Polymer microsphere for battery coating diaphragm as well as preparation method and application of polymer microsphere

Abstract

The invention discloses a polymer microsphere for a battery coating diaphragm as well as a preparation method and application of the polymer microsphere. The polymer microsphere for the battery coating diaphragm comprises the following raw materials in parts 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 aid, wherein the basic monomer comprises a hard monomer and a soft monomer; the functional monomer is selected from a monomer containing at least one group of carboxyl, acylamino, hydroxyl and epoxy group; the reaction type auxiliary agent is selected from one or more of an acrylate-trithiocarbonate copolymer and an acrylic acid-trithiocarbonate copolymer. The polymer microsphere provided by the invention is low in dissolution rate and strong in binding power when being used for a battery coating diaphragm.

Description

Technical Field

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

[0002] In recent years, due to the continuous increase in the market share of new energy vehicles, the demand for their key component, lithium batteries, has also been increasing day by day. As one of the four major components of lithium batteries, the performance of the diaphragm largely determines the performance of the battery itself. Among the existing diaphragms, coated diaphragms are mainly dominant. Among them, the secondary coating of polyvinylidene fluoride (PVDF) is the current market leader, and there is also a process of one-time coating after mixing PVDF with ceramic slurry. Given that PVDF is expensive and dependent on imports, and a toxic solvent, N-methylpyrrolidone (NMP), is required during use, which does not conform to the green and environmental protection concept of new energy itself. Secondly, PVDF itself also has disadvantages such as poor ion conduction ability and high swelling rate. Therefore, it is particularly important to develop a binder that can replace the existing PVDF.

[0003] Some studies have used polymer microspheres to replace PVDF and mix them with ceramic slurry for the coating of lithium battery diaphragms, and only one-time coating can meet the bonding requirements. For example, CN114920873A discloses a polymer microsphere for lithium ion battery diaphragms and a preparation method thereof. Specifically, by using the emulsion polymerization method, monomers and emulsifiers are added to a pre-emulsification reaction kettle, and a high-speed shear dispersion emulsifier is used for pre-emulsification dispersion to form stable latex micelles. Under the action of an initiator, polymer microspheres with uniform particle size are prepared, which have a lower swelling rate and good bonding force, so that there is better adhesion between the diaphragm and the electrode sheet. CN117060010A discloses a narrow distribution diaphragm binder and a preparation method thereof. The invention first prepares a core polymer by suspension polymerization, and then prepares a polymer microsphere diaphragm binder with a narrow particle size distribution by means of seed emulsion polymerization. It only needs to mix and coat the ceramic slurry with the polymer microsphere diaphragm binder once to complete, which will not affect the air permeability of the diaphragm, and has a high bonding force with the electrode sheet. However, the above-mentioned schemes require pretreatment operations such as emulsification and mechanical dispersion during the preparation process, the preparation time is long, and the required equipment requirements are high in the actual production process, which is not conducive to actual industrial production. In addition, the battery diaphragm needs to work in the electrolyte environment for a long time. Through actual research, it is found that the existing polymer microspheres also have the problem of being unstable and easily dissolved in the electrolyte, resulting in poor durability of the bonding performance of the diaphragm coating layer and affecting the battery cycle life. Summary of the Invention

[0004] To solve the above problems, the present invention provides a polymer microsphere for battery-coated separators, its preparation method and application. The polymer microsphere of the present invention can be used as a binder in the separator ceramic coating slurry instead of PVDF, has good adhesion and a suitable swelling rate, has good stability in the electrolyte, a low dissolution rate, and can achieve the persistence of the bonding performance.

[0005] The technical solution of the present invention is as follows: The present invention provides a polymer microsphere for battery-coated separators. By weight, the raw materials include 20-40 parts of a basic monomer, 5-10 parts of a functional monomer, 1-5 parts of initiator I, 3-10 parts of a crosslinking agent, 50-90 parts of solvent I, and 2-8 parts of a reactive auxiliary agent; Among them, the basic monomer includes a hard monomer and a soft monomer; the hard monomer is a monomer with a glass transition temperature Tg1 of 50°C ≤ Tg1 ≤ 120°C and having a double bond structure that can undergo free radical polymerization by itself; the soft monomer is a monomer with a glass transition temperature Tg2 of -80°C ≤ Tg2 < 50°C and having a double bond structure that can undergo free radical polymerization by itself (the glass transition temperature is measured by differential scanning calorimetry (DSC): using a differential scanning calorimeter (DSC) in a nitrogen atmosphere, the test temperature range is -80°C to 150°C, and the heating rate is 10°C / min to test the sample); The functional monomer is selected from monomers containing at least one group among carboxyl, amide, hydroxyl, and epoxy groups; The reactive auxiliary agent is selected from one or more of acrylate-trithiocarbonate copolymer, acrylic acid-trithiocarbonate copolymer.

[0006] In the raw materials of the polymer microsphere of the present invention, a reactive auxiliary agent is added. It has polar and non-polar groups by itself, can be used as a stabilizer, and can participate in the polymerization reaction to regulate the reaction process, reduce by-products in the polymerization process, and improve the yield.

[0007] The participation of the reactive auxiliary agent in the reaction is mainly divided into 5 stages: (1) Chain initiation stage: In the initial stage of the polymerization reaction, initiator I added to the system first generates free radicals through thermal cleavage, and then reacts with the monomer to form chain growth free radicals; (2) Chain transfer and chain growth stage: The chain growth free radicals undergo an addition reaction with the reactive auxiliary agent to generate intermediate free radicals, and then β-cleavage rapidly occurs on one side arm to form leaving group free radicals and dormant species; (3) Re-initiation stage: The newly formed leaving group free radicals continue to initiate the remaining monomers to form new chain growth free radicals; (4) Chain equilibrium stage: The newly generated chain-growth free radicals react with the dormant species to produce new intermediate free radicals, which then break to form new chain-growth free radicals and dormant species, forming the main "initiation-inactivation" equilibrium through the chain transfer process between the dormant species and the chain-growth free radicals. This process is accompanied by a rapidly established exchange equilibrium between the dormant species and the active growing chains. Therefore, polymer chains with similar chain lengths can be formed in the reaction system, resulting in a polymer with a narrow molecular weight distribution. At the same time, the chain growth rate in the reaction system is always less than the addition-fragmentation equilibrium reaction rate, making the number of dormant species much larger than that of active free radicals, thus reducing the chance of chain termination; (5) Chain termination stage: When the polymerization reaction reaches a certain extent, the bimolecular termination reaction accelerates, and the free radicals are quenched due to disproportionation termination or coupling termination.

[0008] The relative molecular mass of the reactive additive has a certain influence on the size of the synthesized microspheres and the adhesion force for coating the separator of the battery. The polymerization degree of the reactive additive is preferably between 200 and 1000.

[0009] Furthermore, the polymerization degree of the reactive additive is preferably 200 - 400.

[0010] Further, the trithiocarbonate in the reactive additive is preferably 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid; Further, the acrylate in the reactive additive is preferably selected from one or more of methyl acrylate, butyl acrylate, isooctyl acrylate, ethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl acrylate; The reactive additive of the present invention can be obtained commercially or by self-preparation. The present invention provides a method for synthesizing a reactive additive, comprising the following steps: (1) Mix 20 - 50 parts by weight 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; (2) React at 70 - 80 °C for 2 - 10 hours under a protective atmosphere; (3) Purify and dry to obtain the reactive additive.

[0011] Further, the initiator II is preferably azobisisobutyronitrile; Further, the solvent II is preferably selected from one of 1,4-dioxane, ethanol, and methanol.

[0012] Further, the reaction time is preferably 4 - 6 h.

[0013] In the raw materials of the polymer microspheres of the present invention, both a hard monomer and a soft monomer are added. The hard monomer provides a certain rigidity and thermal stability to the microspheres, and at the same time ensures that the microspheres have a certain cohesive force under the hot pressing state; while the soft monomer can provide a certain flow ability to the microspheres under the hot pressing condition, promote the infiltration of the microspheres and the interface, thereby improving the adhesiveness. The two act synergistically, enabling the microspheres to be used as a binder in the diaphragm ceramic coating slurry, effectively improving the adhesion between the diaphragm and the electrode sheet.

[0014] Further, the weight ratio of the hard monomer to the soft monomer in the basic monomer is preferably 30-70:70-30.

[0015] Further, the hard monomer is selected from one or more of acrylonitrile, styrene, methyl methacrylate, ethyl methacrylate, methacrylic acid, 2-hydroxyethyl methacrylate, tert-butyl methacrylate, isopropyl methacrylate.

[0016] Further, 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, 2-hydroxypropyl methacrylate.

[0017] The functional monomer of the present invention is preferably selected from one or more of methacrylic acid, diacetone acrylamide, 2-hydroxyethyl acrylate, N-methylolacrylamide, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate. By adding a certain amount of the functional monomer, its functional groups can form chemical bonds with the interface groups of the electrode sheet, further improving the adhesion ability between the microspheres and the interface.

[0018] The initiator Ⅰ of the present invention is preferably an azo initiator; its main function is to generate free radicals under heating to initiate the polymerization reaction.

[0019] Further, the initiator Ⅰ is selected from one or more of azobisisobutyronitrile, azobisisoheptonitrile; Further, the crosslinking agent of the present invention is a monomer with crosslinking function containing two or three double bonds. The addition of the crosslinking agent can promote the polymerization to produce a crosslinked structure, which is beneficial to improving the stability of the microspheres in the electrolyte.

[0020] Still further, the crosslinking agent is preferably selected from one or more of N,N'-methylenebisacrylamide, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, divinylbenzene, allyl methacrylate; Further, the solvent Ⅰ is selected from one or more combinations of methanol, ethanol, isopropanol and water. It mainly serves as a dispersion medium.

[0021] Further, the particle size D50 of the polymer microspheres for battery-coated diaphragms is 1-7 microns.

[0022] The present invention provides a method for preparing polymer microspheres for the above-mentioned battery coating separator, comprising the following steps: Mix a basic monomer, a functional monomer, initiator I, a crosslinking agent, a reactive auxiliary agent and solvent I, and react at 60-70 °C for 8-15 hours under a protective atmosphere to obtain polymer microspheres for a battery coating separator.

[0023] Further, the method for preparing polymer microspheres for a battery coating separator comprises the following steps: (1) Put the weighed monomers (including the basic monomer, the functional monomer and the crosslinking agent) into a reaction kettle, and add 1 / 2-3 / 4 of solvent I, control the temperature at 50-60 °C, and maintain the rotation speed at 150-200 rpm; (2) Subsequently, add the reactive auxiliary agent, keep the temperature unchanged, and increase the rotation speed to 200-300 rpm; (3) Evacuate for 0.5-1 hour to remove the internal oxygen and then introduce nitrogen, and carry out the reaction under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate at the same time; (4) Add initiator I to the remaining 1 / 4-1 / 2 of solvent I, stir until homogeneous, and then dropwise add it into the reaction kettle; (5) After all of initiator I is added, raise the temperature to 60-70 °C, and react at this temperature for 8-15 hours to obtain the target polymer microsphere emulsion; (6) Subsequently, filter the emulsion through a 200-mesh sieve, centrifuge the filtrate, and then redisperse it with a reaction solvent, repeat this process 2-5 times, and finally disperse it with water to obtain polymer microspheres.

[0024] The present invention also provides the application of the above-mentioned polymer microspheres for a battery coating separator in the preparation of a battery coating separator. Specifically, it is applied as a binder in a battery separator coating slurry, such as in the preparation of a lithium-ion battery separator coating slurry.

[0025] Advantages and beneficial effects of the present invention compared with the prior art: (1) The polymer microspheres of the present invention can be used as a binder in a separator ceramic coating slurry instead of PVDF, have good adhesion and a suitable swelling rate, and have good stability and a low dissolution rate in an electrolyte, can achieve the durability of the bonding performance, and meet the cyclic use of the battery at high rates.

[0026] (2) After the polymer microspheres of the present invention are mixed with a ceramic slurry, they can be coated on a battery separator in one step, simplifying the separator coating process. Compared with the existing two-step coating process, the time cost is effectively reduced, and at the same time, the addition of the polymer microspheres can further improve the lithium ion transmission ability.

[0027] (3)The polymer microspheres of the present invention can be prepared by a one-pot method, without the need for cumbersome operation steps, greatly reducing the time cost (only 8 - 15 hours) and equipment cost. Compared with the existing emulsion polymerization, seed polymerization, etc., it has outstanding convenience and is suitable for industrial production. Description of the Drawings

[0028] Figure 1 SEM photograph of the coated separator prepared by scraping the polymer microspheres for battery-coated separators in Example 1. Detailed Description of the Invention

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer, several examples will be listed to further elaborate on the present invention. The listed technical solutions are only used to explain the present invention and do not limit the protection scope of the present invention. Without changing the idea, any replacement or substitution of this technical solution shall fall within the technical protection scope of the present invention.

[0030] To verify the application advantages of the polymer microspheres in the present invention, the polymer microspheres are applied to the formulation of the separator ceramic coating slurry. The formulation includes, by weight: 10 parts of polymer microsphere emulsion, 54 parts of ceramic powder, 3 parts of water-based binder, 2 parts of thickener, 0.5 part of dispersant, 0.2 part of wetting agent, 0.3 part of defoamer, and 40 parts of water.

[0031] Among them, the ceramic powder is boehmite, the water-based binder is a polyacrylate binder, the thickener is a hydroxymethyl cellulose thickener, the dispersant is BYK - 151, the wetting agent is BYK - 346, and the defoamer is BYK - 024.

[0032] The coating process is as follows: (1)Mix and stir the weighed ceramic powder, thickener and water, keep the rotation speed at 500 rpm, and stir for 1 hour; (2)Increase the rotation speed to 700 rpm, add the dispersant drop by drop, and stir for 0.5 hour after adding; (3)Add the polymer microsphere emulsion and the wetting agent, increase the rotation speed to 1200 rpm, and keep it for 0.5 hour under high-speed stirring; (4)Reduce the rotation speed to 400 rpm, add the defoamer and the water-based binder drop by drop, and keep stirring at low speed for 0.5 hour after adding to remove the air bubbles inside the slurry, and the ceramic coating slurry required for the battery separator can be obtained; (5)Coat the ceramic coating slurry on the battery separator, and then dry it at 60 °C to prepare the battery-coated separator. Control the thickness of the separator ceramic slurry coating to be 2 microns. The SEM photograph of the coated separator after coating is as Figure 1 shown; To characterize the advantageous effects of the polymer microspheres in the separator, the prepared separator was tested in combination with currently common testing methods. The tested properties included the average adhesion force to the electrode; meanwhile, the size, electrolyte dissolution rate, and swelling rate of the polymer microspheres themselves were also characterized.

[0033] (1)Adhesion force test with the electrode: The coated separator was cut into rectangles of 6 × 12 cm. The coated slurry side was overlapped with a graphite negative electrode of the battery with the same size. Subsequently, a hot press (Shenzhen Xinyi Hydraulic Equipment Co., Ltd., model XY-Z2118-3T) was used to hot press at 3 MPa and 80 °C for 1 minute. After the sample cooled, the separator was cut into strips with a width of 2 × 12 cm. Subsequently, an electronic tensile machine (Guangzhou Runhu Instrument Co., Ltd., model RH-L600) was used for the adhesion force test. Each group of samples was tested 3 times, and the average value was taken and rounded to 1 decimal place as the final result.

[0034] (2)Electrolyte dissolution and swelling rate test: Take a microsphere aqueous dispersion with a dry powder weight of about 2 g and pour it into a 4 × 4 × 4 cm cube silicone mold, dry it at 70 °C for about 10 hours. Subsequently, take 0.5 - 1.0 g of the dried sample (the weight at this time is m1) and soak it in an electrolyte (where the mass ratio of ethylene carbonate: dimethyl carbonate: diethyl carbonate = 3:5:2). The electrolyte should completely submerge the sample. Subsequently, place the sample soaked in the electrolyte at 60 °C for 24 hours. After cooling, take out the sample from the electrolyte, gently wipe the surface liquid, and then weigh the sample. The weight at this time is m2. Subsequently, dry the sample at 120 °C for 5 hours, and the mass after drying is m3; The calculation formula for the dissolution rate is = (1 - (m3 / m1)) × 100%; The calculation formula for the swelling rate is = ((m2 - m1) / m1) × 100%.

[0035] (3)Microsphere size: Take a small amount of the microsphere aqueous dispersion and use a Malvern 3000 particle size analyzer to analyze the size of the microspheres, and measure the particle size D50 of the microspheres.

[0036] Example 1 This example provides a preparation method of polymer microspheres for battery-coated separators. The raw material components of the polymer microspheres are respectively in parts by weight: 33 parts of basic monomers, 5 parts of functional monomers, 7 parts of cross-linking agents, 2 parts of initiators, 50 parts of solvents, and 3 parts of reactive additives.

[0037] Among them, the basic monomers are a mixture of styrene and n-octyl methacrylate (mass ratio 5:5), the functional monomer is methacrylic acid, the crosslinking agent is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is methanol, and the reactive additive is PMA400.

[0038] In this example, the synthesis method of the reactive additive PMA400 is as follows: (1) By weight, 30 parts of methyl acrylate, 0.3 parts of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid, 1 part of azobisisobutyronitrile, and 68.7 parts of 1,4-dioxane are placed in a round-bottom flask preheated to 70 °C. (2) Nitrogen is passed through for 30 minutes to remove the internal air, and then the reaction is carried out at 70 °C for 4 hours. (3) The sample is recrystallized with n-hexane and then dissolved in 1,4-dioxane, and this is repeated 3 times. (4) The sample is vacuum dried in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PMA400. The degree of polymerization of the reactive additive measured by gel permeation chromatography is 400.

[0039] In this example, the synthesis method of the polymer microspheres is as follows: (1) The weighed monomers (including basic monomers, functional monomers, and crosslinking agents) are put into a reaction kettle, and 3 / 4 of the solvent is added. The temperature is controlled at 50 °C, and the rotation speed is maintained at 150 rpm. (2) Subsequently, the reactive additive is added, the temperature is kept unchanged, and the rotation speed is increased to 250 rpm. (3) Vacuum is applied for 1 hour to remove the internal oxygen, and then nitrogen is passed through. The reaction is carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate. (4) The initiator is added to the remaining 1 / 4 of the solvent and stirred until homogeneous, and then it is dropped into the reaction kettle. (5) After all the initiator is 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. (6) Subsequently, the emulsion is filtered through a 200-mesh sieve, the filtrate is centrifuged, and then it is redispersed with the reaction solvent, and this is repeated 2 times. Finally, it is dispersed with water, and the solid content is controlled at 20% to obtain the polymer microsphere emulsion.

[0040] Subsequently, the coating diaphragm is prepared by doctor blading according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests are carried out.

[0041] Example 2 This example provides a method for preparing polymer microspheres for battery coating diaphragms. 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 additive.

[0042] Among them, the basic monomer is a mixture of methyl methacrylate, butyl methacrylate, and hydroxypropyl methacrylate (mass ratio 3:2:5), the functional monomer is diacetone acrylamide, the crosslinking agent is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is a mixed solvent of methanol and water (mass ratio 8:2), and the reactive additive is PEA300.

[0043] In this example, the synthesis method of the reactive additive PEA300 is as follows: (1) Weigh 30 parts of ethyl acrylate, 0.3 part of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid, 1 part of azobisisobutyronitrile, and 68.7 parts of 1,4-dioxane, and place them in a round-bottom flask preheated to 70 °C. (2) Pass nitrogen for 30 minutes to remove the internal air, and then react at 70 °C for 6 hours. (3) Recrystallize the sample with n-hexane, and then dissolve it with 1,4-dioxane. Repeat this process 3 times. (4) Vacuum-dry the sample in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PEA300. The degree of polymerization of the reactive additive measured by gel permeation chromatography is 300.

[0044] In this example, the synthesis method of the polymer microspheres is as follows: (1) Put the weighed monomers (including basic monomer, functional monomer, and crosslinking agent) into the reaction kettle, add 3 / 4 of the solvent, control the temperature at 50 °C, and maintain the rotation speed at 200 rpm. (2) Then add the reactive additive, keep the temperature unchanged, and increase the rotation speed to 300 rpm. (3) Evacuate for 1 hour to remove the internal oxygen and then pass nitrogen. React under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate. (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then drop it into the reaction kettle. (5) After all the initiator is added, raise the temperature to 65 °C and react at this temperature for 10 hours to obtain the target microsphere emulsion. (6) Then filter the emulsion through a 200-mesh sieve, centrifuge the filtrate, and immediately redisperse it with the reaction solvent. Repeat this process 2 times, and finally disperse it with water to control the solid content at 20% to obtain the polymer microsphere emulsion.

[0045] Subsequently, the coating diaphragm was prepared by doctor blading according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were carried out.

[0046] Example 3 This example provides a method for preparing polymer microspheres for battery coating diaphragms. The raw material components of the polymer microspheres are as follows in parts by weight: 28 parts of basic monomers, 5 parts of functional monomers, 6 parts of crosslinking agents, 2 parts of initiators, 53 parts of solvents, and 6 parts of reactive additives.

[0047] Among them, the basic monomers are a mixture of methyl methacrylate, glycidyl methacrylate, and butyl methacrylate (mass ratio 3:1:6), the functional monomer is 2-hydroxyethyl acrylate, the crosslinking agent is divinylbenzene, the initiator is 2,2'-azobis(2-methylbutyronitrile), the solvent is a mixed solvent of ethanol and water (mass ratio 7:3), and the reactive additive is PAA300.

[0048] The synthesis method of the reactive additive PAA300 in this example is as follows: (1) Weigh 50 parts of acrylic acid, 0.6 part of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid, 1.4 parts of 2,2'-azobis(2-methylpropionitrile), and 48 parts of 1,4-dioxane and place them in a round-bottom flask preheated to 70 °C. (2) Purge with nitrogen for 30 minutes to remove the internal air, and then react at 70 °C for 5 hours. (3) Recrystallize the sample with n-hexane, and then dissolve it with 1,4-dioxane. Repeat this process 3 times. (4) Vacuum dry the sample in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PAA300. The degree of polymerization of the reactive additive measured by gel permeation chromatography is 300.

[0049] The synthesis method of the polymer microspheres in this example is as follows: (1) Put the weighed monomers (including basic monomers, functional monomers, and crosslinking agents) into the reaction kettle, add 3 / 4 of the solvent, control the temperature at 55 °C, and maintain the rotation speed at 150 rpm. (2) Subsequently, add the reactive additive, keep the temperature unchanged, and increase the rotation speed to 200 rpm. (3) Evacuate for 1 hour to remove the internal oxygen and then purge with nitrogen. React under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate. (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then drop it into the reaction kettle. (5) After all the initiator is added, raise the temperature to 65 °C and react at this temperature for 10 hours to obtain the target microsphere emulsion. (6) Subsequently, the emulsion was filtered through a 200-mesh sieve, and the filtrate was centrifuged. Immediately afterwards, it was redispersed with the reaction solvent, and this was repeated twice. Finally, it was dispersed with water, and a polymer microsphere emulsion with a solid content of 20% was obtained.

[0050] Subsequently, a coated separator was prepared by doctor blade coating according to the formula of the separator ceramic coating slurry mentioned above, and relevant tests were carried out.

[0051] Example 4 This example provides a method for preparing polymer microspheres for a battery coated separator. The raw material components of the polymer microspheres are as follows in parts by weight: 30 parts of basic monomers, 10 parts of functional monomers, 7 parts of crosslinking agents, 3 parts of initiators, 45 parts of solvents, and 5 parts of reactive additives.

[0052] Among them, the basic monomers are a mixture of tert-butyl methacrylate, butyl methacrylate, hydroxypropyl methacrylate, and n-pentyl methacrylate (mass ratio 3:1:2:4), the functional monomer is N-hydroxymethylacrylamide, the crosslinking agent is trimethylolpropane triacrylate, the initiator is azobisisobutyronitrile, the solvent is a mixed solvent of ethanol and water (mass ratio 7:3), and the reactive additive is PBA300.

[0053] In this example, the synthesis method of the reactive additive PBA300 is as follows: (1) By weight, 50 parts of butyl acrylate, 0.4 part of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid, 1.6 parts of azobisisobutyronitrile, and 48 parts of methanol were placed in a round-bottom flask preheated to 70 °C. (2) Nitrogen was passed for 30 minutes to remove the internal air, and then the reaction was carried out at 70 °C for 4 hours. (3) The sample was recrystallized with n-hexane and then dissolved in methanol, and this was repeated 3 times. (4) The sample was vacuum dried in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PBA300. The degree of polymerization of the reactive additive was measured to be 300 by a gel permeation chromatograph.

[0054] In this example, the synthesis method of the polymer microspheres is as follows: (1) The weighed monomers (including basic monomers, functional monomers, and crosslinking agents) were put into a reaction kettle, and 3 / 4 of the solvent was added. The temperature was controlled at 55 °C, and the rotation speed was maintained at 200 rpm. (2) Subsequently, the reactive additive was added, and the temperature was kept unchanged while the rotation speed was increased to 250 rpm. (3) The internal oxygen was removed by vacuum pumping for 1 hour and then nitrogen was passed. The reaction was carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate at the same time. (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until it reaches a homogeneous state, and then drop it into the reaction kettle. (5) After all the initiator has been added, raise the temperature to 65 °C and react at this temperature for 10 hours to obtain the target microsphere emulsion. (6) Then filter the emulsion through a 200-mesh sieve, centrifuge the filtrate, and immediately redisperse it with the reaction solvent. Repeat this process twice, and finally disperse it with water. Control the solid content to 20% to obtain the polymer microsphere emulsion.

[0055] Subsequently, prepare the coated separator by doctor blading according to the formula of the diaphragm ceramic coating slurry mentioned above, and conduct relevant tests.

[0056] Example 5 This example provides a method for preparing polymer microspheres for battery coated separators. The raw material components of the polymer microspheres are as follows in parts by weight: 37 parts of basic monomers, 5 parts of functional monomers, 3 parts of crosslinking agents, 2 parts of initiators, 50 parts of solvents, and 3 parts of reactive additives.

[0057] Among them, the basic monomers are a mixture of styrene, acrylonitrile, and butyl methacrylate (mass ratio 2:2:6), the functional monomer is hydroxypropyl methacrylate, the crosslinking agent is allyl methacrylate, the initiator is azobisisobutyronitrile, the solvent is ethanol, and the reactive additive is PEHA400.

[0058] The synthesis method of the reactive additive PEHA400 in this example is as follows: (1) Weigh 20 parts of isooctyl acrylate, 0.1 part of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid, 0.9 part of azobisisobutyronitrile, and 79 parts of ethanol, and place them in a round-bottom flask preheated to 70 °C. (2) Pass nitrogen for 30 minutes to remove the internal air, and then react at 70 °C for 4 hours. (3) Recrystallize the sample with n-hexane, and then dissolve it with ethanol. Repeat this process three times. (4) Vacuum dry the sample in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PEHA400. The degree of polymerization of the reactive additive is measured to be 400 by a gel permeation chromatograph.

[0059] The synthesis method of the polymer microspheres in this example is as follows: (1) Put the weighed monomers (including basic monomers, functional monomers, and crosslinking agents) into the reaction kettle, add 3 / 4 of the solvent, control the temperature at 55 °C, and maintain the rotation speed at 150 rpm. (2) Then add the reactive additive, keep the temperature unchanged, and increase the rotation speed to 200 rpm. (3) Evacuate the air for 1 hour to remove the internal oxygen, then introduce nitrogen gas, and carry out the reaction under a nitrogen atmosphere to increase the polymerization rate while reducing the residue rate; (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until it becomes homogeneous, and then drop it into the reaction kettle; (5) After all the initiator is added, raise the temperature to 70 °C and react at this temperature for 10 hours to obtain the target microsphere emulsion; (6) Then filter the emulsion through a 200-mesh sieve, centrifuge the filtrate, and then redisperse it with the reaction solvent. Repeat this process 2 times, and finally disperse it with water. Control the solid content at 20% to obtain the polymer microsphere emulsion.

[0060] Subsequently, prepare the coated separator by doctor-blading according to the formula of the separator ceramic coating slurry mentioned above, and conduct relevant tests.

[0061] Example 6 This example provides a method for preparing polymer microspheres for battery-coated separators. The raw material components of the polymer microspheres are as follows in parts by weight: 20 parts of basic monomers, 5 parts of functional monomers, 3 parts of crosslinking agents, 1 part of initiators, 65 parts of solvents, and 4 parts of reactive additives.

[0062] Among them, the basic monomers are a mixture of methyl methacrylate, acrylonitrile, butyl methacrylate, and n-hexyl methacrylate (mass ratio 1:2:3:4), the functional monomer is hydroxypropyl acrylate, the crosslinking agent is divinylbenzene, the initiator is azobisisobutyronitrile, the solvent is isopropanol, and the reactive additive is PEHA200.

[0063] The synthesis method of the reactive additive PEHA200 in this example is as follows: (1) Weigh 20 parts of isooctyl acrylate, 0.15 part of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid, 0.55 part of azobisisobutyronitrile, and 79.3 parts of ethanol, and place them in a round-bottom flask preheated to 70 °C; (2) Pass nitrogen gas for 30 minutes to remove the internal air, and then react at 70 °C for 5 hours; (3) Recrystallize the sample with n-hexane, and then dissolve it with ethanol. Repeat this process 3 times; (4) Vacuum-dry the sample in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PEHA200. The degree of polymerization of the reactive additive is measured to be 200 by a gel permeation chromatograph.

[0064] The synthesis method of the polymer microspheres in this example is as follows: (1) Put the weighed monomers (including basic monomers, functional monomers and crosslinking agents) into the reaction kettle, add 3 / 4 of the solvent, control the temperature at 60 °C, and maintain the rotation speed at 150 rpm; (2) Subsequently, add the reactive auxiliary agent, keep the temperature unchanged, and increase the rotation speed to 200 rpm; (3) Evacuate for 1 hour to remove the internal oxygen and then introduce nitrogen. React under a nitrogen atmosphere to increase the polymerization rate while reducing the residue rate; (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then drop it into the reaction kettle; (5) After all the initiator is added, raise the temperature to 70 °C and react at this temperature for 10 hours to obtain the target microsphere emulsion; (6) Subsequently, filter the emulsion through a 200-mesh sieve, centrifuge the filtrate, then redisperse it with the reaction solvent, repeat this 2 times, and finally disperse it with water to control the solid content at 20% to obtain the polymer microsphere emulsion.

[0065] Subsequently, prepare the coated separator by doctor blading according to the formula of the separator ceramic coating slurry mentioned above, and conduct relevant tests.

[0066] Example 7 This example provides a method for preparing polymer microspheres for battery coated separators. The raw material components of the polymer microspheres are as follows in parts by weight: 33 parts of basic monomers, 5 parts of functional monomers, 7 parts of crosslinking agents, 2 parts of initiators, 50 parts of solvents, and 3 parts of reactive auxiliary agents.

[0067] Among them, the basic monomers are a mixture of styrene and n-octyl methacrylate (mass ratio 5:5), the functional monomer is methacrylic acid, the crosslinking agent is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is methanol, and the reactive auxiliary agent is PMA700.

[0068] The synthesis method of the reactive auxiliary agent PMA700 in this example is as follows: (1) Weigh 30 parts of methyl acrylate, 0.15 parts of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid, 1 part of azobisisobutyronitrile, and 68.85 parts of 1,4-dioxane, and place them in a round-bottom flask preheated to 70 °C; (2) Pass nitrogen for 30 minutes to remove the internal air, and then react at 70 °C for 4 hours; (3) Recrystallize the sample with n-hexane, and then dissolve it with 1,4-dioxane, repeat this 3 times; (4) Vacuum dry the sample in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PMA700. The degree of polymerization of the reactive additive is measured to be 700 by gel permeation chromatography.

[0069] The synthesis method of the polymer microspheres in this example is as follows: (1) Put the weighed monomers (including the basic monomer, functional monomer and crosslinking agent) into the reaction kettle, add 3 / 4 of the solvent, control the temperature at 50 °C, and maintain the rotation speed at 150 rpm; (2) Subsequently, add the reactive additive, keep the temperature unchanged, and increase the rotation speed to 250 rpm; (3) Evacuate for 1 hour to remove the internal oxygen, then introduce nitrogen, and carry out the reaction under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate; (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until homogeneous, and then drop it into the reaction kettle; (5) After all the initiator is added, raise the temperature to 65 °C and react at this temperature for 10 hours to obtain the target microsphere emulsion; (6) Subsequently, filter the emulsion through a 200 - mesh sieve, centrifuge the filtrate, and then redisperse it with the reaction solvent. Repeat this process 2 times, and finally disperse it with water to control the solid content at 20% to obtain the polymer microsphere emulsion.

[0070] Subsequently, prepare the coated separator by doctor - blading according to the formula of the separator ceramic coating slurry mentioned above, and conduct relevant tests.

[0071] Example 8 This example provides a preparation method of polymer microspheres for battery - coated separators. 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 additive.

[0072] Among them, the basic monomer is a mixture of styrene and n - octyl methacrylate (mass ratio 5:5), the functional monomer is methacrylic acid, the crosslinking agent is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is methanol, and the reactive additive is PMA900.

[0073] The synthesis method of the reactive additive PMA900 in this example is as follows: (1) By weight, put 30 parts of methyl acrylate, 0.13 parts of 2 - (dodecyltrithiocarbonate) - 2 - methylpropanoic acid, 1 part of azobisisobutyronitrile, and 68.87 parts of 1,4 - dioxane into a round - bottom flask pre - heated at 70 °C; (2) Pass nitrogen for 30 minutes to remove the internal air, and then react at 70 °C for 4 hours; (3) Recrystallize the sample with n - hexane, and then dissolve it with 1,4 - dioxane, and repeat this process three times. (4) Vacuum - dry the sample in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PMA900. The degree of polymerization of the reactive additive is measured to be 900 by gel permeation chromatography.

[0074] The synthesis method of the polymer microspheres in this example is as follows: (1) Put the weighed monomers (including the basic monomer, functional monomer and cross - linker) into the reaction kettle, add 3 / 4 of the solvent, control the temperature at 50 °C, and maintain the rotation speed at 150 rpm. (2) Then add the reactive additive, keep the temperature unchanged, and increase the rotation speed to 250 rpm. (3) Evacuate for 1 hour to remove the internal oxygen and then introduce nitrogen. React under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate at the same time. (4) Add the initiator to the remaining 1 / 4 of the solvent, stir until it is in a homogeneous state, and then drop - add it into the reaction kettle. (5) After all the initiator is added, raise the temperature to 65 °C and react at this temperature for 10 hours to obtain the target microsphere emulsion. (6) Then filter the emulsion through a 200 - mesh sieve, centrifuge the filtrate, and then redisperse it with the reaction solvent, and repeat this process twice. Finally, disperse it with water and control the solid content at 20% to obtain the polymer microsphere emulsion.

[0075] Subsequently, prepare the coated separator by doctor - blading according to the formula of the separator ceramic coating slurry mentioned above, and conduct relevant tests.

[0076] Example 9 This example provides a preparation method of polymer microspheres for battery - coated separators. 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 cross - linker, 2 parts of initiator, 50 parts of solvent, and 3 parts of reactive additive.

[0077] Among them, the basic monomer is a mixture of styrene and n - octyl methacrylate (mass ratio 7:3), the functional monomer is methacrylic acid, the cross - linker is ethylene glycol dimethacrylate, the initiator is azobisisobutyronitrile, the solvent is methanol, and the reactive additive is PMA400.

[0078] The synthesis method of the reactive additive PMA400 in this example is as follows: (1)By weight, 30 parts of methyl acrylate, 0.3 parts of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid, 1 part of azobisisobutyronitrile, and 68.7 parts of 1,4-dioxane were placed in a round-bottom flask preheated to 70 °C; (2)Nitrogen was passed through for 30 minutes to remove the internal air, and then the reaction was carried out at 70 °C for 4 hours; (3)The sample was recrystallized with n-hexane and then dissolved in 1,4-dioxane, and this was repeated 3 times; (4)The sample was vacuum dried in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PMA400. The degree of polymerization of the reactive additive was measured to be 400 by gel permeation chromatography.

[0079] The synthesis method of the polymer microspheres in this example is as follows: (1)The weighed monomers (including basic monomers, functional monomers, and crosslinking agents) were put into a reaction kettle, and 3 / 4 of the solvent was added. The temperature was controlled at 50 °C, and the rotation speed was maintained at 150 rpm; (2)Subsequently, the reactive additive was added, the temperature was kept unchanged, and the rotation speed was increased to 250 rpm; (3)The internal oxygen was removed by vacuum pumping for 1 hour and then nitrogen was passed through. The reaction was carried out under a nitrogen atmosphere to increase the polymerization rate and reduce the residue rate; (4)The initiator was added to the remaining 1 / 4 of the solvent and stirred until homogeneous, and then dropped into the reaction kettle; (5)After all the initiator was added, the temperature was raised to 65 °C, and the reaction was carried out at this temperature for 10 hours to obtain the target microsphere emulsion; (6)Subsequently, the emulsion was filtered through a 200-mesh sieve, the filtrate was centrifuged, and then redispersed with the reaction solvent. This was repeated 2 times, and finally dispersed with water. Controlling the solid content at 20% gave the polymer microsphere emulsion.

[0080] Subsequently, the coated separator was prepared by doctor blade coating according to the formula of the separator ceramic coating slurry mentioned above, and relevant tests were carried out.

[0081] To more clearly highlight the advantages of the present invention, Example 1 was used as a reference benchmark. Only the conventional dispersant polyvinylpyrrolidone (K30) of dispersion polymerization was used to replace PMA400, and other materials and synthesis methods were kept the same as those in Example 1. The microspheres prepared in this way were labeled as Comparative Example 1; the PMA400 in the original Example 1 was replaced with K30, and at the same time, the addition amount was doubled. The microspheres prepared in this way were labeled as Comparative Example 2; to highlight the rationality of the preparation process of the reactive auxiliary agent, 3 parts of PMA400 in the original Example 1 were replaced with 2.97 parts of MA and 0.03 parts of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid. The microspheres prepared in this way were labeled as Comparative Example 3; the functional monomer in the original Example 1 was removed from the preparation raw materials. The microspheres prepared in this way were labeled as Comparative Example 4; the reactive auxiliary agent in the original Example 1 was changed from the original PMA400 to PMA50. The microspheres prepared in this way were labeled as Comparative Example 5.

[0082] The synthesis method of the reactive auxiliary agent PMA50 in the comparative examples is as follows: (1) By weight, 4 parts of methyl acrylate, 0.3 part of 2-(dodecyltrithiocarbonate)-2-methylpropanoic acid, 1 part of azobisisobutyronitrile, and 68.7 parts of 1,4-dioxane were placed in a round-bottom flask preheated to 70 °C. (2) Nitrogen was passed for 30 minutes to remove the internal air, and then the reaction was carried out at 70 °C for 4 hours. (3) The sample was recrystallized with n-hexane and then dissolved with 1,4-dioxane, and this was repeated 3 times. (4) The sample was vacuum dried in a vacuum oven at 40 °C for 20 - 25 hours to obtain the required reactive stabilizer PMA50. The degree of polymerization of the reactive auxiliary agent was measured to be 50 by a gel permeation chromatograph.

[0083] At the same time, the microspheres prepared in the comparative examples were also scrape-coated to prepare a coated separator according to the formula of the diaphragm ceramic coating slurry mentioned above, and relevant tests were carried out.

[0084] The microspheres prepared in the above examples and comparative examples were tested for size, electrolyte dissolution rate, swelling rate, etc., and the coated separators prepared in the above examples and comparative examples were tested for the average adhesion force with the electrode sheet. The detailed test results are summarized in Table 1: Table 1

[0085] Data analysis: As can be seen from the examples in Table 1, the size D50 of the polymer microspheres of the present invention is between 1 and 7 microns, which can meet the design requirements of different scenarios. Secondly, the microspheres of the present invention have a low dissolution rate (the dissolution rate < 4% after soaking in the electrolyte at 60 °C for 24 h) and a suitable swelling rate, which can ensure the smooth transmission of lithium ions between the diaphragms while ensuring that the bonding effect of the microsphere binder itself does not decay. Finally, the introduction of this polymer microsphere binder into the diaphragm ceramic slurry has a high bonding force (after being mixed with the ceramic slurry and coated on the battery diaphragm, the bonding force with the electrode can reach more than 1.7 N / m), which has stronger advantages compared with the equivalent microspheres in the prior art and can meet the current market demand.

[0086] The technical advantages of the present invention can also be seen from Comparative Examples 3-5; secondly, the reactive additives in the present invention cannot be equivalently replaced with common dispersants on the market. Even if the addition amount of the conventional dispersant is increased, the performance of the polymer microspheres prepared for coating the diaphragm is worse than that of Example 1, which further illustrates the advantages of the synthesized reactive additives in the present invention, that is, polymer microspheres with uniform, low dissolution, low swelling, and high bonding force that can meet the coating of battery diaphragms can be prepared with a small addition amount.

Claims

1. A polymer microsphere for a battery coating separator, characterized in that, By weight parts, the raw materials include 20 - 40 parts of basic monomers, 5 - 10 parts of functional monomers, 1 - 5 parts of initiator I, 3 - 10 parts of crosslinking agent, 50 - 90 parts of solvent I, and 2 - 8 parts of reactive assistant; Among them, the basic monomers include hard monomers and soft monomers; the hard monomer is a monomer with a glass transition temperature Tg1 of 50°C ≤ Tg1 ≤ 120°C and having a double bond structure that can undergo free radical polymerization by itself; the soft monomer is a monomer with a glass transition temperature Tg2 of -80°C ≤ Tg2 < 50°C and having a double bond structure that can undergo free radical polymerization by itself; The functional monomer is selected from monomers containing at least one of the groups of carboxyl, acylamino, hydroxyl, and epoxy groups; The reactive assistant is selected from one or more of acrylate - trithiocarbonate copolymer, acrylic acid - trithiocarbonate copolymer.

2. The polymer microspheres for battery coating diaphragms according to claim 1, characterized in that, The degree of polymerization of the reactive assistant is 200 - 1000; The weight ratio of the hard monomer to the soft monomer in the basic monomers is 30 - 70:70 - 30.

3. The polymer microspheres for battery coating diaphragms according to claim 1, characterized in that, The hard monomer is selected from one or more of acrylonitrile, styrene, methyl methacrylate, ethyl methacrylate, methacrylic acid, 2 - hydroxyethyl methacrylate, tert - butyl methacrylate, 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, 2 - hydroxypropyl methacrylate; 4. The polymer microspheres for battery coating diaphragms according to claim 1, characterized in that, The functional monomer is selected from one or more of methacrylic acid, diacetone acrylamide, 2 - hydroxyethyl acrylate, N - hydroxymethyl acrylamide, 2 - hydroxypropyl methacrylate, 2 - hydroxypropyl acrylate; Initiator I is an azo initiator; Initiator I is selected from one or more of azobisisobutyronitrile, azobisisoheptonitrile; The crosslinking agent is a monomer with crosslinking function containing two or three double bonds; the crosslinking agent is selected from one or more of N,N - methylenebisacrylamide, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, divinylbenzene, allyl methacrylate; Solvent I is selected from one or more combinations of methanol, ethanol, isopropanol, and water.

5. The polymer microspheres for battery coating diaphragms according to claim 1, characterized in that, The trithiocarbonate in the reactive assistant is 2 - (dodecyltrithiocarbonate)-2 - methylpropanoic acid; The acrylate in the reactive assistant is selected from one or more of methyl acrylate, butyl acrylate, isooctyl acrylate, ethyl acrylate, 2 - hydroxypropyl acrylate, 2 - hydroxyethyl acrylate; The degree of polymerization of the reactive assistant is 200 - 400.

6. The polymer microspheres for battery coating diaphragms according to claim 1, characterized in that, The synthesis method of the reactive assistant includes the following steps: (1) By weight parts, mix 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; (2) React at 70 - 80 °C for 2 - 10 hours under a protective atmosphere; (3) Purify and dry to obtain the reactive assistant.

7. The polymer microspheres for battery coating separators 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 coating diaphragms according to claim 1, wherein The particle size D50 of the polymer microspheres for battery coating separators is 1 - 7 microns.

9. The preparation method of the polymer microspheres for battery coating diaphragms according to any one of claims 1-8, characterized in that, It includes the following steps: Mix a basic monomer, a functional monomer, initiator I, a crosslinking agent, a reactive auxiliary agent, and solvent I, and react at 60-70 °C for 8-15 hours under a protective atmosphere to obtain polymer microspheres for battery coating diaphragms.

10. Application of the polymer microspheres for battery coating diaphragms according to any one of claims 1-8 in the preparation of battery coating diaphragms.

Images