Composite solid fire extinguishing agent for lithium battery and preparation method thereof

Abstract

This invention relates to a composite lithium battery solid fire extinguishing agent and its preparation method. The preparation method includes: S1. Preparing layered hydroxides: adding sodium hydroxide and sodium benzoate to water to obtain a sodium benzoate solution; adding magnesium nitrate and aluminum nitrate to water to obtain a precursor solution; adding the precursor solution to the sodium benzoate solution; reacting under a protective gas atmosphere; filtering, washing, and drying to obtain layered hydroxides; S2. Adding a silane coupling agent, layered hydroxides, and ammonium polyphosphate to an ethanol-water mixed solvent to obtain a mixture; stirring and reacting; drying to obtain the composite lithium battery solid fire extinguishing agent. In this invention, the layered hydroxides and ammonium polyphosphates are coupled together by a silane coupling agent. The metal oxides produced by the thermal decomposition of the layered hydroxides can promote the cross-linking between ammonium polyphosphate molecules during thermal degradation, producing polyphosphates with higher viscosity, forming an effective heat-insulating barrier layer, thereby improving the fire extinguishing effect.

Description

Technical Field

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

[0002] In recent years, with the widespread use of electric vehicles, mobile phones, and other electronic products, lithium batteries have become indispensable energy storage devices. However, elevated temperatures in lithium batteries can cause thermal runaway, leading to the combustion of internal battery materials. This accelerates the thermal runaway process and generates even more heat. The heat released during combustion is enormous, which can cause a rapid spread of fire. Furthermore, the fire can release toxic gases, endangering the lives and health of rescue personnel and posing a risk of explosion. Currently, most lithium battery fire extinguishers on the market can only extinguish open flames and cannot effectively prevent repeated reignition of lithium batteries.

[0003] To address the technical problem that most lithium battery fire extinguishers on the market can only extinguish open flames and cannot effectively prevent repeated reignition of lithium batteries, patent document CN111905317A discloses a method for preparing a nano-dispersed lithium battery fire extinguisher. The method first prepares derived polyvinyl alcohol benzyl chloride by reacting polyvinyl alcohol with benzyl chloride. Then, the derived polyvinyl alcohol benzyl chloride is dissolved in a solvent, followed by the addition of a tertiary amine. The tertiary amine undergoes an amination reaction with p-vinylbenzyl chloride groups to form derived polyvinyl alcohol benzyl chloride containing quaternary ammonium groups. After concentration and washing, a nitrogen-based flame-retardant fire extinguishing agent is obtained. The preparation principle is as follows:

[0004]

[0005] The nitrogen-based flame-retardant extinguishing agent prepared by this method contains flame-retardant groups (specifically halogen-containing (chlorine) groups) and endothermic degradation groups (specifically nitrogen-containing groups (quaternary amino groups)). By combining the flame retardancy of halogen-based agents with the endothermic decomposition of nitrogen-based agents, the flame-retardant performance can be greatly improved, preventing repeated reignition of lithium batteries. Specifically, after thermal decomposition, the extinguishing agent easily releases non-flammable gases such as ammonia, nitrogen, nitrogen oxides, and water vapor. The generation of non-flammable gases and the endothermic decomposition of the flame retardant (including the endothermic sublimation of some flame retardants) remove most of the heat, greatly reducing the surface temperature of the polymer. The non-flammable gases such as nitrogen not only dilute the concentration of oxygen in the air and the flammable gases produced by the thermal decomposition of polymers, but also react with oxygen in the air to generate nitrogen, water, and nitrogen oxides, achieving a good flame-retardant effect while consuming oxygen on the material surface. A nano-dispersed lithium battery fire extinguishing agent was prepared by mixing a nitrogen-based flame-retardant fire extinguishing agent with clay minerals. During use, the clay isolates the air, extinguishing open flames. Subsequently, the nitrogen-based flame-retardant fire extinguishing agent in the clay minerals acts as a flame-retardant and cooling agent, thus achieving a synergistic flame-retardant effect between the clay minerals and the nitrogen-based flame retardant, significantly improving fire extinguishing performance and preventing problems such as repeated reignition in lithium battery fires. However, the fire extinguishing agent prepared by this method contains halogens, which can easily corrode metal components during combustion, and also produces toxic gases during the fire extinguishing process, posing a threat to human health. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a composite lithium battery solid fire extinguishing agent and its preparation method, so as to solve the technical problems mentioned above, such as most existing lithium battery fire extinguishing agents can only extinguish open flames and cannot effectively prevent repeated reignition of lithium batteries; fire extinguishing agents contain halogens, which can easily cause corrosion to metal parts during combustion, and produce toxic gases during fire extinguishing, which are harmful to human health.

[0007] In some embodiments, the present invention provides a method for preparing a composite lithium battery solid fire extinguishing agent, comprising:

[0008] S1. Preparation of layered hydroxides: Sodium hydroxide and sodium benzoate are added to water to obtain a sodium benzoate solution;

[0009] Magnesium nitrate and aluminum nitrate were added to water to obtain a precursor solution. The precursor solution was then added to a sodium benzoate solution and reacted under a protective gas atmosphere. The mixture was then filtered, washed, and dried to obtain a layered hydroxide.

[0010] S2. Add silane coupling agent, layered hydroxide and ammonium polyphosphate to an ethanol-water mixed solvent to obtain a mixture, stir to react, and dry to obtain the composite lithium battery solid fire extinguishing agent.

[0011] In this invention, layered hydroxides and ammonium polyphosphate are coupled together using a silane coupling agent. During combustion, the layered hydroxides decompose into carbon dioxide, water, and metal oxides. Carbon dioxide and water dilute combustible gases and oxygen, lowering the combustion temperature. Metal oxides promote the formation of a char layer, acting as an insulator to prevent oxygen and heat transfer. Meanwhile, the thermal decomposition of ammonium polyphosphate produces non-flammable gases that also dilute combustible gases and oxygen. Furthermore, the metal oxides produced by the thermal decomposition of the layered hydroxides promote cross-linking between ammonium polyphosphate molecules during thermal degradation, resulting in more viscous polyphosphate that forms an effective heat-insulating barrier layer, thus improving the fire extinguishing effect. In addition, by introducing benzoic acid groups into the layered hydroxides, the aggregation of the layered hydroxide particles is prevented, improving the dispersibility of the layered hydroxides and further enhancing the fire extinguishing effect.

[0012] In some embodiments, in step S1, the mass ratio of sodium hydroxide to sodium benzoate is 1.5-2:1, preferably 1.8-2:1.

[0013] In some embodiments, in step S1, the molar ratio of magnesium nitrate to aluminum nitrate is 1.7-2.2:1, preferably 1.9-2.1:1.

[0014] In some embodiments, in step S1, the mass ratio of magnesium nitrate to sodium benzoate is 1.5-3:1, preferably 1.8-3:1.

[0015] In some embodiments, in step S1, the reaction temperature is 90-100℃, preferably 95-100℃; the reaction duration is 20-30h, preferably 22-30h.

[0016] In some embodiments, in step S1, the drying temperature is 40-50°C and the drying time is 20-28 hours.

[0017] In some embodiments, the precursor solution in step S1 further includes zinc nitrate.

[0018] In some embodiments, in step S1, the molar ratio of zinc nitrate to aluminum nitrate is 0.8-1.1:1, preferably 0.9-1.1:1.

[0019] In this invention, by adding zinc nitrate to the precursor solution, zinc element that promotes the formation of carbonized film can be introduced into the layered hydroxide, thereby improving the fire extinguishing effect.

[0020] In some embodiments, in step S2, the mass ratio of the silane coupling agent to the layered hydroxide is 0.03-0.05:1, preferably 0.035-0.05:1.

[0021] In some embodiments, in step S2, the mass ratio of the layered hydroxide to ammonium polyphosphate is 0.2-0.4:1, preferably 0.25-0.4:1.

[0022] In some embodiments, in step S2, the temperature of the stirring reaction is 60-80°C, and the duration of the stirring reaction is 1-3 hours, preferably 1.5-3 hours.

[0023] In some embodiments, the mixture in step S2 further includes zinc borate.

[0024] In some embodiments, in step S2, the mass ratio of zinc borate to ammonium polyphosphate is 0.3-0.5:1, preferably 0.35-0.5:1.

[0025] In this invention, the metaphosphoric acid and polyphosphoric acid produced during the decomposition of ammonium polyphosphate can decompose with zinc borate to form an emulsion-like substance that covers the surface of the burning material, forming an effective isolation layer and thus improving the fire extinguishing effect.

[0026] In some embodiments, the present invention also provides a composite lithium battery solid fire extinguishing agent prepared according to the method described above. Detailed Implementation

[0027] The present invention will be further illustrated by specific examples below. 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 illustrating the present invention and cannot 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.

[0028] This invention provides a method for preparing a composite lithium battery solid fire extinguishing agent, comprising:

[0029] S1. Preparation of layered hydroxides: Sodium hydroxide and sodium benzoate are added to water to obtain a sodium benzoate solution, wherein the mass ratio of sodium hydroxide to sodium benzoate is 1.5-2:1;

[0030] Magnesium nitrate and aluminum nitrate were added to water to obtain a precursor solution. The precursor solution was then added to a sodium benzoate solution and reacted at 90-100℃ under a protective atmosphere for 20-30 hours. The mixture was filtered, washed, and dried at 40-50℃ for 20-28 hours to obtain a layered hydroxide. The molar ratio of magnesium nitrate to aluminum nitrate was 1.7-2.2:1, and the mass ratio of magnesium nitrate to sodium benzoate was 1.5-3:1.

[0031] S2. Add silane coupling agent, layered hydroxide and ammonium polyphosphate to an ethanol-water mixed solvent to obtain a mixture. Stir the mixture at 60-80℃ for 1-3 hours, and then dry it to obtain a composite lithium battery solid fire extinguishing agent. The mass ratio of silane coupling agent to layered hydroxide is 0.03-0.05:1, and the mass ratio of layered hydroxide to ammonium polyphosphate is 0.2-0.4:1.

[0032] In some embodiments, the precursor solution in step S1 further includes zinc nitrate, wherein the molar ratio of zinc nitrate to aluminum nitrate is 0.8-1.1:1.

[0033] In some embodiments, the mixture in step S2 further includes zinc borate, wherein the mass ratio of zinc borate to ammonium polyphosphate is 0.3-0.5:1.

[0034] In some embodiments, the present invention also provides a composite lithium battery solid fire extinguishing agent prepared according to the method described above.

[0035] 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.

[0036] Example 1

[0037] A method for preparing a composite lithium battery solid fire extinguishing agent, the specific steps of which are as follows:

[0038] S1. Preparation of layered hydroxides: Sodium hydroxide and sodium benzoate are added to distilled water to obtain a sodium benzoate solution. The mass ratio of sodium hydroxide to sodium benzoate is 1.5:1, and the mass ratio of sodium hydroxide to distilled water is 1.5:40.

[0039] Anhydrous magnesium nitrate and anhydrous aluminum nitrate were added to distilled water to obtain a precursor solution. The molar ratio of anhydrous magnesium nitrate to anhydrous aluminum nitrate was 1.7:1, the mass ratio of anhydrous magnesium nitrate to sodium benzoate was 1.5:1, and the mass ratio of anhydrous magnesium nitrate to distilled water was 1.5:40.

[0040] The precursor solution was added to the sodium benzoate solution and reacted under nitrogen atmosphere and 90°C for 30 h. The mixture was then filtered, washed, and dried at 50°C for 20 h to obtain the layered hydroxide.

[0041] S2. Add silane coupling agent KH151, layered hydroxide, and ammonium polyphosphate to an ethanol-water mixed solvent (ethanol to water volume ratio of 1:1) to obtain a mixture. The mass ratio of silane coupling agent KH151 to layered hydroxide is 0.05:1, the mass ratio of layered hydroxide to ammonium polyphosphate is 0.4:1, and the mass ratio of layered hydroxide to ethanol-water mixed solvent is 0.4:80.

[0042] The reaction was stirred at 80℃ for 1 hour and then dried to obtain a composite lithium battery solid fire extinguishing agent.

[0043] Example 2

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

[0045] S1. Preparation of layered hydroxides: Sodium hydroxide and sodium benzoate are added to distilled water to obtain a sodium benzoate solution. The mass ratio of sodium hydroxide to sodium benzoate is 2:1, and the mass ratio of sodium hydroxide to distilled water is 2:60.

[0046] Anhydrous magnesium nitrate and anhydrous aluminum nitrate were added to distilled water to obtain a precursor solution. The molar ratio of anhydrous magnesium nitrate to anhydrous aluminum nitrate was 2.2:1, the mass ratio of anhydrous magnesium nitrate to sodium benzoate was 3:1, and the mass ratio of anhydrous magnesium nitrate to distilled water was 3:60.

[0047] The precursor solution was added to the sodium benzoate solution and reacted under nitrogen atmosphere and 100°C for 20 h. The mixture was then filtered, washed, and dried at 40°C for 28 h to obtain the layered hydroxide.

[0048] S2. Add silane coupling agent KH151, layered hydroxide, and ammonium polyphosphate to an ethanol-water mixed solvent (ethanol to water volume ratio of 1:1) to obtain a mixture. The mass ratio of silane coupling agent KH151 to layered hydroxide is 0.03:1, the mass ratio of layered hydroxide to ammonium polyphosphate is 0.2:1, and the mass ratio of layered hydroxide to ethanol-water mixed solvent is 0.2:60.

[0049] The reaction was stirred at 60℃ for 3 hours and then dried to obtain a composite lithium battery solid fire extinguishing agent.

[0050] Example 3

[0051] A method for preparing a composite lithium battery solid fire extinguishing agent, the specific steps of which are as follows:

[0052] S1. Preparation of layered hydroxides: Sodium hydroxide and sodium benzoate are added to distilled water to obtain a sodium benzoate solution. The mass ratio of sodium hydroxide to sodium benzoate is 1.8:1, and the mass ratio of sodium hydroxide to distilled water is 1.8:50.

[0053] Anhydrous magnesium nitrate and anhydrous aluminum nitrate were added to distilled water to obtain a precursor solution. The molar ratio of anhydrous magnesium nitrate to anhydrous aluminum nitrate was 2:1, the mass ratio of anhydrous magnesium nitrate to sodium benzoate was 2:1, and the mass ratio of anhydrous magnesium nitrate to distilled water was 2:50.

[0054] The precursor solution was added to the sodium benzoate solution and reacted under nitrogen atmosphere and 95°C for 25 h. The mixture was then filtered, washed, and dried at 45°C for 24 h to obtain the layered hydroxide.

[0055] S2. Add silane coupling agent KH151, layered hydroxide, and ammonium polyphosphate to an ethanol-water mixed solvent (ethanol to water volume ratio of 1:1) to obtain a mixture. The mass ratio of silane coupling agent KH151 to layered hydroxide is 0.04:1, the mass ratio of layered hydroxide to ammonium polyphosphate is 0.3:1, and the mass ratio of layered hydroxide to ethanol-water mixed solvent is 0.3:70.

[0056] The reaction was stirred at 70℃ for 2 hours and then dried to obtain a composite lithium battery solid fire extinguishing agent.

[0057] Example 4

[0058] The difference between this embodiment and embodiment 3 is as follows:

[0059] S1. Preparation of layered hydroxides: Sodium hydroxide and sodium benzoate are added to distilled water to obtain a sodium benzoate solution. The mass ratio of sodium hydroxide to sodium benzoate is 1.8:1, and the mass ratio of sodium hydroxide to distilled water is 1.8:50.

[0060] Anhydrous magnesium nitrate, anhydrous aluminum nitrate, and anhydrous zinc nitrate were added to distilled water to obtain a precursor solution. The molar ratio of anhydrous magnesium nitrate to anhydrous aluminum nitrate was 2:1, the mass ratio of anhydrous magnesium nitrate to sodium benzoate was 2:1, the mass ratio of anhydrous magnesium nitrate to distilled water was 2:50, and the molar ratio of anhydrous zinc nitrate to anhydrous aluminum nitrate was 1:1.

[0061] The precursor solution was added to the sodium benzoate solution and reacted under nitrogen atmosphere and 95°C for 25 h. The mixture was then filtered, washed, and dried at 45°C for 24 h to obtain the layered hydroxide.

[0062] The difference between this embodiment and Example 3 is that the precursor solution also contains anhydrous zinc nitrate.

[0063] Example 5

[0064] The difference between this embodiment and embodiment 3 is as follows:

[0065] S2. Add silane coupling agent KH151, layered hydroxide, ammonium polyphosphate, and zinc borate to an ethanol-water mixed solvent (ethanol to water volume ratio of 1:1) to obtain a mixture. The mass ratio of silane coupling agent KH151 to layered hydroxide is 0.04:1, the mass ratio of layered hydroxide to ammonium polyphosphate is 0.3:1, the mass ratio of layered hydroxide to ethanol-water mixed solvent is 0.3:70, and the mass ratio of zinc borate to ammonium polyphosphate is 0.4:1.

[0066] The reaction was stirred at 70℃ for 2 hours and then dried to obtain a composite lithium battery solid fire extinguishing agent.

[0067] The difference between this embodiment and Embodiment 3 is that the mixture also contains zinc borate.

[0068] Comparative Example 1

[0069] A lithium battery solid fire extinguishing agent is prepared according to the following steps:

[0070] Sodium hydroxide and sodium benzoate were added to distilled water to obtain a sodium benzoate solution. The mass ratio of sodium hydroxide to sodium benzoate was 1.5:1, and the mass ratio of sodium hydroxide to distilled water was 1.5:40.

[0071] Anhydrous magnesium nitrate and anhydrous aluminum nitrate were added to distilled water to obtain a precursor solution. The molar ratio of anhydrous magnesium nitrate to anhydrous aluminum nitrate was 1.7:1, the mass ratio of anhydrous magnesium nitrate to sodium benzoate was 1.5:1, and the mass ratio of anhydrous magnesium nitrate to distilled water was 1.5:40.

[0072] The precursor solution was added to the sodium benzoate solution and reacted under nitrogen atmosphere and 90°C for 30 h. After filtration, washing, and drying at 50°C for 20 h, a layered hydroxide was obtained, which is the solid fire extinguishing agent for lithium batteries.

[0073] The difference between this comparative example and Example 1 is that: instead of the treatment in step S2, the layered hydroxide obtained in step S1 is used directly as the solid fire extinguishing agent for lithium batteries.

[0074] Comparative Example 2

[0075] A lithium battery solid fire extinguishing agent is prepared according to the following steps:

[0076] Add silane coupling agent KH151 and ammonium polyphosphate to an ethanol-water mixed solvent (ethanol to water volume ratio of 1:1) to obtain a mixture. The mass ratio of silane coupling agent KH151 to ammonium polyphosphate is 0.05:2.5, and the mass ratio of silane coupling agent KH151 to ethanol-water mixed solvent is 0.05:200.

[0077] The reaction was stirred at 80℃ for 1 hour and then dried to obtain a composite lithium battery solid fire extinguishing agent.

[0078] The difference between this comparative example and Example 1 is that no layered hydroxide was added to the mixture in step S2.

[0079] Performance testing

[0080] Fire extinguishing simulation tests were conducted on the composite lithium battery solid fire extinguishing agents prepared in Examples 1-5 and the lithium battery solid fire extinguishing agents prepared in Comparative Examples 1-2 respectively: the fire was sprayed on the fire part of the lithium battery of the electric vehicle. Specifically, three 3.7V batteries were used, the spraying distance was not more than 700m, the package weight was 1kg, the maximum diameter of the initial flame was 600mm, and the fire extinguishing time was recorded. The results are shown in Table 1.

[0081] Table 1 Test Results

[0082] Group Firefighting time, s Example 1 19 Example 2 18 Example 3 15 Example 4 9 Example 5 7 Comparative Example 1 33 Comparative Example 2 25

[0083] As shown in Table 1, compared with Comparative Example 1 (without step S2 treatment), the fire extinguishing time of Example 1 is significantly shortened. This indicates that in this invention, the layered hydroxide and ammonium polyphosphate are coupled together using a silane coupling agent. During combustion, the layered hydroxide decomposes into substances such as carbon dioxide, water, and metal oxides. Carbon dioxide and water dilute combustible gases and oxygen, lowering the combustion temperature, while metal oxides facilitate the formation of a char layer, effectively isolating oxygen and heat. Compared with Comparative Example 2 (where layered hydroxide was not added to the mixture in step S2), the fire extinguishing time of Example 1 is significantly shortened. This indicates that in this invention, the layered hydroxide and ammonium polyphosphate are coupled together using a silane coupling agent. During the thermal decomposition of ammonium polyphosphate, non-flammable gases are generated, which dilute combustible gases and oxygen. Based on Examples 1, 1, and 2, it is evident that in this invention, layered hydroxides and ammonium polyphosphate are coupled together using a silane coupling agent. During combustion, the layered hydroxides decompose into carbon dioxide, water, and metal oxides. Carbon dioxide and water dilute combustible gases and oxygen, lowering the combustion temperature. Metal oxides facilitate the formation of a char layer, acting as an insulator against oxygen and heat. Meanwhile, the thermal decomposition of ammonium polyphosphate produces non-flammable gases, which further dilute combustible gases and oxygen. Furthermore, the metal oxides produced by the thermal decomposition of the layered hydroxides promote cross-linking between ammonium polyphosphate molecules during thermal degradation, resulting in more viscous polyphosphate that forms an effective heat-insulating barrier layer, thereby improving the fire extinguishing effect. Additionally, introducing benzoic acid groups into the layered hydroxides prevents particle agglomeration, improving the dispersibility of the layered hydroxides and further enhancing the fire extinguishing effect.

[0084] As shown in Table 1, compared with Example 3 (without zinc nitrate added to the precursor solution), the extinguishing time of Example 4 (with zinc nitrate added to the precursor solution) was significantly shortened. This indicates that the present invention, by adding zinc nitrate to the precursor solution, can introduce zinc element, which promotes the formation of a carbon film, into the layered hydroxide, thereby improving the extinguishing effect.

[0085] As shown in Table 1, compared with Example 3 (mixture without zinc borate), the extinguishing time of Example 5 (mixture with zinc borate) was significantly shortened. This indicates that in this invention, the metaphosphoric acid and polyphosphoric acid produced during the decomposition of ammonium polyphosphate can react with zinc borate to form an emulsion-like substance that covers the surface of the burning material, forming an effective insulating layer and thus improving the extinguishing effect.

[0086] 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 composite lithium battery solid fire extinguishing agent, characterized in that, include: S1. Preparation of layered hydroxides: Sodium hydroxide and sodium benzoate are added to water to obtain a sodium benzoate solution; Magnesium nitrate and aluminum nitrate were added to water to obtain a precursor solution. The precursor solution was then added to a sodium benzoate solution and reacted under a protective gas atmosphere. The mixture was then filtered, washed, and dried to obtain a layered hydroxide. S2. Add silane coupling agent, layered hydroxide and ammonium polyphosphate to an ethanol-water mixed solvent to obtain a mixture, stir to react, and dry to obtain the composite lithium battery solid fire extinguishing agent.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of sodium hydroxide to sodium benzoate is 1.5-2:1; And / or, in step S1, the molar ratio of magnesium nitrate to aluminum nitrate is 1.7-2.2:1; And / or, in step S1, the mass ratio of magnesium nitrate to sodium benzoate is 1.5-3:

1.

3. The preparation method according to claim 1, characterized in that, In step S1, the reaction temperature is 90-100℃ and the reaction time is 20-30h; And / or, in step S1, the drying temperature is 40-50℃ and the drying time is 20-28h.

4. The preparation method according to claim 1, characterized in that, The precursor solution in step S1 also includes zinc nitrate.

5. The preparation method according to claim 4, characterized in that, In step S1, the molar ratio of zinc nitrate to aluminum nitrate is 0.8-1.1:

1.

6. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of the silane coupling agent to the layered hydroxide is 0.03-0.05:1; And / or, in step S2, the mass ratio of the layered hydroxide to ammonium polyphosphate is 0.2-0.4:

1.

7. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the stirring reaction is 60-80℃, and the stirring reaction time is 1-3h.

8. The preparation method according to claim 1, characterized in that, The mixture in step S2 also includes zinc borate.

9. The preparation method according to claim 8, characterized in that, In step S2, the mass ratio of zinc borate to ammonium polyphosphate is 0.3-0.5:

1.

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

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