High-strength high-temperature-resistant lithium ion battery diaphragm and preparation method thereof

Abstract

The invention discloses a high-strength high-temperature-resistant lithium ion battery diaphragm and a preparation method thereof, and relates to the technical field of lithium ion batteries, and the high-strength high-temperature-resistant lithium ion battery diaphragm comprises the following raw materials in parts by weight: 50-60 parts of modified polyethylene, 0.5-1.5 parts of an antioxidant, 1-3 parts of polyethylene glycol and 3-5 parts of polyethylene wax. According to the modified polyethylene, nano aluminum nitride, hydroxyl, Zn-MOF and the like are introduced into polyethylene through a melt grafting reaction. The diaphragm has excellent mechanical strength, high temperature resistance, electrolyte wettability and flame retardance, and is worthy of popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a high-strength, high-temperature-resistant lithium ion battery separator and a preparation method thereof. Background Art

[0002] Lithium-ion batteries, with their high specific capacity, long cycle life, lack of memory effect, high safety and reliability, and rapid charge and discharge, have become a research hotspot in the field of new power technologies. Battery separators are a crucial component of lithium-ion batteries, preventing short circuits between the positive and negative electrodes and providing pathways for lithium ion transport. Their performance determines the battery's interface structure and internal resistance, significantly impacting its capacity, cycle performance, and safety.

[0003] Currently, the lithium-ion battery separators on the market are mainly polyolefin separators based on polyethylene and polypropylene. This type of separator has many advantages, such as mature production technology, but it also has shortcomings: 1. Polyolefin separators such as polyethylene have a low melting point and poor flame retardancy. When working under high-power charging and discharging or high-temperature environments, they are prone to thermal shrinkage or even melting and burning, resulting in direct contact between the positive and negative electrodes, causing internal battery short circuits and even explosions and other safety hazards. The insufficient thermal stability and flame retardancy of polyolefin lithium-ion battery separators limit the widespread use of lithium-ion batteries. 2. The mechanical strength of ordinary polyethylene and other polyolefin separators cannot meet the requirements of high-capacity and high-power batteries, which has a negative impact on the battery's cycle performance and service life. 3. Polyolefin separators such as polyethylene have low surface energy and poor affinity for electrolytes, resulting in poor wettability of the electrolyte in the separator, which is not conducive to the transmission of lithium ions and reduces battery performance.

[0004] Existing technologies include directly adding inorganic nanoparticles such as nano-aluminum nitride to polyolefins or coating them onto the surface of polyolefin base membranes to form inorganic coatings to improve the heat resistance of the separator. However, these technologies suffer from issues such as blocking some of the micropores in the polyolefin base membrane, resulting in reduced porosity and air permeability, the tendency for inorganic nanoparticles to agglomerate within the polyolefin, and the tendency for inorganic particles to fall off the base membrane, thus failing to meet the requirements for high-rate rapid charge and discharge. Existing technologies also include directly adding metal-organic frameworks to polyolefin separators to increase their porosity and facilitate lithium-ion transport, but this still suffers from poor compatibility between the metal-organic frameworks and polyolefins, which have low molecular chain polarity.

[0005] Therefore, it is urgent to develop a suitable modification method to apply nano-aluminum nitride with improved agglomeration phenomenon and metal-organic framework with enhanced compatibility with polyolefins to polyolefin separators, while improving the flame retardancy and electrolyte wettability of polyolefin separators, so as to develop a high-strength and high-temperature resistant lithium-ion battery polyolefin separator with better comprehensive performance, which is of practical significance. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a high-strength and high-temperature resistant lithium-ion battery separator and a preparation method thereof.

[0007] The purpose of the present invention can be achieved through the following technical solutions: A high-strength, high-temperature-resistant lithium-ion battery separator, comprising the following raw materials in parts by weight: 50-60 parts of modified polyethylene, 0.5-1.5 parts of an antioxidant, 1-3 parts of polyethylene glycol, and 3-5 parts of polyethylene wax; Furthermore, the antioxidant is prepared by mixing antioxidant 1135 and tris(2,4-di-tert-butylphenyl)phosphite in a mass ratio of 1-1.5:2.5-3; The preparation of the high-strength and high-temperature resistant lithium-ion battery separator comprises the following steps: The modified polyethylene, antioxidant, polyethylene glycol and polyethylene wax are stirred for 1-1.5 hours, then heated and plasticized at 180-190°C, cast into a film, heat treated at 130-135°C, axially stretched at a ratio of 2-2.5 in the longitudinal direction and 3.5-4.0 in the transverse direction to obtain a high-strength and high-temperature resistant lithium-ion battery separator with a thickness of 16-20 μm; The modified polyethylene is prepared by the following steps: Step A1, adding nano-aluminum nitride to the mixed solution and ultrasonically vibrating for 30-40 minutes, then adding a silane coupling agent and continuing ultrasonic dispersion for 10-15 minutes, then reflux stirring at 55-60° C. for 3.5-4 hours, cooling, washing with anhydrous ethanol, and drying to obtain a modified nanofiller; Furthermore, the mixed liquid is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 1:9, the silane coupling agent is KH560, and the dosage ratio of nano-aluminum nitride, the mixed liquid, and the silane coupling agent is 0.5-0.7 g: 60-65 mL: 0.6-0.8 g; During the reaction of step A1, the silane coupling agent modifies the surface of the nano-aluminum nitride to obtain a modified nano-filler containing epoxy groups on the surface; Step A2, adding 1-(4-(methylamino)-3-nitrophenyl)ethanone and the modified nanofiller to dimethyl sulfoxide, stirring and reacting at 50-60° C. for 10-11 hours, filtering, and drying to obtain reaction product 1; adding reaction product 1 to toluene, heating to 45-50° C., adding sodium dithionite under reflux stirring, and stirring and reacting for 3-4 hours to obtain reaction product 2; Furthermore, the usage ratio of 1-(4-(methylamino)-3-nitrophenyl)ethanone, modified nanofiller, and dimethyl sulfoxide is 20-22 g: 6-8 g: 160-170 mL; the usage ratio of reaction product 1, toluene, and sodium dithionite is 9-10 g: 85-95 mL: 5-7 g; During the reaction of step A2, the secondary amino group in 1-(4-(methylamino)-3-nitrophenyl)ethanone reacts with the epoxy group in the modified nanofiller to generate a reaction product 1 containing a hydroxyl group, a nitro group, a ketocarbonyl group, etc.; the nitro group in the reaction product 1 is reduced to a primary amino group to obtain a reaction product 2; Step A3, adding ethyl imidazole-4-carboxylate to methanol and stirring to obtain a mixture 1, then adding zinc nitrate hexahydrate to methanol and stirring to obtain a mixture 2, adding the mixture 2 to the mixture 1 at room temperature, stirring to react for 1.5-2 hours, then washing with methanol and drying at 70-80°C overnight to obtain a Zn-MOF; Furthermore, the amount ratio of ethyl imidazole-4-carboxylate and methanol in the mixed solution 1 is 1.8-2 g: 100-110 mL; the amount ratio of zinc nitrate hexahydrate and methanol in the mixed solution 2 is 1.5-1.6 g: 100-110 mL; the amount ratio of the mixed solution 1 and the mixed solution 2 is 10.5-11.5 mL: 10.5-11.5 mL; During the reaction of step A3, zinc ions and ethyl imidazole-4-carboxylate self-assemble to obtain a Zn-MOF containing ethyl formate groups; Step A4: In a protective gas atmosphere, the Zn-MOF was heated to 80-85° C. under reflux and stirring, and stirred for reaction for 20-30 minutes, then cooled to 50-55° C., methanol and reaction product 2 were added, and then sodium methoxide was added, and the reaction was stirred for 10-12 hours to obtain reaction product 3; Furthermore, the usage ratio of Zn-MOF, methanol, reaction product 2, and sodium methoxide is 3-4 g: 80-90 mL: 10-12 g: 0.15-0.2 g; During the reaction of step A4, the ethyl formate group in the Zn-MOF undergoes an aminolysis reaction with the primary amino group of the reaction product 2, thereby grafting the Zn-MOF with the nano-aluminum nitride to obtain the reaction product 3; Step A5: In a protective gas atmosphere, adding reaction product 3 and methylenetriphenylphosphine to anhydrous tetrahydrofuran, and reacting under reflux stirring at 45-50° C. for 6-7 hours to obtain reaction product 4; melt blending polyethylene, di-tert-butyl peroxide, and reaction product 4 at 140-150° C. to obtain modified polyethylene; Furthermore, the ratio of reaction product 3, methylenetriphenylphosphine, and anhydrous tetrahydrofuran is 8-10 g: 15-17 g: 100-110 mL; the ratio of polyethylene, di-tert-butyl peroxide, and reaction product 4 is 63-65 g: 1.8-2 g: 5-7 g; During the reaction process of step A5, the ketone carbonyl in the reaction product 3 undergoes a ylide reaction with methylenetriphenylphosphine to generate a reaction product 4 containing a terminal carbon-carbon double bond; the reaction product 4 containing a terminal carbon-carbon double bond undergoes an in situ grafting reaction with polyethylene to obtain a modified polyethylene containing nano-aluminum nitride, hydroxyl groups and Zn-MOF.

[0008] Beneficial effects of the present invention: The present invention discloses a high-strength and high-temperature resistant lithium-ion battery separator and a preparation method thereof. The lithium-ion battery separator comprises raw materials such as modified polyethylene, an antioxidant, polyethylene glycol and polyethylene wax.

[0009] The modified polyethylene is obtained by melt grafting a reaction product 4 containing nano-aluminum nitride, hydroxyl group, Zn-MOF and terminal carbon-carbon double bond with polyethylene. Nano-aluminum nitride has excellent thermal conductivity and thermal stability. After being treated and grafted with polyethylene, it is not easy to agglomerate in the matrix. It not only helps to improve the poor high-temperature resistance of ordinary polyethylene membranes and alleviate the thermal shrinkage of polyethylene membranes, but also helps to improve the mechanical strength of modified polyethylene, thereby improving the high-temperature resistance and mechanical strength of the membrane; the hydroxyl groups in the modified polyethylene enhance the polarity of the modified polyethylene, thereby enhancing the wettability of the membrane with the electrolyte and increasing the liquid absorption rate; after Zn-MOF is grafted with polyethylene, the compatibility and dispersibility of the two are enhanced. Due to the porosity of Zn-MOF, it produces an intramolecular synergistic effect with the hydroxyl groups, thereby improving the wettability of the membrane to the electrolyte, further increasing the liquid absorption rate, and facilitating the rapid transmission of lithium ions; furthermore, because a large amount of nitrogen elements are introduced after Zn-MOF is grafted onto polyethylene, non-flammable gases can be generated during combustion to dilute combustible gases, thereby giving the modified polyethylene itself better flame retardancy, thereby improving the flame retardancy of the membrane.

[0010] Therefore, the lithium-ion battery separator of the present invention has excellent high temperature resistance, mechanical strength, electrolyte wettability and flame retardancy, and is worthy of promotion and use. DETAILED DESCRIPTION

[0011] 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.

[0012] Example 1 A modified polyethylene, the preparation of which comprises the following steps: Step A1, adding nano-aluminum nitride to the mixed solution and ultrasonically oscillating for 30 minutes, then adding a silane coupling agent and continuing ultrasonic dispersion for 10 minutes, then reflux stirring and reacting at 55°C for 3.5 hours, cooling, washing with anhydrous ethanol, and drying to obtain a modified nanofiller; the mixed solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 1:9, the silane coupling agent is KH560, and the amount ratio of nano-aluminum nitride, mixed solution, and silane coupling agent is 0.5g:60mL:0.6g; Step A2, adding 1-(4-(methylamino)-3-nitrophenyl)ethanone and the modified nanofiller to dimethyl sulfoxide, stirring and reacting at 50° C. for 10 hours, filtering and drying to obtain reaction product 1; adding reaction product 1 to toluene, heating to 45° C., adding sodium dithionite under reflux stirring, stirring and reacting for 3 hours to obtain reaction product 2; the amount ratio of 1-(4-(methylamino)-3-nitrophenyl)ethanone, modified nanofiller, and dimethyl sulfoxide is 20 g:6 g:160 mL; the amount ratio of reaction product 1, toluene, and sodium dithionite is 9 g:85 mL:5 g; Step A3, adding ethyl imidazole-4-carboxylate to methanol and stirring to obtain a mixed solution 1, then adding zinc nitrate hexahydrate to methanol and stirring to obtain a mixed solution 2, adding the mixed solution 2 to the mixed solution 1 at room temperature, stirring to react for 1.5 hours, and then washing with methanol and drying at 70°C overnight to obtain Zn-MOF; the amount ratio of ethyl imidazole-4-carboxylate to methanol in the mixed solution 1 is 1.8 g:100 mL; the amount ratio of zinc nitrate hexahydrate to methanol in the mixed solution 2 is 1.5 g:100 mL; the amount ratio of the mixed solution 1 to the mixed solution 2 is 10.5 mL:10.5 mL; Step A4: Under a nitrogen atmosphere, the Zn-MOF was heated to 80°C with stirring under reflux, stirred and reacted for 20 minutes, then cooled to 50°C, methanol and reaction product 2 were added, and then sodium methoxide was added, stirred and reacted for 10 hours to obtain reaction product 3; the amount ratio of Zn-MOF, methanol, reaction product 2, and sodium methoxide was 3 g:80 mL:10 g:0.15 g; Step A5. In a nitrogen atmosphere, the reaction product 3 and methylenetriphenylphosphine are added to anhydrous tetrahydrofuran, and the mixture is refluxed with stirring at 45°C for 6 hours to obtain a reaction product 4; polyethylene, di-tert-butyl peroxide, and reaction product 4 are melt-blended at 140°C to obtain modified polyethylene; the amount ratio of reaction product 3, methylenetriphenylphosphine, and anhydrous tetrahydrofuran is 8g:15g:100mL; the amount ratio of polyethylene, di-tert-butyl peroxide, and reaction product 4 is 63g:1.8g:5g.

[0013] Example 2 A modified polyethylene, the preparation of which comprises the following steps: Step A1, adding nano-aluminum nitride to the mixed solution and ultrasonically oscillating for 35 minutes, then adding a silane coupling agent and continuing ultrasonic dispersion for 13 minutes, then reflux stirring at 58° C. for 3.7 hours, cooling, washing with anhydrous ethanol, and drying to obtain a modified nanofiller; the mixed solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 1:9, the silane coupling agent is KH560, and the amount ratio of nano-aluminum nitride, mixed solution, and silane coupling agent is 0.6 g:63 mL:0.7 g; Step A2, adding 1-(4-(methylamino)-3-nitrophenyl)ethanone and the modified nanofiller to dimethyl sulfoxide, stirring and reacting at 55° C. for 10.5 hours, filtering and drying to obtain reaction product 1; adding reaction product 1 to toluene, heating to 47° C., adding sodium dithionite under reflux stirring, stirring and reacting for 3.5 hours to obtain reaction product 2; the amount ratio of 1-(4-(methylamino)-3-nitrophenyl)ethanone, modified nanofiller, and dimethyl sulfoxide is 21 g:7 g:165 mL; the amount ratio of reaction product 1, toluene, and sodium dithionite is 9.5 g:90 mL:6 g; Step A3, adding ethyl imidazole-4-carboxylate to methanol and stirring to obtain a mixed solution 1, then adding zinc nitrate hexahydrate to methanol and stirring to obtain a mixed solution 2, adding the mixed solution 2 to the mixed solution 1 at room temperature, stirring to react for 1.7 hours, then washing with methanol and drying at 75°C overnight to obtain Zn-MOF; the amount ratio of ethyl imidazole-4-carboxylate to methanol in the mixed solution 1 is 1.9 g:105 mL; the amount ratio of zinc nitrate hexahydrate to methanol in the mixed solution 2 is 1.55 g:105 mL; the amount ratio of the mixed solution 1 to the mixed solution 2 is 11 mL:11 mL; Step A4: Under a nitrogen atmosphere, the Zn-MOF was heated to 83° C. with stirring under reflux, and stirred for 25 min. The temperature was then lowered to 53° C., methanol and reaction product 2 were added, and then sodium methoxide was added. The reaction was stirred for 11 h to obtain reaction product 3. The ratio of Zn-MOF, methanol, reaction product 2, and sodium methoxide was 3.5 g:85 mL:11 g:0.17 g. Step A5. In a nitrogen atmosphere, the reaction product 3 and methylenetriphenylphosphine are added to anhydrous tetrahydrofuran, and the mixture is refluxed with stirring at 47°C for 6.5 hours to obtain a reaction product 4; polyethylene, di-tert-butyl peroxide, and reaction product 4 are melt-blended at 145°C to obtain modified polyethylene; the amount ratio of reaction product 3, methylenetriphenylphosphine, and anhydrous tetrahydrofuran is 9g:16g:105mL; the amount ratio of polyethylene, di-tert-butyl peroxide, and reaction product 4 is 64g:1.9g:6g.

[0014] Example 3 A modified polyethylene, the preparation of which comprises the following steps: Step A1, adding nano-aluminum nitride to the mixed solution and ultrasonically oscillating for 40 minutes, then adding a silane coupling agent and continuing ultrasonic dispersion for 15 minutes, then reflux stirring at 60°C for 4 hours, cooling, washing with anhydrous ethanol, and drying to obtain a modified nanofiller; the mixed solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 1:9, the silane coupling agent is KH560, and the amount ratio of nano-aluminum nitride, mixed solution, and silane coupling agent is 0.7g:65mL:0.8g; Step A2, adding 1-(4-(methylamino)-3-nitrophenyl)ethanone and the modified nanofiller to dimethyl sulfoxide, stirring and reacting at 60° C. for 11 hours, filtering and drying to obtain reaction product 1; adding reaction product 1 to toluene, heating to 50° C., adding sodium dithionite under reflux stirring, stirring and reacting for 4 hours to obtain reaction product 2; the amount ratio of 1-(4-(methylamino)-3-nitrophenyl)ethanone, modified nanofiller, and dimethyl sulfoxide is 22 g:8 g:170 mL; the amount ratio of reaction product 1, toluene, and sodium dithionite is 10 g:95 mL:7 g; Step A3, adding ethyl imidazole-4-carboxylate to methanol and stirring to obtain a mixed solution 1, then adding zinc nitrate hexahydrate to methanol and stirring to obtain a mixed solution 2, adding the mixed solution 2 to the mixed solution 1 at room temperature, stirring to react for 2 hours, then washing with methanol and drying at 80°C overnight to obtain Zn-MOF; the amount ratio of ethyl imidazole-4-carboxylate to methanol in the mixed solution 1 is 2 g:110 mL; the amount ratio of zinc nitrate hexahydrate to methanol in the mixed solution 2 is 1.6 g:110 mL; the amount ratio of the mixed solution 1 to the mixed solution 2 is 11.5 mL:11.5 mL; Step A4: Under a nitrogen atmosphere, the Zn-MOF was heated to 85°C with stirring under reflux, stirred and reacted for 30 minutes, then cooled to 55°C, methanol and reaction product 2 were added, and then sodium methoxide was added, and stirred and reacted for 12 hours to obtain reaction product 3; the amount ratio of Zn-MOF, methanol, reaction product 2, and sodium methoxide was 4 g:90 mL:12 g:0.2 g; Step A5. In a nitrogen atmosphere, the reaction product 3 and methylenetriphenylphosphine are added to anhydrous tetrahydrofuran, and the mixture is refluxed with stirring at 50°C for 7 hours to obtain a reaction product 4; polyethylene, di-tert-butyl peroxide, and reaction product 4 are melt-blended at 150°C to obtain modified polyethylene; the amount ratio of reaction product 3, methylenetriphenylphosphine, and anhydrous tetrahydrofuran is 10g:17g:110mL; the amount ratio of polyethylene, di-tert-butyl peroxide, and reaction product 4 is 65g:2g:7g.

[0015] Example 4 A high-strength, high-temperature-resistant lithium-ion battery separator, comprising the following raw materials in parts by weight: 50 parts of modified polyethylene, 0.5 parts of an antioxidant, 1 part of polyethylene glycol, and 3 parts of polyethylene wax; the antioxidant is a mixture of antioxidant 1135 and tris(2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1:2.5; The preparation of the high-strength and high-temperature resistant lithium-ion battery separator comprises the following steps: The modified polyethylene, antioxidant, polyethylene glycol and polyethylene wax obtained in Example 1 were stirred for 1 hour, then heated and plasticized at 180°C, cast into a film, heat treated at 130°C, axially stretched at a ratio of 2.1 in the longitudinal direction and 3.6 in the transverse direction to obtain a high-strength, high-temperature resistant lithium-ion battery separator with a thickness of 16 μm.

[0016] Example 5 A high-strength, high-temperature-resistant lithium-ion battery separator, comprising the following raw materials in parts by weight: 55 parts of modified polyethylene, 1.0 part of an antioxidant, 2 parts of polyethylene glycol, and 4 parts of polyethylene wax; the antioxidant is a mixture of antioxidant 1135 and tris(2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1.2:2.8; The preparation of the high-strength and high-temperature resistant lithium-ion battery separator comprises the following steps: The modified polyethylene, antioxidant, polyethylene glycol and polyethylene wax obtained in Example 2 were stirred for 1.3 hours, then heated and plasticized at 185°C, cast into a film, heat treated at 130°C, axially stretched at a ratio of 2.3 in the longitudinal direction and 3.7 in the transverse direction to obtain a high-strength, high-temperature resistant lithium-ion battery separator with a thickness of 16 μm.

[0017] Example 6 A high-strength, high-temperature-resistant lithium-ion battery separator, comprising the following raw materials in parts by weight: 60 parts of modified polyethylene, 1.5 parts of an antioxidant, 3 parts of polyethylene glycol, and 5 parts of polyethylene wax; the antioxidant is a mixture of antioxidant 1135 and tris(2,4-di-tert-butylphenyl) phosphite in a mass ratio of 1.4:2.8; The preparation of the high-strength and high-temperature resistant lithium-ion battery separator comprises the following steps: The modified polyethylene, antioxidant, polyethylene glycol and polyethylene wax obtained in Example 3 were stirred for 1.5 hours, then heated and plasticized at 190°C, cast into a film, heat treated at 130°C, axially stretched at a ratio of 2.4 in the longitudinal direction and 3.9 in the transverse direction to obtain a high-strength, high-temperature resistant lithium-ion battery separator with a thickness of 16 μm.

[0018] Comparative Example 1 Compared with Example 6, the modified nanofiller in the preparation process of modified polyethylene was replaced with 1,2-epoxydodecane, and 4.2 parts of nano-aluminum nitride was added during the preparation of the diaphragm. The rest was exactly the same as Example 6 to prepare a lithium ion battery diaphragm.

[0019] Comparative Example 2 Compared with Example 6, the Zn-MOF in the preparation process of the modified polyethylene was replaced with ethyl imidazole-4-carboxylate, and the rest was exactly the same as Example 6 to prepare a lithium ion battery separator.

[0020] Comparative Example 3 Compared with Example 6, the modified nanofiller was replaced with the modified nanofiller s, the reaction product 1 was replaced with the reaction product 1a, and the rest was exactly the same as in Example 6 to prepare a lithium ion battery separator; The preparation process of reaction 1a is as follows: step 1, adding nano-aluminum nitride to a mixed solution and ultrasonically oscillating for 40 minutes, then adding 3-chloropropyltrimethoxysilane and continuing ultrasonic dispersion for 20 minutes, then reflux stirring at 60°C for 4.2 hours, cooling, washing with anhydrous ethanol, and drying to obtain a modified nanofiller s; the mixed solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 1:9, and the amount ratio of nano-aluminum nitride, mixed solution, and 3-chloropropyltrimethoxysilane is 0.7g:65mL:0.8g; during the reaction process of step 1, 3-chloropropyltrimethoxysilane modifies the surface of the nano-aluminum nitride to obtain a modified nanofiller s containing alkyl chloride on the surface; Step 2. After mixing the modified nanofiller s, 1-(4-(methylamino)-3-nitrophenyl)ethanone, and DMF, sodium hydroxide was added and the mixture was stirred and reacted at 130° C. for 8 hours to obtain the reaction product 1a; the amount ratio of the modified nanofiller s, 1-(4-(methylamino)-3-nitrophenyl)ethanone, DMF, and sodium hydroxide was 8 g:22 g:80 mL:0.4 g; during the reaction in step 2, the alkyl chloride on the surface of the modified nanofiller s reacted with 1-(4-(methylamino)-3-nitrophenyl)ethanone by dehydrochlorination to obtain the reaction product 1a containing a nitro group and a ketocarbonyl group.

[0021] The lithium-ion battery separator of the present invention was further tested for its effectiveness, and the test results are as follows.

[0022] Tensile strength: refer to GB / T1040.1-2018 "Determination of tensile properties of plastics", the tensile rate is 50 mm / min, and the results are recorded in Table 1; Liquid absorption rate: According to the gravimetric method, the electrolyte is a mixture of ethylene carbonate and dimethyl carbonate with a volume ratio of 3:1. The results are recorded in Table 1. Thermal shrinkage: Cut the obtained diaphragm into test samples using a cutting plate. Measure the length h1 of the cut sample. Place the test sample in a 210°C oven for 1 hour and then take it out. Measure the length h2 of the heated sample. Thermal shrinkage = (h2 - h1) / h1 × 100%. Record the results in Table 1. Oxygen index determination: Use an oxygen index meter to determine the oxygen index, and the results are recorded in Table 1; Table 1: Test results

[0023] According to the data in Table 1, the lithium-ion battery separator of the present invention has excellent mechanical strength, high temperature resistance, electrolyte wettability and flame retardancy. Comparison of Example 6 with Comparative Example 1 shows that the nano-aluminum nitride is not grafted with polyethylene and is easily agglomerated when directly added, so the high temperature resistance of the separator decreases, the thermal shrinkage of the separator increases, and the nano-aluminum nitride is unevenly dispersed in the polyethylene, which also leads to a decrease in mechanical strength. Comparison of Example 6 with Comparative Example 2 shows that after replacing the Zn-MOF in the preparation process of the modified polyethylene with ethyl imidazole-4-carboxylate, the metal organic framework is not introduced, and it cannot synergize with the hydroxyl group to improve the wettability of the separator to the electrolyte, so the liquid absorption rate of the separator decreases. Comparison of Example 6 with Comparative Example 3 shows that after replacing the modified nanofiller with modified nanofiller s and reaction product 1 with reaction product 1a, no hydroxyl group is introduced into the modified polyethylene, and it cannot synergize with the Zn-MOF to improve the wettability of the separator to the electrolyte, so the liquid absorption rate of the separator decreases.

[0024] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A high-strength, high-temperature-resistant lithium-ion battery separator, characterized by: The method comprises the following raw materials in parts by weight: 50-60 parts of modified polyethylene, 0.5-1.5 parts of antioxidant, 1-3 parts of polyethylene glycol and 3-5 parts of polyethylene wax; The modified polyethylene is prepared by the following steps: Step A1, adding nano-aluminum nitride to the mixed solution and ultrasonically vibrating, then adding a silane coupling agent and refluxing and stirring to obtain a modified nano-filler; Step A2, adding 1-(4-(methylamino)-3-nitrophenyl)ethanone and the modified nanofiller to dimethyl sulfoxide, stirring and reacting to obtain reaction product 1; adding reaction product 1 to toluene, adding sodium dithionite, stirring and reacting to obtain reaction product 2; Step A3, adding ethyl imidazole-4-carboxylate to methanol and stirring to obtain a mixed solution 1, then adding zinc nitrate hexahydrate to methanol and stirring to obtain a mixed solution 2, adding the mixed solution 2 to the mixed solution 1 at room temperature, and stirring to react to obtain Zn-MOF; Step A4: In a protective gas atmosphere, the Zn-MOF was refluxed with stirring and heated, then cooled, methanol and reaction product 2 were added, and then sodium methoxide was added, and the mixture was stirred to react to obtain reaction product 3; Step A5: In a protective gas atmosphere, add the reaction product 3 and methylenetriphenylphosphine to anhydrous tetrahydrofuran, and reflux with stirring to react to obtain the reaction product 4; melt-blend polyethylene, di-tert-butyl peroxide, and the reaction product 4 to obtain modified polyethylene.

2. The high-strength, high-temperature-resistant lithium-ion battery separator according to claim 1, characterized in that: The antioxidant is prepared by mixing antioxidant 1135 and tris(2,4-di-tert-butylphenyl)phosphite in a mass ratio of 1-1.5:2.5-3.

3. The high-strength, high-temperature-resistant lithium-ion battery separator according to claim 1, characterized in that: In step A1, the mixed liquid is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 1:9, the silane coupling agent is KH560, and the usage ratio of nano-aluminum nitride, the mixed liquid, and the silane coupling agent is 0.5-0.7 g: 60-65 mL: 0.6-0.8 g.

4. The high-strength, high-temperature-resistant lithium-ion battery separator according to claim 1, characterized in that: In step A2, the usage ratio of 1-(4-(methylamino)-3-nitrophenyl)ethanone, modified nanofiller, and dimethyl sulfoxide is 20-22 g: 6-8 g: 60-70 mL.

5. The high-strength and high-temperature-resistant lithium-ion battery separator according to claim 1, characterized in that: In step A2, the usage ratio of reaction product 1, toluene, and sodium dithionite is 9-10 g:85-95 mL:5-7 g.

6. The high-strength and high-temperature-resistant lithium-ion battery separator according to claim 1, characterized in that: In step A3, the ratio of ethyl imidazole-4-carboxylate to methanol in the mixed solution 1 is 1.8-2 g: 100-110 mL.

7. The high-strength, high-temperature-resistant lithium-ion battery separator according to claim 1, characterized in that: In step A3, the usage ratio of zinc nitrate hexahydrate and methanol in mixed solution 2 is 1.5-1.6 g:100-110 mL; the usage ratio of mixed solution 1 and mixed solution 2 is 10.5-11.5 mL:10.5-11.5 mL.

8. The high-strength, high-temperature-resistant lithium-ion battery separator according to claim 1, characterized in that: In step A4, the usage ratio of Zn-MOF, methanol, reaction product 2, and sodium methoxide is 3-4 g: 80-90 mL: 10-12 g: 0.15-0.2 g.

9. The high-strength, high-temperature-resistant lithium-ion battery separator according to claim 1, characterized in that: In step A5, the usage ratio of reaction product 3, methylenetriphenylphosphine, and anhydrous tetrahydrofuran is 8-10 g:15-17 g:100-110 mL; the usage ratio of polyethylene, di-tert-butyl peroxide, and reaction product 4 is 63-65 g:1.8-2 g:5-7 g.

10. A method for preparing the high-strength, high-temperature-resistant lithium-ion battery separator according to any one of claims 1 to 9, characterized in that: The steps include: The modified polyethylene, antioxidant, polyethylene glycol and polyethylene wax are stirred for 1-1.5 hours, then heated and plasticized at 180-190°C, cast into a film, heat treated at 130-135°C, axially stretched at a ratio of 2-2.5 in the longitudinal direction and 3.5-4.0 in the transverse direction to obtain a high-strength, high-temperature resistant lithium-ion battery separator with a thickness of 16-20 μm.

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