Method for manufacturing current collector foil

Abstract

A method for producing a current collector foil for a liquid battery by bonding a first electrode foil having a pinhole and a second electrode foil, one of the first electrode foil and the second electrode foil being a positive electrode foil and the other being a negative electrode foil, the method comprising: a coating step for coating the first electrode foil with a binder; a suction step in which suction is performed from the surface side of the first electrode foil opposite to the surface to which the binder is applied, and the pinholes are impregnated with the binder; a drying step for drying the binder; and a hot-welding step of bonding the second electrode foil to the surface of the first electrode foil coated with the binder and performing hot welding.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a current collector foil. Background Art

[0002] Conventionally, a current collector foil for a liquid-type battery has been used, which is a laminate of a positive electrode foil and a negative electrode foil.

[0003] For example, Japanese Patent Application Laid-Open No. 2023-053669 discloses a bipolar current collector. The bipolar current collector includes: a positive electrode current collector having an aluminum layer, a negative electrode current collector having a copper layer, and an interlayer between the aluminum layer and the copper layer. The thickness of the copper layer is 3 μm to 10 μm. The interlayer includes a porous aluminum oxide portion and a nickel portion present in the pores of the aluminum oxide portion.

[0004] In addition, Japanese Patent Publication No. 2018-037247 discloses a laminated all-solid secondary battery. The all-solid secondary battery is electrically connected in parallel in a parallel electrode body by stacking a positive electrode, a solid electrolyte layer, and a negative electrode. A plurality of parallel electrode bodies are electrically connected in series via bipolar electrodes. The bipolar electrode is arranged relative to the positive electrode and the negative electrode, and the bipolar electrode collector foil is separated from the positive electrode collector foil of the positive electrode and the negative electrode collector foil of the negative electrode arranged relative to the bipolar electrode. Summary of the invention

[0005] In the past, as a collector foil for liquid-type batteries, a collector foil formed by bonding a positive electrode foil and a negative electrode foil via an adhesive was used. However, in the metal foil used as the positive electrode foil and the negative electrode foil, pinholes are sometimes generated during the manufacturing process. In addition, when a collector foil having pinholes in at least one of the positive electrode foil and the negative electrode foil is used in a liquid-type battery, a through hole penetrating the positive electrode foil, the adhesive layer, and the negative electrode foil is generated, and in the liquid-type battery, a liquid short circuit occurs through the through hole.

[0006] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a method for manufacturing a collector foil capable of reducing the number of pinholes in the collector foil.

[0007] Means for solving the above-mentioned problems include the following aspects. <1> A method for producing a current collector foil, comprising laminating a first electrode foil having pinholes and a second electrode foil to obtain a current collector foil for a liquid battery, wherein: One of the first electrode foil and the second electrode foil is a positive electrode foil, and the other is a negative electrode foil. The manufacturing method has the following features: A coating step of coating a binder on the first electrode foil; a suction step of sucking from a surface side of the first electrode foil opposite to a surface on which the adhesive is applied, so that the adhesive is impregnated into the pinholes; A drying step of drying the binder; and The heat-fusion step is to bond the second electrode foil to the surface of the first electrode foil on which the adhesive is applied, and to heat-fusion bond the second electrode foil. <2> according to <1> In the method for producing a current collector foil, the suction step is a step of bringing a suction member having suction holes on a surface into contact with a surface of the first electrode foil opposite to a surface on which the binder is applied to perform suction. <3> according to <2> In the method for producing a current collector foil, the diameter of the attraction holes is 0.5 mm or more and 15 mm or less. <4> according to <2> In the method for producing a current collector foil, the interval between the attraction holes is 1.0 mm to 20 mm. <5> according to <2> In the method for producing a current collector foil, the suction pressure from the suction holes is 5 kPa or more and 40 kPa or less.

[0008] According to the present disclosure, a method for manufacturing a collector foil capable of reducing the number of pinholes in the collector foil is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements. Figure 1 This is a schematic diagram showing a current collector foil manufacturing apparatus for carrying out the current collector foil manufacturing method according to the embodiment of the present disclosure. Figure 2 This is a schematic cross-sectional view showing a state where a binder is impregnated into a pinhole in a suction step of a method for producing a negative electrode for a battery according to an embodiment of the present disclosure. Figure 3 This is a schematic cross-sectional view showing a state where a binder is impregnated into a pinhole in a suction step of a method for producing a negative electrode for a battery according to an embodiment of the present disclosure. Figure 4 This is a schematic cross-sectional view showing a state where a binder is impregnated into a pinhole in a suction step of a method for producing a negative electrode for a battery according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0010] An embodiment as an example of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In addition, in this specification, the numerical range expressed using "to" means that these numerical values ​​are set as a lower limit and an upper limit and the range includes these numerical values. In the numerical ranges recorded in the stepwise manner in this specification, the upper limit of a certain numerical range can be replaced by the upper limit of other numerical ranges recorded in the stepwise manner, or by the value shown in the embodiments. In addition, the lower limit of a certain numerical range can be replaced by the lower limit of other numerical ranges recorded in the stepwise manner, or by the value shown in the embodiments. In addition, regarding the content, "%" means "mass %" unless otherwise specified.

[0011] Each component may also contain multiple corresponding substances. When referring to the amount of each component in a composition, if a plurality of substances corresponding to each component are present in the composition, unless otherwise specified, it means the total amount of the plurality of substances present in the composition. A “process” is not just an independent process. Even if it cannot be clearly distinguished from other processes, it is also included in this term as long as the desired purpose of the process can be achieved. Method for producing collector foil

[0012] The manufacturing method of the collector foil according to the embodiment of the present disclosure is a manufacturing method of the collector foil for a liquid battery (i.e., a battery having an electrolyte as an electrolyte) obtained by laminating a first electrode foil having pinholes and a second electrode foil. In addition, one of the first electrode foil and the second electrode foil is a positive electrode foil and the other is a negative electrode foil. Furthermore, the method for producing the current collector foil includes the following steps (1) to (4). (1) Coating step: coating the binder on the first electrode foil (2) A suction step of sucking the adhesive from the surface of the first electrode foil opposite to the surface on which the adhesive is applied, so that the adhesive is impregnated into the pinholes. (3) Drying process: drying the adhesive (4) A heat-welding step of attaching the second electrode foil to the surface of the first electrode foil coated with the adhesive and heat-welding the foil.

[0013] The manufacturing method of the collector foil according to the embodiment of the present disclosure can reduce the number of pinholes in the collector foil by including the suction step between the coating step and the drying step as described above. As a result, when the collector foil is used in a liquid battery, the generation of through holes in the collector foil can be suppressed, and the generation of liquid short circuits in the liquid battery can be suppressed.

[0014] Conventionally, a collector foil is used which is formed by bonding a positive electrode foil and a negative electrode foil via a binder. However, in the metal foil used as the positive electrode foil and the negative electrode foil, pinholes (small holes penetrating the metal foil) may be generated during the manufacturing process.

[0015] For example, there is a case where a collector foil obtained by using a positive electrode foil having pinholes and bonding the positive electrode foil and the negative electrode foil via an adhesive is used for a liquid-type battery. In this case, a through hole that penetrates all of the positive electrode foil, the adhesive layer, and the negative electrode foil is sometimes formed at the location of the pinhole in the positive electrode foil. Specifically, at the location of the pinhole in the positive electrode foil, a hole is also formed in the adhesive layer formed on the pinhole, that is, the pinhole is sometimes not blocked by the adhesive. In addition, if the collector foil obtained by bonding the positive electrode foil and the adhesive layer to the negative electrode foil is used in a liquid-type battery, the electrolyte will invade the holes that penetrate the positive electrode foil and the adhesive layer, and the electrolyte will be in contact with the negative electrode foil. If the battery is repeatedly charged and discharged in this state, sometimes due to the reaction with the electrolyte (for example, when copper foil is used as the negative electrode foil, Cu→Cu 2+ +2e - As a result, through holes are formed that completely penetrate the positive electrode foil, the adhesive layer, and the negative electrode foil. In addition, there is a case where a collector foil obtained by using a negative electrode foil having pinholes and laminating the negative electrode foil and the positive electrode foil via an adhesive is used for a liquid battery. In this case, at the location of the pinhole in the positive electrode foil, a through hole that penetrates all of the positive electrode foil, the adhesive layer and the negative electrode foil is sometimes formed. Specifically, at the location of the pinhole in the negative electrode foil, a hole is also formed in the adhesive layer formed on the pinhole, that is, the pinhole is sometimes not blocked by the adhesive. In addition, if the collector foil obtained by laminating the positive electrode foil to the negative electrode foil and the adhesive layer is used for a liquid battery, the electrolyte will invade the holes that penetrate the negative electrode foil and the adhesive layer, and the electrolyte will be in contact with the positive electrode foil. If the battery is repeatedly charged and discharged in this state, the positive electrode foil will sometimes break, and as a result, a through hole that completely penetrates the negative electrode foil, the adhesive layer and the positive electrode foil is formed.

[0016] Furthermore, in the collector foil having through holes penetrating the positive electrode foil, the binder layer, and the negative electrode foil, one side of the collector foil communicates with the other side through the through holes, so that a liquid short circuit occurs.

[0017] Therefore, in the manufacturing method of the collector foil involved in the embodiment of the present disclosure, after the binder is applied to the first electrode foil and before the binder is dried, an suction process is provided for suctioning from the surface side of the first electrode foil opposite to the surface coated with the binder. Through this suction process, the binder before drying (that is, in liquid state) is impregnated into the pinholes of the first electrode foil, and the pinholes can be buried. Thus, even if the collector foil is used for a liquid battery, the situation in which the electrolyte intrudes into the pinholes of the first electrode foil is suppressed, and the situation in which a through hole that completely penetrates the positive electrode foil, the binder layer, and the negative electrode foil is suppressed. As a result, the occurrence of liquid short circuits in liquid batteries can be suppressed.

[0018] Here, one aspect of a method for producing a current collector foil according to an embodiment of the present disclosure will be described in detail using the drawings.

[0019] Figure 1 This is a schematic diagram showing a current collector foil manufacturing apparatus for carrying out the current collector foil manufacturing method according to the embodiment of the present disclosure. Figure 1 The current collector foil manufacturing apparatus 100 shown has a positive electrode foil 12 (such as Al foil) formed into a roll as an example of a first electrode foil and a negative electrode foil 14 (such as Cu foil) formed into a roll as an example of a second electrode foil. The positive electrode foil 12 is a metal foil having pinholes. (1) Coating process

[0020] First, the positive electrode foil 12 is conveyed by a roller pair consisting of a coating roller 22A (e.g., a gravure roller) and a counter roller 22B. A portion of the coating roller 22A is immersed in the adhesive 40, and the adhesive 40 attached to the surface of the coating roller 22A is coated (e.g., gravure coated) on one side of the positive electrode foil 12 from the coating roller 22A. (2) Suction process

[0021] Next, the positive electrode foil 12 coated with the binder 40 on one side is conveyed to a position in contact with a suction roller 24 as an example of a member having a suction mechanism (hereinafter also referred to as a "suction member"). In addition, the suction roller 24 is arranged at a position in contact with the surface of the positive electrode foil 12 on the side where the binder 40 is not coated. And, the surface side of the positive electrode foil 12 not coated with the binder 40 is sucked by the suction roller 24. In this way, the binder 40 can be impregnated into the pinholes opened in the positive electrode foil 12.

[0022] More specifically, if Figure 2 As shown in FIG. 1 , at the location where the pinhole 120 is opened in the positive electrode foil 12, sometimes a hole is also formed in the adhesive 40 applied on the pinhole 120. Figure 3 As shown in FIG. 1 , the positive electrode foil 12 is sucked in the direction of arrow A by the suction roller 24 from the side where the adhesive 40 is not applied. As a result, the pinhole 120 opened in the positive electrode foil 12 becomes negative pressure, and the adhesive 40 flows in the direction of arrow B. As a result, as shown in FIG. Figure 4 As shown, the adhesive 40 is impregnated into the pinhole 120, and the pinhole 120 is blocked.

[0023] Here, a suction member such as a suction roller will be described. The suction roller is a roller capable of performing suction through suction holes provided on the surface. As the suction member used in the suction process, Figure 1The suction roller 24 is shown in the figure, but the present disclosure is not limited thereto. As the suction member used in the embodiment of the present disclosure, any member that can suction from the side of the first electrode foil opposite to the side coated with the adhesive is not particularly limited. For example, a belt having suction holes on the surface (hereinafter referred to as "suction belt") may also be used.

[0024] From the viewpoint of making it easier to reduce the number of pinholes in the collector foil, the suction member ( Figure 1 The diameter of the suction holes provided on the surface of the suction roller 24 (the arithmetic mean of the diameters of 20 suction holes selected at random) is preferably 0.5 mm or more and 15 mm or less, and more preferably 1.0 mm or more and 10 mm or less. From the viewpoint of making it easier to reduce the number of pinholes in the collector foil, the suction member ( Figure 1 The spacing of the suction holes on the surface of the suction roller 24 (the distance between the center points of adjacent suction holes, the arithmetic mean of the distance between the center points of 20 groups of suction holes selected at random) is preferably 1.0 mm or more and 20 mm or less. More preferably, it is 2.0 mm or more and 10 mm or less. From the viewpoint of making it easier to reduce the number of pinholes in the collector foil, the suction member ( Figure 1 The suction pressure of the suction holes in the suction roller 24 is preferably 5 kPa or more and 40 kPa or less. More preferably, it is 10 kPa or more and 30 kPa or less.

[0025] As the suction member, a roller shape (for example Figure 1 The suction roller 24 shown in the figure). From the viewpoint of making it easier to reduce the number of pinholes in the collector foil, the wrap angle of the roller-shaped suction member (that is, the angle formed by the travel direction of the first electrode foil leaving the suction roller side relative to the travel direction of the first electrode foil entering the suction roller side) is preferably 40° or more and 100° or less. More preferably, it is 50° or more and 90° or less.

[0026] In addition, as a roller-shaped attraction member (for example Figure 1 The material of the surface of the suction roller 24 shown is preferably metal, and SUS is particularly preferred. In addition, as the material of the surface of the suction belt, resin and rubber are preferable. (3) Drying process

[0027] Next, if Figure 1 As shown, the positive electrode foil 12 that has been subjected to the suction process by the suction roller 24 is transported to the drying furnace 30 , and the binder 40 on the positive electrode foil 12 is heated and dried in the drying furnace 30 .

[0028] In addition, the heating temperature in the drying process ( Figure 1 The temperature in the drying furnace 30 can be adjusted according to the binder used, and is preferably 80° C. or higher and 200° C. or lower, and more preferably 100° C. or higher and 180° C. or lower, for example. (4) Hot-melt process

[0029] Next, the positive electrode foil 12 after passing through the drying furnace 30 is conveyed to a contact position with the heat roller pair 28A, 28B via the conveying roller 26. In the nip portion of the heat roller pair 28A, 28B, the negative electrode foil 14 conveyed from the other direction is attached to the surface of the positive electrode foil 12 coated with the adhesive 40. The positive electrode foil 12 and the negative electrode foil 14 are thermally fused via the adhesive 40 by heating and pressurizing by the heat roller pair 28A, 28B. Through these steps, the current collector foil 10 in which the positive electrode foil 12 and the negative electrode foil 14 are bonded together is manufactured.

[0030] In addition, the heating temperature in the heat welding process ( Figure 1 The temperature of the hot roller pair 28A, 28B can be adjusted according to the adhesive used, and is preferably 50°C or higher and 150°C or lower, and more preferably 70°C or higher and 120°C or lower. In addition, the pressure applied during the heat welding process ( Figure 1 The clamping pressure by the heat roller pair 28A, 28B is preferably, for example, 0.20 MPa or more and 0.70 MPa or less, and more preferably 0.30 MPa or more and 0.60 MPa or less.

[0031] In addition, Figure 1 In the above, a manufacturing method is described in which a binder 40 is applied to a positive electrode foil 12 having pinholes (a coating process), and then a negative electrode foil 14 is bonded and heat-fused (a heat-fusion process), but the present disclosure is not limited thereto. In other words, a manufacturing method may also be used in which a binder is applied to a negative electrode foil having pinholes (a coating process), and then a positive electrode foil is bonded and heat-fused (a heat-fusion process).

[0032] In the method for producing a current collector foil according to the embodiment of the present disclosure, one of the first electrode foil and the second electrode foil is a positive electrode foil, and the other is a negative electrode foil.

[0033] The positive electrode foil used is preferably a conductive member made of a metal with good conductivity (eg, aluminum). The thickness of the positive electrode foil is, for example, preferably 10 μm to 100 μm, and more preferably 20 μm to 60 μm.

[0034] On the other hand, as the negative electrode foil, a conductive member made of a metal with good conductivity (such as copper) is suitable. As the thickness of the negative electrode foil, for example, it is preferably 1 μm or more and 20 μm or less, and more preferably 3 μm or more and 12 μm or less.

[0035] Regarding the binder used in the method for manufacturing the current collector foil according to the embodiment of the present disclosure, any binder that is liquid before passing through the drying process is acceptable and is not particularly limited. For example, a binder obtained by adding a curing agent (such as an isocyanate curing agent) to a main agent (such as an olefin resin) is preferably used. In addition, a conductive auxiliary agent (such as particles coated with Ni) may be added to the binder. As the thickness of the binder layer formed by coating and drying the binder, for example, it is preferably 0.5 μm or more and 15 μm or less, and more preferably 1.0 μm or more and 10 μm or less. Battery

[0036] Next, each component of the liquid system battery that constitutes the current collector foil obtained by the method for manufacturing the current collector foil according to the embodiment of the present disclosure will be described. Positive electrode active material layer

[0037] The positive electrode composite material layer contains a positive electrode active material and may also contain, for example, a binder. As the positive electrode active material, for example, lithium nickel cobalt manganese composite oxide (hereinafter, sometimes simply referred to as "LNCM") can be cited. The simplest LNCM is represented by the following general formula: LiNi x Co y Mn z O2 (where x, y, and z in the formula are 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1). LNCM may also contain other additive elements in addition to Li, Ni, Co, and Mn, such as transition metal elements other than Ni, Co, and Mn and typical metal elements other than Li. LNCM has a layered crystal structure. LNCM can exceed 50% by mass of the entire positive electrode active material, for example, accounting for 80% to 100% by mass. The positive electrode active material may also be composed only of LNCM. As other positive electrode active materials, for example, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel manganese composite oxide, etc. can be cited.

[0038] As the binder contained in the positive electrode composite material layer, for example, a vinyl halide resin such as polyvinylidene fluoride (PVdF) can be exemplified. The positive electrode composite material layer may also contain other components, such as a conductive material. As the conductive material, for example, non-graphitizable carbon, graphitizable carbon such as carbon black, graphite, etc. can be cited. Negative electrode active material layer

[0039] As the negative electrode active material layer, the negative electrode active material layer described above is used, but the details have been described above and will not be described here. Spacers

[0040] The separator is an electrically insulating porous film. The separator electrically isolates the positive electrode from the negative electrode. The separator may have a thickness of, for example, 5 μm to 30 μm. The separator may be composed of, for example, a porous polyethylene (PE) film, a porous polypropylene (PP) film, etc. The separator may also have a multilayer structure. For example, the separator may also be composed of a porous PP film, a porous PE film, and a porous PP film stacked in sequence. The separator may also have a heat-resistant layer on its surface. The heat-resistant layer contains a heat-resistant material. Examples of heat-resistant materials include metal oxide particles such as aluminum oxide, high melting point resins such as polyimide, and the like. Electrolyte

[0041] The battery according to the embodiment of the present disclosure further comprises an electrolyte solution, and a non-aqueous electrolyte solution is particularly preferred. Solvents

[0042] The non-aqueous electrolyte solution contains a solvent (non-aqueous solvent) and an electrolyte. Examples of the solvent (non-aqueous solvent) include N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(fluorosulfonyl)imide (DEME), 1-ethyl-3-methylimidazole bis(fluorosulfonyl)imide (EMI), and 1-ethyl-2,3-dimethylimidazole bis(fluorosulfonyl)imide (DEMI-FSI). Electrolytes

[0043] As the electrolyte in the electrolytic solution, for example, Li salts can be cited. As the Li salts, lithium bis(fluorosulfonyl)imide (LiFSI), LiPF6 (lithium hexafluorophosphate), lithium tetrafluoroborate (LiBF4), Li[N(CF3SO2)2], etc. can be cited. The amount of the electrolyte may be, for example, 1.0 mol / L to 2.0 mol / L, preferably 1.0 mol / L to 1.5 mol / L.

[0044] The electrolyte may contain various additives in addition to the solvent and the electrolyte, such as a thickener, a film former, a gas generator, etc. The electrolyte is typically a non-aqueous electrolyte that is liquid at room temperature (e.g., 25±10°C). The electrolyte is typically liquid in the battery's operating environment (e.g., a temperature environment of -20°C to +60°C). use

[0045] Examples of applications of the battery according to the embodiment of the present disclosure include power sources for hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and battery electric vehicles (BEV).

[0046] Hereinafter, the present disclosure will be described based on examples, but the present disclosure is not limited to these examples at all. Preparation of binder

[0047] The adhesive 1 is obtained by mixing an olefin resin as a main agent, an isocyanate curing agent, and Ni-plated particles as a conductive auxiliary agent. Production of collector foil

[0048] As Figure 1 The current collector foil manufacturing apparatus 100 shown uses the binder 1 as the binder 40, uses aluminum foil (Al foil) as the positive electrode foil 12, and uses copper foil (Cu foil) as the negative electrode foil 14. The line speed (conveying speed) is set to 15 m / min.

[0049] The adhesive 1 was applied to one side of the Al foil by gravure coating (coating step). A gravure roll (Elongate, 75 lines) was used as the coating roll 22A.

[0050] Next, suction is performed by the suction roller 24 from the surface of the Al foil opposite to the surface on which the adhesive 1 is applied under the following conditions (suction step). (Conditions of suction roller) Diameter of suction hole: Suction hole spacing (distance between the center points of the suction holes): 4mm Suction pressure: 20kPa Wrap angle of suction roller: 50° to 90° Material of suction roller: SUS

[0051] Next, the adhesive 1 is passed through a drying furnace 30 set at a temperature of 150° C. to be dried (drying step). Then, the Cu foil was bonded to the surface of the Al foil conveyed to the heat roller pairs 28A and 28B on which the binder 1 was applied and heat-fused (heat-fusion step) to obtain the collector foil of the example. The conditions of the heat roller pairs 28A and 28B were as follows. Temperature of hot roller pair: 90℃ The clamping pressure of the hot roller pair: 0.45MPa Comparative Example

[0052] Will Figure 1 The suction roller 24 in the collector foil manufacturing apparatus 100 shown was changed to a SUS roller having no suction mechanism, that is, a collector foil of a comparative example was obtained in the same manner as in Example 1 except that the suction step was not performed. Evaluation test Pinhole inspection

[0053] The current collector foils obtained in Examples and Comparative Examples were inspected for the presence or absence of pinholes having a diameter of 0.5 mm or less using an inspection machine. The results are shown in Table 1 below. (Table 1)

[0054] It is found that the number of pinholes in the collector foil of the example in which suction by the suction roller 24 is performed after application of the binder 1 can be reduced compared with the collector foil of the comparative example in which suction is not performed.

Claims

1. A method for producing a current collector foil, comprising laminating a first electrode foil having pinholes and a second electrode foil to obtain a current collector foil for a liquid battery, wherein: One of the first electrode foil and the second electrode foil is a positive electrode foil, and the other is a negative electrode foil. The manufacturing method has the following features: A coating step of coating a binder on the first electrode foil; a suction step of sucking from a surface side of the first electrode foil opposite to a surface on which the adhesive is applied, so that the adhesive is impregnated into the pinholes; A drying step to dry the binder; as well as The heat-fusion step is to bond the second electrode foil to the surface of the first electrode foil on which the adhesive is applied, and to heat-fusion bond the second electrode foil.

2. The method for producing a current collector foil according to claim 1, wherein: The suction step is a step of bringing a suction member having suction holes on its surface into contact with the surface of the first electrode foil opposite to the surface on which the binder is applied to perform suction.

3. The method for producing a current collector foil according to claim 2, wherein: The diameter of the suction hole is greater than or equal to 0.5 mm and less than or equal to 15 mm.

4. The method for producing a current collector foil according to claim 2, wherein: The interval between the suction holes is not less than 1.0 mm and not more than 20 mm.

5. The method for producing a current collector foil according to claim 2, wherein: The suction pressure from the suction hole is 5 kPa or more and 40 kPa or less.

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