Composite current collector, electrode and preparation method

Abstract

This invention provides a composite current collector, an electrode, and a preparation method. The composite current collector is a flexible foil material and includes: a base film comprising a polymer film layer and a metal film layer, the polymer film layer comprising a first film layer and a second film layer; a first metal outer layer located on one side of the metal film layer and the base film in the thickness direction; and a second metal outer layer comprising the first outer layer and the second outer layer in the width direction, the second outer layer being located at the edge of the first outer layer in the width direction and on the other side of the metal film layer in the thickness direction, with the first outer layer connected to the other side of the second film layer. In this invention, the edge metal layer, the first metal outer layer, and the second metal outer layer cooperate to form an electrode tab structure. The all-metal design of the electrode tab ensures the convenience of processing the electrode tab, avoids the influence of polymer materials on the metal welding effect, improves the internal space utilization of the battery cell, and reduces the internal resistance of the battery cell.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a composite current collector, an electrode, and a method for preparing them. Background Technology

[0002] Composite current collectors are multilayer thin-film materials with a "metal-polymer-metal" sandwich structure. Typically, a polymer material serves as the middle layer, with metal layers (such as copper or aluminum) deposited on both sides through a specific process. They are used to replace traditional metal foils (such as copper or aluminum foil) as current collectors for the positive and negative electrodes of batteries. Composite current collectors have advantages such as low density, high toughness, and good elasticity, which greatly improves the energy density and cycle life of battery cells.

[0003] Compared to traditional current collectors, composite current collectors have an additional layer of insulating polymer material. This material is not resistant to high temperatures and will soften, deform, shrink, or even vaporize if the temperature is too high. Therefore, if the multi-layer composite current collector is processed and then laser-welded, the polymer base film material cannot withstand the high temperature of the molten metal. During laser welding of the electrode and current collector, a sudden and violent vaporization will occur, resulting in a "burst point." This causes liquid metal to splatter, making it impossible to directly weld the tab at one end of the core (i.e., the foil without active material coating) to the current collector.

[0004] The current solution involves using ultrasonic welding of pure metal foil as an adapter process. Specifically, a metal adapter layer is ultrasonically welded to each side of the blank area of ​​the composite current collector. These metal adapters are then processed and welded onto the current collector to form an effective electrical connection. However, adding extra metal adapters requires additional assembly steps, encroaches on the internal space of the battery cell, and leads to decreased cell performance and increased costs. Summary of the Invention

[0005] One object of the present invention is to provide a composite current collector, an electrode, and a preparation method, which can reduce the production difficulty and cost of the composite current collector.

[0006] To achieve the above objectives, the present invention provides the following technical solutions.

[0007] According to a first aspect of the present invention, the composite current collector is a flexible foil material, the composite current collector has a length direction, a width direction, and a thickness direction, and the composite current collector includes: a base film, the base film including a polymer film layer and a metal film layer, the polymer film layer having a three-dimensional porous structure, the polymer film layer including a first film layer and a second film layer, the first film layer being connected to one side of the second film layer in the thickness direction, the edge of the second film layer extending beyond the edge of the first film layer in the width direction, the metal film layer being arranged sequentially with the first film layer; and a first metal outer layer, the first metal outer layer being located on one side of the metal film layer and the base film in the thickness direction, the first metal outer layer being connected to the first film layer and the metal film layer respectively. The composite current collector is connected to one side of the first metal film layer; a second metal outer layer, which includes a first outer layer and a second outer layer in the width direction, is located at the edge of the first outer layer in the width direction, and is connected to the edge of the second film layer. In the thickness direction, the second outer layer is located on the other side of the metal film layer, and the first outer layer is connected to the other side of the second film layer. The metal film layer includes an edge metal layer, which is provided at at least one edge of the composite current collector in the width direction. The edge metal layer is connected to the first metal outer layer, the second outer layer, the first film layer, and the second film layer, respectively. The first metal outer layer, the edge metal layer, and the second outer layer cooperate to serve as tabs.

[0008] Optionally, in the thickness direction, the thickness of the first film layer is greater than the thickness of the second film layer.

[0009] Optionally, the thickness of the second outer layer is greater than the thickness of the first outer layer.

[0010] Optionally, on the side of the second outer metal layer 30 away from the base film, the surface of the second outer layer is smooth and continuous with that of the first outer layer.

[0011] Optionally, the polymer film has a three-dimensional spatial network structure; and / or, the metal film is a copper film, aluminum film, iron film, or stainless steel film.

[0012] Optionally, the metal film layer further includes a central metal layer, and the first film layer is disposed between the central metal layer and the edge metal layer in the width direction.

[0013] Optionally, there may be multiple central metal layers, and the first film layer may be provided between two adjacent central metal layers.

[0014] According to a second aspect of the present invention, a method for preparing a composite current collector, wherein the composite current collector is any of the composite current collectors described above, the method for preparing the composite current collector includes the following steps: S1, overlapping a portion of a metal film layer and a second film layer in the thickness direction, heating and pressing the metal film layer and the polymer film layer together, and bonding the metal film layer and the polymer film layer; S2, preparing a first metal outer layer on one side of the base film in the thickness direction and a second metal outer layer on the other side by one or more magnetron sputtering, vacuum evaporation deposition, or electroplating methods to obtain a composite current collector.

[0015] An electrode according to a third aspect of the present invention includes: a composite current collector, wherein the composite current collector is a composite current collector according to any of the above-described embodiments.

[0016] Optionally, the electrode further includes an active coating disposed on the surface of the composite current collector, wherein the edge of the active coating does not extend beyond the edge of the first film layer in the width direction.

[0017] According to the composite current collector of the present invention, a portion of the edge metal layer is not connected to the polymer film layer, allowing for direct processing and welding to the current collector plate without the need for additional ultrasonic welding of the transfer metal foil. This simplifies the cell assembly process and improves the internal space utilization of the cell. Furthermore, by setting a polymer film layer in a localized area, the composite current collector exhibits advantages such as low density, high toughness, and good elasticity, significantly improving the energy density and cycle life of the cell. When the composite current collector of the present application is applied to electrode sheets, for example, during the assembly of electrode groups / cores, the edge metal layer, the first metal outer layer, and the second metal outer layer cooperate to form an electrode tab structure. In this scheme, the all-metal design of the electrode tabs ensures ease of processing, avoids the influence of polymer materials on the metal welding effect, improves the internal space utilization of the cell, and reduces the internal resistance of the cell.

[0018] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0020] Figure 1 This is a cross-sectional view of a composite current collector according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of a polymer film layer according to an embodiment of the present invention; Figure 3 An assembly diagram of a composite current collector according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a composite current collector according to another embodiment of the present invention.

[0021] Attached icon number Composite current collector 100; Base film 10; Polymer film layer 11; First film layer 111; Second film layer 112; Metal film layer 12; Edge metal layer 121; Central metal layer 122; Overlapping region 123; First metal outer layer 20; Second metal outer layer 30; first outer layer 31; second outer layer 32. Detailed Implementation

[0022] Embodiments of the present invention will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] The terms "first" and "second" in the specification and claims of this invention may explicitly or implicitly include one or more of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0024] In the description of this invention, it should be understood that the terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] The composite current collector 100 of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] like Figures 1 to 4 As shown, the composite current collector 100 according to the embodiment of this application is a flexible foil material. The composite current collector 100 has a length direction, a width direction and a thickness direction. The composite current collector 100 includes: a base film 10, a first metal outer layer 20 and a second metal outer layer 30.

[0028] Specifically, the base film 10 includes a polymer film layer 11 and a metal film layer 12. The polymer film layer 11 includes a first film layer 111 and a second film layer 112. In the thickness direction, the first film layer 111 is connected to one side of the second film layer 112. In the width direction, the edge of the second film layer 112 extends beyond the edge of the first film layer 111. The metal film layer 12 is arranged sequentially with the first film layer 111. The first metal outer layer 20 is located on one side of the metal film layer 12 and the base film 10 in the thickness direction. The first metal outer layer 20 is connected to one side of the first film layer 111 and the metal film layer 12 respectively. The second metal outer layer 30 includes a first outer layer 31 and a second outer layer 32 in the width direction. In the width direction, the second outer layer 32 is located at the edge of the first outer layer 31 and is connected to the edge of the second film layer 112. In the thickness direction, the second outer layer 32 is located on the other side of the metal film layer 12. The first outer layer 31 is connected to the other side of the second film layer 112.

[0029] The metal film layer 12 includes an edge metal layer 121, which is provided at at least one edge of the composite current collector 100 in the width direction. Specifically, the metal film layer 12 includes an edge metal layer 121 located at the edge of the base film 10 in its own film surface direction, for example, at the right end of the base film 10. This edge metal layer 121 can be used for the subsequent tab region. Furthermore, the edge metal layer 121 is connected to the first outer metal layer 20, the second outer layer 32, the first film layer 111, and the second film layer 112, respectively. The first outer metal layer 20, the edge metal layer 121, and the second outer layer 32 cooperate to serve as tabs, enabling an all-metal design for the tabs.

[0030] In other words, the composite current collector 100 according to the embodiments of this application is a flexible foil, that is, a flexible sheet. The composite current collector 100 is composed of a base film 10, a first metal outer layer 20 and a second metal outer layer 30. Specifically, the composite current collector 100 has a length direction, a width direction and a thickness direction. Here, the length direction can be the winding direction and the width direction can be perpendicular to the feeding direction.

[0031] The base film 10 is composed of a polymer film layer 11 and a metal film layer 12. The polymer film layer 11 includes a first film layer 111 and a second film layer 112, and the metal film layer 12 includes an edge metal layer 121. In the thickness direction, the first metal outer layer 20 and the second metal outer layer 30 can be spaced apart, with the base film 10 disposed between the first metal outer layer 20 and the second metal outer layer 30. For example, the first metal outer layer 20 is disposed on the upper side of the base film 10, and the second metal outer layer 30 is disposed on the lower side of the base film 10. The first metal outer layer 20 and the second metal outer layer 30 can be, but are not limited to, metal foil.

[0032] Furthermore, the base film 10 can be formed by splicing a polymer film layer 11 and a metal film layer 12. A portion of the first metal outer layer 20 is connected to the first film layer 111, and another portion of the first metal outer layer 20 is connected to the edge metal layer 121. The orthographic projection of the first film layer 111 in the thickness direction lies within the first metal outer layer 20, and the orthographic projection of the edge metal layer 121 in the thickness direction also lies within the first metal outer layer 20. In the width direction, the edge of the second film layer 112 extends beyond the edge of the first film layer 111, that is, the dimension of the second film layer 112 in the width direction is larger than the dimension of the first film layer 111 in the width direction, which can improve the bonding strength between the metal film layer 12 and the polymer film layer 11. A portion of the second metal outer layer 30 is connected to the second film layer 112, and another portion of the second metal outer layer 30 is connected to the edge metal layer 121. The orthographic projection of the second film layer 112 in the thickness direction can be located within the second metal outer layer 30. The edges of the edge metal layer 121 and the second film layer 112 overlap in the thickness direction. A portion of the edge metal layer 121 is sandwiched between the edges of the first metal outer layer 20 and the second film layer 112. The edge of the second film layer 112 is sandwiched between the edge metal layer 121 and the first outer layer 31. Another portion of the edge metal layer 121 is sandwiched between the first metal outer layer 20 and the second outer layer 32, which can improve the bonding strength of the polymer film layer 11, the second metal outer layer 30, and the metal film layer 12. The overlapping area of ​​the edges of the edge metal layer 121 and the second film layer 112 in the thickness direction is the overlapping area 123. That is, in the thickness direction, the first metal outer layer 20 covers the first film layer 111 and the metal film layer 12, and the second metal outer layer 30 covers the second film layer 112 and the local area of ​​the metal film layer 12. The composite current collector 100 according to the embodiment of this application is a foil structure with a local polymer film layer 11 and a local metal film layer 12.

[0033] Furthermore, the base film 10 has a first metal outer layer 20 and a second metal outer layer 30 on both sides in the thickness direction. For example, the two sides of the base film 10 are plated with metal layers as the first metal outer layer 20 and the second metal outer layer 30. In this embodiment, electrical connection can be provided by using the first metal outer layer 20 and the second metal outer layer 30.

[0034] Understandably, a portion of the edge metal layer 121 that is not connected to the polymer film layer 11 can be directly processed and welded to the current collector without the need for additional ultrasonic welding of the transfer metal foil. This simplifies the cell assembly process and improves the utilization rate of the internal space of the cell. In addition, by setting the polymer film layer 11 in a localized area, the composite current collector 100 has advantages such as low density, high toughness, and good elasticity, which greatly improves the energy density and cycle life of the cell.

[0035] When the composite current collector 100 of the present application embodiment is applied to the electrode sheet, for example when assembling into an electrode group / core, the edge metal layer 121, the first metal outer layer 20 and the second metal outer layer 30 cooperate to form an electrode tab structure. Under this scheme, the electrode tab adopts an all-metal design to ensure the convenience of processing the electrode tab, avoid the influence of polymer materials on the metal welding effect, improve the utilization rate of the internal space of the cell, and reduce the internal resistance of the cell.

[0036] According to one embodiment of this application, the thickness of the first film layer 111 is greater than the thickness of the second film layer 112 in the thickness direction. In this embodiment, by using a thicker first film layer 111 and a thinner second film layer 112, during hot pressing, the edge of the second film layer 112 extending beyond the first film layer 111 can be simultaneously connected to the metal film layer 12 and the second metal outer layer 30, while ensuring that the first film layer 111 has a greater thickness, which can improve the bonding strength between the metal film layer 12 and the polymer film layer 11.

[0037] In some specific embodiments of this application, the thickness of the second outer layer 32 is greater than the thickness of the first outer layer 31, and the inner side of the second metal outer layer 30 may be provided with a groove, so that the second film layer 112 can be installed in the groove, which facilitates the positioning of the polymer film layer 11.

[0038] According to one embodiment of this application, on the side of the second outer metal layer 30 away from the base film 10, the surfaces of the second outer layer 32 and the first outer layer 31 are smooth and continuous. That is, on the side of the second outer metal layer 30 near the base film 10, the interface area between the surfaces of the second outer layer 32 and the first outer layer 31 has a step; on the side of the second outer metal layer 30 away from the base film 10, the interface area between the surfaces of the second outer layer 32 and the first outer layer 31 has no abrupt change in step. In this embodiment, the stepless design of the outer surface of the second outer metal layer 30 not only facilitates hot pressing operations but also facilitates the formation of a composite current collector 100 with a uniform thickness.

[0039] In some specific embodiments of the present invention, the polymer film layer 11 has a three-dimensional spatial network structure. For example, the polymer film layer 11 is composed of one or more materials selected from polyethylene terephthalate, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, and polyimide. The above materials are all low-density polymers, which have the advantages of good insulation performance, good toughness, impact resistance, and excellent deformation recovery ability.

[0040] In this embodiment, by using a composite current collector 100 with a three-dimensional mesh structure, the permeability and electrolyte retention performance of the composite current collector 100 can be improved while ensuring the advantages of low density, high toughness and good elasticity. This greatly improves the efficiency of the cell injection and wetting process and the electrolyte retention capacity during the cycle, thereby improving the cell production efficiency and cycle life.

[0041] Moreover, compared to existing metal foils or foamed metals, the foil material of the composite current collector 100 in this embodiment simultaneously possesses a spatial network structure and a flexible polymer substrate, which can significantly improve the cycle life of the corresponding product. Furthermore, the polymer film layer 11 in this embodiment adopts a three-dimensional network structure, which not only gives the foil material the advantages of the composite current collector 100, but also improves the permeability and porosity of the composite current collector 100, which is beneficial for the wetting and retention of the electrolyte and the discharge of gases generated by side reactions.

[0042] According to one embodiment of this application, the metal film layer 12 is a copper film, aluminum film, iron film, or stainless steel film, etc. Using a copper film for the metal film layer 12 provides excellent conductivity and makes it suitable for use as a negative electrode current collector in batteries; using an aluminum film for the metal film layer 12 provides low density and good processing performance, making it suitable for use as a positive electrode current collector in batteries; using an iron film for the metal film layer 12 provides high mechanical strength and low cost; using a stainless steel film for the metal film layer 12 provides high strength, corrosion resistance, and strong structural stability, making it suitable for use in special batteries, etc.

[0043] In some specific embodiments of this application, the metal film layer 12 further includes a central metal layer 122, and a first film layer 111 is provided between the central metal layer 122 and the edge metal layer 121 in the width direction. That is, in the width direction, the metal film layer 12 simultaneously includes a central metal layer 122 and an edge metal layer 121, and a first film layer 111 of polymer film layer 11 is provided between the central metal layer 122 and the edge metal layer 121. Specifically, in the width direction, a portion of the central metal layer 122 is located between the first outer metal layer 20 and the second outer metal layer 32, and another portion of the central metal layer 122 is located between the outer edge of the second film layer 112 extending from the first film layer 111 and the first outer metal layer 20; the outer edge of the second film layer 112 extending from the first film layer 111 is located between the central metal layer 122 and the first outer metal layer 31. In this embodiment, by employing the central metal layer 122 and the edge metal layer 121 in cooperation, the width of the composite current collector 100 can be expanded.

[0044] According to one embodiment of this application, there are multiple central metal layers 122, and a first film layer 111 is provided between two adjacent central metal layers 122. That is, multiple central metal layers 122 are arranged side by side in the width direction. By adding multiple polymer film layers 11 and metal film layers 12 in parallel, not only can the production and coating efficiency be increased in practical applications, but the width of the composite current collector 100 can also be increased, so that multi-width coating can be achieved during coating and rolling.

[0045] This application also discloses a method for preparing a composite current collector 100, wherein the composite current collector 100 is the composite current collector 100 of any of the above embodiments, and the method for preparing the composite current collector 100 includes the following steps: S1. A portion of the metal film layer 12 and the second film layer 112 are overlapped in the thickness direction. The metal film layer 12 and the polymer film layer 11 are then heated and pressed together to bond them. In other words, the edge portions of the metal film layer 12 and the polymer film layer 11 can be overlapped first, and then heated and pressed together to form a single, complete base film 10. In step S1, the edge portion of the polymer film layer 11, i.e., the portion of the second film layer 112 extending beyond the first film layer 111, overlaps with the edge metal layer 121 and can be locally compressed.

[0046] S2. A first metal outer layer 20 is prepared on one side of the base film 10 in the thickness direction by one or more magnetron sputtering, vacuum evaporation, or electroplating methods, and a second metal outer layer 30 is prepared on the other side to obtain a composite current collector 100. In other words, a first metal outer layer 20 and a second metal outer layer 30 can be prepared on both sides of the base film 10 after bonding by one or more magnetron sputtering / vacuum evaporation / electroplating methods to obtain a composite current collector 100.

[0047] It is understandable that when the polymer film 11 has a three-dimensional spatial network structure, a portion of the first metal outer layer 20 can be located on the outside of the polymer film 11, and another portion of the first metal outer layer 20 can penetrate into the gaps in the three-dimensional spatial network structure of the polymer film 11. Similarly, a portion of the second metal outer layer 300 can be located on the outside of the polymer film 11, and another portion of the first metal outer layer 20 can penetrate into the gaps in the three-dimensional spatial network structure of the polymer film 11. In this embodiment, some metal can be deposited within the gaps, which can enhance the bonding force between the two different materials.

[0048] This application also discloses an electrode sheet, including a composite current collector 100, which is the composite current collector 100 according to any of the above embodiments. The composite current collector 100 of some embodiments of the present invention can be used as the negative electrode of a negative electrodeless lithium battery. In this application scenario, the composite current collector 100 of the embodiments of the present invention can be deposited directly in the cell through charging without coating with an active material, and then undergo charge-discharge cycles. The composite current collector 100 of some embodiments of the present invention can also be used in lithium metal batteries, using the composite current collector 100 of the embodiments of the present invention as the negative electrode foil, and depositing lithium metal inside and outside the current collector through pre-evaporation coating, selective electroplating, magnetron sputtering, etc., and participating in subsequent charge-discharge cycles in the lithium metal battery.

[0049] According to one embodiment of the present invention, the electrode further includes an active coating disposed on the surface of the composite current collector 100. In the width direction, the edge of the active coating does not extend beyond the edge of the first film layer 111, meaning the active coating cannot enter the overlapping area of ​​the polymer film layer 11 and the metal film layer 12, and the active coating cannot cover the area where the metal film layer 12 is located. In cell manufacturing, the active material can be coated on the outer region corresponding to the polymer film layer 11, and then slit, so that the active coating is located within the region corresponding to the first film layer 111, while the outer region where the metal film layer 12 is located is not coated with active material. After slitting and winding, it can be used as a tab.

[0050] In this embodiment, the coating area of ​​the active coating is flush with the edge of the area where the first film layer 111 is located or within the area where the first film layer 111 is located. Even if the elasticity and hardness of the polymer film layer 11 and the metal film layer 12 are different, it can prevent the active coating in the junction area of ​​the polymer film layer 11 and the metal film layer 12 from cracking during processing and cycling.

[0051] Therefore, according to the embodiments of this application, the electrode uses a composite current collector 100 and an active coating in combination, so that the active material coating area is entirely located in the area where the first film layer 111 is located in the electrode assembly or core.

[0052] This application also discloses a battery comprising an electrode assembly prepared by any of the above embodiments.

[0053] In summary, the composite current collector 100 according to the embodiments of this application uses a base film 10, a first metal outer layer 20 and a second metal outer layer 30 to cooperate with each other, and an edge metal layer 121, the first metal outer layer 20 and the second metal outer layer 30 to cooperate to form a tab structure. Under this scheme, the tab adopts an all-metal design to ensure the convenience of processing the tab, avoids the influence of polymer materials on the metal welding effect, improves the utilization rate of the internal space of the cell, and reduces the internal resistance of the cell.

[0054] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A composite current collector, characterized in that, The composite current collector is a flexible foil material, and the composite current collector has a length direction, a width direction, and a thickness direction. The composite current collector includes: A base film comprising a polymer film layer and a metal film layer, wherein the polymer film layer comprises a first film layer and a second film layer, wherein in the thickness direction, the first film layer is connected to one side of the second film layer, and in the width direction, the edge of the second film layer extends beyond the edge of the first film layer, and the metal film layer is arranged sequentially with the first film layer; A first metal outer layer is located on one side of the metal film and the base film in the thickness direction, and the first metal outer layer is connected to one side of the first film and the metal film, respectively. The second metal outer layer includes a first outer layer and a second outer layer in the width direction. In the width direction, the second outer layer is located at the edge of the first outer layer and is connected to the edge of the second film layer. In the thickness direction, the second outer layer is located on the other side of the metal film layer, and the first outer layer is connected to the other side of the second film layer. The metal film layer includes an edge metal layer. In the width direction, the edge metal layer is provided at at least one edge of the composite current collector. The edge metal layer is connected to the first outer metal layer, the second outer layer, the first film layer, and the second film layer, respectively. The first outer metal layer, the edge metal layer, and the second outer layer cooperate to serve as tabs.

2. The composite current collector according to claim 1, characterized in that, In the thickness direction, the thickness of the first film layer is greater than the thickness of the second film layer.

3. The composite current collector according to claim 1, characterized in that, The thickness of the second outer layer is greater than the thickness of the first outer layer.

4. The composite current collector according to claim 3, characterized in that, On the side of the second outer metal layer 30 away from the base film, the surface of the second outer layer is smooth and continuous with that of the first outer layer.

5. The composite current collector according to claim 1, characterized in that, The polymer film has a three-dimensional spatial network structure; and / or, The metal film layer is a copper film, aluminum film, iron film, or stainless steel film.

6. The composite current collector according to claim 1, characterized in that, The metal film layer further includes a central metal layer, and the first film layer is disposed between the central metal layer and the edge metal layer in the width direction.

7. The composite current collector according to claim 6, characterized in that, There are multiple central metal layers, and the first film layer is provided between two adjacent central metal layers.

8. A method for preparing a composite current collector, characterized in that, The composite current collector is the composite current collector according to any one of claims 1-7, and the preparation method of the composite current collector includes the following steps: S1. Overlap a portion of the metal film layer and the second film layer in the thickness direction, heat and press the metal film layer and the polymer film layer together, and bond the metal film layer and the polymer film layer together. S2. By one or more magnetron sputtering, vacuum evaporation, or electroplating methods, a first metal outer layer is prepared on one side of the base film in the thickness direction, and a second metal outer layer is prepared on the other side to obtain a composite current collector.

9. An electrode sheet, characterized in that, include: A composite current collector, wherein the composite current collector is the composite current collector according to any one of claims 1-7.

10. The electrode sheet according to claim 9, characterized in that, Also includes: An active coating is disposed on the surface of the composite current collector, wherein the edge of the active coating does not extend beyond the edge of the first film layer in the width direction.

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