 2 Preparation of a neural electrode based on a three-dimensional porous graphene material includes the following steps:(1) A three-dimensional porous graphene electrode4was bonded to a copper wire by a silver adhesive, and then was heated to 50° C. such that the silver adhesive was completely cured, wherein the thickness of the three-dimensional porous graphene electrode4is 2 mm.(2) A connecting portion of the copper wire and the three-dimensional porous graphene electrode4was immersed in a PDMS solution, vacuuming was performed to remove bubbles from the solution, and the temperature was kept at 100° C. for 1 h to cure PDMS, then a protective substrate6with a thickness of 0.5 mm was prepared. 1.5 mm of graphene foam was exposed. Before PDMS is cured, a heart-shaped mold may be lightly pressed on a graphene surface, to produce a heart-shaped deformation on the graphene surface. After PDMS is completely cured, a concave electrode is obtained to better fit a heart region.(3) The three-dimensional porous graphene electrode4with the protective substrate6and a metal platinum electrode were connected to a current generation device1through a copper wire respectively, and then a neural electrode was obtained. Embodiment 3 Preparation of a neural electrode based on a three-dimensional porous graphene material includes the following steps:(1) A three-dimensional porous graphene electrode was bonded to a silver wire by a silver adhesive, and then was heated to 60° C. such that the silver adhesive was completely cured, wherein the thickness of the three-dimensional porous graphene electrode4is 1 mm.(2) A connecting portion of the silver wire and the three-dimensional porous graphene electrode4was immersed in a polyurethane solution, vacuuming was performed to remove bubbles from the solution, the solution was placed at a room temperature for 24 h to cure polyurethane, wherein a protective substrate with a thickness of about 1 mm was prepared. And 0.5 mm of graphene foam was exposed.(3) The three-dimensional porous graphene electrode4with the protective substrate6and a metal gold electrode were connected to a current generation device1through a silver wire respectively, and then a neural electrode was obtained. Embodiment 4 Preparation of a neural electrode based on a three-dimensional porous graphene material includes the following steps:(1) Two three-dimensional porous graphene electrodes were bonded to silver wires by a silver adhesive respectively, and then were heated to 60° C. such that the silver adhesives were completely cured, wherein the thickness of each three-dimensional porous graphene electrode4is 1 mm.(2) A connecting portion between one of the silver wires and the three-dimensional porous graphene electrode4was immersed in a pre-polymer solution of polyacrylic acid, vacuuming was performed to remove bubbles from the solution, the solution was irradiated under ultraviolet light (10 W) for 6 h to cure polyacrylic acid, where the thickness of an obtained protective substrate6is approximately 1 mm. And 0.5 mm of graphene foam was exposed.(3) The three-dimensional porous graphene electrode4with the protective substrate6and the other three-dimensional porous graphene electrode were connected to a current generation device1through a silver wire respectively, and then a neural electrode was obtained. The neural electrode of the present invention has the following working principles: The prepared flexible neural electrode based on three-dimensional porous graphene is applied to cardiac pacemaker. In the soft and flexible neural electrode based on three-dimensional porous grapheme, one electrode is a three-dimensional porous graphene electrode4, and another is a metal titanium electrode. The three-dimensional porous graphene electrode4is implanted in a human's heart for exerting an electrical pulse to the heart to stimulate the heart to beat. The surface of exposed graphene foam is faced to the heart. The metal titanium in a metal titanium electrode may alternatively be platinum or gold. The metal titanium electrode may also alternatively a three-dimensional porous graphene electrode4. The prepared flexible neural electrode based on three-dimensional porous graphene may further be wound on a nerve for use. A typical use process is as follows: a surgery is performed to expose a nerve, and then a three-dimensional porous graphene electrode4in a strip form is lightly wrapped on the nerve. The surface of exposed graphene foam is faced to the nerve. The surgery should be performed as lightly as possible to avoid fracture of graphene, and then the cut tissue is stitched. After testing, the flexible neural electrode based on three-dimensional porous graphene foam has the following effects: a charge injection amount in a unit area is 3 to 100 times that of a conventional electrode. When nerve cells are cultured on the surface, a cell survival rate is higher than 90%. An end surface of graphene may be curled for use. After graphene is curled by 100 times, a resistance change is less than 50%. After graphene is implanted in a body, a resistance change is less than 200% in three months. Embodiment 5 The preparation of a mineralized three-dimensional porous graphene foam material includes the following steps:(1) Three-dimensional porous graphene foam material was fabricated by chemical vapor deposition (CVD) with three-dimensional porous nickel as catalyst. After removing the nickel catalyst, and a three-dimensional porous graphene foam scaffold was obtained.(2) O2plasma treatment was performed on the three-dimensional porous graphene scaffold for 3 min to 5 min, and then the three-dimensional porous graphene scaffold was covered with a filter paper.(3) 2 mmol to 100 mmol bicarbonate ions were added to a simulated body fluid with a tenfold concentration (the simulated body fluid with a tenfold concentration is formed of compounds such as NaCl, CaCl2), MgCl2, NaHCO3and Na2HPO4), filtering was performed by using a filtering system with a 0.22 μm hole diameter, then the three-dimensional porous graphene support was placed on a decoloring shaker for 1 h to 12 h at a room temperature, and a mineralized three-dimensional porous graphene material was obtained, and finally the mineralized three-dimensional porous graphene material was washed with water and ethanol. A mole ratio of carbon, calcium and phosphorus in the mineralized three-dimensional porous graphene material is 1:0.05:0.03 to 1:500:300. The mole ratio is preferably 1:0.5:0.3 to 1:50:30. The mole ratio is further preferably 1:1:0.6 to 1:10:6. A hole diameter of the mineralized three-dimensional porous graphene material is 100 μm to 300 μm. The porosity of the mineralized three-dimensional porous graphene material is 99.3±0.5%. A frame width forming a three-dimensional void is 100 μm to 200 μm. The coverage of hydroxyapatite in the mineralized three-dimensional porous graphene material is 90% to 100%. Particle sizes of the hydroxyapatite are between 5 nm and 50 μm. The mineralized three-dimensional porous graphene material was characterized by scanning electron microscope. Specifically, 10 mmol bicarbonate ions were added to a simulated body fluid with a tenfold concentration, and the simulated body fluid is then placed for 4 h, and a mole ratio of carbon, calcium and phosphorus in the obtained mineralized three-dimensional porous graphene material is 1:0.5:0.3 to 1:2:1.2. The coverage of hydroxyapatite in the mineralized three-dimensional porous graphene material is 90% to 95%. Particle sizes of the hydroxyapatite are between 5 nm and 1 μm, and the porosity of the hydroxyapatite is 99.3±0.5%. The obtained material is shown inFIG.3. The crystal inFIG.3shows that the three-dimensional porous graphene support is successfully mineralized. 100 mmol bicarbonate ions were added to the simulated body fluid with a tenfold concentration, and the simulated body fluid is then placed for 0.5 h, and a mole ratio of carbon, calcium and phosphorus in the obtained mineralized three-dimensional porous graphene material is 1:5:3 to 1:20:12. The coverage of hydroxyapatite in the mineralized three-dimensional porous graphene material is 95% to 100%. Particle sizes of the hydroxyapatite are mostly between 50 nm and 20 μm. Some particles of the hydroxyapatite agglomerate, particle sizes of agglomerated particles are about 50 μm, and the porosity of the hydroxyapatite is 98±1%. Embodiment 6 Preparation of a bone defect filler using a mineralized three-dimensional porous graphene material. The mineralized three-dimensional porous graphene material of the embodiment 5 was immersed in water, after freezing at −20° C., the mineralized three-dimensional porous graphene material was cut into into sheets at −10° C., then the mineralized three-dimensional porous graphene sheets were immersed in 75% ethanol, dried, and radiated for sterilization to obtain the bone defect filler. Embodiment 7 Preparation of a bone defect filler using a mineralized three-dimensional porous graphene material. The mineralized three-dimensional porous graphene material of the embodiment 5 was immersed in tert-Butyl alcohol, after freezing at −0.1° C., the mineralized three-dimensional porous graphene material was cut into sheets at 5° C., then the mineralized three-dimensional porous graphene sheets were immersed in 75% ethanol, washed with pure ethanol, dried, and radiated for sterilization to obtain the bone defect filler. Embodiment 8 Preparation of a bone defect filler using a mineralized three-dimensional porous graphene material. The mineralized three-dimensional porous graphene material of the embodiment 5 was immersed in a 50% aqueous solution of tert-Butyl alcohol, after freezing at −5° C., the mineralized three-dimensional porous graphene material was cut into sheets at 0° C., then the mineralized three-dimensional porous graphene sheets were immersed in 75% ethanol, washed with water, washed with pure ethanol, freeze-dried at low temperature, and radiated for sterilization to obtain the bone defect filler. According to the clinical requirements, a single sheet is used, or a plurality of sheets are stacked or bonded by a biomedical liquid, for filling bone defects having various shapes. As compared with a hydroxyapatite biological ceramic that is used as a conventional synthetic bone replacement, when the mineralized three-dimensional graphene sheet is used as a bone defect filler, the biological compatibility, bone conductivity, and osteogenic induction ability are more desirable, and during the culture of mesenchymal stem cells on surface, the proportion of mesenchymal stem cells that differentiate into osteogenic cells is 2 times to 20 times larger, and the differentiation time is earlier by 1.1 times to 5 times. Compared with a hydroxyapatite biological ceramic (a control group) that is used as a bone defect filling material, when the mineralized three-dimensional porous graphene sheets (an experimental group) are used as bone defect filling materials, in one month to three months after filling in bone defect regions, the bone density changes faster than that in the control group. After three to six months, the bone density in the experimental group can reach 60% to 90% of the original bone density, and the bone density in the control group is only 30% to 60%. The bone density in the experimental group is 1.1 times to 5 times of the bone density in the control group. As observed in a CT image, there is no clear interface in the experimental group, but there is a distinct bone-material interface in the control group. The above preferred embodiments are described for illustration only, and are not intended to limit the scope of the invention. It should be understood, for a person skilled in the art, that various improvements or variations can be made therein without departing from the spirit and scope of the invention, and these improvements or variations should be covered within the protecting scope of the invention. | 16,197 |
11862787 | EMBODIMENTS Next, a negative electrode active material for a lithium-ion battery (hereinafter, sometimes simply referred to as a negative electrode active material) according to an embodiment of the present invention, a lithium-ion battery (hereinafter, sometimes simply referred to as a battery) using the negative electrode active material in a negative electrode will be specifically described. 1. Negative Electrode Active Material The negative electrode active material of the present embodiment is made of a Si—Zr—Sn—X alloy, and contains a Si phase, a Si—Zr compound phase, and a Sn—X compound phase. Here, an element X is at least one element selected from the group consisting of Cu, Ti, Co, Fe, Ni, and Zr. The negative electrode active material of the present embodiment does not contain any other elements than these main elements (Si, Zr, Sn and elements X) except for elements contained inevitably. The Si phase is a phase mainly containing Si. In view of increasing a Li storage amount and the like, it is preferable to consist of a single phase of Si. However, inevitable impurities may be contained in the Si phase. Although the Si—Zr compound phase mainly contains Si2Zr, other Zr silicide phases (Si4Zr, Si3Zr2, SisZr4, SiZr, SiZr2, etc.) may be inevitably contained. A shape of the Si—Zr compound phase dispersed in a matrix phase (Si phase) is not particularly limited, but a flat shape in which a contact area with the Si phase increases is desirable in view of preventing expansion and contraction of the Si phase by the Si—Zr compound phase. On the other hand, the Sn—X compound phase is composed of a compound of Sn and at least one element selected from the group consisting of Cu, Ti, Co, Fe, Ni, and Zr. The Sn—X compound has a higher Li ion diffusivity than the Si—Zr compound. When Li reactivity is compared, the Si—Zr compound is about 100 mAh/g and a Sn simple substance is about 930 mAh/g, while the Sn—X compound is 150 mAh/g to 600 mAh/g. That is, in the negative electrode active material of the present embodiment, a diffusion path of Li-ions is easily ensured through the Sn—X compound phase. On the other hand, the Sn—X compound phase has a smaller degree of expansion due to a reaction with Li-ions as compared with Sn that has a higher reactivity with Li-ions. Therefore, adverse effects on cycle characteristics due to formation of the Sn—X compound can also be reduced. The Sn—X compound phase may include only one kind of compound, and it is also possible to include two or more kinds of compounds, for example, a Sn—Zr compound and a Sn—Cu compound. As described above, the negative electrode active material of the present embodiment is composed of Si, a Si—Zr compound, and a Sn—X compound. However, the negative electrode active material of the present embodiment may contain, as an impurity, Sn in a form of a simple substance, which is in a non-compound form, in a proportion of up to 5 mass % to the whole. A form of the negative electrode active material is not particularly limited. Specifically, examples of the form include a flake form, a powder form and the like. The powder form is preferable in view of being easily applied to production of the negative electrode. The negative electrode active material of the present embodiment may be dispersed in an appropriate solvent. The negative electrode active material of the present embodiment can be produced by a method containing a step of forming a quenched alloy by quenching a molten alloy having a predetermined chemical composition. In the case where the obtained quenched alloy is not in a powder form or is desired to be further reduced in diameter, a step of pulverizing the quenched alloy by a suitable pulverizing means to get a powder form may be added. If necessary, a step of classifying the obtained quenched alloy to adjust it into an appropriate particle size, and the like may be added. It is also possible to produce the negative electrode active material of the present embodiment by separately preparing Si, the Si—Zr compound, and the Sn—X compound and mixing them. A particle diameter (average particle diameter (d50)) of the active material is desirably controlled in a range of 1 μm to 20 μm. The average particle diameter (d50) in the present invention is a volume basis and can be measured by using a laser diffraction and scattering particle size distribution measurement device (Microtrac MT3000). Even in the case where a Si alloy is used as the active material, volume expansion and contraction of the active material itself occurs accompanying the charging and discharging reaction, so that a stress is generated in a binder layer formed by binding the negative electrode active material with a binder, that is, a conductive film. In this case, when the binder cannot withstand the stress, the binder is collapsed, and as a result, the conductive film is peeled off from a current collector, resulting in a decrease in conductivity in an electrode to decrease cycle characteristics during charging and discharging. However, in the case where an average particle diameter of the active material is adjusted to a fine particle of 1 μm to 20 μm, a contact area of the active material with the binder is increased since the active material is fine particles, so that the collapse of the binder is favorably prevented, and as a result, the cycle characteristics can be improved. In the above-described production method, the molten alloy can be obtained, for example, by weighing each raw material so as to have a predetermined chemical composition, and dissolving each weighed raw material by using a dissolving means such as an arc furnace, a high-frequency induction furnace, and a heating furnace. Specific examples of the method of quenching the molten alloy include liquid quenching methods such as a roll-quenching method (a single-roll-quenching method, a twin-roll-quenching method, etc.) and an atomization method (a gas atomization method, a water atomization method, a centrifugal atomization method, etc.). It is particularly desirable to use a roll-quenching method having a high cooling speed. Here, in the case where the negative electrode active material of the present embodiment is produced by using a molten alloy containing Si and Zr, the following method is specifically preferable. That is, in the case where a roll-quenching method is applied, the molten alloy, which is tapped in a chamber such as a quenching and recovery chamber to flow down continuously (in a rod shape), is cooled on a rotation roll (which may be made of a material such as Cu or Fe, and a roll surface of which may be plated) which rotates at a circumferential speed of about 10 m/s to 100 m/s. The molten alloy is made into foil or a foil piece by being cooled on the roll surface. In this case, the alloy material is pulverized by an appropriate pulverization means such as a ball mill, a disk mill, a coffee mill, and mortar pulverization, and then classified or further finely pulverized as necessary to obtain the powdery negative electrode active material. On the other hand, in the case where an atomization method is applied, gas such as N2, Ar, He, or the like is sprayed at a high pressure (e.g., 1 MPa to 10 MPa) to the molten alloy, which is tapped in a spray chamber to flow down continuously (in a rod shape), to cool the molten alloy while pulverizing. The cooled molten alloy approaches a spherical shape while falling freely in semi-molten state in the spray chamber, and the powdery negative electrode active material is obtained. Furthermore, in view of improving a cooling effect, high-pressure water may be sprayed instead of the gas. 2. Battery The battery of the present embodiment is configured by using a negative electrode containing the negative electrode active material of the present embodiment. The negative electrode includes a conductive substrate and a conductive film laminated on a surface of the conductive substrate. The conductive film contains at least the above-described negative electrode active material in a binder. In addition, the conductive film may also contain a conductive auxiliary as necessary. In the case where the conductive auxiliary is contained, it is easy to secure a conductive path of electrons. Besides, the conductive film may contain a frame material if necessary. In the case where the frame material is contained, expansion and contraction of the negative electrode during charging and discharging are easily prevented, and collapse of the negative electrode can be prevented, so that cycle characteristics can be further improved. The conductive substrate functions as a current collector. Examples of the material thereof include Cu, a Cu alloy, Ni, a Ni alloy, Fe, and a Fe alloy. Cu and the Cu alloy are preferable. Specific examples of a form of the conductive substrate include a foil form and a plate form. The foil form is preferable in view of reducing a volume of the battery and improving a degree of freedom of shape. As a material of the binder, use can be suitable made of a polyvinylidene fluoride (PVdF) resin, a fluorine resin such as polytetrafluoroethylene, a polyvinyl alcohol resin, a polyimide resin, a polyamide resin, a polyamide-imide resin, styrene-butadiene rubber (SBR), polyacrylic acid, and the like. These can be used alone or in combination of two or more thereof. Among them, the polyimide resin is particularly preferable since it has a high mechanical strength, can well withstand volume expansion of the active material, and can well prevent detachment of the conductive film from the current collector caused by destruction of the binder. Examples of the conductive auxiliary include carbon black such as ketjen black, acetylene black, and furnace black, graphite, carbon nanotubes, and fullerene. These may be used alone or in combination of two or more thereof. Among them, ketjen black, acetylene black or the like can be suitably used in view of easily ensuring electron conductivity. A content of the conductive auxiliary is preferably in a range of 0 to 30 parts by mass and more preferably 4 to 13 parts by mass with respect to 100 parts by mass of the negative electrode active material in view of a degree of improvement of conductivity, an electrode capacity and the like. An average particle diameter (d50) of the conductive auxiliary is preferably 10 nm to 1 μm and more preferably 20 nm to 50 nm in view of dispersibility, ease of handling and the like. As the frame material, use can be suitably made of a material which does not expand and contract or expands and contracts little, during charging and discharging. Examples thereof include graphite, alumina, calcia, zirconia, and activated carbon. These may be used alone or in combination of two or more thereof. Among them, graphite or the like can be suitably used in view of conductivity, a degree of Li activation and the like. A content of the frame material is preferably in a range of 10 to 400 parts by mass and more preferably 43 to 100 parts by mass with respect to 100 parts by mass of the negative electrode active material in view of improvement of cycle characteristics, and the like. An average particle diameter of the frame material is preferably 10 μm to 50 μm and more preferably 20 μm to 30 μm in view of functionality as a frame material, control of electrode film thickness and the like. The average particle diameter of the frame material is a value measured by using a laser diffraction and scattering particle size distribution measurement device. The negative electrode can be produced, for example, by adding a necessary amount of the negative electrode active material and, if necessary, the conductive auxiliary and the frame material in a binder dissolved in a suitable solvent, to obtain a paste, coating the obtained paste on a surface of the conductive substrate, drying, and applying pressure, heat treatment or the like as necessary. In the case where the negative electrode is used to form a lithium-ion battery, a positive electrode, an electrolyte, a separator, and the like, which are basic constituent elements of the battery other than the negative electrode, are not particularly limited. Specific examples of the positive electrode include those obtained by forming a layer containing a positive electrode active material such as LiCoO2, LiNiO2, LiFePO4, and LiMnO2on a surface of the current collector such as aluminum foil. Specific examples of the electrolyte include an electrolytic solution obtained by dissolving a lithium salt in a non-aqueous solvent. In addition, an electrolyte obtained by dissolving a lithium salt in a polymer, a polymer solid electrolyte obtained by impregnating a polymer with the above-described electrolytic solution, and the like can also be used. Specific examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. These may be used alone or in combination of two or more thereof. Specific examples of the lithium salt can include LiPF6, LiBF4, LiClO4, LiCF3SO3, and LiAsF6. These may be used alone or in combination of two or more thereof. Furthermore, other battery constituent elements such as a separator, a can (battery case) and a gasket may be contained, and any of these can be combined as appropriate to form a battery as long as they are usually employed in a lithium-ion battery. A shape of the battery is not particularly limited, may be any shape such as a cylindrical shape, a square shape or a coin shape, and can be appropriately selected depending on a specific application thereof. EXAMPLES Hereinafter, the present invention will be described more specifically by using Examples. Here, unit % of an alloy composition is mass % unless otherwise specified. 1. Production of Negative Electrode Active Material Each raw material was weighed so as to have the alloy composition shown in the following Table 1. Each weighed raw material was heated and dissolved by using a high-frequency induction furnace to prepare molten alloys. Each of the obtained molten alloys was quenched by using a single-roll-quenching method to obtain quenched alloy ribbons. A roll circumferential speed was 42 m/s, and a nozzle distance was 3 mm. Each of the obtained quenched alloy ribbons was mechanically pulverized by using a mortar to produce powdery negative electrode active materials. Furthermore, miniaturization by using a planetary ball mill was performed so as to obtain a target size of the Si phase as necessary. TABLE 1Chemical components (mass %)SiZrSnCuTiCoFeTarget constituent phasesExamples155.639.43.11.9———95{33[Si]-67[Si2Zr]}-5[Sn5Cu6]255.639.43.11.9———95{33[Si]-67[Si2Zr]}-5[Sn5Cu6]355.639.41.93.1———95{33[Si]-67[Si2Zr]}-5[SnCu3]455.639.43.4—1.6——95{33[Si]-67[Si2Zr]}-5[Sn5Ti6]555.639.44.0——1.0—95{33[Si]-67[Si2Zr]}-5[Sn2Co]655.639.43.3——1.7—95{33[Si]-67[Si2Zr]}-5[SnCo]755.640.83.6————95{33[Si]-67[Si2Zr]}-5[Sn2Zr]855.642.22.2————95{33[Si]-67[Si2Zr]}-5[Sn3Zr5l959.735.33.11.9———95{40[Si]-60[Si2Zr]}-5[Sn5Cu6]1071.523.53.11.9———95{60[Si]-40[Si2Zr]}-5[Sn5Cu6]1177.417.63.11.9———95{70[Si]-30[Si2Zr]}-5[Sn5Cu6]1248.047.03.11.9———95{20[Si]-80[Si2Zr]}-5[Sn5Cu6]1349.735.35.79.3———85{33[Si]-67[Si2Zr]}-15[Sn5Cu6]1455.939.60.20.3———95.5{33[Si]-67[Si2Zr]}-0.5[Sn5Cu6]Comparative158.541.5—————33[Si]-67[Si2Zr]Examples262.937.1—————40[Si]-60[Si2Zr]375.224.8—————60[Si]-40[Si2Zr]458.541.5—————33[Si]-67[Si2Zr]555.639.45.0————95{33[Si]-67[Si2Zr]}-5[Sn]663.3—3.11.9——31.795{33[Si]-67[Si2Fe]}-5[Sn5Cu6] 2. Structure Observation of Negative Electrode Active Material, and the Like Structure observation was performed on negative electrode active materials according to Examples and Comparative Examples by a scanning electron microscope (SEM). Analysis by XRD (X-ray diffraction) was also performed together to confirm whether negative electrode active materials were composed of phases of Si, a Si—Zr compound and a Sn compound. Types of the confirmed compound phase are as shown in the following Table 2. In the XRD analysis, the measurement was performed on an angle range of 120° to 20° by using a Co bulb. TABLE 2Si—XSiSicompoundInitialInitialphasephaseSiphaseSi—XdischargingcoulombCapacityamountsizecompundamountCompoundcapacityefficiencyretentionSynthetic(mass %)(nm)phase(mass %)phase[mAh/g](%)rate [%]judgmentExamples131.3300Si2Zr5Sn5Cu6A (1,152)A (78)A (80)A231.31,000Si2Zr5Sn5Cu6A (1,200)A (80)B (65)B331.3300Si2Zr5SnCu3A (1,102)A (77.8)A (78)A431.3300Si2Zr5Sn5Ti6A (1,143)A (77.2)A (75)A531.3300Si2Zr5Sn2CoA (1,109)A (77.4)A (73)A631.3300Si2Zr5SnCoA (1,094)A (77)A (76)A731.3300Si2Zr5Sn2ZrA (1,143)A (77)A(74)A831.3300Si2Zr5Sn3Zr5A (1,112)A (76.8)A (74)A938.0400Si2Zr5Sn5Cu6A (1,411)A (81.2)A(73)A1057.0500Si2Zr5Sn5Cu6A (1,754)A (83.2)A (70)A1166.5500Si2Zr5Sn5Cu6A (2,021)A (87)B (66)B1219.0200Si2Zr5Sn5Cu6B (556)A (71)A (95)B1328.1300Si2Zr15Sn5Cu6A (1,194)A (79.1)B (66)B1431.5300Si2Zr0.5Sn5Cu6A (1,084)B (68)A (73)BComparative1331,000Si2Zr0NoneB (921)A (77)B (65)CExamples2401,000Si2Zr0NoneA (1,100)A (80)C (54)C360500Si2Zr0NoneA (1,800)A (75)C (55)C433300Si2Zr0NoneB (810)C (62)A (73)C531.4300Si2Zr5SnA (1,200)A (78)C (58)C631.4300Si2Fe5Sn5Cu6A (1,200)A (78)C (58)C As a representative example of Examples, a scanning electron micrograph of a negative electrode active material according to Example 2 made of a Si—Zr—Sn—Cu alloy is shown inFIG.1. It can be found that a large number of flat Si compound phases, which looks gray in the drawing, are dispersed in a matrix phase including a Si phase, which looks black in the drawing. In a process of cooling and solidifying the molten alloy, a Si—Zr compound is crystallized at first, and then Si (Si phase) is crystallized, so that the Si—Zr compound phase is formed in an island form, and the Si phase is formed in a sea form. InFIG.1, the phase, which is dispersed and looks white, is a Sn—Cu compound phase crystallized after Si. 3. Evaluation of Size of Si Phase The Si phase was imaged at a magnification of 10,000 by using a SEM. A size of the Si phase was measured from the image. Specifically, five fields of view were imaged, a maximum length of the Si phase in each field of view was measured, and the maximum value was used as the size of the Si phase. In the case where the Si phase spread in a sea form, a connected Si phase was regarded as one Si phase, and the maximum length was measured. The results are shown in Table 2. 4. Calculation of Si Phase Amount and Sn—X Compound Phase Amount A method of calculating a Si phase amount and a Sn—X compound phase amount shown in Table 2 will be described by taking the case of Example 7 containing Si, Zr, and Sn, as an example. (1) First, constituent phases are confirmed. In the case of Example 7, Si, Si2Zr, and Sn2Zr were confirmed as a result of the XRD analysis (see Table 2). (2) When expressed with a ratio of mass %, Sn2Zr is 72.3 [Sn]-27.7 [Zr]. Since the whole amount of Sn is present as the Sn compound, the amount of Zr constituting the Sn compound is 3.6×27.7/72.3=1.4 (mass %). (3) The amount of the remaining Zr 40.8-1.4=39.4 (mass %) corresponds to the amount of Zr constituting the Si compound. (4) When expressed with a ratio of mass %, Si2Zr is 38.1 [Si]-61.9 [Zr]. Since the amount of Zr constituting the Si compound is 39.4 (mass %) as in the above (3), the amount of Si constituting the Si compound is 39.4×38.1/61.9=24.3 (mass %). (5) Therefore, the Si phase amount obtained by subtracting the amount of the compounded Si from the total Si amount can be calculated as 55.6-24.3=31.3 (mass %). (6) The Sn—X compound (Sn2Zr) phase amount can be calculated as 3.6 (Sn amount)×100/72.3=5.0 (mass %). 5. Evaluation of Negative Electrode Active Material 5.1 Production of Coin-Shape Battery for Charging and Discharging Test First, 100 parts by mass of the respective negative electrode active material, 6 parts by mass of ketjen black (manufactured by Lion Corporation) as a conductive auxiliary, and 19 parts by mass of polyimide (thermoplastic resin) binder as a binding agent were compounded and mixed with N-methyl-2-pyrrolidone (NMP) as a solvent to produce pastes containing the respective negative electrode active material. The coin-shape half battery was produced as follows. Here, in order to obtain a simple evaluation, an electrode produced by using the negative electrode active material was used as a test electrode, and Li foil was used as a counter electrode. First, the respective paste was applied to a surface of SUS316L foil (thickness: 20 m), which serves as a negative electrode current collector, to be a thickness of 50 μm by using a doctor blade method, and dried to form a negative electrode active material layer. After the formation, the negative electrode active material layer was compressed by roll-pressing. Accordingly, test electrodes according to Examples and Comparative Examples were produced. Next, the test electrodes according to Examples and Comparative Examples were punched into a disk shape having a diameter of 11 mm and used as the respective test electrode. Next, Li foil (thickness: 500 μm) was punched into substantially the same shape as the above-mentioned test electrode to produce counter electrodes. LiPF6was dissolved in a mixed solvent consisting of equal amount of ethylene carbonate (EC) and diethyl carbonate (DEC), to be a concentration of 1 mol/l to prepare a non-aqueous electrolytic solution. Then, the respective test electrode was housed in a positive electrode can (the test electrode should be a negative electrode in lithium-ion batteries, but in the case where the Li foil is used as a counter electrode, Li foil becomes negative electrode and the test electrode becomes positive electrode), the counter electrode was housed in a negative electrode can, and a separator of a polyolefin microporous membrane was disposed between the test electrode and the counter electrode. Next, the non-aqueous electrolytic solution was injected into each can, and the negative electrode can and the positive electrode can were swaged and fixed separately. 5.2 Charging and Discharging Test Constant current charging and discharging of a current value of 0.2 mA was performed in one cycle by using the respective coin-shape battery, and a value obtained by dividing a capacity (mAh) used during Li emission by mass of the active material (g) was taken as an initial discharging capacity Co (mAh/g). A ratio of the discharging capacity to a charging capacity in the charging and discharging cycle was determined by a percentage of discharging capacity/charging capacity to obtain an initial coulombic efficiency (%). For the measured initial discharging capacity Co, the cases of 1,000 mAh/g or more was evaluated as “A”, the cases of 500 mAh/g or more and less than 1,000 mAh/g was evaluated as “B”, and the cases of less than 500 mAh/g was evaluated as “C”, and the results are shown in Table 2. For the initial coulombic efficiency, the cases of 70% or more was evaluated as “A”, the cases of 65% or more and less than 70% was evaluated as “B”, and the cases of less than 65% was evaluated as “C”, and the results are shown in Table 2. In the second and subsequent cycles, the charging and discharging test was performed at a ⅕ C rate (C rate: when an electricity amount Co is required for discharging (charging) an electrode, a current value which discharges (charges) the electricity amount Co in one hour is set to “1 C”. “5 C” means that the electricity amount Co is discharged (charged) in 12 minutes, and “⅕ C” means that the electricity amount Co is discharged (charged) in 5 hours.). Then, the cycle characteristics were evaluated by performing the charging/discharging cycle 50 times. Then, a capacity retention ratio (discharging capacity after 50 cycles/initial discharging capacity (charging capacity of first cycle)×100) was determined from the obtained discharging capacities. For the capacity retention rate, the cases of 70% or more was evaluated as “A”, the cases of 60% or more and less than 70% was evaluated as “B”, and the cases of less than 60% was evaluated as “C”, and the results are shown in Table 2. Synthetic judgment in Table 2 is based on the evaluation results of items of the initial discharging capacity, the initial coulombic efficiency, and the capacity retention ratio. Here, the cases where all of the items were “A”: “A (pass)” the cases where any one of the items was “B” and the other items were “A”: “B (pass)” the cases where any two or more of the items were “B” or any one or more of the items was “C”: “C (failed)” From the results shown in Table 2 obtained as described above, the followings can be found. Comparative Examples 1 to 4 are examples including no Sn—X compound phase. In Comparative Examples 2 and 3 in which the Si phase amount is 40% or more, the initial discharging capacity and the initial coulombic efficiency are high, but the capacity retention ratio is low. In Comparative Example 1 in which the Si phase amount is 33%, the capacity retention ratio is improved, but does not reach a target (70% or more). In Comparative Example 4 in which a Si size is miniaturized to 300 nm, the capacity retention ratio is high, but the initial discharging capacity and the initial coulombic efficiency decrease. In all of Comparative Examples 1 to 4, the synthetic judgment is “C”. Comparative Example 5 is an example in which an active material is produced by mechanical milling by using a Si—Zr alloy powder and a Sn powder, and a Sn phase having high reactivity with Li-ions is formed instead of a Sn—X compound. Therefore, in Comparative Example 5, the initial discharging capacity and the initial coulombic efficiency are high, but the capacity retention ratio is low, so the synthetic judgment is “C”. Comparative Example 6 is an example in which a Si—Fe compound is formed instead of the Si—Zr compound phase, but the capacity retention ratio is low, so the synthetic judgment is “C”. In Comparative Example 6, it is estimated that since a sea-island structure where the Si phase is an island form and the silicide phase is a sea form is formed, stress generated when Si expands is applied to the silicide phase to collapse particles and thus, the cycle characteristics deteriorate. In contrast, in each Example, it can be found that the synthetic judgment is “A” or “B”, and the cycle characteristics, the initial discharging capacity, and the initial coulombic efficiency are improved in good balance. Particularly, in Examples in which the Si phase amount is 20% to 65%, the Si phase size is 500 nm or less, and the Sn—X compound phase amount is 1% to 10%, an excellent evaluation result is obtained. Although the negative electrode active material for a lithium-ion battery and the lithium-ion battery of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made within a scope not departing from the spirit of the present invention. The present application is based on Japanese Patent Application No. 2019-019856 filed on Feb. 6, 2019 and Japanese Patent Application No. 2020-006710 filed on Jan. 20, 2020, which contents are incorporated herein by reference. | 27,419 |
11862788 | DETAILED DESCRIPTION OF EMBODIMENTS Hereinafter, a suitable embodiment of a non-aqueous electrolyte secondary battery disclosed herein will be described with reference to the drawings as appropriate, using a lithium-ion secondary battery as an example. Needless to say, the following embodiment is not intended to particularly limit the technique disclosed herein. The non-aqueous electrolyte secondary battery disclosed herein is not limited to the lithium-ion secondary battery described below, and a sodium ion secondary battery, a magnesium ion secondary battery, or a lithium-ion capacitor (included in a so-called physical battery) is also a typical example included in the non-aqueous electrolyte secondary battery referred to here. Further, although the lithium-ion secondary battery including a wound electrode body having a structure in which a plurality of electrode bodies of positive electrodes and negative electrodes are wound via a separator will be described here, the electrode body is not limited to such a configuration, and may have a configuration in which the electrode bodies of the positive electrodes and the negative electrodes are stacked via the separator. Matters other than those specifically mentioned in the present specification, and needed for carrying out the present disclosure can be grasped as design matters of those skilled in the art based on the related art in the field. The present disclosure can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the field. Further, in a case where the numerical range is described as A to B (here, A and B are any numerical values) in the present specification, it means A or more and B or less. In the drawings below, the members and the portions that perform the same effects are designated by the same reference numerals, and duplicate descriptions may be omitted or simplified. Further, the dimensional relationship (length, width, and the like) in the drawings below does not always reflect the actual dimensional relationship, and does not limit the configuration of the secondary battery at all. In the present specification, the term “swellable resin” refers to a resin in which a specific thermal capacity is increased by absorbing a non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery. For example, there is a resin in which the specific thermal capacity is increased as compared with before the resin swells the non-aqueous electrolyte in a case where the resin swells the non-aqueous electrolyte obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) at a volume ratio of 30:40:30, and dissolving LiPF6as a supporting salt at a concentration of 1.0 mol/L. The swelling with the non-aqueous electrolyte can be performed, for example, by immersing the resin in the non-aqueous electrolyte at room temperature for about several tens of minutes to several hours. In the present specification, “substantially formed of swellable resin” means the resin portion mainly formed of the swellable resin, and a trace component is allowed to be mixed as long as the effects of the present disclosure are not significantly impaired. Further, the swellable resin that forms the resin portion is not limited to one type, and the resin portion may be formed of a plurality of types. A content ratio of the swellable resin in the resin portion is, for example, preferably 90% by weight or more, more preferably 95% by weight or more, and still more preferably 98% by weight or more. In the present application, the specific thermal capacity is represented by the specific thermal capacity at 25° C. measured based on a differential scanning calorimetry (DSC) method. The measurement is carried out in a dry nitrogen atmosphere, sapphire (Al2O3) is used as a standard sample, and an aluminum vessel is used as a sample vessel. The specific thermal capacity of the resin before and after being swelling the non-aqueous electrolyte can be measured by using a sample weight before swelling the non-aqueous electrolyte. Schematic diagrams of the lithium-ion secondary battery according to the embodiment are shown inFIGS.1to3. As shown inFIG.1, a lithium-ion secondary battery100has a configuration in which a flat wound electrode body40is accommodated in a flat square battery case20together with a non-aqueous electrolyte80as shown inFIG.2. At least a part of the non-aqueous electrolyte80is impregnated in the wound electrode body40. As shown inFIG.3, at least any one of a positive electrode50and a negative electrode60that configure the wound electrode body40includes a resin portion62a(52a) in a part of a mixture layer non-forming portion62(52). As shown inFIG.1, the battery case20that configures the lithium-ion secondary battery100has a case main body21having an opening and a lid22for closing the opening. The lid22is provided with a positive electrode terminal23and a negative electrode terminal24for external connection, and a safety valve30that has a thin wall and is set to release an internal pressure of the battery case20in a case where the internal pressure rises a predetermined level or more. The positive electrode terminal23and the negative electrode terminal24are electrically connected to a positive electrode current collector plate25and a negative electrode current collector plate26, respectively. Examples of the material of the battery case20include a lightweight metal material having good thermal conductivity, such as aluminum. The lithium-ion secondary battery100having such a configuration can be constructed by, for example, accommodating the wound electrode body40inside through the opening of the case main body21, attaching the lid22to the opening, injecting an appropriate amount of the non-aqueous electrolyte80into the battery case20through the liquid injection port32, and then sealing the liquid injection port32with a sealing material33. The positive electrode current collector plate25and the negative electrode current collector plate26are respectively welded to a positive electrode current collector51and a negative electrode current collector61by resistance welding, ultrasonic welding, or the like. InFIG.1, reference numerals25a,26aeach indicate the welded portion. As shown inFIG.2, the wound electrode body40has a configuration in which the sheet-shaped positive electrode50in which a positive electrode mixture layer53is formed on one side or both sides of the long positive electrode current collector51along a longitudinal direction and the sheet-shaped negative electrode60in which a negative electrode mixture layer63is formed on one side or both sides of the long negative electrode current collector61along the longitudinal direction are overlapped with each other via two long separators72,74and wound in the longitudinal direction. Further, the wound electrode body40includes the positive electrode mixture layer non-forming portion52and the negative electrode mixture layer non-forming portion62to protrude outward from both ends of a winding axis WL. Normally, a width b1of the negative electrode mixture layer63is designed to be wider than a width a1of the positive electrode mixture layer53. Further, normally, widths c1, c2of the separators72,74are designed to be wider than the width b1of the negative electrode mixture layer63(c1, c2>b1>a1). As shown inFIG.3, in at least one of the positive electrode50and the negative electrode60, the mixture layer non-forming portion has the resin portion substantially formed of the swellable resin having a property of swelling the non-aqueous electrolyte. By disposing the swellable resin in the mixture layer non-forming portion, the thermal capacity of the end portion of the electrode body can be increased, and the temperature rise of the end portion of the electrode body can be suppressed. As a result, the non-aqueous electrolyte is suitably held in the electrode body, and the high rate resistance of the lithium-ion secondary battery100can be improved. As the positive electrode current collector51and the positive electrode mixture layer53that configure the positive electrode50, the same positive electrode current collector and positive electrode mixture layer used in the lithium-ion secondary battery in the related art can be used without particular limitation. Examples of the positive electrode current collector51include aluminum foil. Examples of a positive electrode active material contained in the positive electrode mixture layer53include a lithium transition metal oxide (LiNi1/3Co1/3Mn1/3O2, LiNiO2, LiCoO2, LiFeO2, LiMn2O4, LiNi0.5Mn1.5O4, and the like) and a lithium transition metal phosphate compound (LiFePO4and the like). The positive electrode mixture layer53can contain components other than the active material, such as a conductive material or a binder. As the conductive material, for example, carbon black, such as acetylene black (AB), or other carbon materials (graphite and the like) can be suitably used. As the binder, polyvinylidene fluoride (PVDF), an acrylic binder, polyvinylpyrrolidone (PVP), and the like can be used. As the solvent, water or a mixed solvent mainly formed of water can be preferably used, and N-methyl-2-pyrrolidone (NMP) and the like is suitably used. A pasty positive electrode mixture (hereinafter referred to as “positive electrode mixture paste”) can be prepared by mixing the positive electrode active material, the conductive material, the binder, and the solvent as described above by using a known mixing device. Examples of the mixing device include a planetary mixer, a homogenizer, clearmix, filmix, a bead mill, a ball mill, an extrusion kneader and the like. Further, in the present specification, “paste” is used as a term including the form called “slurry” and “ink”. The application of the positive electrode mixture paste to the positive electrode current collector51can be performed according to a known method. For example, the application can be performed by using a coating device, such as a gravure coater, a comma coater, a slit coater, or a die coater. The positive electrode mixture layer53can be formed by drying the applied positive electrode mixture paste by a known method. Specifically, the positive electrode mixture layer53can be formed by drying the positive electrode current collector51coated with the positive electrode mixture paste in a hot air drying furnace, an infrared drying furnace, or the like. As the negative electrode current collector61and the negative electrode mixture layer63that configure the negative electrode60, the same negative electrode current collector and negative electrode mixture layer used in the lithium-ion secondary battery in the related art can be used without particular limitation. Examples of the negative electrode current collector61include copper foil. Examples of the negative electrode active material contained in the negative electrode mixture layer63include a carbon material, such as graphite, hard carbon, or soft carbon is used. Among the above examples, graphite is preferable. The graphite may be natural graphite or artificial graphite, or may be coated with an amorphous carbon material. The negative electrode mixture layer63can contain components other than the active material, such as a binder or a thickener. As the binder, styrene-butadiene rubber (SBR) and the like can be used. As the thickener, carboxymethyl cellulose (CMC) and the like can be used. As the solvent, an aqueous solvent is preferably used. The aqueous solvent need only have aqueous as a whole, and water or the mixed solvent mainly formed of water can be preferably used. A pasty negative electrode mixture (hereinafter referred to as “negative electrode mixture paste”) can be prepared by mixing the negative electrode active material, the conductive material, the binder, and the solvent as described above by using a known mixing device. Examples of the mixing device include a planetary mixer, a homogenizer, clearmix, filmix, a bead mill, a ball mill, an extrusion kneader and the like. The application of the negative electrode mixture paste to the negative electrode current collector61can be performed according to a known method. For example, the application can be performed by using a coating device, such as a gravure coater, a comma coater, a slit coater, or a die coater. The negative electrode mixture layer63can be formed by drying the applied negative electrode mixture paste by a known method. Specifically, the negative electrode mixture layer63can be formed by drying the negative electrode current collector61coated with the negative electrode mixture paste in a hot air drying furnace, an infrared drying furnace, or the like. The resin portions (positive electrode side resin portion52aand negative electrode side resin portion62a) that can be formed on the positive electrode current collector51and the negative electrode current collector61are substantially formed of the swellable resin described above. As the swellable resin contained in the resin portion, a resin that has an excellent swelling property and a high thermal capacity can be preferably used. As the swellable resin, polyvinylpyrrolidone (PVP), SBR, an acrylic resin and the like can be used, but the swellable resin is not limited to this. As the acrylic resin, for example, the acrylic binder that can be used as the binder for the non-aqueous electrolyte secondary battery can be used. The resin portion according to the present embodiment is substantially formed of the swellable resin described above, but may contain other components as long as the effects of the present disclosure are not significantly impaired. The resin portion can be formed by, for example, mixing the swellable resin in the aqueous solvent, applying the mixed solvent to the mixture layer non-forming portion (at least any one of positive electrode mixture layer non-forming portion52and negative electrode mixture layer non-forming portion62), and drying the applied solvent. The thermal capacity of the negative electrode side resin portion62athat can be formed on the negative electrode current collector61is not particularly limited as long as the effects of the present disclosure are exhibited, but is, per unit weight (kg) of the negative electrode mixture layer63, preferably 5 J/(kg·K) or more, more preferably 10 J/(kg·K) or more, still more preferably 20 J/(kg·K). Further, the thermal capacity of the negative electrode side resin portion62ais normally 50 J/(kg·K) or less per unit weight (kg) of the negative electrode mixture layer63. A weight of the negative electrode side resin portion62athat can be formed on the negative electrode current collector61is not particularly limited as long as the effect of the disclosure is exhibited, but is normally 10% or less of the weight of the positive electrode mixture layer53, for example, 5% or less, and more than 0%, for example, 0.1% or more. The thermal capacity of the positive electrode side resin portion52athat can be formed on the positive electrode current collector51is not particularly limited as long as the effects of the present disclosure are exhibited, but is, per unit weight (kg) of the positive electrode mixture layer53, preferably 5 J/(kg·K) or more, more preferably 10 J/(kg·K) or more, still more preferably 20 J/(kg·K) or more. Further, the thermal capacity of the positive electrode side resin portion52ais normally 50 J/(kg·K) or less per unit weight (kg) of the positive electrode mixture layer53. A weight of the positive electrode side resin portion52athat can be formed on the positive electrode current collector51is not particularly limited as long as the effect of the disclosure is exhibited, but is normally 10% or less of the weight of the positive electrode mixture layer53, for example, 5% or less, and more than 0%, for example, 0.1% or more. The cycle resistance can be improved even in a case where the resin portion is provided on any of the positive electrode50and the negative electrode60, but in a case where the resin portion is provided on any one of the positive electrode50and the negative electrode60, the resistance increase rate after application of the cycle can be more suitably suppressed in a case where the resin portion is provided on the negative electrode60side. Although not particularly limited, one of the reasons why the cycle resistance can be further improved by providing the resin portion on the negative electrode60side as compared with the positive electrode50side is considered that the non-aqueous electrolyte80is likely to flow out from the electrode due to the temperature rise in the negative electrode60as compared with the positive electrode50. That is, consideration is made that the effect of suppressing the outflow of the electrolyte is high by suppressing the temperature rise on the negative electrode60side. It is preferable that the resin portion be formed along the mixture layer. By disposing the resin portion as described above, the temperature unevenness at the end portion of the electrode body can be reduced and the thermal capacity of the end portion of the electrode body can be more uniformly improved. As a result, the non-aqueous electrolyte80can be more suitably held in the electrode body40, and the high rate resistance of the lithium-ion secondary battery100can be improved. As the separators72,74, a porous sheet (film) made of polyolefin, such as polyethylene (PE) or polypropylene (PP), is suitably used. Such a porous sheet may have a single layer structure or a stacked structure of two or more layers (for example, a three layer structure in which the PP layers are stacked on both sides of the PE layer). A heat resistant layer (HRL) may be provided on the surfaces of the separators72,74. Then, the wound electrode body40is manufactured by winding the positive electrode50, the negative electrode60, and the separators72,74described above according to a known method. Specifically, the wound electrode body40can be manufactured by winding a stacked body in which the positive electrode50and the negative electrode60are overlapped with each other via two separators72,74in the longitudinal direction with the axis WL as a winding axis, and pressing and bending the stacked body to be flat in one direction orthogonal to the winding axis WL. Typically, the non-aqueous electrolyte80contains a non-aqueous solvent and a supporting salt. As the non-aqueous solvent, various organic solvents, such as carbonates, ethers, esters, nitriles, sulfones, and lactones that are used in the electrolyte of a general lithium secondary battery can be used without particular limitation. Specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyldifluoromethyl carbonate (F-DMC), and trifluorodimethyl carbonate (TFDMC). Such a non-aqueous solvent can be used alone, or two or more types thereof can be used in combination as appropriate. As the supporting salt, for example, a lithium salt, such as LiPF6, LiBF4, and LiClO4(preferably, LiPF6), can be suitably used. A concentration of the supporting salt is preferably 0.7 mol/L or more and 1.3 mol/L or less. In the lithium-ion secondary battery100configured as described above, deterioration due to repeated charging and discharging can be suppressed, and the battery performance can be further maintained for a long period of time. The lithium-ion secondary battery100can be used for various applications. Examples of the suitable applications include the power source for driving mounted on the vehicle, such as the electric vehicle (EV), the hybrid vehicle (HV), and the plug-in hybrid vehicle (PHV). Next, the suitable embodiment will be described below with reference to examples, but the present disclosure is not intended to be limited to such examples. Manufacturing of Lithium-Ion Secondary Battery for Evaluation Preparation of Paste and Swellable resin Mixture The positive electrode mixture paste was prepared by mixing LiNi1/3Co1/3Mn1/3O2(LNCM) as the positive electrode active material, acetylene black (AB) as the conductive material, and polyvinylidene fluoride (PVdF) as the binder with N-methylpyrrolidone (NMP) at a mass ratio of LNCM:AB:PVdF=87:10:3. The negative electrode mixture paste was prepared by mixing natural graphite-based carbon material (C) as the negative electrode active material, styrene-butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) as the thickener with ion-exchanged water with a mass ratio of C:SBR:CMC=98:1:1. Polyvinylpyrrolidone (PVP) as the swellable resin was mixed with ion-exchanged water at a mass ratio of 10% to prepare a PVP solution. Manufacturing of Electrode Example 1 The positive electrode that has the positive electrode mixture layer was manufactured by applying the positive electrode mixture paste to the aluminum foil and drying the applied paste. The negative electrode that has the negative electrode mixture layer was manufactured by applying the negative electrode mixture paste to the copper foil and drying the applied paste. Example 2 The positive electrode having the positive electrode mixture layer was manufactured by applying the positive electrode mixture paste to the aluminum foil and drying the applied paste. The negative electrode that has the negative electrode mixture layer and the negative electrode side resin portion was manufactured by applying the negative electrode mixture paste and the PVP solution to the copper foil and drying the applied paste. The PVP solution was applied such that the thermal capacity of the negative electrode side resin portion was 5 J/(kg·K) per unit weight (kg) of the negative electrode mixture layer. Examples 3 to 8 The positive electrode and the negative electrode were manufactured in the same manner as in Example 2 except that the PVP solution was applied such that the thermal capacity of the negative electrode side resin portion was the value shown in Table 1. Example 9 The positive electrode and the negative electrode were manufactured in the same manner as in Example 2 except that the applied amounts of the negative electrode mixture paste and the PVP solution were 1.2 times the applied amounts in Example 3. Example 10 The positive electrode and the negative electrode were manufactured in the same manner as in Example 2 except that the applied amounts of the negative electrode mixture paste and the PVP solution were 1.2 times the applied amounts in Example 6. Example 11 The positive electrode that has the positive electrode mixture layer and the positive electrode side resin portion was manufactured by applying the positive electrode mixture paste and the PVP solution to the aluminum foil and drying the applied paste. The PVP solution was applied such that the thermal capacity of the positive electrode side resin portion was 20 J/(kg·K) per unit weight (kg) of the positive electrode mixture layer. The negative electrode having the negative electrode mixture layer was manufactured by applying the negative electrode mixture paste to the copper foil and drying the applied paste. Manufacturing of Non-Aqueous Electrolyte A non-aqueous electrolyte for testing was manufactured by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) at a volume ratio of 30:40:30, and dissolving LiPF6as the supporting salt at a concentration of 1.0 mol/L. Manufacturing of Lithium-Ion Secondary Battery Lithium-ion secondary batteries were respectively constructed by using the electrodes (positive electrode and negative electrode) of Examples 1 to 11, two separator sheets, and the non-aqueous electrolyte. As the separator sheet, a separator sheet having a three layer structure made of PP/PE/PP was used. Specifically, the positive electrode, the negative electrode, and the separator sheet were overlapped with each other, wound, and pressed from the side to manufacture the flat wound electrode body. In this case, the two separator sheets were disposed such that the surface on which the heat resistant porous layer was formed faced the positive electrode mixture layer. Then, the wound electrode body was accommodated in the box-shaped battery case made of aluminum, the non-aqueous electrolyte was injected through an injection hole of the battery case, and then the injection hole was sealed. As described above, the lithium-ion secondary batteries respectively provided with the electrodes of Examples 1 to 11 were manufactured. Charge and Discharge Cycle Test The lithium-ion secondary batteries of Examples 1 to 11 were subjected to a charge and discharge cycle test in which charging and discharging were repeated at a high rate. Specifically, in an environment of 25° C., a high rate charge and discharge cycle in which discharging is performed for 150 seconds with a fixed current of 2 C, resting is performed for 10 seconds, charging is performed for 10 seconds with a fixed current of 30 C, and resting is performed for 10 seconds was repeated 1000 times. By using an IV resistance (initial resistance of battery) before the charge and discharge cycle test and an IV resistance after the charge and discharge cycle test, the resistance increase rate (%) was calculated by Equation 1 below. resistance increase rate (%)=(IV resistance after charge and discharge cycle test−IV resistance before charge and discharge cycle test)/IV resistance before charge and discharge cycle test×100 Equation 1: Further, the resistance increase rate (%) of each of Examples 2 to 11 with respect to the resistance increase rate of Example 1 was calculated by Equation 2 below. Table 1 shows the results. resistance increase rate (%) with respect to resistance increase rate of Example 1=resistance increase rate calculated by Equation 1/resistance increase rate of Example 1 calculated by Equation 1×100 Equation 2: Here, “1C” means an amount of current that can charge a battery capacity (Ah) predicted from the theoretical capacity of the positive electrode in one hour. For the IV resistances before and after the charge and discharge cycle was obtained by the inclination obtained by adjusting the battery to SOC 60%, and charging the battery at 1 C, 3 C, and 5 C respectively for 10 seconds in an environment of 25° C., and plotting a voltage drop value ΔV that is a value obtained by subtracting a voltage value at 10 seconds from an initial voltage value on a vertical axis by using the measured current value as the horizontal axis. TABLE 1Thermal capacityResistance increaseJ/(kg · K) ofrate after 1000Electrode in whichresin portion percycles (ratioresin portion (resinunit weight ofwith ExampleExamplelayer) is formedmixture layer1 as 100%)1Without forming0100%2Negative electrode598%3Negative electrode1096%4Negative electrode1395%5Negative electrode1694%6Negative electrode2087%7Negative electrode2578%8Negative electrode2873%9Negative electrode1095%10Negative electrode2088%11Positive electrode2093% As shown in Table 1, as compared with the lithium-ion secondary battery of Example 1 that does not have the resin portion in the positive electrode and the negative electrode, the lithium-ion secondary batteries of Examples 2 to 11 having the resin portion in the positive electrode or the negative electrode had a low resistance increase rate after the high rate charge and discharge cycle (hereinafter, simply referred to as the “resistance increase rate”). It can be seen that the increase in resistance can be suppressed by disposing the swellable resin in the mixture layer non-forming portion. Further, in Examples 1 to 8, the resistance increase rate was decreased as the thermal capacity of the resin portion with respect to the unit weight of the mixture layer was increased. It can be seen that the increase in resistance can be more suitably suppressed by increasing the amount of the swellable resins to be disposed and increasing the thermal capacity of the resin portion. In the comparison between Example 3 and Example 9 and the comparison between Example 6 and Example 10, in a case where the thermal capacity of the resin portion was the same, the resistance increase rate did not change much even in a case where the weight changed. It can be seen that the resistance increase rate is largely contributed by the thermal capacity of the resin portion. In the comparison between Example 6 and Example 11, the resistance increase rate was low in a case where the resin portion was provided on the negative electrode side as compared with a case where the resin portion was provided on the positive electrode side. It can be seen that in a case where the resin portion is provided on any one of the positive electrode side and the negative electrode side, the effect of decreasing the resistance increase rate is high in a case where the resin portion is provided on the negative electrode side as compared with a case where the resin portion was provided on the positive electrode side. From the above, with the lithium-ion secondary battery disclosed herein, the resistance increase rate after the high rate charge and discharge cycle can be suppressed, and the high rate resistance can be improved. Specific examples of the present disclosure have been described in detail above, but these examples are merely examples and do not limit the scope of claims. The disclosures disclosed herein include various modifications and changes of the specific examples. | 29,791 |
11862789 | MODES OF THE INVENTION Hereinafter, the present invention will be described in more detail to facilitate understanding of the present invention. Terms and words used in this specification and claims should not be interpreted as being limited to commonly used meanings or meanings in dictionaries, and, based on the principle that the inventors can appropriately define concepts of terms in order to describe their invention in the best way, the terms and words should be interpreted with meanings and concepts which are consistent with the technical spirit of the present invention. As used herein, the term “polycyclic ring” refers to a condensed ring or condensed nucleus, which is a ring in which two or more rings are linked while sharing two or more atoms thereof, unless otherwise noted. As used herein, the term “alkyl group” refers to a straight-chain, cyclic, or branched hydrocarbon residue unless otherwise noted. As used herein, the term “linear conductive material” refers to a conductive material of a cylindrical type, tube type, or the like having a fibrous structure unless otherwise noted, the term “planar conductive material” refers to a flat, sheet-shaped, or flake-like conductive material unless otherwise noted, and the term “particle-like conductive material” refers to a generally used conductive material which has the form of substantially spherical particles. <Negative Electrode Active Material> One aspect of the present invention provides a negative electrode active material, specifically, a negative electrode active material for a lithium secondary battery. The negative electrode active material according to the present invention includes: an active material core that allows the intercalation and deintercalation of lithium ions; and a conductive material that is attached to a surface of the active material core through an organic linker, wherein the conductive material includes at least one selected from the group consisting of a linear conductive material and a planar conductive material, and the organic linker is a compound that includes a hydrophobic structure and a substituent including a polar functional group. The linear conductive material or the planar conductive material is generally difficult to be dispersed in a solvent, and when it is intended to introduce the conductive materials to a surface of a negative electrode active material or to the inside of a negative electrode, the conductive materials are difficult to be introduced in a uniformly dispersed form due to the phenomenon whereby they are agglomerated due to attraction therebetween. Therefore, when the linear conductive material or the planar conductive material is to be used, it is usually used together with a dispersant (surfactant). However, since most dispersants are based on a weak attraction between materials, there is a difficulty in having the linear conductive material or the planar conductive material bonded in the negative electrode active material and thereby forming a stable electrical network, and when a volume change of the negative electrode active material occurs during charging and discharging, the phenomenon whereby the conductive material is detached from a surface of the negative electrode active material occurs. In this case, it is difficult to avoid a degradation in battery performance even though the linear conductive material or the planar conductive material has been introduced in order to maintain appropriate conductivity in response to the volume change of the negative electrode active material. In order to address the above-described problem, the negative electrode active material of the present invention allows a conductive material to be firmly attached to a surface of an active material core through the organic linker so that the conductive material can stably provide electrical conductivity even when the volume of the negative electrode active material changes. The active material core is not particularly limited as long as it allows the intercalation and deintercalation of lithium ions, but when it is a high-capacity material and undergoes a large volume change during charging and discharging, the effect of using the organic linker and a linear conductive material can be more advantageously exhibited. The active material core that allows the intercalation and deintercalation of lithium ions may be one or more selected from the group consisting of Si, SiOx(0<x<2), Sn, SnO2, and an Si-metal alloy. Examples of a metal capable of forming such an Si-metal alloy include Al, Sn, Ag, Fe, Bi, Mg, Mn, Zn, In, Ge, Pb, and Ti, and examples of a metal oxide include SnO2, TiO2, Co3O4, Fe3O4, and Mn3O4. The conductive material is attached to a surface of the active material core, and specifically, the conductive material may be attached to a surface of the active material core through an organic linker. The conductive material may be at least one selected from the group consisting of a linear conductive material and a planar conductive material. Specifically, when the conductive material is a linear conductive material, it may be in linear contact with or attached to the active material core, and when the conductive material is a planar conductive material, it may be in contact with the active material core in a face-to-face manner, and therefore, stable electrical connection can be achieved. Since the conductive material is therefore positioned between two or more active materials while crossing the active materials, the conductive material allows an electrical contact between the negative electrode active materials to be increased. Therefore, the phenomenon whereby an electrical network is disconnected due to a change in the volume, position, or morphology of the negative electrode active material can be minimized, and further, an increase in the resistance of a negative electrode due to the disconnection of an electrical network can be suppressed. The conductive material is electrochemically stable and has high conductivity, and includes a linear conductive material, a planar conductive material, or both. The linear conductive material may form a fibrous structure, and may be one or more selected from the group consisting of a carbon fiber, a carbon nanofiber (CNF), a metal fiber, a carbon nanotube (CNT), and a conductive whisker, specifically a carbon fiber, more specifically a CNT. In addition, the planar conductive material may be flat, sheet-shaped, or flake-like, and may be one or more selected from the group consisting of graphene, a metal thin film, and a MXene. The conductive material may be included in the negative electrode active material in an amount of 0.05 part by weight to 12 parts by weight, preferably 0.25 part by weight to 3 parts by weight, relative to 100 parts by weight of the active material core. It is preferred that the content of the conductive material is in the above-described range because, within this range, it is possible to sufficiently form an electrical network of the active material while preventing the initial efficiency and capacity of the active material from being lowered due to an excessive addition of a conductive material. The organic linker is a material that is interposed between a surface of the active material core and the conductive material and allows the same to be attached to each other. Specifically, the organic linker may impart a bonding ability between the conductive material and a surface of the active material. The organic linker is a compound that includes a hydrophobic structure and a substituent including a polar functional group in a molecular structure thereof. The hydrophobic structure of the organic linker interacts with and is bonded to the conductive material by van der Waals attraction. Specifically, a conjugated π-electron of a ring having a π-electron conjugated structure may form a van der Waals bond with a π electron included in the conductive material, or an electron of alkylene may form a van der Waals bond with an electron of the conductive material. The substituent of the organic linker, which includes a polar functional group, may be substituted on a ring having a π-electron conjugated structure of the organic linker or on an alkylene structure of the organic linker, and may be bonded to a functional group (e.g., —OH group) located on a surface of the active material core, thereby allowing the organic linker and a linear conductive material bonded to the organic linker to be attached to the surface of the active material core. In addition, since the substituent including a polar functional group has excellent affinity with solvents, the substituent may allow the organic linker to be effectively dispersed in a solvent and, accordingly, a linear conductive material bonded to the organic linker to be effectively dispersed (i.e., debundled) in the solvent without being agglomerated. The substituent including a polar functional group may be linked to a surface of the active material core by being bonded to a functional group, specifically a functional group including —OH, located on the surface of the active material core. The functional group located on the surface of the active material core and including —OH may be formed as the surface of the active material core is oxidized by oxygen in the air. Since the bonding between the substituent including a polar functional group and a functional group including —OH is a chemical bond and thus the organic linker and the linear conductive material are strongly attached to the active material core, an effect of maintaining stable electrical conductivity even when the volume of the active material core changes can be provided. In the negative electrode active material according to one exemplary embodiment of the present invention, the state in which the active material core, the organic linker, and the conductive material are bonded may be expressed as “active material core:chemical bonding of polar functional group with —OH group in active material core:organic linker:π-π interaction:conductive material.” The hydrophobic structure may include one or more selected from the group consisting of a ring having a π-electron conjugated structure and a C3-C20 alkylene structure. The ring having a π-electron conjugated structure may refer to an aromatic ring in which the number of electrons satisfies the “4n+2 rule,” specifically two or more rings which are linked, more specifically two or more rings making up a condensed ring structure. The ring having a π-electron conjugated structure may include, for example, one or more selected from the group consisting of benzene, pyrene, naphthalene, anthracene, benzopyrene, phenanthrene, fluoranthene, chrysene, perylene, benz[a]anthracene, acenaphthylene, coronene, triphenylene, and tetracene. In one exemplary embodiment of the present invention, the ring having a x-electron conjugated structure may be a polycyclic ring in which four or more rings are linked. The “polycyclic ring in which four or more rings are linked” may include the states in which polycyclic rings include four or more rings on the inside thereof, and may include one or more selected from the group consisting of pyrene, benzopyrene, fluoranthene, chrysene, perylene, benz[a]anthracene, coronene, triphenylene, and tetracene. In addition, the alkylene structure may be a C3-C20 alkylene structure. Meanwhile, the substituent of the organic linker, which includes a polar functional group, may be one or more selected from the group consisting of a carboxyl group; a carboxylate group; a phosphoric acid group; a phosphate group; a sulfuric acid group; a sulfate group; and a C1-C8 alkyl group substituted with a carboxyl group, a carboxylate group, a phosphoric acid group, a phosphate group, a sulfuric acid group, or a sulfate group, and is preferably one or more selected from the group consisting of a carboxyl group; and a carboxylate group in terms of the fact that the bonding thereof with a polar functional group in the active material core is excellent. In one exemplary embodiment of the present invention, the organic linker may be one or more selected from the group consisting of 1-pyreneacetic acid, 1-pyrenecarboxylic acid, 1-pyrenebutyric acid, sodium dodecyl sulfonate (SDS), and sodium dodecylbenzenesulfonate (SDBS). The organic linker is preferably 1-pyrenebutyric acid. In this case, in terms of the fact that since the compound has an excellent ability to be bonded to a polar functional group located on a surface of the active material due to the inclusion of a carboxyl group and the compound includes an appropriate amount of linear alkylene groups and thus allows for the improvement of the degree of freedom of the conductive material and the formation of a flexible conductive network between negative electrode active materials, the lifetime characteristics of a battery can be advantageously improved. In addition, the organic linker being 1-pyrenebutyric acid is desirable in terms of the fact that when mixing the organic linker and a conductive material in the preparation of a negative electrode active material, the dispersibility of the conductive material can be improved due to the excellent polarity of a carboxylate group in the organic linker and therefore, the conductive material can be uniformly placed at a surface of the negative electrode active material. In addition, the negative electrode active material according to one exemplary embodiment of the present invention may include, as the organic linker, a mixture of two different organic linkers, that is, a mixture of a first organic linker compound and a second organic linker compound. The first organic linker compound may be a compound that includes a ring having a π-electron conjugated structure and a substituent including a polar functional group, and the second organic linker compound may be: a compound that includes a C3-C20 alkylene structure and a polar functional group; a compound that includes a ring having a π-electron conjugated structure, a C3-C20 alkylene structure, and a polar functional group; or a mixture thereof. When a mixture of the first organic linker compound and the second organic linker compound is used as the organic linker, the conductive material may be more effectively dispersed in a solvent during the preparation of the negative electrode active material, and since the conductive material is therefore attached to a surface of the active material core in a more effectively dispersed manner, the conductive material can be more uniformly positioned at the surface of the active material core. According to one exemplary embodiment of the present invention, the organic linker may include the first organic linker compound and the second organic linker compound at a weight ratio of 1:99 to 99:1, specifically 5:95 to 95:5, more specifically 10:90 to 90:10. When the first organic linker compound and the second organic linker compound satisfy the above-described weight ratio, the conductive material can be more effectively dispersed, and the conductive material may be more effectively attached to the active material core. According to one exemplary embodiment of the present invention, the first organic linker compound may be one or more selected from the group consisting of 1-pyreneacetic acid, 1-pyrenecarboxylic acid, and 1-pyrenebutyric acid, and the second organic linker compound may be one or more selected from the group consisting of SDS and SDBS. The average particle diameter (D50) of the negative electrode active material according to one exemplary embodiment of the present invention may be 0.01 to 30 μm, specifically 0.5 to 30 μm, more specifically 1 to 20 μm. When the average particle diameter of the negative electrode active material satisfies the above-described range, the negative electrode may have an appropriate capacity per volume due to having an appropriate density, and it is possible to prevent the of the negative electrode from becoming excessively thick due to the volume expansion of the negative electrode active material. In the present invention, the average particle diameter (D50) of the negative electrode active material may be defined as a particle diameter corresponding to the 50thpercentile in the particle diameter distribution curve. Although not particularly limited, the average particle diameter may be measured using, for example, a laser diffraction method or a scanning electron microscope (SEM) image. The laser diffraction method generally allows for the measurement of a particle diameter ranging from a submicron level to several millimeters, and may produce a result having high reproducibility and high resolution. The negative electrode active material according to one exemplary embodiment of the present invention may be prepared by a method including first dispersing the organic linker and the conductive material in a solvent, and then adding a material that serves as a core of the negative electrode active material to the resultant. As a result, the organic linker is effectively dispersed in the solvent such that the conductive material becomes effectively dispersed (i.e., debundled) in the solvent without being agglomerated, and since a material that serves as a core of the active material is added to an assembled body consisting of the organic linker and the conductive material which have been dispersed, the organic linker and the conductive material can be evenly dispersed and bonded to the active material core. Specifically, when dispersing the organic linker and the conductive material, a base (e.g., NaOH) may also be added to the solvent. Since the base may allow a polar functional group of the organic linker to have ionic characteristics or strong polarity, the dispersion in the solvent can be made easy, and the bonding between a functional group (—OH) of a surface of the active material core and a polar functional group in the organic linker can be made easy. When the base is not added to the solution along with the above-described components, there is a risk that the organic linker may not be dispersed in the solution, and since it may be difficult for the polar functional group of the organic linker to react with a surface of the active material core, the formation of the negative electrode active material of the present invention may be difficult to achieve. In this case, the process of dispersing the organic linker and the conductive material in the solvent and the process of adding the material serving as a core of the active material may be carried out by a conventional mixing method, for example, a milling method such as a sonication method, a ball-milling method, a bead-milling method, a basket-milling method, or the like or a method using a mixing device such as a homogenizer, a bead mill, a ball mill, a basket mill, an attrition mill, a universal stirrer, a clear mixer, a TK mixer, or the like. <Negative Electrode for Lithium Secondary Battery and Lithium Secondary Battery> Other aspects of the present invention provide a negative electrode for a lithium secondary battery, which includes the above-described negative electrode active material, and a lithium secondary battery. Specifically, the negative electrode for a lithium secondary battery includes: a negative electrode current collector; and a negative electrode active material layer formed on the negative electrode current collector, and the negative electrode active material layer includes: a negative electrode material including the above-described negative electrode active material; and a binder. The negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has high conductivity. Specifically, as the negative electrode current collector, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, or the like may be used. The negative electrode current collector may typically have a thickness of 3 to 100 μm. The negative electrode current collector may have fine irregularities formed in a surface thereof to increase the adhesion of the negative electrode active material. For example, the negative electrode current collector may be used in any of various forms such as a film, a sheet, a foil, a net, a porous material, a foam, a non-woven fabric, and the like. The negative electrode active material layer is formed on the negative electrode current collector, and includes: a negative electrode material including the above-described negative electrode active material; and a binder. The negative electrode material may further include a carbon-based active material along with the above-described negative electrode active material. The carbon-based active material may impart excellent cycle characteristics or excellent battery lifetime characteristics to the negative electrode or the secondary battery of the present invention. Specifically, the carbon-based active material may include at least one selected from the group consisting of graphite, artificial graphite, natural graphite, hard carbon, soft carbon, carbon black, acetylene black, Ketjen black, Super P, graphene, and fibrous carbon, preferably at least one selected from the group consisting of graphite, artificial graphite, and natural graphite. Specifically, it is preferred that both the negative electrode active material and the carbon-based active material are used for the negative electrode material in terms of simultaneously improving capacity characteristics and cycle characteristics, and specifically, it is preferred that the negative electrode material includes the negative electrode active material and the carbon-based active material at a weight ratio of 5:95 to 50:50, preferably 20:80 to 40:60, in terms of simultaneously improving capacity and cycle characteristics. The negative electrode material may be included in an amount of 80 wt % to 99 wt %, preferably 85 wt % to 96 wt %, in the negative electrode active material layer. The negative electrode active material layer includes a binder. The binder may include at least one selected from the group consisting of a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, an ethylene-propylene-diene monomer (EPDM), a sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and materials in which hydrogens thereof have been substituted with Li, Na, Ca, etc., and various copolymers thereof. The negative electrode active material layer may include an additional conductive material, or may not include a separate additional conductive material. The additional conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and, for example, the following may be used: graphite such as natural graphite, artificial graphite, or the like; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, or the like; a conductive fiber such as carbon fiber, metal fiber, or the like; a conductive tube such as a CNT; fluorocarbon; a metal powder such as aluminum powder, nickel powder, or the like; a conductive whisker such as zinc oxide, potassium titanate, or the like; a conductive metal oxide such as titanium oxide or the like; and a conductive material such as a polyphenylene derivative or the like. The thickness of the negative electrode active material layer may be 10 μm to 200 μm, preferably 20 μm to 150 μm. The negative electrode for a lithium secondary battery may be prepared by applying a negative electrode slurry including a negative electrode material, a binder, a conductive material, and/or a solvent for forming a negative electrode slurry onto the negative electrode current collector, and then carrying out drying and rolling. The solvent for forming a negative electrode slurry may be an organic solvent such as N-methyl pyrrolidone (NMP), dimethyl formamide (DMF), acetone or dimethyl acetamide, or water or the like, and these solvents may be used alone or in a combination of two or more. In addition, the present invention provides a lithium secondary battery, which includes: the above-described negative electrode for a lithium secondary battery; a positive electrode, which is the opposite of the negative electrode for a lithium secondary battery; a separator interposed between the negative electrode for a lithium secondary battery and the positive electrode; and an electrolyte. The negative electrode for a lithium secondary battery has been described above. The positive electrode may include: a positive electrode current collector; and a positive electrode active material layer formed on the positive electrode current collector and including a positive electrode active material. In the positive electrode, the positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, etc., or the like may be used. In addition, the positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and may have fine irregularities formed in a surface thereof to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in any of various forms such as a film, a sheet, a foil, a net, a porous material, a foam, a non-woven fabric, and the like. The positive electrode active material may be a typically used positive electrode active material. Specifically, examples of the positive electrode active material may include: a layered compound such as a lithium cobalt oxide (LiCoO2), a lithium nickel oxide (LiNiO2), Li[NixCoyMnzMv]O2(here, M is any one or more elements selected from the group consisting of Al, Ga, and In; and 0.3≤x<1.0, 0≤y, z≤0.5, 0≤v≤0.1, and x+y+z+v=1), Li(LiaMb-a-b′M′b′)O2-cAc(here, 0≤a≤0.2, 0.6≤b≤1, 0≤b′≤0.2, and 0≤c≤0.2; M includes Mn and one or more selected from the group consisting of Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M′ is one or more selected from the group consisting of Al, Mg, and B, and A is one or more selected from the group consisting of P, F, S, and N), or the like or a compound substituted with one or more transition metals; a lithium manganese oxide such as one represented by the chemical formula Li1+yMn2-yO4(here, y is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, or the like; a lithium copper oxide (Li2CuO2); a vanadium oxide such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7, or the like; a Ni-site-type lithium nickel oxide represented by the chemical formula LiNi1-yMyO2(here, M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and y is 0.01 to 0.3); a lithium manganese composite oxide represented by the chemical formula LiMn2-yMyO2(here, M=Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8(here, M=Fe, Co, Ni, Cu, or Zn); LiMn2O4in which some Li in the chemical formula have been substituted with alkaline earth metal ions; a disulfide compound; Fe2(MoO4)3; and the like, but the present invention is not limited thereto. The positive electrode may be a Li-metal. The positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder along with the above-described positive electrode active material. Here, the positive electrode conductive material is used to impart conductivity to the electrode, and may be used without particular limitation as long as it does not cause a chemical change in a battery being produced and has electron conductivity. Specific examples of the positive electrode conductive material include: graphite such as natural graphite, artificial graphite, or the like; a carbon-based material such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, or the like; a metal powder or metal fiber of copper, nickel, aluminum, silver, or the like; a conductive whisker such as zinc oxide, potassium titanate, or the like; a conductive metal oxide such as titanium oxide or the like; and a conductivity polymer such as a polyphenylene derivative or the like, which may be used alone or in combination of two or more thereof. In addition, the positive electrode binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and a positive electrode current collector, Specific examples of the positive electrode binder include PVDF, PVDF-co-HFP polyvinyl alcohol, polyacrylonitrile, CMC, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, an EPDM, a sulfonated-EPDM, SBR, fluororubber, various copolymers thereof and the like, which may be used alone or in combination of two or more thereof. The separator is used to separate the negative electrode from the positive electrode and provide a passage for lithium ion migration. As the separator, a separator commonly used in a secondary battery may be used without particular limitation, and in particular, a separator that exhibits low resistance to the migration of electrolyte ions and has an excellent electrolyte impregnation ability is preferred. Specifically, a porous polymer film, for example, a porous polymer film formed of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, an ethylene/methacrylate copolymer, or the like or a stacked structure having two or more layers thereof, may be used. In addition, a common porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, or the like may be used. Also, in order to ensure heat resistance or mechanical strength, a coated separator that includes a ceramic component or polymer material and is optionally in a single-layer or multi-layer structure may be used. Examples of the electrolyte include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, an inorganic solid electrolyte, a molten-type inorganic electrolyte, and the like which are usable for manufacturing a lithium secondary battery, but the present invention is not limited thereto. Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt. As the non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydro furan, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxy methane, a dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, a propylene carbonate derivative, a tetrahydrofuran derivative, an ether, methyl pyropionate, ethyl propionate, or the like may be used. In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, can be suitably used because they are highly viscous organic solvents that have high dielectric constants and thus effectively dissociate lithium salts. Such a cyclic carbonate can be more suitably used because it may yield an electrolyte having high electrical conductivity when mixed with a linear carbonate having low viscosity and a low dielectric constant, such as dimethyl carbonate or diethyl carbonate, in an appropriate ratio. A lithium salt may be used as the metal salt, and the lithium salt is easily dissolved in the non-aqueous electrolyte. For example, the anion of the lithium salt may be one or more selected from the group consisting of F−, Cl−, I−, NO3−, N(CN)2−, BF4−, ClO4−, PF6−, (CF3)2PF4−, (CF3)3PF3−, (CF3)4PF2−, (CF3)5PF−, (CF3)6P−, CF3SO3−, CF3CF2SO3−, (CF3SO2)2N−, (FSO2)2N−, CF3CF2(CF3)2CO−, (CF3SO2)2CH−, (SF5)3C−, (CF3SO2)3C−, CF3(CF2)7SO3−, CF3CO2−, CH3CO2−, SCN−, and (CF3CF2SO2)2N−. In addition to the above-described electrolyte components, the electrolyte may further include one or more additives, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate and the like, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexamethyl phosphoric triamide, a nitrobenzene derivative, sulfur, a quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, an ethylene glycol dialkyl ether, an ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, or the like for the purpose of improving battery lifetime characteristics, suppressing a reduction in battery capacity, improving battery discharge capacity, and the like. According to another embodiment of the present invention, there is provided a battery module that includes the secondary battery as a unit cell and a battery pack that includes the battery module. Due to the inclusion of the secondary battery that has high capacity, high rate capability, and excellent cycle characteristics, the battery module and the battery pack can be used as a power source for medium-to-large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and a system for storing electric power. EXAMPLES Hereinafter, exemplary embodiments will be provided to facilitate understanding of the present invention, but it will be apparent to those skilled in the art that the exemplary embodiments are merely illustrative of the present disclosure, and that various changes and modifications can be made within the scope and technical spirit of the present disclosure and are encompassed in the scope of the appended claims. Example 1 <Preparation of c-SiOxParticles> The c-SiOxparticles refer to SiOxon which a carbon coating layer has been formed, and were prepared by the following method. After mixing SiOx(x=approximately 1) particles having an average particle diameter (D50) of 5 μm and a petroleum-based pitch at a weight ratio of 93:7, the resultant was thermally treated for two hours at a temperature of 950° C. (temperature elevation rate: 5° C./min) in a calcination furnace under an Ar atmosphere, and thereby a carbon coating layer was formed on the SiOxparticles. The weight ratio of the SiOxparticles and the carbon coating layer was 95:5. <Preparation of c-SiOx/PBA/SWNT 10%> 1 g of 1-pyrenebutyric acid (PBA) was dissolved in 250 g of a 0.5 M aqueous NaOH solution. After adding 0.1 g of single-walled carbon nanotubes (SWNTs) to the prepared solution and then carrying out probe-type sonication for 30 minutes, 1 g of the c-SiOxprepared above was added to the prepared solution, followed by 30-minute probe-type sonication and subsequent one-hour stirring. The dispersion solution prepared as thus was filtered and then washed by carrying out filtration while pouring water several times. The obtained material was dried for 12 hours in a vacuum oven at 130° C., and thereby a negative electrode active material, c-SiOx/PBA/SWNT 10% (indicating the wt % of SWNTs relative to c-SiOx), was finally obtained. Using the above-described negative electrode active material, a negative electrode for evaluating battery performance was prepared as follows. The c-SiOx/PBA/SWNT 10%, graphite, Super-C, and PVDF in a weight ratio of 31.5:58.5:4:6 were added to NMP to prepare a slurry. Subsequently, the slurry was applied to a copper foil and dried for two hours at about 130° C., and thereby a negative electrode was obtained. Example 2 <Preparation of c-SiOx/PBA/SWNT 0.3%> 0.03 g of PBA was dissolved in 100 g of a 0.5 M aqueous NaOH solution. After adding 0.003 g of SWNTs to the prepared solution and then carrying out probe-type sonication for 30 minutes, 1 g of the c-SiOxprepared in the process of Example 1 was added to the prepared solution, followed by 30-minute sonication and subsequent one-hour stirring. Afterward, a negative electrode active material, c-SiOx/PBA/SWNT 0.3% (indicating the wt % of SWNTs relative to c-SiOx), and a negative electrode including the same were prepared in the same manner as in Example 1. Example 3 <Preparation of c-SiOx/PBA/SWNT 0.2%> 0.02 g of PBA was dissolved in 100 g of a 0.5 M aqueous NaOH solution. After adding 0.002 g of SWNTs to the prepared solution and then carrying out probe-type sonication for 30 minutes, 1 g of the c-SiOxprepared in the process of Example 1 was added to the prepared solution, followed by 30-minute sonication and subsequent one-hour stirring. Afterward, a negative electrode active material, c-SiOx/PBA/SWNT 0.2% (indicating the wt % of SWNTs relative to c-SiOx), and a negative electrode including the same were prepared in the same manner as in Example 1. Comparative Examples Comparative Example 1 In Comparative Example 1, a negative electrode was prepared in the same manner as in Example 1 by using the c-SiOxprepared in Example 1 as a negative electrode active material except that a negative electrode slurry in which c-SiOx, graphite, Super-C, and PVDF were mixed in a weight ratio of 31.5:58.5:4:6 was prepared. Comparative Example 2 In Comparative Example 2, a negative electrode was prepared in the same manner as in Example 1 by using the c-SiOxprepared in Example 1 as a negative electrode active material except that a negative electrode slurry in which c-SiOx, graphite, SWNTs, Super-C, and PVDF were mixed in a weight ratio of 31.5:58.4:0.1:4:6 was prepared. Comparative Example 3 In Comparative Example 3, a negative electrode was prepared in the same manner as in Example 1 by using the c-SiOxprepared in Example 1 as a negative electrode active material except that a negative electrode slurry in which c-SiOx, graphite, SWNTs, PBA, Super-C, and PVDF were mixed in a weight ratio of 31.1:57.8:0.1:1:4:6 was prepared. Experimental Examples Coin-type half-cells were manufactured using the negative electrodes prepared in Examples 1 to 3 and Comparative Examples 1 to 3. A metal lithium foil was used as the positive electrode, and an electrode assembly was manufactured by interposing a polyethylene separator between the negative electrode and the positive electrode. After placing the electrode assembly in a battery case, an electrolyte prepared by adding 1 M LiPF6to a non-aqueous solvent which includes a 1:2 (volume ratio) mixture of ethylene carbonate and diethyl carbonate was injected, and thereby a coin-type half-cell was obtained. Experimental Example 1: Charging and Discharging Characteristics of Battery The charging and discharging characteristics of the coin-type half-cells manufactured using the negative electrodes prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated. A first cycle of charging/discharging was carried out at a current density of 0.1 C/0.1 C, and the following 100 cycles of charging/discharging were carried out at a current density of 0.5 C/0.5 C, and detailed conditions thereof are as follows. The charging was carried out with a constant current at a predetermined current density to 5 mV and then with a constant voltage maintained at 5 mV, and was terminated when the current density reached 0.005 C. The discharging was carried out in a CC mode to 1 V at a predetermined current density until completion. The results are summarized in Table 1. TABLE 10.1 C0.1 CchargedischargeInitialCapacitycapacitycapacityefficiencyretention rate(mAh/g)(mAh/g)(%)(@ 100 cycles)Example 1895.3659.473.796.0%Example 2914.8743.481.393.3%Example 3893.7732.682.087.2%Comparative846.6781.480.525% (@ 25 cycles)Example 1Comparative920.1757.682.360.6%Example 2Comparative908.7720.779.35%Example 3 As can be seen from Table 1, the cycle lifetime characteristics of the coin-type batteries according to Examples 1 to 3 were significantly improved compared to Comparative Example 1. It is determined that in Examples 1 to 3, the cycle lifetime characteristics of the negative electrode active material were improved due to the inclusion of a PBA organic linker, and it can be seen that particularly in the case of Example 2, even though SWNTs were included in an amount of only 0.3 wt %, the lifetime characteristics were significantly improved compared to Comparative Example 1 and initial efficiency and discharge capacity were significantly improved. It is determined that this is because the SWNTs have stably formed a conductive network on a surface of the active material through the organic linker, and it is determined that since it is therefore possible to electrically connect the surface of the active material while suppressing the destruction of the high-capacity active material during the charging and discharging of the battery, improved battery characteristics can be achieved. Experimental Example 2: Evaluation Based on SEM Observation FIG.1shows SEM images of a surface of the c-SiOx/PBA/SWNT 0.3% negative electrode active material of Example 2, and it can be seen that a CNT network has been stably formed on a surface of the carbon-coated SiOx. FIGS.2and3are SEM images of surfaces of the negative electrodes prepared in Example 2 and Comparative Example 2, whereinFIG.2A(top) shows a surface of graphite included in the negative electrode,FIG.2B(bottom) shows the surface of the c-SiOx/PBA/SWNT 0.3% negative electrode active material, andFIG.3shows a surface of the negative electrode prepared in Comparative Example 2. Referring toFIG.2, it can be seen that whereas in the case of the negative electrode prepared in Example 2, the SWNTs are present only on the surface of c-SiOxand not on the surface of graphite, in the case of the negative electrode prepared in Comparative Example 2 and shown inFIG.3, the SWNTs are also present on a graphite surface (SWNTs, that is, CNTs, appear as light-colored lines present on the surface of graphite or of c-SiOx). Although in Comparative Example 2, the SWNTs were included in the negative electrode slurry in the same or similar amount as that included in the negative electrode active material of Example 2 in the preparation of the negative electrode, since the SWNTs surround graphite which has excellent inherent electrical conductivity as well as they surround c-SiOx, it can be seen that the desired effect, that is, the effect of imparting effective/high electrical conductivity to a high-capacity active material with large volume expansion, such as c-SiOx, is small relative to the amount of the SWNTs used. This means that in the case of Comparative Example 2, a higher negative-electrode manufacturing cost compared to Example 2 is required, and since CNTs having high irreversibility are used, the initial efficiency of the negative electrode may be reduced. That is, in the negative electrode active material of the present invention, an effective electrical network can be formed on a surface of a high-capacity active material using a small amount of CNTs, and therefore, an effect of significantly improving battery performance can be achieved. | 43,926 |
11862790 | DETAILED DESCRIPTION OF THE EMBODIMENTS According to example embodiments, a lithium secondary battery including a cathode that includes regions having different specific capacities is provided. Hereinafter, a lithium secondary battery according to example embodiments of the present disclosures will be described in detail with reference to the drawings. However, the drawings and embodiments herein are intended to provide examples, and the concepts and the spirits of the present disclosures is not limited thereto. The term “planar direction” used herein refers to a direction in which a cathode and an anode are stacked (e.g., a Z-direction inFIG.2). The term “width direction” used herein of an electrode (the cathode or the anode) active material layer is a direction (e.g., a Y direction ofFIG.2) in which the shortest side (or a short axis) of sides of the electrode active material layer extends when viewed in the planar direction. The term “cross-section in the width direction” refers to a cross-section of the electrode active material layer when the electrode active material layer is cut in the width direction (e.g., along a YZ plane ofFIG.2). The term “length direction” used herein of the electrode (the cathode or the anode) active material layer refers to a direction (e.g., an X direction ofFIG.2) in which the longest side (or a long axis) of sides of the electrode active material layer extends when viewed from the planar direction. The term “cross-section in the length direction” may refer to a cross-section of the electrode active material layer when the electrode active material layer is cut in the length direction (e.g., along an XZ plane ofFIG.2). The “length direction” may be defined based on the surface of the electrode active material layer in the planar direction. FIG.1is a schematic cross-sectional view of a lithium secondary battery in accordance with an example embodiment.FIG.2is an exploded perspective view illustrating constructions of an anode and a cathode in accordance with an example embodiment. Referring toFIGS.1and2, a lithium secondary battery according to example embodiments may include a cathode100and an anode130facing the cathode100. The cathode100may include a cathode current collector105and a cathode active material layer110formed on the cathode current collector105. For example, the cathode active material layer110may be formed on one surface or both surfaces of the cathode current collector105. For example, the cathode active material layer110may include a cathode active material capable of reversibly intercalating and de-intercalating lithium ions. In some embodiments, the cathode active material layer110may further include a cathode binder and a conductive material. The anode130may include an anode current collector125and an anode active material layer120formed on the anode current collector125. For example, the anode active material layer120may be formed on one surface or both surfaces of the cathode current collector125. For example, the anode active material layer120may include an anode active material capable of reversibly intercalating and de-intercalating lithium ions. In some embodiments, the anode active material layer120may further include an anode binder and a conductive material. When viewed in the planar direction, an area of the anode active material layer120may be greater than that of the cathode active material layer110. In one embodiment, the anode active material layer120may entirely cover the cathode active material layer110in the planar direction. The anode active material layer120may include an overlapping portion122covered by the cathode active material layer in the planar direction and a margin portion124that does not overlap the cathode active material layer110. For example, the overlapping portion122may face the cathode active material layer110, and the margin portion124may not face the cathode active material layer110. When the anode active material layer may accommodate only a portion of the lithium ions desorbed from the cathode active material layer, some lithium may be precipitated on a surface of the anode active material layer. As a result, the anode may be deteriorated and a life-span of the lithium secondary battery may be lowered. According to example embodiments, the anode active material layer120may include the margin portion124to substantially entire lithium ions. Accordingly, the lithium precipitation may be suppressed. In one embodiment, a ratio of a volume (or an area) of the overlapping portion122to a total volume (or an area) of the anode active material layer110may be from 0.8 to 0.99, from 0.85 to 0.97, or from 0.9 to 0.95. The area may refer to an area in the planar direction. Within the above range, reduction of an energy density of the lithium secondary battery due to the margin portion124may be prevented while suppressing the lithium precipitation. In some embodiments, in a cross-section of the anode active material layer120in the width direction, a ratio of a width of the margin portion124formed at one side of the overlapping portion122relative to a width of the anode active material layer may be in a range from 0.002 to 0.1, from 0.004 to 0.05, from 0.01 to 0.03, or from 0.015 to 0.025. A width of the margin portion124formed at the other side of the overlapping portion122may also be within the above range. In some embodiments, in a cross-section of the anode active material layer120in the length direction, a ratio of a width of the margin portion124formed at one side of the overlapping portion122relative to a width of the anode active material layer120may be in a range from 0.001 to 0.02, from 0.002 to 0.02, from 0.005 to 0.015, or from 0.01 to 0.015. A width of the margin portion124formed at the other side of the overlapping portion122may also be within the above range. In some embodiments, the width of each of the margin portions124may be from about 0.5 mm to 3 mm, from about 0.75 mm to about 2.5 mm, or from about 1 mm to about 2 mm. When the lithium secondary battery is left after being charged, some lithium ions inserted into the overlapping portion122may be diffused into the margin portion124. Accordingly, a local lithium precipitation may occur locally around a boundary123between the overlapping portion122and the margin portion124. The local lithium precipitation may be effectively suppressed by using the cathode active material layer110according to example embodiments of the present disclosures. FIG.3is a schematic plan view of a cathode according to an example embodiment. Referring toFIG.3, the cathode active material layer110may include an outer portion114formed along a periphery of the cathode active material layer110and a central portion112surrounded by the outer portion114. For example, the central portion112may include a center of the cathode active material layer110. In one embodiment, the outer portion114may be formed to be adjacent to the periphery of the cathode active material layer110. In some embodiments, the outer portion114may include the periphery of the cathode active material layer110. For example, the outer portion114may be in contact with the periphery of the cathode active material layer110. In example embodiments, a specific capacity of the outer portion114may be smaller than that of the central portion112. Accordingly, an amount of intercalated and deintercalated lithium ions may be relatively small around the boundary123of the overlapping portion122and the marginal portion124. Thus, the diffusion of lithium ions into the margin portion124and the local lithium precipitation around the boundary123may be suppressed. For example, the specific capacity refers to a capacity per unit weight (mAh/g). For example, the specific capacity refers to a utilization capacity (a reversible capacity) in a driving voltage range. In one embodiment, a ratio of the specific capacity of the outer portion114relative to the specific capacity of the central portion112may be in a range from 0.5 to 0.95, from 0.7 to 0.97, from 0.85 to 0.97, or from 0.9 to 0.95. Within this range, the capacity of the cathode active material layer110may become higher, and the local lithium precipitation around the boundary123may be further suppressed. In one embodiment, the central portion112may include a first cathode active material, and the outer portion114may include a second cathode active material having a specific capacity lower than that of the first cathode active material. In this case, the specific capacity of the central portion112may be adjusted to be higher than that of the outer portion114. In some embodiments, the first cathode active material may include first lithium metal oxide particles, and the second cathode active material may include second lithium metal oxide particles. A specific capacity of the first lithium metal oxide particle may be greater than that of the second lithium metal oxide particle. In one embodiment, the first lithium metal oxide particles and the second lithium metal oxide particles may include lithium cobalt-based oxide (LCO) particles, lithium manganese-based oxide (LMO) particles, lithium nickel-based oxide (LNO) particles, lithium nickel-cobalt-manganese (NCM) oxide particles, lithium nickel-cobalt-aluminum (NCA) oxide particles, lithium iron phosphate (LFP) oxide particles, lithium excess oxide (OLO) particles, etc. In some embodiments, the first lithium metal oxide particle may include a lithium excess oxide particle represented by Chemical Formula 1 below. In this case, the second lithium metal oxide particle may include a lithium metal oxide particle having a lower specific capacity than that of the lithium excess oxide particle. xLi2MnO3*(1-x)LiMO2[Chemical Formula 1] In Chemical Formula 1, M may include at least one of Ni, Mn, Co, Mg, V, Ti, Al, Fe, Ru, Zr, W, Sn, Nb and Mo, and 0.1≤x≤0.9. In some embodiments, the second lithium metal oxide particle may include a lithium phosphate-iron-based oxide particle represented by Chemical Formula 2 below. In this case, the first lithium metal oxide particle may include the lithium metal oxide particle having a higher specific capacity than that of the lithium phosphate-iron-based oxide particles. LiFe1-xMxPO4[Chemical Formula 2] In Chemical Formula 2, M may include at least one of Ni, Co, Mn, Al, Mg, Y, Zn, In, Ru, Sn, Sb, Ti, Te, Nb, Mo, Cr, Zr, W, Ir and V, and 0≤x≤1. In some embodiments, each of the first lithium metal oxide particle and the second lithium metal oxide particle may contain nickel. A concentration of nickel in the first lithium metal oxide particle may be greater than a concentration of nickel in the second lithium metal oxide particle. The concentration of nickel may refer to a mole percent (mol %) of nickel calculated based on the total number of moles of all elements except lithium and oxygen in the lithium metal oxide particle. In some embodiments, the nickel concentration in the first lithium metal oxide particle may be 80 mol % or more, 85 mol % or more, 88 mol % or more, or 90 mol % or more. In some embodiments, a difference between the concentration of nickel in the first lithium metal oxide particle and the concentration of nickel in the second lithium metal oxide particle may be from about 5 mol % to about 30 mol %, from about 10 mol % to about 25 mole %, or from about 10 mol % to 20 mol %. In some embodiments, the first lithium metal oxide particle may include a lithium metal oxide particle represented by Chemical Formula 3 below, and the second lithium metal oxide particle may include a lithium metal oxide particle represented by Chemical Formula 4 below. Lix1Ni(1-a1-b1)Coa1M1b1Oy1[Chemical Formula 3] In Chemical Formula 3, M1 may include at least one of Al, Zr, Ti, Cr, B, Mg, Mn, Ba, Si, Y, W and Sr, and 0.9≤x1≤1.2, 1.9≤y1≤2.1 and 0≤a1+b1≤0.2. In some embodiments, 0≤a1+b1≤0.12, 0≤a1+b1≤0.15, or 0≤a1+b1≤0.1. Lix2Ni(1-a2-b2)Coa2M2b2Oy2[Chemical Formula 4] In Chemical Formula 4, M2 may include at least one of Al, Zr, Ti, Cr, B, Mg, Mn, Ba, Si, Y, W and Sr, and 0.9≤x2≤1.2, 1.9≤y2≤2.1, and 0≤a2+b2≤0.5. In some embodiments, 0.1≤a2+b2≤0.4 or 0.1≤a2+b2≤0.3. In one embodiment, 0.05≤(a2+b2)−(a1+b1)≤0.3, 0.1≤(a2+b2)−(a1+b1)≤0.25, or 0.1≤(a2+b2)−(a1+b1)≤0.2. In some embodiments, the outer portion114may include both the first lithium metal oxide particle and the second lithium metal oxide particle together (e.g., a mixture). In this case, the diffusion of the lithium ion may be further prevented by the second lithium metal oxide particle. Additionally, the first lithium metal oxide particles may form a uniform conductive network in the central portion112and the outer portion114, so that performance degradation of the lithium secondary battery due to the division of the central portion112and the outer portion114may be prevented. In some embodiments, in the outer portion114, a weight ratio of the second lithium metal oxide particles relative to the first lithium metal oxide particles may be in a range from 1/9 to 9, from 1/4 to 4, 3/7 to 4, or from 3/7 to 2/3. In one embodiment, in a cross-section of the cathode active material layer110in the width direction, a ratio of a width of the outer portion114(d1ofFIG.3) formed at one side of the central portion112relative to a width of the cathode active material layer110(D1ofFIG.3) may be in a range from 0.001 to 0.2, from 0.002 to 0.2, from 0.005 to 0.1, or from 0.005 to 0.02. A width of the outer portion114formed at the other side of the central portion112may also be within the above range. Within the above range, capacity degradation due to the outer portion114may be prevented, and the local lithium precipitation around the boundary123may be further suppressed. In one embodiment, in a cross-section in the length direction of the cathode active material layer110, a ratio of a width of the outer portion114(d2inFIG.3) formed at one side of the central portion112relative to a width of the cathode active material layer110(D2inFIG.3) may be in a range from 0.0005 to 0.05, from 0.001 to 0.05, from 0.0015 to 0.05, from 0.0015 to 0.0025, or from 0.0015 to 0.01, or from 0.0015 to 0.005. A width of the outer portion114formed on the other side of the central portion112may also be within the above range. Within the above range, capacity degradation due to the outer portion114may be prevented, and the local lithium precipitation around the boundary123may be further suppressed. In some embodiments, the width of each of the outer portions114(e.g., d1and d2inFIG.3) may be in a range from about 0.1 mm to about 3 mm, from about 0.2 mm to 2.5 mm, from about 0.3 mm and 2.5 mm, or from about 0.3 mm to about 2.4 mm. Within the above range, the local lithium precipitation around the boundary123may be further suppressed. In one embodiment, a ratio of a volume (or an area) of the central portion112relative to a total volume (or an area) of the cathode active material layer110may be in a range from 0.8 to 0.98, from 0.85 to 0.96, or from 0.9 to 0.95. The area refers to an area in the planar direction. In one embodiment, a density of the cathode active material layer110may be 3.5 g/cc or more, 3.7 g/cc or more, or 3.9 g/cc or more. Further, the density of the cathode active material layer110may be 4.0 g/cc or less. In one embodiment, a thickness of the cathode active material layer110may be in a range from about 20 μm to 500 μm. For example, the outer portion114may be formed on the cathode current collector105, and then the central portion112may be formed. Alternatively, the central portion112may be formed in advance, and then the outer portion114may be formed. For example, a first cathode slurry for forming the central portion112may be prepared. The first cathode slurry may include the first cathode active material, the cathode conductive material, the binder and a dispersion medium. A second cathode slurry for forming the outer portion114may be prepared. The second cathode slurry may include the second cathode active material, the cathode conductive material, the binder and the dispersion medium. For example, the first cathode slurry may be applied to a region of the cathode current collector105to which the central portion112is allocated. The second cathode slurry may be applied to a region of the cathode current collector105to which the outer portion114is allocated. The order of application of the first cathode slurry and the second cathode slurry is not particularly limited. The coated first and second cathode slurries may be dried and pressed to form the cathode active material layer110. For example, the cathode current collector105may include stainless steel, nickel, aluminum, titanium, copper, or an alloy thereof. For example, the cathode binder may include an organic based binder such as polyvinylidenefluoride (PVDF), a vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyacrylonitrile, polymethylmethacrylate, etc., or an aqueous based binder such as styrene-butadiene rubber (SBR) that may be used with a thickener such as carboxymethyl cellulose (CMC). The conductive material may include a carbon-based material such as graphite, carbon black, graphene, carbon nanotube, etc., and/or a metal-based material such as tin, tin oxide, titanium oxide, a perovskite material such as LaSrCoO3or LaSrMnO3, etc. An anode slurry may be prepared by mixing and stirring the anode active material, the anode binder, the conductive material, a solvent, etc. The anode slurry may be coated on the anode current collector125, and then dried and pressed to form the anode130. For example, the anode current collector125may include gold, stainless-steel, nickel, aluminum, titanium, copper or an alloy thereof, preferably, may include copper or a copper alloy. For example, the anode active material may include a lithium alloy, a carbon-based material, a silicon-based material, etc. For example, the lithium alloy may include a metal element such as aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc. For example, the carbon-based active material may include a crystalline carbon, an amorphous carbon, a carbon complex, a carbon fiber, etc. The amorphous carbon may include, e.g., a hard carbon, cokes, a mesocarbon microbead (MCMB) fired at a temperature of 1500° C. or less, a mesophase pitch-based carbon fiber (MPCF), etc. The crystalline carbon may include, e.g., artificial graphite, natural graphite, graphitized cokes, graphitized MCMB, graphitized MPCF, etc. In one embodiment, the anode active material may include the silicon-based active material. The silicon-based active material may include, e.g., Si, SiOx(0<x<2), Si/C, SiO/C, Si-metal, etc. For example, the anode binder and the conductive material may include materials substantially the same as or similar to those used for the cathode. In one embodiment, a separation layer140may be interposed between the cathode100and the anode130. For example, the separation layer140may include a porous polymer film prepared from, e.g., a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, an ethylene/methacrylate copolymer, or the like. The separation layer140may also include a non-woven fabric formed from a glass fiber with a high melting point, a polyethylene terephthalate fiber, or the like. For example, an electrode cell may be formed including the anode100, the cathode130and the separation layer140. A plurality of the electrode cells may be stacked to form an electrode assembly150. For example, the electrode assembly150may be formed by z-folding, winding, or stacking of the separation layer140. FIG.4is a schematic plan view illustrating a lithium secondary battery in accordance with an example embodiment. Referring toFIG.4, the lithium secondary battery may include a cathode lead107connected to the cathode100of the electrode assembly150to protrude to an outside of a case160, and an anode lead127connected to the anode130of the electrode assembly150to protrude to the outside of the case160. For example, the cathode100and the cathode lead107may be electrically connected to each other. The anode130and the anode lead127may be electrically connected to each other. For example, the cathode lead107may be electrically connected to the cathode current collector105. The anode lead130may be electrically connected to the anode current collector125. The cathode current collector105may include a protrusion at one side thereof. For example, the cathode current collector105may include a cathode tab106. The cathode active material layer110may not be formed on the cathode tab106. The cathode tab106may be integral with the cathode current collector105or may be connected to the cathode current collector105by, e.g., welding. The cathode current collector105and the cathode lead107may be electrically connected via the cathode tab106. The anode current collector125may include a protrusion at one side thereof. For example, the anode current collector125may include an anode tab136. The anode active material layer120may not be formed on the anode tab126. The anode tab126may be integral with the anode current collector125or may be connected to the anode current collector125by, e.g., welding. The anode electrode current collector125and the anode lead127may be electrically connected via the anode tab126. For example, the electrode assembly150and an electrolyte may be accommodated together in the case to form the lithium secondary battery. The lithium secondary battery may be fabricated into a cylindrical shape, a prismatic shape, a pouch shape, a coin shape, etc. Hereinafter, preferred embodiments are proposed to more concretely describe the present disclosures. However, the following examples are only given for illustrating the present disclosures and those skilled in the related art will obviously understand that various alterations and modifications are possible within the scope and spirit of the present disclosures. Such alterations and modifications are duly included in the appended claims. Example 1 (1) Fabrication of Cathode LiNi0.8Co0.1Mn0.1O2(hereinafter, that may be referred to as NCM811) was used as a first cathode active material. A first cathode slurry was prepared by dispersing the first cathode active material, polyvinylidene fluoride (PVdF) and carbon black in N-methyl pyrrolidone (NMP) in a weight ratio of 92:4:4. NCM811 and LiNi0.5Co0.2Mn0.3O2(hereinafter, that may be referred to as NCM523) were blended in a weight ratio of 5:5 to be used as a second cathode active material. A second cathode slurry was prepared by dispersing the second cathode active material, PVdF and carbon black in NMP in a weight ratio of 92:4:4. An aluminum foil (12 μm×300 mm×100 mm) was prepared as a cathode current collector. A region of the aluminum foil excluding one end portion in a length direction was allocated as a cathode active material layer region (290 mm×100 mm). The cathode active material layer region is divided into a first region (i.e., an outer portion) located along a periphery of the cathode active material layer region and a second region (i.e., a central portion) surrounded by the first region. A width of the first region (referring toFIG.3, d1and d2) was set to 0.5 mm. The first cathode slurry was coated on the second region, and the second cathode slurry was coated on the first region, followed by drying and pressing to form a cathode. Coating amounts per unit area of the first cathode slurry and the second cathode slurry were the same, and a thickness of the cathode active material layer was 125 μm. (2) Fabrication of Lithium Secondary Battery An anode active material in which artificial graphite and natural graphite were mixed in a weight ratio of 7:3, SBR and carboxymethyl cellulose (CMC) were dispersed in distilled water in a weight ratio of 97:1:2 to prepare an anode slurry. A copper foil was prepared as an anode current collector. The anode slurry was coated on a region of the copper foil excluding one end portion in the length direction, and then dried and pressed to form an anode. A length of the anode active material layer was set to be larger than a length of the cathode active material layer by 2 mm, and a width of the anode active material layer was set to be larger than a width of the cathode active material layer by 2 mm. An electrode assembly was formed by stacking the cathode and the anode with a polyethylene separator (thickness: 20 μm) interposed therebetween. In the planar direction, widths of regions (i.e., margin portions) of the anode active material layer that did not overlap the cathode active material layer were adjusted to be 1 mm. A cathode lead and an anode lead were connected to the one end portions of the aluminum foil and the copper foil, respectively. After preparing a 1 M LiPF6solution (30:70 v/v EC/EMC mixed solvent), 1 wt % of FEC (fluoroethylene carbonate), 0.3 wt % of VC (vinylethylene carbonate), 1 wt % of LiPO2F2(lithium difluorophosphate), 0.5 wt % of PS (1,3-propane sultone) and 0.5 wt % of PRS (prop-1-ene-1,3-sultone) based on 100 wt % of a total electrolyte solution were added to prepare an electrolyte solution. The electrode assembly was housed in a pouch (case) so that partial regions of the cathode lead and the anode lead were exposed to an outside, and three sides except for an electrolyte injection side were sealed. An electrolyte solution was injected into the pouch and the electrolyte injection side was also sealed to prepare a sample of a lithium secondary battery. Comparative Example A lithium secondary battery was fabricated by the same method as that in Example 1, except that the first cathode slurry was coated on an entire region for the cathode active material layer without dividing the first and second regions. Examples 2 to 4 A lithium secondary battery was fabricated by the same method as that in Example 1, except that the width of the first region (the outer portion) was adjusted as shown in Table 1 below. Examples 5 to 7 A lithium secondary battery was fabricated by the same method as that in Example 1, except that the mixing weight ratio of NCM 811 and NCM 523 in the second cathode slurry was adjusted as shown in Table 1 below. Experimental Example (1) Calculation of a Ratio of Specific Capacities of the Second Cathode Active Material to the First Cathode Active Material Based on specific capacities of NCM 811 and NCM 523 below, a specific capacity of the second cathode active material was calculated proportionally according to the mixing weight ratio. Specific capacity of NCM 811 (reversible capacity in 2.5V-4.2V voltage range): about 200 mAh/g Specific capacity of NCM 523 (reversible capacity in 2.5V-4.2V voltage range): about 170 mAh/g A specific capacity ratio was calculated by dividing the specific capacity of the second cathode active material by a specific capacity of the first cathode active material (i.e., the specific capacity of NCM 811). (2) Evaluation on Room Temperature (25° C.) Discharge Capacity The lithium secondary batteries of Examples and Comparative Example were 0.5C CC/CV charged (4.2V 0.05C CUT-OFF) and 0.5C CC discharged (2.5V CUT-OFF). The charging and discharging were repeated three times, and the discharge capacity was measured at the third cycle. (3) Evaluation on Lithium Precipitated Amount The lithium secondary batteries of Examples and Comparative Examples were 3C CC/CV charged (4.2V 0.05C CUT-OFF) and 0.5C CC discharged (2.5V CUT-OFF). The charging and discharging were repeated 10 times. After completing the charging and discharging, the lithium secondary batteries was disassembled to separate the anode. The separated anode was treated with hydrochloric acid and hydrogen peroxide, and then a heat treatment was performed in a heating block to prepare a test solution. The test solution was diluted with ultrapure water and filtered. The filtrate was subjected to an ICP emission spectrometry to measure an amount of precipitated lithium precipitated in the filtrate. The amount of lithium precipitation was calculated as a percentage of a lithium content based on a total weight of the filtrate. TABLE 1specific capacitywidthratio of secondofmixing weight ratiocathode activeouterof second cathodematerial to firstdischargelithiumportionslurrycathode activecapacityprecipitation(mm)NCM811:NCM 523material(mAh/g)(wt %)Example 10.55:5185/200185.410.61Example 215:5185/200185.250.52Example 30.255:5185/200185.500.71Example 42.55:5185/200184.820.50Example 50.56:4188/200185.450.61Example 60.52:8176/200185.300.58Example 70.58:2194/200185.531.5Comparative——200185.602.1Example Referring to Table 1, in the lithium secondary batteries of Examples, the amount of lithium precipitation was reduced compared to that of Comparative Example. | 29,018 |
11862791 | BEST MODE Hereinafter, the present invention will be described in more detail in order to facilitate understanding of the present invention. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and should be construed in a sense and concept consistent with the technical idea of the present invention, based on the principle that the inventor can properly define the concept of a term to describe his invention in the best way possible. Lithium Electrode the present invention provides relates to a lithium electrode comprising a lithium metal and a protective layer formed on at least one side of the lithium metal, wherein the protective layer is formed by a copolymer containing an acetal and a fluorine-based material. In the present invention, the copolymer containing an acetal and a fluorine-based material may be represented by a random copolymer of monomer A containing an acetal and monomer B containing a fluorine-based material. For example, the monomers A and B are not particularly limited to cyclic olefinic compounds, but specific examples thereof comprise norbornene and derivatives thereof. The weight average molecular weight of the random copolymer of monomer A and monomer B may be in the range of 10,000 to 1,000,000, preferably 15,000 to 900,000, more preferably 20,000 to 800,000. The monomer A containing the acetal is a monomer having an acetal functional group, and the acetal functional group may be at least one selected from the group consisting of 1,3-dioxolane, and 2-methyl-1,3-dioxolane, and preferably, 1,3-dioxolane. Specifically, the monomer A containing the acetal may be at least one selected from the group consisting of (N-2,2-dimethyl-1,3-dioxolane-4-methyl)-5-norbornene-exo-2,3-dicarboximide; N-(4-methyl-2,2-dimethyl-1,3-dioxolane)-5-norbornene-2,3-dicarboxylic acid imide; N-(4-methyl-2,2,4-trimethyl-1,3-dioxolane)-5-norbornene-2,3-dicarboxylic acid imide; N-(5-methyl-2,2-dimethyl-1,3-dioxane)-5-norbornene-2,3-dicarboxylic acid imide; N-(5-methyl-2,2,5-trimethyl-1,3-dioxane)-5-norbornene-2,3-dicarboxylic acid imide; and (2,2-dimethyl-1,3-dioxolane-4-yl)methyl-5-norbornene-2-carboxylate, and preferably, (N-2,2-dimethyl-1,3-dioxolane-4-methyl)-5-norbornene-exo-2,3-dicarboximide. In addition, the monomer B containing the fluorine-based material is a monomer containing a fluorine-based functional group, and the fluorine-based functional group may be at least one selected from the group consisting of fluorocarbon and penta-fluorophenyl, and preferably, fluorocarbon. Specifically, the monomer B containing the fluorine-based material may be at least one selected from the group consisting of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl 5-norbornene-2-carboxylate; N-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)-5-norbornene-exo-2,3-dicarboximide; N-(2-(2,2,3,3,4,4,4-heptafluorobutyl))-5-norbornene-2,3-dicarboxylic acid; N-(2-(2,2,3,3,4,4,4-heptafluorobutyl))-5-norbornene-exo-2,3-dicarboximide; N-(pentafluorophenyl)-5-norbornene-2,3-dicarboxylic acid; and N-(pentafluorophenyl)-5-norbornene-exo-2,3-dicarboximide, and preferably, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl 5-norbornene-2-carboxylate. In the copolymer, the molar ratio of monomer A containing the acetal and monomer B containing the fluorine-based material may be 3 to 7:7 to 3, preferably 4 to 6:6 to 4, more preferably 4.5 to 5.5:5.5 to 4.5. If the ratio is out of the above range, the lifetime of the battery may be reduced. The protective layer of the lithium electrode can be formed to have an appropriate thickness in consideration of the performance of the desired electrode or cell. In the present invention, the thickness of the protective layer formed using a copolymer containing an acetal and a fluorine-based material may be 10 μm or less, preferably 0.1 μm to 5 μm, more preferably 0.5 μm to 2 μm. If the thickness is less than the above range, the effect of inhibiting the formation of lithium dendrite by the protective layer is insignificant and a side reaction may occur between the lithium metal and the electrolyte solution. If the thickness exceeds the above range, the electrode may be thickened and thus may be disadvantageous to commercialization. In the present invention, the lithium metal is formed on the current collector as a positive electrode mixture or a negative electrode mixture, and the lithium metal may comprise all the form of a layer, and the form of a structure which is formed by lithium metal aggregated in the form of particle, which is not a structure in which lithium metal is not formed as a layer. The lithium metal may have a thickness of 5 μm to 150 μm, preferably 15 μm to 130 μm, and more preferably 25 μm to 100 μm. If the thickness of the lithium metal is less than the above range, the capacity and lifetime characteristics of the battery may be lowered. If the thickness of the lithium metal exceeds the above range, the thickness of the lithium electrode to be manufactured may be thickened and thus may be disadvantageous to commercialization. In addition, the lithium metal may be formed on one surface of the current collector. In this case, the protective layer may be formed on the entire surface of the lithium metal, except for the surface where the lithium metal layer is in contact with the current collector. In addition, if the current collector is a porous current collector, lithium metal may be contained in the pores in the porous current collector, and at this time, the protective layer may be provided on the entire surface of the porous current collector, except for the terminal connected to the porous current collector and extended to the outside. In addition, the current collector may be one selected from the group consisting of copper, aluminum, nickel, titanium, sintered carbon, and stainless steel. Preferably the current collector may be a copper current collector. Lithium Secondary Battery The present invention also relates to a lithium secondary battery comprising the lithium electrode as described above. In the lithium secondary battery, the lithium electrode may be included as a negative electrode, and the lithium secondary battery may include an electrolyte solution provided between the negative electrode and the positive electrode. The shape of the lithium secondary battery is not limited, and may be, for example, coin type, flat type, cylindrical type, horn type, button type, sheet type, or stacked type. In addition, the lithium secondary battery may further include a respective tank for storing a positive electrode electrolyte solution and a negative electrode electrolyte solution, and a pump for moving each electrolyte solution to the electrode cell, and thus may be manufactured as a flow battery. The electrolyte solution may be an electrolyte solution impregnated with the negative electrode and the positive electrode. The lithium secondary battery may further comprise a separator provided between the negative electrode and the positive electrode. The separator disposed between the positive electrode and the negative electrode is not particularly limited as long as it separates or isolates the positive and negative electrodes from each other, and allows the transport of ions between the positive and negative electrodes, and the separator may be, for example, a non-conductive porous membrane or an insulating porous membrane. More specifically, polymer nonwovens such as nonwoven fabric of polypropylene material or nonwoven fabric of polyphenylene sulfide material; or porous films of olefin resins such as polyethylene and polypropylene may be exemplified, and it is also possible to use 2 or more types of these together. The lithium secondary battery may further include a positive electrode electrolyte solution on the positive electrode side and a negative electrode electrolyte solution on the negative electrode side separated by a separator. The positive electrode electrolyte solution and the negative electrode electrolyte solution may include a solvent and an electrolytic salt, respectively. The positive electrode electrolyte solution and the negative electrode electrolyte solution may be the same or different from each other. The electrolyte solution may be an aqueous electrolyte solution or a non-aqueous electrolyte solution. The aqueous electrolyte solution may contain water as a solvent, and the non-aqueous electrolyte solution may contain a non-aqueous solvent as a solvent. The nonaqueous solvent may be selected from those generally used in the art and is not particularly limited, and for example, may be selected from the group consisting of a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an organosulfur-based solvent, an organophosphorous-based solvent, an aprotic solvent, or a combination thereof. The electrolytic salt refers to those that dissociate into cations and anions in water or non-aqueous organic solvents, and is not particularly limited as long as it can deliver lithium ion in the lithium secondary battery. The electrolytic salt may be selected from those generally used in the art. The concentration of the electrolytic salt in the electrolyte solution may be 0.1 M or more and 3 M or less. In this case, the charging/discharging characteristics of the lithium secondary battery may be effectively expressed. The electrolyte may be a solid electrolyte membrane or a polymer electrolyte membrane. The material of the solid electrolyte membrane and the polymer electrolyte membrane is not particularly limited, and may be those generally used in the art. For example, the solid electrolyte membrane may comprise a composite metal oxide, and the polymer electrolyte membrane may be a membrane having a conductive polymer inside the porous substrate. The positive electrode refers to an electrode that accepts electrons and reduces lithium-containing ions when the battery is discharging in the lithium secondary battery. On the contrary, when the battery is charged, it acts as a negative electrode (oxidation electrode), and the positive electrode active material is oxidized to release electrons and lose lithium-containing ions. The positive electrode may comprise a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. In the present invention, the material of the positive electrode active material of the positive electrode active material layer is not particularly limited as long as it is applied to a lithium secondary battery together with the negative electrode to reduce lithium-containing ions during discharging and oxidize lithium-containing ions during charging. The material of the positive electrode active material can be, for example, a composite material based on a transition metal oxide or sulfur (S), and may specifically include at least one of LiCoO2, LiNiO2, LiFePO4, LiMn2O4, LiNixCoyMnzO2(wherein, x+y+z=1), Li2FeSiO4, Li2FePO4F and Li2MnO3. In addition, if the positive electrode is a composite material based on sulfur (S), the lithium secondary battery may be a lithium-sulfur secondary battery. The composite material based on sulfur (S) is not particularly limited, and a material of a positive electrode commonly used in the art can be selected and applied. The present specification provides a battery module comprising the lithium secondary battery as a unit cell. The battery module may be formed by stacking on a bipolar plate provided between two or more lithium secondary batteries according to one embodiment of the present specification. If the lithium secondary battery is a lithium air battery, the bipolar plate may be porous to supply externally supplied air to a positive electrode comprised in each of the lithium air batteries. The bipolar plate may comprise, for example, porous stainless steel or porous ceramics. Specifically, the battery module may be used as a power source of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a power storage device. Manufacturing Method of Lithium Electrode The present invention also relates to a method for manufacturing a lithium electrode, which may comprise forming a protective layer on one surface of lithium metal by using a copolymer containing an acetal and a fluorine-based material. The structure and specific examples of the copolymer containing an acetal and a fluorine-based material are as described above. The copolymer containing an acetal and a fluorine-based material may be prepared by copolymerizing a monomer containing an acetal functional group and a monomer containing a fluorine-based functional group in a molar ratio of 3 to 7:7 to 3. The types, preferable molar ratios, and critical significance of the acetal and the fluorine-based material used in the preparation of the copolymer are as described above. Thereafter, in order to form a protective layer on one surface of the lithium metal, the copolymer containing the acetal and fluorine-based material is dissolved in a solvent to prepare a coating solution. At this time, the copolymer may be dissolved in an amount of 1 to 15% by weight, preferably 2 to 10% by weight, more preferably 3 to 8% by weight, based on the total weight of the coating solution. If the amount of the copolymer is less than the above range, the protective function for lithium metal may be lowered. If the amount of the copolymer exceeds the above range, the concentration of the coating solution may be excessively increased, making it difficult to proceed with the coating process, and also, even when a protective layer is formed, cracking may occur. In addition, the solvent used to prepare the coating solution may be at least one selected from the group consisting of tetrahydrofuran (THF), toluene, cyclohexane, N-methyl-2-pyrrolidone (NMP), dimethyl formamide (DMF), dimethyl acetamide (DMAc), tetramethyl urea, dimethyl sulfoxide (DMSO), and triethyl phosphate. Preferably, if THF is used to prepare the coating solution, the copolymer may have high solubility and may be advantageous to form a protective layer by a coating process. In addition, the coating method for forming the protective layer may be selected from the group consisting of dip coating, spray coating, spin coating, die coating, roll coating, Slot-die coating, Bar coating, Gravure coating, Comma coating, Curtain coating, and Micro-Gravure coating, but is not limited thereto, and various coating methods that can be used to form a coating layer in the art can be used. The protective layer thus formed may have a thickness of 0.1 μm to 10 μm, preferably 0.1 μm to 5 μm, more preferably 0.5 μm to 2 μm. The protective layer may be formed as a LiF-rich SEI layer on the surface of lithium metal to inhibit the formation of lithium dendrite. In addition, when the protective layer is applied to a lithium-sulfur secondary battery, the side reaction between the lithium metal and the polysulfide eluted from the positive electrode can be prevented, and thus the lifetime of the battery can be increased. On the other hand, the protective layer may be formed on the current collector of the lithium metal, and the specific type and shape of the current collector are as described above. Hereinafter, in order to facilitate understanding of the present invention, preferred examples are presented, but the following examples are intended to illustrate the present invention only. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention, and also it is obvious that such changes and modifications fall within the scope of the appended claims. PREPARATION EXAMPLE 1 Synthesis of Acetal (N-2,2-dimethyl-1,3-dioxolane-4-methyl)-5-norbornene-exo-2,3-dicarboximide) (AceNB) In a 25 mL round bottom flask, 5 g of 5-norbornene-2,3-dicarboxylic acid and 4.8 g of (2,2-dimethyl-1,3-dioxolane-4-yl) methanamine are dissolved in 100 mL of toluene. To this, 0.3 ml of triethylamine is added, a condenser is mounted, and the solution is immersed in an oil bath heated to 120° C. and then refluxed for 12 hours. After the reaction is completed, only the organic layer is separated by separating the layers after washing with saturated ammonium chloride solution. The separated organic layer was purified once more using a silica column and dried to synthesize N-2,2-dimethyl-1,3-dioxolane-4-methyl)-5-norbornene-exo-2,3-dicarboximide (AceNB) represented by the following Formula 1. PREPARATION EXAMPLE 2 Synthesis of Fluorine-Based Material (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl 5-norbornene-2-carboxylate) (C10FNB) In a 25 mL round bottom flask, 5 g of 5-norbornene-2-carboxylic acid and 16 g of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecane-1-ol are dissolved in 100 mL of methylene chloride. To this, 7.5 g of dicyclohexylcarbodiimide and 0.4 g of dimethylaminopyridine were added, and the mixture was allowed to react for 12 hours. After the reaction is completed, only the organic layer is separated by separating the layers after washing with saturated sodium bicarbonate solution. The separated organic layer was purified once more using a silica column and dried to synthesize 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl 5-norbornene-2-carboxylate (C10FNB) represented by the following Formula 2. EXAMPLE 1 A lithium electrode having a protective layer formed of AceNB synthesized in Preparation Example 1 and C10FNB synthesized in Preparation Example 2 in a molar ratio of 7:3 was prepared. In a 25 mL round bottom flask, the above molar ratio of AceNB and C10FNB, and 10.00 g of tetrahydrofuran were added and the inlet was sealed. Oxygen was removed by bubbling nitrogen for 30 minutes, the reaction flask was immersed in an oil bath heated to 55° C., and then the reaction was initiated by the addition of 35.00 mg of Grubs second-generation catalyst. After 4 hours, the reaction was terminated, and the resultant obtained was precipitated twice in ethanol, followed by vacuum-drying to obtain a cyclic olefin copolymer (conversion of 99%, weight average molecular weight of 92,000). 5% by weight of the copolymer prepared by the above method was dissolved in 95% by weight of tetrahydrofuran (THF) solvent to prepare a coating solution for forming a protective layer. (2) Formation of Protective Layer The coating solution was coated on the surface of the lithium metal layer having a thickness of 50 μm formed on the Cu current collector using a Baker Film Applicator to form a protective layer having a thickness of 0.5 μm, thereby manufacturing a lithium electrode comprising the protective layer. (3) Manufacture of Lithium-Sulfur Secondary Battery A lithium-sulfur secondary battery in the form of a coin cell was manufactured by using the above-manufactured electrode as a negative electrode, a S/C complex as positive electrode, a composition containing a solvent, DOL/DME (1:1, v/v) (DOL: dioxolane, DME: dimethoxyethane) and 1 M LiTFSI and 3 wt. % LiNO3, as an electrolyte solution EXAMPLE 2 A lithium electrode and a lithium-sulfur secondary battery were manufactured in the same manner as in Example 1, except that the lithium electrode and the lithium-sulfur secondary battery comprise a protective layer formed using a copolymer (weight average molecular weight of 85,000) copolymerized with AceNB and C10FNB in a molar ratio of 5:5. EXAMPLE 3 A lithium electrode and a lithium-sulfur secondary battery were manufactured in the same manner as in Example 1, except that the lithium electrode and the lithium-sulfur secondary battery comprise a protective layer formed using a copolymer (weight average molecular weight of 62,000) copolymerized with AceNB and C10FNB in a molar ratio of 3:7. EXAMPLE 4 A lithium-lithium battery was manufactured in the same manner as in Example 1, except that the lithium electrodes comprising a protective layer formed using a copolymer copolymerized with AceNB and C10FNB in a molar ratio of 7:3 are used as negative and positive electrodes. EXAMPLE 5 A lithium-lithium battery was manufactured in the same manner as in Example 1, except that the lithium electrodes comprising a protective layer formed using a copolymer copolymerized with AceNB and C10FNB in a molar ratio of 5:5 are used as negative and positive electrodes. EXAMPLE 6 A lithium-lithium battery was manufactured in the same manner as in Example 1, except that the lithium electrodes comprising a protective layer formed using a copolymer copolymerized with AceNB and C10FNB in a molar ratio of 3:7 are used as negative and positive electrodes. EXAMPLE 7 A lithium electrode and a lithium-sulfur secondary battery were manufactured in the same manner as in Example 1, except that the lithium electrode and the lithium-sulfur secondary battery comprise a protective layer formed using a copolymer (weight average molecular weight of 85,000) copolymerized with AceNB and C10FNB in a molar ratio of 2:8. EXAMPLE 8 A lithium electrode and a lithium-sulfur secondary battery were manufactured in the same manner as in Example 1, except that the lithium electrode and the lithium-sulfur secondary battery comprise a protective layer formed using a copolymer (weight average molecular weight of 85,000) copolymerized with AceNB and C10FNB in a molar ratio of 8:2. COMPARATIVE EXAMPLE 1 A lithium-sulfur secondary battery was manufactured in the same manner as in Example 1, except that a lithium electrode without a protective layer is used as a negative electrode, and S/C composite is used as a positive electrode. COMPARATIVE EXAMPLE 2 A lithium-lithium battery was manufactured in the same manner as in Example 1, except that lithium electrodes without a protective layer are used as a negative electrode and a positive electrode, respectively. COMPARATIVE EXAMPLE 3 A lithium electrode and a lithium-sulfur secondary battery were manufactured in the same manner as in Example 1, except that the lithium electrode and the lithium-sulfur secondary battery comprise a protective layer formed using a polymer (weight average molecular weight of 180,000) of AceNB when forming the protective layer. COMPARATIVE EXAMPLE 4 A lithium electrode and a lithium-sulfur secondary battery were manufactured in the same manner as in Example 1, except that the lithium electrode and the lithium-sulfur secondary battery comprise a protective layer formed using a polymer of C10FNB when forming the protective layer. EXPERIMENTAL EXAMPLE 1 Measurement of Discharging Capacity and Coulombic Efficiency of Lithium Electrode After setting the charging and discharging rates in the charging/discharging device to 2.8 mA and 4.7 mA, respectively, the charging/discharging cycles were performed for the coin cells manufactured in the examples and the comparative examples, respectively. FIG.1is a graph showing specific discharging capacity and coulombic efficiency measured by charging/discharging coin cells manufactured in Example 1 and Comparative Example 1, respectively. FIG.2is a graph showing specific discharging capacity and coulombic efficiency measured by charging/discharging coin cells manufactured in Example 2 and Comparative Example 1, respectively. FIG.3is a graph showing specific discharging capacity and coulombic efficiency measured by charging/discharging coin cells manufactured in Example 3 and Comparative Example 1, respectively. Referring toFIG.1, it can be seen that Example 1 which comprises a lithium negative electrode having a protective layer including a copolymer prepared by copolymerizing AceNB and C10FNB at a molar ratio of 7:3 has increased cycle lifetime, as compared to Comparative Example 1 which comprises a lithium negative electrode without a protective layer. Referring toFIG.2, it can be seen that Example 2 which comprises a lithium negative electrode having a protective layer including a copolymer prepared by copolymerizing AceNB and C10FNB at a molar ratio of 5:5 has increased cycle lifetime, as compared to Comparative Example 1 which comprises a lithium negative electrode without a protective layer. Referring toFIG.3, it can be seen that Example 3 which comprises a lithium negative electrode having a protective layer including a copolymer prepared by copolymerizing AceNB and C10FNB at a molar ratio of 3:7 shows high discharging capacity during charging/discharging cycles, as compared to Comparative Example 1 which comprises a lithium negative electrode without a protective layer. FIG.4is a graph showing specific discharging capacity and coulombic efficiency measured by charging/discharging coin cells manufactured in Comparative Example 1 and Comparative Example 3, respectively. Referring toFIG.4, Comparative Example 3, which is a case of forming a protective layer on a lithium negative electrode using only AceNB, shows that discharging capacity and cycle lifetime are reduced, as compared to Comparative Example 1 in which no protective layer is formed on both the positive and negative electrodes. From this, it can be seen that both AceNB and C10FNB are required as materials for forming a protective layer of the lithium negative electrode in order to improve discharging capacity and coulombic efficiency of the battery. FIG.5is a graph showing specific discharging capacity measured by charging/discharging coin cells manufactured in Examples 1, 7, and 8, and Comparative Example 1, respectively. Referring toFIG.5, it was confirmed that Comparative Example 1 has a significantly lower discharging capacity than Examples 1, 7, and 8, and in the case of Example 1 of the examples, discharging capacity is not reduced even if the cycle is repeated. FIG.6is a graph showing specific discharging capacity measured by charging/discharging coin cells manufactured in Comparative Example 1, and Comparative Example 4, respectively. Referring toFIG.6, it was confirmed that in both Comparative Example 1 and Comparative Example 4, the discharging capacity is significantly reduced as the cycle is repeated. EXPERIMENTAL EXAMPLE 2 Observation of the Surface of the Lithium Electrode FIG.7is a photograph showing the surfaces of the lithium negative electrodes in a charged state disassembled and observed after charging and discharging 25 times for the coin cell-type lithium-lithium batteries of Examples 4 to 6 and Comparative Example 2. Referring toFIG.7, it can be seen that the lithium negative electrodes of Examples 4 to 6 have a uniform surface shape as compared to Comparative Example 2 even after several charging/discharging. Although the present invention has been described with reference to the limited examples and drawings, it is to be understood that the present invention is not limited thereto and that various modifications and variations are possible within the technical idea of the present invention and the scope equivalent to the claims set forth below. | 27,199 |
11862792 | DETAILED DESCRIPTION FIG.1shows an embodiment105of the invention, which is a metallic micro-particles101cladded with a layer of MXene103, e.g. Ti3C2Tx. The metallic micro-particle101is preferably zinc but in other embodiments (not illustrated), the micro-particle can be made of another suitable transition metal. MXenes103are a relatively new material, and are ceramics-metallic structures that belong to a class of two-dimensional inorganic compounds. MXenes103were developed and produced following discovery of single layer graphenes. Generally, most MXenes103are layers of carbides, nitrides or carbonitrides interleaved with layers of a transition material, which is most commonly titanium (the transition metal which is part of the MXene is not to be confused with the transition metal which the MXene clads). Hence, MXenes103are typically just a few-atoms-thick. In a flake of MXene103, there is usually n+1 layers of transition metals (M) are interleaved with n layers of carbon or nitrogen (X) with a general formula of Mn+1XnTx. Txrepresents the surface termination, and may be O, OH, F and/or Cl which are bonded to the outer M layers of the MXene103. In the present embodiment, the flakes of MXenes103used are preferably “Few-layered” Mxenes. “Few-layered” is a terminology describing MXenes103of a thickness with less than 5 atomic layers. However, typical MXenes with thickness of 1 to 150 layers are within the contemplation of this application. Also, the preferred MXene has a lateral size ranging from 20 nm to 100 μm. By way of example,FIG.2illustrates a MXene having a structure of Ti—C—Ti—C—Ti, i.e. Ti3C2. The extreme layers of titanium is supplied with —OH functional groups. However, the transition metal M in the MXene does not have to be a single element; a mix of two metal elements is possible, e.g. (Ti,Nb)CTx. Advantageously, MXenes103combine metallic conductivity of transition metal carbides and a hydrophilic nature because of the hydroxyl or oxygen terminated surfaces, and have excellent electrical conductivity (15000 S cm−1). Furthermore, MXenes typically has superior physical flexibility or morph-ability, with Young's modulus reaching about 0.33 TPa and breaking strength reaching around 17 GPa, and is able to adapt and lay over any surface profile intimately. The synthesis of MXene103is known and does not require detailed description here. It suffices to mention that Few-layered Ti3C2TxMXene103may be synthesized by a wet-etching method using HCl/LiF etchant and Ti3AlC2MAX precursor. The method of assimilating MXene and zinc micro-particles is illustrated inFIG.3. The leftmost photograph inFIG.3ashows a water suspension of MXene103. The middle photograph shows a vial of zinc micro-particles that has settled on the bottom of a vial. The rightmost photograph ofFIG.3ashows zinc micro-particles that are cladded with MXenes, annotated as MXene@zinc, which is a specific embodiment (therefore, MXene@zinc is also referenced by the same numeral ‘103’). Upon mixing the zinc micro-particles to the MXenes, the mixture is stirred for 1 hr and left standing for 0.2 hr. The intrinsic electro-negativity of Ti3C2Txmatches the electro-positivity of zinc. Thus, the Ti3C2Txflakes are easily compelled to clad onto the zinc micro-particles. Hence, the MXenes slowly and automatically wraps around the individual zinc micro-particles, encouraged by the electro-attraction between the MXene and the zinc micro-particles, and aided by the flaccid nature of the MXene flakes. The Zeta potential of MXene flakes of −54 mV, which means MXene flakes form a highly stable colloid in water, which is good for mixing with the zinc micro-particles101. The Zeta potential of MXene flakes is opposite to that of the positively charged zinc micro-particles at 17 mV. As shown inFIG.3b, the Zeta potential of MXene@Zn composite is just about 1.5 mV. A low Zeta potential means that solids in the suspension are very likely to cluster together and therefore suitable for use as material in a solid electrode. Hence, upon complete cladding of all the zinc micro-particles, the mixture separates into two distinct parts. The upper layer is just water, and the dense bottom sediment is the electrostatic, self-assembled MXene@Zn composite103. This ability to self-assemble provides that MXene@Zn composite can be produced on an industrial scale. The zinc micro-particles101used is preferably a monodisperse powder that has a diameter of around 5 μm, as shown in the scanning electron microscopic (SEM) image ofFIG.4. The SEM photograph shows that the particle surface is rough and full of protruding spots. However, any zinc powder having a particle size ranging from a tiny 100 nm to a large 200 μm is useable for mixing with MXene103to produce the MXene@Zn composite105.FIG.5is an SEM image of the zinc micro-particles101ofFIG.4wrapped around by Ti3C2Tx. FIG.6schematically shows Zn2+ions gathering around nucleation sites601which can promote uneven deposits603from zinc ions on the surface of a zinc particle. In contrast,FIG.7ashows schematically how MXene cladding over a zinc micro-particle redistributes the charge around the zinc micro-particle, and causes even deposits of Zn2+ions around the MXene-clad zinc micro-particle105. This discourages nucleation sites and formation of dendrites. As MXenes are conductive, even on a grand scale such as a compact electrode made of these MXene cladded zinc micro-particles, the distribution of zinc ion deposit is likely to be even over the entire electrode. FIG.7bis an SEM image of a zinc powder electrode of the prior art after having undergone several rounds of discharging and recharging. Zn2+ions does not deposit back to the original sites in the electrode from which they leaked. Instead, the Zn2+ions tend to grow as dendrites (see the star-like, sharp edged structures) in the subsequent charging process on the surface of the electrode. At this stage, electrical contact failure occurs inside the electrode and results in dramatic deterioration of overpotential value (voltage efficiency). However, in the case of MXene@Zn anode, the deposited surface remains flat and is accompanied with distinct wrinkles.FIG.7cis a SEM image showing that no visible dendritic-like protrusion area can be found even after zinc ions have been allowed to be deposited onto the MXene@Zn anode. As the skilled reader would appreciate, the redistributive function of the MXene cladding also reduces the chance of polarization. FIG.8shows schematically how MXene claddings can mitigate the inevitable problem of electrode volume shrinkage. As an electrode discharges, the atoms in the electrode tend to dissolve and leak away from the electrode. This causes some of the zinc particles101to shrink or vanish, creating cavities801within in the electrode leading to broken contact points and affecting battery performance.FIG.9shows the same dissolution of zinc particles101in an electrode made of MXene cladded zinc micro-particles105. In the event of volume shrinkage, the MXene103remains behind while the zinc dissolves away and, being flexible, may be able to fill in the space left behind by the dissolved zinc like an over-sized garment901, maintaining contact with the neighbouring zinc micro-particles101and MXenes103. This helps prolong use of the battery through more recharging cycles. Ti3C2Txhas an atomic lattice that has a hexagonal close packed (hcp) structure. Zinc ion deposits also have a hexagonal close packed (hcp) structure. This means that Ti3C2Txand zinc are physically compatible. This is illustrated inFIG.10. Having compatible lattice structure means the ion deposit on the surface of the MXene cladding is likely to be even and smooth, which further discourages formation of dendrites. This low physical mismatch between the titanium-terminated surface of (0002) plane of Ti3C2Txand (0002) plane of zinc facilitates the formation of a coherent or semi-coherent interface, and allows reversible and uniform deposition of Zn2+ions. As shown inFIG.11, TEM (Transmission electron microscopy) image of MXene@Zn composite presents a sharp distinction between MXene substrate and Zn deposit. The inherent wrinkled and electron-transparent features are identified in MXene, and the upper Zn deposits hold the flat and neat surficial texture. No dendrite-like Zn deposit can be observed at this micron scale. The corresponding high-angle annular dark-field (HAADF)-scanning TEM and energy dispersive spectroscopy (STEM-EDS) inFIG.12indicate the homogeneous Zn deposition on MXene substrate without other impurities. See in particular the bottom picture inFIG.12, the dots showing presence of zinc ion deposits on the MXene. The zinc ion deposits are spread evenly across the whole MXene surface without any clusters of nucleation or impurities. Accordingly, to provide a novel material useable as a zinc electrode, zinc micro-particles101are cladded in MXenes105so that the zinc micro-particles101are separated from each other but remain in conductive contact with each other through the MXene103. Furthermore, the MXene103around the zinc micro-particles101provides pores or tiny spaces between the micro-particles.FIG.13displays a cross-sectional SEM image of the fabricated MXene@Zn anode. The densely stacked MXene@Zn composite spheres form a flat but rough surface, and the abundantly visible pores remaining inside are conducive to electrolyte filling. In other words, the zinc micro-particles101are sufficiently isolated from each other spatially for optimum contact with electrolytes. However, as MXenes103are conductive, electrical current can flow through both zinc micro-particles101and the MXene103. This allows the MXene-wrapped zinc micro-particles105to be used as an electrode while spacing the zinc micro-particles apart to prevent the degeneration that is often seen in zinc powder electrodes. Advantageously, as the surface of MXene flakes is hydrophilic, MXene cladded zinc micro-particles105provide an electrode material which has improved wettability which can enhance electrode performance. MXene encapsulation of zinc micro-particles101not only breaks the irreversible imprisonment of zinc powder anode but also significantly improves the redox kinetics and cyclic durability of uniform Zn stripping/plating. FIG.14illustrates an electrode having MXene@Zn coated on a copper substrate, paired with a FeHCF cathode. In particular, a FeHCF//MXene@Zn cell has excellent electrochemical performance, the cycle life of which may be improved by nearly 850% against that of the conventional FeHCF//zinc powder battery (see experimental data below). The described MXene@Zn is therefore a stable zinc powder electrode, having the advantages provided by MXene flakes which have high lattice compatibility with zinc, superior hydrophilicity and conductivity as the electrons and ions redistributor to achieve a battery with high charge and discharge recyclability. Although Ti3C2Txcladded zinc micro-particles are mentioned in the above embodiments, other embodiments of different types of MXenes cladding micro-particles of other metals are within the contemplation of this application. For example, in different composites, MXene selected from: Ti3C2Tx, Ti3CNTX, Ti2CTX, Ti2NTX, Nb2CTX, V2CTX, and Zr4C3TX, wherein TXrepresents functional group on the surface of the MXene103, cladding other conductive elements such as copper, aluminium and so on are possible. The preferred pairs of metal and MXene have compatible lattice structure and opposite charge. While there has been described in the foregoing description preferred embodiments of the present invention, it will be understood by those skilled in the technology concerned that many variations or modifications in details of design, construction or operation may be made without departing from the scope of the present invention as claimed. | 11,914 |
11862793 | DESCRIPTION OF EMBODIMENTS Hereinafter, regarding the present invention, an example of a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present embodiment will be described, and then a method for producing the same and a non-aqueous electrolyte secondary battery using the positive electrode active material according to the present embodiment will be described. Note that the present invention is not limited to the following detailed description. 1. Positive Electrode Active Material for Non-Aqueous Electrolyte Secondary Battery The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present embodiment (hereinafter also referred to as “positive electrode active material”) includes a lithium-nickel composite oxide and Li3BO3, and at least a part of a surface of the lithium-nickel composite oxide is coated with Li3BO3. The lithium-nickel composite oxide is represented by general formula (1): LiaNi1−x−yCoxMyO2+α(in which 0.05≤x≤0.35, 0≤y≤0.10, 0.95≤a≤1.10, 0≤α≤0.2, and M represents at least one element selected from Mn, V, Mg, Mo, Mb, Ti, W, and Al) and forms a layered crystal structure. The lithium-nickel composite oxide includes a secondary particle with a plurality of aggregated primary particles. In the general formula (1), (1−x−y) indicating the amount of nickel satisfies 0.55≤(1−x−y)≤0.95. The positive electrode active material according to the present embodiment can sufficiently suppress deterioration of battery characteristics due to the atmosphere by coating a surface of the lithium-nickel composite oxide with Li3BO3even when the amount of nickel is within the above range. In the general formula (I), x indicating the amount of cobalt satisfies 0.05≤x≤0.35. When the amount of cobalt is within the above range, cycle characteristics are excellent while high battery capacity is maintained. M is at least one element selected from the group consisting of Mn, V, Mg, Mo, Nb, Ti, W, and Al, and preferably contains Al from a viewpoint of thermal stability of a positive electrode active material. The value of y indicating the amount of M preferably satisfies 0.01≤y≤0.10. In the above general formula (1), the value of a indicates the amount of Li (Li/Me) with respect to the total amount of Ni, Co, and M (Me amount), and satisfies 0.95≤a≤1.10. Note that the value of a also includes the amount of Li contained in Li3BO3. As described later, Li3BO3is formed by a reaction between a boron compound and a lithium compound in a lithium-nickel composite oxide used as a raw material in a firing step, and therefore the value of a may be 1 or more. The positive electrode active material according to the present embodiment can suppress deterioration of battery characteristics due to contact between the lithium-nickel composite oxide and the atmosphere by coating at least a part of a surface of the lithium-nickel composite oxide with Li3BO3. The positive electrode active material according to the present embodiment may contain lithium borate other than Li3BO3, and may contain, for example, LiBO2, lithium tetraborate, or lithium pentaborate. As the lithium borate other than Li3BO3, LiBO2is preferably contained. Examples of the lithium borate coating a surface of the lithium-nickel composite oxide include LiBO2, lithium tetraborate, and lithium pentaborate in addition to Li3BO3. Among these compounds, Li3BO3alone is particularly preferably used. When a surface of the lithium-nickel composite oxide is coated with Li3BO3alone, the above effect can be exhibited more significantly. Note that presence of lithium borate on a surface of the lithium-nickel composite oxide can be confirmed by powder X-ray diffraction. In the positive electrode active material, Li3BO3alone is more preferably detected as lithium borate by powder X-ray diffraction. Note that a surface of the lithium-nickel composite oxide can be coated with Li3BO3by a method described later. In the positive electrode active material according to the present embodiment, at least a part of a surface of the lithium-nickel composite oxide is more preferably coated with Li3BO3alone. Note that the phrase “coated with Li3BO3alone” refers to a state in which only a diffraction peak of Li3BO3is detected as a diffraction peak other than that derived from the lithium-nickel composite oxide in powder X-ray diffraction. The content of boron contained in the positive electrode active material is 0.001% by mass or more and 0.2% by mass or less, preferably 0.005% by mass or more and 0.1% by mass or less, and more preferably 0.01% by mass or more and 0.08% by mass or less with respect to the entire positive electrode active material. When the content of boron is within the above range, deterioration of battery characteristics such as reduction in discharge capacity due to exposure to the atmosphere can be suppressed in a case of use as a positive electrode active material of a secondary battery. In general, when a surface of the lithium-nickel composite oxide is coated with a compound containing different elements, battery characteristics such as reaction resistance of the positive electrode may be deteriorated. However, Li3BO3has high lithium conductivity. Therefore, when the content of boron is within the above range, even if the surface is coated, deterioration of battery characteristics in a secondary battery can be suppressed. Meanwhile, when the content of boron is less than 0.001% by mass, an effect of suppressing deterioration of battery characteristics due to exposure to the atmosphere cannot be sufficiently obtained. Details of this reason are not clear. However, it is considered that a Li3BO3layer formed on a surface of the lithium-nickel composite oxide becomes too thin. When the content of boron exceeds 0.2% by mass, battery characteristics in a secondary battery may be deteriorated. Details of this reason are not clear. However, it is considered that a Li3BO3layer formed on a surface of the lithium-nickel composite oxide becomes too thick to increase reaction resistance of the positive electrode. Note that it is difficult to directly measure formation of the Li3BO3layer in the positive electrode active material according to the present embodiment. However, as illustrated in Examples described later, by measuring a change amount (%) between initial discharge capacity after leaving the obtained positive electrode active material at 80° C. in the atmosphere for 24 hours and initial discharge capacity before exposure to the atmosphere, the degree of formation of the Li3BO3layer on a surface of the lithium-nickel composite oxide can be indirectly evaluated. For example, in the positive electrode active material according to the present embodiment, the change amount (%) determined by the following formula is preferably 4% or less, and more preferably 2% or less under conditions described in Examples. When the change amount of the initial discharge capacity is within the above range, an evaluation that the Li3BO3layer having an appropriate thickness and coating range has been formed can be made. Note that a lower limit of the change amount (%) can be 0% or more, but may be 0.1% or more or 0.5% or more. Change amount (%) in initial discharge capacity={[Initial discharge capacity before exposure to atmosphere (mAh/g)]−[Initial discharge capacity after exposure to atmosphere (mAh/g)]}×100/[Initial discharge capacity before exposure to atmosphere (mAh/g)] Formula: The positive electrode active material according to the present embodiment does not need to substantially contain one or more of carbon (C), sulfur (S), and silicon (Si). Specifically, in the positive electrode active material, for example, the content of carbon (C) may be 0.04% by mass or less or may be less than 0.01% by mass of the entire positive electrode active material, and the positive electrode active material does not need to contain carbon (C). In the positive electrode active material, for example, the content of sulfur (S) may be 0.04% by mass or less or may be less than 0.01% by mass of the entire positive electrode active material, and the positive electrode active material does not need to contain sulfur (S). In the positive electrode active material, for example, the content of silicon (Si) may be less than 0.01% by mass or may be less than 0.001% by mass of the entire positive electrode active material, and the positive electrode active material does not need to contain silicon (Si). The contents of carbon (C), sulfur (S), and silicon (Si) can be measured with, for example, a carbon sulfur analyzer or an ICP emission spectroscopic analyzer. 2. Method for Producing Positive Electrode Active Material for Non-Aqueous Electrolyte Secondary Battery Next, with reference toFIG.1, a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present embodiment (hereinafter also referred to as “method for producing a positive electrode active material”) will be described.FIG.1is a diagram illustrating an example of a method for producing a positive electrode active material. By this method for producing a positive electrode active material, the above-described positive electrode active material containing a lithium-nickel composite oxide in which at least a part of a surface is coated with Li3BO3can be obtained with high productivity on an industrial scale. The method for producing a positive electrode active material according to the present embodiment includes: mixing a boron compound, at least one of a nickel composite hydroxide and a nickel composite oxide, and a lithium compound to obtain a lithium mixture (step S10); and firing the lithium mixture in an oxygen atmosphere at a temperature of 715° C. or higher and 850° C. or lower to obtain a lithium-nickel composite oxide (step S20). Hereinafter, each step will be described. First, a boron compound, at least one of a nickel composite hydroxide and a nickel composite oxide, and a lithium compound are mixed to obtain a lithium mixture (step S10). As the boron compound, a compound containing boron capable of reacting with lithium can be used. Examples thereof include boron oxide (B2O3), boric acid (H3BO3), ammonium tetraborate tetrahydrate ((NH4)2B4O7·4H2O), ammonium pentaborate octahydrate ((NH4)2O·5B2O3·8H2O), and LiBO2. Among these compounds, at least one selected from H3BO3, B2O5, and LiBO2is preferably used, and at least one of H3BO3and B2O3is more preferably used. H3BO3and B2O3are acidic and therefore highly reactive with Li. These compounds are highly reactive with a lithium salt, and are considered to form Li3BO3after the firing step (step S20) described later. The boron compound is mixed in such an amount that boron in the boron compound is 0.001% by mass or more and 0.2% by mass or less, preferably 0.005% by mass or more and 0.1% by mass or less, and more preferably 0.01% by mass or more and 0.08% by mass or less with respect to the entire positive electrode active material obtained. The nickel composite hydroxide and the nickel composite oxide are not particularly limited, and known compounds can be used. Examples thereof include a nickel composite hydroxide obtained by a crystallization method and a nickel composite oxide obtained by oxidizing and firing (thermally treating) the nickel composite hydroxide. As a method for producing the nickel composite hydroxide, either a batch method or a continuous method can be applied. The continuous method for continuously collecting nickel composite hydroxide particles overflowing from a reaction vessel is preferable from viewpoints of cost and filling property. The batch method is preferable from a viewpoint of obtaining particles with higher uniformity. Examples of the lithium compound include lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate. Among these compounds, lithium hydroxide and lithium carbonate are preferable, and lithium hydroxide is more preferable from a viewpoint of reactivity with the boron compound. The lithium compound is mixed in such an amount that the ratio (Li/Me) of the number of atoms of lithium (Li) to the total number of atoms (Me) of metal elements other than lithium is 0.95 or more and 1.10 or less. When Li/Me is less than 0.95, since reaction resistance of a positive electrode in a secondary battery using the obtained positive electrode active material is large, a battery output is low. When Li/Me exceeds 1.10, the initial discharge capacity of the obtained positive electrode active material is reduced, and the reaction resistance of the positive electrode is also increased. In the mixing step (step S10), the boron compound, the nickel composite hydroxide and/or the nickel composite oxide, and the lithium compound are preferably mixed sufficiently. For mixing these compounds, a general mixer can be used, and examples thereof include a shaker mixer, a Loedige mixer, a Julia mixer, and a V blender. It is only required to perform mixing with the lithium compound sufficiently to such an extent that the shapes of the composite hydroxide particles are not destroyed. Next, the lithium mixture is fired in an oxygen atmosphere at a temperature of 715° C. or higher and 850° C. or lower to obtain a lithium-nickel composite oxide (step S20) By firing the lithium mixture containing the boron compound the lithium-nickel composite oxide is generated, and Li3BO3can be generated at the same time. Note that boron is hardly solid-solved in the lithium-nickel composite oxide. Therefore, it is considered that most of boron added as the boron compound forms Li3BO3. The firing temperature is 715° C. or higher and 850° C. or lower, preferably 715° C. or higher and 800° C. or lower, and more preferably 720° C. or higher and 780° C. or lower. When the firing temperature is within the above range, a surface of the lithium-nickel composite oxide can be uniformly coated with a Li3BO3layer. When the firing temperature is 715° C. or higher, since the melting point of Li3BO3is 715° C., Li3BO3formed by a reaction between the boron compound and the lithium compound can be sufficiently melted. As a result, a surface of the lithium-nickel composite oxide can be uniformly coated with the Li3BO3layer. Meanwhile, when the firing temperature is lower than 715° C., Li3BO3is not melted sufficiently. Therefore, coating with the Li3BO3layer on the surface of the lithium-nickel composite oxide is non-uniform, and deterioration of battery characteristics due to exposure to the atmosphere cannot be sufficiently suppressed. When the firing temperature exceeds 850° C., the lithium-nickel composite oxide is decomposed, and the battery characteristics are deteriorated. Therefore, the firing temperature exceeding 850° C. is not preferable. Holding time at the firing temperature is, for example, about 5 hours or more and 20 hours or less, and preferably about 5 hours or more and 10 hours or less. The atmosphere during firing is an oxygen atmosphere, and is preferably an atmosphere having an oxygen concentration of 100% by volume, for example. 3. Non-Aqueous Electrolyte Secondary Battery The non-aqueous electrolyte secondary battery (hereinafter also referred to as “secondary battery”) according to the present embodiment includes a positive electrode including the positive electrode active material described above as a positive electrode material. The secondary battery can include similar components to those of a conventionally known non-aqueous electrolyte secondary battery. The secondary battery may include, for example, a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, or may include a positive electrode, a negative electrode, and a solid electrolyte. As described above, the positive electrode active material according to the present embodiment can suppress deterioration of battery characteristics such as a decrease in discharge capacity due to exposure to the atmosphere. Therefore, the secondary battery can be assembled in the atmosphere although the assembly has required special equipment such as a dry room so far. Hereinafter, an example of a method for producing a secondary battery according to the present embodiment will be described. Note that an embodiment described below is merely an example, and the non-aqueous electrolyte secondary battery according to the present embodiment can be implemented in various modified forms or improved forms on the basis of knowledge of those skilled in the art on the basis of the embodiment described here. Use of the non-aqueous electrolyte secondary battery according to the present embodiment is not particularly limited. (Positive Electrode) Using the positive electrode active material for a non-aqueous electrolyte secondary battery obtained as described above, for example, a positive electrode of a non-aqueous electrolyte secondary battery is manufactured as follows. First, a powdered positive electrode active material, a conductive material, and a binding agent are mixed, activated carbon and a solvent for viscosity adjustment or the like are further added as necessary, and the resulting mixture is kneaded to manufacture a positive electrode mixture paste. At this time, a mixing ratio among the components in the positive electrode mixture paste is also an important factor for determining performance of a non-aqueous electrolyte secondary battery. When the solid content of the positive electrode mixture excluding the solvent is 100 mass parts, similarly to a positive electrode of a general non-aqueous electrolyte secondary battery, desirably, the content of the positive electrode active material is 60 to 95 mass parts, the content of the conductive material is 1 to 20 mass parts, and the content of the binding agent is 1 to 20 mass parts. The obtained positive electrode mixture paste is applied to, for example, a surface of an aluminum foil current collector and dried to scatter the solvent. Pressurization may be performed by roll press or the like in order to increase electrode density as necessary. In this way, a sheet-like positive electrode can be manufactured. The sheet-like positive electrode can be cut into an appropriate size according to a target battery and used for producing a battery. However, the method for producing a positive electrode is not limited to the above-described example, and another method may be used. In producing a positive electrode, examples of the conductive material include graphite (natural graphite, artificial graphite, expanded graphite, and the like), and a carbon black-based material such as acetylene black or ketjen black. The binding agent plays a role of bonding active material particles together, and examples thereof include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a fluorine-containing rubber, an ethylene propylene diene rubber, styrene butadiene, a cellulose-based resin, and polyacrylic acid. A solvent that disperses the positive electrode active material, the conductive material, and the activated carbon and dissolves the binding agent is added to the positive electrode mixture as necessary. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent. Activated carbon can be added to the positive electrode mixture in order to increase electric double layer capacity. (Negative Electrode) For a negative electrode, metal lithium, a lithium alloy, or the like may be used. Alternatively, a negative electrode may be formed by mixing a binding agent with a negative electrode active material that can occlude and desorb lithium ions, adding an appropriate solvent, thereto to form a paste-like negative electrode mixture, applying the paste-like negative electrode mixture to a surface of a metal foil current collector such as copper, drying the negative electrode mixture, and compressing the resulting product in order to increase the electrode density as necessary. Examples of the negative electrode active material include natural graphite, artificial graphite, a fired organic compound such as a phenol resin, and a powdery carbon material such as coke. In this case, as a negative electrode binding agent, as in the positive electrode, a fluorine-containing resin such as PVDF can be used. As a solvent for dispersing the active material and the binding agent, an organic solvent such as N-methyl-2-pyrrolidone can be used. (Separator) A separator is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode from each other and retains an electrolyte, and a thin film formed of polyethylene, polypropylene, or the like and having many minute holes can be used. (Non-Aqueous Electrolyte) As the non-aqueous electrolyte, a non-aqueous electrolyte solution can be used. As the non-aqueous electrolyte solution, for example, a solution obtained by dissolving a lithium salt as a supporting salt in an organic solvent may be used. As the non-aqueous electrolyte solution, a solution obtained by dissolving a lithium salt in an ionic liquid may be used. Note that the ionic liquid refers to a salt including a cation other than a lithium ion and an anion, and being in a liquid state even at room temperature. As the organic solvent, one selected from a cyclic carbonate such as ethylene carbonate, propylene carbonate, butylene carbonate, or trifluoropropylene carbonate, a chain carbonate such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, or dipropyl carbonate, an ether compound such as tetrahydrofuran, 2-methyltetrahydrofuran, or dimethoxyethane, a sulfur compound such as ethylmethylsulfone or butanesultone, and a phosphorus compound such as triethyl phosphate or trioctyl phosphate may be used singly, or two or more selected from these compounds may be mixed to be used. Examples of the supporting salt include LiPF6, LiBF4, LiClO4, LiAsF6, LiN(CF3SO2)2, and a composite salt thereof. Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like. As the non-aqueous electrolyte, a solid electrolyte may be used. The solid electrolyte can withstand a high voltage. Examples of the solid electrolyte include an inorganic solid electrolyte and an organic solid electrolyte. Examples of the inorganic solid electrolyte include an oxide-based solid electrolyte and a sulfate-based solid electrolyte. The oxide-based solid electrolyte is not particularly limited, and any compound containing oxygen (O) and having lithium ion conductivity and electronic insulation can be used. Examples of the oxide-based solid electrolyte include lithium phosphate (Li3PO4, Li3PO4Nx, LiBO2Nx, LiNbO3, LiTaO3, Li2SiO3, Li4SiO4—Li3PO4, Li4SiO4—Li3VO4, Li2O—B2O3—P2O5, Li2O—SiO2, Li2O—B2O3—ZnO, Li1+xAlxTi2−x(PO4)3(0≤X≤1), Li1+xAlxGe2−x(PO4)3(0≤X≤1), LiTi2(PO4)3, Li3xLa2/4−xTiO3(0≤X≤⅔), Li5La3Ta2O12, Li7La3Zr2O12, Li6BaLa2Ta2O12, and Li3.6Si0.6P0.4O4. The sulfide-based solid electrolyte is not particularly limited, and any compound containing sulfur (S) and having lithium ion conductivity and electronic insulation can be used. Examples of the sulfide-based solid electrolyte include Li2S—P2S5, Li2S—SiS2, LiI—Li2S—SiS2, LiI—Li2S—P2S5, LiI—Li2S—P2O5, and LiI—Li3PO4—P2S5. Note that as the inorganic solid electrolyte, compounds other than the compounds described above may be used. For example, Li3N, LiI, or Li3N—LiI—LiOH may be used. The organic solid electrolyte is not particularly limited as long as being a polymer compound exhibiting ionic conductivity, and examples thereof include polyethylene oxide, polypropylene oxide, and copolymers thereof. The organic solid electrolyte may contain a supporting salt (lithium salt). (Shape of Battery and Configuration Thereof) The non-aqueous electrolyte secondary battery of the present invention, constituted by the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte solution described above can have various shapes such as a cylindrical shape and a laminated shape. Even when the non-aqueous electrolyte secondary battery has any shape, the positive electrode and the negative electrode are laminated via the separator to form an electrode body, the obtained electrode body is impregnated with the non-aqueous electrolyte solution, a positive electrode current collector is connected to a positive electrode terminal communicating with the outside using a current collecting lead or the like, a negative electrode current collector is connected to a negative electrode terminal communicating with the outside using a current collecting lead or the like, and the resulting product is sealed in a battery case to complete the non-aqueous electrolyte secondary battery. EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is never limited by these Examples. Note that Examples and Comparative Examples were evaluated by measurement results obtained by using the following apparatuses and methods. [Composition of Entire Positive Electrode Active Material] The obtained positive electrode active material was dissolved in nitric acid, and then measured with an ICP emission spectroscopic analyzer (ICPS-8100 manufactured by Shimadzu Corporation). [Identification of Compound Species] The obtained positive electrode active material was evaluated with an X-ray diffractometer (trade name: X'Pert PRO manufactured by PANalytical Ltd.). [Evaluation of Battery Characteristics] (Manufacture of Coin-Type Battery for Evaluation) 70% by mass of the obtained positive electrode active material was mixed with 20% by mass of acetylene black and 10% by mass of PTFE, and 150 mg of the resulting mixture was taken out to be manufactured into a pellet. This was used as a positive electrode. Using lithium metal as a negative electrode, and using an equal volume mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) with 1M LiClO4as a supporting salt (manufactured by Toyama Pharmaceutical Co., Ltd.) as an electrolyte solution, a 2032 type coin-type battery CBA as illustrated inFIG.2was manufactured in a globe box in an Ar atmosphere with a dew point controlled at −80° C. Performance of the manufactured coin-type battery CBA was evaluated on the basis of initial discharge capacity. (Initial Discharge Capacity) For the initial discharge capacity, discharge capacity was measured when the coin-type battery CBA was left about 24 hours after manufacture thereof to stabilize an open circuit voltage (OCV), then the battery was charged to a cutoff voltage of 4.3 V at a current density of 0.1 mA/cm2with respect to the positive electrode, the battery paused for one hour, and then the battery was discharged to a cutoff voltage of 3.0 V. This discharge capacity was taken as initial discharge capacity before exposure to the atmosphere. (Initial Discharge Capacity After Exposure to the Atmosphere) For initial discharge capacity after exposure to the atmosphere, the obtained positive electrode active material was left at 80° C. in the atmosphere with a dew point of 15° C. for 24 hours, and then a coin-type battery CBA for evaluation was manufactured under similar conditions to the above. The initial discharge capacity was measured under similar conditions to the above. A change amount (%) in the initial discharge capacity was determined by the following formula. {[Initial discharge capacity before exposure to atmosphere (mAh/g)]−[Initial discharge capacity after exposure to atmosphere (mAh/g)]}×100/[Initial discharge capacity before exposure to atmosphere (mAh/g)] Formula: Example 1 To nickel composite hydroxide particles having an average particle size of 13 μm, H3BO3(manufactured by Wako Pure Chemical Industries, Ltd.) was added in an amount of boron of 0.03% by mass with respect to a positive electrode active material obtained, and lithium hydroxide was mixed therewith such that Li/Me satisfied Li/Me=1.02 to form a mixture. Mixing was performed using a shaker mixer (TURBULA TypeT2C manufactured by Willy A. Bachofen (WAB)). The obtained mixture was fired at 750° C. for eight hours in an oxygen stream (oxygen: 100% by volume), cooled, and then crushed to obtain a positive electrode active material. The obtained positive electrode active material was a lithium-nickel composite oxide containing 0.03% by mass of boron with respect to the positive electrode active material and represented by a composition formula Li1.03Ni0.88Co0.12Al0.03O2. Example 2 In Example 2, a positive electrode active material was obtained in a similar manner to Example 1 except that H3BO3was added such that the amount of boron was 0.005% by mass with respect to the positive electrode active material. Example 3 In Example 3, a positive electrode active material was obtained in a similar manner to Example 1 except that H3BO3was added such that the amount of boron was 0.1% by mass with respect to the positive electrode active material. Example 4 In Example 4, a positive electrode active material was obtained in a similar manner to Example 1 except that B2O3was added such that the amount of boron was 0.02% by mass with respect to the positive electrode active material. Example 5 In Example 5, a positive electrode active material was obtained in a similar manner to Example 1 except that LiBO2was added such that the amount of boron was 0.05% by mass with respect to the positive electrode active material. Comparative Example 1 In Comparative Example 1, a positive electrode active material was obtained in a similar manner to Example 1 except that H3BO3was added such that the amount of boron was 0.0005% by mass with respect to the positive electrode active material. Comparative Example 2 In Comparative Example 2, a positive electrode active material was obtained in a similar manner to Example 1 except that H3BO3was added such that the amount of boron was 0.3% by mass with respect to the positive electrode active material. Comparative Example 3 In Comparative Example 3, a positive electrode active material was obtained in a similar manner to Example 1 except that the firing temperature was 700° C. Comparative Example 4 In Comparative Example 4, a positive electrode active material was obtained in a similar manner to Example 1 without addition of H3BO3. Evaluation Results X-ray diffraction of each of the positive electrode active materials obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was measured, and a peak of Li3BO3was detected in addition to the lithium-nickel composite oxide. Table 1 indicates results of producing coin-type batteries using the positive electrode active materials obtained in Examples and Comparative Examples and measuring initial discharge capacity thereof, and results of leaving the positive electrode active materials in the atmosphere at 80° C. for 24 hours, then producing coin-type batteries similarly, and measuring initial discharge capacity thereof. In Examples 1 to 5, a surface was uniformly coated with Li3BO3, and the initial discharge capacity after exposure to the atmosphere was improved. In Comparative Example 1, since the amount of boron was small, the coating layer formed of Li3BO3was thin, and an effect of suppressing atmospheric deterioration could not be exhibited sufficiently. Therefore, it is considered that the initial discharge capacity after exposure to the atmosphere was reduced. In Comparative Example 2, the amount of boron was large, and the coating layer formed of Li3BO3was thick. Therefore, it is considered that the initial discharge capacity before exposure to the atmosphere was reduced. In Comparative Example 3, since the firing temperature was low, Li3BO3was not dissolved during firing, and coating with Li3BO3was non-uniform. Therefore, it is considered that the initial discharge capacity after exposure to the atmosphere was reduced. In Comparative Example 4, since there was no coating with Li3BO3, the initial discharge capacity after exposure to the atmosphere was largely reduced. TABLE 1Content ofboron toInitial discharge capacitypositiveBeforeAfterelectrodeAddedexposureexposureNickel compositeactiveboronLithiumFiringtotoChangehydroxidematerialcompoundcompoundtemperatureatmosphereatmosphereamountComposition% by massTypeType° C.mAh/gmAh/g%Example 1Li1.03Ni0.88Co0.12Al0.03O20.03H3BO3LiOH7502032001.5Example 20.005H3BO37502041963.9Example 30.1H3BO37501981951.5Example 40.02B2O37502021991.5Example 50.05LiBO27502001981.0ComparativeLi1.03Ni0.88Co0.12Al0.03O20.0005H3BO3LiOH7502041925.9Example 1Comparative0.3H3BO37501941911.5Example 2Comparative0.03H3BO37002021925.0Example 3Comparative0—7502051916.8Example 4 INDUSTRIAL APPLICABILITY The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention suppresses atmospheric deterioration, and can exhibit stable performance at low cost. Therefore, the positive electrode active material is particularly suitable as a positive electrode active material for a lithium ion battery used as a power source for a hybrid car or an electric car. Note that the technical scope of the present invention is not limited to the above embodiment. For example, one or more of the requirements described in the above embodiment may be omitted. The requirements described in the above embodiment can be combined as appropriate. To the extent permitted by law, the contents of Japanese Patent Application No. 2017-162661, which is a Japanese patent application, and all the Literatures cited in the above-described embodiment and the like are incorporated as part of the description of this text. REFERENCE SIGNS LIST CBA Coin-type batteryCA CasePC Positive electrode canNC Negative electrode canGA GasketPE Positive electrodeNE Negative electrodeSE Separator | 34,163 |
11862794 | DETAILED DESCRIPTION Nickel-rich lithium-manganese-cobalt oxide (NMC) cathodes (LiNiXMnyCo1-x-yO2) are promising cathodes for next-generation lithium ion batteries. Such batteries may be used, for example, for long-range electrical vehicles. In particular, NMC cathodes where x≥0.6, the capacity is ≥200 mAh/g, and the cathode is operable at high voltage (>3.8V) are desirable. Traditionally, NMC cathodes are prepared by coprecipitation with aggregation of nano-sized primary particles into micro-sized secondary polycrystalline particles. This aggregated particle structure shortens the diffusion length of the primary particles and increases the number of pores and grain boundaries within the secondary particles, which accelerate the electrochemical reaction and improves the rate capability of NMC. Secondary micron-sized particles formed of agglomerated nano-sized primary particles are the most common morphology for conventional NMC cathodes. However, as the Ni content increases above 0.6, challenges arise. For example, such Ni-rich NMC cathodes are subject to moisture sensitivity, aggressive side reactions, and/or gas generation during cycling, raising safety concerns. These challenges are attributable to the large surface area of the secondary particles. Additionally, while creating spherical-secondary polycrystalline NMC particles reduces the surface/volume ratio, pulverization along the weak internal grain boundaries is generally observed after cycling. These cracks are induced by the non-uniform volume change of primary particles during cycling and exacerbated by the anisotropy among individual particles and grains in the polycrystalline NMC. The intergranular cracking exposes new surfaces to electrolyte for side reactions, which accelerates cell degradation. As the Ni content becomes ≥0.8 in NMC, the major challenge in Ni-rich NMC cathodes becomes quite different from those in conventional NMC. For example, NMC811 is very sensitive to moisture, which creates challenges for manufacturing, storing and transporting the Ni-rich NMC. After extensive cycling gas generation by the side reactions raises safety concerns. This disclosure concerns embodiments of methods for synthesizing single crystalline Ni-rich cathode materials. Some embodiments of the disclosed methods may be used for synthesizing large batches, e.g., 1 kg or more, of single crystal lithium nickel manganese cobalt oxide. In some embodiments, the single crystalline Ni-rich cathodes comprise monocrystalline lithium nickel manganese cobalt oxide. In certain embodiments, single crystalline cathodes include reduced surface areas, phase boundaries, and/or more integrated crystal structures compared to polycrystalline cathodes. Advantageously some embodiments of the single crystalline Ni-rich cathodes demonstrate reduced gassing and/or particle cracking along grain boundaries during cycling. In some embodiments, the monocrystalline lithium nickel manganese cobalt oxide has a formula LiNiXMnyMzCo1-x-y-zO2, where M represents one or more dopant metals, x≥0.6, 0.02≤y<0.2, 0≤z≤0.05, and x+y+z≤1.0. In certain embodiments, the formula is NixMnyCo1-x-yO2where x≥0.6, 0.02≤y<0.2, and x+y≤1.0. I. Definitions and Abbreviations The following explanations of terms and abbreviations are provided to better describe the present disclosure and to guide those of ordinary skill in the art in the practice of the present disclosure. As used herein, “comprising” means “including” and the singular forms “a” or “an” or “the” include plural references unless the context clearly dictates otherwise. The term “or” refers to a single element of stated alternative elements or a combination of two or more elements, unless the context clearly indicates otherwise. Unless explained otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, suitable methods and materials are described below. The materials, methods, and examples are illustrative only and not intended to be limiting. Other features of the disclosure are apparent from the following detailed description and the claims. The disclosure of numerical ranges should be understood as referring to each discrete point within the range, inclusive of endpoints, unless otherwise noted. Unless otherwise indicated, all numbers expressing quantities of components, molecular weights, percentages, temperatures, times, and so forth, as used in the specification or claims are to be understood as being modified by the term “about.” Accordingly, unless otherwise implicitly or explicitly indicated, or unless the context is properly understood by a person of ordinary skill in the art to have a more definitive construction, the numerical parameters set forth are approximations that may depend on the desired properties sought and/or limits of detection under standard test conditions/methods as known to those of ordinary skill in the art. When directly and explicitly distinguishing embodiments from discussed prior art, the embodiment numbers are not approximates unless the word “about” is recited. Although there are alternatives for various components, parameters, operating conditions, etc. set forth herein, that does not mean that those alternatives are necessarily equivalent and/or perform equally well. Nor does it mean that the alternatives are listed in a preferred order unless stated otherwise. Definitions of common terms in chemistry may be found in Richard J. Lewis, Sr. (ed.), Hawley's Condensed Chemical Dictionary, published by John Wiley & Sons, Inc., 2016 (ISBN 978-1-118-13515-0). In order to facilitate review of the various embodiments of the disclosure, the following explanations of specific terms are provided: Active salt: As used herein, the term “active salt” refers to a salt that significantly participates in electrochemical processes of electrochemical devices. In the case of batteries, it refers to charge and discharge processes contributing to the energy conversions that ultimately enable the battery to deliver/store energy. As used herein, the term “active salt” refers to a salt that constitutes at least 5% of the redox active materials participating in redox reactions during battery cycling after initial charging. Annealing: A process in which a material is heated to a specified temperature for a specified period of time and then gradually cooled. The annealing process may remove internal strains from previous operations, and can eliminate distortions and imperfections to produce a stronger and more uniform material. Anode: An electrode through which electric charge flows into a polarized electrical device. From an electrochemical point of view, negatively-charged anions move toward the anode and/or positively-charged cations move away from it to balance the electrons leaving via external circuitry. Areal capacity or specific areal capacity is the capacity per unit area of the electrode (or active material) surface, and is typically expressed in united of mAh cm2. Capacity: The capacity of a battery is the amount of electrical charge a battery can deliver. The capacity is typically expressed in units of mAh, or Ah, and indicates the maximum constant current a battery can produce over a period of one hour. For example, a battery with a capacity of 100 mAh can deliver a current of 100 mA for one hour or a current of 5 mA for 20 hours. Cathode: An electrode through which electric charge flows out of a polarized electrical device. From an electrochemical point of view, positively charged cations invariably move toward the cathode and/or negatively charged anions move away from it to balance the electrons arriving from external circuitry. Cell: As used herein, a cell refers to an electrochemical device used for generating a voltage or current from a chemical reaction, or the reverse in which a chemical reaction is induced by a current. Examples include voltaic cells, electrolytic cells, and fuel cells, among others. A battery includes one or more cells. The terms “cell” and “battery” are used interchangeably when referring to a battery containing only one cell. Coulombic efficiency (CE): The efficiency with which charges are transferred in a system facilitating an electrochemical reaction. CE may be defined as the amount of charge exiting the battery during the discharge cycle divided by the amount of charge entering the battery during the charging cycle. Current density: A term referring to the amount of current per unit area. Current density is typically expressed in units of mA/cm2. Electrolyte: A substance containing free ions that behaves as an electrically conductive medium. Electrolytes generally comprise ions in a solution, but molten electrolytes and solid electrolytes also are known. Microparticle: As used herein, the term “microparticle” refers to a particle with a size measured in microns, such as a particle with a diameter of 1-100 μm. Nanoparticle: As used herein, the term “nanoparticle” particle that has a size measured in nanometers, such as a particle with a diameter of 1-100 nm. Pouch cell: A pouch cell is a battery completely, or substantially completely, encased in a flexible outer covering, e.g., a heat-sealable foil, a fabric, or a polymer membrane. The term “flexible” means that the outer covering is easy to bend without breaking; accordingly, the outer covering can be wrapped around the battery components. Because a pouch cell lacks an outer hard shell, it is flexible and weighs less than conventional batteries. Precursor: A precursor participates in a chemical reaction to form another compound. As used herein, the term “precursor” refers to metal-containing compounds used to prepare lithium nickel manganese cobalt oxide and metal-doped lithium nickel manganese cobalt oxide. Separator: A battery separator is a porous sheet or film placed between the anode and cathode. It prevents physical contact between the anode and cathode while facilitating ionic transport. Solid state: Composed of solid components. As defined herein, a solid-state synthesis proceeds with solid components directly without using sintering agents. Specific capacity: A term that refers to capacity per unit of mass. Specific capacity may be expressed in units of mAh/g, and often is expressed as mAh/g carbon when referring to a carbon-based electrode in Li/air batteries. Specific energy: A term that refers to energy per unit of mass. Specific energy is commonly expressed in units of Wh/kg or J/kg. II. Synthesis of Crystalline Oxide Materials Embodiments of methods for making monocrystalline lithium nickel manganese cobalt oxide (NMC) and metal-doped lithium nickel manganese cobalt oxide are disclosed. In some embodiments, the monocrystalline lithium nickel manganese cobalt oxide has a formula LiNiXMnyMzCo1-x-y-zO2, where M represents one or more dopant metals, x≥0.6, 0.02≤y<0.2, 0≤z≤0.05, and x+y+z≤1.0. More particularly, 0.62≤x+y+z≤1.0. In certain embodiments, z is 0, and the monocrystalline lithium nickel manganese cobalt oxide has a formula LiNiXMnyCo1-x-yO2, where x≥0.6, 0.02≤y<0.2, and x+y≤1.0. More particularly, 0.62≤x+y≤1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-1.0. In certain embodiments, x=0.65-0.9, y=0.05-0.2, z=0-0.02, and x+y+z=0.7-0.95. In some examples, x is 0.7-0.9, such as 0.75-0.9 or 0.8-0.9; y is 0.05-0.15, such as 0.05-0.14 or 0.05-0.1; z is 0-0.02; and x+y+z is 0.8-0.98, such as 0.8-0.95. When the monocrystalline lithium nickel manganese cobalt oxide is doped, the general formula is LiNiXMnyMzCo1-x-y-zO2, where M represents one or more dopant metals. In some embodiments, M represents two or more dopant metals. Thus, Mzmay refer collectively to M1z1+M2z2+M3z3. . . +Mpzp, where M1, M2, M3, etc. represent the dopant metals, and z1+z2+z3 . . . +zp=z. Suitable dopant metals include, but are not limited to, Mg, Ti, Al, Zn, Fe (e.g., Fe3+), Zr, Sn (e.g., Sn4+), Sc, V, Cr, Fe, Cu, Ga, Y, Nb, Mo, Ru, Ta, W, Ir, and combinations thereof. The lithium nickel manganese cobalt oxide crystals prepared by embodiments of the disclosed methods are microparticles. In some embodiments, the single crystals have a mean particle size of 1-5 μm, such as 1-4 μm or 1-3 μm. This feature is in stark contrast to traditional NMC comprising primary nanoparticles particles aggregated into secondary polycrystalline microparticles. A. Hydroxide Precursor Synthesis In any the foregoing or following embodiments, the synthesis may begin with solid precursors comprising hydroxides of nickel, manganese, and cobalt. In some embodiments, the synthesis may further include solid hydroxide precursors of one or more dopant metals, e.g., hydroxides of Mg, Ti, Al, Zn, Fe, Zr, Sn, or any combination thereof. In some embodiments, the hydroxide precursor comprises NiXMnyMzCo1-x-y-z(OH)2, where M represents one or more dopant metals, x≥0.6, 0.01≤y<0.2, z≤0.05, and x+y+z≤1.0. More particularly, 0.62≤x+y+z≤1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-0.98. In another independent embodiment, x=0.65-0.9, y=0.05-0.2, z=0-0.02, and x+y+z=0.7-0.95. In some examples, x is 0.7-0.9, such as 0.75-0.9 or 0.8-0.9; y is 0.05-0.15, such as 0.05-0.14 or 0.05-0.1; z is 0-0.02; and x+y+z is 0.8-0.98, such as 0.8-0.95. In any the foregoing or following embodiments, the method of synthesizing monocrystalline lithium nickel manganese cobalt oxide (including doped variants), includes synthesizing the hydroxide precursors. In some embodiments (FIG.1), the hydroxide precursors are synthesized by preparing a 1.5 M to 2.5 M solution comprising metal salts in water (101), the metal salts comprising a nickel salt, a manganese salt, a cobalt salt, and optionally one or more dopant metal salts; combining the solution comprising metal salts in water with aqueous NH3and aqueous NaOH or KOH to provide a combined solution having a pH of 10.5-12 (102), aging the solution for 5-48 hours to co-precipitate hydroxides of nickel, manganese; and cobalt to provide the solid hydroxide precursor (103); and drying the solid hydroxide precursor (104). In any of the foregoing or following embodiments, the metal salts may include a nickel (II) salt, a manganese (II) salt, and a cobalt (II) salt (if x+y+z<1). The solution comprising metal salts in water has a concentration of 1.5-2.5 M, wherein 1.5 M to 2.5 M is a total concentration of all salts in the water. In some embodiments, the concentration is 1.7 M to 2.3 M, 1.8 M to 2.2 M, or 1.9 M to 2.1 M. In any of the foregoing or following embodiments, the salts may be sulfates, nitrates, chlorides, acetates, or a combination thereof. In one embodiment, the salts are sulfates. In another embodiment, the salts are nitrates. The concentration of each metal salt is selected based on a desired amount of the metal in the final product. For example, when a hydroxide precursor comprising Ni0.76Mn0.14Co0.1(OH)2is prepared, nickel, manganese, and cobalt salts are combined in a Ni:Mn:Co molar ratio of 0.76:0.14:0.1. Similarly, if a hydroxide precursor comprising Ni0.76Mn0.12Co0.1Mg0.01Ti0.01(OH)2is prepared, nickel, manganese, cobalt, magnesium, and titanium salts are combined in a Ni:Mn:Co:Mg:Ti molar ratio of 0.76:0.12:0.01:0.01. In any of the foregoing or following embodiments, combining the solution comprising metal salts in water with aqueous NH3and aqueous NaOH or KOH to provide a pH of 10.5-12 may comprise preparing an aqueous NH3solution comprising 0.5 wt % to 1 wt % or 0.2-0.5 M NH3in water; preheating the aqueous NH3solution to 25° C. to 80° C.; adding the metal salt solution, additional concentrated aqueous ammonia (e.g., 25 wt % to 35 wt % or 13 M to 18 M NH3—H2O), and aqueous NaOH or KOH to provide a pH of 10.5-12 and a final metal salt concentration of 0.1 M to 3 M. In some embodiments, the aqueous NH3solution is preheated to 30° C. to 75° C., such as 35° C. to 70° C. 1-40° C. to 60° C., or 45° C. to 55° C. In some embodiments, the final metal salt concentration is 0.1 M to 2 M, 0.1 M to 1 M, or 0.2 M to 0.8 M. In some embodiments, the metal salt solution and additional concentrated ammonia are added at the same time at a volumetric ratio 2-4 parts metal salt solution to one part concentrated ammonia solution. The aqueous NH3solution may be stirred continuously as the metal salt solution and concentrated ammonia solution are added. In certain examples, the metal salt solution is added at a rate of 3 mL/minute, and the concentrated ammonia is added at a rate of 1 mL/minute. Sufficient aqueous NaOH or KOH is added to provide the combined solution with a pH of 10.5-12, such as a pH of 11-11.5. In some embodiments, the aqueous NaOH or KOH has a concentration of 6 M to 10 M. In any of the foregoing or following embodiments, the combined solution may be aged for 5-48 hours at a temperature of 25° C. to 80° C. to co-precipitate hydroxides of the metals (Ni, Mn, Co, and any dopant metals), thereby producing the hydroxide precursor. In some embodiments, the combined solution is stirred continuously while aging. In certain embodiments, the combined solution is aged for 10 hours to 48 hours, 15 hours to 45 hours, 20 hours to 40 hours, or 25 hours to 35 hours. In some embodiments, the temperature is 30° C. to 75° C., such as 35° C. to 70° C. 1-40° C. to 60° C., or 45° C. to 55° C. In some examples, the combined solution was aged for 30 hours at 50° C. with continuous stirring. In any of the foregoing or following embodiments, the hydroxide precursor may be collected by any suitable method. In some embodiments, the aged combined solution is filtered to collect the co-precipitated hydroxides. The collected hydroxide precursor may be washed, e.g., with deionized water, to remove impurities, such as ammonia, residual NaOH or KOH, and/or soluble sulfate and/or nitrate salts. The hydroxide precursor is then dried. In some embodiments, the hydroxide precursor is dried at a temperature of 80° C. to 120° C., such as 90° C. to 110° C., for a period of 5 hours to 20 hours, such as 10 hours to 15 hours. Advantageously, the low concentration, 1.5 M to 2.5 M, of the metal salt solution facilitates formation of small hydroxide precursor particles. In any of the foregoing embodiments, embodiments, the hydroxide precursor particles may have a mean size of 0.5 μm to 10 μm. In some embodiments, the hydroxide precursor particles have a mean size of 0.5 μm to 7.5 μm, 0.5 μm to 5 μm, or 0.5 μm to 2.5 μm. B. Solid-State Method In some embodiments, monocrystalline lithium nickel manganese cobalt oxide (or a doped variant thereof) is synthesized by a solid-state method. With reference toFIG.2, in some embodiments, the solid-state method comprises heating a solid hydroxide precursor comprising NiXMnyMzCo1-x-y-z(OH)2at a temperature TS1in an oxygen-containing atmosphere for an effective period of time t1to convert the solid hydroxide precursor to a solid oxide precursor (201); combining the solid oxide precursor with a molar excess of a lithium compound (202); heating the solid oxide precursor and the lithium compound at a temperature TS2for an effective period of time t2to produce a first product (203); cooling the first product to ambient temperature (204); reducing a mean particle size of the first product to 0.1 μm to 10 μm (205); heating the first product having the reduced mean particle size at a temperature TS3for an effective period of time t3to produce a second product (206); cooling the second product to ambient temperature (207); reducing a mean particle size of the second product to 0.1 μm to 10 μm (208); and heating the second product having the reduced mean particle size at a temperature TS4for an effective period of time t4to produce monocrystalline lithium nickel manganese cobalt oxide having a formula LiNiXMnyMzCo1-x-y-zO2(209). In the foregoing formulas, M represents one or more dopant metals, x≥0.6, 0.01≤y<0.2, z≤0.05, and x+y+z≤1.0. More particularly, 0.62≤x+y+z≤1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-0.98. In another independent embodiment, x=0.65-0.9, y=0.05-0.2, z=0-0.02, and x+y+z=0.7-0.95. In some examples, x=0.7-0.9, y=0.05-0.15, z=0-0.02, and x+y+z=0.7-0.95. In one embodiment, x is 0.76, y is 0.14, and z is 0. In an independent embodiment, x is 0.76, y is 0.12, and z is 0.02. In another independent embodiment, x is 0.8, y is 0.1, and z is 0. In still another independent embodiment, x is 0.9, y is 0.05, and z is 0. In any of the foregoing or following embodiments, the temperature TS1may be 400° C. to 1000° C. and/or the effective period of time t1may be 1 hour to 30 hours. In some embodiments, the temperature TS1is 500° C. to 1000° C., 600° C. to 1000° C., 800° C. to 1000° C., or 850° C. to 950° C. In certain examples, the temperature TS1was 900° C. Advantageously, the temperature TS1is below a melting point of the hydroxide precursor. In any of the foregoing or following embodiments, the temperature may be increased to the temperature TS1at a ramping rate of 1° C./minute to 300° C./minute, such as a ramping rate of 1° C./minute to 200° C./minute, 1° C./minute to 100° C./minute, 1° C./minute to 50° C./minute, 5° C./minute to 25° C./minute, or 5° C./minute to 15° C./minute. In one example, the ramping rate was 10° C./minute. The temperature TS1is then maintained for the effective period of time t1. In some embodiments, the effective period of time t1is 5 hours to 25 hours, 10 hours to 20 hours, or 12 hours to 18 hours. In certain examples, the effective period of time t1was 15 hours. In any of the foregoing or following embodiments, the oxygen-containing atmosphere may be pure oxygen or air. As used herein, “pure oxygen” means at least 95 mol % oxygen. In any of the foregoing or following embodiments, at a majority or all of the solid hydroxide precursor may be converted to the solid oxide precursor. In some embodiments, 90 wt % to 100 wt %, such as 95 wt % to 100 wt %, 97 wt % to 100 wt %, 98 wt % to 100 wt %, or 99 wt % to 100 wt % of the solid hydroxide precursor is converted to the solid oxide precursor. In certain embodiments, all of the solid hydroxide precursor is converted to the solid oxide precursor. The solid oxide precursor is combined with a molar excess of a Li compound. In any of the foregoing or following embodiments, the Li compound may comprise lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, lithium acetate, lithium oxalate or any combination thereof. In some embodiments, the Li compound comprises lithium hydroxide. The LiOH may be anhydrous or a hydrated salt, e.g., LiOH.H2O. In any of the foregoing or following embodiments, the Li compound may have a mean particle size of 10 μm to 100 μm. In any of the foregoing or following embodiments, the solid oxide precursor and the lithium compound may be combined in a Li:solid oxide precursor molar ratio of 0.8:1 to 3:1, such as a molar ratio of 0.9:1 to 3:1, 1:05:1 to 2:1, 1:05:1 to 1.5:1, 1.1:1 to 1.4:1 or 1.1:1 to 1.2:1. The mixture of solid oxide precursor and the Li compound is subjected to a series of three annealing processes to form a first product, a second product, and the LiNiXMnyMzCo1-x-y-zO2. The mixture of solid oxide precursor and the Li compound is heated at a temperature TS2for an effective period of time t2to produce a first product. In any of the foregoing or following embodiments, the temperature TS2may be 400° C. to 1000° C. and/or the effective period of time t2may be 1 hour to 30 hours. In some embodiments, the temperature TS2is 400° C. to 800° C., 400° C. to 600° C., or 450° C. to 550° C. Advantageously the temperature TS2is less than a melting or vaporization temperature of the oxide precursor and lithium compound. In certain examples, the temperature TS2was 500° C. In some embodiments, the effective period of time h is 1 hour to 5 hours, 1 hour to 20 hours, 1 hours to 10 hours, or 2 hours to 6 hours. In certain examples, the effective period of time t2was 5 hours. The first product is cooled to ambient temperature and a mean particle size of the first product is reduced to 0.1 μm to 10 μm. In some embodiments, the mean particle size is reduced to 0.2 μm to 10 μm, 0.5 μm to 10 μm, or 1 μm to 10 μm. In any of the foregoing or following embodiments, cooling the first product to ambient temperature may comprise cooling the first product to 20° C. to 30° C., such as to 20° C. to 25° C. In any of the foregoing or following embodiments, reducing a mean particle size of the first product to 0.1 μm to 10 μm may comprise grinding or milling the first product to achieve the desired particle size. The first product having the reduced mean particle size is heated at a temperature TS3for an effective period of time t3to produce a second product. In any of the foregoing or following embodiments, the temperature TS3may be 600° C. to 1000° C. and/or the effective period of time t3may be 1-30 hours. In some embodiments, the temperature TS3is 700° C. to 1000° C., 700° C. to 900° C., or 750° C. to 850° C. In certain examples, the temperature TS3was 800° C. In some embodiments, the effective period of time t3is 1-25 hours, 1-20 hours, 1-10 hours, or 2-6 hours. In certain examples, the effective period of time t3was 5 hours. The second product is cooled to ambient temperature and a mean particle size of the second product is reduced to 0.1 μm to 10 μm. In some embodiments, the mean particle size is reduced to 0.2 μm to 10 μm, 0.5 μm to 10 μm, or 1 μm to 10 μm. In any of the foregoing or following embodiments, cooling the second product to ambient temperature may comprise cooling the second product to 20° C. to 30° C., such as to 20° C. to 25° C. In any of the foregoing or following embodiments, reducing a mean particle size of the second product to 0.1 μm to 10 μm may comprise grinding or milling the second product to achieve the desired particle size. The second product having the reduced mean particle size is heated at a temperature TS4for an effective period of time t4to produce monocrystalline lithium nickel manganese cobalt oxide having a formula LiNiXMnyMzCo1-x-y-zO2. In any of the foregoing or following embodiments, the temperature TS4may be 500° C. to 1000° C. and/or the effective period of time t4may be 1-30 hours. In some embodiments, the temperature TS4is 600° C. to 1000° C., 700° C. to 1000° C., 700° C. to 900° C., or 750° C. to 850° C. In certain examples, the temperature TS4was 800° C. In some embodiments, the effective period of time t4is 1 hour to 25 hours, 1 hour to 20 hours, 1 hour to 10 hours, or 2 hours to 6 hours. In certain examples, the effective period of time t4was 5 hours. In any of the foregoing or following embodiments, the solid hydroxide precursor may be prepared as discussed above. In any of the foregoing or following embodiments, the solid hydroxide precursor may have a mean particle size of 0.5-10 μm. In some embodiments, the hydroxide precursor particles have a mean size of 0.5 μm to 7.5 μm, 0.5 μm to 5 μm, or 0.5 μm to 2.5 μm. In any of the foregoing or following embodiments, monocrystalline lithium nickel manganese cobalt oxide may have a mean particle size of 0.5 μm to 5 μm. In some embodiments, the solid hydroxide precursor has a mean particle size of 1 μm to 2 μm. In certain embodiments, the monocrystalline lithium nickel manganese cobalt oxide has a mean particle size of 1 μm to 5 μm, or 1 μm to 3 μm. In any of the foregoing or following embodiments, the dopant metal(s) M may comprise Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Ga, Y, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof. C. Molten-Salt Method In some embodiments, monocrystalline lithium nickel manganese cobalt oxide (or a doped variant thereof) is synthesized by a molten-salt method. With reference toFIG.3, in some embodiments, the molten-salt method comprises heating a solid hydroxide precursor comprising NiXMnyMzCo1-x-y-z(OH)2at a temperature TM1in an oxygen-containing atmosphere for an effective period of time t1to convert the solid hydroxide precursor to a solid oxide precursor (301); combining the solid oxide precursor with a molar excess of a lithium compound and a sintering agent to form a mixture (302); heating the mixture in an oxygen-containing atmosphere at a temperature TM2for a period of time t2(303); increasing the temperature to a temperature TM3, where TM3>TM2, and heating the mixture at the temperature TM3for a period of time t3to produce a first product and the sintering agent (304); cooling the first product and the sintering agent to ambient temperature (305); separating the sintering agent from the first product (306); drying the first product (307); and heating the first product in an oxygen-containing atmosphere at a temperature TM4for an effective period of time t4to restore any lost oxygen in the lattices and produce monocrystalline lithium nickel manganese cobalt oxide having a formula LiNiXMnyMzCo1-x-y-zO2(308). In the foregoing formulas, M represents one or more dopant metals, x≥0.6, 0.01≤y<0.2, z≤0.05, and x+y+z≤1.0. More particularly, 0.62≤x+y+z≤1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-0.98. In another independent embodiment, x=0.65-0.9, y=0.05-0.2, z=0-0.02, and x+y+z=0.7-0.95. In some examples, x is 0.7-0.9, such as 0.75-0.9 or 0.8-0.9; y is 0.05-0.15, such as 0.05-0.14 or 0.05-0.1; z is 0-0.02; and x+y+z is 0.8-0.98, such as 0.8-0.95. In any of the foregoing or following embodiments, the temperature TM1may be 400° C. to 1000° C. and/or the effective period of time t1may be 1 hour to 30 hours. In some embodiments, the temperature TM1is 500° C. to 1000° C., 600° C. to 1000° C., 800° C. to 1000° C., or 850° C. to 950° C. In certain examples, the temperature TM1was 800° C., 900° C., or 1000° C. Advantageously, the temperature TM1is below a melting point of the hydroxide precursor. In any of the foregoing or following embodiments, the temperature may be increased to the temperature TM1at a ramping rate of 1° C./minute to 300° C./minute, such as a ramping rate of 1° C./minute to 200° C./minute, 1° C./minute 100° C./minute, 1° C./minute 50° C./minute, 1° C./minute 25° C./minute, or 1° C./minute 15° C./minute. In one example, the ramping rate was 5° C./minute. The temperature TM1is then maintained for the effective period of time t1. In some embodiments, the effective period of time t1is 5 hours to 25 hours, 10 hours to 20 hours, or 12 hours to 18 hours. In certain examples, the effective period of time t1was 15 hours. In any of the foregoing or following embodiments, the oxygen-containing atmosphere may be air or pure oxygen. In some embodiments, the oxygen-containing atmosphere is air. In any of the foregoing or following embodiments, at a majority or all of the solid hydroxide precursor may be converted to the solid oxide precursor. In some embodiments, 90 wt % to 100 wt %, such as 95 wt % to 100 wt %, 97 wt % to 100 wt %, 98 wt % to 100 wt %, or 99 wt % to 100 wt % of the solid hydroxide precursor is converted to the solid oxide precursor. In certain embodiments, all of the solid hydroxide precursor is converted to the solid oxide precursor. The solid oxide precursor is combined with a molar excess of a Li compound and a sintering agent to form a mixture. In any of the foregoing or following embodiments, the Li compound may comprise lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof. In any of the foregoing or following embodiments, the Li compound may have a mean particle size of 10 μm to 100 μm. In some embodiments, the Li compound comprises lithium oxide (Li2O). In any of the foregoing or following embodiments, the solid oxide precursor and the lithium compound may be combined in a Li:solid oxide precursor molar ratio of 1:1 to 5:1, such as a molar ratio of 1:1 to 4:1, 1:1 to 3:1, 1:1 to 2:1, 1:1 to 1.5:1, 1.1:1 to 1.4:1, or 1.1:1 to 1.2:1. In any of the foregoing or following embodiments, the sintering agent may be NaCl or KCl. In some embodiments, the sintering agent is NaCl. NaCl may reduce the sintering temperature and/or time. In any of the foregoing or following embodiments, a weight ratio of the sintering agent to the combined solid oxide precursor and lithium compound may be 0.2:1 to 1:0.2, such as weight ratio of 0.3:1 to 1:0.3, 0.4:1 to 1:0.4, 0.5:1 to 1:0.5, 0.6:1 to 1:0.6, 0.7:1 to 1:0.7, 0.8:1 to 1:0.8, 0.85:1 to 1:0.85, or 0.9:1 to 1:0.9. In certain examples, the weight ratio was 1:1. The mixture is heated in an oxygen-containing atmosphere at a temperature TM2for a period of time t2. In any of the foregoing or following embodiments, the temperature may be increased to the temperature TM2at a ramping rate of 1° C./minute to 300° C./minute, such as a ramping rate of 1° C./minute to 200° C./minute, 1° C./minute to 100° C./minute, 1° C./minute to 50° C./minute, 5° C./minute to 25° C./minute, or 5° C./minute to 15° C./minute. In one example, the ramping rate was 10° C./minute. The temperature TM2is then maintained for the effective period of time t2. In any of the foregoing or following embodiments, the temperature TM2may be 400-1000° C. and/or the effective period of time t2may be 1-30 hours. In some embodiments, the temperature TM2is 500° C. to 1000° C., 600° C. to 1000° C., 700° C. to 900° C., or 750° C. to 850° C. In certain examples, the temperature TM2was 800° C. In some embodiments, the effective period of time t2is 1 hour to 25 hours, 5 hours to 20 hours, or 5 hours to 15 hours. In certain examples, the effective period of time t2was 10 hours. In any of the foregoing or following embodiments, the oxygen-containing atmosphere may be air or pure oxygen. In some embodiments, the oxygen-containing atmosphere is pure oxygen. The mixture then is heated at a temperature TM3for a period of time t3to produce a first product and the sintering agent. The temperature TM3is greater than the temperature TM2. In any of the foregoing or following embodiments, the temperature TM3may be 600° C. to 1000° C. and/or the effective period of time t3may be 1-30 hours. In some embodiments, the temperature TM3is 700° C. to 1000° C., 800° C. to 1000° C., or 850° C. to 950° C. In certain examples, the temperature TM3was 900° C. In some embodiments, the effective period of time t3is 1 hour to 25 hours, 1 hour to 20 hours, 1 hour to 10 hours, or 2 hours to 6 hours. In certain examples, the effective period of time t3was 5 hours. The first product and sintering agent are cooled to ambient temperature. In any of the foregoing or following embodiments, cooling the first product to ambient temperature may comprise cooling the first product to 20° C. to 30° C., such as to 20° C. to 25° C. In some embodiments, a mean particle size of the first product is reduced to 0.1 μm to 10 μm. In any of the foregoing or following embodiments, reducing a mean particle size of the first product to 0.1 μm to 10 μm may comprise grinding the first product to achieve the desired particle size. The sintering agent is separated from the first product. In any of the foregoing or following embodiments, separating the sintering agent may comprise washing the sintering agent and the first product with a solvent in which the sintering agent is soluble and the first product is insoluble or substantially insoluble (e.g., less than 5 wt % of the first product is soluble in the solvent). In some embodiments, the solvent is water. In certain embodiments, washing the sintering agent and first product comprises stirring the ground sintering agent and first product in water and/or ultrasonicating the ground sintering agent and first product in the water. The resulting solution may be filtered to collect the first product. The first product then is dried to remove water. In any of the foregoing or following embodiments, drying the first product may comprise heating the first product at a temperature effective to evaporate the solvent for a time effective to remove the solvent, e.g., to remove at least 80 wt %, at least 90%, at least 95 wt %, at least 97 wt %, or at least 99 wt % of the solvent. In some embodiments, the solvent is water and the temperature is 60° C. to 95° C., such as 70° C. to 90° C. In certain embodiments, the first product may be heated under a reduced pressure to facilitate solvent removal. In any of the foregoing or following embodiments, the time may be from 1-10 hours, such as from 1-5 hours or from 1-3 hours. In some examples, the first product is heated under vacuum at 80° C. for 2 hours. The first product is heated in an oxygen-containing atmosphere at a temperature TM4for an effective period of time t4and produce monocrystalline lithium nickel manganese cobalt oxide having a formula LiNiXMnyMzCo1-x-y-zO2. In any of the foregoing or following embodiments, the temperature TM4may be 500° C. to 1000° C. and/or the effective period of time t4may be 1 hour to 30 hours. In some embodiments, the temperature TM4is 500° C. to 800° C., 500° C. to 700° C., or 550° C. to 650° C. In certain examples, the temperature TM4was 580° C. In some embodiments, the effective period of time t4is 1 hour to 25 hours, 1 hour to 20 hours, 1 hour to 10 hours, or 2 hours to 6 hours. In certain examples, the effective period of time t4was 4 hours. In any of the foregoing or following embodiments, the oxygen-containing atmosphere may be air or pure oxygen. In some embodiments, the oxygen-containing atmosphere is pure oxygen. In any of the foregoing or following embodiments, the hydroxide precursor may be prepared as discussed above. In any of the foregoing or following embodiments, the solid hydroxide precursor may have a mean particle size of 0.5 μm to 10 μm. In some embodiments, the hydroxide precursor particles have a mean size of 0.5 μm to 7.5 μm, 0.5 μm to 5 μm, or 0.5 μm to 2.5 μm. In any of the foregoing or following embodiments, monocrystalline lithium nickel manganese cobalt oxide may have a mean particle size of 0.5 μm to 5 μm. In some embodiments, the solid hydroxide precursor has a mean particle size of 1 μm to 2 μm. In certain embodiments, the monocrystalline lithium nickel manganese cobalt oxide has a mean particle size of 1 μm to 5 μm, or 1 μm to 3 μm. In any of the foregoing or following embodiments, the dopant metal(s) M may comprise Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Ga, Y, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof. D. Flash-Sintering Method In some embodiments, monocrystalline lithium nickel manganese cobalt oxide (or a doped variant thereof) is synthesized by a flash-sintering method. With reference toFIG.4, in some embodiments, the flash-sintering method comprises combining a solid hydroxide precursor comprising NiXMnyMzCo1-x-y-z(OH)2with a molar excess of a lithium compound to form a hydroxide mixture (401); heating the hydroxide mixture in an oxygen-containing atmosphere at a temperature TF1for an effective period of time t1to form an oxide mixture comprising oxides of nickel, manganese, cobalt, lithium, and, if present, the one or more dopant metals, or a combination thereof (402); increasing the temperature to a temperature TF2at a rate of ≥10° C./min (403); and heating the oxide mixture in an oxygen-containing atmosphere at the temperature TF2for an effective period of time t2to form monocrystalline lithium nickel manganese cobalt oxide having a formula LiNiXMnyMzCo1-x-y-zO2(404). In the foregoing formulas, M represents one or more dopant metals, x≥0.6, 0.01≤y<0.2, z≤0.05, and x+y+z≤1.0. More particularly, 0.62≤x+y+z≤1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.7-0.98. In another independent embodiment, x=0.65-0.9, y=0.05-0.2, z=0-0.02, and x+y+z=0.7-0.95. In some examples, x is 0.7-0.9, such as 0.75-0.9 or 0.8-0.9; y is 0.05-0.15, such as 0.05-0.14 or 0.05-0.1; z is 0-0.02; and x+y+z is 0.8-0.98, such as 0.8-0.95. The solid hydroxide precursor is combined with a molar excess of a Li compound to form a hydroxide mixture. In any of the foregoing or following embodiments, the Li compound may comprise lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxide, lithium peroxide, or any combination thereof. In any of the foregoing or following embodiments, the Li compound may have a mean particle size of 10 μm to 100 μm. In some embodiments, the Li compound comprises lithium hydroxide. The LiOH may be anhydrous or a hydrated salt, e.g., LiOH.H2O. In any of the foregoing or following embodiments, the solid hydroxide precursor and the lithium compound may be combined in a Li:solid hydroxide precursor molar ratio of 0.8:1 to 3:1, such as a molar ratio of 0.9:1 to 3:1, 0.9:1 to 2:1, 0.9:1 to 1.5:1, 1:1 to 1.5:1, 1.1:1 to 1.4:1, or 1.1:1 to 1.2:1. The hydroxide mixture is heated in an oxygen-containing atmosphere at a temperature TF1for an effective period of time t1to form an oxide mixture comprising oxides of nickel, manganese, cobalt, lithium, and, if present, the one or more dopant metals, or a combination thereof. In some embodiments, the hydroxide mixture is heated at the temperature TF1in an absence of a sintering agent. In any of the foregoing or following embodiments, the temperature TF1may be 400° C. to 1000° C. and/or the effective period of time t1may be 1 hour to 30 hours. In some embodiments, the temperature TF1is 400° C. to 900° C., 400° C. to 800° C., 400° C. to 600° C., or 450° C. to 550° C. In certain examples, the temperature TF1was 480° C. In any of the foregoing or following embodiments, the effective period of time t1is 1 hour to hours In some embodiments, the effective period of time t1is 1 hour to 25 hours, 1 hour to 20 hours, 1 hour to 15 hours, or 1 hour to 10 hours. In certain examples, the period of time t1was 5 hours. In any of the foregoing or following embodiments, the oxygen-containing atmosphere may be air or pure oxygen. In some embodiments, the oxygen-containing atmosphere is pure oxygen. In any of the foregoing or following embodiments, a portion or all of the hydroxide mixture is converted to an oxide mixture. In some embodiments, at least 25 wt %, at least 50 wt %, at least 75 wt %, or at least 90 wt % of the hydroxide mixture is converted to an oxide mixture. In certain embodiments, 25-100 wt %, 50-100 wt %, 75-100 wt %, 90-100 wt %, or 95-100 wt % of the hydroxide mixture is converted to an oxide mixture. The temperature is then increased to a temperature TF2at a rate of ≥10° C./minute. In any of the foregoing or following embodiments, the ramping rate may be from 10° C./minute to 3000° C./minute (50° C./second). In some embodiments, the ramping rate is from 10° C./minute to 2000° C./minute, such as 10° C./minute to 1000° C./minute, 10° C./minute to 500° C./minute, 10° C./minute to 250° C./minute, or 10° C./minute to 100° C./minute. In certain examples, the ramping rate was 10-20° C./minute. In any of the foregoing or following embodiments, the temperature TF2may be 600° C. to 1000° C. In some embodiments, the temperature TF2is 700° C. to 800° C. or 750° C. to 850° C. In some examples, the temperature TF2was 800° C. The oxide mixture is heated in an oxygen-containing atmosphere at the temperature TF2for an effective period of time t2to form monocrystalline lithium nickel manganese cobalt oxide having a formula LiNiXMnyMzCo1-x-y-zO2. In any of the foregoing or following embodiments, the effective period of time t2may be 1 hour to 30 hours. In some embodiments, the effective period of time t2is 1 hour to 25 hours, 1 hour to 20 hours, 5 hours to 20 hours, or 5 hours to 15 hours. In certain examples, the period of time t2was 10 hours. In any of the foregoing or following embodiments, the oxygen-containing atmosphere comprises pure oxygen or air. In some embodiments, the oxygen-containing atmosphere is pure oxygen. In any of the foregoing or following embodiments, the hydroxide precursor may be prepared as discussed above. In any of the foregoing or following embodiments, the solid hydroxide precursor may have a mean particle size of 0.5 μm to 10 μm. In some embodiments, the hydroxide precursor particles have a mean size of 0.5 μm to 7.5 μm, 0.5 μm to 5 μm, or 0.5 μm to 2.5 μm. In any of the foregoing or following embodiments, monocrystalline lithium nickel manganese cobalt oxide may have a mean particle size of 0.5 μm to 5 μm. In some embodiments, the solid hydroxide precursor has a mean particle size of 1 μm to 2 μm. In certain embodiments, the monocrystalline lithium nickel manganese cobalt oxide has a mean particle size of 1 μm to 5 μm, or 1 μm to 3 μm. In any of the foregoing or following embodiments, the dopant metal(s) M may comprise Mg, Ti, Al, Zn, Fe, Zr, Sn, Sc, V, Cr, Fe, Cu, Ga, Y, Nb, Mo, Ru, Ta, W, Ir, or any combination thereof. III. Cathodes and Lithium Ion Batteries Monocrystalline lithium nickel manganese cobalt oxide (NMC), and doped variants thereof, made by embodiments of the disclosed methods may be used in cathodes, such as cathodes for lithium ion batteries. In some embodiments, a cathode comprises monocrystalline LiNiXMnyMzCo1-x-y-zO2where M represents one or more dopant metals, x≥0.6, 0.01≤y<0.2, z≤0.05, and x+y+z≤1.0. In some embodiments, x=0.65-0.99, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-1.0. In an independent embodiment, x=0.65-0.95, y=0.01-0.2, z=0-0.02, and x+y+z=0.66-0.98. In another independent embodiment, x=0.65-0.9, y=0.05-0.2, z=0-0.02, and x+y+z=0.7-0.95. In some examples, x is 0.7-0.9, such as 0.75-0.9 or 0.8-0.9; y is 0.05-0.15, such as 0.05-0.14 or 0.05-0.1; z is 0-0.02; and x+y+z is 0.8-0.98, such as 0.8-0.95. In any of the foregoing or following embodiments, a mean particle size of the monocrystalline LiNiXMnyMzCo1-x-y-zO2may be 0.5 μm to 5 μm, such as 1 μm to 5 μm, or 1 μm to 3 μm. In one embodiment, the NMC is LiNi0.76Mn0.14Co0.1O2. In an independent embodiment, the NMC is LiNi0.8Mn0.1Co0.1O2. In another independent embodiment, the NMC is LiNi0.9Mn0.05Co0.05O2. In still another independent embodiment, the NMC is LiNi0.76Mn0.12Co0.1Mg0.01Ti0.01O2. In any of the foregoing or following embodiments, the cathode may have a capacity >180 mAh/g. In some embodiments, the cathode has a capacity >185 mAh/g, >190 mAh/g, or even >200 mAh/g. In any of the foregoing or following embodiments, the cathode may be operable at high voltage, e.g., a voltage of >3.8 V. In some embodiments, the cathode is operable at a voltage from 2-4.6 V, such as a voltage of 2-4.5 V or 2-4.4 V. In any of the foregoing or following embodiments, the cathode may have an NMC loading of 15-25 mg/cm2, such as 18-24 mg/cm2(ca. 3.5-4.5 mAh/cm2). In some embodiments, the coating weight on each side of the cathode may be from 7.5-12.5 mg/cm2, such as 9-12 mg/cm2, providing an areal capacity on each side of 3.5-4.5 mAh/cm2. In any of the foregoing or following embodiments, the cathode may further comprise one or more inactive materials, such as binders and/or additives (e.g., carbon). In some embodiments, the cathode may comprise from 0-10 wt %, such as 2-5 wt % inactive materials. Suitable binders include, but are not limited to, polyvinyl alcohol, polyvinyl fluoride, ethylene oxide polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, epoxy resin, nylon, polyimide and the like. Suitable conductive additives include, but are not limited to, carbon black, acetylene black, Ketjen black, carbon fibers (e.g., vapor-grown carbon fiber), metal powders or fibers (e.g., Cu, Ni, Al), and conductive polymers (e.g., polyphenylene derivatives). In some embodiments, a slurry comprising the NMC and, optionally, inactive materials is coated onto a support, such as aluminum foil. In certain embodiments, the coating may have a thickness of 50-80 μm on each side, such as a thickness of 60-70 μm. In any of the foregoing or following embodiments, the cathode may have an electrode press density of 2.5-3.5 g/cm3, such as 3 g/cm3. In some embodiments, a lithium ion battery includes a cathode comprising monocrystalline NMC as disclosed herein, an anode, an electrolyte, and optionally a separator.FIG.5is a schematic diagram of one exemplary embodiment of a rechargeable battery500including a cathode520as disclosed herein, a separator530which is infused with an electrolyte, and an anode540. In some embodiments, the battery500also includes a cathode current collector510and/or an anode current collector550. The electrolyte may be any electrolyte that is compatible with the anode and suitable for use in a lithium ion battery. In any of the foregoing or following embodiments, the lithium ion battery may be a pouch cell.FIG.6is a schematic side elevation view of one embodiment of a simplified pouch cell600. The pouch cell600comprises an anode610comprising graphite material, an anode current collector630, a cathode640comprising an NMC cathode material650as disclosed herein and a cathode current collector660, a separator670, and a packaging material defining a pouch680enclosing the anode610, cathode640, and separator670. The pouch680further encloses an electrolyte (not shown). The anode current collector630has a protruding tab631that extends external to the pouch680, and the cathode current collector660has a protruding tab661that extends external to the pouch680. The pouch cell weight includes all components of the cell, i.e., anode, cathode, separator, electrolyte, and pouch material. In some embodiments, the pouch cell has a ratio of anode (negative electrode) areal capacity to cathode (positive electrode) areal capacity—N/P ratio—of 0.02-5, 0.1-5, 0.5-5, or 1-5. In certain embodiments, the pouch cell has a ratio of electrolyte mass to cell capacity—E/C ratio—of 1-6 g/Ah, such as 2-6 g/Ah or 2-4 g/Ah. In any of the foregoing or following embodiments, the current collectors can be a metal or another conductive material such as, but not limited to, nickel (Ni), copper (Cu), aluminum (Al), iron (Fe), stainless steel, or conductive carbon materials. The current collector may be a foil, a foam, or a polymer substrate coated with a conductive material. Advantageously, the current collector is stable (i.e., does not corrode or react) when in contact with the anode or cathode and the electrolyte in an operating voltage window of the battery. The anode and cathode current collectors may be omitted if the anode or cathode, respectively, are free standing, e.g., when the anode is a free-standing film, and/or when the cathode is a free-standing film. By “free-standing” is meant that the film itself has sufficient structural integrity that the film can be positioned in the battery without a support material. In any of the foregoing or following embodiments, the anode may be any anode suitable for a lithium ion battery. In some embodiments, the anode is lithium metal, graphite, an intercalation material, or a conversion compound. The intercalation material or conversion compound may be deposited onto a substrate (e.g., a current collector) or provided as a free-standing film, typically, including one or more binders and/or conductive additives. Suitable binders include, but are not limited to, polyvinyl alcohol, polyvinyl chloride, polyvinyl fluoride, ethylene oxide polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, epoxy resin, nylon, polyimide and the like. Suitable conductive additives include, but are not limited to, carbon black, acetylene black, Ketjen black, carbon fibers (e.g., vapor-grown carbon fiber), metal powders or fibers (e.g., Cu, Ni, Al), and conductive polymers (e.g., polyphenylene derivatives). Exemplary anodes for lithium batteries include, but are not limited to, lithium metal, carbon-based anodes (e.g., graphite, silicon-based anodes (e.g., porous silicon, carbon-coated porous silicon, carbon/silicon carbide-coated porous silicon), Mo6S8, TiO2, V2O5, Li4Mn5O12, Li4Ti5O12, C/S composites, and polyacrylonitrile (PAN)-sulfur composites. In some embodiments, the anode is lithium metal. In certain embodiments, the anode may have a lithium coating weight on each side of a current collector of 5-15 mg/cm2, providing an areal capacity on each side of 2-5.1 mAh/cm2. In any of the foregoing or following embodiments, the separator may be glass fiber, a porous polymer film (e.g., polyethylene- or polypropylene-based material) with or without a ceramic coating, or a composite (e.g., a porous film of inorganic particles and a binder). One exemplary polymeric separator is a Celgard® K1640 polyethylene (PE) membrane. Another exemplary polymeric separator is a Celgard® 2500 polypropylene membrane. Another exemplary polymeric separator is a Celgard® 3501 surfactant-coated polypropylene membrane. The separator may be infused with the electrolyte. In any of the foregoing or following embodiments, the electrolyte may comprise a lithium active salt and a solvent. In some embodiments, the lithium active salt comprises LiPF6, LiAsF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB), lithium difluoro(oxalato)borate (LiBF2(C2O4), LiDFOB), lithium bis(pentafluoroethanesulfonyl)imide (LiN(SO2CF2CF3)2, LiBETI), lithium (fluorosulfonyl trifluoromethanesulfonyl)imide (LiN(SO2F)(SO2CF3), LiFTFSI), lithium (fluorosulfonyl pentafluoroethanesulfonyl)imide (LiN(SO2F)N(SO2CF2CF3), LiFBETI), lithium cyclo(tetrafluoroethylenedisulfonyl)imide (LiN(SO2CF2CF2SO2), LiCTFSI), lithium (trifluoromethanesulfonyl)(n-nonafluorobutanesulfonyl)imide (LiN(SO2CF3)(SO2-n-C4F9), LiTNFSI), lithium cyclo-hexafluoropropane-1,3-bis(sulfonyl)imide, or any combination thereof. The solvent is any nonaqueous solvent suitable for use with the lithium active salt, lithium metal anode, and packaging material. Exemplary solvents include, but are not limited to, triethyl phosphate, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) methyl phosphate; trimethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphite; dimethyl methylphosphonate, diethyl ethylphosphonate, diethyl phenylphosphonate, bis(2,2,2-trifluoroethyl) methylphosphonate; hexamethylphosphoramide; hexamethoxyphosphazene, hexafluorophosphazene, 1,2-dimethoxyethane (DME), 1,3-dioxolane (DOL), tetrahydrofuran (THF), allyl ether, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), 4-vinyl-1,3-dioxolan-2-one (vinyl ethylene carbonate, VEC), 4-methylene-1,3-dioxolan-2-one (methylene ethylene carbonate, MEC), 4,5-dimethylene-1,3-dioxolan-2-one, dimethyl sulfoxide (DMSO), dimethyl sulfone (DMS), ethyl methyl sulfone (EMS), ethyl vinyl sulfone (EVS), tetramethylene sulfone (i.e. sulfolane, TMS), trifluoromethyl ethyl sulfone (FMES), trifluoromethyl isopropyl sulfone (FMIS), trifluoropropyl methyl sulfone (FPMS), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), tetraethylene glycol dimethyl ether (tetraglyme), methyl butyrate, ethyl propionate, gamma-butyrolactone, acetonitrile (AN), succinonitrile (SN), adiponitrile, triallyl amine, triallyl cyanurate, triallyl isocyanurate, or any combination thereof. In some embodiments, the solvent comprises a flame retardant compound. The flame retardant compound may comprise the entire solvent. Alternatively, the solvent may comprise at least 5 wt % of the flame retardant compound in combination with one or more additional solvents and/or diluents. Exemplary flame retardant compounds include, but are not limited to, triethyl phosphate, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) methyl phosphate; trimethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphite; dimethyl methylphosphonate, diethyl ethylphosphonate, diethyl phenylphosphonate, bis(2,2,2-trifluoroethyl) methylphosphonate; hexamethylphosphoramide; hexamethoxyphosphazene, hexafluorophosphazene, and combinations thereof. In some embodiments, the electrolyte has a lithium active salt concentration of 0.5-8 M, such as a concentration of 1-8 M, 1-6 M, or 1-5 M. In some examples, the electrolyte comprises LiPF6in a carbonate solvent, such as 1.0 M LiPF6in EC/EMC. In some embodiments, the electrolyte is a localized superconcentrated electrolyte (LSE), also referred to as a localized high concentration electrolyte. A LSE includes an active salt, a solvent in which the active salt is soluble, and a diluent, wherein the active salt has a solubility in the diluent at least 10 times less than a solubility of the active salt in the solvent. In an LSE, lithium ions remain associated with solvent molecules after addition of the diluent. The anions are also in proximity to, or associated with, the lithium ions. Thus, localized regions of solvent-cation-anion aggregates are formed. In contrast, the lithium ions and anions are not associated with the diluent molecules, which remain free in the solution. In an LSE, the electrolyte as a whole is not a concentrated electrolyte, but there are localized regions of high concentration where the lithium cations are associated with the solvent molecules. There are few to no free solvent molecules in the diluted electrolyte, thereby providing the benefits of a superconcentrated electrolyte without the associated disadvantages. The solubility of the active salt in the solvent (in the absence of diluent) may be greater than 3 M, such as at least 4 M or at least 5 M. In some embodiments, the solubility and/or concentration of the active salt in the solvent is of 3 M to 10 M, such as from 3 M to 8 M, from 4 M to 8 M, or from 5 M to 8 M. However, in some embodiments, the molar concentration of the active salt in the LSE as a whole is of 0.5 M to 3 M, 0.5 M to 2 M, 0.75 M to 2 M, or 0.75 M to 1.5 M. Exemplary salts and solvents for LSEs are those disclosed above. In some embodiments, the diluent comprises a fluoroalkyl ether (also referred to as a hydrofluoroether (HFE)), a fluorinated orthoformate, or a combination thereof. Exemplary diluents include, but are not limited to, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), bis(2,2,2-trifluoroethyl) ether (BTFE), 1,1,2,2,-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TFTFE), methoxynonafluorobutane (MOFB), ethoxynonafluorobutane (EOFB), tris(2,2,2-trifluoroethyl)orthoformate (TFEO), tris(hexafluoroisopropyl)orthoformate (THFiPO), tris(2,2-difluoroethyl)orthoformate (TDFEO), bis(2,2,2-trifluoroethyl) methyl orthoformate (BTFEMO), tris(2,2,3,3,3-pentafluoropropyl)orthoformate (TPFPO), tris(2,2,3,3-tetrafluoropropyl)orthoformate (TTPO), or any combination thereof. In certain embodiments where the diluent and solvent are immiscible, the electrolyte may further include a bridge solvent having a different composition than the solvent and a different composition than the diluent, wherein the bridge solvent is miscible with the solvent and with the diluent. Exemplary bridge solvents include acetonitrile, dimethyl carbonate, diethyl carbonate, propylene carbonate, dimethyl sulfoxide, 1,3-dioxolane, dimethoxyethane, diglyme (bis(2-methoxyethyl) ether), triglyme (triethylene glycol dimethyl ether), tetraglyme (tetraethylene glycol dimethyl ether), or any combination thereof. Additional information regarding LSEs may be found in US 2018/0254524 A1, US 2018/0251681 A1, and US 2019/148775 A1, each of which is incorporated in its entirety herein by reference. In any of the foregoing or following embodiments, the lithium ion battery may have a cell energy density of 200 Wh/kg to 400 Wh/kg, such as 200 Wh/kg to 350 Wh/kg, 250 Wh/kg to 300 Wh/kg, or 250 Wh/kg to 275 Wh/kg. In any of the foregoing or following embodiments, the lithium ion battery may have a first cycle capacity of 2 Ah to 5 Ah. In any of the foregoing or following embodiments, the lithium ion battery may be operable at a rate of up to 3 C, such as a rate of 0.1 C to 3 C. In any of the foregoing or following embodiments, the lithium ion battery may demonstrate an average coulombic efficiency of at least 80%, such as 80-100%, 85-100%, 90-100%, 95-100%, or 95-99% over at least 100 cycles, at least 150 cycles, or at least 200 cycles. In any of the foregoing or following embodiments, the lithium ion battery may have a capacity retention of at least 70%, at least 75%, or at least 80% after at least 100 cycles, at least 150 cycles, or at least 200 cycles. In some embodiments, the capacity retention is 70-90%, such as 70-85%, after 200 cycles. Advantageously, the cathode may be more stable (e.g., resistant to cracking) over extensive cycling, undergo fewer side reactions, be less moisture sensitive, and/or generate less gas during cycling compared to conventional Ni-rich cathodes (e.g., Ni≥0.6) prepared with polycrystalline and/or monocrystalline NMC. IV. Examples Example 1 Molten-Salt Synthesis and Characterization of Single Crystal LiNi0.76M0.14C0.1O2(NMC76) Synthesis A Ni0.76Mn0.14Co0.1(OH)2precursor was synthesized by co-precipitation method using a 5 L reactor at 55° C. Before the co-precipitation reaction, 1.5 L deionized (DI) H2O and 65 mL concentrated NH3—H2O (˜28 wt %) were added to the reactor and heated to 55° C. as a starting solution. A 2 mol/L transition metal (TM) sulfate solution (Ni:Mn:Co=0.76:0.14:0.10 in molar ratio) was prepared with Ni(SO4)2.6H2O, MnSO4—H2O, and Co(SO4)2.7H2O, and then pumped into reactor along with 8 M NaOH as well as 10 mol/L NH3—H2O buffer solution. The pumping rates of the TM sulfate and NH3—H2O solution were set at 3 and 1 mL/min, respectively. The pH value was controlled at 11.2 during reaction by adjusting NaOH adding rate. The synthesized precursor was filtered and washed by DI H2O to remove impurities. After drying at 100° C. for 12 hours, the Ni0.76Mn0.14Co0.1(OH)2precursor was obtained. Ni0.76Mn0.14Co0.1(OH)2was heated at 900° C. for 15 hours in air to prepare the oxide precursor. The stoichiometry of the oxide precursor was analyzed by ICP-OES. The oxide precursor and lithium oxide were mixed at 1:0.6 molar ratio (TM:Li=1:1.2), then NaCl (1:1.1 weight ratio) was added to the precursor and mixed uniformly. The mixture was sintered at 800° C. for 10 hours and then 900° C. for 5 hours using a 10° C./minute ramping rate in an oxygen atmosphere. The sintered products were washed and dried at 80° C. in vacuum for 2 hours. Post annealing at 580° C. (10° C./min ramping) in oxygen atmosphere was carried out before collecting the end products. Pure NaCl was used as the molten salt media to lower the sintering time/temperature of the single crystals, thereby reducing the cost of synthesizing the single crystals. Characterization Scanning electron images (SEM) were collected on a Helios NanoLab scanning electron microscope (FEI, Hillsboro, Oreg.). Powder X-ray diffraction (XRD) data were collected at the 28-ID-2 (XPD) beamline of the National Synchrotron Light Source II (NSLS II), Brookhaven National Laboratory (BNL). A Perkin Elmer amorphous-Si flat panel detector was used. The wavelength was 0.1821 Å. Pristine powder was loaded in Kapton® polyimide capillary tubes (1.0 mm diameter) in an Ar-filled glove box and mounted on bases at the beamline. Rietveld refinement of the XRD data was carried out in TOPAS6 (Coelho, J. Appl. Crystallogr. 2018, 51:210-218). Transmission electron microscopy (TEM) specimen preparation was conducted on a FEI Helios Dual-Beam FIB operating at 2-30 kV. TEM images, selected area electron diffraction (SAED), high resolution TEM (HRTEM) images and scanning TEM energy-dispersive X-ray spectroscopy (STEM-EDS) were performed on a FEI Titan 80-300 S/TEM microscope at 300 kV which was equipped with a probe spherical aberration corrector. HRSTEM high-angle annular dark-field (HRSTEM-HAADF) images and STEM-electron energy loss spectroscopy (STEM-EELS) were performed on a probe aberration-corrected JEOL JEM-ARM200CF microscope (JEOL USA, Peabody, Mass.) at 200 kV. Since the TEM sample was very thin and self-absorption in the TEM sample was negligible, EDS quantitation was performed by using a simple ratio technique (Cliff-Lorimer quantification). In this method, peak intensities are proportional to concentration and specimen thickness, and the effects of variable specimen thickness are removed by taking ratios of intensities for elemental peaks and introduced a “k-factor” to relate the intensity ratio to concentration ratio: CA/CB=kAB·IA/IB(1) Where IAis Peak intensity for element A and CAis concentration in weight %. Each pair of elements requires a different k-factor which depends on detector efficiency, ionization cross section and fluorescence yield of the two elements concerned, k-factor kab is calculated as follows: kab=(AaωbQb)/(AbωaQa) (2) Where Aaand Abare the atomic weights of elements giving rise to the analytical lines a and b respectively, Qaand Qbare the ionization cross sections of the shells, that once ionized give rise to the analytical lines at the specified accelerating voltage. The fluorescent yields ωaand ωbgive probability of emission of the lines once the appropriate shell has been ionized. Once the k factor is known, the element concentration in weight % can be calculated. The as-prepared single crystalline NMC76 had a tap density of 2.12 mg/cm3, while polycrystalline NMC76 is 2.08 mg/cm3. The increased tap density will benefit the cell-level energy due to the reduced porosity and improved electrode press density. Electrochemical Test To understand the electrochemical properties of single crystal NMC76 at industry relevantscales, a cathode with reasonably high loading is needed. However, half cells are not a good testing vehicle to evaluate high mass loading of the cathode materials due to the accelerated Li metal degradation when coupled with a thick cathode. Electrochemical performance was evaluated with 2032 type coin cells. Single crystalline MNC76 was mixed with carbon additive (C65 carbon black) and PVDF at 96:2:2 weight ratio in NMP (N-methyl-2-pyriolidone) solvent and loaded on carbon coated Al foil. The areal loading of 5-26 mg/cm2electrodes were prepared by adjusting the height of doctor blade. After drying at 80° C. under vacuum, thick electrodes (˜20 mg/cm2) were calendared (˜32% porosity) and cut into Φ½ inch size discs for assembling cells. Prior to calendaring, the porosity was 62%. Graphite powder was mixed with carbon additive (C65), CMC and SBR at weight ratio of 94.5:1:2.25:2.25 and loaded on copper foil. The dried graphite electrodes were calendared and cut into Φ15 mm size discs. 1.0 M LiPF6in EC/EMC (3:7 weight ratio) with 2 wt % VC was used as electrolyte for both half cell and full cell tests. Half cells were assembling using 450 μm thick Li metal as anode. Negative/Positive (N/P) ratio for full cells assembling was controlled 1.15-1.2 (including ˜0.1 mg Li metal in graphite anode). In all the cell tests, 1 C is named as 200 mA/g. In Situ Electrochemical AFM Measurements (EC-AFM) Fabrication of working electrodes for in situ EC-AFM: Aluminum (Al) foil was chosen as the substrate because of its electronic conductivity and stability during the electrochemical cycles. The synthesized Ni-rich NMC single crystals were dropped on Al foil. Then the Al foil with Ni-rich NMC was placed under a 5 tonnage press machine and held for 100 s. The weakly bound and unfixed Ni-rich NMC crystals were removed by flowing N2gas. The Al foil was then mounted onto the AFM sample holder with epoxy and an electrical contact was made to the bottom side of Al foil with a flattened nickel wire. Silicone grease was used to cover the outer rim of the O-ring to enhance the sealing of solution. The nickel wire was isolated from solution due to the larger diameter of Al foil than O-ring. The cell was ready for in situ AFM testing after cell assembly with an O-ring, sealing cap with Li wire for the counter and reference electrode, and another free sealing cap. All in situ EC-AFM images were captured in peak force or tapping mode at room temperature (23° C.) with a Nanoscope 8 atomic force microscope (J scanner, Bruker, Santa Barbara, Calif.) (Habraken et al.,Nat Commun2013, 4:1507; Tao et al.,PNAS USA2019, 116:13867-13872). The AFM probe consisted of silicon tips on silicon nitride cantilevers (HA_C Series of ETALON probes, k=0.26 N/m, tip radius <10 nm; K-TEK Nanotechnology, https://kteknano.com/product-category/etalon/). The electrolyte solution of 1.0 M LiPF6in EC/EMC (3:7 weight ratio) was used as the testing solution. A working cathode electrode (described above) was connected to Solartron 1287 electrochemistry workstation (Solartron, Farnborough, Hampshire, UK) by the nickel wire. A thin Li wire (counter and reference electrode) with sealing cap was inserted into the testing solution via another channel in liquid cell (Lv etai,Nano Lett2017, 17:1602-1609). An electric signal was input into an AFM liquid cell with a two-electrode configuration by a Solartron 1287 electrochemistry workstation. The applied voltage started at OCV, increased up to 4.50 V and down to 2.70 V with a uniform scan rate of 0.3 mV/s. For typical imaging conditions, images were collected at scanning speeds of 1 Hz. Several protocols were followed to ensure that the AFM images were typical representations of the surface topography evolution. First, the imaging force was reduced to the minimum possible value (˜100 pN) that still allowed the tip to track the surface and no measurable effect of the scanning on the surface cracks. We verified this by zooming out to a larger scan box and comparing the crack number density with the smaller scan area. A consequence of imaging in the same area is that it may cause the less bound particles to move on the surface. This operation ensures that the crack growth kinetics are minimally affected. Images were also collected at different scan angles and trace and retrace images regularly compared to eliminate the possibility of imaging artifacts from tip contamination. The images were analyzed using the image processing software package Nanoscope Analysis 2.0 (Bruker). The average width of these steps almost linearly increases with the higher voltage (vs. Li+/Li) during charging process followed by linear decreases with the lower voltage during the discharge process, with its value of 30.3±0.7 nm at open circuit voltage (OCV), up to 52.5±2.5 nm at 4.50 V at charge status, and down to 38.4±1.3 nm at 4.19 V during discharge. The average step width is calculated by dividing the total width of the lateral face by the total number of steps (between 21 and 43 steps) for each voltage during the in situ AFM monitoring. The error bars in the step width are evaluated by averaging of three times of measurement of lateral face width at each time point. Simulation A cylindrical electrode particle diffusion-induced-stress model was used here along with material properties predicted by density functional theory (DFT) (28, 33). The particle is considered as an isotropic solid with Young's modulus (E) increasing linearly with Li concentration. In the layered Ni-rich electrode, the diffusion of lithium ion is limited in the two-dimensional channels, namely, between the layers, so lithium diffusion along the radial direction is assumed in the model. The dimensionless particle size, time, Li concentration, and stress are used following the definitions in Deshpande et al.,J Electrochem Soc2010, 157:A967-A971). For the parameters in simulation, α=0.0067; E0=59.8 GPa; E=E0+204.2 C; v=0.3 (Qi et al.J Electrochem Soc2014, 161:F3010-F3018); and γ=2.1 J/m2was computed for Li16(Ni14CoMn)O32(Stein et al.,Acter Mater2018, 159:225-240). The analytical solutions are provided inFIGS.29A-29D,30A-30D. The numerical solution by COMSOL5.5 model is provided inFIGS.31A-31D. For the anisotropic chemical strain solved inFIG.31D, the α=(0, 0, 0.02). Results and Discussion The synthesized NMC76 has a mean particle size of 3 μm (FIG.7A). A cross-section view (FIG.17B) shows that NMC76 has a dense structure without cavities or grain boundaries. Pure phases of α-NaFeO2-type layered structures are confirmed by both selected area electron diffraction (SAED,FIG.7C) and X-ray Diffraction (XRD,FIG.7D). Lattice parameters a and c are 2.8756(1) Å and 14.2221 (1) Å, respectively, from Rietveld refinement (Table 1). For comparison, polycrystalline NMC76 is found to contain many internal pores and intergranular boundaries along with surface films (FIGS.8A-8F) formed from the reactions between NMC and air (Jung et al.,J Electrochem Soc2018, 165:A132-A141). In contrast, the surface of single crystalline NMC76 is very uniform (FIGS.7E and7F). Elemental mapping (FIGS.7G and7H) indicates a homogeneous distribution of Ni, Mn and Co with a stoichiometric ratio as designed (Table 2). Continuous phase transitions happen when potential changes (FIG.9), similar to polycrystalline NMC76 (Zheng et al.,Nano Energy2018, 49:538-548). During charge, phase transitions happen in the order of from H1 to M (H and M are hexagonal phase and monoclinic phase, respectively), M to H2, and H2 to H3, similar to polycrystalline NMC76. TABLE 1Rietveld refinement result of the pristine NMC76.a = 2.8756(1) Å, c = 14.2221(1) ÅAtomSitexyZFractionUisoLi3a0000.986(1)0.004(1)Ni3a0000.014(1)0.004(1)Ni3b000.50.746(1)0.005(2)Li3b000.50.014(1)0.005(2)Mn3b000.50.140.005(2)Co3b000.50.10.005(2)O6c000.2403(1)10.009(4) TABLE 2Elemental Ratio obtained from STEM-EDSElementWt %StdevNi48.281.45Mn7.620.9Co6.981.13O37.121.69 Single crystalline NMC76 was further tested in graphite/NMC full cells at realistic conditions. The typical loading of NMC76 cathodes is ca. 20 mg/cm2(=4 mAh/cm2) with ca. 32% porosity, which is needed to build a 250 Wh/kg Li-ion cell (Table 3). At such a high cathode loading, Li metal will worsen the cycling stability (FIGS.10,11) due to the deepened stripping/deposition process of Li. Between 2.7 V and 4.2 V (vs. graphite), single crystalline NMC76 delivered 182.3 mAh/g discharge capacity at 0.1 C, and retained 86.5% of its original capacity after 200 cycles (FIG.12A). With a cutoff of 4.3 V, single crystalline NMC76 delivered 193.4 mAh/g capacity with 81.6% capacity retention after 200 cycles (FIG.12B). Further increasing to 4.4 V, 196.8 mAh/g discharge capacity was seen (FIG.12C) along with a 72.0% capacity retention after 200 cycles. Note that 200 cycles at C/10 charge rate and C/3 discharge rate mean 2600 hours of cycling. The total testing time was equal to a cell undergoing 1300 cycles at 1 C. Increased polarization (FIGS.13A-13C) was observed when the cutoff voltage increased which is presumably assigned to intensified electrolyte decomposition at elevated voltages (FIGS.14A-B,15A-B,16A-B) and thus higher impedance resulting from cathode passivation films and single crystal lattice change. Crystalline gliding and cracking were seen when the cutoff voltage was beyond 4.3V (FIGS.13A-13C). Table 4 summarizes the electrochemical performances and testing conditions of all previously published single crystalline Ni-rich NMC (Ni>0.6) cathode materials. TABLE 3Cell design parameters for 250 Wh/kg lithium ionpouch cell based on graphite/NMC76 chemistryMaterialLiNi0.76Mn0.14Mn0.10O2Cathode1stdischarge200capacity/mAh g−1Active material loading96%Cathode weight (each21side)/mg cm−2Areal capacity (each4.0side)/mAh cm−2Electrode press3.0density/g cm−3Electrode thickness70(each side)/μmNumber of double13side layersElectrode dimension36*54W*L/mmAl foilThickness/μm12AnodeMaterialGraphiteSpecific capacity/mAh g−1360Active material loading96%N/P ratio (cell balance)1.16Coating weight (each13.5side)/mg cm−2Electrode dimension37.5*55.5W*L/mmCu foilThickness/μm8ElectrolyteE/C ratio/g Ah−12.5SeparatorThickness/μm20Packaging foilThickness/μm88CellAverage voltage (1stcycle)/V3.65Capacity (1stcycle)/Ah2.0Cell energy density/Wh kg−1250 TABLE 4Summary of single crystalline Ni-rich NMC (Ni > 0.6) reported in literatureInitial CapacityCyclingCapacityVoltageRetentionTotal cyclingRef.Composition(mAh/g)Rate(V)LoadingNo.(%)Ratetime (hr)*ThisLiNi0.75M0.14C0.1O2196.80.1C4.4 vs. Gr20mg/cm2200720.1/0.33C2389work(full cell)1LiNi0.8M0.1C0.1O21850.1C4.2 vs. Li3mg/cm225500.1/0.1C~500LiNi0.8M0.1C0.1O22400.1C4.6 vs. Li—25500.1/0.1C2LiNi0.58M0.09C0.03O21920.2C4.3 vs. Li12mg/cm2100880.2/0.2C~1000(full cell)3LiNi0.8M0.1C0.1O21900.1C4.3 vs. Li3mAh/cm2100~901/1C~2004LiNi0.83M0.08C0.11O2184.11C4.2 vs47mg/cm260084.81/1C~1200Gr/SiO(tested at 45°C. full cell)5**LiNi0.92M0.01C0.06AlWxMoxO2221.40.1C4.3 vs. Li7.8mg/cm210095.70.5/1C100*Testing time of single crystalline LiNi0.75M0.14C0.1O2is captured from testing data. Testing time for reference results are evaluated according to the current density.**x corresponds to 1000 ppm for W and Mo1Zhu et al.,J Mater Chem A2019, 7: 5463-5474.2Li et al.,J Electrochem Soc2019, 166: A1956-A1963;3Qian et al.,Energy Storage Meter2020, 27: 140-159;4Fan et al.,Nano Energy2020, 70: 104450;5Yan et al.,J Electrochem Soc2020, 167: 120514. Lattice gliding was clearly observed in single crystalline NMC76 at high voltages. Between 2.7 and 4.2 V (vs. graphite), the entire single crystal was well maintained after 200 cycles (FIG.13A). Increasing cutoff voltage to 4.3 V, there were some gliding lines seen on the crystal surfaces after 200 cycles (FIG.13B). Cycled to 4.4 V, single crystals appeared to be “sliced” (FIGS.13C,17A-17F) in parallel, along the (003) plane and vertical to c-axis of the layered structure (FIG.18C), which indicated a model II type crack (in-plane shear) in fracture mechanics. Additionally, small cracks that indicate a model I type fracture (opening) were also discovered at 4.4 V (FIG.13C). All characterizations were done by selecting various regions of NMC76 electrodes and the same phenomenon was repeatedly found (FIGS.19-21). Although single crystalline NMC76 as a whole particle was still intact (FIG.12A), gliding was the major mechanical degradation mode especially when cutoff voltage is above 4.3 V. Of note, the “gliding steps” formed in cycled crystals are quite different from cracking along intergranular boundaries of polycrystalline NMC particles. The scanning transmission electron microscopy (STEM) image for single crystalline NMC76 (FIGS.18B-18D) confirmed that on both sides of a gliding plane (yellow line inFIG.18D), the d-spacing of (003) plane (0.48 nm) was unchanged and the layered structure was well maintained after the “gliding” marks occurred. The long-range lattice symmetry of the bulk material will thereby not be altered. Ni, Mn, Co and O were still uniformly distributed in the vicinity of glided planes based on electron energy loss spectroscopy (EELS) analysis (FIG.18FandFIG.22). The uniform element distribution and intimately attached lattices across the gliding planes strongly demonstrated that although planar gliding occurs, no new boundary was generated, and the “sliced” area maintained the same lattice structure and chemical conditions as in the bulk phase. It should be noted that the gliding line (or the slicing marks) cannot be observed on the cross section of bulk particles by SEM, and are only visible by STEM bright field (BF) on thin sliced TEM samples. Although the internal lattice symmetry was well maintained after the gliding, the repeated gliding near surface eventually will evolve into microcracks exposing new surfaces to the electrolyte (FIGS.13A-13C). To further induce lattice gliding, the cutoff voltage of NMC76 single crystal is raised to 4.8 V (vs. □+/□). “Slicing marks” and microcracks are present in almost every charged single crystal (FIG.23A). Slight deformation of individual single crystals is clearly observed (FIG.18G), probably because the gliding of each layer equally likely moves towards symmetrically equivalent directions. Surprisingly, after discharging back to 2.7 V, the majority of single crystals revert to their original morphologies and the previously observed steps and microcracks disappear (FIG.23B). The “glided” layers within single crystals almost completely “glided” back to their original locations (FIG.18H), fully recovering from the deformation (FIG.18G), although some “traces” are visible (labeled inFIG.18H). Within the “regular” electrochemical window of 2.7-4.4 V (vs. graphite), after extensive cycling, lattice gliding and microcracking are also seen within crystal lattice at charged status (FIG.18I). STEM analysis of the NMC76 crystal (FIG.18J) indicates that the microcracks initiate from inside of the crystal. At the discharge status of those cycled crystals (cut off at 4.4 V), few ridges or cracks are found on the crystals. Although not as visible as in charged crystals, STEM still uncovers some “slicing marks” (FIG.18K) on discharged single crystal NMC76 which probably undergoes reversible “sliding” process back and forth during 120 cycles. No microcracking is identified in those “self-healed” single crystals (FIG.18L), suggesting that the lattice gliding and cracking in some of the crystals are still reversible after 120 cycles. As cycling continues, particle deformation will become dominant. Dislocation was also observed near the tip regions of microcrack of single crystals charged at 4.4 V (FIGS.24A-24D). The accumulation of dislocation was accompanied by the microcrack propagation. A trace amount of nano-sized NiO-like rock salt phase (FIGS.25A-25E) was observed on the gliding exposure step area of single crystalline NMC76 after cycling. In situ AFM has been used to image the crystal surface in real time in an electrochemical cell. A ˜3 μm sized NMC76 single crystal was studied by in situ AFM during charge and discharge (FIGS.26A-26F). Regions B and C inFIG.26Aare enlarged inFIGS.26B and26C, respectively, to probe the origin and evolution of “gliding steps” and microcracks under the electrical field. The formation of nanosized crack domains was observed on the side surface from open circuit voltage (OCV) to 4.50 V (vs. Li+/Li) during charge, while these domains disappeared in the discharge process (FIG.26B). Moreover, planar gliding was characterized by the appearance of wide crystal steps on the side surface due to the uneven movement between neighboring layers during polarization. More wide gliding steps were observed on the side surface starting at 4.20 V charging process and led to the more and wider (˜85 nm) gliding steps at 4.50 V (FIG.26C). When the cell potential decreased to 4.19 V, a few wide gliding steps decreased in their width (FIGS.27A-27B), indicating the atomic layer recovered back to their original position (FIG.26C). The average width of the steps almost linearly increased with increasing voltages (vs. Li+/Li) during the charging process followed by linear decreases with decreasing voltages during the discharge process, with its value of 30.3±0.7 nm at open circuit voltage (OCV), up to 52.5±2.5 nm at 4.50 V at charge status, and down to 38.4±1.3 nm at 4.19 V during discharge. The average step width was calculated by dividing the total width of the lateral face by the total number of steps (between 21 and 43 steps) for each voltage during the in situ AFM monitoring. The error bars in the step width were evaluated by averaging of three times of measurement of lateral face width at each time point. This “first increase then decrease” behavior of average step width vs. voltage indicates the reversible gliding process of these NMC crystals in each cycle. The reversible gliding process is further illustrated inFIG.26F. The observed lattice gliding is a direct observation of the “Lattice-Invariant Shear (LIS)” (Radin et al.,Nano Lett2017, 17:7789-7795). LIS should exist in many layered electrode materials, which experience stacking-sequence-change phase transformations due to lithium concentration change. It was also predicted that LIS will lead to particle deformation and ridges on the particle surface, but these signals are likely to be buried in the internal boundaries in a spherical-secondary polycrystalline. The micron-sized single crystal provides a clear platform to observe gliding or LIS induced mechanical degradation. Electrochemical potential difference is the driving force of lithium-ion diffusion and the formation of the lithium concentration gradient (Xiao,Sci2019, 366:426-427). Stress will be generated during Li+diffusion after establishing a lithium concentration gradient in the lattice. An analytical cylindrical isotropic diffusion-induced stress model was applied to understand the stress generation when lithium ions diffuse along the radial direction in the particle. The analytical solution of the dimensionless principal tress along axial, tangential and radial directions inside this cylindrical particle experienced compression or tension forces during cycling and reached maximum stresses when the Li+ concentration gradient was the highest. The peak tensile stress along tangential and axial directions occurred near the surface at the onset of delithiation (or 0.01 T) (FIGS.28A-28D). Conversely, the peak tensile stress in all three directions occurred at the center of the particle (FIGS.29A-29D) during lithiation. During charge (delithiation), the tensile stress along axial and tangential directions was localized on the surfaces of single crystals, leading to microcrack opening normal to (003) planes.FIGS.30A-30Care SEM images showing microcracks, which propagate from the center to the surface, forming fractures. Local stress also has a shear component along other directions, which is solved numerically via COMSOL. The shear stress component along yz direction that can trigger the gliding along the (003) planes is shown inFIGS.20D and20E. Although the signs of the shear stress during lithiation and delithiation are opposite, which explains the reversible gliding, the absolute values are not the same (FIGS.31A-31D), since the elastic modulus is a function of Li concentration. Therefore, the gliding motion should be largely but not completely reversible. The peak stresses inFIGS.31C and31Dare not exactly the same which provides the explanation of the largely but not completely reversible gliding in single crystalline NMC76 particles. Comparing the stress difference betweenFIGS.31C and31D, the anisotropic volume expansion (chemical strain) will lead to increased shear stress. The peak shear stresses are inside the particle during lithiation and delithiation, suggesting the sliding is likely to initiate inside of the particles. The irreversible gliding can generate small damages, being accumulated into the crack opening over long time cycling, an analog of fatigue crack nucleation. These lead to the ridges and microcracks seen on the surfaces of single crystals after cycling. The simple isotropic diffusion-induced-stress model can be used to predict if the cracks can be stabilized inside of the single crystal. Since the strain energy inside the particle reaches a maximum around the scaled time of Tp=0.1 T during delithiation (FIGS.22A-22D), its comparison with the fracture energy (2γ) is used as a criterion to evaluate the critical size of single crystal NMC76. If the accumulated strain energy is not large enough to cleave entire the crystal, the crack will be stabilized inside of the particle. ∏Tp=∫σ22EdV=π*h*[α⋆E0⋆(CR-C0)1-v]2¯⋆∫0rξ21Erdr<2γ(1) where h is the height of the cylindrical particle, α is the concentration expansion coefficient, E0is Young's modulus of the nonlithiated particle, E is Young's modulus at a given lithium-ion concentration, CRis the lithium-ion concentration at the surface, C0is the lithium-ion concentration at the center, v is Poisson's ratio and ξ represents the dimensionless stress (FIGS.22A-D,23A-D), and γ is the surface energy, A lower bound estimation of the critical size of the single crystal is predicted to be ˜3.5 μm, below which cracks can be considered stable inside of the particle. The simulation result suggests that although fractures along (003) direction appear in single crystals during cycling, the cracks are stable once formed and will not initiate catastrophic reactions to produce a fracture zone that eventually pulverizes the entire single crystal. Increasing the applied current density will lead to higher concentration gradient and higher stress generation. Increasing the cutoff voltage is equivalent to increasing (CR−C0) in equation (1). It means higher stress generation and large strain energies at elevated voltages, which causes more “gliding” and “cracking” (FIGS.7A-7C). The findings provide some strategies to stabilize single crystalline Ni-rich NMC by either reducing the crystal size to below 3.5 μm, absorbing accumulated strain energy through modification of the structure symmetry, or simply optimizing the depth of charge without sacrificing much reversible capacity. FIG.32shows an SEM image of a 20 μm single crystal NMC76 and images obtained by in situ AFM. Selective formation of a passivation film on certain planes of the NMC76 was found. Dissolution and recrystallization were seen on surfaces of the single crystal. Parallel cracking along the [001] surface was directly captured. Example 2 Molten-Salt Synthesis and Characterization of Single Crystal LiNi0.76M0.14C0.1O2(NMC76) Synthesis A hydroxide precursor was prepared as follows. A 2 M solution of transition metal (TM) sulfate solution (Ni:Mn:Co=0.76:0.14:0.10 in molar ratio) was prepared in 805 g deionized water Ni(SO4)2·6H2O, MnSO4·H2O, and Co(SO4)2·7H2O. Separately 160 g NaOH was dissolved in 500 g H2O. Concentrated NH3—H2O (28%) was diluted using DI H2O at 1:1 volume ratio. 1.5 L DI H2O and 50 mL concentrated NH3·H2O (28%) were added into the reactor as the starting solution. The reactor was heated to 50° C. The TMSO4solution, NaOH and NH3·H2O were pumped into the reactor at same time. The pump rates were 3 mL/min and 1 mL/min for TMSO4and NH3·H2O, respectively. The pH was controlled at 11.0-11.5. When all TMSO4solution was added into the reactor, the co-precipitated hydroxides were aged in the reactor for hrs. The precipitates were filtered and washed with DI H2O ·200 g DI H2O was used for every 100 g precipitates in washing for 3-5 times. After drying at 100° C. for 12 hours, the hydroxide precursor Ni0.76Mn0.14Co0.1(OH)2was obtained. Each batch produced ˜150 g of the hydroxide precursor. The mixed hydroxide precursor was heated in air for 15 hours to decompose into mixed oxides. Three different temperatures, 800, 900, and 1000° C., were used to study the influence of temperature on the oxide particle size. The ramping rate was 5° C./minute. The morphology of the pristine hydroxide precursor and the oxides obtained at 800, 900, and 1000° C. are shown inFIGS.33A-33D, respectively. The optimal calcination temperature was found to be 900° C. for Ni0.76Mn0.14Co0.1(OH)2. Suitable temperatures range from 400−1000° C. The oxide precursors were mixed with Li2O at 1:0.6 molar ratio (TM:Li=1:1.2), then the TM-Li mixture was mixed with sintering agent NaCl using a 1:1 weight ratio. The TM-Li—NaCl mixture was heated in a tube furnace filled by flowing pure oxygen gas. The temperature was increased at 10° C./min ramping rate. The mixture was maintained at 800° C. for 10 hours, then at 900° C. for an additional 5 hours. The product was cooled to room temperature. The sintered product (brick) was ground with an agate mortar and then transferred to a beaker for washing away NaCl. For each 15 g of sample, 30 g of water was added. The ground sample was stirred in water for two minutes. After ultrasonication for 2 minutes, the mixture was stirred for an additional 10 minutes to dissolve all residual NaCl. After filtration, the washed powders were heated at 80° C. in vacuum for 2 hours to remove water. The dried samples were further sintered at 580° C. in pure oxygen for four hours to restore some lost oxygen in the lattices. A schematic diagram of the process is shown inFIG.34.FIG.34also shows SEM images of the hydroxide precursor, the oxide precursor, and the single crystal product. In the absence of NaCl as a sintering agent, agglomerated of LiNi0.76Mn0.14Co0.1O2(NMC76) particles are formed instead of single crystals. NaCl is an inexpensive sintering agent, lowering the cost for scaling up the synthesis.FIGS.35A-35Bare SEM images of NMC76 prepared without NaCl sintering agent (FIG.35A) and with NaCl (FIG.35B). Without NaCl, the sample was polycrystalline (FIG.35A). With NaCl, the sample was monocrystalline (FIG.35B). FIG.36Ashows the initial charge-discharge curve of NMC76 prepared with and without NaCl.FIG.36Bshows the cycling stability of a thick single crystal NMC76 electrode (20 mg/cm2) in a full cell using graphite as the anode between 2.7-4.2V, charge at 0.1 C and discharge at 0.33 C. 1 C=200 mA/g.FIG.36Cshows the cycling stability of a single crystal NMC76 electrode (21.5 mg/cm2) in a full cell using graphite as the anode between 2.7-4.3V. Additional samples were prepared to compare washing with water and other solvents. The samples washed with deionized water displayed the best structural integrity and best electrochemical performance.FIGS.37A and37Bare SEM images of single crystal LiNi0.7Mn0.22Co0.08O2washed with water (37A) or formamide (FM) (37B).FIG.37Cshows the initial charge-discharge curves of the two samples. FIG.38is a schematic diagram comparing synthesis processes for polycrystalline and monocrystalline LiNiXMnyCo1-x-yO2. When synthesis proceeds directly from hydroxide precursors, a polycrystalline product is formed. However, when synthesis precedes via oxide precursors as described herein, single crystals are obtained. Example 3 Flash-Sintering Synthesis and Characterization of Single Crystal LiNi0.76M0.14C0.1O2(NMC76) Synthesis Hydroxide precursors were prepared as described in Example 2. The hydroxide precursors and LiOH were mixed in a molar ratio of 1:1.2 and ground with an agate mortar. The mixture was transferred to a flash sintering furnace and heated to 800° C. in a pure oxygen atmosphere at ramping rates ranging from 2° C./minute to 20° C./minute. The temperature was maintained at 800° C. for 10 hours. No sintering agent was used. Ramping rates up to 50° C./second or faster may be used. FIGS.39A-39Care SEM images of LiNi0.76Mn0.14Co0.1O2prepared at ramping rates of 2° C./min (39A), 10° C./min (39B), and 20° C./min (39C). As the ramping rate increased, the particle size increased. The agglomeration of particles was also significantly reduced when heating rate was increased at 20° C., leading to the formation of large single crystals (FIG.39C). At a ramping rate of 2° C., however, the particles are mostly aggregated together forming secondary particles instead of individual single crystals. A preheating process was found to facilitate flash sintering. Without wishing to be bound by a particular theory of operation, preheating reduces mismatch of reaction rates. The hydroxide precursor and lithium hydroxide mixtures were pre-heated at 480° C. for 5 hours before flash sintering. During this pre-heating treatment, mixed oxides (including Li oxide) formed. It was also found that the NMC single crystals derived from preheated precursors demonstrated smaller particle sizes which improved the electrochemical kinetics of single crystal NMC.FIGS.40A and40Bare SEM images of LiNi0.76Mn0.14Co0.1O2prepared without preheating (40A) or with preheating (40B) prior to flash sintering at a ramping rate of 50° C./minute.FIG.41shows the charge-discharge curves of the single crystal NMC samples prepared with and without the preheating process, showing a clear improvement in the reversible capacity with preheating. Example 4 Solid-State Synthesis and Characterization of Single Crystal LiNi0.76M0.14C0.1O2(NMC76) Synthesis A hydroxide precursor was prepared as follows. A 2 M solution of transition metal (TM) sulfate solution (Ni:Mn:Co=0.76:0.14:0.10 in molar ratio) was prepared in 805 g deionized water using Ni(SO4)2·6H2O, MnSO4·H2O, and Co(SO4)2·7H2O. Separately 160 g NaOH was dissolved in 500 g H2O. Concentrated NH3—H2O (28%) was diluted using DI H2O at 1:1 volume ratio. 3 L DI H2O and 50 mL concentrated NH3·H2O (28%) were added into the reactor as the starting solution. The reactor was heated to 50° C. The TMSO4solution, NaOH and NH3·H2O were pumped into the reactor at same time. The pump rates were 3 mL/min and 1 mL/min for TMSO4and NH3·H2O, respectively. The pH was controlled at 10.8. When all TMSO4solution was added into the reactor, the co-precipitated hydroxides were aged in the reactor for 30 hrs. The precipitates were filtered and washed with DI H2O·200 g DI H2O was used for every 100 g precipitates in washing for 3-5 times. After drying at 100° C. for 12 hours, the hydroxide precursor Ni0.76Mn0.14Co0.1(OH)2was obtained. Each batch produced ˜150 g of the hydroxide precursor. The Ni0.76Mn0.14Co0.1(OH)2was heated at 900° C. for 15 hours in an oxygen atmosphere with a 10° C./min ramping rate. The hydroxide precursors were converted to oxide precursors in this step. The oxide precursors were mixed with LiOH at a Li:TM molar ratio of 1:1.07 and annealed at 500° C. for 5 hours. The product was cooled to room temperature and ground. A second annealing was performed at 800° C. for 5 hours. After grinding again at room temperature, a third annealing was performed at 800° C. for an additional 5 hours. The final product was passed through a 400-mesh sieve and collected. FIGS.42A and42Bare SEM images of the small particles of Ni0.76Mn0.14Co0.1(OH)2and the Ni0.76Mn0.14Co0.1O2precursors, respectively.FIG.42Cis an SEM image of the single crystal LiNi0.76Mn0.14Co0.1O2. Use of small hydroxide precursor particles facilitates synthesis of the desired monocrystalline LiNi0.76Mn0.14Co0.1O2.FIG.43shows the first charge and discharge curve of the LiNi0.76Mn0.14Co0.1O2at 0.1 C between 2.7-4.4 V. Cathodes comprising the monocrystalline LiNi0.76Mn0.14Co0.1O2prepared by the molten salt method of Example 2 and the monocrystalline LiNi0.76Mn0.14Co0.1O2prepared by the solid-state method were compared.FIGS.44A and45Ashow the charge-discharge curves of the two cathodes. The monocrystalline LiNi0.76Mn0.14Co0.1O2prepared by the solid-state method delivered ˜184 mAh/g. It is expected that further development will provide a reversible capacity of NMC811 single crystals of >200 mAh/g, competitive with commercially available polycrystalline NMC, but with greatly enhance stability and safety.FIGS.44B and45Bare SEM images of the monocrystalline LiNi0.76Mn0.14Co0.1O2used in each cathode. The individual crystal size inFIG.44Bis ˜3 μm. The individual crystal size inFIG.45Bis ˜1 μm. Example 5 Synthesis and Characterization of Single Crystal LiNi0.76M0.12C0.1Mg0.01Ti0.01O2 Synthesis A hydroxide precursor was prepared as follows. A 2 M solution of transition metal (TM) sulfate solution (Ni:Mn:Co:Mg:Ti=0.76:0.12:0.10:0.01:0.01 in molar ratio) was prepared in 805 g deionized water using Ni(SO4)2·6H2O, MnSO4·H2O, Co(SO4)2·7H2O, MgSO4, and TiOSO4. Separately 160 g NaOH was dissolved in 400 g H2O. Concentrated NH3·H2O (28%) was diluted using DI H2O at 1:1 volume ratio. 1.5 L DI H2O and 50 mL concentrated NH3·H2O (28%) were added into the reactor as the starting solution and preheated to 50° C. The TMSO4solution, NaOH and NH3·H2O were pumped into the reactor at same time. The pump rates were 3 mL/min and 1 mL/min for TMSO4and NH3.H2O, respectively. The pH was controlled at 11.5. When all TMSO4solution was added into the reactor, the co-precipitated hydroxides were aged in the reactor for 30 hrs at 50° C. The precipitates were filtered and washed with DI H2O·200 g DI H2O was used for every 100 g precipitates in washing for 3-5 times. After drying at 100° C. for 12 hours, Mg—Ti-doped hydroxide precursors were obtained. The doped hydroxide precursors were heated at 900° C. for 15 hours in an oxygen atmosphere with a 10° C./minute ramping rate. The hydroxide precursors were converted to oxide precursors in this step. The oxide precursors were mixed with Li2O (1:1.4 molar ratio). NaCl was then added in a NaCl:TM-Li mixture of 1:1.1 by weight. The resulting mixture was then annealed at 800° C. for 10 hours and then 900° C. for 5 hours. The product was cooled to room temperature. The sintered product was ground with an agate mortar and then transferred to a beaker for washing away NaCl. For each 15 g of sample, 30 g of water was added. The ground sample was stirred in water for two minutes. After ultrasonication for 2 minutes, the mixture was stirred for an additional 10 minutes to dissolve all residual NaCl. After filtration, the washed powders were heated at 80° C. in vacuum for 2 hours to remove water. The dried samples were further sintered at 580° C. in pure oxygen for four hours to restore some lost oxygen in the lattices and provide LiNi0.76Mn0.12Co0.1Mg0.01Ti0.01O2, which includes 1 at % Mg and 1 at % Ti. The modified single crystal has a slightly reduced particle size at ca. 2 μm with a very dense structure (FIG.46). The modified single crystal has a reduced peak ration of (003)/(104), suggesting increased cation disorder (FIG.47A). Peak shifting to a lower angle in the modified single crystal indicates expansion of the crystal lattice compared to pristine single crystal NMC76 (47B). FIGS.48A and48Bcompare the charge-discharge curves (48A) and cycling stability (48B) of LiNi0.76Mn0.14Co0.1O2and LiNi0.76Mn0.12Co0.1Mg0.01Ti0.01O2. The modified single crystal NMC76 delivered at slightly slower capacity at ca. 191 mAh/g capacity compared to the pristine single crystal NMC76 in a full cell tested at relevant conditions—high mass loading and thick electrodes. The modified NMC76 displayed improved cycling stability with 81.8% capacity retention after 200 cycles, compared to pristine NMC76 with 72.0% capacity retention. As shown inFIG.49, no obvious cracking was observed in the modified NMC76 after cycling. Example 6 Pouch Cell Design Table 5 provides parameters for 2.2-2.3 Ah pouch cells using graphite/NMC811 and graphite/NMC955 chemistries. Coin cells with similar cathode loading, areal capacity, porosity, press density, N/P ratio, and the like, will be used for initial testing. Replacing graphite with Si or Li metal may increase the cell level energy to 300-350 Wh/kg with the single crystal NMC cathode. TABLE 5Cell design parameters for 2.2-2.3 Ah pouchcell designs based on graphite/NMC chemistryMaterialNMC811NMC955Cathode1stdischarge capacity (mAh g−1)200210Active material loading96%96%Cathode weight (each side)18.318.3(mg cm−2)Areal capacity (each side)3.53.7(mAh cm−2)Electrode press density (g cm−3)3.03.0Electrode thickness (each6161side) (μm)Number of double side layers*1616Al foilThickness (μm)1010AnodeMaterialgraphitegraphiteSpecific capacity (mAh g−1)360360Active material loading96%96%Coating weight (each side)11.412.0(mg cm−2)Areal capacity (each side)3.94.1(mAh cm−2)N/P ratio (cell balance) (μm)1.121.12Cu foilThickness/μm88ElectrolyteElectrolyte/Capacity ratio3.53.4(g Ah−1)SeparatorThickness/μm2020Packet foilThickness/μm8888CellAverage voltage (1stcycle) (V)3.653.7Capacity (1stcycle) (Ah)2.22.3Cell energy density (Wh kg−1)250264*number of cathodes comprising Al foil sandwiched between two NMC coating layers In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims. | 104,712 |
11862795 | The invention is further illustrated by working examples. general remark: Residual LiOH and Li2CO3may be determined as follows. 1 g of electrode active material is mixed with 40 mL of deionized water in a beaker and stirred for minutes. Then the aqueous phase is separated from the solid by using a syringe filter and added to a 100 mL beaker. 15 mL of deionized water is added and the obtained solution is titrated with a 0.1 M aqueous solution of hydrochloric acid. The amounts of LiOH and Li2CO3in % by weight (w(LiOH)and w(Li2CO3)) are calculated using the following equations. w(LiOH)=((VEP1−(VEP2−VEP1))·CHCl*tHCl·MLiOH·100)/(msample·1000) with VEP1and VEP2: volume at the inflection point/equivalence point in ml CHCl: concentration of the standard solution in mol/l tHCl: titer of the standard solution MLiOH: Molar Mass of LiOH (23.95 g/mol) in g/mol msample: mass of sample in g (generated by reweighing) 100: conversion factor to get the result in g/100 g 1000: conversion factor to get the sample weight in mg and w(Li2CO3)=((VEP2−VEP1)·cHCl·tHCl·MLi2CO3·100)/(msample·1000) with VEP1and VEP2: volume at the inflection point/equivalence point in ml cHCl: concentration of the standard solution in mol/l tHCl: titer of the standard solution MLi2CO3: Molar Mass of Li2CO3(73.89 g/mol) in g/mol msample: mass of sample in g (generated by reweighing) 100: conversion factor to get the result in g/100 g 1000: conversion factor to get the sample weight in mg I. Manufacture of a Cathode Active Material I.1 Manufacture of a Precursor A stirred tank reactor was filled with deionized water and 49 g of ammonium sulfate per kg of water. The solution was tempered to 55° C. and a pH value of 12 was adjusted by adding an aqueous sodium hydroxide solution. The co-precipitation reaction was started by simultaneously feeding an aqueous transition metal sulfate solution and aqueous sodium hydroxide solution at a flow rate ratio of 1.8, and a total flow rate resulting in a residence time of 8 hours. The transition metal solution contained Ni, Co and Mn sulfates at a molar ratio of 8.5:1.0:0.5 and a total transition metal concentration of 1.65 mol/kg. The aqueous sodium hydroxide solution was a 25 wt. % sodium hydroxide solution and 25 wt. % ammonia solution in a weight ratio of 6. The pH value was kept at 12 by the separate feed of an aqueous sodium hydroxide solution. Beginning with the start-up of all feeds, mother liquor was removed continuously. After 33 hours all feed flows were stopped. The mixed transition metal (TM) oxyhydroxide precursor was obtained by filtration of the resulting suspension, washing with distilled water, drying at 120° C. in air and sieving. I.2 Lithiated Cathode Active Material (CAM) The mixed transition metal (TM) oxyhydroxide precursor obtained as described above (transition metal composition Ni0.85Co0.1Mn0.05) was mixed with Al2O3to obtain a concentration of 0.3 mole-% Al relative to Ni+Co+Mn+Al, and with LiOH monohydrate to obtain a Li/(TM+Al) molar ratio of 1.06. The resultant mixture was heated to 760° C. and kept for 10 h in a forced flow of a mixture of 60% oxygen and 40% nitrogen (by volume). After cooling to ambient temperature the powder was deagglomerated and sieved through a 32 μm mesh to obtain the Al-doped base CAM.1. II. Treatment of CAM.1 with Water II.1 Treatment of CAM.1 According to the Present Invention CAM.1 was added to demineralized water at ambient temperature in a weight ratio of 1.33 (CAM.1:water). After a 3 minute stirring of the resultant slurry the liquid was immediately removed by filtration through a Buchner funnel. The filter cake so obtained was dried at 40° C. in a membrane pump vacuum overnight followed by a 2nddrying step at 200° C. for 14 hours in membrane pump vacuum as well. CAM.1-W was obtained. The pH value of the filtrate was 12.46. Even better results are obtained if the water treatment is performed on a Buchner funnel for three minutes, and then filtration is started. Even better results are obtained if the water treatment is performed on a Buchner funnel for three minutes, and filtration is started simultaneously the water treatment, that is, water addition and removal of said aqueous medium are started simultaneously. II.2 Comparative Treatment Example II.1 was repeated but the stirring lasted 35 minutes before filtration was commenced. C-CAM.1-W was obtained. The pH value of the filtrate was 12.50. TABLE 1Residual Li values obtained by titration and electrochemicalperformance of Examples II.1 and II.210.1 C dischargeLiOHLi2CO3capacityResistanceSample(wt.-%)(wt.-%)[mAh/g](Ω · cm2)CAM.1-W0.07530.2778186.6166.0C-CAM.1-W0.07430.3252183.4199.1 Determination of residual LiOH and Li2CO3has been carried out as described above. The electrochemical testing was carried out in coin half cells according to the following procedure to obtain a 0.1 C discharge capacity and a resistance as depicted in Table 1. To produce a cathode, the following ingredients were blended under stirring with one another until a lump-free paste was obtained: Electrode active material, a 10 wt.-% solution of polyvinylidene difluoride (“PVdF”), commercially available as Kynar HSV 900 from Arkema Group, dissolved in N-ethylpyrrolidone (NEP), carbon black, BET surface area of 62 m2/g, commercially available as “Super C 65” from Imerys, graphite, commercially available as “SFG6L” from Imerys and additional NEP to obtain a solid content of 62% and a ratio of electrode active material:carbon:graphite:PVdF of 93:1.5:2.5.3 by weight. Cathodes were prepared as follows: On a 20 μm thick aluminum foil, the above paste was applied with a doctor blade followed by drying and calendaring to obtain about a loading of 10.3 mg/cm2and a density of 3.47 g/cm3. Disc-shaped cathodes were punched out of the foil. The cathode discs were then weighed, dried for 16 hours in a vacuum oven at 105° C. and introduced into an argon glove box without exposure to ambient air. Then, cells with the cathodes were built. Electrochemical testing was conducted in coin-type cells. The electrolyte used was a 1 M solution of LiPF6in dimethyl carbonate/ethylene carbonate (weight ratio 1:1). Anode: lithium, separated from the cathode by a glass-fiber separator. The coin cells are charged and discharged in a voltage range from 3.0 to 4.3V. After two cycles at a C-Rate of 0.1 C for charge and discharge and five cycles at 0.5 C charge and 0.2 C discharge the 0.1 C discharge capacity according to Table 1 is obtained by 0.5 C charge and 0.1 C discharge in the 8thcycle. Starting from the 9th cycle the following charge/discharge cycles are carried out until the 19thcycle is reached: 0.5 C/0.2 C, 0.5 C/0.5 C, 0.5 C/1 C, 0.5 C/2 C, 0.5 C/3 C, 0.5 C/5 C, 0.5 C/7 C, 200.5 C/10 C, 0.5 C/0.5 C and 0.5 C/0.2 C. In the 19thcycle the cell is charged at 0.5 C and discharged with 0.2 C for 30 seconds. Then a 2 C discharge pulse is applied for 10 seconds. From the voltage drop observed during this pulse (E(0 s)-E(10 s)) the resistance according to Table 1 (R) is calculated according to the following formula. R=(E(0 s)−E(10 s))/I(10 s)·electrode area with I(10 s) being the current during the 2 C pulse lasting for 10 seconds. The reduced capacity and the increased resistance which is found by this method for the comparative treatment in comparison to the inventive treatment is reflecting a more pronounced damage of the cathode material caused by the comparative treatment. If performed on larger scale, Example II.1 may be performed in a suction filter with stirrer. | 7,575 |
11862796 | DETAILED DESCRIPTION Conventional positive-electrode active materials may fail to achieve both sufficiently high durability and sufficiently high output characteristics for a non-aqueous electrolyte secondary battery. One or more aspects of the present disclosure are directed to a positive-electrode active material for a non-aqueous electrolyte secondary battery with both high durability and high output characteristics, and a method of producing the positive-electrode active material. Specific means for solving the problem are as described below, and the present disclosure includes the aspects described below. A first aspect is a method of producing a positive-electrode active material for a non-aqueous electrolyte secondary battery, including obtaining a precipitate containing nickel and manganese from a solution containing nickel and manganese, heat-treating the resulting precipitate at a temperature of from 850° C. to less than 1100° C. to obtain a first heat-treated product, mixing the first heat-treated product and a lithium compound, and heat-treating the resulting lithium-containing mixture at a temperature of from 550° C. to 1000° C. to obtain a second heat-treated product. The second heat-treated product contains lithium transition metal composite oxide particles. The lithium transition metal composite oxide particles have an average particle diameter, DSEM, based on SEM observation of from 0.5 μm to less than 3 μm, and the ratio of a particle diameter corresponding to 50% in its volume-based cumulative particle size distribution, or D50, to the DSEM, or D50/DSEM, of 1 to 2.5. The lithium transition metal composite oxide particle has a spinel structure based on nickel and manganese. A second aspect is a positive-electrode active material for a non-aqueous electrolyte secondary battery containing lithium transition metal composite oxide particles. The lithium transition metal composite oxide particles have a DSEMof from 0.5 μm to less than 3 μm, and the ratio of D50/DSEMof from 1 to 2.5, where DSEMis an average particle diameter based on SEM observation and D50is a particle diameter corresponding to 50% in its volume-based cumulative particle size distribution. The lithium transition metal composite oxide particle has a spinel structure based on nickel and manganese. The embodiments of the present disclosure will now be described. However, the embodiments described below are for embodying the technical concept of the present invention, and the present invention is not limited to the positive-electrode active material for a non-aqueous electrolyte secondary battery and the production method described below. The term “step” as used herein encompasses not only an independent step but also a step in which the anticipated effect of this step is achieved, even if the step cannot be clearly distinguished from another step. For the amount of each component contained in a composition, when a plurality of substances corresponding to the component are present in the composition, the amount of the component means the total amount of the corresponding substances present in the composition unless otherwise specified. The pHs below are measured at 25° C. Method of Producing Positive-Electrode Active Material for Non-Aqueous Electrolyte Secondary Battery The method of producing a positive-electrode active material for a non-aqueous electrolyte secondary battery according to the present embodiment comprises obtaining a precipitate containing nickel and manganese from a solution containing nickel and manganese (hereinafter also referred to as “precipitate generation step”), heat-treating the resulting precipitate at a temperature of from 850° C. to less than 1100° C. to obtain a first heat-treated product (hereinafter also referred to as “first heat treating step”), mixing the first heat-treated product and a lithium compound, and heat-treating the resulting lithium-containing mixture at a temperature of from 550° C. to 1000° C. to obtain a second heat-treated product (hereinafter also referred to as “second heat treating step”). The second heat-treated product contains a lithium transition metal composite oxide particles. The lithium transition metal composite oxide particles have a DSEMof from 0.5 μm to less than 3 μm, and a ratio of D50/DSEMof 1 to 2.5, where DSEMis an average particle diameter based on SEM observation and D50is a particle diameter corresponding to 50% in its volume-based cumulative particle size distribution. The lithium transition metal composite oxide particle has a spinel structure based on nickel and manganese. The second heat-treated product containing lithium transition metal composite oxide particles is produced by heat-treating a precipitate containing nickel and manganese at a specific temperature to obtain the first heat-treated product, and then heat-treating a mixture containing the first heat-treated product and a lithium compound at a specific temperature. This enables effective production of lithium transition metal composite oxide particles having an average particle diameter based on SEM observation, DSEM, of 0.5 μm to less than 3 μm, which is smaller than the average particle diameters of conventional products, and a ratio of D50/DSEMof 1 to 2.5, where D50is a particle diameter corresponding to 50% in its volume-based cumulative particle size distribution, with one or a few primary particles. The precipitate containing nickel and manganese is formed from secondary particles as an aggregate of a plurality of primary particles. Heat-treating the precipitate allows the particles to be sintered together. This results in composite oxide particles containing secondary particles with a decreased number of primary particles, or primary particles with a larger-size. In the present embodiment, setting the heat-treating temperature in the first heat-treating step to a specific range produces composite oxide particles containing primary particles with a size suitable for obtaining lithium transition metal composite oxide particles having an intended average particle diameter. The composite hydroxide particles obtained in the first heat-treating step seemingly have a weak sintering degree among the particles. This may allow, when lithium transition metal composite oxide particles are formed, the resulting second heat-treated product to have an improved disintegratability and a ratio of D50/DSEMin a specific range. The lithium transition metal composite oxide particles according to the present embodiment have a smaller contact particle boundary area among primary particles, and a uniform particle diameter. Thus, when pressed at a high pressure to form an electrode, the particles are believed to be less broken. This seemingly allows the voids between the particles to be uniform. To form a secondary battery, an electrolyte is filled in the voids among the particles to form a diffusion path for lithium ions. The diffusion paths having a uniform size can reduce variation among particles during charge and discharge. This is believed to allow the lithium transition metal composite oxide particles having a smaller contact particle boundary area among primary particles to have high output characteristics along with high polar plate filling property. Also, a smaller contact particle boundary area is believed to help reduce breakage of the particles during charge and discharge cycles and achieve high durability. An average particle diameter, DSEM, based on SEM observation is obtained by selecting 100 particles with recognizable outlines in an image obtained by an SEM at a magnification of 1000 to 10000 in accordance with the particle diameter, calculating the sphere equivalent diameters of the selected particles using image processing software, and obtaining an arithmetic mean value of the resulting sphere equivalent diameters. Further, a 50% particle diameter, D50is obtained as a particle diameter corresponding to a cumulative 50% from the small diameter side in its volume-based cumulative particle size distribution measured using a laser diffraction particle size analyzer under a wet condition. In the same manner, the later-described 95% particle diameter, D95, 90% particle diameter, D90, 10% particle diameter, D10, and 5% particle diameter, D5are particle diameters corresponding respectively to cumulative 95%, cumulative 90%, cumulative 10%, and cumulative 5% from the small diameter side. Precipitate Generation Step In the precipitate generation step, a precipitate containing nickel and manganese is obtained from a solution containing nickel and manganese using a coprecipitation method. The precipitate obtained in the precipitate generation step preferably contains at least one selected from the group consisting of composite hydroxide composite and carbonate containing nickel and manganese in an intended ratio. The precipitate generation step may include, for example, a seed generation step and a crystallization step. For the precipitate generation step, for example, one may refer to Japanese Patent Application Publication No. 2003-292322, and Japanese Patent Application Publication No. 2011-116580. In the seed generation step, a liquid medium containing a seed crystal can be prepared by adjusting the pH of a mixture solution containing nickel ions and manganese ions in an intended ratio to, for example, 11 to 13. The seed crystal can, for example, include hydroxide particles containing nickel and manganese in an intended ratio. The mixture solution can be prepared by dissolving a nickel salt and a manganese salt in water in an intended ratio. Examples of the nickel salt and the manganese salt may include sulfate, nitrate, and hydrochloride. The mixture solution may contain other metal salts in addition to the nickel salt and the manganese salt as appropriate. The seed generation step can be carried out at a temperature of, for example, from 40° C. to 80° C. The seed generation step can be carried out in a low oxidizing atmosphere, and, for example, preferably maintains the oxygen concentration at 10% by volume or less. In the crystallization step, the generated seed crystal is allowed to grow to form a precipitate as particles containing nickel and manganese with intended characteristics. The seed crystal can be grown by, for example, adding a mixture solution containing nickel ions and manganese ions to a liquid medium containing the seed crystal while maintaining the pH at, for example, from 7 to 12, and preferably from 7.5 to 11.5. The mixture solution may be added in a time period of, for example, 1 to 24 hours, and preferably 3 to 18 hours. The crystallization step can be carried out at a temperature of, for example, from 40° C. to 80° C. The crystallization step can be carried out in the same atmosphere as that in the seed generation step. In the precipitate generation step, the pH may be adjusted using, for example, an acidic aqueous solution, such as a sulfuric acid aqueous solution or a nitric acid aqueous solution; or an alkaline aqueous solution, such as an aqueous sodium hydroxide solution or an aqueous ammonia. In addition to adjusting the pH, carbonic acid may be introduced in the precipitate generation step. Introducing carbonic acid produces carbonate containing nickel and manganese having a smaller primary size as a precipitate. Thus, a second heat-treated product with a smaller DSEMcan be more easily obtained. Carbonic acid may be introduced, for example, by introducing carbonic acid gas, or by adding carbonate or an aqueous solution of carbonate. Carbonic acid may be introduced in an amount appropriately selected in accordance with the amount of the target precipitate. The crystallization step is preferably carried out in a manner to allow the precipitate containing nickel and manganese to have an average particle diameter in an intended range. The precipitate has an average particle diameter of, for example, 0.1 μm or more, and preferably 1 μm or more. Also, the precipitate has an average particle diameter of, for example, 10 μm or less, and preferably 6 μm or less. The average particle diameter of the precipitate is determined as D50corresponding to cumulative 50% point from the small diameter side in its volume-based cumulative particle size distribution. First Heat-Treating Step In the first heat-treating step, the precipitate obtained in the precipitate generation step is heat-treated at a temperature of from 850° C. to less than 1100° C. to obtain a first heat-treated product. The precipitate is heat-treated preferably at a temperature of 900° C. or more, or 950° C. or more. Also, the precipitate is heat-treated preferably at a temperature of 1080° C. or less, or 1060° C. or less. Heat-treating the precipitate in this range can yield composite oxide particles suitable for producing lithium transition metal composite oxide particles. The heat-treating can be carried out, for example, by increasing the temperature from room temperature to a predetermined temperature, and then maintaining the temperature for a predetermined time period. The temperature may be increased to the predetermined temperature at an increase rate of, for example 1.5° C./min to 10° C./min. The heat-treating in the first heat-treating step is carried out in a time period of, for example, from 0.5 hour or more, and preferably 5 hours or more, and also, for example, 72 hours or less, and preferably 48 hours or less. The heat-treating can be carried out, for example, in an air atmosphere. The first heat-treating step can be carried out using, for example, a box furnace, a rotary kiln furnace, a pusher furnace, or a roller hearth kiln furnace. The precipitate to be subjected to the first heat-treating step may undergo dry treatment before the heat-treating step. The dry treatment is to remove at least a part of moisture contained in the precipitate, and preferably reduces the moisture content of the precipitate to 10% by weight or less. The dry treatment is carried out by, for example, heating at a temperature of less than 850° C., preferably at 500° C. or less, and more preferably at 350° C. or less. Also, the dry treatment may be carried out at a temperature of, for example, at 100° C. or more, and preferably at 200° C. or more. The dry treatment may be carried out in a time period of, for example, from 0.5 hour to 48 hours, and preferably from 5 hours to 24 hours. The dry treatment may be carried out, for example, in an air atmosphere, or may be carried out under reduced pressure. The first heat-treated product obtained through the heat-treating may further undergo, for example, cracking treatment, dissociating treatment, or classifying treatment as appropriate. If the first heat-treated product undergoes at least dissociating treatment, lithium transition metal composite oxide particles having, for example, an intended particle size distribution can more efficiently be produced. Dissociating treatment, if carried out, is preferably carried out in a manner not to pulverize primary particles forming the composite oxide particles in the first heat-treated product. Dissociating treatment can be carried out using, for example, a jet mill, a resin ball mill, a roller mill, a pin mill, or a planetary mill. If carried out with a jet mill, dissociating treatment can be carried out under the dissociating conditions of a supply pressure of from 0.1 MPa to 0.6 MPa, and a dissociating pressure of from 0.1 MPa to 0.6 MPa. If classifying treatment is carried out, for example, a dry sieve with an intended opening can be used. The first heat-treated product contains, for example, composite oxide particles containing nickel and manganese. The composite oxide particles have a D50of, for example, from 1 μm to 5 μm, and preferably from 1.1 μm to 4 μm. Also, a particle diameter, D10corresponding to 10%, is, for example, from 0.5 μm to 3 μm, and preferably from 0.6 μm to 2 μm and a particle diameter, D90, corresponding to 90% in its volume-based cumulative particle size distribution is, for example, from 2 μm to 7 μm, and preferably from 2.1 μm to 5 μm. The ratio of D90/D10shows the breadth of the particle size distribution, and the smaller the value, the more uniform the particle diameter is. D90/D10is, for example, 3 or less, and preferably 2.5 or less. With composite oxide particles having a particle size distribution in this range, lithium transition metal composite oxide particles with improved characteristics can more efficiently be produced. The lower limit of D90/D10is, for example, 1.2 or more. Second Heat-Treating Step In the second heat-treating step, the first heat-treated product and a lithium compound are mixed, and the resulting lithium-containing mixture (hereinafter also referred to as “first mixture”) is heat-treated at a temperature of from 550° C. to 1000° C. to obtain a second heat-treated product. The second heat-treated product contains lithium transition metal composite oxide particles. The lithium transition metal composite oxide particles have a DSEMof from 0.5 μm to less than 3 μm, and a D50/DSEMof from 1 to 2.5. The lithium transition metal composite oxide particle has a spinel structure based on nickel and manganese. A non-aqueous electrolyte secondary battery including a positive-electrode active material for a non-aqueous electrolyte secondary battery containing lithium transition metal composite oxide particles with such specific particle characteristics can achieve both high durability and high output characteristics. Examples of the lithium compound to be mixed with the first heat-treated product include lithium hydroxide, lithium carbonate, and lithium oxide. The lithium compound to be mixed has a D50of, for example, from 0.1 μm to 100 μm, and preferably from 2 μm to 20 μm. The ratio of the total number of moles of lithium to the total number of moles of metal elements included in the first heat-treated product in the first mixture is, for example, from 0.5 to 0.65, and preferably from 0.55 to 0.63. The first heat-treated product and the lithium compound can be mixed using, for example, a high-speed shearing mixer. The first mixture may further contain other metals in addition to lithium, nickel, and manganese. Examples of the other metals include Al, Mg, Si, Ti, Cr, Fe, Co, Cu, Zn, Ga, and Nb, and at least one selected from the group consisting of these is preferable, and at least one selected from the group consisting of Al, Ti, Cr, Fe, and Co is more preferable. When the first mixture contains other metals, a simple metal or a metal compound of other metals is mixed together with the first heat-treated product and a lithium compound to obtain the first mixture. Examples of the metal compounds containing other metals include oxide, hydroxide, chloride, nitride, carbonate, sulfate, nitrate, acetate, and oxalate. When the first mixture contains other metals, the ratio of the total number of moles of the metal elements forming the first heat-treated product to the total number of moles of other metal elements included in the first heat-treated product is, for example, from 1:0.015 to 1:0.1, and preferably from 1:0.025 to 1:0.05. The first mixture is heat-treated at a temperature of from 550° C. to 1000° C., preferably from 600° C. or more 950° C., and more preferably from 750° C. to 950° C. Although the lithium-containing mixture may be heat-treated at a single temperature, the mixture is preferably heated at multiple temperatures in consideration of the electric discharge volume at a high voltage. When heat-treated at multiple temperatures, the mixture can be heat-treated at a temperature of, for example, from 750° C. to 1000° C., and then at a temperature of from 550° C. to less than 750° C. The mixture may be heat-treated, for example, from 0.5 hour to 48 hours. When heat-treated at multiple temperatures, each heating can last from 0.2 hour to 47 hours. The heat-treating may be carried out in an air atmosphere, or an oxygen-containing atmosphere. The heat-treating may be carried out using, for example, a box furnace, a rotary kiln furnace, a pusher furnace, or a roller hearth kiln furnace. The second heat-treated product obtained through the heat-treating may further undergo, for example, cracking treatment, dissociating treatment, or classifying treatment as appropriate. This enables intended lithium transition metal composite oxide particles to be obtained. Dissociating treatment, if carried out, is preferably carried out in a manner not to pulverize primary particles forming the lithium transition metal composite oxide particles contained in the second heat-treated product. Dissociating treatment can be carried out using, for example, a jet mill, a resin ball mill, a roller mill, a pin mill, or a planetary mill. If carried out with a jet mill, dissociating treatment can be carried out under the dissociating conditions of a supply pressure of from 0.1 MPa to 0.6 MPa, and a dissociating pressure of from 0.1 MPa to 0.6 MPa. If classifying treatment is carried out, for example, a dry sieve with an intended opening can be used. The second heat-treated product contains lithium transition metal composite oxide particles having a DSEMof from 0.5 μm to less than 3 μm. For improved output characteristics, the particles preferably have a DSEMof from 0.7 μm to 2.5 μm, and more preferably from 1 μm to 2 μm. The ratio of D50/DSEMis from 1 to 2.5. D50/DSEMbeing 1 indicates that the particles are formed from single particles, and the closer to 1, the smaller the number of the primary particles is. D50/DSEMis preferably 2 or less for improved durability. The ratio of D95/D5indicates the breadth of the particle size distribution. The smaller the value, the more uniform the particle diameter of the particle is. The ratio of D95/D5is preferably 4 or less, and more preferably 3 or less. The lower limit of the ratio of D95/D5is, for example, 1.1 or more. Further, the ratio of D90/D10is preferably 2.5 or less, and more preferably 2.3 or less. The lower limit of the ratio of D90/D10is for example, 1.1 or more. With the ratio of D95/D5and/or the ratio of D90/D10being in a specific range, the lithium transition metal composite oxide particles have a uniform particle size. Thus, the lithium transition metal composite oxide particles have less variation among particles in the depth of charge and discharge due to current concentration on a part of the particles even when the cycle is carried out at a high current density. Thus, the particles are seemingly less locally deteriorated during charge-discharge cycles with resistance growth due to current concentration being suppressed. Niobium Adhesion Step A method of producing a positive-electrode active material for a non-aqueous electrolyte secondary battery according to the present embodiment may further include mixing the second heat-treated product or the second heat-treated product in a dispersed state (hereinafter also simply collectively referred to as “second heat-treated product”), and simple niobium or a niobium compound, and heat-treating the resulting niobium-containing mixture (hereinafter also referred to as “second mixture”). This allows a substance containing niobium to adhere to the surfaces of lithium transition metal composite oxide particles contained in the second heat-treated product. A non-aqueous electrolyte secondary battery including the positive-electrode active material for a non-aqueous electrolyte secondary battery containing lithium transition metal composite oxide particles to which a substance containing niobium is adhered can achieve further improved durability. Examples of the niobium compound to be contained in the second mixture include niobium oxide, niobium chloride, niobium nitride, niobium carbide, niobium oxalate, and niobium alkoxide. Simple niobium or the niobium compound to be mixed has a particle diameter, D50of, for example, from 0.001 μm to 1 μm, and preferably from 0.005 μm to 0.1 μm. The mixing ratio of niobium, as a metal niobium, to the lithium transition metal composite oxide in the second mixture is, for example, from 0.1% by mol to 3% by mol, and preferably from 0.5% by mol to 2% by mol. The second heat-treated product and simple niobium or the niobium compound can be mixed, for example, by adding a dispersed substance containing niobium to the second heat-treated product while stirring the second heat-treated product with a mixer. The resulting second mixture is heat-treated to obtain a third heat-treated product containing lithium transition metal composite oxide particles to which the niobium-containing substance is adhered. The second mixture is heat-treated at a temperature of, for example, from 300° C. to 800° C., and preferably from 350° C. to 700° C. The second mixture is heat-treated in a time period of, for example, from 0.5 hour to 48 hours. The second mixture is heat-treated in an air atmosphere or an oxygen-containing atmosphere. The second mixture is heat-treated using, for example, a box furnace, a rotary kiln furnace, a pusher furnace, or a roller hearth kiln furnace. The third heat-treated product obtained through the heat-treating may undergo, for example, cracking treatment, dissociating treatment, or classifying treatment as appropriate. In the present embodiment, the lithium transition metal composite oxide included in the lithium transition metal composite oxide particles in the second heat-treated product has a spinel structure based on nickel and manganese, and preferably has a composition represented by the formula below: LixNipMnqM1rO4 In the formula, x, p, q, and r satisfy 1≤x≤1.3, 0.3≤p≤0.6, 1.2≤q≤1.7, 0≤r≤0.2, and p+q+r≤2, and M1is at least one selected from the group consisting of Al, Mg, Si, Ti, Cr, Fe, Co, Cu, Zn, Ga, and Nb. The lithium transition metal composite oxide having this specific composition can produce a non-aqueous electrolyte secondary battery with further improved durability and output characteristics. Positive-Electrode Active Material for Non-Aqueous Electrolyte Secondary Battery The positive-electrode active material for a non-aqueous electrolyte secondary battery according to the present embodiment (hereinafter also simply referred to as “the positive-electrode active material”) contains lithium transition metal composite oxide particles having a DSEMof 0.5 μm to less than 3 μm, and a ratio of D50/DSEMof from 1 to 2.5. The lithium transition metal composite oxide particles preferably have a DSEMof from 1 μm to 2 μm, and a ratio of D50/DSEMof preferably from 1 to 2. A non-aqueous electrolyte secondary battery including the positive-electrode active material containing lithium transition metal composite oxide particles having those specific particle characteristics can achieve durability and output characteristics both at a high level The lithium transition metal composite oxide particles contained in the positive-electrode active material have a ratio of D95/D5of preferably 4 or less, and more preferably 3 or less. The lower limit of the ratio of D95/D5is, for example, from 1.1 or more. The lithium transition metal composite oxide particles also have a ratio of D90/D10of 2.5 or less, and more preferably 2.3 or less. The lower limit of the ratio of D90/D10is, for example, 1.1 or more. The lithium transition metal composite oxide particles having a ratio of D95/D5and/or a ratio of D90/D10within the specific range have a uniform particle size. Thus, the lithium transition metal composite oxide particles have less variation among particles in the depth of charge and discharge due to partial current concentration even when the cycle is carried out with a high current density. Thus, the particles are less locally deteriorated during charge-discharge cycles with resistance growth due to current concentration being suppressed. The lithium transition metal composite oxide particles contained in the positive-electrode active material preferably contain lithium transition metal composite oxide particles onto the surfaces of which a substance containing niobium is attached. A non-aqueous electrolyte secondary battery including that positive-electrode active material can achieve further improved durability. The lithium transition metal composite oxide included in the lithium transition metal composite oxide particles contained in the positive-electrode active material has a spinel structure based on nickel and manganese, and preferably has a composition represented by the formula below: LixNipMnqM1rO4 In the formula, x, p, q, and r satisfy 1≤x≤1.3, 0.3≤p≤0.6, 1.2≤q≤1.7, 0≤r≤0.2, and p+q+r≤2, and M1is at least one selected from the group consisting of Al, Mg, Si, Ti, Cr, Fe, Co, Cu, Zn, Ga, and Nb. The positive-electrode active material according to the present embodiment can be produced by, for example, the method described above. Electrode for Non-Aqueous Electrolyte Secondary Battery An electrode for a non-aqueous electrolyte secondary battery includes a current collector, and a positive-electrode active material layer containing a positive-electrode active material for a non-aqueous electrolyte secondary battery produced by the above-described method and arranged on the current collector. A non-aqueous electrolyte secondary battery containing such an electrode can achieve both high durability and high output characteristics. Examples of the material for the current collector include aluminum, nickel, and stainless steel. The positive-electrode active material layer can be formed by mixing the positive-electrode active material, a conductive material, and a binder with a solvent to obtain a positive electrode mixture, and applying the positive electrode mixture on the current collector, and subjecting the layer to, for example, dry treatment and pressure treatment. Examples of the conductive material include natural graphite, artificial graphite, and acetylene black. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, and polyamide acryl resin. Non-Aqueous Electrolyte Secondary Battery The non-aqueous electrolyte secondary battery includes the positive electrode for a non-aqueous electrolyte secondary battery. In addition to the positive electrode for a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery mainly includes a negative electrode for a non-aqueous secondary battery, the non-aqueous electrolyte, and a separator. For the negative electrode, the non-aqueous electrolyte, and the separator in a non-aqueous electrolyte secondary battery, those described for a non-aqueous secondary battery in, for example, Japanese Patent Application Publication No. 2002-075367, Japanese Patent Application Publication No. 2011-146390, and Japanese Patent Application Publication No. 2006-012433, which three Japanese Patent Application Publications are incorporated herein in their entirety by reference, can be used as appropriate. EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. The method of determining physical properties in examples and comparative examples below will now be described. The volume-based cumulative particle size distribution of particles was measured using a laser diffraction particle size analyzer (SALD-3100 by Shimadzu), and the particle diameters D5, D10, D50, D90, and D95were determined as particle diameters corresponding to cumulative 5%, 10%, 50%, 90% and 95% from the small diameter side of the volume-based cumulative particle size distribution. The average particle diameter, DSEM, based on SEM observation is obtained by selecting 100 particles with recognizable outlines in an image obtained by an SEM at a magnification of 1000 to 10000, calculating the sphere equivalent diameters of the selected particles using image processing software (ImageJ), and obtaining an arithmetic mean value of the resulting sphere equivalent diameters. D5, D10, D50, D90, D95and DSEMare hereinafter also collectively referred to as, for example, the average particle diameters. Example 1 Seed Generation Step Into a reaction vessel, 30 kg of water was charged, nitrogen gas was passed through the water with stirring, and the temperature within the vessel was set to 50° C. The oxygen concentration in the space within the vessel was maintained to 10% by volume or less, and then 197 g of a 25% by mol aqueous solution of sodium hydroxide was added to adjust the pH of the solution in the reaction vessel to 11 or more. A nickel sulfate solution and a manganese sulfate solution were then mixed, and the aqueous mixture solution was adjusted to have nickel and manganese at a molar ratio of 25:75, and the total concentration of nickel and manganese ion is 1.7 mol/L. To the solution in the reaction vessel, 4.76 L of the aqueous mixture solution was added while stirring the mixture solution to obtain a liquid medium containing a seed crystal. Crystallization Step After the seed generation step, 70% sulfuric acid was added to adjust the pH to 8.9 to 9.2 while the temperature was maintained at 50° C. Subsequently, 452 moles of 25% by mass sodium hydroxide and 201 moles of the aqueous mixture solution were added into the reaction vessel each at a constant rate for 18 hours or more. The pH at this time was maintained to 7.5 to 8.5. After completion of the addition, 2.1 kg of a 25% by mass aqueous solution of sodium hydroxide was added with the reaction vessel being maintained at 50° C. The pH at this time in the reaction vessel was 11.7. The resultant nickel-manganese-containing hydroxide had a D50of 6.0 μm. The generated precipitate was then washed with water and filtered to obtain composite hydroxide particles. The composite hydroxide particles were subjected to dry treatment in an air atmosphere at 300° C. for 12 hours to obtain composite oxide particles having a composition ratio of Ni/Mn=0.25/0.75, D10=4.5 μm, D50=5.9 μm, D90=7.9 μm, and D90/D10=1.8. First Heat-Treating Step The resultant composite oxide particles were heat-treated in an air atmosphere at 1000° C. for 6 hours to have a sintered composite oxide. The sintered composite oxide was disintegrated, subjected once to dissociating treatment using a jet mill adjusted to a supply pressure of 0.55 MPa and a dissociating pressure of 0.55 MPa, and dry-sieved to obtain a first heat-treated product with D10=2.4 μm, D50=3.5 μm, D90=5.3 μm, and D90/D10=2.2. Second Heat-Treating Step The resultant first heat-treated product and lithium carbonate were mixed in a manner to have a ratio of Li:(Ni+Mn)=1.1:2 to obtain a first mixture, or a raw material mixture. The raw material mixture was heat-treated in an air atmosphere at 835° C. for 11 hours, and then at 600° C. for 4 hours to obtain a sintered body. The sintered body was disintegrated, subjected once to dissociating treatment using a jet mill adjusted to a supply pressure of 0.2 MPa and a dissociating pressure of 0.2 MPa so as not to pulverize its primary particles, and dry-sieved to obtain a second heat-treated product as powder. As described above, lithium transition metal composite oxide particles having a composition represented by the formula: Li1.1Ni0.5Mn1.5O4, a DSEMof 2.4 μm, a D5of 2.5 μm, a D10of 2.7 μm, a D50of 3.8 μm, a D90of 5.4 μm, and a D95of 6.3 μm, a ratio of D50/DSEMof 1.6, D90/D10of 2, and D95/D5of 2.5 were obtained. The physical properties of the lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown inFIG.1. Comparative Example 1 Under the same conditions as in Example 1 up to the crystallization step, composite oxide particles were obtained. The composite oxide particles were mixed with lithium carbonate in a manner to have a ratio of Li:(Ni+Mn)=1.1:2, without subjecting them to the first heat-treating step, to obtain a raw material mixture. The raw material mixture was heat-treated in an air atmosphere at 850° C. for 11 hours, and then at 600° C. for 4 hours to obtain a sintered body. The sintered body was disintegrated, and subjected to dissociating treatment for 10 min using a resin ball mill, and dry-sieved to obtain powder. As described above, lithium transition metal composite oxide particles having a composition represented by the formula: Li1.1Ni0.5Mn1.5O4and having a DSEMof 1.5 μm, a D5of 2.8 μm, a D10of 3.4 μm, a D50of 6.2 μm, a D90of 10.5 μm, and a D95of 13.7 μm, a ratio of D50/DSEMof 4.2, a D90/D10of 3.1, and a D95/D5of 4.9 were obtained. The physical properties of the lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown inFIG.2. Example 2 Under the same conditions as in Example 1 up to the crystallization step except that the molar ratio of nickel and manganese in the aqueous mixture solution was changed to 26:74, composite oxide particles having a composition ratio of Ni/Mn of 0.26/0.74, a D10of 4.6 μm, a D50of 6 μm, a D90of 8 μm, and a D90/D10of 1.7 were obtained. The composite oxide particles were heat-treated in an air atmosphere at 975° C. for 6 hours to obtain a sintered body. The sintered body was disintegrated, subjected once to dissociating treatment using a jet mill adjusted to a supply pressure of 0.55 MPa and a dissociating pressure of 0.55 MPa, and dry-sieved to obtain a first heat-treated product with D10=2.5 μm, D50=4 μm, D90=6.8 μm, and D90/D10=2.7. The resultant first heat-treated product, lithium carbonate, and titanium oxide were mixed in a manner to have a ratio of Li:(Ni+Mn):Ti=1.2:1.925:0.075 to obtain a first mixture. The first mixture was heat-treated in an air atmosphere at 835° C. for 11 hours, and then at 600° C. for 4 hours to obtain a sintered body. The sintered body was disintegrated, subjected once to dissociating treatment using a jet mill adjusted to a supply pressure of 0.2 MPa and a dissociating pressure of 0.2 MPa so as not to pulverize its primary particles, and dry-sieved to obtain a second heat-treated product as powder. As described above, lithium transition metal composite oxide particles having a composition represented by the formula: Li1.2Ni0.5Mn1.425Ti0.075O4and having a DSEMof 2.6 μm, a D5of 2.3 μm, a D10of 2.7 μm, a D50of 4.2 μm, a D90of 6 μm, and a D95of 6.4 μm, a ratio of D50/DSEMof 1.6, a ratio of D90/D10of 2.2, and a ratio of D95/D5of 2.8 were obtained. The physical properties of the lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown inFIG.3. Comparative Example 2 Under the same conditions as in Example 2 up to the crystallization step, composite oxide particles were obtained. The composite oxide particles were mixed with lithium carbonate and titanium oxide in a manner to have a ratio of Li:(Ni+Mn):Ti=1.2:1.925:0.075 without subjected to the first heat-treating step to obtain a raw material mixture. The raw material mixture was heat-treated in an air atmosphere at 850° C. for 11 hours, and then at 600° C. for 4 hours to obtain a sintered body. The sintered body was disintegrated, subjected to dissociating treatment in a resin ball mill for 15 min, and dry-sieved to obtain powder. As described above, lithium transition metal composite oxide particles having a composition represented by the formula: Li1.2Ni0.5Mn1.425Ti0.075O4, and having a DSEMof 1.9 μm, a D5of 2.8 μm, a D10of 3.4 μm, a D50of 6.1 μm, a D90of 9.8 μm, and a D95of 12.4 μm, a ratio of D50/DSEMof 3.3, a ratio of D90/D10of 2.9, and a ratio of D95/D5of 4.5 were obtained. The physical properties of the lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown inFIG.4. Comparative Example 3 Under the same conditions as in Comparative Example 2, a sintered body was obtained. The sintered body was disintegrated, subjected once to dissociating treatment using, instead of a resin ball mill, a jet mill adjusted to a supply pressure of 0.55 MPa and a dissociating pressure of 0.55 MPa, and dry-sieved to obtain powder. As described above, lithium transition metal composite oxide particles having a composition represented by the formula: Li1.2Ni0.5Mn1.425Ti0.075O4, and having a DSEMof 1.3 μm, a D5of 1.9 μm, a D10of 2.3 μm, a D50of 3.4 μm, a D90of 4.7 μm, a D95of 5 μm, a ratio of D50/DSEMof 2.7, a ratio of D90/D10of 2, and a ratio of D95/D5of 2.6 were obtained. The physical properties of the lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown inFIG.5. Comparative Example 4 Under the same conditions as in Examples 2 up to the crystallization step, composite oxide particles were obtained. The composite oxide particles were heat-treated in an air atmosphere at 1100° C. for 6 hours to obtain heat-treated composite oxide particles. The composite oxide particles were disintegrated, subjected once to dissociating treatment using a jet mill adjusted to a supply pressure of 0.55 MPa and a dissociating pressure of 0.55 MPa, and dry-sieved to obtain composite oxide particles that have undergone dissociating treatment and having a D10of 2.5 μm, a D50of 3.8 μm, a D90of 5.7 μm, and a D90/D10of 2.3. The resultant composite oxide particles that have undergone dissociating treatment, lithium carbonate, and titanium oxide were mixed in a manner to have a ratio of Li:(Ni+Mn):Ti=1.2:1.925:0.075 to obtain a raw material mixture. The raw material mixture was heat-treated in an air atmosphere at 1000° C. for 11 hours, and then at 600° C. for 4 hours to obtain a sintered body. The sintered body was disintegrated, and subjected once to dissociating treatment using a jet mill adjusted to a supply pressure of 0.2 MPa and a dissociating pressure of 0.2 MPa so as not to pulverize its primary particles, and dry-sieved to obtain powder. As described above, lithium transition metal composite oxide particles having a composition represented by the formula: Li1.2Ni0.5Mn1.425Ti0.075O4, and having a DSEMof 3.7 μm, a D5of 3.3 μm, a D10of 4.4 μm, a D50of 8.7 μm, a D90of 12.4 μm, and a D95of 14.8 μm, a D50/DSEMof 2.4, and a D90/D10of 2.8, and a D95/D5of 4.5 were obtained. The physical properties of the lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown inFIG.6. Example 3 Seed Generation Step Into a reaction vessel, 30 kg of water was charged, and nitrogen gas was passed through the water with stirring, and the temperature within the vessel was set to 60° C. The oxygen concentration in the space within the vessel was maintained to 10% by volume or less, and then 922 g of a 25% by mol aqueous solution of sodium hydroxide was added to adjust the pH of the solution in the reaction vessel to 13.5 or more. A nickel sulfate solution and a manganese sulfate solution were mixed, and the aqueous mixture solution was adjusted to have nickel and manganese at a molar ratio of 26:74, and the total concentration of nickel and manganese ion is 1.7 mol/L. To the solution in the reaction vessel, 4.76 L of the prepared aqueous mixture solution was added while stirring the mixture solution to obtain a liquid medium containing a seed crystal. Crystallization Step After the seed generation step, carbon dioxide was added until the pH becomes 9.1 while the temperature was maintained at 60° C. Subsequently, an aqueous mixture solution with 40 moles of solute, 84 moles of a 25% by mol aqueous solution of sodium hydroxide, and 43 moles of carbon dioxide were simultaneously added into the reaction vessel each at a constant flow rate over 90 min. The pH at this time was maintained to 7.5 to 8.5. After completion of the addition, a 25% by mass aqueous solution of sodium hydroxide was added until the pH within the reaction vessel becomes 9.8 with the reaction vessel being maintained at 60° C. After the completion of dropping, a sample was taken. The resultant carbonate containing nickel and manganese had a D50of 4.6 μm. The resultant product was then washed with water, and filtered to obtain composite carbonate particles. The composite carbonate particles were subjected to dry treatment in an air atmosphere at 300° C. for 10 hours to obtain composite oxide particles having a composition ratio of Ni/Mn=0.26/0.74, with D10=3.2 μm, D50=4.6 μm, D90=6.4 μm, and D90/D10=3.4. First Heat-Treating Step The composite oxide particles were heat-treated in an air atmosphere at 950° C. for 6 hours to obtain a sintered body. The sintered body was disintegrated, subjected once to dissociating treatment using a jet mill adjusted to a supply pressure of 0.55 MPa and a dissociating pressure of 0.55 MPa, and dry-sieved to obtain a first heat-treated product with D10=1.4 μm, D50=2.6 μm, D90=3.9 μm, and D90/D10=2.8. The first heat-treated product, lithium carbonate, and titanium oxide were mixed in a manner to have a ratio of Li:(Ni+Mn):Ti=1.2:1.925:0.075 to obtain a raw material mixture. The raw material mixture was heat-treated in an air atmosphere at 800° C. for 11 hours, and then at 600° C. for 4 hours to obtain a sintered body. The sintered body was disintegrated, subjected once to dissociating treatment using a jet mill adjusted to a supply pressure of 0.2 MPa and a dissociating pressure of 0.2 MPa so as not to pulverize its primary particles, and dry-sieved to obtain powder. As described above, lithium transition metal composite oxide particles were obtained. The particles have a composition represented by the formula: Li1.2Ni0.5Mn1.425Ti0.075O4, and have a DSEMof 1.4 μm, a D5of 1.6 μm, a D10of 1.9 μm, a D50of 3 μm, a D90of 4.8 μm, a D95of 5.9 μm, a D50/DSEMof 2.1, a D90/D10of 2.5, and a D95/D5of 3.8. The physical properties of the lithium transition metal composite oxide particles are shown in Table 1, and an SEM image is shown inFIG.7. Reference Example In the same manner as in the crystallization step of Examples 3, the composite oxide particles were heat-treated in an air atmosphere at 330° C., 800° C., 850° C., 950° C. or 1100° C. for 6 hours to obtain a sintered body. SEM images of the sintered body are shown inFIGS.8A(330° C.),8B (800° C.),8C (850° C.),8D (950° C.), and8E (1100° C.). Example 4 Nb Treatment Step To 900 g of the lithium transition metal composite oxide particles obtained in Example 2, 106 g of Nb sol (a commercial Nb sol by Tagi Kagaku as the Nb source, Nb concentration: 4.2% by weight) was added dropwise with stirring with a mixer. Subsequently, the mixture was heat-treated in an air atmosphere at 350° C. for 9 hours to obtain lithium transition metal composite oxide particles that have undergone Nb treatment. Example 5 In the same manner as in Example 4 except that the heat-treating temperature was changed to 700° C., lithium transition metal composite oxide particles that have undergone Nb treatment were obtained. Comparative Example 5 In the same manner as Example 4 except that the lithium transition metal composite oxide particles obtained in Comparative Example 2 were used in place of the lithium transition metal composite oxide particles obtained in Example 2, lithium transition metal composite oxide particles that had undergone Nb treatment were obtained. Comparative Example 6 In the same manner as in Comparative Example 5 except that the heat-treating temperature was changed to 700° C., lithium transition metal composite oxide particles that had undergone Nb treatment were obtained. Evaluation Using the respective lithium transition metal composite oxide particles obtained above as a positive-electrode active material, batteries for evaluation were prepared in the procedure described below. Preparation of Positive electrode 90 parts by mass of the positive-electrode active material, 5 parts by mass of acetylene black, and 5 parts by mass of polyvinylidene fluoride (PVDF) were dispersed in an N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture. The positive electrode mixture was applied to an aluminum foil serving as a current collector, dried, and compression-molded with a roller press, and then cut into a predetermined size to prepare a positive electrode. Preparation of Negative electrode 97.5 parts by mass of artificial graphite, 1.5 parts by mass of carboxymethylcellulose (CMC), and 1 part by mass of styrene-butadiene rubber (SBR) were dispersed in pure water, and dissolved to prepared a negative electrode slurry. The negative electrode slurry was applied to a current collector formed from copper coil, dried, and then compression-molded with a roller press, and then cut into a predetermined size to prepare a negative electrode. Preparation of Batteries for Evaluation The current collectors of each positive electrode and the negative electrode were each connected to a lead electrode, and then a separator was arranged between the positive electrode and the negative electrode, all of which were packed into a laminated pack or pouch. Subsequently, the laminated pack was vacuum-dried at 65° C. to remove moisture adsorbed onto the members. Under an argon atmosphere, an electrolyte was injected into each laminated pack, and sealed to prepare batteries for evaluation. For the electrolyte, ethylene carbonate (EC) and methyl ethyl carbonate (MEC) were mixed at a volume ratio of 3:7, into which lithium hexafluorophosphate (LiPF6) was dissolved to have a concentration of 1 mol/L. The thus prepared batteries for evaluation were placed into a temperature controlled bath at 25° C., aged using a weak current, and then evaluated as described below. Direct Current Internal Resistance Measurement After aging, the batteries for evaluation were placed in an environment of 25° C. and −25° C., and the direct current internal resistance was measured. A constant current charging was carried out until a charge depth of 50% at a full charge voltage of 4.75 V. Pulse electric discharge was then carried out for 10 seconds with a specific current i, and the voltage V at the 10thsec was measured. With current i on the horizontal axis and voltage V on the vertical axis, the points of intersection were plotted, and the slope of the straight line connecting the points of intersection was defined as a direct current internal resistance (DC-IR). At a temperature of 25° C., current i was 0.06 A, 0.11 A, 0.16 A, 0.21 A or 0.26 A, and at −25° C., current i was 0.03 A, 0.05 A, 0.08 A, 0.105 A or 0.13 A. A low DC-IR indicates good output characteristics. The results are shown in Table 1. Durability A charge and discharge cycle test was carried out under the temperature condition of 60° C. The test was carried out at a constant charge current 1 C (1 C=a current that completes electric discharge in 1 hour) with one cycle of charging to the upper-limit charge voltage of 4.75 V, and discharging to the lower-limit discharge voltage of 3.5 V at a constant current of 1 C. The cycle was repeated 100 times (100 cycles). At every cycle, the electric discharge volume was measured, and durability (%) was calculated using the formula: (100thcycle electric discharge volume/1stcycle electric discharge volume)×100. A high durability indicates that the battery has high lifetime characteristics. The results are shown in Tables 1 and 2. Table 2 shows the durability improved rate (%) of Examples 4 and 5 compared with Example 2, as well as durability improved rate (%) of Comparative Example 5 and 6 compared with Comparative Example 2. TABLE 1DSEMD5D10D50D90D95DurabilityDC-IR (Ω)(μm)(μm)(μm)(μm)(μm)(μm)D50/DSEMD90/D10D95/D5(%)25° C.−25° C.Example 12.42.52.73.85.46.31.62.02.566.51.27.6Comparative1.52.83.46.210.513.74.23.14.962.61.17.8Example 1Example 22.62.32.74.26.06.41.62.22.874.11.17.0Comparative1.92.83.46.19.812.43.32.94.573.41.06.5Example 2Comparative1.31.92.33.44.75.02.72.02.666.81.27.2Example 3Comparative3.73.34.48.712.414.82.42.84.572.61.29.3Example 4Example 31.41.61.93.04.85.92.12.53.876.41.16.7 TABLE 2DurabilityImproved rate(%)(%)Example 274.1—Example 478.34.2Example 580.26.1Comparative73.4—Example 2Comparative77.13.7Example 5Comparative78.34.9Example 6 Comparison between Example 1 and Comparative Example 1, which have a similar composition, and comparison between Example 2 and Comparative Examples 2 and 3, which have a similar composition, reveals that the lithium transition metal composite oxide particles that underwent the first heat-treating have a D50/DSEMof 2.5 or less, achieving both improved durability and output characteristics. Although durability evaluation in Table 1 is based on a test of 100 charge and discharge cycles, if more charge and discharge cycles are repeated, further improvement in durability is rationally predicted because the value D50/DSEMwill become smaller, in other words, because of further reduction in boundary area. Comparison between Example 2 and Comparative Example 4 reveals that when DSEMis 3 μm or more, output characteristics deteriorate even when D50/DSEMis 2.5 or less. Comparison between Example 2 and Example 3 reveals that composite oxide particles formed from carbonate have further improved durability and output characteristics. Table 2 shows that when DSEMis less than 3 μm and D50/DSEMis 2.5 or less, the improvement in characteristics resulting from niobium treatment will be even greater. Although the present disclosure has been described with reference to several exemplary embodiments, it is to be understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the disclosure in its aspects. Although the disclosure has been described with reference to particular examples, means, and embodiments, the disclosure may be not intended to be limited to the particulars disclosed; rather the disclosure extends to all functionally equivalent structures, methods, and uses such as are within the scope of the appended claims. One or more examples or embodiments of the disclosure may be referred to herein, individually and/or collectively, by the term “disclosure” merely for convenience and without intending to voluntarily limit the scope of this application to any particular disclosure or inventive concept. Moreover, although specific examples and embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar purpose may be substituted for the specific examples or embodiments shown. This disclosure may be intended to cover any and all subsequent adaptations or variations of various examples and embodiments. Combinations of the above examples and embodiments, and other examples and embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the description. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure may be not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may be directed to less than all of the features of any of the disclosed embodiments. Thus, the following claims are incorporated into the Detailed Description, with each claim standing on its own as defining separately claimed subject matter. The above disclosed subject matter shall be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments which fall within the true spirit and scope of the present disclosure. Thus, to the maximum extent allowed by law, the scope of the present disclosure may be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description. All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference. | 56,491 |
11862797 | DETAILED DESCRIPTION The embodiments of the present application will be described in detail below. Throughout the specification, the same or similar components and components having the same or similar functions are denoted by similar reference numerals. The embodiments described herein with respect to the drawings are illustrative and graphical, and are used for providing a basic understanding of the present application. The embodiments of the present application should not be interpreted as limitations to the present application. As used in the present application, terms “approximately”, “substantially”, “essentially”, and “about” are used for describing and explaining a small variation. When being used in combination with an event or circumstance, the term may refer to an example in which the event or circumstance occurs precisely, and an example in which the event or circumstance occurs approximately. For example, when being used in combination with a value, the term may refer to a variation range of less than or equal to ±10% of the value, for example, less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to 0.1%, or less than or equal to ±0.05%. For example, if the difference between two numerical values is less than or equal to ±10% of the average of the values (e.g., less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%), the two values may be considered “about” the same. In the present application, unless otherwise particularly indicated or limited, relativistic wordings such as “central”, “longitudinal”, “lateral”, “front”, “back”, “right”, “left”, “inner”, “outer”, “relatively low”, “relatively high”, “horizontal”, “vertical”, “higher than”, “lower than”, “above”, “below”, “top”, “bottom”, and their derived wordings (such as “horizontally”, “downward”, and “upward”) should be construed as referenced directions described in discussion or shown in the appended drawings. These relativistic wordings are merely used for ease of description, and do not require constructing or operating the present application in a specific direction. Further, to facilitate description, “first”, “second”, “third”, and the like may be used in the present application to distinguish among different components in a diagram or a series of diagrams. The wordings “first”, “second”, “third”, and the like are not intended to describe corresponding components. In addition, sometimes, a quantity, a ratio, and another value are presented in a range format in the present application. It should be appreciated that such range formats are for convenience and conciseness, and should be flexibly understood as including not only values explicitly specified to range constraints, but also all individual values or sub-ranges within the ranges, like explicitly specifying each value and each sub-range. In the detailed description and the claims, a list of items connected by the term “at least one of” or similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if items A, B and C are listed, then the phrase “at least one of A, B and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B and C. The item A may include a single component or multiple components. The item B may include a single component or multiple components. The item C may include a single component or multiple components. According to one aspect of the present application, the embodiments of the present application provide a cathode which is of a multilayer structure composed of a material layer including phosphate, lithium titanium phosphate, or combinations thereof. Since the electronic conductivity of phosphate and lithium titanium phosphate is very low, by arranging the material layer including phosphate, lithium titanium phosphate or the combination thereof between a cathode active material layer and a current collector, in a charge and discharge cycle process, the material layer can well protect a high voltage of a cathode end in the charge and discharge cycle process. Moreover, phosphate and lithium titanium phosphate have stable structures under the high voltage, and therefore, the surfaces of phosphate and lithium titanium phosphate do not need to be coated with other materials (such as carbon or metallic oxides), and the oxidation situation of all layers of interfaces in the cathode under the high voltage is reduced. During safety tests such as a nailing test or an impact test, the material layer can well separate direct contact between the current collector of the cathode and an anode material layer, so that the safety performance of an electrochemical device is improved. Compared with other oxide coatings (such as aluminum oxide) in the prior art, phosphate has better processing performance and stability, so that in the whole charge and discharge processes, the cathode has a small thickness change and is not prone to falling off. In addition, the lithium intercalation potential of lithium titanium phosphate is about 2.5 V. Lithium ions are mainly intercalated into the cathode active material layer (a first material layer) in the discharge process, and the material layer (a second material layer) including lithium titanium phosphate does not participate in a lithium intercalation reaction. Therefore, the volume change and the generated reaction current density of the material layer (the second material layer) are very small, which further reduces the influence of the reaction current density difference of all the layers of interfaces on an electrical conduction system and especially reduces damage to interlayer interfaces, so that the stability of the overall impedance of the cathode is ensured. The cathode provided by the embodiments of the present application has lower initial impedance, and impedance growth under high-temperature storage can be lowered. FIG.1is a schematic structural diagram of a cathode according to some embodiments of the present application. As shown in the FIGURE, the cathode10includes a current collector101, first material layers102and second material layers103. The second material layers103are disposed between the current collector101and the first material layers102. In some embodiments, the first material layers102include first materials, and the second material layers103include second materials. The first materials and the second materials may be the same or different. The second materials include at least one of the followings: phosphate represented by a general formula M1PO4and lithium titanium phosphate represented by a general formula Li3Ti2-xM2x(PO4)3. M1 is selected from the group consisting of Co, Mn, Fe, Ti, and combinations thereof, M2 is selected from the group consisting of V, Sc, Ge, Al, and combinations thereof, and 0≤x<2. It should be understood that although both sides of the current collector101of the cathode10in the FIGURE are provided with double-layer structures of the first material layers102and the second material layers103, FIGURE is only used to illustrate exemplary embodiments of a cathode structure. Without violating the spirit of the invention of the present application, those skilled in the art may arrange the double-layer structures on a single side or both sides of the current collector101according to actual demands or design without limitation. In some embodiments, the thickness of the second material layers103is about 2 μm to about 10 μm. The thickness of the second material layers103of the cathode10within the above range can make the second materials (phosphate or lithium titanium phosphate) be more evenly disposed on the current collector, so that an electrochemical device has better cycle performance and higher energy density. In some embodiments, the thickness of the second material layers103is about 3 μm to about 7 μm. In some embodiments, the compacted density of the second material layers103is about 1.8 g/cm3to about 3.1 g/cm3. The compacted density of the second material layers103within the above range can realize a relatively stable structural strength, so that the electrochemical device has better cycle performance and higher energy density. In some embodiments, the compacted density of the second material layers103is about 2.4 g/cm3to about 2.7 g/cm3. In some embodiments, the particle size Dv50 of the second materials is about 0.5 μm to about 5.0 μm. The particle size Dv50 of the second materials of the cathode10within the above range can make the second materials be more evenly disposed on the current collector. In this text, the term “Dv50” is also called “particle size”, which represents a particle size starting from a small particle size side and reaching 50% of a cumulative volume in the particle size distribution of a volume basis. It should be understood that those skilled in the art may select conventional cathode active materials in the art as the first materials according to the actual needs. In some embodiments, the first materials are selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium iron manganese phosphate, lithium manganese oxide, lithium-rich manganese-based material, and combinations thereof. In addition, those skilled in the art may perform cathode active material treatment well known in the art, such as transition metal element doping or inorganic oxide coating, on the first materials according to the actual needs. In some embodiments, the first materials of the present application further include transition metal doping, for example, but not limited to, elements of the group consisting of Sc, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Mg, Ti, Zr, and combinations thereof. In some embodiments, the first materials of the present application further include coating layers. The coating layers include, but are not limited to, at least one element of B, Al, Zr, C and S. In some embodiments, the ratio of the surface densities of the second material layers103and the first material layers102in the thickness direction of the cathode is about 1% to about 5%, so that the electrochemical device has better cycle performance and higher energy density. In this text, the term “surface density” is a mass per unit area. In some embodiments, the thickness of the first material layers102is about 120 μm to about 450 μm. In some embodiments, the compacted density of the first material layers102is about 4.05 g/cm3to about 4.3 g cm3. In some embodiments, the compacted density of the first material layers102is about 4.15 g/cm3to about 4.25 g/cm3. In some embodiments, the particle size Dv50 of the first materials is about 2.5 μm to about 20 μm. In some embodiments, the second material layers103further include at least one of binders and conductive agents. In some embodiments, the content of the binders in the second material layers103is about 1 wt % to about 5 wt % of a total weight of the second material layers103. In some embodiments, the content of the conductive agents in the second material layers is about 1 wt % to about 10 wt % of a total weight of the second material layers103. By adding at least one of the binders and the conductive agents, the electronic conductivity and structural stability of the second material layers103can be adjusted, so as to improve the cycle performance and safety performance of the electrochemical device. In some embodiments, the first material layers102further include at least one of binders and conductive agents. In some embodiments, the content of the binders in the first material layers102is about 0.1 wt % to about 8 wt % of a total weight of the first material layers102. In some embodiments, the content of the conductive agents in the first material layers is about 0.01 wt % to about 10 wt % of a total weight of the first material layers102. By adding at least one of the binders and the conductive agents, the electronic conductivity and structural stability of the first material layers102can be adjusted, so as to improve the cycle performance and safety performance of the electrochemical device. In some embodiments, the binders used in the first material layers102or the second material layers103may be selected from the group consisting of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylic ester, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene butadiene rubber, and combinations thereof. In some embodiments, the conductive agents used in the first material layers102or the second material layers103may be selected from the group consisting of carbon nanotubes, carbon fibers, conductive carbon black, acetylene black, graphene, Ketjen black, and combinations thereof. It should be understood that those skilled in the art may select conventional binders and conductive agents in the art according to the actual needs without limitation. In some embodiments, a preparation method of the cathode of the present application includes the following steps:1. The second materials, the binders and the conductive agents are mixed according to a fixed weight ratio and dissolved into a diluent solvent (N-methylpyrrolidone) to be fully mixed and stirred to form second material layer slurry, and then one or both of surfaces of the current collector are evenly coated with the second material layer slurry. After drying and cold-pressing processes, bottom diaphragms (the second material layers) are obtained.2. Cathode materials (the first materials), the binders and the conductive agents are mixed according to a fixed weight ratio and dissolved into a diluent solvent (N-methylpyrrolidone) to be fully mixed and stirred to form first material layer slurry, and then exposed surfaces of the bottom diaphragms are evenly coated with the first material layer slurry. After drying and cold-pressing processes, the cathode with the double-layer structures is obtained. It should be understood that the preparation method of the cathode in the embodiments of the present application may be a conventional method in the art without limitation. Some embodiments of the present application further provide an electrochemical device including the cathode of the present application. In some embodiments, the electrochemical device is a lithium-ion battery. The lithium-ion battery includes the cathode according to the present application, an anode and a separator. The separator is disposed between the cathode and the anode. In some embodiments, the current collector of the cathode of the present application may be an aluminum foil or a nickel foil. A current collector of the anode may be a copper foil or a nickel foil. However, other cathode and anode current collectors commonly used in the art may be adopted without limitation. In some embodiments, the anode includes anode materials capable of absorbing and releasing lithium (Li) (hereinafter, sometimes called “anode materials capable of absorbing/releasing Li”). Examples of the anode materials capable of absorbing/releasing lithium (Li) may include carbon materials, metal compounds, oxides, sulfides, lithium nitrides such as LiN3, lithium metals, metals forming alloys with lithium, and polymer materials. In some embodiments, the separator includes, but is not limited to, at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide and aramid. For example, polyethylene includes at least one component selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene. Especially polyethylene and polypropylene play a good role in preventing a short circuit, and can improve the stability of the lithium-ion battery through a shutdown effect. The lithium-ion battery of the present application further includes an electrolyte. The electrolyte may be one or more of a gel electrolyte, a solid electrolyte and an electrolytic solution. The electrolytic solution includes a lithium salt and a non-aqueous solvent. In some embodiments, the lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB and lithium difluoroborate. For example, the LiPF6is selected as the lithium salt, because it can give a high ionic conductivity and improve cycle characteristics. The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or combinations thereof. The above carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or combinations thereof. Examples of the above chain carbonate compound are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), propyl propionate (PP), and combinations thereof. Examples of the fluorocarbonate compound are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof. Examples of the above carboxylate compound are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decalactone, valerolactone, mevalonolactone, caprolactone, methyl formate, and combinations thereof. Examples of the above ether compound are dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof. Examples of the above other organic solvents are dimethylsulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, phosphate ester, and combinations thereof. In some embodiments, a preparation method of the lithium-ion battery includes: the cathode, the separator and the anode in the above embodiments are wound, folded or stacked into an electrode assembly in sequence. The electrode assembly is loaded into, for example, an aluminum plastic film, and an electrolytic solution is injected. Then vacuum packaging, still standing, forming, shaping and other processes are performed to obtain the lithium-ion battery. Those skilled in the art will understand that although the above is illustrated with the lithium-ion battery, those skilled in the art can think that the cathode of the present application can be used for other suitable electrochemical devices after reading the present application. Such an electrochemical device includes any device undergoing an electrochemical reaction, and its specific examples include all kinds of primary batteries, secondary batteries, fuel batteries, solar batteries or capacitors. In particular, the electrochemical device is a lithium secondary battery, which includes a lithium metal secondary battery, a lithium-ion secondary battery, a lithium polymer secondary battery or a lithium-ion polymer secondary battery. Some embodiments of the present application further provide an electronic device. The electronic device includes the electrochemical device in the embodiments of the present application. The electronic device of the embodiments of the present application is not particularly defined, and may be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copy machine, a portable printer, a stereo headphone, a video recorder, a liquid crystal display television, a portable cleaner, a portable CD player, a mini disk, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power, a motor, a car, a motorcycle, a power assisted bicycle, a bicycle, a lighting appliance, a toy, a game console, a clock, an electric tool, a flash lamp, a camera, a large household storage battery, a lithium-ion capacitor, and the like. SPECIFIC EXAMPLES Some specific examples and comparative examples are listed below, and the electrochemical devices (lithium-ion batteries) are subjected to a high-temperature storage impedance test, a nailing test and an impact test respectively to better explain the technical solution of the present application. Capacity Test: The lithium-ion batteries of the examples and the comparative examples were put into a constant-temperature box at 25° C.±2° C., charged to 4.45 V by a constant current of 0.5 C, and then charged by a constant voltage of 4.45 V till a current was lower than 0.02 C, so that the lithium-ion batteries were in a fully charged state. After being placed for 30 minutes, the lithium-ion batteries were discharged to 3.0 V at a rate of 0.2 C. After being placed for 30 minutes, discharge capacities were taken as the actual battery capacities of the lithium-ion batteries. 5 lithium-ion batteries were taken for each group to calculate the average of the energy densities (gram capacities) of the lithium-ion batteries. energydensity(gramcapacity)=dischargecapacitytotalweightoffirstmateriallayerandsecondmateriallayer. High-Temperature Storage Impedance Test The lithium-ion batteries of the examples and the comparative examples were put into a constant-temperature box at 25° C.±2° C., charged to 4.45 V by a constant current of 0.5 C, and then charged by a constant voltage of 4.45 V till a current was lower than 0.02 C, so that the lithium-ion batteries were in a fully charged state. The impedance (IMP) of the lithium-ion batteries in the fully charged state was recorded as an initial impedance. Then, the lithium-ion batteries were put into an oven at 85° C.±2° C. and subjected to still standing for 6 h. After high-temperature storage, the impedance of the lithium-ion batteries was recorded as a test impedance. 5 lithium-ion batteries were taken for each group to calculate the average of high-temperature storage impedance growth rates of the lithium-ion batteries. high‐temperaturestorageimpedancegrowthrateoflithium‐ionbattery=testimpedance-initialimpedanceinitialimpedance×100%. Nailing Test The lithium-ion batteries were put into a constant-temperature box at 25° C., and subjected to still standing for 30 mins to reach a constant temperature. The lithium-ion batteries reaching the constant temperature were charged to a voltage of 4.45 V by a constant current of 0.5 C, and then charged by a constant voltage of 4.45 V till a current was lower than 0.02 C, so that the lithium-ion batteries were in a fully charged state. The lithium-ion batteries in the fully charged state were transferred onto a nailing tester. A test ambient temperature was maintained at 25° C.±2° C. Steel nails with a diameter of 4 mm were adopted to penetrate through centers of the lithium-ion batteries at a constant speed of 30 mm/s. The lithium batteries were retained for 300 seconds, and the lithium-ion batteries without smoking, fire breakout or explosion were marked as pass. 10 lithium-ion batteries were tested each time. The number of the lithium-ion batteries passing the nailing test was taken as an index of evaluating the safety performance of the lithium-ion batteries. Impact Test The lithium-ion batteries were put into a constant-temperature box at 25° C., and subjected to still standing for 30 mins to reach a constant temperature. The lithium-ion batteries reaching the constant temperature were charged to a voltage of 4.45 V by a constant current of 0.5 C, and then charged by a constant voltage of 4.45 V till a current was lower than 0.02 C, so that the lithium-ion batteries were in a fully charged state. The lithium-ion batteries in the fully charged state were transferred onto an impact tester. A test ambient temperature was maintained at 25° C.±2° C. Steel bars with a diameter of 15.8±0.2 mm and a length of at least 7 cm were vertically placed at the centers of the lithium-ion batteries. A steel hammer with a weight of 9.1±0.1 kg was adopted to fall down vertically and freely at a distance of 61±2.5 cm from the centers of the lithium-ion batteries to knock the steel bars so as to impact the lithium-ion batteries. After impacting, the lithium-ion batteries were retained for 300 seconds, and the lithium-ion batteries without smoking, fire breakout or explosion were marked as pass. 10 lithium-ion batteries were tested each time. The number of the lithium-ion batteries passing the impact test was taken as an index of evaluating the safety performance of the lithium-ion batteries. Preparation of Anode A copper foil was adopted as an anode current collector. The surface of the anode current collector was evenly coated with a layer of graphite slurry (anode material layer). The graphite slurry was composed of 95 wt % of artificial graphite, 2 wt % of acetylene black, 2 wt % of styrene butadiene rubber and 1 wt % of sodium carboxymethylcellulose. Then the anode current collector coated with the graphite slurry was baked at 120° C. for 1 h, and then cold pressing, slicing and slitting were performed to prepare the anode. Preparation of Electrolytic Solution Under an environment with a water content less than 10 ppm, lithium hexafluorophosphate and a non-aqueous organic solvent (ethylene carbonate (EC): propyl carbonate (PC): diethyl carbonate (DEC)=1:1:1, a mass ratio) were compounded according to a mass ratio of 8:92 to form the electrolytic solution. Preparation of Lithium-Ion Battery A following preparation method was adopted to prepare the cathode in the examples and the comparative examples into a lithium-ion battery. Specifically, a polyethylene film was adopted as the separator. The cathode prepared in the following examples and comparative examples was stacked with the separator and the anode according to the sequence of the cathode, the separator and the above anode. The separator was located between the cathode and the anode to play a role of separation, and then the cathode, the separator and the anode were wound into the electrode assembly. Then, the electrode assembly was loaded into an aluminum plastic film packaging bag, and a dry electrode assembly was obtained after moisture was removed at 80° C. Then, the above electrolytic solution was injected into the dry electrode assembly. The lithium-ion batteries of all the following examples and comparative examples were prepared through vacuum packaging, still standing, forming, shaping and other processes. Example 1 Iron phosphate (FePO4), with a particle size Dv50 of 1.0 μm, taken as second materials was dissolved in an N-methylpyrrolidone (NMP) solution at a weight ratio of 96:2:2 with polyvinylidene difluoride and acetylene black to form second material layer slurry. An aluminum foil was adopted as a current collector. A surface of the current collector was coated with the second material layer slurry. Bottom diaphragms (second material layers) were obtained after drying and cold pressing. The thickness of the second material layers in the bottom diaphragms was 5 μm, and the compacted density was 2.5 g/cm3. Lithium cobalt oxide (Dv50 was 12 μm), acetylene black and polyvinylidene difluoride (PVDF) were dissolved in an N-methylpyrrolidone solution according to a weight ratio of 97:2:1 to form first material layer slurry. Then exposed surfaces of the second material layers in the bottom diaphragms were coated with the first material layer slurry. A cathode was obtained after drying, cold pressing and cutting treatment. The thickness of first material layers was 300 μm, and the compacted density was 4.2 g/cm3. Example 2 The preparation mode was the same as that in Example 1. The difference was that the particle size Dv50 of iron phosphate in Example 2 was 1.5 μm. Example 3 The preparation mode was the same as that in Example 1. The difference was that the particle size Dv50 of iron phosphate in Example 3 was 2.0 μm. Example 4 The preparation mode was the same as that in Example 1. The difference was that the particle size Dv50 of iron phosphate in Example 4 was 2.5 μm. Example 5 The preparation mode was the same as that in Example 1. The difference was that the particle size Dv50 of iron phosphate in Example 5 was 5.0 μm. Example 6 The preparation mode was the same as that in Example 2. The difference was that the thickness of second material layers in Example 6 was 2 μm. Example 7 The preparation mode was the same as that in Example 2. The difference was that the thickness of second material layers in Example 7 was 7 μm. Example 8 The preparation mode was the same as that in Example 2. The difference was that the thickness of second material layers in Example 8 was 10 μm. Examples 9 to 11 The preparation modes were the same as that in Example 2. The differences were that titanium phosphate (TiPO4) was adopted as second materials in Example 9, manganese phosphate (MnPO4) was adopted as second materials in Example 10, and cobaltous phosphate (CoPO4) was adopted as second materials in Example 11. Examples 12 to 19 The preparation modes were the same as those in Examples 1 to 8 sequentially. The differences were that lithium titanium phosphate (Li3Ti2(PO4)3) was adopted as second materials in Examples 12 to 19, and lithium titanium phosphate (Li3Ti2(PO4)3), polyvinylidene difluoride and acetylene black were dissolved in an N-methylpyrrolidone (NMP) solution according to a weight ratio of 96:2.5:1.5. Example 20 The preparation mode was the same as that in Example 13. The difference was that lithium titanium phosphate (Li3Ti2(PO4)3) was adopted as second materials in Example 20, and lithium titanium phosphate (Li3Ti2(PO4)3), polyvinylidene difluoride and acetylene black were dissolved in an N-methylpyrrolidone (NMP) solution according to a weight ratio of 96:3:1. Example 21 The preparation mode was the same as that in Example 13. The difference was that lithium titanium phosphate (Li3Ti2(PO4)3) was adopted as second materials in Example 21, and lithium titanium phosphate (Li3Ti2(PO4)3), polyvinylidene difluoride and acetylene black were dissolved in an N-methylpyrrolidone (NMP) solution according to a weight ratio of 96:2:2. Examples 22 to 25 The preparation modes were the same as that in Example 13. The differences were that vanadium-doped lithium titanium phosphate (L3Ti1.99V0.01(PO4)3) was adopted as second materials in Example 22, scandium-doped lithium titanium phosphate (Li3Ti1.99Sc0.01(PO4)3) was adopted as second materials in Example 23, germanium-doped lithium titanium phosphate (L3Ti1.99Ge0.01(PO4)3) was adopted as second materials in Example 24, and aluminum-doped lithium titanium phosphate (Li3Ti1.99Al0.01(PO4)3) was adopted as second materials in Example 25. Comparative Example 1 Lithium cobalt oxide, acetylene black and polyvinylidene difluoride were dissolved in an N-methylpyrrolidone solution according to a weight ratio of 97:2:1 to form first material layer slurry. An aluminum foil was adopted as a current collector. A surface of the current collector was directly coated with the first material layer slurry. A cathode was obtained after drying, cold pressing and cutting treatment. Comparative Example 2 The preparation mode was the same as that in Example 1. The difference was that lithium iron phosphate (LiFePO4) was adopted as second materials in Comparative Example 2. Comparative Example 3 The preparation mode was the same as that in Example 2. The difference was that the thickness of second material layers in Comparative Example 3 was 2 μm. Comparative Example 4 The preparation mode was the same as that in Example 13. The difference was that the thickness of second material layers in Comparative Example 4 was 2 μm. Comparative Example 5 The preparation mode was the same as that in Example 2. The difference was that aluminum oxide (Al2O3), with a particle size Dv50 of 0.2 μm, taken as second materials in Comparative Example 5 was dissolved in an N-methylpyrrolidone (NMP) solution with polyvinylidene difluoride and acetylene black according to a weight ratio of 96:2:2. The thickness, width, length and weight of the cathode in the above examples and comparative examples were measured. The compacted density of the first material layers or the second material layers and the ratio of the surface densities of the second material layers and the first material layers102along a surface of the cathode were recorded. Then the lithium-ion batteries were subjected to the high-temperature storage impedance test, the nailing test and the impact test, and test results thereof were recorded. Statistic numerical values of the first material layers and the second material layers of Examples 1 to 25 and Comparative Examples 1 to 5 are shown in Table 1 below. TABLE 1SurfaceContent ofParticleThicknessdensity ratioconductivesize DV50of secondof secondagent ofExample/of secondmaterialmaterial layersecondComparativeType of secondmateriallayerand firstmaterial layerExamplematerial(μm)(μm)material layer(wt %)Example 1FePO41.052%2.0Example 2FePO41.552%2.0Example 3FePO42.052%2.0Example 4FePO42.552%2.0Example 5FePO4552%2.0Example 6FePO41.522%2.0Example 7FePO41.572%2.0Example 8FePO41.5102%2.0Example 9TiPO41.552%2.0Example 10MnPO41.552%2.0Example 11CoPO41.552%2.0Example 12Li3Ti2(PO4)31.052%1.5Example 13Li3Ti2(PO4)31.552%1.5Example 14Li3Ti2(PO4)32.052%1.5Example 15Li3Ti2(PO4)32.552%1.5Example 16Li3Ti2(PO4)3552%1.5Example 17Li3Ti2(PO4)31.532%1.5Example 18Li3Ti2(PO4)31.572%1.5Example 19Li3Ti2(PO4)31.5102%1.5Example 20Li3Ti2(PO4)31.552%1.0Example 21Li3Ti2(PO4)31.552%2.0Example 22Li3Ti1.99V0.01(PO4)31.552%1.5Example 23Li3Ti1.99Sc0.01(PO4)31.552%1.5Example 24Li3Ti1.99Ge0.01(PO4)31.552%1.5Example 25Li3Ti1.99Al0.01(PO4)31.552%1.5ComparativeN/AN/AN/AN/AN/AExample 1ComparativeLiFePO41.552%2.0Example 2ComparativeFePO41.522%2.0Example 3ComparativeLi3Ti2(PO4)31.522%1.5Example 4ComparativeAl2O31.552%2.0Example 5 The test results of the lithium-ion batteries of Examples 1 to 11 and Comparative Examples 1 to 3 and 5 passing the high-temperature storage impedance test, the nailing test and the impact test are shown in Table 2 below. TABLE 2Example/InitialHigh-temperatureImpactComparativeimpedancestorage impedanceNailing testtest passExample(IMP)/(mΩ)growth rate/%pass raterateExample 125.721%10\108\10Example 227.620%10\108\10Example 328.618%10\108\10Example 429.816%10\108\10Example 530.315%10\108\10Example 626.923%9\108\10Example 730.619%10\109\10Example 833.517%10\1010\10Example 931.524%10\108\10Example 1036.822%10\109\10Example 1135.919%10\109\10Comparative30.318%0\101\10Example 1Comparative40.668%8\107\10Example 2Comparative24.328%3\101\10Example 3Comparative62.439%2\102\10Example 5 The test results of the lithium-ion batteries of Examples 12 to 25 and Comparative Examples 1 to 2 and 4 to 5 passing the capacity test, the high-temperature storage impedance test, the nailing test and the impact test are shown in Table 3 below. TABLE 3EnergyHigh-densityInitialtemperatureExample/(gramimpedancestorageNailingImpactComparativecapacity)(IMP)/impedancetest passtest passExample(mAh/g)(mΩ)growth rate/%raterateExample 12182.027.221%10\1010\10Example 13181.528.119%10\1010\10Example 14180.830.618%10\1010\10Example 15180.131.717%10\109\10Example 16180.032.216%10\109\10Example 17181.325.425%8\107\10Example 18181.932.416%10\1010\10Example 19181.931.115%10\1010\10Example 20181.332.325%10\109\10Example 21181.727.316%9\108\10Example 22180.727.622%8\107\10Example 23181.729.723%10\1010\10Example 24181.230.224%9\109\10Example 25180.234.719%9\108\10Comparative178.530.318%0\101\10Example 1Comparative180.540.668%8\107\10Example 2Comparative181.022.429%2\103\10Example 4Comparative170.062.439%2\102\10Example 5 It can be known from Tables 1 to 3 that compared with Comparative Example 1, the safety performance of the lithium-ion battery with the cathode of the present application in the examples of the present application is significantly improved. Specifically, by comparing Comparative Example 1 with Examples 1 to 25, it can be known that the pass rate of the electrochemical device with the cathode of the present application can be effectively increased in the nailing test and the impact test. It represents that the second material layers in the cathode of the present application can effectively prevent the current collector in the cathode from making contact with the anode, so that the safety performance of the lithium-ion battery is improved. Moreover, as shown in Table 3, compared with Comparative Example 1, the second materials of the lithium-ion batteries of Examples 12 to 25 of the present application further include lithium doping, which can effectively improve the energy density of the lithium-ion batteries. By comparing Examples 1 to 5 and 12 to 16, it can be known that with the increase of the particle size of the second materials, the initial impedance of the lithium-ion batteries will also be increased, while the high-temperature storage impedance growth rate of the lithium-ion batteries will be decreased. In the present application, by controlling the particle size of the second materials, the high-temperature storage impedance growth rate of the lithium-ion batteries can be optimized under the condition that the initial impedance is kept within a lower range, so that the lithium-ion batteries have good cycle performance and high-temperature storage performance simultaneously. By comparing Examples 13, 20 and 21, it can be known that the doping content of the conductive agents in the second material layers can affect the initial impedance and the high-temperature storage impedance growth rate of the lithium-ion batteries. The higher the doping content of the conductive agents in the second material layers is, the lower the initial impedance and the high-temperature storage impedance growth rate of the lithium-ion batteries are. However, the overhigh content of the conductive agents may decrease the pass rate of the lithium-ion batteries in the nailing and impact tests. The content of the conductive agents in the scope of the embodiments of the present application can make the lithium-ion batteries maintain the lower initial impedance and high-temperature storage impedance growth rate and maintain the pass rate of more than 90% of the nailing and impact tests. By comparing Comparative Example 2 with Examples 2, 9 to 11, 13 and 22 to 25, it can be known that compared with the lithium-ion batteries adopting lithium iron phosphate as the second materials in Comparative Example 2, impedance growth after high-temperature storage can be effectively reduced in the lithium-ion batteries adopting phosphate as the second materials in Examples 2 and 9 to 11 and the lithium-ion batteries adopting lithium titanium phosphate as the second materials in Examples 13 and 22 to 25, and the high-temperature storage impedance growth rate is maintained below 25%. It represents that the second material layers adopting phosphate in the present application have good stability under a high-temperature and high-voltage environment, and the phenomena of expansion, deformation, falling-off, etc. are not prone to being generated. Therefore, the lithium-ion battery of the present application has the lower initial impedance and high-temperature storage impedance growth rate, so as to improve the cycle performance of the lithium-ion battery. By comparing Comparative Examples 3 and 4 with Examples 2, 6 to 8, 13 and 17 to 19, it can be known that the thickness of the second material layers in the cathode has a significant influence on the safety performance of the lithium-ion batteries. The thickness of the second material layers of the lithium-ion batteries in Comparative Examples 3 and 4 is too low, which causes uneven distribution of phosphate and lithium titanium phosphate, and the separation effect of the second material layers on the current collector in the cathode and the anode is weakened. The structural design of the cathode of the lithium-ion battery of the present application can reduce the influence of the second material layers on the energy density and the impedance while improving the safety performance of the lithium-ion battery, so as to optimize the cycle and safety performance of the lithium-ion battery. By comparing the above examples and the above comparative examples, it can be clearly understood that the cathode of the present application is provided with the second material layers and the double-layer structures including at least one of phosphate and lithium titanium phosphate, which further separates contact between the current collector in the cathode and the anode, so that the electrochemical stability and safety performance of the electrochemical device are significantly improved. Meanwhile, by optimizing the design of the second material layers of the cathode of the present application, the impedance of the electrochemical device and the impedance growth of the electrochemical device under the high-temperature and high-voltage environment can be reduced, so that the cycle performance is improved under the condition of optimizing the safety performance. Throughout the specification, references to “embodiment”, “part of embodiments”, “one embodiment”, “another example”, “example”, “specific example” or “part of examples” mean that at least one embodiment or example of the present application includes specific features, structures, materials or characteristics described in the embodiment or example. Thus, the descriptions appear throughout the specification, such as “in some embodiments”, “in an embodiment”, “in one embodiment”, “in another example”, “in an example”, “in a particular example” or “for example”, are not necessarily the same embodiment or example in the application. Furthermore, the specific features, structures, materials is or characteristics in the descriptions can be combined in any suitable manner in one or more embodiments or examples. Although the illustrative embodiments have been shown and described, it should be understood by those skilled in the art that the above embodiments cannot be interpreted as limitations to the present application, and the embodiments can be changed, substituted and modified without departing from the spirit, principle and scope of the present application. | 43,845 |
11862798 | DESCRIPTION OF EMBODIMENTS In the present specification and claims, “to” indicating a numerical range means that the numerical values described before and after “to” are included as the lower limit and the upper limit of the range. FIG.1is a schematic cross-sectional view showing one embodiment of the positive electrode of the present invention for a non-aqueous electrolyte secondary battery, andFIG.2is a schematic cross-sectional view showing one embodiment of the non-aqueous electrolyte secondary battery of the present invention. FIG.1andFIG.2are schematic diagrams for facilitating the understanding of the configurations, and the dimensional ratios and the like of each component do not necessarily represent the actual ones. <Positive Electrode for Non-Aqueous Electrolyte Secondary Battery> In the present embodiment, the positive electrode for a non-aqueous electrolyte secondary battery (also simply referred to as “positive electrode”)1has a positive electrode current collector11and a positive electrode active material layer12. The positive electrode active material layer12is present on at least one surface of the positive electrode current collector11. The positive electrode active material layers12may be present on both sides of the positive electrode current collector11. In the example shown inFIG.1, the positive electrode current collector11has a positive electrode current collector main body14and current collector coating layers15that cover the positive electrode current collector main body14on its surfaces facing the positive electrode active material layers12. The positive electrode current collector main body14alone may be used as the positive electrode current collector11. First Embodiment In the first embodiment of the present invention, the positive electrode1for a non-aqueous electrolyte secondary battery includes a positive electrode current collector11and a positive electrode active material layer12provided on the positive electrode current collector11, wherein: the positive electrode active material layer12includes a positive electrode active material; and an integrated value (a) is 3 to 15%, which is an integrated value of frequency of particle diameters of 1 μm or less, and a frequency (b) is 8 to 20%, which is a frequency of a diameter with a maximum frequency, each determined from a volume-based particle size distribution curve of particles present in the positive electrode active material layer12. The positive electrode1having the above configuration can improve the performance of a non-aqueous electrolyte secondary battery in respect of high-rate cycling performance at high temperatures. Specific descriptions are given below. (Positive Electrode Active Material Layer) The positive electrode active material layer12includes a positive electrode active material. The positive electrode active material layer12preferably further includes a binder. The positive electrode active material layer12may further include a conducting agent. In the context of the present specification, the term “conducting agent” refers to a conductive material of a particulate shape, a fibrous shape, etc., which is mixed with the positive electrode active material for the preparation of the positive electrode active material layer or formed in the positive electrode active material layer, and is caused to be present in the positive electrode active material layer in a form connecting the particles of the positive electrode active material. The shape of the positive electrode active material is preferably particulate. The amount of the positive electrode active material is preferably 80.0 to 99.9% by mass, and more preferably 90 to 99.5% by mass, based on the total mass of the positive electrode active material layer12. The positive electrode active material preferably has, on at least a part of its surface, a coated section including a conductive material (hereinbelow, the positive electrode active material particles having such a coated section are also referred to as “coated particles”). In this context, the expression “at least a part of its surface” means that the coated section of the active material particles covers 50% or more, preferably 70% or more, more preferably 90% or more, particularly preferably 100% of the total area of the entire outer surfaces of the positive electrode active material particles. This ratio (%) of the coated section (hereinafter, also referred to as “coverage”) is an average value for all the positive electrode active material particles present in the positive electrode active material layer. As long as this average value is not less than the above lower limit value, the positive electrode active material layer may contain a small amount of positive electrode active material particles without the coated section. When the positive electrode active material particles without the coated section are present in the positive electrode active material layer, the amount thereof is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less, with respect to the total mass of the positive electrode active material particles present in the positive electrode active material layer. The coverage can be measured by a method as follows. First, the particles in the positive electrode active material layer are analyzed by the energy dispersive X-ray spectroscopy using a transmission electron microscope (TEM-EDX). Specifically, an elemental analysis is performed by EDX with respect to the outer peripheral portion of the positive electrode active material particles in a TEM image. The elemental analysis is performed on carbon to identify the carbon covering the positive electrode active material particles. A section with a carbon coating having a thickness of 1 nm or more is defined as a coated section, and the ratio of the coated section to the entire circumference of the observed positive electrode active material particle can be determined as the coverage. The measurement can be performed with respect to, for example, 10 positive electrode active material particles, and an average value thereof can be used as a value of the coverage. Further, the coated section of the active material is a layer directly formed on the surface of particles (hereinafter, also referred to as “core section”) composed of only the positive electrode active material, which has a thickness of 1 nm to 100 nm, preferably 5 nm to 50 nm. This thickness can be determined by the above-mentioned TEM-EDX used for the measurement of the coverage. The conductive material of the coated section of the active material preferably contains carbon. The conductive material may be composed only of carbon, or may be a conductive organic compound containing carbon and elements other than carbon. Examples of the other elements include nitrogen, hydrogen, oxygen and the like. In the conductive organic compound, the amount of the other elements is preferably 10 atomic % or less, and more preferably 5 atomic % or less. It is more preferable that the conductive material in the coated section of the active material is composed only of carbon. The amount of the conductive material is 0.1 to 3.0% by mass, more preferably 0.5 to 1.5% by mass, and even more preferably 0.7 to 1.3% by mass, based on the total mass of the positive electrode active material including the coated section. Excessive amount of the conductive material is not favorable in that the conductive material may come off the surface of the positive electrode active material particles and remain as isolated conducting agent particles. For example, the coated section of the active material is formed in advance on the surface of the positive electrode active material particles, and is present on the surface of the positive electrode active material particles in the positive electrode active material layer. That is, the coated section of the active material in the present embodiment is not one newly formed in the steps following the preparation step of a positive electrode composition. In addition, the coated section of the active material is not one that comes off in the steps following the preparation step of a positive electrode composition. For example, the coated section stays on the surface of the positive electrode active material even when the coated particles are mixed with a solvent by a mixer or the like during the preparation of a positive electrode composition. Further, the coated section stays on the surface of the positive electrode active material even when the positive electrode active material layer is detached from the positive electrode and then put into a solvent to dissolve the binder contained in the positive electrode active material layer in the solvent. Furthermore, the coated section stays on the surface of the positive electrode active material even when an operation to disintegrate agglomerated particles is implemented for measuring the particle size distribution of the particles in the positive electrode active material layer by the laser diffraction scattering method. Examples of the method for producing the coated particles include a sintering method and a vapor deposition method. Examples of the sintering method include a method that sinters an active material composition (for example, a slurry) containing the positive electrode active material particles and an organic substance at 500 to 1000° C. for 1 to 100 hours under atmospheric pressure. Examples of the organic substance added to the active material composition include salicylic acid, catechol, hydroquinone, resorcinol, pyrogallol, fluoroglucinol, hexahydroxybenzene, benzoic acid, phthalic acid, terephthalic acid, phenylalanine, water dispersible phenolic resins, saccharides (e.g., sucrose, glucose and lactose), carboxylic acids (e.g., malic acid and citric acid), unsaturated monohydric alcohols (e.g., allyl alcohol and propargyl alcohol), ascorbic acid, and polyvinyl alcohol. This sintering method sinters an active material composition to allow carbon in the organic material to be fused to the surface of the positive electrode active material to thereby form the coated section of the active material. Another example of the sintering method is the so-called impact sintering coating method. The impact sintering coating method is, for example, carried our as follows. In an impact sintering coating device, a burner is ignited using a mixed gas of a hydrocarbon and oxygen as a fuel to burn the mixed gas in a combustion chamber, thereby generating a flame, wherein the amount of oxygen is adjusted so as not to exceed its equivalent amount that allows complete combustion of the fuel, to thereby lower the flame temperature. A powder supply nozzle is installed downstream thereof, from which a solid-liquid-gas three-phase mixture containing a combustion gas as well as a slurry formed by dissolving an organic substance for coating in a solvent is injected toward the flame. The injected fine powder is accelerated at a temperature not higher than the transformation temperature, the sublimation temperature, and the evaporation temperature of the powder material by increasing the amount of combustion gas maintained at room temperature to lower the temperature of the injected fine powder. This allows the particles of the powder to be instantly fused on the active material by impact, thereby forming coated particles of the positive electrode active material. Examples of the vapor deposition method include a vapor phase deposition method such as a physical vapor deposition method (PVD) and a chemical vapor deposition method (CVD), and a liquid phase deposition method such as plating. Further, the thickness of the positive electrode active material layer (total thickness of the positive electrode active material layers in the case where the positive electrode active material layers are formed on both sides of the positive electrode current collector) is preferably 30 to 500 μm, more preferably 40 to 400 μm, particularly preferably 50 to 300 μm. When the thickness of the positive electrode active material layer is not less than the lower limit value of the above range, it is possible to provide a positive electrode that can be used for manufacturing a battery having excellent energy density per unit volume. When the thickness is not more than the upper limit value of the above range, the peel strength of the positive electrode active material layer can be improved, thereby preventing delamination of the positive electrode active material layer during charging/discharging. The positive electrode active material preferably contains a compound having an olivine crystal structure. The compound having an olivine crystal structure is preferably a compound represented by the following formula: LiFexMPO(1-x)PO4(hereinafter, also referred to as “formula (I)”). In the formula (I), 0≤x≤1. M is Co, Ni, Mn, Al, Ti or Zr. A minute amount of Fe and M (Co, Ni, Mn, Al, Ti or Zr) may be replaced with another element so long as the replacement does not affect the physical properties of the compound. The presence of a trace amount of metal impurities in the compound represented by the formula (I) does not impair the effect of the present invention. The compound represented by the formula (I) is preferably lithium iron phosphate represented by LiFePO4(hereinafter, also simply referred to as “lithium iron phosphate”). The compound is more preferably lithium iron phosphate particles having, on at least a part of their surfaces, a coated section including a conductive material (hereinafter, also referred to as “coated lithium iron phosphate particles”). It is more preferable that the entire surfaces of lithium iron phosphate particles are coated with a conductive material for achieving more excellent battery capacity and cycling performance. The coated lithium iron phosphate particles can be produced by a known method. For example, the coated lithium iron phosphate particles can be obtained by a method in which a lithium iron phosphate powder is prepared by following the procedure described in Japanese Patent No. 5098146, and at least a part of the surface of lithium iron phosphate particles in the powder is coated with carbon by following the procedure described in GS Yuasa Technical Report, June 2008, Vol. 5, No. 1, pp. 27-31 and the like. Specifically, first, iron oxalate dihydrate, ammonium dihydrogen phosphate, and lithium carbonate are weighed to give a specific molar ratio, and these are pulverized and mixed in an inert atmosphere. Next, the obtained mixture is heat-treated in a nitrogen atmosphere to prepare a lithium iron phosphate powder. Then, the lithium iron phosphate powder is placed in a rotary kiln and heat-treated while supplying methanol vapor with nitrogen as a carrier gas to obtain a powder of lithium iron phosphate particles having at least a part of their surfaces coated with carbon. For example, the particle size of the lithium iron phosphate powder can be adjusted by optimizing the pulverization time in the pulverization process. The amount of carbon coating the particles of the lithium iron phosphate powder can be adjusted by optimizing the heating time and temperature in the step of implementing heat treatment while supplying methanol vapor. It is desirable to remove the carbon particles not consumed for coating by subsequent steps such as classification and washing. The positive electrode active material may contain other positive electrode active materials than the compound having an olivine type crystal structure. Preferable examples of the other positive electrode active materials include a lithium transition metal composite oxide. Specific examples thereof include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel cobalt aluminum oxide (LiNixCoyAlzO2with the proviso that x+y+z=1), lithium nickel cobalt manganese oxide (LiNixCoyMnzO2with the proviso that x+y+z=1), lithium manganese oxide (LiMn2O4), lithium manganese cobalt oxide (LiMnCoO4), lithium manganese chromium oxide (LiMnCrO4), lithium vanadium nickel oxide (LiNiVO4), nickel-substituted lithium manganese oxide (e.g., LiMn1.5Ni0.5O4), and lithium vanadium cobalt oxide (LiCoVO4), as well as nonstoichiometric compounds formed by partially substituting the compounds listed above with metal elements. Examples of the metal element include one or more selected from the group consisting of Mn, Mg, Ni, Co, Cu, Zn and Ge. With respect to the other positive electrode active materials, a single type thereof may be used individually or two or more types thereof may be used in combination. The other positive electrode active material may have, on at least a part of its surface, the coated section described above. The amount of the compound having an olivine type crystal structure is preferably 50% by mass or more, preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the positive electrode active material (including the mass of the coated section if present). This amount may be 100% by mass. When the coated lithium iron phosphate particles are used, the amount of the coated lithium iron phosphate particles is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the positive electrode active material. This amount may be 100% by mass. The average particle size of the positive electrode active material particles (that is, positive electrode active material powder) (including the thickness of the coated section if present) is, for example, preferably 0.1 to 20.0 μm, and more preferably 0.2 to 10.0 μm. When two or more types of positive electrode active materials are used, the average particle size of each of such positive electrode active materials may be within the above range. The average particle size of the positive electrode active material in the present specification is a volume-based median particle size measured using a laser diffraction/scattering particle size distribution analyzer. The binder that can be contained in the positive electrode active material layer12is an organic substance, and examples thereof include polyacrylic acid, lithium polyacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymers, styrene butadiene rubbers, polyvinyl alcohol, polyvinyl acetal, polyethylene oxide, polyethylene glycol, carboxymethyl cellulose, polyacrylic nitrile, and polyimide. With respect to the binder, a single type thereof may be used alone or two or more types thereof may be used in combination. The amount of the binder in the positive electrode active material layer12is, for example, preferably 4.0% by mass or less, and more preferably 2.0% by mass or less, based on the total mass of the positive electrode active material layer12. When the amount of the binder is not more than the above upper limit value, the proportion of the substance that does not contribute to the conduction of lithium ions in the positive electrode active material layer12is reduced, and the battery performance can be further improved. When the positive electrode active material layer12contains a binder, the lower limit of the amount of the binder is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more, based on the total mass of the positive electrode active material layer12. That is, when the positive electrode active material layer12contains a binder, the amount of the binder is preferably 0.1% by mass to 4.0% by mass, and more preferably 0.5 to 2.0% by mass, based on a total mass of the positive electrode active material layer12. Examples of the conducting agent contained in the positive electrode active material layer12include carbon materials such as graphite, graphene, hard carbon, Ketjen black, acetylene black, and carbon nanotube (CNT). With respect to the conducting agent, a single type thereof may be used alone or two or more types thereof may be used in combination. The amount of the conducting agent in the positive electrode active material layer12is, for example, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass or less, relative to 100 parts by mass of the positive electrode active material. When the conducting agent is incorporated into the positive electrode active material layer12, the lower limit value of the amount of the conducting agent is appropriately determined according to the type of the conducting agent, and is, for example, more than 0.1% by mass, based on the total mass of the positive electrode active material layer12. In the context of the present specification, the expression “the positive electrode active material layer12does not contain a conducting agent” or similar expression means that the positive electrode active material layer12does not substantially contain a conducting agent, and should not be construed as excluding a case where a conducting agent is contained in such an amount that the effects of the present invention are not affected. For example, if the amount of the conducting agent is 0.1% by mass or less, based on the total mass of the positive electrode active material layer12, then, it is judged that substantially no conducting agent is contained. (Positive Electrode Current Collector) Examples of the material of the positive electrode current collector main body14include conductive metals such as copper, aluminum, titanium, nickel, and stainless steel. The thickness of the positive electrode current collector main body14is preferably, for example, 8 to 40 μm, and more preferably 10 to 25 μm. The thickness of the positive electrode current collector main body14and the thickness of the positive electrode current collector11can be measured using a micrometer. One example of the measuring instrument usable for this purpose is an instrument with the product name “MDH-25M”, manufactured by Mitutoyo Co., Ltd. (Current Collector Coating Layer) The current collector coating layer15contains a conductive material. The conductive material in the current collector coating layer15preferably contains carbon (conductive carbon), and more preferably consists exclusively of carbon. The current collector coating layer15is preferred to be, for example, a coating layer containing carbon particles such as carbon black and a binder. Examples of the binder for the current collector coating layer15include those listed above as examples of the binder for the positive electrode active material layer12. With regard to the production of the positive electrode current collector11in which the surface of the positive electrode current collector main body14is coated with the current collector coating layer15, for example, the production can be implemented by a method in which a slurry containing the conductive material, the binder, and a solvent is applied to the surface of the positive electrode current collector main body14with a known coating method such as a gravure method, followed by drying to remove the solvent. The thickness of the current collector coating layer15is preferably 0.1 to 4.0 μm. The thickness of the current collector coating layer can be measured by a method of measuring the thickness of the coating layer in a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image of a cross section of the current collector coating layer. The thickness of the current collector coating layer need not be uniform. It is preferable that the current collector coating layer15having a thickness of 0.1 μm or more is present on at least a part of the surface of the positive electrode current collector main body14, and the maximum thickness of the current collector coating layer is 4.0 μm or less. (Method for Producing Positive Electrode) For example, the positive electrode1of the present embodiment can be produced by a method in which a positive electrode composition containing a positive electrode active material, a binder and a solvent is coated on the positive electrode current collector11, followed by drying to remove the solvent to thereby form a positive electrode active material layer12. The positive electrode composition may contain a conducting agent. The thickness of the positive electrode active material layer12can be adjusted by a method in which a layered body composed of the positive electrode current collector11and the positive electrode active material layer12formed thereon is placed between two flat plate jigs and, then, uniformly pressurized in the thickness direction of this layered body. For this purpose, for example, a method of pressurizing (rolling) using a roll press can be used. The solvent for the positive electrode composition is preferably a non-aqueous solvent. Examples of the solvent include alcohols such as methanol, ethanol, 1-propanol and 2-propanol; chain or cyclic amides such as N-methylpyrrolidone and N,N-dimethylformamide; and ketones such as acetone. With respect to these solvents, a single type thereof may be used individually or two or more types thereof may be used in combination. (Particle Size Distribution Curve) In the present specification, the particle size distribution curve of the particles present in the positive electrode active material layer12(hereinafter, also referred to as “particle size distribution curve P”) is a volume-based particle size distribution curve obtained by measurement using a laser diffraction/scattering particle size distribution analyzer. The particle size distribution curve P may be shown as a frequency distribution curve in which particle diameters are plotted on the abscissa, and frequency values (unit: %) are plotted on the ordinate, or an integrated distribution curve in which particle diameters are plotted on the abscissa, and integrated values of the frequency (unit: %) are plotted on the ordinate. A sample used for the measurement is an aqueous dispersion prepared by detaching the positive electrode active material layer12from the positive electrode1and dispersing the particles that had been present in the positive electrode active material layer12in water. It is preferable to ultrasonically treat the aqueous dispersion to sufficiently disperse the particles. In the positive electrode1of the present embodiment, an integrated value (a) is 3 to 15%, which is an integrated value of frequency of particle diameters of 1 μm or less, and a frequency (b) is 8 to 20%, which is a frequency of a diameter with a maximum frequency (mode diameter), each determined from the particle size distribution curve P. The integrated value (a) is preferably 4 to 12%, and more preferably 5 to 10%. The frequency (b) is preferably 9 to 18%, and more preferably 11 to 15%. A smaller integrated value (a) means a smaller ratio of the volume occupied by the fine powder relative to the total volume of the particles present in the positive electrode active material layer12. The fine powders of the positive electrode active material and the conducting agent have large surface areas, and hence show relatively high reactivity. As a result, such fine powders are liable to form sites where side reactions between the positive electrode1and the electrolytic solution vigorously occur due to local current concentration during the high-rate charge/discharge cycle. When the integrated value (a) is not more than the upper limit of the above range, sites of side reactions decrease and deterioration is likely to be suppressed. When the integrated value (a) is not less than the lower limit of the above range, particles with a particle diameter of 1 μm or less fill the voids between the particles, and hence the volume density of the positive electrode tends to improve, which is preferable in terms of improving the volumetric energy density of the battery. A high frequency (b) means the presence of a relatively small amount of fine particles and coarse particles. As described above, the fine powders of the positive electrode active material and the conducting agent are liable to cause deterioration. Coarse particles of the positive electrode active material and the conducting agent tend to result in formation of inactive sites on their surfaces that do not contribute to the reaction during charging and discharging, which tends to cause a decrease in capacity. When the ratio of the positive electrode active material in the positive electrode active material layer12is large and the amount of fine powder is small, or when the particle size distributions of the positive electrode active material and the conducting agent are similar and show large overlap of the peaks, the frequency (b) tends to increase. As the frequency (b) increases, the number of particles having a particle diameter close to the mode diameter increases, so that the amount of fine particles decreases relatively and deterioration is likely to be suppressed. When the frequency (b) is not less than the lower limit of the above range, the abundance ratio of the fine particles and coarse particles decreases relatively, and an effect of avoiding local current concentration during a high rate charge/discharge cycle can be obtained. When the frequency (b) is not more than the upper limit of the above range, a distribution with moderate amounts of small particles and large particles can be obtained, and the small particles fill the gaps between the large particles during the rolling, so that the volume density of the positive electrode is likely to improve, which is favorable in terms of improving the volumetric energy density of the battery. The integrated value (a) can be adjusted by, for example, the amount of fine powder contained in the positive electrode active material. The integrated value (a) can be lowered by using a positive electrode active material with less amount of fine powder. When a conducting agent is used, the integrated value (a) can be controlled by adjusting the blending amount of the conducting agent. The integrated value (a) can be lowered by reducing the blending amount of the conducting agent. The frequency (b) can be controlled, for example, by adjusting the particle size distribution of the positive electrode active material. As the half width of the peak in the frequency distribution curve of the positive electrode active material decreases, the frequency (b) tends to increase. When a conducting agent is used, the frequency (b) can be controlled by adjusting the particle size distribution of the conducting agent and the blending amount of the conducting agent. As the similarity of the particle size distribution of the conducting agent to the particle size distribution of the positive electrode active material increases, the frequency (b) tends to increase. When the particle size distribution curve of the conducting agent is off to the side of smaller particles or to the side of larger particles relative to the particle size distribution curve of the positive electrode active material, the frequency (b) can be increased by reducing the blending amount of the conducting agent as much as possible. When the frequency values are plotted on the ordinate of the particle size distribution curve P, the particle size distribution curve P preferably has a single maximum point (peak), indicating a monomodal particle size distribution. When the particle size distribution curve P has a single maximum point, excellent cycling performance can be achieved. For example, a particle size distribution curve P having a single maximum point can be obtained when the positive electrode active material layer12is formed by using a single type of a positive electrode active material and without using a conducting agent or using a least possible amount of a conducting agent. Of the two normal distributions obtained by waveform separation of the particle size distribution curve P with frequency as ordinate, the one with a smaller average size is defined as first normal distribution, and the one with a larger average size is defined as a second normal distribution. In the obtained first normal distribution, the particle size at a 10% frequency cumulation from a smaller particle side is defined as 10% particle size (D10), and the particle size at a 90% frequency cumulation from a smaller particle side is defined as 90% particle size (D90). The positive electrode1of the present embodiment preferably has a distribution width (c) ((c)=D90−D10) of 2.0 to 20.0 μm, which is obtained by subtracting the 10% particle size from the 90% particle size (c=D90−D10). The distribution width (c) is a value reflecting a situation where the frequency distributions of the fine powder z1 of the positive electrode active material present in the positive electrode active material layer12, the positive electrode active material z2 having a particle size smaller than the most frequent diameter (mode diameter) in the particle size distribution curve P, and the conducting agent z3 having a particle size smaller than the most frequent diameter of the particle size distribution curve P are combined. When the distribution width (c) is not less than the lower limit of the above range and the integrated value (d) described below is 30% or less, the amounts of the z1, z2, and z3 with particle diameters around 1 μm are small. The distribution width (c) being not more than the upper limit indicates that the particles of the positive electrode active material and the conducting agent present in the positive electrode active material layer are not too large. If these particles are too large, the surface area where a reaction can occur during charging and discharging of the positive electrode active material layer is reduced. When the distribution width (c) exceeds 20.0 μm, the effect of the present invention will be lost. In this context, the particles being “large” indicates that the proportion of coarse particles is high and/or the most frequent diameter is large. The distribution width (c) is preferably 2.0 to 15.0 μm, and more preferably 2.5 to 10.0 μm. The distribution width (c) can be controlled, for example, by adjusting the particle size distribution of the positive electrode active material. As the proportions of z1 and z2 decrease, the distribution width (c) is likely to increase. When the conducting agent is used, the distribution width (c) can be controlled by adjusting the blending amount and the particle size of z3. As the amount of z3 decreases and as the particle size of z3 gets closer to the most frequent diameter of the particle size distribution curve P, the distribution width (c) is inclined to decrease. When the particles of the positive electrode active material and the conducting agent are too large, the distribution width (c) increases. The positive electrode1of the present embodiment preferably has an integrated value (d) of 1 to 30%, which is an integrated value of frequency of particle diameters of 1 μm or less in the first normal distribution. The integrated value (d) reflects the distribution of the fine powder z1 of the positive electrode active material and the conducting agent z4 having a particle diameter of 1 μm or less. When the integrated value (d) is not less than the lower limit of the above range, particles with a particle diameter of 1 μm or less fill the voids between the particles during rolling, and hence the volume density of the positive electrode tends to improve, which is preferable in terms of improving the volumetric energy density of the battery. When the integrated value (d) is not more than the upper limit of the above range, the amount of fine powder on which the current locally concentrates during charging/discharging is reduced, so that deterioration is likely to be suppressed. The integrated value (d) is preferably 4 to 27%, and more preferably 7 to 24%. The integrated value (d) can be controlled, for example, by adjusting the amount of fine particles having a particle diameter of 1 μm or less in the positive electrode active material. As the amount of fine powder of 1 μm or less decreases, the integrated value (d) tends to decrease. The amount of fine powder can be reduced by a known treatment method such as classification implemented at the time of producing the positive electrode active material. When the conducting agent is used, the integrated value (d) can be controlled by adjusting the particle size and the blending amount of the conducting agent. As the proportion of particles having a particle diameter of 1 μm or less in the conducting agent decreases, the integrated value (d) tends to decrease. As the amount of the conducting agent having a particle diameter of 1 μm or less in the positive electrode active material layer12decreases, the integrated value (d) tends to decrease. (Volume Density of Positive Electrode Active Material Layer) In the present embodiment, the volume density of the positive electrode active material layer12is preferably 2.05 to 2.80 g/cm3, more preferably 2.15 to 2.50 g/cm3. The volume density of the positive electrode active material layer12can be measured by, for example, the following measuring method. The thicknesses of the positive electrode1and the positive electrode current collector11are each measured with a micrometer, and the difference between these two thickness values is calculated as the thickness of the positive electrode active material layer12. With respect to the thickness of the positive electrode1and the thickness of the positive electrode current collector11, each of these thickness values is an average value of the thickness values measured at five or more arbitrarily chosen points. The thickness of the positive electrode current collector11may be measured at the exposed section13of the positive electrode current collector, which is described below. The mass of the measurement sample punched out from the positive electrode so as to have a predetermined area is measured, from which the mass of the positive electrode current collector11measured in advance is subtracted to calculate the mass of the positive electrode active material layer12. The volume density of the positive electrode active material layer12is calculated by the following formula (1). Volume density (unit: g/cm3)=mass of positive electrode active material layer (unit: g)/[(thickness of positive electrode active material layer (unit: cm))×area of measurement sample (Unit: cm2)] (1) When the volume density of the positive electrode active material layer12is within the above range, the volumetric energy density of the battery can be further improved, and a non-aqueous electrolyte secondary battery with a further improved cycle characteristics can be realized. The volume density of the positive electrode active material layer12can be controlled by, for example, adjusting the amount of the positive electrode active material, the particle size of the positive electrode active material, the thickness of the positive electrode active material layer12, and the like. When the positive electrode active material layer12contains a conducting agent, the volume density can also be controlled by selecting the type of the conducting agent (specific surface area, specific gravity), or adjusting the amount of the conducting agent, and the particle size of the conducting agent. The positive electrode1of the present embodiment preferably has a conductive carbon content of 0.5 to 3.5% by mass, more preferably 1.5 to 3.0% by mass, with respect to the mass of the positive electrode1excluding the positive electrode current collector main body14. When the positive electrode1is composed of the positive electrode current collector main body14and the positive electrode active material layer12, the mass of the positive electrode1excluding the positive electrode current collector main body14is the mass of the positive electrode active material layer12. When the positive electrode1is composed of the positive electrode current collector main body14, the current collector coating layer15, and the positive electrode active material layer12, the mass of the positive electrode1excluding the positive electrode current collector main body14is the sum of the mass of the current collector coating layer15and the mass of the positive electrode active material layer12. The conductive carbon content based on the total mass of the positive electrode active material layer is preferably 0.5% by mass or more and less than 3.0% by mass, more preferably 1.0 to 2.8% by mass, even more preferably 1.3 to 2.6% by mass. The amount of the conductive carbon with respect to the mass of the positive electrode1excluding the positive electrode current collector main body14can be measured by <<Method for measuring conductive carbon content>> described below with respect to a dried product (powder), as a measurement target, obtained by detaching the whole of a layer present on the positive electrode current collector main body14, collecting the whole of substance resulting from the detached layer, and vacuum-drying the collected substance at 120° C. The particle size of the dried powder as the measurement target is not particularly limited as long as the conductive carbon content can be appropriately measured by the method described below. The conductive carbon content based the total mass of the positive electrode active material layer can be measured by <<Method for measuring conductive carbon content>> described below with respect to a dried product (powder), as a measurement target, obtained by vacuum-drying, at 120° C., the positive electrode active material layer detached from the positive electrode. The conductive carbon to be measured by the <<Method for measuring conductive carbon content>> described below includes carbon in the coated section of the positive electrode active material, carbon in the conducting agent, and carbon in the current collector coating layer15. Carbon in the binder is not included in the conductive carbon to be measured. As a method for obtaining the measurement target, for example, the following method can be adopted. First, the layer (powder) present on the positive electrode current collector main body14is completely detached by a method in which the positive electrode1is punched to obtain a piece having a predetermined size, and the piece of the positive electrode current collector main body14is immersed in a solvent (for example, N-methylpyrrolidone) and stirred. Next, after confirming that no powder remains attached to the positive electrode current collector main body14, the positive electrode current collector main body14is taken out from the solvent to obtain a suspension (slurry) containing the detached powder and the solvent. The obtained suspension is dried at 120° C. to completely volatilize the solvent to obtain the desired measurement target (powder). <<Method for Measuring Conductive Carbon Content>> (Measurement Method A) A sample having a weight w1 is taken from a homogeneously mixed product of the measurement target, and the sample is subjected to thermogravimetry differential thermal analysis (TG-DTA) implemented by following step A1 and step A2 defined below, to obtain a TG curve. From the obtained TG curve, the following first weight loss amount M1 (unit: % by mass) and second weight loss amount M2 (unit: % by mass) are obtained. By subtracting M1 from M2, the conductive carbon content (unit: % by mass) is obtained. Step A1: A temperature of the sample is raised from 30° C. to 600° C. at a heating rate of 10° C./min and holding the temperature at 600° C. for 10 minutes in an argon gas stream of 300 m/min to measure a resulting mass w2 of the sample, from which a first weight loss amount M1 is determined by formula (a1): M1=(w1−w2)/w1×100 (a1). Step A2: Immediately after the step A1, the temperature is lowered from 600° C. to 200° C. at a cooling rate of 10° C./min and held at 200° C. for 10 minutes, followed by completely substituting the argon gas stream with an oxygen gas stream. The temperature is raised from 200° C. to 1000° C. at a heating rate of 10° C./min and held at 1000° C. for 10 minutes in an oxygen gas stream of 100 mL/min to measure a resulting mass w3 of the sample, from which a second weight loss amount M2 (unit: % by mass) is calculated by formula (a2): M2=(w1−w3)/w1×100 (a2). (Measurement Method B) 0.0001 mg of a precisely weighed sample is taken from a homogeneously mixed product of the measurement target, and the sample is burnt under burning conditions defined below to measure an amount of generated carbon dioxide by a CHN elemental analyzer, from which a total carbon content M3 (unit: % by mass) of the sample is determined. Also, a first weight loss amount M1 is determined following the procedure of the step A1 of the measurement method A. By subtracting M1 from M3, the conductive carbon content (unit: % by mass) is obtained. (Burning Conditions) Temperature of combustion furnace: 1150° C. Temperature of reduction furnace: 850° C. Helium flow rate: 200 mL/min. Oxygen flow rate: 25 to 30 mL/min. (Measurement Method C) The total carbon content M3 (unit: % by mass) of the sample is measured in the same manner as in the above measurement method B. Further, the carbon amount M4 (unit: % by mass) of carbon derived from the binder is determined by the following method. M4 is subtracted from M3 to determine a conductive carbon content (unit: % by mass). When the binder is polyvinylidene fluoride (PVDF: monomer (CH2CF2), molecular weight64), the conductive carbon content can be calculated by the following formula from the fluoride ion (F−) content (unit: % by mass) measured by combustion ion chromatography based on the tube combustion method, the atomic weight (19) of fluorine in the monomers constituting PVDF, and the atomic weight (12) of carbon in the PVDF. PVDF content (unit: % by mass)=fluoride ion content (unit: % by mass)×64/38 PVDF-derived carbon amountM4 (unit: % by mass)=fluoride ion content (unit: % by mass)×12/19 The presence of polyvinylidene fluoride as a binder can be verified by a method in which a sample or a liquid obtained by extracting a sample with an N,N-dimethylformamide (DMF) solvent is subjected to Fourier transform infrared spectroscopy (FT-IR) to confirm the absorption attributable to the C—F bond. Such verification can be also implemented by 19F-NMR measurement. When the binder is identified as being other than PVDF, the carbon amount M4 attributable to the binder can be calculated by determining the amount (unit: % by mass) of the binder from the measured molecular weight, and the carbon content (unit: % by mass). These methods are described in the following publications: Toray Research Center, The TRC News No. 117 (September 2013), pp. 34-37, [Searched on Feb. 10, 2021], Internet <https://www.toray-research.co.jp/technical-info/trcnews/pdf/TRC117(34-37).pdf> TOSOH Analysis and Research Center Co., Ltd., Technical Report No. T1019 2017.09.20, [Searched on Feb. 10, 2021], Internet <http://www.tosoh-arc.co.jp/techrepo/files/tarc00522/T1719N.pdf> <<Analytical Method for Conductive Carbon>> The conductive carbon in the coated section of the positive electrode active material and the conductive carbon as the conducting agent can be distinguished by the following analytical method. For example, particles in the positive electrode active material layer are analyzed by a combination of transmission electron microscopy-electron energy loss spectroscopy (TEM-EELS), and particles having a carbon-derived peak around 290 eV only near the particle surface can be judged to be the positive electrode active material. On the other hand, particles having a carbon-derived peak inside the particles can be judged to be the conducting agent. In this context, “near the particle surface” means a region to the depth of approximately 100 nm from the particle surface, while “inside” means an inner region positioned deeper than the “near the particle surface”. As another method, the particles in the positive electrode active material layer are analyzed by Raman spectroscopy mapping, and particles showing carbon-derived G-band and D-band as well as a peak of the positive electrode active material-derived oxide crystals can be judged to be the positive electrode active material. On the other hand, particles showing only G-band and D-band can be judged to be the conducting agent. As still another method, a cross section of the positive electrode active material layer is observed with scanning spread resistance microscope (SSRM). When the particle surface has a region with lower resistance than the inside of the particle, the region with lower resistance can be judged to be the conductive carbon present in the coated section of the active material. Other particles that are present isolatedly and have low resistance can be judged to be the conducting agent. In this context, a trace amount of carbon considered to be an impurity and a trace amount of carbon unintentionally removed from the surface of the positive electrode active material during production are not judged to be the conducting agent. Using any of these methods, it is possible to verify whether or not the conducting agent formed of carbon material is contained in the positive electrode active material layer. <Non-Aqueous Electrolyte Secondary Battery> The non-aqueous electrolyte secondary battery10of the present embodiment shown inFIG.2includes a positive electrode1of the present embodiment, a negative electrode3, and a non-aqueous electrolyte. Further, a separator2may be provided. Reference numeral5inFIG.1denotes an outer casing. In the present embodiment, the positive electrode1has a plate-shaped positive electrode current collector11and positive electrode active material layers12provided on both surfaces thereof. The positive electrode active material layer12is present on a part of each surface of the positive electrode current collector11. The edge of the surface of the positive electrode current collector1is an exposed section13of the positive electrode current collector, which is free of the positive electrode active material layer12. A terminal tab (not shown) is electrically connected to an arbitrary portion of the exposed section13of the positive electrode current collector. The negative electrode3has a plate-shaped negative electrode current collector31and negative electrode active material layers32provided on both surfaces thereof. The negative electrode active material layer32is present on a part of each surface of the negative electrode current collector31. The edge of the surface of the negative electrode current collector31is an exposed section33of the negative electrode current collector, which is free of the negative electrode active material layer32. A terminal tab (not shown) is electrically connected to an arbitrary portion of the exposed section33of the negative electrode current collector. The shapes of the positive electrode1, the negative electrode3and the separator2are not particularly limited. For example, each of these may have a rectangular shape in a plan view. With regard to the production of the non-aqueous electrolyte secondary battery10of the present embodiment, for example, the production can be implemented by a method in which the positive electrode1and the negative electrode3are alternately interleaved through the separator2to produce an electrode layered body, which is then packed into an outer casing such as an aluminum laminate bag, and a non-aqueous electrolyte (not shown) is injected into the outer casing, followed by sealing the outer casing.FIG.2shows a representative example of a structure of the battery in which the negative electrode, the separator, the positive electrode, the separator, and the negative electrode are stacked in this order, but the number of electrodes can be altered as appropriate. The number of the positive electrode1may be one or more, and any number of positive electrodes1can be used depending on a desired battery capacity. The number of each of the negative electrode3and the separator2is larger by one sheet than the number of the positive electrode1, and these are stacked so that the negative electrode3is located at the outermost layer. (Negative Electrode) The negative electrode active material layer32includes a negative electrode active material. Further, the negative electrode active material layer32may further include a binder. Furthermore, the negative electrode active material layer32may include a conducting agent as well. The shape of the negative electrode active material is preferably particulate. For example, the negative electrode3can be produced by a method in which a negative electrode composition containing a negative electrode active material, a binder and a solvent is prepared, and coated on the negative electrode current collector31, followed by drying to remove the solvent to thereby form a negative electrode active material layer32. The negative electrode composition may contain a conducting agent. Examples of the negative electrode active material and the conducting agent include carbon materials such as graphite, graphene, hard carbon, Ketjen black, acetylene black, and carbon nanotube (CNT). With respect to each of the negative electrode active material and the conducting agent, a single type thereof may be used alone or two or more types thereof may be used in combination. Examples of the material of the negative electrode current collector31, the binder and the solvent in the negative electrode composition include those listed above as examples of the material of the positive electrode current collector11, the binder and the solvent in the positive electrode composition. With respect to each of the binder and the solvent in the negative electrode composition, a single type thereof may be used alone or two or more types thereof may be used in combination. The sum of the amount of the negative electrode active material and the amount of the conducting agent is preferably 80.0 to 99.9% by mass, and more preferably 85.0 to 98.0% by mass, based on the total mass of the negative electrode active material layer32. (Separator) The separator2is disposed between the negative electrode3and the positive electrode1to prevent a short circuit or the like. The separator2may retain a non-aqueous electrolyte described below. The separator2is not particularly limited, and examples thereof include a porous polymer film, a non-woven fabric, and glass fiber. An insulating layer may be provided on one or both surfaces of the separator2. The insulating layer is preferably a layer having a porous structure in which insulating fine particles are bonded with a binder for an insulating layer. The separator2may contain various plasticizers, antioxidants, and flame retardants. Examples of the antioxidant include phenolic antioxidants such as hindered-phenolic antioxidants, monophenolic antioxidants, bisphenolic antioxidants, and polyphenolic antioxidants; hinderedamine antioxidants; phosphorus antioxidants; sulfur antioxidants; benzotriazole antioxidants; benzophenone antioxidants; triazine antioxidants; and salicylate antioxidants. Among these, phenolic antioxidants and phosphorus antioxidants are preferable. (Non-Aqueous Electrolyte) The non-aqueous electrolyte fills the space between the positive electrode1and the negative electrode3. For example, any of known non-aqueous electrolytes used in lithium ion secondary batteries, electric double layer capacitors and the like can be used. As the non-aqueous electrolyte, a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in an organic solvent is preferable. The organic solvent is preferably one having tolerance to high voltage. Examples of the organic solvent include polar solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrohydrafuran, 2-methyltetrahydrofuran, dioxolane, and methyl acetate, as well as mixtures of two or more of these polar solvents. The electrolyte salt is not particularly limited, and examples thereof include lithium-containing salts such as LiClO4, LiPF6, LiBF4, LiAsF6, LiCF6, LiCF3CO2, LiPF6SO3, LiN(SO2F)2, LiN(SO2CF3)2, Li(SO2CF2CF3)2, LiN(COCF3)2, and LiN(COCF2CF3)2, as well as mixture of two or more of these salts. The non-aqueous electrolyte secondary battery of this embodiment can be used as a lithium ion secondary battery for various purposes such as industrial use, consumer use, automobile use, and residential use. The application of the non-aqueous electrolyte secondary battery of this embodiment is not particularly limited. For example, the battery can be used in a battery module configured by connecting a plurality of non-aqueous electrolyte secondary batteries in series or in parallel, a battery system including a plurality of electrically connected battery modules and a battery control system, and the like. Examples of the battery system include battery packs, stationary storage battery systems, automobile power storage battery systems, automobile auxiliary storage battery systems, emergency power storage battery systems, and the like. Second Embodiment In the second embodiment of the present invention, the positive electrode1for a non-aqueous electrolyte secondary battery includes a positive electrode current collector11and a positive electrode active material layer12provided on the positive electrode current collector11, wherein: the positive electrode active material layer12includes a positive electrode active material; and when two directions perpendicular to a thickness direction of the positive electrode current collector11and orthogonal to each other are defined as a first direction and a second direction, an average thickness a1, a maximum thickness b1 and a minimum thickness c1 in a thickness distribution in the first direction as well as a thickness d1 which is largest in terms of an absolute value of the difference from the average thickness a1 satisfy inequations 1 and 2: 0.990≤(d1/a1)≤1.010 Inequation 1, and (b1−c1)≤5.0 μm Inequation 2, and an average thickness a2, a maximum thickness b2 and a minimum thickness c2 in a thickness distribution in the second direction as well as a thickness d2 which is largest in terms of an absolute value of the difference from the average thickness a2 satisfy inequations 3 and 4: 0.990≤(d2/a2)≤1.010 Inequation 3, and (b2−c2)≤5.0 μm Inequation 4, The positive electrode1having the above configuration can improve the performance of a non-aqueous electrolyte secondary battery in respect of high-rate cycling performance. More specific explanation is made below. (Positive Electrode Active Material Layer) The positive electrode active material layer12includes a positive electrode active material. The positive electrode active material layer12preferably further includes a binder. The positive electrode active material layer12may further include a conducting agent. The shape of the positive electrode active material is preferably particulate. The amount of the positive electrode active material is preferably 80.0 to 99.9% by mass, and more preferably 90 to 99.5% by mass, based on the total mass of the positive electrode active material layer12. The positive electrode active material preferably has, on at least a part of its surface, a coated section including a conductive material (hereinbelow, the positive electrode active material particles having such a coated section are also referred to as “coated particles”). In this context, the expression “at least a part of its surface” means that the coated section of the active material particles covers 50% or more, preferably 70% or more, more preferably 90% or more, particularly preferably 100% of the total area of the entire outer surfaces of the positive electrode active material particles. This coverage (%) is an average value for all the positive electrode active material particles present in the positive electrode active material layer. As long as this average value is not less than the above lower limit value, the positive electrode active material layer may contain positive electrode active material particles without the coated section. When the positive electrode active material particles without the coated section are present in the positive electrode active material layer, the amount thereof is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less, with respect to the total mass of the positive electrode active material particles present in the positive electrode active material layer. The coverage can be measured by a method as follows. First, the particles in the positive electrode active material layer are analyzed by the energy dispersive X-ray spectroscopy (TEM-EDX) using a transmission electron microscope. Specifically, an elemental analysis is performed by EDX with respect to the outer peripheral portion of the positive electrode active material particles in a TEM image. The elemental analysis is performed on carbon to identify the carbon covering the positive electrode active material particles. A section with a carbon coating having a thickness of 1 nm or more is defined as a coated section, and the ratio of the coated section to the entire circumference of the observed positive electrode active material particle can be determined as the coverage. The measurement can be performed with respect to, for example, 10 positive electrode active material particles, and an average value thereof can be used as a value of the coverage. Further, the coated section of the active material is a layer directly formed on the surface of particles (core section) composed of only the positive electrode active material, which has a thickness of 1 nm to 100 nm, preferably 5 nm to 50 nm. This thickness can be determined by the above-mentioned TEM-EDX used for the measurement of the coverage. The conductive material of the coated section of the active material preferably contains carbon. The conductive material may be composed only of carbon, or may be a conductive organic compound containing carbon and elements other than carbon. Examples of the other elements include nitrogen, hydrogen, oxygen and the like. In the conductive organic compound, the amount of the other elements is preferably 10 atomic % or less, and more preferably 5 atomic % or less. It is more preferable that the conductive material in the coated section of the active material is composed only of carbon. The amount of the conductive material is 0.1 to 3.0% by mass, more preferably 0.5 to 1.5% by mass, and even more preferably 0.7 to 1.3% by mass, based on the total mass of the positive electrode active material including the coated section. Excessive amount of the conductive material is not favorable in that the conductive material may come off the surface of the positive electrode active material and remain as isolated conducting agent particles. For example, the coated section of the active material is formed in advance on the surface of the positive electrode active material particles, and is present on the surface of the positive electrode active material particles in the positive electrode active material layer. That is, the coated section of the active material in the present embodiment is not one newly formed in the steps following the preparation step of a positive electrode composition. In addition, the coated section of the active material is not one that comes off in the steps following the preparation step of a positive electrode composition. For example, the coated section stays on the surface of the positive electrode active material even when the coated particles are mixed with a solvent by a mixer or the like during the preparation of a positive electrode composition. Further, the coated section stays on the surface of the positive electrode active material even when the positive electrode active material layer is detached from the positive electrode and then put into a solvent to dissolve the binder contained in the positive electrode active material layer in the solvent. Furthermore, the coated section stays on the surface of the positive electrode active material even when an operation to disintegrate agglomerated particles is implemented for measuring the particle size distribution of the particles in the positive electrode active material layer by the laser diffraction scattering method. Examples of the method for producing the coated particles include a sintering method and a vapor deposition method. Examples of the sintering method include a method that sinters an active material composition (for example, a slurry) containing the positive electrode active material particles and an organic substance at 500 to 1000° C. for 1 to 100 hours under atmospheric pressure. Examples of the organic substance added to the active material composition include salicylic acid, catechol, hydroquinone, resorcinol, pyrogallol, fluoroglucinol, hexahydroxybenzene, benzoic acid, phthalic acid, terephthalic acid, phenylalanine, water dispersible phenolic resins, saccharides (e.g., sucrose, glucose and lactose), carboxylic acids (e.g., malic acid and citric acid), unsaturated monohydric alcohols (e.g., allyl alcohol and propargyl alcohol), ascorbic acid, and polyvinyl alcohol. This sintering method sinters an active material composition to allow carbon in the organic material to be fused to the surface of the positive electrode active material to thereby form the coated section of the active material. Another example of the sintering method is the so-called impact sintering coating method. The impact sintering coating method is, for example, carried our as follows. In an impact sintering coating device, a burner is ignited using a mixed gas of a hydrocarbon and oxygen as a fuel to burn the mixed gas in a combustion chamber, thereby generating a flame, wherein the amount of oxygen is adjusted so as not to exceed its equivalent amount that allows complete combustion of the fuel, to thereby lower the flame temperature. A powder supply nozzle is installed downstream thereof, from which a solid-liquid-gas three-phase mixture containing a combustion gas as well as a slurry formed by dissolving an organic substance for coating in a solvent is injected toward the flame. The injected fine powder is accelerated at a temperature not higher than the transformation temperature, the sublimation temperature, and the evaporation temperature of the powder material by increasing the amount of combustion gas maintained at room temperature to lower the temperature of the injected fine powder. This allows the particles of the powder to be instantly fused on the active material by impact, thereby forming coated particles of the positive electrode active material. Examples of the vapor deposition method include a vapor phase deposition method such as a physical vapor deposition method (PVD) and a chemical vapor deposition method (CVD), and a liquid phase deposition method such as plating. The positive electrode active material preferably contains a compound having an olivine crystal structure. The compound having an olivine crystal structure is preferably a compound represented by the following formula: LiFexM(1-x)PO4(hereinafter, also referred to as “formula (I)”). In the formula (I), 0≤x≤1, M is Co, Ni, Mn, Al, Ti or Zr. A minute amount of Fe and M (Co, Ni, Mn, Al, Ti or Zr) may be replaced with another element so long as the replacement does not affect the physical properties of the compound. The presence of a trace amount of metal impurities in the compound represented by the formula (I) does not impair the effect of the present invention. The compound represented by the formula (I) is preferably lithium iron phosphate represented by LiFePO4(hereinafter, also simply referred to as “lithium iron phosphate”). The compound is more preferably lithium iron phosphate particles having, on at least a part of their surfaces, a coated section including a conductive material (hereinafter, also referred to as “coated lithium iron phosphate particles”). It is more preferable that the entire surfaces of lithium iron phosphate particles are coated with a conductive material for achieving more excellent battery capacity and cycling performance. The coated lithium iron phosphate particles can be produced by a known method. For example, the coated lithium iron phosphate particles can be obtained by a method in which a lithium iron phosphate powder is prepared by following the procedure described in Japanese Patent No. 5098146, and at least a part of the surface of lithium iron phosphate particles in the powder is coated with carbon by following the procedure described in GS Yuasa Technical Report, June 2008, Vol. 5, No. 1, pp. 27-31 and the like. Specifically, first, iron oxalate dihydrate, ammonium dihydrogen phosphate, and lithium carbonate are weighed to give a specific molar ratio, and these are pulverized and mixed in an inert atmosphere. Next, the obtained mixture is heat-treated in a nitrogen atmosphere to prepare a lithium iron phosphate powder. Then, the lithium iron phosphate powder is placed in a rotary kiln and heat-treated while supplying methanol vapor with nitrogen as a carrier gas to obtain a powder of lithium iron phosphate particles having at least a part of their surfaces coated with carbon. For example, the particle size of the lithium iron phosphate powder can be adjusted by optimizing the pulverization time in the pulverization process. The amount of carbon coating the particles of the lithium iron phosphate powder can be adjusted by optimizing the heating time and temperature in the step of implementing heat treatment while supplying methanol vapor. It is desirable to remove the carbon particles not consumed for coating by subsequent steps such as classification and washing. The positive electrode active material may contain other positive electrode active materials than the compound having an olivine type crystal structure. Preferable examples of the other positive electrode active materials include a lithium transition metal composite oxide. Specific examples thereof include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium nickel cobalt aluminum oxide (LiNixCoyAlzO2with the proviso that x+y+z=1), lithium nickel cobalt manganese oxide (LiNixCoyMnzO2with the proviso that x+y+z=1), lithium manganese oxide (LiMn2O4), lithium manganese cobalt oxide (LiMnCoO4), lithium manganese chromium oxide (LiMnCrO4), lithium vanadium nickel oxide (LiNiVO4), nickel-substituted lithium manganese oxide (e.g., LiMn1.5Ni0.5O4), and lithium vanadium cobalt oxide (LiCoVO4), as well as nonstoichiometric compounds formed by partially substituting the compounds listed above with metal elements. Examples of the metal element include one or more selected from the group consisting of Mn, Mg, Ni, Co, Cu, Zn and Ge. With respect to the other positive electrode active materials, a single type thereof may be used individually or two or more types thereof may be used in combination. The other positive electrode active material may have, on at least a part of its surface, the coated section described above. The amount of the compound having an olivine type crystal structure is preferably 50% by mass or more, preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the positive electrode active material (including the mass of the coated section if present). This amount may be 100% by mass. When the coated lithium iron phosphate particles are used, the amount of the coated lithium iron phosphate particles is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the positive electrode active material. This amount may be 100% by mass. The average particle size of the positive electrode active material particles (that is, positive electrode active material powder) (including the thickness of the coated section if present) is, for example, preferably 0.1 to 5.0 μm, more preferably 0.2 to 3.0 μm. When two or more types of positive electrode active materials are used, the average particle size of each of such positive electrode active materials may be within the above range. The average particle size of the positive electrode active material in the present specification is a volume-based median particle size measured using a laser diffraction/scattering particle size distribution analyzer. The binder that can be contained in the positive electrode active material layer12is an organic substance, and examples thereof include polyacrylic acid, lithium polyacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymers, styrene butadiene rubbers, polyvinyl alcohol, polyvinyl acetal, polyethylene oxide, polyethylene glycol, carboxymethyl cellulose, polyacrylic nitrile, and polyimide. With respect to the binder, a single type thereof may be used alone or two or more types thereof may be used in combination. The amount of the binder in the positive electrode active material layer12is, for example, preferably 4.0% by mass or less, and more preferably 2.0% by mass or less, based on the total mass of the positive electrode active material layer12. When the amount of the binder is not more than the above upper limit value, the proportion of the substance that does not contribute to the conduction of lithium ions in the positive electrode active material layer12is reduced, and the battery performance can be further improved. When the positive electrode active material layer12contains a binder, the lower limit of the amount of the binder is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more, based on the total mass of the positive electrode active material layer12. That is, when the positive electrode active material layer12contains a binder, the amount of the binder is preferably 0.1% by mass to 4.0% by mass, and more preferably 0.5 to 2.0% by mass, based on a total mass of the positive electrode active material layer12. Examples of the conducting agent contained in the positive electrode active material layer12include carbon materials such as graphite, graphene, hard carbon, Ketjen black, acetylene black, and carbon nanotube (CNT). With respect to the conducting agent, a single type thereof may be used alone or two or more types thereof may be used in combination. The amount of the conducting agent in the positive electrode active material layer12is, for example, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass or less, relative to 100 parts by mass of the positive electrode active material. When the conducting agent is incorporated into the positive electrode active material layer12, the lower limit value of the amount of the conducting agent is appropriately determined according to the type of the conducting agent, and is, for example, more than 0.1% by mass, based on the total mass of the positive electrode active material layer12. In the context of the present specification, the expression “the positive electrode active material layer12does not contain a conducting agent” or similar expression means that the positive electrode active material layer12does not substantially contain a conducting agent, and should not be construed as excluding a case where a conducting agent is contained in such an amount that the effects of the present invention are not affected. For example, if the amount of the conducting agent is 0.1% by mass or less, based on the total mass of the positive electrode active material layer12, then, it is judged that substantially no conducting agent is contained. (Positive Electrode Current Collector) The positive electrode current collector body14is formed of a metal material. Examples of the metal material include conductive metals such as copper, aluminum, titanium, nickel, and stainless steel. The thickness of the positive electrode current collector main body14is preferably, for example, 8 to 40 μm, and more preferably 10 to 25 μm. The thickness of the positive electrode current collector main body14and the thickness of the positive electrode current collector11can be measured using a micrometer. One example of the measuring instrument usable for this purpose is an instrument with the product name “MDH-25M”, manufactured by Mitutoyo Co., Ltd. (Current Collector Coating Layer) The current collector coating layer15contains a conductive material. The conductive material in the current collector coating layer15preferably contains carbon (conductive carbon), and more preferably consists exclusively of carbon. The current collector coating layer15is preferred to be, for example, a coating layer containing carbon particles such as carbon black and a binder. Examples of the binder for the current collector coating layer15include those listed above as examples of the binder for the positive electrode active material layer12. With regard to the production of the positive electrode current collector11in which the surface of the positive electrode current collector main body14is coated with the current collector coating layer15, for example, the production can be implemented by a method in which a slurry containing the conductive material, the binder, and a solvent is applied to the surface of the positive electrode current collector main body14with a known coating method such as a gravure method, followed by drying to remove the solvent. The thickness of the current collector coating layer15is preferably 0.1 to 4.0 μm. The thickness of the current collector coating layer can be measured by a method of measuring the thickness of the coating layer in a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image of a cross section of the current collector coating layer. The thickness of the current collector coating layer need not be uniform. It is preferable that the current collector coating layer15having a thickness of 0.1 μm or more is present on at least a part of the surface of the positive electrode current collector main body14, and the maximum thickness of the current collector coating layer is 4.0 μm or less. (Method for Producing Positive Electrode) For example, the positive electrode1of the present embodiment can be produced by a method in which a positive electrode composition containing a positive electrode active material, a binder and a solvent is coated on the positive electrode current collector11, followed by drying to remove the solvent to thereby form a positive electrode active material layer12. The positive electrode composition may contain a conducting agent. The thickness of the positive electrode active material layer12can be adjusted by a method in which a layered body composed of the positive electrode current collector11and the positive electrode active material layer12formed thereon is placed between two flat plate jigs and, then, uniformly pressurized in the thickness direction of this layered body. For this purpose, for example, a method of pressurizing using a roll press can be used. The solvent for the positive electrode composition is preferably a non-aqueous solvent. Examples of the solvent include alcohols such as methanol, ethanol, 1-propanol and 2-propanol; chain or cyclic amides such as N-methylpyrrolidone and N,N-dimethylformamide; and ketones such as acetone. With respect to these solvents, a single type thereof may be used individually or two or more types thereof may be used in combination. When at least one of the conductive material and the conducting agent covering the positive electrode active material contains carbon, the conductive carbon content is preferably 0.5 to 3.5% by mass, and preferably 1.0 to 3.0% by mass, based on the total mass of the positive electrode active material layer12. The conductive carbon content based the total mass of the positive electrode active material layer12can be measured by <<Method for measuring conductive carbon content>> described below with respect to a dried product (powder), as a measurement target, obtained by vacuum-drying, at 120° C., the positive electrode active material layer12detached from the current collector. The conductive carbon to be measured by the <<Method for measuring conductive carbon content>> described below includes carbon in the coated section of the positive electrode active material, and carbon in the conducting agent. Carbon in the binder is not included in the conductive carbon to be measured. When the conductive carbon content based the total mass of the positive electrode active material layer12is within the above range, the battery capacity can be further improved, and a non-aqueous electrolyte secondary battery with a further improved cycle characteristics can be realized. When the positive electrode active material layer12includes a binder, the amount of carbon belonging to the binder is preferably 0.1 to 2.0% by mass, more preferably 0.2 to 1.7% by mass, and even more preferably 0.4 to 1.0% by mass, based on a total mass of the positive electrode active material layer12. The amount of carbon belonging to the binder, based the total mass of the positive electrode active material layer12, can be measured by <<Method for measuring conductive carbon content>> described below with respect to a dried product (powder), as a measurement target, obtained by vacuum-drying, at 120° C., the positive electrode active material layer12detached from the current collector. For example, the first weight loss amount M1 in the measurement method A and the measurement method B described below can be measured as amount of carbon belonging to the binder. Alternatively, the carbon amount M4 of carbon belonging to the binder can be determined by the measurement method C described below. As a method for obtaining the measurement target, for example, the following method can be adopted. When the current collector coating layer15is not present on the positive electrode current collector main body14and only the positive electrode active material layer12is present on the positive electrode current collector main body14, first, the positive electrode1is punched to obtain a piece having a predetermined size, and the layer (powder) present on the positive electrode current collector main body14is completely detached from the obtained piece by a method that immerses the piece in a solvent (for example, N-methylpyrrolidone) and stirs the resulting. Next, after confirming that no powder remains attached to the positive electrode current collector main body14, the positive electrode current collector main body14is taken out from the solvent to obtain a suspension (slurry) containing the detached powder and the solvent. The obtained suspension is dried at 120° C. to completely volatilize the solvent to obtain the desired measurement target (powder). When the current collector coating layer15and the positive electrode active material layer12are present on the positive electrode current collector main body14, the measurement target to be used is a dried product (powder) obtained by detaching only the powder constituting the positive electrode active material layer12and vacuum drying the powder in an environment of 120° C. For example, the measurement target may be one obtained by detaching the outermost surface of the positive electrode active material layer12with a depth of several 1 μm using a spatula or the like, and vacuum drying the resulting powder in an environment of 120° C. The positive electrode1preferably has a conductive carbon content of 0.5 to 3.5% by mass, more preferably 1.5 to 3.0% by mass, with respect to the mass of the positive electrode1excluding the positive electrode current collector main body14. When the positive electrode1is composed of the positive electrode current collector main body14and the positive electrode active material layer12, the mass of the positive electrode1excluding the positive electrode current collector main body14is the mass of the positive electrode active material layer12. When the positive electrode1is composed of the positive electrode current collector main body14, the current collector coating layer15, and the positive electrode active material layer12, the mass of the positive electrode1excluding the positive electrode current collector main body14is the sum of the mass of the current collector coating layer15and the mass of the positive electrode active material layer12. The amount of the conductive carbon with respect to the mass of the positive electrode1excluding the positive electrode current collector main body14can be measured by <<Method for measuring conductive carbon content>> described below with respect to a dried product (powder), as a measurement target, obtained by detaching the whole of a layer present on the positive electrode current collector main body14, collecting the whole of substance resulting from the detached layer, and vacuum-drying the collected substance at 120° C. <<Method for Measuring Conductive Carbon Content>> (Measurement Method A) A sample having a weight w1 is taken from a homogeneously mixed product of the measurement target, and the sample is subjected to thermogravimetry differential thermal analysis (TG-DTA) implemented by following step A1 and step A2 defined below, to obtain a TG curve. From the obtained TG curve, the following first weight loss amount M1 (unit: % by mass) and second weight loss amount M2 (unit: % by mass) are obtained. By subtracting M1 from M2, the conductive carbon content (unit: % by mass) is obtained. Step A1: A temperature of the sample is raised from 30° C. to 600° C. at a heating rate of 10° C./min and holding the temperature at 600° C. for 10 minutes in an argon gas stream of 300 mL/min to measure a resulting mass w2 of the sample, from which a first weight loss amount M1 is determined by formula (a1): M1=(w1−w2)/w1×100 (a1). Step A2: Immediately after the step A1, the temperature is lowered from 600° C. to 200° C. at a cooling rate of 10° C./min and held at 200° C. for 10 minutes, followed by completely substituting the argon gas stream with an oxygen gas stream. The temperature is raised from 200° C. to 1000° C. at a heating rate of 10° C./min and held at 1000° C. for 10 minutes in an oxygen gas stream of 100 mL/min to measure a resulting mass w3 of the sample, from which a second weight loss amount M2 (unit: % by mass) is calculated by formula (a2): M2=(w1−w3)/w1×100 (a2). (Measurement Method B) 0.0001 mg of a precisely weighed sample is taken from a homogeneously mixed product of the measurement target, and the sample is burnt under burning conditions defined below to measure an amount of generated carbon dioxide by a CHN elemental analyzer, from which a total carbon content M3 (unit: % by mass) of the sample is determined. Also, a first weight loss amount M1 is determined following the procedure of the step A1 of the measurement method A. By subtracting M1 from M3, the conductive carbon content (unit: % by mass) is obtained. (Burning Conditions) Temperature of combustion furnace: 1150° C. Temperature of reduction furnace: 850° C. Helium flow rate: 200 mL/min. Oxygen flow rate: 25 to 30 mL/min. (Measurement Method C) The total carbon content M3 (unit: % by mass) of the sample is measured in the same manner as in the above measurement method B. Further, the carbon amount M4 (unit: % by mass) of carbon derived from the binder is determined by the following method. M4 is subtracted from M3 to determine a conductive carbon content (unit: % by mass). When the binder is polyvinylidene fluoride (PVDF: monomer (CH2CF2), molecular weight64), the conductive carbon content can be calculated by the following formula from the fluoride ion (F−) content (unit: % by mass) measured by combustion ion chromatography based on the tube combustion method, the atomic weight (19) of fluorine in the monomers constituting PVDF, and the atomic weight (12) of carbon in the PVDF. PVDF content (unit: % by mass)=fluoride ion content (unit: % by mass)×64/38 PVDF-derived carbon amount M4 (unit: % by mass)=fluoride ion content (unit: % by mass)×12/19 The presence of polyvinylidene fluoride as a binder can be verified by a method in which a sample or a liquid obtained by extracting a sample with an N,N-dimethylformamide (DMF) solvent is subjected to Fourier transform infrared spectroscopy (FT-IR) to confirm the absorption attributable to the C—F bond. Such verification can be also implemented by 19F-NMR measurement. When the binder is identified as being other than PVDF, the carbon amount M4 attributable to the binder can be calculated by determining the amount (unit: % by mass) of the binder from the measured molecular weight, and the carbon content (unit: % by mass). These methods are described in the following publications: Toray Research Center, The TRC News No. 117 (September 2013), pp. 34-37, [Searched on Feb. 10, 2021], Internet <https://www.toray-research.co.jp/technical-info/trcnews/pdf/TRC117(34-37).pdf> TOSOH Analysis and Research Center Co., Ltd., Technical Report No. T1019 2017.09.20, [Searched on Feb. 10, 2021], Internet <http://www.tosoh-arc.co.jp/techrepo/files/tarc00522/T1719N.pdf> <<Analytical Method for Conductive Carbon>> The conductive carbon in the coated section of the positive electrode active material and the conductive carbon as the conducting agent can be distinguished by the following analytical method. For example, particles in the positive electrode active material layer are analyzed by a combination of transmission electron microscopy-electron energy loss spectroscopy (TEM-EELS), and particles having a carbon-derived peak around 290 eV only near the particle surface can be judged to be the positive electrode active material. On the other hand, particles having a carbon-derived peak inside the particles can be judged to be the conducting agent. In this context, “near the particle surface” means a region to the depth of approximately 100 nm from the particle surface, while “inside” means an inner region positioned deeper than the “near the particle surface”. As another method, the particles in the positive electrode active material layer are analyzed by Raman spectroscopy mapping, and particles showing carbon-derived G-band and D-band as well as a peak of the positive electrode active material-derived oxide crystals can be judged to be the positive electrode active material. On the other hand, particles showing only G-band and D-band can be judged to be the conducting agent. As still another method, a cross section of the positive electrode active material layer is observed with scanning spread resistance microscope (SSRM). When the particle surface has a region with lower resistance than the inside of the particle, the region with lower resistance can be judged to be the conductive carbon present in the coated section of the active material. Other particles that are present isolatedly and have low resistance can be judged to be the conducting agent. In this context, a trace amount of carbon considered to be an impurity and a trace amount of carbon unintentionally removed from the surface of the positive electrode active material during production are not judged to be the conducting agent. Using any of these methods, it is possible to verify whether or not the conducting agent formed of carbon material is contained in the positive electrode active material layer. (Thickness Distribution of Positive Electrode) The thickness distribution of the positive electrode in the present specification is measured by a method that detects unevenness on the outermost surface of a positive electrode while scanning along a direction perpendicular to the thickness direction of the positive electrode current collector11. For example, a target sheet cut out from the positive electrode is inserted between two rotating rolls (a measuring roll and a backup/feed roll), and the sensor detects vertical movements of the measuring roll to measure the change of thickness (thickness distribution). One example of the measuring device is a desktop thickness gauge (product name “Rotary Caliber Meter RC-19”, manufactured by Maysun Co., Ltd.). In this measuring method, the unevenness of the outermost surface on the measuring roll side is detected as a change in thickness. The unevenness of the outermost surface on the backup/feed roll side is not reflected in the thickness distribution. The size of the target sheet is 50 mm or more in the scanning direction (rotational direction of the roll) and 20 mm or more in the direction perpendicular to the scanning direction. Assuming that the total length to be scanned (from one end to the other end of the target sheet) is 100%, the thickness distribution adopted is a measurement result obtained with respect to a central region that remains when a region with a 20% length at one end (from which the scanning starts) and a region with a 20% length at the other end (at which the scanning ends) are excluded, for the purpose of eliminate errors due to cutting. The target sheet is inserted into the measuring device such that the surface of the positive electrode active material layer12is the outermost surface on the measuring roll side. The measurement of the thickness distribution of the positive electrode is performed with respect to at least any two directions (first direction and second direction) orthogonal to each other as scanning directions. The thickness distribution in the first direction is obtained, and the average thickness a1, the maximum thickness b1, and the minimum thickness c1 are obtained. Further, the thickness d1 which is the largest in terms of an absolute value of difference from the average thickness a1 is obtained. d1 is b1 or c1. The relationship may be d1=b1=c1. That is, if (b1−a1)>(a1−c1), then d1=b1; if (b1−a1)<(a1−c1), then d1=c1; and if (b1−a1)=(a1−c1), then d1=b1=c1. Similarly, the thickness distribution in the second direction is obtained, and the average thickness a2, the maximum thickness b2, and the minimum thickness c2 are obtained. Further, the thickness d2 which is the largest in terms of an absolute value of difference from the average thickness a2 is obtained. d2 is b2 or c2. The relationship may be d2=b2=c2. That is, if (b2−a2)>(a2−c2), then d2=b2; if (b2−a2)<(a2−c2), then d2=c2; and if (b2−a2)=(a2−c2), then d2=b2=c2. In the positive electrode1of the present embodiment, the thickness distribution in the first direction satisfies the following inequations 1 and 2, and the thickness distribution in the second direction satisfies the following inequations 3 and 4: 0.990≤(d1/a1)≤1.010 Inequation 1 (b1−c1)≤5.0 μm Inequation 2 0.990≤(d2/a2)≤1.010 Inequation 3 (b2−c2)≤5.0 μm Inequation 4 As the values of d1/a1 and d2/a2 get closer to 1, the surface smoothness of the positive electrode active material layer12increases. Further, (b1−c1) and (b2−c2) represent the amplitude of unevenness on the surface of the positive electrode active material layer12. The positive electrode1satisfying the above formulae 1 to 4 is excellent in the smoothness of the surface of the positive electrode active material layer12and is excellent in the effect of improving the high-rate cycling performance of a non-aqueous electrolyte secondary battery. The positive electrode1shows such advantages presumably because side reactions between the positive electrode and the electrolytic solution on the outermost surface of the positive electrode are suppressed, and the deterioration in the high-rate charge/discharge cycle is thereby suppressed. The values of d1/a1 and d2/a2 are 0.990 or more and 1.010 or less, preferably 0.991 or more and 1.009 or less, and more preferably 0.992 or more and 1.008 or less. The values of (b1−c1) and (b2−c2) are 5.0 μm or less, preferably 4.0 μm or less, and more preferably 3.0 μm or less. The lower limit of (b1−c1) and (b2−c2) is not particularly limited and may be zero. The smoothness of the surface of the positive electrode active material layer12can be controlled by, for example, adjusting the particle size distribution of the particles present in the positive electrode active material layer12. The median diameter (hereinbelow, also referred to as “D50”) in the particle size distribution of the particles present in the positive electrode active material layer12is preferably 5.0 μm or less, preferably 4.0 μm or less, and more preferably 3.0 μm or less. When D50 is not more than the above upper limit value, it is possible to achieve excellent effect of improving the smoothness. The lower limit of D50 is not particularly limited, but is preferably 1.0 μm or more, more preferably 2.0 μm or more, in view of the likelihood of coarse particles being formed due to agglomeration of fine particles, and the influence of the presence of such coarse particles that decreases the smoothness. D50 can be controlled, for example, by adjusting the amount of fine powder contained in the positive electrode active material. D50 can be decreased by using a positive electrode active material with less fine powder content. When a conducting agent is used, D50 can also be adjusted by the blending amount of the conducting agent. D50 can be decreased by reducing the blending amount of the conducting agent. In the present specification, the particle size distribution of the particles present in the positive electrode active material layer12is a volume-based particle size distribution obtained by measurement using a laser diffraction/scattering particle size distribution analyzer. A sample used for the measurement is an aqueous dispersion prepared by detaching the positive electrode active material layer12from the positive electrode1and dispersing the particles that had been present in the positive electrode active material layer12in water. It is preferable to ultrasonically treat the aqueous dispersion to sufficiently disperse the particles. The surface smoothness of the positive electrode active material layer12can also be controlled by adjusting the blending amount of the binder. When the amount of the binder is small, the particles are less likely to agglomerate and the smoothness is likely to improve. The smaller the blending amount of the binder, the lower the carbon content belonging to the binder. The surface smoothness of the positive electrode active material layer12can also be controlled by adjusting the blending amount of the conducting agent. When the amount of the conducting agent is small, the particles are less likely to agglomerate and the smoothness is likely to improve. When the conducting agent contains carbon, the smaller the amount of the conducting agent, the lower the conductive carbon content. The smoothness of the surface of the positive electrode active material layer12can also be controlled by adjusting the pressure applied for pressing the layered body in which the positive electrode active material layer12is formed on the positive electrode current collector11. The application of higher pressure renders easier the improvement of smoothness. The application of high pressure increases the volume density of the positive electrode active material layer12. The volume density of the positive electrode active material layer12is preferably 2.10 to 2.50 g/cm3, more preferably 2.15 to 2.45 g/cm3and even more preferably 2.20 to 2.35 g/cm3. The volume density of the positive electrode active material layer12can be measured by, for example, the following measuring method. The thicknesses of the positive electrode1and the positive electrode current collector11are each measured with a micrometer, and the difference between these two thickness values is calculated as the thickness of the positive electrode active material layer12. With respect to the thickness of the positive electrode1and the thickness of the positive electrode current collector11, each of these thickness values is an average value of the thickness values measured at five or more arbitrarily chosen points. The thickness of the positive electrode current collector11may be measured at the exposed section13of the positive electrode current collector, which is described below. The mass of the measurement sample punched out from the positive electrode so as to have a predetermined area is measured, from which the mass of the positive electrode current collector11measured in advance is subtracted to calculate the mass of the positive electrode active material layer12. The volume density of the positive electrode active material layer12is calculated by the following formula (1). Volume density (unit: g/cm3)=mass of positive electrode active material layer (unit: g)/[(thickness of positive electrode active material layer (unit: cm))×area of measurement sample (Unit: cm2)] (1) Further, when the positive electrode active material in the positive electrode active material layer12is covered with the conductive material, the smoothness of the surface of the positive electrode active material layer12tends to improve. The unevenness of the surface is alleviated presumably because the pressurization of the layered body having the positive electrode active material layer12formed on the positive electrode current collector11causes the coated section of the active material to be deformed and crushed. Further, when the positive electrode current collector11has the current collector coating layer15, the smoothness of the surface of the positive electrode active material layer12tends to improve. In this case, the unevenness of the surface is alleviated presumably because the pressurization of the layered body having the positive electrode active material layer12formed on the positive electrode current collector11causes the positive electrode active material particles to dig into the current collector coating layer15. <Non-Aqueous Electrolyte Secondary Battery> The non-aqueous electrolyte secondary battery10of the present embodiment shown inFIG.2includes a positive electrode1of the present embodiment, a negative electrode3, and a non-aqueous electrolyte. Further, a separator2may be provided. Reference numeral5inFIG.1denotes an outer casing. In the present embodiment, the positive electrode1has a plate-shaped positive electrode current collector11and positive electrode active material layers12provided on both surfaces thereof. The positive electrode active material layer12is present on a part of each surface of the positive electrode current collector11. The edge of the surface of the positive electrode current collector11is an exposed section13of the positive electrode current collector, which is free of the positive electrode active material layer12. A terminal tab (not shown) is electrically connected to an arbitrary portion of the exposed section13of the positive electrode current collector. The negative electrode3has a plate-shaped negative electrode current collector31and negative electrode active material layers32provided on both surfaces thereof. The negative electrode active material layer32is present on a part of each surface of the negative electrode current collector31. The edge of the surface of the negative electrode current collector31is an exposed section33of the negative electrode current collector, which is free of the negative electrode active material layer32. A terminal tab (not shown) is electrically connected to an arbitrary portion of the exposed section33of the negative electrode current collector. The shapes of the positive electrode1, the negative electrode3and the separator2are not particularly limited. For example, each of these may have a rectangular shape in a plan view. With regard to the production of the non-aqueous electrolyte secondary battery10of the present embodiment, for example, the production can be implemented by a method in which the positive electrode1and the negative electrode3are alternately interleaved through the separator2to produce an electrode layered body, which is then packed into an outer casing such as an aluminum laminate bag, and a non-aqueous electrolyte (not shown) is injected into the outer casing, followed by sealing the outer casing.FIG.2shows a representative example of a structure of the battery in which the negative electrode, the separator, the positive electrode, the separator, and the negative electrode are stacked in this order, but the number of electrodes can be altered as appropriate. The number of the positive electrode1may be one or more, and any number of positive electrodes1can be used depending on a desired battery capacity. The number of each of the negative electrode3and the separator2is larger by one sheet than the number of the positive electrode1, and these are stacked so that the negative electrode3is located at the outermost layer. (Negative Electrode) The negative electrode active material layer32includes a negative electrode active material. Further, the negative electrode active material layer32may further include a binder. Furthermore, the negative electrode active material layer32may include a conducting agent as well. The shape of the negative electrode active material is preferably particulate. For example, the negative electrode3can be produced by a method in which a negative electrode composition containing a negative electrode active material, a binder and a solvent is prepared, and coated on the negative electrode current collector31, followed by drying to remove the solvent to thereby form a negative electrode active material layer32. The negative electrode composition may contain a conducting agent. Examples of the negative electrode active material and the conducting agent include carbon materials such as graphite, graphene, hard carbon, Ketjen black, acetylene black, and carbon nanotube (CNT). With respect to each of the negative electrode active material and the conducting agent, a single type thereof may be used alone or two or more types thereof may be used in combination. Examples of the material of the negative electrode current collector31, the binder and the solvent in the negative electrode composition include those listed above as examples of the material of the positive electrode current collector11, the binder and the solvent in the positive electrode composition. With respect to each of the binder and the solvent in the negative electrode composition, a single type thereof may be used alone or two or more types thereof may be used in combination. The sum of the amount of the negative electrode active material and the amount of the conducting agent is preferably 80.0 to 99.9% by mass, and more preferably 85.0 to 98.0% by mass, based on the total mass of the negative electrode active material layer32. (Separator) The separator2is disposed between the negative electrode3and the positive electrode1to prevent a short circuit or the like. The separator2may retain a non-aqueous electrolyte described below. The separator2is not particularly limited, and examples thereof include a porous polymer film, a non-woven fabric, and glass fiber. An insulating layer may be provided on one or both surfaces of the separator2. The insulating layer is preferably a layer having a porous structure in which insulating fine particles are bonded with a binder for an insulating layer. The separator2may contain various plasticizers, antioxidants, and flame retardants. Examples of the antioxidant include phenolic antioxidants such as hindered-phenolic antioxidants, monophenolic antioxidants, bisphenolic antioxidants, and polyphenolic antioxidants; hinderedamine antioxidants; phosphorus antioxidants; sulfur antioxidants; benzotriazole antioxidants; benzophenone antioxidants; triazine antioxidants; and salicylate antioxidants. Among these, phenolic antioxidants and phosphorus antioxidants are preferable. (Non-Aqueous Electrolyte) The non-aqueous electrolyte fills the space between the positive electrode1and the negative electrode3. For example, any of known non-aqueous electrolytes used in lithium ion secondary batteries, electric double layer capacitors and the like can be used. As the non-aqueous electrolyte, a non-aqueous electrolyte solution in which an electrolyte salt is dissolved in an organic solvent is preferable. The organic solvent is preferably one having tolerance to high voltage. Examples of the organic solvent include polar solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrohydrafuran, 2-methyltetrahydrofuran, dioxolane, and methyl acetate, as well as mixtures of two or more of these polar solvents. The electrolyte salt is not particularly limited, and examples thereof include lithium-containing salts such as LiClO4, LiPF6, LiBF4, LiAsF6, LiCF6, LiCF3CO2, LiPF6SO3, LiN(SO2F)2, LiN(SO2CF3)2, Li(SO2CF2CF3)2, LiN(COCF3)2, and LiN(COCF2CF3)2, as well as mixture of two or more of these salts. With regard to the production of the non-aqueous electrolyte secondary battery of the present embodiment, for example, the production can be implemented by a method that prepares an electrode layered body in which the separator2is disposed between the positive electrode1and the negative electrode3, which is then packed into an outer casing5such as an aluminum laminate bag, and injects a non-aqueous electrolyte into the outer casing. The non-aqueous electrolyte secondary battery of this embodiment can be used as a lithium ion secondary battery for various purposes such as industrial use, consumer use, automobile use, and residential use. The application of the non-aqueous electrolyte secondary battery of this embodiment is not particularly limited. For example, the battery can be used in a battery module configured by connecting a plurality of non-aqueous electrolyte secondary batteries in series or in parallel, a battery system including a plurality of electrically connected battery modules and a battery control system, and the like. Examples of the battery system include battery packs, stationary storage battery systems, automobile power storage battery systems, automobile auxiliary storage battery systems, emergency power storage battery systems, and the like. Further, in the present invention, the features of the first embodiment and the second embodiment described above can be appropriately combined. Specifically, the present invention further provides the following embodiments. [C1] A positive electrode for a non-aqueous electrolyte secondary battery, including a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material, and one or both of (C1-1) and (C1-2) below are satisfied: (C1-1) an integrated value (a) is 3 to 15%, preferably 4 to 12%, more preferably 5 to 10%, which is an integrated value of frequency of particle diameters of 1 μm or less, and a frequency (b) is 8 to 20%, preferably 9 to 18%, more preferably 11 to 15%, which is a frequency of a diameter with a maximum frequency, each determined from a volume-based particle size distribution curve of particles present in the positive electrode active material layer; and (C1-2) when two directions perpendicular to a thickness direction of the positive electrode current collector and orthogonal to each other are defined as a first direction and a second direction, an average thickness a1, a maximum thickness b1 and a minimum thickness c1 in a thickness distribution in the first direction as well as a thickness d1 which is largest in terms of an absolute value of the difference from the average thickness a1 satisfy inequations 1 and 2: 0.990≤(d1/a1)≤1.010 Inequation 1, and (b1−c1)≤5.0 μm Inequation 2, and an average thickness a2, a maximum thickness b2 and a minimum thickness c2 in a thickness distribution in the second direction as well as a thickness d2 which is largest in terms of an absolute value of the difference from the average thickness a2 satisfy inequations 3 and 4: 0.990≤(d2/a2)≤1.010 Inequation 3, and (b2−c2)≤5.0 μm Inequation 4, with the proviso that d1/a1 and d2/a2 in the formulae 1 and 3 are preferably 0.991 or more and 1.009 or less, more preferably 0.992 or more and 1.008 or less, and (b1−c1) and (b2−c2) in the formulae 2 and 4 are preferably 4.0 μm or less, more preferably 3.0 μm or less. [C2] The positive electrode according to [C1], wherein a single peak is present in the particle size distribution curve with frequency as an ordinate. [C3] The positive electrode for a non-aqueous electrolyte secondary battery according to [C1] or [C2], which has a distribution width (c) of 2.0 to 20.0 μm, preferably 2.0 to 15.0 μm, more preferably 2.5 to 10.0 μm, which is a value obtained by subtracting a 10% diameter from a 90% diameter in a first normal distribution with a smaller average diameter of two normal distributions obtained by waveform separation of the particle size distribution curve with frequency as an ordinate. [C4] The positive electrode according to any one of [C1] to [C3], which has an integrated value (d) of 1 to 30%, preferably 4 to 27%, more preferably 7 to 24%, which is an integrated value of frequency of particle diameters of 1 μm or less in a first normal distribution with a smaller average diameter of two normal distributions obtained by waveform separation of the particle size distribution curve with frequency as an ordinate. [C5] The positive electrode active material according to any one of [C1] to [C4], wherein the positive electrode active material comprises a compound represented by a formula LiFexM(1-x)PO4, wherein 0≤x≤1, M is Co, Ni, Mn, Al, Ti or Zr. [C6] The positive electrode according to any one of [C1] to [C5], wherein the positive electrode active material has, on at least a part of its surface, a coated section including a conductive material which preferably includes carbon, with the proviso that an amount of the conductive material is preferably 0.1 to 3.0% by mass, more preferably 0.5 to 1.5% by mass, even more preferably 0.7 to 1.3% by mass, based on a total mass of the positive electrode active material including the coated section. [C7] The positive electrode according to any one of [C1] to [C6], wherein the positive electrode active material layer further includes a conducting agent, which is preferably at least one carbon material selected from the group consisting of graphite, graphene, hard carbon, Ketjen black, acetylene black, and carbon nanotube (CNT). [C8] The positive electrode according to any one of [C1] to [C6], wherein the positive electrode active material layer does not include a conducting agent. [C9] The positive electrode according to any one of [C1] to [C8], wherein a current collector coating layer is present on a surface of the positive electrode current collector on a side of the positive electrode active material layer. [C10] The positive electrode according to any one of [C1] to [C9], wherein the particles present in the positive electrode active material layer have a median diameter of 5.0 μm or less, preferably 1.0 μm to 5.0 μm, preferably 1.0 μm to 4.0 μm, more preferably 2.0 μm to 3.0 μm, based on a volume-based particle size distribution. [C11] The positive electrode according to [C6] or [C7], wherein an amount of conductive carbon is 0.5 to 3.5% by mass, preferably 1.0 to 3.0% by mass, based on a total mass of the positive electrode active material layer. [C12] The positive electrode according to any one of [C1] to [C11], wherein the positive electrode active material layer includes a binder, and an amount of carbon belonging to the binder is 0.1 to 2.0% by mass, preferably 0.2 to 1.7% by mass, more preferably 0.4 to 1.0% by mass, based on a total mass of the positive electrode active material layer. [C13] The positive electrode according to any one of [C1] to [C12], wherein the positive electrode active material layer has a volume density of 2.10 to 2.50 g/cm3, preferably 2.15 to 2.45 g/cm3, more preferably 2.20 to 2.35 g/cm3. [C14] A non-aqueous electrolyte secondary battery, including the positive electrode of any one of [C1] to [C13], a negative electrode, and a non-aqueous electrolyte disposed between the positive electrode and the negative electrode. [C15] A battery module or battery system including a plurality of the non-aqueous electrolyte secondary batteries of [C14]. In these embodiments, it is preferable to satisfy both (C1-1) and (C1-2) for surely obtaining the effects of the present invention. EXAMPLES Hereinbelow, the present invention will be described with reference to Examples which, however, should not be construed as limiting the present invention. <Measurement Method in Examples A1 to A6> (Particle Size Distribution Measuring Method) The outermost surface of the positive electrode active material layer12with a depth of several m was removed with a spatula or the like, and the resulting powder was dispersed in water to obtain a dispersion as a sample. The measurement was implemented using a laser diffraction particle size distribution analyzer (product name “LA-960V2”, manufactured by Horiba, Ltd.), and a flow cell. The sample was circulated, stirred and irradiated with ultrasonic waves (5 minutes), and the particle size distribution was measured while keeping the dispersion state sufficiently stable. A volume-based particle size distribution curve P was obtained, and an integrated value (a) (unit: %) of the frequency of particle diameters of 1 μm or less and a frequency (b) (unit: %) at the mode diameter were obtained. Further, using a peak separation analysis program attached to the laser diffraction particle size distribution analyzer, the particle size distribution curve P was waveform-separated into two normal distributions to obtain a first normal distribution and a second normal distribution. The analysis conditions for waveform separation were as follows: the number of constituent distributions was 2, and the assigned initial values were an average diameter of 1 μm and a variance of 0.5 for the first normal distribution, and an average diameter of 8 μm and a variance of 3 for the second normal distribution. Of the two obtained normal distributions, D90 and D10 in the first normal distribution having the smaller average were obtained, and the value of the distribution width (c) (D90−D10) was calculated. Further, the integrated value (d) of the frequency of particle diameters of 1 μm or less in the first normal distribution was obtained. (Volume Density Measuring Method) The thickness of the positive electrode sheet and the thickness of the positive electrode current collector at its exposed section13were measured using a micrometer. Each thickness was measured at 5 arbitrarily chosen points, and an average value was calculated. 5 sheets of measurement samples were prepared by punching the positive electrode sheet into circles with a diameter of 16 mm. Each measurement sample was weighed with a precision balance, and the mass of the positive electrode active material layer12in the measurement sample was calculated by subtracting the mass of the positive electrode current collector11measured in advance from the measurement result. The volume density of the positive electrode active material layer was calculated from the average value of measured values by the above formula (1). <Evaluation Method in Examples A1 to A6> (High Temperature/High Rate Cycle Test) The capacity retention was evaluated following the procedures (1) to (7) below.(1) A non-aqueous electrolyte secondary battery (cell) was manufactured so as to have a rated capacity of 1 Ah, and a cycle evaluation was carried out in an atmosphere of 50° C.(2) The obtained cell was charged at a constant current rate of 0.2 C (that is, 200 mA) and with a cut-off voltage of 3.6 V, and then charged at a constant voltage with a cut-off current set at 1/10 of the above-mentioned charge current (that is, 20 mA).(3) The cell was discharged for capacity confirmation at a constant current rate of 0.2 C and with a cut-off voltage of 2.5 V. The discharge capacity at this time was set as the reference capacity, and the reference capacity was set as the current value at 1 C rate (that is, 1,000 mA).(4) After charging the cell at a constant current at a cell's 5 C rate (that is, 5000 mA) and with a cut-off voltage of 3.7 V, a 10-second pause was provided. From this state, the cell was discharged at 5 C rate and with a cut-off voltage of 2.0 V, and a 10-second pause was provided.(5) The cycle test of (4) was repeated 1,000 times.(6) After performing the same charging as in (2), the same capacity confirmation as in (3) was performed.(7) By dividing the discharge capacity in the capacity confirmation measured in (6) by the reference capacity before the cycle test to obtain a capacity retention after 1,000 cycles in terms of percentage (1,000-cycle capacity retention, unit: %). Production Example 1: Production of Negative Electrode 100 parts by mass of artificial graphite as a negative electrode active material, 1.5 parts by mass of styrene-butadiene rubber as a binder, 1.5 parts by mass of carboxymethyl cellulose Na as a thickener, and water as a solvent were mixed, to thereby obtain a negative electrode composition having a solid content of 50% by mass. The obtained negative electrode composition was applied onto both sides of a copper foil (thickness 8 μm) and vacuum dried at 100° C. Then, the resulting was pressure-pressed under a load of 2 kN to obtain a negative electrode sheet. The obtained negative electrode sheet was punched to obtain a negative electrode. Examples A1 to A6 Examples A1 to A4 are implementation of the present invention, while Examples A5 and A6 are comparative examples. The powder materials used for the positive electrode active material layer are as follows.Positive electrode active material (1): Carbon-coated lithium iron phosphate, average particle size 1.5 μm, carbon content 1.0% by massPositive electrode active material (2): Carbon-coated lithium iron phosphate, average particle size 1.0 μm, carbon content 1.0% by massPositive electrode active material (3): Carbon-coated lithium iron phosphate, average particle size 10.0 μm, carbon content 1.0% by massConducting agent (1): Carbon blackPolyvinylidene fluoride (PVDF) was used as binder. Example A1 First, a positive electrode current collector11was prepared by coating both the front and back surfaces of a positive electrode current collector main body14with current collector coating layers15by the following method. An aluminum foil (thickness 15 μm) was used as the positive electrode current collector main body14. A slurry was obtained by mixing 100 parts by mass of carbon black, 40 parts by mass of polyvinylidene fluoride as a binder, and N-methylpyrrolidone (NMP) as a solvent. The amount of NMP used was the amount required for applying the slurry. The obtained slurry was applied to both sides of the positive electrode current collector main body14by a gravure method so as to allow the resulting current collector coating layers15after drying (total of layers on both sides) to have a thickness of 2 μm, and dried to remove the solvent, thereby obtaining a positive electrode current collector11. The current collector coating layers15on both surfaces were formed so as to have the same amount of coating and the same thickness. Next, a positive electrode active material layer12was formed by the following method. As shown in Table 1, 100 parts by mass of the positive electrode active material (1), 0.5 part by mass of the conducting agent (1), 1.0 part by mass of PVDF as a binder, and NMP as a solvent were mixed with a mixer to obtain a positive electrode composition. The amount of the solvent used was the amount required for applying the positive electrode composition. (In Table 1, the alphabetical character “A” preceeding the numbers in the notation of the Example numbers A 1 to A6 is omitted. In Table 2 et seq., the alphabetical character (A or B) preceding the numbers is likewise omitted.) The positive electrode composition was applied on both sides of the positive electrode current collector11, and after pre-drying, the applied composition was vacuum-dried at 120° C. to form positive electrode active material layers12. The coating volume of the positive electrode composition was 30 mg/cm2(total volume for both sides). The positive electrode active material layers12on both surfaces of the positive electrode current collector11were formed so as to have the same coating amount and the same thickness. The resulting layered body was pressure-pressed (rolled) with a load of 10 kN to obtain a positive electrode sheet. With respect to the obtained positive electrode sheet, the volume density of the positive electrode active material layer and the particle size distribution of the particles present in the positive electrode active material layer were measured by the above method, and the values of the respective items shown in Table 2 were obtained (hereinbelow, the same applies). The obtained particle size distribution curve is shown inFIG.3. The obtained positive electrode sheet was punched to obtain a positive electrode. A non-aqueous electrolyte secondary battery having a configuration shown inFIG.2was manufactured by the following method. LiPF6as an electrolyte was dissolved at 1 mol/L in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio, EC:DEC, of 3:7, to thereby prepare a non-aqueous electrolytic solution. The positive electrode obtained in this example and the negative electrode obtained in Production Example 1 were alternately interleaved through a separator to prepare an electrode layered body with its outermost layer being the negative electrode. A polyolefin film (thickness 15 μm) was used as the separator. In the step of producing the electrode layered body, the separator2and the positive electrode1were first stacked, and then the negative electrode3was stacked on the separator2. Terminal tabs were electrically connected to the exposed section13of the positive electrode current collector and the exposed section33of the negative electrode current collector in the electrode layered body, and the electrode layered body was put between aluminum laminate films while allowing the terminal tabs to protrude to the outside. Then, the resulting was laminate-processed and sealed at three sides. To the resulting structure, a non-aqueous electrolytic solution was injected from one side left unsealed, and this one side was vacuum-sealed to manufacture a non-aqueous electrolyte secondary battery (laminate cell). The high temperature-high rate cycle test was carried out by the above method to measure the 1,000-cycle capacity retention. The results are shown in Table 2 (the same applies to the other examples). Example A2 100 parts by mass of the positive electrode active material (2) was used instead of the positive electrode active material (1) used in Example A1. Except this point, a positive electrode sheet was prepared in the same manner as in Example A1, and the particle size distribution was measured. The obtained particle size distribution curve is shown inFIG.4. Further, a non-aqueous electrolyte secondary battery was manufactured and evaluated in the same manner as in Example A1. Example A3 100 parts by mass of the positive electrode active material (3) was used instead of the positive electrode active material (1) used in Example A1. Except this point, a positive electrode sheet was prepared in the same manner as in Example A1, and the particle size distribution was measured. Further, a non-aqueous electrolyte secondary battery was manufactured and evaluated in the same manner as in Example A1. Example A4 A positive electrode sheet was prepared in the same manner as in Example A2 except that the conducting agent (1) was omitted, and the particle size distribution was measured to obtain the values of the respective items shown in Table 2. Further, a non-aqueous electrolyte secondary battery was manufactured and evaluated in the same manner as in Example A1. Example A5 The blending amount of the conducting agent was changed from that in Example A1 to 5.0 parts by mass. Except this point, a positive electrode sheet was prepared in the same manner as in Example A1, and the particle size distribution was measured. The obtained particle size distribution curve is shown inFIG.5. Further, a non-aqueous electrolyte secondary battery was manufactured and evaluated in the same manner as in Example A1. Example A6 The blending amounts of the conducting agent and the binder were changed from those in Example A2 to 6.0 parts by mass and 2.0 parts by mass, respectively. Except this point, a positive electrode sheet was prepared in the same manner as in Example A1, and the particle size distribution was measured. Further, a non-aqueous electrolyte secondary battery was manufactured and evaluated in the same manner as in Example A1. TABLE 1POSITIVEPOSITIVEPOSITIVEELECTRODEELECTRODEELECTRODECONDUCTINGACTIVE MATERIALACTIVE MATERIALACTIVE MATERIALAGENT(1)(2)(3)(1)BINDERPARTSPARTSPARTSPARTSPARTSUNITBY MASSBY MASSBY MASSBY MASSBY MASSEx. 1100——0.51.0Ex. 2—100—0.51.0Ex. 3——1000.51.0Ex. 4—100——1.0Ex. 5100——5.01.0Ex. 6—100—6.02.0 TABLE 2PARTICLE SIZEFIRST NORMALDISTRIBUTION CURVEDISTRIBUTIONVOLUMEINTEGRATEDINTEGRATEDDENSITYVALUE (a)VALUE (d)OFFORFORPOSITIVE1,000-CYCLEPARTICLEFREQUENCYPARTICLEELECTRODECAPACITYDIAMETERS(b) OFDIAMETERSACTIVERETENTIONPEAKOF 1 μm ORMODEDISTRIBUTIONOF 1 μm ORMATERIAL(50° C./5 C.NUMBERLESSDIAMETERWIDTH CLESSLAYERRATE)UNIT—vol. %vol. %μmvol. %g/cm3%Ex. 117.411.62.88.72.3082Ex. 2111.49.92.719.92.4079Ex. 323.49.722.44.52.2076Ex. 419.212.13.215.02.5087Ex. 5217.87.61.344.22.2041Ex. 6234.18.61.055.92.1023 As can be understood from the results shown in Table 2, excellent performance in terms of high temperature-high rate charge/discharge cycling performance was achieved in Examples A1 to A4 where the integrated value (a) was 3 to 15%, which is an integrated value of frequency of particle diameters of 1 μm or less, and the frequency (b) was 8 to 20%, which is a frequency of a mode diameter, each determined from the particle size distribution curve P. Such results in Examples A1 to A4 are presumably due to the presence of less amount of fine powder in the positive electrode active material layer, which decreased side reaction sites where local current concentration occurs during the high-rate charge/discharge cycle, and thereby enabled suppression of deterioration when used at a high temperature. On the other hand, in Examples A5 and A6, a large amount of fine powders was present in the positive electrode active material layer, and the high-rate charge/discharge cycling performance was inferior. The fine powder in the positive electrode active material layer is assumed to be small particles of the active material, which resulted due to insufficient crystal growth in the heat treatment step of the production process of the positive electrode active material, fine carbon particles, or a conducting agent present as isolated particles. Such inferior results are presumably due to the large surface area of fine powder, which provided many side reaction sites where local current concentration occurs during the high-rate charge/discharge cycle, and thereby facilitated deterioration when used at a high temperature. <Measurement Method in Examples B1 to B5> (Thickness Distribution Measuring Method) A rectangular sample, which was 300 mm in a lengthwise direction (transportation direction during coating) and 180 mm in a widthwise direction orthogonal to the lengthwise direction, was cut out from the positive electrode sheet. The thickness distribution was measured along the widthwise direction of the sample using a desktop thickness gauge (product name “Rotary Caliber Meter RC-19”, manufactured by Maysun Co., Ltd.) and a sensor with a maximum measurable thickness of 200 μm. The sample was scanned from one end to the other end, and the measurement result obtained with respect to a region excluding 36 mm at both ends was adopted as the thickness distribution. From the obtained thickness distribution, the average thickness a1, the maximum thickness b1 and the minimum thickness c1 as well as a thickness d1 which was the largest in terms of an absolute value of difference from the average thickness a1 were determined, and the values of (d1/a1) and (b1−c1) were calculated. The thickness distribution in the lengthwise direction (transportation direction during coating) of the sample shows higher smoothness than the thickness distribution in the widthwise direction of the sample. That is, d2/a2 is closer to 1 than d1/a1, and b2−c2 is smaller than b1−c1. Therefore, the thickness distribution in the widthwise direction was adopted as the evaluation target. (Particle Size Distribution Measuring Method) The outermost surface of the positive electrode active material layer12with a depth of several μm was removed with a spatula or the like, and the resulting powder was dispersed in water to obtain a dispersion as a sample. The measurement was implemented using a laser diffraction particle size distribution analyzer (product name “LA-960V2”, manufactured by Horiba, Ltd.), and a flow cell. The sample was circulated, stirred and irradiated with ultrasonic waves (5 minutes), and the particle size distribution was measured while keeping the dispersion state sufficiently stable, thereby determining a volume-based median particle size D50. (Volume Density Measuring Method) The thickness of the positive electrode sheet and the thickness of the positive electrode current collector at its exposed section13were measured using a micrometer. Each thickness was measured at 5 arbitrarily chosen points, and an average value was calculated. 5 sheets of measurement samples were prepared by punching the positive electrode sheet into circles with a diameter of 16 mm. Each measurement sample was weighed with a precision balance, and the mass of the positive electrode active material layer12in the measurement sample was calculated by subtracting the mass of the positive electrode current collector11measured in advance from the measurement result. The volume density of the positive electrode active material layer was calculated from the average value of measured values by the above formula (1). <Evaluation Method in Examples B1 to B5> (High temperature-high rate cycle test, DC resistance increase rate measurement) The resistance increase rate was evaluated following the procedures (1) to (7) below.(1) A non-aqueous electrolyte secondary battery (cell) was manufactured so as to have a rated capacity of 1 Ah, and a resistance measurement and a cycle evaluation were carried out at room temperature (25° C.).(2) The obtained cell was charged at a constant current rate of 0.2 C (that is, 200 mA) and with a cut-off voltage of 3.6 V, and then charged at a constant voltage with a cut-off current set at 1/10 of the above-mentioned charge current (that is, 20 mA).(3) The cell was discharged for capacity confirmation at a constant current rate of 0.2 C and with a cut-off voltage of 2.5 V. The discharge capacity at this time was set as the reference capacity, and the reference capacity was set as the current value at 1 C rate (that is, 1,000 mA).(4) After charging the cell at a constant current at a cell's 3 C rate (that is, 3000 mA) and with a cut-off voltage of 3.8 V, a 10-minute pause was provided. From this state, the cell was discharged at 3 C rate and with a cut-off voltage of 2.0 V, and a 10-minute pause was provided. Supposing that the open circuit voltage at which this 3 C rate discharge was started is Va1, the voltage 10 seconds after the start of discharge is Va2, and the discharge current is I (that is, 3000 mA), the DC resistance is expressed by R=(Va1−Va2)/I, based on Ohm's law. According to this equation, the DC resistance at 10-second discharge was calculated.(5) The 3 C rate charge/discharge test of (4) was repeated 1,000 times with the pause times after charging and discharging changed to 10 seconds.(6) The same DC resistance measurement as in (4) was carried out.(7) The DC resistance measured in (6) was divided by the value measured in (4) and the obtained value was converted into percentage to obtain the DC resistance increase rate (unit: %) after 1,000 cycles. Examples B1 to B5 Examples B1 to B3 are implementation of the present invention, while Examples B4 and B5 are comparative examples. The powder materials used for the positive electrode active material layer are a positive electrode active material and a conducting agent as described below. Positive electrode active material: Carbon-coated lithium iron phosphate, average particle size 1.5 μm, carbon content 1.0% by mass Conducting agent: Carbon black Polyvinylidene fluoride (PVDF) was used as binder. Example B1 First, a positive electrode current collector11was prepared by coating both the front and back surfaces of a positive electrode current collector main body14with current collector coating layers15by the following method. An aluminum foil (thickness 15 μm) was used as the positive electrode current collector main body14. A slurry was obtained by mixing 100 parts by mass of carbon black, 40 parts by mass of polyvinylidene fluoride as a binder, and N-methylpyrrolidone (NMP) as a solvent. The amount of NMP used was the amount required for applying the slurry. The obtained slurry was applied to both sides of the positive electrode current collector main body14by a gravure method so as to allow the resulting current collector coating layers15after drying (total of layers on both sides) to have a thickness of 2 μm, and dried to remove the solvent, thereby obtaining a positive electrode current collector11. The current collector coating layers15on both surfaces were formed so as to have the same amount of coating and the same thickness. Next, a positive electrode active material layer12was formed by the following method. As shown in Table 3, 100 parts by mass of the positive electrode active material, 2.0 parts by mass of the conducting agent, 1.5 parts by mass of the binder, and NMP as a solvent were mixed with a mixer to obtain a positive electrode composition. The amount of the solvent used was the amount required for applying the positive electrode composition. The positive electrode composition was applied on both sides of the positive electrode current collector11, and after pre-drying, the applied composition was vacuum-dried at 120° C. to form positive electrode active material layers12. The coating volume of the positive electrode composition was 30 mg/cm2(total volume for both sides). The positive electrode active material layers12on both surfaces of the positive electrode current collector11were formed so as to have the same coating amount and the same thickness. The obtained laminate was pressure-pressed with a load of 10 kN to obtain a positive electrode sheet. Specifically, the positive electrode composition was applied using a bar coater while conveying the long positive electrode current collector11in the lengthwise direction, and a positive electrode sheet was continuously produced by a method that involves pressure-pressing using a roll press machine. With respect to the obtained positive electrode sheet, the thickness distribution of the positive electrode, and the particle size distribution and volume density of the positive electrode active material layer were measured by the above methods, and the values of the respective items shown in Tables 4 were obtained. The measurement results of the thickness distribution are shown inFIG.6. The carbon content and compounding amount of the carbon-coated active material, the carbon content and compounding amount of the conducting agent, and the carbon content and compounding amount of the binder were used to calculate the conductive carbon content and the carbon content belonging to the binder with respect to the total mass of the positive electrode active material layer. The conducting agent was regarded as having an impurity content of less than the quantification limit and a carbon content of 100% by mass. The conductive carbon content and the carbon content belonging to the binder can also be confirmed by the method described in the <<Method for measuring conductive carbon content>> above. The results are shown in Table 4 (the same applies to the other examples). The obtained positive electrode sheet was punched to obtain a positive electrode. A non-aqueous electrolyte secondary battery having a configuration shown inFIG.2was manufactured by the following method. LiPF6as an electrolyte was dissolved at 1 mol/L in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio, EC:DEC, of 3:7, to thereby prepare a non-aqueous electrolytic solution. The positive electrode obtained in this example and the negative electrode obtained in Production Example 1 were alternately laminated through a separator to prepare an electrode layered body with its outermost layer being the negative electrode. A polyolefin film (thickness 15 μm) was used as the separator. In the step of producing the electrode layered body, the separator2and the positive electrode1were first stacked, and then the negative electrode3was stacked on the separator2. Terminal tabs were electrically connected to the exposed section13of the positive electrode current collector and the exposed section33of the negative electrode current collector in the electrode layered body, and the electrode layered body was put between aluminum laminate films while allowing the terminal tabs to protrude to the outside. Then, the resulting was laminate-processed and sealed at three sides. To the resulting structure, a non-aqueous electrolytic solution was injected from one side left unsealed, and this one side was vacuum-sealed to manufacture a non-aqueous electrolyte secondary battery (laminate cell). The high rate cycle test was carried out by the above method to measure the 1,000-cycle resistance increase rate. The results are shown in Table 4 (the same applies to the other examples). Example B2 The blending ratio for the positive electrode composition was changed from that in Example B1 to that shown in Table 3. The load for the pressure-press was adjusted so as to give a volume density higher than Example B1. Except this point, a positive electrode sheet was prepared, and the measurements and evaluations were carried out in the same manner as in Example B1. Example B3 The conducting agent was omitted and the blending ratio for the positive electrode composition was changed from that in Example B1 to that shown in Table 3. The load for the pressure-press was adjusted so as to give a volume density higher than Examples B1 and B2. Except this point, a positive electrode sheet was prepared, and the measurements and evaluations were carried out in the same manner as in Example B1. Example B4 The blending ratio for the positive electrode composition was changed from that in Example B1 to that shown in Table 3. The load for the pressure-press was the same as in Example B2, but the volume density was 2.10 g/cm3, differing from Example B2 due to the increase in the amounts of the conducting agent and the binder. Except this point, a positive electrode sheet was prepared, and the measurements and evaluations were carried out in the same manner as in Example B1. The measurement results of the thickness distribution are shown inFIG.7. Example B5 The blending ratio for the positive electrode composition was changed from that in Example B1 to that shown in Table 3. The load for the pressure-press was the same as in Example B1, but the volume density was 2.00 g/cm3, differing from Example B1 due to the increase in the amounts of the conducting agent and the binder. Except this point, a positive electrode sheet was prepared, and the measurements and evaluations were carried out in the same manner as in Example B1. TABLE 3BLENDING RATIO [PARTS BY MASS]POSITIVEELECTRODEACTIVECONDUCTINGMATERIALAGENTBINDERSOLVENTEx. 196.52.01.5REQUIREDEx. 299.00.50.5AMOUNTEx. 399.5—0.5Ex. 494.04.02.0Ex. 594.04.02.0 TABLE 41,000-CYCLE,CARBONCONDUC-AC 1 HzAVERAGEMAXIMUMMINIMUMCONTENTTIVERESISTANCETHICKNESSTHICKNESSTHICKNESSBELONGINGCARBONVOLUMEINCREASEa1b1c1d1d1/a1b1-c1D50TO BINDERCONTENTDENSITYRATEμmμmμmμm—μmμm% BY MASS% BY MASSg/cm3%Ex. 1147.21148.28145.83145.830.9912.452.71.53.02.25108Ex. 2138.62139.68137.57139.681.0082.113.20.51.52.45104Ex. 3134.47135.31133.79135.311.0061.523.40.51.02.50101Ex. 4173.88177.15170.14170.140.9787.017.82.05.02.10145Ex. 5175.46180.97168.62168.620.96112.352.32.05.02.00189 As can be understood from the results shown in Table 4, excellent performance in terms of high rate charge/discharge cycling performance was achieved in Examples B1 to B3 satisfying the above formulae 1 to 4. Examples B1 to B3 were excellent in the uniformity of the thickness in the planar direction of the positive electrode, and were excellent in the smoothness of the outermost surface of the positive electrode active material layer. This presumably allowed suppression of side reactions between the positive electrode and the electrolytic solution on the outermost surface of the positive electrode, whereby the deterioration in the high-rate charge/discharge cycle was suppressed. In Example B2, as a result of reducing the blending amounts of the conducting agent and the binder as compared to Example B1, the value of b1−c1 decreased and the high-rate charge/discharge cycling performance improved further. On the other hand, in Example B4, by increasing the blending amounts of the conducting agent and the binder as compared to Example B1, the agglomeration of the conducting agent and the binder occurred, and thickness in the planar direction of the positive electrode was less uniform than Example B1. This is presumably because the increase in the unevenness of the outermost surface of the positive electrode active material layer allowed side reactions to occur between the positive electrode and the electrolytic solution on the outermost surface of the positive electrode, whereby the resistance increase rate in the high-rate charge/discharge cycle increased. In Example B5, since the D50 of the particles present in the positive electrode active material layer was small and the volume density was low, the unevenness on the outermost surface of the positive electrode active material layer increased. Further, the small D50 tends to induce agglomeration of the particles. This presumably facilitated side reactions between the positive electrode and the electrolytic solution on the outermost surface of the positive electrode, whereby the resistance increase rate in the high-rate charge/discharge cycle was further raised. REFERENCE SIGNS LIST 1Positive electrode2Separator3Negative electrode5Outer casing10Non-aqueous electrolyte secondary cell11Positive electrode current collector12Positive electrode active material layer13Exposed section of positive electrode current collector14Positive electrode current collector main body15Current collector coating layer31Negative electrode current collector32Negative electrode active material layer33Exposed section of negative electrode current collector | 148,919 |
11862799 | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may properly define the concept of the terms in order to best describe its invention. The terms and words should be construed as meaning and concept consistent with the technical idea of the present invention. Accordingly, the embodiments described in the specification and the configurations described in the drawings are only the most preferred embodiments of the present invention, and do not represent all of the technical ideas of the present invention. It is to be understood that there may be various equivalents and variations in place of them at the time of filing the present application. In the present specification, when a part is “connected” to another part, this includes not only “directly connected” but also “electrically connected” between the parts while having another element therebetween. In this application, it should be understood that terms such as “include” or “have” are intended to indicate that there is a feature, number, step, operation, component, part, or a combination thereof described on the specification, and they do not exclude in advance the possibility of the presence or addition of one or more other features or numbers, steps, operations, components, parts or combinations thereof. Also, when a portion such as a layer, a film, an area, a plate, etc. is referred to as being “on” another portion, this includes not only the case where the portion is “directly on” the another portion but also the case where further another portion is interposed therebetween. On the other hand, when a portion such as a layer, a film, an area, a plate, etc. is referred to as being “under” another portion, this includes not only the case where the portion is “directly under” the another portion but also the case where further another portion is interposed therebetween. In addition, to be disposed “on” in the present application may include the case disposed at the bottom as well as the top. As used throughout this specification, the terms “about”, “substantially”, and the like, are used to mean a value or something like this when unique manufacturing and material tolerances are presented, and the terms are used to prevent unscrupulous infringers from unfair use of the disclosure including accurate or absolute figures in order to aid in the understanding of the present disclosure. Throughout this specification, the term “combination(s) thereof” included in the expression of the Markush form means one or more mixtures or combinations selected from the group consisting of the elements described in the Markush form representation, and it means to include one or more selected from the group consisting of the above components. Hereinafter, the present invention will be described in detail. The negative electrode active material for a secondary battery according to the present invention includes a graphite material as a main component. Specifically, the negative electrode active material is a mixture of artificial graphite and spheroidized natural graphite. In general, artificial graphite has excellent high temperature properties, but has a problem of exhibiting low capacity and low processability, and thus it is possible to improve the capacity of the active material by mixing natural graphite with excellent initial discharge capacity. However, as the natural graphite charge/discharge cycle is repeated, a swelling phenomenon may occur due to an electrolyte decomposition reaction occurring at the edge portion of the natural graphite, and charge/discharge efficiency and capacity may decrease. In addition, natural graphite has a problem in that there are many internal pores, and when the electrode is rolled, the internal pores are clogged and subject to mechanical stress. Therefore, as will be described later, as a mixture of spheroidized natural graphite with a small particle size and uniform particle size is mixed with artificial graphite, it is possible to improve low cycle characteristics, swelling characteristics, and rapid charging characteristics, which were disadvantages of conventional natural graphite, while retaining the advantages of artificial graphite and natural graphite. Specifically, the spheroidized natural graphite may have an average particle diameter (D50) of 12 μm or less, more preferably 9 to 11 μm in view of the initial efficiency of the secondary battery. By using spheroidized natural graphite having an average particle diameter within the above range, it is possible to obtain an advantage of improving the rapid charging ability at a high energy density. When the average particle diameter of the spheroidized natural graphite exceeds 12 μm, as described below, the tap density of the negative electrode and the adhesion property of the active material decrease, thereby reducing the effect of improving the swelling phenomenon of the electrode. Charging and discharging performance of the secondary battery may be reduced. In addition, according to the present invention, in order to improve performance degradation that may occur when using natural graphite, the particle size distribution should be uniform, and in the particle size distribution of the spheroidized natural graphite, the D90−D10value may be 5 to 12 μm, and preferably 7 to 9 μm. Here, D90is a particle size in which the accumulation becomes 90% from the smallest particle in the order of particle diameter, D10is a particle diameter in which the accumulation becomes 10% from the smallest particle in the particle size order, and D50is a particle size in which the accumulation becomes 50% from the smallest particle in the order of particle size. The smaller the D90−D10value, the sharper the particle size distribution curve. When the D90−D10is less than 5 μm, rapid charging characteristics may deteriorate, and when the D90−D10exceeds 12 μm, a problem that it is difficult to obtain an appropriate density may occur. That is, when the D90−D10is out of the above range, a problem in which the active material tap density becomes too low occurs, and the electrode active material layer becomes thicker and the pressability is lowered, so it becomes difficult to implement high energy density. The particle size of the spheroidized natural graphite can be measured, for example, by using a laser diffraction method. The laser diffraction method can generally measure a particle diameter of several mm from a submicron region, and can obtain results of high reproducibility and high resolution. More specifically, the particle size of the spheroidized natural graphite may be performed as follows. After dispersing the spheroidized natural graphite in a solution of ethanol/water, it may be introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with an output power of 60 W of ultrasonic waves of about 28 kHz, and then the particle size of the spheroidized natural graphite may be calculated based on the particle size distribution in the measuring device. Further, the spheroidized natural graphite can be obtained by applying a mechanical external force to general natural graphite and performing the granulated spheroidization treatment. For example, the spheroidized natural graphite is treated with an acid or a base for scaly natural graphite, and then spheroidized for 10 minutes to 30 minutes at a rotor speed of 30 m/s to 100 m/s in a spheroidizing device, but not limited thereto. The tap density of the spheroidized natural graphite may be 1.10 to 1.25 g/cc, more preferably 1.15 to 1.20 g/cc. The tap density of the active material is the apparent density of the powder obtained by vibrating the container under certain conditions when filling the powder. In the present invention, the tap density can be measured after performing tapping 2000 times using TAP-2S, manufactured by LOGAN, a tap density meter. The higher the tap density, the higher the packing density of the electrode. Specifically, after mixing the active material with a binder or conductive material for electrode production, it is coated on the current collector in a thin film, and is then pressed to harden the electrode. At this time, if the filling is not good, the electrode cannot be made thin, and since it occupies a large volume, it is impossible to realize a high capacity in a given battery volume condition. The tap density of the spheroidized natural graphite is affected by the particle diameter of the natural graphite, and the tap density may decrease as the particle size of natural graphite increases, and the tap density may increase as the particle size of natural graphite decreases. In general, in order to improve the adhesion between the active material and the electrode current collector, it is preferable to have a large tap density because the adhesion area is increased when the contact area between the particles is increased, thereby improving the adhesion. When the tap density of the spheroidized natural graphite is less than 1.10 g/cc, the contact area between the particles may not be sufficient, and thus adhesive properties may be deteriorated, and energy density per unit volume may be reduced. On the other hand, when the tap density of the spheroidized natural graphite exceeds 1.25 g/cc, the tortuosity of the electrode and the wettability of the electrolyte decrease, resulting in a decrease in output characteristics during charging and discharging and causing a reduction in initial efficiency and deterioration of high temperature properties. In addition, in the negative electrode active material according to the present invention, the degree of spheroidization of the spheroidized natural graphite may be 0.94 to 0.98, specifically 0.95 to 0.96. The spheronization degree may mean a shorter diameter than a long diameter of the first particles. The spheronization degree can be measured through a particle shape analyzer. Specifically, after deriving the cumulative distribution of the spheroidization degree of the spheroidized natural graphite particles through a particle shape analyzer, the degree of spheroidization, in which the distribution ratio from particles with a large degree of spheroidization corresponds to 50%, can be determined as the degree of spheroidization of the first particle. When the spheroidization degree of the spheroidized natural graphite particles is less than 0.94, a problem of low electrode adhesion may be caused by an excessively curved surface of the first particles. In addition, when the degree of spheroidization of the spheroidized natural graphite particles is greater than 0.98, a large amount of spheroidized natural graphite particles is required to derive a high degree of spheroidization, which may cause a problem of low production yield. In addition, in the negative electrode active material according to the present invention, the adhesion to the current collector after rolling of the spheroidized natural graphite may be 20 to 35 gf/cm, more preferably 25 to 30 gf/cm. In general, natural graphite exhibits excellent adhesion to the current collector compared to artificial graphite with a small amount of functional groups or defects on the surface due to the presence of functional groups on the surface. Hence, when the adhesion to the current collector after rolling of the spheroidized natural graphite is within the above range, the adhesion of the negative electrode active material mixed with artificial graphite to the current collector may be improved afterwards. The adhesion of the spheroidized natural graphite to the current collector may be influenced by particle size, and the larger the particle diameter, the smaller the surface area and the smaller the adhesion to the current collector. When the adhesion of the spheroidized natural graphite to the current collector is less than 20 gf/cm, the capacity of the battery may rapidly decrease as the negative electrode active material is easily peeled off from the current collector. On the other hand, when the electrode adhesion exceeds 35 gf/cm, fast charging characteristics may deteriorate due to an increase in electrode resistance. Next, the artificial graphite used in the present invention will be described. In the negative electrode active material for a secondary battery according to the present invention, artificial graphite contained in the negative electrode active material may be prepared using a carbon precursor such as pitch coke, and the pitch coke can be produced using carbon precursors such as coal tar, coal tar pitch, petroleum pitch or heavy oil. The cokes can be prepared by heat treatment (graphitization) at a temperature of 2800° C. to 3000° C. after being mechanically crushed and polished. The artificial graphite is not limited, and may be in the form of powder, flake, block, plate, or rod. However, in order to exhibit the best output characteristics, the shorter the travel distance of lithium ions, the better. And in order to have a short moving distance in the direction of the electrode, it is preferable that the grain orientation of artificial graphite exhibits isotropy. Hence, a flake shape or a plate shape, and more specifically, a flake shape is preferable. In addition, the tap density of the artificial graphite may be 0.80 to 1.00 g/cc, more preferably 0.85 to 0.95 g/cc. When the tap density of the artificial graphite particles is less than 0.80 g/cc, the contact area between the particles may not be sufficient, and thus adhesive properties may be deteriorated, and energy density per unit volume may be reduced. On the other hand, when the tap density of artificial graphite exceeds 1.00 g/cc, the tortuosity of the electrode and the wettability of the electrolyte decrease, resulting in a decrease in output characteristics during charging and discharging and causing a reduction in initial efficiency and deterioration of high temperature properties. In addition, the average particle diameter (D50) of the artificial graphite may be 9 to 30 μm, preferably 10 to 20 μm. When the average particle diameter of the artificial graphite is less than 9 μm, the initial efficiency of the secondary battery may decrease due to an increase in specific surface area, thereby deteriorating battery performance. On the other hand, when the average particle diameter of the artificial graphite exceeds 30 μm, electrode adhesion may decrease and cycle characteristics of the battery may decrease. In particular, the average particle diameter (D50) of the artificial graphite is 1 to 2 times, preferably 1.2 to 1.7 times the average particle diameter (D50) of the spheroidized natural graphite. When the ratio of the average particle diameter of artificial graphite and the average particle diameter of spheroidized natural graphite is within the above range, the filling density of the active material in the electrode is improved, and the specific surface area of the active material can be reduced to prevent side reactions with the electrolyte. When the ratio of the average particle diameter of the artificial graphite to the average particle diameter of the spheroidized natural graphite is outside the above-mentioned range, the size of either particle is enlarged, so that it becomes difficult for artificial graphite and spheroidized natural graphite to be uniformly distributed, and as a result, output characteristics of the battery may be deteriorated. In addition, the artificial graphite of 65 to 85% by weight, more preferably 70 to 80% by weight, based on the total weight of the negative electrode active material may be contained in the negative electrode active material according to the present invention. In addition, the spheroidized natural graphite may be included in 15 to 35% by weight based on the total weight of the negative electrode active material, preferably 20 to 30% by weight. In the case that the content of the artificial graphite is less than 65% and the content of spheroidized natural graphite exceeds 35% in the negative electrode active material, the content of natural graphite is too large, and thus a side reaction with the electrolyte may occur at a high temperature, a swelling phenomenon may occur, mechanical properties of the electrode may be weakened due to internal pores, and rapid charging performance may decrease. Conversely, when the content of the artificial graphite exceeds 85% by weight and the content of the spheroidized natural graphite is less than 15%, the content of the artificial graphite is excessively large, so that the capacity of the battery decreases, the processability decreases, and the rolling characteristics fall. In addition, when one of artificial graphite and spheroidized natural graphite is used too much, the pores in the negative electrode active material layer are excessively present due to the morphology of each particle, so filling between the artificial graphite and natural graphite is not smoothly performed. As a result, the adhesion between the particles in the negative electrode active material and the adhesion between the negative electrode active material and the current collector may become poor. When the amounts of the artificial graphite and the spheroidized natural graphite are adjusted in the above range, the pores in the negative electrode active material layer are reduced, and since the artificial graphite and the spheroidized natural graphite are smoothly interlocked with each other, electrode adhesion can be improved. In addition, the negative electrode active material according to the present invention may further include an adhesive component that assists in the combination of artificial graphite and spheroidized natural graphite. The pressure-sensitive adhesive is a component that assists in combining spheroidized natural graphite and artificial graphite, and a hard carbon precursor, soft carbon precursor, or the like may be used, but is not limited thereto. When the negative electrode active material further contains the adhesive component in addition to artificial graphite and natural graphite, the adhesive may be included in 1 to 40% by weight. Sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, polyacrylonitrile resin, polyamide resin, furan resin, cellulose resin, styrene resin, polyimide resin, epoxy resin, and vinyl chloride resin, etc. may be used as the hard carbon precursor, and coke, needle coke, polyvinyl chloride, mesophase pitch, tar, heavy oil, etc. may be used as the soft carbon. The present invention also provides a negative electrode for a secondary battery containing the negative electrode active material. The FIGURE is a schematic diagram showing the structure of a negative electrode for a secondary battery including a negative electrode active material according to the present invention. Referring to the FIGURE, the negative electrode10may be prepared by applying a negative electrode mixture containing a negative electrode active material on the current collector11and the drying it, and the negative electrode mixture may optionally further include a binder, a conductive material, and a filling material, if necessary. At this time, as the negative electrode active material, a mixture of the aforementioned artificial graphite12and spheroidized natural graphite13may be used. The sheet for the negative electrode collector generally has a thickness of 3 to 500 micrometers. The negative electrode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel of which the surface has been treated with carbon, nickel, titanium, silver or the like, aluminum-cadmium alloy, or the like. In addition, like the positive electrode current collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric. The conductive material is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as carbon fluoride, aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives and the like. The binder is added in an amount of 1 to 30% by weight, on the basis of the total weight of the mixture containing the positive electrode active material, as a component that assists in bonding between the active material and the conductive material and bonding to the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like. The filler is optionally used as a component for inhibiting expansion of an electrode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fibers and carbon fibers. Other components, such as viscosity modifiers, adhesion promoters, and the like may be further included optionally or in combination of two or more. The viscosity modifier is a component that adjusts the viscosity of the electrode mixture so that the mixing process of the electrode mixture and the coating process on the current collector thereof may be easy, and may be added up to 30% by weight based on the total weight of the negative electrode mixture. Examples of such a viscosity modifier include carboxy methyl cellulose, polyvinylidene fluoride, and the like, but are not limited thereto. In some cases, the solvent described above may serve as a viscosity modifier. The adhesion promoter is an auxiliary component added to improve the adhesion of the active material to the current collector and may be added in less than 10% by weight compared to the binder, and some examples thereof include oxalic acid, adipic acid, formic acid, acrylic acid derivatives, itaconic acid derivatives, and the like. The present invention also provides a secondary battery produced by the method. Specifically, the secondary battery includes at least two secondary battery electrodes manufactured by the present invention and has a structure in which the electrode assembly is embedded in the battery case, wherein the electrode assembly is wound with a separator interposed between the secondary battery electrodes and has a structure in which the electrode assembly is impregnated with a lithium salt-containing non-aqueous electrolyte. The electrode for the secondary battery may be a positive electrode and/or a negative electrode. At this time, the negative electrode described above may be used, and the negative electrode may be manufactured as a lithium secondary battery after being assembled as an electrode assembly and sealed in a battery case together with an electrolyte, followed by an activation process. The secondary battery may be a cylindrical battery, a prismatic battery, a pouch-type battery, or a coin-type battery, and the shape of the battery is not particularly limited. The electrode assembly is not particularly limited as long as it has a structure made of a positive electrode and a negative electrode and a separator interposed therebetween, for example, a folding structure, or a stacked structure, or a stack/folding type (SNF) structure, or lamination/stack-type (LNS) structure. The folding-type electrode assembly includes at least one positive electrode, at least one negative electrode, and at least one separator interposed between the positive electrode and the negative electrode and the positive electrode, the separator, and the negative electrode may have a structure in which one end and the other end do not cross each other. Further, the stack-type electrode assembly includes at least one positive electrode, at least one negative electrode, and at least one separator interposed between the positive electrode and the negative electrode and the positive electrode, the separator, and the negative electrode may have a structure in which one end and the other end cross each other. The stack/folding-type electrode assembly includes at least one positive electrode, at least one negative electrode, and at least one separator interposed between the positive electrode and the negative electrode, and the separator includes a first separator and a second separator. Further, the positive electrode, the first separator, and the negative electrode may have a structure in which one end and the other end do not cross each other. The second separator may have a structure surrounding an electrode side on which an electrode tab is not formed. The electrode assembly of the lamination-stack structure may include one or more improved electrodes having a laminate laminated on one or both surfaces thereof. The improved electrode, for example, may be implemented in a structure in which the separator is bonded to one surface of the positive electrode or the negative electrode. In addition, the separator may be implemented in a structure that is bonded to both sides of the positive electrode or both sides of the negative electrode. In addition, the positive electrode, the separator and the negative electrode may be implemented in a structure that are bonded to each other in a state where the separator is interposed between the positive electrode and the negative electrode. In the secondary battery according to the present invention, the positive electrode may be prepared by applying an electrode mixture containing a positive electrode active material on a current collector and drying it, and the positive electrode mixture may optionally further include a binder, a conductive material, a filler, and the like, if necessary. In the present invention, the positive electrode collector generally has a thickness of 3 to 500 micrometers. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon or aluminum or stainless steel of which the surface has been treated with carbon, nickel, titanium, silver, or the like. The current collector may have fine irregularities on the surface thereof to increase the adhesion of the positive electrode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible. In the present invention, the positive electrode active material is a material capable of causing an electrochemical reaction and a lithium transition metal oxide, and contains two or more transition metals. Examples thereof include: layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2) substituted with one or more transition metals; lithium manganese oxide substituted with one or more transition metals; lithium nickel oxide represented by the formula LiNi1−yMyO2(wherein M=Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn or Ga and contains at least one of the above elements, 0.01≤y≤0.7); lithium nickel cobalt manganese composite oxide represented by the formula Li1+zNibMncCo1−(b+c+d)MdO(2−c)Aesuch as Li1+zNi1/3Co1/3Mn1/3O2, Li1+zNi0.4Mn0.4Co0.2O2etc. (wherein −0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2, 0≤e≤0.2, b+c+d<1, M=Al, Mg, Cr, Ti, Si or Y, and A=F, P or CO; olivine-based lithium metal phosphate represented by the formula Li1+xM1−yM′yPO4−zXz(wherein M=transition metal, preferably Fe, Mn, Co or Ni, M′=Al, Mg or Ti, X=F, S or N, and −0.5≤x≤0.5, 0≤y≤0.5, 0≤z≤0.1). In the positive electrode, additive materials such as a binder, a conductive material, and a filling material are as described above. The separator is interposed between the positive electrode and the negative electrode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 micrometers, and the thickness is generally 5 to 300 micrometers. Examples of such a separator include olefin-based polymers such as polypropylene which is chemically resistant and hydrophobic; a sheet or a nonwoven fabric made of glass fiber, polyethylene or the like. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator. The lithium salt-containing non-aqueous electrolyte solution consists of an electrolyte and a lithium salt. And a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, and the like are used as the electrolyte solution. Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylenecarbonate, dimethyl carbonate, diethyl carbonate, gamma-Butyrolactone, 1,2-dimethoxy ethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate, etc. Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, a polyagitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, a polymerizer including an ionic dissociation group, and the like. Examples of the inorganic solid electrolyte include nitrides, halides, and sulfates of Li such as Li3N, LiI, Li5NI2, Li3N—LiT-LiOH, LiSiO4, LiSiO4—LiT-LiOH, Li2SiS3, Li4SiO4, Li4SiO4—LiI—LiOH, and Li3PO4—Li2S—SiS2. The lithium salt is a substance that is soluble in the non-aqueous electrolyte. The examples of the lithium salt include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBi10Cl10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium 4-phenylborate, imide and the like. For the purpose of improving charge/discharge characteristics, flame retardancy, etc., pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. may be added to the electrolyte. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve the high-temperature storage characteristics, and FEC (Fluoro-EthyleneCarbonate), PRS (Propene sultone), and the like may be further added. In one preferred example, a lithium salt such as LiPF6, LiClO4, LiBF4, and LiN(SO2CF3)2may be added to a mixed solvent of a cyclic carbonate of EC or PC which is a high-dielectric solvent and a linear carbonate of DEC, DMC or EMC which is low viscosity solvent to thereby prepare a non-aqueous electrolyte containing a lithium salt. The method for preparing a negative electrode of the present invention includes preparing a negative electrode mixture and applying the negative electrode mixture on a current collector and then drying it. In addition, the negative electrode active material included in the negative electrode mixture includes a mixture of artificial graphite and spheroidized natural graphite. Specifically, the negative electrode active material described above may be used. More specifically, in the method of manufacturing the negative electrode, preparing the negative electrode mixture may include spheronizing natural graphite; preparing artificial graphite; and mixing the spheroidized natural graphite and artificial graphite. The step of spheronizing the natural graphite is a step of spheronizing by applying a mechanical external force to general scaly natural graphite. As described above, it can be obtained by treating scaly natural graphite with an acid or a base and then spheronizing at a rotor speed of 30 m/s to 100 m/s in a spheronizing device for 10 to 30 minutes. Preparing the artificial graphite may include: preparing a pitch coke by coking a carbon precursor such as coal tar, coal tar pitch, petroleum pitch or heavy oil; and mechanically crushing and polishing the pitch coke and then heat treating the pitch coke (graphitization) at a temperature of 2800° C. to 3000° C. In addition, spheronizing the natural graphite and preparing artificial graphite may further include classifying the spheroidized natural graphite and artificial graphite particles so that the particle size distribution becomes uniform. Through the classifying step, the average particle diameter (D50) of the spheroidized natural graphite and artificial graphite can be adjusted according to the above numerical values, and in particular, the D90−D10value may be adjusted to 5 to 12 μm, preferably 7 to 9 μm, through the classification step. The classification process may be carried out by any method, but it is appropriate to perform it by an air flow classification process. In the case of performing the air flow classification process, the conditions of the air flow classification process can be appropriately adjusted according to the type of the active material. When spheroidized natural graphite and artificial graphite are prepared, the spheroidized natural graphite and artificial graphite are mixed, and the mixing method is not particularly limited. For example, one having a high-speed chopper such as a Henschel mixer or a Spartan Luther, or a Nauter mixer or a ribbon mixer can be used for uniform mixing at high speed. The spheroidized natural graphite and artificial graphite are mixed, a binder and a conductive material are added, and a solvent such as water is added thereto to prepare a negative electrode mixture slurry. If necessary, a thickener such as carboxymethylcellulose (CMC) may be further included. Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided to more fully describe the present invention to those skilled in the art. Example 1 Preparation of Negative Electrode A negative electrode was prepared using a negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D50) of 11 μm in a particle size distribution, D90of 15 μm, D10of 6 μm, and D90−D10of 9 μm. Further, the tap density of the spheroidized natural graphite was 1.15 g/cc (measured by performing 2000 tappings using TAP-2S, manufactured by LOGAN, a tap density measuring instrument), and the electrode adhesive force was 25 gf/cm after rolling. As the artificial graphite, flake-like artificial graphite (tap density: 0.90 g/cc) having an average particle diameter (D50) of 15.5 μm was used. The natural graphite used as a negative electrode active material, SuperC65 used as a conductive material, styrene butadiene high part (SBR) used as a binder, and carboxymethylcellulose (CMC) used as a thickener were mixed at a weight ratio of 96.6:1:1.3:1.1, respectively, and water was added to prepare a slurry. The slurry prepared as described above was applied to a copper foil, and a negative electrode having an area of 1.4875 cm2in vacuum drying at about 130° C. for 10 hours was prepared. At this time, the loading of the negative electrode was prepared to be 3.61 mAh/cm2. Preparation of Battery Cells The negative electrode active material was coated on a copper foil to prepare a negative electrode so that the loading amount was 3.61 mAh/cm2in an area of 1.7671 cm2. Further, a positive electrode mixture containing LiCoO2(LCO) as a positive electrode active material was applied to the aluminum foil to prepare a 1.4875 cm2counter electrode. An electrode assembly was manufactured by interposing a polyethylene separator between the working electrode and the counter electrode. Then, 1M LiPF6was added to a solvent in which 0.5 wt % of the non-aqueous electrolyte additive VC, which was generated by mixing ethylene carbonate (EC) with diethylene carbonate (EMC) in a volume ratio of 1:4, to thereby prepare a non-aqueous electrolyte solution, which was then injected into the electrode assembly. The electrode assembly was put in a case to produce a coin-type full-cell secondary battery. In addition, the negative electrode active material was coated on a copper foil to prepare a working electrode (negative electrode) so that the loading amount was 3.61 mAh/cm2in an area of 1.4875 cm2, and lithium metal having an area of 1.7671 cm2was used as a counter electrode (positive electrode). An electrode assembly was manufactured by interposing a polyethylene separator between the working electrode and the counter electrode. Then, 1M LiPF6was added to a solvent in which 0.5 wt % of the non-aqueous electrolyte additive VC, which was generated by mixing ethylene carbonate (EC) with diethylene carbonate (EMC) in a volume ratio of 1:4, to thereby prepare a non-aqueous electrolyte solution, which was then injected into the electrode assembly. The electrode assembly was put in a case to produce a coin-type half-cell secondary battery. Example 2 Preparation of Negative Electrode A negative electrode was prepared using a negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D50) of 9 μm in a particle size distribution, D90of 13 μm, D10of 6 μm, and D90−D10of 7 μm. In addition, the tap density of the spheroidized natural graphite was 1.20 g/cc, and thus the electrode adhesion was 30 gf/cm after rolling. As the artificial graphite, flake-like artificial graphite (tap density: 0.93 g/cc) having an average particle diameter (D50) of 14.5 μm was used. The natural graphite used as a negative electrode active material, SuperC65 used as a conductive material, styrene butadiene high part (SBR) used as a binder, and carboxymethylcellulose (CMC) used as a thickener were mixed at a weight ratio of 96.6:1:1.3:1.1, respectively, and water was added to prepare a slurry. The slurry prepared as described above was applied to a copper foil, and a negative electrode having an area of 1.4875 cm2in vacuum drying at about 130° C. for 10 hours was prepared. At this time, the loading of the negative electrode was prepared to be 3.61 mAh/cm2. Preparation of Battery Cells The negative electrode active material of Example 2 was used to prepare a battery (coin type full cell and half cell battery) in the same manner as in Example 1. Example 3 A negative electrode and a battery (coin type full cell and half-cell battery) were prepared in the same manner as in Example 1 except that the negative electrode active material containing 85% by weight of the artificial graphite of Example 1 and 15% by weight of the spheroidized natural graphite of Example 1 was used. Example 4 A negative electrode and a battery (coin type full cell and half-cell battery) were prepared in the same manner as in Example 1 except that the negative electrode active material containing 70% by weight of the artificial graphite of Example 1 and 30% by weight of the spheroidized natural graphite of Example 1 was used. Example 5 A negative electrode and a battery (coin type full cell and half-cell battery) were prepared in the same manner as in Example 1 except that the negative electrode active material containing 65% by weight of the artificial graphite of Example 1 and 35% by weight of the spheroidized natural graphite of Example 1 was used. Comparative Example 1 A negative electrode and a battery (coin type full cell and half-cell battery) were prepared in the same manner as in Example 1 except that the negative electrode active material containing 90% by weight of the artificial graphite of Example 1 and 10% by weight of the spheroidized natural graphite of Example 1 was used. Comparative Example 2 A negative electrode and a battery (coin type full cell and half-cell battery) were prepared in the same manner as in Example 1 except that the negative electrode active material containing 60% by weight of the artificial graphite of Example 1 and 40% by weight of the spheroidized natural graphite of Example 1 was used. Comparative Example 3 A negative electrode was prepared using a negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite of Example 1. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D50) of 15 μm in a particle size distribution, D90of 21 μm, D10of 7 μm, and D90-D10of 14 μm. In addition, the tap density of the spheroidized natural graphite was 1.15 g/cc, and thus the electrode adhesion was 15 gf/cm after rolling. A battery was manufactured in the same manner as in Example 1, except that a negative electrode and a coin-type full cell and a coin-type half-cell including the negative electrode were manufactured using the negative electrode active material. Comparative Example 4 A negative electrode was prepared using a negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite of Example 1. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D50) of 17 μm in a particle size distribution, D90of 28 μm, D10of 10 μm, and D90−D10of 18 μm. In addition, the tap density of the spheroidized natural graphite was 1.10 g/cc, and thus the electrode adhesion was 14 gf/cm after rolling. A battery was manufactured in the same manner as in Example 1, except that a negative electrode and a coin-type full cell and a coin-type half-cell including the negative electrode were manufactured using the negative electrode active material. Comparative Example 5 A negative electrode was prepared using a negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite of Example 1. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D50) of 11 μm in a particle size distribution, D90of 21 μm, D10of 6 μm, and D90−D10of 15 μm. In addition, the tap density of the spheroidized natural graphite was 1.05 g/cc, and thus the electrode adhesion was 11 gf/cm after rolling. A battery was manufactured in the same manner as in Example 1, except that a negative electrode and a coin-type full cell and a coin-type half-cell including the negative electrode were manufactured using the negative electrode active material. Comparative Example 6 A negative electrode was prepared using a negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite of Example 1. At this time, the spheroidized natural graphite was added with a binder in the step of granulating and spheroidizing the flaky graphite to act as an adhesive between the flakes. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D50) of 14 μm in a particle size distribution, D90of 27 μm, D10of 8 μm, and D90−D10of 19 μm. In addition, the tap density of the spheroidized natural graphite was 1.00 g/cc, and thus the electrode adhesion was 8 gf/cm after rolling. A battery was manufactured in the same manner as in Example 1, except that a negative electrode and a coin-type full cell and a coin-type half-cell including the negative electrode were manufactured using the negative electrode active material. Table 1 shows the contents of artificial graphite and spheroidized natural graphite used in Examples and Comparative Examples, and Table 2 shows the physical properties of natural graphite used in Examples and Comparative Examples. TABLE 1Artificial graphiteSpheroidized naturalDivisioncontent (w %)graphite content (w %)Example 18020Example 28020Example 38515Example 47030Example 56535Comparative9010Example 1Comparative6040Example 2Comparative8020Example 3Comparative8020Example 4Comparative8020Example 5Comparative8020Example 6 TABLE 2TapAdhe-densitysionDivisionD50(μm)D90(μm)D10(μm)D90-D10(μm)(g/cc)(gf/cm)Example 11115691.1525Example 2913671.2030Example 31115691.1525Example 41115691.1525Example 51115691.1525Comparative1115691.1525Example 1Comparative1115691.1525Example 2Comparative15217141.1515Example 3Comparative172810181.1014Example 4Comparative11216151.0511Example 5Comparative14278191.008Example 6 Experimental Example 1 In-Situ SAC Swelling Test The charging range was determined to allow SOC to become from 0 to 95% by using the manufactured coin-type full cell, and the change in the thickness of the negative electrode during charging and discharging was expressed as a swelling ratio (%) while charging the first cycle at 0.1 C, the second cycle at 0.2 C, and the third to 30th cycles at 0.5 C. The results are shown in Table 3. Experimental Example 2 Li-Plating Test The half-cell was charged and discharged at 1 C for 3 cycles by using the prepared coin-type half-cell, and then charged at 3 C for 15 minutes to first differentiate the profile. At this time, the inflection point appearing in dQ/dV was checked to quantify lithium plating SOC (Li-Plating SOC, %), which is the SOC at the time of lithium precipitation on the negative electrode surface. The results are shown in Table 3. Experimental Example 3 Peel Strength (Adhesion) Test of Negative Electrode The negative electrode was rolled to 28% porosity to perform Peel Strength Test. At this time, by using the slide glass, the electrodes were directed at a 90-degree right angle direction, and the current collector was peeled off to measure electrode adhesion (peeling strength), and the results are shown in Table 3 below. TABLE 3SwellingLi-PlatingElectrodeRatioSOCadhesionDivision(%)(%)(gf/cm)Example 120.14125Example 221.23830Example 322.34020Example 424.83817Example 525.23722Comparative27.43218Example 1Comparative27.9|2823Example 2Comparative28.33215Example 3Comparative29.53114Example 4Comparative26.83411Example 5Comparative30.6308Example 6 As can be seen in Table 3, in Examples 1 and 2 of using the negative electrode active material according to the present invention, spherical natural graphite having a small particle size and a uniform particle size distribution was used. and as a result, the electrode adhesion between the active material and the current collector was improved compared to Comparative Examples 3 to 6 in which the particle size was large and the particle size distribution was not uniform, and accordingly, it can be confirmed that the swelling ratio is reduced and the cycle characteristics are improved. And when comparing the ratio of the spheroidized natural graphite contained in the negative electrode active material of Example 1, Examples 3 to 5, Comparative Example 1 and Comparative Example 2, it can be seen that the swelling ratio and cycle characteristics of the negative electrode and the battery used in the above examples are improved compared to the comparative example. In addition, it can be seen that when going beyond the tap density of the spheroidized natural graphite of the present invention and the electrode adhesion force range, the electrode adhesion to the current collector of the negative electrode active material is improved, and thus the swelling ratio is reduced and the cycle characteristics are improved. The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain the protection scope of the present invention and should be interpreted by the claims below, and it should be interpreted that all technical spirits within the equivalent scope are included in the scope of the present invention. DESCRIPTION OF REFERENCE NUMERALS 10: negative electrode11: current collector12: artificial graphite13: spheroidized natural graphite | 50,924 |
11862800 | DETAILED DESCRIPTION OF THE EMBODIMENTS According to exemplary embodiments of the present invention, an anode active material for a lithium secondary battery including porous carbon-based particles and silicon is provided. According to exemplary embodiments of the present invention, a method forming the anode active material and a lithium secondary battery including the anode active material are also provided. Hereinafter, the present invention will be described in detail with reference to exemplary embodiments and the accompanying drawings. However, those skilled in the art will appreciate that such embodiments are provided to further understand the spirit of the present invention and do not limit subject matters to be protected as disclosed in the detailed description and appended claims. For example, an anode active material may include silicon and carbon-based particles. In this case, carbon components may partially reduce or relieve a volume expansion of silicon. However, as charging and discharging of a secondary battery may be repeated, a difference between volume expansion ratios of silicon (e.g., about 400% or more) and carbon (e.g., about 150% or less) may be increase to cause cracks in the anode active material. As a result, the anode active material may be exposed to an electrolyte, and a side reaction such as a gas generation may occur during the repeated charging and discharging to deteriorate life-span properties of the secondary battery. According to exemplary embodiments of the present invention, the carbon-based particles may include pores in at least one of a surface and an inside of the particle. For example, the carbon-based particle may be a porous particle including a plurality of pores. In exemplary embodiments, silicon may be formed at the inside of the pores. Thus, cracks due to the difference in volume expansion ratios between carbon and silicon during the repeated charging and discharging of the secondary battery may be prevented. In exemplary embodiments, a pore size of the carbon-based particles may be 20 nm or less, preferably less than 10 nm. If the pore size is excessively large (e.g., greater than 20 nm), the difference in volume expansion ratios of carbon and silicon during the charging and discharging of the secondary battery may not be sufficiently reduced. In some embodiments, a minimum value of the pore size of the carbon-based particle may be 0.1 nm. For example, the above-described carbon-based particles may include activated carbon, carbon nanotube (CNT), carbon nano-wire, graphene, carbon fiber, carbon black, graphite, porous carbon (micro/meso/macro porous carbon), pyrolyzed cryogel, pyrolyzed xerogel, pyrolyzed aerogel, etc. These may be used alone or in a combination thereof. In some embodiments, the above-described carbon-based particles may have an amorphous structure or a crystalline structure. Preferably, the carbon-based particles may have the amorphous structure. In this case, durability of the anode active material may be increased to suppress generation of cracks that may be caused by the charging/discharging or an external impact. Accordingly, life-span properties of the secondary battery may be improved. In exemplary embodiments, the anode active material may include silicon formed at the inside the pores of the above-described carbon-based particles or on the surfaces of the carbon-based particles. Thus, the difference in volume expansion ratios with carbon may be reduced while employing high-capacity properties of silicon. Accordingly, micro-cracks and the electrolyte exposure due to the repeated charging and discharging of the secondary battery may be prevented, thereby improving life-span properties while maintaining power properties of the secondary battery. In exemplary embodiments, the above-described silicon may have an amorphous structure or a crystallite size of silicon measured by an X-ray diffraction (XRD) analysis may be 7 nm or less. In a preferable embodiment, the crystallite size may be 4 nm or less. If the crystallite size is excessively large (e.g., greater than 7 nm), cracks may easily occur in the anode active material by, e.g., a pressing process for manufacturing the secondary battery or the repeated charging and discharging. Further, capacity retention may be degraded, and thus life-span properties of the secondary battery may also be degraded. The term “amorphous structure” used herein refers to a case where a shape of a single silicon located at an inside a particle is amorphous or small within a range that a size measurement through Scherrer equation expressed by Equation 1 from the X-ray diffraction (XRD) analysis may not be substantially implemented. In exemplary embodiments, “the crystallite size” is a value measured by the XRD analysis. The crystallite size may be obtained by calculating using Scherrer equation (as shown in Equation 1 below) that includes a full width at half maximum (FWHM) obtained through the XRD analysis. L=0.9λβcosθ[Equation1] In the Equation 1 above, L is the crystallite size, λ is an X-ray wavelength, β is the FWHM of a corresponding peak, and θ is a diffraction angle. In exemplary embodiments, the FWHM in the XRD analysis for measuring the crystallite size may be measured from a peak of a (111) plane. In some embodiments, in the Equation 1 above, β may be a FWHM correcting a value derived from a device. In an embodiment, Si may be used as a standard material for reflecting the device-derived value. In this case, a FWHM profile of Si over an entire 2θ range may be fitted, and the device-derived FWHM may be expressed as a function of 2θ. Thereafter, a value obtained by subtracting and correcting the FWHM value derived from the device in the corresponding 2θ obtained from the above function may be used as β. In some embodiments, the above-mentioned silicon may include the amorphous structure. In this case, the crystallite size of silicon and a peak intensity ratio of a Raman spectrum, which will be described later, may be maintained within an appropriate range. Accordingly, enhanced life-span properties may be achieved while maintaining the capacity properties as described above. In some embodiments, at least one of silicon oxide (SiOx, 0<x<2) and silicon carbide (SiC) may be further formed in the pores of the carbon-based particle or on the surface of the carbon-based particle. In some embodiments, silicon carbide (SiC) may be not formed in the pores of the carbon-based particle or on the surface of the carbon-based particle. For example, only silicon or silicon oxide may be formed in the pores of the carbon-based particle or on the surface of the carbon-based particle. Accordingly, the capacity properties of the lithium secondary battery may be improved. For example, forming of silicon carbide may be suppressed by controlling a temperature and time during silicon deposition process. For example, the crystallite size of silicon included in silicon oxide may be 7 nm or less, preferably 4 nm or less. In exemplary embodiments, the peak intensity ratio of the Raman spectrum of silicon defined as Equation 2 below may be 1.2 or less, preferably 1.0 or less. Peak intensity ratio of Raman spectrum=I(515)/I(480) [Equation 2] In Equation 2, I(515) is a peak intensity of silicon at a wavenumber of 515 cm−1in the Raman spectrum, and I(480) is a peak intensity of silicon at a wavenumber of 480 cm−1in the Raman spectrum. For example, I(515) in Equation 2 may represent a ratio of silicon having a crystalline structure, and I(480) in Equation 2 may represent a ratio of silicon having the amorphous structure. For example, within the above-described peak intensity ratio, the ratio of the amorphous structure in silicon may be increased so that structural stability of the anode active material may be improved. Accordingly, enhanced life-span properties of the secondary battery may be obtained. In some embodiments, the anode active material may have the above-described crystallite size range and the peak intensity ratio range of the Raman spectrum of silicon. In this case, the amorphous property of silicon may be further improved, and thus stability of the anode active material may be improved. Accordingly, an additional improvement in the life-span properties of the anode active material may be provided. Hereinafter, a method of forming the anode active material for a lithium secondary battery according to exemplary embodiments is provided. In exemplary embodiments, carbon-based particles including pores having a size of 20 nm or less may be prepared. In some embodiments, an aromatic compound containing a hydroxyl group and an aldehyde-based compound may be mixed to prepare a resol oligomer. For example, the aromatic compound including the hydroxyl group may be phenol, and the aldehyde-based compound may be formaldehyde. The above-resol oligomer may be cured by adding a curing agent, and the carbon-based particles including pores of 20 nm or less may be obtained after performing a classification, a washing and a firing. In some embodiments, an aromatic compound and a vinyl-based compound may be mixed and polymerized. Thereafter, washing and firing processes may be performed to obtain the carbon-based particles including pores of 20 nm or less. For example, the aromatic compound may be polystyrene, and the vinyl-based compound may be divinylbenzene. In some embodiments, the formation of the carbon-based particles may further include an activation process. In this case, an activity of a pore structure of the carbon-based particles may be easily controlled. For example, the activation process may include a physical activation method in which a gas having a reactivity with carbon (a steam, carbon dioxide, or a mixed gas of steam, carbon dioxide and an inert gas) may be introduced and heated at a temperature of 700° C. to 1000° C. For example, the activation process may include a chemical activation method in which acidic or basic chemicals such as KOH, Na2CO3, NaOH, H3PO4, etc., may be used as an activator. The chemical activation method may be performed at a temperature lower than that in the physical activation method. The pore size of the carbon-based particles obtained by the above-described method may be less than 10 nm. In exemplary embodiments, a silicon-based compound gas may be introduced into a reactor in which the carbon-based particles are loaded and then fired to deposit silicon at an inside of the pores of the carbon-based particles or on surfaces of the carbon-based particles. For example, the silicon-based compound gas may include a silane gas. In some embodiments, the firing may be performed at a temperature less than 600° C. Within the temperature range, silicon may sufficiently include an amorphous structure and may be effectively deposited on the carbon-based particles. Accordingly, enhanced life-span properties may be obtained while satisfying the ranges of the Raman peak intensity ratio defined as Equation 2. FIGS.1and2are a schematic top planar view and a schematic cross-sectional view, respectively, illustrating a lithium secondary battery in accordance with exemplary embodiments. Hereinafter, a lithium secondary battery including an anode prepared from the anode active material for a lithium secondary battery as described above will be described with reference toFIGS.1and2. Referring toFIGS.1and2, the lithium secondary battery may include an electrode assembly including a cathode100, an anode130and a separation layer140interposed between the cathode and the anode. The electrode assembly may be accommodated in a case160together with the electrolyte to be impregnated therein. The cathode100may include a cathode active material layer110formed by coating a mixture containing a cathode active material on a cathode current collector105. The cathode current collector105may include stainless-steel, nickel, aluminum, titanium, copper or an alloy thereof. Preferably, aluminum or an alloy thereof may be used. The cathode current collector105may be surface-treated using carbon, nickel, titan, silver, etc. The cathode active material may include a compound capable of reversibly intercalating and de-intercalating lithium ions. In exemplary embodiments, the cathode active material may include a lithium-transition metal oxide. For example, the lithium-transition metal oxide may include nickel (Ni), and may further include at least one of cobalt (Co) and manganese (Mn). For example, the lithium-transition metal oxide may be represented by Chemical Formula 1 below. LixNi1-yMyO2+z[Chemical Formula 1] In Chemical Formula 1, 0.9≤x≤1.2, 0≤y≤0.7, and −0.1≤z≤0.1. M may be at least one element selected from Na, Mg, Ca, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn or Zr. In some embodiments, a molar ratio or a concentration (1−y) of Ni in Chemical Formula 1 may be 0.8 or more, preferably greater than 0.8. A mixture may be prepared by mixing and stirring the cathode active material in a solvent with a binder, a conductive material and/or a dispersive agent. The mixture may be coated on the cathode current collector105, and then dried and pressed to form the cathode100. The solvent may include a non-aqueous solvent. Non-limiting examples of the solvent may include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. The binder commonly known in the related art may be used. For example, the binder may include an organic based binder such as a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, etc., or an aqueous based binder such as styrene-butadiene rubber (SBR) that may be used with a thickener such as carboxymethyl cellulose (CMC). For example, a PVDF-based binder may be used as a cathode binder. In this case, an amount of the binder for forming the cathode active material layer may be reduced, and an amount of the cathode active material may be relatively increased. Thus, capacity and power of the lithium secondary battery may be further improved. The conductive material may be added to facilitate electron mobility between active material particles. For example, the conductive material may include a carbon-based material such as graphite, carbon black, graphene, carbon nanotube, etc., and/or a metal-based material such as tin, tin oxide, titanium oxide, a perovskite material such as LaSrCoO3or LaSrMnO3, etc. In exemplary embodiments, an anode active material slurry may be prepared from the above-described anode active material including the carbon-based particles and silicon. For example, the anode active material slurry may be prepared by mixing and stirring the anode active material in a solvent with an anode binder, a conductive material and a thickener. For example, the anode binder may be a polymer material such as styrene-butadiene rubber (SBR). The thickener may include carboxylmethyl cellulose (CMC). For example, the conductive material substantially the same as or similar to that used in the formation of the cathode active material layer may also be used. In some embodiments, the anode130may include an anode current collector125and an anode active material layer120formed by coating the anode active material slurry on at least one surface of the anode current collector125, drying and pressing. The anode current collector125may include a metal having high conductivity and improved adhesion to the anode active material slurry and not having a reactivity in a voltage range of the battery. For example, the anode current collector125may include stainless steel, nickel, copper, titanium, or an alloy thereof, preferably copper or a copper alloy may be used. The anode current collector125may be surface-treated with carbon, nickel, titanium, silver, or the like. The separation layer140may be interposed between the cathode100and the anode130. The separation layer140may include a porous polymer film prepared from, e.g., a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, an ethylene/methacrylate copolymer, or the like. The separation layer140may also include a non-woven fabric formed from a glass fiber with a high melting point, a polyethylene terephthalate fiber, or the like. In some embodiments, an area and/or a volume of the anode130(e.g., a contact area with the separation layer140) may be greater than that of the cathode100. Thus, lithium ions generated from the cathode100may be easily transferred to the anode130without a loss by, e.g., precipitation or sedimentation. Thus, improvements of both capacity and life-span properties by employing the above-described anode active material may be more efficiently implemented. In exemplary embodiments, an electrode cell may be defined by the cathode100, the anode130and the separation layer140, and a plurality of the electrode cells may be stacked to form an electrode assembly150that may have e.g., a jelly roll shape. For example, the electrode assembly150may be formed by winding, laminating or folding the separation layer140. The electrode assembly150may be accommodated together with an electrolyte in the case160to define a lithium secondary battery. In exemplary embodiments, a non-aqueous electrolyte may be used as the electrolyte. For example, the non-aqueous electrolyte solution may include a lithium salt and an organic solvent. The lithium salt commonly used in the electrolyte for the lithium secondary battery may be used, and may be represented by Li+X−. An anion of the lithium salt X−may include, e.g., F−, Cl−, Br−, I−, NO3−, N(CN)2−, BF4−, ClO4−, PF6−, (CF3)2PF4−, (CF3)3PF3−, (CF3)4PF2−, (CF3)5PF−, (CF3)6P−, CF3SO3−, CF3CF2SO3−, (CF3SO2)2N−, (FSO2)2N−, CF3CF2(CF3)2CO−, (CF3SO2)2CH−, (SF5)3C−, (CF3SO2)3C−, CF3(CF2)7SO3−, CF3CO2−, CH3CO2−, SCN−, (CF3CF2SO2)2N−, etc. The organic solvent may include, e.g., propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxy ethane, diethoxy ethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, tetrahydrofuran, etc. These may be used alone or in a combination thereof. As illustrated inFIG.1, electrode tabs (a cathode tab and an anode tab) may protrude from the cathode current collector105and the anode electrode current collector125included in each electrode cell to one side of the case160. The electrode tabs may be welded together with the one side of the case160to be connected to an electrode lead (a cathode lead107and an anode127) extending or exposed to an outside of the case160. The lithium secondary battery may be manufactured in, e.g., a cylindrical shape using a can, a square shape, a pouch shape or a coin shape. Hereinafter, preferred embodiments are proposed to more concretely describe the present invention. However, the following examples are only given for illustrating the present invention and those skilled in the related art will obviously understand that various alterations and modifications are possible within the scope and spirit of the present invention. Such alterations and modifications are duly included in the appended claims. Example 1 Preparation of Carbon-Based Particle i) Synthesis of resol oligomer: Phenol and formaldehyde were mixed in a molar ratio of 1:2, and 1.5 wt % of triethylamine was added, followed by a reaction at 85° C. for 4 hours and at a stirring rate of 160 rpm. ii) Suspension stabilization of resol oligomer: 1 g of PVA was dispersed in a water-dispersible medium, and then added to the above resol oligomer. iii) Curing of the resol oligomer: 3 g of a curing agent HMTA was added, and a reaction was performed at 98° C. for 12 hours and at a stirring rate of 400 rpm. iv) Obtaining carbon material: The cured resol oligomer was classified using a sieve, and then washed with H2O. v) Unreacted monomers and oligomers were removed from the washed resol oligomer using ethanol, and then dried. vi) Carbonization and Activation: The dried resol oligomer was fired at 900° C. for 1 hour under a nitrogen atmosphere while CO2gas was introduced at a flow rate of 1 L/min to induce a carbonization at 900° C. Deposition of Silicon Silane gas was injected into a CVD coater at a flow rate of 50 to 100 mL/min, and maintained at a temperature less than 600° C. with a temperature raising rate of 5 to 20° C./min for about 120 to 240 minutes to deposit silicon on the carbon-based particles to prepare an anode active material. Fabrication of Anode 95.5 wt % of a mixture of 15 wt % of the prepared anode active material and 80.5 wt % of artificial graphite, 1 wt % of CNT as a flake type conductive material, 2 wt % of styrene-butadiene rubber (SBR) as a binder and 1.5 wt % of carboxymethyl cellulose (CMC) as a thickener were mixed to obtain an anode active material slurry. The anode active material slurry was coated on a copper substrate, dried and pressed to prepare an anode. Fabrication of Li-Half Cell A lithium secondary battery including the anode prepared as prepared above method and a lithium metal as a counter electrode (cathode) was prepared. A lithium coin half-cell was constructed by interposing a separator (polyethylene, thickness 20 μm) between the anode and the lithium metal (thickness: 1 mm). The assembly of the lithium metal/separator/anode was placed in a coin cell plate, an electrolyte was injected, and then a cap was covered and clamped. 1M LiPF6 solution in a mixed solvent of EC/FEC/EMC/DEC (20/10/20/50; volume ratio) was used as the electrolyte. After clamping and impregnating for more than 12 hours, 3 cycles of charging and discharging were performed at 0.1 C (charge condition CC-CV 0.1 C 0.01V 0.01 C CUT-OFF, discharge condition CC 0.1 C 1.5V CUT-OFF) Example 2 Preparation of Carbon-Based Particle i) Polymerization inhibitors were removed from each of styrene (PS) and divinylbenzene (DVB). ii) Thereafter, styrene and divinylbenzene were polymerized by performing an emulsion-free emulsion polymerization. Specifically, 360 mL of distilled water, 43.2 mL of ethanol, 40 mL of styrene and 4 mL of DVB were placed in a double jacketed reactor equipped with a reflux condenser and stirred at 300 rpm for 30 minutes at room temperature under a nitrogen atmosphere. Subsequently, an aqueous solution of 0.37 g of potassium persulfate (KPS) dissolved in 50 mL of distilled water was added to the reactor and stirred at 70° C. for 24 hours at 300 rpm. iii) Unreacted monomers and oligomers were removed from the stirred polymer using ethanol and dried. vi) Carbonization and Activation: The dried polymer was fired at 900° C. for 1 hour under a nitrogen atmosphere while CO2gas was introduced at a flow rate of 1 L/min to induce a carbonization at 900° C. An anode and a lithium-half cell were fabricated by the same method as that of Example 1 except for the method for preparing the carbon-based particles as described above. Examples 3 and 4 An anode and a lithium-half cell were fabricated by the same method as that in Example 1, except that carbon-based particles having a pore size shown in Table 1 were prepared by controlling a temperature and a stirring time during the synthesis of the resol oligomer, and controlling a firing temperature in the carbonization and activation. Example 5 An anode and a lithium-half cell were fabricated by the same method as that in Example 1, except for operations as follows: i) In the preparation of the carbon-based particles, a temperature and a stirring time during the synthesis of the resol oligomer, and a firing temperature in the carbonization and activation were controlled to prepare carbon-based particles having a pore size shown in Table 1. ii) A firing temperature was 600° C. in the silicon deposition. Comparative Example 1 An anode and a lithium-half cell were fabricated by the same method as that in Example 1, except that carbon-based particles having a pore size shown in Table 1 were prepared by controlling a temperature and a stirring time during the synthesis of the resol oligomer, and controlling a firing temperature in the carbonization and activation. Comparative Example 2 An anode and a lithium-half cell were fabricated by the same method as that in Example 1, except for operations as follows: i) In the carbon-based particle preparation, carbon-based particles having a pore size shown in Table 1 were prepared by controlling a temperature and a stirring time during the synthesis of the resol oligomer and controlling a firing temperature in the carbonization and activation. ii) In the silicon deposition, a silane gas was injected into a CVD coater at a flow rate of 100 to 500 mL/min while being maintained at 600° C. or higher for about 30 to 120 minutes at a temperature raising rate of 5 to 20° C./min to deposit silicon on the carbon-based particles. Comparative Example 3 An anode and a lithium-half cell were fabricated by the same method as that in Example 1, except for operations for preparing the carbon-based particles. Preparation of Carbon-Based Particles i) Silica (SiO2) particles having an average particle diameter of 150 nm and a pitch formed from a petroleum/coal-based hydrocarbon residue were mixed in a weight ratio of 7:3 and mechanically stirred with high energy. ii) The stirred mixture was fired at 900° C. under nitrogen atmosphere for 1 hour. iii) The fired mixture was stirred in 3M NaOH solution for 6 hours to remove silica. Comparative Example 4 An anode and a lithium-half cell were fabricated by the same method as that in Comparative Example 3, except that, in the deposition of silicon, a silane gas was injected into a CVD coater at a flow rate of 100 to 500 mL/min while being maintained at 600° C. or higher for about 30 to 120 minutes at a temperature raising rate of 5 to 20° C./min to deposit silicon on the carbon-based particles. Comparative Example 5 An anode and a lithium-half cell were fabricated by the same method as that in Example 1, except that silicon was deposited by the same method as that in Comparative Example 4. Experimental Example (1) Measurement of Pore Size of Carbon-Based Particles The pore sizes of the carbon-based particles prepared according to the above-described Examples and Comparative Examples were measured using a surface area analyzer (ASAP-2420) manufactured by Micromeritics. Specifically, a maximum peak position of a Barrett-Joyner-Halenda (BJH) pore size distribution curve obtained from a nitrogen gas sorption isotherm curve was measured using samples from Examples and Comparative Examples to measure the pore size of the carbon-based particles. (2) Measurement of Amorphous Property and Crystallite Size of Silicon Crystallite sizes of the anode active materials prepared according to Examples and Comparative Examples were calculated using an XRD analysis and Equation 1 as described above. If a silicon particle size was excessively small to be measured through the XRD analysis, the case was designated as amorphous. Specific XRD analysis equipment/conditions are as shown in Table 1 below. TABLE 1XRD(X-Ray Diffractometer) EMPYREANMakerPANalyticalAnode materialCuK-Alpha1 wavelength1.540598ÅGenerator voltage45kVTube current40mAScan Range10~120°Scan Step Size0.0065°Divergence slit¼°Antiscatter slit½° (3) Measurement of Peak Intensity Ratio from Raman Spectrum A Raman spectroscopy spectrum of silicon was measured using a 532 nm laser Raman spectrometer for the anode active material prepared according to the above-described Examples and Comparative Examples. In the obtained Raman spectrum, a silicon peak intensity in a region having a wavenumber of 515 cm−1and a silicon peak intensity in a region having a wavenumber of 480 cm−1were measured. The measured peak intensities were applied to the above-described Equation 2 to calculate a peak intensity ratio of the Raman spectrum. The results are shown in Table 2 below. TABLE 2Pore SizeCrystallite SizePeak IntensityNo.(nm)(nm)RatioExample 19.5amorphous0.581Example 2640.897Example 311amorphous0.903Example 419amorphous0.771Example 5951.053Comparative20.561.081Example 1Comparative137.51.230Example 2Comparative150amorphous0.95Example 3Comparative200251.21Example 4Comparative2581.37Example 5 (4) Measurement of Volume Expansion Ratio Relative to Capacity of Anode Active Material The lithium secondary batteries of Examples and Comparative Examples were charged (CC/CV 0.1 C 0.01V 0.01 C CUT-OFF). An increasing ratio of an anode volume after charging relative to an initial anode volume was calculated as a percentage, and then divided by a charging capacity to evaluate a volume expansion ratio. (5) Measurement of Capacity Retention (Life-Span Property) During Repeated Charging and Discharging The lithium secondary batteries of Examples and Comparative Examples were charged (CC/CV 0.5 C 0.01V 0.01 C CUT-OFF) and discharged (CC 0.1 C 3.0V CUT-OFF) 50 times. A capacity retention was evaluated as a percentage of a capacity at the 500th cycle relative to a capacity at the 1st cycle. The results are shown in Table 3 below. TABLE 3Volume expanstion ratio (%)/Capacity RetentionNo.charging capacity (mAh/g)(%)Example 13.2598Example 22.595Example 33.690Example 43.890Example 53.587Comparative5.883Example 1Comparative4.681Example 2Comparative7.780Example 3Comparative8.163Example 4Comparative6.975Example 5 Referring to Table 3, Examples where silicon was deposited on the carbon-based particles having the pore size of 20 nm or less to have the amorphous structure or the crystallite size of 7 nm or less generally provided lower volume expansion rations and higher capacity retentions than those of Comparative Examples. In a relative aspect when comparing Examples 1 to 4 with Example 5, Examples 1 to 4 provided higher capacity retentions than that from the case having the crystallite size exceeded 4 nm (e.g., Example 5). In a relative aspect when comparing Examples 1 and 2 with Examples 3 and 4, Examples 1 and 2 provided performance greater than that when the pore size exceeded 10 nm (e.g., Examples 3 and 4). In another aspect, Examples where silicon was deposited on the carbon-based particles having the pore size of 20 nm or less so that the Raman spectrum peak intensity ratio of silicon was 1.2 or less generally provided lower volume expansion rations and higher capacity retentions than those of Comparative Examples. In a relative aspect when comparing Examples 1 to 4 with Example 5, Examples 1 to 4 provided higher capacity retentions than that from the case having the peak intensity ratio of the Raman spectrum exceeded 1.0 (e.g., Example 5). | 31,044 |
11862801 | Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations, and may include exaggerated material for illustrative purposes. In the figures, similar components and/or features may have the same numerical reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components and/or features. If only the first numerical reference label is used in the specification, the description is applicable to any one of the similar components and/or features having the same first numerical reference label irrespective of the letter suffix. DETAILED DESCRIPTION Batteries, and more generally energy storage devices, may include multiple battery cells coupled with one another in a series or a parallel electrical configuration. The cells may also be physically coupled with one another to form the battery. Batteries having cells in a stacked orientation and characterized by z-direction transmission of current through the cells may have current collectors of adjacent cells in physical contact with one another. Using metal current collectors may facilitate through-cell transmission of current, although the metal current collectors may also maintain high conductivity in an xy-direction across the current collectors. Additionally, during cell formation, a seal material may be needed to form a fluid seal of the battery cell between the two conductive current collectors along an edge region of the battery cell. The present technology may overcome many of these issues by utilizing a current collector formed with a polymeric material that may be insulative. A metallization layer may be formed about the polymer current collector to facilitate conductivity through the current collector to an adjacent cell. Additionally, a conductive material may be disposed within apertures of the polymer to provide additional z-direction electrical conductivity, while limiting xy-direction conductivity. The metallization and conductive material may be maintained within a preset region of the current collector, so that an edge region of the current collector may be the polymer. This polymer edge region may be used to couple with an additional polymer material directly to form a seal of the cell, while limiting any short circuit potential. Although the remaining portions of the description will routinely reference lithium-ion batteries, it will be readily understood by the skilled artisan that the technology is not so limited. The present designs may be employed with any number of battery or energy storage devices, including other rechargeable and primary, or non-rechargeable, battery types, as well as electrochemical capacitors also known as supercapacitors or ultracapacitors. Moreover, the present technology may be applicable to batteries and energy storage devices used in any number of technologies that may include, without limitation, phones and mobile devices, handheld electronic devices, laptops and other computers, appliances, heavy machinery, transportation equipment including automobiles, water-faring vessels, air travel equipment, and space travel equipment, as well as any other device that may use batteries or benefit from the discussed designs. Accordingly, the disclosure and claims are not to be considered limited to any particular example discussed, but can be utilized broadly with any number of devices that may exhibit some or all of the electrical or chemical characteristics of the discussed examples. FIG.1depicts a schematic cross-sectional view of an energy storage device according to embodiments of the present technology. The energy storage devices may include a single current collector or coupled current collectors. The energy storage devices may operate in a conventional manner with regard to electronic flow across or through material layers, such as providing electronic mobility across an xy-plane of the current collectors. Additionally, the described devices may operate by electronic flow through the structure in a z-direction through individual cells as opposed to via tabbed current collectors as described above for conventional batteries. As illustrated, the stacked battery100may include a stack of electrochemical cells C1, C2, C3, and C4between end plates102and104. End plates102and104may be metal current collector plates, which can serve both electrical and mechanical functions. In some embodiments, end plates102and104can be support plates that form part of an external housing of the stacked battery. End plates102and104may also provide mechanical support within a housing of the stacked battery. Some or all of the support plates may be electrically conductive, and there may be a terminal within the support plate that is electrically connected to the end plate. In embodiments an additional plate similar to end plates102and104may be disposed within the stack of cells, such as between two cells. This configuration including an additional plate may provide structural rigidity, and the additional plate may also preform electronic functions similar to end plates102,104. End plates102and104may act as positive and negative terminals of the battery. The cells may pass current in the z-direction through individual cells to the end plates, which may transfer current in any direction across the plate and from the battery. The stack of electrochemical cells may include any number of electrochemical cells depending on the selected voltage for the stacked battery100, along with the individual voltage of each individual electrochemical cell. The cell stack may be arranged with as many or as few electrochemical cells in series as desired, as well as with intervening plates for support and current transfer. The cells C may be positioned adjacent, e.g. abutting, one another in some configurations. Each electrochemical cell C may include a cathode110and an anode120, where the cathode110and anode120may be separated by separator130between the cathode and anode. Between the anode120of cell C1and the cathode of adjacent cell C2may be a stacked current collector150. The stacked current collector150may form part of C1and C2. On one side, stacked current collector150may be connected to the seal140of C1and connected on an opposing side to the seal140of C2. In some embodiments, as shown inFIG.1, stacked current collector150may include a first current collector152and a second current collector154. In embodiments one or both of the current collectors may include a metal or a non-metal material, such as a polymer or composite. As shown in the figure, in some embodiments the first current collector152and second current collector154can be different materials. In some embodiments, the first current collector152may be a material selected based on the potential of the anode120, such as copper or any other suitable metal, as well as a non-metal material including a polymer. The second current collector may be a material selected based on the potential of the cathode110, such as aluminum or other suitable metals, as well as a non-metal material including a polymer. In other words, the materials for the first and second current collectors can be selected based on electrochemical compatibility with the anode and cathode active materials used. The first and second current collectors can be made of any material known in the art. For example, copper, aluminum, or stainless steel may be used, as well as composite materials having metallic aspects, and non-metallic materials including polymers. In some instances the metals or non-metals used in the first and second current collector can be the same or different. The materials selected for the anode and cathode active materials can be any suitable battery materials. For example, the anode material can be silicon, graphite, carbon, a tin alloy, lithium metal, a lithium containing material, such as lithium titanium oxide (LTO), or other suitable materials that can form an anode in a battery cell. Additionally, for example, the cathode material can be a lithium-containing material. In some embodiments, the lithium-containing material can be a lithium metal oxide, such as lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, or lithium titanate, while in other embodiments, the lithium-containing material can be a lithium iron phosphate, or other suitable materials that can form a cathode in a battery cell. The first and second current collectors may have any suitable thickness, and may have a thickness that allows for a seal to be formed and provides suitable mechanical stability to prevent failure, such as breakage of the layers, during anticipated usage of the stacked battery. Additionally, the thickness of the current collectors can be sufficiently thin to allow for bending and flexing in the separation region to accommodate expansion anticipated during cycling of the stacked battery, including, for example, up to 10% expansion in the z-direction. Turning toFIG.2, the stacked current collector150may have a connection region153where the first current collector152and second current collector154may be connected, and a gap region155at the peripheral ends of the collector150. In the connection region153, the first current collector and second current collector may be in direct contact or otherwise joined to be electrically-conductive. In some embodiments, the first current collector and second current collector may be directly connected, while in other embodiments the first current collector and second current collector may be indirectly connected via a conductive or adhesive material. To form the connection region153, the first current collector152and the second current collector154may be laminated together. Additionally, the connection region153may be created by welding the first current collector152and the second current collector154together. The connection region153may also be created by using an adhesive, which may be electrically conductive, between the first current collector152and the second current collector154. In other embodiments, the connection region153may be created by the wetting that can occur between the materials of the first current collector152and the second current collector154. In the gap region155, the peripheral ends of the first current collector152and the second current collector154may be spaced apart and moveable relative to each other. As such, there may be a separation distance between the first and second current collectors, which may increase as the electrochemical cell swells. In some embodiments, the spaced apart peripheral ends of the first current collector152and the second current collector154may be of a length that is sufficient to accommodate an anticipated expansion of the individual electrochemical cells of the stacked battery during cycling of the battery. The peripheral ends of the current collectors152aand154amay have a length L, as shown inFIG.2, which may be long enough that up to or at least about 10% expansion in the z-direction can be accommodated. As shown inFIG.1, each cell C1, C2, C3, and C4, also includes a seal140, which, with the current collector layers, may electrochemically isolate the electrochemical cells from each other. Thus, each cathode-anode pair may be electrochemically sealed and isolated from neighboring electrochemical cells. Because the current collectors152and154may be separated at the peripheral ends, separate seals140can be formed on opposing sides, such as a top and bottom, of the stacked current collector150. The seals140may be the same or different materials, and each seal140may also be a laminate, composite, or coupling of two or more materials in embodiments. The seal material may be able to bond with the first and second layers of the stacked current collector to prevent electrolyte leakage. The seal material may be a polymer, an epoxy, or other suitable electrically-insulating material that can bond with first and second current collectors to create a seal, which may be a hermetic seal. In some embodiments, the polymer may be polypropylene, polyethylene, polyethylene terephthalate, polytrimethylene terephthalate, polyimide, or any other suitable polymer that may bond with the first and second current collectors of the stacked current collector to form a hermetic seal and may also provide resistance to moisture ingress. The electrolyte may be a solid, a gel, or a liquid in embodiments. The seal may electrochemically isolate each electrochemical cell by hermetically sealing the cell, thereby preventing ions in the electrolyte from escaping to a neighboring electrochemical cell. The seal material may be any material providing adequate bonding with the metal layers such that the seal may be maintained through a predetermined period of time or battery usage. The separator may be wetted with the electrolyte, such as a fluid electrolyte or gel electrolyte, to incorporate the electrolyte into the stacked battery. Alternatively, a gel electrolyte may coat the separator. In still further alternatives, a gel electrolyte may coat the first metal layer and/or second metal layer before combination. Additionally, the electrolyte may be blended with particles of electrode active material. In various embodiments, incorporating the electrolyte into the components of the stacked battery may reduce gassing in the stacked battery. In variations that include a flexible seal, the stacked battery may accommodate gas resulting from degassing. The individual electrochemical cells may be formed in any suitable manner. In some embodiments, the cathode110, the anode120, and the separator130may be preassembled. A first current collector152may then be connected to the anode while a second current collector154may be connected to the cathode to create a cell. The seal material may be disposed between the first current collector152and the second current collector154to form seals140. Finally, the peripheral ends of the sealed electrochemical cell may be further taped to frame the cell. Tapes145, as well as other coatings, sealing, or material layers, may be disposed around the outer perimeter of the metal layers and seals. The tape145may be substituted with ceramic or polymeric materials. Tape145may be included for various reasons including to prevent shorting to adjacent layers or to surrounding conductive surfaces within the device, to provide improved electrochemical or chemical stability, and to provide mechanical strength. FIGS.1and2illustrate an exemplary stacked battery design according to the present technology. Additional configurations other than illustrated, or as variations on the designs, are also encompassed by the present technology. For example, certain embodiments may not include an additional seal material, and first current collector152and second current collector154may be directly coupled or bonded together. Additionally, the current collectors may include designs including combinations of polymer material and conductive materials, such as within a matrix. An exemplary matrix for a current collector may include a polymer disposed as the matrix material or as part of the matrix material. The matrix may provide an insulative design that limits or reduces xy-directional conductivity. The polymer matrix may be developed with a conductive material to produce a current collector having particular electrochemical or composite properties, such as electrical conductivity in the z-direction or through the cell. For example, conductive particulate material may be incorporated within the matrix. The conductive material may include any of the conductive materials previously identified. In embodiments, the conductive material may include one or more of silver, aluminum, copper, stainless steel, and a carbon-containing material. In this way, the current collector may have a tuned resistivity to provide directional control for electrical conductivity. For example, the produced current collector may be configured to provide an in-plane resistivity across a length in the xy-plane, as well as a through-plane resistivity in the z-direction, which is greater than or about 1×10−4ohm-m in embodiments. Additionally, exemplary current collectors may have an in-plane and through-plane resistivity of between about 1×10−3ohm-m and about 1,000 ohm-m. In other embodiments, more conventional electrical distribution may be employed, where current is transferred along conductive current collectors into and out of the cell. Turning toFIG.3is shown a schematic top plan view of an exemplary current collector300according to some embodiments of the present technology. Current collector300may be included with stacked battery100discussed above, and in embodiments may be included as either or both of the cathode current collector or the anode current collector152,154. Current collector300may include multiple components that provide multiple benefits when utilized in a cell. Current collector300may include a polymer305defining the lateral dimensions of the current collector. In embodiments, current collector300may be less than or about 1 cm in any dimension. In other embodiments, current collector300may be characterized by a length greater than or about 1 cm, greater than or about 10 cm, greater than or about 1 m, or more in any lateral direction across the current collector. Polymer305may have a plurality of apertures310defined through the polymer within a first region312of the polymer. First region312may extend partially or fully within a portion of current collector300intended to be the connection region153, or a region in which the active materials may be disposed across the current collector. A metal315may be disposed across a portion of polymer305. Metal315may be coated as a layer on the polymer305, and in embodiments is not incorporated within the polymer, although it may be coated along several surfaces of the polymer. Metal315may extend towards an edge region325of polymer305, however in some embodiments edge region325may be maintained free of the metal on at least one surface of the polymer. As discussed above, a separator disposed between active materials may also be a polymeric material. When metal or other conductive materials are included through the edge regions of the current collectors, seal140may be used to prevent shorting between the two current collectors. However, when the current collectors include a non-conductive polymer305, the edge region325may be used to produce the battery cell seal. For example, the polymer305may be sealed with the polymer of the separator, and/or an edge region of an additional current collector300. This may produce a seal to enclose the interior of the cell to prevent electrolyte leakage. By using insulative polymers for the current collectors, seal140may not be needed in embodiments according to the present technology because the current collectors may be directly sealed together. Current collector300may also include a conductive material320disposed along one or more surfaces of the polymer305. In embodiments, the conductive material may be disposed over the metal, which may be positioned between the conductive material320and the polymer305. The conductive material320may be located within first region312, and may not extend outward as far as metal315. The conductive material320may be disposed within the apertures of the polymer305, and may extend fully through a thickness of the polymer305in some embodiments as will be described in more detail below. Turning toFIG.4is shown a schematic cross-sectional view of an exemplary current collector400according to some embodiments of the present technology. Current collector400may be current collector300in some embodiments, although current collector400may include some or all aspects of current collector300as discussed above. For example, current collector400may include a polymer405defining a plurality of apertures410through the polymer film. Polymer405may be characterized by a first surface406and a second surface408opposite the first surface406. Although current collector400may be oriented in any direction with respect to active materials disposed on the current collector400, in some embodiments active material may be disposed along second surface408of current collector400. Accordingly, first surface406may face outside of a battery cell including current collector400, and may be coupled with a current collector of an adjacent cell of a battery stack. A metal415may be disposed across one or more surfaces of the polymer405, and as illustrated may be at least partially coated across first surface406and second surface408in some embodiments. Additionally, metal415may extend along sidewalls404of the apertures defined through the polymer405. Depending on the formation process, metal415may not fully coat the sidewalls of the apertures410defined through polymer405, although metal415may substantially line the sidewalls in embodiments, and may line more than 90% of the surface or the exposed surface of the sidewalls in some embodiments. Metal415may be formed in multiple operations, and thus may include a first portion416formed along second surface408of polymer405, and may include a second portion417formed along first surface406, and which may extend along sidewalls404of polymer405in some embodiments. Metal415may substantially line polymer405within first region412of the current collector400along both the first surface406and the second surface408of the polymer. Additionally, metal415may extend further towards an edge region407of the polymer405along first surface406than on second surface408. As noted above, in some embodiments, active material may be disposed along second surface408of the polymer405, and first surface406may face the exterior of a battery cell in which current collector400is used. Second surface408may be included as part of a seal for the battery cell, and thus metal415may not extend into edge region407of polymer405to allow the polymer to be directly sealed with a separator and or another current collector without providing a conductive path for shorting between the two current collectors. Polymeric materials may provide a liquid seal, although the materials may be susceptible to permeation of water vapor from outside the battery cell over time. Accordingly, second portion417of metal415may extend across first surface406towards an edge region407, and may extend fully to an edge of polymer material405. Additionally, second portion417of metal415may not be formed to the same thickness as first portion416, and in some embodiments, second portion417of metal415may be at least twice the thickness of first portion416. In some embodiments second portion417of metal415may extend into what may become a part of gap region155of the current collector where a seal may be formed between current collectors of a battery cell, although the second portion417of metal415may not fully extend to an edge region. By extending to where a seal is formed, water vapor ingress through the polymer current collector may be substantially or essentially prevented. Current collector400may also include a conductive material420disposed across surfaces of the current collector400. Conductive material420may be disposed overlying first surface406and second surface408of polymer405. In some embodiments conductive material420may be disposed overlying metal415, and may not directly contact polymer405, although in other embodiments conductive material420may directly contact polymer405. Similar to the metal415, conductive material420may be provided in multiple segments, and may include coating second side408with a first portion421in one operation, and coating first side406with a second portion422in a second operation. In some embodiments, the metallization and conductive material coating may alternate on sides of the polymer. For example, first portion416of metal415may be formed along second surface408of polymer405. Apertures410may then be formed through the polymer although in other embodiments the apertures may have already been formed. First portion422of conductive material420may then be coated across second surface408of polymer405. Subsequently, second portion417of metal415may be formed across first surface406of polymer405, and which may extend within apertures410to cover a backside of first portion421of conductive material420. Second portion422of conductive material420may then be coated over first surface406of polymer405, and may extend within apertures410. This may provide conductive paths through polymer405allowing current collector400to transmit current in a z-direction, or vertically through the polymer405. Because first portion421may at least partially extend within apertures410, second portion417of metal415may not fully line sidewalls404of polymer405as previously described. However, metal415may line at least about 50% of the sidewalls of apertures410in some embodiments, and may line at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, at least about 99%, or may fully line the apertures410. The materials used in current collector400may be formed to maintain a minimal thickness. For example, polymer405may include any number of polymers including polypropylene, including bi-oriented polypropylene, polyethylene, polyethylene terephthalate, or other insulative materials that may operate as a base for forming the current collector. As noted above, the polymer may have minimal conductivity, and may not include conductive additives, which may allow the polymer to similarly operate as a portion of the battery cell seal. Accordingly, polymer405may also be formed of or include any of the materials discussed above for separator130. The polymer405may be characterized by any thickness, and in some embodiments may be of a reduced thickness to promote thinner battery cells within a battery stack. For example, polymer405may be characterized by a thickness less than or about 100 μm, and in embodiments may be characterized by a thickness less than or about 80 μm, less than or about 60 μm, less than or about 50 μm, less than or about 40 μm, less than or about 30 μm, less than or about 25 μm, less than or about 20 μm, less than or about 15 μm, less than or about 10 μm, less than or about 9 μm, less than or about 8 μm, less than or about 7 μm, less than or about 6 μm, less than or about 5 μm, less than or about 4 μm, less than or about 3 μm, less than or about 2 μm, less than or about 1 μm, or less. A certain minimum thickness may be maintained to facilitate formation of apertures410without damaging the polymer405. Additionally, apertures410may be spaced across the polymer405, such as across the first region, and may have a spacing between apertures of greater than or about 0.1 mm edge-to-edge, and may have a spacing greater than or about 0.3 mm, greater than or about 0.5 mm, greater than or about 0.7 mm, greater than or about 0.9 mm, greater than or about 1.0 mm, greater than or about 1.5 mm, or more. Each aperture may be characterized by a diameter of at least about 50 μm, and may be characterized by a diameter of greater than or about 75 μm, greater than or about 100 μm, greater than or about 200 μm, greater than or about 300 μm, greater than or about 400 μm, greater than or about 500 μm, greater than or about 600 μm, greater than or about 700 μm, greater than or about 800 μm, greater than or about 900 μm, greater than or about 1.0 mm, greater than or about 1.5 mm, or greater. The aperture spacing and aperture sizing may affect conductivity in the z-direction in combination with the conductive material and metal, as well as uniformity of current distribution across surfaces of the current collector. The metal415may be used to facilitate z-direction conductivity while minimizing an increase in xy-direction conductivity. For example, by maintaining the thickness of the metal material below 0.5 μm, a sufficient resistivity may be maintained across the current collector. In some embodiments the metal may be deposited to a thickness of less than or about 0.4 μm, less than or about 0.3 μm, less than or about 0.2 μm, less than or about 0.1 μm, less than or about 80 nm, less than or about 60 nm, less than or about 50 nm, less than or about 40 nm, or less. As previously noted, second portion417of metal415and first portion416may not be the same thickness, although in some embodiments the thicknesses may be similar. For example, first portion416may be characterized by a thickness of less than or about 0.2 μm, or less than or about 0.1 μm, while second portion417may be characterized by a thickness of greater than or about 0.1 μm, or greater than or about 0.2 μm. Second portion417of metal415may also be at least about 50% greater thickness than first portion416, and in some embodiments may be at least twice the thickness, three times the thickness, five times the thickness, ten times the thickness, or more. The metal415may be any metal that may facilitate conductivity through the current collector. Exemplary metal may be or include aluminum, copper, nickel, tin, zinc, titanium, silver, molybdenum, palladium, and platinum. Although the conductive material may limit or prevent interaction of electrolyte with metal415, in some embodiments the metal may be selected based on the electrical potential of the current collector400. For example, in some embodiments, when used as a cathode current collector, metal415may be aluminum, and when used as an anode current collector, metal415may be copper or nickel, although other metals may be used. Conductive material420may include any number of materials that may facilitate z-direction transmission of current across current collector400. Although conductive material420may include metal or other directly conductive materials noted above, conductive material420may include a conductive filler incorporated within a binder to maintain a particular resistivity. Because current collector400may be configured to transmit current through the current collector, which may have a thickness in the micron range, conductivity may be much lower than in conventional cells that may transfer current over millimeters or more in the xy-direction of a current collector. Accordingly, conductive material420may be configured to produce a resistivity in a z-direction through current collector400of between about 0.1 Ω·m and about 1 Ω·m. Metal315may facilitate xy-direction transmission of current within the first region412, although the resistivity may be greater than some conventional current collectors. For example, an xy-direction resistivity across first region412may be between about 0.0001 Ω·m and about 0.1 Ω·m, or between about 0.0005 Ω·m and about 0.01 Ω·m. Because current may transfer through current collector400at specific locations in which the apertures are located, by having a lower xy-direction resistivity, a substantially uniform current may be provided to active materials of the battery cell. However, by maintaining edge region407free of metal material, the xy-directional transmission of current may be limited to the active regions of the battery cells. Exemplary conductive materials may include conductive inks or metallic powder mixed within a binder or adhesive. For example, any of the previously noted metals as well as carbon black, graphite, or other conductive materials may be mixed within a binder in a proportion to produce the z-directional resistivity values noted above. The binder may be used to provide multiple functions including a seal against electrolytic leakage or contact with metal415, as well as facilitate lamination of current collectors between adjacent cells of a stacked battery. Any binder may be used, such as polymeric binders, and may be characterized by a chemical stability with any of the electrolytic materials previously noted. Current collector400may be used as a cathode current collector or an anode current collector in embodiments of the present technology. However, because some anode active materials may be characterized by sufficient conductivity, such as carbon-based anode materials, some current collectors of the present technology may not include metal along a surface of the current collector along which active material may be applied.FIG.5shows a schematic cross-sectional view of an exemplary current collector500according to some embodiments of the present technology. Current collector500may be similar to current collector400, and may include any of the materials previously discussed. For example, current collector500may include a polymer505having apertures510defined there through. Polymer505may be the same as polymer405, or may be different although polymer505may be any of the previously discussed polymeric materials. In some embodiments, a first portion521of a conductive material520may be disposed along a second surface508of polymer505, which may be a surface along which an active material, such as an anode active material, may be disposed. Different from current collector400, first portion521of conductive material520may directly contact polymer505, and a metal material may not be disposed between the conductive material and the polymer. The rest of current collector500may be similarly formed as previously described, and may include a metal515extending across first surface506along first region512, although edge region507may be maintained free of metal515as discussed above. A second portion522of conductive material520may be deposited overlying metal515, and may extend within apertures510in embodiments. This configuration of a current collector may reduce cost and fabrication time when the active material provides sufficient conductivity. FIG.6shows a schematic cross-sectional view of a stacked battery600according to some embodiments of the present technology. Stacked battery600may include a portion of stacked battery100described above, although several components have been removed for illustrative purposes. It is to be understood, however, that any of the components previously discussed may be included in stacked battery600. Stacked battery600illustrates one possible coupling of two battery cells C1and C2, which may include current collectors according to the present technology. For example, each cell may include a cathode active material110, and an anode active material120separated by a separator130as previously described. Cathode active material110of each cell may be disposed along a first region of a current collector400as previously described. Additionally, anode active material120may be disposed along current collector500as previously described, although current collector400may also be used in embodiments. Stacked battery600may not include a seal140as previously discussed because the edge regions407,507of current collectors400,500may be used to form the seal of each cell. As illustrated, edge regions407,507are sealed with separator130to produce a fluid seal for each cell. In other embodiments edge region407may be directly coupled with edge region507to produce the seal, in which separator130may not be included. Because non-conductive polymers may be used for the current collectors, a direct seal may be formed by heat-sealing or otherwise bonding the edge regions of the current collectors together or with the separator130. Additionally, anode current collector500of cell C1may be coupled with cathode current collector400of cell C2along a first surface of each current collector. As illustrated, anode current collector500of cell C1and cathode current collector400of cell C2may be directly connected to facilitate z-directional transmission of current through the battery cells. The conductive material420,520previously described, may facilitate the coupling of the two cells by allowing a bond to be formed across the two current collectors, which may both have the first surfaces coated with a similar conductive material. In this way, current transmission across the cells may be more uniform due to a consistent adhesive surface between the adjacent current collectors. FIG.7shows selected operations in a method700of forming a current collector according to some embodiments of the present technology. The methods may be used in the formation of current collector400and current collector500previously described. Method700may include receiving a polymer material, such as from a roll of polymeric material. The method may optionally include depositing metal along a first surface of the polymer at optional operation705. The operation may be optional depending on whether current collector400is being formed in which metal may be formed across second surface408as previously described. The metal deposition may be performed in a number of ways to produce a uniform coverage of metal at a thickness of less than 1 μm, or less than 0.1 μm. For example, exemplary operations may include chemical vapor deposition, electrodeposition, sputtering, or various other forms of metal deposition to provide a substantially conformal coating across the first surface of the polymer film. The polymer may be perforated at operation710to define a plurality of apertures through the polymer film. For example, the apertures may be formed via a laser ablation, or a roller process, which may use needles to form the perforations. The apertures may not extend fully across the polymer, and may be limited to a first interior region of the polymer in some embodiments, which may maintain a frame of polymer around the first portion including the apertures. At operation715, a conductive material may be coated across the first region of the polymer film along a first surface of the polymer film. The conductive material may include a conductive filler incorporated within a binder or adhesive as previously discussed. The conductive material may be coated in a variety of ways including by spraying, gravure coating, doctor blade coating, or any other way of providing the conductive material over the first region of the polymer film. A metal or other conductive layer may be formed across a second surface of the polymer film opposite the first surface at operation720. During this operation, the metal may at least partially coat sidewalls of the apertures as previously described. Similar processes may be used to form the layer of metal material, and in some embodiments the process may conformally line the second surface as well as along the sidewalls of the apertures. At operation725, the second surface of the polymer film may be coated with the conductive material. This operation may substantially fill the apertures with the conductive material, which may provide, tune, or facilitate a z-direction capability of current transmission through the current collector. The current collector may then be singulated from the roll of material in some embodiments and utilized in a battery cell, or battery, including a stacked battery as discussed throughout the present disclosure. By utilizing current collectors according to the present technology, materials may be saved by removing a seal between current collectors in some embodiments, and a tuned conductivity may be provided in both the z-direction through the current collector as well as across surfaces of the current collector in the xy-direction. In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details. Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology. Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included. Where multiple values are provided in a list, any range encompassing or based on any of those values is similarly specifically disclosed. As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a material” includes a plurality of such materials, and reference to “the cell” includes reference to one or more cells and equivalents thereof known to those skilled in the art, and so forth. Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups. | 42,444 |
11862802 | DETAILED DESCRIPTION OF THE INVENTION This invention discloses a lithium electrode. Please refer toFIG.1, which is a schematic diagram of the lithium electrode of this invention. The lithium electrode10of this invention includes an electrically conductive structure11, a lithium metal layer12, a solid electrolyte layer13, an electrolyte storage layer14and a porous covering layer15. The electrically conductive structure layer11has at least one recess111with one-side opening. Please also refer toFIG.2, which is a schematic diagram of the electrically conductive structure layer of the lithium electrode according toFIG.1of this invention. The width of the opening of the recess111is greater than 0 or not less than 50 micrometers, preferably. The maximum available value is depended on the active range of the battery. Also, the depth of the recess111ranges from 15 to 40 micrometers. The inner surface of the recess111has at least one electrically conductive region113and at least one electrically insulating region112. The lithium metal layer12is disposed in the recess111of the electrically conductive structure layer11and contacts to the electrically conductive region113. The thickness of the lithium metal layer12ranges from 0.3 to 5 micrometers. The solid electrolyte layer13is movably disposed in the recess111of the electrically conductive structure layer11. The bottom of the solid electrolyte layer13covers and contacts to the lithium metal layer12, and the sides of the solid electrolyte layer13are contacted with the electrically insulating region112. The electrolyte storage layer14is disposed in the recess111of the electrically conductive structure layer11. The bottom of the electrolyte storage layer14covers and contacts to the solid electrolyte layer13, and the sides of the electrolyte storage layer14are contacted with the electrically insulating region112. The porous covering layer15is disposed on the electrically conductive structure layer11to cover the opening of the recess111of the electrically conductive structure layer11. The porous covering layer15has a plurality of through holes to allow lithium ions to pass. An adhesive layer16is disposed between the electrically conductive structure layer11and the porous covering layer15to adhere the porous covering layer15to the electrically conductive structure layer11. The liquid and/or gel electrolyte are impregnated in the electrolyte storage layer14. The material of the solid electrolyte layer13may be any solid electrolyte series, such as oxide-based solid electrolyte, sulfide-based solid electrolyte, lithium-aluminum alloy solid electrolyte or lithium azide (LiN3) solid electrolyte, which may be crystalline or glassy. In this invention, the lithium metal layer12and the electrolyte storage layer14are separated by the solid electrolyte layer13. Therefore, the unnecessary contact between the liquid or gel electrolyte impregnated in the electrolyte storage layer14and the active material, the lithium metal layer12are reduced or avoided. The unnecessary consumption for the lithium ions are also reduced or avoided to prevent the performance attenuation of the lithium batteries. Hence, it is preferably that the lithium metal layer12is completely covered by the solid electrolyte layer13. The side edges of the solid electrolyte layer13abuts against the side walls of the recess111to reduce or avoid the unnecessary contact between the liquid or gel electrolyte impregnated in the electrolyte storage layer14and the lithium metal layer12. The lithium metal layer12is disposed at the bottom of the recess111. Therefore, the bottom of the recess111is the electrically conductive region113. When the lithium electrode10is assembled as a battery, the electricity generated during the electrochemical reaction is outputted from the electrically conductive region113. It is necessary that the electrically conductive region113is with an electrical conductive path between the inside and the outside of the battery. The solid electrolyte layer13and the electrolyte storage layer14have to contact with the electrically insulating region112of the recess111. Therefore, the side walls of the recess111are the electrically insulating region112. Moreover, the shape of the recess111of the electrically conductive structure layer11is not limited. As shown inFIG.2, the side walls of the recess111is, but not limited to, vertical. Excepting for the above-mentioned requirements, it has to be considered that the solid electrolyte layer13is moveable to suppress the growth of the lithium dendrites, which only can push the solid electrolyte layer13to press the electrolyte storage layer14. A more detailed description of the present invention is presented below. Therefore, the side walls, for arrangement of the solid electrolyte layer13, of the recess111are preferably smooth and equidistant. For the electrically conductive structure layer11, two embodiments are provided and described in detail with respect to the drawings. Please refer toFIG.3A, which is a schematic diagram of a first embodiment of the electrically conductive structure layer of the lithium electrode of this invention. In this embodiment, an electrically conductive element101is the main body of the electrically conductive structure layer11. An electrically insulating element102is disposed directly on the top surface of the electrically conductive element101. The electrically insulating element102has at least one through hole102h. Parts of the electrically conductive element101are exposed from the through hole102h. Therefore, the recess111with one-side opening is formed thereof. The bottom111bof the recess111is formed by the electrically conductive element101to be defined as the electrically conductive region113. The side wall111wof the recess111is formed by the electrically insulating element102to be defined as the electrically insulating region112. The lithium electrode10constructed by the electrically conductive structure layer11based on the first embodiment is illustrated inFIG.3B. The bottom111bof the recess111is formed by the electrically conductive element101. Therefore, an electrical conductive path between the inside and the outside of the battery can be formed to output the electricity generated thereof. That means the electrically conductive element101serving the current collector of the lithium electrode10. The material of the electrically conductive element101may be metal or any other electrically conductive materials, such as copper, nickel, steel or any combinations thereof. The material of the electrically insulating element102may be insulating polymer material, insulating ceramic material, insulating glass material, insulating glass fiber material and any combinations thereof. The insulating polymer material includes polyimide, polyethylene terephthalate, polyurethane, polyacrylate, epoxy or silicone. The insulating glass fiber material may be FR4-class, such as FR4 epoxy glass fiber material. Then please refer toFIGS.4A and4B, which is a schematic diagram of a second embodiment of the electrically conductive structure layer of the lithium electrode of this invention, and a schematic diagram of the lithium electrode based on the second embodiment of the electrically conductive structure layer shown inFIG.4Aof this invention respectively. The electrically conductive structure layer11of this second embodiment also includes an electrically conductive element101and an electrically insulating element102. More specifically, the electrically conductive element101has a blind hole101bto form the recess111directly. The electrically insulating element102is disposed on a side wall of the blind hole101bto be defined as the electrically insulating region112. A bottom of the blind hole101bis uncovered by the electrically insulating element102and defined as the electrically conductive region113. Similar, the electrically conductive element101is the main body of the electrically conductive structure layer11. The uncovered bottom of the recess111is formed by the electrically conductive element101. Therefore, an electrical conductive path between the inside and the outside of the battery can be formed to output the electricity generated by the battery constructed by lithium electrode10. Also, the electrically conductive element101can be regarded as the current collector of the lithium electrode10. Please refer toFIGS.1,3B and4B, the electrolyte storage layer14contacts and covers the solid electrolyte layer13. When the electrolyte storage layer14is filled in the recess111, the top surface of the electrolyte storage layer14is substantially aligned with the top surface of the electrically conductive structure layer11. In other words, the remaining space is filled by the electrolyte storage layer14. The electrolyte storage layer14is used to impregnate with the liquid and/or gel electrolyte. In this invention, the lithium metal layer12and the electrolyte storage layer14are separated by the solid electrolyte layer13. Therefore, the unnecessary contact between the liquid or gel electrolyte impregnated in the electrolyte storage layer14and the active material (i.e. the lithium metal layer12) are reduced or avoided. The unnecessary consumption for the lithium ions are also reduced or avoided to prevent the performance attenuation of the lithium batteries. The electrolyte storage layer14is porous to impregnate with the liquid and/or gel electrolyte. The material of the electrolyte storage layer14may be polymer material, ceramic material, glass material, fiber material and any combinations thereof. The porous structure of the electrolyte storage layer14is formed by stacked particles and/or crossed fibers. The particles include ceramic particles, polymer particles and/or glass particles. The fibers include polymer fibers and/or glass fibers. The porous covering layer15is adhered to the electrically conductive structure layer11to cover the opening of the recess111. The porous covering layer15has a plurality of through holes to allow lithium ions and the electrolyte to pass for the electrochemical reactions. The through holes may be linear or non-linear (ant holes) formed by chemical or mechanical processes. Moreover, the porous covering layer15may be made of porous materials to offer the through holes. Further, please refer toFIG.5, the adhesive layer16, located between the electrically conductive structure layer11and the porous covering layer15, and the electrically insulating element102are integrated into an electrically insulating glue frame21. As shown in the drawing, the electrically insulating glue frame21is formed between the porous covering layer15and the electrically conductive element101. The electrically insulating glue frame21located on the side walls of the recess111is used for the electrically insulating element102to define as the electrically insulating region112. The electrically insulating glue frame21located between the electrically conductive structure layer11and the porous covering layer15is used to adhere the electrically conductive structure layer11and the porous covering layer15. The material of the electrically insulating glue frame21is selected from the group consisting of thermosetting polymer, thermoplastic polymer and any combinations thereof. The thermosetting polymer is selected from the group consisting of silicone, epoxy, acrylic acid resin and any combinations thereof and the thermoplastic polymer is selected from the group consisting of polyethylene, polypropylene, thermoplastic polyimide, thermoplastic polyurethane and any combinations thereof. Due to the liquid or gel electrolyte is adapted, the material of the electrically insulating glue frame21is preferably selected from the electrolyte-inert material, such as silicone, polyethylene, polypropylene, thermoplastic polyimide and so on. Therefore, the electrically insulating glue frame21will not react with the electrolyte to maintain the adhesion ability. Also, for the embodiment shown inFIG.3B, the adhesive layer16and the electrically insulating element102may be integrated into an electrically insulating glue frame21. The electrically insulating glue frame21is used for the electrically insulating element102of the recess111and is used to adhere the electrically conductive structure layer11and the porous covering layer15. Moreover, excepting for the single-layered structure shown in the drawings, the electrically insulating glue frame21may be multi-layered structure. With the modification of the adhesive material, the adhesive will be better. In general, when the lithium metal is plated, the lithium dendrites will grow vertically. With the arrangement of this invention, the growth of the lithium dendrites is constrained by the solid electrolyte layer13. The vertical growth of the lithium dendrites will push the solid electrolyte layer13. The solid electrolyte layer13is moveably disposed in the recess111. Therefore, the solid electrolyte layer13is pushed to move toward the electrolyte storage layer14. Due the porous covering layer15is adhered on the electrically conductive structure layer11firmly, the movement range of the solid electrolyte layer13is limited. The electrolyte storage layer14is porous to store the liquid and/or gel electrolyte. Also, the electrolyte storage layer14is compressible. When the electrolyte storage layer14is pressed by the solid electrolyte layer13, the electrolyte storage layer14will be deformed to squeeze out parts of the liquid and/or gel electrolyte impregnated therein. Also, the compressibility of the electrolyte storage layer14is limited. As the compression distance increases, the resistive force to compress the electrolyte storage layer14will become larger to inhibit the vertical growth of the lithium dendrites. The lithium dendrites are forced to grow in a horizontal direction. The penetration through issue for the electrical insulator, i.e. the separator, caused by the lithium dendrites can be eliminated to avoid inner shorting. When the lithium metal is striped, the solid electrolyte layer13will move back to the original position and the electrolyte storage layer14will recover to the original state. The squeezed-out liquid and/or gel electrolyte will flow back to be impregnated in the electrolyte storage layer14. Further materials illustrations for the solid electrolyte layer13are described below. The sulfide-based solid electrolyte may be selected from one or more of the groups consisting of a glassy state of Li2S—P2S5, a crystalline state of Lix′My′PSz′, and a glassy ceramic state of Li2S—P2S5. wherein M is selected from one or more of the groups consisting of Si, Ge, and Sn; x′+4y′+5=2Z′,0≤y′≤1. Preferably, the glassy state of Li2S—P2S5may be selected from one or more of the groups consisting of glassy state of 70Li2S-30P2S5, glassy state of 75Li2S-25P2S5, and glassy state of 80Li2S-20P2S5. The glassy ceramic state of Li2S—P2S5may be selected from one or more of the groups consisting of glassy ceramic state of 70Li2S-30P2S5, glassy ceramic state of 75Li2S-25P2S5, and glassy ceramic state of 80Li2S-20P2S5. The crystalline state of Lix′My′PSz′may be selected from one or more of the groups consisting of Li3PS4, Li4SnS4, Li4GeS4, Li10SnP2S12, Li10GeP4S12, Li10SiP2S12, Li10GeP2S12, Li7P3S11, L9.54Si1.74P1.44S11.7Cl0.3, ß-Li3PS4, Li7P2SI, Li7P3S11, 0.4LiI-0.6Li4SnS4, and Li6PS5Cl. The oxide-based solid electrolyte may be a fluorite structure oxide-based solid electrolyte. For example, it may be yttria stabilized zirconia (YSZ) with molar fraction 3-10%. The oxide-based solid electrolyte may be a ABO3oxide-based solid electrolyte, such as doping LaGaO3. Or, the oxide-based solid electrolyte may be Li1+x+4(Al, Ga)x(Ti, Ge)2−xSiyP3−yO12with crystalline structure, where 0≤x≤1 and 0≤y≤1. Moreover, the oxide-based solid electrolyte may be Li2O—Al2O3—SiO2—P2O5—TiO2, Li2O—Al2O3—SiO2—P2O5—TiO2—GeO2, Na3.3Zr1.7La0.3Si3PO12, Li3.5Si0.5P0.5O4, Li3xLa2/3xTiO3, Li7La3Zr2O12, Li0.38La0.56Ti0.99Al0.01O3, or Li0.34LaTiO2.94. The side walls, for arrangement of the solid electrolyte layer13, of the recess111of the electrically conductive structure layer11are smooth and equidistant. Therefore, the solid electrolyte layer13will be move upward and downward smoothly during plating and striping of the lithium metal. When adapting for the battery system, referring toFIG.6A, the electrically conductive structure layer11of the lithium electrode10includes a plurality of recesses111. The porous covering layer15serves as a separator. The positive active material layer31and the positive current collector32are disposed thereon sequentially. The electrically insulating glue frames21of the adjacent recesses111are connected, and the electrically insulating glue frames21in the side edges are adhered with the first adhesive layer22and the second adhesive layer23to the positive current collector32to form the package for the battery system. The materials of the first adhesive layer22and the second adhesive layer23may be the same with the material of the electrically insulating glue frames21. Also, the recess111in theFIG.6Ais only illustrated as a blind hole, such as shown inFIG.4B. However, it is not limited that the recess111only can be a blind hole. The electrically conductive structure layer11, shown inFIG.3A, or the combinations thereof can also be adapted. Further, the size, location, distance or the distribution of the recess111may be varied. Please refer toFIG.6B, one or more recess111, especially located in middle portion or any locations which the adhesive is poor, may have a separate adhesive structure to improve adhesive. The separate electrically insulating glue frame21is also adhered with the first adhesive layer22and the second adhesive layer23to the positive current collector32to form the package for the battery system. As shown inFIG.6B, all the electrically insulating glue frames21of the recesses111are separate, and the separate first adhesive layers22and the separate second adhesive layers23are adhered to the positive current collector32to extremely improve adhesive thereof. Accordingly, this invention provides a lithium electrode. When the lithium metal is plated, the growth of the lithium dendrites is constrained by the solid electrolyte layer to push the solid electrolyte layer to press the electrolyte storage layer. The electrolyte storage layer will be deformed to squeeze out parts of the liquid and/or gel electrolyte impregnated therein. As the compression distance increases, the resistive force to compress the electrolyte storage layer will become larger to inhibit the vertical growth of the lithium dendrites and force the lithium dendrites to grow in a horizontal direction. The penetration through issue for the electrical insulator, i.e. the separator, caused by the lithium dendrites can be eliminated to avoid inner shorting to greatly improve the safety of the lithium batteries. When the lithium metal is striped, the solid electrolyte layer will move back to the original position and the electrolyte storage layer will recover to the original state. The squeezed-out liquid and/or gel electrolyte will flow back to be impregnated in the electrolyte storage layer. Moreover, the lithium metal layer and the liquid and/or gel electrolyte impregnated in the electrolyte storage layer are separated by the solid electrolyte layer. The liquid or gel electrolyte impregnated in the electrolyte storage layer does not contact to the negative active material, the lithium metal layer, to avoid the liquid or gel electrolyte being decomposed or degradation and reduce the irreversible capacity losses. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. | 20,066 |
11862803 | BEST MODE Hereinafter, embodiments of the present disclosure will be described in detail. However, the embodiments of the present disclosure are provided merely for illustration, and the present disclosure is not limited thereto. The present disclosure is defined only by the category of the appended claims. Unless particularly mentioned in this specification, it will be understood that, when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it may be “directly on” the other element or an intervening element may also be present. A radical scavenger according to an embodiment of the present disclosure includes a core particle capable of decomposing a peroxide or a radical, the core particle being any one selected from the group consisting of a transition metal, a noble metal, an ion thereof, a salt thereof, an oxide thereof, and a mixture thereof, and a porous carbon coating layer located on the surface of the core particle. Since the reduction reaction of oxygen at a cathode of a polymer electrolyte membrane fuel cell is performed via hydrogen peroxide (H2O2), hydrogen peroxide may be generated at the cathode, or a hydroxyl radical (·OH−) may be generated from the generated hydrogen peroxide. In addition, as oxygen molecules are transmitted through an ion exchange membrane at an anode of the polymer electrolyte membrane fuel cell, the hydrogen peroxide or hydroxyl radical may also be generated at the anode. The generated hydrogen peroxide or hydroxyl radical deteriorates a polymer including a sulfonic acid group included in the ion exchange membrane or the catalyst electrode. Consequently, the core particle capable of decomposing the peroxide or the radical may be included in order to inhibit generation of a radical from the peroxide or to decompose the generated radical, thereby preventing degradation of the ion exchange membrane or the catalyst electrode and thus improving chemical durability of the ion exchange membrane or the catalyst electrode. Any core particle capable of decomposing the peroxide or the radical may be used in the present disclosure without being particularly restricted, as long as it is possible to rapidly decompose a peroxide (particularly, hydrogen peroxide) or a radical (particularly, a hydroxyl radical) generated during operation of the polymer electrolyte membrane fuel cell. Specifically, for example, the core particle capable of decomposing the peroxide or the radical may be a transition metal capable of decomposing the peroxide or the radical, a noble metal capable of decomposing the peroxide or the radical, an ion thereof, a salt thereof, or an oxide thereof. Specifically, the transition metal capable of decomposing the peroxide or the radical may be any one selected from the group consisting of cerium (Ce), nickel (Ni), tungsten (W), cobalt (Co), chromium (Cr), zirconium (Zr), yttrium (Y), manganese (Mn), iron (Fe), titanium (Ti), vanadium (V), iridium (Ir), molybdenum (Mo), lanthanum (La), and neodymium (Nd). In addition, the noble metal capable of decomposing the peroxide or the radical may be any one selected from the group consisting of silver (Au), platinum (Pt), ruthenium (Ru), palladium (Pd), and rhodium (Rh). In addition, the ion of the transition metal or the noble metal capable of decomposing the peroxide or the radical may be any one selected from the group consisting of a cerium ion, a nickel ion, a tungsten ion, a cobalt ion, a chromium ion, a zirconium ion, an yttrium ion, a manganese ion, an iron ion, a titanium ion, a vanadium ion, an iridium ion, a molybdenum ion, a lanthanum ion, a neodymium ion, a silver ion, a platinum ion, a ruthenium ion, a palladium ion, and a rhodium ion. Specifically, in the case of cerium, a cerium three-valence ion (Ce3+) or a cerium four-valence ion (Ce4+) may be used. In addition, the oxide of the transition metal or the noble metal capable of decomposing the peroxide or the radical may be any one selected from the group consisting of cerium oxide, nickel oxide, tungsten oxide, cobalt oxide, chromium oxide, zirconium oxide, yttrium oxide, manganese oxide, iron oxide, titanium oxide, vanadium oxide, iridium oxide, molybdenum oxide, lanthanum oxide, and neodymium oxide. In addition, the salt of the transition metal or the noble metal capable of decomposing the peroxide or the radical may be any one selected from the group consisting of carbonate, acetate, chloride salt, fluoride salt, sulfate, phosphate, tungstate, hydrate, ammonium acetate, ammonium sulfate, and acetylacetonate of the transition metal or the noble metal. Specifically, in the case of cerium, cerium carbonate, cerium acetate, cerium chloride, cerium sulfate, ammonium cerium (II) acetate, or ammonium cerium (IV) sulfate may be used, and cerium acetylacetonate may be used as the organic metal complex salt. In the case in which the core particle capable of decomposing the peroxide or the radical is dispersed in the ion exchange membrane or the catalyst electrode in order to prevent the ion exchange membrane from being degraded by the radical, however, the core particle capable of decomposing the peroxide or the radical may be eluted during operation of the fuel cell. In the radical scavenger, therefore, a porous carbon coating layer may be formed on the surface of the core particle capable of decomposing the peroxide or the radical in order to reduce mobility of the core particle capable of decomposing the peroxide or the radical, whereby the core particle capable of decomposing the peroxide or the radical is stabilized and thus it is possible to prevent elution of the core particle capable of decomposing the peroxide or the radical. However, it is necessary for the porous carbon coating layer to have a pore size, thickness, and porosity appropriate not to disturb decomposition of the peroxide or the radical performed by the radical scavenger. FIGS.1to3are views schematically showing radical scavengers including porous carbon coating layers having different pore sizes, thicknesses, and porosities. Referring toFIG.1, the pore size, thickness, or porosity of the porous carbon coating layer2formed on the surface of the core particle1capable of decomposing the peroxide or the radical is appropriate. As a result, a hydroxyl radical (·OH−) passes through the porous carbon coating layer2, and then reacts with cerium, which is the core particle1capable of decomposing the peroxide or the radical. A cerium ion (Ce3+/4+), which is a reaction product, passes through the porous carbon coating layer2, and is then discharged outside. Consequently, it can be seen that the radical scavenger is capable of appropriately decomposing the peroxide or the radical. Referring toFIGS.2and3, however, the pore size, thickness, or porosity of the porous carbon coating layer2is not appropriate. As a result, the hydroxyl radical (·OH−) does not pass through the porous carbon coating layer2, or the cerium ion (Ce3+/4+) does not pass through the porous carbon coating layer2. Consequently, it can be seen that the radical scavenger is not capable of appropriately decomposing the peroxide or the radical. In order for the porous carbon coating layer to allow the radical or the reaction product of the radical to smoothly pass therethrough, the pore size of the porous carbon coating layer may range from 1 angstrom (Å) to 20 angstrom (Å), more specifically from 3 angstrom (Å) to 5 angstrom (Å). In addition, the thickness of the porous carbon coating layer may range from 0.5 nm to 10 nm, more specifically from 1 nm to 5 nm. In the case in which each of the pore size and the thickness of the porous carbon coating layer deviate from the above range, it may be difficult for the radical or the reaction product of the radical to smoothly pass through the porous carbon coating layer, whereby it may be difficult for the radical scavenger to smoothly decompose the peroxide or the radical. A method of manufacturing a radical scavenger according to another embodiment of the present disclosure includes a step of coating a carbon precursor on the surface of a core particle capable of decomposing a peroxide or a radical, the core particle being any one selected from the group consisting of a transition metal, a noble metal, an ion thereof, a salt thereof, an oxide thereof, and a mixture thereof, and a step of carbonizing the carbon precursor on the surface of the core particle to form a porous carbon coating layer. A description of the particle capable of decomposing the peroxide or the radical and the porous carbon coating layer is the same as the above description, and therefore a duplicate description thereof will be omitted. Meanwhile, the step of coating the carbon precursor on the surface of the core particle may specifically include a step of adding the carbon precursor to a solvent to manufacture a composition for coating a carbon precursor and a step of adding and stirring the core particle to the composition for coating the carbon precursor. The carbon precursor may be any one selected from the group consisting of dopamine, acrylonitrile, vinylpyrrolidone, lignin, a polymer, and a mixture thereof. More specifically, dopamine may be used as the carbon precursor. In the case in which dopamine is used as the carbon precursor, it is possible to form a uniform coating thickness through polymerization reaction of polydopamine on the surface of the core particle. In order to add the carbon precursor to a solvent to manufacture a composition for coating a carbon precursor, any one selected from the group consisting of water, ethanol, methanol, acetone, 1-propanol, 2-propanol, 1-butanol, 2-butanol, a tris-hydrochloride buffer solution, and a mixture thereof may be used as the solvent. At this time, the composition for coating the carbon precursor may include 0.01 parts by weight to 10 parts by weight, more specifically 0.1 parts by weight to 1 part by weight, of the carbon precursor based on 100 parts by weight of the core particle. In the case in which the content of the carbon precursor is less than 0.01 parts by weight based on 100 parts by weight of the core particle, uniform coating may not be achieved. In the case in which the content of the carbon precursor is greater than 10 parts by weight, a cluster may be formed by the carbon coating layer. The step of adding and stirring the core particle to the composition for coating the carbon precursor may be performed at 0° C. to 80° C. for 0.5 hours to 50 hours at 100 rpm to 500 rpm, more specifically at 20° C. to 40° C. for 8 hours to 16 hours at 200 rpm to 300 rpm. In the case in which the stirring is performed at lower than 0° C. for shorter than 0.5 hours at less than 100 rpm, a nonuniform or too thin coating layer may be formed. In the case in which the stirring is performed at higher than 80° C. for longer than 50 hours, a too thick coating layer may be formed. Subsequently, the carbon precursor on the surface of the core particle is carbonized to form a porous carbon coating layer. A carbonization process may include a stabilization step performed at a low temperature and a carbonization step performed at a high temperature. The stabilization may be performed at 100° C. to 400° C. in a nitrogen or argon atmosphere, more specifically at 200° C. to 300° C. in a nitrogen atmosphere. The carbonization of the carbon precursor may be performed at 600° C. to 900° C. in a nitrogen or argon atmosphere, more specifically at 700° C. to 800° C. in a nitrogen atmosphere. In the case in which the carbonization is performed at lower than 600° C., the carbon precursor may not be completely converted into carbon. In the case in which the carbonization is performed in an atmosphere other than the nitrogen or argon atmosphere, a carbon layer may be oxidized. Through the method of manufacturing the radical scavenger, the porous carbon coating layer may be formed so as to have a pore size, thickness, and porosity appropriate not to disturb decomposition of the peroxide or the radical performed by the radical scavenger. A membrane-electrode assembly according to another embodiment of the present disclosure includes an ion exchange membrane, catalyst electrodes disposed at opposite surfaces of the ion exchange membrane, and the radical scavenger located at any one position selected from the group consisting of in the catalyst electrodes, in the ion exchange membrane, between the ion exchange membrane and the catalyst electrodes, and a combination thereof. FIG.4is a sectional view schematically showing the membrane-electrode assembly. Referring toFIG.4, the membrane-electrode assembly100includes the ion exchange membrane50and electrodes20and20′ disposed at opposite surfaces of the ion exchange membrane50. The electrodes20and20′ respectively include electrode substrates40and40′ and catalyst electrodes30and30′ formed at surfaces of the electrode substrates40and40′, and may further include microporous layers (not shown) disposed between the electrode substrates40and40′ and the catalyst electrodes30and30′, the microporous layers including conductive microparticles, such as carbon powder or carbon black, for easy material diffusion at the electrode substrates40and40′. In the membrane-electrode assembly100, the electrode20, which is disposed at one surface of the ion exchange membrane50to perform an oxidation reaction in which protons and electrons are generated from fuel transferred to the catalyst electrode30via the electrode substrate40, is referred to as an anode, and the electrode20′, which is disposed at the other surface of the ion exchange membrane50to perform a reduction reaction in which water is generated from protons supplied through the ion exchange membrane50and an oxidant transferred to the catalyst electrode30′ via the electrode substrate40′, is referred to as a cathode. Meanwhile, the membrane-electrode assembly100may further include interfacial adhesion layers10and10′ located between the ion exchange membrane50and the catalyst electrodes30and30′. The interfacial adhesion layers10and10′ may enable the membrane-electrode assembly100to have low hydrogen permeability without reducing proton conductivity, may improve interfacial bondability between the catalyst electrodes30and30′ and the ion exchange membrane50, thereby improving durability of the membrane-electrode assembly100, and may improve performance and durability of the membrane-electrode assembly100under high-temperature/low-humidity conditions. InFIG.4, the interfacial adhesion layers10and10′ are shown as being disposed at opposite surfaces of the ion exchange membrane50; however, the present disclosure is not limited thereto. The interfacial adhesion layers10and10′ may be located only at one surface of the ion exchange membrane50. Each of the interfacial adhesion layers10and10′ includes an ionomer and the radical scavenger. The ionomer included in each of the interfacial adhesion layers10and10′ may improve interfacial bondability between the catalyst electrodes30and30′ and the ion exchange membrane50, thereby improving durability of the membrane-electrode assembly100. The ionomer included in each of the interfacial adhesion layers10and10′ may have an equivalent weight (EW) of 1100 g/eq or less, specifically 500 g/eq to 1100 g/eq. The equivalent weight of the ionomer is the molecular mass of the ionomer per ion exchange group included in the ionomer. The interfacial adhesion layers10and10′ may provide positive effects in managing water in the membrane-electrode assembly100under low-humidity conditions through adjustment of the equivalent weight of the ionomer. In the case in which the ionomer having the above equivalent weight is used, it is possible to improve performance of the membrane-electrode assembly100without reducing proton conductivity. Meanwhile, in the case in which the equivalent weight of the ionomer is less than 500 g/eq, an ionomer elution phenomenon or hydrogen fuel permeability may increase. In the case in which the equivalent weight of the ionomer is greater than 1100 g/eq, proton conductivity may be reduced under high-temperature and low-humidity conditions. The ionomer included in each of the interfacial adhesion layers10and10′ may be any one selected from the group consisting of a fluorine-based ionomer, a hydrocarbon-based ionomer, and a mixture thereof. The fluorine-based ionomer may be a fluorine-based polymer having a cation exchange group that is capable of transferring cations, such as protons, or an anion exchange group that is capable of transferring anions, such as hydroxyl ions, carbonate, or bicarbonate, and including fluorine in the main chain thereof, or a partially fluorinated polymer, such as a polystyrene-graft-ethylene tetrafluoroethylene copolymer or a polystyrene-graft-polytetrafluoroethylene copolymer. Concrete examples of the fluorine-based ionomer may be fluorine-based polymers including poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluoro vinyl ether including a sulfonic acid group, and difluorinated polyetherketone sulfide, or a mixture thereof. The cation exchange group may be any one selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphate group, an imide group, a sulfonimide group, a sulfonamide group, and a combination thereof. In general, the cation exchange group may be a sulfonic acid group or a carboxyl group. In addition, the fluorine-based ionomer may be used either alone or as a mixture of two or more materials. In addition, the hydrocarbon-based ionomer is a hydrocarbon-based polymer having a cation exchange group that is capable of transferring cations, such as protons, or an anion exchange group that is capable of transferring anions, such as hydroxyl ions, carbonate, or bicarbonate, and including imidazole, benzimidazole, polyamide, polyamide imide, polyimide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyether imide, polyether sulfone, polyether imide, polycarbonate, polystyrene, polyphenylene sulfide, polyether ether ketone, polyether ketone, polyaryl ether sulfone, polyphosphazene, or polyphenyl quinoxaline in the main chain thereof. Concrete examples of the hydrocarbon-based ionomer may include, but are not limited to, hydrocarbon-based polymers including sulfonated polyimide (S-PI), sulfonated polyarylether sulfone (S-PAES), sulfonated polyetheretherketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyether sulfone, sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, and a mixture thereof. In addition, the hydrocarbon-based ionomer may be used either alone or as a mixture of two or more materials. Meanwhile, the membrane-electrode assembly100includes the radical scavenger located at any one position selected from the group consisting of in the catalyst electrodes30and30′, in the ion exchange membrane50, between the ion exchange membrane50and the catalyst electrodes30and30′, and a combination thereof. Specifically, “between the ion exchange membrane50and the catalyst electrodes30and30′” may mean that the radical scavenger is included in the interfacial adhesion layers10and10′ or that the radical scavenger is included on the surfaces of the ion exchange membrane50, on the surfaces of the catalyst electrodes30and30′, or on the surfaces of the interfacial adhesion layers10and10′. Particularly, in the case in which the radical scavenger is included in the interfacial adhesion layers10and10′, the radical scavenger is not present in the ion exchange membrane50in a dispersed state but is concentrated in the interfacial adhesion layers10and10′, which are inserted between the ion exchange membrane50and the catalyst electrodes30and30′, whereby it is possible to improve chemical durability of the ion exchange membrane50while minimizing loss in ion conductivity of the ion exchange membrane50. That is, the radical generated at the catalyst electrodes30and30′ spreads toward the ion exchange membrane50, but the radical is decomposed by the radical scavenger concentrated in the interfacial adhesion layers10and10′ before reaching the ion exchange membrane50, whereby it is possible to prevent degradation of the ion exchange membrane50. In addition, degradation of the ion exchange membrane50is performed from the interfaces between the ion exchange membrane50and the catalyst electrodes30and30′. In the case in which the radical scavenger is concentrated in the interfacial adhesion layers10and10′, therefore, it is possible to achieve higher chemical durability than in the case in which the radical scavenger is dispersed in the ion exchange membrane50. In the case in which the radical scavenger is included in the interfacial adhesion layers10and10′, however, the radical scavenger may be eluted during operation of the fuel cell. In the radical scavenger, however, the porous carbon coating layer is formed on the surface of the core particle capable of decomposing the peroxide or the radical in order to stabilize the core particle capable of decomposing the peroxide or the radical, whereby it is possible to prevent elution of the core particle capable of decomposing the peroxide or the radical. Each of the interfacial adhesion layers10and10′ may include 0.1 wt % to 70 wt % or 75 wt % to 15 wt % of the radical scavenger based on the total weight of each of the interfacial adhesion layers10and10′. In the case in which the content of the radical scavenger is less than 0.1 wt %, the effect of improving chemical durability may be insignificant. In the case in which the content of the radical scavenger is greater than 70 wt %, ion transfer resistance in the membrane-electrode assembly100may be greatly increased. In addition, the thickness of each of the interfacial adhesion layers10and10′ may be 10 nm to 10 μm or 0.5 μm to 2 μm, and the loading amount of each of the interfacial adhesion layers10and10′ may be 0.01 mg/cm2to 2.0 mg/cm2. In the case in which the thickness of each of the interfacial adhesion layers10and10′ is less than 10 nm or the loading amount of each of the interfacial adhesion layers is less than 0.01 mg/cm2, the effect of improving chemical durability may be insignificant, and interfacial bondability between the ion exchange membrane50and the catalyst electrodes30and30′ may not be improved. In the case in which the thickness of each of the interfacial adhesion layers10and10′ is greater than 10 μm or the loading amount of each of the interfacial adhesion layers is greater than 2.0 mg/cm2, ion transfer resistance in the membrane-electrode assembly100may be greatly increased. Meanwhile, the ion exchange membrane50includes an ionic conductor. The ionic conductor may be a cationic conductor having a cation exchange group that is capable of transferring cations, such as protons, or an anionic conductor having an anion exchange group that is capable of transferring anions, such as hydroxyl ions, carbonate, or bicarbonate. The cation exchange group may be any one selected from the group consisting of a sulfonic acid group, a carboxyl group, a boronic acid group, a phosphate group, an imide group, a sulfonimide group, a sulfonamide group, and a combination thereof. In general, the cation exchange group may be a sulfonic acid group or a carboxyl group. The cationic conductor may be a fluorine-based polymer having the cation exchange group and including fluorine in the main chain thereof, a hydrocarbon-based ionomer, such as benzimidazole, polyamide, polyamide imide, polyimide, polyacetal, polyethylene, polypropylene, acrylic resin, polyester, polysulfone, polyether, polyether imide, polyether sulfone, polyether imide, polycarbonate, polystyrene, polyphenylene sulfide, polyether ether ketone, polyether ketone, polyaryl ether sulfone, polyphosphazene, or polyphenyl quinoxaline, a partially fluorinated polymer, such as a polystyrene-graft-ethylene tetrafluoroethylene copolymer or a polystyrene-graft-polytetrafluoroethylene copolymer, or sulfonyl imide. More specifically, in the case in which the cationic conductor is a proton conductor, each of the polymers may include a cation exchange group selected from the group consisting of a sulfonic acid group, a carboxyl group, a phosphate group, a phosphonic acid group, and a derivative thereof in the side chain thereof. As a concrete example, the cationic conductor may be, but is not limited to, a fluorine-based polymer including poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluoro vinyl ether including a sulfonic acid group, difluorinated polyetherketone sulfide, and a mixture thereof, or a hydrocarbon-based polymer including sulfonated polyimide (S-PI), sulfonated polyarylether sulfone (S-PAES), sulfonated polyetheretherketone (S PEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyether sulfone, sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile, sulfonated polyarylene ether sulfone ketone, or a mixture of thereof. Meanwhile, a hydrocarbon-based ionic conductor, which has excellent ion conductivity and is advantageous in terms of price, is preferably used as the cationic conductor. The anionic conductor is a polymer capable of transporting anions, such as hydroxyl ions, carbonate, or bicarbonate. The anionic conductor is commercially available in the form of hydroxide or halide (generally chloride), and the anionic conductor may be used in an industrial water purification, metal separation, or catalyst process. A polymer doped with metal hydroxide may generally be used as the anionic conductor. Specifically, poly(ether sulfone), polystyrene, a vinyl-based polymer, poly(vinyl chloride), poly(vinylidene fluoride), poly(tetrafluoroethylene), poly(benzimidazole), or poly(ethylene glycol), doped with metal hydroxide, may be used as the anionic conductor. Meanwhile, the ion exchange membrane50may be a reinforcement membrane configured to have a structure in which pores in a fluorine-based porous support, such as e-PTFE, or a porous support, such as a porous nanoweb support manufactured by electrospinning, etc., are filled with the ionic conductor. The ion exchange capacity (IEC) of the ion exchange membrane50may be 0.8 to 4.0 meq/g or 1.0 to 3.5 meq/g. In the case in which the ion exchange capacity of the ion exchange membrane50is less than 1.0 meq/g, movement of protons may be reduced under low-humidity conditions. In the case in which the ion exchange capacity of the ion exchange membrane50is greater than 3.5 meq/g, interfacial transfer resistance may be increased as humidity increases. In addition, the thickness of the ion exchange membrane50may be 3 to 25 μm or 5 to 20 μm. In the case in which the thickness of the ion exchange membrane50is less than 3 μm, hydrogen fuel permeability may be abruptly increased under high-temperature and low-humidity conditions, whereby chemical stability of the ion exchange membrane may be reduced. In the case in which the thickness of the ion exchange membrane50is greater than 25 μm, movement of protons may be reduced under low-humidity conditions, whereby resistance of the ion exchange membrane may be increased and thus ion conductivity may be reduced. Any one may be used as the core particle in each of the catalyst electrodes30and30′, as long as the core particle can be used as a catalyst in hydrogen oxidation reaction and oxygen reduction reaction. Preferably, a platinum-based metal is used as the core particle. The platinum-based metal may include one selected from the group consisting of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), a platinum-M alloy (M being at least one selected from the group consisting of palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), gold (Au), zinc (Zn), tin (Sn), molybdenum (Mo), tungsten (W), lanthanum (La), and rhodium (Rh)), a non-platinum alloy, and a combination thereof. More preferably, a combination of two or more metals selected from the platinum-based catalyst metal group is used. However, the present disclosure is not limited thereto. Any platinum-based catalyst metal that is available in the present technical field may be used without limitation. Specifically, the platinum alloy may be selected from the group consisting of Pt—Pd, Pt—Sn, Pt—Mo, Pt—Cr, Pt—W, Pt—Ru, Pt—Ru—W, Pt—Ru—Mo, Pt—Ru—Rh—Ni, Pt—Ru—Sn—W, Pt—Co, Pt—Co—Ni, Pt—Co—Fe, Pt—Co—Ir, Pt—Co—S, Pt—Co—P, Pt—Fe, Pt—Fe—Ir, Pt—Fe—S, Pt—Fe—P, Pt—Au—Co, Pt—Au—Fe, Pt—Au—Ni, Pt—Ni, Pt—Ni—Ir, Pt—Cr, Pt—Cr—Ir, and a combination thereof, which may be used either alone or as a mixture of two or more thereof. In addition, the non-platinum alloy may be selected from the group consisting of Ir—Fe, Ir—Ru, Ir—Os, Co—Fe, Co—Ru, Co—Os, Rh—Fe, Rh—Ru, Rh—Os, Ir—Ru—Fe, Ir—Ru—Os, Rh—Ru—Fe, Rh—Ru—Os, and a combination thereof, which may be used either alone or as a mixture of two or more thereof. The core particle may be used as a metal (black) alone, or may be used in the state in which a carrier is doped with a catalyst metal. The carrier may be selected from among a carbon-based carrier, porous inorganic oxide, such as zirconia, alumina, titania, silica, or ceria, and zeolite. The carbon-based carrier may be selected from among graphite, super P, carbon fiber, carbon sheet, carbon black, Ketjen black, Denka black, acetylene black, carbon nanotube (CNT), carbon sphere, carbon ribbon, fullerene, activated carbon, carbon nanofiber, carbon nanowire, carbon nanoball, carbon nanohorn, carbon nanocage, carbon nanoring, ordered nano-/meso-porous carbon, carbon aerogel, mesoporous carbon, graphene, stabilized carbon, activated carbon, and a combination of one or more thereof. However, the present disclosure is not limited thereto. Any carrier that is available in the present technical field may be used without limitation. The core particle may be located on the surface of the carrier, or may permeate into the carrier while filling pores in the carrier. In the case in which a noble metal carrier dopant is used as the catalyst, a commercially available catalyst may be used, or the carrier may be doped with the noble metal in order to manufacture the catalyst. The process of doping the carrier with the noble metal is well-known in the art to which the present disclosure pertains and is easily understood by those skilled in the art even though a detailed description thereof is omitted in this specification. The core particle may be included so as to account for 20 wt % to 80 wt % of the overall weight of each of the catalyst electrodes30and30′. If the content of the core particle is less than 20 wt %, catalyst activation may be reduced. If the content of the core particle is greater than 80 wt %, the activation area may be reduced due to cohesion of core particle, whereby catalyst activation may be reduced. In addition, each of the catalyst electrodes30and30′ may include a binder for improving the force of adhesion of the catalyst electrodes30and30′ and transferring protons. Preferably, an ionomer exhibiting ion conductivity is used as the binder. A description of the ionomer is the same as the above description of the interfacial adhesion layers10and10′, and therefore a duplicate description thereof will be omitted. However, the ionomer may be used either alone or in the form of a mixture. In addition, the ion conductor may be optionally used together with a non-conductive compound in order to further increase the force of adhesion with the ion exchange membrane50. Preferably, the amount of the ionomer that is used is adjusted according to the purpose thereof. At least one selected from the group consisting of polytetrafluoroethylene (PTFE), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene/tetrafluoroethylene (ETFE), an ethylene chlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, a polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), dodecylbenzenesulfonic acid, and sorbitol may be used as the non-conductive compound. The binder may be included so as to account for 20 wt % to 80 wt % of the overall weight of each of the catalyst electrodes30and30′. In the case in which the content of the binder is less than 20 wt %, generated ions may not be transferred successfully. In the case in which the content of the binder is greater than 80 wt %, pores are insufficient, whereby it may be difficult to supply hydrogen or oxygen (air), and an active area for reaction may be reduced. In addition, the membrane-electrode assembly100may further include electrode substrates40and40′ located outside the catalyst electrodes30and30′. In order to smoothly supply hydrogen or oxygen, a porous conductive substrate may be used as each of the electrode substrates40and40′. In a representative example, carbon paper, carbon cloth, carbon felt, or metal cloth (a porous film made of fibrous metal cloth or a metal film formed on the surface of cloth made of polymer fiber) may be used. However, the present disclosure is not limited thereto. In addition, preferably, a fluorine-based resin that has undergone water-repellency treatment is used as each of the electrode substrates40and40′, since it is possible to prevent reactant diffusion efficiency from being reduced by water generated during operation of the fuel cell. Polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonylfluoride alkoxy vinyl ether, fluorinated ethylene propylene, polychlorotrifluoroethylene, or a copolymer thereof may be used as the fluorine-based resin. In addition, a microporous layer for improving reactant diffusion efficiency at each of the electrode substrates40and40′ may be further included. The microporous layer may generally include conductive powder having a small particle diameter, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotube, carbon nanowire, carbon nanohorn, or carbon nanoring. The microporous layer is manufactured by coating a composition, including conductive powder, a binder resin, and a solvent, on each of the electrode substrates40and40′. Polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonylfluoride, alkoxy vinyl ether, polyvinyl alcohol, cellulose acetate, or a copolymer thereof is preferably used as the binder resin. Ethanol, alcohol, such as isopropyl alcohol, n-propyl alcohol, or butyl alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, or tetrahydrofuran is preferably used as the solvent. The coating process may be performed using a screen printing method, a spray coating method, or a doctor-blade coating method depending on the viscosity of the composition. However, the present disclosure is not limited thereto. At the time of manufacturing respective components of the membrane-electrode assembly100including the radical scavenger, the radical scavenger may be added to the respective components of the membrane-electrode assembly100depending on the position of the membrane-electrode assembly100at which the radical scavenger is included. For example, in the case in which the radical scavenger is included in the ion exchange membrane50, the radical scavenger may be added to a composition for forming an ion exchange membrane including the ionic conductor, and the composition for forming the ion exchange membrane including the radical scavenger may be coated and dried in order to manufacture a single membrane, or a porous support may be impregnated with the composition for forming the ion exchange membrane including the radical scavenger in order to manufacture an ion exchange membrane50having the form of a reinforcement membrane. Similarly, in the case in which the radical scavenger is included in the catalyst electrodes30and30′, the radical scavenger may be added to a composition for forming catalyst electrodes, and the composition for forming the catalyst electrodes including the radical scavenger may be coated and dried in order to manufacture the catalyst electrodes30and30′ including the radical scavenger. Also, in the case in which the radical scavenger is included between the ion exchange membrane50and the catalyst electrodes30and30′, a solution including the radical scavenger is coated and dried on the surfaces of the ion exchange membrane50or on the surfaces of the catalyst electrodes30and30′ in order to form coating layers. In addition, the radical scavenger may be included in the interfacial adhesion layers10and10′. Hereinafter, a method of manufacturing the membrane-electrode assembly100in the case in which the interfacial adhesion layers10and10′ include the radical scavenger will be described in detail by way of example. The interfacial adhesion layers10and10′ including the radical scavenger may be formed by a step of mixing the radical scavenger and the ionomer with each other to manufacture a composition for forming interfacial adhesion layers and a step of coating and drying the composition for forming the interfacial adhesion layers on the surfaces of the ion exchange membrane50or on the surfaces of the catalyst electrodes30and30′. The composition for forming the interfacial adhesion layers may be manufactured by adding and mixing the radical scavenger and the ionomer to a solvent. The composition for forming the interfacial adhesion layers may include the ionomer in a concentration of 0.1% to 30% or in a concentration of % to 10%. In the specification of the present disclosure, the concentration means percent concentration, and the percent concentration may be calculated as percentage of the mass of a solute to the mass of a solution. In the case in which the composition for forming the interfacial adhesion layers includes the ionomer within the above concentration range, it is possible to improve proton conductivity and interfacial bondability without increasing interfacial resistance of the membrane-electrode assembly. In the case in which the concentration of the ionomer is less than 0.1%, proton transfer ability may be reduced. In the case in which the concentration of the ionomer is greater than 30%, the ionomer may be nonuniformly distributed. Any one selected from the group consisting of ethanol, alcohol, such as isopropyl alcohol, n-propyl alcohol, butyl alcohol, or glycerol, water, dimethylacetamide, dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, and a mixture thereof may be used as the solvent. The interfacial adhesion layers10and10′ may be formed by coating the composition for forming the interfacial adhesion layers on the ion exchange membrane50or on the catalyst electrodes30and30′ and drying the composition for forming the interfacial adhesion layers. The composition for forming the interfacial adhesion layers may be coated on the ion exchange membrane50using slot-die coating, bar coating, deep coating, comma coating, screen printing, spray coating, doctor blade coating, silk screen coating, gravure coating, painting, etc. The drying process may be performed at 25° C. to 90° C. for 12 hours or more. In the case in which the drying temperature is less than 25° C. and the drying time is less than 12 hours, the interfacial adhesion layers10and10′ may be sufficiently dried. In the case in which drying is performed at a temperature higher than 90° C., the interfacial adhesion layers may be cracked. Finally, the membrane-electrode assembly100is manufactured using the ion exchange membrane50including the interfacial adhesion layers10and10′ or the catalyst electrodes30and30′. In the case in which the interfacial adhesion layers10and10′ are formed on the catalyst electrodes30and30′, the ion exchange membrane50and the catalyst electrodes30and30′ may be thermally pressed in order to manufacture the membrane-electrode assembly100. In the case in which the interfacial adhesion layers10and10′ are formed on the ion exchange membrane50, the ion exchange membrane50and the catalyst electrodes30and30′ may be thermally pressed, or the catalyst electrodes30and30′ may be coated on the ion exchange membrane50, in order to manufacture the membrane-electrode assembly100. Thermal pressing of the catalyst electrodes30and30′ and the ion exchange membrane50may be performed under conditions of 80° C. to 2000° C. and 5 kgf/cm2to 200 kgf/cm2. In the case in which thermal pressing is performed under conditions of less than 80° C. and less than 5 kgf/cm2, the catalyst electrodes30and30′ on a release film may not be appropriately transferred. In the case in which the temperature is greater than 200° C., the polymer of the ion exchange membrane50may be denatured. In the case in which the pressure is greater than 200 kgf/cm2, a porous structure in each of the catalyst electrodes30and30′ may collapse, whereby performance of the catalyst electrodes may be reduced. A fuel cell according to a further embodiment of the present disclosure includes the membrane-electrode assembly. FIG.5is a schematic view showing the overall construction of the fuel cell. Referring toFIG.5, the fuel cell200includes a fuel supply unit210for supplying a mixed fuel including fuel and water mixed with each other, a modification unit220for modifying the mixed fuel to generate a modified gas including hydrogen gas, a stack230for inducing electrochemical reaction between the modified gas including the hydrogen gas, supplied from the modification unit220, and an oxidant to generate electrical energy, and an oxidant supply unit240for supplying the oxidant to the modification unit220and the stack230. The stack230includes a plurality of unit cells for inducing oxidation/reduction reaction between the modified gas including the hydrogen gas, supplied from the modification unit220, and the oxidant, supplied from the oxidant supply unit240, to generate electrical energy. Each of the unit cells, which is an independent cell capable of generating electricity, includes the membrane-electrode assembly for inducing an oxidation/reduction reaction between a modified gas including hydrogen gas and oxygen in an oxidant, and a separator (which is also called a bipolar plate; hereinafter referred to as a “separator”) for supplying the modified gas including the hydrogen gas and the oxidant to the membrane-electrode assembly. The separators are disposed at opposite sides of each of the membrane-electrode assemblies in the state in which the membrane-electrode assembly is located between the separators. The separators located at the outermost sides of the stack may be particularly referred to as end plates. One of the end plates is provided with a first supply pipe231for injecting a modified gas including hydrogen gas, supplied from the modification unit220, and a second supply pipe232for injecting oxygen gas, and the other end plate is provided with a first discharge pipe233for discharging the modified gas including the remaining unreacted hydrogen gas in the unit cells to the outside and a second discharge pipe234for discharging the remaining unreacted oxidant in the unit cells to the outside. MODE FOR INVENTION Hereinafter, concrete examples of the present disclosure will be set forth. However, the following examples are given merely to concretely illustrate or describe the present disclosure, and the present disclosure is not limited thereto. In addition, content that is not described herein may be sufficiently technically inferred by those skilled in the art to which the present disclosure pertains, and therefore a description thereof will be omitted. Manufacturing Example 1: Manufacture of Radical Scavenger Example 1-1 Dopamine was added to a tris-hydrochloride buffer solution in order to manufacture a composition for coating a carbon precursor, and a core particle capable of decomposing a peroxide, such as CeO2, or a radical was added to the composition for coating the carbon precursor. At this time, the composition for coating the carbon precursor included 0.3 parts by weight of the carbon precursor based on 100 parts by weight of the core particle. The composition for coating the carbon precursor having the core particle added thereto was stirred at 25° C. for 12 hours at 250 rpm, the carbon precursor was stabilized at 250° C. in a nitrogen atmosphere, and the carbon precursor was carbonized at 700° C. in a nitrogen atmosphere in order to manufacture a radical scavenger having a porous carbon coating layer formed on the surface of the core particle. In the manufactured radical scavenger, the thickness of the porous carbon coating layer was 2 nm to 5 nm. Example 1-2 A composition for coating a carbon precursor identical to the composition for coating the carbon precursor according to Example 1-1 was manufactured, was stirred at 25° C. for 3 hours at 250 rpm, and was carbonized in the same manner as in Example 1-1 in order to manufacture a radical scavenger having a porous carbon coating layer formed thereon. In the manufactured radical scavenger, the thickness of the porous carbon coating layer was 1 to 2 nm. Example 1-3 A composition for coating a carbon precursor identical to the composition for coating the carbon precursor according to Example 1-1 was manufactured, was stirred at 25° C. for 24 hours at 250 rpm, and was carbonized in the same manner as in Example 1-1 in order to manufacture a radical scavenger having a porous carbon coating layer formed thereon. In the manufactured radical scavenger, the thickness of the porous carbon coating layer was 5 nm or more, and a carbon cluster was formed. Manufacturing Example 2: Manufacture of Membrane-Electrode Assembly Examples 2-1 to 2-4: Membrane-Electrode Assemblies Each Including Interfacial Adhesion Layers Including Radical Scavenger In order to manufacture a composition for forming interfacial adhesion layers, the radical scavenger manufactured according to Example 1-1 and an Nafion ionomer were mixed with each other in composition ratios shown in Table 1 below, and the mixture was dispersed in IPA. At this time, the solid content in the solvent was adjusted to 10 wt %. In order to prepare an ion exchange membrane, sulfonated PAES was dissolved in DMAC so as to account for 10 wt %. A prepared composition for forming an ion exchange membrane was coated on a glass plate using a blade coating method, and was dried in an oven of 60° C. for 24 hours in order to manufacture an ion exchange membrane. The manufactured ion exchange membrane was immersed in the composition for forming interfacial adhesion layers for dip coating such that the composition for forming interfacial adhesion layers was coated on each surface of the ion exchange membrane, and was dried in an oven of 60° C. for 24 hours. Subsequently, interfacial adhesion layers were annealed in an oven of 120° C. for 2 hours. TABLE 1ExampleExampleExampleExample2-12-22-32-4Content of CeO2481216based on solidcontent (wt %) Comparative Example 2-1: Membrane-Electrode Assembly Including Interfacial Adhesion Layers Including No Radical Scavenger In order to manufacture a composition for forming interfacial adhesion layers, a Nafion ionomer was dispersed in IPA so as to account for 10 wt %. In order to prepare an ion exchange membrane, sulfonated PAES was dissolved in DMAC so as to account for 10 wt %. A prepared composition for forming an ion exchange membrane was coated on a glass plate using a blade coating method, and was dried in an oven of 60° C. for 24 hours in order to manufacture an ion exchange membrane. The manufactured ion exchange membrane was immersed in the composition for forming interfacial adhesion layers for dip coating such that the composition for forming interfacial adhesion layers was coated on each surface of the ion exchange membrane, and was dried in an oven of 60° C. for 24 hours. Subsequently, interfacial adhesion layers were annealed in an oven of 120° C. for 2 hours. Comparative Example 2-2: Membrane-Electrode Assembly Having Radical Scavenger Dispersed in Ion Exchange Membrane In order to manufacture a composition for forming interfacial adhesion layers, a Nafion ionomer was dispersed in IPA so as to account for 10 wt %. In order to prepare an ion exchange membrane having a radical scavenger dispersed therein, sulfonated PAES and CeO2were dissolved in DMAC. At this time, the solid content in a composition for forming an ion exchange membrane was 10 wt %, and the content of CeO2in the solid content was 2 wt %. The prepared composition for forming an ion exchange membrane was coated on a glass plate using a blade coating method, and was dried in an oven of 60° C. for 24 hours in order to manufacture an ion exchange membrane. The manufactured ion exchange membrane was immersed in the composition for forming interfacial adhesion layers for dip coating such that the composition for forming interfacial adhesion layers was coated on each surface of the ion exchange membrane, and was dried in an oven of 60° C. for 24 hours. Subsequently, interfacial adhesion layers were annealed in an oven of 120° C. for 2 hours. Experimental Example: Evaluation of Manufactured Membrane-Electrode Assemblies In order to confirm the effect of improvement of chemical durability of each of the ion exchange membranes manufactured according to Examples and Comparative Examples, each of the manufactured ion exchange membranes was immersed in a Fenton solution, was left at 60° C., was taken out of the solution after 16 hours in order to measure the residual mass of the ion exchange membrane, whereby chemical durability of the ion exchange membrane was confirmed. Results are shown inFIG.6. At this time, the Fenton solution was an aqueous solution composed of 3 wt % of H2O2and 4 ppm of FeSO4. FIG.6is a graph showing chemical durability of each of the ion exchange membranes manufactured according to Examples and Comparative Examples in terms of residual mass. As chemical durability of the ion exchange membrane increases, the amount of a polymer of the ion exchange membrane dissolved in the Fenton solution is further reduced, the residual mass of the ion exchange membrane is maintained higher. Referring toFIG.6, the ion exchange membrane manufactured according to Comparative Example 2-1, which included no radical scavenger, exhibited the lowest residual mass, and the ion exchange membrane manufactured according to Comparative Example 2-2, which had 2 wt % of the radical scavenger dispersed therein, exhibited the second lowest residual mass. In contrast, ion exchange membranes manufactured according to Examples 2-1 to 2-4, each of which had the radical scavenger included in the interfacial adhesion layers, exhibited residual masses higher than the residual mass of the ion exchange membrane manufactured according to Comparative Example 2-1. In addition, the higher the content of the radical scavenger in the interfacial adhesion layers, the higher the residual mass of the ion exchange membrane. Consequently, it can be seen that the interfacial adhesion layers including the radical scavenger are capable of further improving chemical durability of the ion exchange membrane. Also, in order to confirm the effect of retention of ion conductivity of each of the membrane-electrode assemblies manufactured according to Examples and Comparative Examples, each of the manufactured membrane-electrode assemblies was fastened to an apparatus for evaluating each unit cell of a fuel cell, and proton conductivity based on relative humidity was measured at 80° C. using impedance. Results are shown inFIG.7. FIG.7is a graph showing proton conductivity based on relative humidity of each of the membrane-electrode assemblies manufactured according to Examples and Comparative Examples. The membrane-electrode assembly manufactured according to Comparative Example 2-1, which included no radical scavenger, exhibited the highest proton conductivity, and the membrane-electrode assembly manufactured according to Comparative Example 2-2, which had 2 wt % of the radical scavenger dispersed in the ionic conductor, exhibited the lowest proton conductivity. Meanwhile, it can be confirmed that the membrane-electrode assembly manufactured according to Example 2-1, which had 4 wt % of the radical scavenger concentrated in the interfacial adhesion layers, exhibited proton conductivity similar to the proton conductivity of the membrane-electrode assembly manufactured according to Comparative Example 2-1, although the radical scavenger was included. Also, it can be observed that, as the content of the radical scavenger in the interfacial adhesion layers was increased, proton conductivity of the membrane-electrode assembly was gradually reduced. In the case of Examples 2-1 to 2-3, excluding Example 2-4, each membrane-electrode assembly exhibited proton conductivity higher than the proton conductivity of the membrane-electrode assembly manufactured according to Comparative Example 2. Consequently, it can be confirmed that loss in ion conductivity of the interfacial adhesion layers including the radical scavenger according to the present disclosure is minimized. It can be observed from the results ofFIGS.6and7that Examples 2-1 to 2-3, to which the interfacial adhesion layers were applied, exhibited higher chemical durability and proton conductivity than Comparative Example 2-2, in which the radical scavenger was dispersed in the entire ion exchange membrane, and therefore it can be confirmed that chemical durability of the interfacial adhesion layers including the radical scavenger according to the present disclosure is greatly improved while loss in ion conductivity of the interfacial adhesion layers is minimized. Although the preferred embodiments of the present disclosure have been described above, the scope of the present disclosure is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present disclosure defined in the accompanying claims fall within the scope of the present disclosure. DESCRIPTION OF REFERENCE NUMERALS 1: Core particle capable of decomposing peroxide or radical2: Porous carbon coating layer100: Membrane-electrode assembly10,10′: Interfacial adhesion layers20,20′: Electrodes30,30′: Catalyst electrodes40,40′: Electrode substrates50: Ion exchange membrane200: Fuel cell210: Fuel supply unit220: Modification unit230: Stack231: First supply pipe232: Second supply pipe233: First discharge pipe234: Second discharge pipe240: Oxidant supply unit INDUSTRIAL APPLICABILITY The present disclosure relates to a radical scavenger, a method of manufacturing the same, a membrane-electrode assembly including the same, and a fuel cell including the same. The membrane-electrode assembly is capable of minimizing loss in ion conductivity of an ion exchange membrane while improving chemical durability of the ion exchange membrane, preventing chemical degradation of the ion exchange membrane occurring during long-term operation of a fuel cell, securing excellent long-term performance of the ion exchange membrane, and being commonly used irrespective of the kind of the ion exchange membrane, such as a fluorine-based ion exchange membrane or a hydrocarbon-based ion exchange membrane. | 56,708 |
11862804 | DETAILED DESCRIPTION Batteries designed as discussed below can be used for a variety of different purposes. One purpose for such batteries is in implantable medical devices for example. It is desirable in such a case the batteries have as small a size as possible while maximizing the stored energy. FIG.1shows an implantable system100which can use such a battery, in accordance with one embodiment. The implantable system100includes a pulse generator105and at least one lead120. The pulse generator105includes a housing110. The pulse generator105can be implanted into a subcutaneous pocket made in the wall of a patient's chest. Alternatively, the pulse generator105can be placed in a subcutaneous pocket made in the abdomen, or in other locations. Pulse generator105can include a power supply such as a battery102, a capacitor, and other components104housed in the housing110. The pulse generator105can include microprocessors to provide processing, evaluation, and to deliver electrical shocks and pulses of different energy levels and timing for defibrillation, cardioversion, and pacing to a heart in response to cardiac arrhythmia including fibrillation, tachycardia, heart failure, and bradycardia. In other embodiments, implantable system100can also be suitable for use with implantable electrical stimulators, such as, but not limited to, neuro-stimulators, skeletal stimulators, central nervous system stimulators, or stimulators for the treatment of pain. In some examples, the system can be used for diagnostic devices such as cardiac monitors. The lead120includes a lead body having a proximal end, where a terminal of the lead can be coupled to a header of the pulse generator105. The lead120extends to a distal end, which can be coupled with a portion of a heart, when implanted. The distal end of the lead120includes at least one electrode which electrically couples the lead120with the heart. At least one electrical conductor is disposed within the lead120and extends from the proximal end to the electrode. The electrical conductor carries electrical currents and signals between the pulse generator105and the electrode. Since pulse generator105is typically implanted in the left region of the chest or in the abdomen, a smaller size device, which is still capable of delivering the required level of electrical energy, is desirable. FIG.2shows a schematic view of an implantable medical device200which can also use such a battery, in accordance with one embodiment. Medical device200is a wireless, implantable electrode. Since no leads are involved, the device needs its own power to develop a charge. Device200includes a housing210which includes electrodes202and204and encloses a battery206, which can be formed using one or more features discussed below. In another example, the battery206can be integrated as part of the housing of device200and thus be in contact with the device housing rather than isolated inside the device200. FIG.3shows an isometric view of a battery300, in accordance with one embodiment. The battery300can be useful in devices such as the implantable devices described above for the reason detailed below. Here, the battery300generally includes a battery case310including a housing312having side walls defining a first open end and a second open end, as will be discussed below. The battery case310includes a separate top cover320to cover the first open end of the housing312and a separate bottom cover330to cover the second open end of the housing312. The case310encloses the first and second electrodes. In one embodiment, a first terminal360is coupled to the first electrode and exposed outside the case310, and a second terminal370is coupled to the second electrode and exposed outside the case310. In one embodiment, a backfill hole375is provided in the top cover320to backfill electrolyte in the battery. FIG.4shows the housing312for the battery300, in accordance with one embodiment. The housing312is a metallic housing including side walls defining a first open end314and a second open end316. In this example, the housing312is a cylindrical tube that is open on both ends which provides ease of access to the inner surface402of the housing312. The tubular housing312can be manufactured using many metal fabrication processes including but not limited to extrusion and machining. In one example, the housing312can have a diameter of about 0.125 inches. In other embodiments, the housing312can have a diameter of about 0.125 inches or higher. FIG.5shows a cross section of a portion of the battery300during manufacture, in accordance with one embodiment. In this example, a first electrode340material is laminated and bonded directly to the inner surface402of the housing312. In one example, the first electrode340can include lithium to form an anode electrode. To attach the lithium to the inner surface402, the laminating process includes bonding a sheet of lithium to the inner surface402by using a rolling pin extending through both the first open end314and second open end316of the housing312. By providing an open-ended housing312, the rolling pin can supply sufficient pressure to bond the lithium to the inner surface402. If a typical “can” battery housing is used, such pressure cannot be applied. In other examples, the lithium can be laminated to the inner surface using a pressurized balloon, an expanding plunger, other or methods. In this example, the housing312acts as the current collector for the first electrode340. Thus, a separate current collector is not needed and there does not need to be a separate connector between the current collector of the first electrode340and the terminal. By eliminating a discrete current collector and eliminating an interconnect between the discrete current collector and a terminal, valuable space can be saved. In some embodiments, a cathode material can be pressed against the inner surface402of the housing to make a case positive design. Such cathode designs may require adhesion promoters such as carbon to improve the bond from the cathode to the inner surface402. In some embodiments, another electrode material can be attached to the inner surface, but an interconnect between the electrode material and the housing wall may need to be provided. As shown inFIG.5, there is a first bare space402at the first open end314where no electrode material for the electrode340is applied to the housing312. Likewise, there is a second bare space420at the second open end316of the housing312. Again, using the open-ended housing312allows use of alignment tools for precise placement of the electrode340material so that tight tolerances need for very small batteries can be reached. The open-ended design also allows for close inspection at each end to ensure the electrode340material is positioned precisely. FIG.6shows an exploded view of the battery300, in accordance with one embodiment. Here, the housing312with the first electrode340attached thereto as discussed above is shown. A second electrode assembly349includes a second electrode350which is enclosed in a separator bag540. The top cover320can be already attached to the second electrode assembly349, as will be further discussed below. On the top cover320are the first terminal360which is directly attached to the top cover320and the second terminal370which extends through the top cover320and is insulated from the top cover320. The entire second electrode assembly349can be slipped inside the housing312. The open-ended housing design of battery300allows for precise positioning of the parts. The additional access of the open ends permits more precise component placement by allowing counter force and the use of a hard stop at the bottom open end to precisely locate the second electrode assembly349within the housing312. Moreover, the two open ends also allow for inspection after component placement to ensure no damage was incurred during the assembly process. The bottom and top covers330,320can be welded to the housing312. When the top cover320is welded to the housing312, the terminal360is then electrically connected to the first electrode340. FIG.7shows a cross section of the assembled battery300, in accordance with one embodiment, andFIG.8shows a cross-section of the top portion of the battery300.FIG.8is a side view of the view ofFIG.7. After assembly, the electrodes350,340are aligned such that the second electrode350does not reach either end of the first electrode340. The separator bag540goes all the way up to a bottom surface of the top cover320. There is a small gap552between the separator bag540and the bottom cover330. This is created during assembly when a pin is inserted into the second open end316to provide a hard stop as the cathode assembly is inserted into the housing312. The first terminal360is coupled to the case310and the second terminal370includes a feedthrough372which is insulated from the case310by an insulator502which insulates between the feedthrough372and the top cover320. Feedthrough insulator tape551is position just below the top cover320. Here, the second electrode350includes a current collector510coupled to the feedthrough372and active electrode material520around the current collector510. As part of the second electrode assembly349, the separator bag540covers a bottom and side surfaces of the second electrode350with a top surface of the second electrode350exposed toward the top cover320. A ribbon connector530can be attached to and folded between the current collector510of the electrode350and the feedthrough372. Other embodiments omit the ribbon connector530and the feedthrough372is directly connected to the current collector510. FIG.9shows a battery600in accordance with one embodiment. In this example, instead of a cylindrical housing, the battery600includes a battery case601including a rectangular housing602having side walls defining a first open end608and a second open end610. The battery case601includes a separate top cover604to cover the first open end608of the housing602and a separate bottom cover (not shown) to cover the second open end610of the housing602. Other features as discussed above are also applicable to the battery600. For instance, battery housing602allows for inspection and tight control of tolerances at both ends of the battery600. The rectangular housing602can be useful for battery stack designs where there are a plurality of stacked or wound electrodes. The open end allows for pulling (instead of pushing) the stack into the housing. This helps avoid damaging thin electrodes. Also, the electrode tabs of the stack can be welded through the bottom open end. FIG.10shows a battery700in accordance with one embodiment. Battery700is a case neutral, very small diameter cell especially useful for the wireless, implantable electrode shown inFIG.2. In this example the battery case diameter can be about 0.100 inches or more. The battery700includes a battery case710including a housing711having side walls defining a first open end706and a second open end708. The battery case710includes a separate top cover712to cover the first open end706of the housing711and a separate bottom cover714to cover the second open end708of the housing711. Not shown for ease of example, but as discussed above for battery300, there can be first and second electrodes within the case710. Here, a first terminal702includes a first feedthrough which is insulated from the case710and extends through the top cover712and a second terminal704includes a second feedthrough which is insulated from the case710and extends through the bottom cover714. Other design details and assembly are similar to battery300discussed above. Referring to battery300ofFIGS.3-8, the assembly of the battery300can include laminating the first electrode340material directly to the inner surface of the battery housing312having first and second open ends314,316. The assembly can include inserting a second electrode assembly349into the housing312and positioning the second electrode using counterforce and hard stops if needed. The top cover320is then attached to the housing312over the first open end314. After any necessary inspection of positioning and connections, the bottom cover330is attached to the housing312over the second open end316, and electrolyte can be backfilled into the battery. As noted above, laminating can include bonding a sheet of lithium to the inner surface of the housing312by using a rolling pin extending through both the first open end and second open end of the housing312. The laminating is precisely controlled so that the electrode material partially covers the inner surface402of the housing312such that there is no first electrode material adjacent either the first open end314or the second open end316of the housing312. Instead, there are the bare space410,420at each of the open ends. In one example, the second electrode assembly349can be pre-assembled and includes the current collector510with the active electrode350material around the current collector510and the separator bag540covering the bottom and side surfaces of the active electrode material350. The second electrode assembly can be attached the top cover320by attaching the ribbon connector530between the second terminal370(which is insulated from the top cover320) and the current collector510. The separator bag540extends all the way up to the top cover320. This entire electrode assembly can then be slipped into the housing containing the first electrode340material. As noted above, the open-ended battery housings discussed herein allow access for assembly operations into the battery housing. Providing access on both ends allows for the elimination of some non-active battery materials/components, such as eliminating a current collector and interconnects for the electrode340. This enables a more volumetrically efficient and manufacturable design. In general, the present concept is attractive in very small (<1 cc) cells where volume and access inside the housing is extremely limited. For example, in some embodiments, the batteries discussed above can have a diameter of about 0.100 inches. In some embodiments, the batteries discussed above can have a diameter of about 0.125 inches. In some embodiments, the diameter can range from 0.125 inches or higher. These very small diameters create manufacturing difficulties, but the ability to access both ends for assembly, interconnections, and inspections creates a more robust, manufacturable design. Moreover, this style of battery housing can be beneficial regardless of cell chemistry, including primary and secondary chemistries. Additional Notes The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein. All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls. In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. | 18,256 |
11862805 | DETAILED DESCRIPTION Implementations of the disclosure will now be described, by way of embodiments only, with reference to the drawing. The disclosure is illustrative only, and changes may be made in the detail within the principles of the present disclosure. It will, therefore, be appreciated that the embodiments may be modified within the scope of the claims. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The technical terms used herein are to provide a thorough understanding of the embodiments described herein, but are not to be considered as limiting the scope of the embodiments. FIGS.1and2illustrate an embodiment of a battery100including a packaging shell10, a battery cell20, and a bonding member30. The battery cell20is packaged in the packaging shell10, and is adhered to the packaging shell10by the bonding member30. The battery cell20is a flat battery cell wound by an electrode assembly, that includes a first electrode plate23, a first separator21, a second electrode plate27, a second separator25stacked in that order. A first electrode tab50is connected to the first electrode plate23, a second electrode tab70is connected to the second electrode plate27. The first electrode tab50and the second electrode tab70extend out of the packaging shell10. In the embodiment, the first electrode plate23is a negative electrode plate, the second electrode plate27is a positive electrode plate. The battery cell20includes a first surface22, a second surface24opposite to the first surface22, and two lateral surfaces26. Each of the two lateral surfaces connects the first surface22and the second surface24. The first surface22and the second surface24are adhered to the packaging shell10by the bonding member30. The bonding member30includes a first bonding layer31and a second bonding layer32. The first surface22is adhered to the packaging shell10by the first bonding layer31, the second surface24is adhered to the packaging shell10by the second bonding layer32. Alternatively, the bonding member30can cover only one surface of the battery cell20, the first surface22or the second surface24then being adhered to the packaging shell10by the bonding member30. The first electrode plate23includes a first current collector235and a first active material layer236disposed on opposite surfaces of the first current collector235. The second electrode plate27includes a second current collector275and a second active material layer276disposed on opposite surfaces of the second current collector275. Materials of the first current collector235and the second current collector275can be respectively selected from a group consisting of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn, and any combination (alloy) thereof. Alternatively, the first current collector235is an aluminum foil, the second current collector275is a copper foil. A material of the first active material layer236can be selected from a group consisting of LiCo02, LiFeP04, other electrochemical active materials capable of deintercalation of lithium ions, and any combination thereof. A material of the second active material layer276can be selected from a group consisting of graphite, soft carbon, hard carbon, Li4Ti5012, other electrochemical active materials capable of intercalating lithium ions, and any combination thereof. Materials of the first separator21and the second separator25can be respectively selected from a group consisting of polypropylene (PP), polyethylene (PE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polymethyl methacrylate (PMMA), polyethylene glycol (PEG), and any combination thereof. The first active material layer236defines a first groove237in which the first current collector235is exposed. The first electrode tab50is received in the first groove237, electrically connected to the first current collector235, and configured to conduct electrons of the first current collector235. The second active material layer276defines a second groove277in which the second current collector275is exposed. The second electrode tab70is received in the second groove277, electrically connected to the second current collector275, and configured to conduct electrons of the second current collector275. In a thickness direction T of the battery cell20, the first electrode tab50is not aligned with the second electrode tab70, reducing a thickness of the battery cell20. Alternatively, a material of the first electrode tab50is aluminum, and a material of the second electrode tab70is selected from one or more of Ni and its alloys. The first electrode plate23includes an active material area231and an empty foil area connected to each other. The active material area231includes the first current collector235and the first active material layer236disposed on the first current collector235. The empty foil area only includes the first current collector235, opposite surfaces of the first current collector235do not separately carry the first active material layer236. A part of the active material area231and the empty foil area together constitute an outermost circle of the battery cell20. The empty foil area includes a first empty foil area233, a second empty foil area234, and a third empty foil area232located between the first empty foil area233and the second empty foil area234. The third empty foil area232connects the first empty foil area233and the second empty foil area234. The second empty foil area234is connected to the active material area231. The first empty foil area233is located on the first surface22, and adhered to the packaging shell10by the first bonding layer31. The first bonding layer31partially or completely covers the first empty foil area233. The second empty foil area234is located on the second surface24, and adhered to the packaging shell10by the second bonding layer32. The second bonding layer32partially or completely covers the second empty foil area234. The third empty foil area232is located on one lateral surface26. Referring toFIGS.2to4, in a width direction A of the battery cell20, a width of the battery cell is W, a width of the first empty foil area233is W1, a width of the second empty foil area234is W2, where 0≤(W1+W2)/W≤40%. The width direction A is perpendicular to an extending direction of the electrode tab. In the battery100of the present embodiment, by optimizing a straight line length of the empty foil area located on the outermost circle and adhered to the packaging shell10, a ratio of a width of the empty foil area in the width direction A of the battery cell20to the width of the battery cell20is less than or equal to 40%. This reduces the possibility of generating debris when anyone of the three empty foil areas are impacted, thereby reducing the risk of short circuit. Alternatively, 0≤(W1+W2)/W≤30%. After testing, when the ratio of (W1+W2)/W is 30%, the drop and impact resistance of the battery100is almost optimal. The first bonding layer31partially or completely covers the first surface22, the second bonding layer32partially or completely covers the second surface24. In the width direction A of the battery cell20, a width of the first bonding layer31is W3, a width of the second bonding layer32is W4, where 80%≤W3/W≤100%, and 80%≤W4/W 100%. In a length direction B of the battery cell20, a length of the battery cell20is L, a length of the first bonding layer is L1, a length of the second bonding layer32is L2, where 80%≤L1/L≤100%, and 80%≤L2/L≤100%. The length direction B is parallel to the extending direction of the electrode tab. The first electrode tab50and the second electrode tab70are both located on a top of the battery cell20. The battery cell20includes two end faces in the length direction B. Alternatively, the first electrode tab50and the second electrode tab70can be respectively located on different end faces of the battery cell20or be together on one end face. Furthermore, the bonding member30further includes a third bonding layer33. The third empty foil area232is adhered to the packaging shell10by the third bonding layer33. The third bonding layer33partially or completely covers the third empty foil area232. The bonding member30can be an adhesive layer or an adhesive tape. The adhesive of the adhesive layer or the adhesive tape is a pressure sensitive adhesive or a hot melt adhesive. The hot melt adhesive is selected from a group consisting of polyolefin hot melt adhesive, polyurethane hot melt adhesive, ethylene and copolymer hot melt adhesive, polyester hot melt adhesive, polyamide hot melt adhesive, styrene and its blocks copolymer hot melt adhesive, and any combination thereof. The bonding force of the bonding member30is 100 to 1000 N/m, and the tensile stress of the bonding member30is less than or equal to 4000 N/m. Alternatively, each of the thickness of the first bonding layer31, the second bonding layer32, and the third bonding layer33is less than or equal to 200 μm. FIG.5illustrates an embodiment of an electronic device200including the above battery100. The electronic device200can be any known electronic device, such as a mobile phone, a computer, an electric tool, and an electric vehicle. The present disclosure is illustrated by way of different embodiments and comparative embodiments. EMBODIMENT 1 The battery cell20shown inFIG.2was used to prepare ten groups of finished batteries after being filled with electrolyte, encapsulated, and formatted. The width W1 of the first empty foil area233, the width W2 of the second empty foil area234, and the width W of the battery cell20satisfied (W1+W2)/W=40%. The width W3 of the first bonding layer31satisfied W3/W=80%, the width W4 of the second bonding layer32satisfied W4/W=80%. The length L1 of the first bonding layer31and the length L of the battery cell20satisfied L1/L=80%, and the length L2 of the second bonding layer32satisfied L2/L=80%. EMBODIMENT 2 A finished battery was prepared that was substantially the same as the finished battery of embodiment 1 except that W3/W=100%, and L1/L=100%. EMBODIMENT 3 A finished battery was prepared that was substantially the same as the finished battery of embodiment 1 except that W4/W=100%, and L2/L=100%. EMBODIMENT 4 A finished battery was prepared that was substantially the same as the finished battery of embodiment 1 except that W3/W=100%, W4/W=100%, L1/L=100%, and L2/L=100%. EMBODIMENT 5 A finished battery was prepared that was substantially the same as the finished battery of embodiment 1 except that (W1+W2)/W=30%, L1/L=100%, and L2/L=100%. EMBODIMENT 6 A finished battery was prepared that was substantially the same as the finished battery of embodiment 5 except that W3/W=100%. EMBODIMENT 7 A finished battery was prepared that was substantially the same as the finished battery of embodiment 5 except that W4/W=100%. EMBODIMENT 8 A finished battery was prepared that was substantially the same as the finished battery of embodiment 5 except that W3/W=100%, W4/W=100%. EMBODIMENT 9 A finished battery was prepared that was substantially the same as the finished battery of embodiment 5 except that (W1+W2)/W=15%. EMBODIMENT 10 A finished battery was prepared that was substantially the same as the finished battery of embodiment 9 except that W3/W=100%. EMBODIMENT 11 A finished battery was prepared that was substantially the same as the finished battery of embodiment 9 except that W4/W=100%. EMBODIMENT 12 A finished battery was prepared that was substantially the same as the finished battery of embodiment 9 except that W3/W=100%, W4/W=100%. EMBODIMENT 13 A finished battery was prepared that was substantially the same as the finished battery of embodiment 5 except that (W1+W2)/W=0. EMBODIMENT 14 A finished battery was prepared that was substantially the same as the finished battery of embodiment 13 except that W3/W=100%. EMBODIMENT 15 A finished battery was prepared that was substantially the same as the finished battery of embodiment 13 except that W4/W=100%. EMBODIMENT 16 A finished battery was prepared that was substantially the same as the finished battery of embodiment 13 except that W3/W=100%, and W4/W=100%. COMPARATIVE EMBODIMENT 1 The battery cell20shown inFIG.2was used for ten groups of finished battery after being filled with electrolyte, encapsulated, and formatted. The width W1 of the first empty foil area233, the width W2 of the second empty foil area234, and the width W of the battery cell20satisfied (W1+W2)/W=50%. The width W3 of the first bonding layer31satisfied W3/W=80%, the width W4 of the second bonding layer32satisfied W4/W=80%. The length L1 of the first bonding layer31and the length L of the battery cell20satisfied L1/L=80%, the length L2 of the second bonding layer32satisfied L2/L=80%. COMPARATIVE EMBODIMENT 2 The battery cell20shown inFIG.2was used for ten groups of finished battery after being filled with electrolyte, encapsulated, and formatted. The width W1 of the first empty foil area233, the width W2 of the second empty foil area234, and the width W of the battery cell20satisfied (W1+W2)/W=60%. The width W3 of the first bonding layer31satisfied W3/W=80%, the width W4 of the second bonding layer32satisfied W4/W=80%. The length L1 of the first bonding layer31and the length L of the battery cell20satisfied L1/L=80%, the length L2 of the second bonding layer32satisfied L2/L=80%. COMPARATIVE EMBODIMENT 3 A battery was prepared, which included a packaging shell and a battery cell within. An outermost circle of the battery cell included an empty foil area, a ratio of a width of the empty foil area in a width direction of the battery cell to a width of the battery cell was 50%, the battery was not adhered to the packaging shell by a bonding member. Drop and impact tests were performed on the finished batteries provided in examples 1 to 16 and comparative examples 1 to 3, the test conditions and results are shown in Table 1. The drop testing method is to drop a battery from a height of 1.5 m after installing the battery in a special fixture. After the drop, if an empty foil area of the battery cell was not torn, the drop test is passed. The impact testing method for heavy objects is to place a metal rod with a diameter of 15.8 mm±0.1 mm horizontally at the center of an surface of the battery, and drop a heavy object with a weight of 9.1 kg±0.1 kg from a height of 610 mm±25 mm to hit the metal rod. If the tested battery did not explode or catch fire, it passed the test. TABLE 1Value ofValue ofValue ofValue ofValue ofPass rate ofPass rate of(W1 + W2)/WW3/WW4/WL1/LL2/Ldrop testimpact testEmbodiment 140%80%80%80%80%4/1010/20Embodiment 240%100%80%100%80%5/1010/20Embodiment 340%80%100%80%100%5/1010/20Embodiment 440%100%100%100%100%5/1010/20Embodiment 530%80%80%100%100%9/1017/20Embodiment 630%100%80%100%100%10/1017/20Embodiment 730%80%100%100%100%10/1017/20Embodiment 830%100%100%100%100%10/1018/20Embodiment 915%80%80%100%100%9/1017/20Embodiment 1015%100%80%100%100%10/1017/20Embodiment 1115%80%100%100%100%10/1017/20Embodiment 1215%100%100%100%100%10/1018/20Embodiment 13080%80%100%100%9/1017/20Embodiment 140100%80%100%100%10/1017/20Embodiment 15080%100%100%100%10/1017/20Embodiment 160100%100%100%100%10/1018/20Comparative50%80%80%80%80%2/105/20embodiment 1Comparative60%80%80%80%80%2/105/20embodiment 2Comparative50%————0/105/20embodiment 3 Table 1 shows that the pass rates in drop and impact testing of the batteries prepared in the present disclosure are high. With the decrease of the ratio of (W1+W2)/W, the pass rates are increased. When (W1+W2)/W is greater than 40%, the pass rates through drop and impact testing of the battery are low and when (W1+W2)/W is less than 30%, with the decrease of value of (W1+W2)/W, the pass rate through drop and impact testing increase less. With the increase of the ratio of W3/W and/or the ratio of W4/W, the pass rates through drop and impact testing of the battery also increase. It is to be understood, even though information and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the present embodiments, the disclosure is illustrative only; changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present embodiments to the full extent indicated by the plain meaning of the terms in which the appended claims are expressed. | 16,622 |
11862806 | DESCRIPTION OF REFERENCE NUMBERS 10—case;101—bottom shell;1011—accommodating cavity;102—top cover;1021—opening;1022—first glue-overflow groove;1023—second glue-overflow groove;20—cell;201—first tab;202—second tab;203—cell cavity;30—conductive member;301—liquid injection port;302—first counter bore;303—extension part;40—sealing member;50—sealant ring;60—abutment member;70—first insulating rubber layer;701—first through hole;702—first cut edge;80—second insulating rubber layer;801—second through hole;802—second cut edge;90—third insulating rubber layer;901—third through hole. DETAILED DESCRIPTION Since the interior of a button cell is a closed space, the sealing performance is extremely important for the button cell. However, in the prior art, firstly, an electrolyte solution is injected into an accommodating cavity where a cell is placed, and then a conductive member is configured to pass through an opening of a case, so that the conductive member is riveted to the opening, and an insulated sealant ring is provided between the conductive member and the opening. However, when the conductive member is being riveted to the opening, the case will be shocked, and the electrolyte solution in the accommodating cavity will splash to the sealant ring, causing partial failure of the sealant ring, resulting in inferior sealing performance. In order to solve the above problems, in the button cell provided by the embodiments of the present disclosure, a conductive member covers an opening of a top cover, such that the top cover is connected to the conductive member through a sealant ring in an insulated and sealed manner. A cell is arranged in an accommodating cavity of a bottom shell, with a first tab on the cell being welded to an inner bottom wall of the bottom shell. Then, the top cover having the conductive member is connected to the bottom shell in a sealed manner, with a second tab on the cell being electrically connected to the conductive member. An electrolyte solution is injected into the accommodating cavity through a liquid injection port of the conductive member. After the electrolyte solution is injected, the liquid injection port is covered by a sealing member, and the sealing member is connected to the liquid injection port in a sealed manner by bonding or welding, thereby improving sealing performance of the button cell. In order to make the above objectives, technical features and advantages of the embodiments of the present disclosure more explicit and understandable, the technical solutions in the embodiments of the present disclosure are illustrated clearly and completely in combination with the accompanying drawings in the embodiments of the present disclosure hereinafter. Obviously, the embodiments described are only a part of embodiments of the present disclosure, and are not all of the embodiments thereof. Based on the embodiments of the present disclosure, all the other embodiments obtained by those skilled in the art without creative works are within the protection scope of the present disclosure. Example I As shown inFIG.1andFIG.2, a button cell provided by the examples of the present disclosure includes: a case10, a cell20arranged in an accommodating cavity1011of the case10, and a conductive member30which is arranged on the case10and connected to the case10in an insulated manner. The conductive member30is provided with a liquid injection port301for injecting an electrolyte solution into the accommodating cavity1011, and a sealing member40which covers the liquid injection port301. The sealing member40is connected to the liquid injection port301in a sealed manner. The cell20has thereon a first tab201and a second tab202, where the first tab201is electrically connected to the case10by welding and the like, and the second tab202is also electrically connected to the conductive member30by welding or bonding. The case10and the conductive member30are electrically connected to an electronic device, respectively, so that the cell20provides electrical energy for the electronic device through the case10and the conductive member30. As shown inFIG.2toFIG.4, the case10includes a bottom shell101and a top cover102, the bottom shell101is provided with a sink extending towards a bottom wall of the bottom shell101, forming the accommodating cavity1011for accommodating the cell20. The top cover102covers an opening which is in communication with the accommodating cavity1011, so that the case10having the accommodating cavity1011is enveloped and formed by the bottom shell101and the top cover102. In order to improve the sealing performance, the top cover102and the bottom shell101are connected in a sealed manner, such as by way of welding and the like. The shape of the cross section of the case10can be any shape such as a circle, an ellipse, and a polygon, etc., which is not limited in the present embodiment. Since the cell20provides electrical energy for the electronic device through the case10and the conductive member30, the case10and the conductive member30can be made of stainless steel, copper, iron or other metal materials. The top cover102is provided with an opening1021, so that the top cover102forms a ring structure. The conductive member30covers the opening1021, with a sealant ring50arranged in between, where the sealant ring50makes the conductive member30be connected to the opening1021in an insulated and sealed manner. In other words, the conductive member30is bonded to an edge of the opening1021through the sealant ring50, and covers the opening1021of the top cover102. The shape of the opening1021can be a circle, an ellipse, or a polygon, etc. In order to improve the sealing performance of the connection between the conductive member30and the top cover102, the conductive member30can be bonded to the top cover102through the sealant ring50by heating and pressurizing. In this way, the bonding reliability of the sealant ring50can be improved, thereby improving the sealing performance of the connection between the conductive member30and the top cover102. Furthermore, the conductive member30may protrude out of the surface of the top cover102. Or, a second glue-overflow groove1023for placing the conductive member30may be provided on the top cover102, such that the conductive member30may reside in the second glue-overflow groove1023, as shown inFIG.5, with upper surfaces of the conductive member30and the top cover102being even. When the conductive member30is connected to the top cover102through the sealant ring50in an insulated and sealed manner, glue will overflow at the sealant ring50during the heating and pressurizing. But with the above arrangement, the overflowed glue will be kept within the second glue-overflow groove1023and will not overflow the surface of the top cover102. In this way, the surface of the top cover102is relatively flat, and the overall structure of the button cell is more compact, improving the overall aesthetics of the button cell. In an embodiment, the opening1021is a circular hole, the conductive member30is a disc shape, and the diameter of the opening1021is less than that of the conductive member30. Thus, at least a partial edge of the conductive member30overlaps with a partial edge of the opening1021in the radial direction. The opening1021and the conductive member30are tightly bonded through the sealant ring50by heating and pressurizing. The sealant ring50under high temperature and high pressure can make the opening1021be connected to the conductive member30more tightly, thereby improving the sealing performance of the button cell. Since larger overlapped unilateral part between the edge of the conductive member30and the edge of the opening1021in the radial direction means better sealing performance, the overlapped unilateral part between the conductive member30and the opening1021in the radial direction is greater than or equal to 0.3 mm in an embodiment. In this way, the sealing area between the conductive member30and the opening1021is increased, thereby improving the sealing performance between the conductive member30and the opening1021. Furthermore, as shown inFIG.3, the conductive member30is provided with an extension part303which passes through the opening1021. For example, the conductive member30may be formed into a T-shaped conductive member30. In this way, the extension part303and a hole wall of the opening1021are connected in a sealed manner through the sealant ring50, which further increases the sealing area between the conductive member30and the opening1021, thereby improving the sealing performance between the conductive member30and the opening1021. In that case, the sealant ring50can be made from a soluble material to improve the corrosion resistance and the sealing performance of the sealant ring50against electrolyte solution. In that case, the sealant ring50is shaped as a ring. When the conductive member30and the top cover102is heated and pressurized, an outer edge of the sealant ring50overflows out of the joint of the conductive member30and the top cover102, while an inner edge of the sealant ring50overflows out of the joint of the sealant ring50and an edge of the opening1021of the top cover102. In this way, the connection reliability of the sealant ring50in connecting the conductive member and the top cover102can be ensured. On the basis of the above embodiment, as shown inFIG.1toFIG.4, the conductive member30is also provided with a liquid injection port301for injecting an electrolyte solution into the accommodating cavity1011, where the liquid injection port301can be in any shape, such as a circle, a quadrangle, a polygon, etc. In an embodiment, the liquid injection port301is arranged coaxially with the conductive member30, and the conductive member30is arranged coaxially with the accommodating cavity1011for accommodating the cell20in the case10. In an embodiment, in order to improve the sealing performance between the sealing member40and the liquid injection port301, a first counter bore302is arranged on one end of the liquid injection port301facing away from the accommodating cavity1011, and the diameter of the first counter bore302is greater than that of the liquid injection port301. The first counter bore302is in communication with and arranged coaxially with the liquid injection port301. In that case, the shape of the first counter bore302conforms to the shape of the liquid injection port301. In other words, when the shape of the liquid injection port301is circular, the shape of the first counter bore302is also circular. Exemplarily, the depth of the first counter bore302may be 0.01-0.5 mm. The liquid injection port301is covered with a sealing member40. In other words, the sealing member40is located in the first counter bore302. Since the depth of the first counter bore302is relatively small, the sealing member40may be a sheet structure located in the first counter bore302to cover the liquid injection port301. In order to improve sealing performance, the sealing member40is connected to the liquid injection port301in a sealed manner. For example, the sealing member40can be welded to the liquid injection port301. In other words, after the electrolyte solution is injected into the accommodating cavity1011through the liquid injection port301, welding is performed at the joint between the sealing member40and the first counter bore302outside the case10, so as to improve the sealing performance. Exemplarily, the sealing member40can be a sealing nail. The sealing nail is placed within the first counter bore302, then the joint therebetween is welded together. As shown inFIG.4, when the sealing nail is sealed with the liquid injection port301by welding, in order to facilitate welding, the diameter of the first counter bore302is greater than that of a cap of the sealing nail. The part of the sealing nail located in the first counter bore302has a weld mark, in other words, a welding device can weld the joint between the sealing nail and the conductive member30from the inside of the first counter bore302. For example, a laser beam of a laser welding device can extend into the first counter bore302to weld the sealing nail and the conductive member30together. Alternatively, the sealing member40can also be located in the first counter bore302and bonded with the counter bore through a sealant ring or the like, so as to simplify the manufacturing process. In an alternative implementation, the cell20is a wound-type cell20. Specifically, the wound-type cell20includes a first plate, a second plate and a battery separator separating the two. The first plate is provided with a first tab201, which can be arranged on the first plate by welding. The second plate is provided with a second tab202, which can be arranged on the second plate by welding. In a winding process, the first plate, the second plate, and the battery separator are wound layer by layer in the same direction from a winding head, eventually forming the wound-type cell20. It is understandable that the first plate of the cell20can be a positive plate, and the second plate can be a negative plate. In this case, the first tab201arranged on the first plate is a positive tab, and the second tab202arranged on the second plate is a negative tab. In a specific implementation, the cell20is accommodated within the accommodating cavity1011. The positive tab is electrically connected to an inner bottom wall of the bottom shell101by welding, so that the bottom shell101is formed into a positive electrode of a button cell. The negative tab is electrically connected to the conductive member30, so that the conductive member30is formed into a negative electrode of the button cell. When the button cell is applied to an electronic device, the bottom shell101is electrically connected to a positive electrode of the electronic device, and the conductive member30is electrically connected to a negative electrode of the electronic device, so that the cell20supplies power to the electronic device. Or, the first plate of the cell20can be a negative plate, and the second plate can be a positive plate. In this case, the first tab201arranged on the first plate is a negative tab, and the second tab202arranged on the second plate is a positive tab. In a specific implementation, the cell20is accommodated within the accommodating cavity1011. The negative tab is electrically connected to the bottom shell101by welding, so that the bottom shell101is formed into a negative electrode of a button cell. The positive tab is electrically connected to the conductive member30, so that the conductive member30is formed into a positive electrode of the button cell. When the button cell is applied to an electronic device, the bottom shell101is electrically connected to a negative electrode of the electronic device, and the conductive member30is electrically connected to a positive electrode of the electronic device, so that the cell20supplies power to the electronic device. In an embodiment, the second tab202is electrically connected to an end of the extension part303of the conductive member30extending into the accommodating cavity1011, such that the contact area between the second tab202and the conductive member30can be increased, thereby improving the reliability of the electrical connection. In that case, in order to prevent the top cover102from interfering with the connection between the second tab202and the extension part303, one end of the extension part303facing the accommodating cavity1011is arranged to protrude out of an inner wall of the top cover102after the extension part303is extended into the accommodating cavity1011. In this way, when the second tab202is connected to an end surface of the extension part303, a gap can be found between the second tab202and the inner wall of the top cover102. Or, an insulating layer can be provided between the inner wall of the top cover102and the second tab202, so as to improve the reliability of the electrical connection between the second tab202and the conductive member30. It should be noted that the first tab201is electrically connected to the top cover102in the case10by welding or bonding. Alternatively, in order to improve the reliability of the electrical connection between the first tab201and the second tab202, an insulating layer can be provided on both the first tab201and the second tab202in the circumferential direction, and the first tab201or the second tab202only needs to expose a part to be electrically connected to the bottom shell101or the conductive member30. Alternatively, a cell cavity203can be formed at a center position of the wound-type cell20while winding. After the cell20is placed into the accommodating cavity1011, the cell cavity203and the liquid injection port301are arranged coaxially. In this way, when an electrolyte solution is injected into the accommodating cavity1011, the plates and the battery separator and so on in the cell20will not block the injection of the electrolyte solution, which improves the efficiency of the injection of the electrolyte solution, thereby increasing the production efficiency of the button cell. In an embodiment, as shown inFIG.3, an abutment member60can also be inserted into the cell cavity203via the liquid injection port301, where the abutment member60may be a column structure, such as a cylindrical structure or a prismatic structure. It can be composed of one column piece, or two or more column pieces connected end to end in sequence. When the first tab201is welded to the inner bottom wall of the bottom shell101, the abutment member60is firstly inserted into the cell cavity203, so that a first end of the abutment member60abuts against the first tab201, with pressure applied to a second end of the abutment member60, so that the first tab201is pressed against the inner bottom wall of the bottom shell101by the pressure from the abutment member60before the welding is performed. In this way, the reliability of the welding between the first tab201and the bottom shell101can be improved, thereby improving the reliability of the electrical connection between the first tab201and the bottom shell101. It should be noted that, in order to facilitate a user to operate, the second end of the abutment member60can protrude out of the top cover102of the case10. When the first tab201has been welded to the inner bottom wall of the bottom shell101in the button cell, and the top cover102having conductive member30is connected to the bottom shell101in a sealed manner, the abutment member60can be retracted out of the cell cavity203via the liquid injection port301. Due to the possibility of vibration during a welding process, if the bottom shell101is connected to the top cover102in a sealed manner before the first tab201is welded to the bottom shell101, the vibration will cause a displacement between the bottom shell101and the top cover102, leading to misalignment therebetween. As a result, the sealing connection between the bottom shell101and the top cover102can become loose or fail, eventually leading to inferior sealing performance of the button cell. Therefore, in the present embodiment, the cell20with the first tab201and the second tab202are firstly placed into the accommodating cavity1011of the bottom shell101, and the abutment member60is inserted into the cell cavity203of the cell20to press on the first tab201, so that the first tab201is pressed against the inner bottom wall of the bottom shell101. After that, a welding device is utilized to weld the bottom shell101and the first tab201to create the electrical connection between the first tab201and the bottom shell101, and then, the top cover102having the conductive member30is connected to the bottom shell101in a sealed manner by welding or bonding. Although vibration will still occur when the bottom shell101is being welded to the top cover102, the abutment member60will constantly abut against the first tab201, preventing the problem of connection looseness caused by the vibration, between the first tab201and the inner wall of the bottom shell101. This can, while ensuring the reliability of the connection between the first tab201and the bottom shell101, improve the reliability of the sealing connection between the bottom shell101and the top cover102, thereby improving the sealing performance of the button cell. In a specific implementation of the button cell provided by the embodiments of the present disclosure, the top cover102is firstly connected, by heating and pressurizing, to the conductive member30through a sealant ring50in an insulated and sealed manner, and then the cell20is placed into the accommodating cavity1011in the bottom shell101. The abutment member60is inserted into the cell cavity203, with a first end of the abutment member60abutting against the first tab201, and a second end of the abutment member60protruding out of the top cover102. By pressing on the abutment member60, the first tab201is pressed against the inner bottom wall of the bottom shell101. The first tab201is welded to the bottom shell101by a welding device. Then, the top cover102having the conductive member30covers the bottom shell101, and the bottom shell101is connected to the top cover102in a sealed manner by bonding or welding, and the second tab202on the cell20is electrically connected to the conductive member30. Then, the abutment member60is retracted, and the electrolyte solution is injected into the accommodating cavity through the liquid injection port301. After the electrolyte solution is injected, the sealing member40covers the injection port301, and the sealing member40is connected to the injection port301in a sealed manner by bonding or welding. In the button cell provided by the embodiments of the present disclosure, the conductive member covers the opening of the top cover, and the top cover is connected to the conductive member through a sealant ring in an insulated and sealed manner, the cell is placed in the accommodating cavity of the bottom shell, the first tab on the cell is welded to the inner bottom wall of the bottom shell, then the top cover having the conductive member is connected to the bottom shell in a sealed manner, and then the second tab on the cell be electrically is connected to the conductive member. An electrolyte solution is injected into the accommodating cavity through the liquid injection port of the conductive member. After the electrolyte solution is injected, the sealing member covers the liquid injection port, and the sealing member is connected to the liquid injection port in a sealed manner by bonding or welding, thereby improving the sealing performance of the button cell. Example II As shown inFIG.6toFIG.9, in a button cell provided by the embodiment of the present disclosure, the conductive member30is provided with the extension part303protruding towards the accommodating cavity. The first glue-overflow groove1022, which is in ring shape, is formed between the extension part303and an edge of the opening, such that a glue overflowing from an inner edge of the sealant ring50may reside in the first glue-overflow groove1022. The overflowed glue can further improve the sealing performance between the conductive member30and the top cover102. The width of the first glue-overflow groove1022in a radial direction of the cell20is between 0.1 and 3 mm, such that the overflowed glue can be accommodated, at the same time, the external dimension of the button cell can also be fulfilled. Alternatively, as shown inFIG.8, a second counter bore is arranged on the top cover102, in which the conductive member30is located, and a second glue-overflow groove1023is formed between an outer edge of the conductive member30and a side wall of the second counter bore. A glue overflowing from an outer edge of the sealant ring50may reside in the second glue-overflow groove1023, further improving the sealing performance between the conductive member30and the top cover102, thereby improving the overall sealing performance of the button cell. Moreover, since the overflowed glue is kept within the second glue-overflow groove1023, the surface flatness and the overall aesthetics of the button cell can be improved. Additionally, the width of the second glue-overflow groove1023in the radial direction of the cell20is configured to be between 0.1 and 3 mm, so that the accommodation of the overflowed glue is ensured while the external dimension of the button cell can also be fulfilled. Furthermore, in order to prevent liquid such as water from infiltrating the cavity of the button cell via the second glue-overflow groove1023, a sealant can also be arranged in the second glue-overflow groove1023to seal up any gap between the conductive member30and the case10, so as to improve the sealing performance of the button cell, where the sealant may be a glue made by mixing any one of acrylic acid, epoxy resin and polyurethane with a curing agent, or a sealant made from other sealing materials, which is not limited in the present embodiment. In a process of assembling a button cell, since the cell20is placed into the accommodating cavity before the first tab201on the cell20is electrically connected to the inner bottom wall of the bottom shell101by welding, etc., an abutment member, which can be a cylindrical pin or the like, is typically inserted into the cell cavity203of the cell20in order to improve the reliability of the electrical connection between the first tab201and the inner bottom wall of the bottom shell101. The first tab201is abutted against the inner bottom wall of the bottom shell101by the abutment member before the first tab201and the inner bottom wall of the bottom shell101are welded. It should be noted that a surface of the first tab201facing the cell is provided with a concave weld mark, at which a welding device welds the first tab201and the bottom shell101by way of, e.g., electric-resistance welding or laser welding. When the electric-resistance welding is used, there can be one weld mark, and when the laser welding is used, there can be four weld marks. In order to ensure the reliability of the welding, a depth of the weld mark can be 20-200 μm; or, a height of the weld bump formed after the welding can be 10-120 μm. The weld bump after welding may be formed to be one or more individual weld bumps, or a straight line formed by a plurality of weld bumps, which is not limited in the present embodiment. A first insulating rubber layer70is arranged between a lower end surface of the cell20and an inner bottom wall of the bottom shell101in order to preclude electrical conductivity between the cell20and the bottom shell101. A second insulating rubber layer80is arranged between an upper end surface of the cell20and the top cover102in order to preclude electrical conductivity between the cell20and the top cover102. Thus, in order to facilitate the insertion of the abutment member into the cell cavity203of the cell20to abut against the first tab201, and in order to leeway for a welding device to weld the first tab201and the bottom shell101, the first insulating rubber layer70in the present embodiment is provided with a first through hole701, which is arranged coaxially with the cell cavity203, where the weld mark on the first tab201should be arranged in an area corresponding to the first through hole701and the cell cavity203. In other words, the first insulating rubber layer70is provided with a first through hole701, so that the first insulating rubber layer70will not shadow the weld mark on the first tab201. This facilitates the welding device to weld the first tab201and the bottom shell101, without having to arrange any weld mark on the outer bottom wall of the bottom shell101. That is, an area on an outer bottom wall of the bottom shell101corresponding to the weld mark will be a smooth flat surface or a rounded surface. Had the weld mark been arranged on the outer bottom wall of the bottom shell101, external strong corrosives might corrode the button cell via that weld mark, compromising the safety and reliability of the button cell. In view of this, the weld mark in the present embodiment is arranged on the surface of the first tab201facing the cell to avoid such external strong corrosives from corroding the weld mark, thereby improving the safety and reliability of the button cell. Furthermore, the second insulating rubber layer80is provided with a second through hole801that is arranged coaxially with the cell cavity203, so that the abutment member can pass through the first through hole701, the second through hole801and the cell cavity203to abut against the first tab201to allow for the welding device to weld the first tab201and the bottom shell101, thereby improving the connection reliability between the first tab201and the inner bottom wall of the bottom shell101, simplifying the assembling of the button cell, and improving the safety and reliability of the cell20. Furthermore, in order to facilitate the insertion of the abutment member into the cell cavity203of the cell20, the diameter of the first through hole701can be greater than that of the cell cavity203, and the diameter of the second through hole801can be greater than that of the cell cavity203, such that the edge of the first through hole701and the edge of the second through hole801will not interfere with the insertion of the abutment member. Furthermore, as shown inFIG.7andFIG.8, in order to ensure operational reliability of the first insulating rubber layer70and the second insulating rubber layer80, and to facilitate the insertion of the abutment member, the diameter of the first through hole701in the present embodiment is 0-0.5 mm larger than that of the cell cavity203, and the diameter of the second through hole801is 0-0.5 mm larger than that of the cell cavity203. In other words, under ideal conditions, the diameters of the first through hole701and the second through hole801and the cell cavity203are the same. In case of fabrication error, the diameter of the first through hole701or the second through hole801may be larger than the diameter of the cell cavity203in order to avoid interference of the first insulating rubber layer70and the second insulating rubber layer80in the insertion of the abutment member into the cell cavity203, as long as insulation is ensured between a lower end surface of the cell20and the bottom shell101, as well as between an upper end surface of the cell20and the top cover102. On the basis of the above embodiment, in order to ensure that the second tab202does not form electrical connection with the top cover102when the second tab202is electrically connected to the conductive member30, a third insulating rubber layer90is arranged in the present embodiment between the second tab202and the top cover102. The top cover102is insulated from the second tab202by the third insulating rubber layer90, so as to improve the reliability of the electrical connection between the second tab202and the conductive member30. In an implementable embodiment, the third insulating rubber layer90is a circular ring that is attached to an inner wall of the top cover102, and covers a location on the second tab202corresponding to the top cover102. Specifically, in order to prevent the third insulating rubber layer90from interfering with the welding or bonding between the top cover102and the bottom shell101, a circumference of the third insulating rubber layer90is smaller than a circumference of the top cover102along the radial direction of the cell20. Furthermore, the third insulating rubber layer90is further provided with a third through hole901that is arranged coaxially with the cell cavity203in order to prevent the top cover102from being electrically connected to the second tab202. Thus, in the present embodiment, the diameter of the third through hole901is less than the radial dimension of the opening of the top cover102. In this way, electrical connection between the second tab202and the top cover102can be avoided, while the second tab202can partially pass through the third through hole901and be electrically connected to the conductive member30. In an embodiment, an outer radius of the third insulating rubber layer90is 0.05-2 mm smaller than that of the top cover102along the radial direction of cell20, and the diameter of the third through hole901is 0-2 mm smaller than the radial dimension of the opening of the top cover102, so that the reliability of the connection between the second tab202and the conductive member30is improved. In another implementable embodiment, the third insulating rubber layer90can be attached to a side of the second tab202closer to the top cover102, forming a protective rubber for the second tab202. A distance between an edge of the third insulating rubber layer90on the second tab202and the axis of the cell20is less than a distance between the opening of the top cover102and the axis of the cell20along the radial direction of the cell20. In other words, the protective rubber on the second tab202extends along the radial direction of the cell20towards the axis of the cell20, with the edge of the protective rubber on the second tab202extending beyond the edge of the opening of the top cover102. In this way, electrical connection can be precluded between the second tab202and the top cover102, thereby improving the reliability of the connection between the second tab202and the conductive member30. On the basis of the above embodiment, as shown inFIG.6andFIG.9, in order to prevent the first insulating rubber layer70from interfering with the connection of the first tab201and the plate of the cell20, edge-cutting treatment is applied to the first insulating rubber layer70in the present embodiment, so that the edge of the first insulating rubber layer70can be formed into a straight line cut edge. For ease of description, the cut edge on the first insulating rubber layer70is referred to herein as a first cut edge702. Along an axial direction of the cell20, the first cut edge702is flush with the first tab201, so as to avoid any interference by the first insulating rubber layer70with the connection of the first tab201and the plate of the cell20. Furthermore, in order to avoid the interference in the connection of the second tab202and the plate of the cell20, edge-cutting treatment is also applied to the second insulating rubber layer80, so that the edge of the second insulating rubber layer80can be formed into a straight line cut edge. For ease of description, the cut edge on the second insulating rubber layer80is referred to herein as a second cut edge802. Along an axial direction of the cell20, the second cut edge802is flush with the second tab202, so as to avoid any interference by the second insulating rubber layer80with the connection of the second tab202and the plate of the cell20, thereby improving the operational reliability of the button cell. Alternatively, the conductive member30is also provided with a liquid injection port301. When the cell20is placed in the accommodating cavity, the first tab201of the cell20is electrically connected to the inner bottom wall of the bottom shell101, and the second tab202is electrically connected to the conductive member30, an electrolyte solution is then injected into the accommodating cavity via the liquid injection port301of the conductive member30. After the electrolyte solution is injected, the liquid injection port301is covered by the sealing member40in a sealed manner. Furthermore, in order to improve the surface flatness of the button cell, a first counter bore for accommodating the sealing member40can be arranged on the conductive member30, and the depth of the first counter bore can be equal to the thickness of the sealing member40. In this way, when the sealing member40covers the liquid injection port301, the sealing member40is flush with the surface of the conductive member30, thereby improving the surface flatness of the button cell. In specific implementation of the button cell provided by the embodiment of the present disclosure, the top cover102is firstly connected to the conductive member30via the sealant ring50in an insulated and sealed manner by heating and pressurizing, then the cell20is placed into the accommodating cavity of the bottom shell101, and then the top cover102having the conductive member30is connected to the bottom shell101in a sealed manner by welding and the like. The abutment member60is inserted into the cell cavity203of the cell20, with the first end of the abutment member60abutting against the first tab201, and the second end of the abutment member60protruding out of the top cover102, providing ease of handling for a user. With the first tab201being pressed against the inner bottom wall of the bottom shell101by the abutment member, the first tab201is welded to the bottom shell101by a welding device, and the second tab202on the cell20is electrically connected to the conductive member30by welding and the like. Then, the abutment member60is retracted, and the electrolyte solution is injected into the accommodating cavity through the liquid injection port301. After the electrolyte solution is injected, the sealing member40covers the injection port301, the sealing member40is connected to the injection port301in a sealed manner by bonding or welding, completing the assembly of the button cell. Moreover, in the embodiment of the present disclosure, the first insulating rubber layer70is provided with the first through hole701, the second insulating rubber layer80is provided with the second through hole801, and the third insulating rubber layer90is provided with the third through hole901, such that the abutment member can sequentially pass through the third through hole901, the second through hole801, the cell cavity203of the cell20, and the first through hole701and abut against the first tab201, simplifying the assembling of the button cell, and improving the operational reliability of the button cell. In the button cell provided by the embodiment of the present disclosure, the conductive member is provided with the extension part protruding towards the accommodating cavity, with the first glue-overflow groove being formed between the extension part and the edge of the opening, containing the glue which overflows out of the sealant ring in the first glue-overflow groove. In this way, the glue which overflows out of the first glue-overflow groove can additionally seal the conductive member and the case, thereby improving the sealing performance of the button cell. Example III The examples of the present disclosure further provides an electronic device including an electronic device body and the button cell provided by Embodiment I, the button cell provides electrical energy for the electronic device body. In that case, the structure and operating principle of the button cell have been described in detail in Embodiment I, and will not be repeated herein. The electronic device provided by the present disclosure includes the electronic device body and the button cell which provides electrical energy for the electronic device body. In the button cell, a conductive member covers an opening of a top cover, and the top cover is connected to the conductive member via a sealant ring in an insulated and sealed manner. A cell is placed in an accommodating cavity of a bottom shell, with a first tab on the cell being welded to an inner bottom wall of the bottom shell. Then, the top cover having the conductive member is connected to the bottom shell in a sealed manner, and a second tab on the cell is electrically connected to the conductive member. An electrolyte solution is injected into the accommodating cavity via the liquid injection port of the conductive member. After the electrolyte solution is injected, the sealing member cover the liquid injection port, and the sealing member is connected to the liquid injection port in a sealed manner by bonding or welding, thereby improving the sealing performance of the button cell. Various embodiments or implementations in the specification have been described in a progressive manner, with each embodiment focusing on the differences from other embodiments, and for the same or similar parts among various embodiments, cross-reference can be made to each other. In the description of the specification, reference terms “an embodiment”, “some embodiments”, “illustrative embodiment”, “example”, “specific example” or “some examples” mean that specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present disclosure. In the specification, the illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner. Finally, it should be noted that: the above embodiments are only used to describe the technical solutions of the present disclosure, and do not limit the same. Although the present disclosure has been described in detail referring to the above-mentioned embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the above-mentioned embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions will not make the essentials of the corresponding technical solutions depart from the scope of the technical solutions in the embodiments of the present disclosure. | 41,835 |
11862807 | DETAILED DESCRIPTION The invention can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer readable storage medium; and/or a processor, such as a processor configured to execute instructions stored on and/or provided by a memory coupled to the processor. In this specification, these implementations, or any other form that the invention may take, may be referred to as techniques. In general, the order of the steps of disclosed processes may be altered within the scope of the invention. Unless stated otherwise, a component such as a processor or a memory described as being configured to perform a task may be implemented as a general component that is temporarily configured to perform the task at a given time or a specific component that is manufactured to perform the task. As used herein, the term ‘processor’ refers to one or more devices, circuits, and/or processing cores configured to process data, such as computer program instructions. A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured. A battery ejection system is disclosed. The battery ejection system comprises a pressure vessel, a battery submodule positioned at least partially in the pressure vessel and configured to release gas into the pressure vessel, and a seal. The seal is configured to seal the pressure vessel in a first mode and is configured to release in a second mode. The second mode is triggered in the event a pressure level in the pressure vessel exceeds a threshold pressure level. The battery is configured to be disconnected from an electrical connection in the second mode. In some embodiments, a pressure vessel includes or is a cavity which is formed by a structure and a battery of the battery ejection system is partially or completely sealed in such a cavity. In some embodiments, an electrical contact of the battery is positioned within the cavity. For example, the battery is connected to a wire or any other appropriate electrical component within the cavity. In the event of battery failure or malfunction, the battery may vent gases. In some embodiments, the battery is positioned in the cavity such that vented gases from the battery release into the cavity. In the event pressure in the cavity exceeds a threshold pressure that a seal of the cavity is designed to handle, the seal will release. In some embodiments, the battery is ejected from its electrical connection in the event the seal releases. For example, the seal holds the battery in the cavity to make electrical contact and the battery falls from the cavity in absence of the seal. In some embodiments, the force of the vented gas pushes the battery out of the cavity and ejects the battery electrically. In some embodiments, a battery ejection system is used in an electric aircraft. An electric aircraft powered by batteries may require a lightweight system of detecting malfunctioning batteries and removing them from the aircraft's electrical systems. The pressure-based battery ejection system automatically electrically ejects batteries based on an amount of venting gases, which is a measure of battery malfunction. For example, a battery may release gases when it malfunctions whereas a properly functioning battery does not release gases or releases a low volume of gases. Active monitoring and ejection using monitors, gauges, processors, or other heavy equipment is not required. In some embodiments, the battery ejection system provides a reliable, safe, simple, and lightweight way of electrically ejecting malfunctioning batteries. FIG.1Ais a diagram illustrating an embodiment of a pressure-based battery ejection system prior to battery ejection. In the example shown, battery100is positioned inside structure102. Structure102may comprise part of an electrical load (or electrical connection to such an electrical load) that battery100provides power to. For example, structure102may comprise an aircraft framework. In the example shown, seal106between structure102and battery100creates cavity or pressure vessel104. The seal as shown is positioned near one end of the battery, leaving a small portion of the battery unsealed. In some embodiments, the battery is configured to vent gases from a portion of the battery that is sealed in the cavity. In some embodiments, the battery includes a covering that directs gas released by the battery. For example, the battery may be stored in a can that has venting slots that direct where gas released from the battery may travel; such slots may direct any released gases from battery100into pressure vessel104. As shown, the battery has an electrical connection at the end of the battery that is pointing into cavity104. The electrical connection is positioned at one end of the battery whereas the seal is positioned near the midsection of the battery (at least in this example). Battery100has an electrical connection with structure102. In some embodiments, the electrical connection comprises wiring that allows the battery to provide or draw power. In some embodiments (not shown here), seal106does not wrap around the midsection of the battery but rather surrounds the battery such that all of the battery is within or otherwise enveloped by the cavity or pressure seal (e.g., seal106goes below or underneath battery100). In some embodiments, the battery touches or is in contact with structure102at some portions of the battery such that there is no need for a seal where they make contact. For example, seal106may comprise discrete pieces of material that seal multiple gaps between battery100and structure102. In the event a battery fails, it may release gases. In some embodiments, vented gases are released into cavity104. In some embodiments, seal106is designed to withstand up to a threshold level of pressure. The threshold level of pressure may be determined based on a level of battery malfunction that is critical. For example, using a slightly venting battery may be safer than ejecting the slightly venting battery and flying with less power in some cases of electric aircraft flight. A battery venting a large volume of gas and/or a lot of heat may pose a larger risk where it is worthwhile to eject the battery. The threshold level of pressure of the seal may map to an amount of gas corresponds to a high risk battery which cannot be used any longer. In the event pressure inside cavity104exceeds a threshold pressure of seal106, the seal releases. In some embodiments, the pressure provides a force that ejects the battery from structure102. In some embodiments, the release of the seal allows the battery to disconnect from its electrical connection. For example, gravity may cause the battery to fall from structure102. In the example shown, battery100is positioned under structure102. In some embodiments, battery100is positioned atop structure102. In some embodiments, the battery and structure are positioned on their sides (e.g.FIG.1Bis rotated 90 degrees). In all the examples shown, the positioning of the battery and structure may be implemented in a rotated orientation from what is illustrated. Regardless of the orientation, any venting slots (not shown) in a battery's can may be oriented to be facing upwards. This is because the emitted gases may be hot and rise upwards as a result. Venting slots which are positioned or otherwise oriented to be facing upward will more readily permit the hot gases to exit into the cavity or pressure vessel. FIG.1Bis a diagram illustrating an embodiment of a pressure-based battery ejection system after battery ejection. In the example shown, seal106ofFIG.1Ahas released. In various embodiments, the seal ruptures or is pushed off intact. Release of the seal causes battery100to be ejected from its electrical connection with structure102. In some embodiments, battery100is ejected from a high power electrical connection. In some embodiments, seal106is reversible or replaceable. Battery100may be replaced with a new battery by removing the seal, placing a new battery in position such that it establishes electrical contact with structure102, and replacing the seal or putting a new seal in place. FIG.2Ais a flow diagram illustrating an embodiment of a pressure-based battery ejection system comprising a latch and o-rings prior to battery ejection. In various embodiments, various configurations and combinations of seals are used in the pressure-based battery ejection system. In some embodiments, various components are used in combination to create the pressure vessel. The various components may perform separate functions. For example, one component may be used to hold the battery in a position wherein it maintains an electrical connection. The component may exert a force on the battery that pushes an electrical contact of the battery against an electrical contact of an electrical load it powers. The component may restrain the battery within a structure. Another component may be used to create an airtight seal around at least a portion of the battery and the structure. In the example shown, battery200is positioned within structure202. Battery200is held in place by latch208. In some embodiments, latch208keeps battery200in electrical contact with structure202. The latch may comprise a force-regulating latch that has zero deflection under force until it buckles and completely releases when subjected to a threshold amount of force. The latch may comprise a piece of bowed metal that springs from one stable position to another stable position after subjected to a large amount of force. A bistable spring mechanism may be used. In some embodiments, a latch or spring that has two stable positions and changes from one stable position to a second stable position after a certain amount of pressure is exerted is used, wherein one stable position causes the latch or spring to hold the battery in the cavity and another stable position releases the battery. In some embodiments, the latch or spring comprises a flattened portion that is attached to the structure (e.g. structure202). The rest of the latch or spring may pivot around the flattened portion. In the example shown, o-rings204and210are positioned between battery200and structure202. In some embodiments, the o-rings create an airtight barrier but are not strong enough to hold battery200in place. For example, the o-rings may comprise a flexible material such as rubber. In the example shown, the o-rings are held in place via indents in structure202. As shown, o-rings204and210create pressure vessel206. The o-rings may prevent air from escaping from pressure vessel206. The pressure vessel is bounded by structure202and the o-rings. In some embodiments, the front face of battery200as shown and a back face of battery200are flush against structure202. O-rings204and210may block areas where air may escape from pressure vessel206. In various embodiments, any number of o-rings are positioned between the battery and structure to provide an airtight seal and create pressure vessel206. As shown, about half of battery200is sealed inside pressure vessel206, including a portion of the battery that comprises an electrical contact. The electrical contact is in contact with an electrical contact of structure202, creating an electrical connection. In some embodiments, battery200is configured to release gas into pressure vessel206, causing a force to build up on latch208in the event the battery malfunctions. FIG.2Bis a flow diagram illustrating an embodiment of a pressure-based battery ejection system comprising a latch and o-rings after battery ejection. In the example shown, latch208assumes an inverted position compared to its position inFIG.2A. In some embodiments, the latch is configured to invert when subjected to a threshold amount of force. As shown, latch208no longer holds battery200in position and in electrical contact with structure202. In some embodiments, battery200is ejected such that a pressure vessel no longer exists. In the example shown, battery200is ejected past o-rings204and210. The o-rings are not in contact with the battery and a sealed cavity ceases to exist. The o-rings may be configured to allow the battery to slide past them in the event the battery is not held in position by another element, such as a latch. As shown, battery200is no longer electrically connected to structure202. In some embodiments, the electrical contact of battery200is configured to not reestablish an electrical connection with structure202after ejection, even in the event that battery200falls back into structure202. In some embodiments, battery200is positioned underneath structure202and gravity causes battery200to fall from structure202after latch208ceases to hold battery200in electrical contact with the structure. In some embodiments, battery200and structure202are positioned on their sides such that battery200is ejected to one side rather than ejected down or up from the structure. In some embodiments, pressure from vented gases is sufficient to push battery200away from an electrical contact of the structure. For example, the battery may be pushed sufficiently far from an electrical contact of the structure such that it will not regain electrical contact. In some embodiments, latch208is a reversible seal. For example, latch208may be returned to its original position inFIG.2A. In some embodiments, a reversible seal is used to seal battery replacements that are put in place after an original battery is ejected. FIG.3Ais a flow diagram illustrating an embodiment of a pressure-based battery ejection system comprising bolts prior to battery ejection. In some embodiments, non-reversible seals are utilized. For example, once the seal is broken, it may not be reversed to an original position wherein it creates an airtight cavity surrounding at least a portion of the battery. In the example shown, battery200is held in electrical contact with structure302via panel306. Panel306is bolted into structure302using bolts304and308. O-rings310and312as shown create an airtight seal with battery300, creating pressure vessel314from which air cannot escape. FIG.3Bis a flow diagram illustrating an embodiment of a pressure-based battery ejection system comprising bolts after battery ejection. In the example shown, panel306is fractured into multiple pieces. Panel306may be configured to break under a threshold amount of pressure. Bolts304and308remain intact and hold portions of panel306to structure302. In some embodiments, bolts304and306are configured to shear under a threshold amount of force. In the event the bolts shear, panel306may be removed from structure302in one piece, causing battery300to be ejected from its electrical connection. For example, panel306and battery300may fall away from structure302due to gravity in the event battery300is positioned below structure302. FIG.4Ais a diagram illustrating an embodiment of a pressure-based battery ejection system comprising magnets prior to battery ejection. In the example shown, battery400is completely sealed in pressure vessel414using panel406, magnets404and408, and o-rings410and412. Magnets404and408hold panel406against structure402, keeping battery400in contact with structure402at an end of the battery that comprises an electrical contact. In the example shown, panel404is held adjacent to structure402using magnets404and408, which are attracted to magnets that are embedded in structure402. In some embodiments, the magnets and panel do not create an airtight seal. O-rings410and412may create an airtight seal with battery400, creating pressure vessel414. In some embodiments, o-rings or other components are utilized to create a smaller pressure vessel than would otherwise be created by using a seal that encloses the entire battery in the pressure vessel. The positioning of the o-rings or airtight seal component may be determined based on a threshold pressure level of the magnets or restraining component. For example, in the event the magnets are displaced only under a force that is much larger than a force that maps to a dangerous level of gas venting, the o-rings may be positioned to create a small pressure vessel. The battery's enclosure or covering may ensure that released gas is released into the pressure vessel. The small pressure vessel may cause the magnets to be displaced in the event a dangerous level of gas venting occurs. In some embodiments, the panel and magnets hold battery400in a position wherein an airtight seal is created around a portion of the battery using o-rings410and412. FIG.4Bis a flow diagram illustrating an embodiment of a pressure-based battery ejection system comprising magnets after battery ejection. In some embodiments, magnets404and408are configured to separate from magnets embedded in structure402when subjected to a threshold force. In the example shown, magnets404and408have separated from magnets embedded in structure402, causing panel406to be removed from its prior position. As shown, panel406is not in contact with structure402, allowing battery400to be ejected from its electrical connection. In various embodiments, reversible or irreversible seal components are utilized in various positions around a battery. In some embodiments, seal components are used only between the battery and an electrical load the battery powers. For example, in lieu of o-rings between battery400and structure402, a magnet may be used that is dislodged from its position with a specified amount of force. A latch may be used between a battery and an electrical load the battery provides power to create an airtight cavity. In some embodiments, seal components are used only externally on the battery and powered electrical load. For example, a battery may be completely enclosed in a pressure vessel constrained by a seal. In some embodiments, a combination of seal components in various positions is used. FIG.5Ais a diagram illustrating an embodiment of a pressure-based battery ejection system comprising shear o-rings prior to battery ejection. In the example shown, shear o-rings504and506are positioned on either side of battery500. The shear o-rings are positioned between the battery and structure502. In some embodiments, the shear o-rings each comprise two flexible o-rings connected by a component that shears under a threshold force. In some embodiments, the component consists of a brittle material. In the example shown, structure502and battery500are shaped to accommodate the shear o-rings. Pressure vessel508comprises an airtight cavity bounded by shear o-rings504and506, battery500, and structure502. In some embodiments, shear o-rings504and506hold battery500in a position wherein the battery is in electrical contact with structure502. FIG.5Bis a diagram illustrating an embodiment of a pressure-based battery ejection system comprising shear o-rings after battery ejection. In the example shown, the component that connects the o-rings of each shear o-ring has broken due to pressure created by vented gases. As shown, o-rings510and512previously of shear o-rings504and506respectively remain positioned in a covering of the battery. For example, o-rings510and512remain positioned lodged in indents of a can battery500is stored in. O-rings514and516previously of shear o-rings504and506respectively remain positioned lodged in indents of structure502. Battery500is ejected from its electrical connection with structure502. FIG.6Ais a diagram illustrating an embodiment of a pressure-based battery ejection system which includes an orifice in the pressure cavity. In the example shown, battery600is held in position via latch602while o-rings604and606create an airtight seal to pressure vessel608. In the example shown, pressure vessel608comprises orifice610. In various embodiments, pumps or venturis connected to the orifice are used to modify a pressure level inside the pressure vessel or extract vapor samples for battery health monitoring. In some embodiments, pressure inside pressure vessel608is regulated to change characteristics of the battery ejection so that system can be used with different types of batteries which vent gases at different rates. For example, a vacuum or pressure-regulating device attached at orifice610may be used to calibrate or adjust the pressure inside the pressure vessel so that the battery is ejected at whatever pressure level corresponds to an unsafe and/or undesirable level. Alternatively, in lieu of pressure regulation (e.g., for systems which do not include a vacuum or pressure-regulating device), latch602may be released while battery600is still safe to use. For example, the latch may be released when battery600is venting at low levels if there is no pressure regulation. In an aircraft application, a pressure-regulating device may equalize pressure inside the pressure vessel to match pressure outside the aircraft via the orifice. In some embodiments, the pressure-regulating device ensures that pressure changes due to altitude do not cause the seal of the pressure vessel to release. Over long time scales, the pressure-regulating device may cause pressure to equalize, whereas a sudden venting of gas caused by battery malfunction cannot be equalized quickly enough by the pressure-regulating device and the seal is released. In some embodiments, an interior of the pressure vessel or cavity comprises a thermally resistant coating. Gases released during battery malfunction may be hot. In some embodiments, the coating is ablative and vaporizes when subjected to heat. Vapors created by the coating may be accounted for in calibrating the seal for properly timed battery ejection. FIG.6Bis a diagram illustrating an embodiment of a pressure-based battery ejection system comprising an exhaust monitor. In some embodiments, an exhaust monitor is used to analyze gas in the pressure vessel. In the example shown, exhaust monitor612analyzes gas from pressure vessel608via a tube that connects the exhaust monitor to the pressure vessel. The exhaust monitor may determine whether battery600is (e.g., abnormally and/or dangerously) venting gas based on the composition of gas in the pressure vessel. For example, malfunctioning batteries release electrolytes of specific compositions. In the event exhaust monitor detects the electrolytes in the pressure vessel, the battery may be determined to be (e.g., abnormally and/or dangerously) venting and responsive actions may be performed. In some embodiments, a warning is automatically delivered to relevant systems or persons in the event the battery is determined to be venting. For example, a pilot or autopilot system of an aircraft is automatically and/or in advance warned via an aircraft application of the system. In some embodiments, the pressure-based battery ejection system is calibrated to eject a venting battery only when a volume of released gases indicates the battery cannot be used any longer, which is designed to occur after the indicative electrolytes have been detected. However, a battery that has started to vent or is venting a low volume of gas may provide an (e.g., early) indication to a pilot or autopilot that the aircraft should be landed soon or power intensive aircraft maneuvers should be avoided. In some embodiments, the exhaust monitor is part of a suite of battery management elements. In some embodiments, a pilot or autopilot forcibly ejects a battery based on information collected by the exhaust monitor. For example, batteries of the pressure-based battery ejection system can be actively ejected in addition to passively ejected due to pressure. FIG.7is a flow diagram illustrating an embodiment of an exhaust monitoring process. At700, gas in the pressure vessel is analyzed. At702, it is determined whether threshold levels of venting gases are detected. In some embodiments, various types of gases have different threshold levels. Multiple gases may be required to be detected above their respective threshold levels. In the event threshold levels of venting gases are not detected, gas in the pressure vessel continues to be analyzed. In the event threshold levels of venting gases are detected, at704a warning is provided to a pilot. In some embodiments, a battery corresponding to the pressure vessel is actively ejected in the event a second higher threshold level of venting gases is detected. FIG.8Ais a diagram illustrating an embodiment of a spring contact electrical connection. In various embodiments, the battery is connected to the rest of the electrical system using various configurations of electrical contacts. In some embodiments, the electrical contacts are designed to establish an electrical connection that is easily disconnected. For example, the electrical contacts will not continue to hold the battery in place after the seal of the pressure vessel is released. In some embodiments, the electrical contact of the battery and the electrical contact of the electrical load are configured to disconnect in the event some pushing or pulling force causes the electrical contacts to electrically and/or physically disconnect. In the event the battery is subjected to a force (e.g. pressure from gas build-up or gravity) that causes it to lose contact with the electrical load, the electrical connection is broken. In some embodiments, the electrical contact of the battery must be subjected to a force that pushes it firmly against the electrical contact of the electrical load, otherwise the electrical connection is broken. In the example shown, battery800includes plate802. Plate802is in electrical contact with spring-loaded contact804. In the event the plate and spring are no longer touching, the electrical connection is broken. In some embodiments, a pogo pin is used for spring-loaded contact804. In the event a spring of the pogo pin is compressed, the electrical connection is complete. In the event the pogo pin is not compressed, the electrical connection is broken. In some embodiments, the battery is held in a position that compresses the pogo pin in the event the seal is intact. In some embodiments, the electrical contact is designed such that an electrical connection will not reconnect or reform after battery ejection. For example, the spring of the pogo pin may be able to withstand the weight of the battery. In the event the battery is ejected up from the structure and falls back down, the weight of the battery would not be sufficient to reform the electrical connection. In some embodiments, a seal (e.g. a bolt, a latch, or a magnet) must be replaced to reform the electrical connection. FIG.8Bis a diagram illustrating an embodiment of a blade and spring electrical connection. In the example shown, battery820includes blades822and824. The blades extrude from the battery. The blades are in electrical contact with springs826and828(sometimes referred to as a clip). Spring826comprises two pins that blade822slides in between. In some embodiments, the pins of spring826are tensioned to hold blade822securely and create a secure electrical connection. Blade824is situated in between two pins of spring828. In the event battery820is ejected, blade822and824may slide out from springs826and828. As shown here, in various embodiments, various types of electrical contacts are used. FIG.9is a diagram illustrating an embodiment of an aircraft which includes a pressure-based battery ejection system. In the example shown, aircraft900includes (forward) wing918and (rear) wing936. Wing918includes pylons908and916, on either side of the fuselage. Pylon908includes rotor902and rotor engine904. Pylon908also includes eight batteries, including battery906. In various embodiments, 4, 10, 12, or any appropriate number of batteries are stored in a single pylon. Pylon916includes rotor910and rotor engine912. Pylon916also includes eight batteries, including battery914. Wing936includes pylons926and934, on either side of its fuselage. Pylon926includes rotor920and rotor engine922. Pylon926also includes eight batteries, including battery924. Pylon934includes rotor928and rotor engine930. Pylon934also includes eight batteries, including battery932. In this example, the pressure-based battery ejection system is installed on each battery shown. For example, battery906is stored at least partially within a sealed cavity, wherein a seal on the cavity is configured to release in the event a threshold level of pressure is reached within the sealed cavity. In some embodiments, the batteries are positioned such that an end of the battery that does not have an electrical contact faces downwards towards the ground in normal flight. For example, a latch or panel may be positioned below the battery and hold the battery in place. In the event the latch or panel releases, the battery is dropped and ejected from its electrical connection. The battery may be ejected from its electrical contact via gravity following the release of the seal. In some embodiments, the battery is ejected from its electrical connection but remains in the aircraft. In some embodiments, the battery is ejected completely from the aircraft. In the event the battery is ejected from the aircraft, the aircraft may comprise safety mechanisms to prevent the battery from becoming a projectile. For example, the battery may be attached to the aircraft via a tether. In some embodiments, the batteries are positioned to be ejected upwards from the aircraft or laterally in parallel with the aircraft's wings. For example, a battery may be ejected upwards from the aircraft. The battery may comprise an electrical contact that will not establish an electrical connection with the aircraft after ejection. The battery may be ejected out to one side of the aircraft rather than downwards. In some embodiments, the pressure-based battery ejection system is permitted to eject a central or primary battery of an aircraft if/when appropriate. Alternatively, in some embodiments, the system is only permitted to eject batteries that do not have a significant impact on the aircraft's center of gravity or power levels if/when appropriate. For example, the ejection system is only coupled to smaller or outboard batteries wherein the ejection of the batteries does not have a severe adverse effect on flight. In some embodiments, a battery of the pressure-based battery ejection system is configured to allow vented gases to escape from the battery quickly in the event the battery is disconnected from all electrical connections. FIG.10is a diagram illustrating an embodiment of a barrier between batteries. In some embodiments, multiple batteries implementing the pressure-based battery ejection system are positioned next to each other (see, e.g., how multiple batteries are stored in the same pylon inFIG.9). In some embodiments, a barrier is positioned between batteries. The barrier prevents heat transfer between batteries. For example, barriers1000,1010, and1016may comprise fire-retardant divisions. The barriers prevent hot gas released from battery1002from heating up battery1012. Excessive heat from one battery may cause an adjacent battery to catastrophically fail, creating a domino effect of failing batteries and fire-retardant divisions would prevent this from happening. In the example shown, battery1002and battery1012are positioned in alignment. For example, latches1004and1014are in parallel. FIG.11Ais a diagram illustrating an embodiment of a latch prior to battery ejection. Ejecting multiple adjacent batteries may cause an unsafe change to a center of gravity of a vehicle or aircraft. In some embodiments, ejecting two or more adjacent batteries causes that section of the aircraft to be dangerously underpowered. The weight or power changes that occur due to ejecting multiple batteries in close proximity may pose more danger than continuing to use the venting batteries. In some embodiments, mechanical means are used to prevent a battery from ejecting in the event an adjacent battery has already been ejected. In the example shown, battery1100is held in position via L-shaped latch1102. The latch is used in conjunction with o-rings. Adjacent battery1104is sealed partially in a pressure vessel utilizing o-rings and L-shaped latch1106. FIG.11Bis a diagram illustrating an embodiment of a deployed latch that prevents a neighbor battery from ejecting. In the example shown, L-shaped latch1102has released, allowing1100to be electrically disconnected. L-shaped latch1102is now in a position where it restrains battery1104. In the event latch1106releases, battery1104will remain electrically connected to the electrical load it powers due to latch1102. Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, the invention is not limited to the details provided. There are many alternative ways of implementing the invention. The disclosed embodiments are illustrative and not restrictive. | 33,869 |
11862808 | DETAILED DESCRIPTION Referring now to the drawings, an exemplary embodiment of a battery pack200(FIG.1) and battery exchange station100(FIG.4) will be described. The battery pack200and battery exchange station100can be used, for example, to implement a battery exchange system. A problem in prior art battery exchange systems is the inability to accurately track battery wear during the useful life of the battery. This inability to account for battery wear remains an obstacle to widespread adoption of battery exchange systems. Every kilowatt hour (kWh) stored and withdrawn from a battery causes some battery wear because the chemical constituents do not all always return to their original configuration after a charge-discharge cycle. The wear rate is highly dependent on how the battery is used. Temperature, state of charge, and charge and discharge current levels are all known to effect battery wear rates by as much as a factor of ten or more. Use is under the control of the battery renter while the cost of wear is borne by the battery owner. Battery renting is a risky venture unless the variable cost of wear can be accounted for. As an illustration of the relative importance of battery wear costs consider the following example using battery costs and wear numbers consistent with current trends projected a few years into the future. For example, assume that the rechargeable battery initial cost be $150 per kWh of storage capacity with a residual value of $50 per kWh of capacity after it is worn down too much for further prime vehicle use. When capacity is no longer sufficient for prime vehicle use, it still will likely be useful for utility load leveling, storage of intermittent energy from solar or wind, or rental as a lower grade vehicle battery. The battery would deliver 1500 charge-discharge cycles during its normal wear life at moderate temperatures and cycling between 10% and 90% capacity. Thus, during its normal life, the average capital value of a battery pack would be $100 per kWh of capacity and deliver 0.8 kWh per kWh of gross capacity for each cycle. Battery cycling wear would consume $100 worth of battery capital value during its 1500 cycle lifetime. Each kWh delivered from the battery pack thus has a normal wear cost component $0.083=100/(1500×0.8). Charging or discharging at higher than normal currents, at high or low temperatures, and/or outside the 10% to 90% capacity range can increase wear costs by a factor of 10 or more. Compared to a typical $0.12 per kWh cost of the energy passed through the rechargeable battery, the battery wear cost is very significant and increased wear cost from accelerated wear can cost several times the value of the energy. For vehicle users 10 kWh of energy from a battery delivers about the same propulsive energy to the driving wheels as a gallon of gasoline. Thus, for the driver using the projected current battery technology, battery wear cost is equivalent to about $0.83 to over $8.30 per gallon of gasoline for a fuel powered vehicle. Adding the typical $0.12 per kWh energy charge to the battery wear cost, the total cost of battery energy would be in the range of about $2.03 to over $9.50 for 10 kWh delivering the useful energy equivalent to a gallon of gasoline. If the battery pack is recharged at home with off peak electricity costing $0.06 per kWh, the cost per 10 kWh from the battery could be as low as $1.43. Battery owners can be compensated with rent for the capital value of their rental property. A battery pack with a 25 kWh capacity would be worth on average $2500 during its lifetime using the projected numbers above. At 12% return to the owner, a pack would cost the renter $25 rent per month for continuous use. Renters using these battery packs for long trips could expect to pay about $1.67 rent per day assuming that the packs are in use only half the days available in a year. Rent would be in addition to energy and battery wear charges. Renting several battery packs would be very similar financially to renting a car. Renters with good credit could secure the contract with their credit cards. Others could set up an account secured by a deed of trust on the vehicle at the time of purchase. Continuous renters could be billed an assumed normal monthly wear charge added to the rent with an accurate reckoning when battery packs200are swapped periodically or when battery wear data is sent to the battery exchange station100. The methods and apparatus disclosed herein enable transfer of rental battery wear costs to the renter. In one embodiment, rental costs comprise three components. The first component is a conventional rent charge for use of the capital value of the battery. The second component is a charge for the energy supplied to the renter. The third component is a variable charge for the wear cost imposed by battery use. Wear cost is determined from measured and recorded wear accelerating stress parameters such as state of charge, voltage, current levels, and temperature. A renter can be provided with one or more options for charging battery wear costs. In one embodiment, the renter can elect between a fixed wear cost mode and a variable wear cost mode. In the fixed wear cost mode, the battery wear costs comprises a predetermined cost per kWh based on normal or average usage patterns. When the fixed wear cost mode is selected, the user is given a high wear rate allotment. The high wear rate allotment is a budgeted amount of high wear rate operation based on average usage patterns. The fixed wear cost mode limits battery use to limit high wear situations and reduce wear to some predictable average level with a corresponding average wear charge per kWh. For example, the battery pack200may limit the total operating time above a threshold current for the fixed wear cost mode. The battery pack200can output warning messages to the driver in fixed wear costs mode, which could be either audible or visual warnings, to warn the driver when high current operation is limited. The variable wear cost mode determines battery wear cost based on the stress parameters and displays the instantaneous cost of energy plus wear to let the driver control battery wear stress and rental cost. The variable wear cost mode lets the user control those costs. When fixed wear cost mode is selected, the high wear rate allotment will sometimes be exhausted. There are several ways this situation can be handled. One approach is to limit or prevent high wear operation once the high wear rate allotment is used while issuing a driver warning. For example, current levels in and out of a battery pack can be limited once the high wear rate allotment is exhausted. Another staged method is to reduce the maximum allowable wear rate in steps as the user gets closer to the high wear rate limit. For example, the maximum allowable current can be reduced by a fixed percentage (e.g., 20%) when 80% of the high wear rate allotment is used and then reduced further when the high wear rate limit is reached. A variation of this approach is to gradually reduce a maximum allowable wear rate as allotment exhaustion approaches and issue a driver warning. Limiting high wear rate operation depending on the remaining allotment for high wear rate operation extends the amount of time that high wear rate operations can continue and allows the driver time to adjust to the limitations on high wear rate operation. A different approach is to switch operation modes from fixed wear cost to variable wear cost and issue a driver warning. The driver can be warned about an impending change in the operation mode before the high wear rate limit is reached and warned again when the operation mode is switched. The mode switching method has the advantage of imposing no limits on battery power at an inconvenient time, such as a passing or merging maneuver needing maximum available power. A further variation is to automatically terminate the recently entered variable wear cost mode after perhaps a minute of normal wear rate operation to avoid excessive surprise billing for high wear when the user has chosen the fixed wear cost mode. In some embodiments, the user may be given the option to remain in fixed wear cost mode or to change to variable wear cost mode. If the user elects to remain in fixed wear cost mode, high wear rate operation can be limited as described above. In some embodiments, the default option in case no user input is received is to switch operation modes, i.e. the user must explicitly reject the change. In other embodiments, the default option in case no user input is received is to remain in fixed wear cost mode, i.e. the user must explicitly accept the change. If the wear cost mode has been switched from fixed wear cost mode to variable cost wear cost mode, it can be switched back to fixed wear cost mode by recharging the battery pack to add additional kWh. Each kWh of energy added in the fixed wear cost mode adds to the high wear allotment. Thus, adding kWh resets the high wear allotment to permit continued operation in the fixed wear cost mode. Recharge kWh can come from energy sources external to the vehicle or from regenerative braking. If both fixed and variable wear cost modes are used during a rental period, billing for both modes usage is needed. There may be circumstances in which a battery pack200is recharged during a rental period. In this case, the high wear rate allotment can be adjusted automatically based on the amount of energy added to the battery pack200. FIG.1illustrates an exemplary battery pack200for use in a battery exchange system that enables accounting for battery wear. The battery pack200comprises a case202containing a battery204, a power interface208for coupling the battery pack200to the vehicle or charging station, a current control circuit210for regulating the current supplied to or from the battery204and for supplying power to the other components of the battery pack200, a sensor control212for collecting data from sensors206related to energy consumption and accumulated wear on the battery204, a processing circuit214for controlling data collection, processing collected data and communicating with the battery exchange system, memory216for storing computer programs and data, a data interface218enabling communication between the battery pack200and battery exchange system, and a data connection200for communicatively connecting the battery pack200to the battery exchange system. The case202protects the contents of the battery pack200and is of a standardized configuration to mate with vehicles using a standardized interface. The act of latching the battery pack200into a vehicle or charging station complete connections to the power interface208. Additional connections (not shown) may be provided for any required thermal management fluids. Battery204is an assembly of electrochemical cells205typically connected in parallel to achieve the desired current and in series to achieve the desired voltage for the complete battery. One or more cells205can serve as test cells205T for monitoring battery wear. Alternatively, the vehicle may include one or more test cells205T external to the battery pack200. In some embodiments, the test cells205T can also be used to power to the vehicle. In other embodiments, the test cells205T are used solely to monitor battery wear. The battery204may include maintenance features such as switching elements to disconnect defective cells205and cell balancing capability. As those skilled in the art will recognize, the battery204can also have thermal management connections between cells205and the thermal management fluids supplied by the vehicle or charging station. The battery204also comprises sensors206for all parameters significantly effecting battery wear such as cell voltages, charging and discharging battery current, and temperature. The specific sensors206required depend on the particular cell design chosen. Sensor data is read by sensor control212through sensor connection222and supplied to the remainder of the data handling system via data bus226. Data collection and sensor control is managed by processing circuit214through control bus224which contains an address bus, control lines and a low voltage supply connection. The low voltage supply for the data handling parts comes from a dc-dc converter, which is part of the current control and power supply circuit210. Current control and power supply circuit210also has switching elements to limit charge and discharge currents to control battery wear. Current limiters in the current control and power supply circuit210limit high wear operation when the limit set by the battery pack owner is reached. High voltage power is transferred to and from the battery through connection228. External power for charging or discharging connects through power interface208and power line230. The external voltage at the power interface208is not necessarily the same as the battery voltage because current control and power supply circuit210may contain a power dc-dc converter or inverter in addition to the low voltage dc-dc converter supplying power to the battery pack200. Data interface218and current control210supply the vehicle computer with battery pack data and control means to limit operation as herein described. The processing circuit214reads program code and data from memory216, receives internal data from sensor control212, receives external data from data interface218via data bus226, and issues control signals through control bus224. The processing circuit214stores sensor data and the results of calculations of battery wear, battery state of charge (SOC), battery state of health (SOH), sensor data, and time in memory216using data bus226and control bus224. In some embodiments, the processing circuit214computes the amount of battery wear (e.g., percentage of wear), or battery wear rate (e.g., cost per kWh), at a predetermined measurement interval and stores the amount of battery wear or battery wear rate for each measurement interval in memory216. In some embodiments, the processing circuit214further computes the battery wear cost for the measurement interval based on the battery wear amount or battery wear rate. Processing circuit214can store the battery wear cost for each measurement interval in memory216, and/or may add the battery wear cost for each measurement interval to an accumulated battery wear cost for a usage period (e.g., rental period). Memory216comprises both volatile and non-volatile memory for storing computer program code and data needed by the processing circuit214for operation. Memory216may comprise any tangible, non-transitory computer-readable storage medium for storing data including electronic, magnetic, optical, electromagnetic, or semiconductor data storage. Those skilled in the art will recognize that the memory216must be secure to protect program and data from tampering by battery pack renters since it holds wear cost information for which they will be billed. The processing circuit214also outputs selected data and calculation results to external users through data interface218. Data interface218comprises a circuit for communicating with the battery exchange system100, the vehicle, or other external devices. The data interface218may comprise a wired or wireless interface. Data interface218also enables the battery pack200to share data and control signals with the vehicle computer, for example, to display data on the instrument panel or limit certain operations. Data connector220provides means for coupling the battery pack200to the outside world to enable the communication of data. Connector220can be adapted to the data communication format being employed. For wired communications, the data interface218may comprise a serial interface (e.g. USB interface) or Ethernet interface and the data connector220may comprise a serial port or Ethernet port. For optical communications, connector220may be an optical fiber connector. For wireless communications, the data interface may comprise a cellular radio interface (e.g., LTE or 5G), BLUETOOTH® interface, or wireless local area network (WLAN) interface and the data connector220may comprise an RF antenna or antenna array. For wired interfaces, the data connection would be completed with the vehicle by inserting and latching the battery pack in place. If the data connection is the antenna of a wireless data transfer system then it functions without mechanical latching. A wireless data transfer system has the further advantage that battery packs200can be monitored when they are on storage racks before or after recharging. FIG.2illustrates an exemplary process300implemented by a battery pack200when installed in a vehicle. The process begins when battery current flow exceeding the value required to maintain battery pack standby is detected, indicating that the battery is either being charged or discharged by the vehicle (305). The processing circuit214in the battery pack200reads and records relevant sensor data including at least battery voltage, current, temperature and the time (310). The processing circuit214also records the cost per kWh of the energy if the battery204is being charged and the kWh received at that cost (315). The cost per kWh would be zero for regenerative braking and otherwise a number received from the vehicle through data connection220. In some embodiments, the processing circuit214adds high power ampere seconds available at a fixed rate per kWh received for each battery pack being recharged through power interface208. The processing circuit214reads vehicle ID, user preset parameters, battery owner preset parameters and battery user preset mode of operation (320). The mode choices are either a predetermined fixed wear charge per kWh or a variable cost with a display of current and average wear costs. Preset parameters can include limits on allowable maximum and minimum state of charge, maximum current limits, operating temperature limits, limits on wear cost per kWh, and whether the user desires a cost per kWh display. Battery owners may want to prohibit operation at extreme currents and temperatures for which accurate wear costs cannot be calculated. They may also limit duration and energy consumption at high wear rates for users choosing a fixed wear cost option. Battery owner preset values would also include the initial state of charge achieved at the most recent swap station charging cycle. The processing circuit214uses the initial state of charge and recorded current and voltages to estimate current state of charge and compute wear cost per kWh based upon state of charge, present current and temperature, and past cycling history (325). In some cases, this computation can be reduced to a mathematical formula to be computed. In other cases, depending on the details of battery chemistry and design, simple formula computation will be inadequate and a lookup table in memory will be necessary to convert the relevant controlling variables into a wear cost number. As those skilled in the art will appreciate, a lookup table gives discrete wear cost numbers for discrete values of controlling variables. Since actual variable values are likely to fall between the discrete table values, the processing circuit214can interpolate between the table values. The processing circuit214records the wear cost per kWh, time, and kWh since the last data point in secure memory206(330). In some embodiments, the battery pack200outputs data to be displayed to the user on the vehicle control panel. In this case, the processing circuit214uses the user preset values to determine whether to display kWh cost (335). If the user has chosen a fixed wear cost mode, the battery pack200can output warning messages to the driver, which could be either audible or visual warnings (340). Since the fixed wear cost mode permits some high wear operation to support actions such as passing on 2 lane roads, merging with high speed traffic, and regenerative braking, the driver needs to be informed of the remaining high power energy flow available. Without the information, the driver might create a safety hazard by initiating a high power maneuver without enough available high power battery capacity to complete it. Drivers would also need to be informed if battery power in or out is being limited due to extreme temperatures. If the user has chosen the variable wear cost mode with a cost display, the processing circuit214outputs the total cost per kWh for display to the driver (345). Additionally, some warning messages can be provided if present extreme temperatures are imposing limits on battery power flow in or out or if desired operation is outside the limits set by the battery owner due to inability to accurately compute wear costs (350). In some embodiments, the user may choose to limit current or average trip wear costs or give warnings at some predetermined threshold. The energy cost would be on a last in first out basis for situations in which there is more than a single cost for energy. Thus after regenerative breaking the energy cost would be zero until the saved braking energy is consumed and the total cost per kWh displayed would be just the battery wear cost. As previously noted, the battery packs200can be configured to output data for display to the driver when the vehicle is in use.FIGS.3A-3Cillustrates exemplary displays that can be incorporated into a multifunction display incorporated into the driver's instrument panel. These examples are not the only display configurations which would deliver the relevant information to the driver. The circular display501inFIG.3Adisplays the cost per 10 kWh and is similar to familiar speedometer, tachometer, and fuel gauge displays. The display501include a first indicator502showing the current instantaneous cost and a second indicator503showing the average cost for a trip. The instantaneous cost indicator502tells the driver how much the current driving situation is costing. The trip cost indicator503shows average cost over some travel distance chosen by the driver. The cost per 10 kWh unit is chosen for illustrative purposes because 10 kWh of electrical energy from a battery delivers approximately the same driving wheel propulsive energy as a gallon of gasoline. Thus, this display501gives the driver cost information which can easily be compared to a familiar cost unit. The particular unit shown is simply convenient. Any other energy unit such as cost per one kWh could also be used if desired by the driver. FIG.3Bcomprises a bar chart display504with two bars. The display504includes a first bar505showing the current instantaneous cost and a second bar506showing the average cost for a trip. The bars505,506can change color to provide additional information. For example, green can be used for low costs, yellow for intermediate costs and red for high costs. Because the bar areas grow in area at the same time as they change color, the bars505,506would be more attention getting. The instantaneous cost displays502and505tell the driver how much the current driving situation is costing. The trip cost displays503and506show average cost over some travel distance chosen by the driver. If the battery pack200is charged while the battery pack200is installed in a vehicle, the displays501and504can be used to show any extra wear costs being incurred due to wear acceleration conditions such as high charging currents or extreme temperatures. The display507inFIG.3Cfor remaining high wear battery operation shows the number of ampere seconds remaining if delivered at a rate of 10 C, meaning that a fully charged battery would be depleted in 0.1 hour. The preset wear limits set the maximum values displayed. As the battery discharges under occasional high wear conditions, the bars508shorten. For the purposes of display, any actual wear rate used to determine rental charges would be normalized to equivalent wear at 10 C and normal temperatures. Each bar508shows the remaining accelerated high power wear for each of the installed battery packs. Because battery packs200can be exchanged individually, they will not all have the same remaining high current wear. The cost information for the driver is delivered from the battery packs200through data interface218. If more than one battery pack200is in use delivering or absorbing energy the cost data from the several packs should be averaged for the driver. The battery pack200can be part of a modular system wherein multiple battery packs are installed in a battery compartment in the vehicle. The battery compartment can be designed for use with battery packs200having different capacities. When a vehicle is equipped with multiple battery packs200, it may not be desirable to simply discharge all installed battery packs200in a vehicle at the same rate. A battery pack200which is owned by or on long term lease to a user would not normally be swapped and could be kept charged as a reserve energy source on a trip. The user may prefer that these battery packs200be discharged last. Battery packs200could also have differing technologies, quality levels, and costs. For maximum economy, lowest cost units could get used preferentially. For maximum performance, all battery packs200could be employed to give maximum peak power without exceeding any applicable current limits for any one battery pack200. On trips during peak travel times when battery packs200might be in short supply near the end of the day and rationed, a strategy of fully discharging each battery pack200sequentially to minimize the number to be replaced would be attractive. The battery pack200may provide the user an interface to select between different usage patterns and strategies. User preference data could be stored in battery packs200, in some vehicle memory, in the user's cell phone, in some remote storage, or any other data storage accessible by the processor making the automatic recommendation. The data interface218and current control provides the vehicle computer with means to selectively discharge battery packs when multiple battery packs200are installed. When returning battery packs200for replacement at an exchange station, the user faces several decisions which could be made automatically using driver preference settings and available battery pack condition data. Typical user preferences might include the existence of an installed battery pack200which the user owns or has on long term lease and does not want to unload, the minimum number of battery packs200needed for local use, the desired maximum distance or time between battery swaps or exchange station, the destination programmed into the vehicle navigation system, the distance remaining to the next planned charger, and the preferred battery pack quality level. These preferences together with battery pack condition data enable a calculation of which particular battery packs200to return. The exchange system can obtain the user preference settings for one or more installed battery packs200and automatically select on or more installed battery packs200to be returned based on the battery information and the user preference information. Similarly, user preferences and battery pack parameters can be used to automatically select the battery packs200to install from the stock at the exchange station. The driver would simply have to authorize the computed result if it is satisfactory or make any needed modifications if needed. User preference data could be stored in battery packs200, in some vehicle memory, in the user's cell phone, in some remote storage, or any other data storage accessible by the processor making the automatic recommendation. FIG.4illustrates an exemplary battery exchange station100for swapping battery packs200in a vehicle. The battery exchange station100comprises an automated battery pack handler102for automatically exchanging the battery packs200, a power rack104for storing, charging and discharging the battery packs200, a power interface106coupling the power rack to external power108, a data interface110for reading data stored in the battery packs200, a processing circuit112, a customer interface114and an operator interface116. The automated battery pack handler102is a robotic machine that automates replacement of battery packs200in a vehicle. The battery pack handler102locates indexing markers on a vehicle, orients itself with the vehicle, and reads vehicle data such as VIN and typical energy consumption per mile. It opens any protective cover on the vehicle battery pack compartment, disconnects power, data, and temperature control connections on any packs to be removed, unfastens and removes any packs to be returned and transfers them to the power rack104. The battery pack handler102reconnects the battery packs200placed into the power rack104to power, data connections, and temperature control capability in the power rack104. The battery pack handler102then removes the desired number of recharged battery packs200from the power rack104and installs them in the vehicle. The removal from the power rack104and installation in vehicle process require disconnecting all connections to the power rack104and reestablishing connections between each battery pack200and the vehicle, fastening each battery pack200into the vehicle, and closing and fastening any protective covers on the vehicle battery compartment. The power rack104supports the heavy battery packs200securely while providing connections for data, power, and temperature control for each battery pack200. Power interface106connects each battery pack200to external power108to permit battery recharging and also battery use for utility grid load leveling and spinning reserve. Both load leveling and spinning reserve are very valuable to power grid economics and stability. Load leveling reduces grid peak power use while adding off peak load to more fully utilize the system while avoiding overloads. Battery packs200can supply power during peak times and be recharged off peak. Spinning reserve is a name given to the capability of a power grid to compensate for a large loss of generation in a few milliseconds to prevent system outages. In the past grid operators actually kept generators spinning at less than full power to provide this nearly instant compensation. Now they supplement actual spinning reserve with controlled load shedding and other rapidly starting power sources such as batteries. Both load leveling and spinning reserve provide a significant potential revenue source from unrented batteries in the power rack. The power interface106needs to be bidirectional to realize this revenue. Bidirectional means DC power out and in on the battery connection120and AC power in and out on the power grid and external power connection122. The external power108could be some combination of grid power, local renewable energy, and fuel fired peaking generation. Data interface110enables the exchange station100to communicate with the battery packs200, the vehicle or other external devices as well as the power rack104using wired or wireless technologies. In vehicle battery data could be collected through a wired or optical connection placed by the automated battery pack handler102as part of the exchange process. In vehicle data could also be collected wirelessly using any of several wireless communication protocols. Since most vehicles are cell phone linked via BLUETOOTH® that may be the preferred wireless data transfer means. Cell phone data transfer would permit convenient data collection and monthly billing for battery packs on long term rental which are recharged by users and not swapped. Processing circuit112contains a CPU and memory to receive battery pack data, renter and station operator data inputs, external power data inputs over data bus109and processes the data. Output display data is supplied to both users and operators. Billing information is generated based upon battery pack usage time, wear sustained, and energy supplied and sent to customers. Control outputs are sent on control bus111to operate the battery exchange station100. Battery pack data collected can also be processed to estimate when a particular battery pack200should be removed from its current service level, sent for repair, diverted to static energy storage, or scrapped. Customer interface114supplies the customer with progress information during the swap process. It also gives billing information and lets the renter designate which battery packs200are to be removed and how many are to be installed. If a customer is a few miles from the end of a trip, there would be no reason to replace all the exhausted long trip battery packs200. Also, a renter may have a long term rental battery pack200for local use and could want to keep it as a known familiar quantity rather than take whatever is next in the power rack104. The operator interface116supplies the station operator with necessary information such as power rack battery inventory and charge condition, external power conditions, customer wait times, and customer behavior. Those skilled in that art will appreciate that not all of the elements inFIG.4need to be in the same location. A remote operator could monitor several stations. The processing circuit112could be distributed with station functions handled at the station, operator functions handled near the operator, and billing handled from a central office. FIG.5illustrates an exemplary process400implemented by processing circuit112when a battery pack200is returned to a battery swap station. When the battery pack is detected by the processing circuit, the processing circuit reads the renter identification and directs billing to the correct account (405). If more than one battery pack is in use, they will probably be discharged sequentially as the user drives. Thus, only the depleted packs will need to be returned and some or all replaced with recharged packs. This step transfers the desired battery packs from the vehicle to the recharge station. In one embodiment, the processing circuit112obtains, via the battery pack interface, battery information. the processing circuit112further obtain user preference information for one or more installed battery packs200. The user preference information can be obtained from the battery pack, from the vehicle computer, or some other source. The processing circuit112automatically selects one or more installed battery packs to be returned based on the battery information and the user preference information. The processing circuit112records the battery pack identifying number, use history, return date and time, wear added during the just completed rental period, and accumulated wear for each returned pack (410). In one embodiment, the processing circuit112obtains, via the battery pack interface, battery wear information stored in the each returned battery pack200. The battery wear information may comprise, for example, information indicative of battery wear during a usage period. The processing circuit112determines a wear cost mode for one or more time periods during the usage period. Based on the wear cost mode, the processing circuit112determines a battery wear cost for the usage period and the wear cost mode(s) for the one or more time periods. For time periods using the fixed wear cost mode, the battery information indicative of battery wear comprises a battery wear cost per unit of energy delivered by the battery (e.g., per kWh) and an amount of energy delivered by the battery over the time period. For time periods where variable wear cost mode is used, the battery information indicative of battery wear comprises data indicative of an amount of battery wear, battery wear rate, or both. The processing circuit records the data acquired to a data store for the owner of each battery pack (415). It is likely that if there are several battery packs200in a vehicle, they come from more than one battery pack owner. The exchange system may maintain separate data stores for each owner or may maintain a single data store for all owners. The processing circuit112charges the renter's account for energy estimated to recharge each returned pack, wear costs for each returned battery pack200, and the time charge for use of the capital value for the interval between rental and return (420). The recharge station is credited with the kWh energy charge. Battery pack owners are credited with each time rental charge and wear cost charges for each unit returned. Owner-defined wear parameter limits and recharge limits are loaded into each battery pack memory (425). These numbers are individualized by battery pack because not all will necessarily have the same design or battery chemistry. As batteries age, the required limiting values for parameters such as charge current, recharge current, and temperature may change. Limits on operating parameters serve to limit wear rates for the fixed wear charge operating mode and keep operations out of extreme situations beyond the limits of accurate wear rate determination. The processing circuit112recharges the battery pack200to return the battery pack to the desired maximum state of charge and is an opportunity for routine maintenance such as cell balancing to approximately equalize the state of charge of the individual cells205(430). Other maintenance functions such as fluid replenishment, dendrite removal, or defective cell replacement can also be done at this time. Maintenance may require temporarily attaching or inserting sensors or other implements to or into the battery pack200. The maintenance specifics depend upon the particular cell chemistry and design employed in the battery pack200. The actual kWh used to recharge the battery pack200, the state of charge achieved, and the cost per kWh is recorded for accounting purposes. After recharging is complete a final accounting is made of the actual kWh used to recharge each battery pack200to the original state of charge at the start of the rental period (435). The final accounting is used credit or debit the accounts of the renter and the recharging station. The processing circuit112may also evaluate the battery pack quality and capacity after the battery pack200is returned (440). Capacity can be determined from the kWh used to achieve each 1 percent increase in the state of charge. Energy needed per each 1 percent increase in state of charge can be determined from the beginning and ending state of charge and the energy used for recharging. Battery state of health determination can use variations between individual cell parameters and the internal resistance of the overall battery to estimate health. Accumulated wear would be a significant predictor of reliability. Other parameters such as temperatures during the charge cycle may be useful depending on the cell chemistry and design. The battery pack owner and the next battery pack renter are informed of the battery pack state of health, kWh per percent increase in state of charge, and state of charge to determine the kWh available to the next renter by storing those values in the battery pack memory and also sending them to the battery pack owner (445). The processing circuit112sorts the battery packs200sorted according to quality (450,455). The highest quality battery packs200with the least loss in capability due to wear are identified and designated for premium use (450). Battery packs200that are somewhat worn but still adequate for rental use in vehicles are also identified and designated for economy use (455). Packs suitable for vehicle use would be stored until rented to the next user. If the battery packs200remain in service, the battery information can be updated by the rental computer system to reflect any changes in capacity or costs (460). When the battery pack200is rented, the battery pack200is installed in another vehicle and the process ofFIG.2is performed (465). Battery packs200that do not qualify for premium use or economy use are removed from service (470). Battery packs may be retired from use due to factors such as lack of kWh capacity, inadequate peak current capability for acceleration and regenerative braking, or probable unreliability. The retired battery pack200can be sold or used for some alternative purpose and revenue realized can be credited to the owner's account (475). For example, the battery pack200could be sold for some alternative use such as utility load leveling or storage of intermittent solar or wind energy. Battery packs200removed from vehicle service may also find a market powering fast chargers for vehicle batteries. Fast chargers require large peak powers which place a high demand on the utility power system. Utilities impose demand charges to recover their costs. Inexpensive batteries remove this barrier to fast charging which may be necessary if the supply of fully recharged rental battery packs runs low during peak travel times. It would permit returned packs to be quickly recharged and returned to service without waiting for an overnight charge cycle. The same inexpensive worn batteries used for load leveling could also be used for fast chargers since peak holiday travel times usually coincide with light utility system loads. The charge station owner thus reduces the required inventory of rentable vehicle batteries while still benefiting from utility load leveling revenue. The embodiments shown here are not intended to be limited and those skilled in the art will appreciate that many variations are possible. For example, a battery pack200could be created to self-monitor its wear and report it. Self-wear monitoring could be achieved with an electrochemical indicator or with a specialized electronic microchip. An electrochemical indicator might for example be an increase in internal cell resistance or some chemical memory based on electroplating within one or more test cells205T in the battery pack200or vehicle. The specific order of the steps shown can also be altered. For example, the conversion of battery wear stress parameter data into a wear estimate could be done external to the battery pack200in the vehicle or at some location such as a swap station where the use history could be used to estimate wear. External wear calculations would be more complex since they would have to handle all variations of cell designs in use. Another embodiment could move the required sensors and data collection outside the casing of the battery pack. Battery current, voltage, and temperature could for example be measured with sensors in the vehicle but outside the battery pack. Other battery wear indicating parameters such as vehicle velocities and accelerations could also be measured by sensors either inside or outside the battery case. The measurement interval for repeated stress parameter determinations might be the sampling rate for input into a digital computation or the reciprocal of the frequency limit imposed by analog circuit bandwidth. As another example, battery pack quality could be evaluated earlier in the return process. Further, the sorting of battery packs could be modified to create a continuous range of quality levels with each different quality level having a distinct capital rental charge. For example, 4 battery packs each with 25 kWh full charge capacity would give the same performance as 5 lower quality battery packs each having 20 kWh of full charge capacity. If equal performance is to have equal pricing, the capital rental charge for the lower quality units should be 80% of the rental charge of the higher capacity units. The flexibility permitted by allowing the renter to choose whether to pay a fixed predetermined wear fee or pay only for the wear actually used provides two distinct ways to compensate the battery owner for wear. The predetermined wear cost embodiment gives the user certainty in wear costs but imposes use restrictions. If the wear is predetermined, battery pack use must be restricted to prevent excessive high wear use. Each recharge kWh could come with some number of ampere seconds of high current use at normal temperatures and much less at high or low temperatures. Thus, drivers would have to ration their use of high acceleration or regenerative braking. Long highway grades with heavy loads could easily exceed the imposed average use limits. In contrast if the variable wear cost is chosen the driver is in full control. Conservative low wear driving could keep wear below the usual average predetermined wear and save money by reducing rental costs. Also, high wear operation would be available whenever the driver needed it and was willing to pay for the additional wear. With the continuous kWh display such asFIG.3drivers could adjust their speed on long mountain grades to keep battery wear costs in an acceptable range. Brief periods of high acceleration or regenerative braking would be acceptable because the displayed trip cost per kWh would usually not change much. FIG.6illustrates an exemplary method600implemented by the battery pack200of determining wear on the battery pack during a usage period. It is assumed that the battery pack200contains a processing circuit configured to perform the method. Alternatively, the method600could be performed by a processing circuit in the vehicle, or by a combination of processing circuit in the battery pack200and vehicle. The battery pack200and/or vehicle measures one or more stress parameters indicative of battery wear in a plurality of measurement intervals during the usage periods to obtain stress parameter data (610). The battery pack200and/or vehicle further determines an amount of battery wear, a battery wear rate, or both for each of two or more of the measurement intervals based on the stress parameter data for the respective measurement interval (620). In some embodiments of the method600, the battery pack200and/or vehicle detects a high wear rate condition based on the stress parameter data, and limits battery current during the high wear rate condition. In some embodiments of the method600, the battery pack200and/or vehicle outputs data indicative of the battery wear rate during the usage period for display to a driver of the vehicle. In some embodiments of the method600, the battery wear rate comprises determining the battery wear rate using a look-up table. In some embodiments of the method600, the stress parameter data includes information related to an electrochemical reaction in at least one cell205within said battery pack. In this example, the stress parameter data may comprise measurements of an electrochemical property of the cell. In some embodiments of the method600, the battery pack200and/or vehicle stores the stress parameter data, the amount of battery wear, battery wear rate, or any combination thereof in an internal memory of the battery pack or vehicle (630). In some embodiments of the method600, the battery pack200and/or vehicle outputs the stress parameter data, amount of battery wear, battery wear rate, or any combination thereof, to a battery pack exchange system. In some embodiments of the method600, the battery pack200and/or vehicle determines an amount of battery wear, battery wear cost, or both, for the usage period (640). In one example, the battery pack200and/or vehicle determines a battery wear cost for each of two or more measurement intervals and summing the battery wear cost for each of the two or more measurement intervals to obtain the battery wear cost for the usage period. in another example, the battery pack200and/or vehicle determines an amount of battery wear for each of two or more measurement intervals and summing the amount of battery wear for the two or more measurement intervals to obtain the amount of battery wear for the usage period. In some embodiments of the method600, the battery pack200and/or vehicle outputs the amount of battery wear for the usage period, the battery wear cost for the usage period, or both, to a battery pack exchange system (650). In other embodiments, the battery pack200and/or vehicle outputs the amount of battery wear, battery wear cost, or both, for each of two or more of the measurement intervals to a battery pack exchange system (660). FIG.7illustrates an exemplary method700implemented by a battery exchange system100according to an embodiment. In one embodiment, the battery exchange system100exchanges a returned battery pack in the vehicle for an available battery pack (710) and obtains battery wear information stored in the returned battery pack (720). The battery wear information comprises information indicative of battery wear during a usage period. The battery exchange system100further determines a battery wear cost for the usage period based on the battery wear information (730). In some embodiments of the method700, the usage period comprises a plurality of measurement intervals and the battery wear information comprises an amount of battery wear, battery wear rate, or both, for each of two or more of the measurement intervals. In some embodiments of the method700, battery exchange system100determines a battery wear cost for each of the two or more measurement intervals based on the amount of battery wear, battery wear rate, or both, for each of the two or more measurement intervals and sum the battery wear cost for each of the two or more measurement intervals to obtain the battery wear cost for the usage period. In some embodiments of the method700, the battery wear information comprises an amount of battery wear, battery wear cost, or both, for the usage period. Some embodiments of the method700further comprises recharging the returned battery to the initial state of charge (740). Some embodiments of the method700further comprises determining an initial state of charge of the returned battery pack at the start of the usage period and determining an amount of charge needed to restore the returned battery to the initial state of charge. Some embodiments of the method700further comprise determining an energy cost for the amount of charge needed to restore the returned battery to the initial state of charge (750). Some embodiments of the method700further comprise determining a usage fee based on the battery wear cost and the energy cost (760). Although the operations of the methods herein are shown and described in a particular order, the order of the operations of each method may be altered so that certain operations may be performed in an inverse order or so that certain operation may be performed, at least in part, concurrently with other operations. In another example, instructions or sub-operations of distinct operations may be in an intermittent or alternating manner. The above description of illustrated implementations is not intended to be exhaustive or to limit the scope of the disclosure to the precise forms disclosed. While specific implementations and examples are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present disclosure, as those skilled in the relevant art will recognize. The words “example” or “exemplary” are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. | 51,527 |
11862809 | BEST MODE Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Therefore, the embodiments described in the specification and the configurations illustrated in the drawings are only preferred embodiments of the present disclosure, without representing all technical features of the present disclosure. In addition, in order to help the understanding of the present disclosure, the accompanying drawings are not drawn to scale, but the dimensions of some components may be exaggerated. A separator sealing apparatus according to the present disclosure includes a first sealing unit10, a second sealing unit20and a transfer unit30, and as shown inFIGS.3and4, before finally cutting a semi-finished product that is continuously supplied (seeFIG.1), a process of bonding an upper separator101and a lower separator102in cell units may be performed. Here, the cell semi-finished product refers to a cell semi-finished product before final cutting. The cell semi-finished product before final cutting may include a lower separator102in the form of a continuous film, negative electrode plates103disposed on the lower separator102with a certain width to be spaced apart from each other, and an upper separator101provided on the negative electrode plate103in the form of a continuous film, or may include positive electrode plates104disposed on the upper separator101with a predetermined width to be spaced apart from each other. Before the final cutting, cell semi-finished products, namely mono cell semi-finished products or half cell semi-finished products, may be continuously supplied in one direction by the transfer unit30, and scheduled separator parts D1, D2may be sealed by first sealing unit10and the second sealing unit20. The first sealing unit10and the second sealing unit20may be operated in synchronization with the transfer unit30at a preset speed. For example, if some of the cell semi-finished products before cutting reach a location for the separator sealing process, the transfer unit30stops working for a certain period of time. At this time, the first sealing unit10and the second sealing unit20may operate (move vertically) to press and thermally fuse the separator parts D1, D2, which require sealing, for a certain period of time. Then, the cell pressing operation of the first sealing unit10and the second sealing unit20is released, and the transfer unit30is operated again to move the cell semi-finished products before cutting. After that, the separator is cut using a cutter (not shown) to complete a final mono cell semi-finished product or a final half cell semi-finished product. Hereinafter, the configuration of the first sealing unit10and the second sealing unit20will be described in more detail with reference toFIGS.6to8. The first sealing unit10and the second sealing unit20are means for bonding two separators of the cell semi-finished product, namely the upper separator101and the lower separator102, to each other by applying heat and pressure. Here, the first sealing unit10may be configured to apply heat and pressure to a first region D1, the second sealing unit20may be configured to apply heat and pressure to a second region D2. The first sealing unit10and the second sealing unit20may be embodied using, for example, heating blocks having heating wires therein. Here, the first region D1(seeFIG.5) refers to an outer edge along a width direction of the electrode plate, among portions where the electrode plate, namely outer regions at both short sides of the electrode plate, where the upper separator101and the lower separator102face each other, and the second region D2refers to an outer edge along a length direction of the electrode plate, namely outer regions at both long sides of the electrode plate, among the portions where the separator101and the lower separator102face each other. The first sealing unit10according to this embodiment may include first upper heating blocks11,12and first lower heating blocks13and14, as shown inFIG.6. Two first upper heating blocks11,12are provided in a pair, and the pair of first upper heating blocks11,12are disposed to be spaced apart from each other by a length of the cell semi-finished product (in the Y-axis direction) and extend in one direction (in the X-axis direction) side by side. In this embodiment, the extending length of the first upper heating blocks11,12corresponds to approximately the width of three unit cell semi-finished product before cutting. Here, the extending length may be configured to be longer or shorter than this embodiment. The first lower heating blocks13,14are provided to be vertically symmetric with the first upper heating blocks11,12. That is, two first lower heating blocks13,14are also provided in a pair, and the pair of first lower heating blocks13,14may be provided to be symmetric with the pair of first upper heating blocks11,12. As described above, the first sealing unit10including the pair of first upper heating blocks11,12and the pair of first lower heating blocks13,14may come into contact with the upper and lower portions of the first regions D1of two separators of the plurality of cell semi-finished products and be operated to apply heat and pressure thereto. That is, the first regions D1of the upper separators101of the plurality of cell semi-finished products may be pressed downward at once by the first upper heating block11,12, and simultaneously the first regions D1of the lower separators102may also be pressed upward at once by the first lower heating blocks13,14. At this time, the first region D1of the upper separator101and the first region D1of the lower separator102may be brought into contact with each other and be fused to each other by heat. Meanwhile, the second sealing unit20is a means for sealing the second regions D2of the upper separator101and the lower separator102facing each other, which cannot be sealed by the first sealing unit10, and includes a plurality of second upper heating blocks21and a plurality of second lower heating blocks23. The second upper heating blocks21respectively extend in a direction (Y-axis direction) intersecting with the pair of first upper heating block11,12, and may be coupled to the pair of first upper heating blocks11,12at locations spaced apart at a predetermined interval along the extending direction of the pair of first upper heating blocks11,12. The second lower heating blocks23are provided to be vertically symmetric with the second upper heating blocks21. In other words, the second lower heating blocks23are vertically symmetric with the second upper heating blocks21in one-to-one relationship, and are provided to be coupled to the pair of first lower heating blocks13,14, respectively. The second upper heating blocks21and the second lower heating blocks23are heating blocks corresponding to the second regions D2of the cell semi-finished products, and press the cell semi-finished products like the first sealing unit10to apply heat and pressure to the second regions of D2of two separators. More specifically, the second regions D2of the upper separators101of the plurality of cell semi-finished products may be pressed downward at once by the second upper heating blocks21, and simultaneously the second regions D2of the lower separators102may be pressed upward at once by the second lower heating blocks23. At this time, the second region D2of the upper separator101and the second region D2of the lower separator102may come into contact with each other and be fused to each other by heat. According to the separator sealing apparatus having the above configuration and operation, after final cutting, as the first region D1and the second region D2of the upper separator101and the lower separator102, namely the upper separator101and the lower separator102facing each other at outer regions in the width direction and the length direction of the electrode plate, are completely bonded, it is possible to produce cell semi-finished products where the electrode plate (negative electrode plate) is fundamentally prevented from being exposed to the outside. If a stacking type or stacking/folding type lithium secondary battery is assembled using the cell semi-finished products110, a low voltage defect rate of the lithium secondary battery may be significantly lowered in comparison to the prior art. In addition, by sealing the separators of the plurality of cell semi-finished products while continuously moving the cell semi-finished products before cutting along the production direction in speed synchronization with the transfer unit30, it is possible to continuously mass-produce final cell semi-finished products110. Meanwhile, the first sealing unit10and the second sealing unit20according to an embodiment of the present disclosure may be provided to be assembled and disassembled with each other. Hereinafter, the assembling and disassembling configuration of the first sealing unit10and the second sealing unit20will be described. The assembling and disassembling configuration of the first upper heating block11,12and the second upper heating blocks21is the same as the assembling and disassembling configuration of the first lower heating block13,14and the second lower heating block23. Thus, the assembling and disassembling configuration of the first lower heating block13,14and the second lower heating blocks23will not be described in detail again. As shown inFIGS.7and8, the pair of first upper heating blocks11,12have a plurality of grooves H formed at regular intervals along the extending direction. The second upper heating blocks21may be coupled to the pair of first upper heating blocks11,12by selecting one of the plurality of grooves H and fitting an end of the second upper heating block21into the corresponding groove H. More specifically, the second upper heating blocks21may have connection portions21awith a step formed at both ends thereof, and the connection portions21amay be placed in the grooves H of the first upper heating blocks11,12in a fitting manner and may be fixed to and released from the grooves H by a bolt B. Although not shown in the figures, a hole having a thread formed in may be provided in the groove H of the connection portion21aand the first upper heating blocks11,12so that the bolt B may be vertically fastened. According to the above configuration, it is possible to adjust the interval between the second upper heating blocks21or to further increase or decrease the number of the second upper heating blocks21, which makes it possible to seal separators of various cell semi-finished products with different widths by using one separator sealing apparatus. In addition, if some of the heating blocks in the separator sealing apparatus are damaged, the separator sealing apparatus may be normally used by replacing only the corresponding heating blocks. Therefore, it may be effective in terms of management and maintenance of the separator sealing apparatus. Subsequently, a method of sealing the separators of the cell semi-finished products using the aforementioned separator sealing apparatus will be briefly summarized as follows. Referring toFIGS.3and4again, the cell semi-finished products before cutting may be continuously supplied along the producing direction (X-axis direction) by the transfer unit30. The cell semi-finished products before cutting may be a mono cell semi-finished product in which the lower separator102, the negative electrode plate103, the upper separator101and the positive electrode plate104are stacked in order, or a half cell semi-finished product in which the lower separator102, the negative electrode and the upper separator101are stacked in order. The first sealing unit10and the second sealing unit20may be disposed at one side of the cell semi-finished product production line as above, and may be operated in synchronization with the transfer unit30. As shown inFIG.4, if three cell semi-finished products reach a sealing process area by the transfer unit30, the first sealing unit10and the second sealing unit20operate integrally in the vertical direction to press and thermally fuse the first region D1and the second region D2of each cell semi-finished product during a preset time. If the preset time passes, the first sealing unit10and the second sealing unit20are returned to the original locations, and next three cell semi-finished products in an unsealed state are placed in the sealing process area by the transfer unit30. After the above sealing process, the cell semi-finished products may be cut one by one using a cutter (not-shown) while moving along the production line so as to be produced in the form of a final unit cell semi-finished product. As described above, the separator folding problem may be solved by implementing the separator sealing apparatus and the separator sealing method of the present disclosure, and various kinds of mono cell or half cell semi-finished products of different widths may be mass-produced in the same production line. The present disclosure has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the scope of the disclosure will become apparent to those skilled in the art from this detailed description. Meanwhile, even though the terms expressing directions such as “upper”, “lower”, “left” and “right” are used in the specification, they are just for convenience of description and can be expressed differently depending on the location of a viewer or a subject, as apparent to those skilled in the art. | 14,219 |
11862810 | DESCRIPTION OF THE INVENTION In the present invention, various constitutions such as the following constitutions may be appropriately selected. A fibrous structure constituting the separator for an electrochemical element according to the present invention may be a sheet-like fabric, for example, a fiber web, a nonwoven fabric, a woven fabric or a knitted fabric. The fibrous structure may consist of only one kind of these fabrics, or may be constituted by laminating a plurality of fabrics and/or plural kinds of fabrics. An embodiment of lamination may be appropriately selected. The embodiment of lamination may be an embodiment in which fabric layers are simply overlapped; an embodiment in which fabric layers are integrated with a binder; an embodiment in which fabric layers are integrated by intertwining the constituent fibers of the fabric layers with extending beyond the layers; an embodiment in which fabric layers are integrated by inter-fiber adhesion performed by thermal melting of the constituent fibers of the fabric layers; an embodiment in which fabric layers are integrated by ultrasonic adhesion; or the like. The fibrous structure according to the present invention comprises a first fibrous layer part having short fibers and/or pulp-like fibers. Short fiber as used in the present invention refers to a fiber having a fiber length of 20 mm or less. Pulp-like fiber refers to a fiber having numerous microtine fibers (fibrils) generated from one fiber by a mechanical shear force or the like. As fineness of the short fibers is smaller and/or a fiber length of the short fibers is shorter, the fibrous structure becomes denser. Further, there is a tendency that various pore diameters can be made smaller, and a difference between a maximum pore diameter and an average pore diameter can be made smaller, and further a difference between an average pore diameter and a minimum pore diameter, and a difference between a maximum pore diameter and a minimum pore diameter, can be made smaller. Therefore, the fineness of the short fibers is preferably 5 d or less, more preferably 2 d or less, and even more preferably 1 d or less. On the other hand, the lower limit value of the fineness of the short fibers may be appropriately selected, but it is realistically 0.01 d or more. The fiber length of the short fibers is preferably 15 mm or less, more preferably 10 mm or less, and even more preferably 5 mm or less. On the other hand, the lower limit value of the fiber length of the short fibers may be appropriately selected, but it is realistically 0.5 mm or more. The short fibers may be fibers comprising a known resin such as a polyolefin resin (a polyethylene, a polypropylene, a polymethylpentene, a polyolefin resin having a structure in which a part of the hydrocarbon is substituted with cyano or a halogen such as fluorine and chlorine, etc.), a styrene resin, a polyether resin (a polyether ether ketone, a polyacetal, a phenol resin, a melamine resin, an urea resin, an epoxy resin, a modified polyphenylene ether, an aromatic polyether ketone, etc.), a polyester resin (a polyethylene terephthalate, a polytrimethylene terephthalate, a polybutylene terephthalate, a polyethylene naphthalate, a polybutylene naphthalate, a polycarbonate, a polyarylate, a wholly aromatic polyester resin, an unsaturated polyester resin, etc.), a polyimide resin, a polyamideimide resin, a polyamide resin (an aromatic polyamide resin such as an aramid resin, an aromatic polyether amide resin, a nylon resin, etc.), a resin having a nitrile group (a polyacrylonitrile, etc.), an urethane resin, an epoxy resin, a polysulfone resin (a polysulfone, a polyethersulfone, etc.), a fluorine-based resin (a polytetrafluoroethylene, a polyvinylidene fluoride, etc.), a cellulose resin, a polybenzimidazole resin, an acrylic resin (a polyacrylonitrile resin obtained by copolymerizing an acrylic acid ester or methacrylic acid ester or the like, a modacrylic resin obtained by copolymerizing acrylonitrile and vinyl chloride or vinylidene chloride, etc.), and the like. The short fibers may be fibers composed of a single resin, or may be fibers composed of plural types of resins such as a mixed resin. These resins may be composed of either a linear polymer or a branched polymer. These resins may be a block copolymer or a random copolymer. Further, these resins may be any resins having any three-dimensional structure of the resin and presence or absence of crystallinity. The short fibers may be single fibers or conjugate fibers. A conjugate fiber includes, for example, a core-sheath type conjugate fiber, a sea-island type conjugate fiber, a side-by-side type conjugate fiber, an orange type conjugate fiber, a bimetal type conjugate fiber, or the like. When these fibers are splittable fibers, the fibrous structure may contain an unsplitted conjugate fiber as short fibers, or the conjugate fiber may contain a fiber obtained by split by a mechanical force or the like. The short fibers may include a substantially circular fiber or an elliptical fiber, or a further modified cross section fiber, regarding the cross section shape of the short fibers. Examples of the modified cross section fiber include fibers having a fiber cross section shape including a polygonal shape such as a triangular shape, an alphabetic character shape such as a Y shape, an irregular shape, a multi-leaf shape, a symbolic shape such as an asterisk shape, or a shape in which a plurality of these shapes are combined. The first fibrous layer part can have a higher strength, by an embodiment having the first fibrous layer part in which the fibrous structure comprises short fibers, more preferably an embodiment in which a second fibrous layer part also comprises short fibers as constituent fibers, compared with an embodiment containing only pulp-like fibers as constituent fibers. Further, existence of short fibers can prevent a portion protruding from the electrode surface from penetrating the separator for an electrochemical element at the time of lamination with the electrode or winding, and thereby, a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit hardly occurs, can be preferably provided. In particular, when the short fibers have a function of adhering the short fibers and/or the pulp-like fibers constituting the first fibrous layer part to each other by heating or the like, the first fibrous layer part can have a higher strength by adhering the constituent fibers of the first fibrous layer part to each other, and thereby a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit more hardly occurs, can be preferably provided. An embodiment of fiber adhesion by short fibers may be appropriately selected. When the short fibers are adhered to each other without melting, it can be preferably prevented that openings in the first fibrous layer part are blocked by a molten resin, and electric resistance between the electrodes of the separator for an electrochemical element increases unintentionally. The separator for an electrochemical element having a first fibrous layer part in which the short fibers are adhered to each other without melting, can be provided by heating the short fibers at a temperature equal to or higher than the glass transition temperature of the resin constituting the short fibers (specifically, a polyethylene terephthalate resin, etc.) and below the melting point of the resin, if necessary, pressing in addition to heating. From the viewpoint that openings in the first fibrous layer part can be prevented from being blocked by the molten resin, the first fibrous layer part in which fibers are adhered to each other by short fibers without using a binder and without melting short fibers, is more preferable. When the first fibrous layer part includes pulp-like fibers, as freeness of the pulp-like fibers is smaller, the fibrous structure becomes denser. In addition, various pore diameters can be made smaller, and a difference between a maximum pore diameter and an average pore diameter can be made smaller, and further a difference between an average pore diameter and a minimum pore diameter, and a difference between a maximum pore diameter and a minimum pore diameter, can be made smaller. Therefore, the first fibrous layer part preferably comprises pulp-like fibers. In that case, freeness of the pulp-like fibers is preferably 500 ml CSF or less, more preferably 400 ml CSF or less, and even more preferably 300 ml CSF or less. On the other hand, the lower limit value of freeness of pulp-like fibers may be appropriately selected, but it is realistically 0.1 ml CSF or more. “Freeness” in the present invention refers to a value measured by the Japanese Industrial Standard: JIS P 8121 Canadian Standard Freeness Tester. Pulp-like fibers may be fibers comprising the above mentioned known resin, like short fibers. From the viewpoint of a low moisture content, pulp-like fibers such as an aramid resin, a polyolefin resin, an acrylic resin, a liquid crystal polyester resin and the like, are preferable. Particularly, when a fibrous structure has heat resistance and high strength, a separator for an electrochemical element excellent in heat resistance in which an electric short circuit hardly occurs, can be easily provided, so that the first fibrous layer part preferably contains pulp-like fibers of an aramid resin. The first fibrous layer part may contain respectively one type of short fibers and/or one type of pulp-like fibers as constituent fibers, or may contain plural types of short fibers and/or plural types of pulp-like fibers. The first fibrous layer part in the present invention has a structure in which short fibers and/or pulp-like fibers are intertwined. Here, an embodiment in which short fibers and/or pulp-like fibers are intertwined, means an embodiment in which short fibers and/or pulp-like fibers are randomly intertwined like a fiber web or a nonwoven fabric; or an embodiment in which short fibers and/or pulp-like fibers are regularly intertwined like a woven fabric and a knitted fabric. In particular, the first fibrous layer part is preferably a fibrous layer derived from a fiber web or a nonwoven fabric, more preferably a fibrous layer derived from a fiber web or a nonwoven fabric obtained by a wetlaid process, so as to easily provide a fibrous structure in which some of short fibers and/or pulp-like fibers penetrates deeply into the second fibrous layer part as described later. An embodiment of respective fibers constituting the first fibrous layer part may be appropriately selected. It may be an embodiment in which respective fibers are simply intertwined; an embodiment in which respective fibers are adhered by short fibers as mentioned above; an embodiment in which respective fibers are integrated with a binder; an embodiment in which some of fibers or all of fibers are adhered; or the like. When the first fibrous layer part contains pulp-like fibers, as a percentage by mass of the pulp-like fibers in the constituent fibers of the first fibrous layer part is larger, the fibrous structure becomes denser. In addition, there is a tendency that various pore diameters can be made smaller, and a difference between a maximum pore diameter and an average pore diameter can be made smaller, and further a difference between an average pore diameter and a minimum pore diameter, and a difference between a maximum pore diameter and a minimum pore diameter, can be made smaller. Therefore, a percentage by mass of the pulp-like fibers in relation to the constituent fibers of the first fibrous layer part is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 50% by mass or more. The upper limit value may be appropriately adjusted, but it may be 100% by mass or less, 95% by mass or less, or 90% by mass or less. The first fibrous layer part may be a fibrous layer composed of only short fibers and/or pulp-like fibers as constituent fibers, or may be a fibrous layer composed of short fibers and/or pulp-like fibers as well as other fibers as constituent fiber. A type of the other fibers may be appropriately selected, but it may be long fibers or fibers having a continuous length. The first fibrous layer part may contain adhesive fibers. Examples of the adhesive fibers, include a composite fiber such as a core-sheath fiber or a side by side fiber of a high melting point resin and a low melting point resin; or, for example, an undrawn fiber composed of only a resin which melts or softens at a temperature lower than the melting point or the softening point of the short fibers and/or the pulp-like fibers; or the like. When the first fibrous layer part contains adhesive fibers, adhesion of the short fibers and/or the pulp-like fibers by the adhesive fibers improves the strength of the first fibrous layer part, whereby a separator for an electrochemical element in which an electric short circuit hardly occurs, can be provided. When the first fibrous layer part contains fibers other than short fibers and/or pulp-like fibers, a percentage by mass of the fibers other than short fibers and/or pulp-like fibers in the constituent fibers of the first fibrous layer part may be appropriately selected. The first fibrous layer part may contain a binder. When the first fibrous layer part contains a binder, adhesion of the constituent fibers by the binder improves the strength of the first fibrous layer part, whereby a separator for an electrochemical element in which an electric short circuit hardly occurs, can be provided. A method of preparing the first fibrous layer part containing a binder may be appropriately selected. A method of applying binder powders, a binder solution or a molten binder to the first fibrous layer part by loading, coating or impregnation may be adopted. A mass of the binder contained in the first fibrous layer part may be appropriately selected. It is preferably 0.1 to 35 g/m2, more preferably 0.1 to 25 g/m2, and even more preferably 0.1 to 15 g/m2. A basis weight of the first fibrous layer part may be appropriately selected. However, when the basis weight is too small, as the constituent fibers are less, a fibrous structure excellent in strength can hardly be provided, and as a result, it may be difficult to provide a separator for an electrochemical element capable of providing an electric element in which an electric short circuit hardly occurs. On the other hand, when the basis weight is too large, air permeability decreases, and resistance of ion passage unintentionally increases, so that it may be difficult to provide a separator for an electrochemical element capable of providing an electrochemical element having low electric resistance between electrodes. Therefore, a basis weight of the first fibrous layer part is preferably 0.5 to 40 g/m2, more preferably 1 to 30 g/m2, and even more preferably 2 to 20 g/m2. Basis weight in the present invention refers to a basis weight obtained based on the method defined in the Japanese Industrial Standard: JIS P 8124 (Paper and Paperboard—Method of Measuring Basis Weight). The second fibrous layer part in the fibrous structure is a part mainly supporting and reinforcing the first fibrous layer part. The second fibrous layer part may be a sheet-like fabric, for example, a fibrous layer derived from a fiber web or a nonwoven fabric, a woven fabric or a knitted fabric. A type of fibers constituting the second fibrous layer part may be appropriately selected. The fibers may be short fibers and pulp-like fibers described above as well as long fibers or fibers having a continuous length. The second fibrous layer part can have a higher strength, by an embodiment having a second fibrous layer part in which the fibrous structure comprises short fibers. Further, existence of short fibers can prevent a portion protruding from the electrode surface from penetrating the separator for an electrochemical element at the time of lamination with the electrode or winding, and thereby, a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit hardly occurs, can be preferably provided. In particular, when the short fibers have a function of adhering the short fibers and/or the other fibers constituting the second fibrous layer part to each other by heating or the like, the second fibrous layer part can have a higher strength by adhering the constituent fibers of the second fibrous layer part to each other, and thereby a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit more hardly occurs, can be preferably provided. An embodiment of fiber adhesion by short fibers may be appropriately selected. When the short fibers are adhered to each other without melting, it can be preferably prevented that openings in the second fibrous layer part are blocked by a molten resin, and electric resistance between the electrodes of the separator for an electrochemical element increases unintentionally. The separator for an electrochemical element having the second fibrous layer part in which short fibers are adhered to each other without melting, can be provided by heating the short fibers at a temperature equal to or higher than the glass transition temperature of the resin constituting the short fibers (specifically, a polyethylene terephthalate resin, etc.) and below the melting point of the resin, if necessary, pressing in addition to with heating. From the viewpoint that openings in the second fibrous layer part can be prevented from being blocked by the molten resin, the second fibrous layer part in which fibers are adhered to each other by short fibers without using a binder and without melting short fibers, is more preferable. In particular, the second fibrous layer part is preferably a fibrous layer derived from a fiber web or a nonwoven fabric, more preferably a fibrous layer derived from a fiber web or a nonwoven fabric obtained by a wetlaid process, so as to easily provide a fibrous structure in which some of short fibers and/or pulp-like fibers penetrates deeply into the second fibrous layer part as described later. An embodiment of respective fibers constituting the second fibrous layer part may be appropriately selected. It may be an embodiment in which respective fibers are simply intertwined; an embodiment in which respective fibers are adhered by short fibers as mentioned above; an embodiment in which respective fibers are integrated with a binder; an embodiment in which some of fibers or all of fibers are adhered; or the like. As the fineness of the fibers constituting the second fibrous layer part is smaller and/or the fiber length of the fibers is shorter, the fibrous structure becomes denser. Further, there is a tendency that various pore diameters can be made smaller, and a difference between a maximum pore diameter and an average pore diameter can be made smaller, and further a difference between an average pore diameter and a minimum pore diameter, and a difference between a maximum pore diameter and a minimum pore diameter, can be made smaller. Therefore, the fineness of the fibers is preferably 5 d or less, more preferably 2 d or less, and even more preferably 1 d or less. On the other hand, the lower limit value of the fineness of the fibers may be appropriately selected, but it is realistically 0.01 d or more. A fiber length of the fibers is preferably 20 mm or less, more preferably 15 mm or less, and even more preferably 10 mm or less. On the other hand, the lower limit value of the fiber length of the fibers may be appropriately selected, but it is realistically 0.5 mm or more. The second fibrous layer part may contain adhesive fibers. Examples of the adhesive fibers, include a composite fiber such as a core-sheath fiber or a side by side fiber of a high melting point resin and a low melting point resin; or, for example, an undrawn fiber composed of only a resin which melts or softens at a temperature lower than the melting point or softening point of the constituent fibers of the second fibrous layer part; or the like. When the second fibrous layer part contains adhesive fibers, adhesion of the constituent fibers by the adhesive fibers improves the strength of the second fibrous layer part, whereby a separator for an electrochemical element in which an electric short circuit hardly occurs, can be provided. When the second fibrous layer part contains adhesive fibers, a percentage by mass of the adhesive fibers in the constituent fibers of the second fibrous layer part may be appropriately selected. The second fibrous layer part may contain a binder. When the second fibrous layer part contains a binder, adhesion of the constituent fibers by the binder improves the strength of the second fibrous layer part, whereby a separator for an electrochemical element in which an electric short circuit hardly occurs, can be provided. A method of preparing the second fibrous layer part containing a binder may be appropriately selected. A method of applying binder powders, a binder solution or a molten binder to the second fibrous layer part by loading, coating or impregnation may be adopted. A mass of the binder contained in the second fibrous layer part may be appropriately selected. It is preferably 1 to 50 g/m2, more preferably 2 to 40 g/m2, and even more preferably 3 to 30 g/m2. A basis weight of the second fibrous layer part may be appropriately selected. It is preferably 1 to 50 g/m2, more preferably 2 to 40 g/m2, and even more preferably 3 to 30 g/m2. In the fibrous structure according to the present invention, some of short fibers and/or pulp-like fibers constituting the first fibrous layer part penetrates the second fibrous layer part. With this structure, the first fibrous layer part is firmly integrated with the second fibrous layer part, so that the first fibrous layer part is effectively reinforced by the second fibrous layer part, to provide a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit more hardly occurs. “Some of the short fibers and/or the pulp-like fibers constituting the first fibrous layer part penetrates the second fibrous layer part”, can be determined, in the case where observing the cross section in the thickness direction of the fibrous structure comprising the first fibrous layer part and the second fibrous layer part, some of the short fibers and/or the pulp-like fibers constituting the first fibrous layer part is present in the second fibrous layer part in the fibrous structure (for example, in the case where it is present from the first fibrous layer part to the main surface on the second fibrous layer part side of the fibrous structure). In particular, when some of the short fibers and/or pulp-like fibers constituting the first fibrous layer part penetrates deeply into the second fibrous layer part until being exposed on the main surface on the side opposite to the first fibrous layer part side of the second fibrous layer part, the first fibrous layer part can be more firmly integrated with the second fibrous layer part, to provide preferably a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit more hardly occurs. In addition, the fibrous structure having such a structure, has uniform liquid retention amounts in the first fibrous layer part and the second fibrous layer, and is excellent in the liquid retention performance. Therefore, the separator for an electrochemical element comprising the fibrous structure having the constitution of the present invention is excellent in the liquid retention performance of an electrolyte, so that an electrochemical element having a long battery life, in which an electrogenic reaction can be smoothly performed without shortage of the electrolyte, may be provided. In the item of “Method of determining presence or absence of pinholes”, deep penetration of some of short fibers and/or pulp-like fibers constituting the first fibrous layer part into the second fibrous layer part until being exposed on the main surface on the side opposite to the first fibrous layer part side of the second fibrous layer part, can be determined, in the case where it is confirmed that the short fibers and/or the pulp-like fibers are exposed on the main surface on the exposed side of the second fibrous layer part in the scanning electron microscopic photograph of the main surface derived from the second fibrous layer part. The fibrous structure may have a structure comprising only the first fibrous layer part and the second fibrous layer part described above, or may have a structure additionally comprising other member(s) such as a reinforcing layer or the like separately. Further, the fibrous structure may have a functional material such as particles, or an adhesive material such as a binder that can adhere between layers or fibers, or bind the functional material to the fibrous structure. A kind of the particles such as inorganic particles, etc. which the fibrous structure may include, a method of loading and a loading mass may be appropriately selected. For example, the kind of the inorganic particles is not limited because it may be appropriately selected, but examples thereof include an oxide such as iron oxide, SiO2(silica), Al2O3(alumina), alumina-silica composite oxide, TiO2, SnO2, BaTiO2, ZrO2, tin-indium oxide (ITO) and lithium titanate (LTO); a nitride such as aluminum nitride and silicon nitride; a poorly soluble ionic crystal such as calcium fluoride, barium fluoride and barium sulfate; a covalent crystal such as silicon and diamond; a clay such as talc and montmorillonite; a substance derived from a mineral resource such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite and mica, or an artificial material thereof; an oxide of an inorganic material such as a metal oxide; or the like. In particular, as disclosed in WO 2009/066916 (JP 2011-503828), a separator for an electrochemical element formed by coating at least one surface of a fiber assembly such as a nonwoven fabric with electrode active material particles performing electrochemical oxidation or reduction reaction, is preferable. Examples of the electrode active material particles include anode active material particles selected from the group consisting of natural graphite, artificial graphite, a carbonaceous material, lithium titanate (LTO), silicon (Si) and tin (Sn), and a mixture thereof, or the like. By such a separator for an electrochemical element, thermal stability can be improved, and reduction of battery capacity can be improved. Therefore, a fibrous structure obtained by applying the above described electrode active material particles on at least one side thereof, is preferable for realizing such a separator for an electrochemical element. Effects exhibited by a separator for an electrochemical element having a fiber assembly such as a nonwoven fabric obtained by applying the above described electrode active material particles on at least one side thereof, are also described in WO 2009/048263 (JP 2011-501349), WO 2013/021299 (JP 2014-527266), etc. An average particle diameter (D50) of primary particles included in the fibrous structure may be appropriately adjusted depending on a kind of the particles, a kind of the separator for an electrochemical element, performance and properties required for the separator for an electrochemical element. The average particle diameter may be 10 μm or less, 8 μm or less, or 5 μm or less. The lower limit value thereof may be appropriately adjusted, but it is realistically 50 nm or more. An average particle diameter (D50) of primary particles of the electrode active material particles included in the fibrous structure may be also appropriately adjusted depending on a type of the particles, a type of the separator for an electrochemical element, performance and properties required for the separator for an electrochemical element. The average particle diameter may be in the range of 50 nm to 2 μm, as disclosed in WO 2013/021299 (JP 2014-527266), etc. “Average particle diameter (D50) of primary particles” in the present invention refers to a value obtained from the particle diameter measurement data obtained from the scattering intensity by a continuous measurement for 3 minutes under a dynamic light scattering method using FPRA 1000 (measurement range: 3 nm to 5,000 nm) manufactured by Otsuka Electronics Co., Ltd. More specifically, a particle diameter measurement is performed 5 times, and the particle diameter measurement data obtained by the measurement are arranged in the order from data having the narrowest particle diameter distribution width to data having the broadest one. Then, the data having the third narrowest particle diameter distribution width are selected, and a particle diameter at the cumulative 50% point of the particles in the selected data is defined as an average particle diameter of the primary particles (hereinafter sometimes abbreviated as D50). A measurement solution used for the measurement is adjusted to a temperature of 25° C., and a pure water at 25° C. is used as a blank for scattering intensity. When a particle diameter is described in a web page, a catalog or the like by a manufacturer or a trading company of the particles to be measured, the particle diameter may be regarded as an average particle diameter (D50) of the primary particles. An embodiment of caning the particles may be appropriately selected. It may be an embodiment in which the particles are simply present on the fiber surface without using an adhesive material such as a binder; an embodiment in which the particles are adhered and integrated on the fiber surface by a binder; or the like. An embodiment of existence of the particles in the fibrous structure may also be appropriately selected. It may be an embodiment in which the particles are mainly present in either one of the first fibrous layer part and the second fibrous layer part; an embodiment in which the particles are present approximately uniformly in whole the fibrous structure; an embodiment in which the particles are present such that an existence amount of the particles decreases from one main surface of the fibrous structure toward the other main surface; or the like. A loading mass of the particles included in the fibrous structure is not particularly limited, but it may be 0.1 g/m2or more, 0.5 g/m2or more, or 1 g/m2or more. On the other hand, the upper limit value of the loading mass may be appropriately adjusted. The separator for an electrochemical element having a fibrous structure loading the particles as described above may have a smaller maximum pore diameter and a smaller minimum pore diameter and a narrower pore diameter distribution. Therefore, by the separator for an electrochemical element according to the present constitution, an electrochemical element having functionality exhibited by the provided particles in which an electric short circuit hardly occurs, and higher electric resistance between the electrodes than intended is prevented, can be preferably provided. Thickness of the fibrous structure may be appropriately selected. The thickness is preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less, so as to be a separator for an electrochemical element capable of providing an electrochemical element having a low internal resistance due to low thickness. On the other hand, when the thickness is too thin, the strength decreases and cracks tend to occur in the separator for an electrochemical element. Therefore, the thickness is realistically 5 μm or more. “Thickness” in the present invention refers to an arithmetic average value of values of randomly selected 10 points measured at 5 N load using an outside micrometer (0 to 25 mm) defined in the Japanese Industrial Standard: JIS B 7502: 1994. A basis weight of the fibrous structure may be appropriately selected, but it may be 1 to 50 g/m2, 2 to 40 g/m2, or 3 to 30 g/m2. Porosity of the fibrous structure may be appropriately selected. The porosity is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more, so as to be a separator for an electrochemical element capable of providing an electrochemical element having low internal resistance due to its low resistance of ion passage. On the other hand, when the porosity is too high, the strength decreases and cracks tend to occur in the separator for an electrochemical element. Therefore, the porosity is realistically 80% or less. “Porosity” in the present invention refers to a value obtained by the following formula: Porosity (P)={1−W/(T×d)}×100 wherein W is a basis weight (g/m2) of the measurement object, T is a thickness (μm) of the measurement object, and d is a mass average density (g/cm3) of the material constituting the measurement object. For example, a mass average density (d) is calculated by the following formula: Mass average density (d)=1/{(a/100/d1)+(b/100/d2)} in the case where a parts by mass of the resin A having a density d1 and b parts by mass of the resin B having a density d2 are present in 100 parts by mass of the material. Air permeability of the fibrous structure may be appropriately selected. When the air permeability is too low, ions in the electrolyte hardly pass therethrough, whereby a separator for an electrochemical element capable of providing an electrochemical element having low electric resistance between the electrodes is difficult to be provided. Therefore, the air permeability is preferably 0.05 cm3/cm2/sec or more, more preferably 0.07 cm3/cm2/sec or more, and even more preferably 0.1 cm3/cm2/sec or more. The upper limit value of the air permeability is not limited from the viewpoint of the ion passage performance, but it is realistically 50 cm3/cm2/sec or less, so as to prevent the strength of a separator for an electrochemical element from being too low. Air permeability in the present invention is a value calculated from the air permeability when subjected to a pressure of 125 Pa by a Frazier air permeability tester, which is an air amount defined under the Japanese Industrial Standard: JIS L 1096: 1999 8.27.1 Method A (Frazier method). In a separator for an electrochemical element comprising a fibrous structure having pinholes, high air permeability tends to be exhibited as a fluid easily passes through pinholes. At first glance, the separator for an electrochemical element comprising such a fibrous structure seems to be able to provide an electrochemical element having low internal resistance due to its low resistance of ion passage. However, an electrochemical element comprising such a separator for an electrochemical element easily has an electric short circuit due to existence of pinholes, and ion permeability of each portion of the separator for an electrochemical element tends to become non-uniform. Therefore, the air permeability which is considered preferable as defined above, is a value in a separator for an electrochemical element prepared using a fibrous structure having no pinholes. The fibrous structure in the present invention has a pore diameter distribution satisfying the following formula: 0 μm<Dmax<18 μm, and 0 μm≤(Dmax−Dave)<13 μm wherein Dmax is a maximum pore diameter (μm) of the fibrous structure, and Dave is an average pore diameter (μm) of the fibrous structure. In the present invention, the average pore diameter of the fibrous structure refers to an average flow pore diameter measured by a bubble point method. The maximum pore diameter of the fibrous structure refers to a maximum flow pore diameter measured by the same method as described above, and the minimum pore diameter of the fibrous structure refers to a minimum flow pore diameter measured by the same method as described above. The average flow pore diameter, the maximum flow pore diameter, and the minimum flow pore diameter can be measured by using a polometer manufactured by Coulter. An electrochemical element in which an electric short circuit hardly occurs, can be provided by a separator for an electrochemical element having a fibrous structure having a maximum pore diameter less than 18 μm. As the maximum pore diameter is smaller, a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit more hardly occurs, can be provided. Therefore, the maximum pore diameter is preferably 17 μm or less, more preferably 15 μm or less, and even more preferably 11 μm or less. On the other hand, the maximum pore diameter is larger than 0 μm, but it is realistically 0.5 μm or more. An average pore diameter of the fibrous structure may be appropriately selected. As the average pore diameter is smaller, a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit hardly occurs, can be provided. Therefore, the average pore diameter is preferably 15 μm or less, more preferably 10 μm or less, even more preferably 5 μm or less, and most preferably 4 μm or less. On the other hand, the average pore diameter is larger than 0 μm, but it is realistically 0.5 μm or more. The average pore diameter is equal to or less than the maximum pore diameter. A fibrous structure having a difference between the maximum pore diameter and the average pore diameter of the fibrous structure of 0 μm or more and less than 13 μm, has a uniform pore diameter. Therefore, ion permeability in a separator for an electrochemical element comprising the fibrous structure is uniform, so that a separator for an electrochemical element capable of providing an electrochemical element preventing higher electric resistance between the electrodes than intended, can be provided. As a difference between the maximum pore diameter and the average pore diameter of the fibrous structure is smaller, the fibrous structure has more uniform pore diameter. Therefore, the difference is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, and most preferably 4 μm or less. A minimum pore diameter of the fibrous structure may be appropriately selected, but it may be 0.1 to 9 μm, 0.2 to 7 μm, or 0.5 to 5 μm. The minimum pore diameter is equal to or less than the average pore diameter or the the maximum pore diameter. As the fibrous structure having a difference between the minimum pore diameter and the average pore diameter of the fibrous structure of 0 μm or more and less than 13 μm has a more uniform pore diameter, ion permeability in a separator for an electrochemical element comprising the fibrous structure is uniform, so that a separator for an electrochemical element capable of providing an electrochemical element preventing higher electric resistance between the electrodes than intended, can be provided. Therefore, a difference between the minimum pore diameter and the average pore diameter of the fibrous structure is preferably 8 μm or less, more preferably 6 μm or less, further preferably 4 μm or less, and most preferably 3 μm or less. Furthermore, from the viewpoint of possession of a narrow pore diameter distribution, a difference between the minimum pore diameter and the maximum pore diameter of the fibrous structure is preferably less than 15 more preferably 10 μm or less, even more preferably 8 μm or less, further more preferably 6 μm or less, and most preferably 4 μm or less. As the fibrous structure having the constitution of the present invention has a small difference between the minimum pore diameter and the average pore diameter and a small difference between the minimum pore diameter and the maximum pore diameter, the fibrous structure has a uniform and dense structure having a small distance between constituent fibers, in which pinholes being linear through holes formed from one main surface to the other main surface, hardly exist. Therefore, even when using a thin fibrous structure having a thickness of 20 μm or less, in order to provide a thin separator for an electrochemical element having a thickness of, for example, 20 μm or less, a separator for an electrochemical element having no pinholes can be provided, and an electrochemical element in which an electric short circuit more hardly occurs, can be provided. On the other hand, the separator for an electrochemical element according to the conventional technology as disclosed in, for example, Patent Literature 1, tends to have a larger difference between the maximum pore diameter and the average pore diameter, a larger difference between the average pore diameter and the minimum pore diameter, and a larger difference between the maximum pore diameter and the minimum pore diameter, so that the separator for an electrochemical element has a non-uniform and non-dense structure having a large distance between constituent fibers, in which pinholes are likely to exist. Therefore, under the conventional technology, when using a thin fibrous structure having a thickness of 20 μm or less, in order to provide a thin separator for an electrochemical element having a thickness of, for example, 20 μm or less, it is difficult to provide a separator for an electrochemical element having no pinholes. Whether a fibrous structure or a separator for an electrochemical element has pinholes can be determined by the following determination method. (Method of Determining Presence or Absence of Pinholes) (1) to prepare a photograph sample obtained by placing a fibrous structure alone on a film substrate, or a photograph sample obtained by placing a separator for an electrochemical element comprising a fibrous structure on a film substrate.(2) to take a scanning electron microscope (SEM) photograph with a magnification of 500 times of the main surface of the exposed fibrous structure alone or the separator for an electrochemical element in the photographed sample, from the side of the exposed fibrous structure alone or the separator for an electrochemical element, using a scanning electron microscope (SEM).(3) to confirm presence or absence of a part (pinholes) surrounded by the constituent fibers on the main surface in which the film substrate is exposed, by using the above SEM photograph. The separator for an electrochemical element according to the present invention comprises the above described fibrous structure. The fibrous structure alone may be used as a separator for an electrochemical element. Or the fibrous structure separately having a member such as a reinforcing layer may be used as a separator for an electrochemical element. Further, the separator for an electrochemical element may be punched in a shape according to the shape of the electrochemical element to be used, or processed so as to have a wound shape, or the like. A method of producing a separator for an electrochemical element according to the present invention is explained. The descriptions of the same constitutional items as those described for the separator for an electrochemical element are omitted in the following. A method of producing a separator for an electrochemical element may be appropriately selected. As an example, a separator for an electrochemical element, comprising a fibrous structure according to the present invention can be provided by using a method of producing a fibrous structure, comprising:(1) a step of preparing a sheet-like fabric;(2) a step of forming a dispersion containing short fibers and/or pulp-like fibers on one main surface of the fabric, to form a fiber deposit layer wherein the short fibers and/or the pulp-like fibers are mixed with each other, and some of the short fibers and/or the pulp-like fibers penetrates into the fabric; and(3) a step of drying the laminate comprising the fiber deposit layer formed on one main surface of the fabric. First explanation is (1) a step of preparing a sheet-like fabric. A sheet-like fabric is a member capable of forming a second fibrous layer part. For example, a sheet-like fabric such as a fiber web, a nonwoven fabric, a woven fabric or a knitted fabric may be used. In particular, a sheet-like fabric is preferably a fiber web or a wetlaid nonwoven fabric formed by a wetlaid process. Porosity of the sheet-like fabric is appropriately selected, but it is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more, so that some of the short fibers and/or the pulp-like fibers can penetrates deeply the fabric. On the other hand, when the porosity is too high, the strength decreases and cracks tend to occur in the separator for an electrochemical element. Therefore, the porosity is realistically 85% or less. Next explanation is (2) a step of forming a dispersion containing short fibers and/or pulp-like fibers on one main surface of the fabric, to form a fiber deposit layer wherein the short fibers and/or the pulp-like fibers are mixed with each other, and some of the short fibers and/or the pulp-like fibers penetrates into the fabric. A dispersion medium of the dispersion containing the short fibers and/or the pulp-like fibers may be appropriately selected. As the dispersion medium, a dispersion containing a dispersing agent and/or an active agent, or water containing no dispersing agent and no active agent may be used. Then, the dispersion prepared in this manner is poured and formed on one main surface of the fabric. The dispersion medium of the dispersion may be sucked and removed by a suction device presented on the other main surface side of the fabric. Here, when the dispersion medium of the dispersion is water containing no dispersing agent and no active agent, the dispersion medium can be easily removed at the time of removal of the dispersion medium by suction, and formation of pinholes formed by the dispersion medium passing through the fibrous structure can be prevented, and a fibrous structure in which some of short fibers and/or pulp-like fibers penetrate deeply the fabric, can be preferably prepared. Final explanation is (3) a step of drying the laminate comprising the fiber deposit layer formed on one main surface of the fabric. This step can prepare the fibrous structure by removing the dispersion medium of the dispersion from the laminate. A drying method may be appropriately selected. It includes, for example, a drying method by removing the dispersion medium from the laminate by suction or blowing off; a drying method by removing the dispersion medium from the laminate by subjecting to a drying heater; a drying method of removing the dispersion medium from the laminate by subjecting to hot air, infrared light, or the like; a drying method by removing the dispersion medium from the laminate by allowing it to stand under a room temperature environment or a low pressure environment; a drying method by removing the dispersion medium from the laminate by absorbing the dispersion medium with a fabric having water absorbency such as felt; a drying method by removing the dispersion medium from the laminate by bringing it into contact with a heating roll (if necessary, pressing with the heating roll while bringing it into contact); and the like. When the laminate includes an adhesive material such as a binder or an adhesive fiber, the adhesive material may be melted by subjecting it to a heater in this step to let the fibers or particles be adhered to each other. Due to performing the above preparation steps, a fibrous structure having respective pore diameters as defined by the present invention can be prepared, wherein the first fibrous layer part derived from the fiber deposit layer formed by intertwining the short fibers and/or the pulp-like fibers on one main surface of the second fibrous layer part derived from the fabric is formed, and wherein some of the short fibers and/or the pulp-like fibers constituting the first fibrous layer part penetrates the second fibrous layer part. A separator for an electrochemical element may be used, wherein the first fibrous layer part formed by intertwining the short fibers and/or the pulp-like fibers respectively on both main surfaces of the second fibrous layer part is formed, and wherein some of the short fibers and/or the pulp-like fibers constituting the first fibrous layer part penetrates respectively the second fibrous layer part. Such a separator for an electrochemical element may be prepared by pouring and forming the dispersion liquid prepared as described above on both main surfaces of the fabric. The prepared fibrous structure alone may be used as a separator for an electrochemical element. Or the fibrous structure separately having a member such as a reinforcing layer may be used as a separator for an electrochemical element. Further, the fibrous structure or the laminate including the fibrous structure may be subjected to a hydrophilic treatment step in order to give or improve retention of the electrolyte. Examples of the hydrophilic treatment step include a sulfonation treatment, a fluorine gas treatment, a graft polymerization treatment of a vinyl monomer, a surfactant treatment, a discharge treatment, a hydrophilic resin addition treatment, and the like. Further, the fibrous structure or the laminate including the fibrous structure may be subjected to various secondary processes such as punching in a shape according to the shape of the electrochemical element to be used, processing so as to have a wound shape, to produce a separator for an electrochemical element. EXAMPLE Hereinafter, the present invention is explained specifically with reference to examples, but the present invention is not limited only to these examples. Example 1 A fiber web obtained by a wetlaid process from polyethylene terephthalate short fibers (fiber length: 3 mm, fineness: 0.2 d) was subjected to a heating roll whose surface temperature was adjusted to 180° C., and was heated and pressed, to let polyethylene terephthalate short fibers be crystallized, and to adhere respective polyethylene terephthalate short fibers with polyethylene terephthalate short fibers without melting, and the wetlaid nonwoven fabric A (thickness: 10 basis weight: 6 g/m2, porosity: 56%, fiber length of constituent fibers: 3 mm, fineness of component fibers: 0.2 d) was prepared. Then, polyethylene terephthalate short fibers (fiber length: 3 mm, fineness: 0.2 d) and pulp-like fibers of an aramid resin (freeness: 50 ml CSF) were dispersed in water having no dispersing agent and no active agent at the ratio of polyethylene terephthalate short fibers:pulp-like fibers of an aramid resin=20% by mass:80% by mass to prepare the dispersion A. Subsequently, the dispersion A was formed on one main surface of the wet nonwoven fabric A, and then, the dispersion medium was suctioned and removed from the side of the wet nonwoven fabric A, whereby a fiber deposit layer was formed in which polyethylene terephthalate short fibers and pulp-like fibers of an aramid resin was mixed on the one main surface of the wet nonwoven fabric A. Next, the laminate web prepared as described above was subjected to a heat treatment by exposing it under an atmosphere at a temperature of 145° C. while being supported by a conveyor, and the dispersion medium was removed and dried from the laminate web. Then, the laminate web was heated and pressed using a heating roll whose surface temperature was adjusted to 180° C. to let polyethylene terephthalate short fibers be crystallized, and to adhere respective polyethylene terephthalate short fibers and polyethylene terephthalate short fibers and pulp-like fibers of an aramid resin with polyethylene terephthalate short fibers without melting, and a separator for an electrochemical element was prepared. Comparative Example 1 The dispersion B was prepared by adding a viscosity agent and an active agent to the dispersion A at the ratio of 0.7% by mass of the viscosity agent and 0.01% by mass of the active agent in relation to 100% by mass of the fibers dispersed in the dispersion A. A separator for an electrochemical element was prepared in the same manner as in Example 1 except for using the dispersion B instead of the dispersion A. Example 2 A separator for an electrochemical element was prepared in the same manner as in Example 1 except for increasing the amount of the dispersion A to be formed on one main surface of the wet nonwoven fabric A. Example 3 A fiber web obtained by a wetlaid process from polyethylene terephthalate short fibers (fiber length: 3 mm, fineness: 0.2 d) was subjected to a heating roll whose surface temperature was adjusted to 180° C., and was heated and pressed, to let polyethylene terephthalate short fibers be crystallized, and to adhere respective polyethylene terephthalate short fibers with polyethylene terephthalate short fibers without melting, and the wetlaid nonwoven fabric B (thickness: 8 μm, basis weight: 4.5 g/m2, porosity: 59%, fiber length of constituent fibers: 3 mm, fineness of component fibers: 0.2 d) was prepared. A separator for an electrochemical element was prepared in the same manner as in Example 1 except for using the wetlaid nonwoven fabric B in place of the wetlaid nonwoven fabric A. Example 4 A fiber web obtained by a wetlaid process from polyethylene terephthalate short fibers (fiber length: 3 mm, fineness: 0.2 d) was subjected to a heating roll whose surface temperature was adjusted to 180° C., and was heated and pressed, to let polyethylene terephthalate short fibers be crystallized, and to adhere respective polyethylene terephthalate short fibers with polyethylene terephthalate short fibers without melting, and the wetlaid nonwoven fabric C (thickness: 8 μm, basis weight: 4 g/m2, porosity: 64%, fiber length of constituent fibers: 3 mm, fineness of component fibers: 0.2 d) was prepared. A separator for an electrochemical element was prepared in the same manner as in Example 1 except for using the wetlaid nonwoven fabric C instead of the wetlaid nonwoven fabric A. Example 5 50% by mass of polyethylene terephthalate short fibers (fiber length: 3 mm, fineness: 0.2 d), 30% by mass of another polyethylene terephthalate short fibers (fiber length: 3 mm, fineness: 0.06 d) and 20% by mass of pulp-like fibers of an aramid resin (freeness: 50 ml CSF) were mixed. A fiber web obtained by a wetlaid process from the obtained mixture was subjected to a heating roll whose surface temperature was adjusted to 180° C., and heated and pressed, to let polyethylene terephthalate short fibers be crystallized, and to adhere respective polyethylene terephthalate short fibers and pulp-like fibers of an aramid resin and polyethylene terephthalate short fibers with polyethylene terephthalate short fibers without melting, and the wetlaid nonwoven fabric D (thickness: 11 μm, basis weight: 5 g/m2, porosity: 67%) was prepared. A separator for an electrochemical element was prepared in the same manner as in Example 1 except for using the wetlaid nonwoven fabric D instead of the wetlaid nonwoven fabric A. As a result of subjecting the separators for an electrochemical element prepared in Examples and Comparative Example to the above mentioned “Method of determining presence or absence of pinholes”, the followings were found. When preparing a photograph sample, the main surface derived from the fiber deposit layer of the separator for an electrochemical element (the main surface on the side of the first fibrous layer part) was made to face the film substrate. Therefore, the main surfaces derived from the wetlaid nonwoven fabrics A to D of the separators for an electrochemical element (the main surface on the side of the second fibrous layer part) were taken in the SEM photographs. No pinholes were present in any of the SEM photographs of the separators for an electrochemical element of Examples, whereas presence of pinholes were recognized in the SEM photographs of the separators for an electrochemical element of Comparative Examples. Two SEM photographs of mutually different portions of the separator for an electrochemical element of Example 1 when the separator for an electrochemical element were subjected to “Method of determining presence or absence of pinholes” and were photographed, are shown inFIG.1andFIG.2. Two SEM photographs of mutually different portions of the separator for an electrochemical element of Comparative Example 1 when the separator for an electrochemical element were subjected to “Method of determining presence or absence of pinholes” and were photographed, are shown inFIG.3andFIG.4. Pinholes do not exist in the SEM photographs of Example 1, whereas pinholes exist in the SEM photographs of Comparative Example 1 (see a part surrounded by a broken line inFIG.3, two parts surrounded by a broken line inFIG.4). Some of the short fibers and/or the pulp-like fibers constituting the first fibrous layer part derived from the fiber deposit layer penetrates deeply into the second fibrous layer part until being exposed on the main surface where the second fibrous layer part derived from the wetlaid nonwoven fabrics A to D is exposed. Various physical properties of the separators for an electrochemical element of Examples and Comparative Examples were measured, and are summarized in Table 1. TABLE 1ExampleComparativeExampleExampleExampleExample1Example 12345Basis Weight (g/m2)9911778Thickness (μm)111319101012Air Permeability243332(cm3/cm2/sec)Porosity (%)444860524851Mass Average Density0.790.710.580.650.680.68(g/cm3)Dmax: Maximum Pore51857113Diameter (μm)Dave: Average Pore353342Diameter (μm)Dmax − Dave2132471Minimum Pore Diameter232331(μm)Presence of PinholesNoYesNoNoNoNo The separators for an electrochemical element of Examples 1 to 5 satisfied the pore diameter distribution defined by the present invention and had no pinhole. On the other hand, the separator for an electrochemical element of Comparative Example 1 did not satisfy the pore diameter distribution defined by the present invention, and the separator for an electrochemical element of Comparative Example 1 had pinholes. As described above, the present invention can provide a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit hardly occurs, and higher electric resistance between electrodes than intended is prevented. Further, the present invention can provide a separator for an electrochemical element capable of providing an electrochemical element in which an electric short circuit more hardly occurs, because a thin separator for an electrochemical element having a thickness of, for example, 20 μm or less can be provided in a form without pinholes. Example 6 Silica particles and cellulose nanofibers were added to pure water and mixed using a Disper type stirring blade. After mixing, a polyacrylic acid resin binder was added thereto and continued to be stirred to prepare a coating liquid (liquid temperature: 25° C., concentration of solid contents: 27% by mass). Composition and mass of the solid contents in the coating liquid were as described below:Silica particle (D50: 450 nm): 98 parts by massCellulose nanofiber: 0.01 parts by massPolyacrylic acid resin binder: 2 parts by mass. The coating liquid was applied to the main surface on the side of the fibrous layer derived from the wetlaid nonwoven fabric A in the separator for an electrochemical element prepared in Example 2 using a gravure roll. Then, the wetlaid nonwoven fabric A containing the coating liquid was dried at 100° C. to remove the dispersion medium in the coating liquid to prepare a separator for an electrochemical element. Example 7 A separator for an electrochemical element was prepared in the same manner as in Example 6 except for changing application amount of the coating liquid. Example 8 Silica particles were added to pure water and mixed using a Disper type stirring blade. After mixing, a polyacrylic acid resin binder was added thereto and continued to be stirred to prepare a coating liquid (liquid temperature: 25° C., concentration of solid contents: 27% by mass). Composition and mass of the solid contents in the coating liquid were as described below.Silica particles (D50: 2.1 μm): 98 parts by massPolyacrylic acid resin binder: 2 parts by mass The coating liquid was applied to the main surface on the side of the fibrous layer derived from the wetlaid nonwoven fabric A in the separator for an electrochemical element prepared in Example 2 using a gravure roll. Then, the wetlaid nonwoven fabric A containing the coating liquid was dried at 100° C. to remove the dispersion medium in the coating liquid to prepare a separator for an electrochemical element. Various physical properties of the separators for an electrochemical element having particles supported on their surfaces of Examples prepared as described above were measured, and are summarized in Table 2. TABLE 2Example 6Example 7Example 8Basis Weight (g/m2)171426Thickness (μm)212029Air Permeability0.050.170.27(cm3/cm2/sec)Porosity (%)505257Mass Average Density0.810.700.90(g/cm3)Dmax: Maximum Pore1.02.61.1Diameter (μm)Dave: Average Pore0.51.50.9Diameter (μm)Dmax − Dave0.51.10.2Minimum Pore0.41.20.7Diameter (μm)Presence of PinholesNoNoNo From the results of Examples 6 to 8, the separators for an electrochemical element, loading the particles on the surface thereof according to the present invention, have a further smaller maximum pore diameter and a further smaller minimum pore diameter, and a further narrower pore diameter distribution. Therefore, the separator for an electrochemical element according to the present configuration can provide an electrochemical element in which thermal stability is improved and reduction of battery capacity is improved, and an electric short circuit hardly occurs and the electric resistance between the electrodes is prevented from being higher than intended. INDUSTRIAL APPLICABILITY The separator for an electrochemical element according to the present invention may be used, for example, as a separator for an electrochemical element which separates electrodes from each other, for an electrochemical element such as a primary battery (for example, a lithium battery, a manganese battery, a magnesium battery, etc.) and a secondary battery (for example, a lithium ion battery, a nickel-metal hydride battery, a nickel cadmium battery, a zinc battery, a redox flow battery, etc.), a capacitor, a fuel cell battery and the like, irrespective of an aqueous system or a non-aqueous system. | 63,152 |
11862811 | BEST MODE Hereinafter, the present invention will be described in detail. The functional separator according to the present invention comprises a base separator and a polyethylene oxide (PEO)-conductive carbon composite layer present on the surface of the base separator. The separator is interposed between the positive electrode and the negative electrode (that is, a physical separator having a function of physically separating the electrodes), and enables the transport of lithium ions between the positive electrode and the negative electrode, while separating or insulating the positive electrode and the negative electrode from each other. In particular, the separator is preferred as it has a low resistance to ion migration of the electrolyte and an excellent electrolyte impregnation ability, and the separator can be made of a porous, non-conductive or insulating material. The base separator in which the PEO-conductive carbon composite layer is excluded may be an independent member such as a film or a coating layer added (adhered or faced) to any one or more of positive and negative electrodes. Specifically, as a base separator, porous polymer films, for example, porous polymer films made of polyolefin-based polymers, such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer may be used alone or may be stacked and used, or the base separator may be a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting point glass fiber or polyethylene terephthalate fiber, but is not limited thereto. The conductive carbon constituting the PEO-conductive carbon composite layer is coated with polyethylene oxide (PEO) on the surface of the base separator, and the conductive carbon itself has a pore structure, so the electrolyte solution is free to enter and exit. In addition, the conductive carbon, as its name suggests, has conductivity and is a component that can reduce lithium polysulfide by transferring electrons by such a property. The conductive carbons may be applied without particular limitation as long as they are conductive carbon materials capable of exhibiting the above effects. Among them, carbon nanotubes (CNT), graphene, and reduced graphene oxide (rGO) can be exemplified, and among these, the use of the reduced graphene oxide is preferable, and it is more preferable to use thermally exfoliated reduced graphene oxide (TErGO), which is advantageous in exfoliation due to thermal expansion and can thus coat thin and large areas, thereby exhibiting excellent performance. The thermally exfoliated reduced graphene oxide (TErGO) may be formed by heat-treating graphene oxide to prepare a thermally expanded graphene oxide (or thermally exfoliated graphene oxide) and then reducing it. At this time, the heat treatment for the preparation of the thermally expanded graphene oxide may be performed by a known method or various modified methods thereof, and is not particularly limited in the present invention. For example, the heat treatment may be performed for 10 minutes to 3 hours in a temperature range of 300 to 900° C. In particular, the thermally exfoliated reduced graphene oxide (TErGO) is one which is exfoliated, and may have a thickness of 0.5 to 40 nm, preferably 5 to 30 nm, more preferably 10 to 20 nm, and may have a plate shape or flake shape. In addition, the degree of thermal expansion of the thermally exfoliated reduced graphene oxide (TErGO) may vary from less than 100 m2/g to 900 m2/g in the range of BET, and the degree of reduction can be measured through XPS or EA. In addition, the general graphene oxide may have a mass ratio of carbon and oxygen of about 1:1, whereas the reduced graphene oxide may have a mass ratio of about 9:1. In general, since the reduced graphene oxide before exfoliation has a thickness of about 50 to 500 nm and is easily detached when coated in the form of particles (even if it is not a separator), not only does it require the use of a binder, but also the coating density is low, so that the desired effect cannot be sufficiently obtained. However, according to the present invention, it is possible to uniformly and densely coat on the substrate by using thermally exfoliated reduced graphene oxide in the form of a plate or flake having a range of thickness through exfoliation. On the other hand, a binder may be interposed between the base separator and the PEO-conductive carbon composite layer so that the PEO-conductive carbon composite layer can be more easily coated on the surface of the base separator. However, in the case of using the thermally exfoliated reduced graphene oxide (TErGO) among the conductive carbon, in particular, reduced graphene oxide (rGO), of the present invention, since the conductive carbon is made of a plate-like or flake-like structure, the conductive carbon layer can be free-standing without the binder and easily coated on the surface of the base separator. In addition to the conductive carbon, polyethylene oxide (PEO) or polyethylene glycol constituting the PEO-conductive carbon composite layer is used to maximize the reduction efficiency of the lithium polysulfide, and due to its chemical bonding with the conductive carbon or its physical properties, it is possible to more smoothly transfer lithium ions, while improving the bonding force with the base separator. More specifically, the polyethylene oxide is to form a chemical bond with the conductive carbon, may have a chain type, a branch type, or a radial type, and may be modified to introduce a specific functional group into the terminal. If a functional group is on a terminal of the polyethylene oxide, the functional group may be an amine group (—NH2) and a carboxy group (—COOH). For example, if an amine group is on a terminal of the polyethylene oxide, an amide bond may be formed with the carboxy group of the conductive carbon. If a carboxy group is on a terminal of the polyethylene oxide, an ester bond may be formed with a hydroxy group (—OH) or carboxy group of the conductive carbon, or anhydride may be formed by a dehydration condensation reaction. In addition, if a functional group is not on a polyethylene oxide, the hydroxy group of the polyethylene oxide itself and the carboxy group of the conductive carbon may be bonded to form an ester bond. Meanwhile, the polyethylene oxide having a functional group introduced into the terminal may have a structure of a polyethylene oxide-linker-functional group. Examples of the case where the functional group is an amine group may comprise polyethylene oxide-carbonyl-ethylenediamine, ethylenediamine-carbonyl-polyethylene oxide-carbonyl-ethylenediamine, and the like. In the PEO-conductive carbon composite layer, the weight ratio of the conductive carbon to the polyethylene oxide may be 1:0.01 to 100, preferably 1:0.08 to 0.6, more preferably 1:0.1 to 0.5. If the weight ratio is outside the weight ratio described above, the effects obtained by using polyethylene oxide may be insignificant. In addition, the number average molecular weight (Mn) of the polyethylene oxide may be 200 to 10,000,000, preferably 500 to 50,000. The PEO-conductive carbon composite layer may be formed on a part of the surface of the base separator, but in order to maximize the effect of the use of conductive carbon and polyethylene oxide, it is preferable to form the entire surface of the base separator. The PEO-conductive carbon composite layer has a thickness of 0.1 to 15 μm, preferably 0.5 to 10 μm, more preferably 0.5 to 5 μm. If the thickness of the PEO-conductive carbon composite layer is less than 0.1 μm, since the conductive network is not sufficiently formed, there is a problem that electronic conductivity is lowered. If the thickness of the PEO-conductive carbon composite layer exceeds 15 μm, there is a concern that the passage of lithium ions is hindered, the cell resistance is increased, and an adverse problem occurs in terms of energy density per volume. In addition, the coating weight of the PEO-conductive carbon composite layer is 1 to 300 μg/cm2, preferably 3 to 80 μg/cm2, more preferably 5 to 80 μg/cm2, based on the surface area of the base separator to be coated. If the coating weight of the PEO-conductive carbon composite layer is less than 1 μg/cm2based on the surface area of the base separator, the effect arising from the use of conductive carbon and polyethylene oxide may be insignificant. If the coating weight of the PEO-conductive carbon composite layer exceeds 300 μg/cm2, there may be no additional effect obtained by using conductive carbon and polyethylene oxide. Next, a method of manufacturing a functional separator according to the present invention will be described. The method of manufacturing a functional separator comprises (a) modifying the terminal of polyethylene oxide, (b) preparing a PEO-conductive carbon composite by chemically bonding the terminal functional group of the modified polyethylene oxide with conductive carbon to form a polyethylene oxide-conductive carbon composite, and (c) coating the prepared PEO-conductive carbon composite on the surface of the base separator. In step (a), the method of modifying the terminal of polyethylene oxide (specifically, modifying with a specific functional group) may be general modification methods for introducing a specific functional group into the terminal of the compound, for example, reacting an amine-based compound containing two or more amine groups such as ethylenediamine with polyethylene oxide in a solvent. Examples of the solvent may comprise water, and organic solvents such as ethanol, acetone, IPA, THF, MC, DMF, DMSO, and DMAc. Among them, it may be desirable to apply THF or a compound having similar properties as a solvent. In addition, the reaction in step (a) can be carried out for 1 to 24 hours at room temperature to 100° C., preferably 40 to 70° C. Step (b) is a process for preparing a PEO-conductive carbon composite by chemically bonding the hydroxyl or carboxy group of the conductive carbon to the terminal functional group of the polyethylene oxide modified and introduced or formed in step (a). The chemical bond may be achieved through a reaction under high temperature. The reaction can be carried out, for example, at a temperature of 70 to 150° C., preferably at a temperature of 80 to 120° C., more preferably at a temperature of about 100° C., for 8 to 48 hours, preferably 15 to 30 hours. Through the chemical bonding of the functional group of polyethylene oxide and the hydroxy group or carboxy group of the conductive carbon formed by the above-described reaction, the bonding force between the conductive carbon and polyethylene oxide, as well as the bonding force between the conductive carbon and polyethylene oxide containing PEO-conductive carbon composite and the base separator are excellent, and it is possible to obtain the advantage of smooth delivery of lithium ions. As described above, after the PEO-conductive carbon composite in which conductive carbon and polyethylene oxide are chemically bonded is prepared, a functional separator according to the present invention is prepared by coating the surface of the base separator with the PEO-conductive carbon composite. At this time, the coating may be performed by a drop-cast method, a dip-coating method, a blade coating method, a spray coating method, a Meyer bar coating method, or a vacuum filter. Lastly, a lithium secondary battery comprising the functional separator provided by the present invention will be described. The lithium secondary battery comprising the functional separator comprises a positive electrode, a negative electrode, the functional separator interposed between the positive electrode and the negative electrode, and an electrolyte, and can be exemplified as any lithium secondary battery known in the art, such as a lithium-sulfur battery, a lithium air battery, and a lithium metal battery, and is preferably a lithium-sulfur battery. The description of the functional separator comprised in the lithium secondary battery is as described above. In addition, the positive electrode, the negative electrode, and the electrolyte applied to the lithium secondary battery may be common ones used in the art, and detailed description thereof will be described later. Meanwhile, the present invention can also provide a battery module comprising the lithium secondary battery as a unit cell and a battery pack including the same. The battery module or the battery pack may be used as a power source for any one or more medium and large-sized devices of a power tool; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system. Hereinafter, a description of the positive electrode, the negative electrode, and the electrolyte applied to the lithium secondary battery according to the present invention is added. Positive Electrode The positive electrode used in the present invention will be described below. After preparing a composition for the positive electrode containing the positive electrode active material, the electrically conductive material, and the binder, the slurry prepared by diluting such a composition in a predetermined solvent (disperse medium) can be directly coated and dried on a positive electrode current collector to form a positive electrode layer. Alternatively, after casting the slurry on a separate support, a film obtained by peeling from the support can be laminated on a positive electrode current collector to produce a positive electrode layer. In addition, the positive electrode can be manufactured in a variety of ways using methods well known to those skilled in the art. The electrically conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and for example, graphite; carbon blacks such as Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; electrically conductive fibers such as carbon fibers and metal fibers; carbon fluoride; metal powders such as aluminum, and nickel powder; electrically conductive whiskers such as zinc oxide and potassium titanate; electrically conductive metal oxides such as titanium oxide; electrically conductive materials such as polyphenylene derivatives and the like can be used. Specific examples of commercially available and electrically conductive materials may comprise acetylene black series of products from Chevron Chemical Company or DENKA BLACK (Denka Singapore Private Limited), products from Gulf Oil Company, KETJEN BLACK, EC series of products from Armak Company, products of VULCAN XC-72 from Cabot Company, and SUPER P (products from Timcal Company). The electrically conductive material is not particularly limited as long as it as electrical conductivity without causing chemical changes in the battery, and for example, graphite; carbon blacks such as Denka black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; electrically conductive fibers such as carbon fibers and metal fibers; carbon fluoride: metal powders such as aluminum, and nickel powder; electrically conductive whiskers such as zinc oxide and potassium titanate; electrically conductive metal oxides such as titanium oxide; electrically conductive materials such as polyphenylene derivatives and the like can be used. Specific examples of commercially available and electrically conductive materials may comprise acetylene black series of products from Chevron Chemical Company or Denka black (Denka Singapore Private Limited), products from Gulf Oil Company, Ketjen black, EC series of products from Armak Company, products of Vulcan XC-72 from Cabot Company, and Super P (products from Timcal Company). The binder is for attaching the positive electrode active material to the current collector well. The binder should be well dissolved in the solvent, and should not only constitute the conductive network between the positive electrode active material and the electrically conductive material, but also have a proper impregnation property into the electrolyte solution. The binder may be any binder known in the art, and specifically may be, but is not limited thereto, any one selected from the group consisting of fluororesin-based binders including polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE); rubber-based binders including styrene-butadiene rubber, acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose-based binders including carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose; polyalcohol-based binders; polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders, polyester-based binders, silane-based binders, and mixtures or copolymers of two or more thereof. The content of the binder may be, but is not limited to, 0.5 to 30 wt. % based on the total weight of the composition for the positive electrode. If the content of the binder resin is less than 0.5 wt. %, the physical properties of the positive electrode may be deteriorated and thus positive electrode active material and the electrically conductive material can be broken away. If the content exceeds 30 wt. %, the ratio of the active material and the electrically conductive material in the positive electrode is relatively reduced and thus the battery capacity may be reduced, and the efficiency may be reduced by acting as a resistive element. The composition for the positive electrode comprising the positive electrode active material, the electrically conductive material, and the binder may be diluted in a predetermined solvent and coated on a positive electrode current collector using a conventional method known in the art. First, a positive electrode current collector is prepared. The positive electrode current collector generally has a thickness of 3 to 500 μm. The positive electrode current collector is not particularly limited as long as it has a high electrical conductivity without causing chemical changes in the battery, and for example, may be stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. The current collector can also increase the adhesive force of the positive electrode active material by forming fine irregularities on its surface and can be in various forms such as film, sheet, foil, net, porous body, foam, and non-woven fabric. Next, a slurry obtained by diluting the composition for the positive electrode containing the positive electrode active material, the electrically conductive material, and the binder in a solvent is applied on the positive electrode current collector. The composition for the positive electrode containing the above-described positive electrode active material, electrically conductive material, and binder may be mixed with a predetermined solvent to prepare the slurry. At this time, the solvent should be easy to dry, and it is most preferable to be able to dissolve the binder well, but to keep the positive electrode active material and the electrically conductive material in a dispersed state without dissolving. If the solvent dissolves the positive electrode active material, since the specific gravity (D=2.07) of sulfur in the slurry is high, there is a tendency that the sulfur is submerged in the slurry, which in turn causes sulfur to flow into the current collector during coating and cause problems in the electrically conductive network, thereby causing problems with regard to the operation of the battery. The solvent (disperse medium) may be water or an organic solvent. The organic solvent may be at least one selected from the group consisting of dimethylformamide, isopropyl alcohol, acetonitrile, methanol, ethanol, and tetrahydrofuran. Subsequently, there is no particular limitation on the method of applying the composition for the positive electrode in the slurry state. For example, a coating layer may be prepared by a doctor blade coating method, a dip coating method, a gravure coating method, a slit die coating method, a spin coating method, a comma coating method, a bar coating method, a reverse roll coating method, a screen coating method, and a cap coating method, etc. Thereafter, in the composition for the positive electrode that has undergone such a coating process, evaporation of the solvent (disperse medium), compaction of the coating film, and adhesion between the coating film and the current collector are achieved through a drying process. At this time, drying is performed according to a conventional method, and is not particularly limited. Negative Electrode As the negative electrode, any one capable of intercalation and deintercalation of lithium ions can be used. For example, metal materials such as lithium metal and lithium alloy, and carbon materials such as low crystalline carbon and high crystalline carbon can be exemplified. As the low crystalline carbon, soft carbon and hard carbon are typical. As the high crystalline carbon, high temperature sintered carbon such as natural graphite, Kish graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch derived cokes are typical. In addition, alloy series containing silicon, oxides such as Li4Ti5O12or the like are also well-known negative electrodes. In this case, the negative electrode may comprise a binder. The binder may be various kinds of binder polymers such as polyvinylidenefluoride (PVDF), polyvinylidenefluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyacrylonitrile, polymethylmethacrylate, and styrene-butadiene rubber (SBR). The negative electrode may optionally further comprise a negative electrode current collector for supporting the negative electrode active layer containing the negative electrode active material and the binder. The negative electrode current collector may be specifically selected from the group consisting of copper, stainless steel, titanium, silver, palladium, nickel, alloys thereof, and combinations thereof. The stainless steel may be surface-treated with carbon, nickel, titanium or silver, and an aluminum-cadmium alloy may be used as an alloy. In addition, a sintered carbon, a nonconductive polymer surface-treated with a conductive material, or a conductive polymer may be used. The binder serves to paste the negative electrode active material, to bond the active materials to each other, to bond the active material and the current collector, to buffer the expansion and contraction of the active material and so on. Specifically, the binder is the same as described above for the binder of the positive electrode. Also, the negative electrode may be lithium metal or lithium alloy. The non-limiting examples of the negative electrode may be a thin film of lithium metal, and may be an alloy of lithium and at least one metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al, and Sn. Electrolyte The electrolyte solution comprises solvents and lithium salt, and if necessary, may further contain additives. The solvent can be used without particular limitation, as long as it is a conventional non-aqueous solvent that serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Examples of the non-aqueous solvent may comprise carbonate-based solvents, ester-based solvents, ether-based solvents, ketone-based solvents, alcohol-based solvents, aprotic solvents and the like. More specifically, examples of the carbonate-based solvent may comprise dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), or butylene carbonate (BC), etc. Examples of the ester-based solvent may specifically include methyl acetate, ethyl acetate, n-propyl acetate, 1,1-dimethyl ethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, valerolactone, and mevalonolactone, carprolactone, etc. Examples of the ether-based solvent may specifically include diethyl ether, dipropyl ether, dibutyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane, diethoxyethane, diglyme, triglyme, tetraglyme, tetrahydrofuran, 2-methyltetrahydrofuran, polyethylene glycol dimethyl ether, etc. In addition, examples of the ketone-based solvent may comprise cyclohexanone, etc. Examples of the alcohol-based solvent may comprise ethylalcohol, isopropylalcohol, etc. Examples of the aprotic solvent may comprise nitriles such as acetonitrile, amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane (DOL), sulfolane, etc. The non-aqueous organic solvents may be used alone or in combination of two or more. The mixing ratio when using in combination of two or more may be appropriately adjusted depending on the desired performance of the battery, and a solvent in which 1,3-dioxolane and dimethoxyethane are mixed in a volume ratio of 1:1 can be exemplified. Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely illustrative of the present invention, and it is apparent to those skilled in the art that various changes and modifications can be made within the scope and technical spirit of the present invention, and it is natural that such changes and modifications belong to the appended claims. [Example 1] Preparation of Functional Separator First, through the reaction of Reaction Scheme 1 using a solvent (THF) and ethylenediamine, both terminals of polyethylene oxide were modified with amine groups: In addition, after the graphene oxide (SE2430, Sixth Element, China) was reduced by heat treatment at 300° C. for 1 hour, a thermally exfoliated reduced graphene oxide having a thickness of 15 nm was prepared using a high-speed mixer and an ultrasonic homogenizer. Subsequently, the prepared thermally exfoliated reduced graphene oxide and 10 parts by weight of polyethylene oxide (having amine groups formed in both terminals) relative to 100 parts by weight of thermally exfoliated reduced graphene oxide were reacted at 100° C. for 24 hours to prepare a PEO-conducting carbon composite in which the amine group of polyethylene oxide and the carboxy group of TErGO were chemically bonded. Subsequently, the porous base separator made of polyethylene is coated with the prepared PEO-conductive carbon composite by a vacuum filtration method and then dried to manufacture a functional separator having a weight of the coating layer (PEO-conductive carbon composite layer) of 6 μg/cm2based on the surface area of the base separator and a thickness of 4 μm. [Example 2] Manufacture of Functional Separator A functional separator was manufactured in the same manner as in Example 1, except that the weight of the coating layer (PEO-conductive carbon composite layer) was changed to be 22 μg/cm2based on the surface area of the base separator and the thickness was changed to be 6 μm. [Example 3] Manufacture of Functional Separator A functional separator was manufactured in the same manner as in Example 1, except that the weight of the coating layer (PEO-conductive carbon composite layer) was changed to be 74 μg/cm2based on the surface area of the base separator and the thickness was changed to be 10 μm. [Example 4] Manufacture of Functional Separator A functional separator was manufactured in the same manner as in Example 1, except that the content of polyethylene oxide having amine groups formed in both terminals was changed to be 50 parts by weight relative to 100 parts by weight of TErGO and the weight of the coating layer (PEO-conductive carbon composite layer) was changed to be 16 μg/cm2based on the surface area of the base separator. [Example 5] Manufacture of Functional Separator A functional separator was manufactured in the same manner as in Example 1, except that the content of polyethylene oxide having amine groups formed in both terminals was changed to be 50 parts by weight relative to 100 parts by weight of TErGO, the weight of the coating layer (PEO-conductive carbon composite layer) was changed to be 23 μg/cm2based on the surface area of the base separator, and the thickness was changed to be 6 μm. [Example 6] Manufacture of Functional Separator A functional separator was manufactured in the same manner as in Example 1, except that the content of polyethylene oxide having amine groups formed in both terminals was changed to be 50 parts by weight relative to 100 parts by weight of TErGO, the weight of the coating layer (PEO-conductive carbon composite layer) was changed to be 64 μg/cm2based on the surface area of the base separator, and the thickness was changed to be 10 μm. [Comparative Example 1] Conventional Separator A bare separator made of polyethylene (PE) without a separate coating was manufactured. [Comparative Example 2] Manufacture of Conventional Separator Only the thermally exfoliated reduced graphene oxide (TErGO) which is a conductive carbon was coated on a porous base separator made of polyethylene by vacuum filtration and then dried to manufacture a separator having the weight of the coating layer of 6 μg/cm2based on the surface area of the base separator and the thickness of 4 μm. [Comparative Example 3] Manufacture of Conventional Separator A separator was prepared in the same manner as in Example 1, except that polyethylene imine instead of polyethylene oxide having amine groups formed on both terminals was used. [Examples 1 to 6, Comparative Examples 1 to 3] Manufacture of Lithium-Sulfur Battery A lithium-sulfur battery comprising separators prepared in Examples 1 to 6 or Comparative Examples 1 to 3, 70 μl of electrolyte solution (DOL:DME (1:1 (vol)), 1.0 M LiTFSI, 1 wt. % LiNO3), and a sulfur positive electrode and a lithium metal negative electrode was manufactured. [Experimental Example 1] Evaluation of Discharging Capacity and Lifetime Characteristics of Lithium-Sulfur Battery After the discharging current rate was set to 0.1 C (three times), 0.2 C (three times), and then 0.5 C, the discharging capacity and lifetime characteristics of the manufactured lithium-sulfur battery were observed.FIGS.1to3are graphs comparing discharging capacities of lithium-sulfur batteries according to the examples of the present invention and comparative examples, andFIG.4is a graph comparing the lifetime characteristics of lithium-sulfur batteries according to the examples of the present invention and comparative examples. As a result of evaluating the initial discharging capacities of the prepared lithium-sulfur batteries, it was confirmed that in the case of the batteries of Examples 1 to 3 in which the PEO-conductive carbon composite was applied as the coating layer of the base separator, the discharging amount is higher as compared to the battery of Comparative Example 1 which had no coating on the base separator, as shown inFIG.1. In addition, it was confirmed that in the case of the batteries of Examples 4 to 6 in which the PEO-conductive carbon composite was applied as the coating layer of the base separator, the overvoltage is improved and the discharging amount is also slightly increased as compared to the battery of Comparative Example 1 which had no coating on the base separator, as shown inFIG.2. In addition, it was confirmed that as a result of evaluating the discharge capacity after the initial stage of the prepared lithium-sulfur battery, the batteries of Examples 4 to 6, in which the PEO-conductive carbon composite was applied as a coating layer of the base separator, have an improved overvoltage and a significantly increased discharging amount as compared to the battery of Comparative Example 1 without any coating on the base separator, as shown inFIG.3. Meanwhile, as a result of evaluating the lifetime characteristics of the manufactured lithium-sulfur batteries, it was confirmed that in the case of the batteries of Examples 1 and 2 in which the PEO-conductive carbon composite was applied as the coating layer of the base separator, the lifetimes are increased as compared to the battery of Comparative Example 1 which had no coating on the base separator, the battery of Comparative Example 2 in which only the thermally exfoliated reduced graphene oxide (TErGO) was coated on the base separator, and the battery of Comparative Example 3 using polyethylene imine instead of modified polyethylene oxide, as shown inFIG.4. | 32,955 |
11862812 | DETAILED DESCRIPTION Reference will now be made in more detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of embodiments of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. The subject matter of the present disclosure described below may be subjected to various transformations and may have various embodiments, and certain embodiments are illustrated in the drawings and described in more detail in the detailed description. However, this is not intended to limit the present disclosure to a specific embodiment, and it should be understood that the present disclosure includes all changes, equivalents, and replacements that fall within the spirit and technical scope of the present disclosure. The following terms are used only to describe specific embodiments, and are not intended to limit the present disclosure. The singular expression includes a plurality of expressions unless explicitly differently indicated in the context. Hereinafter, it should be understood that terms such as “include” or “have” are intended to indicate the presence of a feature, a number, a step, an operation, a constituting element, a part, a component, a material, or a combination thereof described in the specification, and do not preclude the presence or addition of one or more other features, numbers, steps, operations, constituting elements, parts, components, materials, or a combination thereof. Hereinafter, “/” may be interpreted as “and” or “or” according to circumstances. In the drawings, in order to clearly represent several layers and regions, the thickness is enlarged or reduced. Like reference numerals refer to like elements throughout the specification. Throughout the specification, when it is assumed that a portion such as a layer, a film, an area, a plate, and the like is “on” or “above” another portion, the portion is not only directly above the other portion but also includes another portion therebetween. Throughout the specification, terms such as first and second may be used to describe various constituting elements, but constituting elements should not be limited by terms. The terms are only used to distinguish one constituting element from another. Hereinafter, a composite separator according to example embodiments, a lithium battery including the composite separator, and a method of preparing the composite separator will be described in more detail. A composite separator according to an embodiment includes: a porous substrate; and a coating layer on at least one surface of the porous substrate, wherein the coating layer includes a water-soluble binder and inorganic particles, the water-soluble binder includes a polyacrylic acid metal salt, and the polyacrylic acid metal salt has a weight average molecular weight of 300,000 Dalton (Da) or more, and the inorganic particles have an average particle diameter (D50) of 500 nm or more. As the composite separator contains a polyacrylic acid metal salt having a weight average molecular weight of 300,000 Dalton or more and inorganic particles having an average particle diameter of 500 nm or more, the composite separator concurrently (e.g., simultaneously) provides enhanced thermal stability and adhesion force, and the amount of the residual moisture included therein may be decreased. In one or more embodiments, rapid contraction and/or deformation of the composite separator at a high temperature is suppressed or reduced, and the adhesion force between the coating layer and the porous substrate, which are included in the composite separator, is improved. Accordingly, the phenomenon in which the coating layer of the composite separator is easily detached from the porous substrate due to the repeated shrinkage/expansion of the electrode volume during the charging and discharging process of a lithium battery, can be suppressed or reduced. Regarding a lithium battery, volume expansion of the lithium battery due to separation of the coating layer, an increase in internal resistance of the lithium battery, and a short circuit of the lithium battery due to melting of a porous substrate at a high temperature may be prevented (or an occurrence of such a short circuit may be reduced). In addition, the thermal stability of the lithium battery including the composite separator may be improved, and the energy density of the lithium battery may be increased due to the suppression or reduction of the increase in volume of the lithium battery. In addition, because the amount of the residual moisture contained in the composite separator is reduced, and thus, side reactions in the charging/discharging process of the lithium battery including the composite separator are suppressed or reduced, the cyclic characteristics of the lithium battery may be improved and the decrease in discharge capacity may be suppressed or reduced. The coating layer may include a binder, and the binder may include, for example, a polyacrylic acid metal salt having a weight average molecular weight of 300,000 Dalton or more. The weight average molecular weight of the polyacrylic acid metal salt included in the composite separator may be, for example, from about 300,000 Dalton to about 500,000 Dalton, from about 300,000 Dalton to about 480,000 Dalton, from about 300,000 Dalton to about 450,000 Dalton, from about 300,000 Dalton to about 420,000 Dalton, from about 300,000 Dalton to about 400,000 Dalton, from about 300,000 Dalton to about 380,000 Dalton, from about 320,000 Dalton to about 380,000 Dalton, or from about 330,000 Dalton to about 370,000 Dalton. When the polyacrylic acid metal salt has an excessively low weight average molecular weight (e.g., is outside of the ranges described herein), the heat shrinkage rate of the composite separator may increase, and thus, the heat resistance of the composite separator may be decreased. When the weight average molecular weight of the polyacrylic acid metal salt is too high (e.g., is outside of the ranges described herein), it may be difficult to dissolve the polyacrylic acid metal salt in a solvent, and thus, it may be difficult to form a suitable coating layer. In the present specification, the weight average molecular weight of the binder included in the composite separator may be measured by, for example, gel permeation chromatography (GPC) with respect to a polystyrene standard sample. The polyacrylic acid metal salt included in the composite separator is, for example, a polyacrylic acid lithium salt. The term “polyacrylic acid lithium salt,” as used herein, refers to a form in which some or all hydrogen at an end group of an acrylic acid repeating unit (e.g., an acidic hydrogen of the acrylic acid group) included in a polyacrylic acid is substituted with lithium ions. The acrylic repeating unit substituted with lithium ions in the acrylic acid repeating unit including the polyacrylic acid metal salt has a mole ratio of greater than 0 and equal to or less than 1.0 (e.g., a mole ratio of the acrylic repeating unit substituted with lithium ions in the polyacrylic acid metal salt to the total number of repeating units (e.g., the sum of the acrylic repeating units substituted with lithium ions and the acrylic acid repeating units in the polyacrylic acid metal salt) is greater than 0 and equal to or less than 1.0). As the composite separator includes the polyacrylic acid metal salt, compared to the composite separator including polyacrylic acid in which lithium ions are not substituted, the heat shrinkage rate may be reduced and the adhesion force between the coating layer and the substrate may be increased. Therefore, the thermal stability of the lithium battery including the polyacrylic acid lithium salt may be enhanced and the deterioration in the charging and discharging process may be suppressed or reduced. The acrylic repeating unit substituted with lithium ions in the acrylic repeating unit included in the polyacrylic acid metal salt (which may also be referred to herein as a polyacrylic acid lithium salt) may have a mole ratio of (e.g., a mole ratio of the acrylic repeating unit substituted with lithium ions in the polyacrylic acid metal salt to the total number of repeating units (e.g., the sum of the acrylic repeating units substituted with lithium ions and the acrylic acid repeating units in the polyacrylic acid metal salt) may be), for example, about 0.1 to about 0.9, about 0.2 to about 0.9, about 0.2 to about 0.8, or about 0.3 to about 0.8. In the present specification, a mole ratio of an acrylic repeating unit substituted with lithium ions in the acrylic repeating unit including a polyacrylic acid metal salt may be defined as, for example, a degree of substitution (DS). As the polyacrylic acid metal salt has such ranges of DS, the heat shrinkage rate of the composite separator may be further reduced, and the adhesion force between the coating layer and the substrate may be further enhanced. For example, the coating layer may further include or may not include a binder other than the polyacrylic acid lithium salt described above. The binder additionally included in the coating layer may be, for example, a water-soluble or water-dispersible binder. The binder additionally included in the coating layer may be, for example, polyacrylic acid, polyvinylidene fluoride, a polyvinylidene fluoride-hexafluoropropylene copolymer, a polyvinylidene fluoride-trichloroethylene copolymer, a polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, an ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, an acrylonitrile styrene butadiene copolymer, polyimide, polyvinylacetamide, polyacrylamide, polyester, polyvinylacetate, polyimide, polyimide, polyamideimide, polyetherimide, polyarylate, polysulfone, polyethersulfone, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, or a combination of two or more thereof. The binder additionally included in the coating layer may be, for example, a fluorine-based binder. The fluorine-based binder may be a binder in which some or all hydrogen connected or coupled to carbon is substituted with fluorine. For example, the fluorine-based binder may be a polymer containing a repeating unit derived from one or more monomers selected from a vinylidine fluoride monomer, an ethylene tetrafluoride monomer, and a propylene hexafluoride monomer. The fluorine-based binder may be, for example, a fluorine-based and/or a fluorine-based copolymer. The fluorine-based binder additionally included in the coating layer may be, for example, a copolymer of the ethylene tetrafluoride monomer and another monomer. The other monomer used together with the ethylene tetrafluoride monomer may be one or more fluorine-containing monomers selected from vinylidene fluoride, hexafluoropropylene, chlorotrifluoroethylene, and perfluoroalkylvinylether. The fluorine-based binder may be, for example, an ethylene tetrafluoride-vinylidene fluoride copolymer, an ethylene tetrafluoride-hexafluoropropylene copolymer, an ethylene tetrafluoride-chlorotrifluoroethylene copolymer, or an ethylene tetrafluoride-perfluoroalkylvinylether. The amount of the ethylene tetrafluoride monomer included in the fluorine-based binder may be, for example, 10 mol % or more, 30 mol % or more, 50 mol % or more, 70 mol % or more, or 90 mol % or more, based on, for example, the total moles of the coating layer or the total moles of the fluorine-based binder. In one or more embodiments, the fluorine-based binder may be, for example, a copolymer of a vinylidine fluoride monomer and another monomer. The fluorine-based binder may be, for example, a copolymer of a vinylidine fluoride monomer and one or more fluorine-containing monomer selected from hexafluoropropylene, chlorotrifluoroethylene, fluorovinyl, and perfluoroalkylvinylether. In more detail, the vinylidine-based monomer may be a vinylidene fluoride homopolymer, a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-chlorotrifluoroethylene copolymer, and/or the like. The amount of the vinylidene fluoride-based monomer included in the fluorine-based binder may be, for example, 50 mol % or more, 60 mol % or more, 70 mol % or more, 80 mol % or more, or 90 mol % or more, based on, for example, the total moles of the coating layer or the total moles of the fluorine-based binder. The fluorine-based binder additionally included in the coating layer may be, for example, polyvinylidene fluoride, a polyvinylidene fluoride-hexafluoropropylene copolymer, a polyvinylidene fluoride-trichloroethylene copolymer, a polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polytetrafluoroethylene, and/or the like. The fluorine-based binder additionally included in the coating layer may be, for example, a vinylidene fluoride-hexafluoropropylene copolymer. The vinylidene fluoride-hexafluoropropylene copolymer additionally included in the coating layer may have a glass transition temperature of −10° C. or less and a melting point of 150° C. or more. The glass transition temperature and/or the melting point of the binder or copolymer may be measured using, for example, differential scanning calorimetry (DSC) or differential thermal analysis (DTA). A glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer additionally included in the coating layer may be, for example, −10° C. or less, −15° C. or less, −20° C. or less, or −25° C. or less. The glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, −80° C. or more, −60° C. or more, −50° C. or more, or −40° C. or more. The glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, from about −80° C. to about −10° C., from about −60° C. to about −15° C., from about −50° C. to about −40° C., and from about −40° C. to about −25° C. When the glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer is too low (e.g., is outside of the ranges described herein), crystallinity of the copolymer is lowered and thus, swelling with respect to an electrolytic solution is increased, resulting in a decrease in bending strength and/bonding strength. When the glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer is too high (e.g., is outside of the ranges described herein), crystallinity of the copolymer is increased and thus, swelling with respect to an electrolytic solution is negligible, resulting in a decrease in bending strength and/bonding strength. A melting point of the vinylidene fluoride-hexafluoropropylene copolymer additionally included in the coating layer may be, for example, 100° C. or more, 120° C. or more, 130° C. or more, or 140° C. or more. The melting point of the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, 200° C. or less, 190° C. or less, 180° C. or less, or 170° C. or less. The melting point of the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, from about 100° C. to about 200° C., from about 120° C. to about 190° C., from about 130° C. to about 180° C., or from about 140° C. to about 170° C. When the glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer is too low (e.g., is outside of the ranges described herein), crystallinity of the copolymer is lowered and thus, swelling with respect to an electrolytic solution is increased, resulting in a decrease in bending strength and/bonding strength. When the glass transition temperature of the vinylidene fluoride-hexafluoropropylene copolymer is too high (e.g., is outside of the ranges described herein), crystallinity of the copolymer is increased and thus, swelling with respect to an electrolytic solution is negligible, resulting in a decrease in bending strength and/bonding strength. The amount of hexafluoropropylene in the vinylidene fluoride-hexafluoropropylene copolymer additionally included in the coating layer may be, for example, 1 mol % or more, 3 mol % or more, or 5 mol % or more, based on, for example, the total moles of the coating layer or the total moles of the vinylidene fluoride-hexafluoropropylene copolymer. The amount of hexafluoropropylene contained in the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, 20 mol % or less, 17 mol % or less, or 15 mol % or less, based on, for example, the total moles of the coating layer or the total moles of the vinylidene fluoride-hexafluoropropylene copolymer. The amount of hexafluoropropylene contained in the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, from about 1 mol % to about 20 mol %, from about 3 mol % to about 17 mol %, or from about 5 mol % to about 15 mol %, based on, for example, the total moles of the coating layer or the total moles of the vinylidene fluoride-hexafluoropropylene copolymer. When the amount of hexafluoropropylene is too low (e.g., is outside of the ranges described herein), crystallinity of the copolymer is increased and swelling of the coating layer with respect to an electrolytic solution is negligible, resulting in a decrease in the bending strength and/bonding strength. The amount of hexafluoropropylene is excessively high (e.g., is outside of the ranges described herein), crystallinity of the copolymer is very high and swelling with respect to an electrolytic solution is excessively increased, resulting in a decrease in bending strength and/bonding strength. The fluorine-based binder additionally included in the coating layer may include, for example, a hydrophilic group. The hydrophilic group additionally included in the fluorine-based binder included in the binder may be one or more selected from a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, an acid anhydride group, a hydroxyl group, and a salt thereof, but is not limited thereto. The hydrophilic group may be any suitable hydrophilic functional group that is used in the art. The introduction of the hydrophilic group (e.g., a polar functional group) into the fluorine-based binder additionally included in the coating layer may be performed by, for example, adding, to the fluorine-containing monomer, a monomer including a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, an acid anhydride group, a hydroxyl group, or a salt thereof, and polymerizing the resultant mixture. Examples of the monomer having a carboxylic acid group include monocarboxylic acid and derivatives thereof, and dicarboxylic acid and derivatives thereof. Examples of the monocarboxylic acid include acrylic acid, methacrylic acid, crotonic acid, and the like. Examples of the monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxy acrylic acid, and β-diaminoacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, and the like. Examples of dicarboxylic acid derivatives include: methylallyl maleic acid, such as methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloro maleic acid, dichloro maleic acid, and fluoro maleic acid; and a maleic acid salt, such as diphenyl maleic acid, nonyl maleic acid, decyl maleic acid, dodecyl maleic acid, octadecyl maleic acid, and fluoroalkyl maleic acid. In addition, an acid anhydride producing a carboxyl group by hydrolysis may also be used. Examples of the acid anhydride of dicarboxylic acid include maleic acid anhydride, acrylic acid anhydride, maleic acid methyl anhydride, and maleic acid dimethyl anhydride. Also, examples of the dicarboxylic acid derivatives include monoesters and diesters of α, β-ethylenically unsaturated polycarboxylic acids such as monoethyl maleic acid, diethyl maleic acid, monobutyl maleic acid, dibutyl maleic acid, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, and dibutyl itaconate. Examples of the monomer having a sulfonic acid group include vinyl sulfonate, methylvinyl sulfonate, (meth)allyl sulfonate, styrene sulfonate, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamide-2-methylpropan sulfonate, 3-allyloxy-2-hydroxypropan sulfonate, and the like. Examples of the monomer having a phosphoric acid group include phosphate 2-(meth)acryloyloxyethyl, methyl phosphate-2-(meth)acryloyloxyethyl, and ethyl phosphate-(meth)acryloyloxyethyl. Examples of the monomer having a hydroxyl group may include: an ethylenically unsaturated alcohol such as (meth)allyl alcohol, 3-butene-1-ol, 5-hexene-1-ol, and the like; alkanol esters of ethylenically unsaturated carboxylic acids such as acrylic acid-2-hydroxyethyl, acrylic acid-2-hydroxypropyl, methacrylic acid-2-hydroxyethyl, methacrylic acid-2-hydroxypropyl, maleic acid di2-hydroxyethyl, maleic acid di4-hydroxybutyl, and itaconic acid di2-hydroxypropyl; an ester of polyalkylene glycol represented by the general formula CH2═CR1—COO—(CnH2nO)m—H (m is an integer of 2 to 9, n is an integer of 2 to 4, and R1represents hydrogen or a methyl group) and (meth)acrylic acid; mono(meth)acrylic acid esters of dicarboxylic acids such as 2-hydroxyethyl-2′-(meth)acryloyloxyphthalate, 2-hydroxyethyl-2′-(meth)acryloyloxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, and the like; a mono(meth)allyl ether of alkylene glycol, such as (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxy butyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, and (meth)allyl-6-hydroxyhexyl ether; polyoxyalkylene glycol(meth)monoallyl ether such as diethyleneglycol mono(meth)allyl ether, dipropyleneglycol mono(meth)allyl ether, and the like; a mono(meth)allyl ether of a halogen and hydroxy substituent of a (poly)alkylene glycol, such as glycerin mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether, (meth)allyl-2-hydroxy-3-chloropropylether; mono(meth)allylethers of polyphenols, such as eugenol and isoeugenol, and halogen substituents thereof; and (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether, (meth)allyl-2-hydroxypropyl thioether. Among them, the hydrophilic group may be a carboxylic acid group or a sulfonic acid group in that these hydrophilic groups have excellent adhesion force with an active material layer. For example, the carboxylic acid group may be used in that the transition metal ions eluted from the positive active material layer may be collected at high efficiency. The vinylidene fluoride-hexafluoropropylene copolymer additionally included in the coating layer may include, for example, a hydrophilic group. Because the vinylidene fluoride-hexafluoropropylene copolymer contains a hydrophilic group, the vinylidene fluoride-hexafluoropropylene copolymer may be strongly bound by, for example, hydrogen bonding with the active material present on the electrode surface or the binder in an electrode. The hydrophilic group included in the vinylidene fluoride-hexafluoropropylene copolymer may be a hydroxyl group, a carboxyl group, a sulfone group, and/or a salt thereof. The hydrophilic group included in the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, a carboxyl group (—COOH), a carboxylic acid ester group, and/or the like. For example, in the preparation of the vinylidene fluoride-hexafluoropropylene copolymer, copolymerizing may be performed with a monomer having a hydrophilic group, such as maleic anhydride, maleic acid, maleic acid ester, maleic acid monomethyl ester, and/or the like, to introduce a hydrophilic group into a main chain or to introduce a hydrophilic group into a side chain by grafting. The amount of the hydrophilic group may be measured by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), titration, etc. For example, in the case of a carboxylic acid group, the amount of a hydrophilic group may be obtained from an absorption intensity ratio of a C—H expansion vibration and a C═O expansion vibration of a carboxyl group based on a homopolymer by using FT-IR. The amount of the hydrophilic group included in the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, 0.1 mol % or more, 0.2 mol % or more, or 0.3 mol % or more, based on, for example, the total moles of the coating layer or the total moles of the vinylidene fluoride-hexafluoropropylene copolymer. The amount of hydrophilic groups included in the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, 5 mol % or less, 3 mol % or less, or 1 mol % or less, based on, for example, the total moles of the coating layer or the total moles of the vinylidene fluoride-hexafluoropropylene copolymer. The amount of the hydrophilic group included in the vinylidene fluoride-hexafluoropropylene copolymer may be, for example, from about 0.1 mol % to about 3 mol %, from about 0.2 mol % to about 2 mol %, or from about 0.3 mol % to about 1 mol %, based on, for example, the total moles of the coating layer or the total moles of the vinylidene fluoride-hexafluoropropylene copolymer. When the amount of the hydrophilic group is too low (e.g., is outside of the ranges described herein), crystallinity of the copolymer is increased, and thus, swelling with respect to the electrolytic solution is negligible, resulting in a decrease in bending strength and/bonding strength. When the amount of the hydrophilic group is excessively high (e.g., is outside of the ranges recited herein), crystallinity of the copolymer is very high and swelling with respect to the electrolytic solution is excessively increased, resulting in a decrease in bending strength and/bonding strength. The weight average molecular weight of the vinylidene fluoride-hexafluoropropylene copolymer additionally included in the coating layer may be, for example, from about 500,000 Dalton to about 1.2 million Dalton, from about 700,000 Dalton to about 1.2 million Dalton, from about 750,000 Dalton to about 1.15 million Dalton, or from about 800,000 Dalton to about 1 million Dalton. Because the vinylidene fluoride-hexafluoropropylene copolymer has a weight average molecular weight in any of the above ranges, a time for dissolving the vinylidene fluoride-hexafluoropropylene copolymer in a solvent is reduced, and thus production efficiency is increased. In addition, because the vinylidene fluoride-hexafluoropropylene copolymer has a weight average molecular weight in any of the ranges above, a certain level of gel strength may be maintained after the swelling of the vinylidene fluoride-hexafluoropropylene copolymer with respect to an electrolytic solution, and bending strength and/bonding strength may be increased. In one or more embodiments of the present specification, the weight average molecular weight is a polystyrene conversion value obtained by gel permeation chromatography. The coating layer includes inorganic particles. Because the coating layer includes the inorganic particles, the possibility of a short circuit between the positive electrode and the negative electrode is reduced, thereby enhancing the stability of the lithium battery. The inorganic particles including the coating layer may have an average particle diameter (D50) of, for example, from about 500 nm to less than about 1000 nm, from about 500 nm to about 950 nm, from about 550 nm to about 950 nm, from about 600 nm to about 950 nm, from about 600 nm to about 900 nm, from about 600 nm to about 850 nm, or from about 600 nm to about 800 nm. When the average particle diameter of the inorganic particles included in the coating layer is excessively reduced (e.g., is outside of the ranges described herein), the amount of the residual moisture included in the composite separator may be excessively increased. Therefore, a side reaction of the lithium battery including the composite separator is increased, thereby degrading cyclic characteristics of the lithium battery and reducing discharge capacity. When the average particle diameter of the inorganic particles included in the coating layer is excessively increased (e.g., is outside of the ranges described herein), the thickness of the coating layer is increased, and thus, the volume of the composite separator including the coating layer and the lithium battery is increased. As a result, energy density per unit volume of the lithium battery may be reduced. The average particle diameter of the inorganic particles may be measured by using, for example, a laser diffraction method and/or a dynamic light scattering method. The average particle diameter of the inorganic particles may be measured by using, for example, a laser scattering particle size distribution system (for example, LA-920, Horiba Co., Ltd.). As used herein, the term “average particle diameter” may refer to a median particle diameter (D50) when 50 vol % (volume percentage) of the inorganic particles are accumulated from the small particle side in terms of the volume. The inorganic particles included in the coating layer may be a metal oxide, a metalloid oxide, or a combination thereof. For example, the inorganic particles may include alumina, titania, boehmite, barium sulfate, calcium carbonate, calcium phosphate, amorphous silica, crystalline glass particles, kaolin, talc, silica-alumina composite oxide particles, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, mica, magnesium oxide, and/or the like. The inorganic particles may include, for example, TiO2, SnO2, CaO, ZnO, ZrO2, CeO2, NiO, MgO, Al2O3, SiO2, Y2O3, SrTiO3, BaTiO3, MgF2, Mg(OH)2, barium sulfate, boehmite, or a combination thereof. In consideration of compatibility with polyacrylic acid lithium salt, economic feasibility, and/or the like, the inorganic particles may include alumina, titania, boehmite, barium sulfate, or a combination thereof. The inorganic particles included in the coating layer may be a sphere, a plate, and/or a fiber, but the inorganic particles are not limited thereto. The plate-shaped inorganic particles may be, for example, alumina, boehmite, and/or the like. In this case, reduction in the area of the separator at a high temperature may be further suppressed or reduced, relatively high porosity of the coating layer may be secured, and penetration evaluation characteristics of the lithium battery may be improved. When the inorganic particles are plate-shaped and/or fibrous, the aspect ratio of the inorganic particles may be from about 1:5 to about 1:100, from about 1:10 to about 1:100, from about 1:5 to about 1:50, or from about 1:10 to about 1:50. Regarding the flat surface of the plate-shaped inorganic particles, a length ratio of a long axis to a short axis may be from 1 to 3, from 1 to 2, or about 1. The aspect ratio and the length ratio of the long axis to the short axis may be measured by a scanning electron microscope (SEM). Within this aspect ratio and these length ranges of the short axis with respect to long axis, shrinkage of the separator may be suppressed or reduced, and the coating layer may secure relatively improved porosity, and penetration characteristics of the lithium battery may be improved. When the inorganic particles are plate-shaped, the average angle of the flat surface of the inorganic particles with respect to one surface of the porous substrate may be from 0 degrees to 30 degrees. For example, the angle of the flat surface of the inorganic particle with respect to one surface of the porous substrate may be converged to 0°. In one or more embodiments, one surface of the porous substrate may be parallel (e.g., substantially parallel) to a flat surface of the inorganic particles. For example, when the average angle of the flat surface of the inorganic compound with respect to one surface of the porous substrate is within these ranges, the heat shrinkage of the porous substrate may be effectively prevented or reduced, and thus, a separator having reduced shrinkage rate may be provided. The coating layer may further include organic particles. The organic particle additionally included in the coating layer may be a cross-linked polymer. The organic particles additionally included in the coating layer may be a highly cross-linked polymer of which glass transition temperature (Tg) does not appear (e.g., which does not have a glass transition temperature (Tg) or does not have any glass transition). When a highly cross-linked polymer is used, heat resistance is improved, and thus shrinkage of the porous substrate may be effectively suppressed or reduced at a high temperature. The organic particles may include, for example, a styrene-based compound and/or a derivative thereof, a methyl methacrylate-based compound and/or a derivative thereof, an acrylate-based compound and/or a derivative thereof, a diallyl phthalate-based compound and/or a derivative thereof, a polyimide-based compound and/or a derivative thereof, a polyurethane-based compound and/or a derivative thereof, a copolymer thereof, and/or a combination thereof, but is not limited thereto. The organic particles may be any suitable material that can be used as organic particles in the art. For example, the organic particles may be cross-linked polystyrene particles and/or cross-linked polymethylmethacrylate particles. Any of the particles described herein may be secondary particles formed by aggregating primary particles. In a composite separator including the secondary particles, the porosity of the coating layer is increased, thereby providing a lithium battery having excellent high output characteristics. The amount of the binder included in the coating layer may be, for example, from about 0.5 parts by weight to about 30 parts by weight, from about 1 part by weight to about 25 parts by weight, from about 1 to about 20 parts by weight, from about 1 part by weight to about 15 parts by weight, from about 1 to about 10 parts by weight, or from about 1 part by weight to about 5 parts by weight of the water-soluble binder based on 100 parts by weight of the inorganic particles. When the amount of the binder included in the coating layer is too low (e.g., is outside of the ranges described herein), an adhesion force between the coating layer and the porous substrate is decreased, and thus, the coating layer is easily separated from the porous substrate, and the inorganic particles may be separated from the coating layer. When the amount of the binder included in the coating layer is excessively high (e.g., is outside of the ranges described herein), the amount of the inorganic particles is relatively reduced, and thus, the effect of enhancing the thermal stability of the lithium battery including the polyacrylic acid lithium salt may be deteriorated or reduced. The coating layer may further include a wetting agent. A weight average molecular weight of the wetting agent additionally included in the coating layer may be, for example, from about 250 Dalton to about 30,000 Dalton, from about 300 Dalton to about 30,000 Dalton, from about 400 Dalton to about 30,000 Dalton, from about 500 Dalton to about 30,000 Dalton, from about 700 Dalton to about 30,000 Dalton, from about 1000 Dalton to about 30,000 Dalton, from about 5,000 Dalton to about 30,000 Dalton, from about 10,000 Dalton to about 30,000 Dalton, from about 15,000 Dalton to about 30,000 Dalton, from about 20,000 Dalton to about 30,000 Dalton, or from about 20,000 Dalton to about 25,000 Dalton. The wetting agent included the coating layer may be, for example, one or more selected from polyvinyl alcohol, polyethylene glycol, sodium dodecyl sulfate, sodium dibutylnaphthalenesulfonate, polyacrylamide, polyethylene glycol fatty acid ester, alkyl polyoxyethylene ether carboxylate, alkyl phenol polyoxyethylene ether, sodium alkylbenzenesulfonate, alkyl phenol polyoxyethylene ether, polyoxyethylene alkyl amine, and polyoxyethylene amide, but is not limited thereto. For example, the wetting agent may be any suitable wetting agent that is used in the art. The coating layer included in the composite separator may be on opposite surfaces of the porous substrate. Because the coating layer is on opposite sides of the porous substrate, the adhesion force between the coating layer and the porous substrate is further enhanced, and as a result, the volume change of the composite separator during charging and discharging of the lithium battery may be suppressed. For example, referring toFIG.1, coating layers12and13each including a binder and inorganic particles are on opposite surfaces of a porous substrate11in the composite separator. The total thickness of a coating layer included in the composite separator may be, for example, 25% or less, 24% or less, 23% or less, 22% or less, 21% or less, or 20% or less of the total thickness of the composite separator. The total thickness of a coating layer included in the composite separator may be, for example, from about 5% to about 25%, from about 8% to about 24%, from about 10% to about 23%, from about 10% to about 22%, from about 10% to about 21%, or from about 10% to about 20% of the total thickness of the composite separator. The total thickness of a coating layer may be, for example, the sum of a thickness of a first coating layer on one surface of the porous substrate and a thickness of a second coating layer on another surface of the porous substrate. Because the coating layer has such a thickness in ranges described herein, the composite separator may provide excellent thermal stability and adhesion force while an increase in the volume of the composite separator is suppressed or reduced. The thickness of the porous substrate including the composite separator may be, for example, from about 1 μm to about 10 μm, from about 3 μm to about 10 μm, from about 5 μm to about 10 μm, from about 7 μm to about 10 μm, or from about 7 μm to about 9 μm. When the porous substrate is too thin, it may be difficult to maintain mechanical properties of the composite separator. For example, the composite separator may be easily torn and/or may have a pin-hole. When the porous substrate is excessively thick, energy density of the lithium battery may be reduced and discharge capacity may be reduced. A thickness of the coating layer on one surface of the porous substrate included in the composite separator may be, for example, 1.2 μm or less, 1.1 μm or less, or 1.0 μm or less. The thickness of the coating layer on one side of the porous substrate may be, for example, from about 0.5 μm to about 1.2 μm, from about 0.6 μm to about 1.2 μm, from about 0.7 μm to about 1.2 μm, or from about 0.8 μm to about 1.2 μm, from about 0.8 μm to about 1.1 μm, or from about 0.8 μm to about 1.0 μm. When the coating layer on one surface of the porous substrate is excessively thin (e.g., is outside of the ranges described herein), heat resistance of the composite separator may be relatively low. When the coating layer on one surface of the porous substrate is excessively thick (e.g., is outside of the ranges described herein), energy density per unit volume of a lithium battery including a composite separator may be reduced and discharge capacity may be reduced, although heat resistance thereof may be increased. When the coating layer is coated on opposite surfaces of the porous substrate included in the composite separator, the total thickness of the coating layer included in the composite separator may be, for example, about two times the thickness of the coating layer on one surface of the porous substrate. The total thickness of the coating layer on opposite sides of the porous substrate included in the composite separator may be, for example, 2.4 μm or less, 2.2 μm or less, or 2.0 μm or less. The total thickness of the coating layer on opposite sides of the porous substrate may be, for example, from about 1.0 μm to about 2.4 μm, from about 1.2 μm to about 2.4 μm, from about 1.4 μm to about 2.4 μm, or from about 1.6 μm to about 2.4 μm, from about 1.6 μm to about 2.2 μm, or from about 1.6 μm to about 2.0 μm. When the total thickness of the coating layer on opposite sides of the porous substrate is excessively thin (e.g., is outside of the ranges described herein), the heat resistance of the composite separator may deteriorate. When the total thickness of the coating layer on opposite surfaces of the porous substrate is excessively thick (e.g., is outside of the ranges described herein), energy density per unit volume of a lithium battery including a composite separator may be reduced and discharge capacity may be reduced, although heat resistance thereof may be increased. The total thickness of the composite separator may be, for example, 10.5 μm or less, 10.4 μm or less, 10.3 μm or less, 10.2 μm or less, 10.1 μm or less, or 10 μm or less. The total thickness of the composite separator may be, for example, from about 5 μm to 10.5 μm, from about 5 μm to about 10.4 μm, from about 5 μm to about 10.3 μm, from about 5 μm to about 10.2 μm, from about 55 μm to about 10.1 μm, or from about 5 μm to about 10 μm. When the total thickness of the composite separator is within any of these ranges, energy density per unit volume of a lithium battery including the composite separator such a small thickness may be increased. Also, when the total thickness of the composite separator is within any of these ranges, the composite separator may provide improved thermal stability and adhesion force. The porous substrate included in the composite separator may have a pore size of, for example, from about 0.01 μm to about 2 μm, from about 0.01 μm to about 1 μm, or from about 0.05 μm to about 1 μm. When the pore size of the porous substrate is too small (e.g., is outside of the ranges described herein), lithium ions may not easily penetrate therethrough, and thus internal resistance of the lithium battery may be increased and cyclic characteristics of the lithium battery may deteriorate. When the pore size of the porous substrate is excessively big (e.g., is outside of the ranges described herein), dendrite(s) may easily grow through the pores. Therefore, due to the growth of the dendrite(s) through the porous substrate, the possibility of a short circuit between the positive electrode and the negative electrode may be increased. The porosity of the porous substrate included in the composite separator may be, for example, from about 5% to about 95%, from about 10% to about 90%, from about 10% to about 80%, from about 20% to about 80%, from about 20% to about 70%, from about 30% to about 70%, or from about 40% to about 70%. When the porosity of the porous substrate is too small (e.g., is outside of the ranges described herein), lithium ions may not easily penetrate therethrough, and thus, internal resistance of the lithium battery may be increased and cyclic characteristics of the lithium battery may deteriorate. When the porosity of the porous substrate is too high (e.g., is outside of the ranges described herein), the mechanical strength of the composite separator may be decreased. The porosity of the porous substrate is a volume occupied by pores in the total volume of the porous substrate. The porosity of the porous substrate can be measured by a nitrogen adsorption method. In one or more embodiments, the porosity of the porous substrate can be calculated by measuring volume and weight of the porous substrate and a theoretical density of the polyolefin resin. The porous substrate included in the composite separator may be a porous film including polyolefin. The polyolefin may have an excellent short-circuit prevention or reduction effect, and may enhance battery stability due to a shut-down effect. For example, the porous substrate may be a porous film formed of a resin such as a polyolefin such as polyethylene, polypropylene, polybutene, polyvinyl chloride, or a mixture or a copolymer thereof, but is not limited thereto. The film may be any suitable porous film that is used in the art. For example, the porous substrate may be a porous film formed of a polyolefin-based resin; a porous film in which polyolefin-based fibers are woven; non-woven fabric including polyolefin; or an aggregate of insulating material particles. For example, in the case of the porous membrane including polyolefin, a binder solution for preparing a porous layer to be formed on a porous substrate has excellent coatability, and the thickness of a composite separator is reduced, and thus, a ratio of an active material in a battery is increased, resulting in an increase in a capacity per unit volume. The porous substrate included in the composite separator may include one or more selected from polyethylene, polypropylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalate. The polyolefin used as a material for the porous substrate may be, for example, a homopolymer, copolymer, or mixture thereof of polyethylene, polypropylene, and/or the like. The polyethylene may be low density, medium density, or high density polyethylene, and in terms of mechanical strength, high-density polyethylene may be used. In addition, two or more kinds of polyethylene may be mixed to provide flexibility. The polymerization catalyst used for the preparation of polyethylene is not particularly limited, and may be a Ziegler-Natta catalyst, a Phillips catalyst, or a metallocene catalyst. In terms of both mechanical strength and high permeability, the weight average molecular weight of polyethylene may be from about 100,000 to about 12 million Dalton, for example, about 200,000 to about 3 million Dalton. The polypropylene may be a homopolymer, a random copolymer, or a block copolymer, and may be used alone or in a mixture of two or more thereof. In addition, the polymerization catalyst is not particularly limited, and may be a Ziegler-Natta catalyst or a metallocene catalyst. In addition, steric regularity is not particularly limited, and isotactic, syndiotactic, or atactic polypropylene may be used. In an embodiment, inexpensive isotactic polypropylene may be used. In addition, as long as the effects of the present disclosure are not damaged or reduced, additives such as polyolefins other than polyethylene or polypropylene and antioxidants may be added to the polyolefin. The porous substrate included in the composite separator may include, for example, a polyolefin such as polyethylene, polypropylene, and/or the like, and may be a multi-layered film of two or more layers, and may be a mixed multi-layered film such as a polyethylene/polypropylene double-layer separator, a polyethylene/polypropylene/polyethylene triple-layer separator, a polypropylene/polyethylene/polypropylene triple-layer separator, or the like, but is not limited thereto. The material or configuration for the porous substrate may be any suitable material or configuration that is used for a porous substrate in the art. The porous substrate included in the composite separator may include, for example, a diene-based polymer prepared by polymerizing a monomer composition including a diene-based monomer. The diene-based monomer may be a conjugated diene-based monomer or a non-conjugated diene-based monomer. For example, the diene-based monomer may include one or more selected from 1, 3-butadiene, isoprene, 2-chloro-1, 3-butadiene, 2, 3-dimethyl-1, 3-butadiene, 2-ethyl-1, 3-butadiene, 1, 3-pentadiene, chloroprene, vinylpyridine, vinylnorbornene, dicyclopentadiene, and 1, 4-hexadiene, but is not limited thereto. The diene-based monomer may be any suitable material that can be used as a diene-based monomer in the art. The composite separator may have a machine direction (MD) shrinkage rate (e.g., a machine direction heat shrinkage rate) and transverse direction (TD) shrinkage rate (e.g., a transverse direction heat shrinkage rate), each being 3% or less, 2.5% or less, or 2% or less, when treated at 150° C. for 1 hour. The composite separator may have a machine direction (MD) shrinkage rate (e.g., a machine direction heat shrinkage rate) and a transverse direction (TD) shrinkage rate (e.g., a transverse direction heat shrinkage rate), each being from about 0.01% to about 3%, from about 0.01% to about 2.5%, or from about 0.01% to about 2%. Because the composite separator has such a low heat shrinkage rate, deformation and shrinkage of the composite separator may be suppressed or reduced during high-temperature charging and discharging. As a result, thermal stability of a lithium battery including the composite separator may be enhanced. The coating layer included in the composite separator may have a peel strength of 10 gf/mm or more, 12 gf/mm or more, 14 gf/mm or more, 16 gf/mm or more, or 18 gf/mm or more, with respect to the porous substrate. The coating layer included in the composite separator may have a peel strength of about 10 gf/mm to about 30 gf/mm, about 12 gf/mm to about 28 gf/mm, about 14 gf/mm to about 26 gf/mm, about 16 gf/mm to about 24 gf/mm, or about 18 gf/mm to about 22 gf/mm, with respect to the porous substrate. When the peel strength between the coating layer and the porous substrate is too low (e.g., is outside of the ranges described herein), the adhesion force between the coating layer and the porous substrate is reduced. Accordingly, the coating layer of the composite separator may be easily detached from the porous substrate due to the repeated shrinkage/expansion of the electrode volume during the charging and discharging process of a lithium battery. As a result, regarding a lithium battery, volume expansion of the lithium battery due to separation of the coating layer, an increase in internal resistance of the lithium battery, and a short circuit of the lithium battery due to melting of a porous substrate at a high temperature may occur. When the adhesion force between the coating layer and the porous substrate is excessively increased (e.g., is outside of the ranges described herein), the coating layer becomes too hard and the flexibility of the coating layer is decreased, resulting in cracks. The composite separator may have a moisture content of 990 ppm or less, 900 ppm or less, 850 ppm or less, 800 ppm or less, 750 ppm or less, 700 ppm or less, 650 ppm or less, or 600 ppm or less, when treated at a temperature of 85° C. for 12 hours. The composite separator may have a moisture content from about 1 ppm. to about 990 ppm, from about 10 ppm to about 900 ppm, from about 50 ppm to about 850 ppm, from about 100 ppm to about 800 ppm, from about 100 ppm to about 750 ppm, from about 100 ppm to about 700 ppm, from about 100 ppm to about 650 ppm, or from about 100 ppm to about 600 ppm, when treated at 85° C. for 12 hours. When the residual moisture content of the composite separator is excessively increased (e.g., is outside of the ranges described herein), a side reaction of the lithium battery including the composite separator is increased, thereby degrading cyclic characteristics of the lithium battery and reducing discharge capacity thereof. A lithium battery according to an embodiment includes an electrode assembly including a positive electrode, a negative electrode, and the composite separator between the positive electrode and the negative electrode. Due to the inclusion of the composite separator, the lithium battery may have increased thermal stability, and an increase in volume thereof is suppressed or reduced, resulting in an increase in the energy density of the lithium battery. In addition, because the amount of the residual moisture contained in the composite separator is reduced and side reactions in the charging/discharging process of the lithium battery including the composite separator are suppressed or reduced, the cyclic characteristics of the lithium battery may be improved and the decrease in discharge capacity may be suppressed or reduced. The lithium battery may be manufactured by, for example, the following method. First, a negative active material composition, in which a negative active material, a conductive material (e.g., an electrically conductive material), a binder, and a solvent are mixed, is prepared. The negative active material composition is coated directly on a metal current collector to manufacture a negative electrode plate. In another embodiment, the negative active material composition may be cast on a separate support, and a film exfoliated from the support may then be stacked on the metal current collector to prepare a negative electrode plate (e.g., to form a stacked structured). Types or kinds of the negative electrode are not limited to those listed above, and the negative electrode may be formed to have a variety of suitable types or kinds other than the above-described types or kinds. The negative active material may be a non-carbon-based material. For example, the negative active material may include one or more selected from a metal that is alloyable with lithium, an alloy of a metal that is alloyable with lithium, and an oxide of a metal that is alloyable with lithium. For example, the metal that is alloyable with lithium may include Si, Sn, Al, Ge, Pb, Bi, Sb, Si—Y alloy (Y is an alkali metal, an alkaline-earth metal, a Group 13 to 16 element, a transition element, a rare earth element, or a combination element thereof, and is not Si), a Sn—Y alloy (Y is an alkali metal, an alkaline-earth metal, a Group 13 to 16 element, a transition element, a rare earth element, or a combination element thereof, and is not Sn), and/or the like. The element Y may be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof. For example, the transition metal oxide may include lithium titanium oxide, vanadium oxide, lithium vanadium oxide, and/or the like. For example, the non-transition metal oxide may include SnO2and/or SiOx(0<x<2). In an embodiment, the negative active material may include one or more selected from the group consisting of Si, Sn, Pb, Ge, Al, SiOx(0<x≤2), SnOy(0<y≤2), Li4Ti5O12, TiO2, LiTiO3, and Li2Ti3O7, but is not limited thereto. The negative active material may be any suitable material that is used as a non-carbon based negative active material in the art. In addition, a composite of the non-carbon based negative active material and the carbon-based material may be used, and the composite may further include a carbon-based negative active material in addition to the non-carbon-based material. The carbon-based material may include crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may include a non-shaped, plate-shaped, flake-shaped, spherical and/or fiber-shaped natural graphite and/or artificial graphite, and the amorphous carbon may be soft carbon (low temperature calcined carbon), hard carbon, mesophase pitch carbide, and/or calcined coke. Examples of the conductive material may include metal powder and/or metal fiber of natural graphite, artificial graphite, carbon black (e.g., acetylene black, KETJENBLACK™), a carbon fiber, copper, nickel, aluminum, silver, and the like; and a combination of one or more conductive materials such as polyphenylene derivatives, but the conductive material is not limited thereto. The conductive material may be any suitable material that can be used as a conductive material in the art. Also, the crystalline carbon-based material may be added as a conductive material (e.g., an electrically conductive material). Examples of the binder include a vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polytetrafluoroethylene, mixtures thereof, and a styrene butadiene rubber polymer, but embodiments are not limited thereto. Any suitable material available as a binding agent in the art may be used as the binder. Examples of the solvent include N-methylpyrrolidone, acetone, and water, but are not limited thereto. Any suitable material that is available in the art as a solvent may be used. Amounts of the negative active material, the conductive material, the binder, and the solvent may be in the ranges generally used in the manufacture of a lithium battery in the art. One or more of the conductive material, the binder, and the solvent may be omitted according to the use and configuration of the lithium battery. In one or more embodiments, the binder used for the negative electrode may be the same as a binder included in the coating layer of the separator. First, a positive active material composition, in which a positive active material, a conductive material (e.g., an electrically conductive material), a binder, and a solvent are mixed, is prepared. The positive active material composition is directly coated on a metal current collector and dried to prepare a positive electrode plate. In another embodiment, a positive electrode plate may be prepared by casting the positive active material composition on a separate support, and then laminating a film exfoliated from the support on the metal current collector. The positive active material may include one or more selected from lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphorous oxide, and lithium manganese oxide, but is not limited thereto. Any suitable material that is used as a positive active material in the art, may be used. For example, the positive active material may include a compound represented by LiaA1−bBbD2(where 0.90≤a≤1.8, and 0≤b≤0.5); LiaE1−bBbO2−cDc(where 0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); LiE2−bBbO4−cDc(where 0≤b≤0.5, and 0≤c≤0.05); LiaNi1−b−cCobBcDα(where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0≤α≤2); LiaNi1−b−cCobBcO2−αFα(where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0≤α≤2); LiaNi1−b−cCobBcO2−αF2(where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2); LiaNi1−b−cMnbBcDα(where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2); LiaNi1−b−cMnbBcO2−αFα(where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2); LiaNi1−b−cMnbBcO2−αF2(where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<a<2); LiaNibEcGdO2(where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, and 0.001≤d≤0.1); LiaNibCocMndGeO2(where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0.001≤e≤0.1); LiaNiGbO2(where 0.90≤a≤1.8, and 0.001≤b≤0.1.); LiaCoGbO2(where 0.90≤a≤1.8, and 0.001≤b≤0.1); LiaMnGbO2(where 0.90≤a≤1.8, and 0.001≤b≤0.1); LiaMn2GbO4(where 0.90≤a≤1.8, and 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li(3−f)J2(PO4)3(0≤f≤2); Li(3−f)Fe2(PO4)3(0≤f≤2); and LiFePO4. In the above formulae: A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. A compound having a coating layer added on the surface thereof and a mixture of the compound and the compound having the coating layer added thereto may also be used. The coating layer may include a coating element compound such as an oxide or a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxy carbonate of the coating element. The compound forming such a coating layer may be amorphous or crystalline. Examples of the coating element included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, and mixtures thereof. Any suitable coating method may be used as a coating layer forming process as long as coating may be performed using a method that does not adversely affect the physical properties of the positive active material (for example, spray coating and/or dipping), and further description thereof is not necessary here because further details of the coating method would be readily recognizable to one skilled in the art. For example, the positive active material may include LiNiO2, LiCoO2, LiMnxO2x(x=1, 2), LiNi1−xMnxO2(0<x<1), LiNi1−x−yCoxMnyO2(0<x≤0.2, 0<y≤0.2), LiNi1−x−yCoxAlyO2(0<x≤0.2, 0<y≤0.2), LiFePO4, V2O5, TiS, MoS, and/or the like. For example, the positive active material may include a lithium transition metal oxide having a layered rock salt type structure. For example, the positive active material may include may include a ternary lithium transition metal oxide expressed as LiNixCoyAlzO2(NCA) (where 0<x<1, 0<y<1, 0<z<1, x+y+z=1), LiNixCoyMnzO2(NCM) (where 0<x<1, 0<y<1, 0<z<1, and x+y+z=1), LiNixCoyAlvMnwO2(NCAM) (where 0<x<1, 0<y<1, 0<v<1, 0<w<1, and x+y+v+w=1), LiNiaCobAlcO2(0.6≤a<1, 0<b<0.5, 0<c<0.5, a+b+c=1), LiNiaCobMneO2(where 0.6≤a<1, 0<b<0.5, 0<c<0.5, a+b+c=1), or LiNiaCobAldMneO2(0.6≤a<1, 0<b<0.5, 0<d<0.5, 0<e<0.5, a+b+d+e=1). The same conductive material, binder, and solvent as those in the above-described negative active material composition may be used in a positive active material composition. In some cases, a plasticizer may be additionally added to the positive active material composition and/or the negative active material composition to enable the formation of pores in electrode plates. Amounts of the positive active material, the conductive material, the binder, and the solvent may be in the ranges generally used in the manufacture of a lithium battery in the art. One or more of the conductive material, the binder, and the solvent may be omitted according to the use and configuration of the lithium battery. In one or more embodiments, the binder used for the positive electrode may be the same as a binder included in the coating layer of the separator. Next, the composite separator is located between the positive electrode and the negative electrode. The composite separator may be separately prepared and located between the positive electrode and the negative electrode. In an embodiment, the composite separator may be prepared by a formation process including: winding an electrode assembly including a positive electrode/separator/negative electrode in a jelly roll shape; placing the jelly roll in a battery case or a pouch; thermally softening and pre-charging the jelly roll under pressure in the battery case or the pouch; hot rolling the charged jelly roll; cold rolling the charged jelly roll; and charging and discharging the charged jelly roll under pressure. Next, an electrolyte is prepared. The electrolyte may be in a liquid or gel state. The electrolyte may include, for example, an organic electrolytic solution. The electrolyte may be a solid. Examples of the solid electrolyte include, but are not limited to, boron oxides, and lithium oxynitrides, and any suitable inorganic solid electrolyte that is used as a solid electrolyte in the art may be used. The solid electrolyte may be formed on the negative electrode by, for example, sputtering. The solid electrolyte may include, for example, a sulfide-based solid electrolyte or an oxide-based solid electrolyte. For example, an organic electrolytic solution may be prepared. The organic electrolytic solution may be prepared by dissolving a lithium salt in an organic solvent. As the organic solvent, any suitable material available as an organic solvent in the art may be used. The organic solvent may include, for example, propylenecarbonate, ethylenecarbonate, fluoroethylenecarbonate, butylenecarbonate, dimethylcarbonate, diethylcarbonate, methylethylcarbonate, methylpropylcarbonate, ethylpropylcarbonate, methylisopropylcarbonate, dipropylcarbonate, dibutylcarbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxorane, 4-methyldioxorane, N,N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethyleneglycol, dimethylether, and mixtures thereof. The lithium salt may also include any suitable material available as a lithium salt in the art. For example, the lithium salt may include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(CxF2x+1SO2)(CyF2y+1SO2)(where x and y are natural numbers of 1 to 10, respectively), LiCl, LiI, or a mixture thereof. As shown inFIG.2, a lithium battery1includes a positive electrode3, a negative electrode2, and a separator4. The positive electrode3, the negative electrode2, and the separator4are wound or folded into a cylindrical jelly-roll type (or kind) of electrode assembly and then placed in a battery case5. Subsequently, an organic electrolytic solution is injected into the battery case5and sealed with a cap assembly6to complete the manufacture of the lithium battery1. The battery case5may be a cylindrical type (or kind), a rectangular type (or kind), or a thin-film type (or kind). The lithium battery1may be a lithium ion battery. The lithium battery1may be a lithium polymer battery. For example, the positive electrode, the negative electrode, and the separator are wound or folded into a flat jelly-roll type (or kind) of electrode assembly and then placed in a pouch. Then, an organic electrolytic solution is injected into a pouch and sealed to complete the manufacture of the lithium battery. In one or more embodiments, the positive electrode, the negative electrode, and the separator are sequentially stacked as a flat electrode assembly and then placed in a pouch. Then, an organic electrolytic solution is injected into the pouch and sealed to complete the manufacture of the lithium battery. Because the lithium battery has excellent high-rate characteristics and lifetime characteristics, the lithium battery is suitable for an electric vehicle (EV). For example, the lithium battery is suitable for a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV). A plurality of lithium batteries may be stacked to form a battery module, and a plurality of the battery modules may form a battery pack. Such a battery pack may be used in any suitable device requiring high capacity and high output. For example, the battery pack may be used in a notebook, a smartphone, an electric vehicle, and/or the like. In an embodiment, the battery module includes a plurality of batteries and a frame holding the batteries. The battery pack may include, for example, a plurality of battery modules and bus bars connecting or coupling the battery modules. The battery module and/or the battery pack may further include a cooling device. A plurality of battery packs may be controlled by a battery management system. A battery management system includes a battery pack and a battery control device connected or coupled to the battery pack. Another aspect of embodiments of the present disclosure provides a method of manufacturing a composite separator, the method including: providing a porous substrate; preparing a stacked structure by coating a composition including a water-soluble binder, inorganic particles, and water, which is used as a solvent, on one surface or opposite surfaces of the porous substrate; and drying the stacked structure to form a coating layer on at least one surface of the porous substrate, wherein the coating layer includes a water-soluble binder and inorganic particles, the water-soluble binder includes a polyacrylic acid metal salt, a weight average molecular weight of the polyacrylic acid metal salt is about 300,000 Dalton or more, and an average particle diameter (D50) of the inorganic particles is about 500 nm or more. A porous substrate is provided. The porous substrate is the same as described in connection with the porous substrate of the composite separator described above. A composition including a water-soluble binder, inorganic particles, and water is prepared. An aqueous binder composition is prepared by mixing the water-soluble binder, the inorganic particles, and water, and then stirring and/or dispersing the mixture. The solvent of the aqueous binder composition may further include water or another solvent miscible with water. Other solvents that are miscible with water include, for example, alcohols such as ethanol. The amount of the water-soluble binder may be, for example, from about 0.1 parts by weight to about 30 parts by weight, from about 0.1 parts by weight to about 20 parts by weight, from about 0.1 parts by weight to about 10 parts by weight, or from about 0.1 parts by weight to about 5 parts by weight, based on 100 parts by weight of the composition. The amount of the inorganic particle may be, for example, from about 1 part by weight to about 30 parts by weight, from about 1 part by weight to about 20 parts by weight, or from about 1 part by weight to about 10 parts by weight, based on 100 parts by weight of the composition. The composition may further include a wetting agent. The amount of the wetting agent may be, for example, from about 0.01 parts by weight to about 3 parts by weight, from about 0.01 parts by weight to about 2 parts by weight, from about 0.01 parts by weight to about 1 part by weight, or from about 0.01 to about 0.5 parts by weight, based on 100 parts by weight of the composition. The amount of the solvent may be, for example, from about 70 parts by weight to about 99.9 parts by weight, from about 80 parts by weight to about 99.9 parts by weight, or from about 90 parts by weight to about 99.9 parts by weight, based on 100 parts by weight of the composition. The composition may further include any other suitable additives used in the art according to desired physical properties. The water-soluble binder may include a polyacrylic acid metal salt, and the polyacrylic acid metal salt may have a weight average molecular weight of about 300,000 Dalton or more, and the inorganic particles may have an average particle diameter (D50) of about 500 nm or more. The water-soluble binder and the inorganic particles may be understood by referring to the water-soluble binder and the inorganic particles included in the composite separator described above. Then, a composition including a water-soluble binder, inorganic particles, and water is coated on one surface or opposite surfaces of the porous substrate to prepare a stacked structure. A method of applying the composition is not particularly limited, and any suitable method generally used in the art may be used. For example, the coating method may include flow coating, roll coating, dip coating, bar coating, etc. A thickness of the coated composition is not particularly limited, and may be determined within a range that satisfies a thickness of the coating layer required or desired for the composite separator. Then, the prepared stacked structure is dried, and a coating layer is on at least one surface of the porous substrate to manufacture a composite separator. The drying condition is not particularly limited, and for example, may be dried at 60° C. for 1 hour, but is not limited thereto. The drying temperature may be, for example, 25° C. to 200° C., and the drying time may be 5 minutes to 24 hours. Referring toFIG.1, coating layers12and13may be on opposite surfaces of the porous substrate11, or may be on one surface of the porous substrate11. Hereinafter, embodiments of the present disclosure will be described in more detail through Examples and Comparative Examples. However, the Examples are provided to illustrate embodiments of the present disclosure, and the scope of the present disclosure is not limited thereto. Preparation of Composite Separator Example 1: PAA Li 10% substitution (polyacrylic acid lithium salt in which 10% of the acrylic acid repeating units have an acidic hydrogen of an acrylic acid group that is substituted with lithium), Mw=345K (the polyacrylic acid lithium salt had a molecular weight of 345,000 Dalton), 0.7 μm inorganic particles, total coating layer thickness of 2 μm A polyethylene porous substrate (Cangzhou mingzhu (CZMZ), China, NW0835) having a thickness of 8 μm was prepared. Boehmite (BG601, Anhui Estone Materials & Technology Co., Ltd.) having an average particle diameter (D50) of 0.7 μm, which is inorganic particles, a salt obtained by substituting the end of polyacrylic acid (weight average molecular weight Mw=345,000 Daltons), e.g., a polyacrylic acid lithium salt, which is a water-soluble binder, polyvinyl alcohol (PVA, Daejung Chemicals & Metals Co., Ltd., Mw=22,000 Dalton), which is a wetting agent, and distilled water were mixed at a weight ratio of 9.52:0.33:0.14:90.01, and then stirred to prepare an aqueous composition. The acrylic repeating unit substituted with lithium ions in the acrylic repeating unit included in the polyacrylic acid lithium salt has a mole ratio of 0.1. For example, the amount of the lithium acrylate repeating unit in the total repeating unit (e.g., the sum of the acrylic acid repeating unit and the lithium acrylate repeating unit) included in the polyacrylic acid lithium salt was 10 mol %. The prepared aqueous compositions were coated on each of opposite surfaces of a porous substrate, followed by drying at 60° C. for 1 hour to form a coating layer having a thickness of 1 μm on each of the opposite surfaces of the porous substrate, thereby completing the manufacture of a composite separator. The total thickness of the coating layer was 2 μm. The total thickness of the composite separator was 10 μm. Example 2: PAA Li 30% substitution (polyacrylic acid lithium salt in which 30% of the acrylic acid repeating units have an acidic hydrogen of an acrylic acid group that is substituted with lithium), Mw=345K (the polyacrylic acid lithium salt had a molecular weight of 345,000 Dalton), 0.7 μm inorganic particles, total coating layer thickness of 2 μm A composite separator was prepared in substantially the same manner as in Example 1, except that the ratio of the acrylic repeating unit substituted with lithium ions in the acrylic repeating unit included in the polyacrylic acid lithium salt was changed to be 0.3. 30 mol % of the acrylic repeating unit included in the polyacrylic acid lithium salt was substituted with lithium ions. Example 3: PAA Li 70% substitution (polyacrylic acid lithium salt in which 70% of the acrylic acid repeating units have an acidic hydrogen of an acrylic acid group that is substituted with lithium), Mw=345K (the polyacrylic acid lithium salt had a molecular weight of 345,000 Dalton), 0.7 μm inorganic particles, total coating layer thickness of 2 μm A composite separator was prepared in substantially the same manner as in Example 1, except that the ratio of the acrylic repeating unit substituted with lithium ions in the acrylic repeating unit included in the polyacrylic acid lithium salt was changed to be 0.7. 70 mol % of the acrylic repeating unit included in the polyacrylic acid lithium salt was substituted with lithium ions. Example 4: PAA Li 80% substitution (polyacrylic acid lithium salt in which 80% of the acrylic acid repeating units have an acidic hydrogen of an acrylic acid group that is substituted with lithium), Mw=345K (the polyacrylic acid lithium salt had a molecular weight of 345,000 Dalton), 0.7 μm inorganic particles, total coating layer thickness of 2 μm A composite separator was prepared in substantially the same manner as in Example 1, except that the ratio of the acrylic repeating unit substituted with lithium ions in the acrylic repeating unit included in the polyacrylic acid lithium salt was changed to be 0.8. 80 mol % of the acrylic repeating unit included in the polyacrylic acid lithium salt was substituted with lithium ions. Example 5: PAA Li 100% substitution (polyacrylic acid lithium salt in which 100% of the acrylic acid repeating units have an acidic hydrogen of an acrylic acid group that is substituted with lithium), Mw=345K (the polyacrylic acid lithium salt had a molecular weight of 345,000 Dalton), 0.7 μm inorganic particles, total coating layer thickness of 2 μm A composite separator was prepared in substantially the same manner as in Example 1, except that a ratio of an acrylic acid repeating unit substituted with lithium ions in an acrylic acid repeating unit included in a polyacrylic acid lithium salt was changed to 1.0. 100 mol % of the acrylic repeating unit included in the polyacrylic acid lithium salt was substituted with lithium ions. Comparative Example 1: PAA Li 0% substitution (polyacrylic acid in which none of the acrylic acid repeating units have an acidic hydrogen of an acrylic acid group that is substituted with lithium), Mw=345K (the polyacrylic acid had a molecular weight of 345,000 Dalton), 0.7 μm inorganic particles, total coating layer thickness of 2 μm A composite separator was prepared in substantially the same manner as in Example 1, except that lithium unsubstituted polyacrylic acid (weight average molecular weight Mw=345,000 Dalton) was used instead of the lithium polyacrylate salt. Comparative Example 2: CMC (Carboxy Methyl Cellulose), 0.5 μm Inorganic Particles, 2 μm of Total Coating Layer Thickness A composite separator was prepared in substantially the same manner as in Example 1, except that sodium carboxymethyl cellulose (CMC, carboxy methyl cellulose, medium viscosity, Sigma-Aldrich, C4888) was used instead of the polyacrylic acid lithium salt. Comparative Example 3: CMC, 0.5 μm inorganic particles, 3 μm of total coating layer thickness A composite separator was prepared in substantially the same manner as in Example 1, except that sodium carboxymethyl cellulose (CMC, carboxy methyl cellulose, medium viscosity, Sigma-Aldrich, C4888) was used instead of the polyacrylic acid lithium salt, and the thickness of the coating layer was changed to be 1.5 μm. As such, a composite separator in which a coating layer having a thickness of 1.5 μm was on each of opposite surfaces of a porous substrate, was prepared. The total thickness of the composite separator was 11 μm. Comparative Example 4: PAA Li 70% substitution (polyacrylic acid lithium salt in which 70% of the acrylic acid repeating units have an acidic hydrogen of an acrylic acid group that is substituted with lithium), Mw=250K (the polyacrylic acid lithium salt had a molecular weight of 250,000 Dalton), 0.7 μm inorganic particles, 2 μm of total coating layer thickness A composite separator was prepared in substantially the same manner as in Example 1, except that a salt obtained by substituting the end of polyacrylic acid having a weight average molecular weight of Mw=250,000 Dalton with lithium ions, that is, a polyacrylic acid lithium salt, is used, and a ratio of an acrylic acid repeating unit substituted with lithium ions in an acrylic acid repeating unit included in a polyacrylic acid lithium salt was changed to be 0.7. Comparative Example 5: PAA Li 70% substitution (polyacrylic acid lithium salt in which 70% of the acrylic acid repeating units have an acidic hydrogen of an acrylic acid group that is substituted with lithium), Mw=345K (the polyacrylic acid lithium salt had a molecular weight of 345,000 Dalton), 0.3 μm inorganic particles, 2 μm of total coating layer thickness A composite separator was prepared in substantially the same manner as in Example 1, except that the ratio of the acrylic acid repeating unit substituted with lithium ions in the acrylic acid repeating unit included in the polyacrylic acid lithium salt is changed to be 0.7, and Boehmite having an average particle diameter (D50) of 0.3 μm was used as inorganic particles. 70 mol % of the acrylic repeating unit in the acrylic repeating unit included in the polyacrylic acid lithium salt was substituted with lithium ions. Evaluation Example 1: Evaluation of Heat Shrinkage Rate The separators prepared according to Examples 1 to 5 and Comparative Examples 1 to 5 were left in a convection oven at 150° C. for 1 hour, and then taken out, cooled at room temperature, and the heat shrinkage rate thereof was measured. The shrinkage rate of the separator was evaluated in such a manner that a linear marker having a length of 10 cm was drawn in each of a machine direction (MD) and a transverse direction (TD) of the separator, and the separator was left in an oven and then taken out thereof, followed by cooling at room temperature, and the degree of shrinkage of each of the markers was calculated using Equation 3. Shrinkage rate=[(initial marker length-reduced marker length)/initial marker length]×100 Equation 3 The heat shrinkage rate measurement results are shown in Table 1. Evaluation Example 2: Substrate Adhesion Force (Peel Strength) Test of Composite Separator Regarding the composite separators prepared in Examples 1 to 5 and Comparative Examples 1 to 5, peel strength between the porous substrate and the porous layer was measured to evaluate adhesion force therebetween. The adhesion force between the porous substrate and the porous layer was measured by performing a 180° peel test (INSTRON). In one or more embodiments, the composite separators prepared according to Examples 1 to 5 and Comparative Examples 1 to 5 were attached to the slide glass by using a double-sided tape and uniformly compressed by a hand roller. A peel strength, which is a force applied when moving by 30 mm while peeling at a tensile speed of 20 mm/min in a 180° direction in an adhesion force measuring device, was measured, and the results are shown in Table 1. Evaluation Example 3: Moisture Content of Composite Separator Moisture contents of the composite separators prepared according to Examples 1 to 5 and Comparative Examples 1 to 5 were measured. The composite separator was stored in an oven at a temperature of 85° C. for 12 hours and then removed to measure the moisture content thereof. The moisture content of the composite separator was measured using a Karl Fischer coulometry moisture analyzer (831 KF Coulometer, Metrohm, Switzerland), and the results are shown in Table 1 below. TABLE 1MachineTransversedirectiondirectionSubstrate(MD)(TD)adhesionMoistureShrinkageShrinkageforcecontentrate [%]rate [%][gf/mm][ppm]Example 1101014567Example 23218580Example 32121599Example 42220741Example 53119980Comparative211911530Example 1Comparative≥30≥305650Example 2Comparative457810Example 3Comparative≥20≥208640Example 4Comparative11201360Example 5 As shown in Table 1, the composite separators of Examples 1-5 exhibited a heat shrinkage rate of 10% or less, a substrate adhesion force of 10 gf/mm or greater, and a moisture content of less than 1000 ppm. In addition, the composite separators of Examples 2 to 4 exhibited a heat shrinkage rate of 3% or less, a substrate adhesion force of 10 gf/mm or more, and a moisture content of less than 600 ppm, thereby exhibiting further improved physical properties as compared to Examples 1 and 5. On the other hand, the composite separators of Comparative Examples 1, 2, and 4 had a heat shrinkage rate of 20% or more, and thus, heat resistance thereof was reduced. The composite separator according to Comparative Example 3 showed improved heat resistance due to an increase in the thickness of the coating layer, but had a substrate adhesion force of 7 gf/mm or less, which was still unsatisfactory. The composite separator of Comparative Example 5 had improved heat resistance and adhesion force to a substrate, but had an excessively increased moisture amount of 1360 ppm. According to one aspect of embodiments, due to the features of the molecular weight of a water-soluble binder and the average particle diameter of inorganic particles included in a coating layer, a composite separator including the coating layer has a reduced volume, improved thermal stability, and enhanced adhesion force. It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the following claims, and equivalents thereof. | 85,788 |
11862813 | DETAILED DESCRIPTION Embodiments of this application are described below in detail. Throughout the entire specification of this application, same or similar components or components having same or similar functions are represented by using similar reference numerals. The embodiments related to the accompanying drawings that are described herein are illustrative and schematic, and are used to provide a basic understanding of this application. The embodiments of this application should not be construed as limitations to this application. As used in this application, the terms “about”, “roughly”, “substantially”, “essentially”, and “approximately” are used for describing and explaining a small variation. When being used in combination with an event or a case, the terms can refer to an example in which the event or case exactly occurs, or an example in which the event or case similarly occurs. For example, when being used in combination with a value, the terms may refer to a variation range being less than or equal to ±10% of the value, for example, less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, if a difference between two values is less than or equal to ±10% of an average value of the values (for example, less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%), it could be considered that the two values are “substantially” the same or “approximate”. In this specification, unless otherwise particularly indicated or limited, relativistic wordings such as “central”, “longitudinal”, “lateral”, “front”, “back”, “right”, “left”, “inner”, “outer”, “relatively low”, “relatively high”, “horizontal”, “vertical”, “higher than”, “lower than”, “above”, “below”, “top”, “bottom”, and derived wordings thereof (such as “horizontally”, “downward”, and “upward”) should be construed as referenced directions described in discussion or shown in the accompanying drawings. These relativistic wordings are merely for ease of description, and require constructing or operating this application in a particular direction. Furthermore, for ease of description, the terms “first”, “second”, “third”, and the like may be used for distinguishing between different components in a diagram or a series of diagrams. The terms “first”, “second”, “third”, and the like are not intended to describe corresponding components. In addition, amounts, ratios and other numerical values are sometimes presented herein in a range format. It should be appreciated that such range formats are for convenience and brevity, and should be interpreted with flexibility, and include not only those numerical values that are specifically designated as range limitations, but also include all individual numerical values or sub-ranges that are within the range, as each value and sub-range is specified explicitly. Embodiments of the present application provide a composite separator and an electrochemical device comprising the same, the composite separator comprising a first porous substrate; and a cation exchange layer, wherein the cation exchange layer comprises a material layer grafted with a functional group, wherein the functional group is selected from the group consisting of an alkali-metal-sulfonic functional group, an alkali-metal-phosphoric functional group and a combination thereof. The cation exchange layer can capture transition metal ions eluted from a cathode, and can effectively increase the transition metal capture rate of the separator in the electrochemical device. At the same time, the present application effectively reduces electrical conductivity of the composite separator by providing various structural forms of the first porous substrate and the cation exchange layer, thereby reducing the self-discharge rate of the electrochemical device. Therefore, the electrochemical stability and cycling performance of the electrochemical device are enhanced, and the safety of the electrochemical device is also significantly improved. The structure and the material composition of the composite separator in the various embodiments of the present application, as well as the configuration of the composite separator in an electrode assembly, will be further described below in conjunction withFIGS.1-3. FIG.1is a structural schematic view of the first form of the composite separator disposed in an electrode assembly according to some embodiments of the present application. As shown inFIG.1, the first form of a composite separator10comprises: a first porous substrate11and a cation exchange layer12, wherein the cation exchange layer12comprises a second porous substrate grafted with a functional group, wherein the functional group is selected from the group consisting of an alkali-metal-sulfonic functional group, an alkali-metal-phosphoric functional group and a combination thereof. Further, the composite separator10further comprises a first coating13(anti-oxidation layer) and two second coatings14(binding layers), wherein the first coating13comprises inorganic particles and a binder and the second coating14comprises a polymer binder. The first coating13is disposed between the first porous substrate11and the cation exchange layer12, and the second coatings14are respectively disposed between the first coating13and the cation exchange layer12and on the surface of the other side, opposite the cation exchange layer, of the first porous substrate11. In other embodiments, the first coating13may also be disposed on the surface of the other side, opposite the cation exchange layer12, of the first porous substrate11, for example, disposed between the first porous substrate11and the second coating14or disposed on the surface, facing an anode16, of the second coating14. In other embodiments, the composite separator10may also comprise more than two first coatings13, wherein at least one of the first coatings13is disposed at a position as shown inFIG.1, and at least another first coating13is disposed between the first porous substrate11and the second coating14or disposed on the surface, facing the anode16, of the second coating14. FIG.2is a structural schematic view of the second form of the composite separator disposed in an electrode assembly according to some embodiments of the present application. As shown inFIG.2, the second form of the composite separator20comprises a first porous substrate21and a cation exchange layer22, wherein the cation exchange layer22comprises a second porous substrate grafted with a functional group, wherein the functional group is selected from the group consisting of an alkali-metal-sulfonic functional group, an alkali-metal-phosphoric functional group and a combination thereof. Further, the composite separator10further comprises a first coating23(anti-oxidation layer) and two second coatings24(binding layers), wherein the first coating23comprises inorganic particles and a binder and the second coating24comprises a polymer binder. Compared with the first form of the composite separator10, the cation exchange layer22of the composite separator20is disposed between the first porous substrate21and the first coating23, wherein the second coatings24are respectively disposed on the surface of the other side, opposite the cation exchange layer22, of the first coating23and the surface of the other side, opposite the cation exchange layer, of the first porous substrate21. In other embodiments, the first coating23may also be disposed on the surface of the other side, opposite the cation exchange layer, of the first porous substrate21, for example, disposed between the first porous substrate21and the second coating24or disposed on the surface, facing the anode16, of the second coating24. In other embodiments, the composite separator20may also comprise more than two first coatings23, wherein at least one of the first coatings23is disposed at a position as shown inFIG.2, and at least another first coating23is disposed between the first porous substrate21and the second coating24or disposed on the surface, facing the anode16, of the second coating24. FIG.3is a structural schematic view of the third form of the composite separator disposed in an electrode assembly according to some embodiments of the present application. As shown inFIG.3, the third form of the composite separator30comprises a first porous substrate31and a cation exchange layer32, wherein the cation exchange layer32comprises a polymer binder grafted with a functional group, wherein the functional group is selected from the group consisting of an alkali-metal-sulfonic functional group, an alkali-metal-phosphoric functional group and a combination thereof. Further, the composite separator30further comprises a first coating33(anti-oxidation layer) and a second coating34(binding layer), wherein the first coating33comprises inorganic particles and a binder and the second coating34comprises a polymer binder. Similar to the first form of the composite separator10, the first coating33of the composite separator30is disposed between the first porous substrate31and the cation exchange layer32, and the second coating34is disposed on the surface of the other side, opposite the cation exchange layer32, of the first porous substrate31. In other embodiments, the first coating33may further be disposed on the surface of the other side, opposite the cation exchange layer32, of the first porous substrate31, for example, disposed between the first porous substrate31and the second coating34or disposed on the surface, facing the anode16, of the second coating34. In other embodiments, the composite separator30may also comprise more than two first coatings33, wherein at least one of the first coatings33is disposed at a position as shown inFIG.3, and at least another first coating33is disposed between the first porous substrate31and the second coating34or disposed on the surface, facing the anode16, of the second coating34. In some embodiments, those skilled in the art can also select whether to dispose or remove the second coating (14,24,34) in the composite separator (10,20,30) according to specific needs without being limited byFIGS.1-3. In some embodiments, as shown inFIGS.1-3, the cation exchange layer (12,22,32) in the composite separator (10,20,30) is disposed on the side adjacent the cathode15. The transition metal ions eluted from the cathode15are captured by the cation exchange layer (12,22,32), thereby effectively increasing the transition metal capture rate of the separator in the electrochemical device and avoiding the safety risk of the transition metal ions passing through the separator to deposit dendrites on the anode. In some embodiments, the thickness of the first porous substrate (11,21,31) is from about 1 μm to about 20 μm. In some embodiments, the thickness of the cation exchange layer (12,22,32) is from about 0.5 μm to about 10 μm. In some embodiments, the thickness of the first coating (13,23,33) is from about 0.5 μm to about 10 μm. In some embodiments, the thickness of the second coating (14,24,34) is from about 0.5 μm to about 10 μm. In the above embodiments, the functional group grafted in the cation exchange layer (12,22and32) comprises at least one of an alkali-metal-sulfonic functional group and an alkali-metal-phosphoric functional group, wherein the alkali-metal-sulfonic functional group comprises at least one of a lithium sulfonate group (—SO3Li), a sodium sulfonate group (—SO3Na) and a potassium sulfonate group (—SO3K), and the alkali-metal-phosphoric functional group comprises at least one of a lithium phosphate group (—PO3Li2), a sodium phosphate group (—PO3Na2) and a potassium phosphate group (—PO3K2). In some embodiments, the alkali-metal-sulfonic functional group is a lithium sulfonate group, and the alkali-metal-phosphoric functional group is a lithium phosphate group. In some embodiments, the cations in the functional group grafted in the cation exchange layer (12,22and32) may be lithium ions, and when the lithium ions are replaced by transition metal ions, they may become a lithium source in an electrolytic solution to further enhance the cycling capability of the electrochemical device. In the above embodiments, the functional-group-grafted material layer (second porous substrate or polymer binder) in the cation exchange layer (12,22and32) can each determine the degree of grafting of the functional group on the material layer and its ability to exchange transition metal ions by measuring a grafting concentration of the functional group thereof, wherein the grafting concentration of the functional group refers to the ratio of the number of moles of the functional group to the mass of the cation exchange layer. In some embodiments, the grafting concentration of the functional group can be measured by acid-base titration, and the steps are as follows: first, a certain mass of cation exchange layer (not yet neutralized with alkali metal ions, only grafted with the sulfonic acid group (—SO3H) or the phosphoric acid group (—PO3H2)) is weighed, then the cation exchange layer is dissolved in water, and phenolphthalein is used as an indicator and titrated with a sodium hydroxide (NaOH) solution to obtain the number of moles of the spent sodium hydroxide solution. In some embodiments, when the functional group employed is a sulfonic acid group, the grafting concentration A of the functional group (sulfonic acid group) in the cation exchange layer can be calculated by the following formula: grafting concentrationA(mmol/g)=(V×N/m), where V is the titration volume (L) of the sodium hydroxide, N is the molar concentration (mmol/L) of the sodium hydroxide solution, and m is the mass (g) of the cation exchange layer. In some embodiments, when the functional group employed is a phosphoric acid group, the grafting concentration A of the functional group (phosphoric acid group) in the cation exchange layer can be calculated by the following formula: grafting concentrationA(mmol/g)=(V×N/(2×m)), where V is the titration volume (L) of the sodium hydroxide, N is the molar concentration (mmol/L) of the sodium hydroxide solution, and m is the mass (g) of the cation exchange layer. In some embodiments, the grafting concentration of the functional-group-grafted material layer (second porous substrate or polymer binder) in the cation exchange layer (12,22and32) is from about 0.15 mmol/g to about 0.95 mmol/g. In some embodiments, the grafting concentration of the functional groups can also be tested by other methods. In some embodiments, the inorganic particles in the above embodiments can be selected from the group consisting of aluminum oxide, silicon dioxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium dioxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium sulfate and combinations thereof. In some embodiments, the binder in the above embodiments can be selected from the group consisting of a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-trichloroethylene copolymer, polyacrylate ester, polyacrylic acid, polyacrylate salt, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose sodium, carboxymethyl cellulose lithium, an acrylonitrile-styrene-butadiene copolymer, polyvinyl alcohol, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene, a styrene-butadiene copolymer, polyvinylidene fluoride and combinations thereof. In some embodiments, the polymer binder in the above embodiments can be selected from the group consisting of a vinylidene fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-trichloroethylene copolymer, polyacrylate ester, polyacrylic acid, polymethyl methacrylate, polyvinylidene fluoride, polyacrylonitrile, polytetrafluoroethylene, polyhexafluoropropylene, a styrene-butadiene copolymer and combinations thereof. The polymer binder may be in the form of granules, fibers, meshes, or other forms, having a strong binding force and capable of binding the electrode in contact therewith. In some embodiments, the first porous substrate in the above embodiments is a polymer film, a multilayer polymer film or a nonwoven fabric formed of any one or a mixture of more than two of the following polymers: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthamide), polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cycloolefin copolymer, polyphenylene sulfide and poly(vinyl-naphthalene). In some embodiments, the second porous substrate in the above embodiments is selected from the group consisting of polyethylene, polypropylene, polyethylene terephthalate, polyimide, an ethylene-styrene copolymer, polysulfone, polyetheretherketone, polystyrene and combinations thereof. The second porous substrate can function to insulate electrons and conduct lithium ions, but has no binding property. In some embodiments, the preparation method of the first form of the composite separator comprises the following steps: Inorganic particles and a binder are mixed and dissolved in a dilution solvent to form a first coating slurry (anti-oxidation layer), and then the first coating slurry is uniformly coated on one or both surfaces of the first porous substrate by microgravure coating. After drying, a double-layer or three-layer structure of the first coating and the first porous substrate is obtained. A polymer binder and an auxiliary binder are mixed and dissolved in a dilution solvent to form a second coating slurry (binding layer), and then the second coating slurry is uniformly coated on one or both surfaces of the double-layer or three-layer structure by microgravure coating. After drying, the first porous substrate, the first coating and the second coating in a multilayer composite structure are obtained. A second porous substrate material is dissolved in a non-aqueous solvent. At least one of a vulcanizing agent and a phosphating agent is added into it, wherein the ratio of at least one of the vulcanizing agent and the phosphating agent to the second porous substrate material is from about 1 mL/g to about 50 mL/g. The mixture is functionalized at a temperature of about 20° C. to about 100° C. for about 0.5 h to 20 h. After that, a lithium hydroxide solution is added into the mixture, wherein the temperature is adjusted to about 45° C. After stirring, the deposit is taken out and dried to obtain a functional-group-grafted second porous substrate material; and the functional-group-grafted second porous substrate material and a binder are dissolved in a dilution solvent to form a cation exchange layer slurry. Then, the cation exchange layer slurry is uniformly coated on the side surface, adjacent the first coating, of the multilayer composite structure by microgravure coating. After drying and cutting, the first form of the composite separator is obtained. In some embodiments, the preparation method of the second form of the composite separator comprises the following steps: A second porous substrate material is dissolved in a non-aqueous solvent. At least one of a vulcanizing agent and a phosphating agent is added into it, wherein the ratio of at least one of the vulcanizing agent and the phosphating agent to the second porous substrate material is from about 1 mL/g to about 50 mL/g. The mixture is functionalized at a temperature of about 20° C. to about 100° C. for about 0.5 h to 20 h. After that, a lithium hydroxide solution is added into the mixture, wherein the temperature is adjusted to about 45° C. After stirring, the deposit is taken out and dried to obtain a functional-group-grafted second porous substrate material; and the functional-group-grafted second porous substrate material and a binder are dissolved in a dilution solvent to form a cation exchange layer slurry. Then, the cation exchange layer slurry is uniformly coated on one surface of the first porous substrate by microgravure coating. After drying, a double-layer structure of the cation exchange layer and the first porous substrate is obtained. Inorganic particles and a binder are mixed and dissolved in a dilution solvent to form a first coating slurry (anti-oxidation layer). The first coating slurry is uniformly coated on one side surface of the cation exchange layer of the double-layer structure or both side surfaces of the double-layer structure of the double-layer structure by microgravure coating. After drying, a composite structure of the first coating and the double-layer structure is obtained. A polymer binder and an auxiliary binder are mixed and dissolved in a dilution solvent to form a second coating slurry (binding layer). And then, the second coating slurry is uniformly coated on one or both surfaces of the composite structure by microgravure coating. After drying and cutting, the second form of the composite separator is obtained. In some embodiments, the preparation method of the third form of the composite separator comprises the following steps: Inorganic particles and a binder are mixed and dissolved in a dilution solvent to form a first coating slurry (anti-oxidation layer). Then, the first coating slurry is uniformly coated on one or both surfaces of the first porous substrate by microgravure coating. After drying, a double-layer or three-layer structure of the first coating and the first porous substrate is obtained. A polymer binder is dissolved in a non-aqueous solvent. At least one of a vulcanizing agent and a phosphating agent is added into it, wherein the ratio of at least one of the vulcanizing agent and the phosphating agent to the second porous substrate material is from about 1 mL/g to about 50 mL/g. The mixture is functionalized at a temperature of about 20° C. to about 100° C. for about 0.5 h to 20 h. A lithium hydroxide solution is added into the mixture, wherein the temperature is adjusted to about 45° C. After stirring, the deposit is taken out and dried to obtain a functional-group-grafted polymer binder material, and. the functional-group-grafted polymer binder material and an auxiliary binder are dissolved in a dilution solvent to form a cation exchange layer slurry. And then, the cation exchange layer slurry is uniformly coated on one side surface, adjacent the first coating, of the double-layer or three-layer structure by microgravure coating. A polymer binder and an auxiliary binder are mixed and dissolved in a dilution solvent to form a second coating slurry (binding layer). The second coating slurry is uniformly coated on one or both surfaces of the composite structure by microgravure coating. After drying and cutting, the third form of the composite separator is obtained. The preparation method of the composite separator in the embodiments of the present application may be a conventional method in the art without being limited thereto. Some embodiments of the present application further provide an electrochemical device comprising the composite separator of the present application. In some embodiments, the electrochemical device is a lithium-ion battery. The lithium-ion battery comprises a cathode, an anode, an electrolytic solution and a composite separator according to the present application, wherein the composite separator is disposed between the cathode and the anode. The cation exchange layer enhances the wetting and liquid retention capabilities of the electrode assembly in the electrochemical device, thereby enhancing the electrochemical stability and cycling performance of the electrochemical device. In the above lithium-ion battery, the cathode comprises a cathode material capable of absorbing and releasing lithium (Li) (hereinafter, sometimes referred to as “a cathode material capable of absorbing/releasing lithium Li”). Examples of the cathode material capable of absorbing/releasing lithium (Li) may comprise one or more of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganate, lithium manganese iron phosphate, lithium vanadium phosphate, oxy-lithium vanadium phosphate, lithium iron phosphate, lithium titanate and lithium-rich manganese-based material. The anode comprises an anode material capable of absorbing and releasing lithium (Li) (hereinafter, sometimes referred to as “an anode material capable of absorbing/releasing lithium (Li)”). Examples of the anode material capable of absorbing/releasing lithium (Li) may comprise carbon materials, metal compounds, oxides, sulfides, nitrides of lithium such as LiN3, lithium metal, metals forming alloys together with lithium, and polymer materials. The lithium-ion battery of the present application further comprises an electrolyte, the electrolyte may be one or more of a gel electrolyte, a solid electrolyte and an electrolytic solution, and the electrolytic solution comprises a lithium salt and a non-aqueous solvent. In some embodiments, the lithium salt is one or more selected from LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB and lithium difluoroborate. For example, the lithium salt is LiPF6because it can provide high ionic conductivity and improve the cycling performance. The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof. The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof. Examples of other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, phosphate and combinations thereof. In some embodiments, the preparation method of the lithium-ion battery comprises: the cathode in the above embodiments, the separator of the present application and the anode are sequentially wound or stacked into an electrode assembly, then the electrode assembly is loaded into, for example, an aluminum plastic film, an electrolytic solution is injected, and then vacuum encapsulation, standing, formation, shaping and the like are performed to obtain the lithium-ion battery. Although the lithium-ion battery is used as an example for the description above, after reading the present application, those skilled in the art will appreciate that the composite separator of the present application can be used in other suitable electrochemical devices. Such electrochemical devices comprise any device for electrochemical reaction, and specific examples thereof comprise all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors. In particular, the electrochemical device is a lithium secondary battery, comprising a lithium metal secondary battery, a lithium-ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery. Some embodiments of the present application further provide an electronic device, comprising the electrochemical device in the embodiments of the present application. The electronic device of the embodiments of the present application is not particularly limited, and may be any electronic device known in the art. In some embodiments, the electronic device may comprise, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copy machine, a portable printer, stereo headphones, a video recorder, a liquid crystal display television, a portable cleaner, a portable CD player, a mini disk player, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power, a motor, a car, a motorcycle, a power bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flash lamp, a camera, a large household battery, a lithium-ion capacitor and the like. SPECIFIC EXAMPLES Some specific examples and a comparative example are listed below, and the electrochemical device (i.e. lithium-ion battery) is subjected to a transition metal capture rate test, a self-discharge test, a nail penetration test and a cycling performance test, respectively, so as to better illustrate the technical solutions of the present application. Preparation of Cathode Aluminum foil was adopted as a cathode current collector. A layer of lithium cobaltate slurry (cathode material layer) was uniformly coated on the surface of the cathode current collector, wherein the lithium cobaltate slurry is composed of 94 wt % of lithium cobaltate, 3 wt % of polyvinylidene fluoride and 3 wt % of acetylene black. Then, the cathode current collector coated with the lithium cobaltate slurry was baked at 120° C. for 1 h, and was subjected to cold pressing, cutting and slitting to obtain the cathode. Preparation of Anode Copper foil was adopted as an anode current collector. A layer of graphite slurry (anode material layer) was uniformly coated on the surface of the anode current collector, wherein the graphite slurry is composed of 95 wt % of artificial graphite, 2 wt % of acetylene black, 2 wt % of styrene-butadiene rubber and 1 wt % of carboxymethyl cellulose sodium. Then, the anode current collector coated with the graphite slurry was baked at 120° C. for 1 h, and was subjected to cold pressing, cutting and slitting to obtain the anode. Preparation of Electrolytic Solution In an environment with a water content of less than 10 ppm, lithium hexafluorophosphate and a non-aqueous organic solvent (ethylene carbonate (EC):propylene carbonate (PC):diethyl carbonate (DEC)=1:1:1, mass ratio) were formulated according to a mass ratio of 8:92 to form the electrolytic solution. Preparation of Lithium-Ion Battery The composite separator in the embodiments and comparative example was prepared into a lithium-ion battery by the following preparation methods. Specifically, the composite separators prepared in the following embodiments and comparative example were sequentially stacked in accordance with the above cathode, the composite separators and the above anode, wherein the side, having the cation exchange layer, of the composite separator faced the cathode and the side, farther away from the cation exchange layer, faced the anode such that the separator was disposed between the cathode and the anode to perform a separation function, and then, they were wound into an electrode assembly. Then, the electrode assembly was placed in an aluminum foil packaging bag, and dehydrated at 80° C. to obtain a dry electrode assembly. The above electrolytic solution was injected into the dry electrode assembly, and subjected to vacuum encapsulation, standing, formation, shaping and the like, thereby completing the preparation of the lithium-ion batteries of the following embodiments and comparative example. Example 1 Aluminum oxide and polyacrylate ester were mixed according to a mass ratio of 90:10 and dissolved in deionized water to form a first coating slurry (anti-oxidation layer), wherein the solid content of the first coating slurry was 45 wt %. The first coating slurry was uniformly coated on one surface of a polyethylene porous substrate at a thickness of 7 μm by microgravure coating. After drying, a double-layer structure of the first coating and the polyethylene substrate was obtained, wherein the thickness of the first coating was 2 μm. Polyvinylidene fluoride and polyacrylate ester were mixed according to a mass ratio of 3:2 and dissolved in deionized water to form a second coating slurry (binding layer), wherein the solid content of the second coating slurry was 30 wt %. The second coating slurry was uniformly coated on both side surfaces of the double-layer structure of the first coating and the polyethylene porous substrate by microgravure coating. After drying, the first porous substrate, the first coating and the second coating in a multilayer composite structure was obtained, wherein the single side thickness of the second coating was 1 μm. Polyethylene particles were dissolved in 1,2-dichloroethane to form a solution having a solid content of 30 wt %. Concentrated sulfuric acid was added to the solution, wherein the ratio of concentrated sulfuric acid to polyethylene particles was 3.0 mL/g, and the mixture was functionalized at a temperature of 60° C. for 4 h. A lithium hydroxide solution having the concentration of 2 mol/L was added such that the molar ratio of lithium hydroxide to concentrated sulfuric acid was 2.4:1, then the temperature was adjusted to about 45° C. After stirring for 1 h, the deposit was taken out and dried to obtain a functional-group-grafted polyethylene material. The functional-group-grafted polyethylene material and polyacrylate ester were mixed according to a mass ratio of 3:2 and dissolved in deionized water to form a cation exchange layer slurry, wherein the solid content of the cation exchange layer was 30 wt %. The cation exchange layer slurry was uniformly coated on a side surface, adjacent the first coating, of the multilayer composite structure by microgravure coating to form a cation exchange layer, wherein the thickness of the cation exchange layer was 3 μm. After drying and cutting, the first form of the composite separator was obtained. Example 2 Polyethylene particles were dissolved in 1,2-dichloroethane to form a solution having a solid content of 30 wt %. Concentrated sulfuric acid was added to the solution, wherein the ratio of concentrated sulfuric acid to polyethylene particles was 3.0 mL/g, and the mixture was functionalized at a temperature of 60° C. for 4 h. A lithium hydroxide solution having the concentration of 2 mol/L was added such that the molar ratio of lithium hydroxide to concentrated sulfuric acid was 2.4:1, wherein the temperature was adjusted to 45° C. After stirring for 1 h, the deposit was taken out and dried to obtain a functional-group-grafted polyethylene material. The functional-group-grafted polyethylene material and polyacrylate ester were mixed according to a mass ratio of 3:2 and dissolved in deionized water to form a cation exchange layer slurry, wherein the solid content of the cation exchange layer was 30 wt %. The cation exchange layer slurry was uniformly coated on one surface of a polyethylene porous substrate at a thickness of 7 μm by microgravure coating, wherein the thickness of the cation exchange layer was 3 μm. After drying, a double-layer structure of the cation exchange layer and the polyethylene porous substrate was obtained. Aluminum oxide and polyacrylate ester were mixed according to a mass ratio of 90:10 and dissolved in deionized water to form a first coating slurry (anti-oxidation layer), wherein the solid content of the first coating slurry was 45 wt %. The first coating slurry was uniformly coated on one side surface of the cation exchange layer of the double-layer structure by microgravure coating. After drying, a composite structure of the first coating and the double-layer structure was obtained, wherein the thickness of the first coating was 2 μm. Polyvinylidene fluoride and polyacrylate ester were mixed according to a mass ratio of 3:2 and dissolved in deionized water to form a second coating slurry (binding layer), wherein the solid content of the second coating slurry was 30 wt %. The second coating slurry was uniformly coated on both side surfaces of the composite structure by microgravure coating, wherein the single side thickness of the second coating was 1 μm. After drying and cutting, the second form of the composite separator was obtained. Example 3 Aluminum oxide and polyacrylate ester were mixed according to a mass ratio of 90:10 and dissolved in deionized water to form a first coating slurry (anti-oxidation layer), wherein a solid content of the first coating slurry was 45 wt %. The first coating slurry was uniformly coated on one surface of a polyethylene porous substrate at a thickness of 7 μm by microgravure coating. After drying, a double-layer structure of the first coating and the polyethylene porous substrate was obtained, wherein the thickness of the first coating was 2 μm. Polyvinylidene fluoride was dissolved in 1,2-dichloroethane to form a solution having the solid content of 30 wt %. Concentrated sulfuric acid was added to the solution, wherein the ratio of concentrated sulfuric acid to polyvinylidene fluoride was 3.0 mL/g, and the mixture was functionalized at a temperature of 60° C. for 4 h. A lithium hydroxide solution having the concentration of 2 mol/L was added such that the molar ratio of lithium hydroxide to concentrated sulfuric acid was 2.4:1, wherein the temperature was adjusted to about 45° C. After stirring for 1 h, the deposit was taken out and dried to obtain a functional-group-grafted polyvinylidene fluoride material. The functional-group-grafted polyvinylidene fluoride material and polyacrylate ester were mixed according to a mass ratio of 3:2 and dissolved in deionized water to form a functional-group-grafted polymer binder slurry (binding layer), wherein the solid content of the functional-group-grafted polymer binder slurry was 30 wt %. The functional-group-grafted polymer binder slurry was uniformly coated on one side surface of the first coating of the double-layer structure of the first coating and the polyethylene substrate by microgravure coating to form a cation exchange layer. The same second coating slurry as in Examples 1 and 2 was coated on the other side surface of the double-layer structure to form a second coating, wherein the thickness of the cation exchange layer was 3 μm and the thickness of the second coating was 1 μm, and after drying and cutting, the third form of the composite separator was obtained. Example 4 The preparation method is the same as that of Example 3. The difference is that in Example 4, concentrated phosphoric acid (H2PO3) was added to the solution of polyvinylidene fluoride and 1,2-dichloroethane, wherein the ratio of concentrated phosphoric acid to polyvinylidene fluoride was 3.0 mL/g; the mixture was functionalized at a temperature of 60° C. for 4 h; and a lithium hydroxide solution having the concentration of 2 mol/L was added such that the molar ratio of lithium hydroxide to concentrated phosphoric acid was 2.4:1. Example 5 The preparation method is the same as that of Example 3. The difference is that in Example 5, the thickness of the cation exchange layer was 1 μm. Example 6 The preparation method is the same as that of Example 3. The difference is that in Example 6, the thickness of the cation exchange layer was 5 μm. Example 7 The preparation method is the same as that of Example 3. The difference is that in Example 7, the thickness of the cation exchange layer was 8 μm. Example 8 The preparation method is the same as that of Example 3. The difference is that in Example 8, the ratio of concentrated sulfuric acid to polyvinylidene fluoride was 1.0 mL/g. Example 9 The preparation method is the same as that of Example 3. The difference is that in Example 9, the ratio of concentrated sulfuric acid to polyvinylidene fluoride was 5.0 mL/g. Example 10 The preparation method is the same as that of Example 3. The difference is that in Example 10, the ratio of concentrated sulfuric acid to polyvinylidene fluoride was 8.0 mL/g. Example 11 The preparation method is the same as that of Example 3. The difference is that in Example 11, the mixture was functionalized at a temperature of 20° C. for 4 h. Example 12 The preparation method is the same as that of Example 3. The difference is that in Example 12, the mixture was functionalized at a temperature of 40° C. for 4 h. Example 13 The preparation method is the same as that of Example 3. The difference is that in Example 13, the mixture was functionalized at a temperature of 80° C. for 4 h. Example 14 The preparation method is the same as that of Example 3. The difference is that in Example 14, the mixture was functionalized at a temperature of 60° C. for 2 h. Example 15 The preparation method is the same as that of Example 3. The difference is that in Example 15, the mixture was functionalized at a temperature of 60° C. for 6 h. Example 16 The preparation method is the same as that of Example 1. The difference is that in Example 16, the mixture was functionalized at a temperature of 60° C. for 8 h. Example 17 The preparation method is the same as that of Example 3. The difference is that in Example 17, the thickness of the cation exchange layer was 0.5 μm. Example 18 The preparation method is the same as that of Example 3. The difference is that in Example 18, the thickness of the cation exchange layer was 15 μm. Example 19 The preparation method is the same as that of Example 3. The difference is that in Example 19, the ratio of concentrated sulfuric acid to polyvinylidene fluoride was 0.5 mL/g. Comparative Example 1 Aluminum oxide and polyacrylate ester were mixed according to a mass ratio of 90:10 and dissolved in deionized water to form a first coating slurry (anti-oxidation layer), wherein the solid content of the first coating slurry was 45 wt %. The first coating slurry was uniformly coated on one surface of a polyethylene porous substrate at a thickness of 7 μm by microgravure coating. After drying, a double-layer structure of the first coating and the polyethylene substrate was obtained, wherein the thickness of the first coating was 2 μm. Polyvinylidene fluoride and polyacrylate ester were mixed according to a mass ratio of 3:2 and dissolved in deionized water to form a second coating slurry (binding layer), wherein the solid content of the second coating slurry was 30 wt %. The second coating slurry was uniformly coated on both surfaces of the double-layer structure of the first coating and the polyethylene porous substrate by microgravure coating. After drying, the first porous substrate, the first coating and the second coating in a multilayer composite structure was obtained, wherein the single side thickness of the second coating was 1 μm. For the composite separators of the above examples and comparative example, the grafting concentration of the cation exchange layer thereof was measured. After the lithium-ion battery was fabricated, battery capacity, thickness, width and length were recorded to determine the volumetric energy density of the lithium-ion battery. Then the lithium-ion battery was subjected to a cycling performance test, a metal capture rate test, a self-discharge test and a nail penetration test. Cycling Performance Test The lithium-ion battery of the following examples and comparative example was in an incubator at 25° C.±2° C., charged at a constant current of 0.7 C to 4.4 V, then charged at a constant voltage of 4.4 V to 0.05 C, and finally discharged at a constant current of 0.5 C to 3.0 V, which was a charge and discharge cycle, and the discharge capacity after the first cycle of the lithium-ion battery was recorded. Then, the charge and discharge cycle was performed 300 times as described above, and the discharge capacity of after the 300th cycle of the lithium-ion battery was recorded. 5 lithium-ion batteries were used for each group to calculate the average of the capacity retention rates of the lithium-ion batteries. Capacity retention rate of lithium-ion battery=discharge capacity (mAh) after the 300th cycle/discharge capacity (mAh) after the first cycle×100%. Transition Metal Capture Rate Test The definition of the transition metal capture rate is as follows: Transition metal capture rate γ=1−(transition metal deposition amount of anode/transition metal loss amount of cathode) The test was performed by an inductive coupled plasma emission spectrometer (ICP) to obtain the amount of transition metal deposition on the anode and the transition metal loss amount of the cathode of the lithium-ion battery. The specific steps are as follows: The uncycled lithium-ion battery was discharged to a range of 2.5 V to 3.0 V, and then disassembled to take out the anode and the cathode, the anode and the cathode were immersed in dimethyl carbonate for 2 h, and the immersed anode and cathode were air dried. The anode and the cathode were respectively loaded into a mold of 1540.25 mm2, and then the inductive coupled plasma emission spectrometer was used to obtain the amount of transition metal deposition on the anode of the uncycled lithium-ion battery and the transition metal loss amount of the cathode of the uncycled lithium-ion battery. The lithium-ion battery subjected to the 300-cycle test was discharged to a range of 2.5 V to 3.0 V, and then disassembled to take out the anode and the cathode, the anode and the cathode were immersed in dimethyl carbonate for 2 h, and the immersed anode and cathode were naturally dried. The anode and the cathode were respectively loaded into a 1540.25 mm2mold, and then an inductive coupled plasma emission spectrometer was used to obtain the amount of transition metal deposition on the anode of the lithium-ion battery subjected to the 300-cycle test and the transition metal loss amount of the cathode of the lithium-ion battery subjected to the 300-cycle test. 5 lithium-ion batteries were used for each of the above two groups to calculate the average amount of transition metal deposition on the anode and the transition metal loss amount of the cathode of the lithium-ion battery, wherein the amount of transition metal deposition on the anode was the amount of transition metal deposition on the anode of the lithium-ion battery subjected to the 300-cycle test minus the amount of transition metal deposition on the anode of the uncycled lithium-ion battery, and the transition metal loss amount of the cathode was the transition metal loss amount of the cathode of the uncycled lithium-ion battery minus the transition metal loss amount of the cathode of the lithium-ion battery subjected to the 300-cycle test. Self-Discharge Test The lithium-ion battery was placed in a 25° C. incubator, charged at a constant current of 0.5 C to 4.4 V and then charged at a constant voltage to 0.05 C, where the initial voltage V1 of the lithium-ion battery was recorded. Then, the lithium-ion battery was kept at a constant voltage of 45° C. for 1000 h, where the final voltage V2 of the lithium-ion battery was determined. The self-discharge rate value was obtained according to the following formula: self-discharge ratek(mV/h)=(V1−V2)/1000 (h), Nail Penetration Test The lithium-ion battery was placed in a 25° C. incubator and allowed to stand for 30 min to bring the lithium-ion battery to a constant temperature. The constant-temperature lithium-ion battery was charged at a constant current of 0.5 C to a voltage of 4.4 V, and then charged at a constant voltage of 4.4 V to a current of 0.025 C. The fully-charged lithium-ion battery was transferred to a nail penetration tester, the test environment temperature was kept at 25° C.±2° C., and a steel nail having the diameter of 4 mm was used to pass through the center of the lithium-ion battery at a uniform speed of 30 mm/s for 300 seconds. A lithium-ion battery not exhibiting smoking, igniting or exploding was recorded as a pass. Each time 10 lithium-ion batteries were tested, and the number of lithium-ion batteries that passed the nail penetration test was used as an indicator to evaluate the safety performance of the lithium-ion batteries. The specific implementation parameters of Examples 1-19 and Comparative Example 1 above and their grafting concentration results are shown in Table 1 below. TABLE 1ThicknessVulcanizing/of CationPhosphating AgentVulcanizing/Vulcanizing/Example/Form ofExchangeto GraftedPhosphatingPhosphatingGraftingComparativeCompositeFunctionalLayerSubstance RatioTemperatureTimeConcentrationExampleSeparatorGroup(μm)(mL/g)(° C.)(h)(mmol/g)Example 1First form—SO3Li33.06040.63Example 2Second form—SO3Li33.06040.63Example 3Third form—SO3Li33.06040.50Example 4Third form—PO3Li233.06040.31Example 5Third form—SO3Li13.06040.63Example 6Third form—SO3Li53.06040.63Example 7Third form—SO3Li83.06040.63Example 8Third form—SO3Li31.06040.37Example 9Third form—SO3Li35.06040.57Example 10Third form—SO3Li38.06040.61Example 11Third form—SO3Li33.02040.13Example 12Third form—SO3Li33.04040.32Example 13Third form—SO3Li33.08040.73Example 14Third form—SO3Li33.06020.28Example 15Third form—SO3Li33.06060.73Example 16Third form—SO3Li33.06080.76Example 17Third form—SO3Li0.53.06040.63Example 18Third form—SO3Li153.06040.91Example 19Third form—SO3Li30.56040.09Comparative//////0.0Example 1 The results of the transition metal capture rate test, the self-discharge test, the nail penetration test and the cycling performance test of the electrochemical devices of Examples 1-19 and Comparative Example 1 are shown in Table 2 below. TABLE 2TransitionSelf-NailExample/MetaldischargePenetrationCapacityComparativeCaptureRate kTest PassRetentionExampleRate γ(mV/h)RateRateExample 10.630.0410/1093.5%Example 20.710.0310/1093.3%Example 30.740.0310/1093.2%Example 40.660.059/1092.2%Example 50.620.058/1092.1%Example 60.930.0210/1093.9%Example 70.970.0210/1093.8%Example 80.640.058/1092.2%Example 90.840.0310/1093.1%Example 100.900.0210/1093.7%Example 110.610.058/1092.7%Example 120.730.0310/1093.3%Example 130.970.0210/1093.7%Example 140.720.0310/1092.1%Example 150.950.0210/1093.7%Example 160.960.0210/1093.5%Example 170.430.086/1090.3%Example 180.980.0210/1078.6%Example 190.470.088/1091.6%Comparative0.260.175/1089.7%Example 1 It can be seen from Table 2 that as compared with Comparative Example 1, the electrochemical device having the composite separator of the embodiments of the present application has a significant enhancement in safety performance and cycling performance. Specifically, when Comparative Example 1 is compared with Examples 1-19, it can be known that the electrochemical device having the composite separator of the embodiments of the present application can effectively increase the transition metal capture rate of the separator and reduce the self-discharge rate in the transition metal capture rate test and the self-discharge test. This represents that the composite separator of the present application can effectively capture transition metal ions with lower electrical conductivity, thereby improving the self-discharge rate of the electrochemical device. In addition, compared with Comparative Example 1, the electrochemical device having the composite separator in Examples 1-19 of the present application also exhibits excellent results in the nail penetration test or the cycling performance test, thereby effectively improving the safety performance and cycling performance of the electrochemical device. It can be seen from Table 1 and Table 2 that the first, second and third forms of the composite separators provided in Examples 1-3 of the present application can achieve a nail penetration success rate of 10/10, a self-discharge rate of less than 0.04 and a capacity retention rate of 93.2% and above. The electrochemical device of Example 4 of the present application also exhibited an excellent nail penetration success rate, a self-discharge rate of 0.05 and a capacity retention rate of 92.2%. It can be seen that the cation exchange layer using a lithium phosphate group as a functional group can also improve the transition metal ion deposition of the electrochemical device, thereby enhancing its safety performance and cycling performance. When Examples 5-7, 17 and 18 are compared, it can be seen that when the thickness of the cation exchange layer in the composite separator of the present application is in the range of 0.5 μm to 10 μm, the electrochemical device can maintain excellent safety performance and cycling performance. According to different specific implementation parameters in the manufacturing process, the grafting concentration of the functional group on the cation exchange layer in the composite separator of the present application is affected by the ratio of the vulcanizing/phosphating agent to the substrate, the operating temperature of the vulcanizing/phosphating process and the operating time of the vulcanizing/phosphating process, thereby affecting the transition metal ion capture capability of the cation exchange layer. When Examples 8-10 and 19 are compared, it can be seen that when the ratio of the vulcanizing/phosphating agent to the substrate is in the range of the embodiments of the present application, the grafting concentration of the functional group on the cation exchange layer can be maintained at a certain value to maintain the transition metal ion capture capability, thereby increasing the transition metal capture rate of the separator in the electrochemical device. Similarly, when Examples 11-16 are compared, it can be seen that when the time or the reaction temperature during the functionalization is in the range of the embodiments of the present application, the grafting concentration of the functional group on the cation exchange layer can be maintained at a certain value to maintain the transition metal ion capture capability, thereby increasing the transition metal capture rate of the separator in the electrochemical device. In addition, the embodiments of the present application may further combine a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS) to illustrate the transition metal ion capture capability of the composite separator of the present application. FIG.4andFIG.5are respectively 3000-fold enlarged views of the anodes of Comparative Example 1 and Example 1 of the present application after passing the self-discharge test under a scanning electron microscope (Zeiss, SIGMA) and energy distribution diagrams of an energy dispersive spectrometer (X-max. EDS). As shown inFIG.5, after the anode in the electrochemical device of Example 1 of the present application passed the 1000 h constant voltage test, the SEM enlarged view has no obvious deposition of transition metals aside from the original anode active material particles. In addition, the EDS spectrum thereof also shows that the anode in the electrochemical device of the present application has no other significant transition metal peaks other than graphite. In contrast, as shown inFIG.4, the anode in the electrochemical device of Comparative Example 1 showed significant transition metal deposition on the SEM enlarged view after passing the 1000 h constant voltage test, and its EDS spectrum also shows that there is a distinct peak in the ranges of O atoms and Co metals, which represents the formation of metal oxides. At the same time, the quantitative comparison of the amount of transition metal deposition on the anode of Comparative Example 1 and Example 1 of the present application can be further made by an ICP.FIG.6is a graph showing the amount of transition metal deposition on the anodes of the lithium-ion battery of Example 1 and Comparative Example 1 after passing the cycle test. As shown inFIG.6, the concentration of transition metal deposition on the anode of Example 1 of the present application is only 1,210 ppm, whereas the concentration of transition metal deposition on the anode of Comparative Example 1 can reach 5030 ppm. It can be seen that the electrochemical device using the composite separator of the present application can effectively reduce transition metal deposition on the anode and reduce the effect of its deposition to ¼ of that of the electrochemical device not using the composite separator of the present application. Through the comparison of the above Examples and Comparative Example, it can be clearly understood that the composite separator of the present application can effectively capture the transition metal ions eluted from the cathode through the cation exchange layer, thereby reducing the deposition of transition metal ions on the anode and the self-discharge rate of the lithium-ion battery. Therefore, electrochemical stability and cycling performance of the electrochemical device are enhanced, and the safety of the electrochemical device is also significantly improved. References throughout the specification of the present application to “embodiments”, “partial embodiments,” “an embodiment,” “another example”, “examples”, “specific examples” or “partial examples” mean that at least one embodiment or example in the embodiments of the present application includes specific features, structures, materials or characteristics described in the embodiment or example. Therefore, descriptions appearing throughout the specification, such as “in some embodiments”, “in the embodiments”, “in an embodiment”, “in another example”, “in an example”, in a particular example” or “examples”, are not necessarily referring to the same embodiments or examples in the embodiments of the present application. Furthermore, the specific features, structures, materials or characteristics in the descriptions can be combined in any suitable manner in one or more embodiments or examples. Although the illustrative embodiments have been shown and described, it should be understood by those skilled in the art that the above embodiments cannot be interpreted as limiting the present application, and the embodiments can be changed, substituted and modified without departing from the spirit, principle and scope of the present application. | 58,476 |
11862814 | DETAILED DESCRIPTION OF THE INVENTION A method for producing a microporous material comprising the steps of: providing an ultrahigh molecular weight polyethylene (herein after UHMWPE); providing a particulate filler; and providing a processing plasticizer where the processing plasticizer is a liquid at room temperature. The UHMWPE, filler and plasticizer are all described in greater detail below. The UHMWPE, filler and plasticizer are mixed together to form a mixture. The mixture is extruded through a die (e.g. slot die or blown film die) to form a sheet. The sheet maybe further processed, by casting onto a chilled roller, or calendered, or blown. The cast or calendered sheet is then subjected to an extraction step to partially (or fully) remove the plasticizer and forms thereby a microporous matrix. The matrix comprises UHMWPE, plasticizer if not fully extracted, and the particulate filler distributed throughout the matrix. The filler constitutes from 5 percent to 95 percent by weight of the microporous matrix. The microporous matrix has a network of interconnecting pores communicating throughout the microporous matrix. The pores constitute from 25 percent to 90 percent by volume of the microporous matrix. The microporous matrix is stretched. The stretching process is described in greater detail below. The stretched microporous matrix is not dimensionally stable at elevated temperatures. The stretched microporous matrix is subsequently calendered to produce the final microporous material that is dimensionally stable even at elevated temperatures. Ultrahigh molecular weight polyethylene (UHMWPE) can be defined as a polyethylene having an intrinsic viscosity of least about 18 deciliters/gram. In many cases the intrinsic viscosity is at least about 19 deciliters/gram. Although there is no particular restriction on the upper limit of the intrinsic viscosity, the intrinsic viscosity is frequently in the range of from about 18 to about 39 deciliters/gram. An intrinsic viscosity in the range of from about 18 to about 32 deciliters/gram is most common. As used herein and in the claims, intrinsic viscosity is determined by extrapolating to zero concentration the reduced viscosities or the inherent viscosities of several dilute solutions of the UHMWPE where the solvent is freshly distilled decahydronaphthalene to which 0.2 percent by weight, 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid, neopentanetetrayl ester [CAS Registry No. 6683-19-8] has been added. The reduced viscosities or the intrinsic viscosities of the UHMWPE are ascertained from relative viscosities obtained at 135° C. using an Ubbelohde No. 1 viscometer in accordance with the general procedures of ASTM D 4020-81, except that several dilute solutions of differing concentration are employed. ASTM D 4020-81 is, in its entirety, incorporated herein by reference. Sufficient UHMWPE should be present in the matrix to provide its properties to the microporous material. Other thermoplastic organic polymers may also be present in the matrix, so long as their presence does not materially affect the properties of the microporous material in an adverse manner. The amount of the other thermoplastic polymers which may be present depends upon the nature of such polymers. In general, a greater amount of other thermoplastic organic polymer may be used if the molecular structure contains little branching, few long sidechains, and few bulky side groups, than when there is a large amount of branching, many long sidechains, or many bulky side groups. For this reason, the exemplary thermoplastic organic polymers that may be mixed with the UHMWPE are low density polyethylene, high density polyethylene, poly(tetrafluoroethylene), polypropylene, copolymers of ethylene, such as ethylene-butene or ethylene-hexene, copolymers of propylene, copolymers of ethylene and acrylic acid, and copolymers of ethylene and methacrylic acid. If desired, all or a portion of the carboxyl groups of carboxyl-containing copolymers may be neutralized with sodium, zinc or the like. Usually at least about 70 percent UHMWPE (or 70 percent UHMWPE and other thermoplastic organic polymers), based on the weight of the matrix, will provide the desired properties to the microporous material. The particulate filler may be in the form of ultimate particles, aggregates of ultimate particles, or a combination of both. In most cases, at least about 90 percent by weight of the filler has gross particle sizes in the range of from about 5 to about 40 micrometers. If the filler used is titanium dioxide (TiO2) the gross particle size can range from 0.005 to 45 micrometers. In another embodiment using titanium dioxide (TiO2) as a filler, the gross particle size ranges from 0.1 to 5 micrometers. In another case, at least about 90 percent by weight of the filler has a gross particle size in the range of from about 10 to about 30 micrometers. It is expected that filler agglomerates will be reduced in size during processing of the ingredients. Accordingly, the distribution of gross particle sizes in the microporous material may be smaller than in the raw filler itself. Particle size is determined by use of a Model TAII Coulter counter (Coulter Electronics, Inc.) according to ASTM C 690-80, but modified by stirring the filler for 10 minutes in Isoton II electrolyte (Curtin Matheson Scientific, Inc.) using a four-blade, 4.445 centimeter diameter propeller stirrer. ASTM C 690-80 is, in its entirety, incorporated herein by reference. The particulate filler will on average have an ultimate particle size (irrespective of whether or not the ultimate particles are agglomerated) which is less than about 30 micrometer as determined by transmission electron microscopy. Often the average ultimate particle size is less than about 0.05 micrometer. In one embodiment the average ultimate particle size of filler is approximately 20 micrometers (when a precipitated silica is used). Use of fillers in a polymer matrix is well documented. In general examples of suitable fillers include siliceous fillers, such as: silica, mica, montmorillonite, kaolinite, asbestos, talc, diatomaceous earth, vermiculite, natural and synthetic zeolites, cement, calcium silicate, clay, aluminum silicate, sodium aluminum silicate, aluminum polysilicate, alumina silica gels, and glass particles. In addition to the siliceous fillers other particulate substantially water-insoluble fillers may also be employed. Examples of such optional fillers include carbon black, activated carbon, carbon fibers, charcoal, graphite, titanium oxide, iron oxide, copper oxide, zinc oxide, lead oxide, tungsten, antimony oxide, zirconia, magnesia, alumina, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, calcium carbonate, and magnesium carbonate. Silica and the clays are the most useful siliceous fillers. Of the silicas, precipitated silica, silica gel, or fumed silica is most often used. The particulate filler which has been found to work well is precipitated silica. It is important to distinguish precipitated silica from silica gel, inasmuch as these different materials have different properties. Reference in this regard is made to R. K. Iler, The Chemistry of Silica, John Wiley & Sons, New York (1979), Library of Congress Catalog No. QD 181.S6144, the entire disclosure of which is incorporated herein by reference. Note especially pages 15-29, 172-176, 218-233, 364-365, 462-465, 554-564, and 578-579. Silica gel is usually produced commercially at low pH by acidifying an aqueous solution of a soluble metal silicate, typically sodium silicate, with acid. The acid employed is generally a strong mineral acid such as sulfuric acid or hydrochloric acid although carbon dioxide is sometimes used. Inasmuch as there is essentially no difference in density between gel phase and the surrounding liquid phase while the viscosity is low, the gel phase does not settle out, that is to say, it does not precipitate. Silica gel, then, may be described as a non-precipitated, coherent, rigid, three-dimensional network of contiguous particles of colloidal amorphous silica. The state of subdivision ranges from large, solid masses to submicroscopic particles, and the degree of hydration from almost anhydrous silica to soft gelatinous masses containing on the order of 100 parts of water per part of silica by weight, although the highly hydrated forms are only rarely used in the present invention. Precipitated silica on the other hand, is usually produced commercially by combining an aqueous solution of a soluble metal silicate, ordinarily alkali metal silicate such as sodium silicate, and an acid so that colloidal particles will grow in weakly alkaline solution and be coagulated by the alkali metal ions of the resulting soluble alkali metal salt. Various acids may be used, including the mineral acids, but the preferred material is carbon dioxide. In the absence of a coagulant, silica is not precipitated from solution at any pH. The coagulant used to effect precipitation may be the soluble alkali metal salt produced during formation of the colloidal silica particles, it may be added electrolyte such as a soluble inorganic or organic salt, or it may be a combination of both. Precipitated silica, then, may be described as precipitated aggregates of ultimate particles of colloidal amorphous silica that have not at any point existed as macroscopic gel during the preparation. The sizes of the aggregates and the degree of hydration may vary widely. Precipitated silica powders differ from silica gels in that they have been pulverized in ordinarily having a more open structure, that is, a higher specific pore volume. However, the specific surface area of precipitated silica as measured by the Brunauer, Emmett, Teller (BET) method using nitrogen as the adsorbate, is often lower than that of silica gel. Many different precipitated silicas may be employed in the present invention, but the preferred precipitated silicas are those obtained by precipitation from an aqueous solution of sodium silicate using a suitable acid such as sulfuric acid or hydrochloric acid. Carbon dioxide can also be used to precipitate the silica. Such precipitated silicas are known and processes for producing them are described in detail in U.S. Pat. No. 2,940,830, the entire disclosure of which is incorporated herein by reference, including the processes for making precipitated silicas and the properties of the products. In the proceeding process for producing a microporous matrix, extrusion and calendering are facilitated when the substantially water-insoluble filler carries much of the processing plasticizer. The capacity of the filler particles to absorb and hold the processing plasticizer is a function of the surface area of the filler. It is therefore preferred that the filler have a high surface area. High surface area fillers are materials of very small particle size, materials having a high degree of porosity or materials exhibiting both characteristics. Usually the surface area of the filler itself is in the range of from about 20 to about 400 square meters per gram as determined by the Brunauer, Emmett, Teller (BET) method according to ASTM C 819-77 using nitrogen as the adsorbate but modified by outgassing the system and the sample for one hour at 130° C. Preferably the surface area is in the range of from about 25 to about 350 square meters per gram. ASTM C 819-77 is, in its entirety, incorporated herein by reference. Inasmuch as it is desirable to essentially retain the filler in the microporous matrix sheet, it is preferred that the substantially water-insoluble filler be substantially insoluble in the processing plasticizer and substantially insoluble in the organic extraction liquid when microporous matrix sheet is produced by the above process. The processing plasticizer is typically a liquid at room temperature and usually it is processing oil such as paraffinic oil, naphthenic oil, or an aromatic oil. Suitable processing oils include those meeting the requirements of ASTM D 2226-82, Types 103 and 104. It has been found that oils which have a pour point of less than 22° C. according to ASTM D 97-66 (reapproved 1978) work well. Oils having a pour point of less than 10° C. also work well. Examples of suitable oils include, but are not limited to, Shellflex® 412 and Shellflex® 371 oil (Shell Oil Co.) which are solvent refined and hydrotreated oils derived from naphthenic crude. ASTM D 2226-82 and ASTM D 97-66 (reapproved 1978) are, in the entireties, incorporated herein by reference. It is expected that other materials, including the phthalate ester plasticizers such as dibutyl phthalate, bis (2-ethylhexyl) phthalate, diisodecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, ditridecyl phthalate and waxes, will function satisfactorily as processing plasticizers. The processing plasticizer has little solvating effect on the thermoplastic organic polymer at 60° C., only a moderate solvating effect at elevated temperatures on the order of about 100° C., and a significant solvating effect at elevated temperatures on the order of about 200° C. Minor amounts, usually less than about 5 percent by weight, of other materials used in processing such as lubricant, organic extraction liquid, surfactant, water, and the like, may optionally also be present. Yet other materials introduced for particular purposes may optionally be present in the microporous material in small amounts, usually less than about 15 percent by weight. Examples of such materials include antioxidants, ultraviolet light absorbers, flame retardants, reinforcing fibers such as carbon fiber or chopped glass fiber strand, dyes, pigments, and the like. The balance of the microporous material, exclusive of filler and any impregnate applied for one or more special purposes, is essentially the thermoplastic organic polymer and plasticizer (if not fully extracted). Then the filler, thermoplastic organic polymer powder, processing plasticizer and other additives are mixed until a substantially uniform mixture is obtained. This uniform mixture may also contain other additives such as minor amounts of lubricant and antioxidant. The weight ratio of filler to polymer powder employed in forming the mixture is essentially the same as that of the stretched microporous material to be produced. The ratio of filler to UHMWPE in this mixture is in the range of from about 1:9 to about 15:1 filler to UHMWPE by weight. The particulate filler constitutes from about 5 percent to about 95 percent by weight of that microporous material. Frequently, such filler constitutes from about 45 percent to about 90 percent by weight of the microporous material. From about 55 percent to about 80 percent by weight is used in one of the embodiments of the invention. The ratio of the UHMWPE to the processing plasticizer is 1:30 to 3:2 by weight. Ratio of filler to processing plasticizer is 1:15 to 3:1 by weight. In the extrusion and calendering process, the mixture, together with additional processing plasticizer, is introduced to the heated barrel of a screw extruder. Attached to the extruder is a sheeting die. A continuous sheet formed by the die is forwarded without drawing to a pair of heated calender rolls acting cooperatively to form continuous sheet of lesser thickness than the continuous sheet exiting from the die. The continuous sheet is subjected to an extraction step where processing plasticizer is partially or fully removed there from. The extraction step may include one or more steps. For example, the continuous sheet from the calender then passes to a first extraction zone where the processing plasticizer is substantially removed by extraction with an organic liquid which is a good solvent for the processing plasticizer, a poor solvent for the organic polymer, and more volatile than the processing plasticizer. Usually, but not necessarily, both the processing plasticizer and the organic extraction liquid are substantially immiscible with water. There are many organic extraction liquids that can be used. Examples of suitable organic extraction liquids include but are not limited to hexane, alkanes of varying chain lengths, 1,1,2-trichloroethylene, perchloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, methylene chloride, chloroform, isopropyl alcohol, diethyl ether and acetone. The continuous sheet then passes to a second extraction zone where the residual organic extraction liquid is substantially removed by: heat, steam and/or water. The continuous sheet is then passed through a forced air dryer for substantial removal of residual water and remaining residual organic extraction liquid. From the dryer the continuous sheet, which is a microporous matrix, is passed to a take-up roll. The microporous matrix comprises a filler, UHMWPE, and optional materials in essentially the same weight proportions as those discussed above in respect of the stretched microporous matrix. The matrix might also have some plasticizer if it is not fully extracted. The residual processing plasticizer content is usually less than 20 percent by weight of the microporous matrix and this may be reduced even further by additional extractions using the same or a different organic extraction liquid. In the microporous matrix, the pores constitute from about 25 to about 90 percent by volume. In many cases, the pores constitute from about 30 to about 80 percent by volume of the microporous matrix. One of the embodiments has from 50 to 75 percent of the volume of the microporous matrix is pores. The porosity of the microporous matrix, expressed as percent by volume. Unless impregnated, the porosity of the stretched microporous matrix is greater than the porosity of the microporous matrix before stretching. As used herein and in the claims, the porosity (also known as void volume) of the microporous material, expressed as percent by volume, is determined according to the equation: Porosity=100[1−d1/d2] where d1is the density of the sample which is determined from the sample weight and the sample volume as ascertained from measurements of the sample dimensions and d2is the density of the solid portion of the sample which is determined from the sample weight and the volume of the solid portion of the sample. The volume of the solid portion of the sample can be determined using a Quantachrome stereopycnometer (Quantachrome Corp.) in accordance with the accompanying operating manual. The volume average diameter of the pores of the microporous sheet can be determined by mercury porosimetry using an Autoscan mercury porosimeter (Quantachrome Corp.). Mercury Intrusion/Extrusion is based on forcing mercury (a non-wetting liquid) into a porous structure under tightly controlled pressures. Since mercury does not wet most substances and will not spontaneously penetrate pores by capillary action, it must be forced into the voids of the sample by applying external pressure. The pressure required to fill the voids is inversely proportional to the size of the pores. Only a small amount of force or pressure is required to fill large voids, whereas much greater pressure is required to fill voids of very small pores. In operating the porosimeter, a scan is made in the high pressure range (from about 138 kilopascals absolute to about 227 megapascals absolute). If about 2 percent or less of the total intruded volume occurs at the low end (from about 138 to about 250 kilopascals absolute) of the high pressure range, the volume average pore diameter is taken as twice the volume average pore radius determined by the porosimeter. Otherwise, an additional scan is made in the low pressure range (from about 7 to about 165 kilopascals absolute) and the volume average pore diameter is calculated according to the equation: d=2[v1r1w1+v2r2w2]/[v1w1+v2w2] where d is the volume average pore diameter, v1is the total volume of mercury intruded in the high pressure range, v2is the total volume of mercury intruded in the low pressure range, r1is the volume average pore radius determined from the high pressure scan, r2is the volume average pore radius determined from the low pressure scan, w1is the weight of the sample subjected to the high pressure scan, and w2is the weight of the sample subjected to the low pressure scan. Large pores require lower pressures for the mercury to intrude into the pore volume while smaller pores require the higher pressures for intrusion into the pore volumes. InFIG.1, approximately 20% of the pores are smaller than 0.02 micrometers. DV/log d represents the change in pore volume with the change in log of pore diameter. Thus as can be seen from FIG.1, there are a large number of pores that have a diameter of approximately 0.016 micrometers, and the peak height is several magnitudes higher than any other peak. In this representation, the peak areas and heights represent the relative number of pores at the corresponding log of pore diameter. The volume average diameter of the pores of the precursor microporous matrix is usually a distribution from about 0.01 to about 1.0 micrometers, as seen inFIG.1. By stretching the precursor material one can obtain pores which are greater than 1 micrometer in size. The resulting pore distribution of this stretched material can be seen inFIGS.2and3. Depending on the amount of stretch it is possible to obtain pores greater than 20 to 30 micrometers. Then through the subsequent calendering step the pore size can be selectively reduced from the enlarged pore distribution. One example at this modified distribution of the average diameter of the pores is in the range of from about 0.01 to about 0.8 micrometers for the resulting microporous material which is stretched and calendered. In another embodiment the resulting microporous material has a distribution of average diameter of the pores of from about 0.01 to about 0.6 micrometers, as seen inFIG.4. The volume average diameter of the pores of the microporous matrix is determined by the mercury porosimetry method. The stretched microporous matrix may be produced by stretching the microporous matrix in at least one stretching direction to a stretch ratio of at least about 1.5. In many cases, the stretch ratio is at least about 1.7. In another embodiment it is at least about 2. Frequently, the stretch ratio is in the range of from about 1.5 to about 15. Often the stretch ratio is in the range of from about 1.7 to about 10. In another embodiment, the stretch ratio is in the range of from about 2 to about 6. As used herein and in the claims, the stretch ratio is determined by the formula: S=L2/L1 where S is the stretch ratio, L1is the distance between two reference points located on the microporous matrix and on a line parallel to the stretching direction, and L2is the distance between the same two reference points located on the stretched microporous material. When the stretching is done in two directions, the stretching in the two directions may be performed either sequentially or simultaneously. The temperatures at which stretching is accomplished may vary widely. Stretching may be accomplished at about ambient room temperature, but usually elevated temperatures are employed. The microporous matrix may be heated by any of a wide variety of techniques prior to, during, and/or after stretching. Examples of these techniques include radiative heating such as that provided by electrically heated or gas fired infrared heaters, convective heating such as that provided by recirculating hot air, and conductive heating such as that provided by contact with heated rolls. The temperatures which are measured for temperature control purposes may vary according to the apparatus used and personal preference. For example, temperature-measuring devices may be placed to ascertain the temperatures of the surfaces of infrared heaters, the interiors of infrared heaters, the air temperatures of points between the infrared heaters and the microporous matrix, the temperatures of circulating hot air at points within the apparatus, the temperature of hot air entering or leaving the apparatus, the temperatures of the surfaces of rolls used in the stretching process, the temperature of heat transfer fluid entering or leaving such rolls, or film surface temperatures. In general, the temperature or temperatures are controlled such that the microporous matrix is stretched about evenly so that the variations, if any, in film thickness of the stretched microporous matrix are within acceptable limits and so that the amount of stretched microporous matrix outside of those limits is acceptably low. It will be apparent that the temperatures used for control purposes may or may not be close to those of the microporous matrix itself since they depend upon the nature of the apparatus used, the locations of the temperature-measuring devices, and the identities of the substances or objects whose temperatures are being measured. In view of the locations of the heating devices and the line speeds usually employed during stretching, gradients of varying temperatures may or may not be present through the thickness of the microporous matrix. Also because of such line speeds, it is impracticable to measure these temperature gradients. The presence of gradients of varying temperatures, when they occur, makes it unreasonable to refer to a singular film temperature. Accordingly, film surface temperatures, which can be measured, are best used for characterizing the thermal condition of the microporous matrix. These are ordinarily about the same across the width of the microporous matrix during stretching although they may be intentionally varied, as for example, to compensate for microporous matrix having a wedge-shaped cross-section across the sheet. Film surface temperatures along the length of the sheet may be about the same or they may be different during stretching. The film surface temperature at which stretching is accomplished may vary widely, but in general they are such that the microporous matrix is stretched about evenly, as explained above. In most cases, the film surface temperatures during stretching are in the range of from about 20° C. to about 220° C. Often such temperatures are in the range of from about 50° C. to about 200° C. From about 75° C. to about 180° C. is another range in this embodiment. Stretching may be accomplished in a single step or a plurality of steps as desired. For example, when the microporous matrix is to be stretched in a single direction (uniaxial stretching), the stretching may be accomplished by a single stretching step or a sequence of stretching steps until the desired final stretch ratio is attained. Similarly, when the microporous matrix is to be stretched in two directions (biaxial stretching), the stretching can be conducted by a single biaxial stretching step or a sequence of biaxial stretching steps until the desired final stretch ratios are attained. Biaxial stretching may also be accomplished by a sequence of one or more uniaxial stretching steps in one direction and one or more uniaxial stretching steps in another direction. Biaxial stretching steps where the microporous matrix is stretched simultaneously in two directions and uniaxial stretching steps may be conducted in sequence in any order. Stretching in more than two directions is within contemplation. It may be seen that the various permutations of steps are quite numerous. Other steps, such as cooling, heating, sintering, annealing, reeling, unreeling, and the like, may optionally be included in the overall process as desired. Various types of stretching apparatus are well known and may be used to accomplish stretching of the microporous matrix according to the present invention. Uniaxial stretching is usually accomplished by stretching between two rollers wherein the second or downstream roller rotates at a greater peripheral speed than the first or upstream roller. Uniaxial stretching can also be accomplished on a standard tentering machine. Biaxial stretching may be accomplished by simultaneously stretching in two different directions on a tentering machine. More commonly, however, biaxial stretching is accomplished by first uniaxially stretching between two differentially rotating rollers as described above, followed by either uniaxially stretching in a different direction using a tenter machine or by biaxially stretching using a tenter machine. The most common type of biaxial stretching is where the two stretching directions are approximately at right angles to each other. In most cases where continuous sheet is being stretched, one stretching direction is at least approximately parallel to the long axis of the sheet (machine direction) and the other stretching direction is at least approximately perpendicular to the machine direction and is in the plane of the sheet (transverse direction). After the microporous matrix has been stretched either uniaxially or biaxially then the stretched microporous matrix is again calendered. The stretched microporous matrix is forwarded to a pair of heated calender rolls acting cooperatively to form a membrane of lesser thickness than the microporous matrix exiting from the stretching apparatus. By regulating the pressure exerted by these calender rolls along with the temperature, the pore size of the final membrane can be controlled as desired. This allows the manufacturer to adjust the average pore size with a degree of control which heretofore has not been seen. The final pore size will affect other properties such as the Gurley value of the membrane, as well as, improving the dimensional stability of the membrane at temperatures above room temperature of 20° to 25° centigrade. The figures provided are plots of data collected from mercury porosimetry.FIG.1is a graph showing pore diameter in micrometers for the precursor membrane extruded through a slot die and calendered, and then partially extracted of plasticizer. The resulting microporous matrix has not been stretched or subsequently calendered.FIG.2is a graph showing pore diameter in micrometers for a membrane stretched uniaxially 400% in the machine direction.FIG.3is a graph showing pore diameter in micrometers for a membrane biaxially stretched.FIG.4is a graph showing pore diameter in micrometers for a membrane biaxially stretched and subsequently calendered through a gap of 25 micrometers.FIG.5is a graph showing pore diameter in micrometers for a membrane biaxially stretched and subsequently calendered at a high compression pressure through a minimal gap. These figures show that compression substantially changes the pore size distribution which is present in the material. Also, it is possible to adjust the pore size distribution by adjusting the compression conditions. The final membrane is the result of stretching a precursor material and subsequently compressing it to have at least a 5% reduction in thickness of the stretched precursor material, which is defined above as the microporous matrix. This microporous material consists essentially of (or comprises): an ultrahigh molecular weight polyethylene (UHMWPE) and a particulate filler distributed throughout the microporous material, where the filler constitutes from about 5 percent to 95 percent by weight of the microporous material. The microporous material has a network of interconnecting pores communicating throughout the microporous material, the pores constituting at least 25 percent by volume of the microporous material. The microporous material has a tensile strength in the machine direction (MD) of greater than 20 N/mm2; the microporous material also has a wet out time of less than 180 seconds when silica is used as the filler. It has been observed that this microporous material has an electrical resistance of less than 130 mohm/mm2. A microporous material where the microporous material consists essentially of: (or comprises) an ultrahigh molecular weight polyethylene (UHMWPE) and a particulate filler distributed throughout the microporous material, where the filler constitutes from about 5 percent to 95 percent by weight of the microporous material. The microporous material has a network of interconnecting pores communicating throughout the microporous material, with the pores constituting at least 25 percent by volume of the microporous material. This microporous material has no pores greater in size than 1.0 micrometers; and where change in volume divided by log d for the pores of this microporous material is less than 2 cc/g. The resulting microporous material which has been both stretched and calendered exhibits shrink in the machine direction of less than 10% and has tensile strength of greater than 25 N/mm2in the machine direction (MD). The microporous material described above can also include a second polymer. The UHMWPE is mixed with a high density (HD) polyethylene to produce a polyolefin mixture, where the polyolefin mixture has at least 50% UHMWPE by weight. The filler used with this polyolefin mixture is in a range of from about 1:9 to about 15:1 filler to polyolefin mixture by weight. The resulting matrix consists essentially of (or comprises) UHMWPE and HD polyethylene and the particulate filler distributed throughout the matrix. This microporous material has a machine direction (MD) tensile strength of greater than 25 N/mm2. With higher compression after the stretch the resulting microporous material consists essentially of: (or comprises) an ultrahigh molecular weight polyethylene (UHMWPE) and a particulate filler distributed throughout the microporous material, where the filler constitutes from about 5 percent to 95 percent by weight of the microporous material. The microporous material has a network of interconnecting pores communicating throughout the microporous material, with the pores constituting at least 25 percent by volume of the microporous material. Since the compression pressure determines the resulting pore size distribution, the pore structure is highly adjustable. For instance, this microporous material inFIG.4has no pores greater in size than 0.50 micrometers. The median pore size is between or equal to 0.01 and 0.3 micrometers and the pores vary in size by plus or minus 0.2 micrometers. The resulting microporous material which has been both stretched and calendered exhibits shrink in the machine direction of less than 10% and has tensile strength of greater than 25 N/mm2in the machine direction (MD). The microporous material described above can also include a second polymer. The UHMWPE is mixed with a high density (HD) polyethylene to produce a polyolefin mixture, where the polyolefin mixture has at least 50% UHMWPE by weight. The filler used with this polyolefin mixture is in a range of from about 1:9 to about 15:1 filler to polyolefin mixture by weight. The resulting matrix comprises (or consists essentially of) UHMWPE and HD polyethylene and the particulate filler distributed throughout the matrix. This microporous material has a machine direction (MD) tensile strength of greater than 25 N/mm2. A process for improving the wet out time of an uncoated microporous membrane was developed comprising the steps of: providing an ultrahigh molecular weight polyethylene (UHMWPE); providing a particulate silica filler; providing a processing plasticizer where said processing plasticizer may be a liquid at room temperature. Then mixing UHMWPE, filler and processing plasticizer together to form a mixture, having a weight ratio of filler to UHMWPE of from 1:9 to 15:1 by weight. The mixture is then extruded to form a sheet. The sheet is then processed, where processing is selected from the group consisting of: calendering, casting or blowing. The processed sheet then undergoes an extraction step where all or part of the processing plasticizer is extracted from the sheet to produce a microporous matrix sheet which comprises UHMWPE and the particulate filler. In this matrix the filler is distributed throughout the matrix. The microporous matrix sheet is then calendered to produce a microporous membrane with a reduction in thickness of at least 5%. The resulting microporous membrane typically exhibits a reduction in wet out time of 50% or more over said microporous matrix sheet without the use of any chemical surface coating treatments. Additionally a process for improving the wet out time of an uncoated microporous membrane comprising the steps of: providing an ultrahigh molecular weight polyethylene (UHMWPE); providing a particulate silica filler; providing a processing plasticizer where said processing plasticizer may be a liquid at room temperature. Then mixing UHMWPE, filler and processing plasticizer together to form a mixture, having a weight ratio of filler to UHMWPE of from 1:9 to 15:1 by weight. The mixture is then extruded to form a sheet. The sheet is then processed, where processing is selected from the group consisting of: calendering, casting or blowing. The processed sheet then undergoes an extraction step where all or part of the processing plasticizer is extracted from the sheet to produce a microporous matrix sheet which comprises UHMWPE and the particulate filler. In this matrix the filler is distributed throughout the matrix. The microporous matrix sheet is then stretched in at least one stretching direction to a stretch ratio of at least about 1.5 to produce a stretched microporous matrix sheet. This stretched microporous matrix sheet is then calendered to produce a microporous membrane with a reduction in thickness of at least 5%. Where the resulting microporous membrane, typically exhibits a reduction in wet out time of 50% or more over the microporous matrix sheet without the use of any chemical surface coating treatments. Test Procedures Thickness—The membrane thickness values are reported in units of micrometers (μm) and were measured using ASTM D374. Puncture Strength—The units of puncture strength are newtons and the test procedure was ASTM D3763. Tensile Strength—Tensile strength was measured using ASTM D882 and the units are N/mm2. Electrical Resistance—The units of electrical resistance are mohm-cm2. Shrink Testing—Both MD and TD shrink values were measured using a modified version of ASTM D4802. The samples were cut into 5 inch (12.7 cm) squares and put into an oven for 10 minutes at 100° C. The units are percentage of change from the original dimension. Basis Weight—Basis weight was determined using ASTM D3776 and the units are grams per square meter. Hg porosity—This was measured using Hg intrusion porosimetry. Gurley—The units are sec/10 cc and were measured by TAPPI T536 method. Wetout Time— A visual technique whereas a sample is gently placed (not immersed) on the surface of water, and the time (in seconds) it takes for the membrane to begin to darken is called the wetout time. Equipment—Calendering rolls used in these tests were stack rolls having a diameter of 8 inches or 20.3 centimeters. As can be seen from the Examples which follow, the resulting stretched then calendered microporous material exhibits improved dimensional stability properties over a membrane which has only been stretched. EXAMPLES Example A is membrane containing the following: RatioPolymerFillerFiller-Example AUHMWPESiO2PlasticizerMinorsPolymerExtrusion9.6%25.0%64.0%1.4%2.6Extraction23.5%61.1%12.0%1.4%2.6 Now taking the material from Example A additional samples were prepared using tenter frame equipment. This equipment allows for both uniaxial and biaxial stretching. The following parameters were used to produce these samples: TABLE 1Stretched Membrane CharacteristicsNetBack-Punc-Modulus-Tensile-Elongation-SampleStretchwebtureMDMDMD#%(μm)(N)(MPa)(N/mm2)%A-103001736.771.211.923A-113001738.369.614.127A-124001479.9170.829.921A-134001447.996.118.522A-145001247.4261.134.317A-155001207.3146.324.019A-163001599.9101.823.340A-1740015011.4149.531.328A-18300 × 350803.323.54.621A-19200 × 3501065.727.311.254 A-18 and A-19 samples were biaxially stretched and produced using a sequential stretching device. The other samples refer to stretched membranes in the MD direction (uniaxial) only. TABLE 2Stretched Membrane Characteristics (Continued)Modulus-Tensile-Elongation-Shrinkage-Shrinkage-BasisSample #TDTDTDMDTDwtGurley(MPa)(N/mm2)%%%(gsm)(sec/100 cc)A-1010.63.7204−3.9<159.558.8A-118.63.9229−3.9<158.756.0A-127.13.7303−11<145.8119.6A-138.83.4205−3<147.559.4A-146.32.8244−7<138.390.2A-157.43.2219−2.3<141.753.4A-1611.63.9234−10.7−0.255.896.3A-178.73.4230−12.3−0.347.686.7A-1821.36.235−32−4415.615.4A-1919.68.354−37−4420.536.8 TABLE 3Stretched/Compressed Membrane Conditions and CharacteristicsTensileTensileCalenderThick-Punc-MDTDSampleGapCalenderTempnesstureN/N/#μmPressure° C.μmNmm2mm2A-16-F0Full11053.39.172.912.1A-17-F0Full11048.310.486.011.5A-16-M25Moderate11076.29.652.68.8A-17-M25Moderate11071.110.577.410.5A-16-S100Slight110149.910.126.94.3A-17-S100Slight110142.210.831.43.7A-16-F0Full13555.910.574.814.2A-17-F0Full13553.311.190.114.2A-16-M25Moderate13586.410.126.35.4A-17-M25Moderate13578.710.939.85.8A-16-S100Slight135157.59.624.74.2A-17-S100Slight135149.910.828.34.2A-18-F0Full12117.84.341.642.0A-18-M20Moderate12122.93.328.528.2A-19-F0Full12120.38.264.954.9A-19-M20Moderate12130.57.047.634.0 TABLE 4Stretched/Compressed Membrane Characteristics (Continued)Elongation-Elongation-Shrinkage-Shrinkage-WetoutMDTDMDTDTimeSample #%%%%secA-16-F47195−0.50.918.0A-17-F34193−0.51.018.0A-16-M52222−2.60.141.0A-17-M39244−1.40.342.0A-16-S46208−6.5−0.2115.0A-17-S31242−7.0−0.3160.0A-16-F51188−0.10.920.5A-17-F36221−0.40.818.5A-16-M46207−0.90.152.0A-17-M36235−1.3−0.146.5A-16-S56208−6.5−0.279.5A-17-S39261−7.0−0.341.0A-18-F2635−0.80.04.5A-18-M2450−3.2−4.69.0A-19-F50470.20.12.5A-19-M5267−2.4−1.69.0 Wetout times for uncalendered A-16, A-17, A-18 and A-19 were not obtained and found to be much greater than 10 minutes. From the data presented in these Tables, several advantages can be seen with the present process compared to the prior art. First, the stretched and then calendered films have greatly improved dimensional stability, even at elevated temperatures. The thickness which can be achieved by the stretching process alone is limited and thinner membranes can be achieved by calendering the membrane after stretching. Physical strength is much improved after the calendering of a stretched microporous material. Finally, the calendering process reduces the pore size and various degrees of calendering can be used to adjust to the desired pore size. The present invention may be embodied in other forms without departing from the spirit and the essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicated the scope of the invention. | 43,019 |
11862815 | DETAILED DESCRIPTION OF THE INVENTION Air Electrode/Separator Assembly FIG.1shows an example of an air electrode/separator assembly including a layered double hydroxide (LDH) separator as a hydroxide ion conductive dense separator. The contents hereinafter described for the LDH separator will also apply to a hydroxide ion conductive dense separator other than the LDH separator, as long as the technical consistency is not lost. Namely, the LDH separator is hereinafter interchangeable with a hydroxide ion conductive dense separator, as long as the technical consistency is not lost. The air electrode/separator assembly10shown inFIG.1comprises a layered double hydroxide (LDH) separator12, an interface layer14, and an air electrode layer16. Interface layer14is a layer that covers one side of LDH separator12and contains a hydroxide ion conductive material and an electron conductive material. Air electrode layer16is a layer provided on interface layer14and contains an outermost catalyst layer20. Air electrode layer16preferably has an internal catalyst layer18between interface layer14and outermost catalyst layer20but may not have internal catalyst layer18as in air electrode/separator assembly10′ shown inFIG.2. Moreover, outermost catalyst layer20is composed of a porous current collector20aand LDH20bcovering the surface thereof and has a porosity of 60% or more. As described above, by providing, on LDH separator12, air electrode layer16comprising outermost catalyst layer20having a porosity of 60% or more and composed of porous current collector20aand LDH20bcovering the surface thereof, via interface layer14containing the hydroxide ion conductive material and the electron conductive material, a metal-air secondary battery including the resulting assembly can exhibit excellent charge/discharge performance. Namely, as described above, the metal-air secondary battery including the LDH separator has an excellent advantage of being capable of preventing both the short circuit between the positive and negative electrodes due to the metal dendrite and the inclusion of carbon dioxide. Moreover, it also has an advantage of inhibiting evaporation of water contained in the electrolyte due to the denseness of the LDH separator. However, since the LDH separator blocks the permeation of the electrolyte into the air electrode, the electrolyte is absent in the air electrode layer, and therefore the hydroxide ion conductivity tends to be low, compared with a zinc-air secondary battery including a general separator (for example, a porous polymer separator) that allows permeation of an electrolyte into an air electrode, leading to a decrease in charge/discharge performance. In this respect, such a problem is conveniently solved according to air electrode/separator assembly10. The details of the mechanism are not necessarily clear, but it is surmised as follows. Since outermost catalyst layer20contains porous current collector20a, it can function as a layer for current collection and gas diffusion as a gas diffusion electrode, and covering the surface of porous current collector20awith LDH20ballows the layer to have both catalytic performance and hydroxide ion conductivity in addition to the above functions, resulting in that a larger reaction region can be secured. This is because LDH20b, i.e., the layered double hydroxide, is a hydroxide ion conductive material and can have a function as an air electrode catalyst as well. It is surmised that when such outermost catalyst layer20is further configured so as to be abundant in voids with a porosity of 60% or more, all of the current collection and gas diffusion functions for a gas diffusion electrode, the catalyst performance, and the hydroxide ion conductivity are extremely effectively realized without being offset by one another. In this way, the three-phase interface composed of the ion conduction phase (LDH20b), the electron conduction phase (porous current collector20a), and the gas phase (air) is present over the entire outermost catalyst layer20, and therefore, the three-phase interface is present not only in the interface (interface layer14) between LDH separator12and air electrode layer16but also in air electrode layer16. Thus, it is surmised that hydroxide ions that contribute to the battery reaction effectively transfer in a wider surface area (i.e., the reaction resistance is lowered). Moreover, it is surmised that interface layer14containing the hydroxide ion conductive material and the electron conductive material allows hydroxide ions to smoothly transfer between air electrode layer16and LDH separator12(i.e., the reaction resistance is lowered). It is surmised that by conveniently combining the various functions of interface layer14and outermost catalyst layer20in such a way, excellent charge/discharge performance can be realized while having the advantage of using LDH separator12. LDH separator12is a separator containing a layered double hydroxide (LDH) and/or an LDH-like compound (hereinafter collectively referred to as a hydroxide ion conductive layered compound) and is defined as a separator that selectively passes hydroxide ions by solely utilizing hydroxide ion conductivity of the hydroxide ion conductive layered compound. The “LDH-like compound” herein is a hydroxide and/or oxide having a layered crystal structure analogous to LDH but is a compound that may not be called LDH, and it can be said to be an equivalent of LDH. However, according to a broad sense of definition, it can be appreciated that “LDH” encompasses not only LDH but also LDH-like compounds. Such LDH separators can be those known as disclosed in Patent literatures 1 to 5 and are preferably LDH separators composited with porous substrates. A particularly preferable LDH separator12contains a porous substrate12amade of a polymer material and a hydroxide ion conductive layered compound12bthat clogs up pores P of the porous substrate, as conceptually shown inFIG.4, and LDH separator12of this type will be described later. The porous substrate containing a polymer material can be bent even when pressurized and hardly cracks, and accordingly, battery components including the substrate and other components (negative electrode, etc.) that are housed in a battery container can be pressurized in the direction such that each battery components are adhered to one another. Such pressurization is particularly advantageous when a plurality of air electrode/separator assemblies10are alternately incorporated into a battery container together with a plurality of metal negative electrodes to constitute a laminated battery. Similarly, it is also advantageous when a plurality of laminated batteries are housed in one module container to constitute a battery module. For example, pressurizing a zinc-air secondary battery minimizes the gap (preferably eliminates the gap) between the negative electrode and LDH separator12which gap allows growth of zinc dendrite, whereby effective inhibition of the zinc dendrite propagation can be expected. However, in the present invention, various hydroxide ion conductive dense separators can be used instead of LDH separator12. The hydroxide ion conductive dense separator is a separator containing the hydroxide ion conductive material and is defined as a separator that selectively passes hydroxide ions by solely utilizing the hydroxide ion conductivity of the hydroxide ion conductive material. Therefore, the hydroxide ion conductive dense separator has gas impermeability and/or water impermeability, particularly gas impermeability. Namely, the hydroxide ion conductive material constitutes all or a part of the hydroxide ion conductive dense separator having high denseness such that it exhibits gas impermeability and/or water impermeability. Definitions of gas impermeability and/or water impermeability will be described later with respect to LDH separator12. The hydroxide ion conductive dense separator may be composited with a porous substrate. Interface layer14contains the hydroxide ion conductive material and the electron conductive material. The hydroxide ion conductive material contained in interface layer14is not particularly limited as long as it has hydroxide ion conductivity, but is preferably an LDH and/or LDH-like compound. The hydroxide ion conductive material (for example, LDH and/or LDH-like compound) contained in interface layer14preferably has the form of a plurality of platy particles13, and more preferably a plurality of platy particles13that are vertically or obliquely bonded to the main surface of LDH separator12as conceptually shown inFIG.3. In particular, the following is considered: since platy particle13of the hydroxide ion conductive material such as LDH has the property of conducting hydroxide ions in the plate surface direction (the direction of (003) plane in the case of LDH), the interfacial resistance between air electrode layer16and LDH separator12is reduced because platy particles13are vertically or obliquely bonded to the main surface of LDH separator12. In particular, when observing the microstructure of the surface of LDH separator12fabricated according to a known method, LDH platy particles13are typically bonded vertically or obliquely to the main surface of LDH separator12, as shown inFIG.3, and in the present invention, the interfacial resistance is significantly reduced by the presence of the platy particles (hydroxide ion conductive material) in such an oriented state and the electron conductive material between LDH separator12and air electrode layer16. Therefore, by adopting a material of the same type as LDH and/or LDH-like compound contained in LDH separator12as the hydroxide ion conductive material contained in interface layer14, LDH platy particles13for constituting interface layer14can be provided when fabricating LDH separator12. On the other hand, the electron conductive material contained in interface layer14preferably contains a carbon material. Preferred examples of the carbon material include, but are not limited to, carbon black, graphite, carbon nanotubes, graphene, reduced graphene oxide, and any combination thereof, and various other carbon materials can also be used. Interface layer14may be fabricated by coating the surface of LDH separator12on which platy particles13are vertically or obliquely bonded, with a slurry or solution containing a carbon material (for example, carbon ink such as graphene ink). Alternatively, when providing internal catalyst layer18, internal catalyst layer18and LDH separator12may be adhered to each other so that platy particles13on the surface of LDH separator12encroach into internal catalyst layer18to fabricate interface layer14, and in this case, the portion where platy particles13encroach into internal catalyst layer18serves as interface layer14. Outermost catalyst layer20contained in air electrode layer16is composed of a porous current collector20aand an LDH20bcovering the surface thereof. Porous current collector20ais not particularly limited as long as it is composed of an electron conductive material having gas diffusivity, but porous current collector20ais preferably composed of at least one selected from the group consisting of carbon, nickel, stainless steel, and titanium, and more preferably carbon. Specific examples of porous current collector20ainclude carbon paper, nickel foam, stainless nonwoven fabric, and any combination thereof, and carbon paper is preferred. A commercially available porous material can be used as the current collector. In view of securing a wide reaction region, i.e., a wide three-phase interface composed of the ion conduction phase (LDH20b), the electron conduction phase (porous current collector20a), and the gas phase (air), the thickness of porous current collector20ais preferably 0.1 to 1 mm, more preferably 0.1 to 0.5 mm, and still more preferably 0.1 to 0.3 mm. The porosity of outermost catalyst layer20is preferably 60% or more, more preferably 70% or more, and still more preferably 70 to 95%. Particularly in the case of carbon paper, it is more preferably 60 to 90%, still more preferably 70 to 90%, and particularly preferably 75 to 85%. The porosity values described above enable securing both excellent gas diffusibility and a wide reaction region. Moreover, the generated water is less likely to clog up pores due to the large pore spaces. The porosity can be measured by a mercury intrusion method. LDH20bcontained in outermost catalyst layer20is known to have at least one of the properties of catalytic performance and hydroxide ion conductivity. Therefore, the composition of LDH20bis not particularly limited, but preferably has a basic composition represented by the formula: M2+1−xM3+x(OH)2An−x/n·mH2O, wherein M2+is at least one divalent cation, and M3+is at least one trivalent cation, An−is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is an arbitrary real number. In the above formula, M2+can be an arbitrary divalent cation, and preferred examples thereof include Ni2+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Cu2+, and Zn2+. M3+can be an arbitrary trivalent cation, and preferred examples thereof include Fe3+, V3+, Al3+, Co3+, Cr3+, and In3+. In particular, in order for LDH20bto have both catalytic performance and hydroxide ion conductivity, M2+and M3+each are desirably a transition metal ion. From this viewpoint, more preferred M2+is a divalent transition metal ion such as Ni2+, Mn2+, Fe2+, Co2+, and Cu2+, and particularly preferably Ni2+, and more preferred M3+is a trivalent transition metal ion such as Fe3+, V3+, Co3+, and Cr3+, and particularly preferably Fe3+, V3+, and/or Co3+. In this case, some of M2+may be replaced with a metal ion other than the transition metal, such as Mg2+, Ca2+, and Zn2+, and some of M3+may be replaced with a metal ion other than the transition metal, such as Al3+and In3+. An−can be an arbitrary anion. Preferred examples thereof include NO3−, CO32−, SO42−, OH−, Cl−, I−, Br−, and F−, and it is more preferably NO3−and/or CO32−. Therefore, in the above formula it is preferred that M2+include Ni2+, M3+include Fe3+, and An−include NO3−and/or CO32−. n is an integer of 1 or more, and preferably 1 to 3. x is 0.1 to 0.4, and preferably 0.2 to 0.35. m is an arbitrary real number and more specifically greater than or equal to 0, typically a real number or an integer greater than 0 or greater than or equal to 1. LDH20bhas a form of a plurality of LDH platy particles, and the plurality of LDH platy particles are preferably bonded vertically or obliquely to the surface of the porous current collector. The plurality of LDH platy particles are preferably connected to one another in outermost catalyst layer20. Such a configuration can reduce the reaction resistance. Such a configuration can be realized by immersing porous current collector20ain the LDH raw material solution and hydrothermally synthesizing the LDH particles by a known method. LDH20bmay be a mixture of two or more types of LDHs having different compositions. In this case, the particle diameter distributions of the two or more types of LDH particles preferably differ from one another in view of securing the strength for being supported on the substrate. It is preferred that the LDH platy particles having the larger average particle diameters be vertical or oblique to the surface of porous current collector20a, in terms of promoting diffusion of oxygen into porous current collector20aand securing a large amount of LHD supported. In outermost catalyst layer20, LDH20bfunctions as the air electrode catalyst and/or the hydroxide ion conductive material, and outermost catalyst layer20may further contain an air electrode catalyst and/or a hydroxide ion conductive material in addition to LDH20b. Examples of catalysts other than LDH include metal oxides, metal nanoparticles, carbon materials, and any combination thereof. A material capable of adjusting a water content is also preferably present in outermost catalyst layer20. In this respect, LDH20bitself functions as a material capable of adjusting a water content, and other examples include zeolite, calcium hydroxide, and corn bination thereof. The method for producing outermost catalyst layer20is not particularly limited, and the production thereof may be carried out by hydrothermally synthesizing LDH20bto deposit it on the surface of porous current collector20a, by a known method. For example, (1) porous current collector20ais provided, (2) porous current collector20ais coated with an iron oxide solution and dried to form an iron oxide layer, (3) the porous substrate is immersed in a raw material aqueous solution containing nickel ions (Ni2+) and urea, and (4) the porous substrate is hydrothermally treated in the raw material aqueous solution to form LDH20b(Ni—Fe-LDH in this case) on the surface of porous current collector20a. Thus, outermost catalyst layer20can be produced. Preferably air electrode layer16further has an internal catalyst layer18between outermost catalyst layer20and interface layer14. In this case, internal catalyst layer18is preferably filled with a mixture18acontaining a hydroxide ion conductive material, an electron conductive material, an organic polymer, and an air electrode catalyst. The hydroxide ion conductive material may be the same material as the air electrode catalyst, and examples of such a material include a LDH containing a transition metal (for example, Ni—Fe-LDH, Co—Fe-LDH, and Ni—Fe—V-LDH). On the other hand, examples of the hydroxide ion conductive material which does not serve as the air electrode catalyst include Mg—Al-LDH. The electron conductive material may be the same material as the air electrode catalyst, and examples of such a material include carbon materials, metal nanoparticles, nitrides such as TiN, and LaSr3Fe3O10. The hydroxide ion conductive material contained in internal catalyst layer18is not particularly limited as long as the material has a hydroxide ion conductivity, and it is preferably LDH and/or LDH-like compounds. The composition of LDH is not particularly limited, and preferably has a basic composition represented by the formula: M2+1−xM3+x(OH)2An−x/n·mH2O, wherein M2+is at least one divalent cation, M3+is at least one trivalent cation, An−is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is an arbitrary real number. In the above formula, M2+can be an arbitrary divalent cation, and preferred examples thereof include Ni2+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Cu2+, and Zn2+. M3+can be an arbitrary trivalent cation, and preferred examples thereof include Fe3+, V3+, Al3+, Co3+, Cr3+, and In3+. In particular, in order for LDH to have both catalytic performance and hydroxide ion conductivity, M2+and M3+each are desirably a transition metal ions. From this viewpoint, more preferred M2+is a divalent transition metal ion such as Ni2+, Mn2+, Fe2+, Co2+, and Cu2+, and particularly preferably Ni2+, and more preferred M3+is a trivalent transition metal ion such as Fe3+, V3+, Co3+, and Cr3+, and particularly preferably Fe3+, V3+, and/or Co3+. In this case, some of M2+may be replaced with a metal ion other than the transition metal, such as Mg2+, Ca2+, and Zn2+, and some of M3+may be replaced with a metal ion other than the transition metal, such as Al3+and In3+. An−can be an arbitrary anion. Preferred examples thereof include NO3−, CO32−, SO42−, OH−, Cl−, I−, Br−, and F−, and it is more preferably NO3−and/or CO32−. Therefore, in the above formula, it is preferred that M2+include Ni2+, M3+include Fe3+, and An−include NO3−and/or CO32−. n is an integer of 1 or more, and preferably 1 to 3. x is 0.1 to 0.4 and preferably 0.2 to 0.35. m is an arbitrary real number and more specifically greater than or equal to 0, typically a real number or an integer greater than 0 or greater than or equal to 1. The electron conductive material contained in internal catalyst layer18is preferably at least one selected from the group consisting of electrically conductive ceramics and carbon materials. In particular, examples of the electrically conductive ceramics include LaNiO3and LaSr3Fe3O10. Examples of carbon materials include, but are not limited to, carbon black, graphite, carbon nanotubes, graphene, reduced graphene oxide, and any combination thereof, and various other carbon materials can also be used. The air electrode catalyst contained in internal catalyst layer18is preferably at least one selected from the group consisting of LDH and other metal hydroxides, metal oxides, metal nanoparticles, and carbon materials, and more preferably at least one selected from the group consisting of LDH, metal oxides, metal nanoparticles, and carbon materials. LDH is as described above for the hydroxide ion conductive material, which is particularly preferable in terms of performing both the functions of the air electrode catalyst and the hydroxide ion conductive material. Examples of the metal hydroxide include Ni—Fe—OH, Ni—Co—OH and any combination thereof, which may further contain a third metal element. Examples of the metal oxide include Co3O4, LaNiO3, LaSr3Fe3O10, and any combination thereof. Examples of the metal nanoparticle (typically metal particle having a particle diameter of 2 to 30 nm) include Pt, Ni—Fe alloy. Examples of the carbon material include, but are not limited to, carbon black, graphite, carbon nanotubes, graphene, reduced graphene oxide, and any combination thereof, as described above, and various other carbon materials can also be used. Preferably the carbon material further contains a metal element and/or other elements such as nitrogen, boron, phosphorus, and sulfur, in view of improving the catalytic performance of the carbon material. A known binder resin can be used as the organic polymer contained in internal catalyst layer18. Examples of the organic polymer include a butyral-based resin, vinyl alcohol-based resin, celluloses, vinyl acetal-based resin, and fluorine-based resin, and the butyral-based resin and fluorine-based resin are preferable. Internal catalyst layer18is desired to have a lower porosity than outermost catalyst layer20in order to efficiently transfer hydroxide ions to and from LDH separator12. Specifically, the porosity of internal catalyst layer18is preferably 30 to 60%, more preferably 35 to 60%, and still more preferably 40 to 55%. For the same reason, the average pore diameter of the internal catalyst layer is preferably 5 μm or less, more preferably 0.5 to 4 μm, and still more preferably 1 to 3 μm. The measurements of the porosity and the average pore diameter of internal catalyst layer18can be carried out by a) polishing the cross section of the LDH separator with a cross section polisher (CP), b) using an SEM (scanning electron microscope) at a magnification of 10,000× to acquire images of two fields of vision of the cross-section of the internal catalyst layer, c) binarizing each image by using an image analysis software (for example, Image-J) based on the image data of the acquired cross-sectional image, and d) determining the area of each pore for two fields of vison, calculating the porosity values and the pore diameter values of pores, and taking the average value thereof as the porosity and the average pore diameter of the internal catalyst layer. The pore diameter can be calculated by converting the length per pixel of the image from the actual size, dividing the area of each pore obtained from the image analysis by pi, on the assumption that each pore is a perfect circle, and multiplying the square root of the quotient by 2 to obtain the average pore diameter. The porosity can be calculated by dividing the number of pixels corresponding to pores by the number of pixels in the total area and multiplying the quotient by 100. Internal catalyst layer18can be fabricated by preparing a paste containing the hydroxide ion conductive material, the electron conductive material, the organic polymer, and the air electrode catalyst, and coating the surface of LDH separator12with the paste. Preparation of the paste can be carried out by appropriately adding the organic polymer (binder resin) and an organic solvent to a mixture of the hydroxide ion conductive material, the electron conductive material, and the air electrode catalyst, and using a known kneader such as a three-roll mill. Preferred examples of the organic solvent include alcohols such as butyl carbitol and terpineol, acetic acid ester-based solvents such as butyl acetate, and N-methyl-2-pyrrolidone. Coating LDH separator12with the paste can be carried out by printing. This printing can be carried out by various known printing methods, but a screen printing is preferred. However, air electrode layer16may not have internal catalyst layer18as in air electrode/separator assembly10′ shown inFIG.2. In this case, it is desirable to take measures to reduce the contact resistance by uniformly applying pressure to air electrode layer16and LDH separator12so that external catalyst layer20and interface layer14are adhered to each other. As described above, air electrode/separator assembly10is preferably used for a metal-air secondary battery. Namely, a preferred aspect of the present invention provides a metal-air secondary battery comprising air electrode/separator assembly10, a metal negative electrode, and an electrolyte, wherein the electrolyte is separated from air electrode layer16by LDH separator12interposed therebetween. A zinc-air secondary battery including a zinc electrode as a metal negative electrode is particularly preferable. Further, a lithium-air secondary battery including a lithium electrode as a metal negative electrode may be used. LDH Separator LDH separator12according to a preferred embodiment of the present invention will be described below. Although the following description assumes a zinc-air secondary battery, LDH separator12according to the present embodiment can also be applied to other metal-air secondary batteries such as a lithium-air secondary battery. As described above, LDH separator12of the present embodiment contains a porous substrate12aand a hydroxide ion conductive layered compound12bwhich is the LDH and/or LDH-like compound, as conceptually shown inFIG.4. InFIG.4, the region of hydroxide ion conductive layered compound12bis drawn so as not to be connected between the upper surface and the lower surface of LDH separator12, but it is because the figure is drawn two-dimensionally as a cross section. When the depth thereof is three-dimensionally taken into account, the region of hydroxide ion conductive layered compound12bis connected between the upper surface and the lower surface of LDH separator12, whereby the hydroxide ion conductivity of LDH separator12is secured. Porous substrate12ais made of a polymer material, and the pores of porous substrate12aare clogged up with hydroxide ion conductive layered compound12b. However, the pores of porous substrate12amay not be completely clogged up, and residual pores P can be slightly present. By clogging up the pores of polymer porous substrate12awith hydroxide ion conductive layered compound12bto make the substrate highly densified in this way, LDH separator12capable of even more effectively inhibiting short circuits due to zinc dendrites can be provided. Moreover, LDH separator12of the present embodiment has excellent flexibility and strength in addition to desirable ion conductivity required of a separator due to the hydroxide ion conductivity of hydroxide ion conductive layered compound12b. This is due to the flexibility and strength of polymer porous substrate12aitself contained in LDH separator12. Namely, since LDH separator12is densified so that the pores of polymer porous substrate12aare sufficiently clogged up with hydroxide ion conductive layered compound12b, polymer porous substrate12aand hydroxide ion conductive layered compound12bare integrated in complete harmony as a highly composited material, and therefore the rigidity and brittleness due to hydroxide ion conductive layered compound12b, which is a ceramic material, can be said to be offset or reduced by the flexibility and strength of polymer porous substrate12a. LDH separator12of the present embodiment desirably has extremely few residual pores P (the pores not clogged up with hydroxide ion conductive layered compound12b). Due to residual pores P, LDH separator12has, for example, an average porosity of 0.03% or more and less than 1.0%, preferably 0.05% or more and 0.95% or less, more preferably 0.05% or more and 0.9% or less, still more preferably 0.05 to 0.8%, and most preferably 0.05 to 0.5%. With an average porosity within the above range, the pores of porous substrate12aare sufficiently clogged up with hydroxide ion conductive layered compound12bto provide an extremely high denseness, which therefore can inhibit short circuits due to zinc dendrites even more effectively. Further, significantly high ionic conductivity can be realized, and LDH separator12can exhibit a sufficient function as a hydroxide ion conductive dense separator. The measurement of the average porosity can be carried out by a) polishing the cross section of the LDH separator with a cross section polisher (CP), and b) using an FE-SEM (field-emission scanning electron microscope) at a magnification of 50,000× to acquire images of two fields of vision of the cross-sectional of the functional layer, and c) calculating the porosity of each of the two fields of vision by using an image inspection software (for example, HDevelop, manufactured by MVTec Software GmbH) based on the image data of the acquired cross-sectional image and determining the average value of the obtained porosities. LDH separator12is a separator containing hydroxide ion conductive layered compound12b, and separates a positive electrode plate and a negative electrode plate such that hydroxide ions can be conducted when the separator is incorporated in a zinc secondary battery. Namely LDH separator12exhibits a function as a hydroxide ion conductive dense separator. Therefore, LDH separator12has gas impermeability and/or water impermeability. Thus, LDH separator12is preferably densified so as to have gas impermeability and/or water impermeability. As described in Patent Literatures 2 and 3, “having gas impermeability” herein means that even when helium gas is brought into contact with one side of the object to be measured in water at a differential pressure of 0.5 atm, no bubbles are generated due to the helium gas from another surface side. Further, as used herein, “having water impermeability” means that water in contact with one side of the object to be measured does not permeate to the other side as described in Patent Literatures 2 and 3. Namely, LDH separator12having gas impermeability and/or water impermeability means LDH separator12having a high degree of denseness such that it does not allow gas or water to pass through, and means that LDH separator12is not a porous film or other porous material that has water permeability or gas permeability. In this way, LDH separator12selectively allows hydroxide ions alone to pass through due to its hydroxide ion conductivity and can exhibit a function as a battery separator. Therefore, the configuration is extremely effective in physically blocking penetration of the separator by the zinc dendrite generated upon charge to prevent a short circuit between the positive and negative electrodes. Since LDH separator12has hydroxide ion conductivity, it is possible to efficiently move the required hydroxide ions between the positive electrode plate and the negative electrode plate, and to realize the charge/discharge reaction in the positive electrode plate and the negative electrode plate. LDH separator12preferably has a He permeability of 3.0 cm/min·atm or less per unit area, more preferably 2.0 cm/min·atm or less, and still more preferably 1.0 cm/min·atm or less. A separator having a He permeability of 3.0 cm/min·atm or less can extremely effectively inhibit Zn permeation (typically permeation of zinc ion or zinc acid ion) in an electrolyte. It is considered in principle that due to such significant inhibition of Zn penetration, the separator of the present embodiment can inhibit effectively the growth of zinc dendrite when used in a zinc secondary battery. The He permeability is measured by supplying He gas to one surface of the separator to allow the He gas to pass through the separator, and calculating the He permeability to evaluate the denseness of the hydroxide ion conductive dense separator. The He permeability is calculated by the formula of F/(P×S) by using the permeation amount F of the He gas per unit time, the differential pressure P applied to the separator when the He gas permeates, and the membrane area S through which the He gas permeates. By evaluating the gas permeability using the He gas in this way, it is possible to evaluate the presence or absence of denseness at an extremely high level, and as a result, it is possible to effectively evaluate a high degree of denseness such that substances other than hydroxide ions (in particular Zn bringing about zinc dendrite growth) can be permeated as little as possible (only a very small amount is permeated). This is because an He gas has the smallest constituent unit among a wide variety of atoms or molecules that can form a gas and also has extremely low reactivity. Namely, He constitutes a He gas by a single He atom without forming a molecule. In this respect, hydrogen gas is composed of H2molecules, and the He atom alone is smaller as a gas constituent unit. In the first place, H2gas is dangerous because it is a flammable gas. Then, by adopting the index of He gas permeability defined by the above formula, it is possible to easily evaluate the denseness objectively regardless of the difference in various sample sizes and measurement conditions. In this way, it is possible to easily, safely and effectively evaluate whether or not the separator has sufficiently high denseness suitable for a zinc secondary battery separator. The measurement of He permeability can be preferably carried out according to the procedure in Evaluation 4 of the Example described later. In LDH separator12, hydroxide ion conductive layered compound12b, which is an LDH and/or LDH-like compound, clogs up the pores of porous substrate12a. As is generally known, LDH is composed of a plurality of hydroxide basic layers and an intermediate layer interposed between the plurality of hydroxide basic layers. The basic hydroxide layer is mainly composed of metal elements (typically metal ions) and OH groups. The intermediate layer of LDH is composed of anions and H2O. The anion is a mono- or higher-valent anion and preferably a monovalent or divalent ion. The anion in LDH preferably contains OH−and/or CO32−. LDH also has excellent ion conductivity due to its unique properties. In general, LDH has been known as a compound represented by the basic composition formula: M2+1−xM3+x(OH)2An−x/n·mH2O wherein M2+is a divalent cation, M3+is a trivalent cation, A is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more. In the above basic composition formula, M2+can be arbitrary divalent cation, but preferred examples thereof include Mg2+, Ca2+and Zn2+, and it is more preferably Mg2+. M3+can be arbitrary trivalent cation, a preferred example thereof includes Al3+or Cr3+, and it is more preferably Al3+. An−can be arbitrary anion, and preferred examples thereof include OH−and CO32−Therefore, in the above basic composition formula, it is preferred that M2+include Mg2+, M3+include Al3+, and An−include OH−and/or CO32−. n is an integer of 1 or more, and is preferably 1 or 2. x is 0.1 to 0.4 and preferably 0.2 to 0.35. m is an arbitrary numeral meaning the number of moles of water, is greater than or equal to 0, typically a real number greater than 0 or greater than or equal to 1. However, the above basic composition formula is merely a representatively exemplified formula of the “basic composition” of LDH, generally, and the constituent ions can be appropriately replaced. For example, in the above basic composition formula, some or all of M3+may be replaced with a tetra- or higher-valent cation, and in that case, the coefficient x/n of anion An−in the above formula may be appropriately changed. For example, the hydroxide basic layer of LDH may contain Ni, Al, Ti and OH groups. The intermediate layer is composed of anions and H2O as described above. The alternating laminated structure of the hydroxide basic layer and the intermediate layer, itself is basically the same as the generally known LDH alternating laminated structure, but the LDH of the present embodiment in which the hydroxide basic layer of LDH is composed of predetermined elements or ions including Ni, Al, Ti and OH groups can exhibit excellent alkali resistance. The reason for this is not necessarily clear, but it is considered that Al, which has been conventionally thought to be easy to elute in an alkaline solution, is less likely to elute in an alkaline solution due to some interaction with Ni and Ti in the LDH of the present embodiment. Nevertheless, LDH of the present embodiment can also exhibit high ion conductivity suitable for use as a separator for an alkaline secondary battery. Ni in LDH can be in the form of nickel ions. Nickel ions in LDH are typically considered to be Ni2+but are not particularly limited thereto as other valences such as Ni3+are possible. Al in LDH can be in the form of aluminum ions. Aluminum ions in LDH are typically considered to be Al3+but are not particularly limited thereto as other valences are possible. Ti in LDH can be in the form of titanium ions. Titanium ions in LDH are typically considered to be Ti4+but are not particularly limited thereto as other valences such as Ti3+are possible. The hydroxide basic layer may contain other elements or ions as long as it contains at least Ni, Al, Ti and OH groups. However, the hydroxide basic layer preferably contains Ni, Al, Ti and OH groups as main components. Namely, the hydroxide basic layer is preferably mainly composed of Ni, Al, Ti and OH groups. Therefore, the hydroxide basic layer is typically composed of Ni, Al, Ti, OH groups and, in some cases, unavoidable impurities. The unavoidable impurity is an arbitrary element that can be unavoidably mixed due to the production process, and can be mixed in LDH, for example, derived from a raw material or a substrate. As described above, the valences of Ni, Al and Ti are not always fixed, and it is impractical or impossible to specify LDH strictly by a general formula. Assuming that the hydroxide basic layer is mainly composed of Ni2+, Al3+, Ti4+and OH groups, the corresponding LDH has the basic composition that can be represented by the formula: Ni2+1−x−yAl3+xTi4+y(OH)2An−(x+2y)/n·mH2O wherein An−is an n-valent anion, n is an integer of 1 or more and preferably 1 or 2, 0<x<1 and preferably 0.01≤x≤0.5, 0<y<1 and preferably 0.01≤y≤0.5, 0<x+y<1, m is 0 or more and typically a real number greater than 0 or greater than or equal to 1. However, the above formula is understood as “basic composition”, and it is understood that elements such as Ni2+, Al3+, and Ti4+are replaceable with other elements or ions (including the same elements or ions having other valences, or elements or ions unavoidably mixed due to the production process) to an extent such that the basic characteristics of LDH are not impaired. The LDH-like compound is a hydroxide and/or oxide having a layered crystal structure like to LDH but is a compound that may not be called LDH, and the LDH-like compound preferably contains Mg, and one or more elements selected from the group consisting of, Ti, Y and Al and containing at least Ti. As described above, by using an LDH-like compound that is a hydroxide and/or an oxide having a layered crystal structure containing at least Mg and Ti, instead of the conventional LDH, as the hydroxide ion conductive substance, a hydroxide ion conductive separator can be provided that is excellent in the alkali resistance and capable of inhibiting a short circuit due to zinc dendrite even more effectively. Therefore, a preferred LDH-like compound is a hydroxide and/or oxide having a layered crystal structure containing Mg, and one or more elements selected from the group consisting of Ti, Y and Al and containing at least Ti. Therefore, a typical LDH-like compound is a composite hydroxide and/or composite oxide of Mg, Ti, optionally Y and optionally Al, and particularly preferably a composite hydroxide and/or composite oxide of Mg, Ti, Y and Al. The above elements may be replaced with other elements or ions to an extent such that the basic properties of the LDH-like compound are not impaired, but the LDH-like compound preferably contains no Ni. LDH-like compounds can be identified by X-ray diffraction. Specifically, when X-ray diffraction is carried out on the surface of the LDH separator, a peak assigned to the LDH-like compound is detected typically in the range of 5°≤2θ≤10°, and more typically in the range of 7°≤2θ≤10°. As described above, the LDH is a substance having an alternating laminated structure in which exchangeable anions and H2O are present as an intermediate layer between the stacked hydroxide basic layers. In this regard, when LDH is analyzed by the X-ray diffraction method, a peak assigned to the crystal structure of LDH (i.e., the peak assigned to (003) of LDH) is originally detected at a position of 2θ=11 to 12°. When the LDH-like compound is analyzed by the X-ray diffraction method, on the other hand, a peak is typically detected in the aforementioned range shifted to the lower angle side than the above peak position of LDH. Further, the interlayer distance of the layered crystal structure can be determined by Bragg's equation using 2θ corresponding to the peak assigned to the LDH-like compound in X-ray diffraction. The interlayer distance of the layered crystal structure of the LDH-like compound thus determined is typically 0.883 to 1.8 nm, and more typically 0.883 to 1.3 nm. The atomic ratio of Mg/(Mg+Ti+Y+Al) in the LDH-like compound, as determined by energy dispersive X-ray analysis (EDS), is preferably 0.03 to 0.25 and more preferably 0.05 to 0.2. Moreover, the atomic ratio of Ti/(Mg+Ti+Y+Al) in the LDH-like compound is preferably 0.40 to 0.97 and more preferably 0.47 to 0.94. Further, the atomic ratio of Y/(Mg+Ti+Y+Al) in the LDH-like compound is preferably 0 to 0.45 and more preferably 0 to 0.37. Further, the atomic ratio of Al/(Mg+Ti+Y+Al) in the LDH-like compound is preferably 0 to 0.05 and more preferably 0 to 0.03. Within the above ranges, the alkali resistance is more excellent, and the effect of inhibiting a short circuit due to zinc dendrite (i.e., dendrite resistance) can be more effectively realized. By the way, LDH conventionally known for LDH separators has the basic composition that can be represented by the formula: M2+1−xM3+x(OH)2An−x/n·mH2O, wherein M2+is a divalent cation, M3+is a trivalent cation, An−is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more. The atomic ratios in the LDH-like compound generally deviate from those in the above formula for LDH. Therefore, the LDH-like compound generally can be said to have a composition ratio (atomic ratio) different from that of the conventional LDH. EDS analysis is preferably carried out with an EDS analyzer (for example, X-act, manufactured by Oxford Instruments Plc.), by 1) capturing an image at an acceleration voltage of 20 kV and a magnification of 5,000×, 2) carrying out three-point analysis at intervals of about 5 μm in the point analysis mode, 3) repeating the above 1) and 2) once more, and 4) calculating the average value of a total of 6 points. As described above, LDH separator12contains hydroxide ion conductive layered compound12band porous substrate12a(typically LDH separator12is composed of porous substrate12aand hydroxide ion conductive layered compound12b), and the hydroxide ion conductive layered compound clogs up pores of the porous substrate so that LDH separator12exhibits hydroxide ion conductivity and gas impermeability (hence to function as an LDH separator exhibiting hydroxide ion conductivity). Hydroxide ion conductive layered compound12bis particularly preferably incorporated over the entire area of polymer porous substrate12ain the thickness direction. The thickness of the LDH separator is preferably 3 to 80 μm, more preferably 3 to 60 μm, and still more preferably 3 to 40 μm. Porous substrate12ais made of a polymer material. Polymer porous substrate12ahas advantages of 1) having flexibility (hence, polymer porous substrate12ahardly cracks even when it is thin), 2) facilitating increase in porosity, and 3) facilitating increase in conductivity (it can be thin while having increased porosity), and 4) facilitating manufacture and handling. Further, taking advantage derived from the flexibility of 1) above, it also has an advantage of 5) ease in bending or sealing/bonding the LDH separator containing a porous substrate made of a polymer material. Preferred examples of the polymer material include polystyrene, polyether sulfone, polypropylene, an epoxy resin, polyphenylene sulfide, a fluororesin (tetrafluororesin: PTFE, etc.), cellulose, nylon, polyethylene and any combination thereof. In view of a thermoplastic resin suitable for heat pressing, more preferred examples include polystyrene, polyether sulfone, polypropylene, an epoxy resin, polyphenylene sulfide, a fluororesin (tetrafluororesin: PTFE, etc.), nylon, polyethylene and any combination thereof. All of the various preferred materials described above have the alkali resistance, which serves as a resistance to the electrolyte of the battery. Particularly preferable polymer materials are polyolefins such as polypropylene and polyethylene and most preferably polypropylene or polyethylene in terms of excellent hot water resistance, acid resistance and alkali resistance as well low cost. When the porous substrate is made of a polymer material, the hydroxide ion conductive layered compound is particularly preferably incorporated over the entire porous substrate in the thickness direction (for example, most or almost all of the pores inside the porous substrate are filled with the hydroxide ion conductive layered compound). As such a polymer porous substrate, a commercially available polymer microporous membrane can be preferably used. The LDH separator of the present embodiment can be produced by (i) fabricating the hydroxide ion conductive layered compound-containing composite material according to a known method (see, for example, Patent Literatures 1 to 3) by using a polymer porous substrate, and (ii) pressing this hydroxide ion conductive layered compound-containing composite material. The pressing method may be, for example, a roll press, a uniaxial pressure press, a CIP (cold isotropic pressure press), etc., and is not particularly limited. The pressing method is preferably by a roll press. This pressing is preferably carried out while heating in terms of softening the porous substrate to enable to clog up sufficiently the pores of the porous substrate with the hydroxide ion conductive layered compound. For example, for polypropylene or polyethylene, the temperature for sufficient softening is preferably heated at 60 to 200° C. Pressing by, for example, a roll press in such a temperature range can significantly reduce the average porosity derived from the residual pores of the LDH separator; as a result, the LDH separator can be extremely highly densified, and hence short circuits due to zinc dendrites can be inhibited even more effectively. When carrying out the roll pressing, the form of the residual pores can be controlled by appropriately adjusting the roll gap and the roll temperature, whereby an LDH separator having a desired denseness or average porosity can be obtained. The method for producing the hydroxide ion conductive layered compound-containing composite material (i.e., the crude LDH separator) before pressing is not particularly limited, and it can be fabricated by appropriately changing the conditions in a known method for producing an LDH-containing functional layer and a composite material (i.e., LDH separator) (see, for example, Patent Literatures 1 to 3). For example, the hydroxide ion conductive layered compound-containing functional layer and the composite material (i.e., an LDH separator) can be produced by (1) providing a porous substrate, (2) coating the porous substrate with a titanium oxide sol or a mixed sol of alumina and titania followed by heat treatment to form a titanium oxide layer or alumina/titania layer, (3) immersing the porous substrate in a raw material aqueous solution containing nickel ions (Ni2+) and urea, and (4) treating hydrothermally the porous substrate in the raw material aqueous solution to form a hydroxide ion conductive layered compound-containing functional layer on the porous substrate and/or in the porous substrate. In particular, forming of the titanium oxide layer or the alumina/titania layer on the porous substrate in the above step (2) provides not only the raw material of the hydroxide ion conductive layered compound, but also the function as a starting point of the crystal growth of the hydroxide ion conductive layered compound to enable to form uniformly a highly densified hydroxide ion conductive layered compound-containing functional layer in the porous substrate. Further, the urea present in the above step (3) generates ammonia in the solution by utilizing the hydrolysis of the urea to raise the pH value, which allows the coexisting metal ions to form a hydroxide to obtain a hydroxide ion conductive layered compound. In addition, since the hydrolysis involves the generation of carbon dioxide, a hydroxide ion conductive layered compound having an anion of carbonate ion type can be obtained. In particular, when fabricating a composite material including a porous substrate made of a polymer material in which the functional layer is incorporated over the entire porous substrate in the thickness direction (i.e., an LDH separator), the substrate is preferably coated with the mixed sol of alumina and titania in the above (2) so as to permeate the whole or most of the inside of the substrate with the mixed sol. In this way, most or almost all the pores inside the porous substrate can be finally filled with the hydroxide ion conductive layered compound. Examples of a preferable coating method include a dip coating and a filtration coating, and a dip coating is particularly preferable. By adjusting the number of times of coating by the dip coating, etc., the amount of the mixed sol adhered can be adjusted. The substrate coated with the mixed sol by dip coating, etc. may be dried and then the above steps (3) and (4) may be carried out. EXAMPLES The present invention will be described in more detail by the following examples. Example A1 LDH separators were fabricated by the following procedure and evaluated. (1) Provision of Polymer Porous Substrate A commercially available polyethylene microporous membrane having a porosity of 50%, an average pore diameter of 0.1 μm and a thickness of 20 μm was provided as a polymer porous substrate, and cut out to a size of 2.0 cm×2.0 cm. (2) Alumina·Titania Sol Coating on Polymer Porous Substrate Amorphous alumina solution (Al-ML15, manufactured by Taki Chemical Co., Ltd.) and titanium oxide sol solution (M6, manufactured by Taki Chemical Co., Ltd.) were mixed in Ti/Al (molar ratio)=2 to fabricate a mixed sol. The substrate provided in (1) above was coated with the mixed sol by dip coating. The dip coating was carried out by immersing the substrate in 100 ml of the mixed sol, pulling it up vertically, and drying it in a dryer at 90° C. for 5 minutes. (3) Preparation of Raw Material Aqueous Solution Nickel nitrate hexahydrate (Ni(NO3)2·6H2O, manufactured by Kanto Chemical Co., Inc., and urea ((NH2)2CO, manufactured by Sigma Aldrich Co. LLC)) were provided as raw materials. Nickel nitrate hexahydrate was weighed so as to give 0.015 mol/L and placed in a beaker, and ion-exchanged water was added thereto to make a total volume 75 ml. After stirring the obtained solution, urea weighed to satisfy the ratio of urea/NO3−(molar ratio)=16 was added in the solution, and the mixture was further stirred to obtain a raw material aqueous solution. (4) Film Formation by Hydrothermal Treatment The raw material aqueous solution and the dip-coated substrate were placed together in a Teflon® airtight container (autoclave container with outer stainless-steel jacket, content of 100 ml), and the container was closed tightly. At this time, the substrate was fixed while being floated from the bottom of the Teflon® airtight container and placed horizontally so that the solution was in contact with both sides of the substrate. Then, LDH was formed on the surface and the inside of the substrate by subjecting it to hydrothermal treatment at a hydrothermal temperature of 120° C. for 24 hours. With an elapse of a predetermined time, the substrate was taken out from the airtight container, washed with ion-exchanged water, and dried at 70° C. for 10 hours to form LDH in the pores of the porous substrate. In this way, a composite material containing LDH was obtained. (5) Densification by Roll Pressing The composite material containing LDH described above was sandwiched between a pair of PET films (Lumirror®, thickness of 40 μm, manufactured by Toray Industries, Inc.) and the roll pressing was carried out at a roll rotation speed of 3 mm/s, a roll temperature of 120° C., and a roll gap of 60 μm to obtain an LDH separator. (6) Evaluation Result The following evaluation was carried out for the obtained LDH separator. Evaluation 1: Identification of LDH separator An XRD profile was obtained by measuring the crystal phase of the LDH separator with an X-ray diffractometer (RINT TTR III manufactured by Rigaku Corporation) under the measurement conditions of voltage: 50 kV, current value: 300 mA, and measurement range: 10 to 70°. For the obtained XRD profile, identification was carried out by using the diffraction peak of LDH (hydrotalcites compound) described in JCPDS card No. 35-0964. The LDH separator of the present example was identified as LDH (hydrotalcites compound). Evaluation 2: Measurement of Thickness The thickness of the LDH separator was measured using a micrometer. The thicknesses were measured at three points, and the average value thereof was taken as the thickness of the LDH separator. As a result, the thickness of the LDH separator of the present example was 13 μm. Evaluation 3: Measurement of Average Porosity The LDH separator was cross-sectionally polished with a cross-section polisher (CP), and two fields of vision of the LDH separator cross-sectional image were acquired with a FE-SEM (ULTRA55, manufactured by Carl Zeiss) at a magnification of 50,000×. Based on this image data, porosity of each of the two fields of vision was calculated by using an image inspection software (HDevelop, manufactured by MVTec Software GmbH) and the average value thereof was taken as the average porosity of the LDH separator. As a result, the average porosity of the LDH separator of the present example was 0.8%. Evaluation 4: Measurement of He Permeation The He permeation test was carried out as follows in order to evaluate the denseness of the LDH separator in terms of He permeability. First, a He permeability measurement system310shown inFIGS.5A and5Bwas constructed. He permeability measurement system310was configured so that He gas from a gas cylinder filled with He gas was supplied to a sample holder316via a pressure gauge312and a flow meter314(digital flow meter) and was allowed to pass from one surface of LDH separator318held in sample holder316to the other surface to be discharged. Sample holder316has a structure comprising a gas supply port316a, a closed space316b, and a gas discharge port316c, and was assembled as follows. First, the outer circumference of LDH separator318was coated with an adhesive322and was attached to a jig324(made of ABS resin) having an opening in the center. Packings made of butyl rubber were arranged as sealing members326aand326bat the upper and lower ends of this jig324and were further sandwiched with support members328aand328b(made of PTFE) with openings, which were flanges, from the outside of sealing members326aand326b. In this way, closed space316bwas defined by LDH separator318, jig324, sealing member326a, and support member328a. Support members328aand328bwere fastened tightly to each other by a fastening means330using screws so that He gas did not leak from a portion other than a gas discharge port316c. A gas supply pipe334was connected to gas supply port316aof sample holder316thus assembled via a joint332. Next, He gas was supplied to He permeability measurement system310through gas supply pipe334and was allowed to pass through LDH separator318held in sample holder316. At this time, the gas supply pressure and the flow rate were monitored by pressure gauge312and flow meter314. After the passage of the He gas for 1 to 30 minutes, the He permeability was calculated. The He permeability was calculated by using the formula: F/(P×S), wherein F (cm3/min) is the amount of the He gas passing per unit time, P (atm) is the differential pressure applied to the LDH separator when the He gas passes, and S (cm2) is the membrane area through which the He gas passes. The amount F (cm3/min) of He gas passing was read directly from flow meter314. Further, differential pressure P was determined by using the gauge pressure read from pressure gauge312. The He gas was supplied so that differential pressure P was in the range of 0.05 to 0.90 atm. As a result, the He permeability per unit area of the LDH separator was 0.0 cm/min·atm. Evaluation 5: Observation of Microstructure of Separator Surface When observing the surface of the LDH separator by SEM, it was observed that innumerable LDH platy particles were bonded vertically or obliquely to the main surface of the LDH separator, as shown inFIG.6. Example B1 An air electrode/separator assembly having two layers of an interface layer and an outermost catalyst layer on the LDH separator fabricated in Example A1 was fabricated by the following procedure and was evaluated. (1) Fabrication of Outermost Catalyst Layer (1a) Iron Oxide Sol Coating on Conductive Porous Substrate 10 ml of iron oxide sol (Fe—C10, iron oxide concentration of 10% by weight, manufactured by Taki Chemical Co., Ltd.) diluted with ion-exchanged water and adjusted to a concentration of 5% by weight was placed in a beaker, and carbon paper (TGP-H-060, thickness of 200 μm, manufactured by Toray Industries, Inc.) was immersed therein. The beaker was evacuated to allow the iron oxide sol to fully penetrate into the carbon paper. The carbon paper was pulled up from the beaker by using tweezers and dried at 80° C. for 30 minutes to obtain a carbon paper to which iron oxide particles were adhered as a substrate. (1b) Preparation of Raw Material Aqueous Solution Nickel nitrate hexahydrate (Ni(NO3)2·6H2O, manufactured by Kanto Chemical Co., Inc., and urea ((NH2)2CO, manufactured by Mitsui Chemicals Inc.)) were provided as raw materials. Nickel nitrate hexahydrate was weighed so as to give a concentration of 0.03 mol/L and placed in a beaker, and ion-exchanged water was added thereto to make the total volume 75 ml. After stirring the obtained solution, urea was added to the solution to 0.96 mol/l, and the mixture was further stirred to obtain a raw material aqueous solution. (1c) Membrane Formation by Hydrothermal Treatment The raw material aqueous solution fabricated in (1b) above and the substrate fabricated in (1a) above were placed together in a Teflon® airtight container (autoclave container with outer stainless-steel jacket, content of 100 ml), and the container was closed tightly. At this time, the substrate was fixed while being floated from the bottom of the Teflon® airtight container and placed horizontally so that the solution was in contact with both sides of the substrate. Then, LDH was formed on the fiber surface inside the substrate by subjecting it to hydrothermal treatment at a hydrothermal temperature of 120° C. for 20 hours. With an elapse of a predetermined time, the substrate was taken out from the airtight container, washed with ion-exchanged water, and dried at 80° C. for 30 minutes to obtain an outermost catalyst layer as the air electrode layer. When the fine structure of the obtained outermost catalyst layer was observed by SEM, the images shown inFIGS.7A to7Cwere obtained.FIG.7Bis an enlarged image of the surface of the carbon fibers constituting the carbon paper shown inFIG.7A, andFIG.7Cis an enlarged cross-sectional image of the vicinity of the surface of the carbon fibers shown inFIG.7A. From these figures, it was observed that innumerable LDH platy particles were vertically or obliquely bonded to the surface of the carbon fibers constituting the carbon paper, and that these LDH platy particles were connected to one another. The porosity of the obtained outermost catalyst layer was measured by the mercury intrusion method and found to be 76%. (2) Joining of Outermost Catalyst Layer and LDH Separator 5% by weight of carbon powder (Denka Black, manufactured by Denka Co., Ltd.) was added to ethanol (purity 99.5%, manufactured by Kanto Chemical Co., Inc.) and the mixture was dispersed by ultrasonic waves to prepare a carbon slurry. The LDH separator obtained in Example A1 was coated with the obtained slurry by spin coating, and then the outermost catalyst layer (air electrode layer) was placed. A weight was placed on the outermost catalyst layer and dried in the air at 80° C. for 2 hours. In this way, the outermost catalyst layer (thickness 200 μm) as an air electrode layer was formed on the LDH separator. At this time, an interface layer (thickness of 0.2 μm) containing LDH platy particles (derived from the LDH separator) and carbon (derived from the carbon slurry) was simultaneously formed between the LDH separator and the air electrode layer. Namely an air electrode/separator assembly was obtained. (3) Assembly and Evaluation of Evaluation Cells A metal zinc plate was laminated as a negative electrode on the LDH separator side of the air electrode/separator assembly. The obtained laminate was sandwiched between the holding jigs with a sealing member firmly bitten on the outer circumferential portion of the LDH separator, and the resultant was firmly fixed with screws. This holding jig had an oxygen inlet on the air electrode side and an injection port on the metal zinc plate side, through which the electrolyte was introduced. A 5.4 M KOH aqueous solution saturated with zinc oxide was added to the negative electrode side portion of the assembly thus obtained to fabricate an evaluation cell. Using an electrochemical measuring device (HZ-Pro S12 manufactured by Hokuto Denko Corporation), the charge/discharge characteristics of the evaluation cell were determined under the following conditions:Air electrode gas: Water vapor saturation (25° C.) oxygen (flow rate of 200 cc/min)Charge/discharge current density: 2 mA/cm2Charge/discharge time: 10 minutes charge/10 minutes discharge The results were as shown inFIG.8. Although the evaluation cell (zinc-air secondary battery) fabricated in the present example has the configuration in which no electrolyte is present in the air electrode layer (hence, the resistance tends to be high in nature), it is found fromFIG.8that the difference between the charge voltage and the discharge voltage is as small as about 1.0 V (i.e., the resistance is low), and that high charge/discharge efficiency can be realized. Example B2 An air electrode/separator assembly having three layers of an interface layer, an internal catalyst layer and an outermost catalyst layer on the LDH separator fabricated in Example A1 was fabricated by the following procedure and was evaluated. (1) Fabrication of Outermost Catalyst Layer The outermost catalyst layer was fabricated in the same manner as in (1) of Example B1. (2) Fabrication of Internal Catalyst Layer To 19 parts by weight of LDH powder (Ni—Fe-LDH powder fabricated by the solgel method) and 20 parts by weight of carbon nanotubes (VGCF®-H, manufactured by Showa Denko K.K.), 11 parts by weight of a butyral resin and 50 parts by weight of a butyl carbitol were added, and the mixture was kneaded with a three-roll mill to prepare a paste. The surface of the LDH separator fabricated in Example Al was coated with the paste by screen printing to form an internal catalyst layer. (3) Fabrication of Air Electrode Layer The outermost catalyst layer prepared in (1) above was placed on the internal catalyst layer formed in (2) above before the paste (internal catalyst layer) was dried. The resultant was dried with a weight placed thereon in the air at 80° C. for 30 minutes. In this way, an air electrode layer composed of an internal catalyst layer (thickness of 10 μm) and an outermost catalyst layer (thickness of 200 μm) was formed on the LDH separator. At this time, an interface layer (thickness 0.2 μm) containing LDH platy particles (derived from the LDH separator), LDH powder (derived from the internal catalyst layer) and carbon nanotubes was simultaneously formed between the LDH separator and the air electrode layer. Namely an air electrode/separator assembly was obtained. When the cross-sectional microstructure of the obtained internal catalyst layer was observed by SEM, the image shown inFIG.9was obtained. When the porosity and the average pore diameter of the internal catalyst layer in the obtained air electrode/separator assembly were measured as follows, the porosity was 48% and the average pore diameter was 1.34 μm. (Measurement of Porosity and Average Pore Diameter) The air electrode/separator assembly was cross-sectionally polished with a cross-section polisher (CP), and images of two fields of vision of the cross-section of the internal catalyst layer were acquired with a SEM (JSM-6610LV, manufactured by JEOL Ltd.) at a magnification of 10,000×. On this image data, an image analysis software (Image-J) was used to binarize the images. Porosity values and pore diameter values of pores of the two fields of vision were calculated, and the average values thereof were taken as the porosity and average pore diameter of the internal catalyst layer, respectively. (4) Assembly and Evaluation of Evaluation Cells The evaluation cell was assembled, and the charge/discharge characteristics were evaluated in the same manner as in (3) of Example B1. The results were as shown inFIG.10. Although the evaluation cell (zinc-air secondary battery) fabricated in the present example has a configuration in which no electrolyte is present in the air electrode layer (hence, the resistance tends to be high in nature), it is found fromFIG.10that the difference between the charge voltage and the discharge voltage is as small as about 0.8 V (i.e., the resistance was low), and that high charge/discharge efficiency can be realized. In particular, the difference of about 0.8 V between the charge voltage and the discharge voltage is smaller than the difference between the charge voltage and the discharge voltage (about 1.0 V) in the evaluation cell of Example B1, which has no internal catalyst layer, and it is thus found that higher charge/discharge efficiency can be realized by sandwiching the internal catalyst layer between the interface layer and the outermost catalyst layer. Example B3 (Comparison) An air electrode/separator assembly having two layers of an interface layer and an internal catalyst layer on the LDH separator was fabricated in the same manner as in Example B2 except that the outermost catalyst layer was not formed, and the evaluation of the assembly was carried out. The results were as shown inFIG.11. It is found fromFIG.11that the evaluation cell (zinc-air secondary battery) fabricated in the present example, which has a configuration without the external catalyst layer, has a difference between the charge voltage and the discharge voltage as large as about 1.4 V (i.e., the resistance is high), and is inferior in the charge/discharge efficiency to the evaluation cells of Examples B1 and B2, which have a configuration with the external catalyst layer. Example B4 An air electrode/separator assembly having three layers of an interface layer, an internal catalyst layer, and an outermost catalyst layer on the LDH separator was fabricated in the same manner as in Example B2 except that the outermost catalyst layer ((1) above) was fabricated as follows, and the evaluation of the assembly was carried out. (Fabrication of Outermost Catalyst Layer) Raw materials were provided, including nickel chloride hexahydrate (NiCl2·6H2O, manufactured by Kojundo Chemical Laboratory Co., Ltd.), iron chloride hexahydrate (FeCl3.6H2O, manufactured by Kanto Chemical Co., Inc.), vanadium chloride (VCl3, manufactured by Kishida Chemical Co., Ltd.), ultra-pure water (H2O, produced by using a Merck Millipore Milli-Q Advantage apparatus), ethanol (C2H5OH, manufactured by Kanto Chemical Co., Inc.), acetylacetone (CH3COCH2COCH3, manufactured by Kanto Chemical Co., Inc.), and propylene oxide (C3H6O, manufactured by Kanto Chemical Co., Inc.). 5 ml of ultrapure water and 7.5 ml of ethanol were placed in an airtight container and mixed. 12.5 mmol of nickel chloride hexahydrate, 1.25 mmol of iron chloride hexahydrate, and 5 mmol of vanadium chloride were weighed, placed in a beaker and stirred to obtain a solution in which the metal salts were dissolved. After adding 650 μl of acetylacetone to the obtained solution and stirring for 30 minutes, 6.55 ml of propylene oxide was added and the mixture was stirred for 1 minute. Carbon paper was immersed in the mixture, and the container was sealed. The mixture was allowed to stand undisturbed at room temperature for 24 hours as it was to obtain a substrate supporting a catalyst (Ni—Fe—V-LDH) as the outermost catalyst layer. The porosity of the obtained outermost catalyst layer was measured by the mercury intrusion method and found to be 62%. (Evaluation Results) The results were as shown inFIG.12. Although the evaluation cell (zinc-air secondary battery) fabricated in the present example has a configuration in which no electrolyte is present in the air electrode layer (hence, the resistance tends to be high in nature), it is found fromFIG.12that the difference between the charge voltage and the discharge voltage is as small as about 0.8 V (i.e., the resistance is low), and that high charge/discharge efficiency can be realized. In particular, the difference of about 0.8 V between the charge voltage and the discharge voltage is smaller than the difference between the charge voltage and the discharge voltage (about 1.0 V) in the evaluation cell of Example B1, which has no internal catalyst layer, and it is thus found that higher charge/discharge efficiency can be realized by sandwiching the internal catalyst layer between the interface layer and the outermost catalyst layer. | 71,663 |
11862816 | DETAILED DESCRIPTION Representative applications of devices and associated methods according to the present application are described in this section. Various representative embodiments are provided to provide context and aid in the understanding of the described teachings. It will be understood by those skilled in the art that various changes may be made and equivalents substituted for elements of the disclosed solutions without departing from the intended inventive scope as recited in the appended claims. Referring to the drawings, wherein like reference numbers refer to like components throughout the several views, a motor vehicle10is depicted schematically inFIG.1having an electric powertrain11. The electric powertrain11includes a high-voltage battery pack (BHV)12. In some embodiments, the battery pack12may be constructed from one or more constituent battery modules12M, with two such battery modules12M depicted inFIG.1. In other embodiments, the battery pack12is not modular, i.e., is constructed and functions as a single battery pack12. For the purposes of the present disclosure, therefore, the terms “battery pack” and “battery module” are used interchangeably, with one or more of the battery modules12M possibly functioning as the battery pack12in different configurations. Each battery module12M is configured as detailed herein with reference toFIGS.2-5in order to provide multiple parallel direct cooling paths to a suitable heat sink located within or in proximity to the battery pack12. Such paths coincide with high-current areas associated with Joule heating within the battery modules12M, and extend from individual cell-to-busbar joints31(seeFIG.2) to such a heat sink, e.g., a resident cooling plate200as shown in a non-limiting exemplary embodiment. The transferred heat is thereby dissipated away from the battery pack12. The battery pack12ofFIG.1may be used in some applications to energize stator windings (not shown) of a rotary electric machine14of the electric powertrain11aboard the motor vehicle10, e.g., a battery electric vehicle as shown or a hybrid electric vehicle using torque from the electric machine14in conjunction with another prime mover13, typically but not necessarily an internal combustion engine. Those of ordinary skill in the art will appreciate that the battery pack12and/or one or more battery modules12M may be used as an onboard power supply in other applications and for other purposes, for instance aboard other types of vehicles such as but not limited to aircraft, watercraft, or rail vehicles, or in non-vehicular applications such as powerplants, hoists, mobile platforms, robots, and the like. Therefore, the exemplary embodiment ofFIG.1is intended to be illustrative of just one possible system use of the battery pack12/battery modules12M. Each battery module12M may include and/or share a respective one of the cooling plates200or other heat sinks arranged adjacent to or along a major surface of the battery modules12M. While the cooling plate200is depicted in a typical configuration in which the heat sink is the cooling plate200and is coextensive with an underside or bottom of the battery modules12M, the actual location of the relevant heat sink may vary in other applications. In addition, the battery pack12may have a relatively flat “pancake” shape as shown, of any number of possible external shapes or aspect ratios, including the depicted rectangular shape ofFIG.1. Such a low-profile configuration may be suitable for reducing packaging space in certain embodiments of the motor vehicle10. As will be appreciated by those of ordinary skill in the art, battery cooling functions aboard the motor vehicle10and other systems equipped with the electric powertrain11often route battery coolant, shown at FF inFIG.1, through and/or around the individual battery modules12M via a network of cooling pipes with the assistance of fans, pumps, valves, chillers, radiators, and other components. To further reduce required packaging space and complexity, some cooling systems utilize direct conductive cooling by positioning the battery modules on or adjacent to a cooling plate, with the cooling plate200ofFIG.1being representative. Some configurations preclude direct contact with the cooling plate200, and thus other structure such as the enclosure or housing20(seeFIG.2) may serve in lieu of or in addition to the cooling plate200. However, given the unique internal construction of the battery modules12M and the configuration of a typical cooling plate, heat transfer remains less than optimal. The present disclosure is thus intended to address this and other issues within battery packs12having one or more battery modules12M constructed as shown inFIGS.2-5. In the non-limiting embodiment ofFIG.1, the electric powertrain11is controlled via associated powertrain control circuitry (not shown) to generate and transmit torque generated by the prime mover13and/or the rotary electric machine(s)14to a driven load, which inFIG.1includes front drive wheels16F and/or rear drive wheels16R. Alternatively, motor torque from the electric machine14may be used solely to crank and start the prime mover13when the prime mover13embodies an internal combustion engine. The battery pack12in the motor vehicle10or other systems may employ a lithium-ion, nickel-metal hydride, or other application-suitable high-energy battery chemistry. By way of example and not limitation, the battery pack12may include foil pouch-, plate-, or can-style battery cells arranged in a cell stack and electrically connected to provide output voltage at a level sufficient for energizing the electric machine14, e.g., 300 VDC or more, or 60 VDC or more in certain propulsion operations. Thus, “high-voltage” may have different meanings in different embodiments, with “high-voltage” generally entailing voltage levels in excess of typical 12-15 VDC auxiliary/low-voltage levels. In order to achieve a relatively high output voltage, the battery modules12M may be arranged in a particular geometric configuration, such as the flat configuration ofFIGS.1and2, and interconnected using a high-voltage bus of the motor vehicle10. Such a connection connects the individual battery modules12M to power electronics and a thermal management system. The simplified thermal management system is shown schematically to include a coolant pump (P)17configured to circulate battery coolant (arrow FF) to and from the cooling plate200in this embodiment, which is adapted as set forth below, and possibly through the battery modules12M. The heat transfer fluid then passes out of the battery pack12through a chiller (C)19to help cool the battery pack12, with the reverse operation likewise possible when warming of the battery pack12is required. Other common thermal management system components are omitted for illustrative simplicity, including directional and thermal expansion valves, thermostats, radiators, heat exchangers, etc. Additionally, while associated power electronics are omitted fromFIG.1for illustrative simplicity, such components typically include a power inverter module using pulse width modulation (PWM)-controlled semiconductor switches to invert a DC voltage from the battery pack12into an alternating current voltage (VAC) for powering the electric machine14, a DC-DC converter or auxiliary power module for reducing the voltage level from the battery pack12to auxiliary (e.g., 12-15 VDC) levels sufficient for powering auxiliary electrical systems aboard the vehicle10. Referring toFIG.2, an exemplary embodiment of the battery module12M is shown with an external dust cover and internal mounting board removed for illustrative clarity. The battery module12M includes an outer enclosure or housing20within which is disposed a cell stack22. As best shown inFIG.4and well understood in the art, the cell stack22includes a plurality of battery cells24, and thus the battery cells24are stacked or otherwise purposefully arranged within the housing20, which in turn may have nominal top, bottom, and side walls for a given orientation. Each respective battery cell24has a pair of cell tabs124forming separate cathode and anode electrode extensions of the respective battery cell24, e.g., at opposing ends of the battery cells24in the illustrated configuration. Referring briefly toFIG.3, the battery module12M also includes an interconnect board assembly (ICBA)25as an integral part of its construction. According to the present disclosure, the ICBA25includes a parallel plurality of conductive busbars26of a high-voltage bus. The busbars26may be optionally embodied as elongated metal plates having a respective first and second distal ends E1and E2and respective longitudinal axis A26, with the longitudinal axes A26of the collective set of busbars26being mutually parallel. The busbars26are constructed from a suitable electrically conductive material, e.g., copper and/or aluminum. Optionally, the busbars26may be plated with a thin layer of nickel, tin, or another application-suitable element to facilitate welding and provide other possible performance benefits such as improved wear and tear, corrosion resistance, etc. Ultimately, the busbars26are conductively joined to a respective one of the battery cells24ofFIG.4via the cell tabs124thereof, e.g., via laser welding, ultrasonic welding, or another suitable conductive joint process, as will be appreciated by those of ordinary skill in the art. The ICBA25ofFIG.2also includes a flexible or rigid interconnect board (ICB)28constructed from a suitable dielectric/electrically non-conductive material. As used herein, the dielectric material is also thermally conductive to facilitate heat transfer according to the present teachings. Mounting flanges27with corresponding mounting holes29may be included as part of the ICB28to enable secure mounting of the ICBA25to the battery module12M ofFIG.2. In various embodiments, the dielectric material may be plastic, e.g., nylon or polypropylene. A thermally-conductive plastic resin or polymer may be used in other embodiments. By way of example, additives such as graphite, graphene, or ceramic fillers may be used with a dielectric base material to further enhance thermal conductivity of the ICB28. As shown inFIGS.2and3, the ICB28is connected to the busbars26overmolded therewith or thereto at the respective first distal end E1, e.g., using a suitable fastener30such as a screw, rivet, or stake. At opposing distal end E2of the busbars26, the dielectric material used to form the remainder of the ICB28is overmolded onto designated portions of each of the busbars26. Thus, when the ICB28is fully formed, the dielectric material wraps around the respective second distal end E2of each the busbars26to form a plurality of overmolded ends32, with an overmolded surface28M of the overmolded ends32forming a dielectric material layer over an underlying surface area of one of the busbars26. In certain embodiments, the dielectric material of the ICB28may be overmolded to define one or more windows or through-openings34proximate each respective one of the overmolded ends32. In a non-limiting embodiment, the through-openings34for each of the busbars26may include multiple side-by-side through-openings34, which may be of approximately equal size as shown or different sizes and/or shapes. The through-openings34extend through the overmolded surface28M to form windows through the overmolded surface28M, thereby exposing some of the surface area of the busbars26at the second distal ends E2. As will be appreciated, the existence of the optional through-openings34may facilitate additional heat transfer from the busbars26and into to thermal interface material (TIM)42optionally disposed within a bracket pocket40P of an elongated bracket40, as described below with reference toFIG.5. Adjacent to some of the overmolded ends32, extensions35of adject areas of the ICB28not overmolded to a corresponding busbar26may be used for added location and structural support, with such extensions35including ribs136that may be configured to engage the elongated bracket40. Referring again toFIG.2, the cooling plate200may be arranged along an outer surface20-S of the battery module12M and configured to conduct battery coolant (arrow FF ofFIG.1) therethrough. Internal coolant manifold construction of the cooling plate200is well understood in the art and, accordingly, is not described further herein for illustrative simplicity. In embodiments in which the cooling plate200is not available nearby, other heat sinks may be used in the manner described below, including but not limited to the above-noted walls of the housing20. Such an alternative approach, as will be appreciated, may require busbars26and an ICB28of a different shape. As in a typical use of the battery pack12the housing20rests on or is in thermal communication with the cooling plate200, heat is absorbed by the housing20is ultimately dissipated to the cooling plate200. External to the battery pack12, at least one elongated bracket40having a longitudinal axis A40defines a respective bracket pocket40P (seeFIG.5). The elongated bracket40is a single continuous bracket40in some embodiments, and may be constructed of a suitable rigid or flexible material, e.g., aluminum, plastic, thermoplastic, or a flexible polymer. Such a bracket40would extend fully along a perimeter edge of the cooling plate200or along a similar edge of another heat sink, e.g., the housing20. Alternatively, elongated bracket40may be divided into multiple smaller brackets140as shown in a phantom line format, e.g., to reduce weight or provide a desired structural response. In either embodiment, the elongated bracket40or140defines a respective bracket pocket40P, either as a single continuous bracket pocket40P or as multiple discrete bracket pockets40P. While a generally U-shaped pocket or trough is depicted in the various Figures, other shapes may be envisioned provided the void defined by such a bracket40or140is capable of holding the TIM42and allowing the TIM42to solidify from a liquid apply state. Exemplary alternative shapes include but are not limited to V-shaped and L-shaped brackets40or140. During connection or racking of the ICBA25(FIG.3) to the remainder of the battery module12M ofFIG.2, each bracket pocket40P receives therein and engages the overmolded ends32of the busbars26. Depending on the configuration of the bracket40, this may entail receiving all of the overmolded ends32ofFIG.3, and the extensions35, in a single continuous bracket pocket40P, or receiving a different one of the overmolded ends32, possibly excluding the extensions35, in a respective one of the smaller brackets140. Multiple direct parallel cooling paths are thereby formed between the busbars26and the relevant heat sink to facilitate cooling of the busbars26and the cell tabs124connected thereto. Referring toFIG.5, to enhance transfer of heat from the overmolded end32of the power busbar27into a heat sink300, e.g., the housing20and/or the above-described cooling plate200, the TIM42may be positioned within the bracket pocket40P as shown. In different embodiments, the TIM42may be a thermally-conductive glue, paste, or pad, e.g., commercially available two-part epoxy adhesives having an application-suitable thermal conductivity. An exemplary thermal conductivity range suitable for battery applications is 1.5-6 W/mK, with required thermal conductivity properties being application-specific, and thus the stated range is illustrative and non-limiting. The TIM42may be applied into and along the bracket pocket(s)40P to partially fill the void defined thereby, e.g., an elongated trough or channel. Once the overmolded ends32are inserted into the bracket pocket40P and engaged with the bracket40, the TIM42and the overmolded surfaces28M together form a high-voltage barrier between the busbars26and the heat sink300. As will be appreciated by ordinary skill in the art, the above teachings lend themselves to the practice of a method for constructing the battery module12M described above. An example embodiment of such a method may include arranging a plurality of the above noted busbars26in parallel, i.e., such that the longitudinal axes A26of the busbars26are mutually parallel across the ICBA25ofFIG.3. The method may also include overmolding the ICB28ofFIG.3onto the busbars26such that the ICB28wraps around the respective second distal end E2of each the busbars26to form a plurality of the above-described overmolded ends32. Once this occurs, the method in this embodiment may include connecting the respective first distal end E1of each of the busbars26to the ICB28to thereby form the ICBA25of the battery module12M shown inFIGS.1,2, and4. Exemplary techniques for connecting the first distal end E1include riveting, staking, and threaded fasteners, to name just a few possibilities. Some embodiments the method may include conductively joining each of a plurality of the battery cell tabs124(seeFIG.2) to a respective one of the plurality of busbars26. In this manner, one may form a plurality of the cell-to-busbar joints31, for instance by performing a laser welding, conductive bonding, or ultrasonic welding process to form the cell-to-busbar joints31. Depending on the extent to which the various components or subassemblies of the battery module12M are to be assembled in house or acquired in a preassembled form, the method may include providing the heat sink300, e.g., the cooling plate200ofFIGS.1,2,4, and5. As noted above, the heat sink300in accordance with the present disclosure includes or is connected to at least one bracket40or140defining one or more bracket pockets40P. The method may include racking the ICBA25with the rest of the battery module12M as indicated by arrow A ofFIG.4, and then welding the cell tabs124to the busbars26(seeFIG.2). Thereafter, the overmolded ends32ofFIG.3may be inserted into the bracket pocket(s)40P as indicated by arrow B to thereby form parallel cooling paths, i.e., one cooling path extending from each respective one of the cell-to-busbar joints31and the heat sink300. In other embodiments, the order of connection to the heat sink300and welding of the cell tabs124may be reversed. The above-described brackets40or140may be joined to the heat sink300by a supplier/manufacturer in some approaches, such that the heat sink300already includes pre-mounted brackets40or140as an integral part of the construction of the cooling plate200. Alternatively, the brackets40or140may be joined to a heat sink300lacking such brackets40or140as part of the production process of the battery module12M, for instance by welding or conductively bonding the brackets40or140along a perimeter edge of the heat sink300. In either embodiment, the TIM42depicted inFIG.5may be applied to the brackets40or140to partially fill the bracket pocket40P. Additional structural support is provided solidification of the applied TIM42. The completed ICBA25ofFIG.3is then inserted into the bracket pocket(s)40P. Once the battery module12M is constructed in this manner, the method may include connecting the battery module12M to a load, such as the rotary electric machine14ofFIG.1in the exemplary embodiment of the motor vehicle10. The solutions disclosed herein facilitate direct cooling of the cell tabs124and busbars26ofFIG.2using passive cooling technology enabled by the specially-adapted cooling plate200or other heat sink300and the integrated HV barrier features of the overmolded surfaces28M and TIM42. The present teachings provide a way to mitigate effects of Joule heating along tab-to-busbar interfaces, including the cell-to-busbar joints31, with multiple parallel direct thermal paths from high-current conductors to the heat sink300. As will be appreciated by one of ordinary skill in the art, the present solutions may help minimize a temperature gradient across the battery module12M and prevent localized “hot spots” within cell stack22ofFIGS.2and4. By virtue of mechanical coupling of the ICBA25to the battery module12M and the cooling plate200, installation of the ICBA25may occur in conjunction with assembly of the battery module12M to help streamline manufacturing. For instance, use of the brackets40or140enable the brackets40or140to serve as locating features that the ICBA25can rest upon during certain assembly or manufacturing steps. Additionally, the integrated electrical isolation of the foregoing solutions is flexible depending on a corresponding requirement for high-voltage barrier requirement for the battery pack12. For instance, the thickness of the overmolded layers28M (seeFIG.3) may vary, as may the particular grade, material, and/or dielectric strength of such layers28M. The disclosed installation also provides structural benefits to the battery pack12ofFIG.1. That is, once the TIM42hardens, and as the bracket40or140may be metal bonded with the cooling plate200or other heat sink300in some embodiments, the ICBA25and battery pack12are effectively reinforced, which in turn provides added robustness, e.g., during road shock/vibrations in the non-limiting embodiment of the motor vehicle10. These and other potential benefits will be readily appreciated by those of ordinary skill in the art in view of the present teachings. While the best modes for carrying out the disclosure have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the disclosure within the scope of the appended claims. Furthermore, the embodiments shown in the drawings or the characteristics of various embodiments mentioned in the present description are not necessarily to be understood as embodiments independent of each other. Rather, it is possible that each of the characteristics described in one of the examples of an embodiment can be combined with one or a plurality of other desired characteristics from other embodiments, resulting in other embodiments not described in words or by reference to the drawings. Accordingly, such other embodiments fall within the framework of the scope of the appended claims. | 22,210 |
11862817 | MODE FOR CARRYING OUT THE INVENTION One aspect of the present invention provides an energy storage apparatus including: an energy storage device group in which a plurality of arrayed energy storage devices including terminals form a terminal surface where the terminals are disposed and a side surface intersecting the terminal surface; and a busbar frame holding a plurality of busbars that connects the terminals adjacent to each other. The busbar frame includes: a body holding the busbars and disposed on the terminal surface; a connector holder having a connector to which an external connector is connected, the connector holder being disposed on the side surface; and a coupling portion coupling the body and the connector holder. According to the energy storage apparatus, the body for holding the busbar is disposed on the terminal surface of the energy storage device group, and the connector holder having the connector is disposed on the side surface of the energy storage device group, thereby enabling a reduction in the dimension of the energy storage apparatus in a direction in which the terminal of the energy storage device protrudes. The coupling portion couples the connector holder to the body variably between a first posture located along the terminal surface and a second posture located along the side surface. According to this aspect, it is possible to improve the workability of installing wires electrically connected to the connector. More specifically, the connector holder is put in a first posture located in a plane with the body, and after the work of installing the wires in this state, the connector holder is put in a second posture located along the side surface of the energy storage device group. Thereby, the wire can be easily and reliably installed without causing swelling in the curved section of the wire located at the corners of the body and the connector holder. The coupling portion is formed integrally with the body and the connector holder and is bendable with respect to the body and the connector holder. According to this aspect, the number of parts can be reduced as compared to a case where the body and the connector holder are constituted separately and integrated by a coupling portion having a hinge structure. The unintended detachment of the connector holder from the body can be prevented, thus improving the convenience in handling. The energy storage device group further includes an outer case surrounding an outer periphery that includes the side surface and having the terminal surface located at one end, and the outer case is provided with a locking portion that locks the connector holder in the second posture. According to this aspect, since the unintended displacement of the connector holder can be prevented, the convenience in handling the energy storage apparatus can be improved. A binding portion surrounding a plurality of wires connected to the connector is formed at an end portion of the connector holder located on the body side. According to this aspect, it is possible to effectively prevent the swelling and dispersion of the curved section of the wire located at the corners of the body and the connector holder. In the connector holder, a void in which the wires are installed is formed around the connector. According to this aspect, it is possible to prevent the dispersion of the wires on the side surface of the energy storage device group. The wires are not exposed to the outside of the connector holder, whereby it is possible to prevent the entanglement of other members to the wire, and improve the convenience in handling. At least one surface of an outer wall constituting the binding portion or the void is made of an openable and closable cover. According to this aspect, it is possible to improve the workability of installing wires. A direction in which the external connector is connected to the connector is located parallel to the side surface. According to this aspect, the external connector and the wire connected to the external connector can be prevented from protruding outward from the energy storage device group, so that the dimension of the energy storage device group on the side surface side can also be reduced. The connector includes a first connector and a second connector juxtaposed against each other. Another aspect of the present invention provides an energy storage apparatus including: an energy storage device group in which a plurality of arrayed energy storage devices including terminals form a terminal surface where the terminals are disposed and a side surface intersecting the terminal surface; and a connector to which an external connector is connected. The connector is disposed on the side surface of the energy storage device group. According to the energy storage apparatus, the connector is disposed on the side surface of the energy storage device group, thereby enabling a reduction in the dimension of the energy storage apparatus in a direction in which the terminal of the energy storage device protrudes. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIGS.1to3illustrate an energy storage apparatus10according to an embodiment of the present invention. The energy storage apparatus10includes a battery module12made up of a plurality (eight in the present embodiment) of battery cells (energy storage devices)14, and a busbar unit40disposed on a terminal surface23of the battery module12. In the present embodiment, connectors70A,70B which are disposed in the busbar unit40are disposed on a long side-surface25(side plate34) different from the terminal surface23to reduce the energy storage apparatus10in the total height. In the following description, the longitudinal direction (short direction of the battery cell14) of the battery module12is referred to as the X-direction. The short direction (the longitudinal direction of the battery cell14) of the battery module12is referred to as the Y-direction. The height direction of the battery module12(battery cell14) is referred to as the Z-direction. (Overview of Battery Module) As illustrated most clearly inFIG.3, the battery module12has the battery cells14arrayed in the X-direction. The battery module12is housed in a square cylindrical outer case31and is restrained by the outer case31. A nonaqueous electrolyte secondary battery such as a lithium ion battery is used as the battery cell14. However, in addition to the lithium ion battery, various battery cells14including a capacitor can also be applied. Each of the battery cells14has a configuration in which an electrode assembly (not illustrated) formed by laminating and winding electrode sheets of a positive electrode and a negative electrode via a separator, a current collector (not illustrated) of the positive electrode and the negative electrode, and an electrolyte solution are stored inside a container15. The container15is prismatic and includes a flat container body16having one surface (the upper surface in the Z-direction) open, and a lid20for closing the opening of the container body16. The container body16is a box body including a pair of short side-walls17extending along the XZ plane, a pair of long side-walls18extending along the YZ plane, and a bottom wall19extending along the XY plane. The dimension of the short side-wall17in the X-direction is shorter than the dimension of the long side-wall18in the Y-direction. The lid20is liquid-tightly attached to the upper opening of the container body16. The container body16and the lid20are both made of aluminum or stainless steel and sealed by welding. On the lid20, a positive terminal21A is disposed on one end side in the Y-direction, and a negative terminal21B is disposed on the other end side in the Y-direction. As described above, in the battery module12, the positive terminal21A and the negative terminal21B are disposed only on one end surface. The positive terminal21A is electrically connected to the positive current collector and is electrically connected to the positive electrode sheet of the electrode assembly via the positive current collector. The negative terminal21B is electrically connected to the negative current collector and is electrically connected to the negative electrode sheet of the electrode assembly via the negative current collector. As illustrated inFIGS.1to3, the battery cell14is disposed such that the terminals21A,21B are located on the upper side in the Z-direction. Spacers28are disposed between adjacent battery cells14, and end spacers29are disposed at both ends in the X-direction of the disposed battery cell14group. The upper side in the Z-direction of the battery cell14group constitutes the terminal surface23on which the terminals21A,21B are disposed. The terminals21A,21B are not disposed on a bottom surface24(the lower side in the Z-direction) of the battery cell14group located on the side opposite to the terminal surface23. The outer periphery of the battery cell14group includes a long side-surface25and a short side-surface26extending in the direction orthogonal to the terminal surface23. The outer case31is made of metal and surrounds the outer periphery of the battery cell14group to restrain the battery cell14to be immovable. Note that the battery cell14group may have the outer case31. The outer case31includes a pair of end plates32extending along the YZ plane and a pair of side plates34extending along the XZ plane. The dimension of the end plate32in the Y-direction is shorter than the dimension of the side plate34in the X-direction. The lower end of the end plate32is provided with a bracket33that protrudes outward of the outer case31and fixes the energy storage apparatus10to an object to be mounted, such as a vehicle body. The lower end of the side plate34is provided with a holding piece35that protrudes inward of the outer case31and holds the outer periphery of the bottom surface24of the battery cell14group. Note that the outer case31may be a resin case. After the end plate32is disposed outside the end spacer29of the battery cell14group, the side plate34is disposed outside the long side-surface25of the battery cell14group. By screwing and integrating the end plate32and the side plate34, the plurality of battery cells14are restrained to be immovable. Thus, the terminal surface23of the battery module12is located at the upper-end opening of the cylindrical outer case31. The busbar unit40is disposed on the upper side of the terminal surface23, and the further upper side thereof is closed by a resin lid37. (Overview of Busbar Unit) As illustrated inFIGS.2to4, the terminals21A,21B of adjacent battery cells14are electrically connected by a plurality (seven sheets in the present embodiment) of busbars42A. The busbars42B,42C are electrically connected to the terminals21A,21B of the battery cell14located at the ends in a direction of current flow. The busbars (conductive members)42A to42C of the present embodiment are held by a busbar frame45and integrated as the busbar unit40. The busbar unit40is formed by disposing the busbars42A to42C and the connectors70A,70B for communication on the resin busbar frame45. Referring toFIGS.5and6, wires73A,73B for communication are installed on a frame body47and a connector holder55. The busbar42A electrically connects between the positive terminals21A of the adjacent battery cells14, between the negative terminals21B of the adjacent battery cells14, or between the positive terminal21A and the negative terminal21B. The busbar42B is electrically connected to the positive terminal21A of the battery cell14located at the end in the direction of current flow. The busbar42C is electrically connected to the negative terminal21B of the battery cell14located at the end opposite to the busbar42B. The busbars42B,42C of the present embodiment are integrally provided with external terminals43, respectively. These external terminals43protrude outward from between the upper end of the outer case31(side plate34) and the lid37(cf.FIG.1). In the case of series connection, the positive terminals21A and the negative terminals21B of the predetermined battery cells14are electrically connected by the busbars42A. In the case of parallel connection, the positive terminals21A of the predetermined battery cells14are electrically connected to each other by the busbar42A, and the negative terminals21B of the predetermined battery cells14are electrically connected to each other by the busbar42A. In the present embodiment, a case is shown where a plurality of battery cells14are connected in series, and the busbars42A are electrically connected to the positive terminals21A and the negative terminals21B of the battery cells14adjacent in the X-direction. However, two or more battery cells14may be taken as one set, and in the same set, the positive terminals21A of the battery cells14may be electrically connected to each other by the busbar42A, while in different sets, the positive terminal21A of the battery cell14and the negative terminal21B of the battery cell14may be electrically connected to each other by the busbar42A. The busbar frame45includes the frame body47for holding busbars42A to42C, the connector holder55for holding connectors70A,70B, and a coupling portion68for connecting the frame body47and the connector holder55. The frame body47is disposed on the terminal surface23, and the connector holder55is disposed on the long side-surface25via the side plate34. As illustrated inFIG.4, the frame body47includes attachment portions48A to48C for attachment of the busbars42A to42C. Four attachment portions48A for attachment of the busbars42A are provided at intervals in the X-direction at one end side in the Y-direction. On the other end side in the Y-direction, the attachment portion48B for attachment of the busbar42B is provided at one end in the X-direction, the attachment portion48C for attachment of the busbar42C is provided at the other end in the X-direction, and three attachment portions48A for attachment of the busbar42A are provided therebetween. Each of the attachment portions48A to48C has a through hole49through which the terminals21A,21B of the battery cell14pass. The inner periphery of the through hole49is provided with a first locking protrusion50for locking the lower surfaces (battery cell14side) of the busbars42A to42C, and a second locking protrusion51for locking the upper surfaces (lid37side) of the busbars42A to42C. The attachment portion48A for the busbar42A is provided with a holder52for holding the lower surface of the busbar42A. The holder52extends in the Y-direction so as to be located between the terminals21A,21B adjacent in the X-direction. The holder52is not provided in the attachment portions48B,48C for the busbars42B,42C. Referring also toFIG.5, the frame body47is provided with wiring grooves53A,53B for installation of the wires73A,73B. The wiring grooves53A,53B are concave recesses opened on the upper surface side (lid37side) of the frame body47and are formed on one end side and the other end side in the X-direction with the center of the frame body47as a reference. The wiring grooves53A,53B are branched so as to communicate with all the attachment portions48A to48C. The connector holder55is provided with attachment portions56A,56B for attachment of the connectors70A,70B. Referring also toFIG.6, at the end portion of the connector holder55located on the frame body47side, a square cylindrical binding portion58surrounding the wires73A,73B is formed. The connector holder55is provided with a pair of voids61around the attachment portions56A,56B (connectors70A,70B) and is provided with a communication portion64for communicating the voids61. The coupling portion68is formed integrally with the frame body47and the connector holder55and is provided at the center of the frame body47and the connector holder55in the X-direction and at a section corresponding to the binding portion58. The connectors70A,70B are for electrically connecting the energy storage apparatus10and external equipment (e.g., battery monitoring unit (BMU)) and are attached to the attachment portions56A,56B of the connector holder55. The connector70A makes the voltage of each battery cell14communicable to the external equipment, and the connector70B makes the temperature of the battery cell14communicable to the external equipment. Note that the temperature sensor75is disposed in the battery cell14at each of both ends where the busbars42B,42C are disposed. As illustrated inFIGS.5and6, the wire73A electrically connected to all the busbars42A to42C is connected to the connector70A, and an external connector71(cf.FIG.2) connected to the external equipment is connected to the connector70A. The wire73B of the temperature sensor75is connected to the connector70B, and an external connector (not illustrated) connected to the external equipment is connected to the connector70B. In this energy storage apparatus10, the busbars42A to42C are disposed in the frame body47, and the frame body47is disposed on the terminal surface23of the battery module12. The connectors70A,70B are disposed in the connector holder55, and the connector holder55is disposed between the side plate34(long side-surface25) of the battery module12, that is, the terminal surface23, and a bottom surface24of the battery module12. As described above, in the energy storage apparatus10of the present embodiment, the connectors70A,70B for communication are not disposed on the terminal surface23of the battery module12where the terminals21A,21B protrude. That is, it is not necessary to ensure a space for placing the connectors70A,70B, the external connector71, and the wires connected to the external connector71on the terminal surface23side of the battery module12. Hence it is possible to reduce the dimension of the energy storage apparatus10in the Z-direction in which the terminals21A,21B protrude. As a result, it is possible to respond to a request from a manufacturer (e.g., automobile manufacturer) for reducing the size of the energy storage apparatus10. Further, in the battery module12, since the positive terminal21A and the negative terminal21B are disposed only on one end surface, the busbar unit40may also be disposed only on one surface (the upper surface in the present embodiment), thereby enabling a reduction in size of the energy storage apparatus10. Note that the connector holder55may be in contact with the side plate34(long side-surface25) of the battery module12or may be disposed with a gap therebetween. That is, the connector holder55only needs to face the long side-surface25. Further, in order to reduce the energy storage apparatus10in the height direction, the connector holder55and the connectors70A,70B are desirably accommodated within the range of the long side-surface25, but the upper end portion of at least one of the connector holder55and the connectors70A,70B may protrude from the long side-surface25. (Details of Busbar Frame) As illustrated inFIGS.1to3, the busbar frame45is formed by coupling the connector holder55to the frame body47with the coupling portion68so as to make the connector holder55deformable into a first posture and a second posture. As illustrated most clearly inFIG.1, the coupling portion68is formed thinner than the frame body47and the connector holder55so as to have flexibility. Thus, the coupling portion68is configured to be bendable with respect to the frame body47and the connector holder55. In the first posture illustrated inFIG.3, the connector holder55is located in parallel along the terminal surface23and is located on a plane with respect to the frame body47. In the second posture illustrated inFIGS.1and2, the connector holder55is located along the long side-surface25and is located in a direction orthogonal to the frame body47toward the bottom surface24. Naturally, the connector holder55can also be displaced from the second posture to a posture located above the frame body47beyond the first posture. The outer case31is provided with a pair of locking portions77for locking the connector holder55in the second posture. The locking portion77is made of a plate spring and has an elastic piece78energized toward the side plate34. The locking portion77is fixed to one side plate34so as to be located below the connector holder55. The connector holder55is provided with a pair of locking pieces57at positions corresponding to the locking portions77. By inserting the locking piece57between the elastic piece78and the side plate34, the connector holder55is locked to the battery module12in the second posture. For example, the work of installing the wires73A,73B on the busbar frame45is performed as follows. First, the frame body47, in which the busbars42A to42C are disposed, is disposed on the terminal surface23of the battery module12, and the terminals21A,21B and the busbars42A to42C are joined by welding. Next, the connector holder55is put in the first posture, the wire73A is connected to each of the busbars42A to42C, and the wire73A is installed from the frame body47to the connector holder55to connect the wire73A to the connector70A. The wire73B connected to the temperature sensor75is installed from the frame body47to the connector holder55to connect the wire73B to the connector70B. Thereafter, the connector holder55is put in the second posture. As thus described, the wires73A,73B are installed to the connector holder55put in the first posture, and then the connector holder55is put in the second posture, so that it is possible to prevent the swelling of the curved sections of the wires73A,73B located at the corners of the frame body47and the connector holder55. The wires73A,73B can be installed on the planar busbar frame45, thereby making the workability highly favorable. Hence the wires73A,73B can be installed easily and reliably. Due to the integral formation of the frame body47and the connector holder55via the coupling portion68, the number of parts can be reduced as compared to a case where the frame body and the connector holder are separately configured and integrated by a coupling portion in a hinge structure. Furthermore, the unintended detachment of the connector holder55from the frame body47can be prevented, thus improving the convenience in handling. Since the connector holder55can be locked in the second posture by the locking portion77, the unintended displacement of the connector holder55can be prevented. It is thereby possible to improve the convenience in handling the energy storage apparatus10. The connection work of the external connector71is performed in this state, so that the connection workability can also be improved. (Details of Wire Arrangement Structure) As described above, in order to install the wires73A,73B, the frame body47is provided with the wiring grooves53A,53B, and the connector holder55is provided with the binding portion58, the void61, and the communication portion64. As illustrated inFIGS.4to6, the wiring grooves53A,53B are concave recesses, and a regulating protrusion53aprotruding into the groove is provided at the upper end of a prescribed position. The regulating protrusion53acovers a part of each of the wiring grooves53A,53B, and prevents the floating of each of the wires73A,73B. The ends of the wiring grooves53A,53B located on the frame body47side are opened so as to face the binding portion58. As illustrated inFIGS.6to8, the connector holder55includes a substrate55acontinuous to the coupling portion68, and a frame plate55bprotruding outward from the outer peripheral edge of the substrate55a. The frame plate55bis not provided between the pair of binding portions58. The attachment portions56A,56B for attachment of the connectors70A,70B are provided on both sides of the substrate55ain the X-direction. The binding portion58is provided at the end of the substrate55alocated on the frame body47side, the void61is provided around the attachment portions56A,56B, and the communication portion64is provided at the end of the substrate55alocated away from the coupling portion68. Referring toFIG.7together withFIG.9, the binding portion58has a square cylindrical shape with an open end located on the frame body47side and is rotatable with respect to the frame body47together with the connector holder55. The outer wall of the square cylindrical shape constituting the binding portion58is made up of a part of the substrate55acontinuous to the coupling portion68and a pair of covers59having an L-shape as viewed from the opening of the binding portion58. The pair of covers59are provided integrally with the frame plate55b(Frame Body47) by elastically deformable coupling portions60. One cover59is provided with a locking protrusion59a, and the other cover59is provided with a locking frame59bdetachably locked to the locking protrusion59a. Referring toFIGS.6to8together withFIG.10, the void61communicates with the binding portion58, extends outwardly in the X-direction on the frame body47side of the attachment portions56A,56B and extends away from the frame body47at the outer end of the substrate55ain the X-direction. On the outer side of the connector holder55in the X-direction, the void61communicates with the attachment portions56A,56B. The void61is defined by the frame plate55b, an inner frame plate61aprovided with a space from the frame plate55b, and an openable and closable cover62. The cover62constitutes one surface of an outer wall surrounding the void61. The cover62is integrally provided with the frame plate55bby an elastically deformable connection portion63. The cover62includes a locking piece62adisposed on the outer surface of the frame plate55b. A locking protrusion55cis provided on the frame plate55b, and a locking hole62bis provided in the locking piece62a. Referring toFIGS.6to8together withFIG.11, the communication portion64communicates with the voids61, located at both ends of the connector holder55in the X-direction, at the outer end of the substrate55afarthest from the frame body47. The communication portion64is defined by the frame plate55b, an inner frame plate64aprovided with a space from the frame plate55b, and an openable and closable cover65. The cover65constitutes one surface of an outer wall surrounding the communication portion64. The cover65is integrally provided with the frame plate55bby an elastically deformable connection portion66. The cover65includes a locking piece65adisposed on the outer surface of the inner frame plate64a. A locking protrusion64bis provided on the inner frame plate64a, and the locking piece65ais provided in a locking hole65b. The wires73A,73B are installed with the connector holder55put in the first posture as illustrated inFIGS.4and5and with the covers59,62,65set in an open state as illustrated inFIGS.9to11. The wires73A,73B are installed along the wiring grooves53A,53B, and then installed in the opened binding portion58. Five wires73A for voltage and two wires73B for temperature are installed in the wiring groove53A. These wires73A,73B are installed from the binding portion58to the void61on the left side inFIG.6. The wire73A for voltage is connected to the connector70A. The wire73B for temperature is installed through the communication portion64to the air void61on the right side inFIG.6, and is connected to the connector70B. Four wires73A for voltage are installed in the wiring groove53B, and two wires73B for temperature are installed in the wiring groove53B. These wires73A,73B are installed from the binding portion58to the void61on the right side inFIG.6. The wire73B for temperature is connected to the connector70B. The wire73A for voltage is installed through the communication portion64to the air void61on the left side inFIG.6, and is connected to the connector70A. When the installation of all the wires73A,73B is completed, the covers59,62,65are closed, and the connector holder55is shifted to the second posture to lock the locking piece57to the locking portion77. As described above, the wires73A,73B are installed in the wiring grooves53A,53B of the frame body47opened upward, and in the binding portion58, the void61, and the communication portion64of the connector holder55opened upward by opening the covers59,62,65. It is thus possible to significantly improve the workability of installing the wires73A,73B. The curved sections of the wires73A,73B located at the corners of the frame body47and the connector holder55come into the state of being surrounded by the binding portion58, so that outward swelling and dispersion can be prevented effectively. Furthermore, with the wires73A,73B being installed in the closed void61and the communication portion64in the connector holder55, the dispersion of the wires73A,73B on the side surface of the battery module12can be prevented. The wires73A,73B are not exposed to the outside of the connector holder55, so that entanglement with other members can also be prevented. Accordingly, it is possible to significantly improve the convenience in handling the energy storage apparatus10. (Details of the Connector Attachment Structure) As illustrated inFIGS.1and2, the attachment portions56A,56B of the connector holder55are provided such that a direction in which the external connector71is connected to the connectors70A,70B is located parallel to the side plate34. That is, the attachment portions56A,56B are provided such that the openings70aof the connectors70A,70B are opened in a direction orthogonal to the XZ plane where the side plate34extends. The pair of attachment portions56A,56B are provided side by side in the array direction of the battery cells14. That is, the pair of attachment portions56A,56B are provided with a space in the X-direction. As most clearly illustrated inFIG.6, the attachment portions56A,56B are provided such that the opening70aof the first connector70A and the opening70aof the second connector70B face each other. In a case where the external connector71is connected to the connectors70A,70B disposed in the connector holder55, the external connector71is disposed between the connectors70A,70B. The external connector71is operated outward in the X-direction to be connected to the corresponding connectors70A,70B. In a case where the openings of the first connector and the second connector are disposed in opposite directions, an operation is performed to dispose the external connectors on both outer sides of the respective connectors and connect the external connectors. In this case, it is necessary to ensure a space for connecting the external connectors on both sides of the two connectors. On the other hand, in the present embodiment, as described above, the external connector71is disposed between the pair of connectors70A,70B, and a connection operation is performed. That is, the first connector70A and the second connector70B can share an operation space for connecting the external connector71. Therefore, the shape of the connector holder55can be reduced as compared to a case where the openings of the first connector and the second connector are disposed in opposite directions. With the external connector71connected, the external connector71and a wire (not illustrated) connected to the external connector71are in the state of being along the side plate34of the battery module12. Hence the external connector71and the wire can be prevented from protruding outward in the Y-direction from the battery module12. As a result, the lateral dimension of the energy storage apparatus10can also be reduced. Note that the energy storage apparatus10of the present invention is not limited to the configuration of the above embodiment, but various modifications are possible. (First Modification) In the above embodiment, the case has been illustrated where the connectors70A,70B and the connector holder55are disposed on the long side-surface25of the battery cell14group via the side plate34In a first modification, a case will be illustrated where the connector and the connector holder are disposed on the short side-surface26of the battery cell14group. FIG.12is a perspective view illustrating an energy storage apparatus10A according to the first modification. In the following description, the same sections as those in the above embodiments may be denoted by the same reference numerals and the description thereof may be omitted. As illustrated inFIG.12, in the energy storage apparatus10A, the connectors70A,70B are disposed in the connector holder55A, and the connector holder55A is provided on the end plate32(short side-surface26) of the battery module12. That is, even in this case, the connector holder55A is disposed between the terminal surface23and the bottom surface24of the battery module12. As described above, in the energy storage apparatus10A of the first modification as well, the connectors70A,70B for communication are not disposed on the terminal surface23of the battery module12where the terminals21A,21B protrude. That is, it is not necessary to ensure a space for disposing the connectors70A,70B, and the like, on the terminal surface23side of the battery module12. Hence it is possible to reduce the dimension of the energy storage apparatus10in the Z-direction in which the terminals21A,21B protrude. (Modification 2) In the above embodiment, the case has been illustrated where the connectors70A,70B are disposed on the long side-surface25of the battery cell14group via the connector holder55In the second modification, an energy storage apparatus10B having no connector holder will be described. FIG.13is a perspective view illustrating the energy storage apparatus10B according to the second modification. In the following description, the same sections as those in the above embodiments may be denoted by the same reference numerals and the description thereof may be omitted. As illustrated inFIG.13, in the energy storage apparatus10B, the connectors70A2,70B2are disposed on the long side-surface25via the side plate34. In this case as well, the connectors70A2,70B2are disposed between the terminal surface23and the bottom surface24of the battery module12. As described above, in the energy storage apparatus10B of the second modification as well, the connectors70A2,70B2for communication are not disposed on the terminal surface23of the battery module12where the terminals21A,21B protrude. That is, it is not necessary to ensure a space for disposing the connectors70A2,70B2, and the like, on the terminal surface23side of the battery module12. Hence it is possible to reduce the dimension of the energy storage apparatus10in the Z-direction in which the terminals21A,21B protrude. As another example, the busbar frame45may be made of a rigid body in which the connector holder55is not rotatable with respect to the frame body47. Further, the outer case31for restraining the plurality of battery cells14need not be provided. In the busbar frame45, the frame body47and the connector holder55may be formed as separate parts. In this case, it is preferable that the coupling portion be integrated as a hinge structure in which a shaft portion is provided on one of the frame body47and the connector holder55and a bearing portion for pivotally supporting the shaft portion is provided on the other. The locking portion77can be changed as necessary so long as being configured to lock the connector holder55in the second posture. The locking portion77is not necessarily provided. The binding portion58, the void61, and the communication portion64can be changed as necessary so long as being configured to prevent the dispersion of the wires73A,73B. In particular, the positions where the covers59,62,65are provided can be changed as necessary. The binding portion58, the void61, and the communication portion64may not necessarily be provided. The directions of the connectors70A,70B disposed in the connector holder55can be changed as necessary. The connectors70A,70B may be disposed in opposite directions such that the openings70ado not face each other, may be disposed such that the openings70aopen in the same direction, or may be disposed side by side in the Z-direction orthogonal to the array direction (X-direction). The number of connectors disposed in the connector holder55may be only one or may be three or more. Further, the connectors70A,70B may be formed integrally with the connector holder55. DESCRIPTION OF REFERENCE SIGNS 10,10A,10B . . . energy storage apparatus12. . . battery module14. . . battery cell (energy storage device)15. . . case16. . . case body17. . . short side-wall18. . . long side-wall19. . . bottom wall20. . . lid21A,21B . . . terminal23. . . terminal surface24. . . bottom25. . . long side-surface26. . . short side-surface28. . . spacer29. . . end spacer31. . . outer case32. . . end plate33. . . bracket34. . . side plate35. . . holding piece37. . . lid40. . . busbar unit42A to42C . . . busbar43. . . external terminal45. . . busbar frame47. . . frame body48A to48C . . . attachment portion49. . . through hole50. . . first locking protrusion51. . . second locking protrusion52. . . holder53A,53B . . . wiring groove53a. . . regulating protrusion55,55A . . . connector holder55a. . . substrate55b. . . frame plate55c. . . Locking protrusion56A,56B . . . attachment portion57. . . locking piece58. . . binding portion59. . . cover59a. . . Locking protrusion59b. . . locking frame60. . . connection portion61. . . void61a. . . Inner frame plate62. . . cover62a. . . locking piece62b. . . locking hole63. . . connection portion64. . . communication portion64a. . . Inner frame plate64b. . . Locking protrusion65. . . cover65a. . . locking piece65b. . . locking hole66. . . connection portion68. . . coupling portion70A,70B,70A2,70B2. . . connector70a. . . opening71. . . external connector73A,73B . . . wire75. . . temperature sensor77. . . locking portion78. . . elastic piece | 37,985 |
11862818 | DESCRIPTION OF THE REFERENCE NUMBERS 10—individual battery,101—top pole,102—shell pole;20—parallel electrical connection structure,201—common adjusting busway,202—electrically connecting branch,203—bending structure,204—large insulating plate;30—series busbar;40—structural adhesive. EMBODIMENTS To make the object, technical solution, and advantages of the present invention understood more clearly, hereunder the technical solution of the present invention will be detailed clearly and completely in examples, with reference to the accompanying drawings of the present invention. In the description of the present invention, it should be noted that the term “or” is usually used with the meaning of including “and/or”, unless otherwise indicated explicitly in the context. It should be noted: in the description of the present invention, unless otherwise specified and defined explicitly, the terms “install”, “interconnect”, and “connect” shall be interpreted in their general meanings, for example, a connection may be a fixed connection, a detachable connection, or an integral connection; a connection may be a mechanical connection or an electrical connection; or a connection may be a direct connection or an indirect connection via an intermediate medium, or internal communication between two elements. Those of ordinary skill in the art can understand the specific meanings of the terms in the present invention in their context. Besides, in the description of the present invention, the terms “first” and “second”, etc., are used only for a distinguishing purpose, and should not be comprehended as indicating or implying any relative importance. Apparently, the examples described herein are only a part of examples of the invention rather than all examples of the present invention. Those of ordinary skill in the art can obtain other examples on the basis of the examples described herein without expending any creative labor; however, all such examples shall be deemed as falling in the scope of protection of the present invention. In order to solve the problems existing in the prior art, the embodiments of the present invention provide a parallel electrical connection structure for battery poles, which comprises a common adjusting busway and a plurality of electrically connecting branches, wherein both the common adjusting busway and the electrically connecting branches are conductors; each of the electrically connecting branches has a first end and a second end; the first end of each electrically connecting branch is configured to be electrically connected to the poles of the same polarity of a plurality of individual batteries or the electrically connecting elements of the poles of the same polarity of the plurality of individual batteries, and the second end of each electrically connecting branch is electrically connected to the common adjusting busway; the poles of the same polarity of different individual batteries are connected in shunt via the common adjusting busway and the electrically connecting branches; the common adjusting busway and each electrically connecting branch are insulated from the poles of the individual batteries, except the first end of each electrically connecting branch; the cross section of each electrically connecting branch is smaller than the cross section of the common adjusting busway; alternatively, the current carrying capacity of each electrically connecting branch is lower than the current carrying capacity of the common adjusting busway. Example 1 In Example 1, a parallel electrical connection structure20for battery poles is provided. The parallel electrical connection structure20for battery poles is used to prepare individual batteries10into a CTP module in which the batteries are connected in series in the rows and connected in shunt between the rows. The parallel electrical connection structure20for battery poles is especially applicable to prepare high-power power battery units in new energy vehicles or large-size energy storage systems, and is also applicable to low-speed electric vehicles, electric bicycles, and other low-power energy storage products. In this example, the individual batteries10are power batteries having high energy density, and may be selected from Type 18650, Type 21700, and Type 46800 cylindrical batteries, but are not limited to those batteries. It should be understood by those skilled in the art that individual batteries10of any size are applicable to the technical solution of this example, such as cylindrical individual batteries10, square batteries, pouch batteries, or cylindrical batteries having a cross section in a rounded rectangular shape, rounded triangular shape, or rounded polygonal shape, and all such batteries may be regarded as the individual batteries10. As shown inFIGS.1to6, the parallel electrical connection structure20in this example may be provided without the individual batteries10shown in the figures; instead, the parallel electrical connection structure20may be provided separately as a structure for grouping the individual batteries10. The parallel electrical connection structure20in this example essentially comprises at least a common adjusting busway201and a plurality of electrically connecting branches202, wherein both the common adjusting busway201and the electrically connecting branches202are conductors; each of the electrically connecting branches202has a first end and a second end, wherein the first end is configured to be electrically connected to the pole of the same polarity of each individual batter10or the electrically connecting element of the pole of the same polarity of each individual battery10, the second end is configured to be electrically connected to the common adjusting busway201, and the poles of the same polarity of different individual batteries10are connected in shunt by the common adjusting busway201and the electrically connecting branches202. Preferably, the common adjusting busway201and the electrically connecting branches202are insulated from the poles of the individual batteries10, except the first ends of the electrically connecting branches202. In an embodiment, the common adjusting busway201and the plurality of electrically connecting branches202are formed from a metal busbar in uniform thickness by punching or cutting, and the cross-sectional area of the common adjusting busway201is greater than the cross-sectional area of each electrically connecting branch202, which is to say, the width of the common adjusting busway201is greater than the width of the electrically connecting branch202, to ensure that the current carrying capacity of the common adjusting busway201is higher than the current carrying capacity of the electrically connecting branch202. Preferably, the first end of the electrically connecting branch202is electrically connected to the pole of the individual battery10through a cold-welding adhesive bonding process, with conductive adhesive that cures at normal temperature as the filler material, to prevent the inherent quality of the individual battery10from being affected by external heat via the battery poles. Optionally, the common adjusting busway201is externally coated with an insulating layer, or the common adjusting busway201is at least arranged on a large insulating plate204for insulation between the common adjusting busway201and the individual batteries10; the external of the electrically connecting branch202is usually insulated by means of a sleeve or by hanging in the air, or by being fixed to an insulating structural element, to ensure a successful over-current fusing process. Preferably, usually there is no restriction on the material and thickness of two conductors to be electrically connected through a cold-welding adhesive bonding process for electrical connection. It should be understood by those skilled in the art that the effect of heat on the battery poles can be avoided by using a cold-welding adhesive bonding process with conductive adhesive. In another embodiment, the first ends are electrically connected to the poles of the individual batteries10or electrically connecting element on the poles, the second ends are electrically connected to the common adjusting busway201; the electrical connections of the first ends and the second ends are achieved respectively through an ultrasonic jump wire bridging process between the first ends and the second ends, so that the electrically connecting branches202are formed between the first ends and the second ends simultaneously. Those skilled in the art should understand: when an ultrasonic jump wire bridging process is used, two conductors to be electrically connected are electrically connected by fusing conductive wires (e.g., aluminum wires) in a molten state to the surfaces of the conductors respectively; therefore, the first end and the second end must be made of the same material, such as aluminum, copper, nickel, or the like, to ensure the uniformity of penetration depth of the welding spot and the reliability of the fusion bonding. Preferably, the plurality of electrically connecting branches202have the same electrical resistance; then the resistance difference between the parallel branches of the plurality of individual batteries10formed via the parallel electrical connection structure20depends on the resistance difference among the batteries. The internal resistance of a battery is a basic characteristic index of the individual battery10. Before the grouping of the individual batteries10, appropriate individual batteries10may be selected by judging the resistance difference in advance to form a parallel battery bank. Besides, the parallel electrical connection structure20is easy to prepare. Preferably, the current carrying capacity of the common adjusting busway201is equal to or greater than the sum of the current carrying capacities of n−1 electrically connecting branches202, where n is the number of the individual batteries10in the parallel battery bank. In the case that thermal runaway occurs in one individual battery10of the n individual batteries10, a short circuit phenomenon will occur in the battery with thermal runaway, and then all other n−1 individual batteries10in normal operating states that are connected in shunt with the battery with thermal runaway will transfer respective incremental currents in the transverse direction to the individual battery10with thermal runaway through respective electrically connecting branches202and the common adjusting busway201. The maximum current increment in the common adjusting busway201is the sum of the incremental currents in the electrically connecting branches202electrically connected to the n−1 batteries10in normal operating states. To prevent the electrically connecting branch202electrically connected to each battery10in normal operating states and the common adjusting busway201from fused owing to over-current or ensure that they still be in a normal operating state and a normal thermal state under the heat generated due to an over-current state, the current carrying capacity of the common adjusting busway201should be at least the sum of the current carrying capacities of the n−1 electrically connecting branches202. Example 2 A plurality of individual batteries10are prepared into a parallel battery bank by using the parallel electrical connection structure20for battery poles in Example 1. The structure of the parallel battery bank is described in Example 2 with reference toFIGS.1-4. The features of the parallel electrical connection structure20for battery poles that have been included in the Example 1 are naturally inherited in this example. As shown inFIG.2, the parallel battery bank described in Example 2 is formed by a plurality of individual batteries10aligned side by side, and all the individual batteries10are arranged in the same orientation. In this example, every individual battery10in each parallel battery bank is from an individual battery10in a different series structure, and the plurality of series structures are connected in shunt. Preferably, in a parallel battery bank, each individual battery10comprises a first pole and a second pole, the first pole and the second pole correspond to the two electrical poles of the individual battery10respectively; in one embodiment, the first pole is the top pole101of the individual battery10, and the second pole is the shell pole102of the individual battery10; in another embodiment, the first pole is the shell pole102of the individual battery10, and the second pole is the top pole101of the individual battery10. Preferably, the first poles of a plurality of individual batteries10are connected in shunt via the parallel electrical connection structure20for battery poles in Example 1, and the second poles of the plurality of individual batteries10are connected in shunt. In a preferred embodiment, the parallel electrical connection structure20for battery poles is made of a metal busbar by punching and cutting, and comprises a common adjusting busway201and a plurality of electrically connecting branches202, wherein a downward bending portion of the two ends of the common adjusting busway201is a bending structure203, which are generally flat strip-shaped for connecting the connection points of a plurality of external circuits respectively or together for monitoring the voltage and capacity of a parallel battery bank. The downward bending is helpful for reducing the total width of the parallel battery bank; the portion of the common adjusting busway201in the parallel battery bank may be cylindrical or strip-shaped, preferably, the bending structures203are generally flat strip-shaped in the width direction of the parallel battery bank to reduce the width of the parallel busbar. Preferably, the common adjusting busway201is a cylindrical structure made of a flat conductor by rolling in multiple layers, each of the electrically connecting branches202is a single-layer structure formed by a plurality of plates made from the same flat conductor by die-cutting and integrated with the flat conductor, and extends to one side. To ensure that the current carrying capacity of the electrically connecting branch202is lower than the current carrying capacity of the common adjusting busway201, the width of the electrically connecting branch202is adjusted to be smaller than the width of the flat conductor unrolled from the common adjusting busway201; the other end of each electrically connecting branch202is electrically connected to the first pole or an electrically connecting element on the first pole of an individual battery10by means of conductive adhesive; thus, each electrically connecting branch202forms a branch circuit connected in series with the corresponding individual battery10between the common adjusting busway201and the second poles in shunt of a plurality of individual batteries10; the plurality of branch circuits electrically connected to the common adjusting busway201are connected in shunt to form a plurality of parallel battery branches; preferably, the intervals between the parallel battery branches is equivalent to the intervals between the individual batteries10, preferably, the intervals between the individual batteries10are the same; referring toFIG.2, the electrically connecting element is the series busbar30, which is a bending conductor or solid conductor electrically connected to the poles having different polarities of the adjacent individual batteries10in the direction of the series battery bank with cold-welding adhesive. Preferably, the electrical resistance of the electrically connecting branch202of each parallel battery branch may be adjusted reversely according to the inherent internal resistance of the individual batteries10, so as to further decrease the resistance difference between the parallel battery branches, i.e., the resistance difference in a parallel battery bank may be smaller than or equal to the inherent resistance difference among the individual batteries10in the parallel battery bank. In an optional embodiment, for example, for a 4P parallel battery bank, when thermal runaway occurs in one individual battery10in the parallel battery bank, if the internal resistance is decreased by 20% in the early stage of the thermal runaway, the current between the internal poles of the individual battery10will be increased by 20%, but the current doesn't flow through the external positive pole and negative pole of the individual battery10; the increments of the current transferred from the other three normal individual batteries10through their respective electrically connecting branches202to the common adjusting busway201are 20% respectively, the current increment in the common adjusting busway201is 3×20%, and the current reaches the electrically connecting branch202of the individual battery10with thermal runaway, the current increment in the electrically connecting branch202of the individual battery10with thermal runaway is 3×20%. After the incremental currents are superposed, the electrically connecting branch202of the individual battery10with thermal runaway is fused and burnt owing to the overcurrent, and the electrically connection of the battery with thermal runaway to the parallel battery bank is broken. Since the 1×20% incremental current in the electrically connecting branches202of the normal individual batteries10and the 3×20% incremental current in the common adjusting busway201haven't reached the design current carrying limits of the electrically connecting branches202and the common adjusting busway201, the electrically connecting branches202of the normal individual batteries10and the common adjusting busway201are not fused but can still operate normally. After the battery with thermal runaway is disconnected, the incremental currents in the electrically connecting branches202of the normal individual batteries10disappear, and the three normal batteries continue to keep a shunt state and supply power externally. Example 3 Referring toFIGS.3-6, a battery pack is provided in this example. The battery pack comprises a parallel electrical connection structure20for battery poles as described in Example 1 and a plurality of series battery banks, each of the series battery banks is formed by a plurality of afore-mentioned individual batteries10aligned side by side, and each individual battery10comprises a top pole101and a shell pole102, which are the two electrical poles of the individual battery10respectively. Preferably, in each series battery bank, four individual batteries10are connected in series by electrically connecting the top pole101and the shell pole102of the adjacent battery through a series busbar30; four series battery banks are arranged to a row in the same orientation, thereby a 4×4 array is obtained. Of course, those skilled in the art should understand that the battery pack may be a 6×4 battery array, 8×4 battery array, 10×4 battery array, 8×20 battery array, or 8×40 battery array, etc. There is no restriction on the expansion of a battery pack in the transverse direction and the longitudinal direction in this example. Preferably, in the series battery bank, the series busbar30extending out of the battery shells has a downward bending structure, the bending structure covers the upper ends of some shells but is insulated from the upper end portion of the shells; preferably, by applying pressure to the two ends of the series battery bank, the bending structure of a series busbar30for one individual battery10is electrically connected to the upper end portions of the shell of the adjacent individual batteries10via conductive adhesive; preferably, in the series battery bank, structural adhesive40is applied between the sides or top cover or the bottom of each individual battery10, to maintain a stable and reliable structure of the series battery bank. Preferably, the top poles101of the plurality of individual batteries10adjacent to each other in the first place of a plurality of series battery banks are connect in shunt via the parallel electrical connection structure20, and the shell poles102of the plurality of individual batteries10adjacent to each other in last place of the plurality of series battery banks are connected in shunt, so as to form a battery pack in which the plurality of series battery banks are connected in shunt. Preferably, a metal busbar is used as the common adjusting busway201in the parallel electrical connection structure20, and the external of the metal busbar is provided with an insulating structure; there are a plurality of short strip-shaped conductors electrically connected on the common adjusting busway201as electrically connecting branches202; preferably, the spacing between the electrically connecting branches202matches the bank spacing between the series battery banks. Preferably, the first end of each electrically connecting branch202is electrically connected to the top poles101of the individual batteries10or the series busbar30via conductive adhesive, so that the top poles101of all adjacent individual batteries10in the same battery bank in the transverse direction are connected in shunt; preferably, other areas of the electrically connecting branch202are also provided with an insulating structure except the electrically connection point of the first end, and a structural adhesive40is provided on the insulating structure; thus, the electrically connecting branch202is connected integrally to the top poles101or the series busbar30via the insulating structure and the structural adhesive40. Preferably, the metal busbar serving as the common adjusting busway201is fixedly connected to the batteries via the insulating structure external to the metal busbar and the structural adhesive40. It should be understood by those skilled in the art that the structural adhesive40may be regarded as an insulating material, and it can create voids and insulation between the individual batteries10, between the individual batteries10and the parallel electrical connection structure20, and between the individual batteries and the series busbar30, so as to improve the squeezing resistance performance and avoid undesired contact between adjacent structures under impacts. Example 4 In this example, the parallel electrical connection structure20for battery poles described in Example 1 and the manufacturing process of the battery pack described in Example 3 are detailed. It should be understood that a battery pack without the parallel electrical connection structure20for battery pole may also be referred to as a battery pack. 1. Preparing Series Battery Banks Electrically connecting a series busbar30to the top poles101of the individual batteries10; Arranging a plurality of individual batteries10having the series busbar30to a row in the same orientation; Applying at least an insulating structural adhesive40between adjacent individual batteries10in the row to create voids between the lateral shells of the individual batteries10, maintaining the lateral shells of adjacent individual batteries10parallel to each other, so as to improve the squeezing resistance performance, and avoid undesired contact between the adjacent lateral shells under impacts; Electrically connecting a series busbar30to the top poles101of adjacent individual batteries10, and electrically connecting the bending structures203of the series busbar30to the shell poles102of adjacent individual batteries10through conductive adhesive; the conductive adhesive is preferably a conductive adhesive that cures at normal temperature, and is used to increase the contact area of electrically connections in the series battery bank and stabilize the electrical flux of the electrically connection points after it cures; Structural adhesive40is applied and cured between the lateral shells of adjacent individual batteries10, so as to prepare and obtain a series battery bank in which the individual batteries10are arranged to a row side by side in the longitudinal direction; The above steps are repeated to obtain a plurality of series battery banks; 2. Preparing Parallel Electrical Connection Structures20 A metal busbar is used as the common adjusting busway201; there are a plurality of short metal strips electrically connected on the metal busbar as the electrically connecting branches202for the corresponding series battery banks; the spacing between the electrically connecting branches202is equivalent to the bank spacing between the series battery banks; The external of the metal busbar is coated with an insulating layer, or the metal busbar is stably arranged on a large insulating plate204in length equivalent to the width of the battery pack; A small insulating plate is stably arranged on the bottom metal surface of the first end of each electrically connecting branch202, the width of the small insulating plate is greater than the width of the electrically connecting branch202, and structural adhesive40is applied to the portion that is widen out of the two sides; preferably, both the large insulating plate204and the small insulating plates are made of a transparent insulating material; Conductive adhesive that cures at normal temperature is applied on the upper metal surface of the first end of each electrically connecting branch202; Thus, a parallel electrical connection structure20for battery poles is obtained; The above steps are repeated to obtain a plurality of parallel electrical connection structures20; 3. Preparing a Battery Pack in which any Individual Battery with Thermal Runaway can be Fused and Electrically Isolated in a Parallel Battery Bank A plurality of above-mentioned series battery banks are arranged in parallel, at least one structural adhesive40is applied between adjacent individual batteries10in adjacent series battery banks and the structural adhesive40is cured, so as to obtain a battery array structure in which the individual batteries10adjacent to each other in the rows are insulated and the structure is stable; The series busbars30on the top poles101of the individual batteries10adjacent to each other in a row in the last place in the plurality of series battery banks in the transverse direction are connected in shunt, to form an external top pole of the battery pack; The common adjusting busway201of a parallel electrical connection structure20is fixed to the plurality of individual batteries10that are adjacent to each other in a row in the transverse direction; the first end of each electrically connecting branch202is electrically connected to the top pole101of each individual battery10through a cold-welding adhesive bonding structure with conductive adhesive, so that the top poles101of the plurality of individual batteries10adjacent to each other in the same row in the transverse direction are connected in shunt; A plurality of parallel electrically connecting elements20are mounted on the top poles101of the plurality of individual batteries10adjacent to each other in different rows in the transverse direction, so that the top poles101of the individual batteries10adjacent to each other in the plurality of rows in the transverse direction are connected in shunt; The shell poles102of the batteries adjacent to each other in the first place of the plurality of series battery banks are connected in shunt, to form an external shell pole of the battery pack; Thus, a battery pack having a stable structure is obtained, in which the batteries are connected in series in the longitudinal direction and connected in shunt in the transverse direction, and any individual battery with thermal runaway can be isolated from the parallel battery bank by over-current fusing. The conductive adhesive cures at normal temperature, and all cold-welded electrically connection points are stable. While some examples of the present invention are described above with reference to the accompanying drawings, the present invention is not limited to those embodiments. The embodiments described above are only illustrative rather than limiting. Various modifications and alternations may be made by those having ordinary skills in the art under the inspiration of the present invention without departing from the spirit of the present invention and the scope of protection defined by the claims. However, all of such modifications and alternations shall be deemed as falling in the scope of protection of the present invention. | 28,578 |
11862819 | DETAILED DESCRIPTION OF THE INVENTION Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. However, these are merely illustrative examples and the present invention is not limited thereto. In descriptions of the embodiments of the present invention, publicly known techniques that are judged to be able to make the purport of the present invention unnecessarily obscure will not be described in detail. Referring to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views. In addition, the terms as used herein are defined by taking functions of the present disclosure into account and can be changed according to the custom or intention of users or operators. Therefore, definition of the terms should be made according to the overall disclosure set forth herein. It should be understood that the technical spirit and scope of the present invention are defined by the appended claims, and the following embodiments are only made to efficiently describe the present invention to persons having common knowledge in the technical field to which the present invention pertains. FIG.1is an exploded perspective view of a battery module1according to an embodiment of the present invention,FIG.2is a perspective view illustrating a state in which a first case unit210and a second case unit220of the battery module1are fastened to each other according to the embodiment of the present invention, andFIG.3is a perspective view and a partially enlarged view illustrating the battery module1according to the embodiment of the present invention. Referring toFIGS.1to3, the battery module1according to the embodiment of the present invention includes: a battery stack10formed by stacking a plurality of battery cells100on each other, each of which includes electrode tabs120; the first case unit210which surround at least a portion of outer surfaces of the battery stack10; and the second case unit220provided so as to be fastened to the first case unit210to surround the remaining outer surfaces of the battery stack10. In this case, the above-described first case unit210may include a bottom section211which surrounds one side (a lower side in the drawings) of the battery stack10, and a pair of first sidewalls212located on both sides of the battery stack10in a direction in which battery cells100are stacked, and the second case unit220may include a top section221which surrounds the other side (an upper side in the drawings) of the battery stack10, and a pair of second sidewalls222located on both sides of the battery stack10in the stacking direction of the battery cells100. The above-described first sidewall212and second sidewall222may be located, in a state in which at least portions thereof are overlapped with each other, and the first sidewalls212and the second sidewalls222may surround both sides of the above-described battery stack10in the stacking direction with being overlapped with each other. Specifically, each of the above-described pair of first sidewalls212may extend perpendicular to the bottom section211from edges of the bottom section211in the stacking direction, and preferably, is formed at a position spaced inwardly from the edges of the bottom section211in the stacking direction. Therefore, when viewed from a direction in which the electrode tabs120are drawn out, seat parts2110protruding to an outside of the first sidewall212may be formed at the edges of the bottom section211in the stacking direction, and the seat parts2110may be formed while protruding by the predetermined distance as described above. In addition, each of the above-described pair of second sidewalls222may extend perpendicular to the top section221from edges of the top section221in the stacking direction, and preferably, is bent downward from the edges of the top section221in the stacking direction so as to surround the first sidewall212. In this case, the second sidewall222may extend to the above-described seat parts2110of the first case unit210, and edges2220of the second sidewalls222in an extending direction (a downward bending direction perpendicular to the top section221) of the second sidewalls222may be seated on and supported by the seat parts2110. Meanwhile, the battery cell100of the battery module1according to the embodiment of the present invention may include a cell body110which is an electrode assembly (not illustrated) enclosed by an outer case (not illustrated), and the electrode tabs120drawn out from the cell body110. In this case, the remaining portions of the battery cell100except for the electrode tabs120may be considered as the cell body110. Furthermore, each of the above-described first sidewall212and the second sidewall222may be formed with an area corresponding to a plane area perpendicular to the stacking direction of the battery cells100. Therefore, the first sidewall212and the second sidewall222overlapped with each other may be located so as to surround an entire outer surface of the battery stack10in the stacking direction. Preferably, each of the above-described first sidewall212and the second sidewall222may be formed with the area corresponding to the plane area perpendicular to the stacking direction of the cell bodies110, and the first sidewall212and the second sidewall overlapped with each other may be located so as to surround the outermost side of the plurality of stacked cell bodies110in the stacking direction while forming a double sidewall structure. Meanwhile, the configuration, in which the above-described battery module1according to the embodiment of the present invention is formed so that the first sidewalls212surround both sides of the battery stack10in the stacking direction, and the second sidewalls222surround outer sides of the first sidewalls212from the outside of the first sidewall212, has been described, but this configuration is only an example and it is not limited thereto. For example, the first sidewalls212are formed outside the second sidewalls222so that the second sidewalls222surround both sides of the battery stack10in the stacking direction. Furthermore, the above-described first case unit210may include a pair of first front and rear sections213which surround at least a portion of both sides of the battery stack10in the direction in which the electrode tabs120are drawn out, and the second case unit220may include a pair of second front and rear sections223which surround at least a portion of both sides of the battery stack10in the direction in which the electrode tabs120are drawn out. In this case, the above-described pair of first front and rear sections213may extend by bending upward from edges of the bottom section211in the direction in which the electrode tabs120are drawn out, and the pair of second front and rear sections223may extend by bending downward from edges of the top section221in the direction in which the electrode tabs120are drawn out. Preferably, the above-described pair of first front and rear sections213may be formed so as to surround a portion of both sides of the battery stack10in the direction in which the electrode tabs120are drawn out, and the pair of second front and rear sections223may be formed so as to surround the remaining portions of both sides of the battery stack10in the direction in which the electrode tabs120are drawn out. Therefore, both of the first front and rear sections213and the second front and rear sections223may surround the entire surface on both sides of the battery stack10in the direction in which the electrode tabs120are drawn out by fastening the first case unit210and the second case unit220to each other. That is, the first case unit210and the second case unit220may be fastened to each other with the battery stack10interposed therebetween, and entire six outer surfaces of the battery stack10may be surrounded by fastening the first case unit210and the second case unit220to each other. Therefore, a housing unit20capable of housing the battery stack10may be formed through the fastening of the first case unit210and the second case unit220. In addition, the battery module1according to the embodiment of the present invention may further include a bus bar assembly40disposed between the first front and rear sections213and the battery stack10. In this case, the bus bar assembly40may include at least one bus bar410for electrically connecting the plurality of electrode tabs120with each other and a bus bar support420for fixing and supporting the at least one bus bar410. Specifically, each of the above-described one or more bus bars410may be formed in a plate shape to electrically connect the plurality of electrode tabs120with each other through contacting and welding with the electrode tabs120. In addition, the above-described bus bar support420may include a frame structure so as to fix one or more bus bars410to each other with being spaced apart from each other, and may be formed so as to surround the entire outer surface of the one or more bus bars410so that the one or more bus bars410are not exposed to the outside. The above-described bus bar support420may be formed of an insulation material such as plastic, thereby blocking the possibility of electrical communication between the one or more bus bars410and between the bus bar410and an external object. Meanwhile, the above-described battery cell100may be formed as a bidirectional battery cell100in which the electrode tabs120are drawn out to both sides of the cell body110. Thereby, the bus bar assembly40for electrical connection between the plurality of battery cells100may be disposed on both sides of the battery stack10in the direction in which the electrode tabs120are drawn out, thus to be connected to each of the electrode tabs120on both sides. Meanwhile, the above-described first case unit210may further include sidewall support parts214which extend perpendicular to each of the first front and rear sections213and the bottom section211from both ends of first front and rear sections213in the stacking direction of the battery cells100, thus to connect the first front and rear sections213and the first sidewall212. In this case, the sidewall support part214extends from the end of the first front and rear sections213and the end of the bottom section211in the above-described stacking direction of the battery cells100, respectively, thus to be located outside from the first sidewall212as viewed from the direction in which the electrode tabs120are drawn out. Furthermore, the above-described sidewall support parts214are located at both ends of the first sidewall212on both sides of the battery cell100in the direction in which the electrode tabs120are drawn out. Therefore, the second sidewall222of the second case unit220is inserted between the above-described sidewall support parts214on both sides, thus to be seated on the seat part2110. In this case, chamfered faces2221may be formed in an inclined manner with respect to the bottom section211at both ends (corners) of an edge2220in the extending direction of the above-described second sidewall222in the direction in which the electrode tabs120of the battery cell100are drawn out. Through the chamfered faces2221, an interference between the second sidewall222and the sidewall support parts214on both sides may be minimized during an assembly process of the first case unit210and the second case unit220, such that the second case unit220may be more easily inserted into the sidewall support parts214and seated on the seat part2110. Meanwhile, the above-described first case unit210and the second case unit220may be coupled with each other by non-welding mechanical fastening. Specifically, a first pair of fastening holes213aand223afor coupling the first case unit210and the second case unit220with each other may be formed in a structure into which first fastening members230acan be inserted in the direction in which the electrode tabs120of the battery stack10are drawn out, and a second pair of fastening holes214band222bfor coupling the first case unit210and the second case unit220with each other may be formed in a structure into which second fastening members230bcan be inserted in the stacking direction of the battery stack10. Preferably, at least one first fastening hole213amay be formed in the first front and rear section213of the above-described first case unit210, and at least one second fastening hole223amay be formed in at least one protrusion portion at an edge of the second front and rear section223of the second case unit220on the first front and rear section213side, which is formed at a position corresponding to the first fastening hole213aby protruding from the edge of the second front and rear section223to the first front and rear section213side. In this case, the first fastening hole213aand the second fastening hole223amay be coaxially disposed with being overlapped with each other as the first case unit210and the second case unit220are assembled, thus to form the first pair of fastening holes213aand223a, then the first fastening members230aare inserted into the coaxial first pair of fastening holes213aand223ain the direction in which the electrode tabs120are drawn out, such that the first case unit210and the second case unit220may be bound with each other by non-welding mechanical fastening. In addition, at least one third fastening hole214bmay be formed in the sidewall support part214. of the first case unit210, and at least one fourth fastening hole222bmay be formed in at least one protrusion portion at the end of the second side wall222of the second case unit220in the above-described direction in which the electrode tabs120are drawn out, which is formed at a position corresponding to the third fastening hole214bby protruding from the end of the second sidewall222to the sidewall support part214. In this case, the third fastening hole214band the fourth fastening hole222bmay be coaxially disposed with being overlapped with each other as the first case unit210and the second case unit220are assembled, thus to form the second pair of fastening holes214band222b, then the second fastening members230bare inserted into the coaxial second pair of fastening holes214band222bin the stacking direction of the battery cells100, such that the first case unit210and the second case unit220may be bound with each other by non-welding mechanical fastening. That is, as the battery module1according to the embodiment of the present invention is coupled, the first case unit210and the second case unit220, which can cover six surfaces of the battery stack10, may be bound with each other by the first fastening member230aand the second fastening member230b. In particular, each of the first fastening member230aand the second fastening member230bmay be inserted into the fastening holes at right angles in the stacking direction of the battery cells100and in the direction in which the electrode tabs120of the battery cells100are drawn out perpendicular to stacking direction, respectively. Therefore, the structural rigidity of the housing unit20may be improved, and furthermore, the above-described first fastening member230aand the second fastening member230bare disposed at right angles to each other, such that even when an external impact is applied thereto, regardless of the direction of the applied impact, the fastening state of any one of the first fastening member230aand the second fastening member230bcan be maintained, and thereby increasing durability. In addition, even when the battery cell100is expanded during using the battery module1according to the embodiment of the present invention, the first case unit210and the second case unit220are bound with each other by the first fastening member230awhich are inserted perpendicular to the direction in which the battery cell100is expanded, such that a deformation of the housing unit20in stacking direction of the battery cells100may be suppressed. Meanwhile, in the drawings, the first fastening member230aand the second fastening member230bare illustrated as a bolt for fastening, but it is not limited thereto, and any fastening means such as a rivet may be sufficiently used so long as it can be inserted into the first pair of fastening holes213aand223aand the second pair of fastening holes214band222bto bind the first case unit210and the second case unit220with each other. As described above, in the battery module1according to the embodiment of the present invention, it is possible to more reduce manufacturing costs and a burden on quality control between coupling processes of the exterior case by decreasing the number of components of the housing unit20for surrounding six outer surfaces of the battery stack10than the conventional six-side exterior case that requires a large number of coupling processes such as welding. Furthermore, in the battery module1according to the embodiment of the present invention, the first case unit210and the second case unit220may be coupled to each other through the non-welding mechanical fastening structure, such that it is possible to prevent an occurrence of quality failures in the process, such as welding failures that occurred in a welding process for coupling the conventional exterior case. FIG.4is a cross-sectional view taken on line I-I of the battery module1according to the embodiment of the present invention shown inFIG.3. Referring toFIG.4, as described above, it is possible to form the double sidewall structure, in which the first sidewall212and the second sidewall222are in surface contact with being overlapped with each other, through the assembly and mechanical fastening between the first case unit210and the second case unit220, and the overlapped first sidewall212and the second sidewall222may be disposed on both sides of the battery stack10in the stacking direction. Meanwhile, in the case of the battery module1according to the embodiment of the present invention, the double overlapping structure of the first sidewall212and the second sidewall222surrounds the outer sides of the battery stack10in the stacking direction, such that the structural rigidity of the housing unit20in the stacking direction of the battery cells100may be improved. Therefore, even when the battery cell100is expanded during using the battery module1according to the embodiment of the present invention, it is possible to suppress an expansion of the battery cell10due to swelling through the double sidewall structure. As described above, the battery module1according to the embodiment of the present invention has the improved structural rigidity of the housing unit20in the stacking direction of the battery cells100, such that the buffer members, which are disposed between a plurality of battery cells100for buffering an expansion in the conventional battery cells100, may be excluded. As a result, internal space efficiency of the housing unit20may be improved by the volume of the buffer members, and thereby increasing the energy density of the battery module1. FIG.5is an exploded perspective view illustrating a state in which a gasket30is mounted in the battery module1according to the embodiment of the present invention. Referring toFIG.5, the battery module1according to the embodiment of the present invention may further include the gasket30disposed between the battery stack10and the top section221of the second case unit220along the edges of the top section221. Specifically, the above-described gasket30may be formed in a rectangular ring shape and serves to minimize an empty space between the battery stack10and the top section221along the edges of the top section221inside the second sidewall222to obtain an increased sealing effect. As described above, in the battery module1according to the embodiment of the present invention, the number of parts of the housing unit20is reduced and the gasket30is disposed therein, such that waterproof and dustproof performances may be improved. FIG.6is an exploded perspective view illustrating a state in which the battery stack10is placed on the first case unit210of the battery module1according to the embodiment of the present invention,FIG.7Ais a partially enlarged view of a portion A inFIG.6as viewed from the bottom, andFIG.7Bis a partially enlarged view of a portion B inFIG.6as viewed from the top. More specifically, for the convenience of description, the above-describedFIG.7Ais a partially enlarged view illustrating a state in which the battery stack10and the bus bar assembly40of the portion A inFIG.6Aare seen from the bottom section211side (lower side in the drawings). Referring toFIGS.6and7, at least one insertion guide2111protruding to the bus bar assembly40side with a predetermined height may be formed at a position of bottom section211of the first case unit210, on which the bus bar assembly40is placed, and at least one guide groove4201, into which the at least one insertion guide2111can be inserted, may be formed in at least a portion of the bus bar assembly40on the bottom section211side by pressing in a predetermined depth inward. Preferably, the above-described at least one guide groove4201may be formed in the bus bar support420of the bus bar assembly40, wherein each of one or more insertion guides2111and each of one or more guide grooves4201may be formed at positions corresponding to each other. Therefore, when the battery stack10and the bus bar assembly40are placed on the first case unit210with being fastened to each other, the at least one insertion guide2111may be inserted into the at least one guide groove4201, thereby guiding the battery stack10and the bus bar assembly40to be placed on the first case unit210in position, and the placing state of the battery stack10may be supported. Meanwhile, in the case of the battery module1according to the embodiment of the present invention, the configuration, in which at least one guide groove4201is formed in the lower side of the bus bar assembly40in the drawings, and at least one insertion guide2111is formed on the upper side of the bottom section211, has been described, but it is not limited thereto. For example, at least one insertion guide2111may protrude on the lower side of the bus bar assembly40, and at least one guide groove4201may be formed by pressing in the bottom section211at a position corresponding thereto. Although the representative embodiments of the present invention have been described in detail, it will be understood by persons who have a common knowledge in the technical field to which the present invention pertains that various modifications and variations may be made therein without departing from the scope of the present invention. Accordingly, the scope of the present invention should not be limited to the embodiments, but be defined by the appended claims as well as equivalents thereof. DESCRIPTION OF REFERENCE NUMERALS 1: Battery module10: Battery stack100: Battery cell110: Cell body120: Electrode tab20: Housing unit210: First case unit211: Bottom section2110: Seat part2111: Insertion guide212: First sidewall213: First front and rear sections213a: First fastening hole214: Sidewall support part214b: Third fastening hole220: Second case unit221: Top section222: Second sidewall222b: Fourth fastening hole223: Second front and rear sections223a: Second fastening hole2220: Edge in extending direction2221: Chamfered face230a: First fastening member230b: Second fastening member30: Gasket40: Bus bar assembly410: Bus bar420: Bus bar support4201: Guide groove | 23,631 |
11862820 | DETAILED DESCRIPTION OF THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments shown below are to exemplify the present invention, and the present invention is not to be limited to the following description. <<First Embodiment>> <Solid-State Battery> A solid-state battery10in accordance with this embodiment, as shown inFIG.1, includes a multilayer body1having a columnar shape, a positive electrode tab21and a negative electrode tab31spirally wound on an outer peripheral surface of the multilayer body1, and a positive electrode terminal22and a negative electrode terminal32disposed at both end portions of the multilayer body1. These are housed in a cylindrical-shape outer body (not shown). In this embodiment, the solid-state battery10is a solid-state lithium ion secondary battery capable of being charged and discharged by absorbing and releasing lithium ions and electrons. (Multilayer Body) A multilayer body1, as shown inFIG.2, is formed by laminating a positive electrode layer20, a negative electrode layer30, and a solid electrolyte layer40disposed between the positive electrode layer20and the negative electrode layer30each having a columnar shape. In this embodiment, the positive electrode layer20is disposed on one laminate end portion of the multilayer body1, and the negative electrode layer30is disposed on the other laminate end portion of the multilayer body1. [Electrode Layer] Electrode layers including a positive electrode layer20and a negative electrode layer30have a columnar shape, and is formed by filling at least a part of a current collector made of a metal porous body with an electrode material mixture. Hereinafter, the positive electrode layer20is described as an example, but the same is true to the negative electrode layer30having the same configuration.FIG.3AandFIG.3Bare sectional views showing the positive electrode layer20as the electrode layer.FIG.3Ais a sectional view of the positive electrode layer20in the diameter direction, andFIG.3Bis a sectional view of the positive electrode layer20in the axial direction. As shown inFIG.3AandFIG.3B, the positive electrode layer20includes a material mixture filled portion20ahaving a current collector filled with an electrode material mixture in the center portion of the diameter direction. Furthermore, the positive electrode layer20includes a material mixture unfilled portion20bin which the current collector is not filled with an electrode material mixture in the outer periphery in the diameter direction. A part of the material mixture unfilled portion20bis provided with a welded portion20cwelded to a positive electrode tab21. By providing the material mixture unfilled portion20bwith the welded portion20c, the positive electrode tab21and the positive electrode layer20can be welded easily and reliably. Note here that when the electrode layer does not include a material mixture unfilled portion, a welded portion to a tab may be provided in the material mixture filled portion. The material mixture unfilled portion20bmay be formed in a part of the outer periphery in the diameter direction of the positive electrode layer20, but the material mixture unfilled portion20bis preferably formed over the entire circumference of the outer periphery in the diameter direction of the positive electrode layer20. Thus, when the multilayer body1is housed in the outer body, pressure can be uniformly applied to the positive electrode layer20from the side surface in the circumferential direction. The material mixture unfilled portion20bhas a metal density being preferably higher than that of the material mixture filled portion20a. Furthermore, the material mixture unfilled portion20bmay be filled with any one of an insulating material, a solid electrolyte, and a heat conductive material. When the material mixture unfilled portion20bis filled with an insulating material or a solid electrolyte, an internal short circuit of the solid-state battery10can be prevented. Furthermore, when the material mixture unfilled portion20bis filled with a heat conductive material, the dissipation efficiency of heat generated in the electrode layers to the outside can be improved. Examples of the insulating material capable of being filled into the material mixture unfilled portion20binclude a synthetic resin, and the like. The synthetic resin is not particularly limited, and examples thereof include a thermosetting resin such as a polyimide resin, an epoxy resin, a silicone resin, a polyurethane resin, and the like; a thermoplastic resin such as a polyolefin resin, a polystyrene resin, a fluorine resin, a polyvinyl chloride resin, a polymethacrylic acid resin, a polyurethane resin, and the like; and a photocurable resin such as a silicone resin, a polymethacrylic acid resin, a polyester resin, and the like. As the solid electrolyte, the same materials as the solid electrolyte materials to be used for the below-mentioned solid electrolyte layer40are used. Examples of the heat conductive material include high-thermal conductive PC (polycarbonate) resin, high-thermal conductive polybutylene terephthalate (PBT) resin, a high-thermal conductive polyamide (PA) resin, a polyphenylene sulfide (PPS) resin, and the like, and further examples include high-thermal conductive resin materials such as a high-thermal conductive silicone materials having thermal conductivity of 30 W/mK or more. Both the positive electrode layer20and the negative electrode layer30may have a material mixture unfilled portion. Furthermore, only one of the positive electrode layer20and the negative electrode layer30may have a material mixture unfilled portion. When only one of the positive electrode layer20and the negative electrode layer30has a material mixture unfilled portion, it is preferable that the positive electrode layer20has a material mixture unfilled portion. Thus, since the material mixture filled portion of the positive electrode layer20is smaller than the material mixture filled portion of the negative electrode layer30, it is possible to suppress precipitation of lithium due to concentration of electric current on the end portion of the negative electrode layer30. [Current Collector] A current collector constituting the positive electrode layer20and the negative electrode layer30is made of a metal porous body. The metal porous body includes mutually continuous pores. The inside of the pores can be filled with an electrode material mixture including an electrode active material. The above-mentioned metal porous body is not particularly limited as long as it includes mutually continuous pores, and examples thereof include foam metals having pores, metal mesh, expanded metal, a punched metal, a metal nonwoven fabric, and the like, having pores formed by foaming. Examples of metal to be used for the metal porous body is not particularly limited as long as it has conductivity, and examples thereof include nickel, aluminum, stainless steel, titanium, copper, silver, and the like. Among them, foamed aluminum, foamed nickel, and foamed stainless steel are preferably used as the current collector constituting the positive electrode, and foamed copper and foamed stainless steel are preferably used as the current collector constituting the negative electrode. The current collector as the metal porous body includes mutually continuous pores inside thereof, and has a larger surface area than that of a metal foil as a conventional current collector. Use of the above-mentioned metal porous body for the current collector makes it possible to fill the electrode material mixture including the electrode active material with the inside of the above-mentioned pores. Thus, the amount of active materials per unit area of the electrode layer can be increased, and as a result, the volumetric energy density of the solid-state battery can be improved. Furthermore, since the electrode material mixture can be fixed easily, unlike conventional electrodes using a metal foil for the current collector, it is not necessary to increase the viscosity of coating slurry forming an electrode material mixture layer for increasing a film thickness of the electrode material mixture layer. This can decrease a binding agent such as an organic polymer compound required for increasing viscosity. Therefore, it is possible to increase capacity per unit area of the electrode, and to achieve high capacity in a solid-state battery. Furthermore, use of the metal porous body for the current collector makes it possible to secure strength of the electrode layer. Therefore, the positive electrode tab and the negative electrode tab can be easily welded to each electrode layer, which has been difficult in a conventional electrode layer in which a current collecting foil is coated with an electrode material mixture. [Electrode Material Mixture] An electrode material mixture filled in a current collector as a metal porous body includes at least an electrode active material. The electrode material mixture that can be applied for this embodiment may include arbitrary other components as long as the electrode material mixture includes an electrode active material as an essential component. Other components are not particularly limited, and may use components that can be used for producing a solid-state battery can be used. For example, a solid electrolyte, a conductive auxiliary agent, a binding agent, and the like, can be included. The positive electrode material mixture constituting the positive electrode layer20contains at least a positive electrode active material, and may contain other components such as a solid electrolyte, a conductive auxiliary agent, and a binding agent. The positive electrode active material is not particularly limited as long as it can absorb and release lithium ions. Examples thereof include LiCoO2, Li(Ni5/10Co2/10Mn3/10)O2, Li(Ni6/10Co2/10Mn2/10)O2, Li(Ni8/10Co1/10Mn1/10)O2, Li(Ni0.8Co0.15Al0.05)O2, Li(Ni1/6Co4/6Mn1/6)O2, Li(Ni1/3Co1/3Mn1/3)O2, LiCoO4, LiMn2O4, LiNiO2, LiFePO4, lithium sulfide, sulfur, and the like. The negative electrode material mixture constituting the negative electrode layer30contains at least a negative electrode active material, and may contain other components such as a solid electrolyte, a conductive auxiliary agent, and a binding agent. The negative electrode active material is not particularly limited as long as it can absorb and release lithium ions, and examples thereof include metallic lithium, a lithium alloy, metal oxide, metal sulfide, metal nitride, Si, SiO, and carbon materials such as an artificial graphite, natural graphite, hard carbon, and soft carbon. [Solid Electrolyte] A solid electrolyte layer40is laminated between the positive electrode layer20and the negative electrode layer30. The solid electrolyte layer40is a layer containing at least a solid electrolyte material. Charge transfer between the positive electrode active material and the negative electrode active material can be carried out through the solid electrolyte material. The solid electrolyte is not particularly limited and well-known solid electrolyte that can be used for the solid-state battery can be used. Examples thereof include a sulfide solid electrolyte material, an oxide solid electrolyte material, a nitride solid electrolyte material, a halide solid electrolyte material, and the like. (Electrode Tab) A positive electrode tab21and a negative electrode tab31as electrode tabs are a belt-like member spirally wound on the outer peripheral surface of a columnar-shaped multilayer body1as shown inFIGS.1and2. The positive electrode tab21is welded and electrically connected to all the positive electrode layers20of the multilayer body1at a welded portion20c. Similarly, the negative electrode tab31is welded and electrically connected to all the negative electrode layers30. Furthermore, the positive electrode tab21is electrically connected to the positive electrode terminal22, and the negative electrode tab31is electrically connected to the negative electrode terminal32. As a result, the electrode layers constituting the multilayer body1are connected in parallel, so that a high-capacity solid-state battery can be obtained. In addition to the above, the multilayer body1having a columnar shape, and the positive electrode tabs21and the negative electrode tabs31can be constructed without providing extending portions of the electrode tabs, so that the above configuration can be housed in a cylindrical-shaped outer body with a space saved. As a result, the energy density of the solid-state battery can be improved, and restraining pressure can be uniformly applied to the electrode layers by the outer body. Materials constituting the positive electrode tab21and the negative electrode tab31are not particularly limited, and the same metal materials constituting the positive current collector and the negative electrode current collector can be used, respectively. Preferably, at least a part of the surface of the positive electrode tab21and the negative electrode tab31excluding a connection portion with respect to the electrode layer and the electrode terminal is insulation-processed or covered with an insulator. Thus, the short circuit of the solid-state battery10can be prevented. The method for insulation processing is not particularly limited, but examples thereof include a method of forming an insulating layer on the surface of the electrode tab by a metal oxide such as alumina or a solid electrolyte having insulating properties. The method for covering with an insulator is not particularly limited, and examples thereof include a method of covering the surface of the electrode tab with an insulating film. (Electrode Terminal) A positive electrode terminal22serving as an electrode terminal is disposed in contact with a positive electrode layer20disposed at one end portion of a multilayer body1. The positive electrode terminal22may be electrically connected to the positive electrode tab21by, for example, welding. Similarly, a negative electrode terminal32serving as an electrode terminal is disposed in contact with a negative electrode layer30disposed at the other end portion of the multilayer body1. The negative electrode terminal32may be electrically connected to the negative electrode tab31by, for example, welding. Materials of the positive electrode terminal22and a negative electrode terminal32are not particularly limited as long as they have conductivity, but from the viewpoint of facilitating welding, the positive electrode terminal22is formed of the same metals as the positive electrode tab21, and examples thereof include aluminum, stainless steel, and the like. Similarly, the negative electrode terminal32is preferably formed of the same metal as the negative electrode tab31, and examples thereof include copper, stainless steel, and the like. (Outer Body) An outer body is a cylindrical-shaped outer body that houses multilayer body1as well as the positive electrode tab21and the negative electrode tab31. The outer body is a sealing member for sealing the both end portions in the axial direction, and it may have a lid body. Materials for the outer body are not particularly limited, and, for example, a metal material can be used. When a metal material is used as the outer body, strong restraining pressure can be applied to the positive electrode layer20and the negative electrode layer30. The above-mentioned metal material is not particularly limited as long as it can be used as an outer body for batteries, and examples thereof include aluminum, stainless steel, and the like. As the materials for the outer body, in addition to the above metal materials, resin such as synthetic resin can be used. The lid body is not particularly limited as long as it can seal both end portions in the axial direction of the outer body. The positive electrode terminal22and a negative electrode terminal32may be used as the lid body. Preferably, the lid body has a configuration capable of moving from the outer side in the axial direction of the cylindrical-shaped outer body toward the center portion of the solid-state battery10. When the lid body is moved as mentioned above, the positive electrode layer20and the negative electrode layer30are pressed via the lid body, so that a restraining pressure can be applied to the positive electrode layer20and the negative electrode layer30. The outer body has a cylindrical shape. When the restraining pressure is applied from the axial direction mentioned above, uniform restraining pressure can be applied to the both ends, which are in contact with the lid, of the positive electrode layer20and the negative electrode layer30. Therefore, even when the solid-state battery10is made into a module, a high restraining component is not required, and the energy density in the module unit can be improved. Furthermore, even at the side surfaces of the positive electrode layer20and the negative electrode layer30, which are in contact with the inner peripheral surface of the outer package, uniform restraining pressure can be applied. When the uniform restraining pressure is applied as mentioned above, the internal resistance of the solid-state battery10can be made uniform, and as a result, the reaction rate of the battery reaction generated inside the solid-state battery10can be made uniform. At a result, preferable battery performance can be obtained. Furthermore, when the side surfaces of the positive electrode layer20and the negative electrode layer30are restrained, in the use of the solid-state battery10as a vehicle-mounted battery, vibration at the time when it is mounted on a vehicle and the lamination displacement at the time of collision can be prevented, and the breakage of the multilayer body can be suppressed, so that the high durability and the high safety of the solid-state battery10can be obtained. <Method for Manufacturing Solid-State Battery10> A method for manufacturing a solid-state battery10is not particularly limited, but the method includes, for example, a filling step of filling a metal porous body with an electrode material mixture to form an electrode layer, and a welding step of welding an electrode tab to a multilayer body1obtained by laminating the electrode layer and a solid electrolyte layer and an electrode terminal. The filling step is a step of impregnating pores of a metal porous body having a columnar shape with an electrode material mixture including an electrode active material, and forming an electrode layer. A method of filling the metal porous body with the electrode material mixture is not particularly limited, and examples of the method include a method for filling the inside of pores of the metal porous body with slurry including an electrode material mixture using a plunger-type die coater, while pressure is applied. In addition to the above, the inside of the metal porous body may be impregnated with an electrode material mixture by a dipping method. The welding step is a step of winding the positive electrode tab21and the negative electrode tab31to the multilayer body1formed by laminating the electrode layer formed by the filling step and a solid electrolyte layer, and welding the electrode tabs and the electrode terminals disposed at both ends of each electrode layer and the multilayer body. The welding method is not particularly limited, and well-known methods can be used. By housing the multilayer body1to which an electrode tab has been welded by the above-mentioned filling step and welding step in a cylindrical-shaped outer body, the solid-state battery10can be manufactured. A step of applying an appropriate restraining pressure to the multilayer body1housed in the cylindrical-shaped outer body from both end portions in the axial direction may be provided. Hereinafter, another embodiment of the present invention is described. The same configuration as that of the above-mentioned first embodiment may be omitted. <<Second Embodiment>> A solid-state battery10ain accordance with this embodiment, as shown inFIG.4, includes a multilayer body1and an insulating film5as an insulator on the outer peripheral surface of the multilayer body1. The insulating film5is, for example, a belt-like member similar to a positive electrode tab21and a negative electrode tab31. It is preferable that the positive electrode tab21, the insulating film5, and the negative electrode tab31are spirally wound on the outer peripheral surface of the multilayer body1sequentially in this order. This can preferably prevent short-circuit of the solid-state battery10a. Furthermore, the insulating film5is preferably disposed on the outer peripheral surface in which the positive electrode tab21and the negative electrode tab31are not disposed in the outer peripheral surface of the multilayer body1, and the insulating film5preferably has the same thickness as the positive electrode tab21and the negative electrode tab31. This can reduce the level difference in the outer peripheral surface of the multilayer body1, which is generated by the positive electrode tab21and the negative electrode tab31, so that the outer body can apply uniform restraining pressure to the side surface portions of the positive electrode layer20and the negative electrode layer30. Materials forming the insulating film5are not particularly limited, and examples thereof include synthetic resin and the like as an example of insulating material to be filled in the material mixture unfilled portion20b. The insulating film5is only required to be disposed at least on the outer peripheral surface on which the positive electrode tab21and the negative electrode tab31are not disposed in the outer peripheral surface of the multilayer body1. For example, the insulating film5may be disposed so as to cover a portion excluding a welded portion to the positive electrode tab21and the negative electrode tab31in the outer peripheral surface of the multilayer body1. When the multilayer body1is wound on the positive electrode tab21and the negative electrode tab31after the multilayer body1has been covered with the insulating film5having the above-mentioned configuration and thereby, short circuit during manufacturing can be prevented. Alternatively, the positive electrode tab21and the negative electrode tab31are wound and welded to the multilayer body1, and then the entire part may be covered with the insulating film5. Thus, the manufacturing step can be simplified. FIGS.5,6, and7are sectional views each showing an example in which the insulating film5is disposed on the outer peripheral surface of the multilayer body1.FIG.5shows an example in which the insulating film5is disposed on the outer peripheral surface on which the positive electrode tab21and the negative electrode tab31are not disposed in the outer peripheral surface of the multilayer body1. In this case, in order to prevent short circuit from occurring between the positive electrode tab21and the negative electrode tab31, and the outer body6, an insulating layer I is preferably provided on a surface in which the positive electrode tab21and the negative electrode tab31are brought into contact with the outer body6. FIG.6shows an example in which the insulating film5is disposed also between the positive electrode tab21and the negative electrode tab31, and the outer body6in addition to the outer peripheral surface in which the positive electrode tab21and the negative electrode tab31are not disposed in the outer peripheral surface of the multilayer body1. A configuration ofFIG.6need not perform insulation treatment with respect to the outer surface of the positive electrode tab21and the negative electrode tab31. The configuration ofFIG.6is obtained by winding the positive electrode tab21and the negative electrode tab31on the multilayer body1, and then covering the entire part with the insulating film5. Similar toFIG.6,FIG.7shows an example in which an insulating film is disposed also between the positive electrode tab21and the negative electrode tab31, and the outer body6in addition to the outer peripheral surface in which the positive electrode tab21and the negative electrode tab31are not disposed in the outer peripheral surface of the multilayer body1. The configuration ofFIG.7is divided into the insulating films51and52, and after the insulating film51is wound, the positive electrode tab21and the negative electrode tab31are wound, and thereby, short circuit during manufacturing can be prevented. Thereafter, the insulating film52is wound so as to cover the outer surfaces of the positive electrode tab21and the negative electrode tab31, so that it is not necessary to perform insulating treatment with respect to the outer surfaces of the positive electrode tab21and the negative electrode tab31. In the above, the preferable embodiments of the present invention are described. The present invention is not necessarily limited to the above embodiments and can be appropriately modified. EXPLANATION OF REFERENCE NUMERALS 10,10asolid-state battery1multilayer body20positive electrode layer21positive electrode tab22positive electrode terminal30negative electrode layer31negative electrode tab32negative electrode terminal40solid electrolyte layer5insulating film (insulator) | 25,440 |
11862821 | BEST MODE The present disclosure will become more apparent by describing in detail the embodiments of the present disclosure with reference to the accompanying drawings. It should be understood that the embodiments disclosed herein are illustrative only for better understanding of the present disclosure, and that the present disclosure may be modified in various ways. In addition, for ease understanding of the present disclosure, the accompanying drawings are not drawn to real scale, but the dimensions of some components may be exaggerated. FIG.1is a diagram for illustrating a battery pack according to an embodiment of the present disclosure. Referring toFIG.1, a battery pack1serving an energy source may be provided to as an energy storage system, a vehicle, or other devices or instruments. At least one battery pack1or a plurality of battery packs1may be provided in the energy storage system or the vehicle. Hereinafter, in this embodiment, it will be described that at least one battery pack1or a plurality of battery packs1are included in the energy storage system. The battery pack1may include a pack case10, battery modules30,40,50, an insulation member70, and an energy drain unit100. The pack case10may form the appearance of the battery pack1. The pack case10may accommodate the battery modules30,40,50and the insulation member70, explained later. To this end, the pack case10may have an accommodation space capable of accommodating the battery module30,40,50and the insulation member70. The battery modules30,40,50are provided in the pack case10and may include at least one battery cell35,45,55provided using secondary batteries. The battery modules30,40,50may be provided in plural. The plurality of battery modules30,40,50may include at least three battery modules, and each battery module may include a plurality of battery cells35,45,55. The plurality of battery modules30,40,50may be stacked on each other along a stacking direction of the plurality of battery cells35,45,55. The plurality of battery modules30,40,50may include a first battery module30, a second battery module40, and a third battery module50. The first battery module30may be provided at one side inside the pack case10. In this embodiment, in the pack case10, the first battery module30may be provided at a left side inside the pack case10. The first battery module30may include a plurality of battery cells35. The plurality of battery cells35are secondary batteries and may be provided as at least one of pouch-type secondary batteries, rectangular secondary batteries, and cylindrical secondary batteries. Hereinafter, in this embodiment, it will be described that the plurality of battery cells35are pouch-type secondary batteries. The second battery module40is provided inside the pack case10, and may be disposed between the first battery module30and the third battery module50, explained later. The second battery module40may be connected to the energy drain unit100, explained later. The second battery module40may include a plurality of battery cells45. The plurality of battery cells45are secondary batteries and may be provided as at least one of pouch-type secondary batteries, rectangular secondary batteries, and cylindrical secondary batteries. Hereinafter, in this embodiment, it will be described that the plurality of battery cells45are pouch-type secondary batteries. The plurality of battery cells45may be connected to the energy drain unit100, explained later. The energy drain unit100connected to the plurality of battery cells45will be described later in more detail. The third battery module50may be provided at one side inside the pack case10. In this embodiment, in the pack case10, the third battery module50may be provided at a right side inside the pack case10. The third battery module50may be disposed opposite to the first battery module30with the second battery module40being interposed therebetween. The third battery module50may include a plurality of battery cells55. The plurality of battery cells55are secondary batteries and may be provided as at least one of pouch-type secondary batteries, rectangular secondary batteries, and cylindrical secondary batteries. Hereinafter, in this embodiment, it will be described that the plurality of battery cells55are pouch-type secondary batteries. The insulation member70may be provided between the plurality of battery modules30,40,50. Hereinafter, the insulation member70according to this embodiment will be examined in more detail. FIG.2is a diagram for illustrating an insulation member ofFIG.1, andFIG.3is a diagram for illustrating another embodiment of the insulation member ofFIG.2. Referring toFIG.2, the insulation member70may be provided in plural so as to be provided between the plurality of battery modules30,40,50, respectively. The plurality of insulation members70may delay thermal propagation to neighboring battery modules when a high temperature occurs due to an abnormal situation in at least one battery module among the plurality of battery modules30,40,50. To this end, the plurality of insulation members70may be made of a material with low thermal conductivity. Referring toFIG.3, each insulation member80may be provided as an assembly of a plurality of insulation layers. The plurality of insulation members70,80may be provided as a single member or a plurality of interlayer structures capable of delaying thermal propagation to neighboring battery modules30,40,50as much as possible. The energy drain unit100may be spaced apart from the at least one insulation member70, be connected to any one battery module40among the plurality of battery modules30,40,50, and externally short-circuit the any one battery module40among the plurality of battery modules30,40,50when thermal runaway occurs in at least one battery module30,40,50. The energy drain unit100may be connected to the battery module40disposed at the center among the at least three battery modules30,40,50. That is, the energy drain unit100may be connected to the second battery module40among the first to third battery modules30,40,50. Hereinafter, the energy drain unit100according to this embodiment will be described in more detail. FIG.4is a diagram for illustrating an energy drain unit ofFIG.1. Referring toFIG.4, the energy drain unit100may externally short-circuit a specific battery module40when an abnormal situation occurs, in order to more quickly prevent the risk of explosion and the like caused by thermal runaway and resultant heat propagation or thermal propagation when a high temperature occurs due to the abnormal situation at the battery cells35,45,55of the plurality of battery modules30,40,50. Specifically, when a thermal runaway situation occurs according to an abnormal situation of any one battery module30,40,50among the plurality of battery modules30,40,50, the energy drain unit100may externally short-circuit a specific battery module40in order to effectively prevent thermal propagation to the battery modules30,40,50adjacent to the battery module30,40,50at which thermal runaway occurs. Hereinafter, the energy drain unit100according to this embodiment will be described in more detail. The energy drain unit100may include a drain case110, a relay unit130, and a resistor unit150. The drain case110is provided out of the pack case10and may accommodate the relay unit130and the resistor unit150. To this end, the drain case110may have an accommodation space for accommodating the relay unit130and the resistor unit150. Meanwhile, the drain case110may be provided to be detachably attached to the pack case10. The relay unit130may be provided inside the drain case110and may be connected to the any one battery module40, namely the battery cell45of the second battery module40, to enable an on/off operation. The on-off operation of the relay unit130may be provided using an electronic or mechanical structure, and the relay unit130may be operated in connection to a control unit or the like or be operated at a predetermined temperature or higher. The resistor unit150is connected to the relay unit130and may be provided out of the pack case10. Specifically, the resistor unit150may be provided inside the drain case110, like the relay unit130. The resistor unit150may include a resistor material connected to the relay unit130and the battery cell45of the second battery module40. Accordingly, when thermal runaway occurs in at least one battery module30,40,50among the plurality of battery modules30,40,50, the relay unit130is switched on, and the storage energy of the at least one battery cell45of the any one battery module40may be converted into heat energy through the resistor material of the resistor unit150. The resistor unit150may be connected to a cooling device200for cooling the resistor material. Specifically, the resistor unit150is connected to the cooling device200out of the energy drain unit100, and the inside of the resistor unit150may be filled with a cooling agent C supplied from the cooling device200. Here, the cooling agent C may be made of an insulating material. The resistor unit150may include a unit body152, a supply pipe154, and a discharge pipe156. The unit body152includes the resistor material, and the cooling agent C may be filled in the unit body152. The unit body152is provided inside the drain case110, and may be disposed to be spaced apart from the relay unit130by a predetermined distance. The supply pipe154is used for receiving the cooling agent C from the cooling device200, and may be provided at one side of the unit body152and be connected to the cooling device200to communicate with the cooling device200. The supply pipe154may receive the cooling agent C from the cooling device200and guide the cooling agent C into the unit body152. The discharge pipe156is used for discharging the cooling agent C to the cooling device200, and may be disposed at one side of the unit body152to be spaced apart from the supply pipe154by a predetermined distance and be connected to the cooling device200to communicate with the cooling device200. The discharge pipe156may guide the cooling agent C inside the unit body152to be discharged to the cooling device200. Hereinafter, the thermal runaway prevention mechanism through the energy drain unit100when an abnormal situation such as thermal runaway occurs in the battery cells35,45,55of the battery pack1according to this embodiment due to overheating or the like will be described in more detail. FIGS.5and6are diagrams for illustrating an operation of the energy drain unit when an abnormal situation at a battery cell of a battery module of the battery pack ofFIG.1. Referring toFIG.5, in the battery pack1, overheating or thermal runaway situation may occur due to an abnormal situation at the battery modules30,50, which are not connected to the energy drain unit100, among the plurality of battery modules30,40,50. For example, an overheating or thermal runaway situation may occur due to an abnormal situation in the battery cell35of the first battery module30among the first to third battery modules30,40,50. In this case, the insulation member70may preferentially block heat transfer to the neighboring battery module40. In addition, when the abnormal situation occurs, the energy drain unit100may close the switch of the relay unit130at a predetermined temperature or higher or through a control unit. Accordingly, the battery module40connected to the energy drain unit100, namely the battery cells45of the second battery module40, may be externally short-circuited through the energy drain unit100. Specifically, the storage energy of the battery cells45of the second battery module40may be converted into heat energy through the resistor unit150of the energy drain unit100. Here, the energy of the battery cells40of the second battery module40may be approximately reduced to less than 30% SOC (State Of Charge). Also, as the SOC of the second battery module40connected to the energy drain unit100decreases, thermal propagation between the battery modules30,40,50may be more effectively prevented. Referring toFIG.6, in the battery pack1, if an overheating or thermal runaway situation occurs due to an abnormal situation in the battery module40connected to the energy drain unit100, the energy drain unit100may close the switch of the relay unit130at a predetermined temperature or above or through a control unit when the abnormal situation occurs. Likewise, the battery cells45of the second battery module40may be externally short-circuited through the energy drain unit100. Specifically, the storage energy of the battery cells45of the second battery module40may be converted into heat energy through the resistor unit150of the energy drain unit100. Accordingly, it is possible to effectively prevent thermal propagation to the neighboring battery modules30,50by rapidly lowering the level of heat energy that may be transferred from the second battery module40to the first battery module30or the third battery module50. At this time, it is also possible to delay heat transfer even through the insulation members70. Meanwhile, when the energy drain unit100is operated, the supply pipe154and the discharge pipe156of the resistor unit150may guide the cooling agent C to be supplied from the cooling device200to the unit body152and to be discharged out of the unit body152, thereby allowing the cooling agent C to be smoothly circulated inside the unit body152. Accordingly, the resistor unit150may effectively convert the storage energy of the battery cells45into heat energy while maintaining safety better. FIG.7is a diagram for illustrating a battery pack according to another embodiment of the present disclosure, andFIG.8is a diagram for illustrating an energy drain unit ofFIG.7. Since a battery pack2according to this embodiment is similar to the battery pack1of the former embodiment, features substantially identical or similar to the former embodiment will not be described again, and features different from the former embodiment will be described in detail. Referring toFIGS.7and8, a battery pack2may include the pack case10, the battery module30,40,50, the insulation member70, and an energy drain unit300. The pack case10, the battery module30,40,50, and the insulation member70are substantially identical or similar to those of the former embodiment, and thus will not be described in detail again. The energy drain unit300may include a drain case310, a relay unit330and a resistor unit350. The drain case310and the relay unit330are substantially identical or similar to the drain case110and the relay unit130of the former embodiment, and thus will not be described in detail again. The resistor unit350includes a resistor material and may be filled with an insulation oil355therein. The insulation oil355may cool the resistor material inside the resistor unit350. In the battery pack2according to this embodiment, since the insulation oil355is filled in the resistor unit350of the energy drain unit300, the resistor unit350may be cooled more conveniently without additionally connecting a separate cooling device200. According to various embodiments as above, it is possible to provide a battery pack1,2, which may more rapidly suppress heat propagation or thermal propagation caused by thermal runaway when an abnormal situation occurs at the battery cell35,45,55of the plurality of battery modules30,40,50, and an energy storage system including the battery pack1,2. While the embodiments of the present disclosure have been shown and described, it should be understood that the present disclosure is not limited to the specific embodiments described, and that various changes and modifications can be made within the scope of the present disclosure by those skilled in the art, and these modifications should not be understood individually from the technical ideas and views of the present disclosure. | 15,980 |
11862822 | DETAILED DESCRIPTION A direct carbon fuel cell (DCFC) is described herein which employs a molten iron alloy for low eutectic melting temperatures (around 850° C.) for high carbon solubility. The molten alloy includes iron, carbon, and in some embodiments includes manganese, silicon, nickel, molybdenum, and tin. The alloy has a low melting temperature for electrolytic operation to transport carbon ions and is viable with materials similar to those employed in steelmaking. The porous ceramic structure receives the oxygen at a porous cathode for diffusion through an electrolyte to the liquid alloy, in which the liquid alloy defines the anode, and tubes in the structure direct CO and CO2bubbles. The bubbles form in the liquid alloy from ionic reactions of the dissolved carbon. The fuel cell provides a method of generating electricity by heating an alloy including iron and carbon to a melting point to form a liquid alloy and circulating the liquid alloy through a tubular structure defined by a porous ceramic in communication with an oxygen source. In some embodiments, the oxygen source includes a flow of ambient air, and the alloy is a eutectic mixture including at least iron and dissolved carbon, typically having a relatively low melting point around 850° C., and thus suitable for use with materials found in steelmaking. The porous ceramic structure receives the oxygen at a porous cathode for diffusion through an electrolyte to the liquid alloy, in which the liquid alloy defines the anode, and tubes in the structure direct CO and CO2bubbles. The bubbles form in the liquid alloy from ionic reactions of the dissolved carbon in the liquid alloy and O2passage through the electrolyte.FIG.4. The exhaust gases are thus limited to CO and CO2, and the low melting temperature of the eutectic alloy allows for high carbon solubility. In some embodiments, the porous ceramic structure includes vertical tubes for transporting molten metal such that the CO and CO2rise upward through the tubes. In other embodiments, horizontal tubes carry air/O2through the molten alloy such that the CO and CO2rises upwards around the horizontal tubes. The former configuration includes circulating the liquid alloy through vertical tubes in the porous ceramic, such that the tubes are lined with layers including the porous cathode and electrolyte for receiving the CO and CO2bubbles rising upwards in the vertical tubes. In the DCFC, a cathode system includes one or more large coarsely porous ceramic blocks having vertical passages thereby allowing internal air flow. The ceramic blocks are coated with porous cathode material and dense solid electrolyte. The vertical passages are filled with the liquid anode alloy, and during operation, CO/CO2bubbles formed inside the passages promote upward gas lift stirring.FIG.2-FIG.15. In the latter structure, liquid alloy circulates around a network of horizontal tubes transporting oxygen, such that the tubes are defined by a layer of a porous cathode and a layer of electrolyte for receiving oxygen ions from the transported oxygen. CO and CO2bubbles are formed from the oxygen ions and rise through the liquid alloy around the horizontal tubes. Several materials are considered coarse porous support material candidates suitable for transporting oxygen or ambient air. These are any refractory ceramic material with decent strength and stability in air, including: stabilized zirconia (e.g., calcia-stabilized zirconia, magnesia-stabilized zirconia, yttria-stabilized zirconia), plain magnesia/periclase, alumina, silica, or fire clays. Some embodiments include forming a slag layer on top of the liquid alloy and receiving impurities including ash and silicon into the slag layer as the liquid alloy circulates beneath it. Liquid Metal Anode The liquid metal anode includes Fe—Sn—C ternary alloys and further includes Mn. In some embodiments the alloy optionally includes Mo, and/or Si to reduce the liquidus temperature. Si reduces liquidus but also reduces carbon solubility, it is found in nearly all carbon fuels and therefore unavoidable. The Fe—Mn—Sn—Mo—Si—C system is observed to exhibit up to 7 wt % (26 mol %) carbon solubility with eutectic temperature as low as 960° C. without tin, and 232° C. with tin. Fe—Mn—C eutectic temperature is observed to be 1076° C. with 16.3 mol % C. The Fe—Mn—Mo—C eutectic temperature is observed to be 1036° C., i.e., 118° below the Fe—C eutectic, with 16.8 mol % C solubility. In the liquid alloy anode near the electrolyte, oxygen from the electrolyte and carbon in the anode inter-diffuse and react to create CO/CO2bubbles, which rise and stir the liquid. A liquid metal anode having configuration is observed to have high electronic conductivity similar to other liquid metals and much higher than carbonates. Further, the liquid allot anode has high carbon solubility with fast carbon diffusion, for much faster reaction kinetics than tin or antimony—nearly removing anode overpotential and potentially reaching 3-6 W/cm2. Because the liquid alloy anode has lower viscosity compared to carbonates strong gas lift stirring is observed which is comparable to basic oxygen furnace steelmaking, and high power density in a very large cell. By adding Sn, Mn, optionally Mo and Si, the eutectic temperature is observed to be hundreds of degrees below the Fe—C eutectic used in a gasifier-type DCFC device, allowing one fuel cell to produce CO2and approach 100% theoretical energy efficiency. Further, because of rapid fuel dissolution kinetics, facilitating fuel flexibility fuel pulverizing is most likely not required. The liquid alloy anode is compatible with oxide-conducting solid electrolytes and steelmaking refractories. Further, if the solid electrolyte cracks, the liquid alloys surface tension may block infiltration, and the surface oxide which forms could prevent short-circuiting, particularly if it is a low-conductivity oxide such as silica or a silicate material. The alloy system thus combines the biggest advantages, and avoids the drawbacks, of all DCFC anode approaches. In some embodiments, liquid slag in contact with the anode absorbs and concentrates solid ash impurities such as Al2O3, CaO, MgO as well as silicon, sulfur and phosphorous. A basic slag composition with high silica capacity removes most silicon from the liquid metal anode, improving carbon solubility, however, could reduce the ability of the alloy to form silicate seals at electrolyte cracks. In some embodiments slag is periodically removed from the system. In some embodiments, a partial dam keeps the slag layer away from the CO/CO2bubbles while liquid metal flows underneath, as shown inFIG.1. In some embodiments, carbon fuel is dropped onto the liquid metal from above. In some embodiments, a non-submerged or submerged lance feeds solid carbon fuel by blowing it in using a carrier gas. In some embodiments, carbon fuel is blown in from a tuyere in the bottom or side of the vessel using a carrier gas. In some embodiments the carrier gas includes CO2and/or CO. In some embodiments the carrier gas includes argon and/or hydrogen and/or nitrogen. In some embodiments excess carbon fuel, above its solubility, is present in the liquid metal anode as solid carbon to maintain carbon saturation. Potential cathode-electrolyte configurations include the horizontal tubular system shown inFIG.1, and/or inverted closed-end tubes rising from the bottom of the cell, and/or one or more ceramic blocks with vertical tubes cut through them. These tubes and/or blocks can be hollow or filled with a large-pore ceramic material such as zirconia or alumina which provides structural support while permitting air flow. The tubes and/or blocks are coated with porous cathode material, then with electrolyte. Immersing the liquid anode-electrolyte-refractory containment triple line below the liquid anode surface eliminates the need for a gas-tight seal, as is required for SOFCs with gaseous fuels, because high liquid anode alloy surface tension seals electrolyte-refractory joints. It also separates the slag on top of the liquid alloy anode from the electrolyte-refractory joint submerged in it, otherwise the slag could potentially wet the electrolyte-refractory joint and penetrate it. In some embodiments, to improve robustness and reduce manufacturing cost, the cathode system consists of one or more large coarsely porous ceramic blocks allowing internal air flow, with vertical passages cut through it, and coated with porous cathode material and dense solid electrolyte as shown inFIG.2A-FIG.2B. Upon insertion into the DCFC, the vertical passages fill with liquid anode alloy, and during operation, CO/CO2bubbles formed inside the passages promote upward gas lift stirring.FIG.3. In manufacturing the ceramic block, solid pieces of carbon or other material(s) which burn out are incorporated into the ceramic to create coarse pores in the body, or even elongated passages through it, to promote air flow. In some embodiments, the coarse pores are created by first sintering the ceramic-carbon green body in a vacuum or reducing environment, for example including hydrogen, CO or methane gas, to densify the ceramic materials while preserving the carbon, and then adding air or oxygen to burn out the carbon and fully oxidizing the structure. This configuration has several additional potential benefits such as: smaller number of cathode-electrolyte bodies with large surface area reduces the number and length of electrolyte-containment joints; reducing the number of components thereby reduces the manufacturing cost of a cell; and geometric flexibility in the blocks allows various vertical passage geometries, such as tubes, cones, or networks of multiple small tubes at the bottom feeding larger tubes toward the top, as could be helpful to facilitate high rates of gas bubble generation and removal from the electrolyte surface, along with gas lift stirring of the liquid metal. In some embodiments, the fuel cell electrolyte includes SOFC electrolyte materials such as yttria- or scandia-stabilized zirconia (YSZ, ScSZ), or samaria- or gadolinia-doped ceria (SDC, GDC). In some embodiments, the fuel cell cathode includes SOFC cathode materials such as strontium-doped lanthanum manganite La0.8Sr0.2MnO3(LSM), strontium-doped lanthanum cobaltite La0.8Sr0.2CoO3(LSC), or similar perovskite materials with electronic conductivity 10 to 100 (Ω·cm)−1at 700° C. At 750° C., theoretical open circuit potential Ethis 1.0 V for the reaction C+O2→CO2at 0.21 atm O2(i.e. air at 1 atm total pressure). Resistance of a 40 μm thick samaria-doped ceria (Sm0.15Ce0.85O1.925-δa.k.a. SDC 15) electrolyte at this temperature is 0.067 Ω·cm2, leading to maximum possible current density over 15 A/cm2. Considering only electrolyte resistance and assuming 100% CO2production, estimated maximum power density would be 3.87 W/cm2at 50% energy efficiency, or the cell could operate at 2 W/cm2with 85% energy efficiency. Electrolyte resistance is lower at higher temperature, but the reaction would produce more CO instead of CO2, reducing energy efficiency. Some SOFCs use electrolytes as thin as 10 μm, in this case such a thin electrolyte could potentially increase power density up to four-fold. Favorable DCFC operation pressure is 0.1-10 atm on the anode side. Higher anode pressure increases the equilibrium CO2/CO ratio particularly in the 650-800° C. temperature range and facilitates CCS. It slightly reduces Ethin the DCFC, for example by about 3% at 700° C., unless accompanied by higher air pressure at the cathode. Emissions should have negligible solid particulates. Because carbon dissolves and remains in the liquid anode until reacting with oxygen, there is minimal soot; electronegative fuel impurities also stay in the anode. Further, an optional slag layer floating on the metal anode in the fuel insertion region absorbs electropositive impurities such as CaO, MgO, Al2O3, and some silicon as SiO2. Depending on the fuel, this slag can include CaF2and various oxides, and can be selected for high sulfur, phosphorous, arsenic, and silicon absorption capacity. Therefore, the slag, replaces a large train of unit operations around gas scrubbing in normal power plants, and produces a stable, vitrified slag, instead of coal plant dust. Multiple cells are electrically connected in series at high temperature to reduce energy losses through the leads. In a single lead, a large-area conductor has low electrical resistance, however, loses heat fast, and vice versa. Thermal energy loss is Q=kA ΔT/L, and electrical energy loss is P=IV=I2L/σA, so the Wiedmann-Franz constraint k≥k el=LeσT creates a constraint PQ≥I2LT ΔT where Leis the Wiedmann-Franz constant 2.45×10−8V2/K2. The lowest possible total loss P+Q is at P=Q with each given by P=Q=I√LeT ΔT. The best lead material has thermal conductivity is as close as possible to 100% electronic (i.e., negligible phonon conductivity), illustratively a highly conductive metal, illustratively copper or nickel. At T=750° C.=1023 K and ΔT=725 K, this loss P+Q/I=0.27 V, for two leads this is 0.54 V, which is greater than voltage output from a single cell at maximum power density. If multiple cells are connected in series, e.g., 10 cells, then total series voltage at maximum power density is 5 V, of which 11% is lost in the leads. Low-resistance connections between the cells not only reduce electrical losses, but also promote temperature uniformity between them, including the cells on the ends of the series which connect to the end leads. In some embodiments, a reactive metal such as Mg, Ca or a rare earth which oxidizes in CO or CO2is placed in the cell. As CO2and CO are produced by the DCFC, the reactive metal reacts to form metal oxide and carbon, and carbon dissolves back into the anode alloy, keeping the carbon in the system. In some embodiments, the refractory lining comprises MgO and/or CaO which are stable in contact with the reactive metal. Because Mg and Ca densities are below that of the liquid anode alloy, and they are immiscible with Fe, Mo and C, they float on the anode, and do not contact or react with the electrolyte components, illustratively zirconia or ceria, which lie fully submerged below the anode alloy surface. With the reactive metal, this overall device functions like a metal-air battery with overall reaction: 2Mg+O2→2 MgO, or Ca and CaO, etc. When the reactive metal fuel is partially or fully consumed, CO/CO2gas pressure increases, providing a measurable indicator for shutting off the cell. One method of shutting off the cell would be to disconnect one or both of its electrical leads, which would stop the reaction and prevent further gas pressure increase in the anode area. Embodiments incorporating reactive metal fuel are potentially useful in zero-emissions transportation vehicles (ships, trains, buses, aircraft) in which CCS is not practical. The novel anode chemistry was designed by high-throughput CALPHAD and includes Fe—Mn—Ni—Sn—Mo—Si—C alloy and melts at 800-840° C. with ≥10 mol % (2.5 wt %) carbon solubility. At 800° C. and 10 bar pressure, CO2:CO ratio is about 55:45 and theoretical efficiency is 75-80%. At 5 mol % ΔC between the bulk liquid alloy and solid electrolyte surface, carbon diffusion across a 0.1 mm boundary layer yields 18 A/cm2current density. Therefore, the anode polarization is low. With 50 μm ScSZ electrolyte the anode polarization reaches 5 W/cm2with 45% efficiency or 3 W/cm2with 62-65% overall efficiency. The CCS plant includes a water separation unit for example a temperature swing and a compressor. This highly efficient, power-dense, robust and simple DCFC dramatically reduces costs of generation with CCS, especially at low-capacity factor (CF). TABLE IComparison of novel DCFC system to presently used DCFC systemsAttributeState of art valueProposed valueDescription/JustificationPower generator typen/an/aDirect Carbon Fuel CellCCS plant technologyn/an/aWater separation andcompressionCapital cost (90% CF)$4,279/kW$1,400/kWFlow sheet simplicityFixed O&M cost3.19¢/kWh3.19¢/kWhAssume same as IGCC fornowVariable O&M cost4.57¢/kWh2.74¢/kWhEfficiency ratio, CCSsimplicityPower generator heat rate10,000 BTU/kWh3~6,000 BTU/kWh3High fuel cell efficiency(assume 57% average)Flexibility enablern/an/aAir flow control, internalheatingCapture rate90%95%+Ease of CO2separation This system scales down at high efficiency to 640-1060 kW cells each occupying 4 m3as shown inFIG.1(6-10 MW series of 10 cells with high-T interconnects); maximum scale is 30-100 MW cells. A “warm” state is achieved by adding excess carbon to the anode followed by short-circuiting a cell series and feeding air slowly as excess carbon dissolves. The resulting levelized cost of electricity is 7.330/kWh at 90% CF and 10.20/kWh at 50% CF, which is best-in-class for solid fuel power plants with or without CCS, but with flexibility needed to follow demand with high renewables. In an embodiment of the DCFC a closed-end tubular cathode/electrolyte arrangement with an outside diameter of approximately 20 mm to 25 mm is used. The arrangement includes a 1-2 mm thick current collector support tube with 30% to 40% porosity surrounded by a 30 μm to 50 μm thick cathode and a 30 μm to 80 μm thick solid oxide electrolyte. Examples for materials for construction of the current collector are silver, nickel, or steel alloy foam. Cathode materials include LSM, lanthanum iron oxide (LSF), lanthanum nickel oxide (LNO), or lanthanum strontium cobalt ferrite (LSCF). Materials for the electrolyte include zirconia doped with yttria or scandia (YSZ or ScSZ), or a ceria-based electrolyte doped with samaria or gadolina (SDC or GDC). In some embodiments, the liquid metal anode is an Fe-based alloy to achieve high carbon solubility and a low enough melting temperature for favorable electrochemical cell operation. The liquid alloy anode is characterized by having low liquidus (melting) temperature by incorporating alloying elements; having high carbon solubility with rapid carbon diffusion; having high electronic conductivity relative to molten carbonates; and is compatible with solid oxide electrolytes and steelmaking refractories Anode Alloy Development The key requirements of the liquid metal anode are a low liquidus temperature and high carbon solubility. Fe exhibits high carbon solubility and is abundantly available at relatively low cost. Therefore, Fe is a great candidate for the DCFC anode alloy design. The eutectic composition of an alloy corresponds to the lowest temperature at which a mixture of substances completely melts or solidifies. Steel, an alloy of Fe and C, has a eutectic composition of 4.3 wt % C around 1150° C. Using the Fe—C eutectic composition in a DCFC would require an operating temperature around 1200° C. which is far too high for desirable electrochemical reactions and overall cell efficiency. Therefore, additional alloying elements were investigated to incorporate into the Fe—C system to lower liquidus temperature. Sn has a melting point of 232° C. and has been investigated for use with solid oxide electrolytes. However, Sn has low carbon solubility, which is one of the requirements of the anode. Fe—Sn—C data is nearly absent from literature and thermodynamic databases as Sn in steel segregates to grain boundaries which has a detrimental effect on mechanical properties. The eutectic composition Fe—Sn is at approximately 30 wt. % Sn. Low melting point alloys in the Fe—Cr—Mn—Mo—C system were examined using Thermo-Calc software for the calculation of phase diagrams (CALPHAD) based on thermodynamic data. By projecting liquidus lines onto temperature-composition planes, it was observed that a eutectic composition of Fe-3.99 C-21.4 Mn-10.4 Mo has a liquidus temperature of 1036° C. This composition allows a decrease in liquidus temperature of over 100° C. from the Fe—C eutectic while maintaining 93% of the carbon solubility, making Mn and Mo alloying elements of great interest to this DCFC anode alloy. Si is commonly alloyed with steel to increase strength and improve magnetic properties. It an important alloying element in cast iron as over approximately 1 wt. % Si forces carbon out of the solution creating the characteristic graphitic microstructure present in grey cast iron. By adding Si to the Fe—Mn—C system results in a liquidus temperature of 1000° C. but reduces C solubility to 0.73 wt. %. Due to the presence of Si in nearly all steels, some percentage of Si is present in the anode alloy. Ni is often alloyed with Fe to increase toughness, hardness, and corrosion resistance. Ni is about half the cost of Mo, $0.014/g vs. $0.027/g, and as such is an attractive alternative alloying element for this liquid anode. The liquidus temperatures of the Fe—Mn—Ni—C were examined by varying Mn and Ni content by increments of 5 wt. % to understand the influence of varying the composition of these elements on the overall liquidus temperature. An initial run of 30 compositions using the TCFE9 Thermo-Calc database resulted in the composition 56.1 Fe-25 Mn-15 Ni-3.9 C that showed a liquidus temperature of 1055° C. A plot showing liquidus temperatures vs. carbon solubility of these 30 compositions is shown inFIG.16. The data show that using over 20 wt. % Mn and Ni in the system had advantageous results in reducing the liquidus temperature and retaining high (over 80% of that present in the Fe—C eutectic) carbon solubility. Further using 30 wt. % and 40 wt. % Mn with varying levels of Ni and Fe were observed to have lower liquidus temperatures. Compositions using 40 wt. % Mn with over 26 wt. % Ni were observed to have a sharp decrease in carbon solubility. Therefore, alloy with low liquidus temperature and high carbon solubility was observed for composition of 40 Mn-30.5 Fe-26 Ni-3.5 C having a liquidus temperature of 982° C. as shown inFIG.17. The data show that the best candidates to alloy with Fe and C in the anode were observed to be: Mn, Mo, Ni, and Sn. High throughput calculations of the Fe—Mn—Ni—Si—C system were performed.FIG.18. Using step size of 2.5 mol. %, 6280 combinations of alloys were tested from 0-20 mol. % of Mn, Ni, Si, and C. The best candidate alloy was observed to be 52.3 Fe-22.6 Mn-20.9 Ni-4.2 C which had a liquidus temperature of 1050° C. The carbon solubility as a function of liquidus temperature from these combinations is visualized inFIG.23. A second round of high throughput calculations were performed using with a step size of 0.5 mol % to find similar compositions with lower liquidus temperatures. 5441 additional compositions were generated, with the optimal composition containing 51.7 Fe-20.3 Mn-24 Ni-4 C showing a liquidus temperature of 1031° C. With the knowledge gathered from this research, four anode alloys were examined in an experimental high-temperature apparatus mimicking the proposed DCFC design. Approximately 900 g of each alloy was measured and placed in an alumina crucible, then melted using a Sentro-Tech ST-1600C-445 induction box furnace at a temperature of 1500° C. for 1.5 hours under atmospheric conditions. To prepare the slurries, components were weighed and mixed overnight by ball milling with 4 mm diameter alumina media. TABLE IIAnode alloys for DCFCAlloyAlloyCalculated compositionCalculatedNo.systemFeMnNiSnMoSiCliquidus ° C.1Fe—Mn—6610——20—410362Fe—Mn—37.530—30——2.5—3Fe—Mn—3040.526———3.59824Fe—Mn—12.976———101.11000 Mass Balance An attractive characteristic of DCFCs is their ability to operate on a variety of carbonaceous fuels. In some embodiments of the DCFC design, impurities from the fuel are expected to be present in the anode alloy as a slag layer or dissolved in the amorphous liquid phase. To better understand the amount of impurities that may accumulate in a commercial version of this cell, a 22-element mass balance was created for 13 different types of carbonaceous solid fuels. Fuel composition was obtained for fuels such as coal, to biomass, to off-specification building materials and charcoal. TABLE IIICompositions of solid carbonaceous fuelsAshPure elements (wt. % of total)Fuel(wt. %)CHNSOClCoal12.570.084.791.510.5910.520.01Pine chips5.9549.665.670.510.0838.070.06Corn straw7.6544.735.870.60.0740.440.64Rape straw4.6546.176.120.460.1042.470.03Biomass Mix12.4949.595.792.430.7428.870.09Pressure31.7948.317.631.03011.190.05ground woodB-Wood1.8550.376.931.03039.750.07Palm kernels5.1448.236.192.610.2637.360.21Olive Res.7.1754.125.361.280.2131.660.20Pepper plant14.4436.114.262.720.4941.860.13Chicken litter37.7937.384.193.760.7415.640.50Meat and23.9543.076.049.161.2715.640.87Bonemeal (MBM)Charcoal4.2757.33.1601.530.000.10 CO/CO2Formation Ratio as a Function of Temperature The mass balance starts by determining the amount of carbon available for the electrochemical reaction. On a per unit mass basis, fuel added to the system was multiplied by the wt. % carbon reported for the fuel type. The amounts of CO and CO2can be calculated accurately by considering the formation of CO and CO2as a function of temperature. The direct and indirect carbon oxidation reactions that occur in a DCFC are as follows: C+O2—→CO+2e−[1] CO+O2—→CO2+2e−[2] C+CO2→2CO [3] 2CO+2O2—→2CO2+4e−[4] At atmospheric pressure the ratio of CO/CO2is equal to around 690° C. Above this temperature, CO formation in [1] is favored, which is undesirable in a DCFC because only two electrons are exchanged per molecule of carbon fuel rather than four as shown in [6]. O2+4e−→2O2− [5] 2O2-+C→CO2+4e−[6] Additionally, CO produced can react with carbon in the anode via the chemical (rather than electrochemical) reaction, known as the reverse Boudouard reaction. This is detrimental to fuel cell performance since it uses carbon in the anode without contributing to cell voltage. The best way to avoid losses associated with CO formation is to operate the cell below the temperature at which equation [3] becomes energetically favorable about 700° C. For an electrochemical cell operating above this temperature, CO2generated from equations [6], [1], [2], and [4] can be purged from the anode chamber to mitigate performance losses from equation [3]. Considered as a partially reacted fuel, CO that leaves the cell with CO2exhaust could be used in a downstream SOFC to improve system efficiency. CO/CO2equilibrium ratio as a function of temperature was calculated based on Gibbs Free Energy (ΔG) of each reaction. The CO2reaction is desirable in the DCFC because four electrons are exchanged per mole of carbon reactant compared to two electrons in the CO reaction. By increasing pressure, the temperature at which CO/CO2evolution is in equilibrium is elevated almost 100° C. shown inFIG.19. Calculating Products from Reactions within the DCFC With the CO/CO2equilibrium data, mass of each product evolved at a specific DCFC operating temperature considering the mass of carbon available, Cm, in a specific fuel type. Cm=mfuelintroduced*wt.%Cinfuel[7]CO=%COevolvedCmMC/MCO[8]CO2=%CO2evolvedCmMC/MCO2[9] Where Mi is the molar mass of species i. The approach used to calculate CO and CO2produced from carbon wt. % in the fuel was also used to calculate oxides of aluminum (Al2O3), calcium (CaO), sulfur (SO2), and silicon (SiO2). For this mass balance it was estimated that 80% of these elements within the fuel would react to produce slag (oxides) with the remaining 20% dispersed in the anode. Total mass of oxygen required for the system was calculated using the formula below: Om,total=ΣOReq. for oxides−Om[20] Total air required for the reactions was calculated by dividing Om, total by the wt. % of oxygen gas in air at 1 atm and multiplying by a factor (e.g. 50%) to account for only a fraction of the oxygen introduced actually taking part in the formation of oxides. Remaining oxygen exits the cathode tube in a nitrogen-rich gas stream. Effects of impurities in the fuels accumulating within the liquid anode alloy include an increase in liquidus temperature and a reduction in carbon solubility, both of which are detrimental to overall DCFC performance. Of all the metals present in these fuel sources, Fe was considered to have the biggest impact on the alloy liquidus temperature due to its high melting point (1536° C.). Al and Ca have liquidus temperatures below (660° C. and 842° C., respectively) the anode alloy, while the amount of Mn present was negligible. Accumulation of Fe causes the anode alloy liquidus temperature to increase, forcing the cell to operate at a higher temperature with associated performance penalties. (wt.%)additionalFeinalloy=wt.%Feinfuel(mfueladdedmalloy,total)where:malloy,total=mfueladded+manodealloy[11] Increasing Si content reduced carbon solubility within the Mn—Fe—Si—C system. Amount of Si dissolved in the anode alloy was determined by: wt.%Siinfueldissolvedinalloy=1-(wt.%Siinfuel*%Sitoslag)[12]wt.%Siinalloy=wt.%Siinfueldissolvedinalloy(mfueladdedmalloy,total)[13]malloyremoved=wt.%contaminedmalloy,totalif:wt.%Siinfueldissolvedinalloy>wt.%Feinfuel,wt.%contaminated=wt.%Siinalloyif:wt.%Siinfueldissolvedinalloy<wt.%Feinfuel,wt.%contamined=wt.%additionalFeinalloy[14] Make-up elements required were determined by the composition of the anode alloy and amount removed. Carbon from the incoming fuel is used to replenish the mass of carbon removed with the contaminated alloy, with [7] becoming: Cm=(mfuel introduced*wt. %C in fuel)−(malloy removed*wt. %C in alloy) [15] The resulting flow diagram for a commercial DCFC is shown inFIG.20. The values shown are for steady state operation. In some embodiments, the anode alloy and slag is removed periodically with fuel and make-up elements introduced via loss-in-weight feeders at corresponding interval to keep the mass of the system in equilibrium. With the mass balance complete, fuel types are ranked based on their suitability for the device. The most economical carbonaceous fuel is one that offers the highest carbon content with the smallest amount of impurities. Higher carbon content allows for more reactant to enter the cell and reduces storage volume and transfer cost per unit mass of fuel. Impurities in the fuel contribute to slag buildup in the feed chamber and contaminated anode alloy, both of which should be reduced as much as possible.FIG.21shows an analysis of the carbon content, ash/slag produced, and make-up alloy required using each fuel type with the 40 Mn-30.5 Fe-26 Ni-3.5 C alloy. Therefore, B-grade wood, palm kernels, and olive residue are the best fuel choices for this alloy, providing the best ratio of carbon content to impurities per unit mass. Energy Balance To forecast the performance of this design, an energy balance was performed. First, enthalpy (H) and entropy (S) for each species was determined via the Shomate Equation with constants obtained from the National Institute of Standards and Technology (NIST) Chemistry WebBook, SRD 69. The data were used to calculate available free energy (G) of a species from 25° C. to 1300° C. at a specified pressure via the following equation: G(p,T)=H−TS[16] With these data obtained for C, O, CO, and CO2, change in Gibbs free energy (ΔG) was calculated using [19], [19a], and [19b] for each of the following reactions below: C+O2→CO2[17] C+½O2→CO [18] ΔG=ΔH−TΔS[19] ΔH=mol.prod.Hprod−(Σmol·i Hi) [19a] ΔS=mol.prod.Sprod.−(Σmol·i Si) [19b] Theoretical voltage of each reaction was calculated across the temperature range using the Nernst equation, which correlates the reduction potential of an electrochemical reaction to electromotive force, E, with units of volts. E is related to ΔG under standard conditions by: ΔG0=−nFE0[20] Where n is the number of electrons transferred in the reaction (2 for CO and 4 for CO2) and F is the Faraday constant, equal to ˜96485 C/mol. Given that the DCFC experiences non-standard conditions due to increased pressure and temperature to improve performance, these conditions are accounted for in the calculation of ΔG for the DCFC energy balance. ΔG=ΔG0+RTln(Q) [21] Substituting expression from [20] for ΔG in [21] and solving for E results in: Eth=Eo-RTnFln(Q)[22] With Q being the reaction quotient, a value that relates quantities of products and reactants in the overall reaction. Here Q was calculated using the partial pressure of oxygen gas from the incoming air and partial pressure of CO or CO2produced as a function of DCFC operating temperature per the reverse Boudouard reaction. QProduct=pO2pProduct(T)[23] Due to the wide range of temperatures that promote both CO and CO2production, total theoretical cell voltage was calculated by multiplying the theoretical voltage of each product by its fraction evolved, shown in [24]. Eth,total=(Eth,CO*% CO evloved)+(Eth,CO2*% CO2 evloved) [24] Current density and power density were then determined using theoretical voltage values for the CO and CO2reactions and properties of the solid electrolyte. Conductivity and resistance values for three potential solid oxide electrolyte materials (YSZ, ScSZ, and SDC) were incorporated into the energy balance. Overall resistance of the electrolyte was calculated via dividing thickness by resistance per unit area: rel.=telectrolytekelectrolyte[25] Current density is the quotient of Eth and rel. as shown below. j=Eth,totalrel.=[Acm2][26] Power density, Pe, was calculated using Eth, total,j, and number of electrons transferred per mole of oxygen. Pe=Eth,totaljn[27] Losses in an Electrochemical Reaction Actual cell voltage is lower than the theoretical value due to losses present in the cell, including ohmic, concentration, and activation polarization (Kakac et al. 2007). Vactual=Eth,total−losses [28] Ohmic polarization accounts for the resistance encountered by electrons as they move through the fuel cell's electrodes. This can be expressed as: ηohm.=j(ASRohm.) [29] Where ASRohmis the area-specific resistance of the cell, and includes ionic resistance of the electrolyte, electronic resistance of the electrodes, and some contact resistance associated with the interfaces between cell components. Examining the electrolyte interfaces at a micro scale there exists a gradient in reactants on the anode and cathode sides. As reactants are combined and carried away (via buoyant force), the concentration of reactants at the electrolyte interface decreases. In a steady state condition, more reactants are continually transported from the bulk to the electrolyte reaction interface, moving from a region of high concentration in the bulk to the lower concentration at the interface. Concentration polarization accounts for this reduction in the concentration of reactants at the electrolyte surface as the reaction proceeds and was calculated using the equation [30] ηcon.=RTnF(1-1n)ln(jLjL-j)[30] Where jLis the limiting current density. This is defined as the minimum flux (the amount of a species flowing through an area, in this case the electrolyte surface) of carbon from the anode and oxygen ions from the cathode to the surface. For the anode, the limiting current density was calculated by: jL,anode=nFJ=nF(DCinmaj.ρmol.,CL)[31] Where D is the diffusivity of C in the major constituent of the alloy and ΔC is the molar density of C in the liquid alloy. The boundary layer thickness, L, was estimated to be 100 μm in the liquid anode. For the cathode, limiting current density was calculated using: jL,cathode=nFJ=nF(ρmol.,O2DO2inN2tcathode)[32] Activation polarization accounts for the portion of energy required to overcome an activation barrier which allows the electron-exchanging reaction to occur. This energy comes from a portion of the reaction voltage generated, decreasing actual cell voltage. The activation polarization is defined as: ηact.=2RTFln[12((iio)+(iio)2+4)][33] Where i0is the exchange current density, a measure of the electrocatalytic activity at the triple phase boundary (the electrolyte-liquid anode interface where O2— reacts with C to produce CO2) and quantifies the rates of reactions at the anode and cathode. Exchange current density is determined by curve fitting empirical voltage data as a function of current density. Without such data, ηact. was omitted from this energy balance. Other Losses Voltage calculated refers to that produced by the anode, cathode and electrolyte arrangement in a single cell. To achieve a desired voltage, many cells can be connected by electrical leads. Using terminology taken from planar fuel cell arrangements, this setup is called a fuel cell stack. Thermal energy lost through the leads can be mitigated by using a material with low thermal conductivity, but the same material will also have low electrical conductivity since thermal and electrical conductivity are coupled through the Wiedmann-Franz law. The voltage drop per lead can be calculated from the minimum total energy lost due to resistance and thermal energy shown below. Vel=2√{square root over (LelTΔT)}where: T=operating temperature ΔT=T−Tambient[34] Some heat from the DCFC is required to raise the temperature of reactants as they enter the device. Heat [kJ/mol] required for incoming air and present in the cathode air exhaust was converted to volts via [20] using the expression below: Vgas,in=(mol.air,introduced/mol.O2inair)Cp,airΔTnF[35]Vgas,out=Vgas,in(mol.air,exhaust/mol.O2inexhaust)[36] The amount of heat lost by the cell is reduced by using waste heat from the exhaust gas to heat incoming air. Industrial heat exchangers used in such applications are referred to as economizers and reach heat transfer efficiencies, ε, up to 90% (Lindeburg, 2020). Using this factor, total heat lost due to the incoming ambient air stream is: Vair=Vgas,in−(1−ε)Vgas,out[37] Energy required to heat incoming solid fuels are similarly reduced by using the CO/CO2exhaust gas stream in a heat exchanger. During operation, heat radiated from the DCFC unit to the surrounding air also contributes to thermal losses. These losses are negligible compared to the thermal and electrical losses calculated and therefore were omitted from the analysis. Overall cell efficiency was calculated by subtracting thermal losses from the heat produced, ΔH, from the CO/CO2reaction at a specified operating temperature. Efficiency=ΔHtotal-Vel-VairnF[38] Modified DCFC Evans Diagram A plot showing the relationship between electric potential and current density is called an Evans diagram. Such a plot is often adapted to show performance of a fuel cell by including power density values as a function of current density on a second vertical axis. Using this format, values obtained from the energy balance are presented for the proposed DCFC operating at 800° C. inFIG.22, with operation at 1000° C. shown inFIG.23. Performance characteristics are dependent on a number of variables, with their values listed in the dashboard at the top of the plot. As current density varies from its minimum to maximum (the limiting value dictated by the anode, cathode or electrolyte), actual cell voltage decreases to zero. Since power density is the product of voltage and current density, it exhibits a parabolic shape with its highest value corresponding to the ideal cell operating condition. Zeta Potential Characterization Two types of zeta potential testing were performed: pH sweeps and surfactant concentration sweeps. For both methods, a 2% wt dispersion of analyte powder in deionized (DI) water was prepared, and then sonicated for 5 minutes and about 12 kJ of energy with a Misonix S-4000 Sonicator. The sonicated dispersion was transferred to a Colloidal Dynamics ZetaProbe. For pH sweeps, the basic titrant was a 0.5M KOH solution and the acidic titrant was a 0.5M HNO3 solution. For surfactant concentration sweeps, the titrant was a 10 wt % solution of Dolapix CE-64 in DI water. Rheology Characterization A Discovery HR-1 rotational rheometer from TA Instruments was used for the rheology. It was equipped with a 2° cone and plate geometry. The method included a constant shear rate of 1 s-1. This low shear rate was selected to represent the shear on the drying slurry due to gravity and is common for ceramic slip characterization. The test lasted either 1 or 2 minutes. Slip Casting Pottery plaster #1 was purchased from the United States Gypsum Company. Plaster and DI water were mixed in a mass ratio of 10 to 7. The plaster was poured into a plastic container case mold and a 1″ diameter aluminum rod was suspended in the plaster as it dried as shownFIG.24. Once the plaster dried, the rod was removed, leaving a negative space into which the slip was poured for casting. In an alternative embodiment, the plaster was prepared in the same way and then poured into smaller case molds and allowed to dry. Then, a shallow tube was drilled into the plaster with a ball-end router tool, which is shown inFIG.25. This method has the advantage of creating a cavity with a hemispherical bottom which minimizes stress concentrations due to shrinking while drying and sintering, compared to flat-bottomed cylindrical molds. A shallow bevel was cut around the edge of the hole with a utility knife so that the cast part would have a flange from which it could be hung during the dip coating process. During casting, the cavity was constantly refilled with slip as the water was absorbed into the mold. The casted part was left to dry in the mold overnight or until it had dried enough to pull away from the mold and be easily removed. Casting time was on the order of minutes but was varied as a parameter of study. A successful cast did not crack, released well from the mold, and had sufficient green strength for further processing. Cast slip was not recycled because it was found that recycled slip cracked in the mold when recast. This is likely due to the faster drying rate of cast slip due to its higher solids content. The increased solids content is the result of the water being drawn out by the mold during casting, before the excess slip is recycled back into the container for re-use. Porosity Characterization by Archimedes Method Density of fired parts was measured by the Archimedes method. In this method, the dry weight wdryof a fired part is measured, and then the part is dipped in a tank of molten paraffin wax until it is well coated. The waxed weight wwaxedis recorded. Then the coated sample is submerged in water and the submerged weight wwetis recorded as well. The density of the part ρ is calculated as ρ=wdrywwaxed-wwet-(wwaxed-wdryρwax)[39] The porosity of the part, p, may then be calculated as p=1-ρρtheoretical[40] Dip Coating of Cathode and Electrolyte The cast LCM support, once removed from its mold, was first thoroughly dried in an Across International CF-1700 muffle furnace at 50° C. for 30 minutes. This drying step increased the green strength of the cast. While the cast was drying, the cathode and electrolyte coating baths were prepared. Initially, the coating bath was a 40 mL beaker. Later, to accommodate longer parts, a 250 mL graduated cylinder was used. The appropriate coating slurry was stirred and then transferred to the coating bath slowly to prevent air entrainment. The dried support was held with tweezers, dipped into the coating bath, withdrawn, and then hung by its flange on a wire holder. The coated parts hanging in their holders are shown inFIG.26AandFIG.26B. The wire holders were made by bending stainless steel wire into the appropriate shape. The part was left hanging on the holder until the most recent coating was dry to the touch. Firing An Across International CF-1700 muffle furnace equipped with a B type thermocouple was used for firing of all samples. Samples were lay-fired in the tray which is designed to maintain the roundness of the tube as it shrinks during sintering and produce a tube of uniform sintered diameter. Two firing programs were used, depicted inFIG.27andFIG.28. Curve #1, depicted inFIG.27, is used for sintering support samples only. The 2 hour hold at 300° C. is designed to burn out the cellulose pore former and the dispersant. Curve #2 adds a 1 hour hold at 700° C. to burn out the carbon black pore former in the cathode layer. Both curves share a common 2 hour hold at 1300° C. to sinter the part. This temperature is selected to produce a fully densified electrolyte while preventing the support from over-sintering. In addition, a small amount of nanoalumina is used in the electrolyte layer as a sintering aid. Over-sintering of the support is not desirable because too much densification would result in closing the open porosity which is required to deliver oxygen to the cathode, where it is ionized. SEM Imaging Before imaging, the part is sectioned with an abrasive saw to produce a flat surface. Then, a mixture of 3 parts Buehler EpoxiCure 2 Epoxy Resin to 1 part Buehler EpoxiCure 2 Hardener is prepared. The sectioned part is mounted in a mold and the mold is filled with the epoxy mixture. The filled mold is held overnight under vacuum in a vacuum desiccator. The cured pucks are removed from the mold and polished with a Buehler AutoMet 250 polishing machine with an appropriate method and abrasives. The polished samples are examined with a Hitachi TM3030 scanning electron microscope (SEM) operating at 15 kV acceleration voltage in backscatter detection mode. Alloy Preparation Alloy 1, described in Table II, was used as the anode. It was prepared by adding the component metals to a crucible and melting until combined. A 2000 g batch of components was prepared, mixed, and divided into four 500 g samples. Each sample was placed in a fireclay crucible surrounded by the heating elements of an Ambrell EasyHeat 8310 LI heater. Another fireclay crucible was placed, inverted, atop the one containing the sample. The top crucible had a port for the argon lance which delivered argon gas at a flow rate of about 4 L/min for the duration of the process. It also contained a viewport so that temperature could be measured by pyrometer. The alloy was heated to about 1400° C. for about 5 minutes. Once melted and cooled, the 500 g samples were cut into approximately cubic chunks, about 1 cm on a side, with an abrasive saw. Apparatus Description and Preparation The apparatus was a Mellen induction furnace with a customized testing insert comprised principally of a platform suspended by threaded rods from a flange. The flange is removable and rests upon a steel pipe set vertically into the furnace. Through the flange are the necessary couplings for thermocouples, inert gas feed, electrolyte tube, and fuel/current collector rod. The apparatus is shown inFIG.29. Ceramabond 503 ceramic cement from Aremco was used to affix the cathode-electrolyte structure to the end of a 1″ diameter open-ended mullite tube. The mullite tube is necessary to provide mechanical support to the cathode-electrolyte structure as it hangs from the flange in the furnace. This assembled structure was inserted through the flange and suspended about lcm above the bottom of an alumina crucible which rested on the bottom plate of the testing insert. Through the other hole in the flange a graphite rod was inserted and hung similarly in the crucible. The graphite rod acted as both the fuel source and the anodic electrical contact. The chunks of anode alloy were piled around the cathode-electrolyte structure in the crucible. A length of Kanthal wire was inserted into the mullite tube until it made contact with the inside of the cathode-electrolyte structure. This served as the cathodic electrical contact. The testing insert was lowered into the furnace and sealed. Argon gas was injected into the furnace through the flange at a flow rate sufficient to maintain less than 0.5% oxygen in the testing chamber. Air was injected into the mullite tube through a nozzle to provide the cathode with oxygen atoms for ionization. Apparatus Operation and Measurement The furnace was heated to 950° C. at a rate of 10° C./min, and then to 1000° C. at a rate of 2° C./min. The open circuit voltage (OCV) was measured by handheld multimeter at the kanthal wire extending from the cathode and at the graphite rod extending from the anode. Fabrication Process Overview A simple description of the fabrication process for the cathode-electrolyte structure is: the support/current collector is slip casted, dried, the cathode is dip-coated, dried, the electrolyte is dip-coated, dried, and fired. While each step was developed with the preceding and following steps in mind, minor steps were added and removed as necessary for development. Notably, the firing and drying steps were moved and modified as development progressed. Active Material Choice LCM is used for the current collector to maximize electrical conductivity and minimize thermal expansion mismatch between the layers of the structure. A blend of LCM and YSZ is used in the cathode to create a shallow thermal expansion coefficient gradient between the current collector and electrolyte, again minimizing thermal expansion mismatch. YSZ is used in the electrolyte because it is widely used in solid-oxide fuel cell (SOFC) technology for its high oxygen ion conductivity. In addition to matching thermal expansion coefficients to prevent delamination during cell heat-up and operation, these materials have similar sintering shrinkages, allowing them to be co-fired. Further, minimal chemical interaction between layers is observed for LCM and YSZ in this configuration. LCM powder with 5% A-site deficiency, 20% Ca dopant, and surface area of 5-8 m2/g was purchased from Nexceris as a custom order. A-site deficient LCM is selected because such deficiency lowers the sintering temperature, increasing co-firing compatibility with YSZ. YSZ powder containing 8 mol % yttria and having a surface area of 1-3 m2/g (part number 312008) was also obtained from Nexceris. YSZ with 8 mol % yttria is selected because it is fully doped, maximizing the oxygen ion vacancies and therefore the ion transport in the electrolyte. Water was chosen as the solvent for all three slurries, because environmentally friendly solvent is always the better option. The LCM was first characterized by pH sweep and the results are given inFIG.30. LCM in water does not reach a ZP of ±40 mV at any reasonable pH. This indicates that a surfactant was required to ensure stable dispersion of the LCM in water. Since LCM in water does not have a strong positive nor negative charge, either a cationic or anionic surfactant may be employed. The anionic dispersant Dolapix CE-64 from Zschimmer & Schwarz was selected. Next, a new sample was characterized by surfactant concentration sweep. The data is plotted as a function of mass ratio of active surfactant material to LCM so that it may be used to guide formulation. These results are shown inFIG.31, which confirms that Dolapix CE-64 is a strong anionic dispersant in this system. However, though it has a strong influence on ZP, pH was measured but not controlled. To account for this, the ZP vs pH data inFIG.30is used to adjust the data inFIG.31for pH. First, a polynomial line of best fit is fit to the ZP vs pH data. This model is used to calculate, for each point of the ZP vs surfactant mass ratio data, what the ZP would be at the relevant pH without any surfactant. Finally, the pH-corrected ZP of the LCM at various surfactant mass ratios is calculated as ζcorrected=ζ−ζequivalent pH The corrected ZP is shown inFIG.32. From these data, it is evident that a surfactant-to-powder mass ratio of 6% provides good electrostatic stabilization and prevent agglomeration, so this was taken as the target for formulation. The same process was followed for calculating the optimal dosage of surfactant in the YSZ electrolyte slurry. The zeta potential of YSZ as a function of pH, as a function of surfactant concentration, and as a pH corrected value are shown inFIG.33,FIG.34, andFIG.35, respectively. The curve inFIG.35shows that a ZP of −40 mV is not achievable with a reasonable amount of Dolapix CE-64 in this system. In addition, there is no significant benefit to increasing the surfactant-to-powder ratio beyond 1%, so this is taken as the target for formulation. TABLE IVGeneral formulation of the LCM support.MaterialPurposeAmountLaCaMnO3 (LCM)Active material20-40 wt % on total wet weightDolapix CE-64Dispersant6 wt % on weight of LCM20 μm cellulosePore former50 vol % on dry volumePVABinder0-2 wt % on total wet weightDI WaterSolvent50-70 wt % on total wet weight 20 μm cellulose was chosen as the pore former to maximize gas flow through the support for good cell performance. The cellulose was obtained from Sigma Aldrich (part number 310697). PVA was used as the binder as it is commonly used in slip casting to give good green strength at low concentrations. Too little binder gives poor green part strength, but too much binder increases viscosity to the point of processability issues. Therefore, the level must be carefully controlled. Samples with 0, 0.25, and 0.5 wt % binder on weight of active powder were formulated and cast. Samples were made with Lanthanum Strontium Manganite (LSM), instead of LCM, due to temporary unavailability of LCM. The LSM was also obtained from Nexceris (part number 121101) and has properties similar to LCM. It should also be noted that these samples did not contain pore former. All samples released well and had adequate green strength. However, the low binder sample had noticeably thinner walls at the top than the bottom. This is an indication that the viscosity of the slurry was too low and that the cast slumped during drying. For each sample, the thickness of the walls was measured at the top and the bottom of the part and the difference divided by the height of the part was reported as taper. Low taper is desirable because uniform wall thickness is expected to lead to uniform cell performance. The rheology of each sample was measured, and the results are shown inFIG.36. Interestingly, the low binder sample displays higher viscosity than the medium binder sample over much of the time of the test. However, from the taper measurements, the low binder sample slumps more than the medium binder sample during drying. It is here envisioned that because samples dry quite quickly in the mold, only the rheology at very short times is relevant. The viscosity of the low binder sample is lower than that of the medium binder sample until the 10 second mark. The crossover in viscosity at 10 seconds is likely due to a thixotropic effect. Therefore, for samples with no pore former, 0.25 wt % binder on weight of active powder is enough to give adequate viscosity to avoid slumping in the mold. This same level of binder gives adequate green strength. The next set of samples were formulated to 77 dry volume % cellulose because it was expected that they would densify to the 50% target during firing. These samples were similarly sent through 1, 2, and 3 firing cycles. As expected, the samples densified to about two-thirds of the formulated porosity, reaching the target of 50%. The porosity did not change after multiple firing cycles. Unfortunately, the samples cracked in the mold during drying. A target of 50% porosity was chosen. Samples formulated to 50% dry volume of cellulose were cast. They released well from the mold and had adequate green strength. These samples were sent through 1, 2, or 3 firing cycles to determine if multiple firing cycles would significantly alter the porosity. The data show that multiple firing cycles do not dramatically alter the porosity of the LCM support, but that only about two-thirds of the formulated porosity is achieved after firing. Additionally, processing the slurry formulated to 77% porosity presented difficulty. Filtering out the mixing media was difficult due to the high viscosity. The 77% porosity sample's viscosity is approximately an order of magnitude higher. This high viscosity also led to problems during casting. Nevertheless, in order to achieve the target porosity, 3 more samples were produced with higher binder to powder ratios. It was here envisioned that more binder in the dry cast would provide additional green strength, preventing cracking. Any additional green strength gained from the additional binder was not sufficient to prevent cracking. With options for fabricating supports with 77% formulated porosity exhausted, a ladder study to determine the maximum formulated porosity was conducted. Samples were formulated to 50%, 58%, and 67% porosity and then cast. The sample formulated to 50 dry volume % pore former was the only one which did not crack in the mold. The broken pieces of each sample were fired and their density was determined by the Archimedes method. The trend of achieving about two thirds of the formulated porosity after firing continued. As a result, 50% formulated porosity was accepted as the maximum for this work. The initial formulation for the cathode slurry is given in Table VI. The final formulation of the LCM support is given in Table V. This formulation was used for the remaining examples. TABLE VThe final formulation for the LCM support.Wt %LCM40.06%Dolapix CE-644.01%Cellulose3.69%PVA0.80%DI Water51.44% TABLE VIThe initial formulation for the cathode slurry.Wt %LCM17.51%YSZ17.51%Dolapix CE-642.89%Carbon black14.49%PVA0.93%Water46.68% The weight ratio of LCM and YSZ is kept to 50-50 so that the thermal expansion and sintering shrinkage of the LCM support and the YSZ electrolyte remain compatible. The Dolapix dispersant was used at a concentration of 4 wt % on weight of active powder to account for the fact that the LCM requires 6% and the YSZ requires only 1%. The initial amount of PVA binder was 2 wt % on weight of water, which was the maximum recommended. The maximum was selected to give a high viscosity which will prevent settling in the slurry. The amount of carbon black was selected to give 40% porosity, as this level of porosity has been shown to give good performance in tubular SOFC cathodes. Two grades of carbon black from Cabot, Regal 250R and ELFTEX 320, were tested in the cathode slurry. Both grades have an average primary particle size of 5 μm. The Regal 250R is powdered while the ELFTEX 320 is pelletized. The ELFTEX 320-containing slurry processed well. The slurry using Regal 250R was too viscous and did not mix well overnight in a ball mill. It was diluted and remixed per the formulation in Table VII. TABLE VIIFormulation for the cathode slurry using Regal 250R carbon black.Wt %LCM13.68%YSZ13.68%Dolapix CE-642.26%Carbon black11.32%PVA0.73%Water58.35% Small samples of both the remixed Regal 250R slurry and the ELFTEX 320 slurry were slip cast and fired, and their porosity was determined with the Archimedes method. The fired porosity of the cathode samples was observed to be high compared to that of the LCM support. One possible explanation for this is that the YSZ is not fully sintering in the samples without nanoalumina sintering aid, even though YSZ densification is possible at 1300° C. To confirm this, a sample with 1 wt % nanoalumina on weight of YSZ was formulated and fired. Further densification was observed in this sample, though still the final porosity was higher than expected with the LCM. This is evidence that the firing program used is well-designed: with the help of a sintering aid, it can barely densify the YSZ components without removing desirable porosity from the LCM components. Lack of densification of the cathode is desirable because the performance of the cell does not depend upon the density of the YSZ in the cathode, as it does the YSZ in the electrolyte. The final cathode formulation was tweaked to use less PVA binder to reduce viscosity, and to use Regal 250R as powdered carbon blacks are more common and available. The formulation is described in Table VIII. TABLE VIIIFinal cathode slurry formulation.Wt %LCM13.68%YSZ13.68%Dolapix CE-642.26%Carbon black11.32%PVA0.73%Water58.35% TABLE IXGeneral formulation of the YSZ electrolyte slurry.Wt %YSZ30-60%Dolapix CE-640.33%PVA1.17%Nanoalumina0.35%Water68-38% The general form of the YSZ slurry is given in Table IX. The PVA binder amount was held at 2 wt % on weight of water to impart some viscosity. The nanoalumina was held at about 1 wt % on weight of YSZ. The purpose of the nanoalumina is to decrease the temperature at which the YSZ sinters. The nanoalumina powder was obtained from Sigma-Aldrich (part number 544833). It is important to use a sintering aid in the YSZ formulation to fully densify the electrolyte without over-sintering the LCM support or the LCM/YSZ cathode. Over-sintering of the support or the cathode would be problematic because it would reduce the oxygen flow to the cathode, limiting the cell's performance. Since electrolyte density is critical to cell performance as well as mechanical integrity, the porosity electrolyte material was characterized by the Archimedes method. Initially, small samples were slip cast as was done with the cathode slurry. However, the electrolyte slurry stuck to the plaster mold and could not be removed for characterization. Next, the electrolyte slurry was tape-cast at a wet thickness of 0.005 in. Excess binder was added to the formulation to ensure that it would release from the polyethylene substrate. It was expected that if the fired porosity was less than or equal to the dry volume percentage of binder, it could be assumed that a formulation with less binder would sinter to full density. Unfortunately, the film wrinkled during sintering to the degree that Archimedes density measurement was impossible. The formulation used here is given in Table X. TABLE XFormulation used for tape-casting the electrolyte slurry.Wt %YSZ28.75%Dolapix CE-641.44%PVA8.21%Water61.60% The conclusion was that the electrolyte layer must be characterized in situ. To that end, a YSZ slurry at 14 vol % total solids was prepared. A support was casted, dried, and the cathode and electrolyte layers were dip coated onto it and dried. This electrolyte slurry produced a very thin coating, so it was dipped and dried twice. The resulting structure was fired and then imaged in cross-section in an SEM. The images gathered are shown inFIG.37andFIG.38. The target thickness for the electrolyte layer was 20 μm.FIG.37shows that with two dips of this electrolyte slurry a thickness of 40 μm was achieved.FIG.38shows the two distinct layers of YSZ and a band between them where the first coating, which had dried, mixed with the second coating when it was applied. It also shows that the electrolyte is almost fully dense after being sintered with firing program #2. One option is to use only one dip of this slurry to achieve a 20 μm thickness. However, the slurry settled quickly due to its low viscosity. The solids loading of the slurry was increased to produce a more stable slurry without dramatically increasing the thickness of the electrolyte. YSZ slurries with total solids loadings of 20 and 26 vol % were formulated. The rheologies of the YSZ slurries at 14, 20, and 26 vol % solids are shown inFIG.39. The expected trend of viscosity increasing with solids loading is seen. Interestingly, no thixotropy is seen. Since viscosity increases with solids loading, wet film thickness will increase as well. Therefore, the increase in thickness of the dry electrolyte film is of the order2, because a thicker wet layer is deposited, and the film loses less material upon drying. The increase in viscosity was marginally successful at preventing settling; however, each YSZ slurry tested settled noticeably after a few days. These slurries were similarly applied (as a single dip) to support-cathode structures and imaged via SEM.FIG.40shows the electrolyte layer produced by one dip of a YSZ slurry of 20 vol % solids;FIG.41shows the electrolyte layer produced by one dip of a YSZ slurry of 26 vol % solids. Both figures show cracks in the electrolyte layer, caused during sintering, as the firing process development work was still in progress. Unfortunately, both of these thicknesses exceeded the target of 20 μm, and the slurries which produced them did not give much benefit in settling resistance. Therefore, a one dip procedure with the initial solids loading of 14 volume % was accepted as optimal for this work. The final formulation is given in Table XI. TABLE XIFinal formulation for the YSZ electrolyte slurry.Wt %YSZ39.65%Dolapix CE-640.33%PVA1.17%Nanoalumina0.35%Water58.49% Dip Coating of Cathode and Electrolyte Initially, unfired LCM support samples were hung from small alligator clips and the coating bath was raised around them. This method had two issues. First, the alligator clips put too much pressure on the unfired LCM part, causing damage. Second, the buoyancy of the support prevented the coating from reaching all the way up the wall of the part as desired. These problems were solved by moving to a new process. In this process, the LCM support is first dried in the oven at 50-75° C. for about 30 min. Then, it is held by the flange with tweezers and dipped into the coating bath before being hung by the flange from a holder. Initially it was not clear if it would be possible to co-fire the three-layer composite structure without it cracking due to differential shrinkages between layers. Neither the LCM support nor the LCM/YSZ cathode densified significantly upon successive firings, so there was full latitude in designing the firing process. On one extreme, all three layers could be co-fired; on the other, the part could be sintered three times: first as the support only, then after the cathode coating was applied, then again after the electrolyte coating was applied. The possibilities are shown inFIG.42. Method 1 represents complete serial firing, where the structure is fired after the formation of each layer. In this method, the support would experience 3 firing cycles. Method 4 represents complete co-firing, where all three layers are formed and then sintered in a single firing cycle. Methods 2 and 3 are intermediate methods, where some layers are serially fired and some are co-fired. Methods 1 and 3 failed when the structure was fired with the cathode layer exposed. In both cases, the cathode layer cracked and peeled off of the support. Since both methods 1 and 3 failed in the same way, this indicated that there was not a large difference in stress due to shrinking at the sintered support-green cathode interface versus at the green support-green cathode interface. However, it does indicate that the cathode layer is unstable if exposed during sintering. Method 2 produced a prototype with a cracked electrolyte. This result shows that there is likely a significant difference in shrinkage during sintering between the already-sintered support and the green electrolyte layer. Firing method 4, which represents full co-firing, yielded the best results. The electrolyte layer does show some pinhole defects, but these are due to entrained air in the slurry, not cracking from differential shrinkage between layers during sintering. Therefore, firing method 4, complete co-firing, was used as the firing method for producing this structure. This method gave the best quality of sintered part. In addition, this method is the least time-consuming and simplest of the possible methods which is important because manufacturability is one of the few remaining hurdles in the path towards commercializing DCFC technology. Composite Characterization by SEM Three full support-cathode-electrolyte structures were characterized by cross-sectional SEM. They are described in Table XII. The goals of the SEM analysis were to confirm the approximate porosity and pore diameter for the support and cathode, to confirm that the electrolyte layer was fully dense, and to develop a relationship between solids content and dry coating thickness for the electrolyte layer. FIG.43A-FIG.43E,FIG.44A-FIG.44E, andFIG.45A-FIG.45Edisplay the images of Cell 1, Cell 3, and Cell 6, respectively. These images show that the intended structure has been achieved. A coarsely porous support has been coated with a finely porous cathode and a fully dense electrolyte. The images confirm that the porosity in both the support and the cathode is open and allows oxygen gas to be ionized in at the cathode-air interface for good cell performance. Further, the approximate average pore size for both the support and the cathode are confirmed to match the targets of 20 μm and 5 μm, respectively. The electrolyte is shown to be almost fully dense. Cracks are present inFIG.44CandFIG.45C, but these are the result of shrinking mismatch during firing and not incomplete sintering. An insignificant amount of closed porosity, which is likely the result of the binder in the electrolyte formulation, can be seen inFIG.43C. A small amount of binder is necessary in the formulation to increase viscosity and is not expected to degrade cell performance. The thickness of the support is confirmed to match the target of 2 mm. The thickness of the cathode layer is confirmed to match the target of 40 μm. Finally, the relationship between electrolyte solids content and dry thickness is shown to be linear, and 14 vol % solids is shown to achieve the target thickness of 20 μM. TABLE XIISummary of samples characterized by SEM cross-section.SupportCathode layerPoreIntendedPoreIntendedElectrolyte layerformeraverage poreformeraverage poreSolidsSamplecontentdiametercontentdiameterloadingThicknessidentifier[vol %][μm][vol %][μm][vol %][μm]Cell 150204051420Cell 32030Cell 62640 FIG.43A-FIG.43E,FIG.44A-FIG.44E, andFIG.45A-FIG.45Edisplay the images of Cell 1, Cell 3, and Cell 6, respectively. These images show that the intended structure has been achieved. A coarsely porous support has been coated with a finely porous cathode and a fully dense electrolyte. The images confirm that the porosity in both the support and the cathode is open and allows oxygen gas to be ionized in at the cathode-air interface for good cell performance. Further, the approximate average pore size for both the support and the cathode are confirmed to match the targets of 20 μm and 5 μm, respectively. The electrolyte is shown to be almost fully dense. Cracks are present inFIG.44CandFIG.45C, but these are the result of shrinking mismatch during firing and not incomplete sintering. An insignificant amount of closed porosity, which is likely the result of the binder in the electrolyte formulation, can be seen inFIG.43C. A small amount of binder is necessary in the formulation to increase viscosity and is not expected to degrade cell performance. The thickness of the support is confirmed to match the target of 2 mm. The thickness of the cathode layer is confirmed to match the target of 40 μm. Finally, the relationship between electrolyte solids content and dry thickness is shown to be linear, and 14 vol % solids is shown to achieve the target thickness of 20 μm. Mechanical and Thermal The cathode-electrolyte structure, which is the focus of this work, maintained mechanical integrity throughout testing. Sensitivity to thermal shock was not an issue for the developed structure. After testing, the cathode-electrolyte structure was observed to be partially coated with solidified anode alloy which confirms that the electrolyte and anode were in good electrical contact during testing. The ceramic cement maintained adhesion and gas-tight sealing between the structure and the mullite support tube. Some discoloration of the electrolyte was observed, however no significant degradation after about 5 hours of operation at high temperature was observed. To discover any differences on the micro scale, two used cathode-electrolyte structures were cross-sectioned and examined by SEM. A structure which was operated at 1000° C. for about 1.5 hours is detailed inFIG.46A-FIG.46E. A structure which was operated between 1000° C. and 1100° C. for about 5 hours is detailed inFIG.47A-FIG.47E. FIG.46A-FIG.46EandFIG.47A-FIG.47Emay be compared toFIG.44A-FIG.44E, which is a cross-section of an unused structure. Differences between the unused structure and the structure which was operated for 1.5 hours are minimal if any. There is perhaps some slight roughness in the outer edge of the structure operated for 1.5 hours. The structure which was operated for 5 hours shows some noticeable differences on the micro scale. Most significant is that the cathode-electrolyte interface is less sharply defined. This may be the result of reaction between the YSZ and LCM, or diffusion of the calcium dopant from the lanthanum manganite into the zirconia. Finally, a slight roughening of the outer edge of the electrolyte is also seen. Complete melting was achieved in the anode alloy. The graphite rod used as the anode current collector was verified to be in good electrical contact with the anode because it too was coated in metal after testing. First, the open circuit voltage (OCV) of the system was measured at 1000° C. OCV measurements over 30 minutes of operation are described inFIG.48. These data are important because they establish that the cathode-electrolyte structure is maintaining structural integrity. The electrolyte coating provides a robust enough separator that the circuit does not short and that the injected oxygen gas does not leak out. Ethfor this cell at 1000° C. and lbar was calculated to be 1.35V. The drop in OCV over 10 minutes of operation is likely due to the carbon in contact with the electrolyte being consumed during operation, which is evidence of the cell functioning as intended. As carbon is consumed in the anode in contact with the electrolyte, the activity of carbon in this region decreases. The cell was disconnected between the 10- and 30-minute measurements; the fact that OCV remains unchanged is further evidence of carbon being consumed during cell operation, and this process pausing when the cell is disconnected. A portion of the embodiments described herein were published Jul. 8, 2021, in a thesis entitled, “High-Efficiency High Power Density Direct Carbon Fuel Cell” by Mr. Christian Faria, under the guidance of inventor Dr. Adam C. Powell, which is hereby incorporated by reference herein in its entirety. Another portion of the embodiments described herein were published December 2021 in a thesis entitled, “Development of a Support-Cathode-Electrolyte Structure for Direct Carbon Fuel Cell” by Mr. Steven Jacek, under the guidance of inventor Dr. Adam C. Powell, which is hereby incorporated by reference herein in its entirety. The inventions described herein are the most practical methods. It is recognized, however, that departures may be made within the scope of the invention and that modifications will occur to a person skilled in the art. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function, steps, and manner of operation, assembly and use, would be apparent to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present inventions. Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. | 76,057 |
11862823 | DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION Elements having the same function and mode of operation are in each case denoted by the same reference signs inFIGS.1to4. FIG.1is a schematic circuit diagram of a fuel cell system100according to the invention comprising a jet pump16, a recirculation section14and an evaporator unit11. The main medium6is conveyed from the pump12to the evaporator unit11and pressurised. The gaseous main medium6enters the jet pump16as the primary flow18downstream of the evaporator unit11. The exhaust gas8recirculated via the recirculation section14enters the jet pump16as the secondary flow20. The primary flow18experiences a pressure drop and is accelerated in the jet pump16. The secondary flow20is accelerated by the primary flow18in the jet pump16and both flows18,20exit the jet pump16mixed together. The mixed flows18,20enter the cathode section K of the regeneratively operated fuel cell stack1via the supply section7downstream of the jet pump16. Air2is delivered to the anode section A via the air supply section3. Exhaust gas8exits the exhaust gas discharge section9. If water is used as the main medium6, hydrogen-rich exhaust gas8, for example, exits the exhaust gas discharge section9. Some of the exhaust gas8is recirculated via the recirculation section14. Exhaust air5enriched with oxygen exits the exhaust air section4. A fuel cell system100designed in this manner allows for an advantageous reducing atmosphere in the supply section7of the fuel cell stack1from within the fuel cell system100itself and, at the same time, a high temperature tolerance and a high functional reliability of the components can be ensured. FIG.2is a schematic circuit diagram of a fuel cell system100according to the invention comprising a jet pump16, a recirculation section14, an evaporator unit11, a second heat exchanger22and an additional recirculation section14for recirculating exhaust air5. Building on the description ofFIG.1,FIG.2shows exhaust air5being introduced into the jet pump16via an additional recirculation section14as a second secondary flow20. This secondary flow20is, like the first secondary flow20, also accelerated by the primary flow18in the jet pump16and exits the jet pump16mixed together with the primary flow18. The embodiment of the fuel cell system100fromFIG.2also shows a second heat exchanger22for heating the gaseous main medium6upstream of the supply section7of the cathode section K of the regeneratively operated fuel cell stack1. By virtue of a second heat exchanger22arranged in this manner, the gas mixture consisting of the primary18and secondary flow20from the jet pump16can be heated to an optimal temperature for the fuel cell stack1and the efficiency of the fuel cell system100can advantageously be increased. FIG.3is a circuit diagram of a fuel cell system100according to the invention comprising a jet pump16, a recirculation section14, an air supply fan28, a first heat exchanger21, a second heat exchanger22and a recirculation fan34. As an alternative to the fuel cell systems100inFIGS.1and2, according to this embodiment of the invention, the liquid main medium6is not evaporated by means of an evaporator unit11, but rather by means of a first heat exchanger21. The liquid main medium6is then heated to a temperature just below the evaporation temperature such that main medium6evaporates on account of the pressure drop upon entry into the jet pump16, which decreases the evaporation temperature of the main medium6. As a result, the costs and effort for an evaporator unit11can be reduced to the lower costs and effort for a first heat exchanger21. An air supply fan28is advantageously provided in order to control the amount of air2in the air supply section3and/or the amount of exhaust air5in the exhaust air section4and to optimise the fuel cell system100. A recirculation fan34may be integrated in the fuel cell system100as an additional solution in order to provide an additional boost. FIG.4is a circuit diagram of a fuel cell system100according to the invention comprising a jet pump16, a recirculation section14, a first heat exchanger21, a second heat exchanger22, a first valve24, a storage volume32and an additional recirculation section14for recirculating exhaust air5. In addition to the design features of the jet pump16, the recirculation rate RR of the exhaust gas8can also be regulated by means of a first valve24. At least one additional gas or gas mixture may be supplied from a storage volume32to the primary flow18and/or the secondary flow20of the jet pump16.FIG.4shows a gas being supplied from a storage volume32to the secondary flow20of the recirculated exhaust air5. The invention allows other design principles in addition to the embodiments set out above. In other words, the invention should not be considered limited to the exemplary embodiments explained with reference to the figures. LIST OF REFERENCE SIGNS 1Fuel cell stack2Air3Air supply section4Exhaust air section5Exhaust air6Main medium7Supply section8Exhaust gas9Exhaust gas discharge section11Evaporator unit12Pump14Recirculation section16Jet pump18Primary flow20Secondary flow21First heat exchanger22Second heat exchanger24First valves26Second valve28Air supply fan30Useful gas supply section32Storage volume34Recirculation fan36Control unit100Fuel cell systemA Anode sectionK Cathode sectionRR Recirculation rate | 5,396 |
11862824 | DETAILED DESCRIPTION FIG.1is a view illustrating a configuration of a fuel cell system according to an embodiment of the present disclosure.FIG.2is a block diagram illustrating control of the fuel cell system according to the embodiment of the present disclosure.FIG.3is a graph illustrating results of the control of the fuel cell system according to the embodiment of the present disclosure.FIG.4is a flowchart illustrating a method of controlling the fuel cell system according to the embodiment of the present disclosure. As illustrated inFIG.1that is the view illustrating the fuel cell system according to the embodiment of the present disclosure, a fuel cell system according to the present disclosure includes a hydrogen supply unit100, a hydrogen discharge unit300, and a controller700. The hydrogen supply unit100is connected to the hydrogen inlet side of a fuel cell stack500. A supply valve120and a sensor130are provided in the hydrogen supply unit100. The hydrogen discharge unit300is connected to the hydrogen outlet side of the fuel cell stack500. A water trap320and a purge valve340are provided in the hydrogen discharge unit300. The controller700calculates an amount of hydrogen discharged through the purge valve340, from an amount of hydrogen supplied to the fuel cell stack500and an amount of hydrogen consumed therein. When the amount of the discharged hydrogen is at or above a reference value, the controller700performs compensation control of the supply valve120. The fuel cell system according to the present disclosure is no longer equipped with a valve that, in the related art, is required to be provided between the water trap320and an outlet of a hydrogen electrode of the fuel cell stack500, and with a water-level sensor that, in the related art, is required to be provided within the water trap320. The fuel cell system is a system based on a technology providing the great advantage of simplifying configuration and thus reducing costs and weight. Specifically, as illustrated inFIG.1, hydrogen and air are supplied to a hydrogen electrode520and an oxygen electrode540, respectively, of the fuel cell stack500. Thus, water is generated, and electric current is produced. The remaining hydrogen is discharged through the purge valve340of the hydrogen discharge unit300. Pressure needs to be adjusted to supply the hydrogen. A blocking valve110is provided to be positioned directly upstream from the supply valve120. The blocking valve110is an on/off valve. The flow rate of a fluid passing through the supply valve120is controlled through a PWM control. Therefore, according to the present disclosure, the hydrogen supply unit100is connected to the hydrogen inlet side of the fuel cell stack500. The supply valve120and the sensor130are provided in the hydrogen supply unit100. The sensor130is a pressure sensor and is provided between the supply valve120and an ejector140. A sensor150is additionally provided to measure pressure of the hydrogen electrode. The hydrogen discharge unit300is connected to the hydrogen outlet side of the fuel cell stack500. The water trap320and the purge valve340are provided in the hydrogen discharge unit300. The purge valve340is provided underneath the water trap320and has a structure where, when the purge valve340is opened, condensate water within the water trap320is first discharged due to gravity, where a flow path is formed thereafter, and where inside hydrogen is then discharged. Therefore, in a case where the water-level sensor is not provided, it is very important to precisely measure a point in time when the condensate water is all discharged and a point in time when the hydrogen starts to be discharged. To this end, the controller700calculates the amount of the hydrogen discharged through the purge valve340, from the amount of the hydrogen supplied to the fuel cell stack500and the amount of the hydrogen consumed therein. When the amount of the discharged hydrogen is at or above the reference value, the controller700performs the compensation control of the supply valve120. For reference, the controller700according to an exemplary embodiment of the present disclosure is realized as a nonvolatile memory (not illustrated) and a processor (not illustrated). The nonvolatile memory is configured to store algorithms for controlling operations of various components of a vehicle or data on software commands for executing the algorithms. The processor is configured to perform operations described blow using the data stored in the nonvolatile memory. The memory and the processor here are realized as individual chips. Alternatively, the memory and the processor may be realized as a single integrated chip. The processor may be a combination of two or more processors. As illustrated inFIG.2that is the block diagram for illustrating the control of the fuel cell system according to the embodiment of the present disclosure, feedback control is performed with a command to the supply valve120in such a manner that FP (measured hydrogen pressure) follows FP T (target hydrogen pressure) that is set according to the degree of output from the fuel cell stack500. When the flow rate of the discharged hydrogen exceeds a reference value after the purge valve340is opened to perform purging, it is possible that a point in time when purging of the condensate water is completed is determined as a point in time for purging the hydrogen. The flow rate of the discharged hydrogen is calculated by the expression “flow rate for supply−flow rate for discharge−flow rate for pressure application”. After the purge valve340is opened, from when the purging of the hydrogen is determined to when the purging is finished, the compensation control is performed with the command to the supply valve120in order to additionally supply as much hydrogen as a flow rate of the purged hydrogen. The reason for performing the compensation control is that, without such compensation, there is a likelihood that an excessive pressure undershoot will occur due to the hydrogen discharge. In addition, when the compensation control is performed too earlier after the purge valve340is opened, there is a likelihood that an excessive pressure overshoot will occur due to the compensation made in advance. Therefore, the controller700calculates the amount of the hydrogen discharged through the purge valve340, from the amount of the hydrogen supplied to the fuel cell stack500and the amount of the hydrogen consumed therein. Then, when the amount of the discharged hydrogen is at or above the reference value, the controller700performs the compensation control of the supply valve120. The amount of the supplied hydrogen is calculated from pressure of the supplied hydrogen, which is measured through the sensor130, or from the flow rate of the hydrogen. Then, the controller700calculates the amount of the consumed hydrogen from electric current that is output from the fuel cell stack500. Specifically, it is possible that the amount of the consumed hydrogen is calculated by the following equation. Amountofconsumption:I×n2F(Calculationofanamountofhydrogenconsumedduetoelectriccurrentinafuelcell) where I is electric current (a measured value) in the fuel cell, n is the number of cells (a design value) in a fuel cell stack, and F is a Faraday constant. The controller700calculates the amount of the discharged hydrogen by subtracting the amount of the consumed hydrogen from the amount of the supplied hydrogen. More specifically, the controller700calculates the amount of the discharged hydrogen from the amount of the supplied hydrogen, the amount of the consumed hydrogen, and an amount of hydrogen pressurized in the fuel cell stack500. The amount of the consumed hydrogen here is calculated from the electric current that is output from the fuel cell stack500. Specifically, it is possible that the amount of the consumed hydrogen is calculated by the following equation. Amountofconsumption:I×n2F(Calculationofanamountofhydrogenconsumedduetoelectriccurrentinafuelcell) where I is electric current (a measured value) in the fuel cell, n is the number of cells (a design value) in a fuel cell stack, and F is a Faraday constant. Then, the controller700calculates the amount of the pressurized hydrogen from internal pressure of the hydrogen electrode of the fuel cell stack500. Specifically, it is possible that the amount of the pressurized hydrogen is calculated by the following equation. Amount of pressurization:PV=nRT(Calculation of an amount of hydrogen for generating pressure for an anode) where V is a volume (a design value) of the anode, P is pressure of the anode (FP is a measured value and FP T is a target value), R is an ideal gas constant, and T is temperature (a measured value) (conversion to absolute temperature) of the anode. As described above, the amount of the discharged hydrogen is obtained as a result of subtracting the amount of the consumed hydrogen and the amount of the pressurized hydrogen from the amount of the supplied hydrogen. A point in time where the amount of the discharged hydrogen is no longer small but starts to be increased can be seen as a point in time where the condensate water is all discharged and where the hydrogen starts to be significantly discharged. That is, the controller700calculates the amount of the discharged hydrogen by subtracting the amount of the consumed hydrogen and the amount of the hydrogen pressurized in the fuel cell stack500from the amount of the supplied hydrogen. Accordingly, when the amount of the discharged hydrogen is at or above the reference value, the controller700calculates a compensation value from the amount of the discharged hydrogen and controls the supply valve120with a value obtained by adding the compensation value to a control value with which the supply valve120is controlled, thereby preventing the undershoot or the overshoot in the amount of the supplied hydrogen. As illustrated inFIG.3that is the graph illustrating the results of the control of the fuel cell system according to the embodiment of the present disclosure, when the purge valve340is opened, the condensate water is first discharged, and then the hydrogen is discharged. Therefore, it is possible that Point A where the amount of the discharged hydrogen is increased is identified from a point in time when the discharging of the condensate water is finished. Therefore, when the compensation control is significantly performed for the hydrogen that is supplied after Point A, a phenomenon where the undershoot in pressure for supplying the hydrogen occurs momentarily as indicated by Line D can be prevented. Furthermore, the overshoot, as indicated by Line C, which occurs when the compensation control is performed before Point A can be prevented. Therefore, the pressure of the hydrogen that is supplied with the control according to the present disclosure is controlled in a manner that reliably follows the target pressure as indicated by Line B. As illustrated inFIG.4that is the flowchart illustrating the method of controlling the fuel cell system according to the embodiment of the present disclosure, the method of controlling the fuel cell system according to the present disclosure includes Steps S100, S110, and S120of calculating the amount of the hydrogen supplied to the fuel cell stack500and the amount of the hydrogen consumed therein; Step S200of calculating the amount of the discharged hydrogen from the amount of the hydrogen supplied to the fuel cell stack500and the amount of the hydrogen consumed therein; Step S210of determining whether or not the amount of the discharged hydrogen is at or above the reference value; and Steps S300and S310of performing the compensation control for the amount of the hydrogen supplied through the supply valve120when the amount of the discharged hydrogen is at or above the reference value. In Step S200of calculating the amount of the discharged hydrogen, the amount of the discharged hydrogen is calculated by subtracting the amount of the consumed hydrogen and the amount of the hydrogen pressurized in the fuel cell stack500from the amount of the supplied hydrogen. Particularly, in Steps S300and S310of performing the compensation control for the amount of the hydrogen, when the amount of the discharged hydrogen is at or above the reference value, the compensation value is calculated from the amount of the discharged hydrogen, and the supply valve120is finally controlled with the value obtained by adding the compensation value to the control value with which the supply valve120is controlled. Thus, the undershoot or the overshoot in the amount of the supplied hydrogen can be prevented. When the amount of the discharged hydrogen is below the reference value, the pressure for supplying the hydrogen is controlled with general feedback control in a manner that follows the target pressure (Steps S400, S410, and S500). With the fuel cell system and the method of controlling the fuel cell system according to the present disclosure, in a process of discharging, in a combined manner, the condensate water within the water trap320and gaseous impurities within the hydrogen electrode of the fuel cell stack500, an amount of gas discharged in a combined manner when adjusting fuel pressure on the hydrogen electrode side of the fuel cell stack500is estimated by performing the control of the supply valve120instead of using a separate sensor, and additional hydrogen is supplied in a manner that corresponds to the amount of the discharged gas. Thus, the overshoot or the undershoot in the amount of the supplied hydrogen can be prevented. Accordingly, the efficiency of the fuel cell stack500in generating electric power can be increased, and the fuel cell stack500can be prevented from degrading. Although the specific embodiment of the present disclosure has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. | 14,206 |
11862825 | DETAILED DESCRIPTION The fuel cell system of the disclosed embodiments is a fuel cell system comprising:a fuel cell stack,an ejector set,a fuel gas supplier which supplies fuel gas to the ejector set,a circulation flow path which recovers fuel off-gas discharged from the fuel cell stack and returns the fuel off-gas as circulation gas to the ejector set,a mixed gas supply flow path which connects the ejector set with the fuel cell stack and enables supply of mixed gas containing the fuel gas and the circulation gas from the ejector set to fuel electrodes of the fuel cell stack,a pressure detector which detects pressure information of a fuel electrode side of the fuel cell stack,a fuel off-gas discharger which discharges the fuel off-gas, in which a concentration of the fuel gas is a predetermined concentration or less, to the outside, anda controller,wherein the ejector set includes a first ejector and a second ejector in parallel, the first ejector being an ejector which supplies first mixed gas to the fuel electrodes of the fuel cell stack, and the second ejector being an ejector which supplies second mixed gas, in which a content ratio of the circulation gas is larger than the first mixed gas, to the fuel electrodes of the fuel cell stack;wherein, for the second elector, a supply flow amount of the mixed gas which can be supplied to the fuel electrodes of the fuel cell stack, is smaller than the first ejector;wherein, as a first control, in the case where the pressure information detected by the pressure detector exceeds a predetermined first threshold value, the controller makes a usage ratio of the second ejector larger than a usage ratio of the first ejector when a total usage ratio of the ejectors of the ejector set is determined as 100%; andwherein, as a second control, in the case where the pressure information detected by the pressure detector exceeds a predetermined second threshold value which is larger than the first threshold value, after the first control, the controller makes the usage ratio of the first ejector larger than the usage ratio of the second ejector when the total usage ratio of the ejectors of the ejector set is determined as 100%. FIG.1is a view of an example of the structure of the fuel cell system according to the disclosed embodiments. A fuel cell system100shown inFIG.1includes the following: a fuel cell stack11; a fuel gas supplier12; a mixed gas supply flow path13; a circulation flow path14which circulates, as circulation gas, fuel off-gas discharged from the fuel electrodes of the fuel cell stack11; a pressure detector15which detects the pressure information of the fuel electrode side of the fuel cell stack11; an ejector set16which supplies mixed gas of the fuel gas and the circulation gas to the fuel electrodes of the fuel cell stack11; a controller17; a fuel gas supply flow path18; a fuel off-gas discharger19; an oxidant gas supplier21; an oxidant gas supply flow path22; and an oxidant gas discharge flow path23. The fuel cell system of the disclosed embodiments includes at least the fuel cell stack, the fuel gas supplier, the mixed gas supply flow path, the circulation flow path, the fuel off-gas discharger, the pressure detector, the ejector set and the controller. In general, the fuel cell system further includes a fuel gas supply flow path, an oxidant gas supplier, an oxidant gas supply flow path, an oxidant gas discharge flow path, a cooling water supplier, a cooling water circulation flow path, etc. The fuel cell stack is composed of stacked unit fuel cells. The number of the stacked unit fuel cells is not particularly limited. For example, 2 to 200 unit fuel cells may be stacked. The fuel cell stack may include an end plate at both stacking-direction ends of each unit fuel cell. Each unit fuel cell includes at least a membrane electrode assembly including an oxidant electrode, an electrolyte membrane and a fuel electrode. As needed, it may include two separators sandwiching the membrane electrode assembly. The separators may have such a gas flow path structure, that a groove is formed as a reaction gas flow path on a surface in contact with a gas diffusion layer. Also, the separators may have such a cooling water flow path structure, that a groove is formed on an opposite surface to the surface in contact with the gas diffusion layer, as a cooling water flow path for keeping the stack temperature at a constant level. The separators may be a gas-impermeable, electroconductive member, etc. As the electroconductive member, examples include, but are not limited to, gas-impermeable dense carbon obtained by carbon densification, and a metal plate obtained by press molding. The separators may have a current collection function. The oxidant electrode includes an oxidant electrode catalyst layer and a gas diffusion layer. The fuel electrode includes a fuel electrode catalyst layer and a gas diffusion layer. The oxidant electrode catalyst layer and the fuel electrode catalyst layer may contain a catalyst metal for accelerating an electrochemical reaction, a proton-conducting electrolyte, electron-conducting carbon particles, for example. As the catalyst metal, for example, platinum (Pt) or an alloy of Pt and another metal (such as Pt alloy mixed with cobalt, nickel or the like) may be used. The electrolyte may be fluorine resin or the like. As the fluorine resin, for example, a Nafion solution may be used. The catalyst metal is supported on carbon particles. In each catalyst layer, the carbon particles supporting the catalyst metal (i.e., catalyst particles) and the electrolyte may be mixed. As the carbon particles for supporting the catalyst metal (i.e., supporting carbon particles), for example, water repellent carbon particles obtained by enhancing the water repellency of commercially-available carbon particles (carbon powder) by heating, may be used. The gas diffusion layer may be a gas-permeable, electroconductive member or the like. As the electroconductive member, examples include, but are not limited to, a porous carbon material such as carbon cloth and carbon paper, and a porous metal material such as metal mesh and foam metal. The electrolyte membrane may be a solid polymer electrolyte membrane. As the solid polymer electrolyte membrane, examples include, but are not limited to, a hydrocarbon electrolyte membrane and a fluorine electrolyte membrane such as a moisture-containing, thin perfluorosulfonic acid membrane. The electrolyte membrane may be a Nafion membrane (manufactured by DuPont), for example. The fuel gas supplier supplies fuel gas to the ejector set. The fuel gas is gas that mainly contains hydrogen. For example, it may be hydrogen gas. As the fuel gas supplier, examples include, but are not limited to, a fuel tank such as a liquid hydrogen tank and a compressed hydrogen tank. The fuel cell system may include the fuel gas supply flow path. The fuel gas supply flow path connects the fuel gas supplier with the ejector set and enables the supply of the fuel gas from the fuel gas supplier to the ejector set. The fuel gas supply flow path is not always necessary when the fuel gas supplier and the ejector set are disposed adjacent to each other, and the fuel gas can be directly supplied from the fuel gas supplier to the ejector set. The circulation flow path enables that it connects the fuel cell stack with the ejector set, recovers the fuel off-gas discharged from the fuel electrodes of the fuel cell stack, and returns the fuel off-gas as the circulation gas to the ejector set. The fuel off-gas mainly contains fuel gas, which passed through the fuel electrode while remaining unreacted, and moisture, which is water generated at the oxidant electrode and delivered to the fuel electrode. In the disclosed embodiments, the fuel off-gas may further contain inert gas such as air and nitrogen gas. The ejector set supplies the mixed gas containing the fuel gas and the circulation gas to the fuel electrodes of the fuel cell stack. The ejector set includes the first ejector and the second ejector in parallel. The first ejector supplies the first mixed gas to the fuel electrodes of the fuel cell stack. The second ejector supplies the second mixed gas, in which the content ratio of the circulation gas is larger than the first mixed gas, to the fuel electrodes of the fuel cell stack. For the second ejector, the supply flow amount of the mixed gas which can be supplied to the fuel electrodes of the fuel cell stack, is smaller than the first ejector. The supply flow amount of the first mixed gas that can be supplied to the fuel electrodes of the fuel cell stack by the first ejector, may be 2 to 20 times larger than the supply flow amount of the second mixed gas that can be supplied to the fuel electrodes of the fuel cell stack by the second ejector, or it may be 3 to 10 times larger than that. In the second mixed gas, the content ratio of the circulation gas may be 2 to 10 times larger than the first mixed gas, or it may be 3 to 4 times larger than the first mixed gas, for example. The ejectors of the ejector set are electrically connected with the controller. The use of the ejectors in combination or the use of any one of the ejectors may be enabled by a signal from the controller. FIG.2is a view showing a difference in performance between the first ejector and the second elector. As shown inFIG.2, the first ejector is such an ejector that the supply flow amount is large and the content ratio of the circulation gas is small (large flow amount+low circulation ratio). The second ejector is such an ejector that the supply flow amount is small and the content ratio of the circulation gas is large (small flow amount T high circulation ratio). The mixed gas supply flow path connects the ejector set with the fuel cell stack and enables the supply of the mixed gas containing the fuel gas and the circulation gas from the ejector set to the fuel electrodes of the fuel cell stack. The fuel off-gas discharger enables the discharge of the fuel off-gas, in which the concentration of the fuel gas is the predetermined concentration or less, to the outside. The outside means the outside of the fuel cell system. The fuel off-gas discharger may include a fuel off-gas discharge valve. As needed, it may further include a fuel off-gas discharge flow path. The fuel off-gas discharge valve controls the fuel off-gas discharge flow amount. The fuel off-gas discharge flow path may branch from the circulation flow path. The fuel off-gas discharger may enable the discharge of the fuel off-gas to the outside when, for example, the concentration of the fuel gas such as hydrogen in the fuel off-gas is the predetermined concentration or less. Also, the fuel off-gas discharger may discharge, for example, inert gas other than the fuel gas, such as air and nitrogen gas, to the outside. The predetermined concentration of the fuel gas is not particularly limited and may be appropriately determined considering the balance between the fuel efficiency of the fuel cell system and the inert gas purging time, for example. The method for detecting the concentration of the fuel gas in the fuel off-gas is not particularly limited. For example, a conventionally-known concentration sensor may be used. A gas-liquid separator for reducing the moisture in the fuel off-gas, may be installed in the circulation flow path. Also, a drain flow path, which branches from, the circulation flow path by the gas-liquid separator, may be installed in the circulation flow path, and a drain valve may be installed in the drain flow path. The moisture separated from the fuel off-gas in the gas-liquid separator may be discharged by opening the drain valve of the drain flow path branching from the circulation flow path. The fuel off-gas subjected to the moisture separation may be suctioned from the circulation flow path by the ejector, while it is in the state of containing a slight amount of remaining mist. The pressure detector detects the pressure information of the fuel electrode side of the fuel cell stack. As the pressure detector, examples include, but are not limited to, a pressure sensor. The installation position of the pressure detector is not particularly limited, as long as the pressure information of the fuel electrode side of the fuel cell stack can be detected. The pressure detector may be installed in the mixed gas supply flow path, or it may be installed in the circulation flow path. From the viewpoint of increasing the accuracy of the pressure information detection, the pressure detector may be installed in the mixed gas supply flow path. The pressure information may be a gas pressure applied to the fuel cell stack. The oxidant gas supplier supplies oxidant gas to at least the oxidant electrodes of the fuel cell stack. As the oxidant gas supplier, for example, an air compressor may be used. The oxidant gas supply flow path enables that it connects the oxidant gas supplier with the fuel cell stack and supplies oxidant gas from the oxidant gas supplier to the oxidant electrodes of the fuel cell stack. The oxidant gas is oxygen-containing gas. It may be air, dry air, pure oxygen or the like. The oxidant gas discharge flow path enables the discharge of the oxidant gas from the oxidant electrodes of the fuel cell stack. The fuel cell system may include a cooling water supplier and a cooling water circulation flow path. The cooling water circulation flow path enables that it communicates between the cooling water inlet port communication hole and cooling water outlet port communication hole installed in the fuel cell stack, circulates the cooling water supplied from the cooling water supplier in and out of the fuel cell stack, and cools down the fuel cell stack. As the cooling water supplier, examples include, but are not limited to, a cooling water pump. The controller controls the fuel cell system. The controller may be connected with the pressure detector, the ejector set, the fuel gas supplier, the oxidant gas supplier and so on through an input-output interface. The controller makes a judgement on whether or not the pressure information of the fuel electrode side of the fuel cell stack detected by the pressure detector exceeds the predetermined first threshold value and on whether or not the pressure information exceeds the predetermined second threshold value. Also, the controller controls the usage ratio of the first and second ejectors of the ejector set, etc. The controller physically includes a processing unit such as a central processing unit (CPU), a memory device such as a read-only memory (ROM) and a random access memory (RAM), and the input-output interface, for example. The ROM is used to store a control program, control data and so on processed by the CPU, and the RAM is mainly used as various workspaces for control processes. (1) Detection of the Pressure Information of the Fuel Electrode Side of the Fuel Cell Stack The pressure detector detects the pressure information of the fuel electrode side of the fuel cell stack at predetermined times. The method for detecting the pressure information of the fuel electrode side of the fuel cell stack, is not particularly limited. For example, the pressure information of the fuel electrode side of the fuel cell stack may be detected by installing a conventionally-known pressure sensor in the fuel cell system and using the pressure sensor. The timing for detecting the pressure information of the fuel electrode side of the fuel cell stack, is not particularly limited. The pressure information of the fuel electrode side of the fuel cell stack may be detected every time a predetermined time elapses after the operation of the fuel cell stack is started; it may be detected when the operation of the fuel cell stack is started; or it may be constantly detected. The detection time may be appropriately determined. (2) Judgement on Whether or not the Pressure Information of the Fuel Electrode Side of the Fuel Cell Stack Exceeds the Predetermined First Threshold Value The controller judges whether or not the pressure information of the fuel electrode side of the fuel cell stack detected by the pressure detector exceeds the predetermined first threshold value. The first threshold value of the pressure information can be appropriately determined as follows, for example: data group showing a correlation between the pressure information of the fuel electrode side of the fuel cell stack and the time to complete the purging of the inert gas from the fuel electrodes of the fuel cell stack, are prepared in advance by an experiment, etc., and the first threshold value is appropriately determined by the performance, etc., of the fuel cell stack obtained from the data group. (3) First Control (3-1) The Case where the Pressure Information of the Fuel Electrode Side of the Fuel Cell Stack Exceeds the Predetermined First Threshold Value As the first control, in the case where the pressure information detected by the pressure detector exceeds the predetermined first threshold value, the controller makes the usage ratio of the second ejector larger than the usage ratio of the first ejector when the total usage ratio of the ejectors of the ejector set is determined as 100%. Before the first control, the supply flow amount of the first mixed gas in which the content ratio of the fuel gas is large, is increased to pressure-fill the fuel electrodes of the fuel cell stack with the fuel gas. The gas which is other than the fuel gas and contains large amounts of nitrogen, etc., is pushed out by the pressure-filling, and the gas circulates and enters the fuel electrodes of the fuel cell stack through the ejector set, again. At this time, the usage ratio of the second ejector in which, compared to the first elector, the supply flow amount of the mixed gas is small and the content ratio of the circulation gas is larger than the fuel gas, is increased, thereby decreasing the supply flow amount of the mixed gas from the ejector set. Accordingly, it is thought that the first mixed gas in which the content ratio of the fuel gas is large, can be quickly diffused in the fuel electrodes of the fuel cell stack. As a result, it is thought that the fuel gas can be quickly introduced into the fuel electrodes of the fuel cells, which are on the side far from the fuel gas supply port of the fuel cell stack. Accordingly, it can be said that the use of the second ejector is appropriate for uniform purging of the inert gas from the fuel electrodes. The usage ratio of the ejectors of the ejector set in the case where the pressure information of the fuel electrode side of the fuel cell stack exceeds the predetermined first threshold value, is not particularly limited, as long as the usage ratio of the second ejector is larger than the usage ratio of the first ejector when the total usage ratio of the ejectors is determined as 100%. From the viewpoint of completing the purging of the inert gas in a shorter time, the usage ratio of the second ejector may be 100%. In other words, in the case where the pressure information of the fuel electrode side of the fuel cell stack detected by the pressure detector exceeds the predetermined first threshold value, the controller may switch from the first ejector to the second ejector and supply the second mixed gas from the second ejector to the fuel electrodes of the fuel cell stack. The method for controlling the usage ratio of the ejectors is not particularly limited. The usage ratio may be controlled by electrically connecting the controller with the ejectors and delivering a signal from the controller to the ejectors. (3-2) The Case where the Pressure Information of the Fuel Electrode Side of the Fuel Cell Stack is the Predetermined First Threshold Value or Less On the other hand, as the first control, in the case where the pressure information of the fuel electrode side of the fuel cell stack detected by the pressure detector is the predetermined first threshold value or less, the controller makes the usage ratio of the first ejector larger than the usage ratio of the second ejector when the total usage ratio of the ejectors of the ejector set is determined as 100%. At the time of starting the fuel cell system, from the viewpoint of quickly pressure-filling the fuel electrodes of the fuel cell stack with the first mixed gas in which the fuel gas ratio is large, the controller makes the usage ratio of the first ejector larger than the usage ratio of the second ejector when the total usage ratio of the ejectors of the ejector set is determined as 100%. The usage ratio of the ejectors of the ejector set in the case where the pressure information of the fuel electrode side of the fuel cell stack detected by the pressure detector is the predetermined first threshold value or less, is not particularly limited, as long as the usage ratio of the first ejector is larger than the usage ratio of the second ejector when the total usage ratio of the ejectors is determined as 100%. From the viewpoint of quickly pressure-filling the fuel electrodes of the fuel cell stack with the first mixed gas in which the fuel gas ratio is large, the usage ratio of the first ejector may be 100%. In other words, in the case where the pressure information of the fuel electrode side of the fuel cell stack detected by the pressure detector is the predetermined first threshold value or less, the controller may switch from the second ejector to the first elector and supply the first mixed gas from the first ejector to the fuel electrodes of the fuel cell stack. (4) Detection of the Pressure Information of the Fuel Electrode Side of the Fuel Cell Stack After the first control, the pressure detector detects the pressure information of the fuel electrode side of the fuel cell stack at predetermined times. The timing for detecting the pressure information of the fuel electrode side of the fuel cell stack, is not particularly limited. The pressure information of the fuel electrode side of the fuel cell stack may be detected every time a predetermined time elapses after the first control, or it may be constantly detected. The detection time may be appropriately determined. (5) Judgement on Whether or not the Pressure Information of the Fuel Electrode Side of the Fuel Cell Stack Exceeds the Predetermined Second Threshold Value After the first control, the controller judges whether or not the pressure information of the fuel electrode side of the fuel cell stack detected by the pressure detector exceeds the predetermined second threshold value. The second threshold value of the pressure information can be appropriately determined as follows, for example: data group showing a correlation between the pressure information of the fuel electrode side of the fuel cell stack and the time to complete the purging of the inert gas from the fuel electrodes of the fuel cell stack, are prepared in advance by an experiment, etc., and the second threshold value can be appropriately determined by the performance, etc., of the fuel cell stack included in the data group. (6) Second Control (6-1) The Case where the Pressure Information of the Fuel Electrode Side of the Fuel Cell Stack Exceeds the Predetermined Second Threshold Value As the second control, in the case where the pressure information detected by the pressure detector exceeds the predetermined second threshold value which is larger than the first threshold value, after the first control, the controller may make the usage ratio of the first ejector larger than the usage ratio of the second ejector when the total usage ratio of the ejectors of the ejector set is determined as 100%, and then the controller may terminate the control. In the case where the pressure information exceeds the predetermined second threshold value, it is thought that the first mixed gas in which the fuel gas ratio is large, is sufficiently diffused in the fuel electrodes of the fuel cell stack, and the fuel gas is introduced into the fuel electrodes of the fuel cells, which are on the side far from the fuel gas supply port of the fuel cell stack. Accordingly, by the second control, the usage ratio of the first ejector in which, compared to the second ejector, the supply flow amount of the mixed gas is large and the content ratio of the fuel gas is larger than the circulation gas, is increased, thereby increasing the supply flow amount of the mixed gas from the ejector set. Accordingly, the pressure information of the fuel electrode side of the fuel cell stack can reach the predetermined target value for operating the fuel cell stack in a short time. Accordingly, it can be said that the use of the first ejector is appropriate for purging of the inert gas from the fuel electrodes in a short time. The usage ratio of the ejectors of the ejector set in the case where the pressure information of the fuel electrode side of the fuel cell stack exceeds the predetermined second threshold value, is not particularly limited, as long as the usage ratio of the first ejector is larger than the usage ratio of the second ejector when the total usage ratio of the ejectors is determined as 100%. From the point of view that the pressure information of the fuel electrode side of the fuel cell stack can reach the predetermined target value for operating the fuel cell stack in a shorter time, the usage ratio of the first ejector may be 100%. In other words, in the case where the pressure information of the fuel electrode side of the fuel cell stack detected by the pressure detector exceeds the predetermined second threshold value, the controller may switch from the second ejector to the first ejector and supply the first mixed gas from the first ejector to the fuel electrodes of the fuel cell stack. (6-2) The Case where the Pressure Information of the Fuel Electrode Side of the Fuel Cell Stack is the Second Threshold Value or Less Meanwhile, as the second control, in the case where the pressure information of the fuel electrode side of the fuel cell stack detected by the pressure detector is the predetermined second threshold value or less, after the first control, the controller may continue to make the usage ratio of the second ejector larger than the usage ratio of the first ejector when the total usage ratio of the ejectors of the ejector set is determined as 100%, or the controller may switch from the first ejector to the second ejector and supply the second mixed gas from the second ejector to the fuel electrodes of the fuel cell stack. FIG.3is a flow chart of an example of the method for controlling the fuel cell system according to the disclosed embodiments. The disclosed embodiments are not limited to this typical example. In the control method shown inFIG.3, first, at the time of starting the fuel cell system, the controller supplies the first mixed gas to the fuel electrodes of the fuel cell stack by using the first ejector. Next, the pressure detector detects the pressure information of the fuel electrode side of the fuel cell stack. Then, in the case where the detected pressure information of the fuel electrode side of the fuel cell stack is the predetermined first threshold value or less, the controller continues to supply the first mixed gas to the fuel electrodes of the fuel cell stack by using the first ejector. On the other hand, in the case where the pressure information exceeds the first threshold value, the controller switches from the first ejector to the second ejector and supplies the second mixed gas to the fuel electrodes of the fuel cell stack. Then, the pressure detector detects the pressure information of the fuel electrode side of the fuel cell stack, again. Then, in the case where the detected pressure information of the fuel electrode side of the fuel cell stack is the predetermined second threshold value or less, the controller continues to supply the second mixed gas to the fuel electrodes of the fuel cell stack by using the second ejector. On the other hand, in the case where the pressure information exceeds the second threshold value, the controller switches from the second ejector to the first ejector and supplies the first mixed gas to the fuel electrodes of the fuel cell stack. Then, the controller terminates the control. FIG.4is a view showing an example of the relationship between time and anode pressure/hydrogen concentration in the case of simulating the control of the fuel cell system according to the disclosed embodiments. InFIG.4, “Large” indicates the use of the first ejector, and “Small” indicates the use of the second ejector. As is clear fromFIG.4, by carrying out the two-step control (the first control and the second control), the anode pressure increases in two steps, and the anode pressure and the hydrogen concentration of the anode can be increased to target values in a short time of 0.75 second. FIG.5is a view showing a gas concentration distribution on the fuel electrode side of the fuel cell stack at a predetermined timing in a simulation trying to purge nitrogen gas from the fuel electrodes of the fuel cell stack by using only the first ejector. InFIG.5, “Inlet port” indicates the fuel gas supply port; “Outlet port” indicates the fuel gas discharge port; “Stacking direction” indicates the direction of stacking the unit fuel cells of the fuel cell stack; and “Back” indicates the furthest side from the fuel gas supply port of the fuel cell stack. The same applies toFIG.6described below. As is clear fromFIG.5, when nitrogen gas purging is carried out by using only the first ejector, there is a large concentration variation in the stacking direction of the unit fuel cells of the fuel cell stack. FIG.6is a view showing a gas concentration distribution on the fuel electrode side of the fuel cell stack at a predetermined timing in a simulation trying to purge nitrogen gas from the fuel electrodes of the fuel cell stack by controlling the fuel cell system of the disclosed embodiments. As is clear fromFIG.6, according to the fuel cell system of the disclosed embodiments, the concentration variation in the stacking direction of the unit fuel cells of the fuel cell stack, is small. From the above results, it is thought that according to the fuel cell system of the disclosed embodiments, even when a hydrogen pump is not installed in the circulation flow path, the gas other than the fuel gas can be purged from the fuel electrodes of the fuel cell stack in a short time, by differently using the second ejector, which is appropriate for uniform purging and has high circulation properties, and the first ejector, which is appropriate for purging in a short time and is large in flow amount, depending on timing. REFERENCE SIGNS LIST 11. Fuel cell stack12. Fuel gas supplier13. Mixed gas supply flow path14. Circulation flow path15. Pressure detector16. Ejector set17. Controller18. Fuel gas supply flow path19. Fuel off-gas discharger21. Oxidant gas supplier22. Oxidant gas supply flow path23. Oxidant gas discharge flow path100. Fuel cell system | 31,267 |
11862826 | DETAILED DESCRIPTION FIG.1shows a fuel cell system designated in total with100, in accordance with the prior art. The fuel cell system100is part of a vehicle (not shown), in particular an electric vehicle, which has an electric traction motor, which is supplied with electrical energy by the fuel cell system100. The fuel cell system100comprises as core component a fuel cell stack10, which comprises a plurality of individual cells11, which are arranged in the form of a stack and which are formed by alternately stacked membrane electrode assemblies (MEAS)14and bipolar plates15(see detailed view). Each individual cell11thus respectively comprises an MEA14with an ion-conductive polymer electrolyte membrane not shown in more detail here and catalytic electrodes arranged thereon on both sides. These electrodes catalyze the respective partial reaction of the fuel conversion. The anode and cathode electrodes are designed as coating on the membrane and comprise a catalytic material, such as platinum, which is provided on an electrically conductive substrate material, with a large specific surface, such as a carbon-based material. As shown in the detailed view ofFIG.1, an anode chamber12is formed between a bipolar plate15and the anode and the cathode chamber13is formed between the cathode and the next bipolar plate15. The bipolar plates15serve to supply the operating media in the anode and cathode chambers12,13and further establishes the electrical connection between the individual fuel cells11. Optionally, gas diffusion layers can be arranged between the membrane electrode assemblies14and the bipolar plates15. In order to supply the fuel cell stack10with the operating medium, the fuel cell system100has an anode supply20, on the one hand, and a cathode supply30, on the other hand. The anode supply20of the fuel cell system100shown inFIG.1comprises an anode supply path21, which serves to supply an anode operating medium (the fuel), for example, hydrogen, to the anode chambers12of the fuel cell stack10. For this purpose, the anode supply path21connects a fuel storage tank23with an anode inlet of the fuel cell stack10. The feed pressure of the anode operating medium into the anode chambers12of the fuel cell stack10is adjusted via a metering valve27.1. The anode supply20also comprises an anode exhaust path22which discharges the anode exhaust gas from the anode chambers12via an anode outlet of the fuel cell stack10. In addition, the anode supply20of the fuel cell system100shown inFIG.1has a recirculation line24, which connects the anode exhaust gas path22with the anode supply path21. The recirculation of fuel is a common practice in order to return the overstoichiometrically used fuel to the fuel cell stack10. A recirculation conveying device25, such as a recirculation fan, along with a flap valve27.2are arranged in the recirculation line24. In addition, a water separator26is installed in the anode supply22of the fuel cell system, in order to discharge the product water resulting from the fuel cell reaction. A drain of the water separator can be connected to the cathode exhaust line32, a water tank or an exhaust system. The cathode supply30of the fuel cell system100shown inFIG.1comprises a cathode supply path31, which supplies an oxygen-containing cathode operating medium, in particular air taken in from the environment, to the cathode chambers13of the fuel cell stack10. The cathode supply30also comprises a cathode exhaust path32, which discharges the cathode exhaust gas (in particular the exhaust air) from the cathode chambers13of the fuel cell stack10and supplies it, if appropriate, to an exhaust system (not shown). For conveying and compacting the cathode operating medium, a compressor33is arranged in the cathode supply path31. In the embodiment shown, the compressor33is designed as a compressor33, which is mainly driven by an electric motor34equipped with appropriate power electronics35. The fuel cell system100shown inFIG.1also has a humidifier module39arranged upstream of the compressor33in the cathode supply line31. The humidifier module39is arranged in the cathode supply path31so that, on the one hand, the cathode operating gas can flow through it. On the other hand, it is arranged in the cathode exhaust path32such that the cathode exhaust gas can flow through it. A humidifier39typically comprises a plurality of water vapor permeable membranes, which are designed to be either flat or in the form of hollow fibers. In this case, the comparatively dry cathode operating gas (air) flows over one side of the membranes and the comparatively moist cathode exhaust gas (exhaust gas) flows over the other side. Driven by the higher partial pressure of water vapor in the cathode exhaust gas, water vapor is transferred across the membranes into the cathode operating gas, which is humidified in this manner. The fuel cell system100also has a humidifier bypass37connecting the cathode supply line upstream and downstream of the humidifier39to each other, with a flap valve arranged therein as bypass control means38. Furthermore, flap valves27.3and27.4are arranged upstream of fuel cell stack10in the anode supply line21and downstream of the fuel cell stack10in the anode exhaust line22. Various other details of anode and cathode supply20,30are not shown inFIG.1for reasons of clarity. For example, the anode exhaust line22can open into the cathode exhaust line32, such that the anode exhaust and the cathode exhaust are discharged via a common exhaust system. FIG.2shows a detailed representation of the fuel cell stack10shown inFIG.1. The fuel cell stack has a plurality of fuel cells stacked flat on top of each other in stack direction S. In the stacking direction, the fuel cell stack10is bounded by a first end plate55and an opposite second end plate56. In a first direction transverse to stack direction S, the fuel cell stack10is bounded by side panels57. In a second direction transverse to the first direction and transverse to stack direction S, the fuel cell stack10is bounded by side panels58. The fuel cell stack10can further comprise a plurality of mounting elements for fastening the fuel cell stack10to a supporting structure, for example, a car body. The fuel cell stack10shown inFIG.2is compressed over a plurality of a total of ten tensioning elements50. Thereby, each tensioning element50is fixed to the first end plate55via a tensioning device (not shown) and to the second end plate via an additional tensioning device54and runs parallel to a side panel58of the fuel cell stack10. Thereby, each of the tensioning elements50has a spacing to the side panel58.FIG.2shows in detail five tensioning elements50.1,50.2,50.3,50.4and50.5, which run parallel to an upper side panel58. In addition, the fuel cell stack has five additional tensioning elements50.6,50.7,50.8,50.9and50.0(not shown), which run parallel to a lower side panel and of which only the tensioning devices54fixed to the second end plate56are shown inFIG.2. The tensioning elements50are made of nylon and have a linear mass distribution μ of 0.152 kg/m. Each of the tensioning devices54is arranged on surfaces of the first end plate55facing outwards in stacking direction S and the second end plate56. Thus, the tensioning elements50fixed to the tensioning devices54initially run along these surfaces, against which they abut, over an edge of the end plates55,56and a narrow side surface of the end plates55,56. The end plates55,56protrude approximately 2 mm beyond the side panels58in the second direction. As a result, each tensioning element50has a first fixed end52at an inner edge of the first end plate55and a second fixed end53at an inner edge of the second end plate56.FIG.2shows an example of the first fixed end52.1of a first tensioning element50.1and the second fixed end53.2of a second tensioning element50.2. Each tensioning element50has a vibratable section51between its first fixed end52and its second fixed end53.FIG.2shows an example of the vibratable section51.2of a second tensioning element50.2and the vibratable section51.3of a third tensioning element50.3. Each of these vibratable sections51has a length of 383 mm. In some embodiments, each vibratable section51of each tensioning element50is deflected manually in the second direction one after the other and thus excited to a transverse vibration. Since the end plates55,56protrude approximately 2 mm beyond the side panels58in the second direction, the vibratable sections51of the clamped tensioning elements50are not in contact with the side panels58and can vibrate freely between the fixed ends52,53with amplitudes of up to 2 mm. For each vibrating vibratable section51, an acoustic signal is initially detected, for example, by means of the microphone of a smartphone. In a next step, a frequency spectrum is determined for each of the recorded acoustic signals by means of a suitable program and from this, or directly for each recorded acoustic signal, a fundamental frequency of the recorded acoustic signal is determined. Programs for determining the frequency spectrum and/or the fundamental frequency are freely available on the market. The following table shows for each vibratable section of each of the ten tensioning elements50the fundamental frequencies f1determined in accordance with the description herein and furthermore the tensile force Fzugacting on the respective vibratable section51, which was determined from the frequency f1of the respective vibratable section51according to the formula mentioned in the description: 50.150.250.350.450.550.650.750.850.950.0f1[Hz]188167173179173173170170179182Fzug[kN]3.12.52.72.92.72.72.62.62.92.9 Under the assumption that the fuel cell stack10as a whole is in equilibrium of forces, the sum of the tensile forces determined for all vibratable sections51corresponds to the total compressive tensile force of 27.6 kN acting on the fuel cell stack10. The fuel cell stack10was originally compressed with a defined pressure force of 28.5 kN and was fixed in the compressed form by means of tensioning elements50. The method described herein thus produces results of the right order of magnitude and also indicates a decreasing compression of the fuel cell stack10. The length deviation Δl of approximately 1 mm shown inFIG.3corresponds to a change in the fundamental frequency Δf of approximately 0.5 Hz. Thus, the method described herein is relatively invariant with respect to smaller measuring errors of the lengths of the vibratable sections51. The change of only 15 N in the tensile force ΔF acting on a vibratable section51, shown inFIG.4, corresponds to a change of its fundamental frequency Δf by 0.5 Hz as well. Thus, the method described herein is sufficiently accurate with respect to the measurement of force. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. | 11,134 |
11862827 | DETAILED DESCRIPTION Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. PEMFC are a popular fuel cell choice for automotive vehicles. The PEMFC generally includes a proton exchange membrane (PEM). The anode and the cathode typically include finely divided catalytic particles, usually platinum, supported on carbon particles and mixed with an ionomer. The catalytic mixture is deposited on opposing sides of the membrane. The combination of the anode-catalytic mixture, the cathode-catalytic mixture, and the PEM form a coated catalyst membrane electrode (CCM). In order to facilitate the transport of reactant gases to and remove the excessive water and heat from the catalytic mixture, a gas diffusion layer (GDL), which may include a microporous layer and a carbon-fiber-based gas diffusion backing layer, may be applied on either side of the CCM to form a membrane electrode assembly (MEA). GDLs also provide mechanical support for the soft goods including the PEM and catalytic mixtures. MEAs are sandwiched between bipolar plates to form unit cells. The bipolar plates typically include an anode side and a cathode side. Anode fuel flow channels are provided on the anode side of the bipolar plates that allow the anode gas to flow to the anode side of the MEA. Cathode oxidant flow channels are provided on the cathode side of the bipolar plates that allow the cathode gas to flow to the cathode side of the MEA. Coolant channels may be disposed between the anode and cathode sides of the bipolar plates to thermally regulate the fuel cell. Several unit cells are typically combined in a fuel-cell stack to generate the desired power. For example, the stack may include two-hundred or more unit cells arranged in series. The fuel-cell stack receives a cathode reacting gas, typically a flow of air forced through the stack by a compressor. Not all the oxygen is consumed by the stack and some of the air is output as a cathode exhaust gas that may include water as a stack byproduct. The fuel-cell stack also receives an anode hydrogen reacting gas that flows into the anode side of the stack. Referring toFIG.1, a vehicle10includes a fuel-cell system19for providing electrical power to at least one electric machine12. The vehicle10may also include a traction battery14electrically connected to the fuel-cell system19and the electric machine12. The electric machine12is connected to the driven wheels16via a drivetrain18. During operation of the vehicle10, hydrogen fuel and air are fed into a fuel cell of the system19creating electrical power. The electric machine12receives the electrical power as an input, and outputs torque for driving the wheels16to propel the vehicle10. The vehicle10also includes at least one controller21that controls one or more systems of the vehicle, such as those systems shown inFIG.1. While illustrated as one controller, the controller21may be part of a larger control system and may be controlled by various other controllers throughout the vehicle10, such as a vehicle system controller (VSC). It should therefore be understood that the controller21and one or more other controllers can collectively be referred to as a “controller” that controls various actuators in response to signals from various sensors to control functions such as controlling the fuel-cell system. Controller21may include a microprocessor or central processing unit (CPU) in communication with various types of computer-readable storage devices or media. Computer-readable storage devices or media may include volatile and nonvolatile storage in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM), for example. KAM is a persistent or non-volatile memory that may be used to store various operating variables while the CPU is powered down. Computer-readable storage devices or media may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, some of which represent executable instructions, used by the controller in controlling the vehicle. The controller communicates with various vehicle sensors and actuators via an input/output (I/O) interface that may be implemented as a single integrated interface that provides various raw data or signal conditioning, processing, and/or conversion, short-circuit protection, and the like. Alternatively, one or more dedicated hardware or firmware chips may be used to condition and process particular signals before being supplied to the CPU. Although not explicitly illustrated, those of ordinary skill in the art will recognize various functions or components that may be controlled by controller21within each of the subsystems identified above. Representative examples of parameters, systems, and/or components that may be directly or indirectly actuated using control logic executed by the controller. The vehicle10includes an accelerometer or acceleration sensor23configured to output data to the controller21. The accelerometer23may be configured to measure a plurality of different accelerations. For example, the accelerometer23may be configured to measure vehicle pitch and output pitch data to the controller21. SeeFIG.4and related text for further details. Referring toFIG.2, an example fuel cell20of the system19includes two unit cells22,24stacked together. The two-cell stack is merely an example and the fuel cell20may include dozens or hundreds of stacked unit cells. The first unit cell22includes an MEA26sandwiched between a first end plate28and a bipolar plate30. The MEA26is comprised of a plurality of different layers including a PEM32, a pair of gas diffusion layers (GDL)34and a pair of catalyst layers36. The endplate28includes an anode side38defining a plurality of flow paths40for the hydrogen fuel. The bipolar plate30includes a cathode side42defining a plurality of flow paths44for air and an anode side46defining a plurality of flow paths48for hydrogen fuel for the second unit cell24. A second MEA50is sandwiched between the bipolar plate30and a last endplate52. The last endplate52includes a cathode side54defining a plurality of flow paths56for air. The coolant channels58,62are configured to circulate coolant, such as ethylene glycol. Referring toFIG.3, the fuel-cell system19includes the fuel cell or fuel-cell stack20. The stack20contains an anode side114, a cathode side116, and a membrane118therebetween. The fuel-cell system20electrically communicates with and provides energy, for example, to a high voltage bus120or a traction battery. The fuel-cell stack20may also have a cooling loop (not shown). During operation of the fuel-cell system19, product water, residual fuel such as hydrogen, and byproducts such as nitrogen, may accumulate at the anode side114of the fuel-cell stack20. Attempts have been made to remove the liquid product water and byproducts and to reuse the residual hydrogen and water vapor. One approach is to collect those constituents in a separator136downstream of the fuel-cell stack112, separate at least a portion of the liquid water and/or nitrogen, and return the remaining constituents to the fuel-cell stack20via a return passageway in a recirculation loop. A primary fuel source122is connected to the anode side114of the fuel-cell stack112, such as a primary hydrogen source. Non-limiting examples of the primary hydrogen source122are a high-pressure hydrogen storage tank or a hydride storage device. The hydrogen source122is connected to one or more ejectors124that control the flow of hydrogen to the stack. The ejector124may be or include a valve configured to control the flow of hydrogen. The ejector124has a nozzle126supplying hydrogen into the converging section of a converging-diverging nozzle128. The diverging section of the nozzle128is connected to the input130of the anode side114. This may be collectively referred to as a hydrogen supply. The output132of the anode side114is connected to a passive recirculation loop134. Typically, an excess of hydrogen gas is provided to the anode side114to ensure that there is sufficient hydrogen available to all of the cells in the stack20. In other words, hydrogen is provided to the fuel-cell stack20above a stoichiometric ratio of one, i.e., at a fuel rich ratio relative to exact electrochemical needs. The recirculation loop134is provided such that excess hydrogen unused by the anode side114is returned to the input130so may be used and not wasted. Additionally, accumulated liquid and vapor phase water is an output of the anode side114. The anode side114requires humidification for efficient chemical conversion and to extend membrane life. The recirculation loop134may be used to provide water to humidify the hydrogen gas before the input130of the anode side114. The recirculation loop134contains a hydrogen-water separator136, or water knock-out device. The separator136receives a stream or fluid mixture of hydrogen gas, nitrogen gas, and water from the output132of the anode side114. The water may be mixed phase and contain both liquid and vapor phase water. The separator136removes at least a portion of the liquid phase water, which exits the separator through drain line138. At least a portion of the nitrogen gas, hydrogen gas, and vapor phase water may also exit the drain line138, and pass through a purge valve139, for example, during a purge process of the fuel-cell stack112. The remainder of the fluid in the separator136exits through passageway140in the recirculation loop134, which is connected to the ejector124. The fluid in passageway140is fed into the converging section of the converging-diverging nozzle128where it mixes with incoming hydrogen from the nozzle126and hydrogen source122. Liquid water may be removed from the anode side114by the separator136to prevent water blockages within the channels and cells of the anode side114. Water blockages within the fuel-cell stack20may lead to decreases in cell voltage and/or voltage instabilities within the fuel-cell stack Liquid water may also be removed by the separator136to prevent a blockage or partial blockage within the ejector124. A liquid water droplet in the diverging section of the converging-diverging nozzle128would effectively create a second venturi section within the nozzle128and lead to pumping instabilities for the ejector124. The cathode side116of the stack112receives oxygen, for example, as a constituent in an air source142. In one embodiment, a compressor144is driven by a motor146to pressurize the incoming oxygen. The pressurized air is then humidified by a humidifier148before entering the cathode side116. Another separator150(shown in phantom) may be positioned downstream of the humidifier148. The separator150may be used to remove liquid water from the humidified air flow before it enters the cathode side116of the stack112at input152. Water droplets may be present downstream of the humidifier148due to liquid water being entrained by air high flow rates within the humidifier148. Liquid water may be removed by the separator150to prevent water blockages within the cells of the cathode side116, leading to decreases in cell voltage and/or instabilities within the fuel-cell stack112. The output154of the cathode side116is connected to a valve156. Drain line138from separator136, and a drain line158from separator150may be connected to an exhaust system160downstream of the valve156. In other embodiments, the drain lines may be plumbed to other locations in the fuel-cell system19. Other system architectures may also be used for the fuel-cell system19. For example, a turbine may be used in addition to the compressor144to induce flow through the cathode side116. In one example, a turbine is positioned downstream of the cathode stack outlet154, with a separator interposed between the cathode side116and the turbine to remove liquid water before the fluid stream enters the turbine. Based on the use of the ejector124to create flow through the anode side114and induce flow through the passive recirculation loop134, the ejector124must overcome any pressure drops in the system, which includes a typically significant pressure drop across the fuel-cell stack20. The system19as shown does not include a pump or other device to induce flow in the recirculation loop134, therefore all the compression work must be accomplished by the ejector, otherwise described as a jet pump. To enable this function, the separator136needs to have a low pressure drop across it. The separator136also needs to remove larger droplets of water from the fluid to prevent water blockages in the recirculating flow in the fuel-cell stack20or ejector124caused by droplets. The separator136permits vapor phase water and smaller water droplets to remain in the recirculating flow in passageway140and return to the ejector124for humidification purposes. In one example, the separator136removes water droplets having a diameter on the order of one millimeter or larger. Additionally, as separator136receives fluid flow from the anode side114, the separator136needs to be designed for use with hydrogen gas. Generally, hydrogen gas may cause material degradation or embrittlement issues and material used in the separator136need to be hydrogen compatible. Additionally, hydrogen is a small molecule, and many conventional separator devices are not suitable for use with hydrogen because their design may permit leaks, for example, with a conventional threaded connection. Other conventional separators may contain rotating or moving parts, such as a rotating vane, or the like, which may not be compatible with hydrogen as the lubricant may poison the fuel-cell stack20, or the hydrogen may degrade or decompose the lubricant. Separator150also needs to remove larger droplets of water from the fluid to prevent water blockages caused by droplets in the flow in the cathode side116of the fuel-cell stack112. The separator150permits vapor phase water, and smaller water droplets to remain in the flow for humidification. In one embodiment, the separator150removes water droplets that are the same size or larger than the cathode side116flow field channel widths. In one example, the cathode side flow field channels are 0.2-1.0 millimeters. FIG.4illustrates a schematic diagram of vehicle pitch170or tilt. Pitch is the rotation of the vehicle10about the traverse axis, i.e., the angle of the vehicle relative to the horizon172. When the vehicle is on flat ground, the pitch is zero. When the vehicle is on a hill, the vehicle is pitched. The pitch may be expressed or quantified in a variety of different ways. In one embodiment, pitch is expressed as an angle relative to the horizon172or alternatively as a percentage. Here, the pitch angle may be expressed in degrees or radians. To quantify the direction of the pitch, e.g., uphill (nose up) or downhill (nose down), a sign convention may be used. In the illustrated example, upward pitch (when the vehicle is facing uphill) has a positive sign and downward pitch (when the vehicles facing downhill) has a negative sign. The acceleration sensor23is configured to measure one or more accelerations and output data indicative of vehicle pitch170. The controller is programmed to receive the pitch data from the accelerometer23and determine the pitch170of the vehicle. The pitch of the vehicle may be used as an input for one or more routines or protocols associated with operating the fuel-cell system19. Referring toFIG.5A, the vehicle10includes an exhaust system160is in fluid communication with the anode side and the cathode side of the fuel-cell112. The exhaust system160receives the cathode exhaust, the product water, hydrogen, and any other contents exiting the fuel-cell112. The exhaust system160may include an exhaust pipe182having a receiving end184that is coupled to the fuel-cell system19and a tailpipe186configured to vent the contents to the outside environment. For example, the fuel-cell system19may include a cathode exhaust line158connected to the receiving end184and a drain line138that is also connected to the receiving end184. The drain line183may extend from the purge valve139at a slope to facilitate draining of water. In order to facilitate draining of the exhaust system160, the exhaust pipe182may also be sloped downwardly at an angle so that water will gravity flow out of the tailpipe186when the vehicle is on relatively flat ground. (The drain lines138and158may be similarly sloped in some embodiments, but this is not required.) For example, the exhaust system180and/or the drain lines138or158may have a 3 percent slope towards the tailpipe186such that the exhaust system160will gravity drain as long as the vehicle pitch is less than −3 degrees. Three percent is just an example for discussion purposes and the slope of the exhaust pipe/drain lines may be more or less in other embodiments. FIG.5Ashows the vehicle on flat ground. Here, the built-in pitch or slope of the exhaust system160allows the system to gravity drain. Therefore, any accumulated water within the exhaust pipe182, for example, is able to drain out of the system through the tailpipe186. FIG.5Bshows a different scenario in which the vehicle10is on a downhill grade in excess of −3 percent, for example. Here, the slope of the exhaust pipe182and/or the drain lines has reversed due to the road grade resulting in a flow reversal. That is, any water left in the vehicle exhaust will flow backwards towards the fuel-cell112rather than out the tailpipe186. This scenario may present issues with regard to purging water from the vehicle. The anode side and/or the cathode side of the fuel-cell112may be periodically purged to remove excess water, nitrogen, or other unwanted elements within the system19. One example purge routine is removing water from the separator136. As explained above, the separator136removes water from the anode. This separated water collects in a collection chamber or reservoir and is periodically purged to the exhaust system160. The purge routine includes controlling the purge valve139and the ejector124to blow the water out of the drain line138using hydrogen as a propellant. To reduce hydrogen fuel consumption, the purge routine is limited in duration and frequency. Given the designed slope of the vehicle exhaust system182, it is normally only necessary to advance the water from the drain line138and to the exhaust pipe182, where gravity takes over. However, as explained above, this is not the case when the vehicle is parked on a sufficiently steep downhill grade as the exhaust system now has a reverse pitch and thus the water must completely clear the drain line in order to prevent flow back to the purge valve or other upstream component. This reverse-slope condition requires additional hydrogen in order to fully clear the system. In order to tailor the purge routine for these different scenarios, the controller21may be programmed with multiple purge routines that are selected based on measured vehicle pitch. For example, a baseline purge routine is used when the vehicle is on relatively flat or uphill grade and an enhanced purge routine is used when the vehicle is on downhill grade. The enhanced purge routine is designed to clear the water through the drain line so that there is minimal or no residual water left in the conduit to flow back into the upstream component, such as the purge valve. The vehicle10may also have one or more freeze preparation routines controlled by the controller21. The freeze preparation routines are similar to the purge routines and that hydrogen gas is used as a propellant to flush the system of any residual water when the ambient air temperature poses a freezing risk. Like the purge routines, the controller may be programmed with a baseline freeze preparation routine that is used when the vehicle pitch is below threshold and in enhanced freeze preparation that is used when the vehicle pitch exceeds a threshold. Control logic or functions performed by controller21may be represented by flow charts or similar diagrams in one or more figures. These figures provide representative control strategies and/or logic that may be implemented using one or more processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various steps or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Although not always explicitly illustrated, one of ordinary skill in the art will recognize that one or more of the illustrated steps or functions may be repeatedly performed depending upon the particular processing strategy being used. Similarly, the order of processing is not necessarily required to achieve the features and advantages described herein, but is provided for ease of illustration and description. The control logic may be implemented primarily in software executed by a microprocessor-based vehicle, engine, and/or powertrain controller, such as controller21. Of course, the control logic may be implemented in software, hardware, or a combination of software and hardware in one or more controllers depending upon the particular application. When implemented in software, the control logic may be provided in one or more computer-readable storage devices or media having stored data representing code or instructions executed by a computer to control the vehicle or its subsystems. The computer-readable storage devices or media may include one or more of a number of known physical devices which utilize electric, magnetic, and/or optical storage to keep executable instructions and associated calibration information, operating variables, and the like. FIG.6is a flowchart200of an algorithm for controlling purge based on vehicle pitch. Control begins at operation202with a purge request being received. At operation204the controller receives data from the accelerometer indicative of a pitch of the vehicle. The controller receives this data and determines the vehicle pitch. The vehicle pitch is then compared to a threshold at operation206. For example, the vehicle pitch may be expressed as a pitch angle and the threshold may be an angle. Alternatively, the pitch and thresholds may be expressed as percentages. The value of the threshold may be based on the slopes of the exhaust system. For example, the threshold corresponds to a change in sign of a slope of the purge valve. That is, the drain line and/or the exhaust pipe slopes such that fluid flows away from the purge valve (or out of the tailpipe) when the pitch is within the threshold, and the drain line and/or the exhaust pipe slopes such that the fluid flows towards the purge valve (or away from the tailpipe) when the pitch is outside of the threshold. In one embodiment, the threshold may be positive 15 degrees, of course this is just one example. Here, if the pitch of the vehicle exceeds positive 15 degrees (or is outside of absolute value control passes to operation208and the enhanced purge strategy is commanded. Conversely, if the pitch is less than or within the threshold, the normal baseline purge strategy is commanded at operation210. The enhanced purge strategy may have a longer duration than the baseline strategy. Alternatively or additionally, the enhanced purge strategy may include a larger opening of the purge valve and/or a larger duty cycle of the ejector to increase hydrogen pressure within the system as compared to the baseline strategy. In some embodiments, the duration of the enhanced purge strategy may be variable and based on the measured pitch of the vehicle. Here, the duration increases as the vehicle pitch increases and the duration decreases as the vehicle pitch decreases. In some embodiments, the controls may utilize absolute values of pitch rather than relying on the above-described sign convention to determine if the vehicle is facing uphill or downhill. FIG.7illustrates controls220for freeze preparation. Control begins at operation202with a request for freeze preparation. At operation224, the controller receives data from an accelerometer or acceleration sensor. In operation226, the controller compares the measured pitch to threshold similar to operation206. If the pitch is outside of or exceeds the threshold control passes to operation228where an enhanced freeze preparation routine is commanded. Conversely, the baseline freeze preparation routine is commanded operation230if the pitch is less than or within the threshold at operation226. The differences between the enhanced strategy and the baseline strategy may be the same as those employed for the purge strategy and that disclosure is incorporated herein for brevity. By providing multiple different purge and freeze preparation routines based on vehicle pitch, the vehicle can conserve hydrogen fuel while also providing sufficient purging of the water to account for variations in road grade. In the above examples, the drain lines and exhaust system sloped downwardly towards the rear of the vehicle. Thus, pitch was the important factor in determining whether or not the water would gravity flow in the desired direction. In other embodiments, the tailpipe may exit to a lateral side of the vehicle. Here, the important factor may be the roll of the vehicle. If this is the case, the above-described controls may be modified to measure vehicle role with the accelerometer and to determine which purge routine to use based on the roll. For example, the controller may command a normal purge routine responsive to the vehicle roll being less than or within a threshold and may command an enhanced purge routine responsive to the vehicle roll being greater than or outside a threshold. Here, the above-described controls may be used, albeit with roll substituted for pitch. In other vehicles, both pitch and roll may be relevant factors to the sloping of the drain lines an exhaust system. In that case, the accelerometer may be configured to measure vehicle pension vehicle roll and compare these two one or more thresholds to determine when to use the baseline purge routine or the enhanced routine. These changes may also be made to the freeze preparation controls to account for the different slopes and placements of the drain lines an exhaust system. While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications. | 28,916 |
11862828 | As noted above, in the above reference Drawings, the present invention is illustrated by way of example, not limitation, and modifications may be made to the elements illustrated therein, as would be apparent to a person of ordinary skill in the art, without departing from the scope or spirit of the invention. DETAILED DESCRIPTION OF EMBODIMENTS Introduction Electrolytic cells are devices that generate products from electrochemical reactions that occur at the surface of the electrodes. These reactions are driven by the current and voltage applied to the cell, which exhibits an electrical load that varies over time depending on a wide variety of electrochemical pathways and other physical and chemical principles. The generation of electrolytic products and the lifetime of the cell are closely related to the current and voltage applied. It is therefore desirable to control these parameters. Since these current-driven reactions are not constant and occur at time scales that vary from microseconds to seconds to hours, proper power management of an electrolytic cell should be performed over those time scales. Fast phenomena that affect the electrical cell load can include, for instance, the electron transfer process to redox species in the fluid at the electrode surface (electrolysis). Applying a current that stays constant over these relatively fast time scales (sub-microseconds to microseconds) can maintain a constant electrolytic production at a first approximation. This current control can be achieved using analog controls as analog constant current regulators. Light emitting diode (LED) drivers can be utilized as power supplies for these applications. Many LED drivers enable adjustment of the current output at a user-defined constant current setpoint via a dimming input to provide an efficient and convenient way to maintain a constant current with variable loads. Alternatively, in the absence of an LED driver, it is possible to use analog regulators to provide a constant current, such as those comprising metal-oxide-semiconductor field-effect (MOSFET) transistors that can be configured to output a constant current. Another phenomenon that occurs at a fast time scale is polarity reversal for removing limescale from the electrodes. Polarity reversal is applicable in ozone-producing electrolytic cells comprising an anode and a cathode made of the same material and compatible with cathodic currents, such as boron-doped diamond (BDD) electrodes. Moreover, zero-gap electrolytic cells comprising proton exchange membrane (PEM) generally behaves as resistive loads. The current polarity reversal takes place typically instantaneously, with the voltage polarity reversal within a few microseconds. Therefore, it is important to managing the power to an electrolytic cell that can maintain the applied current as constant as possible even when these fast changes occur. Variable flow rates (from hundreds of milliseconds and up) and aging of the cell (typically in the thousands of operating hours) occur on a much longer time scale. Cell aging can be asserted from the loss of the electrolytic product yield over time as monitored by a sensor at the output of the cell. Cell aging is also accompanied by an increase in the electrical load, meaning that the applied voltage of the cell will also increase. Based on this, it was found that the applied constant current should be increased over the lifetime to compensate for the loss of the electrolytic production yield. Typically, when the cell ages, yield loss occurs because additional parasitic electron transfer pathways become more prominent while that producing the electrolytic product is reduced. Applied constant current can be adjusted via a dimming signal to the analog constant current regulator to change the current setpoint. Variable fluid flow rate entering the cell, which could typically occur in the hundreds of milliseconds and longer time scale, can cause changes in hydration and dehydration rates and the level of redox contaminants, which can alter the production of the electrolytic product transiently. Therefore, the applied current should be adjusted dynamically to compensate for such changes and maintain a constant electrolytic product yield. For instance, if the water flow rate decreases in an ozone-producing electrolytic cell, the applied current should be deceased to prevent membrane dehydration, overheating, permanent damage, and loss of constant ozone production. Control of the current setpoint can compensate for these phenomena, which could occur on time scales of hundreds of milliseconds to minutes, to hours, and longer. The constant current control over long-timescale phenomena can be achieved via a dimming of the current setpoint of the constant current regulator. Another control can be achieved by pulse width modulation (PWM) of the duty cycle of the applied current at the H-bridge—an H-bridge that is typically used for controlling brushed motor speed and direction. Similarly, an H-bridge can control the applied voltage and the polarity reversal of the electrolytic cell; however, the sole application of PWM to the H-bridge cannot be used to manage the ozone output of zero-gap electrolytic cells for ozone generation. PWM should be paired with a dimming of the current setpoint. This is because electrolytic cells do not behave as capacitive loads like a brushed motor but rather as resistive loads. Consequently, PWM of the duty cycle at the H-bridge would not reduce the applied current to the cell. As a result, the full constant current can be applied at each ON pulse at the typical PWM frequency (typically from 200 Hz to 2 MHz). In the case of variable flow rates, PWM modulation of the duty cycle at the H-bridge alone cannot be used to dim the applied current. Variable flow rates require dimming of the applied constant current at the constant current regulator, as explained above. Since the full current is applied at each ON pulse, the electrolytic cell could experience an excess of current even if the flow rate is low, resulting in excessive dehydration of the membrane, overheating, accelerated aging, and irreversible cell damage. PWM of the duty cycle at the H-bridge does not alter the electrochemical rate of ozone production at the electrode because the current applied is the same; however, PWM of the duty cycle at the H-bridge intermittently stops production during the OFF cycles. During the ON cycles, the process occurs at a rate dictated by the applied constant current, which is adequately dimmed based on chemical and physical requirements, such as flowrate; however, PWM can modulate the ozone production without altering the electrolytic processes, which are determined primarily by the level of hydration (flow rate) and aging of the cell (parasitic currents). Therefore, in combination with the dimming of the applied constant current at the constant current regulator, PWM is beneficial for an additional, temporary, and faster adjustment of the ozone output over intermediate time scales, such as hundreds of milliseconds to seconds, to hours. A power management system in accordance with the principles of the present invention can include a source of AC, an AC/DC converter, a constant current regulator, an H-bridge, a sensor, an electrolytic cell, and a microcontroller. Relevant sensors can include, but not limited to, a flow meter, a current sensor, a voltage sensor, an ozone sensor, temperature sensors, and the like. First, the AC source is converted to a DC current by the AC/DC converter. Next, the DC current enters the constant current regulator that maintains the current constant at a constant current setpoint. The microcontroller controls the constant current setpoint based on sensor input. The constant current enters the H-bridge, which drives the electrolytic cell. The constant current regulator typically includes an analog device that adjusts the output current to maintain the current at a user-defined constant current setpoint. Load regulation, i.e. the accuracy to maintain the current stable, is typical to be less than about +/−2.5%, usually less than about +/−1%, but likely less than about +/−0.5%. As previously described, LED drivers are convenient power supplies for these applications. In addition, many LED drivers enable adjustment of the current output at a user-defined constant current setpoint via a dimming input. In the absence of an LED driver, it is possible to use analog adjustable regulators that can be configured to output a constant current. In this case, the DC current is regulated to the desired current setpoint with a separate current regulator that might include an analog current regulator. The H-bridge can drive the electrolytic cell. Water flows through the electrolytic cell while the constant current is applied, producing electrolytic products. In a preferred embodiment, water flows inside an ozone-generating electrolytic cell comprised of BDD anode and cathode at either side of a PEM. The applied current results also in the production of ozone. The direction change of the H-bridge corresponds to the polarity reversal of applied current, which is helpful in the removal of limescale such as when hard regular tap water is used to produce ozone. The H-bridge direction enables the polarity reversal of the cell and may be controlled by the microcontroller. The polarization reversal, although recommended for electrolytic ozone generators, is not mandatory. The application of polarization reversal is facultative and does not limit the current invention. Water consumption and gas evolution by electrolysis at the electrode surface is a significant limitation for electrolytic generators (Equations 1 and 2). Therefore, it is reasonable to assume that a constant current to be directly proportional, at least in a first-order approximation, to the ability to refurbish water to the electrode surfaces, i.e. to the flow rate. Via a proper process, the microcontroller can adjust the constant current regulator via a dimming of the applied current proportionally to the flow rate. In practice, the constant current dimming by the microcontroller should not be directly proportional to the flow rate. This is because an analytical relationship between the constant current dimming and the flow rate can be very complex; however, this can be established by recording the electrolytic products with a suitable sensor and the flow rate. Without any limitation to the current invention, a particular embodiment can include voltage and current sensors. Typically, voltage and current sensors are placed between the constant current regulator and the H-bridge. These sensors can also be placed after the H-bridge and may not require any particular order. If polarization reversal is applied, when the voltage and current sensors are placed after the H-bridge, current and voltage sign changes would need to be accounted for. Current sensing can be utilized to ensure that the constant current regulator works appropriately. In addition, the relationship between the electrolytic product concentration and the current dimming can also be obtained empirically as a function of the flow rate. Measurement of the voltage enables estimation of the electrolytic cell lifetime. For example, it is typical in electrolytic cells for ozone generation that the applied voltage for a given constant current increases over time as the cell ages. The electrical resistance increase of the cell is typically associated with membrane degradation, loss of sulfonate groups, and mineral crystallization (limescale). In this case, despite the current being kept constant, the degradation process also could reduce the production yield of electrolytic products, such as ozone. Therefore, it is desired to adjust the dimming of the current to compensate for the reduction of ozone production during the lifetime of the cell, which can be in the order of thousands of hours. Monitoring the flow rate allows maintaining electrolytic production constant at the desired level. As explained above, the hydration/dehydration process occurring at the electrode can be compensated with changes in the applied current. Therefore, monitoring the flow rate with a flow sensor is the primary sensing to control the electrolytic process. Other parameters might be desirable to control the electrolytic process. These may be but are not limited to the fluid temperature, conductivity, presence of oxidizable organics, and so on. Many electrolytic products are typically oxidants, which have an intrinsic lifetime: the higher the oxidation potential, the shorter the lifetime. Temperature plays an important role in the decomposition of oxidants: the higher the temperature, the shorter the lifetime. In some cases, it is, therefore, desirable to measure the temperature of the incoming fluid to estimate the expected lifetime of the oxidants. For example, suppose the desired concentration of the electrolytic products is expected at a specific time after production. In that case, the production rate, i.e. the applied current, might be increased proportionally to the temperature to generate more oxidants at the cell and compensate for the higher decomposition rate. Many electrolytic products are typically oxidants, which have an intrinsic lifetime: the higher the oxidation potential, the shorter the lifetime. Temperature plays an important role in the decomposition of oxidants: the higher the temperature, the shorter the lifetime. In some cases, it is, therefore, desirable to measure the temperature of the incoming fluid to estimate the expected lifetime of the oxidants. For example, suppose the desired concentration of the electrolytic products is expected at a specific time after production. In that case, the production rate, i.e. the PWM, might be increased proportionally to the temperature to generate more oxidants at the cell and compensate for the higher decomposition rate. Mechanisms have been described that can cause the electrolytic product concentration to vary over time. Variations of physical and chemical processes can be compensated for by changing the applied constant current. It has been discovered that the improved control of the applied current can provide adjustments over the timescales of the different phenomena occurring during the electrolytic process. This power management also ensures efficient production and preservation of the lifetime of the electrolytic cell. Initial Considerations Generally, one or more different embodiments may be described in the present application. Further, for one or more of the embodiments described herein, numerous alternative arrangements may be described; it should be appreciated that these are presented for illustrative purposes only and are not limiting of the embodiments contained herein or the claims presented herein in any way. One or more of the arrangements may be widely applicable to numerous embodiments, as may be readily apparent from the disclosure. In general, arrangements are described in sufficient detail to enable those skilled in the art to practice one or more of the embodiments, and it should be appreciated that other arrangements may be utilized and that structural, logical, electrical and other changes may be made without departing from the scope or spirit of the present invention. Particular features of one or more of the embodiments described herein may be described with reference to one or more particular embodiments or figures that form a part of the present invention, and in which are shown, by way of illustration, specific arrangements of one or more of the aspects. It should be appreciated, however, that such features are not limited to usage in the one or more particular embodiments or figures with reference to which they are described. The present disclosure is neither a literal description of all arrangements of one or more of the embodiments nor a listing of features of one or more of the embodiments that must be present in all arrangements. Headings of sections provided in this patent application and the title of this patent application are for convenience only and are not to be taken as limiting the present invention in any way. Components and parts that are connected to or in communication with each other need not be in continuous connection or communication with each other, unless expressly specified otherwise. In addition, components and parts that are connected to or in communication with each other may communicate directly or indirectly through one or more connection or communication means or intermediaries, logical or physical. A description of an aspect with several components in connection or communication with each other does not imply that all such components are required. To the contrary, a variety of optional components may be described to illustrate a wide variety of possible embodiments and in order to more fully illustrate one or more embodiments. Similarly, although process steps, method steps or the like may be described in a sequential order, such processes and methods may generally be configured to work in alternate orders, unless specifically stated to the contrary. In other words, any sequence or order of steps that may be described in this patent application does not, in and of itself, indicate a requirement that the steps be performed in that order. The steps of described processes may be performed in any order practical. Further, some steps may be performed simultaneously despite being described or implied as occurring non-simultaneously (e.g., because one step is described after the other step). Also, steps are generally described once per aspect, but this does not mean they must occur once, or that they may only occur once each time a process, or method is carried out or executed. Some steps may be omitted in some embodiments or some occurrences, or some steps may be executed more than once in a given aspect or occurrence. When a single component or article is described herein, it will be readily apparent that more than one component or article may be used in place of a single component or article. Similarly, where more than one component or article is described herein, it will be readily apparent that a single device or article may be used in place of the more than one component or article. The functionality or the features of a component may be alternatively embodied by one or more other components that are not explicitly described as having such functionality or features. Thus, other embodiments need not include the component itself. Techniques and mechanisms described or referenced herein will sometimes be described in singular form for clarity; however, it should be appreciated that particular embodiments may include multiple iterations of a technique or multiple instantiations of a mechanism unless noted otherwise. Alternate implementations are included within the scope or spirit of various embodiments in which, for example, functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those having ordinary skill in the art. Conceptual Architecture A typical, but not limiting, configuration of electronics for power management of an electrolytic cell in accordance with the principals of the present invention is outlined in the block diagram ofFIG.1. An AC/DC converter101is connected to an AC power source. The converted DC voltage enters a constant current regulator102, maintaining the output103at a constant current. The constant current output103is determined by the constant current setpoint controlled by the dimming output of a microcontroller108. The DC output of the AC/DC converter101can also be used to feed a constant voltage regulator107typically used to power the microcontroller108. Typically, the AC/DC converter101and constant current regulator102can be included in an enclosed constant current power supply100, like the ENEDO RCL050 dual dimming LED driver available from Enedo Inc., Martinkyläntie 43, 01720 Vantaa, Finland, which enables adjustment of the current output at a user-defined constant current setpoint via a dimming input to provide an efficient and convenient way to maintain a constant current with variable loads. A voltage sensor104and a current sensor105can be placed along output line103to monitor the voltage and current. The values of voltage and current are used by the microcontroller108, as described in the present invention. An H-bridge106drives an electrolytic cell109. The polarity of output line103is constant, but is reversed by the H-bridge106depending on the reverse polarity signal from the microcontroller108. Polarity reversal changes the anode of the electrolytic cell109into the cathode and vice versa. The H-bridge106can also turn on and off the power applied to the electrolytic cell109with a frequency and duty cycle provided by the H-bridge106via pulse width modulation (PWM). Fluid temperature and flow rate are measured by thermometer110and flow sensor111, respectively. Electrolytic product concentration is preferably measured downstream from the electrolytic cell with a sensor112specific to the type of product. FIG.2illustrates a block diagram of an alternative, but not limiting, configuration of electronics for power management of an electrolytic cell in accordance with the principals of the present invention. In this example, AC/DC converter201and constant current regulator202are not included in a single power supply; constant current regulator202can comprise a regulator comprising a metal-oxide-semiconductor field-effect (MOSFET) transistor such as the standard LM317-based adjustable power supply circuit that can be configured to output a constant current. Constant current203is determined by the constant current setpoint controlled by the dimming output of the microcontroller208. The DC output203of the AC/DC converter201can also be used to feed a constant voltage regulator207, typically used to power the microcontroller208. Voltage sensor204and current sensor205are placed along output line203to monitor the voltage and current, respectively. The values of voltage and current are used by the microcontroller208as described. The electrolytic cell209is driven by an analog device such as a double pole double throw (DPDT) relay206. The DPDT206enables the polarity reversal with a time interval set by timer213, which could be controlled by microcontroller208; however, the timer213is often an independent device with a time interval set manually but the user. Furthermore, the DPDT206does not allow the modulation of the power applied to the electrolytic cell with a PWM like in the previous example. Fluid temperature and flow rate are measured by thermometer210and flow sensor211, respectively. Electrolytic product concentration is ideally measured in line just downstream from the electrolytic cell with a sensor212specific to the type of product. The power management of the electrolytic cell can comprise constant current regulation, H-bridge control by PWM, and dimming control.FIG.3illustrates a time series chart of some possible dynamic ranges of constant current regulation, H-bridge control by PWM, and dimming control power management methods in accordance with the principles of the present invention. A dynamic range is defined as the fastest response time of a current control to maintain the applied constant current within a current deviation of less than about +/−10% of the desired constant current setpoint. It would be desired that the deviation from the applied constant current and the desired constant current setpoint be less than about 5%, ideally less than about 2%, preferably less than about 1%. The dynamic range is also referred to as the rise time of the current control as the minimum time necessary for reaching the desired setpoint within the desired current deviation. For an electrolytic cell device, electric load is not constant and can vary for the reasons described above on various time scales. Therefore, it is appropriate to adjust the applied constant current using the most suitable control. A constant current regulator typically can maintain the constant current close to the desired applied current setpoint within the desired current deviation, even when load changes occur between tenths of microseconds to milliseconds. Fast load fluctuations can be due to fast dynamic changes at the interfaces of the electrode and water due to the erratic evolution of gasses and other electrolytic processes. Another typical fast fluctuation that requires fast current adjustments is the polarity reversal. Typically, the polarity reversal can occur in the sub-millisecond time scale. FIGS.4-10reproduce oscilloscope displays illustrating examples of various applied current profiles over time resulting from the application of power management of an electrolytic cell in accordance with the principals of the present invention.FIG.4is illustrates a typical example of the voltage polarity change that results in a change of the current applied, with current on the vertical axis and time (in 10 μs/div) on the horizontal axis. InFIG.4the current profile is shown in solid line (e.g., ----) and the applied current is shown in the dashed line (e.g., - - -). In this illustrative example, the polarity reversal change happens in less than 10 microseconds within the constant current regulator dynamic range, and the applied current follows the change closely. After the polarity change, it is important to notice that the current is stable around the desired constant current setpoint in less than 1-2 microseconds and remains close to the current setpoint within less than about 2% of the value and even about 0.5% of the setpoint value. This adjustment requires fast response time that is typically in analog devices. An analog constant current regulator can maintain the current constant even when the polarity changes abruptly because of load variability and polarity reversal changes; however, it would be practically impossible to provide such a tight control using digital feedback based on a microcontroller proportional-integral-derivative (PID) loop because the characteristic time constant of the cell changes over time. The characteristic time constant of the cell, i.e. how fast the cell responds to temporal changes like the polarity reversal or electrolytic processes, is highly dependent on the physical and chemical properties of the electrodes, PEM, and fluid. Thus, permanent damage to the electrodes and membrane, transient heat increases and dissipation, and transient changes in the chemical composition of the fluid, such as ionic conductivity, can alter the characteristic time constant of the cell. A possible approach would be a digital PID feedback loop; however, digital PID feedback loops can result in unpredictable current adjustments. A digital PID feedback loop enables control of an electronic device based on an input signal, a user-defined setpoint, and an output signal. A typical PID feedback loop is set to minimize the difference (error) between the input signal and the setpoint in microcontrollers. The feedback loop in a microcontroller typically uses a proportional (P) parameter, an integral (I) parameter, and a differential (D) parameter. The output signal of a PID loop is a train of pulses (squared wave) at a fixed frequency (typically 200 Hz to 2 MHz) but with modulated pulse widths, resulting in a modulated duty cycle known as pulse width modulation (PWM). The duty cycle of the PWM signal is typically a linear combination of the error multiplied by the PID parameters. The duty cycles are usually determined by an empirical process and are unique to the electrolytic system, more precisely to its time constant. If the time constant of the system changes, the PID parameters also change; however, PID parameters do not normally change during operation of the system because the PID parameters would have to be learned empirically again, typically by trial and error. It would be implemented without frequently interrupting the function of the system. Special processes are available to automatically re-learn the new PID parameters, but these processes produce sub-optimal parameters that do not predict well enough the time constant change. For an electrolytic cell, a PID feedback loop that uses sub-optimal PID parameters is either too slow to properly maintain the constant current at the constant current setpoint or overshoots above the current setpoint, causing an excessive overcurrent through parasitic current pathways that can induce transient heating, permanent deformation of the PEM, and irreversible electrode damage. Therefore, digital PID feedback loops cannot substitute for an analog constant current regulator. Fluctuations of the electric load of the cell and the polarity reversal change are too fast for the microcontroller to maintain the current within a reasonable deviation from the setpoint. As a result, the current can easily exceed the desired constant current setpoint by more than 5% of the current setpoint, potentially resulting in permanent damage to the cell. Moreover, continuous use of an electrolytic cell is also often accompanied by an increase in the cell temperature (primarily due to the passage of current in the electrodes and fluid). As the cell time constant changes due to the temperature, the initial set of PID parameters is no longer suitable, resulting in unpredictable current adjustments. In contrast, a PWM control of the H-bridge can be helpful to tune the electrolytic production but only when an analog constant current regulator is already in place. When an H-bridge controls an electrolytic cell, the applied constant current can be modulated by a PWM, as illustrated inFIG.5.FIG.5illustrates an example of the current profile of the specific case of an electrolytic cell for the generation of ozone where the applied current is modulated at the H-bridge with a PWM signal (600 Hz) in conjunction with a change of the dimming of applied constant current at the constant current regulator (see discussion, below). InFIG.5, the solid line (e.g., ----) represents the current profile of an electrolytic cell, the dashed line (e.g., - - - -) represents the applied constant current setpoint as changed by the dimming control, and the dash/dot line (e.g., -⋅-⋅-⋅-) represents the PWM control. The constant current regulator maintains the applied constant current at the desired constant current setpoint. Since a PWM control is used at the H-bridge, the cell is turned on-off at a frequency of about 600 Hz at a respective duty cycle. Since a PEM electrolytic cell for ozone generation behaves primarily as a resistor, the current also is modulated on-off with the same duty cycle. The analog constant current regulator is fast and limits well the applied constant current at the desired setpoint even when the rise of the PWM pulse is very fast, in the order of microseconds: in this illustrative example, the current setpoint change occurs in about 2 ms, within the dimming control dynamic range. PEM electrolytic cells do not behave like brushed motors (capacitance) but rather as resistors. The current applied to the cell closely follows the voltage change during the PWM pulse, which happens in the order of microseconds. Using a PWM signal to the current applied to an electrolytic cell producing ozone results in ozone production being turned on and off with the same duty cycle. This type of control is beneficial to adjust ozone output to compensate for fluctuations that happen as fast as tenths of milliseconds or slower (seeFIG.3). Since the applied current is controlled on the fast time scale by an analog constant current regulator, the sudden changes of current due to the PWM are well maintained at the desired constant current setpoint. One of the benefits of controlling the applied current using an analog constant current regulator in conjunction with a PWM is that the current is constant at the desired setpoint. As explained above, hydration and dehydration of the electrolytic cell during ozone production are strictly dependent on the current. Therefore, maintaining the current constant during the PWM cycles results in constant hydration of the cell, which also preserves better the dynamic behavior of the electrodes and PEM membrane, which in turn results in the extended longevity of the cell and constant ozone production. The applied current setpoint can be adjusted by a dimming control of the analog constant current regulator. This control type is relatively slower than the H-bridge control with PWM and the analog constant current regulator. Typically, for an electrolytic cell producing ozone, the dimming control of the applied constant current is beneficial when the water flow rate varies. As explained above, the hydration of the membrane is important to preserve the integrity of the membrane and allow for constant ozone production. Moreover, the water flow allows for the dissipation of heat generated by the current passage through the electrodes and membrane. If the flow rate is diminished, it is desirable to reduce the applied current to preserve the cell integrity. Dimming control can compensate for flow rate fluctuations in milliseconds to seconds or slower time scales. In addition, dimming control of the applied current setpoint is beneficial in conjunction with managing the applied current of the analog constant current regulator.FIG.6illustrates the case of a dimming control of the applied current setpoint (dashed line).FIG.6illustrates an example of a current profile (the solid line, e.g., ----) of an electrolytic cell upon change of the current setpoint (dashed line, e.g., - - -) with current on the vertical axis and time (in 100 ms/div) on the horizontal axis. In this illustrative example, the current setpoint change occurs in about 20 ms. As the current setpoint changes, the applied current (solid line) follows closely thanks to the analog constant current regulator, which maintains the current within less than about 5%. FIG.7illustrates an example of power management of an electrolytic cell producing ozone, in the absence or at a constant PWM H-bridge control, for maintaining ozone output constant by changing the current setpoint with the dimming control in response to the change of the flow rate, with current on the vertical axis and time (in 10 s/div) on the horizontal axis.FIG.7illustrates how the ozone output is maintained constant even when the flow rate varies, as the constant current setpoint is changed proportionally to the flow rate. FIGS.8and9illustrate other ways to control the ozone output.FIG.8illustrates an example of power management of an electrolytic cell producing ozone, in the absence of a PWM H-bridge control, for obtaining an exemplary ozone output by altering the current setpoint with the dimming control in response to the flowrate change and the desired ozone output, with current on the vertical axis and time (in 10 s/div) on the horizontal axis. InFIG.8, the dimming of the current setpoint is not proportional to the flow rate, with the dimming of the current setpoint used to increase the ozone output momentarily. This situation is typical when the electrolytic cell is not driven by an H-bridge (FIG.2); however, the same ozone output profile can be obtained by the modulation of the PWM duty cycle an H-bridge. This is seen inFIG.9, which illustrates an example of power management of an electrolytic cell producing ozone for obtaining an exemplary ozone output by altering the PWM duty cycle with the H-bridge control in response to the desired ozone output, with current on the vertical axis and time (in 10 s/div) on the horizontal axis. In this example, the current setpoint is changed with the dimming control in response to the change of the flow rate while altering the PWM H-bridge control is used to increase the ozone output momentarily. FIG.10illustrates an example of power management of an electrolytic cell producing ozone, in the absence of a constant PWM H-bridge control, for maintaining ozone output constant by the use of the dimming control of the current setpoint to compensate for the loss of ozone output due to the aging of the cell, with current on the vertical axis and time (in month/div) on the horizontal axis. Typically, the aging of the cell can be easily monitored by the applied voltage as measured by voltage sensors or. Therefore, as the average voltage increases due to the rise of the average cell electrical resistance and parasitic current paths, the dimming of the applied current setpoint also increases to force the cell to produce a constant ozone production. While a system and apparatus in accordance with the principles of the present invention has been described with specific embodiments, other alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it will be intended to include all such alternatives, modifications and variations set forth within the spirit and scope of the appended claims. | 37,387 |
11862829 | DETAILED DESCRIPTION Elements having the same function and mode of operation are each provided with the same reference signs inFIGS.1through3. With reference toFIG.1, a method is described for setting an operating strategy for a fuel cell system2of a power generation device1in the form of a hybrid vehicle depending on an operating mode of the hybrid vehicle. For this purpose, in a first step S1, at least one current operating parameter P1of the hybrid vehicle is ascertained by means of an ascertainment unit3. More precisely, a current operating state of the hybrid vehicle1, a current vehicle speed of the hybrid vehicle, a current operating temperature of at least one system component of the hybrid vehicle, a current state of charge, SOC, of a traction battery4of the hybrid vehicle, and/or a desired power in the vehicle electrical system of the hybrid vehicle are/is ascertained as the at least one current operating parameter P1. In addition, at least one cumulative and/or predictive operating parameter P2, P3, P4of the hybrid vehicle is ascertained by means of the ascertainment unit3. More precisely, information P2regarding the aging state, such as, for example, aging data from at least one functional component of the hybrid vehicle or a number of switch on/switch off instances of the hybrid vehicle, information P3regarding a driver or a driver profile of the driver of the hybrid vehicle, such as frequency and/or duration of stop phases of the hybrid vehicle, frequency and/or duration of shutdown phases of the hybrid vehicle in the form of a vehicle, or an average demand for drive power in the hybrid vehicle, and/or prediction data P4such as navigation data of a navigation system of the hybrid vehicle, and/or Car2X data of a hybrid vehicle are ascertained as the at least one cumulative and/or predictive operating parameter P2, P3, P4of the hybrid vehicle, and utilized as described above. In a second step S2, thereafter, a suitable operating strategy can be ascertained for the fuel cell system2on the basis of the at least one current operating parameter P1and the at least one cumulative and/or predictive operating parameter P2, P3, P4of the power generation device. This can be carried out again by the ascertainment unit3. As soon as the suitable operating strategy has been ascertained, the ascertained operating strategy for the fuel cell system2can be set by a setting unit8in a third step S3. Subsequently, the method can start over in a predefinable way based on the operating parameters that are now present. The switch and/or adaptation of the operating strategy can take place from any variant to any other variant. InFIG.2, a specific part of a circuit arrangement10represented inFIG.3is represented in the form of a block diagram. As is apparent inFIG.2, air from the surroundings17of the hybrid vehicle can be supplied, by means of an air supply unit5of the fuel cell system2, to a fuel cell stack7and/or a cathode section of the fuel cell stack7. The air supply unit5includes an air filter16, a compressor6, and an intercooler12. Downstream from the intercooler a bypass line is formed with a bypass valve13, via which the air can be directed past the cathode section when the fuel cell system2is switched off. Downstream from the fuel cell stack7and/or the cathode section of the fuel cell stack7, a check valve19is arranged, which blocks for the case in which the bypass valve13is opened, in order to introduce an oxygen depletion into the cathode section. Moreover, the system represented inFIG.2includes an electric motor14and an associated inverter15. InFIG.3, a power generation device1is represented in the form of a hybrid vehicle with a traction battery4, a fuel cell system2, and a fuel tank18. The hybrid vehicle includes a circuit arrangement10for setting the operating strategy for the fuel cell system2of the hybrid vehicle depending on an operating mode of the hybrid vehicle. The hybrid vehicle further includes a control unit11with an ascertainment unit3and a setting unit8. In addition, a computer program20for carrying out the above-described method is installed on the control unit11. In addition to the represented embodiments, the invention allows for further design principles. This means, the invention is not to be considered to be limited to the exemplary embodiments explained with reference to the figures. In particular, the method forms explained above in detail with reference to the dependent claims can be carried out within the scope of the flowchart represented inFIG.1and/or the corresponding method. Moreover, it should be noted that, in a hybrid vehicle, usually a hydrogen recirculation blower as well as a coolant pump can be switched off during the switch-off of the hybrid vehicle in an end phase after an after-run procedure. Upon detection of short shutoff phases of the hybrid vehicle, for example, during delivery operation, at least these actuators can nevertheless continue to be operated. | 4,995 |
11862830 | In the figures,1represents an arc heat sink,2represents an ethanol cavity,3represents a heat-dissipation through hole,4represents an anode catalyst layer,5represents an anode diffusion layer,6represents a cathode diffusion layer,7represents a cathode catalyst layer,8represents a PEM,9represents an anode support tube, and10represents a cathode support tube. DESCRIPTION OF THE EMBODIMENTS The present disclosure will be further described below in conjunction with the accompanying drawings and specific examples, but the protection scope of the present disclosure is not limited thereto. As shown inFIG.1andFIG.2, the single tubular DEFC includes a housing, a cathode support tube10, a cathode, a PEM8, an anode, an anode support tube9, and an ethanol cavity2that are sequentially arranged from outside to inside. Variable-cross-section arc heat sinks1are uniformly distributed on a side wall of the housing, such that an intake gas is uniformly distributed and water generated at a cathode side can be drained. Heat-dissipation through holes3are uniformly distributed on a side wall of the housing to realize the passive air intake of the cell, which is conducive to the discharge of water; and the heat-dissipation through holes3may have an opening rate of 50% to 60%. The PEM8may be one or more selected from the group consisting of commercially-available Nafion115, Nafion211, Nafion117, and Nafion112, and may be activated with a mixed acid. The anode includes an anode diffusion layer5and an anode catalyst layer4, and the cathode includes a cathode diffusion layer6and a cathode catalyst layer7. The catalyst layer may have a porosity of 0.4 to 0.6, and the diffusion layer may have a porosity of 0.4 to 0.86. In this example, the catalyst layer may have a porosity of preferably 0.5 to 0.6, and the diffusion layer may have a porosity of preferably 0.6 to 0.8; and a thickness of the diffusion layer may be greater than a thickness of the catalyst layer. The anode, cathode, and PEM8together constitute a MEA for a DEFC. As shown inFIG.3, the cathode catalyst layer7is of a convex and ordered design with a convex curvature radius R1of 0.2 mm to 0.3 mm and a convex angle θ of 40° to 60°. The convex and ordered design can make a surface of the cathode catalyst layer7have a large liquid water contact angle, and the large angle θ is conducive to the separation of liquid water. During the reaction process, since the convex and ordered design allows a large pressure difference inside the cathode catalyst layer7, the generated water can be timely and effectively drained under the action of the pressure difference. In addition, compared with the neat catalyst layer designed in the prior art, an SSA of the catalyst layer is increased to improve the reaction rate and current density, which is also conducive to the timely discharge of the generated heat. As shown inFIG.4, the oxidation reaction of ethanol is mainly considered at the anode; and in order to make ethanol pass through the diffusion layer and reach the catalyst layer for reaction as much as possible and improve the hydrophilic effect at the anode side, the anode catalyst layer4is of a concave and ordered design with a concave curvature radius R2of 0.2 mm to 0.3 mm and a concave angle α of 30° to 45°. The concave and ordered design makes a surface of the anode catalyst layer4have a small liquid water contact angle, which increases the water adsorption capacity. The convex surface of the anode diffusion layer5makes ethanol at the anode largely infiltrate a surface of the anode catalyst layer4, which improves the mass transfer rate and current density. In addition, compared with the neat catalyst layer designed in the prior art, an SSA of the anode catalyst layer4is increased to improve the reaction rate and current density, which is also conducive to the timely discharge of the generated heat. Example 1 As shown inFIG.5, an MEA for a DEFC was fabricated by step-by-step dip coating on an anode support tube9, including the following steps. Step (1): 25.5 g of asphalt microsphere particles, 4.5 g of an XR-72 toner, 20 mL of Tween 80, 5 mL of triethylhexylphosphate, and 0.4 g of ammonium persulfate (APS) were weighed and mixed with 20 g of deionized water, and the resulting mixture was stirred and ultrasonically dispersed, then subjected to injection molding, and sintered in a crucible furnace to obtain a cathode support tube10and an anode support tube9. Step (2): 20 g of an XR-72 carbon powder was weighed and dissolved in a solution with a PTFE content of 15 wt. %, then 5 mL of an analytically-pure solution (a low-concentration methanol solution or low-concentration ethanol solution) was added, and the resulting mixture was ultrasonically dispersed by a magnetic disperser and stirred to obtain a diffusion layer solution. Step (3): The diffusion layer solution was uniformly coated on an outer side of the anode support tube9, and when a weight gain of the anode support tube9reached 4 mg/cm2, the coating was stopped to form the anode diffusion layer5at the outer side of the anode support tube9; a concave surface A2of the nanoimprint mold A was attached to the anode diffusion layer5, and the resulting product was put as a whole in a drying oven, heat-dried for 1 h to be thermally expanded, and taken out; and the nanoimprint mold A was separated to obtain a convex and ordered anode diffusion layer5, and the anode diffusion layer was allowed to stand for half an hour in a dry environment. Step (4): 30 mg of a metal catalyst Pt/C was weighed and mixed with 0.5 mL of pure water, and then 0.5 mL of a polymer electrolyte emulsion, 10 mL of a Nafion emulsion with a mass fraction of 5%, 0.5 mL of a binder, and 5 mL of an analytically-pure solution were added to prepare a catalyst layer slurry; the catalyst layer slurry was coated on a surface of the anode diffusion layer5, and when a weight gain reached 8 mg/cm2, the coating was stopped to obtain an anode catalyst layer4with a smooth outer surface; and the resulting product was put as a whole in a drying oven, heat-dried for 1 h, taken out, and allowed to stand for half an hour in a dry environment, where an inner surface of the anode catalyst layer4was in contact with a surface of the convex anode diffusion layer5and was concave. Step (5): The obtained anode was heated in a constant-temperature water bath for 1 h and then dried at 100° C., and then an activated PEM8was hot-pressed tightly on the surface of the anode catalyst layer4. Step (6): The catalyst layer slurry (the same as in the step (4)) was repeatedly coated on a surface of the PEM8, and when a weight gain reached 8 mg/cm2, the coating was stopped to form a cathode catalyst layer7at an outer side of the PEM8; a concave surface B2of the nanoimprint mold B was attached to the cathode catalyst layer7, and the resulting product was put as a whole in a drying box, heat-dried for 1 h to be thermally expanded, and then taken out; and the nanoimprint mold B was separated to obtain a convex and ordered cathode catalyst layer7, and the cathode catalyst layer was allowed to stand for half an hour in a dry environment. Step (7): The diffusion layer solution (the same as in the step (2)) was repeatedly coated on a surface of the cathode catalyst layer7, and when a weight gain reached 4 mg/cm2, the coating was stopped to form the cathode diffusion layer6with a smooth outer surface on an outer side of the cathode catalyst layer7; and the resulting product was put as a whole in a drying oven, heat-dried for 1 h, taken out, and allowed to stand for half an hour in a dry environment, where an inner surface of the cathode diffusion layer6was in contact with a surface of the convex cathode catalyst layer7and was concave. Example 2 As shown inFIG.6, an MEA for a DEFC was fabricated by gradually fabricating each layer of the MEA on an inner surface and an outer surface of a PEM8, including the following steps. Step (1): An activated PEM8was prepared and placed in a dry environment. Step (2): 30 mg of a metal catalyst Pt/C was weighed and mixed with 0.5 mL of pure water, and then 0.5 mL of a polymer electrolyte emulsion, 10 mL of a Nafion emulsion with a mass fraction of 5%, 0.5 mL of a binder, and 5 mL of an analytically-pure solution were added to prepare a catalyst layer slurry; the catalyst layer slurry was coated on the inner surface of the PEM8, and when a content of the catalyst layer slurry reached 8 mg/cm2, the coating was stopped to obtain an anode catalyst layer4; and a convex surface A1of the nanoimprint mold A was attached to the anode catalyst layer4, the resulting product was put as a whole in a drying oven, heat-dried for 1 h to be thermally expanded, and then taken out, and the nanoimprint mold A was separated to obtain a concave and ordered anode catalyst layer4. Step (3): 20 g of an XR-72 carbon powder was weighed and dissolved in a solution with a PTFE content of 15 wt. %, then 5 mL of an analytically-pure solution was added, and the resulting mixture was ultrasonically dispersed with a magnetic disperser and stirred to obtain a diffusion layer solution; the diffusion layer solution was uniformly coated on an inner surface of the formed anode catalyst layer4, and when a weight gain reached 4 mg/cm2, the coating was stopped to form the anode diffusion layer5with a smooth outer surface; and the resulting product was put as a whole in a drying oven, heat-dried for 1 h, and then taken out, where an inner surface of the anode diffusion layer5was in contact with the concave and ordered anode catalyst layer4and was convex. Step (4): The catalyst layer slurry (the same as in the step (2)) was coated on the outer surface of the PEM8, and when a weight gain reached 8 mg/cm2, the coating was stopped to form a cathode catalyst layer7at an outer side of the PEM8; a concave surface B2of the nanoimprint mold B was attached to the cathode catalyst layer7, and the resulting product was put as a whole in a drying box, heat-dried for 1 h to be thermally expanded, and then taken out; and the nanoimprint mold B was separated to obtain a convex and ordered cathode catalyst layer7, and the cathode catalyst layer was allowed to stand for half an hour in a dry environment. Step (5): The diffusion layer solution (the same as in the step (3)) was repeatedly coated on an outer surface of the cathode catalyst layer7, and when a weight gain reached 4 mg/cm2, the coating was stopped to form the cathode diffusion layer6with a smooth outer surface on an outer side of the cathode catalyst layer7; and the resulting product was put as a whole in a drying oven, heat-dried for 1 h, taken out, and allowed to stand for half an hour in a dry environment, where an inner surface of the cathode diffusion layer6was in contact with the convex cathode catalyst layer7and was concave. FIG.7is a schematic structural diagram of the nanoimprint mold A in Example 1, where A1represents a convex surface of the nanoimprint mold A and A2represents a concave surface of the nanoimprint mold A. The nanoimprint mold B is different from the nanoimprint mold A only in that the curvature radius R and the concave and convex angles are different; and a schematic diagram of the nanoimprint mold B is not listed here. The MEA, anode diffusion layer, anode catalyst layer, cathode diffusion layer, and cathode catalyst layer conventionally fabricated are all designed to be neat, as shown inFIG.8. From the comparison between polarization characteristic curves of the MEAs fabricated by the conventional method and the method of the present disclosure shown inFIG.9, it can be clearly seen that the performance of a cell with an ordered catalyst layer design is higher than the performance of a cell fabricated by the conventional method, which effectively improves the working capacity of the cell. The above examples are preferred implementations of the present disclosure, but the present disclosure is not limited to the above implementations. Any obvious improvement, substitution, or modification made by those skilled in the art without departing from the essence of the present disclosure should fall within the protection scope of the present disclosure. | 12,253 |
11862831 | DETAILED DESCRIPTION Described is a container for a fuel cell system configured to supply power to an external unit. The container includes a system frame configured to house one or more components of a fuel cell system, a plurality of fuel cells supported by the system frame and configured to provide power to an external unit, and a raised floor configured to support the plurality of fuel cells. Referring toFIG.1, an example of a container10for a fuel cell system is shown. The container10can be configured to house a fuel cell system, which can provide power to an external unit. The external unit can be a residential or commercial building. However, it should be understood that the external unit can be any type of electricity demanding structure, system, and the like. The external unit can be configured to request power (e.g., make a power request or demand) from the fuel cell system to receive power from the fuel cell system. The system frame12is configured to house (e.g., support) one or more components of the fuel cell system, for example, a plurality of fuel cell holders18A-18X (fuel cell holders18A-18L are shown inFIG.1), a plurality of DC-DC converters20A-20F (DC-DC converters20A-20C are shown inFIG.1), and a raised floor22. The system frame12can also be configured to support one or more auxiliary load center(s)24. The auxiliary load center(s)24can include one or more components configured to provide power to one or more auxiliary systems of the container10, as described in further detail below With additional reference toFIGS.2and3, the container10includes a system frame12, a housing14, and a housing frame16. The system frame12can be mated to the housing frame16. The housing frame16is configured to connect the system frame12to the housing14. The housing can then house (e.g., envelope, enclose, etc.) one or more of the components of the fuel cell system supported or contained within the system frame12. The housing14protects these components from an external environment26of the housing. The fuel cell holders18A-18X are each configured to hold a fuel cell (not pictured). A simplified version of the container10having fuel cells is shown inFIG.10and will be described later in this specification. The container10can include any suitable number of fuel cell holders18A-18X and fuel cells. For example, as shown, the container10can include twenty-four fuel cell holders and twenty-four fuel cells. The fuel cells can be grouped into fuel cell units. For example, each fuel cell unit can include four fuel cells connected in parallel. In this example, because there are twenty-four fuel cells, if each fuel cell unit includes four fuel cells, this would result in six fuel cell units. Of course, other types of arrangements regarding the number of fuel cells that form a fuel cell unit can also be contemplated. The DC-DC converters20A-20F can each be connected to a fuel cell unit. Accordingly, the container10can include six DC-DC converters, for example. The DC-DC converters20A-20F are electrically connected to the fuel cell units and are configured to regulate the output power and voltage of each fuel cell unit. The plurality of fuel cell holders18A-18X and the plurality of DC-DC converters20A-20F can be supported by the raised floor22. The raised floor22can be formed from metal or fiberglass. In this example, the raised floor22is a metal grating. Referring now toFIG.4, which illustrates a top view of the container10, the fuel cell holders18A-18X can be arranged in two rows of twelve fuel cell holders within the container10.FIG.4shows fuel cell holders18A-18F (with fuel cell holders18G-18L being below fuel cell holders18A-18F) and fuel cell holders18M-18R (with fuel cell holders18S-18X being below fuel cell holders18M-18R). For example, a first row can be made up of fuel cell holders18A-18F (with fuel cell holders18G-18L being below fuel cell holders18A-18F), while a second row can be made up of fuel cell holders18M-18R (with fuel cell holders18S-18X being below fuel cell holders18M-18R). Similar to the fuel cell holders18A-18X, the DC-DC converters20A-20F can be arranged in two rows, for example, two rows of three DC-DC converters, wherein the DC-DC converters20A-20C form a first row, and the DC-DC converters20D-20F form a second row. Between the first row of fuel cell holders18A-18F and/or the DC-DC converters and the second row of fuel cell holders18M-18R and/or the DC-DC converters20D- the container10can include a central aisle28. The central aisle28can be configured to allow interior access to the fuel cell holders18A-18X, the fuel cells, the DC-DC converters20A-20F, and/or other components within the container10, for example, for performing maintenance on these components. The central aisle28can be sized and shaped such that a maintenance worker can enter the container10and access its components. The raised floor22provides the floor for the central aisle28so that a maintenance worker or any other person can walk across the raised floor22through the container10. Referring now toFIG.5, which illustrates a bottom view of the container10, some of the components of the container10can be located underneath the raised floor22, essentially between the raised floor22and a support surface, such as the ground. For example, the container10can include one or more cable tray(s)30located underneath the raised floor22. The cable tray(s)30can be configured to support and direct one or more cables that run through the container10to electrically connect one or more components of the container10, for example, the fuel cells, the DC-DC converters20A-F, the auxiliary load center(s)24, etc. The container10can also include a cooling system. The cooling system can be configured to deliver cooling fluid through the container10to the plurality of fuel cells. One or more components of the cooling system can be located underneath the raised floor22. For example, the cooling system can include a central cooling pipe32located underneath the raised floor22. The central cooling pipe32includes a cooling fluid inlet34and a cooling fluid outlet36. Cooling fluid, for example, cold water, flows into the container10via the cooling fluid inlet34, and as the fuel cells are cooled, the cooling fluid heats up and then exits the container10, for example, as hot water via the cooling fluid outlet36. The cooling system also includes a plurality of fuel cell cooling pipes38A-38F and a cooling pipe valve40. Each fuel cell cooling pipe38A-38F is connected to the central cooling pipe32and a fuel cell. Accordingly, each fuel cell cooling pipe38A-38F is configured to direct cooling fluid upwards through the container10. The cooling pipe valve40is located along the central cooling pipe32. As cooling fluid enters the central cooling pipe32, the cooling pipe valve40is initially closed. This causes pressure to build in the cooling system, which directs the cooling fluid up to the fuel cells to cool the fuel cells. FIG.6illustrates a close-up view of the fuel cell holder18B located within the container10. Because the fuel cell holders18A-18X are substantially similar to each other, a description regarding the fuel cell holder18B and related components is equally applicable to any of the other fuel cell holders18A-18X. Here, a fuel cell located within fuel cell holder18B includes a heat exchanger42to receive the cooling fluid and cool the fuel cell. The heat exchanger42can be a liquid-to-liquid heat exchanger, and the fuel cell cooling pipe38B is configured to deliver the cooling fluid to the heat exchanger42. After the fuel cell located within fuel cell holder18B is cooled, the cooling pipe valve40is opened to release the pressure and allow the cooling fluid to exit the container10via the cooling fluid outlet36. Again, it should be understood that the description regarding the fuel cell holder18B and related components is equally applicable to other fuel cells located within other fuel cell holders. To power the fuel cells, the container10includes a hydrogen supply system. The hydrogen supply system is configured to deliver hydrogen fuel (e.g., hydrogen gas) to each fuel cell. With continued reference toFIG.6, the hydrogen supply system includes a hydrogen header pipe44. The hydrogen header pipe44forms a loop around the upper perimeter of the container around the fuel cells. The loop configuration of the hydrogen header pipe44equalizes the pressure of the hydrogen gas within the hydrogen header pipe44. The hydrogen header pipe44feeds a plurality of fuel cell hydrogen pipes connected to each fuel cell. In this example, the hydrogen header pipe44feeds the fuel cell hydrogen pipe46, which is connected to the fuel cell located within the fuel cell holder18B. As the fuel cell system operates, it may produce exhaust in various forms. For example, it may exhaust air, water, and hydrogen (e.g., condensate). Accordingly, in conjunction with the cooling system, the container10includes a condensate collection system and a ventilation system to cool the various components of the container10, to eliminate combustible build-ups of hydrogen, and remove vapor and condensation from the container10that may have formed during the cooling process. With continued reference toFIG.6, the condensate collection system includes condensate collection pipes48configured to collect condensate within the container10(e.g., liquid water) and direct it towards the bottom of the container10. At the bottom of the container for example, underneath the raised floor22, the container10can include a condensate collection tank50(FIG.5). The condensate collected by the condensate collection pipes48can travel to the condensate collection tank50and be expelled from the container10by a condensate pump connected to the condensate collection tank50. With reference toFIGS.7-9, the ventilation system includes vents52A-52J located on the exterior of the container10along the bottom of the container10. The vents52A-52J can be any suitable type of vent. For example, the one or more of the vents52A-52J can be combination damper/louver-type vents. The combination damper/louver-type vents can be opened and closed using one or more actuators (not shown) inside the container10. Additionally or alternatively, the vents52A-52J and/or the container10can include ventilation fans56A-56I that can work in conjunction with the container10itself to vent exhaust from the container. For example, the container10can include a sloped roof54(FIG.7) so that air, hydrogen gas, and other exhaust can collect at the highest point within the container—more specifically, within the housing14. Additionally, the ventilation system includes ventilation fans56A-56H at either end of the container10near the sloped roof54. The ventilation fans56A-56H are configured to expel from the container10the exhaust collected underneath the sloped roof54. With continued reference toFIGS.8and9, the container10can also include one or more power output conduits58. The power output conduits58can be configured to house one or more electronics cables that connect the components of the container10to the external unit to provide power generated by the fuel cells to the external unit. The power output conduits58, as shown, may exit the container10through the bottom of the container10. As mentioned above, the container10includes auxiliary load center(s)24for housing one or more components configured to provide power to the auxiliary systems/components of the container. The auxiliary systems/components can include a programmable logic controller (PLC), the condensate collection system, the ventilation system, lighting systems, and any other auxiliary system/component not described herein. Referring back toFIG.1, the auxiliary load center(s)24can house one or more power panels, one or more battery units, and/or one or more uninterruptable power supplies (UPSs), among other components, that are configured to provide power to the auxiliary systems/components of the container10. Referring back toFIG.2, the housing14can include one or more components configured to provide access to the components of the container10, including the fuel cells, the DC-DC converters20A-20F, the cooling system, the hydrogen supply system, the condensate collection system, the ventilation system, and the auxiliary load center(s)24. For example, the housing14can include a plurality of doors60A-60G to provide access to the interior of the container10, including the central aisle28. The doors60A-60G may be aligned with the fuel cells and/or the DC-DC converters20A-20F to provide direct access to these components. Additionally, the housing14can include vents62A-62J that may correspond to the vents52A-52J and/or the ventilation fans56A-56I of the container10and that are configured to vent exhaust from the container10. Referring now toFIG.10, to improve the understanding of the container10, a simplified diagram of a portion of the container10is shown. Additionally, it should be understood that the simplified diagram of the portion of the container10is not necessarily drawn to scale but, again, is to improve the understanding of the container10Like before, the container includes a system frame12configured to support one or more components of a fuel cell system, including a plurality of fuel cell holders18A-18C and18G-18I, each configured to hold fuel cells19A-19C and19G-19I, respectively, and a plurality of DC-DC converters20A-20C. As explained previously, the container10includes a raised floor22configured to support the fuel cell holders18A-18C and18G-18I and the DC-DC converters20A-20C. Underneath the raised floor22, the container10can include a cable tray(s)30configured to support and direct one or more cables connecting the various components within the container as well as a central cooling pipe32. The central cooling pipe32is connected to fuel cell cooling pipes38A-38F configured to deliver cooling fluid to the heat exchangers42A-42C and42G-42I connected to the fuel cells. The container10includes a hydrogen header pipe44connected to fuel cell hydrogen pipes46A-46C configured to deliver hydrogen fuel to the fuel cells19A-19C and19G-191. The container10includes a condensate collection system, including condensate collection pipes48A and48B that collect and deliver condensate to a condensate collection tank50. The container10also includes a ventilation system including vents52A, a sloped roof54, and ventilation fans56A-56B. Detailed embodiments are disclosed herein. However, it is to be understood that the disclosed embodiments are intended only as examples. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the aspects herein in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of possible implementations. The following includes definitions of selected terms employed herein. The definitions include various examples and/or forms of components that fall within the scope of a term and may be used for various implementations. The examples are not intended to be limiting. Both singular and plural forms of terms may be within the definitions. References to “one embodiment,” “an embodiment,” “one example,” “an example,” and so on indicate that the embodiment(s) or example(s) so described may include a particular feature, structure, characteristic, property, element, or limitation, but that not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element or limitation. Furthermore, repeated use of the phrase “in one embodiment” does not necessarily refer to the same embodiment, though it may. “PLC,” as used herein, includes a computer or electrical hardware component(s), firmware, a non-transitory computer-readable medium that stores instructions, and/or combinations of these components configured to perform a function(s) or an action(s), and/or to cause a function or action from another logic, method, and/or system. A PLC may include a microprocessor controlled by an algorithm, a discrete logic (e.g., ASIC), an analog circuit, a digital circuit, a programmed logic device, a memory device including instructions that, when executed, perform an algorithm so on. In one or more embodiments, a PLC may include one or more CMOS gates, combinations of gates, or other circuit components. Where multiple PLCs are described, one or more embodiments may include incorporating the multiple modules into one physical module component. Similarly, where a single module is described, one or more embodiments distribute the single module between multiple physical components. In one or more arrangements, one or more of the PLCs described herein can include artificial or computational intelligence elements, e.g., neural network, fuzzy logic, or other machine learning algorithms. Further, in one or more arrangements, one or more of the modules can be distributed among a plurality of the modules described herein. The terms “a” and “an,” as used herein, are defined as one or more than one. The term “plurality,” as used herein, is defined as two or more than two. The term “another,” as used herein, is defined as at least a second or more. The terms “including” and/or “having,” as used herein, are defined as comprising (i.e., open language). The phrase “at least one of . . . and . . . ” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. For example, the phrase “at least one of A, B, and C” includes A only, B only, C only, or any combination thereof (e.g., AB, AC, BC, or ABC). Aspects herein can be embodied in other forms without departing from the spirit or essential attributes thereof. Accordingly, reference should be made to the following claims, rather than to the foregoing specification, as indicating the scope hereof. | 18,193 |
11862832 | DETAILED DESCRIPTION It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. Referring toFIG.1, a modular fuel cell system10is shown according to an exemplary embodiment. The modular system10may contain modules and components described in U.S. patent application Ser. No. 11/656,006, filed on Jan. 22, 2007, and U.S. patent application Ser. No. 14/208,190, filed on Mar. 13, 2014, which are incorporated herein by reference in their entireties. The modular design of the fuel cell system10provides flexible system installation and operation. Modules allow scaling of installed generating capacity, reliable generation of power, flexibility of fuel processing, and flexibility of power output voltages and frequencies with a single design set. The modular design results in an “always on” unit with very high availability and reliability. This design also provides an easy means of scale up and meets specific requirements of customer's installations. The modular design also allows the use of available fuels and required voltages and frequencies which may vary by customer and/or by geographic region. The modular fuel cell system10includes a housing14in which at least one (preferably more than one or plurality) of power modules12, one or more fuel processing modules16, and one or more power conditioning (i.e., electrical output) modules18are disposed. In embodiments, the power conditioning modules18are configured to deliver direct current (DC). In alternative embodiments, the power conditioning modules18are configured to deliver alternating current (AC). In these embodiments, the power conditioning modules18include a mechanism to convert DC to AC, such as an inverter. For example, the system10may include any desired number of modules, such as 2-30 power modules, for example 3-12 power modules, such as 6-12 modules. The system10ofFIG.1includes six power modules12(one row of six modules stacked side to side), one fuel processing module16, and one power conditioning module18on a pad20. The housing14may include a cabinet to house each module12,16,18. Alternatively, as will be described in more detail below, modules16and18may be disposed in a single cabinet. While one row of power modules12is shown, the system may comprise more than one row of modules12. For example, the system10may comprise two rows of power modules18arranged back to back/end to end. Each power module12is configured to house one or more hot boxes13. Each hot box contains one or more stacks or columns of fuel cells (not shown for clarity), such as one or more stacks or columns of solid oxide fuel cells having a ceramic oxide electrolyte separated by conductive interconnect plates. Other fuel cell types, such as PEM, molten carbonate, phosphoric acid, etc. may also be used. The fuel cell stacks may comprise externally and/or internally manifolded stacks. For example, the stacks may be internally manifolded for fuel and air with fuel and air risers extending through openings in the fuel cell layers and/or in the interconnect plates between the fuel cells. Alternatively, the fuel cell stacks may be internally manifolded for fuel and externally manifolded for air, where only the fuel inlet and exhaust risers extend through openings in the fuel cell layers and/or in the interconnect plates between the fuel cells, as described in U.S. Pat. No. 7,713,649, which is incorporated herein by reference in its entirety. The fuel cells may have a cross flow (where air and fuel flow roughly perpendicular to each other on opposite sides of the electrolyte in each fuel cell), counter flow parallel (where air and fuel flow roughly parallel to each other but in opposite directions on opposite sides of the electrolyte in each fuel cell) or co-flow parallel (where air and fuel flow roughly parallel to each other in the same direction on opposite sides of the electrolyte in each fuel cell) configuration. The modular fuel cell system10also contains at least one fuel processing module16. The fuel processing module16includes components for pre-processing of fuel, such as adsorption beds (e.g., desulfurizer and/or other impurity adsorption) beds. The fuel processing module16may be designed to process a particular type of fuel. For example, the system may include a diesel fuel processing module, a natural gas fuel processing module, and an ethanol fuel processing module, which may be provided in the same or in separate cabinets. A different bed composition tailored for a particular fuel may be provided in each module. The processing module(s)16may process at least one of the following fuels selected from natural gas provided from a pipeline, compressed natural gas, methane, propane, liquid petroleum gas, gasoline, diesel, home heating oil, kerosene, JP-5, JP-8, aviation fuel, hydrogen, ammonia, ethanol, methanol, syn-gas, bio-gas, bio-diesel and other suitable hydrocarbon or hydrogen containing fuels. If desired, the fuel processing module16may include a reformer17. Alternatively, if it is desirable to thermally integrate the reformer17with the fuel cell stack(s), then a separate reformer17may be located in each hot box13in a respective power module12. Furthermore, if internally reforming fuel cells are used, then an external reformer17may be omitted entirely. The power conditioning module18includes components for converting the fuel cell stack generated DC power to AC power (e.g., DC/DC and DC/AC converters described in U.S. Pat. No. 7,705,490, incorporated herein by reference in its entirety), electrical connectors for AC power output to the grid, circuits for managing electrical transients, a system controller (e.g., a computer or dedicated control logic device or circuit). The power conditioning module18may be designed to convert DC power from the fuel cell modules to different AC voltages and frequencies. Designs for 208V, 60 Hz; 480V, 60 Hz; 415V, 50 Hz and other common voltages and frequencies may be provided. The fuel processing module16and the power conditioning module18may be housed in one cabinet of the housing14. If a single input/output cabinet is provided, then modules16and18may be located vertically (e.g., power conditioning module18components above the fuel processing module16desulfurizer canisters/beds) or side by side in the cabinet. As shown in one exemplary embodiment inFIG.1, one cabinet is provided for one row of six power modules12, which are arranged linearly side to side on one side of the input/output module. The row of modules may be positioned, for example, adjacent to a building for which the system provides power (e.g., with the backs of the cabinets of the modules facing the building wall). While one row of power modules12is shown, the system may comprise more than one row of modules12. For example, as noted above, the system may comprise two rows of power modules stacked back to back. The linear array of power modules12is readily scaled. For example, more or fewer power modules12may be provided depending on the power needs of the building or other facility serviced by the fuel cell system10. The power modules12and input/output modules may also be provided in other ratios. For example, in other exemplary embodiments, more or fewer power modules12may be provided adjacent to the input/output module16/18. Further, the support functions could be served by more than one input/output module16/18(e.g., with a separate fuel processing module16and power conditioning module18cabinets). Additionally, while in the preferred embodiment, the input/output module16/18is at the end of the row of power modules12, it could also be located in the center of a row power modules12. The modular fuel cell system10may be configured in a way to ease servicing of the components of the system10. All of the routinely or high serviced components (such as the consumable components) may be placed in a single module to reduce amount of time required for the service person. For example, a purge gas (optional) and desulfurizer material for a natural gas fueled system may be placed in a single module (e.g., a fuel processing module16or a combined input/output module16/18cabinet). This would be the only module cabinet accessed during routine maintenance. Thus, each module12,16, and18may be serviced, repaired or removed from the system without opening the other module cabinets and without servicing, repairing or removing the other modules. For example, as described above, the system10can include multiple power modules12. When at least one power module12is taken off line (i.e., no power is generated by the stacks in the hot box13in the off line module12), the remaining power modules12, the fuel processing module16and the power conditioning module18(or the combined input/output module16/18) are not taken off line. Furthermore, the fuel cell system10may contain more than one of each type of module12,16, or18. When at least one module of a particular type is taken off line, the remaining modules of the same type are not taken off line. Thus, in a system comprising a plurality of modules, each of the modules12,16, or18may be electrically disconnected, removed from the fuel cell system10and/or serviced or repaired without stopping an operation of the other modules in the system, allowing the fuel cell system to continue to generate electricity. The entire fuel cell system10does not have to be shut down if one stack of fuel cells in one hot box13malfunctions or is taken off line for servicing. FIG.2illustrates top plan view of a modular fuel cell system200according to various embodiments of the present disclosure. The fuel cell system200is similar to the fuel cell system10ofFIG.1. As such, similar reference numbers are used for similar elements, and only the differences therebetween will be described in detail. Referring toFIG.2, the system200includes power modules12, a power conditioning module18, and a fuel processing module16disposed on a pad210. The system200may include doors30to access the modules12,16,18. The system200may further include cosmetic doors30A. The power modules12may be disposed in a back-to-back configuration. In particular, the power modules12may be disposed in parallel rows, and the fuel processing module16and the power conditioning module may be disposed at ends of the rows. Accordingly, the system200has an overall rectangular configuration, and may be shorter in length than other systems, such as the system10ofFIG.1. As such, the system200can be disposed in locations where space length is an issue. For example, the system200may fit in a parking spot adjacent to a building to which power is to be provided. While the system200is shown to include two rows of three power modules12, the present disclosure is not limited to any particular number of power modules12. For example, the system200may include 2-30 power modules12, 4-12 power modules12, or 6-12 power modules12, in some embodiments. In other words, the system200may include any desired number of power modules12, with the power modules12being disposed in a back-to-back configuration. In addition, the positions of the fuel processing module16and the power conditioning module18may be reversed, and/or the modules16,18may be disposed on either end of the system200. FIG.3Aillustrates a schematic top view of the pad210.FIG.3Billustrates a perspective view of the pad210, andFIG.3Cillustrates a perspective view of the pad210including an edge cover. Referring toFIGS.3A-3C, the pad210includes a base212. The base212may be formed of a concrete or similar material. Alternatively, the base212may be made of any other suitable structural material, such as steel or another metal, and may be pre-cast as a single body or may be cast in sections. The base212may be made by casting the base material in a patterned mold, removing the cast base212from the mold, and then transporting the base212from the location of the mold (e.g., in a base fabrication facility) to the operation site of the fuel cell system (i.e., where the fuel cell system will be located to generate power). The base212may be configured as a single piece, or may include multiple connected sections. The base212may include first and second through holes214,216, a drainage recess218, a wiring recess220, and a plumbing recess222. The base212may also include tie-down pockets224, tie-down inserts226, and pluming brackets228. The drainage recess218may extend along the middle of the base212, between the rows of modules, and may be configured to collect, for example, rain or debris collected on the base212. The tie-down pockets224and tie-down inserts226may be configured to secure corresponding modules to the base212. The plumbing recess222may extend around the perimeter of the base212. In particular, the plumbing recess222may be formed along three or more edges of the base212. The wiring recess220may extend from the first through hole214to the second through hole216, and may be generally U-shaped. The pad210may also include plumbing230, wiring232, and a system electrical connection, such as a bus bar234. In particular, the wiring232may be disposed in the wiring recess220and may be connected to one or more of the modules. For example, the wiring232may be connected to the bus bar234and each of the power modules12. The bus bar234may be connected to the power conditioning module18. The power conditioning module18may be connected to an external load through the second through hole216. The bus bar234may be disposed on an edge of the through hole216, such that the wiring232does not extend across the through hole216. However, the bus bar234may be disposed on an opposing side of the through hole216, such that the wiring232does extend across the through hole216, if such a location is needed to satisfy system requirements. The plumbing230may be disposed in the plumbing recess222. The plumbing230may be connected to an external source of water and/or fuel, via the first through hole214, and may be attached to the plumbing brackets228. In particular, the plumbing230may include a fuel pipe230A connecting the fuel processing module16to the power modules12. The plumbing230may also include a water pipe230B configured to provide water to the power modules12. The plumbing230may extend between the plumbing brackets228to the power modules12. As shown inFIG.3C, the plumbing230may be covered by an edge cover236. In particular, the edge cover236may be configured to cover the plumbing recess222. In some embodiments, the edge cover236may include a number of segments, such that the edge cover236may be removed and/or installed on a piece-by-piece basis. FIG.3Dillustrates a perspective view of a pad211, according to various embodiments of the present disclosure. The pad211is an alternate version of the pad210of the fuel cell system ofFIG.2, in place of the pad210. Accordingly, only the differences between the pads210,211will be described in detail. Referring toFIG.3D, the pad211includes wiring233, but does not include a bus bar. In particular, the wiring233may be in the form of cables configured to attach each power module12to the power conditioning module18and the system electrical connection may comprise a cable assembly input or output237. FIG.4Aillustrates a perspective view of a modular fuel cell system according to various embodiments of the present disclosure.FIG.4Billustrates top plan view of the system400.FIG.4Cillustrates a schematic view of a pad410ofFIG.4A. The fuel cell system400includes similar components to the fuel cell system10ofFIG.1. As such, similar reference numbers are used for similar elements, and only the differences therebetween will be described in detail. Referring toFIGS.4A-C, the system400includes power modules12, a power conditioning module18, and a fuel processing module16disposed on a pad410. The system400may include doors30to access the modules12,16,18. The system400may further include cosmetic doors30A. The power modules12may be disposed in a linear configuration. In particular, the power modules12may be disposed in one row, and the fuel processing module16and the power conditioning module18may be disposed at an end of the row. According to some embodiments, the fuel processing module16and the power conditioning module18may be disposed in the middle of the row. Accordingly, the system400has an overall linear configuration, and may be fit into locations having linear space, but limited width. An example of such a location may be behind a big box store. While the system400is shown to include a row of six power modules12, the present disclosure is not limited to any particular number of power modules12. For example, the system400may include 2-30 power modules12, 4-12 power modules12, or 6-12 power modules12, in some embodiments. In other words, the system500may include any desired number of power modules12, with the modules12,16,18being disposed in a linear configuration. The pad410includes a base412. The base412may include first and second through holes214,216. The base412may also include a wiring recess and a plumbing recess, as discussed below with regard toFIG.10. The base412may be formed of a concrete or similar material. Alternatively, the base412may be made of any other suitable structural material, such as steel or another metal, and may be pre-cast as a single body or may be cast in sections. The base412may be made by casting the base material into a patterned mold, removing the cast base412from the mold and then transporting the base412from the location of the mold (e.g., in a base fabrication facility) to the location of the fuel cell system (i.e., where the fuel cell system will be located to generate power). The pad410may also include plumbing230(for example, water pipe230A and fuel pipe230B), wiring232, and a system bus bar234. In particular, the wiring232may be disposed in a substantially linear wiring recess and may be connected to one or more of the modules. For example, the wiring232may be connected to the bus bar234and each of the power modules12. The bus bar234may be connected to the power conditioning module18. The power conditioning module18may be connected to an external load through the second through hole216. The bus bar234may be disposed on an edge of the second through hole216, such that the wiring232does not extend across the second through hole216. However, the bus bar234may be disposed on an opposing side of the second through hole216, such that the wiring232does extend across the second through hole216, if such a location is needed to satisfy system requirements. According to some embodiments, the plumbing230and the wiring232may be disposed adjacent to the doors30, in order to facilitate connecting the same to the modules12,16,18. In other words, the plumbing230and the wiring232may be disposed adjacent to an edge of the base412. According to some embodiments, the wiring232may be in the form of cables, similar to what is shown inFIG.3D, and the bus bar234may be omitted. FIG.5Aillustrates a top plan view of a modular fuel cell system500according to various embodiments of the present disclosure.FIG.5Billustrates a schematic view of a pad510ofFIG.5A. The fuel cell system500includes similar components to the fuel cell system200. As such, similar reference numbers are used for similar elements, and only the differences therebetween will be described in detail. Referring toFIGS.5A and5B, the system500includes power modules12, a power conditioning module18, and a fuel processing module16, which are disposed on a pad510. The system500may include doors30to access the modules12,16,18. The system500may further include cosmetic doors30A. The power modules12may be disposed in an L-shaped configuration. In particular, the power modules12may be disposed in a first row, and the fuel processing module16, the power conditioning module18, and addition power modules12may be disposed in a second row substantially orthogonal to the first row. In particular, the modules16,18may be disposed at a distal end of the second row. Accordingly, the system500may be configured to operate in locations having linear space, but limited width. An example of such a location may be behind a large store. While the system500is shown to include a row of six power modules12, the present disclosure is not limited to any particular number of power modules12. For example, the system500may include 2-30 power modules12, 4-12 power modules12, or 6-12 power modules12, in some embodiments. In other words, the system500may include any desired number of power modules12, with the modules12,16,18being disposed in an orthogonal configuration. The pad510includes a base512. The base512may include first and second through holes214,216, a wiring recess, and a plumbing recess. The base512may be formed of a concrete or similar material. The base512may be pre-cast as a single body or may be cast in sections. For example, the base512may include a first section512A and a second section512B, which may be precast and then disposed adjacent to one another at an operating location. The division between the sections512A and512B is shown by dotted line L. The first row of modules may be disposed on the first section512A, and the second row of modules may be disposed on the second section512B. The pad510may also include plumbing230(for example, water plumbing230A and fuel plumbing230B), wiring232, and a system bus bar234. In particular, the wiring232may be disposed in a wiring recess and may be connected to one or more of the modules. For example, the wiring232may be connected to the bus bar234and each of the power modules12. The bus bar234may be connected to the power conditioning module18. The power conditioning module18may be connected to an external load through the second through hole216. According to some embodiments, the plumbing230and the wiring232may be disposed adjacent to the doors30, in order to facilitate connecting the same to the modules12,16,18. In other words, the plumbing230and the wiring232may be disposed adjacent to edges of the base512. According to some embodiments, the wiring232may be in the form of cables, similar to what is shown inFIG.3D, and the bus bar234may be omitted. FIG.5Cillustrates a top plan view of a modular fuel cell system550according to various embodiments of the present disclosure.FIG.5Dillustrates a schematic view of a pad560ofFIG.5C. The fuel cell system550includes similar components to the fuel cell system500. As such, similar reference numbers are used for similar elements, and only the differences therebetween will be described in detail. Referring toFIGS.5C and5D, the system550includes power modules12, a power conditioning module18, and a fuel processing module16, which are disposed on a pad560. The power modules12may be disposed in a first row, and fuel processing module16and the power conditioning module18may be disposed in a second row that is generally orthogonal to the first row. As such, the system550may be generally L-shaped. The pad560may include first and second sections560A and560B separated by dotted line L. However, the pad560may be formed of a single piece of material. The first row of modules may be disposed on the first section560A, and the second row of modules may be disposed on the second section560B. The pad560may also include plumbing230(for example, water plumbing230A and fuel plumbing230B), wiring232, a first through hole214, a second through hole216, and a system bus bar234. In particular, the wiring232may be disposed in a wiring recess and may be connected to one or more of the modules. For example, the wiring232may be connected to the bus bar234and each of the power modules12. The bus bar234may be connected to the power conditioning module18. The power conditioning module18may be connected to an external load through the second through hole216. According to some embodiments, the plumbing230and the wiring232may be disposed adjacent to the doors30, in order to facilitate connecting the same to the modules12,16,18. In other words, the plumbing230and the wiring232may be disposed adjacent to edges of the pad560. According to some embodiments, the wiring232may be in the form of cables, similar to what is shown inFIG.3D, and the bus bar234may be omitted. FIG.6Aillustrates a top plan view of a modular fuel cell system600according to various embodiments of the present disclosure.FIG.6Billustrates a schematic view of a pad610ofFIG.6A. The fuel cell system600includes similar components to the fuel cell system500. As such, similar reference numbers are used for similar elements, and only the differences therebetween will be described in detail. Referring toFIGS.6A and6B, the system600includes power modules12, a power conditioning module18, and a fuel processing module16, which are disposed on a pad610. The system600may include doors30to access the modules12,16,18. The system600may further include cosmetic doors30A. The power modules12may be disposed in an L-shaped configuration. In particular, the power modules12may be disposed in a first row, and the fuel processing module16, the power conditioning module18, and addition power modules12may be disposed in a second row substantially orthogonal to the first row. In particular, the modules16,18may be disposed at a distal end of the second row. In contrast to the system500, the system600includes a dummy section630disposed between the first and second rows. The dummy section630may be a portion of the pad610that does not include a module. Plumbing230and wiring232may be routed through the dummy section630and may extend along an edge of the pad610. The pad610may include a first section612A and a second section612B, which are separated by the dummy section630. In some embodiments, the dummy section630may be a separate section of the pad610, or may be a portion of either of the first and second sections612A,612B. In some embodiments, an empty cabinet may be disposed on the dummy section630. The first row of modules may be disposed on the first section612A, and the second row of modules may be disposed on the second section612B. FIG.7Aillustrates a top plan view of a modular fuel cell system700according to various embodiments of the present disclosure.FIG.7Billustrates a schematic view of a pad710ofFIG.7A. The fuel cell system700includes similar components to the fuel cell system500. As such, similar reference numbers are used for similar elements, and only the differences therebetween will be described in detail. Referring toFIGS.7A and7B, the system700includes power modules12, a power conditioning module18, and a fuel processing module16, which are disposed on a pad710. The system700may include doors30to access the modules12,16,18. The system700may further include cosmetic doors30A. The power modules12may be disposed in a stepped configuration. In particular, the power modules12may be disposed in a first row, a second row substantially orthogonal to the first row, and a third row substantially orthogonal to the second row. The fuel processing module16and the power conditioning module18may be disposed at a distal end of the third row. However, the fuel processing module16and the power conditioning module18may be disposed in the first row or the second row, according to some embodiments. The system700includes a dummy section730between the first and second rows. The dummy section730may be a portion of the pad710that does not include a module. In some embodiments, an empty cabinet may be disposed on the dummy section730. Plumbing230and wiring232may be routed through the dummy section730and may extend along an edge of the pad710. The pad710may include a first section712A, a second section712B, and a third section712C. The first and second sections712A,712B may be separated by line L. The second and third sections712B,712C may be separated by the dummy section730. In some embodiments, the dummy section730may be a separate segment of the pad710, or may be a portion of either of the second and third sections712B,712C. The first row of modules may be disposed on the first section712A, the second row of modules may be disposed on the second section712B, and the third row of modules may be disposed on the third section712B. The pad710may also include a second system bus bar235configured to connect wiring232of the first and second sections712A,712B. FIG.8illustrates a perspective view of modular pad section800according to various embodiments of the present disclosure. Referring toFIG.8, the pad section800may be used as any of the sections of the above-described pads. The pad section800may be rectangular, e.g., the pad section800may have two substantially parallel long sides and two substantially parallel short sides extending therebetween. The pad section800may include a first boss802, a second boss804, a third boss806, plumbing brackets828, a wiring recess820, connection recesses822, and a plumbing recess824, which may be formed on an upper surface of the pad section800. The first boss802may be disposed between the second and third bosses804,806. The second boss804may have a larger surface area than the third boss806. For example, the second boss804and the third boss806may have substantially the same width, but the second boss804may be longer than the third boss806. The first boss802may have a larger surface area than the second or third bosses804,806. A portion820A of the wiring recess820that is disposed between the third boss806and adjacent plumbing brackets828may be enlarged, e.g., the enlarged portion820A may be wider than the rest of the wiring recess820. A through hole216may be formed in the enlarged portion820A, according to some embodiments. The wiring recess820may be disposed between the bosses802,804,806and the plumbing brackets828. The bosses802,804,806may include tie-down pockets826, configured to secure modules disposed thereon. The plumbing brackets828may be disposed in a first row, and the bosses802,804,806may be disposed in a second row that is substantially parallel to the first row. The plumbing recess824may be formed on only two or three sides/edges of the pad section800, depending on the shape of a pad constructed using the pad sections. For example, the plumbing recess824may extend along a long side and one short side of the pad section800, if the pad section800is to be used in a fuel cell system having L-shaped or linear configuration. In the alternative, the plumbing recess824a long side and two short sides of the pad section800, if the pad section800is to be used in a fuel cell system having a rectangular configuration. An edge cover832may be disposed on the plumbing recesses822. The pad section800may be precast, delivered, and then assembled on site with one or more other pad sections800. FIGS.9A and9Billustrate perspective views of a modular pad215according to various embodiments of the present disclosure. The pad215may be used as the pad210of the fuel cell system200. Referring toFIGS.9A and9B, the pad215includes two of the pad sections800disposed adjacent to one another. In particular, the pad sections800may be disposed flush with one another, and/or may be physically connected to one another. In particular, each pad section800may be configured such that the connection recesses822and the plumbing recesses824are respectively aligned with one another, when the sections800are assembled, as shown inFIGS.9A and9B. In other words, the connection recesses822of the adjacent pad sections800may form contiguous recesses, and the plumbing recesses824of two adjacent pad sections800may form a contiguous plumbing recess, when the pad sections800are aligned with one another. In addition, the pad sections800may be aligned such that the second bosses804are aligned with (contact) the third bosses806, and the first bosses802are aligned with (contact) one another. In other words, a long side of a first pad section800may be disposed in contact with a long side of a second pad section800(rotated 180 degrees with respect to the identical first pad section). One or more through holes216may be formed the pad sections800, in order to allow for the routing of plumbing and/or wiring. In particular, a through hole216may be formed in the enlarged portion820A of the wiring recess820. FIG.10illustrates a perspective view of a modular pad415according to various embodiments of the present disclosure. The pad415that may be a linear pad that can be substituted for the linear pad410ofFIGS.4A and4B. Referring toFIG.10, the pad415includes two pad sections800aligned together lengthwise. In particular, the third boss806of one pad section800is disposed adjacent to the second boss804of the other pad section800. In other words, a short side of one of the pad sections800may be disposed in contact with a short side of the other pad section800. As such, the wiring recesses820and the plumbing recesses824of the pad sections800may be respectively aligned (contiguous) with one another. In particular, the wiring recesses820may be aligned to form a substantially contiguous and linear wiring recess. FIG.11illustrates a modular pad615according to various embodiments of the present disclosure. The pad615may be substituted for the pad610ofFIG.6B. Referring toFIG.11, the pad615includes two pad sections800that are orthogonally aligned together. In particular, the third boss806of one pad section800is disposed adjacent to the first boss802of the other pad section800. As such, the wiring recesses820may be connected by one of the connection recesses822, and the plumbing recesses824of the pad sections800may be respectively aligned (contiguous) with one another. In other words, a short side of one pad section800may be disposed in contact with a long side of the other pad section800. An additional pad section800may be aligned with one of the above pad sections800, such that a step-shaped pad, such as pad710ofFIG.7B, may be formed. In other words, each section712A,712B,712C may be formed using one of the pad sections800. FIG.12illustrates a modular pad415A according to various embodiments of the present disclosure. The pad415A that may be substituted for the pad410ofFIGS.4A and4B. Referring toFIG.12, the pad415A includes two modular pad sections900. The pad sections900are similar to the pad sections800, so only the differences therebetween will be discussed in detail. In particular, the pad sections900each include a first boss802and second bosses808disposed on opposing sides of the first boss804, on an upper surface of the pad section900. The second bosses808may have the same size and shape. Accordingly, the pad sections900may be symmetrical widthwise, which is not the case for the pad sections800, since the pad sections800include the second and third bosses804and806having different sizes. The pad sections900may be aligned together in a manner similar to the pad sections800in the pad415, as discussed above. FIGS.13A and13Billustrate perspective views of a pad1000of a fuel cell system, according to various embodiments of the present disclosure. Referring toFIGS.13A and13B, the pad1000may be incorporated into any of the above fuel cell systems. The pad1000includes the base1010, a separator1012, and frames1014. The base1010may be formed of concrete or similar material, as described above. In particular, the base1010may be cast on site, or may be precast in one or more sections and then assembled on site. The separator1012may be disposed on an upper surface of the base1010, and may be formed of sheet metal or other similar material. The separator1012may include rails1017disposed on opposing sides of the base1010, and spacers1016disposed on the rails1017. The rails1017may be single pieces, or may include connected rail sections. The frames1014may be attached to the spacers1016using any suitable method, such as by using bolts1018, clamps, or the like. The frames1014are configured to receive modules, such as power modules, fuel processing modules, or the like. The separator1012may be configured to separate the base1010and the frames1014, such that there is a space formed therebetween. The pad1000may include plumbing1020disposed on the base1010. The plumbing1020may extend from a through hole1022formed in the base1010, and may be configured to provide water and/or fuel to modules disposed on the frames1014. The pad1000may include a frame1014A configured to receive a power conditioning module. The pad1000may also include wiring (not shown) configured to connect the power modules to a power conditioning module disposed on the frame1014A. In the alternative, wiring could be routed through openings1015formed in the frames1014. The separator1012is configured to space apart the frames1014from the upper surface of the base1010. Accordingly, the plumbing1020may be disposed directly on the upper surface of the base1010. In other words, the upper surface of the base1010may be substantially planar, e.g., does not need to include recesses for the plumbing1020and/or wiring. The configuration of the pad1000provides advantages over conventional pads, in that plumbing and/or wiring is not required to be set into features cast into the base1010, in order to have a flat surface for the installation of fuel cell system modules. As such, the pad1000may be manufactured at a lower cost, since the base1010does not require cast features. FIG.14is a perspective view of a pad1400for a fuel cell system, according to various embodiments of the present disclosure. Referring toFIG.14, the pad1400includes a base1410and replicators1420disposed on the base1410. The base1410may be a cast on site or precast and delivered to a site. The base1410may be formed of concrete or a similar material. The replicators1420may be attached to the base1410and may be formed of plastic or other non-corrosive material. The replicators1420may replicate features that are molded into bases of the previous embodiments described above. For example, the replicators1420may form bosses such that wiring and/or plumbing channels or recesses are formed on a flat upper surface of the base1410between the replicators1420. Accordingly, the replicators1420may create an elevated structure for supporting the modules12,16,18of a fuel cell system, while the wiring and plumbing is formed on the flat upper surface of the concrete base1410in the channels or recesses between the replicators. The replicators1420may also be used as templates for drilling features into the base1410. The replicators1420may be attached (e.g., snapped) together and/or attached to the base1410using any suitable attachment methods, such as being molded onto the upper base surface. According to some embodiments, multiple pads1400may be attached to one another as pad sections, to create a larger pad1400. For example, the pads1400could be connected using “living hinges” on pad plumbing covers, which may snap lock into position. In other words, the pad1400may be considered a pad section, according to some embodiments. FIG.15is a perspective view of a pad1500for a fuel cell system, according to various embodiments of the present disclosure. Referring toFIG.15, the pad1500includes pad sections1510and a tension cable1520. While one tension cable1520is shown, multiple tension cables1520may be included. The tension cable1520is configured to connect the pad sections1510. In particular, wedges1530may be disposed on the tension cable1520to bias the pad sections1520together. While one wedge1530is shown, wedges may be disposed on opposing ends of each tension cable1520. The pad sections1510may further include alignment pins1512and alignment holes1514. In particular, the alignment pins1512may be interested into the alignment holes1514, in order to align the pad sections1520with one another. According to some embodiments, the alignment pins1512may be pyramid-shaped and the alignment holes1514may have a corresponding shape, in order to facilitate alignment of the pad sections1510. FIG.16is a perspective view of a pad1600for a fuel cell system, according to various embodiments of the present disclosure. Referring toFIG.16, the pad1600includes pad sections1610that are connected together. In particular, the pad sections1610include first and second brackets1612,1614, which mate with one another and are locked together with pins1616inserted there through. The pad sections1610may include recesses or cut-outs1618that may provide space for plumbing and/or wiring. The plumbing and/or wiring may be fed through the pad sections1610to holes1620formed therein. The configuration of the pad1600may allow for the pad1600to have various shape and/or sizes. In some embodiments, the pad sections1600may be disposed on a relatively thin concrete pad. FIG.17illustrates a pad section1700of a fuel cell system, according to various embodiments. Referring toFIG.17, the pad section1700includes tie downs1710extending from an upper surface thereof. The tie downs1710may be formed of forged or toughened metal, and may be inserted into the pad during or after fabrication. The tie downs1710may be mushroom shaped, and may allow for the blind installation of a module on the pad section1700. As such, the tie downs1710allow for a module to be more easily attached to the pad section1700, since the tie downs1710are self-guiding. FIG.18Aillustrates a support frame1800of a fuel cell system, according to various embodiments. The support frame may include water plumbing1810, fuel plumbing1812, and electrical wiring1814, which may extend between a hole1816in the support frame1800and quick connects1818. The support frame1800may be attached and prewired to a module1820of a fuel cell system as shown inFIG.18Bat a manufacturing site and then shipped to a site for assembly where the fuel cell system will generate power. The pre-attached frame1800may be similar to the frame1014shown inFIG.13A. Accordingly, assembly of a fuel cell system may be simplified. FIGS.19A and19Billustrate a top view of a large site fuel cell system of another embodiment with pre-cast concrete trenches before and after the trenches are filled with the plumbing and the wiring, respectively.FIGS.19C and19Dare perspective views of the large site fuel cell system ofFIGS.19A-19B. FIG.FIG.19Eis a schematic side view of components of a gas and water distribution module ofFIG.19C.19F is a side cross-sectional view of a pad for a module of the large site fuel cell system ofFIG.19D.FIG.19Gis a functional schematic of the system. All modules described below may be located in a separate housing from the other modules. The system reduces the number of components, and simplifies component installation, thus reducing the total system cost. The large site fuel cell system contains multiple rows of the above described power modules12(labeled PM5). A single gas and water distribution module (GDM) is fluidly connected to multiple rows of power modules. For example, at least two rows of at least six power modules each, such as four rows of seven power modules each, are fluidly connected to the single gas and water distribution module. As shown inFIG.19E, the single gas and water distribution module GDM may include connections between the above described water and fuel plumbing230and the power modules. The connections may include conduits (e.g., pipes) and valves231F and231W which route the respective fuel and water from the central plumbing230into each power modules. The fuel and water plumbing230may include the above described fuel pipes230A labeled “UG” and the above described water pipes230B labeled “UW”. The gas and water plumbing230may be connected to utility gas and water pipes, respectively. A single system level fuel processing module16which includes components for pre-processing of fuel, such as adsorption beds (e.g., desulfurizer and/or other impurity adsorption) beds, may be connected to all gas pipes230A. Thus, a single desulfurizer may be used to desulfurize natural gas fuel provided to all GDMs in the fuel cell system. Optionally one or more water distribution modules (WDM) may be provided in the system. The WDM may include water treatment components (e.g., water deionizers) and water distribution pipes and valves which are connected to the municipal water supply pipe, and to the individual modules in the system. Each row of power modules12is electrically connected to a single above described power conditioning module18(labeled AC5) which may include a DC to AC inverter and other electrical components. A single mini power distribution module (MPDS) is electrically to each of the power conditioning modules18using the above the described wires232labeled “UE”. For example, at least two rows of at least six power modules12each, such as four rows of seven power modules each, are electrically connected to a single MPDS through the respective power conditioning modules18, such as four power conditioning modules18. The MPDS may include circuit breakers and electrical connections between the plural power conditioning modules18and one of the system power distribution modules PDS-1or PDS-2. One or more telemetry modules (TC) may also be included in the system. The telemetry modules may include system controllers and communication equipment which allows the system to communicate with the central controller and system operators. Thus, four inverters in power conditioning modules18and telemetry cables may be connected to the single MPDS. The system also includes the system power distribution unit (i.e., central power supply unit) that feeds the safety systems within the GDMs and also feeds a telemetry ethernet switch (4:1). This reduces the number of power conduits and telemetry conduits installed by an onsite contractor from 4 into 1. Alternatively, a single connection may be used telemetry data transfer. The single cat 5 cable may be replaced with a wireless transceiver unit for data communications between the power conditioning module18and the telemetry module TC. This eliminates the data cable installation. A set of plural rows of the power modules and their respective power conditioning modules fluidly and electrically connected to the same GDM and the same MPDS, respectively, may be referred to as a subsystem. The fuel cell system may include plural subsystems, such as two to ten subsystems. Four subsystems are shown inFIGS.19A-19B. The fuel cell system may also include a system power distribution unit which is electrically connected to all subsystems of the fuel cell system using the wires232(i.e., “UE”). The system power distribution unit may include at least one system power distribution module, such as two modules PDS-1and PDS-2, at least one transformer, such as two transformers (XFMR-1and XFMR-2) and a disconnect switch gear (SWGR). The transformers XFMR-1and XFMR-2may be electrically connected to the respective PDS-1and PDS-2modules using the wires232. The switch gear may comprise 15 kV switch gear which has inputs electrically connected to the transformers via the wires232, and an output electrically connected to an electrical load and/or grid. An optional uninterruptible power subsystem (UPS) may also be included. Thus, electric power is provided from the power modules through the respective MPDS, PDS-1or PDS-1, XFMR-1or XFMR-2and SWGR to the grid and/or load. FIG.19Kshows one block of a fuel cell system such as shown inFIG.19A. One block includes eight 300 kW (6+1) power modules, eight power conditioning modules18(AC5), one TC, two WDMs, one 3000 kVA transformer, two GDMs and two MPDS. FIG.19Lshows the layout of a system of an alternative embodiment. The system includes eight blocks (with one of the blocks being larger block with two additional rows of power modules. The system includes sixty six 300 KW (6+1) power modules, one centralized desulfurizer module system, 16 GDMs, 16 WDMs, seven 3000 kVA Transformers, one 4000 kVA Transformer, fifteen 2000 Amp MPDS, two secondary 2500 Amp MPDS, and eight TCs. The system ofFIG.19Lprovides a compact layout of the modules, which reduces the length of the electrical connections (e.g., copper wires) between the modules. This reduces the cost of the system. As shown inFIG.19G, the central desulfurization system (e.g., module)1600replaces the separate desulfurizers in each row of power modules. The central desulfurization module1600is fluidly connected to the GDM, which is fluidly connected to the power modules12to provide fuel to the power modules12. The power modules12are electrically connected to the MPDS, which is electrically connected to the electrical load (e.g., the power grid or a stand-alone load)1901. The central desulfurization system (e.g., module)1600is shown inFIG.19H. The central desulfurization system (e.g., module)1600contains one or more vessels1602(e.g., columns) filled with a sulfur adsorbent material (e.g., a sulfur adsorber bed). The GDM is shown inFIG.19I. The GDM distributes fuel to four rows of power modules (which is referred to as a “stamp”). FIG.19Jillustrates flow diagram for the central desulfurization system1600. The system1600may include a filter at the fuel inlet and two parallel fuel flow paths (e.g., fuel lines, i.e., fuel conduits) to each row of power modules (i.e., “stamp”). Furthermore, there may be two sets of two control valves1603, such as mass flow control valves, located in parallel fuel flow paths to each “stamp”. Pressure transducers (PRT) may be located on various lines and used to monitor the line pressure and take the necessary action during system operation. A gas sampling port1604may also be located on the main inlet line. In one embodiment, the system also includes a separate sulfur breakthrough detection line1606(shown in dashed box) which is used to detect sulfur breakthrough. The output of the detection line1606may be fluidly connected to a safety vent1608. A sulfur detection sensor1609may be located on the detection line1606to detect the presence of sulfur in the fuel that is output from the desulfurization system1600. As shown inFIGS.19B-19D, the plumbing230(e.g., fuel and water pipes230A,230B) may be provided from the respective utilities (e.g., gas and water pipes) to the respective GDM in each subsystem through pre-cast concrete trenches1902. Likewise, the wires232may be provided between each MPDS and the system power distribution unit through the same pre-cast concrete trenches1902. The pre-cast concrete trenches1902may have a “U” shape with two vertical sidewalls connected by a horizontal bottom wall or horizontal connecting bars. Openings may be provided in the horizontal bottom wall. The pre-cast concrete trenches1902are located below grade and are covered with cover plates, dirt, gravel and/or asphalt concrete paving. As shown inFIGS.19D and19F, each module of the system, such as a power module12and/or power conditioning module18may be installed on a multi-layer support. The multi-layer support is formed on compacted soil1910. The support includes a cellular concrete (aka concrete foam) base1912, such as Confoam® cellular concrete base. A conventional (non-cellular) concrete pad1914is located on the base1912. The concrete pad1914has a smaller area than the base1912. U-shaped steel mesh formwork1916, such as Novoform®, which surrounds a metal rebar cage, is provided on the sides of the concrete pad1914. The base1912supports the bottom of the framework1916. The top of the concrete pad1914is located between 1.5 and 2 inches above finished grade, which may comprise gravel or asphalt concrete paving1918located over the base1912. As shown inFIGS.19A-19C,19K and19Leach block of the fuel cell system may include at least one transformer. The at least one transformer may be isolated (i.e., physically separated from) the rows of power modules12and may be located on a separate pad from the power modules12, the power conditioning modules18, and optionally the GDMs, the WDMs, the TC units, and the MPDS modules. The at least one transformer may be located on a separate pad containing other components of the system power distribution unit, such as the system power distribution module(s) (PDS-1and PDS-2) and the disconnect switch gear (SWGR). Wires232(i.e., “UE”) may extend through trenches, such as pre-cast concrete trenches1902, between the separate pad containing the at least one transformer and optionally other components of the system power distribution unit to the respective pads containing the rows of power modules12, the power conditioning modules18, and optionally the GDMs, the WDMs, the TC units, and the MPDS modules. In various embodiments, the at least one transformer (e.g., XFMR-1and XFMR-2inFIGS.19A and19Band XFMR inFIGS.19K and19L) may be in a central location of the block such that rows of power modules12may be located on at least two opposite sides of the transformer (i.e., the rows of power modules12are not arranged in-line with the transformer on a single side of the transformer). In some embodiments, the at least one transformer may be located between at least two rows of power modules12within the block. In the embodiment shown inFIGS.19A and19B, XFMR-1may be electrically coupled to a plurality of power modules12, including all of the power modules12, located on a first side (i.e., left side) of the block and XFMR-2may be electrically coupled to a plurality of power modules12, including all of the power modules12, located on a second side (i.e., right side) of the block. In some embodiments, a third transformer (i.e., XFMR-3) may also be located in a central location of the block, such as on the same pad containing the first and second transformers, XFMR-1and XFMR-2. The first and second transformers, XFMR-1and XFMR-2, may feed power to the third transformer XFMR-3, which may have a higher power rating than either of the first and second transformers, XFMR-1and XFMR-2. For example, the first and second transformers XFMR-1and XFMR-2may be 3000 kVA transformers, and the third transformer XFMR-3may be a 5000 kVA transformer. The third transformer XFMR-3may provide a single power output for the entire block. In the embodiment shown inFIG.19L, each transformer XFMR may service a respective block of the fuel cell system, and may provide a single power output that may be transmitted over a wire to a common switchgear (shown on the lower left-hand side ofFIG.19L) that may be coupled to the grid and/or load. Providing one or more transformers in a central location of the block between respective rows of power modules12may significantly decrease the overall length of the electrical connections (e.g., copper wires) that need to be run for each block and within the fuel cell power system as a whole. This may greatly reduce the cost of the fuel cell system. FIGS.20A to20Jare perspective views of steps in a method of installing the large site fuel cell system ofFIGS.19A-19K. As shown inFIGS.20A and20G, trenches are formed in the soil and then compacted using heavy machinery, such as an excavator, and frames are placed into the trenches. As shown inFIGS.20B and20H, the cellular concrete base1912is filled into the trenches. The cellular concrete comprises a flowable fill material (e.g., foam concrete, such as Confoam fill27) which is filled from a pipe or hose and then solidified into the base1912. As shown inFIGS.20C and20I, the U-shaped steel mesh formwork1916and rebar cage are placed on top of the base1912. The framework1916may include polymer sheets that cover the metal mesh. Rebar is located inside the framework, as shown inFIG.20J. The concrete pad1914is then formed inside the bounds of the framework1916. The modules are then placed on the concrete pad1914. As shown inFIGS.20D and20F, additional trenches are formed outside of the bases1912. The pre-cast concrete trenches1902are then placed into the additional trenches. As shown inFIG.20E, the gas pipes230A, water pipes230B and wires232are then placed into the pre-cast concrete trenches1902and connected to the respective GDMs and power components, such as MPDS, PDS-1and PDS-2. The pipes and wires may be attached or clamped (e.g., using clamps1903and/or support bars) inside the pre-cast concrete trenches1902at different vertical levels. The pre-cast concrete trenches1902are then covered with cover plates, dirt, gravel and/or asphalt concrete paving. The method shown inFIGS.20A to20Jachieves 100% consolidation with no mechanical vibration, which eliminates or reduces the need to brace walls during backfill operations. Finally, it is easily excavatable and may be removed with a shovel or cut out with a reciprocating saw or handsaw. FIG.21is a schematic view of one subsystem of the system shown inFIGS.19A-19C. Each row of power modules12may comprise a 300 kW Energy Server® fuel cell power generator from Bloom Energy Corporation, labeled “ES”. Thus, the subsystem includes four rows of 300 kW ES for a total of 1200 kW of power. The entire system containing four subsystems can deliver 4800 kW of power. The 1200 kW ES configuration is comprised of 4×300 kW ES that all converge the standard power, communication, water and gas interconnects into center sections for common tie-in during the installation process. The MPDS inFIGS.22A and22Btakes advantage of the install proximity in two ways. First, a single electrical tie-in to this module can in turn be distributed to the power conditioning modules18by suppling the interconnect cables as part of a site install kit. This reduces the installation from 4 sets of conduits and trenches into one. This configuration also allows omission an output circuit breaker and surge device in each power conditioning module18for a total of 4 breakers and 4 surge devices eliminated from the 1200 kW system. Additional beneficial features include the placement of the WIFI transmitter in the MPDS module and its communication interconnects to the separate ES. The WIFI system may service the entire installation and may lead to omission of 4 sets of conduits and wires, which reduces installation cost and complexity. Thus, reduces system and installation can be realized due to the collection of the separate units into the system. Inclusion of the main breaker into system allows transformers to be placed closer to the rows of power modules, which reduces install costs and requires less electrical lines. FIG.23shows alternative electronics modules according to another embodiment. The configuration inFIG.23shows 4 separate cabinets (i.e., housings) with each cabinet being fully populated for a dedicated purpose. The first cabinet is the location for landing the individual power module from the 4 ES while paralleling them on to a common DC bus. This module includes bussing, fuse protection and internal cabling landing locations. This module may support both 50 and 75 kW rated power modules and may include a fully rated interconnection of the collected output DC as an optional means to extend the DC bus to an adjacent 1200 kW system. The center modules2and3are populated with inverters units only that have large ampacity DC input and AC output. This embodiment may further reduce cost by eliminating the smaller inverter units and making a single monolithic inverter for implementation in the central system power distribution unit. The final module4provides further cost savings. This module houses the start-up and safety equipment for the fuel cell power modules. This reduces the quantity of these items from 4 to 1. This further serves as the collected output terminals for the system and the only location provided for external conduit entry. In one embodiment, each subsystem includes 1200 kW/1200 kVA or 1420 kVA inverter. The subsystem will still retain the individual start-up and safety systems within the grid connected inverters. This will allow an individual safety shutdown within a single 300 kW ES (i.e., row of power modules12). While a safety shutdown request coming from the GDM will shut down all 4 ES in the subsystem. This results in reduced product costs if the circuit breaker is removed within the 4 grid parallel inverters. The protection that these breakers provide may be moved to the integrated system PDS-1or PDS-2. Thus, the 4 redundant surge protection devices and safety systems from each subsystem may be consolidated in the central system power distribution unit. FIGS.24,25A and25Bare photographs of concrete curbs and raceways that may be used during the installation of the system of embodiments of the present disclosure.FIG.24illustrates concrete curbs which may be used instead of a pre-cast concrete pads. This allows the subsystems to be co-located in one area with a single electrical tie in location. The curbs provides pathways under the modules so that wires232and plumbing230can be installed on grade as opposed to below grade. This eliminates trench excavation. Furthermore, excavation and the usage of separate conduits may be reduced or eliminated by using pre-manufactured concrete cable raceways shown inFIGS.25A and25B. The raceways may comprise the pre-cast concrete trenches described above with respect toFIGS.20D and20J. These can be installed on grade or in simple excavated trenches without the earthwork needed for conduit burial. Lastly, fixed cable raceways and improved site design can pre-determine actual conductor lengths allowing pre-manufactured conductor sets for each run of cables from the 1200 kW subsystems to the central electrical gear (i.e., to the system power distribution unit). This improves quality, reduces scrap and labor hours on site. In general, the installation is improved by increased quality, reduced site build time, reduced labor costs (e.g., electrical and plumbing), while still maintaining serviceability with lower overall height of components and simplified rigging. Thus, the open trenches shown inFIGS.24to25Bprovide significant labor and material savings by avoiding to compact and close the trench with Class II/Engineered fill. A self compacting slurry, such as Confoam fill27(cellular concrete) is provided in lieu of Class II AB for subgrade and trench. It also provides better heat dissipation and eliminates RHO concrete, as well as easier servicing and upkeep. FIG.26Ais a top view of a large site fuel cell system according to yet another embodiment of the present disclosure.FIG.26Bis a top view of a block2603of the fuel cell system ofFIG.26A.FIG.26Cis a top view of an alternative configuration of a block2603of the fuel cell system ofFIG.26Aillustrating fuel conduits230A, water conduits230B, and electrical wiring232.FIG.26Dis a perspective view of a block2603of the fuel cell system ofFIG.26Aillustrating side entry of fuel and water conduits230A,230B into a fuel processing module16located at a first end of the rows of power modules12and side entry of electrical wiring232into the powder conditioning module18located at a second end of the rows of power modules12. Thus, in this embodiment, the fuel processing module16and the power conditioning module18are located on opposite ends of a row of power modules12.FIG.26Eis a perspective view of a concrete trench1902containing electrical wiring232extending between the rows of power modules12and a centralized system power distribution unit2604for a block2603of the fuel cell power system. The fuel cell power system as shown inFIGS.26A-26Emay reduce the number of components, including the total amount of electrical wiring, and may simplify component installation, thus reducing the total system cost. The large site fuel cell system shown inFIGS.26A-26Emay be similar to a system as described above with reference toFIGS.19A-19L. In particular, the system may include multiple rows of power modules12(labeled PM5) arranged on pads2601a(e.g., concrete pads) as shown inFIG.26D. Each row of power modules12is electrically connected to a single above-described power conditioning module18(labeled AC5) which may include a DC to AC inverter and other electrical components. The fuel processing modules16(labeled FP5) and power conditioning modules18may be located on the same pads2601awith the power modules12. The system may be configured in a plurality of blocks2603, where each block2603may include a plurality of rows of power modules12(and associated fuel processing modules16and power conditioning modules18). The rows of power modules12are located on different sides of a central system power distribution unit2604of the respective block2603. The system power distribution unit2604may include at least one transformer, such as first and second transformers, XFMR-1and XFMR-2, that may each be electrically connected to a plurality of rows of power modules12on respective sides of the block2603, and a third transformer XFMR-3that is electrically connected to the first and second transformers XFMR-1and XFMR-2, and may provide a single power output for the block2603. The power outputs from each block2603may be provided over an electrical connection (e.g., copper wire) to a common switchgear2605that may couple the system to the grid and/or a load. An above-described system power distribution module (PDS) may be electrically connected to a plurality of power conditioning modules18of the rows of power modules12and may also be electrically connected to a transformer (e.g., XFMR-1or XFMR-2) of the system power distribution unit2604in each block2603. For example, each block2603may include a pair of system power distribution modules, such as the above-described PDS-1and PDS-2, in the system power distribution unit2604, where each of the power distribution modules may be electrically connected to power conditioning modules18on respective sides (e.g., left and right sides) of the block2603, and may provide power to a respective one of the first and second transformers XFMR-1and XFMR-2. Each block2603of the system may optionally also include one or more above-described water distribution modules (WDMs), and one or more above-described telemetry modules (TCs). The system shown inFIG.26Aincludes five blocks2603each including a plurality of rows of power modules12and a system power distribution unit2604. Each row includes seven power modules12and may form a 300 kW Energy Server® fuel cell power generator (ES) as described above with reference toFIG.21. Four of the five blocks2603include fourteen rows of power modules12and may provide 4.2 MW of power. A fifth block2603(located on the right-hand side ofFIG.26A) includes thirteen rows of power modules12. Thus, the system as a whole may provide 20.7 MW of power. It will be understood that various other configurations of the system are within the scope of the present disclosure, including variations in the number of blocks2603of the system, variations in the number of rows of power modules12per block2603, variations in the number of power modules12per row, as well as variations in the layout(s) of the blocks2603and the rows of power modules12within each block2603. The system shown inFIGS.26A-26Emay differ from the system described above with reference toFIGS.19A-19Lin that the system ofFIGS.26A-26Emay not include a central desulfurization system, and may also not include central gas and water distribution modules (GDMs) fluidly-connected to the rows of power modules12. Rather, the system shown in FIGS.26A-26E may include a plurality of the above-described fuel processing modules16(labeled FP5) including components for pre-processing of fuel, such as adsorption beds (e.g., desulfurizer and/or other impurity adsorption beds). Each row of power modules12may include a fuel processing module16fluidly coupled to each of the power modules12within the row. The fuel processing module16may be located on the same pad2601awith the row of power modules12and the associated power conditioning module18. Referring again toFIGS.26A-26E, in various embodiments, within each of the rows of power modules12of the system, a fuel processing module16(i.e., FP5) may be located on a first side of the row of power modules12, and a power conditioning module18(i.e., AC5) may be located on a second side of the row of power modules12, opposite to the first side. As shown inFIG.26B, fuel (indicated by arrows labeled “F”) and water (indicated by arrows labeled “W”) may enter the fuel processing modules16via conduits230A and230B on one side of the rows, and external electrical connections (e.g., wires232) to the power conditioning modules18(indicated by arrows labeled “E”) may be located on the opposite side of the rows. Underground fuel conduits (e.g., pipes)230A and water conduits (e.g., pipes)230B may feed fuel and water, respectively, to the fuel processing module16in each row, as shown inFIGS.26C and26D. In embodiments that include at least one water distribution module (WDM), the water from a municipal water supply pipe may be initially provided to a WDM for treatment, and the treated water may be supplied from the WDM to the fuel processing modules16in each row via the water conduits230B, as shown inFIG.26C. The above-described wires232may couple the power conditioning module18in each row to the centralized system power distribution unit2604of the respective block2603. In some embodiments, the wires232may be located within a pre-cast concrete trench1902as described above with reference toFIGS.19B-19D and20D-20E. The pre-cast concrete trench1902may extend between the power conditioning modules18of the respective rows to the centralized system power distribution unit2604in each block2603of the fuel cell system. Alternatively, the wires232may be located in a concrete curb or raceway as described inFIGS.24,25A and25B. In other embodiments, such as shown inFIG.26D, the wires232may be located in buried conduits that may optionally be encased in a suitable material, such as cement. In various embodiments, separating the fuel processing modules16and the power conditioning modules18on opposite sides of the rows of power modules12may obviate the need to include utility connections (i.e., fuel and water conduits230A and230B) and electrical connections (e.g., copper wires) within the same trenches. Placing the utility and the electrical connections within the same trench may need a deeper trench (e.g., >3 feet, such as up to 5 feet deep) in order to maintain a sufficient vertical separation between the utility and electrical connections. Accordingly, by placing the fuel and water conduits230A and230B in separate trenches from the electrical connections (e.g., wires232), the trenches do not need to be as deep, which can save on excavation time and cost. In addition, the electrical connections may enter on the sides of the rows that are closest to the centralized system power distribution unit2604within each block2603. Thus, the wires232connecting the power conditioning modules18of the rows to the centralized power distribution unit2604of each block2603may traverse shorter distances. This may result in less copper wiring and shorter runs of the trenches (e.g., pre-cast concrete trenches1902) containing the electrical connections, which may provide significant savings in labor and materials cost. Further, the trenches1902containing the electrical connections (e.g., wires232) shown inFIG.26Dmay be relatively shallower compared to the trenches1902shown inFIGS.19B-Dand20D-E since they only contain the electrical connections rather than stacked electrical and utility (e.g., gas and water) connections. Referring toFIGS.26B-26E, in various embodiments, the electrical connections (e.g., wires232) and the utility connections (e.g., fuel and water conduits230A and230B) may enter the rows of power modules12from the sides of the rows rather than entering from beneath the rows as in the embodiments described above with reference to, for example,FIGS.3A-3D,4C,5B,5D,6B,7B,8,9B,16,17,18A,19A-D,19K and19L. In various embodiments, service relocation modules2606amay be located on an external side surface of the fuel processing module16cabinets at the end of each row of power modules12. Fuel and water conduits230A and230B may enter the service relocation modules2606afrom below and may enter the fuel processing module16cabinets from the side (e.g., above finished grade). Additional service relocation modules2606bmay be located on an external side surface of the power conditioning module18cabinets at the opposite end of each row of power modules12. Electrical connections (e.g., wires232) may enter the service relocation modules2606bfrom below (e.g., from pre-cast concrete trenches1902) and may enter the power conditioning module18cabinets from the side (e.g., above finished grade). In various embodiments, by providing side-entry of the electrical and utility connections to each of the rows of power modules12, the use of “cut-outs” in the concrete pads2601a(e.g., the above-described openings214and216through the concrete pads) may be avoided. This may simplify the design and installation of the concrete pads2601aon which the rows of power modules12are supported, and may also reduce labor costs since the need to extend the trenches containing the electrical and/or utility connections beneath the concrete pads to the location(s) of the openings214and216may be eliminated. FIG.27Ais a perspective view of concrete pads2601a,2601band2601cand pre-cast concrete trenches1902of a block2603of a fuel cell power system as shown inFIGS.26A-26E.FIG.27Bis a perspective view of a pre-cast concrete trench1902containing electrical connections (i.e., wires232).FIG.27Cis a top view of the pre-cast concrete trench1902ofFIG.27B. Referring toFIG.27A, the concrete pads2601aand2601con which the rows of power modules12are located may be generally rectangular-shaped pads that do not include interior “cut-outs” or openings through the pad2601a,2601cthrough which utility and electrical connections enter the respective rows. Rather, as described above, the utility and electrical connections may be made through the sides of the module cabinets at opposite ends of the rows. Thus, the pads2601aand2601cmay not include an interior opening (i.e., an opening surrounded on all sides by the pad2601a,2601b) extending through the pad. Concrete pads2601amay each support two rows of power modules12and associated fuel processing modules16and power conditioning modules18at opposite ends of the respective rows. Concrete pad2601cmay support a single row of power modules12with an associated fuel processing module16and power conditioning module18on opposite ends of the row. Plumbing and electrical connections to and between the modules of the row may extend over the upper surface of the concrete pad2601aand2601c. In various embodiments described in further detail below, one or more overlay structures attached to the upper surface of the pads2601a,2601cmay provide a space or separation between the upper surface of the pads2601aand2601cand the lower surface of the fuel cell system modules12,16,18supported on the pad2601a,2601c. The plumbing and electrical connections may extend within the space between the upper surface of the pads2601a,2601cand the lower surface of the fuel cell system modules12,16,18. As in the embodiments described above with reference toFIGS.13A-13B and14, the upper surface of the base1010may be substantially planar, e.g., does not need to include recesses or other features for the plumbing and/or wiring and/or for installation of the fuel cell system modules12,16,18. As such, the concrete pads2601aand2601cmay be manufactured at a lower cost, since the pads2601a,2601bdo not require cast features. Alternatively, the concrete pads2601aand2601cmay include cast features for the plumbing and/or wiring and/or for installation of the fuel cell system modules12,16,18. The block2603shown inFIG.27Amay also include a separate concrete pad2601bon which various components of the system power distribution unit2604, such as the above-described power distribution modules (PDS-1, PDS-2) and transformers (XFMR-1, XFMR-2, XFMR-3) may be located. The pre-cast concrete trench1902may extend between concrete pad2601band each of the concrete pads2601a,2601bcontaining the fuel cell system modules12,16,18. In various embodiments, the fuel cell system modules12,16,18and the system power distribution unit2604may be supported on a multi-layer support that includes a base2607and a concrete pad2601a,2601b,2601clocated over the base2607. The base2607may be a cellular concrete (aka concrete foam) base2607, such as a Confoam® cellular concrete base that may be formed on compacted soil. The concrete pads2601a,2601band2601cmay be conventional (non-cellular) concrete pads. The concrete pads2601a,2601band2601cmay have a smaller area than the base2607on which the concrete pads2601a,2601band2601care located. In some embodiments, the base2607may have a greater thickness than the concrete pads2601a,2601band2601c. For example, the base2607may have a thickness that is greater than 12 inches, such as between 18-30 inches (e.g., about 24 inches). The concrete pads2601a,2601band2601cmay have a thickness that is less than 12 inches, such as between 6-12 inches (e.g., about 8 inches). In some embodiments, the pre-cast concrete trench1902containing the wires232may be located over a portion of a base2607. FIG.28Ais a perspective partially-transparent view of a concrete pad2601afor supporting fuel cell system modules12,16,18.FIG.28Bis a top partially-transparent view of the concrete pad2601aofFIG.28A.FIG.28Cis a top view of the concrete pad2601aofFIG.28Aincluding overlay structures2615attached to the top surface of the concrete pad2601a.FIG.28Dis a top view of a concrete pad2601afor supporting components of a system power distribution unit2604. Referring toFIGS.28A and28B, the concrete pad2601amay be 6 to 10 inches, such as 8 inches thick with a single layer of rebar2612reinforcement. In some embodiments, the concrete pad2601amay include a plurality of embedded struts2613that may be used to attach overlay structures to the top surface of the concrete pad2601a. In other embodiments, other attachment mechanisms, such as anchor bolts, may be used to attach overlay structures to the top surface of the concrete pad2601a. The concrete pad2601amay have cut-out portions along a peripheral side surface of the pad that may abut portions of a pre-cast concrete trench1902containing the electrical connections (e.g., wires232) to the power conditioning modules18located on the concrete pad.FIG.28Cis a top view of the concrete pad2601awith overlay structures2615attached to the top surface of the concrete pad2601a. In some embodiments, the overlay structures2615may include, for example, the above-described frames1014configured to receive the power modules12, the fuel processing modules16and/or the power conditioning modules18, and the above-described separators1012configured to separate the frames1014from the upper surface of the concrete pad2601a, as described above with reference toFIGS.13A and13B. Alternatively, or in addition, the overlay structures2615may include the above-described replicators1420that may form elevated structures for supporting the power modules12, the fuel processing modules16and/or the power conditioning modules18, as described above with reference toFIG.14. Other suitable overlay structures2615are within the contemplated scope of the present disclosure. Referring toFIGS.28D, the concrete pad2601bfor the components of the system power distribution unit2604may include two layers of rebar2612reinforcement. The concrete pad2601bmay have a plurality of cut-out portions2614along peripheral side surface of the pad to accommodate portions of a pre-cast concrete trench1902containing the electrical connections (e.g., wires232) to the system power distribution unit2604. FIGS.29A and29Bare perspective views of service relocation modules2606located adjacent to a side surface of a cabinet of the housing14of a fuel cell system module. As discussed above, the service relocation modules2606may allow side-entry of utility and/or electrical connections into the cabinets of the housing14of the fuel cell system modules (e.g., fuel processing modules16and/or power conditioning modules18). The service relocation modules2606may include a housing2620having a removable cover2621. Utility and/or electrical connections (e.g., gas and water conduits230A and230B in the case of utility connections and wires232in the case of electrical connections) may enter the housing2620from below ground-level through conduits (e.g., tubes)2622. One or more openings2623in the side surface of the cabinet of the housing14allow the utility and/or electrical connections to enter the cabinet from the housing2620. The embodiment inFIG.29Aincludes a plurality of lug connectors2627located inside the housing2620of the service relocation module2606. The lug connectors2627connect a first plurality of underground utility and/or electrical connections to a second set of connections to the interior of the cabinet of the housing14. The embodiment ofFIG.29Billustrates a “pull”-type service relocation module2620in which the underground utility and/or electrical connections extend continuously through the housing2620into the interior of the cabinet of the housing14. Fuel cell systems of the embodiments of the present disclosure are designed to reduce greenhouse gas emissions and have a positive impact on the climate. The arrangements of the fuel cell systems, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present disclosure. Any one or more features of any embodiment may be used in any combination with any one or more other features of one or more other embodiments. | 82,771 |
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