Collector

Abstract

To provide a technique of suppressing an electrode applied on the collector from contacting a metal foil. while making it more difficult for the electrode from peeling off from the collector.SOLUTION: A collector includes: a metal foil; and a resin layer made of resin containing a conductive agent, and arranged on a surface of the metal foil. The resin layer includes a first layer arranged on the surface of the metal foil and a second layer arranged on the first layer. The coefficient of elasticity of the first layer is larger than that of the second layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a current collector. [Background technology]

[0002] Current collectors used in secondary batteries have been improved in various ways to improve their performance. For example, the current collector in 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, the electrode is disposed on the resin layer when the electrode is applied to the current collector. In addition, the electrode is pressurized when it is applied to the current collector, and penetrates into the resin layer. By the electrode penetrating into the resin layer, an anchor effect is generated 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] JP 2013-26192 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the current collector of Patent Document 1, the electrode is pressed when applied to the current collector, so that the electrode penetrates into the resin layer, and an anchor effect occurs between the electrode and the resin layer. However, when the electrode is pressed against the current collector, the electrode may reach the metal foil. When the electrode comes into contact with the metal foil, the metal foil may be damaged, and when the metal foil is damaged and penetrated, the electrode may come into contact with the electrode arranged on the opposite surface and cause a short circuit. In addition, if the rigidity of the resin layer is increased to prevent the electrode from contacting the metal foil, the electrode will not easily penetrate into the resin layer, and the electrode will be easily peeled off from the current collector.

[0005] This specification discloses a technique for preventing an electrode coated on a current collector from coming into contact with a metal foil and for making the electrode less likely to peel off from the current collector. [Means for solving the problem]

[0006] In a first aspect of the present technology, a current collector includes a metal foil and a resin layer made of a resin containing a conductive assistant and disposed on a surface of the metal foil. The resin layer includes a first layer disposed on the surface of the metal foil and a second layer disposed on the first layer. The elastic modulus of the first layer is greater than the elastic modulus of the second layer.

[0007] According to this configuration, since the elastic modulus of the first layer on the metal foil side is large, when the electrode is coated on the current collector, the electrode coated on the current collector is less likely to penetrate into the first layer, and the electrode can be prevented from coming into contact with the metal foil. In addition, since the elastic modulus of the second layer disposed at a position away from the metal foil is small, the electrode coated on the current collector is more likely to penetrate into the second layer, and the electrode can be prevented from peeling off from the current collector. Therefore, it is possible to simultaneously prevent the electrode coated on the current collector from coming into contact with the metal foil and prevent the electrode from peeling off from the current collector.

[0008] In a second aspect, in the first aspect, the conductive assistant may include a first conductive assistant contained in the first layer and a second conductive assistant contained in the second layer, and the elastic modulus of the first conductive assistant may be greater than the elastic modulus of the second conductive assistant.

[0009] According to this configuration, the elastic modulus of the first conductive assistant contained in the first layer is greater than the elastic modulus of the second conductive assistant contained in the second layer, so that the elastic modulus of the first layer can be suitably made greater than the elastic modulus of the second layer.

[0010] In a third aspect, in the first aspect, the resin may include a first resin constituting the first layer and a second resin constituting the second layer, and the elastic modulus of the first resin may be greater than the elastic modulus of the second resin.

[0011] According to this configuration, the elastic modulus of the first resin constituting the first layer is greater than the elastic modulus of the second resin constituting the second layer, so that the elastic modulus of the first layer can be suitably made greater than the elastic modulus of the second layer. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram showing a schematic configuration of a current collector according to Example 1. [Diagram 2] FIG. 2 is a diagram showing a state in which an electrode is applied to a current collector according to Example 1. [Diagram 3] FIG. 4 is a diagram showing a schematic configuration of a current collector according to Example 2.

[0013] Example 1 The current collector 10 of this embodiment will be described with reference to the drawings. The current collector 10 has an electrode coated on its surface and is used in a secondary battery. As shown in FIG. 1, the current collector 10 includes a metal foil 12 and a resin layer 14.

[0014] The metal foil 12 is made of a metal having high electrical conductivity. In this embodiment, the metal foil 12 is a copper foil. The type of metal constituting the metal foil 12 is not particularly limited, and other metals such as aluminum, nickel, and stainless steel may be used.

[0015] The resin layer 14 is disposed on the surface of the metal foil 12. The resin layer 14 is composed of a resin 20 containing a conductive assistant 30. The resin layer 14 includes a plurality of layers, and in this embodiment includes a first layer 16 disposed on the surface of the metal foil 12 and a second layer 18 disposed on the first layer 16.

[0016] The resin layer 14 is made of the same type of resin 20. That is, at any position in the resin layer 14, the resin 20 having approximately the same composition is disposed, and the first layer 16 and the second layer 18 are made of the same type of resin 20. The type of resin 20 is not particularly limited, and either a non-conductive resin or a conductive resin may be used. The non-conductive resin may be selected from thermoplastic resins and thermosetting resins. The non-conductive resin may be, for example, polythiophene, but other conductive resins may be used. For example, when the electrode to be applied to the current collector 10 is used as a positive electrode, the resin 20 may be a polyvinylidene fluoride (PVdF)-based resin, a polyacrylic acid-based resin, or the like, but is not limited thereto. When the electrode to be applied to the current collector 10 is used as a negative electrode, the resin 20 may be a polyacrylic acid-based resin, a polyamideimide, a polyimide, a styrene butadiene rubber, or the like, but is not limited thereto.

[0017] The resin layer 14 contains a plurality of types of conductive assistants 32 and 34, and in this embodiment, two types of conductive assistants 32 and 34 (hereinafter also referred to as the first conductive assistant 32 and the second conductive assistant 34) are contained. Specifically, the first layer 16 contains the first conductive assistant 32, and the second layer 18 contains the second conductive assistant 34. The elastic modulus of the first conductive assistant 32 is greater than that of the second conductive assistant 34. Note that the type of the first conductive assistant 32 and the second conductive assistant 34 is not particularly limited as long as the elastic modulus of the first conductive assistant 32 is greater than that of the second conductive assistant 34. For example, the first conductive assistant 32 and the second conductive assistant 34 can be formed of a carbon material or a metal material. Carbon materials come in various shapes, such as particulate (solid, hollow, porous), fibrous, tubular, brush, and chip (or flat) shapes, and any of these shapes may be used. Metallic materials may be in the form of particles, fibers, or the like, and any of these may be used. The metallic material may be aluminum, nickel, copper, stainless steel, or other metals. Metal-coated carbon materials may be used as the first conductive assistant 32 and the second conductive assistant 34. Combinations of different elastic moduli may be selected from these carbon materials, metallic materials, and metal-coated carbon materials, and a material with a large elastic modulus may be used as the first conductive assistant 32, and a material with a small elastic modulus may be used as the second conductive assistant 34. When a conductive assistant with no data on elastic modulus is used as the first conductive assistant 32 or the second conductive assistant 34, the elastic modulus of the conductive assistant may be obtained using an instrument such as a scanning probe microscope (SPM) or a nanoindentation tester. The method for measuring the elastic modulus of a conductive assistant with no data on elastic modulus is not limited to the method using the above-mentioned instrument, and the elastic modulus of a conductive assistant with no data on elastic modulus may be measured using another method for measuring elastic modulus.

[0018] The resin layer 14 includes a first layer 16 and a second layer 18. The first layer 16 is made of a resin 30 containing a first conductive assistant 32, and the second layer 18 is made of a resin 30 containing a second conductive assistant 34. That is, the first layer 16 and the second layer 18 are made of the same type of resin 20 constituting each layer, but contain different conductive assistants 32, 34. The elastic modulus of the first conductive assistant 32 contained in the first layer 16 is greater than the elastic modulus of the second conductive assistant 34 contained in the second layer 18. Therefore, the elastic modulus of the first layer 16 is greater than the elastic modulus of the second layer 18. The elastic modulus of the first layer 16 and the second layer 18 can also be measured using, for example, a scanning probe microscope (SPM) or a nanoindentation tester. The method for measuring the elastic modulus of the first layer 16 and the second layer 18 is not limited to the method using the above-mentioned equipment, and the elastic modulus of the first layer 16 and the second layer 18 may be measured using other methods for measuring the elastic modulus.

[0019] In this embodiment, the first layer 16 contains one type of conductive assistant 32, and the second layer 18 contains one type of conductive assistant 34, but the present invention is not limited to this configuration. As long as the elastic modulus of the conductive assistant 32 contained in the first layer 16 is greater than the elastic modulus of the conductive assistant 34 contained in the second layer 18, each layer 16, 18 may contain multiple types of conductive assistants. For example, the first conductive assistant 32 may be one type of metal particles (e.g., only aluminum or only stainless steel), or may be two or more types of metal particles (e.g., aluminum and stainless steel). The second conductive assistant 34 may also contain two or more types of conductive assistants as long as the elastic modulus of the second conductive assistant 34 is smaller than that of the first conductive assistant 32.

[0020] The current collector 10 having the above configuration is used as a secondary battery with an electrode coated on its surface. As shown in Fig. 2, when the electrode 40 is coated on the surface of the current collector 10, the electrode 40 is pressurized, so that the electrode 40 penetrates into the resin layer 14. The electrode 40 penetrates into the resin layer 14, and an anchor effect is generated between the electrode 40 and the resin layer 14, so that the electrode 40 is unlikely to peel off from the current collector 10.

[0021] In this embodiment, the elastic modulus of the first conductive assistant 32 contained in the first layer 16 is greater than the elastic modulus of the second conductive assistant 34 contained in the second layer 18, so that the elastic modulus of the first layer 16 is greater than the elastic modulus of the second layer 18. For example, if the resin layer 14 contains the same type of conductive assistant and has a uniform elastic modulus within the resin layer 14, the electrode 40 may penetrate into the entire resin layer 14 and reach the metal foil 12 by applying pressure when applying the electrode 40 to the surface of the current collector 10. If the electrode 40 reaches the metal foil 12, the metal foil 12 may be damaged. In addition, if the rigidity of the resin layer 14 is increased in order to prevent the electrode 40 from reaching the metal foil 12, the electrode 40 will be less likely to penetrate into the resin layer 14 when applied to the surface of the current collector 10, and the anchor effect between the electrode 40 and the resin layer 14 will be reduced. In this embodiment, by making the elastic modulus of the first layer 16 larger than that of the second layer 18, when the electrode 40 is coated on the surface of the current collector 10, the electrode 40 easily penetrates into the second layer 18 on the electrode 40 side, which has a smaller elastic modulus. On the other hand, the electrode 40 does not easily penetrate into the first layer 16 on the metal foil 12 side, because the first layer 16 has a larger elastic modulus. Therefore, while the electrode 40 easily penetrates into the second layer 18, it hardly penetrates into the first layer 16. Therefore, in the current collector 10 of this embodiment, the electrode 40 coated on the current collector 10 does not easily come into contact with the metal foil 12, and the electrode 40 does not easily peel off from the current collector 10.

[0022] Example 2 In the above-mentioned Example 1, the first layer 16 and the second layer 18 are formed by the conductive assistants 32, 34 having different elastic moduli, but the present invention is not limited to such a configuration. For example, as shown in Fig. 3, the first layer 116 and the second layer 118 may be formed by resins 122, 124 having different elastic moduli. Note that, in this example, the metal foil 12 may be the same as the metal foil 12 in the above-mentioned Example 1. Therefore, a detailed description of the metal foil 12 will be omitted.

[0023] The current collector 110 of this embodiment includes a metal foil 12 and a resin layer 114. The resin layer 114 is composed of a resin 120 containing a conductive auxiliary agent 130. The resin layer 114 includes a plurality of layers. In this embodiment, it includes a first layer 116 disposed on the surface of the metal foil 12 and a second layer 118 disposed on the first layer 116.

[0024] The resin layer 114 includes a plurality of types of resins 122 and 124. In this embodiment, it includes two types of resins 122 and 124 (hereinafter also referred to as the first resin 122 and the second resin 124). The first resin 122 and the second resin 124 have different compositions. Specifically, the first layer 116 is composed of the first resin 122, and the second layer 118 is composed of the second resin 124. The elastic modulus of the first resin 122 is greater than that of the second resin 124. For example, among PVdF-based resins, two materials with different molecular weights and molecular structures can be selected, and the material with a large elastic modulus can be used as the first resin 122, and the material with a small elastic modulus can be used as the second resin 124 to form the resin layer 114.

[0025] The resin layer 114 contains the same type of conductive auxiliary agent 130. That is, the first layer 116 and the second layer 118 contain the same type of conductive auxiliary agent 130. The type of the conductive auxiliary agent 130 is not particularly limited. For example, the conductive auxiliary agent 130 can be formed of a carbon material or a metal material. The carbon material has various shapes such as particulate (solid, hollow, porous), fibrous, tubular, brush-shaped, chip-shaped (or flat-shaped), etc., and any of them can be used. The metal material has shapes such as particulate and fibrous, and any of them can be used. Also, metal-coated carbon can be used as the conductive auxiliary agent 130.

[0026] In this embodiment, the first layer 116 is composed of a first resin 122 containing a conductive aid 130, and the second layer 118 is composed of a second resin 124 containing a conductive aid 130. Also, the elastic modulus of the first resin 122 is greater than that of the second resin 124. As a result, the elastic modulus of the first layer 16 becomes greater than that of the second layer 18. Therefore, also in this embodiment, when the electrode 40 is applied to the surface of the current collector 110, the electrode 40 easily penetrates into the second layer 118 while hardly penetrating into the first layer 116. Accordingly, also in the current collector 110 of Example 2, it becomes difficult for the electrode 40 applied to the current collector 110 to contact the metal foil 12, and it becomes difficult for the electrode 40 to peel off from the current collector 110.

[0027] Note that in the above Example 1, by using conductive aids 32 and 34 having different elastic moduli, the elastic modulus of the first layer 16 was made greater than that of the second layer 18, and in the above Example 2, by using resins 122 and 124 having different elastic moduli, the elastic modulus of the first layer 116 was made greater than that of the second layer 118. However, the configuration is not limited to this. For example, the conductive aids 32 and 130 contained in the first layers 16 and 116 and the conductive aids 34 and 130 contained in the second layers 18 and 118 may be selected such that the individual densities of the conductive aids 32 and 130 contained in the first layers 16 and 116 are greater than the individual densities of the conductive aids 34 and 130 contained in the second layers 18 and 118. Also, the conductive aids 32 and 130 contained in the first layers 16 and 116 and the conductive aids 34 and 130 contained in the second layers 18 and 118 may be selected such that the specific surface areas of the conductive aids 32 and 130 contained in the first layers 16 and 116 are greater than the specific surface areas of the conductive aids 34 and 130 contained in the second layers 18 and 118. Even when these conductive aids are used, the elastic modulus of the first layers 16 and 116 becomes even greater than that of the second layers 18 and 118. Therefore, it becomes difficult for the electrode 40 applied to the current collectors 10 and 110 to contact the metal foil 12, and it becomes even more difficult for the electrode 40 to peel off from the current collectors 10 and 110.

[0028] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0029] 10, 110: Current collector 12: Metal foil 14, 114: resin layer 16, 116: 1st layer 18, 118: 2nd layer 20, 120: Resin 30, 130: Conductive additive 32: First conductive additive 34: Second conductive additive 40: Electrode 122: First resin 124: Second resin

Claims

1. Metal foil; a resin layer made of a resin containing a conductive assistant and disposed on a surface of the metal foil; the resin layer includes a first layer disposed on a surface of the metal foil and a second layer disposed on the first layer; A current collector, wherein the first layer has a greater elastic modulus than the second layer.

2. The current collector according to claim 1 , The conductive assistant includes a first conductive assistant contained in the first layer and a second conductive assistant contained in the second layer, A current collector, wherein the elastic modulus of the first conductive assistant is greater than the elastic modulus of the second conductive assistant.

3. The current collector according to claim 1 , The resin includes a first resin constituting the first layer and a second resin constituting the second layer, The current collector, wherein the first resin has a greater elastic modulus than the second resin.

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