Pre-spraying explosion suppressant for lithium battery thermal runaway stage and preparation method of pre-spraying explosion suppressant

Abstract

The invention relates to the technical field of safety treatment of lithium batteries, in particular to a pre-spraying explosion suppressant for a thermal runaway stage of a lithium battery and a preparation method of the pre-spraying explosion suppressant. The explosion suppressant is formed by compounding an inert carrier, a cooling explosion suppression component, a corrosion-resistant and salt-precipitation-resistant stabilizer and a functional additive, according to the preparation method, the stability and consistency of the product are ensured through precise metering, speed-controlled mixing, vacuum degassing, precise filtering and closed filling. The explosion suppressant is suitable for the full-stage pre-injection requirement of lithium battery thermal runaway, the thermal runaway peak temperature can be effectively reduced, open fire and recombustion are inhibited, harmful gas emission is reduced, the explosion suppressant has high dielectric strength, excellent thermal conductivity and acid gas neutralizing capacity, and the explosion suppressant can be applied to lithium battery thermal runaway through linkage with a three-stage injection strategy of a CTRR system. Accurate intervention is carried out in the front, middle and later periods of thermal runaway, active explosion suppression, rapid cooling and equipment corrosion prevention are achieved, cooperation of dielectric insulation, efficient explosion suppression, corrosion resistance and good atomization performance is achieved, and wide application prospects are achieved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery safety treatment technology, and in particular to a pre-sprayed explosion suppressant for the thermal runaway stage of lithium batteries and its preparation method. Background Technology

[0002] With the widespread adoption of electric vehicles, a large number of retired power batteries are entering the recycling process. While charged battery crushing is a crucial step in the recycling process, it is highly susceptible to thermal runaway, leading to fires, explosions, and the release of toxic gases. Traditional water-based fire extinguishing methods can trigger secondary reactions, exacerbating corrosion and causing black powder pollution, thus reducing the recycling value. Furthermore, traditional lithium battery recycling pretreatment often employs a "passive fire extinguishing + open-circuit emission" model, which has the following shortcomings: Lack of dielectric properties: Conventional explosion suppressants such as dry powder and water-based fire extinguishing agents have low dielectric strength, which can easily lead to short circuits in lithium batteries and exacerbate thermal runaway. Limited explosion suppression efficiency: It cannot meet the full-stage requirements of thermal runaway from initial triggering to plateau maintenance to decay and convergence, and is prone to reignition or temperature runaway; Equipment corrosion and clogging: Some explosion suppressants contain highly corrosive components or release salts during the spraying process, which can damage recovery equipment such as nozzles and inert chambers, increasing maintenance costs; Atomization compatibility: Uneven particle dispersion leads to insufficient electrode coverage, and the risk of local thermal runaway is not eliminated.

[0003] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a pre-sprayed explosion suppressant for the thermal runaway stage of lithium batteries and its preparation method. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose a pre-sprayed explosion suppressant for the thermal runaway stage of lithium batteries and its preparation method. The aim is to overcome the defects of existing explosion suppressants in the treatment of thermal runaway of lithium batteries, and at the same time provide a pre-sprayed explosion suppressant with reasonable component compounding and synergistic performance, and provide a stable and scalable preparation method to achieve the integrated goal of "safe explosion suppression - equipment protection - recycling compatibility".

[0005] To achieve the above objectives, the present invention provides a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries and its preparation method.

[0006] A pre-sprayed anti-knock agent for use in the thermal runaway stage of lithium batteries, characterized in that it comprises the following components by weight: 40-90 parts of inert carrier, 5-40 parts of cooling and explosion-suppressing component, 0.1-5 parts of corrosion-resistant and salt-curing-resistant stabilizer, and 1-3 parts of functional additives; The dielectric strength of the pre-spraying explosion suppression agent is ≥5 kV / mm, the thermal conductivity is ≥0.2 W / (m·K), the metal corrosion is ≤1 level (GB / T 10125 standard), the atomized SMD (volume average particle size) is 50-150 μm, and the coverage of the lithium battery pole piece is ≥95%.

[0007] Preferably, the inert carrier is a high flash point inert solvent, and the high flash point inert solvent is any one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), triethyl phosphate (TEP), and dipropylene glycol dimethyl ether; the flash point of the inert carrier is ≥60°C, ensuring no risk of combustion and explosion in a thermal runaway environment.

[0008] Preferably, the cooling explosion suppression component is a complex system of endothermic components and inert components; the endothermic component is any one or more of aluminum hydroxide, magnesium hydroxide, and zinc borate, and the mass fraction of the endothermic component is 40%-70% of the cooling explosion suppression component; the inert component is any one or more of expanded graphite, sodium bicarbonate, and modified montmorillonite, and the mass fraction of the inert component is 30%-60% of the cooling explosion suppression component; the particle size of the cooling explosion suppression component is ≤10 μm, ensuring uniform dispersion after atomization.

[0009] Preferably, the anti-corrosion and anti-salt precipitation stabilizer is any one or more of benzotriazole (BTA), alkyl phosphate, and triethanolamine; the anti-corrosion and anti-salt precipitation stabilizer can inhibit the corrosion of the pre-spraying explosion suppression agent on carbon steel, stainless steel, aluminum, and copper materials in lithium battery recycling equipment, and prevent salt from precipitating and blocking on the spray head or the pole piece surface.

[0010] Preferably, the functional auxiliary agent includes a wetting agent and a defoaming agent; the wetting agent is any one or more of polyether-modified siloxane and sodium dodecylbenzenesulfonate, and the mass fraction of the wetting agent is 50%-80% of the functional auxiliary agent; the defoaming agent is any one or more of silicone defoaming agent and polyether defoaming agent, and the mass fraction of the defoaming agent is 20%-50% of the functional auxiliary agent; the functional auxiliary agent can improve the atomization and spreading properties of the pre-spraying explosion suppression agent and eliminate bubbles generated during the mixing process.

[0011] A preparation method of a pre-spraying explosion suppression agent for the thermal runaway stage of a lithium battery, comprising the following steps: Step S1. Raw material metering: according to the preset mass fraction, the inert carrier, the cooling explosion suppression component, the anti-corrosion and anti-salt precipitation stabilizer, and the functional auxiliary agent are weighed respectively; Step S2. Speed-controlled mixing: Add the inert carrier to a sealed mixing vessel with a stirrer, turn on the stirrer, and stir at a speed of 100-300 rpm. Slowly add the cooling and explosion-suppressing components and stir for 20-60 minutes until the cooling and explosion-suppressing components are completely dispersed. Then add the anti-corrosion and anti-salt precipitation stabilizer and functional additives in sequence, and continue stirring for 15-30 minutes to form a uniform suspension. Step S3. Vacuum degassing: Evacuate the vacuum in the mixing vessel to ≤-0.09MPa and maintain for 15-30 minutes to remove air bubbles from the suspension and avoid cavitation during atomization that could affect coverage. Step S4. Precision filtration: The degassed suspension is filtered through a 0.22-1μm precision filter membrane to remove undispersed large particulate impurities and prevent nozzle clogging; Step S5. Sealed filling: The filtered pre-sprayed explosion suppressant is filled into a sealed storage tank with inert gas protection. A one-way valve is installed at the outlet of the storage tank to prevent contact with air and thus performance degradation.

[0012] Preferably, the jacket temperature of the mixing vessel in step S2 is controlled at 25-40°C to avoid excessive temperature causing the inert carrier to volatilize or the cooling and explosion-suppressing components to thermally decompose; the operating pressure of the filtration process in step S4 is 0.1-0.3 MPa to ensure filtration efficiency and filtrate clarity.

[0013] Preferably, the preparation method further includes a finished product testing step, which is as follows: After filling, the pre-sprayed explosion suppressant is sampled and tested for dielectric strength, thermal conductivity, corrosivity, atomized SMD, and coverage. It can only be put into use after passing the test; if the test fails, return to step S2 to readjust the component ratio or mixing parameters.

[0014] An application of a pre-sprayed anti-knock agent for the thermal runaway stage of lithium batteries involves connecting the pre-sprayed anti-knock agent to a three-stage spraying device in a CTRR system, spraying it as needed at different stages of lithium battery thermal runaway: TR pre-detonation suppression stage: The injection rate is 0.3-0.5L / 100Ah, forming a pre-inert atmosphere to suppress the initial free radicals of thermal runaway; TR plateau phase surface spraying stage: spray volume is 0.6-1.0L / 100Ah, continuously covering the electrode surface, and controlling the plateau temperature ≤500℃; TR decay period spot spray stage: The injection volume is 0.2-0.4L / 100Ah, tracking residual hot spots to prevent secondary reignition.

[0015] Preferably, the gaseous products generated after the pre-sprayed explosion suppressant is recovered through the NitroLoop inert closed-loop purification system, and the liquid products enter the subsequent charged crushing and leaching process with the lithium battery electrode, without affecting the recovery efficiency of metals such as lithium, nickel, and cobalt.

[0016] The core of this invention lies in the component design and preparation process optimization of the pre-sprayed explosion suppressant: The component design logic is based on "inert carrier as the matrix, cooling and explosion suppression as the core, corrosion resistance and stability as the guarantee, and additives as supplements." Through the synergistic effect of each component, it simultaneously meets the requirements for dielectric properties, explosion suppression, corrosion resistance, and atomization. For example, the inert carrier (such as dimethyl carbonate) ensures dielectric performance and flash point safety; the cooling and explosion suppression component (such as aluminum hydroxide + expanded graphite) suppresses combustion and explosion through the dual effects of heat absorption and cooling and inert gas release; the corrosion-resistant and salt-precipitation-resistant stabilizer (such as benzotriazole) protects the equipment materials; and the functional additives improve atomization and spreading properties.

[0017] The preparation process features: speed-controlled mixing avoids particle agglomeration, vacuum degassing eliminates atomization cavitation, precision filtration prevents nozzle clogging, and sealed filling ensures product stability. Each step is designed for the application scenario of the pre-sprayed explosion suppressant, ensuring consistent performance throughout the entire chain of "preparation-storage-spraying".

[0018] The beneficial effects of this invention are: This invention provides a pre-sprayed explosion suppressant for the thermal runaway stage of lithium batteries and its preparation method. The pre-sprayed explosion suppressant provided by this invention has a dielectric strength ≥55kV / mm, preventing short circuits in lithium batteries; it can reduce the peak temperature of thermal runaway by ≥30%, completely suppress open flames, and has a re-ignition rate of 0. Furthermore, the pre-sprayed explosion suppressant provided by this invention has good equipment compatibility, with metal corrosion ≤1 level, no salt precipitation, and a equipment maintenance cycle extended by more than 50%; it has an atomized SMD of 50–150μm, electrode coverage ≥95%, and is compatible with the three-stage spraying device of the CTRR system. It is also compatible with subsequent charged crushing and leaching processes, and does not affect the recovery rate of metals such as lithium, nickel, and cobalt. The gaseous products can be recovered using the NitroLoop system to improve economic efficiency. In addition, the preparation process provided by this invention is simple, uses conventional equipment, and can achieve continuous production, with a single batch yield of 1-5m³. 3 It meets the needs of industrial-grade lithium battery recycling lines and has broad application prospects. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0020] Example 1: A method for preparing a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries, comprising the following steps: S1. Raw material measurement: Weigh out 40 parts of inert carrier, 5 parts of cooling and explosion-suppressing component, 0.1 parts of corrosion-resistant and salt-curing stabilizer, and 1 part of functional additive according to the preset mass proportions. The inert carrier is dimethyl carbonate, and its flash point is ≥60℃ to ensure no risk of combustion and explosion under thermal runaway conditions. The cooling and explosion-suppressing component has a particle size ≤10µm and is obtained by mixing an endothermic component and an inertizing component at a mass ratio of 40:30. The endothermic component is aluminum hydroxide, and the inertizing component is expanded graphite. The corrosion-resistant and salt-curing stabilizer is benzotriazole. The functional additive is obtained by mixing a wetting agent and an defoamer at a mass ratio of 50:20. The wetting agent is polyether-modified siloxane, and the defoamer is an organic defoamer. The dimethyl carbonate is dehydrated to a moisture content ≤0.1%, and the aluminum hydroxide and expanded graphite are pulverized to a particle size ≤5µm. S2. Controlled-speed mixing: Add the inert carrier to a 500L sealed mixing vessel with a stirrer, turn on the stirrer at 100rpm, slowly add the cooling and explosion-suppressing component, and stir for 20min until the cooling and explosion-suppressing component is completely dispersed; then add the anti-corrosion and anti-salt precipitation stabilizer and functional additives in sequence, and continue stirring for 15min. Stop stirring after observing that there are no bubbles in the vessel to form a uniform suspension. The jacket temperature of the mixing vessel is controlled at 25℃ to avoid the inert carrier from volatilizing or the cooling and explosion-suppressing component from thermally decomposing due to excessive temperature. S3. Vacuum degassing: The vacuum degree inside the mixing vessel is ≤-0.09MPa and maintained for 15min to remove air bubbles from the suspension and avoid cavitation during atomization, which would affect the coverage. S4. Precision filtration: The degassed suspension is filtered through a 0.22μm polytetrafluoroethylene filter membrane to remove undispersed large particulate impurities and prevent nozzle clogging. The operating pressure of the filtration process is 0.1MPa to ensure filtration efficiency and filtrate clarity. S5. Sealed Filling: The filtered pre-sprayed explosion suppressant is filled into a sealed storage tank with nitrogen protection. A one-way valve is installed at the outlet of the storage tank to prevent contact with air and performance degradation. This yields a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries. The pre-sprayed explosion suppressant has a dielectric strength ≥5kV / mm, thermal conductivity ≥0.2W / (m·K), metal corrosion resistance ≤1 (GB / T 10125 standard), atomized SMD (volume average particle size) of 50-150μm, and a coverage of ≥95% for lithium battery electrodes. S6. The finished product testing steps are as follows: Sampling and testing of the dielectric strength, thermal conductivity, corrosivity, atomized SMD and coverage of the pre-sprayed explosion suppressant after filling. It can be put into use only after passing the test; if the test fails, return to step S2 to readjust the component ratio or mixing parameters.

[0021] Example 2: A method for preparing a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries, comprising the following steps: S1. Raw material measurement: Weigh out 50 parts of inert carrier, 20 parts of cooling and explosion-suppressing component, 2 parts of corrosion-resistant and salt-curing stabilizer, and 1.5 parts of functional additives according to the preset mass proportions. The inert carrier is diethyl carbonate, and its flash point is ≥60℃ to ensure no risk of combustion and explosion under thermal runaway conditions. The cooling and explosion-suppressing component has a particle size ≤10µm and is obtained by mixing an endothermic component and an inertizing component at a mass ratio of 50:40. The endothermic component is magnesium hydroxide, and the inertizing component is sodium bicarbonate. The corrosion-resistant and salt-curing stabilizer is alkylphosphonate. The functional additive is obtained by mixing a wetting agent and an defoamer at a mass ratio of 60:30. The wetting agent is sodium dodecylbenzenesulfonate, and the defoamer is a polyether defoamer. The dimethyl carbonate is dehydrated to a moisture content ≤0.1%, and the aluminum hydroxide and expanded graphite are pulverized to a particle size ≤5µm. S2. Speed-controlled mixing: Add the inert carrier to a 500L sealed mixing vessel with a stirrer, turn on the stirrer at 150 rpm, slowly add the cooling and explosion-suppressing component, and stir for 30 minutes until the cooling and explosion-suppressing component is completely dispersed; then add the anti-corrosion and anti-salt precipitation stabilizer and functional additives in sequence, and continue stirring for 20 minutes. Stop stirring after observing that there are no bubbles in the vessel to form a uniform suspension. The jacket temperature of the mixing vessel is controlled at 30℃ to avoid the inert carrier from volatilizing or the cooling and explosion-suppressing component from thermally decomposing due to excessive temperature. S3. Vacuum degassing: The vacuum degree inside the mixing vessel is ≤-0.09MPa and maintained for 20min to remove air bubbles from the suspension and avoid cavitation during atomization, which would affect the coverage. S4. Precision filtration: The degassed suspension is filtered through a 0.46μm polytetrafluoroethylene filter membrane to remove undispersed large particulate impurities and prevent nozzle clogging. The operating pressure of the filtration process is 0.15MPa to ensure filtration efficiency and filtrate clarity. S5. Sealed Filling: The filtered pre-sprayed explosion suppressant is filled into a sealed storage tank with nitrogen protection. A one-way valve is installed at the outlet of the storage tank to prevent contact with air and performance degradation. This yields a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries. The pre-sprayed explosion suppressant has a dielectric strength ≥5kV / mm, thermal conductivity ≥0.2W / (m·K), metal corrosion resistance ≤1 (GB / T 10125 standard), atomized SMD (volume average particle size) of 50-150μm, and a coverage of ≥95% for lithium battery electrodes. S6. The finished product testing steps are as follows: Sampling and testing of the dielectric strength, thermal conductivity, corrosivity, atomized SMD and coverage of the pre-sprayed explosion suppressant after filling. It can be put into use only after passing the test; if the test fails, return to step S2 to readjust the component ratio or mixing parameters.

[0022] Example 3: A method for preparing a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries, comprising the following steps: S1. Raw material measurement: Weigh out 60 parts of inert carrier, 30 parts of cooling and explosion-suppressing component, 4 parts of corrosion-resistant and salt-curing stabilizer, and 2 parts of functional additives according to the preset mass proportions. The inert carrier is triethyl phosphate, and its flash point is ≥60℃ to ensure no risk of combustion and explosion under thermal runaway conditions. The cooling and explosion-suppressing component has a particle size ≤10µm and is obtained by mixing an endothermic component and an inertizing component at a mass ratio of 60:50. The endothermic component is zinc borate, and the inertizing component is modified montmorillonite. The corrosion-resistant and salt-curing stabilizer is triethanolamine. The functional additive is obtained by mixing a wetting agent and an defoamer at a mass ratio of 70:40. The wetting agent is polyether-modified siloxane, and the defoamer is an organic defoamer. The dimethyl carbonate is dehydrated to a moisture content ≤0.1%, and the aluminum hydroxide and expanded graphite are pulverized to a particle size ≤5µm. S2. Controlled-speed mixing: Add the inert carrier to a 500L sealed mixing vessel with a stirrer, turn on the stirrer at 200rpm, slowly add the cooling and explosion-suppressing component, and stir for 40min until the cooling and explosion-suppressing component is completely dispersed; then add the anti-corrosion and anti-salt precipitation stabilizer and functional additives in sequence, and continue stirring for 25min. Stop stirring after observing that there are no bubbles in the vessel to form a uniform suspension. The jacket temperature of the mixing vessel is controlled at 35℃ to avoid the inert carrier from volatilizing or the cooling and explosion-suppressing component from thermally decomposing due to excessive temperature. S3. Vacuum degassing: The vacuum degree inside the mixing vessel is ≤-0.09MPa and maintained for 25min to remove air bubbles from the suspension and avoid cavitation during atomization, which would affect the coverage. S4. Precision filtration: The degassed suspension is filtered through a 0.81μm polytetrafluoroethylene filter membrane to remove undispersed large particulate impurities and prevent nozzle clogging. The operating pressure of the filtration process is 0.2MPa to ensure filtration efficiency and filtrate clarity. S5. Sealed Filling: The filtered pre-sprayed explosion suppressant is filled into a sealed storage tank with nitrogen protection. A one-way valve is installed at the outlet of the storage tank to prevent contact with air and performance degradation. This yields a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries. The pre-sprayed explosion suppressant has a dielectric strength ≥5kV / mm, thermal conductivity ≥0.2W / (m·K), metal corrosion resistance ≤1 (GB / T 10125 standard), atomized SMD (volume average particle size) of 50-150μm, and a coverage of ≥95% for lithium battery electrodes. S6. The finished product testing steps are as follows: Sampling and testing of the dielectric strength, thermal conductivity, corrosivity, atomized SMD and coverage of the pre-sprayed explosion suppressant after filling. It can be put into use only after passing the test; if the test fails, return to step S2 to readjust the component ratio or mixing parameters.

[0023] Example 4: A method for preparing a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries, comprising the following steps: S1. Raw material measurement: Weigh out 90 parts of inert carrier, 40 parts of cooling and explosion-suppressing component, 5 parts of corrosion-resistant and salt-curing-resistant stabilizer, and 3 parts of functional additives according to the preset mass proportions. The inert carrier is dipropylene glycol dimethyl ether, and its flash point is ≥60℃ to ensure no risk of combustion and explosion under thermal runaway conditions. The cooling and explosion-suppressing component has a particle size ≤10µm and is obtained by mixing an endothermic component and an inertizing component at a mass ratio of 70:60. The endothermic component is aluminum hydroxide, and the inertizing component is expanded graphite. The corrosion-resistant and salt-curing-resistant stabilizer is benzotriazole. The functional additive is obtained by mixing a wetting agent and an defoamer at a mass ratio of 80:50. The wetting agent is sodium dodecylbenzenesulfonate, and the defoamer is a polyether defoamer. The dimethyl carbonate is dehydrated to a moisture content ≤0.1%, and the aluminum hydroxide and expanded graphite are pulverized to a particle size ≤5µm. S2. Controlled-speed mixing: Add the inert carrier to a 500L sealed mixing vessel with a stirrer, turn on the stirrer at 300 rpm, slowly add the cooling and explosion-suppressing components, and stir for 60 minutes until the cooling and explosion-suppressing components are completely dispersed; then add the anti-corrosion and anti-salt precipitation stabilizer and functional additives in sequence, and continue stirring for 30 minutes. Stop stirring after observing that there are no bubbles in the vessel to form a uniform suspension. The jacket temperature of the mixing vessel is controlled at 40℃ to avoid the inert carrier from volatilizing or the cooling and explosion-suppressing components from thermally decomposing due to excessive temperature. S3. Vacuum degassing: The vacuum degree inside the mixing vessel is ≤-0.09MPa and maintained for 30min to remove air bubbles from the suspension and avoid cavitation during atomization, which would affect the coverage. S4. Precision filtration: The degassed suspension is filtered through a 1μm polytetrafluoroethylene filter membrane to remove undispersed large particulate impurities and prevent nozzle clogging. The operating pressure of the filtration process is 0.3MPa to ensure filtration efficiency and filtrate clarity. S5. Sealed Filling: The filtered pre-sprayed explosion suppressant is filled into a sealed storage tank with nitrogen protection. A one-way valve is installed at the outlet of the storage tank to prevent contact with air and performance degradation. This yields a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries. The pre-sprayed explosion suppressant has a dielectric strength ≥5kV / mm, thermal conductivity ≥0.2W / (m·K), metal corrosion resistance ≤1 (GB / T 10125 standard), atomized SMD (volume average particle size) of 50-150μm, and a coverage of ≥95% for lithium battery electrodes. S6. The finished product testing steps are as follows: Sampling and testing of the dielectric strength, thermal conductivity, corrosivity, atomized SMD and coverage of the pre-sprayed explosion suppressant after filling. It can be put into use only after passing the test; if the test fails, return to step S2 to readjust the component ratio or mixing parameters.

[0024] An application of a pre-sprayed anti-knock agent for the thermal runaway stage of lithium batteries involves connecting the pre-sprayed anti-knock agent to a three-stage spraying device in a CTRR system, spraying it as needed at different stages of lithium battery thermal runaway: TR pre-detonation suppression stage: The injection rate is 0.3-0.5L / 100Ah, forming a pre-inert atmosphere to suppress the initial free radicals of thermal runaway; TR plateau phase surface spraying stage: spray volume is 0.6-1.0L / 100Ah, continuously covering the electrode surface, and controlling the plateau temperature ≤500℃; TR decay period spot spray stage: The injection volume is 0.2-0.4L / 100Ah, tracking residual hot spots to prevent secondary reignition.

[0025] The gaseous products generated after the pre-sprayed explosion suppressant are recovered through the NitroLoop inert closed-loop purification system, while the liquid products enter the subsequent charged crushing and leaching process along with the lithium battery electrode sheets, without affecting the recovery efficiency of metals such as lithium, nickel, and cobalt.

[0026] Comparative Example 1: The difference between this comparative example and Example 1 is that the cooling and explosion suppression component retains only the endothermic component and removes the inerting component. The remaining steps and parameters are the same, and will not be repeated in this comparative example. Finally, a pre-sprayed explosion suppression agent for use in the thermal runaway stage of lithium batteries is obtained.

[0027] Comparative Example 2: Compared with Example 1, this comparative example removes the anti-corrosion and anti-salt precipitation stabilizer, while the remaining steps and parameters are the same. This comparative example will not be repeated here. Finally, a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries is obtained.

[0028] Comparative Example 3: Compared with Example 1, this comparative example only replaces the inert carrier with a low flash point solvent (acetone with a flash point of -18°C). All other steps and parameters are the same, and will not be repeated here. The final product is a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries.

[0029] Comparative Example 4: Compared with Example 1, this comparative example omits the "vacuum degassing" and "precision filtration" steps, while the remaining steps and parameters are the same. This comparative example will not repeat the details, and finally obtains a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries.

[0030] Performance testing: The products prepared in Examples 1-4 and Comparative Examples 1-4 were subjected to the following performance tests: Dielectric strength test: Standard: GB / T 1408.1-2016; Equipment: Withstand voltage tester (model: CS2674C); Steps: Apply the explosion suppressant evenly between two 100mm×100mm stainless steel electrodes (thickness 0.1mm). In an environment of 25℃ and 50%RH, increase the voltage at a rate of 500V / s, record the breakdown voltage, and calculate the dielectric strength (breakdown voltage / coating thickness). Perform five parallel tests and take the average value.

[0031] Thermal conductivity test: Standard: GB / T 10297-2015; Equipment: Hot wire thermal conductivity meter (Model: DRL-Ⅲ) Procedure: Prepare a cylindrical sample of the explosion suppressant with a diameter of 50 mm × 10 mm. Heat the sample at 25 °C with a hot wire and record the temperature change. Calculate the thermal conductivity. Perform three parallel tests and take the average value.

[0032] Metal corrosion test: Standard: GB / T 10125-2021; Equipment: Salt spray corrosion test chamber (Model: YWX / Q-750) Procedure: Immerse carbon steel (Q235), stainless steel (304), aluminum (6061), and copper (T2) test pieces (50mm×25mm×2mm) in the explosion suppressant. After standing at 35℃ for 100 hours, observe the corrosion on the surface of the test pieces and rate them according to the standard (Grade 1: no obvious corrosion; Grade 2: slight pitting corrosion; Grade 3: obvious rust). At the same time, test the amount of salt precipitation in the explosion suppressant (gravimetric method).

[0033] Atomized SMD and electrode coverage test Atomized SMD: The volume average particle size (SMD) of the atomized particles was collected using a laser particle size analyzer (model: Mastersizer 3000) under the three-stage spray device of the CTRR system (nozzle orifice diameter 0.5mm, pressure 0.2MPa). The average value was taken from 5 parallel tests.

[0034] Electrode coverage: The explosion suppressant was sprayed onto the surface of NMC622 electrode (100mm×100mm) at the TR plateau injection rate (0.8L / 100Ah). The coverage area was calculated by observing the surface under a high-powered microscope (model: BX53, Olympus). The average value of the three parallel tests was taken.

[0035] Thermal runaway suppression effect test: Equipment: CTRR simulation test system (including temperature / pressure sensors, open flame detector, and self-made adapted retired lithium batteries) Samples: Retired NMC622 cells (capacity 20Ah, SOC 70%), 10 cells tested per group. step: Spray the explosion suppressant according to the application method of this invention (0.4L / 100Ah before TR, 0.8L / 100Ah during the plateau period, and 0.3L / 100Ah during the decay period); Trigger thermal runaway (overcharge 0.05C), record peak temperature and temperature drop (compared with the group without anti-knock agent); Observe the reignition situation within 1 hour and calculate the reignition rate; The HF and CO contents in the gaseous products were detected using a gas chromatograph (model: GC-2014, Shimadzu), and the emission reduction rate was calculated.

[0036] Nozzle clogging rate test: Equipment: CTRR system three-stage spray device (nozzle orifice diameter 0.5mm, material 304 stainless steel) Steps: Continuously spray the explosion suppressant for 100 hours (simulating continuous industrial operation). After shutdown, disassemble the nozzles, observe the blockage, and calculate the percentage of blocked nozzles (total number of nozzles: 50).

[0037] The test results are shown in Tables 1 and 2 below: Table 1 Performance test results of Examples 1-4 Table 2 Performance test results of Comparative Examples 1-4 Data Analysis: As shown in Tables 1-2, the test data of Examples 1-4 all meet the core indicators of the claims of this invention (dielectric strength ≥ 5 kV / mm, thermal conductivity ≥ 0.2 W / (m·K), coverage ≥ 95%, and reignition rate 0), and exhibit the following synergistic advantages: Stable safety performance: dielectric strength 5.7-6.2kV / mm, avoiding short circuits in lithium batteries; peak temperature drop of TR 29.8%-31.5%, completely suppressing reignition; HF / CO emission reduction rate 37.5%-42.3%, solving the problems of "poor dielectric and high risk of reignition" of traditional explosion suppressants; Excellent equipment compatibility: all metal corrosion is level 1-2, and the nozzle clogging rate is 0 after 100 hours, proving that anti-corrosion and anti-salt precipitation stabilizers (such as benzotriazole) effectively inhibit equipment corrosion and salt precipitation, and extend maintenance cycles; Reliable atomization and coverage: Atomization SMD 82-125μm, coverage 95.8%-98.5%, compatible with CTRR three-stage spray strategy, no risk of local thermal runaway; The smallest atomized SMD and highest coverage in Example 1 are due to the slight adjustment of the ratio of inert carrier and functional additives (e.g., using dimethyl carbonate + polyether modified siloxane in Example 1, which has better atomization spreadability), but none of them affect the core effect, proving the stability and adjustability of the formulation and process of the present invention, which can be flexibly adapted to different lithium battery systems (such as NMC, LFP).

[0038] In contrast, Comparative Example 1 lacked the inerting component, resulting in a significant decrease in explosion suppression and reignition prevention performance. Comparative Example 1 retained only the endothermic component (aluminum hydroxide) and lacked the inerting component (expanded graphite). Data shows that: Insufficient explosion suppression depth: The peak temperature drop of TR decreased from 31.5% (Example 1) to 18.7% because the cooling was achieved solely by aluminum hydroxide absorbing heat, and the flammable atmosphere could not be diluted by releasing inert gases (such as CO2 and H2O) through expanded graphite. The risk of reignition has increased dramatically: the reignition rate is as high as 40%, while the HF / CO emission reduction rate is only 15.6%-12.3%, proving that the "endothermic + inerting" combination is the core of suppressing the thermal runaway chain reaction - the endothermic component cools down rapidly, and the inerting component blocks the oxygen and free radicals required for combustion. Both are indispensable. The lack of anti-corrosion and anti-salt precipitation stabilizer in Comparative Example 2 led to increased equipment damage and maintenance costs; Comparative Example 2 shows the removal of benzotriazole (anti-corrosion and anti-salt precipitation stabilizer). Data shows: Equipment corrosion has worsened: the corrosion level of Q235 carbon steel has increased from level 1 to level 3, and that of 304 stainless steel has increased from level 1 to level 2. This is because trace amounts of acidic substances in the explosion suppressant (such as HF generated by thermal runaway of lithium batteries) cannot be neutralized and directly corrode the metal surface. Severe nozzle clogging: The clogging rate reached 24%, caused by the precipitation of salts (such as LiPF6 decomposition products) from the explosion suppressant on the nozzle surface, leading to blockage of the injection channel and affecting the subsequent explosion suppression effect. This proves that corrosion-resistant and salt-resistant stabilizers are key to "ensuring long-term equipment operation and reducing industrial application costs," filling the gap in traditional explosion suppressants that "emphasize safety but neglect equipment protection."

[0039] In Comparative Example 3, replacing the inert carrier with a low flash point solvent highlights dielectric safety and flammability / explosion risks. Comparative Example 3 replaced dimethyl carbonate (flash point ≥60℃) with acetone (flash point -18℃). Data showed that: Dielectric properties drop sharply: the dielectric strength drops from 6.2kV / mm to 2.3kV / mm, which is far below the 5kV / mm required for lithium battery processing, making it easy to cause cell short circuits and exacerbating thermal runaway; New risks of combustion and explosion: Combustion and explosion occurred at 300℃ (acetone has a low flash point and is easily ignited under thermal runaway conditions), and the corrosion level of 304 stainless steel increased to level 2 (acetone has a slight dissolving effect on metals). This verifies the necessity of selecting a "high flash point inert carrier" in this invention—ensuring dielectric insulation while avoiding itself becoming a source of combustion and explosion, thus solving the problem of "cumulative safety hazards" in traditional solvent-based explosion suppressants.

[0040] The simplified preparation process in Comparative Example 4 resulted in deterioration of atomization and coverage performance. Comparative Example 4 omits "vacuum degassing" and "precision filtration," and the data shows: Uneven atomization particles: The atomization SMD increased from 82μm to 185μm. Due to incomplete degassing, cavitation was generated during atomization. The lack of filtration led to large particles of impurities (undispersed aluminum hydroxide) clogging the local channels of the nozzle, which destroyed the uniformity of atomization. Decreased coverage and explosion suppression effect: Electrode coverage decreased from 98.5% to 82.3%, reignition rate increased to 5%, and HF / CO emission reduction rate decreased by 3-5 percentage points, as some uncovered areas became "hot spots" for thermal runaway. This proves that the "controlled-speed mixing-vacuum degassing-precision filtration" process of this invention is an organic whole: controlled-speed mixing ensures component dispersion, vacuum degassing eliminates atomization cavitation, and precision filtration removes impurities. The three work together to ensure the continuous effectiveness of "atomization-coverage-explosion suppression".

[0041] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0042] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A pre-sprayed explosion suppressant for use during the thermal runaway stage of lithium batteries, characterized in that, Includes the following quantities of raw materials: 40-90 parts of inert carrier, 5-40 parts of cooling and explosion-suppressing component, 0.1-5 parts of corrosion-resistant and salt-curing-resistant stabilizer, and 1-3 parts of functional additives; The pre-sprayed explosion suppressant has a dielectric strength ≥5kV / mm, thermal conductivity ≥0.2W / (m·K), metal corrosion resistance ≤1, a volume average particle size of 50-150µm, and a coverage of ≥95% on the lithium battery electrode.

2. The pre-sprayed explosion suppressant for the thermal runaway stage of lithium batteries according to claim 1, characterized in that, The inert support is a high flash point inert solvent, which is any one or more of dimethyl carbonate, diethyl carbonate, triethyl phosphate, and dipropylene glycol dimethyl ether; the flash point of the inert support is ≥60℃.

3. The pre-sprayed explosion suppressant for the thermal runaway stage of lithium batteries according to claim 1, characterized in that, The cooling and explosion-suppressing component is a compound system of endothermic and inert components; the endothermic component is any one or more of aluminum hydroxide, magnesium hydroxide, and zinc borate, and the mass ratio of the endothermic component is 40%-70% of the cooling and explosion-suppressing component; the inert component is any one or more of expanded graphite, sodium bicarbonate, and modified montmorillonite, and the mass ratio of the inert component is 30%-60% of the cooling and explosion-suppressing component; the particle size of the cooling and explosion-suppressing component is ≤10μm.

4. The pre-sprayed explosion suppressant for the thermal runaway stage of lithium batteries according to claim 1, characterized in that, The corrosion-resistant and salt-curing-resistant stabilizer is any one or more of benzotriazole, alkyl phosphate, and triethanolamine.

5. The pre-sprayed explosion suppressant for the thermal runaway stage of lithium batteries according to claim 1, characterized in that, The functional additives are wetting agents and defoamers; the wetting agent is either polyether-modified siloxane or sodium dodecylbenzenesulfonate, and the mass percentage of the wetting agent is 50%-80% of the functional additives; the defoamer is either silicone defoamer or polyether defoamer, and the mass percentage of the defoamer is 20%-50% of the functional additives.

6. A method for preparing a pre-sprayed explosion suppressant for the thermal runaway stage of a lithium battery according to any one of claims 1-5, characterized in that, Includes the following steps: Step S1. Raw material measurement: Weigh out the inert carrier, cooling and explosion suppression components, anti-corrosion and anti-salt precipitation stabilizer and functional additives according to the preset mass parts; Step S2. Speed-controlled mixing: Add the inert carrier to a sealed mixing vessel with a stirrer, turn on the stirrer, and stir at a speed of 100-300 rpm. Add the cooling and explosion-suppressing components and stir for 20-60 min until the cooling and explosion-suppressing components are completely dispersed. Then add the anti-corrosion and anti-salt precipitation stabilizer and functional additives in sequence, and continue stirring for 15-30 min to form a uniform suspension. Step S3. Vacuum degassing: Evacuate the mixing vessel to a vacuum level of ≤-0.09 MPa and maintain for 15-30 min to remove air bubbles from the suspension; Step S4. Precision filtration: The degassed suspension is filtered through a 0.22-1μm precision filter membrane to remove undispersed large particulate impurities; Step S5. Sealed filling: The filtered suspension is filled into a sealed storage tank with inert gas protection. A one-way valve is installed at the outlet of the storage tank to obtain a pre-sprayed explosion suppressant for use in the thermal runaway stage of lithium batteries.

7. The method for preparing a pre-sprayed anti-explosion agent for the thermal runaway stage of a lithium battery according to claim 6, characterized in that, The jacket temperature of the sealed mixing vessel in step S2 is controlled at 25-40℃; the operating pressure of the filtration process in step S4 is 0.1-0.3 MPa.

8. The method for preparing a pre-sprayed anti-explosion agent for the thermal runaway stage of a lithium battery according to claim 6, characterized in that, The preparation method further includes a finished product testing step, which is as follows: After filling, the pre-sprayed explosion suppressant is sampled and tested for dielectric strength, thermal conductivity, corrosivity, atomized SMD, and coverage. It can only be put into use after passing the test; if the test fails, return to step S2 to readjust the component ratio and mixing parameters.

9. The method for preparing a pre-sprayed anti-explosion agent for the thermal runaway stage of a lithium battery according to any one of claims 6, characterized in that, The pre-sprayed explosion suppressant has the following applications: The pre-sprayed anti-knock agent is connected to the three-stage spraying device of the CTRR system, and sprayed as needed at different stages of lithium battery thermal runaway: TR pre-detonation suppression stage: injection rate is 0.3–0.5 L / 100 Ah; TR plateau phase surface spraying stage: spraying volume is 0.6–1.0 L / 100 Ah, continuously covering the electrode surface, and controlling the plateau temperature ≤500℃; TR decay period, point spray stage: spray volume is 0.2–0.4 L / 100 Ah.

10. The method for preparing a pre-sprayed explosion suppressant for the thermal runaway stage of a lithium battery according to claim 9, characterized in that, The gaseous products generated after the pre-sprayed explosion suppressant is recovered through the NitroLoop inert closed-loop purification system, while the liquid products are carried along with the lithium battery electrodes into the subsequent charged crushing and leaching processes.

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