Manufacturing method of current collector foil

Abstract

To provide a manufacturing method of a current collector foil that can suppress warping.SOLUTION: A manufacturing method of a current collector foil includes a first step of applying an adhesive to one side of a first metal foil, a second step of laminating a second metal foil to the adhesive-coated side of the first metal foil and heating and pressurizing the resulting laminated foil, and a third step of rolling up the laminated foil and then heating it, and in the second step, the difference in elongation between the first metal foil and the second metal foil is set to 0.8 mm or less, or in the third step, the laminated foil is rolled up such that the first metal foil or the second metal foil with the larger linear expansion coefficient is on the outside.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a current collector foil for use in a battery. [Background technology]

[0002] Patent Document 1 discloses a technology related to bipolar batteries, and describes that the current collector foil used therein is, for example, a foil made of aluminum foil and copper foil laminated together. It is known that such current collector foil is manufactured by rolling aluminum foil and copper foil.

[0003] Patent Document 2 discloses a current collector having a positive electrode current collector with an aluminum layer, a negative electrode current collector with a copper layer, and an intermediate layer interposed between the aluminum layer and the copper layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 08-007926 [Patent Document 2] JP 2023-053669 A Summary of the Invention [Problem to be solved by the invention]

[0005] When a current collector foil is manufactured by laminating different metal foils, there is a problem that the manufactured current collector foil may be warped in the width direction.

[0006] Therefore, an object of the present disclosure is to provide a method for manufacturing a current collecting foil that can suppress warping. [Means for solving the problem]

[0007] As a result of intensive research, the inventors discovered that one of the causes of the warping is the generation of residual stress during the temperature increase and decrease process before and after thermal lamination (a process in which two sheets of foil are sandwiched between a heated roll and a rubber roll and laminated together) due to the difference in the linear expansion coefficient of the foils being laminated together. Based on this discovery, the inventors then embodied a solution and completed the invention according to the present disclosure.

[0008] The present application discloses a method for manufacturing a current collector foil, comprising a first step of applying an adhesive to one side of a first metal foil, a second step of laminating a second metal foil to the adhesive-coated side of the first metal foil and heating and pressing to obtain a laminated foil, and a third step of rolling up the laminated foil and then heating it, wherein in the second step, the difference in elongation between the first metal foil and the second metal foil is 0.8 mm or less, or in the third step, the laminated foil is rolled up so that the first metal foil or the second metal foil with the larger linear expansion coefficient is on the outside.

[0009] In the second step, the first metal foil and the second metal foil may be heated and pressed using two opposing roll members, and the pressure between the two roll members may be 0.3 MPa or more.

[0010] In the second step, the difference in temperature between the first metal foil and the second metal foil may be 10° C. or less.

[0011] The present application discloses a method for producing a battery, comprising the steps of producing a current collector foil by any of the above methods, and forming a positive electrode active material layer on one side of the current collector foil and a negative electrode active material layer on the other side thereof. Effect of the Invention

[0012] According to the method for producing a current collector foil of the present disclosure, warping of the current collector foil can be suppressed. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a schematic diagram of an electricity storage module. [Diagram 2]FIG. 2 is a diagram illustrating a method for manufacturing a current collector foil. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. For ease of understanding, some repeated reference numerals may be omitted.

[0015] 1. Structure of secondary batteries First, the structure of a secondary battery 10 according to one example to which a current collecting foil produced by the manufacturing method of the present disclosure is applied will be described. Fig. 1 is a schematic cross-sectional view illustrating the structure of the secondary battery 10, showing one power storage module 11 of the secondary battery 10. The secondary battery 10 comprises a laminate in which a plurality of such power storage modules 11 and conductive plates (not shown) are alternately arranged. The secondary battery 10 is typically used as a battery for hybrid vehicles, electric vehicles, etc.

[0016] The power storage module 11 is a flat plate-shaped cell as a whole, and the power storage module 11 in this embodiment is a bipolar type lithium ion secondary battery. The energy storage module 11 includes an electrode stack formed by stacking a plurality of bipolar electrodes 12, and a plurality of sealing bodies 20 provided for each bipolar electrode 12. The plurality of bipolar electrodes 12 are stacked in the thickness direction (thickness direction in a flat plate shape), and a sealing body 20 is disposed on each bipolar electrode 12.

[0017] 1.1. Electrode laminate [Bipolar electrode] Hereinafter, in the explanation of each component, the terms "upper surface" and "lower surface" may be used, but in Fig. 1, "upper surface" means the upper side of the page and "lower surface" means the lower side of the page. Although these terms are used for convenience, the "upper surface" can also be referred to as the "first surface" and the "lower surface" as the "second surface." The bipolar electrode 12 includes a current collecting foil 13, a positive electrode active material layer 14 (first active material layer) provided on the lower surface of the current collecting foil 13, a negative electrode active material layer 15 (second active material layer) provided on the upper surface of the current collecting foil 13, and a separator 16.

[0018] In this embodiment, the current collector foil 13 is a foil-shaped conductive member having a rectangular shape in a plan view, and is a laminated foil in which a plurality of different metal foils are laminated. The type of metal to be laminated is not particularly limited, but an example of the metal to be laminated is a foil in which an aluminum foil and a copper foil are laminated together so that the upper surface is an aluminum layer and the lower surface is a copper layer. Other examples of metals include titanium, nickel, stainless steel (e.g., SUS304, SUS316, SUS301, etc., as specified in JIS G 4305:2015), steel (e.g., cold-rolled steel plate (SPCC, etc.) as specified in JIS G 3141:2005), etc. The present disclosure relates to the manufacture of the current collector foil, and details regarding the manufacture are provided below.

[0019] The positive electrode active material layer 14 constitutes the positive electrode of the bipolar electrode 12, and in this embodiment is disposed on the lower surface of the current collector foil 13 via an adhesive layer such as acetylene black. The positive electrode active material layer 14 can contain a positive electrode active material, a conductive assistant, and a binder. Examples of the positive electrode active material include a composite oxide, metallic lithium, and sulfur. The composition of the composite oxide includes at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of the composite oxide include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, and LiNiMnCoO2. The binder serves to bind the active material or conductive assistant to the surface of the current collector foil 13 and maintain the conductive network in the electrode. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, acrylic resins containing monomer units such as acrylic acid and methacrylic acid, styrene-butadiene rubber (SBR), carboxymethyl cellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked bodies, and starch-acrylic acid graft polymers. These binders can be used alone or in combination. Examples of the conductive assistant include acetylene black, carbon black, and graphite.

[0020] The negative electrode active material layer 15 constitutes the negative electrode of the bipolar electrode 12, and is disposed on the upper surface of the current collector foil 13 in this embodiment. The negative electrode active material layer 15 may contain a negative electrode active material, a conductive additive, and a binder. The conductive additive and the binder may be considered to be similar to those of the positive electrode active material layer 14. Examples of the negative electrode active material include carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, metal compounds, elements capable of being alloyed with lithium or compounds of such elements, boron-doped carbon, etc. Examples of elements capable of being alloyed with lithium include silicon and tin.

[0021] The separator 16 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains an electrolyte, and is placed on the upper surface of the negative electrode active material layer 15 in this embodiment. Examples of materials constituting the separator 16 include polypropylene, polyethylene, polyolefin, polyester, etc. The separator 16 may have a single-layer structure or a multi-layer structure. Examples of the electrolyte absorbed and held in the separator 16 include a liquid electrolyte (electrolytic solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, or a polymer gel electrolyte containing an electrolyte held in a polymer matrix. When the separator 16 is impregnated with an electrolyte, known lithium salts such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, and LiN(CF3SO2)2 can be used as the electrolyte salt. In addition, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, and ethers can be used as the non-aqueous solvent.

[0022] The current collector foil 13, the positive electrode active material layer 14, the negative electrode active material layer 15, and the separator 16 are configured to have different sizes in a plan view. More specifically, the current collector foil 13 is the largest, the separator 16 is the next largest, the negative electrode active material layer 15 is the next largest, and the positive electrode active material layer 14 is the smallest. As can be seen from FIG. 1, the current collector foil 13, the positive electrode active material layer 14, the negative electrode active material layer 15, and the separator 16 are arranged with their centers aligned in a plan view, and the difference in size is expressed by the degree of protrusion (overhang) of the edges. Therefore, the edge of the current collector foil 13 protrudes the most, and the edges of the separator 16, the negative electrode active material layer 15, and the positive electrode active material layer 14 protrude in this order so as to be inside the current collector foil 13.

[0023] To form the positive electrode active material layer 14 and the negative electrode active material layer 15 on the current collector foil 13, a conventionally known method such as roll coating, die coating, dip coating, doctor blade coating, spray coating, curtain coating, etc. is used. Specifically, an active material, a solvent, and, if necessary, a binder and a conductive assistant are mixed to produce a slurry-like active material layer forming composition, which is then applied to the upper and lower surfaces of the current collector foil 13 and then dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water.

[0024] [Layer structure of electrode laminate] In the electrode laminate, adjacent bipolar electrodes 12 in the lamination direction are laminated such that the positive electrode active material layer 14 of one electrode overlaps with the separator 16 of the other electrode.

[0025] In addition, the electrode laminate has a positive terminal electrode 17 at the upper end and a negative terminal electrode 18 at the lower end of the laminate made of bipolar electrodes 12 in the lamination direction. The positive terminal electrode 17 has a current collecting foil 13 and a positive active material layer 14 provided on the lower surface of the current collecting foil 13, with the positive active material layer 14 laminated on the adjacent bipolar electrode 12 and the current collecting foil 13 laminated on its upper surface. The negative terminal electrode 18 has a current collector 13, a negative electrode active material layer 15 provided on the upper surface of the current collector foil 13, and a separator 16 laminated on the upper surface of the separator 16, which is laminated on the adjacent bipolar electrode 12, with the negative electrode active material layer 15 on its lower surface and the current collector foil 13 further laminated on its lower surface. The positive terminal electrode 17 and the negative terminal electrode 18 are each formed by laminating a current collecting foil 13 on an adjacent conductive plate.

[0026] 1.2. Sealing body The sealing body 20 is a member that is disposed on the outer peripheral end of the bipolar electrode 12 to seal the bipolar electrode 12. This also serves to seal the space between adjacent bipolar electrodes 12 in the stacking direction. In this embodiment, the sealing body 20 has a first sealing member 21, a second sealing member 22, and a spacer 23.

[0027] [First sealing member] The first sealing member 21 is a frame-shaped member that is disposed along the outer peripheral end (outer edge) of the bipolar electrode 12. Specifically, as can be seen from Fig. 1, the first sealing member 21 is disposed and joined between the upper surface of the current collecting foil 13 and the lower surface of the separator 16 at the outer peripheral end of the bipolar electrode 12, thereby disposing the negative electrode active material layer 15 within the frame. In this embodiment, a predetermined gap is provided between the inner edge of the first seal member 21 and the negative electrode active material layer 15 to form a space. On the other hand, the outer edge of the first seal member 21 is configured so that the first seal member 21 protrudes outward beyond the current collector foil 13.

[0028] The first sealing member 21 has electrical insulation properties and can be made of a known material, for example, an electrolyte-resistant resin material such as acid-modified polyethylene (acid-modified PE), acid-modified polypropylene (acid-modified PP), polyethylene, or polypropylene.

[0029] [Second sealing material] The second sealing member 22 is a frame-shaped member that is disposed along the outer peripheral end (outer edge) of the bipolar electrode 12. Specifically, as can be seen from Fig. 1, the second sealing member 22 is disposed and joined between the lower surface of the current collecting foil 13 and the upper surface of the spacer 23 at the outer peripheral end of the bipolar electrode 12, and the positive electrode active material layer 14 is disposed within the frame together with the spacer 23. In this embodiment, a predetermined gap is provided between the inner edge of the second seal member 22 and the positive electrode active material layer 14 to form a space. On the other hand, the outer edge of the second seal member 22 is configured so that the second seal member 22 protrudes outward from the current collector foil 13, and the upper surface of the second seal member 22 and the lower surface of the first seal member 21 are joined. The material of the second seal member 22 can be considered to be similar to that of the first seal member 21 .

[0030] [Spacer] The spacer 23 is a frame-shaped member that is disposed along the outer peripheral edge of the bipolar electrode 12. Specifically, as can be seen from Fig. 1, the spacer 23 is combined with the second seal member 22, so that the spacer 23 is disposed and joined between the lower surface of the second seal member 22 and the upper surface of the separator 16 of the adjacent bipolar electrode 12 at the outer peripheral edge of the bipolar electrode 12, and the positive electrode active material layer 14 is disposed within the frame. In this embodiment, the inner edge of the spacer member 23 is disposed so as to be spaced apart from the positive electrode active material layer 14. On the other hand, the outer edge of the spacer 23 protrudes outward from the separator 16, and the lower surface of the spacer 23 is joined to the upper surface of the first seal member 21 of the adjacent sealing body 20. The material of the spacer 23 can be considered to be similar to that of the first seal member 21 .

[0031] 2. Manufacturing method of current collector foil The manufacturing method of the current collector foil will be described below. Two examples (first and second embodiments) will be described here. Figure 2 shows a diagram for explaining the manufacturing method of the current collector foil. Figure 2 is common to both the first and second embodiments. Here, the first metal foil F1, the second metal foil F2, and the laminated foil F are continuously fed in the direction of the straight arrow in the figure.

[0032] 2.1.First form The current collector foil manufacturing method S10 according to the first embodiment includes a first step S11, a second step S12, and a third step S13. Each step will be described below.

[0033] [1st process S11] In the first step S11, an adhesive is applied to one side of the first metal foil F1. Specifically, the first metal foil F1 is unwound from a roll 30 around which the first metal foil F1 is wound, and an adhesive is applied to one side of the first metal foil F1.

[0034] The material of the first metal foil F1 is not particularly limited, but examples include aluminum, titanium, nickel, stainless steel (e.g., SUS304, SUS316, SUS301, etc. as specified in JIS G 4305:2015), steel (e.g., cold-rolled steel plate (SPCC, etc.) as specified in JIS G 3141:2005), etc.

[0035] The type of adhesive to be applied is not particularly limited, and any known adhesive used in manufacturing metal laminated foils can be used. Specifically, an adhesive using an olefin resin as a base material and an epoxy resin as a hardener can be used. The adhesive may also contain a conductive assistant. As the conductive assistant, acetylene black, carbon black, graphite, etc. described in the positive electrode active material layer 14, or particles plated with a metal such as Ni can also be used.

[0036] The coating method is not particularly limited, but for example, the coating can be performed by gravure coating using a gravure coater 40 .

[0037] The first metal foil F1 with the adhesive applied on one side is then sent to a drying furnace 41 to dry the adhesive.

[0038] [Second process S12] In the second step S12, the second metal foil F2 is laminated to the adhesive-coated surface of the first metal foil F1 produced in the first step S11, and then heated and pressed to obtain a laminated foil F. Specifically, the process is as follows. The second metal foil F2 is unwound from the roll 31 around which it is wound, and supplied to a thermal laminator 42. Meanwhile, the first metal foil F1 to which the adhesive is applied, produced in the first step S11, is also supplied to the thermal laminator 42, and the two are superimposed and heated and pressed to form a laminated foil F.

[0039] The material of the second metal foil F2 is not particularly limited, but is at least a material different from that of the first metal foil F1. Specific materials that can be used are those described for the first metal foil F1.

[0040] The thermal laminator 42 is not particularly limited as long as it is a device that can overlap the first metal foil F1 and the second metal foil F2 and apply pressure and heat to them. For example, the thermal laminator 42 includes a heat roll 42a with a metal surface and a rubber roll 42b with a rubber surface that is disposed opposite the heat roll 42a, and the first metal foil F1 and the second metal foil F2 are fed between the two rolls to overlap them.

[0041] At this time, the force with which the heat roll 42a and the rubber roll 42b press against each other can be changed by changing the center position of the two rolls, and this force presses the first metal foil F1 and the second metal foil F2 together. The pressing force is not particularly limited, but is preferably 0.3 MPa or more.

[0042] The heat roll 42a and the rubber roll 42b are configured so that their temperatures can be changed by heating, and the first metal foil F1 and the second metal foil F2 can be heated by this temperature to adjust the temperature. In this embodiment, the heat roll 42a and the rubber roll 42b can be individually temperature controlled. The temperature conditions of the first metal foil F1 and the second metal foil F2 during thermal lamination are not particularly limited, but it is preferable to provide a temperature difference according to the linear expansion coefficient of each foil, and more preferably the temperature difference is 10°C or less.

[0043] In addition, in the second step S12 in the first embodiment, when the first metal foil F1 and the second metal foil F2 are bonded together, the temperatures (temperature difference) of the metal foils are adjusted so that the difference in the amount of elongation between the two metal foils is 0.8 mm or less, thereby making it possible to suppress warping in the final current collector foil obtained. A specific temperature difference can be determined by the linear expansion coefficients of the first metal foil F1 and the second metal foil F2 and the size (width: band width of a continuous band-shaped metal foil, for example, about 1000 mm to 1400 mm). The method for adjusting the temperature of each metal foil is not particularly limited, but examples thereof include a method of heating with the heat roll 42a and the rubber roll 42b, and a method of heating with a heater (not shown).

[0044] [Third process S13] In the third step S13, the laminated foil is wound up and then heated. More specifically, the laminated foil F obtained in the second step S12 is wound up into a roll 32, and the roll 32 is heated to a temperature equal to or higher than the melting point of the adhesive. In this way, a continuous current collector foil is obtained as a roll, and the current collector foil 13 is obtained by cutting the current collector foil to the required size while unwinding it.

[0045] 2.2.Second form The current collector foil manufacturing method S20 according to the second embodiment includes a first step S21, a second step S22, and a third step S23. Each step will be described below.

[0046] [1st process S21] In the first step S21, an adhesive is applied to one side of the first metal foil. Specifically, the first metal foil F1 is unwound from the roll 30 on which the first metal foil F1 is wound, and the adhesive is applied to one side of the first metal foil F1. The first metal foil F1, the adhesive, and the application of the adhesive can be considered to be similar to those described in the first step S11 of the first embodiment.

[0047] The first metal foil F1 with the adhesive applied on one side is then sent to a drying furnace 41 to dry the adhesive.

[0048] [Second process S22] In the second step S22, the second metal foil F2 is laminated to the adhesive-coated surface of the first metal foil F1 produced in the first step S21, and then heated and pressed to obtain a laminated foil F. Specifically, the process is as follows. The second metal foil F2 is unwound from the roll 31 around which it is wound, and is supplied to a thermal laminator 42. Meanwhile, the first metal foil F1 to which the adhesive is applied, which is produced in the first step S21, is also supplied to the thermal laminator 42, and the two are superimposed and heated and pressed to form a laminated foil.

[0049] The material of the second metal foil F2 is not particularly limited, but is at least a material different from that of the first metal foil F1. Specifically, the same material as that of the first metal foil F1 described in the first embodiment can be used.

[0050] The thermal laminator 42 can be considered to be similar to that described in the first embodiment. In the second step S22 in the second embodiment, the difference in the elongation between the first metal foil F1 and the second metal foil F2, as specified in the second step S12 in the first embodiment described above, does not necessarily have to be 0.8 mm or less. However, it is not limited to this, and the difference in the elongation between the first metal foil F1 and the second metal foil F2 in the second step S22 may be 0.8 mm or less, as in the second step S12 described above. This makes it possible to further suppress warping in the finally obtained current collector foil.

[0051] [Third step S23] In the third step S23, the laminated foil F is wound up and then heated. More specifically, the laminated foil F obtained in the second step S22 is wound up into a roll 32, and the roll 32 is heated to a temperature equal to or higher than the melting point of the adhesive. In this way, a continuous current collector foil is obtained as a roll, and the current collector foil 13 is obtained by cutting the current collector foil 13 to the required size while unwinding it.

[0052] In the third step S23 of the second embodiment, when the laminated foil F is wound into the roll 32, the metal foil that was more elongated in the second step is wound on the outside (the direction farther from the center in the radial direction of the roll). This makes it possible to more effectively relieve the residual stress caused by heating the roll 32 to a temperature equal to or higher than the melting point of the adhesive, and suppress warping of the current collecting foil. EXAMPLES

[0053] 3. Working Example The warpage of the laminated foil was observed according to the manufacturing method S10 of the electrolytic foil of the first embodiment and the manufacturing method S20 of the electrolytic foil of the second embodiment. The common conditions for each example are as follows.

[0054] 3.1.Common matters [First metal foil] The first metal foil is aluminum foil (linear expansion coefficient 23.9 × 10 -6 / ℃) was used. The aluminum foil had a thickness of 50 μm and a width of 1265 mm. [Second metal foil] The second metal foil is copper foil (linear expansion coefficient 17.7×10 ー6 / ℃) was used. The thickness of the copper foil was 8 μm and the width was 1265 mm. [glue] The adhesive used an olefin resin as the base agent and an epoxy resin as the hardener, and contained Ni-plated particles as a conductive aid.

[0055] [Operating conditions] Line speed: 15m / min Gravure roll: Elongated, 75 lines Drying oven temperature: 150℃ - Drying furnace length: approx. 12m Heat roll temperature: Temperature of the first metal foil (temperature will be described later) Rubber roll temperature: Temperature of the second metal foil (temperature will be described later) Pressing force between heat roll and rubber roll (nip pressure): 0.45MPa

[0056] 3.2. Example 1 and Example 2 In Examples 1 and 2, following the manufacturing method S10 of the current collector foil of the first embodiment, a laminated foil F was produced by the first step S11 and the second step S12, and the presence or absence of warping was visually observed. The temperature and elongation conditions are shown in Table 1. In Example 2, the second metal foil was heated with a heater before lamination in order to increase the temperature of the second metal foil.

[0057] 3.3. Example 3 In Example 3, the first step S21 to the third step S23 were carried out following the method S20 for producing a current collector foil of the second embodiment. The temperature and elongation conditions in the second step S22 are shown in Table 1. In addition, the laminated foil F in the third step S23 was wound up with the first metal foil (aluminum foil) on the outside, and then the roll was maintained at 80°C for 3 days.

[0058] 3.4. Comparative Example 1 In Comparative Example 1, the conditions were the same as in Example 3, except that in the third step, the second metal foil (copper foil) was wound on the outside.

[0059] 3.5.Results The conditions and results are shown in Table 1. Table 1 shows the temperature conditions, the difference in the amount of elongation between the first metal foil and the second metal foil when they were bonded together (calculated from the temperature), and the visual observation results for warpage.

[0060] [Table 1]

[0061] In Comparative Example 1, warping occurred at both ends of the laminated foil in the width direction, but no warping occurred in Examples 1 to 3. More specifically, in Examples 1 and 2, warping could be suppressed by limiting the difference in elongation to 0.8 mm or less. In Example 3, the difference in elongation was greater than 0.8 mm, but warping could be suppressed by making the first metal foil the outer side during winding in the third process. [Explanation of symbols]

[0062] Reference Signs List 10: secondary battery, 11: power storage module, 12: bipolar electrode, 13: current collecting foil, 14: positive electrode active material layer (first active material layer), 15: negative electrode active material layer (second active material layer), 16: separator, 20: sealing body, 21: first sealing member, 22: second sealing member, 23: spacer

Claims

1. A method for manufacturing a current collecting foil, comprising the steps of: A first step of applying an adhesive to one side of a first metal foil; A second step of laminating a second metal foil to the adhesive-coated surface of the first metal foil and applying heat and pressure to obtain a laminated foil; A third step of winding up the laminated foil and then heating it, In the second step, the difference in elongation between the first metal foil and the second metal foil is 0.8 mm or less; or In the third step, the laminated foil is wound up so that one of the first metal foil and the second metal foil having a larger linear expansion coefficient is on the outside. Manufacturing method of current collecting foil.

2. 2. The method for producing a current collector foil according to claim 1, wherein in the second step, the heating and the pressurization of the first metal foil and the second metal foil are performed using two opposing roll members, and the pressure of the portions sandwiched between the two roll members is set to 0.3 MPa or more.

3. The method for producing a current collector foil according to claim 1 , wherein in the second step, a difference in temperature between the first metal foil and the second metal foil is 10° C. or less.

4. A current collector foil is manufactured by the method according to any one of claims 1 to 3, forming a positive electrode active material layer on one surface of the current collector foil and a negative electrode active material layer on the other surface of the current collector foil.

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