Low-temperature closed-cell low-moisture lithium battery diaphragm and preparation method thereof

Abstract

The invention discloses a low-temperature closed-pore low-moisture lithium battery diaphragm and a preparation method thereof in the technical field of lithium battery diaphragms, and the low-temperature closed-pore low-moisture lithium battery diaphragm is composed of a base membrane and lithium battery coating slurry, the lithium battery coating slurry is prepared from the following components: magnesium oleate, an organic solvent, ceramic particles, ultrapure water, a dispersing agent, an adhesive and a wetting agent. According to the invention, magnesium oleate is added into the coating slurry, so that the water content of the ceramic coating diaphragm is reduced, and meanwhile, the ceramic coating slurry containing magnesium oleate is coated on the surface of the base diaphragm, so that the hole closing temperature of the battery diaphragm is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium battery separators, and particularly relates to a low-temperature closed-pore low-moisture lithium battery separator and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries are core components of pure electric new energy vehicles, and their safety problems have become one of the key factors restricting their further development; in addition to battery pack design defects, misuse during use and external environmental impact, the composition, design and manufacturing process of single batteries are also important reasons for safety accidents, especially the influence of battery composition on safety performance is more significant; as one of the four main materials of lithium ion batteries, the separator plays a crucial role in the comprehensive performance of lithium ion batteries, especially in safety performance.

[0003] Research on the thermal runaway reaction kinetics mechanism of lithium ion batteries shows that the process can be divided into three stages: first, the internal thermal runaway stage of the battery, due to heating or short circuit and other factors, the internal temperature of the battery rises to about 100 DEG C, at this time the anode SEI film begins to decompose, lithium embedded in graphite reacts with electrolyte, further increasing the internal temperature of the battery; second, the battery swelling stage, when the battery temperature rises to 200 DEG C, the cathode material decomposes, releasing a large amount of heat and gas, in the temperature range of 250-350 DEG C, the lithium-embedded anode begins to react with the electrolyte; third, the overall thermal runaway stage of the battery, with the rapid rise of the internal pressure of the lithium ion battery, the outer package of the battery is broken, the external oxygen, electrolyte vapor and various reaction produced flammable smoke combustion reaction, and then cause combustion, leading to the overall thermal runaway of the lithium ion battery.

[0004] In the thermal runaway process of lithium ion batteries, the separator mainly plays a role in the first stage, the polyolefin separator will melt, closing the pore structure, thereby preventing the transmission of lithium ions, making the battery circuit break, and thereby limiting the further thermal runaway of the lithium ion battery; although the industry continues to make various researches, there are still defects such as complex process for improving the closing mechanism of the separator, low scalability and large coating amount; solving the existing problems in the separator and making it more conducive to large-scale use and promotion has become one of the key problems that many frontline researchers and research-oriented enterprises need to solve.

[0005] Magnesium oleate is an organic magnesium compound with the chemical formula C 36 H 66 MgO4, which is generated by the reaction of oleic acid with magnesium oxide or magnesium hydroxide, belongs to the class of fatty acid metal salts, and has a melting point of 130-140 DEG C and can be dissolved in organic solvents.

[0006] The prior art mainly has the following problems: 1. The high pore closure temperature of the battery separator cannot limit thermal runaway; 2. The ceramic coated separator currently used has high water content, which can easily cause battery short circuit. SUMMARY

[0007] In view of the above problems, the present application provides a low-temperature pore closure low-moisture lithium battery separator and a preparation method thereof, in order to solve the problems of high pore closure temperature of the battery separator and high water content of the ceramic coated separator, the present application proposes adding magnesium oleate to the coating slurry, thereby reducing the water content of the ceramic coated separator, and coating the ceramic coating slurry containing magnesium oleate on the surface of the base film, thereby reducing the pore closure temperature of the battery separator.

[0008] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: the present application provides a low-temperature pore closure low-moisture lithium battery separator, which is composed of a base film and a lithium battery coating slurry.

[0009] Preferably, the lithium battery coating slurry is prepared from the following components: magnesium oleate, an organic solvent, ceramic particles, ultrapure water, a dispersing agent, an adhesive and a wetting agent.

[0010] Preferably, the organic solvent includes one of methanol, ethanol, isopropyl alcohol and diethyl ether.

[0011] Further, the organic solvent is methanol.

[0012] Preferably, the ceramic particles include one of alumina, boehmite and zirconia.

[0013] Further, the ceramic particles are alumina, the particle size D50 is 0.587-0.624 microns, and the D99 is 2.341-2.462 microns.

[0014] Preferably, the dispersing agent is an acrylate copolymer, the adhesive is an acrylate adhesive, the wetting agent is an alkyl phenol polyoxyethylene ether, and the base film is a PE base film.

[0015] Preferably, the preparation method of the lithium battery coating slurry specifically includes the following steps:

[0016] S1. Add 16-23 g of magnesium oleate to a reactor, then add 67-76 g of an organic solvent, and heat and stir to obtain a magnesium oleate solution;

[0017] S2. Add 18-24 g of ceramic particles to 34-39 g of ultrapure water, then add 1.1-1.5 g of a dispersing agent, and use a double-planetary mixer to stir and disperse under the condition of 27-28℃ to obtain a dispersion liquid;

[0018] S3. Take 5.1-7.1g of the magnesium oleate solution obtained in S1 and add it to the dispersion obtained in S2. Mix the mixture using a double planetary mixer to obtain a mixture.

[0019] S4. Add 2.4-2.8g of adhesive and 0.3-0.41g of wetting agent to the mixture obtained in S3, and continue to stir and mix at a speed of 65-70rpm for 30min to obtain lithium battery coating slurry.

[0020] Preferably, in S1, the temperature for heat preservation and stirring is 80-85℃, the speed is 45-50 rpm, and the time is 35-45 min.

[0021] Preferably, in S2, the rotation speed of the dual planetary mixer is 2000-2500 rpm, the revolution speed is 40 rpm, and the time is 45-50 min.

[0022] Preferably, in S3, the speed of the dual planetary mixer is 55-60 rpm and the time is 10 min.

[0023] Preferably, in S4, the viscosity of the lithium battery coating slurry is 92.7-94.8 mPa·s, and the particle size is D50: 0.627-0.674 μm, D90: 1.343-1.441 μm.

[0024] The present invention also provides a method for preparing a low-temperature closed-cell low-moisture lithium battery separator, which specifically includes the following steps: applying a lithium battery coating slurry to a base film with a thickness of 9 μm on one side at a speed of 40 m / min to form a coating with a thickness of 2.1-2.3 μm, and drying it at 90-100℃ for 1.5-2 min to obtain a low-temperature closed-cell low-moisture lithium battery separator.

[0025] The beneficial effects achieved by this invention are as follows:

[0026] By coating the separator surface with a ceramic slurry containing magnesium oleate, the pore-closing temperature of the battery separator is effectively reduced while maintaining or improving the original ceramic coating characteristics, thus solving the problem of battery thermal runaway. Simultaneously, this slurry can reduce the water content of the ceramic coating, maintaining low moisture content in the battery separator even under high ambient humidity. By adding specially treated magnesium oleate to the ceramic coating slurry and coating it onto the base film surface using methods such as roller coating or dip coating, the magnesium oleate begins to gradually melt when the internal temperature of the battery cell reaches 130°C, thereby blocking the lithium-ion transport channels and preventing thermal runaway at its source. Furthermore, magnesium oleate has a certain degree of hydrophobicity, which can reduce the water content of the ceramic-coated separator, thereby reducing the short-circuit rate of the battery cell. The slurry of this invention has good adhesion to the PE separator, resulting in a separator with low-temperature pore-closing characteristics and low water content. Attached Figure Description

[0027] Figure 1 The figures show the results of air permeability tests for Examples 1-5 and Comparative Example 1 of this invention;

[0028] Figure 2 The results of closed-cell temperature tests in Examples 1-5 and Comparative Example 1 of this invention are shown in the figure.

[0029] Figure 3 The figures show the results of the extreme water absorption tests for Examples 1-5 and Comparative Example 1 of the present invention.

[0030] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0033] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; unless otherwise specified, the experimental materials used in the following embodiments are all purchased from commercial channels.

[0034] Example 1

[0035] A low-temperature closed-cell low-moisture lithium battery separator is composed of a PE base film and a lithium battery coating slurry.

[0036] The lithium battery coating slurry is prepared from the following components: magnesium oleate, organic solvent, alumina ceramic particles, ultrapure water, dispersant, binder and wetting agent.

[0037] The preparation method of lithium battery coating slurry specifically includes the following steps:

[0038] S1. Add 16g of magnesium oleate to the reactor, then add 67g of methanol, keep warm at 80℃ and stir at 45rpm for 35min to obtain magnesium oleate solution.

[0039] S2. Add 18g of alumina ceramic particles to 34g of ultrapure water, followed by 1.1g of acrylate copolymer. Under the condition of keeping warm at 28℃, use a double planetary mixer to stir and disperse the mixture. The rotation speed of the double planetary mixer is 2000rpm, the revolution speed is 40rpm, and the time is 45min to obtain a dispersion. The particle size of the alumina ceramic particles is D50: 0.587μm, D99: 2.462μm.

[0040] S3. Take 5.1g of the magnesium oleate solution obtained in S1 and add it to the dispersion obtained in S2. Mix the mixture using a double planetary mixer at 55 rpm for 10 min to obtain the mixture.

[0041] S4. Add 2.4g of acrylate adhesive and 0.3g of alkylphenol polyoxyethylene ether to the mixture obtained in S3, and continue to stir and mix at 65rpm for 30min to obtain a lithium battery coating slurry with a viscosity of 92.7mPa·s and particle sizes D50: 0.674μm and D90: 1.429μm.

[0042] The present invention also provides a method for preparing a low-temperature closed-cell low-moisture lithium battery separator, which specifically includes the following steps: applying a lithium battery coating slurry to a PE base film with a thickness of 9 μm at a speed of 40 m / min on one side to form a coating with a thickness of 2.1 μm, and drying it at 90°C for 2 min to obtain a low-temperature closed-cell low-moisture lithium battery separator.

[0043] Example 2

[0044] A low-temperature closed-cell low-moisture lithium battery separator is composed of a PE base film and a lithium battery coating slurry.

[0045] The lithium battery coating slurry is prepared from the following components: magnesium oleate, organic solvent, alumina ceramic particles, ultrapure water, dispersant, binder and wetting agent.

[0046] The preparation method of lithium battery coating slurry specifically includes the following steps:

[0047] S1. Add 19g of magnesium oleate to the reactor, then add 71g of methanol, keep warm at 85℃ and stir at 45rpm for 40min to obtain magnesium oleate solution.

[0048] S2. Add 20g of alumina ceramic particles to 37g of ultrapure water, then add 1.3g of acrylate copolymer. Under the condition of keeping warm at 27℃, use a double planetary mixer to stir and disperse the mixture. The rotation speed of the double planetary mixer is 2500rpm, the revolution speed is 40rpm, and the time is 45min to obtain a dispersion. The particle size of the alumina ceramic particles is D50: 0.603μm, D99: 2.341μm.

[0049] S3. Take 6.3g of the magnesium oleate solution obtained in S1 and add it to the dispersion obtained in S2. Mix the mixture using a double planetary mixer at 55 rpm for 10 minutes to obtain the mixture.

[0050] S4. Add 2.6g of acrylate adhesive and 0.38g of alkylphenol polyoxyethylene ether to the mixture obtained in S3, and continue to stir and mix at 70rpm for 30min to obtain a lithium battery coating slurry with a viscosity of 94.8mPa·s and particle sizes D50: 0.657μm and D90: 1.441μm.

[0051] The present invention also provides a method for preparing a low-temperature closed-cell low-moisture lithium battery separator, which specifically includes the following steps: applying a lithium battery coating slurry to a PE base film with a thickness of 9 μm at a speed of 40 m / min on one side to form a coating with a thickness of 2.3 μm, and drying it at 95°C for 2 min to obtain a low-temperature closed-cell low-moisture lithium battery separator.

[0052] Example 3

[0053] A low-temperature closed-cell low-moisture lithium battery separator is composed of a PE base film and a lithium battery coating slurry.

[0054] The lithium battery coating slurry is prepared from the following components: magnesium oleate, organic solvent, alumina ceramic particles, ultrapure water, dispersant, binder and wetting agent.

[0055] The preparation method of lithium battery coating slurry specifically includes the following steps:

[0056] S1. Add 23g of magnesium oleate to the reactor, then add 76g of methanol, keep warm at 85℃ and stir at 50rpm for 45min to obtain magnesium oleate solution.

[0057] S2. Add 24g of alumina ceramic particles to 39g of ultrapure water, followed by 1.5g of acrylate copolymer. Under the condition of keeping warm at 27℃, use a double planetary mixer to stir and disperse the mixture. The rotation speed of the double planetary mixer is 2500rpm, the revolution speed is 40rpm, and the time is 50min to obtain a dispersion. The particle size of the alumina ceramic particles is D50: 0.624μm, D99: 2.428μm.

[0058] S3. Take 7.1g of the magnesium oleate solution obtained in S1 and add it to the dispersion obtained in S2. Mix the mixture using a double planetary mixer at 60 rpm for 10 min to obtain the mixture.

[0059] S4. Add 2.8g of acrylate adhesive and 0.41g of alkylphenol polyoxyethylene ether to the mixture obtained in S3, and continue to stir and mix at 70rpm for 30min to obtain a lithium battery coating slurry with a viscosity of 94.3mPa·s and particle sizes D50: 0.627μm and D90: 1.343μm.

[0060] The present invention also provides a method for preparing a low-temperature closed-cell low-moisture lithium battery separator, which specifically includes the following steps: applying a lithium battery coating slurry to a PE base film with a thickness of 9 μm at a speed of 40 m / min on one side to form a coating with a thickness of 2.2 μm, and drying it at 100°C for 1.5 min to obtain a low-temperature closed-cell low-moisture lithium battery separator.

[0061] Example 4

[0062] A low-temperature closed-cell low-moisture lithium battery separator is composed of a PE base film and a lithium battery coating slurry.

[0063] The lithium battery coating slurry is prepared from the following components: magnesium oleate, organic solvent, alumina ceramic particles, ultrapure water, dispersant, binder and wetting agent.

[0064] The preparation method of lithium battery coating slurry specifically includes the following steps:

[0065] S1. Add 16g of magnesium oleate to the reactor, then add 67g of methanol, keep warm at 85℃ and stir at 50rpm for 45min to obtain magnesium oleate solution.

[0066] S2. Add 18g of ceramic particles to 34g of ultrapure water, then add 1.1g of dispersant. Under the condition of keeping warm at 28℃, use a double planetary mixer to stir and disperse the particles. The rotation speed of the double planetary mixer is 2500rpm, the revolution speed is 40rpm, and the time is 50min to obtain a dispersion; alumina, particle size D50: 0.596μm, D99: 2.413μm;

[0067] S3. Take 5.1g of the magnesium oleate solution obtained in S1 and add it to the dispersion obtained in S2. Mix the mixture using a double planetary mixer at 60 rpm for 10 min to obtain the mixture.

[0068] S4. Add 2.4g of acrylate adhesive and 0.3g of alkylphenol polyoxyethylene ether to the mixture obtained in S3, and continue to stir and mix at 70rpm for 30min to obtain a lithium battery coating slurry with a viscosity of 93.6mPa•s and particle sizes D50: 0.636μm and D90: 1.396μm.

[0069] The present invention also provides a method for preparing a low-temperature closed-cell low-moisture lithium battery separator, which specifically includes the following steps: applying a lithium battery coating slurry to a base film with a thickness of 9 μm on one side at a speed of 40 m / min to form a coating with a thickness of 2.1 μm, and drying it at 100°C for 2 min to obtain a low-temperature closed-cell low-moisture lithium battery separator.

[0070] Example 5

[0071] A low-temperature closed-cell low-moisture lithium battery separator is composed of a PE base film and a lithium battery coating slurry.

[0072] The lithium battery coating slurry is prepared from the following components: magnesium oleate, organic solvent, alumina ceramic particles, ultrapure water, dispersant, binder and wetting agent.

[0073] The preparation method of lithium battery coating slurry specifically includes the following steps:

[0074] S1. Add 23g of magnesium oleate to the reactor, then add 76g of methanol, keep warm at 80℃ and stir at 45rpm for 35min to obtain magnesium oleate solution.

[0075] S2. Add 24g of ceramic particles to 39g of ultrapure water, then add 1.5g of dispersant. Under the condition of keeping warm at 28℃, use a double planetary mixer to stir and disperse the particles. The rotation speed of the double planetary mixer is 2000rpm, the revolution speed is 40rpm, and the time is 45min to obtain a dispersion. Alumina, particle size D50: 0.615μm, D99: 2.396μm;

[0076] S3. Take 7.1g of the magnesium oleate solution obtained in S1 and add it to the dispersion obtained in S2. Mix the mixture using a double planetary mixer at 55 rpm for 10 min to obtain the mixture.

[0077] S4. Add 2.8g of acrylate adhesive and 0.41g of alkylphenol polyoxyethylene ether to the mixture obtained in S3, and continue to stir and mix at 65rpm for 30min to obtain a lithium battery coating slurry with a viscosity of 93.9mPa•s and particle sizes D50: 0.661μm and D90: 1.363μm.

[0078] The present invention also provides a method for preparing a low-temperature closed-cell low-moisture lithium battery separator, which specifically includes the following steps: applying a lithium battery coating slurry to a base film with a thickness of 9 μm on one side at a speed of 40 m / min to form a coating with a thickness of 2.3 μm, and drying it at 90°C for 1.5 min to obtain a low-temperature closed-cell low-moisture lithium battery separator.

[0079] Comparative Example 1

[0080] This comparative example provides a battery separator that differs from Example 3 only in that it does not contain magnesium oleate; the other components and their contents are the same as in Example 3.

[0081] A battery separator, comprising a PE base film and a coating slurry.

[0082] The coating slurry is prepared from the following components: alumina ceramic particles, ultrapure water, dispersant, binder and wetting agent.

[0083] The preparation method of the coating slurry specifically includes the following steps:

[0084] S1. Add 24g of alumina ceramic particles to 39g of ultrapure water, then add 1.5g of acrylate copolymer. Under the condition of keeping warm at 27℃, use a double planetary mixer to stir and disperse the mixture. The rotation speed of the double planetary mixer is 2500rpm, the revolution speed is 40rpm, and the time is 50min to obtain a dispersion. The particle size of the alumina ceramic particles is D50: 0.624μm, D99: 2.428μm.

[0085] S2. Add 2.8g of acrylate adhesive and 0.41g of alkylphenol polyoxyethylene ether to the dispersion obtained in S1, and continue to stir and mix at 70rpm for 30min to obtain the coating slurry.

[0086] This invention provides a method for preparing a battery separator, which specifically includes the following steps: coating a slurry on a PE base film with a thickness of 9 μm at a speed of 40 m / min on one side to form a coating with a thickness of 2.2 μm, and drying it at 100°C for 1.5 min to obtain the battery separator.

[0087] Experimental Example

[0088] 1. Diaphragm performance testing

[0089] The battery separators obtained in Examples 1-5 and Comparative Example 1 of this invention were subjected to performance tests, including appearance observation, thickness test, areal density test, breakdown voltage test, needle penetration strength test, and separator moisture content test.

[0090] Table 1 shows the test results of the separator performance of Examples 1-5 and Comparative Example 1 of the present invention. As shown in the table, Examples 1-5 and Comparative Example 1 have basically the same appearance and thickness. The areal density, breakdown voltage and needle penetration strength of Examples 1-5 are higher than those of Comparative Example 1. The water content of the separator of Examples 1-5 is significantly lower than that of Comparative Example 1. The reduction of the water content of the separator can greatly reduce the short circuit rate of the battery and increase the cycle life of the separator. The separator performance of Examples 1-5 is better than that of Comparative Example 1.

[0091] ; Table 1. Results of membrane performance test

[0092] 2. Air permeability test

[0093] According to GB / T36363-2018, the air permeability of the separators obtained in Examples 1-5 and Comparative Example 1 of this invention was tested using a battery separator air permeability tester at a pressure of 1.21 kPa. The area through which 100 mL of air passed was recorded as 6.45 cm². 2 The time required for the diaphragm to function is the air permeability.

[0094] Figure 1 The results of the air permeability test for Examples 1-5 and Comparative Example 1 are shown in the figure. As shown, the air permeability (sec / 100mL) of Examples 1-5 and Comparative Example 1 are 186, 191, 189, 187, 190 and 224, respectively. The air permeability of Examples 1-5 is significantly better than that of Comparative Example 1.

[0095] 3. Closed-cell temperature test

[0096] The resistance of the diaphragm was tested using the resistance mutation method. The resistance of the diaphragms obtained in Examples 1-5 and Comparative Example 1 was tested in the range of 100-170°C. The temperature at which the diaphragm resistance increased significantly was recorded as the diaphragm closure temperature.

[0097] Figure 2 The figures show the results of the pore-closure temperature tests for Examples 1-5 and Comparative Example 1 of the present invention. As shown in the figures, the pore-closure temperatures of Examples 1-5 and Comparative Example 1 are 143℃, 146℃, 144℃, 143℃, 145℃, and 163℃, respectively. Compared with Comparative Example 1, Examples 1-5, with other performances being basically the same or slightly improved, have pore-closure temperatures reduced by 20℃, 17℃, 19℃, 20℃, and 18℃, respectively. The pore-closure temperatures of Examples 1-5 are significantly lower than those of Comparative Example 1. This indicates that the use of magnesium oleate effectively reduces the pore-closure temperature of the separator, thereby improving the safety and reliability of the separator. It can cut off the ion transport channels at a lower temperature in the early stage of thermal runaway of the battery, thereby improving the safety of the battery and exhibiting superior performance.

[0098] 4. Ultimate water absorption test

[0099] Take the diaphragms obtained in Examples 1-5 and Comparative Example 1, test and record the initial water content, then place them on A4 paper and put them together in a constant temperature and humidity oven, keep the oven temperature at 40°C and humidity at 85%RH, and leave for 24 hours. Then test and record the water content again after leaving in a humid environment for 24 hours.

[0100] Figure 3The figures show the results of the extreme water absorption tests for Examples 1-5 and Comparative Example 1 of the present invention. As shown in the figures, the initial water contents of Examples 1-5 and Comparative Example 1 were 427 ppm, 441 ppm, 435 ppm, 422 ppm, 439 ppm and 857 ppm, respectively. After being placed in a humid environment for 24 hours, the water contents of Examples 1-5 and Comparative Example 1 were 449 ppm, 463 ppm, 457 ppm, 443 ppm, 461 ppm and 1343 ppm, respectively. The water absorption rate of Examples 1-5 to the environment was significantly lower than that of Comparative Example 1. This indicates that the use of magnesium oleate effectively reduced the water absorption rate of the diaphragm, thereby improving the safety and reliability of the diaphragm.

[0101] Magnesium oleate begins to melt when the temperature reaches 140℃. The melted liquid blocks the ion channels of the base membrane, thereby blocking ion exchange. Furthermore, the hydrophobicity of magnesium oleate reduces the absorption of moisture from the environment by the membrane, thus reducing the water content of the membrane.

[0102] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0103] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A low-temperature closed-cell low-moisture lithium battery separator, wherein the low-temperature closed-cell low-moisture lithium battery separator is composed of a base film and a lithium battery coating slurry, wherein the base film is a PE base film, characterized in that: The lithium battery coating slurry is prepared from the following components: magnesium oleate, organic solvent, ceramic particles, ultrapure water, dispersant, binder and wetting agent.

2. The low-temperature closed-cell low-moisture lithium battery separator according to claim 1, characterized in that: The organic solvent includes one of methanol, ethanol, isopropanol, and diethyl ether; the ceramic particles include one of alumina, boehmite, and zirconium oxide; the dispersant is an acrylate copolymer, the binder is an acrylate binder, and the wetting agent is an alkylphenol polyoxyethylene ether.

3. The low-temperature closed-cell low-moisture lithium battery separator according to claim 2, characterized in that: The ceramic particles are alumina with a particle size D50 of 0.587-0.624 μm and D99 of 2.341-2.462 μm.

4. A method for preparing a low-temperature closed-cell, low-moisture lithium battery separator according to claim 1, characterized in that: Specifically, the process includes the following steps: applying lithium battery coating slurry to a base film with a thickness of 9 μm on one side at a speed of 40 m / min to form a coating with a thickness of 2.1-2.3 μm, and drying it at 90-100℃ for 1.5-2 min to obtain a low-temperature closed-cell low-moisture lithium battery separator.

5. The method for preparing a low-temperature closed-cell, low-moisture lithium battery separator according to claim 4, characterized in that: The preparation method of the lithium battery coating slurry specifically includes the following steps: S1. Add 16-23g of magnesium oleate to the reactor, then add 67-76g of organic solvent, and keep warm and stir to obtain magnesium oleate solution; S2. Add 18-24g of ceramic particles to 34-39g of ultrapure water, then add 1.1-1.5g of dispersant. Under the condition of keeping warm at 27-28℃, use a double planetary mixer to stir and disperse to obtain a dispersion. S3. Take 5.1-7.1g of the magnesium oleate solution obtained in S1 and add it to the dispersion obtained in S2. Mix the mixture using a double planetary mixer to obtain a mixture. S4. Add 2.4-2.8g of adhesive and 0.3-0.41g of wetting agent to the mixture obtained in S3, and continue to stir and mix at a speed of 65-70rpm for 30min to obtain lithium battery coating slurry.

6. The method for preparing a low-temperature closed-cell, low-moisture lithium battery separator according to claim 5, characterized in that: In S1, the temperature for heat preservation and stirring is 80-85℃, the speed is 45-50 rpm, and the time is 35-45 min.

7. The method for preparing a low-temperature closed-cell, low-moisture lithium battery separator according to claim 6, characterized in that: In S2, the dual planetary mixer rotates at 2000-2500 rpm, revolves at 40 rpm, and operates for 45-50 minutes.

8. The method for preparing a low-temperature closed-cell, low-moisture lithium battery separator according to claim 7, characterized in that: In S3, the dual planetary mixer operates at 55-60 rpm for 10 minutes.

9. The method for preparing a low-temperature closed-cell, low-moisture lithium battery separator according to claim 8, characterized in that: In S4, the viscosity of the lithium battery coating slurry is 92.7-94.8 mPa·s, and the particle size is D50: 0.627-0.674 μm, D90: 1.343-1.441 μm.

Images