Method for manufacturing a current collector and an electrode structure equipped with a current collector

Abstract

This invention provides a technology to prevent electrodes pressed onto a current collector from coming into contact with metal foil, and to make it difficult for the electrodes to detach from the current collector. [Solution] The current collector comprises a metal foil and a resin layer disposed on the metal foil, wherein the electrodes are placed on the resin layer and the electrodes are pressed against the resin layer at a predetermined pressing temperature. The resin layer comprises a first resin layer disposed on the metal foil and a second resin layer disposed on the first resin layer. The glass transition temperature of the first resin layer and the glass transition temperature of the second resin layer are higher than the pressing temperature, and the glass transition temperature of the first resin layer and the glass transition temperature of the second resin layer are lower than the pressing temperature.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a current collector and a method for manufacturing an electrode structure including the current collector.

Background Art

[0002] Current collectors used in secondary batteries have been variously improved to enhance performance. For example, the current collector of Patent Document 1 includes a metal foil and a resin layer disposed on the surface of the metal foil. By disposing the resin layer on the surface of the metal foil, when an electrode is pressure-bonded to the current collector, the electrode is disposed on the resin layer. Further, when the electrode is pressure-bonded to the current collector, it penetrates into the resin layer. When the electrode penetrates into the resin layer, an anchor effect occurs between the electrode and the resin layer, making it difficult for the electrode to peel off from the current collector.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the current collector of Patent Document 1, when the electrode is pressure-bonded to the current collector, the electrode penetrates into the resin layer, and an anchor effect occurs between the electrode and the resin layer. However, when the electrode is pressure-bonded to the current collector, the electrode may reach the metal foil. When the electrode contacts the metal foil, the metal foil may be damaged. If the metal foil is damaged and penetrated, the electrode may contact the electrode disposed on the opposite surface and cause a short circuit. Further, if the rigidity of the resin layer is increased to avoid the electrode contacting the metal foil, it becomes difficult for the electrode to penetrate into the resin layer, and the electrode is likely to peel off from the current collector.

[0005] This specification discloses a technique for suppressing the contact between the electrode pressure-bonded to the current collector and the metal foil and making it difficult for the electrode to peel off from the current collector. [Means for solving the problem]

[0006] In a first aspect of this technology, the current collector comprises a metal foil and a resin layer disposed on the metal foil, wherein the electrodes are placed on the resin layer and the electrodes are pressed against the resin layer at a predetermined pressing temperature. The resin layer comprises a first resin layer disposed on the metal foil and a second resin layer disposed on the first resin layer. The glass transition temperature of the first resin layer and the glass transition temperature of the second resin layer are higher than the pressing temperature, and the glass transition temperature of the first resin layer and the glass transition temperature of the second resin layer are lower than the pressing temperature.

[0007] In this configuration, one of the first and second resin layers has a glass transition temperature higher than the bonding temperature, so that resin layer becomes glassy when the electrode is pressed against the current collector. The other of the first and second resin layers has a glass transition temperature lower than the bonding temperature, so that resin layer becomes rubbery when the electrode is pressed against the current collector. Therefore, when the electrode is pressed against the current collector, the resin layer of the current collector becomes a laminated state of a rubbery resin layer and a glassy resin layer. This lamination of the rubbery resin layer and the glassy resin layer prevents the electrode from reaching the metal foil and ensures adhesion between the current collector and the electrode.

[0008] In a second aspect of this technology, in the first aspect described above, the glass transition temperature of the first resin layer may be higher than the bonding temperature.

[0009] In this configuration, when electrodes are pressed against the current collector, the first resin layer becomes glass-like, and the second resin layer becomes rubber-like. Because the second resin layer that comes into contact with the electrodes when they are pressed against the current collector becomes soft and rubbery, the electrodes can easily penetrate the second resin layer. On the other hand, the first resin layer on the metal foil side becomes hard and glass-like, so even if the electrodes penetrate the second resin layer and reach the first resin layer, it is difficult for the electrodes to penetrate the first resin layer and reach the metal foil. Therefore, it is possible to suppress the electrodes from reaching the metal foil and to ensure adhesion between the current collector and the electrodes.

[0010] In a third aspect of this technology, in the first aspect described above, the glass transition temperature of the second resin layer may be higher than the bonding temperature.

[0011] In this configuration, when electrodes are pressed against the current collector, the second resin layer becomes glass-like, and the first resin layer becomes rubber-like. Because the second resin layer that comes into contact with the electrodes when they are pressed against the current collector becomes hard and brittle glass-like, the glass-like second resin layer is easily cracked by the pressure applied when the electrodes are pressed against the current collector. As a result, the electrodes can easily penetrate the second resin layer. On the other hand, the first resin layer on the metal foil side becomes flexible and rubber-like, making it less prone to cracking. Therefore, even if the electrodes penetrate the second resin layer and reach the first resin layer, it is difficult for the electrodes to penetrate the first resin layer and reach the metal layer. As a result, it is possible to suppress the electrodes from reaching the metal foil and to ensure adhesion between the current collector and the electrodes.

[0012] In a fourth aspect of this technology, the method for manufacturing an electrode structure is a method for manufacturing an electrode structure comprising a current collector and an electrode that is crimped to the current collector. The current collector comprises a metal foil, a first resin layer disposed on the metal foil, and a second resin layer disposed on the first resin layer. The manufacturing method comprises a placement step of placing the electrode on the second resin layer, and a crimping step of crimping the electrode placed on the second resin layer in the placement step to the current collector at a predetermined crimping temperature. The glass transition temperature of the first resin layer and the glass transition temperature of the second resin layer are higher than the crimping temperature, and the glass transition temperature of the first resin layer and the glass transition temperature of the second resin layer are lower than the crimping temperature.

[0013] According to this configuration, the current collector used in the manufacturing method of the electrode structure has a glass transition temperature of the first resin layer and a glass transition temperature of the second resin layer that is higher than the crimping temperature, while the other is lower than the crimping temperature. Therefore, it can achieve the same effects as the current collector of the first embodiment described above. [Brief explanation of the drawing]

[0014] [Figure 1] A diagram showing the schematic configuration of the current collector according to Example 1. [Figure 2] A flowchart showing an example of a method for manufacturing an electrode structure using the current collector of Example 1. [Figure 3] This figure illustrates a method for manufacturing an electrode structure using the current collector of Example 1. (a) shows the electrode placed on the current collector, and (b) shows the electrode being crimped onto the current collector. [Figure 4] A diagram showing the schematic configuration of the current collector according to Example 2. [Figure 5] This figure illustrates the manufacturing method of the electrode structure using the current collector of Example 2. (a) shows the electrode placed on the current collector, and (b) shows the electrode being crimped onto the current collector. [Modes for carrying out the invention]

[0015] (Example 1) The current collector 10 of this embodiment will be described with reference to the drawings. As shown in Figure 1, the current collector 10 comprises a metal foil 12 and a resin layer 14. An electrode 40 is pressed onto the surface of this current collector 10 to manufacture an electrode structure 100 (see Figures 2 and 3). The electrode structure 100 is used in a secondary battery.

[0016] The metal foil 12 is made of a conductive metal. In this embodiment, the metal foil 12 is copper foil. However, the type of metal that makes up the metal foil 12 is not particularly limited, and the metal foil 12 may be made using other metals such as aluminum, nickel, or stainless steel.

[0017] The resin layer 14 is located on the surface of the metal foil 12. The resin layer 14 is composed of a resin 20 containing a plurality of conductive additives 30. The resin layer 14 comprises a plurality of layers, and in this embodiment, it comprises a first resin layer 16 located on the surface of the metal foil 12 and a second resin layer 18 located on the first resin layer 16. The resin 20 comprises a first resin 22 and a second resin 24.

[0018] The first resin layer 16 is composed of the first resin 22. The glass transition temperature of the first resin 22 is higher than a predetermined temperature (hereinafter also referred to as the crimping temperature) when the electrode 40 (see FIG. 3) is crimped to the current collector 10. In this embodiment, the first resin 22 is polytetrafluoroethylene. Also, in this embodiment, the crimping temperature is 80°C. The glass transition temperature of polytetrafluoroethylene is 126°C, which is higher than the crimping temperature of 80°C. Note that the first resin 22 constituting the first resin layer 16 only needs to have a glass transition temperature higher than the crimping temperature. For example, the first resin 22 may be another resin having a glass transition temperature higher than 80°C. Also, 80°C is just an example for the crimping temperature, and other temperatures may also be used. Therefore, the first resin 22 constituting the first resin layer 16 can be appropriately selected from resins having a glass transition temperature higher than the crimping temperature.

[0019] The second resin layer 18 is composed of the second resin 24. The glass transition temperature of the second resin 24 is lower than the crimping temperature. In this embodiment, the second resin 24 is polyvinylidene fluoride. The glass transition temperature of polyvinylidene fluoride is 35°C, which is lower than the crimping temperature of 80°C. Note that the second resin 24 constituting the second resin layer 18 only needs to have a glass transition temperature lower than the crimping temperature. For example, the second resin 24 may be another resin having a glass transition temperature lower than 80°C. Also, as described above, the crimping temperature is not limited to 80°C. Therefore, the second resin 24 constituting the second resin layer 18 can be appropriately selected from resins having a glass transition temperature lower than the crimping temperature.

[0020] The resin layer 14 contains the same type of conductive additive 30. That is, the first resin layer 16 and the second resin layer 18 contain the same type of conductive additive 30. In this embodiment, the conductive additive 30 is acetylene black. The type of conductive additive 30 is not particularly limited. For example, the conductive additive 30 may be made of a carbon material or a metal material. Carbon materials come in various shapes such as particulate (solid, hollow, porous), fibrous, tubular, brush-like, tip-like (or flat), and the conductive additive 30 may be any of these shapes. Metal materials come in various shapes such as particulate and fibrous, and the conductive additive 30 may be any of these shapes. Furthermore, the conductive additive 30 can be made of metals such as aluminum, nickel, copper, and stainless steel, but it may also be made of metal materials other than those mentioned above. In addition, the conductive additive 30 may be made of a metal-coated carbon material. In this embodiment, the resin layer 14 contains one type of conductive additive 30, but it may also contain multiple types of conductive additives.

[0021] Next, a method for manufacturing the electrode structure 100 (see Figure 3(b)) equipped with the current collector 10 of this embodiment will be described. As shown in Figure 2, first, the electrode 40 is placed on the second resin layer 18 of the current collector 10 (S12). As shown in Figure 3(a), with the electrode 40 placed on the second resin layer 18, the electrode 40 hardly penetrates into the interior of the current collector 10 (specifically, the second resin layer 18).

[0022] Next, the electrode 40 is pressure-bonded to the current collector 10 (S14). During the pressure-bonding, the electrode 40 is pressed against the current collector 10 at the pressure-bonding temperature (80°C in this embodiment). As described above, in the current collector 10 of this embodiment, the first resin 22 that constitutes the first resin layer 16 has a glass transition temperature higher than the pressure-bonding temperature. Therefore, the first resin 22 becomes glassy when the electrode 40 is pressure-bonded to the current collector 10. On the other hand, the second resin 24 that constitutes the second resin layer 18 has a glass transition temperature lower than the pressure-bonding temperature. Therefore, the second resin 24 becomes rubbery when the electrode 40 is pressure-bonded to the current collector 10. For this reason, when the electrode 40 is pressure-bonded to the current collector 10, the first resin layer 16 on the metal foil 12 side becomes glassy, and the second resin layer 18 on the electrode 40 side becomes rubbery.

[0023] As shown in FIG. 3(b), when the electrode 40 is pressure-bonded to the current collector to the current collector 10 (specifically, the second resin layer 18). Since the second resin 24 is in a soft rubber state, when the electrode 40 is pressed toward the current collector 10, the electrode 40 easily enters the second resin layer 18. As a result, an anchor effect occurs between the electrode 40 and the second resin layer 18 (that is, the resin layer 14), making it difficult for the electrode 40 to peel off from the current collector 10. On the other hand, since the first resin 22 is in a hard glass state, even if the electrode 40 reaches the first resin layer 16 beyond the second resin layer 18, the electrode 40 hardly enters the first resin layer 16. Therefore, it is difficult for the electrode 40 to reach the metal foil 12. For this reason, it is possible to simultaneously achieve making it difficult for the electrode 40 pressure-bonded to the current collector 10 to contact the metal foil 12 and making it difficult for the electrode 40 to peel off from the current collector 10.

[0024] (Example 2) In the above-described Example 1, the first resin layer 16 was composed of a first resin 22 having a glass transition temperature higher than the bonding temperature, and the second resin layer 18 was composed of a second resin 24 having a glass transition temperature lower than the bonding temperature. However, the invention is not limited to this configuration. For example, as shown in Figure 4, the first resin layer 116 may be composed of a second resin 24 having a glass transition temperature lower than the bonding temperature, and the second resin layer 118 may be composed of a first resin 22 having a glass transition temperature higher than the bonding temperature.

[0025] The current collector 110 of this embodiment comprises a metal foil 12 and a resin layer 114. The resin layer 114 comprises a first resin layer 116 placed on the metal foil 12 and a second resin layer 118 placed on the first resin layer 116. The first resin layer 116 is composed of a second resin 24 whose glass transition temperature is lower than the bonding temperature. The second resin layer 118 is composed of a first resin 22 whose glass transition temperature is higher than the bonding temperature. In this embodiment, the bonding temperature is 80°C. Furthermore, the second resin 24 constituting the first resin layer 116 is polyvinylidene fluoride (glass transition temperature 35°C), and the first resin 22 constituting the second resin layer 118 is polytetrafluoroethylene (glass transition temperature 126°C). In this embodiment, the current collector 110 has the resin constituting the first resin layer 116 and the resin constituting the second resin layer 118 arranged in the opposite order to the current collector 10 of Embodiment 1, but the other configurations are the same. In this embodiment as well, the crimping temperature is not limited to 80°C. Furthermore, the second resin 24 constituting the first resin layer 116 can be appropriately selected from resins with a glass transition temperature lower than the crimping temperature, and the first resin 22 constituting the second resin layer 118 can be appropriately selected from resins with a glass transition temperature higher than the crimping temperature.

[0026] When manufacturing the electrode structure 200 using the current collector 110 of this embodiment, it can be manufactured using the method shown in Figure 2, similar to the first embodiment described above. That is, as shown in Figure 5(a), the electrode 40 is placed on the second resin layer 118 of the current collector 110, and then, as shown in Figure 5(b), the electrode 40 is pressed onto the current collector 110. As described above, in the current collector 110 of this embodiment, the second resin 24 constituting the first resin layer 116 has a glass transition temperature lower than the pressing temperature, and the first resin 22 constituting the second resin layer 118 has a glass transition temperature higher than the pressing temperature. Therefore, when the electrode 40 is pressed onto the current collector 110, the second resin 24 constituting the first resin layer 116 on the metal foil 12 side becomes rubbery, and the first resin 22 constituting the second resin layer 118 on the electrode 40 side becomes glassy.

[0027] Because the first resin 22 is hard and brittle and glass-like, when pressure is applied to the electrode 40 toward the current collector 10, the first resin 22 is prone to cracking. When the first resin 22 cracks, the surface area of ​​the second resin layer 118, which is composed of the first resin 22, increases. The electrode 40 penetrates into the crack in the first resin 22. This creates an anchoring effect between the electrode 40 and the second resin layer 118 (i.e., the resin layer 114), making it difficult for the electrode 40 to detach from the current collector 110. On the other hand, because the second resin 24 is flexible and rubber-like, it is not prone to cracking even when pressure is applied to the electrode 40 toward the current collector 10. Therefore, even if the electrode 40 extends beyond the second resin layer 118 to the first resin layer 116, it is difficult for the electrode 40 to penetrate the first resin layer 116 and reach the metal foil 12. Therefore, in this embodiment as well, it is possible to simultaneously make it difficult for the electrode 40 pressed onto the current collector 110 to come into contact with the metal foil 12, and to make it difficult for the electrode 40 to peel off from the current collector 110.

[0028] The specific examples of the technology disclosed herein have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above. Furthermore, the technical elements described herein or in the drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated herein or in the drawings achieves multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0029] 10, 110: Current collector 12: Metal foil 14, 114: Resin layer 16, 116: 1st resin layer 18, 118: Second resin layer 20: Resin 22: First resin 24: Second resin 30: Conductive additive 40: Electrode 100, 200: Electrode structure

Claims

1. Metal foil and It comprises a resin layer disposed on the metal foil, A current collector in which electrodes are placed on the resin layer and the electrodes are pressed against the resin layer at a predetermined pressing temperature, The aforementioned resin layer is A first resin layer is placed on the metal foil, It comprises a second resin layer disposed on the first resin layer, A current collector wherein one of the glass transition temperatures of the first resin layer and the second resin layer is higher than the bonding temperature, and the other of the glass transition temperatures of the first resin layer and the second resin layer is lower than the bonding temperature.

2. A current collector according to claim 1, A current collector in which the glass transition temperature of the first resin layer is higher than the crimping temperature.

3. A current collector according to claim 1, A current collector in which the glass transition temperature of the second resin layer is higher than the crimping temperature.

4. A method for manufacturing an electrode structure comprising a current collector and an electrode pressed against the current collector, The current collector comprises a metal foil, a first resin layer disposed on the metal foil, and a second resin layer disposed on the first resin layer. The aforementioned manufacturing method is The process of placing the electrode on the second resin layer, The process includes a crimping step in which the electrode placed on the second resin layer in the arrangement step is crimped to the current collector at a predetermined crimping temperature, A method for manufacturing an electrode structure, wherein one of the glass transition temperature of the first resin layer and the glass transition temperature of the second resin layer is higher than the bonding temperature, and the other of the glass transition temperature of the first resin layer and the glass transition temperature of the second resin layer is lower than the bonding temperature.

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