阅读说明：本技术 一种低面电阻的锂离子电池隔膜及制备方法 (Lithium ion battery diaphragm with low surface resistance and preparation method thereof ) 是由 赵洪亮 刘涛涛 沈亚定 于 2021-08-31 设计创作，主要内容包括：本发明公开了一种低面电阻的锂离子电池隔膜及制备方法,包括以下步骤：(1)制备微孔膜：取聚乙烯、致孔剂、辅料混合,挤出,纵向拉伸,一次横向拉伸,萃取,二次横向拉伸,得到微孔膜；(2)制备添加剂层：将电解液功能性添加剂涂在微孔膜表面,烘干,热定型,收卷,得到电池隔膜。本发明通过对锂离子电池隔膜中组分及其制备工艺的设置,能够提高隔膜的吸水性、耐碱性,便于锂离子通过隔膜的传输,从而降低电池卷绕后的内阻,提高电池的容量保持率和电池倍率放电性能。(The invention discloses a lithium ion battery diaphragm with low surface resistance and a preparation method thereof, and the lithium ion battery diaphragm comprises the following steps: (1) preparing a microporous membrane: mixing polyethylene, a pore-foaming agent and auxiliary materials, extruding, longitudinally stretching, transversely stretching for the first time, extracting, and transversely stretching for the second time to obtain a microporous membrane; (2) preparing an additive layer: and coating the functional additive of the electrolyte on the surface of the microporous membrane, drying, heat setting and rolling to obtain the battery diaphragm. According to the invention, through the arrangement of the components in the lithium ion battery diaphragm and the preparation process thereof, the water absorption and alkali resistance of the diaphragm can be improved, and the lithium ions can be conveniently transmitted through the diaphragm, so that the internal resistance of the battery after winding is reduced, and the capacity retention rate and the rate discharge performance of the battery are improved.)

1. A preparation method of a lithium ion battery diaphragm with low surface resistance is characterized by comprising the following steps: the method comprises the following steps:

(1) preparing a microporous membrane:

mixing polyethylene, a pore-foaming agent and auxiliary materials, extruding, longitudinally stretching, transversely stretching for the first time, extracting, and transversely stretching for the second time to obtain a microporous membrane;

(2) preparing an additive layer:

and coating the functional additive of the electrolyte on the surface of the microporous membrane, drying, heat setting and rolling to obtain the battery diaphragm.

2. The preparation method of the lithium ion battery separator with low sheet resistance according to claim 1, wherein the preparation method comprises the following steps: the functional additive of the electrolyte is vinylene carbonate.

3. The preparation method of the lithium ion battery separator with low sheet resistance according to claim 1, wherein the preparation method comprises the following steps: the polyethylene comprises ultrahigh molecular weight polyethylene resin and high density polyethylene, the pore-foaming agent is white oil, the auxiliary materials comprise polyvinyl alcohol, an antistatic agent, cotton pulp and light calcium carbonate, and the polyvinyl alcohol is polyhydroxy polyvinyl alcohol.

4. The preparation method of the lithium ion battery separator with low sheet resistance according to claim 3, wherein the preparation method comprises the following steps: the step (1) comprises the following processes:

a. mixing:

mixing an antistatic agent and ultra-high molecular weight polyethylene to obtain antistatic polyethylene resin;

pulping cotton pulp, wherein the pulping degree is 65-75 DEG SR;

mixing and dissolving antistatic polyethylene resin, high-density polyethylene resin, white oil, polyvinyl alcohol, boric acid ester, cotton pulp and light calcium carbonate to obtain a mixture;

b. extruding:

mixing the mixture with a pore-foaming agent white oil, and then extruding to obtain a molten extrusion sheet;

c. stretching:

longitudinally stretching the molten extruded sheet, wherein the process comprises the following steps: the temperature is 50-120 ℃, and the stretching ratio is 5-9;

carrying out once transverse stretching, and the process comprises the following steps: the temperature is 90-140 ℃, and the stretching ratio is 6-12, so that a film A is obtained;

d. and (3) extraction:

removing white oil in the film A by an extraction solution to obtain a film B;

e. secondary transverse stretching:

and (3) performing secondary transverse stretching on the film B, wherein the process comprises the following steps: and (3) obtaining the microporous membrane at the temperature of 120-140 ℃ and the stretching ratio of 1.2-2.0.

5. The preparation method of the lithium ion battery separator with low sheet resistance according to claim 3, wherein the preparation method comprises the following steps: the microporous membrane is prepared from the following components in percentage by weight: 68 to 78 percent of white oil, 10 to 15 percent of ultra-high molecular weight polyethylene, 10 to 15 percent of high density polyethylene, 0.1 to 0.5 percent of polyvinyl alcohol, 0.1 to 0.55 percent of antistatic agent, 0.5 to 1 percent of cotton pulp and 0.5 to 1 percent of light calcium carbonate.

6. The preparation method of the lithium ion battery separator with low sheet resistance according to claim 3, wherein the preparation method comprises the following steps: the weight average molecular weight of the ultra-high molecular weight polyethylene resin is 3 multiplied by 10⁶～5×10⁶High-density polyethylene resin weight average molecular weight of 5X 10⁵～8×10⁵(ii) a The molecular weight of the white oil is 300-1000.

7. The preparation method of the lithium ion battery separator with low sheet resistance according to claim 1, wherein the preparation method comprises the following steps: preparing the functional additive of the electrolyte into solution in the step (2), and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; the heat setting temperature is 70-100 ℃.

8. The preparation method of the lithium ion battery separator with low sheet resistance according to claim 1, wherein the preparation method comprises the following steps: the battery diaphragm has a thickness of 3-20 μm, a porosity of 40-60%, and a pore size distribution interval of 0.02-0.1 μm.

9. The preparation method of the lithium ion battery separator with low sheet resistance according to claim 2, wherein the preparation method comprises the following steps: the functional additive for the electrolyte also comprises vinylene carbonate modified polymer, and the preparation process of the modified polymer comprises the following steps:

drying trimethylolpropane to constant weight in a nitrogen atmosphere, heating to 75-80 ℃, adding anhydrous methanol and potassium methoxide, stirring and reacting for 30-50 min, vacuumizing to remove methanol, adding glycidol, reacting for 5-6 h, dissolving in anhydrous sodium methoxide, passing through a column, performing rotary evaporation, and drying at 60-80 ℃ for 12-24 h to obtain a product A;

taking toluene and pyridine, drying and dehydrating in sequence, adding the product A, mixing, heating to 30-40 ℃, slowly adding thionyl chloride, reacting for 24-36 hours at constant temperature, taking the upper layer solution after reaction, filtering, washing the lower layer solution by using toluene, mixing the two solutions, removing thionyl chloride and toluene by rotary evaporation, cooling, filtering, taking the filtrate, and distilling to obtain a product B;

in a nitrogen atmosphere, taking carbon disulfide, adding the product B and sodium hydroxide, mixing, adjusting the temperature of the system to 30-60 ℃, reacting for 1-8 h, filtering, distilling, washing and drying to obtain a product C;

dissolving the product C in tetrahydrofuran, adding methyl iodide, stirring at room temperature for reaction for 15h, filtering, washing with deionized water, filtering, and drying the precipitate; heating to 200-250 ℃ for reaction to obtain a product D;

taking two or more of vinylene carbonate, 2- (allyloxy) -1H-benzimidazole, acrylonitrile, acrylamide, acrylic acid, styrene, butadiene, ethylene, vinylidene fluoride, tetrafluoroethylene and trifluoroethylene as monomers, adding an initiator dibenzoyl peroxide, and mixing to obtain a monomer solution;

and in a nitrogen atmosphere, taking the product D, heating to 118-125 ℃, slowly adding the monomer solution, and reacting for 1-3 hours to obtain the modified polymer.

10. A low sheet resistance lithium ion battery separator made by the method of any one of claims 1-9.

Technical Field

The invention relates to the technical field of battery diaphragms, in particular to a lithium ion battery diaphragm with low surface resistance and a preparation method thereof.

Background

The lithium ion battery is composed of four parts, namely a positive electrode material, a negative electrode material, a diaphragm and electrolyte. The diaphragm is an important component of the lithium battery and plays a role in isolating the positive electrode and the negative electrode of the battery and preventing the two electrodes from contacting and short-circuiting; in addition, the electrolyte has the functions of preventing electron conduction and enabling electrolyte ions to freely pass between the positive electrode and the negative electrode; and when the battery is overheated, the current conduction in the battery can be prevented through the closed hole function, so that the safety of the battery is realized. The size of the surface resistance of the diaphragm is directly related to the size and rate capability of the internal resistance of the lithium battery. The higher the surface resistance of the diaphragm is, the higher the internal resistance of the lithium battery is, so that large-current discharge is blocked, the internal resistance is increased, the self heat loss is increased, the temperature of the battery is increased in use, and the performance deterioration of the battery is aggravated. Therefore, the lithium ion battery separator with low sheet resistance and the preparation method are provided.

Disclosure of Invention

The invention aims to provide a lithium ion battery diaphragm with low surface resistance and a preparation method thereof, so as to solve the problems in the background technology.

In order to solve the technical problems, the invention provides the following technical scheme: a preparation method of a lithium ion battery diaphragm with low surface resistance comprises the following steps:

(1) preparing a microporous membrane:

mixing polyethylene, a pore-foaming agent and auxiliary materials, extruding, stretching, extracting and stretching for the second time to obtain a microporous membrane;

(2) preparing an additive layer:

and coating the functional additive of the electrolyte on the surface of the microporous membrane, drying, heat setting and rolling to obtain the battery diaphragm.

Further, the functional additive of the electrolyte is vinylene carbonate.

Further, the polyethylene comprises ultrahigh molecular weight polyethylene resin and high density polyethylene, the pore-foaming agent is white oil, the auxiliary materials comprise polyvinyl alcohol, an antistatic agent, cotton pulp and light calcium carbonate, and the polyvinyl alcohol is polyhydroxy polyvinyl alcohol.

In the technical scheme, the polyhydroxy polyvinyl alcohol has good hydrophilicity, so that the surface resistance of the prepared battery diaphragm in the electrolyte is reduced; the antistatic agent adopts boric acid ester, and the boric acid ester is added into the polyethylene resin to prepare the antistatic polyethylene resin so as to achieve the purpose of reducing the surface resistance of the prepared battery diaphragm; the cotton pulp is a porous position, has good hydrophilic and liquid-retaining properties and alkali resistance, and can reduce the surface resistance of the prepared battery diaphragm in an electrolyte; the light calcium carbonate is coated on the surface of the polyethylene, so that the hydrophilic property of the polyethylene can be improved, the phenomenon of uneven mixing of cotton pulp can be improved during mixing, and the conductivity of the prepared battery diaphragm is improved;

further, the microporous membrane is prepared from the following components in percentage by weight: 68 to 78 percent of white oil, 10 to 15 percent of ultra-high molecular weight polyethylene, 10 to 15 percent of high density polyethylene, 0.1 to 0.5 percent of polyvinyl alcohol, 0.1 to 0.55 percent of antistatic agent, 0.5 to 1 percent of cotton pulp and 0.5 to 1 percent of light calcium carbonate.

Further, the step (1) comprises the following processes:

a. mixing:

mixing an antistatic agent and ultra-high molecular weight polyethylene to obtain antistatic polyethylene resin;

pulping cotton pulp, wherein the pulping degree is 65-75 DEG SR;

mixing and dissolving antistatic polyethylene resin, high-density polyethylene resin, white oil, polyvinyl alcohol, boric acid ester, cotton pulp and light calcium carbonate to obtain a mixture;

b. extruding:

mixing the mixture with pore-foaming agent white oil, and then extruding, wherein the rotating speed of an extrusion screw is 35-42 rpm, so as to obtain a molten state extrusion sheet;

c. stretching:

longitudinally stretching the molten extruded sheet, wherein the process comprises the following steps: the temperature is 50-120 ℃, and the stretching ratio is 5-9; carrying out once transverse stretching, and the process comprises the following steps: the temperature is 90-140 ℃, and the stretching ratio is 6-12, so that a film A is obtained;

d. and (3) extraction:

removing white oil in the film A by an extraction solution to obtain a film B;

e. and (3) secondary stretching:

and (3) performing secondary transverse stretching on the film B, wherein the process comprises the following steps: and (3) obtaining the microporous membrane at the temperature of 120-140 ℃ and the stretching ratio of 1.2-2.0.

Further, the ultra-high molecular weight polyethyleneThe weight average molecular weight of the olefin resin is 3X 10⁶～5×10⁶High-density polyethylene resin weight average molecular weight of 5X 10⁵～8×10⁵(ii) a The molecular weight of the white oil is 300-1000.

Further, the functional additive of the electrolyte in the step (2) is prepared into a solution and sprayed on the surface of the microporous membrane in a mist form to form a thin film layer; the heat setting temperature is 70-100 ℃.

Furthermore, the thickness of the battery diaphragm is 3-20 μm, the porosity is 40-60%, and the pore size distribution interval is 0.02-0.1 μm.

In the technical scheme, the antistatic agent is mixed with the ultra-high molecular weight polyethylene to prepare the antistatic polyethylene resin; beating, wherein the beating degree of the cotton pulp is about 70 degrees SR, so that the cotton pulp has optimal lyophilic and liquid-retaining property; the super-high molecular weight polyethylene resin, the high-density polyethylene resin, the white oil and the additive are mixed, so that the water absorption and alkali resistance of the prepared battery diaphragm can be improved; mixing and dissolving antistatic polyethylene resin, high-density polyethylene resin, white oil, polyvinyl alcohol, boric acid ester, cotton pulp and light calcium carbonate, and obtaining a polyethylene microporous membrane by using the operations;

the preparation method is characterized in that production and preparation are carried out through related processes, and an electrolyte functional additive is sprayed on the surface of the diaphragm in the form of a thin film layer at a 2TD outlet through a newly added mist spraying process, so that the porosity of the prepared battery diaphragm is improved, the hydrophilicity and the liquid retention performance are good, the electric conductivity is enhanced, and the thermal shrinkage is reduced; the prepared battery diaphragm can obviously reduce the lithium removal potential of lithium ions in the battery and reduce the irreversible specific capacity generated by the reduction and decomposition of silver electrolyte, thereby achieving the effect of reducing the surface resistance when in use, and improving the initial discharge capacity and the cycling stability of the battery; the surface resistance of the diaphragm is reduced, and the stability and safety of the diaphragm are improved;

the battery diaphragm prepared by the process has the thickness of 3-20 mu m, the porosity of more than or equal to 40%, the pore size distribution interval of 0.02-0.1 mu m and the tensile strength of more than 2000;

further, the functional additive for the electrolyte also comprises vinylene carbonate modified polymer, and the preparation process of the modified polymer is as follows:

drying trimethylolpropane to constant weight in a nitrogen atmosphere, heating to 75-80 ℃, adding anhydrous methanol and potassium methoxide, stirring and reacting for 30-50 min, vacuumizing to remove methanol, adding glycidol, reacting for 5-6 h, dissolving in anhydrous sodium methoxide, passing through a column, performing rotary evaporation, and drying at 60-80 ℃ for 12-24 h to obtain a product A;

taking toluene and pyridine, drying and dehydrating in sequence, adding the product A, mixing, heating to 30-40 ℃, slowly adding thionyl chloride, reacting for 24-36 hours at constant temperature, taking the upper layer solution after reaction, filtering, washing the lower layer solution by using toluene, mixing the two solutions, removing thionyl chloride and toluene by rotary evaporation, cooling, filtering, taking the filtrate, and distilling to obtain a product B;

in a nitrogen atmosphere, taking carbon disulfide, adding the product B and sodium hydroxide, mixing, adjusting the temperature of the system to 30-60 ℃, reacting for 1-8 h, filtering, distilling, washing and drying to obtain a product C;

dissolving the product C in tetrahydrofuran, adding methyl iodide, stirring at room temperature for reaction for 15h, filtering, washing with deionized water, filtering, and drying the precipitate; heating to 200-250 ℃ for reaction to obtain a product D;

taking two or more of vinylene carbonate, 2- (allyloxy) -1H-benzimidazole, acrylonitrile, acrylamide, acrylic acid, styrene, butadiene, ethylene, vinylidene fluoride, tetrafluoroethylene and trifluoroethylene as monomers, adding an initiator dibenzoyl peroxide, and mixing to obtain a monomer solution;

and in a nitrogen atmosphere, taking the product D, heating to 118-125 ℃, slowly adding the monomer solution, and reacting for 1-3 hours to obtain the modified polymer.

In the technical scheme, potassium methoxide is utilized to react trimethylolpropane and glycidol to obtain hyperbranched polyglycidyl glycerol; chlorinating the mixture by using thionyl chloride to obtain chlorinated polyglycidyl glycerol; then utilizing elimination reaction to obtain hyperbranched polymer (product D) with double bonds at the end, and polymerizing the hyperbranched polymer with monomers containing vinylene carbonate, benzimidazole, acrylic acid and the like to obtain vinylene carbonate modified polymer;

the introduced hyperbranched structure enables the prepared final product to have better mechanical property, flexibility, lower viscosity and higher cohesiveness; introducing halogen to enable subsequent elimination reaction to occur, introducing a carbon-carbon double bond at the end of the hyperbranched polyglycidyl, and then copolymerizing the carbon-carbon double bond with vinylene carbonate, 2- (allyloxy) -1H-benzimidazole, acrylic acid and other monomers to obtain a high polymer with vinylene carbonate, polybenzimidazole and the like, so that the cohesiveness between the prepared electrolyte functional additive film layer and a polyethylene microporous membrane can be improved, the transmission of lithium ions in the prepared battery diaphragm is promoted, the thermal stability and the chemical stability of the lithium ion battery are improved, and after the hyperbranched polyglycidyl is applied to a lithium ion battery, the electrochemical impedance can be reduced, the cycle performance of the battery is improved, and the safety and the stability of the battery are ensured;

compared with the prior art, the invention has the following beneficial effects:

according to the lithium ion battery diaphragm with low sheet resistance and the preparation method thereof, the components in the lithium ion battery diaphragm and the preparation process thereof are arranged, so that the water absorption and alkali resistance of the diaphragm can be improved, and the lithium ions can be conveniently transmitted through the diaphragm, so that the internal resistance of the wound battery is reduced, and the capacity retention rate and the rate discharge performance of the battery are improved.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

(1) Preparing a microporous membrane:

a. mixing:

mixing an antistatic agent and ultra-high molecular weight polyethylene to obtain antistatic polyethylene resin;

pulping cotton pulp with a pulping degree of 65 DEG SR;

mixing and dissolving antistatic polyethylene resin, high-density polyethylene resin, white oil, polyvinyl alcohol, boric acid ester, cotton pulp and light calcium carbonate to obtain a mixture; the weight average molecular weight of the ultra-high molecular weight polyethylene resin is 3000000, and the weight average molecular weight of the high density polyethylene resin is 600000; the molecular weight of the white oil is 500;

the mass ratio of white oil to ultrahigh molecular weight polyethylene resin to high density polyethylene resin to polyvinyl alcohol to boric acid ester to cotton pulp to light calcium carbonate is 7.8:1.0:1.0:0.02:0.02:0.06: 0.06;

b. extruding:

mixing the mixture with pore-foaming agent white oil, and extruding at the rotating speed of an extrusion screw of 40rpm to obtain a molten state extrusion sheet;

c. stretching:

longitudinally stretching the molten extruded sheet, wherein the process comprises the following steps: the temperature is 110 ℃, and the stretching ratio is 8.0; carrying out once transverse stretching, and the process comprises the following steps: the temperature is 130 ℃, and the stretching ratio is 11.3, so that a film A is obtained;

d. and (3) extraction:

removing white oil in the film A by an extraction solution to obtain a film B;

e. and (3) secondary stretching:

and (3) performing secondary transverse stretching on the film B, wherein the process comprises the following steps: the temperature is 130 ℃, and the stretching ratio is 1.7, so that a microporous membrane is obtained;

(2) preparing an additive layer:

preparing the functional additive of the electrolyte into solution, and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; and drying, heat setting at 100 ℃, and rolling to obtain the battery diaphragm with the thickness of 20 microns.

Example 2

(1) Preparing a microporous membrane:

a. mixing:

mixing an antistatic agent and ultra-high molecular weight polyethylene to obtain antistatic polyethylene resin;

pulping cotton pulp with a pulping degree of 70 DEG SR;

mixing and dissolving antistatic polyethylene resin, high-density polyethylene resin, white oil, polyvinyl alcohol, boric acid ester, cotton pulp and light calcium carbonate to obtain a mixture; the weight average molecular weight of the ultra-high molecular weight polyethylene resin is 3000000, and the weight average molecular weight of the high density polyethylene resin is 600000; the molecular weight of the white oil is 500;

the mass ratio of white oil to the ultrahigh molecular weight polyethylene resin to the high density polyethylene resin to the polyvinyl alcohol to the boric acid ester to the cotton pulp to the light calcium carbonate is 7.8:1.0:1.0:0.03:0.03:0.06: 0.06;

b. extruding:

mixing the mixture with pore-foaming agent white oil, and extruding at the rotating speed of an extrusion screw of 40rpm to obtain a molten state extrusion sheet;

c. stretching:

longitudinally stretching the molten extruded sheet, wherein the process comprises the following steps: the temperature is 110 ℃, and the stretching ratio is 8.0; carrying out once transverse stretching, and the process comprises the following steps: the temperature is 130 ℃, and the stretching ratio is 11.3, so that a film A is obtained;

d. and (3) extraction:

removing white oil in the film A by an extraction solution to obtain a film B;

e. and (3) secondary stretching:

and (3) performing secondary transverse stretching on the film B, wherein the process comprises the following steps: the temperature is 130 ℃, and the stretching ratio is 1.7, so that a microporous membrane is obtained;

(2) preparing an additive layer:

preparing the functional additive of the electrolyte into solution, and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; and drying, heat setting at 100 ℃, and rolling to obtain the battery diaphragm with the thickness of 20 microns.

Example 3

(1) Preparing a microporous membrane:

a. mixing:

mixing an antistatic agent and ultra-high molecular weight polyethylene to obtain antistatic polyethylene resin;

pulping cotton pulp with a pulping degree of 75 DEG SR;

mixing and dissolving antistatic polyethylene resin, high-density polyethylene resin, white oil, polyvinyl alcohol, boric acid ester, cotton pulp and light calcium carbonate to obtain a mixture; the weight average molecular weight of the ultra-high molecular weight polyethylene resin is 3000000, and the weight average molecular weight of the high density polyethylene resin is 600000; the molecular weight of the white oil is 500;

the mass ratio of white oil to ultrahigh molecular weight polyethylene resin to high density polyethylene resin to polyvinyl alcohol to boric acid ester to cotton pulp to light calcium carbonate is 7.8:1.0:1.0:0.01:0.01:0.08: 0.08;

b. extruding:

mixing the mixture with pore-foaming agent white oil, and extruding at the rotating speed of an extrusion screw of 40rpm to obtain a molten state extrusion sheet;

c. stretching:

longitudinally stretching the molten extruded sheet, wherein the process comprises the following steps: the temperature is 110 ℃, and the stretching ratio is 8.0; carrying out once transverse stretching, and the process comprises the following steps: the temperature is 130 ℃, and the stretching ratio is 11.3, so that a film A is obtained;

d. and (3) extraction:

removing white oil in the film A by an extraction solution to obtain a film B;

e. and (3) secondary stretching:

and (3) performing secondary transverse stretching on the film B, wherein the process comprises the following steps: the temperature is 130 ℃, and the stretching ratio is 1.7, so that a microporous membrane is obtained;

(2) preparing an additive layer:

preparing the functional additive of the electrolyte into solution, and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; and drying, heat setting at 100 ℃, and rolling to obtain the battery diaphragm, wherein the thickness of the battery diaphragm is 20 microns.

Example 4

Step (1) is the same as in example 2;

(2) preparing an additive layer:

drying trimethylolpropane to constant weight in nitrogen atmosphere, heating to 75 ℃, adding anhydrous methanol and potassium methoxide, stirring and reacting for 30min, vacuumizing to remove methanol, adding glycidol, reacting for 5h, dissolving in anhydrous sodium methoxide, passing through a column, performing rotary evaporation, and drying at 60 ℃ for 12h to obtain a product A;

taking toluene and pyridine, drying and dehydrating in sequence, adding the product A, mixing, heating to 30 ℃, slowly adding thionyl chloride, reacting at constant temperature for 24 hours, taking the upper solution after reaction, filtering, washing the lower solution by using toluene, mixing the two solutions, removing thionyl chloride and toluene by rotary evaporation, cooling, filtering, taking filtrate, and distilling to obtain a product B;

in a nitrogen atmosphere, taking carbon disulfide, adding the product B and sodium hydroxide, mixing, adjusting the temperature of the system to 30 ℃, reacting for 1h, filtering, distilling, washing and drying to obtain a product C;

dissolving the product C in tetrahydrofuran, adding methyl iodide, stirring at room temperature for reaction for 15h, filtering, washing with deionized water, filtering, and drying the precipitate; heating to 225 ℃ for reaction to obtain a product D;

taking vinylene carbonate, 2- (allyloxy) -1H-benzimidazole, methacrylic acid and styrene as monomers, adding an initiator dibenzoyl peroxide, and mixing to obtain a monomer solution;

taking the product D, heating to 118 ℃ in a nitrogen atmosphere, slowly adding a monomer solution, reacting for 1h to obtain a modified polymer, and adding vinylene carbonate serving as an electrolyte functional additive;

preparing into solution, and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; and drying, heat setting at 100 ℃, and rolling to obtain the battery diaphragm with the thickness of 20 microns.

Example 5

Step (1) is the same as in example 2;

(2) preparing an additive layer:

drying trimethylolpropane to constant weight in nitrogen atmosphere, heating to 78 ℃, adding anhydrous methanol and potassium methoxide, stirring and reacting for 40min, vacuumizing to remove methanol, adding glycidol, reacting for 5.5h, dissolving in anhydrous sodium methoxide, passing through a column, performing rotary evaporation, and drying at 70 ℃ for 18h to obtain a product A;

taking toluene and pyridine, drying and dehydrating in sequence, adding the product A, mixing, heating to 35 ℃, slowly adding thionyl chloride, reacting at constant temperature for 32 hours, taking the upper solution after reaction, filtering, washing the lower solution by using toluene, mixing the two solutions, removing thionyl chloride and toluene by rotary evaporation, cooling, filtering, taking filtrate, and distilling to obtain a product B;

in a nitrogen atmosphere, taking carbon disulfide, adding the product B and sodium hydroxide, mixing, adjusting the temperature of the system to 45 ℃, reacting for 4 hours, filtering, distilling, washing and drying to obtain a product C;

dissolving the product C in tetrahydrofuran, adding methyl iodide, stirring at room temperature for reaction for 15h, filtering, washing with deionized water, filtering, and drying the precipitate; heating to 225 ℃ for reaction to obtain a product D;

taking vinylene carbonate, 2- (allyloxy) -1H-benzimidazole, acrylic acid, styrene and tetrafluoroethylene as monomers, adding an initiator dibenzoyl peroxide, and mixing to obtain a monomer solution;

taking the product D in a nitrogen atmosphere, heating to 120 ℃, slowly adding a monomer solution, reacting for 2 hours to obtain a modified polymer, and adding vinylene carbonate serving as an electrolyte functional additive;

preparing into solution, and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; and drying, heat setting at 100 ℃, and rolling to obtain the battery diaphragm with the thickness of 20 microns.

Example 6

Step (1) is the same as in example 2;

(2) preparing an additive layer:

drying trimethylolpropane to constant weight in nitrogen atmosphere, heating to 80 ℃, adding anhydrous methanol and potassium methoxide, stirring and reacting for 50min, vacuumizing to remove methanol, adding glycidol, reacting for 6h, dissolving in anhydrous sodium methoxide, passing through a column, performing rotary evaporation, and drying at 80 ℃ for 24h to obtain a product A;

taking toluene and pyridine, drying and dehydrating in sequence, adding the product A, mixing, heating to 40 ℃, slowly adding thionyl chloride, reacting at a constant temperature for 36 hours, taking an upper layer solution after reaction, filtering, washing a lower layer solution by using toluene, mixing the two solutions, removing thionyl chloride and toluene by rotary evaporation, cooling, filtering, taking filtrate, and distilling to obtain a product B;

in a nitrogen atmosphere, taking carbon disulfide, adding the product B and sodium hydroxide, mixing, adjusting the temperature of the system to 60 ℃, reacting for 8 hours, filtering, distilling, washing and drying to obtain a product C;

dissolving the product C in tetrahydrofuran, adding methyl iodide, stirring at room temperature for reaction for 15h, filtering, washing with deionized water, filtering, and drying the precipitate; heating to 250 ℃ for reaction to obtain a product D;

taking vinylene carbonate, 2- (allyloxy) -1H-benzimidazole, acrylic acid, styrene and tetrafluoroethylene as monomers, adding an initiator dibenzoyl peroxide, and mixing to obtain a monomer solution;

taking a product D, heating to 125 ℃ in a nitrogen atmosphere, slowly adding a monomer solution, reacting for 3 hours to obtain a modified polymer, and adding vinylene carbonate serving as an electrolyte functional additive;

preparing into solution, and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; and drying, heat setting at 100 ℃, and rolling to obtain the battery diaphragm with the thickness of 20 microns.

Comparative example 1

(1) Preparing a microporous membrane:

a. mixing:

mixing and dissolving ultra-high molecular weight polyethylene resin, high-density polyethylene resin and white oil to obtain a mixture; the weight average molecular weight of the ultra-high molecular weight polyethylene resin is 3000000, and the weight average molecular weight of the high density polyethylene resin is 600000; the molecular weight of the white oil is 500; the ratio of white oil to the ultrahigh molecular weight polyethylene resin to the high density polyethylene resin is 7.8:1.1: 1.1;

b. extruding:

mixing the mixture with pore-foaming agent white oil, and extruding at the rotating speed of an extrusion screw of 40rpm to obtain a molten state extrusion sheet;

c. stretching:

longitudinally stretching the molten extruded sheet, wherein the process comprises the following steps: the temperature is 110 ℃, and the stretching ratio is 8.0; carrying out once transverse stretching, and the process comprises the following steps: the temperature is 130 ℃, and the stretching ratio is 11.3, so that a film A is obtained;

d. and (3) extraction:

removing white oil in the film A by an extraction solution to obtain a film B;

e. and (3) secondary stretching:

and (3) performing secondary transverse stretching on the film B, wherein the process comprises the following steps: the temperature is 130 ℃, and the stretching ratio is 1.7, so that a microporous membrane is obtained;

(2) preparing an additive layer:

preparing the functional additive of the electrolyte into solution, and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; and drying, heat setting at 100 ℃, and rolling to obtain the battery diaphragm with the thickness of 20 microns.

Comparative example 2

a. Mixing:

mixing and dissolving ultra-high molecular weight polyethylene resin, high-density polyethylene resin and white oil to obtain a mixture; the weight average molecular weight of the ultra-high molecular weight polyethylene resin is 3000000, and the weight average molecular weight of the high density polyethylene resin is 600000; the molecular weight of the white oil is 500; the ratio of white oil to the ultrahigh molecular weight polyethylene resin to the high density polyethylene resin is 7.8:1.1: 1.1;

b. extruding:

mixing the mixture with pore-foaming agent white oil, and extruding at the rotating speed of an extrusion screw of 40rpm to obtain a molten state extrusion sheet;

c. stretching:

longitudinally stretching the molten extruded sheet, wherein the process comprises the following steps: the temperature is 110 ℃, and the stretching ratio is 8.0; carrying out once transverse stretching, and the process comprises the following steps: the temperature is 130 ℃, and the stretching ratio is 11.3, so that a film A is obtained;

d. and (3) extraction:

removing white oil in the film A by an extraction solution to obtain a film B;

e. and (3) secondary stretching:

and (3) performing secondary transverse stretching on the film B, wherein the process comprises the following steps: the temperature is 130 ℃, the stretching ratio is 1.7, and the microporous membrane is obtained as a battery diaphragm.

Comparative example 3

Step (1) was the same as in example 5;

(2) preparing an additive layer:

taking toluene and pyridine, drying and dehydrating in sequence, adding polyglycidyl into the mixture, mixing the mixture, heating the mixture to 35 ℃, slowly adding thionyl chloride, reacting the mixture at a constant temperature for 32 hours, taking an upper layer solution after reaction, filtering the upper layer solution, washing a lower layer solution by using the toluene, mixing the two solutions, removing the thionyl chloride and the toluene by rotary evaporation, cooling the solution, filtering the solution, taking filtrate, and distilling the filtrate to obtain a product A;

in a nitrogen atmosphere, taking carbon disulfide, adding the product A and sodium hydroxide, mixing, adjusting the temperature of the system to 45 ℃, reacting for 4 hours, filtering, distilling, washing and drying to obtain a product B;

dissolving the product B in tetrahydrofuran, adding methyl iodide, stirring at room temperature for reaction for 15h, filtering, washing with deionized water, filtering, and drying the precipitate; heating to 225 ℃ for reaction to obtain a product C;

taking vinylene carbonate, 2- (allyloxy) -1H-benzimidazole, acrylic acid, styrene and tetrafluoroethylene as monomers, adding an initiator dibenzoyl peroxide, and mixing to obtain a monomer solution;

taking the product C, heating to 120 ℃ in a nitrogen atmosphere, slowly adding a monomer solution, reacting for 2 hours to obtain a modified polymer, and adding vinylene carbonate serving as an electrolyte functional additive;

preparing into solution, and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; and drying, heat setting at 100 ℃, and rolling to obtain the battery diaphragm with the thickness of 20 microns.

Comparative example 4

Step (1) was the same as in example 5;

(2) preparing an additive layer:

taking toluene and pyridine, drying and dehydrating in sequence, adding polyglycidyl into the mixture, mixing the mixture, heating the mixture to 35 ℃, slowly adding thionyl chloride, reacting the mixture at a constant temperature for 32 hours, taking an upper layer solution after reaction, filtering the upper layer solution, washing a lower layer solution by using the toluene, mixing the two solutions, removing the thionyl chloride and the toluene by rotary evaporation, cooling the solution, filtering the solution, taking filtrate, and distilling the filtrate to obtain a product A;

in a nitrogen atmosphere, taking carbon disulfide, adding the product A and sodium hydroxide, mixing, adjusting the temperature of the system to 45 ℃, reacting for 4 hours, filtering, distilling, washing and drying to obtain a product B;

dissolving the product B in tetrahydrofuran, adding methyl iodide, stirring at room temperature for reaction for 15h, filtering, washing with deionized water, filtering, and drying the precipitate; heating to 225 ℃ for reaction to obtain a product C;

taking vinylene carbonate, acrylic acid, styrene and tetrafluoroethylene as monomers, adding an initiator dibenzoyl peroxide, and mixing to obtain a monomer solution;

taking the product C, heating to 120 ℃ in a nitrogen atmosphere, slowly adding a monomer solution, reacting for 2 hours to obtain a modified polymer, and adding vinylene carbonate serving as an electrolyte functional additive;

preparing into solution, and spraying the solution on the surface of the microporous membrane in a mist form to form a thin film layer; and drying, heat setting at 100 ℃, and rolling to obtain the battery diaphragm with the thickness of 20 microns.

Experiment of

The battery separators obtained in examples 1 to 6 and comparative examples 1 to 4 were used to prepare samples, and the performance thereof was measured and the measurement results were recorded:

measuring the area resistance of the test sample according to the standard SJ/T10171.5-1991 in the electronic industry;

from the data in the table above, it is clear that the following conclusions can be drawn:

the battery separators obtained in examples 1 to 6 were compared with the battery separators obtained in comparative examples 1 to 4, and it was found that,

compared with a comparative example 2, the battery diaphragm obtained in the examples 1 to 6 has obviously better comprehensive experimental data, which fully shows that the invention realizes the reduction of the surface resistance of the manufactured battery diaphragm and promotes the improvement of the bonding strength between the thin film layer and the microporous film, the mechanical property of the diaphragm and the battery performance;

the battery separator obtained in comparative examples 1-2 was significantly deteriorated in the comprehensive experimental data, compared to example 2; the battery separators obtained in comparative examples 3 to 4 were significantly deteriorated in the comprehensive experimental data, as compared with example 5; it can be known that the microporous film, the components of the film layer and the preparation process thereof can reduce the surface resistance of the battery diaphragm, and promote the bonding strength between the film layer and the microporous film, the mechanical property of the diaphragm and the battery performance.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process method article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process method article or apparatus.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.