Composite current collector and preparation method thereof, pole piece and battery

Abstract

The invention relates to the technical field of batteries, and provides a composite current collector and a preparation method thereof, a pole piece and a battery, and the preparation method comprises the following steps: providing a base film layer, and at least one side surface of the base film layer comprises a first region and a second region which are alternately arranged along a first direction; a first release layer and a second release layer are sequentially arranged in the first area in the direction away from the base film layer, so that a plurality of composite layers which are arranged at intervals in the first direction are formed on the surface of at least one side of the base film layer. And coating the surface of one side, with the composite layer, of the base film layer to form a first metal layer comprising a first metal part and a second metal part. Wherein the first metal part covers the surface of the side, away from the base film layer, of the second release layer, the second metal part covers the second area of the base film layer, and the release force between the second release layer and the first metal part is larger than that between the first release layer and the base film layer. According to the composite current collector, the composite layer can be peeled off, the base film layer is exposed, and the use requirement of partitioned film coating is met.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a composite current collector and a preparation method thereof, a pole piece and a battery. Background Art

[0002] The composite current collector is composed of a base film layer of a polymer material and a metal layer arranged on the surface of the base film layer. Among them, the base film layer has good insulation properties and is light in weight. Compared with the traditional metal foil as a current collector, it can improve battery safety and energy density. In the traditional process of preparing a composite current collector, the surface of the base film layer is coated with a metal layer, and then the composite current collector is cut according to the size requirements of use. However, with the development of technology, the same current collector is required to meet different coating requirements at the same time, so it is necessary to provide a composite current collector with different coating partitions. However, it is difficult to prepare a composite current collector with different coating partitions using traditional preparation processes. Summary of the Invention

[0003] Based on this, in order to solve the problem of a single coating form of the composite current collector, it is necessary for the embodiments of the present application to provide a composite current collector capable of realizing zoned coating, a preparation method thereof, a pole piece, and a battery.

[0004] In a first aspect, the present application provides a method for preparing a composite current collector, the preparation method comprising:

[0005] Providing a base film layer, wherein at least one side surface of the base film layer includes first areas and second areas alternately arranged along a first direction;

[0006] Disposing a first release layer and a second release layer in sequence in each of the first regions in a direction away from the base film layer, so as to form a plurality of composite layers spaced apart along the first direction on at least one side surface of the base film layer;

[0007] The surface of one side of the base film layer having the composite layer is plated to form a first metal layer including a first metal part and a second metal part; wherein, the first metal part covers the surface of the second release layer on the side away from the base film layer, the second metal part covers the second area of ​​the base film layer, and the release force between the second release layer and the first metal part is greater than the release force between the first release layer and the base film layer.

[0008] In some embodiments, the preparation method further includes: peeling off the composite layer having the first metal portion formed on the base film layer after plating to expose the base film layer.

[0009] In some embodiments, the method of peeling off the composite layer includes: adhering the first metal part via an adhesive, so that the first metal part and the composite layer are peeled off from the base film layer.

[0010] In some embodiments, the preparation method further comprises: forming a second metal layer on a surface of the base film layer facing away from the composite layer.

[0011] In some embodiments, the thickness of the first release layer and the thickness of the second release layer are each independently 0.5 μm to 1 μm.

[0012] In some embodiments, the release force between the first release layer and the base film layer is 0.03 N / 25 mm to 0.15 N / 25 mm.

[0013] In some embodiments, a release force between the second release layer and the first metal portion is 0.15 N / 25 mm to 0.90 N / 25 mm.

[0014] In some embodiments, the release force between the first release layer and the second release layer is greater than the release force between the second release layer and the first metal part, and the release force between the first release layer and the second release layer is 0.3N / 25mm~1.2N / 25mm.

[0015] In some embodiments, the thickness of the first metal portion and the thickness of the second metal portion are each independently 0.8 μm to 1.2 μm, and the ratio of the thickness of the composite layer to the thickness of the second metal portion is (0.9-2.5):1.

[0016] In some embodiments, the material of the first release layer and the material of the second release layer each independently include at least one of a silane-based release agent, a fluorosilane-based release agent, and a non-silane-based release agent.

[0017] In some embodiments, the base film layer includes at least one of a polypropylene film, a polyester film, a polyimide film, a polyethylene film, and a polyphenylene sulfide film.

[0018] In some embodiments, the method for forming the composite layer includes:

[0019] preparing the first release layer on the first region of the base film layer by a first thermal coating method;

[0020] The second release layer is prepared by a second thermal coating method on a side of the first release layer away from the base film layer:

[0021] The first release layer and the second release layer are cured to form the composite layer.

[0022] In some embodiments, the preparation method further includes: opening a plurality of through holes on the base film layer along a dividing line between adjacent first regions and second regions.

[0023] In some embodiments, the diameter of the through hole is 0.5 mm to 2 mm.

[0024] In some embodiments, a distance between adjacent through holes along the extending direction of the dividing line is 2 mm to 10 mm.

[0025] In some embodiments, the material of the first metal layer includes aluminum, and the first metal layer is formed by vacuum evaporation.

[0026] In some embodiments, the vacuum evaporation rate is 10 m / min to 20 m / min, and the temperature of the evaporation main roller is -20°C to 20°C.

[0027] In some embodiments, the winding tension and the unwinding tension of the vacuum evaporation are independently 100N to 300N.

[0028] In some embodiments, the melting temperature of the second release layer is less than or equal to the heating temperature of the second release layer during the vacuum evaporation.

[0029] In some embodiments, the material of the first metal layer includes copper, and the plating method of the first metal layer includes:

[0030] A seed layer is formed by magnetron sputtering on the surface of the base film layer on one side having the composite layer, and the melting temperature of the second release layer is less than or equal to the heating temperature of the second release layer during the magnetron sputtering, and then electroplating is performed on the surface of the seed layer to form the first metal layer.

[0031] In some embodiments, the seed layer has a thickness of 20 nm to 100 nm.

[0032] In some embodiments, the temperature of the main roller of the magnetron sputtering is -20°C to 20°C.

[0033] In some embodiments, the winding tension and the unwinding tension of the magnetron sputtering are independently 100N to 200N.

[0034] In some embodiments, the winding tension and unwinding tension of the electroplating are independently 50N to 100N.

[0035] In a second aspect, the present application provides a composite current collector, comprising:

[0036] A base film layer, wherein at least one side surface of the base film layer includes a first area and a second area alternately arranged along a first direction;

[0037] A composite layer, each of which is disposed on the first region, and includes a first release layer and a second release layer sequentially stacked along a surface away from the base film layer;

[0038] a first metal layer, the first metal layer comprising a first metal portion and a second metal portion, the first metal layer covering a surface of the base film layer on a side having the composite layer; wherein the first metal portion covers a surface of the second release layer away from the base film layer, and the second metal portion covers the second region of the base film layer;

[0039] Wherein, the release force between the second release layer and the first metal part is greater than the release force between the first release layer and the base film layer.

[0040] In some embodiments, the composite layer can be peeled off and disposed on the base film layer, and the composite layer can be peeled off to expose the first area of ​​the base film layer.

[0041] In some embodiments, the composite current collector further includes a second metal layer, and the second metal layer is disposed on a surface of the base film layer facing away from the composite layer.

[0042] In some embodiments, a plurality of through holes are formed on the composite current collector, and the plurality of through holes are spaced apart along a dividing line between the first region and the second region.

[0043] In a third aspect, the present application provides a pole piece, which includes a composite current collector prepared by the preparation method of the composite current collector as described in the first aspect or a composite current collector as described in the second aspect, and an active material layer is provided on at least one side surface of the composite current collector.

[0044] In a fourth aspect, the present application provides a battery, comprising the electrode as described in the third aspect.

[0045] Compared with traditional technologies, this application has at least the following beneficial effects:

[0046] The present application sets a composite layer having a first release layer and a second release layer in a partial area of ​​the base film layer. During the coating process, the composite layer can shield the base film layer, thereby forming a first metal part covering the composite layer, and a second metal part covering the base film layer. Since the bonding force between the first release layer and the base film layer is relatively low, the bonding force between the first metal part and the second release layer is relatively high. Therefore, the composite layer covered with the first metal part can be separated from the base film layer by peeling to expose the base film layer. Then, a current collector with different coating partitions can be formed by cutting. In addition, since the composite layer has a certain thickness, there is a height difference between the first metal part and the second metal part formed by the coating, which is further conducive to the complete peeling of the first metal part and ensures that the edge of the second metal part is flat after peeling.

[0047] At the same time, during the preparation process, the provision of the second release layer can prevent the base film layer with the composite layer attached thereto from adhering to each other or to the base film layer on the other side when the base film layer is wound. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the planar structure of a composite current collector provided in one embodiment of the present application;

[0049] Figure 2 This is a schematic cross-sectional view of an unpeeled composite layer of a composite current collector provided in one embodiment of the present application;

[0050] Figure 3 This is a schematic cross-sectional view of the composite current collector provided in one embodiment of the present application after the composite layer is peeled off.

[0051] Among them, 10-base film layer; 11-first region; 12-second region; 20-composite layer; 21-first release layer; 22-second release layer; 30-first metal layer; 31-first metal part; 32-second metal part; 40-second metal layer; 50-through hole. DETAILED DESCRIPTION

[0052] Below in conjunction with embodiment and example, the application is further described in detail These embodiment and example are only used to illustrate the application and are not used to limit the scope of the application, and the purpose of providing these embodiment and example is to make the understanding of the disclosure of the application more thorough and comprehensive. It should also be understood that the application can be implemented in many different forms and is not limited to the embodiment and example described herein. Those skilled in the art can make various changes or modifications without violating the connotation of the application, and the equivalent form obtained also falls within the protection scope of the application. In addition, in the description below, a large amount of specific details are given in order to provide a more complete understanding of the application, and it should be understood that the application can be implemented without one or more of these details.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0054] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0055] In this application, the terms "first" and "second" in "the first aspect" and "the second aspect" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor should they be understood as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, "first" and "second" serve only as non-exhaustive enumeration and description and should be understood not to constitute a closed-ended limitation on quantity.

[0056] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0057] In this application, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is deemed to be continuous and includes the two numerical endpoints of the numerical interval (i.e., the minimum and maximum values), as well as each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe a feature or characteristic, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. "Numerical interval" is broadly allowed to include quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0058] All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the application purpose and / or technical solution of this application, the cited documents involved in this application are cited in their entirety and for all purposes. When cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When cited documents are involved in this application, the examples and preferred embodiments of the cited relevant technical features may also be incorporated into this application as references, but are limited to the ability to implement this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be adaptively amended according to the description in this application.

[0059] It should be noted that the release layer in this application refers to a film layer that can be separated by peeling. The release force test is conducted according to the standard GB / T 25256-2010, and the test environment conditions meet the requirements of 23±2℃ and 50±5%RH.

[0060] In this application, the first direction may be the machine direction, i.e., the direction along which the base film layer moves during the production process. The second direction is the transverse direction, which is the direction perpendicular to the machine direction in the plane where the base film layer is located. It should be noted that the first direction and the second direction are respectively parallel to the plane where the base film layer is located.

[0061] In conventional technology, a composite current collector is prepared by coating the entire surface of a base film layer with a metal layer. However, the entire surface of the composite current collector is covered with a metal layer, which makes it difficult to meet the requirements of using a portion of the current collector without a coating.

[0062] The first aspect of the present application provides a method for preparing a composite current collector, the preparation method comprising:

[0063] Provide a base film layer 10, such as Figure 1 As shown, at least one side surface of the base film layer 10 includes first areas 11 and second areas 12 alternately arranged along a first direction;

[0064] like Figure 2 As shown, a first release layer 21 and a second release layer 22 are sequentially arranged in each first area 11 in a direction away from the base film layer to form a plurality of composite layers 20 spaced apart along a first direction on at least one side surface of the base film layer 10 .

[0065] For example Figure 2As shown, the surface of the base film layer 10 having the composite layer 20 is plated to form a first metal layer 30 including a first metal portion 31 and a second metal portion 32. The first metal portion 31 covers the surface of the second release layer 22 on the side away from the base film layer 10, and the second metal portion 32 covers the second region 12 of the base film layer 10. The release force between the second release layer 22 and the first metal portion 31 is greater than the release force between the first release layer 21 and the base film layer 10.

[0066] In the present application, a composite layer 20 having a first release layer 21 and a second release layer 22 is provided in a partial area of ​​the base film layer 10. During the coating process, the composite layer 20 can shield the base film layer 10, thereby forming a first metal portion 31 covering the composite layer 20, and a second metal portion 32 covering the base film layer 10. Since the bonding force between the first release layer 21 and the base film layer 10 is relatively low, the bonding force between the first metal portion 31 and the second release layer 22 is relatively high. Therefore, the composite layer 20 covered with the first metal portion 31 can be separated from the base film layer 10 by peeling to expose the base film layer 10. Then, a current collector with different coating partitions can be formed by cutting. In addition, since the composite layer 20 has a certain thickness, there is a height difference between the first metal portion 31 and the second metal portion 32 formed by the coating, which is further conducive to the complete peeling of the first metal portion 31 and ensures that the edge of the second metal portion 32 is flat after peeling.

[0067] At the same time, during the preparation process, the provision of the second release layer 22 can prevent the base film layer 10 with the composite layer 20 attached thereto from adhering to each other or adhering to the base film layer 10 on the other side when the base film layer 10 is wound.

[0068] It is understood that in this application, the first region 11 may be a non-coated region, and the second region 12 may be a coated region. The non-coated region refers to a region without a metal layer, and the coated region refers to a region with a metal layer. Furthermore, the shape and size of the first region 11 and the second region 12 can be adjusted according to actual design requirements.

[0069] In some embodiments, the preparation method further includes: peeling off the composite layer 20 having the first metal portion 31 formed on the plated base film layer 10 to expose the base film layer 10 . Figure 3 It is a cross-sectional schematic diagram of the composite current collector after the composite layer 20 is peeled off.

[0070] Optionally, the method for peeling the composite layer 20 includes: adhering the first metal portion 31 with an adhesive, so as to peel the first metal portion 31 and the composite layer 20 from the base film layer 10. The adhesive may be a tape roll or tape. Specifically, the adhesive is adhered to the first metal portion 31, and the adhesion force between the adhesive and the first metal portion 31 is greater than the release force between the first release layer 21 and the base film layer 10. Thus, the adhesive is used to peel the composite layer 20 having the first metal portion 31 from the base film layer 10.

[0071] It is understood that when the composite layer 20 is provided on both sides of the base film layer 10, the two sides of the base film layer 10 are plated to form the first metal layer 30. When the composite layer 20 is provided on one side of the base film layer 10, when the first metal layer 30 is formed by plating on the side of the base film layer 10 having the composite layer 20, the preparation method further includes: forming a second metal layer 40 by plating on the side of the base film layer 10 facing away from the composite layer 20. The second metal layer 40 can completely cover the side of the base film layer 10 facing away from the composite layer 20. It is understood that the first metal layer 30 and the second metal layer 40 can be formed simultaneously or separately. The formation methods of the first metal layer 30 and the second metal layer 40 can be the same or different.

[0072] In some embodiments, the thickness of the first release layer 21 and the thickness of the second release layer 22 are independently 0.5 μm to 1 μm, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm.

[0073] The thickness of the first release layer 21 is selected as described above in this application to ensure that the first release layer 21 has an appropriate bonding strength with the base film layer 10. If the thickness of the first release layer 21 is relatively large, the release force between the first release layer 21 and the base film layer 10 will be relatively large, resulting in a large peeling force required during the peeling process, or even inability to peel. Within the range of 0.5-1.0μm, the release force tends to slowly decrease as the coating thickness increases. If the thickness of the first release layer 21 is relatively small, the release force between the first release layer 21 and the base film layer 10 will be relatively small, and the first release layer 21 may fall off during the preparation process, affecting the coating zoning.

[0074] The thickness of the second release layer 22 is selected as above in this application, and the problem of the composite current collector being too thick locally and difficult to roll up and cut is avoided while ensuring that the second release layer 22 has sufficient adhesive force. If the thickness of the second release layer 22 is relatively large, the height difference between the composite layer 20 and the base film layer 10 will be large, which will cause difficulty in rolling up and cutting during the preparation process. If the thickness of the second release layer 22 is relatively small, it may cause the bonding strength between the second release layer 22 and the first metal part 31 to be poor after coating, resulting in the composite layer 20 not being separated from the base film layer 10 during the subsequent peeling process, affecting the use of the composite current collector.

[0075] In some embodiments, the release force between the first release layer 21 and the base film layer 10 is 0.03N / 25mm~0.15N / 25mm, for example, it can be 0.03N / 25mm, 0.04N / 25mm, 0.05N / 25mm, 0.06N / 25mm, 0.07N / 25mm, 0.08N / 25mm, 0.09N / 25mm, 0.10N / 25mm, 0.11N / 25mm, 0.12N / 25mm, 0.13N / 25mm, 0.14N / 25mm or 0.15N / 25mm.

[0076] The release force between the first release layer 21 and the base film layer 10 selected in this application can ensure that the composite layer 20 covered with the first metal part 31 can be peeled off smoothly after coating, and can also ensure that the composite layer 20 used for partitioning before coating will not fall off prematurely.

[0077] In some embodiments, the release force between the second release layer 22 and the first metal portion 31 is 0.15N / 25mm~0.90N / 25mm, for example, it can be 0.15N / 25mm, 0.20N / 25mm, 0.25N / 25mm, 0.30N / 25mm, 0.35N / 25mm, 0.40N / 25mm, 0.45N / 25mm, 0.50N / 25mm, 0.55N / 25mm, 0.60N / 25mm, 0.65N / 25mm, 0.70N / 25mm, 0.75N / 25mm, 0.80N / 25mm, 0.85N / 25mm or 0.90N / 25mm.

[0078] As described above, the present application selects the release force between the second release layer 22 and the first metal part 31 to ensure that there is sufficient bonding force between the second release layer 22 and the first metal part 31, and no composite layer 20 remains during the peeling process; and it can avoid the composite layer 20 from being too thick, ensuring smooth winding and slitting during the preparation process.

[0079] In some embodiments, the release force between the first release layer 21 and the second release layer 22 is greater than the release force between the second release layer 22 and the first metal portion 31. The release force between the first release layer 21 and the second release layer 22 is 0.3N / 25mm to 1.2N / 25mm, for example, 0.3N / 25mm, 0.4N / 25mm, 0.5N / 25mm, 0.6N / 25mm, 0.7N / 25mm, 0.8N / 25mm, 0.9N / 25mm, 1.0N / 25mm, 1.1N / 25mm, or 1.2N / 25mm. The release force between the first release layer 21 and the second release layer 22 is set as described above in the present application to ensure the bonding strength between the first release layer 21 and the second release layer 22, prevent them from falling off during use, and ensure that the composite layer 20 can be completely peeled off. At the same time, since the bonding force between the first release layer 21 and the second release layer 22 is strong, after the composite current collector is peeled off from the first metal part 31 and the composite layer 20, the composite layer 20 as a whole can be completely separated from the first metal part 31, which facilitates the subsequent recovery of the first metal part 31.

[0080] In some embodiments, the thickness of the first metal portion 31 and the thickness of the second metal portion 32 are independently 0.8 μm to 1.2 μm, for example, 0.80 μm, 0.85 μm, 0.90 μm, 0.95 μm, 1.00 μm, 1.05 μm, 1.10 μm, 1.15 μm or 1.20 μm.

[0081] Optionally, the ratio of the thickness of the composite layer 20 to the thickness of the second metal portion 32 is (0.9-2.5):1, for example, 0.9:1, 1.0:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, or 2.5:1. The thickness of the composite layer 20 and the thickness of the second metal portion 32 are selected as described above in the present application to ensure a good winding effect and to facilitate separation of the first and second metal portions 31, 32 during the glass forming process, forming flush edges. If the thickness ratio is relatively large, a protrusion may form on the composite layer 20 during the winding process, affecting contact between the composite current collector and the guide roller. If the thickness ratio is relatively small, the height difference between the first and second metal portions 31, 32 may be small, and uneven burrs may form on the edges of the second metal portion 32 during the peeling process of the first metal portion 31, which may reduce battery safety.

[0082] In some embodiments, the material of the first release layer 21 and the material of the second release layer 22 each independently include at least one of a silane-based release agent, a fluorosilane-based release agent, and a non-silane-based release agent. For example, the material of the first release layer 21 and the second release layer 22 each independently include at least one of vinyl silicone oil, hydroxy polydimethylsiloxane, amino silicone oil, vinyl fluorosilicone oil, methyl fluorosilicone oil, a polyvinyl aliphatic hydrocarbon mixture, a long-chain alkyl acrylate, a polyethyleneimine polymer, and paraffin wax.

[0083] Furthermore, the release force of the release agent can be adjusted by adjusting the molecular weight, the amount of the cross-linking agent, the type and amount of the catalyst, and other methods known to those skilled in the art.

[0084] In some embodiments, the base film layer 10 includes at least one of a polypropylene film, a polyester film, a polyimide film, a polyethylene film, and a polyphenylene sulfide film.

[0085] In some embodiments, the method of forming the composite layer 20 includes:

[0086] A first release layer 21 is prepared on the first area 11 of the base film layer 10 by a first thermal coating method;

[0087] A second release layer 22 is prepared on the surface of the first release layer 21 away from the base film layer 10 by a second thermal coating method:

[0088] The first release layer 21 and the second release layer 22 are cured to form a composite layer 20 .

[0089] It should be noted that in this application, the first release layer 21 and the second release layer 22 are applied separately and then cooled and solidified. This allows the first release layer 21 and the second release layer 22 to combine in a slightly fused state, thereby improving the bonding strength between the first release layer 21 and the second release layer 22. This prevents the release force between the first release layer 21 and the second release layer 22 from being less than the release force between the second release layer 22 and the first metal portion 31.

[0090] In some embodiments, the preparation method further comprises: dividing the adjacent first region 11 and the second region 12 along a dividing line, such as Figure 1 As shown, a plurality of through holes 50 are provided on the base membrane layer 10. The dividing line between the first region 11 and the second region 12 can be arranged along the second direction, thereby dividing the base membrane layer 10 along the first direction into a plurality of alternating first regions 11 and second regions 12. Optionally, the through holes 50 can also be provided after the metal layer is formed by plating.

[0091] It can be understood that, since the first area 11 and the second area 12 are arranged alternately, the dividing line between the first area 11 and the second area 12 is the edge line where the first area 11 and the second area 12 touch each other. Figure 1 As shown, there are dividing lines on both sides of the first area 11 located in the center, so the through hole 50 can be opened along one of the dividing lines, or the through holes 50 can be opened on both dividing lines. Figure 1 As shown, the through hole 50 is only opened on one of the dividing lines where the first area 11 and the second area 12 contact each other.

[0092] In the present application, through holes 50 are opened on the base film layer 10, which not only facilitates the discharge of air during the winding process and avoids wrinkles in the composite current collector, but also is beneficial to the appearance quality of slitting and winding; and multiple through holes 50 are opened along the dividing line, which facilitates secondary processing and slitting, and avoids the formation of burrs at the cutting point, which affects the performance of the composite current collector.

[0093] In some embodiments, the diameter of the through hole 50 is 0.5 mm to 2 mm, for example, 0.5 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm or 2.0 mm. The spacing between adjacent through holes 50 in the extension direction along the dividing line is 2 mm to 10 mm, for example, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm. The diameter and spacing of the through holes 50 are set as above in the present application to effectively ensure the discharge of air during the winding process and avoid affecting the tensile strength of the base film layer 10 in the first direction and the second direction, so as to meet the processing and use requirements of the composite current collector.

[0094] In some embodiments, the material of the first metal layer 30 includes aluminum, and the first metal layer 30 is formed by vacuum evaporation.

[0095] Optionally, the evaporation rate of vacuum evaporation is 10m / min~20m / min, for example, it can be 10m / min, 11m / min, 12m / min, 13m / min, 14m / min, 15m / min, 16m / min, 17m / min, 18m / min, 19m / min or 20m / min. Wherein, vacuum evaporation uses aluminum wire as raw material, and the diameter of the aluminum wire can be 1mm~3mm, for example, it can be 2mm. The wire feeding speed of the aluminum wire can be 400mm / min~500mm / min. The evaporation rate of vacuum evaporation selected in this application as above can ensure production efficiency and finished product yield at the same time, and effectively avoid excessive production costs.

[0096] Optionally, the temperature of the main evaporation roller for vacuum evaporation is between -20°C and 20°C, for example, -20°C, -16°C, -12°C, -8°C, -4°C, 0°C, 4°C, 8°C, 12°C, 16°C, or 20°C. It is understood that during the vacuum evaporation process, the main evaporation roller is used to support and transport the base film layer 10. The temperature of the main evaporation roller is selected as described above in the present application to ensure that the base film layer 10 has a good heat dissipation effect, effectively preventing high-temperature damage (such as melting or aging) to the first release layer 21 and the second release layer 22 during the evaporation process, thereby effectively ensuring the stable performance of the first release layer 21 and the second release layer 22.

[0097] Optionally, the winding tension and unwinding tension of the vacuum evaporation are independently 100N~300N, for example, they can be 100N, 120N, 140N, 160N, 180N, 200N, 220N, 240N, 260N, 280N or 300N. It can be understood that the unwinding tension refers to the unwinding tension of the feed roller entering the vacuum evaporation device, and the winding tension refers to the winding tension of the take-up roller on the output side of the vacuum evaporation device. The present application controls the winding tension and unwinding tension during the vacuum evaporation process as described above, which can avoid the problem of cracks in the metal layer causing heat loss in the composite current collector and affecting the peeling effect.

[0098] Optionally, the melting temperature of the second release layer 22 is less than or equal to the heating temperature of the second release layer 22 during vacuum evaporation. By setting the temperature as described above, the second release layer 22 can be slightly melted during the vacuum evaporation process, thereby improving the bonding strength between the second release layer 22 and the first metal portion 31.

[0099] In some embodiments, the material of the first metal layer 30 includes copper, and the plating method of the first metal layer 30 includes:

[0100] A seed layer is formed by magnetron sputtering on the side of the base film layer 10 having the composite layer 20, and then electroplating is performed on the surface of the seed layer to form the first metal layer 30. Optionally, the melting temperature of the second release layer 22 is less than or equal to the heating temperature of the second release layer 22 during magnetron sputtering. The seed layer can also be made of copper.

[0101] In some embodiments, the seed layer has a thickness of 20 nm to 100 nm, for example, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm.

[0102] The present application sets a seed layer as described above to ensure that the seed layer has both good conductivity and compactness. If the thickness of the seed layer is relatively small, it is difficult to ensure the compactness of the seed layer, resulting in the electroplating process. The electroplating solution contacts the base film layer 10 and the composite layer 20, thereby damaging the composite layer 20 and the base film layer 10 structure.

[0103] In some embodiments, the temperature of the main roller of magnetron sputtering is -20°C~20°C, for example, it can be -20°C, -16°C, -12°C, -8°C, -4°C, 0°C, 4°C, 8°C, 12°C, 16°C or 20°C. It is understood that in the process of forming the seed layer by magnetron sputtering, it is transported by the main roller set in the magnetron sputtering device. The present application controls the temperature of the main roller of magnetron sputtering as described above to ensure that the base film layer 10 has a good heat dissipation effect during the magnetron sputtering process, thereby preventing the first release layer 21 and the second release layer 22 from being damaged by high temperature and affecting the peeling effect.

[0104] In some embodiments, the winding tension and unwinding tension of the magnetron sputtering are independently 100N to 200N, for example, 100N, 110N, 120N, 130N, 140N, 150N, 160N, 170N, 180N, 190N or 200N. It is understood that the unwinding tension refers to the unwinding tension of the feed roller on the side where the base film layer 10 enters the magnetron sputtering; the winding tension refers to the winding tension of the take-up roller on the output side of the magnetron sputtering. The present application selects the unwinding tension as above to avoid cracks in the seed layer, thereby preventing heat loss from affecting the base film layer 10 and the composite layer 20, and further affecting the peeling effect and the performance of the composite current collector.

[0105] Optionally, the electroplating adopts a side-clamping rewinding and unwinding structure with a winding speed of 1m / min to 10m / min, for example, it can be 1m / min, 2m / min, 3m / min, 4m / min, 5m / min, 6m / min, 7m / min, 8m / min, 9m / min or 10m / min.

[0106] In some embodiments, the winding tension and unwinding tension of the electroplating are independently 50N to 100N, for example, 50N, 55N, 60N, 65N, 70N, 75N, 80N, 85N, 90N, 95N or 100N. The present application sets the winding and unwinding tension during the electroplating process as described above to ensure the stability of the seed layer and the metal layer formed by electroplating. This avoids the problem of cracks in the seed layer and the seed layer falling off, so that the electroplating solution contacts the base film layer 10 and the composite layer 20 and causes structural damage.

[0107] In some embodiments, the material of the second metal layer 40 may be the same as or different from the material of the first metal layer 30. For example, if the material of the first metal layer 30 is aluminum, the material of the second metal layer 40 may also be aluminum.

[0108] Exemplarily, a method for preparing the composite current collector is provided, comprising the following steps:

[0109] S1. Provide a base film layer 10 and divide it into a first area 11 and a second area 12.

[0110] S2. A first release layer 21 and a second release layer 22 are sequentially arranged on the first region 11 of the base film layer 10 to form a composite layer 20 in the first region 11 of the base film layer 10 .

[0111] S3 , punching the base film layer 10 provided with the composite layer 20 : opening through holes 50 at intervals along the dividing line between the first area 11 and the second area 12 .

[0112] S4. Plating one side of the base film layer 10 having the composite layer 20 to form a first metal layer 30 covering the base film layer 10 and the composite layer 20. The first metal layer 30 includes a first metal portion 31 covering the composite layer 20 and a second metal portion 32 of the base film layer 10 covering adjacent composite layers 20. It is understood that if composite layers 20 are provided on both sides of the base film layer 10, plating can be performed simultaneously on both sides of the base film layer 10 to form the first metal layer 30. If the composite layer 20 is provided on one side of the base film layer 10, a second metal layer 40 can be formed on the side of the base film layer 10 facing away from the composite layer 20.

[0113] S4. If the composite layer 20 needs to be completely peeled off, an adhesive can be used to adhere the coated base film layer 10. Because the bonding force between the adhesive and the first metal portion 31 is greater than the bonding force between the first release layer 21 and the base film layer 10, and because there is a height difference between the first metal portion 31 and the second metal portion 32, the composite layer 20 can be peeled off from the base film layer 10, exposing the first region 11 of the base film layer 10. In addition, a second rubber roller can be provided to separate the composite layer 20 with the first metal portion 31 bonded to the first rubber roller.

[0114] A second aspect of the present application provides a composite current collector, comprising:

[0115] A base film layer 10, wherein at least one side surface of the base film layer 10 includes first regions 11 and second regions 12 alternately arranged along a first direction;

[0116] The composite layer 20 is disposed on the first region 11 . The composite layer 20 includes a first release layer 21 and a second release layer 22 that are sequentially stacked along a surface away from the base film layer 10 .

[0117] The first metal layer 30 includes a first metal portion 31 and a second metal portion 32. The first metal layer 30 covers the surface of the base film layer 10 having the composite layer 20. The first metal portion 31 covers the surface of the second release layer 22 away from the base film layer 10, and the second metal portion 32 covers the second region 12 of the base film layer 10.

[0118] The release force between the second release layer 22 and the first metal portion 31 is greater than the release force between the first release layer 21 and the base film layer 10 .

[0119] A composite layer 20 having a first release layer 21 and a second release layer 22 is provided in the composite current collector of the present application. During use, the composite layer 20 can be peeled off as needed to expose the base film layer 10 in the area where the composite layer 20 is located, thereby meeting the use requirements of composite current collectors with different coating partitions.

[0120] In some embodiments, the composite layer 20 is peelably disposed on the base film layer 10. After the composite layer 20 is peeled off, the first region 11 of the base film layer 10 is exposed. It is understood that the composite layer 20 is peelably disposed on the base film layer 10 means that the first release layer 21 can be peeled off from the base film layer 10, and the second release layer 22 and the first metal portion 31 can be removed at the same time, thereby exposing the first region 11 of the base film layer 10. This forms a current collector having a plurality of second metal portions 32 spaced apart on the base film layer 10.

[0121] It is understood that if both sides of the base film layer 10 have a composite layer 20, then both sides of the base film layer 10 are covered with a first metal layer 30. If one side of the base film layer 10 has a composite layer 20, the composite current collector further includes a second metal layer 40, which is provided on the surface of the base film layer 10 facing away from the composite layer 20.

[0122] In some embodiments, a plurality of through holes 50 are formed on the composite current collector, and the plurality of through holes 50 are spaced apart along a dividing line between the first region 11 and the second region 12 .

[0123] The third aspect of the present application provides a pole piece, which includes a composite current collector prepared by the preparation method of the composite current collector as described in the first aspect or the composite current collector as described in the second aspect, and an active material layer is provided on at least one side surface of the composite current collector.

[0124] In the present application, the electrode sheet may be either a positive electrode sheet or a negative electrode sheet. The material of the first metal layer and / or the second metal layer of the composite current collector in the positive electrode sheet may be aluminum. The positive electrode material may be a ternary positive electrode material or a lithium iron phosphate positive electrode material. The material of the first metal layer and / or the second metal layer of the composite current collector in the negative electrode material may be copper. The negative electrode material may be at least one of artificial graphite, natural graphite, silicon carbon, hard carbon, and lithium titanate.

[0125] A fourth aspect of the present application provides a battery, comprising the electrode as described in the third aspect.

[0126] It should be noted that the battery of the present application can be assembled from a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The current collectors in the positive and negative electrode sheets can employ the aforementioned composite current collectors. The separator can employ a polypropylene-based material, and the electrolyte can employ an electrolyte commonly used in the art, comprising an organic solvent, a lithium salt, and additives.

[0127] The embodiments of the present application will be described in detail below with reference to the examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are preferably referred to the guidance provided in the present application, and can also be based on the experimental manuals or conventional conditions in this area, or according to the conditions recommended by the manufacturer, or with reference to experimental methods known in the art.

[0128] Example 1

[0129] S1. Provide a base film layer 10 made of polyester and divide it into a first area 11 and a second area 12.

[0130] S2. Sequentially disposing a first release layer 21 and a second release layer 22 on the first region 11 of one side surface of the base film layer 10 to form a composite layer 20 on the first region 11 of one side surface of the base film layer 10. The first release layer 21 is formed by coating with a first release solution comprising 100 parts by mass of a release agent (methyl fluorosilicone oil and vinyl polysiloxane in a mass ratio of 2:98), 5 parts by mass of a cross-linking agent (methyl hydrogenated silicone oil), 3 parts by mass of a platinum catalyst, and 300 parts by mass of a solvent. The thickness of the first release layer 21 is 1 μm, and the release force between the first release layer 21 and the base film layer 10 is 0.08 N / 25 mm. The second release layer 22 is formed by coating with a second release solution. The difference between the second release solution and the first release solution is that the release agent is a polyethylene aliphatic hydrocarbon mixture. The thickness of the second release layer 22 is 0.5 μm, and the release force between the second release layer 22 and the first release layer 21 is 0.6 N / 25 mm.

[0131] S3. Punch the base film layer 10 provided with the composite layer 20: open through holes 50 at intervals along the dividing line between the first area 11 and the second area 12. The diameter of the through holes 50 is 1 mm and the interval distance is 5 mm.

[0132] S4. Using 72 sets of evaporation boats and aluminum wire with a diameter of 2 mm, the aluminum wire was vacuum evaporated on the opposite sides of the base film layer 10 to form a first metal layer 30 and a second metal layer 40 with a thickness of 1 μm, respectively, to produce a composite current collector. The first metal layer 30 covers the surface of the base film layer 10 having the composite layer 20. It includes a first metal portion 31 covering the surface of the composite layer 20 and a second metal portion 32 covering the second area 12 of the base film layer 10. The release force between the first metal portion 31 and the second release layer is 0.5N / 25mm. The second metal layer 40 completely covers the side of the base film layer 10 away from the composite layer 20. The process parameters of vacuum evaporation include: aluminum wire feeding speed of 450mm / min, evaporation rate of 15m / min, evaporation main roller temperature of -10°C, evaporation winding tension of 200N, and the distance between the vacuum evaporation evaporation boat and the polymer composite film is 300mm.

[0133] S5. Use the first rubber roller to roll the composite current collector, bonding the area where the first metal portion 31 is located and peeling the first release layer 21 and the base film layer 10 in the composite layer 20. The bonding force between the first rubber roller and the first metal portion 31 is 5N / 25mm, exposing the base film layer 10 in the first area 11 of the composite current collector. It is understood that a second rubber roller can also be used, positioned opposite the first rubber roller, so that the second rubber roller contacts the first rubber roller, so that the second rubber roller removes the composite layer 20 with the first metal portion 31 bonded to the first rubber roller, thereby achieving a continuous peeling operation with the first rubber roller.

[0134] Example 2

[0135] A composite current collector is prepared according to the method of Example 1, except that the copper plating in step S4 specifically includes:

[0136] S4. Using a copper target as the sputtering target, a 30 nm thick seed layer was deposited on opposite sides of the base film layer 10 using a magnetron sputtering device. The magnetron sputtering process conditions were: 24 copper targets (99.99% purity), 7 kW target power, 150 sccm argon flow, 0.3 Pa coating vacuum, 10 m / min linear speed, -20°C main roller temperature during the coating process, and 100 N winding and unwinding tension.

[0137] The base film layer 10 with the seed layer is then placed in the electroplating solution using a side-clamped reel-and-wind structure for electroplating, forming a first metal layer 30 and a second metal layer 40, respectively. The electroplating solution meets the following requirements: a copper sulfate concentration of 130 g / L, a sulfuric acid concentration of 90 g / L, a chloride ion mass fraction of 50 ppm, a brightener of sodium polydisulfide (sodium bis(propylene disulfide)sulfonate) at 0.4 mL / L, and a carrier of polyethylene glycol at 3 mL / L. The winding speed during the electroplating process is 5 m / min, and the winding and unwinding tensions are 80 N, respectively.

[0138] The first metal layer 30 includes a seed layer and a copper layer formed by electroplating along the thickness direction, with a total thickness of 1 μm, which covers the side surface of the base film layer 10 having the composite layer 20, and the release force between the first metal part 31 and the second release layer 22 is 0.5N / 25mm; the second metal layer 40 includes a seed layer and a copper layer formed by electroplating, which covers the side surface of the base film layer 10 facing away from the composite layer 20.

[0139] Example 3

[0140] The composite current collector is prepared according to the method of Example 1, except that the release agent in the first release solution forming the first release layer 21 is a silane-based release agent, specifically vinyl polysiloxane.

[0141] Example 4

[0142] The composite current collector is prepared according to the method of Example 1, except that the release agent in the second release solution forming the second release layer 22 is a silane-based release agent, specifically vinyl polysiloxane.

[0143] Example 5

[0144] A composite current collector was prepared in the same manner as in Example 2, except that in step S4, the thickness of the seed layer was 100 nm.

[0145] Example 6

[0146] A composite current collector was prepared according to the method of Example 1, except that the thickness of the first release layer 21 was 0.5 μm, and the thickness of the second release layer 22 was 0.5 μm.

[0147] Example 7

[0148] A composite current collector was prepared according to the method of Example 1, except that the thickness of the first release layer 21 was 1.0 μm, and the thickness of the second release layer 22 was 0.1 μm.

[0149] Example 8

[0150] A composite current collector was prepared according to the method of Example 1, except that the winding tension and the unwinding tension of the vacuum evaporation in step S4 were each independently 400N.

[0151] Example 9

[0152] A composite current collector was prepared according to the method of Example 2, except that the winding tension and unwinding tension of the electroplating in step S4 were each independently 200N.

[0153] Comparative Example 1

[0154] A composite current collector was prepared according to the method of Example 1, except that the composite layer 20 only included the second release layer 22 , and the release force between the second release layer 22 and the base film layer 10 was 0.5 N / 25 mm.

[0155] Comparative Example 2

[0156] A composite current collector was prepared according to the method of Example 1, except that the composite layer 20 only included the first release layer 21 , and the release force between the first release layer 21 and the first metal portion 31 was 0.08 N / 25 mm.

[0157] The composite current collector after the stripping is tested, including:

[0158] (1) Observe the surface morphology of the composite current collector to see if there are obvious crack defects.

[0159] (2) Observe whether there is a coating on the first area 11 after stripping, and whether there is a residual composite layer 20.

[0160] Table 1

[0161]

[0162] From the table above we can see that:

[0163] (1) Example 1 has the best peeling effect. Compared with Example 6, Example 1 has a thinner first release layer 21, and the release force increases, resulting in a poor peeling effect. There is a residual composite layer 20, but the metal coating is dense and complete. Compared with Example 1 and Example 7, Example 1 has a thicker second release layer 22, which results in an increased release force, resulting in a poor peeling effect. There is a residual composite layer 20, and the coating is not dense enough.

[0164] (2) Comparing Example 1 and Example 3, the material composition of the first release layer 21 is changed. It can be seen that the bonding force of the first release layer 21 made of the silane-based release agent is not as good as that of the fluorosilane-based and silane-based release agents, resulting in a worse peeling effect than that of Example 1. A small amount of the composite layer 20 remains on the first area 11, and the coating is complete.

[0165] (3) Compared with Example 1 and Example 4, the material composition of the second release layer 22 was changed. Because Example 4 used the same type of release agent, the multiple layers would affect each other during coating, resulting in changes in the release force of the first release layer 21 and the second release layer 22. Therefore, the bonding force of the second release layer 22 made of the silane-based release agent could not meet the requirements, resulting in insufficient bonding between the second release layer 22 and the first metal portion 31, making it impossible to completely peel off the composite layer 20, resulting in a small amount of composite layer 20 remaining on the first region 11.

[0166] (4) Compared with Example 2 and Example 5, the change in the coating metal results in poor bonding between the release layer and the metal, and the thickness of the seed layer needs to be increased to prevent the water plating solution from entering the base film layer 10. When the seed layer is thickened to 100 nm, the bonding between the seed layer and the first metal layer 30 and the second metal layer 40 is better, and the base film layer 10 is also more effectively affected by the water plating solution.

[0167] (5) Compared with Example 1 and Example 8, the winding tension and unwinding tension of vacuum evaporation are increased, and the difference in stretching between the coating layer and the release layer is formed, resulting in cracks and the presence of a coating film; however, there is residue in the composite layer 20 because the bonding force between the second release layer 22 and the first metal layer 30 is destroyed by the cracks, resulting in residue in the composite layer 20.

[0168] (6) Compared with Example 2 and Example 9, the winding tension and unwinding tension of the electroplating are moderate, the first metal layer 30 has no obvious cracks, the plating layer is complete, and no composite layer 20 remains.

[0169] (7) Comparing Example 1 with Comparative Examples 1-2, it can be seen that in Comparative Example 1, only the second release layer 22 is present. There is no significant difference in bonding strength between the second release layer 22 and the base film layer 10, or between the second release layer 22 and the first metal layer 30, and the coating cannot be completely peeled off during peeling. Due to the strong release force, there are no cracks, and a complete and dense coating exists. In Comparative Example 2, only the second release layer 22 is present. There is no significant difference in bonding strength between the second release layer 22 and the base film layer 10, or between the second release layer 22 and the first metal layer 30, and the coating cannot be completely peeled off during peeling. Due to the weak release force of the second release layer 22, the coating is not dense, resulting in gaps and cracks.

[0170] In summary, the present application sets a composite layer 20 having a first release layer 21 and a second release layer 22 in a partial area of ​​the base film layer 10. During the coating process, the composite layer 20 can block the base film layer 10, thereby forming a first metal part 31 covering the composite layer 20, and a second metal part 32 covering the base film layer 10. Since the bonding force between the first release layer 21 and the base film layer 10 is relatively low, the bonding force between the first metal part 31 and the second release layer 22 is relatively high. Therefore, the composite layer 20 covered with the first metal part 31 can be separated from the base film layer 10 by peeling to expose the base film layer 10. Then, a current collector with different coating partitions can be formed by cutting. In addition, since the composite layer 20 has a certain thickness, there is a height difference between the first metal part 31 and the second metal part 32 formed by coating, which is further conducive to the complete peeling of the first metal part 31 and ensures that the edge of the second metal part 32 is flat after peeling.

[0171] At the same time, during the preparation process, the provision of the second release layer 22 can prevent the base film layer 10 with the composite layer 20 attached thereto from adhering to each other or adhering to the base film layer 10 on the other side when the base film layer 10 is wound.

[0172] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0173] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A method for preparing a composite current collector, characterized in that: The preparation method comprises: Providing a base film layer, wherein at least one side surface of the base film layer includes first areas and second areas alternately arranged along a first direction; Disposing a first release layer and a second release layer in sequence in each of the first regions in a direction away from the base film layer, so as to form a plurality of composite layers spaced apart along the first direction on at least one side surface of the base film layer; The surface of one side of the base film layer having the composite layer is plated to form a first metal layer including a first metal part and a second metal part; wherein, the first metal part covers the surface of the second release layer on the side away from the base film layer, the second metal part covers the second area of ​​the base film layer, and the release force between the second release layer and the first metal part is greater than the release force between the first release layer and the base film layer.

2. The method for preparing the composite current collector according to claim 1, wherein: The preparation method further includes: forming a second metal layer by plating on the surface of the base film layer on the side facing away from the composite layer.

3. The method for preparing the composite current collector according to claim 1, wherein: The composite current collector satisfies at least one of the following conditions: (1) The thickness of the first release layer and the thickness of the second release layer are each independently 0.5 μm to 1 μm; (2) The release force between the first release layer and the base film layer is 0.03N / 25mm~0.15N / 25mm; (3) The release force between the second release layer and the first metal part is 0.15 N / 25 mm to 0.90 N / 25 mm; (4) The release force between the first release layer and the second release layer is greater than the release force between the second release layer and the first metal portion, and the release force between the first release layer and the second release layer is 0.3 N / 25 mm to 1.2 N / 25 mm; (5) The thickness of the first metal portion and the thickness of the second metal portion are each independently 0.8 μm to 1.2 μm, and the ratio of the thickness of the composite layer to the thickness of the second metal portion is (0.9-2.5):1; (6) The material of the first release layer and the material of the second release layer each independently include at least one of a silane release agent, a fluorosilane release agent, and a non-silane release agent; (7) The base film layer includes at least one of a polypropylene film, a polyester film, a polyimide film, a polyethylene film, and a polyphenylene sulfide film.

4. The method for preparing the composite current collector according to claim 1, wherein: The method for forming the composite layer includes: preparing the first release layer on the first region of the base film layer by a first thermal coating method; preparing the second release layer on the surface of the first release layer away from the base film layer by a second thermal coating method; The first release layer and the second release layer are cured to form the composite layer.

5. The method for preparing the composite current collector according to claim 1, wherein: The preparation method further includes: opening a plurality of through holes on the base film layer along a dividing line between adjacent first areas and second areas.

6. The method for preparing the composite current collector according to claim 5, wherein: The through hole satisfies at least one of the following conditions: (1) The diameter of the through hole is 0.5 mm to 2 mm; (2) The spacing between adjacent through holes along the extending direction of the dividing line is 2 mm to 10 mm.

7. The method for preparing a composite current collector according to any one of claims 1, wherein: The material of the first metal layer includes aluminum, and the first metal layer is formed by vacuum evaporation, and the vacuum evaporation method satisfies at least one of the following conditions: (1) The vacuum evaporation rate is 10 m / min to 20 m / min, and the temperature of the evaporation main roller is -20°C to 20°C; (2) The winding tension and unwinding tension of the vacuum evaporation are independently 100N to 300N; (3) The melting temperature of the second release layer is less than or equal to the heating temperature of the second release layer during the vacuum evaporation.

8. The method for preparing a composite current collector according to any one of claims 1, wherein: The material of the first metal layer includes copper, and the plating method of the first metal layer includes: A seed layer is formed by magnetron sputtering on the surface of the base film layer on one side having the composite layer, and the melting temperature of the second release layer is less than or equal to the heating temperature of the second release layer during the magnetron sputtering, and then electroplating is performed on the surface of the seed layer to form the first metal layer.

9. The method for preparing the composite current collector according to claim 8, wherein: The coating method of the first metal layer satisfies at least one of the following conditions: (1) The thickness of the seed layer is 20 nm to 100 nm; (2) The main roller temperature of the magnetron sputtering is -20°C to 20°C; (3) The winding tension and unwinding tension of the magnetron sputtering are independently 100N to 200N; (4) The winding tension and unwinding tension of the electroplating are independently 50N~100N.

10. The method for preparing a composite current collector according to any one of claims 1 to 9, wherein: The preparation method further includes: peeling off the composite layer having the first metal portion formed on the base film layer after plating to expose the base film layer.

11. The method for preparing a composite current collector according to claim 10, wherein: The method for peeling off the composite layer includes: adhering the first metal part through an adhesive so that the first metal part and the composite layer are peeled off from the base film layer.

12. A composite current collector, characterized in that: The composite current collector comprises: A base film layer, wherein at least one side surface of the base film layer includes first areas and second areas alternately arranged along a first direction; a composite layer, each of which is disposed on the first region, the composite layer comprising a first release layer and a second release layer sequentially stacked along a surface away from the base film layer; and a first metal layer, the first metal layer comprising a first metal portion and a second metal portion, the first metal layer covering a surface of the base film layer on a side having the composite layer; wherein the first metal portion covers a surface of the second release layer on a side away from the base film layer, and the second metal portion covers the second region of the base film layer; Wherein, the release force between the second release layer and the first metal part is greater than the release force between the first release layer and the base film layer.

13. The composite current collector according to claim 12, wherein: The composite layer is peelably disposed on the base film layer, and the composite layer is peeled off to expose the first area of ​​the base film layer; and / or, The composite current collector further includes a second metal layer, which is disposed on a surface of the base film layer facing away from the composite layer; and / or, A plurality of through holes are formed on the composite current collector, and the plurality of through holes are spaced apart along a dividing line between the first region and the second region.

14. A pole piece, characterized in that: The pole piece comprises a composite current collector prepared by the preparation method of a composite current collector according to any one of claims 10-11 or a composite current collector according to claim 12 or 13, and an active material layer is provided on at least one surface of the composite current collector.

15. A battery, characterized in that: The battery comprises the pole piece according to claim 14.

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