current collector

Abstract

The utility model relates to a current collector, provide a kind of for the technology for making the metal foil possessed by current collector not easy to break. Current collector is the current collector contacted with electrode. Current collector possesses metal foil and resin layer comprising multiple conductive adjuvants and being arranged on the metal foil. The resin layer possesses the 1st face contacted with the metal foil and the 2nd face located in the side opposite to the 1st face and contacted with the electrode. Each conductive adjuvant is formed by carbon material, possesses base surface and edge surface. Each conductive adjuvant is arranged in the resin layer in the mode that the edge surface does not contact at least one of the 1st face and the 2nd face.

Description

Technical Field

[0001] The technology disclosed in this specification relates to current collectors. Background Technology

[0002] Current collectors used in secondary batteries are subject to various improvements to enhance performance. For example, the current collector in Patent Document 1 comprises a metal foil and a resin layer disposed on the metal foil. By disposing of the resin layer on the metal foil, when an electrode is coated on the current collector, the electrode is disposed on the resin layer. A conductive additive is included in the resin layer. Due to the inclusion of the conductive additive in the resin layer, the conductivity from the electrode to the metal foil is improved when the electrode is disposed on the resin layer.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-26192 Utility Model Content

[0006] Problems to be solved by utility models

[0007] Conductive additives are sometimes formed from carbon materials such as graphene. Carbon materials such as graphene have a structure with six-membered carbon rings, possessing basal and edge faces. The basal faces make it difficult for ions to pass through, while the edge faces allow ions to pass through easily. Therefore, when electrodes are disposed on a resin layer, if the edge face of the carbon material forming the conductive additive is in contact with both the electrode and the metal foil, ions within the electrode (e.g., lithium ions) can easily pass through the edge face of the carbon material forming the conductive additive and reach the metal foil from the electrode. If the ions reach the metal foil, the metal foil may be damaged due to an alloying reaction.

[0008] This specification discloses a technique for making the metal foil of a current collector less prone to breakage.

[0009] Solution for solving the problem

[0010] In the first embodiment of this technology, the current collector is a current collector in contact with an electrode. The current collector includes a metal foil and a resin layer disposed on the metal foil and containing a plurality of conductive additives. The resin layer has a first surface in contact with the metal foil and a second surface located on the opposite side of the first surface and in contact with the electrode. Each of the conductive additives is formed of a carbon material and has a base surface and an edge surface. Each of the conductive additives is disposed in the resin layer such that the edge surface does not contact at least one of the first surface and the second surface.

[0011] According to this structure, the conductive additive is disposed such that its edge surface does not contact at least one of the first and second surfaces of the resin layer. That is, the conductive additive is disposed in the resin layer such that its edge surface contacts only one of the first and second surfaces, or does not contact either the first or second surface. Therefore, when an electrode is coated on the current collector, it is possible to suppress ions from reaching the metal foil from the electrode via the conductive additive. Thus, it is possible to suppress damage to the metal foil caused by ions moving from the electrode.

[0012] In the second technical solution of this invention, according to the first technical solution described above, the resin layer may also include a first layer disposed on the metal foil and a second layer disposed on the first layer. Alternatively, none of the conductive additives included in the first layer may be partially located within the second layer; all of them may be disposed within the first layer. Similarly, none of the conductive additives included in the second layer may be partially located within the first layer; all of them may be disposed within the second layer.

[0013] According to this structure, the resin layer is a stacked structure of a first layer and a second layer. Furthermore, the conductive additive is disposed separately in the first layer and the second layer, without crossing between the two layers. This prevents the conductive additive from being disposed in contact with both the first surface of the metal foil and the second surface of the electrode.

[0014] In the third technical solution of this technology, according to the first or second technical solution described above, each of the conductive additives may be a carbon nanotube. Attached Figure Description

[0015] Figure 1 This is a diagram showing a schematic structure of the current collector in an embodiment.

[0016] Figure 2 This is a diagram showing the base and edge surfaces of a carbon nanotube as an example of a conductive additive.

[0017] Figure 3 This diagram shows the state in which the current collector in the embodiment is coated with electrodes.

[0018] Figures 4(a) to 4(c) These are diagrams illustrating the manufacturing method of the current collector in the embodiments. Figure 4(a) shows the state in which the resin slurry is coated on the metal foil, Figure 4(b) shows the state in which the resin slurry coated on the metal foil is dried, and Figure 4(c) shows the state in which the second layer is disposed on the surface of the first layer.

[0019] Figure 5 This is a diagram showing the basal and edge surfaces of graphene, another example of a conductive additive.

[0020] Figure 6This is a diagram showing the schematic structure of the collector in a modified example.

[0021] Explanation of reference numerals in the attached figures

[0022] 10, 110, Current collector; 12, Metal foil; 14, Resin layer (first resin layer); 14a, Lower surface of resin layer; 14b, Upper surface of resin layer; 16, First layer; 18, Second layer; 20, Resin; 22, Conductive additive; 24, Base surface; 26, Edge surface; 28, Second resin layer; 30, Electrode; 40, Resin slurry. Detailed Implementation

[0023] The current collector 10 of this embodiment will be described with reference to the accompanying drawings. The current collector 10 has electrodes 30 coated on its surface (see figure). Figure 3 ), used in secondary batteries. For example... Figure 1 As shown, the current collector 10 has a metal foil 12 and a resin layer 14.

[0024] The metal foil 12 is formed of a conductive metal. In this embodiment, the metal foil 12 is a copper foil. Furthermore, the type of metal constituting the metal foil 12 is not particularly limited; other metals such as aluminum, nickel, and stainless steel can also be used to form the metal foil 12.

[0025] A 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 plurality of conductive additives 22. Hereinafter, in the resin layer 14, the surface in contact with the metal foil 12 is sometimes referred to as the lower surface 14a, and the surface opposite to the lower surface 14a is referred to as the upper surface 14b. When the electrode 30 is coated on the current collector 10, the electrode 30 is disposed on the upper surface 14b (see reference). Figure 3 The resin layer 14 has multiple layers. In this embodiment, the resin layer 14 has a first layer 16 disposed on the metal foil 12 and a second layer 18 disposed on the first layer 16. Therefore, in this embodiment, the lower surface of the first layer 16 becomes the lower surface 14a of the resin layer 14, and the upper surface of the second layer 18 becomes the upper surface 14b of the resin layer 14.

[0026] The resin layer 14 is composed of the same type of resin 20 (the first layer 16 and the second layer 18 are composed of the same type of resin). That is, resin 20 with approximately the same composition is disposed at all locations within the resin layer 14. Furthermore, the type of resin 20 is not particularly limited; both non-conductive and conductive resins can be used. As a non-conductive resin, thermoplastic resins and thermosetting resins can be selected. Conductive resins include, for example, polythiophene, but other conductive resins can also be used. For example, when the electrode 30 coated on the current collector 10 is used as a positive electrode, polyvinylidene fluoride (PVdF) based resins, polyacrylic acid based resins, etc., can be used, but are not limited to these. Furthermore, when the electrode 30 coated on the current collector 10 is used as a negative electrode, polyacrylic acid based resins, polyamide-imide, polyimide, styrene-butadiene rubber, etc., can be used, but are not limited to these.

[0027] The resin layer 14 contains multiple conductive additives 22 of the same type. That is, the first layer 16 and the second layer 18 each contain multiple conductive additives 22 of the same type. Each conductive additive 22 is formed of a carbon material, in this embodiment, carbon nanotubes. Carbon materials such as carbon nanotubes have a structure with six-membered rings; the plane in which the six-membered rings are arranged is called the basal plane, and the plane orthogonal to the basal plane is called the edge plane. Figure 2 As shown, in a carbon nanotube, the cylindrical portion becomes the base surface 24, and the surface orthogonal to the axial direction of the carbon nanotube (the surface orthogonal to the base surface 24) becomes the edge surface 26. In the carbon nanotube, the edge surface 26 exists at two locations at both ends of the base surface 24. Figure 2 (Left and right sides). The base surface 24 makes it difficult for ions to pass through, while the edge surface 26 makes it easy for ions to pass through. For example, when the electrode 30 is coated on the current collector 10 (refer to...) Figure 3 When a battery (e.g., a lithium-ion battery) is formed, ions (e.g., lithium ions) penetrate from the electrode 30 into the resin layer 14. Even if the ions penetrating the resin layer 14 reach the base surface 24 of each conductive additive 22, the ions have difficulty penetrating the conductive additive 22. On the other hand, when the ions penetrating the resin layer 14 reach the edge surface 26 of the conductive additive 22, the ions penetrate the conductive additive 22 from the edge surface 26, pass through the conductive additive 22, and move to other locations within the resin layer 14. For example, in carbon nanotubes, ions enter from one edge surface 26 (e.g., ... Figure 2 Invading from the left side, it passes through the carbon nanotube along the axial direction and moves to the edge face on the other side (e.g., the left side), and moves to the edge face on the other side. Figure 2 (to the right).

[0028] In this embodiment, each conductive additive 22 is disposed within the resin layer 14 such that its edge surface 26 does not contact at least one of the lower surface 14a and the upper surface 14b of the resin layer 14. That is, the edge surface 26 of each conductive additive 22 does not contact both the lower surface 14a and the upper surface 14b of the resin layer 14, or it contacts one of the lower surface 14a and the upper surface 14b of the resin layer 14 but not the other. Each conductive additive 22 is not disposed across both the first layer 16 and the second layer 18, but is located in either the first layer 16 or the second layer 18. For each conductive additive 22 contained in the first layer 16, there is no case where it is partially located within the second layer 18; it is entirely disposed within the first layer 16. Similarly, for each conductive additive 22 contained in the second layer 18, there is no case where it is partially located within the first layer 16; it is entirely disposed within the second layer 18. Therefore, the edge surface 26 of the conductive additive 22 does not come into contact with the lower surface 14a (i.e., the lower surface of the first layer 16) and the upper surface 14b (i.e., the upper surface of the second layer 18) of the resin layer 14.

[0029] For example, if the edge surface 26 of the conductive additive 22 is in contact with both the lower surface 14a and the upper surface 14b of the resin layer 14, then an electrode 30 is coated on the current collector 10 (see reference). Figure 3 In this state, the edge surface 26 of the conductive additive 22 is in contact with both the electrode 30 and the metal foil 12. Therefore, ions within the electrode 30 sometimes pass through the conductive additive 22 and move towards the metal foil 12. When the ions reach the metal foil 12, sometimes a chemical reaction occurs between the metal foil 12 and the ions, causing the metal foil 12 to break.

[0030] In this embodiment, the edge surface of the conductive additive 22 does not contact at least one of the lower surface 14a and the upper surface 14b of the resin layer 14. For example, as Figure 3 (in particular Figure 3 As shown by the dashed arrow, if one edge of the conductive additive 22 contacts the electrode 30, ions within the electrode 30 can pass through the conductive additive 22 from one edge 26 to the other edge 26. However, since the other edge 26 of the conductive additive 22 does not contact the metal foil 12, the ions that have passed through the conductive additive 22 are released into the interior of the resin layer 14 and are unlikely to reach the metal foil 12. Therefore, in this embodiment, the conductive additive 22 is disposed within the resin layer 14 such that the edge of the conductive additive 22 does not contact at least one of the lower surface 14a and the upper surface 14b of the resin layer 14, thereby suppressing the movement of ions from the electrode 30 to the metal foil 12 via the conductive additive 22. Thus, damage to the metal foil 12 due to ions within the electrode 30 can be suppressed.

[0031] Next, the manufacturing method of the current collector 10 will be described. As shown in FIG4(a), firstly, a resin slurry 40 containing resin 20 and a plurality of conductive additives 22 is coated on the surface of the metal foil 12 using a coating jig 50. In addition, the resin slurry 40 may also contain other substances such as dispersants and dispersion media. At this time, the resin slurry 40 is coated in such a way that the thickness of the resin slurry 40 is smaller than the length of the shortest conductive additive 22 among the plurality of conductive additives 22 (in the case of carbon nanotubes in this embodiment, the length in the axial direction). By making the thickness of the resin slurry 40 smaller than the length of the shortest conductive additive 22 among the plurality of conductive additives 22 (hereinafter also simply referred to as "the length of the conductive additive 22"), the individual conductive additives 22 in the resin slurry 40 will not stand upright.

[0032] Next, the resin slurry 40 coated on the surface of the metal foil 12 is dried. Thus, as shown in FIG. 4(b), a first layer 16 is formed on the surface of the metal foil 12. The dried first layer 16 is thinner than the resin slurry 40 coated on the surface of the metal foil 12. When the resin slurry 40 is coated on the surface of the metal foil 12, by making the thickness of the resin slurry 40 smaller than the length of the shortest conductive additive 22, the conductive additives 22 do not stand upright. Therefore, even when the resin slurry 40 is dried, the conductive additives 22 will not stand upright.

[0033] Next, resin slurry 40 is further coated onto the surface of the first layer 16. At this time, the resin slurry 40 is also coated in such a way that its thickness is less than the length of the shortest conductive additive 22. Then, the coated resin slurry 40 is allowed to dry. Thus, as shown in FIG. 4(c), a second layer 18 is formed on the surface of the first layer 16. In the second layer 18, by also making the thickness of the resin slurry 40 less than the length of the shortest conductive additive 22, the conductive additive 22 will not stand upright.

[0034] In this embodiment, instead of applying the resin slurry 40 only once to achieve the desired thickness of the resin layer 14, the resin layer 14 is divided into multiple layers (in this embodiment, layer 16 and layer 28), and the thickness of the resin slurry 40 applied when forming each layer is less than the length of the shortest conductive additive 22. For example, if the resin layer 14 is not divided into multiple layers, but only one application of the resin slurry 40 is made to form a thicker resin layer 14, the thickness of the resin slurry 40 may sometimes be greater than the length of the longest conductive additive 22. As a result, some of the conductive additives 22 within the resin layer 14 may stand upright. When the resin slurry 40 is applied to the surface of the metal foil 12, since the thickness of the resin slurry 40 is greater than the length of the longest conductive additive 22, the edge surface 26 will not contact both the upper and lower surfaces of the resin slurry 40, regardless of the orientation of the conductive additives 22. However, during the drying of the resin slurry 40, the thickness of the resin layer 14 sometimes becomes smaller than the thickness of the coated resin slurry 40. Consequently, the thickness of the resin layer 14 is sometimes smaller than the length of the conductive additive 22. In this case, in the resin layer 14 formed by drying the resin slurry 40, the conductive additive 22 is in contact with both the upper and lower surfaces of the resin layer 14 (or protrudes from the resin layer 14).

[0035] In this embodiment, the resin layer 14 is divided into multiple layers, such that the thickness of the resin slurry 40 applied during the formation of each layer is smaller than the length of the shortest conductive additive 22. By dividing the resin layer 14 into multiple layers and forming each layer sequentially, it is possible to avoid contact between the edge surface 26 of the conductive additive 22 and both the lower surface 14a and the upper surface 14b of the resin layer 14. Furthermore, in this embodiment, the resin layer 14 is composed of a first layer 16 and a second layer 18, but this structure is not limited to this; the resin layer 14 may also be composed of three or more layers.

[0036] In addition, in this embodiment, the resin layer 14 is divided into multiple layers, but the structure is not limited to this. As long as the conductive additives 22 contained in the resin layer 14 are configured not to contact at least one of the lower surface 14a and the upper surface 14b of the resin layer 14, the resin layer 14 may not be divided into a first layer 16 and a second layer 18, but may consist of only one layer.

[0037] Furthermore, in this embodiment, carbon nanotubes are used as the conductive agent 22, but the structure is not limited to this. The conductive agent 22 can be formed from any carbon material having a structure with six-membered rings. For example, the conductive agent 22 can also be graphene. Figure 5As shown, in graphene, the plane is called the base plane 24, and the plane orthogonal to the base plane 24 is called the edge plane 26. When using graphene as the conductive additive 22, the conductive additive 22 can be disposed in the resin layer 14 in such a way that the edge plane does not contact at least one of the lower surface 14a and the upper surface 14b of the resin layer 14. By disposing the conductive additive 22 in this way, when using graphene as the conductive additive 22, ions are also less likely to move from the electrode 30 to the metal foil 12 via the conductive additive 22 (graphene), thus suppressing the metal foil 12 from being damaged by ions in the electrode 30.

[0038] Furthermore, the resin layer 14 may contain various conductive additives 22. For example, it may contain two or more of carbon nanotubes, graphene, and carbon black. Additionally, it may contain materials that can be structurally classified as carbon nanotube systems, such as vapor-grown carbon fibers (VGCF). In this case, each conductive additive 22 is disposed within the resin layer 14 such that its edge surface does not contact at least one of the lower surface 14a and upper surface 14b of the resin layer 14. Therefore, ions are less likely to migrate from the electrode 30 to the metal foil 12 via the conductive additives 22, thus suppressing damage to the metal foil 12 caused by ions within the electrode 30.

[0039] Furthermore, the current collector 10 of this embodiment includes a metal foil 12 and a resin layer 14 (i.e., a resin layer 14 configured to suppress the movement of ions within the electrode 30 towards the metal foil 12), but is not limited to such a structure. For example, such as Figure 6 As shown, the current collector 110 may also include a metal foil 12, a resin layer 14 (hereinafter also referred to as the first resin layer 14), and a resin layer 28 (hereinafter also referred to as the second resin layer 28) having a different function from the first resin layer 14. Furthermore, the metal foil 12 and the first resin layer 14 have the same structure as those of the current collector 10 described above, therefore, detailed descriptions are omitted.

[0040] The second resin layer 28 is disposed on the surface of the first resin layer 14. The second resin layer 28 is composed of resin 120 containing conductive additive 122. The second resin layer 28 is configured such that when an electrode 30 is coated on the surface of the current collector 110 (specifically, the surface of the second resin layer 28), pressure is applied to force the electrode 30 into the second resin layer 28. Furthermore, the types of resin 120 and conductive additive 122 are not particularly limited.

[0041] The current collector 110, like the current collector 10 described above, includes a first resin layer 14. Because the current collector 110 includes the first resin layer 14, the edge surface of the conductive additive 22 does not contact either the lower surface 14a or the upper surface 14b of the first resin layer 14. Therefore, even if ions coated within the electrode 30 of the current collector 110 penetrate the second resin layer 28 and enter the first resin layer 14, the ions have difficulty penetrating the first resin layer 14 to reach the metal foil 12. Thus, within the current collector 110, ions have difficulty moving from the electrode 30 to the metal foil 12, suppressing damage to the metal foil 12 caused by ions within the electrode 30. Figure 6 In the first resin layer, a conductive additive is contained in the second resin layer 28 and the first resin layer 14 respectively, but multiple conductive additives can be contained as long as they perform the same function.

[0042] Furthermore, a first resin layer 14 is disposed between the metal foil 12 and the second resin layer 28 in the current collector 110, but this structure is not limited to this. The first resin layer 14 may also be disposed at a position that contacts the electrode 30 when the current collector 110 is coated with the electrode 30. Alternatively, the first resin layer 14 may be disposed at a position that does not contact either the electrode 30 or the metal foil 12 when the current collector 110 is coated with the electrode 30 (for example, the central layer when the resin layer is a three-layer structure). Regardless of where the first resin layer 14 is disposed in the current collector 110, ion movement is suppressed within the first resin layer 14. Therefore, ions are difficult to move from the electrode 30 to the metal foil 12, and damage to the metal foil 12 due to ions within the electrode 30 can be suppressed.

[0043] The above description details specific examples of this utility model, but these are merely illustrative and not intended to limit the scope of the claims. The technology described in the claims includes techniques derived from various modifications and alterations of the above-described specific examples. The technical elements described in this specification or drawings are technically useful individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful.

Claims

1. A current collector in contact with an electrode, characterized in that, This current collector has the following features: Metal foil; and A resin layer disposed on the metal foil, the resin layer comprising a plurality of conductive additives. The resin layer has a first side that contacts the metal foil and a second side that is located on the opposite side of the first side and contacts the electrode. Each of the aforementioned conductive additives is formed of carbon material and has a base surface and an edge surface. Each of the conductive additives is disposed within the resin layer such that the edge surface does not contact at least one of the first surface and the second surface.

2. The current collector according to claim 1, characterized in that, The resin layer comprises a first layer disposed on the metal foil and a second layer disposed on the first layer. None of the conductive additives contained in the first layer are partially located within the second layer; they are all disposed within the first layer. None of the conductive additives contained in the second layer are located within the first layer; all of them are disposed within the second layer.

3. The current collector according to claim 1 or 2, characterized in that, The conductive additives mentioned are carbon nanotubes.

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