Current collector

Abstract

The invention relates to a current collector. Provided is a technique for suppressing contact between an electrode coated on a current collector and a metal foil and making it difficult for the electrode to peel off from the current collector. The current collector is provided with a metal foil and a resin layer that is formed from a resin containing a conductive auxiliary agent and that is disposed on the surface of the metal foil. The resin layer is provided with 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.

Description

Technical Field

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

[0002] In order to improve performance, various improvements have been made to the current collector used in the secondary battery. 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 the electrode is coated on the current collector, the electrode is disposed on the resin layer. In addition, when the electrode is coated on the current collector, it is pressurized so that the electrode enters the resin layer. By allowing the electrode to enter the resin layer, an anchoring effect is generated between the electrode and the resin layer, making it difficult for the electrode to peel off from the current collector.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-26192 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In the collector of Patent Document 1, the electrode is pressed when it is applied to the collector, so that the electrode enters the resin layer, and an anchoring effect is generated between the electrode and the resin layer. However, when the electrode is pressed against the collector, the electrode sometimes reaches the metal foil. If the electrode contacts the metal foil, the metal foil is sometimes damaged. If the metal foil is damaged and penetrated, it is possible that the electrode contacts the electrode arranged on the opposite side and short-circuits. In addition, if the rigidity of the resin layer is increased in order to avoid contact between the electrode and the metal foil, it is difficult for the electrode to enter the resin layer, so that the electrode is easy to peel off from the collector.

[0008] This specification discloses a technology for suppressing contact between an electrode coated on a current collector and a metal foil and making it difficult for the electrode to peel off from the current collector.

[0009] Solutions for solving problems

[0010] In a first technical solution of the present technology, the current collector comprises: a metal foil; and a resin layer formed of a resin containing a conductive auxiliary agent, the resin layer being arranged on the surface of the metal foil. The resin layer comprises a first layer arranged on the surface of the metal foil and a second layer arranged on the first layer. The elastic modulus of the first layer is greater than the elastic modulus of the second layer.

[0011] According to this structure, since the elastic modulus of the first layer on the metal foil side is large, when the electrode is applied to the collector, it is difficult for the electrode applied to the collector to enter the first layer, which can suppress the electrode from contacting the metal foil. In addition, since the elastic modulus of the second layer arranged at a position far from the metal foil is small, the electrode applied to the collector easily enters the second layer, which can suppress the electrode from peeling off the collector. Therefore, it is possible to simultaneously achieve the electrode applied to the collector being difficult to contact with the metal foil and the electrode being difficult to peel off from the collector.

[0012] In a second technical solution, according to the above-mentioned first technical solution, the conductive auxiliary agent may include a first conductive auxiliary agent contained in the first layer and a second conductive auxiliary agent contained in the second layer. The elastic modulus of the first conductive auxiliary agent may be greater than that of the second conductive auxiliary agent.

[0013] According to this configuration, by making the elastic modulus of the first conductive agent contained in the first layer larger than the elastic modulus of the second conductive agent contained in the second layer, the elastic modulus of the first layer can be preferably larger than the elastic modulus of the second layer.

[0014] In a third aspect, according to the first aspect, the resin may include a first resin constituting the first layer and a second resin constituting the second layer. The first resin may have a larger elastic modulus than the second resin.

[0015] According to this configuration, by making the elastic modulus of the first resin constituting the first layer larger than the elastic modulus of the second resin constituting the second layer, the elastic modulus of the first layer can be preferably made larger than the elastic modulus of the second layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram showing a schematic structure of a current collector of Example 1.

[0017] Figure 2 This is a diagram showing a state where an electrode is applied to the current collector of Example 1.

[0018] Figure 3 This is a diagram showing a schematic structure of a current collector of Example 2.

[0019] Description of Reference Numerals

[0020] 10, 110, current collector; 12, metal foil; 14, 114, resin layer; 16, 116, first layer; 18, 118, second layer; 20, 120, resin; 30, 130, conductive aid; 32, first conductive aid; 34, second conductive aid; 40, electrode; 122, first resin; 124, second resin. DETAILED DESCRIPTION

[0021] (Example 1)

[0022] The collector 10 of this embodiment will be described with reference to the accompanying drawings. The collector 10 has an electrode coated on its surface and is used in a secondary battery. Figure 1 As shown, the current collector 10 includes a metal foil 12 and a resin layer 14 .

[0023] The metal foil 12 is made of a metal having high conductivity. In this embodiment, the metal foil 12 is a copper foil. In addition, the type of metal constituting the metal foil 12 is not particularly limited, and other metals such as aluminum, nickel, and stainless steel may also be used.

[0024] 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 auxiliary agent 30. The resin layer 14 includes a plurality of layers. In this embodiment, the resin layer 14 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.

[0025] The resin layer 14 is composed of the same type of resin 20. That is, no matter where in the resin layer 14, a resin 20 having substantially the same composition is disposed, and the first layer 16 and the second layer 18 are composed of the same type of resin 20. In addition, the type of resin 20 is not particularly limited, and either a non-conductive resin or a conductive resin can be used. As a non-conductive resin, it can also be selected from thermoplastic resins and thermosetting resins. Non-conductive resins are, for example, polythiophene, but other non-conductive resins can also be used. For example, when the electrode coated on the collector 10 is used as a positive electrode, the resin 20 can use polyvinylidene fluoride (PVdF) resins, polyacrylic resins, etc., but is not limited to this. In addition, when the electrode coated on the collector 10 is used as a negative electrode, the resin 20 can use polyacrylic resins, polyamide-imide, polyimide, styrene-butadiene rubber, etc., but is not limited to this.

[0026] The resin layer 14 includes a plurality of types of conductive aids 32 and 34. In the present embodiment, two types of conductive aids 32 and 34 (hereinafter, also referred to as the first conductive aid 32 and the second conductive aid 34) are included. Specifically, the first layer 16 includes the first conductive aid 32, and the second layer 18 includes the second conductive aid 34. The elastic modulus of the first conductive aid 32 is greater than the elastic modulus of the second conductive aid 34. In addition, as long as the elastic modulus of the first conductive aid 32 is greater than the elastic modulus of the second conductive aid 34, the types of the first conductive aid 32 and the second conductive aid 34 are not particularly limited. For example, the first conductive aid 32 and the second conductive aid 34 can be formed of a carbon material or a metal material. For carbon materials, there are various shapes such as granular (solid, hollow, porous), fibrous, tubular, brush-like, sheet-like (or flat), and any of them can be used. For metal materials, there are shapes such as granular and fibrous, and any of them can be used. The material of the metal is aluminum, nickel, copper, stainless steel, etc., and metals other than these can also be used. In addition, as the first conductive aid 32 and the second conductive aid 34, metal-coated carbon materials can also be used. It is also possible to select a combination of different elastic moduli from these carbon materials, metal materials, and metal-coated carbon materials, and use a material with a large elastic modulus for the first conductive aid 32, and a material with a small elastic modulus for the second conductive aid 34. In addition, as the first conductive aid 32 or the second conductive aid 34, when using a conductive aid without data on the elastic modulus, for example, a scanning probe microscope (SPM), a nanoindentation tester, and other devices can also be used to obtain the elastic modulus of the conductive aid. In addition, the method for measuring the elastic modulus of the conductive aid without data on the elastic modulus is not limited to the method using the above-mentioned device, and other elastic modulus measurement methods can also be used to measure the elastic modulus of the conductive aid without data on the elastic modulus.

[0027] The resin layer 14 includes a first layer 16 and a second layer 18. In addition, the first layer 16 is composed of a resin 30 containing a first conductive aid 32, and the second layer 18 is composed of a resin 30 containing a second conductive aid 34. That is, for the first layer 16 and the second layer 18, the type of the resin 20 constituting each layer is the same, and on the other hand, the conductive aids 32 and 34 contained are different. In addition, the elastic modulus of the first conductive aid 32 contained in the first layer 16 is larger than the elastic modulus of the second conductive aid 34 contained in the second layer 18. Therefore, the elastic modulus of the first layer 16 is larger than the elastic modulus of the second layer 18. The elastic modulus of the first layer 16 and the second layer 18 can be measured using a device such as 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 apparatus, and the elastic modulus of the first layer 16 and the second layer 18 may be measured using other elastic modulus measurement methods.

[0028] In addition, in the present embodiment, one type of conductive aid 32 is included in the first layer 16, and one type of conductive aid 34 is included in the second layer 18, but the present invention is not limited to such a structure. As long as the elastic modulus of the conductive aid 32 included in the first layer 16 is greater than the elastic modulus of the conductive aid 34 included in the second layer 18, multiple types of conductive aids can be included in each layer 16, 18. For example, the first conductive aid 32 can also be one type of metal particles (for example, only aluminum or only stainless steel), or two or more types of metal particles (for example, aluminum and stainless steel). The second conductive aid 34 can also include two or more types of conductive aids as long as the elastic modulus is smaller than that of the first conductive aid 32.

[0029] The collector 10 having the above-mentioned structure is used as a secondary battery in a state where an electrode is coated on the surface. Figure 2 As shown, when the electrode 40 is coated on the surface of the collector 10, the electrode 40 is pressed so that the electrode 40 enters the resin layer 14. By allowing the electrode 40 to enter the resin layer 14, an anchoring effect is generated between the electrode 40 and the resin layer 14, making it difficult for the electrode 40 to peel off from the collector 10.

[0030] In addition, in the present embodiment, since the elastic modulus of the first conductive aid 32 contained in the first layer 16 is greater than the elastic modulus of the second conductive aid 34 contained in the second layer 18, the elastic modulus of the first layer 16 is greater than the elastic modulus of the second layer 18. For example, when the same kind of conductive aid is contained in the resin layer 14 and the elastic modulus in the resin layer 14 is uniform, by applying pressure when the electrode 40 is applied to the surface of the collector 10, it is possible that the electrode 40 enters the entire resin layer 14 and reaches the metal foil 12. If the electrode 40 reaches the metal foil 12, there is a possibility that the metal foil 12 is 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, when the electrode 40 is applied to the surface of the collector 10, it is difficult for the electrode 40 to enter the resin layer 14, and the anchoring effect generated between the electrode 40 and the resin layer 14 is small. In the present embodiment, by making the elastic modulus of the first layer 16 larger than the elastic modulus of the second layer 18, when the electrode 40 is applied to the surface of the current collector 10, the electrode 40 easily enters the second layer 18 on the side of the electrode 40 having a smaller elastic modulus. On the other hand, since the elastic modulus of the first layer 16 on the side of the metal foil 12 is larger, it is difficult for the electrode 40 to enter. Therefore, the electrode 40 easily enters the second layer 18, and on the other hand, it hardly enters the first layer 16. Therefore, in the current collector 10 of the present embodiment, the electrode 40 applied to the current collector 10 is difficult to contact the metal foil 12, and the electrode 40 is difficult to peel off from the current collector 10.

[0031] (Example 2)

[0032] In the above-mentioned first embodiment, the first layer 16 and the second layer 18 are composed of the conductive additives 32 and 34 having different elastic moduli, but the present invention is not limited to such a structure. Figure 3 As shown, the first layer 116 and the second layer 118 may be formed of resins 122 and 124 having different elastic moduli. In this embodiment, the metal foil 12 may be the same as the metal foil 12 of the above-mentioned embodiment 1. Therefore, the detailed description of the metal foil 12 is omitted.

[0033] 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, and in this embodiment, the resin layer 114 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.

[0034] The resin layer 114 includes a plurality of types of resins 122 and 124. In the present embodiment, the resin layer 114 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 the elastic modulus of the second resin 124. For example, two materials having different molecular weights and molecular structures in PVdF-based resins may be selected, and the material having a large elastic modulus may be used for the first resin 122, and the material having a small elastic modulus may be used for the second resin 124 to form the resin layer 114.

[0035] The same type of conductive aid 130 is contained in the resin layer 114. That is, the same type of conductive aid 130 is contained in the first layer 116 and the second layer 118. In addition, the type of conductive aid 130 is not particularly limited. For example, the conductive aid 130 can be formed of a carbon material or a metal material. For carbon materials, there are various shapes such as granular (solid, hollow, porous), fibrous, tubular, brush-like, and sheet (or flat), and any of them can be used. For metal materials, there are shapes such as granular and fibrous, and any of them can be used. In addition, metal-coated carbon can also be used as the conductive aid 130.

[0036] In the present embodiment, the first layer 116 is composed of the first resin 122 containing the conductive auxiliary agent 130, and the second layer 118 is composed of the second resin 124 containing the conductive auxiliary agent 130. In addition, the elastic modulus of the first resin 122 is larger than the elastic modulus of the second resin 124. Therefore, the elastic modulus of the first layer 16 is larger than the elastic modulus of the second layer 18. Therefore, in the present embodiment as well, when the electrode 40 is applied to the surface of the collector 110, the electrode 40 easily enters the second layer 118, and on the other hand, hardly enters the first layer 116. Therefore, in the collector 110 of Example 2 as well, the electrode 40 applied to the collector 110 is difficult to contact the metal foil 12, and the electrode 40 is difficult to peel off from the collector 110.

[0037] In the above-mentioned first embodiment, the elastic modulus of the first layer 16 is made larger than the elastic modulus of the second layer 18 by using the conductive additives 32 and 34 having different elastic moduli, and in the above-mentioned second embodiment, the elastic modulus of the first layer 116 is made larger than the elastic modulus of the second layer 118 by using the resins 122 and 124 having different elastic moduli, but the present invention is not limited to such a structure. For example, the conductive additives 32 and 130 contained in the first layer 16 and 116 and the conductive additives 34 and 130 contained in the second layer 18 and 118 may be selected so that the density of each conductive additive 32 and 130 contained in the first layer 16 and 116 is larger than the density of each conductive additive 34 and 130 contained in the second layer 18 and 118. Furthermore, the conductive aid 32, 130 contained in the first layer 16, 116 and the conductive aid 34, 130 contained in the second layer 18, 118 may be selected so that the specific surface area of ​​the conductive aid 32, 130 contained in the first layer 16, 116 is larger than the specific surface area of ​​the conductive aid 34, 130 contained in the second layer 18, 118. When these conductive aids are used, the elastic modulus of the first layer 16, 116 is also made larger than the elastic modulus of the second layer 18, 118. Therefore, the electrode 40 applied to the collector 10, 110 is more difficult to contact the metal foil 12, and the electrode 40 is more difficult to peel off from the collector 10, 110.

[0038] The specific examples of the present invention are described in detail above, but these are only examples and are not intended to limit the claims. The technologies described in the claims include technologies that have undergone various deformations and changes to the specific examples illustrated above. The technical elements described in this specification or the drawings are technically useful alone or in various combinations, and are not limited to the combinations described in the claims at the time of application. In addition, the technologies illustrated in this specification or the drawings can achieve multiple purposes at the same time, and achieving one of the purposes itself has technical usefulness.

Claims

1. A current collector, wherein: The current collector has: Metal foil; and a resin layer formed of a resin containing a conductive auxiliary agent, the resin layer being disposed on the 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 larger than the elastic modulus of the second layer.

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

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

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