Method for manufacturing power storage device

Abstract

This method for manufacturing a power storage device includes an electrode forming process. The electrode forming process includes a bonding step, a winding step, a corona discharge step, a carbon coat layer forming step, and an active material layer forming step. The bonding step is for bonding a rolled aluminum foil and an electrolytic copper foil to form a laminate having an aluminum surface composed of the rolled aluminum foil and a copper surface composed of the electrolytic copper foil. The winding step is for forming a roll body by winding the laminate in the form of a roll. The corona discharge step is for performing corona discharge processing on the copper surface of the laminate unwound from the roll body. The carbon coat layer forming step is for forming a carbon coat layer on the copper surface after the corona discharge step.

Description

Method for manufacturing an electricity storage device

[0001] The present invention relates to a method for manufacturing an electricity storage device.

[0002] In recent years, research has been conducted on energy storage devices using bipolar electrodes. The bipolar electrode includes a bipolar current collector having a positive electrode current collector and a negative electrode current collector, a positive electrode active material layer provided on the surface of the positive electrode current collector, and a negative electrode active material layer provided on the surface of the negative electrode current collector. Energy storage devices using bipolar electrodes are expected to be superior to other energy storage devices in terms of improved volumetric energy density and output.

[0003] Patent Document 1 discloses a bipolar electrode using a clad material formed by rolling aluminum foil and copper foil as a bipolar current collector. In the bipolar current collector of Patent Document 1, an aluminum layer formed by rolling aluminum foil serves as a positive electrode current collector, and a copper layer formed by rolling copper foil serves as a negative electrode current collector.

[0004] Japanese Patent Application Publication No. 08-007926

[0005] From the viewpoint of reducing the weight of a power storage device using a bipolar electrode and improving the volumetric energy density, it is preferable to form a thin bipolar current collector. One possible method for thinning the bipolar current collector is to bond a rolled aluminum foil to an electrolytic copper foil. However, a bipolar current collector having a structure in which a rolled aluminum foil and an electrolytic copper foil are bonded together has a problem in that it has low adhesion to the sealing resin that bonds the bipolar current collector in the power storage device.

[0006] a carbon coating layer forming step of forming an active material layer on a portion of the aluminum surface and a portion of the copper surface, and the adhering step includes adhering the sealing resin to the bipolar electrode. The adhering step includes a laminating step of laminating a rolled aluminum foil and an electrolytic copper foil to form a laminate having an aluminum surface constituted by the rolled aluminum foil and a copper surface constituted by the electrolytic copper foil; a winding step of winding the laminate into a roll to form a roll body; a corona discharging step of performing a corona discharge treatment on the copper surface of the laminate unwound from the roll body; a carbon coating layer forming step of forming a carbon coating layer on the copper surface after the corona discharging step; and an active material layer forming step of forming an active material layer on each of a portion of the aluminum surface and a portion of the copper surface after the carbon coating layer forming step. The adhering step includes adhering the sealing resin to portions of the copper surface where the active material layer is not formed and where the carbon coating layer is formed.

[0007] According to the above configuration, the rolling oil transferred to the electrolytic copper foil in the winding process is removed by the corona discharge treatment, thereby suppressing a decrease in the adhesive strength of the copper surface due to the rolling oil. Furthermore, the formation of a carbon coating layer on the copper surface ensures the adhesion of the carbon coating layer to the sealing resin even after prolonged exposure to a high-temperature environment in the electrode formation process. Therefore, the adhesion of the electrolytic copper foil surface to the sealing resin is improved.

[0008] In the method for manufacturing an electricity storage device, it is preferable that the corona discharge step and the carbon coating layer forming step are performed consecutively. This configuration can suppress the decrease of hydrophilic functional groups generated by the corona discharge step, and as a result, the carbon coating layer can be firmly bonded to the laminate.

[0009] In the method for producing an electricity storage device, the corona discharge step and the carbon coating layer forming step are preferably performed on both the aluminum surface and the copper surface of the laminate.

[0010] According to the above-mentioned configuration, the aluminum foil surface can be prevented from suffering from a decrease in adhesive strength due to rolling oil and from being exposed to a high-temperature environment for a long period of time, as in the case of the electrolytic copper foil surface, thereby improving the adhesiveness to the sealing resin on both the electrolytic copper foil surface and the aluminum foil surface.

[0011] In the method for manufacturing an electricity storage device, the sealing resin is preferably an acid-modified polyolefin resin. In the method for manufacturing an electricity storage device, the bipolar electrode preferably includes a bipolar current collector formed by stacking an aluminum current collector made of the rolled aluminum foil and a copper current collector made of the electrolytic copper foil, a positive electrode active material layer provided on a surface of the aluminum current collector of the bipolar current collector, and a negative electrode active material layer provided on a surface of the copper current collector of the bipolar current collector. In the method for manufacturing an electricity storage device, the electricity storage device preferably includes a plurality of bipolar electrodes arranged so that the positive electrode active material layer and the negative electrode active material layer face each other, a separator arranged between the bipolar electrodes adjacent in the stacking direction, and a sealing resin arranged between the bipolar electrodes adjacent in the stacking direction so as to surround the positive electrode active material layer and the negative electrode active material layer and adhered to the bipolar current collector to form an enclosed space for containing a liquid electrolyte between the bipolar electrodes.

[0012] According to the present invention, it is possible to improve the adhesion of a bipolar electrode having a bipolar current collector made of rolled aluminum foil and electrolytic copper foil to a sealing resin.

[0013] Fig. 1 is a cross-sectional view of an electricity storage device. Fig. 2 is a cross-sectional view of a bipolar electrode. Fig. 3 is an explanatory diagram of a bonding step. Fig. 4 is an explanatory diagram of a first carbon coat forming step. Fig. 5 is an explanatory diagram of a second carbon coat forming step. Fig. 6 is a graph showing the analysis results by X-ray photoelectron spectroscopy.

[0014] An embodiment of the present invention will now be described with reference to the drawings. First, a description will be given of a power storage device 20 manufactured by the manufacturing method of this embodiment. <Power Storage Device> The power storage device 20 is, for example, a lithium ion secondary battery. The power storage device 20 is, for example, a power storage module used in batteries for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 20 may also be an electric double layer capacitor.

[0015] 1, the power storage device 20 includes a laminate 21, a sealing resin 22, and an electrolyte solution L. The laminate 21 has a plurality of bipolar electrodes 23, a positive terminal electrode 24, a negative terminal electrode 25, and a plurality of separators 26.

[0016] (Bipolar Electrode) As shown in FIG. 2 , the bipolar electrode 23 includes a bipolar current collector 30 , a positive electrode active material layer 31 , and a negative electrode active material layer 32 .

[0017] [Bipolar Current Collector] The bipolar current collector 30 is a chemically inactive electrical conductor that continues to pass current through the positive electrode active material layer 31 and the negative electrode active material layer 32 during discharge or charge of the electricity storage device 20. The bipolar current collector 30 has a first main surface 30a and a second main surface 30b. The first main surface 30a and the second main surface 30b are surfaces perpendicular to the thickness direction of the bipolar current collector 30. The second main surface 30b is located opposite the first main surface 30a in the thickness direction of the bipolar current collector 30. A plan view described below means a view in the thickness direction of the bipolar current collector 30.

[0018] The bipolar current collector 30 is a laminate formed by integrally bonding a sheet-shaped positive electrode current collector 33 and a sheet-shaped negative electrode current collector 34 together in the thickness direction. One example of the bipolar current collector 30 has an adhesive layer (not shown) located between the positive electrode current collector 33 and the negative electrode current collector 34, bonding the positive electrode current collector 33 and the negative electrode current collector 34 together.

[0019] The adhesive layer is conductive and electrically connects the positive electrode current collector 33 and the negative electrode current collector 34. The adhesive layer includes, for example, an adhesive component and a conductive component dispersed in the adhesive component. Examples of the adhesive component include polyolefin-based resins such as polypropylene and polyethylene. The adhesive component may be a single type or a combination of two or more types. The adhesive component may include a curing agent such as an isocyanate-based curing agent or an epoxy-based curing agent. An example of the adhesive component includes a polyolefin-based resin and an epoxy-based curing agent. In this case, gas generation associated with the curing reaction can be suppressed. Examples of the conductive component include conductive particles and conductive fillers. Examples of the conductive particles include metal particles such as aluminum particles, nickel particles, SUS particles, silver particles, gold particles, copper particles, titanium particles, and alloy particles, and carbon particles such as graphite particles. The conductive particles may also be spherical particles having a metal coating formed on the surface of a core particle such as a resin or ceramic. Examples of the conductive filler include carbon nanotubes. The conductive component may be one type or a combination of two or more types. The adhesive component may also be an adhesive component having electrical conductivity. Examples of adhesive components having electrical conductivity include conductive polymer materials. When the adhesive component has electrical conductivity, the conductive component dispersed in the adhesive component may be omitted.

[0020] A first main surface 30a of the bipolar current collector 30 is formed by a positive electrode current collector 33. A second main surface 30b of the bipolar current collector 30 is formed by a negative electrode current collector 34. The bipolar current collector 30 has, for example, a rectangular shape in a plan view. Note that the bipolar current collector 30 is illustrated in a simplified form in FIG. 1 .

[0021] The positive electrode current collector 33 is a chemically inactive electrical conductor that allows current to continue to flow through the positive electrode active material layer 31 during discharging or charging of the power storage device 20. The positive electrode current collector 33 is an aluminum current collector made of rolled aluminum foil. The thickness of the rolled aluminum foil that makes up the positive electrode current collector 33 is, for example, 10 μm or more and 200 μm or less.

[0022] The negative electrode current collector 34 is a chemically inactive electrical conductor that allows current to continue to flow through the negative electrode active material layer 32 during discharging or charging of the power storage device 20. The negative electrode current collector 34 is a copper current collector made of electrolytic copper foil. The thickness of the electrolytic copper foil that constitutes the negative electrode current collector 34 is, for example, 1 μm or more and 20 μm or less.

[0023] A carbon coating layer C1 is provided on the surface of the positive electrode current collector 33, which is the first main surface 30a of the bipolar current collector 30. The carbon coating layer C1 is provided on the entire first main surface 30a. Therefore, the first main surface 30a is bonded to a sealing resin 22, which will be described later.

[0024] A carbon coating layer C2 is provided on the surface of the negative electrode current collector 34, which is the second main surface 30b of the bipolar current collector 30. The carbon coating layer C2 is provided on the entire second main surface 30b. Therefore, the second main surface 30b is bonded to a sealing resin 22, which will be described later.

[0025] Each of the carbon coating layers C1 and C2 contains carbon particles and a coating layer binder. Details of the carbon particles and the coating layer binder will be described later in the description of the manufacturing method of the bipolar current collector 30.

[0026] The thickness of each of the carbon coating layers C1 and C2 is, for example, 0.1 μm or more and 5 μm or less, and preferably 0.5 μm or more and 2 μm or less. The basis weight of each of the carbon coating layers C1 and C2 is, for example, 0.2 g / m ２ 1.0g / m or more ２ The thickness is preferably 0.6 μm or more and 1.8 μm or less.

[0027] The carbon coating layers C1 and C2 may all have the same composition, thickness, and basis weight, or one or all of them may be different. [Positive Electrode Active Material Layer] The positive electrode active material layer 31 is provided on the first main surface 30a of the bipolar current collector 30 via the carbon coating layer C1. The positive electrode active material layer 31 contains a positive electrode active material that can absorb and release charge carriers such as lithium ions. Examples of the positive electrode active material include olivine-type lithium iron phosphate (LiFePO ４Examples of the positive electrode active material include polyanion compounds such as lithium ion secondary batteries, lithium composite metal oxides having a layered rock salt structure, and metal oxides having a spinel structure. The positive electrode active material used is one that can be used as a positive electrode active material for power storage devices such as lithium ion secondary batteries.

[0028] The positive electrode active material layer 31 may contain other components, such as a conductive additive for increasing electrical conductivity, a binder, an electrolyte (polymer matrix, ion-conductive polymer, liquid electrolyte, etc.), an electrolyte supporting salt (lithium salt) for increasing ion conductivity, etc. The types of other components contained in the positive electrode active material layer 31 and their blending ratios are not particularly limited.

[0029] The thickness of the positive electrode active material layer 31 is, for example, 2 to 150 μm. The positive electrode active material layer 31 has, for example, a rectangular shape in a plan view. The outer shape of the positive electrode active material layer 31 is slightly smaller than the outer shape of the bipolar current collector 30. As shown in FIG. 1 , the first main surface 30a of the bipolar current collector 30 includes a first uncoated region 30c. The first uncoated region 30c is a region where the positive electrode active material layer 31 is not provided. The first uncoated region 30c is located in the peripheral portion of the first main surface 30a.

[0030] [Negative Electrode Active Material Layer] The negative electrode active material layer 32 is provided on the second main surface 30b of the bipolar current collector 30 via a carbon coating layer C2. The negative electrode active material layer 32 includes a negative electrode active material capable of absorbing and releasing charge carriers such as lithium ions. The negative electrode active material can be any element, alloy, or compound capable of absorbing and releasing charge carriers such as lithium ions. Examples of the negative electrode active material include Li, carbon, metal compounds, elements or compounds thereof that can be alloyed with lithium, etc. Examples of carbon include natural graphite, artificial graphite, hard carbon (non-graphitizable carbon), and soft carbon (easily graphitizable carbon). Examples of artificial graphite include highly oriented graphite and mesocarbon microbeads. Examples of elements that can be alloyed with lithium include silicon and tin.

[0031] The negative electrode active material layer 32 may contain other components, such as a conductive additive for increasing electrical conductivity, a binder, an electrolyte (polymer matrix, ion-conductive polymer, liquid electrolyte, etc.), an electrolyte supporting salt (lithium salt) for increasing ion conductivity, etc. The types and blending ratios of the other components contained in the negative electrode active material layer 32 are not particularly limited.

[0032] The thickness of the negative electrode active material layer 32 is, for example, 2 to 150 μm. The negative electrode active material layer 32 is, for example, rectangular in plan view. The outer shape of the negative electrode active material layer 32 is slightly smaller than the outer shape of the bipolar current collector 30. As shown in FIG. 1 , the second main surface 30b of the bipolar current collector 30 includes a second uncoated region 30d. The second uncoated region 30d is a region where the negative electrode active material layer 32 is not provided. The second uncoated region 30d is located in the peripheral portion of the second main surface 30b.

[0033] (Sealing Resin Material) The sealing resin 22 is made of an acid-modified polyolefin resin. Examples of acid-modified polyolefin resins include acid-modified polyethylene, acid-modified polypropylene, acid-modified isoprene, and acid-modified polybutene. Examples of acid-modified groups include carboxylic acid groups, maleic acid groups, and maleic anhydride groups. The acid-modified polyolefin resins constituting the sealing resin 22 may be one type or a combination of two or more types. The acid-modified polyolefin resins constituting the sealing resin 22 may be a thermoplastic resin or a thermosetting resin.

[0034] As shown in FIG. 1 , the sealing resin 22 includes a plurality of first sealing resins 27 and one second sealing resin 28. The first sealing resin 27 has a rectangular frame shape. The first sealing resin 27 has a first sealing surface 27a and a second sealing surface 27b. The first sealing surface 27a and the second sealing surface 27b are surfaces perpendicular to the thickness direction of the first sealing resin 27. The second sealing surface 27b is located on the opposite side of the first sealing surface 27a in the thickness direction of the first sealing resin 27. The second sealing resin 28 has, for example, a rectangular frame shape.

[0035] (Laminate) The laminate 21 is formed by stacking a plurality of bipolar electrodes 23, a positive terminal electrode 24, a negative terminal electrode 25, and a plurality of separators 26. The direction in which the plurality of bipolar electrodes 23, the positive terminal electrode 24, the negative terminal electrode 25, and the plurality of separators 26 are stacked is defined as the stacking direction.

[0036] The separator 26 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains the liquid electrolyte. Examples of materials that make up the separator 26 include polypropylene, polyethylene, polyolefin, and polyester. The separator 26 may have a single-layer structure or a multi-layer structure. The multi-layer structure may include, for example, an adhesive layer, a ceramic layer as a heat-resistant layer, and the like.

[0037] The bipolar electrodes 23 and the separators 26 are alternately stacked between the positive terminal electrode 24 and the negative terminal electrode 25. In two bipolar electrodes 23 adjacent to each other in the stacking direction, the positive electrode active material layer 31 of one bipolar electrode 23 faces the negative electrode active material layer 32 of the other bipolar electrode 23 with the separator 26 sandwiched therebetween.

[0038] The positive electrode terminal 24 includes a sheet-like positive electrode current collector 24a and a positive electrode active material layer 24b provided on one main surface of the positive electrode current collector 24a. The positive electrode current collector 24a may be, for example, the same as described for the positive electrode current collector 33. The positive electrode active material layer 24b may be the same as described for the positive electrode active material layer 31.

[0039] The negative electrode terminal electrode 25 includes a sheet-like terminal negative electrode current collector 25 a and a terminal negative electrode active material layer 25 b provided on one main surface of the terminal negative electrode current collector 25 a. The terminal negative electrode current collector 25 a can be the same as that described for the negative electrode current collector 34. The terminal negative electrode active material layer 25 b can be the same as that described for the negative electrode active material layer 32.

[0040] A first sealing resin 27 is disposed between the bipolar current collectors 30 of two bipolar electrodes 23 adjacent in the stacking direction. The first sealing resin 27 surrounds the positive electrode active material layer 31 of one bipolar electrode 23 and the negative electrode active material layer 32 of the other bipolar electrode 23 for each of the two bipolar electrodes 23 adjacent in the stacking direction. A first sealing surface 27a of the first sealing resin 27 is welded to a first uncoated region 30c of the first main surface 30a of the bipolar current collector 30. A second sealing surface 27b of the first sealing resin 27 is welded to a second uncoated region 30d of the second main surface 30b of the bipolar current collector 30. The first sealing resin 27 can be welded to the bipolar current collector 30 by known welding methods such as thermal welding, ultrasonic welding, or infrared welding.

[0041] A first sealing resin 27 is arranged between the bipolar electrode 23 located at the end on one side of the stacking direction and the positive terminal electrode 24, and between the bipolar electrode 23 located at the end on the other side of the stacking direction and the negative terminal electrode 25, in the same manner as between adjacent bipolar electrodes 23.

[0042] The second seal resin 28 is disposed so as to surround the stack 21. The second seal resin 28 has a portion positioned so as to surround the plurality of first seal resins 27, and a portion interposed between the first seal resins 27 adjacent to each other in the stacking direction.

[0043] (Electrolyte) The electrolyte L is contained in a space partitioned by the bipolar current collectors 30 of two bipolar electrodes 23 adjacent in the stacking direction and the first seal resin 27 located between these two bipolar current collectors 30. The electrolyte L is also contained in a space partitioned by the bipolar electrode 23, the positive terminal electrode 24, and the first seal resin 27 located therebetween, and in a space partitioned by the bipolar electrode 23, the negative terminal electrode 25, and the first seal resin 27 located therebetween.

[0044] The electrolyte solution L may be, for example, an electrolyte solution containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the electrolyte salt include LiClO ４ , LiAsF ６ , LiPF６ , LiBF ４ , LiCF ３ SO ３ , LiN(FSO ２ ) ２ , LiN(CF ３ SO ２ ) ２ Examples of the non-aqueous solvent include known lithium salts such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers. Two or more of these known solvent materials may be used in combination.

[0045] (Electricity storage cells) The electricity storage device 20 is configured to include a plurality of electricity storage cells 29 stacked in the stacking direction of the laminate 21. The plurality of electricity storage cells 29 are formed of the laminate 21, a sealing resin 22, and an electrolytic solution L. Two electricity storage cells 29 adjacent to each other in the stacking direction share one bipolar electrode 23 and are connected in series via the shared bipolar electrode 23. Therefore, the electricity storage device 20 includes a plurality of electricity storage cells 29 connected in series via the bipolar electrode 23.

[0046] <Method of Manufacturing the Energy Storage Device> Next, an example of a method of manufacturing the energy storage device 20 of this embodiment will be described. The energy storage device 20 is manufactured by sequentially performing an electrode formation process and an energy storage cell formation process.

[0047] (Electrode Forming Process) The electrode forming process includes a bonding process, a winding process, a corona discharge process, a carbon coating layer forming process, and an intermediate winding process. The bipolar current collector 30 is formed by sequentially performing each of these processes. The corona discharge process includes a first corona discharge process and a second corona discharge process. The carbon coating layer forming process includes a first carbon coating layer forming process and a second carbon coating layer forming process. In this embodiment, the bonding process, winding process, first corona discharge process, first carbon coating layer forming process, second corona discharge process, and second carbon coating layer forming process are performed in this order.

[0048] As shown in FIG. 3 , the lamination step is a step of forming a laminate 40 by laminating a rolled aluminum foil 41 and an electrolytic copper foil 42 together. The laminate 40 has an aluminum surface 40a formed by the rolled aluminum foil 41 and a copper surface 40b formed by the electrolytic copper foil 42. The laminate 40 is formed, for example, by overlapping and bonding a rolled aluminum foil 41 drawn from a roll of rolled aluminum foil with an electrolytic copper foil 42 drawn from a roll of electrolytic copper foil. Examples of methods for bonding the rolled aluminum foil 41 and the electrolytic copper foil 42 include a method using a conductive adhesive. The conductive adhesive is an adhesive that forms an adhesive layer upon curing. The conductive adhesive is, for example, a solvent-based adhesive containing the adhesive component, the conductive component, and a solvent. Examples of solvents include organic solvents such as aromatic solvents (e.g., toluene and xylene), aliphatic solvents, alicyclic solvents, ester solvents, ketone solvents, and alcohols. These solvents may be used alone or in combination.

[0049] The winding step is a step of forming a first roll body by winding the laminate 40 formed in the laminating step into a roll. At this time, the laminate 40 is stacked in a rolled state, so that the rolling oil adhering to the rolled aluminum foil is transferred to the electrolytic copper foil. The effect of the rolling oil transferred to the electrolytic copper foil will be described later.

[0050] The first corona discharge step is a step of performing a corona discharge treatment on the aluminum surface 40a of the laminate 40 unwound from the first roll. A specific method for the first corona discharge step will be described later.

[0051] As shown in Figure 4, the first carbon coating layer forming step is a step of forming a carbon coating layer C1 on the aluminum surface 40a of the corona discharge-treated laminate 40. Specific methods for the first corona discharge step will be described later. The first carbon coating layer forming step is performed consecutively after the first corona discharge step. "Consecutively" means that the first corona discharge step and the first carbon coating layer forming step are performed in the unwound state without rewinding between steps.

[0052] Between the first corona discharge step and the first carbon coating layer forming step, a surface cleaning step may be additionally performed to clean the aluminum surface 40a of the corona discharge-treated laminate 40. Examples of the surface cleaning step include a plasma treatment step. Even if the surface cleaning step is performed, the first corona discharge step and the first carbon coating layer forming step are still performed without rewinding the laminate between the steps, as long as the laminate remains unwound.

[0053] The intermediate winding step is a step of winding the laminate 40 on which the carbon coating layer C1 has been formed into a roll to form a second roll body. The second corona discharge step is a step of performing a corona discharge treatment on the copper surface 40b of the laminate 40 unwound from the second roll body. A specific method for the second corona discharge step will be described later.

[0054] As shown in Figure 5, the second carbon coating layer forming step is a step of forming a carbon coating layer C2 on the copper surface 40b of the corona discharge-treated laminate 40. Specific methods for the second corona discharge step will be described later. The second carbon coating layer forming step is performed consecutively after the second corona discharge step. "Consecutively" means that the second corona discharge step and the second carbon coating layer forming step are performed in the unwound state without rewinding between steps.

[0055] Between the second corona discharge step and the second carbon coating layer forming step, a surface cleaning step may be additionally performed to clean the copper surface 40b of the corona discharge-treated laminate 40. Examples of the surface cleaning step include a plasma treatment step. Even if the surface cleaning step is performed, the second corona discharge step and the second carbon coating layer forming step are still performed without rewinding the laminate between the steps, as long as the laminate remains unwound.

[0056] The bipolar current collector 30 is formed through the above steps. The aluminum surface 40a of the laminate 40 on which the carbon coating layer C1 is formed becomes the first main surface 30a of the bipolar current collector 30, and the copper surface 40b on which the carbon coating layer C2 is formed becomes the second main surface 30b of the bipolar current collector 30. The formed bipolar current collector 30 is wound into a roll as needed. In this case, a long bipolar current collector 30 can be continuously manufactured using a roll-to-roll method.

[0057] [Corona Discharge Treatment] The corona discharge treatment in the first corona discharge step and the second corona discharge step is performed, for example, by placing the unwound laminate 40 between electrodes and applying a high voltage between the electrodes in air at normal pressure to discharge electricity. The output power is, for example, 0.1 kW or more and 5.0 kW or less. The moving speed of the laminate 40 is, for example, 5 m / min or more and 100 m / min or less. The treatment conditions for the corona discharge treatment are not particularly limited and can be changed as appropriate.

[0058] Furthermore, the first corona discharge step and the second corona discharge step may be performed under the same treatment conditions, or may be performed under different treatment conditions. [Method for Forming Carbon Coating Layer] As a method for forming the carbon coating layer in the first carbon coating layer forming step and the second carbon coating layer forming step, a known method applied to forming a coating, such as a solution-based process or a vapor deposition-based process, can be used. An example of a solution-based process is described below.

[0059] First, a carbon paste is prepared by kneading carbon particles, a coating layer binder, and an aqueous solvent. A coating film is formed by adhering the carbon paste to a predetermined thickness to the aluminum surface 40a or copper surface 40b of the laminate 40. The formed coating film is dried and solidified to form a carbon coating layer. Examples of treatments for solidifying the carbon paste coating include drying the coating to volatilize the solvent, heating it to a temperature equal to or higher than the glass transition temperature of the coating layer binder, and then cooling it to solidify it.

[0060] As the carbon particles, known carbon materials applicable to carbon coating layers such as graphite, acetylene black, etc. can be used. The content of the carbon particles in the solid content contained in the carbon paste is, for example, 13 mass % or more and 90 mass % or less.

[0061] Examples of materials constituting the coating layer binder include acrylic resins and carboxy-modified styrene-butadiene rubber, and the material constituting the coating layer binder is preferably acrylic resins.

[0062] Examples of the acrylic resin include homopolymers of acrylic monomers such as acrylic acid, methacrylic acid, and (meth)acrylic acid esters, and (meth)acrylic copolymers containing the above acrylic monomers. In this embodiment, (meth)acrylic acid refers to acrylic acid or methacrylic acid.

[0063] Examples of the (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate.

[0064] In the (meth)acrylic copolymer, other comonomers copolymerized with the acrylic monomer include α-olefins, styrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, and vinyl acetate. These comonomers can be present in the acrylic resin in the form of random copolymers, graft copolymers, or block copolymers. Examples of the (meth)acrylic copolymer include silicon-modified acrylic-styrene resins, carboxy-modified acrylic-styrene resins, and hydroxyl-modified acrylic resins.

[0065] The coating layer binder may be made of one material or a combination of two or more materials. The carbon paste may contain other components such as a dispersant. Examples of dispersants include carboxyethyl cellulose.

[0066] Examples of aqueous solvents used in the carbon paste include water and mixed solvents of water and organic solvents. Examples of organic solvents used in mixed solvents include N-methyl-2-pyrrolidone (NMP).

[0067] In the first carbon coating layer forming step and the second carbon coating layer forming step, the carbon coating layers may be formed by the same method or by different methods.

[0068] [Active Material Layer Forming Step] The electrode forming step further includes an active material layer forming step of forming an active material layer on a portion of the aluminum surface 40a and a portion of the copper surface 40b of the laminate 40 after the carbon coating layer forming step. The active material layer forming step is a step of forming a positive electrode active material layer 31 on a portion of the first main surface 30a of the bipolar current collector 30 and forming a negative electrode active material layer 32 on a portion of the second main surface 30b.

[0069] The laminate 40 used in the active material layer forming step may be a long sheet, or may be a sheet cut from a long sheet into a predetermined shape. When a long sheet is used, after the active material layer forming step, a process of cutting the long sheet on which the active material layer has been formed into a predetermined shape is performed. Below, as an example, a case will be described in which the laminate 40 used in the active material layer forming step is a sheet cut from a long sheet into a predetermined shape.

[0070] The electrode formation process includes a coating process and a drying process. The coating process is a process in which the electrode composite is coated on the aluminum surface 40a of the bipolar current collector 30 so as to form a first uncoated region 30c, and the electrode composite is coated on the copper surface 40b so as to form a second uncoated region 30d. Examples of methods for coating the electrode composite include a roll method, a die coating method, a reverse roll method, a doctor blade method, a knife method, a gravure method, a dipping method, and a squeeze method.

[0071] The electrode mixture applied to the aluminum surface 40a is a positive electrode mixture. The positive electrode mixture is a mixture that becomes the positive electrode active material layer 31 upon solidification. The positive electrode mixture is, for example, a slurry. The positive electrode mixture contains a positive electrode active material, a binder, and an aqueous solvent, and may contain other components as needed. The components contained in the positive electrode mixture other than the aqueous solvent are the same as those described in the section on the positive electrode active material layer above.

[0072] The electrode mixture applied to the copper surface 40b is a negative electrode mixture. The negative electrode mixture is a mixture that becomes the negative electrode active material layer 32 upon solidification. The negative electrode mixture is, for example, a slurry. The negative electrode mixture contains a negative electrode active material, a binder, and an aqueous solvent, and may contain other components as needed. The components contained in the negative electrode mixture other than the aqueous solvent are the same as those described in the negative electrode active material layer section above.

[0073] The aqueous solvent used for the electrode mixture is water or a mixed solvent of water and an organic solvent. The aqueous solvent is preferably a solvent in which the mass proportion of water is 50 to 100 mass%. The aqueous solvent is blended into the electrode mixture so that the solids proportion of the electrode mixture is, for example, 60 mass% to 80 mass%.

[0074] The drying step is a step of removing the aqueous solvent and solidifying the coating layer by drying the coating layer of the electrode mixture formed on the laminate 40. The coating layer solidified through the drying step becomes the positive electrode active material layer 31 and the negative electrode active material layer 32, which are active material layers. Examples of methods for drying the coating layer include natural drying, low-temperature air, hot air, vacuum, infrared rays, far-infrared rays, electron beams, and microwaves. Two or more of these drying methods may be combined. The drying temperature is, for example, 100°C or higher and 240°C or lower. The drying time is, for example, 10 seconds or higher and 20 hours or lower.

[0075] In the electrode formation step, the order in which the positive electrode active material layer 31 and the negative electrode active material layer 32 are formed may be arbitrary. For example, after the coating step of coating the positive electrode composite and the negative electrode composite, the drying step of drying the coating layer of the positive electrode composite and the coating layer of the negative electrode composite may be performed. Alternatively, the coating step of coating the positive electrode composite and the drying step of drying the coating layer of the positive electrode composite may be performed first, and then the coating step of coating the negative electrode composite and the drying step of drying the coating layer of the negative electrode composite may be performed later.

[0076] Furthermore, in order to increase the electrode density, a compression step may be performed after the drying step to compress the positive electrode active material layer 31 and the negative electrode active material layer 32. Examples of the compression method used in the compression step include a mold press method and a calendar press method. The compression step may be performed on only one of the positive electrode active material layer 31 and the negative electrode active material layer 32.

[0077] (Storage Cell Formation Process) In the storage cell formation process, first, a plurality of bipolar electrodes 23, positive electrode terminal electrodes 24, and negative electrode terminal electrodes 25 are arranged so that the positive electrode active material layers 31 and the negative electrode active material layers 32 face each other in the stacking direction with the separator 26 sandwiched therebetween. Then, sealing resin 22 is arranged between the bipolar electrodes 23, between the bipolar electrodes 23 and the positive electrode terminal electrodes 24, and between the bipolar electrodes 23 and the negative electrode terminal electrodes 25.

[0078] At this time, the sealing resin 22 is arranged so that at least a portion thereof contacts the portion where the carbon coating layer C1 is formed in the first uncoated region 30c of the first main surface 30a of the bipolar current collector 30 that constitutes the bipolar electrode 23. In other words, the sealing resin 22 is arranged so as to contact the portion of the aluminum surface 40a of the laminate 40 that is the bipolar current collector 30 where the positive electrode active material layer 31 is not formed and where the carbon coating layer C1 is formed.

[0079] Furthermore, the sealing resin 22 is arranged so that at least a portion thereof contacts the portion where the carbon coating layer C2 is formed in the second uncoated region 30d of the second main surface 30b of the bipolar current collector 30 constituting the bipolar electrode 23. In other words, the sealing resin 22 is arranged so as to contact the portion where the negative electrode active material layer 32 is not formed and the portion where the carbon coating layer C2 is formed on the copper surface 40b of the laminate 40 which is the bipolar current collector 30.

[0080] Thereafter, the bipolar electrode 23, the positive terminal electrode 24, and the negative terminal electrode 25 are welded to the sealing resin 22 to form an integrated assembly. The bonding process used to form the assembly corresponds to the bonding step of bonding the sealing resin 22 to the bipolar electrode 23. The bonding step is a step of bonding the sealing resin 22 to the portion of the copper surface 40b of the laminate 40, which is the bipolar current collector 30, where the active material layer (negative active material layer 32) is not formed and where the carbon coating layer C2 is formed.

[0081] Next, a liquid electrolyte is injected into the sealed space inside the assembly through an injection port provided in a part of the sealing resin 22, and the injection port is then sealed, thereby forming the electricity storage device 20 including a plurality of electricity storage cells 29 connected in series via the bipolar electrodes 23.

[0082] <Function> Next, the function of this embodiment will be described. First, the cause of the decrease in adhesion to the sealing resin of the bipolar electrode 23 having a bipolar current collector made of rolled aluminum foil and electrolytic copper foil will be described. In order to clarify the cause, the following test was conducted.

[0083] By performing the following "Step 1" to "Step 2A" in order, the state in which rolling oil adhering to the rolled aluminum foil is transferred to the electrolytic copper foil in the winding process after the lamination process in the manufacturing process of an electricity storage device was reproduced. Furthermore, by performing the following "Step 1" to "Step 2B" to "Step 3" to "Step 4" in order, the electrolytic copper foil was given a temperature history simulating the manufacturing process of a bipolar current collector and the manufacturing process of a bipolar electrode. Steps 2B and 3 simulate the lamination process and the carbon coating layer formation process in manufacturing a bipolar current collector. Step 4 simulates the electrode formation process in manufacturing a bipolar electrode.

[0084] Step 1: Prepare an electrolytic copper foil (thickness: 8 μm). Step 2A: Place a rolled aluminum foil on a specific surface of the electrolytic copper foil prepared in Step 1, transfer the rolling oil adhering to the rolled aluminum foil to the specific surface of the electrolytic copper foil, and then peel the rolled aluminum foil from the electrolytic copper foil.

[0085] Step 2B: The electrolytic copper foil prepared in Step 1 is heated at 70°C for 3 days. Then, it is returned to room temperature. Step 3: The electrolytic copper foil after Step 2B is heated at 100°C for 40 seconds, at 120°C for 40 seconds, and at 150°C for 20 seconds, in that order. Then, it is returned to room temperature.

[0086] Step 4: The electrodeposited copper foil after Step 3 was heated at 100°C for 8 hours, and then returned to room temperature. After each of the above steps, the surface of the electrodeposited copper foil was subjected to measurement of wettability, measurement of adhesive strength of the electrodeposited copper foil to the sealing resin, and surface structure analysis.

[0087] (Measurement of Wettability) A 4 μL drop of water was dropped onto the surface of the electrolytic copper foil using a dropper, and the contact angle of the drop formed on the surface of the electrolytic copper foil was measured. The results are shown in Table 1.

[0088] (Measurement of Adhesion Strength) Rectangular sheet materials measuring 10 mm long x 50 mm wide were cut from the electrolytic copper foil after each step. A rectangular sealing material measuring 10 mm long x 50 mm wide was also prepared. An acid-modified polyethylene sheet having a thickness of 120 μm and a melting point of 120°C was used as the sealing material. The sealing material was laminated on the sheet material with the edges aligned to obtain a laminate. The laminate was heated at 150°C for 10 seconds using an impulse sealer and then cooled to prepare a measurement sample in which the sheet material and the sealing material were bonded. A 180-degree peel test was performed on the obtained measurement sample at a pulling rate of 10 mm / min and a temperature of 25°C. The peel strength of the measurement sample was calculated by dividing the strength measured in the 180-degree peel test by the line width of 10 mm, and the calculated value was used as the adhesive strength. The results are shown in Table 1.

[0089] (Surface Structure Analysis) The surface structure of the electrodeposited copper foil after each step was analyzed by X-ray photoelectron spectroscopy, and the results are shown in FIG.

[0090] As shown in Table 1, an increase in the contact angle on the surface of the electrodeposited copper foil and a decrease in adhesive strength can be confirmed in step 2A. Referring to Fig. 6, the peak shape in step 2A is the same as that in step 1, which indicates that the surface structure does not change in step 2A. Therefore, the decrease in adhesive strength in step 2A is thought to be caused by some of the hydrophilic functional groups, such as hydroxyl groups, present on the surface of the electrodeposited copper foil being covered by rolling oil transferred from the rolled aluminum foil.

[0091] Furthermore, as shown in Table 1, a significant increase in the contact angle on the surface of the electrodeposited copper foil and a significant decrease in adhesive strength can be confirmed in step 4. Referring to Fig. 6, the peak shape in step 4 is significantly different from that in step 1. Specifically, the peak for "Cu" decreases, and the peak for the oxide "CuO" increases. Therefore, the decrease in adhesive strength in step 4 is considered to be caused by the oxidation of the surface of the electrodeposited copper foil due to long-term exposure to a high-temperature environment, resulting in a decrease in hydrophilic functional groups such as hydroxyl groups.

[0092] As described above, in bipolar current collectors made of rolled aluminum foil and electrolytic copper foil, the causes of reduced adhesion to the sealing resin are the rolling oil adhering to the rolled aluminum foil and heating during the electrode formation process.

[0093] In the manufacturing method of the energy storage device 20 of this embodiment, in the electrode formation step, the laminate 40, which is made by bonding together a rolled aluminum foil and an electrolytic copper foil, is first wound into a roll to form a roll, and then a corona discharge treatment is performed on the copper surface 40b of the laminate 40 unwound from the roll. In this case, rolling oil that was transferred from the rolled aluminum foil to the electrolytic copper foil during winding into a roll or due to other factors and adhered to the surface of the electrolytic copper foil (copper surface 40b of the laminate 40) is removed by the corona discharge treatment. As a result, a decrease in the adhesive strength of the sealing resin due to the rolling oil adhering to the copper surface 40b is suppressed.

[0094] Additionally, in the manufacturing method of the electricity storage device 20 of this embodiment, after the corona discharge step, a carbon coating layer C2 is formed on the copper surface 40b of the laminate 40. As a result, the copper surface 40b is covered with the carbon coating layer C2, and the electrolytic copper foil and the carbon coating layer C2 are bonded to each other. This bond is either an ester bond or a hydrogen bond, or both.

[0095] The ester bond is a bonding structure (-COOCu) formed by an ester bond between a hydroxyl group (Cu-OH) bonded to a copper atom constituting the electrolytic copper foil and a carboxyl group (-COOH) of the coating layer binder. The hydrogen bond is a bonding structure formed by a hydrogen bond between a hydroxyl group (Cu-OH) bonded to a copper atom constituting the electrolytic copper foil and either or both of a hydroxyl group and a carboxyl group of a material constituting the carbon coating layer C2. The hydroxyl group is either or both of a hydroxyl group (C-OH) on the surface of the carbon particle and a hydroxyl group (C-OH) of the coating layer binder. The carboxyl group is a carboxyl group (-COOH) of the coating layer binder.

[0096] In particular, the corona discharge treatment has the effect of newly generating hydrophilic functional groups such as hydroxyl groups on the copper surface 40b before the carbon coating layer C2 is formed, i.e., on the surface of the electrolytic copper foil. Therefore, on the copper surface 40b after the corona discharge treatment, many hydrophilic functional groups are formed, and the electrolytic copper foil and the carbon coating layer C2 are firmly bonded to each other. Therefore, the corona discharge treatment also has the effect of strengthening the bond between the electrolytic copper foil and the carbon coating layer C2 in the subsequent carbon coating layer formation step.

[0097] The formation of the copper surface 40b in which the hydrophilic functional groups of the electrolytic copper foil are bonded to the carbon coating layer C2 suppresses oxidation of the electrolytic copper foil due to prolonged exposure to a high-temperature environment in the electrode formation process. Furthermore, the hydroxyl and carboxyl groups of the substances contained in the carbon coating layer C2 are retained without oxidation even after the electrode formation process, compared with the hydrophilic functional groups of the electrolytic copper foil, and therefore the carbon coating layer C2 can be bonded to the sealing resin 22. As a result, the adhesive strength to the sealing resin 22 can be increased compared to when the sealing resin 22 is bonded to a copper surface 40b on which the carbon coating layer C2 is not formed.

[0098] <Effects> According to this embodiment, the following effects can be achieved. (1) The manufacturing method of the energy storage device 20 includes an electrode formation process for forming the bipolar electrodes 23 and an adhesion process for adhering the sealing resin 22 to the bipolar electrodes 23. The electrode formation process includes a bonding process, a winding process, a corona discharge process, a carbon coating layer formation process, and an active material layer formation process. The bonding process is a process for bonding a rolled aluminum foil 41 and an electrolytic copper foil 42 together to form a laminate 40 having an aluminum surface 40a formed by the rolled aluminum foil 41 and a copper surface 40b formed by the electrolytic copper foil 42. The winding process is a process for winding the laminate 40 into a roll to form a roll body. The corona discharge process is a process for performing a corona discharge treatment on the copper surface 40b of the laminate 40 unwound from the roll body. The carbon coating layer formation process is a process for forming a carbon coating layer C2 on the copper surface 40b after the corona discharge process. In the bonding step, the sealing resin 22 is bonded to the portion of the copper surface 40b where the negative electrode active material layer 32 is not formed and where the carbon coating layer C2 is formed.

[0099] According to the above configuration, the rolling oil transferred to the electrolytic copper foil 42 during the winding process is removed by the corona discharge treatment, thereby suppressing a decrease in adhesive strength of the copper surface 40b due to the rolling oil. Furthermore, since the copper surface 40b is provided with the carbon coating layer C2, the adhesion of the carbon coating layer C2 to the sealing resin 22 can be ensured even after prolonged exposure to a high-temperature environment during the electrode formation process. Therefore, for a bipolar electrode 23 including a bipolar current collector 30 made of rolled aluminum foil and electrolytic copper foil, the adhesion of the copper surface 40b (first main surface 30a) to the sealing resin 22 is improved.

[0100] (2) The corona discharge step and the carbon coat layer forming step are performed consecutively. If the time between the corona discharge step and the carbon coat layer forming step is long, as in the case where the laminate 40 after the corona discharge step is wound up and stored, the hydrophilic functional groups generated in the corona discharge step are oxidized and gradually reduced. By performing the carbon coat layer forming step consecutively after the corona discharge step, the reduction in the hydrophilic functional groups generated in the corona discharge step can be suppressed. As a result, the carbon coat layer can be firmly bonded to the laminate 40.

[0101] (3) The corona discharge step and the carbon coating layer formation step are performed on both the aluminum surface 40a and the copper surface 40b of the laminate 40. According to the above configuration, the aluminum surface 40a of the laminate 40 (the first main surface 30a of the bipolar current collector 30) can also suppress a decrease in adhesive strength caused by rolling oil and a decrease in adhesive strength caused by prolonged exposure to a high-temperature environment, similar to the copper surface 40b of the laminate 40. Therefore, the adhesion of both the copper surface 40b and the aluminum surface 40a of the laminate 40 (both the second main surface 30b and the first main surface 30a of the bipolar current collector 30) to the sealing resin 22 is improved.

[0102] This embodiment can be modified as follows. This embodiment and the following modifications can be combined and implemented as long as there is no technical contradiction. Regarding the second corona discharge process, the area where the corona discharge treatment is performed is not limited to the entire copper surface 40b of the laminate 40, as long as it includes the area on the copper surface 40b where the sealing resin 22 is bonded. Similarly, regarding the first corona discharge process, the area where the corona discharge treatment is performed is not limited to the entire aluminum surface 40a of the laminate 40, as long as it includes the area on the aluminum surface 40a where the sealing resin 22 is bonded.

[0103] In the second carbon coating layer forming step, the area where the carbon coating layer C2 is formed is not limited to the entire copper surface 40b of the laminate 40, but may be any area including the portion of the copper surface 40b to which the sealing resin 22 is bonded. Similarly, in the first carbon coating layer forming step, the area where the carbon coating layer C1 is formed is not limited to the entire aluminum surface 40a of the laminate 40, but may be any area including the portion of the aluminum surface 40a to which the sealing resin 22 is bonded.

[0104] The order of the first corona discharge step, the second corona discharge step, the first carbon coating layer forming step, and the second carbon coating layer forming step may be changed. For example, the first corona discharge step and the second corona discharge step may be performed after the first carbon coating layer forming step and the second carbon coating layer forming step. In this case, the first corona discharge step and the second corona discharge step may be performed simultaneously or separately. Furthermore, the first carbon coating layer forming step and the second carbon coating layer forming step may be performed simultaneously or separately.

[0105] Either or both of the first corona discharge step and the second carbon coating layer forming step may be omitted. That is, the corona discharge step may be a step of performing a corona discharge treatment on at least the copper surface 40b of the laminate 40. Similarly, the carbon coating layer forming step may be a step of forming a carbon coating layer C2 on at least the copper surface 40b of the laminate 40.

[0106] Next, the technical ideas that can be understood from the above-described embodiment and modified examples will be additionally described below. a carbon coating layer forming step of forming a carbon coating layer on the copper surface of the laminate unwound from the rolled aluminum foil; and an active material layer forming step of forming an active material layer on each of a portion of the aluminum surface and a portion of the copper surface after the carbon coating layer forming step. [Aspect 1] A method for manufacturing an electricity storage device including: an electrode forming step of forming the bipolar electrode; and an adhering step of adhering the sealing resin to the bipolar electrode. The electrode forming step includes: a laminating step of laminating a rolled aluminum foil and an electrolytic copper foil to form a laminate having an aluminum surface constituted by the rolled aluminum foil and a copper surface constituted by the electrolytic copper foil; a winding step of winding the laminate into a roll to form a roll body; a corona discharging step of performing a corona discharge treatment on the copper surface of the laminate unwound from the roll body;

[0107] [Aspect 2] The method for producing an electricity storage device according to Aspect 1, wherein the corona discharge step and the carbon coating layer forming step are carried out continuously.

[0108] [Aspect 3] The method for producing an electricity storage device according to Aspect 1 or Aspect 2, wherein the corona discharge step and the carbon coating layer forming step are performed on both the aluminum surface and the copper surface of the laminate.

[0109] [Aspect 4] The method for producing an electricity storage device according to aspect 4, wherein the sealing resin is an acid-modified polyolefin resin.

[0110] [Aspect 5] The method for manufacturing an electricity storage device according to any one of Aspects 1 to 4, wherein the bipolar electrode comprises: a bipolar current collector in which an aluminum current collector formed from the rolled aluminum foil and a copper current collector formed from the electrolytic copper foil are laminated together; a positive electrode active material layer provided on a surface of the aluminum current collector of the bipolar current collector; and a negative electrode active material layer provided on a surface of the copper current collector of the bipolar current collector.

[0111] Aspect 6 The method for manufacturing an electricity storage device according to Aspect 5, wherein the electricity storage device includes: a plurality of the bipolar electrodes arranged such that the positive electrode active material layer and the negative electrode active material layer face each other; a separator arranged between the bipolar electrodes adjacent in the stacking direction; and a sealing resin arranged between the bipolar electrodes adjacent in the stacking direction so as to surround the positive electrode active material layer and the negative electrode active material layer, and adhered to the bipolar current collector to form an enclosed space for accommodating a liquid electrolyte between the bipolar electrodes.

[0112] C1, C2 Carbon coating layer 20 Electricity storage device 22 Sealing resin 23 Bipolar electrode 30 Bipolar current collector 31 Positive electrode active material layer 32 Negative electrode active material layer 40 Laminate 40a Aluminum surface 40b Copper surface 41 Rolled aluminum foil 42 Electrolytic copper foil

Claims

1. A manufacturing method for an electricity storage device comprising a bipolar electrode and a sealing resin adhered to the bipolar electrode, comprising: an electrode formation step of forming the bipolar electrode; and an adhesion step of adhering the sealing resin to the bipolar electrode, the electrode formation step comprising: a lamination step of laminating a rolled aluminum foil and an electrolytic copper foil to form a laminate having an aluminum surface constituted by the rolled aluminum foil and a copper surface constituted by the electrolytic copper foil; a winding step of winding the laminate into a roll to form a roll body; a corona discharge step of performing a corona discharge treatment on the copper surface of the laminate unwound from the roll body; a carbon coat layer formation step of forming a carbon coat layer on the copper surface after the corona discharge step; and an active material layer formation step of forming an active material layer on each of a part of the aluminum surface and a part of the copper surface after the carbon coat layer formation step, the adhesion step being characterized in that the sealing resin is adhered to a part of the copper surface on which the active material layer is not formed and on which the carbon coat layer is formed.

2. The method for producing an electricity storage device according to claim 1, wherein the corona discharge step and the carbon coat layer forming step are carried out consecutively.

3. The method for producing an electricity storage device according to claim 1, wherein the corona discharge step and the carbon coating layer forming step are performed on both the aluminum surface and the copper surface of the laminate.

4. The method for manufacturing an electricity storage device according to any one of claims 1 to 3, wherein the sealing resin is an acid-modified polyolefin resin.

5. A method for manufacturing an electricity storage device according to any one of claims 1 to 4, wherein the bipolar electrode comprises: a bipolar current collector in which an aluminum current collector formed from the rolled aluminum foil and a copper current collector formed from the electrolytic copper foil are laminated together; a positive electrode active material layer provided on a surface of the aluminum current collector of the bipolar current collector; and a negative electrode active material layer provided on a surface of the copper current collector of the bipolar current collector.

6. A method for manufacturing an electricity storage device as described in claim 5, comprising: a plurality of the bipolar electrodes arranged such that the positive electrode active material layer and the negative electrode active material layer face each other; a separator arranged between the bipolar electrodes adjacent in the stacking direction; and a sealing resin arranged between the bipolar electrodes adjacent in the stacking direction so as to surround the positive electrode active material layer and the negative electrode active material layer and adhered to the bipolar current collector to form an enclosed space for containing a liquid electrolyte between the bipolar electrodes.

Images