A pmma material for uniform high-bonding lithium battery separator and a preparation method thereof

Abstract

The present application relates to the technical field of PMMA glue, and particularly discloses a PMMA material for lithium battery diaphragm with uniform high adhesion and a preparation method thereof.The material comprises the following raw materials in parts by weight: 20-50 parts of PMMA microspheres, 0.5-1 part of a wetting agent, 1-1.2 parts of a dispersing agent, 2-6 parts of modified beta-cyclodextrin and 30-60 parts of deionized water.The PMMA material for lithium battery diaphragm disclosed by the present application has good uniformity when coated, strong adhesion, and no influence on the performance of the diaphragm, and can still maintain the stability and integrity of the lithium battery diaphragm under large environmental changes, and has excellent performance.

Description

Technical Field

[0001] This invention relates to the field of PMMA adhesive technology, and specifically discloses a uniform and highly adhesive PMMA material for lithium battery separators and its preparation method. Background Technology

[0002] In recent years, the new energy industry, especially the new energy vehicle industry, has experienced rapid development. Among them, lithium-ion batteries play a crucial role due to their technological and product characteristics. The lithium-ion battery separator, as one of the four main materials of lithium-ion batteries, serves to isolate the positive and negative electrodes and conduct lithium ions, requiring good heat resistance and low impedance. However, the strength of traditional lithium batteries decreases significantly with thinning, especially large-size batteries which not only have poor hardness but are also prone to twisting and deformation, affecting device applications and even significantly impacting battery performance and safety. Currently, the industry's solution is to use water-based or oil-based PVDF polymers to coat polyolefin separators / ceramic-coated separators, and then hot-press the electrodes and separator together to provide sufficient battery hardness and prevent twisting and deformation. Existing technologies attempt to use binders to coat ceramic particles onto the separator substrate surface to create ceramic / polymer composite separators. The heat resistance of the ceramic particles reduces the thermal shrinkage of the separator, while the polymer improves the adhesion between the separator and the electrode interface, thereby preventing short circuits between the positive and negative electrodes and improving cell hardness.

[0003] Commonly used binders for separators include PVDF (polyvinylidene fluoride) binders, PAA (polyacrylic acid) binders, CMC (carboxymethyl cellulose) binders, and PTFE (polytetrafluoroethylene) binders. However, they have problems such as insufficient adhesion, easy wetting and swelling, which reduces the adhesion between the cathode material and the current collector, and are not conducive to the long-term use of the battery. Therefore, more and more new binder materials are being developed.

[0004] Chinese patent application CN115260403B discloses an aqueous binder, a modified separator, a battery, and a method for preparing the aqueous binder. The aqueous binder comprises binder particles with a core-shell structure. The core of the binder particles is polymer A, and the shell is polymer B. The glass transition temperature of the core is 80℃~150℃, and the glass transition temperature of the shell is 30℃~70℃. The core-shell structured binder particles provided by this patent are coated onto the surface of a separator substrate. After hot pressing, the separator and positive and negative electrodes are bonded together, resulting in a battery with higher strength, better resistance to torsional deformation, and improved separator permeability, thus reducing battery production costs. However, under high-temperature conditions, the performance of the separator may be damaged, and the manufacturing cost is relatively high.

[0005] Chinese patent application CN118027313B discloses a polymer particle with multiple synapses on its surface. The polymer particle is swellable in electrolyte and consists of three polymer layers from the inside out. This polymer particle, with its surface having multiple secondary synaptic structures, has a larger specific surface area compared to traditional spherical particles, allowing for greater contact area and enhanced adhesion strength. Furthermore, when combined with other commonly used film-forming binders, this polymer particle can maintain excellent permeability of the separator. The application of this binder to the separator and secondary battery can significantly suppress battery deformation and improve cycle performance and high-temperature performance. However, this polymer particle may still have the technical problem of low adhesion, which could affect the performance of the separator. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention discloses a uniform and highly adhesive PMMA material for lithium-ion battery separators and its preparation method. The material disclosed in this invention exhibits excellent uniformity and strong adhesion during coating, without affecting the separator's performance. It maintains the stability and integrity of the lithium-ion battery separator even under significant environmental changes, demonstrating superior performance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a uniform and highly adhesive PMMA material for lithium battery separators, characterized in that the material comprises the following raw materials in parts by weight: 20-50 parts PMMA microspheres, 0.5-1 part wetting agent, 1-1.2 parts dispersant, 2-6 parts modified β-cyclodextrin and 30-60 parts deionized water.

[0009] In some embodiments of the present invention, the preparation steps of the modified β-cyclodextrin are as follows:

[0010] (1) Mix sodium alginate and alkaline solution, add β-cyclodextrin and epichlorohydrin in sequence, heat to 55-60℃ and react for 10-20 min, adjust pH to neutral, filter and dry to obtain sodium alginate modified β-cyclodextrin.

[0011] (2) Mix sodium alginate-modified β-cyclodextrin, octadecyl acrylate and initiator, introduce an inert atmosphere, and heat to 65-70℃ with stirring. React for 0.5-1.5h to obtain modified β-cyclodextrin.

[0012] Preferably, in step (1), the mass ratio of sodium alginate, β-cyclodextrin and epichlorohydrin is (1-3):1:(0.2-0.8).

[0013] More preferably, in step (1), the mass ratio of sodium alginate, β-cyclodextrin and epichlorohydrin is 2:1:0.5.

[0014] In some embodiments of the present invention, in step (2), the mass ratio of sodium alginate-modified β-cyclodextrin to octadecyl acrylate is 1:(2.5-4).

[0015] Preferably, in step (2), the mass ratio of sodium alginate-modified β-cyclodextrin to octadecyl acrylate is 1:3.

[0016] In existing technologies, a suitable degree of swelling can improve the permeability and adhesion of batteries. However, inappropriate swelling of the binder can damage its basic bonding performance and may even obstruct ion transport channels. This invention prepares sodium alginate-modified β-cyclodextrin and further modifies it by introducing octadecyl acrylate, effectively improving the wettability of the modified β-cyclodextrin. Simultaneously, a certain amount of hydrophobic cavities are retained, forming a stable penetrating bond structure with the long carbon chains of the introduced octadecyl acrylate, thereby mitigating the adverse effects of swelling changes. The applicant also discovered that when PMMA materials are cured by heating during use, cross-linking may occur between the abundant active groups such as hydroxyl and ether bonds on the modified β-cyclodextrin. Under the influence of its good dispersion and the bonding effect of PMMA, a three-dimensional network structure is formed within the system, further improving the adhesion of the PMMA material. Simultaneously, its mechanical properties are also further enhanced. The complete and dense bonding network can maintain the stability and integrity of the lithium battery separator under significant environmental changes, exhibiting excellent performance.

[0017] In some embodiments of the present invention, the preparation steps of the PMMA microspheres are as follows:

[0018] 1) Preparation of core layer emulsion: Styrene, methyl methacrylate, N-methylacetamide, and hydroxyethyl methacrylate are added to a mixture containing dispersant, deionized water and ethanol and dispersed. Then, the first part by weight of initiator 1 is added for pre-emulsification. The mixture is then heated to 50-70℃ and stirred. Then, the second part by weight of initiator 1 is added and reacted for 1-3 hours to obtain the core layer emulsion.

[0019] 2) Preparation of PMMA microspheres: 2-hydroxyethyl acrylate, 2-carboxyethyl acrylate, and ethylene glycol dimethacrylate were added to a mixture containing sodium dodecyl sulfonate, epoxy resin, and modified graphite. The mixture was stirred to obtain a shell emulsion. The temperature was raised to 70-80°C, and the core emulsion from step 1) and initiator 2 were added while stirring. The mixture was kept at a constant temperature for 1-5 hours to obtain PMMA microspheres.

[0020] In some embodiments of the present invention, the particle size of the PMMA microspheres is 1–5 μm.

[0021] In some embodiments of the present invention, the preparation steps of the modified graphite are as follows:

[0022] Add phosphorus-containing acrylic acid monomer and 4-vinylbenzoic acid to a solvent, then add graphite, and ultrasonically stir for 1-3 hours. Then add initiator 3 and continue ultrasonic stirring for 10-30 minutes to obtain modified graphite.

[0023] Preferably, the phosphorus-containing acrylic monomer is β-hydroxyethyl methacrylate phosphate.

[0024] Preferably, the graphite is expandable graphite.

[0025] In some embodiments of the present invention, the mass ratio of the phosphorus-containing acrylic monomer, 4-vinylbenzoic acid and graphite is (0.8-1):(0.4-0.8):1.

[0026] Preferably, the mass ratio of the phosphorus-containing acrylic acid monomer, 4-vinylbenzoic acid, and graphite is 0.9:0.6:1.

[0027] Preferably, in step 1), the mass ratio of styrene, methyl methacrylate, N-methylacetamide, and hydroxyethyl methacrylate is 1:(0.2-0.4):(1-3):(0.1-0.3).

[0028] More preferably, in step 1), the mass ratio of styrene, methyl methacrylate, N-methylacetamide, and hydroxyethyl methacrylate is 1:0.3:2:0.2.

[0029] Preferably, in step 2), the mass ratio of 2-hydroxyethyl acrylate, 2-carboxyethyl acrylate, ethylene glycol dimethacrylate and the modified graphite in the mixture is 1:(0.1-0.3):(0.4-0.6):(0.3-0.5).

[0030] More preferably, in step 2), the mass ratio of 2-hydroxyethyl acrylate, 2-carboxyethyl acrylate, ethylene glycol dimethacrylate and the modified graphite in the mixture is 1:0.2:0.5:0.4.

[0031] In existing technologies, membrane binders play a crucial role in lithium-ion batteries. They not only contribute to improved battery safety but also enhance the integrity of the electrode structure. PMMA binders, unlike commonly used polyvinylidene fluoride (PVDF), exhibit superior chemical and electrochemical stability, ensuring stability during battery charge and discharge and minimizing the likelihood of side reactions. However, the heat resistance of PMMA membrane binders is often limited by the inherent physical properties of PMMA. This invention addresses this issue by incorporating modified graphite into the emulsion polymerization process of PMMA microspheres, resulting in PMMA microspheres with a particle size of 1–5 μm. The aromatic rings and phosphorus-containing groups introduced onto the modified graphite effectively increase the heat resistance of PMMA as a battery membrane binder, thereby reducing the internal resistance of lithium-ion batteries to some extent. Simultaneously, the specific particle size of the PMMA microspheres maintains contact surfaces with other components in the system, further enhancing adhesion. The smoother particle surface also reduces the moisture content of the membrane and the amount of redundant electrolyte adsorbed, significantly lowering costs.

[0032] In some embodiments of the present invention, the wetting agent is an acrylic leveling agent.

[0033] In some embodiments of the present invention, the dispersant is at least one of polyvinylpyrrolidone, polyethylene glycol, and sodium polyacrylate.

[0034] Preferably, the dispersant is polyethylene glycol.

[0035] Another aspect of the present invention provides a method for preparing a uniform and highly adhesive PMMA material for lithium battery separators, comprising the following steps: adding PMMA microspheres to deionized water and mixing and stirring, adding a dispersant, stirring, and then adding modified β-cyclodextrin and a wetting agent, and stirring evenly to obtain the material.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) The PMMA material for lithium battery separators disclosed in this invention has good uniformity and strong adhesion when coated, and has no effect on the performance of the separator.

[0038] (2) This invention prepares sodium alginate-modified β-cyclodextrin and then introduces octadecyl acrylate for further modification, which effectively improves the wettability of the modified β-cyclodextrin. At the same time, a certain amount of hydrophobic cavities are retained to form a stable penetrating bonding structure with the long carbon chain of the introduced octadecyl acrylate, thereby reducing the adverse effects of swelling changes in the system. When PMMA materials are used, the modified β-cyclodextrin may also participate in the cross-linking and curing of the system, promoting the bonding effect of the three-dimensional network structure between the systems, further improving the adhesion of PMMA materials and further enhancing mechanical properties. The complete and dense bonding network can maintain the stability and integrity of the lithium battery separator under large environmental changes, and has excellent performance.

[0039] (3) This invention prepares modified graphite to participate in the emulsion polymerization process of PMMA microspheres, thereby obtaining PMMA microspheres with a particle size of 1 to 5 μm. This effectively increases the heat resistance and air permeability of PMMA material as a battery separator binder, and reduces the internal resistance of the battery to a certain extent. At the same time, the specific particle size of the microspheres maintains the contact surface between them and other components in the system, further improving the adhesion. Their hydrophobicity and relatively smooth particle surface also reduce the moisture content of the separator and the amount of redundant electrolyte adsorbed, significantly reducing the cost. Detailed Implementation

[0040] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Furthermore, all technical terms mentioned below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Other combinations and various modifications within the scope of the present invention can be made without departing from the spirit or scope of the invention.

[0041] Unless otherwise specified, all reagents used below are readily available from commercial companies.

[0042] Unless otherwise specified, the alginate used below was purchased from Hebei Kelongduo Biotechnology Co., Ltd., β-cyclodextrin from Jiangsu Bosite Chemical Technology Co., Ltd., epoxy resin (model CYDW-100) from Zhengzhou Wubaotong Trading Co., Ltd., graphite (average particle size of 80 mesh) from Hebei Hengguang Mineral Products Co., Ltd., methacrylate-β-hydroxyethyl phosphate was prepared according to section 2.2 of "Wang Xiaoshuang. Preparation of phosphorus-containing acrylate emulsion and its application in flame-retardant air filter paper [D]. South China University of Technology, 2017". The polyvinylpyrrolidone model was PVP K30.

[0043] Unless otherwise specified, the post-processing steps such as "ultrasound", "rotary evaporation", "stirring", and "vacuum filtration" used below are routine operations for those skilled in the art, and can be selected according to actual operation.

[0044] Unless otherwise specified, the wetting agents used below are all acrylic leveling agents (model WT4103), and the dispersants are all polyethylene glycol (model PEG600).

[0045] Preparation Example 1

[0046] The preparation steps of modified β-cyclodextrin are as follows:

[0047] (1) Mix 2g sodium alginate and 8mL 20wt% sodium hydroxide aqueous solution, add 1g β-cyclodextrin and 0.5mL epichlorohydrin in sequence, heat to 58℃ and react for 15min, adjust pH to 7, filter and dry to obtain sodium alginate modified β-cyclodextrin.

[0048] (2) Mix 1g sodium alginate-modified β-cyclodextrin, 3g octadecyl acrylate and 0.15g ammonium persulfate, introduce nitrogen atmosphere, heat to 67℃ under stirring, and react for 1h to obtain modified β-cyclodextrin.

[0049] Preparation Example 2

[0050] The preparation steps of the modified β-cyclodextrin are the same as those in Preparation Example 1, except that the amount of octadecyl acrylate added in step (2) is 4.5g.

[0051] Preparation Example 3

[0052] The preparation steps of modified graphite are as follows:

[0053] Add 9g of β-hydroxyethyl methacrylate phosphate and 6g of 4-vinylbenzoic acid to 100mL of N,N-dimethylformamide, then add 10g of graphite, sonicate for 2h, then add 0.02g of azobisisobutyronitrile, continue sonicating for 20min, and then obtain modified graphite by rotary evaporation.

[0054] Preparation Example 4

[0055] The preparation steps for modified graphite are the same as in Preparation Example 3, except that the amount of β-hydroxyethyl methacrylate phosphate added is 11g.

[0056] Preparation Example 5

[0057] The preparation steps for modified graphite are the same as in Preparation Example 3, except that the amount of 4-vinylbenzoic acid added is 9g.

[0058] Preparation Example 6

[0059] The preparation steps for PMMA microspheres are as follows:

[0060] 1) Preparation of core layer emulsion: 10g styrene, 3g methyl methacrylate, 20g N-methylacetamide, and 2g hydroxyethyl methacrylate were added to a mixture containing 2g polyvinylpyrrolidone, 20mL deionized water, and 80mL ethanol and dispersed. Then, 0.05g azobisisobutyronitrile was added and stirred at 700r / min for 10min for pre-emulsification. The mixture was then heated to 60℃ and stirred, and then 0.03g azobisisobutyronitrile was added. The reaction was carried out for 2h to obtain the core layer emulsion.

[0061] 2) Preparation of PMMA microspheres: 5g of 2-hydroxyethyl acrylate, 1g of 2-carboxyethyl acrylate, and 2.5g of ethylene glycol dimethacrylate were added to a mixture containing 10mL of sodium dodecyl sulfonate, 0.5g of epoxy resin, and 4g of modified graphite. The mixture was stirred to obtain a shell emulsion. The temperature was raised to 75℃, and then 100g of the core emulsion from step 1) and 0.02g of sodium persulfate were added while stirring. The mixture was reacted at a constant temperature for 3h to obtain PMMA microspheres.

[0062] The modified graphite used was obtained from Preparation Example 3.

[0063] Preparation Example 7

[0064] The preparation steps for PMMA microspheres are the same as in Preparation Example 6, except that the modified graphite used was obtained from Preparation Example 4.

[0065] Preparation Example 8

[0066] The preparation steps for PMMA microspheres are the same as in Preparation Example 6, except that the modified graphite used was obtained from Preparation Example 5.

[0067] Preparation Example 9

[0068] The preparation steps for PMMA microspheres are the same as in Preparation Example 6, except that the modified graphite is replaced with an equal amount of graphite.

[0069] Example 1

[0070] A uniform and highly adhesive PMMA material for lithium battery separators comprises the following raw materials in parts by weight: 35 parts PMMA microspheres, 0.7 parts wetting agent, 1.1 parts dispersant, 4 parts modified β-cyclodextrin and 45 parts deionized water.

[0071] The preparation method of the uniform and highly adhesive PMMA material for lithium battery separators in this embodiment includes the following steps: adding PMMA microspheres to deionized water and mixing, adding a dispersant, stirring, and then adding modified β-cyclodextrin and a wetting agent, and stirring evenly to obtain the material.

[0072] The modified β-cyclodextrin used in this embodiment was obtained from Preparation Example 1, and the PMMA microspheres used were obtained from Preparation Example 6.

[0073] Example 2

[0074] A uniform and highly adhesive PMMA material for lithium battery separators comprises the following raw materials in parts by weight: 20 parts PMMA microspheres, 0.5 parts wetting agent, 1 part dispersant, 2 parts modified β-cyclodextrin and 30 parts deionized water.

[0075] The preparation method of the uniform and highly adhesive PMMA material for lithium battery separators in this embodiment is the same as in Example 1.

[0076] The modified β-cyclodextrin used in this embodiment was obtained from Preparation Example 1, and the PMMA microspheres used were obtained from Preparation Example 6.

[0077] Example 3

[0078] A uniform and highly adhesive PMMA material for lithium battery separators comprises the following raw materials in parts by weight: 50 parts PMMA microspheres, 1 part wetting agent, 1.2 parts dispersant, 6 parts modified β-cyclodextrin and 60 parts deionized water.

[0079] The preparation method of the uniform and highly adhesive PMMA material for lithium battery separators in this embodiment is the same as in Example 1.

[0080] The modified β-cyclodextrin used in this embodiment was obtained from Preparation Example 1, and the PMMA microspheres used were obtained from Preparation Example 4.

[0081] Example 4

[0082] A uniform and highly adhesive PMMA material for lithium battery separators and its preparation method, the difference being that the modified β-cyclodextrin used is obtained from Preparation Example 2.

[0083] Example 5

[0084] A uniform and highly adhesive PMMA material for lithium battery separators and its preparation method, the difference being that the PMMA microspheres used are obtained from Preparation Example 7.

[0085] Example 6

[0086] A uniform and highly adhesive PMMA material for lithium battery separators and its preparation method, the difference being that the PMMA microspheres used are obtained from Preparation Example 8.

[0087] Example 7

[0088] A uniform and highly adhesive PMMA material for lithium battery separators and its preparation method, the difference being that the PMMA microspheres used are obtained from Preparation Example 9.

[0089] Comparative Example 1

[0090] A uniform and highly adhesive PMMA material for lithium battery separators and its preparation method, the difference being that modified β-cyclodextrin is replaced in equal amounts with β-cyclodextrin.

[0091] Performance testing

[0092] (1) Heat resistance test: heat shrinkage test: the materials obtained in Examples 1-7 and Comparative Example 1 were bonded to a 12μm thick ordinary polyethylene diaphragm, coated with a thickness of 3μm, and heated at 135℃ for 1h. The shrinkage value in the MD direction was tested to characterize the thermal stability of the PMMA material. The specific test results are shown in Table 1.

[0093] (2) Adhesion performance test: The materials obtained in Examples 1-7 and Comparative Example 1 were coated on ordinary polyethylene separators with a thickness of 12 μm and a coating thickness of 3 μm. They were hot-pressed with the battery electrode at 80°C and 3 MPa for 1 min and cut into 25 mm × 200 mm samples. The peel strength was tested using a KT-PSA-1056 peel strength tester to characterize the adhesion performance of the PMMA material. The specific test results are shown in Table 1.

[0094] Table 1

[0095] project Peel strength (N / m) Shrinkage value (%) Example 1 32.5 0.43 Example 2 31.0 0.48 Example 3 31.8 0.46 Example 4 29.1 0.51 Example 5 29.8 0.57 Example 6 29.6 0.60 Example 7 29.2 0.67 Comparative Example 1 27.5 0.75

[0096] As shown in Table 1, the PMMA materials provided in Examples 1 to 3 of this invention have good bonding and heat resistance properties, and their shrinkage is minimal.

[0097] As can be seen from the comparison between Example 4 and Example 1, when the amount of octadecyl acrylate added in the preparation of modified β-cyclodextrin is changed, the density of the bonding network of the system may decrease due to the large steric hindrance and instability caused by the structure of modified β-cyclodextrin, which further leads to a significant decrease in the bonding performance of PMMA material, but the heat resistance is less affected.

[0098] As can be seen from the comparison between Examples 5 and 6 and Example 1, when the amount of modified graphite added to the preparation of PMMA microspheres is changed, the heat resistance of PMMA microspheres will decrease significantly. At the same time, the shell's coating effect on the core will be poor, which in turn leads to a decrease in the bonding performance and heat resistance of PMMA materials.

[0099] As can be seen from the comparison between Example 7 and Example 1, when unmodified graphite is added during the preparation of PMMA microspheres, the structural stability of PMMA microspheres decreases when heated, which in turn leads to a decrease in the bonding performance and heat resistance of PMMA materials.

[0100] As can be seen from the comparison between Comparative Example 1 and Example 1, when the modified β-cyclodextrin is directly replaced by an equal amount of β-cyclodextrin, the uniformity of the three-dimensional network structure of the system decreases, which in turn leads to a decrease in the overall performance of the PMMA material.

[0101] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A uniform, highly adhesive PMMA material for lithium battery separators, characterized in that, The material comprises the following raw materials in parts by weight: 20-50 parts PMMA microspheres, 0.5-1 part wetting agent, 1-1.2 parts dispersant, 2-6 parts modified β-cyclodextrin and 30-60 parts deionized water; The preparation steps of the modified β-cyclodextrin are as follows: (1) Sodium alginate and alkaline solution are mixed, β-cyclodextrin and epichlorohydrin are added in sequence, the temperature is raised to 55~60℃ and reacted for 10~20 min, the pH is adjusted to neutral, and sodium alginate modified β-cyclodextrin is obtained after filtration and drying. (2) Sodium alginate-modified β-cyclodextrin, octadecyl acrylate and initiator are mixed, an inert atmosphere is introduced, and the mixture is heated to 65~70℃ under stirring and reacted for 0.5~1.5h to obtain modified β-cyclodextrin. The preparation steps of the PMMA microspheres are as follows: 1) Preparation of core layer emulsion: Styrene, methyl methacrylate, N-methylacetamide, and hydroxyethyl methacrylate are added to a mixture containing dispersant, deionized water, and ethanol and dispersed. Then, the first part by weight of initiator 1 is added for pre-emulsification. The mixture is then heated to 50~70℃ and stirred before the second part by weight of initiator 1 is added. The reaction is carried out for 1~3 hours to obtain the core layer emulsion. 2) Preparation of PMMA microspheres: 2-hydroxyethyl acrylate, 2-carboxyethyl acrylate, and ethylene glycol dimethacrylate were added to a mixture containing sodium dodecyl sulfonate, epoxy resin, and modified graphite. The mixture was stirred to obtain a shell emulsion. The temperature was raised to 70-80°C, and the core emulsion from step 1) and initiator 2 were added while stirring. The mixture was reacted at a constant temperature for 1-5 hours to obtain PMMA microspheres. The PMMA microspheres have a particle size of 1~5μm; In step 2), the preparation steps of the modified graphite are as follows: Add phosphorus-containing acrylic acid monomer and 4-vinylbenzoic acid to a solvent, then add graphite, and ultrasonically stir for 1-3 hours. Then add initiator 3 and continue ultrasonic stirring for 10-30 minutes to obtain modified graphite.

2. The PMMA material for a uniform, highly adhesive lithium battery separator according to claim 1, characterized in that, In step (2), the mass ratio of sodium alginate-modified β-cyclodextrin to octadecyl acrylate is 1:(2.5~4).

3. The PMMA material for a uniform, highly adhesive lithium battery separator according to claim 1, characterized in that, The mass ratio of the phosphorus-containing acrylic acid monomer, 4-vinylbenzoic acid and graphite is (0.8~1):(0.4~0.8)1.

4. The PMMA material for a uniform, highly adhesive lithium battery separator according to claim 1, characterized in that, The wetting agent is an acrylic leveling agent.

5. The PMMA material for a uniform, highly adhesive lithium battery separator according to claim 1, characterized in that, The dispersant is at least one of polyvinylpyrrolidone, polyethylene glycol, and sodium polyacrylate.

6. A method for preparing a uniform, highly adhesive PMMA material for lithium-ion battery separators according to any one of claims 1-5, characterized in that, The process includes the following steps: adding PMMA microspheres to deionized water and mixing, adding a dispersant, stirring, then adding modified β-cyclodextrin and a wetting agent, and stirring until homogeneous to obtain the material.