Composite current collector, positive and negative pole pieces and lithium ion battery

Abstract

The utility model belongs to the field of batteries, and particularly relates to a composite current collector, positive and negative pole pieces and a lithium ion battery. The composite current collector comprises a polymer layer, an aluminum metal layer arranged on one side of the polymer layer and a copper metal layer arranged on the other side of the polymer layer; and a chromium metal layer is arranged on one side, far away from the polymer layer, of the copper metal layer. According to the composite current collector disclosed by the utility model, the aluminum metal layer and the copper metal layer are respectively arranged on two sides of the macromolecule layer, so that the positive electrode and the negative electrode can be simultaneously coated on two sides of the same current collector, and the middle macromolecule layer is non-conductive, so that short circuit of a pole piece is avoided; the manufacturing process of the current collector and the manufacturing process of the pole piece can be reduced, so that the cost can be reduced.

Description

Technical Field

[0001] The utility model belongs to the field of batteries, and specifically relates to a composite current collector, positive and negative electrode sheets and a lithium ion battery. Background Art

[0002] The most commonly used current collectors for lithium batteries include copper foil for negative electrodes and aluminum foil for positive electrodes. In order to increase the energy density of the battery, the current collector is required to be thinner and thinner, and the surface density is lower and lower. The latest copper foil thickness reaches 3.5μm, and the aluminum foil is reduced to 8μm. Since the foil has a manufacturing limit thickness, the yield rate decreases after the thickness is reduced, resulting in a significant increase in the cost of ultra-thin foil compared to conventional thicknesses such as 6μm copper foil and 12μm aluminum foil. In order to reduce the surface density of the current collector and improve the safety performance of the battery, a "sandwich" structure composite current collector appears.

[0003] The currently used "sandwich" structure composite current collector uses composite aluminum foil for the positive electrode and composite copper foil for the negative electrode.

[0004] Composite aluminum foil structure for positive electrode Figure 1 As shown in FIG. 1 , it includes a polymer layer 1′ and aluminum metal layers 2′ arranged on both sides of the polymer layer; the composite copper foil structure for the negative electrode is as shown in FIG. Figure 2 As shown in the figure, a chromium metal layer 4', a copper metal layer 3', a polymer layer 1', a copper metal layer 3' and a chromium metal layer 4' are sequentially arranged, wherein the chromium metal layer is used to increase its anti-oxidation performance.

[0005] The method of using composite aluminum foil for positive electrode and composite copper foil for negative electrode in batteries is the same as that of traditional aluminum foil and traditional copper foil. The positive electrode active material is coated on both sides of the composite aluminum foil to form a positive electrode sheet, and the negative electrode active material is coated on both sides of the composite copper foil to form a negative electrode sheet. A separator and electrolyte are added between the positive and negative electrode sheets, and a battery shell is added to the outside to assemble into cylindrical, square or soft-pack batteries. However, the existing composite current collector imitates the current conventional current collector, using aluminum foil for the positive electrode and copper foil for the negative electrode. Two current collectors need to be prepared in the same battery. Utility Model Content

[0006] The purpose of the utility model is to overcome the defects in the prior art and provide a composite current collector, positive and negative electrode sheets and a lithium ion battery.

[0007] In order to achieve the above-mentioned purpose, the utility model adopts the following technical solutions:

[0008] A composite current collector comprises a polymer layer, an aluminum metal layer arranged on one side of the polymer layer and a copper metal layer arranged on the other side of the polymer layer; a chromium metal layer is arranged on the side of the copper metal layer away from the polymer layer.

[0009] The thickness of the polymer layer is 2-10 μm.

[0010] The thickness of the aluminum metal layer is 0.3-2 μm.

[0011] The thickness of the copper metal layer is 0.3-2 μm.

[0012] The thickness of the chromium metal layer is 10nm-300nm.

[0013] Adhesive layers are independently arranged between the aluminum metal layer and the polymer layer, and between the copper metal layer and the polymer layer.

[0014] A carbon coating layer is arranged on the surface of the aluminum metal layer away from the polymer layer.

[0015] The utility model also includes a positive and negative electrode sheet, which includes the composite current collector and an active material coating arranged on the surface of the composite current collector.

[0016] The active material coating includes a positive electrode active material coating and a negative electrode active material coating; the surface of the aluminum metal layer of the composite current collector is provided with a positive electrode active material coating to form a positive electrode; the surface of the chromium metal layer of the composite current collector is provided with a negative electrode active material coating to form a negative electrode; the pole piece as a whole forms a positive and negative pole piece that includes both a positive pole piece and a negative pole piece.

[0017] The utility model also comprises a lithium ion battery, characterized in that it comprises the positive and negative electrode sheets.

[0018] Compared with the prior art, the beneficial effects of the utility model are:

[0019] The composite current collector of the utility model is provided with an aluminum metal layer and a copper metal layer on both sides of the polymer layer, respectively, so that the positive electrode and the negative electrode can be coated on both sides of the same current collector at the same time. Since the middle polymer layer is not conductive, the pole piece will not short-circuit. Compared with the two current collector modes of the traditional separate composite copper foil current collector and composite aluminum foil current collector, the utility model only needs to use one current collector in the battery; compared with the need to use the positive pole piece and the negative pole piece at the same time in the prior art battery, the utility model can only need to coat one positive and negative pole piece; compared with the prior art positive pole piece and negative pole piece separately rolling, cutting and other manufacturing processes, the utility model can reduce the manufacturing process to one positive and negative pole piece to complete the rolling, cutting and other processes at the same time. Because the manufacturing process of the current collector and the manufacturing process of the pole piece can be reduced, the cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the overall structure of the positive electrode current collector composite aluminum foil in the prior art of the utility model;

[0021] Figure 2 It is a schematic diagram of the overall structure of the negative electrode current collector composite copper foil in the prior art of the utility model;

[0022] Figure 3 This is a schematic diagram of the structure of the composite current collector in Example 1 of the utility model;

[0023] Figure 4 This is a schematic diagram of the structure of the composite current collector in Example 2 of the utility model;

[0024] Figure 5 This is a schematic diagram of the structure of the composite current collector in Example 3 of the utility model;

[0025] Figure 6 This is a schematic diagram of the structure of the composite current collector in Example 4 of the utility model. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and the best embodiment.

[0027] Figure 3-6 A composite current collector is shown, comprising a polymer layer 1, an aluminum metal layer 2 arranged on one side of the polymer layer, and a copper metal layer 3 arranged on the other side of the polymer layer; a chromium metal layer 4 is arranged on the side of the copper metal layer away from the polymer layer.

[0028] The polymer layer is composed of one or more of polyethylene terephthalate, polypropylene or polyimide; the thickness is 2-10 μm, specifically 2 μm, 4.5 μm, 6 μm or 10 μm.

[0029] The thickness of the aluminum metal layer is 0.3-2 μm, specifically 0.3 μm, 1 μm, or 2 μm.

[0030] The thickness of the copper metal layer is 0.3-2 μm, specifically 0.3 μm, 1 μm, or 2 μm.

[0031] The thickness of the chromium metal layer is 10nm-300nm, specifically 10nm, 50nm, 100nm, and 300nm.

[0032] Example 1

[0033] like Figure 3 It shows a composite current collector, comprising a polymer layer 1, an aluminum metal layer 2 arranged on one side of the polymer layer, and a copper metal layer 3 arranged on the other side of the polymer layer; a chromium metal layer 4 is arranged on the side of the copper metal layer away from the polymer layer.

[0034] The polymer layer 1 is a substrate, an aluminum metal layer 2 is deposited on one side of the polymer layer 1 by vacuum evaporation, a copper metal layer 3 is deposited on the other side of the substrate by magnetron sputtering, and a chromium metal layer 4 is subsequently deposited on the outer layer of the copper metal layer 3 by magnetron sputtering. The preparation of the copper metal layer can also be carried out by depositing a thin copper metal layer 3 on the other side of the substrate by magnetron sputtering, and then thickening the copper metal layer 3 by electroplating to achieve the purpose of reducing costs.

[0035] Example 2

[0036] like Figure 4 It shows a composite current collector, comprising a polymer layer 1, an aluminum metal layer 2 disposed on one side of the polymer layer, and a copper metal layer 3 disposed on the other side of the polymer layer; a chromium metal layer 4 is disposed on the side of the copper metal layer away from the polymer layer. Adhesive layers 5 are independently disposed between the aluminum metal layer 2 and the polymer layer 1, and between the copper metal layer 3 and the polymer layer 1.

[0037] The polymer layer 1 is used as a substrate, and an aluminum metal layer 2 is adhered to one side of the polymer layer 1 using an adhesive to form a bonding layer 5. An adhesive is used to adhere a copper metal layer 3 to the other side of the polymer layer 1 to form a bonding layer on the other side. A chromium metal layer 4 is deposited on the outer layer of the copper metal layer 3 by electroplating.

[0038] Example 3

[0039] like Figure 5 It is shown that in the composite current collector obtained in Example 1, a carbon coating layer 6 is provided on the surface of the aluminum metal layer 2 away from the polymer layer 1. The polymer layer 1 is a substrate, and the aluminum metal layer 2 is deposited on one side of the polymer layer 1 by vacuum evaporation, and then a carbon layer is coated on the outside of the aluminum metal layer 2 to obtain a carbon coating layer 6, so as to increase the dyne value of the aluminum foil surface, thereby improving the adhesion of the pole piece after coating the positive electrode active material; at the same time, the conductivity of the pole piece is improved, thereby improving the fast charging performance and high-rate discharge performance of the battery. A thin copper metal layer 3 is deposited on the other side of the substrate by magnetron sputtering, and then the copper metal layer 3 is thickened by electroplating to achieve the purpose of reducing costs, and then a chromium metal layer 4 is deposited on the outer layer of the copper metal layer 3 by electroplating.

[0040] Example 4

[0041] like Figure 6 It is shown that in the composite current collector obtained in Example 2, the surface of the aluminum metal layer 2 away from the polymer layer 1 is provided with a carbon coating layer 6, so as to increase the dyne value of the aluminum foil surface, thereby improving the bonding force of the electrode sheet after coating the positive electrode active material; at the same time, the conductivity of the electrode sheet is improved, thereby improving the fast charging performance and high rate discharge performance of the battery.

[0042] A pole piece comprises the composite current collector obtained in the above-mentioned embodiments 1-4 and an active material coating arranged on the surface of the composite current collector.

[0043] The active material coating includes a positive electrode active material coating and a negative electrode active material coating; the surface of the aluminum metal layer of the composite current collector is provided with a positive electrode active material coating; the surface of the chromium metal layer of the composite current collector is provided with a negative electrode active material coating.

[0044] The pole pieces, diaphragm, electrolyte, battery shell cover, etc. are assembled into a lithium-ion battery; the lithium-ion battery includes a battery shell cover, electrolyte, diaphragm, and pole pieces arranged on both sides of the diaphragm; the positions of the pole pieces on both sides close to the diaphragm are respectively the positive electrode active material coating and the negative electrode active material coating.

[0045] From the above, it can be seen that the composite current collector of the utility model has an aluminum metal layer and a copper metal layer respectively arranged on both sides of the polymer layer, so that the positive electrode and the negative electrode can be coated on both sides of the same current collector at the same time. Since the middle polymer layer is not conductive, the pole piece will not short-circuit. Compared with the traditional separate composite copper foil current collector and composite aluminum foil current collector, the utility model only needs to use one current collector in the battery; compared with the need to use positive and negative pole pieces at the same time in the prior art battery, the utility model can only need to coat one positive and negative pole piece; compared with the prior art positive and negative pole pieces, which are separately rolled and cut, the manufacturing process of the utility model can be reduced to one positive and negative pole piece to complete the rolling and cutting processes at the same time. Because the manufacturing process of the current collector and the manufacturing process of the pole piece can be reduced, the cost can be reduced.

[0046] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, according to the concept of the present invention, there will be changes in the specific implementation methods and application scopes. The contents of this specification should not be understood as limiting the present invention.

Claims

1. A composite current collector, characterized in that: It comprises a polymer layer, an aluminum metal layer arranged on one side of the polymer layer and a copper metal layer arranged on the other side of the polymer layer; a chromium metal layer is arranged on the side of the copper metal layer away from the polymer layer.

2. The composite current collector according to claim 1, characterized in that: The thickness of the polymer layer is 2-10 μm.

3. The composite current collector according to claim 1, characterized in that: The thickness of the aluminum metal layer is 0.3-2 μm.

4. The composite current collector according to claim 1, characterized in that: The thickness of the copper metal layer is 0.3-2 μm.

5. The composite current collector according to claim 1, characterized in that: The thickness of the chromium metal layer is 10nm-300nm.

6. The composite current collector according to claim 1, characterized in that: Adhesive layers are independently arranged between the aluminum metal layer and the polymer layer, and between the copper metal layer and the polymer layer.

7. The composite current collector according to claim 1, characterized in that: A carbon coating layer is arranged on the surface of the aluminum metal layer away from the polymer layer.

8. A positive and negative electrode sheet, characterized in that: The invention comprises the composite current collector according to any one of claims 1 to 7 and an active material coating arranged on the surface of the composite current collector.

9. The positive and negative electrode sheets according to claim 8, characterized in that: The active material coating includes a positive electrode active material coating and a negative electrode active material coating; the surface of the aluminum metal layer of the composite current collector is provided with a positive electrode active material coating; the surface of the chromium metal layer of the composite current collector is provided with a negative electrode active material coating.

10. A lithium ion battery, characterized in that: Including the positive and negative electrode sheets as described in claim 9.

Images