High-infiltration and ultralow-water-absorption lithium battery diaphragm and preparation method thereof

Abstract

The invention provides a high-infiltration and ultralow-water-absorption lithium battery diaphragm and a preparation method thereof. The diaphragm is prepared by coating a PP diaphragm or a PE diaphragm with coating slurry in a double-sided or single-sided manner, wherein the coating slurry is mainly prepared from the following raw materials in parts by mass: 25 to 38 parts of aryl alkyl modified organic silicon, 84 to 110 parts of ultrapure water, 40 to 55 parts of boehmite and 4.48 to 8.02 parts of a modifying agent. According to the diaphragm, through the improvement of the proportion, effective interaction among all substances is realized on the microscopic level, so that the affinity and the rigidity among the diaphragms are enhanced; the electrolyte can better permeate into pores of the diaphragm, so that the wettability of the diaphragm is improved, and the battery cyclicity of the diaphragm is improved; meanwhile, the safety and the stability of the diaphragm can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery separators, and in particular to a lithium battery separator with high wettability and ultra-low water absorption and a preparation method thereof. Background Art

[0002] With the development of new energy technologies, lithium-ion batteries are being used in digital products, electric vehicles, and energy storage devices due to their high energy density, long life, and high safety performance. Lithium batteries are primarily composed of four components: the positive electrode, electrolyte, separator, and negative electrode. The performance of the separator affects key lithium-ion battery properties such as capacity, internal resistance, and cycle life. Currently, most commercial separators are polyolefin separators. Because the material is primarily non-polar, they have poor wetting properties with water and electrolytes, which affects the conduction of lithium ions in the battery. Therefore, improving the separator's wettability with electrolytes is of great significance.

[0003] The quality requirements for power lithium-ion batteries have increased significantly, and the moisture content of lithium-ion battery separator materials has become a key quality indicator. Excessive moisture content not only causes the decomposition of electrolyte lithium salts but also adversely affects the film formation and stability of positive and negative electrode materials, leading to a significant deterioration in the safety and electrochemical properties of lithium-ion batteries. A new separator is urgently needed to address these battery cycling, safety, and stability issues.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The first purpose of the present invention is to provide a lithium battery separator with high wettability and ultra-low water absorption. The separator achieves effective interaction between the various substances at the microscopic level through the improvement of the ratio, thereby enhancing the affinity and rigidity between the separators; enables the electrolyte to better penetrate into the pores of the separator, improves the wettability of the separator, and thus improves the battery cycle performance of the separator; at the same time, it can effectively improve the safety and stability of the separator.

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned lithium battery separator, which can achieve rapid preparation of the product, optimize the preparation method, and effectively increase the affinity and rigidity of the lithium battery separator.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: The present invention provides a lithium battery separator with high wettability and ultra-low water absorption, which is prepared by coating a coating slurry on both sides or one side of a PP separator or a PE separator; The coating slurry is mainly prepared from the following raw materials in parts by mass: 25-38 parts of aromatic alkyl modified silicone, 84-110 parts of ultrapure water, 40-55 parts of boehmite, and 4.48-8.02 parts of a modifier.

[0008] In this invention, the aromatic alkyl-modified silicone molecule features a silicon-oxygen bond (Si-O-Si) as its backbone, with aromatic and alkyl groups attached to the silicon atoms. The introduced alkyl and aromatic groups increase the hydrophobicity of the membrane surface. The combination of the alkyl and aromatic groups with the silicone further repels water molecules, reducing their adsorption and retention on the membrane surface, thereby reducing the membrane's moisture content. Furthermore, a relatively dense protective film forms on the membrane surface, preventing external water from entering the membrane while also inhibiting the outward diffusion of internal moisture. This film acts as a barrier to water, helping to maintain a low moisture content. Improved membrane wettability is achieved by increasing interaction with the electrolyte. The structural characteristics of the aromatic and alkyl groups enable the modified silicone to interact with organic solvents and solutes in the electrolyte. Aromatic groups can attract certain aromatic compounds in the electrolyte through stacking, while alkyl groups can interact with hydrocarbon groups in the organic solvent through van der Waals forces and other interactions. These interactions can enhance the affinity between the diaphragm liquid, allowing the electrolyte to better penetrate into the pores of the diaphragm and improve the wettability of the diaphragm.

[0009] The introduced boehmite can further enhance the mechanical properties of the diaphragm, increase the tensile strength of the diaphragm to a certain extent, and make it more stable.

[0010] The modifier can achieve better fusion between the added aromatic alkyl modified silicone, PP diaphragm or PE diaphragm and boehmite, and at the same time change their properties to achieve improvement of their performance.

[0011] Preferably, as a further specific embodiment, the modifier is prepared from the following raw materials in parts by mass: 0.5-1.2 parts of dispersant, 1.3-2.9 parts of pore-forming agent, 2.6-3.8 parts of adhesive, and 0.08-0.12 parts of wetting agent.

[0012] Preferably, as a further specific embodiment, the aromatic alkyl modified silicone comprises 28 parts, ultrapure water 88 parts, boehmite 42 parts, and a modifier 4.88 parts.

[0013] In the actual preparation process, the content of aromatic alkyl-modified silicone, boehmite, ultrapure water and modifiers all need to be controlled within a certain range: when there is an excess of aromatic alkyl-modified silicone and boehmite, the gaps in the diaphragm may be clogged, thereby reducing the conductivity of the ions, increasing the internal resistance of the battery, and affecting the rate performance and cycle life; in addition, an excess of aromatic alkyl-modified silicone may also form an excessively thick coating, hindering the infiltration of the electrolyte, increasing the interfacial impedance, or reducing the flexibility of the diaphragm and increasing its brittleness, making it easy to break during battery assembly or circulation, causing a short circuit risk.

[0014] However, when the amount of aromatic alkyl modified silicone is insufficient, it may lead to insufficient wettability of the diaphragm, uneven distribution of the electrolyte, reduced ion migration efficiency, increased battery polarization and accelerated capacity decay; or it may cause the diaphragm's puncture resistance to decrease, making it difficult to inhibit lithium dendrite penetration, especially under fast charging or low temperature conditions, which can easily cause safety hazards.

[0015] Similarly, using too little boehmite can result in incomplete coating coverage (e.g., "island-like" distribution), significant local variations in performance (e.g., thermal stability, strength), reduced batch consistency, or decreased chemical and electrical stability of the separator. Using too much boehmite can make the separator susceptible to oxidative degradation after long-term cycling, leading to decreased porosity or structural collapse. Furthermore, direct contact between the electrolyte and the separator substrate (e.g., polyolefin) increases, potentially exacerbating side reactions (e.g., solvent decomposition, SEI thickening), and accelerating capacity fading.

[0016] In actual applications, modifiers can be selected based on the desired membrane properties, including but not limited to reinforcing agents, anti-aging agents, or conductive additives. Modifiers should be added in trace amounts during actual applications. Excessive or insufficient amounts can negatively impact the performance of the membrane, thus preventing the achievement of the technical benefits of the present invention.

[0017] Preferably, as a further specific embodiment, the aromatic alkyl modified silicone is any one or more of phenylmethylpolysiloxane, phenylvinylsiloxane, fluorophenylsiloxane or epoxyphenylsiloxane; Preferably, the aromatic alkyl modified silicone is a mixture of epoxyphenylsiloxane and phenylvinylsiloxane in a mass ratio of 1:(1-3); Preferably, the aromatic alkyl modified silicone is a mixture of epoxyphenylsiloxane and phenylvinylsiloxane in a mass ratio of 1:2.

[0018] In the present invention, epoxyphenylsiloxane and phenylvinylsiloxane are selected. Both can coexist and cross-link in the diaphragm coating to form a certain microstructure. When the epoxyphenylsiloxane is excessive, it is easy to make the diaphragm material too brittle, and too much vinyl will affect the wettability of the electrolyte. Therefore, the mass ratio is controlled at 1: (1-3), preferably 1:2, which can better take into account various performances.

[0019] Preferably, as a further specific embodiment, the pore size of the PP membrane or PE membrane is 5 μm-20 μm; Preferably, a PE membrane with a pore size of 9 μm is selected.

[0020] The choice of PP or PE separators requires consideration of ion permeability and dendrite resistance. Large-pore separators can reduce the separator's mechanical strength, making it susceptible to puncture and potentially increasing the risk of internal short circuits in the battery. Small-pore separators, on the other hand, increase ion transport resistance, leading to increased internal resistance at high rates, thus impacting charge and discharge performance. Furthermore, they reduce electrolyte wettability, lowering overall battery efficiency. Therefore, in this invention, the separator's pore size is selected to be between 5 μm and 20 μm. PE membranes, compared to PP membranes, have a significantly lower pore closure temperature. When the internal battery temperature rises abnormally, the PE membrane rapidly melts and closes its pores, blocking ion migration and electrochemical reactions, effectively preventing thermal runaway and offering enhanced safety. Therefore, a 9 μm pore size PE separator was ultimately selected for this invention.

[0021] Preferably, as a further specific embodiment, the dispersant is any one or more of polyacrylate, anionic sodium lauryl sulfate or polyvinyl pyrrolidone; The pore-forming agent is any one or more of polyethylene glycol or polyvinyl alcohol; The adhesive is polyimide; The wetting agent is methacrylate.

[0022] The present invention also provides a method for preparing a lithium battery separator with high wettability and ultra-low water absorption, comprising the following steps: Dissolving aromatic alkyl modified silicone with ultrapure water at 85° C. to 95° C. and stirring to obtain a first aqueous solution; Take boehmite, add the first aqueous solution, soak and stir at 50° C.-60° C. for 30 min-35 min, filter, and break up to obtain modified boehmite; The modified boehmite is mixed with ultrapure water, a modifier is added while continuously stirring, and then ultrasonically mixed to obtain a coating material; The coating material is coated on one side or both sides of a PP diaphragm or a PE diaphragm, and then dried at 60° C.-85° C. to obtain the coating material.

[0023] Preferably, as a further specific embodiment, in the step of soaking at 50° C.-60° C. for 30 min-35 min while stirring, the stirring rate is 15 r / min-25 r / min.

[0024] Preferably, as a further specific embodiment, in the ultrasonic mixing step, the following steps are specifically included: vacuuming, stirring by planetary stirring, the rotation speed is 2000 r / min-2500 r / min, and the revolution speed is 35 r / min-45 r / min; the ultrasonic frequency is 5 kHz-8 kHz.

[0025] In the present invention, by controlling the reaction conditions, the stability of the prepared separator can be improved. At the same time, it can achieve batch production, improve batch stability, and effectively reduce batch-to-batch variability. In addition, the controlled conditions of this preparation method can effectively increase the affinity and rigidity of the lithium battery separator.

[0026] Preferably, as a further specific embodiment, the boehmite is nano-scale boehmite.

[0027] The boehmite selected in the present invention is nano-sized, rather than micron-sized, boehmite, and has a smaller particle size. This is because larger boehmite particle sizes can lead to poor dispersion in the coating slurry, making it difficult to evenly distribute on the PP or PE separator, thereby reducing the separator's tensile strength and electrolyte affinity. On the other hand, if the particle size is too small, the boehmite will agglomerate during the preparation process, making the reaction process difficult to control and reducing batch stability. The nano-sized boehmite selected in the present invention has a particle size between 100 nm and 900 nm, preferably between 300 nm and 400 nm.

[0028] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses a quantitative transfer coating technique to coat a layer of specially treated nano-boehmite slurry on one or both sides of a polyethylene (PE) or polypropylene (PP) diaphragm, thereby significantly improving the membrane's wettability, cyclability, safety, and stability. This coating not only imparts excellent hydrophobic properties to the diaphragm, effectively reducing its moisture content, but also remains non-water-absorbing and non-diffusing under extreme environmental conditions, ensuring that the membrane's water content is always maintained at a low level, further improving the safety and reliability of the battery. DETAILED DESCRIPTION

[0029] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially. Example 1

[0030] A. Preparation of the first aqueous solution: Take 25 g of epoxyphenylsiloxane, add 54 g of ultrapure water, maintain the temperature at 85° C., stir at a speed of 40 r / min, and stir for 35 minutes to obtain the first aqueous solution.

[0031] B. Preparation of the second powder: Take 40g of nano-boehmite, add all the prepared first aqueous solution, maintain the temperature at 50°C, soak and stir at a speed of 15r / min for 30min, filter to obtain a solid, use a starting pressure of 6Mpa to break up the solid to obtain modified boehmite. The particle size of the obtained second powder is D50: 280nm, D90: 750nm.

[0032] C. Preparation of a high-wetting, ultra-low water-absorption ceramic coating slurry: 32g of the second powder was added to 30g of ultrapure water and 0.5g of polyacrylate. The mixture was dispersed by stirring for 60 minutes. Then, 1.3g of polyethylene glycol was added under ultrasonic mixing and the mixture was dispersed by stirring for another 30 minutes. Then, 2.6g of polyimide and 0.08g of methacrylate were added and ultrasonic mixing was continued for 15 minutes to obtain a lithium battery separator slurry. Ultrasonic mixing was performed in a planetary agitator under vacuum conditions. The agitator's rotation speed was 2000 r / min, its orbital speed was 35 r / min, and the ultrasonic frequency was 5 kHz. The resulting slurry had a particle size D50 of 280nm, a D90 of 760nm, and a viscosity of 132.2 mPa·s.

[0033] D. The finished slurry was applied to one side of a PE separator with a pore size of 5 μm using a quantitative transfer coating technique. The ceramic layer was dried for 2 minutes at 65°C. The coating machine speed was 45 m / min. The resulting coating thickness was 1.1 μm. Example 2

[0034] A. Preparation of the first aqueous solution: 19 g of epoxyphenylsiloxane and 19 g of phenylvinylsiloxane were added to 65 g of ultrapure water. The mixture was stirred at 95° C. and 40 rpm for 35 min to obtain the first aqueous solution.

[0035] B. Preparation of a second powder: 55 g of nano-boehmite was added to the prepared first aqueous solution, the temperature was maintained at 60°C, and the mixture was stirred at 25 rpm for 35 min. The mixture was filtered to obtain a solid. The solid was then broken up using a starting pressure of 6 MPa to obtain modified boehmite. The particle size of the obtained second powder was D50: 288 nm and D90: 793 nm.

[0036] C. Preparation of a high-wetting, ultra-low water-absorption ceramic coating slurry: 32g of the second powder was added to 45g of ultrapure water and 1.2g of polyacrylate. The mixture was dispersed by stirring for 60 minutes. Then, 2.9g of polyethylene glycol was added under ultrasonic mixing and the mixture was dispersed by stirring for another 30 minutes. Then, 3.8g of polyimide and 0.12g of methacrylate were added and ultrasonic mixing was continued for 15 minutes to obtain a lithium battery separator slurry. The ultrasonic mixing was performed in a planetary agitator under vacuum conditions. The agitator had an autorotation speed of 2500 rpm, an orbital speed of 45 rpm, and an ultrasonic frequency of 7 kHz. The resulting slurry had a particle size of D50: 293nm, a D90: 786nm, and a viscosity of 135.8mPa·s.

[0037] D. The finished slurry was applied to both sides of a 20 μm pore size PE separator using a quantitative transfer coating technique. The ceramic layer was dried for 2 minutes at 85°C. The coating machine speed was 45 m / min. The resulting coating thickness was 1.3 μm. Example 3

[0038] A. Preparation of the first aqueous solution: 9.3 g of epoxyphenylsiloxane and 18.7 g of phenylvinylsiloxane were added to 58 g of ultrapure water. The mixture was stirred at 45 rpm and maintained at 85° C. for 35 minutes to obtain the first aqueous solution.

[0039] B. Preparation of a second powder: Take 42 g of nano-boehmite, add all the prepared first aqueous solution, maintain the temperature at 50°C, stir at 25 r / min for 35 minutes, filter to obtain a solid, use a starting pressure of 8 MPa to break up the solid to obtain modified boehmite. The resulting second powder has a particle size of D50: 252 nm and D90: 853 nm.

[0040] C. Preparation of a high-wetting, ultra-low water-absorption ceramic coating slurry: 38g of the second powder was added to 35g of ultrapure water and 0.65g of polyacrylate. The mixture was dispersed by stirring for 60 minutes. Then, 1.35g of polyethylene glycol was added under ultrasonic mixing and the mixture was dispersed by stirring for another 30 minutes. Then, 2.8g of polyimide and 0.08g of methacrylate were added and ultrasonic mixing was continued for 20 minutes to obtain a lithium battery separator slurry. The ultrasonic mixing was performed under vacuum in a planetary agitator with a rotation speed of 2500 r / min, an orbital speed of 35 r / min, and an ultrasonic frequency of 8 kHz. The resulting slurry had a particle size of D50: 323nm and a D90: 796nm. The viscosity was 135.6 mPa·s.

[0041] D. The finished slurry was applied to one side of a 9μm pore size PE separator using a quantitative transfer coating technique. The ceramic layer was dried for 2 minutes at 70°C. The coating machine speed was 45 m / min. The resulting coating thickness was 1.5 μm. Example 4

[0042] The specific implementation method is consistent with Example 3, except that the mass ratio of epoxyphenylsiloxane to phenylvinylsiloxane is changed to 1:1, that is, 14g of epoxyphenylsiloxane and 14g of phenylvinylsiloxane are used. Example 5

[0043] The specific implementation method is consistent with Example 3, except that the mass ratio of epoxyphenylsiloxane to phenylvinylsiloxane is changed to 6:1, that is, 24g epoxyphenylsiloxane and 4g phenylvinylsiloxane are used. Example 6

[0044] The specific implementation method is consistent with Example 3, except that the mass ratio of epoxyphenylsiloxane to phenylvinylsiloxane is changed to 0.6:3, that is, 4.7g epoxyphenylsiloxane and 23.3g phenylvinylsiloxane are used. Comparative Example 1

[0045] To prepare a lithium battery separator slurry, 35g of untreated raw boehmite powder was added to 35g of ultrapure water, followed by 1.12g of polyacrylate. The mixture was stirred and dispersed in a dual planetary mixer for 60 minutes. Then, 2.25g of polyethylene glycol was added under ultrasonic mixing, and stirring and dispersion continued for 30 minutes. Then, 3.6g of polyimide and 0.12g of methacrylate were added, and ultrasonic mixing continued for 15 minutes to obtain the lithium battery separator slurry. The ultrasonic mixing was performed in a planetary mixer under vacuum conditions, with a rotation speed of 2000 rpm, an orbital speed of 40 rpm, and an ultrasonic frequency of 6 kHz. The resulting slurry had a particle size of 389nm (D50) and 946nm (D90). The viscosity was 148.2mPa·s.

[0046] The finished slurry was applied to one side of the PE separator using a quantitative transfer coating technique. The ceramic layer was dried for 3 minutes at 80°C. The coating machine speed was 45 m / min. The resulting coating had a thickness of 2.0 μm. Comparative Example 2

[0047] The specific implementation method is consistent with that of Example 1, except that the mass of epoxyphenylsiloxane is changed to 45 g. Comparative Example 3

[0048] The specific implementation method is consistent with that of Example 1, except that the mass of epoxyphenylsiloxane is changed to 15 g. Comparative Example 4

[0049] The specific implementation method is consistent with that of Example 3, except that the mass of boehmite is changed to 68 g. Comparative Example 5

[0050] The specific implementation method is consistent with that of Example 3, except that the mass of boehmite is changed to 22 g.

[0051] The performance of the battery separators obtained in the above embodiments and comparative examples was tested, and the test results are shown in Table 1.

[0052] Table 1: Diaphragm characteristics test results

[0053] Diaphragm water absorption experiment under extreme environment: For the above embodiments and comparative examples, the same sized diaphragms were taken and their initial water content was tested. A layer of A4 paper was pressed on the top and bottom, and the membranes were placed in a constant temperature (40°C) and constant humidity (85% RH) oven for 24 hours. The membrane water content was tested again and recorded as the extreme environment water content. The results are shown in Table 2.

[0054] Table 2: Limit water absorption test results

[0055] Based on the above data, we can draw the following conclusions: Technical analysis of the experimental results in Tables 1 and 2 shows that the separators prepared by the present invention have significantly lower contact angles, ranging from 7.6° to 8.1°, significantly lower than the contact angles of conventional separators, less than half the latter. This low contact angle clearly demonstrates the superior wettability of the separators of the present invention.

[0056] In addition, the water content of the diaphragm of the present invention is properly controlled and does not exceed 400ppm. In contrast, the water content of ordinary diaphragms exceeds 1200ppm. The water content of the diaphragm of the present invention is only about 1 / 3 of that of ordinary diaphragms, showing its significant advantage in reducing moisture content. Water absorption experiments conducted under extreme environmental conditions show that the diaphragm of the present invention exhibits excellent anti-water absorption performance in high temperature and high humidity environments, and its water absorption is negligible. In contrast, after the traditional diaphragm is placed under the same conditions, its water content increases significantly, almost reaching twice the initial level. This result highlights the significant advantage of the diaphragm of the present invention in maintaining low moisture content. The diaphragm of the present invention does not need to rely on specific drying conditions during the production process, which not only effectively reduces production costs, but also further improves the air permeability of the battery due to its extremely low moisture content. This improvement significantly reduces the possibility of battery expansion during use, thereby greatly improving the overall safety of the battery.

[0057] Comparing Example 1 with Comparative Examples 2-3, it can be seen that when only the mass of the epoxyphenylsiloxane is changed so that it is not within the technical solution of the present invention, the prepared membrane has a thicker thickness, good surface air permeability, good water content, and excellent wetting properties; however, when the mass of the epoxyphenylsiloxane is not within the range set by the present invention, its various performance properties are poor. From this, it can be inferred that when the amount of aromatic alkyl modified silicone is too much, a thicker coating may be formed, resulting in poor performance of the prepared diaphragm; and when the amount of aromatic alkyl modified silicone is too little, the aromatic alkyl modified silicone will be unevenly distributed on the membrane surface, unable to form a stable microstructure, resulting in a significant reduction in the wetting properties of the diaphragm.

[0058] Comparing Example 3 with Comparative Examples 4-5 reveals that changes in boehmite mass also significantly impact membrane performance. During its action, boehmite can partially absorb acidic impurities in the electrolyte, reducing corrosion to the separator. High boehmite content can directly alter the substrate's performance, leading to decreased porosity or structural collapse, significantly reducing membrane performance. Low boehmite content can lead to incomplete coating, reducing wettability and contact angle, and ultimately, diminishing membrane performance.

[0059] By comparing Examples 3-4 with Examples 5-6, it can be seen that when the epoxyphenylsiloxane is excessive, the mass of phenylvinylsiloxane will inevitably decrease, and vice versa. When the ratio of the two is not within a reasonable range, its cross-linking performance will deteriorate and a stable microstructure will not be formed, resulting in a decrease in the wettability of the membrane. At the same time, it is also easy to cause the manufactured battery separator to be too brittle, and the technical effect of the present invention cannot be achieved.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium battery separator with high wettability and ultra-low water absorption, characterized in that: It is made by coating the slurry on both sides or one side of the PP diaphragm or PE diaphragm; The coating slurry is mainly prepared from the following raw materials in parts by mass: 25-38 parts of aromatic alkyl modified silicone, 84-110 parts of ultrapure water, 40-55 parts of boehmite, and 4.48-8.02 parts of a modifier.

2. The highly wettable and ultra-low water absorption lithium battery separator according to claim 1, characterized in that: The modifier is prepared from the following raw materials in parts by mass: 0.5-1.2 parts of a dispersant, 1.3-2.9 parts of a pore-forming agent, 2.6-3.8 parts of a binder, and 0.08-0.12 parts of a wetting agent.

3. The highly wettable and ultra-low water absorption lithium battery separator according to any one of claims 1 to 2, characterized in that: 28 parts of the aromatic alkyl modified silicone, 88 parts of ultrapure water, 42 parts of boehmite, and 4.88 parts of a modifier.

4. The highly wettable and ultra-low water absorption lithium battery separator according to claim 1, characterized in that: The aromatic alkyl modified silicone is any one or more of phenylmethylpolysiloxane, phenylvinylsiloxane, fluorophenylsiloxane or epoxyphenylsiloxane; Preferably, the aromatic alkyl modified silicone is a mixture of epoxyphenylsiloxane and phenylvinylsiloxane in a mass ratio of 1:(1-3); Preferably, the aromatic alkyl modified silicone is a mixture of epoxyphenylsiloxane and phenylvinylsiloxane in a mass ratio of 1:

2.

5. The highly wettable and ultra-low water absorption lithium battery separator according to claim 1, characterized in that: The pore size of the PP or PE membrane is 5 μm to 20 μm; Preferably, a PE membrane with a pore size of 9 μm is selected.

6. The highly wettable and ultra-low water absorption lithium battery separator according to claim 2, characterized in that: The dispersant is any one or more of polyacrylate, anionic sodium lauryl sulfate or polyvinyl pyrrolidone; The pore-forming agent is any one or more of polyethylene glycol or polyvinyl alcohol; The adhesive is polyimide; the wetting agent is methacrylate.

7. A method for preparing a lithium battery separator with high wettability and ultra-low water absorption according to any one of claims 1 to 6, characterized in that: The steps include: Dissolving aromatic alkyl modified silicone with ultrapure water at 85° C. to 95° C. and stirring to obtain a first aqueous solution; Take boehmite, add the first aqueous solution, soak and stir at 50° C.-60° C. for 30 min-35 min, filter, and break up to obtain modified boehmite; The modified boehmite is mixed with ultrapure water, a modifier is added while continuously stirring, and then ultrasonically mixed to obtain a coating material; The coating material is coated on one side or both sides of a PP diaphragm or a PE diaphragm, and then dried at 60° C.-85° C. to obtain the coating material.

8. The method for preparing a lithium battery separator with high wettability and ultra-low water absorption according to claim 8, characterized in that: In the step of soaking at 50° C. to 60° C. for 30 min to 35 min while stirring, the stirring rate is 15 r / min to 25 r / min.

9. The method for preparing a lithium battery separator with high wettability and ultra-low water absorption according to claim 8, characterized in that: The ultrasonic mixing step specifically includes the following steps: vacuuming, stirring by planetary stirring, with a rotation speed of 2000 r / min-2500 r / min and a revolution speed of 35 r / min-45 r / min; the ultrasonic frequency is 5 kHz-8 kHz.

10. The lithium battery separator with high wettability and ultra-low water absorption according to claim 8, characterized in that: The boehmite is nano-scale boehmite.

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