capacitor

Abstract

The capacitor device comprises a laminate (2) and an encapsulation body (3). The bipolar electrode (21) has a current collector (24) comprising a surface (24a) and a surface (24b) opposite to the surface (24a), a positive electrode active material layer (25) formed on the surface (24a), and a negative electrode active material layer (26) formed on the surface (24b). The encapsulation body (3) has a seal member (4). The current collector (24) has a first metal foil (241) having a surface (24a) and a rectangular shape having at least one side length greater than 1 m when viewed in the stacking direction (D) of the laminate (2), a second metal foil (242) having a surface (24b) and being thinner than the first metal foil (241), and an adhesive layer (243) formed between the first metal foil (241) and the second metal foil (242) and bonding the first metal foil (241) and the second metal foil (242). The adhesive layer (243) is thinner than the second metal foil (242).

Description

Technology Field

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

[0002] A capacitor is known having a laminate comprising a stacked bipolar electrode and a sealing body that encapsulates the side of the laminate, wherein the bipolar electrode has a current collector in which two metal foils of different thicknesses are integrated by a conductive resin layer (see, for example, Patent Document 1). Prior art literature

[0003] Japanese Patent Publication No. 2010-277862 The problem to be solved

[0004] In the capacitor device described above, a resin seal member having a coefficient of linear expansion greater than that of the metal foil may be bonded to the surface of the current collector. In this case, due to temperature changes during the use of the capacitor, the metal foil may be repeatedly subjected to tension or compression by the seal member, potentially leading to fatigue damage. In particular, for large-area current collectors with at least one side exceeding 1 m, the difference in expansion and contraction between the seal member and the metal foil is significant, making the metal foil susceptible to fatigue damage.

[0005] In the current collector of Patent Document 1, one of the two metal foils is formed to be thinner than the other metal foil. Therefore, when a sealing member is bonded to the current collector, there is a risk that the one metal foil may be particularly fatigue-damaged.

[0006] The present disclosure aims to provide a capacitor capable of suppressing fatigue damage to both metal foils in a current collector in which two metal foils of different thicknesses are integrated by a conductive resin layer. means of solving the problem

[0007] The capacitor of the present disclosure is a capacitor comprising a laminate including a stacked bipolar electrode and a sealing body that encapsulates the laminate, wherein the bipolar electrode has a current collector including a first main surface and a second main surface opposite to the first main surface, a first active material layer formed on the first main surface, and a second active material layer formed on the second main surface, and the sealing body has a resin seal member bonded to the outer edge of at least one side of the first main surface and the second main surface, and the current collector has a rectangular shape having at least one side length exceeding 1 m when viewed from the stacking direction of the laminate, and has a first metal foil including a first main surface, a second metal foil including a second main surface and thinner than the first metal foil, and a conductive adhesive layer formed between the first metal foil and the second metal foil and bonding the first metal foil and the second metal foil, and the conductive adhesive layer is thinner than the second metal foil.

[0008] In this capacitor, the current collector has a conductive adhesive layer formed between a first metal foil and a second metal foil and bonding the first metal foil and the second metal foil. Here, the second metal foil is thinner than the first metal foil and is therefore susceptible to damage. However, since the conductive adhesive layer is thinner than the second metal foil, even if the conductive adhesive layer is softer than the first metal foil and the second metal foil, it is possible to reinforce the thin second metal foil with the thick first metal foil. Therefore, fatigue damage to both metal foils, particularly the second metal foil, can be suppressed.

[0009] The thickness of the conductive adhesive layer may be 5 μm or less. In this case, since the reinforcing effect between the metal foils becomes more easily obtained, fatigue damage between the metal foils can be further suppressed.

[0010] The thickness of the conductive adhesive layer may be less than or equal to half the thickness of the second metal foil. In this case, since the reinforcing effect between the metal foils becomes more easily obtained, fatigue damage to both metal foils can be further suppressed.

[0011] The thickness of the second metal foil may be less than 10 μm. In this case, since the second metal foil is thin, the enlargement of the current collector can be suppressed. Even if the second metal foil is thin in this way, since reinforcement by the first metal foil is possible, fatigue damage of the second metal foil is suppressed.

[0012] The Young's modulus of the conductive adhesive layer may be higher than the Young's modulus of the seal member. In this case, compared to a configuration where the Young's modulus of the conductive adhesive layer is lower than the Young's modulus of the seal member, fatigue damage to the metal foil caused by the expansion and contraction of the seal member can be suppressed.

[0013] The seal member may be joined to the outer edge of each of the first and second sides. In this case, the tensile and compressive stress imparted by the seal member to the current collector is increased compared to a configuration in which the seal member is joined to the outer edge of either the first or second side. Therefore, a configuration in which reinforcement between metal foils is possible is particularly effective. Effects of the invention

[0014] According to the present disclosure, in a current collector in which two metal foils of different thicknesses are integrated by a conductive resin layer, it is possible to provide a capacitor capable of suppressing fatigue damage to both metal foils. Brief explanation of the drawing

[0015] FIG. 1 is a schematic cross-sectional view of a capacitor device related to an embodiment. Figure 2 is a partial enlarged view of Figure 1. Specific details for implementing the invention

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or substantial parts are given the same reference numerals, and redundant descriptions are omitted.

[0017] The storage device (1) shown in FIG. 1 is a storage module used in batteries for, for example, forklifts, hybrid vehicles, electric vehicles, etc. The storage device (1) is a secondary battery such as, for example, a nickel-hydrogen secondary battery or a lithium-ion secondary battery. In this embodiment, the storage device (1) is a lithium-ion secondary battery.

[0018] As shown in FIG. 1, the capacitor device (1) comprises a laminate (2) and a sealing body (3). The laminate (2) includes a bipolar electrode (21) stacked in the stacking direction (D), a positive terminal electrode (22), and a negative terminal electrode (23). In this embodiment, the laminate (2) includes a plurality of bipolar electrodes (21). The bipolar electrode (21) has a current collector (24), a positive active material layer (25), and a negative active material layer (26).

[0019] The current collector (24) has a rectangular shape with at least one side having a length exceeding 1 m when viewed in the stacking direction (D). In this embodiment, the current collector (24) has a rectangular shape with each side having a length exceeding 1 m when viewed in the stacking direction (D). When viewed in the stacking direction (D), for example, the length of the long side of the current collector (24) is 1.5 m and the length of the short side is 1.2 m. The current collector (24) includes a surface (first surface) (24a) and a surface (second surface) (24b) opposite to the surface (24a). The positive electrode active material layer (25) is formed on the surface (24a). The positive electrode active material layer (25) has a rectangular shape when viewed in the stacking direction (D), for example. The surface (24a) includes an uncoated region where the positive electrode active material layer (25) is not formed. The uncoated region surrounds the positive electrode active material layer (25) when viewed from the stacking direction (D).

[0020] The negative electrode active material layer (26) is formed on the surface (24b). The negative electrode active material layer (26) has a rectangular shape, for example, when viewed from the stacking direction (D). The surface (24b) includes an uncoated area where the negative electrode active material layer (26) is not formed. The uncoated area surrounds the negative electrode active material layer (26) when viewed from the stacking direction (D). A plurality of 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 another bipolar electrode (21) face each other. That is, a plurality of bipolar electrodes (21) are stacked such that the surface (24a) of the current collector (24) of one of the adjacent bipolar electrodes (21) and the surface (24b) of the current collector (24) of the other bipolar electrode (21) face each other.

[0021] The positive terminal electrode (22) is positioned on one side in the stacking direction (D) relative to the plurality of bipolar electrodes (21). The positive terminal electrode (22) has a current collector (24) and a positive active material layer (25). The positive terminal electrode (22) is different from the bipolar electrode (21) in that it does not have a negative active material layer (26). The other configuration of the positive terminal electrode (22) is the same as that of the bipolar electrode (21). The positive terminal electrode (22) is positioned 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 such that the surface (24a) of the current collector (24) of the positive terminal electrode (22) and the surface (24b) of the current collector (24) of the bipolar electrode (21) adjacent to the positive terminal electrode (22) face each other.

[0022] The negative terminal electrode (23) is positioned on the other side in the stacking direction (D) relative to the plurality of bipolar electrodes (21). The negative terminal electrode (23) has a current collector (24) and a negative active material layer (26). The negative terminal electrode (23) is different from the bipolar electrode (21) in that it does not have a positive active material layer (25). The other configuration of the negative terminal electrode (23) is the same as that of the bipolar electrode (21). The negative terminal electrode (23) is positioned 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 such that the surface (24b) of the current collector (24) of the negative terminal electrode (23) and the surface (24a) of the current collector (24) of the bipolar electrode (21) adjacent to the negative terminal electrode (23) face each other. Between each bipolar electrode (21), between the bipolar electrode (21) and the positive terminal electrode (22), and between the bipolar electrode (21) and the negative terminal electrode (23), an internal space (S) containing an electrolyte is formed.

[0023] The laminate (2) includes a plurality of separators (27). The separators (27) are disposed between each bipolar electrode (21), between the bipolar electrode (21) and the positive electrode terminal electrode (22), and between the bipolar electrode (21) and the negative electrode terminal electrode (23). The separators (27) are located between the positive electrode active material layer (25) and the negative electrode active material layer (26) facing each other. The separators (27) are, for example, in the form of a sheet. When viewed from the stacking direction (D), the separators (27) are, for example, in the form of a rectangle. When viewed from the stacking direction (D), the outer edge of the separators (27) is located further outward than the outer edge of the positive electrode active material layer (25) and the outer edge of the negative electrode active material layer (26), respectively. The main portion of the separator (27) is located between the seal member (4) and the spacer (5) described later. The separator (27) is a member that allows a charge carrier, such as lithium ions, to pass through. The separator (27) isolates each electrode (21, 22, 23) that is adjacent to each other. By doing so, an electrical short circuit caused by contact between each electrode (21, 22, 23) is prevented.

[0024] The current collector (24) is a chemically inert electrical conductor for allowing current to continue flowing through the positive electrode active material layer (25) and the negative electrode active material layer (26) during the discharge or charging of the capacitor (1). The current collector (24) may be, for example, plate-shaped, thin-walled, sheet-shaped, film-shaped, etc. If the current collector (24) is thin-walled, the thickness of the current collector (24) may be within the range of 10 μm or more and 200 μm or less.

[0025] 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 positive electrode active materials include composite oxides, metallic lithium, and sulfur. The composition of the composite oxide includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of composite oxides include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, LiNiMnCoO2, etc.

[0026] 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 negative electrode active materials include carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon micro beads, hard carbon, and soft carbon, metal compounds, elements or compounds capable of alloying with lithium, and boron-doped carbon. Examples of elements capable of alloying with lithium include silicon and tin.

[0027] Each of the positive electrode active material layer (25) and the negative electrode active material layer (26) may contain, in addition to the active material, a binder and a conductivity aid. The binder serves to connect and fix the active material or the conductivity aid to each other, thereby maintaining a 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-based resins such as polyimide and polyamideimide; alkoxysilyl group-containing resins; acrylic-based resins such as polyacrylic acid or polymethacrylic acid; styrene-butadiene rubber; carboxymethylcellulose; alginates such as sodium alginate and ammonium alginate; water-soluble cellulose ester crosslinkers; and starch-acrylic acid graft polymers. These binders may be used alone or in multiples. Conductivity aids are conductive materials such as, for example, acetylene black, carbon black, and graphite, and can increase electrical conductivity. For viscosity adjusting solvents, for example, N-methyl-2-pyrrolidone is used.

[0028] For the formation of the positive electrode active material layer (25) on the surface (24a) and the negative electrode active material layer (26) on the surface (24b), conventionally known methods such as roll coating, die coating, dip coating, doctor blade method, spray coating, and curtain coating are used. Specifically, a composition for forming an active material layer in the form of a slurry is prepared by mixing an active material, a solvent, and, if necessary, a binder and a conductivity aid, and the composition for forming the active material layer is applied to the surface (24a) or the surface (24b) and then dried. The solvent is, for example, N-methyl-2-pyrrolidone, methanol, methylisobutyl ketone, or water. To increase the electrode density, the dried material may be compressed.

[0029] The separator (27) is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains an electrolyte. The material of the separator (27) is, for example, polypropylene, polyethylene, polyolefin, polyester, etc. The separator (27) may have a single-layer structure or a multi-layer structure. If the separator (27) has a multi-layer structure, the separator (27) may, for example, include a substrate layer and a pair of adhesive layers, and may be 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 include a ceramic layer that serves as a heat-resistant layer. The separator (27) may be reinforced with a vinylidene fluoride resin compound.

[0030] The electrolyte impregnated in the separator (27) may include, 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 maintained in a polymer matrix. When the electrolyte is impregnated in the separator (27), known lithium salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2 may be used as the electrolyte salt. Also, as the non-aqueous solvent, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers may be used. Additionally, two or more of these known solvent materials may be used in combination. In this embodiment, the electrolyte impregnated in the separator (27) is an electrolyte solution.

[0031] The sealing body (3) is a member that seals the internal space (S). The sealing body (3) is formed on the side of the laminate (2). The sealing body (3) seals the side of the laminate (2). The sealing body (3) is, for example, rectangular. 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).

[0032] A seal member (4) is formed on the surface of a current collector (24) so ​​as to surround a positive electrode active material layer (25) and a negative electrode active material layer (26) when viewed in the stacking direction (a direction perpendicular to the surface (24a)) (D). The seal member (4) is made of resin. The seal member (4) is bonded to the outer edge of at least one side of the surface (24a) and the surface (24b). That is, the seal member (4) is bonded to at least one side of the outer edge (24d) of the surface (24a) and the outer edge (24e) of the surface (24b). In this embodiment, the seal member (4) is bonded to the outer edge of each of the surface (24a) and the surface (24b). That is, the seal member (4) is joined to the outer edge (24d) of the surface (24a) and the outer edge (24e) of the surface (24b), respectively.

[0033] A spacer (5) is formed between adjacent electrodes (21, 22, 23) in the stacking direction (D). The spacer (5) is, for example, shaped like a rectangular frame. The spacer (5) is, for example, made of resin. The welded portion (6) is, for example, shaped like a rectangular shape. The welded portion (6) extends to both ends of the laminate (2) in the stacking direction (D). The welded portion (6) is formed integrally.

[0034] As shown in FIG. 2, the current collector (24) comprises a first metal foil (241), a second metal foil (242), and an adhesive layer (conductive adhesive layer) (243). The current collector (24) is a laminated foil formed by laminating the first metal foil (241) and the second metal foil (242). The first metal foil (241) comprises a surface (24a). The surface (24a) of the current collector (24) is the surface on the side of the positive electrode active material layer (25) in the first metal foil (241). The first metal foil (241) exhibits, for example, a rectangular shape when viewed from the lamination direction (D). The first metal foil (241) contains aluminum, for example, aluminum foil. The first metal foil (241) may be, for example, a nickel foil, a titanium foil, or a stainless steel foil. The first metal foil (241) may be an alloy foil of the above metal. A coating layer formed on the surface (24a) of the first metal foil (241) by a known method such as plating or spray coating may be formed.

[0035] The second metal foil (242) is formed on the side opposite to the positive electrode active material layer (25) with respect to the first metal foil (241). The second metal foil (242) includes a surface (24b). The surface (24b) of the current collector (24) is the surface on the negative electrode active material layer (26) side of the second metal foil (242). The second metal foil (242) exhibits, for example, a rectangular 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) roughly coincides with the side (outer edge) (241c) of the first metal foil (241). In this embodiment, the second metal foil (242) contains copper, for example, copper foil. The second metal foil (242) may be, for example, a nickel foil, a titanium foil, or a stainless steel foil. The second metal foil (242) may be an alloy foil of the above metal. A coating layer formed on the surface (24b) of the second metal foil (242) by a known method such as plating or spray coating may be formed.

[0036] The adhesive layer (243) is formed between the first metal foil (241) and the second metal foil (242). The adhesive layer (243) has a rectangular shape, for example, when viewed in the lamination direction (D). When viewed in the lamination direction (D), the side (outer edge) (243c) of the adhesive layer (243) roughly coincides with the side (241c) of the first metal foil (241) and the side (242c) of the second metal foil (242), respectively. The side (outer edge) (24c) of the current collector (24) is composed of the side (241c), the side (242c), and the side (243c).

[0037] The adhesive layer (243) adheres the first metal foil (241) and the second metal foil (242). The adhesive layer (243) is adhered to each of the first metal foil (241) and the second metal foil (242). The adhesive layer (243) is a conductive adhesive layer having conductivity. The adhesive layer (243) includes, for example, a conductive resin material. Examples of conductive resin materials include, for example, a conductive polymer material, or a resin in which a conductive filler is added to a non-conductive polymer material.

[0038] In this embodiment, the adhesive layer (243) comprises an adhesive component and a conductive component. The adhesive component functions as an adhesive to bond the first metal foil (241) and the second metal foil (242). The adhesive component is, for example, a thermosetting resin or a thermoplastic resin. The resin of the adhesive component is, for example, an olefin-based resin such as polypropylene or polyethylene, or an acrylic-based resin such as polyacrylic acid. When the adhesive component is a thermosetting resin, the adhesive component may additionally include a curing agent such as an isocyanate-based curing agent or an epoxy-based curing agent. When bonding the first metal foil (241) and the second metal foil (242) with the adhesive layer (243) in which the olefin-based resin is the adhesive component, an epoxy-based curing agent that generates less gas accompanying the curing reaction of the adhesive component may be used. The adhesive component may have electrolyte resistance. In this case, even if an electrolyte penetrates between the first metal foil (241) and the second metal foil (242) due to a pinhole defect or the like occurring on one side of the first metal foil (241) and the second metal foil (242), the adhesive layer (243) prevents the electrolyte from reaching the other side of the first metal foil (241) and the second metal foil (242), thereby preventing a short circuit. The conductive component is, for example, a conductive particle dispersed in the adhesive component. The conductive component electrically connects the first metal foil (241) and the second metal foil (242). The material of the conductive component is, for example, graphite or metal. The conductive particle is, for example, a graphite particle or a metal particle. The conductive particle may be composed of the aforementioned material alone, or may be composed by coating the aforementioned material on the surface of resin particles, etc. As conductive particles, spherical particles formed by creating a metal film on the surface of a core particle made of resin or ceramic may be used.

[0039] The thickness of the first metal foil (241) (length in the lamination direction (D) of the first metal foil (241)) is, for example, 20 μm or more and 150 μm or less. The second metal foil (242) is thinner than the first metal foil (241). The thickness of the second metal foil (242) (length in the lamination direction (D) of the second metal foil (242)) is, for example, less than 10 μm. The adhesive layer (243) is thinner than the second metal foil (242). The thickness of the adhesive layer (243) (length in the lamination direction (D) of the adhesive layer (243)) is, for example, 1 / 2 or less of the thickness of the second metal foil (242). The thickness of the adhesive layer (243) is, for example, 5 μm or less, and may be 3 μm or less.

[0040] Here, regarding the metal foil generally used in the current collector (24), it is known that the strength against fatigue damage of the metal foil increases as the thickness of the metal foil increases. In this embodiment, since the thickness of the first metal foil (241), which is aluminum foil, is greater than twice the thickness of the second metal foil (242), which is copper foil, the strength against fatigue damage in the first metal foil (241) alone is higher than the strength against fatigue damage in the second metal foil (242) alone. That is, the strength against fatigue damage in the second metal foil (242) alone is lower than the strength against fatigue damage in the first metal foil (241) alone.

[0041] The seal member (4) includes a seal portion (41), a seal portion (42), and a seal portion (43). The seal portion (41) is formed on the surface (24a). The seal portion (41) appears, for example, as a rectangular frame when viewed in the stacking direction (D). The seal portion (41) surrounds the positive electrode active material layer (25) and the negative electrode active material layer (26) when viewed in the stacking direction (D). The outer edge (41c) of the seal portion (41) roughly coincides with the side (24c) of the current collector (24) when viewed in the stacking direction (D). The inner edge (41d) of the seal portion (41) is separated from the positive electrode active material layer (25). The seal portion (41) is joined to the outer edge (24d) of the surface (24a).

[0042] The seal portion (42) is formed on the surface (24b). The seal portion (42) appears, for example, as a rectangular frame when viewed in the stacking direction (D). The seal portion (42) surrounds the positive electrode active material layer (25) and the negative electrode active material layer (26) when viewed in the stacking direction (D). The outer edge (42c) of the seal portion (42) roughly coincides with the side (24c) of the current collector (24) when viewed in the stacking direction (D). The inner edge (42d) of the seal portion (42) is separated from the negative electrode active material layer (26). The seal portion (42) is bonded to the outer edge (24e) of the surface (24b). The inner edge (42d) of the seal portion (42) roughly coincides with the inner edge (41d) of the seal portion (41) when viewed in the stacking direction (D). The thickness of the seal portion (42) (length in the stacking direction (D) of the seal portion (42)) is, for example, roughly the same as the thickness of the seal portion (41) (length in the stacking direction (D) of the seal portion (41)) and is 80 μm or more and 160 μm or less. The thickness of the seal portion (41) and the thickness of the seal portion (42) are each greater than the thickness of the first metal foil (241) and greater than the thickness of the second metal foil (242).

[0043] The seal portion (43) is formed on the side (24c) of the current collector (24). The seal portion (43) is located on the side (24c) of the current collector (24), the outer edge (41c) of the seal portion (41), and the outer edge (42c) of the seal portion (42). The seal portion (43) is connected to each of the seal portion (41) and the seal portion (42). The seal portion (43) covers the side (24c) of the current collector (24). The seal portion (43) covers each of the side (241c) of the first metal foil (241), the side (242c) of the second metal foil (242), and the side (243c) of the adhesive layer (243).

[0044] The seal portion (43) is bonded to the side (24c) of the current collector (24). The seal portion (43) is bonded to the side (241c) of the first metal foil (241), the side (242c) of the second metal foil (242), and the side (243c) of the adhesive layer (243), respectively. The seal portion (43) encloses the side (24c) of the current collector (24). Each of the seal portion (41), the seal portion (42), and the seal portion (43) is an area of ​​part of the seal member (4) formed integrally by the same material.

[0045] A spacer (5) is formed between adjacent seal members (4) in the stacking direction (D). The spacer (5) is, for example, shaped like a rectangular frame. When viewed in the stacking direction (D), the inner edge (5d) of the spacer (5) is separated from the positive electrode active material layer (25) or the negative electrode active material layer (26) by the inner edge (41d) of the seal portion (41) and the inner edge (42d) of the seal portion (42), respectively. In short, when viewed in the stacking direction (D), the inner edge (41d) of the seal 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 seal 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 different component from the seal component (4).

[0046] The spacer (5) is sandwiched by a pair of adjacent seal members (4) in the stacking direction (D). The spacer (5) is in contact with the seal members (4). The spacer (5), together with a pair of adjacent bipolar electrodes (21) in the stacking direction (D) and a pair of adjacent seal members (4) in the stacking direction (D), forms an internal space (S) for receiving an electrolyte. Additionally, the spacer (5) has an injection port formed therein for injecting the electrolyte into the internal space (S).

[0047] The thickness of the spacer (5) (length in the stacking direction (D) of the spacer (5)) is greater than the respective thicknesses of the seal portion (41) and the seal portion (42). The thickness of the spacer (5) is, for example, more than twice the thickness of the seal portion (41) or the seal portion (42). The thickness of the spacer (5) is thinner than the thickness of the seal member (4) (length in the stacking direction (D) of the seal member (4). In short, the thickness of the spacer (5) is 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 seal portion (41), and the thickness of the seal portion (42).

[0048] The spacer (5) is welded to the seal member (4) on the outer side (24c) of the current collector (24) (i.e., the welded portion (6)). Specifically, the welded portion (6) is formed by the outer edges of the seal member (4) and the spacer (5) being melted and then solidified again. In short, the welded portion (6) is formed by the outer edges of the seal member (4) and the spacer (5) being welded to each other.

[0049] Here, the respective outer edges of the seal member (4) and the spacer (5) refer to the respective outer edges of the seal member (4) and the spacer (5) before welding. The outer edge of the seal member (4) is the part located on the opposite side of the current collector (24) with respect to the seal portion (43) in the seal member (4) before welding. The outer edge of the spacer (5) is the part that overlaps with the outer edge of the seal member (4) when viewed from the stacking direction (D) in the spacer (5) before welding. The welded portion (6) does not extend to the side (24c) of the current collector (24). The welded portion (6) is separated from the side (24c) of the current collector (24). Additionally, a liquid injection port is formed in the weld portion (6) that is connected to the liquid injection port of the spacer (5). The weld portion (6) may be formed to extend to the side (24c) of the current collector (24). In this case, the seal portion (43) in the seal member (4) after welding is not formed.

[0050] Each of the seal member (4) and the spacer (5) comprises a thermoplastic resin. The respective materials of the seal member (4) and the spacer (5) are, for example, acid-modified polyethylene (acid-modified PE), acid-modified polypropylene (acid-modified PP), polyethylene, or polypropylene. Each of the seal member (4) and the spacer (5) has electrolyte resistance. The respective materials of the seal member (4) and the spacer (5) may be the same or different from each other. In this embodiment, the material of the seal 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. The seal portion (41), the seal portion (42), and the spacer (5) may be composed of a plurality of resin layers. In this case, different materials may be used for each resin layer.

[0051] Acid-modified polyethylene and acid-modified polypropylene are easier to bond to metal compared to non-acid-modified polyethylene and non-acid-modified polypropylene. Since the respective materials of the first metal foil (241) and the second metal foil (242) of the current collector (24) are metal, by composing the seal portions (41, 42, 43) with acid-modified polyethylene or acid-modified polypropylene, the bonding strength of the seal portions (41, 42, 43) to the first metal foil (241) or the second metal foil (242) can be improved.

[0052] The Young's modulus of the adhesive layer (243) is higher than the Young's modulus of the seal member (4). The Young's modulus of the adhesive layer (243) is higher than the respective Young's modulus of the seal portion (41) and the seal portion (42). In this embodiment, since the seal member (4) is integrally formed from the same material, the seal portion (41) and the seal portion (42) have the same Young's modulus.

[0053] The Young's modulus of the adhesive layer (243) is lower than that of the first metal foil (241) and the second metal foil (242). For example, the Young's modulus of the first metal foil (241) and the second metal foil is approximately 100 times greater than that of the adhesive layer (243). The coefficient of linear expansion of the seal member (4) (seal portions (41, 42)) is greater than that of the first metal foil (241) and the second metal foil (242). For example, the coefficient of linear expansion of the seal portions (41, 42) is approximately 5 times greater than that of the first metal foil (241) and the second metal foil (242).

[0054] The heat resistance temperature of the adhesive layer (243) (hereinafter simply referred to as "heat resistance temperature") is higher than the melting point of each of the seal portion (41), seal portion (42), seal portion (43), and spacer (5). Specifically, the heat resistance temperature of the adhesive component of the adhesive layer (243) is higher than the melting point of each of the seal portion (41), seal portion (42), seal portion (43), and spacer (5). The melting point of each of the seal portion (41), seal portion (42), seal portion (43), and spacer (5) is, for example, lower than 150 degrees. The heat resistance temperature of the adhesive layer (243) is, for example, 150 degrees or higher.

[0055] The heat resistance temperature of the adhesive layer (243) is a limit temperature at which a good adhesive state of the first metal foil (241) and the second metal foil (242) is maintained. Specifically, the heat resistance temperature of the adhesive layer (243) is a limit temperature at which the adhesive strength of the first metal foil (241) and the second metal foil (242) by the adhesive layer (243) is greater than or equal to a predetermined threshold value. The predetermined threshold value 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) rises due to heating, the adhesive strength of the adhesive layer (243) tends to decrease compared to before heating. And, when the temperature of the adhesive layer (243) rises above the heat resistance temperature, the adhesive strength of the adhesive layer (243) decreases to a value lower than the above predetermined threshold value. If the adhesive strength of the adhesive layer (243) is lower than the above-mentioned predetermined threshold, the good adhesive state between the first metal foil (241) and the second metal foil (242) is not maintained, and as a result, there is a risk that damage to the current collector (24) may occur. In this embodiment, since the heat resistance temperature of the adhesive layer (243) is higher than the melting point of each of the seal portion (41), seal portion (42), seal portion (43) and the spacer (5), when welding the seal portion (41), seal portion (42), seal portion (43) or the spacer (5), even if the temperature of the adhesive layer (243) reaches the melting point of the seal portion (41), seal portion (42), seal portion (43) or the spacer (5), damage to the current collector (24) is unlikely to occur. Damage to the entire current (24) may include, for example, peeling of the first metal foil (241) or the second metal foil (242), a change in the relative position of the first metal foil (241) and the second metal foil (242) (misalignment of the positions 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) (e.g., wrinkles).

[0056] In this embodiment, the adhesive strength of the adhesive layer (243) heated to a 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) is maintained by the adhesive layer (243). If 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 a good adhesive state between the first metal foil (241) and the second metal foil (242) is maintained. In this embodiment, since the heat resistance temperature of the adhesive layer (243) is greater than the melting point of each of the seal portion (41), seal portion (42), seal portion (43) and spacer (5), when welding the seal portion (41), seal portion (42), seal portion (43) or spacer (5), even if the temperature of the adhesive layer (243) reaches the melting point of the seal portion (41), seal portion (42), seal portion (43) or spacer (5), the adhesive strength of the adhesive layer (243) is 1% or more of the room temperature strength. In short, even if the temperature of the adhesive layer (243) reaches the melting point of the seal portion (41), seal portion (42), seal portion (43) or spacer (5), the good adhesion between the first metal foil (241) and the second metal foil (242) by the adhesive layer (243) is maintained, so damage to the current collector (24) is unlikely to occur.

[0057] Room temperature strength is measured, for example, as follows. That is, first, a current collector (24) (a current collector (24) in which none of the positive electrode active material layer (25), negative electrode active material layer (26) and seal member (4) are formed) 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 (in accordance with JIS Z 0237:2009 as an example). High temperature strength is measured, for example, as follows. That is, first, a current collector (24) is prepared in the same way as the room temperature strength measurement. Next, the current collector (24) is heated to a heat-resistant temperature. Next, while maintaining the temperature of the current collector (24) heated to a heat-resistant temperature, the peel strength when the first metal foil (241) is peeled off from the second metal foil (242) is measured as high-temperature strength, just like the measurement of room-temperature strength.

[0058] The current collector (24) is formed by bonding a first metal foil (241) and a second metal foil (242) with an adhesive layer (243), for example, by a dry lamination method. In the dry lamination method, first, an adhesive solution is applied to the first metal foil (241). Next, the adhesive solution is dried to form a uniform adhesive on the surface of the first metal foil (241). Subsequently, the second metal foil (242) is bonded to the first metal foil (241) on which the adhesive has been formed by heat pressing. Heat pressing is performed at constant pressure using a pair of heating rollers. One of the heating rollers is a movable roller. By moving the movable roller, the spacing between the pair of heating rollers can be adjusted, thereby adjusting the pressure during heat pressing. As a result of lamination, a current collector (24) is obtained in which the first metal foil (241) and the second metal foil (242) are bonded by an adhesive layer (243).

[0059] The first metal foil (241) and the second metal foil (242) have a large thickness tolerance. When measuring the thickness of the adhesive layer (243) by measuring the thickness of the current collector (24) in the state of the current collector (24) after laminating the first metal foil (241) and the second metal foil (242), the thickness of the adhesive layer (243) cannot be accurately measured because the thickness tolerance of the first metal foil (241) and the second metal foil (242) greatly affects the measurement result of the thickness of the current collector (24). Therefore, the thickness of the adhesive layer (243) is managed by measuring the thickness of the adhesive formed on the surface of the first metal foil (241) before lamination. For example, it is determined whether the thickness of the adhesive falls within the numerical range of a good product, and if it does not fall within it, the corresponding part is removed from the line before lamination or the corresponding part is cut off after lamination. Also, before lamination, since the adhesive is not covered by the second metal foil (242), the thickness of the adhesive alone can be measured. Here, when heat pressing is performed on the first metal foil (241) and the second metal foil (242), the adhesive (adhesive layer (243)) which is sufficiently softer than the first metal foil (241) and the second metal foil (242) is mainly compressed. For this reason, when heat pressing of the first metal foil (241) and the second metal foil (242) is performed at constant pressure, the correlation between the thickness of the adhesive layer (243) after heat pressing and the thickness of the adhesive before lamination when a predetermined pressure is applied is investigated in advance, so that the thickness of the adhesive layer (243) after lamination can be appropriately managed based on the thickness of the adhesive applied to the first metal foil (241).

[0060] As described above, in the capacitor (1), a seal member (4) having a coefficient of linear expansion greater than that of the first metal foil (241) and the second metal foil (242) of the capacitor (24) is bonded to the capacitor (24). Because of this, due to repeated temperature changes during use of the capacitor (1), the seal member (4) expands and contracts more than the first metal foil (241) and the second metal foil (242), thereby repeatedly applying tensile and compressive stress to the first metal foil (241) and the second metal foil (242). The capacitor (24) has an adhesive layer (243) formed between the first metal foil (241) and the second metal foil (242) and bonding the first metal foil (241) and the second metal foil (242). Here, as previously mentioned, the second metal foil (242) is thinner than the first metal foil (241) and is therefore susceptible to fatigue damage. However, the adhesive layer (243) is even thinner than the second metal foil (242). Because of this, the Young's modulus of the adhesive layer (243) is lower than that of the first metal foil (241) and the second metal foil (242), so even though the adhesive layer (243) is softer than the first metal foil (241) and the second metal foil (242), the tensile compressive stress of the seal member (4) on the first metal foil (241) and the second metal foil (242) is difficult to absorb into the adhesive layer (243). Therefore, the effect of the first metal foil (241) and the second metal foil (242) reinforcing each other's strength is obtained. Specifically, the thin second metal foil (242) can be reinforced by the thick first metal foil (241). As a result, fatigue damage to both the first metal foil (241) and the second metal foil (242), particularly to the second metal foil (242), is suppressed. Since there is no need to secure strength capable of withstanding repeated tensile and compressive stress by the seal member (4) in each of the first metal foil (241) and the second metal foil (242), the enlargement of the current collector (24) can be suppressed.As a result of suppressing the enlargement of the entire current collection unit (24), the energy storage device (1) can be made smaller.

[0061] The results of a thermal shock test (in accordance with JIS C 60068-2-14: 2011) performed on a plurality of test pieces simulating a capacitor device related to the experimental example are described. Each test piece was formed by forming a seal member (4) on a single current collector (24). The length of the long side of the current collector (24) is 1.5 m, and the length of the short side is 1.2 m. The current collector (24) is constructed using aluminum foil (JIS A3003) as the first metal foil (241), copper foil (electrolytic copper foil) as the second metal foil (242), and olefin resin as the adhesive layer (243). Acid-modified polyethylene is used as the material for the seal member (4), and the thickness of the portion corresponding to the seal portion (41) and the seal portion (42) is set to 120 μm. Multiple test pieces were each constructed using a current collector (24) in which the thickness of the copper foil was fixed at 7.8 μm and the thickness of the olefin resin was fixed at 3 μm, while the thickness of the aluminum foil was varied to 40 μm, 45 μm, and 50 μm. Multiple test pieces were constructed under the same conditions except for the thickness of the aluminum foil.

[0062] Table 1 shows the results of the thermal shock test. Table 1 shows the number of times the copper foil breaks for cases where the aluminum foil thickness is 40 μm, 45 μm, and 50 μm, as a ratio with the case where the aluminum foil thickness is 40 μm as the reference (1 time). The number of times the copper foil breaks is the number of thermal shocks (thermal cycles) until the copper foil breaks. The copper foil breaks faster than the aluminum foil. As shown in Table 1, increasing the thickness of the aluminum foil also increases the number of times the copper foil breaks. Based on these results, it was confirmed that the reinforcing effect of the aluminum foil on the copper foil is achieved.

[0063] Thickness of aluminum foil 40 ㎛ 45 ㎛ 50 ㎛ Number of times until copper foil fracture 1x 1.3 times 1.6 times

[0064] Since the thickness of the second metal foil (242) is less than 10 μm, the enlargement of the current collector (24) can be further suppressed. Even though the second metal foil (242) is thin, the second metal foil (242) can be reinforced by the first metal foil (241), so fatigue damage to the second metal foil (242) is suppressed.

[0065] The thickness of the adhesive layer (243) is less than or equal to half the thickness of the second metal foil (242). This makes it easier to obtain a reinforcing effect between the first metal foil (241) and the second metal foil (242). Therefore, fatigue damage to the second metal foil (242) can be further suppressed.

[0066] The Young's modulus of the adhesive layer (243) is higher than the Young's modulus of the seal member (4). As such, since the adhesive layer (243) is harder than the seal member (4), the Young's modulus of the adhesive layer (243) is lower than the Young's modulus of the seal member (4), and the deformation of the current collector (24) due to the expansion and contraction of the seal member (4) is suppressed compared to the configuration where the adhesive layer (243) is softer than the seal member (4). Therefore, fatigue damage to the first metal foil (241) and the second metal foil (242) can be suppressed.

[0067] The seal member (4) includes a seal portion (41) joined to the outer edge (24d) of the surface (24a) of the current collector (24) and a seal portion (42) joined to the outer edge (24e) of the surface (24b). Because of this, the tensile compressive stress imparted by the seal member (4) to the current collector (24) is increased compared to a configuration in which the seal member (4) includes either the seal portion (41) or the seal portion (42). Therefore, a configuration of the capacitor device (1) capable of reinforcing the first metal foil (241) and the second metal foil (242) is particularly effective.

[0068] The present disclosure is not limited to the embodiments described above.

[0069] In the embodiment, the current collectors (24) of the bipolar electrode (21), the positive terminal electrode (22), and the negative terminal electrode (23) all show the same example, but the current collectors (24) of the positive terminal electrode (22) and the negative terminal electrode (23) may differ from the current collector (24) of the bipolar electrode (21) in terms of material or thickness. The current collectors (24) of the positive terminal electrode (22) and the negative terminal electrode (23) may not be current collectors made of laminated foil, for example, but may be current collectors made of a single sheet of metal foil.

[0070] In the embodiment, the seal member (4) is shown as having an example including a seal portion (41), a seal portion (42), and a seal portion (43), but the seal member (4) only needs to include at least the seal portion (41) or the seal portion (42). That is, the seal member (4) only needs to be joined to at least the outer edge (24d) of the surface (24a) of the current collector (24) or the outer edge (24e) of the surface (24b).

[0071] In the embodiment, an example was shown in which the periphery of the separator (27) is located between the seal member (4) and the spacer (5), but the periphery of the separator (27) does not have to reach the spacer (5). The periphery of the separator (27) may be welded to the seal member (4).

[0072] In the embodiment, the first metal foil (241) and the second metal foil (242) are directly bonded to the adhesive layer (243), but they may also be bonded to the adhesive layer (243) via a carbon coating layer (not shown). That is, the current collector (24) may additionally include a carbon coating layer formed between the first metal foil (241) and the adhesive layer (243), and between the second metal foil (242) and the adhesive layer (243), respectively. The carbon coating layer is conductive. The carbon coating layer includes, for example, a binder and graphite. The carbon coating layer may be formed between the first metal foil (241) and the adhesive layer (243), and between the second metal foil (242) and the adhesive layer (243). In short, the carbon coating layer needs to be formed between the first metal foil (241) and the adhesive layer (243), and between the second metal foil (242) and the adhesive layer (243). With such a configuration, for example, compared to the case where the first metal foil (241) or the second metal foil (242) is directly adhered to the adhesive layer (243), the binder resin included in the carbon coating layer is strongly adhered by the adhesive layer (243), so 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) can be more reliably secured. Also, for example, even if a pinhole is formed in the first metal foil (241), the second metal foil (242), or the adhesive layer (243), the liquid connection between adjacent internal spaces (S) can be suppressed by the carbon coating layer. Additionally, the carbon coating layer may be additionally formed on the surface (24a) or surface (24b) of the current collector (24). In this case, the carbon coating layer is also interposed between the surface (24a) and the seal portion (41), or between the surface (24b) and the seal portion (42).

[0073] The inner edge (5d) of the spacer (5) may be positioned closer to the positive electrode active material layer (25) or the negative electrode active material layer (26) than the inner edge (41d) of the seal portion (41) and the inner edge (42d) of the seal portion (42), respectively, when viewed in the stacking direction (D). In short, when viewed in the stacking direction (D), the inner edge (5d) of the spacer (5) may be located between the inner edge (41d) of the positive electrode active material layer (25) and the seal portion (41), or between the inner edge (42d) of the negative electrode active material layer (26) and the seal portion (42). Explanation of the symbols

[0074] 1 : Energy storage device 2 : Laminate 3 : Bag type 4: Absence of time 21: Bipolar electrode 24 : Whole house 24a: Surface (1st circumference) 24b : Surface (secondary face) 24d : outer edge 24e : outer edge 25 : Positive electrode active material layer (1st active material layer) 26 : Negative electrode active material layer (second active material layer) 241: First metal foil 242 : Second metal foil 243 : Adhesive layer (conductive adhesive layer)

Claims

Claim 1 A capacitor device comprising a laminate including stacked bipolar electrodes and a sealing body encapsulating the laminate, wherein the bipolar electrode has a current collector including a first main surface and a second main surface opposite to the first main surface, a first active material layer formed on the first main surface, and a second active material layer formed on the second main surface, and the sealing body has a resin sealing member bonded to the outer edge of at least one side of the first main surface and the second main surface, and the current collector has a first metal foil including the first main surface, a second metal foil including the second main surface and thinner than the first metal foil, and a conductive adhesive layer formed between the first metal foil and the second metal foil and bonding the first metal foil and the second metal foil, wherein the conductive adhesive layer is thinner than the second metal foil, and the Young's modulus of the conductive adhesive layer is higher than the Young's modulus of the sealing member. A capacitor, wherein the thickness of the first metal foil is greater than twice the thickness of the second metal foil. Claim 2 A capacitor device comprising a laminate including stacked bipolar electrodes and a sealing body encapsulating the laminate, wherein the bipolar electrode has a current collector including a first main surface and a second main surface opposite to the first main surface, a first active material layer formed on the first main surface, and a second active material layer formed on the second main surface, and the sealing body has a resin sealing member bonded to the outer edge of at least one side of the first main surface and the second main surface, and the current collector has a first metal foil including the first main surface, a second metal foil including the second main surface and thinner than the first metal foil, and a conductive adhesive layer formed between the first metal foil and the second metal foil and bonding the first metal foil and the second metal foil, wherein the conductive adhesive layer is thinner than the second metal foil, and the Young's modulus of the conductive adhesive layer is higher than the Young's modulus of the sealing member. A capacitor device comprising a conductive adhesive layer, the olefin-based resin and an epoxy-based curing agent. Claim 3 A capacitor according to claim 1 or 2, wherein the thickness of the conductive adhesive layer is 1 / 2 or less of the thickness of the second metal foil. Claim 4 A capacitor device according to claim 1 or 2, wherein the thickness of the second metal foil is less than 10 μm. Claim 5 A capacitor according to claim 1 or 2, wherein the thickness of the conductive adhesive layer is 3 μm or less. Claim 6 A capacitor device according to claim 1 or 2, wherein the seal member is joined to the outer edge of each of the first main surface and the second main surface. Claim 7 A capacitor according to claim 1 or 2, wherein the current collector further has a side connecting the first main surface and the second main surface, and the seal member is formed on the side. Claim 8 A capacitor according to claim 1 or 2, wherein the heat resistance temperature of the conductive adhesive layer is higher than the melting point of the seal member. Claim 9 In claim 8, the capacitor device wherein the heat resistance temperature of the conductive adhesive layer is 150 degrees or higher. Claim 10 A capacitor according to claim 1 or 2, wherein the adhesive strength of the conductive adhesive layer heated to a heat-resistant temperature is 1% or more of the adhesive strength of the conductive adhesive layer at room temperature. Claim 11 A storage device according to claim 1 or 2, wherein the current collector has a rectangular shape with at least one side having a length of 1 m when viewed from the stacking direction of the laminate. Claim 12 A capacitor according to claim 1 or 2, wherein the thickness of the first metal foil is 40 μm or more and 150 μm or less. Claim 13 A capacitor device according to claim 1 or 2, wherein the conductive adhesive layer comprises conductive particles.

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