Meta-aramid polymers with a network structure, methods for producing the same, and applications

Abstract

The present invention discloses a meta-type aramid polymer with a network structure, a method for producing the same, and applications, belonging to the technical field of lithium battery materials. In the present invention, when forming the meta-type aramid polymer, an alkyl group is introduced between macromolecules by an alkylation reaction, and adjacent molecular chains are bonded by chemical bonds to form a network structure. A coating slurry prepared using the meta-type aramid polymer having a network structure, a pore former, and a dissolution aid is applied to the surface of a polyolefin porous separator to obtain a high-performance coating separator for a lithium battery. Compared with the coating separator produced by the conventional method, the present invention has higher heat resistance, heat shrinkage rate, and puncture strength, better wettability with the electrolyte, and can further extend the cycle life of the battery. In addition, the meta-type aramid coating separator having a network structure can enhance the oxidation resistance of the separator and contribute to the achievement of high potential and the improvement of energy density.

Description

Technical Field

[0003]

[0001] The present invention belongs to the field of battery separators, and particularly relates to a meta-type aramid polymer with a mesh structure, a method for producing the same, and applications thereof. [[ID=,7]]

Background Art

[0002] With the booming development of new energy electric vehicles, the lithium battery industry has been promoted to develop by leaps and bounds. A lithium-ion battery mainly includes a positive electrode, a negative electrode, a separator, and an electrolyte. As one of the main components of a lithium battery, the separator separates the positive electrode and the negative electrode to prevent a short circuit due to contact between the two electrodes, absorbs the electrolyte, allows lithium ions to permeate, and plays a role of blocking the conduction of current by shutting down during overcharging or temperature rise to prevent explosion. Since commercial polyolefin separators do not have sufficient heat resistance, a series of safety problems have occurred. Coated separators have become the main solution for separators of lithium batteries for new energy electric vehicles. However, at present, for mainstream ceramic-coated separators, for example, a binder needs to be added to bond an inorganic material and an organic polymer substrate, and there are demerits such as its heat resistance and further the high-temperature stability of the ceramic coating being affected.

[0003] In recent years, aramid-coated separators have become a new solution for lithium-ion battery separators. Many separator manufacturers are placing their hopes on aramid materials as coating separators that can withstand high temperatures, but technically, they are limited to manufacturing meta-aramid or para-aramid itself, and sometimes even mix ceramics into aramid slurry before coating. For example, Japanese Patent Publication CN110707265 discloses an aramid coating solution and a method for producing the same, as well as a separator based on the aramid coating solution and its applications. This document describes mixing meta-aramid with ceramics to form a mixed slurry with a relatively high proportion of ceramics, which is then applied to a polyolefin separator. However, low thermal shrinkage is only ensured below 130°C, and it is not possible to satisfy the heat resistance at higher temperatures. Therefore, the development of separators and methods for producing them is urgently needed. [Overview of the project] [Problems that the invention aims to solve]

[0004] This invention provides a meta-aramid polymer with a mesh structure, a method for producing the same, and its applications to address the shortcomings of conventional coated separators in terms of high temperature resistance, thermal shrinkage resistance, and puncture strength. This coated separator exhibits excellent high temperature resistance, thermal shrinkage resistance, puncture strength, and oxidation resistance, contributing to the achievement of higher potential, increasing energy density and safety, and improving wettability with the electrolyte, thereby extending the battery cycle life. The coated separator made from the meta-aramid polymer with a mesh structure is suitably used in lithium batteries for electric vehicles. The manufacturing method is time-efficient, increases production efficiency, and results in high-quality and stable products. [Means for solving the problem]

[0005] The present invention is achieved by the following technical solutions.

[0006] According to a first aspect, the present invention provides a meta-aramid polymer having a network structure represented by the following structural formula. [C1] JPEG0007912094000001.jpg36170 (In the formula, m, n, x, and y represent the degree of polymerization, and R1 and R2 are alkane groups with 3 to 5 carbon atoms.)

[0007] According to a second aspect, the present invention provides a method for producing a meta-aramid polymer with a network structure, as shown in the reaction process described below. [Case 2] JPEG0007912094000002.jpg114170 (In the formula, m, n, x, and y represent the degree of polymerization, and R1 and R2 are alkane groups with 3 to 5 carbon atoms.)

[0008] According to the third aspect, a method for producing a meta-aramid polymer with a network structure is provided, the production process being as follows. (1) Condensation polymerization: A meta-aramid polymer is prepared by solution polymerization, metaphenylenediamine (MPD) is dissolved in an organic solvent, and then isophthaloyl chloride (IPC) is charged into the solution in four steps to carry out a condensation polymerization reaction. Alkylating agents and metal halides are charged in the first and second condensation polymerization steps, and the reaction temperature, stirring speed, reaction time, and viscosity of the system are controlled at each step to obtain a polymer molecular structure having a network structure. (2) Washing: The polymer solution prepared above is washed in an aqueous solvent and washed three times with water to remove oligomers and metal salts from the polymer, thereby obtaining a meta-aramid polymer having a network structure. When dissolving metaphenylenediamine (MPD) in an organic solvent, the solution is maintained at 0-10°C, and isophthaloyl chloride (IPC) is divided into four equal parts by weight and added to the system in four steps to carry out condensation polymerization reactions, resulting in condensation polymerization 1, condensation polymerization 2, condensation polymerization 3, and condensation polymerization 4. In condensation polymerization 1, the reaction temperature is 5-10°C, the stirring speed is 500-1000 r / min, an alkylating agent and a metal halide are added, the reaction time is 30-60 min, a neutralizing agent is added to remove reaction by-products, and the viscosity of the system after completion of condensation polymerization 1 is 100-300 mPa·s. In condensation polymerization 2, the reaction temperature is 10-30°C, the stirring speed is 500-700 r / min, the alkylating agent is added again, the reaction time is 30-45 min, and the neutralizing agent is added to remove the by-products in this stage. The viscosity of the system after completion of condensation polymerization 2 is 500-1000 mPa·s. In condensation polymerization 3, the reaction temperature is 25-45°C, the stirring speed is 200-350 r / min, and the reaction time is 15-20 min. The viscosity of the system after condensation polymerization 3 is 2000-3000 mPa·s. In condensation polymerization 4, the reaction temperature is 40-55°C, the stirring speed is 80-200 r / min, and the reaction time is 10-30 min. The viscosity of the system after condensation polymerization 4 is 100,000-150,000 mPa·s.

[0009] Furthermore, the organic solvent is one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), or dimethyl sulfoxide (DMSO). The alkylating agent is a chlorinated alkane / alkene or a brominated alkane / alkene (an integer with 3 to 5 carbon atoms). The metal halide is one of AlCl3, FeCl3, SbCl5, or SnCl4. The neutralizing agent is one of ammonia, calcium hydroxide, calcium oxide, or sodium hydroxide. The aqueous solvent includes one of deionized water or a mixture of deionized water and a polymerization reaction solvent.

[0010] Furthermore, while the chemical structural formulas of the alkylating agents can be represented by the following substances, they are not limited to these. [C3] JPEG0007912094000003.jpg44170

[0011] Furthermore, the molar ratio of MPC to IPC is 1:(1~1.05). The polymer content after the completion of the condensation polymerization reaction is 11~35 wt%. The molar equivalent ratio of the neutralizing agent to IPC is 1:1. The ratio of the total moles of alkylating agent to the moles of MPD in condensation polymerization 1 and condensation polymerization 2 is (1~20):(180~199), and the alkylating agent is charged in equal amounts in condensation polymerization 1 and condensation polymerization 2, respectively. The amount of metal halide charged accounts for 0.1~0.6 wt% of the total mass of the reaction system.

[0012] According to the fourth aspect, the meta-aramid polymer is applied to the fabrication of coating separators for lithium batteries.

[0013] Furthermore, a mesh-structured meta-aramid polymer, a pore-forming agent, and a solubilizing agent are dissolved in an organic solvent to form a coating slurry. The slurry is then extruded from a die and applied to one or both sides of a polyolefin separator. After molding in a solidification bath, the material is washed with water and dried to obtain a mesh-structured meta-aramid coated separator for lithium batteries.

[0014] Furthermore, the mass ratio of the network-structured meta-aramid polymer, pore-forming agent, solubilizer, and organic solvent is (2-8):(2-6):(1-8):(78-95). The pore-forming agent is one of polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP). The solubilizer is one of calcium chloride or lithium chloride. The polyolefin separator is one of polyethylene separator or polypropylene separator. The coating method is one of microgravure roll coating, commarol coating, or slit press coating. The organic solvent in the coagulation bath is one or more of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), or dimethyl sulfoxide (DMSO). The coagulation bath has a bath liquid concentration of 20-65% and a bath liquid temperature of 5-45°C. The water washing temperature is 45-65°C. The aforementioned drying temperature is 120 to 155°C. [Effects of the Invention]

[0015] The present invention has the following advantageous technical effects as compared with the prior art. (1) When forming meta-aramid, C-alkylation proceeds, and the structures of adjacent molecules are chemically bonded to form a network structure, thereby increasing the degree of crosslinking and eliminating the gel phenomenon caused by a high degree of crosslinking. (2) A separator formed by coating a meta-aramid polymer having a network structure on the surface of a polyolefin porous separator has strong puncture strength, heat resistance, and thermodynamic properties. The puncture strength is improved by 20% or more, the fuse temperature of the separator is higher than 250 °C, the thermal shrinkage rate is less than 3%, the air permeability increases by 15 s / 100 cc or more, the tensile strength is higher than 150 MPa, and the elongation is 100% or more. (3) A meta-aramid-coated separator having a network structure significantly improves the wettability of the surface with respect to the electrolyte, contributes to an improvement in the cycle life of a lithium battery, and enhances the oxidation resistance of the separator, and can contribute to the achievement of a high potential and an improvement in energy density.

Brief Description of the Drawings

[0016] Hereinafter, the present invention will be further described with reference to the drawings. [Figure 1] It is a flowchart of the production process of the present invention. [Figure 2] It is a SEM diagram of a meta-aramid-coated separator having a network structure prepared in Example 1. [Figure 3] It is a photograph of the electrolyte contact angle of the coated separator of Example 1. [Figure 4] It is a photograph of the electrolyte contact angle of a polyethylene separator of the comparative example.

Modes for Carrying Out the Invention

[0017] Hereinafter, the present invention will be described in detail based on examples. However, the examples given are for interpreting the present invention and do not limit the technical scope of the present invention.

[0018] Example 1 8.2 kg of MPD was dissolved in 82 kg of DMAc. After complete dissolution, it was maintained at 5°C, and IPC was charged stepwise to initiate the polycondensation reaction. In polycondensation 1, the reaction temperature was controlled at 8°C, the stirring speed was 800 r / min, 196.5 g of allyl chloride and 200 g of AlCl3 were charged, the reaction time was 45 min, and then calcium hydroxide was charged to remove hydrogen chloride generated in the reaction. The viscosity of the system was 189 mPa·s. Then, polycondensation 2 was carried out. The reaction temperature was controlled at 22°C, the stirring speed was 500 r / min, 196.5 g of allyl chloride was charged, the reaction time was 30 min, and then calcium hydroxide was charged to remove hydrogen chloride generated in the reaction. The viscosity of the system was 695 mPa·s. Then, IPC was continuously added to carry out polycondensation 3. The reaction temperature was controlled at 36°C, the stirring speed was 220 r / min, the reaction time was 20 min, and the viscosity of the system was 2246 mPa·s. Then, the last remaining IPC was charged to carry out polycondensation 4. The reaction temperature was controlled at 45°C, the stirring speed was 120 r / min, the reaction time was 25 min. When the entire polycondensation reaction was completed, the viscosity of the system reached 125000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 105000 mPa·s, and a meta-type aramid polymer solution with a network structure was obtained. The polymer solution formed after the polymerization was completed was mixed with deionized water. After the polymer was completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The obtained solid polymer material was sealed in a light-shielded manner for later use. After preparing a coating slurry such that the mass ratio of the meta-type aramid polymer having a network structure, PEG, lithium chloride, and DMAc was 5:3:5:87, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating. Then, it was put into a coagulation bath (the coagulation bath was a solution of water and DMAc), and the bath solution concentration was 45% and the temperature was 15°C. After taking it out from the coagulation bath, it was washed with water at 55°C, and the separator was immediately dried, with the drying temperature being 145°C. By winding it up, a meta-type aramid-coated polyethylene separator with a coating thickness of 2 μm on both sides was obtained.

[0019] Example 2 8.2 kg of MPD was dissolved in 82 kg of DMAc, and after complete dissolution, the mixture was maintained at 8°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 14.5 g of allyl chloride and 200 g of AlCl3 were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 151 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 22°C, and 14.5 g of allyl chloride was added at a stirring speed of 500 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 701 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2316 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 45°C, the stirring speed 120 r / min, and the reaction time 25 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 121,000 mPa·s. Next, calcium hydroxide was added to neutralize the solution. After the neutralization reaction was completed, the viscosity of the polymer solution was 101,000 mPa·s, and a meta-aramid polymer solution with a network structure was obtained. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMAc in a mass ratio of 5:3:5:87. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMAc) with a bath solution concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0020] Example 3 8.2 kg of MPD was dissolved in 82 kg of DMAc, and after complete dissolution, the mixture was maintained at 8°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 289.3 g of allyl chloride and 3200 g of AlCl were added at a stirring speed of 800 r / min for a reaction time of 45 min. Calcium hydroxide was then added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 213 mPa·s. Subsequently, condensation polymerization 2 was carried out, with the reaction temperature controlled to 22°C, and 289.3 g of allyl chloride added at a stirring speed of 500 r / min for a reaction time of 30 min. Calcium hydroxide was then added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 712 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2446 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 45°C, the stirring speed 120 r / min, and the reaction time 25 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 135,000 mPa·s. Next, calcium hydroxide was added to neutralize the solution. After the neutralization reaction was completed, the viscosity of the polymer solution was 113,000 mPa·s, and a meta-aramid polymer solution with a network structure was obtained. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMAc in a mass ratio of 5:3:5:87. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMAc) with a bath solution concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0021] Example 4 5.0 kg of MPD was dissolved in 89 kg of DMAc, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 120.2 g of allyl chloride and 3200 g of AlCl were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 149 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 22°C, and 120.2 g of allyl chloride was added at a stirring speed of 500 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 595 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 1846 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 45°C, the stirring speed 120 r / min, and the reaction time 25 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 101,000 mPa·s. Calcium hydroxide was added to neutralize the solution. After the neutralization reaction was completed, the viscosity of the polymer solution was 85,000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMAc in a mass ratio of 5:3:5:87. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMAc) with a bath solution concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0022] Example 5 15.9 kg of MPD was dissolved in 65 kg of DMAc, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 382.5 g of allyl chloride and 3200 g of AlCl were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 210 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 22°C, and 382.5 g of allyl chloride was added at a stirring speed of 500 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 701 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2446 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 45°C, the stirring speed 120 r / min, and the reaction time 25 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 145,000 mPa·s. Next, calcium hydroxide was added to neutralize the solution. After the neutralization reaction was completed, the viscosity of the polymer solution was 120,000 mPa·s, and a meta-aramid polymer solution with a network structure was obtained. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMAc in a mass ratio of 5:3:5:87. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMAc) with a bath solution concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0023] Example 6 8.2 kg of MPD was dissolved in 82 kg of DMAc, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 196.5 g of allyl chloride and 200 g of AlCl3 were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 178 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 22°C, and 196.5 g of allyl chloride was added at a stirring speed of 500 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 688 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2301 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 45°C, the stirring speed 120 r / min, and the reaction time 25 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 120,000 mPa·s. Calcium hydroxide was added to neutralize the solution. After the neutralization reaction was completed, the viscosity of the polymer solution was 100,000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMAc in a mass ratio of 2:2:1:95. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMAc) with a bath solution concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0024] Example 7 8.2 kg of MPD was dissolved in 82 kg of DMAc, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 196.5 g of allyl chloride and 200 g of AlCl3 were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 201 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 22°C, and 196.5 g of allyl chloride was added at a stirring speed of 500 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 699 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2312 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 45°C, the stirring speed 120 r / min, and the reaction time 25 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 130,000 mPa·s. Calcium hydroxide was added to neutralize the solution, and after the neutralization reaction was completed, the viscosity of the polymer solution was 109,000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMAc in a mass ratio of 8:6:8:78. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMAc) with a bath solution concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0025] Example 8 8.2 kg of MPD was dissolved in 82 kg of DMAc, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 196.5 g of allyl chloride and 200 g of AlCl3 were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 202 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 22°C, and 196.5 g of allyl chloride was added at a stirring speed of 500 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 685 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2100 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 45°C, the stirring speed 120 r / min, and the reaction time 25 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 115,000 mPa·s. Calcium hydroxide was added to neutralize the solution. After the neutralization reaction was completed, the viscosity of the polymer solution was 95,000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMAc in a mass ratio of 5:3:5:87. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMAc) at a bath concentration of 20% and a temperature of 5°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding the separator, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0026] Example 9 8.2 kg of MPD was dissolved in 82 kg of DMAc, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 196.5 g of allyl chloride and 200 g of AlCl3 were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 191 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 22°C, and 196.5 g of allyl chloride was added at a stirring speed of 500 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 500 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2220 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 45°C, the stirring speed 120 r / min, and the reaction time 25 min. After completing the entire condensation polymerization reaction, the viscosity of the system was 131,000 mPa·s. Calcium hydroxide was added to neutralize the solution. After the neutralization reaction was completed, the viscosity of the polymer solution was 111,000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMAc in a mass ratio of 5:3:5:87. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMAc) with a bath solution concentration of 65% and a temperature of 45°C. After removal from the solidification bath, the separator was washed with water at 45°C and immediately dried at a drying temperature of 155°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0027] Example 10 8.2 kg of MPD was dissolved in 82 kg of DMF, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 232.7 g of methylchloropropene and 3200 g of FeCl were added at a stirring speed of 1000 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 100 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 22°C, and 232.7 g of methylchloropropene was added at a stirring speed of 500 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 679 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2000 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 45°C, the stirring speed 120 r / min, and the reaction time 25 min. After completing the entire condensation polymerization reaction, the viscosity of the system was 100,000 mPa·s. Calcium hydroxide was added to neutralize the solution. After the neutralization reaction was complete, the viscosity of the polymer solution was 81,000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMF in a mass ratio of 5:3:5:87. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating and placed in a solidification bath (solidification bath being a solution of water and DMF) at a bath concentration of 65% and a temperature of 45°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 120°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0028] Example 11 8.2 kg of MPD was dissolved in 82 kg of NMP, and after complete dissolution, the mixture was maintained at 10°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 10°C, and 196.5 g of allyl chloride and 3200 g of AlCl were added at a stirring speed of 700 r / min for a reaction time of 60 min. Calcium hydroxide was then added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 300 mPa·s. Subsequently, condensation polymerization 2 was carried out, with the reaction temperature controlled to 30°C, and 196.5 g of allyl chloride added at a stirring speed of 500 r / min for a reaction time of 30 min. Calcium hydroxide was then added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 669 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 42°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2009 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 50°C, the stirring speed 120 r / min, and the reaction time 25 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 120,000 mPa·s. Calcium hydroxide was added to neutralize the solution, and after the neutralization reaction was completed, the viscosity of the polymer solution was 81,000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and NMP in a mass ratio of 5:3:5:87. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and NMP) with a bath solution concentration of 65% and a temperature of 45°C. After removal from the solidification bath, the separator was washed with water at 65°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0029] Example 12 8.2 kg of MPD was dissolved in 82 kg of DMSO, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 196.5 g of allyl chloride and 200 g of AlCl3 were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 171 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 22°C, and 196.5 g of allyl chloride was added at a stirring speed of 600 r / min for a reaction time of 30 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 721 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 20 min. The viscosity of the system was 2349 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 50°C, the stirring speed 120 r / min, and the reaction time 25 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 150,000 mPa·s. Calcium hydroxide was added to neutralize the solution, and after the neutralization reaction was completed, the viscosity of the polymer solution was 130,000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMSO in a mass ratio of 5:3:5:87. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMSO) with a bath solution concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0030] Example 13 8.2 kg of MPD was dissolved in 82 kg of DMAc, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 196.5 g of allyl chloride and 200 g of AlCl3 were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 178 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 10°C, and 196.5 g of allyl chloride was added at a stirring speed of 700 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 1000 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 36°C, the stirring speed 220 r / min, and the reaction time 15 min. The viscosity of the system was 3000 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 55°C, the stirring speed 80 r / min, and the reaction time 25 min. After completing the entire condensation polymerization reaction, the viscosity of the system was 119000 mPa·s. Calcium hydroxide was added to neutralize the solution. After the neutralization reaction was complete, the viscosity of the polymer solution was 100000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, lithium chloride, and DMAc in a mass ratio of 2:2:1:95. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by microgravure coating. The separator was then placed in a solidification bath (solidification bath being a solution of water and DMAc) with a bath solution concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0031] Example 14 8.2 kg of MPD was dissolved in 82 kg of DMAc, and after complete dissolution, the mixture was maintained at 5°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 5°C, and 196.5 g of allyl chloride and 200 g of SnCl 4 were added at a stirring speed of 800 r / min for a reaction time of 45 min. Subsequently, ammonia was ablated to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 201 mPa·s. After filtration, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 10°C, and 196.5 g of allyl chloride was added at a stirring speed of 700 r / min for a reaction time of 45 min. Subsequently, calcium hydroxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 870 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled to 25°C, the stirring speed 350 r / min, and the reaction time 15 min. The viscosity of the system was 2980 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled to 40°C, the stirring speed 200 r / min, and the reaction time 10 min. The entire condensation polymerization reaction was completed, and the viscosity of the system was 107000 mPa·s. Calcium hydroxide was added to neutralize the solution, and after the neutralization reaction was completed, the viscosity of the polymer solution was 90000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water, and the moisture was removed by drying with a blower. The resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PVP, lithium chloride, and DMAc in a mass ratio of 2:2:1:95. The slurry was then uniformly applied to a 9 μm thick polyethylene separator by slit press coating, and the separator was placed in a solidification bath (solidification bath being a solution of water and DMAc) at a bath solution concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0032] Example 15 8.2 kg of MPD was dissolved in 82 kg of DMAc, and after complete dissolution, the mixture was maintained at 0°C. IPC was then added in stages to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled to 8°C, and 196.5 g of 3-bromo-1-propene and 5200 g of SbCl were added at a stirring speed of 500 r / min for a reaction time of 45 min. Subsequently, calcium oxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 170 mPa·s. Then, condensation polymerization 2 was carried out, and the reaction temperature was controlled to 15°C, and 196.5 g of allyl chloride was added at a stirring speed of 700 r / min for a reaction time of 45 min. Subsequently, calcium oxide was added to remove the hydrogen chloride produced in the reaction, and the viscosity of the system was 801 mPa·s. Subsequently, IPC was added to carry out condensation polymerization 3, with the reaction temperature controlled at 45°C, the stirring speed at 200 r / min, and the reaction time at 15 min. The viscosity of the system was 2480 mPa·s. Then, the remaining IPC was added to carry out condensation polymerization 4, with the reaction temperature controlled at 45°C, the stirring speed at 80 r / min, and the reaction time at 30 min. After completing the entire condensation polymerization reaction, the viscosity of the system was 100,000 mPa·s. Calcium oxide was added to neutralize the solution. After the neutralization reaction was completed, the viscosity of the polymer solution was 80,000 mPa·s, yielding a meta-aramid polymer solution with a network structure. The polymer solution obtained after polymerization was mixed with deionized water. After the polymer had completely precipitated, it was washed three times with deionized water and DMAc (mass ratio of deionized water to DMAc was 95%:5%), moisture was removed by drying with a blower, and the resulting solid polymer material was sealed in a light-shielding container in preparation for future use. A coating slurry was prepared by combining a meta-aramid polymer with a network structure, PEG, calcium chloride, and DMAc in a mass ratio of 2:2:1:95. The slurry was then uniformly applied to a 9 μm thick polypropylene separator by commarol coating, and the separator was placed in a solidification bath (solidification bath being a solution of water and DMAc) at a bath concentration of 45% and a temperature of 15°C. After removal from the solidification bath, the separator was washed with water at 55°C and immediately dried at a drying temperature of 145°C. By winding, a meta-aramid coated polyethylene separator with a coating thickness of 2 μm on each side was obtained.

[0033] Comparative Example A commercially available polyethylene separator product was selected. The required performance specifications are: thickness 13 μm, tensile strength MD ≥ 160 MPa, TD ≥ 160 MPa, elongation MD ≥ 100%, TD ≥ 100%, air permeability 170 ± 40 s / 100 cc, puncture strength ≥ 5 N, heat shrinkage rate at 105°C for 1 hour MD ≤ 3%, TD ≤ 1.5%, and porosity 40 ± 2%.

[0034] [Table 1] Table 1: Comparison of performance data of separators in the examples and comparative examples. JPEG0007912094000004.jpg129170 Note that "~" means that under these conditions, severe contraction occurs and measurement is impossible. MD is the vertical direction, and TD is the horizontal direction.

[0035] Table 1 compares the performance data of the separators in the examples and comparative examples. The test methods for the separator samples obtained in the examples and comparative examples are shown below. The thickness of the separator was measured in accordance with GB / T6672-2001 "Mechanical measurement method for measuring the thickness of plastic films and sheets". Tensile strength and elongation were measured in accordance with GB / T1040.3-2006 "Measurement of tensile properties of plastics". Air permeability was measured in accordance with GB / T1038-2000 "Test method for gas permeability of plastic films and sheets - differential pressure method". Puncture strength was measured in accordance with the relevant provisions for puncture strength in GB / T 10004-2008 "Plastic laminate films for packaging, dry laminates and extruded laminates of bags". Heat shrinkage ratio was measured in accordance with GB / T13519-2016 "Polyethylene heat shrinkable films for packaging". Porosity was determined in accordance with GB / T6672-2001 "Mechanical Measurement Method for Thickness of Plastic Films and Sheets". Fuse temperature was measured by the TMA method.

[0036] By introducing alkane groups between the molecular chains of meta-aramid, a meta-aramid polymer having a network structure was prepared. Furthermore, by applying a slurry prepared using this polymer to the surface of a polyethylene separator, a battery separator with a fine and dense nanoporous structure on the coated surface was obtained. Results from the examples show that this preparation method improves the puncture strength of the separator by more than 20% and significantly increases the fuse temperature of the separator. Under conditions of 180°C, the polyethylene substrate film becomes transparent and shrinks severely, whereas the meta-aramid coating with a network structure prepared by the present invention maintains a good shape, and thermal shrinkage in the lateral and vertical directions is suppressed to within 3%. In addition, the meta-aramid coated separator with a network structure shows a significant improvement in the wettability of the surface to the electrolyte, contributing to an improved cycle life of lithium batteries.

[0037] The above are merely preferred embodiments of the present invention and do not limit it. Those skilled in the art can make various changes and modifications to the present invention. Any modifications, equivalent substitutions, improvements, etc., that are consistent with the spirit and intent of the present invention are included within the technical scope of the present invention.

Claims

1. A method for producing a meta-aramid polymer having a network structure represented by the following structural formula, (1) Condensation polymerization: In preparing a meta-aramid polymer by solution polymerization, metaphenylenediamine MPD is dissolved in an organic solvent to form a solution, and then isophthaloyl chloride IPC is charged into the solution in four steps to carry out a condensation polymerization reaction. Alkylating agents and metal halides are charged in the first and second condensation polymerization steps, and the reaction temperature, stirring speed, reaction time, and viscosity of the system are controlled at each step to obtain a polymer molecular structure having a network structure. (2) Washing: The polymer solution prepared above is washed in an aqueous solvent and washed three times with water to remove oligomers and metal salts from the polymer, thereby obtaining a meta-aramid polymer having a network structure. When dissolving metaphenylenediamine MPD in an organic solvent, the solution is maintained at 0-10°C, and isophthaloyl chloride IPC is divided into four equal parts by weight and added to the system in four steps to carry out condensation polymerization reactions, resulting in condensation polymerization 1, condensation polymerization 2, condensation polymerization 3, and condensation polymerization 4. In condensation polymerization 1, the reaction temperature is 5-10°C, the stirring speed is 500-1000 r / min, an alkylating agent and a metal halide are charged, the reaction time is 30-60 min, a neutralizing agent is charged to remove reaction by-products, and the viscosity of the system after completion of condensation polymerization 1 is 100-300 mPa·s. In condensation polymerization 2, the reaction temperature is 10-30°C, the stirring speed is 500-700 r / min, the alkylating agent is added again, the reaction time is 30-45 min, and a neutralizing agent is added to remove the by-products at this stage. The viscosity of the system after completion of condensation polymerization 2 is 500-1000 mPa·s. In condensation polymerization 3, the reaction temperature was 25-45°C, the stirring speed was 200-350 r / min, and the reaction time was 15-20 min. The viscosity of the system after condensation polymerization 3 was 2000-3000 mPa·s. In condensation polymerization 4, the reaction temperature was 40-55°C, the stirring speed was 80-200 r / min, and the reaction time was 10-30 min. The viscosity of the system after condensation polymerization 4 was 100,000-150,000 mPa·s. The alkylating agent is a chlorinated alkane / alkene or a brominated alkane / alkene. The aforementioned metal halide is AlCl ３ FeCl ３ SbCl ５ SnCl ４ A method for producing a meta-aramid polymer with a network structure, characterized by being one of the following types. (In the formula, m, n, x, and y represent the degree of polymerization, R １ , R ２ (This is an alkane group with 3 to 5 carbon atoms.)

2. The method for producing a network-structured meta-aramid polymer according to claim 1, characterized in that the organic solvent is one of N,N-dimethylacetamide DMAc, N,N-dimethylformamide DMF, N-methylpyrrolidone NMP, and dimethyl sulfoxide DMSO, the neutralizing agent is one of ammonia, calcium hydroxide, and calcium oxide, and the aqueous solvent includes one of deionized water and a mixture of deionized water and a polymerization reaction solvent.

3. The method for producing a network-structured meta-aramid polymer according to claim 1, characterized in that the molar ratio of MPD to IPC is 1:(1 to 1.05), the molar equivalent ratio of the neutralizing agent to IPC is 1:1, the ratio of the total moles of the alkylating agent to the moles of MPD in condensation polymerization 1 and condensation polymerization 2 is (1 to 20):(180 to 199), the alkylating agent is charged in equal amounts in condensation polymerization 1 and condensation polymerization 2, and the amount of the metal halide charged accounts for 0.1 to 0.6 wt% of the total mass of the reaction system.

4. A method for manufacturing a coating separator for a lithium battery, using a meta-aramid polymer with a network structure obtained by the manufacturing method described in any one of claims 1 to 3.

5. A method for manufacturing a coating separator for a lithium battery according to Claim 4, A method for producing a mesh-structured meta-aramid polymer, a pore-forming agent, and a solubilizing agent, which are dissolved in an organic solvent to form a coating slurry; the slurry is extruded from a die and applied to one or both sides of a polyolefin separator; the separator is molded in a solidification bath, and then washed with water and dried to obtain a mesh-structured meta-aramid coated separator for lithium batteries.

6. The manufacturing method according to claim 5, characterized in that the mass ratio of the network-structured meta-aramid polymer, the pore-forming agent, the solubilizer, and the organic solvent is (2-8):(2-6):(1-8):(78-95), the pore-forming agent is one of polyethylene glycol PEG and polyvinylpyrrolidone PVP, the solubilizer is one of calcium chloride and lithium chloride, the polyolefin separator is one of polyethylene and polypropylene separator, the organic solvent in the coagulation bath is one of N,N-dimethylacetamide DMAc, N,N-dimethylformamide DMF, N-methylpyrrolidone NMP, and dimethyl sulfoxide DMSO, the coagulation bath has a bath liquid concentration of 20-65%, a bath liquid temperature of 5-45°C, the water washing temperature is 45-65°C, and the drying temperature is 120-155°C.

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