Silicon dioxide aerogel heat insulation pad, and preparation method therefor and use thereof

Abstract

The present application relates to the technical field of battery heat insulation pads. Provided are a silicon dioxide aerogel heat insulation pad, and a preparation method therefor and the use thereof. In the present application, a silicon source, an alcohol solvent, water and an acidic catalyst are mixed to obtain a silica sol; the silica sol, a basic catalyst and an additive are mixed, and then compounded with a fiber sheet, so as to obtain a composite wet gel fiber sheet; and the composite wet gel fiber sheet is aged and modified, and then dried, pre-pressed and subjected to hot-press molding, so as to obtain a silicon dioxide aerogel heat insulation pad. The silicon dioxide aerogel heat insulation pad provided in the present application has strong heat insulation capacity, good high-temperature resistance, good impact resistance and strong resistance to compressive deformation, can avoid extrusion deformation of an automobile battery pack, thereby providing a more reliable heat insulation effect, and can also effectively reduce unnecessary impact and heat transfer on the battery pack, thereby improving the safety and durability of the automobile battery and reducing the maintenance and replacement costs.

Description

A silica aerogel thermal insulation pad, its preparation method and application Technical Field

[0001] This application relates to the field of battery heat insulation pad technology, and in particular to a silica aerogel heat insulation pad, its preparation method and application. Background Technology

[0002] Lithium-ion batteries have become the primary power source for electric vehicles due to their high energy density, long lifespan, and excellent charging performance. However, lithium-ion batteries also present some safety hazards, one of which is thermal runaway. When one battery pack experiences thermal runaway, if the fire cannot be contained in time, it could ignite the entire battery pack, posing a serious safety risk. Therefore, the thermal insulation performance of automotive batteries is crucial. Existing automotive battery thermal insulation technology primarily uses thermal pads to isolate individual battery packs, preventing a thermally runaway battery pack from igniting adjacent packs.

[0003] Traditional automotive batteries use flame-retardant plastic separators such as PP, ABS, and PVC as heat insulation pads. However, these plastic separators offer poor insulation and are prone to melting and ignition when battery temperatures are too high. Currently, ceramic fibers and aerogel felts can also be used to prepare heat insulation pads. Ceramic fibers and aerogel felts have excellent insulation properties, effectively preventing heat transfer between battery packs. However, commercially available ceramic fiber and aerogel felt heat insulation pads have poor impact resistance. When a car encounters bumps during normal driving, they are easily compressed and deformed upon impact. This impact force may be transmitted through the heat insulation pad, causing excessive impact on each battery pack, potentially leading to battery compression deformation and spontaneous combustion.

[0004] In conclusion, there is an urgent need to provide a heat 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, this application provides a silica aerogel thermal insulation pad, its preparation method, and its application. The silica aerogel thermal insulation pad provided by this application has good thermal insulation effect, good impact resistance, strong resistance to compression deformation, and good high-temperature resistance, maintaining good thermal insulation performance even under high-temperature conditions. Beneficial effects:

[0006] This application pre-presses the aerogel before hot pressing, which not only preserves the aerogel structure and densifies it, but also improves the impact resistance of the heat insulation pad, giving it better resistance to compressive deformation and preventing the automotive battery pack from being squeezed and deformed. This provides a more reliable heat insulation effect, while also effectively reducing unnecessary impacts and heat transfer to the battery pack, improving the safety and durability of the automotive battery, extending its lifespan, and reducing maintenance and replacement costs. This application also adds additives to reduce the thermal conductivity of the heat insulation pad at high temperatures, thereby improving its heat insulation capacity and high-temperature resistance. Furthermore, this application adds a hydrophobic modifier during aging, which improves the waterproof performance of the heat insulation pad, effectively preventing moisture from the external environment from entering the aerogel heat insulation pad. This allows it to maintain good heat insulation performance in humid environments and avoids problems such as reduced heat insulation effect due to moisture.

[0007] Furthermore, this application uses a gasket to control the pre-compression thickness during the pre-compression process, which can further ensure the effective preservation of the aerogel structure, while achieving controllable thickness and better thickness consistency of the encapsulated thermal insulation pad. Furthermore, the fiber sheet used in this application can be single-layer or multi-layered, wherein using multi-layered fiber sheets can further improve the thermal insulation performance of the thermal insulation pad. Attached Figure Description

[0008] Figure 1 is a schematic diagram of the thermal insulation temperature difference test process in an embodiment of this application. Detailed Implementation

[0009] This application provides a method for preparing a silica aerogel heat insulation pad, comprising the following steps:

[0010] A silica sol is obtained by mixing a silicon source, an alcohol solvent, water, and an acidic catalyst.

[0011] The silica sol, alkaline catalyst, and additives are mixed, and the resulting mixed sol is compounded with fiber sheets to obtain composite wet gel fiber sheets; the additives are inorganic particles.

[0012] The composite wet gel fiber sheet is aged and modified in an aging modification solution to obtain a modified wet gel fiber sheet; the components of the aging modification solution include alcohol and hydrophobic modifier.

[0013] The modified wet gel fiber sheet is dried to obtain a silica aerogel fiber sheet;

[0014] The silica aerogel fiber sheet is pre-compressed to obtain a pre-compressed sheet;

[0015] After covering the upper and lower surfaces of the pre-compressed sheet with encapsulation material, it is hot-pressed to obtain the silica aerogel heat insulation pad.

[0016] This application mixes a silicon source, an alcohol solvent, water, and an acidic catalyst to obtain a silica sol. In this application, the silicon source preferably includes one or more of silicate esters and alkylalkoxysilanes; the silicate ester preferably includes one or both of tetraethyl orthosilicate and methyl orthosilicate; the alkylalkoxysilane preferably includes one or more of methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, vinyltriethoxysilane, and propyltrimethoxysilane; 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 adjusted to a pH of 2-6.

[0017] In this application, the mixing temperature of the silicon source, alcohol solvent, water, and acid catalyst is preferably 20–60°C, more preferably 50°C, and the mixing time is preferably 180–480 min, more preferably 360 min. During the mixing process, the silicon source undergoes hydrolysis under the action of the acid catalyst to obtain silica sol.

[0018] In a specific embodiment of this application, it is preferable to first mix the silicon source, alcohol solvent and water evenly, then add the acid catalyst dropwise until the pH of the system is 2 to 6, and then carry out the hydrolysis reaction under heat preservation and stirring conditions.

[0019] After obtaining the silica sol, this application mixes the silica sol, an alkaline catalyst, and an additive, and then composites the resulting mixed sol with a fiber sheet to obtain a composite wet gel fiber sheet; the additive is inorganic particles. In this application, the alkaline catalyst preferably includes one or more of sodium hydroxide, potassium hydroxide, ammonia, and ammonium fluoride aqueous solution; the pH value of the mixed sol is preferably 6.5–8.5, and the gelation time is preferably 1–5 min, more preferably 2 min; in this application, the amount of the alkaline catalyst is controlled within the above range based on the pH value and gelation time of the mixed sol. In a specific embodiment of this application, it is preferable to add the alkaline catalyst to the silica sol first, and then add the additive.

[0020] In this application, 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 silica sol is 1:30 to 300, specifically 1:50, 1:100, or 1:150. By adding the above-mentioned additives, this application can reduce the thermal conductivity of the heat insulation pad at 500-600℃ and improve the heat insulation performance of the heat insulation pad at high temperatures.

[0021] In this application, the fibers in the fiber sheet are preferably one or more selected from quartz fibers, glass fibers, high-silica fibers, pre-oxidized fibers, mullite fibers, basalt fibers, and ceramic fibers; the fiber sheet is specifically a fiber felt; the thickness of the fiber sheet is preferably determined based on the thickness of the target silica aerogel insulation pad and the thickness tolerance during pre-compression; specifically, the thickness of the silica aerogel insulation pad can be 0.5–4 mm, specifically 0.5 mm, 1 mm, 1.5 mm, 1.8 mm, 2.5 mm, 3 mm, or 4 mm. When the thickness of the silica aerogel insulation pad is ≤2 mm, the thickness tolerance during pre-compression is ≤±0.2 mm; when the thickness of the silica aerogel insulation pad is >2 mm, the thickness tolerance during pre-compression is ≤±0.3 mm; in specific embodiments of this application, the thickness of the fiber sheet can be selected according to actual needs.

[0022] In this application, the fiber sheet has at least one layer, meaning it can be a single layer or multiple layers stacked together, preferably multiple layers stacked together. When multiple layers are stacked together, it is preferably 2 to 10 layers, specifically 2, 3, 4, or 5 layers. When the fiber sheet is stacked in multiple layers, the thickness of each layer can be the same or different; specifically, when the fiber sheet is stacked in multiple layers, it is preferably a fiber sheet with a thickness ≤1mm, more preferably a fiber sheet with a thickness ≤0.5mm. In this application, using multiple layers of fiber sheets stacked together can further improve the thermal insulation capacity of the resulting thermal insulation pad.

[0023] In this application, the preferred method for combining the mixture and the fiber sheet is to impregnate the fiber sheet in the mixed sol; this application does not have a specific requirement for the impregnation time, which can be 10 seconds.

[0024] After obtaining the composite wet gel fiber sheet, this application ages and modifies the composite wet gel fiber sheet in an aging modification solution to obtain a modified wet gel fiber sheet. In this application, the aging modification solution comprises an alcohol and a hydrophobic modifier. The alcohol is preferably a low-carbon alcohol with 1 to 6 carbon atoms, more preferably a low-carbon alcohol with 1 to 3 carbon atoms, 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 solution, specifically 5%, 8%, or 10%. By adding a hydrophobic modifier, this application can improve the hydrophobicity of the thermal insulation pad, ensuring that its structure does not change and its performance does not degrade in a humid environment.

[0025] In this application, the aging modification temperature is preferably 30–60°C, specifically 40°C, 50°C, or 60°C; the aging modification time is preferably 3–48 hours, specifically 5 hours, 10 hours, 24 hours, or 48 hours. The aging modification is preferably carried out under sealed, static conditions.

[0026] After obtaining the modified wet gel fiber sheet, this application dries the modified wet gel fiber sheet to obtain a silica aerogel fiber sheet. In this application, the drying method is preferably supercritical CO2 drying; the pressure of the supercritical CO2 drying is preferably 10-20 MPa, specifically 12 MPa, 15 MPa, or 18 MPa; the drying temperature is preferably 40-80℃, specifically 50℃ or 60℃; and the drying time is preferably 3-10 h, specifically 4 h or 6 h.

[0027] After obtaining the silica aerogel fiber sheet, this application pre-compresses the silica aerogel fiber sheet to obtain a pre-compressed sheet. In this application, the pre-compressing pressure is preferably 120-160 kg / cm². 2 Specifically, it can be 130 kg / cm². 2 150kg / cm 2 Or 160kg / cm 2 The pre-compression time is preferably 20-30 seconds, specifically 20 seconds or 25 seconds. During pre-compression, gaskets are placed on both sides of the silica aerogel fiber sheet. These gaskets are preferably made of rigid material, specifically stainless steel. The thickness of the gaskets is preferably selected according to the thickness requirements of the target aerogel insulation pad. During pre-compression, the thickness deviation of the resulting silica aerogel sheet is controlled within the thickness tolerance. This application uses gaskets in the pre-compression process, achieving controllable thickness, improving thickness uniformity, and effectively preserving the aerogel structure, thereby improving the impact resistance of the aerogel insulation pad.

[0028] After obtaining the pre-pressed sheet, this application covers the upper and lower surfaces of the pre-pressed sheet with an encapsulation material and then performs hot pressing to obtain the silica aerogel heat insulation pad. In this application, the encapsulation material is preferably a polymer film; the polymer film is preferably one or more of polyester film, polyimide film, polyvinyl chloride film, polycarbonate film, polyethylene film, and polyphenylene sulfide film; the hot pressing temperature is preferably 80–100°C, specifically 80°C, 85°C, 90°C, or 100°C; and the hot pressing pressure is preferably 120–140 kg / cm². 2 Specifically, it can be 130 kg / cm². 2 The hot pressing time is preferably 30-50 seconds, specifically 40 seconds or 50 seconds. The hot pressing is preferably performed using a vacuum hot press.

[0029] This application also provides a silica aerogel heat insulation pad prepared by the preparation method described above, comprising a silica aerogel fiber sheet and a polymer film disposed on the surface of the silica aerogel fiber sheet; the silica aerogel fiber sheet comprises a fiber sheet and silica aerogel filling the gaps between the fiber sheets.

[0030] This application also provides the application of the silica aerogel heat insulation pad described above in automotive batteries; specifically, the automotive battery is a battery used in new energy vehicles.

[0031] The technical solutions of this application will be clearly and completely described below with reference to the embodiments therein. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0032] Example 1

[0033] 200g of tetramethyl orthosilicate, 520g of anhydrous methanol, and 130g of distilled water were poured into a container and stirred for 10 minutes to mix thoroughly. Then, concentrated nitric acid was added dropwise to adjust the pH to 3. After stirring at 50℃ for 360 minutes, an alkaline catalyst, ammonia, was added to adjust the pH to 8. Then, 6g of titanium dioxide and 6g of diatomaceous earth were added. The mixed sol was then combined with 5 layers of fiber mat (each layer 0.3mm thick, made of glass fiber) to obtain a composite wet gel fiber sheet. The composite wet gel fiber sheet was added to an aging modification solution (prepared from methanol and hexamethyldisilazane, with hexamethyldisilazane comprising 3% of methanol by volume) and aged at 55℃ in a sealed, static environment for 10 hours to obtain a modified wet gel fiber sheet. The modified wet gel fiber sheet was then subjected to supercritical CO2 drying at 50℃, a drying pressure of 12 MPa, and a drying time of 4 hours. The dried silica aerogel fiber sheet was pre-compressed at a pressure of 160 kg / cm². 2 The pressing time is 20 seconds. 0.9mm thick stainless steel gaskets are placed on both sides of the silica aerogel fiber sheet to control the thickness of the pre-pressed sheet between 0.9mm and 1.1mm. The hot press temperature is set to 80℃ and the pressure to 130kg / cm². 2 The process takes 50 seconds. The upper polyester film, the pre-pressed sheet, and the lower polyester film are placed in the hot press in sequence for encapsulation to obtain a silica aerogel heat insulation pad.

[0034] Example 2

[0035] The other conditions are the same as in Example 1, except that the fiber felt is replaced with a 3-layer stacked fiber felt with a single layer thickness of 0.5 mm.

[0036] Example 3

[0037] The other conditions are the same as in Example 1, except that the fiber felt is replaced with a single layer of 1.5 mm fiber felt.

[0038] Example 4

[0039] The other conditions are the same as in Example 1, except that the fiber felt is replaced with two layers of 1mm + two layers of 0.3mm fiber felt stacked together; at the same time, 2mm thick stainless steel pads are placed on both sides of the silica aerogel fiber sheet during pre-compression to control the thickness of the pre-compression sheet to be between 1.9mm and 2.1mm.

[0040] Example 5

[0041] Other conditions are the same as in Example 1, except that the fiber felt is replaced with a 2.5mm layer of fiber felt; at the same time, 2mm thick stainless steel pads are placed on both sides of the silica aerogel fiber sheet during pre-compression to control the thickness of the pre-compression sheet to be between 1.9mm and 2.1mm.

[0042] Comparative Example 1 omits the pre-compression process.

[0043] Other conditions were the same as in Example 1, except that the fiber felt was replaced with a single 1mm layer of fiber felt, and the pre-pressing process was omitted, with the resulting silica aerogel fiber sheet directly subjected to hot pressing. The hot press temperature was set to 80℃ and the pressure to 100kg / cm². 2 The process takes 50 seconds. Then, the upper polyester film, the dried silica aerogel fiber sheet, and the lower polyester film are placed in the hot press in sequence for encapsulation to obtain a silica aerogel heat insulation pad.

[0044] Comparative Example 2 omits the pre-compression process.

[0045] Other conditions were the same as in Example 1, except that the fiber felt was replaced with a single 2mm layer of fiber felt, and the pre-pressing process was omitted, with the resulting silica aerogel fiber sheet directly subjected to hot pressing. The hot press temperature was set to 80℃ and the pressure to 100kg / cm². 2 The process takes 50 seconds. Then, the upper polyester film, the dried silica aerogel fiber sheet, and the lower polyester film are placed in the hot press in sequence for encapsulation to obtain a silica aerogel heat insulation pad.

[0046] Comparative Example 3 (without additives)

[0047] The other conditions are the same as in Example 1, except that the addition of titanium dioxide and diatomaceous earth is omitted.

[0048] Comparative Example 4 (excluding hydrophobic modifier)

[0049] The other conditions are the same as in Example 1, except that the hydrophobic modifier is omitted from the aging and modification liquid, and only methanol is used for aging.

[0050] Performance testing

[0051] The room temperature thermal conductivity, high temperature thermal conductivity, bulk density, thickness, 1 MPa strain, 2 MPa strain, and thermal insulation temperature difference of the silica aerogel insulation pads prepared in Examples 1-5 and Comparative Examples 1-4 were tested. Among them:

[0052] The test method for thermal insulation temperature difference is as follows: The heating platform is heated. When the hot surface temperature reaches 430℃, the following components are placed in the order of: an 18mm calcium silicate board insulation layer, a 1mm aluminum block (with PI glue to fix the T2 sensor to the aluminum block), a silica aerogel insulation pad, and another 1mm aluminum block (with PI glue to fix the T1 sensor to the aluminum block). A pressure of 0.7MPa is applied. Timing begins when the hot surface temperature reaches 500℃. The temperatures T2 and T1 are recorded after 10 minutes. The thermal insulation temperature difference is T1-T2. A schematic diagram of the thermal insulation temperature difference test process is shown in Figure 1.

[0053] The testing methods for 1MPa and 2MPa strain are 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 and the inlet force is 35N. The 1MPa and 2MPa strains are recorded. The thickness retention rate at 2MPa is also recorded.

[0054] The specific test results are shown in Table 1.

[0055] Table 1 Performance test results of silica aerogel thermal insulation pads

[0056] As shown in Table 1, the silica aerogel insulation pads prepared in Examples 1-5 exhibit significantly lower strain under 1 MPa and 2 MPa loads compared to Comparative Examples 1-2. Furthermore, the thickness retention rate at 2 MPa is significantly higher than that of Comparative Examples 1-2, indicating that the aerogel structure can be completely maintained under this pre-compression pressure, while simultaneously densifying it and improving the impact resistance of the insulation pad. The resulting insulation pads are less prone to compression deformation. Based on Examples 3 and 1, and Examples 5 and 2, it can be seen that when using single-layer fiber sheets, the insulation performance of the insulation pads obtained in Examples 3 and 5 is superior to that in Comparative Examples 1 and 2. This is because the added pre-compression process improves the insulation performance. In addition, when using single-layer fiber sheets (Example 3), the insulation pads obtained also exhibit excellent performance in various aspects. However, when the insulation pad thickness is similar, the insulation performance of the insulation pads obtained in Examples 1-2 is superior to that in Example 3. This is because the gaps between each layer of fiber sheet are filled with aerogel in the multi-layer stacking method, reducing heat conduction between fibers and thus improving the insulation performance. Furthermore, as can be seen from Comparative Example 3, omitting the additives significantly increases the thermal conductivity of the resulting insulation pad, resulting in poorer insulation performance at high temperatures.

[0057] The hydrophobicity of Examples 1-5 and Comparative Examples 1-4 was tested. The obtained thermal insulation pads were treated at 50°C and 95%RH for 24 hours, and then their thermal conductivity at room temperature was tested again. The test results are shown in Table 2.

[0058] Table 2. Test results of hydrophobic properties of silica aerogel thermal insulation pads

[0059] As can be seen from the data in Table 2, the silica aerogel heat insulation pad prepared in this application has a high hydrophobicity and can maintain good heat insulation performance in a humid environment. In Comparative Example 4, the use of hydrophobic modifier was omitted, and the resulting heat insulation pad was non-hydrophobic. After treatment in a humid environment, the thermal conductivity increased significantly.

[0060] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

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