A fire-resistant foam extinguishing agent for lithium batteries and its preparation method

Abstract

This invention discloses an anti-burning foam fire extinguishing agent for lithium batteries and its preparation method, relating to the field of fire extinguishing agent technology. The anti-burning foam fire extinguishing agent for lithium batteries prepared by this invention mainly comprises a foaming agent system, a foam stabilizer, and a heat-absorbing material. The foaming agent system contains sodium perfluorocrown ether sulfonate, the foam stabilizer is modified silica, and the heat-absorbing material contains modified microcapsules. The anti-burning foam fire extinguishing agent for lithium batteries prepared by this invention exhibits good foam stability and fire extinguishing performance.

Description

Technical Field

[0001] This invention relates to the field of fire extinguishing agent technology, specifically to an anti-burning foam fire extinguishing agent for lithium batteries and its preparation method. Background Technology

[0002] The prevention and control of lithium battery fires is a major challenge facing the global new energy industry. Existing foam fire extinguishing agents have significant shortcomings in dealing with the thermal runaway of lithium batteries. Traditional foam fire extinguishing agents mainly form an air foam covering layer through foaming agents and foam stabilizers, and achieve fire extinguishing by utilizing the dual mechanism of isolating oxygen and absorbing heat to cool down. Its core components usually include fluorocarbon surfactants, polysaccharide thickeners, and inorganic salts (such as sodium bicarbonate).

[0003] These types of fire extinguishing agents are effective against conventional liquid fuel fires (such as gasoline and diesel), but they reveal three serious shortcomings in lithium battery fire scenarios: First, the interfacial stability of conventional foam is doubly damaged by high temperatures and organic solvents in the electrolyte (such as carbonates); second, the heat capacity of traditional heat-absorbing materials is insufficient, and existing fire extinguishing agents cannot absorb enough heat in a very short time to interrupt the chain reaction of internal SEI film decomposition, positive electrode oxygen release, and electrolyte combustion; third, although halogenated flame retardants (such as 2-bromotetrafluoropropane, 2-BTP) can inhibit combustion by capturing free radicals, their pyrolysis releases highly corrosive gases such as hydrobromic acid (HBr) and hydrogen fluoride (HF), which not only accelerates the corrosion of the battery metal casing, creating a risk of secondary short circuits, but also causes the accumulation of persistent environmental pollutants.

[0004] Therefore, an ideal fire extinguishing agent specifically designed for lithium batteries needs to overcome the above three major technical bottlenecks: promote the transformation of fire extinguishing agents from simple physical isolation to thermochemical regulation, and provide key guarantees for the safe application of high-energy-density battery systems. Summary of the Invention

[0005] The purpose of this invention is to provide an anti-burning foam fire extinguishing agent for lithium batteries and its preparation method, so as to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A method for preparing an anti-burning foam fire extinguishing agent for lithium batteries includes the following preparation steps:

[0008] (1) 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene and perfluorohexyliodoane were reacted to obtain perfluorocrown ether; the perfluorocrown ether was sulfonated to obtain sodium perfluorocrown ether sulfonate.

[0009] (2) Using melamine, phenylphosphamide, and formaldehyde as wall materials and sodium sulfate decahydrate as core material, modified microcapsules were obtained.

[0010] (3) Modified silica is obtained by reacting pretreated silica, N,N-dimethylferrocene methylamine and potassium iodide.

[0011] (4) Weigh the following components: pure water, foaming agent system, foam stabilizer, heat-absorbing material, sodium benzoate preservative, thickener, and organic solvent; mix the above components to obtain the anti-burning foam fire extinguishing agent for lithium batteries.

[0012] As an optimization, the preparation method of sodium perfluorocrown ether sulfonate in step (1) is as follows: at -5℃, chlorosulfonic acid and chloroform are mixed at a mass ratio of 1:(10-12) to obtain a chlorosulfonic acid solution, and fluorinated crown ether and chloroform are mixed at a mass ratio of 1:(30-40) to obtain a crown ether solution. The molar ratio of chlorosulfonic acid to crown ether is (10-12):1. The chlorosulfonic acid solution is added dropwise to the crown ether solution, and the reaction is carried out for 4-5 hours to obtain sulfonic acid crown ether. Sodium perchlorate and acetonitrile are mixed at a mass ratio of 1:(10-12) to obtain a sodium perchlorate-acetonitrile solution. The sulfonic acid crown ether and acetonitrile are mixed at a mass ratio of 1:(30-50), and the sodium perchlorate-acetonitrile solution is added to obtain sodium perfluorocrown ether sulfonate. The molar ratio of sulfonic acid crown ether to sodium perchlorate is 1:(12-14).

[0013] As an optimization, the preparation method of the sodium perfluorocrown ether sulfonate is as follows: triethylamine, dimethyl sulfoxide, 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene, and perfluorohexyl iodide are mixed and heated to 100-110℃ and refluxed for 5-6 hours to obtain perfluorocrown ether; the molar ratio of 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene and perfluorohexyl iodide is 1:(1.2-1.4); the mass ratio of triethylamine, dimethyl sulfoxide, and perfluorohexyl iodide is 1:(50-60):(2-3).

[0014] As an optimization, the preparation method of the modified microcapsules in step (2) is as follows: melamine, phenylphosphamide, formaldehyde solution, and pure water are mixed in a mass ratio of 1:(0.9-1.1):(4-6):(4-6), the pH is adjusted to 8-9 using anhydrous sodium carbonate, the temperature is raised to 60-70℃, and the mixture is stirred at 500r / min for 1-2h. Then, 50-60 times the mass of pure water of melamine is added to obtain emulsion A; sodium sulfate decahydrate, cyclohexane, and potassium perfluorooctanoate are mixed in a mass ratio of 1:(0.8-1.0):(0.5-0.7) to obtain emulsion B; emulsion A and emulsion B are mixed in a mass ratio of (5-6):1 to obtain modified microcapsules; the formaldehyde solution is a 40wt% formaldehyde aqueous solution.

[0015] As an optimization, the preparation method of the modified silica in step (3) is as follows: pretreated silica, N,N-dimethylferrocene methylamine, acetone and potassium iodide are ultrasonically mixed in a mass ratio of 1:(0.2-0.5):(50-60):(0.05-0.08), and the mixture is refluxed at 60-70℃ for 24h under nitrogen protection to obtain modified silica.

[0016] As an optimization, the preparation method of the pretreated silica is as follows: silica and ethanol are ultrasonically mixed at a mass ratio of 1:(40-50) to obtain a dispersion, 3-chloropropyltriethoxysilane and pure water are mixed at a mass ratio of 1:(2-5) and added to the dispersion, and the mixture is refluxed at 60-70℃ for 6-7 hours to obtain pretreated silica.

[0017] As an optimization, the amounts of the components in step (4) are as follows: by mass, 60-70 parts of pure water, 5-6 parts of foaming agent system, 0.2-0.4 parts of foam stabilizer, 10-12 parts of heat-absorbing material, 0.1-0.2 parts of preservative sodium benzoate, 0.1-0.2 parts of thickener xanthan gum, and 1-2 parts of organic solvent ethylene glycol.

[0018] As an optimization, the foaming agent system in step (4) is obtained by mixing sodium perfluorocrown ether sulfonate, cocamidopropyl betaine, and dodecyl dimethylamine oxide in a mass ratio of 1:(3-4):(1-2); the heat-absorbing material is obtained by mixing modified microcapsules and expanded graphite in a mass ratio of 1:(0.2-0.4); and the foam stabilizer is modified silica.

[0019] The present invention also provides a lithium battery anti-burning foam fire extinguishing agent prepared according to the above-described method for preparing lithium battery anti-burning foam fire extinguishing agent.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] First, by introducing sodium perfluorocrown ether sulfonate, which possesses high thermal stability and chemical inertness, as the core foaming agent, the fire extinguishing agent is endowed with excellent high-temperature resistance and anti-reignition ability. The perfluorocarbon chain in sodium perfluorocrown ether sulfonate can effectively reduce the surface energy of the material, enhancing the stability of the foam under the high-temperature thermal runaway environment of lithium batteries. At the same time, its crown ether structure can chelate lithium ions in the electrolyte, inhibiting the violent reaction caused by internal short circuits in the battery. The strong hydrophilicity of the sulfonic acid group further improves the spreadability and coverage efficiency of the foam, forming a dense isolation layer on the flame surface, rapidly isolating oxygen and blocking the combustion chain reaction.

[0022] Secondly, the microencapsulation technology using a blend of sodium sulfate decahydrate and cyclohexane enables precise controlled release of the fire-extinguishing active ingredient. The modified microcapsule shell is composed of a melamine-phenylphosphine diamide cross-linked network, which undergoes endothermic decomposition at high temperatures. This endothermic decomposition reaction efficiently reduces the temperature of the combustion system while simultaneously exerting a chemical inhibitory effect to interfere with free radical chain propagation. The sustained-release properties of the microcapsules allow the fire extinguishing agent to maintain its control capabilities after the initial extinguishing, effectively addressing secondary reignition caused by lithium battery thermal runaway.

[0023] Furthermore, modified silica grafted with N,N-dimethylferrocene methylamine through the formation of quaternary ammonium salt structures serves as a foam stabilizer. The hydrophobic modification of silica by the ferrocene groups significantly enhances the mechanical strength and environmental adaptability of the foam system. The ferrocene groups introduced onto the silica surface can catalyze the decomposition of toxic gases (such as HF and CO) produced by combustion, reducing secondary hazards. The quaternary ammonium salt structure is adsorbed at the gas-liquid interface through electrostatic interactions, synergistically forming a dense molecular film with dodecyl dimethylamine oxide, effectively inhibiting foam coalescence and liquid film drainage, and improving the mechanical strength of the foam and its resistance to collapse at high temperatures.

[0024] The heat absorption and expansion properties of expanded graphite can form a gradient heat insulation barrier inside the foam, delaying the transfer of heat to unburned areas and further suppressing the spread of fire.

[0025] This fire extinguishing agent combines multiple mechanisms, including physical asphyxiation, chemical inhibition, heat absorption and cooling, and barrier protection, providing highly effective control over the characteristics of lithium battery combustion, such as electrolyte splashing and spontaneous combustion of lithium dendrites. Its perfluorinated composition and environmentally friendly solvent system meet green chemistry requirements, leaving non-corrosive and easily cleanable residues, making it suitable for fire suppression needs of different types of lithium batteries in scenarios such as electric vehicles and energy storage power stations. Detailed Implementation

[0026] 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.

[0027] The silica particles described in the following examples and comparative examples have a diameter of 30 nm; the xanthan gum is USP grade.

[0028] Example 1:

[0029] A method for preparing a fire-resistant foam extinguishing agent for lithium batteries, the method comprising the following preparation steps:

[0030] (1) Triethylamine, dimethyl sulfoxide, 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene, and perfluorohexyl iodide were mixed and heated to 110°C under reflux for 6 h. After the reaction was completed, the mixture was cooled to room temperature and dimethyl sulfoxide was removed by rotary evaporation under reduced pressure. The mixture was dissolved in chloroform, washed with 1 wt% dilute hydrochloric acid, dried with anhydrous magnesium sulfate, and then rotary evaporated to obtain perfluorocrown ether. The molar ratio of 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene to perfluorohexyl iodide was 1:1.2; the mass ratio of triethylamine, dimethyl sulfoxide, and perfluorohexyl iodide was 1:50:2.

[0031] At -5°C, chlorosulfonic acid and chloroform were mixed at a mass ratio of 1:10 to obtain a chlorosulfonic acid solution. A fluorinated crown ether and chloroform were mixed at a mass ratio of 1:30 to obtain a crown ether solution. The molar ratio of chlorosulfonic acid to crown ether was 10:1. The chlorosulfonic acid solution was added dropwise to the crown ether solution at a rate of 0.3 mL / min. The reaction was continued for 5 hours while maintaining the reaction temperature at -5°C. The precipitate was collected by filtration, dissolved in pure water, and the pH was adjusted using tetraethylammonium hydroxide. H to 7, after vacuum rotary evaporation, phosphorus pentoxide was dried under vacuum and recrystallized with acetonitrile / acetone to obtain sulfonate crown ether; sodium perchlorate and acetonitrile were mixed at a mass ratio of 1:10 to obtain a sodium perchlorate-acetonitrile solution, sulfonate crown ether and acetonitrile were mixed at a mass ratio of 1:30, added to the sodium perchlorate-acetonitrile solution, sonicated for 360s, filtered, and washed and dried with acetonitrile and dichloromethane to obtain perfluorocrown ether sodium sulfonate; the molar ratio of sulfonate crown ether to sodium perchlorate was 1:12;

[0032] (2) Melamine, phenylphosphamide, formaldehyde solution, and pure water were mixed in a mass ratio of 1:0.9:4:4. The pH was adjusted to 9 using anhydrous sodium carbonate. The mixture was heated to 70°C and stirred at 500 r / min for 2 h. Then, 50 times the mass of pure water was added to obtain emulsion A. Sodium sulfate decahydrate, cyclohexane, and potassium perfluorooctanoate were mixed in a mass ratio of 1:0.8:0.5 to obtain emulsion B. Emulsion A and emulsion B were mixed in a mass ratio of 5:1 and stirred at 800 r / min for 8 h. After standing for 6 h, the modified microcapsules were obtained by washing, centrifugation, and drying. The formaldehyde solution was a 40 wt% aqueous formaldehyde solution.

[0033] (3) A dispersion was obtained by ultrasonically mixing silica and ethanol at a mass ratio of 1:40. 3-chloropropyltriethoxysilane and pure water were mixed at a mass ratio of 1:2 and added to the dispersion. The mixture was refluxed at 70°C for 7 hours. After filtration, washing and drying, pretreated silica was obtained. The mass ratio of silica to 3-chloropropyltriethoxysilane was 1:0.2. Pretreated silica, N,N-dimethylferrocene methylamine, acetone and potassium iodide were ultrasonically mixed at a mass ratio of 1:0.2:50:0.05. The mixture was refluxed at 70°C for 24 hours under nitrogen protection. After filtration, washing and drying, modified silica was obtained.

[0034] (4) Sodium perfluorocrown ether sulfonate, cocamidopropyl betaine, and dodecyl dimethylamine oxide were mixed in a mass ratio of 1:3:1 to obtain a foaming agent system; modified microcapsules and expanded graphite were mixed in a mass ratio of 1:0.2 to obtain a heat-absorbing material; the following components were weighed: 60 parts of pure water, 5 parts of foaming agent system, 0.2 parts of foam stabilizer modified silica, 10 parts of heat-absorbing material, 0.1 parts of preservative sodium benzoate, 0.1 parts of thickener xanthan gum, and 1 part of organic solvent ethylene glycol; the above components were mixed in a high-pressure homogenizer to obtain a fire-resistant foam extinguishing agent for lithium batteries; the pressure of the high-pressure homogenizer was 500 MPa.

[0035] Example 2:

[0036] A method for preparing a fire-resistant foam extinguishing agent for lithium batteries, the method comprising the following preparation steps:

[0037] (1) Triethylamine, dimethyl sulfoxide, 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene, and perfluorohexyl iodide were mixed and heated to 105 °C under reflux for 5.5 h. After the reaction was completed, the mixture was cooled to room temperature and dimethyl sulfoxide was removed by rotary evaporation under reduced pressure. The mixture was dissolved in chloroform, washed with 1 wt% dilute hydrochloric acid, dried with anhydrous magnesium sulfate, and then rotary evaporated to obtain perfluorocrown ether. The molar ratio of 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene to perfluorohexyl iodide was 1:1.3; the mass ratio of triethylamine, dimethyl sulfoxide, and perfluorohexyl iodide was 1:55:2.5.

[0038] At -5°C, chlorosulfonic acid and chloroform were mixed at a mass ratio of 1:11 to obtain a chlorosulfonic acid solution. A fluorinated crown ether and chloroform were mixed at a mass ratio of 1:35 to obtain a crown ether solution. The molar ratio of chlorosulfonic acid to crown ether was 11:1. The chlorosulfonic acid solution was added dropwise to the crown ether solution at a rate of 0.3 mL / min. The reaction was continued at -5°C for 4.5 h. The precipitate was collected by filtration, dissolved in pure water, and the pH was adjusted using tetraethylammonium hydroxide. H to 6.5, evaporated under reduced pressure, dried under vacuum with phosphorus pentoxide, and recrystallized from acetonitrile / acetone to obtain sulfonate crown ether; sodium perchlorate and acetonitrile were mixed at a mass ratio of 1:11 to obtain a sodium perchlorate-acetonitrile solution, sulfonate crown ether and acetonitrile were mixed at a mass ratio of 1:40, added to the sodium perchlorate-acetonitrile solution, sonicated for 50 seconds, filtered, and washed and dried with acetonitrile and dichloromethane to obtain sodium perfluorocrown ether sulfonate; the molar ratio of sulfonate crown ether to sodium perchlorate was 1:13;

[0039] (2) Melamine, phenylphosphamide, formaldehyde solution, and pure water were mixed in a mass ratio of 1:1:5:5. The pH was adjusted to 8.5 using anhydrous sodium carbonate. The mixture was heated to 65°C and stirred at 500 r / min for 1.5 h. Then, 55 times the mass of pure water was added to obtain emulsion A. Sodium sulfate decahydrate, cyclohexane, and potassium perfluorooctanoate were mixed in a mass ratio of 1:0.9:0.6 to obtain emulsion B. Emulsion A and emulsion B were mixed in a mass ratio of 5.5:1 and stirred at 800 r / min for 8 h. After standing for 5.5 h, the modified microcapsules were obtained by washing, centrifugation, and drying. The formaldehyde solution was a 40 wt% aqueous formaldehyde solution.

[0040] (3) A dispersion was obtained by ultrasonically mixing silica and ethanol at a mass ratio of 1:45. 3-Chloropropyltriethoxysilane and pure water were mixed at a mass ratio of 1:4 and added to the dispersion. The mixture was refluxed at 65°C for 6.5 h. After filtration, washing and drying, pretreated silica was obtained. The mass ratio of silica to 3-chloropropyltriethoxysilane was 1:0.35. Pretreated silica, N,N-dimethylferrocene methylamine, acetone and potassium iodide were ultrasonically mixed at a mass ratio of 1:0.35:55:0.06. The mixture was refluxed at 65°C for 24 h under nitrogen protection. After filtration, washing and drying, modified silica was obtained.

[0041] (4) Sodium perfluorocrown ether sulfonate, cocamidopropyl betaine, and dodecyl dimethylamine oxide were mixed in a mass ratio of 1:3.5:2 to obtain a foaming agent system; modified microcapsules and expanded graphite were mixed in a mass ratio of 1:0.3 to obtain a heat-absorbing material; the following components were weighed: 65 parts of pure water, 5.5 parts of foaming agent system, 0.3 parts of foam stabilizer modified silica, 11 parts of heat-absorbing material, 0.15 parts of preservative sodium benzoate, 0.15 parts of thickener xanthan gum, and 1.5 parts of organic solvent ethylene glycol; the above components were mixed in a high-pressure homogenizer to obtain a fire-resistant foam extinguishing agent for lithium batteries; the pressure of the high-pressure homogenizer was 500 MPa.

[0042] Example 3:

[0043] A method for preparing a fire-resistant foam extinguishing agent for lithium batteries, the method comprising the following preparation steps:

[0044] (1) Triethylamine, dimethyl sulfoxide, 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene, and perfluorohexyl iodide were mixed and heated to 100°C and refluxed for 5 h. After the reaction was completed, the mixture was cooled to room temperature and dimethyl sulfoxide was removed by rotary evaporation under reduced pressure. The mixture was dissolved in chloroform, washed with 1 wt% dilute hydrochloric acid, dried with anhydrous magnesium sulfate, and then rotary evaporated to obtain perfluorocrown ether. The molar ratio of 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene and perfluorohexyl iodide was 1:1.4. The mass ratio of triethylamine, dimethyl sulfoxide, and perfluorohexyl iodide was 1:60:3.

[0045] At -5°C, chlorosulfonic acid and chloroform were mixed at a mass ratio of 1:12 to obtain a chlorosulfonic acid solution. A fluorinated crown ether and chloroform were mixed at a mass ratio of 1:40 to obtain a crown ether solution. The molar ratio of chlorosulfonic acid to crown ether was 12:1. The chlorosulfonic acid solution was added dropwise to the crown ether solution at a rate of 0.3 mL / min. The reaction was continued at -5°C for 4 hours. The precipitate was collected by filtration, dissolved in pure water, and the pH was adjusted using tetraethylammonium hydroxide. H to 6, after vacuum rotary evaporation, phosphorus pentoxide was dried under vacuum and recrystallized with acetonitrile / acetone to obtain perfluorocrown ether sulfonate; sodium perchlorate and acetonitrile were mixed at a mass ratio of 1:12 to obtain a sodium perchlorate-acetonitrile solution, and the perfluorocrown ether sulfonate and acetonitrile were mixed at a mass ratio of 1:50. The mixture was added to the sodium perchlorate-acetonitrile solution, sonicated for 30 seconds, filtered, and washed and dried with acetonitrile and dichloromethane to obtain sodium perfluorocrown ether sulfonate; the molar ratio of perfluorocrown ether sulfonate to sodium perchlorate was 1:14.

[0046] (2) Melamine, phenylphosphamide, formaldehyde solution, and pure water were mixed in a mass ratio of 1:1.1:6:6. The pH was adjusted to 8 using anhydrous sodium carbonate. The mixture was heated to 60°C and stirred at 500 r / min for 1 h. Then, 60 times the mass of pure water was added to obtain emulsion A. Sodium sulfate decahydrate, cyclohexane, and potassium perfluorooctanoate were mixed in a mass ratio of 1:1.0:0.7 to obtain emulsion B. Emulsion A and emulsion B were mixed in a mass ratio of 6:1 and stirred at 800 r / min for 8 h. After standing for 6 h, the mixture was washed, centrifuged, and dried to obtain modified microcapsules. The formaldehyde solution was a 40 wt% aqueous formaldehyde solution.

[0047] (3) A dispersion was obtained by ultrasonically mixing silica and ethanol at a mass ratio of 1:50. 3-chloropropyltriethoxysilane and pure water were mixed at a mass ratio of 1:5 and added to the dispersion. The mixture was refluxed at 60°C for 7 hours. After filtration, washing and drying, pretreated silica was obtained. The mass ratio of silica to 3-chloropropyltriethoxysilane was 1:0.5. Pretreated silica, N,N-dimethylferrocene methylamine, acetone and potassium iodide were ultrasonically mixed at a mass ratio of 1:0.5:60:0.08. The mixture was refluxed at 60°C for 24 hours under nitrogen protection. After filtration, washing and drying, modified silica was obtained.

[0048] (4) Sodium perfluorocrown ether sulfonate, cocamidopropyl betaine, and dodecyl dimethylamine oxide were mixed in a mass ratio of 1:4:2 to obtain a foaming agent system; modified microcapsules and expanded graphite were mixed in a mass ratio of 1:0.4 to obtain a heat-absorbing material; the following components were weighed: 70 parts of pure water, 6 parts of the foaming agent system, 0.4 parts of the foam stabilizer modified silica, 12 parts of the heat-absorbing material, 0.2 parts of the preservative sodium benzoate, 0.2 parts of the thickener xanthan gum, and 2 parts of the organic solvent ethylene glycol; the above components were mixed in a high-pressure homogenizer to obtain a fire-resistant foam extinguishing agent for lithium batteries; the pressure of the high-pressure homogenizer was 500 MPa.

[0049] Comparative Example 1:

[0050] The preparation method of the lithium battery anti-burning foam fire extinguishing agent in Comparative Example 1 differs from that in Example 2 in that it does not contain sodium perfluorocrown ether sulfonate, specifically step (1) is omitted, and step (4) is modified as follows: sodium perfluorohexyl sulfonate, cocamidopropyl betaine, and dodecyl dimethylamine oxide are mixed in a mass ratio of 1:3.5:2 to obtain a foaming agent system; modified microcapsules and expanded graphite are mixed in a mass ratio of 1:0.3 to obtain a heat-absorbing material; the following components are weighed: 65 parts of pure water, 5.5 parts of the foaming agent system, 0.3 parts of the foam stabilizer modified silica, 11 parts of the heat-absorbing material, 0.15 parts of the preservative sodium benzoate, 0.15 parts of the thickener xanthan gum, and 1.5 parts of the organic solvent ethylene glycol; the above components are mixed using a high-pressure homogenizer to obtain the lithium battery anti-burning foam fire extinguishing agent; the pressure of the high-pressure homogenizer is 500 MPa. The remaining steps are the same as in Example 2.

[0051] Comparative Example 2:

[0052] The preparation method of the lithium battery anti-burning foam fire extinguishing agent in Comparative Example 2 differs from that in Example 2 in that it does not contain modified microcapsules, specifically step (2). Step (4) is modified as follows: Sodium perfluorocrown ether sulfonate, cocamidopropyl betaine, and dodecyl dimethylamine oxide are mixed in a mass ratio of 1:3.5:2 to obtain a foaming agent system; the following components are weighed: 65 parts of pure water, 5.5 parts of the foaming agent system, 0.3 parts of the foam stabilizer modified silica, 11 parts of the heat-absorbing material expanded graphite, 0.15 parts of the preservative sodium benzoate, 0.15 parts of the thickener xanthan gum, and 1.5 parts of the organic solvent ethylene glycol; the above components are mixed using a high-pressure homogenizer to obtain the lithium battery anti-burning foam fire extinguishing agent; the pressure of the high-pressure homogenizer is 500 MPa. The remaining steps are the same as in Example 2.

[0053] Comparative Example 3:

[0054] The preparation method of the lithium battery anti-burning foam fire extinguishing agent in Comparative Example 3 differs from that in Example 2 in that it does not contain modified silica. Specifically, step (4) is modified as follows: sodium perfluorocrown ether sulfonate, cocamidopropyl betaine, and dodecyl dimethylamine oxide are mixed in a mass ratio of 1:3.5:2 to obtain a foaming agent system; modified microcapsules and expanded graphite are mixed in a mass ratio of 1:0.3 to obtain a heat-absorbing material; the following components are weighed: 65 parts of pure water, 5.5 parts of the foaming agent system, 11 parts of the heat-absorbing material, 0.15 parts of sodium benzoate preservative, 0.15 parts of xanthan gum thickener, and 1.5 parts of ethylene glycol organic solvent; the above components are mixed using a high-pressure homogenizer to obtain the lithium battery anti-burning foam fire extinguishing agent; the pressure of the high-pressure homogenizer is 500 MPa. The remaining steps are the same as in Example 2.

[0055] Test Example 1:

[0056] Foam stability testing:

[0057] The Ross-Miles method was used to test the foam stability. At 25°C, 5 mL of foam extinguishing agent was placed in a 50 mL stoppered graduated cylinder and shaken to generate foam. The initial foam height was recorded. After standing for 30 min, the foam height was recorded again. The results are shown in Table 1.

[0058] Table 1

[0059] Initial foam height (cm) Foam height (cm) after settling Example 1 28 22 Example 2 30 23 Example 3 30 25 Comparative Example 1 28 17 Comparative Example 2 27 20 Comparative Example 3 27 16

[0060] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-3 in Table 1 shows that the foam extinguishing agent prepared by the present invention has good foam stability.

[0061] The foam stability of Examples 1-3 is superior to that of Comparative Examples 1-3, indicating that the perfluorocarbon chain in sodium perfluorocrown ether sulfonate can effectively reduce the surface energy of the material and enhance the stability of the foam under the high-temperature thermal runaway environment of lithium batteries. Modified silica grafted with N,N-dimethylferrocene methylamine through the formation of a quaternary ammonium salt structure serves as a foam stabilizer. The hydrophobic modification of silica by the ferrocene group significantly improves the mechanical strength and environmental adaptability of the foam system. The quaternary ammonium salt structure is adsorbed at the gas-liquid interface through electrostatic interactions, synergistically forming a dense molecular film with dodecyl dimethylamine oxide, effectively inhibiting foam coalescence and liquid film drainage, and improving the mechanical strength and anti-collapse ability of the foam at high temperatures.

[0062] Test Example 2:

[0063] Fire extinguishing performance testing:

[0064] Test method: The lithium battery (60Ah square lithium iron phosphate battery cell) was fixed on the heating plate and heated. The heating plate was composed of nickel-chromium furnace wire and high-temperature refractory plate, with a length of 200mm, a width of 400mm, and a power of 2.0kW. After the battery thermally ran away and the outer shell exploded, 30 seconds later, extinguishing agent was sprayed from directly above. The extinguishing time was recorded, and whether the fire reignited within 30 minutes was recorded. The results are shown in Table 2.

[0065] Table 2

[0066] Firefighting time Whether it reignites Example 1 8s no Example 2 7s no Example 3 7s no Comparative Example 1 30s yes Comparative Example 2 24s yes Comparative Example 3 32s yes

[0067] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-3 in Table 2 shows that the fire extinguishing agent prepared by the present invention has good fire extinguishing performance.

[0068] Examples 1-3 exhibit superior fire extinguishing performance compared to Comparative Example 3. This demonstrates that, firstly, by introducing sodium perfluorocrown ether sulfonate, which possesses high thermal stability and chemical inertness, as the core foaming agent, the fire extinguishing agent is endowed with excellent high-temperature resistance and anti-reignition ability. The crown ether structure in sodium perfluorocrown ether sulfonate can chelate lithium ions in the electrolyte, suppressing the violent reaction caused by internal short circuits in the battery. The strong hydrophilicity of the sulfonic acid groups further enhances the foam's spreadability and coverage efficiency, forming a dense insulating layer on the flame surface, rapidly isolating oxygen and blocking the combustion chain reaction.

[0069] The modified microcapsule shell is composed of a melamine-phenylphosphine diamide cross-linked network, which decomposes endothermally at high temperatures. This endothermic decomposition reaction efficiently reduces the temperature of the combustion system while simultaneously exerting a chemical inhibitory effect to interfere with free radical chain propagation. The slow-release properties of the microcapsules enable the extinguishing agent to maintain its fire-fighting capability after the initial extinguishing, effectively addressing secondary reignition caused by lithium battery thermal runaway.

[0070] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing an anti-burning foam fire extinguishing agent for lithium batteries, characterized in that, The preparation steps include the following: (1) 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene and perfluorohexyliodoane were reacted to obtain perfluorocrown ether; the perfluorocrown ether was sulfonated to obtain sodium perfluorocrown ether sulfonate. (2) Modified microcapsules were obtained using melamine, phenylphosphamide, and formaldehyde as wall materials and sodium sulfate decahydrate as core material; (3) Modified silica is obtained by reacting pretreated silica, N,N-dimethylferrocene methylamine and potassium iodide. (4) Weigh the following components: pure water, foaming agent system, foam stabilizer, heat-absorbing material, sodium benzoate preservative, thickener, and organic solvent; mix the above components to obtain the anti-burning foam fire extinguishing agent for lithium batteries; The preparation method of the perfluorocrown ether is as follows: triethylamine, dimethyl sulfoxide, 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene, and perfluorohexyl iodoane are mixed and heated to 100-110℃ and refluxed for 5-6 hours to obtain the perfluorocrown ether; the molar ratio of 5,6,14,15-dibenzo-4,7,13,16-tetraoxa-1,10-diazacyclooctadec-5,14-diene and perfluorohexyl iodoane is 1:(1.2-1.4); the mass ratio of triethylamine, dimethyl sulfoxide, and perfluorohexyl iodoane is 1:(50-60):(2-3); The preparation method of the perfluorocrown ether sodium sulfonate is as follows: at -5℃, chlorosulfonic acid and chloroform are mixed at a mass ratio of 1:(10-12) to obtain a chlorosulfonic acid solution; perfluorocrown ether and chloroform are mixed at a mass ratio of 1:(30-40) to obtain a crown ether solution; the molar ratio of chlorosulfonic acid to crown ether is (10-12):1; the chlorosulfonic acid solution is added to the crown ether solution, and the reaction is carried out for 4-5 hours to obtain sulfonic acid crown ether; sodium perchlorate and acetonitrile are mixed at a mass ratio of 1:(10-12) to obtain a sodium perchlorate-acetonitrile solution; sulfonic acid crown ether and acetonitrile are mixed at a mass ratio of 1:(30-50), and added to the sodium perchlorate-acetonitrile solution to obtain perfluorocrown ether sodium sulfonate; the molar ratio of sulfonic acid crown ether to sodium perchlorate is 1:(12-14); The modified microcapsules are prepared as follows: melamine, phenylphosphamide, formaldehyde solution, and pure water are mixed in a mass ratio of 1:(0.9-1.1):(4-6):(4-6). The pH is adjusted to 8-9 using anhydrous sodium carbonate, the temperature is raised to 60-70℃, and the mixture is stirred for 1-2 hours. Then, 50-60 times the mass of melamine in pure water is added to obtain emulsion A. Sodium sulfate decahydrate, cyclohexane, and potassium perfluorooctanoate are mixed in a mass ratio of 1:(0.8-1.0):(0.5-0.7) to obtain emulsion B. Emulsion A and emulsion B are mixed in a mass ratio of (5-6):1 to obtain modified microcapsules. The formaldehyde solution is a 40wt% formaldehyde aqueous solution. The modified silica is prepared by mixing pretreated silica, N,N-dimethylferrocene methylamine, acetone, and potassium iodide in a mass ratio of 1:(0.2-0.5):(50-60):(0.05-0.08), heating to 60-70℃ and reacting for 24 hours to obtain modified silica. The method for preparing the pretreated silica is as follows: silica and ethanol are mixed at a mass ratio of 1:(40-50) to obtain a dispersion, 3-chloropropyltriethoxysilane and pure water are mixed at a mass ratio of 1:(2-5) and added to the dispersion, and the mixture is reacted at 60-70℃ for 6-7h to obtain pretreated silica. The foaming agent system is obtained by mixing sodium perfluorocrown ether sulfonate, cocamidopropyl betaine, and dodecyl dimethylamine oxide in a mass ratio of 1:(3-4):(1-2); the heat-absorbing material is obtained by mixing modified microcapsules and expanded graphite in a mass ratio of 1:(0.2-0.4); and the foam stabilizer is modified silica.

2. The method for preparing a fire-resistant foam extinguishing agent for lithium batteries according to claim 1, characterized in that, The amounts of the components used in step (4) are as follows: by mass, 60-70 parts of pure water, 5-6 parts of foaming agent system, 0.2-0.4 parts of foam stabilizer, 10-12 parts of heat-absorbing material, 0.1-0.2 parts of preservative sodium benzoate, 0.1-0.2 parts of thickener xanthan gum, and 1-2 parts of organic solvent ethylene glycol.

3. A lithium battery anti-burning foam fire extinguishing agent prepared by the preparation method of the lithium battery anti-burning foam fire extinguishing agent according to any one of claims 1-2.