LU603003B1 - Gel-type water-based fire extinguishing agent specially designed for lithium batteries with low conductivity and high stability and its preparation method - Google Patents

Abstract

The present invention relates to the field of fire extinguishing materials, specifically to a gel-type water-based fire extinguishing agent specially designed for lithium batteries with low conductivity and high stability. It comprises the following ingredients by weight: modified nano-silica aerogel 1–3 parts; nano-aluminium hydroxide 1–3 parts; trimethyl phosphate 1–3 parts; emulsifier OP-10 20–35 parts; antifreeze agent 10–15 parts; fluorocarbon surfactant 0.5–1.5 parts; antibacterial agent 0.5–1.5 parts; foam stabiliser 0.5–2 parts; xanthan gum 0.3–1.5 parts; calcium lactate 0.1–0.8 parts; bentonite 0.5–2 parts; Mica 0.5–2 parts; Regulator 0.1–1 parts; Deionised water 40–60 parts. The prepared porous insulating network, phosphate ester radical capture, and xanthan gum–calcium lactate gel synergistic action endow the fire extinguishing agent with low electrical conductivity, rapid cooling, and long-lasting flame-retardant properties, making it suitable for emergency protection against lithium-ion battery fires in electric vehicles and energy storage systems.

Description

GEL-TYPE WATER-BASED FIRE EXTINGUISHING AGENT SPECIALLY DESIGNED "20%

FOR LITHIUM BATTERIES WITH LOW CONDUCTIVITY AND HIGH STABILITY AND

ITS PREPARATION METHOD

Technical field

The present invention relates to the field of fire extinguishing materials, specifically to a gel-type water-based fire extinguishing agent specially designed for lithium batteries with low conductivity and high stability and its preparation method.

Background Art

Lithium-ion batteries are widely used in energy storage systems, electric vehicles, and portable electronic devices due to their high energy density and long cycle life. However, they are prone to thermal runaway under operating or misuse conditions, releasing large amounts of flammable gases and highly toxic hydrogen fluoride, accompanied by intense flames, localised high temperatures, and electrochemical side reactions, which can easily lead to severe fire accidents. Given the unique nature of lithium-ion battery fires, existing fire extinguishing materials have revealed numerous issues during application.

Water-based extinguishing agents, while possessing excellent cooling capabilities, have a high electrical conductivity (typically exceeding 100 uS/em), which can cause secondary hazards such as electrical short circuits when used on battery modules, posing significant safety risks. Dry powder extinguishing agents can suppress combustion through powder coating, but their cooling capacity is limited, and the residues after extinguishing are difficult to clean up, potentially contaminating battery packs and precision electronic equipment. Gaseous extinguishing agents like heptafluoropropane have non-conductive properties, but in practical applications, they often fail to meet the full-process response requirements for lithium-ion battery thermal runaway due to low cooling efficiency, limited spray areas, and the risk of reignition after extinguishing.

In recent years, some studies have attempted to introduce foam or gel structures into water-based systems to enhance the adhesion and coverage of extinguishing agents on high-temperature surfaces, prolong the duration of action, and improve extinguishing efficiency.

However, such systems often still face prominent issues such as high conductivity, poor structural stability, non-degradable components, and single functional mechanisms, making it difficult to achieve efficient and long-lasting extinguishing effects while ensuring electrical safety. Additionally, 1 reducing ionic components to lower electrical conductivity further weakens thermal conductivigy 0 and foam performance, impairing the rapid cooling process during the initial stages of fire suppression. The introduction of polymer additives or inorganic particles to enhance film-forming and stability may also lead to biodegradability issues, increasing environmental burdens.

Furthermore, existing extinguishing agents primarily rely on physical cooling or oxygen-blocking mechanisms, making it difficult to address the chain combustion reactions triggered by a large number of free radicals during lithium-ion battery fires, resulting in a risk of reignition after extinguishing.

Current technologies lack a water-based fire extinguishing agent that combines low electrical conductivity with high stability, high cooling efficiency, and multiple fire extinguishing mechanisms. In particular, gel-type products suitable for lithium-ion battery thermal runaway fires remain unavailable, necessitating synergistic innovation in material systems and structural design to achieve performance breakthroughs.

Invention Summary

To overcome the technical challenges associated with existing lithium-ion battery fire extinguishing materials, such as high electrical conductivity, insufficient cooling capacity, structural instability, single functional mechanism, and poor environmental adaptability, this invention provides a low-conductivity, high-stability gel-type water-based fire extinguishing agent specifically designed for lithium batteries, along with its preparation method. By constructing an organic-inorganic composite system, modified aerogel is introduced to enhance thermal insulation and structural stability. Trimethyl phosphate is utilised to capture free radicals, while a non-ionic emulsion system and pH-responsive gel network are combined to form a stable foam layer, balancing electrical conductivity safety, coverage durability, and synergistic fire extinguishing functionality. This extinguishing agent has low conductivity, rapid cooling, and strong adhesion, effectively preventing lithium-ion battery short circuits and suppressing the spread of thermal runaway. The system is environmentally friendly and biodegradable, suitable for various lithium-ion battery applications, and has excellent engineering practicality and application prospects.

The objective of this invention can be achieved through the following technical solution:

A low-conductivity, high-stability gel-type water-based fire extinguishing agent specifically designed for lithium batteries, comprising the following raw materials by weight: modified 2 nano-silica aerogel 1-3 parts; nano-aluminium hydroxide 1-3 parts; trimethyl phosphate 1-3 parte, 2003 emulsifier OP-10 20-35 parts; antifreeze agent 10-15 parts; fluorocarbon surfactant 0.5—1.5 parts; antiseptic phenoxyethanol 0.5-1.5 parts; foam stabiliser 0.5-2 parts; xanthan gum 0.3—1.5 parts; calcium lactate 0.1-0.8 parts; bentonite 0.5-2 parts; mica 0.5-2 parts; regulator 0.1-1 part; deionised water 40-60 parts.

Optionally, modified nano-silica aerogel, comprising the following raw materials by weight: ethyl orthosilicate 10-20 parts; ethanol 60-100 parts; deionised water 10-20 parts; hydrochloric acid 0.5-1.5 parts; ammonia water 05-15 parts; methyl triethoxysilane 2-6 parts; 3-(dimethoxyphosphinylmethylamino)propyl triethoxysilane 1-3 parts; the hydrochloric acid concentration is 0.01 mol/L; the ammonia water volume fraction is 25%.

Optionally, the emulsifier OP-10 is octylphenol polyethylene glycol ether; the antifreeze agent is a mixture of ethylene glycol and glycerol in a mass ratio of 2:1 to 1:1; The fluorocarbon surfactant is a mixture of potassium hexafluorohexylsulfonate and a surfactant containing perfluoroalkyl carboxylate salts in a mass ratio of 1:2 to 1:3; The antibacterial agent is phenoxyethanol; The regulator is a mixture of triethanolamine and sodium hydroxide solution in a mass ratio of 2:1 to 3:1.

Optionally, the preparation method for modified nano-silica aerogel includes the following steps: (1) Mix ethyl orthosilicate with ethanol uniformly, then add deionised water and hydrochloric acid while stirring to undergo hydrolysis, forming a transparent sol; (2) Slowly add ammonia water to the transparent sol while continuing to stir; (3) Add methyl triethoxysilane and 3-(dioxophosphomethylamino)propyl triethoxysilane sequentially; (4) Age the reaction product, then add ethanol for multiple solvent exchanges; (5) Dry to obtain a dry gel; (6) Heat-treat the dry gel to obtain a structurally stable, surface-functional group-coordinated modified nano-silica aerogel.

Optionally, the hydrolysis reaction in step (1) is conducted at a temperature of 25-35°C, for 30-60 minutes, with a pH of 2.5-3.5; the condensation reaction in step (2) is conducted at a pH of 8-9, for 1-2 hours; the surface modification reaction in step (3) is conducted at a temperature of 20-30°C, for 2—4 hours; In step (5), the drying temperature is 50-80°C, and the drying time is 12— 3

24 hours; In step (6), the heat treatment temperature is 600-800°C, and the holding time is 1097008 hours.

Optionally, a method for preparing a low-conductivity, high-stability gel-type water-based fire extinguishing agent specifically for lithium batteries includes the following steps:

S1: Add modified nano-silica aerogel and nano-aluminium hydroxide to deionised water, and disperse uniformly under stirring conditions to form the first dispersion solution;

S2, mix trimethyl phosphate with emulsifier OP-10 until uniformly mixed, then add to the first dispersion solution and continue stirring to form an emulsion system;

S3, add antifreeze agent, fluorocarbon surfactant, antibacterial agent phenoxyethanol, and foam stabiliser to the emulsion, stir and mix to form a uniform main system solution;

S4: Add xanthan gum and calcium lactate to the main system solution, and slowly add the pH adjuster to adjust the pH, while continuing to stir to promote gel structure formation;

SS: After gel formation, add bentonite and mica, and stir thoroughly to improve system stability and adhesion performance;

S6. Add deionised water, mix thoroughly again, and obtain a low-conductivity, high-stability gel-type water-based fire extinguishing agent specifically designed for lithium-ion batteries.

Optionally, the formation temperature of the first dispersion solution in step S1 is 25-35°C.

Optionally, the pH during gel formation in step S4 is 6.5-7.5.

The beneficial effects of the present invention are:

The low-conductivity, high-stability lithium-ion battery-specific gel-type water-based fire extinguishing agent proposed in this invention addresses the electrical risks, re-ignition tendencies, and insufficient fire extinguishing efficiency associated with lithium-ion battery thermal runaway processes. By employing a multi-component synergistic approach to construct a foam-gel fire extinguishing system with composite functionality, it demonstrates outstanding comprehensive performance.

The extinguishing agent incorporates modified nano-silica aerogel and nano-aluminium hydroxide, combined with a low-electrolyte solvent system, effectively reducing ion mobility in the system. The conductivity can be controlled below 8 uS/cm, significantly enhancing protection against short-circuit risks during the extinguishing process and meeting lithium-ion battery electrical safety requirements. 4

The pH-responsive gel network exhibits excellent thermal stability and film-forming 0 capability, maintaining prolonged coverage time under high-temperature conditions to form a dense foam membrane that isolates oxygen while enabling continuous cooling, significantly extending the electrolyte leakage time. The extinguishing agent demonstrates superior spreadability and adhesion on battery surfaces, effectively covering complex geometric structures to enhance extinguishing efficiency for thermal runaway sources.

This fire extinguishing agent is particularly suitable for applications in lithium-ion battery energy storage systems, electric vehicle battery packs, consumer electronics battery packs, and testing platforms, offering significant engineering practicality and broad application prospects.

Brief Description Of The Drawings

The following description of the present invention is provided with reference to the accompanying drawings.

Fig. 1 shows a comparison of the infrared spectra of nano-silica and modified nano-silica aerogel.

Fig. 2 shows a scanning electron microscope (SEM) image of modified nano-silica aerogel.

Fig. 3 is a bar chart comparing the conductivity test results of low-conductivity, high-stability lithium battery gels with different formulations.

Fig. 4 is a bar chart comparing the foaming performance test results of low-conductivity, high-stability lithium battery gels with different formulations.

Fig. 5 is a bar chart comparing the liquid separation time of low-conductivity, high-stability lithium battery gels with different formulations.

Fig. 6 is a bar chart comparing the cooling rate test results of low-conductivity, high-stability lithium battery gels with different formulations.

Fig. 7 is a bar chart comparing the surface tension test results of low-conductivity, high-stability lithium battery gels with different formulations.

Specific Implementation Methods

The following examples are provided to further illustrate the present invention, but the invention is not limited to the following embodiments. Equivalent modifications made without departing from the spirit and scope of the invention should also be considered within the scope of the invention.

Example 1:

In this embodiment, nano-aluminium hydroxide and modified nano-silica are selected 38009 inorganic insulating reinforcing components, combined with trimethyl phosphate and OP-10 emulsifier to form an inhibitor system, and integrated with ethylene glycol as the main antifreeze and film-forming component, to construct a gel-type water-based fire extinguishing agent through multi-component synergy.

As shown in Figure 1, the original nano-silica exhibits a broad, intense —OH stretching absorption peak at 3400 cm”, indicating a high surface hydroxyl content and strong water adsorption capacity; the modified nano-silica aerogel shows a significant reduction in peak intensity at the same wavelength, indicating that the hydroxyl groups have been replaced by organosilane groups, resulting in significantly enhanced hydrophobicity. Correspondingly, the H-O-H bending vibration at 1630 cm”! decreases from moderate intensity to a weak peak, further confirming the reduced adsorbed water content. In the 2960 cm”! and 2850 cm”! regions, the modified sample exhibits new C—H stretching absorption peaks, which are absent in the original sample, confirming the successful grafting of methyl/propyl chains; a distinct Si—CHs bending vibration peak appears at 1270 cm, further confirming the fixation of methyl triethoxysilane on the surface. The Si—O-Si asymmetric stretching absorption at 1090 cm”! is the main peak in both samples, but the peak shape is sharper after modification, indicating that the siloxane network remains intact and its density has increased; the Si-O-Si symmetric stretching at 800 cm”! and the Si—O bending peak at 470 cm”! remain stable, showing that the main framework structure has not been damaged.

The modified sample exhibits a shoulder peak at 1030 cm”! corresponding to the P-O-Si bond, and sharp peaks related to P-N and P-O-C in the 970-950 em”! region; additionally, a Si—C absorption peak appears at 780 cm”. These new peaks indicate that 3-(dimethoxyphosphinylmethylamino)propyl triethoxysilane has been co-grafted, introducing phosphorus-nitrogen flame-retardant functional groups and forming Si-C covalent bonds.

Comprehensive infrared comparisons reveal that the modified nano-silica aerogel retains the SiO: framework while achieving hydroxyl substitution, hydrophobic layer construction, and the introduction of phosphorus-nitrogen functional groups, laying the molecular structural foundation for enhanced comprehensive properties such as low electrical conductivity insulation, thermal insulation, and radical inhibition.

Figure 2 provides a more intuitive view of the three-dimensional porous structure of the modified nano-silica aerogel. 6

Preparation steps: 0603003

S1: Mix 10 parts of ethyl orthosilicate with 80 parts of ethanol, then add 20 parts of deionised water and 1 part of 0.01 mol/L hydrochloric acid. Stir for 30 minutes at room temperature (25— °C) to promote hydrolysis, forming a uniform transparent sol; Slowly add 25% (v/v) ammonia water to adjust the pH to 8.5, and continue stirring for 1 hour to promote the condensation reaction, obtaining an initial colloidal system; add 4 parts of methyl triethoxysilane and 3-(dioxophosphomethylamino)propyl triethoxysilane to the system, and continue stirring at 20— 30 °C for 3 hours to uniformly graft the organosilane onto the silica framework surface; After aging the system for 24 hours, perform three ethanol exchanges to remove by-products, then dry at 60°C for 18 hours to obtain a dry gel; finally, heat-treat the dry gel at 700°C for 2 hours to obtain a structurally dense and surface-hydrophobic modified nano-silica aerogel powder for use in fire extinguishing agent formulations;

S2: Take 1 part nano-aluminium hydroxide and 1 part surface-modified nano-silica, add 10 parts deionised water, and disperse uniformly under magnetic stirring to obtain component À;

S3: Mix 1 part trimethyl phosphate with 30 parts OP-10 emulsifier, then slowly add 20 parts deionised water while continuing to stir to form an emulsion, yielding component B;

S4: Mix 10 parts of antifreeze agent, 1 part of fluorocarbon surfactant, 1 part of phenoxyethanol antibacterial agent, and 1 part of foam stabiliser, then add 10 parts of deionised water and stir to form component C;

SS: Mix components A, B, and C in a volume ratio of 1:1:1, stir slowly until uniform, forming composite component D;

S6: Add a pH adjuster (ammonia water) to component D to adjust the pH to 8-9, and add deionised water to achieve an appropriate system concentration;

S7: Add the xanthan gum and calcium lactate composite, stir at room temperature until a uniform transparent gel is formed, and obtain the finished fire extinguishing agent.

Example 2:

In this example, the amount of trimethyl phosphate added is increased to 2 parts compared to

Example 1 to enhance its inhibitory effect on free radical chain reactions, and the stabiliser ratio is appropriately adjusted.

Preparation steps: 7

S1: Take 2 parts of nano-aluminium hydroxide and 1 part of modified nano-silica, add 10-00% parts of deionised water, and stir evenly to form component A;

S2: Mix 2 parts of trimethyl phosphate with 30 parts of OP-10, add 20 parts of deionised water, and emulsify at high speed to form component B;

S3: Mix 10 parts of antifreeze agent, 1 part of fluorocarbon surfactant, 1 part of phenoxyethanol, and 1 part of foam stabiliser, then add 10 parts of deionised water and stir to form component C;

S4: Combine components A, B, and C in equal volume ratios, and stir thoroughly to form component D;

SS: Adjust the pH to 8 using ammonia water, then add an appropriate amount of deionised water to adjust the dilution ratio;

S6: Add xanthan gum-calcium lactate composite gel agent to D to form a gel-type fire extinguishing system with good adhesion.

Example 3:

In this example, the proportion of nano-silica is further increased to 2 parts, while the content of phenoxyethanol is increased to 1.5 parts to enhance the thermal insulation and microbial stability of the system.

Preparation steps:

S1: Weigh 1 part nano-aluminium hydroxide and 2 parts modified nano-silica, mix, then add parts deionised water. Ultrasonically disperse to obtain component A;

S2: Mix 2 parts of trimethyl phosphate with 30 parts of emulsifier, then slowly add 20 parts of deionised water while stirring to form component B;

S3: Prepare 10 parts of antifreeze agent, 1 part of fluorocarbon surfactant, 1.5 parts of phenoxyethanol, and 1 part of foam stabiliser, then add 10 parts of deionised water and stir to form component C;

S4: Mix components A, B, and C in sequence to obtain component D;

SS: Adjust the pH of the D system to 8.5, then add an appropriate amount of deionised water to adjust to the target concentration;

S6: Add xanthan gum and calcium lactate mixture dropwise, stir to form a transparent high-viscosity gel, and complete the preparation of the fire extinguishing agent.

Comparison ratio 1: 8

No trimethyl phosphate is used; only emulsifiers, water, and inorganic particles are used 033003 form the system, to verify the performance differences under conditions without free radical inhibitors.

Preparation steps:

S1: Mix 1 part nano-aluminium hydroxide with 1 part modified nano-silica, then add 10 parts deionised water to form component A;

S2: Directly mix 30 parts of OP-10 emulsifier with 20 parts of deionised water to obtain component B;

S3: Prepare 10 parts of antifreeze agent, 1 part of fluorocarbon surfactant, 1 part of phenoxyethanol, and 1 part of foam stabiliser, add 10 parts of deionised water, and stir to form component C;

S4: Mix components A, B, and C to obtain component D;

SS: Adjust the pH to neutral using ammonia water, and add a small amount of deionised water to adjust the concentration;

S6: Add xanthan gum-calcium lactate composite agent to form an initial gel, producing the control sample.

Control Sample 2:

This comparative sample removes all inorganic fillers (aluminium hydroxide and silica), retaining only the emulsifier, antimicrobial agent, and organic film-forming agent, to analyse the impact of the absence of inorganic insulating components on overall performance.

Preparation steps:

S1: Do not add component A (which does not contain inorganic particles);

S2: Mix 2 parts trimethyl phosphate with 30 parts OP-10, then add 20 parts deionised water to form component B;

S3: Mix 10 parts of antifreeze agent, 1 part of fluorocarbon surfactant, 1.5 parts of phenoxyethanol, 1 part of foam stabiliser, and 10 parts of water to form component C;

S4: Combine B and C and stir thoroughly to form component D;

S5: Adjust the pH to 8-9 and add water to achieve the target viscosity;

S6: Add xanthan gum and calcium lactate to form a colloidal structure, obtaining a fire extinguishing agent sample without inorganic reinforcing agents.

Performance Testing 9

Conductivity Testing Method 0603003

Use a standard laboratory conductivity meter to measure the ionic conductivity of the fire extinguishing agent sample at room temperature. Before testing, thoroughly shake and mix the sample, let it stand for 10 minutes, then take the supernatant and pour it into the measurement cell for measurement. This method directly reflects whether the fire extinguishing agent has the electrical safety protection capability for lithium-ion battery systems during fire extinguishing. The lower the conductivity, the lower the risk of leakage and short circuits.

Foaming Performance Test Method

Mechanical stirring is used to simulate the foaming capability of the fire extinguishing agent during actual spraying. The fire extinguishing agent sample is placed in a graduated cylinder and stirred for 30 seconds using a stirrer at a fixed speed. After stirring stops, the foam height and remaining liquid height are immediately observed to assess the foam volume growth capability. The foam system is then left to settle, and the time required for the first noticeable collapse of the foam top is recorded to assess the stability of the foam structure. This test reflects the expandability and adhesion time of the fire extinguishing agent when actually sprayed over the surface of a lithium-ion battery, particularly its retention properties in high-temperature smoke environments.

Gel Stability and pH Response Test Method

Pour the fire extinguishing agent sample into a transparent cuvette, place it in a constant-temperature environment, and let it stand for 24 hours. Observe whether there are any phenomena such as layering, settling, or collapse to evaluate the stability of the gel's three-dimensional network structure under normal temperature static storage conditions.

Subsequently, adjust the system's pH by gradually adding acid or base, and observe whether the gel undergoes changes such as transparency, disintegration, or structural compaction to determine its pH responsiveness. This method is used to evaluate the adaptability and structural reversibility of the cross-linked gel network formed by the xanthan gum-calcium lactate coordination system to environmental changes.

Cooling rate test method

To simulate the high-temperature environment of lithium-ion battery thermal runaway, a metal aluminium powder is heated to a temperature # it lithium-ion battery combustion temperature using an electric heating plate, and the initial surface temperature is recorded using an infrared thermometer. Pre-prepared fire extinguishing agent foam is rapidly sprayed onto the 1 high-temperature aluminium powder surface, while the temperature change trend is continuousty 0 monitored using an infrared thermometer, and the rapid temperature drop within the first 5 seconds after spraying is recorded. This test evaluates the evaporative heat absorption capacity of the fire extinguishing agent foam and its fire suppression and cooling efficiency in high-temperature environments, serving as an important means to assess the fire extinguishing agent's ability to control thermal diffusion.

Surface Tension Test Method

An automatic surface tension meter is used to measure the surface tension of the fire extinguishing agent solution via the hanging film method. Samples are tested at room temperature, and lower tension values indicate that the fire extinguishing agent spreads and adheres more easily to the burning surface, facilitating rapid coverage of the fire source and suppression of diffusion.

This testing method is used to verify whether the synergistic effects of introduced fluorocarbon surfactants, emulsifiers, and other components effectively reduce interfacial energy, thereby enhancing the fire extinguishing agent's rapid wetting and anti-reignition performance.

Table 1 Performance test results of gel-type water-based fire extinguishing agent with low conductivity and high stability specifically designed for lithium batteries sample conductivity | Foam drainage maximum surface tension (uS/cm) expansion time(min) cooling rate | (mN/m) ratio (°C/s)

To comprehensively validate the overall performance advantages of the low-conductivity, high-stability lithium-ion battery-specific gel-type water-based fire extinguishing agent of the present invention in terms of electrical insulation, foam stability, cooling capacity, and surface spreadability, systematic tests were conducted on the samples prepared in Examples 1, 2, 3, and

Comparative Examples 1 and 2. The test items included foam conductivity, foam expansion ratio, de-foaming time, maximum cooling rate, and surface tension. The test results are shown in the table and Figures 3-7. 1

As shown in the foam conductivity data, the foam conductivity of Examples 1-3 Hag 00 controlled between 7.8 and 8.3 uS/em, significantly lower than that of Comparative Examples 1 (15.4 uS/cm) and 2 (22.8 uS/em). This performance is attributed to the composite insulating framework formed by modified nano-silica aerogel and nano-alumina hydroxide, whose high specific surface area and three-dimensional porous structure effectively restrict the migration paths of electrolyte ions. Additionally, the aerogel, which has undergone high-temperature surface modification, distributes in the system in a stable hydrophobic state, further reducing the likelihood of ion concentration forming conductive pathways in the foam. This invention does not add traditional high-ion-content salt-based flame retardants, which is one of the key reasons for the significant reduction in conductivity.

In terms of foam expansion and stability, the foam expansion ratios of Examples 1-3 were 8.2, 9.1, and 10.0, respectively, significantly higher than those of Comparative Example 1 (6.5) and

Comparative Example 2 (5.3). The excellent foam performance is attributed to the synergistic interfacial regulation capability between the emulsifier OP-10 and the fluorocarbon surfactant, which effectively reduces the interfacial tension between gas and liquid while enhancing the elasticity of the bubble membrane. In terms of liquid separation time, the samples in the examples all maintained a time of over 12.5 minutes, significantly outperforming the comparative examples (all under 9 minutes), indicating that the pH-responsive gel structure formed a physical support network within the foam system, effectively locking in liquid, slowing down the gravitational collapse of the foam and the water separation process, and enhancing the foam layer's coverage and oxygen-blocking sealing efficiency.

In terms of thermal response performance, the maximum cooling rates of Examples 1-3 reached 200, 213, and 232 °C/s, respectively, while those of Comparisons 1 and 2 were only 128 and 95 °C/s, respectively. This high-efficiency thermal suppression performance primarily relies on the decomposition of trimethyl phosphate at high temperatures to produce PO- and other phosphate radicals. These intermediate products can rapidly combine with chain radicals such as H+ and OH- during combustion, terminating the chain reaction process; simultaneously, aerogel and nano-alumina hydroxide absorb a large amount of thermal energy during decomposition and form insulating particles, creating an inert protective barrier on the surface of the heat source, effectively reducing the rate of temperature propagation and preventing the spread of thermal runaway in lithium batteries. 1

In surface tension tests, the foam tension of Examples 1-3 was controlled between 15.230000 16.5 mN/m, lower than the control ratio (20.4-23.8 mN/m), facilitating rapid spreading, penetration, and tight coverage of the foam on the lithium-ion battery surface, enhancing fire extinguishing efficiency, and preventing the escape of flammable vapours and the risk of reignition.

In summary, this invention constructs a multi-phase synergistic network to achieve foam stability, electrical insulation, and rapid thermal suppression without introducing any high-conductivity components. It systematically addresses the common issues of high conductivity, foam instability, and poor adaptability to lithium-ion battery fire extinguishing in water-based fire extinguishing agents, demonstrating excellent comprehensive fire extinguishing performance and application engineering feasibility. 1

Claims (8)

CLAIMS LU603003

1. À gel-type water-based fire extinguishing agent specially designed for lithtum batteries with low conductivity and high stability, characterised by containing the following ingredients by weight: modified nano-silica aerogel 1-3 parts; nano-aluminium hydroxide 1-3 parts; trimethyl phosphate 1-3 parts; emulsifier OP-10 20-35 parts; antifreeze agent 10-15 parts; fluorocarbon surfactant 0.5—

1.5 parts; antibacterial agent phenoxyethanol 0.5-1.5 parts; foam stabiliser 0.5-2 parts, Xanthan gum 0.3—1.5 parts; calcium lactate 0.1-0.8 parts; bentonite 0.5-2 parts; mica 0.5-2 parts; regulator

0.1-1 part; deionised water 40-60 parts.

2. The gel-type water-based fire extinguishing agent specially designed for lithium batteries with low conductivity and high stability according to claim 1, characterised in that the modified nano-silica aerogel comprises the following raw materials by weight: ethyl orthosilicate 10-20 parts; ethanol 60-100 parts; deionised water 10-20 parts; hydrochloric acid 0.5-1.5 parts; ammonia water

0.5-1.5 parts; methyl triethoxysilane 2-6 parts; 3-(dimethoxyphosphinylmethylamino)propyl triethoxysilane 1-3 parts; the concentration of hydrochloric acid is 0.01 mol/L; the volume fraction of ammonia water is 25%.

3. The gel-type water-based fire extinguishing agent specially designed for lithium batteries with low conductivity and high stability according to claim 1, characterised in that the emulsifier OP-10 is octylphenol polyethylene glycol ether; the antifreeze agent is a mixture of ethylene glycol and glycerol in a mass ratio of 2:1 to 1:1; the fluorocarbon surfactant is a mixture of potassium hexafluorohexyl sulfonate and a surfactant containing perfluoroalkyl carboxylate salts in a mass ratio of 1:2 to 1:3; the antibacterial agent is phenoxyethanol; the regulator is a mixture of triethanolamine and sodium hydroxide solution in a mass ratio of 2:1 to 3:1.

4. The gel-type water-based fire extinguishing agent specially designed for lithium batteries with low conductivity and high stability according to claim 1 or 2, characterised in that the preparation method of the modified nano-silica aerogel includes the following steps: (1) Mix ethyl orthosilicate with ethanol uniformly, then add deionised water and hydrochloric acid while stirring to undergo hydrolysis, forming a transparent sol; (2) Slowly add ammonia water to the transparent sol gel while continuing to stir; 1

(3) Add methyl triethoxysilane and 3-(dioxophosphomethylamino)propyl triethoxyst ame © sequentially; (4) Age the reaction product, then add ethanol for multiple solvent exchanges; (5) Dry to obtain a dry gel; (6) Heat-treat the dry gel to obtain a structurally stable, surface-functional group-coordinated modified nano-silica aerogel.

5. The gel-type water-based fire extinguishing agent specially designed for lithium batteries with low conductivity and high stability according to claim 4, characterised in that: the hydrolysis reaction in step (1) is conducted at a temperature of 25-35°C, for a duration of 30-60 minutes, with a pH of 2.5-3.5; the condensation reaction in step (2) is conducted at a pH of 8-9, for a duration of 1-2 hours; the surface modification reaction in step (3) is carried out at a temperature of 20-30°C for 2-4 hours; the drying temperature in step (5) is 50-80°C, and the drying time is 12-24 hours; the heat treatment temperature in step (6) is 600-800°C, and the holding time is 1-3 hours.

6. A method for preparing a low-conductivity, high-stability gel-type water-based fire extinguishing agent specifically for lithium batteries as described in any one of claims 1 to S is characterised by including the following steps: S1, adding modified nano-silica aerogel and nano-aluminium hydroxide to deionised water, dispersing uniformly under stirring conditions to form a first dispersion solution; S2, mix trimethyl phosphate with emulsifier OP-10 until uniformly mixed, then add to the first dispersion solution and continue stirring to form an emulsion system; S3, add antifreeze agent, fluorocarbon surfactant, antibacterial agent phenoxyethanol, and foam stabiliser to the emulsion, stir and mix to form a uniform main system solution; S4, add xanthan gum and calcium lactate to the main system solution, and slowly add the pH regulator to adjust the pH, while continuing to stir to promote gel structure formation; SS, after gel formation, add bentonite and mica, and stir thoroughly to improve system stability and adhesion performance; S6, add deionised water, mix thoroughly again, and obtain A gel-type water-based fire extinguishing agent specially designed for lithium batteries with low conductivity and high stability. 2

7. The method for preparing a low-conductivity, high-stability gel-type water-based Hog 00> extinguishing agent specifically for lithium batteries according to claim 6, characterised in that the formation temperature of the first dispersion solution in step S1 is 25-35°C.

8. The method for preparing a low-conductivity, high-stability gel-type water-based fire extinguishing agent specifically for lithium batteries according to claim 6, characterised in that the pH during gel formation in step S4 is 6.5-7.5. 3