A magnesium hydroxide-based battery separator and process for its preparation

Abstract

The application relates to the technical field of battery diaphragm, in particular to a battery diaphragm based on magnesium hydroxide and a preparation process thereof. In the coating slurry of the lithium ion battery diaphragm, magnesium hydroxide nanotubes are introduced, COPNA resin is used as an adhesive, 2,2'-diallyl bisphenol A and polysulfone are used to modify the naphthol-based COPNA resin, then 3,3',4,4'-diphenyl tetracarboxylic dianhydride, p-phenylenediamine and 2,2'-di(trifluoromethyl)-4,4'-diaminobiphenyl are used to prepare copolymerized COPNA resin, the COPNA resin still maintains the adhesion at high temperature, the thermal expansion coefficient of the battery diaphragm is improved, the battery diaphragm has a relatively low dielectric constant, the magnesium hydroxide nanotubes are modified, the uniformity of the dispersion of the magnesium hydroxide nanotubes in the coating slurry is improved without adding a dispersant, the diaphragm is homogenized, modified magnesium hydroxide nanotubes are prepared from the magnesium hydroxide nanotubes, hyperbranched tannic acid compounds and aminated metal frameworks, and the safety of the lithium ion battery is improved.

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, specifically a battery separator based on magnesium hydroxide and its preparation process. Background Technology

[0002] Energy is a vital foundation for human survival and development. With the depletion of traditional fossil fuels, developing renewable and clean energy has become crucial to alleviating the energy crisis. Lithium-ion batteries, as a type of rechargeable battery, are widely used in electronic devices, electric vehicles, and energy storage due to their lightweight, rechargeable, and high energy density.

[0003] Lithium-ion batteries primarily rely on the movement of lithium ions between the positive and negative electrodes to achieve charging and discharging. The lithium-ion separator, located between the positive and negative electrodes, mainly serves as an electrical insulator and provides microporous channels for lithium ions. The separator's properties, such as high-temperature resistance, puncture resistance, and ability to prevent lithium dendrite penetration, determine the safety and energy storage capacity of the lithium-ion battery, making it a core component.

[0004] Currently, most of the separators circulating in the market are polyolefin separators. However, the optimization of the performance of polyolefin separators faces the following challenges: (1) The heat resistance and thermal shrinkage rate of polyolefin separators are difficult to meet the increasingly high safety requirements of batteries. For example, lithium-ion batteries for electric vehicles require the separator to have a shrinkage rate of less than 5% at 200°C. However, commonly used polyolefin separators have low melting points and are prone to shrinkage when heated, which will cause dimensional instability. (2) In order to ensure the safe operation of lithium-ion batteries, lithium-ion battery separators need to have good tensile strength and puncture resistance. However, the mechanical strength of polyolefin separators is difficult to eliminate the risk of lithium dendrite puncture, which can easily lead to the risk of battery short circuit. (3) Most of the commonly used polyolefin separators are non-polar materials. They have poor affinity with polar electrolytes and lithium salts, which will cause the separator to have high internal resistance and low ionic conductivity, which greatly limits the improvement of lithium-ion battery performance. Summary of the Invention

[0005] The purpose of this invention is to provide a battery separator based on magnesium hydroxide and its preparation process, so as to solve the problems in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A magnesium hydroxide-based battery separator includes a base film and a coating layer. By mass percentage, the coating layer comprises: 10-30% magnesium hydroxide nanotubes, 0-0.6% dispersant, 0.4-0.7% thickener, 0.5-1% binder, 0.05-0.2% wetting agent, and the balance being ultrapure water.

[0008] This invention introduces magnesium hydroxide nanotubes into the coating slurry of lithium-ion battery separators. While maintaining the excellent flame retardancy and liquid absorption and retention capacity of magnesium hydroxide nanotubes, it significantly improves the mechanical strength and thermal shrinkage performance of the separator. Because the introduced magnesium hydroxide nanotubes have a hollow structure, the specific surface area of ​​the material is greatly increased, which improves the lithium-ion conductivity and also significantly enhances the liquid absorption and retention capacity of the separator.

[0009] Furthermore, the carbonized layer formed by the endothermic decomposition of the crystal water of the introduced magnesium hydroxide nanotubes not only prevents the entry of oxygen and heat but also decomposes to generate magnesium oxide, thereby improving the high temperature resistance and thermal conductivity of the membrane.

[0010] Furthermore, the dispersant is a hydrolyzed polymaleic anhydride dispersant; the thickener is sodium carboxymethyl cellulose; the binder is a COPNA resin-based binder; and the wetting agent is a silanol nonionic surfactant.

[0011] Furthermore, the preparation of magnesium hydroxide nanotubes includes the following steps: hydrophilic silica nanowires and magnesium sulfate solution are mixed and stirred for 70-80 min, ultrasonically dispersed for 4-5 h, heated to 65-70 °C, ammonia water is added until the pH reaches 8-10 to stop the reaction, filtered, washed, and dried for 16 h, with the vacuum degree controlled at 0.08 MPa during vacuum drying, then added to sodium hydroxide solution and maintained for 4 h, filtered, washed, and dried at 75-80 °C for 10-12 h, after which magnesium hydroxide nanotubes are obtained.

[0012] Using COPNA resin as an adhesive, polyimide copolymerization is performed on COPNA resin to maintain its adhesiveness at high temperatures while improving the thermal expansion coefficient of the battery separator, giving it a lower dielectric constant, thereby enhancing its ability to resist thermal runaway risk.

[0013] Naphthol-based COPNA resin was first modified with 2,2'-diallylbisphenol A and polysulfone to improve its toughening effect and low dielectric properties. Then, a copolymer COPNA resin was prepared with 3,3',4,4'-biphenyltetracarboxylic dianhydride, p-phenylenediamine, and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl to give it the characteristics of low expansion, high heat resistance, high strength and high modulus, thus meeting the thermal performance requirements of the diaphragm.

[0014] Furthermore, the adhesive is a copolymer COPNA resin, and its preparation includes the following steps:

[0015] (1) Mix 1-naphthol, benzaldehyde, p-toluenesulfonic acid and ethanol, and stir until the reaction solution shows the phenomenon of "rod wrapping" to obtain naphthol-based COPNA resin;

[0016] (2) Mix naphthol-based COPNA resin and n-butanol, keep warm at 50℃ for 60 min, add magnesium hydroxide powder, cool down to 35-40℃, add 2,2'-diallylbisphenol A, polysulfone, and N-methylpyrrolidone, stir ultrasonically for 10-20 min, heat up to 140-180℃ and keep warm for 1-3 h to obtain pretreated COPNA resin.

[0017] (3) Under nitrogen protection, 3,3',4,4'-biphenyltetracarboxylic dianhydride, N-methylpyrrolidone and deionized water are mixed and stirred for 1-2 hours. Then, p-phenylenediamine, 2,2'-di(trifluoromethyl)-4,4'-diaminobiphenyl and N-methylpyrrolidone are added and kept at the temperature for 22-24 hours. Then, pretreated COPNA resin is added, heated until dissolved, kept at the temperature for 20-30 minutes, and cured to obtain copolymer COPNA resin.

[0018] Furthermore, the mass ratio of naphthol-based COPNA resin, 2,2'-diallyl bisphenol A, and polysulfone is 10:1:1.

[0019] Furthermore, the mass ratio of 3,3',4,4'-biphenyltetracarboxylic dianhydride, p-phenylenediamine, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, and pretreated COPNA resin is 1.67:0.49:0.36:1.1.

[0020] Furthermore, a process for preparing a magnesium hydroxide-based battery separator includes the following steps:

[0021] S1: Preparation of magnesium hydroxide nanotubes;

[0022] S2: Mix the dispersant, magnesium hydroxide nanotubes, and ultrapure water for 5-25 minutes at a speed of 250-350 rpm; add the thickener and continue stirring for 15-55 minutes at a speed of 250-450 rpm; add the binder and stir for 25-55 minutes at a speed of 350-550 rpm; add the wetting agent and stir for 15-35 minutes at a speed of 350-650 rpm; filter to remove iron, and obtain the magnesium hydroxide nanotube coating slurry;

[0023] S3: Using a micro-gravure roller coating process, the magnesium hydroxide nanotube coating slurry in S2 is rolled onto both sides of the polyolefin separator in stages, baked at 65-70℃, and then wound up to obtain a battery separator based on magnesium hydroxide.

[0024] Modifying magnesium hydroxide nanotubes can improve the uniformity of their dispersion in the coating slurry without the addition of a dispersant, thus homogenizing the diaphragm.

[0025] Furthermore, the magnesium hydroxide nanotubes are modified to obtain modified magnesium hydroxide nanotubes. The preparation process includes the following steps:

[0026] 1) Mix zirconium tetrachloride, 2-aminoterephthalic acid, acetic acid, and N,N-dimethylformamide, stir ultrasonically for 10-15 min, transfer to a reaction vessel and keep warm at 115-120℃ for 22-24 h, centrifuge, wash, and dry to obtain an aminated metal framework.

[0027] 2) Mix magnesium hydroxide nanotubes, 3-aminopropyltriethoxysilane, hyperbranched tannic acid complex, and N,N-dimethylformamide, and sonicate for 10-15 min. Add an aminated metal framework and sonicate for 10-15 min. Heat to 55-60℃ and maintain for 12-14 h. Centrifuge, wash, and dry to obtain modified magnesium hydroxide nanotubes.

[0028] Furthermore, the preparation of the hyperbranched tannic acid complex includes the following steps: mixing tannic acid, pyridine, and methyltetrahydrophthalic anhydride, heating to 85-90℃ and keeping in an oil bath for 46-48 hours, precipitating with anhydrous diethyl ether, and drying to obtain the hyperbranched tannic acid complex.

[0029] Furthermore, the mass ratio of magnesium hydroxide nanotubes, hyperbranched tannic acid complex, and aminated metal framework is 2:0.1:0.6.

[0030] The preparation of modified magnesium hydroxide nanotubes using magnesium hydroxide nanotubes, hyperbranched tannic acid complexes, and aminated metal frameworks helps to enhance the strong interaction between magnesium hydroxide nanotubes and copolymerized COPNA resin, improve the adhesion between the coating slurry and the base film, thereby strengthening the interfacial compatibility between the two and improving the dimensional stability of the battery separator.

[0031] Magnesium hydroxide nanotubes were treated with a tannic acid complex with a hyperbranched structure and then grafted with an aminated metal framework. Both the hyperbranched tannic acid and the aminated metal framework have high flame retardancy. While the magnesium hydroxide nanotubes synergistically improve the flame retardancy of the battery separator, the hyperbranched tannic acid complex, the aminated metal framework and the COPNA resin have good compatibility, which can improve the toughness and thermal stability of the blend system, thereby further improving the thermal stability of the battery separator and improving the safety of lithium-ion batteries.

[0032] The beneficial effects of this invention are:

[0033] This invention provides a battery separator based on magnesium hydroxide and its preparation process. By introducing magnesium hydroxide nanotubes to prepare a coating for the lithium-ion battery separator, a lithium-ion battery separator with high flame retardancy, high wettability, and high mechanical strength is obtained.

[0034] Introducing magnesium hydroxide nanotubes into the coating slurry of lithium-ion battery separators significantly improves the mechanical strength and thermal shrinkage performance of the separator while maintaining the excellent flame retardancy and liquid absorption / retention capacity of the magnesium hydroxide nanotubes themselves. Because the introduced magnesium hydroxide nanotubes have a hollow structure, they greatly increase the specific surface area of ​​the material, which improves both the lithium-ion conductivity and the liquid absorption / retention capacity of the separator. Furthermore, the carbonization layer formed by the thermal decomposition of the crystal water of the introduced magnesium hydroxide nanotubes not only prevents the entry of oxygen and heat but also decomposes to generate magnesium oxide, thereby improving the high-temperature resistance and thermal conductivity of the separator.

[0035] Using COPNA resin as an adhesive, polyimide copolymerization is performed on COPNA resin to maintain its adhesiveness at high temperatures while improving the thermal expansion coefficient of the battery separator, giving it a lower dielectric constant, thereby enhancing its ability to resist thermal runaway risk.

[0036] Naphthol-based COPNA resin was first modified with 2,2'-diallylbisphenol A and polysulfone to improve its toughening effect and low dielectric properties. Then, a copolymer COPNA resin was prepared with 3,3',4,4'-biphenyltetracarboxylic dianhydride, p-phenylenediamine, and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl to give it the characteristics of low expansion, high heat resistance, high strength and high modulus, thus meeting the thermal performance requirements of the diaphragm.

[0037] Modification treatment of magnesium hydroxide nanotubes improves the uniformity of dispersion of magnesium hydroxide nanotubes in coating slurry without the addition of dispersant, thereby homogenizing the diaphragm.

[0038] The preparation of modified magnesium hydroxide nanotubes using magnesium hydroxide nanotubes, hyperbranched tannic acid complexes, and aminated metal frameworks helps to enhance the strong interaction between magnesium hydroxide nanotubes and copolymerized COPNA resin, improve the adhesion between the coating slurry and the base film, thereby strengthening the interfacial compatibility between the two and improving the dimensional stability of the battery separator.

[0039] Magnesium hydroxide nanotubes were treated with a tannic acid complex with a hyperbranched structure, and then grafted with an aminated metal framework. Both the hyperbranched tannic acid and the aminated metal framework have high flame retardancy. While the magnesium hydroxide nanotubes synergistically improve the flame retardancy of the battery separator, the hyperbranched tannic acid complex, the aminated metal framework, and the COPNA resin have good compatibility. By controlling the mass ratio of the introduced magnesium hydroxide nanotubes, hyperbranched tannic acid complex, and aminated metal framework, a complex and stable network structure is constructed, which effectively promotes the proton conduction performance of the battery separator, thereby improving the wettability of the battery separator, reducing the risk of thermal runaway of the separator, and further improving the thermal stability of the battery separator and the safety of lithium-ion batteries. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be noted that if the embodiments of the present invention involve directional indicators such as up, down, left, right, front, back, etc., these directional indicators are only used to explain the relative positional relationship and movement of components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0042] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0043] Example 1

[0044] A process for preparing a battery separator based on magnesium hydroxide includes the following steps:

[0045] S1: Preparation of magnesium hydroxide nanotubes;

[0046] 1.6965 g of hydrophilic silica nanowires and 250 mL of 1.91 mol / L magnesium sulfate solution were mixed and stirred for 70 min, ultrasonically dispersed for 4 h, heated to 65 °C, and 2 mol / L ammonia water was added at a flow rate of 38 mL / min until the pH reached 8 and the reaction was stopped. The mixture was filtered, washed, and dried for 16 h, with the vacuum degree controlled at 0.08 MPa. Then, it was added to 5.0 mol / L sodium hydroxide solution and kept for 4 h, filtered, washed, and dried at 75 °C for 12 h. After drying, magnesium hydroxide nanotubes were obtained.

[0047] S2: Mix the dispersant, magnesium hydroxide nanotubes, and ultrapure water for 5 minutes at 350 rpm; add the thickener and continue stirring for 15 minutes at 450 rpm; add the binder and stir for 25 minutes at 550 rpm; add the wetting agent and stir for 15 minutes at 650 rpm; filter to remove iron, and obtain the magnesium hydroxide nanotube coating slurry.

[0048] The raw material composition, by mass percentage, is: 10% magnesium hydroxide nanotubes, 0.25% dispersant, 0.4% thickener, 0.5% binder, 0.05% wetting agent, and the balance being ultrapure water;

[0049] The dispersant is hydrolyzed polymaleic anhydride dispersant; the thickener is sodium carboxymethyl cellulose; the wetting agent is a silanol nonionic surfactant.

[0050] The adhesive is a COPNA resin-based adhesive;

[0051] S3: Using a micro-gravure roller coating process, the magnesium hydroxide nanotube coating slurry in S2 is rolled onto both sides of a 9μm polyethylene separator at 3μm in stages, baked at 65℃, and then wound up to obtain a battery separator based on magnesium hydroxide.

[0052] Example 2

[0053] A process for preparing a battery separator based on magnesium hydroxide includes the following steps:

[0054] S1: Preparation of magnesium hydroxide nanotubes;

[0055] 1.6965 g of hydrophilic silica nanowires and 250 mL of 1.91 mol / L magnesium sulfate solution were mixed and stirred for 75 min, ultrasonically dispersed for 4.5 h, heated to 68 °C, and 2 mol / L ammonia water was added at a flow rate of 38 mL / min until the pH reached 9 and the reaction was stopped. The mixture was filtered, washed, and dried for 16 h, with the vacuum degree controlled at 0.08 MPa. Then, it was added to 5.0 mol / L sodium hydroxide solution and kept for 4 h. The mixture was filtered, washed, and dried at 78 °C for 11 h. After drying, magnesium hydroxide nanotubes were obtained.

[0056] Modified magnesium hydroxide nanotubes are obtained by modifying magnesium hydroxide nanotubes. The preparation process includes the following steps:

[0057] 1) Mix 0.15g zirconium tetrachloride, 0.12g 2-aminoterephthalic acid, 3.7mL acetic acid and 80mL N,N-dimethylformamide, sonicate for 12min, transfer to a reaction vessel and keep warm at 118℃ for 23h, centrifuge, wash and dry to obtain an aminated metal framework.

[0058] 2) Mix 2g magnesium hydroxide nanotubes, 0.1g 3-aminopropyltriethoxysilane, 0.1g hyperbranched tannic acid complex, and N,N-dimethylformamide, and sonicate for 12 min. Add 0.6g aminated metal framework and sonicate for 12 min. Heat to 58℃ and maintain for 13 h. Centrifuge, wash, and dry to obtain modified magnesium hydroxide nanotubes.

[0059] The preparation of the hyperbranched tannic acid complex includes the following steps: 2g of tannic acid, 20mL of pyridine and 9.2mL of methyltetrahydrophthalic anhydride are mixed, heated to 88℃ and kept in an oil bath for 47h, precipitated with anhydrous diethyl ether and dried to obtain the hyperbranched tannic acid complex.

[0060] S2: Mix the dispersant, magnesium hydroxide nanotubes, and ultrapure water for 15 minutes at 300 rpm; add the thickener and continue stirring for 30 minutes at 350 rpm; add the binder and stir for 40 minutes at 400 rpm; add the wetting agent and stir for 30 minutes at 500 rpm; filter to remove iron, and obtain the magnesium hydroxide nanotube coating slurry.

[0061] By mass percentage, the raw material composition is: 20% magnesium hydroxide nanotubes, 0.25% dispersant, 0.68% thickener, 0.77% binder, 0.08% wetting agent, and the balance is ultrapure water;

[0062] The dispersant is hydrolyzed polymaleic anhydride dispersant; the thickener is sodium carboxymethyl cellulose; the wetting agent is a silanol nonionic surfactant.

[0063] The adhesive is a COPNA resin-based adhesive;

[0064] The adhesive is a copolymer COPNA resin, and its preparation includes the following steps:

[0065] (1) Mix 1g of 1-naphthol, 1g of benzaldehyde, 0.07g of p-toluenesulfonic acid and 10mL of ethanol, and stir until the reaction solution shows the phenomenon of "rod wrapping" to obtain naphthol-based COPNA resin.

[0066] (3) Mix 1g of naphthol-based COPNA resin and 10mL of n-butanol, keep warm at 50℃ for 60min, add 0.5mg of magnesium hydroxide powder, cool down to 38℃, add 0.1g of 2,2'-diallyl bisphenol A, 0.1g of polysulfone and 5mL of N-methylpyrrolidone, stir ultrasonically for 15min, heat up to 160℃ and keep warm for 2h to obtain pretreated COPNA resin;

[0067] (3) Under nitrogen protection, 1.67g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 6mL of N-methylpyrrolidone, and 0.05g of deionized water were mixed and stirred for 1.5h. Then, 0.49g of p-phenylenediamine, 0.36g of 2,2'-di(trifluoromethyl)-4,4'-diaminobiphenyl, and 4mL of N-methylpyrrolidone were added. The mixture was kept warm for 23h. Then, 1.1g of pretreated COPNA resin was added, heated until dissolved, kept warm for 25min, and cured to obtain copolymer COPNA resin.

[0068] S3: Using a micro-gravure roller coating process, the magnesium hydroxide nanotube coating slurry in S2 is rolled onto both sides of a 9μm polyethylene separator at 3μm in stages, baked at 68℃, and then wound up to obtain a battery separator based on magnesium hydroxide.

[0069] Example 3

[0070] A process for preparing a battery separator based on magnesium hydroxide includes the following steps:

[0071] S1: Preparation of magnesium hydroxide nanotubes;

[0072] 1.6965 g of hydrophilic silica nanowires and 250 mL of 1.91 mol / L magnesium sulfate solution were mixed and stirred for 80 min, ultrasonically dispersed for 5 h, heated to 70 °C, and 2 mol / L ammonia water was added at a flow rate of 38 mL / min until the pH reached 10 and the reaction was stopped. The mixture was filtered, washed, and dried for 16 h under vacuum at a vacuum degree of 0.08 MPa. Then, it was added to a 5.0 mol / L sodium hydroxide solution and kept for 4 h. The mixture was filtered, washed, and dried at 80 °C for 10 h. After drying, magnesium hydroxide nanotubes were obtained.

[0073] S2: Mix the dispersant, magnesium hydroxide nanotubes, and ultrapure water for 25 minutes at 250 rpm; add the thickener and continue stirring for 55 minutes at 250 rpm; add the binder and stir for 55 minutes at 350 rpm; add the wetting agent and stir for 35 minutes at 350 rpm; filter to remove iron, and obtain the magnesium hydroxide nanotube coating slurry.

[0074] By mass percentage, the raw material composition is: 30% magnesium hydroxide nanotubes, 0.6% dispersant, 0.7% thickener, 1% binder, 0.2% wetting agent, and the balance is ultrapure water;

[0075] The dispersant is hydrolyzed polymaleic anhydride dispersant; the thickener is sodium carboxymethyl cellulose; the wetting agent is a silanol nonionic surfactant.

[0076] The adhesive is a COPNA resin-based adhesive;

[0077] S3: Using a micro-gravure roller coating process, the magnesium hydroxide nanotube coating slurry in S2 is rolled onto both sides of a 9μm polyethylene separator at 3μm in stages, baked at 70℃, and then wound up to obtain a battery separator based on magnesium hydroxide.

[0078] Example 4

[0079] A process for preparing a battery separator based on magnesium hydroxide includes the following steps:

[0080] S1: Preparation of magnesium hydroxide nanotubes;

[0081] 1.6965 g of hydrophilic silica nanowires and 250 mL of 1.91 mol / L magnesium sulfate solution were mixed and stirred for 70 min, ultrasonically dispersed for 4 h, heated to 65 °C, and 2 mol / L ammonia water was added at a flow rate of 38 mL / min until the pH reached 8 and the reaction was stopped. The mixture was filtered, washed, and dried for 16 h, with the vacuum degree controlled at 0.08 MPa. Then, it was added to 5.0 mol / L sodium hydroxide solution and kept for 4 h, filtered, washed, and dried at 75 °C for 12 h. After drying, magnesium hydroxide nanotubes were obtained.

[0082] Modified magnesium hydroxide nanotubes are obtained by modifying magnesium hydroxide nanotubes. The preparation process includes the following steps:

[0083] 1) Mix 0.15g zirconium tetrachloride, 0.12g 2-aminoterephthalic acid, 3.7mL acetic acid and 80mL N,N-dimethylformamide, sonicate for 10min, transfer to a reaction vessel and keep warm at 115℃ for 24h, centrifuge, wash and dry to obtain an aminated metal framework.

[0084] 2) Mix 2g magnesium hydroxide nanotubes, 0.1g 3-aminopropyltriethoxysilane, 0.1g hyperbranched tannic acid complex, and N,N-dimethylformamide, and sonicate for 10 min. Add 0.6g aminated metal framework and sonicate for 10-15 min. Heat to 55℃ and maintain for 14 h. Centrifuge, wash, and dry to obtain modified magnesium hydroxide nanotubes.

[0085] The preparation of the hyperbranched tannic acid complex includes the following steps: 2g of tannic acid, 20mL of pyridine and 9.2mL of methyltetrahydrophthalic anhydride are mixed, heated to 85℃ and kept in an oil bath for 48h, precipitated with anhydrous diethyl ether and dried to obtain the hyperbranched tannic acid complex.

[0086] S2: Mix magnesium hydroxide nanotubes and ultrapure water for 5 minutes at 350 rpm; add thickener and continue stirring for 15 minutes at 450 rpm; add binder and stir for 25 minutes at 550 rpm; add wetting agent and stir for 15 minutes at 650 rpm; filter to remove iron, and obtain magnesium hydroxide nanotube coating slurry;

[0087] The raw material composition, by mass percentage, is: 10% magnesium hydroxide nanotubes, 0.4% thickener, 0.5% binder, 0.05% wetting agent, and the balance being ultrapure water;

[0088] The thickener is sodium carboxymethyl cellulose; the wetting agent is a silanol nonionic surfactant.

[0089] The adhesive is a copolymer COPNA resin, and its preparation includes the following steps:

[0090] (1) Mix 1g of 1-naphthol, 1g of benzaldehyde, 0.07g of p-toluenesulfonic acid and 10mL of ethanol, and stir until the reaction solution shows the phenomenon of "rod wrapping" to obtain naphthol-based COPNA resin.

[0091] (4) Mix 1g of naphthol-based COPNA resin and 10mL of n-butanol, keep warm at 50℃ for 60min, add 0.5mg of magnesium hydroxide powder, cool down to 35℃, add 0.1g of 2,2'-diallyl bisphenol A, 0.1g of polysulfone and 5mL of N-methylpyrrolidone, stir ultrasonically for 10min, heat up to 140℃ and keep warm for 3h to obtain pretreated COPNA resin;

[0092] (3) Under nitrogen protection, 1.67g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 6mL of N-methylpyrrolidone, and 0.05g of deionized water were mixed and stirred for 1h. Then, 0.49g of p-phenylenediamine, 0.36g of 2,2'-di(trifluoromethyl)-4,4'-diaminobiphenyl, and 4mL of N-methylpyrrolidone were added and kept at the temperature for 22h. Then, 1.1g of pretreated COPNA resin was added, heated until dissolved, kept at the temperature for 20min, and cured to obtain copolymer COPNA resin.

[0093] S3: Using a micro-gravure roller coating process, the magnesium hydroxide nanotube coating slurry in S2 is rolled onto both sides of a 9μm polyethylene separator at 3μm in stages, baked at 65℃, and then wound up to obtain a battery separator based on magnesium hydroxide.

[0094] Example 5

[0095] A process for preparing a battery separator based on magnesium hydroxide includes the following steps:

[0096] S1: Preparation of magnesium hydroxide nanotubes;

[0097] 1.6965 g of hydrophilic silica nanowires and 250 mL of 1.91 mol / L magnesium sulfate solution were mixed and stirred for 75 min, ultrasonically dispersed for 4.5 h, heated to 68 °C, and 2 mol / L ammonia water was added at a flow rate of 38 mL / min until the pH reached 9 and the reaction was stopped. The mixture was filtered, washed, and dried for 16 h, with the vacuum degree controlled at 0.08 MPa. Then, it was added to 5.0 mol / L sodium hydroxide solution and kept for 4 h. The mixture was filtered, washed, and dried at 78 °C for 11 h. After drying, magnesium hydroxide nanotubes were obtained.

[0098] Modified magnesium hydroxide nanotubes are obtained by modifying magnesium hydroxide nanotubes. The preparation process includes the following steps:

[0099] 1) Mix 0.15g zirconium tetrachloride, 0.12g 2-aminoterephthalic acid, 3.7mL acetic acid and 80mL N,N-dimethylformamide, sonicate for 12min, transfer to a reaction vessel and keep warm at 118℃ for 23h, centrifuge, wash and dry to obtain an aminated metal framework.

[0100] 2) Mix 2g magnesium hydroxide nanotubes, 0.1g 3-aminopropyltriethoxysilane, 0.1g hyperbranched tannic acid complex, and N,N-dimethylformamide, and sonicate for 12 min. Add 0.6g aminated metal framework and sonicate for 12 min. Heat to 58℃ and maintain for 13 h. Centrifuge, wash, and dry to obtain modified magnesium hydroxide nanotubes.

[0101] The preparation of the hyperbranched tannic acid complex includes the following steps: 2g of tannic acid, 20mL of pyridine and 9.2mL of methyltetrahydrophthalic anhydride are mixed, heated to 88℃ and kept in an oil bath for 47h, precipitated with anhydrous diethyl ether and dried to obtain the hyperbranched tannic acid complex.

[0102] S2: Mix magnesium hydroxide nanotubes and ultrapure water for 15 minutes at 300 rpm; add thickener and continue stirring for 30 minutes at 350 rpm; add binder and stir for 40 minutes at 400 rpm; add wetting agent and stir for 30 minutes at 500 rpm; filter to remove iron, and obtain magnesium hydroxide nanotube coating slurry;

[0103] By mass percentage, the raw material composition is: 20% magnesium hydroxide nanotubes, 0.68% thickener, 0.77% binder, 0.08% wetting agent, and the balance is ultrapure water;

[0104] The thickener is sodium carboxymethyl cellulose; the wetting agent is a silanol nonionic surfactant.

[0105] The adhesive is a copolymer COPNA resin, and its preparation includes the following steps:

[0106] (1) Mix 1g of 1-naphthol, 1g of benzaldehyde, 0.07g of p-toluenesulfonic acid and 10mL of ethanol, and stir until the reaction solution shows the phenomenon of "rod wrapping" to obtain naphthol-based COPNA resin.

[0107] (5) Mix 1g naphthol-based COPNA resin and 10mL n-butanol, keep warm at 50℃ for 60min, add 0.5mg magnesium hydroxide powder, cool down to 38℃, add 0.1g 2,2'-diallyl bisphenol A, 0.1g polysulfone and 5mL N-methylpyrrolidone, sonicate for 15min, heat up to 160℃ and keep warm for 2h to obtain pretreated COPNA resin;

[0108] (3) Under nitrogen protection, 1.67g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 6mL of N-methylpyrrolidone, and 0.05g of deionized water were mixed and stirred for 1.5h. Then, 0.49g of p-phenylenediamine, 0.36g of 2,2'-di(trifluoromethyl)-4,4'-diaminobiphenyl, and 4mL of N-methylpyrrolidone were added. The mixture was kept warm for 23h. Then, 1.1g of pretreated COPNA resin was added, heated until dissolved, kept warm for 25min, and cured to obtain copolymer COPNA resin.

[0109] S3: Using a micro-gravure roller coating process, the magnesium hydroxide nanotube coating slurry in S2 is rolled onto both sides of a 9μm polyethylene separator at 3μm in stages, baked at 68℃, and then wound up to obtain a battery separator based on magnesium hydroxide.

[0110] Example 6

[0111] A process for preparing a battery separator based on magnesium hydroxide includes the following steps:

[0112] S1: Preparation of magnesium hydroxide nanotubes;

[0113] 1.6965 g of hydrophilic silica nanowires and 250 mL of 1.91 mol / L magnesium sulfate solution were mixed and stirred for 80 min, ultrasonically dispersed for 5 h, heated to 70 °C, and 2 mol / L ammonia water was added at a flow rate of 38 mL / min until the pH reached 10 and the reaction was stopped. The mixture was filtered, washed, and dried for 16 h under vacuum at a vacuum degree of 0.08 MPa. Then, it was added to a 5.0 mol / L sodium hydroxide solution and kept for 4 h. The mixture was filtered, washed, and dried at 80 °C for 10 h. After drying, magnesium hydroxide nanotubes were obtained.

[0114] Modified magnesium hydroxide nanotubes are obtained by modifying magnesium hydroxide nanotubes. The preparation process includes the following steps:

[0115] 1) Mix 0.15g zirconium tetrachloride, 0.12g 2-aminoterephthalic acid, 3.7mL acetic acid and 80mL N,N-dimethylformamide, sonicate for 15min, transfer to a reaction vessel and keep at 120℃ for 22h, centrifuge, wash and dry to obtain an aminated metal framework.

[0116] 2) Mix 2g magnesium hydroxide nanotubes, 0.1g 3-aminopropyltriethoxysilane, 0.1g hyperbranched tannic acid complex, and N,N-dimethylformamide, and sonicate for 15 min. Add 0.6g aminated metal framework and sonicate for 15 min. Heat to 60℃ and maintain for 12 h. Centrifuge, wash, and dry to obtain modified magnesium hydroxide nanotubes.

[0117] The preparation of the hyperbranched tannic acid complex includes the following steps: 2g of tannic acid, 20mL of pyridine and 9.2mL of methyltetrahydrophthalic anhydride are mixed, heated to 90℃ and kept in an oil bath for 46h, precipitated with anhydrous diethyl ether and dried to obtain the hyperbranched tannic acid complex.

[0118] S2: Mix magnesium hydroxide nanotubes and ultrapure water for 25 minutes at 250 rpm; add thickener and continue stirring for 55 minutes at 250 rpm; add binder and stir for 55 minutes at 350 rpm; add wetting agent and stir for 35 minutes at 350 rpm; filter to remove iron, and obtain magnesium hydroxide nanotube coating slurry;

[0119] By mass percentage, the raw material composition is: 30% magnesium hydroxide nanotubes, 0.7% thickener, 1% binder, 0.2% wetting agent, and the balance is ultrapure water;

[0120] The thickener is sodium carboxymethyl cellulose; the wetting agent is a silanol nonionic surfactant.

[0121] The adhesive is a copolymer COPNA resin, and its preparation includes the following steps:

[0122] (1) Mix 1g of 1-naphthol, 1g of benzaldehyde, 0.07g of p-toluenesulfonic acid and 10mL of ethanol, and stir until the reaction solution shows the phenomenon of "rod wrapping" to obtain naphthol-based COPNA resin.

[0123] (6) Mix 1g naphthol-based COPNA resin and 10mL n-butanol, keep warm at 50℃ for 60min, add 0.5mg magnesium hydroxide powder, cool down to 40℃, add 0.1g 2,2'-diallyl bisphenol A, 0.1g polysulfone and 5mL N-methylpyrrolidone, sonicate for 20min, heat up to 180℃ and keep warm for 1h to obtain pretreated COPNA resin;

[0124] (3) Under nitrogen protection, 1.67g of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 6mL of N-methylpyrrolidone, and 0.05g of deionized water were mixed and stirred for 2h. Then, 0.49g of p-phenylenediamine, 0.36g of 2,2'-di(trifluoromethyl)-4,4'-diaminobiphenyl, and 4mL of N-methylpyrrolidone were added and kept warm for 24h. Then, 1.1g of pretreated COPNA resin was added, heated until dissolved, kept warm for 30min, and cured to obtain copolymer COPNA resin.

[0125] S3: Using a micro-gravure roller coating process, the magnesium hydroxide nanotube coating slurry in S2 is rolled onto both sides of a 9μm polyethylene separator at 3μm in stages, baked at 70℃, and then wound up to obtain a battery separator based on magnesium hydroxide.

[0126] Comparative Example 1

[0127] Using Example 5 as a control group, no 2,2'-diallylbisphenol A or polysulfone was added during the preparation of the copolymer COPNA resin, and other processes were normal.

[0128] Comparative Example 2

[0129] Using Example 5 as a control group, no 3,3',4,4'-biphenyltetracarboxylic dianhydride was added during the preparation of the copolymer COPNA resin, and other processes were normal.

[0130] Comparative Example 3

[0131] Using Example 5 as a control group, no 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl was added during the preparation of the copolymer COPNA resin, and other processes were normal.

[0132] Comparative Example 4

[0133] Using Example 5 as a control group, no aminated metal framework was added during the preparation of modified magnesium hydroxide nanotubes, and other processes were normal.

[0134] Comparative Example 5

[0135] Using Example 5 as a control group, tannic acid was used to replace the hyperbranched tannic acid complex, while other processes were normal.

[0136] Comparative Example 6

[0137] Using Example 5 as a control group, the mass ratio of magnesium hydroxide nanotubes, hyperbranched tannic acid complex, and aminated metal framework was 2:0.08:0.5, and other processes were normal.

[0138] Comparative Example 7

[0139] Example 5 served as a control group, where no coating was applied and other processes were performed normally.

[0140] The preparation of COPNA resin in Examples 1-3 includes the following steps: 1g of 1-naphthol, 1g of benzaldehyde, 0.07g of p-toluenesulfonic acid, and 10mL of ethanol are mixed and the reaction is stopped when the "rod entanglement" phenomenon occurs, thus obtaining COPNA resin.

[0141] The sources of raw materials used in the above embodiments and comparative examples are as follows:

[0142] Hydrophilic silica nanowires TSP-H10 (particle size 20nm): Nanjing Tianxing New Materials Co., Ltd.; 2-Aminoterephthalic acid A824727, 3-aminopropyltriethoxysilane A800524, tannic acid T818845, pyridine P816288, methyltetrahydrophthalic anhydride M915856, 2,2'-diallylbisphenol AD838649, polysulfone P875323, N-methylpyrrolidone M812729, 3,3',4,4'-biphenyltetracarboxylic dianhydride B802649, p-phenylenediamine P816015: Shanghai Maclean Biochemical Technology Co., Ltd.; 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl S46156: Shanghai Yuanye Biotechnology Co., Ltd.; 1-Naphthol N103797, Benzaldehyde B110463, p-Toluenesulfonic acid T305333, Dimethylacetamide D108096, N,N-Dimethylformamide D111999: Shanghai Aladdin Biochemical Technology Co., Ltd.; n-Butanol, Magnesium hydroxide, Anhydrous ethanol, Sodium hydroxide, Potassium hydroxide, Anhydrous diethyl ether, Zirconium tetrachloride, Acetic acid, Magnesium sulfate, Ammonia, Analytical grade: Sinopharm Chemical Reagent Co., Ltd.; Hydrolyzed polymaleic anhydride dispersant is polyisoprene-grafted maleic anhydride 460060, Sodium hydroxymethyl cellulose 419273, 2-(Dodecyltrithiocarbonate)-2-methylpropionic acid 723010: Merck Reagent.

[0143] Performance testing:

[0144] The performance of the battery separators prepared in Examples 1-6 and Comparative Examples 1-7 was tested.

[0145] Determination of Limiting Oxygen Index (LOI): Refer to ISO 4589-2. In a combustion chamber, introduce an oxygen-nitrogen mixture flowing upwards in a laminar flow pattern, place a diaphragm inside, and maintain a temperature of 25°C. The flame ignited on the top surface should be in contact with the top surface for less than 30 seconds, and removed every 5 seconds. Observe whether the diaphragm is burning. The LIO is the minimum oxygen concentration required to maintain combustion. The LIO of combustible materials is 18-25, and the LIO of flame-retardant materials is above 25.

[0146] Liquid absorption rate determination: The sample (M) was cut into 50mm × 50mm pieces, dried for 24 hours, and then weighed. It was then immersed in a beaker containing electrolyte for 10 minutes, removed, and immediately weighed (M1). The liquid absorption rate was (M1 - M) / M (accurate to 0.01g). Liquid retention rate determination: The sample (M) was cut into 50mm × 50mm pieces, dried for 24 hours, and then weighed. It was then immersed in a beaker containing electrolyte for 10 minutes, removed, suspended for 3 minutes to allow some electrolyte to drip off naturally, and then weighed (M2). The liquid retention rate was (M2 - M) / M (accurate to 0.01g). Thickness, air permeability, needle penetration strength, and heat shrinkage were tested according to GB / T36363-2018. The results are shown in Table 1.

[0147]

[0148] Table 1

[0149] This invention provides a battery separator based on magnesium hydroxide and its preparation process. By introducing magnesium hydroxide nanotubes to prepare a coating for the lithium-ion battery separator, a lithium-ion battery separator with high flame retardancy, high mechanical strength, and high wettability is obtained.

[0150] Comparing Examples 1, 2, and 3 with Comparative Example 7, the introduction of magnesium hydroxide nanotubes into the coating slurry of the lithium-ion battery separator significantly improves the mechanical strength and thermal shrinkage performance of the separator while maintaining the excellent flame retardancy and liquid absorption / retention capacity of the magnesium hydroxide nanotubes themselves. Because the introduced magnesium hydroxide nanotubes have a hollow structure, the specific surface area of ​​the material is greatly increased, which improves both the lithium-ion conductivity and the liquid absorption / retention capacity of the separator. Furthermore, the carbonization layer formed by the thermal decomposition of the crystal water of the introduced magnesium hydroxide nanotubes not only prevents the entry of oxygen and heat but also decomposes to generate magnesium oxide, thereby improving the high-temperature resistance and thermal conductivity of the separator.

[0151] Example 5 was compared with Comparative Examples 1, 2, and 3. COPNA resin was used as an adhesive and polyimide copolymerization was performed on the COPNA resin. This improved the thermal expansion coefficient of the battery separator while maintaining its adhesiveness at high temperatures, resulting in a lower dielectric constant and thus enhancing its ability to resist thermal runaway.

[0152] Example 5 was compared with Comparative Example 1. Naphthol-based COPNA resin was modified with 2,2'-diallylbisphenol A and polysulfone to improve its toughening effect and low dielectric properties. Example 5 was also compared with Comparative Examples 2 and 3. Copolymerized COPNA resin was prepared with 3,3',4,4'-biphenyltetracarboxylic dianhydride, p-phenylenediamine, and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl to give it the characteristics of low expansion, high heat resistance, high strength and high modulus, which meet the thermal performance requirements of the diaphragm.

[0153] Comparing Example 5 with Comparative Examples 4, 5, and 6, the magnesium hydroxide nanotubes were modified to improve the uniformity of dispersion of magnesium hydroxide nanotubes in the coating slurry without the addition of a dispersant, thus homogenizing the separator. The modified magnesium hydroxide nanotubes prepared by using magnesium hydroxide nanotubes, hyperbranched tannic acid complex, and aminated metal framework help to improve the strong interaction between magnesium hydroxide nanotubes and copolymerized COPNA resin, improve the adhesion between the coating slurry and the base film, thereby strengthening the interfacial compatibility between the two and improving the dimensional stability of the battery separator.

[0154] Comparing Example 5 with Comparative Examples 4 and 5, magnesium hydroxide nanotubes were treated with a tannic acid complex having a hyperbranched structure, and then an aminated metal framework was grafted onto them. Both the hyperbranched tannic acid and the aminated metal framework have high flame retardancy, and the magnesium hydroxide nanotubes synergistically improve the flame retardancy of the battery separator. Comparing Example 5 with Comparative Example 6, by controlling the mass ratio of the introduced magnesium hydroxide nanotubes, hyperbranched tannic acid complex, and aminated metal framework, a complex and stable network structure was constructed, which effectively promoted the proton conduction performance of the battery separator, thereby improving the wettability of the battery separator, reducing the risk of thermal runaway of the separator, and further improving the thermal stability of the battery separator and the safety of lithium-ion batteries.

[0155] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the present invention's specification under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A process for the preparation of a magnesium hydroxide based battery separator, characterized in that, The method comprises the following steps: S1: preparing magnesium hydroxide nanotubes; S2: mixing dispersant, magnesium hydroxide nanotubes, ultrapure water for 5-25 min at a rotation speed of 250-350 rpm; adding thickening agent and continuing to stir for 15-55 min at a rotation speed of 250-450 rpm; adding adhesive and stirring for 25-55 min at a rotation speed of 350-550 rpm; adding wetting agent and stirring for 15-35 min at a rotation speed of 350-650 rpm; filtering to remove iron to obtain magnesium hydroxide nanotube coating slurry; S3: using micro-gravure roll coating process, step-by-step roll coating the magnesium hydroxide nanotube coating slurry in S2 on both sides of the polyolefin separator, baking at 65-70℃, winding to obtain a magnesium hydroxide-based battery separator; The raw material composition of the magnesium hydroxide nanotube coating slurry is 10-30% magnesium hydroxide nanotubes, 0-0.6% dispersant, 0.4-0.7% thickening agent, 0.5-1% adhesive, 0.05-0.2% wetting agent, and the balance is ultrapure water, by mass percentage; The adhesive is a copolymer COPNA resin, and the preparation comprises the following steps: (1) mixing 1-naphthol, benzaldehyde, p-toluenesulfonic acid and ethanol, stopping stirring when the reaction solution appears "rod winding" phenomenon to obtain naphthol-based COPNA resin; (2) mixing naphthol-based COPNA resin and n-butanol, keeping at 50℃ for 60 min, adding magnesium hydroxide powder, cooling to 35-40℃, adding 2,2'-diallyl bisphenol A, polysulfone and N-methyl pyrrolidone, ultrasonic stirring for 10-20 min, heating to 140-180℃ and keeping for 1-3 h to obtain pretreated COPNA resin; (3) mixing 3,3',4,4'-biphenyl tetracarboxylic dianhydride, N-methyl pyrrolidone and deionized water under nitrogen protection, stirring for 1-2 h, adding p-phenylenediamine, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and N-methyl pyrrolidone, keeping for 22-24 h, adding pretreated COPNA resin, heating to dissolve, keeping for 20-30 min, solidifying to obtain copolymer COPNA resin; The magnesium hydroxide nanotubes are modified to obtain modified magnesium hydroxide nanotubes, and the preparation comprises the following steps: 1) mixing zirconium tetrachloride, 2-amino terephthalic acid, acetic acid and N,N-dimethylformamide, ultrasonic stirring for 10-15 min, transferring to a reaction kettle, keeping at 115-120℃ for 22-24 h, centrifuging, washing and drying to obtain aminated metal framework; 2) mixing magnesium hydroxide nanotubes, 3-aminopropyl triethoxysilane, hyperbranched tannic acid complex and N,N-dimethylformamide, ultrasonic stirring for 10-15 min, adding aminated metal framework and ultrasonic treating for 10-15 min, heating to 55-60℃ and keeping for 12-14 h, centrifuging, washing and drying to obtain modified magnesium hydroxide nanotubes.

2. The process for the preparation of a magnesium hydroxide based battery separator according to claim 1, characterized in that, The dispersant is hydrolyzed polymaleic anhydride dispersant; the thickening agent is sodium hydroxymethyl cellulose; and the wetting agent is a silicon alcohol nonionic surfactant.

3. The process for the preparation of a magnesium hydroxide based battery separator according to claim 1, characterized in that, The preparation of the magnesium hydroxide nanotube comprises the following steps: mixing and stirring hydrophilic silicon dioxide nanowires and magnesium sulfate solution for 70-80 min, ultrasonic dispersion for 4-5 h, heating to 65-70 DEG C, adding ammonia water to stop the reaction until the pH is 8-10, filtering, washing, drying for 16 h, adding sodium hydroxide solution and keeping for 4 h, filtering, washing, drying at 75-80 DEG C for 10-12 h, and obtaining the magnesium hydroxide nanotube after drying.

4. The process for preparing a magnesium hydroxide based battery separator according to claim 1, wherein In the preparation of the copolymerized COPNA resin, the mass ratio of naphthol-based COPNA resin, 2,2'-diallyl bisphenol A and polysulfone is 10:1:

1.

5. The process for the preparation of a magnesium hydroxide based battery separator according to claim 1, characterized in that, In the preparation of the copolymerized COPNA resin, the mass ratio of 3,3',4,4'-diphenyl tetracarboxylic dianhydride, p-phenylenediamine, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and pretreated COPNA resin is 1.67:0.49:0.36:1.

1.

6. The process for the preparation of a magnesium hydroxide based battery separator according to claim 1, characterized in that, The preparation of the hyperbranched tannic acid complex comprises the following steps: mixing tannic acid, pyridine and methyl tetrahydrophthalic anhydride, heating to 85-90 DEG C in an oil bath for 46-48 h, precipitating with anhydrous ether, and drying to obtain the hyperbranched tannic acid complex.

7. The process for the preparation of a magnesium hydroxide based battery separator according to claim 1, characterized in that, In the preparation of the modified magnesium hydroxide nanotube, the mass ratio of magnesium hydroxide nanotube, hyperbranched tannic acid complex and aminated metal framework is 2:0.1:0.6.

Images