Composite current collector

Abstract

The utility model relates to the field of batteries, and particularly discloses a composite current collector which comprises a polymer base material, conductive layers and an active substance layer, the conductive layers are arranged on two opposite surfaces of the polymer base material, the active substance layer is arranged on one surface, far away from the polymer base material, of each conductive layer, and micropores for releasing stress are formed in the surface of the polymer base material. And a plurality of micropores are arranged and penetrate through the polymer base material. The composite current collector provided by the utility model can overcome the defect that the conductive layer is easy to fall off from the surface of the polymer base material when being subjected to roll pressure, and the stability of the composite current collector is greatly improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a composite current collector. Background Art

[0002] The function of the current collector is to collect current and carry the positive and negative active materials. The working principle of lithium batteries is that lithium ions move between the positive and negative electrodes to achieve charging and discharging. In this process, the current collector is the key material used to attach active materials to the positive and negative electrodes. It acts as a conductor to collect and output current by contacting the active materials, thereby realizing the process of converting chemical energy into electrical energy. It has a great influence on the internal resistance and cycle performance of lithium-ion batteries.

[0003] At present, in order to improve the performance of the battery, a composite current collector has been proposed. The composite current collector has been innovated from the material level and adopts a "sandwich" structure. The middle layer is a polymer organic matter, and the upper and lower layers are copper, aluminum and other metals. Taking composite copper foil as an example, lithium battery composite copper foil is used as the negative electrode current collector of lithium battery. It has a "polymer substrate + thin conductive layer" structure. The middle layer is not conductive. When a short circuit occurs in the battery, it can cut off the short-circuit current by fusing itself, effectively preventing thermal runaway of the battery.

[0004] The production process of the composite current collector involves a rolling process of the composite current collector. Since the elastic modulus of the polymer substrate is smaller than that of the conductive layer, that is, the ductility of the polymer substrate is higher than that of the conductive layer, under the same rolling pressure, the deformation amplitude of the polymer substrate is greater than the deformation amplitude of the metal conductive layer, which will cause the adhesion between the conductive layer and the polymer substrate to weaken. In severe cases, the conductive layer directly falls off from the polymer substrate, greatly reducing the stability of the composite current collector. Utility Model Content

[0005] In order to solve the above technical problems, the present application provides a composite current collector, which can improve the defect that the conductive layer is easily detached from the surface of the polymer substrate when subjected to roller pressure, thereby greatly improving the stability of the composite current collector.

[0006] The present application provides a composite current collector, which adopts the following technical solution:

[0007] A composite current collector comprises a polymer substrate, a conductive layer and an active material layer, wherein the conductive layer is arranged on two opposite sides of the polymer substrate, the active material layer is arranged on a side of the conductive layer away from the polymer substrate, and micropores for releasing stress are arranged on the surface of the polymer substrate, wherein the micropores are arranged in a plurality and penetrate the polymer substrate.

[0008] Preferably, the plurality of micropores are arranged in an array along the length direction of the polymer substrate.

[0009] Preferably, the end cross-section of the micropore is circular or elliptical.

[0010] Preferably, the end cross-section of the micropore is elliptical, and the major axis of the ellipse is arranged parallel to the length direction of the polymer substrate.

[0011] Preferably, continuous grooves are provided on the surface of the conductive layer.

[0012] Preferably, the end cross-section of the groove is set to be "U"-shaped.

[0013] Preferably, the groove is opened along the width direction of the conductive layer.

[0014] Preferably, the thickness of the polymer substrate is 1 μm-15 μm.

[0015] Preferably, the thickness of the conductive layer is 4 μm-10 μm.

[0016] The composite current collector provided in the present application can release internal stress when rolled by opening micropores on the polymer substrate and grooves on the conductive layer, so as to improve the situation where the conductive layer and the polymer substrate are easily separated due to inconsistent deformation when rolled, reduce the risk of the conductive layer falling off the polymer substrate, and improve the overall stability of the composite current collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the composite current collector structure in an embodiment of the present application;

[0018] Figure 2 is a schematic diagram of the structure of a polymer substrate in an embodiment of the present application;

[0019] Figure 3 It is a schematic diagram of the structure of the conductive layer in the embodiment of the present application.

[0020] Figure numerals: 1. polymer substrate; 2. conductive layer; 3. active material layer; 4. micropore; 5. groove. DETAILED DESCRIPTION

[0021] The following is combined with Figure 1-3 This application is described in further detail. Example

[0022] The present application embodiment discloses a composite current collector. Figure 1 The composite current collector includes a polymer substrate 1, a conductive layer 2, and an active material layer 3. The conductive layer 2 is arranged on two opposite sides of the polymer substrate 1, and the active material layer 3 is arranged on a side of the conductive layer 2 away from the polymer substrate 1.

[0023] The polymer substrate 1 can be made of polymer insulating materials such as PET, PP, PI, PA, PS, PTFE, etc., with a thickness of 1 μm-15 μm. In this embodiment, a PET film with a thickness of 8 μm is preferred.

[0024] The conductive layer 2 can be made of metal materials such as copper, aluminum, titanium, silver, or carbon-based conductive materials such as graphite, graphene, and carbon nanotubes, with a thickness of 4 μm-10 μm. In this embodiment, aluminum foil is preferred, with a thickness of 4.5 μm.

[0025] The active material layer 3 may be made of lithium manganese oxide, lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, etc. In this embodiment, lithium manganese oxide is preferred.

[0026] The conductive layer 2 can be formed on both sides of the polymer substrate 1 by vapor deposition, chemical plating, direct bonding, etc. In this embodiment, direct bonding is preferred, that is, adhesive is first applied to both sides of the PET film, then aluminum foil is attached to both sides of the PET film, and finally rolled and thermally laminated.

[0027] The active material can be formed on the surface of the conductive layer 2 by coating. That is, in this embodiment, lithium manganese oxide is directly coated on the surface of the copper foil, and then dried and rolled.

[0028] Reference Figure 2 The surface of the polymer substrate 1 is provided with micropores 4 for relieving stress, and the micropores 4 are provided in a plurality and arranged in an array along the length direction of the polymer substrate 1. The end cross section of the micropore 4 can be provided in a circular or elliptical shape. In this embodiment, the end cross section of the micropore 4 is provided in an elliptical shape, and the long axis of the ellipse is provided in parallel with the length direction of the polymer substrate 1.

[0029] From the above, it can be seen that the composite of the polymer substrate 1 and the conductive layer 2, and the formation of the active material on the surface of the polymer substrate 1, all need to be processed by rolling, and the setting of the micropores 4 can release the stress between the polymer substrate 1 and the conductive layer 2 at the micropores 4 during the rolling process, thereby avoiding the separation of the conductive layer 2 from the polymer substrate 1. In the production process of the composite current collector, the rolling direction is carried out along the length direction of the polymer substrate 1 and the conductive layer 2, and the micropores 4 are set to be elliptical, which can provide a larger deformation margin for the polymer substrate 1, that is, provide conditions for releasing stress of the polymer substrate 1 and the conductive layer 2 to a greater extent.

[0030] In this embodiment, the polymer substrate 1 and the conductive layer 2 are formed by bonding with an adhesive and roller pressing and heat compounding. The setting of the micropores 4 in this application allows the adhesive to penetrate into the micropores 4 and bond the polymer substrate 1 and the conductive layer 2, thereby further improving the composite stability of the polymer substrate 1 and the conductive layer 2.

[0031] Further, see Figure 3The surface of the conductive layer 2 is also provided with a continuous groove 5 with a "U"-shaped end face, and the groove 5 is opened along the width direction of the conductive layer 2, that is, the length direction of the groove 5 is parallel to the width direction of the conductive layer 2. The continuous groove 5 is arranged so that two-dimensional wrinkles are formed on the surface of the conductive layer 2. In the production process of the composite current collector, the rolling direction is carried out along the length direction of the conductive layer 2, and the two-dimensional wrinkles are flattened, thereby releasing the stress between the conductive layer 2 and the polymer substrate 1.

[0032] In addition, the groove 5 can be set as a long hole that penetrates the upper and lower surfaces of the conductive layer 2. The conductive layer 2 is deformed by rolling, and the long hole can provide deformation margin for the conductive layer 2. In this embodiment, the strength and overall resistance of the composite current collector are given priority, and the groove 5 is chosen not to penetrate the conductive layer 2. The continuous groove 5 forms a two-dimensional wrinkle. When the conductive layer 2 is rolled, the two-dimensional wrinkle tends to flatten, thereby releasing the internal stress of the conductive layer 2 when it is rolled.

[0033] There are two sources of roller pressure: one is that the active material layer 3 needs to be roller-pressed to make it evenly distributed on the surface of the conductive layer 2, and the other is that the polymer substrate 1 and the conductive layer 2 are rolled when they are bonded and compounded.

[0034] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A composite current collector, characterized in that: The invention comprises a polymer substrate (1), a conductive layer (2), and an active material layer (3), wherein the conductive layer (2) is arranged on two opposite sides of the polymer substrate (1), and the active material layer (3) is arranged on a side of the conductive layer (2) away from the polymer substrate (1). Micropores (4) for releasing stress are arranged on the surface of the polymer substrate (1), and the micropores (4) are arranged in plurality and penetrate the polymer substrate (1).

2. The composite current collector according to claim 1, characterized in that: The plurality of micropores (4) are arranged in an array along the length direction of the polymer substrate (1).

3. The composite current collector according to claim 1, characterized in that: The end cross-section of the micropore (4) is circular or elliptical.

4. The composite current collector according to claim 3, characterized in that: The end cross-section of the micropore (4) is elliptical, and the major axis of the ellipse is arranged parallel to the length direction of the polymer substrate (1).

5. The composite current collector according to claim 1, characterized in that: The surface of the conductive layer (2) is provided with continuous grooves (5).

6. The composite current collector according to claim 5, characterized in that: The end cross-section of the groove (5) is arranged to be "U"-shaped.

7. The composite current collector according to claim 5, characterized in that: The groove (5) is opened along the width direction of the conductive layer (2).

8. The composite current collector according to claim 1, characterized in that: The thickness of the polymer substrate (1) is 1 μm-15 μm.

9. The composite current collector according to claim 1, characterized in that: The thickness of the conductive layer (2) is 4 μm-10 μm.

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