Current collector and preparation method therefor and application thereof

Abstract

Provided are a current collector and a preparation method therefor and an application thereof. The current collector comprises a support layer and a functional layer on at least one side surface of the support layer, wherein the functional layer comprises a protective layer, a metal layer and a priming layer, which are stacked in sequence, the priming layer being close to one side surface of the support layer; and a coarsening ring structure is provided on a surface of the current collector. Using the current collector as a substrate to prepare an electrode sheet can improve the bonding force between the current collector and an electrode material, thereby improving the stability of the electrode sheet and the cyclic charging and discharging performance of a battery.

Description

A current collector and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of battery current collectors, and relates to a current collector and a preparation method and application thereof. Background Art

[0002] At present, composite copper current collectors based on polypropylene films have received widespread attention and application in the new energy industry. The preparation process of this composite current collector is usually: a layer of metal (aluminum, copper, etc.) material is deposited on a polypropylene film by physical vapor deposition (PVD). The prepared surface metallized film with a certain conductivity is the composite current collector. Compared with traditional current collectors, composite current collectors based on polypropylene films have the characteristics of low cost, light weight, and good internal insulation. These characteristics enable the composite current collector to reduce the cost of the battery and improve the energy density and safety of the battery when used in the battery.

[0003] For example, CN 114883574A discloses a composite current collector, a preparation method thereof, an electrode plate, and a secondary battery. The composite current collector comprises: a porous polymer membrane and an aluminum-plated layer disposed on both side surfaces of the porous polymer membrane. The pore size D50 of the porous polymer membrane is less than 60 nm, and the porosity is less than 80%. During the production of lithium batteries, the composite current collector undergoes a rolling process, significantly reducing the likelihood of plate breakage, and the unit weight of the composite current collector is reduced, significantly improving the energy density of the battery.

[0004] For example, CN 116014147A discloses a polypropylene-based composite current collector comprising a stacked polypropylene layer, a modified layer, and a metal layer. The modified layer is formed by grafting a hydroxyl-terminated acrylate and a layered double hydroxide onto the polypropylene layer via ultraviolet light-induced polymerization. The combined effect of the layered double hydroxide and the hydroxyl-terminated acrylate increases the hydroxyl content on the surface of the modified layer, thereby increasing surface tension and surface roughness. These increases in surface tension and roughness jointly promote adhesion between the modified polypropylene layer and the metal layer. Furthermore, the hydroxyl groups in the layered double hydroxide form hydrogen bonds with those in the hydroxyl-terminated polyacrylate molecules, enhancing interfacial compatibility and reducing surface defects in the modified layer.

[0005] However, the current composite copper current collector based on polypropylene film has the problem of low surface roughness, which leads to weak bonding between the composite copper current collector and the negative electrode material in the negative electrode plate prepared with it as the substrate, thus causing the battery based on this negative electrode plate to have a rapid capacity decay and poor stability during the cycle charge and discharge process.

[0006] Based on the above research, it is necessary to provide a current collector with a roughened surface, which improves the bonding strength between the substrate and the negative electrode material, thereby improving the cycle charge and discharge performance of the battery based on this electrode sheet. Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] The purpose of this application is to provide a current collector and its preparation method and application, and in particular to a surface-roughened composite copper current collector, wherein the current collector has a surface roughening ring structure. The electrode plate is prepared using this current collector as a substrate, which can improve the adhesion between the current collector and the electrode material, thereby improving the stability of the electrode plate and the cycle charge and discharge performance of the battery.

[0009] To achieve this goal, this application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a current collector, comprising a support layer and a functional layer on at least one surface of the support layer, wherein the functional layer comprises a protective layer, a metal layer, and a primer layer stacked in sequence, wherein the primer layer is close to one surface of the support layer;

[0011] The surface of the current collector has a roughened ring structure.

[0012] The current collector described in the present application is a multi-layer structure, and has a roughened ring structure on the surface. The surface roughened ring structure increases the adhesion between the current collector and the electrode material, the setting of the base layer improves the adhesion between the support layer and the metal layer, and the protective layer prevents the metal layer from being chemically corroded or physically damaged. Therefore, the current collector of the present application improves the stability of the electrode plate and the cycle performance of the battery.

[0013] The current collector described in the present application may further optionally have functional layers on both sides of the support layer. When functional layers are provided on both sides, the current collector structure includes a protective layer, a metal layer, a base layer, a support layer, a base layer, a metal layer and a protective layer stacked in sequence.

[0014] In one embodiment, the surface of the support layer has a roughened ring structure.

[0015] The support layer of the present application also has a roughening ring structure. Even after the base layer, metal layer and protective layer are stacked on the surface of the support layer, the surface of the current collector can still have a roughening ring structure, which is the basis of the roughening ring on the surface of the current collector.

[0016] In one embodiment, the major axis length of the roughened ring structure is 80-300 μm, for example, 100 μm, 200 μm or 300 μm, and the minor axis length is 50-200 μm, for example, 50 μm, 100 μm, 150 μm or 200 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] The roughening circle of the present application is elliptical in shape, and the major axis length and minor axis length are as described above.

[0018] In one embodiment, the support layer comprises a polypropylene film with a thickness of 2-10 μm, for example, 2 μm, 4 μm, 6 μm, 8 μm or 10 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] The support layer described in this application is a commercial PP (polypropylene) film, which provides support for the current collector. Considering the application requirements of the current collector and the difficulty and cost of the preparation process, the thickness of the polypropylene film can be further selected to be between 2-10 μm.

[0020] In one embodiment, the polypropylene film has a polypropylene beta crystal content of 5-30%, for example, 5%, 10%, 15%, 20%, 25%, or 30%, but is not limited to the values ​​listed above, and other values ​​not listed within the numerical range are also applicable. In one embodiment, the metal layer includes a bottom thin layer and a top thick layer stacked in sequence, wherein the bottom thin layer is adjacent to a surface of the primer layer.

[0021] The thickness of the metal layer described in the present application should not be too thick, as too thick will affect the energy density of the battery, but too thin will affect the conductivity of the current collector.

[0022] In one embodiment, the thickness of the bottom thin layer is 50-200 nm, for example, 50 nm, 100 nm, 150 nm or 200 nm, and the thickness of the top thick layer is 700-1300 nm, for example, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm or 1300 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] In one embodiment, the bottom thin layer is prepared by physical vapor deposition, and the top thick layer is prepared by electroplating, wherein the physical vapor deposition includes any one of resistance heating vacuum evaporation, electron beam heating vacuum evaporation, laser heating vacuum evaporation or magnetron sputtering, or a combination of at least two of them.

[0024] The metal layer described in this application is prepared by different methods to form a thin bottom layer and a thick top layer in order to match a specific preparation method. Specifically, a thin layer of copper is first prepared on the surface of the base film by magnetron sputtering before the subsequent electroplating process is used to thicken the copper layer. That is, the composite film entering the electroplating process needs to have a certain conductivity, otherwise the electroplating thickening of the copper layer cannot be achieved.

[0025] In one embodiment, the metal layer is made of copper or a copper alloy.

[0026] In one embodiment, the material of the bottom thin layer includes amorphous copper or a copper alloy.

[0027] The bottom thin layer of the present application can be further optionally obtained by magnetron sputtering, which can obtain an amorphous metal. Thanks to the presence of the amorphous state, the surface roughening structure of the base film will be transferred to the surface of the magnetron sputtering layer.

[0028] In one embodiment, the thickness of the base layer is 5-20 nm, for example, 5 nm, 10 nm, 15 nm or 20 nm, and the material of the base layer includes any one of nickel, chromium, nickel-chromium, nickel-chromium-copper, aluminum oxide, silicon oxide or titanium oxide, or a combination of at least two thereof.

[0029] The present application aims to improve the problem that the bonding force between the copper current collector and the negative electrode material is weak, which causes the battery based on this negative electrode plate to have a rapid capacity decay and poor stability during the cycle charge and discharge process.

[0030] In one embodiment, the material of the protective layer includes any one or a combination of at least two of nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper-chromium oxide, graphite, carbon black, acetylene black, Ketjen black, carbon nano-quantum dots, carbon nanotubes, carbon nanofibers or graphene.

[0031] In one embodiment, the thickness of the protective layer is 10-100 nm, for example, it can be 10 nm, 30 nm, 50 nm, 70 nm, 90 nm or 100 nm, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, and can be further optionally 20-80 nm, and the thickness of the protective layer does not exceed one tenth of the thickness of the metal layer.

[0032] In one embodiment, the protective layer is prepared by any one of physical vapor deposition, chemical vapor deposition, in-situ forming or coating, or a combination of at least two thereof.

[0033] When protective layers are provided on both sides of the current collector of the present application, the materials of the two protective layers may be consistent or inconsistent, and the thicknesses may be consistent or inconsistent.

[0034] In one embodiment, the surface roughness Ra of the current collector is greater than 50 nm, for example, it can be 51 nm, 60 nm, 70 nm, 80 nm, 100 nm, 110 nm or 120 nm, the tensile strength is ≥140 MPa, for example, it can be 140 MPa, 150 MPa, 160 MPa, 170 MPa, 180 MPa, 190 MPa or 200 MPa, and the adhesion to the electrode material is ≥1 N / cm, for example, it can be 1 N / cm, 1.3 N / cm, 1.5 N / cm, 1.7 N / cm, 1.9 N / cm, 2.2 N / cm, 2.5 N / cm or 3 N / cm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] In a second aspect, the present application provides a method for preparing the current collector as described in the first aspect, the preparation method comprising the following steps:

[0036] The support layer is heat-treated, and then a primer layer, a metal layer and a protective layer are sequentially prepared on at least one side surface of the support layer to obtain the current collector.

[0037] In this application, the support layer is first heat-treated to form a roughened ring structure on its surface, which serves as a basis for preparing a current collector with a roughened surface. Then, a base layer, a metal layer and a protective layer are deposited to obtain a current collector with a roughened ring structure.

[0038] In one embodiment, the heat treatment includes a first-stage heat treatment and a second-stage heat treatment performed sequentially, wherein the treatment temperature of the first-stage heat treatment is 100-130°C, for example, it can be 100°C, 110°C, 120°C or 130°C, and the treatment time is 5-30min, for example, it can be 5min, 10min, 20min or 30min, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, and can further be selected as 5-15min.

[0039] In one embodiment, the treatment temperature of the second stage heat treatment is 140-150°C, for example, it can be 140°C, 142°C, 144°C, 146°C, 148°C or 150°C, and the treatment time is 5-30min, for example, it can be 5min, 10min, 20mi or 30min, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, and can further be selected as 5-15min.

[0040] In one embodiment, after the first stage of heat treatment, the polypropylene β-crystal content in the support layer is 5-30%, for example, 5%, 10%, 15%, 20%, 25% or 30%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] The purpose of the first-stage heat treatment of the support layer in this application is to increase the content of β crystals in the polypropylene film, while the purpose of the second-stage heat treatment is to promote the transformation of β crystals to α crystals in the polypropylene film. During the transformation process, a roughening ring structure is formed on the surface of the polypropylene film, which serves as a basis for preparing a surface-roughened current collector.

[0042] In one embodiment, the coating layer is prepared by magnetron sputtering, wherein the target power for preparing the coating layer by magnetron sputtering is 2-10kW, for example, 2kW, 5kW or 10kW, the argon flow rate is 10-200mL / min, for example, 10mL / min, 50mL / min, 100mL / min, 150mL / min or 200mL / min, the vacuum degree is less than or equal to 0.5Pa, for example, 0.5Pa, 0.4Pa, 0.3Pa, 0.2Pa or 0.1Pa, the processing time is 1-10s, for example, 1s, 3s, 5s, 7s, 9s or 10s, the cooling temperature of the coating roller is less than or equal to 0°C, for example, 0°C, -2.5°C, -5°C or -10°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] The target material for preparing the base layer by magnetron sputtering in this application is any one of nickel, chromium, nickel-chromium, nickel-chromium-copper, silicon-aluminum, aluminum oxide, silicon oxide or titanium oxide, or a combination of at least two thereof, with a purity greater than or equal to 99.9%, for example, it can be 99.9%, 99.95% or 99.99%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] In one embodiment, the bottom thin layer in the metal layer is prepared by magnetron sputtering, wherein the target power for preparing the bottom thin layer by magnetron sputtering is 5-20kW, for example, it can be 5kW, 10kW, 15kW or 20kW, the argon flow rate is 10-200mL / min, for example, it can be 10mL / min, 50mL / min, 100mL / min, 150mL / min or 200mL / min, the vacuum degree is less than or equal to 0.5Pa, for example, it can be 0.5Pa, 0.4Pa, 0.3Pa, 0.2Pa or 0.1Pa, the processing time is 1-15s, for example, it can be 1s, 5s, 10s or 15s, and the cooling temperature of the coating roller is less than or equal to 0°C, for example, it can be 0°C, -2.5°C, -5°C or -10°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] The target material for preparing the bottom thin layer by magnetron sputtering in this application is copper or copper alloy with a purity greater than or equal to 99.9%, for example, it can be 99.9%, 99.95% or 99.99%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] During magnetron sputtering in this application, the cooling temperature of the coating roller should not be too high. Too high a temperature will cause the deposited metal grains to be too large, resulting in the inability of the roughened ring structure on the PP film surface to be transferred to the current collector surface.

[0047] In one embodiment, the top thick layer in the metal layer is prepared by electroplating, wherein the electrolyte components for preparing the top thick layer by electroplating include 70-150 g / L of copper sulfate, for example, 70 g / L, 90 g / L, 110 g / L, 130 g / L or 150 g / L, 80-200 g / L of sulfuric acid, for example, 80 g / L, 100 g / L, 150 g / L or 200 g / L, 20-100 mg / L of chloride ions, for example, 20 mg / L, 50 mg / L or 100 mg / L, 2 -20ppm of brightener, for example, can be 2ppm, 5ppm, 10ppm, 15ppm or 20ppm, 0.05-0.5ppm of leveling agent, for example, can be 0.05ppm, 0.1ppm, 0.2ppm, 0.3ppm, 0.4ppm or 0.5ppm, 10-200ppm of wetting agent, for example, can be 10ppm, 50ppm, 100ppm, 150ppm or 200ppm, but are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] When electroplating is performed in this application, the amount of leveling agent should not be too high. Excessive amount of leveling agent will cause the roughened ring structure on the surface of the PP film to be filled with metal particles, thereby causing the roughened ring structure on the surface of the PP film to be unable to be transferred to the surface of the composite copper current collector.

[0049] In one embodiment, the brightener includes sodium polydisulfide dipropane sulfonate and / or sodium 3-mercapto-1-propane sulfonate, the leveler includes any one or a combination of at least two of polyethyleneimine, benzotriazole, 3,3'-dicarbazole quaternary ammonium salt or N-butylmethylpiperidinium bromide, and the wetting agent includes any one or a combination of at least two of polyethylene glycol, polypropylene glycol or polyoxyethylene ether.

[0050] In one embodiment, the average cathode current density of the electroplating process is 1-3 A / dm 2 , for example, it can be 1A / dm 2 , 2A / dm 2 or 3A / dm 2The plating solution temperature is 15-35°C, for example, it can be 15°C, 25°C or 35°C, and the time is 3-10min, for example, it can be 3min, 5min, 7min or 10min, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0051] In one embodiment, the preparation method of the protective layer includes any one of physical vapor deposition, chemical vapor deposition, in-situ forming or coating, or a combination of at least two thereof, wherein the vapor deposition method can be further selected as vacuum evaporation or magnetron sputtering; the chemical vapor deposition method can be further selected as atmospheric pressure chemical vapor deposition or plasma enhanced chemical vapor deposition; the in-situ forming method can be further selected as a method of in-situ forming a metal oxide passivation layer on the surface of the metal layer; the coating method can be further selected as die coating, blade coating or extrusion coating.

[0052] As an optional technical solution of the preparation method described in this application, the preparation method comprises the following steps:

[0053] (1) subjecting the support layer to a first-stage heat treatment and a second-stage heat treatment, wherein the treatment temperature of the first-stage heat treatment is 100-130°C, the treatment time is 5-30 min, and the treatment temperature of the second-stage heat treatment is 140-150°C, the treatment time is 5-30 min, and then a base layer is prepared on at least one side surface of the support layer by magnetron sputtering, wherein the target power of the magnetron sputtering method for preparing the base layer is 2-10 kW, the argon flow rate is 10-200 mL / min, the vacuum degree is less than or equal to 0.5 Pa, the treatment time is 1-10 s, and the cooling temperature of the coating roller is less than or equal to 0°C;

[0054] (2) preparing a bottom thin layer of the metal layer on the surface of the base layer by magnetron sputtering, wherein the target power for preparing the bottom thin layer by magnetron sputtering is 5-20 kW, the argon flow rate is 10-200 mL / min, the vacuum degree is less than or equal to 0.5 Pa, the processing time is 1-15 s, and the cooling temperature of the coating roller is less than or equal to 0° C.;

[0055] (3) preparing a top thick layer of the metal layer on the surface of the bottom thin layer by electroplating, wherein the electrolyte composition of the top thick layer prepared by electroplating includes 70-150 g / L of copper sulfate, 80-200 g / L of sulfuric acid, 20-100 mg / L of chloride ions, 2-20 ppm of brightener, 0.05-0.5 ppm of leveler and 10-200 ppm of wetting agent, and the average cathode current density of the electroplating method is 1-3 A / dm 2 , the plating temperature is 15-35℃, and the time is 3-10min;

[0056] (4) A protective layer is prepared on the surface of the top thick layer by using any one of physical vapor deposition, chemical vapor deposition, in-situ forming or coating, or a combination of at least two methods to obtain the current collector.

[0057] In a third aspect, the present application provides an electrode plate, which includes the current collector as described in the first aspect.

[0058] In a fourth aspect, the present application provides a battery, comprising the electrode plate as described in the third aspect.

[0059] Compared with the prior art, this application has the following beneficial effects:

[0060] The current collector described in the present application increases the adhesion between the current collector and the electrode material through the roughened ring structure on the surface, improves the stability of the electrode plate and the cycle performance of the battery; the preparation method of the current collector described in the present application is simple and easy, low cost, high processing efficiency and easy to scale up. By heat treating the supporting layer, a roughened ring structure is formed on the surface of the supporting layer, and then the film with the roughened ring structure is used as the base film, and the coating process is adjusted to prepare a current collector with a roughened surface.

[0061] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0063] FIG1 is a 100-fold magnified surface morphology image of the PP film before heat treatment described in Example 1 of the present application;

[0064] FIG2 is a 100-fold magnified surface morphology image of the PP film after heat treatment described in Example 1 of the present application;

[0065] FIG3 is a surface morphology image of the current collector described in Example 1 of the present application magnified 100 times;

[0066] FIG4 is a surface morphology image of the current collector described in Comparative Example 1 of the present application magnified 100 times. DETAILED DESCRIPTION

[0067] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0068] Example 1

[0069] This embodiment provides a current collector, comprising a protective layer, a metal layer, a primer layer, a support layer, a primer layer, a metal layer, and a protective layer stacked in sequence, wherein the surface of the current collector has a roughened ring structure, the surface of the support layer has a roughened ring structure, the primer layer has a thickness of 10 nm, the metal layer comprises a bottom thin layer and a top thick layer stacked in sequence, wherein a surface of the bottom thin layer close to the primer layer has a thickness of 100 nm, the thickness of the top thick layer has a thickness of 930 nm, and the thickness of the protective layer is 10 nm;

[0070] The preparation method of the current collector comprises the following steps:

[0071] (1) A PP film (thickness: 4.5 μm, manufacturer: Jiadeli, model: 6014HS) was subjected to a first-stage heat treatment and a second-stage heat treatment, wherein the treatment temperature of the first-stage heat treatment was 100° C. and the treatment time was 5 min, and the treatment temperature of the second-stage heat treatment was 140° C. and the treatment time was 5 min, to obtain a PP film with a β-crystal content of 10%. The treated PP film was then placed in a magnetron sputtering machine, and a nickel-chromium target (purity: 99.95%) was first used as a target material to prepare a base layer, wherein the target power was 3 kW, the argon flow rate was 50 mL / min, the vacuum degree was 0.1 Pa, the treatment time was 2 s, and the cooling temperature of the coating roller was 0° C. to prepare a base layer;

[0072] The surface morphology of the PP film before heat treatment at a magnification of 100 times is shown in FIG1 , and the surface morphology of the PP film after heat treatment at a magnification of 100 times is shown in FIG2 ;

[0073] (2) A bottom thin layer of the metal layer was prepared on the surface of the base layer by magnetron sputtering, wherein a copper target (purity: 99.95%) was used as the target material, the target power was 10 kW, the argon flow rate was 80 mL / min, the vacuum degree was 0.1 Pa, the processing time was 13 s, and the cooling temperature of the coating roller was 0°C to prepare the bottom thin layer of the metal layer;

[0074] (3) A top thick layer of the metal layer is prepared on the surface of the bottom thin layer by electroplating, wherein the electrolyte composition for preparing the top thick layer by electroplating includes 80 g / L copper sulfate, 120 g / L sulfuric acid, 50 mg / L chloride ion, 5 ppm sodium polydisulfide dipropane sulfonate, 0.5 ppm N-butylmethylpiperidinium bromide, and 50 ppm polyethylene glycol 8000, and the average cathode current density of the electroplating is 2 A / dm 2 , the plating temperature is 25℃, and the time is 5min;

[0075] (4) After the electroplating treatment is completed, the plated film is washed in a clean water tank, and then a surface protective layer is prepared in a protective layer preparation tank containing a 5g / L potassium dichromate aqueous solution. The treatment temperature is 25°C and the treatment is performed for 25s. Finally, the film is washed in a clean water tank and dried in an oven at a temperature of 65°C to obtain a current collector with a total thickness of 6.6μm. The surface morphology of the current collector is shown in Figure 3.

[0076] Example 2

[0077] This embodiment provides a current collector, which is the same as that of embodiment 1 except that in the preparation method of the current collector, the temperature of the heat treatment in step (1) is 120° C. to adapt the current collector.

[0078] Example 3

[0079] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the temperature of the heat treatment in step (1) is 130° C. to adapt the current collector.

[0080] Example 4

[0081] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the heat treatment time in step (1) is 10 minutes to adapt the current collector.

[0082] Example 5

[0083] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the heat treatment time in step (1) is 15 minutes to adapt the current collector.

[0084] Example 6

[0085] This embodiment provides a current collector, which is the same as that of embodiment 1 except that in its preparation method, the temperature of the second stage heat treatment in step (1) is 150° C. to adapt the current collector.

[0086] Example 7

[0087] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the time of the second stage heat treatment in step (1) is 10 minutes to make the current collector adaptable.

[0088] Example 8

[0089] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the time of the second stage heat treatment in step (1) is 15 minutes to make the current collector adaptable.

[0090] Example 9

[0091] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the cooling temperature of the coating roller in steps (1) and (2) is -5°C to make the current collector adaptable.

[0092] Example 10

[0093] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the cooling temperature of the coating roller in steps (1) and (2) is -10°C to make the current collector adaptable.

[0094] Example 11

[0095] This embodiment provides a current collector, which is the same as that in Example 1 except that in the preparation method, the concentration of N-butylmethylpiperidinium bromide in step (3) is 0.2 ppm to adapt the current collector.

[0096] Example 12

[0097] This embodiment provides a current collector, which is the same as that of Example 1 except that in the preparation method, the N-butylmethylpiperidinium bromide in step (3) is 0.05 ppm to adapt the current collector.

[0098] Example 13

[0099] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the temperature of the heat treatment in step (1) is 90° C. to adapt the current collector.

[0100] Example 14

[0101] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the temperature of the heat treatment in step (1) is 140° C. to adapt the current collector.

[0102] Example 15

[0103] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the heat treatment time in step (1) is 3 minutes to adapt the current collector.

[0104] Example 16

[0105] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the heat treatment time in step (1) is 20 minutes to adapt the current collector.

[0106] Example 17

[0107] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the temperature of the second stage heat treatment in step (1) is 130° C. to adapt the current collector.

[0108] Example 18

[0109] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the temperature of the second stage heat treatment in step (1) is 155° C. to adapt the current collector.

[0110] Example 19

[0111] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the time of the second stage heat treatment in step (1) is 3 minutes to make the current collector adaptable.

[0112] Example 20

[0113] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the time of the second stage heat treatment in step (1) is 20 minutes to make the current collector adaptable.

[0114] Example 21

[0115] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the cooling temperature of the coating roller in steps (1) and (2) is 5°C to make the current collector adaptable.

[0116] Example 22

[0117] This embodiment provides a current collector, which is the same as that in Example 1 except that in the preparation method, the concentration of N-butylmethylpiperidinium bromide in step (3) is 0.6 ppm to adapt the current collector.

[0118] Example 23

[0119] This embodiment provides a current collector, which is the same as that of Example 1 except that in its preparation method, the concentration of N-butylmethylpiperidinium bromide in step (3) is 0.03 ppm to adapt the current collector.

[0120] Example 24

[0121] This embodiment provides a current collector. The current collector is the same as Example 1 except that in its preparation method, the method for preparing the top thick layer in step (3) is the same as the method for preparing the bottom thin layer in step (2), both of which are magnetron sputtering methods, so that the current collector can be adaptively changed.

[0122] Comparative Example 1

[0123] This comparative example provides a current collector, which is the same as Example 1 except that in the preparation method, the PP film in step (1) is not heat-treated to change the adaptability of the current collector;

[0124] FIG4 is a 100-fold magnified surface morphology of the current collector in this comparative example.

[0125] Comparative Example 2

[0126] This comparative example provides a current collector, which is the same as Example 1 except that in its preparation method, the PP film in step (1) is not heat-treated, the cooling temperature of the coating roller in steps (1) and (2) is 10°C, and the concentration of N-butylmethylpiperidinium bromide in step (3) is 1ppm, so that the current collector adapts to changes.

[0127] Comparative Example 3

[0128] This comparative example provides a current collector, which is the same as Example 1 except that in its preparation method, the PP film is not heat-treated in step (1), but the first and second heat treatments are performed after the protective layer is prepared in step (4) to adapt the current collector.

[0129] Performance testing:

[0130] The above examples and comparative examples were used to determine the β-crystal content in the heat-treated PP film, the surface roughness and tensile strength of the current collector, the adhesion between the electrode material and the current collector in the negative electrode sheet based on the current collector, and the cycle performance test of the battery based on the current collector. The specific test methods are as follows:

[0131] The β-crystal content of polypropylene in the heat-treated PP film was tested according to DB35 / T 1914-2020 Determination of β-crystal content in β-crystal polypropylene pipes and fittings (X-ray diffraction method).

[0132] The roughness and tensile strength test methods of the current collector are as follows:

[0133] ① Roughness: Take three pieces of 10 mm × 10 mm current collectors, place them in a roughness tester (MarSurf M400), and test their surface roughness (Ra). The result is the average of the three measurement results.

[0134] ②Tensile strength: Samples were taken longitudinally along the prepared current collector film roll, and then the tensile strength of the film was tested according to the national standard GB / T1040.3-2006.

[0135] The performance test method of the battery based on this current collector is as follows:

[0136] Battery assembly: The positive electrode current collector uses a traditional 12μm aluminum foil, and the positive electrode active material is NCM622 (LiNi 0.6 Mn 0.2 Co 0.2 O2), the conductive agent is carbon nanotubes, the binder is PVDF (polyvinylidene fluoride), and the solvent is NMP (N-methylpyrrolidone). The positive electrode active material, the conductive agent, the binder and the solvent are prepared into a positive electrode slurry in a mass ratio of 67.2:9.4:1.1:22.3. The positive electrode slurry is coated on both sides of the positive electrode current collector and dried to form a positive electrode sheet;

[0137] The negative electrode current collector is the current collector prepared in the above embodiments and comparative examples, the negative electrode active material is artificial graphite, the conductive agent is carbon nanotubes, the binder is CMC (sodium carboxymethyl cellulose), and the solvent is pure water. The above negative electrode active material, conductive agent, binder and solvent are prepared into a negative electrode slurry according to a mass ratio of 48:5:19.4:27.6. The negative electrode slurry is coated on both sides of the negative electrode current collector and dried to form a negative electrode sheet. The above positive electrode sheet and negative electrode sheet are prepared into a lithium ion battery through processes such as rolling, slicing, assembly, injection, and packaging. The separator uses a polyethylene diaphragm coated with alumina ceramic (thickness 25 μm), and the electrolyte uses 1 mol·L -1 The carbonate solution of LiPF6 is a mixed solution of propylene carbonate, ethylene carbonate and ethyl methyl carbonate, and the mass ratio of the three is 1:1:1.

[0138] Adhesion test: a layer of Permacel P-94 double-sided tape was adhered to a 1 mm thick aluminum foil, the negative electrode based on the above current collector was adhered on the double-sided tape, and a layer of ethylene acrylic acid copolymer film (DuPont Nurcel0903, thickness of 50 μm) was covered on the negative electrode. 5 N / cm 2 The film was hot-pressed at 120°C for 10 seconds, cooled to room temperature, and cut into 150mm x 15mm strips. The ethylene acrylic acid copolymer film strip was secured to the upper fixture of the tensile testing machine, while the remaining film strip was secured to the lower fixture. The two strips were then peeled at an angle of 180° and a speed of 100mm / min to measure the peel force, which represents the adhesion between the current collector and the negative electrode material in the negative electrode sheet.

[0139] Cyclic performance test:

[0140] The assembled lithium-ion battery was cycled 2000 times at a charge / discharge rate of 1C. The battery capacity retention rate after the cycle was recorded. The voltage range of the cycle charge / discharge was 3.0V-4.2V. The capacity retention rate after 2000 cycles (%) = the specific capacity of the battery after 2000 cycles / the initial specific capacity of the battery × 100%.

[0141] The test results are shown in Table 1:

[0142] Table 1

[0143] From Table 1 we can see that:

[0144] ① The current collector obtained in this application has a surface roughness Ra > 50 nm, a tensile strength ≥ 140 MPa, and an adhesion to the electrode material ≥ 1 N / cm. After forming a battery, the battery capacity retention rate after 2000 cycles at a 1C charge / discharge rate is > 60%. Examples 1, 2, 3, 13, and 14 show that increasing the pre-coating heat treatment temperature first increases the roughness, tensile strength, adhesion to the negative electrode material, and capacity retention of the battery after 2000 charge / discharge cycles of the composite copper current collector. This is because increasing the pre-coating heat treatment temperature first increases and then decreases the crystallization rate of β crystals in polypropylene, i.e., the crystallinity first increases and then decreases. This change in crystallinity causes the tensile strength and roughness of the polypropylene film to first increase and then decrease, which in turn causes the tensile strength and roughness of the composite copper current collector to first increase and then decrease. The roughness of the composite copper current collector first increases and then decreases, which causes the bonding force between the composite copper current collector and the negative electrode material to first increase and then decrease, that is, the structural stability of the composite copper current collector electrode sheet first increases and then decreases, thereby causing the charge and discharge cycle performance of the battery based on the composite copper current collector electrode sheet to first increase and then decrease.

[0145] ② From Examples 1, 4, 5, 15, and 16, it can be seen that increasing the pre-coating heat treatment time causes the roughness of the prepared composite copper current collector to first increase and then remain constant, while the tensile strength of the composite copper current collector first increases and then decreases, the adhesion between the composite copper current collector and the negative electrode material first increases and then remains constant, and the battery capacity retention of the battery based on the composite copper current collector after 2000 charge-discharge cycles first increases and then decreases. This is because increasing the pre-coating heat treatment time causes the crystallinity of the β crystals in the polypropylene to first increase and then reach a limit before remaining constant. Therefore, the change in roughness caused by the transformation of the β crystals to α crystals in the polypropylene shows a trend of first increasing and then remaining constant, which in turn causes the adhesion between the composite copper current collector and the negative electrode material to first increase and then remain constant. While the polypropylene polymer in the polypropylene film crystallizes, it also undergoes deorientation. Initially, because the polymer crystallization outweighs deorientation, the tensile strength of the polypropylene film increases. However, when the duration of the first pre-coating heat treatment reaches a certain level, crystallization reaches its limit, and the polymer deorientation continues, resulting in a decrease in the tensile strength of the polypropylene film. Specifically, as the duration of the first pre-coating heat treatment increases, the tensile strength of the polypropylene film first increases and then decreases, causing the tensile strength of the composite copper current collector prepared with it to first increase and then decrease. The bonding force between the composite copper current collector and the negative electrode material first increases and then remains unchanged, while its tensile strength first increases and then decreases. Together, these factors lead to the battery capacity retention of the composite copper current collector first increasing and then decreasing after 2000 charge and discharge cycles.

[0146] ③ From Examples 1, 6, 17, and 18, it can be seen that increasing the temperature of the second heat treatment before coating causes the roughness of the prepared composite copper current collector, the tensile strength of the composite copper current collector, the adhesion between the composite copper current collector and the negative electrode material, and the battery capacity retention rate of the battery based on the composite copper current collector after 2000 charge and discharge cycles to increase first and then decrease. This is because increasing the temperature of the second heat treatment before coating increases the rate of β-to-α crystal transformation in polypropylene. When the temperature exceeds 150°C, the polymer in the polypropylene transforms from a crystalline form to a de-orientation, which causes the roughness of the composite copper current collector to increase first and then decrease. At the same time, the tensile strength of the polypropylene film also increases first and then decreases, causing the tensile strength of the composite copper current collector based on this polypropylene film to increase first and then decrease. Due to the increase and then decrease in the roughness and tensile strength of the composite copper current collector, the battery capacity retention of the battery based on the composite copper current collector after 2000 charge and discharge cycles first increases and then decreases.

[0147] ④ From Examples 1, 7, 8, 19, and 20, it can be seen that increasing the treatment time of the second stage of heat treatment before coating causes the roughness of the prepared composite copper current collector to first increase and then remain unchanged, while the tensile strength of the composite copper current collector first increases and then decreases, the adhesion between the composite copper current collector and the negative electrode material first increases and then remains unchanged, and the battery capacity retention of the battery based on the composite copper current collector after 2000 charge and discharge cycles first increases and then decreases. This is because increasing the time of the second stage of heat treatment before coating increases the degree of transformation from β crystals to α crystals in polypropylene, which remains unchanged after reaching a limit. This causes the surface roughness of the polypropylene film to first increase and then remain unchanged, which in turn causes the roughness of the composite copper current collector prepared using this polypropylene film as the base film to first increase and then remain unchanged, which in turn causes the adhesion between the composite copper current collector and the negative electrode material to first increase and then remain unchanged. While the polypropylene polymer in the polypropylene film undergoes a β-crystal to α-crystal transformation, it also undergoes polymer deorientation. Initially, because the degree of polymer crystal transformation is greater than the degree of deorientation, the tensile strength of the polypropylene film increases. However, when the duration of the second pre-coating heat treatment reaches a certain level, the crystal transformation reaches its limit, and polymer deorientation continues, resulting in a decrease in the tensile strength of the polypropylene film. Specifically, as the duration of the second pre-coating heat treatment increases, the tensile strength of the polypropylene film first increases and then decreases, causing the tensile strength of the composite copper current collector prepared with this material to first increase and then decrease. The bonding force between the composite copper current collector and the negative electrode material first increases and then remains unchanged, while its tensile strength first increases and then decreases. Together, these factors lead to the battery capacity retention of the composite copper current collector first increasing and then decreasing after 2000 charge and discharge cycles.

[0148] ⑤ From Examples 1, 9, 10, and 21, it can be seen that lowering the temperature of magnetron sputtering leads to an increase in the roughness of the prepared composite copper current collector, the tensile strength of the composite copper current collector, the bonding force between the composite copper current collector and the negative electrode material, and the battery capacity retention rate of the battery based on the composite copper current collector after 2000 charge and discharge cycles. The reason is that lowering the temperature of magnetron sputtering reduces the grain size of the base layer and the bottom layer of the metal layer prepared on the surface of the polypropylene film during the magnetron sputtering process, which results in a smaller grain size of the top layer of the metal layer prepared by the subsequent electroplating method. This transfers the roughened structure of the polypropylene film surface to the surface of the composite copper current collector, resulting in an increase in the roughness of the prepared composite copper current collector, thereby increasing the bonding force between the composite copper current collector and the negative electrode material. Due to the refinement of the metal layer grains, the tensile strength of the composite copper current collector increases. The increase in bonding force and tensile strength together increases the battery capacity retention rate of the battery based on the composite copper current collector after 2000 charge and discharge cycles.

[0149] ⑥ From Examples 1, 11, 12, 22 and 23, it can be seen that: by reducing the concentration of the leveling agent in the electroplating solution, the roughness of the prepared composite copper current collector increases, the tensile strength of the composite copper current collector first increases and then decreases, the bonding force between the composite copper current collector and the negative electrode material first increases and then decreases, and the battery capacity retention of the battery based on the composite copper current collector after 2000 charge and discharge cycles first increases and then decreases. The reason is: by reducing the concentration of the leveling agent in the electroplating solution, the roughened structure of the base film transferred to the surface of the composite current collector semi-finished product is better maintained during the electroplating process, thereby increasing the roughness of the prepared composite copper current collector, causing the bonding force between the composite copper current collector and the negative electrode material to increase first. When the leveling agent content is too low (0.03ppm), the leveling effect is extremely poor, causing uneven grains in the metal layer, resulting in excessively high and uneven surface roughness, which in turn leads to a decrease in the bonding force between the composite copper current collector and the negative electrode material, that is, the bonding force between the composite copper current collector and the negative electrode material is reduced. The adhesion first increases and then decreases; while reducing the concentration of the leveler in the electroplating solution, the ratio between the brightener and the leveler increases, resulting in smaller grains of the prepared metal layer, causing the tensile strength of the composite copper current collector to first increase. When the concentration of the leveler is too low, the ratio of the two is unbalanced, resulting in extremely uneven grain size of the metal layer, causing the tensile strength of the composite copper current collector to first increase and then decrease. The trend of the adhesion and tensile strength first increasing and then decreasing jointly leads to the battery capacity retention of the battery based on the composite copper current collector after 2000 charge and discharge cycles first increasing and then decreasing.

[0150] ⑦ It can be seen from Examples 1 and 24 that the bottom thin layer of the metal layer of the present application is prepared by magnetron sputtering, and the top thick layer is prepared by electroplating, and the electroplating method cannot be used alone. Magnetron sputtering is required to first construct the metal layer so that the PP film has a certain conductivity before electroplating can be achieved; if magnetron sputtering is used alone to deposit the metal layer, such as in Example 24, due to the high thickness of the deposition, the energy during deposition is high, and the morphology and grain size of the metal layer are difficult to control, resulting in a decrease in the surface roughness, tensile strength, adhesion of the current collector and the battery capacity retention rate after 2000 cycles.

[0151] ⑧It can be seen from Examples 1-12 and Comparative Examples 1-3 that: under the conditions of no heat treatment before PP film coating, no heat treatment before PP film coating + magnetron sputtering main roller cooling temperature of 10°C + electroplating solution leveling agent concentration of 1ppm, and no heat treatment before PP film coating + final heat treatment, the roughness of the prepared composite copper current collector, the tensile strength of the composite copper current collector, the adhesion between the composite copper current collector and the negative electrode material, and the battery capacity retention rate of the battery based on the composite copper current collector after 2000 charge and discharge cycles are all reduced; and even if heat treatment is performed after the current collector is finally prepared, surface roughening cannot be achieved, because heat treatment after the composite current collector is prepared can only affect the morphology of the PP film surface, and since the metal layer on the surface of the current collector has been formed, heat treatment will not change the morphology of the metal layer on the surface of the current collector, resulting in the inability to achieve surface roughening.

[0152] In order to prove that the structure of the PP film surface changes before and after the heat treatment before coating, and to verify the existence of the surface roughening ring structure of the prepared composite copper current collector, this application uses a metallographic microscope to characterize the surface morphology of the samples prepared in Example 1 and Comparative Example 1. The characterization results are shown in Figures 1 to 4, which prove that the current collector obtained in this application has a surface roughening ring structure.

[0153] In summary, the present application provides a current collector and its preparation method and application. The current collector has a surface roughening ring structure. Using this current collector as a substrate to prepare electrode plates can improve the adhesion between the current collector and the electrode material, thereby improving the stability of the electrode plates and the cycle charge and discharge performance of the battery.

[0154] The above description is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art should understand that any changes or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application fall within the protection scope and disclosure scope of the present application.

Claims

1. A current collector, comprising a support layer and a functional layer on at least one side of the support layer, wherein the functional layer comprises a protective layer, a metal layer and a primer layer stacked in sequence, wherein: The surface of the base layer is close to the supporting layer; The surface of the current collector has a roughened ring structure.

2. The current collector according to claim 1, wherein: The surface of the support layer has a roughened ring structure; Optionally, the length of the major axis of the roughened ring structure is 80-300 μm, and the length of the minor axis is 50-200 μm; Optionally, the support layer comprises a polypropylene film having a thickness of 2-10 μm; Optionally, in the polypropylene film, the polypropylene β-crystal content is 5-30%.

3. The current collector according to claim 1 or 2, wherein: The metal layer comprises a bottom thin layer and a top thick layer stacked in sequence, wherein the bottom thin layer is close to a side surface of the base layer, the bottom thin layer has a thickness of 50-200 nm, and the top thick layer has a thickness of 700-1300 nm; Optionally, the bottom thin layer is prepared by physical vapor deposition, and the top thick layer is prepared by electroplating; Optionally, the material of the metal layer includes copper or copper alloy; Optionally, the material of the bottom thin layer includes amorphous copper or copper alloy.

4. The current collector according to claim 1 or 2, wherein: The thickness of the bottom layer is 5-20 nm, and the material of the bottom layer includes any one of nickel, chromium, nickel-chromium, nickel-chromium-copper, aluminum oxide, silicon oxide or titanium oxide, or a combination of at least two thereof; Optionally, the material of the protective layer includes any one of nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, nickel oxide, chromium oxide, cobalt oxide, copper-chromium oxide, graphite, carbon black, acetylene black, Ketjen black, carbon nano-quantum dots, carbon nanotubes, carbon nanofibers or graphene, or a combination of at least two thereof; Optionally, the thickness of the protective layer is 10-100 nm and does not exceed one tenth of the thickness of the metal layer.

5. The current collector according to claim 1 or 2, wherein: The surface roughness of the current collector is greater than 50 nm, the tensile strength is greater than or equal to 140 MPa, and the bonding force with the electrode material is greater than or equal to 1 N / cm.

6. A method for preparing the current collector according to any one of claims 1 to 5, comprising the following steps: The support layer is heat-treated, and then a primer layer, a metal layer and a protective layer are sequentially prepared on at least one side of the support layer to obtain the current collector.

7. The preparation method according to claim 6, wherein: The heat treatment comprises a first stage heat treatment and a second stage heat treatment performed sequentially, wherein the treatment temperature of the first stage heat treatment is 100-130°C and the treatment time is 5-30min, and the treatment temperature of the second stage heat treatment is 140-150°C and the treatment time is 5-30min; Optionally, after the first stage heat treatment, the content of polypropylene β crystals in the support layer is 5-30%.

8. The preparation method according to claim 6 or 7, wherein: The coating layer is prepared by magnetron sputtering, wherein the target power of the coating layer prepared by magnetron sputtering is 2-10kW, the argon gas flow rate is 10-200mL / min, the vacuum degree is less than or equal to 0.5Pa, the processing time is 1-10s, and the cooling temperature of the coating roller is less than or equal to 0°C.

9. The preparation method according to claim 6 or 7, wherein: The bottom thin layer in the metal layer is prepared by magnetron sputtering, wherein the target power of the magnetron sputtering method for preparing the bottom thin layer is 5-20kW, the argon gas flow rate is 10-200mL / min, the vacuum degree is less than or equal to 0.5Pa, the processing time is 1-15s, and the cooling temperature of the coating roller is less than or equal to 0°C; Optionally, the top thick layer in the metal layer is prepared by electroplating, wherein the electrolyte components for preparing the top thick layer by electroplating include 70-150 g / L copper sulfate, 80-200 g / L sulfuric acid, 20-100 mg / L chloride ions, 2-20 ppm brightener, 0.05-0.5 ppm leveler and 10-200 ppm wetting agent; Optionally, the average cathode current density of the electroplating method is 1-3A / dm 2 , the plating temperature is 15-35℃, and the time is 3-10min; Optionally, the preparation method of the protective layer includes any one of physical vapor deposition, chemical vapor deposition, in-situ forming or coating, or a combination of at least two of them.

10. The preparation method according to claim 6 or 7, wherein: The preparation method comprises the following steps: (1) subjecting the support layer to a first-stage heat treatment and a second-stage heat treatment, wherein the treatment temperature of the first-stage heat treatment is 100-130° C., the treatment time is 5-30 min, and the treatment temperature of the second-stage heat treatment is 140-150° C., the treatment time is 5-30 min, and then a coating layer is prepared on at least one side of the support layer by a magnetron sputtering method, wherein the target power of the magnetron sputtering method for preparing the coating layer is 2-10 kW, the argon gas flow rate is 10-200 mL / min, the vacuum degree is less than or equal to 0.5 Pa, the treatment time is 1-10 s, and the cooling temperature of the coating roller is less than or equal to 0° C.; (2) preparing a bottom thin layer of the metal layer on the surface of the base layer by magnetron sputtering, wherein the target power of the magnetron sputtering method for preparing the bottom thin layer is 5-20 kW, the argon gas flow rate is 10-200 mL / min, the vacuum degree is less than or equal to 0.5 Pa, the processing time is 1-15 s, and the cooling temperature of the coating roller is less than or equal to 0° C.; (3) preparing a top thick layer of the metal layer on the surface of the bottom thin layer by electroplating, wherein the electrolyte composition of the top thick layer prepared by electroplating includes 70-150 g / L of copper sulfate, 80-200 g / L of sulfuric acid, 20-100 mg / L of chloride ions, 2-20 ppm of brightener, 0.05-0.5 ppm of leveler and 10-200 ppm of wetting agent, and the average cathode current density of the electroplating method is 1-3 A / dm 2 , the plating temperature is 15-35℃, and the time is 3-10min; (4) A protective layer is prepared on the surface of the top thick layer by using any one of physical vapor deposition, chemical vapor deposition, in-situ forming or coating, or a combination of at least two of them, to obtain the current collector.

11. An electrode sheet comprising the current collector according to any one of claims 1 to 5.

12. A battery comprising the electrode sheet according to claim 11.

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