Meta-type aramid polymer having a mesh structure, method for producing the same, and applications thereof

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

[0001] The present invention belongs to the field of battery separators, and particularly relates to a meta-type aramid polymer having a mesh structure, a method for producing the same, and an application thereof.

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 shuts down during overcharging or temperature rise to cut off the conduction of current and 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, it is necessary to add a binder to bond an inorganic material and an organic polymer substrate, and there are disadvantages 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 separators used in lithium batteries. Many separator manufacturers have high hopes for aramid materials as high-temperature resistant coated separators. However, technically, the production of meta-aramid or para-aramid itself is restricted. As a result, there are even cases where ceramics are mixed and coated in aramid slurries. For example, Patent Publication No. CN110707265 discloses an aramid coating solution and its preparation method, a separator based on the aramid coating solution, and its applications. The document describes mixing meta-aramid with ceramics to form a mixed slurry with a relatively high proportion of ceramics, and then coating it on a polyolefin separator. However, the low thermal shrinkage rate is only ensured at 130°C or below, and it cannot satisfy the heat resistance at higher temperatures. Therefore, the development of separators and their manufacturing methods is urgently required.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to solve the deficiencies in high-temperature resistance, heat shrinkage rate, and puncture strength of coated separators in the prior art, the present invention provides a meta-aramid polymer with a mesh structure, its manufacturing method, and applications. This coated separator is excellent in high-temperature resistance, heat shrinkage rate, puncture strength, and oxidation resistance performance. It contributes to the achievement of high potential, enhances energy density and safety, has better wettability with the electrolyte, and can extend the cycle life of the battery. A coated separator made from a meta-aramid polymer with a mesh structure is preferably used in lithium batteries for electric vehicles. Such a manufacturing method saves time and effort, has high production efficiency, and the product has high quality and excellent stability.

Means for Solving the Problems

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

[0006] According to the first aspect, the present invention provides a meta-type aramid polymer having a network structure represented by the following structural formula. [Chemical formula 1] JPEG2025522207000002.jpg36170(wherein m, n, x, and y represent the degree of polymerization, and R1 and R2 are alkane groups having 3 to 5 carbon atoms.)

[0007] According to the second aspect, the present invention provides a method for producing a meta-type aramid polymer having a network structure, which is represented by the following reaction process. [Chemical formula 2] JPEG2025522207000003.jpg114170(wherein m, n, x, and y represent the degree of polymerization, and R1 and R2 are alkane groups having 3 to 5 carbon atoms.)

[0008] According to the third aspect, there is provided a method for producing a meta-type aramid polymer having a network structure, and the production process is as follows. (1) Condensation polymerization: A meta-type aramid polymer is produced by solution polymerization. Metaphenylenediamine (MPD) is dissolved in an organic solvent, and then isophthaloyl chloride (IPC) is charged into the above solution in four steps to carry out a condensation polymerization reaction. An alkylating agent and a metal halide are charged in the first and second condensation polymerization steps, and by controlling the reaction temperature, stirring speed, reaction time, and viscosity of the system in each step, a polymer molecular structure having a network structure is obtained. (2) Washing: The polymer solution prepared above is washed in an aqueous solvent and washed with water three times to remove oligomers and metal salts from the polymer, thereby obtaining a meta-type aramid polymer having a network structure. When dissolving metaphenylenediamine (MPD) in an organic solvent, the solution is maintained at 0 to 10°C, and isophthaloyl chloride (IPC) is divided into four equal parts by weight and charged into the system in four steps to carry out a condensation polymerization reaction, which are designated as condensation polymerization 1, condensation polymerization 2, condensation polymerization 3, and condensation polymerization 4, respectively. In the condensation polymerization 1, the reaction temperature is 5 to 10 °C, the stirring speed is 500 to 1000 r / min, an alkylating agent and a metal halide are charged, the reaction time is 30 to 60 min, a neutralizing agent is charged to remove reaction by-products, and the viscosity of the system after the completion of the condensation polymerization 1 is 100 to 300 mPa·s. In the condensation polymerization 2, the reaction temperature is 10 to 30 °C, the stirring speed is 500 to 700 r / min, the alkylating agent is charged again, the reaction time is 30 to 45 min, a neutralizing agent is charged to remove by-products at this stage, and the viscosity of the system after the completion of the condensation polymerization 2 is 500 to 1000 mPa·s. In the condensation polymerization 3, the reaction temperature is 25 to 45 °C, the stirring speed is 200 to 350 r / min, the reaction time is 15 to 20 min, and the viscosity of the system after the completion of the condensation polymerization 3 is 2000 to 3000 mPa·s. In the condensation polymerization 4, the reaction temperature is 40 to 55 °C, the stirring speed is 80 to 200 r / min, the reaction time is 10 to 30 min, and the viscosity of the system after the completion of the condensation polymerization 4 is 100000 to 150000 mPa·s.

[0009] Furthermore, the organic solvent is one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and 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, and SnCl4. The neutralizing agent is one of ammonia, calcium hydroxide, calcium oxide, and sodium hydroxide. The aqueous solvent includes one of deionized water and a mixture of deionized water and a polymerization reaction solvent.

[0010] Furthermore, examples of the substance represented by the chemical structural formula of the alkylating agent typically include, but are not limited to, the following substances. [Chemical formula 3] JPEG2025522207000004.jpg44170

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

[0012] According to the fourth aspect, it is an application in the preparation of a coating separator for a lithium battery of a meta-type aramid polymer.

[0013] Furthermore, a meta-type aramid polymer having a network structure, a pore former, and a dissolution aid 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, and after being formed in a coagulation bath, it is washed with water and dried to obtain a meta-type aramid-coated separator having a network structure for a lithium battery.

[0014] Furthermore, the mass ratio of the meta-type aramid polymer having the network structure, the pore former, the dissolution aid, and the organic solvent is (2 to 8):(2 to 6):(1 to 8):(78 to 95). The pore former is one of polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP). The dissolution aid is one of calcium chloride and lithium chloride. The polyolefin separator is one of a polyethylene separator and a polypropylene separator. The coating method is one of microgravure roll coating, comma roll coating, and 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), and dimethyl sulfoxide (DMSO). The coagulation bath has a bath solution concentration of 20 to 65% and a bath solution temperature of 5 to 45 °C. The water washing temperature is 45 to 65 °C. The drying temperature is 120 to 155 °C.

Advantages of the Invention

[0015] The present invention has the following advantageous technical effects as compared with the prior art. (1) When forming the meta-type aramid, C-alkylation proceeds, and the structures of adjacent molecules are bonded by chemical bonds to form a network structure, thereby increasing the degree of crosslinking and eliminating the gel phenomenon due to the high degree of crosslinking. (2) A separator formed by coating a meta-type 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 heat 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) The meta-type 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 the lithium battery, and enhances the oxidation resistance of the separator, and can contribute to the achievement of a high potential and an improvement in the energy density.

Brief Description of the Drawings

[0016] Hereinafter, the present invention will be further described with reference to the drawings.

Figure 1

Figure 2

Figure 3

Figure 4

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, and when the entire polycondensation reaction was completed, the viscosity of the system became 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 having a network structure was obtained. After the polymerization was completed, the polymer solution obtained was mixed with deionized water. After the polymer was completely precipitated, it was washed 3 times with deionized water, and moisture was removed by drying with a blower. The obtained solid polymer material was sealed in a light-shielded manner for later use. A coating slurry was prepared 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. Then, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating, and further placed in a coagulation bath (the coagulation bath was a solution of water and DMAc), with the bath solution concentration of 45% and the temperature of 15 °C. After being taken 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. After complete dissolution, it was maintained at 8°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, 14.5 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 the hydrogen chloride generated in the reaction. The viscosity of the system was 151 mPa·s. Then, polycondensation 2 was carried out. The reaction temperature was controlled at 22°C, the stirring speed was 500 r / min, 14.5 g of allyl chloride was charged, the reaction time was 30 min, and then calcium hydroxide was charged to remove the hydrogen chloride generated in the reaction. The viscosity of the system was 701 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 2316 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, and when the entire polycondensation reaction was completed, the viscosity of the system became 121000 mPa·s. Then, calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 101000 mPa·s, and a meta-type aramid polymer solution having a network structure was obtained. The polymer solution formed after the polymerization 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. A coating slurry was prepared such that a meta-type aramid polymer having a mesh structure, PEG, lithium chloride, and DMAc had a mass ratio of 5:3:5:87. After that, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating, and then placed in a coagulation bath (the coagulation bath was a solution of water and DMAc), with the bath solution concentration being 45% and the temperature being 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.

[0020] Example 3 8.2 kg of MPD was dissolved in 82 kg of DMAc. After complete dissolution, it was held at 8°C, and IPC was charged stepwise to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled at 8°C, the stirring speed was 800 r / min, 289.3 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 the hydrogen chloride generated in the reaction. The viscosity of the system was 213 mPa·s. Then, condensation polymerization 2 was carried out. The reaction temperature was controlled at 22°C, the stirring speed was 500 r / min, 289.3 g of allyl chloride was charged, the reaction time was 30 min, and then calcium hydroxide was charged to remove the hydrogen chloride generated in the reaction. The viscosity of the system was 712 mPa·s. Then, IPC was continuously added to carry out condensation polymerization 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 2446 mPa·s. Then, the last remaining IPC was charged to carry out condensation polymerization 4. The reaction temperature was controlled at 45°C, the stirring speed was 120 r / min, the reaction time was 25 min, and when the entire condensation polymerization reaction was completed, the viscosity of the system became 135000 mPa·s. Then, calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 113000 mPa·s, and a meta-type aramid polymer solution having a mesh structure was obtained. After the polymerization was completed, the resulting polymer solution 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 obtained solid polymer material was sealed in the dark in preparation for later use. A coating slurry was prepared 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. Then, the slurry was uniformly coated onto a polyethylene separator with a thickness of 9 μm by microgravure coating. Further, it was placed in a coagulation bath (the coagulation bath was a solution of water and DMAc), with the bath solution concentration set at 45% and the temperature at 15°C. After being taken out from the coagulation bath, it was washed with water at 55°C, and the separator was immediately dried, with the drying temperature set at 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.

[0021] Example 4 5.0 kg of MPD was dissolved in 89 kg of DMAc. After complete dissolution, it was kept 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, 120.2 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 the hydrogen chloride generated in the reaction. The viscosity of the system was 149 mPa·s. Thereafter, polycondensation 2 was carried out. The reaction temperature was controlled at 22 °C, the stirring speed was 500 r / min, 120.2 g of allyl chloride was charged, the reaction time was 30 min, and then calcium hydroxide was charged to remove the hydrogen chloride generated in the reaction. The viscosity of the system was 595 mPa·s. Thereafter, 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 1846 mPa·s. Thereafter, 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 101000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 85000 mPa·s, and a meta-type aramid polymer solution having a network structure was obtained. After the polymerization was completed, the resulting polymer solution 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 the dark for later use. A coating slurry was prepared 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. Then, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating. Further, it was placed in a coagulation bath (the coagulation bath is 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.

[0022] Example 5 15.9 kg of MPD was dissolved in 65 kg of DMAc. After complete dissolution, it was maintained at 5 °C, and IPC was charged stepwise to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled at 8 °C, the stirring speed was 800 r / min, 382.5 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 210 mPa·s. Thereafter, condensation polymerization 2 was carried out. The reaction temperature was controlled at 22 °C, the stirring speed was 500 r / min, 382.5 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 701 mPa·s. Thereafter, IPC was continuously added to carry out condensation polymerization 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 2446 mPa·s. Thereafter, the last remaining IPC was charged to carry out condensation polymerization 4. The reaction temperature was controlled at 45 °C, the stirring speed was 120 r / min, the reaction time was 25 min, and when the entire condensation polymerization reaction was completed, the viscosity of the system reached 145000 mPa·s. Then, calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 120000 mPa·s, and a meta-type aramid polymer solution having a network structure was obtained. The polymer solution formed after the polymerization was mixed with deionized water. After the polymer was completely precipitated, it was washed three times with deionized water, and moisture was removed by drying with a blower. The obtained solid polymer material was sealed in a light-shielded manner for later use. A coating slurry was prepared 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. Then, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating, and further placed in a coagulation bath (the coagulation bath was a solution of water and DMAc), with the bath solution concentration being 45% and the temperature being 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.

[0023] Example 6 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, then calcium hydroxide was charged to remove hydrogen chloride generated in the reaction, and the viscosity of the system was 178 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, then calcium hydroxide was charged to remove hydrogen chloride generated in the reaction, and the viscosity of the system was 688 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 2301 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, and when the entire polycondensation reaction was completed, the viscosity of the system reached 120000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 100000 mPa·s, and a meta-type aramid polymer solution with a network structure was obtained. After the polymerization was completed, the polymer solution formed was mixed with deionized water. After the polymer was completely precipitated, it was washed 3 times with deionized water, and the moisture was removed by drying with a blower. The obtained solid polymer material was sealed in the dark for later use. A coating slurry was prepared such that the mass ratio of the meta-type aramid polymer with a network structure, PEG, lithium chloride, and DMAc was 2:2:1:95. Then, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating, and further placed in a coagulation bath (the coagulation bath was a solution of water and DMAc), with the bath solution concentration of 45% and the temperature of 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 of 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.

[0024] Example 7 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, then calcium hydroxide was charged to remove the hydrogen chloride generated in the reaction, and the viscosity of the system was 201 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, then calcium hydroxide was charged to remove the hydrogen chloride generated in the reaction, and the viscosity of the system was 699 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 2312 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, and when the entire polycondensation reaction was completed, the viscosity of the system became 130000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 109000 mPa·s, and a meta-type aramid polymer solution having a network structure was obtained. The polymer solution formed after the polymerization was mixed with deionized water. After the polymer was completely precipitated, it was washed 3 times with deionized water, and the moisture was removed by drying with a blower. The obtained solid polymer material was sealed in the dark for later use. A coating slurry was prepared such that a meta-type aramid polymer having a mesh structure, PEG, lithium chloride, and DMAc had a mass ratio of 8:6:8:78. Then, by microgravure coating, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm. Further, it was placed in a coagulation bath (the coagulation bath was a solution of water and DMAc), with the bath solution concentration being 45% and the temperature being 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.

[0025] Example 8 8.2 kg of MPD was dissolved in 82 kg of DMAc. After complete dissolution, it was held at 5°C, and IPC was charged stepwise to initiate the condensation polymerization reaction. In condensation polymerization 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 the hydrogen chloride generated in the reaction. The viscosity of the system was 202 mPa·s. Thereafter, condensation polymerization 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 the hydrogen chloride generated in the reaction. The viscosity of the system was 685 mPa·s. Thereafter, IPC was continuously added to carry out condensation polymerization 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 2100 mPa·s. Thereafter, the last remaining IPC was charged to carry out condensation polymerization 4. The reaction temperature was controlled at 45°C, the stirring speed was 120 r / min, the reaction time was 25 min, and when the entire condensation polymerization reaction was completed, the viscosity of the system became 115000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 95000 mPa·s, and a meta-type aramid polymer solution having a mesh structure was obtained. After the polymerization was completed, the resulting polymer solution 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 the dark for later use. A coating slurry was prepared such that a meta-type aramid polymer having a network structure, PEG, lithium chloride, and DMAc had a mass ratio of 5:3:5:87. Then, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating, and further placed in a coagulation bath (the coagulation bath is a solution of water and DMAc), with a bath solution concentration of 20% and a temperature of 5 °C. After taking it out from the coagulation bath, it was washed with water at 55 °C, and the separator was immediately dried, with a drying temperature of 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.

[0026] Example 9 8.2 kg of MPD was dissolved in 82 kg of DMAc. After complete dissolution, it was held at 5 °C, and IPC was charged stepwise to initiate the condensation polymerization reaction. In condensation polymerization 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 the hydrogen chloride generated in the reaction. The viscosity of the system was 191 mPa·s. Then, condensation polymerization 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 the hydrogen chloride generated in the reaction. The viscosity of the system was 500 mPa·s. Then, IPC was continuously added to carry out condensation polymerization 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 2220 mPa·s. Then, the last remaining IPC was charged to carry out condensation polymerization 4. The reaction temperature was controlled at 45 °C, the stirring speed was 120 r / min, the reaction time was 25 min, and when the entire condensation polymerization reaction was completed, the viscosity of the system was 131000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 111000 mPa·s, and a meta-type aramid polymer solution having a network structure was obtained. After the polymerization was completed, the resulting polymer solution 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 the dark for later use. A coating slurry was prepared such that a meta-type aramid polymer having a network structure, PEG, lithium chloride, and DMAc had a mass ratio of 5:3:5:87. Then, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating, and further placed in a coagulation bath (the coagulation bath was a solution of water and DMAc), with the bath solution concentration set at 65% and the temperature at 45°C. After being taken out from the coagulation bath, it was washed with water at 45°C, and the separator was immediately dried, with the drying temperature set at 155°C. By winding it up, a meta-type aramid-coated polyethylene separator with a coating thickness of 2 μm on both sides was obtained.

[0027] Example 10 8.2 kg of MPD was dissolved in 82 kg of DMF. After complete dissolution, it was maintained at 5 °C, and IPC was charged stepwise to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled at 8 °C, the stirring speed was 1000 r / min, 232.7 g of methylchloropropene and 200 g of FeCl3 were charged, the reaction time was 30 min, and then calcium hydroxide was charged to remove the hydrogen chloride generated in the reaction. The viscosity of the system was 100 mPa·s. Thereafter, condensation polymerization 2 was carried out. The reaction temperature was controlled at 22 °C, the stirring speed was 500 r / min, 232.7 g of methylchloropropene was charged, the reaction time was 30 min, and then calcium hydroxide was charged to remove the hydrogen chloride generated in the reaction. The viscosity of the system was 679 mPa·s. Thereafter, IPC was continuously added to carry out condensation polymerization 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 2000 mPa·s. Thereafter, the last remaining IPC was charged to carry out condensation polymerization 4. The reaction temperature was controlled at 45 °C, the stirring speed was 120 r / min, the reaction time was 25 min, and when the entire condensation polymerization reaction was completed, the viscosity of the system reached 100000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 81000 mPa·s, and a meta-type aramid polymer solution having a network structure was obtained. After the polymerization was completed, the polymer solution formed 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. A coating slurry was prepared such that the mass ratio of the meta-type aramid polymer having a network structure, PEG, lithium chloride, and DMF was 5:3:5:87. Then, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating, and further placed in a coagulation bath (the coagulation bath was a solution of water and DMF). The bath solution concentration was 65% and the temperature was 45 °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 120 °C. By winding it up, a meta-type aramid-coated polyethylene separator with a coating thickness of 2 μm on both sides was obtained.

[0028] Example 11 8.2 kg of MPD was dissolved in 82 kg of NMP. After complete dissolution, it was kept at 10 °C, and IPC was charged stepwise to initiate the polycondensation reaction. In polycondensation 1, the reaction temperature was controlled at 10 °C, the stirring speed was 700 r / min, 196.5 g of allyl chloride and 200 g of AlCl3 were charged, the reaction time was 60 min, then calcium hydroxide was charged to remove hydrogen chloride generated in the reaction, and the viscosity of the system was 300 mPa·s. Thereafter, polycondensation 2 was carried out. The reaction temperature was controlled at 30 °C, the stirring speed was 500 r / min, 196.5 g of allyl chloride was charged, the reaction time was 30 min, then calcium hydroxide was charged to remove hydrogen chloride generated in the reaction, and the viscosity of the system was 669 mPa·s. Thereafter, IPC was continuously added to carry out polycondensation 3. The reaction temperature was controlled at 42 °C, the stirring speed was 220 r / min, the reaction time was 20 min, and the viscosity of the system was 2009 mPa·s. Thereafter, the last remaining IPC was charged to carry out polycondensation 4. The reaction temperature was controlled at 50 °C, the stirring speed was 120 r / min, the reaction time was 25 min, and when the entire polycondensation reaction was completed, the viscosity of the system became 120000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 81000 mPa·s, and a meta-type aramid polymer solution having a network structure was obtained. The polymer solution formed after the polymerization was mixed with deionized water. After the polymer was completely precipitated, it was washed 3 times with deionized water, and moisture was removed by drying with a blower. The obtained solid polymer material was sealed in a light-shielded manner for later use. A coating slurry was prepared such that the mass ratio of the meta-type aramid polymer having a network structure, PEG, lithium chloride, and NMP was 5:3:5:87. Then, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by microgravure coating, and further placed in a coagulation bath (the coagulation bath is a solution of water and NMP), with the bath solution concentration of 65% and the temperature of 45 °C. After taking it out from the coagulation bath, it was washed with water at 65 °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.

[0029] Example 12 8.2 kg of MPD was dissolved in 82 kg of DMSO. 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 171 mPa·s. Then, polycondensation 2 was carried out. The reaction temperature was controlled at 22 °C, the stirring speed was 600 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 721 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 2349 mPa·s. Then, the last remaining IPC was charged to carry out polycondensation 4. The reaction temperature was controlled at 50 °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 150000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 130000 mPa·s, and a meta-type aramid polymer solution with a network structure was obtained. The polymer solution obtained after the polymerization was completed was mixed with deionized water. After the polymer was completely precipitated, it was washed 3 times with deionized water, and the moisture was removed by drying with a blower. The obtained solid polymer material was sealed in the dark 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 DMSO 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 DMSO), with the bath solution concentration of 45% and the temperature of 15 °C. After being taken 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.

[0030] Example 13 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 178 mPa·s. Then, polycondensation 2 was carried out. The reaction temperature was controlled at 10°C, the stirring speed was 700 r / min, 196.5 g of allyl chloride was 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 1000 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 15 min, and the viscosity of the system was 3000 mPa·s. Then, the last remaining IPC was charged to carry out polycondensation 4. The reaction temperature was controlled at 55°C, the stirring speed was 80 r / min, the reaction time was 25 min, and when the entire polycondensation reaction was completed, the viscosity of the system became 119000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 100000 mPa·s, and a meta-type aramid polymer solution having a network structure was obtained. The polymer solution obtained after the polymerization was completed was mixed with deionized water. After the polymer was completely precipitated, it was washed 3 times with deionized water, and the moisture was removed by drying with a blower. The obtained solid polymer material was sealed in the dark for later use. A coating slurry was prepared such that a meta-aramid polymer having a mesh structure, PEG, lithium chloride, and DMAc had a mass ratio of 2:2:1:95. Then, the slurry was uniformly coated onto a polyethylene separator with a thickness of 9 μm by microgravure coating. Further, it was placed in a coagulation bath (the coagulation bath was a solution of water and DMAc), with the bath solution concentration set at 45% and the temperature at 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 set at 145°C. By winding it up, a meta-aramid-coated polyethylene separator with a coating thickness of 2 μm on both sides was obtained.

[0031] Example 14 8.2 kg of MPD was dissolved in 82 kg of DMAc. After complete dissolution, it was held at 5°C, and IPC was charged stepwise to initiate the polycondensation reaction. In polycondensation 1, the reaction temperature was controlled at 5°C, the stirring speed was 800 r / min, 196.5 g of allyl chloride and 200 g of SnCl4 were charged, the reaction time was 45 min, and then ammonia was bubbled through to remove the hydrogen chloride generated in the reaction. The viscosity of the system was 201 mPa·s. After filtration, polycondensation 2 was carried out. The reaction temperature was controlled at 10°C, the stirring speed was 700 r / min, 196.5 g of allyl chloride was charged, the reaction time was 45 min, and then calcium hydroxide was charged to remove the hydrogen chloride generated in the reaction. The viscosity of the system was 870 mPa·s. Then, IPC was continuously added to carry out polycondensation 3. The reaction temperature was controlled at 25°C, the stirring speed was 350 r / min, the reaction time was 15 min, and the viscosity of the system was 2980 mPa·s. Then, the last remaining IPC was charged to carry out polycondensation 4. The reaction temperature was controlled at 40°C, the stirring speed was 200 r / min, the reaction time was 10 min, and when the entire polycondensation reaction was completed, the viscosity of the system reached 107000 mPa·s. Calcium hydroxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 90000 mPa·s, and a meta-aramid polymer solution having a mesh structure was obtained. After the polymerization was completed, the resulting polymer solution 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 obtained solid polymer material was sealed in the dark in preparation for later use. A coating slurry was prepared such that a meta-type aramid polymer having a mesh structure, PVP, lithium chloride, and DMAc had a mass ratio of 2:2:1:95. Then, the slurry was uniformly coated on a polyethylene separator with a thickness of 9 μm by slit press coating. Further, it was placed in 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 being taken 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.

[0032] Example 15 8.2 kg of MPD was dissolved in 82 kg of DMAc. After complete dissolution, it was maintained at 0 °C, and IPC was charged stepwise to initiate the condensation polymerization reaction. In condensation polymerization 1, the reaction temperature was controlled at 8 °C, the stirring speed was 500 r / min, 196.5 g of 3-bromo-1-propene and 200 g of SbCl5 were charged, the reaction time was 45 min, and then calcium oxide was charged to remove hydrogen chloride generated in the reaction. The viscosity of the system was 170 mPa·s. Then, condensation polymerization 2 was carried out. The reaction temperature was controlled at 15 °C, the stirring speed was 700 r / min, 196.5 g of allyl chloride was charged, the reaction time was 45 min, and then calcium oxide was charged to remove hydrogen chloride generated in the reaction. The viscosity of the system was 801 mPa·s. Then, IPC was continuously added to carry out condensation polymerization 3. The reaction temperature was controlled at 45 °C, the stirring speed was 200 r / min, the reaction time was 15 min, and the viscosity of the system was 2480 mPa·s. Then, the last remaining IPC was charged to carry out condensation polymerization 4. The reaction temperature was controlled at 45 °C, the stirring speed was 80 r / min, the reaction time was 30 min. When the entire condensation polymerization reaction was completed, the viscosity of the system reached 100000 mPa·s. Calcium oxide was charged for neutralization. After the neutralization reaction was completed, the viscosity of the polymer solution was 80000 mPa·s, and a meta-type aramid polymer solution with a network structure was obtained. After the polymerization was completed, the polymer solution obtained was mixed with deionized water. After the polymer was completely precipitated, it was washed three times with deionized water and DMAc (the mass ratio of deionized water to DMAc was 95%:5%). Moisture was removed by drying with a blower, and the obtained solid polymer material was sealed in the dark in preparation for later use. A coating slurry was prepared such that the mass ratio of the meta-type aramid polymer with a network structure, PEG, calcium chloride, and DMAc was 2:2:1:95. Then, the slurry was uniformly coated on a polypropylene separator with a thickness of 9 μm by comma roll coating. Further, it was placed in 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 being taken out from the coagulation bath, it was washed with water at 55 °C, and the separator was immediately dried at a drying temperature of 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.

[0033] Comparative Example A commercially available polyethylene separator product was selected. For the performance, it is required to have a thickness of 13 μm, a tensile strength MD ≥ 160 MPa, TD ≥ 160 MPa, an elongation MD ≥ 100%, TD ≥ 100%, an air permeability of 170 ± 40 s / 100 cc, a puncture strength ≥ 5 N, a heat shrinkage rate MD ≤ 3%, TD ≤ 1.5% at 105 °C for 1 h, and a porosity of 40 ± 2%.

[0034] [Table 1] Table 1 Comparison of Performance Data of Separators in Examples and Comparative Examples JPEG2025522207000005.jpg129170 Note that "~" means that it shrinks severely under this condition and the measurement is impossible. MD is the longitudinal direction and TD is the transverse direction.

[0035] Table 1 compares the performance data of the separators in the examples and the comparative examples. The test methods for the separator samples obtained in the examples and the comparative examples are shown below. The thickness of the separator conforms to GB / T6672 - 2001 "Measurement of Thickness of Plastic Films and Sheets - Mechanical Measurement Method". The tensile strength and elongation conform to GB / T1040.3 - 2006 "Plastics - Determination of Tensile Properties". The air permeability conforms to GB / T1038 - 2000 "Test Method for Gas Permeability of Plastic Films and Sheets - Differential Pressure Method". The puncture strength was carried out in accordance with the relevant regulations on puncture strength in GB / T 10004 - 2008 "Plastic Laminated Films for Packaging, Dry Laminates and Extrusion Laminates of Bags". The heat shrinkage rate conforms to GB / T13519 - 2016 "Polyethylene Heat Shrinkable Films for Packaging". The porosity conforms to GB / T6672 - 2001 "Measurement of Thickness of Plastic Films and Sheets - Mechanical Measurement Method". The fuse temperature was measured by the TMA method.

[0036] By introducing an alkane group between the molecular chains of a meta-type aramid, a meta-type aramid polymer having a network structure was prepared. Further, a slurry prepared using the polymer was applied to the surface of a polyethylene separator to obtain a battery separator having a fine and dense nanoporous structure on the coating surface. From the results of the examples, by this production method, the puncture strength of the separator was improved by 20% or more, and the fuse temperature of the separator increased significantly. Under the condition of 180 °C, the polyethylene base film became transparent and shrinkage progressed severely, while the meta-type aramid coating having a network structure produced according to the present invention maintained a good form, and the thermal shrinkage in the horizontal and vertical directions was suppressed within 3%. Also, the meta-type aramid-coated separator having a network structure was shown to significantly improve the wettability with respect to the electrolyte solution on the surface, contributing to an improvement in the cycle life of the lithium battery.

[0037] The above are merely preferred embodiments of the present invention and do not limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. that are in line with the spirit and gist of the present invention shall be included in the technical scope of the present invention.

Claims

1. A meta-type aramid polymer with a network structure, characterized by being represented by the following structural formula. [Chemical Formula 1] (In the formula, m, n, x, and y represent the degree of polymerization, and R １ , R ２ is an alkane group having 3 to 5 carbon atoms.)

2. A method for producing the meta-type aramid polymer with a network structure according to Claim 1, characterized in that the reaction process is as follows, a method for producing a meta-type aramid polymer with a network structure. [Chemical Formula 2] (wherein, m, n, x, and y represent the degree of polymerization, and R １ , R ２ is an alkane group having 3 to 5 carbon atoms.)

3. (1) Condensation polymerization: Produce a meta-type aramid polymer by solution polymerization, dissolve metaphenylenediamine (MPD) in an organic solvent, and then charge isophthaloyl chloride (IPC) into the above solution in four steps to carry out a condensation polymerization reaction. In the first and second condensation polymerization steps, an alkylating agent and a metal halide are charged, and by controlling the reaction temperature, stirring speed, reaction time and viscosity of the system at each step, a polymer molecular structure with a network structure is obtained; (2) Washing: Wash the polymer solution prepared above in an aqueous solvent and wash it with water three times to remove oligomers and metal salts from the polymer, thereby obtaining a meta-type aramid polymer with a network structure. The method for producing a meta-type aramid polymer with a network structure according to Claim 2, characterized by including the above.

4. When dissolving metaphenylenediamine (MPD) in an organic solvent, keep the solution at 0 to 10 °C, divide isophthaloyl chloride (IPC) into four equal parts by weight and charge it into the system in four steps to carry out a condensation polymerization reaction, which are respectively designated as condensation polymerization 1, condensation polymerization 2, condensation polymerization 3, and condensation polymerization 4. In condensation polymerization 1, the reaction temperature is 5 to 10 °C, the stirring speed is 500 to 1000 r / min, an alkylating agent and a metal halide are charged, the reaction time is 30 to 60 min, a neutralizing agent is charged to remove reaction by-products, and the viscosity of the system after the end of condensation polymerization 1 is 100 to 300 mPa·s. In condensation polymerization 2, the reaction temperature is 10 to 30 °C, the stirring speed is 500 to 700 r / min, the alkylating agent is charged again, the reaction time is 30 to 45 min, a neutralizing agent is charged to remove by-products at this stage, and the viscosity of the system after the end of condensation polymerization 2 is 500 to 1000 mPa·s. In condensation polymerization 3, the reaction temperature is 25 to 45 °C, the stirring speed is 200 to 350 r / min, and the reaction time is 15 to 20 min. The viscosity of the system after the end of condensation polymerization 3 is 2000 to 3000 mPa·s. In the condensation polymerization 4, the reaction temperature is 40 to 55 °C, the stirring speed is 80 to 200 r / min, the reaction time is 10 to 30 min, and the viscosity of the system after the completion of the condensation polymerization 4 is 100,000 to 150,000 mPa·s. A method for producing a meta-type aramid polymer having a network structure according to claim 3, characterized in that.

5. The organic solvent is one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO), and the metal halide is AlCl ３ , FeCl ３ , SbCl ５ , SnCl ４ One of them, 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. A method for producing a network-structured meta-type aramid polymer according to claim 4, characterized in that

6. The molar ratio of the MPD to the IPC is 1:(1 to 1.05), the molar equivalent ratio of the neutralizing agent to the IPC is 1:1, and the ratio of the total moles of the alkylating agent to the moles of the MPD in the condensation polymerization 1 and the condensation polymerization 2 is (1 to 20):(180 to 199). In the condensation polymerization 1 and the condensation polymerization 2, the alkylating agent is charged in the same amount, and the charged amount of the metal halide accounts for 0.1 to 0.6 wt% of the total mass of the reaction system. A method for producing a meta-type aramid polymer having a network structure according to claim 4, characterized in that.

7. Application of the meta-type aramid polymer having a network structure according to claim 1 in the production of a coating separator for a lithium battery.

8. The application method is to dissolve a meta-type aramid polymer having a network structure, a pore-forming agent, and a dissolution aid in an organic solvent to form a coating slurry, extrude the slurry from a die and apply it to one or both sides of a polyolefin separator, and then form it in a coagulation bath. After that, it is washed with water and dried to obtain a meta-type aramid-coated separator having a network structure for a lithium battery. The application according to claim 7, characterized in that.

9. The mass ratio of the meta-type aramid polymer having a network structure, the pore-forming agent, the dissolution aid, and the organic solvent is (2 to 8):(2 to 6):(1 to 8):(78 to 95). The pore-forming agent is one of polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP). The dissolution aid is one of calcium chloride and lithium chloride. The polyolefin separator is one of polyethylene and polypropylene separators. 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 solution concentration of 20 to 65% and a bath solution temperature of 5 to 45 °C. The water washing temperature is 45 to 65 °C, and the drying temperature is 120 to 155 °C. The application according to claim 8, characterized in that.

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