A thermally responsive ceramicized fire-resistant explosion-proof pad and its preparation method

Abstract

This invention discloses a thermally responsive ceramicized fire-resistant explosion-proof pad and its preparation method. Specifically, inorganic nanofibers and flux are first ultrasonically dispersed to form a uniform dispersion. Then, a cryogenic binder is added to the dispersion, and inorganic nanofiber aerogel is obtained through freeze-drying. Finally, the pad undergoes pre-impregnation of the inorganic nanofiber aerogel, impregnation with silicone rubber, solvent replacement, and drying and curing to obtain the thermally responsive ceramicized fire-resistant explosion-proof pad. This explosion-proof pad can utilize the physical and chemical cross-linking of PDMS elastomer to encapsulate the three-dimensional network of inorganic materials at low temperatures, providing a certain elastic support, thus exhibiting high toughness and excellent impact resistance. At high temperatures, the PDMS on the surface will decompose to generate a dense ceramic layer, which can isolate the internal materials from external high-temperature flames and oxygen, thereby achieving flame-retardant and fire-resistant effects. It has broad application prospects in battery protection, cable fireproofing, heat insulation, and impact resistance.

Description

Technical Field

[0001] This invention belongs to the technical field of battery protection material preparation, specifically relating to a thermally responsive ceramicized fire-resistant explosion-proof pad and its preparation method. Background Technology

[0002] With socio-economic development and the introduction of "dual-carbon" goals, the number of new energy vehicles, large-scale energy storage devices, electronic devices, and medical devices powered primarily by battery systems is increasing. This places higher demands on battery systems for energy density, consequently increasing the likelihood of battery system combustion and explosion. Battery system combustion and explosion can lead to the combustion and explosion of the entire device, endangering human life and property, and in severe cases, causing death. Among the three mandatory national standards for electric vehicles released in 2020, the "Safety Requirements for Power Batteries for Electric Vehicles" requires that after a single battery cell experiences thermal runaway, the battery system should not catch fire or explode within 5 minutes. Therefore, improving the safety of battery systems is crucial.

[0003] Currently, the most common material for battery flame retardant protection is inorganic aerogel. While it possesses advantages such as high strength, high flame retardancy, and high-temperature stability, its toughness is poor, making it difficult to withstand the impact of a battery explosion. Polymer aerogel, although possessing high toughness and elasticity, has poor thermal stability, typically decomposing at 400–500°C, and exhibits poor flame retardant properties. In recent years, it has been discovered that ceramicized silicone rubber retains the basic properties of silicone rubber at room temperature, such as impact resistance, shock absorption, excellent toughness, and resilience. At high temperatures, it transforms into an inorganic ceramic material, exhibiting excellent fire resistance, superior flame retardancy, outstanding electrical insulation, excellent chemical resistance, and excellent mechanical properties. Ceramicized silicone rubber is a new type of material prepared by adding special fillers to a silicone rubber matrix and is widely used in cable insulation layers, fireproof layers, battery insulation felts, and other fields. However, there are many problems with the use of ceramicized silicone rubber. For example, the addition of too much inorganic filler to ceramicized silicone rubber can cause agglomeration between inorganic fillers, leading to a decrease in the mechanical properties of the polymer. Due to the difference in thermal expansion rates between the ceramic layer and the silicone rubber, the ceramic layer may delaminate or detach. Therefore, researchers have modified ceramicized silicone rubber materials and used its high-temperature ceramicization mechanism to combine it with inorganic materials to prepare new flame-retardant, fire-resistant, and explosion-proof battery protection materials.

[0004] Ceramicized silicone rubber exhibits excellent toughness at low temperatures and can decompose into amorphous ceramics at high temperatures. It possesses excellent thermal stability, chemical corrosion resistance, water resistance, electrical insulation, and environmental stability, showing broad application prospects in areas such as cable flame retardancy, thermal insulation, hydrophobic agents, and insulation. Impregnation crosslinking is a rapid method for constructing a chemical and physical dual crosslinked network, enabling organic materials to coat inorganic materials. This further improves the bonding stability between inorganic materials while providing elastic support for the three-dimensional crosslinked network. Through a two-step impregnation crosslinking process, the polymer is coated onto the surface of inorganic nanofibers, providing elastic support while increasing the bonding force between fibers. This allows for energy absorption and shock absorption through the spatial movement of organic chains during low-temperature use, while chemical crosslinking ensures that the aerogel composite material's structure is not destroyed under impact. During use, the ceramicized silicone rubber, when eroded by flame, forms an amorphous ceramic layer, hindering external oxygen and flame from contacting the internal polymer, thus achieving a flame-retardant effect. Meanwhile, inorganic aerogel materials with a stable three-dimensional network were prepared by freeze-drying. Inorganic nanofibers can act as flux and a stable three-dimensional skeleton, making the ceramic layer more compact. Therefore, the preparation of high-temperature thermally responsive nanofiber composite aerogels is of great significance for the fire resistance and explosion protection of batteries.

[0005] Lin et al. (Xin-Cen Lin, Shu-Liang Li, Wen-Xiong Li, et al. Thermo-Responsive Self-Ceramifiable Robust Aerogel with Exceptional Strengthening and Thermal Insulating Performance at Ultrahigh Temperatures[J]. ADVANCED FUNCTIONAL MATERIALS, 2023, 33(2214913):1-11) prepared polyorganosiloxane aerogels via freeze-drying. By adding ammonium polyphosphate / zinc borate (APP / ZB) as a flux and montmorillonite (MMT) / mica as a refractory component to the aerogel, they obtained a thermally protective aerogel with unique thermal response ceramization ability, excellent thermal insulation performance, and high strength at high temperatures. However, the addition of too much inorganic filler to this aerogel led to its agglomeration during preparation, resulting in a decrease in the mechanical properties of the polyorganosiloxane aerogel.

[0006] He Chunjiang (He Chunjiang. Effect of the combined use of mica powder / glass powder / sintering aid on the properties of silicone rubber [J]. Rubber Industry, 2022, 69(01):34-38) The combined use of mica powder / glass powder / sintering aid promotes the rapid formation of a uniform, dense and continuous ceramic layer in silicone rubber at high temperature. This layer can block heat and oxygen from entering the interior of silicone rubber, thus achieving the purpose of flame retardancy. However, the combined system introduces too much inorganic filler, which reduces the tensile properties of silicone rubber.

[0007] Chinese patent "A Ceramizable Flame-Retardant Coated Silicone Rubber Foam and Its Preparation Process" (Application No.: 202210886260.8, Authorization No.: CN115073921B, Publication Date: 2024.01.26) discloses a ceramizable flame-retardant coated silicone rubber foam and its preparation process. First, silicone rubber foam is prepared, and then a sandwich-structured silicone rubber foam is prepared by coating it with a ceramizable coating slurry, resulting in a silicone rubber foam with a limiting oxygen index of 42%. However, this method requires supercritical foaming in a nitrogen atmosphere, making the preparation process complex. Furthermore, the silicone rubber matrix has a low temperature tolerance range, making it difficult to provide a stable support structure. Summary of the Invention

[0008] The purpose of this invention is to provide a thermally responsive ceramicized fire-resistant explosion-proof pad and its preparation method, which solves the problems in the prior art where the ceramic layer falls off due to the difference in thermal expansion coefficients between the ceramic layer and the polymer, and where excessive inorganic fillers easily agglomerate, leading to a decrease in the mechanical properties of the polymer.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A thermally responsive ceramicized fire-resistant explosion-proof pad and its preparation method are specifically implemented according to the following steps:

[0011] Step 1, Preparation of dispersion

[0012] Inorganic nanofibers and flux were dispersed in deionized water and ultrasonically mixed to obtain a uniform dispersion.

[0013] Step 2, Preparation of inorganic nanofiber aerogel

[0014] Add the cryogenic binder to the dispersion prepared in step 1, heat in a water bath to mix evenly, and then place it in a refrigerator to pre-freeze to obtain a wet gel; pour the wet gel into a cryogenic mold, and place the mold in a freeze dryer for freeze drying to obtain an inorganic nanofiber aerogel;

[0015] Step 3, Aerogel Pre-impregnation

[0016] The silane coupling agent, organic solvent and deionized water were mixed evenly to obtain a pre-impregnation solution. The inorganic nanofiber aerogel prepared in step 2 was impregnated in the pre-impregnation solution until the inorganic nanofiber aerogel was completely saturated. Then the inorganic nanofiber aerogel was placed in a drying oven to dry. The dried inorganic nanofiber aerogel was repeatedly washed with anhydrous ethanol solution.

[0017] Step 4, Impregnate with silicone

[0018] Hydroxyl-terminated PDMS, vinyl-terminated PDMS, catalyst, and organic solvent were mixed uniformly with the aid of ultrasound and stirring to obtain a silica gel impregnation solution. The inorganic nanofiber aerogel obtained in step 3 was impregnated in the silica gel impregnation solution until saturated, and then placed in a high-temperature reactor for cross-linking reaction. Subsequently, the inorganic nanofiber aerogel was immersed in a mixed solution of anhydrous ethanol and ethylene glycol, and the mixed solution of anhydrous ethanol and ethylene glycol was replaced multiple times to achieve solvent replacement.

[0019] Step 5, drying and curing treatment

[0020] The impregnated crosslinked aerogel prepared in step 4 was placed in a drying oven for drying and curing to obtain a thermally responsive ceramic fire-resistant explosion-proof pad.

[0021] Furthermore, in step 1, the inorganic nanofibers are SiO2, TiO2, Si3N4, SiC, etc.; the flux is any one of boron trioxide (B2O3), zinc borate (Zn3B2O6), boric acid (H3BO3), vanadium pentoxide (V2O5), and silicon dioxide (SiO2).

[0022] The mass ratio of flux to inorganic nanofibers is 1:10 to 1:15, the mass ratio of inorganic nanofibers to deionized water is 1:10 to 1:20, the ultrasonic time is 15 to 30 minutes, the ultrasonic power is 200 to 300 W, and the frequency is 140 to 160 Hz.

[0023] Further, in step 2, the cryogenic binder is either polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP), the mass fraction of the cryogenic binder is between 7 wt.% and 15 wt.%, the mass ratio of the cryogenic binder to the dispersion is 1:20 to 1:30, the water bath temperature is 50 to 80°C, the stirring time is 30 to 60 min, the refrigerator temperature is 0 to 10°C, the refrigeration time is 1 to 3 h, the freezing temperature of the freeze dryer is -50 to -40°C, and the freezing time is 24 to 48 h.

[0024] Further, in step 3, the silane coupling agent is any one of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; the organic solvent is any one of ethylene glycol, anhydrous ethanol, n-butanol, acetonitrile, tetrahydrofuran, and dimethylformamide; the pre-impregnation solution is composed of the following substances by mass percentage: silane coupling agent 20%–30%, organic solvent 40%–50%, deionized water 20%–30%, the total of the above components is 100%; the inorganic nanofiber aerogel impregnation time is 12–18 h; the drying temperature is 50–70 °C; the drying time is 2–4 h; and the number of washings with anhydrous ethanol is 10–20 times.

[0025] Further, in step 4, the catalyst is any one of tetrabutylammonium difluorotriphenylsilicate and organic cyclic polyphosphazene base, and the organic solvent is any one of ethylene glycol, anhydrous ethanol, n-butanol, acetonitrile, tetrahydrofuran, and dimethylformamide; the silica gel impregnation solution includes, by mass percentage, 5%–7% hydroxyl-terminated PDMS, 4%–8% vinyl-terminated PDMS, 20%–30% catalyst, and 55%–71% organic solvent, with the total of the above components being 100%; the inorganic nanofiber aerogel is ultrasonicated for 20–30 min in an ultrasonic machine with a power of 200–300 W and a frequency of 140–160 Hz, followed by stirring for 30–60 min; the impregnation time of the inorganic nanofiber aerogel is 12–18 h; the crosslinking temperature is 80–90 °C; the crosslinking time is 3–4 h; the inorganic nanofiber aerogel is soaked in a mixed solution of anhydrous ethanol and ethylene glycol for 20–30 min each time; the mixed solution of anhydrous ethanol and ethylene glycol is replaced 3–5 times.

[0026] Anhydrous ethanol and ethylene glycol solution are mixed in a 1:1 ratio, with 50-100 ml of each mixture.

[0027] Furthermore, in step 5, the impregnated cross-linked aerogel is placed in a drying oven at 60–120°C and dried for 3–5 hours.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] The thermally responsive ceramicized fire-resistant and explosion-proof pad prepared by this invention can maintain high toughness and excellent impact resistance of aerogel at low temperatures. It utilizes the physical and chemical cross-linking of PDMS elastomer to encapsulate the three-dimensional network of inorganic materials. Under external impact, energy dissipation can be achieved through chain elongation or contraction and fiber slippage. The chemical cross-linking avoids damage to the material structure by external forces, thus enabling the material to maintain high toughness. At high temperatures, the PDMS on the surface will decompose, and with the assistance of flux, a dense SiO2 ceramic layer will be generated, which can isolate the internal material from the external high-temperature flame and oxygen, thereby achieving flame retardant and fire-resistant effects. It has broad application prospects in battery protection, cable fireproofing, heat insulation, impact resistance and other fields. Attached Figure Description

[0030] Figure 1 This is a partial cross-sectional schematic diagram of the thermally responsive ceramicized fire-resistant and explosion-proof composite aerogel prepared according to the present invention;

[0031] Figure 2 This is the XRD pattern of the ceramic layer formed after combustion of the PDMS impregnation layer of the thermally responsive ceramicized fire-resistant and explosion-proof composite aerogel prepared in this invention.

[0032] In the attached figure, 1-PDMS impregnation layer, 2-inorganic nanofibers. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0034] A method for preparing a thermally responsive ceramicized fire-resistant explosion-proof pad, specifically implemented according to the following steps:

[0035] Step 1, Preparation of dispersion

[0036] The flux and inorganic nanofibers were dispersed in deionized water and ultrasonicated for 15-20 minutes using an ultrasonic machine with an ultrasonic power of 200-300W and a frequency of 140-160Hz to obtain a uniform dispersion. The inorganic nanofibers were SiO2, TiO2, Si3N4, SiC, etc., and the flux was any one of boron trioxide (B2O3), zinc borate (Zn3B2O6), boric acid (H3BO3), vanadium pentoxide (V2O5), and silicon dioxide (SiO2). The mass ratio of inorganic nanofibers to deionized water was 1:10-1:20, and the mass ratio of flux to inorganic nanofibers was 1:10-1:15.

[0037] Step 2, Preparation of inorganic nanofiber aerogel

[0038] The dispersion obtained in step 1 is added to a cryogenic binder at a mass ratio of 1:20 to 1:30. The mixture is stirred in a water bath at 50–80°C for 30–60 min, then cooled to room temperature. The solution is then pre-frozen in a refrigerator at 0–10°C for 1–3 h to obtain a wet gel. The wet gel is poured into a cryogenic mold, and the mold is placed in a freeze dryer for freeze-drying to obtain an inorganic nanofiber aerogel. The freeze-drying temperature is -50 to -40°C, and the freeze-drying time is 24–48 h. The cryogenic binder is any one of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), or polystyrene (PS), and its mass fraction should be between 7 wt.% and 15 wt.%.

[0039] Step 3, Aerogel Pre-impregnation

[0040] The silane coupling agent, organic solvent, and deionized water are mixed evenly to obtain a pre-impregnation solution. The pre-impregnation solution is prepared according to the following mass percentages: silane coupling agent 20%–30%, organic solvent 40%–50%, and deionized water 20%–30%, with the total of the above components being 100%.

[0041] The inorganic nanofiber aerogel from step 2 is immersed in the above pre-impregnation solution for 12-18 hours until it is completely saturated. Then, the inorganic nanofiber aerogel is placed in a drying oven at 50-70°C and dried for 2-4 hours. Finally, the inorganic nanofiber aerogel is repeatedly washed with anhydrous ethanol solution 10-20 times. The silane coupling agent is any one of vinyltriethoxysilane (A151), vinyltrimethoxysilane (A171), vinyltri(β-methoxyethoxy)silane (A172), γ-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), γ-methacryloyloxypropyltrimethoxysilane (KH570), etc., and the organic solvent is any one of ethylene glycol, anhydrous ethanol, n-butanol, acetonitrile (ACN), tetrahydrofuran (THF), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), etc.

[0042] Step 4, Impregnate with silicone

[0043] Hydroxyl-terminated PDMS, vinyl-terminated PDMS, catalyst, and organic solvent are ultrasonicated for 20-30 minutes using an ultrasonic machine with a power of 200-300W and a frequency of 140-160Hz, followed by stirring for 30-60 minutes to obtain a silica gel impregnation solution. The silica gel impregnation solution is prepared according to the following mass percentages: 5%-7% hydroxyl-terminated PDMS, 4%-8% vinyl-terminated PDMS, 20%-30% catalyst, and 55%-71% organic solvent, with the total of the above components being 100%.

[0044] The inorganic nanofiber aerogel obtained in step 3 is immersed in the above solution for 12-18 hours until the inorganic nanofiber aerogel is completely saturated by the immersion solution. It is then placed in a high-temperature reactor and crosslinked at 80-90°C for 3-4 hours to obtain an impregnated crosslinked aerogel. 50-100 ml of anhydrous ethanol and 50-100 ml of ethylene glycol solution are mixed evenly. The impregnated crosslinked aerogel is then immersed in the mixed solution of anhydrous ethanol and ethylene glycol for 20-30 minutes. The mixed solution of anhydrous ethanol and ethylene glycol is then replaced, and the impregnated crosslinked aerogel is immersed in the mixed solution of anhydrous ethanol and ethylene glycol 3-5 times. The ratio of anhydrous ethanol to ethylene glycol is 1:1. The catalyst is any one of tetrabutylammonium difluorotriphenylsilane (TBAT) or an organic cyclic polyphosphazene base. The organic solvent is any one of ethylene glycol, anhydrous ethanol, n-butanol, acetonitrile (ACN), tetrahydrofuran (THF), dimethylformamide (DMF), or dimethyl sulfoxide (DMSO).

[0045] Step 5, drying and curing treatment

[0046] The impregnated crosslinked aerogel obtained in step 4 is placed in a drying oven at 60-120℃ and dried for 3-5 hours to obtain a thermally responsive ceramicized fire-resistant explosion-proof pad.

[0047] Figure 1 This is a partial cross-sectional schematic diagram of the thermally responsive, fire-resistant, and impact-resistant composite material prepared according to the present invention. From... Figure 1 As can be seen, after two-step impregnation and crosslinking, the thermally responsive PDMS impregnation layer 1 is uniformly coated on the surface of the inorganic nanofibers 2, and the bonding force between the fibers depends on PDMS.

[0048] Figure 2 This is the XRD pattern of the ceramic layer formed after the PDMS impregnation layer is burned. From Figure 2 As can be seen, a pure amorphous SiO2 ceramic layer is generated after PDMS combustion, which does not contain carbon impurities.

[0049] This invention employs inorganic nanofibers to construct a stable three-dimensional network. When PDMS undergoes a phase transition at high temperatures, the stable three-dimensional network can support the PDMS structure and prevent it from collapsing, thereby reducing the probability of cracking in the SiO2 ceramic layer. Simultaneously, the inorganic nanofibers can act as a flux to promote the formation of a dense ceramic layer. Inorganic nanofiber aerogels are prepared using a freeze-drying method to ensure the aerogel's thermal insulation properties. When the outer aerogel is subjected to flame erosion, its excellent thermal insulation performance allows the inner aerogel to maintain its high toughness and resilience even when a ceramic layer is formed, thus resisting the impact of a battery explosion. An impregnation crosslinking method is used to coat the inorganic nanofiber network with a layer of highly tough PDMS elastomer. Physical crosslinking enables effective energy dissipation, while chemical crosslinking enhances the bonding force between fibers. Under impact, it can dissipate energy to a certain extent while ensuring the three-dimensional network remains intact, thus achieving the integrated fire-resistant and explosion-proof function of the composite aerogel.

[0050] This invention prepares a highly elastic fire-resistant and explosion-proof composite aerogel with high-temperature thermal response through freeze-drying and two-step impregnation crosslinking. It makes full use of the three-dimensional network of inorganic fibers as a supporting skeleton to ensure that the ceramic layer does not crack due to excessive polymer shrinkage during high-temperature phase transition. At the same time, PDMS elastomer is uniformly coated on the outside of the three-dimensional network. The purpose is to use the physical crosslinking of the elastomer to ensure reversible energy dissipation under impact, while chemical crosslinking increases the bonding force between nanofibers and prevents delamination between fibers. This composite aerogel has broad application prospects in the fields of battery fire and explosion protection, cable fire and insulation, battery thermal shock resistance, and aerospace device thermal insulation.

[0051] Example 1: Preparation of SiO2 / PDMS composite aerogel

[0052] First, 5g of SiO2 inorganic nanofibers and 0.5g of B2O3 flux were dispersed in 50ml of deionized water and sonicated for 30min using an ultrasonic machine with a power of 200W and a frequency of 140Hz to obtain a uniform dispersion.

[0053] Then, 2.7775 g of PVA solution with a mass fraction of 7 wt.% was added to the above dispersion, and the mixture was stirred in a water bath at 50°C for 60 min and then cooled to room temperature. The mixture was placed in a refrigerator at 10°C for 3 h to pre-freeze and obtain a wet gel. The wet gel was poured into a mold for directional freeze drying and placed in a freeze dryer at -50°C for 24 h to obtain SiO2 fiber aerogel.

[0054] Mix 2.36g KH560, 5.9g DMF and 5ml deionized water evenly, and immerse the SiO2 fiber aerogel in the mixed solution for 12h until the SiO2 fiber aerogel is completely saturated with the solution. Then place the SiO2 fiber aerogel in a 50℃ drying oven for 2h and wash the SiO2 fiber aerogel repeatedly 10 times with anhydrous ethanol solution.

[0055] A silica gel impregnation solution was prepared by sonicating 5.0 g of hydroxyl-terminated PDMS, 4.0 g of vinyl-terminated PDMS, 20.0 g of TBAT, and 71.0 g of DMF solution for 30 min using an ultrasonic machine with a power of 200 W and a frequency of 140 Hz, followed by stirring for 30 min. 50 ml of anhydrous ethanol and 50 ml of ethylene glycol solution were then mixed uniformly. The SiO2 fiber aerogel was then immersed in the mixed solution for 20 min. The anhydrous ethanol and ethylene glycol solutions were then replaced, and the SiO2 fiber aerogel was re-immersed in the replaced anhydrous ethanol and ethylene glycol solutions. This process of replacing the anhydrous ethanol and ethylene glycol solutions was repeated 5 times.

[0056] The SiO2 fiber aerogel, after repeated soaking, was dried in a drying oven at 60°C for 5 hours to obtain a thermally responsive ceramicized fire-resistant and explosion-proof pad.

[0057] Example 2: Preparation of SiC / PDMS composite aerogel

[0058] First, 4.0g of SiC inorganic nanofibers and 0.33g of Zn3B2O6 flux were dispersed in 60ml of deionized water and ultrasonicated for 20min using an ultrasonic machine with a power of 250W and a frequency of 150Hz to obtain a uniform dispersion.

[0059] Then, 2.57 g of PVP solution with a mass fraction of 12 wt.% was added to the above dispersion, and the mixture was stirred in a water bath at 60 °C for 40 min and then cooled to room temperature. The mixture was placed in a refrigerator at 6 °C for 2 h to pre-freeze and obtain a wet gel. The wet gel was poured into a mold for directional freeze drying and placed in a freeze dryer at -45 °C for 36 h to obtain SiC fiber aerogel.

[0060] Mix 2.48g KH570, 4.46g ethylene glycol and 5ml deionized water evenly, and immerse the SiC fiber aerogel in the mixed solution for 17h until the SiC fiber aerogel is completely saturated with the mixed solution. Then place the SiC fiber aerogel in a 60℃ drying oven for 3h and wash the SiC fiber aerogel repeatedly 15 times with anhydrous ethanol solution.

[0061] 5.03g of hydroxyl-terminated PDMS, 5.0g of vinyl-terminated PDMS, 20.95g of TBAT, and 48.3g of acetonitrile solution were sonicated for 25 minutes using an ultrasonic machine with a power of 250W and a frequency of 150Hz, followed by stirring for 40 minutes to obtain a silica gel impregnation solution. 70ml of anhydrous ethanol and 70ml of ethylene glycol solution were mixed evenly, and then the SiC fiber aerogel was immersed in the mixed solution for 25 minutes. Then, the anhydrous ethanol and ethylene glycol solutions were replaced, and the SiC fiber aerogel was re-immersed in the replaced anhydrous ethanol and ethylene glycol solutions. This process of replacing the anhydrous ethanol and ethylene glycol solutions was repeated 4 times.

[0062] The SiC fiber aerogel, after repeated soaking, was dried in a drying oven at 90°C for 4 hours to obtain a thermally responsive ceramicized fire-resistant and explosion-proof pad.

[0063] Example 3: Preparation of SI3N4 / PDMS composite aerogel

[0064] First, 2.8g of Si3N4 inorganic nanofibers and 0.18g of H3BO3 flux were dispersed in 50ml of deionized water and sonicated for 15min using an ultrasonic machine with a power of 300W and a frequency of 160Hz to obtain a uniform dispersion.

[0065] Then, 1.77 g of PVA solution with a mass fraction of 15 wt.% was added to the above dispersion, and the mixture was stirred in a water bath at 80 °C for 30 min and then cooled to room temperature. The mixed solution was placed in a refrigerator at 1 °C for 1 h to pre-freeze and obtain a wet gel. The wet gel was poured into a mold for directional freeze drying and placed in a freeze dryer at -40 °C for 48 h to obtain Si3N4 fiber aerogel.

[0066] Mix 6.42A171, 10.7g ethylene glycol, and 10ml deionized water thoroughly, and immerse the Si3N4 fiber aerogel in the mixed solution for 18 hours until the Si3N4 fiber aerogel is completely saturated with the solution. Then, place the Si3N4 fiber aerogel in a 70℃ drying oven for 2 hours and wash the Si3N4 fiber aerogel repeatedly 20 times with anhydrous ethanol solution.

[0067] 4.96g of hydroxyl-terminated PDMS, 5.67g of vinyl-terminated PDMS, 14.17g of organic cyclic polyphosphazene base, and 46.06g of n-butanol solution were ultrasonicated for 20 minutes using an ultrasonic machine with a power of 300W and a frequency of 160Hz, followed by stirring for 60 minutes to obtain a silica gel impregnation solution. 100ml of anhydrous ethanol and 100ml of ethylene glycol solution were mixed evenly, and then Si3N4 fiber aerogel was immersed in the mixed solution for 30 minutes. Then, the anhydrous ethanol and ethylene glycol solutions were replaced, and the Si3N4 fiber aerogel was re-immersed in the replaced anhydrous ethanol and ethylene glycol solutions. This process of replacing the anhydrous ethanol and ethylene glycol solutions was repeated 5 times.

[0068] The Si3N4 fiber aerogel, after repeated soaking, was dried in a drying oven at 120°C for 3 hours to obtain a thermally responsive ceramicized fire-resistant and explosion-proof pad.

[0069] Example 4: Preparation of TiO2 / PDMS composite aerogel

[0070] First, 3.97g of TiO2 inorganic nanofibers and 0.283g of H3BO3 flux were dispersed in 75ml of deionized water and sonicated for 20min using an ultrasonic machine with a power of 300W and a frequency of 160Hz to obtain a uniform dispersion.

[0071] Then, 7.01 g of PVA solution with a mass fraction of 12 wt.% was added to the above dispersion, and the mixture was stirred in a water bath at 60 °C for 50 min and then cooled to room temperature. The mixture was placed in a refrigerator at 5 °C for 2 h to pre-freeze and obtain a wet gel. The wet gel was poured into a mold for directional freeze drying and placed in a freeze dryer at -50 °C for 48 h to obtain TiO2 fiber aerogel.

[0072] Mix 4.05g A151, 7.29g anhydrous ethanol, and 10ml deionized water thoroughly. Immerse the TiO2 fiber aerogel in the mixed solution for 18 hours until the TiO2 fiber aerogel is completely saturated with the mixed solution. Then, place the TiO2 fiber aerogel in a 60℃ drying oven for 2 hours and wash the TiO2 fiber aerogel repeatedly with anhydrous ethanol solution 15 times.

[0073] 4.87g of hydroxyl-terminated PDMS, 4.17g of vinyl-terminated PDMS, 17.39g of organic cyclic polyphosphazene base, and 43.13g of n-butanol solution were ultrasonicated for 25 minutes using an ultrasonic machine with a power of 200W and a frequency of 140Hz, followed by stirring for 30 minutes to obtain a silica gel impregnation solution. 100ml of anhydrous ethanol and 100ml of ethylene glycol solution were mixed evenly, and then TiO2 fiber aerogel was immersed in the mixed solution for 30 minutes. Then, the anhydrous ethanol and ethylene glycol solutions were replaced, and the TiO2 fiber aerogel was re-immersed in the replaced anhydrous ethanol and ethylene glycol solutions. This process of replacing the anhydrous ethanol and ethylene glycol solutions was repeated 5 times.

[0074] The TiO2 fiber aerogel, after repeated soaking, was placed in a drying oven at 120℃ and dried for 3 hours to obtain a thermally responsive ceramicized fire-resistant and explosion-proof pad.

[0075] Table 1 compares the flame retardant and mechanical properties of the battery protective aerogel materials in Examples 1-4. As shown in Table 1, in terms of mechanical properties, the PDMS-impregnated inorganic nanofiber aerogel exhibits excellent room temperature tensile strength and high temperature tensile strength. Furthermore, at high temperatures, PDMS, flux, and inorganic nanofibers synergistically form a dense ceramic layer, resulting in a high temperature tensile strength higher than the room temperature tensile strength. This ceramic layer can resist the impact of an explosion to a certain extent. Simultaneously, data on heat release rate, total heat release rate, and limiting oxygen index indicate that the ceramic layer formed by PDMS at high temperatures can isolate external oxygen and heat, thus providing a certain flame retardant effect.

[0076] Table 1. Flame retardant and mechanical properties of battery protective aerogel materials in Examples 1-4

[0077]

[0078]

[0079] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a thermally responsive ceramicized fire-resistant explosion-proof pad, characterized in that, The specific steps are as follows: Step 1, Preparation of dispersion Inorganic nanofibers and flux were dispersed in deionized water and ultrasonically mixed to obtain a uniform dispersion. Step 2, Preparation of inorganic nanofiber aerogel Add the cryogenic binder to the dispersion prepared in step 1, heat in a water bath to mix evenly, and then place it in a refrigerator to pre-freeze to obtain a wet gel; pour the wet gel into a cryogenic mold, and place the mold in a freeze dryer for freeze drying to obtain an inorganic nanofiber aerogel; Step 3, Aerogel Pre-impregnation A pre-impregnation solution is prepared by uniformly mixing silane coupling agent, organic solvent, and deionized water. The pre-impregnation solution consists of the following components by mass percentage: 20%–30% silane coupling agent, 40%–50% organic solvent, and 20%–30% deionized water, with the total of the above components being 100%. The inorganic nanofiber aerogel prepared in step 2 is impregnated in the pre-impregnation solution until the inorganic nanofiber aerogel is completely saturated. Subsequently, the inorganic nanofiber aerogel is placed in a drying oven for drying and repeatedly washed with anhydrous ethanol solution. Step 4, Impregnate with silicone Hydroxyl-terminated PDMS, vinyl-terminated PDMS, catalyst and organic solvent are ultrasonicated in an ultrasonic machine with a power of 200-300W and a frequency of 140-160Hz for 20-30 minutes, and then stirred and mixed evenly for 30-60 minutes to obtain a silica gel impregnation solution. The inorganic nanofiber aerogel obtained in step 3 was impregnated in a silica gel impregnation solution for 12-18 hours. After saturation, it was placed in a high-temperature reactor for cross-linking reaction. The cross-linking temperature was 80-90℃ and the cross-linking time was 3-4 hours. The inorganic nanofiber aerogel was then immersed in a mixed solution of anhydrous ethanol and ethylene glycol, with the solution being replaced multiple times to achieve solvent replacement. The immersion time of the inorganic nanofiber aerogel in the mixed solution of anhydrous ethanol and ethylene glycol was 20-30 minutes each time, and the mixed solution was replaced 3-5 times. The anhydrous ethanol and ethylene glycol solutions were mixed in a 1:1 ratio. Step 5, drying and curing treatment The impregnated crosslinked aerogel prepared in step 4 was placed in a drying oven for drying and curing to obtain a thermally responsive ceramic fire-resistant explosion-proof pad.

2. The method for preparing a thermally responsive ceramicized fire-resistant explosion-proof pad according to claim 1, characterized in that, In step 1, the inorganic nanofibers are SiO2, TiO2, Si3N4, or SiC nanofibers; the flux is any one of boron trioxide (B2O3), zinc borate (Zn3B2O6), boric acid (H3BO3), vanadium pentoxide (V2O5), or silicon dioxide (SiO2); the mass ratio of flux to inorganic nanofibers is 1:10 to 1:15, the mass ratio of inorganic nanofibers to deionized water is 1:10 to 1:20, the ultrasonic time is 15 to 30 minutes, the ultrasonic power is 200 to 300 W, and the frequency is 140 to 160 Hz.

3. The method for preparing a thermally responsive ceramicized fire-resistant explosion-proof pad according to claim 1, characterized in that, In step 2, the cryogenic binder is either polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP), with a mass fraction between 7 wt.% and 15 wt.%. The mass ratio of the cryogenic binder to the dispersion is 1:20 to 1:

30. The water bath temperature is 50 to 80°C, the stirring time is 30 to 60 minutes, the refrigerator temperature is 0 to 10°C, the refrigeration time is 1 to 3 hours, and the freeze dryer temperature is -50 to -40°C for 24 to 48 hours.

4. The method for preparing a thermally responsive ceramicized fire-resistant explosion-proof pad according to claim 1, characterized in that, In step 3, the silane coupling agent is any one of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane. The organic solvent is any one of ethylene glycol, anhydrous ethanol, n-butanol, acetonitrile, tetrahydrofuran, and dimethylformamide. The inorganic nanofiber aerogel impregnation time is 12–18 h, the drying temperature is 50–70 °C, the drying time is 2–4 h, and the number of times of washing with anhydrous ethanol is 10–20.

5. The method for preparing a thermally responsive ceramicized fire-resistant explosion-proof pad according to claim 1, characterized in that, In step 4, the catalyst is any one of tetrabutylammonium difluorotriphenylsilicate or an organic cyclic polyphosphazene base, and the organic solvent is any one of ethylene glycol, anhydrous ethanol, n-butanol, acetonitrile, tetrahydrofuran, or dimethylformamide. The silica gel impregnation solution comprises, by mass percentage, 5%–7% hydroxyl-terminated PDMS, 4%–8% vinyl-terminated PDMS, 20%–30% catalyst, and 55%–71% organic solvent, with the total of the above components being 100%.

6. The method for preparing a thermally responsive ceramicized fire-resistant explosion-proof pad according to claim 1, characterized in that, In step 5, the impregnated cross-linked aerogel is placed in a drying oven at 60–120°C and dried for 3–5 hours.

7. A thermally responsive ceramicized fire-resistant explosion-proof pad prepared by the method described in any one of claims 1-6.

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