A composite modified aerogel felt and its preparation method and application

Abstract

This invention relates to a composite modified aerogel felt, its preparation method, and its application. The preparation method of the composite modified aerogel felt includes the following steps: (1) mixing ethanol, pure water, silicon source, and acid catalyst in the first mixture, and then mixing the resulting solution with a composite modifier to obtain an impregnation liquid; (2) impregnating a carbon fiber substrate in the impregnation liquid obtained in step (1) to obtain a composite modified aerogel felt precursor; spraying an alkaline catalyst onto the surface of the obtained composite modified aerogel felt precursor, allowing it to stand until a gel forms on the surface, and then sequentially curing, aging, and drying to obtain the composite modified aerogel felt. This invention uses cationic surfactants and aromatic alcohol compounds as composite modifiers to prepare a composite modified aerogel felt with strong hydrophobicity, high temperature resistance, and good thermal insulation effect through in-situ synthesis. The process conditions are mild and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of aerogel preparation technology, specifically to a composite modified aerogel felt, its preparation method, and its application. Background Technology

[0002] Aerogels, also known as dry gels, are formed when most of the solvent is removed from the gel, resulting in a much lower liquid content than solid content, or when the gel's spatial network structure is filled with gas, giving it a solid appearance. Aerogels possess extremely low density, extremely low thermal conductivity, high specific surface area, and high porosity, making them widely used in high-end technology fields such as aerospace and military industries. Aerogel felts, on the other hand, are flexible thermal insulation felts made primarily of nano-silica or metallic aerogels, combined with ceramic fibers, glass fibers, or pre-oxidized filaments through a special process. They are characterized by low thermal conductivity and certain tensile and compressive strength, finding wide application in industries such as manufacturing, construction, automotive, and electronics.

[0003] The substrates used in the preparation of existing aerogel felts are mostly glass fiber, ceramic fiber, pre-oxidized fiber, etc., and the modifiers used are mostly silane coupling agents. Although the hydrophobicity of the aerogel felt prepared in this way can be improved, the combustion performance will decrease as the amount of modifier increases, which will limit its application.

[0004] CN 108821741A discloses a method for preparing aerogel felt. The method involves mixing a silicon source with ethanol, adding an acidic catalyst and a basic catalyst to adjust the pH, and stirring to obtain a sol solution. A substrate felt is then immersed in the sol solution, removed, and allowed to solidify. A modifier is then added for modification, followed by drying. Finally, a high-temperature resistant gelling agent is coated onto the surface of the fiber felt, and a flame-retardant cloth is attached to obtain the aerogel felt. The prepared aerogel felt exhibits excellent corrosion resistance, but the preparation steps are relatively cumbersome, and adding the modifier after solidification can reduce the modification effect of the gel.

[0005] CN 116396450A discloses a method for aerogel composite modification. Specifically, deionized water is added to a reaction vessel, followed by the sequential addition of an emulsifier, methyl acrylate, butyl acrylate, and a functional monomer. The mixture is stirred at high speed to obtain a pre-emulsion. An initiator is dissolved in a small amount of deionized water, and vinylsiloxane is added to prepare an initiator solution. Half of the initiator solution is added to the pre-emulsion, and the mixture is stirred and heated to begin the reaction. The reaction is stopped when the emulsion begins to emit blue light, and the temperature is lowered. Aerogel powder is added to the reaction vessel and, after thorough dispersion, the remaining initiator solution is added dropwise. The temperature is raised to continue the reaction. After the initiator addition is complete, the reaction is maintained at this temperature, and then naturally cooled to room temperature to obtain an aerogel-modified emulsion. The aerogel-modified emulsion is placed in a vacuum chamber and dried. The dried product is pulverized and sieved to obtain a composite modified aerogel. Although this method improves the strength of the aerogel material, the modifier formulation contains too many components, making it unsuitable for industrial use.

[0006] CN 107117932A discloses a hydrophobic modifier and a method for preparing aerogel insulation felt using the hydrophobic modifier. Castor oil and oleamide are used instead of silane coupling agents as hydrophobic modifiers for the aerogel felt. The resulting aerogel felt can reach a maximum service temperature of 757℃, achieves an A1 flammability rating, and has a thermal conductivity of less than 7.715 W / mK. While this method reduces production costs, it requires more stringent process conditions.

[0007] Therefore, in view of the shortcomings of the existing technology, there is a need to provide a preparation method with mild process conditions, suitable for industrial production, and which produces aerogel felt with strong hydrophobicity, excellent heat insulation effect and temperature resistance. Summary of the Invention

[0008] The purpose of this invention is to provide a composite modified aerogel felt, its preparation method and application. Carbon fiber is selected as the base material, and cationic surfactants and aromatic alcohol compounds are used as composite modifiers. The composite modified aerogel felt with excellent hydrophobicity, heat insulation effect and temperature resistance is prepared by in-situ synthesis.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a composite modified aerogel mat, the method comprising the following steps:

[0011] (1) The first mixture of ethanol, pure water, silicon source and acid catalyst is mixed with the composite modifier to obtain the impregnation solution.

[0012] (2) The carbon fiber substrate is immersed in the impregnation liquid obtained in step (1) to obtain the composite modified aerogel felt precursor; an alkaline catalyst is sprayed onto the surface of the obtained composite modified aerogel felt precursor, and after standing until the surface forms a gel, it is cured, aged and dried in sequence to obtain the composite modified aerogel felt.

[0013] The present invention provides a method for preparing a composite modified aerogel felt, using carbon fiber as the substrate and preparing the aerogel felt through in-situ synthesis. First, the carbon fiber is immersed in an acidic hydrolysate containing a silicon source, then removed and uniformly sprayed with an alkaline catalyst. Simultaneously, a composite modifier is added during the preparation process to modify the aerogel felt. Finally, the composite modified aerogel felt is obtained through curing, aging, and drying. The preparation method employs mild process conditions, and the resulting composite modified aerogel felt combines the advantages of both modified aerogel and carbon fiber, exhibiting strong hydrophobicity, high-temperature resistance, and excellent thermal insulation properties, making it suitable for industrial production.

[0014] Preferably, step (1) of the first mixing step specifically includes: uniformly mixing ethanol, pure water and silicon source, and adding an acid catalyst to the resulting solution to adjust the pH value.

[0015] Preferably, the molar ratio of ethanol, pure water and silicon source is 20:1:(2-6), for example, it can be 20:1:2, 20:1:3, 20:1:4, 20:1:5 or 20:1:6 but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, the silicon source includes silicon tetrachloride.

[0017] The silicon source chosen is silicon tetrachloride because it is easier to obtain and cheaper than ethyl silicate and other materials.

[0018] Preferably, the amount of acid catalyst used is such that the pH value of the solution is adjusted to 2-3, for example, 2, 2.2, 2.5, 2.8 or 3, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the acid catalyst comprises an inorganic acid.

[0020] The acid catalyst is an inorganic acid, which, compared to organic acids, does not cause side reactions and is more conducive to the formation of aerogel structures.

[0021] Preferably, the inorganic acid includes any one or a combination of at least two of hydrochloric acid, sulfuric acid, or nitric acid. Typical but non-limiting combinations include a combination of hydrochloric acid and sulfuric acid, a combination of sulfuric acid and nitric acid, or a combination of hydrochloric acid, sulfuric acid, and nitric acid.

[0022] Preferably, the composite modifier in step (1) comprises a mixture of cationic surfactants and aromatic alcohol compounds.

[0023] The cationic surfactant used in the composite modifier can reduce the surface tension of the liquid in the gel, thereby obtaining a complete pore structure after drying; aromatic alcohol compounds can improve the hydrophobicity and heat insulation properties of the aerogel; and the carbon fiber selected as the substrate is also a material with excellent heat resistance and corrosion resistance. The composite modified aerogel felt thus formed has the advantages of both aerogel and carbon fiber materials, and has a wider range of application prospects.

[0024] Preferably, the molar ratio of the cationic surfactant to the aromatic alcohol compound is 1:(3-8), for example, it can be 1:3, 1:4, 1:5, 1:6 or 1:8, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the cationic surfactant comprises any one or a combination of at least two of dodecyltrimethylammonium bromide, dodecyl dimethylammonium oxide, or octadecyltrimethylammonium chloride. Typical but non-limiting combinations include a combination of dodecyltrimethylammonium bromide and dodecyl dimethylammonium oxide, a combination of dodecyl dimethylammonium oxide and octadecyltrimethylammonium chloride, or a combination of dodecyltrimethylammonium bromide, dodecyl dimethylammonium oxide, and octadecyltrimethylammonium chloride.

[0026] Preferably, the aromatic alcohol compound includes any one or a combination of at least two of p-hydroxyanisole, triphenylmethanol, or ethyl p-hydroxybenzoate. Typical but non-limiting combinations include a combination of p-hydroxyanisole and triphenylmethanol, a combination of triphenylmethanol or ethyl p-hydroxybenzoate, or a combination of p-hydroxyanisole, triphenylmethanol, and ethyl p-hydroxybenzoate.

[0027] Preferably, the mass percentage of the composite modifier in the impregnation solution in step (1) is 5-20 wt%, for example, it can be 5 wt%, 8 wt%, 10 wt%, 15 wt% or 20 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the temperature of the second mixing in step (1) is 20-30°C, for example, it can be 20°C, 22°C, 25°C, 28°C or 30°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the mixing time in step (1) is 8-12 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, in step (1), the first mixing and the second mixing are carried out in a hydrolysis reactor.

[0031] Preferably, the alkaline catalyst in step (2) is obtained by mixing an alkali with pure water.

[0032] Preferably, the concentration of alkali in the alkali catalyst in step (2) is 6-7%, for example, it can be 6%, 6.2%, 6.5%, 6.8% or 7%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the alkali includes any one or a combination of at least two of sodium hydroxide, sodium bicarbonate, or ammonia. Typical but non-limiting combinations include a combination of sodium hydroxide and sodium bicarbonate, a combination of sodium bicarbonate and ammonia, or a combination of sodium hydroxide, sodium bicarbonate, and ammonia.

[0034] Preferably, the pH value of the alkaline catalyst sprayed onto the surface of the composite modified aerogel felt precursor in step (2) is adjusted to 7-7.5, for example, it can be 7, 7.1, 7.2, 7.3 or 7.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the curing and aging temperature in step (2) is 60-65℃, for example, it can be 60℃, 61℃, 62℃, 63℃ or 65℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] The curing and aging temperature needs to be strictly controlled. Too high a temperature may pose a safety risk and may cause the collapse of the internal pores of the aerogel; too low a temperature may affect the formation and distribution of the internal pore structure of the aerogel.

[0037] Preferably, the curing and aging time in step (2) is 11-13 hours, for example, 11 hours, 11.5 hours, 12 hours, 12.5 hours or 13 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, the curing and aging process in step (2) is carried out in an integrated curing and aging reactor.

[0039] Preferably, the drying temperature in step (2) is 78-85°C, for example, 78°C, 79°C, 80°C, 82°C or 85°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the drying time in step (2) is 7-9 hours, for example, 7 hours, 7.5 hours, 8 hours, 8.5 hours or 9 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] As a preferred embodiment of the preparation method described in this invention, the preparation method includes the following steps:

[0042] (1) Ethanol, pure water and silicon source are uniformly mixed in a molar ratio of 20:1:(2-6) in a hydrolysis reactor. An acid catalyst is added to the resulting solution to adjust the pH value to 2-3. The resulting solution and composite modifier are then mixed again in a hydrolysis reactor at 20-30℃ for 8-12 hours to obtain an impregnation solution. The composite modifier comprises a mixture of cationic surfactant and aromatic alcohol compounds in a molar ratio of 1:(3-8). The mass percentage of the composite modifier in the impregnation solution is 5-20 wt%.

[0043] (2) The carbon fiber substrate is immersed in the impregnation solution obtained in step (1) to obtain a composite modified aerogel felt precursor; an alkaline catalyst is sprayed onto the surface of the obtained composite modified aerogel felt precursor until the pH value is adjusted to 7-7.5. The alkaline catalyst is obtained by mixing alkali and pure water, and the concentration of alkali in the alkaline catalyst is 6-7%; after standing until the surface forms a gel, it is cured and aged at 60-65℃ for 11-13h in a curing and aging integrated kettle, and then dried at 78-85℃ for 7-9h to obtain the composite modified aerogel felt.

[0044] In a second aspect, the present invention provides a composite modified aerogel felt, which is prepared by the preparation method described in the first aspect.

[0045] The composite modified aerogel felt provided by this invention has good hydrophobic properties, high temperature resistance and excellent thermal insulation effect, and combines the advantages of both aerogel and carbon fiber materials.

[0046] Thirdly, the present invention provides an application of the composite modified aerogel felt as described in the second aspect, wherein the composite modified aerogel felt is used as a battery protection material for new energy vehicles.

[0047] The use of the composite modified aerogel felt is an effective means of reducing the hazards caused by thermal runaway in lithium-ion batteries. Utilizing the excellent thermal insulation and flame-retardant properties of the composite modified aerogel felt, the battery is isolated from the vehicle body, preventing heat transfer and effectively reducing safety hazards in new energy vehicles.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention provides a method for preparing composite modified aerogel felt, which uses carbon fiber as the substrate and cationic surfactant and aromatic alcohol compounds as composite modifiers to prepare composite modified aerogel felt through in-situ synthesis. The preparation process of the method is mild, and the resulting composite modified aerogel felt has the advantages of both modified aerogel and carbon fiber. It has strong hydrophobicity, high temperature resistance and excellent heat insulation effect. The hydrophobicity can reach 99.92%, and the temperature resistance shows no significant change after being burned at 1200℃ for 30 minutes. The thermal conductivity at an average temperature of 25℃ is 0.016 and the thermal conductivity at an average temperature of 300℃ is 0.035, which can be used for industrial production. Detailed Implementation

[0050] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0051] Example 1

[0052] This embodiment provides a composite modified aerogel felt, the preparation method of which includes the following steps:

[0053] (1) Ethanol, pure water and silicon tetrachloride are uniformly mixed in a hydrolysis reactor at a molar ratio of 20:1:4. Hydrochloric acid is added to the resulting solution to adjust the pH value to 2.5. The resulting solution and the composite modifier are then mixed for a second time in a hydrolysis reactor at 25°C for 10 hours to obtain an impregnation solution. The composite modifier includes a mixture of dodecyltrimethylammonium bromide and p-hydroxyanisole in a molar ratio of 1:5. The mass percentage of the composite modifier in the impregnation solution is 10 wt%.

[0054] (2) The carbon fiber substrate is immersed in the impregnation solution obtained in step (1) to obtain a composite modified aerogel felt precursor; an alkaline catalyst is sprayed onto the surface of the obtained composite modified aerogel felt precursor until the pH value is adjusted to 7.2. The alkaline catalyst is obtained by mixing sodium hydroxide and pure water, and the concentration of sodium hydroxide in the alkaline catalyst is 6.5%; after standing until the surface forms a gel, it is cured and aged at 62°C for 12 hours in a curing and aging integrated kettle, and then dried at 80°C for 8 hours to obtain the composite modified aerogel felt.

[0055] Example 2

[0056] This embodiment provides a composite modified aerogel felt, the preparation method of which includes the following steps:

[0057] (1) Ethanol, pure water and silicon tetrachloride are uniformly mixed in a hydrolysis reactor at a molar ratio of 20:1:2. Sulfuric acid is added to the resulting solution to adjust the pH value to 2. The resulting solution and the composite modifier are mixed again in a hydrolysis reactor at 20°C for 12 hours to obtain an impregnation solution. The composite modifier includes a mixture of dodecyl dimethyl ammonium oxide and triphenylmethanol in a molar ratio of 1:3. The mass percentage of the composite modifier in the impregnation solution is 5 wt%.

[0058] (2) The carbon fiber substrate is immersed in the impregnation solution obtained in step (1) to obtain a composite modified aerogel felt precursor; an alkaline catalyst is sprayed onto the surface of the obtained composite modified aerogel felt precursor until the pH value is adjusted to 7. The alkaline catalyst is obtained by mixing sodium bicarbonate and pure water, and the concentration of sodium bicarbonate in the alkaline catalyst is 6%; after standing until the surface forms a gel, it is cured and aged at 60°C for 13 hours in a curing and aging integrated kettle, and then dried at 78°C for 9 hours to obtain the composite modified aerogel felt.

[0059] Example 3

[0060] This embodiment provides a composite modified aerogel felt, the preparation method of which includes the following steps:

[0061] (1) Ethanol, pure water and silicon tetrachloride are uniformly mixed in a hydrolysis reactor at a molar ratio of 20:1:6. Nitric acid is added to the resulting solution to adjust the pH value to 3. The resulting solution and the composite modifier are mixed for a second time in a hydrolysis reactor at 30°C for 8 hours to obtain an impregnation solution. The composite modifier includes a mixture of octadecyltrimethylammonium chloride and ethyl p-hydroxybenzoate in a molar ratio of 1:8. The mass percentage of the composite modifier in the impregnation solution is 20 wt%.

[0062] (2) The carbon fiber substrate is immersed in the impregnation solution obtained in step (1) to obtain a composite modified aerogel felt precursor; an alkaline catalyst is sprayed onto the surface of the obtained composite modified aerogel felt precursor until the pH value is adjusted to 7.5. The alkaline catalyst is obtained by mixing ammonia water and pure water, and the concentration of ammonia water in the alkaline catalyst is 7%; after standing until the surface forms a gel, it is cured and aged at 65°C for 11 hours in a curing and aging integrated kettle, and then dried at 85°C for 7 hours to obtain the composite modified aerogel felt.

[0063] Example 4

[0064] This embodiment provides a composite modified aerogel felt. The preparation method of the composite modified aerogel felt is different from that of Example 1. Except for replacing the equimolar amount of silicon tetrachloride in step (1) with tetraethyl silicate, the rest is the same as that of Example 1.

[0065] Example 5

[0066] This embodiment provides a composite modified aerogel felt. The preparation method of the composite modified aerogel felt is different from that of Example 1. Except that the hydrochloric acid in step (1) is replaced with oxalic acid, and the amount of oxalic acid is used to adjust the pH value of the solution to 2.5, the rest is the same as that of Example 1.

[0067] Example 6

[0068] This embodiment provides a composite modified aerogel felt. The preparation method of the composite modified aerogel felt is different from that of Example 1. Except for adjusting the molar ratio of dodecyltrimethylammonium bromide to p-hydroxyanisole in step (1) to 1:1, the rest is the same as that of Example 1.

[0069] Example 7

[0070] This embodiment provides a composite modified aerogel felt. The preparation method of the composite modified aerogel felt is different from that of Example 1. Except for adjusting the molar ratio of dodecyltrimethylammonium bromide to p-hydroxyanisole in step (1) to 1:10, the rest is the same as that of Example 1.

[0071] Example 8

[0072] This embodiment provides a composite modified aerogel felt. The preparation method of the composite modified aerogel felt is different from that of Embodiment 1. Except for adjusting the curing and aging temperature in step (2) to 55°C, the rest is the same as that of Embodiment 1.

[0073] Example 9

[0074] This embodiment provides a composite modified aerogel felt. The preparation method of the composite modified aerogel felt is different from that of Embodiment 1. Except for adjusting the curing and aging temperature in step (2) to 70°C, the rest is the same as that of Embodiment 1.

[0075] Comparative Example 1

[0076] This comparative example provides a composite modified aerogel felt. The preparation method of the composite modified aerogel felt differs from that of Example 1 in that, except that the composite modifier in step (1) is replaced by an equal mass of methyltrimethoxysilane, the rest is the same as that of Example 1.

[0077] Comparative Example 2

[0078] This comparative example provides a composite modified aerogel felt. The preparation method of the composite modified aerogel felt differs from that of Example 1 in that, except that the composite modifier in step (1) is replaced by an equal mass of a single dodecyltrimethylammonium bromide, the rest is the same as that of Example 1.

[0079] Comparative Example 3

[0080] This comparative example provides a composite modified aerogel felt. The preparation method of the composite modified aerogel felt differs from that of Example 1 in that, except that the composite modifier in step (1) is replaced by a single p-hydroxyanisole in equal mass, the rest is the same as that of Example 1.

[0081] Comparative Example 4

[0082] This comparative example provides a modified aerogel felt, which is prepared using the aerogel felt preparation method disclosed in CN108821741A.

[0083] The composite modified aerogel felts provided in Examples 1-9 and Comparative Examples 1-4 were tested for hydrophobicity according to GB / T 10299; their thermal conductivity (25℃, 300℃) was tested according to GB / T 10295; and their high-temperature resistance was tested by burning at 1200℃ for 30 min. If there was no significant change, the result was indicated as "high-temperature resistant"; if there was damage, the result was indicated as "not resistant to high temperatures". The results are shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] As can be seen from Table 1, the composite modified aerogel felt prepared by the preparation method provided by the present invention has the advantages of good hydrophobicity, high temperature resistance and excellent heat insulation effect.

[0088] A comparison of Examples 1 and 4 shows that using other silicon sources does not improve performance compared to the silicon tetrachloride provided by this invention. A comparison of Examples 1 and 5 shows that using inorganic acid as an acid catalyst eliminates side reactions and makes the reaction more thorough. A comparison of Examples 1 and Examples 6 and 7 shows that when the molar ratio of cationic surfactant to aromatic alcohol compound in the composite modifier exceeds the limit, it affects the formation of the aerogel structure and leads to a decrease in performance. A comparison of Examples 1 and Examples 8 and 9 shows that when the curing and aging temperature exceeds the limit, it causes changes in the internal pore structure of the aerogel, leading to a decrease in performance.

[0089] As can be seen from the comparison between Example 1 and Comparative Examples 1-3, the combustion performance, high temperature resistance and heat insulation effect of the aerogel felt are all reduced when a single modifier or other types of modifier are used; as can be seen from the comparison between Example 1 and Comparative Example 4, the modification effect of the aerogel felt is reduced when the modifier is added after solidification.

[0090] In summary, the method for preparing the composite modified aerogel felt provided by this invention uses carbon fiber as the substrate and cationic surfactants and aromatic alcohol compounds as composite modifiers to prepare the composite modified aerogel felt through in-situ synthesis. The preparation process of the method is mild, and the resulting composite modified aerogel felt combines the advantages of modified aerogel and carbon fiber. It exhibits strong hydrophobicity, high temperature resistance, and excellent thermal insulation effect, with a hydrophobicity of up to 99.92%. Its temperature resistance shows no significant change after being burned at 1200℃ for 30 minutes. The thermal conductivity at an average temperature of 25℃ is 0.016, and the thermal conductivity at an average temperature of 300℃ is 0.035, making it suitable for industrial production.

[0091] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a composite modified aerogel felt, characterized in that, The preparation method includes the following steps: (1) A first mixture of ethanol, pure water, silicon source and acid catalyst is mixed with a composite modifier to obtain an impregnation solution; the silicon source includes silicon tetrachloride; the amount of acid catalyst is used to adjust the pH of the solution to 2-3; the acid catalyst includes an inorganic acid; the inorganic acid includes any one or a combination of at least two of hydrochloric acid, sulfuric acid or nitric acid. The composite modifier comprises a mixture of a cationic surfactant and an aromatic alcohol compound in a molar ratio of 1:(3-8); the cationic surfactant comprises any one or a combination of at least two of dodecyltrimethylammonium bromide, dodecyldimethylammonium oxide, or octadecyltrimethylammonium chloride; the aromatic alcohol compound comprises any one or a combination of at least two of p-hydroxyanisole, triphenylmethanol, or ethyl p-hydroxybenzoate; the mass percentage of the composite modifier in the impregnation solution is 5-20 wt%. (2) The carbon fiber substrate is immersed in the impregnation solution obtained in step (1) to obtain a composite modified aerogel felt precursor; an alkaline catalyst is sprayed onto the surface of the obtained composite modified aerogel felt precursor, and after standing until the surface forms a gel, it is cured and aged at 60-65℃ for 11-13h and dried in sequence. The curing and aging are carried out in a curing and aging integrated kettle to obtain the composite modified aerogel felt.

2. The preparation method according to claim 1, characterized in that, Step (1) The first mixing step specifically includes: uniformly mixing ethanol, pure water and silicon source, and adding an acid catalyst to the resulting solution to adjust the pH value.

3. The preparation method according to claim 2, characterized in that, The molar ratio of ethanol, pure water and silicon source is 20:1:(2-6).

4. The preparation method according to claim 1, characterized in that, In step (1), the temperature of the second mixture is 20-30℃.

5. The preparation method according to claim 1, characterized in that, Step (1) The second mixing time is 8-12 hours.

6. The preparation method according to claim 1, characterized in that, Step (1) The first mixing and the second mixing are carried out in a hydrolysis reactor.

7. The preparation method according to claim 1, characterized in that, The alkaline catalyst in step (2) is obtained by mixing alkali with pure water.

8. The preparation method according to claim 7, characterized in that, The concentration of alkali in the alkali catalyst in step (2) is 6-7%.

9. The preparation method according to claim 8, characterized in that, The alkali includes any one or a combination of at least two of sodium hydroxide, sodium bicarbonate, or ammonia water.

10. The preparation method according to claim 1, characterized in that, In step (2), the pH value of the sprayed alkaline catalyst on the surface of the composite modified aerogel felt precursor is adjusted to 7-7.

5.

11. The preparation method according to claim 1, characterized in that, The drying temperature in step (2) is 78-85℃.

12. The preparation method according to claim 1, characterized in that, The drying time in step (2) is 7-9 hours.

13. A composite modified aerogel felt, characterized in that, The composite modified aerogel felt is prepared by the preparation method according to any one of claims 1-12.

14. An application of the composite modified aerogel felt as described in claim 13, characterized in that, The composite modified aerogel felt is used as a battery protection material for new energy vehicles.

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