Lithium ion battery diaphragm, preparation method and battery thereof

Abstract

The invention discloses a lithium ion battery diaphragm, a preparation method and a battery thereof, the lithium ion battery diaphragm comprises a base membrane and a coating layer coated on the single side surface of the base membrane, the coating layer comprises the following raw materials by mass: 0.6%-2% of polymer particles, 38%-39.4% of a binder, 42%-54% of a solvent, and 6%-18% of a dispersant; the polymer particles are prepared by polymerizing 2, 4-diamino-6-chloropyrimidine or 2, 4-diamino-6-fluoropyrimidine and terephthalaldehyde, so that collaborative optimization of thermal stability and wettability of the diaphragm is realized, and meanwhile, the cycling stability and rate discharge performance of a battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a lithium-ion battery separator, its preparation method, and the battery thereof. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and environmental friendliness, have been widely used in new energy vehicles, energy storage devices, and portable electronic devices. The separator, as one of the core components of a lithium-ion battery, plays a crucial role in separating the positive and negative electrodes, preventing short circuits, and allowing lithium ions to pass through. Its performance directly affects key indicators such as battery safety, cycle stability, and charge / discharge rate.

[0003] Currently, lithium-ion battery separators are mainly made of polyolefin materials (such as polyethylene and polypropylene). These materials are characterized by abundant raw materials, environmental friendliness, and moderate mechanical strength, giving them a dominant position in the separator market. However, polyolefin materials lack any polar chemical functional groups on their surface, resulting in inherent defects such as low surface energy, high surface tension, and surface chemical inertness, leading to poor wettability with electrolytes. During the battery electrolyte injection formation process, polyolefin separators require a long time to be fully wetted by the electrolyte, which not only prolongs the battery manufacturing cycle but also increases the battery's electrochemical impedance, affecting its charge and discharge performance.

[0004] In addition, polyolefin porous membranes have a low melting point (usually between 130°C and 170°C). When a lithium-ion battery experiences thermal runaway, the rapid increase in temperature can cause the polyolefin porous membrane to shrink or even melt, resulting in direct contact between the positive and negative electrodes, causing a short circuit in the battery and seriously threatening the safety of battery use.

[0005] To address these issues, the industry commonly employs a technique of coating the surface of polyolefin separators with inorganic ceramic microparticles (such as alumina and silicon dioxide), leveraging the high melting point of these microparticles to enhance the separator's thermal stability. However, this approach faces significant technical bottlenecks: firstly, the interfacial adhesion between the inorganic ceramic microparticles and the porous polyolefin membrane is weak, making them prone to detachment during battery cycling and affecting the battery's long-term stability; secondly, the high density and uneven particle size distribution of the inorganic ceramic microparticles can easily clog the separator's microporous structure after coating, leading to decreased separator permeability, increased contact resistance between the separator and the positive and negative electrodes, and consequently affecting lithium-ion migration efficiency and the battery's rate discharge performance.

[0006] Therefore, there is an urgent need to design a lithium-ion battery separator, a preparation method, and a battery thereof to solve the problems mentioned above. Summary of the Invention

[0007] The purpose of this invention is to provide a lithium-ion battery separator, a preparation method thereof, and a battery thereof, so as to achieve synergistic optimization of the separator's thermal stability and wettability, while improving the battery's cycle stability and rate discharge performance.

[0008] To achieve the above objectives, the present invention provides a lithium-ion battery separator, a preparation method thereof, and a specific technical solution for the battery as follows: A lithium-ion battery separator includes a base film and a coating layer coated on one side of the base film. The coating layer, by mass percentage, comprises: 0.6%~2% polymer particles, 38%~39.4% binder, 42%~54% solvent, and 6%~18% dispersant. The polymer particles are prepared by polymerizing 2,4-diamino-6-chloropyrimidine or 2,4-diamino-6-fluoropyrimidine with terephthalaldehyde.

[0009] Furthermore, the polymer particles contain chlorine polar functional groups or fluorine polar functional groups, amino polar functional groups and benzene ring rigid groups.

[0010] Furthermore, the porosity of the base membrane is 30% to 70%.

[0011] Furthermore, the polymer microparticles have a particle size of 500 nm to 2 μm and a porous structure.

[0012] Furthermore, the base film includes one or more of polyethylene, polypropylene, nonwoven fabric, polymethylpentene, polyimide, polyacrylonitrile, polyvinylidene fluoride, aramid, and cellulose.

[0013] Furthermore, the adhesive is selected from one or more of polyvinylidene fluoride, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, polyacrylic acid, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, and polyacrylonitrile.

[0014] Further, the solvent includes one or more of acetonitrile, alcohol, toluene, N,N-dimethylformamide, and dichloromethane, and the dispersant is selected from one or more of polyethylene glycol, ethanol, and isopropanol. The mass ratio of the solvent to the dispersant is a:10-a, where a ranges from 7 to 9.

[0015] A method for preparing a lithium-ion battery separator includes the following steps: S1. 2,4-Diamino-6-chloropyrimidine or 2,4-diamino-6-fluoropyrimidine and terephthalaldehyde are added to dimethyl sulfoxide to form a mixed system, and the mixed system is subjected to a polymerization reaction to obtain polymer microparticles; S2. Add the polymer particles to the mixture of solvent and dispersant, and stir until homogeneous to obtain a polymer particle dispersion; S3. Add a binder to the polymer microparticle dispersion and stir to obtain a coating solution; S4. After stirring and filtering the coating liquid, it is coated on one side of the base film and dried to obtain a lithium-ion battery separator.

[0016] Furthermore, step S1 also includes the following steps: The mixed system was subjected to a gradient temperature program: the temperature was increased by 8-12°C every 4-8 hours in the 50°C-140°C range, and by 10°C every 10-14 hours in the 140°C-170°C range, until the temperature was finally raised to 170°C and maintained for more than 72 hours. After the reaction was completed, the temperature was lowered to room temperature to obtain a reaction turbid liquid. The reaction turbid liquid was washed by centrifugation with N,N-dimethylformamide and dichloromethane in sequence, the precipitate was collected, and the precipitate was dried to obtain polymer microparticles.

[0017] A lithium battery includes: a positive electrode; a negative electrode; a separator, which is a lithium-ion battery separator as described in any one of claims 1 to 7; a current collector; and an electrolyte.

[0018] The lithium-ion battery separator, its preparation method, and the battery of the present invention have the following advantages: 1. Excellent wettability: The chlorine or fluorine polar functional groups and amino polar functional groups contained in the polymer particles can form hydrogen bonds and van der Waals forces with the binder and the base film, which significantly reduces the surface tension of the base film and reduces the contact angle of the separator to the electrolyte to below 47.4°. The electrolyte wettability is fast, shortening the battery liquid filling and formation cycle, and reducing the electrochemical impedance.

[0019] 2. Outstanding thermal stability: The rigid benzene ring groups in the polymer microparticles can effectively resist the shrinkage stress of the base film when heated, so that the thermal shrinkage rate of the separator at 105℃ for 1h is ≤0.92% (longitudinal and transverse), which is much lower than that of existing ceramic coated separators (1.8% / 1.1%), significantly improving the thermal safety performance of the battery and avoiding the risk of short circuit in case of thermal runaway.

[0020] 3. Good air permeability: The polymer microparticles have small particle size (500nm~2μm), low addition ratio (0.6%~2%), and a porous structure, which does not easily clog the micropores of the base film. The air permeability of the separator is reduced, which ensures the smooth migration of lithium ions and provides a basis for high-rate discharge of the battery.

[0021] 4. Excellent cycle stability: The hydrogen bonds and van der Waals forces between the polar functional groups of polymer particles and lithium ions can promote lithium ion migration and inhibit lithium dendrite growth. Lithium batteries using this separator have a capacity retention rate of ≥89% after 1000 cycles at 1C and a capacity retention rate of ≥94% at 2C rate discharge. The cycle decay trend is gradual, and the long-term stability is excellent.

[0022] 5. Simple preparation process: The preparation method of the present invention does not require complex equipment, has a short process cycle, uses abundant and environmentally friendly raw materials, and the coating layer is tightly bonded to the base film and is not easy to fall off. It is suitable for large-scale industrial production and has a low production cost.

[0023] 6. High battery safety: The coated separator is non-flammable, and its thermal stability and wettability are optimized in synergy, which fundamentally reduces the risk of battery short circuit and thermal runaway, and improves the overall safety performance of lithium batteries. Attached Figure Description

[0024] Figure 1 This is a SEM image of the coating surface of the lithium-ion battery separator prepared in Example 1 of the present invention; Figure 2 (a) Contact angle diagram of the coating surface of the lithium-ion battery separator prepared in Example 1 of the present invention; Figure 2 (b) Contact angle diagram of the coating surface of the lithium-ion battery separator prepared in Example 2 of the present invention; Figure 2 (c) Contact angle diagram of the coating surface of the lithium-ion battery separator prepared in Example 3 of the present invention; Figure 2 (d) Contact angle diagram of the coating surface of the lithium-ion battery separator prepared in Example 4 of the present invention; Figure 3 This is a comparison chart of the cycle capacity retention rate of lithium batteries in Examples 1-4 of the present invention and the comparative examples. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0027] The following is a reference to the appendix. Figure 1 To be continued Figure 3 This invention describes a lithium-ion battery separator, its preparation method, and the battery thereof.

[0028] A lithium-ion battery separator includes a base film and a coating layer coated on one side of the base film. The coating layer, by mass percentage, comprises: 0.6%~2% polymer particles, 38%~39.4% binder, 42%~54% solvent, and 6%~18% dispersant. The polymer particles are prepared by polymerizing 2,4-diamino-6-chloropyrimidine or 2,4-diamino-6-fluoropyrimidine with terephthalaldehyde.

[0029] Furthermore, the polymer particles contain chlorine polar functional groups or fluorine polar functional groups, amino polar functional groups and benzene ring rigid groups. The above-mentioned polar functional groups (chlorine or fluorine, amino) can form hydrogen bonds and van der Waals forces with the binder and the polyolefin base film, significantly reducing the surface tension of the base film and improving the wettability of the separator to the electrolyte; while the benzene ring rigid groups can resist the shrinkage stress generated when the polyolefin base film is heated, effectively suppressing the thermal shrinkage of the base film and improving the thermal stability of the separator.

[0030] Furthermore, the porosity of the base film is 30% to 70%, which ensures the smooth migration of lithium ions and provides a good adhesion basis for the coating layer.

[0031] Furthermore, the polymer particles have a particle size of 500 nm to 2 μm and a porous structure. The addition ratio of polymer particles in this particle size range is low (only 0.6% to 2%), which makes it less likely to clog the micropores of the base membrane and ensures the air permeability of the membrane. The porous structure can increase the contact area between the polymer particles and the electrolyte, further improving the wetting effect.

[0032] Furthermore, the base film includes one or more of polyethylene, polypropylene, nonwoven fabric, polymethylpentene, polyimide, polyacrylonitrile, polyvinylidene fluoride, aramid, and cellulose, preferably polyethylene or polypropylene base film, which has low raw material cost, moderate mechanical strength, and is suitable for large-scale production.

[0033] Furthermore, the adhesive is selected from one or more of polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and polyacrylonitrile (PAN), preferably PVDF or PMMA, which have good compatibility with the base film and polymer particles and high bonding strength.

[0034] Furthermore, the solvent includes one or more of acetonitrile, alcohol, toluene, N,N-dimethylformamide, and dichloromethane, and the dispersant is selected from one or more of polyethylene glycol, ethanol, and isopropanol. The mass ratio of the solvent to the dispersant is a:10-a, where a ranges from 7 to 9. This mass ratio range ensures that the polymer particles are uniformly dispersed in the mixture, avoids agglomeration, and ensures the uniformity of the coating layer.

[0035] A method for preparing a lithium-ion battery separator includes the following steps: S1. 2,4-Diamino-6-chloropyrimidine or 2,4-diamino-6-fluoropyrimidine and terephthalaldehyde are added to dimethyl sulfoxide (DMSO) to form a mixed system, and the mixed system is subjected to a polymerization reaction to obtain polymer microparticles; Preferably, the polymerization reaction in step S1 is carried out in an inert gas atmosphere (nitrogen or argon) or a vacuum glove box to avoid oxidation of monomers and products and to ensure the structural integrity of polymer particles; the drying process is vacuum drying at 100°C to remove residual solvents from the precipitate and to ensure the stability of the porous structure of polymer particles.

[0036] S2. Add the polymer particles to the mixture of solvent and dispersant, and stir until homogeneous to obtain a polymer particle dispersion; Preferably, in step S2, the polymer particles need to be ground in a mortar for 10-30 minutes before being added to the mixture of solvent and dispersant and stirred for 90-180 minutes to ensure uniform dispersion of the polymer particles and avoid agglomeration. The stirring process adopts a combination of mechanical stirring and ultrasonic dispersion, with an ultrasonic power of 100-300W and an ultrasonic time of 20-40 minutes to further improve the dispersion uniformity. S3. Add a binder to the polymer microparticle dispersion and stir to obtain a coating solution; Preferably, in step S3, the mass ratio of the adhesive to the polymer particles is 95~98.5:5~1.5, and after stirring for 20~50 minutes, a coating liquid with a solid content of 40wt% is obtained. This solid content and mass ratio can ensure the bonding strength and uniformity of the coating layer. S4. After stirring and filtering the coating liquid, it is coated on one side of the base film and dried to obtain a lithium-ion battery separator.

[0037] Preferably, in step S4, the coating liquid is first filtered through a magnetic filter, stirred for 5-20 minutes, and then filtered through a 250-mesh filter to remove impurities and agglomerated particles. It is then coated on one side of the base film using a gravure coating machine and vacuum dried at 60°C to form a coating layer with a thickness of 3μm. This coating method and drying conditions can ensure a tight bond between the coating layer and the base film, while avoiding deformation of the base film.

[0038] Furthermore, step S1 also includes the following steps: The mixed system was subjected to a gradient temperature program: the temperature was increased by 8-12°C every 4-8 hours in the 50°C-140°C range, and by 10°C every 10-14 hours in the 140°C-170°C range, until the temperature was finally raised to 170°C and maintained for more than 72 hours. After the reaction was completed, the temperature was lowered to room temperature to obtain a reaction turbid liquid. The reaction turbid liquid was washed by centrifugation with N,N-dimethylformamide (DMF) and dichloromethane in sequence, the precipitate was collected, and the precipitate was dried to obtain polymer microparticles.

[0039] A lithium battery includes: a positive electrode; a negative electrode; a separator, which is a lithium-ion battery separator as described in any one of claims 1 to 7; a current collector; and an electrolyte.

[0040] Preferably, the positive electrode sheet is prepared by mixing lithium iron phosphate, conductive carbon black Super-P, graphene conductive paste, and polyvinylidene fluoride in an N-methylpyrrolidone solvent at a mass ratio of 96.8:0.7:0.3:2.2 to form a positive electrode paste. This paste is then coated on both sides of an aluminum foil current collector, dried, cold-pressed, and sliced ​​to form the positive electrode sheet. The double-sided areal density of the positive electrode is 328 g / m³. 2 ; The negative electrode sheet is prepared by mixing graphite, conductive carbon black Super-P, CMC, and styrene-butadiene rubber in deionized water at a mass ratio of 96.2:1:0.6:1.2 to form a negative electrode slurry. This slurry is then coated onto a copper foil current collector, dried, cold-pressed, and sliced ​​to form the negative electrode sheet. The negative electrode has a double-sided areal density of 160 g / m³. 2 ; The electrolyte is a 1 mol / L lithium hexafluorophosphate (LiPF6) electrolyte, and the solvent is a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1. A 3Ah lithium-ion battery is assembled by stacking positive electrode, separator, and negative electrode, and then the finished lithium battery is obtained after electrolyte injection and encapsulation.

[0041] The present invention will be further illustrated by specific embodiments below, but these embodiments do not limit the scope of protection of the present invention.

[0042] Example 1 Under a nitrogen atmosphere, 0.1 mol / L of 2,4-diamino-6-chloropyrimidine and 0.2 mol / L of terephthalaldehyde (molar ratio 1:2) were added to pure dimethyl sulfoxide (DMSO) to form a mixed system. The mixed system was subjected to a gradient temperature program: the temperature was increased by 10°C every 6 hours in the range of 50°C to 140°C, and by 10°C every 12 hours in the range of 140°C to 170°C, and finally the temperature was raised to 170°C and maintained for 72 hours. After the reaction was completed, the temperature was lowered to room temperature to obtain a reaction turbidity. The reaction turbidity was washed three times by centrifugation with N,N-dimethylformamide (DMF) and dichloromethane in sequence, and the precipitate was collected. The precipitate was dried in a vacuum environment at 100°C for 12 hours to obtain porous polymer microparticles with a particle size of about 1 μm.

[0043] The structural formula of the 2,4-diamino-6-chloropyrimidine is: The structural formula of the terephthalaldehyde is: The polymer microparticle structure in this embodiment is: The polymer particles were ground in a mortar for 10 minutes. 0.6 g of the powder was added to a mixture of 54 g of solvent (DMF) and 6 g of dispersant (polyethylene glycol) (solvent to dispersant mass ratio 9:1). The mixture was stirred for 120 minutes to obtain a polymer particle dispersion. 39.4 g of binder (PVDF) was added to the dispersion, with a binder to polymer particle mass ratio of 98.5:1.5. The mixture was stirred for another 30 minutes to obtain a coating liquid with a solid content of 40 wt%. The coating liquid was filtered through a magnetic filter and stirred for 10 minutes before being filtered through a 250-mesh filter to obtain a high-temperature resistant adhesive coating liquid.

[0044] A polyethylene base film with a thickness of 9μm and a porosity of 45% was selected. The above coating liquid was coated onto one side of the base film using a gravure coating machine. The film was then vacuum dried at 60°C for 1 hour to form a coating layer with a thickness of 3μm, thus obtaining a lithium-ion battery separator.

[0045] Assemble a 3Ah lithium-ion battery according to the lithium battery manufacturing method.

[0046] Example 2 The raw materials for preparing the polymer microparticles are 2,4-diamino-6-fluoropyrimidine (0.1 mol / L) and terephthalaldehyde (0.2 mol / L). The remaining steps are the same as in Example 1, resulting in a lithium-ion battery separator and a lithium battery.

[0047] The structural formula of the 2,4-diamino-6-chloropyrimidine is: The polymer microparticle structure in this embodiment is: Example 3 PMMA was selected as the binder, and the remaining steps were the same as in Example 1, resulting in a lithium-ion battery separator and a lithium battery.

[0048] Example 4 The difference between this embodiment and Example 3 is that the raw materials for preparing the polymer microparticles are 2,4-diamino-6-fluoropyrimidine (0.1 mol / L) and terephthalaldehyde (0.2 mol / L), while the remaining steps are the same as in Example 1, resulting in a lithium-ion battery separator and a lithium battery.

[0049] Comparative Example A 3Ah lithium-ion battery was assembled using an alumina ceramic-coated separator (with a base membrane of polyethylene, a thickness of 9μm, and a porosity of 45%) according to the above-mentioned lithium battery preparation method. This battery was designated as the control battery.

[0050] The performance of the lithium-ion battery separators prepared in Examples 1-4 and the comparative examples was tested. The test items included air permeability, contact angle, and thermal shrinkage rate at 105℃ / 1h. The electrochemical performance of the lithium-ion batteries prepared in Examples 1-4 and the comparative examples was tested. The test items included 2C rate discharge capacity retention rate and 1000 1C cycle capacity retention rate. The test results are shown in Tables 1 and 2 below: Table 1 shows the separator performance test results, and Table 2 shows the battery electrochemical performance test results.

[0051] Table 1. Test Results of Diaphragm Performance Table 2. Results of Battery Electrochemical Performance Tests As can be seen from Tables 1 and 2: The air permeability of the diaphragms in Examples 1 to 4 of this invention is reduced by 11 s / 100mL, the contact angle is lower than 47.4°, and the heat shrinkage rate is lower than 0.92%, which are significantly better than the diaphragms in the comparative examples, proving that the diaphragms of this invention have better air permeability, wettability, and thermal stability. The lithium batteries using the separators of Examples 1 to 4 of this invention all have a 2C rate discharge capacity retention rate of over 94% and a 1C cycle capacity retention rate of over 89% after 1000 cycles, which is much higher than the comparative examples. This proves that the separator of this invention can effectively improve the rate discharge performance and long-term cycle stability of lithium batteries.

[0052] Figure 1 This is a SEM image of the coating surface of the lithium-ion battery separator prepared in Example 1 of the present invention; Figure 2(a) Contact angle diagram of the coating surface of the lithium-ion battery separator prepared in Example 1 of the present invention; Figure 2 (b) Contact angle diagram of the coating surface of the lithium-ion battery separator prepared in Example 2 of the present invention; Figure 2 (c) Contact angle diagram of the coating surface of the lithium-ion battery separator prepared in Example 3 of the present invention; Figure 2 (d) Contact angle diagram of the coating surface of the lithium-ion battery separator prepared in Example 4 of the present invention; Figure 3 This is a comparison chart of the cycle capacity retention rate of lithium batteries in Examples 1-4 of the present invention and the comparative examples.

[0053] Figure 1 As can be seen, the polymer particles and binder are evenly distributed on the surface of the base film, the coating layer is dense and there is no obvious agglomeration, the microporous structure is clear and there is no blockage. Figure 2 The contact angles of Examples 1 to 4 are all significantly smaller than those of the comparative example, proving that the wettability of the diaphragm of the present invention is superior. Figure 3 The cycle capacity retention rates of Examples 1 to 4 were all higher than those of the comparative examples. The horizontal axis represents the number of cycles (0 to 1000 times), and the vertical axis represents the capacity retention rate (%). The degradation trend was also more gradual, indicating that the separator of the present invention can improve the long-term cycle stability of the battery.

[0054] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A lithium-ion battery separator, characterized in that, The coating comprises a base film and a coating layer applied to one side of the base film. By mass percentage, the raw material composition of the coating layer is: 0.6%~2% polymer particles, 38%~39.4% binder, 42%~54% solvent, and 6%~18% dispersant. The polymer particles are prepared by polymerizing 2,4-diamino-6-chloropyrimidine or 2,4-diamino-6-fluoropyrimidine with terephthalaldehyde.

2. The lithium-ion battery separator according to claim 1, characterized in that, The polymer particles contain chlorine polar functional groups or fluorine polar functional groups, amino polar functional groups and benzene ring rigid groups.

3. The lithium-ion battery separator according to claim 1, characterized in that, The porosity of the base membrane is 30%~70%.

4. The lithium-ion battery separator according to claim 1, characterized in that, The polymer microparticles have a particle size of 500 nm to 2 μm and have a porous structure.

5. The lithium-ion battery separator according to claim 1, characterized in that, The base film includes one or more of polyethylene, polypropylene, nonwoven fabric, polymethylpentene, polyimide, polyacrylonitrile, polyvinylidene fluoride, aramid, and cellulose.

6. The lithium-ion battery separator according to claim 1, characterized in that, The adhesive is selected from one or more of polyvinylidene fluoride, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, polyacrylic acid, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, and polyacrylonitrile.

7. The lithium-ion battery separator according to claim 1, characterized in that, The solvent includes one or more of acetonitrile, alcohol, toluene, N,N-dimethylformamide, and dichloromethane, and the dispersant is selected from one or more of polyethylene glycol, ethanol, and isopropanol. The mass ratio of the solvent to the dispersant is a:10-a, where a ranges from 7 to 9.

8. A method for preparing a lithium-ion battery separator as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. 2,4-Diamino-6-chloropyrimidine or 2,4-diamino-6-fluoropyrimidine and terephthalaldehyde are added to dimethyl sulfoxide to form a mixed system, and the mixed system is subjected to a polymerization reaction to obtain polymer microparticles; S2. Add the polymer particles to the mixture of solvent and dispersant, and stir until homogeneous to obtain a polymer particle dispersion; S3. Add a binder to the polymer microparticle dispersion and stir to obtain a coating solution; S4. After stirring and filtering the coating liquid, it is coated on one side of the base film and dried to obtain a lithium-ion battery separator.

9. The method for preparing a lithium-ion battery separator according to claim 8, characterized in that, Step S1 also includes the following steps: The mixed system was subjected to a gradient temperature program: the temperature was increased by 8-12°C every 4-8 hours in the 50°C-140°C range, and by 10°C every 10-14 hours in the 140°C-170°C range, until the temperature was finally raised to 170°C and maintained for more than 72 hours. After the reaction was completed, the temperature was lowered to room temperature to obtain a reaction turbid liquid. The reaction turbid liquid was washed by centrifugation with N,N-dimethylformamide and dichloromethane in sequence, the precipitate was collected, and the precipitate was dried to obtain polymer microparticles.

10. A lithium battery, characterized in that, include: Positive electrode plate; Negative electrode plate; The separator is a lithium-ion battery separator as described in any one of claims 1 to 7; current collector; as well as Electrolyte.

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