A fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent and its preparation method

Abstract

This invention relates to the field of fire extinguishing agent technology, specifically to a fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression extinguishing agent and its preparation method. The extinguishing agent uses deionized water as the base cooling medium, compounded with inorganic flame-retardant and cooling components such as magnesium carbonate and sodium bicarbonate, and combined with propylene glycol antifreeze and penetration aids. A suspension thickening system is constructed using fumed silica and xanthan gum, and a highly stable, salt-resistant foam system is formed by combining a fluorine-free foaming agent, a foam stabilizing agent, and a salt-resistant co-solvent. This invention employs a process of stepwise feeding at room temperature, gradient speed stirring, and static aging, maintaining ambient temperature and pressure throughout. It features rapid heat absorption and cooling, interruption of the lithium battery thermal runaway chain reaction, dense foam oxygen and heat insulation, and long-lasting anti-reignition properties. It contains no perfluorinated harmful substances, exhibits ultra-low metal corrosion, excellent low-temperature performance, low biotoxicity, and good storage stability, making it suitable for lithium battery protection in various scenarios such as new energy vehicles and electrochemical energy storage.

Description

Technical Field

[0001] This invention relates to the field of fire extinguishing agent technology, specifically to a fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression extinguishing agent and its preparation method. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, long cycle life, and low self-discharge rate, have been widely adopted in new energy vehicles, large-scale electrochemical energy storage, and portable electronic devices. However, under conditions such as overcharging, over-discharging, external short circuits, mechanical compression, and high-temperature thermal stimulation, lithium-ion batteries are highly susceptible to triggering thermal runaway chain reactions. They exhibit significant characteristics such as high combustion temperature, rapid heat release rate, strong concealment of internal smoldering, extremely high probability of reignition, large emissions of toxic fumes, and poor extinguishing effects of conventional fire extinguishing agents. These issues have become a key hidden danger restricting the safe development of the lithium battery industry.

[0003] In response to the need for lithium battery fire prevention and control, the industry has conducted numerous technological studies. Chinese invention patent application CN120789564A discloses a compound lithium-ion battery fire extinguishing agent and its preparation method. This fire extinguishing agent uses vermiculite, fire extinguishing filler, and modified zeolite as core functional components, compounded with stabilizers, dispersants, thickeners, foaming agents, and water. The fire extinguishing filler is prepared by intercalating graphene oxide with montmorillonite, modifying its surface with dopamine, and then mixing it with amphoteric starch, saponins, and potassium perfluorobutyl sulfonate. The modified zeolite is obtained by activating zeolite with hydrochloric acid to load iron ions, followed by encapsulation with organosilicon gel. This solution relies on the solid-phase barrier layer formed by vermiculite, montmorillonite, and zeolite to isolate oxygen and adsorb combustion free radicals, while the high-temperature charring structure of starch and polydopamine enhances the anti-reignition performance.

[0004] However, the above-mentioned technical solutions still have several technical defects: First, the formulation contains potassium perfluorobutyl sulfonate, a type of perfluorinated organic compound. These substances are highly persistent in the environment, have high bioaccumulation toxicity, and are difficult to degrade naturally, which does not comply with current global environmental regulations restricting perfluorinated compounds and the trend of green fire protection development. Second, the system contains a large amount of vermiculite, zeolite, and clay-based solid powder fillers, which are solid-liquid multiphase suspension systems. During long-term storage, powder sedimentation, agglomeration, and stratification are prone to occur, which not only causes the performance of the extinguishing agent to deteriorate but also easily clogs the nozzles and pipelines of fire extinguishing equipment. Firstly, it is difficult to adapt to fixed fire protection systems and long-term pressurized applications. Secondly, the preparation process is complex, requiring multiple chemical reactions, ultrasonic treatment, and high-temperature drying processes for both the fire extinguishing filler and modified zeolite. This results in a long production cycle, high energy consumption, and high raw material costs, which is not conducive to large-scale industrial promotion. Finally, the fire extinguishing mechanism is mainly based on solid-phase physical barrier, while the deep heat absorption and cooling capacity of the liquid phase is limited, making it difficult to quickly terminate the thermal runaway chain reaction inside the battery cell. Furthermore, the foam system lacks high salt and high temperature stability, and the foam is prone to rapid foam rupture and failure in high-temperature fire environments, resulting in poor long-term oxygen barrier protection.

[0005] In addition, existing conventional fire extinguishing agents still have significant shortcomings: traditional water-based fire extinguishing agents rely solely on water vaporization to absorb heat for cooling, failing to form a stable protective layer on the battery surface, exhibiting weak oxygen barrier capabilities, and are highly susceptible to secondary reignition after extinguishing the fire; traditional fluoroprotein and aqueous film-forming foam fire extinguishing agents generally contain perfluorinated compounds such as PFOS, PFOA, and PFAS, which are difficult to degrade and highly biotoxic, and have been strictly restricted and phased out by domestic and international environmental regulations; ordinary zwitterionic foam systems have poor resistance to inorganic salts, and are prone to foam breakage, stratification, and failure in high-ion concentration fire extinguishing systems, with short foam half-lives and insufficient high-temperature survival capabilities; dry powder fire extinguishing agents have extremely poor cooling capabilities, only able to suppress surface flames, unable to terminate the thermal runaway reaction inside the battery cell, resulting in severe dust pollution and significant corrosion damage to equipment after a disaster. Most existing lithium battery-specific fire extinguishing agents also generally suffer from high corrosion rates, poor low-temperature performance, insufficient system storage stability, poor foam adhesion, and high raw material costs, making it difficult to meet the needs of large-scale, all-weather, and all-scenario safety applications.

[0006] Therefore, developing a fluorine-free, environmentally friendly, low-corrosion, high-salt resistant, foam-stable, foam-type lithium battery-specific fire extinguishing agent with strong cooling and long-lasting oxygen barrier capabilities, low-temperature antifreeze, and long storage period is a core technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression extinguishing agent and its preparation method, in order to solve the problems mentioned in the background art, such as high re-ignition rate, fluorine content and lack of environmental friendliness, and poor foam salt resistance of existing lithium battery extinguishing agents.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent, comprising the following components by mass percentage: magnesium carbonate 1.0%–2.0%, sodium bicarbonate 0.5%–1.0%, sodium acetate 0.2%–1.0%, sodium chloride 0.2%–1.0%, propylene glycol 0.2%–0.5%, fumed silica 0.1%–0.2%, xanthan gum 0.1%–0.2%, sodium formate 0.01%–0.02%, fluorine-free foaming agent 0.8%–1.2%, foam stabilizing agent 0.05%–0.10%, salt-resistant co-solvent 0.2%–0.3%, with the balance being deionized water; the total mass percentage of all components is 100%.

[0009] Preferably, the fluorine-free foaming agent is cocamidopropyl betaine, the foam stabilizing agent is dodecyl alcohol, and the salt-resistant cosolvent is ethylene glycol butyl ether.

[0010] As a preferred embodiment, the specific proportions of each component by mass percentage are as follows: magnesium carbonate 1.50%, sodium bicarbonate 0.80%, sodium acetate 0.60%, sodium chloride 0.50%, propylene glycol 0.40%, fumed silica 0.15%, xanthan gum 0.13%, sodium formate 0.02%, cocamidopropyl betaine 1.00%, dodecanol 0.08%, ethylene glycol butyl ether 0.22%, with the balance being deionized water; the total mass percentage of each component is 100%.

[0011] Preferably, at 25°C, the extinguishing agent has a viscosity of 35–50 mPa·s, an electrical conductivity of 600–700 μS / cm, and a pH value of 8.0–8.5; a freezing point not higher than -5°C; a corrosion rate to Q235A steel not higher than 1.5 mg / (d·dm²), and a corrosion rate to 3A21 aluminum not higher than 0.8 mg / (d·dm²); a foaming ratio not less than 8 times, and a foam half-life not less than 15 min.

[0012] Preferably, the extinguishing agent is free of perfluorinated organic compounds such as PFOS, PFOA, and PFAS, contains no ozone-depleting substances, has a mortality rate of 0 in acute toxicity tests on fish, and is biodegradable.

[0013] On the other hand, the present invention also provides a method for preparing the above-mentioned fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent, comprising the following steps: S1. Preparation of base solution: Under normal temperature conditions of 20-35℃, add the measured amount of deionized water into a closed dispersion reaction vessel, turn on the stirrer and control the speed to 300-500 r / min to obtain a uniform base aqueous solution. S2. Preparation of suspension thickening substrate: Add fumed silica and xanthan gum to the base aqueous solution and stir continuously for 20-30 minutes until the powder is completely swollen and there is no agglomeration or clumping, to obtain a stable suspension substrate liquid. S3. Dissolution of inorganic functional components: Add magnesium carbonate, sodium bicarbonate, sodium acetate, sodium chloride, and sodium formate sequentially to the suspension base liquid. Increase the stirring speed to 600-800 r / min and stir for 25-35 min to completely disperse and dissolve the inorganic salt components. S4. Addition of antifreeze and wetting agent: Add propylene glycol to the system, maintain the system temperature at 20-35℃ and stir for 10-15 minutes to obtain a mixed base liquid; S5. Blending of fluorine-free foam system: Add fluorine-free foaming agent, foam stabilizer and salt-resistant co-solvent to the mixed base liquid in sequence, adjust the stirring speed to 800-1000 r / min, stir for 40-60 min, so that the foaming system is completely compatible with the high-salt inorganic system. S6. Low-speed maturation and static aging: Reduce the stirring speed to 200-300 r / min and stir for 60-80 min to complete the defoaming and homogenization treatment; then let it stand and age for 10-15 days under room temperature and sealed conditions to stabilize the rheological properties and foaming properties of the system. S7. Filtration, quality inspection and packaging: Impurities in the system are removed by filtration using a 100-200 mesh filter. After passing performance testing, the system is sealed and packaged to obtain the finished fire extinguishing agent.

[0014] Preferably, step S2 specifically includes: S21. While maintaining a stirring speed of 300-500 r / min, slowly sprinkle the fumed silica into the base aqueous solution in 2-3 batches, with an interval of 5-8 min between each batch. After all the materials have been added, continue stirring for 10-15 min. S22. While maintaining the stirring speed, slowly add xanthan gum to the system. After the addition is complete, continue stirring for 10 to 15 minutes until there are no visible agglomerated particles in the system, forming a uniform suspension thickening base liquid.

[0015] Preferably, step S5 specifically includes: S51. Keep the system temperature at 20-35℃, add the fluorine-free foaming agent first, and stir at 800-1000r / min for 15-20min until completely dissolved; S52. Reduce the rotation speed to 600-700 r / min, add the foam stabilizer, and stir for 10-15 min until evenly dispersed; S53. Restore the rotation speed to 800-1000 r / min, add salt-resistant co-solvent, and continue stirring for 15-25 min until the system shows no stratification, no oil separation, and no defoaming.

[0016] Preferably, in step S6, the static aging process is carried out in a dark, cool, and closed environment with a temperature fluctuation range not exceeding ±3℃; the reaction vessel must not be opened or the system must not be stirred or disturbed during the aging process; after the aging is completed, the uniformity of the system is tested, and the next process can only proceed after confirming that there is no sediment, no stratification, and no floating oil.

[0017] As a preferred option, in step S7, the performance testing items should include at least pH value, metal corrosion rate, freezing point, electrical conductivity, foaming ratio, perfluorinated substance content, and acute biological toxicity. Only after all indicators pass the test can the product be sealed and packaged. The packaging containers should be corrosion-resistant sealed plastic drums or metal storage tanks, and the temperature of the finished product storage environment should be controlled between 5 and 35°C.

[0018] Compared with the prior art, the beneficial effects of the present invention are: First, this invention constructs a multi-mechanism synergistic thermal runaway prevention system with outstanding anti-reignition performance. This invention integrates inorganic flame-retardant cooling components with a fluorine-free foam system. On one hand, it relies on the high specific heat capacity of the water-based medium to rapidly absorb the heat from thermal runaway, combined with the endothermic decomposition of magnesium carbonate and sodium bicarbonate and the release of inert gases, to achieve deep cooling of the battery cell. On the other hand, it achieves surface oxygen and heat insulation through a continuous foam layer, while sodium acetate and sodium formate can capture combustion free radicals, inhibiting electrolyte decomposition and chain combustion reactions. The synergistic effect of these multiple mechanisms can terminate the thermal runaway process of lithium batteries at its source, effectively solving the technical problems of incomplete thermal runaway prevention and high reignition rates with single cooling or single oxygen isolation solutions, resulting in a significant long-term anti-reignition effect.

[0019] Secondly, this invention achieves a balance between complete fluorine-free environmental protection and low corrosion. The formula of this invention does not contain PFOS, PFOA, PFAS, or potassium perfluorobutyl sulfonate, which are perfluorinated controlled substances. The foaming agent uses a biodegradable amphoteric surfactant with low biotoxicity and no risk of environmental accumulation, complying with current environmental regulations and the development requirements of green fire protection. Simultaneously, through optimized component compounding and control of the weakly alkaline system, the corrosion rate of the extinguishing agent on commonly used metal materials such as Q235A steel and 3A21 aluminum is far below the national standard limit. After extinguishing the fire, the corrosion damage to battery modules, fire-fighting equipment, and supporting facilities is minimal, resulting in a high residual value retention rate for the equipment.

[0020] Third, the system of this invention exhibits excellent salt resistance and adaptability to various operating conditions. This invention regulates the rheological properties of the system by combining fumed silica and xanthan gum, and enhances the compatibility of the surfactant in high-ionic-strength environments by using a salt-resistant co-solvent, overcoming the technical bottleneck of conventional amphoteric foam systems that are prone to foam breakage, stratification, and failure under high-salt conditions. The resulting foam liquid film has high strength, long half-life, and good wall adhesion, forming a long-lasting protective layer on the surface of complex battery structures. Propylene glycol and sodium chloride synergistically regulate the freezing point, broadening the product's low-temperature application range. The system is a homogeneous liquid, exhibiting no precipitation or stratification during long-term storage, making it suitable for various fire extinguishing equipment and application scenarios, avoiding the application defects of solid-phase filler-type fire extinguishing agents that are prone to sedimentation and clogging of pipelines and nozzles.

[0021] Fourth, the preparation process of this invention is simple and controllable, with strong industrial feasibility. The entire preparation process is carried out under normal temperature and pressure conditions, employing a step-by-step feeding, gradient speed stirring, and static aging process. The system construction can be completed solely through physical dispersion and dissolution, without the need for complex raw material modification, high-temperature reactions, or ultrasonic treatment. All raw materials used are readily available industrial products, with stable sources and controllable costs. The process is short, energy-efficient, and has good batch repeatability, making it easy to achieve large-scale industrial production and possessing significant industrial application value. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are explained in detail together with the embodiments of the invention, but do not constitute a limitation thereof.

[0023] Figure 1 This is a schematic diagram of the preparation process of the fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent of the present invention. Figure 2 This is a flowchart illustrating the preparation of the base liquid and the suspension thickening substrate of this invention. Figure 3 This is a schematic diagram of the process for dissolving inorganic functional components and compounding foam systems according to the present invention; Figure 4 This is a schematic diagram of the low-speed ripening, static aging and post-processing process of the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] like Figures 1-4 As shown, the present invention relates to a fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent. It uses deionized water as the base cooling medium, and combines multiple inorganic flame-retardant and cooling components to construct an endothermic flame-suppressing system. A suspension thickening framework is constructed using fumed silica and xanthan gum, and propylene glycol is added to optimize low-temperature and penetration performance. Finally, a highly stable foam system is formed by combining a fluorine-free amphoteric foaming agent, foam stabilizer, and salt-resistant co-solvent. The components work synergistically to simultaneously achieve deep cooling, dense oxygen barrier, block thermal runaway propagation, and long-term prevention of reignition.

[0026] The extinguishing agent, by mass percentage, comprises: 1.0% to 2.0% magnesium carbonate, 0.5% to 1.0% sodium bicarbonate, 0.2% to 1.0% sodium acetate, 0.2% to 1.0% sodium chloride, 0.2% to 0.5% propylene glycol, 0.1% to 0.2% fumed silica, 0.1% to 0.2% xanthan gum, 0.01% to 0.02% sodium formate, 0.8% to 1.2% fluorine-free foaming agent, 0.05% to 0.10% foam stabilizer, 0.2% to 0.3% salt-resistant co-solvent, with the balance being deionized water. The total mass percentage of all components is 100%.

[0027] Furthermore, cocamidopropyl betaine is selected as the fluorine-free blowing agent, dodecanol as the foam stabilizer, and ethylene glycol butyl ether as the salt-resistant solubilizer. Cocamidopropyl betaine is an amphoteric surfactant with strong high-salt resistance, excellent foaming performance, and is biodegradable with no environmental cumulative toxicity. Dodecanol can accumulate on the surface of the foam liquid film, improving the elasticity and mechanical strength of the liquid film and extending the high-temperature retention time of the foam. Ethylene glycol butyl ether can adjust the surface tension of the system, improve the compatibility of the surfactant in high-concentration inorganic salt systems, and avoid problems such as foam breakage, oil separation, and stratification failure.

[0028] The preparation method of the fire extinguishing agent is carried out under normal temperature and pressure conditions, and the specific steps are as follows: S1 base solution preparation. Under an ambient temperature of 20℃ to 35℃, the metered deionized water is added to a closed dispersion reactor, the stirring device is turned on, and the stirring speed is controlled at 300r / min to 500r / min to form a homogeneous base aqueous solution.

[0029] Preparation of S2 suspension thickening substrate. Fumed silica and xanthan gum were added to a base aqueous solution and stirred continuously for 20 to 30 minutes until the powder was completely swollen and free of agglomeration, thus obtaining a stable suspension substrate liquid.

[0030] S3 Inorganic functional components are dissolved. Magnesium carbonate, sodium bicarbonate, sodium acetate, sodium chloride, and sodium formate are added sequentially to the suspension base solution. The stirring speed is increased to 600 r / min to 800 r / min, and the mixture is stirred for 25 min to 35 min to ensure that the inorganic salt components are completely dispersed and dissolved.

[0031] S4 antifreeze wetting agent addition. Propylene glycol was added to the system and stirred at a constant temperature for 10 to 15 minutes to improve the system's penetration wetting ability and low-temperature antifreeze performance, resulting in a mixed base liquid.

[0032] S5 fluorine-free foam system compounding. Add fluorine-free foaming agent, foam stabilizing agent and salt-resistant co-solvent to the mixed base liquid in sequence, adjust the stirring speed to 800 r / min to 1000 r / min, stir for 40 min to 60 min to make the foaming system completely compatible with the high-salt inorganic system.

[0033] S6 low-speed maturation and static aging. Reduce the stirring speed to 200 r / min to 300 r / min and stir for 60 min to 80 min to complete the defoaming and homogenization process. Then, let it stand and age for 10 to 15 days under room temperature and sealed conditions to allow the rheological and foaming properties of the system to fully stabilize.

[0034] S7 Filtration Quality Inspection and Packaging. Impurities in the system are removed by filtration using 100-200 mesh filters. After passing performance testing, the system is sealed and packaged to obtain the finished fire extinguishing agent. Example 1

[0035] This embodiment represents the optimal formulation. By mass percentage, the components are: magnesium carbonate 1.50%, sodium bicarbonate 0.80%, sodium acetate 0.60%, sodium chloride 0.50%, propylene glycol 0.40%, fumed silica 0.15%, xanthan gum 0.13%, sodium formate 0.02%, cocamidopropyl betaine 1.00%, dodecanol 0.08%, ethylene glycol butyl ether 0.22%, with the balance being deionized water. The total mass percentage of all components is 100%.

[0036] The preparation process in this embodiment is as follows: Preparation of S1 base solution. The ambient temperature was controlled at 25℃. Metered deionized water was added to a closed dispersion reactor, and stirring was started at 400 r / min for 5 minutes to obtain a homogeneous base aqueous solution.

[0037] Preparation of S2 suspension thickening substrate. While maintaining a constant stirring speed, fumed silica was slowly added to the base aqueous solution in two batches, with a 6-minute interval between each batch. After all the materials were added, stirring continued for 12 minutes. Xanthan gum was then slowly added, and stirring continued for 12 minutes after the addition was complete, until no visible agglomerates were observed in the system, forming a homogeneous suspension substrate.

[0038] Dissolve the S3 inorganic functional component. Add magnesium carbonate, sodium bicarbonate, sodium acetate, sodium chloride, and sodium formate sequentially. Increase the stirring speed to 700 r / min and stir for 30 min until the inorganic salt component is completely dispersed and dissolved, and the system is homogeneous and free of precipitate.

[0039] S4 antifreeze and wetting agent was added. Propylene glycol was added to the system, and the mixture was stirred at a constant temperature of 25°C for 12 minutes to obtain a mixed base solution.

[0040] S5 fluorine-free foam system formulation. First, add cocamidopropyl betaine and stir at 900 rpm for 18 minutes until completely dissolved. Reduce the stirring speed to 650 rpm, add dodecanol, and stir for 12 minutes until uniformly dispersed. Restore the stirring speed to 900 rpm, add ethylene glycol butyl ether, and continue stirring for 20 minutes until the system shows no stratification, no oil separation, and no defoaming.

[0041] S6 Low-speed maturation and static aging. Reduce the stirring speed to 250 r / min and stir for 70 min for degassing and homogenization. After completion, seal the reactor and let it stand for 12 days in a dark, cool environment with temperature fluctuations not exceeding ±3℃. During the aging period, do not open the reactor or disturb the system.

[0042] S7 Filter Quality Inspection and Packaging. Using a 150-mesh filter system, after all performance indicators have passed testing, the filters are sealed and packaged into corrosion-resistant plastic drums and stored in an environment between 5℃ and 35℃.

[0043] The performance test results of the finished product in this embodiment are as follows: viscosity at 25℃ is 42 mPa·s, conductivity is 665 μS / cm, pH value is 8.3, freezing point is -5℃, and corrosion rate on Q235A steel is 1.3 mg·d⁻¹. -1 ·dm -2 The corrosion rate of 3A21 aluminum is 0.6 mg·d⁻¹. -1 ·dm -2 The foaming ratio is 9.2 times, the foam half-life is 18 minutes, no perfluorinated substances were detected, and the mortality rate in acute toxicity tests on fish was 0. Verified by lithium battery thermal runaway fire extinguishing tests, the open flame was extinguished within 30 seconds after spraying, the cell temperature rapidly dropped below 100℃, and there was no reignition after 24 hours of standing. Example 2

[0044] This embodiment uses a lower proportion of components. By mass percentage, the amounts of each component are: magnesium carbonate 1.0%, sodium bicarbonate 0.5%, sodium acetate 0.2%, sodium chloride 0.2%, propylene glycol 0.2%, fumed silica 0.1%, xanthan gum 0.1%, sodium formate 0.01%, cocamidopropyl betaine 0.8%, dodecanol 0.05%, ethylene glycol butyl ether 0.2%, with the balance being deionized water. The total mass percentage of all components is 100%.

[0045] The preparation process in this embodiment is as follows: Preparation of S1 base solution. The ambient temperature was controlled at 20℃. Metered deionized water was added to a closed dispersion reactor, and stirring was started at 300 r / min for 8 minutes to obtain a homogeneous base aqueous solution.

[0046] Preparation of S2 suspension thickening substrate. While maintaining a constant stirring speed, fumed silica was slowly added to the base aqueous solution in two batches, with a 5-minute interval between each batch. After all the materials were added, stirring continued for 10 minutes. Xanthan gum was then slowly added, and stirring continued for 10 minutes after the addition was complete, until no visible agglomerates were observed in the system, forming a homogeneous suspension substrate.

[0047] Dissolve the S3 inorganic functional component. Add magnesium carbonate, sodium bicarbonate, sodium acetate, sodium chloride, and sodium formate in sequence, increase the stirring speed to 600 r / min, and stir for 25 min until the inorganic salt component is completely dispersed and dissolved.

[0048] S4 antifreeze and wetting agent was added. Propylene glycol was added to the system, and the mixture was stirred at a constant temperature of 20°C for 10 minutes to obtain a mixed base solution.

[0049] S5 fluorine-free foam system formulation. First, add cocamidopropyl betaine and stir at 800 rpm for 15 min until completely dissolved. Reduce the stirring speed to 600 rpm, add dodecanol, and stir for 10 min until uniformly dispersed. Restore the stirring speed to 800 rpm, add ethylene glycol butyl ether, and continue stirring for 15 min until the system is homogeneous and stable.

[0050] S6 Low-speed maturation and static aging. Reduce the stirring speed to 200 rpm and stir for 60 minutes to degas and homogenize. After completion, seal the reactor and let it stand for 10 days in a dark, cool environment.

[0051] S7 Filter Quality Inspection and Packaging. A 100-mesh filter system is used; after passing all performance tests, the filters are sealed and packaged.

[0052] The performance test results of the finished product in this embodiment are as follows: viscosity at 25℃ is 36 mPa·s, conductivity is 610 μS / cm, pH value is 8.0, freezing point is -3℃, and corrosion rate on Q235A steel is 1.1 mg·d⁻¹. -1 ·dm -2 The corrosion rate of 3A21 aluminum is 0.5 mg·d⁻¹. -1 ·dm -2 The foaming ratio is 8.1 times, the foam half-life is 15 minutes, no perfluorinated substances were detected, and the mortality rate in acute toxicity tests on fish was 0. Verified by lithium battery thermal runaway fire extinguishing tests, the open flame was extinguished within 40 seconds after spraying, the cell temperature rapidly dropped below 120℃, and there was no reignition after 24 hours of standing. Example 3

[0053] This embodiment uses a relatively high proportion of components. By mass percentage, the amounts of each component are: magnesium carbonate 2.0%, sodium bicarbonate 1.0%, sodium acetate 1.0%, sodium chloride 1.0%, propylene glycol 0.5%, fumed silica 0.2%, xanthan gum 0.2%, sodium formate 0.02%, cocamidopropyl betaine 1.2%, dodecanol 0.10%, ethylene glycol butyl ether 0.3%, with the balance being deionized water. The total mass percentage of all components is 100%.

[0054] The preparation process in this embodiment is as follows: Preparation of S1 base solution. The ambient temperature was controlled at 35℃. Metered deionized water was added to a closed dispersion reactor, and stirring was started at 500 r / min for 5 minutes to obtain a homogeneous base aqueous solution.

[0055] Preparation of S2 suspension thickening substrate. While maintaining a constant stirring speed, fumed silica was slowly added to the base aqueous solution in three batches, with an 8-minute interval between each batch. After all batches were added, stirring continued for 15 minutes. Xanthan gum was then slowly added, and stirring continued for 15 minutes after the addition was complete, until no visible agglomerates were observed in the system, forming a homogeneous suspension substrate.

[0056] Dissolve the S3 inorganic functional component. Add magnesium carbonate, sodium bicarbonate, sodium acetate, sodium chloride, and sodium formate in sequence, increase the stirring speed to 800 r / min, and stir for 35 min until the inorganic salt component is completely dispersed and dissolved.

[0057] S4 antifreeze and wetting agent was added. Propylene glycol was added to the system, and the mixture was stirred at a constant temperature of 35°C for 15 minutes to obtain a mixed base solution.

[0058] S5 fluorine-free foam system formulation. First, add cocamidopropyl betaine and stir at 1000 rpm for 20 min until completely dissolved. Reduce the stirring speed to 700 rpm, add dodecanol, and stir for 15 min until uniformly dispersed. Restore the stirring speed to 1000 rpm, add ethylene glycol butyl ether, and continue stirring for 25 min until the system is homogeneous and stable.

[0059] S6 Low-speed maturation and static aging. Reduce the stirring speed to 300 rpm and stir for 80 minutes to degas and homogenize. After completion, seal the reactor and let it stand for 15 days in a dark, cool environment.

[0060] S7 Filter Quality Inspection and Packaging. A 200-mesh filter system is used; after passing all performance tests, the filters are sealed and packaged.

[0061] The performance test results of the finished product in this embodiment are as follows: viscosity at 25℃ is 48 mPa·s, conductivity is 690 μS / cm, pH value is 8.5, freezing point is -5℃, and corrosion rate on Q235A steel is 1.4 mg·d⁻¹. -1 ·dm -2 The corrosion rate of 3A21 aluminum is 0.7 mg·d⁻¹. -1 ·dm -2 The foaming ratio is 10.5 times, the foam half-life is 21 minutes, no perfluorinated substances were detected, and the mortality rate in acute toxicity tests on fish was 0. Verified by lithium battery thermal runaway fire extinguishing tests, the open flame was extinguished within 25 seconds after spraying, the cell temperature rapidly dropped below 90℃, and there was no reignition after 24 hours of standing. Comparative Example 1

[0062] This comparative example uses a common water-based lithium battery fire extinguishing agent formulation, a foam-free system. By mass percentage, the components are: sodium bicarbonate 1.5%, sodium chloride 0.8%, and the remainder is deionized water. The total mass percentage of all components is 100%.

[0063] The preparation method involves adding each inorganic salt component to deionized water at room temperature, stirring until completely dissolved, and then filtering to obtain the finished product.

[0064] The performance test results of the comparative example are as follows: viscosity at 25℃ is 5 mPa·s, conductivity is 720 μS / cm, pH value is 8.2, freezing point is -1℃, and corrosion rate on Q235A steel is 6.8 mg·d⁻¹. -1 ·dm -2 The corrosion rate of 3A21 aluminum is 3.2 mg·d⁻¹. -1 ·dm -2 It has no foaming ability. Verified in a lithium battery thermal runaway fire extinguishing test under the same conditions, the surface flames were extinguished within 60 seconds after spraying, but the cell cooled down slowly, with significant reignition occurring within 30 minutes, requiring multiple sprays to control the fire. Comparative Example 2

[0065] This comparative example uses a traditional fluorinated aqueous film-forming foam fire extinguishing agent. The components, by mass percentage, are: perfluorooctyl sulfonate 0.8%, sodium dodecyl sulfate 1.2%, urea 1.0%, ethylene glycol 0.5%, with the remainder being deionized water. The total mass percentage of all components is 100%.

[0066] The preparation method involves adding each component sequentially at room temperature, stirring to dissolve evenly, and then filtering to obtain the finished product.

[0067] The performance test results of the comparative example are as follows: viscosity at 25℃ is 12 mPa·s, conductivity is 580 μS / cm, pH value is 7.8, freezing point is -2℃, and corrosion rate on Q235A steel is 3.5 mg·d⁻¹. -1 ·dm -2 The corrosion rate of 3A21 aluminum is 1.8 mg·d⁻¹. -1 ·dm -2 The foaming ratio was 7.5 times, the foam half-life was 8 minutes, perfluorooctane sulfonate was detected, and the mortality rate in acute toxicity tests on fish was 35%. Verified by lithium battery thermal runaway fire extinguishing tests under the same conditions, the open flame was extinguished 45 seconds after spraying, but the foam ruptured rapidly at high temperatures, and reignition occurred within 2 hours.

[0068] The core performance indicators of the three sets of embodiments and two sets of comparative examples are shown in the following table:

[0069] This table compares the three sets of embodiments of the present invention with two types of prior art from five dimensions: physicochemical properties, corrosion performance, foaming performance, environmental safety, and fire extinguishing effectiveness. The core conclusions are as follows: The flame extinguishing time of the three embodiments of the present invention is 25-40 seconds, and there is no reignition after 24 hours of standing. The ordinary water-based fire extinguishing agent of Comparative Example 1 has a slow fire extinguishing speed and reignites multiple times within 30 minutes. The traditional fluorinated foam fire extinguishing agent of Comparative Example 2 has rapid foam rupture at high temperature and reignites within 2 hours. Its ability to prevent reignition is far lower than that of the present invention.

[0070] The foaming ratio of the embodiments of the present invention reaches 8.1 to 10.5 times, the foam half-life is 15 to 21 minutes, and the freezing point is as low as -5 to -3℃; Comparative Example 1 has no foaming ability, and Comparative Example 2 has a foam half-life of only 8 minutes and poor low-temperature performance, which cannot meet the requirements of long-term oxygen isolation in lithium battery fires and application in all regions.

[0071] The corrosion rates of steel and aluminum in all three examples were significantly lower than those in the two comparative examples, resulting in less equipment damage. Furthermore, no perfluorinated substances were detected throughout the process, and the acute mortality rate of fish was 0. Comparative Example 2 contained harmful perfluorinated substances and exhibited significant biotoxicity, failing to meet environmental regulations; Comparative Example 1, although fluorine-free, had an excessively high corrosion rate.

[0072] As the proportion of functional components increases in Examples 1 to 3, the foaming capacity and fire extinguishing speed gradually increase, while the corrosion rate remains at an extremely low level, proving that the component ratio range defined by the present invention has good performance adjustability and stability.

[0073] First, this invention constructs a multi-mechanism synergistic thermal runaway prevention system with outstanding anti-reignition performance. This invention integrates inorganic flame-retardant cooling components with a fluorine-free foam system. On one hand, it relies on the high specific heat capacity of the water-based medium to rapidly absorb the heat from thermal runaway, combined with the endothermic decomposition of magnesium carbonate and sodium bicarbonate and the release of inert gases, to achieve deep cooling of the battery cell. On the other hand, it achieves surface oxygen and heat insulation through a continuous foam layer, while sodium acetate and sodium formate can capture combustion free radicals, inhibiting electrolyte decomposition and chain combustion reactions. The synergistic effect of these multiple mechanisms can terminate the thermal runaway process of lithium batteries at its source, effectively solving the technical problems of incomplete thermal runaway prevention and high reignition rates with single cooling or single oxygen isolation solutions, resulting in a significant long-term anti-reignition effect.

[0074] Secondly, this invention achieves a balance between complete fluorine-free environmental protection and low corrosion. The formula of this invention does not contain PFOS, PFOA, PFAS, or potassium perfluorobutyl sulfonate, which are perfluorinated controlled substances. The foaming agent uses a biodegradable amphoteric surfactant with low biotoxicity and no risk of environmental accumulation, complying with current environmental regulations and the development requirements of green fire protection. Simultaneously, through optimized component compounding and control of the weakly alkaline system, the corrosion rate of the extinguishing agent on commonly used metal materials such as Q235A steel and 3A21 aluminum is far below the national standard limit. After extinguishing the fire, the corrosion damage to battery modules, fire-fighting equipment, and supporting facilities is minimal, resulting in a high residual value retention rate for the equipment.

[0075] Third, the system of this invention exhibits excellent salt resistance and adaptability to various operating conditions. This invention regulates the rheological properties of the system by combining fumed silica and xanthan gum, and enhances the compatibility of the surfactant in high-ionic-strength environments by using a salt-resistant co-solvent, overcoming the technical bottleneck of conventional amphoteric foam systems that are prone to foam breakage, stratification, and failure under high-salt conditions. The resulting foam liquid film has high strength, long half-life, and good wall adhesion, forming a long-lasting protective layer on the surface of complex battery structures. Propylene glycol and sodium chloride synergistically regulate the freezing point, broadening the product's low-temperature application range. The system is a homogeneous liquid, exhibiting no precipitation or stratification during long-term storage, making it suitable for various fire extinguishing equipment and application scenarios, avoiding the application defects of solid-phase filler-type fire extinguishing agents that are prone to sedimentation and clogging of pipelines and nozzles.

[0076] Fourth, the preparation process of this invention is simple and controllable, with strong industrial feasibility. The entire preparation process is carried out under normal temperature and pressure conditions, employing a step-by-step feeding, gradient speed stirring, and static aging process. The system construction can be completed solely through physical dispersion and dissolution, without the need for complex raw material modification, high-temperature reactions, or ultrasonic treatment. All raw materials used are readily available industrial products, with stable sources and controllable costs. The process is short, energy-efficient, and has good batch repeatability, making it easy to achieve large-scale industrial production and possessing significant industrial application value.

[0077] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent, characterized in that, By mass percentage, it consists of the following components: magnesium carbonate 1.0%–2.0%, sodium bicarbonate 0.5%–1.0%, sodium acetate 0.2%–1.0%, sodium chloride 0.2%–1.0%, propylene glycol 0.2%–0.5%, fumed silica 0.1%–0.2%, xanthan gum 0.1%–0.2%, sodium formate 0.01%–0.02%, fluorine-free foaming agent 0.8%–1.2%, foam stabilizer 0.05%–0.10%, salt-resistant co-solvent 0.2%–0.3%, with the balance being deionized water; the total mass percentage of all components is 100%.

2. The fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent according to claim 1, characterized in that: The fluorine-free foaming agent is cocamidopropyl betaine, the foam stabilizing agent is dodecyl alcohol, and the salt-resistant cosolvent is ethylene glycol butyl ether.

3. The fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent according to claim 2, characterized in that, The specific proportions of each component by mass percentage are as follows: magnesium carbonate 1.50%, sodium bicarbonate 0.80%, sodium acetate 0.60%, sodium chloride 0.50%, propylene glycol 0.40%, fumed silica 0.15%, xanthan gum 0.13%, sodium formate 0.02%, cocamidopropyl betaine 1.00%, dodecanol 0.08%, ethylene glycol butyl ether 0.22%, with the balance being deionized water; the total mass percentage of each component is 100%.

4. The fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent according to claim 1, characterized in that: At 25℃, the extinguishing agent has a viscosity of 35-50 mPa·s, an electrical conductivity of 600-700 μS / cm, and a pH of 8.0-8.5; a freezing point not higher than -5℃; a corrosion rate to Q235A steel not higher than 1.5 mg / (d·dm²) and a corrosion rate to 3A21 aluminum not higher than 0.8 mg / (d·dm²); a foaming ratio not less than 8 times and a foam half-life not less than 15 min.

5. The fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent according to claim 1, characterized in that: The extinguishing agent does not contain PFOS, PFOA, or PFAS perfluorinated organic compounds, does not contain ozone-depleting substances, has a mortality rate of 0 in acute toxicity tests on fish, and is biodegradable.

6. A method for preparing the fluorine-free, environmentally friendly, highly stable liquid foam-type lithium battery thermal runaway suppression and extinguishing agent according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Preparation of base solution: Under normal temperature conditions of 20-35℃, add the measured amount of deionized water into a closed dispersion reaction vessel, turn on the stirrer and control the speed to 300-500 r / min to obtain a uniform base aqueous solution. S2. Preparation of suspension thickening substrate: Add fumed silica and xanthan gum to the base aqueous solution and stir continuously for 20-30 minutes until the powder is completely swollen and there is no agglomeration or clumping, to obtain a stable suspension substrate liquid. S3. Dissolution of inorganic functional components: Add magnesium carbonate, sodium bicarbonate, sodium acetate, sodium chloride, and sodium formate sequentially to the suspension base liquid. Increase the stirring speed to 600-800 r / min and stir for 25-35 min to completely disperse and dissolve the inorganic salt components. S4. Addition of antifreeze and wetting agent: Add propylene glycol to the system, maintain the system temperature at 20-35℃ and stir for 10-15 minutes to obtain a mixed base liquid; S5. Blending of fluorine-free foam system: Add fluorine-free foaming agent, foam stabilizer and salt-resistant co-solvent to the mixed base liquid in sequence, adjust the stirring speed to 800-1000 r / min, stir for 40-60 min, so that the foaming system is completely compatible with the high-salt inorganic system. S6. Low-speed maturation and static aging: Reduce the stirring speed to 200-300 r / min and stir for 60-80 min to complete the defoaming and homogenization process; Subsequently, the system was left to stand and age for 10 to 15 days under normal temperature and closed conditions to stabilize the rheological and foam properties. S7. Filtration, quality inspection and packaging: Impurities in the system are removed by filtration using a 100-200 mesh filter. After passing performance testing, the system is sealed and packaged to obtain the finished fire extinguishing agent.

7. The preparation method according to claim 6, characterized in that, Step S2 specifically includes: S21. While maintaining a stirring speed of 300-500 r / min, slowly sprinkle the fumed silica into the base aqueous solution in 2-3 batches, with an interval of 5-8 min between each batch. After all the materials have been added, continue stirring for 10-15 min. S22. While maintaining the stirring speed, slowly add xanthan gum to the system. After the addition is complete, continue stirring for 10 to 15 minutes until there are no visible agglomerated particles in the system, forming a uniform suspension thickening base liquid.

8. The preparation method according to claim 6, characterized in that, Step S5 specifically includes: S51. Keep the system temperature at 20-35℃, add the fluorine-free foaming agent first, and stir at 800-1000r / min for 15-20min until completely dissolved; S52. Reduce the rotation speed to 600-700 r / min, add the foam stabilizer, and stir for 10-15 min until evenly dispersed; S53. Restore the rotation speed to 800-1000 r / min, add salt-resistant co-solvent, and continue stirring for 15-25 min until the system shows no stratification, no oil separation, and no defoaming.

9. The preparation method according to claim 6, characterized in that: In step S6, the static aging process is carried out in a closed environment that is protected from light, cool, and with temperature fluctuations not exceeding ±3℃. During the aging process, the reactor must not be opened and the system must not be stirred or disturbed. After the aging is completed, the uniformity of the system is tested, and the next process can only proceed after confirming that there is no sediment, no stratification, and no floating oil.

10. The preparation method according to claim 6, characterized in that: In step S7, the performance testing items include at least pH value, metal corrosion rate, freezing point, conductivity, foaming ratio, perfluorinated substance content, and acute biological toxicity. Only after all indicators pass the test can the product be sealed and packaged. The packaging containers are corrosion-resistant sealed plastic drums or metal storage tanks, and the temperature of the finished product storage environment is controlled at 5-35℃.

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