A composite ceramic diaphragm with temperature resistance and liquid retention, and a preparation method and application thereof

Abstract

The application relates to the field of ceramic diaphragms, in particular to a composite ceramic diaphragm with temperature resistance and liquid retention, a preparation method and application thereof, the diaphragm comprises a ceramic-coated diaphragm and a modified coating layer coated on at least one surface of the ceramic-coated diaphragm; the modified coating layer is obtained by coating a coating slurry on the surface of the ceramic-coated diaphragm, drying and then soaking in an impregnating solution; the boron-containing reinforcing agent is a boron acid-coated carbon nanotube; the impregnating material is an aqueous solution containing borate ions; the coating slurry is prepared by adding the boron-containing reinforcing agent into a hydroxyl-containing polymer, the boron acid-coated carbon nanotube provided in the application has synergistic effects with the hydroxyl-containing polymer and the impregnating solution, so that the finally-prepared ceramic diaphragm has a lower thermal shrinkage, that is, higher temperature resistance, and also has higher liquid absorption and liquid retention, and therefore has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ceramic separators, in particular to a composite ceramic separator with consideration of temperature resistance and liquid retention, and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries have become a hot spot in power supply technology research in recent years due to their high specific energy, long cycle life, no memory effect (compared to nickel-chromium batteries), safety, reliability, and ability to carry fast recharge and discharge. In widely used electronic devices such as mobile phones, notebook computers, and currently emerging electric vehicles and hybrid electric vehicles, lithium ion batteries play an irreplaceable role.

[0003] The main structure of lithium ion batteries includes positive / negative electrode materials, electrolyte, battery separator, and battery shell packaging materials. The battery separator is an important component of lithium ion batteries, which directly separates the positive and negative electrodes and prevents short circuiting. The performance of the battery separator directly determines the interface performance, cycle performance, and safety performance of the battery. Therefore, a separator with excellent performance plays a crucial role in improving the overall performance of the battery.

[0004] Ceramics can be dispersed in water and are environmentally friendly, and have been widely used in the coating of separators to produce high-temperature-resistant ceramic coating separators with good thermal stability. The wettability of electrolyte is an important indicator for evaluating the separator. Excellent electrolyte wettability is beneficial to improve the ionic conductivity of the battery. To further improve the ability of lithium battery separators to absorb electrolyte, a high molecular adhesive containing a polar hydrophilic group is usually introduced into the separator coating. For example, patent document CN108305972B discloses a ceramic coating separator and a preparation method and application thereof. The ceramic coating separator includes a base film and a ceramic coating, wherein the ceramic coating is coated by inorganic particles grafted with polyethylene glycol. Although the use of polyethylene glycol with hydroxyl groups for grafting inorganic particles achieves a fast liquid absorption rate and high liquid absorption rate of the ceramic coating separator, the ceramic coating separator exhibits a large thermal shrinkage under high temperature conditions, resulting in poor mechanical strength and temperature resistance of the ceramic coating separator under high temperature conditions.

[0005] To solve the above problems, a cross-linkable polymer binder can be introduced into the coating of the diaphragm to form a three-dimensional network structure on the surface of the diaphragm, thereby increasing the mechanical strength and temperature resistance of the ceramic coated diaphragm. Patent document CN113964450A discloses a battery diaphragm coating liquid, a preparation method thereof, a battery diaphragm and a battery. In the battery diaphragm coating liquid, there is an interaction force or hydrogen bond between the ceramic, the adhesive, the nanowire and the coupling agent, so that a structure of …ceramic-coupling agent-nanowire-ceramic-coupling agent-nanowire… is formed, thereby making the finally prepared battery diaphragm have good heat resistance. However, the ceramic diaphragm prepared by the method has a high cross-linking degree, so that the system is tightly packed, resulting in poor liquid retention of the finally prepared ceramic diaphragm. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a composite ceramic diaphragm with good temperature resistance and liquid retention, a preparation method thereof and application, so as to solve the problems of poor temperature resistance and liquid retention of the ceramic diaphragm in the prior art.

[0007] Based on the above purpose, the present application provides a composite ceramic diaphragm with good temperature resistance and liquid retention, which comprises a ceramic coated diaphragm and a modified coating layer coated on at least one surface thereof.

[0008] The modified coating layer is obtained by coating a coating slurry on the surface of the ceramic coated diaphragm, drying and then soaking in an impregnating solution.

[0009] The mass ratio of the coating slurry and the impregnating material is 100:10-20.

[0010] The coating slurry comprises the following raw materials in parts by mass: 0.1-0.3 parts of an alkali metal compound, 3-5 parts of a binder, 40-80 parts of a hydroxyl-containing polymer, 20-50 parts of a boron-containing reinforcing agent, 0.5-1.5 parts of an additive and 80-100 parts of deionized water.

[0011] The hydroxyl-containing polymer is any one of nano-bamboo charcoal powder, polyvinyl alcohol and polyethylene glycol.

[0012] The boron-containing reinforcing agent is a carbon nanotube coated with boric acid.

[0013] The impregnating material is an aqueous solution containing borate ions.

[0014] Preferably, the preparation method of the boron-containing reinforcing agent is as follows:

[0015] S11. Carbon nanotubes are added to concentrated sulfuric acid, stirred for 10-12 hours, sodium nitrate and potassium permanganate are added, heated in an oil bath at 38-42°C for 25-32 minutes, deionized water and 30% mass fraction hydrogen peroxide solution are added, stirred for 20-30 minutes, washed, freeze-dried to obtain modified carbon nanotubes;

[0016] S12. The modified carbon nanotubes are ultrasonically dispersed in deionized water for 1.5-2 hours, anhydrous ethanol solution of boric acid is added, the dispersed modified carbon nanotube aqueous solution is added dropwise to the anhydrous ethanol solution of boric acid, stirred in a water bath at 60-65°C until dry, then dried at 65-70°C for 4-5 hours to obtain a boron-containing reinforcing agent.

[0017] Preferably, the amount of carbon nanotubes, concentrated sulfuric acid, sodium nitrate, potassium permanganate, deionized water and 30% mass fraction hydrogen peroxide solution in step S1 is 8-12g: 20-25mL: 0.3-0.4g: 0.8-1.2g: 35-40mL: 8-12mL.

[0018] Preferably, the mass ratio of modified carbon nanotubes, deionized water and anhydrous ethanol solution of boric acid in step S2 is 3-7: 18-22: 50-60, and the mass fraction of the anhydrous ethanol solution of boric acid is 8%-12%.

[0019] Preferably, the basic metal compound is any one of nano-aluminum oxide, aluminum hydroxide and magnesium hydroxide.

[0020] Preferably, the binder is any one of styrene-butadiene rubber, polyvinyl alcohol and polyvinylidene fluoride.

[0021] Preferably, the auxiliary agent is any one of succinic acid, fluoroalkyl methoxy ether alcohol, sodium polyacrylate, acetylenic diol vinyl ether, fatty acid polyoxyethylene ether and polyether modified siloxane.

[0022] Preferably, the concentration of the aqueous solution containing borate ions is 3%-7%;

[0023] The aqueous solution containing borate ions is obtained by dissolving a boron-containing inorganic compound in water;

[0024] The boron-containing inorganic compound is any one of borax, potassium tetraborate, lithium tetraborate and ammonium borate.

[0025] Preferably, the coating method is any one of micro-gravure coating, dip coating, blade coating, spray coating and spot coating.

[0026] Further, the present application also provides a preparation method of a composite ceramic diaphragm with both temperature resistance and liquid retention, comprising the following steps:

[0027] S21. Mixing the binder, the hydroxyl-containing polymer and deionized water, stirring for 30-60 min to obtain mixture A;

[0028] S22. Adding the basic metal compound, the boron-containing reinforcing agent and the auxiliary agent to mixture A, stirring for 30-60 min to obtain mixture B;

[0029] S23. Passing mixture B through a magnetic filtration device, filtering with a 250-mesh filter screen after stirring for 5-20 min to obtain a coating slurry;

[0030] S24. Coating the coating slurry on one side or both sides of the polyolefin-based film, and drying to obtain a composite film;

[0031] S25. Immersing the composite film in the impregnating solution for 10-20 min, and drying to obtain a composite ceramic separator with both temperature resistance and liquid retention.

[0032] Further, the application also provides a composite ceramic separator with both temperature resistance and liquid retention, which can be used in lithium ion batteries.

[0033] The application has the following beneficial effects:

[0034] The boron-containing reinforcing agent provided by the application is a boron acid-coated carbon nanotube, which, when used in combination with the hydroxyl-containing polymer, can increase the liquid retention of the ceramic separator, and effectively improve the liquid absorption rate and temperature resistance of the ceramic separator.

[0035] The impregnating solution provided by the application is an aqueous solution containing borate ions, which can further enhance the cross-linking degree inside the system and the affinity of the system to the electrolyte after the composite film prepared from the boron-containing reinforcing agent is soaked, thereby further increasing the temperature resistance of the ceramic separator while further improving the liquid absorption and retention of the ceramic separator.

[0036] The ceramic separator prepared by the application has high temperature resistance, low thermal shrinkage rate at high temperature, and high liquid absorption and retention, and therefore has a wide application prospect. DETAILED DESCRIPTION

[0037] To make the purpose, technical scheme and advantages of the application clearer, the application is further described in detail below with reference to specific examples.

[0038] Example 1: A preparation method of a composite ceramic separator with both temperature resistance and liquid retention, comprising the following steps:

[0039] S1. 8 g carbon nanotubes were added to 20 g concentrated sulfuric acid, stirred for 10 h, 0.3 g sodium nitrate and 0.8 g potassium permanganate were added, heated in an oil bath at 38℃ for 25 min, then 35 g deionized water and 8 g 30% mass fraction hydrogen peroxide aqueous solution were added, stirred for 20 min, then washed, freeze-dried to obtain modified carbon nanotubes;

[0040] S2. 3 g modified carbon nanotubes were ultrasonically dispersed in 18 g deionized water for 1.5 h, the dispersed modified carbon nanotube aqueous solution was added dropwise to 50 g 8% mass fraction boric acid in anhydrous ethanol solution, stirred in a water bath at 60℃ until dry, then dried at 65℃ for 4 h to obtain a boron-containing reinforcing agent;

[0041] S3. 3 g butadiene styrene rubber, 40 g nano bamboo carbon powder and 80 g deionized water were mixed, stirred for 30 min to obtain a mixture A;

[0042] S4. 0.1 g nano alumina, 20 g boron-containing reinforcing agent and 0.5 g succinic acid were added to 123 g mixture A, stirred for 30 min to obtain a mixture B;

[0043] S5. The mixture B was filtered through a magnetic filter device, and after stirring for 5 min, it was filtered with a 250 mesh filter screen to obtain a coating slurry;

[0044] S6. The coating slurry was coated on both sides of a polyolefin-based film, and after drying, a composite film was obtained;

[0045] S7. 30 g borax was dissolved in 1000 g water to obtain an impregnating material;

[0046] S8. The composite film was immersed in 10 g of the impregnating material for 10 min, and after drying, a composite ceramic separator with both temperature resistance and liquid retention was obtained.

[0047] Example 2: A preparation method of a composite ceramic separator with both temperature resistance and liquid retention, comprising the following steps:

[0048] S1. 9 g carbon nanotubes were added to 22 g concentrated sulfuric acid, stirred for 11 h, 0.33 g sodium nitrate and 1 g potassium permanganate were added, heated in an oil bath at 40℃ for 28 min, then 36 g deionized water and 10 g 30% mass fraction hydrogen peroxide aqueous solution were added, stirred for 23 min, then washed, freeze-dried to obtain modified carbon nanotubes;

[0049] S2. 5 g modified carbon nanotubes were ultrasonically dispersed in 19 g deionized water for 1.7 h, the dispersed modified carbon nanotube aqueous solution was added dropwise to 53 g 9% mass fraction boric acid in anhydrous ethanol solution, stirred in a water bath at 62℃ until dry, then dried at 67℃ for 4.3 h to obtain a boron-containing reinforcing agent;

[0050] S3. Mix 3.7 g of polyvinyl alcohol, 60 g of polyvinyl alcohol and 87 g of deionized water, stir for 40 min to obtain mixture A;

[0051] S4. Add 0.2 g of aluminum hydroxide, 30 g of boron-containing reinforcing agent and 0.8 g of fluoroalkyl methoxy ether alcohol to 150 g of mixture A, stir for 40 min to obtain mixture B;

[0052] S5. Pass mixture B through a magnetic filtration device, filter with a 250 mesh screen after stirring for 10 min to obtain a coating slurry;

[0053] S6. Apply the coating slurry to both sides of the polyolefin-based film, and after drying, obtain a composite film;

[0054] S7. Dissolve 40 g of potassium tetraborate in 1000 g of water to obtain an impregnating material;

[0055] S8. Dip the composite film in 13 g of the impregnating material for 17 min, and after drying, obtain a composite ceramic separator with both temperature resistance and liquid retention.

[0056] Example 3: A method for preparing a composite ceramic separator with both temperature resistance and liquid retention, comprising the following steps:

[0057] S1. Add 10 g of carbon nanotubes to 24 g of concentrated sulfuric acid, stir for 11 h, add 0.36 g of sodium nitrate and 1.1 g of potassium permanganate, heat in an oil bath at 41 °C for 30 min, then add 38 g of deionized water and 11 g of 30% mass fraction hydrogen peroxide aqueous solution, stir for 26 min, then wash, freeze-dry to obtain modified carbon nanotubes;

[0058] S2. Ultrasonically disperse 6 g of modified carbon nanotubes in 20 g of deionized water for 1.9 h, add the dispersed modified carbon nanotube aqueous solution dropwise to 56 g of 11% mass fraction boric acid in anhydrous ethanol solution, stir in a water bath at 64 °C until dry, then dry at 69 °C for 4.6 h to obtain a boron-containing reinforcing agent;

[0059] S3. Mix 4.3 g of polyvinylidene fluoride, 70 g of polyethylene glycol and 94 g of deionized water, stir for 50 min to obtain mixture A;

[0060] S4. Add 0.2 g of magnesium hydroxide, 40 g of boron-containing reinforcing agent and 1.2 g of sodium polyacrylate to 170 g of mixture A, stir for 50 min to obtain mixture B;

[0061] S5. Pass mixture B through a magnetic filtration device, filter with a 250 mesh screen after stirring for 15 min to obtain a coating slurry;

[0062] S6. The coating slurry is coated on both sides of the polyolefin-based film, and a composite film is obtained after drying;

[0063] S7. 50 g of lithium tetraborate is dissolved in 1000 g of water to obtain an impregnating agent;

[0064] S8. The composite film is immersed in 16 g of the impregnating agent for 18 min, and a composite ceramic separator with both temperature resistance and liquid retention is obtained after drying.

[0065] Example 4: A preparation method of a composite ceramic separator with both temperature resistance and liquid retention, comprising the following steps:

[0066] S1. 12 g of carbon nanotubes is added to 25 g of concentrated sulfuric acid, stirred for 12 h, 0.4 g of sodium nitrate and 1.2 g of potassium permanganate are added, heated in a 42℃ oil bath for 32 min, then 40 g of deionized water and 12 g of 30% mass fraction hydrogen peroxide aqueous solution are added, stirred for 30 min, then washed, freeze-dried to obtain modified carbon nanotubes;

[0067] S2. 7 g of modified carbon nanotubes is ultrasonically dispersed in 22 g of deionized water for 2 h, the dispersed modified carbon nanotube aqueous solution is added dropwise to 60 g of 12% mass fraction boric acid in anhydrous ethanol solution, stirred in a 65℃ water bath until dry, then dried at 70℃ for 5 h to obtain a boron-containing reinforcing agent;

[0068] S3. 5 g of polyvinylidene fluoride, 80 g of polyethylene glycol and 100 g of deionized water are mixed to obtain a mixture A;

[0069] S4. 0.3 g of magnesium hydroxide, 50 g of the boron-containing reinforcing agent and 1.5 g of acetylenic glycol vinyl ether are added to 185 g of the mixture A, and stirred for 60 min to obtain a mixture B;

[0070] S5. The mixture B is filtered through a magnetic filter device, and filtered through a 250 mesh filter screen after stirring for 20 min to obtain a coating slurry;

[0071] S6. The coating slurry is coated on both sides of the polyolefin-based film, and a composite film is obtained after drying;

[0072] S7. 70 g of ammonium borate is dissolved in 1000 g of water to obtain an impregnating agent;

[0073] S8. The composite film is immersed in 20 g of the impregnating agent for 20 min, and a composite ceramic separator with both temperature resistance and liquid retention is obtained after drying.

[0074] Comparative Example 1:

[0075] The comparative example is compared with example 1, and no boron-containing reinforcing agent is added in the preparation process of the composite ceramic separator with consideration of temperature resistance and liquid retention. The remaining steps and parameters are the same, and the comparative example will not be repeated. Finally, the ceramic separator is obtained.

[0076] Comparative Example 2:

[0077] The comparative example is compared with example 1, and only the "boric acid coated carbon nanotube" is replaced with "carbon nanotube". The remaining steps and parameters are the same, and the comparative example will not be repeated. Finally, the ceramic separator is obtained.

[0078] Comparative Example 3:

[0079] The comparative example is compared with example 1, and only the "boric acid coated carbon nanotube" is replaced with "borate". The remaining steps and parameters are the same, and the comparative example will not be repeated. Finally, the ceramic separator is obtained.

[0080] Comparative Example 4:

[0081] The comparative example is compared with example 1, and no impregnating solution is added in the preparation process of the composite ceramic separator with consideration of temperature resistance and liquid retention. The remaining steps and parameters are the same, and the comparative example will not be repeated. Finally, the ceramic separator is obtained.

[0082] Comparative Example 5:

[0083] The comparative example is compared with example 1, and the impregnating solution and coating slurry are mixed uniformly before being coated on the surface of the ceramic coated separator. The remaining steps and parameters are the same, and the comparative example will not be repeated. Finally, the ceramic separator is obtained.

[0084] Performance test

[0085] According to the GB / T6672-2001 "Plastic Film and Sheet Thickness Determination Mechanical Measurement Method" standard, the thickness of each group of samples in examples 1-4 and comparative examples 1-5 is tested by THI-1801 thickness tester;

[0086] According to the GB / T135I9-2016 standard, the thermal shrinkage rate (%) of each group of samples in examples 1-4 and comparative examples 1-5 is measured by FST-3102 film thermal shrinkage performance tester after being placed at 150°C for 1h;

[0087] According to the ISO15105-1:2007 "Plastics-Film and Sheeting Part 1: Diferential pressure Methods" standard, the air permeability value s / 100ml of each group of samples in examples 1-4 and comparative examples 1-5 is measured by GTR-704R air permeability tester;

[0088] According to QB / T 2303.11-2008 "Battery Sizing Layer Paper Part 11: Determination of Liquid Absorption Rate", the liquid absorption rate (%) and the liquid retention amount (%) of each group of samples in Examples 1-4 and Comparative Examples 1-5 were measured by weighing method. Each group of samples to be tested was soaked in electrolyte for 120 min to obtain the liquid absorption rate. The calculation formula of the liquid absorption rate is as follows:

[0089] ε (%) = [(M1-M0)] / M0x100%

[0090] Wherein ε is the liquid absorption rate (%); M0 is the dry film mass (g); M1 is the mass of the wet film (g);

[0091] According to GB / T 30447-2013 standard, the contact angle of each group of samples in Examples 1-4 and Comparative Examples 1-5 to the electrolyte was measured by JC2000D1 type contact angle tester.

[0092] The adhesion of the ceramic separators prepared in Examples 1-4 and Comparative Examples 1-5 was tested by using a plastic sealing roller press and a universal tensile testing machine. The roller temperature was set to 113°C. Two ceramic separators were folded and the edges were aligned, and were sandwiched between two PET films. The temperature of the hot roller was tested by using a temperature gun. After the set temperature was reached, the roller press switch was turned on, and the films were placed parallel in the plastic sealing machine. After the films completely left the plastic sealing machine, the PET films were peeled off, and the adhesion between the ceramic separators was tested by using the universal tensile testing machine peeling method. The results are shown in Table 1 below:

[0093] Table 1

[0094]

[0095] Data analysis:

[0096] As can be seen from Table 1, the ceramic separators prepared in Examples 1-4 have lower thermal shrinkage, higher air permeability, higher liquid absorption rate, higher liquid retention amount, smaller contact angle and larger adhesion.

[0097] In Comparative Example 1, no boron-containing reinforcing agent was added; in Comparative Example 2, the carbon nanotubes were not coated with boric acid; in Comparative Example 3, the "boric acid coated carbon nanotubes" were replaced with "borate"; in Comparative Example 4, no impregnation liquid was added; and in Comparative Example 5, the impregnation liquid and the coating slurry were mixed uniformly before being coated on the surface of the ceramic coated separator. The final ceramic separators prepared in Comparative Examples 1-5 have poor comprehensive performance.

[0098] The boron-containing reinforcing agent provided by the application is a borate-coated carbon nanotube, which has a large cavity and can increase the liquid retention of the ceramic separator; meanwhile, the outer coating of borate and the compounding of the impregnating solution can increase the cross-linking degree inside the system, so that the temperature resistance of the ceramic separator is increased; in addition, the introduction of the impregnating solution increases the affinity of the ceramic separator to the electrolyte, so that the ceramic separator has high liquid absorption rate and liquid retention while having temperature resistance.

[0099] Those skilled in the art should understand that the above discussion of any of the embodiments is only exemplary and is not intended to imply that the scope of the application is limited to these examples; under the idea of the application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the application as described above, which are not provided in details for the sake of simplicity.

Claims

1. A composite ceramic separator that balances temperature resistance and liquid retention, characterized by, The diaphragm comprises a ceramic coated diaphragm and a modified coating layer coated on at least one surface thereof; The modified coating layer is obtained by coating a coating slurry on the surface of the ceramic coated diaphragm, drying and then soaking in an impregnating agent; The mass ratio of the coating slurry and the impregnating agent is 100:10-20; The coating slurry comprises the following raw materials in parts by mass: 0.1-0.3 parts of an alkaline metal compound, 3-5 parts of a binder, 40-80 parts of a hydroxyl-containing polymer, 20-50 parts of a boron-containing reinforcing agent, 0.5-1.5 parts of an auxiliary agent, and 80-100 parts of deionized water; The hydroxyl-containing polymer is any one of polyvinyl alcohol and polyethylene glycol; The boron-containing reinforcing agent is a borate-coated carbon nanotube; The impregnating agent is an aqueous solution containing borate ions; The preparation method of the boron-containing reinforcing agent is as follows: S11. Carbon nanotubes are added to concentrated sulfuric acid, stirred for 10-12 hours, sodium nitrate and potassium permanganate are added, heated in an oil bath at 38-42°C for 25-32 minutes, deionized water and a 30% mass fraction hydrogen peroxide aqueous solution are then added, stirred for 20-30 minutes, and then washed, freeze-dried to obtain modified carbon nanotubes; S12. The modified carbon nanotubes are ultrasonically dispersed in deionized water for 1.5-2 hours, the dispersed modified carbon nanotube aqueous solution is added dropwise to a borate anhydrous ethanol solution, stirred in a water bath at 60-65°C until dry, and then dried at 65-70°C for 4-5 hours to obtain the boron-containing reinforcing agent; The aqueous solution containing borate ions has a mass concentration of 3%-7%; The aqueous solution containing borate ions is obtained by dissolving a boron-containing inorganic compound in water; The boron-containing inorganic compound is any one of borax, potassium tetraborate, lithium tetraborate, and ammonium borate.

2. The composite ceramic separator according to claim 1, wherein In step S11, the mass ratio of the carbon nanotubes, concentrated sulfuric acid, sodium nitrate, potassium permanganate, deionized water, and a 30% mass fraction hydrogen peroxide aqueous solution is 8-12g:20-25mL:0.3-0.4g:0.8-1.2g:35-40mL:8-12mL.

3. The composite ceramic separator according to claim 1, wherein the composite ceramic separator has a temperature resistance of 1000°C or higher. In step S12, the mass ratio of the modified carbon nanotubes, deionized water, and a borate anhydrous ethanol solution is 3-7:18-22:50-60, and the mass fraction of the borate anhydrous ethanol solution is 8%-12%.

4. The composite ceramic separator according to claim 1, wherein, The alkaline metal compound is any one of nano-aluminum oxide, aluminum hydroxide, and magnesium hydroxide.

5. The composite ceramic separator according to claim 1, wherein the composite ceramic separator has a temperature resistance of 1000°C or higher. The binder is any one of styrene-butadiene rubber, polyvinyl alcohol, and polyvinylidene fluoride.

6. The composite ceramic separator of claim 1, wherein the ceramic layer is made of a material selected from the group consisting of alumina, zirconia, titania, and combinations thereof. The auxiliary agent is any one of succinic acid, a fluoroalkyl methoxy ether alcohol, sodium polyacrylate, an acetylenic diol vinyl ether, a fatty acid polyoxyethylene ether, and a polyether-modified siloxane.

7. A method for preparing the composite ceramic separator with temperature resistance and liquid retention according to any one of claims 1-6, characterized in that, The method comprises the following steps: S21. The binder, hydroxyl-containing polymer, and deionized water are mixed and stirred for 30-60 minutes to obtain a mixture A; S22. The alkaline metal compound, boron-containing reinforcing agent, and auxiliary agent are added to the mixture A and stirred for 30-60 minutes to obtain a mixture B; S23. The mixture B is filtered through a magnetic filter device, stirred for 5-20 minutes, and then filtered through a 250-mesh filter screen to obtain a coating slurry; S24. Coating the coating slurry on one side or both sides of the ceramic-coated polyolefin-based film, and drying to obtain a composite film; S25. Immersing the composite film in the impregnating material for 10-20 min, and drying to obtain a composite ceramic diaphragm with both temperature resistance and liquid retention.

8. The use of the composite ceramic separator according to any one of claims 1 to 6, which is resistant to temperature and retains liquid, characterized in that, For lithium ion batteries.

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