Preparation method of multistage dynamic protection refractory sheet for thermal runaway of battery module

Abstract

The invention discloses a preparation method of a multistage dynamic protection refractory sheet for thermal runaway of a battery module, and the preparation method specifically comprises the following steps: firstly preparing MAP powder by adopting a water bath method, secondly adding the MAP powder into an MOFs precursor solution, preparing MAP / MOFs powder by adopting a hydrothermal method, then constructing three-dimensional porous MAP / MOFs aerogel by adopting a freeze-drying method, and finally preparing the multistage dynamic protection refractory sheet for thermal runaway of the battery module. The MAP / MOFs aerogel is subjected to vacuum impregnation in a PDMS diluted solution, the multi-stage dynamic protection refractory sheet with an elastic-rigid dual-network structure is finally obtained through thermocuring treatment, and the multi-stage dynamic protection refractory sheet realizes multi-stage dynamic protection of thermal runaway of a battery module through multi-stage linkage of gas inhibition, catalytic carbonization and composite phase barrier, so that the thermal runaway of the battery module is prevented, and the service life of the battery module is prolonged. Due to the multi-protection mechanism, the refractory sheet has a wide application prospect in the field of thermal runaway protection of the battery module.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of battery module protective materials, and specifically relates to a method for preparing a multi-stage dynamic protective refractory sheet for thermal runaway of a battery module. Background Art

[0002] With the widespread use of lithium-ion batteries in electric vehicles, energy storage systems, and portable electronic devices, their safety issues are receiving increasing attention. Thermal runaway is one of the most serious safety hazards of lithium-ion batteries. Thermal runaway is typically triggered by overcharging, short circuits, mechanical damage, or high temperatures, causing a sharp rise in the battery's internal temperature. This in turn triggers a chain reaction, including electrolyte decomposition and reactions between positive and negative electrode materials, leading to combustion of the battery cells. Ultimately, the flames spread, causing fire or explosion throughout the battery module, endangering human life and property. To effectively suppress the spread of thermal runaway flames, the development of high-performance flame-retardant materials has become a research hotspot in the field of battery safety.

[0003] Aerogel is a three-dimensional nanoporous structure material formed by interconnected nanoparticles. It has excellent properties such as low density, large specific surface area, high porosity, and low thermal conductivity. However, its specific application still faces key challenges: although inorganic aerogel has excellent high temperature resistance, its intrinsic brittleness leads to insufficient impact resistance, making it difficult to effectively dissipate the dynamic load generated by the battery module when it is subjected to mechanical impact; and although organic aerogel has better flexibility, its thermal stability is poor, and the carbonaceous residual layer formed on the surface under flame erosion has a secondary combustion risk (limiting oxygen index <28%), and the carbonaceous residual layer is prone to lose its protective function due to brittle fracture. At present, researchers have constructed an intelligent fire extinguishing and multi-stage flame retardant mechanism by combining organic and inorganic aerogels. While relying on gas phase flame retardancy and condensed phase flame retardancy to reduce the degree of flame combustion, it can also prevent flame propagation and improve flame retardancy.

[0004] In situ synthesis is a method that directly generates the target product on a substrate by controlling reaction conditions. This method does not compromise the inherent properties of the substrate material and often results in a good interfacial bond between the product and the underlying material. In situ synthesis has been used to grow MOFs on the surface of struvite (MgNH₄PO₄·6H₂O, MAP) to construct a bimetallic composite material that not only catalyzes the formation of a carbon layer but also adsorbs some toxic gases, achieving flame retardancy and smoke suppression. The impregnation cross-linking method simultaneously constructs a chemically and physically cross-linked network at the nanoscale through in situ polymerization. This technique, by coating the inorganic component with an organic component, enhances the heterogeneous interfacial bonding strength while creating a three-dimensional interconnected elastic network that effectively dissipates mechanical stress, enabling precise control of the material's stiffness-toughness properties. The impregnation cross-linking method allows polydimethylsiloxane (PDMS) to elastically encapsulate the MAP / MOFs three-dimensional network. Upon impact, the PDMS molecular chain movement dissipates energy and resists impact through bond rupture, thereby enhancing the material's structural stability and mechanical properties. In addition, when thermal runaway occurs in the battery cell, the PDMS-MAP / MOFs composite aerogel will release H2O during the battery self-heating stage (80℃~140℃), which can reduce the local temperature of the battery, slow the temperature rise rate, and avoid the chain reaction in the early stage of thermal runaway; when the temperature continues to rise, the PDMS-MAP / MOFs composite aerogel will release NH3, which can not only dilute the O2 concentration around the battery cell, but also form a flame-retardant gas layer on the surface of the protective material. When the temperature of the battery cell rises further or even explodes, the MAP and MOFs materials decompose and react eutectic to generate a mixture of magnesium pyrophosphate and phosphate. This mixture and the carbon layer will form a dense new bimetallic composite flame-retardant layer. This flame-retardant layer can not only hinder the further transfer of heat, but also isolate oxygen and flame, thereby further improving the flame retardant properties of the material.

[0005] Tian et al. (Feiyu Tian, Wuyu Tao, et al. Preparation of ZIF67-modifiedphosphate compounds for enhancing fire safety of strandboards[J]. Chemical Engineering Journal, 2024, 483(149393): 1-10.) used piperazine-modified ammonium polyphosphate (APz) as raw material and grew Co on its surface. 2+, synthesized a core-shell structure flame retardant (APz@ZIF67) and added APz@ZIF67 to wood particleboard, which greatly improved the flame retardancy and mechanical properties of the wood particleboard. However, when the particleboard was eroded by flame, a brittle carbon layer was generated on the surface. This carbon layer was difficult to resist the impact of the flame and peeled off. At the same time, the carbon layer was prone to secondary combustion.

[0006] Guo Xin et al. (Guo Xin, Su Hongxi, Zhao Hong et al. Study on the influence of sepiolite / in situ generated magnesium hydroxide on the performance of agar-based aerogels [J]. Materials Guide, 2023, 37(5): 21090278) generated magnesium hydroxide (MH) in situ in an agar (AG) / polyvinyl alcohol (PVA) matrix by hydrating magnesium hydroxide, and introduced sepiolite clay (SP) into the composite system to compound MH. Finally, a composite aerogel was prepared by freeze-drying. The limiting oxygen index of the aerogel can reach 31.6%. However, when the composite aerogel is eroded by flame, it can only be flame-retarded by the carbon layer generated on the surface of the aerogel. The flame retardant effect is poor, and the carbon layer generated on the surface is brittle, which has the risk of secondary re-ignition.

[0007] The Chinese patent "A boron-modified Kevlar aerogel flame-retardant thermal insulation material and its preparation method" (application number: 202510005031.4, publication number: CN119410023A, publication date: 2025.02.11) discloses a boron-modified Kevlar aerogel flame-retardant thermal insulation material and its preparation method, which uses a solvent thermal method to prepare a boron-modified Kevlar initial gel. The boron-modified Kevlar aerogel flame-retardant thermal insulation material has a three-dimensional nanoporous network structure and the aerogel has excellent thermal stability. However, when the aerogel is eroded by flame, the aerogel will generate a brittle flame-retardant carbon layer, causing the three-dimensional nanoporous network structure to collapse. At the same time, the aerogel will decompose in the middle and late stages of thermal runaway, resulting in poor flame retardancy. Summary of the Invention

[0008] In response to the problems existing in the prior art, the present invention provides a multi-stage dynamic protective refractory sheet for battery module thermal runaway and a preparation method thereof, which solves the problem in the prior art that the flame-retardant carbon layer generated when the battery module protective material is eroded by flame has low mechanical properties, resulting in the collapse of the protective material structure and the carbon layer is prone to secondary reignition. At the same time, it solves the problem that the current protective material can only play a role in the middle and late stages of battery thermal runaway, resulting in poor protective performance.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A method for preparing a multi-stage dynamic protection refractory sheet for thermal runaway of a battery module is specifically implemented according to the following steps:

[0011] Step 1, prepare MAP precursor solution

[0012] Anhydrous magnesium chloride, sodium dihydrogen phosphate, and ammonium chloride are dissolved in deionized water, the obtained mixed solution is preheated in a water bath, and sodium hydroxide solution is slowly added dropwise to the mixed solution until the pH of the mixed solution is alkaline. The mixed solution is then heated in a water bath and stirred to obtain a MAP precursor solution.

[0013] Step 2: Preparation of MAP powder

[0014] The MAP precursor solution prepared in step 1 was centrifuged to obtain a white precipitate, and the white precipitate was repeatedly washed with deionized water, and then the white precipitate was freeze-dried to obtain MAP powder;

[0015] Step 3: Preparation of MOFs precursor solution

[0016] Dissolving metal salt and organic ligand powder in an organic solvent to obtain a MOFs precursor solution;

[0017] Step 4: Preparation of MAP / MOFs powder

[0018] The MAP powder prepared in step 2 is added to the MOFs precursor solution prepared in step 3, and stirred until the MAP powder is evenly dispersed in the MOFs precursor solution; the obtained mixed solution is hydrothermalized, and the hydrothermal mixed solution is centrifuged to obtain a precipitate, and the precipitate is repeatedly washed and dried to obtain MAP / MOFs powder;

[0019] Step 5: Preparation of MAP / MOFs aerogel

[0020] Adding a cryo-binder to the MAP / MOFs powder prepared in step 4, uniformly dispersing the powder in the cryo-binder under magnetic stirring to obtain a mixed solution, and then freeze-drying the mixed solution to obtain a MAP / MOFs aerogel;

[0021] Step 6: Preparation of PDMS-MAP / MOFs aerogel

[0022] The PDMS main agent and the curing agent are mixed, and then an organic solvent is slowly added, and the mixture is placed on a magnetic stirrer for stirring to obtain a PDMS diluted solution; the MAP / MOFs aerogel prepared in step 5 is placed in the PDMS diluted solution and immersed in a vacuum drying oven to obtain a PDMS-MAP / MOFs aerogel;

[0023] Step 7: Drying and curing

[0024] The PDMS-MAP / MOFs aerogel prepared in step 6 is dried to obtain a multi-stage dynamic protective refractory sheet.

[0025] Furthermore, in step 1, the stoichiometric ratio of anhydrous magnesium chloride, sodium dihydrogen phosphate and ammonium chloride is (1-1.5):1:1, the volume of deionized water is 100ml-300ml, and NH4 + The molar concentration is 0.001mol / L~0.1mol / L, the water bath temperature is 30℃~50℃, the preheating time is 30min~60min, the mass fraction of the sodium hydroxide solution is 10wt.%~30wt.%, the pH of the mixed solution is adjusted to 9.0~10.0, and the water bath growth time is 60min~120min.

[0026] Furthermore, in step 2, the centrifugal speed is 5000 r / min to 10000 r / min, the single centrifugation time is 3 min to 10 min, the white precipitate is washed 3 to 10 times, the freezing temperature is -50°C to -40°C, the freezing time is 10 to 30 min, the drying temperature is 30°C to 55°C, and the drying time is 24 to 96 h.

[0027] Furthermore, in step 3, the metal salt is any one of ferric nitrate nonahydrate, cobalt nitrate hexahydrate, chromium nitrate nonahydrate, zinc nitrate hexahydrate, and copper nitrate trihydrate, the organic ligand powder is any one of terephthalic acid, trimesic acid, phthalic acid, and 2-methylimidazole, and the organic solvent is any one or two of anhydrous ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and N-methylpyrrolidone.

[0028] Furthermore, the molar ratio of the organic ligand powder to the metal salt is 0.5 to 2, and the molar concentration of the metal salt in the organic solvent is 0.001 mol / L to 0.1 mol / L.

[0029] Furthermore, in step 4, the molar ratio of the MOFs precursor solution to the MAP powder is 0.1 to 3, the stirring speed is 400 r / min to 800 r / min, the stirring time is 60 min to 90 min, the hydrothermal temperature is 40°C to 60°C, the hydrothermal time is 24 h to 48 h, the centrifugal speed is 5000 r / min to 10000 r / min, the single centrifugation time is 3 min to 10 min, the number of precipitation washings is 5 to 10 times, the precipitation drying temperature is 40°C to 60°C, and the drying time is 6 h to 10 h.

[0030] Furthermore, in step 5, the frozen binder is any one of polyvinyl alcohol, polyvinyl pyrrolidone, polystyrene, and chitosan, the mass fraction of the frozen binder is between 2.5wt.% and 5wt.%, the mass ratio of MAP / MOFs powder to the frozen binder is 0.1 to 0.7, the magnetic stirring speed is 400r / min to 800r / min, the stirring time is 30min to 60min, the freezing temperature is -50℃ to -40℃, the freezing time is 10 to 30min, the drying temperature is 30℃ to 55℃, and the drying time is 24 to 96h.

[0031] Furthermore, in step 6, the mass ratio of the PDMS main agent to the curing agent is 10:1, the mass fraction of the PDMS main agent in the organic solvent is 10wt.% to 30wt.%, the organic solvent is any one of n-hexane, cyclohexane, toluene, isopropanol, tetrachloroethylene, ethanol, methanol, and tert-butanol, the magnetic stirring speed is 400r / min to 800r / min, the magnetic stirring time is 30min to 60min, the immersion temperature in the vacuum drying oven is 30°C to 50°C, and the immersion time is 15min to 60min.

[0032] Furthermore, in step 7, the drying temperature is 30° C. to 50° C., and the drying time is 4 h to 6 h.

[0033] The multi-stage dynamic protection refractory sheet is prepared according to the above-mentioned method for preparing a multi-stage dynamic protection refractory sheet for thermal runaway of a battery module.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention prepares a multi-stage dynamic protection refractory sheet for thermal runaway of battery modules. The material uses a green inorganic flame retardant - MAP to construct a stable three-dimensional rigid network structure, and is physically and chemically cross-linked and encapsulated by PDMS elastomer, thereby providing elastic support and enhancing the structural stability of the material. In order to further improve the interfacial bonding strength between MAP and PDMS, the present invention uses MAP as a matrix and in situ grows MOFs on its surface, making it a bridge connecting MAP and PDMS elastomer, significantly improving the room temperature mechanical properties of the refractory sheet; when thermal runaway occurs in a battery cell, the material can realize the combination of intelligent fire extinguishing and multiple flame retardant protection: first, MAP will self-generate heat from the thermal runaway stage of the battery. Starting in the first stage, as the temperature continues to rise, flammable gases such as H2O are released. This not only effectively dilutes the oxygen concentration around the battery cells but also reduces their temperature, thereby delaying thermal runaway and achieving intelligent fire extinguishing. Secondly, as the temperature of the battery cells continues to rise, MAP further decomposes to produce NH3. The high temperature surrounding the battery causes NH3 to form a flammable gas layer on the surface of the protective material, further improving the flame retardancy. Finally, when the thermal runaway temperature of the battery cells rises further and a deflagration occurs, the MOFs material, with its excellent adsorption and catalytic properties, not only efficiently absorbs toxic gases such as CO released during thermal runaway, but also catalyzes the formation of a flame-retardant carbon layer from organic ligands. Simultaneously, the MOFs material and MAP undergo a eutectic reaction at high temperatures, forming a mixed ceramic phase of magnesium pyrophosphate and a phosphate compound. This ceramic phase and the carbon layer form a new, dense composite flame-retardant layer. This multiple protection mechanism gives this material broad application prospects in the field of thermal runaway protection for battery modules. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of the preparation of PDMS-MAP / MOFs aerogels according to the present invention;

[0037] Figure 2 is the SEM image of the MAP / MOFs powder prepared by the present invention;

[0038] Figure 3 It is a compressive stress-strain curve diagram of the PDMS-MAP / MOFs aerogel prepared by the present invention. DETAILED DESCRIPTION

[0039] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] like Figure 1 As shown, a multi-stage dynamic protection refractory sheet for thermal runaway of battery modules and a preparation method thereof are specifically implemented in the following steps:

[0041] Step 1, prepare MAP precursor solution

[0042] Dissolve anhydrous magnesium chloride, sodium dihydrogen phosphate and ammonium chloride in 100ml to 300ml of deionized water at a stoichiometric ratio of (1 to 1.5): 1: 1, place the mixed solution in a 30°C to 50°C water bath and preheat at 300r / min to 600r / min for 30min to 60min, dropwise add sodium hydroxide solution into the mixed solution until the pH of the mixed solution reaches 9.0 to 10.0, and continue stirring the mixed solution in a 30°C to 50°C water bath at 300r / min to 600r / min for 60min to 120min to obtain a MAP precursor solution. + The molar concentration is 0.001 mol / L to 0.1 mol / L, and the mass fraction of the sodium hydroxide solution is 10 wt.% to 30 wt.%.

[0043] Step 2: Preparation of MAP powder

[0044] The MAP precursor solution in step 1 is centrifuged at 5,000 to 10,000 rpm for 3 to 10 minutes to obtain a white precipitate. The white precipitate is repeatedly washed with deionized water 3 to 10 times, and then freeze-dried in a freeze dryer to obtain MAP powder. The freezing temperature is -50°C to -40°C, the freezing time is 10 to 30 minutes, and the drying temperature is 30°C to 55°C, and the drying time is 24 to 96 hours.

[0045] Step 3: Preparation of MOFs precursor solution

[0046] The metal salt and the organic ligand powder are dissolved in an organic solvent in a certain molar ratio to obtain a MOFs precursor solution; wherein the metal salt is any one of ferric nitrate nonahydrate (Fe(NO3)3·9H2O), cobalt nitrate hexahydrate (Co(NO3)2·6H2O), chromium nitrate nonahydrate (Cr(NO3)3·9H2O), zinc nitrate hexahydrate (Zn(NO3)2·6H2O), copper nitrate trihydrate (Cu(NO3)2·3H2O), etc., and the organic ligand powder is terephthalic acid (BDC ), any one of trimesic acid (BTC), phthalic acid (DOP), 2-methylimidazole (2-MI), etc., the molar ratio of the organic ligand powder to the metal salt is 0.5 to 2, the organic solvent is any one or two of anhydrous ethanol, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), tetrahydrofuran (THF), N-methylpyrrolidone (NMP), etc., and the molar concentration of the metal salt in the organic solvent is 0.001 mol / L to 0.1 mol / L.

[0047] Step 4: Preparation of MAP / MOFs powder

[0048] The MAP powder from step 2 is added to the MOF precursor solution from step 3 and stirred at a stirring speed of 400-800 rpm for 60-90 minutes to ensure that the MAP powder is evenly dispersed in the MOF precursor solution. The mixed solution is poured into a polytetrafluoroethylene-lined container and hydrothermally heated in a 40-60°C hydrothermal drying oven for 24-48 hours. The hydrothermal mixed solution is centrifuged at 5000-10000 rpm for 3-10 minutes to obtain a precipitate. The precipitate is washed repeatedly with anhydrous ethanol 5-10 times and then dried in a 40-60°C drying oven for 6-10 hours to obtain a MAP / MOF powder. The molar ratio of MOFs to MAP is 0.1-3.

[0049] Step 5: Preparation of MAP / MOFs aerogel

[0050] A freeze binder is added to the MAP / MOFs powder in step 4, and the mixture is stirred at a stirring speed of 400 to 800 rpm for 30 to 60 minutes to ensure that the powder is evenly dispersed in the freeze binder. The mixed solution is then poured into a freezing mold and placed in a freeze dryer for freeze drying to obtain a MAP / MOFs aerogel. The freeze binder is any one of polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polystyrene (PS), chitosan (CHI), etc., with a mass fraction of the freeze binder between 2.5 wt.% and 5 wt.%, a mass ratio of MAP / MOFs powder to freeze binder between 0.1 and 0.7, a freezing temperature between -50°C and -40°C, a freezing time between 10 and 30 minutes, and a drying temperature between 30°C and 55°C, for a drying time between 24 and 96 hours.

[0051] Step 6: Preparation of PDMS-MAP / MOFs aerogel

[0052] The PDMS base and curing agent are mixed in a mass ratio of 10:1, and then an organic solvent is slowly added dropwise. The mixture is stirred on a magnetic stirrer at 400-800 rpm for 30-60 minutes to obtain a PDMS dilute solution. The MAP / MOFs aerogel from step 5 is placed in the PDMS dilute solution and immersed in a vacuum drying oven at 30-50°C for 15-60 minutes to obtain a PDMS-MAP / MOFs aerogel. The organic solvent is any one of n-hexane, cyclohexane, toluene, isopropanol, tetrachloroethylene, ethanol, methanol, tert-butanol, etc., and the mass fraction of the PDMS base in the organic solvent is 10-30 wt.%.

[0053] Step 7: Drying and curing

[0054] The PDMS-MAP / MOFs aerogel in step 6 was placed in a drying oven at 30° C. to 50° C. and dried for 4 to 6 hours to obtain a multi-stage dynamic protective refractory sheet.

[0055] Figure 2 This is the SEM spectrum of the MAP / MOFs powder prepared by the present invention. Figure 2 It can be seen that the MOFs prepared by the hydrothermal method are uniformly coated on the MAP surface, and the size of the MOFs particles is between 20nm and 50nm.

[0056] Figure 3 : is the compressive stress-strain curve of the PDMS-MAP / MOFs aerogel prepared by the present invention. Figure 3 It can be seen that the PDMS-MAP / MOFs aerogel can reach a compressive strength of about 16 MPa at 80% strain. Impregnation of PDMS on the surface of the MAP rigid network improves the toughness of the material and reduces the brittleness of the rigid network.

[0057] The present invention selects the green inorganic flame retardant - MAP to construct a stable three-dimensional rigid network, and uses PDMS elastomer to encapsulate the MAP aerogel. By adjusting the PDMS coating amount, physical and chemical cross-linking of the molecular chains is achieved to provide elastic support for the MAP aerogel, thereby enabling the composite aerogel to have excellent structural stability and outstanding impact resistance. At the same time, MOFs are generated in situ on the MAP surface to enhance the bonding force between MAP and PDMS elastomer, thereby improving the mechanical properties of the composite aerogel. When a battery cell experiences thermal runaway, during the self-heating phase of thermal runaway, MAP decomposes to produce flame-retardant gases such as H2O. This not only dilutes the O2 concentration around the battery cell, but also reduces the temperature of the cell, delaying the onset of thermal runaway. As the thermal runaway temperature rises further, MAP further decomposes to produce NH3, forming a flame-retardant gas layer on the surface of the protective material, improving its flame retardancy. When the battery thermal runaway temperature continues to rise and deflagration occurs, by regulating the loading of MOFs on the MAP surface, the protective material can effectively adsorb toxic gases such as CO when eroded by flames, and catalyze its organic ligands to form a flame-retardant carbon layer, further improving the flame retardancy of the protective material. Simultaneously, MOFs and MAP undergo a eutectic reaction at high temperatures, forming a mixed ceramic phase of magnesium pyrophosphate and phosphate compounds. This ceramic phase and the carbon layer form a dense new composite flame-retardant layer, further improving the flame retardancy while imparting certain mechanical properties to the flame-resistant layer.

[0058] Example 1 Preparation of PDMS-MAP / (Fe-BDC) refractory sheet

[0059] First, 0.0609 g of anhydrous magnesium chloride, 0.0468 g of sodium dihydrogen phosphate, and 0.016 g of ammonium chloride were dissolved in 300 ml of deionized water. The mixed solution was then placed in a 30°C water bath and preheated at 300 rpm for 30 min. Subsequently, 10 wt.% NaOH solution was added dropwise to the mixed solution to adjust the pH of the solution to 9.0. The mixed solution was stirred in a 30°C water bath at 300 rpm for 60 min to obtain a MAP precursor solution.

[0060] The MAP precursor solution was centrifuged at 5000 r / min for 3 min to obtain a white precipitate, which was then washed three times with deionized water. The white precipitate was then placed in a freeze dryer and frozen at -50°C for 10 min and then dried at 30°C for 24 h to obtain MAP powder.

[0061] 0.019 g of Fe(NO3)3·9H2O and 0.013 g of BDC were dissolved in 80 ml of DMF to obtain a Fe-BDC precursor solution;

[0062] 24.5 g of MAP powder was added to the Fe-BDC precursor solution and stirred at 400 r / min for 60 min. The mixed solution was then poured into a polytetrafluoroethylene-lined container and placed in a hydrothermal drying oven at 40°C for 24 h. The hydrothermal solution was then centrifuged at 5000 r / min for 3 min to obtain a precipitate. The precipitate was washed repeatedly with anhydrous ethanol five times and dried in a drying oven at 40°C for 6 h to obtain MAP / (Fe-BDC) powder.

[0063] 5 g of MAP / (Fe-BDC) powder was added to 50 g of 2.5 wt.% PVA solution and stirred at 400 rpm for 30 min. The mixed solution was poured into a freezing mold, frozen at -50°C for 10 min, and then dried at 30°C for 24 h to obtain MAP / (Fe-BDC) aerogel.

[0064] 5 g of PDMS base agent and 0.5 g of PDMS curing agent were mixed, 49.5 g of n-hexane solution was added, and the mixture was stirred on a magnetic stirrer at 400 rpm for 30 min to obtain a PDMS diluted solution. The MAP / (Fe-BDC) aerogel was placed in the PDMS diluted solution and immersed in a vacuum drying oven at 30°C for 15 min.

[0065] The PDMS-MAP / (Fe-BDC) aerogel was placed in a drying oven at 30° C. and dried for 4 h to obtain a refractory sheet.

[0066] Control group 1: preparation of PDMS-MAP refractory sheet

[0067] First, 0.0609 g of anhydrous magnesium chloride, 0.0468 g of sodium dihydrogen phosphate, and 0.016 g of ammonium chloride were dissolved in 300 ml of deionized water. The mixed solution was then placed in a 30°C water bath and preheated at 300 rpm for 30 min. Subsequently, 10 wt.% NaOH solution was added dropwise to the mixed solution to adjust the pH of the solution to 9.0. The mixed solution was stirred in a 30°C water bath at 300 rpm for 60 min to obtain a MAP precursor solution.

[0068] The MAP precursor solution was centrifuged at 5000 rpm for 3 minutes to obtain a white precipitate, which was then washed three times with deionized water. The white precipitate was then placed in a freeze dryer, frozen at -50°C for 10 minutes, and then dried at 30°C for 24 hours to obtain MAP powder. 5 g of MAP powder was added to 50 g of a 2.5 wt.% PVA solution, stirred at 400 rpm for 30 minutes, and the mixed solution was poured into a freezing mold, frozen at -50°C for 10 minutes, and then dried at 30°C for 24 hours to obtain MAP aerogel.

[0069] 5 g of PDMS main agent and 0.5 g of PDMS curing agent were mixed, 49.5 g of n-hexane solution was added, and stirred on a magnetic stirrer at 400 r / min for 30 min to obtain a PDMS diluted solution; MAP aerogel was placed in the PDMS diluted solution and immersed in a vacuum drying oven at 30°C for 15 min; the PDMS-MAP aerogel was placed in a drying oven at 30°C and dried for 4 h to obtain a refractory sheet.

[0070] Example 2 Preparation of PDMS-MAP / (Co-BTC) refractory sheet

[0071] First, 22.363 g of anhydrous magnesium chloride, 12.098 g of sodium dihydrogen phosphate, and 5.349 g of ammonium chloride were dissolved in 100 ml of deionized water. The mixed solution was placed in a 40°C water bath and preheated at 400 rpm for 50 min. Subsequently, a 15 wt.% NaOH solution was added dropwise to the mixed solution to adjust the pH of the solution to 9.6. The mixed solution was stirred in a 40°C water bath at 400 rpm for 90 min to obtain a MAP precursor solution.

[0072] The MAP precursor solution was centrifuged at 8000 r / min for 5 min to obtain a white precipitate, which was then washed five times with deionized water. The white precipitate was then placed in a freeze dryer and frozen at -40°C for 20 min and then dried at 36°C for 36 h to obtain MAP powder.

[0073] 16.705 g of Co(NO3)2·6H2O and 21.014 g of BTC were dissolved in 20 ml of DMA to obtain a Co-BTC precursor solution;

[0074] 12.25 g of MAP powder was added to the Co-BTC precursor solution and stirred at 600 r / min for 80 min. The mixed solution was then poured into a polytetrafluoroethylene-lined container and placed in a hydrothermal drying oven at 50°C for 36 h. The hydrothermal mixed solution was then centrifuged at 8000 r / min for 5 min to obtain a precipitate. The precipitate was washed repeatedly with anhydrous ethanol seven times and dried in a drying oven at 50°C for 8 h to obtain MAP / (Fe-BDC) powder.

[0075] 10 g of MAP / (Fe-BDC) powder was added to 20 g of a 3 wt.% PVP solution and stirred at 700 rpm for 40 min. The mixed solution was poured into a frozen mold, which was placed in a freeze dryer and frozen at -40°C for 20 min and then dried at 36°C for 36 h to obtain MAP / (Co-BTC) aerogel.

[0076] 6 g of PDMS base agent and 0.6 g of PDMS curing agent were mixed, 26.4 g of n-hexane solution was added, and the mixture was stirred on a magnetic stirrer at 600 rpm for 40 min to obtain a PDMS diluted solution. The MAP / (Fe-BDC) aerogel was placed in the PDMS diluted solution and immersed in a vacuum drying oven at 40°C for 30 min.

[0077] The PDMS-MAP / (Co-BTC) aerogel was placed in a drying oven at 40°C and dried for 5 h to obtain a refractory sheet.

[0078] Control group 2: Preparation of PDMS-MAP refractory sheet

[0079] First, 22.363 g of anhydrous magnesium chloride, 12.098 g of sodium dihydrogen phosphate, and 5.349 g of ammonium chloride were dissolved in 100 ml of deionized water. The mixed solution was placed in a 40°C water bath and preheated at 400 rpm for 50 min. Subsequently, a 15 wt.% NaOH solution was added dropwise to the mixed solution to adjust the pH of the solution to 9.6. The mixed solution was stirred in a 40°C water bath at 400 rpm for 90 min to obtain a MAP precursor solution.

[0080] The MAP precursor solution was centrifuged at 8000 r / min for 5 min to obtain a white precipitate, which was then washed five times with deionized water. The white precipitate was then placed in a freeze dryer and frozen at -40°C for 20 min and then dried at 36°C for 36 h to obtain MAP powder.

[0081] 10g of MAP powder was added to 20g of a 3wt.% PVP solution, stirred at 700r / min for 40min, and the mixed solution was poured into a frozen mold. The mold was placed in a freeze dryer, frozen at -40°C for 20min, and then dried at 36°C for 36h to obtain a MAP aerogel. 6g of PDMS main agent and 0.6g of PDMS curing agent were mixed, 26.4g of n-hexane solution was added, and stirred on a magnetic stirrer at 600r / min for 40min to obtain a PDMS diluted solution. The MAP aerogel was placed in the PDMS diluted solution and immersed in a vacuum drying oven at 40°C for 30min. The PDMS-MAP aerogel was placed in a drying oven at 40°C and dried for 5h to obtain a refractory sheet.

[0082] Example 3 Preparation of PDMS-MAP / (Cr-DOP) refractory sheet

[0083] First, 9.135 g of anhydrous magnesium chloride, 4.68 g of sodium dihydrogen phosphate, and 1.6047 g of ammonium chloride were dissolved in 300 ml of deionized water. The mixed solution was placed in a 50°C water bath and preheated at 600 rpm for 60 min. Subsequently, a 30 wt.% NaOH solution was added dropwise to the mixed solution to adjust the pH of the solution to 10.0. The mixed solution was stirred in a 50°C water bath at 600 rpm for 120 min to obtain a MAP precursor solution.

[0084] The MAP precursor solution was centrifuged at 10,000 r / min for 3 minutes to obtain a white precipitate, which was then washed repeatedly with deionized water 10 times. The white precipitate was then placed in a freeze dryer, frozen at -50°C for 30 minutes, and then dried at 55°C for 48 hours to obtain MAP powder.

[0085] 5.950 g of Cr(NO3)2·9H2O and 8.3 g of DOP were dissolved in 50 ml of THF to obtain a Cr-DOP precursor solution;

[0086] 6.125 g of MAP was added to the Cr-DOP precursor solution and stirred at 800 rpm for 90 min. The mixed solution was then poured into a polytetrafluoroethylene-lined container and placed in a hydrothermal drying oven at 60°C for 48 h. The hydrothermal solution was then centrifuged at 10,000 rpm for 3 min to obtain a precipitate. The precipitate was washed repeatedly with anhydrous ethanol 10 times and dried in a drying oven at 60°C for 10 h to obtain MAP / (Cr-DOP) powder.

[0087] 10 g of MAP / (Cr-DOP) powder was added to 14.3 g of a 5 wt.% PS solution and stirred at 800 rpm for 60 min. The mixed solution was poured into a freezing mold, which was then placed in a freeze dryer and frozen at -50°C for 30 min and then dried at 55°C for 48 h to obtain a MAP / (Cr-DOP) aerogel.

[0088] 6 g of PDMS base agent and 0.6 g of PDMS curing agent were mixed, 15.4 g of cyclohexane solution was added, and the mixture was stirred on a magnetic stirrer at 800 rpm for 60 min to obtain a PDMS diluted solution. The MAP / (Cr-DOP) aerogel was placed in the PDMS diluted solution and immersed in a vacuum drying oven at 50°C for 60 min.

[0089] The PDMS-MAP / (Cr-DOP) aerogel was placed in a drying oven at 50°C and dried for 6 h to obtain a refractory sheet.

[0090] Control group 3: Preparation of PDMS-MAP refractory sheet

[0091] First, 9.135 g of anhydrous magnesium chloride, 4.68 g of sodium dihydrogen phosphate, and 1.6047 g of ammonium chloride were dissolved in 300 ml of deionized water. The mixed solution was placed in a 50°C water bath and preheated at 600 rpm for 60 min. Subsequently, a 30 wt.% NaOH solution was added dropwise to the mixed solution to adjust the pH of the solution to 10.0. The mixed solution was stirred in a 50°C water bath at 600 rpm for 120 min to obtain a MAP precursor solution.

[0092] The MAP precursor solution was centrifuged at 10,000 r / min for 3 minutes to obtain a white precipitate, which was then washed repeatedly with deionized water 10 times. The white precipitate was then placed in a freeze dryer, frozen at -50°C for 30 minutes, and then dried at 55°C for 48 hours to obtain MAP powder.

[0093] 10g of MAP powder was added to 14.3g of a 5wt.% PS solution, stirred at 800r / min for 60min, and the mixed solution was poured into a frozen mold. The mold was placed in a freeze dryer and frozen at -50°C for 30min and then dried at 55°C for 48h to obtain MAP aerogel. 6g of PDMS main agent and 0.6g of PDMS curing agent were mixed, 15.4g of cyclohexane solution was added, and stirred on a magnetic stirrer at 800r / min for 60min to obtain a PDMS diluted solution. The MAP aerogel was placed in the PDMS diluted solution and immersed in a vacuum drying oven at 50°C for 60min. The PDMS-MAP aerogel was placed in a drying oven at 50°C and dried for 6h to obtain a refractory sheet.

[0094] Example 4 Preparation of PDMS-MAP / (Cu-2-MI) Refractory Sheet

[0095] First, 9.135 g of anhydrous magnesium chloride, 4.68 g of sodium dihydrogen phosphate, and 1.6047 g of ammonium chloride were dissolved in 300 ml of deionized water. The mixed solution was placed in a 50°C water bath and preheated at 600 rpm for 60 min. Subsequently, a 30 wt.% NaOH solution was added dropwise to the mixed solution to adjust the pH of the solution to 10.0. The mixed solution was stirred in a 50°C water bath at 600 rpm for 120 min to obtain a MAP precursor solution.

[0096] The MAP precursor solution was centrifuged at 10,000 rpm for 3 minutes to obtain a white precipitate, which was then washed repeatedly with deionized water 10 times. The white precipitate was then placed in a freeze dryer and frozen at -50°C for 30 minutes and then dried at 55°C for 48 hours to obtain MAP powder.

[0097] 5.950 g of Cr(NO3)2·9H2O and 8.3 g of DOP were dissolved in 50 ml of THF to obtain a Cr-DOP precursor solution;

[0098] 6.125 g of MAP was added to the Cr-DOP precursor solution and stirred at 800 rpm for 90 min. The mixed solution was then poured into a polytetrafluoroethylene-lined container and placed in a hydrothermal drying oven at 60°C for 48 h. The hydrothermal solution was then centrifuged at 10,000 rpm for 3 min to obtain a precipitate. The precipitate was washed repeatedly with anhydrous ethanol 10 times and dried in a drying oven at 60°C for 10 h to obtain MAP / (Cr-DOP) powder.

[0099] 10 g of MAP / (Cr-DOP) powder was added to 14.3 g of a 5 wt.% PS solution and stirred at 800 rpm for 60 min. The mixed solution was poured into a freezing mold, which was then placed in a freeze dryer and frozen at -50°C for 30 min and then dried at 55°C for 48 h to obtain a MAP / (Cr-DOP) aerogel.

[0100] 6 g of PDMS base agent and 0.6 g of PDMS curing agent were mixed, 15.4 g of cyclohexane solution was added, and the mixture was stirred on a magnetic stirrer at 800 rpm for 60 min to obtain a PDMS diluted solution. The MAP / (Cr-DOP) aerogel was placed in the PDMS diluted solution and immersed in a vacuum drying oven at 50°C for 60 min.

[0101] The PDMS-MAP / (Cr-DOP) aerogel was placed in a drying oven at 50°C and dried for 6 h to obtain a refractory sheet.

[0102] Control group 4: preparation of PDMS-MAP refractory sheet

[0103] First, 9.135 g of anhydrous magnesium chloride, 4.68 g of sodium dihydrogen phosphate, and 1.6047 g of ammonium chloride were dissolved in 300 ml of deionized water. The mixed solution was placed in a 50°C water bath and preheated at 600 rpm for 60 min. Subsequently, a 30 wt.% NaOH solution was added dropwise to the mixed solution to adjust the pH of the solution to 10.0. The mixed solution was stirred in a 50°C water bath at 600 rpm for 120 min to obtain a MAP precursor solution.

[0104] The MAP precursor solution was centrifuged at 10,000 rpm for 3 minutes to obtain a white precipitate, which was then washed repeatedly with deionized water 10 times. The white precipitate was then placed in a freeze dryer and frozen at -50°C for 30 minutes and then dried at 55°C for 48 hours to obtain MAP powder.

[0105] 10g of MAP powder was added to 14.3g of a 5wt.% PS solution, stirred at 800r / min for 60min, and the mixed solution was poured into a frozen mold. The mold was placed in a freeze dryer and frozen at -50°C for 30min and then dried at 55°C for 48h to obtain MAP aerogel. 6g of PDMS main agent and 0.6g of PDMS curing agent were mixed, 15.4g of cyclohexane solution was added, and stirred on a magnetic stirrer at 800r / min for 60min to obtain a PDMS diluted solution. The MAP aerogel was placed in the PDMS diluted solution and immersed in a vacuum drying oven at 50°C for 60min. The PDMS-MAP aerogel was placed in a drying oven at 50°C and dried for 6h to obtain a refractory sheet.

[0106] Table 1 is a performance comparison of the existing battery flame retardant material and the fire-resistant sheets prepared in Examples 1-4 of the present invention and Control Groups 1-4 of Examples 1-4.

[0107] Table 1 Comparison of performance of existing battery flame retardant materials and fire-resistant sheets

[0108]

[0109]

[0110] As can be seen from Table 1, the HRR of the existing battery flame retardant material APz@ZIF6 is 100KW / m 2, the LOI index is 55%, indicating that the flame retardant performance is much lower than that of the refractory sheet. The LOI of the PDMS-MAP refractory sheet in the control group is less than the LOI of the refractory sheet in the corresponding embodiment, and the HRR and THR in each control group are much greater than the refractory sheet in the corresponding embodiment, proving that the flame retardant performance of the refractory sheet prepared in Examples 1-4 is better than that of the control group, and the compressive strength of the refractory sheet in the embodiment after treatment at 800°C for 30 minutes is much greater than that of the control group, indicating that a dense composite ceramic layer is generated after high-temperature treatment of the refractory sheet in Examples 1-4. The introduction of PDMS elastomer into the MAP / MOFs rigid network system to construct a two-phase structure not only improves the room temperature mechanical properties of PDMS-MAP / MOFs, but also gives the material superhydrophobic properties. When the battery undergoes thermal runaway, MAP decomposes in different temperature ranges to release different flame retardant gases, which can not only dilute the O2 concentration around the battery cell, but also generate a flame retardant gas layer on the surface of the composite aerogel, thereby improving the flame retardant performance of the material. The introduction of MOFs not only catalyzes the formation of a flame-retardant carbon layer but also absorbs toxic gases like CO, further enhancing the material's flame retardancy and enabling the LOI of the refractory sheet to exceed 60%. When the composite aerogel is exposed to flames, MAP and MOFs react at high temperatures to form a mixed ceramic phase of magnesium pyrophosphate and phosphate. This ceramic phase and the carbon layer interpenetrate through molecules to form a new, dense composite flame-retardant layer with a compressive strength of approximately 2.5 MPa.

[0111] The above-described embodiments merely represent specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing a multi-stage dynamic protection refractory sheet for thermal runaway of a battery module, characterized in that: Please follow the steps below to implement it: Step 1, prepare MAP precursor solution Anhydrous magnesium chloride, sodium dihydrogen phosphate, and ammonium chloride are dissolved in deionized water, the obtained mixed solution is preheated in a water bath, and sodium hydroxide solution is slowly added dropwise to the mixed solution until the pH of the mixed solution is alkaline. The mixed solution is then heated in a water bath and stirred to obtain a MAP precursor solution. Step 2: Preparation of MAP powder The MAP precursor solution prepared in step 1 was centrifuged to obtain a white precipitate, and the white precipitate was repeatedly washed with deionized water, and then the white precipitate was freeze-dried to obtain MAP powder; Step 3: Preparation of MOFs precursor solution Dissolving metal salt and organic ligand powder in an organic solvent to obtain a MOFs precursor solution; Step 4: Preparation of MAP / MOFs powder The MAP powder prepared in step 2 is added to the MOFs precursor solution prepared in step 3, and stirred until the MAP powder is evenly dispersed in the MOFs precursor solution; the obtained mixed solution is hydrothermalized, and the hydrothermal mixed solution is centrifuged to obtain a precipitate, and the precipitate is repeatedly washed and dried to obtain MAP / MOFs powder; Step 5: Preparation of MAP / MOFs aerogel Adding a cryo-binder to the MAP / MOFs powder prepared in step 4, uniformly dispersing the powder in the cryo-binder under magnetic stirring to obtain a mixed solution, and then freeze-drying the mixed solution to obtain a MAP / MOFs aerogel; Step 6: Preparation of PDMS-MAP / MOFs aerogel The PDMS main agent and the curing agent are mixed, and then an organic solvent is slowly added, and the mixture is placed on a magnetic stirrer for stirring to obtain a PDMS diluted solution; the MAP / MOFs aerogel prepared in step 5 is placed in the PDMS diluted solution and immersed in a vacuum drying oven to obtain a PDMS-MAP / MOFs aerogel; Step 7: Drying and curing The PDMS-MAP / MOFs aerogel prepared in step 6 is dried to obtain a multi-stage dynamic protective refractory sheet.

2. The method for preparing a multi-stage dynamic protective refractory sheet for thermal runaway of a battery module according to claim 1, characterized in that: In step 1, the stoichiometric ratio of anhydrous magnesium chloride, sodium dihydrogen phosphate and ammonium chloride is (1-1.5):1:1, the volume of deionized water is 100ml-300ml, NH4 + The molar concentration is 0.001mol / L~0.1mol / L, the water bath temperature is 30℃~50℃, the preheating time is 30min~60min, the mass fraction of the sodium hydroxide solution is 10wt.%~30wt.%, the pH of the mixed solution is adjusted to 9.0~10.0, and the water bath growth time is 60min~120min.

3. The method for preparing a multi-stage dynamic protective refractory sheet for thermal runaway of a battery module according to claim 1, characterized in that: In step 2, the centrifugal speed is 5000 r / min to 10000 r / min, the single centrifugation time is 3 min to 10 min, the white precipitate is washed 3 to 10 times, the freezing temperature is -50°C to -40°C, the freezing time is 10 to 30 min, the drying temperature is 30°C to 55°C, and the drying time is 24 to 96 h.

4. The method for preparing a multi-stage dynamic protective refractory sheet for thermal runaway of a battery module according to claim 1, characterized in that: In step 3, the metal salt is any one of ferric nitrate nonahydrate, cobalt nitrate hexahydrate, chromium nitrate nonahydrate, zinc nitrate hexahydrate, and copper nitrate trihydrate; the organic ligand powder is any one of terephthalic acid, trimesic acid, phthalic acid, and 2-methylimidazole; and the organic solvent is any one or two of anhydrous ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and N-methylpyrrolidone.

5. The method for preparing a multi-stage dynamic protective refractory sheet for thermal runaway of a battery module according to claim 4, characterized in that: The molar ratio of the organic ligand powder to the metal salt is 0.5-2, and the molar concentration of the metal salt in the organic solvent is 0.001 mol / L-0.1 mol / L.

6. The method for preparing a multi-stage dynamic protective refractory sheet for thermal runaway of a battery module according to claim 1, characterized in that: In step 4, the molar ratio of MOFs precursor solution to MAP powder is 0.1 to 3, the stirring speed is 400 r / min to 800 r / min, the stirring time is 60 min to 90 min, the hydrothermal temperature is 40°C to 60°C, the hydrothermal time is 24 h to 48 h, the centrifugal speed is 5000 r / min to 10000 r / min, the single centrifugation time is 3 min to 10 min, the number of precipitation washings is 5 to 10 times, the precipitation drying temperature is 40°C to 60°C, and the drying time is 6 h to 10 h.

7. The method for preparing a multi-stage dynamic protective refractory sheet for thermal runaway of a battery module according to claim 1, characterized in that: In step 5, the frozen binder is any one of polyvinyl alcohol, polyvinyl pyrrolidone, polystyrene, and chitosan, the mass fraction of the frozen binder is between 2.5wt.% and 5wt.%, the mass ratio of MAP / MOFs powder to the frozen binder is 0.1 to 0.7, the magnetic stirring speed is 400r / min to 800r / min, the stirring time is 30min to 60min, the freezing temperature is -50℃ to -40℃, the freezing time is 10 to 30min, the drying temperature is 30℃ to 55℃, and the drying time is 24 to 96h.

8. The method for preparing a multi-stage dynamic protective refractory sheet for thermal runaway of a battery module according to claim 1, characterized in that: In step 6, the mass ratio of the PDMS main agent to the curing agent is 10:1, the mass fraction of the PDMS main agent in the organic solvent is 10wt.% to 30wt.%, the organic solvent is any one of n-hexane, cyclohexane, toluene, isopropanol, tetrachloroethylene, ethanol, methanol, and tert-butanol, the magnetic stirring speed is 400r / min to 800r / min, the magnetic stirring time is 30min to 60min, the immersion temperature in the vacuum drying oven is 30°C to 50°C, and the immersion time is 15min to 60min.

9. The method for preparing a multi-stage dynamic protective refractory sheet for thermal runaway of a battery module according to claim 1, characterized in that: In step 7, the drying temperature is 30° C. to 50° C., and the drying time is 4 h to 6 h.

10. A multi-stage dynamic protection refractory sheet prepared by the method for preparing a multi-stage dynamic protection refractory sheet for thermal runaway of a battery module according to any one of claims 1 to 9.

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