High-temperature-resistant modified acrylic acid composite material and preparation method thereof

Abstract

The invention relates to the technical field of lithium ion battery diaphragms, in particular to a high-temperature-resistant modified acrylic acid composite material and a preparation method thereof. The high-temperature-resistant modified acrylic acid composite material comprises a polypropylene diaphragm and coating slurry coated on at least one side of the polypropylene diaphragm, the coating slurry is prepared from the following raw materials: n-butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocynate, methacrylic anhydride, graphene oxide, nanoscale ceramic powder, polyvinylidene fluoride, vinyltriethoxysilane, polysiloxane, a dispersing agent, a catalyst and a solvent. According to the invention, high safety can be brought to the battery, high temperature resistance is realized, the diaphragm can tolerate high temperature, the service life of the battery is obviously prolonged, and the safety is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery separators, and particularly to a high-temperature resistant modified acrylic composite material and a preparation method thereof. Background Art

[0002] The separator is a key inner component in a lithium-ion battery. The key performance of the battery, such as capacity, cycle performance, charge and discharge current density, high-temperature resistance, high strength, and safety guarantee, is directly related to the separator.

[0003] Conventional lithium-ion battery separators mostly use polyolefin PP or PE materials as the first choice. With the increasing requirements for battery safety performance, ceramic-coated separators can effectively solve the problem that conventional separators are not resistant to high-potential oxidation during long-term cycling, and effectively improve the safety of lithium-ion batteries. After the polyolefin base film is first infiltrated with a volatile solvent, and then through a certain concentration of ceramic adhesive solution, a certain amount of adhesive solution is adhered to the surface of the base film, and after drying, the adhesive solution is fixed on the surface of the base film to form a coated separator.

[0004] The high-temperature resistance, heat shrinkage rate, and strength of existing ceramic-coated separators cannot meet the requirements under certain temperature conditions. Graphene has excellent mechanical properties, heat resistance, and advantages such as significantly improving the specific energy of the battery. How to add graphene to the ceramic-coated separator to improve the heat resistance stability, heat shrinkage rate, and strength of the lithium battery separator has excellent research prospects. Summary of the Invention

[0005] The purpose of the present invention is to solve the disadvantages existing in the prior art, and to propose a high-temperature resistant modified acrylic composite material and a preparation method thereof.

[0006] A high-temperature resistant modified acrylic composite material includes a polypropylene separator and a coating slurry coated on at least one side of the polypropylene separator; the raw materials of the coating slurry include, by mass parts: 50-150 parts of n-butyl acrylate, 5-15 parts of methyl methacrylate, 5-15 parts of ethyl acrylate, 20-50 parts of toluene diisocyanate, 1-3 parts of methacrylic anhydride, 5-15 parts of graphene oxide, 50-100 parts of nano-ceramic powder, 5-15 parts of polyvinylidene fluoride, 1-2 parts of vinyltriethoxysilane, 50-65 parts of polysiloxane, 1-2 parts of dispersant, 1-2 parts of catalyst, and 50-100 parts of solvent.

[0007] Preferably, the thickness of the polypropylene separator is 10-20 μm, and the porosity is 35-45%.

[0008] Preferably, the polysiloxane is at least one of polydimethylsiloxane, cyclomethicone, amino-modified polydimethylsiloxane, and polymethylphenylsiloxane.

[0009] Preferably, the dispersant is ammonium polyacrylate.

[0010] Preferably, the catalyst is stannous octoate.

[0011] Preferably, the solvent is toluene and / or ethyl acetate.

[0012] Preferably, the coating slurry is prepared by the following steps: S1. Add graphene oxide to deionized water and stir evenly. Add methacrylic anhydride thereto and stir at 50 - 70 °C for 2 - 5 h, then freeze-dry to obtain pretreated graphene. S2. Add nanoscale ceramic powder to an ethanol aqueous solution and ultrasonically treat for 1 - 2 h. Adjust the pH value of the system to 4 - 5, add vinyltriethoxysilane and ultrasonically treat for 10 - 20 min. Add the pretreated graphene and stir at 50 - 80 °C for 1 - 3 h, then filter, wash, and vacuum-dry to obtain pretreated ceramics. S3. Add n-butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocyanate, catalyst, and solvent to the pretreated ceramics and stir at 70 - 90 °C for 5 - 10 h. Then add polyvinylidene fluoride, polysiloxane, and dispersant and stir at 50 - 80 °C for 10 - 30 min.

[0013] Preferably, in S2, the ultrasonic frequency is 5 - 12 kHz.

[0014] The preparation method of the above high-temperature resistant modified acrylic composite material includes the following steps: Coating the coating slurry on the surface of a polypropylene separator, curing at 70 - 90 °C for 6 - 12 min, and drying; then placing it in an aqueous solution containing ammonia water and vitamin C, performing reduction treatment at 120 - 140 °C for 2 - 4 h, and drying; the obtained coating thickness is 2 - 6 μm.

[0015] Preferably, in the aqueous solution containing ammonia water and vitamin C, the ammonia concentration is 12 - 18%, and the vitamin C concentration is 0.5 - 1 g / mL.

[0016] Beneficial effects: In the present invention, methacrylic anhydride is combined into the lamellar structure of graphene oxide, which can not only play a steric hindrance role and prevent the aggregation of the lamellar structure, but also combine with activated nanoscale ceramic powder in one step. It can not only improve the thermal conductivity of the material and have better high-temperature resistance, but also have excellent dispersion and compatibility with acrylic resin, and can significantly enhance the high-temperature strength of acrylic resin.

[0017] The present invention forms a network structure between the pretreated ceramic and the acrylic resin, which can effectively prevent the movement of nanoparticles during the cycling process, maintain the stability of the electrode structure, is beneficial to the cycling stability of the electrode, and at the same time makes the obtained composite material have high mechanical strength. The present invention can not only ensure the low shrinkage rate and high safety of the composite material at high temperatures, but also make it have a high conductivity at room temperature. It can not only greatly improve the charging speed of lithium-ion batteries and increase the specific energy of the batteries, but also the good network structure formed between the ceramic particles and the acrylic resin enables the composite material to withstand a temperature of up to 180 °C, effectively avoiding problems such as shrinkage or fusing caused by high temperatures.

[0018] The present invention can bring relatively high safety to the battery, is resistant to high temperatures, can reduce the shrinkage rate of the separator under high-temperature conditions, effectively improve the high-temperature resistance of the battery during charge and discharge, the separator can withstand a relatively high temperature, and the shrinkage rate of the separator is significantly reduced compared with the existing ceramic-coated separator, the battery life is significantly extended, and the safety is greatly improved.

[0019] The composite material formed after the coating slurry of the present invention is coated has good performance, can effectively enhance the adhesion between the coating slurry and the polypropylene separator, and the product has high stability. Brief Description of the Drawings

[0020] Figure 1 It is a comparison chart of the tensile strength of the composite materials obtained in Examples 1-5 and Comparative Examples 1-2.

[0021] Figure 2 It is a comparison chart of the thermal shrinkage rate of the composite materials obtained in Examples 1-5 and Comparative Examples 1-2.

[0022] Figure 3 It is a comparison chart of the liquid absorption rate and ionic conductivity of the composite materials obtained in Examples 1-5 and Comparative Examples 1-2.

[0023] Figure 4 It is a comparison chart of the capacity retention rate of the button batteries prepared from the composite materials obtained in Examples 1-5 and Comparative Examples 1-2. Detailed Embodiments

[0024] The present invention will be further explained below in conjunction with specific embodiments.

[0025] The following polypropylene film used was purchased from a certain new material company in Wenzhou, with a thickness of 16 μm and a porosity of 40%. The following nanoscale ceramic powder used was purchased from a certain new material company in Hangzhou, with an alumina composition, an average particle size of 0.5 μm, and a purity of 99.9%. The following ammonium polyacrylate used was purchased from a certain new material company in Shandong, with a model of 5027, a pH value of 6.5 - 7.5, and a density of 1.2 g / cm 3 。

[0026] Example 1: A high-temperature resistant modified acrylic composite material, comprising a polypropylene separator and a coating slurry coated on at least one side of the polypropylene separator.

[0027] The raw materials of the coating slurry include: 50 g of n-butyl acrylate, 5 g of methyl methacrylate, 5 g of ethyl acrylate, 20 g of toluene diisocyanate, 1 g of methacrylic anhydride, 5 g of graphene oxide, 50 g of nano-ceramic powder, 5 g of polyvinylidene fluoride, 1 g of vinyltriethoxysilane, 50 g of cyclomethylsiloxane, 1 g of ammonium polyacrylate, 1 g of stannous octoate, and 50 g of toluene.

[0028] The coating slurry is prepared by the following steps: S1. Add graphene oxide to 20 g of deionized water and stir evenly. Add methacrylic anhydride thereto and stir at a temperature of 50 °C for 2 h, and then freeze-dry to obtain pretreated graphene. S2. Add nano-ceramic powder to 200 g of an ethanol aqueous solution with a mass fraction of 40% and perform ultrasonic treatment for 1 h at an ultrasonic frequency of 5 kHz. Adjust the pH value of the system to 4-5 with 1 mol / L hydrochloric acid, add vinyltriethoxysilane and perform ultrasonic treatment for 10 min, add the pretreated graphene, stir at a temperature of 50 °C for 1 h at a stirring speed of 300 r / min, filter, wash, and vacuum-dry to obtain pretreated ceramics. S3. Add n-butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocyanate, stannous octoate, and toluene to the pretreated ceramics and stir at a temperature of 70 °C for 5 h. Then add polyvinylidene fluoride, cyclomethylsiloxane, and ammonium polyacrylate and stir at a temperature of 50 °C for 10 min at a stirring speed of 1000 r / min.

[0029] The preparation method of the above high-temperature resistant modified acrylic composite material comprises the following steps: Coating the coating slurry on the surface of the polypropylene separator, curing at a temperature of 70 °C for 6 min, and drying; then placing it in an aqueous solution containing ammonia water and vitamin C (ammonia concentration is 12%, vitamin C concentration is 0.5 g / mL), performing reduction treatment at a temperature of 120 °C for 2 h, and drying; the obtained coating thickness is 2 μm.

[0030] Example 2: A high-temperature resistant modified acrylic composite material, comprising a polypropylene separator and a coating slurry coated on at least one side of the polypropylene separator.

[0031] The raw materials of the coating slurry include: 150 g of n-butyl acrylate, 15 g of methyl methacrylate, 15 g of ethyl acrylate, 50 g of toluene diisocyanate, 3 g of methacrylic anhydride, 15 g of graphene oxide, 100 g of nano-ceramic powder, 15 g of polyvinylidene fluoride, 2 g of vinyltriethoxysilane, 65 g of amino-modified polydimethylsiloxane, 2 g of ammonium polyacrylate, 2 g of stannous octoate, and 100 g of toluene.

[0032] The coating slurry is prepared by the following steps: S1. Add graphene oxide to 60 g of deionized water and stir evenly. Add methacrylic anhydride thereto, stir at 70 °C for 5 h, and freeze-dry to obtain pretreated graphene; S2. Add nano-ceramic powder to 400 g of an ethanol aqueous solution with a mass fraction of 60% and perform ultrasonic treatment for 2 h. The ultrasonic frequency is 12 kHz. Adjust the pH value of the system to 4 - 5 with hydrochloric acid with a concentration of 2 mol / L. Add vinyltriethoxysilane and perform ultrasonic treatment for 20 min. Add the pretreated graphene, stir at 80 °C for 3 h, and the stirring speed is 500 r / min. Filter, wash, and vacuum-dry to obtain pretreated ceramics; S3. Add n-butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocyanate, stannous octoate, and toluene to the pretreated ceramics, stir at 90 °C for 10 h, add polyvinylidene fluoride, amino-modified polydimethylsiloxane, and ammonium polyacrylate salt thereto, and stir at 80 °C for 30 min. The stirring speed is 3000 r / min.

[0033] The preparation method of the above high-temperature resistant modified acrylic composite material includes the following steps: Coat the coating slurry on the surface of the polypropylene diaphragm, cure at 90 °C for 12 min, and dry; then place it in an aqueous solution containing ammonia water and vitamin C (the ammonia concentration is 18% and the vitamin C concentration is 1 g / mL), perform reduction treatment at 140 °C for 4 h, and dry; the obtained coating thickness is 6 μm.

[0034] Example 3: A high-temperature resistant modified acrylic composite material, including a polypropylene diaphragm and a coating slurry coated on at least one side of the polypropylene diaphragm.

[0035] The raw materials of the coating slurry include: 80 g of n-butyl acrylate, 12 g of methyl methacrylate, 8 g of ethyl acrylate, 40 g of toluene diisocyanate, 1.5 g of methacrylic anhydride, 12 g of graphene oxide, 70 g of nano-ceramic powder, 12 g of polyvinylidene fluoride, 1.3 g of vinyltriethoxysilane, 60 g of polymethylphenylsiloxane, 1.3 g of ammonium polyacrylate salt, 1.8 g of stannous octoate, and 70 g of ethyl acetate.

[0036] The coating slurry is prepared by the following steps: S1. Add graphene oxide to 50 g of deionized water and stir evenly. Add methacrylic anhydride thereto, stir at 55 °C for 4 h, and freeze-dry to obtain pretreated graphene; S2. Add nanoscale ceramic powder into 260 g of ethanol aqueous solution with a mass fraction of 55%, and ultrasonically treat it for 80 min at an ultrasonic frequency of 9 kHz. Adjust the pH value of the system to 4 - 5 with hydrochloric acid at a concentration of 1.5 mol / L. Add vinyltriethoxysilane and ultrasonically treat it for 12 min. Add pretreated graphene, stir at 70 °C for 1.5 h with a stirring speed of 450 r / min, filter, wash, and vacuum dry to obtain pretreated ceramic; S3. Add n-butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocyanate, stannous octoate, and ethyl acetate into the pretreated ceramic, stir at 75 °C for 8 h, add polyvinylidene fluoride, polymethylphenylsiloxane, and ammonium polyacrylate salt thereto, and stir at 60 °C for 25 min with a stirring speed of 1500 r / min.

[0037] The preparation method of the above high-temperature resistant modified acrylic composite material comprises the following steps: Coating the coating slurry on the surface of a polypropylene diaphragm, curing at 85 °C for 8 min, and drying; then placing it in an aqueous solution containing ammonia water and vitamin C (ammonia concentration is 17%, vitamin C concentration is 0.6 g / mL), and performing reduction treatment at 135 °C for 2.5 h, and drying; the obtained coating thickness is 5 μm.

[0038] Example 4: A high-temperature resistant modified acrylic composite material, comprising a polypropylene diaphragm and a coating slurry coated on at least one side of the polypropylene diaphragm.

[0039] The raw materials of the coating slurry include: 120 g of n-butyl acrylate, 8 g of methyl methacrylate, 12 g of ethyl acrylate, 30 g of toluene diisocyanate, 2.5 g of methacrylic anhydride, 8 g of graphene oxide, 90 g of nanoscale ceramic powder, 8 g of polyvinylidene fluoride, 1.7 g of vinyltriethoxysilane, 55 g of polydimethylsiloxane, 1.7 g of ammonium polyacrylate salt, 1.2 g of stannous octoate, and 90 g of ethyl acetate.

[0040] The coating slurry is prepared by the following steps: S1. Add graphene oxide into 30 g of deionized water and stir evenly. Add methacrylic anhydride thereto, stir at 65 °C for 3 h, and freeze-dry to obtain pretreated graphene; S2. Add nanoscale ceramic powder into 340 g of ethanol aqueous solution with a mass fraction of 45%, and ultrasonically treat it for 100 min at an ultrasonic frequency of 6 kHz. Adjust the pH value of the system to 4 - 5 with hydrochloric acid at a concentration of 1.5 mol / L. Add vinyltriethoxysilane and ultrasonically treat it for 18 min. Add pretreated graphene, stir at 60 °C for 2.5 h with a stirring speed of 350 r / min, filter, wash, and vacuum dry to obtain pretreated ceramic; S3. Add butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocyanate, stannous octoate, and ethyl acetate to the pretreated ceramic, stir at 85 °C for 6 h, add polyvinylidene fluoride, polydimethylsiloxane, and ammonium polyacrylate salt thereto, and stir at 70 °C for 15 min at a stirring speed of 2500 r / min.

[0041] The preparation method of the above high-temperature resistant modified acrylic composite material comprises the following steps: coat the coating slurry on the surface of a polypropylene separator, cure at 75 °C for 10 min, and dry; then place it in an aqueous solution containing ammonia water and vitamin C (ammonia concentration is 13%, vitamin C concentration is 0.9 g / mL), perform reduction treatment at 125 °C for 3.5 h, and dry; the obtained coating thickness is 3 μm.

[0042] Example 5: A high-temperature resistant modified acrylic composite material, comprising a polypropylene separator and a coating slurry coated on at least one side of the polypropylene separator.

[0043] The raw materials of the coating slurry include: 100 g of butyl acrylate, 10 g of methyl methacrylate, 10 g of ethyl acrylate, 35 g of toluene diisocyanate, 2 g of methacrylic anhydride, 10 g of graphene oxide, 80 g of nano-ceramic powder, 10 g of polyvinylidene fluoride, 1.5 g of vinyltriethoxysilane, 58 g of polydimethylsiloxane, 1.5 g of ammonium polyacrylate salt, 1.5 g of stannous octoate, and 80 g of ethyl acetate.

[0044] The coating slurry is prepared by the following steps: S1. Add graphene oxide to 40 g of deionized water and stir evenly, add methacrylic anhydride thereto, stir at 60 °C for 3.5 h, and perform freeze-drying to obtain pretreated graphene. S2. Add nano-ceramic powder to 300 g of an ethanol aqueous solution with a mass fraction of 50%, perform ultrasonic treatment for 90 min at an ultrasonic frequency of 7.5 kHz, adjust the pH value of the system to 4 - 5 with 1.5 mol / L hydrochloric acid, add vinyltriethoxysilane and perform ultrasonic treatment for 15 min, add the pretreated graphene, stir at 65 °C for 2 h at a stirring speed of 400 r / min, filter, wash, and perform vacuum drying to obtain pretreated ceramic. S3. Add butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocyanate, stannous octoate, and ethyl acetate to the pretreated ceramic, stir at 80 °C for 7 h, add polyvinylidene fluoride, polydimethylsiloxane, and ammonium polyacrylate salt thereto, and stir at 68 °C for 20 min at a stirring speed of 2000 r / min.

[0045] The preparation method of the above high-temperature resistant modified acrylic composite material comprises the following steps: Coating the coating slurry on the surface of the polypropylene separator, curing at 80°C for 9 minutes, and drying; then placing it in an aqueous solution containing ammonia water and vitamin C (ammonia concentration is 15%, vitamin C concentration is 0.8 g / mL), performing reduction treatment at 130°C for 3 hours, and drying; the obtained coating thickness is 4 μm.

[0046] Comparative Example 1: A high-temperature resistant modified acrylic composite material, comprising a polypropylene separator and a coating slurry coated on at least one side of the polypropylene separator.

[0047] The raw materials of the coating slurry include: 100 g of n-butyl acrylate, 10 g of methyl methacrylate, 10 g of ethyl acrylate, 35 g of toluene diisocyanate, 10 g of graphene oxide, 80 g of nano-ceramic powder, 10 g of polyvinylidene fluoride, 1.5 g of vinyltriethoxysilane, 58 g of polydimethylsiloxane, 1.5 g of ammonium polyacrylate, 1.5 g of stannous octoate, and 80 g of ethyl acetate.

[0048] The coating slurry is prepared by the following steps: S1. Adding the nano-ceramic powder to 300 g of an ethanol aqueous solution with a mass fraction of 50%, performing ultrasonic treatment for 90 minutes, with an ultrasonic frequency of 7.5 kHz, adjusting the pH value of the system to 4 - 5 using hydrochloric acid with a concentration of 1.5 mol / L, adding vinyltriethoxysilane and performing ultrasonic treatment for 15 minutes, adding graphene oxide, stirring at 65°C for 2 hours, with a stirring speed of 400 r / min, filtering, washing, and vacuum drying to obtain the pretreated ceramic; S2. Adding n-butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocyanate, stannous octoate, and ethyl acetate to the pretreated ceramic, stirring at 80°C for 7 hours, adding polyvinylidene fluoride, polydimethylsiloxane, and ammonium polyacrylate thereto, and stirring at 68°C for 20 minutes, with a stirring speed of 2000 r / min.

[0049] The preparation method of the above high-temperature resistant modified acrylic composite material comprises the following steps: Coating the coating slurry on the surface of the polypropylene separator, curing at 80°C for 9 minutes, and drying; then placing it in an aqueous solution containing ammonia water and vitamin C (ammonia concentration is 15%, vitamin C concentration is 0.8 g / mL), performing reduction treatment at 130°C for 3 hours, and drying; the obtained coating thickness is 4 μm.

[0050] Comparative Example 2: A high-temperature resistant modified acrylic composite material, comprising a polypropylene separator and a coating slurry coated on at least one side of the polypropylene separator.

[0051] The raw materials of the coating slurry include: 100 g of n-butyl acrylate, 10 g of methyl methacrylate, 10 g of ethyl acrylate, 35 g of toluene diisocyanate, 2 g of methacrylic anhydride, 10 g of graphene oxide, 80 g of nano-ceramic powder, 10 g of polyvinylidene fluoride, 1.5 g of vinyltriethoxysilane, 58 g of polydimethylsiloxane, 1.5 g of ammonium polyacrylate, 1.5 g of stannous octoate, and 80 g of ethyl acetate.

[0052] The coating slurry is prepared by the following steps: S1. Add graphene oxide to 40 g of deionized water and stir evenly. Add methacrylic anhydride thereto, stir at a temperature of 60 °C for 3.5 h, and freeze-dry to obtain pretreated graphene. S2. Add nano-ceramic powder to 300 g of an ethanol aqueous solution with a mass fraction of 50% and perform ultrasonic treatment for 90 min at an ultrasonic frequency of 7.5 kHz. Adjust the pH value of the system to 4 - 5 with 1.5 mol / L hydrochloric acid, add vinyltriethoxysilane and perform ultrasonic treatment for 15 min, filter, wash, and vacuum-dry to obtain pretreated ceramics. S3. Add n-butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocyanate, stannous octoate, and ethyl acetate to the pretreated ceramics, stir at a temperature of 80 °C for 7 h, add polyvinylidene fluoride, pretreated graphene, polydimethylsiloxane, and ammonium polyacrylate thereto, and stir at a temperature of 68 °C for 20 min at a stirring speed of 2000 r / min.

[0053] The preparation method of the above high-temperature resistant modified acrylic composite material includes the following steps: Coating the coating slurry on the surface of a polypropylene separator, curing at a temperature of 80 °C for 9 min, and drying; then placing it in an aqueous solution containing ammonia water and vitamin C (ammonia concentration is 15%, vitamin C concentration is 0.8 g / mL), performing reduction treatment at a temperature of 130 °C for 3 h, and drying; the obtained coating thickness is 4 μm.

[0054] Cut the composite materials obtained in Examples 1 - 5 and Comparative Examples 1 - 2 into 15 mm × 200 mm, stretch them under a constant tensile force with a tensile testing machine at a tensile speed of 50 mm / min until the separator breaks.

[0055] As Figure 1 shown, the tensile strength of the composite material obtained in Example 5 is the highest, significantly superior to those of Example 1, Example 2, Example 4, Comparative Example 1, and Comparative Example 2 (P < 0.05); the tensile strength of the composite material obtained in Example 5 is also higher than that of Example 3, but there is no significant difference between the two.

[0056] The composite materials obtained in Examples 1-5 and Comparative Examples 1-2 were cut into 100 mm × 100 mm, and then the thermal shrinkage rate was tested. The thermal shrinkage test conditions were 200 °C × 1 h.

[0057] As Figure 2 shown, the thermal shrinkage rates of the composite materials obtained in Example 5 were the lowest, significantly better than those in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 (P < 0.05); the thermal shrinkage rates of the composite materials obtained in Example 5 were also lower than those in Example 3 and Example 4, but there was no significant difference among the three.

[0058] The composite materials obtained in Examples 1-5 and Comparative Examples 1-2 were subjected to a diaphragm electrolyte (EC:PC:EMC:EP = 1:1:1:1) absorption test. The sample size was 50 mm × 100 mm, and it was weighed (denoted as M 0 ), and then weighed again after soaking in the electrolyte for 24 h (denoted as M 1 ).

[0059] Liquid absorption rate = (M 1 —M 0 ) ÷ M 0 × 100%.

[0060] Button cells were assembled using the composite materials obtained in Examples 1-5 and Comparative Examples 1-2, together with ternary cathode electrodes and graphite anode electrodes. The ionic conductivity was tested at room temperature (25 °C) with a frequency range of 0 - 100000 Hz and a perturbation voltage of 5 mV.

[0061] As Figure 3 shown, the composite materials obtained in Example 5 had the highest liquid absorption rate and ionic conductivity, significantly better than those in Examples 1-4 and Comparative Examples 1-2 (P < 0.05).

[0062] The above button cells were subjected to a discharge rate test as follows: The button cells were charged at a constant current of 0.5C to 4.35V under constant current and constant voltage, and then charged at a constant voltage until the current dropped to 0.05C for cutoff. Then, they were discharged to 3.0V at currents of 0.2C, 1.0C, and 2.0C respectively, and the discharge capacities at different discharge rates were recorded. Taking the discharge capacity at 0.2C as 100%, the corresponding battery capacity retention rate was calculated.

[0063] As Figure 4 shown, the button cells made of the composite materials obtained in Example 5 had the highest battery capacity retention rate, significantly better than those in Comparative Examples 1-2 (P < 0.05). The battery capacity retention rates of the button cells made of the composite materials obtained in Example 5 were also better than those in Examples 1-4, but there was no significant difference among them.

[0064] The applicant believes that the reason for the above results is as follows: In the present invention, methacrylic anhydride is combined with the graphene oxide sheet structure, which not only plays a steric hindrance role and prevents the aggregation of the sheet structure, but also combines with the activated nanoscale ceramic powder in one step. This can not only improve the thermal conductivity of the material and have better high-temperature resistance performance, but also has excellent dispersion and compatibility with the acrylic resin, and can significantly enhance the high-temperature strength of the acrylic resin. The present invention forms a network structure between the pretreated ceramic and the acrylic resin, which can effectively prevent the movement of nanoparticles during the cycle, maintain the stability of the electrode structure, is beneficial to the cycle stability of the electrode, and at the same time makes the obtained composite material have high mechanical strength. The present invention can not only ensure low shrinkage rate and high safety of the composite material at high temperatures, but also make it have high conductivity at room temperature. It can not only greatly improve the charging speed of the lithium-ion battery and increase the specific energy of the battery, but also the good network structure formed between the ceramic particles and the acrylic resin enables the composite material to withstand a temperature of up to 180 °C, effectively avoiding problems such as shrinkage or melting caused by high temperatures.

[0065] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A high temperature resistant modified acrylic composite material, characterized in that: It includes a polypropylene diaphragm and a coating slurry coated on at least one side of the polypropylene diaphragm; The raw materials of the coating slurry include, by mass, 50-150 parts of n-butyl acrylate, 5-15 parts of methyl methacrylate, 5-15 parts of ethyl acrylate, 20-50 parts of toluene diisocyanate, 1-3 parts of methacrylic anhydride, 5-15 parts of graphene oxide, 50-100 parts of nano-scale ceramic powder, 5-15 parts of polyvinylidene fluoride, 1-2 parts of vinyl triethoxy silane, 50-65 parts of polysiloxane, 1-2 parts of dispersant, 1-2 parts of catalyst, and 50-100 parts of solvent.

2. The high temperature resistant modified acrylic composite material according to claim 1, characterized in that: The thickness of the polypropylene separator is 10-20 μm and the porosity is 35-45%.

3. The high temperature resistant modified acrylic composite material according to claim 1, characterized in that: The polysiloxane is at least one of polydimethylsiloxane, cyclomethicone, amino-modified polydimethylsiloxane and polymethylphenylsiloxane.

4. The high temperature resistant modified acrylic composite material according to claim 1, characterized in that: The dispersant is ammonium polyacrylate.

5. The high temperature resistant modified acrylic composite material according to claim 1, characterized in that: The catalyst is stannous octoate.

6. The high temperature resistant modified acrylic composite material according to claim 1, characterized in that: The solvent is toluene and / or ethyl acetate.

7. The high temperature resistant modified acrylic composite material according to claim 1, characterized in that: The coating slurry is prepared by the following steps: S1. Add graphene oxide to deionized water and stir evenly, add methacrylic anhydride thereto, stir at 50-70° C. for 2-5 h, and freeze-dry to obtain pretreated graphene; S2, adding nano-scale ceramic powder to ethanol aqueous solution and ultrasonically treating for 1-2 hours, adjusting the pH value of the system to 4-5, adding vinyl triethoxysilane and ultrasonically treating for 10-20 minutes, adding pretreated graphene, stirring at 50-80° C. for 1-3 hours, filtering, washing, and vacuum drying to obtain pretreated ceramics; S3. Add n-butyl acrylate, methyl methacrylate, ethyl acrylate, toluene diisocyanate, a catalyst, and a solvent to the pretreated ceramic, stir at 70-90° C. for 5-10 hours, add polyvinylidene fluoride, polysiloxane, and a dispersant, and stir at 50-80° C. for 10-30 minutes.

8. The high temperature resistant modified acrylic composite material according to claim 7, characterized in that: In S2, the ultrasound frequency is 5-12kHz.

9. A method for preparing the high temperature resistant modified acrylic composite material according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: applying the coating slurry on the surface of a polypropylene diaphragm, curing at 70-90°C for 6-12 minutes, and drying; then placing the coating slurry in an aqueous solution containing ammonia and vitamin C, performing reduction treatment at 120-140°C for 2-4 hours, and drying; the obtained coating has a thickness of 2-6 μm.

10. The method for preparing the high temperature resistant modified acrylic composite material according to claim 9, characterized in that: In the aqueous solution containing ammonia and vitamin C, the ammonia concentration is 12-18%, and the vitamin C concentration is 0.5-1 g / mL.

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