Electricity storage device

Abstract

This electricity storage device is provided with: an electrode having a current collector and a positive electrode active material layer provided on the surface of the current collector; and a sealing member provided on the surface of the current collector so as to surround the positive electrode active material layer when viewed in the lamination direction. The current collector includes: a first metal foil including a surface; a second metal foil provided on the opposite side from the positive electrode active material layer with respect to the first metal foil; and an adhesive layer which is provided between the first metal foil and the second metal foil and which adheres the first metal foil and the second metal foil to each other. The sealing member includes a sealing portion fused to the surface and a sealing portion fused to a side surface of the current collector including a side surface of the adhesive layer. The heat resistance temperature of the adhesive layer is greater than the melting point of each of the sealing portion and the sealing portion.

Description

Technical Field

[0001] The present disclosure relates to a power storage device. Background Art

[0002] Conventionally, there is known a power storage device including a plurality of electrodes stacked in a stacking direction (see, for example, Patent Document 1). The electrodes include a positive electrode collector, a negative electrode collector, and an adhesive layer provided between the positive electrode collector and the negative electrode collector.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-317468 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] However, in the above-mentioned power storage device, there is a case where the sealing member for sealing the side surfaces of the plurality of electrodes is fused to the surface of the electrode. In such a case, the heat when the sealing member is fused to the electrode is transferred to the adhesive layer, resulting in a decrease in the adhesive strength of the adhesive layer, thereby possibly causing damage to the electrode.

[0008] An object of the present invention is to provide a power storage device capable of suppressing damage to electrodes.

[0009] Solutions for solving problems

[0010] The power storage device disclosed in the present invention comprises: an electrode having a collector and an active material layer arranged on the first main surface of the collector; and a sealing component, which is arranged on the surface of the collector in a manner to surround the active material layer when viewed from a direction perpendicular to the first main surface, the collector comprising: a first metal foil, which comprises a first main surface; a second metal foil, which is arranged on the side opposite to the active material layer relative to the first metal foil; and an adhesive layer, which is arranged between the first metal foil and the second metal foil and bonds the first metal foil to the second metal foil, the sealing component comprising a first sealing portion welded to the first main surface and a second sealing portion welded to the side surface of the collector including the side surface of the adhesive layer, and the heat-resistant temperature of the adhesive layer is greater than the melting point of each of the first sealing portion and the second sealing portion.

[0011] In the power storage device, the current collector includes an adhesive layer that is arranged between the first metal foil and the second metal foil and bonds the first metal foil to the second metal foil. In addition, the first sealing portion is fused to the first main surface of the first metal foil, and the second sealing portion is fused to the side of the current collector. Here, the heat-resistant temperature of the adhesive layer of the current collector is greater than the melting point of each of the first sealing portion and the second sealing portion. Therefore, even if the heat when the first sealing portion and the second sealing portion are fused to the current collector is transferred to the adhesive layer, the reduction in the bonding strength of the adhesive layer is suppressed. As a result, the damage to the current collector caused by the reduction in the bonding strength of the adhesive layer is suppressed. Therefore, according to the power storage device, the damage to the electrode can be suppressed.

[0012] Alternatively, the power storage device further includes a spacer, the electrode is each of a plurality of electrodes stacked in the stacking direction, the spacer is disposed between adjacent electrodes in the stacking direction and is fused to the sealing member, and the heat-resistant temperature of the adhesive layer is greater than the melting point of the spacer. Thus, even if the heat when the spacer is fused to the sealing member is transferred to the adhesive layer, the reduction in the bonding strength of the adhesive layer is suppressed. Therefore, the damage to the collector caused by the reduction in the bonding strength of the adhesive layer is suppressed, and as a result, the damage to the electrode is suppressed.

[0013] Alternatively, the sealing member further includes a third sealing portion welded to the second main surface of the current collector on the side opposite to the first main surface, and the heat-resistant temperature of the adhesive layer is greater than the melting point of the third sealing portion. Thus, even if the heat when the third sealing portion is welded to the current collector is transferred to the adhesive layer, the reduction in the bonding strength of the adhesive layer is suppressed. Therefore, the damage to the current collector caused by the reduction in the bonding strength of the adhesive layer is suppressed, and as a result, the damage to the electrode is suppressed.

[0014] Alternatively, the adhesive layer may include a thermosetting resin and the sealing member may include a thermoplastic resin. Thus, by using a thermosetting resin as a component of the adhesive layer, the heat resistance temperature of the adhesive layer can be increased, and by using a thermoplastic resin as a component of the sealing member, the sealing performance of the sealing member can be improved.

[0015] Alternatively, the current collector further includes a carbon coating disposed between at least one of the first metal foil and the adhesive layer and between the second metal foil and the adhesive layer. Thus, the bonding strength between the first metal foil and the adhesive layer or the bonding strength between the second metal foil and the adhesive layer can be more reliably ensured.

[0016] Effects of the Invention

[0017] According to the present disclosure, it is possible to provide a power storage device capable of suppressing damage to electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1It is a schematic cross-sectional view of a power storage device according to an embodiment.

[0019] Figure 2 yes Figure 1 A partial enlarged view of .

[0020] Figure 3 It is shown Figure 1 A diagram showing the steps of a method for manufacturing an electricity storage device shown in FIG.

[0021] Figure 4 It is shown Figure 1 A diagram showing the steps of a method for manufacturing an electricity storage device shown in FIG.

[0022] Figure 5 It is shown Figure 1 A diagram showing the steps of a method for manufacturing an electricity storage device shown in FIG.

[0023] Figure 6 It is shown Figure 1 A diagram showing the steps of a method for manufacturing an electricity storage device shown in FIG.

[0024] Figure 7 It is a partially enlarged view of a power storage device according to a modification. DETAILED DESCRIPTION

[0025] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in each figure, the same reference numerals are attached to the same or corresponding parts, and repeated descriptions are omitted.

[0026] Figure 1 The power storage device 1 shown is, for example, a power storage module used in batteries of forklifts, hybrid vehicles, electric vehicles, etc. The power storage device 1 is, for example, a secondary battery such as a nickel-hydrogen secondary battery or a lithium-ion secondary battery. In the present embodiment, the power storage device 1 is a lithium-ion secondary battery.

[0027] like Figure 1 As shown, the power storage device 1 includes a stack 2 and a sealing body 3. The stack 2 includes a plurality of bipolar electrodes 21 stacked in a stacking direction D, a positive terminal electrode 22, and a negative terminal electrode 23. The stack 2 is formed by stacking a plurality of bipolar electrodes 21 between the positive terminal electrode 22 and the negative terminal electrode 23. The bipolar electrode 21 includes a current collector 24, a positive active material layer 25, and a negative active material layer 26.

[0028] The collector 24 is, for example, rectangular in shape when viewed from the stacking direction D. The collector 24 includes a first main surface 24a as one surface, and a second main surface 24b as another surface on the side opposite to the first main surface 24a. That is, the collector 24 has a first main surface 24a and a second main surface 24b that are opposite to each other in the stacking direction D. The positive electrode active material layer 25 is provided on the first main surface 24a of the collector 24. The positive electrode active material layer 25 is, for example, rectangular in shape when viewed from the stacking direction D. The first main surface 24a of the collector 24 includes an uncoated area where the positive electrode active material layer 25 is not provided. The uncoated area surrounds the positive electrode active material layer 25 when viewed from the stacking direction D.

[0029] The negative electrode active material layer 26 is provided on the second main surface 24b of the current collector 24. The negative electrode active material layer 26 is, for example, rectangular when viewed from the stacking direction D. The second main surface 24b of the current collector 24 includes an uncoated region where the negative electrode active material layer 26 is not provided. The uncoated region surrounds the negative electrode active material layer 26 when viewed from the stacking direction D. The plurality of bipolar electrodes 21 are stacked in such a manner that the positive electrode active material layer 25 of one bipolar electrode 21 adjacent in the stacking direction D faces the negative electrode active material layer 26 of another bipolar electrode 21. That is, the plurality of bipolar electrodes 21 are stacked in such a manner that the first main surface 24a of the current collector 24 of one bipolar electrode 21 among the bipolar electrodes 21 adjacent in the stacking direction D faces the second main surface 24b of the current collector 24 of another bipolar electrode 21.

[0030] The positive terminal electrode 22 is stacked on one end of a plurality of bipolar electrodes 21 arranged in the stacking direction D. The positive terminal electrode 22 includes a current collector 24 and a positive electrode active material layer 25 provided on a first main surface 24a of the current collector 24. The positive terminal electrode 22 is different from the bipolar electrode 21 in that it does not include a negative electrode active material layer 26 provided on a second main surface 24b of the current collector 24. In addition, the positive electrode active material layer 25 or the negative electrode active material layer 26 is not provided on the second main surface 24b of the current collector 24 of the positive terminal electrode 22. The second main surface 24b of the current collector 24 of the positive terminal electrode 22 serves as the positive terminal surface of the power storage device 1. The other configurations of the positive terminal electrode 22 may be the same as those of the bipolar electrode 21. The positive terminal electrode 22 is arranged so that the positive electrode active material layer 25 of the positive terminal electrode 22 faces the negative electrode active material layer 26 of the bipolar electrode 21. That is, the positive terminal electrode 22 is stacked such that the first main surface 24 a of the current collector 24 of the positive terminal electrode 22 faces the second main surface 24 b of the current collector 24 of the bipolar electrode 21 adjacent to the positive terminal electrode 22 in the stacking direction D.

[0031] The negative terminal electrode 23 is arranged on the side opposite to the positive terminal electrode 22 with respect to the plurality of bipolar electrodes 21. That is, the positive terminal electrode 22 is stacked and arranged at one end of the plurality of bipolar electrodes 21 in the stacking direction D, and the negative terminal electrode 23 is stacked and arranged at the other end of the plurality of bipolar electrodes 21 in the stacking direction D. The negative terminal electrode 23 includes a current collector 24 and a negative electrode active material layer 26 provided on a second main surface 24b of the current collector 24. The negative terminal electrode 23 is different from the bipolar electrode 21 in that it does not include a positive electrode active material layer 25 provided on a first main surface 24a of the current collector 24. In addition, the positive electrode active material layer 25 or the negative electrode active material layer 26 is not provided on the first main surface 24a of the current collector 24 of the negative terminal electrode 23. The first main surface 24a of the current collector 24 of the negative terminal electrode 23 serves as a negative terminal surface of the power storage device 1. The other structures of the negative terminal electrode 23 may be the same as those of the bipolar electrode 21. The negative terminal electrode 23 is arranged so that the negative active material layer 26 of the negative terminal electrode 23 faces the positive active material layer 25 of the bipolar electrode 21. That is, the negative terminal electrode 23 is stacked so that the second main surface 24b of the collector 24 of the negative terminal electrode 23 faces the first main surface 24a of the collector 24 of the bipolar electrode 21 adjacent to the negative terminal electrode 23 in the stacking direction D. An internal space S for storing an electrolyte is formed between the adjacent bipolar electrodes 21 in the stacking direction D, between the bipolar electrode 21 and the positive terminal electrode 22, and between the bipolar electrode 21 and the negative terminal electrode 23.

[0032] The stack 2 includes a plurality of separators 27. The separators 27 are respectively arranged between the bipolar electrodes 21 adjacent to each other in the stacking direction D, between the bipolar electrode 21 and the positive terminal electrode 22, and between the bipolar electrode 21 and the negative terminal electrode 23. The separator 27 is located between the positive electrode active material layer 25 and the negative electrode active material layer 26 facing each other. The separator 27 is, for example, in the form of a sheet. When the separator 27 is viewed from the stacking direction D, for example, it is in the form of a rectangle. When viewed from the stacking direction D, the outer edge of the separator 27 is located at a position closer to the outside than each of the outer edges of the positive electrode active material layer 25 and the outer edge of the negative electrode active material layer 26. The peripheral edge of the separator 27 is located between the sealing member 4 and the spacer 5 described later. The separator 27 is a member that allows charge carriers such as lithium ions to pass through. The separator 27 isolates the bipolar electrodes 21 adjacent to each other in the stacking direction D, the bipolar electrode 21 and the positive terminal electrode 22, and the bipolar electrode 21 and the negative terminal electrode 23. Thus, electrical short circuits caused by contact between the bipolar electrodes 21 adjacent to each other in the stacking direction D, the bipolar electrode 21 and the positive terminal electrode 22, and the bipolar electrode 21 and the negative terminal electrode 23 can be prevented.

[0033] The current collector 24 is a chemically inert electrical conductor used to allow current to continue to flow through the positive electrode active material layer 25 and the negative electrode active material layer 26 during the discharge or charge of the power storage device 1. The current collector 24 can be, for example, in the form of a plate, a foil, a sheet, a film, a mesh, etc. In the case where the current collector 24 is in the form of a foil, the thickness of the current collector 24 can be in the range of 1 μm or more and 100 μm or less. A coating layer formed by a known method such as plating or spraying can also be formed on the surface of the current collector 24. In addition, for example, the thickness of some of the current collectors 24 of each of the bipolar electrode 21, the positive terminal electrode 22, and the negative terminal electrode 23 can also be 100 μm or more. In this case, the structural stability of the stack 2 is improved.

[0034] The positive electrode active material layer 25 contains a positive electrode active material that can absorb and release charge carriers such as lithium ions. Examples of the positive electrode active material include composite oxides, metallic lithium, and sulfur. The composite oxide composition includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum and lithium. Examples of the composite oxide include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, and LiNiMnCoO2.

[0035] The negative electrode active material layer 26 contains a negative electrode active material that can absorb and release charge carriers such as lithium ions. Examples of the negative electrode active material include graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, soft carbon and other carbons, metal compounds, elements that can alloy with lithium or their compounds, and carbon with added boron. Examples of elements that can alloy with lithium include silicon and tin.

[0036] In addition to the active material, each of the positive electrode active material layer 25 and the negative electrode active material layer 26 may also contain a binder and a conductive aid. The binder serves to bind the active material or the conductive aid to each other and maintain the conductive network in the electrode. As a binder, fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamide-imide, resins containing alkoxysilyl groups, acrylic resins such as polyacrylic acid or polymethacrylic acid, styrene-butadiene rubber, carboxymethyl cellulose, sodium alginate, alginate such as ammonium alginate, water-soluble cellulose ester crosslinked products, starch-acrylic acid graft polymers can be exemplified. These binders can be used alone or in combination. Conductive aids are conductive materials such as acetylene black, carbon black, and graphite, which can improve electrical conductivity. Viscosity adjustment solvents, for example, use N-methyl-2-pyrrolidone.

[0037] The formation of the positive electrode active material layer 25 on the first main surface 24a and the formation of the negative electrode active material layer 26 on the second main surface 24b are, for example, formed by a known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, a curtain coating method, etc. Specifically, an active material, a solvent, and a binder and a conductive aid as required are mixed to produce a slurry-like active material layer forming composition, and the active material layer forming composition is applied to the first main surface 24a or the second main surface 24b, and the applied active material layer forming composition is dried to obtain a positive electrode active material layer 25 or a negative electrode active material layer 26. The solvent is, for example, N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried positive electrode active material layer 25 or the negative electrode active material layer 26 may also be further compressed.

[0038] The separator 27 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains electrolytes. The material of the separator 27 is, for example, polypropylene, polyethylene, polyolefin, polyester, etc. The separator 27 can be a single-layer structure or a multi-layer structure. In the case where the separator 27 is a multi-layer structure, the separator 27 can, for example, include a substrate layer and a pair of adhesive layers, and is bonded and fixed to the positive electrode active material layer 25 and the negative electrode active material layer 26 by the pair of adhesive layers. The separator 27 can also include a ceramic layer as a heat-resistant layer. The separator 27 can also be reinforced with a vinylidene fluoride resin compound.

[0039] As the electrolyte impregnated into the separator 27, for example, a liquid electrolyte (electrolyte) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, or a polymer gel electrolyte containing an electrolyte retained in a polymer matrix, etc. can be listed. In the case of impregnating the electrolyte in the separator 13, as the electrolyte salt, well-known lithium salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2 can be used. In addition, as the non-aqueous solvent, well-known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers can be used. In addition, two or more of these well-known solvent materials can also be used in combination. In the present embodiment, the electrolyte impregnated into the separator 27 is an electrolyte.

[0040] The sealing body 3 is a member for sealing the internal space S. The sealing body 3 is provided on the side of the stacked body 2. The sealing body 3 seals the side of the stacked body 2. The sealing body 3 is, for example, in the shape of a rectangular cylinder. The sealing body 3 has electrical insulation. The sealing body 3 has a plurality of sealing members 4, a plurality of spacers 5, and a welded portion 6.

[0041] The sealing member 4 is provided on the surface of the collector 24 so as to surround the positive electrode active material layer 25 and the negative electrode active material layer 26 when viewed from the stacking direction (direction perpendicular to the first main surface 24a) D. The spacers 5 are respectively provided between the bipolar electrodes 21 adjacent to each other in the stacking direction D, between the bipolar electrode 21 and the positive terminal electrode 22, and between the bipolar electrode 21 and the negative terminal electrode 23. The spacer 5 is, for example, in the shape of a rectangular frame when viewed from the stacking direction D. The welded portion 6 is, for example, in the shape of a rectangular cylinder. The welded portion 6 reaches both ends of the stacked body 2 in the stacking direction D. The welded portion 6 is integrated by welding the outer edge portions of each sealing member 4 and each spacer 5.

[0042] Below, refer to Figure 2 , focusing on one electrode (for example, the bipolar electrode 21) for explanation. Figure 2 As shown, the current collector 24 includes a first metal foil 241, a second metal foil 242, and an adhesive layer 243. One surface of the first metal foil 241 is a first main surface 24a. That is, a positive electrode active material layer 25 is provided on one surface of the first metal foil 241, which is the first main surface 24a of the current collector 24. The first metal foil 241 is, for example, rectangular in shape when viewed from the stacking direction D. The first metal foil 241 is, for example, an aluminum foil. The first metal foil 241 may also be, for example, a nickel foil, a titanium foil, or a stainless steel foil. The first metal foil 241 may also be an alloy foil or a clad foil of the above metals.

[0043] The second metal foil 242 is arranged on the side opposite to the positive electrode active material layer 25 relative to the first metal foil 241. One surface of the second metal foil 242 is the second main surface 24b. That is, the negative electrode active material layer 26 is arranged on one surface of the second metal foil 242 which is the second main surface 24b of the collector 24. The second metal foil 242 is, for example, rectangular in shape when viewed from the stacking direction D. When viewed from the stacking direction D, the side (outer edge) 242c of the second metal foil 242 is roughly consistent with the side (outer edge) 241c of the first metal foil 241. In the present embodiment, the second metal foil 242 is, for example, a copper foil. The second metal foil 242 may also be, for example, a nickel foil, a titanium foil, or a stainless steel foil. The second metal foil 242 may also be an alloy foil or a cladding foil of the above-mentioned metals.

[0044] The adhesive layer 243 is provided between the first metal foil 241 and the second metal foil 242. The adhesive layer 243 is, for example, rectangular in shape when viewed from the stacking direction D. When viewed from the stacking direction D, the side surface (outer edge) 243c of the adhesive layer 243 is substantially consistent with each of the side surface 241c of the first metal foil 241 and the side surface 242c of the second metal foil 242. The side surface (outer edge) 24c of the collector 24 is composed of the side surface 241c, the side surface 242c, and the side surface 243c.

[0045] The adhesive layer 243 bonds the first metal foil 241 and the second metal foil 242. The adhesive layer 243 is bonded to the first metal foil 241 and the second metal foil 242, respectively. The adhesive layer 243 has conductivity. The adhesive layer 243, for example, includes a conductive resin material. As the conductive resin material, for example, a conductive polymer material or a resin in which a conductive filler is added to a non-conductive polymer material can be cited.

[0046] In the present embodiment, the adhesive layer 243 includes an adhesive component and a conductive component. The adhesive component acts as an adhesive for bonding the first metal foil 241 and the second metal foil 242. The adhesive component is, for example, a thermosetting resin. The adhesive component includes, for example, a resin and a curing agent mixed in the resin. The resin of the adhesive component is, for example, an olefin resin. Specifically, the resin of the adhesive component is, for example, polypropylene or polyethylene. The curing agent of the adhesive component is, for example, an isocyanate curing agent or an epoxy curing agent. When two metal foils are bonded together using an adhesive layer using an olefin resin as an adhesive component, an epoxy curing agent with less gas generation caused by the curing reaction of the adhesive component can be appropriately used. The conductive component electrically connects the first metal foil 241 and the second metal foil 242. The conductive component is, for example, conductive particles dispersed in the adhesive component. The conductive particles are, for example, graphite particles or metal particles. Furthermore, as the conductive particles, for example, spherical particles in which a metal film is formed on the surface of core particles of resin, ceramic, or the like can be used.

[0047] The sealing member 4 includes a first sealing portion 41, a third sealing portion 42, and a second sealing portion 43. The first sealing portion 41 is provided on the first main surface 24a. The first sealing portion 41 is, for example, in a rectangular frame shape when viewed from the stacking direction D. The first sealing portion 41 surrounds the positive electrode active material layer 25 and the negative electrode active material layer 26 when viewed from the stacking direction D. The first sealing portion 41 is provided in an uncoated area of ​​the first main surface 24a of the current collector 24. The outer edge 41c of the first sealing portion 41 is substantially consistent with the side surface 24c of the current collector 24 when viewed from the stacking direction D. The inner edge 41d of the first sealing portion 41 is separated from the positive electrode active material layer 25. When viewed from the stacking direction D, the first main surface 24a of the current collector 24 is exposed to the internal space S between the positive electrode active material layer 25 and the inner edge 41d of the first sealing portion 41. The first sealing portion 41 is welded to the first main surface 24 a .

[0048] The third sealing portion 42 is provided on the second main surface 24b. When viewed from the stacking direction D, the third sealing portion 42 is, for example, in a rectangular frame shape. When viewed from the stacking direction D, the third sealing portion 42 surrounds the positive electrode active material layer 25 and the negative electrode active material layer 26. The third sealing portion 42 is provided in an uncoated area of ​​the second main surface 24b of the current collector 24. When viewed from the stacking direction D, the outer edge 42c of the third sealing portion 42 is substantially consistent with the side surface 24c of the current collector 24. The inner edge 42d of the third sealing portion 42 is separated from the negative electrode active material layer 26. When viewed from the stacking direction D, the second main surface 24b of the current collector 24 is exposed to the internal space S between the negative electrode active material layer 26 and the third sealing portion 42. When viewed from the stacking direction D, the inner edge 42d of the third sealing portion 42 is substantially consistent with the inner edge 41d of the first sealing portion 41. The thickness of the third sealing portion 42 is substantially the same as the thickness of the first sealing portion 41. The third sealing portion 42 is welded to the second main surface 24b.

[0049] The second sealing portion 43 is provided on the side surface 24c of the current collector 24. The second sealing portion 43 is located outside the side surface 24c of the current collector 24, the outer edge 41c of the first sealing portion 41, and the outer edge 42c of the third sealing portion 42. The second sealing portion 43 is connected to each of the first sealing portion 41 and the third sealing portion 42. The second sealing portion 43 covers the side surface 24c of the current collector 24. The second sealing portion 43 covers each of the side surface 241c of the first metal foil 241, the side surface 242c of the second metal foil 242, and the side surface 243c of the adhesive layer 243.

[0050] The second sealing portion 43 may also be welded to the side surface 24c of the current collector 24. For example, the second sealing portion 43 may also be welded to each of the side surface 241c of the first metal foil 241, the side surface 242c of the second metal foil 242, and the side surface 243c of the adhesive layer 243. The second sealing portion 43 seals the side surface 24c of the current collector 24. The first sealing portion 41, the third sealing portion 42, and the second sealing portion 43 are each a partial region of the sealing member 4 formed integrally with the same material.

[0051] The spacer 5 is provided between the sealing members 4 adjacent to each other in the stacking direction D. The spacer 5 is, for example, in a rectangular frame shape. When viewed from the stacking direction D, the inner edge 5d of the rectangular frame-shaped spacer 5 is farther from the positive electrode active material layer 25 or the negative electrode active material layer 26 than each of the inner edge 41d of the rectangular frame-shaped first sealing portion 41 and the inner edge 42d of the rectangular frame-shaped third sealing portion 42. In the present embodiment, when viewed from the stacking direction D, the inner edge 41d of the first sealing portion 41 is located between the positive electrode active material layer 25 and the inner edge 5d of the spacer 5, and the inner edge 42d of the third sealing portion 42 is located between the negative electrode active material layer 26 and the inner edge 5d of the spacer 5. The spacer 5 is a member independent of the sealing member 4. Alternatively, when viewed in the stacking direction D, the inner edge 5 d of the separator 5 may be closer to the positive electrode active material layer 25 or the negative electrode active material layer 26 than the inner edge 41 d of the first sealing portion 41 and the inner edge 42 d of the third sealing portion 42 .

[0052] The spacer 5 is sandwiched by a pair of sealing members 4 adjacent to each other in the stacking direction D. The spacer 5 is in contact with the sealing member 4. The spacer 5 forms an internal space S for accommodating an electrolyte together with a pair of bipolar electrodes 21 adjacent to each other in the stacking direction D and a pair of sealing members 4 adjacent to each other in the stacking direction D. In addition, a liquid injection port for injecting an electrolyte into the internal space S is formed in the spacer 5.

[0053] The thickness of the spacer 5 in the stacking direction D may be greater than the thickness of each of the first sealing portion 41 and the third sealing portion 42. The thickness of the spacer 5 is, for example, twice or more the thickness of the first sealing portion 41 or the thickness of the third sealing portion 42. That is, the thickness of the spacer 5 may be smaller than the sum of the thickness of the first metal foil 241, the thickness of the second metal foil 242, the thickness of the adhesive layer 243, the thickness of the first sealing portion 41, and the thickness of the third sealing portion 42.

[0054] The separator 5 is welded to the sealing member 4 at the outer side (welding portion 6) of the side surface 24c of the current collector 24. Specifically, the outer edge portions of each sealing member 4 and each separator 5 are melted and then solidified again to form the welding portion 6. That is, the welding portion 6 is formed by welding the outer edge portions of the sealing member 4 and the separator 5 to each other. That is, in the welding portion 6, the region of the separator 5 with a predetermined width from the outer edge is welded to the region of the sealing member 4 with a predetermined width from the outer edge. In addition, in the welding portion 6, the separator 5 and the sealing member 4 are mutually fused.

[0055] The outer edge of the sealing member 4 is a portion of the sealing member 4 that is located on the side opposite to the collector 24 relative to the second sealing portion 43. The outer edge of the sealing member 4 is a portion before the sealing member 4 and the spacer 5 are welded. The outer edge of the spacer 5 is a portion of the spacer 5 that overlaps with the outer edge of the sealing member 4 when viewed from the stacking direction D. The outer edge of the spacer 5 is a portion before the spacer 5 and the sealing member 4 are welded. In the present embodiment, the welded portion 6 does not reach the side 24c of the collector 24. The welded portion 6 may also reach the side 24c of the collector 24. In addition, a liquid injection port connected to the liquid injection port of the spacer 5 is formed in the welded portion 6.

[0056] The sealing member 4 and the spacer 5 each contain a thermoplastic resin. The materials of the sealing member 4 and the spacer 5 are, for example, acid-modified polyethylene (acid-modified PE), acid-modified polypropylene (acid-modified PP), polyethylene, or polypropylene. The sealing member 4 and the spacer 5 each have electrolyte resistance. The materials of the sealing member 4 and the spacer 5 can be the same or different from each other. In the present embodiment, the material of the sealing member 4 is, for example, acid-modified polyethylene or acid-modified polypropylene. In the present embodiment, the material of the spacer 5 is, for example, polyethylene or polypropylene.

[0057] Acid-modified polyethylene and acid-modified polypropylene are easier to bond with metals than unacid-modified polyethylene and unacid-modified polypropylene. That is, acid-modified polyethylene and acid-modified polypropylene are resin materials with higher adhesion to metals than unacid-modified polyethylene and unacid-modified polypropylene. Since the first metal foil 241 and the second metal foil 242 of the collector 24 are each made of metal, by forming each of the first sealing portion 41, the third sealing portion 42, and the second sealing portion 43 with acid-modified polyethylene or acid-modified polypropylene, the bonding strength of the first sealing portion 41, the third sealing portion 42, and the second sealing portion 43 relative to the first metal foil 241 or the second metal foil 242 can be improved.

[0058] The heat-resistant temperature of the adhesive layer 243 (hereinafter, sometimes referred to as "heat-resistant temperature") is higher than the melting points of the first sealing portion 41, the third sealing portion 42, the second sealing portion 43, and the spacer 5. Specifically, the heat-resistant temperature of the adhesive component of the adhesive layer 243 is higher than the melting points of the first sealing portion 41, the third sealing portion 42, the second sealing portion 43, and the spacer 5. The melting points of the first sealing portion 41, the third sealing portion 42, the second sealing portion 43, and the spacer 5 are, for example, lower than 150 degrees. The heat-resistant temperature of the adhesive layer 243 is, for example, 150 degrees or more.

[0059] The heat-resistant temperature of the adhesive layer 243 is the limit temperature at which the good bonding state of the first metal foil 241 and the second metal foil 242 is maintained. Specifically, the heat-resistant temperature of the adhesive layer 243 is the limit temperature at which the bonding strength of the adhesive layer 243 to the first metal foil 241 and the second metal foil 242 becomes above a predetermined threshold. The predetermined threshold may be, for example, 1% of the bonding strength of the adhesive layer 243 at room temperature. Generally speaking, when the temperature of the adhesive layer 243 rises by heating, the bonding strength of the adhesive layer 243 tends to decrease compared to before heating. Furthermore, when the temperature of the adhesive layer 243 becomes greater than the heat-resistant temperature, the bonding strength of the adhesive layer 243 decreases to a value lower than the above-defined threshold. When the bonding strength of the adhesive layer 243 is lower than the above-defined threshold, the good bonding state of the first metal foil 241 and the second metal foil 242 is not maintained, and as a result, the collector 24 may be damaged. In the present embodiment, since the heat-resistant temperature of the adhesive layer 243 is higher than the melting points of the first sealing portion 41, the third sealing portion 42, the second sealing portion 43, and the spacer 5, the current collector 24 is not easily damaged even if the temperature of the adhesive layer 243 reaches the melting point of the first sealing portion 41, the third sealing portion 42, the second sealing portion 43, or the spacer 5 during the welding. Damage to the current collector 24 includes, for example, peeling of the first metal foil 241 or the second metal foil 242, change in the relative position of the first metal foil 241 and the second metal foil 242 (positional deviation of the first metal foil 241 and the second metal foil 242), or deformation of the first metal foil 241 or the second metal foil 242 (for example, wrinkles, etc.).

[0060] In the present embodiment, the adhesive strength of the adhesive layer 243 after being heated to the heat-resistant temperature (hereinafter referred to as "high temperature strength") is 1% or more of the adhesive strength of the adhesive layer 243 at room temperature (hereinafter referred to as "room temperature strength"). If the adhesive strength of the adhesive layer 243 after being heated is 1% or more of the room temperature strength, the good bonding state of the adhesive layer 243 to the first metal foil 241 and the second metal foil 242 is maintained. That is, when the temperature of the adhesive layer 243 is below the heat-resistant temperature, the adhesive strength of the adhesive layer 243 becomes 1% or more of the room temperature strength, and the good bonding state of the first metal foil 241 and the second metal foil 242 is maintained. In the present embodiment, since the heat-resistant temperature of the adhesive layer 243 is higher than the melting points of the first sealing portion 41, the third sealing portion 42, the second sealing portion 43, and the spacer 5, respectively, during the fusion of the first sealing portion 41, the third sealing portion 42, the second sealing portion 43, or the spacer 5, even if the temperature of the adhesive layer 243 reaches the melting point of the first sealing portion 41, the third sealing portion 42, the second sealing portion 43, or the spacer 5, the adhesive strength of the adhesive layer 243 becomes 1% or more of the strength at room temperature. That is, even if the temperature of the adhesive layer 243 reaches the melting point of the first sealing portion 41, the third sealing portion 42, the second sealing portion 43, or the spacer 5, since the adhesive layer 243 maintains a good bonding state to the first metal foil 241 and the second metal foil 242, it is difficult to damage the collector 24.

[0061] The room temperature strength is measured, for example, as follows. That is, first, prepare the collector 24 (the collector 24 in which the positive electrode active material layer 25, the negative electrode active material layer 26 and the sealing member 4 are not provided). Next, at room temperature, for example, by a 180-degree peel strength test (as an example, in accordance with JIS Z 0237:2009), the peel strength when the first metal foil 241 is peeled off from the second metal foil 242 is measured as the room temperature strength. The high temperature strength is measured, for example, as follows. That is, first, prepare the collector 24 in the same manner as the measurement of the room temperature strength. Next, the collector 24 is heated to the heat resistant temperature of the bonding layer 243. Next, while maintaining the temperature of the collector 24 after being heated to the heat resistant temperature of the bonding layer 243, the peel strength when the first metal foil 241 is peeled off from the second metal foil 242 is measured as the high temperature strength in the same manner as the measurement of the room temperature strength.

[0062] Next, a method for manufacturing the power storage device 1 is described. Figure 3As shown, the bipolar electrode 21, the first sealing member 71 and the second sealing member 72 are prepared. Next, the first sealing member 71 is arranged on the first main surface 24a of the collector 24, and the second sealing member 72 is arranged on the second main surface 24b of the collector 24. The first sealing member 71 and the second sealing member 72 are each arranged in a manner protruding from the side surface 24c of the collector 24. That is, when viewed from the stacking direction D, the first sealing member 71 arranged on the first main surface 24a of the collector 24 and the second sealing member 72 arranged on the second main surface 24b of the collector 24 respectively have a portion overlapping with the collector 24 and a portion not overlapping with the collector 24. When the first sealing member 71 and the second sealing member 72 are each arranged in a manner extending along each side of the collector 24, the first sealing member 71 and the second sealing member 72 can also be temporarily fixed to the collector 24 by spot welding using ultrasound, heat, etc.

[0063] Next, if Figure 4 As shown, the first sealing member 71 and the second sealing member 72 are each heated by a pair of heaters 73. In addition, the first sealing member 71 and the second sealing member 72 are each pressurized toward the collector 24 by a pair of heaters 73. The pair of heaters 73 is, for example, an impulse sealer. The heating of the first sealing member 71 and the second sealing member 72 is performed in a state where a pair of heaters 73 sandwich the collector 24 respectively via the first sealing member 71 and the second sealing member 72. The first sealing member 71 is heated to melt. Similarly, the second sealing member 72 is heated to melt. The first sealing member 71 and the second sealing member 72 heated to melt are pressurized toward the collector 24 by a pair of heaters 73. Afterwards, when the heating of the pair of heaters 73 is stopped, the first sealing member 71 and the second sealing member 72 are cooled, and along with this, the first sealing member 71 and the second sealing member 72 will be fused with the collector 24. Thus, the portion of the first sealing member 71 overlapping the first main surface 24a is welded to the first main surface 24a, thereby forming the first sealing portion 41, and the portion of the second sealing member 72 overlapping the second main surface 24b is welded to the second main surface 24b, thereby forming the third sealing portion 42. In addition, the portion of the first sealing member 71 located outside the side surface 24c of the collector 24 and the portion of the second sealing member 72 located outside the side surface 24c of the collector 24 are melted and fused to each other, thereby forming the second sealing portion 43. That is, the sealing member 4 is formed on the bipolar electrode 21. Similarly, the sealing member 4 is also formed on the positive terminal electrode 22 and the negative terminal electrode 23.

[0064] Next, if Figure 5As shown in FIG. 1 , the bipolar electrode 21 formed with the sealing member 4, the positive terminal electrode 22 and the negative terminal electrode 23, and the separators 5 are stacked. The separators 5 are arranged between the sealing members 4. Next, as shown in FIG. Figure 6 As shown, the outer side surfaces of each sealing member 4 and each spacer 5 are melted by a heating device 8. The heating device 8 is, for example, an infrared heater. The heating device 8 irradiates infrared rays to the outer side surfaces of the sealing member 4 and the spacer 5. When the infrared rays are irradiated to the outer side surfaces of the sealing member 4 and the spacer 5, the temperature of the sealing member 4 and the spacer 5 rises. The sealing member 4 and the spacer 5 are heated until the sealing member 4 and the spacer 5 are melted. As a result, the outer edge portions of the sealing member 4 and the spacer 5 are melted. The outer edge portions of the melted sealing member 4 and the spacer 5 are solidified to form a welded portion 6. Next, an electrolyte is injected into each internal space S through the injection port. Next, the injection port is closed. Thus, the manufacturing Figure 1 The power storage device 1 is shown.

[0065] As described above, in the power storage device 1, the current collector 24 includes the adhesive layer 243 which is provided between the first metal foil 241 and the second metal foil 242 and bonds the first metal foil 241 and the second metal foil 242. In addition, the first sealing portion 41 is fused to the first main surface 24a of the current collector 24, and the second sealing portion 43 is fused to the side surface 24c of the current collector 24. Therefore, there is a case where the heat when the first sealing portion 41 and the second sealing portion 43 are fused to the current collector 24 is transferred to the adhesive layer 243. In particular, since the second sealing portion 43 is in contact with the side surface 243c of the adhesive layer 243, the heat when the second sealing portion 43 is fused to the current collector 24 is easily transferred to the adhesive layer 243. Here, the heat resistance temperature of the adhesive layer 243 of the current collector 24 is higher than the melting point of each of the first sealing portion 41 and the second sealing portion 43. Therefore, even if the heat when the first sealing portion 41 and the second sealing portion 43 are welded to the current collector 24 is transferred to the adhesive layer 243, the decrease in the bonding strength of the adhesive layer 243 is suppressed. Thus, damage to the current collector 24 caused by the decrease in the bonding strength of the adhesive layer 243 is suppressed. Therefore, according to the power storage device 1, damage to the bipolar electrode 21 can be suppressed.

[0066] The power storage device 1 includes a spacer 5. The spacer 5 is provided between the bipolar electrodes 21 adjacent to each other in the stacking direction D and is fused to the sealing member 4. The heat-resistant temperature of the adhesive layer 243 is higher than the melting point of the spacer 5. Thus, even if the heat when the spacer 5 is fused to the sealing member 4 is transferred to the adhesive layer 243, the decrease in the adhesive strength of the adhesive layer 243 is suppressed. Therefore, the damage to the collector 24 caused by the decrease in the adhesive strength of the adhesive layer 243 is suppressed, and as a result, the damage to the bipolar electrode 21 is suppressed.

[0067] The sealing member 4 includes a third sealing portion 42 welded to the second main surface 24b of the current collector 24. The heat-resistant temperature of the adhesive layer 243 is higher than the melting point of the third sealing portion 42. Therefore, even if the heat when the third sealing portion 42 is welded to the current collector 24 is transferred to the adhesive layer 243, the reduction in the bonding strength of the adhesive layer 243 is suppressed. Therefore, the damage to the current collector 24 caused by the reduction in the bonding strength of the adhesive layer 243 is suppressed, and as a result, the damage to the bipolar electrode 21 is suppressed.

[0068] The adhesive layer 243 contains a thermosetting resin. Thus, by using a thermosetting resin as a component of the adhesive layer 243, the heat-resistant temperature of the adhesive layer 243 can be increased. In addition, by using a thermosetting resin as a component of the adhesive layer 243, the deformation of the adhesive layer 243 caused by heating can be suppressed, and the deformation of the collector 24 can be suppressed. The sealing member 4 contains a thermoplastic resin. Thus, by using a thermoplastic resin as a component of the sealing member 4, when the sealing member 4 is fused to the collector 24, the close adhesion of the sealing member 4 to the collector 24 can be improved, and the sealing performance of the sealing member 4 can be improved.

[0069] As mentioned above, although one embodiment of the present disclosure has been described, the present disclosure is not limited to the above embodiment.

[0070] like Figure 7As shown, the current collector 24 may also include a carbon coating 244 disposed between the first metal foil 241 and the adhesive layer 243, and between the second metal foil 242 and the adhesive layer 243. The carbon coating 244 has conductivity. The carbon coating 244 includes, for example, a binder and graphite. The carbon coating 244 may also be disposed between the first metal foil 241 and the adhesive layer 243 and between the second metal foil 242 and the adhesive layer 243. That is, the carbon coating 244 only needs to be disposed between the first metal foil 241 and the adhesive layer 243 and between the second metal foil 242 and the adhesive layer 243. According to such a configuration, for example, compared with the case where the first metal foil 241 or the second metal foil 242 is directly bonded to the bonding layer 243, since the binder resin contained in the carbon coating 244 is firmly bonded through the bonding layer 243, the bonding strength between the first metal foil 241 and the bonding layer 243 or the bonding strength between the second metal foil 242 and the bonding layer 243 can be more reliably ensured. In addition, for example, even if a pin hole is formed in the first metal foil 241, the second metal foil 242 or the bonding layer 243, the liquid interface between the adjacent internal spaces S can be suppressed by the carbon coating 244. In addition, the carbon coating 244 can also be provided on the first main surface 24a or the second main surface 24b of the collector 24. In this case, the carbon coating 244 is interposed between the first main surface 24a and the first sealing portion 41 or between the second main surface 24b and the third sealing portion 42.

[0071] In the embodiment, the description is made focusing on one bipolar electrode 21, but the description may also focus on the positive terminal electrode 22 or the negative terminal electrode 23. When focusing on the negative terminal electrode 23, the second main surface 24b of the collector 24 of the negative terminal electrode 23 is equivalent to the first main surface, the first main surface 24a of the collector 24 of the negative terminal electrode 23 is equivalent to the second main surface, the layer including the second main surface 24b in the collector 24 is equivalent to the first metal foil, and the layer including the first main surface 24a is equivalent to the second metal foil.

[0072] In the embodiment, an example is shown in which the adhesive layer 243 includes a thermosetting resin, but the adhesive layer 243 may include a thermoplastic resin. In this case, the heat-resistant temperature of the adhesive layer 243 may be the melting point of the adhesive layer 243 .

[0073] In the embodiment, the example in which the peripheral edge of the spacer 27 is located between the sealing member 4 and the spacer 5 is shown, but the peripheral edge of the spacer 27 may not reach the spacer 5. The peripheral edge of the spacer 27 may be welded to the sealing member 4.

[0074] The gist of the present disclosure is as shown in the following [1] to [5].

[0075] [1] A power storage device comprising: an electrode having a current collector and an active material layer disposed on a first main surface of the current collector; and a sealing member disposed on the surface of the current collector in a manner so as to surround the active material layer when viewed from a direction perpendicular to the first main surface, the current collector comprising: a first metal foil comprising the first main surface; a second metal foil disposed on a side opposite to the active material layer relative to the first metal foil; and an adhesive layer disposed between the first metal foil and the second metal foil and bonding the first metal foil to the second metal foil, the sealing member comprising a first sealing portion welded to the first main surface and a second sealing portion welded to a side surface of the current collector including a side surface of the adhesive layer, the heat-resistant temperature of the adhesive layer being greater than the melting points of the first sealing portion and the second sealing portion.

[0076] [2] The power storage device according to [1] further comprises a spacer, wherein the electrode is each of a plurality of electrodes stacked in a stacking direction, the spacer is arranged between the electrodes adjacent to each other in the stacking direction and is fused to the sealing member, and the heat-resistant temperature of the adhesive layer is greater than the melting point of the spacer.

[0077] [3] The power storage device according to [1] or [2], wherein the sealing member further includes a third sealing portion welded to the second main surface of the collector on the opposite side of the first main surface, and the heat resistance temperature of the adhesive layer is greater than the melting point of the third sealing portion.

[0078] [4] The power storage device according to any one of [1] to [3], wherein the adhesive layer includes a thermosetting resin, and the sealing member includes a thermoplastic resin.

[0079] [5] The power storage device according to any one of [1] to [4], wherein the current collector further includes a carbon coating layer provided at least one of between the first metal foil and the adhesive layer and between the second metal foil and the adhesive layer.

[0080] Description of Reference Numerals

[0081] 1…electricity storage device, 4…sealing member, 5…spacer, 21…bipolar electrode, 22…positive terminal electrode, 23…negative terminal electrode, 24…current collector, 24a…first main surface, 24b…second main surface, 25…positive electrode active material layer, 26…negative electrode active material layer, 41…first sealing portion, 42…third sealing portion, 43…second sealing portion, 241…first metal foil, 242…second metal foil, 243…adhesive layer, 244…carbon coating layer.

Claims

1. A power storage device, characterized in that: have: An electrode comprising a current collector and an active material layer provided on a first main surface of the current collector; and a sealing member provided on the surface of the current collector so as to surround the active material layer when viewed from a direction perpendicular to the first main surface, The current collector includes: a first metal foil including the first main surface; a second metal foil provided on the side opposite to the active material layer relative to the first metal foil; and an adhesive layer provided between the first metal foil and the second metal foil and bonding the first metal foil to the second metal foil. The sealing member includes a first sealing portion welded to the first main surface and a second sealing portion welded to a side surface of the current collector including a side surface of the adhesive layer. The heat-resistant temperature of the adhesive layer is higher than the melting points of the first sealing portion and the second sealing portion.

2. The power storage device according to claim 1, wherein Also provided with a spacer, The electrode is each electrode of a plurality of electrodes stacked in a stacking direction, The spacer is provided between the electrodes adjacent to each other in the stacking direction and is welded to the sealing member. The heat-resistant temperature of the adhesive layer is higher than the melting point of the spacer.

3. The power storage device according to claim 1 or 2, wherein: The sealing member further includes a third sealing portion welded to a second main surface of the current collector on the opposite side to the first main surface. The heat-resistant temperature of the adhesive layer is higher than the melting point of the third sealing portion.

4. The power storage device according to claim 1 or 2, wherein: The adhesive layer comprises a thermosetting resin, The sealing member includes a thermoplastic resin.

5. The power storage device according to claim 1 or 2, wherein: The current collector further includes a carbon coating layer provided at least one of between the first metal foil and the adhesive layer and between the second metal foil and the adhesive layer.

Images