Manufacturing method of current collector foil

Abstract

To provide a manufacturing method for a current collector foil whereby generation of pinholes can be reduced.SOLUTION: A manufacturing method for a current collector foil, includes: a first step of applying an adhesive to one surface of a first metal foil; a second step of bonding a second metal foil to the surface of the first metal foil to which the adhesive has been applied, and applying heat and pressure thereto to obtain a bonded foil; and a third step of winding the bonded foil; wherein the surface tension of the adhesive agent is 60 mN / m or less, and a contact angle between the adhesive agent and the first metal foil is 60° or less.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Various techniques have been proposed regarding a method for manufacturing a current collector foil as disclosed in Patent Documents 1 and 2.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, a clad material in which an aluminum (Al) foil and a copper (Cu) foil are laminated is used as the current collector foil used in a bipolar battery. And it is known that the current collector foil is manufactured by rolling an aluminum foil and a copper foil. From the viewpoint of improving the battery capacity, it is preferable that the current collector foil is thin. When the current collector foil is made thin, pinholes may occur in the current collector foil. If there are pinholes, the pinholes may grow with charge and discharge. As a solution to the above problems, for example, Patent Document 2 proposes a current collector foil having an anodic oxide layer in which Ni portions are formed in pores between Al and Cu. However, the anodic oxidation treatment is costly. Further, since this technique forms an anodic oxide layer on the Al foil, there are problems such as that the anodic oxide layer is not formed in the pinhole portions existing in the Al foil if there are pinholes in the Al foil.

[0005] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide a method for manufacturing a current collector foil capable of reducing the occurrence of pinholes. [Means for solving the problem]

[0006] In other words, this disclosure includes the following aspects: <1> The first step involves applying adhesive to one side of the first metal foil, The second step involves bonding the second metal foil to the surface of the first metal foil to which the adhesive has been applied, and then heating and pressurizing it to obtain a bonded foil. The process includes a third step of winding up the laminated foil, The surface tension of the adhesive is 60 mN / m or less. A method for manufacturing a current collector foil, wherein the contact angle between the adhesive and the first metal foil is 60° or less.

[0007] <2> The adhesive contains a leveling agent, The content of the leveling agent is 0.1% by mass or more and 1% by mass or less with respect to the total mass of the adhesive. <1> A method for manufacturing current collector foil as described above.

[0008] <3> The adhesive contains water as a solvent, <1> or the above <2> A method for manufacturing current collector foil as described above.

[0009] <4> The first metal foil is aluminum foil, <1> ~the aforementioned <3> A method for manufacturing current collector foil as described in any one of the following.

[0010] <5> The aforementioned <1> ~the aforementioned <4> A method for manufacturing a battery using a current collector foil obtained by any one of the manufacturing methods described. [Effects of the Invention]

[0011] The current collector foil manufacturing method described herein can reduce the occurrence of pinholes. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a flowchart of Example 1. [Figure 2]FIG. 2 is a schematic diagram showing an example of a laminating apparatus (dry lamination). [Figure 3] FIG. 3 is a flowchart of Comparative Example 1. MODE FOR CARRYING OUT THE INVENTION

[0013] Hereinafter, embodiments according to the present disclosure will be described. Note that matters other than those specifically mentioned in this specification and necessary for implementing the present disclosure (for example, general configurations and manufacturing processes of current collector foils that do not characterize the present disclosure) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. Also, the dimensional relationships (length, width, thickness, etc.) in the figures do not reflect actual dimensional relationships.

[0014] In the present disclosure, there is a first step of applying an adhesive to one side of a first metal foil, a second step of laminating a second metal foil onto the surface of the first metal foil to which the adhesive has been applied, and heating and pressing to obtain a laminated foil, and a third step of winding up the laminated foil. The surface tension of the adhesive is 60 mN / m or less, and the contact angle between the adhesive and the first metal foil is 60° or less, and a method for manufacturing a current collector foil is provided.

[0015] In the present disclosure, a laminated foil obtained by laminating a first metal foil and a second metal foil is produced using a dry laminator.

[0016] The method for manufacturing a current collector foil of the present disclosure includes a first step, a second step, and a third step.

[0017] (First Step) The first step is a step of applying an adhesive to one side of a first metal foil. The method of applying the adhesive is not particularly limited. For example, a roll-shaped first metal foil may be unwound, and the adhesive may be applied using a doctor blade, a gravure roll, or the like. Thereafter, the solvent or the like in the adhesive may be dried by hot air or the like in a drying furnace. The temperature of the drying furnace may be, for example, 150 °C or higher.

[0018] The surface tension of the adhesive is 60 mN / m or less. The contact angle between the adhesive and the first metal foil is 60° or less. The main component of the adhesive is preferably an aqueous polyester resin solution. Here, the aqueous polyester resin solution refers to a solution containing water as a solvent and a polyester resin as a solute. Examples of the aqueous polyester resin solution include Aron Melt (Aron Melt is a registered trademark) PES1000 and Aron Melt PES2000 series manufactured by Toagosei Co., Ltd. The content of the main component may be 50% by mass or more based on the total mass of the adhesive. The adhesive may contain a conductive auxiliary agent. The conductive auxiliary agent may be Ni-plated particles or the like. The content of the conductive auxiliary agent is not particularly limited. The adhesive may contain a leveling agent. Here, the leveling agent refers to a compound that lowers the surface tension of the adhesive when added to the adhesive as compared with before addition. By lowering the surface tension of the adhesive by adding the leveling agent, the adhesive easily enters the pinholes of the first metal foil. Therefore, even if there are pinholes in the first metal foil, it is possible to fill the pinholes with the adhesive and prevent the penetration of the liquid into the current collector foil. The content of the leveling agent may be 0.1% by mass or more and 1% by mass or less based on the total mass of the adhesive. The leveling agent may be a hydrocarbon-based resin, a silicone-based resin, a fluorine-based resin, or the like, or may be BYK-ET 3033 (BYK is a registered trademark) manufactured by BYK Co., Ltd. The adhesive may contain water as a solvent.

[0019] Examples of metals that can be used as the first metal foil include aluminum, copper, stainless steel (SUS), and nickel. The first metal foil may be aluminum foil. The thickness of the first metal foil is, for example, 0.1 μm or more and 100 μm or less.

[0020] (2nd process) The second step is to bond the second metal foil to the surface of the first metal foil to which the adhesive has been applied, and then heat and pressurize it to obtain a bonded foil.

[0021] The heating and pressurizing method in the second step is not particularly limited. For example, the workpiece, in which a roll-shaped second metal foil has been unwound and bonded onto the surface of the first metal foil to which adhesive has been applied, may be heated and pressurized using a heat roll and a rubber roll, etc. The heat roll temperature may be, for example, 90°C or higher. The hot roll nip pressure may be, for example, 0.45 MPa or higher.

[0022] The metal used as the second metal foil can be of a different type than the metal used as the first metal foil. Examples of metals that can be used as the second metal foil include copper, stainless steel (SUS), and nickel. For example, aluminum could be selected as the metal for the first metal foil and copper as the metal for the second metal foil. The second metal foil may be copper foil. The thickness of the second metal foil is, for example, 0.1 μm or more and 100 μm or less.

[0023] (3rd step) The third step is to wind up the laminated foil. The method for winding the laminated foil is not particularly limited, and the laminated foil obtained in the second step may be wound up using a roller or the like. After winding up the laminated foil, the laminated foil in roll form may be heated. The winding line speed may be, for example, 15 m / min or more.

[0024] The current collector foil obtained by the manufacturing method of the present disclosure comprises a laminated foil in which a first metal foil and a second metal foil are bonded together with an adhesive. The current collector foil may be a bipolar current collector foil. A bipolar current collector foil has a positive electrode current collector foil on one side and a negative electrode current collector foil on the other side. Preferably, the first metal foil is the positive electrode current collector foil and the second metal foil is the negative electrode current collector foil. The thickness of the current collector foil is, for example, between 0.2 μm and 200 μm.

[0025] This disclosure provides a method for manufacturing a battery using a current collector foil obtained by the method for manufacturing the current collector foil described above. The current collector foil of this disclosure is used in the manufacture of batteries. The type of battery using current collector foil is not particularly limited, but lithium-ion secondary batteries are an example. The battery may be a liquid-type battery using an electrolyte solution, or a solid-state battery using a solid electrolyte solution. Examples of battery applications include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline cars, and diesel cars. In particular, it may be used as a power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Furthermore, batteries may be used as power sources for mobile devices other than vehicles (e.g., railways, ships, aircraft), or as power sources for electrical products such as information processing devices. [Examples]

[0026] (Example 1) Aluminum foil was used as the first metal foil, and copper foil was used as the second metal foil. The adhesive used consisted of a water-based polyester resin solution (manufactured by Toagosei Co., Ltd.) as the main component, Ni-plated particles as a conductive additive, and BYK-ET 3033 (manufactured by BYK Corporation) as a leveling agent. The amount of leveling agent added was set to 0.1% by mass or more and 1% by mass or less relative to the total mass of the adhesive. The surface tension of the adhesive was set to 30 mN / m or more and 60 mN / m or less, and the contact angle with the aluminum foil was 60°. Figure 1 is a flowchart of Example 1. Figure 2 is a schematic diagram showing an example of a lamination device (dry lamination). The conditions for dry lamination shown in Figure 2 were set as follows. Line speed: 15m / min • Gravure roll: Elongated, 75 lines ·Drying oven temperature: 150℃ • Heat roll temperature: 90℃ • Hot roll nip pressure: 0.45 MPa In Example 1, as shown in Figure 1, a mixture of a main agent, a conductive additive, and a leveling agent was used as the adhesive. As shown in Figure 2, in the first step, the first metal foil 1 was unwound, and adhesive 2 was applied to one side of the first metal foil 1 using a gravure roll 3 to impregnate the pinholes present in the first metal foil 1 with the adhesive. The solvent of adhesive 2 was then dried in a drying oven 4. In the second step, the unwound second metal foil 5 was placed on the side of the first metal foil 1 to which adhesive 2 had been applied, and these were bonded together using a heat roll 6 while heating and pressing. In the third step, the bonded foil 7 was wound up to obtain a current collector foil.

[0027] (Comparative Example 1) Figure 3 is a flowchart of Comparative Example 1. In Comparative Example 1, the current collector foil was obtained in the same manner as in Example 1, except that a leveling agent was not used as an adhesive, as shown in Figure 3. The surface tension of the adhesive in Comparative Example 1 was 72.8 mN / m, and the contact angle with the aluminum foil was 102.3°.

[0028] We evaluated whether the current collector foils prepared in Example 1 and Comparative Example 1 contained pinholes of 0.5 mm or less. The results are shown in Table 1. Since the pinholes in the current collector foil are considered to be capillaries, it is assumed that they are filled by the rise in liquid level h due to capillary action as shown in Equation 1 below. If the value of the rise in liquid level h due to capillary action is positive, capillary action is triggered, and the adhesive can easily penetrate the pinholes in the first and second metal foils, resulting in the current collector foil being evaluated as having no pinholes. Equation 1: h = (2T cosθ) / (ρgr) h: Height of liquid level rise due to capillary action T: Surface tension of adhesive θ: Contact angle between the adhesive and the first metal foil ρ: Density of adhesive (1000 kg / m³) 3 ) g: Gravitational acceleration (9.8m / s 2 ) r: pinhole radius

[0029] [Table 1]

[0030] As shown in Table 1, it has been demonstrated that the current collector foil obtained by the manufacturing method of this disclosure can reduce the occurrence of pinholes. [Explanation of symbols]

[0031] 1. First metal foil 2. Adhesive 3. Gravure Roll 4.Drying oven 5. Second Metal Foil 6. Hot Roll 7. Laminated foil

Claims

1. The first step involves applying adhesive to one side of the first metal foil, The second step involves bonding the second metal foil to the surface of the first metal foil to which the adhesive has been applied, and then heating and pressurizing it to obtain a bonded foil. The process includes a third step of winding up the laminated foil, The surface tension of the adhesive is 60 mN / m or less. The contact angle between the adhesive and the first metal foil is 60° or less. A method for manufacturing current collector foil, wherein the adhesive contains a leveling agent.

2. The method for manufacturing a current collector foil according to Claim 1, wherein the content of the leveling agent is 0.1% by mass or more and 1% by mass or less with respect to the total mass of the adhesive.

3. The method for manufacturing a current collector foil according to claim 1, wherein the adhesive contains water as a solvent.

4. The method for manufacturing a current collector foil according to claim 3, wherein the first metal foil is aluminum foil.

5. A method for manufacturing a battery using a current collector foil obtained by the manufacturing method described in any one of claims 1 to 4.

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