Meta-aramid polymer with grid structure, and preparation method therefor and use thereof

Abstract

In the process of forming the meta-aramid polymer, alkyl is introduced among macromolecules through alkylation, such that adjacent molecular chains are linked by a chemical bond so as to form a grid structure. A coating slurry prepared from the meta-aramid polymer with a grid structure, a pore-forming agent and a cosolvent are coated on the surface of a polyolefin porous separator so as to obtain a high-performance lithium battery coated separator. Compared with a coated separator prepared by a traditional method, the coated separator prepared by the present disclosure has higher heat resistance, thermal shrinkage resistance and puncture strength, has better wettability with an electrolyte, and thus can prolong a cycle life of a battery. The coated separator of the meta-aramid with a grid structure can further improve the oxidation resistance, is beneficial to realizing high potential and improves energy density.

Claims

1. A meta-aramid polymer with a grid structure whose structural formula is as follows: ##STR00004## wherein m, n, x and y represent polymerization degrees; each of R.sub.1 and R.sub.2 is alkyl groups with 3-5 carbon atoms; and wherein the meta-aramid polymer is prepared from a method comprising the following steps: (1) polycondensation: preparing a meta-aramid polymer by using solution polymerization including dissolving m-phenylenediamine (MPD) in an organic solvent, then adding isophthaloyl chloride (IPC) into a solution in 4 stages for polycondensation, independently 1st polycondensation stage, 2nd polycondensation stage, 3rd polycondensation stage and 4th polycondensation stage, adding an alkylating agent and a metal halide in the 1st and 2nd polycondensation stages, and controlling a reaction temperature, a stirring speed, reaction time and a system viscosity of each stage so as to obtain a prepared polymer solution comprising a polymer molecular structure with a grid structure; and (2) washing: washing the prepared polymer solution in an aqueous solvent, and removing an oligomer and a metal salt in the polymer by water washing for 3 times so as to obtain the meta-aramid polymer with the grid structure; when the m-phenylenediamine (MPD) is dissolved in the organic solvent, the solution is kept at 0-10 C., the isophthaloyl chloride (IPC) is divided into 4 equal parts by weight and added into a system in the 4 stages for the polycondensation, the polycondensation in the 4 stages is defined as polycondensation 1, polycondensation 2, polycondensation 3 and polycondensation 4 respectively; the reaction temperature of the polycondensation 1 is 5-10 C., the stirring speed is 500-1,000 r/min, the alkylating agent and the metal halide are added, the reaction time is 30-60 min, a neutralizing agent is added, a reaction byproduct is removed, and the system viscosity is 100-300 mPa.Math.s after the polycondensation 1 is completed; the reaction temperature of the polycondensation 2 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, the neutralizing agent is added, a reaction byproduct of this stage is removed, and the system viscosity is 500-1,000 mPa.Math.s after the polycondensation 2 is completed; the reaction temperature of the polycondensation 3 is 25-45 C., the stirring speed is 200-350 r/min, the reaction time is 15-20 min, and the system viscosity is 2,000-3,000 mPa.Math.s after the polycondensation 3 is completed; and the reaction temperature of the polycondensation 4 is 40-55 C., the stirring speed is 80-200 r/min, the reaction time is 10-30 min, and the system viscosity is 100,000-150,000 mPa.Math.s after the polycondensation 4 is completed; the alkylating agent is chloro or bromo alkylolefin; and the metal halide is one of AlCl.sub.3, FeCl.sub.3, SbCl.sub.5 and SnCl.sub.4.

2. The meta-aramid polymer according to claim 1, wherein the organic solvent is one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP) and dimethylsulfoxide (DMSO); the neutralizing agent is one of ammonia, calcium hydroxide and calcium oxide; and the aqueous solvent comprises one of deionized water and a mixture of deionized water and a polymerization solvent.

3. The meta-aramid polymer according to claim 1, wherein a molar ratio of the MPD to the IPC is 1:(1-1.05); a molar equivalent ratio of the neutralizing agent to the IPC is 1:1; a molar ratio of a total mole of the alkylating agents in the polycondensation 1 and the polycondensation 2 to a mole of the MPD is (1-20):(180-199), and the alkylating agents are added in equal parts respectively in the processes of the polycondensation 1 and the polycondensation 2; and the addition amount of the metal halide accounts for 0.1-0.6 wt % of the mass of the whole reaction system.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The following describes the present disclosure in further detail with reference to the accompanying drawings.

(2) FIG. 1 is a flow diagram of a preparation process of the present disclosure;

(3) FIG. 2 is an SEM image of a coated separator of meta-aramid with a grid structure prepared in example 1;

(4) FIG. 3 is a photograph of a contact angle of an electrolyte of the coated separator of example 1; and

(5) FIG. 4 is a photograph of a contact angle of an electrolyte of a polyethylene separator of comparative example.

DETAILED DESCRIPTION

(6) The present disclosure will be described below with reference to the examples. The examples are only intended to explain the present disclosure, but not to limit the scope of the present disclosure.

Example 1

(7) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 196.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 189 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 196.5 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 695 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,246 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 125,000 m.Math.Pas, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 105,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(8) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(9) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 2

(10) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 8 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 14.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 151 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 14.5 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 701 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,316 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 121,000 mPa.Math.s, then the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 101,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(11) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(12) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 3

(13) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 8 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 289.3 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 213 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 289.3 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 712 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,446 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 135,000 mPa.Math.s, then the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 113,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(14) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(15) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 4

(16) 5.0 kg of MPD was dissolved in 89 kg of DMAc, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 120.2 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 149 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 120.2 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 595 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 1,846 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 101,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 85,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(17) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(18) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 5

(19) 15.9 kg of MPD was dissolved in 65 kg of DMAc, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 382.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 210 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 382.5 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 701 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,446 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 145,000 mPa.Math.s, then the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 120,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(20) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(21) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 6

(22) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 196.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 178 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 196.5 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 688 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,301 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 120,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 100,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(23) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(24) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 2:2:1:95, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 7

(25) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 196.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 201 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 196.5 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 699 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,312 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 130,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 109,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(26) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(27) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 8:6:8:78, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 8

(28) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 196.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 202 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 196.5 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 685 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,100 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 115,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 95,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(29) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(30) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 20% and a temperature was 5 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 9

(31) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 196.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 191 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 196.5 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 500 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,220 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 131,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 111,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(32) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(33) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 65% and a temperature was 45 C. The separator was taken out from the coagulating tank, washed with water at 45 C., and immediately dried at a temperature of 155 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 10

(34) 8.2 kg of MPD was dissolved in 82 kg of DMF, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 1,000 r/min, 232.7 g of methyl allyl chloride and 200 g of FeCl.sub.3 were added, wherein reaction time was 30 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 100 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 500 r/min, 232.7 g of the methyl allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 679 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,000 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 100,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 81,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(35) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(36) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMF according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMF), wherein the concentration of a bath solution was 65% and a temperature was 45 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 120 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 11

(37) 8.2 kg of MPD was dissolved in 82 kg of NMP, a temperature was kept at 10 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 10 C. in the process of polycondensation 1, wherein a stirring speed was 700 r/min, 196.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 60 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 300 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 30 C., wherein the stirring speed was 500 r/min, 196.5 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 669 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 42 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,009 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 50 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 120,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 81,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(38) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(39) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the NMP according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and NMP), wherein the concentration of a bath solution was 65% and a temperature was 45 C. The separator was taken out from the coagulating tank, washed with water at 65 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 12

(40) 8.2 kg of MPD was dissolved in 82 kg of DMSO, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 196.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 171 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 22 C., wherein the stirring speed was 600 r/min, 196.5 g of the allyl chloride was added, wherein the reaction time was 30 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 721 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 20 min and the system viscosity was 2,349 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 50 C., wherein the stirring speed was 120 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 150,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 130,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(41) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(42) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMSO according to the mass ratio of 5:3:5:87, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMSO), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 13

(43) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 196.5 g of allyl chloride and 200 g of AlCl.sub.3 were added, wherein reaction time was 45 min, then calcium hydroxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 178 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 10 C., wherein the stirring speed was 700 r/min, 196.5 g of the allyl chloride was added, wherein the reaction time was 45 min, then the calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 1,000 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 36 C., wherein the stirring speed was 220 r/min, the reaction time was 15 min and the system viscosity was 3,000 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 55 C., wherein the stirring speed was 80 r/min and the reaction was 25 min, the whole polycondensation was completed, the system viscosity reached 119,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 100,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(44) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(45) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, lithium chloride and the DMAc according to the mass ratio of 2:2:1:95, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using microgravure coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 14

(46) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 5 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 5 C. in the process of polycondensation 1, wherein a stirring speed was 800 r/min, 196.5 g of allyl chloride and 200 g of SnCl.sub.4 were added, wherein reaction time was 45 min, then ammonia was introduced to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 201 mPa.Math.s; then polycondensation 2 was performed after filtration, the reaction temperature was controlled at 10 C., wherein the stirring speed was 700 r/min, 196.5 g of allyl chloride was added, wherein the reaction time was 45 min, then calcium hydroxide was added to remove the hydrogen chloride produced by the reaction, wherein the system viscosity was 870 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 25 C., wherein the stirring speed was 350 r/min, the reaction time was 15 min and the system viscosity was 2,980 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 40 C., wherein the stirring speed was 200 r/min and the reaction was 10 min, the whole polycondensation was completed, the system viscosity reached 107,000 mPa.Math.s, the calcium hydroxide was added for neutralization, and a viscosity of a polymer solution was 90,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(47) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, then the polymer was washed for 3 times by using the deionized water, then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(48) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PVP, lithium chloride and the DMAc according to the mass ratio of 2:2:1:95, then the slurry was uniformly coated on a polyethylene separator with the thickness of 9 m by using slit type extrusion coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Example 15

(49) 8.2 kg of MPD was dissolved in 82 kg of DMAc, a temperature was kept at 0 C. after the complete dissolution, IPC was started to be added in stages for polycondensation, a reaction temperature was controlled at 8 C. in the process of polycondensation 1, wherein a stirring speed was 500 r/min, 196.5 g of 3-bromo-1-propene and 200 g of SbCl.sub.5 were added, wherein reaction time was 45 min, then calcium oxide was added to remove hydrogen chloride produced by the reaction, wherein a system viscosity was 170 mPa.Math.s; then polycondensation 2 was performed, the reaction temperature was controlled at 15 C., wherein the stirring speed was 700 r/min, 196.5 g of allyl chloride was added, wherein the reaction time was 45 min, then the calcium oxide was added to remove hydrogen chloride produced by the reaction, wherein the system viscosity was 801 mPa.Math.s; then the IPC was continuously added for polycondensation 3, the reaction temperature was controlled at 45 C., wherein the stirring speed was 200 r/min, the reaction time was 15 min and the system viscosity was 2,480 mPa.Math.s; then the last IPC was added for polycondensation 4, the reaction temperature was controlled at 45 C., wherein the stirring speed was 80 r/min and the reaction was 30 min, the whole polycondensation was completed, the system viscosity reached 100,000 mPa.Math.s, the calcium oxide was added for neutralization, and a viscosity of a polymer solution was 80,000 mPa.Math.s after the neutralization was completed so as to obtain a solution of a meta-aramid polymer with a grid structure.

(50) The prepared polymer solution after the polymerization was completed was mixed with deionized water, after the polymer was completely separated out, the polymer was washed for 3 times by using the deionized water and the DMAc (the mass ratio of the deionized water to the DMAc was 95%:5%), then the polymer was dried by using a fan to remove moisture, and an obtained solid polymer material was sealed at a dark place for later use.

(51) A coating slurry was prepared from the meta-aramid polymer with a grid structure, PEG, calcium chloride and the DMAc according to the mass ratio of 2:2:1:95, then the slurry was uniformly coated on a polypropylene separator with the thickness of 9 m by using comma roll coating, and then the separator was fed into a coagulating bath tank (a coagulating bath was a solution of water and DMAc), wherein the concentration of a bath solution was 45% and a temperature was 15 C. The separator was taken out from the coagulating tank, washed with water at 55 C., and immediately dried at a temperature of 145 C. The separator was rolled so as to obtain a meta-aramid coated polyethylene separator with the thickness of each of two coatings of 2 m.

Comparative Example

(52) The performance requirements of a commercial polyethylene separator product are as follows: the thickness of 13 m, the tensile strength MD160 MPa and TD160 MPa, an elongation rate MD100% and TD100%, a ventilation value of 17040 s/100 cc, the puncture strength5 N, a thermal shrinkage rate at 105 C. for 1 h MD3% and TD1.5%, and the porosity of 402%.

(53) TABLE-US-00001 TABLE 1 Comparison of performance data of separators in examples and comparative example Thermal Thermal shinkage Tensile shinkage rate rate % strength Elongation Ventilation Puncture % (105 C., (108 C., Fusing Thickness MPa % value strength 1 h) 1 h) Porosity temperature m MD TD MD TD s/100 cc N MD TD MD TD % C. Example 1 13 176 165 127 112 206 8.1 0 0 1.5 1.4 45 269 Example 2 13 165 159 121 105 215 7.0 0 0 2.7 2.5 44 261 Example 3 13 175 162 125 106 221 7.6 0 0 1.6 1.4 41 268 Example 4 13 162 158 118 105 211 7.1 0 0 2.4 2.1 43 264 Example 5 13 171 168 122 108 228 7.5 0 0 1.8 1.5 42 266 Example 6 13 160 154 116 104 209 7.2 0 0 2.8 2.7 44 256 Example 7 13 172 164 119 108 231 8.0 0 0 1.8 1.4 41 267 Example 8 13 163 158 120 109 221 7.8 0 0 2.5 2.1 43 258 Example 9 13 165 156 118 105 216 7.5 0 0 2.3 2.0 40 259 Example 13 168 159 119 106 220 7.6 0 0 2.2 1.9 42 256 10 Example 13 167 155 117 104 216 7.4 0 0 2.0 2.0 41 255 11 Example 13 172 166 119 108 211 7.0 0 0 2.4 2.2 42 261 12 Example 13 161 157 116 104 211 7.1 0 0 2.3 2.1 41 260 13 Example 13 164 159 117 106 213 7.3 0 0 2.2 1.8 42 263 14 Example 13 169 155 115 110 208 7.0 0 0 2.4 1.9 41 259 15 Comparative 13 168 163 120 110 195 5.5 1.7 1.0 ~ ~ 40 155 example Note: ~ indicated that the shrinkage was severe under the condition and cannot be measured. MD represents machine direction and TD represents transverse direction.

(54) Table 1 showed performance data of the separators of the examples and the comparative example. Test methods of the separator samples obtained in the examples and the comparative example were as follows: the thickness of the separator was tested according to GB/T6672-2001 Plastics film and sheetingDetermination of thickness by mechanical scanning; the tensile strength and the elongation rate were tested according to GB/T1040.3-2006 PlasticsDetermination of tensile properties; the ventilation value was tested according to GB/T1038-2000 PlasticsFilm and sheetingDetermination of gas transmissionDifferential-pressure method; the puncture strength was tested according to the operation according to the relevant regulations of the puncture strength in GB/T10004-2008 Plastic laminated films and pouches for packagingDry lamination and extrusion lamination; the thermal shrinkage rate was tested according to GB/T13519-2016 Polyethylene heat-shrinkable film for packaging applications; the porosity was tested according to GB/T6672-2001 Plastics film and sheetingDetermination of thickness by mechanical scanning; and the fusing temperature was tested by a TMA method.

(55) An alkane group was introduced among meta-aramid molecular chains to prepare a meta-aramid polymer with a grid structure. The polymer was used for preparing a slurry to be coated on the surface of a polyethylene separator so as to obtain a battery separator with the coating surface of a fine and dense nano-scale pore structure. The results of the examples showed that the preparation method improved the puncture strength of the separator by 20% or greater and greatly improved the fusing temperature of the separator. Under the condition of 180 C., a polyethylene base film was transparent and shrunk seriously. However, the meta-aramid coating with a grid structure prepared by the present disclosure still kept a good form and the thermal shrinkage rates in the transverse direction and the machine direction can be controlled within 3%. In addition, the surface of the coated separator of the meta-aramid with a grid structure obviously improved the wettability of an electrolyte. The separator is beneficial to prolonging a cycle life of a lithium battery.

(56) The above description is merely preferred examples of the present disclosure and is not intended to limit the present disclosure, and various changes and modifications may be made to the present disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present disclosure should be included within the protection scope of the present disclosure.