Composite current collector and preparation method thereof

Abstract

The invention relates to the technical field of battery manufacturing, in particular to a composite current collector and a preparation method thereof.The composite current collector comprises a base material belt and further comprises a first base layer, a second base layer and a third base layer, the first base layer comprises a negative electrode active domain and a positive electrode lug welding domain, and a first blank domain is formed between the negative electrode active domain and the positive electrode lug welding domain; the second base layer comprises a positive electrode active domain and a negative electrode lug welding domain, and a second blank domain is formed between the positive electrode active domain and the negative electrode lug welding domain; wherein the area of the negative electrode active domain is larger than that of the positive electrode lug welding domain, or / and the area of the positive electrode active domain is larger than that of the negative electrode lug welding domain. Different conductive materials are plated on the front surface and the back surface of a layer of polymeric membrane through the characteristic that a base material has polymeric membrane insulation, so that the different conductive materials share one layer of polymeric membrane, the use amount of the polymeric membranes such as PET (Polyethylene Terephthalate), PP (Polypropylene) and PI (Polyimide) of the composite current collector is further reduced, more active substances are stored in the saved space, and the service life of the composite current collector is prolonged. And the energy density of the battery is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery manufacturing, and in particular to a composite current collector and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have rapidly occupied the global new energy market due to their advantages such as high energy density, good cycle stability, and environmental friendliness. Currently, they have been applied in various fields ranging from small 3C products to large-scale electric vehicles and ships.

[0003] The current collector of a lithium-ion battery is a very crucial component in the battery. It not only bears the active materials but also is responsible for collecting and transmitting the electrons generated by the electrochemical reaction to the external circuit, realizing the conversion of chemical energy into electrical energy. Currently, the commonly used current collector generally has a three-layer structure, including a metal layer, a polymer layer, and another metal layer. In order to further expand its advantages and reduce the usage cost of the battery, it is necessary to optimize the design in various aspects such as the materials and structure of the battery. As an important part of the lithium-ion battery, the currently used metal foil current collector accounts for about 15% of the battery weight, which not only occupies a large amount of cost but also restricts the further improvement of the battery energy density. Therefore, there is an urgent need for a composite current collector and a preparation method thereof that can improve the battery energy density. Summary of the Invention

[0004] In this part, as well as in the abstract and title of the present application, some simplifications or omissions may be made to avoid obscuring the purpose of this part, the abstract, and the title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] To solve the deficiencies of the prior art, an object of the present invention is to provide a composite current collector.

[0006] To achieve the above object, the present invention adopts the following technical solution: A composite current collector, including a base material tape, further including,

[0007] A first base layer, which is disposed on the upper end surface of the base material tape, and has electrically conductive negative active regions and positive electrode tab welding regions spaced apart along the end surface direction,

[0008] A first blank region is formed between the negative active region and the positive electrode tab welding region; and,

[0009] A second base layer, which is disposed on the lower end surface of the base material tape, and has electrically conductive positive active regions and negative electrode tab welding regions spaced apart along the end surface direction,

[0010] A second blank region is formed between the positive active region and the negative electrode tab welding region;

[0011] Wherein, the area of the negative active region is larger than the area of the positive electrode tab welding region, or / and,

[0012] The area of the positive electrode active region is larger than the area of the negative electrode tab welding region.

[0013] As a preferred embodiment of the composite current collector of the present invention, wherein:

[0014] The negative electrode active region and the negative electrode tab welding region are located on the same side of the base material tape, and the conductive materials are the same;

[0015] The positive electrode active region and the positive electrode tab welding region are located on the same side of the base material tape, and the conductive materials are the same.

[0016] As a preferred embodiment of the composite current collector of the present invention, wherein: the roughness of the positive electrode tab welding region and the negative electrode tab welding region is greater than the roughness of the negative electrode active region and the positive electrode active region.

[0017] As a preferred embodiment of the composite current collector of the present invention, wherein: any one or more of the following conditions are satisfied:

[0018] (1) The material of the base material tape is at least one of polyethylene terephthalate, polypropylene, polyamide, polyimide, polyvinyl chloride, polystyrene, metal particles, and carbon materials;

[0019] (2) The conductive materials of the first base layer and the second base layer are at least one of copper, aluminum, nickel, chromium, silver, carbon materials, copper alloys, or aluminum alloys;

[0020] (3) The thicknesses of the first base layer and the second base layer are both 700 - 2000 nm;

[0021] (4) The thickness of the base material tape is 3 - 12 μm;

[0022] (5) The widths of the first blank region and the second blank region along the end face direction are both 1 - 10 mm.

[0023] Beneficial effects of a composite current collector of the present invention: By virtue of the insulating property of the polymer film of the base material tape, different conductive materials are plated on the front and back sides of a polymer film, so as to achieve the sharing of a polymer film by different conductive materials, thereby reducing the usage amount of polymer films such as PET, PP, and PI in the composite current collector, and placing more active substances in the saved space, thereby improving the energy density of the battery.

[0024] In addition, by providing blank regions between the active regions of the electrode and the tab welding regions of the electrode to ensure that the two electrodes do not contact, as a buffer zone, it can better realize the infiltration of the electrolyte from the end face of the current collector and effectively provide a buffer for the expansion of the electrode.

[0025] To solve the deficiencies of the prior art, another object of the present invention is to provide a method for preparing a composite current collector.

[0026] To achieve the above object, the present invention adopts the following technical solution: A method for preparing a composite current collector for preparing the composite current collector, comprising the following operating steps:

[0027] Take a polymer material with an appropriate thickness, clean and activate its surface to obtain a base material tape;

[0028] Deposit a conductive material with an appropriate thickness on the upper and lower end faces of the base material tape in a partitioned manner to obtain a first base layer and a second base layer;

[0029] Cut off the regions on the end faces of the base material tape that are not coated with the conductive material except for the first blank region and the second blank region according to the process dimensions to obtain the composite current collector.

[0030] As a preferred embodiment of the method for preparing the composite current collector of the present invention, wherein: the depositing a conductive material with an appropriate thickness on the upper and lower end faces of the base material tape includes,

[0031] Divide the negative electrode active region on the upper end face of the base material tape and the negative electrode tab welding region on the lower end face to the same side of the base material tape, and deposit a conductive material of the same material;

[0032] Divide the positive electrode active region on the lower end face of the base material tape and the positive electrode tab welding region on the upper end face to the same side of the base material tape, and deposit a conductive material of the same material.

[0033] As a preferred embodiment of the method for preparing the composite current collector of the present invention, wherein: the method of depositing the conductive material with an appropriate thickness is at least one of evaporation coating, magnetron sputtering, electroless plating, electroplating, coating, and adhesive lamination.

[0034] As a preferred embodiment of the method for preparing the composite current collector of the present invention, wherein: the depositing the conductive material with an appropriate thickness includes,

[0035] Deposit a layer of copper on the negative electrode active region and the negative electrode tab welding region by magnetron sputtering; and,

[0036] Deposit a layer of aluminum on the positive electrode active region and the positive electrode tab welding region by evaporation coating.

[0037] As a preferred embodiment of the method for preparing the composite current collector of the present invention, wherein: the depositing the conductive material with an appropriate thickness further includes,

[0038] When depositing the conductive material on the target region of one end face of the base material tape,

[0039] First block the remaining regions on the same end face, and deposit the conductive material with the set thickness on the target region of this end face.

[0040] As a preferred embodiment of the preparation method of the composite current collector of the present invention, it further includes:

[0041] After plating a conductive material on the positive electrode tab welding area or / and the negative electrode tab welding area, roll pressing is carried out using an embossing roller to improve the roughness.

[0042] As a preferred embodiment of the preparation method of the composite current collector of the present invention, wherein:

[0043] The process conditions of the magnetron sputtering are as follows: using a copper target with a purity of not less than 99.99% as the target, the power density is 10 - 80 W / cm 2 , using argon as the gas source, the argon flow rate is 20 - 100 mL / min, the coating vacuum degree is less than 0.1 Pa, and the temperature of the main roller during the coating process is -20 - 20 °C;

[0044] The process conditions of the evaporation coating are as follows: melting and evaporating and coating high-purity aluminum wire with a purity of not less than 99.99% in a metal evaporation chamber at a high temperature of 700 - 1800 °C.

[0045] The beneficial effects of a preparation method of a composite current collector of the present invention: The beneficial effects are the same as those of a composite current collector, which will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0047] Figure 1 It is a three-dimensional structure schematic diagram of the composite current collector of the present invention.

[0048] Figure 2 It is a side view structure schematic diagram of the composite current collector of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] In order to make the objectives, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below with reference to the drawings in the specification.

[0050] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0051] Secondly, the "one embodiment" or "embodiment" referred to herein means a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or alternative embodiments that exclude each other with other embodiments.

[0052] Embodiment 1

[0053] Referring to Figure 1 and Figure 2 , this embodiment is the first embodiment of the invention, including a base material tape 100, a first base layer 200, and a second base layer 300. The base material tape 100 is made of an insulating material and is in the form of a thin film, which serves as a support. Its thickness is generally set between 3 μm and 12 μm; conductive materials are provided on the first base layer 200 and the second base layer 300, and their thickness is generally set between 700 nm and 2000 nm.

[0054] As Figure 1 shown, in this embodiment, the width direction of the base material tape 100 is defined as the X direction, the length direction of the base material tape 100 is defined as the Y direction, and the thickness direction of the base material tape 100 is defined as the Z direction. The base material tape 100 has an upper end face and a lower end face in the thickness direction. The first base layer 200 is provided on the upper end face of the base material tape 100, and the second base layer 300 is provided on the lower end face of the base material tape 100. The pole piece active regions and the tab welding regions are respectively provided on both end faces of the base material tape 100. The pole piece active regions include a negative electrode active region A1 provided on the first base layer 200 and a positive electrode active region B1 provided on the second base layer 300, which respectively correspond to the negative electrode plate and the positive electrode plate of the battery. The two are separated by the base material tape 100, which is convenient for processing and can improve stability; the tab welding regions include a positive tab welding region A3 provided on the first base layer 200 and a negative tab welding region B3 provided on the second base layer 300, which respectively correspond to the positive tab and the negative tab of the battery. The two are also separated by the base material tape 100, which is convenient for processing and can improve stability.

[0055] Further, the positive electrode active region B1 and the negative electrode tab welding region B3, and the negative electrode active region A1 and the positive electrode tab welding region A3 are separated by blank regions with a width of 1-10 mm on their respective end faces, avoiding direct contact between the active region of the electrode sheet and the tab welding region. The area of the active region of the electrode sheet is larger than that of the tab welding region, thereby increasing the usage amount of the active material and further enhancing the energy density of the battery. A first blank region A2 is formed between the negative electrode active region A1 and the positive electrode tab welding region A3 to avoid direct contact between the two, and a second blank region B2 is formed between the positive electrode active region B1 and the negative electrode tab welding region B3 to avoid direct contact between the two. By covering the negative electrode active region A1, the positive electrode tab welding region A3, the positive electrode active region B1, and the negative electrode tab welding region B3 with a conductive material, the positive electrode active region B1 and the negative electrode active region A1 are mainly used for storing and releasing electric energy. By coating the active material on the end face of the base material strip 100, an electrochemical reaction occurs during the charge and discharge process of the active material, realizing the insertion and extraction of lithium ions, thereby realizing the charge and discharge function of the battery; the negative electrode tab welding region B3 and the positive electrode tab welding region A3 are mainly responsible for leading out the current converged by the composite current collector. The composite current collector is welded to the tab through this region to ensure that the current can be smoothly transmitted to the external circuit of the battery, thereby realizing the normal use of the battery.

[0056] In this embodiment, the material of the base material strip 100 is at least one of polyethylene terephthalate, polypropylene, polyamide, polyimide, polyvinyl chloride, polystyrene, metal particles, and carbon materials; the conductive materials of the first base layer 200 and the second base layer 300 are at least one of copper, aluminum, nickel, chromium, silver, carbon materials, copper alloys, and aluminum alloys.

[0057] Furthermore, the negative electrode active region A1 and the negative electrode tab welding region B3 are located on the same side of the base material strip 100 and have the same conductive material. The positive electrode active region B1 and the positive electrode tab welding region A3 are located on the same side of the base material strip 100 and have the same conductive material. As Figure 2 shown, the three regions A1, A2, and A3 of the first base layer 200 are arranged from left to right in sequence, and the three regions B1, B2, and B3 of the second base layer 300 are arranged from right to left in sequence, that is, A1 and B3 have the same material, and A3 and B1 have the same material. The advantage of such a design is that when welding the conductive material, since the thickness of the conductive material is relatively thin, the phenomenon of the conductive material penetrating may occur, that is, when welding the conductive material of the first base layer 200, it may dissolve into the conductive material of the second base layer 300. At this time, if the existing technology is adopted and the conductive materials of the first base layer 200 and the second base layer 300 are the same and there is no blank area for separation, this will result in two types of metal materials in the metal material of the first base layer 200 or the second base layer 300 of the base material strip, and the situation of connection between the two metal materials will occur, which belongs to a non-conforming product; in this solution, the same conductive material on one side is arranged on the upper and lower two surfaces, that is, as Figure 2As shown, the materials in area A1 and area B3 are the same, and the width of A1 is wider than that of B3. At this time, the size of the material in B3 only needs to meet the size of the welding point. During welding, it can be directly welded without worrying about welding through. Even if it is welded through, it will directly contact the B3 area and will be isolated by the B2 area at the same time, so that there will be no problem of two conductive materials on the same side of the blank area contacting each other. This effectively improves the yield rate and at the same time improves the efficiency of the welding process.

[0058] Preferably, the roughness of the tab welding area is greater than that of the electrode active area. The length directions of the electrode active area and the tab welding area are set to the same value, and the width of the electrode active area is greater than the width of the tab welding area. For example, as Figure 2 shown, the conductive materials A1 and B3 on the left side of A2 and B2 are of the same material, but the width of B3 is smaller than that of A1, and the roughness of B3 is greater than the roughness of the surface of A1. The advantage of this design is that B3 is used to prevent the problem of two-pole conductive material contact caused by welding through the conductive material; at the same time, by increasing the roughness of the surface of the metal material in the B3 area, heat dissipation is increased, and at the same time, the electrical conductivity of the metal material here is reduced, the current is reduced, and the heat is reduced, ensuring that the main electrons can be exported from area A1 or B1. This not only meets the positive and negative poles required by the battery, but also improves the welding quality while ensuring heat dissipation. After the positive tab welding area and the negative tab welding area are formed at A3 and B3 respectively, a embossing roller can be used to roll them to increase the roughness.

[0059] In summary, the present invention mainly coats the conductive material on the front and back of a layer of polymer film through the insulating characteristics of the base material tape 100 polymer film, so as to achieve the sharing of a layer of polymer film by the conductive material to reduce the usage of polymer films such as PET, PP, and PI in the composite current collector, and put more electrodes (active substances) in the saved space to improve the energy density of the battery.

[0060] Furthermore, the present invention changes the positions of the positive and negative electrodes of the existing battery, that is, the materials belonging to one electrode are respectively installed on the upper and lower surfaces of the battery, so that it can be ensured that there will be no phenomenon of welding through during welding, resulting in the positive and negative electrodes being welded together, resulting in battery loss and inability to be used normally. And in the invention of our side, welding points are set on the corresponding surfaces of the welding positions, such as B3 and A3. When welding, there is no need to worry about battery loss caused by welding failure.

[0061] At the same time, two blank areas A2 and B2 are used to ensure that the two electrodes will not contact each other in the future. In addition, the two blank areas can also be used as buffer areas, which can not only better realize the infiltration of the electrolyte from the end face of the current collector, but also effectively provide a buffer for the expansion of the electrode. In addition, the materials of the same electrode are installed on two surfaces of the battery. The advantage of this design is that riveting is realized at the welding position, effectively enhancing the firmness and stability of the welding.

[0062] Example 2

[0063] Reference Figure 1 and Figure 2 In this example, a method for preparing the composite current collector of Example 1 is provided. The polymer material-based material tape 100 used can be purchased from the chemical raw material market, and the conductive materials used for the first base layer 200 and the second base layer 300 can be purchased from the metal raw material market. It includes the following operating steps:

[0064] First, a polymer material with a thickness of 3 - 12 μm is taken. After cleaning and activating its surface, the base material tape 100 is obtained. The polymer material is generally unrolled in the form of a tape, which can be prepared and stored in advance on a pay-off reel. The provided base material tape 100 travels along a preset direction, and the direction perpendicular to the length direction is the width direction of the base material tape 100.

[0065] Next, the upper and lower end faces in the thickness direction of the base material tape 100 are partitioned to form a pole piece active area and a tab welding area that are spaced apart along the end face direction. A blank area with a width of 1 - 10 mm is divided between the pole piece active area and the tab welding area. On the parts of both end faces of the base material tape 100 except for the blank area, a conductive material with a thickness of 700 - 2000 nm is plated to obtain the first base layer 200 and the second base layer 300. The method of plating a conductive material with a thickness of 700 - 2000 nm can be selected from at least one of evaporation plating, magnetron sputtering, electroless plating, electroplating, coating, and adhesive lamination.

[0066] In this example, the pole piece active area is divided into a negative electrode active domain A1 provided on the first base layer 200 of the base material tape 100, and a positive electrode active domain B1 provided on the second base layer 300 of the base material tape 100; the tab welding area is divided into a positive tab welding domain A3 provided on the first base layer 200 of the base material tape 100, and a negative tab welding domain B3 provided on the second base layer 300 of the base material tape 100; the blank area is divided into a first blank domain A2 formed between the negative electrode active domain A1 and the positive tab welding domain A3, and a second blank domain B2 formed between the positive electrode active domain B1 and the negative tab welding domain B3. Among them, the negative electrode active domain A1 and the negative tab welding domain B3 are located on the same side of the base material tape 100, and the positive electrode active domain B1 and the positive tab welding domain A3 are located on the same side of the base material tape 100.

[0067] Such as Figure 2As shown, in this embodiment, a layer of copper is plated on the negative electrode active area A1 and the negative electrode ear welding area B3 by magnetron sputtering, and the A2 and A3 areas are blocked by metal baffles on the first base layer 200 of the base material strip 100, and a negative electrode active area of ​​a set thickness is formed at A1 by magnetron sputtering, and the B1 and B2 areas are blocked by metal baffles on the second base layer 300 of the base material strip 100 in the same way, and a negative electrode ear welding area of ​​a set thickness is formed at B3, and the negative electrode active area A1 and the negative electrode ear welding area B3 are strip-shaped and extend along the length direction of the base material strip 100.

[0068] Furthermore, a layer of aluminum is plated on the positive electrode active area B1 and the positive electrode ear welding area A3 by evaporation, and the B2 and B3 areas are blocked by metal baffles on the second base layer 300 of the base material strip 100, and a positive electrode active area of ​​a set thickness is formed at B1 by multiple evaporation methods, and the A1 and A2 areas are blocked by metal baffles on the first base layer 200 of the base material strip 100 in the same way, and a positive electrode ear welding area of ​​a set thickness is formed at A3. The positive electrode active area B1 and the positive electrode ear welding area A3 are strip-shaped and extend along the length direction of the base material strip 100. After the extension, the unsputtered first blank area A2 and the unevaporated second blank area B2 remain.

[0069] Furthermore, the process parameters of magnetron sputtering in this embodiment are: using a copper target (purity: 99.99%) as the target material, a power density of 55 W / cm 2 , using argon as the gas source, the argon flow rate is 45mL / min, the coating vacuum is 0.08Pa, the temperature of the main roller during the coating process is 0°C, the thickness of the coating to the metal layer is 1000nm, and the conductive layer 200 thus obtained is composed of copper alone; the process parameters of the evaporation are: the high temperature of 1300°C is used to melt the high-purity aluminum wire (purity greater than 99.99%) in the metal evaporation chamber for evaporation coating.

[0070] Finally, the areas on both end surfaces of the base material strip 100 that are not plated with conductive material except the blank areas are cut off according to the process size, that is, the edge parts on both sides of the both end surfaces of the base material strip 100 along the width direction that are not plated with copper and aluminum are cut off according to the process size to obtain a composite current collector.

[0071] Experimental Example 1

[0072] In this comparative example, the method of Example 2 was used to prepare the composite current collector of Example 1, and the square resistance of the positive electrode ear end and the square resistance of the negative electrode ear end were measured by a four-probe resistivity tester. The process method of Example 2 was used to process the base material strips 100 of different thicknesses, and the effects of the base material strips 100 of different thicknesses on the composite current collector were shown in Table 1.

[0073]

[0074] Table 1 Influence of Base Material Tapes with Different Thicknesses on Composite Current Collectors

[0075] As can be seen from Table 1, the composite current collector prepared in this embodiment has more space to accommodate active materials, which can improve the energy density of the battery. Moreover, it is preferably to use the base material tape thickness and conductive material thickness in Experiment 2, and the improvement effect is the most significant compared with the existing composite current collectors.

[0076] Furthermore, through the following data comparison, when the aluminum layer is thickened on the tab side, its sheet resistance is continuously decreasing and the fracture rate of the aluminum layer is also decreasing. It should be noted that this experiment takes a 1560135 square aluminum shell battery as an example, where the thicknesses of the positive and negative current collectors are the same, and the materials, process parameters, and manufacturing conditions of the positive and negative active materials are all the same. As shown in Table 2 below, by comparing and testing the battery parameters composed of base materials with the same thickness, the comparison of the battery energy density of the composite current collector of the present invention with traditional aluminum foils, composite current collectors, and existing double-sided current collectors is obtained.

[0077]

[0078] Table 2 Comparison of Battery Energy Densities

[0079] It can be verified from Table 2 that compared with traditional aluminum foils, composite current collectors, and existing double-sided current collectors, both the volumetric energy density and mass energy density of the composite current collector of the present invention are more excellent.

[0080] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A composite current collector, comprising a base material strip (100), characterized in that: Also includes, The first base layer (200) is arranged on the upper end surface of the base material strip (100), and has conductive negative electrode active domains (A1) and positive electrode tab welding domains (A3) spaced apart along the end surface direction. A first blank area (A2) is formed between the negative electrode active area (A1) and the positive electrode tab welding area (A3); and, The second base layer (300) is arranged on the lower end surface of the base material strip (100), and has conductive positive electrode active domains (B1) and negative electrode ear welding domains (B3) spaced apart along the end surface direction. A second blank area (B2) is formed between the positive electrode active area (B1) and the negative electrode ear welding area (B3); Wherein, the area of ​​the negative electrode active domain (A1) is larger than the area of ​​the positive electrode ear welding domain (A3), or / and, The area of ​​the positive electrode active domain (B1) is larger than the area of ​​the negative electrode ear welding domain (B3).

2. The composite current collector according to claim 1, characterized in that: The negative electrode active domain (A1) and the negative electrode ear welding domain (B3) are located on the same side of the base material strip (100) and are made of the same conductive material; The positive electrode active domain (B1) and the positive electrode tab welding domain (A3) are located on the same side of the base material strip (100) and are made of the same conductive material.

3. The composite current collector according to claim 1, characterized in that: The roughness of the positive electrode tab welding domain (A3) and the negative electrode tab welding domain (B3) is greater than the roughness of the negative electrode active domain (A1) and the positive electrode active domain (B1).

4. The composite current collector according to any one of claims 1 to 3, characterized in that: Meet any one or more of the following conditions: (1) The material of the base material belt (100) is at least one of polyethylene terephthalate, polypropylene, polyamide, polyimide, polyvinyl chloride, polystyrene, metal particles, and carbon materials; (2) The conductive material of the first base layer (200) and the second base layer (300) is at least one of copper, aluminum, nickel, chromium, silver, carbon material, copper alloy or aluminum alloy; (3) The thickness of the first base layer (200) and the second base layer (300) are both 700 to 2000 nm; (4) The base material strip (100) has a thickness of 3 to 12 μm; (5) The width of the first blank area (A2) and the second blank area (B2) along the end surface direction are both 1 to 10 mm.

5. A method for preparing a composite current collector, for preparing the composite current collector, characterized in that: The steps include: Taking a polymer material of suitable thickness, cleaning and activating its surface to obtain a base material strip (100); Plating conductive material of appropriate thickness on the upper and lower end surfaces of the base material strip (100) to obtain a first base layer (200) and a second base layer (300); The region of the end surface of the base material strip (100) not plated with conductive material except the first blank region (A2) and the second blank region (B2) is cut off according to the process size to obtain a composite current collector.

6. The method for preparing the composite current collector according to claim 5, characterized in that: The step of plating a conductive material of suitable thickness on the upper and lower end surfaces of the base material strip (100) comprises: Dividing the negative electrode active domain (A1) on the upper end surface of the base material strip (100) and the negative electrode ear welding domain (B3) on the lower end surface to the same side of the base material strip (100), and plating the same conductive material; The positive electrode active domain (B1) at the lower end surface of the base material strip (100) and the positive electrode ear welding domain (A3) at the upper end surface are divided to the same side of the base material strip (100) and plated with conductive materials of the same material.

7. The method for preparing a composite current collector according to claim 5 or 6, characterized in that: The method of coating the conductive material with a suitable thickness is at least one of evaporation, magnetron sputtering, chemical plating, electroplating, coating, and adhesive bonding.

8. The method for preparing a composite current collector according to claim 6, wherein: The conductive material of suitable thickness is plated, including: A layer of copper is plated on the negative electrode active area (A1) and the negative electrode ear welding area (B3) by magnetron sputtering; and, A layer of aluminum is plated on the positive electrode active area (B1) and the positive electrode ear welding area (A3) by evaporation.

9. The method for preparing a composite current collector according to claim 8, characterized in that: The said coating of the conductive material with suitable thickness also includes: When a conductive material is plated on a target area of ​​one end surface of a base material strip (100), First, the remaining areas on the same end face are blocked, and then a conductive material with a set thickness is plated on the target area of ​​the end face.

10. The method for preparing a composite current collector according to any one of claims 5 to 6, 8 to 9, characterized in that: Also includes, After the positive electrode tab welding area (A3) and / or the negative electrode tab welding area (B3) are plated with a conductive material, an embossing roller is used to perform rolling to increase the roughness.

11. The method for preparing a composite current collector according to claim 8 or 9, characterized in that: The process conditions of the magnetron sputtering are: using a copper target with a purity of not less than 99.99% as the target material, and a power density of 10 to 80 W / cm 2 , using argon as the gas source, the argon flow rate is 20-100 mL / min, the coating vacuum is less than 0.1 Pa, and the temperature of the main roller during the coating process is -20-20°C; The evaporation process conditions are: melting high-purity aluminum wire with a purity of not less than 99.99% in a metal evaporation chamber at a high temperature of 700-1800° C. to evaporate and coat the film.

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