Preparation process of composite current collector

Abstract

The present application belongs to the field of current collector technology, and specifically relates to a preparation process of a composite current collector, comprising the following steps: S1, adding PET resin, polypropylene, maleic anhydride grafted polypropylene, a cross-linking agent, a filler, an antioxidant and a lubricant to a high-speed mixer, stirring, adding the mixture to a twin-screw extruder for melt extrusion, casting, and then obtaining a base film layer through a biaxial stretching process; S2, coating the slurry on both surfaces of the base film layer using a slit extruder, drying, and curing to obtain a bonding layer; S3, sputtering metallic copper on the surface of the bonding layer to obtain a composite film; S4, placing the composite film with a metal layer in a coating device, uniformly coating the coating liquid on the surfaces of the metal layers on both sides, drying, forming a protective layer, and finally obtaining a composite current collector; the prepared composite current collector has excellent mechanical properties, a low defective rate, and good chemical stability and high temperature resistance.

Description

Technical Field

[0001] The present application belongs to the technical field of current collectors, and specifically relates to a preparation process of a composite current collector. Background Art

[0002] With the rapid development of modern science and technology, lithium-ion batteries have been widely used in consumer electronics, electric vehicles and other fields. With the continuous development of the battery industry, current collectors with better performance are needed. Composite current collectors are a new type of current collector material, usually made of a polymer substrate layer and a metal layer plated on both sides of the polymer substrate layer, forming a "sandwich structure". Compared with pure metal current collectors, the weight of composite current collectors can be reduced by 50-80%. The presence of a polymer substrate layer in a composite current collector can reduce the temperature rise of the battery, reduce the risk of thermal runaway of the battery, and improve the safety of the battery. However, the substrate layer is generally PP, PET or PI, which has low surface tension and poor affinity with the metal, resulting in poor bonding with the metal layer. During the preparation of the composite current collector, the metal layer is easy to fall off, resulting in a low yield of the composite current collector. In addition, the mechanical properties of the substrate layer are poor, and there is a risk of demolding during the preparation process. The prepared composite current collector has defects such as poor corrosion resistance and poor high temperature resistance. Therefore, the present application provides a preparation process for a composite current collector. Summary of the Invention

[0003] In order to solve the problems of low yield, poor corrosion resistance and poor high temperature resistance of composite current collectors, the present application provides a preparation process of a composite current collector.

[0004] In order to achieve the above purpose, the technical solution adopted in this application is:

[0005] A preparation process of a composite current collector comprises the following steps:

[0006] S1. Add PET resin, polypropylene, maleic anhydride grafted polypropylene, crosslinking agent, filler, antioxidant and lubricant to a high-speed mixer and stir for 25-40 minutes to obtain a premix; add the premix to a twin-screw extruder for melt extrusion, cast molding, and then obtain a base film layer through a biaxial stretching process;

[0007] S2. Coating the slurry on both surfaces of the base film layer using a slot extruder, then drying at 80-90°C for 1-2 hours, and then keeping the temperature at 120-140°C for 30-45 minutes to obtain a bonding layer;

[0008] S3, sputtering metallic copper on the surface of the bonding layer to form a metal layer with a thickness of 0.5-2 μm to obtain a composite film;

[0009] S4. Place the composite film with the metal layer in a coating device, and evenly coat the coating liquid on the surface of the metal layer through a die coating process, dry it, form a protective layer, and finally obtain a composite current collector.

[0010] Preferably, the mass parts of the raw materials in step S1 are as follows: 60-80 parts of PET resin, 30-40 parts of polypropylene, 4-6 parts of maleic anhydride grafted polypropylene, 1-3 parts of cross-linking agent, 8-12 parts of filler, 0.5-2 parts of antioxidant and 0.5-0.8 parts of lubricant.

[0011] Preferably, the filler in step S1 is prepared by the following method:

[0012] The silk fibroin solution was mixed with a calcium chloride solution having a mass fraction of 8-12%, and heated and stirred for 10-15 minutes to obtain a silk fibroin solution; ammonium persulfate was then added, and the mixture was heated and stirred until uniform; acrylic acid was added, and the mixture was heated and reacted for 2-4 hours; acetone was then added, and the mixture was allowed to stand, centrifuged, and dried to obtain a modified silk fibroin solution;

[0013] Modified silk fibroin and deionized water are mixed at a mass ratio of 0.5-1:100 to obtain a modified silk fibroin solution, disuccinimidyl glutarate and graphene oxide are added to the modified silk fibroin solution, heated for reaction for 2-3 hours, centrifuged, washed, and dried to obtain the filler.

[0014] Preferably, the mass ratio of the silk fibroin to the calcium chloride solution is 0.9-1.2:30-40; the mass of the ammonium persulfate is 0.5-0.8% of the mass of the silk fibroin solution; the mass of the acrylic acid is 1-2% of the mass of the silk fibroin solution; and the mass of the acetone is 15-25% of the mass of the silk fibroin solution.

[0015] Preferably, the mass of the disuccinimidyl glutarate is 0.1-0.3% of the mass of the modified silk fibroin solution; the mass of the graphene oxide is 5-8% of the mass of the modified silk fibroin solution.

[0016] Preferably, the slurry in step S2 is prepared by mixing the following raw materials in parts by mass: 50-70 parts of water-based epoxy resin, 1-3 parts of auxiliary agent, 6-8 parts of zirconium oxide, 0.5-1 parts of surfactant and 5-8 parts of curing agent.

[0017] Preferably, the auxiliary agent in step S2 is prepared by compounding ethylene glycol diglycidyl ether, modified styrene-butadiene-vinyl pyridine and dimethylbenzylamine in a mass ratio of 1-3:4-6:0.5-1.

[0018] Preferably, the modified styrene-butadiene-vinyl pyridine is prepared by the following method:

[0019] A1. Styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene are mixed, heated and stirred for 3-5 hours to obtain a mixed solution 1. After cooling, hydroquinone is added, stirred evenly, and allowed to stand for 3-5 minutes. The mixture is then distilled under reduced pressure and dried to obtain styrene-butadiene-vinyl pyridine containing epoxy groups; wherein the mass ratio of styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene is 2-4:3-5:0.5-0.8:0.3-0.5:0.1-0.2:40-60, and the mass of hydroquinone is 1-2% of the mass of the mixed solution 1.

[0020] A2, styrene-butadiene-vinyl pyridine containing epoxy group, PEG-400 and tetrahydrofuran are mixed, stirred to obtain mixed solution 2, triethylamine is added, heated with stirring for 5-8h, cooled, centrifuged, washed, and dried to obtain the modified styrene-butadiene-vinyl pyridine, wherein the mass ratio of styrene-butadiene-vinyl pyridine containing epoxy group, PEG-400 and tetrahydrofuran is 2-4:0.2-0.4:40-60, and the mass of triethylamine is 0.1-0.2% of the mass of mixed solution 2.

[0021] Preferably, the coating liquid in step S4 is prepared by mixing carbon nanotubes and N-methylpyrrolidone in a mass ratio of 0.2-0.5:100.

[0022] Another object of the present application is to provide a composite current collector prepared by the preparation process.

[0023] This application has the following beneficial effects:

[0024] The present application mixes silk fibroin, calcium chloride, ammonium persulfate and acrylic acid to obtain modified silk fibroin, and then modifies graphene oxide with the modified silk fibroin and disuccinimidyl glutarate to obtain a filler; under the action of ammonium persulfate, the silk fibroin reacts with acrylic acid, thereby increasing the hydrophilicity and stability of the silk fibroin, providing more active groups for subsequent reactions, which is beneficial to subsequent modification treatments; disuccinimidyl glutarate reacts with the active groups on the modified silk fibroin molecular chain and reacts with the functional groups on the surface of the graphene oxide to form a filler, and the dispersion of the treated graphene oxide in the base film layer is greatly improved, effectively reducing its The agglomeration phenomenon is eliminated, and the uniform dispersion of graphene oxide is achieved in the base membrane layer. At the same time, the excellent dispersibility of graphene oxide promotes the formation of a conductive path. The interaction between the modified silk fibroin and graphene oxide can further stabilize the conductive path and prevent the decline of conductivity caused by the agglomeration of graphene oxide. The introduction of disuccinimidyl glutarate can form a more stable cross-linked network in the base membrane, thereby improving the high temperature resistance of the base membrane layer. The toughness of the modified silk fibroin and the strength of graphene oxide cooperate with each other, so that the base membrane layer can better disperse stress and improve mechanical properties. The synergistic effect of the modified silk fibroin and graphene oxide also helps to improve the stability and service life of the base membrane layer.

[0025] The modified styrene-butadiene-vinyl pyridine prepared in the present application contains vinyl pyridine groups, which can form a strong chemical bond with the current collector base film layer. At the same time, structural units such as styrene and butadiene can provide flexibility, so that the bonding layer can better adapt to different surface morphologies when bonding the current collector and the metal layer, filling microscopic gaps, thereby enhancing the bonding effect, and preventing the bonding layer from brittle cracking when subjected to external force impact, thereby protecting the integrity of the current collector; the introduction of glycidyl methacrylate can increase the cross-linking degree of the polymer, thereby helping to improve corrosion resistance and high temperature resistance;

[0026] The introduction of PEG-400 can improve the wettability of the bonding layer in the aqueous system, help the electrolyte to better penetrate and distribute between the bonding layer and the electrode material, and is conducive to the uniform dispersion of zirconium oxide in the bonding layer, making the performance of the bonding layer more uniform and consistent; the structural units such as styrene and vinylpyridine in the modified styrene-butadiene-vinylpyridine stabilize the molecular structure through conjugated systems, etc., reduce the corrosion of chemical substances on the bonding layer, and enhance the high-temperature resistance of the bonding layer, thereby extending the service life of the bonding layer.

[0027] In this application, ethylene glycol diglycidyl ether, modified styrene-butadiene-vinyl pyridine and dimethylbenzylamine are mixed to form an auxiliary agent, which is added to the molding process of the bonding layer. The modified styrene-butadiene-vinyl pyridine can adjust the overall performance of the auxiliary agent to make it have better wettability, which helps to spread the slurry on the surface of the base film layer and fill the microscopic pores on the surface, thereby increasing the effective contact area and improving the bonding effect; the synergistic effect of the epoxy group of ethylene glycol diglycidyl ether and other components can optimize the wetting properties of the bonding layer; ethylene glycol diglycidyl ether can regulate the interaction between polymer chains to a certain extent, and combined with the flexibility of modified styrene-butadiene-vinyl pyridine, the bonding layer has better mechanical properties and high temperature resistance. The network structure formed after the reaction of ethylene glycol diglycidyl ether and modified styrene-butadiene-vinyl pyridine can effectively prevent the corrosion of chemical substances such as electrolyte on the current collector, thereby extending the service life of the current collector. The synergistic efficiency of the three further gives the bonding layer better high temperature resistance and chemical stability. DETAILED DESCRIPTION

[0028] The present application is further described in detail below with reference to the examples. Unless otherwise specified, the materials, reagents, etc. used in this application can be obtained from commercial sources.

[0029] PET resin, brand: CZ-5011, purchased from Suzhou Chenzhituo Polymer Materials Co., Ltd.; polypropylene, purchased from Shanghai Kaishun Plastics Co., Ltd.; maleic anhydride grafted polypropylene, purchased from Kangjin New Materials Technology Co., Ltd.; diphenylmethane diisocyanate, CAS number: 101-68-8, purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.; 2,6-di-tert-butyl-4-methylphenol, CAS number: 128-37-0, purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.; silk fibroin, purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd. Co., Ltd.; disuccinimidyl glutarate, CAS No.: 79642-50-5, purchased from Shanghai Dibai Biotechnology Co., Ltd.; water-based epoxy resin, purchased from Guangzhou Haihong Chemical Co., Ltd.; zirconium oxide, product No.: YT-OY-06-1, average particle size: 1 μm, purchased from Shanghai Yaotian New Materials Technology Co., Ltd.; graphene oxide, purchased from Nangong Longjian Alloy Materials Co., Ltd., brand: LJ-124; carbon nanotubes, purchased from Jiangsu Tiannai Technology Co., Ltd., average particle size: 10-25 nm, specific surface area: 110-250 m 2 / g.

[0030] Example 1

[0031] A preparation process of a composite current collector comprises the following steps:

[0032] S1. Add 60 parts of PET resin, 30 parts of polypropylene, 4 parts of maleic anhydride grafted polypropylene, 1 part of a cross-linking agent, 8 parts of a filler, 0.5 parts of an antioxidant and 0.5 parts of a lubricant into a high-speed mixer, and stir at a speed of 1000 rpm for 40 minutes to obtain a premix; add the premix into a twin-screw extruder for melt extrusion at a melt temperature of 200°C, cast molding, and then obtain a base film layer with a thickness of 3 μm by a biaxial stretching process; wherein the cross-linking agent is diphenylmethane diisocyanate, the antioxidant is 2,6-di-tert-butyl-4-methylphenol, the lubricant is ethylene bis stearamide, the stretching temperature is 85°C, the stretching rate is 9 cm / s, the heat setting temperature is 180°C, and the stretching ratio is 3:1;

[0033] S2. The slurry was coated on both surfaces of the base film layer using a slot extruder, and then dried at 80° C. for 2 h and kept at 120° C. for 45 min to obtain a bonding layer with a thickness of 2 μm; wherein the slurry was prepared by mixing the following raw materials in parts by mass: 50 parts of a water-based epoxy resin, 1 part of an auxiliary agent, 6 parts of zirconium oxide, 0.5 parts of a surfactant, and 5 parts of a curing agent, wherein the surfactant was polyalkylene hydroxylammonium acrylate and the curing agent was isophorone diamine;

[0034] S3. sputtering metal copper on the surface of the bonding layer to form a metal layer with a thickness of 0.5 μm to obtain a composite film; wherein the sputtering time of the metal copper is 5 minutes, the sputtering power is 480 W, the sputtering voltage is 160 V, and the sputtering temperature is 160° C.;

[0035] S4. Place the composite film with the metal layer in a coating device, and evenly apply the coating liquid to the surface of the metal layer through a die coating process. Dry it at 70°C for 2 hours to form a protective layer with a thickness of 20 nm, and finally obtain a composite current collector; wherein the coating liquid is prepared by mixing carbon nanotubes and N-methylpyrrolidone in a mass ratio of 0.2:100.

[0036] Wherein, the filler in step S1 is prepared by the following method:

[0037] Silk fibroin in a mass ratio of 0.9:30 and a calcium chloride solution with a mass fraction of 8% were mixed, and the mixture was stirred at 30°C and 100 rpm for 10 minutes to obtain a silk fibroin solution; ammonium persulfate was added, and the mixture was stirred at 100 rpm for 15 minutes, and then acrylic acid was added, and the mixture was reacted at 70°C for 4 hours. Acetone was added, and the mixture was allowed to stand for 10 minutes. The mixture was centrifuged at 5000 rpm for 3 minutes, and dried at 45°C for 3 hours to obtain a modified silk fibroin; wherein the mass of ammonium persulfate was 0.5% of the mass of the silk fibroin solution, the mass of acrylic acid was 1% of the mass of the silk fibroin solution, and the mass of acetone was 15% of the mass of the silk fibroin solution;

[0038] Modified silk fibroin and deionized water in a mass ratio of 0.5:100 were mixed and stirred at a speed of 100 rpm for 3 minutes to obtain a modified silk fibroin solution. Disuccinimidyl glutarate and graphene oxide were added to the modified silk fibroin solution, stirred at 100 rpm for 12 minutes, reacted at 70°C for 3 hours, centrifuged at 8000 rpm for 5 minutes, washed three times with ethanol, and dried at 80°C for 5 hours to obtain the filler; the mass of disuccinimidyl glutarate was 0.1% of the mass of the modified silk fibroin solution, and the mass of the graphene oxide was 5% of the mass of the modified silk fibroin solution.

[0039] The auxiliary agent in step S2 is prepared by compounding ethylene glycol diglycidyl ether, modified styrene-butadiene-vinyl pyridine and dimethylbenzylamine in a mass ratio of 1:4:0.5.

[0040] Wherein, modified styrene-butadiene-vinyl pyridine is prepared by the following method:

[0041] A1. Styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene were mixed and stirred at 50°C and 100 rpm for 5 h to obtain a mixed solution 1. The solution was cooled to room temperature, and hydroquinone was added. The mixture was allowed to stand for 5 min, and vacuum distilled. The mixture was dried at 60°C for 6 h to obtain a styrene-butadiene-vinyl pyridine containing epoxy groups. The mass ratio of styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene was 2:3:1:0.3:0.1:40, and the mass of hydroquinone was 1% of the mass of the mixed solution 1.

[0042] A2. Styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran containing an epoxy group were mixed and stirred at a speed of 100 rpm for 15 min to obtain a mixed solution 2. Triethylamine was then added and the mixture was stirred at 60° C. for 8 h. The stirring rate was controlled to be 100 rpm. After cooling to room temperature, the mixture was centrifuged at a speed of 8000 rpm for 5 min, washed three times with ethanol, and dried at 60° C. for 6 h to obtain a modified styrene-butadiene-vinyl pyridine; wherein the mass ratio of styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran was 2:0.2:40, and the mass of triethylamine was 0.1% of the mass of the mixed solution 2.

[0043] Example 2

[0044] A preparation process of a composite current collector comprises the following steps:

[0045] S1. Add 80 parts of PET resin, 40 parts of polypropylene, 6 parts of maleic anhydride grafted polypropylene, 3 parts of a cross-linking agent, 12 parts of a filler, 2 parts of an antioxidant and 0.8 parts of a lubricant into a high-speed mixer, and stir at a speed of 1200 rpm for 25 minutes to obtain a premix; add the premix into a twin-screw extruder for melt extrusion at a melt temperature of 240°C, cast molding, and then obtain a base film layer with a thickness of 6 μm through a biaxial stretching process; wherein the cross-linking agent is diphenylmethane diisocyanate, the antioxidant is 2,6-di-tert-butyl-4-methylphenol, the lubricant is ethylene bis stearamide, the stretching temperature is 95°C, the stretching rate is 12 cm / s, the heat setting temperature is 220°C, and the stretching ratio is 5:1;

[0046] S2. The slurry was coated on both surfaces of the base film layer using a slot extruder, and then dried at 90° C. for 1 hour and kept at 140° C. for 30 minutes to obtain a bonding layer with a thickness of 4 μm. The slurry was prepared by mixing the following raw materials in parts by mass: 70 parts of a water-based epoxy resin, 3 parts of an auxiliary agent, 8 parts of zirconium oxide, 1 part of a surfactant, and 8 parts of a curing agent; the surfactant was polyalkylene hydroxylammonium acrylate, and the curing agent was isophorone diamine.

[0047] S3. sputtering metallic copper on the surface of the bonding layer to form a metal layer with a thickness of 2 μm, thereby obtaining a composite film; wherein the sputtering time of the metallic copper is 8 min, the sputtering power is 500 W, the sputtering voltage is 200 V, and the sputtering temperature is 180° C.;

[0048] S4. Place the composite film with the metal layer in a coating device, and evenly apply the coating liquid to the surface of the metal layer through a die coating process. Dry it at 90°C for 1 hour to form a protective layer with a thickness of 30 nm, and finally obtain a composite current collector; wherein the coating liquid is prepared by mixing carbon nanotubes and N-methylpyrrolidone in a mass ratio of 0.5:100.

[0049] Wherein, the filler in step S1 is prepared by the following method:

[0050] Silk fibroin in a mass ratio of 1.2:40 and a 12% calcium chloride solution were mixed, and the mixture was stirred at 40°C and 200 rpm for 15 minutes to obtain a silk fibroin solution; ammonium persulfate was added, and the mixture was stirred at 200 rpm for 10 minutes, and then acrylic acid was added, and the mixture was reacted at 80°C for 2 hours. Acetone was added, and the mixture was allowed to stand for 15 minutes. The mixture was centrifuged at 7000 rpm for 1 minute, and dried at 55°C for 2 hours to obtain a modified silk fibroin; wherein the mass of ammonium persulfate was 0.8% of the mass of the silk fibroin solution, the mass of acrylic acid was 2% of the mass of the silk fibroin solution, and the mass of acetone was 25% of the mass of the silk fibroin solution;

[0051] Modified silk fibroin and deionized water in a mass ratio of 1.0:100 were mixed and stirred at 150 rpm for 2 minutes to obtain a modified silk fibroin solution. Disuccinimidyl glutarate and graphene oxide were added to the modified silk fibroin solution, stirred at 200 rpm for 8 minutes, reacted at 80°C for 2 hours, centrifuged at 10,000 rpm for 3 minutes, washed with ethanol five times, and dried at 100°C for 3 hours to obtain the filler; wherein the mass of disuccinimidyl glutarate was 0.3% of the mass of the modified silk fibroin solution, and the mass of the graphene oxide was 8% of the mass of the modified silk fibroin solution.

[0052] The auxiliary agent in step S2 is prepared by compounding ethylene glycol diglycidyl ether, modified styrene-butadiene-vinyl pyridine and dimethylbenzylamine in a mass ratio of 3:6:1.

[0053] Wherein, modified styrene-butadiene-vinyl pyridine is prepared by the following method:

[0054] A1. Styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene were mixed and stirred at 70°C and 200 rpm for 3 h to obtain a mixed solution 1. The solution was cooled to room temperature, and hydroquinone was added. The mixture was allowed to stand for 5 min, and vacuum distilled. The mixture was dried at 80°C for 4 h to obtain a styrene-butadiene-vinyl pyridine containing epoxy groups. The mass ratio of styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene was 4:5:2:0.5:0.2:60, and the mass of hydroquinone was 2% of the mass of the mixed solution 1.

[0055] A2. Styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran containing an epoxy group were mixed and stirred at a speed of 200 rpm for 10 min to obtain a mixed solution 2. Triethylamine was then added and the mixture was stirred at 80° C. for 8 h. The stirring rate was controlled to be 300 rpm. After cooling to room temperature, the mixture was centrifuged at a speed of 10,000 rpm for 3 min, washed with ethanol 5 times, and dried at 80° C. for 6 h to obtain a modified styrene-butadiene-vinyl pyridine; wherein the mass ratio of styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran was 4:0.4:60, and the mass of triethylamine was 0.2% of the mass of the mixed solution 2.

[0056] Example 3

[0057] A preparation process of a composite current collector comprises the following steps:

[0058] S1. Add 70 parts of PET resin, 35 parts of polypropylene, 5 parts of maleic anhydride grafted polypropylene, 2 parts of a cross-linking agent, 10 parts of a filler, 1 part of an antioxidant and 0.7 parts of a lubricant into a high-speed mixer, and stir at a speed of 1100 rpm for 30 minutes to obtain a premix; add the premix into a twin-screw extruder for melt extrusion at a melt temperature of 220°C, cast molding, and then obtain a base film layer with a thickness of 4 μm through a biaxial stretching process; wherein the cross-linking agent is diphenylmethane diisocyanate, the antioxidant is phenyltriazole, the lubricant is methylphenyl silicone oil, the stretching temperature is 90°C, the stretching rate is 10 cm / s, the heat setting temperature is 200°C, and the stretching ratio is 4:1;

[0059] S2. The slurry was coated on both surfaces of the base film layer using a slot extruder, and then dried at 85° C. for 1.5 hours and kept at 130° C. for 40 minutes to obtain a bonding layer with a thickness of 3 μm; wherein the slurry was prepared by mixing the following raw materials in parts by mass: 60 parts of a water-based epoxy resin, 2 parts of an auxiliary agent, 7 parts of zirconium oxide, 0.8 parts of a surfactant, and 7 parts of a curing agent, wherein the surfactant was polyalkylene hydroxylammonium acrylate and the curing agent was isophorone diamine;

[0060] S3. sputtering metal copper on the surface of the bonding layer to form a metal layer with a thickness of 1 μm, thereby obtaining a composite film; wherein the sputtering time of the metal copper is 7 minutes, the sputtering power is 490 W, the sputtering voltage is 180 V, and the sputtering temperature is 170°C;

[0061] S4. Place the composite film with the metal layer in a coating device, and evenly apply the coating liquid to the surface of the metal layer through a die coating process. Dry it at 80°C for 1.5 hours to form a protective layer with a thickness of 25 nm, and finally obtain a composite current collector; wherein the coating liquid is prepared by mixing carbon nanotubes and N-methylpyrrolidone in a mass ratio of 0.4:100.

[0062] Wherein, the filler in step S1 is prepared by the following method:

[0063] Silk fibroin in a mass ratio of 1:35 and a 10% calcium chloride solution were mixed, and the mixture was stirred at 35°C and 150 rpm for 12 minutes to obtain a silk fibroin solution; ammonium persulfate was added, and the mixture was stirred at 150 rpm for 12 minutes, and then acrylic acid was added, and the mixture was reacted at 75°C for 3 hours. Acetone was added, and the mixture was allowed to stand for 12 minutes. The mixture was centrifuged at 6000 rpm for 2 minutes, and dried at 50°C for 2.5 hours to obtain a modified silk fibroin; wherein the mass of ammonium persulfate was 0.6% of the mass of the silk fibroin solution, the mass of acrylic acid was 1.5% of the mass of the silk fibroin solution, and the mass of acetone was 20% of the mass of the silk fibroin solution;

[0064] Modified silk fibroin and deionized water in a mass ratio of 0.8:100 were mixed and stirred at 120 rpm for 3 minutes to obtain a modified silk fibroin solution. Disuccinimidyl glutarate and graphene oxide were added to the modified silk fibroin solution, stirred at 150 rpm for 10 minutes, reacted at 75°C for 2.5 hours, centrifuged at 9000 rpm for 4 minutes, washed four times with ethanol, and dried at 90°C for 4 hours to obtain the filler; wherein the mass of disuccinimidyl glutarate was 0.2% of the mass of the modified silk fibroin solution, and the mass of the graphene oxide was 6% of the mass of the modified silk fibroin solution.

[0065] The auxiliary agent in step S2 is prepared by compounding ethylene glycol diglycidyl ether, modified styrene-butadiene-vinyl pyridine and dimethylbenzylamine in a mass ratio of 2:5:0.8.

[0066] Wherein, modified styrene-butadiene-vinyl pyridine is prepared by the following method:

[0067] A1. Styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene were mixed and stirred at 60°C and 150 rpm for 4 hours to obtain a mixed solution 1. The mixture was cooled to room temperature, and hydroquinone was added. The mixture was allowed to stand for 4 minutes, and vacuum distilled. The mixture was dried at 70°C for 6 hours to obtain a styrene-butadiene-vinyl pyridine containing epoxy groups. The mass ratio of styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene was 3:5:1.5:0.4:0.1:50, and the mass of hydroquinone was 1.5% of the mass of the mixed solution 1.

[0068] A2. Styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran containing an epoxy group were mixed and stirred at a speed of 150 rpm for 12 min to obtain a mixed solution 2. Triethylamine was then added and the mixture was stirred at 70°C for 7 h. The stirring rate was controlled to be 200 rpm. After cooling to room temperature, the mixture was centrifuged at a speed of 9000 rpm for 4 min, washed four times with ethanol, and dried at 70°C for 5 h to obtain a modified styrene-butadiene-vinyl pyridine; wherein the mass ratio of styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran was 3:0.3:50, and the mass of triethylamine was 0.1% of the mass of the mixed solution 2.

[0069] Comparative Example 1

[0070] Comparative Example 1 is the same as Example 1, except that the preparation method of the filler is different, as follows:

[0071] The filler is prepared by the following method:

[0072] Silk fibroin in a mass ratio of 0.9:30 and a calcium chloride solution with a mass fraction of 8% were mixed, and the mixture was stirred at 30°C and 100 rpm for 10 minutes to obtain a silk fibroin solution; ammonium persulfate was added, and the mixture was stirred at 100 rpm for 15 minutes, and then acrylic acid was added, and the mixture was reacted at 70°C for 4 hours. Acetone was added, and the mixture was allowed to stand for 10 minutes. The mixture was centrifuged at 5000 rpm for 3 minutes, and dried at 45°C for 3 hours to obtain a modified silk fibroin; wherein the mass of ammonium persulfate was 0.5% of the mass of the silk fibroin solution, the mass of acrylic acid was 1% of the mass of the silk fibroin solution, and the mass of acetone was 15% of the mass of the silk fibroin solution;

[0073] Modified silk fibroin and deionized water in a mass ratio of 0.5:100 were mixed and stirred at 100 rpm for 3 minutes to obtain a modified silk fibroin solution. Graphene oxide was added to the modified silk fibroin solution, stirred at 100 rpm for 12 minutes, reacted at 70° C. for 3 hours, centrifuged at 8000 rpm for 5 minutes, washed three times with ethanol, and dried at 80° C. for 5 hours to obtain the filler; wherein the mass of the graphene oxide was 5% of the mass of the modified silk fibroin solution.

[0074] Comparative Example 2

[0075] Comparative Example 2 is the same as Example 1, except that the preparation method of the filler is different, as follows:

[0076] The filler is prepared by the following method:

[0077] Silk fibroin and deionized water in a mass ratio of 0.5:100 were mixed and stirred at 100 rpm for 3 minutes to obtain a silk fibroin solution. Disuccinimidyl glutarate and graphene oxide were added to the silk fibroin solution, stirred at 100 rpm for 12 minutes, reacted at 70°C for 3 hours, centrifuged at 8000 rpm for 5 minutes, washed three times with ethanol, and dried at 80°C for 5 hours to obtain the filler; wherein the mass of disuccinimidyl glutarate was 0.1% of the mass of the silk fibroin solution, and the mass of the graphene oxide was 5% of the mass of the silk fibroin solution.

[0078] Comparative Example 3

[0079] Comparative Example 3 is the same as Example 1, except that the preparation method of the modified styrene-butadiene-vinyl pyridine is different, as follows:

[0080] Modified styrene-butadiene-vinyl pyridine is prepared by the following method:

[0081] A1. Styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene were mixed and stirred at 50°C and 100 rpm for 5 h to obtain a mixed solution 1. The solution was cooled to room temperature, and hydroquinone was added. The mixture was allowed to stand for 5 min, and vacuum distilled. The mixture was dried at 60°C for 6 h to obtain a styrene-butadiene-vinyl pyridine containing epoxy groups. The mass ratio of styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene was 2:3:1:0.3:0.1:40, and the mass of hydroquinone was 1% of the mass of the mixed solution 1.

[0082] A2. Styrene-butadiene-vinyl pyridine containing an epoxy group and tetrahydrofuran were mixed, stirred at a speed of 100 rpm for 15 min to obtain a mixed solution 2, and triethylamine was added. The mixture was stirred at 60° C. for 8 h, with a stirring rate of 100 rpm. After cooling to room temperature, the mixture was centrifuged at a speed of 8000 rpm for 5 min, washed three times with ethanol, and dried at 60° C. for 6 h to obtain a modified styrene-butadiene-vinyl pyridine; wherein the mass ratio of styrene-butadiene-vinyl pyridine containing an epoxy group to tetrahydrofuran was 2:40, and the mass of triethylamine was 0.1% of the mass of the mixed solution 2.

[0083] Comparative Example 4

[0084] Comparative Example 4 is the same as Example 1, except that the preparation method of the modified styrene-butadiene-vinyl pyridine is different, as follows:

[0085] Modified styrene-butadiene-vinyl pyridine is prepared by the following method:

[0086] A1. Styrene, butadiene, vinyl pyridine, dibenzoyl peroxide, and xylene were mixed and stirred at 50°C and 100 rpm for 5 h to obtain a mixed solution 1. After cooling to room temperature, hydroquinone was added, the mixture was allowed to stand for 5 min, and vacuum distilled. The mixture was dried at 60°C for 6 h to obtain a styrene-butadiene-vinyl pyridine containing epoxy groups; wherein the mass ratio of styrene, butadiene, vinyl pyridine, dibenzoyl peroxide, and xylene was 2:3:1:0.1:40, and the mass of hydroquinone was 1% of the mass of the mixed solution 1.

[0087] A2. Styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran containing an epoxy group were mixed and stirred at a speed of 100 rpm for 15 min to obtain a mixed solution 2. Triethylamine was then added and the mixture was stirred at 60° C. for 8 h. The stirring rate was controlled to be 100 rpm. After cooling to room temperature, the mixture was centrifuged at a speed of 8000 rpm for 5 min, washed three times with ethanol, and dried at 60° C. for 6 h to obtain a modified styrene-butadiene-vinyl pyridine; wherein the mass ratio of styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran was 2:0.2:40, and the mass of triethylamine was 0.1% of the mass of the mixed solution 2.

[0088] Comparative Example 5

[0089] Comparative Example 5 is the same as Example 1, except that the auxiliary agent is prepared by compounding ethylene glycol diglycidyl ether and modified styrene-butadiene-vinyl pyridine in a mass ratio of 1:4.

[0090] Comparative Example 6

[0091] Comparative Example 6 is the same as Example 1, except that the auxiliary agent is prepared by compounding modified styrene-butadiene-vinyl pyridine and dimethylbenzylamine in a mass ratio of 4:0.5.

[0092] Comparative Example 7

[0093] Comparative Example 7 is the same as Example 1, except that the auxiliary agent is prepared by compounding ethylene glycol diglycidyl ether and dimethylbenzylamine in a mass ratio of 1:0.5.

[0094] Performance Testing

[0095] The following performance tests were performed on the composite current collectors prepared in Examples 1-3 and Comparative Examples 1-7:

[0096] Defective rate: the ratio of the number of unqualified products caused by membrane breakage during the preparation process to the total number of products;

[0097] Tensile strength: tested in accordance with GB / T1040.3-2006;

[0098] Adhesion strength between the base film layer and the metal layer in the composite current collector (N / cm): A layer of Permacel P-94 double-sided tape was adhered to a 1 mm thick aluminum foil, the composite current collector was adhered on top of the double-sided tape, and a layer of ethylene acrylic acid copolymer film (DuPont Nurcel0903, thickness of 50 μm) was covered on the composite current collector. 5 N / m 2, hot pressing at 120°C for 10 seconds, cooling to room temperature, and cutting into 150mm x 15mm strips. Finally, the ethylene acrylic acid copolymer film of the sample strip is fixed to the upper fixture of the tensile testing machine, and the rest of the film is fixed to the lower fixture. After fixing, the two are peeled at an angle of 180° and a speed of 100mm / min to test the peel force, that is, the adhesion between the modified polymer film and the metal layer;

[0099] Chemical stability: The square resistance of the composite current collector was tested using a four-probe square resistance meter. According to GB / T10125-2021, the composite current collector was placed in a neutral salt spray at a temperature of 35°C and a relative humidity of 95% for 48 hours, and the square resistance before and after placement was tested;

[0100] High temperature resistance: According to the GB / T1457-2005 test standard, the composite current collectors prepared in Examples 1-3 and Comparative Examples 1-7 were placed at 85°C for 7 days, and the square resistance before and after 7 days of storage was tested.

[0101] The test results are shown in the following table:

[0102] Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-7

[0103]

[0104]

[0105] It can be seen from the test results in Table 1 that in the present application, the graphene oxide treated with grafted modified silk fibroin is mixed with a polymer to construct a stable interface, which promotes the crystallization of the polymer. The base film prepared in this way has good mechanical properties and the bonding effect with the binding layer is improved. The use of the base film to prepare a composite current collector can reduce its defective rate, enhance the mechanical properties of the composite current collector, and significantly improve its corrosion resistance and high temperature resistance.

[0106] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A process for preparing a composite current collector, characterized in that: The following steps are involved: S1. Add PET resin, polypropylene, maleic anhydride grafted polypropylene, crosslinking agent, filler, antioxidant and lubricant to a high-speed mixer and stir for 25-40 minutes to obtain a premix; add the premix to a twin-screw extruder for melt extrusion, cast molding, and then obtain a base film layer through a biaxial stretching process; S2. Coating the slurry on both surfaces of the base film layer using a slot extruder, then drying at 80-90°C for 1-2 hours, and then keeping the temperature at 120-140°C for 30-45 minutes to obtain a bonding layer; S3, sputtering metallic copper on the surface of the bonding layer to form a metal layer with a thickness of 0.5-2 μm to obtain a composite film; S4, placing the composite film with the metal layer in a coating device, and evenly coating the surface of the metal layer with the coating liquid through a die coating process, drying to form a protective layer, and finally obtaining a composite current collector; The filler in step S1 is prepared by the following method: Silk fibroin and a calcium chloride solution with a mass fraction of 8-12% are mixed, heated and stirred for 10-15 minutes to obtain a silk fibroin solution; ammonium persulfate is then added, heated and stirred until uniform, acrylic acid is added, heated and reacted for 2-4 hours, acetone is added, allowed to stand, centrifuged, and dried to obtain modified silk fibroin; Mixing modified silk fibroin and deionized water at a mass ratio of 0.5-1:100 to obtain a modified silk fibroin solution, adding disuccinimidyl glutarate and graphene oxide to the modified silk fibroin solution, heating to react for 2-3 hours, centrifuging, washing, and drying to obtain the filler; The slurry in step S2 is prepared by mixing the following raw materials in parts by mass: 50-70 parts of water-based epoxy resin, 1-3 parts of auxiliary agent, 6-8 parts of zirconium oxide, 0.5-1 parts of surfactant and 5-8 parts of curing agent; The auxiliary agent is prepared by compounding ethylene glycol diglycidyl ether, modified styrene-butadiene-vinyl pyridine and dimethylbenzylamine in a mass ratio of 1-3:4-6:0.5-1; The modified styrene-butadiene-vinyl pyridine is prepared by the following method: A1. Styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene are mixed, heated and stirred for 3-5 hours to obtain a mixed solution 1. After cooling, hydroquinone is added, stirred evenly, and allowed to stand for 3-5 minutes. The mixture is distilled under reduced pressure and dried to obtain styrene-butadiene-vinyl pyridine containing epoxy groups, wherein the mass ratio of styrene, butadiene, vinyl pyridine, glycidyl methacrylate, dibenzoyl peroxide, and xylene is 2-4:3-5:0.5-0.8:0.3-0.5:0.1-0.2:40-60, and the mass of hydroquinone is 1-2% of the mass of the mixed solution 1. A2, styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran containing epoxy group are mixed, stirring obtains mixed solution 2, triethylamine is added, heated and stirred 5-8h, cooling, centrifugal, washing, drying obtains described modified styrene-butadiene-vinyl pyridine, wherein, the mass ratio of styrene-butadiene-vinyl pyridine, PEG-400 and tetrahydrofuran containing epoxy group is 2-4:0.2-0.4:40-60, and the mass of triethylamine is 0.1-0.2% of the mass of mixed solution 2.

2. The preparation process of the composite current collector according to claim 1, characterized in that: The raw materials in step S1 are as follows in parts by weight: 60-80 parts of PET resin, 30-40 parts of polypropylene, 4-6 parts of maleic anhydride grafted polypropylene, 1-3 parts of a cross-linking agent, 8-12 parts of a filler, 0.5-2 parts of an antioxidant, and 0.5-0.8 parts of a lubricant.

3. The preparation process of the composite current collector according to claim 1, characterized in that: The mass ratio of the silk fibroin to the calcium chloride solution is 0.9-1.2:30-40; the mass of the ammonium persulfate is 0.5-0.8% of the mass of the silk fibroin solution, the mass of the acrylic acid is 1-2% of the mass of the silk fibroin solution, and the mass of the acetone is 15-25% of the mass of the silk fibroin solution.

4. The preparation process of the composite current collector according to claim 1, characterized in that: The mass of the disuccinimidyl glutarate is 0.1-0.3% of the mass of the modified silk fibroin solution, and the mass of the graphene oxide is 5-8% of the mass of the modified silk fibroin solution.

5. The preparation process of the composite current collector according to claim 1, characterized in that: The coating liquid in step S4 is prepared by mixing carbon nanotubes and N-methylpyrrolidone in a mass ratio of 0.2-0.5:

100.

6. A composite current collector, characterized in that: Prepared according to the preparation process according to any one of claims 1 to 5.

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