Composite current collector and its preparation method, electrode sheet, secondary battery

Abstract

This application relates to the field of secondary battery technology, specifically to composite current collectors and their preparation methods, electrode sheets, and secondary batteries. The preparation method of the composite current collector of this application includes the following steps: taking a polymer base film, performing a first treatment with a first conductive material to prepare a first conductive seed layer on at least one side surface of the polymer base film; using the side surface of the first conductive seed layer away from the polymer base film as the opening surface, performing an opening treatment on the first conductive seed layer and the polymer base film to give the first conductive seed layer and the polymer base film a micropore array structure; performing a second treatment with a second conductive material to seal the micropore openings in the micropore array structure to prepare a second conductive seed layer; and preparing a metal layer on the surface of the second conductive seed layer opposite to the polymer base film; wherein the first treatment is a chemical plating method or a vapor deposition method, the second treatment is a magnetron sputtering process in vapor deposition, and the metal layer is a copper layer or an aluminum layer.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, specifically to composite current collectors and their preparation methods, electrode sheets, and secondary batteries. Background Technology

[0002] Composite current collectors typically consist of a polymer support layer and conductive metal layers disposed on two opposing surfaces of the support layer. Compared to traditional pure copper foil current collectors or pure aluminum foil current collectors, the introduction of the polymer support layer in the aforementioned composite current collectors reduces the areal density of the current collector, resulting in advantages such as high energy density and significant cost reduction potential.

[0003] To further pursue lightweight composite current collectors, traditional methods involve perforation. However, this method, perforating the polymer support layer before preparing the conductive metal layer, creates micropores on the surface of the polymer support layer that affect the bonding force between the subsequent conductive metal layer and the polymer support layer. If perforation is performed after preparing the conductive metal layer on the polymer support layer, the resulting micropores will cause the electrode active slurry to flow into the micropores during subsequent coating, blocking the micropores and resulting in uneven coating of the electrode active slurry. This leads to surface defects on the coated electrode sheet, and assembling a battery with electrode sheets exhibiting surface defects will result in reduced battery performance. Summary of the Invention

[0004] Based on this, this application provides a composite current collector and its preparation method, an electrode sheet, and a secondary battery. The preparation method of the composite current collector provided in this application can seal the micropores in the microporous array structure, and the micropores have a cavity structure, thereby improving the adhesion between the metal layer and the conductive seed layer while maintaining the lightweight of the composite current collector. After sealing the micropores, it can not only avoid surface defects caused by the electrode active slurry flowing into the micropores during coating, but also reduce the internal resistance, improve the current carrying capacity of the current collector, and thus improve the battery performance.

[0005] A first aspect of this application provides a method for preparing a composite current collector, comprising the following steps:

[0006] Take a polymer base film, perform a first treatment using a first conductive material, and prepare a first conductive seed layer on at least one side surface of the polymer base film;

[0007] Using the side of the first conductive seed layer away from the polymer base film as the opening surface, the first conductive seed layer and the polymer base film are subjected to opening treatment, so that the first conductive seed layer and the polymer base film have a micropore array structure;

[0008] A second conductive material is used for a second treatment to seal the micropore openings in the micropore array structure, thereby preparing a second conductive seed layer;

[0009] A metal layer is prepared on the surface of the second conductive seed layer that is opposite to the polymer base film.

[0010] Wherein, the first treatment is chemical plating or vapor deposition, the second treatment is magnetron sputtering in vapor deposition, the second treatment is a second magnetron sputtering treatment, and the sputtering power of the second magnetron sputtering treatment is 2kW~15kW; the metal layer is a copper layer or an aluminum layer.

[0011] In some embodiments, the first process uses a magnetron sputtering process, the first process being a first magnetron sputtering process, and the sputtering power of the first magnetron sputtering process is 2kW~15kW.

[0012] In some embodiments, the difference between the sputtering power of the second magnetron sputtering process and the sputtering power of the first magnetron sputtering process is 1kW to 3kW.

[0013] In some embodiments, the second conductive material is the same as the first conductive material.

[0014] In some embodiments, the polymer-based film comprises, by weight, 92 to 95 parts of polymer and 5 to 8 parts of composite rubber.

[0015] The polymer includes one or more of polyethylene terephthalate, polypropylene, and polyimide;

[0016] The particle size of the composite rubber is 0.5µm to 2µm.

[0017] In some embodiments, the composite rubber includes a core material and a shell disposed on the surface of the core material;

[0018] The core material comprises liquid rubber and a vulcanizing agent; the shell comprises melamine resin.

[0019] In some embodiments, the second conductive material and the first conductive material each independently comprise one or more alloys of copper, aluminum, nickel, gold, chromium, and titanium.

[0020] In some embodiments, after the opening process, the average pore size of the micropores in the micropore array structure is 10μm~20μm.

[0021] In some embodiments, after the opening process, the spacing between any two adjacent micropores in the micropore array structure is 0.04mm to 3mm.

[0022] In some embodiments, the step of preparing a metal layer on the surface of the second conductive seed layer includes:

[0023] The metal layer is prepared by electrochemical deposition using an aqueous electroplating method, with the second conductive seed layer as the cathode, and a current of 1A to 10A applied.

[0024] A second aspect of this application provides a composite current collector, comprising a polymer base film and a first conductive seed layer, a second conductive seed layer, and a metal layer sequentially disposed on the surface of the polymer base film along the thickness direction of the composite current collector; the first conductive seed layer comprises a first conductive material, and the second conductive seed layer comprises a second conductive material.

[0025] Wherein, along the thickness direction of the composite current collector, the first conductive seed layer and the polymer base film have a microporous array structure; and the micropore openings in the microporous array structure are blocked by the second conductive material;

[0026] The metal layer is a copper layer or an aluminum layer.

[0027] In some embodiments, the micropore walls in the micropore array structure have the second conductive material.

[0028] In some embodiments, the micropore array structure has cavities.

[0029] In some embodiments, the second conductive material and the first conductive material each independently comprise one or more alloys of copper, aluminum, nickel, gold, chromium, and titanium.

[0030] In some embodiments, the polymer-based film comprises, by weight, 92 to 95 parts of polymer and 5 to 8 parts of composite rubber.

[0031] The polymer includes one or more of polyethylene terephthalate, polypropylene, and polyimide.

[0032] The composite rubber has a particle size of 0.5µm to 2µm; the composite rubber includes a core material and a shell disposed on the surface of the core material, the core material includes liquid rubber and a vulcanizing agent; the shell includes melamine resin.

[0033] A third aspect of this application provides an electrode sheet comprising a composite current collector prepared by any of the preparation methods described in any of the first aspects of this application, or comprising a composite current collector described in any of the second aspects of this application.

[0034] A fourth aspect of this application provides a secondary battery including the electrode sheet described in the third aspect of this application.

[0035] The method for preparing the composite current collector provided in this application has at least the following beneficial effects:

[0036] In the preparation method of the composite current collector provided in this application, a first conductive material is used for a first treatment to prepare a first conductive seed layer on the surface of a polymer base film. Then, an opening treatment is performed. During laser drilling, the first conductive seed layer and the polymer base film are completely penetrated. At this time, the micropores appearing on the surface of the first conductive seed layer form a micropore array structure, and there are protrusions formed by laser drilling around the micropores. The presence of this protrusion structure can increase the bonding force with the subsequent metal layer to be plated. In the next step, a second conductive material is used for a second treatment. At this time, a second magnetron sputtering treatment with a specific sputtering power can form a second conductive seed layer on the surface of the first conductive seed layer. The second conductive material can seal the opening of the micropores and sputter onto the pore walls of the micropores. At this time, the inside of the micropores remains in a cavity state. This can achieve the lightweight of the composite current collector, and the sealing of the micropores can further improve the adhesion between the metal layer and the first and second conductive seed layers. Finally, a metal layer is electroplated on the surface of the second conductive seed layer to obtain the composite current collector of this application. Furthermore, due to the sealing effect of the second conductive seed layer on the micropore openings, the composite current collector prepared in this application can not only effectively prevent the electrode active slurry from flowing into the micropores during coating, but also ensure that the coated electrode sheet will not have surface defects and will not cause a reduction in battery performance. The presence of the second conductive material sealing the micropore openings and the second conductive material sputtered onto the pore walls of the micropores can also reduce the internal resistance of the composite current collector, improve the conductivity of the composite current collector, and enhance battery performance.

[0037] Therefore, the composite current collector preparation method provided in this application can improve the adhesion between the metal layer and the conductive seed layer while maintaining the lightweight of the composite current collector. It not only avoids coating defects caused by electrode active slurry flowing into micropores, but also reduces the internal resistance of the battery, improves the conductivity of the composite current collector, and enhances battery performance. Furthermore, the above preparation method is simple, efficient, and easy to implement for industrial production. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A process flow diagram of the composite current collector provided in this application;

[0040] Figure 2 A schematic diagram of the composite current collector provided in this application;

[0041] Figure 3The images are: SEM images of three micropores in Example 1 after the opening process in step (3) of Embodiment 1 of this application; SEM images of three micropores in Example 1 after the preparation of a conductive seed layer by the second magnetron sputtering process in step (4) to seal the micropore openings; and SEM images of three micropores in Example 1 after the preparation of a copper layer on the surface of the intermediate in step (5).

[0042] Explanation of reference numerals in the attached figures

[0043] 100, Polymer base film; 201, First conductive seed layer; 202, Second conductive seed layer; 110, Micropore array structure; 120, Protrusion; 300, Metal layer. Detailed Implementation

[0044] The composite current collector, its preparation method, electrode sheet, and secondary battery of this application are further described in detail below with reference to specific embodiments. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0045] See Figure 1 The first aspect of this application provides a method for preparing a composite current collector, comprising the following steps:

[0046] S11: Take a polymer base film 100, perform a first treatment using a first conductive material, and prepare a first conductive seed layer 201 on at least one side surface of the polymer base film 100.

[0047] S12: Using the side surface of the first conductive seed layer 201 away from the polymer base film 100 as the opening surface, the first conductive seed layer 201 and the polymer base film 100 are subjected to opening treatment, so that the first conductive seed layer 201 and the polymer base film 100 have a micropore array structure 110.

[0048] S13: A second conductive material is used for a second treatment to seal the micropore openings in the micropore array structure 110, thereby preparing a second conductive seed layer 202.

[0049] S14: Prepare a metal layer 300 on the surface of the second conductive seed layer 202 that is away from the polymer base film 100.

[0050] The first treatment is chemical plating or vapor deposition. The second treatment is magnetron sputtering within vapor deposition. The second treatment is a second magnetron sputtering process with a sputtering power of 2kW to 15kW. The metal layer is either copper or aluminum.

[0051] Understandably, the metal layer is a copper layer, and the composite current collector is a composite negative electrode current collector. Alternatively, the metal layer is an aluminum layer, and the composite current collector is a composite positive electrode current collector.

[0052] In the method for preparing the composite current collector provided in this application, a first conductive material is used and a first treatment is performed to create a continuous first conductive seed layer 201 on the surface of an insulating polymer base film 100. The first conductive seed layer 201 helps to protect the polymer base film 100 during the subsequent hole-opening process and reduces the thermal damage it suffers during drilling. Subsequently, the hole-opening process is performed, and the first conductive seed layer 201 and the polymer base film 100 are completely penetrated during laser drilling. At this time, the micropores appearing on the surface of the first conductive seed layer 201 can form a micropore array structure 110, and there are protrusions 120 formed by laser drilling around the micropores. The presence of the protrusions 120 can increase the bonding force with the subsequent electroplated metal layer 300. With the synergy of the second conductive material and the second magnetron sputtering power, a second conductive seed layer 202 is formed on the surface of the first conductive seed layer 201. The second conductive material seals the micropore openings, maintaining a cavity state inside the micropores. This achieves lightweight composite current collectors while further enhancing the adhesion between the metal layer 300 and the first and second conductive seed layers 201 and 202 through micropore sealing. Furthermore, due to the sealing effect of the second conductive seed layer 202 on the micropore openings and the presence of the metal layer 300, the composite current collector prepared in this application effectively prevents the electrode active slurry from flowing into the micropores during coating. The coated electrode sheet will not have surface defects, thus preventing a reduction in battery performance. It also reduces the internal resistance of the composite current collector, improves its conductivity, and enhances battery performance.

[0053] Therefore, the composite current collector preparation method provided in this application can improve the adhesion between the metal layer 300 and the first conductive seed layer 201 and the second conductive seed layer 202 while maintaining the lightweight of the composite current collector. It not only avoids coating defects caused by electrode active slurry flowing into micropores, but also reduces the internal resistance of the battery, improves the conductivity of the composite current collector, and enhances battery performance. Furthermore, the above preparation method is simple, efficient, and easy to implement for industrial production.

[0054] In some of these examples, the first process uses a magnetron sputtering process.

[0055] As a further example, in step S11, the first process is a first magnetron sputtering process. In step S13, the second process is a second magnetron sputtering process.

[0056] In some examples, in step S11, the sputtering power of the first magnetron sputtering process is 2kW to 15kW. The sputtering power of the first magnetron sputtering process includes, but is not limited to, 2kW, 3kW, 4kW, 5kW, 6kW, 7kW, 8kW, 10kW, 11kW, 12kW, 13kW, 14kW or 15kW, or any two of the above point values ​​as endpoint values ​​within the range.

[0057] In some of these examples, the first conductive material and the second conductive material each independently comprise one or more alloys of copper, aluminum, nickel, gold, chromium, and titanium.

[0058] A first conductive seed layer 201 is prepared on the surface of the polymer base film 100 using a first magnetron sputtering process. This seed layer can construct a conductive layer on the insulating polymer base film 100, thereby providing a conductive surface for the subsequent preparation of the metal layer 300. Understandably, the target material for the first magnetron sputtering process can be selected based on the material of the first conductive seed layer 201. Understandably, the ion source power for different target materials is selected from the above-mentioned range, but the sputtering power varies slightly for different target materials.

[0059] In some examples, the first conductive seed layer 201 is copper. The sputtering power of the copper target is 2kW to 15kW. For example, the sputtering power of the copper target includes, but is not limited to, 2kW, 3kW, 4kW, 5kW, 6kW, 7kW, 8kW, 10kW, 11kW, 12kW, 13kW, 14kW, or 15kW, or any two of the above values ​​as endpoints.

[0060] In other examples, the first conductive seed layer 201 is a nickel-chromium layer. The sputtering power of the nickel-chromium target is 2kW to 4kW. For example, the sputtering power of the nickel-chromium target includes, but is not limited to, 2kW, 3kW, or 4kW, or any two of the above values ​​as endpoints.

[0061] In some examples, a first conductive seed layer 201 is prepared by a roll-to-roll production line using a first magnetron sputtering process. At this time, the winding tension of the polymer base film 100 is 50N~70N, the unwinding tension is 55N~75N, and the linear speed is 8m / min~15m / min.

[0062] The first conductive seed layer 201 is prepared by magnetron sputtering using a roll-to-roll production line, enabling continuous and large-scale preparation of the first conductive seed layer 201. This method combines high deposition efficiency with stable film uniformity and effectively adapts to the processing requirements of flexible substrates such as the polymer-based film 100, reducing product manufacturing costs. For example, the winding tension of the polymer-based film 100 includes, but is not limited to, 50N, 55N, 60N, 65N, or 70N, or any two of these values ​​as endpoints. The unwinding tension includes, but is not limited to, 55N, 58N, 60N, 65N, 70N, or 75N, or any two of these values ​​as endpoints. The linear speed includes, but is not limited to, 8m / min, 9m / min, 12m / min, 14m / min, or 15m / min, or any two of these values ​​as endpoints.

[0063] In some examples, in step S12, the hole-opening process is laser drilling. Specifically, during laser drilling, the flow of molten metal and polymer base film material on the surface of the first conductive seed layer (first conductive material) caused by laser heating creates protrusions around the micropores. These protrusions help to improve the bonding force between the first conductive seed layer and the metal layer to be deposited.

[0064] In some examples, after the opening process in step S12, the average pore size of the micropores in the micropore array structure 110 is 10 μm to 20 μm. For example, the average pore size of the micropores in the micropore array structure 110 includes, but is not limited to, 10 μm, 12 μm, 15 μm, 17 μm or 20 μm, or any two of the above point values ​​as endpoint values ​​within the range.

[0065] In some examples, after the aperture opening process, the spacing between any two adjacent micropores in the micropore array structure 110 is 0.04 mm to 3 mm. For example, the spacing between two adjacent micropores includes, but is not limited to, 0.04 mm, 0.1 mm, 0.3 mm, 0.5 mm, 0.9 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, or 3 mm, or any two of the above values ​​as endpoints. Specifically, during the aperture opening process, the larger the micropore diameter formed on the aperture surface of the first conductive seed layer 201, the smaller the spacing between adjacent micropores, the greater the areal density of the micropore array, the smaller the internal resistance of the composite current collector, and the stronger the current conduction capability of the composite current collector. Furthermore, the more cavities inside the micropores, the more significant the lightweight effect of the prepared composite current collector.

[0066] In step S12, the first conductive seed layer 201 is used as the opening surface for the hole-opening process. At this time, along the thickness direction, the first conductive seed layer 201 and part of the polymer base film 100 have a micropore array structure 110. This application found that the laser-opened area around the micropores causes a protrusion 120 in the surrounding area, which can improve the adhesion between the metal layer 300 and the second conductive seed layer 202; and is beneficial to improving the adhesion between the subsequent electrode active material and the composite current collector. In addition, when the first conductive seed layer 201 is used as the opening surface for the hole-opening process, the first conductive seed layer 201 prepared by the first process acts as an "energy absorption layer" and a "thermal buffer layer" during the laser hole-opening process. It can reduce the thermal impact and physical damage range of the laser on the polymer base film 100 (especially the area around the micropores), thereby protecting the overall mechanical integrity of the polymer base film 100 and avoiding the diffusion of laser energy, which can increase the control accuracy of hole drilling.

[0067] In some examples, in step S13, the sputtering power of the second magnetron sputtering process is 2kW to 15kW. The sputtering power includes, but is not limited to, 2kW, 3kW, 4kW, 5kW, 6kW, 7kW, 8kW, 10kW, 11kW, 12kW, 13kW, 14kW or 15kW, or any two of the above point values ​​as endpoint values ​​within the range.

[0068] This application finds that when the sputtering power of the second magnetron sputtering process is within the above-mentioned range, the second conductive seed layer 202 sputtered on the surface of the first conductive seed layer 201 can achieve the sealing of the micropore opening and maintain the cavity of the micropore.

[0069] Preferably, the difference between the sputtering power of the second magnetron sputtering process and the sputtering power of the first magnetron sputtering process is 1kW to 3kW. Understandably, a positive difference between the sputtering power of the second magnetron sputtering process and the sputtering power of the first magnetron sputtering process indicates that the sputtering power of the second magnetron sputtering process is 1kW to 3kW higher than that of the first magnetron sputtering process. For example, the difference between the ion source power of the second magnetron sputtering process and the sputtering power of the first magnetron sputtering process includes, but is not limited to, 1kW, 1.5kW, 1.8kW, 2kW, 2.5kW, or 3kW, or any two of the above values ​​as endpoints within a range.

[0070] In some examples, the first conductive material is the same as the second conductive material. Therefore, after the second magnetron sputtering process in step S13, a second conductive seed layer 202 of the same material is prepared.

[0071] Understandably, the parameters and target material of the second magnetron sputtering process in this application are basically the same as those of the first magnetron sputtering process. The main difference lies in the sputtering power difference between the second and first magnetron sputtering processes, which is 1kW to 3kW. This application has found that in the second magnetron sputtering process with higher sputtering power, metal ions exhibit good circumferential deposition properties, enabling the metal target material to penetrate the micropores and better cover the pore walls. Furthermore, the inner edge of the 120° protrusion around the micropores is also covered with a thin metal film. In addition, at the pore opening, the first conductive seed layer 201 prepared in the first magnetron sputtering process is exposed after the opening treatment. At this time, some of the metal ions deposited in the second magnetron sputtering process with relatively higher sputtering power tend to grow laterally along the exposed edge of the first conductive seed layer 201, thereby forming a second conductive seed layer 202 that seals the pore opening. Moreover, the second conductive seed layer 202 of the second sputtering process can cover the pore walls and pore opening, helping to seal microcracks or defects caused by the laser. Therefore, the difference between the sputtering power of the second magnetron sputtering treatment and the sputtering power of the first magnetron sputtering treatment is 1kW~3kW. This not only seals the opening of the micropore, but also makes it easier to sputter the second conductive material onto the pore wall of the micropore, further improving conductivity.

[0072] In some examples, in step S12, the time of the second magnetron sputtering process is related to the linear speed of the microporous membrane unwinding. For example, the linear speed of the microporous membrane unwinding is 2 m / min to 7 m / min; wherein the microporous membrane is a polymer-based film with a first conductive seed layer on its surface and has undergone an opening process. For example, the linear speed of the microporous membrane unwinding includes, but is not limited to, 2 m / min, 3 m / min, 4 m / min, 5 m / min, 6 m / min, or 7 m / min.

[0073] Because the laser drilling process in step S12 causes thermal damage to the polymer base film 100, resulting in thermal shrinkage and defects, these defects will affect the yield of the composite current collector after it is fabricated, leading to issues such as wrinkles and poor mechanical properties. Simultaneously, defects on the hole walls will affect the bonding between the metal layer 300 and the polymer base film 100. Therefore, this application also provides an improved scheme for the composition of the polymer base film 100.

[0074] In some examples, the polymer base film 100 comprises, by weight parts, 92 to 95 parts of a polymer and 5 to 8 parts of a composite rubber. For example, the mass parts of the polymer include, but are not limited to, 92, 93, 94, or 95 parts. The mass parts of the composite rubber include, but are not limited to, 5, 6, 7, or 8 parts.

[0075] In some of these examples, the thickness of the polymer base film 100 is 3µm to 10µm.

[0076] The polymer includes one or more of polyethylene terephthalate, polypropylene, and polyimide.

[0077] The particle size of the composite rubber is 0.5µm~2µm.

[0078] In some of these examples, the composite rubber comprises a core and a shell disposed on the surface of the core.

[0079] The core material comprises liquid rubber and a vulcanizing agent; the shell comprises melamine resin. Melamine resin has a high heat resistance temperature, exceeding 280℃.

[0080] The polymer-based film 100 provided in this application incorporates a specific mass fraction of composite rubber, which helps to increase the tensile strength of the composite current collector. The composite rubber comprises a core material of liquid rubber and a vulcanizing agent, and a shell with high heat resistance. After the micropore-opening process, the opening process generates localized high temperatures when the pore walls are punctured. At this point, the shell of the composite rubber surrounding the micropores melts and ruptures, releasing liquid rubber that fills the thermal cracks created by the opening. Simultaneously, the residual heat activates the vulcanizing agent, allowing the rubber to cure in a short time (e.g., within 10 seconds), thereby repairing the thermal damage caused by the micropore-opening process on the composite current collector.

[0081] Furthermore, in the core material of the composite rubber, the mass ratio of liquid rubber to vulcanizing agent is (7:3) to (9:1). Understandably, in the core material, the mass fraction of liquid rubber is 70% to 90%, and the mass fraction of vulcanizing agent is 10% to 30%. This mass ratio of liquid rubber to vulcanizing agent ensures that the amount of liquid rubber in the core material can fill the thermal cracks caused by the openings, thus repairing the thermal damage to the composite current collector; and the amount of vulcanizing agent used is limited to this range, ensuring that the liquid rubber can cure in a short time, achieving rapid repair. For example, the mass ratio of liquid rubber to vulcanizing agent includes, but is not limited to, 7:3, 8:2, or 9:1, or any two of the above values ​​as endpoints within the range.

[0082] Furthermore, in the composite rubber, the mass ratio of liquid rubber to shell is (20~200):1. For example, the mass ratio of liquid rubber to shell includes, but is not limited to, 20:1, 30:1, 50:1, 90:1, 100:1, 110:1, 150:1, 180:1 or 200:1, or any two of the above points as endpoints.

[0083] For example, a method for preparing composite rubber includes:

[0084] P10: Mix the liquid rubber and emulsifier, stir at 1000 rpm to 3000 rpm, and add deionized water to form an oil-in-water emulsion. The solid content of the oil-in-water emulsion is 20% to 40%. For example, in step P10, the stirring equipment includes, but is not limited to, a high-speed shear emulsifier. For example, in this step, the stirring time at 1000 rpm to 3000 rpm, i.e., the emulsification time, is 30 min to 60 min. The emulsifier includes, but is not limited to, alkylphenol polyoxyethylene ether. The mass ratio of emulsifier to liquid rubber is (0.01 to 0.03): 1.

[0085] P20: Disperse the vulcanizing agent in deionized water to prepare a suspension. The mass fraction of the vulcanizing agent in the suspension is 5%–10%. Add the suspension to the oil-in-water emulsion and stir at 500–1000 rpm for 15–30 minutes to prepare the first mixture. Understandably, in this step, the mixing ratio of the suspension and the oil-in-water emulsion can be adjusted according to the mass ratio of the vulcanizing agent to the liquid rubber.

[0086] P30: Melamine resin is prepared into an aqueous solution using deionized water. The mass fraction of melamine resin in the aqueous solution is 5%~15%. Pre-dispersing the melamine resin to form an aqueous solution allows for more uniform dispersion in the oil-in-water emulsion.

[0087] P40: Slowly add the melamine resin aqueous solution to the first mixture from step P20, stirring at 500-1000 rpm to form a second mixture. Add ammonium chloride catalyst to the second mixture, adjust the pH to 4-5, and heat to 60-70℃, reacting for 1-2 hours to allow the melamine resin to crosslink on the surface of the liquid rubber and vulcanizing agent, forming a shell and preparing a core-shell structure precursor. The mass ratio of ammonium chloride catalyst to the second mixture is (0.005-0.02):1. Understandably, in this step, the mixing ratio of the melamine resin aqueous solution and the first mixture can be adjusted according to the mass ratio of liquid rubber to melamine resin in the composite rubber. In this step, citric acid or hydrochloric acid can be used to adjust the pH to 4-5.

[0088] P50: The core-shell precursor is heated to 80℃~90℃ and reacted for 1h~2h to solidify the shell. After cooling to room temperature, it is filtered and washed to prepare a composite rubber slurry. The composite rubber slurry is then vacuum dried at 50℃~60℃ for 20h~40h to remove moisture and prepare a powdered composite rubber.

[0089] In some of these examples, the liquid resin includes one or more of liquid polybutadiene rubber, liquid polyurethane rubber, and liquid acrylic rubber.

[0090] In some of these examples, the vulcanizing agent includes one or more of zinc oxide and phenolic resin.

[0091] Understandably, the preparation steps of the polymer-based film 100 include:

[0092] S10: Prepare polymer and composite rubber according to the mass proportions, melt and extrude them, and then cast them into a film to prepare polymer base film 100.

[0093] In some of these examples, step S14, which involves preparing a metal layer 300 on the surface of the second conductive seed layer 202, includes:

[0094] Metal layer 300 was prepared by electrochemical deposition using a water electroplating method, with the second conductive seed layer 202 as the cathode and a current of 1A to 10A applied.

[0095] For example, the current applied includes, but is not limited to, 1A, 2A, 3A, 4A, 5A, 6A, 7A, 8A, 9A or 10A, or any two of the above point values ​​as endpoint values ​​within the range.

[0096] Furthermore, the step of preparing the metal layer 300 by electrochemical deposition using an aqueous electroplating method includes: immersing the cleaned second conductive seed layer 202 in an acidic copper sulfate electroplating solution, using the second conductive seed layer 202 formed in S13 as the cathode, and applying current to perform electrochemical deposition. This continues until the thickness of the metal layer 300 is 0.8 μm to 1.5 μm.

[0097] In some examples, a roll-to-roll production line is used to prepare the metal layer 300 by electrochemical deposition using an electroplating method. In this case, the winding tension of the intermediate is 55N~65N, the unwinding tension is 50N~60N, and the linear speed is 3m / min~5m / min.

[0098] Metal layer 300 is prepared by electrochemical deposition using a roll-to-roll production line. This enables continuous, large-scale, and efficient deposition of metal layer 300, and results in high density of metal layer 300.

[0099] For example, the winding tension of the intermediate is including, but not limited to, 55N, 60N, or 65N, or any two of the above values ​​as endpoints. The unwinding tension is including, but not limited to, 50N, 55N, 58N, or 60N, or any two of the above values ​​as endpoints. The linear speed is including, but not limited to, 3m / min, 4m / min, or 5m / min, or any two of the above values ​​as endpoints.

[0100] The metal layer 300 is prepared by electroplating, which effectively increases the thickness at the micropore openings, forming stable metal connection points and ultimately completely covering and sealing the micropores. This prevents the second conductive seed layer 202 or the metal layer 300 from detaching during subsequent electrode active material coating. Furthermore, the polymer base film 100 has a much lower density than the metal layer 300, and the hollow micropores help further reduce the overall weight, contributing to increased battery energy density.

[0101] The polymer-based film 100 exhibits excellent flexibility, and the presence of internal pores (covered by copper) can be considered as introducing controllable "hinge points," making the composite current collector easier to bend and deform in specific directions without easily experiencing metal fatigue fracture. This is beneficial for manufacturing flexible batteries or improving the battery's resistance to mechanical shock in applications.

[0102] Furthermore, on the one hand, because the pores of the micropores are sealed by the second conductive seed layer, the inflow of electrode active material during coating is prevented, and the coated electrode sheet will not have surface defects, thus preventing a reduction in battery performance; it can also reduce the internal resistance of the composite current collector, improve its conductivity, and enhance battery performance. On the other hand, the presence of cavities inside the micropores enables the lightweighting of the composite current collector, which helps to reduce battery weight and increase battery energy density.

[0103] See Figure 2 In a second aspect, this application provides a composite current collector, comprising a polymer base film 100 and a first conductive seed layer 201, a second conductive seed layer 202, and a metal layer 300 sequentially disposed on two opposing surfaces of the polymer base film 100 along the thickness direction of the composite current collector; the first conductive seed layer 201 comprises a first conductive material; the second conductive seed layer 202 comprises a second conductive material;

[0104] Along the thickness direction of the composite current collector, the first conductive seed layer 201 and the polymer base film 100 have a microporous array structure 110; and the micropore openings in the microporous array structure 110 are sealed by the second conductive seed layer 202 or the second conductive material. The metal layer is a copper layer or an aluminum layer.

[0105] Understandably, the properties of each functional layer of the composite current collector prepared in the second aspect of this application are the same as those in the first aspect of this application, so they will not be described again here. In addition, it is understood that, similar to the first aspect of this application, the micropores in the micropore array structure 110 are sealed, and the micropore array structure 110 is a cavity.

[0106] In some embodiments, the micropore openings in the micropore array structure 110 are blocked by a second conductive seed layer 202 or a second conductive material.

[0107] In some embodiments, the micropore walls in the micropore array structure 110 have a second conductive seed layer 202 or a second conductive material.

[0108] In some of these examples, the micropore array structure 110 has cavities.

[0109] Understandably, in the composite current collector prepared in this application, the pore walls and pore openings of the micropore array structure 110 both have a second conductive material; however, the micropores still have a cavity structure.

[0110] In some of these examples, the first conductive seed layer 201 and the second conductive seed layer 202 each independently comprise one or more alloys of copper, aluminum, nickel, gold, chromium, and titanium.

[0111] In some of these examples, the polymer base film 100 comprises, by weight, 92 to 95 parts of a polymer and 5 to 8 parts of a composite rubber.

[0112] The polymers include one or more of polyethylene terephthalate, polypropylene, and polyimide;

[0113] The particle size of the composite rubber is 0.5µm~2µm.

[0114] A third aspect of this application provides an electrode sheet comprising a composite current collector prepared by any of the preparation methods of the first aspect of this application, or a composite current collector comprising the second aspect of this application.

[0115] A fourth aspect of this application provides a secondary battery, including the electrode sheet of the third aspect of this application.

[0116] The following detailed embodiments illustrate this application in more detail. It should also be understood that the following embodiments are for further explanation only and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of this application fall within the scope of protection of this application. The specific process parameters, etc., in the following embodiments are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not necessarily limited to the specific values ​​in the embodiments below.

[0117] Preparation Example 1

[0118] The composite rubbers used in Examples 1-3 and Examples 6-7 below were prepared using Preparation Example 1. The preparation steps of the composite rubbers included:

[0119] (1) Liquid rubber and emulsifier alkylphenol polyoxyethylene ether are mixed at a mass ratio of 1:0.002 and stirred for 40 minutes at 2000 rpm in a high-speed shear emulsifier. Deionized water is then added to form an oil-in-water emulsion. The solid content of the oil-in-water emulsion is 30%.

[0120] (2) The vulcanizing agent is dispersed in deionized water to prepare a suspension. The mass fraction of the vulcanizing agent in the suspension is 8%. The suspension is added to the oil-in-water emulsion and stirred at 800 rpm for 20 min to prepare the first mixture. In this step, the mixing ratio of the suspension and the oil-in-water emulsion is adjusted according to the mass ratio of the vulcanizing agent to the liquid rubber in the example.

[0121] (3) Use deionized water to prepare a 10% melamine resin aqueous solution.

[0122] (4) Slowly add the melamine resin aqueous solution to the first mixture from step (2) and stir at 800 rpm to form a second mixture. Add ammonium chloride catalyst to the second mixture, adjust the pH to 4-5, heat to 65°C, and react for 1.5 h to allow the melamine resin to crosslink on the surface of the liquid rubber and vulcanizing agent to form a shell, thus preparing a core-shell structure precursor. The mass ratio of the ammonium chloride catalyst to the second mixture is 0.01:1. In this step, the mixing ratio of the melamine resin aqueous solution and the first mixture is adjusted according to the mass ratio of the liquid rubber and melamine resin in the composite rubber.

[0123] (5) The core-shell precursor was heated to 85°C and reacted for 1.5 h to solidify the shell. After cooling to room temperature, it was filtered, washed, and a composite rubber slurry was prepared. The composite rubber slurry was vacuum dried at 60°C for 24 h to remove moisture and a composite rubber (powder) was prepared. In this preparation example, the types and / or models of the corresponding liquid rubber, vulcanizing agent, and melamine resin were selected according to the types and / or models in the following examples.

[0124] Preparation Example 2

[0125] The composite rubber used in Example 5 below was prepared in Preparation Example 2. The preparation steps of the composite rubber included:

[0126] (1) Liquid rubber and emulsifier alkylphenol polyoxyethylene ether are mixed at a mass ratio of 1:0.002 and stirred for 40 minutes at 2000 rpm in a high-speed shear emulsifier. Deionized water is then added to form an oil-in-water emulsion. The solid content of the oil-in-water emulsion is 30%.

[0127] (2) Use deionized water to prepare a 10% melamine resin aqueous solution.

[0128] (3) The melamine resin aqueous solution is slowly added to the oil-in-water emulsion from step (1), and stirred at 800 rpm to form a second mixture. Ammonium chloride catalyst is added to the second mixture, the pH is adjusted to 4-5, and then heated to 65°C for 1.5 h to allow the melamine resin to crosslink on the surface of the liquid rubber to form a shell, thus preparing a core-shell structure precursor. The mass ratio of the ammonium chloride catalyst to the second mixture is 0.01:1. In this step, the mixing ratio of the melamine resin aqueous solution and the oil-in-water emulsion is adjusted according to the mass ratio of the liquid rubber and the melamine resin in the composite rubber.

[0129] (4) The core-shell precursor was heated to 85°C and reacted for 1.5 h to solidify the shell. After cooling to room temperature, the mixture was filtered and washed to prepare a composite rubber slurry. The composite rubber slurry was vacuum dried at 60°C for 24 h to remove moisture, and then a composite rubber (powder) was prepared. In this preparation example, the types and / or models of the corresponding liquid rubber and melamine resin were selected according to the types and / or models in the following examples.

[0130] Example 1

[0131] See Figure 2 The composite negative electrode current collector structure includes a polymer base film 100 and a first conductive seed layer 201, a second conductive seed layer 202, and a metal layer 300 sequentially disposed on the surface of the polymer base film 100. Along the thickness direction of the composite negative electrode current collector, the first conductive seed layer 201 and the polymer base film 100 have a micropore array structure 110; the micropore openings in the micropore array structure 110 are blocked by the second conductive seed layer 202; and the micropore walls have the second conductive seed layer 202. It can be understood that... Figure 2 Only the single-sided structure of the composite negative electrode current collector is shown. In Example 1, the two surfaces of the polymer base film 100 that are set opposite to each other are provided with a first conductive seed layer 201, a second conductive seed layer 202 and a metal layer 300, and the thickness, material and structure of the conductive seed layer and the metal layer 300 on the two surfaces are the same.

[0132] The preparation method of the composite negative electrode current collector includes the following steps:

[0133] (1) Preparation of polymer-based film 100:

[0134] Take 93 parts of polyethylene terephthalate (CAS No. 25038-59-9) and 7 parts of composite rubber (particle size 1µm); wherein, the composite rubber includes a core material and a shell disposed on the surface of the core material, the core material includes liquid polyurethane rubber (terminated mercapto-based liquid polyurethane rubber, model: STPU, purchased from Yuyao Huihong Plastics Factory) and zinc oxide vulcanizing agent in a mass ratio of 7:3, and the shell is melamine resin (purchased from Allnex, USA, model: CYMEL® 385), the mass ratio of liquid polyurethane rubber to melamine resin is 100:1. After melting and extruding the polyethylene terephthalate and composite rubber, cast the mixture into a film to prepare a polymer base film 100 with a thickness of 4.5µm.

[0135] (2) Preparation of the first conductive seed layer 201 by first magnetron sputtering:

[0136] A polymer base film 100 is used, and a first conductive seed layer 201 is prepared on both surfaces of the polymer base film 100 by a first magnetron sputtering treatment (the target material is copper). The sputtering power of the first magnetron sputtering treatment is 3kW. The first conductive seed layer 201 with a thickness of 0.05µm is prepared by using a roll-to-roll production line. At this time, the winding tension of the polymer base film 100 is 60N, the unwinding tension is 65N, and the linear speed is 12m / min.

[0137] (3) Hole opening treatment:

[0138] Using the surface of the first conductive seed layer 201 furthest from the polymer base film 100 as the opening surface, the intermediate body after the formation of the first conductive seed layer 201 is subjected to laser aperture processing, so that the first conductive seed layer 201 and the polymer base film 100 have a through-hole micropore array structure 110; and at this time, the periphery of the micropore has a protrusion 120 after laser aperture. After the aperture processing, the average pore diameter of the micropores in the micropore array structure 110 is 15µm. After the aperture processing, the average spacing between any two adjacent micropores in the micropore array structure 110 is 1.7mm.

[0139] (4) The second conductive seed layer 202 is prepared by second magnetron sputtering to seal the micropore openings:

[0140] The walls and openings of the micropores in the micropore array structure 110 are sealed by a second magnetron sputtering process (with copper as the target material), forming a second conductive seed layer 202 with a thickness of 0.15 μm, thus preparing an intermediate. The micropores have cavities. The sputtering power of the second magnetron sputtering process is 8 kW, and the linear velocity is 5 m / min.

[0141] (5) Prepare a metal layer 300 on the surface of the intermediate:

[0142] The cleaned intermediate was immersed in an acidic copper sulfate electroplating solution. Using the second conductive seed layer 202 formed in step (4) as the cathode, a current of 5A was applied for electrochemical deposition until the thickness of the metal layer 300 (copper layer) was 1.1 μm. The metal layer 300 was prepared by electrochemical deposition using a roll-to-roll production line. At this time, the winding tension of the intermediate was 60 N, the unwinding tension was 55 N, and the linear speed was 4 m / min.

[0143] The scanning electron microscope (SEM) images of the three micropores after the opening process in step (3) of Example 1 are shown below. Figure 3 As shown in (b), (c) and (d). Figure 3 The hole spacings in (a), (e), and (i) represent the observation areas between the holes on the sample surface. Example 1, step (4): Second magnetron sputtering treatment to prepare the second conductive seed layer 202. After sealing the micropore openings, the scanning electron microscope images of the three micropores in the example are shown below. Figure 3 As shown in (f), (g), and (h). In Example 1, after step (5) of preparing a metal layer 300 on the surface of the intermediate, an example scanning electron microscope image of three micropores is shown. Figure 3 As shown in (j), (k), and (l), since the average pore size of the micropore structure is small, at the micrometer level, it is difficult to find the micropores again in the scanning electron microscope image after reprocessing. Therefore, the holes 1#, 2#, and 3# after the opening process in step (3) in Example 1 are not completely corresponding to the micropores after the second magnetron sputtering process in step (4). Similarly, the micropores processed in step (4) and those processed in step (5) are not completely corresponding. Figure 1 The accompanying drawings are for illustrative purposes only, demonstrating that the preparation method of this composite current collector can be implemented. Figure 3 As can be seen, after the opening process in step (3), the micropores are formed into depressions. After the second magnetron sputtering process in step (4), the surface of the micropores is sealed, and the walls of the micropores are completely covered by the second conductive material. Moreover, after the second magnetron sputtering process, the protrusions 120 around the micropores still exist, so the protrusions 120 can enhance the adhesion for the subsequent preparation of the metal layer 300 and increase the difficulty of peeling off the metal layer 300. This allows a dense metal layer 300 to be further deposited on the surface of the micropores after the preparation of the metal layer 300.

[0144] Example 2

[0145] Composite negative electrode current collector structure: same as in Example 1.

[0146] The preparation methods of Example 2 and Example 1 are basically the same, the main difference being that the following steps are different:

[0147] (1) Preparation of polymer-based film 100:

[0148] Take 92 parts of polyethylene terephthalate (CAS No. 25038-59-9) and 8 parts of composite rubber (particle size 2µm). The core material consists of liquid polyurethane rubber and zinc oxide vulcanizing agent in a mass ratio of 9:1, and the shell is melamine resin with a mass ratio of liquid polyurethane rubber to melamine resin of 20:1.

[0149] (2) Preparation of the first conductive seed layer 201 by first magnetron sputtering:

[0150] The sputtering power of the first magnetron sputtering process is 2kW.

[0151] (3) Hole opening treatment:

[0152] After the aperture opening process, the average pore diameter of the micropores in the micropore array structure 110 is 20µm. After the aperture opening process, the average spacing between any two adjacent micropores in the micropore array structure 110 is 0.04mm.

[0153] (4) The second conductive seed layer 202 is prepared by second magnetron sputtering to seal the micropore openings:

[0154] An intermediate body is prepared by sealing the walls and openings of the micropores in the micropore array structure 110 using a second magnetron sputtering process; wherein the micropores have cavities. The sputtering power of the second magnetron sputtering process is 15kW.

[0155] Example 3

[0156] Composite negative electrode current collector structure: same as in Example 1.

[0157] The preparation methods of Example 3 and Example 1 are basically the same, the main difference being that the following steps are different:

[0158] (1) Preparation of polymer-based film 100:

[0159] Take 95 parts of polyethylene terephthalate (CAS No. 25038-59-9) and 5 parts of composite rubber (particle size 1µm). The core material consists of liquid polyurethane rubber and zinc oxide vulcanizing agent in a mass ratio of 7:3, and the shell is melamine resin with a mass ratio of liquid polyurethane rubber to melamine resin of 200:1.

[0160] (2) Preparation of the first conductive seed layer 201 by first magnetron sputtering:

[0161] The sputtering power of the first magnetron sputtering process is 15kW.

[0162] (3) Hole opening treatment:

[0163] After the aperture opening process, the average pore diameter of the micropores in the micropore array structure 110 is 10µm. After the aperture opening process, the average spacing between any two adjacent micropores in the micropore array structure 110 is 3mm.

[0164] (4) The second conductive seed layer 202 is prepared by second magnetron sputtering to seal the micropore openings:

[0165] An intermediate body is prepared by sealing the walls and openings of the micropores in the micropore array structure 110 using a second magnetron sputtering process; wherein the micropores have cavities. The sputtering power of the second magnetron sputtering process is 15kW.

[0166] Example 4

[0167] Composite negative electrode current collector structure: same as in Example 1.

[0168] The preparation method of the composite negative electrode current collector is basically the same as that in Example 1, except that the preparation of the polymer base film 100 in Example 4 is different from that in Example 1. Step (1) of Example 4 is as follows:

[0169] (1) Preparation of polymer-based film 100:

[0170] Take 100 parts of polyethylene terephthalate, melt and extrude it, and then cast it into a film to prepare a polymer base film 100 with a thickness of 4.5µm.

[0171] Example 5

[0172] Composite negative electrode current collector structure: same as in Example 1.

[0173] The preparation method of the composite negative electrode current collector is basically the same as that in Example 1, except that the preparation of the polymer base film 100 in Example 5 is different from that in Example 1. Step (1) of Example 5 is as follows:

[0174] (1) Preparation of polymer-based film 100:

[0175] Take 93 parts of polyethylene terephthalate (CAS No. 25038-59-9) and 7 parts of composite rubber (particle size 1µm); wherein, the composite rubber includes a core material and a shell disposed on the surface of the core material, the core material is liquid polyurethane rubber (terminated thiol-terminated liquid polyurethane rubber, model: STPU, purchased from Yuyao Huihong Plastics Factory), and the shell is melamine resin (purchased from Allnex, USA, model: CYMEL® 385), the mass ratio of liquid polyurethane rubber to melamine resin is 100:1. After melting and extruding the polyethylene terephthalate and composite rubber, cast them into a film to prepare a polymer base film 100 with a thickness of 4.5µm.

[0176] Example 6

[0177] Composite negative electrode current collector structure: same as in Example 1.

[0178] The preparation method of the composite negative electrode current collector is basically the same as that in Example 1, except that the step of opening the hole in Example 6 is different from that in Example 1. Step (3) of Example 6 is as follows:

[0179] (3) Hole opening treatment:

[0180] Laser drilling is performed on the perforated surface. After the perforation process, the average pore diameter of the micropores in the micropore array structure 110 is 30 μm. After the perforation process, the spacing between any two adjacent micropores in the micropore array structure 110 is 0.03 mm.

[0181] Example 7

[0182] Composite negative electrode current collector structure: same as in Example 1.

[0183] The preparation method of the composite negative electrode current collector is basically the same as that in Example 1. The main difference is that the step of sealing the micropore openings in Example 7, which involves preparing the second conductive seed layer 202 by the second magnetron sputtering process, is different from that in Example 1. Step (4) of Example 7 is as follows:

[0184] (4) The second conductive seed layer 202 is prepared by second magnetron sputtering to seal the micropore openings:

[0185] An intermediate body is prepared by sealing the walls and openings of the micropores in the micropore array structure 110 using a second magnetron sputtering process; wherein the micropores have cavities and the walls of the micropores are not completely covered by the second conductive material. The sputtering power of the second magnetron sputtering process is 2kW.

[0186] Comparative Example 1

[0187] The preparation method of the composite negative electrode current collector is basically the same as that in Example 1. The main difference is that step (4) is different; step (4) of Comparative Example 1 is:

[0188] (4) Prepare the second conductive seed layer 202 by performing a second magnetron sputtering process:

[0189] The sputtering power of the second magnetron sputtering process is 0.5kW. The second magnetron sputtering power is too small to block the opening of the micropore array. The micropores do not have cavities. The second conductive seed layer 202 is deposited at the bottom of the micropores, which in turn causes micropore defects on the surface of the composite current collector.

[0190] Performance test case

[0191] In the composite negative electrode current collectors prepared in the above embodiments and comparative examples, the thicknesses of the polymer base film 100, the first conductive seed layer 201, the second conductive seed layer 202, and the metal layer 300 are all consistent. Relevant performance tests were performed on the composite negative electrode current collectors prepared in the embodiments and comparative examples, and the corresponding test results are shown in Table 1.

[0192] (1) Peel strength / adhesion strength test

[0193] The specific testing method is as follows: use a peel force tester, 180° peel test, peel speed is 300mm / min.

[0194] (2) Internal resistance (sheet resistance) test

[0195] The specific testing method is as follows: use the four-probe test method.

[0196] (3) Coating defects

[0197] The specific testing method is to check whether there are unsealed micropores on the surface of the prepared composite current collector.

[0198] (4) Tensile strength test

[0199] The specific testing method is as follows: use a universal tensile testing machine to take the MD direction for testing, and the testing standard is the national standard GB / T1040.3-2006.

[0200] Table 1

[0201]

[0202] As shown in Table 1, compared to Comparative Example 1, the composite current collectors of Examples 1 to 7 exhibit good adhesion between their layers, and Examples 1 to 7 also avoid micropore defects. Therefore, the surface defects of the electrode sheets after coating with the composite current collectors of Examples 1 to 7 are reduced, thereby improving battery performance. In addition, the internal resistance of the composite current collector in Comparative Example 1 is lower than that of the examples, and its tensile strength is higher. This is mainly because the micropores in Comparative Example 1 are blocked by the second conductive layer prepared by the second magnetron sputtering. The sputtering power is insufficient to block the pore openings, resulting in the second conductive material being deposited throughout the micropores. The absence of micropore cavities leads to micropore defects and also hinders the lightweighting of the composite current collector.

[0203] In each embodiment, Embodiments 1, 4, and 5 are basically the same, the main difference being that the raw materials for preparing the polymer base film 100 are different in each embodiment. The polymer base film 100 of Embodiment 1 contains a composite rubber consisting of a core material (liquid rubber and vulcanizing agent) and a shell, while Embodiment 4 does not contain the above-mentioned composite rubber, and the core material of the composite rubber in Embodiment 5 only contains liquid rubber. From the test results in Table 1, the adhesion and internal resistance of Embodiments 1, 4, and 5 are basically the same, but the tensile strength of the composite current collector in each embodiment is Example 1 > Example 4 > Example 5. This indicates that when composite rubber is added to the polymer base film 100 of Embodiment 1, the liquid rubber released by the composite rubber, along with the local high temperature generated during the opening process of penetrating the hole wall, will quickly fill and solidify the thermal cracks generated by the opening, in conjunction with the vulcanizing agent; therefore, the composite rubber is beneficial for filling the thermal cracks generated by the opening process, thereby enhancing the tensile strength of the composite current collector in Embodiment 1. The tensile strength of Example 5 is between that of Example 1 and Example 4. This indicates that no vulcanizing agent was used when preparing the polymer base film 100 in Example 5, resulting in a long curing time for the liquid rubber and untimely sealing of cracks around the micropores. Consequently, the increase in tensile strength of the composite current collector by the liquid rubber is limited.

[0204] Example 1 and Example 6 are basically the same, the main difference being that the average pore diameter of the micropores and the spacing between any two adjacent micropores are different in the micropore array structure. Compared with Example 1, Example 6 has larger and more numerous micropores, resulting in increased micropore surface density and thus reduced internal resistance. Furthermore, since the opening process in Example 6 requires processing multiple micropores, the number of protrusions formed around the multiple micropores is also greater than in Example 1, leading to improved adhesion and tensile strength in Example 6 compared to Example 1.

[0205] Example 1 and Example 7 are basically the same, the main difference being that the sputtering power of the second magnetron sputtering process in Example 7 is slightly lower. In this case, the lower magnetron sputtering power results in the second conductive material not being sputtered onto the walls of the deeper micropores, leading to only the portion of the micropore walls near the opening containing the second conductive material, which then blocks the opening of the micropore. Therefore, the internal resistance of Example 7 is higher than that of Example 1, and its conductivity is reduced. The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0206] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method of making a composite current collector, characterized by, The method comprises the following steps: taking a polymer base film, performing first treatment on the polymer base film with a first conductive material to prepare a first conductive seed layer on at least one side surface of the polymer base film; taking the side surface of the first conductive seed layer away from the polymer base film as an opening surface, performing opening treatment on the first conductive seed layer and the polymer base film to make the first conductive seed layer and the polymer base film have a micropore array structure; the micropore array structure penetrates through the first conductive seed layer and the polymer base film after the opening treatment; and there are protrusions around the micropores of the micropore array structure after the opening treatment; performing second treatment on the micropore array structure with a second conductive material to block the micropore orifices in the micropore array structure, and the micropore array structure has cavities, and a second conductive seed layer is prepared on the side surface of the first conductive seed layer away from the polymer base film; a metal layer is prepared on the surface of the second conductive seed layer away from the polymer base film; wherein the first treatment is chemical plating or gas deposition, the second treatment is a magnetic sputtering process in the gas deposition, the second treatment is a second magnetic sputtering treatment, the sputtering power of the second magnetic sputtering treatment is 2kW-15kW; and the metal layer is a copper layer or an aluminum layer.

2. The method of making a composite current collector of claim 1, wherein, The first treatment uses a magnetic sputtering process, the first treatment is a first magnetic sputtering treatment, and the sputtering power of the first magnetic sputtering treatment is 2kW-15kW; and / or, the difference between the sputtering power of the second magnetic sputtering treatment and the sputtering power of the first magnetic sputtering treatment is 1kW-3kW; and / or, the second conductive material is the same as the first conductive material.

3. The method of making a composite current collector according to claim 1 or 2, wherein, The polymer base film comprises, by mass fraction, 92-95 parts of a polymer, and 5-8 parts of a composite rubber; wherein the polymer comprises one or more of polyethylene terephthalate, polypropylene, and polyimide; The particle size of the composite rubber is 0.5µm-2µm.

4. The method of making a composite current collector of claim 3, wherein, The composite rubber comprises a core material and a shell arranged on the surface of the core material; wherein the core material comprises a liquid rubber and a vulcanizing agent; and the shell comprises a melamine resin.

5. The method of making a composite current collector of claim 4, wherein, In the core material of the composite rubber, the mass ratio of the liquid rubber to the vulcanizing agent is (7:3)-(9:1); and / or, The mass ratio of the liquid rubber to the shell is (20-200):1; and / or, The liquid rubber comprises one or more of liquid polybutadiene rubber, liquid polyurethane rubber, and liquid acrylic rubber; and / or, The vulcanizing agent comprises one or more of zinc oxide and phenolic resin.

6. The method of making a composite current collector of claim 1 or 2, wherein, The second conductive material and the first conductive material each independently comprise one or more alloys of copper, aluminum, nickel, gold, chromium, and titanium; and / or, after the opening treatment, the average pore diameter of the micropores in the micropore array structure is 10µm-20µm; and / or, after the opening treatment, the spacing between any two adjacent micropores in the micropore array structure is 0.04mm-3mm.

7. The method of making a composite current collector of claim 1 or 2, wherein, The step of preparing a metal layer on the surface of the second conductive seed layer comprises: The metal layer is prepared by electrochemical deposition with the second conductive seed layer as a cathode and a current of 1A-10A.

8. The composite current collector prepared by the method of any one of claims 1 to 7, characterized in that, The composite current collector comprises a polymer base film, a first conductive seed layer, a second conductive seed layer and a metal layer arranged on the surface of the polymer base film in sequence along the thickness direction of the composite current collector; the first conductive seed layer comprises a first conductive material, and the second conductive seed layer comprises a second conductive material. In the thickness direction of the composite current collector, the first conductive seed layer and the polymer base film have a micropore array structure; the micropore apertures in the micropore array structure are blocked by the second conductive material; and the micropore array structure has cavities. The metal layer is a copper layer or an aluminum layer.

9. The composite current collector of claim 8, wherein, The micropore apertures in the micropore array structure are blocked by the second conductive material. The second conductive material and the first conductive material each independently comprise one or more alloys of copper, aluminum, nickel, gold, chromium and titanium.

10. The composite current collector of claim 8 or 9, wherein, The polymer base film comprises, by mass fraction, 92-95 parts of a polymer and 5-8 parts of a composite rubber. The polymer comprises one or more of polyethylene terephthalate, polypropylene and polyimide. The composite rubber has a particle size of 0.5-2 µm; the composite rubber comprises a core material and a shell arranged on the surface of the core material; the core material comprises liquid rubber and a vulcanizing agent; and the shell comprises melamine resin.

11. An electrode sheet, characterized by The composite current collector is prepared by the preparation method of any one of claims 1-7 or is the composite current collector of any one of claims 8-10.

12. A secondary battery characterized by comprising: The electrode sheet comprises the electrode sheet of claim 11.

Images