Polymer microspheres for battery coating diaphragm and preparation method and application thereof

Abstract

The present invention discloses polymer microspheres for battery separator coating, and a preparation method and application thereof. The polymer microspheres for battery separator coating of the present invention comprise, by weight, 20-40 parts of a basic monomer, 5-10 parts of a functional monomer, 1-5 parts of an initiator I, 3-10 parts of a cross-linking agent, 50-90 parts of a solvent I, and 2-8 parts of a reactive auxiliary agent. The basic monomers include hard monomers and soft monomers; the functional monomers are selected from monomers containing at least one of a carboxyl group, an amide group, a hydroxyl group, and an epoxy group; and the reactive auxiliary agent is selected from one or more of an acrylate-trithiocarbonate copolymer and an acrylic acid-trithiocarbonate copolymer. The polymer microspheres of the present invention have a low dissolution rate and strong adhesion when used for battery separator coating.

Description

Technical Field

[0001] The present invention relates to the technical field of battery coating diaphragms, and in particular to polymer microspheres for battery coating diaphragms, and a preparation method and application thereof. Background Art

[0002] In recent years, driven by the growing market share of new energy vehicles, demand for lithium batteries, a key component, has also been growing. As one of the four major components of lithium batteries, the performance of the separator largely determines the performance of the battery itself. Existing separators are primarily coated, with polyvinylidene fluoride (PVDF) secondary coating currently dominating the market. Alternatively, a single coating process involving mixing PVDF with a ceramic slurry is also possible. However, PVDF is expensive and relies on imports, and its use requires the toxic solvent N-methylpyrrolidone (NMP), which is inconsistent with the green and environmentally friendly philosophy of new energy vehicles. PVDF also has inherent drawbacks such as poor ion conductivity and a high swelling rate. Therefore, developing a binder that can replace existing PVDF is crucial.

[0003] Some studies have used polymer microspheres instead of PVDF to mix with ceramic slurry for lithium battery separator coating, and only one coating is needed to meet the bonding requirements. For example, CN114920873A discloses a polymer microsphere for lithium-ion battery separator and its preparation method. Specifically, by adopting the emulsion polymerization method, monomers and emulsifiers are added to a pre-emulsification reactor, and pre-emulsification and dispersion are carried out using a high-speed shear dispersing emulsifier to form stable latex micelles. Under the action of an initiator, polymer microspheres with uniform particle size are prepared, with a lower swelling rate and good bonding strength, thereby achieving better bonding between the separator and the electrode. CN117060010A discloses a narrow distribution separator adhesive and its preparation method. The invention first uses suspension polymerization to prepare a core polymer, and then uses seed emulsion polymerization to prepare a polymer microsphere separator adhesive with a narrow particle size distribution. Only ceramic slurry and polymer microsphere separator adhesive need to be mixed and coated once to complete the process. It does not affect the air permeability of the separator and has a high bonding strength with the electrode. However, the aforementioned method requires pretreatment steps such as emulsification and mechanical dispersion during the preparation process, which takes a long time and places high demands on the equipment required during actual production, making it unsuitable for industrial production. Furthermore, battery separators require long-term exposure to electrolytes. Research has found that existing polymer microspheres are unstable and easily dissolve in electrolytes, resulting in poor adhesion and durability of the separator coating, which in turn affects the battery's cycle life. Summary of the Invention

[0004] To address these challenges, the present invention provides polymer microspheres for battery separator coating, as well as their preparation method and application. These polymer microspheres can replace PVDF as a binder in separator ceramic coating slurries. They exhibit excellent adhesion and a suitable swelling ratio, and exhibit excellent stability and low dissolution rate in electrolytes, ensuring durable bonding performance.

[0005] The technical solutions of the present invention are as follows:

[0006] The present invention provides polymer microspheres for coating battery separators. The raw materials include, by weight, 20-40 parts of basic monomers, 5-10 parts of functional monomers, 1-5 parts of initiator I, 3-10 parts of cross-linking agent, 50-90 parts of solvent I, and 2-8 parts of reactive auxiliary agent.

[0007] Among them, the basic monomers include hard monomers and soft monomers; the hard monomers are monomers with a glass transition temperature Tg1 of 50°C ≤ Tg1 ≤ 120°C and a double bond structure that can undergo free radical polymerization; the soft monomers are monomers with a glass transition temperature Tg2 of -80°C ≤ Tg2 < 50°C and a double bond structure that can undergo free radical polymerization (the glass transition temperature is measured by differential thermal analysis (DSC): the sample is tested using a differential scanning calorimeter (DSC) in a nitrogen atmosphere with a test temperature range of -80°C to 150°C and a heating rate of 10°C / min);

[0008] The functional monomer is selected from monomers containing at least one of carboxyl, amido, hydroxyl and epoxy groups;

[0009] The reactive auxiliary agent is selected from one or more of acrylate-trithiocarbonate copolymer and acrylic acid-trithiocarbonate copolymer.

[0010] The reactive auxiliary agent added to the polymer microsphere raw material of the present invention has polar and non-polar groups and can serve as a stabilizer. At the same time, it can participate in the polymerization reaction, regulate the reaction process, reduce by-products in the polymerization process, and improve the yield.

[0011] The participation of reactive additives in the reaction is mainly divided into five stages:

[0012] (1) Chain initiation stage: At the beginning of the polymerization reaction, initiator I added to the system first generates free radicals through thermal decomposition, and then reacts with the monomer to form chain-growing free radicals;

[0013] (2) Chain transfer and chain growth stage: Chain growth free radicals react with reactive additives to produce intermediate free radicals, which then rapidly undergo β-breakage at a certain side arm to form leaving radicals and dormant species;

[0014] (3) Re-initiation stage: the newly formed leaving radical continues to initiate the remaining monomers to form new chain-growing radicals;

[0015] (4) Chain equilibrium stage: The newly generated chain growth free radicals react with dormant species to produce new intermediate free radicals, which then break to form new chain growth free radicals and dormant species. The chain transfer process between dormant species and chain growth free radicals forms the main equilibrium of "initiation-inactivation". This process is accompanied by the rapid establishment of exchange equilibrium between dormant species and active growth chains. Therefore, polymer chains with similar chain lengths can be formed in the reaction system, thereby forming polymers with a narrow molecular weight distribution. At the same time, the chain growth rate of the reaction system is always lower than the addition-fragmentation equilibrium reaction rate, so that the number of dormant species is much larger than that of active free radicals, thereby reducing the chance of chain termination.

[0016] (5) Chain termination stage: When the polymerization process reaches a certain extent, the diradical termination reaction accelerates, and the free radicals are quenched due to disproportionation termination or coupling termination.

[0017] The relative molecular weight of the reactive auxiliary agent has a certain influence on the size of the synthesized microspheres and the adhesive force used for coating the battery separator. The polymerization degree of the reactive auxiliary agent is preferably between 200-1000.

[0018] Furthermore, the polymerization degree of the reactive auxiliary agent is preferably 200-400.

[0019] Furthermore, the trithiocarbonate in the reactive auxiliary agent is preferably 2-(dodecyl trithiocarbonate)-2-methylpropionic acid;

[0020] Furthermore, the acrylate in the reactive auxiliary agent is preferably one or more selected from methyl acrylate, butyl acrylate, isooctyl acrylate, ethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl acrylate;

[0021] The reactive auxiliary agent of the present invention can be obtained commercially or by self-production. The present invention provides a method for synthesizing the reactive auxiliary agent, comprising the following steps:

[0022] (1) By weight, 20-50 parts of acrylic acid or acrylate monomer, 0.1-2 parts of trithiocarbonate, 1-5 parts of initiator II, and 50-70 parts of solvent II are mixed;

[0023] (2) React at 70-80°C under protective atmosphere for 2-10 hours;

[0024] (3) Purify and dry to obtain the reactive auxiliary agent.

[0025] Furthermore, the initiator II is preferably azobisisobutyronitrile;

[0026] Furthermore, the solvent II is preferably selected from 1,4-dioxane, ethanol, and methanol.

[0027] Furthermore, the reaction time is preferably 4-6 h.

[0028] The polymer microspheres of the present invention are prepared by adding both hard and soft monomers. The hard monomers provide the microspheres with a certain degree of rigidity and thermal stability, while ensuring a certain degree of cohesion under hot pressing. The soft monomers, on the other hand, provide the microspheres with a certain degree of flowability under hot pressing conditions, promoting wetting between the microspheres and the interface, thereby improving adhesion. The synergistic effect of the two allows the microspheres to be used as a binder in the diaphragm ceramic coating slurry, effectively improving the adhesion between the diaphragm and the electrode.

[0029] Furthermore, the weight ratio of the hard monomer to the soft monomer in the basic monomer is preferably 30-70:70-30.

[0030] Furthermore, the hard monomer is selected from one or more of acrylonitrile, styrene, methyl methacrylate, ethyl methacrylate, methacrylic acid, hydroxyethyl methacrylate, tert-butyl methacrylate, and isopropyl methacrylate.

[0031] Furthermore, the soft monomer is selected from one or more of glycidyl methacrylate, butyl methacrylate, n-pentyl methacrylate, propyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, and hydroxypropyl methacrylate.

[0032] The functional monomers of the present invention are preferably selected from one or more of methacrylic acid, diacetone acrylamide, hydroxyethyl acrylate, N-methylol acrylamide, hydroxypropyl methacrylate, and hydroxypropyl acrylate. By adding a certain amount of the functional monomers, their functional groups can form chemical bonds with the electrode interface groups, further improving the bonding ability between the microspheres and the interface.

[0033] The initiator I of the present invention is preferably an azo initiator; its main function is to generate free radicals under heating to initiate polymerization reaction.

[0034] Furthermore, the initiator I is selected from one or more of azobisisobutyronitrile and azobisisoheptanenitrile;

[0035] Furthermore, the crosslinking agent of the present invention is a monomer having two or three double bonds and having a crosslinking function. The addition of the crosslinking agent can promote polymerization to produce a crosslinked structure, which is beneficial to improving the stability of the microspheres in the electrolyte.

[0036] Furthermore, the crosslinking agent is preferably selected from one or more of N,N-methylenebisacrylamide, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, divinylbenzene, and allyl methacrylate;

[0037] Furthermore, the solvent I is selected from one or more combinations of methanol, ethanol, isopropanol and water, and is mainly used as a dispersion medium.

[0038] Furthermore, the particle size D50 of the polymer microspheres for coating the battery separator is 1-7 microns.

[0039] The present invention provides a method for preparing the above-mentioned polymer microspheres for battery diaphragm coating, comprising the following steps:

[0040] The basic monomer, functional monomer, initiator I, crosslinking agent, reactive auxiliary agent and solvent I are mixed, and reacted at 60-70° C. for 8-15 hours under a protective atmosphere to obtain polymer microspheres for battery coating diaphragm.

[0041] Furthermore, the preparation method of polymer microspheres for battery coating separators comprises the following steps:

[0042] (1) Place the weighed monomers (including basic monomers, functional monomers, and cross-linking agents) into the reactor, add 1 / 2-3 / 4 of solvent I, control the temperature at 50-60°C, and maintain the speed at 150-200 rpm;

[0043] (2) Then add the reactive additive, keep the temperature constant, and increase the speed to 200-300 rpm;

[0044] (3) Vacuum for 0.5-1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0045] (4) Add initiator I to the remaining 1 / 4-1 / 2 of solvent I, stir until homogeneous, and then add dropwise to the reactor;

[0046] (5) After all initiator I is added, the temperature is raised to 60-70°C and the reaction is carried out at this temperature for 8-15 hours to obtain the target polymer microsphere emulsion;

[0047] (6) The emulsion is then filtered through a 200-mesh sieve, the filtrate is centrifuged, and then redispersed with a reaction solvent. This process is repeated 2-5 times, and finally dispersed with water to obtain polymer microspheres.

[0048] The present invention also provides the use of the polymer microspheres for battery separator coating in the preparation of battery separator coating, specifically as a binder in battery separator coating slurry, such as the preparation of lithium-ion battery separator coating slurry.

[0049] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0050] (1) The polymer microspheres of the present invention can replace PVDF as a binder in the diaphragm ceramic coating slurry, have good bonding strength and suitable swelling rate, and have good stability in the electrolyte and low dissolution rate, which can achieve long-lasting bonding performance and meet the recycling requirements of the battery at high rates.

[0051] (2) The polymer microspheres of the present invention can be coated on the battery separator in one step after being mixed with the ceramic slurry, which simplifies the separator coating process and effectively reduces the time cost compared with the existing secondary coating process. At the same time, the addition of polymer microspheres can further improve the lithium ion transmission capacity.

[0052] (3) The polymer microspheres of the present invention can be prepared by a one-pot method without the need for tedious operating steps, which greatly reduces the time cost (only 8-15 hours) and equipment cost. Compared with existing emulsion polymerization, seed polymerization, etc., they have outstanding convenience and are suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a SEM photograph of the coated separator prepared by blade coating with polymer microspheres for the battery coating of Example 1. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present invention more clear, several examples will be given to further illustrate the present invention in detail. The technical solutions listed are only used to explain the present invention and do not limit the scope of protection of the present invention. If the concept remains unchanged, any replacement or substitution of the technical solution shall be within the technical protection scope of the present invention.

[0055] In order to verify the application advantages of the polymer microspheres in the present invention, the polymer microspheres are applied to the formulation of the diaphragm ceramic coating slurry, which includes, by weight: 10 parts of polymer microsphere emulsion, 54 parts of ceramic powder, 3 parts of aqueous binder, 2 parts of thickener, 0.5 parts of dispersant, 0.2 parts of wetting agent, 0.3 parts of defoaming agent, and 40 parts of water.

[0056] Among them, the ceramic powder is boehmite, the water-based binder is polyacrylate binder, the thickener is hydroxymethyl cellulose thickener, the dispersant is BYK-151, the wetting agent is BYK-346, and the defoaming agent is BYK-024.

[0057] The coating process is as follows:

[0058] (1) Mix the weighed ceramic powder, thickener, and water at a speed of 500 rpm for 1 hour.

[0059] (2) Increase the speed to 700 rpm, add the dispersant dropwise, and stir for 0.5 hours after addition;

[0060] (3) Add polymer microsphere emulsion and wetting agent, increase the speed to 1200 rpm, and maintain high-speed stirring for 0.5 hours;

[0061] (4) Reduce the rotation speed to 400 rpm, add the defoamer and aqueous binder dropwise, and keep stirring at a low speed for 0.5 hours after adding to eliminate the bubbles inside the slurry, and the ceramic coating slurry required for battery separator can be obtained;

[0062] (5) The ceramic coating slurry is coated on the battery separator and then dried at 60°C to prepare the battery coated separator. The thickness of the separator ceramic slurry coating is controlled to be 2 microns. The SEM photo of the coated separator after coating is as follows: Figure 1 As shown;

[0063] In order to characterize the advantages of polymer microspheres in the diaphragm, the prepared diaphragm was tested in combination with the currently commonly used test methods. The tested performance included the average adhesion to the electrode; at the same time, the size of the polymer microspheres themselves, the electrolyte dissolution rate, and the swelling rate were also characterized.

[0064] (1) Adhesion test with the electrode: Cut the coated diaphragm into 6 The slurry coating surface was overlapped with the battery negative electrode graphite plate of the same size, and then a hot press (Shenzhen Xinyi Hydraulic Equipment Co., Ltd., model XY-Z2118-3T) was used to press the sample at 80 ° C for 1 minute under 3 MPa. After the sample cooled, the separator was cut into pieces with a width of 2 The 12 cm specimens were then subjected to adhesion test using an electronic tensile testing machine (Guangzhou Runhu Instrument Co., Ltd., model RH-L600). Each group of samples was tested 3 times, and the average value was taken and rounded to 1 decimal place as the final result.

[0065] (2) Electrolyte dissolution and swelling rate test: Take a microsphere aqueous dispersion with a dry powder weight of about 2g and pour it into 4 4 A 4cm cube of silicone mold is dried at 70°C for approximately 10 hours. A sample (0.5-1.0 g, weight at this point, is m1) is then soaked in an electrolyte solution (ethylene carbonate: dimethyl carbonate: diethyl carbonate, mass ratio = 3:5:2) to completely submerge the sample. The sample is then placed at 60°C for 24 hours. After cooling, the sample is removed from the electrolyte solution, the surface liquid is gently wiped dry, and the sample is weighed. The sample is then dried at 120°C for 5 hours, and the mass after drying is m3.

[0066] The calculation formula of dissolution rate is = (1-(m3 / m1)) 100%;

[0067] The calculation formula of swelling rate is =((m2-m1) / m1) 100%.

[0068] (3) Microsphere size: Take a small amount of aqueous dispersion of microspheres and use Malvern 3000 particle size analyzer to analyze the size of the microspheres and measure the particle size D50 of the microspheres.

[0069] Example 1

[0070] This example provides a method for preparing polymer microspheres for battery separator coating. The raw material components of the polymer microspheres are as follows, in parts by weight: 33 parts of basic monomer, 5 parts of functional monomer, 7 parts of crosslinking agent, 2 parts of initiator, 50 parts of solvent, and 3 parts of reactive auxiliary agent.

[0071] Among them, the basic monomer is a mixture of styrene and n-octyl methacrylate (mass ratio is 5:5), the functional monomer is methacrylic acid, the cross-linking agent is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is methanol, and the reactive auxiliary agent is PMA400.

[0072] The synthesis method of the reactive auxiliary agent PMA400 in this example is:

[0073] (1) By weight, 30 parts of methyl acrylate, 0.3 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 1 part of azobisisobutyronitrile, and 68.7 parts of 1,4-dioxane were placed in a round-bottom flask preheated at 70°C;

[0074] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 4 hours;

[0075] (3) The sample was recrystallized with n-hexane and then dissolved with 1,4-dioxane, and this process was repeated three times;

[0076] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PMA400. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 400.

[0077] The synthesis method of polymer microspheres in this example is:

[0078] (1) Put the weighed monomers (including basic monomers, functional monomers and cross-linking agents) into the reactor, add 3 / 4 of the solvent, control the temperature to 50 ° C, and maintain the speed at 150 rpm;

[0079] (2) Then, the reactive additive was added, the temperature was kept constant, and the rotation speed was increased to 250 rpm;

[0080] (3) Vacuum for 1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0081] (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then add dropwise to the reactor;

[0082] (5) After all the initiators are added, the temperature is raised to 65°C and the reaction is carried out at this temperature for 10 hours to obtain the target microsphere emulsion;

[0083] (6) The emulsion was then filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with a reaction solvent. This process was repeated twice, and finally dispersed with water. The solid content was controlled at 20% to obtain a polymer microsphere emulsion.

[0084] Subsequently, the coated diaphragm was prepared by scraping according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were performed.

[0085] Example 2

[0086] This example provides a method for preparing polymer microspheres for battery separator coating. The raw material components of the polymer microspheres are as follows, in parts by weight: 20 parts of basic monomer, 6 parts of functional monomer, 5 parts of crosslinking agent, 3 parts of initiator, 63 parts of solvent, and 3 parts of reactive auxiliary agent.

[0087] Among them, the basic monomer is a mixture of methyl methacrylate, butyl methacrylate and hydroxypropyl methacrylate (mass ratio of 3:2:5), the functional monomer is diacetone acrylamide, the cross-linking agent is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is a mixed solvent of methanol and water (mass ratio of 8:2), and the reactive auxiliary agent is PEA300.

[0088] The synthesis method of the reactive additive PEA300 in this example is:

[0089] (1) By weight, 30 parts of ethyl acrylate, 0.3 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 1 part of azobisisobutyronitrile, and 68.7 parts of 1,4-dioxane were placed in a round-bottom flask preheated at 70°C;

[0090] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 6 hours;

[0091] (3) The sample was recrystallized with n-hexane and then dissolved with 1,4-dioxane, and this process was repeated three times;

[0092] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PEA300. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 300.

[0093] The synthesis method of polymer microspheres in this example is:

[0094] (1) Put the weighed monomers (including basic monomers, functional monomers and cross-linking agents) into the reactor, add 3 / 4 of the solvent, control the temperature to 50 ° C, and maintain the speed at 200 rpm;

[0095] (2) Then, the reactive additive was added, the temperature was kept constant, and the rotation speed was increased to 300 rpm;

[0096] (3) Vacuum for 1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0097] (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then add dropwise to the reactor;

[0098] (5) After all the initiators are added, the temperature is raised to 65°C and the reaction is carried out at this temperature for 10 hours to obtain the target microsphere emulsion;

[0099] (6) The emulsion was then filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with a reaction solvent. This process was repeated twice, and finally dispersed with water. The solid content was controlled at 20% to obtain a polymer microsphere emulsion.

[0100] Subsequently, the coated diaphragm was prepared by scraping according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were performed.

[0101] Example 3

[0102] This example provides a method for preparing polymer microspheres for battery separator coating. The raw material components of the polymer microspheres are as follows, in parts by weight: 28 parts of basic monomer, 5 parts of functional monomer, 6 parts of crosslinking agent, 2 parts of initiator, 53 parts of solvent, and 6 parts of reactive auxiliary agent.

[0103] Among them, the basic monomer is a mixture of methyl methacrylate, glycidyl methacrylate and butyl methacrylate (mass ratio is 3:1:6), the functional monomer is hydroxyethyl acrylate, the cross-linking agent is divinylbenzene, the initiator is azobisisoheptanenitrile, the solvent is a mixed solvent of ethanol and water (mass ratio is 7:3), and the reactive auxiliary agent is PAA300.

[0104] The synthesis method of the reactive additive PAA300 in this example is:

[0105] (1) By weight, 50 parts of acrylic acid, 0.6 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 1.4 parts of azobisisobutyronitrile, and 48 parts of 1,4-dioxane were placed in a round-bottom flask preheated at 70°C;

[0106] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 5 hours;

[0107] (3) The sample was recrystallized with n-hexane and then dissolved with 1,4-dioxane, and this process was repeated three times;

[0108] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PAA300. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 300.

[0109] The synthesis method of polymer microspheres in this example is:

[0110] (1) The weighed monomers (including basic monomers, functional monomers and cross-linking agents) were put into the reactor, and 3 / 4 of the solvent was added. The temperature was controlled at 55 °C and the speed was maintained at 150 rpm.

[0111] (2) Then add the reactive additive, keep the temperature constant, and increase the speed to 200 rpm:

[0112] (3) Vacuum for 1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0113] (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then add dropwise to the reactor;

[0114] (5) After all the initiators are added, the temperature is raised to 65°C and the reaction is carried out at this temperature for 10 hours to obtain the target microsphere emulsion;

[0115] (6) The emulsion was then filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with a reaction solvent. This process was repeated twice, and finally dispersed with water. The solid content was controlled at 20% to obtain a polymer microsphere emulsion.

[0116] Subsequently, the coated diaphragm was prepared by scraping according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were performed.

[0117] Example 4

[0118] This example provides a method for preparing polymer microspheres for battery separator coating. The raw material components of the polymer microspheres are as follows, in parts by weight: 30 parts of basic monomer, 10 parts of functional monomer, 7 parts of crosslinking agent, 3 parts of initiator, 45 parts of solvent, and 5 parts of reactive auxiliary agent.

[0119] Among them, the basic monomer is a mixture of tert-butyl methacrylate, butyl methacrylate, hydroxypropyl methacrylate and n-pentyl methacrylate (mass ratio of 3:1:2:4), the functional monomer is N-hydroxymethyl acrylamide, the crosslinker is trimethylolpropane triacrylate, the initiator is azobisisobutyronitrile, the solvent is a mixed solvent of ethanol and water (mass ratio of 7:3), and the reactive auxiliary agent is PBA300.

[0120] The synthesis method of the reactive auxiliary agent PBA300 in this example is:

[0121] (1) By weight, 50 parts of butyl acrylate, 0.4 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 1.6 parts of azobisisobutyronitrile, and 48 parts of methanol were placed in a round-bottom flask preheated at 70°C;

[0122] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 4 hours;

[0123] (3) The sample was recrystallized with n-hexane and then dissolved in methanol, and this process was repeated three times;

[0124] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PBA300. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 300.

[0125] The synthesis method of polymer microspheres in this example is:

[0126] (1) Put the weighed monomers (including basic monomers, functional monomers and cross-linking agents) into the reactor, add 3 / 4 of the solvent, control the temperature at 55 °C, and maintain the speed at 200 rpm;

[0127] (2) Then, the reactive additive was added, the temperature was kept constant, and the rotation speed was increased to 250 rpm;

[0128] (3) Vacuum for 1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0129] (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then add dropwise to the reactor;

[0130] (5) After all the initiators are added, the temperature is raised to 65°C and the reaction is carried out at this temperature for 10 hours to obtain the target microsphere emulsion;

[0131] (6) The emulsion was then filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with a reaction solvent. This process was repeated twice, and finally dispersed with water. The solid content was controlled at 20% to obtain a polymer microsphere emulsion.

[0132] Subsequently, the coated diaphragm was prepared by scraping according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were performed.

[0133] Example 5

[0134] This example provides a method for preparing polymer microspheres for battery separator coating. The raw material components of the polymer microspheres are as follows, in parts by weight: 37 parts of basic monomer, 5 parts of functional monomer, 3 parts of crosslinking agent, 2 parts of initiator, 50 parts of solvent, and 3 parts of reactive auxiliary agent.

[0135] Among them, the basic monomer is a mixture of styrene, acrylonitrile and butyl methacrylate (mass ratio is 2:2:6), the functional monomer is hydroxypropyl methacrylate, the cross-linking agent is allyl methacrylate, the initiator is azobisisobutyronitrile, the solvent is ethanol, and the reactive auxiliary agent is PEHA400.

[0136] The synthesis method of the reactive additive PEHA400 in this example is:

[0137] (1) By weight, 20 parts of isooctyl acrylate, 0.1 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 0.9 parts of azobisisobutyronitrile, and 79 parts of ethanol were placed in a round-bottom flask preheated at 70°C;

[0138] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 4 hours;

[0139] (3) The sample was recrystallized with n-hexane and then dissolved in ethanol, and this process was repeated three times;

[0140] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PEHA400. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 400.

[0141] The synthesis method of polymer microspheres in this example is:

[0142] (1) The weighed monomers (including basic monomers, functional monomers and cross-linking agents) were put into the reactor, and 3 / 4 of the solvent was added. The temperature was controlled at 55 °C and the speed was maintained at 150 rpm.

[0143] (2) Then, the reactive additive was added, the temperature was kept constant, and the rotation speed was increased to 200 rpm;

[0144] (3) Vacuum for 1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0145] (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then add dropwise to the reactor;

[0146] (5) After all the initiators are added, the temperature is raised to 70°C and the reaction is carried out at this temperature for 10 hours to obtain the target microsphere emulsion;

[0147] (6) The emulsion was then filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with a reaction solvent. This process was repeated twice, and finally dispersed with water. The solid content was controlled at 20% to obtain a polymer microsphere emulsion.

[0148] Subsequently, the coated diaphragm was prepared by scraping according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were performed.

[0149] Example 6

[0150] This example provides a method for preparing polymer microspheres for battery separator coating. The raw material components of the polymer microspheres are as follows, in parts by weight: 20 parts of basic monomer, 5 parts of functional monomer, 3 parts of crosslinking agent, 1 part of initiator, 65 parts of solvent, and 4 parts of reactive auxiliary agent.

[0151] Among them, the basic monomer is a mixture of methyl methacrylate, acrylonitrile, butyl methacrylate and n-hexyl methacrylate (mass ratio is 1:2:3:4), the functional monomer is hydroxypropyl acrylate, the cross-linking agent is divinylbenzene, the initiator is azobisisobutyronitrile, the solvent is isopropyl alcohol, and the reactive auxiliary agent is PEHA200.

[0152] The synthesis method of the reactive additive PEHA200 in this example is:

[0153] (1) By weight, 20 parts of isooctyl acrylate, 0.15 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 0.55 parts of azobisisobutyronitrile, and 79.3 parts of ethanol were placed in a round-bottom flask preheated at 70°C;

[0154] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 5 hours;

[0155] (3) The sample was recrystallized with n-hexane and then dissolved in ethanol, and this process was repeated three times;

[0156] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PEHA200. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 200.

[0157] The synthesis method of polymer microspheres in this example is:

[0158] (1) Put the weighed monomers (including basic monomers, functional monomers and cross-linking agents) into the reactor, add 3 / 4 of the solvent, control the temperature at 60 ° C, and maintain the speed at 150 rpm;

[0159] (2) Then, the reactive additive was added, the temperature was kept constant, and the rotation speed was increased to 200 rpm;

[0160] (3) Vacuum for 1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0161] (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then add dropwise to the reactor;

[0162] (5) After all the initiators are added, the temperature is raised to 70°C and the reaction is carried out at this temperature for 10 hours to obtain the target microsphere emulsion;

[0163] (6) The emulsion was then filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with a reaction solvent. This process was repeated twice, and finally dispersed with water. The solid content was controlled at 20% to obtain a polymer microsphere emulsion.

[0164] Subsequently, the coated diaphragm was prepared by scraping according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were performed.

[0165] Example 7

[0166] This example provides a method for preparing polymer microspheres for battery separator coating. The raw material components of the polymer microspheres are as follows, in parts by weight: 33 parts of basic monomer, 5 parts of functional monomer, 7 parts of crosslinking agent, 2 parts of initiator, 50 parts of solvent, and 3 parts of reactive auxiliary agent.

[0167] Among them, the basic monomer is a mixture of styrene and n-octyl methacrylate (mass ratio is 5:5), the functional monomer is methacrylic acid, the cross-linking agent is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is methanol, and the reactive auxiliary agent is PMA700.

[0168] The synthesis method of the reactive auxiliary agent PMA700 in this example is:

[0169] (1) By weight, 30 parts of methyl acrylate, 0.15 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 1 part of azobisisobutyronitrile, and 68.85 parts of 1,4-dioxane were placed in a round-bottom flask preheated at 70°C;

[0170] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 4 hours;

[0171] (3) The sample was recrystallized with n-hexane and then dissolved with 1,4-dioxane, and this process was repeated three times;

[0172] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PMA700. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 700.

[0173] The synthesis method of polymer microspheres in this example is:

[0174] (1) Put the weighed monomers (including basic monomers, functional monomers and cross-linking agents) into the reactor, add 3 / 4 of the solvent, control the temperature to 50 ° C, and maintain the speed at 150 rpm;

[0175] (2) Then, the reactive additive was added, the temperature was kept constant, and the rotation speed was increased to 250 rpm;

[0176] (3) Vacuum for 1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0177] (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then add dropwise to the reactor;

[0178] (5) After all the initiators are added, the temperature is raised to 65°C and the reaction is carried out at this temperature for 10 hours to obtain the target microsphere emulsion;

[0179] (6) The emulsion was then filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with a reaction solvent. This process was repeated twice, and finally dispersed with water. The solid content was controlled at 20% to obtain a polymer microsphere emulsion.

[0180] Subsequently, the coated diaphragm was prepared by scraping according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were performed.

[0181] Example 8

[0182] This example provides a method for preparing polymer microspheres for battery separator coating. The raw material components of the polymer microspheres are as follows, in parts by weight: 33 parts of basic monomer, 5 parts of functional monomer, 7 parts of crosslinking agent, 2 parts of initiator, 50 parts of solvent, and 3 parts of reactive auxiliary agent.

[0183] Among them, the basic monomer is a mixture of styrene and n-octyl methacrylate (mass ratio is 5:5), the functional monomer is methacrylic acid, the cross-linking agent is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is methanol, and the reactive auxiliary agent is PMA900.

[0184] The synthesis method of the reactive auxiliary agent PMA900 in this example is:

[0185] (1) By weight, 30 parts of methyl acrylate, 0.13 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 1 part of azobisisobutyronitrile, and 68.87 parts of 1,4-dioxane were placed in a round-bottom flask preheated at 70°C;

[0186] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 4 hours;

[0187] (3) The sample was recrystallized with n-hexane and then dissolved with 1,4-dioxane, and this process was repeated three times;

[0188] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PMA900. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 900.

[0189] The synthesis method of polymer microspheres in this example is:

[0190] (1) Put the weighed monomers (including basic monomers, functional monomers and cross-linking agents) into the reactor, add 3 / 4 of the solvent, control the temperature to 50 ° C, and maintain the speed at 150 rpm;

[0191] (2) Then, the reactive additive was added, the temperature was kept constant, and the rotation speed was increased to 250 rpm;

[0192] (3) Vacuum for 1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0193] (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then add dropwise to the reactor;

[0194] (5) After all the initiators are added, the temperature is raised to 65°C and the reaction is carried out at this temperature for 10 hours to obtain the target microsphere emulsion;

[0195] (6) The emulsion was then filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with a reaction solvent. This process was repeated twice, and finally dispersed with water. The solid content was controlled at 20% to obtain a polymer microsphere emulsion.

[0196] Subsequently, the coated diaphragm was prepared by scraping according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were performed.

[0197] Example 9

[0198] This example provides a method for preparing polymer microspheres for battery separator coating. The raw material components of the polymer microspheres are as follows, in parts by weight: 33 parts of basic monomer, 5 parts of functional monomer, 7 parts of crosslinking agent, 2 parts of initiator, 50 parts of solvent, and 3 parts of reactive auxiliary agent.

[0199] Among them, the basic monomer is a mixture of styrene and n-octyl methacrylate (mass ratio is 7:3), the functional monomer is methacrylic acid, the cross-linking agent is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is methanol, and the reactive auxiliary agent is PMA400.

[0200] The synthesis method of the reactive auxiliary agent PMA400 in this example is:

[0201] (1) By weight, 30 parts of methyl acrylate, 0.3 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 1 part of azobisisobutyronitrile, and 68.7 parts of 1,4-dioxane were placed in a round-bottom flask preheated at 70°C;

[0202] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 4 hours;

[0203] (3) The sample was recrystallized with n-hexane and then dissolved with 1,4-dioxane, and this process was repeated three times;

[0204] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PMA400. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 400.

[0205] The synthesis method of polymer microspheres in this example is:

[0206] (1) Put the weighed monomers (including basic monomers, functional monomers and cross-linking agents) into the reactor, add 3 / 4 of the solvent, control the temperature to 50 ° C, and maintain the speed at 150 rpm;

[0207] (2) Then, the reactive additive was added, the temperature was kept constant, and the rotation speed was increased to 250 rpm;

[0208] (3) Vacuum for 1 hour to remove internal oxygen and then pass nitrogen through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate;

[0209] (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then add dropwise to the reactor;

[0210] (5) After all the initiators are added, the temperature is raised to 65°C and the reaction is carried out at this temperature for 10 hours to obtain the target microsphere emulsion;

[0211] (6) The emulsion was then filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with a reaction solvent. This process was repeated twice, and finally dispersed with water. The solid content was controlled at 20% to obtain a polymer microsphere emulsion.

[0212] Subsequently, the coated diaphragm was prepared by scraping according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were performed.

[0213] In order to more clearly highlight the advantages of the present invention, Example 1 is used as a reference benchmark, and only polyvinyl pyrrolidone (K30), a conventional dispersant for dispersion polymerization, is used instead of PMA400. Other materials and synthesis methods are consistent with Example 1. The microspheres prepared in this way are marked as Comparative Example 1; PMA400 in the original Example 1 is replaced by K30, and the addition amount is increased by 1 times. The microspheres prepared in this way are marked as Comparative Example 2; in order to highlight the rationality of the preparation process of the reactive auxiliary agent, 3 parts of PMA400 in the original Example 1 are replaced by 2.97 parts of MA and 0.03 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid. The microspheres prepared in this way are marked as Comparative Example 3; the functional monomer in the original Example 1 is removed from the preparation raw materials, and the microspheres prepared in this way are marked as Comparative Example 4; the reactive auxiliary agent in the original Example 1 is changed from the original PMA400 to PMA50, and the microspheres prepared in this way are marked as Comparative Example 5.

[0214] The synthesis method of the reactive auxiliary agent PMA50 in the comparative example is:

[0215] (1) By weight, 4 parts of methyl acrylate, 0.3 parts of 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, 1 part of azobisisobutyronitrile, and 68.7 parts of 1,4-dioxane were placed in a round-bottom flask preheated at 70°C;

[0216] (2) Nitrogen was passed through for 30 minutes to remove the internal air, followed by reaction at 70°C for 4 hours;

[0217] (3) The sample was recrystallized with n-hexane and then dissolved with 1,4-dioxane, and this process was repeated three times;

[0218] (4) The sample was dried in a vacuum oven at 40°C for 20-25 hours to obtain the desired reactive stabilizer PMA50. The degree of polymerization of the reactive additive was measured by gel permeation chromatography and was 50.

[0219] At the same time, the microspheres prepared in the comparative example were also scraped according to the formula of the diaphragm ceramic coating slurry mentioned above to prepare a coated diaphragm, and relevant tests were performed.

[0220] The microspheres prepared in the above examples and comparative examples were tested for size, electrolyte dissolution rate, and swelling rate. The coated diaphragms prepared in the above examples and comparative examples were tested for average adhesion to the electrode. The detailed test results are summarized in Table 1:

[0221] Table 1

[0222]

[0223] Data Analysis:

[0224] As can be seen from the examples in Table 1, the polymer microspheres of the present invention have a size D50 between 1 and 7 microns, meeting the design requirements of various scenarios. Furthermore, the microspheres of the present invention have a low dissolution rate (less than 4% after immersion in electrolyte at 60°C for 24 hours) and a suitable swelling ratio, ensuring smooth lithium ion transmission across the separator while maintaining the bonding effect of the microsphere binder itself. Finally, this polymer microsphere binder exhibits high adhesion when incorporated into the separator ceramic slurry (after mixing with the ceramic slurry and coating the battery separator, the bonding strength to the electrode can reach over 1.7 N / m). This offers significant advantages over comparable microspheres in the prior art and meets current market demands.

[0225] The technical advantages of the present invention can also be seen from Comparative Examples 3-5; secondly, the reactive auxiliary agent in the present invention cannot be replaced by an equal amount of a common dispersant on the market. Even if the amount of conventional dispersant added is increased, the performance of the polymer microspheres prepared for coating the diaphragm is worse than that in Example 1, which further illustrates the advantages of the reactive auxiliary agent synthesized in the present invention, that is, a smaller amount of addition can prepare uniform, low-dissolution, low-swelling, high-adhesion polymer microspheres that can meet the requirements of battery diaphragm coating.

Claims

1. A polymer microsphere for battery diaphragm coating, characterized in that: The raw materials include 20-40 parts of basic monomer, 5-10 parts of functional monomer, 1-5 parts of initiator I, 3-10 parts of cross-linking agent, 50-90 parts of solvent I and 2-8 parts of reactive auxiliary agent by weight; The basic monomers include hard monomers and soft monomers; the hard monomers are monomers with a glass transition temperature Tg1 of 50°C ≤ Tg1 ≤ 120°C and a double bond structure capable of free radical polymerization; the soft monomers are monomers with a glass transition temperature Tg2 of -80°C ≤ Tg2 < 50°C and a double bond structure capable of free radical polymerization; The functional monomer is selected from monomers containing at least one of carboxyl, amido, hydroxyl and epoxy groups; The reactive auxiliary agent is selected from one or more of acrylate-trithiocarbonate copolymer and acrylic acid-trithiocarbonate copolymer, and the polymerization degree of the reactive auxiliary agent is 200-1000; the acrylate in the reactive auxiliary agent is selected from one or more of methyl acrylate, butyl acrylate, isooctyl acrylate, ethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl acrylate.

2. The polymer microspheres for battery separator coating according to claim 1, characterized in that: The weight ratio of the hard monomer to the soft monomer in the basic monomer is 30-70:70-30.

3. The polymer microspheres for battery separator coating according to claim 1, characterized in that: The hard monomer is selected from one or more of acrylonitrile, styrene, methyl methacrylate, ethyl methacrylate, hydroxyethyl methacrylate, tert-butyl methacrylate, and isopropyl methacrylate; The soft monomer is selected from one or more of glycidyl methacrylate, butyl methacrylate, n-pentyl methacrylate, propyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, and hydroxypropyl methacrylate.

4. The polymer microspheres for battery separator coating according to claim 1, characterized in that: The functional monomer is selected from one or more of methacrylic acid, diacetone acrylamide, hydroxyethyl acrylate, N-methylol acrylamide, hydroxypropyl methacrylate, and hydroxypropyl acrylate; Initiator I is selected from one or more of azobisisobutyronitrile and azobisisoheptanenitrile; The crosslinking agent is selected from one or more of N,N-methylenebisacrylamide, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, divinylbenzene, and allyl methacrylate; Solvent I is selected from one or more combinations of methanol, ethanol, isopropanol and water.

5. The polymer microspheres for battery separator coating according to claim 1, characterized in that: The trithiocarbonate in the reactive auxiliary agent is 2-(dodecyl trithiocarbonate)-2-methylpropionic acid; The polymerization degree of the reactive auxiliary agent is 200-400.

6. The polymer microspheres for battery separator coating according to claim 1, characterized in that: The synthesis method of the reactive auxiliary agent comprises the following steps: (1) By weight, 20-50 parts of acrylic acid or acrylate monomer, 0.1-2 parts of trithiocarbonate, 1-5 parts of initiator II, and 50-70 parts of solvent II are mixed; (2) React at 70-80°C under protective atmosphere for 2-10 hours; (3) Purify and dry to obtain the reactive auxiliary agent.

7. The polymer microspheres for battery separator coating according to claim 6, characterized in that: Initiator II is azobisisobutyronitrile; Solvent II is selected from one of 1,4-dioxane, ethanol and methanol.

8. The polymer microspheres for battery separator coating according to claim 1, characterized in that: The particle size D50 of the polymer microspheres for coating a battery separator is 1-7 microns.

9. The method for preparing polymer microspheres for battery separator coating according to any one of claims 1 to 8, characterized in that: The following steps are involved: The basic monomer, functional monomer, initiator I, crosslinking agent, reactive auxiliary agent and solvent I are mixed, and reacted at 60-70° C. for 8-15 hours under a protective atmosphere to obtain polymer microspheres for battery coating diaphragm.

10. Use of the polymer microspheres for battery coating separators according to any one of claims 1 to 8 in the preparation of battery coating separators.

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