Hydrogen sensor for lithium battery safety monitoring and sensitive material preparation method

Abstract

The invention relates to the technical field of gas sensors, in particular to a hydrogen sensor for lithium battery safety monitoring and a sensitive material preparation method, and aims at solving the problems that an existing hydrogen sensitive material is low in recovery speed and insufficient in sensitivity. Tungsten trioxide is adopted as a matrix of the sensitive material, compared with common materials such as tin oxide and zinc oxide, the sensitive material has the response characteristic of being more sensitive to hydrogen, the intrinsic sensitivity and the reaction rate of the material to hydrogen are improved through the synergistic dual sensitization effect of K + bulk phase doping and palladium nanoparticle surface catalysis, and the sensitivity of the material to hydrogen is improved. A sacrificial template is introduced into a tungsten trioxide sensitive layer prepared by aerosol deposition, and a segmented annealing process is adopted, so that a controllable porous structure is constructed while sufficient removal of the template and film continuity are ensured, and the sensitivity and response / recovery performance of the hydrogen sensor are improved; the sensor is suitable for lithium ion battery thermal runaway safety monitoring scenes with extremely harsh early warning requirements.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, specifically to a hydrogen sensor for lithium battery safety monitoring and a method for preparing the sensitive material. Background Technology

[0002] With the widespread application of lithium-ion batteries in electric vehicles, energy storage systems, and consumer electronics, their operational safety has received continuous attention. Studies have shown that in the early stages of overcharging, short circuits, or thermal runaway in lithium-ion batteries, a series of side reactions occur between the electrode materials and the electrolyte, accompanied by the generation and release of flammable gases such as hydrogen. Compared with changes in temperature or voltage, hydrogen generation occurs earlier and is more indicative. Therefore, detecting changes in hydrogen concentration in the environment to reflect the safety status of lithium-ion batteries is considered a monitoring method with significant advantages. Using hydrogen sensors for lithium battery safety monitoring can help provide early warning information before thermal runaway occurs, thereby reducing the risk of accidents.

[0003] Among existing hydrogen sensing materials, metal oxide semiconductor materials have been widely studied due to their stable structure, low cost, and mature processing technology. Among them, tungsten trioxide (TTO) exhibits a more sensitive response to hydrogen than common materials such as tin oxide and zinc oxide. In addition to the resistance change caused by the surface adsorption-reaction mechanism of traditional metal oxides, TTO also undergoes a significant gas-induced discoloration phenomenon under the action of hydrogen, indicating that its hydrogen response process involves not only surface reactions but also bulk hydrogen injection and valence state changes. This synergistic mechanism of surface and bulk reactions gives TTO high sensitivity to hydrogen and good application potential. However, although TTO hydrogen-sensitive materials prepared by aerosol deposition methods usually have a fast response speed, they still generally suffer from slow recovery speed and need further improvement in sensitivity in practical applications.

[0004] Therefore, the hydrogen sensor and its sensitive material preparation method for lithium battery safety monitoring of the present invention are of great significance in the field of gas sensor technology. Summary of the Invention

[0005] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a hydrogen sensor for lithium battery safety monitoring and a method for preparing sensitive materials, which solves the problems of slow recovery speed and insufficient sensitivity of existing hydrogen sensitive materials.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, this application provides a method for preparing a sensitive material for lithium battery safety monitoring, comprising the following steps: Step a1: Add sodium tungstate, potassium sulfate, and deionized water to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 300 rpm for 30 min. Adjust the pH to 2-3 with hydrochloric acid solution. Transfer to a hydrothermal reactor and heat to 180℃ at a rate of 2-5℃ / min for 12 h. Centrifuge and discard the supernatant. Wash the precipitate 2-3 times with distilled water and dry in a vacuum drying oven at 60℃ for 4-6 h. Add anhydrous ethanol and ultrasonically disperse for 30 min. Add polyvinylpyrrolidone and potassium chloride and mix and stir at 400-600 rpm for 12-24 h. Centrifuge and discard the supernatant. Wash the precipitate 2-3 times with distilled water and dry in a vacuum drying oven at 60℃ for 4-6 h. Transfer to a muffle furnace and calcine at 400℃ for 2-3 h to obtain the intermediate product. Step a2: Add the intermediate product and ethanol solution to a three-necked flask equipped with a stirrer and thermometer, sonicate for 30 min, place in an ice-water bath at 0-5℃, stir at 400-600 r / min for 30 min, add palladium acetate solution, continue stirring for 10-15 min, add sodium borohydride solution, continue stirring for 10-15 min, centrifuge, discard the supernatant, wash the precipitate 2-3 times with anhydrous ethanol and distilled water respectively, dry in a vacuum drying oven at 60℃ for 4-6 h, transfer to a mortar and grind, and sieve to obtain modified tungsten trioxide with a particle size of 0.5-2 μm; Step a3: Wash styrene 2-3 times with sodium hydroxide solution and distilled water, add anhydrous magnesium sulfate and dry for 12-24 hours. Under nitrogen protection, distill under reduced pressure and add the solution to a three-necked flask equipped with a stirrer and thermometer. Add ethanol solution and dispersant, mix and stir for 30 minutes, place in an oil bath at 70°C, add initiator, stir at 200-250 r / min for 24 hours, cool naturally to 25°C, centrifuge at 8000 r / min for 10-15 minutes, discard the supernatant, add anhydrous ethanol, ultrasonically disperse for 5-10 minutes, filter, dry in a vacuum drying oven at 60°C for 12 hours, and sieve to obtain monodisperse polystyrene microspheres. Add modified tungsten trioxide and monodisperse polystyrene microspheres to a container and dry mix for 0.5-2 hours. Sieve through a 20-200 mesh sieve to obtain the sensitive material.

[0007] In a preferred embodiment of the present invention, the ratio of sodium tungstate, potassium sulfate, deionized water, anhydrous ethanol, polyvinylpyrrolidone, and potassium chloride in step a1 is 1.5-2g: 0.4-0.6g: 40-80mL: 40-80mL: 0.5-0.8g: 0.1-0.2g; the concentration of the hydrochloric acid solution is 3mol / L; and the polyvinylpyrrolidone is PVP-K30.

[0008] In a preferred embodiment of the present invention, the ratio of the intermediate product, ethanol solution, palladium acetate solution, and sodium borohydride solution in step a2 is 100-150 mg: 30-50 mL: 0.2-0.5 mL: 1-2 mL; the mass fraction of the ethanol solution is 20%; the concentration of the palladium acetate solution is 5 g / L; and the concentration of the sodium borohydride solution is 10 g / L.

[0009] In a preferred embodiment of the present invention, the ratio of styrene, anhydrous magnesium sulfate, ethanol solution, dispersant, initiator, anhydrous ethanol, and modified tungsten trioxide in step a3 is 3-15 mL: 3-5 g: 80-100 mL: 2-3 g: 0.1-0.2 g: 50-60 mL: 10-15 g; the mass fraction of the sodium hydroxide solution is 5%; the mass fraction of the ethanol solution is 80%; the dispersant is polyvinylpyrrolidone PVP-K30; and the initiator is azobisisobutyronitrile.

[0010] Secondly, this application provides a method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries, comprising the following steps: The substrate is washed sequentially with acetone, anhydrous ethanol, and deionized water 1-2 times, dried at 60-80℃ for 1-2 hours, and plasma activated for 1-10 minutes. Electrodes are then mounted on the surface. The sensitive material is added to an aerosol generator, and the powder is atomized into an aerosol using a carrier gas and delivered to a nozzle. Under pressure differential, the aerosol is sprayed at high speed onto the substrate surface. The carrier gas flow rate is 0.5-10 L / min, the nozzle-substrate distance is 1-30 mm, the scanning speed is 1-50 mm / s, and the number of sprays per round trip is [not specified]. The composite film is obtained by performing 1-4 depositions, with a deposition time of 0.5-60 min and a substrate temperature of 25-100℃. The composite film is then subjected to segmented heat treatment in air or an oxygen-rich atmosphere and cooled to 25℃ at a rate of 1-5℃ / min to obtain the sensitive layer. The sensitive layer is then subjected to sputter deposition of an enhancement layer with a sputtering power of 5-100W and a time of 5-600s. The layer is then activated at 150-350℃ for 0.5-3h. A micro heater is then installed on the back of the substrate to obtain the hydrogen sensor.

[0011] In a preferred embodiment of the present invention, the hydrogen sensor includes a substrate, an electrode disposed on the surface of the substrate, a sensitive layer covering the electrode, and a microheater located on the back side of the substrate; the surface of the sensitive layer also includes a sensitizing layer; the microheater provides an operating temperature of 50-350°C.

[0012] In a preferred embodiment of the present invention, the sensitive layer is prepared by the method for preparing the sensitive material in the first aspect; the substrate is one of alumina ceramic, aluminum nitride ceramic, glass or silicon-based insulating substrate; the electrode is an interdigitated electrode structure or a counter electrode structure, and the material is one of Pt, Au, Ag or their alloys; the sensitizing layer is a nanolayer / nanoparticle layer formed by one or more of Pd, Pt, and Au.

[0013] In a preferred embodiment of the present invention, the thickness of the sensitive layer is 0.5-30 μm and the pore size distribution is 0.5-10 μm; the thickness of the sensitizing layer is 0.5-20 nm.

[0014] In a preferred embodiment of the present invention, the segmented heat treatment includes the following temperature program: Heat to 120℃ at a rate of 1-3℃ / min, and hold for 30-60 minutes. Heat to 280℃ at a rate of 0.5-2℃ / min and hold for 30-90 minutes. Heat to 360℃ at a rate of 0.5-1℃ / min and hold for 30-90 minutes. Heat to 450℃ at a rate of 1℃ / min, and hold for 60-120 minutes. Heat to 475℃ at a rate of 0.5-1℃ / min and hold for 30-60 minutes.

[0015] In a preferred embodiment of the present invention, when the thickness of the sensitive layer is greater than 10 μm or the volume fraction of polystyrene in the sensitive material is greater than 40 vol%, the holding time of the 280°C and 360°C platforms is extended to 90-120 min, or the heating rate of 360-450°C is reduced to 0.5°C, so as to reduce the risk of residual carbon caused by the restricted diffusion of thermal decomposition products and reduce the probability of cracking / peeling.

[0016] The beneficial effects of this invention are: This invention discloses a method for fabricating a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries. The method involves washing, drying, and activating a substrate, then mounting electrodes on its surface. Sensitive materials are added to an aerosol generator, and a carrier gas is used to atomize the powder into an aerosol, which is then delivered to a nozzle and sprayed at high speed onto the substrate surface under differential pressure to obtain a composite film. The composite film undergoes segmented heat treatment and cooling to obtain a sensitive layer. A sensitizing layer is then deposited on the sensitive layer via sputtering, activated, and a microheater is mounted on the back of the substrate to obtain the hydrogen sensor. Using tungsten trioxide as the substrate for the sensitive material exhibits a more sensitive response to hydrogen compared to common materials such as tin oxide and zinc oxide. By introducing a sacrificial template into the tungsten trioxide sensitive layer prepared by aerosol deposition and employing a segmented annealing process, a controllable porous structure is constructed while ensuring sufficient template removal and film continuity. This significantly improves the sensitivity and response / recovery performance of the hydrogen sensor, making it suitable for early warning scenarios such as lithium-ion battery safety monitoring.

[0017] In the preparation of a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries, the sensitive material was first prepared. Tungsten trioxide was synthesized hydrothermally from sodium tungstate under hydrothermal conditions. Potassium chloride was then added, and under the dispersion and complexation effect of polyvinylpyrrolidone, K… + Adsorbed on the surface of tungsten trioxide, and calcined, it forms K + Doped and modified tungsten trioxide yields an intermediate product; K + As a donor dopant, it provides additional electrons to the conduction band of tungsten trioxide, increasing the carrier concentration, K + Introducing lattice distortion increases the oxygen vacancy concentration. Oxygen vacancies are active sites for gas adsorption and reaction, enhancing the material's resistive response to hydrogen, improving intrinsic sensitivity, and increasing stability. Under ice bath conditions, palladium acetate is reduced to palladium nanoparticles in sodium borohydride solution, which are then deposited in situ on the surface of intermediate products to obtain modified tungsten trioxide. Low temperature and slow reduction inhibit the rapid aggregation of palladium particles. Palladium is a highly efficient hydrogen dissociation catalyst; hydrogen molecules dissociate into active hydrogen atoms on the palladium surface, which then overflow to the tungsten trioxide surface and react with adsorbed oxygen species. This process lowers the activation energy of the hydrogen reaction, allowing the reaction to proceed more rapidly and completely at lower temperatures. Styrene, under the steric hindrance stabilization of a dispersant, forms monodisperse polystyrene microspheres in ethanol solution, which are then blended with modified tungsten trioxide to obtain a sensitive material. Using K... + Doping with tungsten trioxide optimizes the electronic structure and surface active sites, and palladium modification enhances its hydrogen sensing performance, exhibiting high sensing response, low operating temperature, and fast response time. Monodisperse polystyrene microspheres occupy space in the sensitive layer. During the preparation of the hydrogen sensor, these microspheres are gently and thoroughly removed through segmented annealing, leaving interconnected channels that match the size and distribution of the microspheres. This increases the contact area between the gas and the interior of the sensitive material, ensuring rapid diffusion of hydrogen and rapid expulsion of products, thus achieving a fast response. Attached Figure Description

[0018] The invention will now be further described with reference to the accompanying drawings.

[0019] Figure 1 This is a schematic diagram showing the alarm response time test results of the hydrogen sensor used for early warning of thermal runaway in lithium-ion batteries in Examples 1-3 and Comparative Examples 1-3 of the present invention.

[0020] Figure 2 This is a schematic diagram showing the minimum response value test results of the hydrogen sensor used for early warning of thermal runaway in lithium-ion batteries in Examples 1-3 and Comparative Examples 1-3 of the present invention.

[0021] Figure 3 This is a schematic diagram showing the recovery speed test results of the hydrogen sensor used for early warning of thermal runaway in lithium-ion batteries in Examples 1-3 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1:

[0024] This embodiment describes a method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries, comprising the following steps: Step S1: Add 1.5g sodium tungstate, 0.4g potassium sulfate, and 40mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 300r / min for 30min. Adjust the pH to 2 with 3mol / L hydrochloric acid solution. Transfer to a hydrothermal reactor and heat to 180℃ at a rate of 2℃ / min for 12h. Centrifuge and discard the supernatant. Wash the precipitate twice with distilled water and dry in a vacuum drying oven at 60℃ for 4h. Add 40mL anhydrous ethanol and ultrasonically disperse for 30min. Add 0.5g polyvinylpyrrolidone (PVP-K30) and 0.1g potassium chloride. Mix and stir at 400r / min for 12h. Centrifuge and discard the supernatant. Wash the precipitate twice with distilled water and dry in a vacuum drying oven at 60℃ for 4h. Transfer to a muffle furnace and calcine at 400℃ for 2h to obtain the intermediate product. Step S2: Add 100 mg of intermediate product and 30 mL of 20% ethanol solution to a three-necked flask equipped with a stirrer and thermometer. Sonicate for 30 min, place in an ice-water bath at 0 °C, stir at 400 r / min for 30 min, add 0.2 mL of 5 g / L palladium acetate solution, continue stirring for 10 min, add 1 mL of 10 g / L sodium borohydride solution, continue stirring for 10 min, centrifuge, discard the supernatant, wash the precipitate twice with anhydrous ethanol and distilled water respectively, dry in a vacuum drying oven at 60 °C for 4 h, transfer to a mortar and grind, and sieve to obtain modified tungsten trioxide with a particle size of 0.5 μm. Step S3: Wash 3 mL of styrene twice with 5% sodium hydroxide solution and distilled water, respectively. Add 3 g of anhydrous magnesium sulfate and dry for 12 h. Under nitrogen protection, distill under reduced pressure and transfer the solution to a three-necked flask equipped with a stirrer and thermometer. Add 80 mL of 80% ethanol solution and 2 g of polyvinylpyrrolidone (PVP-K30). Mix and stir for 30 min. Place in an oil bath at 70 °C. Add 0.1 g of azobisisobutyronitrile (AIBN). Stir at 200 r / min for 24 h. Allow to cool naturally to 25 °C. Centrifuge at 8000 r / min for 10 min. Discard the supernatant. Add 50 mL of anhydrous ethanol and sonicate for 5 min. Filter and dry in a vacuum drying oven at 60 °C for 12 h. Sieve through a sieve to obtain monodisperse polystyrene microspheres. Add 10 g of modified tungsten trioxide and monodisperse polystyrene microspheres to a container and dry mix for 0.5 h. Sieve through a 20-mesh sieve to obtain the sensitive material. Step S4: The alumina ceramic substrate is washed sequentially with acetone, anhydrous ethanol, and deionized water, dried at 60℃ for 1 hour, and plasma activated for 1 minute. A Pt electrode with an interdigitated electrode structure is then mounted on the surface. The sensitive material is added to an aerosol generator, and the powder is atomized into an aerosol using a carrier gas and delivered to a nozzle. Under pressure differential, the aerosol is sprayed at high speed onto the substrate surface. The carrier gas flow rate is 0.5 L / min, the nozzle-to-substrate distance is 10 mm, the scanning speed is 10 mm / s, the number of sprays / round trips is 1, the deposition time is 20 minutes, and the substrate temperature is 40℃, resulting in a composite film. The composite film is then subjected to segmented heat treatment in air or an oxygen-rich atmosphere according to the following temperature program: Heating to 120℃ at a rate of 1℃ / min, holding for 30 minutes; heating to 280℃ at a rate of 0.5℃ / min. The temperature was maintained for 30 min; then increased to 360℃ at a rate of 0.5℃ / min and maintained for 30 min; then increased to 450℃ at a rate of 1℃ / min and maintained for 60 min; finally increased to 475℃ at a rate of 0.5℃ / min and maintained for 30 min; and then cooled to 25℃ at a rate of 1℃ / min to obtain a sensitive layer with a thickness of 0.5 μm and a pore size distribution of 0.5 μm. A Pd sensitizing layer with a thickness of 0.5 nm was sputtered onto the sensitive layer at a sputtering power of 20 W for 100 s, followed by activation at 150℃ for 0.5 h. A microheater providing the operating temperature was then mounted on the back side of the substrate to obtain a hydrogen sensor. The hydrogen sensor includes a substrate, an electrode disposed on the surface of the substrate, a sensitive layer covering the electrode, and a microheater located on the back side of the substrate. The surface of the sensitive layer also includes a sensitizing layer.

[0025] Example 2:

[0026] This embodiment describes a method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries, comprising the following steps: Step S1: Add 1.8g sodium tungstate, 0.5g potassium sulfate, and 60mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 300r / min for 30min. Adjust the pH to 3 with 3mol / L hydrochloric acid solution. Transfer to a hydrothermal reactor and heat to 180℃ at a rate of 3℃ / min for 12h. Centrifuge, discard the supernatant, wash the precipitate three times with distilled water, and dry in a vacuum drying oven at 60℃ for 5h. Add 60mL anhydrous ethanol and ultrasonically disperse for 30min. Add 0.7g polyvinylpyrrolidone (PVP-K30) and 0.15g potassium chloride. Mix and stir at 500r / min for 16h. Centrifuge, discard the supernatant, wash the precipitate three times with distilled water, and dry in a vacuum drying oven at 60℃ for 5h. Transfer to a muffle furnace and calcine at 400℃ for 2.5h to obtain the intermediate product. Step S2: Add 125 mg of intermediate product and 40 mL of 20% ethanol solution to a three-necked flask equipped with a stirrer and thermometer. Sonicate for 30 min, place in an ice-water bath at 3°C, stir at 500 r / min for 30 min, add 0.3 mL of 5 g / L palladium acetate solution, continue stirring for 13 min, add 1.5 mL of 10 g / L sodium borohydride solution, continue stirring for 13 min, centrifuge, discard the supernatant, wash the precipitate three times with anhydrous ethanol and distilled water respectively, dry in a vacuum drying oven at 60°C for 5 h, transfer to a mortar and grind, and sieve to obtain modified tungsten trioxide with a particle size of 1 μm. Step S3: Wash 10 mL of styrene three times with 5% sodium hydroxide solution and distilled water, respectively. Add 4 g of anhydrous magnesium sulfate and dry for 18 h. Under nitrogen protection, distill under reduced pressure and transfer the solution to a three-necked flask equipped with a stirrer and thermometer. Add 90 mL of 80% ethanol solution and 2.5 g of polyvinylpyrrolidone (PVP-K30). Mix and stir for 30 min. Place in a 70°C oil bath and add 0.15 g of azobisisobutyronitrile (AIBN). The mixture was stirred at 230 rpm for 24 h, then naturally cooled to 25 °C. After centrifugation at 8000 rpm for 13 min, the supernatant was discarded. 55 mL of anhydrous ethanol was added, and the mixture was ultrasonically dispersed for 8 min. After filtration, the mixture was dried in a vacuum drying oven at 60 °C for 12 h and then sieved to obtain monodisperse polystyrene microspheres. 13 g of modified tungsten trioxide and monodisperse polystyrene microspheres were added to a container and dry-mixed for 1 h. The mixture was then sieved through a 100-mesh sieve to obtain the sensitive material. Step S4: The alumina ceramic substrate is washed twice sequentially with acetone, anhydrous ethanol, and deionized water, dried at 70℃ for 1.5h, and plasma activated for 5min. A Pt electrode with an interdigitated electrode structure is then mounted on the surface. The sensitive material is added to an aerosol generator, and the powder is atomized into an aerosol using a carrier gas and delivered to a nozzle. Under pressure differential, the aerosol is sprayed at high speed onto the substrate surface. The carrier gas flow rate is 5L / min, the nozzle-to-substrate distance is 20mm, the scanning speed is 30mm / s, the number of sprays / round trips is 3, the deposition time is 30min, and the substrate temperature is 80℃, resulting in a composite film. The composite film is then subjected to segmented heat treatment in air or an oxygen-rich atmosphere according to the following temperature program: Heating to 120℃ at a rate of 2℃ / min, holding for 45min; heating to 280℃ at a rate of 1℃ / min. The temperature was increased to 360℃ at a rate of 0.8℃ / min and held for 100 min; then increased to 450℃ at a rate of 1℃ / min and held for 90 min; finally increased to 475℃ at a rate of 0.8℃ / min and held for 45 min; and then cooled to 25℃ at a rate of 3℃ / min to obtain a sensitive layer with a thickness of 20 μm and a pore size distribution of 5 μm. A 10 nm thick Pd sensitizing layer was sputtered onto the sensitive layer at a sputtering power of 60 W for 400 s, followed by activation at 200℃ for 2 h. A microheater providing the operating temperature was then mounted on the back of the substrate to obtain a hydrogen sensor. The hydrogen sensor includes a substrate, an electrode disposed on the surface of the substrate, a sensitive layer covering the electrode, and a microheater located on the back of the substrate. The surface of the sensitive layer also includes a sensitizing layer.

[0027] Example 3:

[0028] This embodiment describes a method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries, comprising the following steps: Step S1: Add 2g sodium tungstate, 0.6g potassium sulfate, and 80mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 300r / min for 30min. Adjust the pH to 3 with 3mol / L hydrochloric acid solution. Transfer to a hydrothermal reactor and heat to 180℃ at a rate of 5℃ / min for 12h. Centrifuge, discard the supernatant, wash the precipitate three times with distilled water, and dry in a vacuum drying oven at 60℃ for 6h. Add 80mL anhydrous ethanol and ultrasonically disperse for 30min. Add 0.8g polyvinylpyrrolidone (PVP-K30) and 0.2g potassium chloride. Mix and stir at 600r / min for 24h. Centrifuge, discard the supernatant, wash the precipitate three times with distilled water, and dry in a vacuum drying oven at 60℃ for 6h. Transfer to a muffle furnace and calcine at 400℃ for 3h to obtain the intermediate product. Step S2: Add 150 mg of intermediate product and 50 mL of 20% ethanol solution to a three-necked flask equipped with a stirrer and thermometer. Sonicate for 30 min, place in an ice-water bath at 5 °C, stir at 600 r / min for 30 min, add 0.5 mL of 5 g / L palladium acetate solution, continue stirring for 15 min, add 2 mL of 10 g / L sodium borohydride solution, continue stirring for 15 min, centrifuge, discard the supernatant, wash the precipitate three times with anhydrous ethanol and distilled water respectively, dry in a vacuum drying oven at 60 °C for 6 h, transfer to a mortar and grind, and sieve to obtain modified tungsten trioxide with a particle size of 2 μm. Step S3: Wash 15 mL of styrene three times with 5% sodium hydroxide solution and distilled water, add 5 g of anhydrous magnesium sulfate and dry for 24 h. Under nitrogen protection, distill under reduced pressure and add to a three-necked flask equipped with a stirrer and thermometer. Add 100 mL of 80% ethanol solution and 3 g of polyvinylpyrrolidone (PVP-K30), mix and stir for 30 min, place in an oil bath at 70 °C, add 0.2 g of azobisisobutyronitrile (AIBN), stir at 250 r / min for 24 h, cool naturally to 25 °C, centrifuge at 8000 r / min for 15 min, discard the supernatant, add 60 mL of anhydrous ethanol, ultrasonically disperse for 10 min, filter, dry in a vacuum drying oven at 60 °C for 12 h, and sieve to obtain monodisperse polystyrene microspheres. Add 15 g of modified tungsten trioxide and monodisperse polystyrene microspheres to a container and dry mix for 2 h. Sieve through a 200-mesh sieve to obtain the sensitive material. Step S4: The alumina ceramic substrate is washed twice sequentially with acetone, anhydrous ethanol, and deionized water, dried at 80℃ for 2 hours, and plasma activated for 10 minutes. A Pt electrode with an interdigitated electrode structure is then mounted on the surface. The sensitive material is added to an aerosol generator, and the powder is atomized into an aerosol using a carrier gas and delivered to a nozzle. Under pressure differential, the aerosol is sprayed at high speed onto the substrate surface. The carrier gas flow rate is 10 L / min, the nozzle-to-substrate distance is 30 mm, the scanning speed is 50 mm / s, the number of sprays / round trips is 4, the deposition time is 60 minutes, and the substrate temperature is 100℃, resulting in a composite film. The composite film is then subjected to segmented heat treatment in air or an oxygen-rich atmosphere according to the following temperature program: Heating to 120℃ at a rate of 3℃ / min and holding for 60 minutes; heating to 280℃ at a rate of 2℃ / min. n, hold at 360℃ for 120 min; heat to 450℃ at 1℃ / min and hold for 120 min; heat to 475℃ at 1℃ / min and hold for 60 min; cool to 25℃ at a rate of 5℃ / min to obtain a sensitive layer with a thickness of 30 μm and a pore size distribution of 10 μm; sputter to deposit a Pd sensitizing layer with a thickness of 20 nm on the sensitive layer at a sputtering power of 100 W for 600 s, and activate at 350℃ for 3 h; install a micro heater to provide the working temperature on the back of the substrate to obtain a hydrogen sensor; the hydrogen sensor includes a substrate, an electrode disposed on the surface of the substrate, a sensitive layer covering the electrode, and a micro heater located on the back of the substrate; the surface of the sensitive layer also includes a sensitizing layer.

[0029] Comparative Example 1: This comparative example illustrates a method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries, comprising the following steps: Step S1: Add 1.8g sodium tungstate, 0.5g potassium sulfate and 60mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 300r / min for 30min. Adjust the pH to 3 with 3mol / L hydrochloric acid solution. Transfer to a hydrothermal reactor and heat to 180℃ at a rate of 3℃ / min for 12h. Centrifuge and discard the supernatant. Wash the precipitate three times with distilled water. Dry in a vacuum drying oven at 60℃ for 5h. Transfer to a mortar and grind. Sieve through a sieve to obtain tungsten trioxide with a particle size of 1μm. Step S2: Wash 25 mL of styrene three times with 5% sodium hydroxide solution and distilled water, add 4 g of anhydrous magnesium sulfate and dry for 18 h. Under nitrogen protection, distill under reduced pressure and add the styrene to a three-necked flask equipped with a stirrer and thermometer. Add 90 mL of 80% ethanol solution and 2.5 g of polyvinylpyrrolidone (PVP-K30), mix and stir for 30 min, place in an oil bath at 70 °C, add 0.15 g of azobisisobutyronitrile (AIBN), stir at 230 r / min for 24 h, cool naturally to 25 °C, centrifuge at 8000 r / min for 13 min, discard the supernatant, add 55 mL of anhydrous ethanol, ultrasonically disperse for 8 min, filter, dry in a vacuum drying oven at 60 °C for 12 h, and sieve to obtain monodisperse polystyrene microspheres. Add 13 g of tungsten trioxide and monodisperse polystyrene microspheres to a container and dry mix for 1 h. Sieve through a 100-mesh sieve to obtain the sensitive material. Step S3: The alumina ceramic substrate is washed twice sequentially with acetone, anhydrous ethanol, and deionized water, dried at 70℃ for 1.5h, and plasma activated for 5min. A Pt electrode with an interdigitated electrode structure is then mounted on the surface. The sensitive material is added to an aerosol generator, and the powder is atomized into an aerosol using a carrier gas and delivered to a nozzle. Under pressure differential, the aerosol is sprayed at high speed onto the substrate surface. The carrier gas flow rate is 5L / min, the nozzle-to-substrate distance is 20mm, the scanning speed is 30mm / s, the number of sprays / round trips is 3, the deposition time is 30min, and the substrate temperature is 80℃, resulting in a composite film. The composite film is then subjected to segmented heat treatment in air or an oxygen-rich atmosphere according to the following temperature program: [temperature range to be specified in the original text]. The temperature was increased at a rate of 2℃ / min and held for 45 min; then increased to 280℃ at a rate of 1℃ / min and held for 100 min; then increased to 360℃ at a rate of 0.8℃ / min and held for 100 min; then increased to 450℃ at a rate of 1℃ / min and held for 90 min; then increased to 475℃ at a rate of 0.8℃ / min and held for 45 min; finally cooled to 25℃ at a rate of 3℃ / min to obtain a sensitive layer with a thickness of 20 μm and a pore size distribution of 5 μm; a microheater providing the operating temperature was installed on the back of the substrate to obtain a hydrogen sensor; the hydrogen sensor includes a substrate, an electrode disposed on the surface of the substrate, a sensitive layer covering the electrode, and a microheater located on the back of the substrate.

[0030] Comparative Example 2: This comparative example illustrates a method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries, comprising the following steps: Step S1: Add 1.8g sodium tungstate, 0.5g potassium sulfate, and 60mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 300r / min for 30min. Adjust the pH to 3 with 3mol / L hydrochloric acid solution. Transfer to a hydrothermal reactor and heat to 180℃ at a rate of 3℃ / min for 12h. Centrifuge to separate the precipitate, discard the supernatant, wash the precipitate three times with distilled water, and dry in a vacuum drying oven at 60℃ for 5h. Add 60 mL of anhydrous ethanol, sonicate for 30 min, add 0.7 g of polyvinylpyrrolidone PVP-K30 and 0.15 g of potassium chloride, mix and stir at 500 r / min for 16 h, centrifuge, discard the supernatant, wash the precipitate 3 times with distilled water, dry in a vacuum drying oven at 60 °C for 5 h, transfer to a muffle furnace, calcine at 400 °C for 2.5 h, transfer to a mortar and grind, and sieve to obtain modified tungsten trioxide with a particle size of 1 μm; Step S2: Wash 25 mL of styrene three times with 5% sodium hydroxide solution and distilled water, respectively. Add 4 g of anhydrous magnesium sulfate and dry for 18 h. Under nitrogen protection, distill under reduced pressure and transfer the solution to a three-necked flask equipped with a stirrer and thermometer. Add 90 mL of 80% ethanol solution and 2.5 g of polyvinylpyrrolidone (PVP-K30). Mix and stir for 30 min. Place in a 70°C oil bath and add 0.15 g of azobisisobutyronitrile (AIBN). The mixture was stirred at 230 rpm for 24 h, then naturally cooled to 25 °C. After centrifugation at 8000 rpm for 13 min, the supernatant was discarded. 55 mL of anhydrous ethanol was added, and the mixture was ultrasonically dispersed for 8 min. After filtration, the mixture was dried in a vacuum drying oven at 60 °C for 12 h and then sieved to obtain monodisperse polystyrene microspheres. 13 g of modified tungsten trioxide and monodisperse polystyrene microspheres were added to a container and dry-mixed for 1 h. The mixture was then sieved through a 100-mesh sieve to obtain the sensitive material. Step S3: The alumina ceramic substrate is washed twice sequentially with acetone, anhydrous ethanol, and deionized water, dried at 70℃ for 1.5h, and plasma activated for 5min. A Pt electrode with an interdigitated electrode structure is then mounted on the surface. The sensitive material is added to an aerosol generator, and the powder is atomized into an aerosol using a carrier gas and delivered to a nozzle. Under pressure differential, the aerosol is sprayed at high speed onto the substrate surface. The carrier gas flow rate is 5L / min, the nozzle-to-substrate distance is 20mm, the scanning speed is 30mm / s, the number of sprays / round trips is 3, the deposition time is 30min, and the substrate temperature is 80℃, resulting in a composite film. The composite film is then subjected to segmented heat treatment in air or an oxygen-rich atmosphere according to the following temperature program: Heating to 120℃ at a rate of 2℃ / min, holding for 45min; heating to 280℃ at a rate of 1℃ / min. The temperature was increased to 360℃ at a rate of 0.8℃ / min and held for 100 min; then increased to 450℃ at a rate of 1℃ / min and held for 90 min; finally increased to 475℃ at a rate of 0.8℃ / min and held for 45 min; and then cooled to 25℃ at a rate of 3℃ / min to obtain a sensitive layer with a thickness of 20 μm and a pore size distribution of 5 μm. A 10 nm thick Pd sensitizing layer was sputtered onto the sensitive layer at a sputtering power of 60 W for 400 s, followed by activation at 200℃ for 2 h. A microheater providing the operating temperature was then mounted on the back of the substrate to obtain a hydrogen sensor. The hydrogen sensor includes a substrate, an electrode disposed on the surface of the substrate, a sensitive layer covering the electrode, and a microheater located on the back of the substrate. The surface of the sensitive layer also includes a sensitizing layer.

[0031] Comparative Example 3: This comparative example illustrates a method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries, comprising the following steps: Step S1: Add 1.8g sodium tungstate, 0.5g potassium sulfate, and 60mL deionized water to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 300r / min for 30min. Adjust the pH to 3 with 3mol / L hydrochloric acid solution. Transfer to a hydrothermal reactor and heat to 180℃ at a rate of 3℃ / min for 12h. Centrifuge, discard the supernatant, wash the precipitate three times with distilled water, and dry in a vacuum drying oven at 60℃ for 5h. Add 40mL of 20% ethanol solution. The liquid was ultrasonically dispersed for 30 min, placed in an ice-water bath at 3℃, and stirred at 500 r / min for 30 min. 0.3 mL of 5 g / L palladium acetate solution was added, and stirring was continued for 13 min. 1.5 mL of 10 g / L sodium borohydride solution was added, and stirring was continued for 13 min. The mixture was centrifuged, the supernatant was discarded, and the precipitate was washed three times with anhydrous ethanol and distilled water, respectively. It was dried in a vacuum drying oven at 60℃ for 5 h, transferred to a mortar and ground, and sieved to obtain modified tungsten trioxide with a particle size of 1 μm. Step S2: Wash 25 mL of styrene three times with 5% sodium hydroxide solution and distilled water, respectively. Add 4 g of anhydrous magnesium sulfate and dry for 18 h. Under nitrogen protection, distill under reduced pressure and transfer the solution to a three-necked flask equipped with a stirrer and thermometer. Add 90 mL of 80% ethanol solution and 2.5 g of polyvinylpyrrolidone (PVP-K30). Mix and stir for 30 min. Place in a 70°C oil bath and add 0.15 g of azobisisobutyronitrile (AIBN). The mixture was stirred at 230 rpm for 24 h, then naturally cooled to 25 °C. After centrifugation at 8000 rpm for 13 min, the supernatant was discarded. 55 mL of anhydrous ethanol was added, and the mixture was ultrasonically dispersed for 8 min. After filtration, the mixture was dried in a vacuum drying oven at 60 °C for 12 h and then sieved to obtain monodisperse polystyrene microspheres. 13 g of modified tungsten trioxide and monodisperse polystyrene microspheres were added to a container and dry-mixed for 1 h. The mixture was then sieved through a 100-mesh sieve to obtain the sensitive material. Step S3: The alumina ceramic substrate is washed twice sequentially with acetone, anhydrous ethanol, and deionized water, dried at 70℃ for 1.5h, and plasma activated for 5min. A Pt electrode with an interdigitated electrode structure is then mounted on the surface. The sensitive material is added to an aerosol generator, and the powder is atomized into an aerosol using a carrier gas and delivered to a nozzle. Under pressure differential, the aerosol is sprayed at high speed onto the substrate surface. The carrier gas flow rate is 5L / min, the nozzle-to-substrate distance is 20mm, the scanning speed is 30mm / s, the number of sprays / round trips is 3, the deposition time is 30min, and the substrate temperature is 80℃, resulting in a composite film. The composite film is then subjected to segmented heat treatment in air or an oxygen-rich atmosphere according to the following temperature program: Heating to 120℃ at a rate of 2℃ / min, holding for 45min; heating to 280℃ at a rate of 1℃ / min. The temperature was increased to 360℃ at a rate of 0.8℃ / min and held for 100 min; then increased to 450℃ at a rate of 1℃ / min and held for 90 min; finally increased to 475℃ at a rate of 0.8℃ / min and held for 45 min; and then cooled to 25℃ at a rate of 3℃ / min to obtain a sensitive layer with a thickness of 20 μm and a pore size distribution of 5 μm. A 10 nm thick Pd sensitizing layer was sputtered onto the sensitive layer at a sputtering power of 60 W for 400 s, followed by activation at 200℃ for 2 h. A microheater providing the operating temperature was then mounted on the back of the substrate to obtain a hydrogen sensor. The hydrogen sensor includes a substrate, an electrode disposed on the surface of the substrate, a sensitive layer covering the electrode, and a microheater located on the back of the substrate. The surface of the sensitive layer also includes a sensitizing layer.

[0032] The hydrogen sensors for lithium-ion battery thermal runaway early warning prepared in Examples 1-3 and Comparative Examples 1-3 were tested according to GB 12358-2024 standard. The alarm response time, minimum response value, and recovery speed of the hydrogen sensors were found to be slow. The test results are as follows: Figure 1-3 As shown: Comparison of Examples 1-3 and Comparative Examples 1-3: In Example 1, the sensitive layer is thin with small pores, resulting in the shortest gas diffusion path and thus a faster response / recovery speed. However, the total active material is limited, and the performance is not the highest. In Example 2, the sensitive layer has a moderate thickness, ideal pore size, and optimized process, achieving synergistic optimization of gas diffusion efficiency, total active sites, and Pd catalytic efficiency, resulting in the best overall performance. In Example 3, the sensitive layer is thick with large pores, possessing the largest total amount of active material and high intrinsic sensitivity. However, gas diffusion at deep depths and product desorption are difficult, leading to the slowest response and recovery speed. Comparing Example 2 with Comparative Example 1, it can be seen that Comparative Example 1 lacks "bulk doping sensitization" and "surface catalytic acceleration," resulting in a weak intrinsic response to hydrogen, slow reaction kinetics, and poor pore structure, leading to poor performance. Comparing Example 2 with Comparative Example 2, it can be seen that Comparative Example 2 underwent K... +Doping optimizes the electronic structure of tungsten trioxide, solving the "bulk sensitivity" problem. However, the lack of palladium nanoparticles as a "reaction trigger" results in a high energy barrier for hydrogen molecule dissociation on the metal oxide surface. Therefore, the material cannot efficiently initiate the reaction, leading to a slow response speed and sensitivity far lower than that of the palladium catalytic system. Comparing Example 2 with Comparative Example 3, it can be seen that Comparative Example 3, with palladium loading, solves the "surface reaction initiation" problem, but lacks K... + With doping, the oxygen vacancy concentration in the tungsten trioxide framework is low, resulting in insufficient electron supply and thus lower performance.

[0033] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0034] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a sensitive material for lithium battery safety monitoring, characterized in that, Includes the following steps: Step a1: Mix sodium tungstate, potassium sulfate and deionized water and stir magnetically. Adjust the pH with hydrochloric acid solution, heat the reaction, centrifuge, discard the supernatant, wash the precipitate, dry, add anhydrous ethanol, disperse ultrasonically, add polyvinylpyrrolidone and potassium chloride, mix and stir, centrifuge, discard the supernatant, wash the precipitate, dry, calcine to obtain the intermediate product. Step a2: The intermediate product and ethanol solution were ultrasonically dispersed, stirred in an ice-water bath, palladium acetate solution was added and stirred, sodium borohydride solution was added and stirred, centrifuged and separated, the supernatant was discarded, the precipitate was washed with anhydrous ethanol and distilled water respectively, dried, ground and sieved to obtain modified tungsten trioxide. Step a3: Wash styrene with sodium hydroxide solution and distilled water respectively, add anhydrous magnesium sulfate to dry, distill under reduced pressure, add ethanol solution and dispersant, mix and stir, place in an oil bath, add initiator, stir to react, cool, centrifuge, discard the supernatant, add anhydrous ethanol, ultrasonically disperse, filter, dry, and sieve to obtain monodisperse polystyrene microspheres; dry mix modified tungsten trioxide and monodisperse polystyrene microspheres, sieve to obtain sensitive material.

2. The method for preparing a sensitive material for lithium battery safety monitoring according to claim 1, characterized in that, In step a1, the ratio of sodium tungstate, potassium sulfate, deionized water, anhydrous ethanol, polyvinylpyrrolidone, and potassium chloride is 1.5-2g: 0.4-0.6g: 40-80mL: 40-80mL: 0.5-0.8g: 0.1-0.2g; the concentration of the hydrochloric acid solution is 3mol / L; and the polyvinylpyrrolidone is PVP-K30.

3. The method for preparing a sensitive material for lithium battery safety monitoring according to claim 1, characterized in that, In step a2, the ratio of the intermediate product, ethanol solution, palladium acetate solution, and sodium borohydride solution is 100-150 mg: 30-50 mL: 0.2-0.5 mL: 1-2 mL; the mass fraction of the ethanol solution is 20%; the concentration of the palladium acetate solution is 5 g / L; and the concentration of the sodium borohydride solution is 10 g / L.

4. The method for preparing a sensitive material for lithium battery safety monitoring according to claim 1, characterized in that, In step a3, the ratio of styrene, anhydrous magnesium sulfate, ethanol solution, dispersant, initiator, anhydrous ethanol, and modified tungsten trioxide is 3-15 mL: 3-5 g: 80-100 mL: 2-3 g: 0.1-0.2 g: 50-60 mL: 10-15 g; the mass fraction of the sodium hydroxide solution is 5%; the mass fraction of the ethanol solution is 80%; the dispersant is polyvinylpyrrolidone (PVP-K30); and the initiator is azobisisobutyronitrile (AIBN).

5. A method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries, characterized in that, Includes the following steps: The substrate was washed with acetone, anhydrous ethanol and deionized water, dried and activated, and electrodes were mounted on the surface. The sensitive material is added to an aerosol generator and sprayed at high speed onto the substrate surface to obtain a composite film; the composite film is then subjected to segmented heat treatment and cooled to obtain the sensitive layer; A sensitizing layer was sputter-deposited onto the sensitive layer, followed by activation treatment. A microheater was then installed on the back of the substrate to obtain a hydrogen sensor.

6. A method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries according to claim 5, characterized in that, The hydrogen sensor includes a substrate, electrodes disposed on the surface of the substrate, a sensitive layer covering the electrodes, and a microheater located on the back side of the substrate; the surface of the sensitive layer also includes a sensitizing layer; the microheater provides an operating temperature of 50-350°C.

7. A method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries according to claim 5, characterized in that, The sensitive layer is prepared by the method for preparing the sensitive material in the first aspect; the substrate is one of alumina ceramic, aluminum nitride ceramic, glass or silicon-based insulating substrate; the electrode is an interdigitated electrode structure or a counter electrode structure, and the material is one of Pt, Au, Ag or their alloys; the sensitizing layer is a nanolayer / nanoparticle layer formed by one or more of Pd, Pt, Au.

8. A method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries according to claim 5, characterized in that, The thickness of the sensitive layer is 0.5-30 μm, and the pore size distribution is 0.5-10 μm; the thickness of the sensitizing layer is 0.5-20 nm.

9. A method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries according to claim 5, characterized in that, The segmented heat treatment includes the following temperature program: Heat to 120℃ at a rate of 1-3℃ / min, and hold for 30-60 minutes. Heat to 280℃ at a rate of 0.5-2℃ / min, and hold for 30-90 minutes. Heat to 360℃ at a rate of 0.5-1℃ / min and hold for 30-90 minutes. Heat to 450℃ at a rate of 1℃ / min, and hold for 60-120 minutes. Heat to 475℃ at a rate of 0.5-1℃ / min and hold for 30-60 minutes.

10. A method for preparing a hydrogen sensor for early warning of thermal runaway in lithium-ion batteries according to claim 9, characterized in that, When the thickness of the sensitive layer is greater than 10 μm or the volume fraction of polystyrene in the sensitive material is greater than 40 vol%, the holding time at 280℃ and 360℃ should be extended to 90-120 min, or the heating rate at 360-450℃ should be reduced to 0.5℃, in order to reduce the risk of residual carbon caused by the restricted diffusion of thermal decomposition products and reduce the probability of cracking / peeling.

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