A lithium battery diaphragm coating based on nanomaterials and its application

Abstract

The present application discloses a lithium battery separator coating based on nanomaterials and its application, relating to the technical field of lithium battery separators. The coating raw materials include, by weight: 15-25 parts of polystyrene maleic anhydride copolymer modified polyvinylidene fluoride, 10-20 parts of polystyrene, 2-4 parts of nano silicon nitride, 3-6 parts of boehmite / alumina@silicon dioxide composite material, 1-2 parts of dispersant, and 65-90 parts of solvent. The lithium battery separator coating provided by the present application significantly improves the wettability and absorptivity of the separator to the electrolyte. At the same time, it also has excellent thermal stability, which can effectively prevent the separator from thermal shrinkage or melting under high temperature conditions, thereby significantly enhancing the safety performance of the battery.

Description

Technical Field

[0001] The present application relates to the field of lithium battery separator technology, and in particular to a lithium battery separator coating based on nanomaterials and its application. Background Art

[0002] Lithium batteries are high-performance, environmentally friendly batteries with high energy density and a long lifespan. Compared to traditional alkaline and nickel-metal hydride batteries, lithium batteries provide more stable and long-lasting power while being lightweight and portable.

[0003] Lithium batteries primarily consist of positive electrode materials, negative electrode materials, electrolyte, separator, and casing, with the separator being a crucial component. Traditional lithium battery separators primarily include polyethylene, polypropylene, and composite films. However, lithium batteries often operate at elevated temperatures during use. Once the temperature exceeds the operating temperature of the polyolefin separator, the separator undergoes three stages: shrinkage, cell closure, and melting. Because the temperature difference between the melting point and cell closure temperature of polyolefin films is relatively small, residual heat generated after cell closure can cause the separator temperature to continue to rise, potentially leading to meltdown and fire.

[0004] To address this issue, existing polyolefin battery separators are primarily modified by coating their surfaces with inorganic materials, heat-resistant polymers, or a combination of the two. This modification method allows the separator to retain its original shape after reaching the polyolefin's softening temperature, effectively preventing short circuits and significantly improving battery safety. Furthermore, a suitable coating can enhance the separator's affinity with the electrolyte, improving its absorption of the electrolyte and accelerating the ion exchange rate, thereby increasing battery power.

[0005] The Chinese invention patent with announcement number CN116435712B discloses a reinforced modified coating for lithium battery separators, its preparation method and lithium battery separators. The coating includes the following raw material components in parts by weight: 10-35 parts of modified reinforcing particles, 15-32 parts of polyvinylidene fluoride, 50-85 parts of solvent, and 1.5-12 parts of additives.

[0006] However, with respect to the above-mentioned related technologies, the inventors found that although commonly used adhesives such as polyvinylidene fluoride have good electrolyte compatibility and mechanical properties, their own thermal stability is relatively poor, and the bonding effect will be significantly reduced at high temperatures, affecting the bonding strength of the coating, thereby affecting the stability of the diaphragm, and its hydrophilicity is weak, and its electrolyte absorption performance is weak. Summary of the Invention

[0007] In order to solve the above technical problems, the present application provides a lithium battery diaphragm coating based on nanomaterials and its application.

[0008] This application provides a lithium battery separator coating based on nanomaterials, which adopts the following technical solution:

[0009] A lithium battery separator coating based on nanomaterials comprises raw materials, in parts by weight, 15-25 parts of polystyrene maleic anhydride copolymer modified polyvinylidene fluoride, 10-20 parts of polystyrene, 2-4 parts of nano silicon nitride, 3-6 parts of boehmite / alumina@silicon dioxide composite material, 1-2 parts of dispersant, and 65-90 parts of solvent.

[0010] Preferably, the raw materials include, by weight: 20 parts of polystyrene maleic anhydride copolymer modified polyvinylidene fluoride, 15 parts of polystyrene, 3 parts of nano-silicon nitride, 4.5 parts of boehmite / alumina@silicon dioxide composite material, 1.5 parts of dispersant, and 80 parts of solvent.

[0011] Preferably, the polystyrene maleic anhydride copolymer modified polyvinylidene fluoride is prepared from the following raw materials in parts by weight: 7-8 parts of polyvinylidene fluoride, 0.8-1.6 parts of polystyrene maleic anhydride copolymer, 7-9 parts of polyethylene glycol, and 35-45 parts of N,N-dimethylethylamine.

[0012] Preferably, the preparation method of the polystyrene maleic anhydride copolymer modified polyvinylidene fluoride comprises the following steps:

[0013] Add polyvinylidene fluoride and polystyrene maleic anhydride copolymer to N,N-dimethylethylamine and stir thoroughly until dissolved; then stir in a 50-60°C water bath for 5-7 hours; then add polyethylene glycol that has been dried at 50-70°C and stir to react for 20-30 hours; degas the product in a vacuum oven to obtain polystyrene maleic anhydride copolymer-modified polyvinylidene fluoride.

[0014] Preferably, the boehmite / alumina@silica composite material is prepared from the following raw materials in parts by weight: 0.17-0.34 parts of sodium aluminate, 30-50 parts of water, 0.5-1 parts of urea, and 0.1-0.2 parts of alumina@silica composite material.

[0015] Preferably, the alumina@silica composite material is prepared from the following raw materials in parts by weight: 0.2-0.5 parts of alumina microspheres, 31-55 parts of anhydrous ethanol, 3-5 parts of water, 1-2 parts of ammonia water, and 0.28-0.7 parts of ethyl orthosilicate.

[0016] Preferably, the method for preparing the alumina@silicon dioxide composite material comprises the following steps:

[0017] 0.2-0.5 parts of alumina microspheres are dispersed in a mixed solution of 21-35 parts of anhydrous ethanol and 3-5 parts of water, and ultrasonically treated for 3-5 minutes; then a mixed solution of 10-20 parts of anhydrous ethanol, 1-2 parts of ammonia water and 0.28-0.7 parts of tetraethyl orthosilicate is added, and ultrasonically treated at 30-50°C for 3-5 hours. The product is washed with deionized water and ethanol, and then vacuum-dried at 55-65°C for 8-10 hours to obtain an alumina@silica composite material.

[0018] Preferably, the preparation method of the boehmite / alumina@silica composite material comprises the following steps:

[0019] Sodium aluminate is added to water and stirred until completely dissolved, followed by addition of urea and stirring for 0.5-1.5 hours. Alumina@silica composite material is then added, ultrasonically dispersed, and reacted at 180-200°C for 5-8 hours. After the reaction, a solid product is obtained by centrifugation, washed several times with deionized water, and vacuum dried at 50-60°C for 12-16 hours to obtain a boehmite / alumina@silica composite material.

[0020] Preferably, the preparation method of the lithium battery separator coating comprises the following steps:

[0021] S1. The polystyrene was treated with ammonia plasma; to obtain modified polystyrene; the power of the ammonia plasma treatment was 200-400W; the treatment time was 120-180s; the ammonia flow rate was 200-300mL / min;

[0022] S2. Concentrated nitric acid was added to the nano-silicon nitride, stirred and heated at 60-90 ° C for 14-20h; after the reaction, cooled to room temperature, filtered, centrifuged and washed with deionized water until neutral, and dried to obtain acidified nano-silicon nitride powder;

[0023] S3. The polystyrene maleic anhydride copolymer modified polyvinylidene fluoride and modified polystyrene are added to the solvent and stirred at 70-80 ° C until completely dissolved; then the acidified nano-silicon nitride powder, boehmite / alumina@silica composite material and dispersant are added and stirred for 1-2 hours; then placed in a vacuum oven for degassing to obtain a lithium battery separator coating;

[0024] The solid-liquid ratio of the nano-silicon nitride to concentrated nitric acid in S2 is 0.2-0.4 g:1 mL.

[0025] This application provides an application of a lithium battery separator coating based on nanomaterials, which adopts the following technical solution:

[0026] An application of a lithium battery diaphragm coating based on nanomaterials, wherein the lithium battery diaphragm coating is used to coat the surface of a lithium battery diaphragm; the coating has a thickness of 5-10 μm.

[0027] In summary, this application includes at least one of the following beneficial technical effects:

[0028] 1. By adopting the above technical solution, the present application adopts a polystyrene maleic anhydride copolymer with good hydrophilicity and blends it with polyvinylidene fluoride, introduces polar groups such as carboxyl groups, and effectively improves the surface properties of PVDF and its compatibility with other materials; then by adding polyethylene glycol, its hydroxyl group reacts with the unreacted anhydride groups in the polystyrene maleic anhydride copolymer to undergo esterification reaction to form a graft copolymer, which effectively enhances the hydrophilicity of polyvinylidene fluoride, thereby effectively enhancing the liquid absorption rate of the lithium battery separator to the electrolyte.

[0029] 2. By adopting the above-mentioned technical solution, the present application first uses the sol-gel method to coat a layer of silica on the surface of alumina microspheres; then, with the assistance of urea, a liquid-phase hydrothermal synthesis method is used to successfully prepare a gradient-structured boehmite / alumina@silica composite material; it has excellent thermal stability, mechanical strength and chemical stability. The silica layer can improve the hydrophilicity of boehmite and its compatibility with thickeners, thereby increasing the liquid absorption rate of the diaphragm.

[0030] 3. By adopting the above-mentioned technical scheme, the present application treats polystyrene with ammonia plasma to perform hydrophilic modification on the surface of the polystyrene material; and acidifies the nano silicon nitride powder with concentrated acid; introduces more hydroxyl groups on the surface of silicon nitride to enhance its hydrophilicity, thereby effectively improving its dispersibility and compatibility in the system; the obtained lithium battery diaphragm coating based on nanomaterials has a larger specific surface area and better hydrophilicity, which can improve the electrolyte wettability of the diaphragm and enhance the electrolyte absorption rate, and at the same time has good thermal stability, which can prevent the diaphragm from thermal shrinkage or melting at high temperatures, thereby improving the safety factor of the battery. DETAILED DESCRIPTION

[0031] The present application is further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0032] The chemical reagents used in the preparation examples, embodiments and comparative examples provided by the present invention are all commercially available products, and their brands and manufacturers are as follows:

[0033] Polystyrene maleic anhydride copolymer, Shanghai MacLean Biochemical Technology Co., Ltd., S909954;

[0034] Polyvinylidene fluoride, Shanghai MacLean Biochemical Technology Co., Ltd., P822261;

[0035] Polyethylene glycol, Shanghai Aladdin Biochemical Technology Co., Ltd., P615519;

[0036] Alumina microspheres, Forsman Technology (Beijing) Co., Ltd., 15-45 μm;

[0037] Polystyrene, Guangdong Wengjiang Chemical Reagent Co., Ltd., PA072475;

[0038] Nano-silicon nitride, Shanghai Aladdin Biochemical Technology Co., Ltd., S106135, China.

[0039] Preparation Example 1 Preparation of polystyrene maleic anhydride copolymer modified polyvinylidene fluoride

[0040] Preparation Example 1.1

[0041] 7 g of polyvinylidene fluoride and 0.8 g of polystyrene maleic anhydride copolymer were added to 35 g of N,N-dimethylethylamine and stirred thoroughly until dissolved; then stirred in a 50°C water bath for 5 h; then 7 g of polyethylene glycol, which had been dried at 50°C, was added and stirred for 20 h; the product was degassed in a vacuum oven to obtain polystyrene maleic anhydride copolymer-modified polyvinylidene fluoride.

[0042] Preparation Example 1.2

[0043] 7.5 g of polyvinylidene fluoride and 1.2 g of polystyrene maleic anhydride copolymer were added to 40 g of N,N-dimethylethylamine and stirred thoroughly until dissolved; then stirred in a 55°C water bath for 6 h; then 8 g of polyethylene glycol, which had been dried at 55°C, was added and stirred for 25 h; the product was degassed in a vacuum oven to obtain polystyrene maleic anhydride copolymer-modified polyvinylidene fluoride.

[0044] Preparation Example 1.3

[0045] 8 g of polyvinylidene fluoride and 1.6 g of polystyrene maleic anhydride copolymer were added to 45 g of N,N-dimethylethylamine and stirred thoroughly until dissolved; then stirred in a 60°C water bath for 7 h; then 9 g of polyethylene glycol, which had been dried at 60°C, was added and stirred for 30 h; the product was degassed in a vacuum oven to obtain polystyrene maleic anhydride copolymer-modified polyvinylidene fluoride.

[0046] Preparation Example 2 Preparation of Boehmite / Alumina@Silica Composite Material

[0047] Preparation Example 2.1

[0048] S1. 0.2 g of alumina microspheres were dispersed in a mixture of 21 g of anhydrous ethanol and 3 g of high-purity water and ultrasonically treated for 3 minutes. A mixture of 10 g of anhydrous ethanol, 1 g of aqueous ammonia, and 0.28 g of tetraethyl orthosilicate was then added and ultrasonically treated at 30°C for 3 hours. The product was washed with deionized water and ethanol and then vacuum-dried at 55°C for 8 hours to obtain an alumina-silica composite.

[0049] S2. Add 0.17 g of sodium aluminate to 30 g of high-purity water, stir until completely dissolved, add 0.5 g of urea, and stir for 0.5 h; then add 0.1 g of the alumina@silica composite material prepared in S1, ultrasonically disperse, and react at 180°C for 5 h; after the reaction, obtain a solid product by centrifugation, wash it three times with deionized water, and vacuum dry it at 50°C for 12 h to obtain a boehmite / alumina@silica composite material.

[0050] Preparation Example 2.2

[0051] S1. Disperse 0.35 g of alumina microspheres in a mixture of 28 g of anhydrous ethanol and 4 g of high-purity water and ultrasonically treat for 4 minutes. Then, add a mixture of 15 g of anhydrous ethanol, 1.5 g of aqueous ammonia, and 0.49 g of tetraethyl orthosilicate and ultrasonically treat at 40°C for 4 hours. The product is washed with deionized water and ethanol and then vacuum-dried at 60°C for 9 hours to obtain an alumina-silica composite.

[0052] S2. Add 0.26 g of sodium aluminate to 40 g of high-purity water, stir until completely dissolved, then add 0.75 g of urea and stir for 1 hour; then add 0.15 g of the alumina@silica composite material prepared in S1, ultrasonically disperse it, and react at 190°C for 6.5 hours; after the reaction, obtain a solid product by centrifugation, wash it with deionized water four times, and vacuum dry it at 55°C for 14 hours to obtain a boehmite / alumina@silica composite material.

[0053] Preparation Example 2.3

[0054] S1. Disperse 0.5 g of alumina microspheres in a mixture of 35 g of anhydrous ethanol and 5 g of high-purity water and ultrasonically treat for 5 minutes. Then, add a mixture of 20 g of anhydrous ethanol, 2 g of aqueous ammonia, and 0.7 g of tetraethyl orthosilicate, and ultrasonically treat at 50°C for 5 hours. The product is washed with deionized water and ethanol, and then vacuum-dried at 65°C for 10 hours to obtain an alumina-silica composite.

[0055] S2. Add 0.34 g of sodium aluminate to 50 g of high-purity water, stir until completely dissolved, add 1 g of urea, and stir for 1.5 hours; then add 0.2 g of the alumina@silica composite material prepared in S1, ultrasonically disperse it, and react at 200°C for 8 hours; after the reaction, obtain a solid product by centrifugation, wash it with deionized water 5 times, and vacuum dry it at 60°C for 16 hours to obtain a boehmite / alumina@silica composite material.

[0056] Example 1

[0057] S1 10g of polystyrene was treated with ammonia plasma to obtain modified polystyrene; the ammonia plasma treatment power was 200W; the treatment time was 120s; the ammonia flow rate was 200mL / min;

[0058] S2. 10 mL of concentrated nitric acid was added to 2 g of nano-silicon nitride, stirred, and heated at 60 ° C for 14 h; after the reaction, the mixture was cooled to room temperature, filtered, centrifuged, and washed with deionized water until neutral, and dried to obtain an acidified nano-silicon nitride powder;

[0059] S3. 15 g of the polystyrene maleic anhydride copolymer modified with polyvinylidene fluoride obtained in Preparation Example 1.1 and the modified polystyrene obtained in S1 were added to 65 g of N,N-dimethylethylamine solvent and stirred at 70°C until completely dissolved; then the acidified nano-silicon nitride powder obtained in S2, 3 g of the boehmite / alumina@silica composite material obtained in Preparation Example 2.1, and 1 g of a dispersant were added and stirred for 1 h; the mixture was then placed in a vacuum oven for degassing to obtain a lithium battery separator coating;

[0060] The dispersant used in this embodiment is sodium lauryl sulfate.

[0061] Example 2

[0062] S1 15g of polystyrene was treated with ammonia plasma to obtain modified polystyrene; the ammonia plasma treatment power was 200W; the treatment time was 120s; the ammonia flow rate was 200mL / min;

[0063] S2. 10 mL of concentrated nitric acid was added to 3 g of nano-silicon nitride, stirred, and heated at 60 ° C for 14 h; after the reaction, the mixture was cooled to room temperature, filtered, centrifuged, and washed with deionized water until neutral, and dried to obtain an acidified nano-silicon nitride powder;

[0064] S3. 20 g of the polystyrene maleic anhydride copolymer modified polyvinylidene fluoride obtained in Preparation Example 1.1 and the modified polystyrene obtained in S1 were added to 80 g of N,N-dimethylethylamine solvent and stirred at 70 ° C until completely dissolved; then the acidified nano-silicon nitride powder obtained in S2, 4.5 g of the boehmite / alumina@silica composite material obtained in Preparation Example 2.1, and 1.5 g of the dispersant were added and stirred for 1 h; then the mixture was placed in a vacuum oven for degassing to obtain a lithium battery separator coating;

[0065] The dispersant used in this embodiment is sodium lauryl sulfate.

[0066] Example 3

[0067] S1 20g of polystyrene was treated with ammonia plasma to obtain modified polystyrene; the ammonia plasma treatment power was 200W; the treatment time was 120s; the ammonia flow rate was 200mL / min;

[0068] S2. 10 mL of concentrated nitric acid was added to 4 g of nano-silicon nitride, stirred, and heated at 60 ° C for 14 h; after the reaction, the mixture was cooled to room temperature, filtered, centrifuged, and washed with deionized water until neutral, and dried to obtain an acidified nano-silicon nitride powder;

[0069] S3. 25 g of the polystyrene maleic anhydride copolymer modified with polyvinylidene fluoride obtained in Preparation Example 1.1 and the modified polystyrene obtained in S1 were added to 90 g of N,N-dimethylethylamine solvent and stirred at 70°C until completely dissolved; then the acidified nano-silicon nitride powder obtained in S2, 6 g of the boehmite / alumina@silica composite material obtained in Preparation Example 2.1, and 2 g of a dispersant were added and stirred for 1 h; the mixture was then placed in a vacuum oven for degassing to obtain a lithium battery separator coating;

[0070] The dispersant used in this embodiment is sodium lauryl sulfate.

[0071] Example 4

[0072] S1 10g of polystyrene was treated with ammonia plasma to obtain modified polystyrene; the ammonia plasma treatment power was 300W; the treatment time was 150s; the ammonia flow rate was 250mL / min;

[0073] S2. 10 mL of concentrated nitric acid was added to 2 g of nano-silicon nitride, stirred, and heated at 75 ° C for 17 h; after the reaction, the mixture was cooled to room temperature, filtered, centrifuged, and washed with deionized water until neutral, and dried to obtain an acidified nano-silicon nitride powder;

[0074] S3. 15 g of the polystyrene maleic anhydride copolymer modified with polyvinylidene fluoride obtained in Preparation Example 1.1 and the modified polystyrene obtained in S1 were added to 65 g of N,N-dimethylethylamine solvent and stirred at 75 ° C until completely dissolved; then the acidified nano-silicon nitride powder obtained in S2, 3 g of the boehmite / alumina@silica composite material obtained in Preparation Example 2.1, and 1 g of the dispersant were added and stirred for 1.5 h; then the mixture was placed in a vacuum oven for degassing to obtain a lithium battery separator coating;

[0075] The dispersant used in this embodiment is sodium lauryl sulfate.

[0076] Example 5

[0077] S1 10g of polystyrene was treated with ammonia plasma to obtain modified polystyrene; the ammonia plasma treatment power was 400W; the treatment time was 180s; the ammonia flow rate was 300mL / min;

[0078] S2. 10 mL of concentrated nitric acid was added to 2 g of nano-silicon nitride, stirred, and heated at 90 ° C for 20 h; after the reaction, the mixture was cooled to room temperature, filtered, centrifuged, and washed with deionized water until neutral, and dried to obtain an acidified nano-silicon nitride powder;

[0079] S3. 15 g of the polystyrene maleic anhydride copolymer modified with polyvinylidene fluoride obtained in Preparation Example 1.1 and the modified polystyrene obtained in S1 were added to 65 g of N,N-dimethylethylamine solvent and stirred at 80°C until completely dissolved; then the acidified nano-silicon nitride powder obtained in S2, 3 g of the boehmite / alumina@silica composite material obtained in Preparation Example 2.1, and 1 g of a dispersant were added and stirred for 2 h; then the mixture was placed in a vacuum oven for degassing to obtain a lithium battery separator coating;

[0080] The dispersant used in this embodiment is sodium lauryl sulfate.

[0081] Example 6

[0082] The difference between Example 6 and Example 1 is that the polystyrene maleic anhydride copolymer modified polyvinylidene fluoride used in Example 6 comes from Preparation Example 1.2.

[0083] Example 7

[0084] The difference between Example 7 and Example 1 is that the polystyrene maleic anhydride copolymer modified polyvinylidene fluoride used in Example 7 comes from Preparation Example 1.3.

[0085] Example 8

[0086] The difference between Example 8 and Example 1 is that the boehmite / alumina@silica composite material used in Example 8 comes from Preparation Example 2.2.

[0087] Example 9

[0088] The difference between Example 9 and Example 1 is that the boehmite / alumina@silica composite material used in Example 8 comes from Preparation Example 2.3.

[0089] Comparative Example 1

[0090] The difference between Comparative Example 1 and Example 1 is that the polyvinylidene fluoride used in Comparative Example 1 is not modified.

[0091] Comparative Example 2

[0092] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, commercially available nano-boehmite is used instead of the boehmite / alumina@silica composite material; the nano-boehmite is purchased from Wuhan Lvjing Fenghua Biotechnology Co., Ltd.

[0093] Application Example 1

[0094] A polypropylene / polyethylene / polypropylene three-layer composite membrane with a thickness of 20 μm was selected as the substrate, and the lithium battery separator coating prepared in Example 1 was coated on both sides of the substrate, with a coating thickness of 5 μm on both sides; a lithium battery separator was obtained.

[0095] Application Example 2

[0096] A polypropylene / polyethylene / polypropylene three-layer composite membrane with a thickness of 20 μm was selected as the substrate, and the lithium battery separator coating prepared in Example 1 was coated on both sides of the substrate, with a coating thickness of 8 μm on both sides; a lithium battery separator was obtained.

[0097] Application Example 3

[0098] A polypropylene / polyethylene / polypropylene three-layer composite membrane with a thickness of 20 μm was selected as the substrate, and the lithium battery separator coating prepared in Example 1 was coated on both sides of the substrate, with a coating thickness of 10 μm on both sides; a lithium battery separator was obtained.

[0099] Application Example 4-11

[0100] The difference between Application Examples 4-11 and Application Example 1 is that the lithium battery separator coatings used in Application Examples 4-11 are from Examples 2-9, respectively, and the coating thickness on both sides is 5 μm.

[0101] Comparative Application Example 1

[0102] The difference between Comparative Application Example 1 and Application Example 1 is that the lithium battery separator coating used in Comparative Application Example 1 is from Example 1, and the coating thickness on both sides is 2 μm.

[0103] Comparative Application Example 2

[0104] The difference between Comparative Application Example 2 and Application Example 1 is that the lithium battery separator coating used in Comparative Application Example 2 is from Example 1, and the coating thickness on both sides is 13 μm.

[0105] Comparative Application Examples 3-4

[0106] The difference between Comparative Application Examples 3-4 and Application Example 1 is that the lithium battery separator coatings used in Comparative Application Examples 3-4 are from Comparative Examples 1-2, respectively, and the coating thickness on both sides is 5 μm.

[0107] Performance testing

[0108] 1. Longitudinal and transverse shrinkage test: The lithium battery separators obtained from Examples 1-11 and Comparative Application Examples 1-4 were heated at 180°C for 4 hours, and the longitudinal and transverse dimensional changes before and after heating were tested; the results are shown in Table 1.

[0109] 2. Liquid absorption rate test: The lithium battery separators obtained from the corresponding use cases 1-11 and comparative application examples 1-4 were immersed in electrolyte, taken out and weighed after 2 hours, and the liquid absorption rate was calculated based on the weight change before and after. The electrolyte composition was: 1 mol / L LiPF6 ethylene carbonate and dimethyl carbonate solution, in which the volume ratio of solvent ethylene carbonate and dimethyl carbonate was 1:1; the results are shown in Table 1.

[0110] 3. Limiting Oxygen Index Test: The limiting oxygen index of the lithium battery separator obtained by immersion in Example 1-11 and Comparative Application Example 1-4 was tested with reference to the standard JIS-K7201-3-2008; the results are shown in Table 1.

[0111] The specific test results are as follows:

[0112] Table 1 Performance test results

[0113] It can be seen from the test results in Table 1 that the lithium battery separator coating provided by the present application has low longitudinal and transverse shrinkage rates in the lithium battery separator, which indicates that the obtained lithium battery separator has good high-temperature stability; the limiting oxygen index of the lithium battery separator is >50%, which indicates that the lithium battery separator provided by the present application has excellent flame retardancy; the liquid absorption rate of the lithium battery separator is >230%, which indicates that the lithium battery separator provided by the present application has good wettability to the electrolyte.

[0114] 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 lithium battery separator coating based on nanomaterials, characterized by: The raw materials include, by weight: 15-25 parts of polystyrene maleic anhydride copolymer modified polyvinylidene fluoride, 10-20 parts of polystyrene, 2-4 parts of nano silicon nitride, 3-6 parts of boehmite / alumina@silicon dioxide composite material, 1-2 parts of dispersant, and 65-90 parts of solvent; The polystyrene maleic anhydride copolymer modified polyvinylidene fluoride is prepared from the following raw materials in parts by weight: 7-8 parts of polyvinylidene fluoride, 0.8-1.6 parts of polystyrene maleic anhydride copolymer, 7-9 parts of polyethylene glycol, and 35-45 parts of N,N-dimethylethylamine; The preparation method of the boehmite / alumina@silica composite material comprises the following steps: Sodium aluminate is added to water and stirred until completely dissolved. Urea is then added and stirred for 0.5-1.5 hours. The alumina@silica composite material is then added, ultrasonically dispersed, and reacted at 180-200°C for 5-8 hours. After the reaction, a solid product is obtained by centrifugation, washed several times with deionized water, and vacuum dried at 50-60°C for 12-16 hours to obtain a boehmite / alumina@silica composite material. The polystyrene is treated with ammonia plasma, and the preparation method thereof comprises the following steps: treating the polystyrene with ammonia plasma to obtain modified polystyrene; the power of the ammonia plasma treatment is 200-400W; the treatment time is 120-180s; and the ammonia flow rate is 200-300mL / min; The nano silicon nitride is acidified with concentrated nitric acid, and the preparation method thereof comprises the following steps: adding concentrated nitric acid to the nano silicon nitride, stirring evenly, and heating at 60-90° C. for reaction for 14-20 hours; after the reaction, cooling to room temperature, filtering, centrifuging, washing with deionized water until neutral, and drying to obtain acidified nano silicon nitride powder; The solid-liquid ratio of the nano-silicon nitride to concentrated nitric acid is 0.2-0.4 g:1 mL.

2. The lithium battery separator coating based on nanomaterials according to claim 1, characterized in that: The raw materials include, by weight: 20 parts of polystyrene maleic anhydride copolymer modified polyvinylidene fluoride, 15 parts of polystyrene, 3 parts of nano silicon nitride, 4.5 parts of boehmite / alumina@silicon dioxide composite material, 1.5 parts of dispersant, and 80 parts of solvent.

3. The lithium battery separator coating based on nanomaterials according to claim 1, characterized in that: The preparation method of the polystyrene maleic anhydride copolymer modified polyvinylidene fluoride comprises the following steps: Add polyvinylidene fluoride and polystyrene maleic anhydride copolymer to N,N-dimethylethylamine and stir thoroughly until dissolved; then stir in a 50-60°C water bath for 5-7 hours; then add polyethylene glycol that has been dried at 50-70°C and stir to react for 20-30 hours; degas the product in a vacuum oven to obtain polystyrene maleic anhydride copolymer-modified polyvinylidene fluoride.

4. The lithium battery separator coating based on nanomaterials according to claim 1 or 2, characterized in that: The boehmite / alumina@silica composite material is prepared from the following raw materials in parts by weight: 0.17-0.34 parts of sodium aluminate, 30-50 parts of water, 0.5-1 parts of urea, and 0.1-0.2 parts of the alumina@silica composite material.

5. The lithium battery separator coating based on nanomaterials according to claim 4, characterized in that: The alumina@silica composite material is prepared from the following raw materials in parts by weight: 0.2-0.5 parts of alumina microspheres, 31-55 parts of anhydrous ethanol, 3-5 parts of water, 1-2 parts of ammonia water, and 0.28-0.7 parts of tetraethyl orthosilicate.

6. The lithium battery separator coating based on nanomaterials according to claim 5, characterized in that: The preparation method of the alumina@silicon dioxide composite material comprises the following steps: 0.2-0.5 parts of alumina microspheres are dispersed in a mixed solution of 21-35 parts of anhydrous ethanol and 3-5 parts of water, and ultrasonically treated for 3-5 minutes; then a mixed solution of 10-20 parts of anhydrous ethanol, 1-2 parts of ammonia water and 0.28-0.7 parts of tetraethyl orthosilicate is added, and ultrasonically treated at 30-50°C for 3-5 hours. The product is washed with deionized water and ethanol, and then vacuum-dried at 55-65°C for 8-10 hours to obtain an alumina@silica composite material.

7. The lithium battery separator coating based on nanomaterials according to claim 1, characterized in that: The preparation method of the lithium battery separator coating comprises the following steps: S1. The polystyrene is treated with ammonia plasma to obtain modified polystyrene; S2. The nano-silicon nitride was acidified with concentrated nitric acid to obtain an acidified nano-silicon nitride powder; S3. Add polystyrene maleic anhydride copolymer modified polyvinylidene fluoride and modified polystyrene to a solvent and stir at 70-80°C until completely dissolved; then add acidified nano-silicon nitride powder, boehmite / alumina@silica composite material and dispersant, and stir for 1-2 hours; then place in a vacuum oven for degassing to obtain a lithium battery separator coating.

8. An application of a lithium battery separator coating based on nanomaterials, characterized by: The lithium battery separator coating according to any one of claims 1 to 7 is coated on the surface of the lithium battery separator; the coating has a thickness of 5 to 10 μm.

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