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 and heating the bonded foil; wherein, in the third step, the winding tensile force of the bonded foil is 316 N / m or more; and wherein, in the third step, the heating temperature of the bonded foil is equal to or higher than a fusing point of a main agent of the adhesive.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 become larger during 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] In view of the above circumstances, the present disclosure is made, 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 and heating it, In the third step, the winding tension of the laminated foil is 316 N / m or more. A method for manufacturing current collector foil, wherein in the third step, the heating temperature of the bonded foil is equal to or greater than the melting point of the main component of the adhesive.

[0007] <2> In the third step, the laminated foil is wound up so that a pressure of 1.6 kPa or more is applied. <1> A method for manufacturing current collector foil as described above.

[0008] <3> The main component of the adhesive is a polyolefin resin, <1> or the above <2> A method for manufacturing current collector foil as described above.

[0009] <4> <1> ~ <3> A method for manufacturing a battery using a current collector foil obtained by any one of the manufacturing methods described. [Effects of the Invention]

[0010] The current collector foil manufacturing method described herein can reduce the occurrence of pinholes. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram showing an example of a lamination device (dry lamination). [Figure 2] Figure 2 is a graph showing the results of CAE calculations of the compressive stress applied to the laminated foil during winding, with respect to the radial position from the center of the roll, in the third step of Examples 1 and 2 and Comparative Example 1. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure are described below. Matters other than those specifically mentioned herein but necessary for the implementation of this disclosure (for example, the general structure and manufacturing process of current collector foils that do not characterize this disclosure) can be understood as design matters for those skilled in the art based on the prior art. This disclosure can be implemented based on the content disclosed herein and common technical knowledge in the art. Furthermore, the dimensions (length, width, thickness, etc.) shown in the diagram do not necessarily reflect the actual dimensions.

[0013] This disclosure includes a first step of applying an adhesive to one side of a 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 and heating it, In the third step, the winding tension of the laminated foil is 316 N / m or more. The present invention provides a method for manufacturing current collector foil, wherein in the third step, the heating temperature of the bonded foil is equal to or greater than the melting point of the main component of the adhesive.

[0014] In this disclosure, a laminated foil is manufactured by bonding a first metal foil and a second metal foil together using a dry laminator. By setting the winding tension of the laminated foil to a predetermined value or higher, and setting the heating temperature of the laminated foil during aging to a value above the melting point of the adhesive, the adhesive between the first metal foil and the second metal foil is made to flow, so that the adhesive flows into pinhole areas on the metal foil where there is no adhesive during bonding, thereby reducing the occurrence of pinholes in the current collector foil.

[0015] The method for manufacturing current collector foil according to this disclosure includes a first step, a second step, and a third step.

[0016] (1st step) The first step is to apply an adhesive to one side of the first metal foil. The method of applying the adhesive is not particularly limited. For example, the roll-shaped first metal foil may be unwound and the adhesive may be applied using a doctor blade, a gravure roll, or the like. Then, the adhesive may be dried by hot air or the like in a drying oven. The temperature of the drying oven may be, for example, 150°C or higher.

[0017] The main component of the adhesive may be a polyolefin-based resin or the like. Here, the polyolefin-based resin refers to a resin containing 50% by mass or more of olefin as a constituent unit with respect to the total mass of the constituent units contained in the entire resin. By using a polyolefin-based resin, the corrosion resistance against the electrolytic solution can be improved. The polyolefin-based resin is preferably an acid-modified polyolefin-based resin. Examples of the acid-modified polyolefin-based resin include a polyolefin-based resin acid-modified with an unsaturated carboxylic acid; a polyolefin-based resin acid-modified with an unsaturated carboxylic acid anhydride; and the like. Examples of the acid-modified polyolefin-based resin include maleic anhydride-modified polypropylene. Specific examples of the acid-modified polyolefin-based resin include acid-modified polyolefin-based resins contained in Unistol (R-200X, R-303XE, E-200EM, A-200PM, A-201PM, H-100, H-200, XP01A, XP01B / 11B, XP03F, XP04A, etc.) manufactured by Mitsui Chemicals, Inc. Unistol is a registered trademark. The content of the main component may be 50% by mass or more with respect to the total mass of the adhesive.

[0018] The melting point of the main component of the adhesive is preferably, for example, 30°C or higher and 80°C or lower, more preferably 40°C or higher and 75°C or lower, and even more preferably 45°C or higher and 70°C or lower. The melting point of the main component is a value measured by a known melting point measuring device.

[0019] 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 hardening agent. The amount of hardening agent is not particularly limited. The hardening agent can be epoxy resin or similar.

[0020] 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.

[0021] (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.

[0022] 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.

[0023] 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.

[0024] (3rd step) The third step is to wind up the laminated foil and heat it. In the third step, the winding tension of the laminated foil is 316 N / m or more. In the third step, the laminated foil may be wound up so that a pressure of 1.6 kPa or more is applied. In the third step, the heating temperature of the bonded foil should be at or above the melting point of the main component of the adhesive. The heating time for the laminated foil in the third step is not particularly limited and may be, for example, three days or more. The method for winding the laminated foil is not particularly limited, and the laminated foil obtained in the second step may be wound using a roller or the like. After winding the laminated foil, the rolled laminated foil is heated to a temperature above the melting point of the main component of the adhesive. The winding line speed may be, for example, 15 m / min or more.

[0025] 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. 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.

[0026] 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]

[0027] (Example 1) Aluminum foil was used as the first metal foil, and copper foil was used as the second metal foil. The adhesive used was a polyolefin resin (Mitsui Chemicals, Unistol XP11B, melting point: 80°C) as the main component, Ni-plated particles as a conductive additive, and epoxy resin as a curing agent. Figure 1 is a schematic diagram showing an example of a lamination device (dry lamination). The conditions for dry lamination shown in Figure 1 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, the first step was to unwind the first metal foil 1, apply adhesive 2 to one side of the first metal foil 1 using a gravure roll 3, and dry the adhesive 2 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 the adhesive 2 had been applied, and these were bonded together using a heat roll 6 and a rubber roll 7 while heating and pressing. In the third step, the bonded foil 8 was wound up so that the winding tension was 316 N / m. After that, as an aging treatment, the bonded foil 8 was subjected to a heat history of 80°C for 3 days while in the winding roll state to obtain a current collector foil.

[0028] (Example 2) In Example 2, the current collector foil was obtained in the same manner as in Example 1, except that in the third step, the laminated foil 8 was wound up so that the winding tension was 474 N / m.

[0029] (Comparative Example 1) In Comparative Example 1, the current collector foil was obtained in the same manner as in Example 1, except that in the third step, the laminated foil 8 was wound so that the winding tension was 158 N / m.

[0030] Figure 2 is a graph showing the results of CAE calculations of the compressive stress applied to the laminated foil during winding, with respect to the radial position from the center of the roll, in the third step of Examples 1 and 2 and Comparative Example 1. The calculation software used was Wind Master, manufactured by SUNAMI Corporation. Table 1 also shows the winding tension in the third step of Examples 1-2 and Comparative Example 1, the average compressive stress (pressure) calculated from Figure 2, and the results of evaluating whether or not the current collector foils produced in Examples 1-2 and Comparative Example 1 contained pinholes. As shown in Figure 2, the compressive stress decreases as you move away from the center of the roll. However, as shown in Table 1, if the winding tension is 316 N / m or more and the minimum compressive stress on the laminated foil is guaranteed to be 1.6 kPa or more, sufficient pressure is applied to the entire laminated foil. By heating the laminated foil above the melting point of the main component of the adhesive, the adhesive is made to flow, and it is considered that the pinholes in the resulting current collector foil can be filled with the adhesive. Thus, the current collector foil was evaluated as having no pinholes.

[0031] [Table 1]

[0032] 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]

[0033] 1. First metal foil 2. Adhesive 3. Gravure Roll 4.Drying oven 5. Second Metal Foil 6. Hot Roll 7. Rubber Roll 8. 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 and heating it, In the third step, the winding tension of the laminated foil is 316 N / m or more. In the third step, the heating temperature of the laminated foil is equal to or greater than the melting point of the main component of the adhesive. A method for manufacturing a current collector foil, wherein in the third step, the laminated foil is wound up so that a pressure of 1.6 kPa or more is applied.

2. The method for manufacturing a current collector foil according to claim 1, wherein the main component of the adhesive is a polyolefin resin.

3. A method for manufacturing a battery using a current collector foil obtained by the manufacturing method described in claim 1 or 2.

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