High-temperature-resistant ceramic coating slurry and application thereof

Abstract

The invention discloses high-temperature-resistant ceramic coating slurry and application thereof, and relates to the technical field of secondary batteries, the high-temperature-resistant ceramic coating slurry comprises ceramic particles, a PAA binder, a composite emulsion, a wetting agent and water as a solvent; the addition mass ratio of the ceramic particles to the PAA binder to the composite emulsion to the wetting agent is 1: (0.5-2): (5-10): (0.05-0.2); the adding mass percentage of the ceramic particles is 30-50%. The heat resistance of the prepared ceramic coating is remarkably improved, so that the effect of improving the use safety of the battery is achieved. Based on the corresponding components, the obtained ceramic coating forms a heat-resistant PAA framework and a composite body which are mixed to coat ceramic particles, and the effect of remarkably improving the heat resistance is further achieved.

Description

Technical Field

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

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

[0003] In the prior art, the temperature resistance of the PE ceramic coated diaphragm used in non-aqueous secondary batteries generally only meets the level of thermal shrinkage <3% at 130°C / 30min. When a micro-short circuit occurs inside the battery or a local temperature rise occurs outside, the internal temperature of the battery using a conventional PE ceramic coated diaphragm exceeds 130°C, and the diaphragm inside the battery experiences large-scale thermal shrinkage. When the PE ceramic diaphragm shrinks to a certain size, a large-scale internal short circuit will occur between the positive and negative electrodes inside the battery, causing a sharp increase in heat generation inside the battery, leading to thermal runaway of the battery, and ultimately causing the battery to explode or deflagrate, causing a safety accident. This needs to be improved. Summary of the Invention

[0004] In view of this, the first object of this application is to provide a high-temperature resistant ceramic coating slurry to achieve the purpose of improving the heat resistance of PE ceramic coated separators and improving the safety of aqueous secondary batteries. The specific scheme is as follows: A high-temperature resistant ceramic coating slurry, comprising: Ceramic particles, PAA binder, Composite emulsion, Wetting agents, and water as a solvent; The added 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 added mass percentage of the ceramic particles is 30-50%.

[0005] Preferably, the ceramic particles are obtained by grinding at least one of α-alumina, boehmite, magnesium hydroxide, and zirconium oxide as metal oxides, and have a particle size distribution D50 of 0.3-1.8 μm.

[0006] Preferably, the ceramic particles are ground by high-energy ball milling, wherein the metal oxide is placed in a ball mill, anhydrous ethanol is used as a 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 is performed for 8-12 hours to obtain ground ceramic particles.

[0007] Preferably, the method further comprises modifying the ground ceramic particles, and the modification method comprises the steps of ① adding the ground ceramic particles to a toluene solvent and ultrasonically dispersing them for 15-20 minutes to obtain a ceramic dispersion; ② adding a silane coupling agent in an amount of 1-3% by mass of the ground ceramic particles to the ceramic dispersion, controlling the reaction temperature to 60-80°C for modification treatment for 2-3 hours, washing with ethanol, and then drying at 75-85°C for 4-6 hours to obtain modified ceramic particles; and ③ adding tetrabutyl titanate. Ester, anhydrous ethanol and deionized water are mixed in a volume ratio of 1:4.5-5.5:1.8-2.2, stirred evenly, and then nitric acid is added to adjust the pH to 2-3 to prepare a TiO2 sol, and then the modified ceramic particles are added to the TiO2 sol and ultrasonically dispersed evenly to obtain an adsorption sol; step ④ is to place the adsorption sol at 55-65°C to dry to form a gel layer, and then calcined the gel layer at 450-550°C for 1.8-2.2 hours to obtain ceramic particles with a surface coated with a nano-TiO2 coating.

[0008] Preferably, the PAA binder is obtained by mixing a PAA solution and a melamine formaldehyde resin in a mass ratio of (9-11):1, adding a catalyst, and controlling the temperature to 60-80° C. with stirring for 2-3 hours. The PAA solution has a solid content of 10-30%, a viscosity greater than 300 cp, and a solvent of deionized water. The molecular weight is greater than 5000.

[0009] Preferably, the PAA binder is further included in the composite treatment, and the composite treatment method includes the steps of ① uniformly dispersing the nano-montmorillonite in deionized water by ultrasonication to obtain a montmorillonite dispersion; ② adding the PAA binder to the montmorillonite dispersion and stirring evenly to obtain a mixed dispersion; and ③ controlling the temperature to 55-65° C. to vacuum dry the mixed dispersion to obtain a PAA / nano-montmorillonite composite material.

[0010] 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).

[0011] Preferably, the wetting agent is a silicone ether wetting agent.

[0012] The second object of the present invention is to provide an application of a high-temperature resistant ceramic coating slurry, comprising mixing a 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 it to a porous isolation membrane and curing it at a high temperature of 55-65°C to form a ceramic coating.

[0013] Preferably, the ceramic coating comprises ceramic particles, a heat-resistant PAA skeleton and a composite. The ceramic coating has a thickness of 3-20 μm, an air permeability of 10-500 s / 100 ml, a high temperature resistance of 180°C / 30 min, and a thermal shrinkage of MD <3% and TD <3%.

[0014] From the above scheme, it can be seen that the present application provides a high-temperature resistant ceramic coating slurry and its application. The high-temperature resistant ceramic coating slurry is achieved by mixing the corresponding components and synergistically constructing an interpenetrating network structure between the ceramic particles and the PAA binder, thereby achieving a synergistic improvement in heat resistance based on the effective enhancement of the interfacial bonding strength between the two. The application of the high-temperature resistant ceramic coating slurry has the effect of significantly improving the heat resistance of the prepared ceramic coating, thereby achieving the effect of improving the safety of battery use. Based on the corresponding components, the obtained ceramic coating forms a heat-resistant PAA skeleton and a composite mixed with ceramic particles, thereby achieving a significant improvement in heat resistance. Therefore, when the high-temperature resistant ceramic coating slurry is applied to the surface of the porous separator, after drying and film formation, the ceramic coating forms a support and heat-resistant structural skeleton with a heat-resistant PAA skeleton on the surface of the porous separator, and at the same time forms a heat-resistant bonding system at the interface between the porous separator and the ceramic particles, so that the ceramic coating meets the performance requirements of 180°C / 30min and the thermal shrinkage of the separator is less than 3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0016] Figure 1 This is a schematic diagram of the composite structure of the porous isolation membrane and ceramic coating disclosed in this application.

[0017] Explanation of the accompanying symbols: 1. porous isolation membrane; 2. ceramic particles; 3. heat-resistant PAA skeleton; 4. composite. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0019] The following is a detailed description of a high-temperature resistant ceramic coating slurry and its application in this application.

[0020] 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, PAA binder, composite emulsion, and wetting agent is 1:0.5-2%:5-10%:0.05-0.2%, and the mass percentage of the ceramic particles is 30-50%.

[0021] It should be noted that the ceramic particles are obtained by grinding at least one of α-alumina, boehmite, magnesium hydroxide, and zirconium oxide as metal oxides, and have a particle size distribution D50 of 0.3-1.8 μm. The ceramic particles are ground using a high-energy ball milling method. The high-energy ball milling method is to place the metal oxide in a ball mill, use anhydrous ethanol as a dispersion medium, control the ball-to-material ratio to (8-12):1, rotate at a speed of 250-350 r / min, and grind for 8-12 hours to obtain ground ceramic particles.

[0022] In order to further enhance 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 a modified ground ceramic particle, and the modification method includes the steps of ① adding the ground ceramic particles to a toluene solvent and ultrasonically dispersing them for 15-20 minutes to obtain a ceramic dispersion; ② adding a silane coupling agent of 1-3% by mass of the ground ceramic particles to the ceramic dispersion, controlling the reaction temperature to 60-80°C, performing the modification treatment for 2-3 hours, washing with ethanol, and then drying at 75-85°C for 4-6 hours to obtain a ceramic dispersion. Modified ceramic particles are obtained; step ③ tetrabutyl titanate, anhydrous ethanol and deionized water are mixed in a volume ratio of 1:4.5-5.5:1.8-2.2, and after stirring evenly, nitric acid is added to adjust the pH to 2-3 to prepare a TiO2 sol, and then the modified ceramic particles are added to the TiO2 sol and ultrasonically dispersed evenly to obtain an adsorption sol; step ④ the adsorption sol is placed at 55-65°C to dry to form a gel layer, and then the gel layer is calcined at 450-550°C for 1.8-2.2 hours to obtain ceramic particles with a surface coated with a nano-TiO2 coating.

[0023] The PAA binder is obtained by mixing a PAA solution and a melamine-formaldehyde resin in a mass ratio of (9-11):1, adding a catalyst, and stirring the reaction at a temperature of 60-80°C for 2-3 hours. The PAA solution has a solids content of 10-30%, a viscosity greater than 300 cp, and a molecular weight greater than 5000. To further enhance the PAA binder's effect on the heat resistance of the high-temperature ceramic coating slurry, the present embodiment also includes a composite treatment of the PAA binder. The composite treatment method includes the steps of: ① ultrasonically dispersing nano-montmorillonite in deionized water to obtain a montmorillonite dispersion; ② adding the PAA binder to the montmorillonite dispersion and stirring to obtain a mixed dispersion; and ③ vacuum drying the mixed dispersion at a temperature of 55-65°C to obtain a PAA / nano-montmorillonite composite material.

[0024] Meanwhile, the composite emulsion in the embodiment of the present application 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). The wetting agent is a silicone ether wetting agent.

[0025] An application of a high temperature resistant ceramic coating slurry, comprising mixing the high temperature resistant ceramic coating slurry as described above with 1-1.2% of an initiator based on the mass of the ceramic particles and applying the mixture to a porous isolation membrane, and then polymerizing and curing the mixture at a temperature of 55-65°C to form a ceramic coating. Figure 1 As shown, the ceramic coating includes ceramic particles, a heat-resistant PAA skeleton and a complex, and the thickness of the ceramic coating in the embodiment of the present application is 3-20 μm, the air permeability is 10-500s / 100ml, the high temperature resistance is 180°C / 30min, and the thermal shrinkage is MD <3%, TD <3%.

[0026] Example 1 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, PAA binder, composite emulsion, and wetting agent is 1:0.5%:5%:0.05%, with the mass percentage of the ceramic particles being 30%.

[0027] That is, in the embodiment of the present application, 600 kg of water is used as a solvent, and ceramic particles accounting for 30% of the total mass of the high-temperature resistant ceramic coating slurry are added. The high-temperature resistant ceramic coating slurry also contains a PAA binder, a composite emulsion and a wetting agent in a mass ratio of 1:0.5%:5%:0.05% to the ceramic particles.

[0028] It should be noted that the ceramic particles are obtained by mixing α-alumina and zirconia as metal oxides in a mass ratio of 7:3 and grinding them, with a particle size distribution D50 of 0.3-1.8μm. The ceramic particles are ground using a high-energy ball milling method. The high-energy ball milling method involves placing α-alumina and zirconia in a ball mill, using anhydrous ethanol as the dispersion medium, controlling the ball-to-material ratio to 8:1, and grinding at a speed of 250r / min for 12 hours to obtain ground ceramic particles.

[0029] In order to further enhance 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 modified ground ceramic particles, and the modification method includes the steps of ① adding the ground ceramic particles to a toluene solvent and ultrasonically dispersing them for 15 minutes to obtain a ceramic dispersion; ② adding a silane coupling agent of 1% of the mass of the ground ceramic particles to the ceramic dispersion, controlling the reaction temperature to 60°C for modification treatment for 2 hours, washing with ethanol, and then drying at 75°C for 6 hours to obtain modified ceramic particles; step ③ mixing tetrabutyl titanate, anhydrous ethanol and deionized water in a volume ratio of 1:4.5:1.8, stirring evenly, adding nitric acid to adjust the pH to 2 to prepare a TiO2 sol, and then adding the modified ceramic particles to the TiO2 sol and ultrasonically dispersing them evenly to obtain an adsorption sol; step 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 with a surface coated with a nano-TiO2 coating.

[0030] The silane coupling agent in the embodiment of the present application is KH-560, which is commercially available and will not be described in detail here.

[0031] The PAA binder is prepared by mixing a PAA solution and melamine-formaldehyde resin in a 9:1 mass ratio, adding a catalyst, and stirring the reaction at 60°C for 3 hours. The PAA solution has a solids content of 10%, the solvent is deionized water, and the molecular weight is greater than 5000. To further enhance the PAA binder's effect on the heat resistance of the high-temperature ceramic coating slurry, the present embodiment also includes a composite treatment of the PAA binder. The composite treatment method includes the following steps: 1. Ultrasonic dispersion of nano-montmorillonite in deionized water to obtain a montmorillonite dispersion; 2. Adding the PAA binder to the montmorillonite dispersion and stirring to obtain a mixed dispersion; 3. Vacuum drying the mixed dispersion at 55°C to obtain a PAA / nano-montmorillonite composite material.

[0032] Meanwhile, the composite emulsion in the embodiment of the present application 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 silicone ether wetting agent.

[0033] An application of a high temperature resistant ceramic coating slurry, comprising mixing the high temperature resistant ceramic coating slurry as described above with an initiator at 1% of the mass of the ceramic particles and applying the mixture to a porous isolation membrane, and then polymerizing and curing the mixture at 55°C to form a ceramic coating. Figure 1 As shown, the ceramic coating includes ceramic particles, a heat-resistant PAA skeleton and a complex, and the thickness of the ceramic coating in the embodiment of the present application is 3 μm, the air permeability is 10-500s / 100ml, the high temperature resistance is 180°C / 30min, and the thermal shrinkage is MD <3%, TD <3%.

[0034] Example 2 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, PAA binder, composite emulsion, and wetting agent is 1:1%:7%:0.1%, with the mass percentage of the ceramic particles being 40%.

[0035] That is, in the embodiment of the present application, 600 kg of water is used as a solvent, and ceramic particles accounting for 40% of the total mass of the high-temperature resistant ceramic coating slurry are added. The high-temperature resistant ceramic coating slurry also contains a PAA binder, a composite emulsion and a wetting agent in a mass ratio of 1: 1%:7%:0.1% to the ceramic particles.

[0036] 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 them, with a particle size distribution D50 of 0.3-1.8 μm. The ceramic particles are prepared by high-energy ball milling. The high-energy ball milling method is to place α-alumina and magnesium hydroxide in a ball mill, use anhydrous ethanol as the dispersion medium, control the ball-to-material ratio to 10:1, and grind at a speed of 300 r / min for 10 hours to obtain ground ceramic particles.

[0037] In order to further enhance 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 modified ground ceramic particles, and the modification method includes the steps of ① adding the ground ceramic particles to a toluene solvent and ultrasonically dispersing them for 17 minutes to obtain a ceramic dispersion; ② adding a silane coupling agent of 2% of the mass of the ground ceramic particles to the ceramic dispersion, controlling the reaction temperature to 70°C for modification treatment for 2.5 hours, washing with ethanol, and then drying at 80°C for 5 hours to obtain modified ceramic particles; step ③ mixing tetrabutyl titanate, anhydrous ethanol and deionized water in a volume ratio of 1:5:2, stirring evenly, adding nitric acid to adjust the pH to 2.5 to prepare a TiO2 sol, and then adding the modified ceramic particles to the TiO2 sol and ultrasonically dispersing them evenly to obtain an adsorption sol; step ④ placing the adsorption sol at 60°C to dry to form a gel layer, and then calcining the gel layer at 500°C for 2 hours to obtain ceramic particles with a surface coated with a nano-TiO2 coating.

[0038] The PAA binder is prepared by mixing a PAA solution and melamine-formaldehyde resin in a 10:1 mass ratio, adding a catalyst, and stirring the reaction at 70°C for 2.5 hours. The PAA solution has a solids content of 20%, the solvent is deionized water, and the molecular weight is greater than 5000. To further enhance the PAA binder's effect on the heat resistance of the high-temperature ceramic coating slurry, the present embodiment also includes a composite treatment of the PAA binder. The composite treatment method includes the following steps: 1. Ultrasonic dispersion of nano-montmorillonite in deionized water to obtain a montmorillonite dispersion; 2. Adding the PAA binder to the montmorillonite dispersion and stirring to obtain a mixed dispersion; 3. Vacuum drying the mixed dispersion at 60°C to obtain a PAA / nano-montmorillonite composite material.

[0039] Meanwhile, the composite emulsion in the embodiment of the present 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 silicone ether wetting agent.

[0040] An application of a high temperature resistant ceramic coating slurry, comprising mixing the high temperature resistant ceramic coating slurry as described above with an initiator at 1.1% of the mass of the ceramic particles and applying the mixture to a porous isolation membrane, and then polymerizing and curing the mixture at 60°C to form a ceramic coating. Figure 1 As shown, the ceramic coating includes ceramic particles, a heat-resistant PAA skeleton and a complex, and the thickness of the ceramic coating in the embodiment of the present application is 3 μm, the air permeability is 10-500s / 100ml, the high temperature resistance is 180°C / 30min, and the thermal shrinkage is MD <3%, TD <3%.

[0041] Example 3 A high-temperature-resistant ceramic coating slurry includes 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%.

[0042] That is, in the embodiment, the water as solvent is 600 kg, and the 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%.

[0043] 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.

[0044] 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 also includes modifying the ground ceramic particles, and the modification method 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 3% of the silane coupling agent based on the mass of the ground ceramic particles into the ceramic dispersion liquid, controlling the reaction temperature to be 80℃, modifying for 2 h, then washing with ethanol, and drying at 85℃ for 4 h 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, 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; and 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.

[0045] 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 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 65℃ to obtain a PAA / nano-montmorillonite composite material.

[0046] 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.

[0047] 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%.

[0048] Comparative Example 1 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.

[0049] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that the grinding ceramic particles in Comparative Example 2 are not subjected to modification treatment.

[0050] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that the PAA binder in Comparative Example 3 is not subjected to composite treatment.

[0051] Comparative Example 4 The difference between Comparative Example 4 and Example 2 is that the polyacrylate is used to replace the composite emulsion in Comparative Example 4.

[0052] Performance test: 1. Sample preparation: Use a 7-micron porous isolation membrane and a 3-micron film thickness. The test sample size is 50mm*50mm. 2.MD and TD thermal shrinkage tests: Using a thermal shrinkage tester, maintain the temperature at 180°C for 30 minutes, then cool and measure the length in the MD and TD directions, and then calculate the shrinkage rate. 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°C at a rate of 10°C / min under a nitrogen atmosphere with a nitrogen flow rate of 50 mL / min, and record the mass change. The performance test results are shown in Table 1 below.

[0053] Table 1 Performance test results

[0054] As can be seen from Table 1 above, in Comparative Example 1 of the present application, after the CMC aqueous solution was used to replace the PAA binder, due to the poor heat resistance of CMC, the molecular chain was easily degraded at high temperature, resulting in a significant increase in the thermal shrinkage rate; in Comparative Example 2, since the ceramic particles were not modified, the compatibility between the ceramic particles and the binder was poor, which led to stress concentration at high temperature, resulting in increased thermal shrinkage; in Comparative Example 3, since the PAA binder was not composited, its heat resistance was insufficient and it could not form an effective synergistic effect with the ceramic particles; in Comparative Example 4, since polyacrylate was used to replace the composite emulsion, the overall structural stability of the coating was affected, resulting in an increase in the thermal shrinkage rate.

[0055] According to the thermogravimetric analysis test results, it can be seen that in Comparative Example 1, significant mass loss began to occur at 150°C, and the mass loss reached more than 50% at 400°C, indicating that CMC has poor heat resistance and decomposes rapidly at high temperatures. In Comparative Example 2, since its mass loss rate accelerated after 300°C and the residual mass at 500°C was less than 70%, it can be seen that the unmodified ceramic particles could not effectively hinder heat transfer, resulting in aggravated decomposition of the coating. In Comparative Example 3, during the test, it experienced a large mass loss at 350°C and a residual mass of 75% at 500°C. It can be seen that the PAA binder without compound treatment has insufficient structural stability at high temperatures. At the same time, in Comparative Example 4, since its mass loss was significant between 300 and 400°C and the residual mass was less than 75% at 500°C, it can be seen that the heat resistance of the coating decreased after the composite emulsion was replaced.

[0056] In summary, the present application provides a high-temperature resistant ceramic coating slurry and its application, which achieves the effect of synergistically improving heat resistance by mixing the corresponding components and synergistically constructing an interpenetrating network structure between ceramic particles and PAA binder, thereby effectively enhancing the interfacial bonding strength of the two. Among them, the acrylate monomer polymerizes between the ceramic particles and the PAA binder to form a polymer network, which is interpenetrating with the PAA binder and wraps the ceramic particles to build an interfacial interpenetrating network structure. During the titanium dioxide wrapping process, 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 transfer speed of heat to the interior of the ceramic particles, further enhancing the stability of the ceramic particles at high temperatures, and thus improving the heat resistance of the entire coating. The application of this high-temperature resistant ceramic coating slurry has the effect of significantly improving the heat resistance of the prepared ceramic coating, thereby achieving the effect of improving the safety of battery use. Based on the corresponding components, the obtained ceramic coating forms a ceramic particle with a heat-resistant PAA skeleton and a composite mixed coating, thereby achieving the effect of significantly improving heat resistance. Therefore, when the high-temperature resistant ceramic coating slurry is coated on the surface of the porous isolation membrane and dried to form a film, the ceramic coating forms a support and heat-resistant structural skeleton with a heat-resistant PAA skeleton on the surface of the porous isolation membrane, and at the same time forms a heat-resistant bonding system at the interface between the porous isolation membrane and the ceramic particles, so that the ceramic coating meets the performance requirements of 180°C / 30min and the thermal shrinkage of the membrane is less than 3%.

[0057] References to "first," "second," "third," "fourth," and the like (if any) herein are intended to distinguish similar objects and are not necessarily intended to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions, e.g., a process, method, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, or apparatus.

[0058] It should be noted that the descriptions of "first", "second", etc. in this application are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0059] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A high temperature resistant ceramic coating slurry, characterized in that: include: Ceramic particles, PAA binder, Composite emulsion, Wetting agents, and water as a solvent; The added 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 added mass percentage of the ceramic particles is 30-50%.

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

3. The high temperature resistant ceramic coating slurry according to claim 2, characterized in that: The ceramic particles are ground by high-energy ball milling, wherein the metal oxide is placed in a ball mill, anhydrous ethanol is used as a 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 is performed for 8-12 hours to obtain ground ceramic particles.

4. The high temperature resistant ceramic coating slurry according to claim 3, characterized in that: The invention also includes modifying the ground ceramic particles, and the modification method includes the steps of ① adding the ground ceramic particles to a toluene solvent and ultrasonically dispersing them for 15-20 minutes to obtain a ceramic dispersion; ② adding a silane coupling agent in an amount of 1-3% by mass of the ground ceramic particles to the ceramic dispersion, controlling the reaction temperature to 60-80°C for modification treatment for 2-3 hours, washing with ethanol, and then drying at 75-85°C for 4-6 hours to obtain modified ceramic particles; and ③ adding tetrabutyl titanate, Anhydrous ethanol and deionized water are mixed in a volume ratio of 1:4.5-5.5:1.8-2.2, stirred evenly, and then nitric acid is added to adjust the pH to 2-3 to prepare a TiO2 sol, and then the modified ceramic particles are added to the TiO2 sol and ultrasonically dispersed evenly to obtain an adsorption sol; step ④ is to place the adsorption sol at 55-65°C to dry to form a gel layer, and then calcined the gel layer at 450-550°C for 1.8-2.2 hours to obtain ceramic particles with a surface coated with a nano-TiO2 coating.

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

6. The high temperature resistant ceramic coating slurry according to claim 5, characterized in that: The invention also includes a composite treatment of the PAA binder, and the composite treatment method includes the steps of ① ultrasonically dispersing the nano-montmorillonite into deionized water to obtain a montmorillonite dispersion; ② adding the PAA binder to the montmorillonite dispersion and stirring evenly to obtain a mixed dispersion; and ③ controlling the temperature to 55-65° C. to vacuum dry the mixed dispersion to obtain a PAA / nano-montmorillonite composite material.

7. The high temperature resistant ceramic coating slurry according to claim 1, characterized in that: 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 50cp, and the addition ratio of polyacrylic acid, polyacrylamide and styrene-butadiene rubber is 1:(0.9-1.1):(0.9-1.1).

8. The high temperature resistant ceramic coating slurry according to claim 1, characterized in that: The wetting agent is a silicone ether wetting agent.

9. An application of a high temperature resistant ceramic coating slurry, characterized by: The method comprises mixing a high-temperature resistant ceramic coating slurry as described in any one of claims 1 to 8 with an initiator in an amount of 1-1.2% by mass of ceramic particles, coating the slurry on a porous isolation membrane, and curing the slurry at a high temperature of 55-65° C. to form a ceramic coating.

10. The use of a high temperature resistant ceramic coating slurry according to claim 9, characterized in that: The ceramic coating includes ceramic particles, a heat-resistant PAA skeleton and a composite. The ceramic coating has a thickness of 3-20 μm, an air permeability of 10-500 s / 100 ml, a high temperature resistance of 180° C. / 30 min, and a thermal shrinkage of MD <3% and TD <3%.

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