阅读说明：本技术 一种低水分耐高温高剥离强度的涂覆浆料及其应用 (Coating slurry with low moisture, high temperature resistance and high peel strength and application thereof ) 是由 裴海乐 尚文滨 陈朝晖 于 2021-08-02 设计创作，主要内容包括：本发明公开了一种低水分耐高温高剥离强度的涂覆浆料及其应用。涂覆浆料的原料包括以下成分：按重量计,30～60份溶剂、0.5～5份分散剂、20～50份陶瓷材料、1～10份增稠剂、2～10份粘结剂a、3～12份粘结剂b、0.05～0.1份润湿剂。有益效果：(1)制备涂覆浆料体系同时满足低水分、耐高温、高强度要求,且浆料体系稳定,浆料保质期长,使用过程中的浆料气泡少。(2)粘结剂a使用没质子酸进行改性,使得粘性强度更为持久,从而增强了锂电池隔膜的使用寿命；(3)利用锂电池隔膜的中硼原子的缺电子效应,促进锂离子传导,弥补涂层覆盖造成离子传导率降低的问题,从而增加锂电池隔膜在电池使用过程中的稳定性和电容量。(The invention discloses a coating slurry with low moisture, high temperature resistance and high peel strength and application thereof. The raw materials of the coating slurry comprise the following components: 30-60 parts of solvent, 0.5-5 parts of dispersing agent, 20-50 parts of ceramic material, 1-10 parts of thickening agent, 2-10 parts of binder a, 3-12 parts of binder b and 0.05-0.1 part of wetting agent. Has the advantages that: (1) the prepared coating slurry system simultaneously meets the requirements of low moisture, high temperature resistance and high strength, and has the advantages of stable slurry system, long slurry shelf life and less slurry bubbles in the using process. (2) The adhesive a is modified by using aprotic acid, so that the adhesive strength is more durable, and the service life of the lithium battery diaphragm is prolonged; (3) the lithium ion conduction is promoted by utilizing the electron deficiency effect of the boron atoms in the lithium battery diaphragm, and the problem of reduction of the ionic conductivity caused by coating coverage is solved, so that the stability and the electric capacity of the lithium battery diaphragm in the use process of the battery are improved.)

1. The coating slurry with low moisture, high temperature resistance and high peel strength is characterized in that: the raw materials of the coating slurry comprise the following components: 30-60 parts of solvent, 0.5-5 parts of dispersing agent, 20-50 parts of ceramic material, 1-10 parts of thickening agent, 2-10 parts of binder a, 3-12 parts of binder b and 0.05-0.1 part of wetting agent.

2. The coating slurry with low moisture, high temperature resistance and high peel strength according to claim 1, wherein: the binder a is a modified polyacrylic acid aqueous binder; the binder b is a modified fluorine acrylic acid aqueous binder.

3. The coating slurry with low moisture, high temperature resistance and high peel strength according to claim 1, wherein: the solvent is water; the dispersing agent is one or more mixed solvents of methanol, propanol, n-butanol, isopropanol, ethylene glycol, methyl ether, diethyl ether, propylene glycol, glycerol, propanol and butanone; the ceramic material is one or a mixture of more of aluminum oxide, titanium dioxide, boehmite, magnesium dioxide or magnesium hydroxide; the thickening agent is at least one of carboxymethyl cellulose amine or sodium carboxymethyl cellulose; the wetting agent is an alcohol or siloxane product.

4. The coating slurry with low moisture, high temperature resistance and high peel strength according to claim 3, wherein: the dispersant is at least one of isopropanol, butanone and methyl ether; the ceramic material is at least one of aluminum trioxide or boehmite.

5. A lithium ion battery separator, characterized in that: uniformly coating the coating slurry of any one of claims 1 to 4 on a base film, and baking to obtain a finished product.

6. The lithium ion battery separator according to claim 5, wherein: the preparation process comprises the following steps:

step 1: (1) placing the solvent, the dispersing agent and the ceramic material in a stirrer, and stirring for 5-15 minutes at a set rotating speed of 1000-1800 r/min to obtain an A1 solution; (2) adding the thickening agent into the A1 solution, and stirring for 1-2 hours at a rotation speed of 800-1500 r/min; obtaining a B2 solution; (3) adding the binder a into the B2 solution, and stirring for 0.5-1 hour at the set rotating speed of 800-1000 r/min to obtain a C3 solution; (4) grinding the solution C3 by a grinder to obtain a C3-1 solution; (5) standing the C3-1 for 10-15 minutes, adding a binder b, and stirring at a rotation speed of 30-100 r/min for 0.5-2 hours to obtain a D4 solution; (6) adding a wetting agent into the D4 solution, and stirring for 5-10 minutes at a set rotating speed of 30-80r/min to obtain coating slurry;

step 2: and uniformly coating the coating slurry on the base film, and baking for 2-6 minutes at the set temperature of 65-80 ℃ to obtain the lithium battery diaphragm.

7. The lithium ion battery separator according to claim 6, wherein: in the step 2, the coating mode is gravure roll coating, the number of gravure rolls is 80-140, and the operating speed ratio of the gravure rolls is 80% -98%.

8. The lithium ion battery separator according to claim 6, wherein: in the step (6) of the step 1, sequentially adding a wetting agent and 1, 3-dimethyl imidazole-2-subunit borane into a D4 solution, and stirring for 5-10 minutes at a set rotating speed of 30-80r/min to obtain coating slurry; in the step 2, uniformly coating the coating slurry on a base film, and baking for 2-6 minutes at the set temperature of 65-80 ℃; and (3) setting gamma-rays, taking Co-60 as a radiation source, carrying out intermittent irradiation for 2-3 times with the fixed dose of 30-50 kGy and the irradiation time of 30-40 minutes each time, and irradiating the gamma-rays to obtain the lithium battery diaphragm.

9. The lithium ion battery separator according to claim 6, wherein: the preparation method of the binder a comprises the following steps: adding the mixed acrylic monomer A into absolute ethyl alcohol; adding ammonium persulfate, setting the temperature to be 65-70 ℃, and reacting for 10-12 hours in a nitrogen atmosphere; washing and drying; dispersing the product in tetrahydrofuran, adding 4-dimethylaminopyridine and aprotic acid, setting the temperature to be 0-5 ℃, dropwise adding a catalyst, and reacting for 8-9 hours to obtain a binder a; the preparation method of the binder b comprises the following steps: adding the mixed acrylic monomer B into water, sequentially adding an emulsifier, a neutralizer and ammonium persulfate, and uniformly stirring and dispersing to obtain a pre-emulsion; setting the temperature of 1/2 pre-emulsion at 65-90 ℃, reacting for 0.5-1 hour in nitrogen atmosphere, dropwise adding the rest pre-emulsion for 2-4 hours, and continuing to react for 2-4 hours after dropwise adding is finished to obtain the binder b.

10. The lithium ion battery separator according to claim 9, wherein: the mixed acrylic monomer A comprises butyl acrylate, iso-borate acrylate and hydroxypropyl methacrylate in a mass ratio of 1 (1.5-2) to 0.3-0.6; the addition amount of the aprotic acid accounts for 18-24% of the total mass of the mixed acrylic monomer A; the catalyst is N, N-dicyclohexyl carbodiimide; the mixed acrylic monomer B comprises a fluorine-containing acrylic monomer, hydroxypropyl acrylate and iso-borate in a mass ratio of 1 (0.2-0.3) to (0.5-0.8); the emulsifier is sodium vinyl sulfonate; the neutralizing agent is lithium hydroxide.

Technical Field

The invention relates to the technical field of battery lithium battery diaphragms, in particular to coating slurry with low moisture, high temperature resistance and high peel strength and application thereof.

Background

At present, with the development of lithium battery diaphragm technology, a coated lithium battery diaphragm is favored by the market because the coated lithium battery diaphragm has the characteristics of higher electrolyte infiltration, higher safety strength and the like compared with a pure PE lithium battery diaphragm, however, in the current products and patents, only the research is carried out aiming at the above aspects, and a comprehensive solution cannot be given; for example, patent CN109301129A only emphasizes low moisture content of coating, and does not describe high temperature resistance and peeling strength; for example, patent CN112490580A only studies the high temperature resistance, and does not describe the moisture and stripping; for example, patent CN111554858A only examines the peel strength, and does not describe moisture and heat shrinkage. The three main performance requirements of low moisture, high temperature resistance and high peel resistance of coated lithium battery separators are not always well met at the same time. In addition, the LiPF6 in the electrolyte is easily decomposed to generate HF due to high moisture, so that SEI is damaged, and copper and aluminum foils are corroded; the high temperature resistance is low, and the shrinkage of the coated lithium battery diaphragm is large under the high temperature condition of the battery, so that the positive and negative electrodes are exposed, the battery is short-circuited to cause the battery to be on fire, and safety accidents occur; the peeling strength of the coating is low, so that the coating is easy to fall off, and the additional effect of the coating is lost for the lithium battery diaphragm. In addition, the coverage of the coating layer reduces the porosity of the base film, thereby increasing the lithium ion migration resistance and reducing the ionic conductivity of the lithium battery.

In conclusion, the preparation of the coating slurry with low moisture, high temperature resistance and high peel strength, and the application of the coating slurry to the lithium battery diaphragm are of great significance in solving the problems.

Disclosure of Invention

The invention aims to provide a coating slurry with low moisture, high temperature resistance and high peel strength and application 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:

the coating slurry with low moisture, high temperature resistance and high peel strength comprises the following raw materials: 30-60 parts of solvent, 0.5-5 parts of dispersing agent, 20-50 parts of ceramic material, 1-10 parts of thickening agent, 2-10 parts of binder a, 3-12 parts of binder b and 0.05-0.1 part of wetting agent.

Preferably, the binder a is a modified polyacrylic acid aqueous binder; the binder b is a modified fluorine acrylic acid aqueous binder.

Preferably, the solvent is water; the dispersing agent is one or more mixed solvents of methanol, propanol, n-butanol, isopropanol, ethylene glycol, methyl ether, diethyl ether, propylene glycol, glycerol, propanol and butanone; the ceramic material is one or a mixture of more of aluminum oxide, titanium dioxide, boehmite, magnesium dioxide or magnesium hydroxide; the thickening agent is at least one of carboxymethyl cellulose amine or sodium carboxymethyl cellulose; the wetting agent is an alcohol or siloxane product.

Preferably, the dispersant is at least one of isopropanol, butanone and methyl ether; the ceramic material is at least one of aluminum trioxide or boehmite.

Optimally, the lithium ion battery diaphragm is prepared by uniformly coating the coating slurry on a base film and baking to obtain a finished product.

Preferably, the preparation process comprises the following steps:

step 1: (1) placing the solvent, the dispersing agent and the ceramic material in a stirrer, and stirring for 5-15 minutes at a set rotating speed of 1000-1800 r/min to obtain an A1 solution; (2) adding the thickening agent into the A1 solution, and stirring for 1-2 hours at a rotation speed of 800-1500 r/min; obtaining a B2 solution; (3) adding the binder a into the B2 solution, and stirring for 0.5-1 hour at the set rotating speed of 800-1000 r/min to obtain a C3 solution; (4) grinding the solution C3 by a grinder to obtain a C3-1 solution; (5) standing the C3-1 for 10-15 minutes, adding a binder b, and stirring at a rotation speed of 30-100 r/min for 0.5-2 hours to obtain a D4 solution; (6) adding a wetting agent into the D4 solution, and stirring for 5-10 minutes at a set rotating speed of 30-80r/min to obtain coating slurry;

step 2: and uniformly coating the coating slurry on the base film, and baking for 2-6 minutes at the set temperature of 65-80 ℃ to obtain the lithium battery diaphragm.

Preferably, in the step 2, the coating mode is gravure roll coating, the number of gravure rolls is 80-140, and the operating speed ratio of the gravure rolls is 80% -98%.

Optimally, in the step (6) of the step 1, the wetting agent and the organoborane complex are sequentially added into the D4 solution, and the mixture is stirred for 5-10 minutes at the set rotating speed of 30-80r/min to obtain coating slurry; in the step 2, uniformly coating the coating slurry on a base film, and baking for 2-6 minutes at the set temperature of 65-80 ℃; and (3) setting gamma-rays, taking Co-60 as a radiation source, carrying out intermittent irradiation for 2-3 times with the fixed dose of 30-50 kGy and the irradiation time of 30-40 minutes each time, and irradiating the gamma-rays to obtain the lithium battery diaphragm.

Preferably, the organoborane complex is 1, 3-dimethyl imidazole-2-subunit borane, and the addition amount accounts for 6-10% of the total mass of the coating slurry.

Preferably, the preparation method of (1) the binder a comprises the following steps: adding the mixed acrylic monomer A into absolute ethyl alcohol; adding ammonium persulfate, setting the temperature to be 65-70 ℃, and reacting for 10-12 hours in a nitrogen atmosphere; washing and drying; dispersing the product in tetrahydrofuran, adding 4-dimethylaminopyridine and aprotic acid, setting the temperature to be 0-5 ℃, dropwise adding a catalyst, and reacting for 8-9 hours to obtain a binder a; (2) the preparation method of the binder b comprises the following steps: adding the mixed acrylic monomer B into water, sequentially adding an emulsifier, a neutralizer and ammonium persulfate, and uniformly stirring and dispersing to obtain a pre-emulsion; setting the temperature of 1/2 pre-emulsion at 65-90 ℃, reacting for 0.5-1 hour in nitrogen atmosphere, dropwise adding the rest pre-emulsion for 2-4 hours, and continuing to react for 2-4 hours after dropwise adding is finished to obtain the binder b.

Preferably, the mixed acrylic monomer A comprises butyl acrylate, iso-borate acrylate and hydroxypropyl methacrylate in a mass ratio of 1 (1.5-2) to 0.3-0.6; the addition amount of the aprotic acid accounts for 18-24% of the total mass of the acrylic monomer; the catalyst is N, N-dicyclohexyl carbodiimide; the mixed acrylic monomer B comprises a fluorine-containing acrylic monomer, hydroxypropyl acrylate and iso-borate in a mass ratio of 1 (0.2-0.3) to (0.5-0.8); the emulsifier is sodium vinyl sulfonate; the neutralizing agent is lithium hydroxide.

In the scheme, two binders are mixed for use, the coating slurry is prepared in an optimized and complementary manner, the lithium battery diaphragm with low moisture, high temperature resistance and high peel strength is prepared, and the high-standard requirements of the battery on three aspects of low moisture, strong high temperature resistance and high peel strength of the coated lithium battery diaphragm can be met.

(1) The prepared coating slurry meets the requirements of low moisture, high temperature resistance and high strength, and has the advantages of stable slurry system, long slurry shelf life and less slurry bubbles in the using process. In the preparation process of the coating slurry: the ceramic material is preferably at least one of aluminum oxide or boehmite, and the specific surface area is small, and the shape is preferably close to a sphere; the addition of the wetting agent enhances the surface tension of a degraded ceramic slurry system, so that the ceramic can be more tightly adhered to the surface of the base film, and meanwhile, the stirring speed of the wetting agent after the addition is lower than that of the binder b; in the grinding process, the size of zirconium beads of the grinding machine is required to be consistent with the grain size of the ceramic.

(2) The adhesive a is a modified polyacrylic acid aqueous adhesive, preferably a solution system which is thermodynamically stable and has high filling density for gaps among ceramic particles; the adhesive b is a modified fluorine acrylic acid aqueous adhesive, and is an emulsion system with preferential adhesive property and mechanical stability. The combined use of the two adhesives produces the effects of rigid connection and elastic bonding, and synergistically produces the effect of reinforcing steel bars and cement, effectively strengthens the adaptive resistance of the diaphragm to the thermal expansion in the charging and discharging processes of the battery, prolongs the service life of the diaphragm, and increases the cycle times of the lithium battery.

Specifically, the method comprises the following steps: acrylic binders are both selected because of their higher electrochemical stability compared to polysaccharides and polyvinylidene fluorides. Wherein, the adhesive a has stronger water absorption and strong adhesiveness, and the water content of the coating is influenced due to the stronger water absorption, so that the electrolyte resistance and the heat resistance of the lithium battery diaphragm are influenced, and the safety of the battery is influenced; therefore, a binder b containing a fluorine chain is required as an auxiliary, and has hydrophobicity, electrolyte resistance and heat resistance can be enhanced, and the performance of the lithium battery separator can be effectively improved. And the single use of the binder b has lower binding property than that of the binder a due to fluorine chains and poorer affinity when being adhered to a polyolefin film, so that ceramic particles lose water at high temperature in the actual use process of the lithium battery diaphragm, and the ceramic particles fall off from the surface of the lithium battery diaphragm. In addition, both adhesives have acrylate linkages with similar compatibility; therefore, the two adhesives are combined for use, the advantages are complementary, and the performance of the lithium battery diaphragm is enhanced in multiple aspects.

(3) The adhesive a is modified by using an aprotic acid, and the adhesive a has high viscosity and strong water absorption, so that the spreading wetting condition is poor under the condition of no surfactant or wetting agent; therefore, the non-protonic acid is used for modifying the composite material, so that the creep property of the composite material is increased on the basis of not reducing the viscosity, and the spreading wettability of the composite material is enhanced; meanwhile, the introduction of no protonic acid enhances the molecular rigidity, so that the elastic deformation ratio is increased, the fatigue resistance of the binder a is increased, the viscous strength is more durable, and the service life of the lithium battery diaphragm is prolonged.

(4) Since the polyolefin-based film is coated with the slurry on the surface thereof, the pores are more or less covered, thereby decreasing the porosity, increasing the lithium ion conduction resistance, and affecting the conductivity. In the scheme, gamma rays are used for generating activity on a polyolefin film, and borane molecules in the slurry are grafted on the film; meanwhile, fragment isoboronate in the adhesive is enabled to generate free radicals to be connected with the surface of the polyolefin; enhancing the adhesion of the coating. Meanwhile, due to the functionalization of electron-deficient groups of borane molecules, a conducting path of an electrolyte in a lithium battery diaphragm is opened; the lithium battery diaphragm has the advantages that the electron-deficient effect of boron atoms in the whole lithium battery diaphragm is utilized to promote lithium ion conduction and make up for the defects caused by coating coverage, so that the stability of the battery in the use process is improved, and good electric capacity is kept.

Compared with the prior art, the invention has the following beneficial effects: (1) the prepared ceramic slurry system simultaneously meets the requirements of low moisture, high temperature resistance and high strength, and has the advantages of stable slurry system, long slurry shelf life and less slurry bubbles in the using process. (2) The two adhesives are combined for use, the advantages are complementary, and the performance of the lithium battery diaphragm is enhanced in multiple aspects. (3) The adhesive a is modified by using aprotic acid, so that the adhesive strength is more durable, and the service life of the lithium battery diaphragm is prolonged; (4) the lithium ion conduction is promoted by utilizing the electron deficiency effect of the boron atoms in the lithium battery diaphragm, and the problem of reduction of the ionic conductivity caused by coating coverage is solved, so that the stability and the electric capacity of the lithium battery diaphragm in the use process of the battery are improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is an explanatory view of a form of a lithium battery separator;

the figure is as follows: 1, a base film; 2 ceramic particles; 3, adhesive a; 4, adhesive b.

Detailed Description

The preferred embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. 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:

step 1: (1) the method comprises the following specific steps: (1) 50kg of solvent, 1.5kg of dispersant and 40kg of ceramic material are placed in a double-planet stirrer, and stirred for 10 minutes at the set rotating speed of 1200r/min to obtain A1 solution; (2) adding 8kg of thickening agent into the A1 solution, and stirring for 1.5 hours at the set rotating speed of 1200 r/min; obtaining a B2 solution; (3) adding 8kg of the binder a into the B2 solution, and stirring for 40 minutes at the set rotating speed of 1000r/min to obtain a C3 solution; (4) grinding the solution C3 by a grinder to obtain a C3-1 solution; (5) standing the C3-1 for 10 minutes, adding 8kg of binder b, and stirring at the set rotation speed of 40r/min for 1 hour to obtain a D4 solution; (6) adding 0.07kg of wetting agent into the D4 solution, and stirring for 10 minutes at a set rotating speed of 35r/min to obtain coating slurry;

step 2: setting the number of gravure rollers to be 120 and the running speed ratio of the gravure rollers to be 92%, uniformly rolling the coating slurry on a base film, and baking for 3 minutes at the set temperature of 75 ℃ to obtain the lithium battery diaphragm.

In the scheme, the binder a is a modified polyacrylic acid water-based binder; the binder b is a modified fluoroacrylic acid aqueous binder; two are common commercial binders. The solvent is water; the dispersing agent is isopropanol; the ceramic material is aluminum oxide; the thickening agent is carboxymethyl cellulose amine; the wetting agent is 3- (methacryloyloxy) propyl trimethoxy silane; are all purchased from the market.

Example 2:

step 1: (1) the method comprises the following specific steps: (1) placing 50kg of solvent, 2kg of dispersing agent and 50kg of ceramic material in a double-planet stirrer, and stirring for 15min at a set rotating speed of 1500r/min to obtain an A1 solution; (2) adding 10kg of thickening agent into the A1 solution, and stirring for 1.5 hours at the set rotating speed of 1200 r/min; obtaining a B2 solution; (3) adding 9kg of the binder a into the B2 solution, and stirring for 60 minutes at the set rotating speed of 900r/min to obtain a C3 solution; (4) grinding the solution C3 by a grinder to obtain a C3-1 solution; (5) standing the C3-1 for 10 minutes, adding 7kg of the binder b, and stirring for 40 minutes at a set rotation speed of 50r/min to obtain a D4 solution; (6) adding 0.06kg of wetting agent into the D4 solution, and stirring for 10 minutes at a set rotating speed of 30r/min to obtain coating slurry;

step 2: setting the number of gravure rollers as 100 and the running speed ratio of the gravure rollers as 90%, uniformly rolling the coating slurry on a base film, and baking for 4 minutes at the set temperature of 70 ℃ to obtain the lithium battery diaphragm.

In the scheme, the binder a is a modified polyacrylic acid water-based binder; the binder b is a modified fluorine acrylic acid aqueous binder. Two are common commercial binders. The solvent is water; the dispersing agent is butanone; the ceramic material is boehmite; the thickening agent is sodium carboxymethyl cellulose; the wetting agent is pentaerythritol fatty acid ester; are all purchased from the market.

Example 3:

step 1: preparation of the adhesive: (1) the preparation method of the adhesive a comprises the following steps: weighing butyl acrylate, iso-borate acrylate and hydroxypropyl methacrylate according to the mass ratio of 1:1.5:0.3, and sequentially adding the butyl acrylate, the iso-borate acrylate and the hydroxypropyl methacrylate into absolute ethyl alcohol to be uniformly dispersed; adding ammonium persulfate, setting the temperature to 65 ℃, and reacting for 10 hours in a nitrogen atmosphere; washing and drying; dispersing the product in tetrahydrofuran, adding 4-dimethylamino pyridine and aprotic acid, setting the temperature to be 0 ℃, dropwise adding N, N-dicyclohexyl carbodiimide, and reacting for 8 hours to obtain a binder a; (2) the preparation method of the binder b comprises the following steps: weighing fluorine-containing acrylic acid monomer, hydroxypropyl acrylate and iso-borate in a mass ratio of 1:0.2:0.5, and sequentially adding into water to disperse uniformly; sequentially adding sodium vinyl sulfonate, lithium hydroxide and ammonium persulfate, and uniformly stirring and dispersing to obtain a pre-emulsion; setting the temperature of the 1/2 pre-emulsion at 65 ℃, reacting for 0.5 hour in nitrogen atmosphere, dropwise adding the rest pre-emulsion for 2 hours, and continuing to react for 2 hours after the dropwise adding is finished to obtain the binder b.

Step 2: (1) placing 30kg of solvent, 0.5kg of dispersant and 20kg of ceramic material in a double-planet stirrer, and stirring for 5min at the set rotating speed of 1000r/min to obtain A1 solution; (2) adding 1kg of thickening agent into the A1 solution, and stirring for 1 hour at the set rotating speed of 800 r/min; obtaining a B2 solution; (3) adding 2kg of the binder a into the B2 solution, and stirring for 0.5 hour at the set rotating speed of 800r/min to obtain a C3 solution; (4) grinding the solution C3 by a grinder to obtain a C3-1 solution; (5) standing the C3-1 for 10 minutes, adding 3kg of the binder b, and stirring at a rotation speed of 30r/min for 0.5 hour to obtain a D4 solution; (6) sequentially adding 0.05kg of wetting agent and 1, 3-dimethyl imidazole-2-subunit borane into the D4 solution, and stirring for 5 minutes at a set rotating speed of 30r/min to obtain coating slurry;

and step 3: setting the number of gravure rollers to be 80, setting the operation speed ratio of the gravure rollers to be 80%, uniformly rolling the coating slurry on a base film, and baking for 2 minutes at the set temperature of 65 ℃; and (3) setting gamma-rays, taking Co-60 as a radiation source, carrying out intermittent irradiation for 2 times with the fixed dose of 30kGy and the irradiation time of 30 minutes each time, and irradiating the gamma-rays to obtain the lithium battery diaphragm.

In the scheme, the solvent is water; the dispersant is a mixed solvent of methyl ether and isopropanol; the ceramic material is boehmite; the thickening agent is carboxymethyl cellulose amine; the wetting agent is pentaerythritol fatty acid ester. The amount of the aprotic acid added was 18% based on the total mass of the acrylic monomer. The addition amount of the 1, 3-dimethyl imidazole-2-subunit borane accounts for 6 percent of the total mass of the coating slurry.

Example 4:

step 1: preparation of the adhesive: (1) the preparation method of the adhesive a comprises the following steps: weighing butyl acrylate, iso-borate acrylate and hydroxypropyl methacrylate in a mass ratio of 1:2:0.6, sequentially adding the butyl acrylate, iso-borate acrylate and hydroxypropyl methacrylate into absolute ethyl alcohol, and uniformly dispersing; adding ammonium persulfate, setting the temperature at 70 ℃, and reacting for 12 hours in a nitrogen atmosphere; washing and drying; dispersing the product in tetrahydrofuran, adding 4-dimethylamino pyridine and aprotic acid, setting the temperature to be 5 ℃, dropwise adding N, N-dicyclohexyl carbodiimide, and reacting for 9 hours to obtain a binder a; (2) the preparation method of the binder b comprises the following steps: weighing fluorine-containing acrylic acid monomer, hydroxypropyl acrylate and iso-borate in a mass ratio of 1:0.3:0.8, and sequentially adding into water to disperse uniformly; sequentially adding sodium vinyl sulfonate, lithium hydroxide and ammonium persulfate, and uniformly stirring and dispersing to obtain a pre-emulsion; setting the temperature of the 1/2 pre-emulsion at 90 ℃, reacting for 1 hour in a nitrogen atmosphere, dropwise adding the rest pre-emulsion for 4 hours, and continuing to react for 4 hours after the dropwise adding is finished to obtain the binder b.

Step 2: (1) placing 60kg of solvent, 5kg of dispersing agent and 50kg of ceramic material in a double-planet stirrer, and stirring for 15 minutes at the set rotating speed of 1800r/min to obtain an A1 solution; (2) adding 10kg of thickening agent into the A1 solution, and stirring for 2 hours at the set rotating speed of 1500 r/min; obtaining a B2 solution; (3) adding 10kg of the binder a into the B2 solution, and stirring for 1 hour at the set rotating speed of 1000r/min to obtain a C3 solution; (4) grinding the solution C3 by a grinder to obtain a C3-1 solution; (5) standing the C3-1 for 15 minutes, adding 12 parts of the binder b, and stirring for 2 hours at a rotation speed of 100r/min to obtain a D4 solution; (6) sequentially adding 0.1kg of wetting agent and 1, 3-dimethyl imidazole-2-subunit borane into the D4 solution, setting the rotating speed at 80r/min, and stirring for 10 minutes to obtain coating slurry;

and step 3: setting the number of gravure rollers as 140 and the running speed ratio of the gravure rollers as 98%, uniformly rolling the coating slurry on a base film, and baking for 6 minutes at the set temperature of 80 ℃; and (3) setting gamma-rays, taking Co-60 as a radiation source, carrying out intermittent irradiation for 3 times with the fixed dose of 0kGy and the irradiation time of 40 minutes each time, and irradiating the gamma-rays to obtain the lithium battery diaphragm.

In the scheme, the solvent is water; the dispersant is a mixed solvent of methyl ether and isopropanol; the ceramic material is boehmite; the thickening agent is carboxymethyl cellulose amine; the wetting agent is pentaerythritol fatty acid ester. The amount of the aprotic acid added was 24% based on the total mass of the acrylic monomer. The addition amount of the 1, 3-dimethyl imidazole-2-subunit borane accounts for 10% of the total mass of the coating slurry.

Example 5:

step 1: preparation of the adhesive: (1) the preparation method of the adhesive a comprises the following steps: weighing butyl acrylate, iso-borate acrylate and hydroxypropyl methacrylate according to the mass ratio of 1:1.8:0.5, and sequentially adding the butyl acrylate, the iso-borate acrylate and the hydroxypropyl methacrylate into absolute ethyl alcohol to be uniformly dispersed; adding ammonium persulfate, setting the temperature at 68 ℃, and reacting for 11 hours in a nitrogen atmosphere; washing and drying; dispersing the product in tetrahydrofuran, adding 4-dimethylamino pyridine and aprotic acid, setting the temperature to be 3 ℃, dropwise adding N, N-dicyclohexyl carbodiimide, and reacting for 8.5 hours to obtain a binder a; (2) the preparation method of the binder b comprises the following steps: weighing fluorine-containing acrylic acid monomer, hydroxypropyl acrylate and iso-borate in a mass ratio of 1:0.25:0.6, and sequentially adding into water to disperse uniformly; sequentially adding sodium vinyl sulfonate, lithium hydroxide and ammonium persulfate, and uniformly stirring and dispersing to obtain a pre-emulsion; setting the temperature of the 1/2 pre-emulsion at 68 ℃, reacting for 0.8 hour in nitrogen atmosphere, dropwise adding the rest pre-emulsion for 3 hours, and continuing to react for 3 hours after the dropwise adding is finished to obtain the binder b.

Step 2: 50kg of solvent, 1.5kg of dispersant and 40kg of ceramic material are placed in a double-planet stirrer, and stirred for 10 minutes at the set rotating speed of 1200r/min to obtain A1 solution; (2) adding 8kg of thickening agent into the A1 solution, and stirring for 1.5 hours at the set rotating speed of 1200 r/min; obtaining a B2 solution; (3) adding 8kg of the binder a into the B2 solution, and stirring for 40 minutes at the set rotating speed of 1000r/min to obtain a C3 solution; (4) grinding the solution C3 by a grinder to obtain a C3-1 solution; (5) standing the C3-1 for 10 minutes, adding 8kg of binder b, and stirring at the set rotation speed of 40r/min for 1 hour to obtain a D4 solution; (6) sequentially adding 0.07kg of wetting agent and 1, 3-dimethyl imidazole-2-subunit borane into the D4 solution, and stirring for 10 minutes at the set rotating speed of 35r/min to obtain coating slurry;

and step 3: setting the number of gravure rollers as 120, the operating speed ratio of the gravure rollers as 92%, uniformly roll-coating the coating slurry on a base film, baking for 3 minutes at the set temperature of 75 ℃, setting gamma-rays, taking Co-60 as a radiation source, performing intermittent irradiation for 3 times with the fixed dose of 40kGy and the irradiation time of 30 minutes each time, and irradiating the radiation to obtain the lithium battery diaphragm.

In the scheme, the solvent is water; the dispersant is a mixed solvent of methyl ether and isopropanol; the ceramic material is boehmite; the thickening agent is carboxymethyl cellulose amine; the wetting agent is pentaerythritol fatty acid ester. The addition amount of the aprotic acid accounts for 18-24% of the total mass of the acrylic monomer. The addition amount of the 1, 3-dimethyl imidazole-2-subunit borane accounts for 6-10% of the total mass of the coating slurry.

Example 6: no modification with aprotic acid; the rest is the same as in example 5.

Example 7: no 1, 3-dimethylimidazol-2-ylideneborane is added; the rest is the same as in example 5.

Example 8: no adhesive a is added; the rest is the same as in example 1.

Example 9: no adhesive b is added; the rest is the same as in example 1.

Experiment 1: the lithium battery separator prepared in examples 1 to 7 was subjected to various performance tests using a polyethylene film as a base film. And base film comparative example 1 including coating thickness, porosity, moisture content, heat shrinkage, peel strength; and carrying out peel strength test on the lithium battery diaphragm baked for half an hour at the temperature of 130 ℃ again to obtain peel strength B; all results are shown in the following table:

and (4) conclusion: the lithium battery diaphragm prepared by the embodiments 1-5 can be coated with a thickness of about 4 μm; the average porosity is about 45%; the water content is less than 600 ppm; high temperature resistance: TD and MD are both less than 2.5% at 130 ℃/0.5 h; the peel strength is about 160N/M; after baking for half an hour at 130 ℃, the reduction of the peeling strength is less than 8 percent; the ionic conductivity is up to 1.28; therefore, the prepared lithium battery diaphragm has excellent performance.

Comparing example 5 with examples 6 and 7, it can be found that: the adhesive without protonic acid modification is not used, so that the peel strength is reduced, and the reduction range of the peel strength B is increased; the reason is that: the protonic acid is not used for modifying the composite material, so that the creep property of the composite material is increased on the basis of not reducing the viscosity, and the spreading wettability of the composite material is enhanced; meanwhile, the introduction of no protonic acid enhances the molecular rigidity, so that the elastic deformation ratio is increased, the fatigue resistance of the adhesive a is increased, and the adhesive strength is more durable. On the other hand, example 6, in which 1, 3-dimethylimidazol-2-ylideneborane was not added, resulted in a decrease in ionic conductivity; since the surface of the polyolefin membrane is coated with the slurry, pores are more or less covered, so that the porosity is reduced, the lithium ion conduction resistance is increased, and the conductivity is influenced; but the borane molecules in the slurry are grafted on the polyolefin film by gamma radiation to create activity on the film; meanwhile, fragment isoboronate in the adhesive is enabled to generate free radicals to be connected with the surface of the polyolefin; making a conductive path of an electrolyte in a lithium battery separator open; the electron-deficient effect of boron atoms in the whole lithium battery diaphragm is utilized to promote lithium ion conduction and make up for the defects caused by coating coverage.

Based on the comparison, the comparison between the example 1 and the example 5 shows that the isobornyl acrylate in the self-made binder can increase the ionic conductivity and the adhesion; the reason is that the isoboronate acrylate segments generate free radicals to link with the polyolefin surface; enhancing the adhesion of the coating. And boron-assisted 1, 3-dimethylimidazol-2-ylideneborane contained to open the lithium ion channel.

Experiment 2: example 1, example 5, example 8, and example 9 were applied to a lithium battery, and a commercially available coated separator was used as comparative example 2, and after charging and discharging for half an hour at normal temperature for one cycle, 1000 cycles were performed to test the actual capacity of the battery. The data obtained are shown below:

examples	Example 1	Example 5	Example 8	Example 9	Comparative example 2
						Capacity remaining rate	88.2％	90.0％	73.9％	76.1％	75.6％

And (4) conclusion: the capacity remaining rate in the table is a ratio of the actual capacity after the cycle to the rated capacity. The larger the number, the longer the service life of the battery separator was. From the data in the table it can be seen that: the battery diaphragm in the scheme is stronger than diaphragms on the market, and the reason for strengthening the performance is that the synergistic effect of the binder a and the binder b produces the effect similar to reinforced concrete, so that the adaptive resistance of the diaphragm to thermal expansion in the charging and discharging processes is effectively enhanced; meanwhile, the modification of the aprotic acid effectively enhances the bonding durability of the bonding agent a, and further prolongs the service life of the lithium battery diaphragm in practical application under the assistance of electron-deficient boron.

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, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.