Powder fire extinguishing agent, preparation method and application of powder fire extinguishing agent in metal and lithium battery fire disasters

Abstract

The invention belongs to the technical field of fire extinguishing agents, and particularly relates to a powder fire extinguishing agent, a preparation method of the powder fire extinguishing agent and application of the powder fire extinguishing agent in metal and lithium battery fire disasters. The inner core comprises a eutectic solvent or a eutectic solvent mixture formed by mixing the eutectic solvent with a flame retardant; the eutectic solvent is composed of a hydrogen bond donor and a hydrogen bond acceptor, has low volatility, high thermal stability and good dissolving capacity, forms a powdery structure after being wrapped with hydrophobic silicon dioxide, and enhances the fire extinguishing effect; hydrophobic silicon dioxide has excellent hydrophobicity and chemical stability and can prevent a system from absorbing moisture, a formed protective layer can isolate oxygen from being in contact with combustible materials, and combustion is further inhibited. The flame retardant is decomposed at high temperature to generate non-combustible gas, the product can form a heat insulation layer, the oxygen concentration is diluted by the gas, and flame spreading is inhibited.

Description

Technical Field

[0001] The present invention belongs to the technical field of fire extinguishing agents, and particularly relates to a powder fire extinguishing agent, a preparation method thereof, and an application thereof in metal and lithium battery fires. Background Art

[0002] Metal fires (such as the combustion of metals such as magnesium, aluminum, lithium, and sodium) and lithium battery fires (especially ternary lithium-ion batteries) have high reactivity and high-temperature characteristics. The unique combustion characteristics make it difficult to effectively extinguish them with traditional fire extinguishing agents (such as water, foam, dry powder, etc.). For example, when metals burn, the temperature can reach above 2000 °C, and some metals (such as lithium and sodium) will have explosive reactions with water or carbon dioxide. Metal oxides (such as MgO and Al2O3) will decompose at high temperatures, releasing oxygen, rendering the traditional suffocation fire extinguishing method ineffective; moreover, the molten droplets of the burning metal will ignite the surrounding combustibles, expanding the fire. Internal short circuits in lithium batteries will cause the decomposition of the positive electrode (releasing oxygen), the combustion of the electrolyte (low flash point of organic solvents), and spread to adjacent battery cells. And even if the surface open fire is extinguished, the battery may still catch fire again due to residual heat (>300 °C).

[0003] Currently, traditional dry powder (ABC type) not only cannot cool metals or block internal reactions in lithium batteries, but may even intensify the fire (such as the reaction between CO2 and lithium), and has poor stability, is prone to moisture absorption and caking, affecting its storage and use performance. Special D-class fire extinguishing agents have limitations. Metal fire extinguishing agents such as graphite powder are ineffective for lithium batteries and are difficult to cover the inside of battery modules. Water-based fire extinguishing agents will react explosively with metals and cause short circuits in lithium batteries, leading to secondary thermal runaway. Therefore, there is currently no fire extinguishing agent that can efficiently extinguish both metal fires and lithium battery fires, and at the same time has environmental friendliness and economy. Those skilled in the art urgently need to develop a new fire extinguishing technology that can not only isolate oxygen, cool high temperatures, but also neutralize toxic substances and adapt to complex fire field environments.

[0004] A temperature-reducing ultrafine dry powder fire extinguishing agent is disclosed in the prior art, which is composed of a hydrophobic ammonium polyphosphate powder and mixed material particles; the mixed material particles include a core and a coating layer, and the coating layer covers at least a part of the surface of the core layer. Among them, the coating layer includes hydrophobic nano-silica, and the core layer includes water. Although this fire extinguishing agent can achieve advantages such as efficient fire extinguishing, good temperature-reducing performance, non-toxic and harmless itself, no secondary pollution, and easy cleaning after fire extinguishing, due to the water-containing core layer, its extinguishing effect on sodium, magnesium, aluminum, etc. is not good, and it may even intensify combustion.

[0005] In addition, emulsion templating method, microencapsulation method, etc. are more commonly used to prepare core-shell structures at present. Among them, the emulsion templating method not only requires emulsification and curing, with high process complexity, but also uses emulsifiers, organic solvents, etc., which have high costs. The microencapsulation method not only requires interfacial polymerization, with high process complexity, but also uses monomers and initiators, resulting in increased costs. The mechanical mixing method not only does not require complex chemical reactions, reduces energy consumption, but also can reduce the generation of by-products, making it suitable for large-scale industrial production. Therefore, it is of great significance to develop an efficient, environmentally friendly fire extinguishing agent applicable to complex environments. Summary of the Invention

[0006] The object of the present invention is to provide a powder fire extinguishing agent, a preparation method thereof, and its application in metal and lithium battery fires, so as to overcome the deficiencies of the prior art. Through the synergistic effect of hydrophobic silica particles, deep eutectic solvents, and flame retardants, it is applicable to efficiently extinguish complex fire environments such as metals and lithium batteries, and has excellent flame retardancy, heat insulation, and environmental friendliness.

[0007] The overall inventive concept adopted by the present invention is that the structure of the fire powder extinguishing agent is similar to "dry water", including a hydrophobic silica shell and a core mixture wrapped inside the hydrophobic silica shell. The core mixture is uniformly mixed by a deep eutectic solvent and a flame retardant. Among them, hydrophobic silica (SiO2) is used as the outer wrapping material, which has excellent hydrophobicity and chemical stability, can prevent the system from absorbing moisture, and at the same time provides good dispersibility and fluidity. The inner core is a deep eutectic solvent mixture formed by mixing a deep eutectic solvent and a flame retardant. The deep eutectic solvent does not contain water, has low volatility, high thermal stability, and good solubility, and can be used as a carrier to disperse the flame retardant. The flame retardant decomposes at high temperatures to generate non-combustible gases, forming a heat insulation layer, inhibiting the spread of flames, and enhancing the stability and flame retardant effect of the system.

[0008] Efficient fire extinguishing is achieved through the following mechanisms:

[0009] (1) Flame retardant effect: The flame retardant decomposes at high temperatures to generate non-combustible gases, and the products will form a heat insulation layer, and the gases dilute the oxygen concentration, inhibiting the spread of flames.

[0010] (2) Cooling effect: The deep eutectic solvent evaporates and absorbs heat at high temperatures, reducing the temperature of the combustion area.

[0011] (3) Isolation effect: The protective layer formed by the hydrophobic silica shell can isolate the contact between oxygen and combustibles, further inhibiting combustion.

[0012] (4) Synergistic effect: The powder material obtained by wrapping the deep eutectic solvent with hydrophobic silica decomposes at high temperatures to generate non-combustible gases (such as ammonia, carbon dioxide, etc.), further enhancing the fire extinguishing effect.

[0013] To achieve the above object, the technical solution of the present invention is as follows:

[0014] In a first aspect, the present invention provides a powder fire extinguishing agent, comprising a hydrophobic silica shell and a core wrapped in the hydrophobic silica shell; the core comprises a deep eutectic solvent.

[0015] The deep eutectic solvent is composed of a hydrogen bond donor and a hydrogen bond acceptor.

[0016] The hydrogen bond donor is selected from one or more of urea, lactic acid, sulfamic acid, ethylene glycol, and glycerol.

[0017] The hydrogen bond acceptor is selected from one or more of betaine, urea, choline chloride, and sulfamic acid.

[0018] Urea and sulfamic acid can be used as the hydrogen bond donor and / or the hydrogen bond acceptor.

[0019] Preferably, the powder fire extinguishing agent further comprises a flame retardant, and the flame retardant and the deep eutectic solvent are mixed to form a deep eutectic solvent mixture as the core.

[0020] Preferably, the flame retardant is selected from one or more of melamine, chitosan, magnesium hydroxide, aluminum hydroxide, ammonium polyphosphate, and zinc borate; wherein, the degree of polymerization n of ammonium polyphosphate in the flame retardant is > 1500; the degree of deacetylation of chitosan is 80.0 - 95.0%.

[0021] Preferably, the deep eutectic solvent is selected from one or more of choline chloride - urea, betaine - lactic acid, ethylene glycol - choline chloride, lactic acid - zinc chloride, sulfamic acid - urea, and glycerol - choline chloride.

[0022] Preferably, the mass ratio of the hydrophobic silica to the core is 1:(15 - 25); more preferably, the mass ratio of the hydrophobic silica to the deep eutectic solvent mixture is 1:20.

[0023] During the mixing process of the hydrophobic silica and the deep eutectic solvent, if the amount of the deep eutectic solvent is too small, after high - speed shearing, there will be more uncoated silica, resulting in material waste. If the amount of the deep eutectic solvent is too large, after high - speed shearing, there will be more uncoated deep eutectic solvent, leading to an increase in the viscosity of the overall powder, easy to form lumps, and being unfavorable for the spraying of the fire - extinguishing powder.

[0024] Preferably, the mass ratio of the deep eutectic solvent to the flame retardant is 1:(50 - 150); more preferably, the mass ratio of the deep eutectic solvent to the flame retardant is 1:100.

[0025] Preferably, the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 3:1 - 1:3.

[0026] Second aspect, the present invention provides a preparation method of the powder fire extinguishing agent described in the first aspect, comprising the following steps:

[0027] Mix a hydrogen bond donor and a hydrogen bond acceptor in a certain proportion and heat to complete mutual solubility to form a eutectic solvent; then mix the eutectic solvent with hydrophobic silica and perform mechanical mixing to obtain the powder fire extinguishing agent.

[0028] Preferably, the preparation method further comprises uniformly dispersing a flame retardant in the eutectic solvent to obtain a eutectic solvent mixture, then mixing the eutectic solvent mixture with hydrophobic silica and performing mechanical mixing to obtain the powder fire extinguishing agent.

[0029] Preferably, the mechanical mixing means that hydrophobic silica is uniformly coated on the surface of the eutectic solvent mixture by a high-speed shearing process.

[0030] More preferably, the rotation speed of the high-speed shearing process is 18,000 - 25,000 rpm and the time is 0.8 - 1.2 min.

[0031] Third aspect, the present invention provides an application of the powder fire extinguishing agent described in the first aspect in extinguishing metal fires or lithium battery fires.

[0032] Preferably, the metal is magnesium, aluminum, lithium or sodium.

[0033] Fourth aspect, the present invention provides a fire extinguishing device, comprising a container and the powder fire extinguishing agent described in the first aspect filled therein.

[0034] Advantages of the present invention:

[0035] (1) The present invention realizes efficient, environmentally friendly fire extinguishing applicable to metal and lithium battery fires through the synergistic effect of hydrophobic silica, eutectic solvent and flame retardant. The present invention obtains a powdery fire extinguishing agent by first using hydrophobic silica to coat the eutectic solvent (or coat the eutectic solvent mixture). A single DES is a viscous liquid, and some of its components, such as choline-based ones, are prone to moisture absorption, so it must be stored sealed and moisture-proof. At the same time, the high viscosity requires a special spraying device during application. In this application, the DES is coated with a layer of silica to prepare a powder, which not only has good fluidity and is easy to spray, but also does not volatilize and does not absorb moisture at room temperature, achieving the purpose of long-term storage without performance degradation.

[0036] (2) The powder fire extinguishing agent prepared by the present invention is non-toxic, harmless, has no secondary pollution, is insulating, is easy to clean after fire extinguishing, has a simple preparation process, is easy to operate, has a low production cost, is suitable for mass production and popularization. Description of the drawings

[0037] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0038] Figure 1 It is a schematic structural diagram of the powder fire extinguishing agent prepared in Example 4 of the present invention;

[0039] Figure 2 It is a macroscopic powder sample diagram of the powder fire extinguishing agent prepared in Example 4 of the present invention;

[0040] Figure 3 It is an optical microscope diagram of the powder fire extinguishing agent prepared in Example 4 of the present invention. Detailed implementation manners

[0041] Those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions are not indicated in the examples, and they are carried out according to conventional conditions or conditions recommended by the manufacturer. Components not indicated by the manufacturer are all conventional products that can be obtained commercially.

[0042] Example 1: This example provides a powder fire extinguishing agent and its preparation method

[0043] (1) Mix choline chloride and urea in a molar ratio of 1:2, and heat and stir at 80 °C until completely miscible to form a eutectic solvent.

[0044] (2) Mix the eutectic solvent with hydrophobic silica particles AEROSIL R972 in a mass ratio of 25:1, and through a high-speed shearing process (20000 rpm, 1 min), make the hydrophobic silica uniformly coat the surface of the eutectic solvent, and finally obtain a white powdery composite fire extinguishing agent, named: DS25.

[0045] Example 2: This example provides a powder fire extinguishing agent and its preparation method

[0046] (1) Mix choline chloride and urea in a molar ratio of 1:2, and heat and stir at 80 °C until completely miscible to form a eutectic solvent.

[0047] (2) Mix the eutectic solvent with hydrophobic silica particles AEROSIL R972 in a mass ratio of 20:1, and through a high-speed shearing process (20000 rpm, 1 min), make the hydrophobic silica uniformly coat the surface of the eutectic solvent, and finally obtain a white powdery composite fire extinguishing agent, named: DS20.

[0048] Example 3: This example provides a powder fire extinguishing agent and its preparation method

[0049] (1) Mix choline chloride and urea in a molar ratio of 1:2, heat and stir at 80 °C until completely miscible to form a eutectic solvent.

[0050] (2) Uniformly disperse ammonium polyphosphate particles (n > 1500) in the eutectic solvent (mass ratio 1:100) to form a eutectic solvent mixture.

[0051] (3) Mix the eutectic solvent mixture with hydrophobic silica particles AEROSIL R972 in a mass ratio of 20:1, and through a high-speed shearing process (20000 rpm, 1 min), make the hydrophobic silica uniformly coat the surface of the eutectic solvent mixture, and finally obtain a white powdery composite fire extinguishing agent, named: DAS.

[0052] Example 4: This example provides a powder fire extinguishing agent and its preparation method

[0053] (1) Mix choline chloride and urea in a molar ratio of 1:2, heat and stir at 80 °C until completely miscible to form a eutectic solvent.

[0054] (2) Uniformly disperse chitosan (deacetylation degree 80.0 - 95.0%) in the eutectic solvent (mass ratio 1:100) to form a eutectic solvent mixture.

[0055] (3) Mix the eutectic solvent mixture with hydrophobic silica particles AEROSIL R972 in a mass ratio of 20:1, and through a high-speed shearing process (20000 rpm, 1 min), make the hydrophobic silica uniformly coat the surface of the eutectic solvent mixture, and finally obtain a white powdery composite fire extinguishing agent, named: DCS.

[0056] As Figures 1-2 shown, the powder fire extinguishing agent prepared in Example 4 is in a powder state, specifically including a hydrophobic silica shell and a eutectic solvent mixture core coated inside the hydrophobic silica shell, and the eutectic solvent mixture is formed by mixing a flame retardant and a eutectic solvent.

[0057] As Figure 3As shown in the figure, the optical microscope image shows that the composite powder fire extinguishing agent presents an irregular spherical shape. Among them, hydrophobic silica, as the outer wrapping material, has excellent hydrophobicity and chemical stability, can prevent the system from absorbing moisture, and at the same time provides good dispersibility and fluidity. The eutectic solvent in the eutectic solvent mixture is composed of choline chloride and urea, has low volatility, high thermal stability and good solubility, can be used as a carrier to disperse the flame retardant, and at the same time forms a powdery structure after wrapping the hydrophobic silica, enhancing the fire extinguishing effect; chitosan, as a natural polymer material, has good biocompatibility and film-forming properties. When used as a flame retardant, it decomposes into non-combustible gases at high temperatures, and the products will form a heat-insulating layer, and the gases dilute the oxygen concentration, inhibiting the spread of the flame.

[0058] Comparative Example 1

[0059] Different from Example 4, water was used to replace the eutectic solvent, and other preparation methods were the same as those in Example 4.

[0060] The study found that due to the water in the inner core layer, water will react violently with some active metals (such as sodium, potassium, magnesium, aluminum, etc.) at high temperatures, generating hydrogen and releasing a large amount of heat, which instead intensifies the fire. At the same time, the generated hydrogen may cause an explosion at high temperatures, increasing the danger.

[0061] Comparative Example 2

[0062] Different from Example 4, one of the existing other types of eutectic solvents such as DES of phosphate (such as phosphoric acid-urea / ammonium dihydrogen phosphate-ethylene glycol), DES of borate (such as boric acid-glycerol), DES of inorganic salt (such as lithium chloride-acetamide) and DES of silicate (such as sodium silicate-ethylene glycol) was used to replace the eutectic solvent composed of choline chloride and urea in step (1); other preparation methods were the same as those in Example 4.

[0063] The study found that the eutectic solvent used in the powder fire extinguishing agent prepared in Example 4 of the present invention has reduced corrosion, reduced environmental toxicity, reduced hygroscopicity, reduced powder viscosity and cost compared with the existing other types of eutectic solvents; for example, phosphates and silicates may corrode metals or equipment; such as borates and inorganic salts may be harmful to the environment or human body; such as inorganic salts are easy to absorb moisture and destroy the hydrophobicity of the system; such as phosphates, borates and silicates have high viscosities, affecting the fluidity and dispersibility of the powder; such as inorganic salts have high costs, increasing the economic burden of the system.

[0064] Test Example: This test example tested the performance of the powder fire extinguishing agents prepared in Examples 1 to 4

[0065] (1) Fluidity

[0066] Powder fluidity is one of the key factors affecting the spraying performance of fire extinguishing materials, directly influencing the powder diffusion effect. The outflow rate and angle of repose can be used to test (standard characterization methods for powder fluidity). The faster the outflow rate, the more uniform and stable the powder shape, the smaller the adhesion force between particles, the relatively smaller friction force, and the smaller the free-fall resistance, resulting in a relatively faster outflow rate. The smaller the angle of repose of the powder, the better its fluidity.

[0067] In this test example, the outflow rate test results of the powders in Examples 1 to 4 are shown in Table 1;

[0068] The angle of repose test results of the powders in Examples 1 to 4 are shown in Table 2;

[0069] The bulk density test results of the powders in Examples 1 - 4 are shown in Table 3.

[0070] Table 1 Outflow rate of the powders in Examples 1 to 4

[0071]

[0072] Table 2 Angle of repose of the powders in Examples 1 to 4

[0073]

[0074] As can be seen from Table 1, the three test values and the average value of the outflow rate of sample DCS (i.e., the sample prepared in Example 4) are all greater than those of Examples 1 to 3. This is because the ratio of the core material to the silica shell in DCS is appropriate, the friction force between the powders is relatively small, and the prepared particle sizes are relatively uniform. Therefore, a faster outflow rate is measured.

[0075] As can be seen from Table 2, the three test values and the average value of the angle of repose of sample DCS (the sample prepared in Example 4) and sample DAS (the sample prepared in Example 3) are close and are significantly smaller than those of Examples 1 to 2. This is because the ratio of the core material to the silica shell in DCS is appropriate, the adhesion force between the powders is small, the free-fall resistance is small, and the powder dispersibility is good. Therefore, a smaller angle of repose is measured.

[0076] Based on Tables 1 and 2, it is not difficult to see that Example 4 - DCS has better powder characteristics.

[0077] Table 3 Bulk density of the powders in Examples 1 to 4

[0078]

[0079] As can be seen from Table 3, the powder bulk density of the samples prepared in Examples 1 to 4 shows an increasing trend, indicating that under the same conditions, more Example 4-DCS can be filled, thereby increasing the content of the flame retardant component in the entire container and the actual fire extinguishing ability. This will significantly improve the fire extinguishing efficiency and thus quickly prevent the spread of fire.

[0080] As can be seen from the above powder fluidity test results, the powders prepared in Examples 1-4 of the present invention all have good fluidity, so as to meet the spraying performance of the fire extinguishing material.

[0081] (3) Sodium metal block fire extinguishing test

[0082] The fire extinguishing performance of the powder prepared in Example 4 with the best fluidity was tested. The specific test process is as follows:

[0083] (1) Ignite a 1 g sodium block. When the surface of the sodium block is completely burning, stop heating, and use the fire extinguishing agent of Example 4 to spray and test the fire extinguishing effect. The results are shown in Table 2. The sodium block without spraying the fire extinguishing agent was completely burned out at 23 s, while after spraying the fire extinguishing powder on the burning sodium block of the same mass for intervention, the flame of the sodium block was completely extinguished at about 7 s, and there was no phenomenon of reignition. The substance covered by the extinguished fire extinguishing powder was scraped off and ignited again, and the substance could still be ignited, indicating that the residue still contained unreacted sodium metal, thus verifying that the hydrophobic silica-coated deep eutectic solvent mixture powder fire extinguishing agent DCS can successfully extinguish the flame of the sodium metal block and prevent the further spread of fire.

[0084] (2) Ignite a magnesium ribbon group composed of 2.5 m magnesium ribbons. When the magnesium ribbon group is burning, stop heating, and use the fire extinguishing agent of Example 4 to spray and test the fire extinguishing effect. The results are shown in Table 4. The magnesium ribbon group without spraying the fire extinguishing agent was completely burned out at 25 s, while after spraying the fire extinguishing powder on the burning magnesium ribbon group of the same mass for intervention, the flame of the magnesium ribbon group was completely extinguished at about 13 s, and there was no phenomenon of reignition. After using Example 4 to extinguish the fire of the magnesium ribbon, it can be clearly observed that there are still unburned magnesium ribbons in the residue, indicating that the residue still contains unreacted magnesium metal, thus verifying that the hydrophobic silica-coated deep eutectic solvent mixture powder fire extinguishing agent DCS can successfully extinguish the flame of the magnesium ribbon and prevent the further spread of fire.

[0085] Table 4 Metal fire extinguishing data of Example 4

[0086]

[0087] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A powder fire extinguishing agent, characterized in that, It includes a hydrophobic silica shell and a core encapsulated in the hydrophobic silica shell; the core includes a deep eutectic solvent; The deep eutectic solvent is composed of a hydrogen bond donor and a hydrogen bond acceptor; The hydrogen bond donor is selected from one or more of urea, lactic acid, sulfamic acid, ethylene glycol, and glycerol; The hydrogen bond acceptor is selected from one or more of betaine, urea, choline chloride, and sulfamic acid.

2. The powder fire extinguishing agent according to claim 1, wherein It also includes a flame retardant, and the flame retardant and the deep eutectic solvent are mixed to form a deep eutectic solvent mixture as the core; Preferably, the flame retardant is selected from one or more of melamine, chitosan, magnesium hydroxide, aluminum hydroxide, ammonium polyphosphate, and zinc borate; among them, the degree of polymerization n of ammonium polyphosphate in the flame retardant is > 1500; the degree of deacetylation of chitosan is 80.0 - 95.0%.

3. The dry powder fire extinguishing agent according to claim 1, characterized in that, The deep eutectic solvent is selected from one or more of choline chloride - urea, betaine - lactic acid, ethylene glycol - choline chloride, lactic acid - zinc chloride, sulfamic acid - urea, and glycerol - choline chloride.

4. The dry powder fire extinguishing agent according to claim 1, wherein, The mass ratio of the hydrophobic silica to the core is 1:(15 - 25); the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 3:1 - 1:3; preferably, the mass ratio of the hydrophobic silica to the core is 1:

20.

5. The powder fire extinguishing agent according to claim 2, wherein The mass ratio of the deep eutectic solvent to the flame retardant is 1:(50 - 150); preferably, the mass ratio of the deep eutectic solvent to the flame retardant is 1:

100.

6. A method for preparing the dry powder fire extinguishing agent according to any one of claims 1 to 5, characterized in that, It includes the following steps: Mix the hydrogen bond donor and the hydrogen bond acceptor in a certain proportion, heat until completely miscible to form a deep eutectic solvent; then mix the deep eutectic solvent with hydrophobic silica and carry out mechanical mixing to obtain the powder fire extinguishing agent.

7. The preparation method of the powder fire extinguishing agent according to claim 6, characterized in that, The preparation method further includes uniformly dispersing the flame retardant in the deep eutectic solvent to obtain a deep eutectic solvent mixture, then mixing the deep eutectic solvent mixture with hydrophobic silica and carrying out mechanical mixing to obtain the powder fire extinguishing agent.

8. The preparation method of the powder fire extinguishing agent according to any one of claims 6 to 7, characterized in that, The mechanical mixing means that through a high - speed shearing process, the hydrophobic silica uniformly coats the surface of the deep eutectic solvent mixture; preferably, the rotation speed of the high - speed shearing process is 18000 - 25000 rpm and the time is 0.8 - 1.2 min.

9. Application of the powder fire extinguishing agent according to any one of claims 1 - 5 in extinguishing metal fires or lithium - battery fires.

10. A fire extinguishing device, characterized in that, It includes a container and the powder fire extinguishing agent according to any one of claims 1 - 5 filled therein.

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