Composite ceramic heat-resistant high-infiltration lithium battery diaphragm and preparation method thereof

Abstract

The invention discloses a composite ceramic heat-resistant high-infiltration lithium battery diaphragm and a preparation method thereof.The composite ceramic heat-resistant high-infiltration lithium battery diaphragm comprises a base membrane and a coating on the base membrane, the coating is obtained by coating slurry, and raw materials for preparing the slurry comprise a dispersing agent, inorganic ceramic particles, a bio-based aramid fiber solution, a binder and a wetting agent; the dispersing agent comprises naphthalene sulfonic acid formaldehyde condensate sodium salt and sodium polyacrylate, the binder comprises waterborne polyurethane and butadiene styrene rubber, and the preparation method of the composite ceramic heat-resistant high-infiltration lithium battery diaphragm comprises the following steps: firstly, carrying out corona treatment on a base membrane, then coating the base membrane with slurry, drying to obtain a coating on the base membrane, and drying to obtain the composite ceramic heat-resistant high-infiltration lithium battery diaphragm. The composite ceramic heat-resistant high-infiltration lithium battery diaphragm is obtained. The diaphragm provided by the invention has excellent heat resistance, wettability and cohesiveness.

Description

Technical Field

[0001] This invention belongs to the field of battery separator technology, specifically relating to a composite ceramic heat-resistant high-wetting lithium battery separator and its preparation method. Background Technology

[0002] As lithium batteries develop towards higher rate and higher energy density, higher requirements are placed on lithium-ion battery separators. Traditional polyethylene (PE) lithium-ion battery separators suffer from insufficient heat resistance (heat shrinkage rate often exceeds 20% at 150℃ / 1h), making them prone to melting and deformation under high-temperature conditions, leading to battery short circuits. Existing solutions for improving the heat resistance of lithium-ion battery separators either suffer from slow electrolyte wetting and high interfacial impedance due to the strong hydrophobicity of the coating, or delamination and cracking problems due to uneven slurry dispersion and weak adhesion between the coating and the base film (often below 32N / m). It is difficult to balance heat resistance, wettability, and structural stability. Therefore, developing a lithium-ion battery separator that combines high heat resistance, rapid electrolyte wetting ability, strong interfacial adhesion, and environmental friendliness has become the key to solving the current technical pain points. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a composite ceramic heat-resistant, highly wettable lithium battery separator.

[0004] Another object of the present invention is to provide a method for preparing the above-mentioned composite ceramic heat-resistant high wettability lithium battery separator.

[0005] The objective of this invention is achieved through the following technical solution.

[0006] A composite ceramic heat-resistant, highly wettable lithium-ion battery separator includes: a base film and a coating on the base film. The coating is obtained by coating with a slurry. The raw materials for preparing the slurry include: a dispersant, inorganic ceramic particles, a bio-based aramid solution, a binder, and a wetting agent. The dispersant includes: sodium salt of naphthalenesulfonic acid formaldehyde condensate and sodium polyacrylate (PAAS). The binder includes: waterborne polyurethane (WPU) and styrene-butadiene rubber (SBR). The bio-based aramid in the bio-based aramid solution has the following structural formula: n is 46~766.

[0007] In the above technical solution, the content (solid content) of bio-based aramid in the bio-based aramid solution is 8~10wt%.

[0008] In the above technical solution, the viscosity of the slurry is 30~100 mPa·s.

[0009] The preparation method of the above-mentioned composite ceramic heat-resistant high wettability lithium battery separator includes: first, subjecting the base film to corona treatment (to introduce hydroxyl and carboxyl groups on the surface of the base film), then coating the base film with slurry, drying, and obtaining a coating on the base film to obtain the composite ceramic heat-resistant high wettability lithium battery separator.

[0010] In the above technical solution, the thickness of the coating on one side (each side) is 1.0~2μm.

[0011] In the above technical solution, the voltage of the corona treatment is 0.5~1.0KV.

[0012] In the above technical solution, the base film is a polyolefin film, such as PE film or PP film.

[0013] The method for preparing the above-mentioned slurry includes: mixing a first water, a dispersant, inorganic ceramic particles, a bio-based aramid solution, a binder, and a wetting agent until homogeneous to obtain a slurry, wherein the dispersant is a mixture of sodium naphthalene sulfonic acid formaldehyde condensate solution and sodium polyacrylate (PAAS) solution, and the binder is a mixture of waterborne polyurethane (WPU) emulsion and styrene-butadiene rubber (SBR) emulsion. The ratio of the first water, dispersant, inorganic ceramic particles, bio-based aramid solution, binder, and wetting agent by mass parts is (50~70):(0.4~2):(20~35):(3~10):(2~8):(0.1~0.8).

[0014] In the above technical solution, the ratio of sodium naphthalenesulfonic acid formaldehyde condensate solution to sodium polyacrylate (PAAS) solution by mass parts is (0.2~1):(0.2~1).

[0015] In the above technical solution, the ratio of waterborne polyurethane (WPU) emulsion to styrene-butadiene rubber (SBR) emulsion by mass parts is (3~5):(2~4).

[0016] In the above technical solution, the inorganic ceramic particles are at least one of titanium dioxide, silicon dioxide, barium sulfate, boehmite, α-alumina, porous alumina, aluminum hydroxide, and magnesium oxide.

[0017] In the above technical solution, the particle size of the inorganic ceramic particles is D10=0.1~0.15μm, D50=0.2~0.4μm, and D90=0.8~1.2μm.

[0018] In the above technical solution, the wetting agent includes: polyoxyethylene alkylphenol ether, such as nonylphenol polyoxyethylene ether.

[0019] The method for preparing the bio-based aramid solution includes the following steps:

[0020] Step 1: Under a nitrogen or inert gas atmosphere at 0~5℃ and with stirring (200~300 r / min), the first system is added dropwise to the second system. After the addition is complete, the temperature is raised to 25~30℃ and the polycondensation reaction is carried out at 25~30℃ for 3~4 hours to obtain the first composite system. The first system includes furanyl chloride (FDC) and a first solvent. The second system includes 5,5'-methylenedifurfural (MBF) and a second solvent. The ratio of furanyl chloride (FDC) to 5,5'-methylenedifurfural (MBF) is 1:1 by molar ratio.

[0021] Step 2: Add a third solvent to the first composite system to dilute it, thereby obtaining a second composite system with a solid content of 5% to 18%.

[0022] Step 3: Add triethylamine to the second composite system (to neutralize the hydrogen chloride produced by the polycondensation reaction and adjust the pH to 7.0~7.5) to obtain the bio-based aramid solution precursor. The ratio of triethylamine to furanyl dicarboxylate (FDC) is (2.1~2.2):1 by molar amount.

[0023] Step 4: Add sodium polyacrylate (PAAS) solution to the bio-based aramid solution precursor and mix until homogeneous to obtain a bio-based aramid solution. The amount of sodium polyacrylate (PAAS) solution added in step 4 is 0.1~0.5 wt% of the bio-based aramid solution precursor.

[0024] In the method for preparing a bio-based aramid solution, the method for obtaining the first system includes: mixing furanyl chloride (FDC) and a first solvent at room temperature until homogeneous to obtain the first system, wherein the concentration of furanyl chloride (FDC) in the first system is 0.2~0.3 mol / L; the method for obtaining the second system includes: mixing 5,5'-methylenedifurfural (MBF) and a second solvent at room temperature until homogeneous to obtain the second system, wherein the concentration of 5,5'-methylenedifurfural (MBF) in the second system is 0.2~0.3 mol / L.

[0025] In the method for preparing bio-based aramid solution, the first solvent is N,N-dimethylacetamide (DMAc), and the second solvent is N,N-dimethylacetamide (DMAc).

[0026] In the method for preparing bio-based aramid solution, the first system is added dropwise to the second system at a dropping rate of 1~2 mL / min.

[0027] In the method for preparing bio-based aramid solution, the third solvent is a mixture of second water and N,N-dimethylacetamide (DMAc), wherein the ratio of second water to N,N-dimethylacetamide (DMAc) in the third solvent is 1:1 by volume.

[0028] In the above technical solution, the water content of N,N-dimethylacetamide (DMAc) is ≤50ppm.

[0029] The method for preparing the above-mentioned slurry specifically includes the following steps:

[0030] S1, mix the first water and the dispersant until homogeneous to obtain the first solution;

[0031] S2, mix the first solution and inorganic ceramic particles until homogeneous to obtain the second solution;

[0032] S3, mix the second solution and the bio-based aramid solution until homogeneous to obtain the third solution;

[0033] S4, mix the third solution and the adhesive until homogeneous to obtain the fourth solution;

[0034] S5, the fourth solution and wetting agent are mixed until homogeneous to obtain a slurry.

[0035] The application of bio-based aramid, sodium salt of naphthalenesulfonic acid formaldehyde condensate, sodium polyacrylate, waterborne polyurethane, and styrene-butadiene rubber to synergistically improve the heat resistance, peel strength, and wettability of diaphragms. The structural formula of the bio-based aramid in the bio-based aramid solution is as follows: n is 46~766.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] 1. This invention improves the heat resistance of the separator through the synergistic effect of inorganic ceramic particles and bio-based aramid. The rigid furan ring structure and strong interaction between the amide bonds in the molecular chain of bio-based aramid maintain the stability of the molecular chain morphology at high temperatures of 180-200℃. Meanwhile, the high thermal conductivity and high-temperature resistance of the inorganic ceramic particles can quickly disperse heat, mitigating the thermal aging rate of the bio-based aramid. The nanoscale rough surface of the inorganic ceramic particles forms an "anchoring effect" with the molecular chain of the bio-based aramid, which not only improves the overall density of the coating (porosity controlled at 40-55%), preventing electrolyte leakage, but also provides a path for electrolyte transport through the gaps between the inorganic ceramic particles, achieving the technical effect of heat resistance without clogging pores. The synergy between inorganic ceramic particles and bio-based aramid results in a thermal shrinkage rate of <5% for the composite ceramic heat-resistant high-wetting lithium battery separator, meeting the high-temperature safety requirements of high-rate lithium batteries.

[0038] 2. This invention uses a sodium naphthalene sulfonate formaldehyde condensate solution and a sodium polyacrylate (PAAS) solution as dispersants. The naphthalene ring hydrophobic group in the sodium naphthalene sulfonate formaldehyde condensate molecule reduces the interparticle forces in the ceramic particles, achieving dispersion and preventing slurry agglomeration and viscosity runaway. Simultaneously, the sulfonate hydrophilic group in the sodium naphthalene sulfonate formaldehyde condensate solution enhances the compatibility of the inorganic ceramic particles, controlling the slurry viscosity to 30-100 mPa·s. The linear molecular chain of sodium polyacrylate (PAAS) forms a weak interaction with the carboxyl groups of bio-based aramid and the hydroxyl groups of the inorganic ceramic particles, homogenizing the slurry particle size through steric hindrance. More importantly, the linear molecular chain of sodium polyacrylate (PAAS) acts as a "bridge," laying the foundation for the bonding of bio-based aramid with subsequent binders.

[0039] 3. This invention uses waterborne polyurethane (WPU) emulsion and styrene-butadiene rubber (SBR) emulsion as binders. The urethane bonds (-NHCOO-) and hydroxyl groups (-OH) in the WPU molecular chain can form hydrogen bonds with the hydroxyl and carboxyl groups on the base film surface, as well as with the amide bonds of the bio-based aramid. The simultaneous presence of these two types of hydrogen bonds constitutes double hydrogen bonds, resulting in a maximum peel strength of 156 N / m for the composite ceramic heat-resistant high-wetting lithium battery separator. At the same time, the elastic properties of the WPU can alleviate the rigidity of the inorganic ceramic particles and the bio-based aramid, preventing the coating from becoming brittle. The butadiene soft segments in the butadiene-styrene copolymer can form an elastic network inside the coating. When the separator is bent, the deformation of the butadiene soft segments can still absorb stress, preventing cracks in the coating.

[0040] 4. The contact angle of the electrolyte in the composite ceramic heat-resistant high-wetting lithium battery separator prepared by this invention is ≤4.2°.

[0041] 5. This invention constructs three-dimensional microchannels within the coating by controlling the particle size distribution of inorganic ceramic particles and the amount of bio-based aramid solution added. This ensures rapid electrolyte penetration and continuously provides electrolyte to the electrodes through the "capillary action" of the three-dimensional microchannels, thereby improving the cycle stability of the battery. Attached Figure Description

[0042] Figure 1 SEM image of the composite ceramic heat-resistant high-wetting lithium battery separator prepared in Example 1. Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0044] The sodium naphthalene sulfonic acid formaldehyde condensate condensate (purchased from BASF, model: Tamol NN8906) was diluted with deionized water to obtain a sodium naphthalene sulfonic acid formaldehyde condensate condensate solution with a solid content of 40 wt%.

[0045] Sodium polyacrylate solution: solid content 45wt%, BASF, PA 25X.

[0046] Waterborne polyurethane (WPU) emulsion: Hanwha Chemical, South Korea, WPU-4100.

[0047] Styrene-butadiene rubber (SBR) emulsion: Zeon Corporation of Japan, model MB-451B, solid content approximately 40wt% (butadiene-styrene copolymer content approximately 40wt%).

[0048] The method for obtaining the wetting agent includes: diluting NP-10 (whose core component is nonylphenol polyoxyethylene ether) purchased from Dow Chemical Company of the United States with deionized water to obtain a nonylphenol polyoxyethylene ether dilution with a solid content of 65 wt%, which is used as a wetting agent.

[0049] In this invention, the water content of N,N-dimethylacetamide (DMAc) is ≤50ppm.

[0050] In this invention, both the first water and the second water are ultrapure water.

[0051] In this invention, the base film is a PE film with a thickness of 5 μm.

[0052] In this invention, the slurry is coated using a Xinjiatuo double-sided coating machine (XJT-200).

[0053] In this invention, the electrolyte is a mixture of electrolyte and solvent. The electrolyte is LiPF6, and the solvent is a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate). The volume ratio of ethylene carbonate to dimethyl carbonate is 1:1, and the concentration of the electrolyte in the electrolyte is 1 mol / L.

[0054] Peel strength: Prepare a standard-sized sample (10-25mm wide, 150mm long) of composite ceramic heat-resistant high-wetting lithium battery separator. Attach 3M transparent tape to the coating surface of the sample, leaving a sufficient peel end (at least 20mm). Press the sample evenly three times with a standard roller. Fix both ends of the sample in the upper and lower clamps respectively. Peel in the direction of 180°. Tear off one end of the 3M transparent tape using a tensile tester to obtain the peel strength.

[0055] Heat shrinkage rate: The composite ceramic heat-resistant high-wetting lithium battery separator was cut into 4cm × 6cm pieces. Its length and width were measured after heat treatment in an oven at T℃ for 1 hour. The longitudinal (MD) and transverse (TD) heat shrinkage rates were obtained, respectively. T℃ = 180℃ or 200℃. Longitudinal (MD) heat shrinkage rate = (Length of the composite ceramic heat-resistant high-wetting lithium battery separator before heat treatment - Length of the composite ceramic heat-resistant high-wetting lithium battery separator after heat treatment) / Length of the composite ceramic heat-resistant high-wetting lithium battery separator before heat treatment * 100%; Transverse (TD) heat shrinkage rate = (Width of the composite ceramic heat-resistant high-wetting lithium battery separator before heat treatment - Width of the composite ceramic heat-resistant high-wetting lithium battery separator after heat treatment) / Width of the composite ceramic heat-resistant high-wetting lithium battery separator before heat treatment * 100%.

[0056] Test method for membrane breakage temperature: Cut the composite ceramic heat-resistant high-wetting lithium battery separator into a sample with a length of 8 mm and a width of 2 mm. Place the sample in a dynamic thermomechanical analyzer (TMA instrument), clamp the two sides of the sample with clamps, apply a tension of 0.03 N, start heating from room temperature until the composite ceramic heat-resistant high-wetting lithium battery separator breaks, and record the temperature at which it breaks as the membrane breakage temperature.

[0057] In the following examples, furanyl chloride (FDC) is 2,5-furanyl chloride.

[0058] Example 1

[0059] A method for preparing a composite ceramic heat-resistant, highly wettable lithium-ion battery separator includes: firstly, subjecting both sides of a base film to corona treatment at 1.0 kV (during corona treatment, the base film passes through the electrode at a speed of 1 m / s); secondly, coating a slurry onto both sides of the base film at a coating speed of 55 m / min; and thirdly, drying at 65°C for 30 s to obtain a coating with a single-sided thickness of 1.0 μm on the base film, thus obtaining the composite ceramic heat-resistant, highly wettable lithium-ion battery separator; the method for preparing the slurry includes the following steps:

[0060] S1, mix the first water and the dispersant in a double planetary mixer, and stir for 25 minutes at a rotation speed of 2200 r / min and a revolution speed of 45 r / min until uniform to obtain the first solution. The dispersant is a mixture of sodium naphthalene sulfonic acid formaldehyde condensate solution and sodium polyacrylate (PAAS) solution. The ratio of sodium naphthalene sulfonic acid formaldehyde condensate solution to sodium polyacrylate (PAAS) solution by mass is 0.75:0.75.

[0061] S2, the first solution and inorganic ceramic particles are mixed and stirred at a rotation speed of 1300 r / min and a revolution speed of 45 r / min for 60 min, and then subjected to a Cenomic mill. TMGrind in a zirconia ball with a diameter of 0.4~0.6mm for 20 minutes until homogeneous (grinding is done using zirconia balls with a diameter of 0.4~0.6mm as grinding beads) to obtain a second solution with D50=0.3μm, wherein the inorganic ceramic particles are α-alumina and the particle sizes of the inorganic ceramic particles are D10=0.12μm, D50=0.3μm, and D90=1.0μm;

[0062] S3, mix the second solution and the bio-based aramid solution, and stir at a rotation speed of 500 r / min and a revolution speed of 40 r / min for 30 min until homogeneous to obtain the third solution;

[0063] S4. The third solution and the binder are mixed and stirred at a rotation speed of 350 r / min and a revolution speed of 40 r / min for 25 min until homogeneous to obtain the fourth solution. The binder is a mixture of waterborne polyurethane (WPU) emulsion and styrene-butadiene rubber (SBR) emulsion, and the ratio of waterborne polyurethane (WPU) emulsion to styrene-butadiene rubber (SBR) emulsion by mass is 3.5:2.

[0064] S5, mix the fourth solution and wetting agent, and stir at a rotation speed of 350 r / min and a revolution speed of 38 r / min for 55 min until uniform to obtain a slurry;

[0065] The ratio of water, dispersant, inorganic ceramic particles, bio-based aramid solution, binder and wetting agent by mass parts is 60.4:1.5:30:8:4:0.1.

[0066] The method for preparing the bio-based aramid solution in Example 1 includes the following steps:

[0067] Step 1: Under a nitrogen atmosphere and stirring conditions (250 r / min), the first system is added dropwise to the second system at a dropping rate of 1.5 mL / min. After the addition is complete, the temperature is raised to 28°C, and the polycondensation reaction is carried out at 28°C for 3.5 h to obtain the first composite system. The method for obtaining the first system includes: mixing furanyl chloride (FDC) and the first solvent at room temperature (25°C) and stirring at 400 r / min for 30 min until homogeneous to obtain the first system. The concentration of furanyl chloride (FDC) in the first system is 0.2 mol / L. The method for obtaining the second system is as follows: The method includes: mixing 5,5'-methylenedifurfural (MBF) and a second solvent at room temperature (25°C), stirring at a revolution speed of 40 r / min and a rotation speed of 2000 r / min for 30 min until homogeneous, to obtain a second system. The concentration of 5,5'-methylenedifurfural (MBF) in the second system is 0.2 mol / L, and the ratio of furanyl dicarboxylate chloride (FDC) to 5,5'-methylenedifurfural (MBF) is 1:1 by molar ratio. The first solvent is N,N-dimethylacetamide (DMAc), and the second solvent is N,N-dimethylacetamide (DMAc).

[0068] Step 2: At 25°C, a third solvent is added to the first composite system to dilute it, resulting in a second composite system. The solid content of the second composite system is 18%. The third solvent is a mixture of second water and N,N-dimethylacetamide (DMAc). In the third solvent, the ratio of second water to N,N-dimethylacetamide (DMAc) is 1:1 by volume.

[0069] Step 3: At 25°C, triethylamine is added dropwise to the second composite system to neutralize the hydrogen chloride produced by the polycondensation reaction and to adjust the pH to 7.5, thus obtaining the bio-based aramid solution precursor. The ratio of triethylamine to furanyl dicarboxylate (FDC) is 2.15:1 by molar amount.

[0070] Step 4: Add sodium polyacrylate (PAAS) solution to the bio-based aramid solution precursor (to improve the compatibility between bio-based aramid and inorganic ceramic particles), and stir at 25°C and 40 r / min for 30 min until homogeneous to obtain the bio-based aramid solution. The amount of sodium polyacrylate (PAAS) solution added in step 4 is 0.5 wt% of the bio-based aramid solution precursor.

[0071] The bio-based aramid solution contains 10 wt% bio-based aramid (solid content). The structural formula of the bio-based aramid in the solution is: In Example 1, n is 613.

[0072] Figure 1SEM image of the composite ceramic heat-resistant high-wetting lithium battery separator prepared in Example 1.

[0073] Example 2

[0074] A method for preparing a composite ceramic heat-resistant and highly wettable lithium battery separator is basically the same as that in Example 1, except that the inorganic ceramic particles are silicon dioxide.

[0075] Example 3

[0076] A method for preparing a composite ceramic heat-resistant and highly wettable lithium battery separator is basically the same as that in Example 1, except that the ratio of first water, dispersant, inorganic ceramic particles, bio-based aramid solution, binder and wetting agent by mass parts is 52:1:25:5:5:0.4.

[0077] Comparative Example 1

[0078] A method for preparing a composite ceramic heat-resistant and highly wettable lithium battery separator is basically the same as that in Example 1, except that: no bio-based aramid solution is added.

[0079] Comparative Example 2

[0080] A method for preparing a composite ceramic heat-resistant, highly wettable lithium battery separator is basically the same as that in Example 1, except that the dispersant is sodium polyacrylate (PAAS) solution.

[0081] Comparative Example 3

[0082] A method for preparing a composite ceramic heat-resistant, highly wettable lithium battery separator is basically the same as that in Example 1, except that the dispersant is a sodium salt solution of naphthalenesulfonic acid formaldehyde condensate.

[0083] Comparative Example 4

[0084] A method for preparing a composite ceramic heat-resistant high-wetting lithium battery separator is basically the same as that in Example 1, except that the binder is an aqueous polyurethane (WPU) emulsion.

[0085] Comparative Example 5

[0086] A method for preparing a composite ceramic heat-resistant high-wetting lithium battery separator is basically the same as that in Example 1, except that the binder is styrene-butadiene rubber (SBR) emulsion.

[0087] Comparative Example 6

[0088] The preparation method of a composite ceramic heat-resistant high wettability lithium battery separator is basically the same as that in Example 1, except that the base film is not subjected to corona treatment.

[0089] The viscosities of the slurries prepared in Examples 1-3 and Comparative Examples 1-6 were 45.5 mPa·s, 46.5 mPa·s, 45.8 mPa·s, 55.5 mPa·s, 30.5 mPa·s, 81.2 mPa·s, 73.2 mPa·s, 64.5 mPa·s, and 74.5 mPa·s, respectively.

[0090] The test data of the composite ceramic heat-resistant and highly wettable lithium battery separators prepared in Examples 1-3 and Comparative Examples 1-6 are shown in Table 1.

[0091] Table 1

[0092]

[0093] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A composite ceramic heat-resistant, highly wettable lithium battery separator, characterized in that, include: A base film and a coating on the base film, wherein the coating is obtained by coating with a slurry, the raw materials for preparing the slurry include: a dispersant, inorganic ceramic particles, a bio-based aramid solution, a binder, and a wetting agent, wherein the dispersant includes: sodium salt of naphthalenesulfonic acid formaldehyde condensate and sodium polyacrylate, the binder includes: waterborne polyurethane and styrene-butadiene rubber, and the structural formula of the bio-based aramid in the bio-based aramid solution is: n is 46~766.

2. The composite ceramic heat-resistant high-wetting lithium battery separator according to claim 1, characterized in that, The bio-based aramid solution contains 8-10 wt% bio-based aramid.

3. The composite ceramic heat-resistant high-wetting lithium battery separator according to claim 2, characterized in that, The method for preparing the bio-based aramid solution includes the following steps: Step 1: Under a nitrogen or inert gas atmosphere at 0-5℃ and with stirring, the first system is added dropwise to the second system. After the addition is complete, the temperature is raised to 25-30℃, and the polycondensation reaction is carried out at 25-30℃ for 3-4 hours to obtain the first composite system. The first system includes furanyl chloride and a first solvent. The second system includes 5,5'-methylenedifurfuralamine and a second solvent. The ratio of furanyl chloride to 5,5'-methylenedifurfuralamine is 1:1 by molar ratio. Step 2: Add a third solvent to the first composite system to dilute it, thereby obtaining a second composite system with a solid content of 5% to 18%. Step 3: Add triethylamine to the second composite system to obtain a bio-based aramid solution precursor. The ratio of triethylamine to furanyl chloride is (2.1~2.2):1 by molar amount. Step 4: Add sodium polyacrylate solution to the bio-based aramid solution precursor and mix until homogeneous to obtain a bio-based aramid solution. The amount of sodium polyacrylate solution added in step 4 is 0.1~0.5 wt% of the bio-based aramid solution precursor.

4. The preparation method of the composite ceramic heat-resistant high-wetting lithium battery separator as described in claim 1, characterized in that, include: First, the base film is subjected to corona treatment, then the slurry is coated on the base film and dried to obtain a coating on the base film, thus obtaining a composite ceramic heat-resistant high wettability lithium battery separator.

5. A method for preparing a slurry, characterized in that, include: The first water, dispersant, inorganic ceramic particles, bio-based aramid solution, binder and wetting agent are mixed until uniform to obtain a slurry. The dispersant is a mixture of sodium naphthalene sulfonic acid formaldehyde condensate solution and sodium polyacrylate solution, and the binder is a mixture of waterborne polyurethane emulsion and styrene-butadiene rubber emulsion. The ratio of the first water, dispersant, inorganic ceramic particles, bio-based aramid solution, binder and wetting agent by mass is (50~70):(0.4~2):(20~35):(3~10):(2~8):(0.1~0.8).

6. The method according to claim 4, characterized in that, The ratio of sodium naphthalenesulfonic acid formaldehyde condensate solution to sodium polyacrylate solution by mass parts is (0.2~1):(0.2~1).

7. The method according to claim 4, characterized in that, The ratio of waterborne polyurethane emulsion to styrene-butadiene rubber emulsion by mass parts is (3~5):(2~4).

8. The method according to claim 4, characterized in that, The inorganic ceramic particles are at least one of titanium dioxide, silicon dioxide, barium sulfate, boehmite, α-alumina, porous alumina, aluminum hydroxide, and magnesium oxide.

9. The method according to claim 4, characterized in that, Wetting agents include: Polyoxyethylene alkylphenol ether.

10. Application of bio-based aramid, sodium salt of naphthalenesulfonic acid formaldehyde condensate, sodium polyacrylate, waterborne polyurethane, and styrene-butadiene rubber to synergistically improve the heat resistance, peel strength, and wettability of diaphragms. The structural formula of the bio-based aramid in the bio-based aramid solution is: n is 46~766.

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