A chitosan-based fire extinguishing gel, its preparation method and application

Abstract

This invention provides a chitosan-based fire extinguishing gel, formed by cross-linking a chitosan solution with a cross-linking agent; the cross-linking agent includes a polyaldehyde compound containing phosphoryl groups. Compared with the prior art, the main components of the chitosan-based fire extinguishing gel provided by this invention are chitosan, water, and a polyaldehyde compound containing phosphoryl groups. The chitosan-based fire extinguishing gel can adhere to the surface of a lithium battery experiencing thermal runaway, effectively isolating oxygen and heat, preventing the lithium battery from reigniting, and efficiently extinguishing lithium battery fires. Simultaneously, the water in the fire extinguishing gel releases a large amount of water vapor under strong heat, effectively diluting the concentration of flammable gases in the combustion zone and inhibiting combustion. Furthermore, the water vaporization process absorbs a large amount of heat, thereby effectively reducing the temperature of the combustion zone. Therefore, this chitosan-based fire extinguishing gel has advantages such as safety, environmental friendliness, non-toxicity, strong adhesion, and excellent fire extinguishing ability, with significant fire extinguishing effects. It has targeted application value and great potential for fire extinguishing and rescue in lithium battery fires.

Description

Technical Field

[0001] This invention belongs to the field of fire prevention and extinguishing materials technology, and particularly relates to a chitosan-based fire extinguishing gel, its preparation method and application. Background Technology

[0002] Lithium-ion batteries are widely used in electronics, new energy vehicles, and aerospace due to their advantages such as high energy density, long cycle life, no memory effect, high voltage, wider application, and environmental friendliness. However, with the continuous improvement of energy density, lithium-ion batteries, under conditions such as overcharging, short circuits, or mechanical damage (collision, puncture, and bending, etc.), release a large amount of chemical energy, which is converted into heat energy, leading to battery thermal runaway and subsequent lithium-ion battery fires. In recent years, lithium-ion battery fires have occurred frequently both domestically and internationally, causing significant property damage and casualties. For example, in 2019, a warehouse in South Korea exploded and burned completely due to the spontaneous combustion of stored Samsung batteries; in 2021, a fire and explosion occurred at an energy storage power station in Fengtai District, Beijing, caused by a short circuit in lithium-ion batteries, resulting in the deaths of two firefighters; and in 2022, a lithium-ion battery explosion in Shanghai resulted in three deaths. Lithium-ion battery fires are characterized by rapid temperature rise, suddenness, and high degree of danger; therefore, the development of environmentally friendly and efficient lithium-ion battery fire extinguishing agents is of great significance.

[0003] Currently, commonly used lithium battery fire extinguishing agents mainly include gaseous fire extinguishing agents, dry powder fire extinguishing agents, water-based fire extinguishing agents, and aerosol fire extinguishing agents (Journal of Energy Chemistry.2021; 62:262-80). Halon fire extinguishing agents are gaseous fire extinguishing agents used in the aviation field, but their ability to extinguish lithium battery fires is limited, and there is still a risk of reignition (Journal of Physical Chemistry A.2015; 119(28):7611-26). Moreover, halon fire extinguishing agents can damage the ozone layer, so they are prohibited from use. Other gaseous fire extinguishing agents containing halogenated hydrocarbons, such as heptafluoropropane, are expensive and cannot effectively suppress battery thermal runaway. The disadvantage of dry powder fire extinguishing agents is that they have a low heat capacity and cannot effectively reduce the temperature of lithium batteries, and there is still a risk of reignition (Journal of Power Sources.2019; 418:1-10; Developmental and Comparative Immunology.2014; 44(1):70-5). Aerosol extinguishing agents are only suitable for small, enclosed spaces and are relatively expensive. Water-based extinguishing agents are less expensive, have good wettability, and high specific heat capacity, which allows lithium batteries to cool down quickly, making them the best-performing extinguishing agents overall. However, water as an extinguishing agent also has the following drawbacks: (1) most of the water is lost during the extinguishing process, resulting in low extinguishing efficiency; (2) water has very low adhesion and cannot effectively cover the surface of combustibles, leading to reignition (Fire Safety Journal. 2021; 120; Procedia Engineering. 2018; 211:531-7).

[0004] Therefore, developing chitosan-based fire extinguishing gels specifically for lithium battery fires is a forward-looking and innovative technology, considering the characteristics of lithium battery fires. Domestic fire extinguishing technology for lithium battery fires is currently limited to using existing extinguishing agents, lacking dedicated environmentally friendly and highly efficient extinguishing agents for lithium battery fires. This invention can fill the gap in my country's emergency response technology for lithium battery fire accidents. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a chitosan-based fire extinguishing gel, its preparation method and application. The chitosan-based fire extinguishing gel is mainly aimed at lithium battery fires. By spraying and adhering to the surface of lithium batteries that have experienced thermal runaway, it can effectively isolate oxygen and heat, prevent the lithium battery from reigniting, and efficiently extinguish lithium battery fires. Furthermore, the chitosan-based fire extinguishing gel is derived from renewable natural resources, is green and environmentally friendly, and will not cause secondary pollution to the environment.

[0006] This invention provides a chitosan-based fire extinguishing gel, which is formed by cross-linking a chitosan solution with a cross-linking agent;

[0007] The crosslinking agent includes a polyaldehyde compound containing a phosphoryl group.

[0008] Preferably, the polyaldehyde compound containing a phosphoryl group is shown in formula (I):

[0009]

[0010] R1 and R2 are each independently selected from hydrogen, C1-C10 alkyl groups, or C1-C10 alkoxy groups;

[0011] R3 is selected from C1-C10 alkyl, C1-C10 alkoxy, phenolic or substituted phenolic groups;

[0012] The substituents in the substituted phenolic group are selected from one or more of C1-C10 alkyl, C1-C10 alkoxy and C1-C10 aldehyde groups.

[0013] Preferably, the polyaldehyde compound containing a phosphoryl group is shown in formula (II):

[0014]

[0015] Preferably, R1 and R2 are each independently selected from hydrogen or methoxy groups;

[0016] R3 is selected from one of the following structures:

[0017]

[0018] Preferably, the mass of the phosphoryl-containing polyaldehyde compound is 2% to 8% of the mass of chitosan in the chitosan solution.

[0019] This invention also provides a method for preparing chitosan fire extinguishing gel, comprising the following steps:

[0020] The cross-linking agent was mixed with the chitosan solution, and after heating and reacting, chitosan fire extinguishing gel was obtained.

[0021] The crosslinking agent includes a polyaldehyde compound containing a phosphoryl group.

[0022] Preferably, the chitosan solution is prepared according to the following method:

[0023] Chitosan and an aqueous acetic acid solution were mixed and heated to obtain a chitosan solution;

[0024] The polyaldehyde compound containing a phosphoryl group is prepared according to the following method:

[0025] The aldehyde-containing compound shown in formula (A) is reacted with a phosphorylating agent in the presence of an acid-binding agent to obtain a polyaldehyde compound containing a phosphoryl group.

[0026]

[0027] R1 and R2 are each independently selected from hydrogen, C1-C10 alkyl groups, or C1-C10 alkoxy groups.

[0028] Preferably, the aldehyde-containing compound represented by formula (A) is selected from one or more of p-hydroxybenzaldehyde, aromatic aldehydes, and syringaldehyde;

[0029] The phosphorylating agent is selected from one or more of phosphorus oxychloride, methylphosphonodichloride, phenylphosphonodichloride and phenyl phosphate dichloride;

[0030] The acid-binding agent is selected from one or more of triethylamine, pyridine, sodium carbonate, and potassium carbonate;

[0031] The molar ratio of the aldehyde-containing compound to the phosphorylating agent shown in formula (A) is (2-3):1;

[0032] The aldehyde-containing compound shown in formula (A) reacts with a phosphorylating agent in an ice bath in the presence of an acid-binding agent, and then reacts with heating to obtain a polyaldehyde compound containing a phosphoryl group.

[0033] The reaction time under ice bath is 2-4 hours; the reaction temperature under heating is 50℃-60℃; and the reaction time under heating is 6-8 hours.

[0034] Preferably, the chitosan solution contains 1% to 3% by mass.

[0035] The temperature of the heating reaction is 50℃~60℃; the heating reaction time is 10~20h.

[0036] The present invention also provides an application of the above-mentioned chitosan fire extinguishing gel in the preparation of lithium battery fire extinguishing materials.

[0037] This invention provides a chitosan-based fire extinguishing gel, formed by cross-linking a chitosan solution with a cross-linking agent; the cross-linking agent includes a polyaldehyde compound containing phosphoryl groups. Compared with the prior art, the main components of the chitosan-based fire extinguishing gel provided by this invention are chitosan, water, and a polyaldehyde compound containing phosphoryl groups. During the fire extinguishing and rescue process of lithium battery fires, the chitosan-based fire extinguishing gel can adhere to the surface of the lithium battery that has experienced thermal runaway, effectively isolating oxygen and heat, preventing the lithium battery from reigniting, and efficiently extinguishing lithium battery fires. At the same time, the water in the fire extinguishing gel releases a large amount of water vapor under strong heat, which can effectively dilute the concentration of flammable gases in the combustion area and inhibit combustion; and the water vaporization process absorbs a large amount of heat, thereby effectively reducing the temperature of the combustion area. Therefore, this chitosan-based fire extinguishing gel has the advantages of being safe and environmentally friendly, non-toxic, having strong adhesion, and excellent fire extinguishing ability, with significant fire extinguishing effect. It is mainly targeted at fire extinguishing and rescue of lithium battery fires, and can effectively solve the pollution problems of traditional gaseous fire extinguishing agents and the problem of easy reignition of water-based fire extinguishing agents. It has targeted application value for fire extinguishing and rescue of lithium battery fires. Attached Figure Description

[0038] Figure 1 This is a graph showing the temperature change of the thermocouple over time when chitosan-based fire extinguishing gel A is used for fire extinguishing of lithium batteries in Example 3 of the present invention.

[0039] Figure 2 This is a graph showing the temperature change of the thermocouple over time when chitosan-based fire extinguishing gel B is used for fire extinguishing of lithium batteries in Example 4 of the present invention.

[0040] Figure 3 This is a graph showing the temperature change of the thermocouple over time when water is used for extinguishing fires in lithium batteries in Comparative Example 1 of the present invention.

[0041] Figure 4 This is a graph showing the temperature change of the thermocouple over time when perfluorohexanone is used for fire extinguishing of lithium batteries in Comparative Example 2 of this invention. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] This invention provides a chitosan-based fire extinguishing gel, which is formed by crosslinking a chitosan solution with a crosslinking agent; the crosslinking agent includes a polyaldehyde compound containing a phosphoryl group.

[0044] The chitosan solution can be any chitosan solution known to those skilled in the art, and there are no special limitations. In this invention, it is preferably prepared from chitosan and an aqueous solution of acetic acid. The mass concentration of chitosan in the chitosan solution is preferably 1% to 3%, more preferably 1.5% to 2.5%, and even more preferably 2%. The degree of deacetylation of the chitosan is preferably 80% to 95%. The viscosity of the chitosan is preferably 50 to 800 mPa·s (0.5% of a 0.5% acetic acid solution at 20°C).

[0045] The crosslinking agent comprises a polyaldehyde compound containing a phosphoryl group; the polyaldehyde compound containing a phosphoryl group is preferably as shown in formula (I):

[0046]

[0047] R1 and R2 are each independently hydrogen, C1-C10 alkyl or C1-C10 alkoxy, preferably hydrogen, C1-C5 alkyl or C1-C5 alkoxy, more preferably hydrogen, C1-C3 alkyl or C1-C3 alkoxy, even more preferably hydrogen, methyl, ethyl, methoxy or ethoxy, and most preferably hydrogen or methoxy.

[0048] R3 is a C1-C10 alkyl, C1-C10 alkoxy, phenolic, or substituted phenolic group, preferably a C1-C5 alkyl, C1-C5 alkoxy, phenolic, or substituted phenolic group, more preferably a C1-C3 alkyl, C1-C3 alkoxy, phenolic, or substituted phenolic group, and even more preferably methyl, ethyl, methoxy, ethoxy, phenolic, or substituted phenolic group; the halogen atom can be any halogen atom known to those skilled in the art and is not particularly limited, but in this invention it is preferably chlorine or bromine, more preferably chlorine.

[0049] The substituent in the substituted phenolic group is one or more of C1-C10 alkyl, C1-C10 alkoxy, and C1-C10 aldehyde groups, preferably one or more of C1-C5 alkyl, C1-C5 alkoxy, and C1-C5 aldehyde groups, more preferably one or more of C1-C3 alkyl, C1-C3 alkoxy, and C1-C3 aldehyde groups, and even more preferably one or more of methyl, ethyl, methoxy, ethoxy, formaldehyde, and acetaldehyde groups.

[0050] According to the present invention, most preferably, R3 is one of the following structures:

[0051]

[0052] According to the present invention, more preferably, the polyaldehyde compound containing a phosphoryl group is as shown in formula (II):

[0053]

[0054] R1, R2, and R3 are all as described above, and will not be repeated here.

[0055] According to the present invention, the mass of the polyaldehyde compound containing phosphoryl groups is preferably 2% to 8% of the mass of chitosan in the chitosan solution, more preferably 4% to 7%, even more preferably 4% to 6%, and most preferably 5%.

[0056] The present invention also provides a method for preparing the above-mentioned chitosan fire extinguishing gel, comprising the following steps: mixing a crosslinking agent with a chitosan solution, heating and reacting to obtain a chitosan fire extinguishing gel; wherein the crosslinking agent comprises a polyaldehyde compound containing a phosphoryl group.

[0057] The present invention does not impose any special restrictions on the source of the raw materials; they can be commercially available.

[0058] In this invention, the chitosan solution is preferably prepared by the following method: mixing chitosan with an aqueous acetic acid solution and heating to obtain a chitosan solution; the volume concentration of acetic acid in the aqueous acetic acid solution is preferably 2% to 5%; the mixing and heating temperature is preferably 50°C to 60°C; the mixing and heating time is preferably 6 to 8 hours; and the mass concentration of chitosan in the chitosan solution is preferably 1% to 3%.

[0059] The phosphoryl-containing polyaldehyde compound is preferably prepared by the following method: reacting the aldehyde compound of formula (A) with a phosphorylating agent in the presence of an acid-binding agent to obtain the phosphoryl-containing polyaldehyde compound;

[0060]

[0061] R1 and R2 are each independently selected from hydrogen, C1-C10 alkyl groups, or C1-C10 alkoxy groups; R1 and R2 are as described above and will not be repeated here.

[0062] According to the present invention, more preferably, the aldehyde-containing compound represented by formula (A) is one or more of p-hydroxybenzaldehyde, aromatic aldehyde and syringaldehyde.

[0063] According to the present invention, the phosphorylating agent is preferably as shown in formula (B):

[0064]

[0065] Wherein, X is a halogen atom, and R3 is a C1-C10 alkyl, C1-C10 alkoxy, phenolic, or substituted phenolic group; the halogen atom can be any halogen atom well known to those skilled in the art, and there are no special limitations. In this invention, chlorine or bromine is preferred, and chlorine is more preferred; the R3 is the same as described above, and will not be repeated here. In this invention, it is further preferred that the phosphorylating agent is one or more of phosphorus oxychloride, methylphosphonodichloro, phenylphosphonodichloro, and phenyl phosphate dichloride.

[0066] According to the present invention, the acid binding agent can be any acid binding agent well known to those skilled in the art, and there are no special limitations. In the present invention, one or more of triethylamine, pyridine, sodium carbonate and potassium carbonate are preferred.

[0067] The aldehyde-containing compound shown in formula (A) is reacted with a phosphorylating agent in the presence of an acid-binding agent; the molar ratio of the aldehyde-containing compound shown in formula (A) to the phosphorylating agent is preferably (2-3):1; the molar ratio of the aldehyde-containing compound shown in formula (A) to the acid-binding agent is preferably 1:(1-2); the reaction is preferably carried out in an organic solvent; the organic solvent can be any organic solvent well known to those skilled in the art, and there are no special limitations. In this invention, trichloromethane, dichloromethane, acetone, tetrahydrofuran, acetonitrile, and 1,4-dichloromethane are preferred. One or more of oxane, toluene, and xylene; in this invention, it is preferred to first mix the aldehyde-containing compound of formula (A) with the phosphorylating agent in an organic solvent, and then add the phosphorylating agent dropwise; the phosphorylating agent is preferably added under ice bath conditions; in this invention, the aldehyde-containing compound of formula (A) and the phosphorylating agent are preferably reacted first under ice bath conditions in the presence of an acid-binding agent, and then heated to react; the reaction time under ice bath conditions is 2 to 4 hours; the temperature of the heated reaction is 50°C to 60°C; the reaction time is 6 to 8 hours.

[0068] After the reaction is complete, the compound is preferably washed with water and the solvent is removed to obtain a polyaldehyde compound containing a phosphoryl group; or after the reaction is complete, the compound is preferably washed multiple times with water and ethanol and then dried to obtain a polyaldehyde compound containing a phosphoryl group.

[0069] A crosslinking agent is mixed with a chitosan solution, and after heating and reacting, a chitosan fire extinguishing gel is obtained. In this invention, it is preferable to first dissolve the crosslinking agent in an organic solvent before mixing it with the chitosan solution. The organic solvent can be any organic solvent well known to those skilled in the art and is not particularly limited. In this invention, it is preferably one or more of acetone, chloroform, dichloromethane, tetrahydrofuran, acetonitrile, 1,4-dioxane, toluene, and xylene. The mass of the polyaldehyde compound containing a phosphoryl group is preferably 2% to 8% of the mass of chitosan in the chitosan solution. The temperature of the heating reaction is preferably 50°C to 60°C. The heating reaction time is preferably 10 to 20 hours.

[0070] The present invention also provides an application of the above-mentioned chitosan fire extinguishing gel in the preparation of lithium battery fire extinguishing materials.

[0071] The chitosan-based fire extinguishing gel provided by this invention has good coverage and high specific heat capacity, effectively isolates oxygen and heat, prevents lithium battery reignition, and efficiently extinguishes lithium battery fires. Moreover, it is derived from renewable natural resources, is green and environmentally friendly, and will not cause secondary pollution to the environment.

[0072] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a chitosan-based fire extinguishing gel, its preparation method, and its applications.

[0073] All reagents used in the following examples are commercially available. The degree of deacetylation of the chitosan used in the examples is 80.0%–95.0%, and the viscosity is 50–800 mPa·s. It is from Sinopharm Chemical Reagent Co., Ltd.

[0074] Example 1

[0075] 0.9 mol vanillin and 0.9 mol triethylamine were mixed in a chloroform solvent and the reaction system was placed in an ice bath. 0.3 mol of phosphorus oxychloride was weighed and slowly added dropwise to the vanillin solution. The reaction was continued to be stirred at 0°C for 2 h. Subsequently, the temperature was raised to 50°C and the reaction was continued to be stirred for 6 h. Afterward, the mixture was cooled to room temperature, filtered, and washed three times with deionized water and ethanol, respectively. The product was then dried in a vacuum oven to obtain target product I, whose chemical structure is shown below:

[0076]

[0077] Target product I was analyzed by proton nuclear magnetic resonance (NMR) spectrum (H1N). 1 H-NMR) and phosphorus nuclear magnetic resonance (NMR) spectrum 31 Characterization by p-NMR confirmed its chemical structure as follows: 1 H-NMR(400MHz,DMSO-d6,ppm):3.83(s,9H,-O-CH3),7.57-7.65(m,9H,Ar-H),9.97(s,3H,-CHO). 31 P-NMR (400MHz, DMSO-d6, ppm): -18.10.

[0078] Example 2

[0079] 1 mol of vanillin and 1 mol of triethylamine were mixed in chloroform and the reaction mixture was placed in an ice bath. 0.5 mol of phenyl phosphate dichloride was weighed and slowly added dropwise to the vanillin solution. The reaction was continued to be stirred at 0°C for 2 h. Subsequently, the temperature was raised to 50°C and the reaction was continued to be stirred for 6 h. Afterward, the mixture was cooled to room temperature and washed six times with deionized water. An appropriate amount of anhydrous sodium sulfate was added to remove water. The liquid product was obtained by rotary evaporation. This liquid product was then dried in a vacuum oven to obtain the target product II, whose chemical structure is shown below:

[0080]

[0081] Target product II was analyzed by proton nuclear magnetic resonance (NMR) spectrum (H1N). 1 H-NMR) and phosphorus nuclear magnetic resonance (NMR) spectrum 31 Characterization by p-NMR confirmed its chemical structure as follows: 1 H-NMR(400MHz,DMSO-d6,ppm):3.82(s,6H,-O-CH3),7.22-7.50(m,11H,Ar-H),9.94(s,2H,-CHO). 31 P-NMR (400MHz, DMSO-d6, ppm): -18.35.

[0082] Example 3

[0083] Weigh glacial acetic acid and water, and stir well to prepare a 2% (v / v) dilute acetic acid aqueous solution. Add chitosan to the prepared dilute acetic acid aqueous solution, then heat to 55°C and stir slowly for 6 hours to obtain a 2 wt% chitosan solution.

[0084] The target product I obtained in Example 1 was dissolved in acetone (the mass ratio of target product I to acetone was 1:20). A 5% acetone solution of target product I (the mass of target product I was 5% of the mass of chitosan) was added to the chitosan solution. The mixture was stirred at 55°C for 10 h to obtain chitosan-based fire extinguishing gel A.

[0085] A lithium battery (18650 cylindrical battery pack) with four thermocouples connected to its surface was continuously heated (700℃, 10 min) until it experienced thermal runaway, resulting in an explosion and violent combustion. The sprinkler system was immediately activated to spray fire extinguishing gel A, and the temperature change over time was obtained as shown in the graph below. Figure 1As shown. When gel A was used as the extinguishing agent, the spray was smooth and mist-like, with no blockage in the delivery pipeline. The battery produced a large amount of irritating gas smoke upon spraying. After 10 seconds of continuous spraying, the water pump was turned off to stop the spraying system, ultimately consuming 0.16L of gel A. With the spraying of gel A, the surface temperature of the lithium battery rapidly decreased from 531℃ to 76℃. The exothermic reaction inside the lithium battery had not completely ceased, and the surface temperature subsequently rose to 94℃. Observing the temperature change of the second thermocouple, it was found that during the free combustion stage of the lithium battery, the upper surface temperature reached a maximum of 137℃. With the spraying of gel A, the upper surface temperature of the lithium battery also rapidly decreased to 32℃, and then slowly rose to 70℃. The lithium battery did not reignite.

[0086] The data results are shown in Table 1:

[0087] Table 1 Fire extinguishing performance of Example 3

[0088]

[0089] Example 4

[0090] Weigh glacial acetic acid and water, and stir well to prepare a 2% (v / v) dilute acetic acid aqueous solution. Add chitosan to the prepared dilute acetic acid aqueous solution, then heat to 55°C and stir slowly for 6 hours to obtain a 2 wt% chitosan solution.

[0091] The target product II obtained in Example 2 was dissolved in acetone (the mass ratio of target product I to acetone was 1:20). A 5% acetone solution of target product II (the mass of target product II was 5% of the mass of chitosan) was added to the chitosan solution. The mixture was stirred at 55°C for 10 h to obtain chitosan-based fire extinguishing gel B.

[0092] A lithium battery (18650 cylindrical battery pack) with four thermocouples connected to its surface was continuously heated (700℃, 10 min) until it experienced thermal runaway, resulting in an explosion and violent combustion. The sprinkler system was immediately activated to spray fire extinguishing gel B, and the temperature change over time was obtained as shown in the graph below. Figure 2As shown, when gel B was used as the extinguishing agent, the spraying was smooth and produced a mist, without any blockage in the delivery pipeline. The battery produced a large amount of irritating gas smoke upon spraying. After 15 seconds of continuous spraying, the water pump was turned off to stop the spraying system, ultimately consuming 0.18L of gel B. With the spraying of gel B, the surface temperature of the lithium battery rapidly decreased from 654℃ to 67℃. The exothermic reaction inside the lithium battery had not completely ceased, and the surface temperature subsequently rose to 259℃ before decreasing to 120℃. Observing the temperature change of the second thermocouple, it was found that during the free combustion stage of the lithium battery, the upper surface temperature reached a maximum of 96℃. With the spraying of gel B, the upper surface temperature of the lithium battery also rapidly decreased to 48℃, but after the spraying ended, its temperature slowly rose to 78℃. The lithium battery did not reignite.

[0093] The data results are shown in Table 2:

[0094] Table 2 Fire extinguishing performance of Example 3

[0095]

[0096] Comparative Example 1

[0097] A lithium battery (18650 cylindrical battery pack) with four thermocouples connected to its surface was continuously heated (700℃, 10 min) until it experienced thermal runaway, resulting in an explosion and violent combustion. The spray system was immediately activated to spray water for 15 seconds at a rate of 0.24 L. The temperature change over time is shown in the graph below. Figure 3 As shown, with the water spray, the surface temperature of the lithium battery rapidly decreased from 654℃ to 67℃. However, due to the low viscosity of water, it did not remain on the surface of the lithium battery after the spraying. The exothermic reaction inside the lithium battery had not completely stopped, and the surface temperature subsequently rose to 125℃. At this point, the lithium battery temperature remained unchanged, but there was still a risk of reignition. Observing the temperature change of the second thermocouple, it was found that during the free combustion stage of the lithium battery, the surface temperature of the upper surface reached a maximum of 215℃. With the water spray, the surface temperature of the upper surface of the lithium battery also dropped rapidly, but after the spraying ended, it slowly rose to 110℃. This indicates that the water had been completely drained and would not remain on the surface of the lithium battery, further suppressing the thermal runaway of the lithium battery. However, the lithium battery still has a significant risk of reignition.

[0098] The data results are shown in Table 3:

[0099] Table 3 Fire extinguishing performance of Comparative Example 1

[0100]

[0101] Comparative Example 2

[0102] A lithium battery (18650 cylindrical battery pack) with four thermocouples connected to its surface was continuously heated (700℃, 10 min) until it experienced thermal runaway, resulting in an explosion and violent combustion. The spray system was immediately activated to spray perfluorohexanone for 38 seconds at a rate of 0.72 L. The battery produced a large amount of irritating gas fumes upon spraying. The temperature change over time is shown in the graph below. Figure 4 As shown, with the spraying of perfluorohexanone, the surface temperature of the lithium battery rapidly decreased from 656°C to 125°C, and then slowly decreased to 65°C. Observing the temperature change of the second thermocouple, it was found that during the free combustion stage of the lithium battery, the surface temperature of the lithium battery reached a maximum of 470°C. With the spraying of perfluorohexanone, the surface temperature of the lithium battery also rapidly decreased to 15°C, but after the spraying ended, it slowly rose to 60°C. The lithium battery did not reignite.

[0103] The data results are shown in Table 4:

[0104] Table 4 Fire extinguishing performance of Comparative Example 2

[0105]

[0106] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a chitosan fire extinguishing gel in the preparation of lithium battery fire extinguishing materials; wherein the chitosan-based fire extinguishing gel is formed by crosslinking a chitosan solution with a crosslinking agent; The chitosan solution contains 1% to 3% by mass; The crosslinking agent comprises a polyaldehyde compound containing a phosphoryl group; the mass of the polyaldehyde compound containing a phosphoryl group is 2% to 8% of the mass of chitosan in the chitosan solution. The polyaldehyde compound containing a phosphoryl group is shown in formula (II): Formula (II); R1 and R2 are each independently selected from hydrogen or methoxy groups; R3 is selected from one of the following structures: 。 2. The application according to claim 1, characterized in that, The preparation method of chitosan fire extinguishing gel includes the following steps: The cross-linking agent was mixed with the chitosan solution, and after heating and reacting, chitosan fire extinguishing gel was obtained. The crosslinking agent includes a polyaldehyde compound containing a phosphoryl group.

3. The application according to claim 2, characterized in that, The chitosan solution was prepared according to the following method: Chitosan and an aqueous acetic acid solution were mixed and heated to obtain a chitosan solution; The polyaldehyde compound containing a phosphoryl group is prepared according to the following method: An aldehyde-containing compound is reacted with a phosphorylating agent in the presence of an acid-binding agent to obtain a polyaldehyde compound containing a phosphoryl group. The aldehyde-containing compound is selected from one or more of p-hydroxybenzaldehyde, vanillin, and syringaldehyde; The phosphorylating agent is selected from one or more of phosphorus oxychloride and phenyl phosphate dichloride; The acid-binding agent is selected from one or more of triethylamine, pyridine, sodium carbonate, and potassium carbonate; The molar ratio of the aldehyde-containing compound to the phosphorylating agent is (2~3):1; The aldehyde-containing compound and the phosphorylating agent react first in an ice bath in the presence of an acid-binding agent, and then react by heating to obtain a polyaldehyde compound containing a phosphoryl group. The reaction time under ice bath is 2-4 h; the reaction temperature under heating is 50℃-60℃; the reaction time under heating is 6-8 h.

4. The application according to claim 2, characterized in that, The temperature of the heating reaction is 50℃~60℃; the heating reaction time is 10~20 h.

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