High-temperature-resistant ceramic coating slurry and application thereof

Abstract

The application discloses a high-temperature-resistant ceramic coating slurry and application thereof, and relates to the technical field of secondary batteries, and comprises ceramic particles, a PAA binder, a composite emulsion, a wetting agent and water as a solvent; the adding mass ratio of the ceramic particles, the PAA binder, the composite emulsion and the wetting agent is 1:0.5-2%:5-10%:0.05-0.2%; and the adding mass percentage of the ceramic particles is 30-50%. The application has the effect of significantly improving the heat resistance of a ceramic coating prepared thereby, thereby improving the use safety of a battery. Based on the corresponding components, the ceramic coating obtained has a heat-resistant PAA skeleton and a composite mixedly coated ceramic particle, and the heat resistance is significantly improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of secondary batteries, in particular to a high-temperature-resistant ceramic coating slurry and application thereof. BACKGROUND

[0002] In the field of non-aqueous secondary batteries, especially in the field of lithium ion batteries and sodium ion batteries, PE ceramic coated separators are widely used, and the heat resistance of PE ceramic coated separators is very important for the safety of the batteries.

[0003] In the prior art, the temperature resistance of the PE ceramic coated separators used in non-aqueous secondary batteries generally only meets the level of 130 DEG C / 30 min heat shrinkage < 3%, when a micro-short circuit occurs in the battery or a local temperature rise occurs outside, after the internal temperature of the battery using a conventional PE ceramic coated separator breaks through 130 DEG C, the separator in the battery appears a large size heat shrinkage, when the PE ceramic separator shrinks to a certain size, a large-scale internal short circuit occurs between the positive and negative electrodes in the battery, thereby causing the heat generation in the battery to increase sharply, and further leading to thermal runaway of the battery, and finally causing explosion or deflagration of the battery, and triggering a safety accident, which needs to be improved. SUMMARY

[0004] Therefore, a first object of the application is to provide a high-temperature-resistant ceramic coating slurry to achieve the purposes of improving the heat resistance of PE ceramic coated separators and improving the use safety of aqueous secondary batteries. The specific scheme is as follows:

[0005] A high-temperature-resistant ceramic coating slurry comprises:

[0006] ceramic particles,

[0007] a PAA binder,

[0008] a composite emulsion,

[0009] a wetting agent,

[0010] and water as a solvent.

[0011] The adding mass ratio of the ceramic particles, the PAA binder, the composite emulsion and the wetting agent is 1:0.5-2%:5-10%:0.05-0.2%;

[0012] The adding mass percentage of the ceramic particles is 30-50%.

[0013] Preferably, the ceramic particles are at least one of alpha alumina, boehmite, magnesium hydroxide and zirconium oxide as a metal oxide, which is obtained by grinding, and the particle size distribution D50 is 0.3-1.8 microns.

[0014] Preferably, the grinding of the ceramic particles is prepared by high-energy ball milling, in which the metal oxide is put into a ball mill, anhydrous ethanol is used as the dispersion medium, the ball-to-material ratio is controlled to be (8-12):1, the rotation speed is 250-350 r / min, and the grinding time is 8-12 hours to obtain the ground ceramic particles.

[0015] Preferably, the ground ceramic particles are further modified, and the modification method comprises the following steps: ① adding the ground ceramic particles into toluene solvent and ultrasonic dispersion for 15-20 min to obtain a ceramic dispersion liquid; ② adding 1-3% silane coupling agent based on the mass of the ground ceramic particles into the ceramic dispersion liquid, controlling the reaction temperature to be 60-80 ℃, and modifying for 2-3 h, then washing with ethanol, and drying at a temperature of 75-85 ℃ for 4-6 h to obtain modified ceramic particles; ③ mixing tetrabutyl titanate, anhydrous ethanol and deionized water in a volume ratio of 1:4.5-5.5:1.8-2.2, stirring uniformly, adding nitric acid to adjust the pH to 2-3 to prepare TiO2 sol, and then adding the modified ceramic particles into the TiO2 sol and ultrasonic dispersion to obtain an adsorption sol; ④ placing the adsorption sol at 55-65 ℃ to dry to form a gel layer, and calcining the gel layer at 450-550 ℃ for 1.8-2.2 hours to obtain ceramic particles coated with a nano-TiO2 coating.

[0016] Preferably, the PAA binder is obtained by mixing PAA solution and melamine formaldehyde resin in a mass ratio of (9-11):1, adding a catalyst, and controlling the temperature to be 60-80 ℃ for stirring reaction for 2-3 h, and the PAA solution has a solid content of 10-30%, a viscosity greater than 300 cp, a solvent of deionized water, and a molecular weight greater than 5000.

[0017] Preferably, the PAA binder is further compounded, and the compounding method comprises the following steps: ① adding nano-montmorillonite into deionized water and ultrasonic dispersion to obtain a montmorillonite dispersion liquid; ② adding the PAA binder into the montmorillonite dispersion liquid and stirring uniformly to obtain a mixed dispersion liquid; and ③ controlling the temperature to be 55-65 ℃ for vacuum drying treatment of the mixed dispersion liquid to obtain a PAA / nano-montmorillonite composite material.

[0018] Preferably, the composite emulsion is a composite emulsion of polyacrylic acid, polyacrylamide and styrene-butadiene rubber with a solid content of 20-50% and a viscosity greater than 50 cp, and the addition ratio of polyacrylic acid, polyacrylamide and styrene-butadiene rubber is 1:(0.9-1.1):(0.9-1.1).

[0019] Preferably, the wetting agent is a silicon ether wetting agent.

[0020] The second object of the present application is to provide an application of the high-temperature-resistant ceramic coating slurry, which comprises mixing the high-temperature-resistant ceramic coating slurry as described above with 1-1.2% of the initiator by mass of the ceramic particles and applying the mixture to coat a porous separator film to form a ceramic coating layer through high-temperature polymerization and solidification at 55-65°C.

[0021] Preferably, the ceramic coating layer comprises ceramic particles, a heat-resistant PAA framework and a composite, the thickness of the ceramic coating layer is 3-20μm, the air permeability value is 10-500s / 100ml, the high-temperature-resistant performance is 180°C / 30min, and the thermal shrinkage is MD<3% and TD<3%.

[0022] As can be seen from the above solution, the present application provides a high-temperature-resistant ceramic coating slurry and an application thereof. The high-temperature-resistant ceramic coating slurry builds an interpenetrating network structure between the ceramic particles and the PAA binder by mixing the corresponding components, thereby effectively enhancing the interface bonding force between the two and achieving the effect of synergistically improving the heat resistance. The application of the high-temperature-resistant ceramic coating slurry significantly improves the heat resistance of the ceramic coating layer prepared therefrom, thereby achieving the effect of improving the use safety of the battery. Based on the corresponding components, the ceramic coating layer obtained forms a heat-resistant PAA framework and a composite mixedly coated ceramic particles, and further achieves the effect of significantly improving the heat resistance. Therefore, when the high-temperature-resistant ceramic coating slurry is coated on the surface of the porous separator film, after drying to form a film, the ceramic coating layer forms a heat-resistant PAA framework support and a heat-resistant structural framework on the surface of the porous separator film, and simultaneously forms a heat-resistant bonding system between the interface between the porous separator film and the ceramic particles, so that the ceramic coating layer meets the performance requirements of 180°C / 30min and the thermal shrinkage of the separator <3%. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0024] Figure 1 A schematic view of the composite structure of the porous separator film and the ceramic coating layer disclosed in the present application.

[0025] Legend of the drawings: 1, porous separator film; 2, ceramic particles; 3, heat-resistant PAA framework; 4, composite. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0027] The high-temperature-resistant ceramic coating slurry and the application thereof will be specifically described below.

[0028] The high-temperature-resistant ceramic coating slurry comprises ceramic particles, PAA binder, composite emulsion, wetting agent, and water as a solvent. The added mass ratio of the ceramic particles, the PAA binder, the composite emulsion, and the wetting agent is 1:0.5-2%:5-10%:0.05-0.2%, and the added mass percentage of the ceramic particles is 30-50%.

[0029] It should be noted that the ceramic particles are obtained by grinding at least one of alpha-alumina, boehmite, magnesium hydroxide, and zirconium oxide as metal oxides, and the particle size distribution D50 is 0.3-1.8 μm. The grinding of the ceramic particles is prepared by using a high-energy ball milling method. The high-energy ball milling method is to put the metal oxides into a ball mill, use anhydrous ethanol as a dispersion medium, control the ball-to-material ratio to be (8-12):1, the rotation speed to be 250-350 r / min, and the grinding time to be 8-12 hours to obtain the ground ceramic particles.

[0030] In order to further improve the promoting effect of the ground ceramic particles on the heat resistance of the high-temperature-resistant ceramic coating slurry, the embodiments of the present application also include modified ground ceramic particles, and the method for modifying the ground ceramic particles comprises the following steps: ① adding the ground ceramic particles into a toluene solvent for ultrasonic dispersion for 15-20 min to obtain a ceramic dispersion liquid; ② adding 1-3% of a silane coupling agent based on the mass of the ground ceramic particles into the ceramic dispersion liquid, controlling the reaction temperature to be 60-80 ℃, modifying for 2-3 h, then washing with ethanol, and drying at a temperature of 75-85 ℃ for 4-6 h to obtain modified ceramic particles; ③ mixing tetrabutyl titanate, anhydrous ethanol, and deionized water at a volume ratio of 1:4.5-5.5:1.8-2.2, uniformly stirring, adding nitric acid to adjust the pH to 2-3, preparing TiO2 sol, and then uniformly ultrasonic dispersing the modified ceramic particles in the TiO2 sol to obtain an adsorption sol; and ④ placing the adsorption sol at 55-65 ℃ to dry to form a gel layer, and then calcining the gel layer at 450-550 ℃ for 1.8-2.2 hours to obtain ceramic particles coated with a nano-TiO2 coating.

[0031] The PAA binder is obtained by mixing PAA solution and melamine formaldehyde resin in a mass ratio of (9-11):1, adding a catalyst and controlling the temperature at 60-80℃ to stir for 2-3h, and the PAA solution has a solid content of 10-30%, a viscosity greater than 300cp, a solvent of deionized water and a molecular weight greater than 5000. In order to further improve the promoting effect of the PAA binder on the heat resistance of the high-temperature-resistant ceramic coating slurry, the PAA binder is further compounded in the embodiment, and the method for compounding includes the following steps: ① uniformly dispersing nano-montmorillonite in deionized water by ultrasonic dispersion to obtain a montmorillonite dispersion liquid; ② uniformly stirring the PAA binder into the montmorillonite dispersion liquid to obtain a mixed dispersion liquid; and ③ vacuum drying the mixed dispersion liquid at a temperature of 55-65℃ to obtain a PAA / nano-montmorillonite composite material.

[0032] Meanwhile, the composite emulsion in the embodiment includes polyacrylic acid, polyacrylamide and styrene-butadiene rubber in a compound emulsion with a solid content of 20-50% and a viscosity greater than 50cp, and the addition ratio of polyacrylic acid, polyacrylamide and styrene-butadiene rubber is 1:(0.9-1.1):(0.9-1.1). The wetting agent is a silicon ether wetting agent.

[0033] An application of a high-temperature-resistant ceramic coating slurry includes mixing the high-temperature-resistant ceramic coating slurry as described above with 1-1.2% of an initiator based on the mass of the ceramic particles and applying the mixture to coat a porous separation film to form a ceramic coating layer by high-temperature polymerization and solidification at 55-65℃. As shown in FIG. 1, the ceramic coating layer includes ceramic particles, a heat-resistant PAA framework and a composite body, and the thickness of the ceramic coating layer in the embodiment is 3-20μm, the air permeability value is 10-500s / 100ml, the high-temperature-resistant performance is 180℃ / 30min, and the thermal shrinkage is MD<3% and TD<3%. Figure 1

[0034] Embodiment One

[0035] A high-temperature-resistant ceramic coating slurry includes ceramic particles, a PAA binder, a composite emulsion, a wetting agent and water as a solvent. The addition mass ratio of the ceramic particles, the PAA binder, the composite emulsion and the wetting agent is 1:0.5%:5%:0.05%, and the addition mass percentage of the ceramic particles is 30%.

[0036] That is, in the embodiment, the water as a solvent is 600kg, and the ceramic particles account for 30% of the total mass of the high-temperature-resistant ceramic coating slurry, and the PAA binder, the composite emulsion and the wetting agent are also contained in the high-temperature-resistant ceramic coating slurry in a mass ratio of 1:0.5%:5%:0.05% based on the mass of the ceramic particles.

[0037] ​It should be noted that the ceramic particles are obtained by mixing and grinding α-alumina and zirconia as metal oxides in a mass ratio of 7:3, and the particle size distribution D50 is 0.3-1.8 μm. The grinding of the ceramic particles is prepared by using a high-energy ball milling method. The high-energy ball milling method is to put α-alumina and zirconia into a ball mill, use anhydrous ethanol as a dispersion medium, control the ball-to-material ratio to be 8:1, the rotation speed is 250 r / min, and grind for 12 hours to obtain the ground ceramic particles.

[0038] In order to further improve the promoting effect of the ground ceramic particles on the heat resistance of the high-temperature-resistant ceramic coating slurry, the application embodiment also includes modifying the ground ceramic particles, and the modification method includes the following steps: ① adding the ground ceramic particles into toluene solvent and ultrasonic dispersion for 15 min to obtain a ceramic dispersion liquid; ② adding 1% silane coupling agent based on the mass of the ground ceramic particles into the ceramic dispersion liquid, controlling the reaction temperature to be 60°C, modifying for 2h, then washing with ethanol, and drying at a temperature of 75°C for 6h to obtain modified ceramic particles; ③ mixing tetrabutyl titanate, anhydrous ethanol and deionized water in a volume ratio of 1:4.5:1.8, stirring uniformly, adding nitric acid to adjust the pH to 2 to prepare TiO2 sol, and then adding the modified ceramic particles into the TiO2 sol and ultrasonic dispersion to obtain an adsorption sol; and ④ placing the adsorption sol at 55°C to dry to form a gel layer, and then calcining the gel layer at 450°C for 2.2 hours to obtain ceramic particles coated with a nano-TiO2 coating layer.

[0039] The silane coupling agent in the application embodiment is KH-560, which is commercially available and will not be described here.

[0040] The PAA binder is obtained by mixing PAA solution and melamine formaldehyde resin in a mass ratio of 9:1, adding a catalyst and controlling the temperature to be 60°C for stirring reaction for 3h, and the solid content of the PAA solution is 10%, the solvent is deionized water, and the molecular weight is greater than 5000. In order to further improve the promoting effect of the PAA binder on the heat resistance of the high-temperature-resistant ceramic coating slurry, the application embodiment also includes composite treatment of the PAA binder, and the composite treatment method includes the following steps: ① adding nano-montmorillonite into deionized water and ultrasonic dispersion to obtain a montmorillonite dispersion liquid; ② adding the PAA binder into the montmorillonite dispersion liquid and stirring uniformly to obtain a mixed dispersion liquid; and ③ controlling the temperature to be 55°C for vacuum drying treatment of the mixed dispersion liquid to obtain a PAA / nano-montmorillonite composite material.

[0041] At the same time, the composite emulsion in the application embodiment is a composite emulsion of polyacrylic acid, polyacrylamide and styrene-butadiene rubber with a solid content of 20%, and the addition ratio of polyacrylic acid, polyacrylamide and styrene-butadiene rubber is 1:0.9:0.9. The wetting agent is a siloxane wetting agent.

[0042] The application of a high-temperature-resistant ceramic coating slurry includes mixing an initiator at 1% of the mass of ceramic particles and applying the high-temperature-resistant ceramic coating slurry as described above to coat a porous separation film, and polymerizing and curing the porous separation film at a high temperature of 55°C to form a ceramic coating layer. Figure 1 As shown in the figure, the ceramic coating layer includes ceramic particles, a heat-resistant PAA framework, and a composite, and the thickness of the ceramic coating layer in the embodiment is 3 μm, the air permeability value is 10-500 s / 100 ml, the high-temperature-resistant performance is 180°C / 30 min, and the thermal shrinkage is MD<3% and TD<3%.

[0043] Embodiment two

[0044] A high-temperature-resistant ceramic coating slurry includes ceramic particles, a PAA binder, a composite emulsion, a wetting agent, and water as a solvent. The mass ratio of the ceramic particles, the PAA binder, the composite emulsion, and the wetting agent is 1:1%:7%:0.1%, and the mass percentage of the ceramic particles is 40%.

[0045] That is, in the embodiment, the water as a solvent is 600 kg, the ceramic particles accounting for 40% of the total mass of the high-temperature-resistant ceramic coating slurry are added, and the high-temperature-resistant ceramic coating slurry also contains the PAA binder, the composite emulsion, and the wetting agent in a mass ratio of 1:1%:7%:0.1% to the ceramic particles.

[0046] It should be noted that the ceramic particles are obtained by mixing α-alumina and magnesium hydroxide as metal oxides in a mass ratio of 1:1 and grinding, and the particle size distribution D50 is 0.3-1.8 μm. The ceramic particles are prepared by using a high-energy ball milling method. The high-energy ball milling method is to put α-alumina and magnesium hydroxide into a ball mill, use anhydrous ethanol as a dispersion medium, control the ball-to-material ratio to be 10:1, the rotation speed to be 300 r / min, and grind for 10 hours to obtain the ground ceramic particles.

[0047] In order to further improve the promoting effect of the abrasive ceramic particles on the heat resistance of the high-temperature-resistant ceramic coating slurry, the abrasive ceramic particles are modified in the embodiment of the application, and the modification method comprises the following steps: ① adding the abrasive ceramic particles into toluene solvent and ultrasonic dispersion for 17 min to obtain a ceramic dispersion liquid; ② adding 2% of silane coupling agent based on the mass of the abrasive ceramic particles into the ceramic dispersion liquid, controlling the reaction temperature to be 70°C, modifying for 2.5 h, washing with ethanol, and drying at 80°C for 5 h to obtain modified ceramic particles; ③ mixing tetrabutyl titanate, anhydrous ethanol and deionized water at a volume ratio of 1:5:2, stirring uniformly, adding nitric acid to adjust the pH to 2.5 to prepare TiO2 sol, and then adding the modified ceramic particles into the TiO2 sol and ultrasonic dispersion to obtain an adsorption sol; and ④ placing the adsorption sol at 60°C to dry to form a gel layer, and calcining the gel layer at 500°C for 2 hours to obtain ceramic particles coated with a nano-TiO2 coating layer.

[0048] The PAA binder is obtained by mixing PAA solution and melamine formaldehyde resin at a mass ratio of 10:1, adding a catalyst and controlling the temperature to be 70°C for stirring reaction for 2.5 h, and the solid content of the PAA solution is 20%, the solvent is deionized water, and the molecular weight is greater than 5000. In order to further improve the promoting effect of the PAA binder on the heat resistance of the high-temperature-resistant ceramic coating slurry, the PAA binder is compounded in the embodiment of the application, and the compounding method comprises the following steps: ① adding nano-montmorillonite into deionized water and ultrasonic dispersion to obtain a montmorillonite dispersion liquid; ② adding the PAA binder into the montmorillonite dispersion liquid and stirring uniformly to obtain a mixed dispersion liquid; and ③ controlling the temperature to be 60°C for vacuum drying treatment of the mixed dispersion liquid to obtain a PAA / nano-montmorillonite composite material.

[0049] At the same time, the composite emulsion in the embodiment of the application is a composite emulsion of polyacrylic acid, polyacrylamide and styrene-butadiene rubber with a solid content of 35%, and the addition ratio of polyacrylic acid, polyacrylamide and styrene-butadiene rubber is 1:1:1. The wetting agent is a silicon ether wetting agent.

[0050] An application of a high-temperature-resistant ceramic coating slurry, comprising mixing the high-temperature-resistant ceramic coating slurry as described above with 1.1% of an initiator based on the mass of the ceramic particles and applying it to coat a porous isolation film to form a ceramic coating layer by high-temperature polymerization and solidification at 60°C. Figure 1 As shown in the figure, the ceramic coating layer comprises ceramic particles, a heat-resistant PAA framework and a composite, and the thickness of the ceramic coating layer in the embodiment of the application is 3 μm, the air permeability value is 10-500 s / 100 ml, the high-temperature-resistant performance is 180°C / 30 min, and the thermal shrinkage is MD<3% and TD<3%.

[0051] Example Three

[0052] A high-temperature-resistant ceramic coating slurry, comprising ceramic particles, PAA binder, composite emulsion, wetting agent, and water as solvent. The mass ratio of the ceramic particles, PAA binder, composite emulsion, and wetting agent is 1:2%:10%:0.2%, and the mass percentage of the ceramic particles is 50%.

[0053] That is, in the embodiment of the present application, the water as the solvent is 600 kg, and ceramic particles accounting for 50% of the total mass of the high-temperature-resistant ceramic coating slurry are added, and the high-temperature-resistant ceramic coating slurry also contains PAA binder, composite emulsion, and wetting agent in a mass ratio of 1:2%:10%:0.2% to the ceramic particles.

[0054] It should be noted that the ceramic particles are boehmite and zirconia as metal oxides mixed in a mass ratio of 1:1 and obtained by grinding, and the particle size distribution D50 is 0.3-1.8 μm. The grinding of the ceramic particles is prepared by using a high-energy ball milling method. The high-energy ball milling method is to put the metal oxides into a ball mill, use anhydrous ethanol as a dispersion medium, control the ball-to-material ratio to be 12:1, the rotation speed is 350 r / min, and the grinding time is 8 hours to obtain the ground ceramic particles.

[0055] In order to further improve the promoting effect of the ground ceramic particles on the heat resistance of the high-temperature-resistant ceramic coating slurry, the embodiment of the present application also includes modifying the ground ceramic particles, and the method of modification includes the following steps: ① adding the ground ceramic particles into a toluene solvent and ultrasonic dispersing for 20 min to obtain a ceramic dispersion liquid; ② adding a silane coupling agent accounting for 3% of the mass of the ground ceramic particles into the ceramic dispersion liquid, controlling the reaction temperature to be 80℃, modifying for 2h, then washing with ethanol, and drying at a temperature of 85℃ for 4h to obtain modified ceramic particles; ③ mixing tetrabutyl titanate, anhydrous ethanol, and deionized water in a volume ratio of 1:5.5:2.2, stirring uniformly, then adding nitric acid to adjust the pH to 3 to prepare TiO2 sol, and then adding the modified ceramic particles into the TiO2 sol and ultrasonic dispersing uniformly to obtain an adsorption sol; ④ placing the adsorption sol at 65℃ to dry to form a gel layer, and then calcining the gel layer at 550℃ for 1.8 hours to obtain ceramic particles coated with a nano-TiO2 coating.

[0056] The PAA binder is obtained by mixing PAA solution with mass ratio of 11:1 and melamine formaldehyde resin, adding catalyst and controlling temperature at 80℃ to stir for 2h, and the solid content of the PAA solution is 30%, the solvent is deionized water, and the molecular weight is greater than 5000. In order to further improve the heat resistance promoting effect of the PAA binder on the high-temperature-resistant ceramic coating slurry, the PAA binder in the embodiment of the application is also subjected to composite treatment, and the method for composite treatment comprises the following steps: ① uniformly dispersing nano-montmorillonite in deionized water by ultrasonic to obtain a montmorillonite dispersion liquid; ② uniformly stirring the PAA binder into the montmorillonite dispersion liquid to obtain a mixed dispersion liquid; and ③ vacuum drying the mixed dispersion liquid at a temperature of 65℃ to obtain a PAA / nano-montmorillonite composite material.

[0057] At the same time, the composite emulsion in the embodiment of the application is a composite emulsion of polyacrylic acid, polyacrylamide and styrene-butadiene rubber with a solid content of 50%, and the addition ratio of polyacrylic acid, polyacrylamide and styrene-butadiene rubber is 1:1.1:1.1. The wetting agent is a silicon ether wetting agent.

[0058] An application of a high-temperature-resistant ceramic coating slurry comprises mixing the high-temperature-resistant ceramic coating slurry as described above with 1.2% of an initiator based on the mass of the ceramic particles and applying it to coat a porous separation membrane to form a ceramic coating layer by high-temperature polymerization and solidification at 65℃. As shown in Figure 1 The ceramic coating layer comprises ceramic particles, a heat-resistant PAA framework and a composite body, and the thickness of the ceramic coating layer in the embodiment of the application is 3μm, the air permeability value is 10-500s / 100ml, the high-temperature-resistant performance is 180℃ / 30min, and the thermal shrinkage is MD<3% and TD<3%.

[0059] Comparative Example 1

[0060] The difference between Comparative Example 1 and Example 2 is that the CMC aqueous solution with a solid content of 5% is used to replace the PAA binder in Comparative Example 1.

[0061] Comparative Example 2

[0062] The difference between Comparative Example 2 and Example 2 is that the ceramic particles in Comparative Example 2 are not subjected to modification treatment.

[0063] Comparative Example 3

[0064] The difference between Comparative Example 3 and Example 2 is that the PAA binder in Comparative Example 3 is not subjected to composite treatment.

[0065] Comparative Example 4

[0066] The difference between Comparative Example 4 and Example 2 is that the polyacrylate is used to replace the composite emulsion in Comparative Example 4.

[0067] Performance test:

[0068] 1. Sample preparation: The size of the test sample is 50mm*50mm, using 7-micron porous separator film and 3-micron film layer thickness;

[0069] 2. MD heat shrinkage and TD heat shrinkage test: using a heat shrinkage tester, based on 180℃, after keeping for 30min, test the length in MD and TD directions after cooling, and then calculate the shrinkage rate;

[0070] 3. Thermogravimetric analysis test: using a thermogravimetric analyzer, first record the initial mass of the sample, then increase the temperature from room temperature to 600℃ at a rate of 10℃ / min, test under the protection of nitrogen atmosphere, record the mass change under the test conditions of nitrogen flow control at 50mL / min;

[0071] The performance test results are shown in Table 1 below.

[0072] Table 1 Performance test results

[0073]

[0074] As can be seen from Table 1 above, in the present application Comparative Example 1, after using CMC aqueous solution to replace PAA binder, due to the poor heat resistance of CMC, the molecular chain is easy to degrade at high temperature, resulting in a significant increase in heat shrinkage; in Comparative Example 2, since the ceramic particles are not modified, the compatibility of the ceramic particles with the binder is poor, thereby causing stress concentration at high temperature, resulting in an increase in heat shrinkage; in Comparative Example 3, since the PAA binder is not subjected to composite treatment, it has insufficient heat resistance and cannot form an effective synergistic effect with the ceramic particles; in Comparative Example 4, since polyacrylate is used to replace the composite emulsion, the overall structural stability of the coating is affected, resulting in an increase in heat shrinkage.

[0075] According to the thermogravimetric analysis test results, it can be seen that in Comparative Example 1, there is a significant mass loss at 150℃, and the mass loss is more than 50% at 400℃, indicating that CMC has poor heat resistance and rapidly decomposes at high temperature. In Comparative Example 2, the mass loss rate accelerates after 300℃, and the residual mass at 500℃ is less than 70%, indicating that the unmodified ceramic particles cannot effectively hinder heat transfer, resulting in intensified decomposition of the coating. In Comparative Example 3, there is a large mass loss at 350℃ during the test, and the residual mass at 500℃ is 75%, indicating that the PAA binder without composite treatment has insufficient structural stability at high temperature. At the same time, in Comparative Example 4, there is a significant mass loss at 300-400℃, and the residual mass at 500℃ is less than 75%, indicating that after the composite emulsion is replaced, the heat resistance of the coating decreases.

[0076] In summary, the application provides a high-temperature-resistant ceramic coating slurry and its application. The high-temperature-resistant ceramic coating slurry is obtained by mixing the corresponding components and synergistically constructing an interpenetrating network structure between the ceramic particles and the PAA binder, thereby effectively enhancing the interface bonding force between the two and synergistically improving the heat resistance. The acrylate monomer is polymerized between the ceramic particles and the PAA binder to form a polymer network, interpenetrated with the PAA binder, while wrapping the ceramic particles, thereby constructing an interfacial interpenetrating network structure. During the TiO2 coating process, the nano-TiO2 itself has high thermal stability, and the coating can form a thermal resistance layer on the surface of the ceramic particles, slowing down the heat transfer speed to the interior of the ceramic particles, further enhancing the stability of the ceramic particles at high temperatures, and thereby improving the heat resistance of the entire coating. The application of the high-temperature-resistant ceramic coating slurry significantly improves the heat resistance of the ceramic coating prepared, thereby achieving the effect of improving the safety of the battery. Based on the corresponding components, the ceramic coating obtained forms a heat-resistant PAA skeleton and a composite mixed coating ceramic particle, and further achieves the effect of significantly improving the heat resistance. Therefore, when the high-temperature-resistant ceramic coating slurry is coated on the surface of the porous separator membrane, after drying to form a film, the ceramic coating forms a heat-resistant PAA skeleton support and heat-resistant structure skeleton on the surface of the porous separator membrane, and at the same time forms a heat-resistant bonding system between the interface between the porous separator membrane and the ceramic particles, so that the ceramic coating meets the performance requirements of 180℃ / 30min and the membrane heat shrinkage <3%.

[0077] The terms "first", "second", "third", "fourth" and the like, if any, used in this application are used to distinguish similar objects, and are not necessarily used to describe a particular sequential or chronological order. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method or device comprising a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods or devices.

[0078] It should be noted that the terms "first", "second", and the like in the description and in the claims do not denote any particular importance, but are merely used to distinguish one element from another. Thus, a "first" and "second" feature can be presented explicitly or implicitly, and can include at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, nor is it within the scope of protection required by the present application.

[0079] The principles and implementation manners of the present application are described by applying specific examples herein, and the above description of the examples is only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application, and in view of the above, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A high temperature resistant ceramic coating slurry, characterized in that, Comprise: ceramic particles, PAA binder, composite emulsion, wetting agent, and water as solvent; The mass ratio of the ceramic particles, PAA binder, composite emulsion and wetting agent is 1:0.5-2%:5-10%:0.05-0.2%; The mass percentage of the ceramic particles is 30-50%; And further comprising modified treatment of abrasive ceramic particles, and the method of modification treatment comprises the following steps: step ① adding abrasive ceramic particles into toluene solvent and ultrasonic dispersion for 15-20 min to obtain ceramic dispersion liquid; step ② adding 1-3% silane coupling agent based on the mass of abrasive ceramic particles into the ceramic dispersion liquid, controlling the reaction temperature at 60-80℃, modifying for 2-3h, then washing with ethanol, and drying at 75-85℃ for 4-6h to obtain modified ceramic particles; step ③ mixing tetrabutyl titanate, anhydrous ethanol and deionized water at a volume ratio of 1:4.5-5.5:1.8-2.2, stirring uniformly, adding nitric acid to adjust the pH to 2-3 to prepare TiO2 sol, then adding the modified ceramic particles into the TiO2 sol and ultrasonic dispersion to obtain adsorption sol; step ④ placing the adsorption sol at 55-65℃ to dry into gel layer, then calcining the gel layer at 450-550℃ for 1.8-2.2h to obtain ceramic particles coated with nano-TiO2 coating; The composite emulsion is a composite emulsion of polyacrylic acid, polyacrylamide and styrene-butadiene rubber with solid content of 20-50% and viscosity greater than 50cp, and the addition ratio of polyacrylic acid, polyacrylamide and styrene-butadiene rubber is 1:(0.9-1.1):(0.9-1.1); The high-temperature-resistant ceramic coating slurry is mixed with 1-1.2% initiator based on the mass of ceramic particles to form ceramic coating.

2. The high temperature resistant ceramic coating slurry according to claim 1, characterized in that: The ceramic particles are at least one of α-alumina, boehmite, magnesium hydroxide and zirconium oxide as metal oxide, which are obtained by grinding, and the particle size distribution D50 is 0.3-1.8μm.

3. The high temperature resistant ceramic coating slurry according to claim 1, characterized in that: The grinding of the ceramic particles is prepared by high-energy ball milling method, which is putting metal oxide into ball mill, using anhydrous ethanol as dispersion medium, controlling the ball-to-material ratio at (8-12):1, rotating speed at 250-350r / min, and grinding for 8-12h to obtain abrasive ceramic particles.

4. The high temperature resistant ceramic coating slurry according to claim 1, characterized in that: The PAA binder is obtained by mixing PAA solution and melamine formaldehyde resin at a mass ratio of (9-11):1, adding catalyst and controlling the temperature at 60-80℃ for 2-3h, and the PAA solution has solid content of 10-30%, viscosity greater than 300cp, solvent of deionized water and molecular weight greater than 5000.

5. The high temperature resistant ceramic coating slurry according to claim 4, characterized in that: Further comprising composite treatment of the PAA binder, and the method of composite treatment comprises the following steps: step ① putting nano-montmorillonite into deionized water and ultrasonic dispersion to obtain montmorillonite dispersion liquid; step ② adding PAA binder into the montmorillonite dispersion liquid and stirring uniformly to obtain mixed dispersion liquid; step ③ controlling the temperature at 55-65℃ for vacuum drying treatment of the mixed dispersion liquid to obtain PAA / nano-montmorillonite composite material.

6. The high temperature resistant ceramic coating slurry according to claim 1, wherein: The wetting agent is a siloxane wetting agent.

7. Use of a high temperature resistant ceramic coating slurry, characterized in that: The application relates to a high-temperature-resistant ceramic coating slurry, which is prepared by mixing 1-1.2% of an initiator with ceramic particles according to the mass of the ceramic particles and applying the mixture to coat a porous isolation film, and then polymerizing and curing the coated porous isolation film at a high temperature of 55-65 DEG C to form a ceramic coating.

8. Use of a high-temperature resistant ceramic coating slurry according to claim 7, characterized in that: The ceramic coating comprises ceramic particles, a heat-resistant PAA framework and a composite body, the thickness of the ceramic coating is 3-20 microns, the air permeability value is 10-500 s / 100ml, the high-temperature-resistant performance is 180 DEG C / 30min, and the thermal shrinkage is MD<3% and TD<3%.

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