Power storage device

Abstract

This power storage device comprises: an electrode having a current collector and a positive electrode active material layer provided to a surface of the current collector; and a sealing member provided to the surface of the current collector so as to surround the positive electrode active material layer when viewed from the lamination direction. The current collector includes: a first metal foil including a surface; a second metal foil provided on a side opposite to the positive electrode active material layer relative to the first metal foil; and a bonding layer that is provided between the first metal foil and the second metal foil and that bonds the first metal foil and the second metal foil. The sealing member includes: a sealing portion welded to the surface; and a sealing portion welded to a side surface, of the current collector, including a side surface of the bonding layer. The heat resistant temperature of the bonding layer is greater than the melting point of each of the sealing portions.

Description

[Technical Field]

[0001] The present disclosure relates to an electricity storage device. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-317468 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described energy storage device, sealing members for sealing the side surfaces of the electrodes may be welded to the surfaces of the electrodes. In such cases, heat generated when the sealing members are welded to the electrodes is transferred to the adhesive layer, reducing the adhesive strength of the adhesive layer and potentially damaging the electrodes.

[0005] An object of the present invention is to provide an electricity storage device that can suppress damage to electrodes. [Means for solving the problem]

[0006] The electricity storage device of the present disclosure includes a current collector, an electrode having 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 in a direction perpendicular to the first main surface, wherein the current collector includes a first metal foil including the first main surface, a second metal foil provided on the opposite side of the first metal foil from the active material layer, and an adhesive layer provided between the first metal foil and the second metal foil and adhering the first metal foil to the second metal foil, and the sealing member includes a first sealing portion welded to the first main surface and a second sealing portion welded to a side of the current collector including the side of the adhesive layer, and the heat resistance temperature of the adhesive layer is higher than the melting points of the first sealing portion and the second sealing portion.

[0007] In this electricity storage device, the current collector includes an adhesive layer disposed between the first metal foil and the second metal foil and bonding the first metal foil and the second metal foil together. A first seal portion is welded to a first main surface of the first metal foil, and a second seal portion is welded to a side surface of the current collector. The heat resistance temperature of the adhesive layer of the current collector is higher than the melting points of the first seal portion and the second seal portion. Therefore, even if heat is transferred to the adhesive layer when the first seal portion and the second seal portion are welded to the current collector, a decrease in adhesive strength due to the adhesive layer is suppressed. This suppresses damage to the current collector due to a decrease in adhesive strength due to the adhesive layer. Therefore, this electricity storage device can suppress damage to the electrodes.

[0008] The energy storage device further includes a spacer, and the electrode is each of a plurality of electrodes stacked in the stacking direction. The spacer is provided between adjacent electrodes in the stacking direction and welded to the sealing member. The heat resistance temperature of the adhesive layer may be higher than the melting point of the spacer. This prevents a decrease in adhesive strength due to the adhesive layer even if heat is transferred to the adhesive layer when the spacer is welded to the sealing member. Therefore, damage to the current collector due to a decrease in adhesive strength due to the adhesive layer is prevented, and as a result, damage to the electrode is prevented.

[0009] The sealing member may further include a third sealing portion welded to a second main surface of the current collector opposite the first main surface, and the heat resistance temperature of the adhesive layer may be higher than the melting point of the third sealing portion. This prevents a decrease in adhesive strength due to the adhesive layer even if heat is transferred to the adhesive layer when the third sealing portion is welded to the current collector. Therefore, damage to the current collector due to a decrease in adhesive strength due to the adhesive layer is prevented, and as a result, damage to the electrode is prevented.

[0010] The adhesive layer may contain a thermosetting resin, and the sealing member may contain a thermoplastic resin. 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.

[0011] The current collector may further include a carbon coating layer provided between the first metal foil and the adhesive layer or between the second metal foil and the adhesive layer, thereby more reliably ensuring the adhesive strength between the first metal foil and the adhesive layer or the adhesive strength between the second metal foil and the adhesive layer. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide an electricity storage device that can suppress damage to electrodes. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view of a power storage device according to an embodiment. [Figure 2] FIG. 2 is a partially enlarged view of FIG. [Figure 3] FIG. 3 is a diagram showing steps of a method for manufacturing the electricity storage device shown in FIG. [Figure 4] FIG. 4 is a diagram showing steps of a method for manufacturing the electricity storage device shown in FIG. [Figure 5] FIG. 5 is a diagram showing steps of a method for manufacturing the electricity storage device shown in FIG. [Figure 6]FIG. 6 is a diagram showing steps of a method for manufacturing the electricity storage device shown in FIG. [Figure 7] FIG. 7 is a partially enlarged view of a power storage device according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0015] 1 is a power storage module used in batteries for, for example, forklifts, hybrid vehicles, electric vehicles, etc. The power storage device 1 is a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. In this embodiment, the power storage device 1 is a lithium-ion secondary battery.

[0016] As shown in Fig. 1, the energy storage device 1 includes a laminate 2 and a sealing body 3. The laminate 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 laminate 2 is formed by stacking the 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 electrode active material layer 25, and a negative electrode active material layer 26.

[0017] The current collector 24 has, for example, a rectangular shape when viewed from the stacking direction D. The current collector 24 includes a first main surface 24a, which is one surface, and a second main surface 24b, which is the other surface opposite to the first main surface 24a. That is, the current collector 24 has the first main surface 24a and the second main surface 24b, which face 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 current collector 24. The positive electrode active material layer 25 has, for example, a rectangular shape when viewed from the stacking direction D. The first main surface 24a of the current collector 24 includes an uncoated region where the positive electrode active material layer 25 is not provided. The uncoated region surrounds the positive electrode active material layer 25 when viewed from the stacking direction D.

[0018] The negative electrode active material layer 26 is provided on the second main surface 24b of the current collector 24. When viewed from the stacking direction D, the negative electrode active material layer 26 has, for example, a rectangular shape. 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. When viewed from the stacking direction D, the uncoated region surrounds the negative electrode active material layer 26. The multiple bipolar electrodes 21 are stacked such that the positive electrode active material layer 25 of one bipolar electrode 21 and the negative electrode active material layer 26 of the other bipolar electrode 21, which are adjacent to each other in the stacking direction D, face each other. That is, the multiple bipolar electrodes 21 are stacked such that the first main surface 24a of the current collector 24 of one bipolar electrode 21 faces the second main surface 24b of the current collector 24 of the other bipolar electrode 21, which are adjacent to each other in the stacking direction D.

[0019] The positive terminal electrode 22 is stacked at one end of the plurality of bipolar electrodes 21 in the stacking direction D. The positive terminal electrode 22 has 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 differs from the bipolar electrode 21 in that it does not have a negative electrode active material layer 26 provided on a second main surface 24b of the current collector 24. The positive terminal electrode 22 does not have a positive electrode active material layer 25 or a negative electrode active material layer 26 provided on the second main surface 24b of the current collector 24. The second main surface 24b of the current collector 24 of the positive terminal electrode 22 serves as a positive electrode terminal surface of the energy storage device 1. The other configuration of the positive terminal electrode 22 may be the same as that of the bipolar electrode 21. The positive terminal electrode 22 is disposed so that the positive active material layer 25 of the positive terminal electrode 22 faces the negative active material layer 26 of the bipolar electrode 21. That is, the positive terminal electrode 22 is stacked so that the first main surface 24a of the current collector 24 of the positive terminal electrode 22 faces the second main surface 24b of the current collector 24 of the bipolar electrode 21 adjacent to the positive terminal electrode 22 in the stacking direction D.

[0020] The negative electrode terminal electrode 23 is disposed on the opposite side of the plurality of bipolar electrodes 21 from the positive electrode terminal electrode 22. That is, the positive electrode terminal electrode 22 is disposed at one end of the plurality of bipolar electrodes 21 in the stacking direction D, and the negative electrode terminal electrode 23 is disposed at the other end of the plurality of bipolar electrodes 21 in the stacking direction D. The negative electrode 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 electrode terminal electrode 23 differs 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. Note that the first main surface 24a of the current collector 24 of the negative electrode terminal electrode 23 does not include the positive electrode active material layer 25 or the negative electrode active material layer 26. The first main surface 24a of the current collector 24 of the negative electrode terminal electrode 23 serves as the negative electrode terminal surface of the energy storage device 1. Other configurations of the negative terminal electrode 23 may be the same as those of the bipolar electrode 21. The negative terminal electrode 23 is disposed so that the negative electrode active material layer 26 of the negative terminal electrode 23 faces the positive electrode 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 current collector 24 of the negative terminal electrode 23 faces the first main surface 24a of the current collector 24 of the bipolar electrode 21 adjacent to the negative terminal electrode 23 in the stacking direction D. An internal space S containing an electrolyte is formed between each of 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.

[0021] The laminate 2 includes a plurality of separators 27. The separators 27 are respectively disposed between 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. The separators 27 are located between the opposing positive electrode active material layers 25 and negative electrode active material layers 26. The separators 27 are, for example, sheet-shaped. When viewed from the stacking direction D, the separators 27 are, for example, rectangular. When viewed from the stacking direction D, the outer edges of the separators 27 are located outside the outer edges of the positive electrode active material layers 25 and the negative electrode active material layers 26. The peripheral edge of the separators 27 is located between a sealing member 4 and a spacer 5, which will be described later. The separators 27 are a member that allows charge carriers such as lithium ions to pass through. The separators 27 isolate adjacent bipolar electrodes 21 from each other in the stacking direction D, and isolate the bipolar electrodes 21 from the positive terminal electrode 22 and the negative terminal electrode 23 from each other in the stacking direction D. This prevents electrical short circuits due to contact between adjacent bipolar electrodes 21 in the stacking direction D, between the bipolar electrodes 21 from each other, between the bipolar electrodes 21 from the positive terminal electrode 22, and between the bipolar electrodes 21 from the negative terminal electrode 23.

[0022] The current collector 24 is a chemically inactive electrical conductor that continues to pass current through the positive electrode active material layer 25 and the negative electrode active material layer 26 during discharge or charge of the energy storage device 1. The current collector 24 may be, for example, plate-shaped, foil-shaped, sheet-shaped, film-shaped, mesh-shaped, or the like. When the current collector 24 is foil-shaped, the thickness of the current collector 24 may be in the range of 1 μm to 100 μm. A coating layer may be formed on the surface of the current collector 24 by a known method such as plating or spray coating. Note that, for example, some of the current collectors 24 of each bipolar electrode 21, positive terminal electrode 22, and negative terminal electrode 23 may have a thickness of 100 μm or more. In this case, the structural stability of the laminate 2 is enhanced.

[0023] The positive electrode active material layer 25 includes a positive electrode active material capable of absorbing and releasing charge carriers such as lithium ions. Examples of the positive electrode active material include composite oxides, metallic lithium, and sulfur. The composite oxides include at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of the composite oxides include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, and LiNiMnCoO2.

[0024] The negative electrode active material layer 26 includes a negative electrode active material capable of absorbing and releasing charge carriers such as lithium ions. Examples of the negative electrode active material include carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, metal compounds, elements or compounds thereof that can be alloyed with lithium, and boron-doped carbon. Examples of elements that can be alloyed with lithium include silicon and tin.

[0025] In addition to the active material, each of the positive electrode active material layer 25 and the negative electrode active material layer 26 may contain a binder and a conductive additive. The binder serves to connect the active material or conductive additive to each other and maintain the conductive network within the electrode. Examples of binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide resins such as polyimide and polyamideimide; alkoxysilyl group-containing resins; acrylic resins such as polyacrylic acid and polymethacrylic acid; styrene-butadiene rubber; carboxymethyl cellulose; alginates such as sodium alginate and ammonium alginate; water-soluble cellulose ester crosslinked bodies; and starch-acrylic acid graft polymers. These binders may be used alone or in combination. The conductive additive is, for example, a conductive material such as acetylene black, carbon black, or graphite, and can enhance electrical conductivity. Examples of viscosity-adjusting solvents include N-methyl-2-pyrrolidone.

[0026] Formation of the positive electrode active material layer 25 on the first principal surface 24a and the negative electrode active material layer 26 on the second principal surface 24b can be achieved by known methods such as roll coating, die coating, dip coating, doctor blade coating, spray coating, and curtain coating. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive additive are mixed to produce a slurry-like active material layer-forming composition. The active material layer-forming composition is then applied to the first principal surface 24a or the second principal surface 24b, and the applied active material layer-forming composition is then dried to obtain the positive electrode active material layer 25 or the negative electrode active material layer 26. Examples of solvents include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. To increase electrode density, the dried positive electrode active material layer 25 or the negative electrode active material layer 26 may be further compressed.

[0027] The separator 27 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains electrolyte. The separator 27 may be made of, for example, polypropylene, polyethylene, polyolefin, polyester, or the like. The separator 27 may have a single-layer structure or a multi-layer structure. When the separator 27 has a multi-layer structure, the separator 27 may include, for example, a substrate layer and a pair of adhesive layers, and may be 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 may also include a ceramic layer that serves as a heat-resistant layer. The separator 27 may also be reinforced with a vinylidene fluoride resin compound.

[0028] Examples of the electrolyte impregnated into the separator 27 include a liquid electrolyte (electrolytic solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, and a polymer gel electrolyte containing an electrolyte held in a polymer matrix. When the separator 13 is impregnated with an electrolyte, known lithium salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2 can be used as the electrolyte salt. Also, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers can be used as the non-aqueous solvent. Two or more of these known solvent materials may be used in combination. In this embodiment, the electrolyte impregnated into the separator 27 is an electrolytic solution.

[0029] The sealing body 3 is a member that seals the internal space S. The sealing body 3 is provided on the side surface of the stack 2. The sealing body 3 seals the side surface of the stack 2. The sealing body 3 has, for example, a rectangular cylindrical shape. The sealing body 3 has electrical insulation properties. The sealing body 3 has a plurality of sealing members 4, a plurality of spacers 5, and a welded portion 6.

[0030] The sealing member 4 is provided on the surface of the current 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 D (a direction perpendicular to the first main surface 24a). Spacers 5 are provided between adjacent bipolar electrodes 21 in the stacking direction D, between the bipolar electrodes 21 and the positive electrode terminal electrode 22, and between the bipolar electrode 21 and the negative electrode terminal electrode 23. When viewed from the stacking direction D, the spacers 5 have, for example, a rectangular frame shape. The welded portion 6 has, for example, a rectangular cylindrical shape. The welded portion 6 extends to both ends of the stack 2 in the stacking direction D. The welded portion 6 is integrated by welding the outer edges of each sealing member 4 and each spacer 5.

[0031] The following description will be focused on one electrode (e.g., bipolar electrode 21) with reference to FIG. 2. As shown in FIG. 2, 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 the 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 has, for example, a rectangular 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 be, for example, a nickel foil, a titanium foil, a stainless steel foil, or the like. The first metal foil 241 may also be an alloy foil or clad foil of the above metals.

[0032] The second metal foil 242 is provided on the opposite side of the first metal foil 241 from the positive electrode active material layer 25. One surface of the second metal foil 242 is the second main surface 24b. That is, the negative electrode active material layer 26 is provided on one surface of the second metal foil 242, which is the second main surface 24b of the current collector 24. The second metal foil 242 has, for example, a rectangular shape when viewed from the stacking direction D. When viewed from the stacking direction D, the side surface (outer edge) 242c of the second metal foil 242 approximately coincides with the side surface (outer edge) 241c of the first metal foil 241. In this embodiment, the second metal foil 242 is, for example, a copper foil. The second metal foil 242 may be, for example, a nickel foil, a titanium foil, a stainless steel foil, or the like. The second metal foil 242 may be an alloy foil or a clad foil of the above metals.

[0033] The adhesive layer 243 is provided between the first metal foil 241 and the second metal foil 242. When viewed from the stacking direction D, the adhesive layer 243 has, for example, a rectangular shape. When viewed from the stacking direction D, a side surface (outer edge) 243c of the adhesive layer 243 approximately coincides with a side surface 241c of the first metal foil 241 and a side surface 242c of the second metal foil 242. The side surface (outer edge) 24c of the current collector 24 is made up of the side surface 241c, the side surface 242c, and the side surface 243c.

[0034] The adhesive layer 243 bonds the first metal foil 241 and the second metal foil 242 together. The adhesive layer 243 is bonded to each of the first metal foil 241 and the second metal foil 242. The adhesive layer 243 is conductive. The adhesive layer 243 contains, for example, a conductive resin material. Examples of the conductive resin material include a conductive polymer material, or a resin in which a conductive filler is added to a non-conductive polymer material.

[0035] In this embodiment, the adhesive layer 243 contains an adhesive component and a conductive component. The adhesive component functions as an adhesive that bonds 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 with the resin. The resin of the adhesive component is, for example, an olefin-based 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-based curing agent or an epoxy-based curing agent. When two metal foils are bonded with an adhesive layer containing an olefin-based resin as the adhesive component, an epoxy-based curing agent is preferably used, as it generates little gas during the curing reaction of the adhesive component. 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 such as resin or ceramic can also be used.

[0036] 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. When viewed from the stacking direction D, the first sealing portion 41 has, for example, 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. The first sealing portion 41 is provided in an uncoated region of the first main surface 24a of the current collector 24. When viewed from the stacking direction D, an outer edge 41c of the first sealing portion 41 approximately coincides with the side surface 24c of the current collector 24. An 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 seal portion 41. The first seal portion 41 is welded to the first main surface 24a.

[0037] 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 has, for example, 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 region on 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 substantially coincides with the side surface 24c of the current collector 24. When viewed from the stacking direction D, the inner edge 42d of the third sealing portion 42 is spaced apart 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 seal portion 42 substantially coincides with the inner edge 41d of the first seal portion 41. The thickness of the third seal portion 42 is substantially the same as the thickness of the first seal portion 41. The third seal portion 42 is welded to the second main surface 24b.

[0038] The second seal portion 43 is provided on the side surface 24c of the current collector 24. The second seal portion 43 is located outside the side surface 24c of the current collector 24, the outer edge 41c of the first seal portion 41, and the outer edge 42c of the third seal portion 42. The second seal portion 43 is connected to each of the first seal portion 41 and the third seal portion 42. The second seal portion 43 covers the side surface 24c of the current collector 24. The second seal 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.

[0039] The second seal portion 43 may be welded to the side surface 24c of the current collector 24. For example, the second seal portion 43 may 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 seal portion 43 seals the side surface 24c of the current collector 24. The first seal portion 41, the third seal portion 42, and the second seal portion 43 are each a partial region of the seal member 4 that is integrally formed from the same material.

[0040] The spacer 5 is provided between adjacent sealing members 4 in the stacking direction D. The spacer 5 has, for example, a rectangular frame shape. When viewed from the stacking direction D, the inner edge 5d of the rectangular frame-shaped spacer 5 may be farther from the positive electrode active material layer 25 or the negative electrode active material layer 26 than 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 separate member from the sealing member 4. When viewed from the stacking direction D, the inner edge 5d of the spacer 5 may be closer to the positive electrode active material layer 25 or the negative electrode active material layer 26 than the inner edge 41d of the first seal portion 41 or the inner edge 42d of the third seal portion 42, respectively.

[0041] The spacer 5 is sandwiched between a pair of sealing members 4 adjacent to each other in the stacking direction D. The spacer 5 is in contact with the sealing members 4. The spacer 5, 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, forms an internal space S for accommodating an electrolyte solution. The spacer 5 is formed with a liquid injection port for injecting the electrolyte solution into the internal space S.

[0042] The thickness of the spacer 5 in the stacking direction D may be greater than the thickness of each of the first seal portion 41 and the third seal portion 42. The thickness of the spacer 5 is, for example, at least twice the thickness of the first seal portion 41 or the thickness of the third seal portion 42. In other words, the thickness of the spacer 5 may be less 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 seal portion 41, and the thickness of the third seal portion 42.

[0043] The spacers 5 are welded to the sealing member 4 at a portion (welded portion 6) outside the side surface 24c of the current collector 24. Specifically, the outer edge portions of each of the sealing members 4 and each of the spacers 5 are melted and then solidified again, thereby forming the welded portion 6. That is, the outer edge portions of the sealing members 4 and the spacers 5 are welded to each other, thereby forming the welded portion 6. That is, in the welded portion 6, a region of a predetermined width from the outer edge of the spacer 5 is welded to a region of a predetermined width from the outer edge of the sealing member 4. Furthermore, in the welded portion 6, the spacers 5 and the sealing member 4 are compatible with each other.

[0044] The outer edge of the seal member 4 is a portion of the seal member 4 that is located on the opposite side of the second seal portion 43 from the current collector 24. The outer edge of the seal member 4 is a portion before the seal member 4 and the spacer 5 are welded together. The outer edge of the spacer 5 is a portion of the spacer 5 that overlaps with the outer edge of the seal member 4 when viewed from the stacking direction D. The outer edge of the spacer 5 is a portion before the seal member 4 and the spacer 5 are welded together. In this embodiment, the welded portion 6 does not reach the side surface 24c of the current collector 24. The welded portion 6 may reach the side surface 24c of the current collector 24. A liquid inlet that communicates with a liquid inlet of the spacer 5 is formed in the welded portion 6.

[0045] The sealing member 4 and the spacer 5 each contain a thermoplastic resin. The material of the sealing member 4 and the spacer 5 is, for example, acid-modified polyethylene (acid-modified PE), acid-modified polypropylene (acid-modified PP), polyethylene, polypropylene, or the like. The sealing member 4 and the spacer 5 each have electrolyte resistance. The materials of the sealing member 4 and the spacer 5 may be the same or different from each other. In this embodiment, the material of the sealing member 4 is, for example, acid-modified polyethylene or acid-modified polypropylene. In this embodiment, the material of the spacer 5 is, for example, polyethylene or polypropylene.

[0046] Acid-modified polyethylene and acid-modified polypropylene are more easily bonded to metals than non-acid-modified polyethylene and non-acid-modified polypropylene. That is, acid-modified polyethylene and acid-modified polypropylene are resin materials that have higher adhesion to metals than non-acid-modified polyethylene and non-acid-modified polypropylene. Because the first metal foil 241 and the second metal foil 242 of the current collector 24 are made of metal, the first seal portion 41, the third seal portion 42, and the second seal portion 43 are made of acid-modified polyethylene or acid-modified polypropylene, respectively, thereby improving the bonding strength of the first seal portion 41, the third seal portion 42, and the second seal portion 43 to the first metal foil 241 or the second metal foil 242.

[0047] The heat resistance temperature of the adhesive layer 243 (hereinafter sometimes simply referred to as "heat resistance temperature") is higher than the melting points of the first seal portion 41, the third seal portion 42, the second seal portion 43, and the spacer 5. Specifically, the heat resistance temperature of the adhesive component of the adhesive layer 243 is higher than the melting points of the first seal portion 41, the third seal portion 42, the second seal portion 43, and the spacer 5. The melting points of the first seal portion 41, the third seal portion 42, the second seal portion 43, and the spacer 5 are lower than 150°C, for example. The heat resistance temperature of the adhesive layer 243 is, for example, 150°C or higher.

[0048] The heat resistance temperature of the adhesive layer 243 is the limit temperature at which a good adhesive state between the first metal foil 241 and the second metal foil 242 is maintained. Specifically, the heat resistance temperature of the adhesive layer 243 is the limit temperature at which the adhesive strength between the first metal foil 241 and the second metal foil 242 by the adhesive layer 243 becomes equal to or greater than a predetermined threshold. The predetermined threshold may be, for example, 1% of the adhesive strength of the adhesive layer 243 at room temperature. Generally, when the temperature of the adhesive layer 243 increases due to heating, the adhesive strength of the adhesive layer 243 tends to decrease compared to before heating. When the temperature of the adhesive layer 243 exceeds the heat resistance temperature, the adhesive strength of the adhesive layer 243 decreases to a value lower than the predetermined threshold. When the adhesive strength of the adhesive layer 243 becomes lower than the predetermined threshold, the good adhesive state between the first metal foil 241 and the second metal foil 242 is not maintained, which may result in damage to the current collector 24. In the present embodiment, the heat resistance temperature of the adhesive layer 243 is higher than the melting points of the first seal portion 41, the third seal portion 42, the second seal portion 43, and the spacer 5. Therefore, even if the temperature of the adhesive layer 243 reaches the melting point of the first seal portion 41, the third seal portion 42, the second seal portion 43, or the spacer 5 when welding the first seal portion 41, the third seal portion 42, the second seal portion 43, or the spacer 5, the current collector 24 is unlikely to be damaged. Examples of damage to the current collector 24 include peeling of the first metal foil 241 or the second metal foil 242, a change in the relative position between the first metal foil 241 and the second metal foil 242 (misalignment between 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.).

[0049] In this embodiment, the adhesive strength of the adhesive layer 243 heated to its 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 heated adhesive layer 243 is 1% or more of the room-temperature strength, a good adhesive state between the first metal foil 241 and the second metal foil 242 by the adhesive layer 243 is maintained. In other words, when the temperature of the adhesive layer 243 is equal to or lower than the heat-resistant temperature, the adhesive strength of the adhesive layer 243 is 1% or more of the room-temperature strength, and a good adhesive state between the first metal foil 241 and the second metal foil 242 is maintained. In this embodiment, the heat resistance temperature of the adhesive layer 243 is higher than the melting points of the first seal portion 41, the third seal portion 42, the second seal portion 43, and the spacer 5. Therefore, even if the temperature of the adhesive layer 243 reaches the melting point of the first seal portion 41, the third seal portion 42, the second seal portion 43, or the spacer 5 when welding the first seal portion 41, the third seal portion 42, the second seal portion 43, or the spacer 5, the adhesive strength of the adhesive layer 243 is 1% or more of its strength at room temperature. In other words, even if the temperature of the adhesive layer 243 reaches the melting point of the first seal portion 41, the third seal portion 42, the second seal portion 43, or the spacer 5, the adhesive layer 243 maintains a good adhesive state between the first metal foil 241 and the second metal foil 242, and therefore the current collector 24 is less likely to be damaged.

[0050] The room-temperature strength is measured, for example, as follows. That is, first, a current collector 24 (a current collector 24 on which neither the positive electrode active material layer 25, the negative electrode active material layer 26, nor the sealing member 4 is provided) is prepared. Next, at room temperature, the peel strength when the first metal foil 241 is peeled from the second metal foil 242 is measured as the room-temperature strength, for example, by a 180-degree peel strength test (for example, in accordance with JIS Z 0237:2009). The high-temperature strength is measured, for example, as follows. That is, first, a current collector 24 is prepared, similar to the measurement of the room-temperature strength. Next, the current collector 24 is heated to the heat-resistant temperature of the adhesive layer 243. Next, while the temperature of the current collector 24 heated to the heat-resistant temperature of the adhesive layer 243 is maintained, the peel strength when the first metal foil 241 is peeled from the second metal foil 242 is measured as the high-temperature strength, similar to the measurement of the room-temperature strength.

[0051] Next, a method for manufacturing the electricity storage device 1 will be described. First, as shown in FIG. 3, a bipolar electrode 21, a first sealing member 71, and a second sealing member 72 are prepared. Next, the first sealing member 71 is disposed on the first main surface 24a of the current collector 24, and the second sealing member 72 is disposed on the second main surface 24b of the current collector 24. The first sealing member 71 and the second sealing member 72 are disposed so as to protrude beyond the side surface 24c of the current collector 24. That is, when viewed from the stacking direction D, the first sealing member 71 disposed on the first main surface 24a of the current collector 24 and the second sealing member 72 disposed on the second main surface 24b of the current collector 24 each have a portion that overlaps with the current collector 24 and a portion that does not overlap with the current collector 24. When the first sealing member 71 and the second sealing member 72 are positioned so as to extend along each side of the current collector 24, the first sealing member 71 and the second sealing member 72 may be temporarily fixed to the current collector 24 by spot welding using ultrasound, heat, or the like.

[0052] Next, as shown in FIG. 4 , the first seal member 71 and the second seal member 72 are each heated by a pair of heaters 73. The first seal member 71 and the second seal member 72 are each pressed toward the current collector 24 by the pair of heaters 73. The pair of heaters 73 is, for example, an impulse sealer. The first seal member 71 and the second seal member 72 are heated in a state in which the pair of heaters 73 sandwich the current collector 24 via the first seal member 71 and the second seal member 72, respectively. The first seal member 71 is heated until it melts. Similarly, the second seal member 72 is heated until it melts. The first seal member 71 and the second seal member 72, which have been heated until they melt, are pressed toward the current collector 24 by the pair of heaters 73. Thereafter, when the heating of the pair of heaters 73 is stopped, the first seal member 71 and the second seal member 72 cool, and accordingly, the first seal member 71 and the second seal member 72 are welded to the current collector 24. As a result, the portion of the first seal member 71 overlapping the first main surface 24a is welded to the first main surface 24a, thereby forming the first seal portion 41. The portion of the second seal member 72 overlapping the second main surface 24b is welded to the second main surface 24b, thereby forming the third seal portion 42. Furthermore, the portion of the first seal member 71 located outside the side surface 24c of the current collector 24 and the portion of the second seal member 72 located outside the side surface 24c of the current collector 24 melt and become compatible with each other, thereby forming the second seal portion 43. In other words, the seal member 4 is formed on the bipolar electrode 21. Similarly, the seal members 4 are formed on the positive terminal electrode 22 and the negative terminal electrode 23.

[0053] Next, as shown in FIG. 5 , the bipolar electrodes 21, the positive terminal electrode 22, the negative terminal electrode 23, and the spacers 5, each having a sealing member 4 formed thereon, are stacked. The spacers 5 are disposed between the sealing members 4. Next, as shown in FIG. 6 , the outer surfaces of the sealing members 4 and the spacers 5 are melted by a heating device 8. The heating device 8 is, for example, an infrared heater. The heating device 8 irradiates the outer surfaces of the sealing members 4 and the spacers 5 with infrared rays. When the outer surfaces of the sealing members 4 and the spacers 5 are irradiated with infrared rays, the temperatures of the sealing members 4 and the spacers 5 increase. The sealing members 4 and the spacers 5 are heated until they melt. As a result, the outer edges of the sealing members 4 and the spacers 5 melt. The outer edges of the melted sealing members 4 and the spacers 5 solidify, forming a welded portion 6. Next, an electrolyte is injected into each internal space S through the liquid inlet. The liquid inlet is then sealed. In this way, the electricity storage device 1 shown in FIG. 1 is manufactured.

[0054] As described above, in the energy storage device 1, the current collector 24 includes the adhesive layer 243 provided between the first metal foil 241 and the second metal foil 242 and adhering the first metal foil 241 and the second metal foil 242. The first seal portion 41 is welded to the first main surface 24a of the current collector 24, and the second seal portion 43 is welded to the side surface 24c of the current collector 24. Therefore, heat generated when the first seal portion 41 and the second seal portion 43 are welded to the current collector 24 may be transferred to the adhesive layer 243. In particular, because the second seal portion 43 is in contact with the side surface 243c of the adhesive layer 243, heat generated when the second seal portion 43 is welded to the current collector 24 is easily transferred to the adhesive layer 243. The heat-resistant temperature of the adhesive layer 243 of the current collector 24 is higher than the melting points of the first seal portion 41 and the second seal portion 43. Therefore, even if heat is transferred to the adhesive layer 243 when the first seal portion 41 and the second seal portion 43 are welded to the current collector 24, a decrease in the adhesive strength of the adhesive layer 243 is suppressed. This suppresses damage to the current collector 24 due to a decrease in the adhesive strength of the adhesive layer 243. Therefore, according to the energy storage device 1, damage to the bipolar electrode 21 can be suppressed.

[0055] The energy storage device 1 includes a spacer 5. The spacer 5 is provided between adjacent bipolar electrodes 21 in the stacking direction D and is welded to the sealing member 4. The heat resistance temperature of the adhesive layer 243 is higher than the melting point of the spacer 5. This prevents a decrease in the adhesive strength of the adhesive layer 243 even if heat is transferred to the adhesive layer 243 when the spacer 5 is welded to the sealing member 4. Therefore, damage to the current collector 24 due to a decrease in the adhesive strength of the adhesive layer 243 is prevented, and as a result, damage to the bipolar electrode 21 is prevented.

[0056] The seal member 4 includes a third seal portion 42 welded to the second main surface 24b of the current collector 24. The heat resistance temperature of the adhesive layer 243 is higher than the melting point of the third seal portion 42. This prevents a decrease in the adhesive strength of the adhesive layer 243 even if heat is transferred to the adhesive layer 243 when the third seal portion 42 is welded to the current collector 24. Therefore, damage to the current collector 24 due to a decrease in the adhesive strength of the adhesive layer 243 is prevented, and as a result, damage to the bipolar electrode 21 is prevented.

[0057] The adhesive layer 243 contains a thermosetting resin. By using a thermosetting resin as a component of the adhesive layer 243, the heat resistance temperature of the adhesive layer 243 can be increased. Furthermore, by using a thermosetting resin as a component of the adhesive layer 243, deformation of the adhesive layer 243 due to heating can be suppressed, and deformation of the current collector 24 can be suppressed. The sealing member 4 contains a thermoplastic resin. By using a thermoplastic resin as a component of the sealing member 4, the adhesion of the sealing member 4 to the current collector 24 can be increased when the sealing member 4 is welded to the current collector 24, and the sealing performance of the sealing member 4 can be improved.

[0058] Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment.

[0059] 7, the current collector 24 may further include a carbon coating layer 244 provided 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 layer 244 is electrically conductive. The carbon coating layer 244 includes, for example, a binder and graphite. The carbon coating layer 244 may be provided either between the first metal foil 241 and the adhesive layer 243 or between the second metal foil 242 and the adhesive layer 243. In other words, it is sufficient that the carbon coating layer 244 is provided at least either between the first metal foil 241 and the adhesive layer 243 or between the second metal foil 242 and the adhesive layer 243. According to this configuration, for example, compared to when the first metal foil 241 or the second metal foil 242 is directly bonded to the adhesive layer 243, the binder resin contained in the carbon coating layer 244 is more firmly bonded by the adhesive layer 243, thereby more reliably ensuring the adhesive strength between the first metal foil 241 and the adhesive layer 243 or the adhesive strength between the second metal foil 242 and the adhesive layer 243. Furthermore, even if pinholes are formed in the first metal foil 241, the second metal foil 242, or the adhesive layer 243, the carbon coating layer 244 can suppress liquid junctions between adjacent internal spaces S. The carbon coating layer 244 may be further provided on the first main surface 24a or the second main surface 24b of the current collector 24. In this case, the carbon coating layer 244 is also interposed between the first main surface 24a and the first seal portion 41 or between the second main surface 24b and the third seal portion 42.

[0060] In the embodiment, the description focuses 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 current collector 24 of the negative terminal electrode 23 corresponds to the first main surface, the first main surface 24a of the current collector 24 of the negative terminal electrode 23 corresponds to the second main surface, the layer of the current collector 24 including the second main surface 24b corresponds to the first metal foil, and the layer including the first main surface 24a corresponds to the second metal foil.

[0061] In the embodiment, an example in which the adhesive layer 243 contains a thermosetting resin has been described, but the adhesive layer 243 may contain a thermoplastic resin. In this case, the heat resistance temperature of the adhesive layer 243 may be the melting point of the adhesive layer 243.

[0062] In the embodiment, an example has been shown in which the peripheral edge portion of the separator 27 is located between the sealing member 4 and the spacer 5, but the peripheral edge portion of the separator 27 does not have to reach the spacer 5. The peripheral edge portion of the separator 27 may be welded to the sealing member 4.

[0063] The gist of this disclosure is as follows [1] to [5]. [1] An electricity storage device comprising: a current collector; an electrode having an active material layer provided on a first main surface of the current collector; and a sealing member provided on a surface of the current collector so as to surround the active material layer when viewed in a direction perpendicular to the first main surface, wherein the current collector includes a first metal foil including the first main surface, a second metal foil provided on the side of the first metal foil opposite the active material layer, and an adhesive layer provided between the first metal foil and the second metal foil and adhering the first metal foil to the second metal foil, and the sealing member includes a first seal portion welded to the first main surface and a second seal portion welded to a side surface of the current collector including a side surface of the adhesive layer, and the heat resistant temperature of the adhesive layer is higher than the melting points of the first seal portion and the second seal portion. [2] The energy storage device according to [1], further comprising a spacer, wherein the electrode is each of a plurality of electrodes stacked in a stacking direction, the spacer is provided between adjacent electrodes in the stacking direction and is welded to the sealing member, and the heat resistance temperature of the adhesive layer is higher than the melting point of the spacer. [3] The energy storage device according to [1] or [2], wherein the sealing member further includes a third sealing portion welded to a second main surface of the current collector opposite the first main surface, and the heat resistance temperature of the adhesive layer is higher than the melting point of the third sealing portion. [4] The electricity storage device according to any one of [1] to [3], wherein the adhesive layer contains a thermosetting resin, and the sealing member contains a thermoplastic resin. [5] The electricity storage device according to any one of [1] to [4], wherein the current collector further includes a carbon coating layer provided between the first metal foil and the adhesive layer and / or between the second metal foil and the adhesive layer. [Explanation of symbols]

[0064] 1...electricity storage device, 4...sealing member, 5...spacer, 21...bipolar electrode, 22...positive electrode terminal electrode, 23...negative electrode 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. an electrode having a current collector and an active material layer provided on a first main surface of the current collector; a sealing member provided on a 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 first metal foil on the opposite side to the active material layer, and an adhesive layer provided between the first metal foil and the second metal foil and adhering 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 resistance temperature of the adhesive layer is higher than the melting points of the first seal portion and the second seal portion.

2. Further comprising a spacer, the electrode is each 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 power storage device according to claim 1 , wherein the adhesive layer has a heat resistance temperature higher than a melting point of the spacer.

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

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

5. 3. The power storage device according to claim 1, wherein the current collector further includes a carbon coating layer provided between the first metal foil and the adhesive layer and / or between the second metal foil and the adhesive layer.

Images