Silicon dioxide aerogel heat insulation pad as well as preparation method and application thereof

Abstract

The invention relates to the technical field of battery heat insulation pads, and provides a silicon dioxide aerogel heat insulation pad as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing a silicon source, an alcohol solvent, water and an acidic catalyst to obtain silica sol; mixing silica sol, a basic catalyst and an additive, and compounding with the fiber sheet to obtain a composite wet gel fiber sheet; and aging and modifying the composite wet gel fiber sheet, drying, pre-pressing, and carrying out hot press molding to obtain the silicon dioxide aerogel heat insulation pad. The silicon dioxide aerogel heat insulation pad provided by the invention is high in heat insulation capacity, good in high temperature resistance, good in impact resistance and high in compressive deformation resistance, and can avoid extrusion deformation of an automobile battery pack, so that a more reliable heat insulation effect is provided, unnecessary impact and heat transfer on the battery pack can be effectively reduced, and the service life of the battery pack is prolonged. The safety and durability of the automobile battery are improved, and the maintenance and replacement cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of battery thermal insulation pads, and in particular to a silicon dioxide aerogel thermal insulation pad and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have become the main power source for electric vehicles due to their high energy density, long life and good charging performance. However, lithium-ion batteries also have some safety hazards, one of which is battery thermal runaway. When one of the battery packs goes into thermal runaway, if the fire cannot be stopped in time, it may cause the entire car battery to ignite, posing a serious safety risk. Therefore, the thermal insulation performance of automotive batteries is crucial. Existing automotive battery thermal insulation technology mainly uses insulation pads to isolate individual battery packs to prevent thermal runaway battery packs from igniting adjacent battery packs.

[0003] Traditional car batteries use flame-retardant plastic partitions such as PP, ABS, and PVC as thermal insulation pads, but the thermal insulation effect of plastic partitions is not good, and when the battery temperature is too high, the partitions are prone to dissolution and fire. At present, ceramic fibers, aerogel felts, etc. can also be used to prepare thermal insulation pads. Ceramic fibers and aerogel felts have good thermal insulation properties and can effectively prevent heat transfer between battery packs. However, the ceramic fiber and aerogel felt thermal insulation pads on the market have poor impact resistance. When a car encounters bumps during daily driving, it is easy to be compressed and deformed after the impact. The impact force may be transmitted through the thermal insulation pad, causing each battery pack to be subjected to excessive impact, which may cause the battery to be squeezed and deformed and spontaneously combust.

[0004] In summary, there is an urgent need to provide a thermal insulation pad with good thermal insulation and strong impact resistance to improve the safety and durability of automotive batteries. Summary of the invention

[0005] In view of this, the present invention provides a silica aerogel thermal insulation pad and a preparation method and application thereof. The silica aerogel thermal insulation pad provided by the present invention has good thermal insulation effect, good impact resistance, strong resistance to compression deformation, and good high temperature resistance, and can still maintain good thermal insulation performance under high temperature conditions.

[0006] Beneficial effects:

[0007] The present invention performs pre-pressing before hot pressing, which can not only completely maintain the aerogel structure and make it densified, but also improve the impact resistance of the thermal insulation pad, so that the thermal insulation pad has better resistance to compression deformation, avoid extrusion deformation of the automobile battery pack, thereby providing a more reliable thermal insulation effect, and at the same time effectively reduce unnecessary impact and heat transfer on the battery pack, improve the safety and durability of the automobile battery, extend the service life of the automobile battery, and reduce the cost of maintenance and replacement; the present invention reduces the thermal conductivity of the thermal insulation pad at high temperature by adding additives, thereby improving its thermal insulation capacity and high temperature resistance; the present invention also adds a hydrophobic modifier during aging, which can improve the waterproof performance of the thermal insulation pad, and can effectively block water vapor in the external environment from entering the interior of the aerogel thermal insulation pad, so that it can maintain good thermal insulation performance in a humid environment, and avoid problems such as reduced thermal insulation effect due to moisture.

[0008] Furthermore, the present invention uses a gasket to control the pre-pressing thickness during the pre-pressing process, which can further ensure the effective retention of the aerogel structure, while achieving controllable thickness, and better thickness consistency of the thermal insulation pad after packaging. Furthermore, the fiber sheet used in the present invention can be a single layer or multiple layers, and when multiple layers of fiber sheets are stacked, the thermal insulation performance of the thermal insulation pad can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Schematic diagram of the thermal insulation temperature difference test process in an embodiment of the present invention. DETAILED DESCRIPTION

[0010] The present invention provides a method for preparing a silica aerogel thermal insulation pad, comprising the following steps:

[0011] Mixing a silicon source, an alcohol solvent, water and an acid catalyst to obtain a silica sol;

[0012] The silica sol, alkaline catalyst and additive are mixed, and the obtained mixed sol is compounded with a fiber sheet to obtain a composite wet gel fiber sheet; the additive is an inorganic particle;

[0013] The composite wet gel fiber sheet is subjected to aging modification in an aging modification liquid to obtain a modified wet gel fiber sheet; the aging modification liquid comprises alcohol and a hydrophobic modifier;

[0014] Drying the modified wet gel fiber sheet to obtain a silica aerogel fiber sheet;

[0015] Pre-pressing the silica aerogel fiber sheet to obtain a pre-pressed sheet;

[0016] The upper and lower surfaces of the pre-pressed sheet are covered with packaging materials and then hot-pressed to obtain the silica aerogel thermal insulation pad.

[0017] The present invention mixes a silicon source, an alcohol solvent, water and an acidic catalyst to obtain a silica sol. In the present invention, the silicon source preferably includes one or more of silicate and alkyl alkoxy silane; the silicate preferably includes one or both of ethyl orthosilicate and methyl orthosilicate; the alkyl alkoxy silane preferably includes one or more of methyl trimethoxy silane, dimethyl dimethoxy silane, methyl triethoxy silane, dimethyl diethoxy silane, vinyl triethoxy silane and propyl trimethoxy silane; the alcohol solvent preferably includes one or more of methanol, ethanol, n-propanol and isopropanol; the molar ratio of the silicon source, alcohol and water is preferably 1: (5-30): (2-10), more preferably 1: (10-20): (5-8); the acidic catalyst preferably includes one or more of sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, acetic acid or citric acid; the amount of the acidic catalyst is preferably based on the pH value of the adjustment system being 2-6.

[0018] In the present invention, the temperature for mixing the silicon source, alcohol solvent, water and acid catalyst is preferably 20-60° C., more preferably 50° C., and the time is preferably 180-480 min, more preferably 360 min. During the mixing process, the silicon source is hydrolyzed under the action of the acid catalyst to obtain silica sol.

[0019] In a specific embodiment of the present invention, it is preferred to firstly mix the silicon source, alcohol solvent and water uniformly, then add the acid catalyst dropwise until the pH value of the system is 2-6, and then carry out the hydrolysis reaction under heat preservation and stirring conditions.

[0020] After obtaining the silica sol, the present invention mixes the silica sol, an alkaline catalyst and an additive, and composites the obtained mixed sol with a fiber sheet to obtain a composite wet gel fiber sheet; the additive is an inorganic particle. In the present invention, the alkaline catalyst preferably includes one or more of sodium hydroxide, potassium hydroxide, ammonia water and ammonium fluoride aqueous solution; the pH value of the mixed sol is preferably 6.5 to 8.5, and the gel time is preferably 1 to 5 minutes, more preferably 2 minutes; in the present invention, the amount of the alkaline catalyst is based on the pH value and gel time of the mixed sol being controlled within the above range. In a specific embodiment of the present invention, it is preferred to first add the alkaline catalyst to the silica sol and then add the additive.

[0021] In the present invention, the additive preferably includes one or more of titanium dioxide, silicon carbide, diatomaceous earth, aluminum hydroxide, magnesium hydroxide, hollow glass microspheres, hollow silica microspheres, and hollow ceramic microspheres; the mass ratio of the additive to the silica sol is 1:30 to 300, specifically 1:50, 1:100 or 1:150. By adding the above additives, the present invention can reduce the thermal conductivity of the thermal insulation pad at 500 to 600°C and improve the thermal insulation performance of the thermal insulation pad at high temperatures.

[0022] In the present invention, the fibers in the fiber sheet are preferably one or more of quartz fiber, glass fiber, high silica fiber, pre-oxidized silk fiber, mullite fiber, basalt fiber and ceramic fiber; the fiber sheet is specifically a fiber felt; the thickness of the fiber sheet is preferably determined according to the thickness of the target silica aerogel insulation pad and the thickness tolerance during pre-pressing; specifically, the thickness of the silica aerogel insulation pad can be 0.5-4mm, specifically 0.5mm, 1mm, 1.5mm, 1.8mm, 2.5mm, 3mm or 4mm, when the thickness of the silica aerogel insulation pad is ≤2mm, the thickness tolerance during pre-pressing is ≤±0.2mm; when the thickness of the silica aerogel insulation pad is >2mm, the thickness tolerance during pre-pressing is ≤±0.3mm; in a specific embodiment of the present invention, the thickness of the fiber sheet can be selected according to actual needs.

[0023] In the present invention, the number of layers of the fiber sheet is ≥ 1, that is, the fiber sheet can be a single layer or a multi-layer stack, preferably a multi-layer stack. When a multi-layer stack is adopted, it is preferably 2 to 10 layers, specifically 2 layers, 3 layers, 4 layers or 5 layers. When the fiber sheet is a multi-layer stack, the thickness of each layer of the fiber sheet can be the same or different; specifically, when the fiber sheet is a multi-layer stack, it is preferred to use a fiber sheet with a thickness of ≤1mm, and more preferably a fiber sheet with a thickness of ≤0.5mm. In the present invention, the use of multiple layers of fiber sheets for stacking can further improve the thermal insulation capacity of the resulting thermal insulation pad.

[0024] In the present invention, the mixed solution and the fiber sheet are preferably compounded by immersing the fiber sheet in the mixed sol; the present invention has no special requirements on the specific immersion time, which can be specifically 10 seconds.

[0025] After obtaining the composite wet gel fiber sheet, the present invention performs aging modification on the composite wet gel fiber sheet in an aging modification liquid to obtain a modified wet gel fiber sheet. In the present invention, the components of the aging modification liquid include alcohol and a hydrophobic modifier, and the alcohol is preferably a low-alcohol with a carbon number of 1 to 6, and more preferably a low-alcohol with a carbon number of 1 to 3, specifically methanol, ethanol, n-propanol or isopropanol; the hydrophobic modifier preferably includes one or more of trimethylmethoxysilane, hexamethyldisilazane and trimethylchlorosilane; the volume of the hydrophobic modifier is preferably 2 to 10% of the volume of the alcohol in the aging modification liquid, specifically 5%, 8% or 10%; the present invention can improve the hydrophobicity of the thermal insulation pad by adding a hydrophobic modifier, so that its structure will not change in a humid environment and its performance will not decay.

[0026] In the present invention, the aging modification temperature is preferably 30-60°C, specifically 40°C, 50°C, or 60°C; the aging modification time is preferably 3-48h, specifically 5h, 10h, 24h, or 48h. The aging modification is preferably carried out under sealed and static conditions.

[0027] After obtaining the modified wet gel fiber sheet, the present invention dries the modified wet gel fiber sheet to obtain a silica aerogel fiber sheet. In the present invention, the drying method is preferably supercritical CO2 drying; the supercritical CO2 drying pressure is preferably 10 to 20 MPa, specifically 12 MPa, 15 MPa, or 18 MPa, the drying temperature is preferably 40 to 80°C, specifically 50°C or 60°C, and the drying time is preferably 3 to 10 hours, specifically 4 hours or 6 hours.

[0028] After obtaining the silica aerogel fiber sheet, the present invention pre-presses the silica aerogel fiber sheet to obtain a pre-pressed sheet. In the present invention, the pre-pressing pressure is preferably 120 to 160 kg / cm 2 , specifically 130kg / cm 2 、150kg / cm 2 or 160kg / cm 2 ; The pre-pressing time is preferably 20 to 30 seconds, specifically 20 seconds or 25 seconds; during the pre-pressing, gaskets are placed on both sides of the silica aerogel fiber sheet; the gaskets are preferably rigid material gaskets, specifically stainless steel gaskets; the thickness of the gaskets is preferably selected according to the thickness requirements of the target aerogel thermal insulation pad; during the pre-pressing, the thickness deviation of the obtained silica aerogel sheet is controlled within the thickness tolerance. The present invention uses gaskets in the pre-pressing process to achieve controllable thickness and improve the uniformity of thickness. At the same time, it can effectively retain the aerogel structure and improve the impact resistance of the aerogel thermal insulation pad.

[0029] After obtaining the pre-compressed tablet, the present invention covers the upper and lower surfaces of the pre-compressed tablet with packaging materials and then performs hot pressing to obtain the silica aerogel thermal insulation pad. In the present invention, the packaging material is preferably a polymer film; the polymer film is preferably one or more of a polyester film, a polyimide film, a polyvinyl chloride film, a polycarbonate film, a polyethylene film and a polyphenylene sulfide film; the temperature of the hot pressing is preferably 80 to 100°C, specifically 80°C, 85°C, 90°C or 100°C, and the pressure of the hot pressing is preferably 120 to 140 kg / cm 2 , specifically 130kg / cm 2 The time of the hot pressing molding is preferably 30 to 50 seconds, specifically 40 seconds or 50 seconds. The hot pressing molding is preferably performed using a vacuum hot pressing machine.

[0030] The present invention also provides a silica aerogel insulation pad prepared by the preparation method described in the above scheme, comprising a silica aerogel fiber sheet and a polymer film arranged on the surface of the silica aerogel fiber sheet; the silica aerogel fiber sheet comprises a fiber sheet and silica aerogel filled in the gaps of the fiber sheet.

[0031] The present invention also provides the use of the silica aerogel insulation pad described in the above scheme in an automobile battery; the automobile battery is specifically a battery used in new energy vehicles.

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] 200g of tetramethyl orthosilicate, 520g of anhydrous methanol and 130g of distilled water were poured into a container and stirred for 10min to mix evenly, and then concentrated nitric acid was added dropwise to adjust the pH value to 3. After stirring at 50℃ for 360min, alkaline catalyst ammonia water was added to adjust the pH value to 8, and then 6g of titanium dioxide and 6g of diatomaceous earth were added. The mixed sol was compounded with 5 layers of superimposed fiber felt (single layer thickness was 0.3mm, and the fiber was glass fiber) to obtain a composite wet gel fiber sheet. The composite wet gel fiber sheet was added to the aging modification liquid (prepared with methanol and hexamethyldisilazane, and the volume fraction of hexamethyldisilazane in methanol was 3%), sealed at 55℃, and aged for 10h to obtain a modified wet gel fiber sheet. The modified wet gel fiber sheet was supercritically dried with CO2, the drying temperature was 50℃, the drying pressure was 12Mpa, and the drying time was 4h. The dried silica aerogel fiber sheet was pre-pressed, and the press pressure was set to 160kg / cm 2 The pressing time is 20 seconds. 0.9 mm thick stainless steel gaskets are placed on both sides of the silica aerogel fiber sheet to control the thickness of the pre-pressed sheet to be between 0.9 mm and 1.1 mm. The hot press temperature is set to 80 ° C and the pressure is 130 kg / cm 2 , time is 50s, and the upper polyester film, the pre-pressed sheet and the lower polyester film are placed in the hot press in sequence for packaging to obtain a silica aerogel insulation pad.

[0035] Example 2

[0036] The other conditions are the same as those in Example 1, except that the fiber felt is replaced by three layers of stacked fiber felt, with a single layer thickness of 0.5 mm.

[0037] Example 3

[0038] The other conditions were the same as those in Example 1, except that the fiber felt was replaced with a layer of 1.5 mm fiber felt.

[0039] Example 4

[0040] The other conditions were the same as those in Example 1, except that the fiber felt was replaced with 2 layers of 1 mm + 2 layers of 0.3 mm stacked fiber felt; at the same time, 2 mm thick stainless steel gaskets were placed on both sides of the silica aerogel fiber sheet during pre-pressing, and the thickness of the pre-pressed sheet was controlled to be 1.9 mm to 2.1 mm.

[0041] Example 5

[0042] The other conditions were the same as those in Example 1, except that the fiber felt was replaced with a layer of 2.5 mm fiber felt. At the same time, 2 mm thick stainless steel gaskets were placed on both sides of the silica aerogel fiber sheet during pre-pressing, and the thickness of the pre-pressed sheet was controlled to be between 1.9 mm and 2.1 mm.

[0043] Comparative Example 1: Omitting the pre-pressing process

[0044] The other conditions were the same as those in Example 1, except that the fiber mat was replaced with a layer of 1 mm fiber mat, and the pre-pressing process was omitted. The obtained silica aerogel fiber sheet was directly hot-pressed. The hot press temperature was set at 80 °C and the pressure was 100 kg / cm 2 , time 50s, placing the upper polyester film, the dried silica aerogel fiber sheet and the lower polyester film in the hot press in sequence for packaging to obtain a silica aerogel insulation pad.

[0045] Comparative Example 2: Omitting the pre-pressing process

[0046] The other conditions were the same as those in Example 1, except that the fiber mat was replaced with a layer of 2 mm fiber mat, and the pre-pressing process was omitted. The obtained silica aerogel fiber sheet was directly hot-pressed. The hot press temperature was set at 80 °C and the pressure was 100 kg / cm 2 , time 50s, placing the upper polyester film, the dried silica aerogel fiber sheet and the lower polyester film in the hot press in sequence for packaging to obtain a silica aerogel insulation pad.

[0047] Comparative Example 3 Omitting Additives

[0048] The other conditions were the same as those in Example 1, except that the addition of titanium dioxide and diatomaceous earth was omitted.

[0049] Comparative Example 4 Omitting the Hydrophobic Modifier

[0050] The other conditions were the same as those in Example 1, except that the addition of the hydrophobic modifier was omitted in the aging modification solution, and only methanol was used for aging.

[0051] Performance Testing

[0052] The room temperature thermal conductivity, high temperature thermal conductivity, bulk density, thickness, 1MPa strain, 2MPa strain and thermal insulation temperature difference of the silica aerogel thermal insulation pads prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were tested. Among them:

[0053] The test method of thermal insulation temperature difference is as follows: heat the heating table, and when the hot surface temperature reaches 430℃, place the 18mm calcium silicate board insulation layer, 1mm aluminum block (fix the T2 sensor on the aluminum block with PI glue), silica aerogel insulation pad, and 1mm aluminum block (fix the T1 sensor on the aluminum block with PI glue) in this order, and place them on the heating table, applying a pressure of 0.7MPa; start timing when the hot surface temperature reaches 500℃, record the T2 and T1 temperatures at 10min, and the thermal insulation temperature difference is T1-T2. See the schematic diagram of the thermal insulation temperature difference test process. Figure 1 .

[0054] The test method of 1MPa strain and 2MPa strain is as follows: the sample size is 5×5cm, the sample is placed in a universal testing machine for testing, the maximum force is set to 20kN, the inlet force is 35N, and the 1MPa strain and 2MPa strain are recorded. At the same time, the thickness retention rate under 2MPa is recorded.

[0055] The specific test results are shown in Table 1.

[0056] Table 1 Silica aerogel insulation pad performance test results

[0057]

[0058] According to the data in Table 1, it can be seen that the strain of the silica aerogel thermal insulation pad prepared in Examples 1 to 5 under 1Mpa and 2MPa loads is significantly smaller than that of Comparative Examples 1 to 2, and the thickness retention rate under 2MPa is significantly higher than that of Comparative Examples 1 to 2, indicating that the aerogel structure can be completely maintained under this pre-compression pressure, and at the same time it can be densified, thereby improving the impact resistance of the thermal insulation pad, and the resulting thermal insulation pad is not easy to be compressed and deformed. According to Example 3 and Comparative Example 1, and Example 5 and Comparative Example 2, it can be seen that when a single-layer fiber sheet is used, the thermal insulation performance of the thermal insulation pad obtained in Example 3 and Example 5 is better than that of Comparative Example 1 and Comparative Example 2. This is because the thermal insulation performance is improved by adding the pre-compression process. In addition, when a single-layer fiber sheet (Example 3) is used, the performance of the resulting thermal insulation pad is also relatively excellent in all aspects, but when the thickness of the thermal insulation pad is similar, the thermal insulation performance of the thermal insulation pad obtained in Examples 1 to 2 is better than that of Example 3. This is because the gaps between each layer of fiber sheets in the multi-layer stacking method are filled with aerogel, which reduces the heat conduction between the fibers, thereby improving the thermal insulation performance. In addition, it can be seen from Comparative Example 3 that after omitting the additive, the high thermal conductivity of the obtained thermal insulation pad is significantly increased, and the thermal insulation performance at high temperature becomes worse.

[0059] The water repellency of Examples 1 to 5 and Comparative Examples 1 to 4 was tested, and the obtained thermal insulation pads were treated at 50° C. and 95% RH for 24 hours, and then their room temperature thermal conductivity was tested again. The test results are shown in Table 2.

[0060] Table 2 Test results of hydrophobicity of silica aerogel thermal insulation pad

[0061]

[0062] It can be seen from the data in Table 2 that the silica aerogel thermal insulation pad prepared by the present invention has a high hydrophobicity and can maintain good thermal insulation performance even in a humid environment. In Comparative Example 4, the use of a hydrophobic modifier is omitted, and the resulting thermal insulation pad has no hydrophobicity. After treatment in a humid environment, the thermal conductivity coefficient is significantly increased.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a silica aerogel thermal insulation pad, characterized in that: The following steps are involved: Mixing a silicon source, an alcohol solvent, water and an acid catalyst to obtain a silica sol; The silica sol, alkaline catalyst and additive are mixed, and the obtained mixed sol is compounded with a fiber sheet to obtain a composite wet gel fiber sheet; the additive is an inorganic particle; The composite wet gel fiber sheet is subjected to aging modification in an aging modification liquid to obtain a modified wet gel fiber sheet; the aging modification liquid comprises alcohol and a hydrophobic modifier; Drying the modified wet gel fiber sheet to obtain a silica aerogel fiber sheet; Pre-pressing the silica aerogel fiber sheet to obtain a pre-pressed sheet; The upper and lower surfaces of the pre-pressed sheet are covered with packaging materials and then hot-pressed to obtain the silica aerogel thermal insulation pad.

2. The preparation method according to claim 1, characterized in that: The silicon source includes one or more of silicate and alkylalkoxysilane; the alcohol solvent includes one or more of methanol, ethanol, n-propanol and isopropanol; the molar ratio of the silicon source, alcohol and water is 1:(5-30):(2-10); The acidic catalyst includes one or more of sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, acetic acid or citric acid; the amount of the acidic catalyst used is based on adjusting the pH value of the system to 2-6.

3. The preparation method according to claim 1, characterized in that: The alkaline catalyst includes one or more of sodium hydroxide, potassium hydroxide, ammonia water and ammonium fluoride aqueous solution; the pH value of the mixed sol is 6.5-8.5, and the gel time is 1-5 minutes; The additive comprises one or more of titanium dioxide, silicon carbide, diatomaceous earth, aluminum hydroxide, magnesium hydroxide, hollow glass microspheres, hollow silica microspheres and hollow ceramic microspheres; the mass ratio of the additive to the silica sol is 1:30-300.

4. The preparation method according to claim 1, characterized in that: The fibers in the fiber sheet are one or more of quartz fibers, glass fibers, high silica fibers, pre-oxidized silk fibers, mullite fibers, basalt fibers and ceramic fibers; The number of layers of the fiber sheet is ≥1.

5. The preparation method according to claim 1, characterized in that: The alcohol in the aging modification liquid is a low-alcohol having 1 to 6 carbon atoms, and the hydrophobic modifier includes one or more of trimethylmethoxysilane, hexamethyldisilazane and trimethylchlorosilane; the volume of the hydrophobic modifier is 2 to 10% of the volume of the alcohol in the aging modification liquid; The aging modification temperature is 30-60° C. and the time is 3-48 hours.

6. The preparation method according to claim 1, characterized in that: The drying method is supercritical CO2 drying; the supercritical CO2 drying pressure is 10-20MPa, the temperature is 40-80°C, and the drying time is 3-10h.

7. The preparation method according to claim 1, characterized in that: The pre-pressing pressure is 120-160 kg / cm 2 , the time is 20 to 30 seconds; during the pre-pressing, gaskets are placed on both sides of the silica aerogel fiber sheet.

8. The preparation method according to claim 1, characterized in that: The packaging material is a polymer film; the temperature of the hot pressing molding is 80-100°C and the pressure is 120-140kg / cm 2 , time is 30 to 50 seconds.

9. The silica aerogel thermal insulation pad prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the silica aerogel thermal insulation pad according to claim 9 in automobile batteries.

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