Fireproof and heat-insulating nanoceramic coating for lithium battery and preparation method thereof

Abstract

The application belongs to the technical field of paint preparation, and provides a fireproof and heat-insulating nano ceramic paint for lithium batteries and a preparation method thereof. The paint is a water-based two-component system. The first component is constructed by bisphenol A diglycidyl ether, compounded colloidal silicon dioxide, boehmite and nano zirconium oxide and / or nano aluminum oxide to form a ceramic framework, combined with aerogel, hollow glass microbeads, expanded vermiculite and / or flaky mica and inorganic fibers to form a heat-insulating network. The fire-retardant system contains ammonium polyphosphate, pentaerythritol, melamine components, zinc borate and sealing glass powder, and introduces silane interface bonding components and thermal expansion microspheres. When heated, an expanded heat-insulating layer is formed and densified into a hard shell at high temperature. The second component is a water-dispersed amine curing agent. The interface bonding components are added step by step, and the inorganic phase and the fire-retardant and heat-insulating phase are compounded in sequence to obtain a two-component packaged paint, which is suitable for the safety protection of lithium battery systems.

Description

Technical Field

[0001] This invention belongs to the field of coating preparation technology, and relates to a fireproof and heat-insulating nano-ceramic coating for lithium batteries and its preparation method. Background Technology

[0002] When lithium-ion batteries are used under conditions of high energy density and compact integration, they may experience localized overheating and thermal runaway due to factors such as external heat sources, mechanical damage, electrical abuse, or internal defects. This can easily trigger chain reactions and expand the scope of accidents. Existing coating systems for battery protection mainly include two categories: organic flame-retardant coatings and inorganic fire-resistant coatings. Organic coatings mostly use resins such as epoxy, acrylic, or polyurethane as the film-forming matrix, combined with an intumescent flame-retardant system to form an expanded char layer to block heat and oxygen. However, under the conditions of high-temperature flames and high-speed jet airflow, the expanded char layer is prone to pulverization, cracking, and peeling, resulting in insufficient structural strength of the heat insulation layer. At the same time, the organic matrix is ​​prone to softening and decomposition at high temperatures, leading to a decrease in coating integrity and adhesion, making it difficult to maintain a stable barrier in thermal shock and continuous burning environments.

[0003] Inorganic refractory coatings typically employ silicate, phosphate, or sol-gel systems, exhibiting good high-temperature resistance. However, they often suffer from brittleness, insufficient toughness, and insufficient impact resistance. After thermal cycling, microcracks easily appear and propagate along the interface, weakening the insulation effect. Furthermore, inorganic fillers tend to agglomerate and settle in aqueous systems, causing fluctuations in application and defects in the film. To improve insulation performance, some systems introduce lightweight insulating fillers such as aerogel powder, hollow microspheres, or layered minerals. However, high specific surface area materials like aerogels are easily wetted by resin and fill pores, leading to damage to the insulating pore structure and increased system viscosity. The use of multiple fillers can also result in poor compatibility, difficulty in dispersion, and weak interfacial bonding. On the other hand, in order to improve the resistance to erosion and pulverization in the fire, some schemes have tried to introduce ceramicizable components such as glass powder to form a hard shell structure at high temperatures. However, if there is a lack of synergistic design with the ceramic skeleton and interface chemical bonding, the softening flow of the glass phase may lead to shrinkage cracks or poor bonding with the expanded carbon layer, making it difficult to form a continuous and dense protective layer. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries and its preparation method. The coating is an aqueous two-component system. Component A uses an epoxy resin aqueous dispersion as the matrix, compounded with colloidal silica, boehmite, and nano-oxides, and introduces aerogel, hollow glass microspheres, and layered fillers to construct a heat-insulating structure. It is combined with a polyphosphate-pentaerythritol-melamine flame retardant system, zinc borate, and sealing glass powder to achieve thermal ceramization. Combined with silane interfacial bonding and thermally expanding microspheres, it forms an expandable heat-insulating layer and a hard shell, thereby meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries, wherein the coating is a water-based two-component coating comprising component A and component B;

[0007] Component A includes bisphenol A diglycidyl ether, colloidal silica, nano-ceramic framework, lightweight thermal insulation filler, intumescent flame retardant reaction package, zinc borate, interfacial bonding components, thermally expanding microspheres, low melting point glass powder, water-based additives, and water.

[0008] Component B is a water-dispersible amine curing agent;

[0009] The nano-ceramic framework includes boehmite, nano-zirconia, and nano-alumina.

[0010] The lightweight thermal insulation filler includes silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica, and chopped inorganic fibers;

[0011] The intumescent flame retardant reaction package includes ammonium polyphosphate, pentaerythritol, melamine, and melamine polyphosphate;

[0012] The silica aerogel powder is obtained by reacting n-octadecyltriethoxysilane with the silanol groups on the surface of silica aerogel.

[0013] The aqueous additives include dispersants, wetting agents, defoamers, thickeners, thixotropic anti-settling agents, pH adjusters, and preservatives.

[0014] Preferably, the mass ratio of bisphenol A diglycidyl ether, colloidal silica, nano-ceramic framework, lightweight thermal insulation filler, intumescent flame retardant reaction package, zinc borate, interfacial bonding component, thermally expanding microspheres, low melting point glass powder, water-based additives and water in component A is (10-18):(4-8):(8-16):(25-45):(12-24):(1-4):(0.2-1.5):(0.3-2):(2-12):(1-6):(20-60); and the mass fraction of component B is 40-60 wt.%.

[0015] Preferably, the interfacial bonding component is γ-aminopropyltriethoxysilane and / or γ-glycidyl etherpropyltrimethoxysilane.

[0016] Preferably, the low-melting-point glass powder is a sealing glass powder containing at least three oxides selected from SiO2, B2O3, ZnO, and Al2O3; the softening point of the sealing glass powder is 350-550℃; and the length of the chopped fibers is 1-6 mm and the diameter is 7-15 μm.

[0017] Preferably, the mass ratio of boehmite, nano-zirconia, and nano-alumina in the nano-ceramic framework is 1:1:1; and the mass ratio of silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica, and chopped inorganic fibers in the lightweight thermal insulation filler is 0.3:1:0.7:1:0.5.

[0018] Preferably, the mass ratio of ammonium polyphosphate, pentaerythritol, melamine, and melamine polyphosphate in the intumescent flame retardant reaction package is 6:2:1:1; and the mass ratio of dispersant, wetting agent, defoamer, thickener, thixotropic anti-settling agent, pH adjuster, and preservative in the water-based additives is 4:2:1:3:3:1:1.

[0019] Preferably, the dispersant is selected from one or more of sodium polyacrylate, sodium polymethacrylate, ammonium polyacrylate, sodium hexametaphosphate, sodium polyaspartate, and polycarboxylate dispersants.

[0020] Preferably, the wetting agent is selected from one or more of alkyl glycosides, fatty alcohol polyoxyethylene ethers, polyoxyethylene-polyoxypropylene block copolymers, and 2,4,7,9-tetramethyl-5-decyn-4,7-diol.

[0021] Preferably, the defoamer is selected from one or more of polydimethylsiloxane emulsion, polyether-modified polysiloxane, mineral oil defoamer, and hydrophobic silica.

[0022] Preferably, the thickener is selected from one or more of hydroxyethyl cellulose, hydroxypropyl methyl cellulose, xanthan gum, polyurethane associative thickeners, and cross-linked polyacrylic acid.

[0023] Preferably, the thixotropic antisettling agent is selected from one or more of attapulgite, sepiolite, bentonite, and fumed silica.

[0024] Preferably, the pH adjuster is selected from one or more of ammonia, triethylamine, 2-amino-2-methyl-1-propanol and sodium hydroxide.

[0025] Preferably, the preservative is selected from one or more of 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

[0026] Preferably, the water-dispersible amine curing agent is an amine curing agent with water as the dispersion medium, and the amine active component of the amine curing agent includes one or more of isophorone diamine, diethylenetriamine, triethylenetetramine, m-xylenediamine, 4,4'-diaminodicyclohexylmethane, polyoxypropylene diamine, and trimethylolpropane polyoxypropylene triamine.

[0027] Secondly, the present invention provides a method for preparing a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries, specifically comprising:

[0028] S1, add water-based additives to water and mix, then add colloidal silica and some interfacial bonding components, keep at 40-90℃ for 0.5-3h, then add boehmite, nano-zirconia and nano-alumina at 1500-4000rpm to obtain inorganic nano slurry;

[0029] S2, silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica and short-cut inorganic fibers are added sequentially to the inorganic nano slurry under conditions of 200-1000 rpm to obtain a thermal insulation filler composite slurry.

[0030] S3, under conditions of 200-1200 rpm, add ammonium polyphosphate, pentaerythritol, melamine, melamine polyphosphate, zinc borate and low melting point glass powder to the heat insulation filler composite slurry and mix evenly to obtain flame retardant heat insulation base material.

[0031] S4, Bisphenol A diglycidyl ether is added to the flame-retardant and heat-insulating base material at 200-1200 rpm, the remaining interfacial bonding components and thermally expanded microspheres are added and mixed to obtain component A; component A and component B are packaged separately to obtain a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries.

[0032] Preferably, the method for preparing the silica aerogel powder is as follows: silica aerogel is added to anhydrous ethanol and stirred at 300-800 rpm for 20-40 min to obtain a suspension. Octadecyltriethoxysilane and glacial acetic acid are added to the suspension and kept at 60-80℃ for 2-4 h. The mixture is filtered and washed to obtain a wet solid phase. The wet solid phase is dried at 80-120℃ for 4-12 h to obtain silica aerogel powder. The mass ratio of silica aerogel, anhydrous ethanol, octadecyltriethoxysilane and glacial acetic acid is 100:(400-600):(5-15):(0.5-2).

[0033] Preferably, the amount of the interfacial bonding component in S1 is 50-70% of the total mass of the interfacial bonding component.

[0034] The main chemical processes in the room-temperature curing stage of the coating system involve the parallel occurrence of amine curing and silane hydrolysis-condensation reactions. The amine curing agent in component B provides active hydrogen from the primary / secondary amines, which undergoes nucleophilic ring-opening addition with the epoxy groups in the epoxy resin aqueous dispersion of component A, forming β-hydroxyamine bonds and initiating further crosslinking to obtain a three-dimensional network containing hydroxyl and ether bonds. γ-aminopropyltriethoxysilane and / or γ-glycidyl etherpropyltrimethoxysilane can undergo alkoxy hydrolysis in the aqueous phase to generate silanols. These silanols condense with each other and with silanols on the surface of colloidal silica to form Si-O-Si bonds. Simultaneously, the amino groups in the silane molecules can react with epoxy groups, and the glycidyl ether groups can participate in the ring-opening process of amine curing, thereby forming covalent or condensation bonds between the inorganic phase surface and the organic crosslinking network. The hydroxyl groups on the surface of boehmite and nano-alumina / zirconia can also condense with silanols to form Si-O-Al or Si-OM bonds, changing the interfacial polarity and bonding mode. The result of this stage is the formation of an interfacial structure with chemical connections and hydrogen bonding between the organic cross-linked network, the silicon-oxygen network and the hydroxyl-containing inorganic surface, which inhibits the secondary aggregation of fillers in the aqueous system and reduces the defect density at the phase interface.

[0035] The main chemical processes during the heating stage consist of the acid-carbon-gas source reaction of the intumescent flame-retardant system, the dehydration and transformation of inorganic components, and the softening flow and secondary condensation of the glassy phase. Ammonium polyphosphate, upon heating, produces metaphosphoric acid / polyphosphoric acid and provides an acidic catalytic environment, undergoing esterification and dehydration with pentaerythritol, promoting the transformation of oxygen-containing organic structures into carbon-rich structures. Melamine and melamine polyphosphate decompose, releasing nitrogen-containing small molecules and participating in the condensation of phosphorus and nitrogen structures. The gaseous products expand in the viscous phosphate-esterified molten phase, forming a phosphorus-nitrogen-containing expanded carbon layer. Zinc borate undergoes dehydration during heating, forming a borate / boron-oxygen network, which can blend or react with the phosphate phase and glassy phase, altering the inorganic phase composition of the carbon layer surface. Boehmite undergoes thermal dehydroxylation to generate alumina and release water. The aqueous product participates in gas-phase dilution, while the newly generated alumina surface provides Lewis acidic sites that can bond with silanols or the glass phase. Colloidal silica further condenses and densifies at high temperatures, forming a continuous Si-O-Si network. The sealing glass powder softens and flows after reaching the softening range, wetting and coating the surface of the expanded carbon layer and the inorganic filler. The glass phase undergoes ion diffusion and structural rearrangement with SiO2, Al2O3, and zirconium / alumina particles in the system, forming a borosilicate or aluminosilicate glass-ceramic phase. Nano-zirconia / alumina, as a high-temperature stable phase, participates in the necking between particles and the liquid-phase sintering process, limiting excessive flow of the glass phase and providing connection points for the inorganic framework. Thermally expanding microspheres undergo shell softening and internal volatile component expansion in the lower temperature range, forming a closed pore structure and altering the heat transfer path. Silica aerogel and hollow glass microspheres provide a porous structure with low solid-phase thermal conductivity. When heated, the flaky mica / expanded vermiculite undergoes interlayer water removal and lamellar unfolding, further introducing layered pores. Inorganic fibers and lamellar fillers form a through-phase in the carbon layer and glass-ceramic phase, providing continuous physical support and deflecting crack propagation paths. The above reactions and phase transformations enable the coating to form a thermal barrier composed of a porous insulating phase and a dense inorganic phase on the surface.

[0036] Compared with existing technologies, the beneficial effects of this invention are as follows: The fireproof and heat-insulating nano-ceramic coating provided by this invention is a water-based two-component system. It uses an epoxy resin aqueous dispersion and a water-dispersible amine curing agent. An inorganic framework is constructed through colloidal silica, boehmite, and nano-oxides. Silane interfacial bonding components are used to promote the combination of inorganic phase and organic network, reducing interfacial defects and sedimentation / stratification tendency of the multiphase system, and improving the structural integrity and heat resistance stability of the coating. In the heat-insulating filler, aerogel powder, hollow glass microspheres, and layered minerals synergistically form a porous heat-insulating structure with inorganic fibers, changing the heat transfer path and inhibiting rapid heat transfer. The intumescent flame-retardant system and thermally expandable microspheres form an intumescent heat-insulating layer during heating, limiting the direct effect of flame and thermal radiation on the substrate. The sealing glass powder and ceramic components soften, wet, and densify at high temperatures, promoting the formation of a continuous inorganic protective phase on the carbon layer surface, enhancing the coating's retention capacity under thermal shock and airflow scouring conditions, thereby maintaining the continuity and reliability of the heat insulation barrier. Attached Figure Description

[0037] Figure 1 This is a SEM image of the cross-section of the fireproof and heat-insulating nano-ceramic coating after a flame impact resistance test, provided in Embodiment 1 of the present invention. Detailed Implementation

[0038] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0039] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0040] Example 1

[0041] This embodiment provides a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries and its preparation method, specifically including:

[0042] The coating is a water-based two-component coating, comprising component A and component B;

[0043] Component A comprises bisphenol A diglycidyl ether, colloidal silica, nano-ceramic framework, lightweight thermal insulation filler, intumescent flame retardant reaction package, zinc borate, interfacial bonding component γ-aminopropyltriethoxysilane, thermally expandable microspheres, low melting point glass powder, water-based additives, and water, in a mass ratio of 10:6:16:30:22:2:0.5:2:11.5:3:50;

[0044] The nano-ceramic framework comprises boehmite, nano-zirconia, and nano-alumina in a mass ratio of 1:1:1.

[0045] The lightweight thermal insulation filler comprises silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica, and chopped inorganic fibers in a mass ratio of 0.3:1:0.7:1:0.5; the chopped fibers have a length of 1 mm and a diameter of 7 μm.

[0046] The intumescent flame retardant reaction package comprises ammonium polyphosphate, pentaerythritol, melamine, and melamine polyphosphate in a mass ratio of 6:2:1:1.

[0047] The low-melting-point glass powder is a sealing glass powder containing B2O3, ZnO and Al2O3 in a mass ratio of 1:1:1; the softening point of the sealing glass powder is 350℃.

[0048] The aqueous additives include dispersant sodium polyacrylate, wetting agent alkyl glycoside, defoamer polydimethylsiloxane emulsion, thickener hydroxyethyl cellulose, thixotropic anti-settling agent attapulgite, pH adjuster 25 wt.% ammonia water, and preservative 1,2-benzisothiazolin-3-one, in a mass ratio of 4:2:1:3:3:1:1;

[0049] Component B is an amine curing agent with water as the dispersion medium, and the active amine component is isophorone diamine with a mass fraction of 40 wt.%.

[0050] The preparation method specifically includes:

[0051] S1. Prepare the above-mentioned water-based additives according to the proportion, add them to water and mix, then add 30 wt.% of colloidal silica, add 50% of the total mass of the interfacial bonding components, keep at 40°C for 3 hours, and then stir at 4000 rpm to add boehmite, nano-zirconia and nano-alumina to obtain inorganic nano slurry.

[0052] S2, silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica and chopped inorganic fibers are added sequentially to the inorganic nano slurry at 200 rpm to obtain a thermal insulation filler composite slurry;

[0053] S3, under conditions of 200 rpm, ammonium polyphosphate, pentaerythritol, melamine, melamine polyphosphate, zinc borate and low melting point glass powder are stirred and added to the heat insulation filler composite slurry and mixed evenly to obtain flame retardant heat insulation base material;

[0054] S4, Bisphenol A diglycidyl ether, the remaining interfacial bonding components and thermally expanded microspheres are added to the flame-retardant and heat-insulating base material under stirring at 200 rpm and mixed to obtain component A; component A and the above component B are packaged separately to obtain a fireproof and heat-insulating nano-ceramic coating for lithium batteries.

[0055] The preparation method of the silica aerogel powder described in S2 is as follows: silica aerogel is added to anhydrous ethanol and stirred at 300 rpm for 40 min to obtain a suspension. Octadecyltriethoxysilane and glacial acetic acid are added to the suspension and kept at 60°C for 4 h. The suspension is filtered and washed to obtain a wet solid phase. The wet solid phase is dried at 80°C for 12 h to obtain silica aerogel powder. The mass ratio of silica aerogel, anhydrous ethanol, octadecyltriethoxysilane and glacial acetic acid is 100:400:5:0.5.

[0056] Figure 1 The image shows a cross-sectional SEM image of the fireproof and heat-insulating nano-ceramic coating after a flame impact resistance test. The coating cross-section shows a structure in which a porous expanded carbon layer and a dense inorganic ceramic skeleton coexist, and aerogel and hollow microspheres form continuous heat-insulating pores.

[0057] Example 2

[0058] This embodiment provides a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries and its preparation method, specifically including:

[0059] The coating is a water-based two-component coating, comprising component A and component B;

[0060] Component A comprises bisphenol A diglycidyl ether, colloidal silica, nano-ceramic framework, lightweight thermal insulation filler, intumescent flame retardant reaction package, zinc borate, interfacial bonding component γ-aminopropyltriethoxysilane, thermally expandable microspheres, low melting point glass powder, water-based additives, and water, in a mass ratio of 18:4:12:25:24:3:1.5:0.5:12:4:45;

[0061] The nano-ceramic framework comprises boehmite, nano-zirconia, and nano-alumina in a mass ratio of 1:1:1.

[0062] The lightweight thermal insulation filler comprises silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica, and chopped inorganic fibers in a mass ratio of 0.3:1:0.7:1:0.5; the chopped fibers have a length of 6 mm and a diameter of 15 μm.

[0063] The intumescent flame retardant reaction package comprises ammonium polyphosphate, pentaerythritol, melamine, and melamine polyphosphate in a mass ratio of 6:2:1:1.

[0064] The low-melting-point glass powder is a sealing glass powder containing SiO2, ZnO and Al2O3 in a mass ratio of 1:1:1; the softening point of the sealing glass powder is 550℃.

[0065] The water-based additives contain a polycarboxylate dispersant, a wetting agent 2,4,7,9-tetramethyl-5-decyn-4,7-diol, a mineral oil defoamer, a polyurethane associative thickener, a thixotropic antisettling agent fumed silica, a pH adjuster 2-amino-2-methyl-1-propanol, and a preservative 2-methyl-4-isothiazolin-3-one in a mass ratio of 4:2:1:3:3:1:1.

[0066] Component B is an amine curing agent with water as the dispersion medium, and the active amine component is 4,4'-diaminodicyclohexylmethane with a mass fraction of 60 wt.%.

[0067] The preparation method specifically includes:

[0068] S1. Prepare the above-mentioned water-based additives according to the proportion, add them to water and mix, then add 30 wt.% of colloidal silica and 70% of the total mass of the interfacial bonding components. Keep at 90°C for 0.5 h, then stir at 1500 rpm and add boehmite, nano-zirconia and nano-alumina to obtain inorganic nano slurry.

[0069] S2, silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica and chopped inorganic fibers are added sequentially to the inorganic nano slurry at 1000 rpm to obtain a thermal insulation filler composite slurry;

[0070] S3, under conditions of 1200 rpm, ammonium polyphosphate, pentaerythritol, melamine, melamine polyphosphate, zinc borate and low melting point glass powder are stirred and added to the heat insulation filler composite slurry and mixed evenly to obtain flame retardant heat insulation base material.

[0071] S4, Bisphenol A diglycidyl ether, the remaining interfacial bonding components and thermally expanded microspheres are added to the flame-retardant and heat-insulating base material under stirring at 1200 rpm and mixed to obtain component A; component A and component B are packaged separately to obtain a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries.

[0072] The preparation method of the silica aerogel powder described in S2 is as follows: silica aerogel is added to anhydrous ethanol and stirred at 800 rpm for 20 min to obtain a suspension. Octadecyltriethoxysilane and glacial acetic acid are added to the suspension and kept at 80°C for 2 h. The suspension is filtered and washed to obtain a wet solid phase. The wet solid phase is dried at 120°C for 4 h to obtain silica aerogel powder. The mass ratio of silica aerogel, anhydrous ethanol, octadecyltriethoxysilane and glacial acetic acid is 100:600:15:2.

[0073] Example 3

[0074] This embodiment provides a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries and its preparation method, specifically including:

[0075] The coating is a water-based two-component coating, comprising component A and component B;

[0076] Component A comprises bisphenol A diglycidyl ether, colloidal silica, nano-ceramic framework, lightweight thermal insulation filler, intumescent flame retardant reaction package, zinc borate, interfacial bonding component γ-glycidyl ether propyltrimethoxysilane, thermally expandable microspheres, low melting point glass powder, water-based additives, and water, in a mass ratio of 14:8:8:45:12:4:0.2:1:7.8:5:60;

[0077] The nano-ceramic framework comprises boehmite, nano-zirconia, and nano-alumina in a mass ratio of 1:1:1.

[0078] The lightweight thermal insulation filler comprises silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica, and chopped inorganic fibers in a mass ratio of 0.3:1:0.7:1:0.5; the chopped fibers have a length of 3 mm and a diameter of 10 μm.

[0079] The intumescent flame retardant reaction package comprises ammonium polyphosphate, pentaerythritol, melamine, and melamine polyphosphate in a mass ratio of 6:2:1:1.

[0080] The low-melting-point glass powder is a sealing glass powder containing SiO2, B2O and Al2O3 in a mass ratio of 1:1:1; the softening point of the sealing glass powder is 450℃.

[0081] The aqueous additives include dispersant sodium hexametaphosphate, wetting agent fatty alcohol polyoxyethylene ether, defoamer polyether modified polysiloxane, thickener xanthan gum, thixotropic anti-settling agent sepiolite, pH adjuster triethylamine, and preservative 1,2-benzisothiazolin-3-one, in a mass ratio of 4:2:1:3:3:1:1;

[0082] Component B is an amine curing agent with water as the dispersion medium, and the active amine component is m-xylenediamine with a mass fraction of 50 wt.%.

[0083] The preparation method specifically includes:

[0084] S1. Prepare the above-mentioned water-based additives according to the proportion, add them to water and mix, then add 30 wt.% of colloidal silica, add 60% of the total mass of the interfacial bonding components, keep at 65°C for 1.5 h, and then add boehmite, nano-zirconia and nano-alumina by stirring at 2500 rpm to obtain inorganic nano slurry.

[0085] S2, silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica and chopped inorganic fibers are added sequentially to the inorganic nano slurry at 500 rpm to obtain a thermal insulation filler composite slurry;

[0086] S3, under conditions of 800 rpm, ammonium polyphosphate, pentaerythritol, melamine, melamine polyphosphate, zinc borate and low melting point glass powder are stirred and added to the heat insulation filler composite slurry and mixed evenly to obtain flame retardant heat insulation base material;

[0087] S4, Bisphenol A diglycidyl ether, the remaining interfacial bonding components and thermally expanded microspheres are added to the flame-retardant and heat-insulating base material under stirring at 800 rpm and mixed to obtain component A; component A and component B are packaged separately to obtain a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries.

[0088] The preparation method of the silica aerogel powder described in S2 is as follows: silica aerogel is added to anhydrous ethanol and stirred at 500 rpm for 30 min to obtain a suspension. Octadecyltriethoxysilane and glacial acetic acid are added to the suspension and kept at 70°C for 3 h. The suspension is filtered and washed to obtain a wet solid phase. The wet solid phase is dried at 100°C for 8 h to obtain silica aerogel powder. The mass ratio of silica aerogel, anhydrous ethanol, octadecyltriethoxysilane and glacial acetic acid is 100:500:10:1.2.

[0089] Example 4

[0090] This embodiment provides a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries and its preparation method, specifically including:

[0091] The coating is a water-based two-component coating, comprising component A and component B;

[0092] Component A comprises bisphenol A diglycidyl ether, colloidal silica, nano-ceramic framework, lightweight thermal insulation filler, intumescent flame retardant reaction package, zinc borate, interfacial bonding component γ-glycidyl ether propyltrimethoxysilane, thermally expandable microspheres, low melting point glass powder, water-based additives, and water, in a mass ratio of 16:5:14:40:19:1:1:0.3:3.7:2:55;

[0093] The nano-ceramic framework comprises boehmite, nano-zirconia, and nano-alumina in a mass ratio of 1:1:1.

[0094] The lightweight thermal insulation filler comprises silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica, and chopped inorganic fibers in a mass ratio of 0.3:1:0.7:1:0.5; the chopped fibers have a length of 4 mm and a diameter of 12 μm.

[0095] The intumescent flame retardant reaction package comprises ammonium polyphosphate, pentaerythritol, melamine, and melamine polyphosphate in a mass ratio of 6:2:1:1.

[0096] The low-melting-point glass powder is a sealing glass powder containing SiO2, B2O3, ZnO and Al2O3 in a mass ratio of 1:1:1:1; the softening point of the sealing glass powder is 500℃.

[0097] The aqueous additives include dispersant sodium polyaspartate, wetting agent polyoxyethylene-polyoxypropylene block copolymer, defoamer hydrophobic silica, thickener crosslinked polyacrylic acid, thixotropic antisettling agent bentonite, pH adjuster sodium hydroxide, and preservative 2-methyl-4-isothiazolin-3-one, in a mass ratio of 4:2:1:3:3:1:1;

[0098] Component B is an amine curing agent with water as the dispersion medium, and the active amine component is polyoxypropylene diamine with a mass fraction of 55 wt.%.

[0099] The preparation method specifically includes:

[0100] S1. Prepare the above-mentioned water-based additives according to the proportion, add them to water and mix, then add 30 wt.% colloidal silica, add 65% of the total mass of the interfacial bonding components, keep at 80°C for 1 h, and then add boehmite, nano-zirconia and nano-alumina by stirring at 3000 rpm to obtain inorganic nano slurry.

[0101] S2, silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica and chopped inorganic fibers are added sequentially to the inorganic nano slurry at 600 rpm to obtain a thermal insulation filler composite slurry;

[0102] S3, under conditions of 600 rpm, ammonium polyphosphate, pentaerythritol, melamine, melamine polyphosphate, zinc borate and low melting point glass powder are stirred and added to the heat insulation filler composite slurry and mixed evenly to obtain flame retardant heat insulation base material.

[0103] S4, Bisphenol A diglycidyl ether, the remaining interfacial bonding components and thermally expanded microspheres are added to the flame-retardant and heat-insulating base material under stirring at 600 rpm and mixed to obtain component A; component A and the above component B are packaged separately to obtain a fireproof and heat-insulating nano-ceramic coating for lithium batteries.

[0104] The preparation method of the silica aerogel powder described in S2 is as follows: silica aerogel is added to anhydrous ethanol and stirred at 600 rpm for 35 min to obtain a suspension. Octadecyltriethoxysilane and glacial acetic acid are added to the suspension and kept at 75°C for 2.5 h. The suspension is filtered and washed to obtain a wet solid phase. The wet solid phase is dried at 90°C for 10 h to obtain silica aerogel powder. The mass ratio of silica aerogel, anhydrous ethanol, octadecyltriethoxysilane and glacial acetic acid is 100:450:8:1.5.

[0105] Comparative Example 1

[0106] This comparative example provides a fireproof and heat-insulating nano-ceramic coating for lithium batteries and its preparation method. The difference between this example and Example 1 is that in step S3, a lightweight heat-insulating filler is used to replace the low-melting-point glass powder by mass. Other process parameters and operating conditions are exactly the same as in Example 1.

[0107] Comparative Example 2

[0108] This comparative example provides a fireproof and heat-insulating nano-ceramic coating for lithium batteries and its preparation method. The difference between this example and Example 1 is that unmodified silica aerogel is directly used in the lightweight heat-insulating filler. Other process parameters and operating conditions are exactly the same as in Example 1.

[0109] Comparative Example 3

[0110] This comparative example provides a fireproof and heat-insulating nano-ceramic coating for lithium batteries and its preparation method. The difference between this example and Example 1 is that an inorganic network precursor is used to replace the interfacial bonding components in steps S1 and S4. Other process parameters and operating conditions are exactly the same as in Example 1.

[0111] Test method:

[0112] Curing steps: Component B was added to component A at a mass ratio of 10:3 (bisphenol A diglycidyl ether to component B) and mixed evenly. The mixture was then allowed to stand to defoam. The resulting mixed coating was applied to the substrate surface to form a film. After leveling at room temperature, the coating was pre-dried at 60°C for 30 min, then cured at 80°C for 2 h. After curing, the coating was placed at 25°C for 24 h to obtain the cured coating sample as the test object.

[0113] The flame impact resistance test method is as follows: Prepare a cured coating sample according to the curing steps. After the film is formed on a metal plate as the substrate and completely cured, place the coating surface of the sample directly facing the burner flame. The distance from the burner nozzle to the coating surface is fixed at 50 mm. The center of the flame is aligned with the center of the sample and the angle is maintained at 90°. After ignition, the flame is continuously sprayed onto the coating surface for 15 minutes. The judgment criteria are: if a through hole appears during the flame impact and flame or high-temperature gas flow can be observed continuously spraying from the back, or if a through hole appears that allows the flame to directly penetrate, it is judged as burn-through and the burn-through time is recorded; if it does not burn-through within 15 minutes, it is judged as qualified.

[0114] The thermal shock resistance test method is as follows: Prepare the cured coating sample according to the curing steps, place the sample in a two-temperature zone thermal shock chamber, and cycle between -40℃ and 120℃. Each cycle is set to hold at -40℃ for 30 minutes, then transfer to 120℃ and hold at 120℃ for 30 minutes, and then transfer back to -40℃. Each transfer time does not exceed 5 minutes, and a total of 30 cycles are performed. After the cycle is completed, place the sample at 25℃ for 2 hours and then perform a visual inspection. The judgment criterion is: after the cycle is completed and the recovery is completed, the coating is deemed to be qualified if no appearance defects (cracks, blistering, peeling, delamination) are found.

[0115] The test method for thermal conductivity is GB / T 10295-2008.

[0116] The method for testing electrolyte resistance is as follows: Prepare a cured coating sample according to the curing steps, and completely immerse the sample in a sealed container in 1M LiPF6 / EC (ethylene carbonate):DMC (dimethyl carbonate) (volume ratio 1:1) electrolyte solution. Soak the sample at 25℃ for 72 hours. After soaking, quickly rinse the surface with DMC to remove residual liquid and dry it. Then, conduct a visual inspection. The judgment criteria are: the coating is considered qualified if it does not soften, crack, blister, peel off or delaminate after soaking.

[0117] The test results of fireproof and heat-insulating nano-ceramic coatings for lithium batteries in Examples 1-4 and Comparative Examples 1-3 are shown in Table 1.

[0118] Table 1. Test results of fire-retardant and heat-insulating nano-ceramic coatings used in lithium batteries for Examples 1-4 and Comparative Examples 1-3.

[0119]

[0120] As shown in Table 1, compared with Example 1, Comparative Example 1 showed decreased flame impact resistance, decreased thermal shock resistance, unchanged thermal conductivity, and decreased electrolyte resistance; Comparative Example 2 showed decreased flame impact resistance, decreased thermal shock resistance, increased thermal conductivity, and decreased electrolyte resistance; and Comparative Example 3 showed decreased flame impact resistance, decreased thermal shock resistance, increased thermal conductivity, and decreased electrolyte resistance.

[0121] This is because Comparative Example 1 did not include sealing glass powder, resulting in a lack of bonding and liquid-phase sintering between the molten, relatively expanded carbon layer and boehmite / zirconia at high temperatures. Consequently, a dense, continuous ceramicized hard shell was difficult to form on the carbon layer surface, leading to erosion and the appearance of through-holes during flame erosion, thus shortening the burn-through time. In Comparative Example 2, the aerogel was not hydrophobically modified, making it easier for the epoxy dispersion to enter and partially fill the aerogel channels during mixing and curing. This decreased porosity led to an increase in thermal conductivity, and further solvent penetration and swelling during electrolyte immersion resulted in softening, whitening, and localized cracking and blistering. In Comparative Example 3, no silane interface bonding components were added, resulting in primarily physical embedding of inorganic particles and the epoxy network, leading to particle agglomeration and increased interfacial porosity. The thermal stress generated by thermal shock cycling concentrated at the interface, easily inducing delamination and peeling.

[0122] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A fire-retardant and heat-insulating nano-ceramic coating for lithium batteries, characterized in that, The coating is a water-based two-component coating, comprising component A and component B; Component A includes bisphenol A diglycidyl ether, colloidal silica, nano-ceramic framework, lightweight thermal insulation filler, intumescent flame retardant reaction package, zinc borate, interfacial bonding components, thermally expanding microspheres, low melting point glass powder, water-based additives, and water. Component B is a water-dispersible amine curing agent; The nano-ceramic framework includes boehmite, nano-zirconia, and nano-alumina. The lightweight thermal insulation filler includes silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica, and chopped inorganic fibers; The intumescent flame retardant reaction package includes ammonium polyphosphate, pentaerythritol, melamine, and melamine polyphosphate; The silica aerogel powder is obtained by reacting n-octadecyltriethoxysilane with the silanol groups on the surface of silica aerogel. The aqueous additives include dispersants, wetting agents, defoamers, thickeners, thixotropic anti-settling agents, pH adjusters, and preservatives; The mass ratio of bisphenol A diglycidyl ether, colloidal silica, nano-ceramic framework, lightweight thermal insulation filler, intumescent flame retardant reaction package, zinc borate, interfacial bonding component, thermally expanding microspheres, low melting point glass powder, water-based additives and water in component A is (10-18):(4-8):(8-16):(25-45):(12-24):(1-4):(0.2-1.5):(0.3-2):(2-12):(1-6):(20-60); the mass fraction of component B is 40-60 wt.%.

2. The fire-retardant and heat-insulating nano-ceramic coating for lithium batteries according to claim 1, characterized in that, The interfacial bonding component is γ-aminopropyltriethoxysilane and / or γ-glycidyl ether propyltrimethoxysilane; The low-melting-point glass powder is a sealing glass powder containing at least three oxides selected from SiO2, B2O3, ZnO, and Al2O3; the softening point of the sealing glass powder is 350-550℃; the length of the chopped inorganic fibers is 1-6mm and the diameter is 7-15μm.

3. The fire-retardant and heat-insulating nano-ceramic coating for lithium batteries according to claim 1, characterized in that, The mass ratio of boehmite, nano-zirconia, and nano-alumina in the nano-ceramic framework is 1:1:

1. The mass ratio of silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica, and chopped inorganic fibers in the lightweight thermal insulation filler is 0.3:1:0.7:1:0.

5.

4. The fire-retardant and heat-insulating nano-ceramic coating for lithium batteries according to claim 1, characterized in that, The mass ratio of ammonium polyphosphate, pentaerythritol, melamine, and melamine polyphosphate in the intumescent flame retardant reaction package is 6:2:1:1; The mass ratio of dispersant, wetting agent, defoamer, thickener, thixotropic anti-settling agent, pH adjuster and preservative in the water-based additive is 4:2:1:3:3:1:

1.

5. A fire-retardant and heat-insulating nano-ceramic coating for lithium batteries according to claim 1, characterized in that, The dispersant is selected from one or more of sodium polyacrylate, sodium polymethacrylate, ammonium polyacrylate, sodium hexametaphosphate, sodium polyaspartate, and polycarboxylate dispersants; The wetting agent is selected from one or more of alkyl glycosides, fatty alcohol polyoxyethylene ethers, polyoxyethylene-polyoxypropylene block copolymers, and 2,4,7,9-tetramethyl-5-decyn-4,7-diol; The defoamer is selected from one or more of polydimethylsiloxane emulsion, polyether-modified polysiloxane, mineral oil defoamer, and hydrophobic silica; The thickener is selected from one or more of hydroxyethyl cellulose, hydroxypropyl methyl cellulose, xanthan gum, polyurethane associative thickener, and cross-linked polyacrylic acid; The thixotropic antisettling agent is selected from one or more of attapulgite, sepiolite, bentonite, and fumed silica; The pH adjuster is selected from one or more of ammonia, triethylamine, 2-amino-2-methyl-1-propanol and sodium hydroxide; The preservative is selected from one or more of 1,2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

6. The fire-retardant and heat-insulating nano-ceramic coating for lithium batteries according to claim 1, characterized in that, The water-dispersible amine curing agent is an amine curing agent with water as the dispersion medium. The amine active component of the amine curing agent includes one or more of isophorone diamine, diethylenetriamine, triethylenetetramine, m-xylenediamine, 4,4'-diaminodicyclohexylmethane, polyoxypropylene diamine, and trimethylolpropane polyoxypropylene triamine.

7. A method for preparing a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries according to any one of claims 1-6, characterized in that, Specifically, it includes: S1, add water-based additives to water and mix, then add colloidal silica, add some interfacial bonding components, heat and keep warm to react, stir and add boehmite, nano-zirconia and nano-alumina to obtain inorganic nano slurry; S2, under stirring, silica aerogel powder, hollow glass microspheres, expanded vermiculite, flaky mica and short-cut inorganic fibers are added sequentially to the inorganic nano slurry to obtain a heat insulation filler composite slurry; S3, under stirring, add ammonium polyphosphate, pentaerythritol, melamine, melamine polyphosphate, zinc borate and low melting point glass powder to the heat insulation filler composite slurry and mix evenly to obtain flame retardant heat insulation base material; S4, add bisphenol A diglycidyl ether to the flame-retardant and heat-insulating base material, add the remaining interfacial bonding components and thermally expanded microspheres and mix to obtain component A; package component A and component B separately to obtain a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries.

8. The method for preparing a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries according to claim 7, characterized in that, The method for preparing the silica aerogel powder is as follows: Add silica aerogel to anhydrous ethanol and stir at 300-800 rpm for 20-40 min to obtain a suspension. Add n-octadecyltriethoxysilane and glacial acetic acid to the suspension and keep at 60-80℃ for 2-4 h. Filter and wash to obtain a wet solid phase. Dry the wet solid phase at 80-120℃ for 4-12 h to obtain silica aerogel powder. The mass ratio of silica aerogel, anhydrous ethanol, n-octadecyltriethoxysilane and glacial acetic acid is 100:(400-600):(5-15):(0.5-2).

9. The method for preparing a fire-retardant and heat-insulating nano-ceramic coating for lithium batteries according to claim 7, characterized in that, The amount of the interfacial bonding component mentioned in S1 is 50-70% of the total mass of the interfacial bonding component.

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