Anti-reheat gel foam suitable for lithium ion battery fire extinguishing and preparation method thereof

Abstract

The application discloses a kind of anti-reheat gel foams suitable for lithium ion battery fire extinguishing and preparation method thereof.The anti-reheat gel foams suitable for lithium ion battery fire extinguishing, by weight percentage, its raw materials include: surfactant 0.1%-0.6%, gelling agent 0.3%-0.4%, coagulation accelerator 2.5%-3.5%, crosslinking agent 10%-14%, and the balance is water.The anti-reheat gel foams provided by the application have controllable gelling time and strong cooling performance, compared with other lithium ion battery extinguishing agents, show good fire extinguishing and sustained cooling effect, can quickly extinguish lithium ion battery open fire, and solve the problem of lithium ion battery easy reheat and reignition.

Description

Technical Field

[0001] This invention relates to the field of fire prevention and extinguishing technology for lithium-ion batteries, specifically to a heat-resistant gel foam suitable for fire extinguishing of lithium-ion batteries and its preparation method. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, long cycle life, and short charge / discharge time, making them promising for applications in new energy vehicles and electrochemical energy storage. However, their high energy density leads to violent combustion and a high risk of reignition in fires, severely hindering their widespread use. Based on the characteristics of lithium-ion battery fires, extinguishing fires requires not only rapid suppression of open flames but also continuous cooling of the battery to suppress spontaneously generating chemical reactions within the battery materials and prevent reignition. Therefore, selecting appropriate extinguishing agents is crucial for the efficient suppression of lithium-ion battery fires.

[0003] Currently, fire extinguishing agents commonly used to extinguish lithium-ion battery fires can be categorized into water-based, solid, and gaseous extinguishing agents. Commonly used water-based extinguishing agents, such as ordinary fine water mist and fine water mist containing additives, have superior cooling capabilities. However, after spraying ceases, the batteries are prone to reignition. Furthermore, due to the conductivity of water, the sprayed battery packs are difficult to recycle. Solid extinguishing agents are primarily dry powder extinguishing agents. After spraying, they can extinguish open flames in lithium-ion batteries, and their high-temperature decomposition products can interrupt the combustion chain reaction. However, the coverage of dry powder on the battery surface is limited, and it cannot effectively inhibit the exothermic chemical reactions inside the battery, making reignition easy after extinguishing. Gaseous fire extinguishing agents extinguish fires by diluting oxygen. Commonly used gaseous fire extinguishing agents include heptafluoropropane and perfluorohexanone. Heptafluoropropane can extinguish lithium-ion battery flames in a relatively confined space in a short time, but its cooling capacity is poor, making it difficult to suppress the problem of battery reignition. Although perfluorohexanone has a better fire extinguishing and cooling effect, it is toxic, and the threat of its toxicity still needs to be considered after extinguishing open flames of lithium-ion batteries.

[0004] Therefore, developing a fire extinguishing agent that can quickly extinguish open flames of lithium-ion batteries and has a sustained cooling capacity to prevent them from reigniting is an important problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a reheat-resistant gel foam suitable for extinguishing lithium-ion battery fires and its preparation method, thereby solving the technical problems of existing lithium-ion battery fire extinguishing agents having poor extinguishing effect on open flames of lithium-ion batteries, lacking sustained cooling ability, and being prone to reheating and reignition.

[0006] In a first aspect, the present invention provides a heat-resistant gel foam suitable for extinguishing fires in lithium-ion batteries. By weight percentage, its raw materials include: 0.1%-0.6% surfactant, 0.3%-0.4% gelling agent, 2.5%-3.5% accelerator, 10%-14% crosslinking agent, and the balance being water.

[0007] Secondly, the present invention provides a method for preparing a reheat-resistant gel foam suitable for extinguishing fires in lithium-ion batteries, comprising the following steps:

[0008] Prepare surfactant solutions and mixtures of gelling agents and coagulants;

[0009] The surfactant solution is foamed, and a mixture of gelling agent and coagulant and crosslinking agent are added sequentially during the foaming process. After sufficient foaming, a heat-resistant gel foam suitable for lithium-ion battery fire extinguishing is obtained.

[0010] Compared with the prior art, the beneficial effects of the present invention include:

[0011] The anti-reignition gel foam provided by this invention has a controllable gelation time and strong cooling performance. Compared with other lithium-ion battery fire extinguishing agents, it exhibits good fire extinguishing and continuous cooling effects, can quickly extinguish open flames of lithium-ion batteries, and solve the problem of easy reignition of lithium-ion batteries. Attached Figure Description

[0012] Figure 1 This is a schematic diagram showing the arrangement of the lithium-ion battery, heating rod, and thermocouple used in the fire extinguishing experiment of this invention.

[0013] Figure 2 This is a fire extinguishing effect curve of the lithium-ion battery using anti-heat-recovery gel foam in Embodiment 1 of the present invention;

[0014] Figure 3 This is a microstructure diagram of the anti-thermal gel foam after gelation and solidification in Example 1 of the present invention;

[0015] Figure 4 This is a fire extinguishing effect curve of lithium-ion battery using anti-heat-recovery gel foam in Embodiment 2 of the present invention;

[0016] Figure 5 This is a fire extinguishing effect curve of the lithium-ion battery using anti-heat-recovery gel foam in Embodiment 3 of the present invention;

[0017] Figure 6 This is a fire extinguishing effect curve of lithium-ion battery using anti-heat-recovery gel foam in Embodiment 4 of the present invention;

[0018] Figure 7 This is a combustion temperature curve of the lithium-ion battery in Comparative Example 1 of the present invention without the use of any fire extinguishing agent;

[0019] Figure 8 This is a fire extinguishing effect curve of the lithium-ion battery using water mist in Comparative Example 2 of the present invention;

[0020] Figure 9 This is a fire extinguishing effect curve of the lithium-ion battery using gel foam in Comparative Example 3 of the present invention;

[0021] Figure 10 This is a graph showing the fire extinguishing effect of the lithium-ion battery using gel foam in Comparative Example 4 of this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] In a first aspect, the present invention provides a heat-resistant gel foam suitable for extinguishing fires in lithium-ion batteries. By weight percentage, its raw materials include: 0.1%-0.6% surfactant, 0.3%-0.4% gelling agent, 2.5%-3.5% accelerator, 10%-14% crosslinking agent, and the balance being water.

[0024] The anti-reignition gel foam of the present invention has good thermal stability and cooling properties. In the initial stage, it quickly extinguishes the open flame of the lithium-ion battery in the form of foam. In the later stage, it covers the battery surface and solidifies to form a gel isolation layer with high water content, which continuously cools the battery surface and inhibits the spontaneous heat generation chemical reaction of the internal materials of the battery, thereby effectively preventing the lithium-ion battery from re-igniting.

[0025] Preferably, the heat-resistant gel foam suitable for extinguishing fires in lithium-ion batteries comprises, by weight percentage: 0.4% surfactant, 0.35% gelling agent, 3% accelerator, 12% crosslinking agent, and the balance being water.

[0026] Preferably, the surfactant system consists of amphoteric surfactants and anionic surfactants.

[0027] Furthermore, the zwitterionic surfactant is selected from one or more of myristyl betaine, lauramidopropyl betaine, alkyl dimethyl betaine, and sodium dodecylaminopropionate.

[0028] As a preferred option, the zwitterionic surfactant is lauramidopropyl betaine.

[0029] Furthermore, the anionic surfactant is selected from one or more of sodium alkylbenzene sulfonate, sodium fatty alcohol ether sulfate, sodium secondary alkyl sulfonate, and alcohol ether carboxylates.

[0030] Preferably, the anionic surfactant is sodium alkylbenzene sulfonate.

[0031] Furthermore, the mass ratio of zwitterionic surfactant to anionic surfactant in the surfactant is 1:(2-9).

[0032] Preferably, the mass ratio of zwitterionic surfactant to anionic surfactant is 1:9.

[0033] Furthermore, the gelling agent is selected from one or more of konjac gum, carrageenan, and xanthan gum.

[0034] Konjac gum is preferred as the gelling agent.

[0035] Furthermore, the coagulant is selected from one or both of sodium bicarbonate and potassium bicarbonate. The acidic environment provided by bicarbonate can reduce the charge repulsion of silicate (sodium silicate, potassium silicate) particles, accelerate particle aggregation, and ultimately form an inorganic gel.

[0036] Furthermore, the crosslinking agent is selected from one or two of sodium silicate and potassium silicate.

[0037] Preferably, sodium silicate is used as the crosslinking agent.

[0038] Secondly, the present invention provides a method for preparing a reheat-resistant gel foam suitable for extinguishing fires in lithium-ion batteries, comprising the following steps:

[0039] S1. Prepare a surfactant solution and a mixture of gelling agent and coagulant;

[0040] S2. The surfactant solution is foamed, and a mixture of gelling agent and coagulant and crosslinking agent are added sequentially during the foaming process. After sufficient foaming, a heat-resistant gel foam suitable for lithium-ion battery fire extinguishing is obtained.

[0041] In this invention, it should be noted that "fully foamed" refers to the foam volume no longer expanding and increasing during the stirring process, and tending to a stable state.

[0042] Preferably, in step S1, the preparation process of the surfactant solution includes: mixing the surfactant with water until homogeneous to obtain a surfactant solution (i.e., a foaming agent).

[0043] Furthermore, the water used in the preparation of the surfactant solution accounts for 70%-80% of the total water volume, and even more specifically 75%.

[0044] Furthermore, the mixture is stirred until homogeneous, at room temperature, at a speed of 1000-1500 r / min, and further to 1200 r / min, for a time of 1-3 min.

[0045] Furthermore, after stirring evenly, the mixture is allowed to stand at room temperature for 20-40 minutes. This invention, through standing, allows surfactant molecules to reach equilibrium at the water-air interface, reducing surface tension. Additionally, since stirring produces some foam, standing further improves solution stability.

[0046] Preferably, in step S1, the preparation process of the mixture of gelling agent and accelerator includes: mixing gelling agent, accelerator and water evenly to obtain the mixture of gelling agent and accelerator.

[0047] Furthermore, the water used in the preparation of the mixture of gelling agent and coagulant accounts for 20%-30% of the total water volume, and even further, 25%.

[0048] Furthermore, the mixture is stirred evenly at a temperature of 35-45℃, or 40℃, at a speed of 800-1200 r / min, or 1000 r / min, for a duration of 5-10 min.

[0049] Preferably, in step S2, the surfactant solution is foamed by high-speed stirring. This invention, through high-speed stirring, can generate a large amount of foam. Initially, this large amount of foam can more quickly cover the battery surface and penetrate into the gaps around the battery, providing a continuous cooling effect after gelation and solidification.

[0050] Furthermore, the high-speed stirring temperature is room temperature, the high-speed stirring speed is 1000-1500 r / min, and even more specifically 1200 r / min, and the high-speed stirring time is 1-3 min, and even more specifically 2 min.

[0051] To avoid redundancy, in the following embodiments and comparative examples of the fire extinguishing (or combustion) experiments of this invention, a cylindrical heating rod is used to heat the battery pack. The heating rod is 65mm long and 18mm in diameter, and is fixed in the middle of the battery. Figure 1 As shown, #1-#4 are 1mm diameter K-type armored thermocouples with a response time of 1s, a range of 0-1300℃, and an accuracy error of ±1.0℃, fixed to the battery surface to record the battery surface temperature. The battery pack consists of four 2000mAh, 3.2V commercial 18650 lithium-ion batteries. A battery testing system was used to prepare the batteries for testing. The procedure was as follows: first, the lithium-ion batteries were left to stand for 20 minutes; then, they were discharged at a constant current of 1A to a voltage of 2V, left to stand for 20 minutes, and finally charged at a constant current and constant voltage to 3.65V until the charging current dropped below 20mA. This cycle was repeated three times. After charging, the batteries were left to stand for 12 hours to ensure their stability before testing.

[0052] Example 1

[0053] A heat-resistant gel foam suitable for extinguishing fires involving lithium-ion batteries, comprising, by weight percentage: 0.04% lauramidopropyl betaine, 0.36% sodium alkylbenzene sulfonate (LAS-90), 0.35% konjac gum, 3% sodium bicarbonate, 12% sodium silicate, with the balance being water.

[0054] The preparation method includes: first, amphoteric surfactants and anionic surfactants are compounded in proportion, and 75% of the total water volume is added to the mixture. The mixture is stirred at 1200 r / min for 2 min at room temperature and then allowed to stand for 30 min as a foaming agent. Then, a gelling agent and a coagulant are placed in a magnetic stirrer and 25% of the total water volume is added. The stirring temperature is 40℃, the stirring speed is 1000 r / min, and the stirring time is 6 min to obtain a mixture of gelling agent and coagulant. Finally, the foaming agent is foamed by high-speed mechanical stirring at room temperature, 1200 r / min, and for 2 min. During the stirring process, the mixture of gelling agent and coagulant and a crosslinking agent are added sequentially. After sufficient foaming, a heat-resistant gel foam suitable for lithium-ion battery fire extinguishing is obtained, and a fire extinguishing experiment is conducted.

[0055] Heating the battery induces thermal runaway in the battery pack. When the battery opens the safety valve and flammable gas is released, use an electric ignition device to ignite the flammable gas. After ignition (when a jet fire appears at 530s), spray gel foam at 40cm above the battery pack for 30s.

[0056] After the gel foam was applied, the open flame was immediately extinguished. The gel foam quickly covered the battery surface, forming an insulating layer that effectively prevented external oxygen from contacting the battery and suppressed the spread of the fire. Figure 2 It can be seen that the highest surface temperature of the battery was 204℃, which rapidly dropped to 100℃ within 30 seconds, with a cooling rate of 3.47℃ / s. Afterward, the battery surface temperature fluctuated slightly because the spontaneously generating chemical reaction inside the battery was still ongoing, continuously releasing heat, and finally tended to cool down continuously. The total time from 100℃ to the safe temperature of 50℃ was 260 seconds, and no battery reheating was observed during the entire process. According to... Figure 3 It is known that after the gel foam solidifies, it extends a gel skeleton in all directions, and at the same time, the surface exhibits an irregular porous structure, which is interconnected to form a three-dimensional network structure containing holes.

[0057] Example 2

[0058] The only difference from Example 1 is the content of lauramidopropyl betaine and sodium alkylbenzene sulfonate: lauramidopropyl betaine 0.12% and sodium alkylbenzene sulfonate (LAS-90) 0.28%. The remaining components and preparation methods are the same as in Example 1. The above-mentioned gel foam was prepared for fire extinguishing experiments.

[0059] Heating the battery induces thermal runaway in the battery pack. When the battery opens the safety valve and flammable gas is released, use an electric ignition device to ignite the flammable gas. After ignition (when a jet fire appears at 533 seconds), spray gel foam at 40 cm above the top of the battery pack for 30 seconds.

[0060] After the gel foam is applied, the open flame is immediately extinguished, according to Figure 4 It can be seen that the highest surface temperature of the battery was 210℃, which dropped to 100℃ within 35 seconds, with a cooling rate of 3.14℃ / s. After that, the surface temperature of the battery rose slightly and fluctuated, eventually tending to cool down continuously. The total time from the initial cooling to 100℃ to the subsequent cooling to the safe temperature of 50℃ was 320 seconds. This is because when the surfactant system was not at the preferred concentration of Example 1, the foaming properties and stability of the gel foam decreased, making it more prone to collapse and breakage after covering the battery surface. This resulted in a thinner insulating layer after gelation and solidification, poorer cooling performance, and a longer cooling time. However, the battery did not eventually reheat, and the fire extinguishing effect was good.

[0061] Example 3

[0062] The only difference from Example 1 is the content of the coagulant: sodium bicarbonate 2.5%. The other components and preparation methods are the same as in Example 1. The above-mentioned gel foam was prepared for fire extinguishing experiments.

[0063] Heating the battery induces thermal runaway in the battery pack. When the battery opens the safety valve and flammable gas is released, use an electric ignition device to ignite the flammable gas. After ignition (when a jet fire appears at 535 seconds), spray gel foam at 40 cm above the battery pack for 30 seconds.

[0064] After the gel foam is applied, the open flame is immediately extinguished, according to Figure 5It can be seen that the battery surface temperature reached a maximum of 212℃, rapidly dropping to 100℃ within 35 seconds, at a cooling rate of 3.2℃ / s. Afterward, the battery surface temperature rebounded to some extent for a short period, but the maximum rebound temperature only reached 117℃. Then, the battery surface temperature fluctuated slightly before finally trending towards continuous cooling. The total time from the initial drop to 100℃ to the subsequent drop to the safe temperature of 50℃ was 385 seconds. This is because the use of sodium bicarbonate at the optimal concentration prolonged the gelation time of the gel foam. When sprayed onto the lithium-ion battery surface, it failed to gel and solidify in time to form an effective insulating layer, resulting in a slight rebound in battery surface temperature after the fire was extinguished and a prolonged cooling time. However, the battery did not subsequently reheat, indicating a good fire extinguishing effect.

[0065] Example 4

[0066] The only difference from Example 1 is that the gelling agent is carrageenan and the crosslinking agent is potassium silicate. The remaining components and preparation methods are the same as in Example 1. The above-mentioned gel foam was prepared for fire extinguishing experiments.

[0067] Heating the battery induces thermal runaway in the battery pack. When the battery opens the safety valve and flammable gas is released, use an electric ignition device to ignite the flammable gas. After ignition (when a jet fire appears at 535 seconds), spray gel foam at 40 cm above the battery pack for 30 seconds.

[0068] After the gel foam is applied, the open flame is immediately extinguished, according to Figure 6 It can be seen that the highest surface temperature of the battery was 209℃, which dropped to 100℃ within 35 seconds, with a cooling rate of 3.11℃ / s. Afterward, the surface temperature of the battery rose slightly and fluctuated, eventually trending towards continuous cooling. The total time from the initial cooling to 100℃ to the subsequent cooling to the safe temperature of 50℃ was 345 seconds. This is because the gelling agent and crosslinking agent were not formulated optimally, resulting in poor synergy between them. This led to reduced water retention of the gel foam, poorer cooling effect of the insulating layer, and a longer cooling time. However, the battery did not experience any reheating, and the fire extinguishing effect was good.

[0069] Comparative Example 1

[0070] A lithium-ion battery combustion experiment without the use of any extinguishing agents.

[0071] Heating the battery induces thermal runaway in the battery pack. When the battery opens its safety valve and flammable gas is released, an electric ignition device is used to ignite the flammable gas.

[0072] according to Figure 7It can be seen that the highest surface temperature of the battery is 205℃. Without the use of any fire extinguishing agent, the surface temperature of the battery naturally cools down slowly, dropping to 100℃ within 700s, with a cooling rate of 0.14℃ / s. The total time taken to cool down from 100℃ to the safe temperature of 50℃ is 1700s.

[0073] Comparative Example 2

[0074] A water mist fire extinguishing experiment was conducted.

[0075] Heating the battery induces thermal runaway in the battery pack. When the battery opens the safety valve and flammable gas is released, use an electric ignition device to ignite the flammable gas. After ignition (when a jet fire appears at 520 seconds), spray water mist at 40 cm above the top of the battery pack. Set the spray angle to 40°, the water pressure to 1.5 MPa, and spray for 30 seconds.

[0076] After the water mist was sprayed, the open flame was immediately extinguished, according to Figure 8 It was observed that the battery surface temperature reached a maximum of 215℃ after water mist spraying, dropping to 100℃ within 30 seconds, a cooling rate of 3.83℃ / s. However, after water mist spraying ceased, the battery surface temperature gradually rebounded, reaching a maximum of 150℃, before entering a slow cooling phase. The total cooling time from the initial drop to 100℃ to the safe temperature of 50℃ was 850 seconds. This is because after the open flame on the battery was extinguished, the water mist could not suppress the spontaneous heat-generating chemical reactions of the battery's internal materials. Therefore, there was no sustained cooling effect after water mist spraying stopped, leading to the battery warming up again.

[0077] Comparative Example 3

[0078] The only difference from Example 1 is that the organic and inorganic composite gel composed of gelling agent and crosslinking agent is replaced with a single inorganic gel: 12% sodium silicate and 3% sodium bicarbonate. No gelling agent is added. The remaining components and preparation methods are the same as in Example 1. The above-mentioned gel foam is prepared for fire extinguishing experiments.

[0079] Heating the battery induces thermal runaway in the battery pack. When the battery opens the safety valve and flammable gas is released, use an electric ignition device to ignite the flammable gas. After ignition (when a jet fire appears at 522 seconds), spray gel foam at 40 cm above the battery pack for 30 seconds.

[0080] After the gel foam is applied, the open flame is immediately extinguished, according to Figure 9It can be seen that the highest surface temperature of the battery was 213℃, which dropped to 100℃ within 35 seconds, with a cooling rate of 3.23℃ / s. However, the surface temperature gradually rose again, reaching a maximum of 138℃, and finally entered a slow cooling phase. The total time from the initial cooling to 100℃ to the subsequent cooling to the safe temperature of 50℃ was 530 seconds. This is because the gel foam prepared in this comparative example lacked organic polymer materials to act as a gelling agent. The resulting gel foam had low viscosity in the early stage, and the foam drained quickly, leading to a large loss of water. In the later stage, it could not provide sufficient water for the inorganic gel, resulting in a decrease in water retention performance. The water content of the gel separator layer became lower, and the effect of continuous cooling deteriorated, ultimately causing the battery to reheat.

[0081] Comparative Example 4

[0082] The only difference from Example 1 is that the organic and inorganic composite gel composed of gelling agent and crosslinking agent is replaced with a single organic gel: 0.35% konjac gum. No coagulant or crosslinking agent is added. The remaining components and preparation methods are the same as in Example 1. The above-mentioned gel foam is prepared for fire extinguishing experiments.

[0083] Heating the battery induces thermal runaway in the battery pack. When the battery opens the safety valve and flammable gas is released, use an electric ignition device to ignite the flammable gas. After ignition (when a jet fire appears at 519 seconds), spray gel foam at 40 cm above the battery pack for 30 seconds.

[0084] After the gel foam is applied, the open flame is immediately extinguished, according to Figure 10 It can be seen that the battery surface temperature reached a maximum of 216℃, dropping to 100℃ within 30 seconds, with a cooling rate of 3.86℃ / s. However, the battery surface temperature gradually rose again, reaching a maximum of 135℃, and finally entered a slow cooling phase. The total time from the initial cooling to 100℃ to the subsequent cooling to the safe temperature of 50℃ was 635 seconds. This is because the gel foam prepared in this comparative example lacked inorganic silicates to act as crosslinking agents. Although the resulting gel foam had high viscosity and water content in the early stages, the particles could not aggregate due to the lack of crosslinking agents. Consequently, it could not form an inorganic solidified gel in the later stages, and the moisture could not be retained in the insulating layer, resulting in a poorer continuous cooling effect and ultimately causing the battery to reheat.

[0085] Comparative Example 5

[0086] Using the same formulation as Example 1, the only difference is the order in which the mixture of gelling agent and accelerator and the crosslinking agent are added: First, amphoteric surfactant and anionic surfactant are compounded in proportion, and 75% of the total water volume is added. The mixture is stirred at 1200 r / min for 2 minutes at room temperature and then allowed to stand for 30 minutes as a foaming agent. Then, the gelling agent and accelerator are placed in a magnetic stirrer and 25% of the total water volume is added. The stirring temperature is 40°C, the stirring speed is 1000 r / min, and the stirring time is 6 minutes to obtain a mixture of gelling agent and accelerator. Finally, the foaming agent is foamed by high-speed mechanical stirring at room temperature, 1200 r / min, and for 2 minutes. During the stirring process, the crosslinking agent and the mixture of gelling agent and accelerator are added sequentially. After sufficient foaming, this gel foam is obtained.

[0087] In this comparative example, due to the change in the order of adding gelling agent, coagulant, and crosslinking agent in the preparation method, the crosslinking agent added first destroyed the surface activity of the surfactant, reduced the foaming performance, and made the solution viscous. The mixture of gelling agent and coagulant added later further accelerated the gelation and solidification process of the viscous solution. Therefore, the gel foam lost its fluidity after preparation and could not spread to cover the battery surface. Thus, it was unnecessary to continue the subsequent fire extinguishing experiment.

[0088] Comparative Example 6

[0089] Using the same formulation as Example 1, the only difference is the order in which the gelling agent, accelerator, and crosslinking agent are added: First, amphoteric and anionic surfactants are compounded in proportion, and 75% of the total water volume is added. The mixture is stirred at 1200 rpm for 2 minutes at room temperature and then allowed to stand for 30 minutes as a foaming agent. Then, the gelling agent and accelerator are placed in magnetic stirrers and 12.5% ​​and 12.5% ​​of the total water volume are added respectively. The stirring speed is 1000 rpm, the stirring temperature is 40°C, and the stirring time is 6 minutes, resulting in gelling agent solution and accelerator solution respectively. Finally, the foaming agent is foamed by high-speed mechanical stirring at room temperature, 1200 rpm, and for 2 minutes. During the stirring process, the gelling agent solution, accelerator solution, and crosslinking agent are added simultaneously. After sufficient foaming, the gel foam is obtained.

[0090] In this comparative example, due to the change in the order of adding gelling agent, accelerator, and crosslinking agent in the preparation method, the accelerator and crosslinking agent added at the same time reacted directly, causing sodium bicarbonate and silicate particles to aggregate and form an irreversible inorganic solidified gel in advance. As a result, the gel foam lost its fluidity after preparation and could not diffuse to cover the battery surface. Therefore, it was unnecessary to continue the subsequent fire extinguishing experiment.

[0091] In summary, compared with the prior art, the beneficial effects of the present invention include:

[0092] (1) The heat-resistant gel foam for extinguishing lithium-ion battery fires provided by this invention has good foaming properties and stability. Amphoteric surfactants can reduce the electrostatic repulsion between anionic surfactants and form cross-adsorption with anionic surfactants at the gas-liquid interface, making the molecular arrangement at the gas-liquid interface more compact and orderly, effectively reducing surface tension and forming a more viscoelastic liquid film. Through the synergistic effect between the two, the gel foam has good foaming properties and stability. Furthermore, the gelling agent, as a biopolymer polysaccharide, can increase the viscosity of the liquid phase, thereby increasing the thickness of the foam liquid film, while slowing down the drainage rate of the liquid film, further enhancing the stability of the gel foam and reducing its breakage. In summary, good foaming properties and stability ensure that sufficient and long-lasting gel foam is provided for extinguishing open flames of lithium-ion batteries in a short time. Compared with hydrogels, the gel foam of this invention, when used for extinguishing lithium-ion battery fires, has stronger flow and coverage due to its initial foam form.

[0093] (2) The anti-heat-recovery gel foam for extinguishing lithium-ion battery fires provided by this invention can form an effective insulating layer encapsulating the lithium-ion battery. By using bicarbonate as a coagulant, it has good cross-linking activity with sodium silicate or potassium silicate, and can form an inorganic gel. The gel foam has good fluidity in the early stage, diffuses and covers the battery surface, and penetrates into the gaps around the thermally runaway battery in the battery pack, quickly extinguishing the open flame. Then it quickly loses fluidity, encapsulates the battery surface and gels and solidifies, providing an effective insulating layer to suppress the chemical reaction that causes spontaneous heat generation in lithium batteries. By changing the concentration of the cross-linking agent and the coagulant, the gelation and solidification time of the gel foam can be adjusted and controlled to meet different needs.

[0094] (3) The anti-heat-recovery gel foam for lithium-ion battery fire extinguishing provided by this invention has good water retention and cooling capabilities. The gelling agent, as a biopolymer polysaccharide, rapidly swells and absorbs a large amount of water, forming a high-viscosity organic gel, thus slowing down water loss. Then, the crosslinking agent and coagulant react chemically, reducing the repulsive force of the charge on the silicate particles, causing particle aggregation and forming an irreversible inorganic solidified gel, completely locking in the water. The organic gel formed by the gelling agent and the inorganic gel formed by the crosslinking agent work together to completely retain water in the gel foam, effectively preventing water loss between the gel foam skeletons and providing sufficient water for continuous cooling of the lithium-ion battery. Simultaneously, the gel foam ultimately forms a stable three-dimensional network structure, which not only improves the density and thermal stability of the gel foam insulating layer but also significantly enhances oxygen isolation and flame retardancy. Furthermore, the gel foam provided by this invention does not lose water, is not easily conductive, and the battery pack after spraying the gel foam can still be recycled.

[0095] (4) The method for preparing the anti-heating gel foam suitable for fire extinguishing of lithium-ion batteries provided by the present invention is simple, the raw materials are easy to obtain and inexpensive, and it is non-toxic and non-polluting to the environment after use, making it suitable for large-scale production and use.

[0096] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A process for the preparation of a re-heat resistant gel foam suitable for use in the extinguishing of lithium ion batteries, characterized in that, The method comprises the following steps: Preparation of a surfactant solution and a mixed solution of gelling agent and coagulant; The surfactant solution is foamed, and the mixed solution of gelling agent and coagulant and a crosslinking agent are sequentially added during the foaming process, and after sufficient foaming, an anti-reheat gel foam suitable for lithium ion battery fire extinguishing is obtained; wherein, The raw materials of the anti-reheat gel foam suitable for lithium ion battery fire extinguishing include, by weight percentage, 0.1%-0.6% of surfactant, 0.3%-0.4% of gelling agent, 2.5%-3.5% of coagulant, and 10%-14% of crosslinking agent, with the balance being water; The surfactant is composed of zwitterionic surfactant and anionic surfactant; The gelling agent is selected from one or more of konjac gum, carrageenan, and xanthan gum; The coagulant is selected from one or both of sodium bicarbonate and potassium bicarbonate; The crosslinking agent is selected from one or both of sodium silicate and potassium silicate.

2. The process for the preparation of a re-heat resistant gel foam suitable for use in the fire extinguishing of lithium ion batteries according to claim 1, characterized in that, The zwitterionic surfactant is selected from one or more of myristyl betaine, lauryl amidopropyl betaine, alkyl dimethyl betaine, and sodium dodecyl amino propionate; The anionic surfactant is selected from one or more of sodium alkyl benzene sulfonate, sodium fatty alcohol ether sulfate, sodium secondary alkyl sulfonate, and alcohol ether carboxylate; The mass ratio of zwitterionic surfactant to anionic surfactant in the surfactant is 1: (2-9).

3. The process for the preparation of anti-reheat gel foam suitable for extinguishing lithium ion battery fires as claimed in claim 1, wherein, The raw materials of the anti-reheat gel foam suitable for lithium ion battery fire extinguishing include, by weight percentage, 0.4% of surfactant, 0.35% of gelling agent, 3% of coagulant, and 12% of crosslinking agent, with the balance being water.

4. The process for the preparation of anti-reheat gel foam suitable for extinguishing lithium ion battery fires as claimed in claim 1, wherein, The preparation process of the surfactant solution comprises: uniformly mixing the surfactant with water to obtain a surfactant solution; wherein, The water used in the preparation process of the surfactant solution accounts for 70%-80% of the total water amount; The mixing is uniformly carried out by stirring, the stirring temperature is room temperature, the stirring speed is 1000-1500 r / min, and the stirring time is 1-3 min; After uniform stirring, the mixture is left to stand, the standing temperature is room temperature, and the standing time is 20-40 min.

5. The process for the preparation of anti-reheat gel foam suitable for extinguishing lithium ion battery fires as claimed in claim 1 wherein, The preparation process of the mixed solution of gelling agent and coagulant comprises: uniformly mixing the gelling agent, coagulant, and water to obtain a mixed solution of gelling agent and coagulant; wherein, The water used in the preparation process of the mixed solution of gelling agent and coagulant accounts for 20%-30% of the total water amount; The mixing is uniformly carried out by stirring, the stirring temperature is 35-45℃, the stirring speed is 800-1200 r / min, and the stirring time is 5-10 min.

6. The process for the preparation of anti-reheat gel foam suitable for extinguishing lithium ion battery fires as claimed in claim 1, wherein, The surfactant solution is foamed by high-speed stirring; wherein, The high-speed stirring temperature is room temperature, the high-speed stirring speed is 1000-1500 r / min, and the high-speed stirring time is 1-3 min.

7. A re-heat resistant gel foam suitable for use in extinguishing lithium ion battery fires, characterised in that, The anti-reheat gel foam suitable for lithium ion battery fire extinguishing is obtained by the preparation method of the anti-reheat gel foam suitable for lithium ion battery fire extinguishing according to any one of claims 1-6.

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