Uniform high-adhesion PMMA (polymethyl methacrylate) material for lithium battery diaphragm and preparation method of uniform high-adhesion PMMA material

Abstract

The invention relates to the technical field of PMMA glue, and particularly discloses a uniform high-adhesion PMMA material for a lithium battery diaphragm and a preparation method of the uniform high-adhesion PMMA material. 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 the lithium battery diaphragm, disclosed by the invention, is good in uniformity and strong in cohesiveness during coating, has no influence on the performance of the diaphragm, can still keep the stability and integrity of the lithium battery diaphragm under a relatively large environmental change, and is excellent in performance.

Description

Technical Field

[0001] The invention relates to the technical field of PMMA glue, and specifically discloses a uniform and highly-adhesive PMMA material for a lithium battery separator and a preparation method thereof. Background Art

[0002] In recent years, the new energy industry, especially the new energy vehicle industry, has developed rapidly. Among them, lithium-ion batteries play an important role in the new energy industry due to their technology and product characteristics. As one of the four main materials of lithium-ion batteries, lithium-ion battery separators play the role of isolating positive and negative electrodes and conducting lithium ions. They need to have good heat resistance and low impedance. However, the strength of traditional lithium batteries is significantly weakened as the thickness is reduced. In particular, large-size batteries not only have poor hardness, but are also prone to distortion and deformation, which affects device applications and even has a great impact on battery performance and safety. The current solution adopted by the industry is to use water-based or oily PVDF polymers to coat polyolefin separators / ceramic coated separators, and to composite the pole pieces and separators together by hot pressing to provide sufficient battery hardness and prevent distortion. In the prior art, attempts are made to use a binder to coat ceramic particles on the surface of the separator substrate to form a ceramic / polymer composite separator, and to use the heat resistance of ceramic particles to reduce the thermal shrinkage of the separator. At the same time, polymers are used to improve the adhesion between the separator and the pole piece interface, thereby preventing the battery from short-circuiting the positive and negative poles and improving the hardness of the battery core.

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

[0004] The invention patent with publication number CN115260403B discloses a water-based binder, a modified diaphragm, a battery, and a method for preparing a water-based binder, which involves a water-based binder, the water-based binder comprising binder particles with a core-shell structure, wherein the core of the binder particles with the core-shell structure is polymer A and the shell is polymer B; the glass transition temperature of the core is 80°C to 150°C; the glass transition temperature of the shell is 30°C to 70°C. The binder particles with a core-shell structure provided by the invention patent are coated on the surface of the diaphragm substrate, and after the prepared battery cell is hot-pressed, the diaphragm is bonded to the positive and negative electrodes, so that the battery has higher strength and good resistance to distortion and deformation, while improving the air permeability of the diaphragm and reducing battery production. However, it may be affected by temperature under high temperature conditions, causing damage to the performance of the diaphragm, and the production cost is relatively high.

[0005] The invention patent with publication number CN118027313B discloses a polymer particle, the surface of which has multiple synapses; the polymer particle is swellable in an electrolyte; the polymer particle is composed of three polymer layers from the inside to the outside. The surface of the polymer particle has a plurality of colloid particles with secondary structural synapses. Compared with traditional spherical colloid particles, such colloid particles with multiple secondary structural synapses have a larger specific surface area, can achieve a larger area of ​​contact, and enhance the bonding strength. At the same time, when the polymer particles are combined with other commonly used film-forming adhesives, the diaphragm can maintain very excellent air permeability. The battery deformation of the diaphragm and secondary battery using the adhesive can be significantly suppressed, and the battery's cycle performance and high temperature performance can be improved. However, the polymer particles may also have a technical problem of low adhesion, which will affect the performance of the diaphragm. Summary of the invention

[0006] In view of the defects of the prior art, the present invention discloses a uniform and highly adhesive PMMA material for lithium battery separator and a preparation method thereof. The material disclosed in the present invention has good uniformity and strong adhesion during coating, and has no effect on the performance of the separator. It can maintain the stability and integrity of the lithium battery separator under large environmental changes and has excellent performance.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, 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 to 50 parts of PMMA microspheres, 0.5 to 1 part of a wetting agent, 1 to 1.2 parts of a dispersant, 2 to 6 parts of modified β-cyclodextrin and 30 to 60 parts of deionized water.

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

[0010] (1) Mixing sodium alginate and alkali solution, adding β-cyclodextrin and epichlorohydrin in sequence, heating to 55-60° C. for reaction for 10-20 min, adjusting the pH to neutral, filtering and drying to obtain sodium alginate modified β-cyclodextrin;

[0011] (2) Sodium alginate modified β-cyclodextrin, octadecyl acrylate and an initiator are mixed, introduced into an inert atmosphere, heated to 65-70° C. while stirring, and reacted for 0.5-1.5 h 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] Further 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 the sodium alginate-modified β-cyclodextrin to octadecyl acrylate is 1:(2.5-4).

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

[0016] In the prior art, a suitable swelling degree can improve the air permeability and adhesion of the battery. When the swelling degree of the binder is inappropriate, its basic adhesion performance will be damaged, and the ion transfer channel may be blocked. The present 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 inner cavity is retained and a stable penetrating bonding structure is formed between the long carbon chain of the introduced octadecyl acrylate, thereby reducing the adverse effects of swelling changes. The applicant also found that when the PMMA material is heated and cured during use, it may be due to the cross-linking between the rich active groups such as hydroxyl and ether bonds on the modified β-cyclodextrin. Under its good dispersion and the bonding effect of PMMA, the bonding effect of the three-dimensional network structure between the systems is promoted, which further improves the bonding of the PMMA material. At the same time, its mechanical properties are further enhanced. The complete and dense bonding network can still maintain the stability and integrity of the lithium battery separator under large environmental changes, and the performance is excellent.

[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, hydroxyethyl methacrylate are added to a mixture containing a dispersant, deionized water and ethanol for dispersion, and then the first weight portion of initiator 1 is added for pre-emulsification, and then the temperature is raised to 50-70° C. and stirred, and then the second weight portion of initiator 1 is added, and the reaction is carried out 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 are added to a mixture containing sodium dodecyl sulfate, epoxy resin, and modified graphite, and stirred to obtain a shell emulsion. The temperature is raised to 70-80° C., and then the core emulsion of step 1) and initiator 2 are added under stirring, and the reaction is carried out at a constant temperature for 1-5 hours to obtain PMMA microspheres.

[0020] In some embodiments of the present invention, the PMMA microspheres have a particle size of 1 to 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 monomer and 4-vinylbenzoic acid to a solvent, then add graphite, and stir ultrasonically for 1 to 3 hours. Then add initiator 3, and continue stirring ultrasonically for 10 to 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 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] Further 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] Further 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 the prior art, diaphragm binders play a vital role in lithium-ion batteries. They not only help to improve the safety performance of the battery, but also enhance the integrity of the electrode structure. The PMMA binder is different from the commonly used polyvinylidene fluoride (PVDF). Its chemical stability and electrochemical stability make it stable during the charge and discharge process of the battery and not prone to side reactions. However, the PMMA diaphragm binder is affected by the physical properties of PMMA itself, and its heat resistance is often limited. The present invention obtains PMMA microspheres with a particle size of 1 to 5 μm by adding modified graphite to participate in the emulsion polymerization process of PMMA microspheres. The aromatic rings and phosphorus-containing groups introduced on the modified graphite effectively increase the heat resistance of the PMMA material as a battery diaphragm binder, thereby reducing the internal resistance of the lithium electronic battery to a certain extent. At the same time, the PMMA microspheres of a specific particle size maintain the contact surface between it and other components in the system, further improving the bonding force. Its relatively smooth particle surface also reduces the moisture content of the diaphragm, and also reduces the adsorption amount of redundant electrolyte, significantly reducing the cost.

[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 polyvinyl pyrrolidone, polyethylene glycol and sodium polyacrylate.

[0034] Preferably, the dispersant is polyethylene glycol.

[0035] On the other hand, the present invention also 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, and then adding modified β-cyclodextrin and a wetting agent after stirring, and stirring evenly to obtain the material.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

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

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

[0039] (3) The present invention prepares PMMA microspheres by participating in the emulsion polymerization process of modified graphite to obtain PMMA microspheres with a particle size of 1 to 5 μm, which effectively increases the heat resistance and air permeability of PMMA materials as battery diaphragm binders and reduces the internal resistance of the battery to a certain extent. At the same time, the microspheres with a specific particle size maintain the contact surface between them and other components in the system, further improving the bonding force. The hydrophobicity and relatively smooth particle surface also reduce the moisture content of the diaphragm and the adsorption amount of redundant electrolyte, significantly reducing the cost. DETAILED DESCRIPTION

[0040] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. At the same time, all the professional terms mentioned below have the same meaning as those generally understood by those skilled in the art. The professional 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 improvements within the concept of the present invention may be performed without departing from the gist or scope of the present invention.

[0041] Unless otherwise specified, the reagents used below can be easily obtained from commercial companies.

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

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

[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) 2 g of sodium alginate and 8 mL of 20 wt % sodium hydroxide aqueous solution were mixed, 1 g of β-cyclodextrin and 0.5 mL of epichlorohydrin were added in sequence, the temperature was raised to 58° C. for reaction for 15 min, the pH was adjusted to 7, and sodium alginate-modified β-cyclodextrin was obtained after filtration and drying;

[0048] (2) 1 g of sodium alginate-modified β-cyclodextrin, 3 g of octadecyl acrylate and 0.15 g of ammonium persulfate were mixed, nitrogen atmosphere was introduced, the temperature was raised to 67° C. under stirring, and the reaction was carried out for 1 h to obtain modified β-cyclodextrin.

[0049] Preparation Example 2

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

[0051] Preparation Example 3

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

[0053] 9 g of β-hydroxyethyl methacrylate phosphate and 6 g of 4-vinylbenzoic acid were added to 100 mL of N,N-dimethylformamide, and then 10 g of graphite was added. The mixture was ultrasonically stirred for 2 h, and then 0.02 g of azobisisobutyronitrile was added. The mixture was ultrasonically stirred for 20 min and then rotary evaporated to obtain modified graphite.

[0054] Preparation Example 4

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

[0056] Preparation Example 5

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

[0058] Preparation Example 6

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

[0060] 1) Preparation of core layer emulsion: 10g styrene, 3g methyl methacrylate, 20g N-methylacetamide, 2g hydroxyethyl methacrylate were added to a mixture containing 2g polyvinyl pyrrolidone, 20mL deionized water and 80mL ethanol for dispersion, and then 0.05g azobisisobutyronitrile was added and stirred at 700r / min for 10min for pre-emulsification, and then the temperature was raised to 60°C and stirred, and then 0.03g azobisisobutyronitrile was added and reacted for 2h to obtain the core layer emulsion;

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

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

[0063] Preparation Example 7

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

[0065] Preparation Example 8

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

[0067] Preparation Example 9

[0068] The preparation steps of PMMA microspheres are the same as those of Preparation Example 6, except that an equal amount of graphite is used to replace the modified graphite.

[0069] Example 1

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

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

[0072] The modified β-cyclodextrin used in this example is obtained from Preparation Example 1, and the PMMA microspheres used are obtained from Preparation Example 6.

[0073] Example 2

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

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

[0076] The modified β-cyclodextrin used in this example is obtained from Preparation Example 1, and the PMMA microspheres used are obtained from Preparation Example 6.

[0077] Example 3

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

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

[0080] The modified β-cyclodextrin used in this example is obtained from Preparation Example 1, and the PMMA microspheres used are obtained from Preparation Example 4.

[0081] Example 4

[0082] A uniform high-adhesion PMMA material for lithium battery separator and a preparation method thereof, 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 separator and a preparation method thereof, 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 separator and a preparation method thereof, 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 separator and a preparation method thereof, the difference being that the PMMA microspheres used are obtained from Preparation Example 9.

[0089] Comparative Example 1

[0090] A uniform high-adhesion PMMA material for lithium battery separator and a preparation method thereof, the difference being that modified β-cyclodextrin is replaced by an equal amount of 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 common polyethylene separator with a thickness of 12 μm, with a coating thickness of 3 μm. The materials were heated at 135° C. for 1 h, and 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 a common polyethylene diaphragm with a thickness of 12 μm, with a coating thickness of 3 μm, and hot-pressed with the battery pole piece at 80°C and 3 MPa for 1 min. The samples were cut into 25 mm × 200 mm size and the peel strength was tested using a KT-PSA-1056 peel force 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] It can be seen from Table 1 that the PMMA materials provided by Examples 1 to 3 of the present invention have good bonding properties and heat resistance, and their shrinkage changes are extremely small.

[0097] By comparing Example 4 with Example 1, it can be seen that 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 decreases, which may be due to the greater steric hindrance and instability brought about by the structure of the modified β-cyclodextrin, further resulting in a significant decrease in the bonding performance of the PMMA material, but the heat resistance is less affected.

[0098] By comparing Example 5 and Example 6 with Example 1, it can be seen that when the amount of methacrylate-β-hydroxyethyl phosphate and 4-vinylbenzoic acid added in the preparation of modified graphite added to the PMMA microspheres is changed respectively, the heat resistance of the PMMA microspheres will be greatly reduced, and the coating effect of the shell on the core will be poor, which will lead to a decrease in the bonding performance and heat resistance of the PMMA material.

[0099] By comparing Example 7 with Example 1, it can be seen that when unmodified graphite is added during the preparation of PMMA microspheres, the structural stability of the PMMA microspheres decreases when heated, which in turn causes a decrease in both the bonding performance and the heat resistance of the PMMA material.

[0100] It can be seen from the comparison between Comparative Example 1 and Example 1 that when β-cyclodextrin is directly used to replace the modified β-cyclodextrin in equal amounts, the uniformity of the three-dimensional network structure of the system will decrease, thereby causing the comprehensive performance of the PMMA material to decrease.

[0101] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A uniform and highly bonded PMMA material for lithium battery separator, characterized in that: The material comprises the following raw materials in parts by weight: 20 to 50 parts of PMMA microspheres, 0.5 to 1 part of a wetting agent, 1 to 1.2 parts of a dispersant, 2 to 6 parts of modified beta-cyclodextrin and 30 to 60 parts of deionized water.

2. The uniform high-bonding PMMA material for lithium battery separator according to claim 1, characterized in that: The preparation steps of the modified β-cyclodextrin are as follows: (1) Mixing sodium alginate and alkali solution, adding β-cyclodextrin and epichlorohydrin in sequence, heating to 55-60° C. for reaction for 10-20 min, adjusting the pH to neutral, filtering and drying to obtain sodium alginate modified β-cyclodextrin; (2) Sodium alginate modified β-cyclodextrin, octadecyl acrylate and an initiator are mixed, introduced into an inert atmosphere, heated to 65-70° C. while stirring, and reacted for 0.5-1.5 h to obtain modified β-cyclodextrin.

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

4. The uniform high-bonding PMMA material for lithium battery separator according to claim 1, characterized in that: The preparation steps of the PMMA microspheres are as follows: 1) Preparation of core layer emulsion: styrene, methyl methacrylate, N-methylacetamide, hydroxyethyl methacrylate are added to a mixture containing a dispersant, deionized water and ethanol for dispersion, and then the first weight portion of initiator 1 is added for pre-emulsification, and then the temperature is raised to 50-70° C. and stirred, and then the second weight portion of initiator 1 is added, and 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 are added to a mixture containing sodium dodecyl sulfate, epoxy resin, and modified graphite, and stirred to obtain a shell emulsion. The temperature is raised to 70-80° C., and then the core emulsion of step 1) and initiator 2 are added under stirring, and the reaction is carried out at a constant temperature for 1-5 hours to obtain PMMA microspheres.

5. The uniform high-bonding PMMA material for lithium battery separator according to claim 4, characterized in that: The PMMA microspheres have a particle size of 1 to 5 μm.

6. The uniform high-bonding PMMA material for lithium battery separator according to claim 4, characterized in that: 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 stir ultrasonically for 1 to 3 hours. Then add initiator 3, and continue stirring ultrasonically for 10 to 30 minutes to obtain modified graphite.

7. The uniform high-bonding PMMA material for lithium battery separator according to claim 6, characterized in that: The mass ratio of the phosphorus-containing acrylic monomer, 4-vinylbenzoic acid and graphite is (0.8-1):(0.4-0.8)1.

8. The uniform high-bonding PMMA material for lithium battery separator according to claim 1, characterized in that: The wetting agent is an acrylic leveling agent.

9. The uniform high-bonding PMMA material for lithium battery separator according to claim 1, characterized in that: The dispersant is at least one of polyvinyl pyrrolidone, polyethylene glycol and sodium polyacrylate.

10. A method for preparing a uniform high-bonding PMMA material for lithium battery separator according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: adding PMMA microspheres into deionized water, mixing and stirring, adding a dispersant, stirring, then adding modified beta-cyclodextrin and a wetting agent, and stirring evenly to obtain the material.