High-heat-resistance battery diaphragm and preparation method of battery

Abstract

The invention discloses a high-heat-resistance battery diaphragm and a preparation method of a battery, and relates to the technical field of battery diaphragms. The preparation method of the high-heat-resistance battery diaphragm comprises the following steps: step 1, preparing the modified porous silicon dioxide fiber membrane; step 2, preparing porous silicon dioxide modified polyimide; and step 3, preparing the high-heat-resistance battery diaphragm: (1) adding the porous silicon dioxide modified polyimide and a photoinitiator into dimethylacetamide, and uniformly stirring and mixing to obtain a to-be-coated solution; and (2) uniformly coating two surfaces of the modified porous silicon dioxide fiber membrane with the to-be-coated liquid, and carrying out vacuum drying and ultraviolet crosslinking to obtain the high-heat-resistance battery diaphragm. The preparation method of the battery comprises the following steps: winding and assembling the high-heat-resistance battery diaphragm, the positive electrode active material and the negative electrode active material, and injecting electrolyte to obtain the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separators, and in particular to a method for preparing a high-heat-resistant battery separator and a battery thereof. Background Art

[0002] As a core technology in the new energy sector, lithium-ion batteries have always been a research focus on safety and performance optimization. Traditional battery separators, often made of polyolefin materials (such as polyethylene (PE) and polypropylene (PP), offer cost advantages but suffer from poor thermal stability (heat shrinkage temperature ≤ 120°C). They can easily soften, shrink, or even melt at high temperatures, leading to contact between the positive and negative electrodes, causing short circuits and thermal runaway, posing a serious threat to battery safety. This is especially true during fast charging or extreme operating conditions for high-energy-density batteries, where traditional separators struggle to meet safety requirements.

[0003] To address these issues, highly heat-resistant separator materials have become a research hotspot. Polyimide (PI) is considered an ideal alternative due to its excellent thermal stability (thermal decomposition temperature ≥ 400°C), mechanical strength, and chemical inertness. However, traditional PI separators are complex to prepare and difficult to control their pore structure, resulting in insufficient ionic conductivity and thus impacting battery performance.

[0004] Based on this, the present invention will provide a high-heat-resistant battery separator, which will be applied to lithium batteries to further ensure the safety performance of lithium-ion batteries, which is of great significance for promoting the widespread application of lithium batteries in electric vehicles, energy storage systems and other fields. Summary of the Invention

[0005] The object of the present invention is to provide a high heat-resistant battery separator and a method for preparing the battery thereof, so as to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A method for preparing a high-heat-resistant battery separator comprises the following steps:

[0008] Step 1. Preparation of modified porous silica fiber membrane: (1) Electrospinning and calcining a silica spinning solution containing polystyrene nanospheres to obtain a porous silica fiber membrane; (2) Modifying the porous silica fiber membrane with a vinyl silane coupling agent to obtain a modified porous silica fiber membrane;

[0009] Step 2. Preparation of porous silica-modified polyimide: (1) adding hexafluorodianhydride to a mixed solution containing 4,4'-diaminodiphenyl ether, 3,5-diaminobenzoic acid, and maleic acid diamine, stirring and reacting to obtain a polyamic acid solution; (2) adding acetic anhydride and triethylamine to the polyamic acid solution, stirring and reacting, adding methanol to precipitate, filtering, washing, and vacuum drying to obtain polyimide; (3) reacting and grafting the polyimide with the modified porous silica to obtain a porous silica-modified polyimide;

[0010] Step 3. Preparation of a high-heat-resistant battery separator: (1) Adding porous silica-modified polyimide and a photoinitiator to dimethylacetamide, stirring and mixing evenly to obtain a coating liquid with a solid content of 5 to 15 wt%; (2) Uniformly coating the coating liquid on both surfaces of the modified porous silica fiber membrane, vacuum drying, and UV crosslinking to obtain a high-heat-resistant battery separator.

[0011] Furthermore, the preparation method of the modified porous silica fiber membrane is as follows: (1) dispersing polystyrene nanospheres into deionized water, and then adding tetraethyl orthosilicate and oxalic acid thereto at 30-50° C. with stirring, and after the addition is completed, continuing to stir and hydrolyze for 6-12 hours to obtain a silica spinning solution; (2) electrospinning the silica spinning solution to obtain a silica fiber membrane; (3) placing the silica fiber membrane in a muffle furnace and calcining it to obtain a porous silica fiber membrane; (4) adding a vinyl silane coupling agent, deionized water, and anhydrous ethanol into a reaction container, and adding acetic acid to adjust the pH of the solution to 4-6, stirring and mixing for 10-30 minutes to obtain a vinyl silane hydrolyzate; (5) soaking the porous silica fiber membrane in the vinyl silane hydrolyzate for 30-60 minutes, taking it out, and vacuum drying to obtain a modified porous silica fiber membrane.

[0012] Furthermore, the mass ratio of the polystyrene nanospheres, tetraethyl orthosilicate, oxalic acid and deionized water is (1-3):6:(0.02-0.06):50.

[0013] Furthermore, the particle size of the polystyrene nanospheres is 20 to 50 nm.

[0014] Furthermore, the electrospinning parameters are: spinning voltage of 15 to 25 kV, receiving distance of 15 to 20 cm, and injection speed of 0.5 to 1.5 mL / h.

[0015] Furthermore, the thickness of the silica fiber membrane is 4 to 10 μm.

[0016] Furthermore, the calcination parameters are: heating to 450-550° C. at a heating rate of 2-10° C. / min and calcining for 3-9 hours.

[0017] Furthermore, the mass ratio of the vinyl silane coupling agent, deionized water and anhydrous ethanol is 1:1:4.

[0018] Furthermore, the vinyl silane coupling agent includes but is not limited to any one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, and vinyldimethylethoxysilane.

[0019] Furthermore, the preparation method of the porous silica modified polyimide is as follows: (1) adding 4,4'-diaminodiphenyl ether, 3,5-diaminobenzoic acid and maleic acid diamine to dimethylacetamide, stirring and mixing uniformly, then adding hexafluorodianhydride to the solution under nitrogen protection, and stirring and reacting at 10-20°C for 12-36 hours to obtain a polyamic acid solution; (2) adding acetic anhydride and triethylamine to the polyamic acid solution under nitrogen protection, stirring and reacting for 12-24 hours; then adding Add sufficient methanol to precipitate, filter, wash, and vacuum dry at 250-300°C for 12-24 hours to obtain polyimide; (3) Under nitrogen protection, add polyimide, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine to dimethylacetamide, stir and mix evenly, then add modified porous silica to the solution, stir and react for 12-36 hours, then add sufficient methanol to the reaction system to precipitate, filter, wash, and vacuum dry to obtain porous silica-modified polyimide.

[0020] Furthermore, the raw materials required for preparing the porous silica-modified polyimide include the following components: by weight, 9.2 to 9.6 parts of 4,4'-diaminodiphenyl ether, 7 to 7.3 parts of 3,5-diaminobenzoic acid, 0.46 to 0.92 parts of maleic diamine, 44.4 to 46.6 parts of hexafluorodianhydride, 40 to 45 parts of acetic anhydride, 10 to 12 parts of triethylamine, 9 to 10 parts of dicyclohexylcarbodiimide, 4.5 to 5 parts of 4-dimethylaminopyridine, 6 to 8 parts of modified porous silica, and 300 parts of dimethylacetamide.

[0021] Furthermore, the preparation method of the modified porous silica is as follows: (1) adding an aminosilane coupling agent, deionized water, and anhydrous ethanol into a reaction container, and adding acetic acid to adjust the pH of the solution to 4-6, stirring and mixing for 10-30 minutes to obtain an aminosilane hydrolyzate; (2) adding the porous silica into a blender, stirring at a rate of 100-200 r / min, and uniformly spraying the aminosilane hydrolyzate therein, and after spraying, continuing to stir and mix for 1-3 hours, and drying to obtain the modified porous silica.

[0022] Furthermore, the mass ratio of the amino silane coupling agent, deionized water and anhydrous ethanol is 1:1:4.

[0023] Furthermore, the amount of the amino silane coupling agent added is 1 to 5% of the mass of the porous silica.

[0024] Furthermore, the amino silane coupling agent includes but is not limited to any one of 3-aminopropyltrimethoxysilane, bis[(3-trimethoxysilyl)propyl]amine, 3-aminopropyltriethoxysilane, bis[(3-triethoxysilyl)propyl]amine, 3-aminopropylmethyldimethoxysilane, and 3-aminopropylmethyldiethoxysilane.

[0025] Furthermore, the amount of the photoinitiator added is 1 to 3% of the mass of the porous silica-modified polyimide.

[0026] Furthermore, the parameters of the ultraviolet cross-linking are: ultraviolet wavelength is 300-400nm.

[0027] Furthermore, the thickness of the high heat-resistant battery separator is 16 to 30 μm.

[0028] A method for preparing a battery comprises the following steps: winding and assembling a high-heat-resistant battery separator, a positive electrode active material, and a negative electrode active material, and injecting an electrolyte to obtain a battery.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention uses polystyrene nanospheres as a template, combined with electrospinning and calcination processes, to produce a porous silica fiber membrane. This porous silica fiber membrane, as a separator matrix, can impart excellent mechanical strength and high-temperature stability to the separator, thereby improving the safety performance of the resulting battery.

[0031] 2. In the present invention, 4,4'-diaminodiphenyl ether, 3,5-diaminobenzoic acid, maleic diamine, and hexafluorodianhydride are first subjected to a condensation reaction (to obtain a polyamic acid having carboxyl groups and unsaturated bonds), followed by the addition of acetic anhydride and triethylamine for catalytic dehydration, followed by vacuum drying at 250-300°C (thermal imidization) to obtain a polyimide, and finally the polyimide is subjected to amidation grafting with modified porous silica to obtain a porous silica-modified polyimide. The polyimide itself has excellent heat resistance, and after further grafting with porous silica, its high-temperature stability is further enhanced.

[0032] 3. Because the porous silica-modified polyimide contains unsaturated bonds, the present invention further uses a vinyl silane coupling agent to modify the porous silica fiber membrane. The porous silica-modified polyimide is then formulated into a coating solution and applied to the modified porous silica fiber membrane. UV cross-linking forms a stable three-dimensional cross-linked network between the porous silica fiber membrane and the porous silica-modified polyimide, further strengthening the structural stability of the separator and preventing delamination due to extreme causes.

[0033] 4. Due to the synergistic effect of the porous silica fiber membrane and the porous silica-modified polyimide, the prepared high-heat-resistant battery separator has excellent heat resistance, mechanical strength and structural stability;

[0034] 5. The high heat-resistant battery separator prepared in the present invention has a high porosity, which is conducive to electrolyte infiltration. At the same time, its pore size is small, which can inhibit dendrite penetration, greatly ensuring the ion conduction efficiency and safety performance of the battery. DETAILED DESCRIPTION

[0035] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0036] It should be noted that the following parts are calculated by weight, and the purchasers of all raw materials involved in the present invention include, without any special restrictions, the following examples:

[0037] In the following examples,

[0038] The particle size of polystyrene nanospheres is 30 nm, model number PS01003, purchased from Ruige Biotechnology Co., Ltd.;

[0039] Tethyl orthosilicate (98% purity), vinyltrimethoxysilane (99.5% purity), 4,4'-diaminodiphenyl ether (99.5% purity), 3,5-diaminobenzoic acid (99.5% purity), diamine maleate (98% purity), hexafluorodianhydride (98% purity), 3-aminopropyltrimethoxysilane (99% purity), lithium iron phosphate (97% purity, particle size ≤ 5 μm), and graphite (99.8% purity) were purchased from MacLean Reagent Co., Ltd.

[0040] Porous silica with an average particle size of 2 μm and a pore size of 2 nm and photoinitiator, model Irgacure 2959, were purchased from Merck;

[0041] PP separator, model Celgard 2500, thickness 25 μm, purchased from Shenzhen Kejing Zhida Technology Co., Ltd.

[0042] LB-266 electrolyte, batch number: E843.250.032, was purchased from Zhengzhou Aikemu Chemical Co., Ltd.; the rest were commercially available;

[0043] In the following examples, each portion is 10 g.

[0044] Example 1: A method for preparing a high heat-resistant battery separator and a battery thereof:

[0045] Step 1. Preparation of modified porous silica fiber membrane: (1) Disperse polystyrene nanospheres into deionized water, then add tetraethyl orthosilicate and oxalic acid thereto at 40°C with stirring, and continue stirring and hydrolyzing for 9 hours to obtain silica spinning solution (the mass ratio of polystyrene nanospheres, tetraethyl orthosilicate, oxalic acid and deionized water is 2:6:0.04:50); (2) Electrospin the silica spinning solution to obtain a 6 μm thick silica fiber membrane (the parameters of electrospinning are: spinning voltage of 20 kV, receiving distance of 17 cm, and injection speed of 1 mL / h); (3) Place the silica fiber membrane on a The porous silica fiber membrane was placed in a muffle furnace and calcined (the calcination parameters were: heating to 500°C at a heating rate of 5°C / min and calcining for 6 hours); (4) vinyl trimethoxysilane, deionized water, and anhydrous ethanol were added to the reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain a vinyl silane hydrolyzate (the mass ratio of vinyl trimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4); (5) the porous silica fiber membrane was placed in the vinyl silane hydrolyzate and soaked for 45 minutes, taken out, and vacuum dried at 70°C for 6 hours to obtain a modified porous silica fiber membrane;

[0046] Step 2.

[0047] 1. Preparation of modified porous silica: (1) 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol were added to a reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain an aminosilane hydrolyzate (the mass ratio of 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4; the amount of 3-aminopropyltrimethoxysilane added was 3% of the mass of the porous silica); (2) The porous silica was added to a blender, stirred at a rate of 150 r / min, and the aminosilane hydrolyzate was uniformly sprayed therein. After spraying, the mixture was stirred for 2 hours, and dried to obtain the modified porous silica;

[0048] 2. Preparation of porous silica modified polyimide: (1) 9.4 parts (0.47 mol) of 4,4'-diaminodiphenyl ether, 7.15 parts (0.47 mol) of 3,5-diaminobenzoic acid, and 0.68 parts (0.06 mol) of maleic diamine were added to 200 parts of dimethylacetamide and stirred to mix uniformly. Then, under nitrogen protection, 45 parts (1.01 mol) of hexafluorodianhydride were added to the solution and stirred at 15°C for 24 hours to obtain a polyamic acid solution; (2) under nitrogen protection, 43 parts of acetic anhydride and 11 parts of triethylamine were added to the polyamic acid solution and stirred. The mixture was reacted for 18 hours; sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 280°C for 18 hours to obtain polyimide; (3) under nitrogen protection, the polyimide obtained in (2), 9.5 parts of dicyclohexylcarbodiimide, and 4.75 parts of 4-dimethylaminopyridine were added to 100 parts of dimethylacetamide, and the mixture was stirred and mixed uniformly. 7 parts of modified porous silica was then added to the solution, and the mixture was stirred and reacted for 24 hours. Subsequently, sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 140°C for 6 hours to obtain porous silica-modified polyimide;

[0049] Step 3. Preparation of a high-heat-resistant battery separator: (1) Adding porous silica-modified polyimide and Irgacure 2959 to dimethylacetamide, stirring and mixing uniformly to obtain a coating liquid with a solid content of 10 wt%; (2) Uniformly coating the coating liquid on both surfaces of the modified porous silica fiber membrane, vacuum drying at 140°C for 6 h, and then UV cross-linking under ultraviolet light with a wavelength of 365 nm to obtain a high-heat-resistant battery separator with a thickness of 25 μm.

[0050] Example 2: A method for preparing a high heat-resistant battery separator and a battery thereof:

[0051] Step 1. Preparation of modified porous silica fiber membrane: (1) Disperse polystyrene nanospheres into deionized water, then add tetraethyl orthosilicate and oxalic acid thereto at 40°C with stirring, and after the addition is complete, continue stirring and hydrolyzing for 9 hours to obtain silica spinning solution (the mass ratio of polystyrene nanospheres, tetraethyl orthosilicate, oxalic acid, and deionized water is 1:6:0.02:50); (2) The silica spinning solution is electrospun to obtain a 6 μm thick silica fiber membrane (the parameters of electrospinning are: spinning voltage of 20 kV, receiving distance of 17 cm, and injection speed of 1 mL / h); (3) Place the silica fiber membrane The porous silica fiber membrane was placed in a muffle furnace and calcined (the calcination parameters were: heating to 500°C at a heating rate of 5°C / min and calcining for 6 hours); (4) vinyl trimethoxysilane, deionized water, and anhydrous ethanol were added to the reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain a vinyl silane hydrolyzate (the mass ratio of vinyl trimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4); (5) the porous silica fiber membrane was placed in the vinyl silane hydrolyzate and soaked for 45 minutes, taken out, and vacuum dried at 70°C for 6 hours to obtain a modified porous silica fiber membrane;

[0052] Step 2.

[0053] 1. Preparation of modified porous silica: (1) 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol were added to a reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain an aminosilane hydrolyzate (the mass ratio of 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4; the amount of 3-aminopropyltrimethoxysilane added was 3% of the mass of the porous silica); (2) The porous silica was added to a blender, stirred at a rate of 150 r / min, and the aminosilane hydrolyzate was uniformly sprayed therein. After spraying, the mixture was stirred for 2 hours, and dried to obtain the modified porous silica;

[0054] 2. Preparation of porous silica modified polyimide: (1) 9.4 parts (0.47 mol) of 4,4'-diaminodiphenyl ether, 7.15 parts (0.47 mol) of 3,5-diaminobenzoic acid, and 0.68 parts (0.06 mol) of maleic diamine were added to 200 parts of dimethylacetamide and stirred to mix uniformly. Then, under nitrogen protection, 45 parts (1.01 mol) of hexafluorodianhydride were added to the solution and stirred at 15°C for 24 hours to obtain a polyamic acid solution; (2) under nitrogen protection, 43 parts of acetic anhydride and 11 parts of triethylamine were added to the polyamic acid solution and stirred. The mixture was reacted for 18 hours; sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 280°C for 18 hours to obtain polyimide; (3) under nitrogen protection, the polyimide obtained in (2), 9.5 parts of dicyclohexylcarbodiimide, and 4.75 parts of 4-dimethylaminopyridine were added to 100 parts of dimethylacetamide, and the mixture was stirred and mixed uniformly. 7 parts of modified porous silica was then added to the solution, and the mixture was stirred and reacted for 24 hours. Subsequently, sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 140°C for 6 hours to obtain porous silica-modified polyimide;

[0055] Step 3. Preparation of a high-heat-resistant battery separator: (1) Adding porous silica-modified polyimide and Irgacure 2959 to dimethylacetamide, stirring and mixing uniformly to obtain a coating liquid with a solid content of 10 wt%; (2) Uniformly coating the coating liquid on both surfaces of the modified porous silica fiber membrane, vacuum drying at 140°C for 6 h, and then UV cross-linking under ultraviolet light with a wavelength of 365 nm to obtain a high-heat-resistant battery separator with a thickness of 25 μm.

[0056] Example 3: A method for preparing a high heat-resistant battery separator and a battery thereof:

[0057] Step 1. Preparation of modified porous silica fiber membrane: (1) Disperse polystyrene nanospheres into deionized water, then add tetraethyl orthosilicate and oxalic acid thereto at 40°C with stirring, and continue stirring and hydrolyzing for 9 hours to obtain silica spinning solution (the mass ratio of polystyrene nanospheres, tetraethyl orthosilicate, oxalic acid and deionized water is 3:6:0.06:50); (2) Electrospin the silica spinning solution to obtain a 6 μm thick silica fiber membrane (the parameters of electrospinning are: spinning voltage of 20 kV, receiving distance of 17 cm, and injection speed of 1 mL / h); (3) Place the silica fiber membrane on a The porous silica fiber membrane was placed in a muffle furnace and calcined (the calcination parameters were: heating to 500°C at a heating rate of 5°C / min and calcining for 6 hours); (4) vinyl trimethoxysilane, deionized water, and anhydrous ethanol were added to the reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain a vinyl silane hydrolyzate (the mass ratio of vinyl trimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4); (5) the porous silica fiber membrane was placed in the vinyl silane hydrolyzate and soaked for 45 minutes, taken out, and vacuum dried at 70°C for 6 hours to obtain a modified porous silica fiber membrane;

[0058] Step 2.

[0059] 1. Preparation of modified porous silica: (1) 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol were added to a reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain an aminosilane hydrolyzate (the mass ratio of 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4; the amount of 3-aminopropyltrimethoxysilane added was 3% of the mass of the porous silica); (2) The porous silica was added to a blender, stirred at a rate of 150 r / min, and the aminosilane hydrolyzate was uniformly sprayed therein. After spraying, the mixture was stirred for 2 hours, and dried to obtain the modified porous silica;

[0060] 2. Preparation of porous silica modified polyimide: (1) 9.4 parts (0.47 mol) of 4,4'-diaminodiphenyl ether, 7.15 parts (0.47 mol) of 3,5-diaminobenzoic acid, and 0.68 parts (0.06 mol) of maleic diamine were added to 200 parts of dimethylacetamide and stirred to mix uniformly. Then, under nitrogen protection, 45 parts (1.01 mol) of hexafluorodianhydride were added to the solution and stirred at 15°C for 24 hours to obtain a polyamic acid solution; (2) under nitrogen protection, 43 parts of acetic anhydride and 11 parts of triethylamine were added to the polyamic acid solution and stirred. The mixture was reacted for 18 hours; sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 280°C for 18 hours to obtain polyimide; (3) under nitrogen protection, the polyimide obtained in (2), 9.5 parts of dicyclohexylcarbodiimide, and 4.75 parts of 4-dimethylaminopyridine were added to 100 parts of dimethylacetamide, and the mixture was stirred and mixed uniformly. 7 parts of modified porous silica was then added to the solution, and the mixture was stirred and reacted for 24 hours. Subsequently, sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 140°C for 6 hours to obtain porous silica-modified polyimide;

[0061] Step 3. Preparation of a high-heat-resistant battery separator: (1) Adding porous silica-modified polyimide and Irgacure 2959 to dimethylacetamide, stirring and mixing uniformly to obtain a coating liquid with a solid content of 10 wt%; (2) Uniformly coating the coating liquid on both surfaces of the modified porous silica fiber membrane, vacuum drying at 140°C for 6 h, and then UV cross-linking under ultraviolet light with a wavelength of 365 nm to obtain a high-heat-resistant battery separator with a thickness of 25 μm.

[0062] Based on Example 1, Examples 4 and 5 are set as follows:

[0063] Example 4: A method for preparing a high heat-resistant battery separator and a battery thereof:

[0064] Step 1. Preparation of modified porous silica fiber membrane: (1) Disperse polystyrene nanospheres into deionized water, then add tetraethyl orthosilicate and oxalic acid thereto at 40°C with stirring, and continue stirring and hydrolyzing for 9 hours to obtain silica spinning solution (the mass ratio of polystyrene nanospheres, tetraethyl orthosilicate, oxalic acid and deionized water is 2:6:0.04:50); (2) Electrospin the silica spinning solution to obtain a 6 μm thick silica fiber membrane (the parameters of electrospinning are: spinning voltage of 20 kV, receiving distance of 17 cm, and injection speed of 1 mL / h); (3) Place the silica fiber membrane on a The porous silica fiber membrane was placed in a muffle furnace and calcined (the calcination parameters were: heating to 500°C at a heating rate of 5°C / min and calcining for 6 hours); (4) vinyl trimethoxysilane, deionized water, and anhydrous ethanol were added to the reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain a vinyl silane hydrolyzate (the mass ratio of vinyl trimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4); (5) the porous silica fiber membrane was placed in the vinyl silane hydrolyzate and soaked for 45 minutes, taken out, and vacuum dried at 70°C for 6 hours to obtain a modified porous silica fiber membrane;

[0065] Step 2.

[0066] 1. Preparation of modified porous silica: (1) 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol were added to a reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain an aminosilane hydrolyzate (the mass ratio of 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4; the amount of 3-aminopropyltrimethoxysilane added was 3% of the mass of the porous silica); (2) The porous silica was added to a blender, stirred at a rate of 150 r / min, and the aminosilane hydrolyzate was uniformly sprayed therein. After spraying, the mixture was stirred for 2 hours, and dried to obtain the modified porous silica;

[0067] 2. Preparation of porous silica modified polyimide: (1) 9.2 parts (0.46 mol) of 4,4'-diaminodiphenyl ether, 7 parts (0.46 mol) of 3,5-diaminobenzoic acid, and 0.92 parts (0.08 mol) of maleic acid diamine were added to 200 parts of dimethylacetamide, and stirred to mix uniformly. Then, under nitrogen protection, 45 parts (1.01 mol) of hexafluorodianhydride were added to the solution, and stirred at 15°C for 24 hours to obtain a polyamic acid solution; (2) under nitrogen protection, 43 parts of acetic anhydride and 11 parts of triethylamine were added to the polyamic acid solution, and stirred to react. 18h; then add sufficient methanol to the reaction system to precipitate, filter, wash, and vacuum dry at 250℃ for 12h to obtain polyimide; (3) under nitrogen protection, add the polyimide obtained in (2), 9.5 parts of dicyclohexylcarbodiimide, and 4.75 parts of 4-dimethylaminopyridine to 100 parts of dimethylacetamide, stir and mix evenly, then add 6 parts of modified porous silica to the solution, stir and react for 12h, then add sufficient methanol to the reaction system to precipitate, filter, wash, and vacuum dry at 140℃ for 6h to obtain porous silica-modified polyimide;

[0068] Step 3. Preparation of a high-heat-resistant battery separator: (1) Adding porous silica-modified polyimide and Irgacure 2959 to dimethylacetamide, stirring and mixing uniformly to obtain a coating liquid with a solid content of 10 wt%; (2) Uniformly coating the coating liquid on both surfaces of the modified porous silica fiber membrane, vacuum drying at 140°C for 6 h, and then UV cross-linking under ultraviolet light with a wavelength of 365 nm to obtain a high-heat-resistant battery separator with a thickness of 25 μm.

[0069] Example 5: A method for preparing a high heat-resistant battery separator and a battery thereof:

[0070] Step 1. Preparation of modified porous silica fiber membrane: (1) Disperse polystyrene nanospheres into deionized water, then add tetraethyl orthosilicate and oxalic acid thereto at 40°C with stirring, and continue stirring and hydrolyzing for 9 hours to obtain silica spinning solution (the mass ratio of polystyrene nanospheres, tetraethyl orthosilicate, oxalic acid and deionized water is 2:6:0.04:50); (2) Electrospin the silica spinning solution to obtain a 6 μm thick silica fiber membrane (the parameters of electrospinning are: spinning voltage of 20 kV, receiving distance of 17 cm, and injection speed of 1 mL / h); (3) Place the silica fiber membrane on a The porous silica fiber membrane was placed in a muffle furnace and calcined (the calcination parameters were: heating to 500°C at a heating rate of 5°C / min and calcining for 6 hours); (4) vinyl trimethoxysilane, deionized water, and anhydrous ethanol were added to the reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain a vinyl silane hydrolyzate (the mass ratio of vinyl trimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4); (5) the porous silica fiber membrane was placed in the vinyl silane hydrolyzate and soaked for 45 minutes, taken out, and vacuum dried at 70°C for 6 hours to obtain a modified porous silica fiber membrane;

[0071] Step 2.

[0072] 1. Preparation of modified porous silica: (1) 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol were added to a reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain an aminosilane hydrolyzate (the mass ratio of 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4; the amount of 3-aminopropyltrimethoxysilane added was 3% of the mass of the porous silica); (2) The porous silica was added to a blender, stirred at a rate of 150 r / min, and the aminosilane hydrolyzate was uniformly sprayed therein. After spraying, the mixture was stirred for 2 hours, and dried to obtain the modified porous silica;

[0073] 2. Preparation of porous silica modified polyimide: (1) 9.6 parts (0.48 mol) of 4,4'-diaminodiphenyl ether, 7.3 parts (0.48 mol) of 3,5-diaminobenzoic acid, and 0.46 parts (0.04 mol) of maleic diamine were added to 200 parts of dimethylacetamide, and the mixture was stirred and mixed uniformly. Then, under nitrogen protection, 45 parts (1.01 mol) of hexafluorodianhydride was added to the solution, and the mixture was stirred and reacted at 15°C for 24 hours to obtain a polyamic acid solution; (2) under nitrogen protection, 43 parts of acetic anhydride and 11 parts of triethylamine were added to the polyamic acid solution, and the mixture was stirred and reacted. The mixture was stirred for 18 hours; sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 300°C for 24 hours to obtain polyimide; (3) under nitrogen protection, the polyimide obtained in (2), 9.5 parts of dicyclohexylcarbodiimide, and 4.75 parts of 4-dimethylaminopyridine were added to 100 parts of dimethylacetamide, and the mixture was stirred and mixed evenly. 8 parts of modified porous silica were added to the solution, and the mixture was stirred and reacted for 36 hours. Then, sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 140°C for 6 hours to obtain porous silica-modified polyimide;

[0074] Step 3. Preparation of a high-heat-resistant battery separator: (1) Adding porous silica-modified polyimide and Irgacure 2959 to dimethylacetamide, stirring and mixing uniformly to obtain a coating liquid with a solid content of 10 wt%; (2) Uniformly coating the coating liquid on both surfaces of the modified porous silica fiber membrane, vacuum drying at 140°C for 6 h, and then UV cross-linking under ultraviolet light with a wavelength of 365 nm to obtain a high-heat-resistant battery separator with a thickness of 25 μm.

[0075] The following comparative experiments are conducted based on Example 1, and comparative examples 1 to 4 are set as follows:

[0076] Comparative Example 1: Comparative Example 1 is based on Example 1, with the following adjustments: no polystyrene nanospheres are added to the silica spinning solution, and other processes remain unchanged, specifically:

[0077] A high heat-resistant battery separator and a method for preparing the same:

[0078] Step 1. Preparation of modified silica fiber membrane: (1) Adding ethyl orthosilicate and oxalic acid to deionized water at 40°C with stirring, and continuing to stir and hydrolyze for 9 hours to obtain silica spinning solution (the mass ratio of ethyl orthosilicate, oxalic acid and deionized water is 6:0.04:50); (2) The silica spinning solution is electrospun to obtain a 6 μm thick silica fiber membrane (the parameters of electrospinning are: spinning voltage of 20 kV, receiving distance of 17 cm, injection speed of 0.05 mm, and injection speed of 0.05 mm). (3) adding vinyl trimethoxysilane, deionized water and anhydrous ethanol into a reaction vessel, and adding acetic acid to adjust the pH of the solution to 5, stirring and mixing for 20 minutes to obtain a vinyl silane hydrolyzate (the mass ratio of vinyl trimethoxysilane, deionized water and anhydrous ethanol is 1:1:4); (5) soaking the silica fiber membrane in the vinyl silane hydrolyzate for 45 minutes, taking it out, and vacuum drying it at 70°C for 6 hours to obtain a modified silica fiber membrane;

[0079] Step 2.

[0080] 1. Preparation of modified porous silica: (1) 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol were added to a reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain an aminosilane hydrolyzate (the mass ratio of 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4; the amount of 3-aminopropyltrimethoxysilane added was 3% of the mass of the porous silica); (2) The porous silica was added to a blender, stirred at a rate of 150 r / min, and the aminosilane hydrolyzate was uniformly sprayed therein. After spraying, the mixture was stirred for 2 hours, and dried to obtain the modified porous silica;

[0081] 2. Preparation of porous silica modified polyimide: (1) 9.4 parts (0.47 mol) of 4,4'-diaminodiphenyl ether, 7.15 parts (0.47 mol) of 3,5-diaminobenzoic acid, and 0.68 parts (0.06 mol) of maleic diamine were added to 200 parts of dimethylacetamide and stirred to mix uniformly. Then, under nitrogen protection, 45 parts (1.01 mol) of hexafluorodianhydride were added to the solution and stirred at 15°C for 24 hours to obtain a polyamic acid solution; (2) under nitrogen protection, 43 parts of acetic anhydride and 11 parts of triethylamine were added to the polyamic acid solution and stirred. The mixture was reacted for 18 hours; sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 280°C for 18 hours to obtain polyimide; (3) under nitrogen protection, the polyimide obtained in (2), 9.5 parts of dicyclohexylcarbodiimide, and 4.75 parts of 4-dimethylaminopyridine were added to 100 parts of dimethylacetamide, and the mixture was stirred and mixed uniformly. 7 parts of modified porous silica was then added to the solution, and the mixture was stirred and reacted for 24 hours. Subsequently, sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 140°C for 6 hours to obtain porous silica-modified polyimide;

[0082] Step 3. Preparation of a high-heat-resistant battery separator: (1) Adding porous silica-modified polyimide and Irgacure 2959 to dimethylacetamide, stirring and mixing uniformly to obtain a coating liquid with a solid content of 10 wt%; (2) Uniformly coating the coating liquid on both surfaces of the modified silica fiber membrane, vacuum drying at 140°C for 6 hours, and then UV cross-linking under ultraviolet light with a wavelength of 365 nm to obtain a high-heat-resistant battery separator with a thickness of 25 μm.

[0083] Comparative Example 2: Comparative Example 2 is based on Example 1, with the following adjustments: the porous silica fiber membrane is not modified, and other processes remain unchanged, specifically:

[0084] A high heat-resistant battery separator and a method for preparing the same:

[0085] Step 1. Preparation of modified porous silica fiber membrane: (1) Disperse polystyrene nanospheres in deionized water, and then add tetraethyl orthosilicate and oxalic acid thereto at 40°C with stirring. After the addition is complete, continue stirring and hydrolyzing for 9 hours to obtain silica spinning solution (the mass ratio of the polystyrene nanospheres, tetraethyl orthosilicate, oxalic acid, and deionized water is 2:6:0.04:50); (2) Electrospin the silica spinning solution to obtain a 6 μm thick silica fiber membrane (the electrospinning parameters are: spinning voltage of 20 kV, receiving distance of 17 cm, and injection speed of 1 mL / h); (3) Place the silica fiber membrane in a muffle furnace and calcine to obtain a porous silica fiber membrane (the calcination parameters are: heating to 500°C at a heating rate of 5°C / min and calcining for 6 hours);

[0086] Step 2.

[0087] 1. Preparation of modified porous silica: (1) 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol were added to a reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain an aminosilane hydrolyzate (the mass ratio of 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4; the amount of 3-aminopropyltrimethoxysilane added was 3% of the mass of the porous silica); (2) The porous silica was added to a blender, stirred at a rate of 150 r / min, and the aminosilane hydrolyzate was uniformly sprayed therein. After spraying, the mixture was stirred for 2 hours, and dried to obtain the modified porous silica;

[0088] 2. Preparation of porous silica modified polyimide: (1) 9.4 parts (0.47 mol) of 4,4'-diaminodiphenyl ether, 7.15 parts (0.47 mol) of 3,5-diaminobenzoic acid, and 0.68 parts (0.06 mol) of maleic diamine were added to 200 parts of dimethylacetamide and stirred to mix uniformly. Then, under nitrogen protection, 45 parts (1.01 mol) of hexafluorodianhydride were added to the solution and stirred at 15°C for 24 hours to obtain a polyamic acid solution; (2) under nitrogen protection, 43 parts of acetic anhydride and 11 parts of triethylamine were added to the polyamic acid solution and stirred. The mixture was reacted for 18 hours; sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 280°C for 18 hours to obtain polyimide; (3) under nitrogen protection, the polyimide obtained in (2), 9.5 parts of dicyclohexylcarbodiimide, and 4.75 parts of 4-dimethylaminopyridine were added to 100 parts of dimethylacetamide, and the mixture was stirred and mixed uniformly. 7 parts of modified porous silica was then added to the solution, and the mixture was stirred and reacted for 24 hours. Subsequently, sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 140°C for 6 hours to obtain porous silica-modified polyimide;

[0089] Step 3. Preparation of a high-heat-resistant battery separator: (1) Adding porous silica-modified polyimide and Irgacure 2959 to dimethylacetamide, stirring and mixing uniformly to obtain a coating liquid with a solid content of 10 wt%; (2) Uniformly coating the coating liquid on both surfaces of the porous silica fiber membrane, vacuum drying at 140°C for 6 h, and then UV cross-linking under ultraviolet light with a wavelength of 365 nm to obtain a high-heat-resistant battery separator with a thickness of 25 μm.

[0090] Comparative Example 3: Comparative Example 3 is based on Example 1, with the following adjustments: modified porous silica is not added to modify the polyimide, and other processes remain unchanged, specifically:

[0091] A high heat-resistant battery separator and a method for preparing the same:

[0092] Step 1. Preparation of modified porous silica fiber membrane: (1) Disperse polystyrene nanospheres into deionized water, then add tetraethyl orthosilicate and oxalic acid thereto at 40°C with stirring, and after the addition is complete, continue stirring and hydrolyzing for 9 hours to obtain silica spinning solution (the mass ratio of the polystyrene nanospheres, tetraethyl orthosilicate, oxalic acid and deionized water is 2:6:0.04:50); (2) Electrospin the silica spinning solution to obtain a 6 μm thick silica fiber membrane (the electrospinning parameters are: spinning voltage of 20 kV, receiving distance of 17 cm, and injection speed of 1 mL / h); (3) Spin the silica fiber membrane The porous silica fiber membrane was placed in a muffle furnace and calcined (the calcination parameters were: heating to 500°C at a heating rate of 5°C / min and calcining for 6 hours); (4) vinyl trimethoxysilane, deionized water, and anhydrous ethanol were added to the reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain a vinyl silane hydrolyzate (the mass ratio of vinyl trimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4); (5) the porous silica fiber membrane was placed in the vinyl silane hydrolyzate and soaked for 45 minutes, taken out, and vacuum dried at 70°C for 6 hours to obtain a modified porous silica fiber membrane;

[0093] Step 2. Preparation of polyimide: (1) Add 9.4 parts (0.47 mol) of 4,4'-diaminodiphenyl ether, 7.15 parts (0.47 mol) of 3,5-diaminobenzoic acid, and 0.68 parts (0.06 mol) of maleic acid diamine to 200 parts of dimethylacetamide, stir and mix uniformly, then add 45 parts (1.01 mol) of hexafluorodianhydride to the solution under nitrogen protection, and stir and react at 15°C for 24 hours to obtain a polyamic acid solution; (2) Add 43 parts of acetic anhydride and 11 parts of triethylamine to the polyamic acid solution under nitrogen protection, and stir and react for 18 hours; then add sufficient methanol to the reaction system to precipitate, filter, wash, and vacuum dry at 280°C for 18 hours to obtain polyimide;

[0094] Step 3. Preparation of a high-heat-resistant battery separator: (1) Adding polyimide and Irgacure 2959 to dimethylacetamide, stirring and mixing uniformly to obtain a coating liquid with a solid content of 10 wt%; (2) Uniformly coating the coating liquid on both surfaces of the modified porous silica fiber membrane, vacuum drying at 140°C for 6 hours, and then UV cross-linking under ultraviolet light with a wavelength of 365 nm to obtain a high-heat-resistant battery separator with a thickness of 25 μm.

[0095] Comparative Example 4: Comparative Example 4 is based on Example 1, with the following modifications: the porous silica-modified polyimide is coated on the aluminum-plastic film, dried, formed, and demolded to obtain a high-heat-resistant battery separator. Other processes remain unchanged, specifically:

[0096] A high heat-resistant battery separator and a method for preparing the same:

[0097] Step 1.

[0098] 1. Preparation of modified porous silica: (1) 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol were added to a reaction vessel, and acetic acid was added to adjust the pH of the solution to 5, and the mixture was stirred for 20 minutes to obtain an aminosilane hydrolyzate (the mass ratio of 3-aminopropyltrimethoxysilane, deionized water, and anhydrous ethanol was 1:1:4; the amount of 3-aminopropyltrimethoxysilane added was 3% of the mass of the porous silica); (2) The porous silica was added to a blender, stirred at a rate of 150 r / min, and the aminosilane hydrolyzate was uniformly sprayed therein. After spraying, the mixture was stirred for 2 hours, and dried to obtain the modified porous silica;

[0099] 2. Preparation of porous silica modified polyimide: (1) 9.4 parts (0.47 mol) of 4,4'-diaminodiphenyl ether, 7.15 parts (0.47 mol) of 3,5-diaminobenzoic acid, and 0.68 parts (0.06 mol) of maleic diamine were added to 200 parts of dimethylacetamide and stirred to mix uniformly. Then, under nitrogen protection, 45 parts (1.01 mol) of hexafluorodianhydride were added to the solution and stirred at 15°C for 24 hours to obtain a polyamic acid solution; (2) under nitrogen protection, 43 parts of acetic anhydride and 11 parts of triethylamine were added to the polyamic acid solution and stirred. The mixture was reacted for 18 hours; sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 280°C for 18 hours to obtain polyimide; (3) under nitrogen protection, the polyimide obtained in (2), 9.5 parts of dicyclohexylcarbodiimide, and 4.75 parts of 4-dimethylaminopyridine were added to 100 parts of dimethylacetamide, and the mixture was stirred and mixed uniformly. 7 parts of modified porous silica was then added to the solution, and the mixture was stirred and reacted for 24 hours. Subsequently, sufficient methanol was added to the reaction system to precipitate, which was filtered, washed, and vacuum dried at 140°C for 6 hours to obtain porous silica-modified polyimide;

[0100] Step 2. Preparation of a high-heat-resistant battery separator: (1) Adding porous silica-modified polyimide to dimethylacetamide, stirring and mixing uniformly to obtain a coating liquid with a solid content of 10 wt%; (2) Uniformly coating the coating liquid on the surface of the aluminum-plastic film, vacuum drying at 140°C for 6 hours, removing the aluminum-plastic film, and obtaining a high-heat-resistant battery separator with a thickness of 25 μm.

[0101] Performance Test 1: The heat resistance, mechanical properties, and air permeability of the high heat-resistant battery separators prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were tested. The specific test methods are as follows:

[0102] (1) Heat resistance: Cut the high heat-resistant battery separator into 20 cm × 20 cm square test samples, place them in an oven, and heat and bake them at 130 ° C for 10 min and 410 ° C for 10 s, respectively. Measure the change in side length and calculate the thermal shrinkage rate to evaluate the heat resistance.

[0103] (2) Mechanical properties: The high heat-resistant battery separator was cut into rectangular test samples of 1 cm × 10 cm and subjected to a tensile strength test in the longitudinal direction at a speed of 5 cm / min using a universal testing machine to evaluate its mechanical properties;

[0104] (3) Air permeability: The air permeability of high heat-resistant battery separators was tested using a BTY-B2P air permeability tester at a temperature of 23°C and a pressure of 1.22 kPa, using dry nitrogen as the test gas.

[0105] The test data results of the above high heat-resistant battery separator are shown in Table 1 below:

[0106] Table 1

[0107]

[0108] Analysis of results: From the data in Table 1 above, it can be seen that: in the present invention, a battery separator with high heat shrinkage resistance, excellent tensile strength and excellent air permeability is comprehensively prepared by combining the resin with the matrix. In the present invention, by introducing polystyrene nanospheres into the silica spinning solution, the porous silica fiber membrane finally obtained has a certain pore structure, which can effectively enhance the heat shrinkage rate and air permeability of the high heat-resistant battery separator; by modifying the porous silica fiber membrane, the combination of the porous silica-modified polyimide and it can be enhanced, which has a certain effect on the tensile strength and air permeability of the high heat-resistant battery separator; and the modification of the polyimide by porous silica has a significant modification effect on the heat shrinkage rate, tensile strength and air permeability of the high heat-resistant battery separator.

[0109] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high heat-resistant battery separator, characterized in that: The following steps are involved: Step 1. Preparation of modified porous silica fiber membrane: (1) A silica spinning solution containing polystyrene nanospheres is electrospun and calcined to obtain a porous silica fiber membrane; (2) The porous silica fiber membrane is modified by a vinyl silane coupling agent to obtain a modified porous silica fiber membrane; Step 2. Preparation of porous silica-modified polyimide: (1) adding hexafluorodianhydride to a mixed solution containing 4,4'-diaminodiphenyl ether, 3,5-diaminobenzoic acid, and maleic diamine, stirring and reacting to obtain a polyamic acid solution; (2) adding acetic anhydride and triethylamine to the polyamic acid solution, stirring to react, adding methanol to precipitate, filtering, washing, and vacuum drying to obtain polyimide; (3) polyimide is reacted and grafted with modified porous silica to obtain porous silica-modified polyimide; Step 3. Preparation of high heat-resistant battery separator: (1) adding porous silica-modified polyimide and a photoinitiator to dimethylacetamide, stirring and mixing uniformly to obtain a coating solution having a solid content of 5 to 15 wt %; (2) The coating liquid is evenly coated on both surfaces of the modified porous silica fiber membrane, and then vacuum dried and UV cross-linked to obtain a high heat-resistant battery separator.

2. The method for preparing a high heat-resistant battery separator according to claim 1, wherein: The preparation method of the modified porous silica fiber membrane is as follows: (1) Dispersing polystyrene nanospheres in deionized water, then adding ethyl orthosilicate and oxalic acid thereto at 30-50° C. with stirring, and then continuing to stir and hydrolyze for 6-12 hours to obtain a silica spinning solution; (2) electrospinning the silica spinning solution to obtain a silica fiber membrane; (3) placing the silica fiber membrane in a muffle furnace and calcining it to obtain a porous silica fiber membrane; (4) adding a vinyl silane coupling agent, deionized water, and anhydrous ethanol into a reaction vessel, and adding acetic acid to adjust the pH of the solution to 4 to 6, stirring and mixing for 10 to 30 minutes to obtain a vinyl silane hydrolyzate; (5) Soaking the porous silica fiber membrane in a vinyl silane hydrolyzate for 30 to 60 minutes, taking it out, and vacuum drying it to obtain a modified porous silica fiber membrane.

3. The method for preparing a high heat-resistant battery separator according to claim 2, characterized in that: The mass ratio of the polystyrene nanospheres, tetraethyl orthosilicate, oxalic acid and deionized water is (1-3):6:(0.02-0.06):50; The particle size of the polystyrene nanospheres is 20 to 50 nm; The electrospinning parameters are as follows: spinning voltage of 15-25 kV, receiving distance of 15-20 cm, and injection speed of 0.5-1.5 mL / h; The thickness of the silica fiber membrane is 4 to 10 μm; The calcination parameters are: heating to 450-550°C at a heating rate of 2-10°C / min and calcining for 3-9h; The mass ratio of the vinyl silane coupling agent, deionized water and anhydrous ethanol is 1:1:4; The vinyl silane coupling agent includes any one of vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tri(2-methoxyethoxy)silane, vinyl triisopropoxysilane, and vinyl dimethylethoxysilane.

4. The method for preparing a high heat-resistant battery separator according to claim 1, wherein: The preparation method of the porous silica-modified polyimide is: (1) adding 4,4'-diaminodiphenyl ether, 3,5-diaminobenzoic acid, and maleic acid diamine to dimethylacetamide, stirring and mixing uniformly, then adding hexafluorodianhydride to the solution under nitrogen protection, and stirring and reacting at 10-20°C for 12-36 hours to obtain a polyamic acid solution; (2) Under nitrogen protection, acetic anhydride and triethylamine are added to the polyamic acid solution, and the mixture is stirred and reacted for 12 to 24 hours; sufficient methanol is then added to the reaction system to precipitate the precipitate, which is filtered, washed, and vacuum dried at 250 to 300° C. for 12 to 24 hours to obtain polyimide; (3) Under nitrogen protection, polyimide, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine are added to dimethylacetamide and stirred to mix evenly. Modified porous silica is then added to the solution and stirred to react for 12 to 36 hours. Sufficient methanol is then added to the reaction system to precipitate, which is then filtered, washed, and vacuum-dried to obtain porous silica-modified polyimide.

5. The method for preparing a high heat-resistant battery separator according to claim 4, characterized in that: The raw materials required for the preparation of the porous silica modified polyimide, The invention comprises the following components: by weight, 9.2-9.6 parts of 4,4'-diaminodiphenyl ether, 7-7.3 parts of 3,5-diaminobenzoic acid, 0.46-0.92 parts of diamine maleate, 44.4-46.6 parts of hexafluorodianhydride, 40-45 parts of acetic anhydride, 10-12 parts of triethylamine, 9-10 parts of dicyclohexylcarbodiimide, 4.5-5 parts of 4-dimethylaminopyridine, 6-8 parts of modified porous silica and 300 parts of dimethylacetamide.

6. The method for preparing a high heat-resistant battery separator according to claim 4, characterized in that: The preparation method of the modified porous silica is: (1) adding an aminosilane coupling agent, deionized water, and anhydrous ethanol into a reaction vessel, and adding acetic acid to adjust the pH of the solution to 4 to 6, stirring and mixing for 10 to 30 minutes to obtain an aminosilane hydrolyzate; (2) The porous silica is added into a mixer and stirred at a rate of 100 to 200 r / min, while the aminosilane hydrolyzate is evenly sprayed therein. After the spraying is completed, the mixture is stirred and mixed for 1 to 3 hours, and the modified porous silica is obtained after drying.

7. The method for preparing a high heat-resistant battery separator according to claim 6, characterized in that: The mass ratio of the amino silane coupling agent, deionized water and anhydrous ethanol is 1:1:4; The amount of the amino silane coupling agent added is 1 to 5% of the mass of the porous silica; The amino silane coupling agent includes any one of 3-aminopropyltrimethoxysilane, bis[(3-trimethoxysilyl)propyl]amine, 3-aminopropyltriethoxysilane, bis[(3-triethoxysilyl)propyl]amine, 3-aminopropylmethyldimethoxysilane, and 3-aminopropylmethyldiethoxysilane.

8. The method for preparing a high heat-resistant battery separator according to claim 1, characterized in that: The amount of the photoinitiator added is 1 to 3% of the mass of the porous silica modified polyimide; The parameters of the UV cross-linking are: UV wavelength of 300 to 400 nm; The thickness of the high heat-resistant battery separator is 16 to 30 μm.

9. A method for preparing a battery, characterized in that: The high heat-resistant battery separator prepared by the method for preparing the high heat-resistant battery separator according to any one of claims 1 to 8 is wound and assembled with a positive electrode active material and a negative electrode active material, and an electrolyte is injected to obtain a battery.

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