High-temperature-resistant and low-water-absorption lithium battery diaphragm and preparation method thereof

Abstract

The invention provides a high-temperature-resistant and low-water-absorption lithium battery diaphragm and a preparation method thereof. The diaphragm is prepared by coating double surfaces or single surface of a base membrane with coating slurry, wherein the coating slurry is mainly prepared by mixing nano calcium stearate and aluminum oxide in a mass ratio of (25-38): (40-55). According to the preparation method, the surface of the base membrane is coated with a layer of aluminum oxide slurry treated by a special process, and meanwhile, the heat resistance of the diaphragm is remarkably enhanced by optimizing the raw material ratio of the coating slurry and the process flow. The coating slurry not only endows the diaphragm with excellent hydrophobic characteristics and effectively reduces the absorption of moisture, but also can maintain extremely low moisture content under extreme environmental conditions, thereby ensuring that the moisture content of the diaphragm is continuously in a low-level state. The innovative method provides a new technical approach for improving the performance of the lithium ion battery diaphragm.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery separator, and particularly relates to a high-temperature-resistant and low-water-absorption lithium battery separator and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries have been widely used in the field of electronic technology, especially in computers, automobiles and mobile phones, due to their excellent energy density, wide working temperature range, smooth discharge characteristics and long storage and cycle life. As one of the key components of lithium ion batteries, the performance of the separator directly affects the safety and electrochemical performance of the battery. Polyolefin materials, such as polypropylene (PP) and polyethylene (PE), have become the mainstream substrate materials for lithium ion battery separators due to their cost-effectiveness and processing convenience. However, these materials will shrink and deform due to melting when approaching the melting point, increasing the safety risk of the battery.

[0003] In view of the development needs of high-energy-density power batteries, the technology for improving the thermal stability of the separator has become a research focus. Based on the ceramic coating modification technology of the polyolefin-based film, a ceramic functional layer can be coated on the surface of the base film to effectively improve the high-temperature resistance of the separator. The current commercial ceramic separator generally uses aluminum oxide as the coating material to form a ceramic support layer on the surface of the base film to improve its thermal stability. However, the existing ceramic slurry for lithium ion battery separators has a difficulty in controlling the moisture content, resulting in a high water content in the coated separator. This problem may cause the release of gas inside the battery and increase the internal pressure, thereby adversely affecting the capacity retention rate and discharge performance of the battery.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The first object of the present application is to provide a high-temperature-resistant and low-water-absorption lithium battery separator. The separator can effectively solve the problems of poor heat resistance and high moisture content of the battery separator in the prior art by improving the raw material ratio, thereby improving the heat resistance of the battery separator and reducing the water content of the separator, and effectively improving the safety of the battery.

[0006] The second object of the present application is to provide a preparation method of the high-temperature-resistant and low-water-absorption lithium battery separator. The preparation method is simple, green and environmentally friendly, in line with the concept of green chemistry, and can effectively increase the heat resistance of the battery separator, providing a new technical approach to improve the performance of the lithium ion battery separator.

[0007] In order to achieve the above objects of the present application, the following technical solutions are adopted:

[0008] The present application provides a high-temperature-resistant and low-water-absorption lithium battery separator, which is prepared by coating the slurry on both sides or one side of the base film.

[0009] wherein the coating slurry is prepared by mixing nano calcium stearate and alumina in a mass ratio of (25-38):(40-55).

[0010] The nano calcium stearate is prepared by the reaction of stearic acid and calcium hydroxide or calcium oxide, and contains a long carbon chain group in its molecular structure. The long carbon chain structure can form a hydrophobic covering layer on the surface of the separator, significantly reducing the surface free energy of the material. According to the theory of surface energy, low surface energy materials have poor wettability, thus exhibiting hydrophobicity. Specifically, the hydrophobic long carbon chain group in the nano calcium stearate molecule is arranged in order on the surface of the separator, forming a dense hydrophobic film layer that effectively blocks the contact of water molecules with the material surface, thus imparting excellent hydrophobic properties to the material.

[0011] The alumina can form a dense alumina coating on the surface of the base film, which can significantly improve the bulk density of the base film and enhance the rigid support of the base film, thereby improving the heat resistance of the separator. However, due to the large specific surface area and strong water absorption of ultra-fine alumina, the obtained separator has a high water content (usually more than 1000 ppm), and a high water content will adversely affect the safety and cycle performance of the battery.

[0012] The long carbon chain hydrophobic group in the nano calcium stearate molecule can construct a dense hydrophobic film layer on the surface of the separator, effectively preventing water molecules from contacting the material surface. Based on this property, a certain amount of nano calcium stearate molecules is introduced into the alumina. Through a large amount of creative labor, it is found that when nano calcium stearate and alumina are mixed in a mass ratio of (25-38):(40-55), the heat resistance of the battery separator slurry prepared therefrom is significantly improved, while also taking into account the characteristics of low water content and water absorption.

[0013] Preferably, as a further specific embodiment, the nano calcium stearate and alumina are mixed in a mass ratio of 30:48.

[0014] Under this ratio, the long chain group on the surface of the nano calcium stearate can better cover the surface of the alumina, making the coating on the surface of the alumina more dense and more effective in improving the heat resistance of the separator.

[0015] Preferably, as a further specific embodiment, the base film is any one of a PE separator, a PP separator, a PVDF separator, a PI separator, or aramid nanofiber.

[0016] Preferably, as a further specific embodiment, the pore size of the base film is 6-20 μm.

[0017] Preferably, the pore size of the base film is 9 μm.

[0018] In the present application, PP separator or PE separator is mainly used, both of which are more widely used in lithium batteries, have high safety performance, are more resistant to high temperature and have closed pore characteristics, and the technology is more mature. When the prepared coating material is coated on the above two separators, the high temperature resistance of the separator can be better improved, and the mechanical strength is moderate, and the closed pore effect is better.

[0019] In addition, the present application also finds that PVDF separator, PI separator or aramid nanofiber can also be used as a base film of the coating material, and when the coating material is coated on the above-mentioned material, the heat resistance of the base film can still be effectively improved. However, due to the difficulty in processing PVDF separator, PI separator or aramid nanofiber itself, the cost is high, and the heat resistance is more suitable for extreme environment, and the application is more limited.

[0020] In the present application, the pore size of the base film is limited. In the case that the pore size of the base film is large, the electrode material is likely to penetrate the separator, resulting in direct contact of the positive and negative electrodes, thereby causing internal short circuit; and if the ion pore size is too small, the resistance of ion transmission will be significantly increased, and the conductivity will be significantly reduced. Therefore, in the present application, the pore size of the battery is controlled between 6 μm and 20 μm, and the more preferred pore size is 9 μm.

[0021] Preferably, as a further specific embodiment, the coating slurry further comprises a pore forming agent, a thickening agent, a binder and a wetting agent;

[0022] The mass ratio of the surfactant, thickening agent, binder, wetting agent and dispersant is (3-6):(2-5):(1.8-4.3):(0.1-0.2):(0.5-1.2);

[0023] The mass ratio of the surfactant, thickening agent, binder, wetting agent and dispersant is 4.9:3.2:3.12:0.13:0.83;

[0024] Preferably, as a further specific embodiment, the surfactant is any one or more of polyethylene glycol or PEO-PPO-PEO block copolymer;

[0025] The thickening agent is any one or more of sodium carboxymethyl cellulose or hydroxypropyl methyl cellulose;

[0026] The binder is any one or more of polyimide or polyacrylate;

[0027] The wetting agent is any one or more of methacrylic acid or sorbitol anhydride ester;

[0028] The dispersant is polyacrylate.

[0029] In the present application, the pore-forming agent, thickening agent, binder and wetting agent are also added to realize the modification of the properties of the coating material, thereby realizing the adjustment of the porosity and stability of the finished battery separator.

[0030] Preferably, as a further specific embodiment, the molecular weight of the polyethylene glycol is 200-20000.

[0031] In the present application, the focus is on the selection of surfactants. Among them, the polyethylene glycol surfactant is a single ethylene oxide chain, which is simple in structure, easy to be compatible with polar solvents, suitable for various slurry systems, and different molecular weights of polyethylene glycol are suitable for different base films, which can better improve the electrolyte wettability of the base film. The hydrophilic PEO segment and the hydrophobic PPO segment in the PEO-PPO-PEO block copolymer form micelles, which can accurately design the pore size and porosity of the separator by changing the PEO / PPO ratio.

[0032] The polyethylene glycol with a molecular weight of 400 can also be used in combination with PVDF to significantly improve the wettability of the base film.

[0033] Preferably, as a further specific embodiment, the particle size of the alumina is 300nm-500nm.

[0034] Preferably, the particle size of the alumina is 450nm.

[0035] In the present application, the particle size of alumina is limited. When the particle size of alumina is too large, it is easy to cause poor dispersibility of the coating slurry and difficult to be uniformly distributed on the base film, thereby reducing the mechanical strength of the finished separator and the affinity of the electrolyte. If the particle size is too small, agglomeration will occur during preparation, making it difficult to control the reaction process and thus reducing the stability of the batch.

[0036] The present application also provides a preparation method of the high-temperature-resistant and low-water-absorbing lithium battery separator as described above, comprising the following steps:

[0037] Dissolve and stir the nano calcium stearate with water to obtain a first solution, and then dissolve and stir the alumina with water to obtain a second solution;

[0038] Mix and stir the first solution and the second solution, and sequentially add a dispersing agent, a pore-forming agent, a thickening agent, a binder and a wetting agent to obtain a coating slurry;

[0039] Coat the coating slurry on the base film to obtain the product.

[0040] Preferably, as a further specific embodiment, the stirring temperature during the dissolution and stirring of the nano calcium stearate with water and the dissolution and stirring of the alumina with water is 80-95℃.

[0041] The application effectively improves the heat resistance of the battery separator by optimizing the reaction conditions and the reaction process, provides a new technical approach for improving the performance of the lithium ion battery separator. At the same time, the production of the separator is industrialized, the batch stability is effectively improved, and the batch difference is reduced.

[0042] Compared with the prior art, the application has the beneficial effects that:

[0043] The application significantly enhances the heat resistance of the separator by coating a layer of alumina slurry treated by a special process on the surface of the base film, and optimizing the raw material ratio and process flow of the coating slurry. The coating slurry not only imparts excellent hydrophobic properties to the separator, effectively reducing water absorption, but also can maintain extremely low moisture content under extreme environmental conditions, thereby ensuring that the moisture content of the separator remains at a low level. This innovative method provides a new technical approach for improving the performance of the lithium ion battery separator. DETAILED DESCRIPTION

[0044] The technical solutions of the application will be described clearly and completely in combination with specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the application, not all the embodiments, and are only used to illustrate the application, and should not be regarded as limiting the scope of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application. The specific conditions are not specified in the embodiments, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0045] Example 1

[0046] Preparation of the first solution: 25 g of nano calcium stearate was taken, 65 g of ultrapure water was added, and stirring was carried out at 85℃ and a stirring speed of 45 r / min for 35 min until dissolution to obtain the first solution.

[0047] Preparation of the second solution: 40 g of alumina with a particle size of 300 nm was taken, 72 g of ultrapure water was added, and stirring was carried out at 85℃ and a stirring speed of 45 r / min for 30 min to obtain the second solution.

[0048] The first solution and the second solution were mixed and added to a double planetary mixer, 0.5 g of polyacrylate was added, and the initial mixed slurry was prepared by dispersion stirring for 60 min, wherein the stirring speed of the double planetary mixer was 55 r / min and the dispersion speed was 2500 r / min.

[0049] Take 3g PEG 400, add to the above initial mixed slurry, dispersed in a double planetary mixer for 30min to obtain a premixed slurry, wherein the double planetary mixer stirring speed is 50r / min, the dispersion speed is 2200r / min.

[0050] Take 2g sodium carboxymethyl cellulose and add to the above premixed slurry, dispersed in a double planetary mixer for 1h to obtain a semi-finished slurry, wherein the double planetary mixer stirring speed is 45r / min, the dispersion speed is 2500r / min.

[0051] The uniformly dispersed semi-finished slurry is introduced into a vacuum stirrer, 1.8g of polyimide and 0.1g of methacrylic acid are added and stirred, wherein the stirring speed of the vacuum stirrer is 35r / min.

[0052] After the above steps are completed, the slurry is subjected to ultrasonic and vacuum, the vacuum degree is above -0.8Mpa, this step is to eliminate hidden bubbles in the slurry to obtain a finished product slurry. The ultrasonic frequency is 6kHz, and the ultrasonic and vacuum time is 15min, to obtain a coating slurry.

[0053] The above finished product slurry is coated on the surface of a PP film with a pore size of 6μm by a quantitative transfer coating technique, wherein the drying time of the ceramic layer after coating is 3min, the temperature is 85℃. The line speed of the coating machine is 35m / min. The thickness of the coating layer formed by coating is 1.5μm.

[0054] Example 2

[0055] Prepare the first solution: take 38g of nano calcium stearate, add 85g of ultrapure water, stir at 45r / min for 35min at 95℃ until dissolved to obtain the first solution.

[0056] Prepare the second solution: take 55g of alumina with a particle size of 500nm, add 85g of ultrapure water, stir at 45r / min for 30min at 95℃ to obtain the second solution.

[0057] Mix the first solution and the second solution, add to a double planetary mixer, add 1.2g of polyacrylate, and stir for 60min by dispersion to prepare an initial mixed slurry, wherein the double planetary mixer stirring speed is 55r / min, the dispersion speed is 2500r / min.

[0058] Take 3g PEG 400, add to the above initial mixed slurry, dispersed in a double planetary mixer for 30min to obtain a premixed slurry, wherein the double planetary mixer stirring speed is 50r / min, the dispersion speed is 2200r / min.

[0059] Take 5g carboxymethyl cellulose sodium to the above pre-mixed slurry, dispersed in double planetary mixer for 1h to get semi-finished slurry, wherein the double planetary mixer stirring speed is 45r / min, dispersion speed is 2500r / min.

[0060] The uniformly dispersed semi-finished slurry is introduced into a vacuum stirrer, 4.3g of polyimide and 0.2g of methacrylic acid are added and stirred, wherein the stirring speed of the vacuum stirrer is 35r / min.

[0061] After the above steps are completed, the slurry is subjected to ultrasonic and vacuum, the vacuum degree is above -0.8Mpa, this step is to eliminate hidden bubbles in the slurry to get finished product slurry. Among them, the ultrasonic frequency is 6kHz, the ultrasonic and vacuum time is 15min, and the coating slurry is obtained.

[0062] The above finished product slurry is coated on the surface of a PP film with a pore size of 20μm by quantitative transfer coating technology, wherein the drying time of the ceramic layer after coating is 3min, the temperature is 85℃. The line speed of the coating machine is 35m / min. The thickness of the coating formed by coating is 1.5μm.

[0063] Example 3

[0064] Prepare the first solution: take 30g nano calcium stearate, add 77g ultrapure water, stir at 45r / min for 35min at 85℃ until dissolved to get the first solution.

[0065] Prepare the second solution: take 48g of alumina with a particle size of 450nm, add 78g of ultrapure water, stir at 45r / min for 30min at 85℃ to get the second solution.

[0066] Mix the first solution and the second solution, add to the double planetary mixer, add 1.2g of polyacrylate, and stir for 60min to make the initial mixed slurry, wherein the double planetary mixer stirring speed is 55r / min, dispersion speed is 2500r / min.

[0067] Take 6g PEG 400, add to the above initial mixed slurry, disperse in double planetary mixer for 30min to get pre-mixed slurry, wherein the double planetary mixer stirring speed is 50r / min, dispersion speed is 2200r / min.

[0068] Take 5g carboxymethyl cellulose sodium to the above pre-mixed slurry, dispersed in double planetary mixer for 1h to get semi-finished slurry, wherein the double planetary mixer stirring speed is 45r / min, dispersion speed is 2500r / min.

[0069] The uniformly dispersed semi-finished slurry was poured into a vacuum stirrer, 4.3 g of polyimide and 0.2 g of methacrylic acid were added, and stirring was performed at a stirring speed of 35 r / min.

[0070] After the above steps were completed, the slurry was subjected to ultrasonic and vacuum extraction, and the vacuum degree was above -0.8 MPa. This step was to eliminate hidden bubbles in the slurry to obtain a finished product slurry. The ultrasonic frequency was 6 kHz, and the ultrasonic and vacuum extraction time was 15 min, and a coating slurry was obtained.

[0071] The finished product slurry was coated on one side of a PP film with a pore size of 9 μm by a quantitative transfer coating technique. The ceramic layer was dried at a temperature of 85°C for 3 min after coating. The line speed of the coating machine was 35 m / min. The thickness of the coating layer formed by coating was 1.5 μm.

[0072] Example 4

[0073] The specific implementation was consistent with that of Example 3, and only the base film was replaced with a PE film.

[0074] Example 5

[0075] The specific implementation was consistent with that of Example 3, and only the molecular weight of PEG was changed to 600.

[0076] Example 6

[0077] The specific implementation was consistent with that of Example 3, and only PEG 400 was replaced with Pluronic F127 (PEO-PPO-PEO block copolymer).

[0078] Example 7

[0079] The specific implementation was consistent with that of Example 3, and the base film was replaced with a PI film, and PEG 6000 and PEG 20000 were added.

[0080] Example 8

[0081] The specific implementation was consistent with that of Example 3, and only the molecular weight of PEG used was adjusted to 35,000.

[0082] Example 9

[0083] The specific implementation was consistent with that of Example 3, and only the particle size of alumina was adjusted to 900 nm.

[0084] Example 10

[0085] The specific implementation was consistent with that of Example 3, and only the particle size of alumina was adjusted to 200 nm.

[0086] Comparative Example 1

[0087] A lithium battery separator slurry was prepared by adding 35 g of superfine alumina powder, 35 g of ultrapure water, 0.9 g of polyacrylate, and dispersing for 60 min by stirring, then adding 2.2 g of PEG 400 under ultrasonic mixing, continuing to stir and disperse for 30 min, adding 4.5 g of sodium carboxymethyl cellulose and continuing to stir and disperse for 30 min, finally adding 3.3 g of polyimide and 0.15 g of methacrylic acid, and continuing to ultrasonic mix for 15 min. The ultrasonic mixing was performed in a planetary stirring device under vacuum conditions, wherein the rotation speed of the planetary stirring device was 2000 / min, the revolution speed was 40 r / min, and the frequency of the ultrasonic wave was 6 kHz.

[0088] Comparative Example 2

[0089] The specific embodiment was consistent with Example 3, and only the amount of nano calcium stearate was increased to 40 g, at which time the mass ratio of nano calcium stearate to alumina was 1:1.

[0090] Comparative Example 3

[0091] The specific embodiment was consistent with Example 3, and only the amount of nano calcium stearate was reduced to 15 g, at which time the mass ratio of nano calcium stearate to alumina was 15:40.

[0092] Experimental Example 1

[0093] The battery separator obtained in the example and comparative example was tested, and the test results are shown in Table 1.

[0094] Table 1: Comparison of battery separator performance

[0095]

[0096] According to the above data, the following conclusions can be drawn:

[0097] According to the experimental data in Table 1, the separator prepared by the preparation method and ratio of the present application has stronger heat shrinkage resistance. The heat shrinkage of the separator prepared by the present application is within 2% in MD and TD at 150℃*1h, and the heat resistance is 22 times that of ordinary lithium battery separator. Moreover, the water content of the separator of the present application is properly controlled and does not exceed 400 ppm.

[0098] From the experimental data in Examples 5-7, it can be seen that when the type of base film and the surfactant change, the performance of the battery separator prepared will be affected. When the base film is selected as a PE film, its actual performance will be better than that of a PP film, because the closure temperature of the PE film is significantly lower than that of the PP film. When the internal temperature of the battery abnormally rises, the PE film will quickly melt and close the pores, thus having better heat resistance; in actual use, both PE and PP films can be used as base films to adapt to different scenarios. When the base film is selected as a PI film, the molecular weight of the PEG used needs to be adjusted, in which PEG 6000 realizes the flexibility enhancement of the PI film, and PEG 20000 realizes the skeleton support of the PI film. At this time, the PI film prepared is a composite film, which can more effectively optimize the heat resistance and mechanical strength of the battery, and is more suitable for complex battery environments. However, due to the high cost of raw materials selected by this preparation method, the application is more limited.

[0099] Comparing Example 3 with Example 8, it can be found that when the molecular weight of PEG is large, although it can provide rigid support for the separator, the mechanical performance of the prepared separator is better, but the low porosity and high crystallinity of the prepared separator lead to a tortuous ion transport path, and the conductivity performance is reduced to a certain extent, thus being more suitable for solid-state electrolyte carriers.

[0100] Comparing Example 3 with Examples 9-10, it can be seen that the particle size of alumina will affect the water content of the separator, thereby affecting the wettability. When the particle size of alumina is large, it is easy to cause poor dispersibility of the coating slurry, making it difficult to uniformly distribute on the base film, thereby reducing the tensile strength of the separator and the affinity of the electrolyte. When the particle size is too small, agglomeration will occur during the preparation of alumina, making it difficult to control the reaction process, not only reducing the stability of the batch, but also affecting the water content and peeling performance of the prepared separator.

[0101] In contrast, the water content of the ordinary separator in Comparative Example 1 is more than 1200 ppm, and the water content of the separator of the present application is only 1 / 3 of that of the ordinary separator, showing its significant advantage in reducing water content. Comparing Example 3 with Comparative Examples 2 and 3, it can be seen that the mass ratio of nano calcium stearate to alumina is very important. When the amount of nano calcium stearate is excessive,

[0102] the content of alumina will inevitably decrease, and when the amount of nano calcium stearate is small, the amount of alumina will be excessive. In these two cases, the long carbon chain hydrophobic group in the nano calcium stearate molecule and the alumina cannot form a dense and stable hydrophobic structure on the surface of the base film, thereby greatly affecting the performance of the finished battery separator.

[0103] Experimental Example 2: Water absorption test of the separator under extreme environment

[0104] The battery separators prepared in the examples and comparative examples were subjected to a water absorption test under extreme environment. The same size separator was taken and its initial water content was tested. One layer of A4 paper was pressed on the top and bottom of the separator, and then the separator was placed in a constant temperature (40°C) and constant humidity (humidity 85%RH) oven for 24 hours. The water content of the separator was tested again, and was recorded as the water content under extreme environment. The results are shown in Table 2.

[0105] Table 2: Comparison of water absorption test results under extreme environment

[0106]

[0107] From the above data, the following conclusions can be drawn:

[0108] The water absorption test under extreme environment conditions shows that the separator of the present application exhibits excellent water absorption resistance in high temperature and high humidity environment, and its water absorption is minimal. In contrast, the water content of the separators prepared in Comparative Examples 1-3 increases significantly, almost reaching twice the initial level.

[0109] This result highlights the significant advantage of the separator of the present application in maintaining low moisture content. The separator of the present application does not need to rely on special drying conditions during production, which not only effectively reduces the production cost, 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 swelling during use, thereby greatly improving the overall safety of the battery.

[0110] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limiting. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that they can still modify the technical solutions described in the above examples, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the examples of the present application.

Claims

1. A high-temperature resistant and low-water-absorption lithium battery separator, characterized in that, The diaphragm is made by coating a slurry onto a base film on both or one side. The coating slurry is mainly prepared by mixing nano-calcium stearate and alumina in a mass ratio of (25-38):(40-55).

2. The high-temperature resistant and low-water-absorption lithium battery separator according to claim 1, characterized in that, The nano-calcium stearate and alumina were prepared by mixing them in a mass ratio of 30:

48.

3. The high-temperature resistant and low-water-absorption lithium battery separator according to claim 1, characterized in that, The base membrane is any one of PE membrane, PP membrane, PVDF membrane, PI membrane or aramid nanofiber.

4. The high-temperature resistant and low-water-absorption lithium battery separator according to claim 3, characterized in that, The pore size of the base membrane is 6μm-20μm; Preferably, the pore size of the base film is 9 μm.

5. The high-temperature resistant and low-water-absorption lithium battery separator according to claim 1, characterized in that, The coating slurry also includes a pore-forming agent, a thickener, a binder, and a wetting agent; The mass ratio of the surfactant, thickener, binder, wetting agent and dispersant is (3-6): (2-5): (1.8-4.3): (0.1-0.2): (0.5-1.2).

6. The high-temperature resistant and low-water-absorption lithium battery separator according to claim 5, characterized in that, The mass ratio of the surfactant, thickener, binder, wetting agent, and dispersant is 4.9:3.2:3.12:0.13:0.

83. The surfactant is any one or more of polyethylene glycol or PEO-PPO-PEO block copolymer; The thickener is any one or more of sodium carboxymethyl cellulose or hydroxypropyl methyl cellulose; The adhesive is any one or more of polyimide or polyacrylate; The wetting agent is any one or more of methacrylic acid or sorbitan ester; The dispersant is polyacrylate.

7. The high-temperature resistant and low-water-absorption lithium battery separator according to claim 6, characterized in that, The molecular weight of the polyethylene glycol is 200-20000.

8. The high-temperature resistant and low-water-absorption lithium battery separator according to claim 1, characterized in that, The alumina has a particle size of 300nm-500nm; Preferably, the alumina has a particle size of 450 nm.

9. A method for preparing a high-temperature resistant and low-water-absorption lithium battery separator as described in any one of claims 1-8, characterized in that, Includes the following steps: Nano-calcium stearate was dissolved in water and stirred to obtain the first solution. Then, aluminum oxide was dissolved in water and stirred to obtain the second solution. The first solution and the second solution are mixed and stirred, and then a dispersant, a pore-forming agent, a thickener, a binder and a wetting agent are added in sequence to obtain a coating slurry; The coating slurry is applied to the base film to obtain the final product.

10. The method for preparing a high-temperature resistant and low-water-absorption lithium battery separator according to claim 9, characterized in that, During the process of dissolving and stirring the nano-calcium stearate in water and the alumina in water, the stirring temperature is 80℃-95℃.

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