Lithium battery fire extinguishing agent, preparation method and application thereof

Abstract

This invention belongs to the field of fire extinguishing agent technology, specifically relating to a lithium battery fire extinguishing agent, its preparation method, and its application. The preparation method includes: S1. Aluminum oxalate modification: Aluminum oxalate, trimethylmethoxysilane, and melamine cyanurate are added to water under stirring, heated to react, filtered, and dried to obtain modified aluminum oxalate; S2. Modified aluminum oxalate is added to a water-ethanol mixed solvent, stirred evenly, and then a foaming agent, emulsifier, and talc are added to obtain a mixture. After stirring, the mixture is poured into a container, and gas is introduced into the container under pressure. This invention couples aluminum oxalate and melamine cyanurate together via trimethylmethoxysilane, introducing cyanamide groups into the aluminum oxalate. The cyanamide groups decompose upon heating to produce charcoal and non-combustible gases such as nitrogen and carbon dioxide. These gases dilute the oxygen concentration, thereby reducing the fire spread rate and further enhancing the fire extinguishing effect.

Description

Technical Field

[0001] This invention belongs to the field of fire extinguishing agent technology, specifically relating to a lithium battery fire extinguishing agent, its preparation method, and its application. Background Technology

[0002] New energy vehicles have advantages such as being clean, energy-saving, and efficient. However, safety accidents involving new energy vehicles occur frequently. This is because new energy vehicles generally use lithium batteries as their energy source. Lithium batteries have high energy density, and once a battery experiences a short circuit, overcharge, impact, or compression, it can cause thermal runaway, which can easily lead to a fire. In addition, lithium batteries have high combustion temperatures and fast combustion speeds, producing a large amount of harmful and toxic fumes. There is also a risk of explosion during combustion, making the fire difficult to extinguish and posing a great safety hazard.

[0003] To address the aforementioned technical problems, patent document CN113262420B discloses a fire extinguishing agent for lithium batteries. This fire extinguishing agent comprises 30-50 parts by weight of clay with a particle size of 500-600 mesh, 2-6 parts by weight of a foaming agent, 35-70 parts by weight of water, silicone oil, and ethylene glycol. The amount of silicone oil is 1wt%-3wt% based on the total mass of the clay, foaming agent, and water. The amount of ethylene glycol is 0.5wt%-1wt% based on the total mass of the clay, foaming agent, and water. The foaming agent is a mixture selected from sodium dodecyl sulfate and pine oil, with a mass ratio of sodium dodecyl sulfate to pine oil of 1:1-3. When used, this fire extinguishing agent forms a clay aerosol to effectively cover the burning area. However, this extinguishing agent is an aerosol extinguishing agent, which cannot suppress the spread of thermal runaway within the module. The continuous release of a large amount of smoke causes heat to accumulate rapidly in the confined space, making the battery module prone to reignition. Furthermore, the extinguishing time of this extinguishing agent is relatively long, and its extinguishing performance needs to be further improved. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a lithium battery fire extinguishing agent, its preparation method and application, in order to solve the technical problems that the above-mentioned fire extinguishing agent cannot suppress the spread of thermal runaway in the module, the continuous release of a large amount of smoke causes heat to rise rapidly in a limited space, the battery module is prone to reignition, and the fire extinguishing agent has a long extinguishing time and the fire extinguishing performance needs to be further improved.

[0005] In some embodiments, the present invention provides a method for preparing a lithium battery fire extinguishing agent, comprising:

[0006] S1. Modified aluminum oxalate: Add aluminum oxalate, trimethylmethoxysilane and melamine cyanurate to water under stirring, heat to react, filter, and dry to obtain modified aluminum oxalate;

[0007] S2. Add modified aluminum oxalate to a water-ethanol mixed solvent, stir evenly, then add foaming agent, emulsifier and talc to obtain a mixture, stir and pour into a container, then introduce gas into the container to pressurize it, thus obtaining the fire extinguishing agent.

[0008] When using the lithium battery fire extinguishing agent of this invention, aluminum oxalate can absorb heat from the combustion zone, reducing its temperature. It can also decompose upon heating to produce carbon dioxide, carbon monoxide, and aluminum oxide with a high melting point. The aluminum oxide covers the surface of the burning material, insulating it from heat and thus extinguishing the fire. Carbon dioxide dilutes the oxygen concentration, enhancing the extinguishing effect. By coupling aluminum oxalate with melamine cyanurate via trimethylmethoxysilane, cyanamide groups are introduced into the aluminum oxalate. These cyanamide groups decompose upon heating to produce charcoal and non-combustible gases such as nitrogen and carbon dioxide. These gases dilute the oxygen concentration, reducing the fire's spread and further enhancing the extinguishing effect. Furthermore, trimethylmethoxysilane generates a carbon protective layer containing -Si-O bonds during heating. This protective layer isolates oxygen and heat transfer, further enhancing the extinguishing effect.

[0009] In some embodiments, in step S1, the mass ratio of trimethylmethoxysilane to aluminum oxalate is 0.01-0.05:1, preferably 0.02-0.05:1.

[0010] In some embodiments, in step S1, the mass ratio of melamine cyanurate to aluminum oxalate is 0.7-1:1, preferably 0.75-1:1.

[0011] In some embodiments, in step S1, the temperature of the heating reaction is 90-110°C, preferably 100-110°C; and the duration of the heating reaction is 1-3 hours, preferably 1.5-3 hours.

[0012] In some embodiments, in step S2, the foaming agent includes fatty alcohol polyoxyethylene ether sulfate, alkyl polysaccharide glycoside, or a combination of both.

[0013] In some embodiments, the foaming agent comprises fatty alcohol polyoxyethylene ether sulfate and alkyl polysaccharide glycoside.

[0014] In some embodiments, the mass ratio of the fatty alcohol polyoxyethylene ether sulfate to the alkyl polysaccharide is 1:3-5, preferably 1:4-5.

[0015] In this application, the combination of fatty alcohol polyoxyethylene ether sulfate and alkyl polysaccharide glycoside can improve the wetting ability of water, reduce the surface tension of water, increase the wetting power of water, prolong the action time of water, and improve the fire extinguishing effect.

[0016] In some embodiments, in step S2, the mass ratio of the water-ethanol mixed solvent to the modified aluminum oxalate is 30-60:2-5, preferably 30-60:3-5.

[0017] In some embodiments, in the water-ethanol mixed solvent of step S2, the volume ratio of water to ethanol is 3-5:1.

[0018] In some embodiments, in step S2, the mass ratio of the foaming agent to the modified aluminum oxalate is 1-1.5:2-5, preferably 1.2-1.5:2-5.

[0019] In some embodiments, in step S2, the mass ratio of talc to modified aluminum oxalate is 6-10:2-5, preferably 7-10:2-5.

[0020] In some embodiments, in step S2, the mass ratio of the emulsifier to the modified aluminum oxalate is 0.8-1.3:2-5, preferably 0.9-1.3:2-5.

[0021] In some embodiments, the mass ratio of deionized water-ethanol mixed solvent to modified aluminum oxalate is 15-20:2-5, preferably 16-20:2-5.

[0022] In some embodiments, the mixture in step S2 further includes triphenyl phosphate.

[0023] In some embodiments, in step S2, the mass ratio of triphenyl phosphate to modified aluminum oxalate is 0.1-0.2:2-5, preferably 0.12-0.2:2-5.

[0024] When using the extinguishing agent of this application, triphenyl phosphate can promote the formation of char, and trimethylmethoxysilane can increase the stability of the char layer formed by the char, thereby further improving the extinguishing effect.

[0025] In some embodiments, the mixture in step S2 further includes a drag-reducing agent.

[0026] In some embodiments, the drag-reducing agent comprises a polyacrylamide emulsion.

[0027] In some embodiments, in step S2, the mass ratio of the drag-reducing agent to the modified aluminum oxalate is 0.6-1:2-5, preferably 0.7-1:2-5.

[0028] In this application, polyacrylamide emulsion can reduce the resistance of the extinguishing agent during the water hose transportation process, reduce the pressure loss of the extinguishing agent during the flow of the extinguishing agent during the water hose transportation process, increase the pressure of the extinguishing agent at the end nozzle, and thus improve the fire extinguishing effect.

[0029] In some embodiments, this application also provides a lithium battery fire extinguishing agent prepared according to the preparation method described above.

[0030] In some embodiments, this application provides the use of lithium battery fire extinguishing agents prepared according to the preparation method described above and / or lithium battery fire extinguishing agents as described above in lithium battery fire extinguishing. Detailed Implementation

[0031] The present invention will be further illustrated below through specific examples. However, it should be noted that the specific material ratios, process conditions, and results described in the embodiments of the present invention are only for illustrative purposes and should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention. It should be noted that, unless otherwise specified, all parts mentioned in the present invention refer to parts by weight.

[0032] This invention provides a method for preparing a lithium battery fire extinguishing agent, comprising:

[0033] S1. Modification of aluminum oxalate: Add aluminum oxalate, trimethylmethoxysilane and melamine cyanurate to water under stirring. The mass ratio of trimethylmethoxysilane to aluminum oxalate is 0.01-0.05:1, and the mass ratio of melamine cyanurate to aluminum oxalate is 0.7-1:1. Heat the mixture at 90-110℃ for 1-3 hours, filter, and dry to obtain modified aluminum oxalate.

[0034] S2. Add modified aluminum oxalate to a water-ethanol mixed solvent, stir evenly, then add foaming agent, emulsifier and talc to obtain a mixture. The mass ratio of water-ethanol mixed solvent to modified aluminum oxalate is 30-60:2-5, the mass ratio of foaming agent to modified aluminum oxalate is 1-1.5:2-5, the mass ratio of talc to modified aluminum oxalate is 6-10:2-5, the mass ratio of emulsifier to modified aluminum oxalate is 0.8-1.3:2-5, and the volume ratio of water to ethanol in the water-ethanol mixed solvent is 3-5:1.

[0035] After stirring, the mixture is poured into a container, and gas is introduced into the container to pressurize it, thus obtaining the lithium battery fire extinguishing agent.

[0036] The foaming agent includes fatty alcohol polyoxyethylene ether sulfate, alkyl polysaccharide glycoside, or a combination thereof, and the emulsifier includes sorbitan monooleate.

[0037] In some embodiments, the foaming agent includes fatty alcohol polyoxyethylene ether sulfate and alkyl polysaccharide glycoside, wherein the mass ratio of fatty alcohol polyoxyethylene ether sulfate to alkyl polysaccharide glycoside is 1:3-5.

[0038] In some embodiments, the mixture in step S2 further includes triphenyl phosphate, wherein the mass ratio of triphenyl phosphate to modified aluminum oxalate is 0.1-0.2:2-5.

[0039] In some embodiments, the mixture in step S2 further includes a drag-reducing agent, which includes a polyacrylamide emulsion, and the mass ratio of the drag-reducing agent to the modified aluminum oxalate is 0.6-1:2-5.

[0040] In some embodiments, this application also provides a lithium battery fire extinguishing agent prepared according to the preparation method described above.

[0041] In some embodiments, this application also provides the use of lithium battery fire extinguishing agents prepared according to the preparation method described above and / or the lithium battery fire extinguishing agents described above in lithium battery fire extinguishing.

[0042] The present invention will be described in detail below through specific examples and embodiments. It should also be understood that the following embodiments are only for specific illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0043] Example 1

[0044] A method for preparing a lithium battery fire extinguishing agent, the specific steps of which are as follows:

[0045] S1. Modification of aluminum oxalate: Aluminum oxalate, trimethylmethoxysilane and melamine cyanurate were added to deionized water under stirring. The mass ratio of trimethylmethoxysilane to aluminum oxalate was 0.01:1, the mass ratio of melamine cyanurate to aluminum oxalate was 0.7:1, and the mass ratio of deionized water to aluminum oxalate was 20:1. The mixture was heated at 110℃ for 1 hour, filtered, and dried to obtain modified aluminum oxalate.

[0046] S2. Add modified aluminum oxalate to a deionized water-ethanol mixed solvent (volume ratio of deionized water to ethanol is 5:1), with a mass ratio of deionized water-ethanol mixed solvent to modified aluminum oxalate of 15:5.

[0047] After stirring evenly, add the foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES), the emulsifier sorbitan monooleate, and talc to obtain a mixture. The mass ratio of foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES) to modified aluminum oxalate is 1:5, the mass ratio of emulsifier sorbitan monooleate to modified aluminum oxalate is 0.8:5, and the mass ratio of talc to modified aluminum oxalate is 10:5.

[0048] After stirring, the mixture is poured into a container, and nitrogen gas is introduced into the container to pressurize it to 0.8 MPa, thus obtaining the lithium battery fire extinguishing agent.

[0049] Example 2

[0050] A method for preparing a lithium battery fire extinguishing agent, the specific steps of which are as follows:

[0051] S1. Modification of aluminum oxalate: Aluminum oxalate, trimethylmethoxysilane and melamine cyanurate were added to deionized water under stirring. The mass ratio of trimethylmethoxysilane to aluminum oxalate was 0.05:1, the mass ratio of melamine cyanurate to aluminum oxalate was 1:1, and the mass ratio of deionized water to aluminum oxalate was 10:1. The mixture was heated at 90°C for 3 hours, filtered, and dried to obtain modified aluminum oxalate.

[0052] S2. Add modified aluminum oxalate to a deionized water-ethanol mixed solvent (the volume ratio of deionized water to ethanol is 3:1), with the mass ratio of the deionized water-ethanol mixed solvent to the modified aluminum oxalate being 20:2.

[0053] After stirring evenly, add the foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES), the emulsifier sorbitan monooleate, and talc to obtain a mixture. The mass ratio of foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES) to modified aluminum oxalate is 1.5:2, the mass ratio of emulsifier sorbitan monooleate to modified aluminum oxalate is 1.3:2, and the mass ratio of talc to modified aluminum oxalate is 6:2.

[0054] After stirring, the mixture is poured into a container, and nitrogen gas is introduced into the container to pressurize it to 0.8 MPa, thus obtaining the lithium battery fire extinguishing agent.

[0055] Example 3

[0056] The difference between this embodiment and Embodiment 1 is that:

[0057] S2. Add modified aluminum oxalate to a deionized water-ethanol mixed solvent (volume ratio of deionized water to ethanol is 5:1), with a mass ratio of deionized water-ethanol mixed solvent to modified aluminum oxalate of 15:5.

[0058] After stirring evenly, add the foaming agent decyl glucoside APG0810, the emulsifier sorbitan monooleate, and talc to obtain a mixture. The mass ratio of foaming agent decyl glucoside APG0810 to modified aluminum oxalate is 1:5, the mass ratio of emulsifier sorbitan monooleate to modified aluminum oxalate is 0.8:5, and the mass ratio of talc to modified aluminum oxalate is 10:5.

[0059] After stirring, the mixture is poured into a container, and nitrogen gas is introduced into the container to pressurize it to 0.8 MPa, thus obtaining the lithium battery fire extinguishing agent.

[0060] The difference between the two is that the foaming agent used is decyl glucoside APG0810.

[0061] Example 4

[0062] The difference between this embodiment and Embodiment 1 is that:

[0063] S2. Add modified aluminum oxalate to a deionized water-ethanol mixed solvent (volume ratio of deionized water to ethanol is 5:1), with a mass ratio of deionized water-ethanol mixed solvent to modified aluminum oxalate of 15:5.

[0064] After stirring evenly, add foaming agent (composed of sodium fatty alcohol polyoxyethylene ether sulfate AES and decyl glucoside APG0810 in a mass ratio of 1:4), emulsifier sorbitan monooleate, and talc to obtain a mixture. The mass ratio of foaming agent to modified aluminum oxalate is 1:5, the mass ratio of emulsifier sorbitan monooleate to modified aluminum oxalate is 0.8:5, and the mass ratio of talc to modified aluminum oxalate is 10:5.

[0065] After stirring, the mixture is poured into a container, and nitrogen gas is introduced into the container to pressurize it to 0.8 MPa, thus obtaining the lithium battery fire extinguishing agent.

[0066] Example 5

[0067] The difference between this embodiment and Embodiment 1 is that:

[0068] S2. Add modified aluminum oxalate to a deionized water-ethanol mixed solvent (volume ratio of deionized water to ethanol is 5:1), with a mass ratio of deionized water-ethanol mixed solvent to modified aluminum oxalate of 15:5.

[0069] After stirring evenly, add the foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES), the emulsifier sorbitan monooleate, talc, and triphenyl phosphate to obtain a mixture. The mass ratio of foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES) to modified aluminum oxalate is 1:5, the mass ratio of talc to modified aluminum oxalate is 10:5, the mass ratio of emulsifier sorbitan monooleate to modified aluminum oxalate is 0.8:5, and the mass ratio of triphenyl phosphate to modified aluminum oxalate is 0.15:5.

[0070] After stirring, the mixture is poured into a container, and nitrogen gas is introduced into the container to pressurize it to 0.8 MPa, thus obtaining the lithium battery fire extinguishing agent.

[0071] The difference between the two is that the mixture also contains triphenyl phosphate.

[0072] Example 6

[0073] The difference between this embodiment and Embodiment 1 is that:

[0074] S2. Add modified aluminum oxalate to a deionized water-ethanol mixed solvent (volume ratio of deionized water to ethanol is 5:1), with a mass ratio of deionized water-ethanol mixed solvent to modified aluminum oxalate of 15:5.

[0075] After stirring evenly, add the foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES), the emulsifier sorbitan monooleate, talc, and polyacrylamide emulsion BIBO-PAM to obtain a mixture. The mass ratio of foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES) to modified aluminum oxalate is 1:5, the mass ratio of talc to modified aluminum oxalate is 10:5, the mass ratio of emulsifier sorbitan monooleate to modified aluminum oxalate is 0.8:5, and the mass ratio of polyacrylamide emulsion BIBO-PAM to modified aluminum oxalate is 0.8:5.

[0076] After stirring, the mixture is poured into a container, and nitrogen gas is introduced into the container to pressurize it to 0.8 MPa, thus obtaining the lithium battery fire extinguishing agent.

[0077] The difference between the two is that the mixture also includes polyacrylamide emulsion.

[0078] Comparative Example 1

[0079] A method for preparing a lithium battery fire extinguishing agent, the specific steps of which are as follows:

[0080] Aluminum oxalate was added to a deionized water-ethanol mixed solvent (the volume ratio of deionized water to ethanol was 5:1), and the mass ratio of the deionized water-ethanol mixed solvent to aluminum oxalate was 15:5.

[0081] After stirring evenly, add the foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES), the emulsifier sorbitan monooleate, and talc to obtain a mixture. The mass ratio of foaming agent sodium fatty alcohol polyoxyethylene ether sulfate (AES) to aluminum oxalate is 1:5, the mass ratio of emulsifier sorbitan monooleate to aluminum oxalate is 0.8:5, and the mass ratio of talc to aluminum oxalate is 10:5.

[0082] After stirring, the mixture is poured into a container, and nitrogen gas is introduced into the container to pressurize it to 0.8 MPa, thus obtaining the lithium battery fire extinguishing agent.

[0083] The difference between this comparative example and Example 1 is that aluminum oxalate was not modified.

[0084] Fire extinguishing performance testing

[0085] Fire extinguishing simulation tests were conducted on the lithium battery fire extinguishing agents of Examples 1-6 and Comparative Example 1 respectively: the fire-prone parts of the lithium battery of the electric vehicle were sprayed, specifically using 3 3.7V batteries, the spraying distance was no more than 700m, the package weight was 1kg, and the maximum diameter of the initial flame was 600mm. The results are shown in Table 1.

[0086] Table 1 Test Results

[0087] Group Firefighting time, s Example 1 18 Example 2 21 Example 3 20 Example 4 13 Example 5 11 Example 6 14 Comparative Example 1 31

[0088] As shown in Table 1, compared with Comparative Example 1, the extinguishing time of Examples 1-6 was significantly shortened. This indicates that the present invention significantly improves the extinguishing effect of lithium battery fire extinguishing agents.

[0089] As shown in Table 1, compared with Comparative Example 1 (without modification of aluminum oxalate), the fire extinguishing time of Example 1 (with modification of aluminum oxalate) was significantly shortened. The results show that when using the extinguishing agent of the present invention, aluminum oxalate can absorb heat from the combustion zone, reduce the temperature of the combustion zone, and decompose upon heating to produce carbon dioxide, carbon monoxide, and aluminum oxide with a high melting point. The aluminum oxide covers the surface of the burning material to insulate against heat, thus playing a role in extinguishing the fire. Carbon dioxide can dilute the oxygen concentration and improve the extinguishing effect. By coupling aluminum oxalate with melamine cyanurate through trimethylmethoxysilane, cyanamide groups can be introduced into aluminum oxalate. The cyanamide groups decompose upon heating to produce carbides and non-combustible gases such as nitrogen and carbon dioxide. These gases can dilute the oxygen concentration and react with oxygen to produce nitrogen oxides, hydroxides, etc., thereby reducing the fire spread rate and further improving the extinguishing effect. In addition, trimethylmethoxysilane generates a carbon protective layer containing -Si-O- bonds during heating. This protective layer insulates against oxygen and heat transfer, thereby further improving the extinguishing effect.

[0090] As shown in Table 1, compared with Example 1 (using sodium fatty alcohol polyoxyethylene ether sulfate as the foaming agent) and Example 3 (using decyl glucoside as the foaming agent), the extinguishing time of Example 4 (the foaming agent is composed of sodium fatty alcohol polyoxyethylene ether sulfate and decyl glucoside in a mass ratio of 1:4) was significantly shortened. This result indicates that the combined use of fatty alcohol polyoxyethylene ether sulfate and alkyl polysaccharide glycosides can improve the wetting ability of water, reduce the surface tension of water, increase the wetting power of water, prolong the action time of water, and improve the extinguishing effect.

[0091] As shown in Table 1, compared with Example 1 (without triphenyl phosphate in the mixture), the extinguishing time of Example 5 (with triphenyl phosphate in the mixture) was significantly shortened. This result indicates that when using the extinguishing agent of this application, triphenyl phosphate promotes the formation of charcoal, and trimethylmethoxysilane increases the stability of the char layer formed by the charcoal, thereby further improving the extinguishing effect.

[0092] As shown in Table 1, compared with Example 1 (no polyacrylamide emulsion was added to the mixture), the extinguishing time of Example 5 (polyacrylamide emulsion was added to the mixture) was significantly shortened. This result indicates that polyacrylamide emulsion can reduce the resistance of the extinguishing agent during hose delivery, reduce the pressure loss of the extinguishing agent during hose delivery, and increase the pressure of the extinguishing agent at the end nozzle, thereby improving the extinguishing effect.

[0093] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a lithium battery fire extinguishing agent, characterized in that, include: S1. Modified aluminum oxalate: Add aluminum oxalate, trimethylmethoxysilane and melamine cyanurate to water under stirring, heat to react, filter, and dry to obtain modified aluminum oxalate; S2. Add modified aluminum oxalate to a water-ethanol mixed solvent, stir evenly, then add foaming agent, emulsifier and talc to obtain a mixture, stir and pour into a container, then introduce gas into the container to pressurize it, thus obtaining the fire extinguishing agent.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of trimethylmethoxysilane to aluminum oxalate is 0.01-0.05:1; And / or, in step S1, the mass ratio of melamine cyanurate to aluminum oxalate is 0.7-1:1; And / or, in step S1, the temperature of the heating reaction is 90-110°C, and the duration of the heating reaction is 1-3 hours; And / or, in step S2, the foaming agent includes fatty alcohol polyoxyethylene ether sulfate, alkyl polysaccharide glycoside, or a combination of both; And / or, in step S2, the emulsifier includes sorbitan monooleate.

3. The preparation method according to claim 2, characterized in that, The foaming agent includes fatty alcohol polyoxyethylene ether sulfate and alkyl polysaccharide glycoside.

4. The preparation method according to claim 3, characterized in that, The mass ratio of fatty alcohol polyoxyethylene ether sulfate to alkyl polysaccharide is 1:3-5.

5. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of the water-ethanol mixed solvent to the modified aluminum oxalate is 30-60:2-5; And / or, in step S2, the mass ratio of the foaming agent to the modified aluminum oxalate is 1-1.5:2-5; And / or, in step S2, the mass ratio of talc to modified aluminum oxalate is 6-10:2-5; And / or, in step S2, the mass ratio of the emulsifier to the modified aluminum oxalate is 0.8-1.3:2-5.

6. The preparation method according to claim 1, characterized in that, The mixture in step S2 also includes triphenyl phosphate; And / or, the mixture in step S2 may also include a drag-reducing agent.

7. The preparation method according to claim 6, characterized in that, In step S2, the mass ratio of triphenyl phosphate to modified aluminum oxalate is 0.1-0.2:2-5.

8. The preparation method according to claim 6, characterized in that, In step S2, the drag-reducing agent includes a polyacrylamide emulsion; And / or, in step S2, the mass ratio of the drag-reducing agent to the modified aluminum oxalate is 0.6-1:2-5.

9. A lithium battery fire extinguishing agent prepared by the preparation method according to any one of claims 1-8.

10. The application of the lithium battery fire extinguishing agent prepared by the preparation method according to any one of claims 1-8 and / or the lithium battery fire extinguishing agent according to claim 9 in lithium battery fire extinguishing.