Negative current collector, negative plate and secondary battery

Abstract

The utility model discloses a cathode current collector, which comprises a carrier layer, the carrier layer is of an insulating structure, the carrier layer is provided with an upper surface and a lower surface in the thickness direction, and a plurality of through holes are formed in the carrier layer in the thickness direction; the first copper layer is arranged on the upper surface of the carrier layer; the second copper layer is arranged on the lower surface of the carrier layer; each through hole is filled with a conductive part, and the two ends of each conductive part are connected with the first copper layer and the second copper layer respectively. According to the negative electrode current collector, the first copper layer and the second copper layer can be electrically conducted, the subsequent welding process is avoided, the process is simplified, the cost is reduced, and the conductivity, the stability and the reliability of the negative electrode current collector are improved at the same time. The utility model also provides a negative plate containing the negative current collector and a secondary battery containing the negative plate.

Description

Technical Field

[0001] The utility model relates to the technical field of secondary batteries, and more specifically to a negative electrode current collector and a preparation method thereof, a negative electrode sheet and a secondary battery. Background Art

[0002] With the development of science and technology and the improvement of environmental protection awareness, secondary batteries, especially lithium-ion batteries, have become an important energy source widely used in 3C digital products, two-wheeled vehicles, passenger cars, commercial vehicles, power tools, communication base station backup power supplies, and energy storage systems due to their advantages such as long recycling life, environmental protection and energy saving. As a key component of lithium-ion batteries, the current collector plays a vital role in loading active materials, collecting and transporting electrons. Therefore, the current collector needs to have high ionic conductivity, thermal stability, electrochemical stability, and resistance to electrolyte corrosion.

[0003] Traditional current collector materials, such as aluminum foil for positive current collectors and copper foil for negative current collectors, meet the basic needs of current collectors to a certain extent, but there are many problems and challenges. For example, when traditional electrolytic copper foil is used as a negative current collector, its electronic breakdown problem and the risk of battery explosion caused by thermal runaway of the battery pose a great hidden danger to the safe use of the battery. In addition, pure metal copper foil has a low elongation (<10%), poor flexibility, and is easy to break during the coating process, which seriously affects production efficiency. More importantly, the density of traditional copper foil is high, and the weight of the metal current collector itself becomes a major obstacle to improving the energy density of the battery.

[0004] In order to solve the above problems, the research on composite copper foil has gradually increased. Composite copper foil is composed of polymer materials (such as PET and PP) as the middle layer, and the two sides of the polymer material are made of pure copper. This structure is designed to improve the flexibility and ductility of the copper foil, while reducing the weight of the current collector, thereby increasing the energy density of the battery. However, the insulating layer formed by the middle polymer material of the composite current collector makes the metal coating on both sides unable to conduct, which has become a major problem in the application of composite copper foil.

[0005] At present, in order to solve the problem of non-conductivity of the metal coating on both sides of the composite copper foil, the commonly used tab welding methods include ultrasonic welding and laser welding. However, the temperature of laser welding is too high, which can easily cause the foil to shrink and deform, increasing the defective rate. Although ultrasonic welding can weld, it cannot eliminate the insulating layer, resulting in poor conductivity of the metal coating on both sides, which in turn increases the internal resistance of the battery and the temperature rise during charging and discharging. Utility Model Content

[0006] The utility model aims to provide a negative electrode current collector and a preparation method thereof, a negative electrode sheet and a secondary battery, which do not require welding technology to conduct the copper foils on both sides, thereby simplifying the process and reducing costs, while also improving the conductivity, stability and reliability of the negative electrode current collector.

[0007] In order to achieve the above object, the utility model discloses a negative electrode current collector, comprising:

[0008] A carrier layer, wherein the carrier layer is an insulating structure, has an upper surface and a lower surface in a thickness direction of the carrier layer, and is provided with a plurality of through holes in the thickness direction of the carrier layer;

[0009] a first copper layer disposed on the upper surface of the carrier layer;

[0010] a second copper layer disposed on the lower surface of the carrier layer;

[0011] Each of the through holes is filled with a conductive part, and two ends of the conductive part are respectively connected to the first copper layer and the second copper layer.

[0012] Compared with the prior art, the negative electrode current collector of the present application has good flexibility by providing the first copper layer and the second copper layer on both sides of the carrier layer, and the composite copper foil obtained is also thinner and lighter in weight by replacing part of the copper foil with the carrier layer, which can effectively reduce the weight of the copper foil and improve the volume energy density. In particular, by filling the conductive part in the through hole and connecting the conductive part with the first copper layer and the second copper layer, the first copper layer and the second copper layer can be electrically conductive, avoiding the use of subsequent welding processes, simplifying the process, reducing costs, and also improving the conductivity, stability and reliability of the negative electrode current collector.

[0013] Preferably, the carrier layer is selected from a PET (polyethylene terephthalate) layer, a PI (polyimide) layer, a PE (polyethylene) layer, a PP (polypropylene) layer, a PEN (polyethylene naphthalate) layer, a PTFE (polytetrafluoroethylene) layer, a PS (polystyrene) layer or a PAN (polyacrylonitrile) layer.

[0014] Preferably, the through hole has a diameter of 50 μm to 200 μm.

[0015] Preferably, the hole distance between two adjacent through holes is 2 μm to 10 μm.

[0016] Preferably, the thickness of the first copper layer is 0.5 μm to 2 μm; the thickness of the second copper layer is 0.5 μm to 2 μm.

[0017] Preferably, the conductive part is made of copper.

[0018] Accordingly, the utility model also provides a method for preparing a negative electrode current collector, comprising the following steps:

[0019] (1) providing a carrier layer;

[0020] (2) punching holes in the thickness direction of the carrier layer to form a plurality of through holes;

[0021] (3) The carrier layer is processed by vacuum magnetron sputtering to form a seed layer, and then an electroplating or chemical plating process is performed to form a first copper layer and a second copper layer on both sides of the carrier layer in the thickness direction, and a conductive metal is filled in the through hole to form a conductive part.

[0022] Correspondingly, the utility model also provides a negative electrode sheet, comprising the above-mentioned negative electrode current collector or the negative electrode current collector prepared by the above-mentioned method for preparing the negative electrode current collector, and also comprising a negative electrode active material layer located on at least one side of the negative electrode current collector.

[0023] Preferably, the negative electrode current collector extends along the length direction to expose the negative electrode active material layer to form a negative electrode ear.

[0024] Correspondingly, the utility model also provides a secondary battery, which adopts the above-mentioned negative electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of the negative electrode current collector of the utility model.

[0026] Figure 2 It is a schematic structural diagram of the negative electrode sheet of the utility model.

[0027] Figure 3 It is a structural schematic diagram of another embodiment of the negative electrode sheet of the utility model.

[0028] Explanation of symbols:

[0029] A negative electrode current collector 100 , a carrier layer 10 , a through hole 11 , a first copper layer 20 , a second copper layer 30 , a conductive portion 40 , a negative electrode active material layer 200 , and a negative electrode ear 300 . DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0031] Please refer to Figure 1The utility model provides a negative electrode current collector 100, including a carrier layer 10, a first copper layer 20, and a second copper layer 30. The carrier layer 10 is an insulating structure. The carrier layer 10 has an upper surface and a lower surface in the thickness direction. A plurality of through holes 11 are provided in the thickness direction K of the carrier layer 10. The first copper layer 20 is provided on the upper surface of the carrier layer 10, and the second copper layer 30 is provided on the lower surface of the carrier layer 10. A conductive part 40 is filled in each through hole 11, and two ends of the conductive part 40 are respectively connected to the first copper layer 20 and the second copper layer 30.

[0032] In the above technical solution, by providing the first copper layer 20 and the second copper layer 30 on both sides of the carrier layer 10, the composite copper foil obtained has good flexibility, and by replacing part of the copper foil with the carrier layer 10, the copper layer is thinner and the weight is reduced, which can effectively reduce the weight of the copper foil and improve the volume energy density. In particular, by filling the conductive part 40 in the through hole 11, and the conductive part 40 is connected to the first copper layer 20 and the second copper layer 30, the first copper layer 20 and the second copper layer 30 can be electrically conductive, avoiding the use of subsequent welding processes, simplifying the process, reducing costs, and also improving the conductivity, stability and reliability of the negative electrode current collector 100.

[0033] In some preferred embodiments, the carrier layer 10 is selected from a PET (polyethylene terephthalate) layer, a PI (polyimide) layer, a PE (polyethylene) layer, a PP (polypropylene) layer, a PEN (polyethylene naphthalate) layer, a PTFE (polytetrafluoroethylene) layer, a PS (polystyrene) layer or a PAN (polyacrylonitrile) layer. The carrier layer 10 is a polymer material, an insulating layer, and has flexibility, which can effectively prevent the copper foil from stretching and shrinking during the charge and discharge process, improve the stability of the negative electrode active material, and reduce capacity loss and safety hazards. Preferably, the carrier layer 10 is selected from a PET layer, a PI layer, or a PP layer.

[0034] In some preferred embodiments, the through holes 11 of the carrier layer 10 may be arranged in an array or in an irregular arrangement, preferably in a regular array arrangement. In some embodiments, the aperture of the through hole 11 is 50 μm to 200 μm, about 50 μm to 150 μm, about 50 μm to 100 μm, about 50 μm to 80 μm, about 70 μm to 100 μm, about 70 μm to 150 μm. By way of example, the aperture of the through hole 11 may be, but is not limited to, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm.

[0035] It can be understood that the spacing between the through holes 11 refers to the distance between the centers of the two through holes 11. The spacing between the through holes 11 can be selected as needed, and the utility model is not limited to it. Preferably, the hole spacing between two adjacent through holes 11 is 2μm to 10μm, optionally, 2μm to 8μm, 2μm to 6μm, 4μm to 8μm, 4μm to 10μm. As an example, the spacing between the through holes 11 can be but is not limited to 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm.

[0036] In some preferred embodiments, the thickness of the first copper layer 20 is 0.5 μm to 2 μm, optionally, about 0.5 μm to 1.5 μm, about 0.5 μm to 1.0 μm, about 1 μm to 2 μm; the thickness of the second copper layer 30 is 0.5 μm to 2 μm, optionally, about 0.5 μm to 1.5 μm, about 0.5 μm to 1.0 μm, about 1 μm to 2 μm. It should be noted that the thickness of the first copper layer 20 and the second copper layer 30 may be the same or different. Preferably, the thickness of the first copper layer 20 and the second copper layer 30 is the same. As an example, the thickness of the first copper layer 20 may be, but not limited to, 0.5 μm, 1 μm, 1.5 μm, 2 μm; the thickness of the second copper layer 30 may be, but not limited to, 0.5 μm, 1 μm, 1.5 μm, 2 μm.

[0037] In some preferred embodiments, the conductive part 40 is electrically connected to the first copper layer 20 and the second copper layer 30, preferably with good conductivity. In some preferred embodiments, the conductive part 40 is made of copper, and may also be made of copper-nickel alloy.

[0038] Accordingly, the present invention also provides a method for preparing a negative electrode current collector 100, comprising the following steps:

[0039] (1) providing a carrier layer 10;

[0040] (2) punching in the thickness direction K of the carrier layer 10 to form a plurality of through holes 11;

[0041] (3) The carrier layer 10 is processed by vacuum magnetron sputtering to form a seed layer, and then an electroplating or chemical plating process is performed to form a first copper layer 20 and a second copper layer 30 on both sides of the carrier layer 10 in the thickness direction K, and a conductive metal is filled in the through hole 11 to form a conductive portion 40.

[0042] In some preferred embodiments, the punching method in step (2) can be performed by laser punching, mechanical punching or ultrasonic punching, and the shape of the through hole 11 can be circular or square, or triangular or trapezoidal, which is not limited here.

[0043] It is understandable that the carrier layer 10 is processed by vacuum magnetron sputtering to form a seed layer. Of course, the seed layer can also be formed by chemical plating, water electroplating, chemical copper deposition and other technical means. The first copper layer 20, the second copper layer 30, and the conductive part 40 can be formed by, but not limited to, electroplating, chemical plating or chemical copper deposition and other technical means. Among them, the material of the seed layer can be a metallic copper material, or it can be metallic nickel, copper-nickel alloy, etc. It is preferably metallic copper. The method of electroplating after treating the plastic with a seed layer is a conventional technology, and this utility model will not be specifically elaborated.

[0044] Correspondingly, please refer to Figure 2-Figure 3 The utility model also provides a negative electrode sheet, comprising the above-mentioned negative electrode current collector 100 and a negative electrode active material layer 200 located on at least one side of the negative electrode current collector 100. The negative electrode active material layer 200 includes a negative electrode material, a binder, a thickener, and a conductive agent. As an example, the negative electrode sheet comprises the above-mentioned negative electrode current collector 100 and a negative electrode active material layer 200 located on one side of the negative electrode current collector 100 (such as Figure 2 In another embodiment, the negative electrode sheet includes the negative electrode current collector 100 and the negative electrode active material layer 200 (as shown in FIG. Figure 3 In a preferred embodiment, the negative electrode current collector 100 extends along the length direction to expose the negative electrode active material layer 200 to form a negative electrode tab 300, avoiding the use of a tab welding process to achieve conductivity, reducing the process, reducing costs and improving reliability.

[0045] The utility model also provides a secondary battery. The secondary battery adopts the negative electrode sheet. The negative electrode sheet can increase the current density and the energy density of the battery, thereby improving the performance of the secondary battery.

[0046] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope covered by the present invention.

Claims

1. A negative electrode current collector, characterized in that: include: A carrier layer, wherein the carrier layer is an insulating structure, has an upper surface and a lower surface in a thickness direction of the carrier layer, and is provided with a plurality of through holes in the thickness direction of the carrier layer; a first copper layer disposed on the upper surface of the carrier layer; a second copper layer disposed on the lower surface of the carrier layer; Each of the through holes is filled with a conductive part, and two ends of the conductive part are respectively connected to the first copper layer and the second copper layer.

2. The negative electrode current collector according to claim 1, characterized in that: The carrier layer is selected from a PET layer, a PI layer, a PE layer, a PP layer, a PEN layer, a PTFE layer, a PS layer or a PAN layer.

3. The negative electrode current collector according to claim 1, characterized in that: The through hole has a diameter of 50 μm to 200 μm.

4. The negative electrode current collector according to claim 1, characterized in that: The hole distance between two adjacent through holes is 2 μm to 10 μm.

5. The negative electrode current collector according to claim 1, characterized in that: The thickness of the first copper layer is 0.5 μm to 2 μm; the thickness of the second copper layer is 0.5 μm to 2 μm.

6. The negative electrode current collector according to claim 1, characterized in that: The conductive part is made of copper.

7. A negative electrode sheet, characterized in that: The negative electrode current collector comprises the negative electrode current collector as claimed in any one of claims 1 to 6, and further comprises a negative electrode active material layer located on at least one side of the negative electrode current collector.

8. The negative electrode sheet according to claim 7, characterized in that: The negative electrode current collector extends along a length direction to expose the negative electrode active material layer to form a negative electrode ear.

9. A secondary battery, characterized in that: A negative electrode sheet as described in any one of claims 7 to 8 is used.

Images