Composite current collector base film with high chemical stability and preparation method thereof

Abstract

The invention relates to the technical field of composite current collectors, and discloses a high-chemical-stability composite current collector base film and a preparation method thereof. The composite current collector base film is prepared from the following raw materials in parts by weight: 70 to 90 parts of PET (Polyethylene Terephthalate) resin, 10 to 20 parts of PP (Polypropylene) resin, 8 to 12 parts of modified organic silicon, 6 to 10 parts of reinforcing filler, 0.3 to 0.6 part of lubricating agent, 0.5 to 1.5 parts of antioxidant and 1.5 to 2.5 parts of compatilizer, according to the base film, PET resin serves as a main raw material, PP resin, modified organic silicon, reinforcing filler and other auxiliaries are added, the base film has excellent chemical stability under the combined action, and meanwhile the poor acid and alkali resistance of a traditional PET base film is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite current collectors, and particularly relates to a composite current collector base film with high chemical stability and a preparation method thereof. Background Art

[0002] A composite current collector is a new type of battery material with a "sandwich" structure, which consists of a polymer material layer and a metal conductive layer. It usually uses a polymer material (such as PET, PP or PI) as the middle layer, and metal conductive layers (such as aluminum or copper) are plated on both the upper and lower surfaces. Among them, the middle layer material is usually a film material synthesized from PET resin, which has characteristics such as light weight, corrosion resistance, and flexible processing, and is regarded as a potential candidate for matrix materials.

[0003] However, pure PET films still face challenges in applications: insufficient chemical stability. PET itself has a certain tolerance to weak acids, weak bases, and some organic solvents, but in the presence of high-concentration lithium salts (such as LiPF 6 ), ester solvents (such as carbonates), strong acids and bases, and high-temperature cycling conditions, its molecular chains may undergo swelling or hydrolysis reactions, resulting in the decline of the mechanical properties of the base film and interface failure, and further leading to the decrease of the conductivity of the current collector and even battery failure. Moreover, the insufficient chemical stability of the PET base film also affects the adhesion between the PET base film and the metal layer, resulting in poor adhesion between the film and the metal layer, and further affecting battery performance. Therefore, researchers need to develop a composite current collector base film with high chemical stability and high adhesion to meet practical applications. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a composite current collector base film with high chemical stability and a preparation method thereof.

[0005] The object of the present invention can be achieved by the following technical solutions: A composite current collector base film with high chemical stability, comprising the following raw materials in parts by weight: 70-90 parts of PET resin, 10-20 parts of PP resin, 8-12 parts of modified silicone, 6-10 parts of reinforcing filler, 0.3-0.6 parts of lubricant, 0.5-1.5 parts of antioxidant, and 1.5-2.5 parts of compatibilizer; The lubricant is pentaerythritol stearate; The antioxidant is one of antioxidant 1010 or antioxidant 168; The compatibilizer is maleic anhydride grafted polypropylene; The modified silicone is prepared by the following steps: Step A1: Stir p-aminophenol, triethylamine, and dichloromethane evenly, transfer them to an ice-water bath, add dimethyl chlorophosphate and stir for 1 h, then raise the temperature to 25 - 35 °C and stir for 12 - 16 h. Filter, wash, and dry to obtain the phosphate ester product; Further, in step A1, the molar ratio of p-aminophenol, dimethyl chlorophosphate, and triethylamine is 1:1:1; Step A2: Stir epichlorohydrin and methanol evenly, raise the temperature to 65 °C under an oil bath condition, add 1-vinylimidazole and stir for 6 h. Carry out vacuum distillation, wash, and collect the product. Add the phosphate ester product, tetrabutylammonium bromide, and DMF (N,N-dimethylformamide) to the product and stir evenly, then raise the temperature to 90 °C and react for 4 h. Filter, wash, and dry to obtain the imidazole-phosphate ester product; Further, in step A2, the dosage ratio of epichlorohydrin to 1-vinylimidazole is 10 - 20 mL:3 - 6 mL, the molar ratio of the phosphate ester product to 1-vinylimidazole is 1:1, and the mass of tetrabutylammonium bromide is 0.1 - 0.3 g; Step A3: Under a nitrogen atmosphere, mix and stir dimethyldimethoxysilane, 2,4,6,8-tetramethylcyclotetrasiloxane, tridecafluorooctyltrimethoxysilane, and trifluoromethanesulfonic acid for reaction for 24 h. Add anhydrous sodium bicarbonate and stir for 1 h, then add anhydrous sodium sulfate and stir for 1 h. Filter, rotary evaporate, and dry to collect the organosilicon precursor; then drop the organosilicon precursor into a mixed solution containing the imidazole-phosphate ester product, KARSTEDT catalyst, and toluene, and react at 90 - 100 °C under nitrogen for 18 - 24 h. Rotary evaporate, purify, and dry to obtain the modified organosilicon; Further, in step A3, the molar ratio of dimethyldimethoxysilane, 2,4,6,8-tetramethylcyclotetrasiloxane, and tridecafluorooctyltrimethoxysilane in the organosilicon precursor is 1 - 2:3 - 6:0.5 - 1, trifluoromethanesulfonic acid accounts for 0.25 wt% - 0.35 wt% of the total amount of reactants, anhydrous sodium bicarbonate and anhydrous sodium sulfate respectively account for 20 wt% - 30 wt% and 35 wt% - 45 wt% of the total amount of reactants; Further, in step A3, the molar ratio of the imidazole-phosphate ester product to 2,4,6,8-tetramethylcyclotetrasiloxane in the modified organosilicon is 5 - 10:1, and the KARSTEDT catalyst accounts for 0.001 wt% - 0.003 wt% of the total amount of reactants.

[0006] The reinforcing filler is prepared by the following steps: Step B1: Ultrasonically disperse chitosan evenly in water, add h-BN (hexagonal boron nitride) and ultrasonically treat for 30 min, transfer to a planetary ball mill and ball mill at a speed of 450 rpm for 12 h, let it stand, take the upper layer solution for suction filtration, and dry to obtain the pretreated boron nitride nanosheets; The surface of boron nitride after wet ball milling treatment contains chitosan with good dispersibility, which can improve the dispersibility of boron nitride; Further, in step B1, the dosage ratio of chitosan, water and h-BN is 3-5 g: 50 mL: 2-4 g; Step B2: Mix pyromellitic dianhydride and 4,4'-diaminodiphenyl ether in DMF and stir in an ice-water bath for 30-50 min to obtain a PAA precursor solution. Then add a modified boron nitride nanosheet DMF solution to the PAA precursor solution, heat to 60 °C and age at a constant temperature for 45 h, filter and dry to obtain PAA@boron nitride. Then heat PAA@boron nitride in a nitrogen atmosphere at 320-340 °C for 1-1.5 h to obtain the reinforcing filler; Further, in step B2, the dosage ratio of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and modified boron nitride nanosheets is 0.101-0.203 mol: 0.1-0.2 mol: 200 mL; Further, in the modified boron nitride nanosheet DMF solution, the dosage ratio of modified boron nitride nanosheets to DMF is 5-10 g: 200 mL; Further, the PAA in step B2 is polyamic acid.

[0007] Using boron nitride with good thermal conductivity as the matrix of the reinforcing filler can improve the thermal conductivity of the base film, enable the base film to effectively conduct and disperse heat, avoid local overheating, and thus improve the thermal stability of the battery; it can also keep the structure stable in a high-temperature environment and reduce mechanical stress caused by thermal expansion or contraction.

[0008] Using polyimide with good acid and alkali resistance to protect boron nitride can reduce the corrosion of boron nitride by acids and alkalis, thereby improving the acid resistance of the base film and further improving the chemical stability of the base film.

[0009] A preparation method of a high chemical stability composite current collector base film includes the following steps: Weigh the raw materials by weight. Heat and mix PET resin, PP resin, modified silicone, reinforcing filler, lubricant, antioxidant and compatibilizer evenly at 230-240 °C, then transfer to a twin-screw extruder for extrusion, casting and calendaring to form a thick film base film, and then perform biaxial stretching on the thick film base film to form a composite current collector base film; Further, the extrusion temperature of the twin-screw extruder is 260-270 °C, and the stretching ratio in biaxial stretching is 3.5-4:1.

[0010] The beneficial effects of the present invention: The composite current collector base film in this application uses PET resin as the main raw material, and adds PP resin, modified silicone, reinforcing filler and other additives. Through their combined action, the base film has excellent chemical stability, while improving the poor acid and alkali resistance of traditional PET base films.

[0011] The modified silicone is introduced into the current collector base film in this application. By using the fluorine element, phosphate group and imidazole structure in the modified silicone and their synergistic effect, the chemical stability of the base film is improved. Among them, a strongly polar phosphate group is introduced into the side chain. The phosphate can improve the adsorption ability of the base film to the metal layer by chemical bonding or physical adsorption with the metal surface, and at the same time endow the base film with certain flame retardant properties. The C-F bond with high bond energy can effectively resist the chemical corrosion of the electrolyte and still has excellent chemical stability under acidic and alkaline conditions. The Si-O bond in the main chain has a relatively high bond energy, and the higher the bond energy, the more stable it is, so that it is difficult to break in high-temperature or chemically corrosive environments and has good stability. In addition, the modified silicone can also physically entangle or chemically react with the resin molecular chain in the base film, thereby improving the density of the base film and making it difficult to be chemically corroded.

[0012] The introduction of the reinforcing filler in this application can form protrusions on the surface of the base film, increasing the surface roughness of the base film, thereby improving the bonding force between the base film and the metal layer and reducing the shedding of the metal layer caused by insufficient adhesion. The reinforcing filler is evenly dispersed in the base film, and forms a physical barrier in the base film by virtue of its layered structure and dense structure to hinder the penetration of corrosive media. At the same time, the filler itself has high chemical stability and can maintain the structural integrity in the corrosive environment, thereby improving the chemical stability of the base film. Detailed implementation mode

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0014] Example 1: The modified silicone is prepared by the following steps: Step A1: Stir 0.1 mol of p-aminophenol, 0.1 mol of triethylamine and 100 mL of dichloromethane evenly, transfer them to an ice-water bath, add 0.1 mol of dimethyl chlorophosphate and stir for 1 h, then raise the temperature to 25 °C and stir for 12 h. Filter, wash and dry to obtain the phosphate product; Step A2: Stir 10 mL of epichlorohydrin and 100 mL of methanol evenly, heat up to 65 °C under an oil bath condition, add 3 mL of 1-vinylimidazole and stir for 6 h, carry out vacuum distillation and washing, collect the product, add 0.1 mol of phosphate product, 0.1 g of tetrabutylammonium bromide and 50 mL of DMF to the product, stir evenly, and heat up to 90 °C for reaction for 4 h, filter, wash and dry to obtain the imidazole-phosphate product; Step A3: Under nitrogen condition, mix 0.1 mol of dimethyldimethoxysilane, 0.3 mol of 2,4,6,8-tetramethylcyclotetrasiloxane, 0.05 mol of trifluorooctyltrimethoxysilane and trifluoromethanesulfonic acid and stir for reaction for 24 h, add anhydrous sodium bicarbonate and stir for 1 h, then add anhydrous sodium sulfate and stir for 1 h, filter, rotary evaporate and dry to collect the organosilicon precursor; then drop the organosilicon precursor into a mixed solution containing 0.9 mol of imidazole-phosphate product, KARSTEDT catalyst and 200 mL of toluene, and react at 90 °C under nitrogen for 18 h, rotary evaporate, purify and dry to obtain the modified organosilicon. The trifluoromethanesulfonic acid accounts for 0.25 wt% of the total amount of reactants, the anhydrous sodium bicarbonate and anhydrous sodium sulfate respectively account for 20 wt% and 35 wt% of the total amount of reactants, and the KARSTEDT catalyst accounts for 0.001 wt% of the total amount of reactants.

[0015] The reinforcing filler is prepared by the following steps: Step B1: Ultrasonically disperse 3 g of chitosan evenly in 50 mL of water, add 2 g of h-BN and carry out ultrasonic treatment for 30 min, transfer to a planetary ball mill and ball mill at a speed of 450 rpm for 12 h, let it stand, take the upper layer solution for suction filtration and drying to obtain the pretreated boron nitride nanosheets; Step B2: Mix 0.101 mol of pyromellitic dianhydride and 0.1 mol of 4,4'-diaminodiphenyl ether in 200 mL of DMF, and stir in an ice-water bath for 30 min to obtain the PAA precursor solution. Then add the DMF solution of modified boron nitride nanosheets to the PAA precursor solution, and heat up to 60 °C for constant-temperature aging for 45 h, filter and dry to prepare PAA@boron nitride. Then heat PAA@boron nitride at 320 °C for 1 h under a nitrogen atmosphere to obtain the reinforcing filler; Furthermore, the dosage ratio of the modified boron nitride nanosheets to DMF in the DMF solution of modified boron nitride nanosheets is 5 g:200 mL.

[0016] Example 2: The modified organosilicon is prepared by the following steps: Step A1: Stir 0.1 mol of p-aminophenol, 0.1 mol of triethylamine and 100 mL of dichloromethane evenly, transfer to an ice-water bath, add 0.1 mol of dimethyl chlorophosphate and stir for 1 h, then heat up to 30 °C and stir for 14 h, filter, wash and dry to obtain the phosphate product; Step A2: Stir 15 mL of epichlorohydrin and 100 mL of methanol evenly, heat up to 65 °C under an oil bath condition, add 4.5 mL of 1-vinylimidazole and stir for 6 h, carry out vacuum distillation and washing, collect the product, add 0.1 mol of phosphate ester product, 0.2 g of tetrabutylammonium bromide and 50 mL of DMF to the product, stir evenly, and heat up to 90 °C for reaction for 4 h, filter, wash and dry to obtain the imidazole-phosphate ester product; Step A3: Under a nitrogen condition, mix and stir 0.15 mol of dimethyldimethoxysilane, 0.45 mol of 2,4,6,8-tetramethylcyclotetrasiloxane, 0.075 mol of trifluorooctyltrimethoxysilane and trifluoromethanesulfonic acid for reaction for 24 h, add anhydrous sodium bicarbonate and stir for 1 h, then add anhydrous sodium sulfate and stir for 1 h, filter, rotary evaporate and dry to collect the organosilicon precursor; then drop the organosilicon precursor into a mixed solution containing 1.8 mol of imidazole-phosphate ester product, KARSTEDT catalyst and 200 mL of toluene, and react at 95 °C under nitrogen for 21 h, rotary evaporate, purify and dry to obtain the modified organosilicon. The trifluoromethanesulfonic acid accounts for 0.3 wt% of the total amount of reactants, the anhydrous sodium bicarbonate and anhydrous sodium sulfate respectively account for 25 wt% and 40 wt% of the total amount of reactants, and the KARSTEDT catalyst accounts for 0.002 wt% of the total amount of reactants.

[0017] The reinforcing filler is prepared by the following steps: Step B1: Ultrasonically disperse 4 g of chitosan evenly in 50 mL of water, add 3 g of h-BN and carry out ultrasonic treatment for 30 min, transfer to a planetary ball mill and ball mill at a speed of 450 rpm for 12 h, let it stand, take the upper layer solution for suction filtration and drying to obtain the pretreated boron nitride nanosheets; Step B2: Mix 0.151 mol of pyromellitic dianhydride and 0.15 mol of 4,4'-diaminodiphenyl ether in 200 mL of DMF, and stir in an ice-water bath for 40 min to obtain the PAA precursor solution. Then add the modified boron nitride nanosheet DMF solution to the PAA precursor solution, and heat up to 60 °C for constant-temperature aging for 45 h, filter and dry to prepare PAA@boron nitride. Then heat PAA@boron nitride at 330 °C for 1.2 h under a nitrogen atmosphere to obtain the reinforcing filler; Furthermore, the dosage ratio of the modified boron nitride nanosheets to DMF in the modified boron nitride nanosheet DMF solution is 7.5 g:200 mL.

[0018] Example 3: The modified organosilicon is prepared by the following steps: Step A1: Stir 0.1 mol of p-aminophenol, 0.1 mol of triethylamine, and 100 mL of dichloromethane evenly, transfer them to an ice-water bath, add 0.1 mol of dimethyl chlorophosphate, stir for 1 h, then raise the temperature to 35 °C and stir for 16 h. Filter, wash, and dry to obtain the phosphate ester product. Step A2: Stir 20 mL of epichlorohydrin and 100 mL of methanol evenly, raise the temperature to 65 °C under an oil bath condition, add 6 mL of 1-vinylimidazole, stir for 6 h, perform vacuum distillation and washing, collect the product. Add 0.1 mol of the phosphate ester product, 0.3 g of tetrabutylammonium bromide, and 50 mL of DMF to the product, stir evenly, and raise the temperature to 90 °C to react for 4 h. Filter, wash, and dry to obtain the imidazole-phosphate ester product. Step A3: Under a nitrogen atmosphere, mix and stir 0.2 mol of dimethyldimethoxysilane, 0.6 mol of 2,4,6,8-tetramethylcyclotetrasiloxane, 0.1 mol of trifluorooctyltrimethoxysilane, and trifluoromethanesulfonic acid and react for 24 h. Add anhydrous sodium bicarbonate and stir for 1 h, then add anhydrous sodium sulfate and stir for 1 h. Filter, rotary evaporate, and dry to collect the organosilicon precursor. Then, drop the organosilicon precursor into a mixed solution containing 3 mol of the imidazole-phosphate ester product, KARSTEDT catalyst, and 200 mL of toluene, and react at 100 °C under nitrogen for 24 h. Rotary evaporate, purify, and dry to obtain the modified organosilicon. The trifluoromethanesulfonic acid accounts for 0.35 wt% of the total amount of reactants, anhydrous sodium bicarbonate and anhydrous sodium sulfate respectively account for 30 wt% and 45 wt% of the total amount of reactants, and the KARSTEDT catalyst accounts for 0.003 wt% of the total amount of reactants.

[0019] The reinforcing filler is prepared by the following steps: Step B1: Ultrasonically disperse 5 g of chitosan evenly in 50 mL of water, add 4 g of h-BN, perform ultrasonic treatment for 30 min, transfer to a planetary ball mill, and ball mill at a speed of 450 rpm for 12 h. Let it stand, take the upper layer solution for suction filtration and drying to obtain the pretreated boron nitride nanosheets. Step B2: Mix 0.203 mol of pyromellitic dianhydride and 0.2 mol of 4,4'-diaminodiphenyl ether in 200 mL of DMF, and stir in an ice-water bath for 50 min to obtain the PAA precursor solution. Then, add the DMF solution of the modified boron nitride nanosheets to the PAA precursor solution, raise the temperature to 60 °C, and age at a constant temperature for 45 h. Filter and dry to obtain PAA@boron nitride. Then, heat PAA@boron nitride in a nitrogen atmosphere at 340 °C for 1.5 h to obtain the reinforcing filler. Furthermore, the dosage ratio of the modified boron nitride nanosheets to DMF in the DMF solution of the modified boron nitride nanosheets is 10 g:200 mL.

[0020] Example 4: A preparation method of a high chemical stability composite current collector base film comprises the following steps: Weigh the raw materials by weight parts. Heat and mix 70 parts of PET resin, 10 parts of PP resin, 8 parts of the modified silicone prepared in Example 1, 6 parts of the reinforcing filler prepared in Example 1, 0.3 part of pentaerythritol stearate, 0.5 part of antioxidant 1010, and 1.5 parts of maleic anhydride grafted polypropylene evenly at 230 °C, then transfer to a twin-screw extruder and extrude, cast, and form a thick film base at a temperature of 260 °C. Then, biaxially stretch the thick film base at a stretching ratio of 3.5:1 to form a composite current collector base film.

[0021] Example 5: A preparation method of a high chemical stability composite current collector base film comprises the following steps: Weigh the raw materials by weight parts. Heat and mix 80 parts of PET resin, 15 parts of PP resin, 10 parts of the modified silicone prepared in Example 2, 8 parts of the reinforcing filler prepared in Example 2, 0.5 part of pentaerythritol stearate, 1 part of antioxidant 168, and 2 parts of maleic anhydride grafted polypropylene evenly at 235 °C, then transfer to a twin-screw extruder and extrude, cast, and form a thick film base at a temperature of 265 °C. Then, biaxially stretch the thick film base at a stretching ratio of 4:1 to form a composite current collector base film.

[0022] Example 6: A preparation method of a high chemical stability composite current collector base film comprises the following steps: Weigh the raw materials by weight parts. Heat and mix 90 parts of PET resin, 20 parts of PP resin, 12 parts of the modified silicone prepared in Example 3, 10 parts of the reinforcing filler prepared in Example 3, 0.6 part of pentaerythritol stearate, 1.5 parts of antioxidant 168, and 2.5 parts of maleic anhydride grafted polypropylene evenly at 240 °C, then transfer to a twin-screw extruder and extrude, cast, and form a thick film base at a temperature of 270 °C. Then, biaxially stretch the thick film base at a stretching ratio of 4:1 to form a composite current collector base film.

[0023] Comparative Example 1: This comparative example is a composite current collector base film. The difference from Example 6 is that h-BN is used instead of the reinforcing filler prepared in Example 3, and the rest are the same.

[0024] Comparative Example 2: This comparative example is a composite current collector base film. The difference from Example 6 is that commercially available silicone is used instead of the modified silicone prepared in Example 3, and the rest are the same.

[0025] Comparative Example 3: This comparative example is a composite current collector base film. The difference from Example 6 is that the modified silicone prepared in Example 3 and the reinforcing filler prepared in Example 3 are not added, and the rest are the same.

[0026] The composite current collector base films prepared in Examples 4-6 and Comparative Examples 1-3 were subjected to performance tests: Tensile property test: The tensile strength test was carried out according to ASTM D638-2014; Adhesion property test: Copper was magnetron sputtered on the composite current collector base films prepared in Examples 4-6 and Comparative Examples 1-3 to form a 0.2 mm copper plating layer on the composite current collector base film, and an adhesion / stripping experiment was carried out with 3M tape, and the number of stripping times was recorded; Chemical property test: The composite current collector base films were respectively cut into samples of 10 cm×10 cm in size and soaked in a 5wt% HCl solution, a 5wt% NaOH solution and an electrolyte at 25°C for 7 days, then taken out, washed and dried, and the mass before and after was compared to calculate the mass loss rate. The electrolyte is a mixture formed by mixing ethylene carbonate, diethyl carbonate and methyl ethyl carbonate in a mass ratio of 1:2:1; Thermal stability test: The thermal shrinkage rate test of the composite current collector base film was carried out with reference to ASTM D1204. The smaller the value, the higher the heat resistance stability. The thermal shrinkage rate of the film after being placed at 150°C for 30 min was tested; The test results are shown in Table 1: Table 1: Performance test results

[0027] As can be seen from Table 1, the composite current collector base film prepared by the present invention has excellent tensile strength, adhesion, acid and alkali resistance, electrolyte resistance and thermal stability. Therefore, it has good application prospects as the base film of the current collector.

[0028] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of the present technology make various modifications or supplements to the described specific embodiments or use similar methods to replace them. As long as they do not deviate from the scope defined by the concept of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A composite current collector substrate with high chemical stability, characterized in that: The invention comprises the following raw materials in parts by weight: 70-90 parts of PET resin, 10-20 parts of PP resin, 8-12 parts of modified organic silicon, 6-10 parts of reinforcing filler, 0.3-0.6 parts of lubricant, 0.5-1.5 parts of antioxidant, and 1.5-2.5 parts of compatibilizer; the lubricant is pentaerythritol stearate, the antioxidant is one of antioxidant 1010 or antioxidant 168, and the compatibilizer is maleic anhydride grafted polypropylene; the modified organic silicon is prepared by a silicon dioxide addition reaction between an organic silicon precursor and an imidazole-phosphate product. The organosilicon precursor is obtained by the reaction of dimethyldimethoxysilane, 2,4,6,8-tetramethylcyclotetrasiloxane and tridecafluorooctyltrimethoxy; the imidazole-phosphate product is obtained by the reaction of epichlorohydrin, 1-vinylimidazole and a phosphate product; the phosphate product is obtained by the reaction of p-aminophenol and dimethyl chlorophosphate; the reinforcing filler is obtained by the reaction of pyromellitic acid, 4,4'-diaminodiphenyl ether and pre-treated boron nitride nanosheets; the pre-treated boron nitride nanosheets are obtained by wet ball milling of h-BN and chitosan.

2. The high chemical stability composite current collector base film according to claim 1, characterized in that: The modified silicone is prepared by the following steps: Step A1, stir p-aminophenol, triethylamine and dichloromethane evenly, transfer to an ice water bath, add dimethyl chlorophosphate and stir for 1 hour, then heat to 25-35° C. and stir for 12-16 hours, filter, wash and dry to obtain a phosphate product; Step A2, epichlorohydrin and methanol are stirred evenly, heated to 65°C under oil bath conditions, 1-vinylimidazole is added and stirred for 6 hours, distilled under reduced pressure, washed, and the product is collected, and the phosphate product, tetrabutylammonium bromide and DMF are added to the product and stirred evenly, and the temperature is raised to 90°C for reaction for 4 hours, filtered, washed, and dried to obtain the imidazole-phosphate product; Step A3, under nitrogen conditions, dimethyldimethoxysilane, 2,4,6,8-tetramethylcyclotetrasiloxane, tridecafluorooctyltrimethoxysilane and trifluoromethanesulfonic acid are mixed and stirred for 24 hours, anhydrous sodium bicarbonate is added and stirred for 1 hour, and then anhydrous sodium sulfate is added and stirred for 1 hour, filtered, rotary evaporated, and dried to collect the organosilicon precursor; then the organosilicon precursor is added dropwise to a mixed solution containing imidazole-phosphate product, KARSTEDT catalyst and toluene, and reacted under nitrogen at 90-100°C for 18-24 hours, rotary evaporated, purified, and dried to obtain modified organosilicon.

3. A composite current collector substrate with high chemical stability according to claim 2, characterized in that: In step A1, the molar ratio of p-aminophenol, dimethyl chlorophosphate and triethylamine is 1:1:

1.

4. The high chemical stability composite current collector base film according to claim 2, characterized in that: In step A2, the dosage ratio of epichlorohydrin and 1-vinylimidazole is 10-20mL:3-6mL, the molar ratio of the phosphate product and 1-vinylimidazole is 1:1, and the mass of tetrabutylammonium bromide is 0.1-0.3g.

5. The high chemical stability composite current collector base film according to claim 2, characterized in that: In step A3, the molar ratio of dimethyldimethoxysilane, 2,4,6,8-tetramethylcyclotetrasiloxane and tridecafluorooctyltrimethoxysilane in the organosilicon precursor is 1-2:3-6:0.5-1, trifluoromethanesulfonic acid accounts for 0.25wt%-0.35wt% of the total amount of reactants, and anhydrous sodium bicarbonate and anhydrous sodium sulfate account for 20wt%-30wt% and 35wt%-45wt% of the total amount of reactants, respectively.

6. The high chemical stability composite current collector base film according to claim 2, characterized in that: Step A3, the molar ratio of the imidazole-phosphate product and 2,4,6,8-tetramethylcyclotetrasiloxane in the modified silicone is 5-10:1, and the KARSTEDT catalyst accounts for 0.001wt%-0.003wt% of the total reactants.

7. The high chemical stability composite current collector base film according to claim 1, characterized in that: The reinforcing filler is prepared by the following steps: Step B1, uniformly dispersing chitosan in water by ultrasonication, adding h-BN and ultrasonically treating for 30 min, transferring to a planetary ball mill and ball milling at a speed of 450 rpm for 12 h, standing, taking the upper layer solution by suction filtration, and drying to obtain pre-treated boron nitride nanosheets; Step B2, mixing pyromellitic anhydride and 4,4'-diaminodiphenyl ether in DMF, and stirring in an ice water bath for 30-50 minutes to obtain a PAA precursor solution, then adding a modified boron nitride nanosheet DMF solution to the PAA precursor solution, and heating to 60°C for constant temperature aging for 45 hours, filtering and drying to obtain PAA@boron nitride, and then heating PAA@boron nitride at 320-340°C for 1-1.5 hours under a nitrogen atmosphere to obtain a reinforced filler.

8. The high chemical stability composite current collector base film according to claim 7, characterized in that: In step B1, the usage ratio of chitosan, water and h-BN is 3-5 g:50 mL:2-4 g.

9. The high chemical stability composite current collector base film according to claim 7, characterized in that: In step B2, the dosage ratio of pyromellitic anhydride, 4,4'-diaminodiphenyl ether and modified boron nitride nanosheets is 0.101-0.203 mol: 0.1-0.2 mol: 200 mL, and the dosage ratio of modified boron nitride nanosheets and DMF in the modified boron nitride nanosheet DMF solution is 5-10 g: 200 mL.

10. A method for preparing a composite current collector substrate film with high chemical stability according to any one of claims 1 to 9, characterized in that: The following steps are involved: The raw materials are weighed by weight, and PET resin, PP resin, modified silicone, reinforcing filler, lubricant, antioxidant and compatibilizer are heated and mixed at 230-240°C, and then transferred to a twin-screw extruder for extrusion, casting and casting to form a thick base film, and then the thick base film is biaxially stretched to form a composite current collector base film. The extrusion temperature of the twin-screw extruder is 260-270°C, and the stretching ratio in the biaxial stretching is 3.5-4:1.

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