Silica-based aerogel felt, its preparation method and application

Abstract

The application provides a silica-based aerogel felt and a preparation method and application thereof. The silica-based aerogel felt comprises a fiber felt and silica-based aerogel skeletons distributed in the fiber felt, and the silica-based aerogel skeletons have a nanoscale pore structure. In the application, an aluminum source is added to a silica sol to form a uniform silicon-aluminum binary system, so that part of silicon atoms in Si-O-Si bonds in the formed silica-based aerogel felt is replaced by aluminum atoms to form Si-O-Al bonds with higher high-temperature resistance, and the occurrence of the structure collapse of the silica aerogel under high temperature in the prior art can be reduced. Research shows that the thermal conductivity of the silica-based aerogel felt is not more than 0.025 W / (m*K), the silica-based aerogel felt can be applied at 1000 DEG C, and the cyclic compression performance is good, which indicates that the silica-based aerogel felt has excellent heat insulation performance, high-temperature resistance and elasticity.

Description

Technical Field

[0001] This invention belongs to the field of aerogel technology, specifically relating to a silica-based aerogel felt, its preparation method, and its application. Background Technology

[0002] Aerogels are porous solid materials with a three-dimensional network structure, characterized by high porosity (80–99%), high specific surface area, low thermal conductivity, low density, and low dielectric constant. Silica aerogels, due to their excellent porous structure, exhibit extremely low density (3 kg / m³). 3 With its extremely low thermal conductivity (0.012 W / (m·K)), silica aerogel is a high-performance lightweight insulation material. When combined with fiber felt, it forms aerogel felt, which can be used as an excellent insulation material. However, because silica aerogel is prone to sintering and structural collapse at high temperatures, its long-term operating temperature is only around 600℃, and its performance deteriorates at higher temperatures. Therefore, research focuses on improving the high-temperature resistance of silica aerogel by adjusting its skeletal structure and structural properties. Currently, most studies involve combining alumina sol and silica sol to obtain an alumina-silica composite wet gel, followed by drying to obtain an alumina-silica composite aerogel. This method utilizes alumina aerogel to coat silica aerogel for composite formation, allowing the Si-OH and Si-OR bonds (where R is an alkyl group) on the silica gel surface to react with the -Al-O- bonds to form a silicon-alumina aerogel composite network structure, effectively reducing the occurrence of silica aerogel structural collapse at high temperatures. However, alumina particles are prone to crystal transformation at high temperatures, which leads to volume shrinkage, causing the pore structure to collapse, resulting in a decrease in specific surface area, and ultimately reducing the thermal insulation properties of the aerogel.

[0003] Furthermore, the existing technology for preparing silica aerogel felts mainly consists of two parts: gel preparation and drying. Gel preparation is relatively simple; the raw materials are mixed with a solvent and allowed to stand to obtain the gel. Currently, gel drying mostly employs supercritical drying, atmospheric pressure drying, or freeze-drying methods. While supercritical drying can produce silica aerogels, it involves multiple solvent replacements in actual production and suffers from long drying cycles and high costs, significantly limiting the application of silica aerogel felts. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a silica-based aerogel felt, its preparation method, and its application. The silica-based aerogel felt has a highly porous structure with uniformly distributed Si-O-Al molecular bonds within the aerogel, exhibiting excellent high-temperature resistance, superinsulation, and elasticity. Furthermore, the drying process does not require multiple solvent replacements and has a short drying time.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a silica-based aerogel felt, comprising a fiber felt and a silica-based aerogel skeleton distributed within the fiber felt.

[0007] The silica-based aerogel framework has a nanoscale porous structure.

[0008] The silica-based aerogel framework contains Si-O-Al bonds.

[0009] Preferably, the average pore size of the pore structure is 18–25 nm.

[0010] Preferably, the fiber felt is selected from any one or more of glass fiber felt, mullite fiber felt, aluminosilicate fiber felt, silicon carbide fiber felt, basalt fiber felt or pre-oxidized fiber felt.

[0011] Secondly, the present invention provides a method for preparing the above-mentioned silica-based aerogel felt, comprising the following steps:

[0012] S1: Provide silica sol, mix the aluminum source and silica sol to obtain a silicon-aluminum binary hydrolysate;

[0013] S2: Mix the silicon-aluminum binary hydrolysate with a pH adjuster and adjust the pH to 6-8 to obtain a silicon-aluminum binary sol.

[0014] S3: The fiber felt is impregnated in the above-mentioned silica-alumina binary sol to obtain silica-alumina binary wet gel felt, and then subjected to supercritical drying treatment to obtain silica-based aerogel felt.

[0015] Preferably, the temperature of the supercritical drying process is increased to 150-350°C at a rate of 1-15°C / min, the pressure is 1-10 MPa, and the time is 0.1-2 h.

[0016] Preferably, the supercritical drying process is carried out in a drying apparatus.

[0017] Preferably, the drying device includes a drying chamber body, a heating layer and a drying chamber disposed inside the drying chamber body, and a pressure relief device disposed outside the drying chamber body.

[0018] Preferably, the silica sol is obtained by mixing a silicon source, ethanol, and water.

[0019] Preferably, the silicon source is selected from any one or more of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate, and alkylalkoxysilanes.

[0020] Preferably, the alkylalkoxysilane is selected from any one or more of methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, and vinyltriethoxysilane.

[0021] Preferably, the molar ratio of the silicon source, aluminum source, ethanol, and water is (60-400):1:(2500-3000):(500-1000).

[0022] Preferably, the aluminum source is selected from any one or more of aluminum chloride hexahydrate, aluminum nitrate, aluminum isopropoxide, or aluminum sec-butoxide.

[0023] Preferably, the pH adjuster is selected from any one or more of sodium hydroxide, potassium hydroxide, ammonia, ammonium fluoride, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, propylamine, dipropylamine, isopropanolamine, or 3-aminopropyltriethoxysilane.

[0024] Thirdly, the present invention provides a heat insulation material for lithium-ion batteries, including the silica-based aerogel felt involved in the above technical solution.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) This invention provides a silica-based aerogel felt, comprising a fiber felt and a silica-based composite aerogel skeleton distributed within the fiber felt, wherein a nanoscale porous structure is formed between the silica-based composite aerogel skeletons. This invention, by adding an aluminum source to silica sol, forms a uniform silicon-aluminum binary system, causing some silicon atoms in the Si-O-Si bonds of the formed silica-based aerogel felt to be replaced by aluminum atoms, forming Si-O-Al bonds with better high-temperature resistance, which can reduce the occurrence of silica aerogel structure collapse at high temperatures in the prior art. Studies have shown that the prepared silica-based aerogel felt has a thermal conductivity of no more than 0.025 W / (m·K), can be used at 1000℃, and exhibits good compression cycle performance, indicating that it has excellent thermal insulation, high-temperature resistance, and elasticity.

[0027] (2) Traditional supercritical drying methods require solvent exchange and modification of the aerogel, and the drying process is time-consuming and requires solvent replacement, which is not conducive to industrial production. Furthermore, the preparation of silica-alumina binary aerogels is prone to inhomogeneity and phase separation. Compared with traditional supercritical drying methods, the silica-based aerogel felt preparation method provided in this invention employs an in-situ supercritical drying process, directly drying the silica-alumina binary wet aerogel felt. This allows for rapid and uniform cross-linking and solidification of the silica-alumina binary phases, forming uniformly distributed Si-O-Al molecular bonds and a nanoscale pore structure in the aerogel. This drying process does not require the replacement of multiple solvents and has a short drying time. Simultaneously, the supercritical temperature and pressure of the drying process can be adjusted by controlling the ratio of water and alcohol in the silica sol. The process is simple and easy to operate, and within a certain range, the pore structure of the aerogel is adjustable, possessing the potential to expand the application range of aerogel composite materials in high-temperature fields. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the in-situ supercritical drying device used in Example 1 of the present invention;

[0029] Wherein, 1 is the drying oven body; 2 is the heating layer; 3 is the pressure relief device; 3-1 is the pressure gauge; 3-2 is the valve; 4 is the screw groove;

[0030] Figure 2 This is a macroscopic view of the silica-based aerogel felt prepared in Example 2;

[0031] Figure 3 SEM image of the aerogel in the silica-based aerogel felt prepared in Example 2;

[0032] Figure 4 TEM image of the aerogel in the silica-based aerogel felt prepared in Example 2;

[0033] Figure 5 The pore size distribution diagram of the silica-based aerogel felt prepared in Example 2 is shown.

[0034] Figure 6 The N2 adsorption-desorption curve of the silica-based aerogel felt prepared in Example 1 is shown.

[0035] Figure 7 The compression cycle performance characterization diagram is shown for the silica-based aerogel felt prepared in Example 1.

[0036] Figure 8 The fatigue resistance characterization diagram is shown for the silica-based aerogel felt prepared in Example 1.

[0037] Figure 9The graph shows the characterization of the superheat insulation performance of the silica-based aerogel felt prepared in Example 3.

[0038] Wherein, a is a schematic diagram of the device for testing the super thermal insulation performance; b is a schematic diagram of the sampling points of the silica-based aerogel felt; c is a diagram of the super thermal insulation performance test results at different points in the silica-based aerogel felt;

[0039] Figure 10 The image shows the high-temperature resistance of the silica-based aerogel felt prepared in Example 3. Detailed Implementation

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] In existing technologies, alumina particles in alumina-silica composite aerogels are prone to crystal transformation at high temperatures, leading to volume shrinkage, pore structure collapse, and a decrease in specific surface area, ultimately reducing the thermal insulation properties of the aerogel. Furthermore, the drying process of silica aerogel felts involves multiple solvent replacements, resulting in long drying cycles and high costs. This invention provides a silica-based aerogel felt, comprising a fiber felt and a silica-based aerogel framework distributed within the fiber felt. This invention does not impose specific limitations on the source of the fiber felt; commercially available products are acceptable. Specifically, the fiber felt can be selected from any one or more of glass fiber felt, mullite fiber felt, aluminosilicate fiber felt, silicon carbide fiber felt, basalt fiber felt, or pre-oxidized fiber felt. In this invention, the silica-based aerogel framework is composed of nanospherical aerogel secondary particles, which can form a nanoscale porous structure, as illustrated in the schematic diagram. Figures 3-4 As shown. Testing revealed that the pore size of the nanoscale porous structure ranges from 1 to 200 nm, such as 1 nm, 1.5 nm, 2 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 60 nm, 100 nm, 150 nm, or 200 nm, etc., with an average pore size of 18 to 25 nm, specifically 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, or 25 nm, etc.

[0042] The silica-based aerogel felt provided by the present invention forms a uniform silicon-aluminum binary system by adding an aluminum source to the silica sol. This results in some silicon atoms in the Si-O-Si bonds of the formed silica-based aerogel felt being replaced by aluminum atoms, forming Si-O-Al bonds with better high-temperature resistance. This can reduce the occurrence of silica aerogel structure collapse at high temperatures in the prior art.

[0043] The present invention also provides a method for preparing the above-mentioned silica-based aerogel felt, comprising the following steps:

[0044] S1: Provide silica sol, mix the aluminum source and silica sol to obtain a silicon-aluminum binary hydrolysate;

[0045] S2: Mix the silicon-aluminum binary hydrolysate with a pH adjuster and adjust the pH to 6-8 to obtain a silicon-aluminum binary sol.

[0046] S3: The fiber felt is impregnated in the above-mentioned silica-alumina binary sol to obtain silica-alumina binary wet gel felt, and then subjected to supercritical drying treatment to obtain silica-based aerogel felt.

[0047] According to the present invention, a silica sol is first provided. The present invention does not impose any particular limitations on the preparation of the silica sol; it can be prepared using techniques well known to those skilled in the art. In some embodiments of the present invention, the silica sol is obtained by mixing a silicon source and a solvent, preferably under stirring conditions. The present invention does not impose any particular limitations on the stirring rate. The silicon source may be selected from any one or more of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate, or alkylalkoxysilanes, wherein the alkylalkoxysilanes include any one or more of methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, or vinyltriethoxysilane. The solvent preferably includes ethanol and water, wherein the water can be deionized water, distilled water, or ultrapure water. The preferred molar ratio of ethanol to water is 65:(10-40), and can be 65:10, 65:12, 65:14, 65:18, 65:20, 65:23, 65:25, 65:28, 65:30, 65:32, 65:35, 65:38, or 65:40, etc. It should be noted that this invention controls the degree of silicon source hydrolysis by adjusting the initial ratio of ethanol and water, i.e., the relative content of hydrolysis products (ethanol) and water, thereby controlling the ratio of ethanol to water in the gel skeleton to determine the supercritical temperature point of the drying process, thus controlling the supercritical point and degree of hydrolysis of the mixed solvent. This invention does not have particular limitations on the source of the silicon source and solvent; commercially available products are acceptable.

[0048] After obtaining the silica sol, the present invention preferably mixes the aluminum source and the silica sol to obtain a silicon-aluminum binary hydrolysate. The mixing is preferably carried out under stirring conditions, and the present invention does not have a particular limitation on the stirring rate. The present invention does not have a particular limitation on the source of the aluminum source; any commercially available product is acceptable, specifically, it can be selected from any one or more of aluminum chloride hexahydrate, aluminum nitrate, aluminum isopropoxide, or aluminum sec-butoxide. In the present invention, the silica sol is obtained by mixing a silicon source, ethanol, and water, and then mixing it with the aluminum source under stirring conditions to obtain the silicon-aluminum binary hydrolysate. Therefore, the silicon source, aluminum source, ethanol, and water should be considered as a whole, and the preferred molar ratio of the silicon source, aluminum source, ethanol, and water is (60–400):1:(1500–3500):(500–1000). Wherein, (60-400) can be 60, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380 or 400, etc.; (1500-3500) can be 1500, 1800, 2000, 2200, 2500, 2800, 3000, 3200 or 3500, etc.; and (500-1000) can be 500, 600, 700, 800, 900 or 1000, etc.

[0049] Since the silica-alumina binary hydrolysate cannot form a gel if its pH is too high or too low, the present invention preferably mixes the silica-alumina binary hydrolysate with a pH adjuster to adjust the pH to 6-8, preferably 6.5-8, and more preferably 7-7.5, to obtain a silica-alumina binary sol. This invention does not impose any particular restriction on the source of the pH adjuster; any commercially available product is acceptable. It can be selected from either acidic or alkaline pH adjusters. Specifically, the acidic pH adjuster can be hydrochloric acid, and the alkaline pH adjuster can be selected from any one or more of the following: sodium hydroxide, potassium hydroxide, ammonia, ammonium fluoride, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, propylamine, dipropylamine, isopropanolamine, or 3-aminopropyltriethoxysilane. In this invention, the concentration of the pH adjuster is 0.3 to 1 mol / L, preferably 0.5 mol / L, and the volume ratio of the pH adjuster to water is generally (1 to 1.5):1, which can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1, etc.

[0050] The list of point values ​​involved in this invention is merely for illustrative purposes and is not limited thereto. Other point values ​​within the numerical range are also applicable, but to avoid complexity, they will not be described in detail.

[0051] After obtaining the silica-alumina binary sol, the present invention preferably impregnates a fiber felt in the silica-alumina binary sol to obtain a silica-alumina binary wet gel felt. The selection of the fiber felt is as described in the relevant content of the above technical solution and will not be repeated here. Then, the silica-alumina binary wet gel felt is subjected to supercritical drying treatment to obtain a silica-based aerogel felt. In the present invention, the supercritical drying treatment is preferably in-situ supercritical drying treatment. "In-situ" means placing the fiber felt in a drying device and then directly pouring the silica-alumina binary sol into the device to combine with the fiber felt, preferably in a supercritical drying device. A schematic diagram of the structure of the supercritical drying device is shown below. Figure 1 As shown, the device includes a drying oven body 1, a heating layer 2 and a drying chamber disposed inside the drying oven body, a pressure relief device 3, and a screw groove 4. The pressure relief device includes a pressure gauge 3-1 and a valve 3-2. The heating layer comprises an upper heating layer and a lower heating layer symmetrically disposed at the top and bottom of the drying oven body, and at least two heating tubes are disposed inside the heating layer. The pressure relief device is an automatic pressure relief device; when the pressure exceeds a set threshold, it will automatically and slowly release the pressure, releasing the solvent inside the device to prevent excessive pressure and reduce the risk to personnel and equipment during the experiment. In some embodiments of the present invention, during the supercritical drying process, the preset pressure inside the drying device is 1–10 MPa, preferably 5–9 MPa, more preferably 6–8 MPa. Then, the temperature is increased to 150–350°C, preferably 200–300°C, more preferably 255–280°C, at a rate of 1–15°C / min, preferably 3–12°C / min, more preferably 5–10°C / min, and dried for 0.1–2 h, preferably 0.3–1.5 h, more preferably 0.7–1 h, to obtain a silica-based aerogel felt. It should be noted that during the drying process, when the pressure inside the device reaches 4–9 MPa, the valve will open for dynamic automatic pressure relief. After automatic pressure relief is completed, the device is cooled to room temperature to obtain the silica-based aerogel felt. Furthermore, the automatic pressure relief value is higher than the preset pressure due to the supercritical solvent, but the specific increase depends on the amount of wet gel to be dried; the more wet gel, the more solvent it carries, and the higher the pressure relief value. In some embodiments of the present invention, when the preset pressure inside the device is 6 MPa, the automatic pressure relief value is 8 MPa; when the preset pressure inside the device is 5 MPa, the automatic pressure relief value is 7 MPa; when the preset pressure inside the device is 5 MPa, the automatic pressure relief value is 6 MPa; and when the preset pressure inside the device is 7 MPa, the automatic pressure relief value is 9 MPa. In some embodiments of the present invention, the silicon-aluminum binary wet gel felt occupies 40-95% of the volume of the drying device, preferably 60-95%, and more preferably 80-95%.

[0052] In some preferred embodiments of the present invention, the obtained silicon-aluminum binary wet gel felt is preferably aged for 20-30 hours, more preferably 24-28 hours, before undergoing supercritical drying. The aging process is a commonly used technique by those skilled in the art, specifically involving: allowing the silicon-aluminum binary wet gel felt to stand at room temperature for a period of time, or immersing the silicon-aluminum binary wet gel felt in ethanol and allowing it to stand at room temperature for a period of time.

[0053] The method for preparing the silica-based aerogel felt provided by this invention is simple and convenient, employing an in-situ supercritical drying process that eliminates the need for solvent replacement and results in a short drying time. Furthermore, the supercritical temperature and pressure during the drying process can be adjusted by controlling the ratio of water to alcohol in the silica sol, simplifying the operation and facilitating industrial production. Additionally, the pore structure of the aerogel is tunable within a certain range, potentially expanding the application range of aerogel composite materials in high-temperature fields.

[0054] The prepared silica-based aerogel felt was tested and found to have a thermal conductivity of 0.013–0.025 W / (m·K) and a density of 0.19–0.24 g / cm³. 3 The specific surface area can reach up to 920m². 2 / g, which can be used at 1000℃, indicates that it has excellent thermal insulation performance, high temperature resistance and elasticity, and has a rich porous structure, while also being lightweight.

[0055] Based on the excellent properties of the silica-based aerogel felt mentioned above, the present invention also provides a thermal insulation material for lithium-ion batteries, which includes the silica-based aerogel felt involved in the above technical solution.

[0056] Studies have shown that the silica-based aerogel felt has excellent fatigue resistance and can meet the requirements of thermal insulation materials for lithium-ion batteries.

[0057] To further illustrate the present invention, the following embodiments provide a detailed description. The experimental materials used in the following embodiments of the present invention are all commercially available products.

[0058] Preparation Example 1

[0059] This preparation example provides an in-situ supercritical drying device, the schematic diagram of which is shown below. Figure 1 As shown, 1 is the drying oven body; 2 is the heating layer; 3 is the pressure relief device; 3-1 is the pressure gauge; 3-2 is the valve; and 4 is the screw groove.

[0060] Example 1

[0061] This embodiment provides a silica-based aerogel felt, the preparation method of which is as follows:

[0062] (1) Preparation of silica sol: Take a silicon source, ethanol and water and mix them evenly at room temperature;

[0063] (2) Preparation of silicon-aluminum binary sol: Add aluminum source to the solution in step (1), wherein the molar ratio of silicon source, aluminum source, ethanol and water is 260:1:2600:560;

[0064] (3) Gel: Add ammonia water to the silica-alumina binary sol described in step (2) and adjust the pH of the sol to 6.5;

[0065] (4) Impregnation: Immediately after step (3) is completed, the sol that is about to gel is poured into a mold containing glass fiber mat to obtain a silicon-aluminum co-precursor wet gel mat composite material.

[0066] (5) Aging treatment of composite gel: The silicon-aluminum co-precursor wet gel felt composite material obtained in step (4) is aged at room temperature for 24 hours.

[0067] (6) Drying: The silicon-aluminum co-precursor wet gel felt composite material obtained in step (5) is placed in the in-situ supercritical drying device described in Preparation Example 1. After the device is sealed, the preset pressure is 6 MPa. The composite material to be dried occupies 90% of the volume of the drying device. The heating rate is 1℃ / min. The temperature is raised to 290℃ and held at this temperature for 0.3h. The pressure relief value of the automatic pressure relief device is 8 MPa. After the automatic pressure relief is completed within the heat preservation period, the device is allowed to cool naturally to room temperature to obtain silica-based aerogel felt.

[0068] In step (1), the silicon source is tetraethyl orthosilicate; in step (2), the aluminum source is aluminum chloride hexahydrate.

[0069] The silica-based aerogel felt obtained in this embodiment has a thermal conductivity of 0.0197 W / (m·K) and a specific surface area of ​​916 m². 2 / g, the dimensional shrinkage rate after treatment at 800℃ for 120min was 10.81%.

[0070] Example 2

[0071] This embodiment provides a silica-based aerogel felt, the preparation method of which is as follows:

[0072] (1) Preparation of silica sol: Take a silicon source, ethanol and water and mix them evenly at room temperature;

[0073] (2) Preparation of silicon-aluminum binary sol: Add aluminum source to the solution in step (1), wherein the molar ratio of silicon source, aluminum source, ethanol and water is 64:1:2600:700;

[0074] (3) Gel: Add ammonia water to the silica-alumina binary sol described in step (2) and adjust the pH of the sol to 7.0;

[0075] (4) Impregnation: Immediately after step (3) is completed, the sol that is about to gel is poured into a mold containing glass fiber mat to obtain a silicon-aluminum co-precursor wet gel mat composite material.

[0076] (5) Aging treatment of composite gel: The silicon-aluminum co-precursor wet gel felt composite material obtained in step (4) is aged at room temperature for 24 hours.

[0077] (6) Drying: The silicon-aluminum co-precursor wet gel felt composite material obtained in step (5) is placed in an in-situ supercritical drying device. After the device is sealed, the preset pressure is 5 MPa. The composite material to be dried occupies 80% of the volume of the drying device. The heating rate is 3℃ / min. The temperature is raised to 255℃ and held at this temperature for 1 hour. The pressure relief value of the automatic pressure relief device is 7 MPa. After the automatic pressure relief is completed within the heat preservation period, the device is allowed to cool naturally to room temperature to obtain silica-based aerogel felt.

[0078] In step (1), the silicon source is methyltrimethoxysilane; in step (2), the aluminum source is aluminum chloride hexahydrate.

[0079] The macroscopic image of the silica-based aerogel felt obtained in this embodiment is as follows: Figure 2 As shown, the SEM and TEM images of the silica-based aerogel inside are as follows. Figures 3-4 As shown, a rich porous structure is formed between the nanospherical aerogel secondary particles. The pore size distribution of the silica-based aerogel mat is as follows. Figure 5 As shown, the average pore size of the aerogel felt is between 18 and 25 nm.

[0080] The silica-based aerogel felt obtained in this embodiment has a thermal conductivity of 0.0243 W / (m·K) and a specific surface area of ​​756 m². 2 / g, the dimensional shrinkage rate after treatment at 800℃ for 120min was 13.74%.

[0081] Example 3

[0082] This embodiment provides a silica-based aerogel felt, the preparation method of which is as follows:

[0083] (1) Preparation of silica sol: Take a silicon source, ethanol and water and mix them evenly at room temperature;

[0084] (2) Preparation of silicon-aluminum binary sol: Add aluminum source to the solution in step (1), wherein the molar ratio of silicon source, aluminum source, ethanol and water is 370:1:2600:900;

[0085] (3) Gel: Add ammonia water to the silica-alumina binary sol described in step (2) and adjust the pH of the sol to 6.5;

[0086] (4) Impregnation: Immediately after step (3) is completed, the sol that is about to gel is poured into a mold containing aluminum silicate fiber felt to obtain a silicon-aluminum co-precursor wet gel felt composite material.

[0087] (5) Aging treatment of composite gel: The silicon-aluminum co-precursor wet gel felt composite material obtained in step (4) is aged at room temperature for 4 hours.

[0088] (6) Drying: The silicon-aluminum co-precursor wet gel felt composite material obtained in step (5) is placed in an in-situ supercritical drying device. After the device is sealed, the preset pressure is 5.5 MPa. The composite material to be dried occupies 80% of the volume of the drying device. The heating rate is 3℃ / min. The temperature is raised to 270℃ and held at this temperature for 1 hour. The pressure relief value of the automatic pressure relief device is 7 MPa. After the automatic pressure relief is completed within the heat preservation period, the device is allowed to cool naturally to room temperature to obtain silica-based aerogel felt.

[0089] In step (1), the silicon source is tetraethyl orthosilicate; in step (2), the aluminum source is aluminum nitrate.

[0090] The silica-based aerogel felt obtained in this embodiment has a thermal conductivity of 0.0216 W / (m·K) and a specific surface area of ​​893 m². 2 / g, the dimensional shrinkage rate after treatment at 800℃ for 120min was 12.93%.

[0091] Example 4

[0092] This embodiment provides a silica-based aerogel felt, the preparation method of which is as follows:

[0093] (1) Preparation of silica sol: Take a silicon source, ethanol and water and mix them evenly at room temperature;

[0094] (2) Preparation of silicon-aluminum binary sol: Add aluminum source to the solution in step (1), wherein the molar ratio of silicon source, aluminum source, ethanol and water is 60:1:2000:900;

[0095] (3) Gel: Add ammonia water to the silica-alumina binary sol described in step (2) and adjust the pH of the sol to 7.0;

[0096] (4) Impregnation: Immediately after step (3) is completed, the sol that is about to gel is poured into a mold containing silicon carbide fiber felt to obtain silicon-aluminum co-precursor wet gel felt composite material.

[0097] (5) Aging treatment of composite gel: The silicon-aluminum co-precursor wet gel felt composite material obtained in step (4) is aged at room temperature for 6 hours.

[0098] (6) Drying: The silicon-aluminum co-precursor wet gel felt composite material obtained in step (5) is placed in an in-situ supercritical drying device. After the device is sealed, the preset pressure is 7 MPa. The composite material to be dried occupies 90% of the volume of the drying device. The heating rate is 2℃ / min. The temperature is rapidly increased to 280℃ and held at this temperature for 0.5h. The pressure relief value of the automatic pressure relief device is 9 MPa. After the automatic pressure relief is completed within the heat preservation period, the device is allowed to cool naturally to room temperature to obtain silica-based aerogel felt.

[0099] In step (1), the silicon source is tetraethyl orthosilicate; in step (2), the aluminum source is aluminum chloride hexahydrate.

[0100] The silica-based aerogel felt obtained in this embodiment has a thermal conductivity of 0.0221 W / (m·K) and a specific surface area of ​​786 m². 2 / g, the dimensional shrinkage rate after treatment at 800℃ for 120min was 11.56%.

[0101] Performance testing

[0102] The present invention tests the N2 adsorption and desorption of the silica-based aerogel felt obtained in Example 1. The test method is as follows:

[0103] Fully automated specific surface area analysis involves changing the pressure under isothermal conditions to measure the change in the amount of gas adsorbed by the sample, thereby plotting the adsorption-desorption isotherms. Nitrogen gas at low temperature is typically used as the adsorption / desorption gas. Mathematical models are then applied to calculate data such as the sample's specific surface area, pore volume, pore capacity, and pore size distribution. The fully automated specific surface area analyzer used in this study is the Micron 2460.

[0104] Test results are as follows Figure 6 As shown, by Figure 6 The N2 adsorption and desorption curves show that the silica-based aerogel felt has a high specific surface area.

[0105] The present invention tests the compression cycle performance of the silica-based aerogel felt obtained in Example 1, and the test method is as follows:

[0106] The universal testing machine performs compression cycles on the material at a speed of 60 mm / min, with the compression deformation reaching 43% of the material thickness. The curves of compression stress and deformation are obtained. Then, based on the original thickness and area of ​​the material, the stress-strain curve, as well as data such as maximum stress, height retention, and energy loss coefficient, are calculated. The universal testing machine used in this study is an Instron E3000K8953.

[0107] Test results are as follows Figure 7 As shown, the silica-based aerogel felt exhibits good compression cycle performance, indicating its excellent elasticity.

[0108] The fatigue resistance of the silica-based aerogel felt obtained in Example 1 was tested using the following method:

[0109] Dynamic thermomechanical analysis (DMA) measures the relationship between the mechanical properties of elastic materials and time, temperature, or frequency. The basic principle of DMA testing is to apply an alternating load to the sample, record the sample's response, and simultaneously calculate and output the material's dynamic performance parameters, such as storage modulus, loss modulus, loss factor, and glass transition temperature.

[0110] Test results are as follows Figure 8 As shown, the loss factor is relatively small, indicating that the silica-based aerogel felt has excellent fatigue resistance.

[0111] The present invention tested the superheat insulation performance of the silica-based aerogel felt prepared in Example 3. A schematic diagram of the testing device is shown below. Figure 9 As shown in Figure a, the method is as follows (a schematic diagram of point selection is shown in Figure a). Figure 9 (as shown in b):

[0112] The front side of the aerogel mat was directly heated by a butane torch flame (temperatures up to 1200℃), and the temperature change on the back side of the aerogel mat was measured in real time using an infrared imager. To make the results more convincing, three points (sp1-3, e.g.) were selected. Figure 9 (as shown in b).

[0113] Test results are as follows Figure 9 As shown in Figure c, the temperature at the three points rises slowly and then remains below 46°C, indicating that the silica-based aerogel felt has excellent thermal insulation properties.

[0114] The high-temperature resistance of the silica-based aerogel felt prepared in Example 3 was tested using the following method:

[0115] The prepared aerogel felt was heat-treated in air for 2 hours at temperatures of 100℃, 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, and 1000℃. XRD patterns were used to observe whether there were any changes in the crystal phase.

[0116] Test results are as follows Figure 10 As shown, silica-based aerogel felt has excellent high-temperature resistance.

[0117] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A silica-based aerogel felt, characterized in that, It includes a fiber mat and a silica-based aerogel skeleton distributed inside the fiber mat; The silica-based aerogel framework has a nanoscale porous structure. The silica-based aerogel framework contains Si-O-Al bonds; The silica-based aerogel felt is prepared by a method comprising the following steps: S1: Provide silica sol, mix the aluminum source and silica sol to obtain a silicon-aluminum binary hydrolysate; S2: Mix the silicon-aluminum binary hydrolysate with a pH adjuster and adjust the pH to 6-8 to obtain a silicon-aluminum binary sol. S3: The fiber felt is impregnated in the above-mentioned silica-alumina binary sol to obtain silica-alumina binary wet gel felt, and then subjected to supercritical drying treatment to obtain silica-based aerogel felt. The silica sol is obtained by mixing a silicon source, ethanol, and water. The molar ratio of silicon source, aluminum source, ethanol, and water is (60~400):1:(2500~3000):(500~1000).

2. The silica-based aerogel felt according to claim 1, characterized in that, The average pore size of the pore structure is 18~25 nm.

3. The silica-based aerogel felt according to claim 1, characterized in that, The fiber mat is selected from any one or more of glass fiber mat, aluminosilicate fiber mat, silicon carbide fiber mat, basalt fiber mat, or pre-oxidized fiber mat.

4. A method for preparing a silica-based aerogel felt according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1: Provide silica sol, mix the aluminum source and silica sol to obtain a silicon-aluminum binary hydrolysate; S2: Mix the silicon-aluminum binary hydrolysate with a pH adjuster and adjust the pH to 6-8 to obtain a silicon-aluminum binary sol. S3: The fiber felt is impregnated in the above-mentioned silica-alumina binary sol to obtain silica-alumina binary wet gel felt, and then subjected to supercritical drying treatment to obtain silica-based aerogel felt. The silica sol is obtained by mixing a silicon source, ethanol, and water. The molar ratio of silicon source, aluminum source, ethanol, and water is (60~400):1:(2500~3000):(500~1000).

5. The preparation method according to claim 4, characterized in that, The supercritical drying process involves increasing the temperature to 150-350℃ at a rate of 1-15℃ / min, applying a pressure of 1-10 MPa, and holding the temperature for 0.1-2 hours.

6. The preparation method according to claim 4 or 5, characterized in that, The supercritical drying process is carried out in a drying device; The drying device includes a drying chamber body, a heating layer and a drying chamber disposed inside the drying chamber body, and a pressure relief device disposed outside the drying chamber body.

7. The preparation method according to claim 4, characterized in that, The silicon source is selected from any one or more of tetraethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate, and alkylalkoxysilanes; The alkylalkoxysilane is selected from any one or more of methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, and vinyltriethoxysilane.

8. The preparation method according to claim 4, characterized in that, The aluminum source is selected from any one or more of aluminum chloride hexahydrate, aluminum nitrate, aluminum isopropoxide, or aluminum sec-butoxide. The pH adjuster is selected from any one or more of sodium hydroxide, potassium hydroxide, ammonia, ammonium fluoride, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, propylamine, dipropylamine, isopropanolamine, or 3-aminopropyltriethoxysilane.

9. A heat-insulating material for lithium-ion batteries, characterized in that, Includes silica-based aerogel felt according to any one of claims 1 to 3 or silica-based aerogel felt prepared by any one of claims 4 to 8.

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