Flame-retardant heat-insulating material for battery cell and preparation method of flame-retardant heat-insulating material

Abstract

The invention relates to the technical field of thermal insulation materials, and discloses a flame-retardant thermal insulation material for a battery cell and a preparation method of the flame-retardant thermal insulation material. According to the invention, cellulose is subjected to dissolution, crosslinking and flame-retardant modification, and gel forming and drying, such that the flame-retardant thermal insulation material for the battery cell is obtained. An active intermediate released by an oxazine ring during ring-opening polymerization at a high temperature can catalyze a cross-linking reaction between molecular chains to form a three-dimensional network structure, so that the flame retardant property of the material is improved; boric acid ester is decomposed at a high temperature to generate boric oxide or boric acid, a transparent glassy coating is formed after melting, the surface of the material is tightly covered, oxygen and heat transfer are physically blocked, and the flame-retardant effect is achieved; phosphorus-containing free radicals generated by decomposition of phosphate can be combined with active free radicals in flames, so that a combustion chain reaction is interrupted, the flame temperature is reduced, and the flame retardant property of the material is further improved. And non-combustible or flame-retardant substances such as silicon dioxide generated by decomposition of silane can form a compact protective layer on the surface of the material, so that flame propagation is prevented, and a flame-retardant effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation materials technology, specifically to a flame-retardant thermal insulation material for battery cells and its preparation method. Background Technology

[0002] With the rapid development of the new energy industry, the safety requirements for energy storage devices such as lithium-ion batteries are becoming increasingly stringent. Among these, fires caused by thermal runaway of power batteries have become a key issue restricting the industry's development. High-efficiency thermal insulation materials, as core components for blocking heat propagation and delaying thermal runaway, directly affect the safety and reliability of battery cells. Thermal insulation materials are mainly divided into traditional thermal insulation materials and aerogels. Traditional thermal insulation materials include foam boards, fiberglass wool, and vacuum insulation panels, but their thermal insulation performance, physical properties, and environmental performance are insufficient to meet the requirements. In recent years, cellulose aerogel has been regarded as an ideal green thermal insulation material due to its advantages such as low density, high porosity, low thermal conductivity, and biodegradability. However, the inherent flammability of cellulose aerogel severely limits its application in power battery cells. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this invention provides a flame-retardant and heat-insulating material for battery cells and its preparation method, thereby solving the problem of poor flame-retardant performance of cellulose aerogel.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a flame-retardant and heat-insulating material for battery cells, wherein the method comprises: adding sodium hydroxide, urea, and water to a reactor, stirring and mixing, and pre-cooling to -14 to -10°C to obtain a cellulose solvent; dispersing cotton cellulose at a mass fraction of 5.8%-6.2% in the cellulose solvent; stirring for 25-35 minutes to obtain a transparent sol; and adding 4.5%-5.5% by mass of the transparent sol. The epoxy crosslinking agent is reacted for 1-1.5 hours, and then 10%-12% of borate ester modified benzoxazine flame retardant and 2.4%-3.2% sodium montmorillonite are added sequentially. After ultrasonic dispersion for 30-40 minutes, the gel is poured into a mold and cured at 48-52℃ for 8-14 hours. Then, the gel is freeze-dried at -50--45℃ for 20-24 hours using an ethanol-tert-butanol gradient replacement, followed by drying at 55-65℃ for 42-48 hours to obtain a flame-retardant and heat-insulating material for battery cells.

[0007] Preferably, the mass ratio of sodium hydroxide, urea, and water is 1:1.6-1.8:11.3-11.9.

[0008] Preferably, the method for preparing the borate ester modified benzoxazine flame retardant includes the following steps:

[0009] (1) Add 4.55-4.85g of 4-aminopyridine and 3-3.2g of paraformaldehyde to 40-60mL of toluene solvent, react at 32-36℃ for 1-2h, add 8.3-8.9g of 4-bromophenol, raise the temperature to 78-84℃ and continue the reaction for 4-6h. After the reaction is completed, wash with 4%-4.5% sodium hydroxide solution and remove the solvent by rotary evaporation to obtain benzoxazine intermediate;

[0010] (2) Dissolve 5.4-6.3g of benzoxazine intermediate and 6-6.2g of pinacol diborate in 80-100mL of 1,4-dioxane solvent, add 1.45-1.55g of catalyst and 8-8.2g of potassium carbonate, and react at 90-110℃ for 3.5-5.5h under nitrogen atmosphere. After the reaction is completed, remove the solvent by rotary evaporation, wash and vacuum dry to obtain borate ester modified benzoxazine flame retardant.

[0011] Preferably, the catalyst in step (2) is [1,1-bis(diphenylphosphine)ferrocene]palladium dichloride.

[0012] Preferably, the method for preparing the epoxy crosslinking agent includes the following steps:

[0013] S1. Add 2.9-3g of N-methyldiethanolamine to 60-80mL of anhydrous ethanol solvent, stir to dissolve, and add 5.1-5.3g of 3-chloropropyltrimethoxysilane dropwise. After the addition is complete, heat to 75-85℃ and reflux for 13-16h. After the reaction is complete, remove the solvent by rotary evaporation to obtain the silane quaternary ammonium salt intermediate.

[0014] S2. Under a nitrogen atmosphere, 4.4-4.5 g of silane quaternary ammonium salt intermediate and 0.8-1.2 mL of acid-binding agent are added to 40-50 mL of dichloromethane solvent and stirred to dissolve at 6-12 °C. 1.62-1.72 g of phenylphosphodichlorophosphate is added dropwise over 20-30 min. After the addition is complete, the reaction is allowed to proceed for 10-14 h. After the reaction is complete, the solvent is removed by rotary evaporation, and the product is washed and dried under vacuum to obtain phosphate-modified silane quaternary ammonium salt.

[0015] S3. Add 7.2-7.9 g of phosphate-modified silane quaternary ammonium salt and 18.4-18.6 g of epichlorohydrin to 80-90 mL of isopropanol solvent, heat to 48-54 °C, purge with nitrogen for protection, stir to dissolve, and continue heating to 65-70 °C. Add 0.78-0.82 g of sodium hydroxide and continue the reaction for 3-4 h. After the reaction is complete, remove the solvent by vacuum filtration, wash and vacuum dry to obtain the epoxy crosslinking agent.

[0016] Preferably, the dropping time of 3-chloropropyltrimethoxysilane in S1 is 40-50 min.

[0017] Preferably, the acid-binding agent in S2 is triethylamine.

[0018] This invention provides a flame-retardant and heat-insulating material for battery cells prepared by the method described above.

[0019] (iii) Beneficial technical effects

[0020] This invention obtains a flame-retardant and heat-insulating material for battery cells by dissolving, cross-linking and flame-retardant modification of cellulose, gel forming and drying.

[0021] In borate-modified benzoxazine flame retardants, the active intermediates released during the ring-opening polymerization of the oxazine ring at high temperatures can catalyze the cross-linking reaction between molecular chains, forming a three-dimensional network structure. This structure is not easily decomposed into small molecule combustible substances during combustion, but instead promotes the formation and stability of the char layer, improving the flame retardant performance of the material. Borate esters decompose at high temperatures to generate boron oxide or boric acid, which melts to form a transparent glassy coating that tightly covers the material surface, physically blocking oxygen and heat transfer, while preventing the escape of combustible gases, thus achieving a flame retardant effect. In epoxy cross-linking agents, the phosphorus-containing free radicals generated by the decomposition of phosphate esters can combine with active free radicals in the flame, interrupting the combustion chain reaction, reducing the flame temperature, and further improving the flame retardant performance of the material. Non-combustible or flame-retardant substances such as silica generated by the decomposition of silanes form a dense protective layer on the material surface, thereby preventing flame propagation and achieving a flame retardant effect. Attached Figure Description

[0022] Figure 1 It is the synthetic reaction formula for borate ester modified benzoxazine flame retardant.

[0023] Figure 2 It is the synthesis reaction formula for epoxy crosslinking agents. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] (1) Add 4.55 g of 4-aminopyridine and 3 g of paraformaldehyde to 40 mL of toluene solvent, react at 32 °C for 1 h, add 8.3 g of 4-bromophenol, raise the temperature to 78 °C and continue the reaction for 4 h. After the reaction is completed, wash with 4% sodium hydroxide solution and remove the solvent by rotary evaporation to obtain benzoxazine intermediate;

[0028] (2) Dissolve 5.4 g of benzoxazine intermediate and 6 g of pinacol diborate in 80 mL of 1,4-dioxane solvent, add 1.45 g of [1,1-bis(diphenylphosphine)ferrocene]palladium dichloride catalyst and 8 g of potassium carbonate, and heat to 90 °C for 3.5 h under nitrogen atmosphere. After the reaction is completed, remove the solvent by rotary evaporation, wash and vacuum dry to obtain borate ester modified benzoxazine flame retardant;

[0029] (3) Add 2.9 g of N-methyldiethanolamine to 60 mL of anhydrous ethanol solvent, stir to dissolve, add 5.1 g of 3-chloropropyltrimethoxysilane dropwise over 40 min, and after the addition is complete, heat to 75 °C and reflux for 13 h. After the reaction is complete, remove the solvent by rotary evaporation to obtain the silane quaternary ammonium salt intermediate.

[0030] (4) Under a nitrogen atmosphere, 4.4 g of silane quaternary ammonium salt intermediate and 0.8 mL of triethylamine acid binder were added to 40 mL of dichloromethane solvent and stirred and dissolved at 6 °C. 1.62 g of phenylphosphodichloro was added dropwise over a period of 20 min. After the addition was complete, the reaction was allowed to proceed for 10 h. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed and dried under vacuum to obtain phosphate ester modified silane quaternary ammonium salt.

[0031] (5) Add 7.2g of phosphate-modified silane quaternary ammonium salt and 18.4g of epichlorohydrin to 80mL of isopropanol solvent, heat to 48℃, purge with nitrogen for protection, stir to dissolve and continue heating to 65℃, add 0.78g of sodium hydroxide and continue the reaction for 3h. After the reaction is completed, remove the solvent by vacuum filtration, wash and vacuum dry to obtain epoxy crosslinking agent;

[0032] (6) Add sodium hydroxide, urea and water to the reactor, stir and mix and pre-cool to -14°C. The mass ratio of sodium hydroxide, urea and water is 1:1.6:11.3 to obtain cellulose solvent. Disperse 5.8% cotton cellulose in the cellulose solvent and stir for 25 min to obtain transparent sol. Add 4.5% epoxy crosslinking agent to the transparent sol and react for 1 h. Then add 10% borate ester modified benzoxazine flame retardant and 2.4% sodium montmorillonite to it in sequence. After ultrasonic dispersion for 30 min, pour the gel into the mold and cure at 48°C for 8 h. Then use ethanol → tert-butanol gradient replacement, freeze dry at -50°C for 20 h, and dry at 55°C for 42 h to obtain flame retardant and heat insulation material for battery cells.

[0033] Example 2

[0034] (1) Add 4.85 g of 4-aminopyridine and 3.2 g of paraformaldehyde to 60 mL of toluene solvent, react at 36 °C for 2 h, add 8.9 g of 4-bromophenol, raise the temperature to 84 °C and continue the reaction for 6 h. After the reaction is completed, wash with 4.5% sodium hydroxide solution and remove the solvent by rotary evaporation to obtain benzoxazine intermediate;

[0035] (2) Dissolve 6.3g of benzoxazine intermediate and 6.2g of pinacol diborate in 100mL of 1,4-dioxane solvent, add 1.55g of [1,1-bis(diphenylphosphine)ferrocene]palladium dichloride catalyst and 8.2g of potassium carbonate, and react at 110℃ for 5.5h under nitrogen atmosphere. After the reaction is completed, remove the solvent by rotary evaporation, wash and vacuum dry to obtain borate ester modified benzoxazine flame retardant;

[0036] (3) Add 3g of N-methyldiethanolamine to 80mL of anhydrous ethanol solvent, stir to dissolve, add 5.3g of 3-chloropropyltrimethoxysilane dropwise over 50min, and after the addition is complete, heat to 85℃ and reflux for 16h. After the reaction is complete, remove the solvent by rotary evaporation to obtain the silane quaternary ammonium salt intermediate.

[0037] (4) Under a nitrogen atmosphere, 4.5 g of silane quaternary ammonium salt intermediate and 1.2 mL of triethylamine acid binder were added to 50 mL of dichloromethane solvent and stirred and dissolved at 12 °C. 1.72 g of phenylphosphodichloro was added dropwise over a period of 30 min. After the addition was complete, the reaction was allowed to proceed for 14 h. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed and dried under vacuum to obtain phosphate-modified silane quaternary ammonium salt.

[0038] (5) Add 7.9 g of phosphate-modified silane quaternary ammonium salt and 18.6 g of epichlorohydrin to 90 mL of isopropanol solvent, heat to 54 °C, purge with nitrogen for protection, stir to dissolve and continue heating to 70 °C, add 0.82 g of sodium hydroxide and continue reaction for 4 h. After the reaction is completed, remove the solvent by vacuum filtration, wash and vacuum dry to obtain epoxy crosslinking agent;

[0039] (6) Add sodium hydroxide, urea and water to the reactor, stir and mix and pre-cool to -10℃, wherein the mass ratio of sodium hydroxide, urea and water is 1:1.8:11.9 to obtain cellulose solvent. Disperse cotton cellulose with a mass fraction of 6.2% in the cellulose solvent and stir for 35 min to obtain transparent sol. Add epoxy crosslinking agent with a mass fraction of 5.5% to the transparent sol and react for 1.5 h. Then add borate ester modified benzoxazine flame retardant with a mass fraction of 12% and sodium montmorillonite with a mass fraction of 3.2% in sequence. After ultrasonic dispersion for 40 min, pour the gel into the mold and cure at 52℃ for 14 h. Then use ethanol → tert-butanol gradient replacement, freeze dry at -45℃ for 24 h, and dry at 65℃ for 48 h to obtain flame retardant and heat insulation material for battery cells.

[0040] Example 3

[0041] (1) Add 4.7 g of 4-aminopyridine and 3.1 g of paraformaldehyde to 50 mL of toluene solvent, react at 34 °C for 1.5 h, add 8.6 g of 4-bromophenol, raise the temperature to 81 °C and continue the reaction for 5 h. After the reaction is completed, wash with 4.25% sodium hydroxide solution and remove the solvent by rotary evaporation to obtain benzoxazine intermediate;

[0042] (2) Dissolve 5.85 g of benzoxazine intermediate and 6.1 g of pinacol diborate in 90 mL of 1,4-dioxane solvent, add 1.5 g of [1,1-bis(diphenylphosphine)ferrocene]palladium dichloride catalyst and 8.1 g of potassium carbonate, and react at 100 °C for 4.5 h under nitrogen atmosphere. After the reaction is completed, remove the solvent by rotary evaporation, wash and vacuum dry to obtain borate ester modified benzoxazine flame retardant;

[0043] (3) Add 2.95 g of N-methyldiethanolamine to 70 mL of anhydrous ethanol solvent, stir to dissolve, add 5.2 g of 3-chloropropyltrimethoxysilane dropwise over a period of 45 min, and after the addition is complete, heat to 80 °C and reflux for 14.5 h. After the reaction is complete, remove the solvent by rotary evaporation to obtain the silane quaternary ammonium salt intermediate.

[0044] (4) Under a nitrogen atmosphere, 4.45 g of silane quaternary ammonium salt intermediate and 1 mL of triethylamine acid binder were added to 45 mL of dichloromethane solvent and stirred at 9 °C to dissolve. 1.67 g of phenylphosphodichloro was added dropwise over a period of 25 min. After the addition was complete, the reaction was allowed to proceed for 12 h. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed and dried under vacuum to obtain phosphate-modified silane quaternary ammonium salt.

[0045] (5) Add 7.55g of phosphate-modified silane quaternary ammonium salt and 18.5g of epichlorohydrin to 85mL of isopropanol solvent, heat to 51℃, purge with nitrogen for protection, stir to dissolve and continue heating to 68℃, add 0.8g of sodium hydroxide, continue reaction for 3.5h, after the reaction is completed, remove solvent by vacuum filtration, wash and vacuum dry to obtain epoxy crosslinking agent;

[0046] (6) Add sodium hydroxide, urea and water to the reactor, stir and mix and pre-cool to -12°C, wherein the mass ratio of sodium hydroxide, urea and water is 1:1.7:11.6 to obtain cellulose solvent. Disperse 6% cotton cellulose in the cellulose solvent and stir for 30 min to obtain transparent sol. Add 5% epoxy crosslinking agent to the transparent sol and react for 1.2 h. Then add 11% borate ester modified benzoxazine flame retardant and 2.8% sodium montmorillonite to it in sequence. After ultrasonic dispersion for 35 min, pour the gel into the mold and cure at 50°C for 11 h. Then use ethanol → tert-butanol gradient replacement, freeze dry at -48°C for 22 h, and dry at 60°C for 45 h to obtain flame retardant and heat insulation material for battery cells.

[0047] Example 4

[0048] (1) Add 4.55 g of 4-aminopyridine and 3 g of paraformaldehyde to 40 mL of toluene solvent, react at 32 °C for 1 h, add 8.3 g of 4-bromophenol, raise the temperature to 78 °C and continue the reaction for 4 h. After the reaction is completed, wash with 4% sodium hydroxide solution and remove the solvent by rotary evaporation to obtain benzoxazine intermediate;

[0049] (2) Dissolve 5.4 g of benzoxazine intermediate and 6 g of pinacol diborate in 80 mL of 1,4-dioxane solvent, add 1.45 g of [1,1-bis(diphenylphosphine)ferrocene]palladium dichloride catalyst and 8 g of potassium carbonate, and heat to 90 °C for 3.5 h under nitrogen atmosphere. After the reaction is completed, remove the solvent by rotary evaporation, wash and vacuum dry to obtain borate ester modified benzoxazine flame retardant;

[0050] (3) Add 3g of N-methyldiethanolamine to 80mL of anhydrous ethanol solvent, stir to dissolve, add 5.3g of 3-chloropropyltrimethoxysilane dropwise over 50min, and after the addition is complete, heat to 85℃ and reflux for 16h. After the reaction is complete, remove the solvent by rotary evaporation to obtain the silane quaternary ammonium salt intermediate.

[0051] (4) Under a nitrogen atmosphere, 4.5 g of silane quaternary ammonium salt intermediate and 1.2 mL of triethylamine acid binder were added to 50 mL of dichloromethane solvent and stirred and dissolved at 12 °C. 1.72 g of phenylphosphodichloro was added dropwise over a period of 30 min. After the addition was complete, the reaction was allowed to proceed for 14 h. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed and dried under vacuum to obtain phosphate-modified silane quaternary ammonium salt.

[0052] (5) Add 7.55g of phosphate-modified silane quaternary ammonium salt and 18.5g of epichlorohydrin to 85mL of isopropanol solvent, heat to 51℃, purge with nitrogen for protection, stir to dissolve and continue heating to 68℃, add 0.8g of sodium hydroxide, continue reaction for 3.5h, after the reaction is completed, remove solvent by vacuum filtration, wash and vacuum dry to obtain epoxy crosslinking agent;

[0053] (6) Add sodium hydroxide, urea and water to the reactor, stir and mix and pre-cool to -12°C, wherein the mass ratio of sodium hydroxide, urea and water is 1:1.7:11.6 to obtain cellulose solvent. Disperse 6% cotton cellulose in the cellulose solvent and stir for 30 min to obtain transparent sol. Add 5% epoxy crosslinking agent to the transparent sol and react for 1.2 h. Then add 11% borate ester modified benzoxazine flame retardant and 2.8% sodium montmorillonite to it in sequence. After ultrasonic dispersion for 35 min, pour the gel into the mold and cure at 50°C for 11 h. Then use ethanol → tert-butanol gradient replacement, freeze dry at -48°C for 22 h, and dry at 60°C for 45 h to obtain flame retardant and heat insulation material for battery cells.

[0054] Example 5

[0055] (1) Add 4.7 g of 4-aminopyridine and 3.1 g of paraformaldehyde to 50 mL of toluene solvent, react at 34 °C for 1.5 h, add 8.6 g of 4-bromophenol, raise the temperature to 81 °C and continue the reaction for 5 h. After the reaction is completed, wash with 4.25% sodium hydroxide solution and remove the solvent by rotary evaporation to obtain benzoxazine intermediate;

[0056] (2) Dissolve 5.85 g of benzoxazine intermediate and 6.1 g of pinacol diborate in 90 mL of 1,4-dioxane solvent, add 1.5 g of [1,1-bis(diphenylphosphine)ferrocene]palladium dichloride catalyst and 8.1 g of potassium carbonate, and react at 100 °C for 4.5 h under nitrogen atmosphere. After the reaction is completed, remove the solvent by rotary evaporation, wash and vacuum dry to obtain borate ester modified benzoxazine flame retardant;

[0057] (3) Add 2.9 g of N-methyldiethanolamine to 60 mL of anhydrous ethanol solvent, stir to dissolve, add 5.1 g of 3-chloropropyltrimethoxysilane dropwise over 40 min, and after the addition is complete, heat to 75 °C and reflux for 13 h. After the reaction is complete, remove the solvent by rotary evaporation to obtain the silane quaternary ammonium salt intermediate.

[0058] (4) Under a nitrogen atmosphere, 4.4 g of silane quaternary ammonium salt intermediate and 0.8 mL of triethylamine acid binder were added to 40 mL of dichloromethane solvent and stirred and dissolved at 6 °C. 1.62 g of phenylphosphodichloro was added dropwise over a period of 20 min. After the addition was complete, the reaction was allowed to proceed for 10 h. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed and dried under vacuum to obtain phosphate ester modified silane quaternary ammonium salt.

[0059] (5) Add 7.9 g of phosphate-modified silane quaternary ammonium salt and 18.6 g of epichlorohydrin to 90 mL of isopropanol solvent, heat to 54 °C, purge with nitrogen for protection, stir to dissolve and continue heating to 70 °C, add 0.82 g of sodium hydroxide and continue reaction for 4 h. After the reaction is completed, remove the solvent by vacuum filtration, wash and vacuum dry to obtain epoxy crosslinking agent;

[0060] (6) Add sodium hydroxide, urea and water to the reactor, stir and mix and pre-cool to -10℃, wherein the mass ratio of sodium hydroxide, urea and water is 1:1.8:11.9 to obtain cellulose solvent. Disperse cotton cellulose with a mass fraction of 6.2% in the cellulose solvent and stir for 35 min to obtain transparent sol. Add epoxy crosslinking agent with a mass fraction of 5.5% to the transparent sol and react for 1.5 h. Then add borate ester modified benzoxazine flame retardant with a mass fraction of 12% and sodium montmorillonite with a mass fraction of 3.2% in sequence. After ultrasonic dispersion for 40 min, pour the gel into the mold and cure at 52℃ for 14 h. Then use ethanol → tert-butanol gradient replacement, freeze dry at -45℃ for 24 h, and dry at 65℃ for 48 h to obtain flame retardant and heat insulation material for battery cells.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 5 is that step (6) does not contain borate ester modified benzoxazine flame retardant.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 5 is that epichlorohydrin is used instead of epoxy crosslinking agent in step (6).

[0065] The flame-retardant and heat-insulating materials used in the battery cells of Examples 1-5 and Comparative Examples 1-2 were subjected to vertical burning tests according to the UL94 flammability test method. The limiting oxygen index of the flame-retardant and heat-insulating materials used in the battery cells of Examples 1-5 and Comparative Examples 1-2 was tested using an oxygen index meter. The test results are shown in Table 1.

[0066] Table 1: Flame retardant performance test.

[0067] project flammability rating Limiting oxygen index (%) Example 1 V0 46.3 Example 2 V0 45.7 Example 3 V0 46.1 Example 4 V0 45.9 Example 5 V0 46.4 Comparative Example 1 V1 39.2 Comparative Example 2 V1 41.7

[0068] As shown in Table 1, the flame-retardant and heat-insulating materials in Examples 1-5 of the present invention have better flame-retardant properties than the flame-retardant and heat-insulating materials in Comparative Examples 1-2.

[0069] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0070] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0071] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a fire-retardant thermal barrier material for use in an electrical cell, characterized in that, The preparation method of the fire-retardant thermal insulation material for the battery cell comprises the following steps: adding sodium hydroxide, urea and water into a reactor, stirring and mixing, and pre-cooling to minus 14 to minus 10 DEG C to obtain a cellulose dissolving agent; dispersing cotton cellulose with a mass fraction of 5.8%-6.2% in the cellulose dissolving agent; stirring for 25-35 min to obtain a transparent sol; adding an epoxy cross-linking agent with a mass fraction of 4.5%-5.5% into the transparent sol; reacting for 1-1.5 h; then adding a borate modified benzoxazine fire-retardant agent with a mass fraction of 10%-12% and sodium-based montmorillonite with a mass fraction of 2.4%-3.2% into the transparent sol; ultrasonic dispersing for 30-40 min; pouring the gel into a mold; curing at 48-52 DEG C for 8-14 h; using ethanol and t-butyl alcohol gradient replacement; freezing and drying at minus 50 to minus 45 DEG C for 20-24 h; drying at 55-65 DEG C for 42-48 h; and obtaining the fire-retardant thermal insulation material for the battery cell.

2. The method of claim 1, wherein the method further comprises, The mass ratio of the sodium hydroxide, the urea and the water is 1:1.6-1.8:11.3-11.

9.

3. The method of claim 1, wherein the method further comprises: The preparation method of the borate modified benzoxazine fire-retardant agent comprises the following steps: (1) adding 4.55-4.85 g of 4-aminopyridine and 3-3.2 g of polyformaldehyde into 40-60 mL of a toluene solvent, reacting at 32-36 DEG C for 1-2 h, adding 8.3-8.9 g of 4-bromophenol into the toluene solvent, and continuing to react at 78-84 DEG C for 4-6 h; after the reaction is completed, washing with a sodium hydroxide solution with a mass fraction of 4%-4.5%, and removing the solvent by rotary evaporation to obtain a benzoxazine intermediate; (2) dissolving 5.4-6.3 g of the benzoxazine intermediate and 6-6.2 g of pinacol diboronic acid in 80-100 mL of a 1,4-dioxane solvent, adding 1.45-1.55 g of a catalyst and 8-8.2 g of potassium carbonate into the 1,4-dioxane solvent, reacting at 90-110 DEG C for 3.5-5.5 h under a nitrogen atmosphere, and after the reaction is completed, removing the solvent by rotary evaporation, washing and vacuum drying to obtain the borate modified benzoxazine fire-retardant agent.

4. The method of claim 3, wherein the method further comprises, The catalyst in the step (2) is [1,1-bis(diphenylphosphino)ferrocene]palladium dichloride.

5. The method of claim 1, wherein the method further comprises, The preparation method of the epoxy cross-linking agent comprises the following steps: S1. adding 2.9-3 g of N-methyldiethanolamine into 60-80 mL of anhydrous ethanol, stirring and dissolving, and adding 5.1-5.3 g of 3-chloropropyltrimethoxysilane dropwise into the anhydrous ethanol; after the dropwise addition is completed, heating to 75-85 DEG C to reflux for 13-16 h; after the reaction is completed, removing the solvent by rotary evaporation to obtain a silane quaternary ammonium salt intermediate; S2. Under a nitrogen atmosphere, 4.4-4.5 g of the silane quaternary ammonium salt intermediate, 0.8-1.2 mL of the acid binding agent, were added to 40-50 mL of dichloromethane solvent, and stirred and dissolved at 6-12°C, 1.62-1.72 g of phenyl phosphorodichloridate was added dropwise, the dropwise addition time was 20-30 min, after the dropwise addition was completed, the reaction was carried out for 10-14 h, after the reaction was completed, the solvent was removed by rotary evaporation, washed and vacuum dried, to obtain the phosphonate-modified silane quaternary ammonium salt; S3. 7.2-7.9 g of the phosphonate-modified silane quaternary ammonium salt, 18.4-18.6 g of epichlorohydrin were added to 80-90 mL of isopropanol solvent, heated to 48-54°C, and protected by nitrogen gas, after stirring and dissolving, the temperature was further increased to 65-70°C, 0.78-0.82 g of sodium hydroxide was added, and the reaction was continued for 3-4 h, after the reaction was completed, the solvent was removed by vacuum filtration, washed and vacuum dried, to obtain the epoxy crosslinking agent.

6. The method of claim 5, wherein the method further comprises, The dropwise addition time of the 3-chloropropyltrimethoxysilane in S1 was 40-50 min.

7. The method of claim 5, wherein the method further comprises, The acid binding agent in S2 was triethylamine.

8. A flame-retardant thermal insulation material for an electric core prepared by the preparation method according to any one of claims 1-7.

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