Rewarming-resistant gel foam suitable for fire extinguishing of lithium ion battery and preparation method of rewarming-resistant gel foam

Abstract

The invention discloses an anti-rewarming gel foam suitable for lithium ion battery fire extinguishing and a preparation method thereof. The anti-rewarming type gel foam suitable for extinguishing the fire of the lithium ion battery comprises the following raw materials in percentage by weight: 0.1%-0.6% of a surfactant, 0.3%-0.4% of a gelling agent, 2.5%-3.5% of a coagulant, 10%-14% of a cross-linking agent and the balance of water. The anti-rewarming gel foam provided by the invention has controllable gelling time and relatively strong cooling performance, shows good fire extinguishing and continuous cooling effects compared with other lithium ion battery fire extinguishing agents, can quickly extinguish open fire of a lithium ion battery, and solves the problem that the lithium ion battery is easy to rewarm and reburn.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery fire prevention and extinguishing, and in particular to an anti-rewarming gel foam suitable for lithium ion battery fire extinguishing and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, and short charge and discharge time. They have broad application prospects in new energy vehicles, electrochemical energy storage and other fields. However, the high energy density causes lithium-ion battery fires to burn violently and are easy to reheat and reignite. The above safety issues have seriously hindered the widespread application of lithium-ion batteries. Based on the fire characteristics of lithium-ion batteries, in the process of fire extinguishing, it is necessary not only to quickly extinguish the open flame, but also to continuously cool the battery to inhibit the chemical reaction of the spontaneous heat generation of the internal materials of the battery to prevent the battery from reheating and reigniting. Therefore, the selection of a suitable fire extinguishing agent is particularly important for the efficient extinguishing of lithium-ion battery fires.

[0003] At present, the types of fire extinguishing agents commonly used to extinguish lithium-ion battery fires can be divided into water-based fire extinguishing agents, solid fire extinguishing agents and gas fire extinguishing agents. Commonly used water-based fire extinguishing agents, such as ordinary fine water mist, fine water mist containing additives, etc., have excellent cooling capabilities, but after stopping spraying, the battery is prone to reheating and reigniting. At the same time, due to the conductivity of water, the battery pack after spraying is difficult to recycle. Solid fire extinguishing agents are mainly dry powder fire extinguishing agents, which can extinguish the open flame of lithium-ion batteries after spraying. Its decomposition products at high temperatures can interrupt the combustion chain reaction, but the dry powder has limited coverage on the battery surface and cannot effectively inhibit the exothermic chemical reaction inside the battery. The battery is prone to reheating and reigniting after extinguishing the fire. Gaseous fire extinguishing agents extinguish fires by diluting oxygen. Commonly used gaseous fire extinguishing agents include heptafluoropropane, perfluorohexanone, etc. Heptafluoropropane can extinguish lithium-ion battery flames in a relatively closed space for a short time, but its cooling capacity is poor and it is difficult to suppress the problem of battery re-ignition. Although perfluorohexanone has good fire extinguishing and cooling effects, it is toxic. After extinguishing the open flame of the lithium-ion battery, it is still necessary to consider reducing the threat of its toxicity.

[0004] Therefore, developing a fire extinguishing agent that can quickly extinguish open flames in lithium-ion batteries and has a long-lasting cooling capability to prevent them from reheating and reigniting is an important issue that needs to be urgently addressed in this field. Summary of the invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies, propose an anti-rewarming gel foam suitable for lithium ion battery fire extinguishing and a preparation method thereof, and solve the technical problems in the prior art that lithium ion battery fire extinguishing agents have poor effect in extinguishing lithium ion battery open flames, do not have a long-term cooling ability, and are easy to reheat and reignite.

[0006] In a first aspect, the present invention provides an anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing. The raw materials thereof include, by weight percentage: 0.1%-0.6% surfactant, 0.3%-0.4% gelling agent, 2.5%-3.5% coagulant, 10%-14% cross-linking agent, and the balance is water.

[0007] In a second aspect, the present invention provides a method for preparing an anti-rewarming gel foam suitable for lithium ion battery fire extinguishing, comprising the following steps: preparing a surfactant solution and a mixed solution of a gelling agent and a coagulant; The surfactant solution is foamed, and a mixed solution of a gelling agent and a coagulant and a cross-linking agent are added in sequence during the foaming process. After sufficient foaming, an anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing is obtained.

[0008] Compared with the prior art, the beneficial effects of the present invention include: The anti-rewarming gel foam provided by the present invention has a controllable gelling 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 rewarming and reignition of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A schematic diagram of the arrangement of lithium-ion batteries, heating rods and thermocouples used in the fire extinguishing experiment of the present invention; Figure 2 This is a curve diagram of the fire extinguishing effect of using the anti-rewarming gel foam on the lithium ion battery in Example 1 of the present invention; Figure 3 This is a microstructure diagram of the rewarming resistant gel foam after gelation and curing of Example 1 of the present invention; Figure 4 This is a curve diagram of the fire extinguishing effect of using the anti-rewarming gel foam for lithium-ion batteries in Example 2 of the present invention; Figure 5 This is a curve diagram of the fire extinguishing effect of using the anti-rewarming gel foam for lithium-ion batteries in Example 3 of the present invention; Figure 6 This is a curve diagram of the fire extinguishing effect of using the anti-rewarming gel foam for lithium-ion batteries in Example 4 of the present invention; Figure 7 This is a combustion temperature curve of the lithium ion battery in Comparative Example 1 of the present invention without using any fire extinguishing agent; Figure 8 This is a curve diagram of the fire extinguishing effect of using water mist on a lithium ion battery in Comparative Example 2 of the present invention; Fig. 9 This is a curve diagram of the fire extinguishing effect of using gel foam on lithium ion batteries in Comparative Example 3 of the present invention; Fig.10 This is a curve diagram of the fire extinguishing effect of using gel foam on lithium ion batteries in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0011] In a first aspect, the present invention provides an anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing. The raw materials thereof include, by weight percentage: 0.1%-0.6% surfactant, 0.3%-0.4% gelling agent, 2.5%-3.5% coagulant, 10%-14% cross-linking agent, and the balance is water.

[0012] The anti-reheating gel foam of the present invention has good thermal stability and cooling properties. It can quickly extinguish the open fire of the lithium-ion battery in the foam state in the early stage, and later cover the battery surface to gel and solidify to form a high-water gel isolation layer, which continuously cools the battery surface and inhibits the chemical reaction of the spontaneous heat generation of the internal battery materials, thereby effectively preventing the lithium-ion battery from reheating and reigniting.

[0013] Preferably, the anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing comprises, by weight percentage, 0.4% surfactant, 0.35% gelling agent, 3% coagulant, 12% cross-linking agent, and the balance is water.

[0014] Preferably, the surfactant system consists of a zwitterionic surfactant and an anionic surfactant.

[0015] Furthermore, the zwitterionic surfactant is selected from one or more of myristyl betaine, lauryl amide propyl betaine, alkyl dimethyl betaine, and sodium dodecylaminopropionate.

[0016] Preferably, the zwitterionic surfactant is lauramidopropyl betaine.

[0017] 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 carboxylate.

[0018] Preferably, the anionic surfactant is sodium alkylbenzene sulfonate.

[0019] Furthermore, the mass ratio of the zwitterionic surfactant to the anionic surfactant in the surfactant is 1:(2-9).

[0020] Preferably, the mass ratio of the zwitterionic surfactant to the anionic surfactant is 1:9.

[0021] Furthermore, the gelling agent is selected from one or more of konjac gum, carrageenan and xanthan gum.

[0022] Preferably, the gelling agent is konjac gum.

[0023] 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 finally form an inorganic gel.

[0024] Furthermore, the cross-linking agent is selected from one or both of sodium silicate and potassium silicate.

[0025] Preferably, the crosslinking agent is sodium silicate.

[0026] In a second aspect, the present invention provides a method for preparing an anti-rewarming gel foam suitable for lithium ion battery fire extinguishing, comprising the following steps: S1, preparing a surfactant solution and a mixed solution of a gelling agent and a coagulant; S2. Foaming the surfactant solution, and sequentially adding a mixed solution of a gelling agent and a coagulant and a cross-linking agent during the foaming process, and after sufficient foaming, obtaining an anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing.

[0027] In the present invention, it should be pointed out that sufficient foaming means that the volume of the foam no longer expands and tends to a stable state during the stirring process.

[0028] Preferably, in step S1, the preparation process of the surfactant solution includes: uniformly mixing the surfactant and water to obtain the surfactant solution (ie, the foaming agent).

[0029] Furthermore, the water used in the preparation process of the surfactant solution accounts for 70%-80% of the total water, and further 75%.

[0030] Furthermore, the mixture is mixed evenly by stirring, the stirring temperature is room temperature, the stirring speed is 1000-1500 r / min, further 1200 r / min, and the stirring time is 1-3 min.

[0031] Further, after stirring evenly, the solution is allowed to stand at room temperature for 20-40 minutes. The present invention allows the surfactant molecules to reach equilibrium at the water-air interface and reduce surface tension by standing. Since some foam is generated after stirring, the solution stability can be improved by standing.

[0032] Preferably, in step S1, the preparation process of the mixed solution of the gelling agent and the coagulant includes: uniformly mixing the gelling agent, the coagulant and water to obtain the mixed solution of the gelling agent and the coagulant.

[0033] Furthermore, the water used in the preparation process of the mixed solution of the gelling agent and the coagulant accounts for 20%-30% of the total water volume, and further 25%.

[0034] Furthermore, the mixture is mixed evenly by stirring, the stirring temperature is 35-45° C., further 40° C., the stirring speed is 800-1200 r / min, further 1000 r / min, and the stirring time is 5-10 min.

[0035] Preferably, in step S2, the surfactant solution is foamed by high-speed stirring. The present invention can generate a large amount of foam by high-speed stirring. The large amount of foam can cover the battery surface more quickly and penetrate into the gaps around the battery in the initial stage, and provide a continuous cooling effect after gelation and solidification.

[0036] Furthermore, the temperature of the high-speed stirring is room temperature, the rotation speed of the high-speed stirring is 1000-1500 r / min, further 1200 r / min, and the time of the high-speed stirring is 1-3 min, further 2 min.

[0037] To avoid redundancy, in the fire extinguishing experiments (or combustion experiments) of the following embodiments and comparative examples of the present invention, a cylindrical heating rod is used to heat the battery pack. The heating rod is 65 mm long and 18 mm in diameter and is fixed in the middle of the battery. Figure 1 As shown, #1-#4 are k-type armored thermocouples with a diameter of 1mm, with a response time of 1s, a range of 0-1300℃, and an accuracy error of ±1.0℃. They are fixed on the surface of the battery to record the surface temperature of the battery. The battery pack consists of four commercial 18650 lithium-ion batteries with a capacity of 2000mAh and a rated voltage of 3.2V. Use a battery test system to prepare the batteries required for the test. Follow the steps to first let the lithium-ion battery stand for 20 minutes, then discharge it at a constant current of 1A to a voltage of 2V, let it stand for 20 minutes, and finally charge it to 3.65V with a constant current and constant voltage until the charging current drops below 20mA, and repeat this cycle 3 times. After charging is completed, let the battery stand for 12h to ensure the stability of the battery before testing.

[0038] Example 1 The invention discloses an anti-rewarming gel foam suitable for extinguishing a lithium-ion battery fire. The raw materials thereof include, by weight percentage, 0.04% lauramide propyl betaine, 0.36% sodium alkylbenzene sulfonate (LAS-90), 0.35% konjac gum, 3% sodium bicarbonate, 12% sodium silicate, and the balance being water.

[0039] The preparation method comprises: firstly, compounding a zwitterionic surfactant and anionic surfactant in proportion, adding 75% of the total water as a foaming agent, stirring at room temperature at a stirring speed of 1200 r / min for 2 minutes, and then standing for 30 minutes; then placing a gelling agent and a coagulant in a magnetic stirrer, adding 25% of the total water and stirring, the stirring temperature is 40°C, the stirring speed is 1000 r / min, the stirring time is 6 minutes, and a mixed solution of the gelling agent and the coagulant is obtained; finally, the foaming agent is foamed by a high-speed mechanical stirring method, the stirring temperature is room temperature, the stirring speed is 1200 r / min, the stirring time is 2 minutes, and the mixed solution of the gelling agent and the coagulant and the cross-linking agent are added in sequence during the stirring process, and after sufficient foaming, an anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing is obtained, and a fire extinguishing experiment is carried out.

[0040] The battery was heated to induce thermal runaway of the battery pack. When the battery safety valve was opened and flammable gas came out, an electric ignition device was used to ignite the flammable gas. After ignition (when a jet fire appeared at the 530th second), gel foam was sprayed 40 cm from the top of the battery pack for 30 seconds.

[0041] After the gel foam is applied, the open flame is immediately extinguished, and the gel foam quickly covers the surface of the battery, forming an isolation layer that effectively isolates the external oxygen from contacting the battery and inhibits the development of the fire. Figure 2 It can be seen that the highest battery surface temperature is 204℃, which quickly drops to 100℃ within 30s, with a cooling rate of 3.47℃ / s. After that, the battery surface temperature fluctuates slightly. This is because the spontaneous heat-generating chemical reaction inside the battery is still ongoing, continuously releasing heat, and finally tends to continue to cool down. It takes a total of 260s to drop from 100℃ to the safe temperature of 50℃. No battery reheating phenomenon is observed during the whole process. Figure 3 It can be seen that after the gel foam is gelled and solidified, a gel skeleton is extended in all directions, and at the same time, the surface presents an irregular porous structure, which is interconnected to form a three-dimensional network structure containing holes.

[0042] Example 2 The only difference from Example 1 is that the contents of lauramidopropyl betaine and sodium alkylbenzene sulfonate are different: 0.12% lauramidopropyl betaine and 0.28% sodium alkylbenzene sulfonate (LAS-90), and the remaining components and preparation method are the same as those in Example 1. The above gel foam is prepared for fire extinguishing experiments.

[0043] The battery was heated to induce thermal runaway of the battery pack. When the battery safety valve was opened and flammable gas came out, an electric ignition device was used to ignite the flammable gas. After ignition (when a jet fire appeared at the 533th second), gel foam was sprayed 40 cm from the top of the battery pack for 30 seconds.

[0044] After applying the gel foam, the open flame is extinguished immediately, according to Figure 4 It can be seen that the battery surface temperature is up to 210°C, and drops to 100°C within 35s, with a cooling rate of 3.14°C / s. After that, the battery surface temperature rises slightly and fluctuates up and down, and finally tends to continue to cool down. It takes a total of 320s from the first cooling to 100°C to the cooling to the safe temperature of 50°C. This is because after the surfactant system does not adopt the preferred concentration of Example 1, the foaming property and stability of the gel foam decrease, and it is easier to collapse and rupture after covering the battery surface, resulting in the thinning of the isolation layer after gelation and curing, the cooling performance deteriorates, and the time required for cooling becomes longer, but the battery does not reheat in the end, and the fire extinguishing effect is good.

[0045] Example 3 The only difference from Example 1 is that the content of the coagulant is different: 2.5% sodium bicarbonate, and the remaining components and preparation method are the same as those in Example 1. The above-mentioned gel foam is prepared for fire extinguishing experiments.

[0046] The battery was heated to induce thermal runaway of the battery pack. When the battery safety valve was opened and flammable gas came out, an electric ignition device was used to ignite the flammable gas. After ignition (when a jet fire appeared at the 535th second), gel foam was sprayed 40 cm from the top of the battery pack for 30 seconds.

[0047] After applying the gel foam, the open flame is extinguished immediately, according to Figure 5 It can be seen that the battery surface temperature was as high as 212°C, and it quickly dropped to 100°C within 35 seconds, with a cooling rate of 3.2°C / s. After that, the battery surface temperature rebounded to a certain extent in a short period of time, but the maximum temperature recovery only reached 117°C. Then the battery surface temperature showed a small fluctuation trend, and finally tended to continue to cool down. It took a total of 385 seconds from the first cooling to 100°C to the cooling to the safe temperature of 50°C. This is because the gelling time of the gel foam was prolonged due to the failure to use the preferred concentration of sodium bicarbonate. When it was sprayed and covered on the surface of the lithium-ion battery, it failed to gel and solidify in time to form an effective isolation layer, resulting in a slight rebound in the battery surface temperature after the open fire was extinguished, and the cooling time was prolonged, but the battery did not reheat later, and the fire extinguishing effect was good.

[0048] Example 4 The only difference from Example 1 is that the gelling agent is carrageenan, the cross-linking agent is potassium silicate, and the remaining components and preparation method are the same as those in Example 1. The above gel foam is prepared for fire extinguishing experiments.

[0049] The battery was heated to induce thermal runaway of the battery pack. When the battery safety valve was opened and flammable gas came out, an electric ignition device was used to ignite the flammable gas. After ignition (when a jet fire appeared at the 535th second), gel foam was sprayed 40 cm from the top of the battery pack for 30 seconds.

[0050] After applying the gel foam, the open flame is extinguished immediately, according to Figure 6 It can be seen that the battery surface temperature was as high as 209°C, and dropped to 100°C within 35 seconds, with a cooling rate of 3.11°C / s. After that, the battery surface temperature rose slightly and showed an up-and-down trend, and finally tended to continue to cool down. It took a total of 345 seconds from the first cooling to 100°C to the next cooling to the safe temperature of 50°C. This is because the gelling agent and the cross-linking agent did not use the preferred formula, and the synergistic effect of the gelling agent and the cross-linking agent was not good, resulting in reduced water retention of the gel foam, poor cooling effect of the isolation layer, and longer cooling time, but the battery did not reheat in the end, and the fire extinguishing effect was good.

[0051] Comparative Example 1 Lithium-ion battery combustion experiment without using any fire extinguishing agent.

[0052] The battery is heated to induce thermal runaway of the battery pack. When the battery safety valve opens and flammable gas comes out, an electric ignition device is used to ignite the flammable gas.

[0053] according to Figure 7 It can be seen that the maximum battery surface temperature is 205°C. Without using any fire extinguishing agent, the battery naturally cools down the surface temperature slowly, dropping to 100°C within 700s, with a cooling rate of 0.14°C / s. It takes a total of 1700s to cool from 100°C to the safe temperature of 50°C.

[0054] Comparative Example 2 Water mist fire extinguishing experiment.

[0055] The battery is heated to induce thermal runaway of the battery pack. When the battery opens the safety valve and flammable gas comes out, an electric ignition device is used to ignite the flammable gas. After ignition (when a jet fire appears at the 520th second), water mist is sprayed 40 cm from the top of the battery pack. The spray angle is set to 40°, the water pressure is set to 1.5 MPa, and the spraying lasts for 30 seconds.

[0056] After spraying water mist, the open flame will be extinguished immediately. Figure 8 It can be seen that after spraying water mist, the battery surface temperature reached a maximum of 215°C, and dropped to 100°C within 30 seconds, with a cooling rate of 3.83°C / s. However, after stopping spraying water mist, the battery surface temperature gradually recovered, reaching a maximum of 150°C, and then entered a slow cooling stage. It took a total of 850 seconds from the first cooling to 100°C to the next cooling to the safe temperature of 50°C. This is because after the battery open flame is extinguished, the water mist cannot suppress the chemical reaction of the spontaneous heat generation of the battery internal materials. After stopping spraying water mist, there is no continuous cooling effect, resulting in the battery reheating.

[0057] Comparative Example 3 The only difference from Example 1 is that the organic and inorganic composite gel composed of the gelling agent and the cross-linking agent is replaced with a single inorganic gel: 12% sodium silicate and 3% sodium bicarbonate, and no gelling agent is added. The remaining components and preparation method are the same as those in Example 1. The above-mentioned gel foam is prepared for fire extinguishing experiments.

[0058] The battery was heated to induce thermal runaway of the battery pack. When the battery safety valve was opened and flammable gas came out, an electric ignition device was used to ignite the flammable gas. After ignition (when a jet fire appeared at the 522th second), gel foam was sprayed 40 cm from the top of the battery pack for 30 seconds.

[0059] After applying the gel foam, the open flame is extinguished immediately, according to Fig. 9 It can be seen that the battery surface temperature is up to 213°C, and it drops to 100°C within 35s, with a cooling rate of 3.23°C / s, but then the battery surface temperature gradually rises, rising to a maximum of 138°C, and finally enters a slow cooling stage, which takes a total of 530s from the first cooling to 100°C to the cooling to a safe temperature of 50°C. This is because the gel foam prepared in this comparative example lacks organic polymer materials to act as a gelling agent, and the gel foam formed has low viscosity in the early stage, and the foam discharges quickly, resulting in a large amount of water loss. In the later stage, it is unable to provide sufficient water for the inorganic gel, the water retention performance decreases, the water content of the gel isolation layer becomes low, and the effect of continuous cooling and cooling becomes worse, and finally the battery reheats.

[0060] Comparative Example 4 The only difference from Example 1 is that the organic and inorganic composite gel composed of the gelling agent and the cross-linking agent is replaced with a single organic gel: 0.35% of konjac gum, and no coagulant and cross-linking agent are added. The remaining components and preparation method are the same as those in Example 1. The above gel foam is prepared for fire extinguishing experiments.

[0061] The battery was heated to induce thermal runaway of the battery pack. When the battery safety valve was opened and flammable gas came out, an electric ignition device was used to ignite the flammable gas. After ignition (when a jet fire appeared at the 519th second), gel foam was sprayed 40 cm from the top of the battery pack for 30 seconds.

[0062] After applying the gel foam, the open flame is extinguished immediately, according to Fig.10It can be seen that the battery surface temperature is up to 216°C, and it drops to 100°C within 30s, with a cooling rate of 3.86°C / s, but then the battery surface temperature gradually rises, rising to a maximum of 135°C, and finally enters a slow cooling stage, from the first cooling to 100°C to the cooling to the safe temperature of 50°C, it takes a total of 635s. This is because the gel foam prepared in this comparative example lacks inorganic silicates as cross-linking agents. Although the formed gel foam has high viscosity and water content in the early stage, due to the lack of cross-linking agents, the particles cannot aggregate, and inorganic cured gel cannot be formed in the later stage, and moisture cannot be retained in the isolation layer, resulting in a poor continuous cooling effect, and finally the battery reheats.

[0063] Comparative Example 5 The same formula as in Example 1 is used, except that the order of adding the mixed solution of the gelling agent and the coagulant and the cross-linking agent in the preparation method is different: first, the zwitterionic surfactant and the anionic surfactant are compounded in proportion, and 75% of the total water is added to the mixture, stirred at room temperature at a stirring speed of 1200 r / min for 2 minutes, and then allowed to stand for 30 minutes as a foaming agent; then the gelling agent and the coagulant are placed in a magnetic stirrer and 25% of the total water is added to the mixture and stirred at a stirring temperature of 40° C., a stirring speed of 1000 r / min, and a stirring time of 6 minutes to obtain a mixed solution of the gelling agent and the coagulant; finally, the foaming agent is foamed by a high-speed mechanical stirring method, the stirring temperature is room temperature, the stirring speed is 1200 r / min, and the stirring time is 2 minutes, and the cross-linking agent and the mixed solution of the gelling agent and the coagulant are added in sequence during the stirring process, and after sufficient foaming, the gel foam is obtained.

[0064] In this comparative example, due to the change in the order of adding the gelling agent, coagulant and cross-linking agent in the preparation method, the cross-linking agent added first destroyed the surface activity of the surfactant, reduced the foaming performance, and made the solution viscous. The gelling agent and coagulant mixture 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 diffuse and cover the battery surface. Therefore, there was no need to continue the subsequent fire extinguishing experiment.

[0065] Comparative Example 6 The same formula as in Example 1 is used, except that the order of adding the gelling agent, the coagulant and the cross-linking agent in the preparation method is different: first, the zwitterionic surfactant and the anionic surfactant are compounded in proportion, and 75% of the total water is added to the mixture, stirred at a stirring speed of 1200 r / min for 2 min at room temperature, and then allowed to stand for 30 min as a foaming agent; then the gelling agent and the coagulant are placed in a magnetic stirrer, and 12.5% ​​and 12.5% ​​of the total water are added to the mixture, respectively, and stirred at a stirring speed of 1000 r / min, a stirring temperature of 40° C., and a stirring time of 6 min, to obtain a gelling agent solution and a coagulant solution, respectively; finally, the foaming agent is foamed by a high-speed mechanical stirring method, the stirring temperature is room temperature, the stirring speed is 1200 r / min, the stirring time is 2 min, and the gelling agent solution, the coagulant solution and the cross-linking agent are added simultaneously during the stirring process, and after sufficient foaming, the gel foam is obtained.

[0066] In this comparative example, due to the change in the order of adding the gelling agent, the coagulant and the cross-linking agent in the preparation method, the coagulant and the cross-linking agent added simultaneously reacted directly, and the sodium bicarbonate and silicate particles aggregated to form an irreversible inorganic solidified gel in advance, resulting in the gel foam losing fluidity after preparation and being unable to diffuse and cover the battery surface. Therefore, there is no need to continue the subsequent fire extinguishing experiment.

[0067] In summary, compared with the prior art, the beneficial effects of the present invention include: (1) The anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing provided by the present invention has good foaming and stability. Zwitterionic surfactants can reduce the electrostatic repulsion between anionic surfactants, form cross-adsorption with anionic surfactants at the gas-liquid interface, make the molecular arrangement on the gas-liquid interface more compact and orderly, effectively reduce the surface tension, and form a more viscoelastic liquid film. Through the synergistic effect between the two, the gel foam has good foaming and stability. In addition, the gelling agent, as a biopolymer polysaccharide polymer, 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 the rupture of the gel foam. In summary, good foaming and stability can ensure that sufficient and long-lasting gel foam is provided for extinguishing open fires of lithium-ion batteries in a short time. Compared with hydrogel, when the gel foam of the present invention is used for lithium-ion battery fire extinguishing, it has stronger flow coverage because its initial form is foam.

[0068] (2) The anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing provided by the present invention can form an effective isolation layer that wraps 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 initial stage, diffuses and covers the battery surface, and penetrates into the gaps around the thermal runaway battery in the battery pack, quickly extinguishing the open fire, and then quickly loses fluidity, wraps around the battery surface and gels and solidifies, providing an effective isolation layer for inhibiting the chemical reaction of spontaneous heat generation of lithium batteries. By changing the concentration of the cross-linking agent and the coagulant, the gelation and curing time of the gel foam can be adjusted to meet different needs.

[0069] (3) The anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing provided by the present invention has good water retention and cooling capabilities. The gelling agent, as a biopolymer polysaccharide polymer, absorbs a large amount of water after rapid swelling to form a high-viscosity organic gel, which slows down water loss; then the cross-linking agent and the coagulant react chemically, the repulsive force of the charge carried by the silicate particles is reduced, the particles aggregate, and an irreversible inorganic solidified gel is formed to completely lock the water. The organic gel formed by the gelling agent and the inorganic gel formed by the cross-linking agent cooperate with each other to completely retain the water in the gel foam, effectively preventing the loss of water between the gel foam skeletons, and providing sufficient water for the continuous cooling of the lithium-ion battery. At the same time, the gel foam eventually forms a stable three-dimensional network structure, which can not only improve the density and thermal stability of the gel foam isolation layer, but also significantly enhance the oxygen isolation capacity and flame retardancy. In addition, the gel foam provided by the present invention does not lose water, is not easy to conduct electricity, and the battery pack after spraying the gel foam can still be recycled.

[0070] (4) The preparation method of the anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing provided by the present invention is simple, the raw materials are easily available and inexpensive, and it is non-toxic and pollution-free to the environment after use, and is suitable for large-scale production.

[0071] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing, characterized in that: Calculated by weight percentage, the raw materials include: 0.1%-0.6% surfactant, 0.3%-0.4% gelling agent, 2.5%-3.5% coagulant, 10%-14% cross-linking agent, and the balance is water.

2. The anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing according to claim 1, characterized in that: The surfactant is composed of a zwitterionic surfactant and an anionic surfactant; wherein, The zwitterionic surfactant is selected from one or more of myristyl betaine, lauryl amide propyl betaine, alkyl dimethyl betaine, and sodium dodecyl aminopropionate; 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 carboxylate; The mass ratio of the zwitterionic surfactant to the anionic surfactant in the surfactant is 1:(2-9).

3. The anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing according to claim 1, characterized in that: The gelling agent is selected from one or more of konjac gum, carrageenan and xanthan gum.

4. The anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing according to claim 1, characterized in that: The coagulant is selected from one or both of sodium bicarbonate and potassium bicarbonate.

5. The anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing according to claim 1, characterized in that: The cross-linking agent is selected from one or both of sodium silicate and potassium silicate.

6. The anti-rewarming gel foam suitable for lithium-ion battery fire extinguishing according to claim 1, characterized in that: Calculated by weight percentage, the raw materials include: 0.4% surfactant, 0.35% gelling agent, 3% coagulant, 12% cross-linking agent, and the balance is water.

7. A method for preparing the rewarming-resistant gel foam suitable for lithium-ion battery fire extinguishing as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: preparing a surfactant solution and a mixed solution of a gelling agent and a coagulant; The surfactant solution is foamed, and the mixed solution of the gelling agent and the coagulant and the cross-linking agent are sequentially added during the foaming process. After sufficient foaming, an anti-rewarming gel foam suitable for lithium ion battery fire extinguishing is obtained.

8. The method for preparing the rewarming-resistant gel foam suitable for lithium-ion battery fire extinguishing according to claim 7, characterized in that: The preparation process of the surfactant solution includes: uniformly mixing the surfactant and water to obtain the surfactant solution; wherein, The water used in the preparation process of surfactant solution accounts for 70%-80% of the total water; The mixture is mixed evenly by stirring at room temperature, a stirring speed of 1000-1500 r / min, and a stirring time of 1-3 min; After stirring evenly, let it stand at room temperature for 20-40 minutes.

9. The method for preparing the rewarming-resistant gel foam suitable for lithium-ion battery fire extinguishing according to claim 7, characterized in that: The preparation process of the mixed solution of the gelling agent and the coagulant comprises: uniformly mixing the gelling agent, the coagulant and water to obtain the mixed solution of the gelling agent and the coagulant; wherein: The water used in the preparation process of the mixed solution of the gelling agent and the coagulant accounts for 20%-30% of the total water; The mixture is mixed evenly by stirring at a temperature of 35-45°C, a speed of 800-1200 r / min, and a time of 5-10 min.

10. The method for preparing the rewarming-resistant gel foam suitable for lithium-ion battery fire extinguishing according to claim 7, characterized in that: The surfactant solution is foamed by high-speed stirring; wherein, The temperature of the high-speed stirring is room temperature, the rotation speed of the high-speed stirring is 1000-1500 r / min, and the time of the high-speed stirring is 1-3 min.

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