Multifunctional thermal protection composite coating and preparation method and application thereof

Abstract

The present invention relates to the technical field of safety protection of commercial lithium-ion batteries, and in particular, to a multifunctional thermal protection composite coating and a preparation method and application thereof. The multifunctional thermal protection composite coating consists of an organic-inorganic hybrid coating and an inorganic ceramic coating sequentially disposed on a surface of a base, wherein the materials for preparing the organic-inorganic hybrid coating comprise at least a polymer compound, an inorganic filler, and a solvent, and the materials for preparing the inorganic ceramic coating comprise at least an aqueous emulsion, a silicate, and an inorganic compound. The composite coating can controllably form a composite coating structure including a thermal conduction weakening layer, an air layer, and a thermal convection weakening layer during the fire process. While ensuring that the overall coating thickness is thin to meet the actual requirements of an aluminum housing of a battery, the design of three-layer composite structure can effectively weaken thermal conduction and thermal convection, and fully realize functions of high temperature resistance, flame retardant, and thermal insulation.

Description

TECHNICAL FIELD 5 The present invention relates to the technical field of safety protection of commercial lithium-ion batteries, and in particular to a multifunctional thermal protection composite coating and a preparation method and application thereof. BACKGROUND 10 In recent years, the popularity of new-energy vehicles has caused a sudden increase in the usage of lithium-ion batteries, and battery fire and explosion accidents have become increasingly frequent. A main reason for battery fire and explosion is that when a single cell in a lithium-ion battery pack is subjected to thermal runaway, heat is uncontrollably rapidly transferred to the surrounding individual cells through an aluminum housing of the 15 battery cell, resulting in thermal runaway and fire and explosion of the whole battery pack. Research suggests that coating a layer of thermal protection coating on an aluminum housing of each individual cell would be an effective strategy to delay battery fire and explosion. 20 As is well known, there are three forms of heat transfer, namely thermal radiation, thermal convection, and thermal conduction. If it is desired to prevent heat distribution, these three heat transfer ways should be inhibited or delayed. A method to inhibit a single way of heat transfer is not ideal. Therefore, researchers suggested a design concept of a composite coating of thermal protection and conducted extensive investigations. For example, a 25 Chinese invention patent application (publication No.: CN 115 849 958 A) discloses a preparation method and application of a ceramic-based thermal protection coating. By constructing a thermal protection composite coating consisting of a pore sealing layer, a silicon-based anti-oxidation layer, and a heat-insulating and ablation-resistant layer, the pore-sealing, anti-oxidation, and heat-insulating and ablation-resistant coatings having 30 different functions are combined to fully realize their respective advantages to form a composite system with a three-layer structure and improve a temperature-resistant effect. A Chinese invention patent application (authorization announcement No.: CN 113 800 955 B) provides a multi-layer ceramic-based thermal protection composite coating and a method of preparing the same and use thereof. A composite coating including a buffer 35 layer, a strong self-healing anti-oxidation layer, an intermediate chemical barrier layer, a ceramic thermal insulation layer, and a reinforced isolation layer sequentially from inside 2024370142  15 Apr 2026 to outside is prepared by chemical vapor deposition, so as to prolong the service life of a material under the condition of high-temperature chemical oxidation and corrosion. A Chinese invention patent application (authorization announcement No.: CN 103 847 189 B) provides a thermal protection coating for a launch pad. The thermal protection coating 5 includes an organic bottom layer and an organic-inorganic composite skin layer, and can withstand erosion of combustion gas flow, so that a metal back surface is at a temperature not greater than 200°C. Although a variety of thermal protection composite coatings have been developed, it is difficult to apply these composite coatings to thermal protection of aluminum housings of batteries because of factors such as high technical difficulty, 10 complex preparation conditions, and thicker coatings. Therefore, it is still of great significance to continuously develop a simple and efficient method to prepare an ultra-thin multifunctional thermal protection composite coating for an aluminum housing of a battery. CN 112 940 611 A discloses a multifunctional thermal protection composite coating, 15 consisting of an organosilicon ceramic coating and an intumescent fireproof coating sequentially disposed on a surface of a base. The materials for preparing the organosilicon ceramic coating comprise at least a siloxane, propylene glycol butyl ether, nano-silica sol, titanium dioxide as pigments and alumina as fillers. And the materials for preparing the intumescent fireproof coating comprise at least nano silica sol and silicone 20 acrylic emulsion. CN 111 100 526 A discloses a fireproof and heat-insulating coating layer for an aluminum alloy battery pack, comprising an inner heat-insulating layer formed by an aerogel heatinsulating coating and an outer fireproof layer. The materials for preparing the aerogel 25   heat-insulating coating comprise at least a film forming water-based epoxy resin emulsion, an aerogel of silica, pigments, water and ethylene glycol. The materials for preparing the outer fireproof layer comprise at least a water-based emulsion, aluminum oxide, silica / silicon oxide, and zirconium oxide as inorganic ceramic filler. 30 WO 2022 / 255943 A9 refers to a fire protection and insulation coating composition comprising sodium and / or lithium silicate. and an additional or other filler or binder material, Fumed silica and / or aerogel may be used as thermal insulation filler, and boron nitride, aluminum nitride, aluminum oxide, and / or magnesium oxide may be used as thermal conductive filler. The binder material may be selected from silicone rubber, silane- 35 grafted polyurethane, water-based acrylic, siloxane. This coating acts as a thermally insulative barrier for a battery cell when exposed to higher temperatures since the silicate undergoes hydrothermal crystallization into amorphous silica. 2024370142   30 Sep 2026 The discussion of the background to the invention herein is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any aspect of the discussion was part of the common general knowledge as at the priority date of the application. 5 SUMMARY Unless the context requires otherwise, where the terms “comprise”, “comprises”, “comprised” or “comprising” are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or 10 components, but not precluding the presence of one or more other features, integers, steps or components, or group thereof. The present invention provides a design and preparation of a multifunctional thermal protection composite coating. The composite coating can controllably form a composite 15 coating structure including a thermal conduction weakening layer, an air layer, and a thermal convection weakening layer during a fire process. While ensuring that the overall coating thickness is thin to meet the actual requirements of an aluminum housing of a battery, the design of three-layer composite structure can effectively weaken thermal conduction and thermal convection, and / or fully utilize functions of high temperature 20 resistance, flame retardant, and / or thermal insulation. An aspect of the present invention provides a multifunctional thermal protection composite coating, consisting of an organic-inorganic hybrid coating and an inorganic ceramic coating sequentially disposed on a surface of a base, wherein the materials for preparing 25 the organic-inorganic hybrid coating comprise at least a polymer compound, an inorganic filler, and a solvent, wherein the inorganic filler is a combination of silicon dioxide and potassium silicate or a combination of aluminum oxide and silicon dioxide and potassium silicate. The materials for preparing the inorganic ceramic coating comprise at least an aqueous emulsion, a silicate, and an inorganic compound which is aluminum oxide. The 30 silicate is at least one of sodium silicate and potassium silicate, and a mass ratio of the inorganic compound to the silicate is (10-15):1. The composite coating of multifunctional thermal protection may have a thickness of 11000 pm. 35 The polymer compound may be selected from at least one of an organosilicon resin, an epoxy resin, and a polyurethane. 2024370142   30 Sep 2026 The organosilicon resin may have a solid content of 50-60 wt%, typically 50 ± 2 wt%. The organosilicon resin may be selected from at least one of CFS18050, CFS18250, CFS18350, CFS18450, CFS18550, CFS18650, CFS15030, CFS16030, CFS7060W, 5   CFS7030W, and CFS6020W, and is typically CFS18350, from Weifang Fuller New Materials Co., Ltd. The silicon dioxide may have a particle size of 20-50 nm, and a loss on ignition (950°C, 2 h) < 8%. The silicon dioxide may have a particle size of 30 ± 10 nm, and a loss on ignition 10   (950°C, 2 h) < 6%. The silicon dioxide VK-SP30T as an example is purchased from Crystal Clear Electronic Material Co., Ltd. The solvent may be at least one of propylene glycol methyl ether and ethylene glycol. 15 The aqueous emulsion YF6189 as an example is purchased from Shanghai Chaozhan Industrial Development Co., Ltd. The aqueous emulsion YF-6189 is water-based and comprises nano alumina and nano zirconium as inorganic components without organic pollution. 20 The aluminum oxide may have a specific surface area of 9-11 m2 / g, and the aluminum oxide SAO-020 as example is purchased from Shandong Sinocera Functional Materials Co., Ltd. Another aspect of the present invention provides a method of preparing a multifunctional 25 thermal protection composite coating, comprising at least the following steps: S1: adding a polymer compound and an inorganic filler to a solvent at a mass ratio, ultrasonic treating and stirring to obtain an organic-inorganic hybrid coating; S2: adding an inorganic compound and a silicate, which is at least one of sodium silicate and potassium silicate, to an aqueous emulsion at a mass ratio of the inorganic compound 30 to the silicate being (10-15):1, ultrasonic treating and stirring to obtain an inorganic ceramic coating; S3: pretreating an aluminum plate of a housing of a commercial lithium-ion battery to obtain the pretreated aluminum plate; S4: spraying the organic-inorganic hybrid coating onto a surface of the pretreated 35 aluminum plate, drying to obtain a single-layer coating film, and repeating the step to obtain an organic-inorganic hybrid coating; and 2024370142   30 Sep 2026 S5: spraying the inorganic ceramic coating onto a surface of the organic-inorganic hybrid coating, drying to obtain a single-layer coating film, and repeating the step to obtain an inorganic ceramic coating. 5 The mass ratio of the polymer compound to the inorganic filler may be 5:(5-15). The organosilicon resin, silicon dioxide or a combination of silicon dioxide and aluminum oxide, and potassium silicate may be at a mass ratio of 5:(5-10):1. A mass proportion of the organosilicon resin in the organic-inorganic hybrid coating may 10 be 50-60 wt%, typically 50 ± 2 wt%. A mass proportion of the inorganic compound in the inorganic ceramic coating may be 5070 wt%, typically 70 ± 2 wt%. 15 The ultrasonic treating may comprise: ultrasonic treating by an ultrasonic cleaning machine with power of 180 W for 20-60 min, typically 30 min. The stirring may comprise: stirring by a magnetic stirrer at a stirring speed of 600-1000 r / min for 0.5-1.5 h. 20 The pretreatment may comprise: taking the aluminum plate of the housing of the commercial lithium-ion battery, ultrasonically cleaning the aluminum plate by using acetone and ethanol for 30 min respectively, and then completely drying the aluminum plate in a blast drying oven at 60°C. Then, sandblasting is performed on the aluminum 25 plate by using 180-mesh corundum sand. The aluminum plate after sandblasting is ultrasonically cleaned by using ethanol until there are no particles adhering to the surface of the aluminum plate, and then the aluminum plate is dried in the blast drying oven at 60°C to obtain the pretreated aluminum plate. 30 The drying in step S4 may comprise: drying at 20-30°C for 10-12 h and then drying at 6080°C for 0.5-2 h. The drying in step S4 may comprise: drying at 25 ± 2°C for 12 h and then drying at 70 ± 2°C for 1 h. In step S4, the single-layer coating film may have a thickness of 80-100 pm, and the 35 organic-inorganic hybrid coating may have a thickness of 80-200 pm. 2024370142   30 Sep 2026 The drying in step S5 may comprise: drying at 20-30°C for 10-12 h. The drying in step S5 may comprise: drying at 25 ± 2°C for 12 h. In step S5, the single-layer coating film may have a thickness of 80-100 pm, and the inorganic ceramic coating may have a thickness of 300-420 pm. It is desirable for the present invention to provide an ultra-thin thermal protection coating for an aluminum housing of a battery. During research, the inventors have found that by the pretreatment of the aluminum plate of the housing of the commercial lithium-ion battery, which is combined with a specific organic-inorganic hybrid coating, especially by optimization of the mass proportions of the polymer compound and the inorganic filler in the organic-inorganic hybrid coating, the provided organic-inorganic hybrid coating meets spraying process requirements, and at the same time, there is a strong bonding effect between the formed organic-inorganic hybrid coating and the pretreated aluminum plate, so as to at least partially address the problem that the composite coating falls off after being subjected to fire. Further, the organosilicon resin CFS18350 having a solid content of 50 ± 2 wt% is used, and combined with silicon dioxide and potassium silicate, or aluminum oxide, silicon dioxide and potassium silicate, so that the provided organic-inorganic hybrid coating has strong adhesion and little volume change after being subjected to fire. However, during the thermal insulation performance test, it was found that the thermal insulation effect needs to be further improved. By further combination with the inorganic ceramic coating, the inventors sequentially spray the organic-inorganic hybrid coating and the inorganic ceramic coating onto the surface of the aluminum plate of the housing of the commercial lithium-ion battery to form the multifunctional thermal protection composite coating including the organic-inorganic hybrid coating and the inorganic ceramic coating. In particular, the thicknesses of the organic-inorganic hybrid coating and the inorganic ceramic coating are controlled, thus achieving an excellent thermal insulation effect with the ultra-thin composite coating, meeting fireproof and thermal insulation requirements of the commercial lithium-ion battery, and / or having low cost. In addition, the implementation method is simple, and can be suitable for large-scale industrial production and application. Further, by controlling the mass proportions of aluminum oxide and the silicate in the inorganic ceramic coating, a large number of bubbles are generated in the provided composite coating while being subjected to fire. While abundant air chambers are formed in the coating, a part of a top layer is separated from a bottom layer to form a large number of air layers, and finally a composite coating structure including a thermal conduction weakening layer, an air layer, and a 6 2024370142   30 Sep 2026 thermal convection weakening layer is formed. It is desirable for the overall coating thickness to be thin to meet the actual requirements, and functions of high temperature resistance, flame retardant, and / or thermal insulation. According to the present invention, by optimization of the design of the composite coating, an impact of external heat on cells inside the aluminum housing may be comprehensively reduced from two aspects, i.e., weakening thermal conduction and / or weakening thermal convection, thus greatly improving safety of the commercial lithium-ion battery. A third aspect of the present invention provides the application of a multifunctional thermal protection composite coating on a surface of an aluminum housing of a commercial lithium-ion battery. 1. The present invention provides a design and preparation of a multifunctional thermal protection composite coating. The composite coating can controllably form a composite coating structure including a thermal conduction weakening layer, an air layer, and a thermal convection weakening layer during a fire process. While ensuring that the overall coating thickness is thin to meet the actual requirements of an aluminum housing of a battery, the design of three-layer composite structure design can effectively weaken thermal conduction and thermal convection, and / or fully realize functions of high temperature resistance, flame retardant, and thermal insulation. 2. According to the present invention, by the pretreatment of the aluminum plate of the housing of the commercial lithium-ion battery, combined with a specific organic-inorganic hybrid coating, especially by optimization of the mass proportions of the polymer compound and the inorganic filler in the organic-inorganic hybrid coating, the provided organic-inorganic hybrid coating meets spraying process requirements, and at the same time, there may be a strong bonding effect between the formed organic-inorganic hybrid coating and the pretreated aluminum plate, so as to at least partially address the problem that the composite coating falls off after being subjected to fire. 3. According to the present invention, by further combination with the inorganic ceramic coating, the inventors sequentially spray the organic-inorganic hybrid coating and the inorganic ceramic coating onto the surface of the aluminum plate of the housing of the commercial lithium-ion battery to form the multifunctional thermal protection composite coating including the organic-inorganic hybrid coating and the inorganic ceramic coating. In particular, the thicknesses of the organic-inorganic hybrid coating and the inorganic ceramic coating are controlled, thus achieving an excellent thermal insulation effect with the ultra-thin composite coating, meeting fire-proof and thermal insulation requirements of 7 2024370142   30 Sep 2026 the commercial lithium-ion battery, and / or having low cost. In addition, the implementation method is simple and can be suitable for large-scale industrial production and application. 4. According to the present invention, by controlling the mass proportions of aluminum oxide and the silicate in the inorganic ceramic coating, a large number of bubbles are 5 generated in the provided composite coating while being subjected to fire. While abundant air chambers are formed in the coating, a part of a top layer is separated from a bottom layer to form a large number of air layers, and finally a composite coating structure including a thermal conduction weakening layer, an air layer, and a thermal convection weakening layer is formed. It is ensured that the overall coating thickness is thin to meet 10 the actual requirements, and functions of high temperature resistance, flame retardant, and / or thermal insulation are fully realized. 5. According to the present invention, by optimization of the design of the composite coating, an impact of external heat on cells inside the aluminum housing is comprehensively reduced from two aspects, i.e., weakening thermal conduction and / or 15 weakening thermal convection, thus greatly improving safety of the commercial lithium-ion battery. BRIEF DESCRIPTION OF DRAWINGS 20 FIG. 1 is optical photos of the multifunctional thermal protection composite coating provided in Example 1 before (a) and after (b) being subjected to fire. FIG. 2 is scanning electron microscope (SEM) front views (a and b) and side views (c and d) of the composite coating of multifunctional thermal protection provided in Example 1 after being subjected to fire. 25 FIG. 3 is a comparison diagram of test results of thermal insulation performance of a blank control (a), Example 1(b), Comparative Example 1(c), and Comparative Example 2(d). DETAILED DESCRIPTION OF EMBODIMENTS 30 Example 1 In an aspect, Example 1 of the present invention provides a multifunctional thermal protection composite coating, consisting of an organic-inorganic hybrid coating and an inorganic ceramic coating sequentially on a surface of a base, wherein the materials for preparing the organic-inorganic hybrid coating comprise a polymer compound, an 35 2024370142  15 Apr 2026 inorganic filler, and a solvent, and the materials for preparing the inorganic ceramic coating comprise an aqueous emulsion, a silicate, and an inorganic compound. The polymer compound is an organosilicon resin. The exemplary organosilicon resin has 5 a solid content of 50 ± 2 wt% and is CFS18350 purchased from Weifang Fuller New Materials Co., Ltd. The inorganic filler is a combination of silicon dioxide and potassium silicate. 10 The silicon dioxide has a particle size of 30 ± 10 nm, and a loss on ignition (950°C, 2 h) < 6%. The exemplary silicon dioxide is VK-SP30T purchased from Crystal Clear Electronic Material Co., Ltd. The solvent is propylene glycol methyl ether. 15 The exemplary aqueous emulsion is YF6189 purchased from Shanghai Chaozhan Industrial Development Co., Ltd. The aqueous emulsion YF-6189 is water-based and comprises nano alumina and nano zirconium as inorganic components without organic pollution. 20 The silicate is potassium silicate. The inorganic compound is aluminum oxide. The aluminum oxide has a specific surface area of 9-11 m2 / g, and the exemplary aluminum oxide is SAO-020 purchased from 25 Shandong Sinocera Functional Materials Co., Ltd. In another aspect, Example 1 of the present invention provides a method of preparing a multifunctional thermal protection composite coating, including the following steps: S1: adding a polymer compound and an inorganic filler to a solvent at a mass ratio, 30 ultrasonic treating and stirring to obtain an organic-inorganic hybrid coating; S2: adding an inorganic compound and a silicate to an aqueous emulsion at a mass ratio, ultrasonic treating and stirring to obtain an inorganic ceramic coating; S3: pretreating an aluminum plate of a housing of a commercial lithium-ion battery to obtain the pretreated aluminum plate; 35   S4: spraying the organic-inorganic hybrid coating onto a surface of the pretreated aluminum plate, drying to obtain a single-layer coating film, and repeating the step to obtain an organic-inorganic hybrid coating; and 2024370142  15 Apr 2026 S5: spraying the inorganic ceramic coating onto a surface of the organic-inorganic hybrid coating, drying to obtain a single-layer coating film, and repeating the step to obtain an inorganic ceramic coating. 5 The mass ratio of organosilicon resin, silicon dioxide, and potassium silicate is 5:10:1. A mass proportion of the organosilicon resin in the organic-inorganic hybrid coating is 50 wt%. 10 The mass ratio of the inorganic compound to the silicate is 10:1. A mass proportion of the inorganic compound in the inorganic ceramic coating is 70 wt%. The ultrasonic treating specifically includes: ultrasonic treating by an ultrasonic cleaning 15 machine with power of 180 W for 30 min. The stirring specifically includes: stirring by a magnetic stirrer at a stirring speed of 1000 r / min for 1 h. 20 The pretreatment specifically includes: taking the aluminum plate of the housing of the commercial lithium-ion battery, ultrasonically cleaning the aluminum plate by using acetone and ethanol for 30 min respectively, and then completely drying the aluminum plate in a blast drying oven at 60°C. Then, the sandblasting is performed on the aluminum plate by using 180-mesh corundum sand. The aluminum plate after sandblasting is 25 ultrasonically cleaned by using ethanol until there are no particles adhering to a surface of the aluminum plate, and then the aluminum plate is dried in the blast drying oven at 60°C to obtain the pretreated aluminum plate. The drying in step S4 specifically includes: drying at 25 ± 2°C for 12 h and then drying at 30   70 ± 2°C for 1 h. In step S4, the single-layer coating film has a thickness of 100 pm, and the organic-inorganic hybrid coating has a thickness of 200 pm. 35 The drying in step S5 specifically includes: drying at 25 ± 2°C for 12 h. 2024370142  15 Apr 2026 In step S5, the single-layer coating film has a thickness of 100 pm, and the inorganic ceramic coating has a thickness of 300 pm. Example 2 5 Example 2 of the present invention provides a multifunctional thermal protection composite coating and a preparation method thereof, and its specific implementations are the same as those of Example 1, except that the mass ratio of organosilicon resin, silicon dioxide, and potassium silicate is 5:5:1. 10 Example 3 Example 3 of the present invention provides a multifunctional thermal protection composite coating and a preparation method thereof, and its specific implementations are the same as those of Example 1, except that in step S4, the single-layer coating film has a thickness of 100 pm, and the organic-inorganic hybrid coating has a thickness of 100 pm. 15 In step S5, the single-layer coating film has a thickness of 100 pm, and the organic-inorganic hybrid coating has a thickness of 400 pm. Example 4 Example 4 of the present invention provides a multifunctional thermal protection 20 composite coating and a preparation method thereof, and its specific implementations are the same as those of Example 1, except that the silicon dioxide is replaced by a combination of aluminum oxide and silicon dioxide, and the mass ratio of the aluminum oxide to the silicon dioxide is 1:1. 25 Example 5 Example 5 of the present invention provides a multifunctional thermal protection composite coating and a preparation method thereof, and its specific implementations are the same as those of Example 1, except that the mass ratio of the inorganic compound to the silicate is 15:1. 30 Comparative Example 1 Comparative Example 1 of the present invention provides an inorganic ceramic coating and a preparation method thereof. The materials for preparing the inorganic ceramic coating comprise an aqueous emulsion, a silicate, and an inorganic compound. The 35 exemplary aqueous emulsion is YF6189 purchased from Shanghai Chaozhan Industrial Development Co., Ltd. 2024370142  15 Apr 2026 The silicate is potassium silicate. The inorganic compound is aluminum oxide. The aluminum oxide has a specific surface area of 9-11 m2 / g, and the exemplary aluminum oxide is SAO-020 purchased from 5 Shandong Sinocera Functional Materials Co., Ltd. The method of preparing the inorganic ceramic coating includes the following steps: S1: adding an inorganic compound and a silicate to an aqueous emulsion at a mass ratio, ultrasonic treating and stirring to obtain an inorganic ceramic coating; 10   S2: pretreating an aluminum plate of a housing of a commercial lithium-ion battery to obtain the pretreated aluminum plate; and S3: spraying the inorganic ceramic coating onto a surface of the pretreated aluminum plate, drying to obtain a single-layer coating film, and repeating the step to obtain an inorganic ceramic coating. 15 The mass ratio of the inorganic compound to the silicate is 10:1. A mass proportion of the inorganic compound in the inorganic ceramic coating is 70 wt%. 20 The ultrasonic treating specifically includes: ultrasonic treating by an ultrasonic cleaning machine with power of 180 W for 30 min. The stirring specifically includes: stirring by a magnetic stirrer at a stirring speed of 1000 r / min for 1 h. 25 The pretreatment specifically includes: taking the aluminum plate of the housing of the commercial lithium-ion battery, ultrasonically cleaning the aluminum plate by using acetone and ethanol for 30 min respectively, and then completely drying the aluminum plate in a blast drying oven at 60°C. Then, the sandblasting is performed on the aluminum 30 plate by using 180-mesh corundum sand. The aluminum plate after sandblasting is ultrasonically cleaned by using ethanol until there are no particles adhering to a surface of the aluminum plate, and then the aluminum plate is dried in the blast drying oven at 60°C to obtain the pretreated aluminum plate. 35 The drying specifically includes: drying at 25 ± 2°C for 12 h. 2024370142  15 Apr 2026 The single-layer coating film has a thickness of 100 pm, and the inorganic ceramic coating has a thickness of 500 pm. Comparative Example 2 5 Comparative Example 2 of the present invention provides an organic-inorganic hybrid coating and a preparation method thereof. The materials for preparing organic-inorganic hybrid coating comprise a polymer compound, an inorganic filler, and a solvent, and the polymer compound is an organosilicon resin. The exemplary organosilicon resin has a solid content of 50 ± 2 wt% and is CFS18350 purchased from Weifang Fuller New 10 Materials Co., Ltd. The inorganic compound is a combination of silicon dioxide and potassium silicate. The silicon dioxide has a particle size of 30 ± 10 nm, and a loss on ignition (950°C, 2 h) < 15   6%. The exemplary silicon dioxide is VK-SP30T purchased from Crystal Clear Electronic Material Co., Ltd. The solvent is propylene glycol methyl ether. 20 The method of preparing the organic-inorganic hybrid coating includes the following steps: S1: adding a polymer compound and an inorganic filler to a solvent at a mass ratio, ultrasonic treating and stirring to obtain an organic-inorganic hybrid coating; S2: pretreating an aluminum plate of a housing of a commercial lithium-ion battery to obtain the pretreated aluminum plate; and 25   S3: spraying the organic-inorganic hybrid coating onto a surface of the pretreated aluminum plate, drying to obtain a single-layer coating film, and repeating the step to obtain an organic-inorganic hybrid coating. The mass ratio of organosilicon resin, silicon dioxide, and potassium silicate is 5:10:1. 30 A mass proportion of the organosilicon resin in the organic-inorganic hybrid coating is 50 wt%. The ultrasonic treating specifically includes: ultrasonic treating by an ultrasonic cleaning 35 machine with power of 180 W for 30 min. 2024370142  15 Apr 2026 The stirring specifically includes: stirring by a magnetic stirrer at a stirring speed of 1000 r / min for 1 h. The pretreatment specifically includes: taking the aluminum plate of the housing of the 5 commercial lithium-ion battery, ultrasonically cleaning the aluminum plate by using acetone and ethanol for 30 min respectively, and then completely drying the aluminum plate in a blast drying oven at 60°C. Then, the sandblasting is performed on the aluminum plate by using 180-mesh corundum sand. The aluminum plate after sandblasting is ultrasonically cleaned by using ethanol until there are no particles adhering to a surface of 10 the aluminum plate, and then the aluminum plate is dried in the blast drying oven at 60°C to obtain the pretreated aluminum plate. The drying specifically includes: drying at 25 ± 2°C for 12 h and then drying at 70 ± 2°C for 1 h. 15 In step S4, the single-layer coating film has a thickness of 100 pm, and the organic-inorganic hybrid coating has a thickness of 500 pm. Blank control 20 The blank control of the present invention is the pretreated aluminum plate in Example 1. Performance test method 1. Optical photo characterization: The appearance and heat resistance of the composite coating were characterized by optical photos of the composite coating provided in 25 Examples 1-5 before and after being subjected to fire. Results are shown in Table 1, and the optical photos of the composite coating provided in Example 1 before and after being subjected to fire are shown in FIG. 1. 2. SEM characterization: The structure of the composite coating was characterized by the SEM front views and side views of the composite coating provided in Examples 1-5 after 30 being subjected to fire. Results are shown in Table 1, and the SEM front views and side views of the composite coating provided in Example 1 after being subjected to fire are shown in FIG. 2. 3. Thermal insulation performance: The thermal insulation effects of Examples 1-5, Comparative Examples 1 and 2 and blank control were tested by using a thermal 35 insulation experimental device (self-made), in which a surface subjected to fire was the surface provided with a coating, with a flame temperature of 800°C. Results are shown in Table 1 and FIG. 3. 2024370142  15 Apr 2026 Table 1 Example Optical photo characterization results SEM characterization results Thermal insulation performance test results Example 1 The surface of the composite coating was smooth and flat, and adhered closely to the aluminum plate. After being subjected to fire, the composite coating did not fall off, and a large number of evenly distributed bubbles appeared on the surface of the coating. The SEM front views show that the coating was composed of a large number of irregular particles, and a large number of micron-sized pores were distributed on the whole plane of the coating. The SEM side views show that there were a large number of air holes distributed in a top coating, which can effectively inhibit thermal convection and prevent rapid transfer of heat. The composite coating showed a better thermal insulation effect, with a temperature maintained at 156°C after being subjected to fire for 5 min. Example 2 The surface of the composite coating was smooth and flat, and adhered closely to the aluminum plate. After being subjected to fire, the composite coating did not fall off, and a large number of evenly distributed bubbles appeared on the surface of the coating. The SEM front views show that the coating was comprised of a large number of irregular particles, and a large number of micron-sized pores of different sizes were distributed on the whole plane of the coating. The SEM side views show that there were a large number of air holes distributed in a top coating. The composite coating showed a better thermal insulation effect, with a temperature maintained at 160°C after being subjected to fire for 5 min. Example 3 The surface of the composite coating was smooth and flat, and adhered closely to the aluminum plate. After being subjected to fire, the composite coating did not fall off, and a The SEM front views show that the coating was comprised of a large number of irregular particles, and a large number of micron-sized pores of different sizes were distributed on the whole plane of the coating. The The composite coating showed a better thermal insulation effect, with a temperature maintained at 160°C after being subjected to fire for 5 min. 2024370142  15 Apr 2026 large number of evenly distributed bubbles appeared on the surface of the coating. SEM side views show that there were a large number of air holes distributed in a top coating. Example 4 The surface of the composite coating was smooth and flat, and adhered closely to the aluminum plate. After being subjected to fire, the composite coating did not fall off, and a large number of evenly distributed bubbles appeared on the surface of the coating. The SEM front views show that the coating was comprised of a large number of irregular particles, and a large number of micron-sized pores of different sizes were distributed on the whole plane of the coating. The SEM side views show that there were a large number of air holes distributed in a top coating. The composite coating showed a better thermal insulation effect, with a temperature maintained at 160°C after being subjected to fire for 5 min. Example 5 The surface of the composite coating was smooth and flat, and adhered closely to the aluminum plate. After being subjected to fire, the composite coating did not fall off, and a large number of evenly distributed bubbles appeared on the surface of the coating. The SEM front views show that the coating was comprised of a large number of irregular particles, and a large number of micron-sized pores of different sizes were distributed on the whole plane of the coating. The SEM side views show that there were a large number of air holes distributed in a top coating. The composite coating showed a better thermal insulation effect, with a temperature maintained at 165°C after being subjected to fire for 5 min. Blank control - - The pretreated aluminum plate had a poor thermal insulation effect, with a temperature maintained at 413°C after being subjected to fire for 5 min. 2024370142  15 Apr 2026 Comparative Example 1 - - The inorganic ceramic coating had a poor thermal insulation effect, with a temperature maintained at 205°C after being subjected to fire for 5 min. Comparative Example 2 - - The organic-inorganic hybrid coating had a poor thermal insulation effect, with a temperature maintained at 295°C after being subjected to fire for 5 min.

Claims

1. Multifunctional thermal protection composite coating, comprising an organic-inorganic hybrid coating and an inorganic ceramic coating sequentially disposed on a surface of a base, wherein the materials for preparing the organic-inorganic hybrid coating comprise at least a polymer compound, an inorganic filler, and a solvent,wherein the inorganic filler is a combination of silicon dioxide and potassium silicate or a combination of aluminum oxide and silicon dioxide and potassium silicate, andthe materials for preparing the inorganic ceramic coating comprise at least an aqueous emulsion, a silicate, and an inorganic compound which is aluminum oxide,wherein the silicate is at least one of sodium silicates and potassium silicate, and wherein a mass ratio of the inorganic compound to the silicate is (10-15):1.

2. Multifunctional thermal protection composite coating according to claim 1,wherein the polymer compound is selected from at least one of an organosilicon resin, an epoxy resin, and a polyurethane.

3. Method of preparing the multifunctional thermal protection composite coatingaccording to claim 1 or 2, comprising at least the following steps:S1: adding a polymer compound and an inorganic filler to a solvent at a mass ratio, ultrasonic treating and stirring to obtain an organic-inorganic hybrid coating;S2: adding an inorganic compound and a silicate, which is at least one of sodium silicate and potassium silicate, to an aqueous emulsion at a mass ratio of the inorganic compound to the silicate being (10-15):1, ultrasonic treating and stirring to obtain an inorganic ceramic coating;S3: pretreating an aluminum plate of a housing of a commercial lithium-ion battery to obtain the pretreated aluminum plate;S4: spraying the organic-inorganic hybrid coating onto a surface of the pretreated aluminum plate, drying to obtain a single-layer coating film, and repeating the step to obtain an organic-inorganic hybrid coating; andS5: spraying the inorganic ceramic coating onto a surface of the organic-inorganic hybrid coating, drying to obtain a single-layer coating film, and repeating the step to2024370142   30 Sep 2026obtain an inorganic ceramic coating.

4. Method of preparing the multifunctional thermal protection composite coatingaccording to claim 3, wherein the mass ratio of the polymer compound to the inorganic filler is 5:(5-15).

5. Method of preparing the multifunctional thermal protection composite coatingaccording to claim 3, wherein in step S4, the single-layer coating film has a thickness of 80-100 pm, and the organic-inorganic hybrid coating has a thickness of 80-200 pm.

6. Method of preparing the multifunctional thermal protection composite coatingaccording to claim 5, wherein in step S5, the single-layer coating film has a thickness of 80-100 pm, and the organic-inorganic hybrid coating has a thickness of 300-420 pm.

7. Use of the multifunctional thermal protection composite coating according toclaim 1 or 2 on a surface of an aluminum housing of a commercial lithium-ion battery.

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