A battery thermal runaway coating based on metal organic framework materials

Abstract

The application provides a battery thermal runaway coating based on a metal organic framework material and belongs to the technical field of new energy battery thermal management and safety protection. The application uses a high-temperature-resistant diaphragm as a base material, coats a mixture of A components (amine-functionalized ZIF-8, surface magnetic modification hexagonal boron nitride nanosheet, soluble polyimide, light-cured monomer and photoinitiator) and B components (natural camphor microparticles and AIBN) and uses a magnetic field to drive two-dimensional boron nitride to be arranged in a forced orientation, uses ultraviolet light to pre-cure and lock the orientation, makes camphor sublimate to form micron-level through holes through step-by-step heating, uses primary amines on the ZIF-8 to irreversibly capture hydrogen fluoride gas, uses the hexagonal boron nitride nanosheet to eliminate local hot spots, uses camphor sublimation to provide a rapid diffusion channel, uses light-cured crosslinked monomers to enhance the toughness of a gel network and prevent high-temperature cracking, so that a long-acting thermal runaway safety protection coating is obtained and the application is used in the fields of aviation power batteries and closed space power supply systems.

Description

Technical Field

[0001] This invention relates to the field of thermal management and safety protection technology for new energy batteries, specifically to a battery thermal runaway coating based on metal-organic framework materials. Background Technology

[0002] Currently, research on battery thermal runaway safety protective coatings mainly focuses on single-function directions such as physical barrier, phase change heat absorption, or chemical inhibition. These coatings suffer from common defects such as slow response, limited heat absorption capacity, inability to simultaneously eliminate toxic gases, and difficulty in recycling. In particular, there is a lack of multi-functional synergistic protection solutions for the extreme requirements of gas toxicity control in confined spaces such as aviation and energy storage power stations.

[0003] To address the numerous problems mentioned above, CN121427393A discloses a battery intelligent thermal management coating based on a reversible Diels-Alder reaction, its preparation method, and its application. This coating utilizes the endothermic reverse reaction between furan and maleimide groups in the early stages of thermal runaway, allowing for recycling. However, it relies on an organic polymer system, resulting in insufficient long-term thermal stability. Furthermore, it requires a protective isolation layer to block the electrolyte, leading to a complex structure. Additionally, the reverse reaction temperature window is narrow, making it difficult to adapt to the early thermal runaway characteristics of different battery systems. The coating thickness also has a certain impact on energy density. CN121293788A discloses a battery thermal runaway self-suppression coating based on an endothermic reverse aluminothermic reaction, its preparation method, and its application. This coating triggers a strong endothermic reaction between specific oxides and aluminum powder at a high temperature, generating a ceramic-metal composite insulation layer. However, its triggering temperature is too high, lagging behind the early critical point of thermal runaway. Moreover, the reaction is irreversible and requires one-time consumption, significantly increasing the coating thickness and weight. Furthermore, the presence of metal powder may pose insulation risks.

[0004] In summary, existing technologies still lack a coating solution that can respond rapidly in the early stages of thermal runaway, simultaneously and efficiently capture highly toxic HF and flammable gases, and combine in-plane rapid thermal conduction and microporous pressure relief functions. There is an urgent need to develop a battery thermal runaway coating based on metal-organic framework materials, which can achieve integrated synergistic protection of gas purification and thermal barrier through functionalized MOF chemical adsorption, directional arrangement of thermally conductive enhanced phases, and in-situ through-pore formation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a battery thermal runaway coating based on metal-organic framework (MOF) materials. This invention uses a high-temperature resistant membrane as the substrate. It involves coating a mixture of two components: component A (amine-functionalized ZIF-8, surface-magnetically modified hexagonal boron nitride nanosheets, soluble polyimide, photocurable monomers, and photoinitiator) and component B (natural camphor microparticles and AIBN). A magnetic field drives the two-dimensional boron nitride to align in a forced orientation, ultraviolet light pre-curing locks the orientation, and then step-by-step heating causes camphor sublimation to form micron-sized interconnected channels. The primary amines on ZIF-8 irreversibly capture hydrogen fluoride gas, the hexagonal boron nitride nanosheets eliminate local hot spots, camphor sublimation provides rapid diffusion channels, and photocurable crosslinking monomers enhance the gel network toughness to prevent high-temperature cracking. This results in a long-lasting thermal runaway safety protective coating, solving existing MOF coating problems such as insufficient selective capture of acidic gases like HF, poor adsorption and pressure buildup delay during thermal runaway, uncontrollable pore structure due to moisture absorption and premature decomposition of pore-forming agents, and random orientation of high thermal conductivity fillers (BNNS) in the coating, making it difficult to form effective thermal conduction pathways.

[0006] This invention proposes a battery thermal runaway coating based on metal-organic framework materials, which is mainly composed of functionalized MOF adsorbent, high-temperature resistant binder, thermally conductive reinforcing phase, and photocrosslinking monomer, with a mass ratio of (15~30):(30~45):(20~40):(8~15).

[0007] This invention also proposes a method for preparing a battery thermal runaway coating based on a metal-organic framework material, the specific technical solution of which is as follows: Step 1: Disperse ZIF-8 in solvent A and add a coupling agent. After stirring continuously under nitrogen protection, centrifuge and wash the product, then vacuum dry to obtain amino-functionalized ZIF-8 particles. Disperse hexagonal boron nitride nanosheets in solvent B and add nano-iron oxide coated with a silica shell. Adjust the pH and add dopamine. After heating and stirring, centrifuge and wash the product, then dry it under a nitrogen atmosphere to obtain surface magnetically modified hexagonal boron nitride nanosheets.

[0008] Step 2: Amine-functionalized ZIF-8 particles, surface magnetically modified hexagonal boron nitride nanosheets, soluble polyimide resin, photocurable crosslinking monomer, and photoinitiator are dispersed in a first solvent and then dispersed by high-shear grinding to obtain component A slurry.

[0009] Step 3: After pre-cooling the A component slurry, mix it together with camphor micro powder in a low-temperature homogenizer. Then, output the mixture as a coating liquid and immediately coat it onto the substrate surface. Immediately send the coated wet film into a magnetic field zone to apply a uniform magnetic field. When removing the magnetic field zone, apply ultraviolet light to it and then place it in an oven for preheating and curing.

[0010] Step 4: The irradiated substrate is placed in a stepped heating oven to be heated in multiple stages, and then naturally cooled to room temperature to obtain a battery thermal runaway coating based on MOF material.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Camphor is used as a sublimation pore-forming agent. Due to its hydrophobicity and thermal stability, no special humidity control equipment is required during the entire process of storage, mixing and coating. This avoids engineering failures such as clumping, blockage and premature decomposition caused by hygroscopic pore-forming agents such as ammonium carbonate. Camphor is widely available and inexpensive. Moreover, there is no residue after sublimation, and it does not contaminate the MOF pores or binder interface.

[0012] 2. By combining magnetic field orientation with UV pre-curing, boron-nitrogen nanosheets can be rapidly oriented in a wet film state, unaffected by the airflow disturbance of subsequent hot air drying. Furthermore, the surface gel network formed by UV pre-curing is in a semi-cured state, which does not affect subsequent heat transfer or camphor sublimation and escape.

[0013] 3. Polyimide, as a binder, can withstand short-term high temperatures without decomposition or detachment. When the temperature rises in the early stage of thermal runaway, the amine-functionalized ZIF-8 on the pore walls of the camphor sublimation-formed through-hole channels can quickly adsorb the generated HF and flammable gases. The in-plane thermally conductive network formed by the oriented arrangement of boron and nitrogen nanosheets can rapidly diffuse local hot spots and delay heat accumulation. The coupling effect of these three functions in a single coating makes the coating respond faster in the thermal runaway state. Attached Figure Description

[0014] Figure 1 This is a SEM scan of the cross-section of the sample prepared in Example 1. Detailed Implementation

[0015] Obviously, based on the above description of the present invention, and in accordance with common technical knowledge and conventional methods in the field, various other modifications, substitutions, or alterations can be made without departing from the basic technical concept of the present invention.

[0016] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0017] This invention proposes a battery thermal runaway coating based on metal-organic framework materials, the specific technical solution of which is as follows: 1. Preparation of Functionalized Powders ZIF-8 and hexagonal boron nitride were grafted with coupling agents and loaded with magnetic nanoparticles, respectively, to obtain amino-functionalized ZIF-8 and surface-magnetically modified hexagonal boron nitride. The silanol groups generated from the hydrolysis of the alkoxy group at one end of the coupling agent molecule can form covalent or coordinate bonds with the hydroxyl groups or metal nodes on the ZIF-8 surface, thereby anchoring the molecule to the crystal surface. Meanwhile, the primary amino group carried at the other end is exposed, forming an organic modification layer rich in active sites. This functionalization of ZIF-8 transforms the originally physi-adsorption-dependent ZIF-8 into an adsorbent with chemical capture capabilities.

[0018] During thermal runaway, electrolyte decomposition produces large amounts of highly toxic and corrosive hydrogen fluoride gas. After amine functionalization modification of ZIF-8, the nitrogen atom on the primary amino group possesses a lone pair of electrons, allowing it to act as a Lewis base and undergo an irreversible acid-base neutralization reaction with hydrogen fluoride molecules (which are Lewis acids), forming a stable ammonium salt complex. This chemical immobilization permanently removes hydrogen fluoride from the gas phase, fundamentally preventing its diffusion to the outside of the battery or adjacent cells. Furthermore, the introduction of the amino group does not disrupt the original microporous structure of ZIF-8; the synergistic effect of physical adsorption and chemical capture significantly improves the overall adsorption capacity and adsorption rate for hydrogen fluoride and some oxygen-containing acidic gases.

[0019] Superparamagnetic iron oxide nanoparticles modified with a silica shell are dispersed in a system containing exfoliated boron nitride sheets via electrostatic self-assembly. By adjusting interfacial interactions, the magnetic particles are uniformly attached to the surface of the boron nitride sheets, forming a stable magnetic composite structure. This endows boron nitride with a rapid response to an applied magnetic field, enabling precise control over the orientation of the thermally conductive filler. Simultaneously, the iron oxide is completely encapsulated in a silica shell before magnetic modification, preventing direct contact with the electrolyte inside the battery and avoiding side reactions, thus improving battery safety. While boron nitride possesses extremely high in-plane thermal conductivity, its thermal conductivity is highly anisotropic, achieving optimal thermal conductivity only when the large plane of the sheet is parallel to the heat flow direction. Through surface magnetic modification, when the wet film enters the applied magnetic field region, each sheet is subjected to magnetic torque, forcing it to rotate until its large plane is parallel to the magnetic field direction. This forced orientation process causes a large number of boron nitride sheets to be arranged neatly in a nearly parallel orientation to the film surface, overlapping each other to form a continuous in-plane thermal conductivity network. This allows the heat generated by local hot spots to be rapidly diffused along the film surface to a larger area, preventing heat concentration from triggering a chain thermal runaway reaction.

[0020] 2. Preparation of coating liquid slurry Two modified functionalized powders were dispersed with resin, monomer, and photoinitiator in an organic solvent via high-shear grinding to prepare a slurry. Since both functionalized powders are micro / nano-scale, with large specific surface areas and high surface energies, they readily form soft or hard agglomerates under van der Waals forces, electrostatic attraction, and mechanical interlocking. These agglomerates cause rough surfaces and uneven thickness during subsequent coating processes, and may even clog slit coating dies. Furthermore, within the cured coating, the agglomerates encapsulate the adsorption sites of ZIF-8 particles, preventing their exposure, and the BNNS sheets cannot form a continuous in-plane thermally conductive network, severely degrading gas adsorption and thermal management performance.

[0021] High-shear grinding utilizes high-hardness grinding media, such as zirconia beads, filled within a closed mill. The high-speed rotation of the rotor causes the media to exert intense impact, shearing, and friction on the material. This mechanical energy input is sufficient to overcome the adhesive forces within agglomerates, forcibly deagglomerating them into original particle sizes. Simultaneously, the shear force causes organic solvents and soluble polyimide molecules to rapidly wet and adsorb onto the surface of fresh particles, forming a steric hindrance layer or electrostatic repulsion layer. This prevents the particles from re-agglomerating after grinding, resulting in a kinetically stable homogeneous dispersion system. Furthermore, during grinding, the resin molecular chains are appropriately cut or extended, reducing the slurry viscosity and improving thixotropy, which is beneficial for subsequent slot coating to form a uniform, defect-free wet film.

[0022] 3. Coating, magnetic field orientation and UV pre-curing The pre-cooled slurry was mixed with camphor micropowder and AIBN at a low temperature and applied to the substrate as a mixed coating solution. It was then immediately placed in a magnetic field zone and pre-cured by short-term ultraviolet light irradiation followed by heating. Since camphor has a certain solubility in NMP, but this solubility decreases significantly with decreasing temperature, controlling the mixing of the slurry and camphor micropowder at a low temperature minimizes the dissolution rate of the camphor micropowder upon contact with NMP, allowing it to maintain a stable solid particle morphology for a period of time. Immediate coating after mixing further shortens the contact time between camphor and the solvent, thereby maximizing the preservation of the in-situ pore-forming function of the camphor particles.

[0023] When the mixed coating liquid is evenly spread onto the surface of the moving substrate through the slit die, a wet film of a certain thickness is formed. At this time, the surface magnetically modified boron nitride sheets in the wet film are in a suspended state and can rotate and translate freely in the liquid. Immediately after the wet film is sent into a uniform magnetic field region, the superparamagnetic nanoparticles loaded on the boron nitride sheets are magnetized in the magnetic field, generating a magnetic moment along the magnetic field direction parallel to the substrate film surface. The entire sheet is subjected to magnetic torque. When the magnetic torque exceeds the viscous resistance experienced by the sheet in the viscous fluid, the sheet will be forced to rotate until its large plane is parallel to the magnetic field direction.

[0024] Because the layers may rotate and relax under external disturbances when the wet film is removed from the magnetic field, tending to revert to a disordered arrangement, ultraviolet light is rapidly applied upon removal from the magnetic field. The photoinitiator pre-added to the coating solution undergoes photolysis under specific wavelengths of ultraviolet light, generating free radicals. These free radicals rapidly initiate chain polymerization of the unsaturated double bonds in the photocurable crosslinking monomers, transforming the monomers into a highly crosslinked three-dimensional polymer network in a very short time. This network interweaves within the original resin system, changing the rheological state of the entire coating from a viscous liquid to a semi-cured gel. This effectively resists the thermal motion, gravitational settling, and convective disturbances caused by solvent evaporation during subsequent drying of the boron nitride layers, thus permanently fixing the established orientation state. Simultaneously, the thermal initiator AIBN pre-added to the coating solution slowly decomposes during subsequent heating, generating free radicals that further initiate crosslinking of the uncured monomers in the underlying layer, forming a uniform gel network that runs through the coating thickness direction. This compensates for the insufficient penetration depth of ultraviolet light, ensuring that the underlying orientation is also reliably locked.

[0025] 4. Stepped temperature rise thermosetting and pore formation The UV-precured coating is placed in an oven for stepped heating, followed by natural cooling to obtain the desired coating. The coating undergoes four stages of stepped heating after being placed in the oven. In the first and second heating stages, the system temperature rises to near the boiling point of the solvent, causing solvent molecules to diffuse from the interior of the coating to the surface and evaporate into a gaseous phase. Meanwhile, the solid content within the coating continuously increases, and resin molecules gradually entangle and form a preliminary aggregated structure, but chemical cross-linking has not yet occurred. At this point, the camphor particles inside the coating remain solid, existing as temporary space occupiers.

[0026] The temperature in the third heating stage falls within the sublimation temperature range of natural camphor. Camphor is an organic solid with a high vapor pressure. During sublimation, camphor molecules escape from the surface of the solid particles, forming gas molecules that diffuse outwards. Since the camphor particles were previously uniformly distributed within the coating, the space they occupied becomes cavities after sublimation. As the gas escapes, these cavities interconnect, forming three-dimensional, micron-sized interconnected channels. This avoids capillary forces damaging the pore walls and also utilizes the endothermic effect of sublimation to locally slow down the heating rate, preventing premature solidification and shrinkage of the pore walls.

[0027] The fourth heating stage is the imidization crosslinking temperature of the soluble polyimide resin. The polyimide prepolymer contains unclosed ammonium acid structures, which undergo intramolecular dehydration condensation at high temperatures to form imide rings. Simultaneously, crosslinking reactions occur between molecular chains to form a rigid three-dimensional network structure, thereby transforming the coating from a thermoplastic, flowable state to a thermosetting, insoluble, and infusible state, permanently fixing the geometry of the pores. Since crosslinking occurs after camphor is completely removed, the pore walls will not be squeezed and closed by resin shrinkage during curing. After thermosetting, the coating becomes stable after natural cooling to room temperature. When the coating is installed in the battery, it releases the high-pressure gas generated by thermal runaway through the perforated pores during thermal runaway. At the same time, the amino-functionalized ZIF-8 on the inner wall of the pores irreversibly captures highly toxic hydrogen fluoride, while the oriented boron nitride nanosheets rapidly diffuse and homogenize the heat from local hot spots along the film surface. These three factors work together to achieve integrated thermal runaway management of pressure relief, detoxification, and thermal diffusion.

[0028] The following are some specific embodiments of the present invention. Table 1 shows the main information of the raw materials used in the embodiments.

[0029] Table 1 Raw Material Information Table

[0030] Example 1 S1: Weigh 100g of pure ZIF-8 powder and disperse it in 1000mL of 95% ethanol aqueous solution. Slowly add 4mL of KH-550 dropwise while stirring at 500rpm. Place the system under nitrogen protection and stir continuously at 85℃ for 8h. After the reaction is complete, separate the mixture by centrifugation at 8000rpm. Then wash the precipitate three times with anhydrous ethanol to remove free silane. Place the washed filter cake in a vacuum drying oven and dry it under vacuum at 80℃ and -0.08MPa for 24h. Then grind it through an 80-mesh sieve to obtain amino-functionalized modified ZIF-8-NH2 micro powder. Weigh 200g of hexagonal boron nitride nanosheets and add them to a 6% sodium dodecylbenzenesulfonate aqueous solution. Pre-disperse the nanosheets under 20kHz ultrasound. 2 h later, another 25 g of nano Fe3O4 powder was dispersed in an 80% ethanol aqueous solution, 2 mL of ammonia was added, and 2 mL of tetraethyl orthosilicate was slowly added dropwise while stirring at room temperature for 4 h. After the reaction was completed, the product was separated by a magnet, washed three times with anhydrous ethanol, and dried under vacuum at 60 °C for 2 h to obtain Fe3O4@SiO2 core-shell particles. Then, the core-shell particles were added to a hexagonal boron nitride nanosheet dispersion, and the pH of the system was adjusted to 8.5 with sodium bicarbonate. 2 g of dopamine was added dropwise at 35 °C and stirred continuously for 15 h. Then, the mixture was filtered and washed three times with anhydrous ethanol, centrifuged at 8000 rpm, and dried under vacuum at 80 °C and -0.08 MPa for 24 h to obtain magnetized modified m-boron nitride nanosheets (m-BNNS).

[0031] S2: Weigh 20g of ZIF-8-NH2, 30g of m-BNNS, 35g of soluble polyimide resin, 10g of HEMA monomer and 1g of photoinitiator TPO, and put the above materials into a reactor containing 200g of N-methylpyrrolidone. Stir at 350rpm for 45min, and then transfer the system to a high-energy closed sand mill. Use zirconium dioxide beads as the grinding medium with a filling rate of 55% and grind the material at 30℃ for 1.5h to obtain component A slurry.

[0032] S3: Cool the A component slurry to 15°C in an ice bath. Then, add the A component slurry, 0.1g of azobisisobutyronitrile (AIBN), and 1.05g of camphor micropowder to a homogenizer pre-cooled to 10°C. Mix the mixture at 600 rpm for 30 seconds. Immediately afterward, continuously coat the mixed slurry onto the surface of the polyimide membrane substrate using a slot coating die at a linear velocity of 8 m / min, controlling the wet film thickness to 50 μm. Within 3 seconds of coating, immediately place the wet film into a magnetic field orientation zone and apply a uniform magnetic field of 0.3T parallel to the film surface. As soon as the substrate is removed from the magnetic field zone, immediately use a 365nm ultraviolet light source at 5W / cm². 2 The substrate film was irradiated with a power density of 5s to obtain a semi-cured substrate film. Then, the semi-cured substrate film was placed in a 50℃ oven for 2min to obtain a pre-cured substrate film.

[0033] S4: The pre-cured substrate film is placed in a multi-stage stepped heating intelligent vacuum drying oven. First, the oven is heated to 100°C and held for 4 hours under a vacuum of -0.08MPa. Then, the vacuum environment is removed, and high-purity nitrogen is introduced into the drying oven to make the pressure inside the oven slightly positive at 2kPa. The temperature is then raised to 180°C and held for 1 hour. The temperature is then raised to 250°C and held for 4 hours. After that, it is naturally cooled to room temperature. After removal, the MOF-based battery thermal runaway management coating is obtained on the surface of the polyimide separator.

[0034] Example 2 The difference from the preparation method in Example 1 is as follows: S1: Replace KH550 with KH602; S2: Replace HEMA with HPMA monomer and replace photoinitiator TPO with photoinitiator TMO; S3: Replace the polyimide membrane with a polyetheretherketone membrane; the remaining steps are the same.

[0035] Example 3 The difference from the preparation method in Example 1 is as follows: S1: Replace KH550 with KH792; S2: Replace HEMA with 2-PEA, and replace the photoinitiator TPO with the photoinitiator TPO-L. All other steps are the same.

[0036] Example 4: The difference from the preparation method in Example 1 is as follows: S1: The ZIF-8 stirring temperature was 75℃, the stirring time was 4h, the pH of the system was adjusted to 7.5, the dopamine was added at 25℃, and the reaction time was 8h. S2: Zirconia filling rate is 40%, grinding time is 0.5h, grinding temperature is 20℃; S3: Coating linear velocity is 5 m / min, magnetic field strength is 0.1 T, UV power density is 2 W / cm². 2 The UV irradiation time is 2 seconds; S4: The first stage temperature is 90℃ and the holding time is 2h; the second stage temperature is 170℃ and the holding time is 0.5h; the third stage temperature is 230℃ and the holding time is 2h. All other steps are the same.

[0037] Example 5 The difference from the preparation method in Example 1 is as follows: S1: The ZIF-8 stirring temperature was 90℃, the stirring time was 12h, the pH of the system was adjusted to 9.0, the temperature of dopamine addition was 45℃, and the reaction time was 24h; S2: Zirconia filling rate is 70%, grinding time is 3h, grinding temperature is 40℃; S3: Coating linear velocity is 10 m / min, magnetic field strength is 0.5 T, and UV power density is 10 W / cm². 2 The UV irradiation time is 10 seconds; S4: The first stage temperature is 110℃ and the holding time is 8h; the Diehl stage temperature is 190℃ and the holding time is 2h; the third stage temperature is 280℃ and the holding time is 6h. The remaining steps are the same.

[0038] Example 6 The difference from the preparation method in Example 1 is as follows: S1: The ZIF-8 stirring temperature was 80℃, the stirring time was 10h, the pH of the system was adjusted to 8.0, the dopamine was added at 40℃, and the reaction time was 12h. S2: Zirconia filling rate is 60%, grinding time is 2 hours, grinding temperature is 25℃; S3: Coating linear velocity is 3 m / min, magnetic field strength is 0.2 T, UV power density is 8 W / cm². 2 The UV irradiation time is 8 seconds; S4: The first stage temperature is 105℃ and the holding time is 5h; the second stage temperature is 175℃ and the holding time is 1.5h; the third stage temperature is 240℃ and the holding time is 5h. All other steps are the same.

[0039] Example 7 The difference from the preparation method in Example 1 is as follows: S2: Weigh 15g of ZIF-8-NH2, 20g of m-BNNS, 30g of soluble polyimide resin, 8g of HEMA monomer and 1g of photoinitiator TPO, and the rest of the steps are the same.

[0040] Example 8 The difference from the preparation method in Example 1 is as follows: S2: Weigh 30g of ZIF-8-NH2, 40g of m-BNNS, 45g of soluble polyimide resin, 15g of HEMA monomer and 1g of photoinitiator TPO, and the rest of the steps are the same.

[0041] Comparative Example 1 The difference from the preparation steps in Example 1 is as follows: S2: Replace camphor with ammonium carbonate and 5% SDS aqueous solution with anhydrous ethanol. All other steps are the same.

[0042] Comparative Example 2 The difference from the preparation steps in Example 1 is as follows: S3: Canceling the magnetic field treatment, UV pre-curing is performed directly after coating, and the remaining steps are the same.

[0043] Comparative Example 3 The difference from the preparation steps in Example 1 is as follows: S3: UV pre-curing is cancelled. After magnetic field treatment, the product is directly sent into the drying oven for drying. All other steps are the same.

[0044] Comparative Example 4 The difference from the preparation steps in Example 1 is as follows: S1: Amine functionalization of ZIF-8 was performed without adding KH550; subsequent steps used only ordinary ZIF-8, with all other steps remaining the same. Comparative Example 5 The difference from the preparation steps in Example 1 is as follows: S2: Eliminate the separate preparation of components A and B, put all ingredients into 200g of cyclohexanone, stir at 350rpm for 45min and then grind. The remaining steps are the same.

[0045] Experimental Example 1 Weigh 1.00g of the coating samples prepared in Examples 1-8 and Comparative Examples 1-5, and load them into a polytetrafluoroethylene tubular fixed reaction bed with an inner diameter of 10mm and a length of 200mm. The two ends are filled with quartz wool. A N2 mixture containing 100ppm is introduced at a flow rate of 50mL / min at a constant temperature of 25℃. The outlet gas is introduced into a gas washing bottle containing 0.1M NaOH absorbent. Simultaneously, a fluoride ion selective electrode is inserted to monitor the fluoride ion concentration in the absorbent in real time. The time from the start of gas introduction until the outlet fluoride ion concentration reaches 10% of the inlet concentration is recorded. Gas introduction continues until the outlet concentration equals the inlet concentration. Based on the integral area from the penetration point to the saturation point, combined with the total gas flow rate and the initial HF concentration, the saturated HF adsorption capacity per unit mass of coating is calculated.

[0046] Weigh 0.5g of the coating samples prepared in Examples 1-8 and Comparative Examples 1-5 and place them into the sample tube of the fully automatic gas adsorption instrument. Degas the samples under vacuum at 200℃ for 6h. Then, under constant temperature conditions at 25℃, use ethylene as the adsorbate and set the relative pressure P / P0 from 0.01 to 0.99. Measure the equilibrium adsorption amount at each pressure. Obtain the saturated adsorption amount by fitting the adsorption isotherm using the Langmuir equation and calculate the molar amount of ethylene adsorbed per gram of coating.

[0047] Weigh 1.0 g of the coating samples prepared in Examples 1-8 and Comparative Examples 1-5 and load them into a polytetrafluoroethylene fixed-bed reactor. A mixture of HF / CO2 / N2 gas is introduced at a constant temperature of 25°C, with a volume fraction ratio of 5:10:85 and a total flow rate of 50 mL / min. The outlet gas is dried and then introduced into a gas chromatograph-mass spectrometer to analyze the concentrations of HF and CO2 at the outlet in real time. After the adsorption reaches steady state, the HF / CO2 selective adsorption ratio is calculated according to the formula: HF / CO2 selective adsorption ratio = (x...) HF,ads / x CO2,ads ) / (x HF,gas / x CO2,gas ), where x HF,ads and x CO2,ads x represents the mole fractions of HF and CO2 in the adsorbed phase, respectively. HF,gas and x CO2,gas The values ​​represent the inlet gas phase mole fraction, respectively. The test results are shown in Table 2.

[0048] Table 2 Gas adsorption capacity of the examples and comparative samples

[0049] As shown in Table 2, the coated samples prepared in the examples all have high HF adsorption capacity, ethylene adsorption capacity and HF / CO2 selectivity ratio, indicating that the standard process and the parameter offset process have effectively constructed the chemisorption sites, through-pores and directional heat conduction network of amine-functionalized ZIF-8, thus demonstrating excellent gas purification and thermal runaway protection performance. Comparative Example 1: Using ammonium carbonate instead of camphor resulted in premature decomposition of the pore-forming agent, collapse of the pore structure, and blockage by residues, leading to extremely low HF adsorption capacity, extremely low ethylene adsorption capacity, and extremely low selectivity. Comparative Example 2: Eliminating the magnetic field orientation resulted in random arrangement of BNNS, resulting in a loose coating structure but partial retention of gas adsorption channels, thus leading to relatively low HF adsorption capacity, ethylene adsorption capacity, and selectivity. Comparative Example 3: Eliminating UV pre-curing caused the coating structure to collapse and the pores to partially close in the oven, resulting in relatively low HF adsorption capacity, ethylene adsorption capacity, and selectivity. Comparative Example 4: The lack of amino functionalization of ZIF-8 resulted in the absence of chemical adsorption sites, relying solely on physical adsorption, thus leading to extremely low HF adsorption capacity and extremely low selectivity. Comparative Example 5: The one-pot mixing method resulted in premature dissolution of camphor in NMP, failure of pore-forming, and very few pores, thus leading to extremely low HF adsorption capacity, ethylene adsorption capacity, and selectivity.

[0050] Experiment Example 2 The coated separators of Examples 1-8 and Comparative Examples 1-5 were assembled into square soft-pack batteries with a rated capacity of not less than 5Ah. The batteries were fully charged to 100% SOC and placed in an explosion-proof box. A thermocouple was attached to the center of the battery surface to monitor temperature changes. The batteries were then heated from room temperature at a rate of 5°C / min. When the temperature inside the box reached 200°C, it was kept constant for 30 minutes. During this period, the changes in battery surface temperature and terminal voltage were continuously recorded. The temperature at which the battery surface temperature began to rise uncontrollably and rapidly was recorded as the thermal runaway trigger temperature.

[0051] The coated separators of Examples 1-8 and Comparative Examples 1-5 were assembled into square soft-pack batteries with a rated capacity of not less than 5Ah. The batteries were fully charged to 100% SOC and placed in an explosion-proof box. Thermocouples and pressure sensors were arranged on the battery surface and at the positive and negative terminals. The batteries were charged at a constant current of 1C until the battery voltage reached 1.5 times the rated voltage or thermal runaway occurred. The voltage at the time of thermal runaway was recorded, and the overcharge capacity ratio was calculated according to the formula: actual charging capacity / rated capacity.

[0052] The coated separators from Examples 1-8 and Comparative Examples 1-5 were assembled into two adjacent square pouch cells, each with a capacity of not less than 5Ah and fully charged to 100% SOC. A separator coated with the present invention was tightly sandwiched between the two cells as a thermal isolation layer. A 200W heating element was attached to the surface of cell A, and a thermocouple was placed at the center of cell B to continuously monitor its temperature. Cell A was then forcibly heated at a heating rate of 10℃ / min until thermal runaway occurred. The onset time t0 of thermal runaway of cell A and the time t1 when the surface temperature of cell B first reached 150℃ were recorded. The thermal diffusion delay time Δt = t1 - t0 was calculated according to the formula. The test results are shown in Table 3.

[0053] Table 3. Extreme environmental safety tests of the examples and comparative samples.

[0054] As shown in Table 3, the coated samples of the examples all exhibited high thermal runaway trigger temperature, thermal runaway voltage, overcharge capacity ratio, and thermal diffusion retardation time. This indicates that the standard process and the parameter offset processes effectively constructed the directional thermal conduction network, interconnected channels, and amine chemisorption sites of the BNNS, thus demonstrating excellent thermal runaway suppression and thermal diffusion blocking performance. In Comparative Example 1, the replacement of camphor with ammonium carbonate led to premature decomposition of the pore-forming agent, collapse of the pore structure, and blockage by residues. Therefore, the thermal runaway temperature, thermal runaway voltage, and overcharge capacity ratio were extremely low, and the thermal diffusion retardation time was extremely short. In Comparative Example 2, the removal of the magnetic field orientation resulted in random arrangement of the BNNS, making it impossible to form a continuous in-plane thermal conduction network. Therefore, the thermal runaway temperature, thermal runaway voltage, overcharge capacity ratio, and thermal diffusion delay time were all poor. Comparative Example 3, by canceling UV pre-curing, caused the coating structure to collapse and the pores to partially close in the oven, resulting in poor thermal runaway temperature, thermal runaway voltage, overcharge capacity ratio, and thermal diffusion delay time. Comparative Example 4, by not functionalizing ZIF-8 with amino groups, resulted in the absence of chemical adsorption sites, and the toxic gas accelerated heat propagation during thermal runaway, thus the sample's thermal stability was also extremely poor. Comparative Example 5, by using a one-pot mixing method, caused camphor to dissolve prematurely in NMP, resulting in pore formation failure and very few pores, thus the temperature and voltage during thermal runaway were extremely low, the overcharge capacity ratio was extremely poor, and the thermal diffusion temperature was the shortest.

[0055] Experimental Example 3 The coated substrate film prepared in Example 1 was immersed in liquid nitrogen and cooled for 5 minutes to achieve complete vitrification. It was then rapidly broken in the liquid nitrogen environment. Subsequently, the cross-section was precisely cut using gallium ion beams via FIB technology to obtain a smooth plane. A Pt layer was then sprayed onto the cross-sectional surface using an ion sputtering instrument. The sprayed sample was then observed under a field emission electron scanning microscope at an accelerating voltage of 15 kV. The observation results are as follows: Figure 1 As shown.

[0056] from Figure 1 As can be seen, the sample exhibits a highly interconnected network of micron-sized cavities. These cavities are formed by the gentle and continuous sublimation of camphor micropowder. The sublimated camphor gas forms channels through extrusion within the incompletely cross-linked polyimide precursor. Magnification reveals that there are permeable connecting necks between adjacent microcavities, indicating that these pores are not independent voids but form a macroscopic exhaust network system, providing a low-resistance pressure relief valve space for thermal runaway. Further reduction in the observation size to the nanoscale shows that, due to magnetic field induction and UV cross-linking network locking, the two-dimensional boron nitride nanosheets exhibit a layered morphology highly parallel to the surface of the separator substrate. Therefore, it can be seen that boron nitride provides in-plane thermal conduction channels, the resin network buffers stress, and ZIF-8-NH2 particles dispersed on the surface of the resin network adsorb toxic and flammable gases generated during thermal runaway. These three factors synergistically reduce the risk of thermal runaway during battery use.

Claims

1. A battery thermal runaway coating based on a metal-organic framework material, wherein the coating is applied to a high-temperature resistant separator substrate, characterized in that: The product is composed of a functionalized MOF adsorbent, a high-temperature resistant binder, a thermally conductive reinforcing phase, and a photocrosslinking monomer, with a mass ratio of (15~30):(30~45):(20~40):(8~15).

2. The battery thermal runaway coating based on metal-organic framework material according to claim 1, characterized in that: The functionalized MOF adsorbent is ZIF-8 with amine functionalization; the high-temperature resistant binder is soluble polyimide resin; the thermally conductive reinforcing phase is magnetized boron nitride nanosheets; the magnetized boron nitride nanosheets are distributed in a direction parallel to the surface of the substrate.

3. The battery thermal runaway coating based on metal-organic framework materials according to claim 1, characterized in that: The high-temperature resistant membrane substrate is one of polyimide substrate or polyetheretherketone substrate; the photocrosslinking monomer is one or more of HEMA, HPMA, and 2-PEA.

4. A method for preparing a battery thermal runaway coating based on a metal-organic framework material as described in any one of claims 1 to 3, characterized in that, It is prepared according to the following method: S1: ZIF-8 was dispersed in solvent A and a coupling agent was added. After continuous stirring under nitrogen protection, the mixture was centrifuged, washed, and then dried under vacuum to obtain amino-functionalized ZIF-8 particles. Hexagonal boron nitride nanosheets were dispersed in solvent B and nano-iron oxide nanosheets coated with a silica shell were added. The pH was adjusted and dopamine was added. After heating and stirring, the mixture was centrifuged, washed, and dried under a nitrogen atmosphere to obtain surface magnetically modified hexagonal boron nitride nanosheets. Solvent A was a 95% aqueous ethanol solution, and solvent B was a 6% aqueous solution of sodium dodecylbenzenesulfonate. S2: Amine-functionalized ZIF-8 particles, surface magnetically modified hexagonal boron nitride nanosheets, soluble polyimide resin, photocurable crosslinking monomer, and photoinitiator are dispersed in N-methylpyrrolidone and dispersed by high-shear grinding to obtain component A slurry; S3: After pre-cooling the A component slurry, it is mixed with the B component material in a low-temperature homogenizer. The mixture is then output as a coating liquid and immediately coated onto the substrate surface. The coated wet film is immediately sent into a magnetic field zone to apply a uniform magnetic field. When the magnetic field zone is removed, it is irradiated with ultraviolet light and then placed in an oven for preheating and curing. The B component material is a mixture of camphor micro powder and azobisisobutyronitrile. S4: The irradiated substrate is placed in a stepped heating oven to be heated in multiple stages, and then naturally cooled to room temperature to obtain a battery thermal runaway coating based on MOF material.

5. The method for preparing a battery thermal runaway coating based on a metal-organic framework material according to claim 4, characterized in that: The coupling agent mentioned in S1 is one or more of KH-550, KH-602, and KH-792.

6. The method for preparing a battery thermal runaway coating based on a metal-organic framework material according to claim 4, characterized in that: The continuous stirring temperature in S1 is 75~90℃, and the stirring time is 4~12h; the pH adjustment is to adjust the pH to 7.5~9.0; the heating and stirring temperature is 25~45℃, and the stirring time is 8~24h.

7. The method for preparing a battery thermal runaway coating based on a metal-organic framework material according to claim 4, characterized in that: The photoinitiator described in S2 is one or more of TPO, TMO, and TPO-L.

8. The method for preparing a battery thermal runaway coating based on a metal-organic framework material according to claim 4, characterized in that: The grinding media filling rate during the grinding process described in S2 is 40%~70%, the grinding time is 0.5~3h, and the grinding temperature is 20~40℃.

9. The method for preparing a battery thermal runaway coating based on a metal-organic framework material according to claim 4, characterized in that: The linear velocity of the coating in S3 is 5~10 m / min; the magnetic field strength is 0.1~0.5T; and the power density of the ultraviolet light irradiation is 2~10 W / cm². 2 The irradiation time is 2~10s.

10. The method for preparing a battery thermal runaway coating based on a metal-organic framework material according to claim 4, characterized in that: In the multi-stage heating process described in S4, the first stage temperature is 90~110℃ and the holding time is 2~8h; the second stage temperature is 170~190℃ and the holding time is 0.5~2h; and the third stage temperature is 230~280℃ and the holding time is 2~6h.

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