Low-temperature lithium battery diaphragm material containing nano ceramic material

Abstract

The invention relates to the technical field of battery diaphragms, and discloses a low-temperature lithium battery diaphragm material containing a nano ceramic material, and a preparation method of the low-temperature lithium battery diaphragm material containing the nano ceramic material comprises the following preparation steps: mixing a modified nano ceramic material, modified lamellar graphene oxide, a binder and deionized water to obtain mixed slurry; spraying the mixed slurry onto the upper and lower surfaces of a polyolefin diaphragm, drying and curing to obtain the lithium battery diaphragm material. The modified nano ceramic material and the modified lamellar graphene oxide are coated on the polyolefin diaphragm, and the prepared lithium battery diaphragm material has relatively high temperature resistance and mechanical property.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of battery separator membranes, in particular to a low-temperature lithium battery separator membrane material containing nano ceramic materials. BACKGROUND

[0002] In the structure of a lithium ion battery, a separator membrane, as an inner layer component, can separate the positive and negative electrodes of the battery, prevent the two electrodes from contacting and short-circuiting, and allow ions to transmit in the battery, thereby improving the comprehensive performance of the lithium ion battery, such as the capacity, cycle and safety performance of the battery, and the separator membrane material used in the lithium ion battery is mainly based on a polyolefin film, such as a polypropylene separator membrane, a polyethylene separator membrane and a polytetrafluoroethylene separator membrane.

[0003] The polyolefin film can improve the electrochemical performance of the lithium ion battery as the lithium battery separator membrane material, but the polyolefin separator membrane material has poor temperature resistance, is prone to shrinkage or melting rupture when heated, and the pores of the separator membrane are prone to collapse and shrink at low temperatures, which leads to internal short circuit of the lithium battery and affects the electrochemical performance of the lithium battery; the nano ceramic material is coated on the surface of the polyolefin film through a binder, which can improve the high-temperature resistance of the lithium battery separator membrane material, but the nano ceramic material is prone to agglomeration, which affects the electrochemical performance of the lithium battery, and in addition, the polyolefin film also has the defect of poor mechanical performance. SUMMARY

[0004] The application provides a low-temperature lithium battery separator membrane material containing nano ceramic materials, and solves the problems of poor temperature resistance of the lithium battery separator membrane material and agglomeration of the nano ceramic material on the surface of the separator membrane.

[0005] The technical scheme of the application is as follows: A low-temperature lithium battery separator membrane material containing nano ceramic materials, and a preparation method thereof, the preparation method comprising the following preparation steps: S1. mixing modified nano ceramic materials, modified layered graphene oxide, a binder and deionized water to obtain a mixed slurry; S2. spraying the mixed slurry onto the upper and lower surfaces of a polyolefin separator membrane, and drying and curing to obtain a lithium battery separator membrane material; The modified nano ceramic material is obtained by synthesizing porous carbon on the surface of nano ceramic materials and then depositing the porous carbon on the surface of polydopamine-modified silicon carbide whiskers. The modified layered graphene oxide is obtained by modifying the layered graphene oxide with tannic acid and then mixing and reacting the modified layered graphene oxide with a zinc source and dimethyl imidazole. Further, in step S1, the mass ratio of the modified nano ceramic materials, the modified layered graphene oxide, the binder and the deionized water is (20-25):(10-15):(0.5-1):(40-60).

[0006] Further, in step S2, the spraying amount of the mixed slurry on the upper surface and the lower surface of the polyolefin separator is 18-22 g / m 2 , and the spraying pressure is 0.3-0.5 MPa.

[0007] Further, in step S2, the polyolefin separator is selected from any one of a polypropylene separator, a polyethylene separator, and a polytetrafluoroethylene separator.

[0008] Further, in step S2, the drying and curing temperature is 40-60℃, and the time is 30-50 min.

[0009] Further, the thickness of the polyolefin separator is 10-15 μm.

[0010] Further, the thickness of the lithium battery separator material is 30-40 μm.

[0011] Further, the modified nano-ceramic material is prepared by the following steps: A1. The nano-ceramic material, glucose, and citric acid are added to ethanol, stirred uniformly, hydrochloric acid is added, stirred and reacted, filtered, washed, dried, mixed with a potassium hydroxide solution, nitrogen is introduced, carbonized at 750-850℃ for 3-5 h, cooled to room temperature, taken out, washed, and dried to obtain a nano-ceramic material loaded with porous carbon; A2. The silicon carbide whisker is added to a Tris-HCl buffer solution, stirred uniformly, dopamine is added, stirred and reacted, filtered, washed, and dried to obtain a polydopamine-modified silicon carbide whisker; A3. The polydopamine-modified silicon carbide whisker and the nano-ceramic material loaded with porous carbon are added to deionized water, stirred, and after standing, filtered, washed, and dried to obtain a modified nano-ceramic material.

[0012] Further, in the above A1 reaction process, the large number of hydroxyl groups contained in the citric acid can be combined with the nano-ceramic material through hydrogen bonds, and the citric acid can also be combined with the glucose through chemical bonds, so that the glucose adheres to the surface of the nano-ceramic material through the citric acid, and after high-temperature carbonization, the glucose decomposes to form a dense carbon layer. The potassium hydroxide solution acts as an activator and can form pores on the surface of the dense carbon layer, thereby synthesizing a porous carbon structure on the surface of the nano-ceramic material to obtain a nano-ceramic material loaded with porous carbon.

[0013] Further, in the above A2 reaction process, in the Tris-HCl buffer solution, dopamine can self-polymerize on the surface of the silicon carbide whisker to form polydopamine, so that the silicon carbide whisker carries a large number of phenolic hydroxyl groups, thereby obtaining a polydopamine-modified silicon carbide whisker, improving the surface activity of the silicon carbide whisker, and facilitating the deposition of the nano-ceramic material loaded with porous carbon on the surface of the silicon carbide whisker.

[0014] Furthermore, during the above-mentioned A3 reaction process, the polydopamine-modified silicon carbide whiskers have excellent adhesion and contain a large number of phenolic hydroxyl groups, so that the nanoceramic material loaded with porous carbon adheres to the surface of the polydopamine-modified silicon carbide whiskers to obtain a modified nanoceramic material.

[0015] Furthermore, in step A1, the ratio of the amount of nano-ceramic material, glucose, citric acid, ethanol, hydrochloric acid and potassium hydroxide solution is (5-6) g: (3-4) g: (0.5-0.7) g: (80-120) mL: (0.4-0.6) mL: (4-6) mL.

[0016] Furthermore, in step A2, the ratio of silicon carbide whiskers, Tris-HCl buffer and dopamine is (5.1-5.5) g: (75-85) mL: (0.5-0.7) g.

[0017] Furthermore, in step A3, the ratio of the polydopamine-modified silicon carbide whiskers, the porous carbon-loaded nanoceramic material, and deionized water is (4-5) g: (3-3.6) g: (90-110) mL.

[0018] Furthermore, the nano-ceramic material is selected from any one of aluminum oxide particles, silicon dioxide particles, and titanium dioxide particles.

[0019] Furthermore, the particle size of the nano-ceramic material is 400-600nm.

[0020] Furthermore, the silicon carbide whisker has a diameter of 1-2µm and a length of 10-50µm.

[0021] Furthermore, the modified sheet graphene oxide is specifically prepared by the following steps: B1. Add tannic acid to ethanol and stir until completely dissolved, add flake graphene oxide, stir evenly, filter, wash, and dry to obtain tannic acid-modified flake graphene oxide; B2. Add zinc nitrate hexahydrate, 2-aminobenzothiazole, and 2-methylimidazole to methanol and stir evenly. Add sodium formate and tannic acid-modified flake graphene oxide and stir evenly. Pass nitrogen gas through the mixture and react at 60-70°C for 3-5 hours. Collect the precipitate by centrifugation, wash it, and dry it to obtain modified flake graphene oxide.

[0022] Furthermore, during the above-mentioned reaction B1, tannic acid contains a large number of phenolic hydroxyl groups, has good adhesion properties, and can be chemically bonded to the hydroxyl groups on the surface of the flake graphene oxide, so that the tannic acid is coated on the surface of the flake graphene oxide to obtain tannic acid-modified flake graphene oxide.

[0023] Further, in the above B1 reaction process, the zinc ions in the zinc nitrate hexahydrate can be combined with the oxygen-containing functional groups on the surface of the tannic acid modified sheet layer of graphene oxide, so that the zinc ions are deposited on the surface of the tannic acid modified sheet layer of graphene oxide, 2-methyl imidazole and 2-amino benzothiazole are used as organic ligands, the zinc ions react with the organic ligands to form a three-dimensional network structure of zinc-based metal organic framework, so that the zinc-based metal organic framework is deposited on the surface of the tannic acid modified sheet layer of graphene oxide, and the modified sheet layer of graphene oxide is obtained.

[0024] Further, in step B1, the tannic acid, ethanol and sheet layer of graphene oxide are used in a ratio of (0.6-1) g:(45-55) mL:(2-2.4) g.

[0025] Further, in step B2, the zinc nitrate hexahydrate, 2-amino benzothiazole, 2-methyl imidazole, methanol, sodium formate and the tannic acid modified sheet layer of graphene oxide are used in a ratio of (1.5-2.5) g:(1.6-2) g:(2.5-2.9) g:(75-85) mL:(1.3-1.7) g:(5.5-5.9) g.

[0026] Further, the sheet layer of graphene oxide has a thickness of 1-1.5 nm and a sheet diameter of 1-2 µm.

[0027] A low-temperature lithium battery diaphragm material containing a nano ceramic material is prepared by the above method.

[0028] The present application has the following beneficial effects: (1) In the technical scheme of the present application, a porous carbon structure is synthesized on the surface of the nano ceramic material. On the one hand, the synthesized porous carbon has a high pore structure and pore capacity, accelerates the transmission performance of lithium ions, enhances the migration rate of lithium ions, improves the electrochemical performance, and synthesizes the porous carbon on the surface of the nano ceramic material to increase the roughness of the surface of the nano ceramic material, increase the contact area of the nano ceramic material and the electrolyte, and improve the number of lithium ion migrations. On the other hand, the porous carbon and the nano ceramic material as the coating of the diaphragm have high heat resistance and low temperature resistance, improve the thermal shrinkage rate of the lithium battery diaphragm material, and the nano ceramic material loaded with the porous carbon can hinder the collapse of the diaphragm hole shrinkage at low temperature, so that the diaphragm still maintains the lithium ion transmission performance at low temperature. In addition, the nano ceramic material loaded with the porous carbon adheres to the surface of the diaphragm to form a surface layer provided with small pores by the porous carbon to inhibit low temperature dendrites, and a large hole of the bottom layer diaphragm to store electrolyte, thereby ensuring low temperature ion transmission.

[0029] (2) In the technical scheme of the present application, the use of polydopamine modified silicon carbide whiskers improves the surface activity of the silicon carbide whiskers, which is conducive to the deposition of porous carbon loaded nano ceramic materials on the surface of the silicon carbide whiskers. On the one hand, the polydopamine modified silicon carbide whiskers serve as carriers for the porous carbon loaded nano ceramic materials, preventing the agglomeration of the porous carbon loaded nano ceramic materials and affecting the transmission of lithium ions by the separator. In addition, the silicon carbide whiskers have excellent aspect ratios and are randomly distributed on the surface of the separator to form a network structure that can absorb and weaken external forces, thereby improving the mechanical properties of the separator. On the other hand, the silicon carbide whiskers have good low-temperature resistance, which enables the separator to have good lithium ion transmission performance at low temperatures. In addition, the surface of the silicon carbide whiskers contains porous carbon, which can form lithium ion transmission channels on the surface of the separator, shorten the lithium ion transmission path, and improve the charge and discharge efficiency of the lithium ion battery.

[0030] (3) In the technical scheme of the present application, the use of tannic acid to modify the surface of the layered graphene oxide is conducive to the synthesis of zinc-based metal organic frameworks on the surface of the layered graphene oxide, which can be coated on the surface of the separator to improve the lithium ion transmission performance, temperature resistance, and mechanical properties of the separator. The synthesis of zinc-based metal organic frameworks on the surface of the layered graphene oxide, on the one hand, improves the adsorption performance of the synthesized zinc-based metal organic frameworks for lithium ions, increases the enrichment of lithium ions on the surface of the separator, shortens the distance of lithium ion diffusion from the electrolyte to the electrode, and improves the transmission performance of lithium ions. In addition, the layered graphene oxide serves as a carrier for the zinc-based metal organic frameworks, which enables the zinc-based metal organic frameworks to be well dispersed on the surface of the separator. On the other hand, the layered graphene oxide has high low-temperature resistance, which enhances the low-temperature lithium ion transmission performance of the separator. The interpenetration of the layered graphene oxide can withstand external loads and significantly improve the mechanical properties of the lithium battery separator. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0032] The raw materials used in the embodiments of the present application are shown below, and all the reagents used are analytical grade.

[0033] The polyolefin separator is a polypropylene separator, and the polypropylene film is purchased from Xinxiang City Zhongke Technology Co., Ltd.

[0034] The binder is carboxymethyl cellulose.

[0035] The nano ceramic material is aluminum oxide particles with a particle size of 500 nm.

[0036] The silicon carbide whisker has a diameter of 1.5 µm and a length of 35 µm.

[0037] The graphene oxide sheet has a thickness of 1.2 nm and a sheet diameter of 1.5 µm.

[0038] Example 1 A low-temperature lithium battery separator material containing a nano ceramic material, the preparation method comprising the following preparation steps: S1. mixing modified nano ceramic material, modified sheet graphene oxide, carboxymethyl cellulose and deionized water to obtain a mixed slurry; S2. spraying the mixed slurry onto the upper and lower surfaces of the polypropylene separator, drying and curing at 40°C for 50 min to obtain a lithium battery separator material.

[0039] In step S1, the mass ratio of modified nano ceramic material, modified sheet graphene oxide, carboxymethyl cellulose and deionized water is 20:10:0.5:40; In step S2, the spraying amount of the mixed slurry onto the upper and lower surfaces of the polypropylene separator is 18 g / m 2 , and the spraying pressure is 0.3 MPa; The thickness of the polypropylene separator is 10 µm, and the thickness of the lithium battery separator material is 30 µm.

[0040] The modified nano ceramic material is prepared by the following steps: A1. 5 g of nano ceramic material, 3 g of glucose and 0.5 g of citric acid are added to 80 mL of ethanol, stirred uniformly, 0.4 mL of 36% hydrochloric acid is added, stirred at 70°C for 35 min, filtered, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, placed in a tube furnace, 4 mL of 30% potassium hydroxide solution is added, nitrogen gas is introduced, the nitrogen flow rate is 30 mL / min, the temperature is raised to 750°C, carbonization is carried out for 3 h, the temperature rising rate is 10°C / min, cooled to room temperature, taken out, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, to obtain a nano ceramic material loaded with porous carbon; A2. 5.1 g of silicon carbide whisker is added to 75 mL of Tris-HCl buffer solution with pH 8.5, stirred uniformly, 0.5 g of dopamine is added, stirred at 25°C and 800 r / min for 3.5 h, filtered, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, to obtain polydopamine modified silicon carbide whisker; A3. 4 g of polydopamine modified silicon carbide whiskers and 3 g of porous carbon loaded nanoceramic material were added to 90 mL of deionized water, stirred at 900 r / min for 25 min, and after standing for 1 h, filtered, washed with deionized water 3 times, and dried in an oven at 70 °C for 10 min to obtain the modified nanoceramic material.

[0041] The modified layered graphene oxide was prepared by the following steps: B1. 0.6 g of tannic acid was added to 45 mL of ethanol, stirred until completely dissolved, 2 g of layered graphene oxide was added, stirred at 50 °C for 30 min, filtered, washed with deionized water 3 times, and dried in an oven at 70 °C for 10 min to obtain tannic acid modified layered graphene oxide; B2. 1.5 g of zinc nitrate hexahydrate, 1.6 g of 2-amino benzothiazole and 2.5 g of 2-methyl imidazole were added to 75 mL of methanol, stirred until uniform, 1.3 g of sodium formate and 5.5 g of tannic acid modified layered graphene oxide were added, stirred until uniform, nitrogen was introduced, reacted at 60 °C for 3 h, centrifuged at a speed of 8000 r / min, washed with methanol 3 times, washed with deionized water 3 times, and dried in an oven at 60 °C for 10 min to obtain the modified layered graphene oxide.

[0042] Example 2 A low-temperature lithium battery separator material containing nanoceramic material, the preparation method comprising the following preparation steps: S1. The modified nanoceramic material, the modified layered graphene oxide, the carboxymethyl cellulose and the deionized water were mixed to obtain a mixed slurry; S2. The mixed slurry was sprayed onto the upper and lower surfaces of the polypropylene separator, and dried and cured at 50 °C for 40 min to obtain a lithium battery separator material.

[0043] In step S1, the mass ratio of the modified nanoceramic material, the modified layered graphene oxide, the carboxymethyl cellulose and the deionized water was 23:13:0.8:50; In step S2, the spraying amount of the mixed slurry onto the upper and lower surfaces of the polypropylene separator was 20 g / m 2 , and the spraying pressure was 0.4 MPa; The thickness of the polypropylene separator was 13 μm, and the thickness of the lithium battery separator material was 35 μm.

[0044] The modified nanoceramic material was prepared by the following steps: A1. 5.5 g of nanoceramic material, 3.5 g of glucose and 0.6 g of citric acid were added to 100 mL of ethanol, stirred until uniform, 0.5 mL of 36% hydrochloric acid was added, stirred at 70°C for 35 min, filtered, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, placed in a tube furnace, 5 mL of 30% potassium hydroxide solution was added, nitrogen was introduced, the nitrogen flow rate was 30 mL / min, the temperature was raised to 800°C, carbonization was carried out for 4 h, the heating rate was 10°C / min, cooled to room temperature, taken out, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, to obtain a nanoceramic material loaded with porous carbon; A2. 5.3 g of silicon carbide whiskers were added to 80 mL of Tris-HCl buffer with pH of 8.5, stirred until uniform, 0.6 g of dopamine was added, stirred at 25°C, 800 r / min for 3.5 h, filtered, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, to obtain polydopamine modified silicon carbide whiskers; A3. 4.5 g of polydopamine modified silicon carbide whiskers and 3.3 g of nanoceramic material loaded with porous carbon were added to 100 mL of deionized water, stirred at 900 r / min for 25 min, stood for 1 h, filtered, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, to obtain modified nanoceramic material.

[0045] The modified layered graphene oxide was prepared by the following steps: B1. 0.8 g of tannic acid was added to 50 mL of ethanol, stirred until completely dissolved, 2.2 g of layered graphene oxide was added, stirred at 50°C for 30 min, filtered, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, to obtain tannic acid modified layered graphene oxide; B2. 2 g of zinc nitrate hexahydrate, 1.8 g of 2-amino benzothiazole and 2.7 g of 2-methyl imidazole were added to 80 mL of methanol, stirred until uniform, 1.5 g of sodium formate and 5.7 g of tannic acid modified layered graphene oxide were added, stirred until uniform, nitrogen was introduced, reacted at 65°C for 4 h, centrifuged at a speed of 8000 r / min, washed with methanol for 3 times, washed with deionized water for 3 times, dried in an oven at 60°C for 10 min, to obtain modified layered graphene oxide.

[0046] Example 3 A low-temperature lithium battery separator material containing nanoceramic material, the preparation method comprising the following preparation steps: S1. The modified nanoceramic material, the modified layered graphene oxide, the carboxymethyl cellulose and the deionized water were mixed to obtain a mixed slurry; S2. The mixed slurry is sprayed onto the upper and lower surfaces of the polypropylene separator, and dried and cured at 60°C for 30 min to obtain a lithium battery separator material.

[0047] In step S1, the mass ratio of the modified nanoceramic material, the modified layered graphene oxide, carboxymethyl cellulose, and deionized water is 25:15:1:60; In step S2, the spraying amount of the mixed slurry on the upper and lower surfaces of the polypropylene separator is 22 g / m 2 , and the spraying pressure is 0.5 MPa. The thickness of the polypropylene separator is 15 μm, and the thickness of the lithium battery separator material is 40 μm.

[0048] The modified nanoceramic material is prepared by the following steps: A1. 6 g of nanoceramic material, 4 g of glucose, and 0.7 g of citric acid are added to 120 mL of ethanol, stirred uniformly, 0.6 mL of 36% hydrochloric acid is added, stirred at 70°C for 35 min, filtered, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, placed in a tube furnace, 6 mL of 30% potassium hydroxide solution is added, nitrogen gas is introduced at a flow rate of 30 mL / min, heated to 850°C, carbonized for 5 h at a heating rate of 10°C / min, cooled to room temperature, taken out, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, to obtain a nanoceramic material loaded with porous carbon; A2. 5.5 g of silicon carbide whiskers are added to 85 mL of Tris-HCl buffer solution with a pH of 8.5, stirred uniformly, 0.7 g of dopamine is added, stirred at 25°C and 800 r / min for 3.5 h, filtered, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, to obtain polydopamine modified silicon carbide whiskers; A3. 5 g of polydopamine modified silicon carbide whiskers and 3.6 g of nanoceramic material loaded with porous carbon are added to 110 mL of deionized water, stirred at 900 r / min for 25 min, left to stand for 1 h, filtered, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, to obtain a modified nanoceramic material.

[0049] The modified layered graphene oxide is prepared by the following steps: B1. 1 g of tannic acid is added to 55 mL of ethanol, stirred until completely dissolved, 2.4 g of layered graphene oxide is added, stirred at 50°C for 30 min, filtered, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, to obtain tannic acid modified layered graphene oxide; B2. Add 2.5 g of zinc nitrate hexahydrate, 2 g of 2-aminobenzothiazole, and 2.9 g of 2-methylimidazole to 85 mL of methanol and stir well. Then add 1.7 g of sodium formate and 5.9 g of tannic acid-modified flake graphene oxide and stir well. Pour nitrogen into the mixture and react at 70°C for 5 h. Centrifuge at 8000 r / min, wash three times with methanol and three times with deionized water, and dry in an oven at 60°C for 10 min to obtain modified flake graphene oxide.

[0050] Comparative Example 1 A low-temperature lithium battery separator material containing nano-ceramic material, the preparation method of which comprises the following preparation steps: S1. The modified nano-ceramic material, modified sheet graphene oxide, carboxymethyl cellulose and deionized water are mixed to obtain a mixed slurry; S2. Spray the mixed slurry onto the upper and lower surfaces of the polypropylene separator, and dry and cure it at 60°C for 30 minutes to obtain a lithium battery separator material.

[0051] Wherein, in step S1, the mass ratio of the modified nano-ceramic material, the modified flake graphene oxide, the carboxymethyl cellulose and the deionized water is 25:15:1:60; In step S2, the mixed slurry is sprayed on the upper and lower surfaces of the polypropylene diaphragm at a spraying amount of 22 g / m 2 , the spraying pressure is 0.5MPa; The thickness of the polypropylene separator is 15 μm and the thickness of the lithium battery separator material is 40 μm.

[0052] The modified nano-ceramic material is specifically prepared by the following steps: A1. 5.5 g of silicon carbide whiskers were added to 85 mL of Tris-HCl buffer (pH 8.5) and stirred. 0.7 g of dopamine was added and the mixture was stirred at 25°C and 800 rpm for 3.5 h. The mixture was filtered, washed three times with deionized water, and dried in a 70°C oven for 10 min to obtain polydopamine-modified silicon carbide whiskers. A2. Add 5 g of polydopamine-modified silicon carbide whiskers and 3.6 g of nanoceramic material to 110 mL of deionized water, stir at 900 rpm for 25 min, let stand for 1 h, filter, wash three times with deionized water, and dry in a 70°C oven for 10 min to obtain the modified nanoceramic material.

[0053] The modified sheet graphene oxide is specifically prepared by the following steps: B1. Add 1 g of tannic acid to 55 mL of ethanol and stir until completely dissolved. Then add 2.4 g of flake graphene oxide and stir at 50°C for 30 min. Filter, wash three times with deionized water, and dry in an oven at 70°C for 10 min to obtain tannic acid-modified flake graphene oxide. B2. Add 2.5 g of zinc nitrate hexahydrate, 2 g of 2-aminobenzothiazole, and 2.9 g of 2-methylimidazole to 85 mL of methanol and stir well. Then add 1.7 g of sodium formate and 5.9 g of tannic acid-modified flake graphene oxide and stir well. Pour nitrogen into the mixture and react at 70°C for 5 h. Centrifuge at 8000 r / min, wash three times with methanol and three times with deionized water, and dry in an oven at 60°C for 10 min to obtain modified flake graphene oxide.

[0054] Comparative Example 2 A low-temperature lithium battery separator material containing nano-ceramic material, the preparation method of which comprises the following preparation steps: S1. The modified nano-ceramic material, modified sheet graphene oxide, carboxymethyl cellulose and deionized water are mixed to obtain a mixed slurry; S2. Spray the mixed slurry onto the upper and lower surfaces of the polypropylene separator, and dry and cure it at 60°C for 30 minutes to obtain a lithium battery separator material.

[0055] Wherein, in step S1, the mass ratio of the modified nano-ceramic material, the modified flake graphene oxide, the carboxymethyl cellulose and the deionized water is 25:15:1:60; In step S2, the mixed slurry is sprayed on the upper and lower surfaces of the polypropylene diaphragm at a spraying amount of 22 g / m 2 , the spraying pressure is 0.5MPa; The thickness of the polypropylene separator is 15 μm and the thickness of the lithium battery separator material is 40 μm.

[0056] The modified nano-ceramic material is specifically prepared by the following steps: A1. 6 g of nanoceramic material, 4 g of glucose, and 0.7 g of citric acid were added to 120 mL of ethanol and stirred. 0.6 mL of 36% hydrochloric acid was added and stirred at 70°C for 35 min. The mixture was filtered, washed three times with deionized water, and dried in a 70°C oven for 10 min. The mixture was placed in a tube furnace, and 6 mL of 30% potassium hydroxide solution was added. Nitrogen was introduced at a flow rate of 30 mL / min. The temperature was raised to 850°C and carbonized for 5 h at a heating rate of 10°C / min. The mixture was cooled to room temperature, removed, washed three times with deionized water, and dried in a 70°C oven for 10 min to obtain a porous carbon-loaded nanoceramic material. A2. Add 5 g of silicon carbide whiskers and 3.6 g of porous carbon-loaded nanoceramic material to 110 mL of deionized water, stir at 900 rpm for 25 min, let stand for 1 h, filter, wash three times with deionized water, and dry in a 70°C oven for 10 min to obtain a modified nanoceramic material.

[0057] The modified sheet graphene oxide is specifically prepared by the following steps: B1. Add 1 g of tannic acid to 55 mL of ethanol and stir until completely dissolved. Then add 2.4 g of flake graphene oxide and stir at 50°C for 30 min. Filter, wash three times with deionized water, and dry in an oven at 70°C for 10 min to obtain tannic acid-modified flake graphene oxide. B2. Add 2.5 g of zinc nitrate hexahydrate, 2 g of 2-aminobenzothiazole, and 2.9 g of 2-methylimidazole to 85 mL of methanol and stir well. Then add 1.7 g of sodium formate and 5.9 g of tannic acid-modified flake graphene oxide and stir well. Pour nitrogen into the mixture and react at 70°C for 5 h. Centrifuge at 8000 r / min, wash three times with methanol and three times with deionized water, and dry in an oven at 60°C for 10 min to obtain modified flake graphene oxide.

[0058] Comparative Example 3 A low-temperature lithium battery separator material containing nano-ceramic material, the preparation method of which comprises the following preparation steps: S1. The modified nano-ceramic material, modified sheet graphene oxide, carboxymethyl cellulose and deionized water are mixed to obtain a mixed slurry; S2. Spray the mixed slurry onto the upper and lower surfaces of the polypropylene separator, and dry and cure it at 60°C for 30 minutes to obtain a lithium battery separator material.

[0059] Wherein, in step S1, the mass ratio of the modified nano-ceramic material, the modified flake graphene oxide, the carboxymethyl cellulose and the deionized water is 25:15:1:60; In step S2, the mixed slurry is sprayed on the upper and lower surfaces of the polypropylene diaphragm at a spraying amount of 22 g / m 2 , the spraying pressure is 0.5MPa; The thickness of the polypropylene separator is 15 μm and the thickness of the lithium battery separator material is 40 μm.

[0060] The modified nano-ceramic material is specifically prepared by the following steps: A1. 6 g of nanoceramic material, 4 g of glucose and 0.7 g of citric acid were added to 120 mL of ethanol, stirred until uniform, 0.6 mL of 36% hydrochloric acid was added, stirred at 70°C for 35 min, filtered, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, placed in a tube furnace, 6 mL of 30% potassium hydroxide solution was added, nitrogen was introduced, the nitrogen flow rate was 30 mL / min, the temperature was raised to 850°C, carbonization was carried out for 5 h, the heating rate was 10°C / min, cooled to room temperature, taken out, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, to obtain a nanoceramic material loaded with porous carbon; A2. 5.5 g of silicon carbide particles (particle size 2 µm, purchased from Rizhao Hengqiao Trade Co., Ltd.) were added to 85 mL of Tris-HCl buffer with pH 8.5, stirred until uniform, 0.7 g of dopamine was added, stirred at 25°C, 800 r / min for 3.5 h, filtered, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, to obtain polydopamine modified silicon carbide particles; A3. 5 g of polydopamine modified silicon carbide particles and 3.6 g of nanoceramic material loaded with porous carbon were added to 110 mL of deionized water, stirred at 900 r / min for 25 min, stood for 1 h, filtered, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, to obtain modified nanoceramic material.

[0061] The modified layered graphene oxide was prepared by the following steps: B1. 1 g of tannic acid was added to 55 mL of ethanol, stirred until completely dissolved, 2.4 g of layered graphene oxide was added, stirred at 50°C for 30 min, filtered, washed with deionized water for 3 times, dried in an oven at 70°C for 10 min, to obtain tannic acid modified layered graphene oxide; B2. 2.5 g of zinc nitrate hexahydrate, 2 g of 2-amino benzothiazole and 2.9 g of 2-methyl imidazole were added to 85 mL of methanol, stirred until uniform, 1.7 g of sodium formate and 5.9 g of tannic acid modified layered graphene oxide were added, stirred until uniform, nitrogen was introduced, reacted at 70°C for 5 h, centrifuged at a speed of 8000 r / min, washed with methanol for 3 times, washed with deionized water for 3 times, dried in an oven at 60°C for 10 min, to obtain modified layered graphene oxide.

[0062] Comparative Example 4 A low-temperature lithium battery separator material containing nanoceramic material, the preparation method comprising the following preparation steps: S1. The modified nanoceramic material, the modified layered graphene oxide, the carboxymethyl cellulose and the deionized water were mixed to obtain a mixed slurry; S2. The mixed slurry is sprayed onto the upper and lower surfaces of the polypropylene separator, and dried and cured at 60°C for 30 min to obtain a lithium battery separator material.

[0063] In step S1, the mass ratio of the modified nanoceramic material, the modified layered graphene oxide, carboxymethyl cellulose and deionized water is 25:15:1:60; In step S2, the spraying amount of the mixed slurry on the upper and lower surfaces of the polypropylene separator is 22 g / m 2 , and the spraying pressure is 0.5 MPa; The thickness of the polypropylene separator is 15 μm, and the thickness of the lithium battery separator material is 40 μm.

[0064] The modified nanoceramic material is prepared by the following steps: A1. 6 g of nanoceramic material, 4 g of glucose and 0.7 g of citric acid are added to 120 mL of ethanol, stirred uniformly, 0.6 mL of 36% hydrochloric acid is added, stirred at 70°C for 35 min, filtered, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, placed in a tube furnace, 6 mL of 30% potassium hydroxide solution is added, nitrogen is introduced, the nitrogen flow is 30 mL / min, the temperature is raised to 850°C, carbonization is carried out for 5 h, the temperature rising rate is 10°C / min, cooled to room temperature, taken out, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, to obtain a nanoceramic material loaded with porous carbon; A2. 5.5 g of silicon carbide whiskers are added to 85 mL of Tris-HCl buffer solution with pH 8.5, stirred uniformly, 0.7 g of dopamine is added, stirred at 25°C and 800 r / min for 3.5 h, filtered, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, to obtain polydopamine modified silicon carbide whiskers; A3. 5 g of polydopamine modified silicon carbide whiskers and 3.6 g of nanoceramic material loaded with porous carbon are added to 110 mL of deionized water, stirred at 900 r / min for 25 min, stand for 1 h, filtered, washed with deionized water for 3 times, dried in a 70°C oven for 10 min, to obtain a modified nanoceramic material.

[0065] The modified layered graphene oxide is prepared by the following steps: 2.5 g of zinc nitrate hexahydrate, 2 g of 2-amino benzothiazole and 2.9 g of 2-methyl imidazole are added to 85 mL of methanol, stirred uniformly, 1.7 g of sodium formate and 5.9 g of layered graphene oxide are added, stirred uniformly, nitrogen is introduced, reacted at 70°C for 5 h, centrifuged at a speed of 8000 r / min, washed with methanol for 3 times, washed with deionized water for 3 times, dried in a 60°C oven for 10 min, to obtain modified layered graphene oxide.

[0066] Comparative Example 5 A low-temperature lithium battery separator material containing a nano-ceramic material, the preparation method comprising the following preparation steps: S1. mixing modified nano-ceramic material, tannic acid modified layered graphene oxide, carboxymethyl cellulose and deionized water to obtain a mixed slurry; S2. spraying the mixed slurry onto the upper and lower surfaces of the polypropylene separator, drying and curing at 60°C for 30 min to obtain a lithium battery separator material.

[0067] In step S1, the mass ratio of modified nano-ceramic material, tannic acid modified layered graphene oxide, carboxymethyl cellulose and deionized water is 25:15:1:60; In step S2, the spraying amount of the mixed slurry onto the upper and lower surfaces of the polypropylene separator is 22 g / m 2 , and the spraying pressure is 0.5 MPa; The thickness of the polypropylene separator is 15 μm, and the thickness of the lithium battery separator material is 40 μm.

[0068] The modified nano-ceramic material is prepared by the following steps: A1. Add 6 g of nano-ceramic material, 4 g of glucose and 0.7 g of citric acid to 120 mL of ethanol, stir uniformly, add 0.6 mL of 36% hydrochloric acid, stir at 70°C for 35 min, filter, wash with deionized water for 3 times, dry in a 70°C oven for 10 min, place in a tube furnace, add 6 mL of 30% potassium hydroxide solution, pass nitrogen gas, nitrogen flow rate is 30 mL / min, heat to 850°C, carbonize for 5 h, heating rate is 10°C / min, cool to room temperature, take out, wash with deionized water for 3 times, dry in a 70°C oven for 10 min, to obtain nano-ceramic material loaded with porous carbon; A2. Add 5.5 g of silicon carbide whiskers to 85 mL of Tris-HCl buffer solution with pH 8.5, stir uniformly, add 0.7 g of dopamine, stir at 25°C and 800 r / min for 3.5 h, filter, wash with deionized water for 3 times, dry in a 70°C oven for 10 min, to obtain polydopamine modified silicon carbide whiskers; A3. Add 5 g of polydopamine modified silicon carbide whiskers and 3.6 g of nano-ceramic material loaded with porous carbon to 110 mL of deionized water, stir at 900 r / min for 25 min, stand for 1 h, filter, wash with deionized water for 3 times, dry in a 70°C oven for 10 min, to obtain modified nano-ceramic material.

[0069] The tannic acid modified layered graphene oxide is prepared by the following steps: 1 g of tannic acid was added to 55 mL of ethanol and stirred until completely dissolved. 2.4 g of flake graphene oxide was added and stirred at 50°C for 30 min. The mixture was filtered, washed with deionized water three times, and dried in an oven at 70°C for 10 min to obtain tannic acid-modified flake graphene oxide.

[0070] The performance of the lithium battery separator materials prepared in Examples 1-3 and Comparative Examples 1-5 is now tested.

[0071] The lithium battery separator material used in the test has a width of 20 mm, a length of 40 mm, and a thickness of 35 μm.

[0072] Tensile strength test: The longitudinal and transverse tensile strength of the lithium battery separator material prepared above were tested using a Xieqiang CTM universal testing machine. Five specimens were tested in each direction and the average value was calculated. The test temperature was 25°C.

[0073] Heat resistance test: The thermal shrinkage rate of battery separator was measured using a thermal shrinkage tester.

[0074] Electrochemical performance test: Lithium iron phosphate: carbon black: polyvinylidene fluoride (PVDF) was mixed in an 8:1:1 ratio and coated on aluminum foil. The mixture was dried at 110°C and cut into 13mm diameter discs as the positive electrode material. Pure lithium sheets were used as the negative electrode material. The separator was the lithium battery separator material prepared above. The positive and negative electrode shells were CR2032 models. The batteries were assembled. The battery was placed at 25°C and -25°C, with a voltage of 3V, and was charged and discharged at a constant current rate of 1C for 200 cycles. The voltage protection was set between 0-4.25V, and the discharge capacity of the battery at 25°C and -25°C was recorded.

[0075] The test results are shown in Table 1 below.

[0076] Table 1 Performance test of lithium battery separator materials prepared in Examples 1-3 and Comparative Examples 1-5

[0077] It can be seen from the data in Table 1 that the lithium battery separator materials prepared in Examples 1-3 have relatively high mechanical properties, high and low temperature resistance, and electrochemical properties.

[0078] The modified nanoceramic material prepared by replacing the porous carbon loaded nanoceramic material with the nanoceramic material is coated on the lithium battery separator material, and the mechanical properties and high and low temperature resistance performance thereof are decreased, which proves that the porous carbon synthesized on the surface of the nanoceramic material has higher pore structure and pore capacity, accelerates the transmission performance of lithium ions, enhances the migration rate of lithium ions, and increases the surface roughness of the nanoceramic material, increases the contact area of the nanoceramic material and the electrolyte, and improves the migration number of lithium ions. In addition, it can hinder the collapse of the hole shrinkage of the separator at low temperature, so that the lithium ion transmission performance of the separator at low temperature is still maintained.

[0079] The modified nanoceramic material prepared by replacing the polydopamine modified silicon carbide whisker with the silicon carbide whisker is coated on the lithium battery separator material, and the mechanical properties and high and low temperature resistance performance thereof are decreased, which proves that the polydopamine modified silicon carbide whisker improves the surface activity of the silicon carbide whisker, which is beneficial to the deposition of the porous carbon loaded nanoceramic material on the surface of the silicon carbide whisker, avoids the agglomeration of the porous carbon loaded nanoceramic material, and affects the mechanical properties and high and low temperature resistance performance of the separator material.

[0080] The modified nanoceramic material prepared by replacing the silicon carbide whisker with the silicon carbide particle is coated on the lithium battery separator material, and the mechanical properties and high and low temperature resistance performance thereof are decreased, which proves that the silicon carbide whisker has excellent aspect ratio and is randomly distributed on the surface of the separator to form a network structure capable of absorbing and weakening external force, thereby improving the mechanical properties of the separator. In addition, the silicon carbide whisker has good low temperature resistance, so that the lithium ion transmission performance of the separator at low temperature is good. In addition, the silicon carbide whisker surface contains porous carbon, so that the silicon carbide whisker forms a lithium ion transmission channel on the surface of the separator, shortens the lithium ion transmission path, and improves the charge and discharge efficiency of the lithium ion battery.

[0081] The modified nanoceramic material prepared by replacing the silicon carbide whisker with the silicon carbide particle is coated on the lithium battery separator material, and the mechanical properties and high and low temperature resistance performance thereof are decreased, which proves that the silicon carbide whisker has excellent aspect ratio and is randomly distributed on the surface of the separator to form a network structure capable of absorbing and weakening external force, thereby improving the mechanical properties of the separator. In addition, the silicon carbide whisker has good low temperature resistance, so that the lithium ion transmission performance of the separator at low temperature is good. In addition, the silicon carbide whisker surface contains porous carbon, so that the silicon carbide whisker forms a lithium ion transmission channel on the surface of the separator, shortens the lithium ion transmission path, and improves the charge and discharge efficiency of the lithium ion battery.

[0082] The modified nanoceramic material prepared by replacing the silicon carbide whisker with the silicon carbide particle is coated on the lithium battery separator material, and the mechanical properties and high and low temperature resistance performance thereof are decreased, which proves that the silicon carbide whisker has excellent aspect ratio and is randomly distributed on the surface of the separator to form a network structure capable of absorbing and weakening external force, thereby improving the mechanical properties of the separator. In addition, the silicon carbide whisker has good low temperature resistance, so that the lithium ion transmission performance of the separator at low temperature is good. In addition, the silicon carbide whisker surface contains porous carbon, so that the silicon carbide whisker forms a lithium ion transmission channel on the surface of the separator, shortens the lithium ion transmission path, and improves the charge and discharge efficiency of the lithium ion battery.

[0083] In the description, references to "one embodiment," "an example," "certain examples" etc. mean that the particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the application. The appearances of an item in various examples or embodiments is not necessarily indicative of a frequency of occurrence in the various examples or embodiments. Moreover, descriptions of well-known methods associated are omitted so as not to obscure the disclosure.

[0084] The foregoing merely illustrates the principles of the application. Various modifications and adaptations will occur to those skilled in the art after consideration of the preceding description. All such modifications and adaptations employing the principles of the application are intended to be within the scope of the claims.

Claims

1. A low-temperature lithium battery separator material containing nano-ceramic material, characterized in that: The preparation method comprises the following steps: S1. The modified nano-ceramic material, the modified sheet graphene oxide, the binder and deionized water are mixed to obtain a mixed slurry; S2. The mixed slurry is sprayed onto the upper and lower surfaces of the polyolefin separator, dried and cured to obtain a lithium battery separator material; Among them, the modified nano-ceramic material is obtained by synthesizing porous carbon on the surface of nano-ceramic material and then depositing it on the surface of polydopamine-modified silicon carbide whiskers; The modified flake graphene oxide is prepared by modifying the surface of flake graphene oxide with tannic acid and then reacting the surface with a zinc source and dimethylimidazole.

2. The low-temperature lithium battery separator material containing nano-ceramic material according to claim 1, characterized in that: The modified nano-ceramic material is specifically prepared by the following steps: A1. Add the nanoceramic material, glucose, and citric acid to ethanol and stir evenly. Add hydrochloric acid and stir the mixture. After stirring, filter, wash, dry, mix with potassium hydroxide solution, introduce inert gas, and carbonize at 750-850°C for 3-5h. Cool to room temperature, remove, wash, and dry to obtain a porous carbon-loaded nanoceramic material. A2. Silicon carbide whiskers were added to Tris-HCl buffer, stirred evenly, dopamine was added, stirred for reaction, filtered, washed, and dried to obtain polydopamine-modified silicon carbide whiskers; A3. Add polydopamine-modified silicon carbide whiskers and porous carbon-loaded nanoceramic materials into deionized water, stir, let stand, filter, wash, and dry to obtain a modified nanoceramic material.

3. The low-temperature lithium battery separator material containing nano-ceramic material according to claim 2, characterized in that: In step A1, the ratio of the nano-ceramic material, glucose, citric acid, ethanol, hydrochloric acid and potassium hydroxide solution is (5-6) g: (3-4) g: (0.5-0.7) g: (80-120) mL: (0.4-0.6) mL: (4-6) mL.

4. The low-temperature lithium battery separator material containing nano-ceramic material according to claim 2, characterized in that: In step A2, the ratio of the silicon carbide whiskers, Tris-HCl buffer and dopamine is (5.1-5.5) g: (75-85) mL: (0.5-0.7) g.

5. The low-temperature lithium battery separator material containing nano-ceramic material according to claim 2, characterized in that: In step A3, the ratio of the polydopamine-modified silicon carbide whiskers, the porous carbon-loaded nanoceramic material, and deionized water is (4-5) g: (3-3.6) g: (90-110) mL.

6. The low-temperature lithium battery separator material containing nano-ceramic material according to claim 1, characterized in that: The modified sheet graphene oxide is specifically prepared by the following steps: B1. Add tannic acid to ethanol and stir until completely dissolved, add flake graphene oxide, stir evenly, filter, wash, and dry to obtain tannic acid-modified flake graphene oxide; B2. Zinc nitrate hexahydrate, 2-aminobenzothiazole, and 2-methylimidazole were added to methanol and stirred. Then, sodium formate and tannic acid-modified flake graphene oxide were added. After stirring, an inert gas was introduced and the mixture was reacted at 60-70°C for 3-5 hours. The mixture was centrifuged, washed, and dried to obtain modified flake graphene oxide.

7. The low-temperature lithium battery separator material containing nano-ceramic material according to claim 6, characterized in that: In step B1, the ratio of the tannic acid, ethanol and flake graphene oxide is (0.6-1) g: (45-55) mL: (2-2.4) g.

8. The low-temperature lithium battery separator material containing nano-ceramic material according to claim 6, characterized in that: In step B2, the ratio of zinc nitrate hexahydrate, 2-aminobenzothiazole, 2-methylimidazole, methanol, sodium formate and tannic acid-modified sheet graphene oxide is (1.5-2.5) g: (1.6-2) g: (2.5-2.9) g: (75-85) mL: (1.3-1.7) g: (5.5-5.9) g.

9. The low-temperature lithium battery separator material containing nano-ceramic material according to claim 1, characterized in that: In step S1, the mass ratio of the modified nano-ceramic material, modified flaky graphene oxide, binder and deionized water is (20-25):(10-15):(0.5-1):(40-60).

10. The low-temperature lithium battery separator material containing nano-ceramic material according to claim 1, characterized in that: In step S2, the mixed slurry is sprayed on the upper and lower surfaces of the polyolefin diaphragm in an amount of 18-22 g / m 2 , the spraying pressure is 0.3-0.5MPa.

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