Current collector for bipolar battery and bipolar battery

Abstract

The present disclosure provides a current collector for a bipolar battery capable of improving battery performance, and a bipolar battery having such a current collector for a bipolar battery.SOLUTION: In the current collector 100 for a bipolar battery of the present disclosure, the first current collector 11 and the second current collector 12 are adhered to each other via the conductive adhesive layer 13, and the welded portion 10 in which the first current collector and the second current collector are welded to each other is provided over the peripheral portion of the current collector for a bipolar battery, whereby the conductive adhesive layer is sealed. The bipolar battery 1 of the present disclosure has the negative electrode active material layer 110, the current collector for a bipolar battery of the present disclosure, and the positive electrode active material layer 120 in this order.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a current collector for a bipolar battery and a bipolar battery. [Background technology]

[0002] As disclosed in Patent Documents 1 to 5, a current collector for a bipolar battery is known in which a positive electrode active material layer is formed on one surface and a negative electrode active material layer is formed on the other surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-075283 [Patent Document 2] International Publication No. 2023 / 218864 [Patent Document 3] International Publication No. 2024 / 053312 [Patent Document 4] Japanese Patent Publication No. 2023-092421 [Patent Document 5] Japanese Patent Application Publication No. 2023-110291 Summary of the Invention [Problem to be solved by the invention]

[0004] A current collector for a bipolar battery may be composed of a first current collector and a second current collector bonded to each other via a conductive adhesive layer. In a battery using such a current collector for a bipolar battery, there is room for improvement in terms of battery performance.

[0005] An object of the present disclosure is to provide a current collector for a bipolar battery that can improve battery performance, and a bipolar battery having such a current collector for a bipolar battery. [Means for solving the problem]

[0006] The present inventors have found that the above problems can be solved by the following means. <Aspect 1> A current collector for a bipolar battery, the first current collector and the second current collector are bonded to each other via a conductive adhesive layer; a welded portion at which the first current collector and the second current collector are welded to each other around the periphery of the bipolar battery current collector, thereby sealing the conductive adhesive layer; Current collector for bipolar batteries. <Aspect 2> 2. The bipolar battery current collector of claim 1, wherein the conductive adhesive layer comprises a water-based adhesive. <Aspect 3> 3. The current collector for a bipolar battery according to claim 1, wherein the width of the weld is 1 mm or more and 10 mm or less. <Aspect 4> 4. The current collector for a bipolar battery according to any one of aspects 1 to 3, further comprising a sealing member that seals the welded portion. <Aspect 5> A bipolar battery comprising, in this order, a negative electrode active material layer, the bipolar battery current collector according to any one of Aspects 1 to 4, and a positive electrode active material layer. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a current collector for a bipolar battery that can improve battery performance, and a bipolar battery having such a current collector for a bipolar battery. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a current collector for a bipolar battery according to the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of a current collector for a bipolar battery according to the present disclosure. [Figure 3] FIG. 3 is a schematic cross-sectional view showing an example of a bipolar battery of the present disclosure. [Figure 4]FIG. 4 is a schematic cross-sectional view showing an example of a current collector for a bipolar battery according to the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present disclosure.

[0010] <Current collector for bipolar batteries> In the bipolar battery current collector of the present disclosure, the first current collector and the second current collector are bonded to each other via a conductive adhesive layer, and the bipolar battery current collector has a welded portion where the first current collector and the second current collector are welded to each other around the periphery, thereby sealing the conductive adhesive layer.

[0011] The present inventors have believed that one of the causes of deterioration in battery performance in a bipolar battery current collector composed of a first current collector and a second current collector bonded to each other via a conductive adhesive layer is moisture contained in the conductive adhesive layer. Specifically, without intending to be bound by any theory, this is presumed as follows. That is, in a bipolar battery current collector 200 according to the prior art as illustrated in FIG. 4, moisture remaining in the conductive adhesive layer 23 even after the manufacturing process is gradually released from the edge of the conductive adhesive layer 23, which is believed to result in deterioration in battery performance.

[0012] In this regard, the present inventors have discovered that by providing a welded portion where the first current collector and the second current collector are welded to each other around the periphery of the current collector for a bipolar battery, thereby sealing the conductive adhesive layer, it is possible to prevent moisture remaining in the conductive adhesive layer even after the manufacturing process from being released from the edge of the conductive adhesive layer, thereby improving battery performance.

[0013] Hereinafter, elements constituting the current collector for a bipolar battery of the present disclosure will be described with reference to the drawings. Note that the dimensional relationships in the drawings do not reflect the actual dimensional relationships.

[0014] <First current collector and second current collector> As illustrated in FIG. 1, in the bipolar battery current collector 100 of the present disclosure, a first current collector 11 and a second current collector 12 are bonded to each other via a conductive adhesive layer 13, thereby functioning as a current collector for a bipolar battery.

[0015] The first and second current collectors are not particularly limited. For example, when a battery using the bipolar battery current collector of the present disclosure is a lithium-ion secondary battery, the first and second current collectors may be copper foil, copper alloy foil, nickel foil, aluminum foil, aluminum alloy foil, stainless steel foil, carbon sheet, or the like. In particular, the first and second current collectors may be different. That is, for example, when a negative electrode active material layer and a positive electrode active material layer are disposed on the surfaces of the first and second current collectors opposite to the surfaces bonded by the conductive adhesive layer, the first current collector may be copper foil, and the second current collector may be aluminum foil.

[0016] The thickness of the first and second current collectors is not particularly limited as long as the thickness is such that the current collectors can be welded to each other.

[0017] The shape and size of the first and second current collectors are not particularly limited as long as they allow the formation of a welded portion, which will be described later, around the periphery of the current collector for a bipolar battery.

[0018] <Conductive adhesive layer> 1, the conductive adhesive layer 13 is interposed between the first current collector 11 and the second current collector 12, and bonds the first current collector 11 and the second current collector 12. The first and second current collectors bonded in this manner function as current collectors for the bipolar battery.

[0019] The material of the conductive adhesive layer is not particularly limited. The conductive adhesive layer may be made of a conductive adhesive, that is, for example, a mixture of an adhesive and a conductive component.

[0020] The adhesive may contain a curable resin. Examples of the curable resin include a thermosetting resin and a photocurable resin. More specifically, examples of the curable resin include an olefin-based resin and an acrylic-based resin.

[0021] The conductive adhesive layer 13 may contain a water-based adhesive as the adhesive. When the adhesive in the conductive adhesive layer 13 is a water-based adhesive, moisture is likely to remain in the conductive adhesive layer after the manufacturing process, and therefore, application of the water-based adhesive to the bipolar battery current collector of the present disclosure is more advantageous. Examples of water-based adhesives include, but are not limited to, water-based curable resins. Examples of water-based curable resins include water-dispersible olefin resins.

[0022] The conductive component is not particularly limited as long as it has a higher conductivity than the adhesive, and examples thereof include metal particles such as gold, silver, platinum, zinc, stainless steel, nickel, copper, cobalt, molybdenum, antimony, iron, and chromium; alloy particles such as aluminum-magnesium alloys and aluminum-nickel alloys; metal oxide particles such as tin oxide and indium oxide; particles in which metal particles such as nickel are coated with precious metals such as gold, silver, and platinum; particles in which non-conductive particles such as glass, ceramic, and plastic are coated with precious metals such as gold, silver, and platinum, or particles in which non-conductive particles such as plastic are plated with metals such as nickel; graphites such as natural graphite and artificial graphite; and carbon particles such as carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black.

[0023] The thickness of the conductive adhesive layer is not particularly limited.

[0024] The size of the conductive adhesive layer is not particularly limited as long as it is smaller than the first and second current collectors and allows for the formation of welds, which will be described later.

[0025] <Welded parts> 1 , the bipolar battery current collector 100 of the present disclosure has a weld 10 where a first current collector 11 and a second current collector 12 are welded to each other around the periphery of the bipolar battery current collector 100, thereby sealing the conductive adhesive layer 13. In the context of the present disclosure, the "periphery of the bipolar battery current collector" may particularly refer to the portions of the first and second current collectors that extend beyond the conductive adhesive layer.

[0026] The width of the weld may be 1 mm or more and 10 mm or less. The width of the weld may be 1 mm or more, 3 mm or more, 4 mm or more, or 5 mm or more, and may be 10 mm or less, 8 mm or less, 6 mm or less, or 5 mm or less. When the width of the weld is within the above range, the weld can be formed without impairing the volumetric efficiency of the battery. In the context of the present disclosure, the "width of the weld" may refer to the shortest length from the inside to the outside of the bipolar battery current collector.

[0027] The method for forming the welded portion is not particularly limited, and any conventionally known welding method can be used, such as ultrasonic welding.

[0028] The method for producing the current collector for a bipolar battery of the present disclosure is not particularly limited. The current collector for a bipolar battery of the present disclosure can be produced, for example, by the following method: First, a dry laminator is used to bond the first current collector and the second current collector together with a conductive adhesive, and then the first current collector and the second current collector are ultrasonically welded together along the periphery of the bipolar battery current collector.

[0029] <Sealing material> 2, the bipolar battery current collector 100 of the present disclosure may further include a sealing member 14 that seals the welded portion 10. With this configuration, for example, in cases where the conductive adhesive layer 13 is not properly sealed by the welded portion 10, the sealing member 14 can prevent moisture from being released from the conductive adhesive layer 13.

[0030] Although FIG. 2 illustrates an embodiment in which the sealing member 14 is formed only on one end of the bipolar battery current collector 100, as exemplified in FIG. 3, which shows an example of a bipolar battery according to the present disclosure, sealing members may be formed on both ends of the bipolar battery current collector, as will be described later.

[0031] The shape of the sealing member is not particularly limited. For example, as illustrated in Fig. 2, it may have a shape that covers the side surface and part of the surface of the bipolar battery current collector 100. Furthermore, for example, Fig. 3 illustrates an embodiment in which multiple sealing members are spaced apart from each other in the stacking direction, but in the bipolar battery of the present disclosure, the sealing members may be connected to each other in the stacking direction.

[0032] The material of the sealing member is not particularly limited, but may be, for example, a resin. Examples of resins include thermoplastic resins. When the sealing member is made of a thermoplastic resin, the sealing member can be formed by welding the thermoplastic resin to a bipolar battery current collector. Examples of thermoplastic resins include acid-modified polyethylene, acid-modified polypropylene, polyethylene, and polypropylene.

[0033] Bipolar battery The bipolar battery of the present disclosure has, in this order, a negative electrode active material layer, a bipolar battery current collector of the present disclosure, and a positive electrode active material layer.

[0034] In the bipolar battery of the present disclosure, the first current collector and the second current collector are welded to each other along the periphery of the bipolar battery current collector, thereby sealing the conductive adhesive layer, which can suppress the release of moisture from the edge of the conductive adhesive layer, thereby improving battery performance.

[0035] In the present disclosure, a laminate composed of a first electrode active material layer, a bipolar battery current collector of the present disclosure, and a second electrode active material layer may be referred to as a "bipolar electrode laminate."

[0036] In addition to the bipolar electrode stack, the bipolar battery of the present disclosure may further include an electrolyte layer.

[0037] 3, the bipolar battery 1 of the present disclosure may be configured by stacking a plurality of bipolar electrode stacks and electrolyte layers 130. The number of bipolar electrode stacks and electrolyte layers is not particularly limited.

[0038] The bipolar battery of the present disclosure may be a secondary battery, and in particular a lithium-ion secondary battery.

[0039] The bipolar battery of the present disclosure may be a liquid-based battery or a solid-state battery. In the context of the present disclosure, a "solid-state battery" refers to a battery that uses at least a solid electrolyte as an electrolyte. Therefore, a solid-state battery may use a combination of a solid electrolyte and a liquid electrolyte as an electrolyte. Alternatively, the solid-state battery of the present disclosure may be an all-solid-state battery, i.e., a battery that uses only a solid electrolyte as an electrolyte.

[0040] The elements that make up the bipolar battery of the present disclosure will be described below.

[0041] <Negative Electrode Active Material Layer and Positive Electrode Active Material Layer> In the bipolar battery 1 of the present disclosure, the anode active material layer 110, the bipolar battery current collector 100 of the present disclosure, and the cathode active material layer 120 are arranged in this order. As illustrated in Fig. 3 , the anode active material layer 110 may be arranged on the first current collector 11 side of the bipolar battery current collector 100, and the cathode active material layer 120 may be arranged on the second current collector 12 side of the bipolar battery current collector 100.

[0042] The negative electrode active material layer may be formed from a negative electrode mixture containing a negative electrode active material and optionally containing a conductive additive, a binder, etc., and the positive electrode active material layer may be formed from a positive electrode mixture containing a positive electrode active material and optionally containing a conductive additive, a binder, etc.

[0043] In the present disclosure, a "composite" refers to a composition that can constitute an electrode active material layer either as is or by further containing other components. Also, in the present disclosure, a "composite slurry" refers to a slurry that contains a "composite" and a dispersion medium and that can be applied and dried to form an electrode active material layer.

[0044] (Negative electrode active material) The negative electrode active material is not particularly limited as long as it has a lower potential than the positive electrode active material. When the bipolar battery of the present disclosure is a lithium ion secondary battery, examples of the negative electrode active material include carbonaceous materials such as graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon; metal-based materials mainly composed of tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, and aluminum alloys; conductive polymers such as polyacene, polyacetylene, and polypyrrole; metallic lithium; and Li4Ti5O 12 and lithium alloys such as Li-Si alloys, Li-Sn alloys, Li-Al alloys, Li-Ga alloys, Li-Mg alloys, and Li-In alloys. These negative electrode active materials may be used singly or in combination of two or more.

[0045] The content of the negative electrode active material in the negative electrode mixture is not particularly limited, but may be 50 mass % or more, 70 mass % or more, 90 mass % or more, or 95 mass % or more.

[0046] The negative electrode active material may be in the form of particles, for example.

[0047] (Cathode active material) The positive electrode active material is not particularly limited as long as it has a more noble potential than the negative electrode active material. When the bipolar battery of the present disclosure is a lithium ion secondary battery, the positive electrode active material may be, for example, lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), lithium manganese oxide (LiMnO), solid solution oxide (LiMnO-LiMO (M=Co, Ni, etc.)), lithium nickel manganese oxide (LiNi 1 / 2 Mn 1 / 2 O2), lithium nickel cobalt manganese oxide (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 Examples of the cathode active materials that can be used include composite oxides such as lithium phosphate oxide (LiFePO4), olivine-type lithium phosphate oxide (LiFePO4), and conductive polymers such as polyaniline and polypyrrole; sulfide-based cathode active materials such as LiS, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, Li-Mo-S compounds, Li-Ti-S compounds, and Li-VS compounds; and sulfur-based active materials such as sulfur-impregnated acetylene black, sulfur-impregnated porous carbon, and mixed powders of sulfur and carbon. These cathode active materials may be used alone or in combination of two or more.

[0048] The content of the positive electrode active material in the positive electrode mixture is not particularly limited, but may be 50 mass % or more, 70 mass % or more, 90 mass % or more, or 95 mass % or more.

[0049] The positive electrode active material may be in the form of particles, for example.

[0050] (Conductive additive) The conductive additive is not particularly limited, but when the bipolar battery of the present disclosure is a lithium ion secondary battery, examples include graphites such as natural graphite and artificial graphite; carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; carbon fibers such as carbon nanotubes, conductive fibers such as metal fibers; metal powders such as aluminum powder; conductive whiskers such as zinc oxide whiskers and conductive potassium titanate whiskers; conductive metal oxides such as titanium oxide; organic conductive materials such as phenylene derivatives; etc. These conductive additives may be used alone or in combination of two or more.

[0051] The content of the conductive additive in the negative electrode mixture and the positive electrode mixture is not particularly limited and can be set appropriately depending on the desired conductivity and the like.

[0052] (binder) The binder is not particularly limited, but when the bipolar battery of the present disclosure is a lithium ion secondary battery, examples of the binder include polyvinylidene fluoride (PVdF), polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, polyhexafluoropropylene, styrene-butadiene rubber, carboxymethyl cellulose, etc. These binders may be used alone or in combination of two or more.

[0053] The content of the conductive additive in the negative electrode mixture and the positive electrode mixture is not particularly limited, and can be set appropriately depending on the desired binding properties, etc.

[0054] In accordance with the present disclosure, a bipolar electrode stack can be manufactured, for example, by the following method: A solvent is added to and mixed with an anode (or cathode) composite to prepare an anode (or cathode) composite slurry, and the slurry is applied to one side of a bipolar battery current collector using an applicator or the like, followed by drying to form an anode (or cathode) active material layer; A solvent is added to and mixed with a positive electrode (or negative electrode) composite to prepare a positive electrode (or negative electrode) composite slurry, and the slurry is applied to the other side of a bipolar battery current collector using an applicator or the like, followed by drying to form a positive electrode (or negative electrode) active material layer, thereby obtaining a laminate; The resulting laminate is pressed by a roll press or the like while applying a predetermined load.

[0055] <Electrolyte layer> The electrolyte layer 130 may be disposed between the negative electrode active material layer 110 and the positive electrode active material layer 120 .

[0056] The electrolyte layer may be a porous separator impregnated with a non-aqueous electrolyte solution, a solid electrolyte layer containing a solid electrolyte, or a combination thereof.

[0057] The porous separator is not particularly limited as long as it electrically insulates the negative electrode active material layer from the positive electrode active material layer and, when the bipolar battery of the present disclosure is a lithium ion secondary battery, allows lithium ions to pass through. For example, a porous membrane can be used as the porous separator. Examples of the porous membrane include microporous polymer films, and examples of materials for the porous membrane include polyolefin, polyimide, polyvinylidene fluoride, and polyester.

[0058] A non-aqueous electrolyte is a solution of an electrolyte dissolved in a solvent. Any known lithium salt can be used as the electrolyte, and the electrolyte can be selected depending on the type of active material. For example, LiClO4, LiBF4, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl 10, LiAlCl4, LiCl, LiBr, LiB(C2H5)4, CF3SO3Li, CH3SO3Li, LiCF3SO3, LiC4F9SO3, Li(CF3SO2)2N, lithium carboxylates of lower fatty acids, etc.

[0059] The solvent for dissolving the electrolyte is not particularly limited as long as it is a liquid that is commonly used to dissolve electrolytes, and examples thereof include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; Examples of suitable organic solvents include sulfoxides such as methyl sulfoxide, oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane, nitrogen-containing compounds such as acetonitrile, nitromethane, formamide, and dimethylformamide, organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and ethyl propionate, phosphate triesters and diglymes, triglymes, sulfolanes such as sulfolane and methyl sulfolane, oxazolidinones such as 3-methyl-2-oxazolidinone, and sultones such as 1,3-propane sultone, 1,4-butane sultone, and naphthasultone. These may be used alone or in combination of two or more.

[0060] The solid electrolyte constituting the solid electrolyte layer is not particularly limited, and when the bipolar battery of the present disclosure is a lithium ion secondary battery, examples thereof include inorganic solid electrolytes such as sulfide-based solid electrolytes, oxide-based solid electrolytes, and other lithium-based inorganic solid electrolytes; and organic solid electrolytes such as polymer electrolytes.

[0061] Examples of sulfide-based solid electrolytes include, for example, Li2S-P2S5, Li2S-SiS2, Li2S-GeS2, Li2S-Al2S3, Li2S-SiS2-Li3PO4, Li2S-P2S5-GeS2, Li2S-Li2O-P2S5-SiS2, Li2S-GeS2-P2S5-SiS2, Li2S-SnS2-P2S5-SiS2, and the like. These may be used alone or in combination of two or more.

[0062] Examples of oxide-based solid electrolytes include NASICON types such as LiTi2(PO4)3, LiZr2(PO4)3, LiGe2(PO4)3, and perovskite types such as (La 0.5+x Li 0.5-3x )TiO3, and the like.

[0063] Examples of other lithium-based inorganic solid electrolytes include, for example, LiPON, LiNbO3, LiTaO3, Li3PO4, LiPO 4-x N x (where x is 0 < x ≦ 1), LiN, LiI, LISICON, and the like.

[0064] Furthermore, glass ceramics obtained by precipitating crystals of these inorganic solid electrolytes can also be used as solid electrolytes.

[0065] Examples of organic-based solid electrolytes include, for example, polymer electrolytes such as dry polymer electrolytes and gel electrolytes. As the polymer electrolyte, those generally used in lithium-ion secondary batteries can be used.

[0066] The shape of the solid electrolyte may be, for example, particulate.

Examples

[0067] 《Examples》 〈Manufacture of current collector for bipolar battery〉 (Lamination of current collectors) A copper foil serving as a first current collector and an aluminum foil serving as a second current collector were bonded together using a dry laminator. More specifically, a conductive adhesive was applied to the aluminum foil so that the film thickness after drying would be 3 μm, and the aluminum foil and copper foil were bonded together using a hot roll press. The conductive adhesive used was a water-dispersible olefin resin (NZ-1015, manufactured by Toyobo MC Co., Ltd.) with nickel-plated particles dispersed therein. This resulted in a first current collector and a second current collector bonded together via a conductive adhesive layer. The dry lamination conditions were as follows: Line speed: 15m / min Gravure roll: elongated, 75 lines ·Drying oven temperature: 110℃ ·Drying time: 40 seconds Heat roll temperature: 90℃ Heat roll nip pressure: 0.4MPa

[0068] (Welding of current collector) The first and second current collectors, bonded to each other via a conductive adhesive layer, were cut into a rectangular shape in plan view, and the peripheral edges of the current collectors were ultrasonically welded to form a weld. The weld was formed so as to include the edge of the current collector, and the width of the weld was approximately 5 mm. This resulted in the bipolar battery current collector of the example.

[0069] Comparative Example A current collector for a bipolar battery of Comparative Example was obtained in the same manner as in Example, except that welding of the current collector was not performed.

[0070] "evaluation" The obtained bipolar battery current collector was heated to 150°C, and the amount of moisture generated during heating was measured using a Karl Fischer moisture meter. When the moisture content of the bipolar battery current collector of the Comparative Example was taken as 100, the moisture content of the bipolar battery current collector of the Example was 5, which was significantly smaller. [Explanation of symbols]

[0071] 1. Bipolar battery 10 Welded parts 11, 21 First current collector 12, 22 Second current collector 13, 23 Conductive adhesive layer 14 Sealing material 100, 200 Bipolar battery current collector 110 Negative electrode active material layer 120 Cathode active material layer 130 Electrolyte layer

Claims

1. A current collector for a bipolar battery, the first current collector and the second current collector are bonded to each other via a conductive adhesive layer; a welded portion at which the first current collector and the second current collector are welded to each other around the periphery of the bipolar battery current collector, thereby sealing the conductive adhesive layer; Current collector for bipolar batteries.

2. 10. The current collector for a bipolar battery according to claim 1, wherein the conductive adhesive layer comprises a water-based adhesive.

3. 2. The current collector for a bipolar battery according to claim 1, wherein the width of the welded portion is 1 mm or more and 10 mm or less.

4. 2. The current collector for a bipolar battery according to claim 1, further comprising a seal member sealing the welded portion.

5. A bipolar battery comprising, in this order, a negative electrode active material layer, the current collector for a bipolar battery according to any one of claims 1 to 4, and a positive electrode active material layer.

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