Ceramic EVA composite material, preparation method thereof and application of ceramic EVA composite material as thermal runaway propagation barrier material of lithium ion battery

Abstract

The invention discloses a ceramizable EVA composite material and a preparation method and application thereof. The composite material comprises the following raw materials in parts by weight: 50-60 parts of an ethylene-vinyl acetate copolymer EVA; 15 to 20 parts of mica powder MP; 3 to 8 parts of organic montmorillonite (OMMT); 1 to 20 parts of multi-level ceramic structure CHS; and 4-25 parts of hollow silicon dioxide microspheres HSM-M at BP wrapped by a flame retardant. The carbon residue rate and the limit oxygen index of the prepared ceramizable EVA composite material CEVA are remarkably increased, the heat release rate and the total heat release amount are greatly reduced, heat transfer and flame spreading in the lithium battery thermal runaway process can be effectively blocked only by using the CEVA with the thickness of 2 mm, and the ceramizable EVA composite material is suitable for inhibiting thermal runaway spreading of the lithium battery.

Description

Technical Field

[0001] This invention relates to the field of flame retardant materials technology, specifically to a ceramicizable EVA composite material, its preparation method, and its application as a material to block the propagation of thermal runaway in lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries (LIBs) are widely used in portable electronic devices, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and low self-discharge rate. However, as the energy density of lithium-ion batteries increases, they become more susceptible to thermal runaway (TR) under mechanical, thermal, and electrical abuse. This can lead to a rapid rise in internal temperature, and in extreme cases, even fire or explosion. In practical applications, to meet the demand for higher voltage and capacity, multiple batteries are often connected in series or parallel to form a battery module. However, this configuration introduces the risk of thermal runaway propagation (TRP). When one battery experiences thermal runaway, the resulting heat and gas can trigger thermal runaway in adjacent batteries, leading to catastrophic failure of the entire battery module or even the entire system.

[0003] Existing methods for ensuring battery safety involve improving the safety performance of internal battery materials and interrupting the propagation path of thermal runaway between batteries. However, modifying the internal structure of lithium batteries to prevent thermal runaway chemical reactions requires balancing the battery's electrochemical performance with its safety performance. Therefore, most of these methods are currently in the laboratory research stage, and large-scale application requires complex and comprehensive evaluation methods, which will take time to achieve. On the other hand, interrupting the propagation path of thermal runaway between batteries by placing barrier materials between them is an important protective measure to prevent the spread of thermal runaway. Currently, materials used to suppress the propagation of thermal runaway in batteries mainly include phase change materials such as paraffin wax, fatty acids, and hydrates, as well as inorganic thermal insulation materials such as ceramic fiber felt, aerogel, and mica sheets. However, these materials have significant limitations: the phase change temperature of phase change materials is uncontrollable, they have low thermal conductivity, pose a risk of leakage, and have limited effectiveness in suppressing flame propagation. Inorganic thermal insulation materials are brittle, lack flexibility, are difficult to process, and are prone to cracking; they are also relatively heavy, which is not conducive to the lightweighting of battery modules. Therefore, developing new barrier materials that combine lightweight, high heat insulation, and strong flame retardancy is key to breaking through existing technological bottlenecks.

[0004] Chinese patent application document with publication number CN116874879A discloses an inorganic nano-flame retardant material PR-MoS. x For thermal runaway prevention materials used in power battery packs, the material thickness needs to be controlled at 3 mm to achieve complete prevention of the propagation of effective battery thermal runaway. Although it exhibits good blocking effect, a thickness of 3 mm will reduce the energy density of the entire battery module.

[0005] Chinese patent application CN116891595A discloses a polyimide-based composite aerogel material PI@SiO2 and its applications. The XRD pattern of the cathode material in a battery that did not experience thermal runaway shows that I... (003) / I (104) The ratio is 0.69, which characterizes the cation rearrangement of Ni in XPS tests. 2+ / Ni 3+ The peak intensity ratio is 0.43, while the I in the fresh battery cathode material... (003) / I (104) and Ni 2+ / Ni 3+ The peak intensity ratios were 1.99 and 1.39, respectively. Although thermal runaway can be prevented, the layered structure of the cathode material is still damaged to some extent.

[0006] Ethylene-vinyl acetate copolymer (EVA) is a thermoplastic elastomer synthesized from ethylene and vinyl acetate through a copolymerization reaction. It possesses excellent elasticity, cushioning properties, ease of processing, chemical resistance, strong adhesion, lightweight, thermal insulation, moisture resistance, and sound insulation. EVA exhibits superior softness and elasticity, forming a flexible insulating layer between battery cells to absorb and buffer the mechanical shocks and expansion pressures generated during thermal runaway, reducing the risk of cascading reactions. EVA is easily processed through various methods such as hot pressing, coating, lamination, and injection molding, and can be flexibly used as a separator coating, overlay, or thermal insulation gasket in battery modules, facilitating large-scale applications. Compared to inorganic thermal insulation materials, EVA is lightweight and flexible, without significantly increasing the weight of the battery module, contributing to lightweight design. However, EVA itself has a certain degree of flammability, which could exacerbate a fire during thermal runaway in a power battery pack; therefore, improving the flame-retardant properties of EVA is crucial. Summary of the Invention

[0007] The technical problem to be solved by this invention is how to improve the flame retardant properties of EVA materials.

[0008] The present invention solves the above-mentioned technical problems through the following technical means: A ceramicizable EVA composite material, the raw materials of which include, by weight: 50-60 parts of ethylene-vinyl acetate copolymer EVA; 15-20 parts of mica powder MP; 3-8 parts of organo-modified montmorillonite OMMT; 1-20 parts of multi-level ceramicized structure CHS; and 4-25 parts of flame retardant-coated hollow silica microspheres HSM-M@BP. The preparation method of the multi-level ceramicized structure includes the following steps: S1. Hydroxyapatite nanorods coated with zinc borate were prepared using hydroxyapatite nanorods, zinc acetate and sodium tetraborate as raw materials. S2. Layered Mg-Zn-Al hydroxide nanosheets were grown on the surface of zinc borate-coated hydroxyapatite nanorods to obtain a multi-level ceramic structure. The preparation method of the flame retardant-coated hollow silica microspheres includes the following steps: mixing black phosphorus BP nanosheets, phytic acid PA and water to form a uniform dispersion, adding melamine MA aqueous solution to react and obtain M@BP; modifying hollow silica microspheres HSM with silane coupling agent to obtain silane-modified hollow silica microspheres; mixing M@BP and silane-modified hollow silica microspheres, stirring to react and obtain the flame retardant-coated hollow silica microspheres.

[0009] Preferably, the preparation method of the hydroxyapatite nanorods includes the following steps: dissolving P2O5 in ethanol, adding Ca(NO3)2 aqueous solution for reaction, ensuring that the pH value of the solution is stably maintained at 9.0 during the reaction, then transferring the treated solution to a hydrothermal reactor for reaction, and after the reaction is completed, cooling the reaction solution to room temperature, washing, and drying to obtain hydroxyapatite nanorods (HANRs).

[0010] Preferably, the mass ratio of P2O5 to Ca(NO3)2 is 1:1 to 3.5.

[0011] Preferably, the mass ratio of P2O5 to ethanol is 1:60~120.

[0012] Preferably, NH4OH is used to ensure that the pH value of the solution is stably maintained at 9.0.

[0013] Preferably, the mass ratio of P2O5 to NH4OH is 1:0.3~0.9.

[0014] Preferably, the reaction is carried out in a hydrothermal reactor at a temperature of 170 °C for 12 h.

[0015] Preferably, P2O5 is added to ethanol and magnetically stirred at 4 °C until completely dissolved; then, an aqueous solution of Ca(NO3)2·4H2O is added dropwise to the above solution. NH4OH is added dropwise during the reaction to ensure the pH of the solution is maintained stably at 9.0. The reaction lasts for 30 min, with the mass ratio of P2O5, ethanol, Ca(NO3)2·4H2O, and NH4OH being 1:(60~120):(1~3.5):(0.3~0.9). The treated solution is then transferred to an autoclave lined with polytetrafluoroethylene (PTFE) and hydrothermally reacted at 170 °C for 12 h. After the reaction, the reaction solution is cooled to room temperature, and the product is washed repeatedly with alternating ethanol and deionized water, followed by drying to obtain hydroxyapatite nanorods (HANRs).

[0016] Preferably, in the preparation process of the multi-level ceramicized structure, S1 specifically includes the following steps: hydroxyapatite nanorods, zinc acetate Zn(CH3COO)2, and water are mixed evenly, sodium tetraborate is added, and the mixture is heated to react and obtain the zinc borate-coated hydroxyapatite nanorods.

[0017] Preferably, the reaction temperature is 75-80 °C and the reaction time is 20-30 h.

[0018] Preferably, the reaction is carried out at a temperature of 80 °C for 24 h.

[0019] Preferably, the mass ratio of the hydroxyapatite nanorods, zinc acetate Zn(CH3COO)2, and sodium tetraborate is 1:2~3:4~10.

[0020] Preferably, the hydroxyapatite nanorods are in a water mass ratio of 1:50~100.

[0021] Preferably, in the preparation process of the multi-level ceramicized structure, S1 specifically includes the following steps: hydroxyapatite nanorods (HANRs) and zinc acetate (Zn(CH3COO)2) are added to water and mixed evenly, then sodium tetraborate decahydrate (Na2B4O7·10H2O) is added, wherein the mass ratio of HANRs, Zn(CH3COO)2, water, and Na2B4O7·10H2O is 1:(2~3):(50~100):(4~10). After reacting at 80℃ for 24 h, zinc borate-coated hydroxyapatite nanorods (ZB@HANRs) are obtained.

[0022] Preferably, in the preparation process of the multi-level ceramic structure, S2 specifically includes the following steps: using water as a solvent, and using zinc borate-coated hydroxyapatite nanorods, sodium carbonate, magnesium nitrate, zinc nitrate and aluminum nitrate as raw materials to prepare a reaction solution, adjusting the pH value of the reaction solution to be constant at 9~10 before proceeding with the reaction to obtain the multi-level ceramic structure.

[0023] Preferably, the reaction in S2 is carried out at room temperature for 25-35 minutes.

[0024] Preferably, in the reaction solution, Mg:Zn:Al:CO3 2- The molar ratio is controlled at 2~3:1:1~2:2~3.

[0025] Preferably, zinc borate-coated hydroxyapatite nanorods are dispersed in an aqueous solution, and aqueous solutions of sodium carbonate (Na₂CO₃), magnesium nitrate hexahydrate (Mg(NO₃)₂·6H₂O), zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O), and aluminum nitrate nonahydrate (Al(NO₃)₃·9H₂O) are added dropwise, while maintaining the pH of the solution constant at 9-10. (Mg:Zn:Al:CO₃)2- The molar ratio was controlled at (2~3):1:(1~2):(2~3). A stirred reaction was performed to grow layered Mg-Zn-Al hydroxide nanosheets on the ZB@HANRs surface, resulting in a multi-level ceramicized CHS structure.

[0026] Preferably, in the preparation process of the flame retardant-coated hollow silica microspheres, the mass ratio of the black phosphorus nanosheets, phytic acid, and melamine is 0.8:0.4:12.

[0027] Preferably, in the preparation process of hollow silica microspheres coated with flame retardant, the mass ratio of the hollow silica microspheres to the silane coupling agent is 1:5~10.

[0028] Preferably, in the preparation process of flame retardant-coated hollow silica microspheres, the mass ratio of M@BP to silane-modified hollow silica microspheres is 5~10:1.

[0029] Preferably, during the preparation of M@BP, the reaction temperature is 85-95 ℃ and the time is 5-10 h; during the preparation of silane-modified hollow silica microspheres, the modification temperature is 65-75 ℃ and the time is 3-5 h; after mixing M@BP and silane-modified hollow silica microspheres, the stirring temperature is 55-65 ℃ and the time is 1-3 h.

[0030] Preferably, the ceramicizable EVA composite material comprises, by weight, the following raw materials: 50-60 parts of ethylene-vinyl acetate copolymer; 15-20 parts of mica powder; 3-8 parts of organo-modified montmorillonite; 4.5-19 parts of multi-level ceramicized structure; and 4.5-20 parts of hollow silica microspheres encapsulated with flame retardant.

[0031] Preferably, the ceramicizable EVA composite material comprises, by weight, the following raw materials: 55 parts ethylene-vinyl acetate copolymer; 17 parts mica powder; 5 parts organic montmorillonite; 4.6-18.4 parts multi-level ceramicized structure; and 4.6-18.4 parts hollow silica microspheres encapsulated with flame retardant.

[0032] Preferably, bulk black phosphorus (BP) crystals are ground into powder, then added to N,N-dimethylformamide (DMF) and ultrasonically dispersed for 2 h. The BP nanosheets are collected by centrifugation at 1200 rpm, wherein the mass-to-volume ratio of BP to DMF is 1:500-1000 g / mL.

[0033] Preferably, BP nanosheets and phytic acid (PA) are added to water and ultrasonically dispersed to form a homogeneous dispersion. Simultaneously, melamine (MA) is added to water and heated at 90-100 °C until the MA is completely dissolved. Then, the dispersion is added to the MA solution, and the reaction continues for 6 h. The M@BP product is collected by vacuum filtration.

[0034] Preferably, the silane coupling agent is silane coupling agent KH550.

[0035] Preferably, the hollow silica microspheres are alkali-treated hollow silica microspheres.

[0036] Preferably, hollow silica microspheres (HSM) and sodium hydroxide (NaOH) are added to water and stirred at 65-75 °C for 3-5 h, with a mass ratio of NaOH, HSM, and water of 1:(2-3):(25-40). After centrifugation, the mixture is dried in an oven at 55-65 °C for 24 h to obtain purified HSM. The purified HSM is then added to ethanol and stirred for 1 h. γ-aminopropyltriethoxysilane (KH550) is added, with a mass ratio of HSM, ethanol, and KH550 of 1:(9-15):(5-10). The mixture is stirred continuously at 65-75 °C for 2-4 h to obtain silane-modified hollow silica microspheres (HSM-KH550).

[0037] Preferably, M@BP is added to ethanol and stirred in an oil bath at 60 °C for 2 h to obtain an M@BP solution. The M@BP solution is then added dropwise to an HSM-KH550 ethanol solution, and stirring is continued in an oil bath at 60 °C for 2 h. The mass ratio of M@BP, ethanol, and HSM-KH550 is (5~10):(25~40):1. The resulting mixture is filtered, washed with distilled water, and dried at room temperature for 12 h to obtain flame retardant-coated hollow silica microspheres HSM-M@BP.

[0038] Preferably, the ceramicizable EVA composite material is prepared by mixing ethylene-vinyl acetate copolymer EVA, mica powder, organo-modified montmorillonite, multi-level ceramicized structure, and hollow silica microspheres HSM-M@BP encapsulated with flame retardant, followed by intensive mixing and hot pressing.

[0039] The present invention also proposes a method for preparing the ceramizable EVA composite material, comprising the following steps: mixing and hot-pressing ethylene-vinyl acetate copolymer, mica powder, organo-modified montmorillonite, multi-level ceramicized structure, and hollow silica microspheres coated with flame retardant to obtain the ceramizable EVA composite material.

[0040] Preferably, the mixing temperature is 170~190 ℃ and the time is 15~25 min.

[0041] Preferably, the hot pressing temperature is 160~180℃, the pressure is 8~12 MPa, and the time is 3~8 min.

[0042] Preferably, the raw materials are dried in a vacuum oven at 50-70 °C for 9-12 h; the dried components are added to a mixing apparatus in proportion and mixed at 170-190 °C and 60-80 r / min for 15-25 min; the mixture is placed in a mold and hot-pressed at 160-180 °C and 8-12 MPa for 3-8 min, and then cooled to room temperature under pressure to obtain the ceramicizable EVA composite material.

[0043] This invention also proposes the application of the aforementioned ceramizable EVA composite material as a barrier material for thermal runaway propagation in lithium-ion batteries.

[0044] Preferably, the thickness of the ceramizable EVA composite material is 2 mm.

[0045] The ceramicizable EVA composite material CEVA prepared by this invention has significantly improved char residue and limiting oxygen index, and greatly reduced heat release rate and total heat release. Furthermore, using only 2 mm thick CEVA can effectively block heat transfer and flame spread during the thermal runaway process of lithium batteries, making it suitable for suppressing the propagation of thermal runaway in lithium batteries.

[0046] Invention Principle: Mica powder and organically modified montmorillonite possess a layered structure, maintaining a stable framework at high temperatures, preventing material shrinkage and collapse, and the layered shielding effect effectively extends the heat and flame transfer path. Hydroxyapatite in the multi-level ceramicized structure provides a high-temperature resistant and stable inorganic phase framework; zinc borate dehydrates and forms a glassy phase upon heating, promoting rapid ceramicization of the matrix and enhancing its density; layered trihydroxyl groups release moisture and metal oxides at high temperatures, providing both flame retardancy and framework reinforcement. The hollow cavity of hollow silica contains a low thermal conductivity gas, exhibiting even lower thermal conductivity compared to solid particles, extending the heat conduction path and forming a dual thermal resistance of "gas phase + solid phase," significantly reducing heat transfer; when the material is heated or burned, HSM is uniformly dispersed in the matrix, forming a continuous inorganic ceramic layer on the surface, effectively preventing further penetration of heat, oxygen, and combustible small molecules. Black phosphorus can be oxidized to polyphosphoric acid at high temperatures, further promoting carbonization and ceramic layer formation, improving flame retardancy and thermal stability.

[0047] This invention involves incorporating rapidly ceramizable fillers into EVA polymers, followed by mixing and hot pressing to obtain a ceramicized EVA composite material. At high temperatures, the ceramicized EVA undergoes organic phase pyrolysis, while the inorganic fillers and ceramic additives sinter, generating a continuous and dense inorganic ceramic layer. This ceramic layer exhibits high temperature resistance and low thermal conductivity, significantly reducing heat transfer efficiency to adjacent cells and thus blocking the propagation path of thermal runaway. The EVA composite material provided by this invention offers excellent flame retardant and thermal insulation properties, effectively delaying the propagation time of thermal runaway.

[0048] The advantages of this invention are: (1) The ceramicizable EVA composite material CEVA prepared by the present invention has advantages in thermal runaway prevention performance and structural adaptability: only 2 mm thickness is needed to prevent the second battery from thermal runaway.

[0049] (2) The ceramizable EVA composite material CEVA prepared by this invention has a greater advantage in protecting the structural stability of battery materials: when the highest thermal runaway temperature of the first battery reaches 598.7 ℃, the positive electrode material I of the battery did not experience thermal runaway after being blocked by CEVA. (003) / I (104) The ratio is 1.74, with only a slight shift, indicating that the lattice arrangement still maintains a high degree of regularity; meanwhile, Ni 2+ / Ni 3+ The peak intensity ratio was 1.15, a relatively small decrease. Attached Figure Description

[0050] Figure 1 This is a SEM image of the hydroxyapatite prepared in Example 1 of the present invention; Figure 2 This is a TEM image of the multi-level ceramicized CHS structure prepared in Example 1 of the present invention; Figure 3 This is a SEM image of the black phosphorus nanosheets prepared in Example 1 of this invention; Figure 4 This is a SEM image of the HSM-M@BP prepared in Example 1 of the present invention; Figure 5 Here is a cross-sectional SEM image of EVA and its composite material CEVA from Test Example 1 of this invention; Figure 6 This is a graph showing the TGA and DTG data of EVA and its composite material CEVA in Test Example 2 of this invention; Figure 7 The image shows the LOI of EVA and its composite material in Test Example 3 of this invention; Figure 8 The thermal conductivity images are of EVA and its composite materials in Test Example 5 of this invention; Figure 9The XPS spectrum of CEVA residue in the EVA composite material of Test Example 6 of this invention; Figure 10 This is a schematic diagram of the experimental platform for battery thermal runaway and its propagation in Test Example 7 of the present invention; Figure 11 The results of using EVA of different thicknesses to block the propagation of battery thermal runaway in Test Example 7 of this invention are as follows: (a) 2 mm, (b) 3 mm; Figure 12 SEM images of the positive electrode material of the fresh battery and the battery that did not experience thermal runaway after being blocked with 2 mm CEVA2 in Test Example 8 of this invention; Figure 13 XPS spectra of the fresh battery and the positive electrode material of the battery that did not experience thermal runaway after being blocked by 2 mm CEVA2 in Test Example 9 of this invention; Figure 14 The XRD patterns are those of the fresh battery in Test Example 10 of this invention and the positive electrode material of the battery that did not experience thermal runaway after being blocked with 2 mm CEVA2. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0053] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0054] The sources of some of the raw materials and reagents used in the following examples and test cases are shown below: The ethylene-vinyl acetate copolymer was purchased from Dongguan Yuehaoxuan Plastics Co., Ltd. Montmorillonite was purchased from Hebei Mingzhe Mineral Products Co., Ltd.; The mica powder was purchased from ASUS Mineral Products Processing Plant; NH4OH was purchased from Jinan Hongquan Titanium Industry Co., Ltd., with specification model AS-5; Calcium nitrate tetrahydrate was purchased from Merck Millipore, a subsidiary of Merck Life Sciences, and its specification is MQ200. Phosphorus pentoxide was purchased from Maclean Biochemical Technology Co., Ltd., specification AR, purity ≥99.0%; Sodium tetraborate decahydrate was purchased from Maclean Biochemical Technology Co., Ltd., specification AR. Zinc acetate was purchased from Lianyungang Guansu Industrial Co., Ltd., specification AR, purity 99%; Magnesium nitrate hexahydrate was purchased from Loba Chemie, specification AR, purity 98%. Zinc nitrate hexahydrate was purchased from Shenzhen Fulin Instrument Technology Co., Ltd., model number AR; Aluminum nitrate nonahydrate was purchased from Maclean Biochemical Technology Co., Ltd., specification AR, purity 99%; Black phosphorus was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a purity of ≥99.9%. Melamine was purchased from Sinopharm Chemical Reagent Co., Ltd., specification AR, purity ≥99.0%; Phytic acid aqueous solution was purchased from Sinopharm Chemical Reagent Co., Ltd., specification AR, mass fraction 70%; Hollow silica microspheres were purchased from Foshan Lanling Chemical Co., Ltd. γ-aminopropyltriethoxysilane was purchased from Maclean Biochemical Technology Co., Ltd., specification AR, purity 99%; Sodium hydroxide was purchased from Maclean Biochemical Technology Co., Ltd., specification AR. N,N-Dimethylformamide was purchased from Maclean Biotechnology Co., Ltd., specification AR, purity 99.8%; Ethanol was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with specifications of chromatographic grade and purity ≥99.8%.

[0055] Example 1 Step S1: Slowly add 5.0 g of P2O5 to 500 ml of ethanol and stir magnetically at 4 °C until completely dissolved. Then, dissolve 12.5 g of Ca(NO3)2·4H2O in 20 ml of deionized water and add it dropwise to the above solution. During the reaction, slowly add 3.0 g of NH4OH and ensure the pH of the solution is maintained at 9.0. After reacting for 30 min, transfer the solution to an autoclave and hydrothermally react at 170 °C for 12 h. After the reaction, cool to room temperature and wash repeatedly with alternating ethanol and deionized water. After drying, hydroxyapatite nanorods (HANRs) are obtained, and their SEM images are shown below. Figure 1 As shown, by Figure 1It can be seen that the HANRs prepared by the hydrothermal method exhibit a nanorod structure with a diameter of about 10-20 nm and a length of more than 20 μm. Furthermore, due to the van der Waals effect, HANRs powder easily aggregates and accumulates. Subsequently, 7.0 g of HANRs and 17.5 g of Zn(CH3COO)2 were added to 550 ml of deionized water and mixed evenly. Then, 49.0 g of Na2B4O7·10H2O was slowly added, and the mixture was reacted at 80 °C for 24 h to obtain zinc borate-coated hydroxyapatite nanorods ZB@HANRs. 10.5 g of ZB@HANRs were redispersed in 600 ml of deionized water. Then, an aqueous solution containing 32.0 g of Mg(NO3)2·6H2O, 14.87 g of Zn(NO3)2·6H2O, and 28.14 g of Al(NO3)3·9H2O, and an aqueous solution containing 13.25 g of Na2CO3 were added dropwise, keeping the pH of the solution constant at 9. The reaction was continued at room temperature for 30 min to obtain a multi-layered ceramicized CHS structure. This is an advanced composite material structure with multi-layered coating and functional integration, constructed at the microscale through a stepwise synthesis process. The first layer is the core framework HANRS; the second layer is zinc borate covering the nanorods to form the first functional layer; and the third layer is a layered double hydroxide generated through a hydrothermal reaction. Its TEM image is shown below. Figure 2 As shown; by Figure 2 It can be seen that the surface of the nanorods is significantly roughened, and there are sheet-like substances attached to the surface of the nanorods, forming a burr-like covering layer, which proves that the multi-level ceramicized structure CHS was successfully prepared.

[0056] Step S2: Grind 1.0 g of bulk black phosphorus (BP) crystals into powder, then add it to 600 ml of DMF and sonicate for 2 h. Centrifuge at 1200 rpm for 20 min, collect the exfoliated BP nanosheets, and their SEM images are shown below. Figure 3 As shown, by Figure 3The exfoliated BP nanosheets exhibited a good nanosheet morphology with a diameter of several micrometers. Subsequently, 0.8 g of BP nanosheets and 0.4 g of phytic acid (PA) were added to 80 ml of water and sonicated to form a homogeneous dispersion. Simultaneously, 12 g of melamine (MA) was added to 250 mL of water and heated to dissolve at 90 °C. The dispersion was slowly added to the MA solution, and after reacting for 6 h, the product, melamine-coated black phosphorus nanosheet composite material M@BP, was collected by vacuum filtration. 10.0 g of hollow silica microspheres (HSM) and 4.0 g of NaOH were added to 130 ml of deionized water and reacted in an oil bath at 70 °C for 4.5 h. The product was collected by centrifugation and dried in a 60 °C oven for 24 h to obtain purified HSM. 10 g of purified HSM was added to 120 ml of ethanol and stirred for 1 h. Then, 80 ml of KH550 was slowly added, and the mixture was reacted at 70 ℃ for 4 h to obtain a silane-modified HSM (HSM-KH550) dispersion. Next, 52 g of M@BP was added to 240 ml of ethanol and stirred in an oil bath at 60 ℃ for 2 h to obtain an M@BP solution. The obtained M@BP solution was slowly added dropwise to the silane-modified HSM dispersion, and stirring was continued in an oil bath at 60 ℃ for 2 h. The mixture was filtered and washed with distilled water, then dried at room temperature for 12 h to obtain HSM-M@BP. Its SEM image is shown below. Figure 4 As shown; by Figure 4 As can be seen, the HSM particles exhibit a relatively regular spherical structure. A layer of M@BP nanosheets was successfully attached to the surface of the HSM particles. These M@BP nanosheets are wrinkled and uniformly cover the surface of the HSM particles, forming a distinct core-shell structure. This structure indicates that a strong interfacial bond was established between the HSM particles and the M@BP nanosheets through modification with the silane coupling agent KH550, thereby constructing a stable composite material.

[0057] Step S3: EVA, MP, OMMT, HSM-M@BP, and CHS in a mass ratio of 55:17:5:4.6:18.4 were dried in a vacuum oven at 60 °C for 10 h. Then, EVA and MP were mixed with OMMT to obtain material A, and HSM-M@BP and CHS were mixed to obtain material B. Material A and material B were then mixed to obtain a mixture. The mixture was melt-mixed in a torque rheometer at 180 °C and 70 r / min for 20 min. After removing the mixture, it was placed in a mold and pressed for 5 min at 170 °C and 10 MPa using a plate vulcanizing machine. After natural cooling, the ceramizable EVA composite material sample CEVA1 was removed from the mold and subjected to different experiments. The microstructure of its fracture surface is shown below. Figure 5 As shown in (b, f).

[0058] Example 2 Steps S1 and S2 are the same as S1 and S2 in Example 1.

[0059] The difference between step S3 and the preparation of CEVA1 lies only in the following: In this embodiment, the mass ratio of EVA, MP, OMMT, HSM-M@BP, and CHS in the preparation of CEVA2 is 55:17:5:15.3:7.7, and its cross-sectional microstructure is as follows. Figure 5 As shown in (c, g).

[0060] Example 3 Steps S1 and S2 are the same as S1 and S2 in Example 1.

[0061] The preparation method of the CEVA3 composite material provided in step S3 differs from that of CEVA1 in Example 1 only in that the mass ratio of EVA, MP, OMMT, HSM-M@BP, and CHS in the preparation process of CEVA3 in this example is 55:17:5:18.4:4.6, and its fracture surface microstructure is as follows. Figure 5 As shown in (d, h).

[0062] Example 4 The difference from Example 1 is that in step S3, the mass ratio of EVA, MP, OMMT, HSM-M@BP and CHS is 55:17:5:4:1, resulting in CEVA4.

[0063] Example 5 Steps S1 and S2 are the same as S1 and S2 in Example 1.

[0064] The only difference between step S3 and the preparation of CEVA1 in Example 1 is that the mass ratio of EVA, MP, OMMT, HSM-M@BP and CHS in the preparation of CEVA5 in this example is 55:17:5:25:20.

[0065] Comparative Example 1 First, EVA, OMMT, and MP were dried in a vacuum oven at 60 °C for 10 h. Then, EVA and MP were mixed with OMMT at a mass ratio of 55:17:5. The mixture was melt-mixed in a torque rheometer at 180 °C and 70 r / min for 20 min. After melting, the mixture was removed and placed in a custom mold, then pressed for 5 min at 170 °C and 10 MPa using a plate vulcanizing machine. After natural cooling, the EVA sample was removed from the mold and subjected to different experiments. The fracture surface microstructure is shown below. Figure 5 As shown in (a, e).

[0066] Comparative Example 2 The only difference from Example 2 is that CHS is not added, EVA and MP are added, and the mass ratio of OMMT to HSM-M@BP is 55:17:5:15.3. All other steps are the same as in Example 2, and CEVA6 is prepared.

[0067] Comparative Example 3 The difference from Example 2 is that HSM-M@BP is not added separately, the mass ratio of EVA and MP, OMMT and CHS is 55:17:5:7.7, and the remaining steps are the same as in Example 2, and CEVA7 is prepared.

[0068] Test Example 1 Cross-sectional micromorphology analysis Figure 5 SEM images of cross-sections of EVA and its composite materials. Figure 5 (a) and Figure 5 (e) Tensile cross-sectional images of the EVA material prepared in Comparative Example 1, taken at different magnifications. Overall, the tensile cross-sections are smooth, containing only the EVA resin matrix. The fracture surface exhibits simple resin bonding failure, and the toughness characteristics are relatively uniform. Figure 5 (b) and Figure 5 (f) shows the tensile cross-section of CEVA1 material. Due to the addition of 4.6% HSM-M@BP, 18.4% CHS, 5% OMMT, and 17% MP, the cross-section exhibits a rough, fibrous structure. The dispersion of HSM-M@BP, CHS particles, and OMMT and MP fillers is not uniform. Figure 5 (f) clearly shows a large sheet-like structure, which leads to a decrease in mechanical properties. Figure 5 (c) and Figure 5 (g) is a tensile cross-section of CEVA2 material. The addition amount of HSM-M@BP is 15.3% and the addition amount of CHS is 7.7%. Irregular pores and particle agglomeration are observed in the mechanical cross-section. The increase in HSM-M@BP content leads to uneven dispersion and local stress concentration. Figure 5 (d) and Figure 5 (h) shows the tensile cross-section of CEVA3 material. With the addition of HSM-M@BP increasing to 18.4% and CHS further decreasing to 4.6%, the cross-section exhibits numerous bulges and deep grooves. The higher proportion of HSM-M@BP exacerbates phase separation and reduces dispersibility. During fracture, filler agglomerates are peeled off, resulting in ductile fracture of the matrix. Figure 5It is proved that for the composites prepared by simple blending, the deterioration of the microstructure is the fundamental reason for the decline of the macroscopic mechanical properties, and it is necessary to find the best balance between the flame retardant efficiency and the mechanical properties. For the current formulations, CEVA2 and CEVA3 have better flame retardant effects (CEVA1 < CEVA2 < CEVA3), and CEVA1 has the best mechanical strength (CEVA1 > CEVA2 > CEVA3).

[0069] Test Example 2 Thermal Stability Test Thermogravimetric tests were carried out on the EVA and its composites prepared in Examples 1-5 and Comparative Examples 1-3 under a nitrogen atmosphere. The specific test objects and methods are as follows: Thermogravimetric test under nitrogen atmosphere: 5-10 mg of EVA and EVA composites were respectively placed in crucibles and placed in a thermogravimetric instrument. The selected temperature range was 30-800 °C, and the nitrogen flow rate was controlled at 20 ml / min. Figure 6 represents the relationship between the weight change rate and temperature. MMLR1 and MMLR2 respectively correspond to the maximum mass loss rates at the two lowest points of decline in the figure. The larger the MMLR, the more intense the decomposition reaction at this temperature.

[0070] From Figure 6 and Table 1, characteristic parameters such as the initial temperature of thermal decomposition, the temperature corresponding to the maximum mass loss rate, and the char residue rate of EVA and its composites can be obtained to determine the thermogravimetric situation of the materials under a nitrogen atmosphere. T 5% refers to the temperature corresponding to a 5% mass loss of the material, representing the starting point of the initial thermal degradation of the material; T 30% is the temperature corresponding to a 30% mass loss of the material, reflecting the temperature level of the mid-term thermal decomposition of the material; while T max1 and T max2 respectively correspond to the temperatures when the thermal decomposition rate reaches the first and second peaks.

[0071] Compared with the EVA sample in Comparative Example 1, after introducing different types and contents of flame retardants into EVA, the nanosheet structure of OMMT hinders the heat transfer and the diffusion of combustible gases, and HSM-M@BP shows a catalytic effect on the dehydration carbonization process of EVA, resulting in a certain degree of decrease in the thermal decomposition temperature of the material. At the same time, CHS can delay the initial thermal decomposition process of the material to a certain extent. As the addition ratio of HSM-M@BP increases and the addition ratio of CHS decreases, the T 5% and T 30% temperatures of the composites both show a further decreasing trend. Under a nitrogen atmosphere, the decomposition of EVA and its composites occurs in two stages. The T 5% 、T 30% 、T max1 and T max2The temperature ranges were 336.6 °C, 442.3 °C, 352.3 °C, and 463.8 °C, respectively. Compared to EVA, the T... of the EVA composite material... 5% and T max1 Slightly ahead of schedule, T 30% and T max2 The effect was slightly delayed, and both MMLR (Mean Molecular Weight and Laminar Fiber) decreased. Specifically, the residual char rate of EVA was 0.15%, while the residual char rates of CEVA1, CEVA2, CEVA3, CEVA4, CEVA5, CEVA6, and CEVA7 increased to 29.1%, 35.2%, 32.9%, 28.6%, 27.3%, 24.5%, and 21.8%, respectively. Compared with EVA, the residual char rate of CEVA was significantly improved, indicating that the addition of fillers can promote the formation of a high-quality char layer, thereby better protecting the EVA matrix.

[0072] Table 1. Thermogravimetric parameters of samples under nitrogen atmosphere

[0073] Test Example 3 Combustion performance test Combustion performance tests were conducted on the EVA and its composite materials prepared in Examples 1-5 and Comparative Examples 1-3.

[0074] The oxygen index test involves vertically fixing a sample in a transparent glass combustion chamber filled with an upward-flowing mixture of oxygen and nitrogen gas, igniting the top of the sample, and observing its combustion characteristics to estimate the minimum oxygen concentration required to sustain combustion of the material. The plate dimensions are 100 × 10 × 4 mm. 3 .

[0075] from Figure 7 It can be seen that the LOI value of EVA in Comparative Example 1 is only 18.3%. For CEVA1, CEVA2, and CEVA3, while maintaining a constant total addition of 23% of flame retardants HSM-M@BP and CHS, the LOI value of the composites initially increases and then stabilizes with increasing HSM-M@BP addition. Although CEVA3 has the highest proportion of HSM-M@BP, its LOI value is lower than that of CEVA2. This phenomenon may be attributed to a specific synergistic effect between HSM-M@BP and CHS, which is more pronounced in CEVA2. Furthermore, the addition of OMMT and MP better hinders heat transfer, resulting in a higher limiting oxygen index for CEVA2.

[0076] Test Example 4 Cone Calorimeter Testing and Analysis Testing Procedure: The EVA and CEVA materials prepared in Examples 1-5 and Comparative Examples 1-3 were analyzed using a cone calorimeter (FTT, Co., Ltd., UK). The sample dimensions were 100×100×3mm. 3 It uses electric spark ignition and has a heat radiation flux of 35 kW / m². 2 .

[0077] As shown in Table 2, compared to the EVA in Comparative Example 1, the EVA composite materials in Examples 1-5 exhibit certain flame-retardant and smoke-suppressing effects, with a significant reduction in toxic CO release. The peak heat release rate, total heat release, maximum smoke production rate, total smoke production, total CO release, and total CO2 release of the EVA in Comparative Example 1 were 915.7 kW / m³. 2 120.2 MJ / m 2 0.096 m 2 / s, 12.3 m 2 76.5 g and 61.0 g.

[0078] By comparing Examples 1-5 with Comparative Examples 1-3, it can be found that the smoke and toxic CO release of the EVA composite material are reduced to varying degrees, indicating that the EVA composite material has a synergistic inhibitory effect on the release of combustion smoke. Among them, CEVA2 in Example 2 showed the best performance, with the peak heat release rate, total heat release, maximum smoke production rate, total smoke production, total CO release, and total CO2 release decreasing by 77.7%, 46.6%, 71.9%, 41.5%, 46.7%, and 27.5%, respectively.

[0079] Table 2. Cone Measurement Results of EVA and its Composites

[0080] Test Example 5 Thermal conductivity test Testing Procedure: The thermal conductivity of the EVA and CEVA materials prepared in Examples 1-5 and Comparative Examples 1-3 was tested. The materials to be tested were cut into circular samples with a diameter of 30 mm and a thickness of 2 mm. The test surfaces were ensured to be flat, smooth, and with a parallelism deviation of less than 0.02 mm. The transient planar heat source method was used for testing.

[0081] Figure 8The figure shows the thermal conductivity test results for EVA and CEVA materials. As can be seen from the figure, the thermal conductivity of EVA in Comparative Example 1 is 0.4 W / (m·K), while the thermal conductivity of the CEVA composite materials all decreased, with CEVA2 showing the best effect, its thermal conductivity decreasing by 30% compared to EVA. This study introduced HSM-M@BP with a specific core-shell structure and a multi-layered ceramicized structure CHS, and synergized with OMMT and MP. This not only constructs a dense, continuous, and high-strength multi-layered ceramicized barrier layer on the matrix surface during combustion, effectively blocking heat and combustible gas transfer; but also, this unique multi-component, multi-scale composite structure forms an extremely complex thermal conductivity barrier network within the material body. The hollow insulating properties of HSM, the numerous heterogeneous interfaces between components, and the resulting strong phonon scattering effect collectively lead to a significant reduction in the material's thermal conductivity.

[0082] Test Example 6 Morphology and composition of char residue after combustion Figure 9 XPS test for residual carbon in CEVA material. Figure 9 (a) shows the C 1s spectrum. The peaks near 289.8, 286.8, and 285.7 eV correspond to C=O, CO, and CN bonds, respectively, while the peak near 284.6 eV belongs to CC / C=C bonds. The higher the proportion of CC / C=C bonds, the higher the degree of graphitization and the stronger the stability of the carbon residue. The proportions of CC / C=C bonds in CEVA1, CEVA2, and CEVA3 are 67.4%, 69.2%, and 67%, respectively. Figure 9 (e) shows the N 1s spectrum. The peaks near 402.5, 401.6, and 399.5 eV correspond to NQ, N-5, and N-6, respectively. The higher the proportion of NQ bonds, the better the heat and oxidation resistance of the char residue. The proportions of NQ bonds in CEVA1, CEVA2, and CEVA3 are 12.4%, 28.4%, and 17.1%, respectively. Figure 9 (d) shows the Si 2p spectrum. The peaks near 103.3 and 102.8 eV belong to Si-O and Si-C bonds, respectively. The proportions of Si-O bonds in CEVA1, CEVA2, and CEVA3 are 50.3%, 47.5%, and 56%, respectively, while the proportions of Si-C bonds are 49.7%, 52.5%, and 44%, respectively. The Si element originates from OMMT. The Si-O bonds indicate that after combustion, OMMT formed a large number of silicate structures, which tightly cover the outer surface of the carbon layer, significantly enhancing the overall heat resistance of the carbon layer. The Si-O bonds are formed by the chemical bonding of some Si elements with the carbon layer, constructing a denser and continuous carbon layer network structure. Figure 9(c) shows the P 2p spectrum. The peaks near 135.5, 134.3, and 133.8 eV correspond to O=PO-Si, O=POC, and POP, respectively. During the cone combustion test, phosphorus is converted into phosphorus oxides with O=POC and POP bonds. These two compounds are tightly bound to carbon, forming a robust cross-linked carbon layer structure that enhances the strength of the carbon layer. The O=PO-Si bond is formed by the cross-linking of the composite material with silicon during combustion, which allows most of the phosphate to be retained in the condensed phase. Figure 9 (b) is the B 1s spectrum. During the combustion of the composite material, the B element reacts with oxygen to generate boron trioxide (B2O3). B2O3 forms a glassy substance at high temperature, which can effectively isolate the transmission of oxygen and heat.

[0083] Test Example 7 Battery thermal runaway propagation experiment A commercially available 2 Ah ternary lithium-ion battery was selected as the experimental subject. Figure 10 Experiments were conducted on the battery thermal runaway and propagation experimental platform shown.

[0084] EVA and the prepared CEVA1, CEVA2, CEVA3, CEVA4, CEVA5, CEVA6, and CEVA7 were customized according to the size of the lithium-ion battery, specifically measuring 55 × 35 mm (length × width), and fabricated into 2 mm and 3 mm samples, which were placed between two batteries. The batteries, heating copper blocks, and barrier materials were fixed to the experimental platform using a fixing bracket, and the heating block, batteries, and barrier materials were tightly fitted using adjusting bolts. At the start of the experiment, the heating module heated the lithium-ion battery at a heating rate of 20 °C / min. The heating module transferred heat to the surface of battery 1 through thermal conduction, inducing it to enter a thermal runaway state. Once battery 1 experienced thermal runaway, the heating module immediately stopped working. Subsequently, the heat released by the thermal runaway of battery 1 was transferred to the adjacent battery 2 through thermal conduction or thermal radiation. To comprehensively monitor the experimental process, two thermocouples were placed on the sides of both batteries and on the back away from the heating module to monitor the temperature changes of the batteries. Simultaneously, a voltage data acquisition device was connected to the battery tabs via a clamp to dynamically monitor voltage fluctuations in the lithium-ion battery pack during thermal runaway and its propagation. Furthermore, a camera and infrared thermal imager were used to record key dynamic phenomena such as smoke release and flame behavior during thermal runaway. By analyzing data on the thermal runaway characteristics and internal structural changes of battery 2, combined with the performance of the barrier material, the effectiveness of the barrier material in suppressing the propagation of thermal runaway in lithium-ion batteries was comprehensively evaluated.

[0085] Battery thermal runaway propagation suppression tests were conducted on EVA and the prepared CEVA1, CEVA2, CEVA3, CEVA4, CEVA5, CEVA6, and CEVA7 materials. T1 is the thermal runaway temperature of battery 1, t1 is the thermal runaway time of battery 1, and T2 and t2 are the thermal runaway temperature and time of battery 2, respectively. t is the time interval between the thermal runaway of the two lithium-ion batteries. 1max T 2max These are the highest temperatures for batteries 1 and 2, respectively. Figure 11 It can be seen that neither 2 mm nor 3 mm EVA samples can suppress the propagation of thermal runaway. Both batteries experienced thermal runaway, with peak temperatures exceeding 600 °C. Table 3 shows that when using 2 mm CEVA1 batteries, under heating, battery 1 experienced thermal runaway at 817 s, with a temperature of 217.8 °C, reaching a maximum temperature of 613.3 °C at 838 s. After heat propagation, battery 2 also experienced a temperature increase, reaching a maximum temperature of 189.6 °C, but did not experience thermal runaway. When using 2 mm CEVA2 for the barrier experiment, battery 1 showed a significant temperature increase around 500 s and experienced thermal runaway at 229.4 °C, reaching a maximum temperature of 598.7 °C. Battery 2's maximum temperature was 147.8 °C. When using a 2mm CEVA3, battery 1 heats up slowly initially, then accelerates its temperature rise after approximately 500 seconds, experiencing thermal runaway at 201.4℃, with a maximum temperature of 560.5℃. Battery 2's maximum temperature is 159.6℃. When using a 2mm CEVA4, battery 1 heats up relatively quickly initially, experiencing thermal runaway at 236.8℃, with a maximum temperature of 575.4℃. Battery 2 experiences thermal runaway after 178 seconds, with a maximum temperature of 693.2℃. When using a 2mm CEVA5, battery 1 heats up rapidly initially, experiencing thermal runaway at 225.5℃, with a maximum temperature of 562.8℃. Battery 2 experiences thermal runaway after 182 seconds, with a maximum temperature of 678.4℃. When using 2 mm CEVA6, battery 1 experienced rapid temperature rise in the initial stage, reaching 244.1 °C before thermal runaway, with a maximum temperature of 598.2 °C. Battery 2 subsequently experienced thermal runaway after 170 seconds, with a maximum temperature of 698.5 °C. When using 2 mm CEVA7, battery 1 also experienced rapid temperature rise in the initial stage, reaching 253.5 °C before thermal runaway, with a maximum temperature of 610.7 °C. Battery 2 subsequently experienced thermal runaway after 167 seconds, with a maximum temperature of 700.6 °C. The table shows that CEVA2 provides the best barrier effect.

[0086] Table 3 Parameters of EVA composite cells during the TRP process

[0087] Test Example 8 Since the 2 mm CEVA2 membrane showed the best effect in blocking the propagation of battery thermal runaway, it was disassembled and analyzed, and samples from the barrier interface and interior were collected. Subsequently, the microstructure of the samples was observed using scanning electron microscopy (SEM). Figure 12 In (a), the NCM spherical particles and the lithium manganese oxide agglomerate structure exhibit particle aggregation. The particle size distribution is relatively concentrated, and no obvious large agglomerations were observed, which is conducive to ion diffusion within the electrode. Figure 12 In (b), NCM particles aggregate to form a porous structure. This structure facilitates electrolyte permeation and improves interfacial reactions. Figure 12 In (c) and (d), the anodes show a continuous layered structure without obvious cracks and voids, indicating that no severe volume expansion caused structural damage. Figure 12 Figures (e) and (f) show the morphological characteristics of the battery's positive electrode material after successful barrier removal. Figure 12 (e) It can be observed that the material surface is composed of dense NCM spherical particles and lithium manganese oxide agglomerates, with clear particle boundaries and a loose structure. At higher magnification... Figure 12 (f) shows some cracks and voids, and NCM particles break down after being heated at high temperature. Figure 12 (g) and Figure 12 (h) is a morphological feature diagram of the battery negative electrode material. Figure 12 (g) The surface is relatively flat, with localized protrusions and depressions. The flat areas may be formed by recrystallization after localized melting of the material at high temperatures, while the depressed areas are caused by lattice collapse. At higher magnification... Figure 12 (h) contains white layered oxides, which increase the impedance of the interface and affect the performance of the battery.

[0088] Test Example 9 The elemental composition and chemical state of the samples were analyzed using XPS. The C 1s, Li 1s, Ni 2p, Co 2p, and Mn 2p spectra of the cathode material are shown below. Figure 13 As shown. Figure 13 (a) The total spectrum shows the types of elements and the positions of their corresponding peaks. Figure 13In (d), 284.8, 286.2, 288.1, and 290.1 ​​eV correspond to CC, CN, CO, and C=O bonds, respectively. The C=O bond peak has a higher intensity, indicating that the carbon-based material has undergone significant oxidation. In (e), a double peak of Li-F (56.5 eV) and Li2O (55.8 eV) is observed. The formation of Li2O may be related to the change in the oxidation state of lithium in the material. In the Ni 2p spectrum of 13(f), the four peaks at 856.2, 858.4, 873.5, and 877.3 eV correspond to Ni 2p3 / 2 (II), Ni 2p3 / 2 (III), Ni 2p1 / 2 (II), and Ni 2p1 / 2 (III), respectively. The peaks at 861.2 and 880.9 eV are accompanying satellite peaks. The peak at 850.4 eV corresponds to Ni(0). The appearance of Ni(0) may be due to the thermal decomposition and reduction reaction of nickel compounds in the material under high temperature conditions, which reduces nickel ions to elemental nickel and precipitates out. 3+ / Ni 2+ The value is 1.15, Ni 3+ / Ni 2+ A decrease in the ratio indicates that high-valence metal ions are gradually shifting to lower valence states. This change leads to intensified cation rearrangement, increased disruption, and overall instability.

[0089] Test Case 10 The crystal structure of the sample was determined by XRD. Figure 14 The image shows the XRD characterization of the positive electrode material of the battery that did not experience thermal runaway after being blocked with 2 mm CEVA2. The XRD results show the Ig of the positive electrode material after blocking. (003) / I (104) The ratio is 1.81, which is lower than the original state battery's 1.99, indicating that the material's lattice arrangement is relatively regular and has fewer defects, which is beneficial for lithium-ion diffusion and structural stability.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ceramicizable EVA composite material, characterized in that: The raw materials, by weight, include: 50-60 parts of ethylene-vinyl acetate copolymer; 15-20 parts of mica powder; 3-8 parts of organic montmorillonite; 1-20 parts of multi-level ceramic structure; and 4-25 parts of hollow silica microspheres coated with flame retardant. The preparation method of the multi-level ceramicized structure includes the following steps: S1. Hydroxyapatite nanorods coated with zinc borate were prepared using hydroxyapatite nanorods, zinc acetate and sodium tetraborate as raw materials. S2. Layered Mg-Zn-Al hydroxide nanosheets were grown on the surface of zinc borate-coated hydroxyapatite nanorods to obtain a multi-level ceramic structure. The preparation method of the flame retardant-coated hollow silica microspheres includes the following steps: mixing black phosphorus nanosheets, phytic acid and water to form a uniform dispersion, adding melamine aqueous solution to react and obtain M@BP; modifying the hollow silica microspheres with a silane coupling agent to obtain silane-modified hollow silica microspheres; mixing M@BP with silane-modified hollow silica microspheres and stirring to react and obtain the flame retardant-coated hollow silica microspheres.

2. The ceramizable EVA composite material according to claim 1, characterized in that: In the preparation process of the multi-level ceramic structure, S1 specifically includes the following steps: hydroxyapatite nanorods, zinc acetate, and water are mixed evenly, sodium tetraborate is added, and the mixture is heated to react and obtain the zinc borate-coated hydroxyapatite nanorods.

3. The ceramizable EVA composite material according to claim 2, characterized in that: The reaction is carried out at a temperature of 75-80 °C for 20-30 h.

4. The ceramizable EVA composite material according to claim 1, characterized in that: The mass ratio of the hydroxyapatite nanorods, zinc acetate, and sodium tetraborate is 1:2~3:4~10.

5. The ceramizable EVA composite material according to claim 1, characterized in that: In the preparation process of the multi-level ceramic structure, S2 specifically includes the following steps: using water as a solvent, a reaction solution is prepared using zinc borate-coated hydroxyapatite nanorods, sodium carbonate, magnesium nitrate, zinc nitrate, and aluminum nitrate as raw materials. The pH value of the reaction solution is adjusted to be constant at 9-10 before the reaction is carried out to obtain the multi-level ceramic structure.

6. The ceramizable EVA composite material according to claim 5, characterized in that: The reaction described in S2 is carried out at room temperature for 25-35 minutes.

7. The ceramizable EVA composite material according to claim 5, characterized in that: In the reaction solution, Mg:Zn:Al:CO3 2- The molar ratio is controlled at 2~3:1:1~2:2~3.

8. The ceramizable EVA composite material according to claim 1, characterized in that: In the preparation of flame retardant-coated hollow silica microspheres, the mass ratio of black phosphorus nanosheets, phytic acid, and melamine is 0.8:0.4:

12.

9. The ceramizable EVA composite material according to claim 1, characterized in that: In the preparation process of hollow silica microspheres coated with flame retardant, the mass ratio of the hollow silica microspheres to the silane coupling agent is 1:5~10.

10. The ceramizable EVA composite material according to claim 1, characterized in that: In the preparation of flame retardant-coated hollow silica microspheres, the mass ratio of M@BP to silane-modified hollow silica microspheres is 5~10:

1.

11. The ceramizable EVA composite material according to claim 1, characterized in that: During the preparation of M@BP, the reaction temperature was 85-95 ℃ and the time was 5-10 h; during the preparation of silane-modified hollow silica microspheres, the modification temperature was 65-75 ℃ and the time was 3-5 h; after mixing M@BP and silane-modified hollow silica microspheres, the stirring temperature was 55-65 ℃ and the time was 1-3 h.

12. The ceramizable EVA composite material according to any one of claims 1-11, characterized in that: The raw materials, by weight, include: 50-60 parts of ethylene-vinyl acetate copolymer; 15-20 parts of mica powder; 3-8 parts of organic montmorillonite; 4.5-19 parts of multi-level ceramic structure; and 4.5-20 parts of hollow silica microspheres coated with flame retardant.

13. The ceramizable EVA composite material according to any one of claims 1-11, characterized in that: The raw materials, by weight, include: 55 parts of ethylene-vinyl acetate copolymer; 17 parts of mica powder; 5 parts of organic montmorillonite; 4.6-18.4 parts of multi-level ceramic structure; and 4.6-18.4 parts of hollow silica microspheres coated with flame retardant.

14. A method for preparing a ceramizable EVA composite material as described in any one of claims 1-13, characterized in that: Includes the following steps: The ceramicizable EVA composite material is obtained by mixing and hot pressing ethylene-vinyl acetate copolymer, mica powder, organo-modified montmorillonite, multi-level ceramicized structure, and hollow silica microspheres coated with flame retardant.

15. The application of a ceramicizable EVA composite material as described in any one of claims 1-13 as a material for blocking the propagation of thermal runaway in lithium-ion batteries.

16. The application of the ceramizable EVA composite material according to claim 15 as a material for blocking thermal runaway propagation in lithium-ion batteries, characterized in that: The thickness of the ceramicizable EVA composite material is 2 mm.

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