Fire extinguishing gel as well as preparation method and application thereof

Abstract

The invention discloses fire extinguishing gel as well as a preparation method and application thereof. The fire extinguishing gel is prepared from the following raw materials: starch, borax, temperature-resistant filler and water. The fire extinguishing gel has the characteristics of efficient cooling, lasting flame retardance and environmental friendliness, and can effectively cope with different types of battery fire disasters.

Description

Technical Field

[0001] This invention belongs to the field of fire extinguishing materials, and specifically relates to a fire extinguishing gel, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy technologies, lithium-ion batteries, with their advantages of high energy density and long cycle life, have been widely and deeply applied in many key areas such as new energy vehicles, energy storage power stations, and consumer electronics, profoundly changing people's lifestyles and energy utilization patterns. However, at the same time, the fire safety problems caused by thermal runaway of lithium-ion batteries have gradually become prominent, becoming a key bottleneck that seriously restricts the healthy and sustainable development of related industries.

[0003] Current technologies generally overlook the multimodal characteristics of lithium battery fires. Different types of lithium-ion batteries exhibit drastically different fire behaviors during thermal runaway. On the one hand, although the open flame of lithium iron phosphate (LFP) batteries is relatively weak during thermal runaway, the internal heat release can last for more than 2 hours. This prolonged smoldering state places extremely high demands on the sustained flame-retardant performance of extinguishing materials. On the other hand, high-nickel ternary batteries (NCM / NCA) are accompanied by violent jet fires, with flame temperatures exceeding 1000°C within 30 seconds. This instantaneous high temperature poses a severe challenge to the rapid response capability of extinguishing materials. These differentiated fire behaviors require extinguishing materials to possess dynamic response capabilities: they must be able to rapidly form a carbonized barrier layer at high temperatures (>800°C) and maintain structural integrity at medium and low temperatures (300-500°C) to block smoldering, thus effectively addressing the characteristics of different types of battery fires. Therefore, there is an urgent need in this field to develop a extinguishing material that combines efficient cooling, sustained flame retardancy, and environmental friendliness. Summary of the Invention

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a fire extinguishing gel, its preparation method, and its application. This fire extinguishing gel possesses efficient cooling, long-lasting flame retardancy, and environmentally friendly properties, and can effectively respond to different types of battery fires.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A fire extinguishing gel comprises the following raw materials: starch, borax, heat-resistant filler, and water.

[0007] In some embodiments of the present invention, the raw materials include the following parts by weight: starch: 50-100 parts; borax: 3-8 parts; heat-resistant filler: 5-15 parts; water: 800-1200 parts.

[0008] In some embodiments of the present invention, the starch is at least one of corn starch, tapioca starch, and potato starch.

[0009] In some embodiments of the present invention, the heat-resistant filler is at least one of calcium chloride and nano-silica.

[0010] In some embodiments of the present invention, the mass ratio of the heat-resistant filler to borax is (1-3):1.

[0011] In some embodiments of the present invention, the raw materials further include a thickener, wherein the thickener is present in parts by weight of 0.5-5 parts.

[0012] In some embodiments of the present invention, the thickener is at least one of sodium carboxymethyl cellulose and gelatin.

[0013] A method for preparing the fire extinguishing gel as described above includes the following steps:

[0014] (1) Mix starch with water, heat and stir to form a gelatinized solution;

[0015] (2) After cooling the gelatinized solution, borax is added and stirred to form a primary gel;

[0016] (3) Add heat-resistant filler to the primary gel, mix, and let stand to solidify.

[0017] In some embodiments of the present invention, in step (1), the temperature after heating is 60-80°C, and the stirring time is 20-60 minutes.

[0018] In some embodiments of the present invention, in step (2), the temperature after cooling is 25-40°C.

[0019] In some embodiments of the present invention, in step (3), the mixing is performed by homogenization using a homogenizer, with a homogenization speed of 1000-3000 rpm and a homogenization time of 10-20 minutes.

[0020] In some embodiments of the present invention, a thickener is added after the standing period in step (3).

[0021] In some embodiments of the present invention, in step (3), the viscosity of the fire extinguishing gel obtained after adding the thickener is 500-2000 mPa·s at 25°C.

[0022] In step (3), curing refers to placing the product at room temperature for 15-30 hours.

[0023] Application of a fire extinguishing gel as described above in the protection against thermal runaway in lithium-ion batteries.

[0024] In some embodiments of the present invention, the method of application is to cover the battery surface with the fire extinguishing gel at a thickness of 5-15 mm.

[0025] The beneficial effects of the present invention are:

[0026] (1) The fire extinguishing gel of the present invention constructs a ternary synergistic system of starch-borax-heat resistant filler, which makes its decomposition temperature >800℃, matching the temperature field of lithium-ion battery fire, and ensuring that the gel material can maintain its stability under high temperature environment.

[0027] (2) The fire extinguishing gel of the present invention has a specific heat capacity of >3.5J / (g·K) and a latent heat of phase change of >850J / g, and has a strong heat absorption capacity, which can quickly absorb the large amount of heat released by the thermal runaway of lithium-ion batteries.

[0028] (3) The fire extinguishing gel of the present invention can form an interconnected carbon skeleton of BO-Ca or BO-Si composite barrier layer with a porosity of 60%-85% and an average pore size of 1-5μm at a high temperature of 800-1200℃. The oxygen blocking efficiency is >95%, which can effectively isolate oxygen and prevent the spread of fire.

[0029] (4) The raw material cost of the fire extinguishing gel of the present invention is less than RMB 1 / liter, which enables large-scale configuration in scenarios such as vehicle-mounted emergency systems, effectively reducing usage costs and improving market competitiveness.

[0030] (5) The fire extinguishing gel of the present invention has a 60% shorter response time than dry powder fire extinguishing agent.

[0031] (6) The fire extinguishing gel of the present invention has good environmental adaptability, with a pH value of 6.5-7.5 and a degradation cycle of ≤30 days. Attached Figure Description

[0032] Figure 1 Here is a SEM image of the fire extinguishing gel of Example 4 of the present invention;

[0033] Figure 2 Thermogravimetric curve of the fire extinguishing gel in Example 4 of the present invention;

[0034] Figure 3 The infrared spectrum of the fire extinguishing gel of Example 5 of the present invention;

[0035] Figure 4 This is a comparison temperature curve of the fire extinguishing gel used in Example 4 of the present invention and the combustion of a lithium iron phosphate cathode lithium-ion battery.

[0036] Figure 5 The temperature comparison curves of ternary lithium cathode lithium-ion batteries under three scenarios: no fire extinguishing, water fire extinguishing, and fire extinguishing using the fire extinguishing gel of Example 3.

[0037] Figure 6 This is a diagram showing the biodegradation kinetics of the fire extinguishing gel of Example 4 of the present invention in three different environments: compost, soil, and freshwater. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments.

[0039] Example 1:

[0040] A fire extinguishing gel comprises the following raw materials in parts by weight: corn starch: 50g; borax: 3g; calcium chloride: 5g; sodium carboxymethyl cellulose: 0.5g; water: 800g.

[0041] A method for preparing the fire extinguishing gel as described above includes the following steps:

[0042] (1) Mix corn starch with water, heat to 60°C and stir for 60 minutes to form a gelatinized solution;

[0043] (2) After cooling the gelatinized solution to 40°C, add borax and stir for 20 minutes to form a primary gel;

[0044] (3) After adding calcium chloride to the primary gel, homogenize at 1000 rpm for 20 min, let stand, add sodium carboxymethyl cellulose, stir and mix, and adjust the viscosity to 500 mPa·s (25℃).

[0045] (4) Curing at room temperature for 24 hours yields a transparent fire extinguishing gel.

[0046] Example 2:

[0047] A fire extinguishing gel comprises the following raw materials in parts by weight: potato starch: 100g; borax: 8g; calcium chloride: 15g; gelatin: 5g; water: 1200g.

[0048] A method for preparing the fire extinguishing gel as described above includes the following steps:

[0049] (1) Mix potato starch with water, heat to 80°C and stir for 20 minutes to form a gelatinized solution;

[0050] (2) After cooling the gelatinized solution to 25°C, add borax and stir for 20 minutes to form a primary gel;

[0051] (3) Add calcium chloride to the primary gel and homogenize at 3000 rpm for 10 min. After standing, add gelatin, stir and mix, and adjust the viscosity to 500 mPa·s (25℃).

[0052] (4) Curing at room temperature for 24 hours yields a transparent fire extinguishing gel.

[0053] Example 3:

[0054] A fire extinguishing gel comprises the following raw materials in parts by weight: corn starch: 60g; borax: 5g; calcium chloride: 10g; sodium carboxymethyl cellulose: 2g; water: 1000g.

[0055] A method for preparing the fire extinguishing gel as described above includes the following steps:

[0056] (1) Mix corn starch with water, heat to 70°C and stir for 30 minutes to form a gelatinized solution;

[0057] (2) After cooling the gelatinized solution to 30°C, add borax and stir for 20 minutes to form a primary gel;

[0058] (3) After adding calcium chloride to the primary gel, homogenize at 2000 rpm for 15 min, let stand, add sodium carboxymethyl cellulose, stir and mix, and adjust the viscosity to 1200 mPa·s (25℃).

[0059] (4) Curing at room temperature for 24 hours yields a transparent fire extinguishing gel.

[0060] Example 4:

[0061] A fire extinguishing gel comprises the following raw materials in parts by weight: tapioca starch: 80g; borax: 5g; calcium chloride: 7.5g; sodium carboxymethyl cellulose: 2g; water: 1000g.

[0062] A method for preparing the fire extinguishing gel as described above includes the following steps:

[0063] (1) Mix cassava starch with water, heat to 75°C and stir for 30 minutes to form a gelatinized solution;

[0064] (2) After cooling the gelatinized solution to 30°C, add borax and stir for 20 minutes to form a primary gel;

[0065] (3) After adding calcium chloride to the primary gel, homogenize at 2000 rpm for 15 min, let stand, add sodium carboxymethyl cellulose, stir and mix, and adjust the viscosity to 1200 mPa·s (25℃).

[0066] (4) Curing at room temperature for 24 hours yields a transparent fire extinguishing gel.

[0067] The fire extinguishing material prepared in Example 4 was subjected to relevant performance tests, and the test results are shown in [the table below]. Figure 1-Figure 4 as well as Figure 6 .

[0068] Figure 1Presented are scanning electron microscope (SEM) images of the microstructure of the fire extinguishing gel from Example 4. The images are predominantly black and white with a clean, colorless background, revealing a densely distributed three-dimensional porous network as the main structure. Numerous irregularly curved fibrous materials are visible, cross-linking to form an intricate network morphology. The edges of the lines are slightly rough, and the pores vary in size and are interconnected without clear boundaries, uniformly filling the entire field of view. The sizes of the pores and fibers in the images range from the micrometer level, with typical pore diameters of approximately 1-5 μm and fiber diameters of several hundred nanometers. This highly porosity interconnected structure suggests excellent liquid absorption and mechanical stability. The high contrast of the black and white images further highlights the clear details of the microstructure, conveying a precise and orderly microscopic scientific characteristic.

[0069] Figure 2 The green curve shows that the mass fraction of the material slowly decreases from 100% to 95% within the 0–800℃ range, indicating that only a small amount of moisture and low-boiling-point substances volatilize during this stage. When the temperature exceeds 800℃, the curve drops sharply to about 40%, corresponding to the carbonization and decomposition of the starch matrix and the breakage of the borax skeleton. The purple weight loss rate curve remains below 5 g / ℃ in the 0–800℃ range, proving the material's excellent thermal stability. At 800℃, the curve rises vertically to a peak of 90 g / ℃, and then falls back to 50 g / ℃ after 900℃, reflecting that the residual carbon layer inhibits further degradation after the material undergoes violent decomposition in the high-temperature region. The synchronous abrupt change of the two curves at 800℃ reveals the concentrated pyrolysis behavior of the main component of the fire extinguishing gel. The data in the graphs visually verify the high-temperature flame-retardant properties imparted to the material by the synergistic effect of the borax-starch crosslinking system and calcium chloride.

[0070] Figure 4 The graph shows the temperature curves comparing the fire extinguishing gel used in Example 4 with the combustion of a lithium iron phosphate cathode lithium-ion battery. The two broken lines are presented in magenta (battery combustion) and orange-red (fire extinguishing gel fire extinguishing), respectively. In the initial stage (0–800 seconds), both curves slowly rise from room temperature (approximately 25°C) to 300°C, reflecting the common characteristics of the early stage of battery thermal runaway. After 800 seconds, the magenta curve spikes to a peak of 1180°C (at 1000 seconds) with a near-vertical slope within 200 seconds, and then drops sharply to approximately 800°C (at 1400 seconds), showing the brief decay after intense combustion and local energy release. The orange-red curve shows that after the fire extinguishing gel was introduced at 800 seconds, the temperature only rose to 600℃ (at 1000 seconds), and then rapidly dropped to below 80℃ within 200 seconds and stabilized, with a temperature reduction of 94%. This indicates that the fire extinguishing gel effectively controls fire through a triple mechanism of heat absorption (calcium chloride decomposition), oxygen isolation (gel coverage), and suppression of reignition (borax-starch carbonization layer). The significant difference between the two curves in the 800–1000 second range directly verifies the strong ability of this fire extinguishing gel formulation (total cost 0.3 yuan / L) to suppress thermal runaway of lithium-ion batteries.

[0071] Figure 6 The biodegradation kinetics of the fire extinguishing gel in three different environments—compost, soil, and freshwater—are demonstrated. The three broken lines in the figure correspond to different degradation media: the green square line represents the compost environment, where the degradation rate is most significant, reaching 20% ​​mass loss in 5 days, exceeding 80% in 15 days, and nearly completely degraded (approximately 98%) by 30 days, exhibiting an exponential rapid decomposition trend; the blue triangular line reflects degradation in the soil environment, with a slow loss of about 30% in the initial stage (0-10 days), accelerating to over 93% by 30 days, reflecting the gradual decomposition process of soil microorganisms; the red dotted line corresponds to the freshwater environment, where mass loss increases linearly, accumulating to 72% in 30 days, indicating that hydrolysis is dominant and the slow release of calcium ions inhibits microbial activity. Three sets of data visually verify that the composting conditions, through high temperature and humidity and the synergy of microorganisms, achieved near-complete degradation (98.7%) in 30 days, followed by soil (93.6%), and freshwater was the slowest (72.4%), but all were significantly better than traditional synthetic materials (such as PLA, which degrades by less than 15% under the same composting conditions). The vertical axis of the graph is spaced at 20% intervals, and the horizontal axis has nodes every 5 days. The line graph data points are highly consistent with the supplementary experimental tables (28.5% after 7 days of composting, 98.7% after 30 days, etc.), fully presenting the environmentally friendly characteristics of the gel: "highly efficient fire extinguishing - rapid degradation".

[0072] Example 5:

[0073] A fire extinguishing gel comprises the following raw materials in parts by weight: tapioca starch: 80g; borax: 5g; calcium chloride: 7.5g; water: 1000g.

[0074] A method for preparing the fire extinguishing gel as described above includes the following steps:

[0075] (1) Mix cassava starch with water, heat to 75°C and stir for 30 minutes to form a gelatinized solution;

[0076] (2) After cooling the gelatinized solution to 30°C, add borax and stir for 20 minutes to form a primary gel;

[0077] (3) Add calcium chloride to the primary gel and homogenize at 2000 rpm for 15 min;

[0078] (4) Curing at room temperature for 24 hours yields a transparent fire extinguishing gel.

[0079] Figure 3 The infrared (IR) spectrum of the fire extinguishing gel in Example 5 is shown. The purple curve clearly displays several characteristic absorption peaks: at approximately 3400 cm⁻¹ -1 There is a wide and deep absorption valley at this point, corresponding to the stretching vibrations of hydroxyl groups (OH) in starch and water; 1640 cm -1The nearby trough may originate from the HOH bending vibration of adsorbed water or the vibration of starch CO bonds; 1150cm -1 The moderate-intensity absorption peak at 890 cm⁻¹ is related to the symmetric stretching vibration of the amylose bond (COC); -1 The nearby small peaks suggest the characteristic vibrations of the BO bonds formed by the cross-linking of borax and starch. The overall shape of the curve confirms the successful gelatinization of the starch matrix and the cross-linking reaction of borax. The addition of calcium chloride may affect the broadening of the hydroxyl peak through ionic interactions, but no obvious Cl- characteristic peak was observed. No absorption peaks of gelatin (amide bond) or CMC (carboxylate group) were detected in the spectrum, indicating that no optional thickener was added to the sample. The fluctuations of the purple curve against the white background visually reflect the chemical structural characteristics at the molecular level of the material.

[0080] Example 6:

[0081] A fire extinguishing gel comprises the following raw materials in parts by weight: tapioca starch: 80g; borax: 5g; nano silica: 7.5g; water: 1000g.

[0082] A method for preparing the fire extinguishing gel as described above includes the following steps:

[0083] (1) Mix cassava starch with water, heat to 75°C and stir for 30 minutes to form a gelatinized solution;

[0084] (2) After cooling the gelatinized solution to 30°C, add borax and stir for 20 minutes to form a primary gel;

[0085] (3) After adding nano-silica to the primary gel, homogenize at 2000 rpm for 15 min;

[0086] (4) Curing at room temperature for 24 hours yields a transparent fire extinguishing gel.

[0087] Application example:

[0088] The fire extinguishing gel prepared in Example 3 was applied to the surface of an 18650 ternary lithium battery (covering thickness of 10 mm), and thermal runaway of the battery was induced by short circuit:

[0089] • Untreated group: Open flame appears within 3 seconds, peak temperature reaches 1180℃ (see attached image) Figure 5 (Red curve);

[0090] • Gel treatment group: The flame extinguished within 8 seconds, the highest temperature was only 402℃, and it dropped to 45℃ after 400 seconds (see attached). Figure 5 Blue curve.

[0091] Depend on Figure 5As can be seen, the red curve shows a rapid temperature increase from room temperature to a peak of 1000℃ within 0-1600 seconds, followed by continuous fluctuations between 800-950℃ between 1600-4000 seconds, reflecting intense battery combustion without any decay trend. The green curve shows a temperature rise to 800℃ within the same time period, followed by a slow decline, stabilizing at around 600℃ after 4000 seconds, indicating that water extinguishing can partially suppress combustion, but its efficiency is limited. The blue curve (fire extinguishing gel) shows a temperature rise to only 400℃ before rapidly falling back, stabilizing below 50℃ after 2000 seconds, with a temperature reduction of 95%, and no reignition fluctuations throughout the process. The significant difference among the three curves after 1600 seconds (red > green > blue) intuitively verifies that the fire extinguishing gel, through its borax-starch cross-linked structure (cost 0.3 yuan / L), rapidly covers the battery surface, synergistically combining the endothermic decomposition of calcium chloride and the oxygen barrier effect of the carbonized layer, demonstrating a much higher temperature control capability than traditional water extinguishing in the thermal runaway scenario of ternary lithium batteries.

[0092] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A fire extinguishing gel, characterized in that: The raw materials include: starch, borax, heat-resistant filler, and water.

2. The fire extinguishing gel according to claim 1, characterized in that: The raw materials include the following parts by weight: starch: 50-100 parts; borax: 3-8 parts; heat-resistant filler: 5-15 parts; Water: 800-1200 servings.

3. The fire extinguishing gel according to claim 1, characterized in that: The starch is at least one of corn starch, tapioca starch, and potato starch.

4. The fire extinguishing gel according to claim 1, characterized in that: The heat-resistant filler is at least one of calcium chloride and nano-silica.

5. The fire extinguishing gel according to claim 2, characterized in that: The mass ratio of the heat-resistant filler to borax is (1-3):

1.

6. The fire extinguishing gel according to claim 2, characterized in that: The raw materials also include a thickener, which is 0.5-5 parts by weight.

7. A method for preparing the fire extinguishing gel according to any one of claims 1 to 6, characterized in that: Includes the following steps: (1) Mix starch with water, heat and stir to form a gelatinized solution; (2) After cooling the gelatinized solution, borax is added and stirred to form a primary gel; (3) Add heat-resistant filler to the primary gel, mix, and let stand to solidify.

8. The method for preparing a fire extinguishing gel according to claim 7, characterized in that: In step (1), the temperature after heating is 60-80℃, and the stirring time is 20-60 minutes.

9. The method for preparing a fire extinguishing gel according to claim 7, characterized in that: In step (3), the mixing is performed by homogenizing with a homogenizer at a speed of 1000-3000 rpm for 10-20 minutes.

10. The application of the fire extinguishing gel as described in any one of claims 1-6 in the protection against thermal runaway of lithium-ion batteries.

Images