Method of making a composite aerogel, composite aerogel, thermal management system, and battery

Abstract

The application provides a preparation method of composite aerogel, the composite aerogel, a thermal management system and a battery, and relates to the technical field of batteries. The specific technical scheme is as follows: a fiber gel body and an organic sol are provided, the fiber gel body comprises a silicon-based gel body and a fiber matrix; the organic sol is coated on the outer surface of the fiber gel body to obtain a composite gel body; the composite gel body is subjected to drying treatment to obtain a composite material, the silicon-based gel body forms a silicon-based aerogel, and the fiber gel body forms a fiber aerogel; finally, the composite material is subjected to carbonization treatment to obtain a composite aerogel, and the organic sol forms a carbon aerogel; the composite aerogel prepared by the above method not only has a synergistic heat insulation and heat conduction function, but also has a relatively stable structure, and can be applied to a battery as a thermal protection material to improve the overall safety of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a method for preparing a composite aerogel, the composite aerogel, a thermal management system, and a battery. Background Technology

[0002] With the development of new energy technologies, batteries have become a major power source, and their thermal safety has gradually attracted attention. Under extreme conditions such as high-rate charging and discharging and mechanical impact, individual battery cells are prone to thermal runaway. If the thermal protection of individual cells is inadequate, it can easily lead to overall battery thermal runaway, resulting in serious safety accidents such as combustion or even explosion. Therefore, developing thermal insulation materials with high-efficiency thermal insulation properties to improve the thermal protection effect of batteries has become a research hotspot in the field of battery technology.

[0003] Aerogels are widely used in thermal insulation materials due to their extremely low thermal conductivity. However, traditional aerogels suffer from structural fragility and poor thermal conductivity at high temperatures, making it difficult to meet the comprehensive requirements of actual batteries for thermal protection materials in terms of thermal conductivity and structural stability while ensuring thermal insulation performance.

[0004] Therefore, there is an urgent need to develop a thermal protection material with stable structure and synergistic thermal insulation and conduction functions, and to apply it to batteries to improve the overall safety of batteries. Summary of the Invention

[0005] This application provides a method for preparing a composite aerogel, the composite aerogel, a thermal management system, and a battery. The prepared composite aerogel not only has synergistic heat insulation and heat conduction functions, but also has a relatively stable structure. It can be used as a thermal protection material in batteries to improve the overall safety of the battery.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] In a first aspect, a method for preparing a composite aerogel is provided, the method comprising:

[0008] First, a fiber gel and an organosol are provided, the fiber gel comprising a silicone-based gel and a fiber matrix, the silicone-based gel filling the gaps between the fibers of the fiber matrix; and / or, the silicone-based gel coating the fiber surface.

[0009] Then, the organic sol is coated on the outer surface of the fiber gel to obtain the composite gel.

[0010] Subsequently, the composite gel is dried to form a silica-based aerogel and a fibrous aerogel, thus obtaining the composite material. The fibrous aerogel includes silica-based aerogel.

[0011] Silicon-based aerogels have low thermal conductivity and good insulation properties. The fiber matrix in fibrous aerogels can provide macroscopic support structure for silicon-based aerogels, preventing them from becoming brittle, enhancing their processability and compressive strength, and thus improving the overall structural stability.

[0012] Finally, the composite material is carbonized to form a carbon aerogel from the organic sol, resulting in a composite aerogel located on the outer surface of the fiber aerogel. The carbon aerogel exhibits better high-temperature resistance, is less flammable, and has good thermal conductivity.

[0013] By coating the outer surface of the fibrous aerogel with organic sol and then drying and carbonizing it, a unique dual-network structure can be constructed, achieving organic synergy between the carbon aerogel network and the fibrous aerogel network.

[0014] In summary, fiber aerogels exhibit low thermal conductivity, good thermal insulation performance, and structural stability; carbon aerogels demonstrate better high-temperature resistance and thermal conductivity. Therefore, the composite aerogels prepared using the above methods not only provide synergistic thermal insulation and conduction but also possess structural stability, making them suitable as thermal protection materials in batteries to enhance overall battery safety.

[0015] In addition, the above preparation method is simple and easy to operate, safe and reliable, and has low production cost, making it suitable for continuous and large-scale production.

[0016] When the composite aerogel prepared by the above method is combined with the battery's cold plate to construct a thermal management system, this system not only possesses excellent thermal isolation and thermal conductivity regulation capabilities, but also effectively limits temperature rise during battery charging and discharging. Under extreme conditions such as thermal runaway, it can effectively prevent the propagation of thermal runaway, ensuring the safe and stable operation of the battery. Therefore, the synergistic design of the composite aerogel and the cold plate can balance mechanical strength, heat dissipation performance, thermal insulation performance, and thermal response speed, meeting the diverse operating requirements of batteries.

[0017] In one possible implementation of the first aspect, the method for preparing the fiber gel includes: first, providing a silicon source, ethanol, water, an aluminum source, a pH adjuster, and a fiber matrix; then, mixing the silicon source, ethanol, water, and aluminum source to form a first mixture, adding the pH adjuster to the first mixture to obtain a silica-alumina sol; and finally, immersing the fiber matrix in the silica-alumina sol to obtain the fiber gel.

[0018] The aforementioned pH adjuster can create an alkaline reaction environment. Under this alkaline environment, on the one hand, it can promote further condensation reactions of the hydroxyl groups inside the gel skeleton and facilitate the entry of Al into the Si-O-Si network, forming a denser and more complete Al-O-Si cross-linked network. On the other hand, the alkaline reaction environment can promote the condensation reaction between the monosilicic acid or disilicate generated by hydrolysis in the reaction system and the hydroxyl groups on the surface of the gel skeleton, forming a silicon shell structure in situ on the skeleton surface. This silicon shell structure helps to enhance the structural stability and chemical resistance of the gel skeleton, and improve the interfacial integrity and finished product performance of the fiber gel in subsequent processing.

[0019] In one possible implementation of the first aspect, the method for preparing the organosol includes: first, providing phenols, aldehydes, ethanol, and a crosslinking agent; then, mixing the phenols, aldehydes, and ethanol to form a second mixture, and adding the crosslinking agent to the second mixture to obtain an organosol. The crosslinking agent slowly forms an alkaline environment under heating conditions, where the phenols and aldehydes undergo an aldehyde-phenol condensation reaction to form a three-dimensional crosslinked organosol network.

[0020] In one possible implementation of the first aspect, the silicon source includes at least one selected from tetraethyl orthosilicate, methyl orthosilicate, water glass, methyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, and phenyltriethoxysilane. The aluminum source includes at least one selected from aluminum nitrate, anhydrous aluminum chloride, aluminum chloride hexahydrate, polyaluminum chloride, aluminum isopropoxide, aluminum triethanolamine, and aluminum sulfate.

[0021] The aforementioned silicon and aluminum sources are prone to hydrolysis under the action of crosslinking agents, which helps them form an Al-O-Si crosslinked network and a "silicon" shell structure. Furthermore, the silicon source can provide a SiO2 network framework, determining the thermal stability and mechanical strength of the silicon-aluminum aerogel; the introduction of the aluminum source can improve the high-temperature resistance and chemical stability of the silicon-aluminum aerogel.

[0022] In one possible implementation of the first aspect, the pH adjuster includes at least one selected from ammonia, sodium hydroxide, potassium hydroxide, triethanolamine, and urea. All of the aforementioned pH adjusters can adjust the first mixture to an alkaline state, allowing the aluminum source and silicon source to react in an alkaline environment.

[0023] In one possible implementation of the first aspect, the fiber matrix includes at least one selected from aluminosilicate fibers, glass fibers, mullite fibers, quartz fibers, pre-oxidized fiber mats, and basalt fiber mats. Using the above-mentioned materials as the fiber matrix of the fiber gel can provide a macroscopic support structure for the fiber gel, preventing the final fiber aerogel from becoming brittle and contributing to enhanced processability and compressive strength. Mullite fibers, in particular, possess high-temperature resistance; when combined with the aforementioned silica-based aerogels to form fiber aerogels, they can reduce the thermal conductivity of the fiber aerogels, significantly inhibiting heat conduction.

[0024] In one possible implementation of the first aspect, the molar ratio of silicon source, ethanol, water and aluminum source is (50~160):(500~1250):(100~300):1.

[0025] It should be noted that a higher molar ratio of silicon to aluminum source in the first mixture indicates a higher molar concentration of silicon. Insufficient aluminum ion doping in the system causes the gelation process to tend towards the formation of isolated silicon-oxygen tetrahedra, resulting in a lower crosslinking density and a greater susceptibility to structural defects in the final silicon-aluminum aerogel. Conversely, a lower molar ratio of silicon to aluminum source in the first mixture indicates a higher molar concentration of aluminum, leading to higher crosslinking density, branching degree, and rigidity. However, the uniformity of the resulting Al-O-Si crosslinked network may decrease.

[0026] When the molar ratio of silicon source, ethanol, water and aluminum source is within a suitable range, aluminum moderately replaces silicon sites, which can maintain the stability of the Si-O-Si main chain, introduce charge imbalance through Si-O-Al bonds, enhance alkali-activated activity, promote the formation of dense network, and help reduce the thermal conductivity of silicon-aluminum aerosol.

[0027] In one possible implementation of the first aspect, the phenols include at least one of phenol, resorcinol, catechol, and hydroquinone. Resorcinol has two hydroxyl groups in the meta position, resulting in less steric hindrance and making it readily hydroxymethylated and polymerized with formaldehyde; phenol is inexpensive and widely available; catechol's ortho-diol structure exhibits strong reducing and coordinating abilities, making it suitable for preparing conductive aerogels; hydroquinone possesses stable structural units, and its symmetrical structure facilitates the formation of a regular network, making it suitable for preparing thermally stable aerogels.

[0028] In one possible implementation of the first aspect, the aldehyde includes at least one of formaldehyde, furfural, glutaraldehyde, benzaldehyde, and acrolein. Formaldehyde can be synthesized with resorcinol to form resorcinol-formaldehyde aerogel, which is low-cost and has a mature process; furfural has high reactivity, contains a furan ring and an aldehyde group, and can participate in condensation reactions to form furfural-phenolic carbon aerogel 53, which has high specific surface area, good electrical conductivity, and thermal stability. Glutaraldehyde has a dialdehyde structure with a relatively long interval between the two aldehyde groups, which can form a more flexible cross-linked network; the benzene ring in benzaldehyde can enhance the thermal stability and mechanical strength of the aerogel; acrolein has high reactivity and can rapidly form a cross-linked network.

[0029] In one possible implementation of the first aspect, the crosslinking agent includes at least one of hexamethylenetetramine, melamine, urea, sulfuric acid, hydrochloric acid, and sodium hydroxide. Hexamethylenetetramine decomposes under acidic conditions to produce formaldehyde and ammonia, providing formaldehyde for the phenol-aldehyde condensation reaction and acting as a curing agent to promote the formation of a three-dimensional network. Melamine contains three active amino groups and reacts with formaldehyde to produce hydroxymethylmelamine; urea has moderate reactivity with formaldehyde, buffering the intensity of the phenol-aldehyde condensation reaction and making the curing process more stable. Sulfuric acid, hydrochloric acid, and sodium hydroxide are mainly used to adjust the pH of the reaction system to control the phenol-aldehyde condensation and crosslinking rates.

[0030] In one possible implementation of the first aspect, the molar ratio of phenols, aldehydes, ethanol and crosslinking agents is (10-16):(300-425):(100-150):1.

[0031] It should be noted that when the ratio of phenols to aldehydes is too high, i.e., too much phenol and too little aldehyde, linear or poorly cross-linked organic precursors are easily formed under acidic catalytic conditions. These precursors have a low degree of polymerization, and the molecular chain ends are mostly phenolic hydroxyl groups, making it difficult to spontaneously form a dense three-dimensional network. When the ratio of phenols to aldehydes is too low, i.e., too little phenol and too much aldehyde, the reaction is prone to violent reactions and local overheating, producing bubbles or heterogeneous networks and reducing pore order.

[0032] When the proportion of crosslinking agent is too small, it can easily lead to insufficient crosslinking and a loose network, affecting the strength and thermal stability of the final carbon aerogel. When the proportion of crosslinking agent is too large, it may cause localized rapid gelation, uneven structure, or even brittleness, thus destroying the uniformity of the pore structure.

[0033] Therefore, by controlling the molar ratio of phenols, aldehydes, ethanol, and crosslinking agents within a suitable range, it is possible to ensure that phenols and aldehydes react fully to form a dense three-dimensional network, and also to ensure the structural stability and porosity of the final carbon aerogel.

[0034] In one possible implementation of the first aspect, the method for drying the composite gel includes: placing the composite gel in carbon dioxide and keeping it in the carbon dioxide for a first preset time; the temperature of the carbon dioxide is 30°C to 70°C, the pressure of the carbon dioxide is 10 MPa to 12 MPa, and the first preset time is 3 h to 8 h.

[0035] By controlling the temperature of carbon dioxide at 30℃~70℃ and the pressure at 10MPa~12MPa for 3h~8h, carbon dioxide is brought into a stable supercritical state. Under these conditions, carbon dioxide possesses both near-liquid density and near-gas diffusion properties, effectively extracting organic solvents from the pores of organosols and fibrous gels. Simultaneously, because supercritical fluids lack a liquid-gas interface, the interfacial tension of the system approaches zero, thus avoiding capillary pressure damage to the three-dimensional framework structure of the gel during drying and ensuring the integrity of the composite material's nanoporous structure.

[0036] If the temperature or pressure of carbon dioxide is too low, it is difficult for carbon dioxide to remain stable in a supercritical state. A liquid-gas interface may form in the system, creating capillary stress, which can easily lead to gel skeleton shrinkage, pore structure collapse, and a decrease in specific surface area. If the temperature is above 70℃, although the diffusion rate of the system increases, the density of carbon dioxide decreases and its solubility weakens. In the case of silica-based gels that are aluminosilicate gels, excessively high temperatures may cause structural rearrangement of the aluminosilicate skeleton; excessively high temperatures may also cause thermal shrinkage of the carbon aerogel skeleton, leading to changes in pore size distribution and a decrease in microstructural stability.

[0037] If the pressure of carbon dioxide is too high, although it can further increase the density of carbon dioxide and the extraction capacity of organic solvents, excessive pressure may cause swelling or structural rearrangement of the gel skeleton, which is not conducive to maintaining the original pore structure.

[0038] By controlling the temperature, pressure, and first preset duration of carbon dioxide within the above range, the influence of capillary stress on the porous network structure can be significantly reduced while ensuring that the organic solvent in the pores is fully replaced. This results in obtaining silica-alumina aerogel and carbon aerogel with complete pore structure, high specific surface area, and stable morphology, which is to say, forming a composite aerogel with complete pore structure, high specific surface area, and stable morphology.

[0039] In one possible implementation of the first aspect, the method for carbonizing the composite material includes: placing the composite material in an inert gas and maintaining it in the inert gas for a second preset time; the temperature of the inert gas is 600℃~800℃, and the second preset time is 2h~5h.

[0040] It should be noted that when the temperature of the inert gas is too low, the organic sol cannot be fully carbonized, leaving behind a large amount of non-carbon elements (such as hydrogen, oxygen, and nitrogen), resulting in incomplete carbonization of the composite material. This leads to low graphitization, poor electrical and thermal conductivity, and weak mechanical strength. When the temperature of the inert gas is too high, it can easily cause structural collapse, microporous sintering, and a decrease in specific surface area. At the same time, Si-O-Si bond breakage may occur at high temperatures, leading to defects in the graphite structure.

[0041] If the second preset time is too short, even if the reaction temperature reaches the set value, if the time held at that temperature is insufficient, the pyrolysis reaction inside the organic gel will not proceed fully, leading to incomplete carbonization of the composite material. This results in a significant amount of volatile components and non-carbon elements remaining in the composite material, causing problems such as low specific surface area, poor electrical and thermal conductivity, and weak structural stability. If the second preset time is too long, it can easily lead to micropore sintering, pore wall thickening, or even collapse, resulting in a decrease in specific surface area.

[0042] Therefore, by reacting the composite material in an inert gas at a temperature of 600℃~800℃ for a second preset time, the composite material can be pyrolyzed and carbonized, so that the organic sol in the composite material can form carbon aerogel, ensuring that the organic sol can be completely carbonized, and ensuring the specific surface area, thermal conductivity and structural stability of the formed carbon aerogel.

[0043] The aforementioned drying process, combined with pyrolysis carbonization under inert gas, ensures the integrity of the composite aerogel's microstructure and its excellent thermal stability. Furthermore, the entire preparation process for the composite aerogel does not require high temperature or high pressure, significantly improving safety and economic efficiency.

[0044] In a second aspect, a composite aerogel is provided, comprising a fiber aerogel and a carbon aerogel. The fiber aerogel comprises a silica-based aerogel and a fiber matrix, wherein the silica-based aerogel fills the voids between the fibers of the fiber matrix; and / or, the silica-based aerogel coats the fiber surface. The carbon aerogel is disposed on at least one side surface of the fiber aerogel in the thickness direction.

[0045] Thirdly, a thermal management system is provided, comprising a composite aerogel and a cold plate, wherein the carbon aerogel in the composite aerogel is thermally connected to the cold plate. The composite aerogel is prepared by the method for preparing composite aerogel according to any of the technical solutions in the first aspect described above. The composite aerogel can also be the composite aerogel provided in the second aspect described above.

[0046] Understandably, the beneficial effects that the thermal management system described in the third aspect above can achieve can be referenced to the beneficial effects in the first aspect, the second aspect and any possible implementation thereof, which will not be repeated here.

[0047] Additionally, it should be noted that the thermally conductive connection between the carbon aerogel and the cold plate allows some of the heat from the carbon aerogel to be transferred to the cold plate, thereby cooling the carbon aerogel and ultimately the individual battery cells. The synergistic design of the composite aerogel and the cold plate balances mechanical strength, heat dissipation performance, thermal insulation performance, and thermal response speed, meeting the diverse operating requirements of batteries.

[0048] Fourthly, a battery is provided, the battery including a thermal management system and multiple battery cells, the thermal management system being the thermal management system provided in the third aspect above; the thermal management system includes a composite aerogel, the composite aerogel being disposed between two adjacent battery cells to achieve thermal insulation between the two adjacent battery cells.

[0049] Understandably, the beneficial effects that the battery described in the fourth aspect above can achieve can be referenced to the beneficial effects in the first aspect, the second aspect, the third aspect and any possible implementation thereof, which will not be repeated here. Attached Figure Description

[0050] Figure 1 This application provides schematic diagrams of the battery structure for some embodiments.

[0051] Figure 2 According to Figure 1 The exploded view of the battery shown;

[0052] Figure 3 A schematic diagram illustrating the preparation process of aerogels provided in some embodiments of this application;

[0053] Figure 4 This is a schematic diagram of the structure of the composite aerogel provided in some embodiments of this application;

[0054] Figure 5 The image shows a physical sample of the composite aerogel prepared in Example 1.

[0055] Figure 6 The image shows the microstructure of the composite aerogel prepared in Example 1 under a scanning electron microscope.

[0056] Figure 7 This is a schematic diagram showing the thermal conductivity of the composite aerogel prepared in Example 1 at different temperatures.

[0057] Figure 8 Temperature-time curves of batteries during charge-discharge cycles provided in some embodiments of this application;

[0058] Figure 9 Temperature-time curves of batteries provided in thermal runaway barrier tests for some embodiments of this application Figure 1 ;

[0059] Figure 10These are physical images of batteries after thermal runaway barrier tests provided in some embodiments of this application;

[0060] Figure 11 This is a schematic diagram of the microstructure of the composite aerogel prepared in Example 1 after undergoing a thermal runaway.

[0061] Figure 12 Temperature-time curves of batteries provided in thermal runaway barrier tests for some embodiments of this application Figure 2 .

[0062] Figure Labels

[0063] 100. Battery; 10. Battery cell; 101. First battery cell; 102. Second battery cell; 103. Third battery cell; 11. First tab; 12. Second tab; 2. Outer shell; 21. Side plate; 210. Through hole; 22. Base plate; 3. Thermal insulation material; 4. Thermal protection material; 40. Heat insulation board; 5. Composite aerogel; 50. Fiber aerogel; 52. Fiber matrix; 53. Carbon aerogel; 6. Cold plate; 7. Thermal management system. Detailed Implementation

[0064] Hereinafter, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this embodiment, unless otherwise stated, "a plurality of" means two or more.

[0065] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0066] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0067] To facilitate understanding, before providing a detailed description of the preparation method of the composite aerogel, the composite aerogel, the thermal management system, and the battery in the embodiments of this application, the relevant terms involved in the embodiments of this application will be explained first.

[0068] 1C charge / discharge: This means that the battery operates at a rate of fully charging or discharging its charge in 1 hour.

[0069] Supercritical drying is a technique that utilizes the properties of supercritical fluids to dry porous materials. This method controls pressure and temperature to bring the solvent to a supercritical state, eliminating the gas-liquid interface to prevent capillary forces from damaging the material structure. It is widely used in the preparation of nanoporous materials such as aerogels.

[0070] Molar ratio: A physical quantity that expresses the ratio of the amounts of different substances. For example, the molar ratio of silicon, ethanol, water, and aluminum refers to the ratio of the amounts of silicon-containing molecules, ethanol and water molecules, and aluminum-containing molecules. The amount of substance indicates the quantity of a substance and is counted in terms of quantity. If the substance is molecules, it refers to the number of molecules; if the substance is atoms, it refers to the number of atoms.

[0071] This application provides a battery, which may include lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., and this application is not limited to any particular type. The battery may be cylindrical, flat, cuboid, or other shapes, and this application is not limited to any particular shape. Batteries can be classified into cylindrical batteries, prismatic batteries, and pouch batteries according to their packaging method. The above-mentioned battery can be applied to transportation vehicles such as aircraft (e.g., electric aircraft), vehicles, and ships; or it can be applied to energy storage systems; or it can be applied to electronic devices such as laptops and power banks.

[0072] For ease of explanation, the following description uses lithium-ion batteries and their application in electric aircraft as examples, but this should not be construed as a limitation of this application.

[0073] Reference Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the structure of the battery 100 provided in some embodiments of this application; Figure 2 According to Figure 1 The exploded view of the battery 100 shown; the battery 100 includes a housing 2, a plurality of battery cells 10 and a thermal management system 7, the battery cells 10 and the thermal management system 7 being housed within the housing 2.

[0074] The battery cell 10 is the most basic energy storage unit, completing charging and discharging through internal electrochemical reactions. Multiple battery cells 10 are combined in series and parallel to form the battery 100, thereby meeting the voltage, capacity, and power requirements of electrical equipment. The thermal management system 7 is used for heat dissipation and insulation of the battery cells 10, ensuring that the battery cells 10 are within an efficient and safe operating temperature range, thus improving the battery 100's range and lifespan. The outer casing 2 serves as the external protective structure of the battery 100, enclosing the battery cells 10, thermal management system 7, and other components, isolating them from external impacts, moisture, dust, and other adverse factors, providing protection for the internal components.

[0075] Against the backdrop of the global acceleration towards a low-carbon energy system, batteries are becoming a major power source. Especially in the field of electric aviation, electric aircraft (especially electric vertical takeoff and landing aircraft) are approaching the stage of commercial application due to their significant advantages such as zero emissions, low noise, and high maneuverability.

[0076] Lithium-ion batteries, with their high specific energy, long cycle life, and excellent power characteristics, have become a core energy storage solution for electric propulsion systems. However, compared to ground applications, batteries in electric aircraft must withstand more extreme operating conditions, including frequent high-speed charging and discharging, drastic ambient temperature fluctuations, and highly integrated packaging structures. High integration refers not only to a compact spatial layout but also to the coordinated optimization of multiple systems in an electric aircraft. Electric aircraft can integrate traditionally separate components (such as motors, inverters, and battery management systems) into a shared housing or platform through System-in-Package (SiP) or similar technologies, reducing connection losses, increasing power density, and enhancing overall reliability.

[0077] The aforementioned factors all pose challenges to the thermal management system 7 of battery 100. When battery 100 operates at high power, heat rapidly accumulates inside the battery cells 10, forming a significant temperature gradient, which may lead to localized overheating or even thermal runaway (TR). During thermal runaway, the temperature of the battery cells 10 may instantly rise above 900°C, releasing a large amount of high-temperature flammable gas. This high-temperature flammable gas will spread throughout battery 100 within a short period of time (e.g., two, three, four, or five minutes), triggering a chain reaction of thermal runaway propagation events, posing a serious threat to the structural integrity and flight safety of the electric aircraft. Therefore, developing an advanced thermal management system 7 for battery 100 that can ensure efficient heat dissipation during rapid charging and discharging and suppress thermal runaway propagation under extreme conditions such as thermal runaway is crucial for achieving safe and reliable electric flight.

[0078] The thermal management system 7 includes a cold plate 6 and a thermal protection material 4. The cold plate 6 is thermally connected to the battery cell 10, allowing heat from the battery cell 10 to be transferred to the cold plate 6; in other words, the cold plate 6 dissipates heat from the battery cell 10. For example, the cold plate 6 can be a liquid cooling plate, which includes a metal substrate and a coolant. The metal substrate has flow channels for coolant circulation. The metal substrate is thermally connected to the battery cell 10, allowing heat generated by the battery cell 10 to be transferred to the metal substrate. The flowing coolant carries away the heat from the metal substrate, thus dissipating heat from the battery cell 10. Through holes 210 can be formed on the outer casing 2, communicating with the flow channels, allowing coolant to be transported into the flow channels through the through holes 210.

[0079] For example, the cold plate 6 can also be a direct-cooling plate, which achieves efficient cooling by absorbing heat through the internal refrigerant phase change (liquid to gas phase transition).

[0080] In some embodiments, refer to Figure 2 The cold plate 6 can be disposed between the battery cell 10 and the casing 2. The battery cell 10 includes a first tab 11 and a second tab 12, one of which is a positive tab and the other is a negative tab. The first tab 11 and the second tab 12 are located on the same side of the battery cell 10, and the cold plate 6 can be located on the side of the battery cell 10 opposite to the first tab 11.

[0081] Thermal protection material 4 can be disposed between two adjacent battery cells 10 to achieve thermal insulation between different battery cells 10. Aerogel is a nanoscale porous material with advantages such as low density, low thermal conductivity, high porosity, and high specific surface area, and is commonly used as thermal protection material 4 in the thermal management system 7. For example, a 2 mm thick aerogel insulating sheet can effectively suppress the thermal runaway propagation of a cylindrical battery 100 with a diameter of 18 mm and a length of 65 mm. However, although adding aerogel can improve the thermal insulation effect, its low thermal conductivity may affect the heat dissipation efficiency of the thermal management system 7 of the battery 100 under normal operating conditions.

[0082] Furthermore, traditional aerogels suffer from structural fragility and poor thermal conductivity at high temperatures, making it difficult to meet the comprehensive requirements of actual battery thermal protection materials 4 in terms of thermal conductivity and structural stability while ensuring thermal insulation performance.

[0083] Therefore, it is urgent to develop a thermal protection material 4 with stable structure, synergistic thermal insulation and thermal conduction functions, and thermal response characteristics, and apply it to battery 100 to improve the overall safety of battery 100.

[0084] To solve the above-mentioned technical problems, this application provides a method for preparing composite aerogel 5, referring to... Figure 3 , Figure 3This is a schematic diagram of the preparation process of aerogels provided in some embodiments of this application; the preparation method includes:

[0085] First, a fiber gel and an organosol are provided. The fiber gel includes a silicone-based gel and a fiber matrix 52. The silicone-based gel fills the gaps between the fibers of the fiber matrix 52; or, the silicone-based gel coats the fiber surface; or, the silicone-based gel both fills the gaps between the fibers of the fiber matrix 52 and coats the fiber surface.

[0086] Then, the organic sol is uniformly coated onto the outer surface of the fiber gel to obtain a composite gel. The coating method can be at least one of scraping or brushing.

[0087] Subsequently, the composite gel is dried to form a silicon-based aerogel and a fiber aerogel 50, thus obtaining the composite material. The fiber aerogel 50 includes a silicon-based aerogel. Silicon-based aerogels have low thermal conductivity and good insulation properties. The fiber matrix 52 in the fiber aerogel 50 provides a macroscopic support structure for the silicon-based aerogel, preventing it from becoming brittle, enhancing its processability and compressive strength, and improving the overall structural stability.

[0088] For example, the silicon-based aerogel can be a silica-alumina aerogel. Silica-alumina aerogels have a dense and complete Al-O-Si cross-linked network, which provides a high specific surface area and ultra-low thermal conductivity, enabling efficient thermal insulation. In other examples, the silicon-based aerogel can also be a silica aerogel, which also has a low thermal conductivity and good thermal insulation performance.

[0089] Finally, the composite material is carbonized to form carbon aerogel 53 from the organic sol, resulting in composite aerogel 5. The carbon aerogel 53 is located on the outer surface of the fiber aerogel 50. The carbon aerogel 53 has better high-temperature resistance, is less flammable, and has good thermal conductivity.

[0090] By coating the outer surface of the fiber gel with organic sol and then drying and carbonizing it, a unique dual-network structure can be constructed, achieving organic synergy between the carbon aerogel 53 network and the fiber aerogel 50 network.

[0091] In summary, fiber aerogel 50 exhibits low thermal conductivity, good thermal insulation performance, and structural stability; carbon aerogel 53 demonstrates better high-temperature resistance and thermal conductivity. Therefore, the composite aerogel 5 prepared by the above method not only possesses synergistic thermal insulation and thermal conductivity functions but also exhibits structural stability, making it suitable as a thermal protection material 4 in battery 100 to enhance the overall safety of battery 100. Furthermore, the above preparation method is simple, easy to operate, safe, reliable, and has low production costs, making it suitable for continuous and large-scale production.

[0092] When the composite aerogel 5 prepared by the above method is combined with the cold plate 6, a thermal management system 7 is constructed, wherein the carbon aerogel 53 in the composite aerogel 5 is thermally connected to the cold plate 6. This thermal management system 7 can exert excellent thermal safety performance in the battery 100. The thermal management system 7 not only possesses excellent thermal isolation and thermal conductivity regulation capabilities, but also effectively limits the temperature rise of the battery 100 during 1C charge-discharge processes, for example, controlling the temperature of the battery 100 below 35°C. Under extreme conditions such as thermal runaway, it can effectively block the propagation of thermal runaway, ensuring the safe and stable operation of the battery 100. Furthermore, the synergistic design of the composite aerogel 5 and the cold plate 6 takes into account mechanical strength, heat dissipation performance, thermal insulation performance, and thermal response speed, meeting the diverse operating requirements of the battery 100.

[0093] In some embodiments, the drying process described above for the composite gel may include atmospheric pressure drying and supercritical drying. Supercritical drying can avoid capillary forces from damaging the composite gel structure, which helps to obtain high-performance composite aerogels.

[0094] The method for supercritical drying of the composite gel includes: placing the composite gel in carbon dioxide and maintaining it in carbon dioxide for a first preset time; the temperature of the carbon dioxide is 30℃~70℃, the pressure of the carbon dioxide is 10MPa~12MPa, and the first preset time is 3 hours (h)~8 hours. Furthermore, the heating rate of the carbon dioxide to 30℃~70℃ is 1℃ / min~5℃ / min.

[0095] For example, the temperature of carbon dioxide can be 31℃, 32℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, or 70℃; the pressure of carbon dioxide can be 10MPa, 10.5MPa, 10.8MPa, 11MPa, 11.5MPa, 11.8MPa, or 12MPa; the first preset duration can be 3h, 4h, 5h, 6h, 7h, or 8h; and the heating rate can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, or 5℃ / min.

[0096] By controlling the temperature of carbon dioxide at 30℃~70℃ and the pressure at 10MPa~12MPa for 3h~8h, carbon dioxide is brought into a stable supercritical state. Under these conditions, carbon dioxide possesses both near-liquid density and near-gas diffusion properties, effectively extracting organic solvents from the pores of organosols and fibrous gels. Simultaneously, because supercritical fluids lack a liquid-gas interface, the interfacial tension of the system approaches zero, thus avoiding capillary pressure damage to the three-dimensional framework structure of the gel during drying and ensuring the integrity of the composite material's nanoporous structure.

[0097] If the temperature (e.g., below 30°C) or pressure (e.g., below 10 MPa) of carbon dioxide is too low, it is difficult for carbon dioxide to remain stable in a supercritical state. A liquid-gas interface may form in the system, creating capillary stress, which can easily lead to gel skeleton shrinkage, pore structure collapse, and a decrease in specific surface area. If the temperature is above 70°C, although the diffusion rate of the system increases, the density of carbon dioxide decreases and its solubility weakens. In the case of silica-based gels that are aluminosilicate gels, excessively high temperatures may cause structural rearrangement of the aluminosilicate skeleton; excessively high temperatures may also cause thermal shrinkage of the carbon aerogel 53 skeleton, leading to changes in pore size distribution and a decrease in microstructural stability.

[0098] If the pressure is too high (e.g., above 12 MPa), although the density of carbon dioxide and the extraction capacity of organic solvents can be further increased, the excessive pressure may cause swelling or structural rearrangement of the gel skeleton, which is not conducive to maintaining the original pore structure.

[0099] By controlling the temperature, pressure, and first preset duration of carbon dioxide within the above range, the influence of capillary stress on the porous network structure can be significantly reduced while ensuring that the organic solvent in the pores is fully replaced. This results in obtaining silica-alumina aerogel and carbon aerogel 53 with complete pore structure, high specific surface area, and stable morphology, which is to say, forming a composite aerogel 5 with complete pore structure, high specific surface area, and stable morphology.

[0100] In addition, carbon dioxide, as a supercritical drying medium, has critical conditions close to room temperature and pressure, which are far lower than the critical conditions of water (374℃, 22.1MPa). It can achieve a supercritical state at near room temperature, which greatly reduces energy consumption and equipment requirements.

[0101] For example, the equipment used for supercritical drying of the composite gel is a supercritical equipment. Since the formation process of carbon aerogel is relatively long, before placing the composite gel in the supercritical equipment for supercritical drying, it can be transferred to a sealed reaction vessel and aged at 70°C for 3 to 7 days (e.g., 3, 4, 5, 6, or 7 days). During this process, resorcinol and furfural undergo a condensation reaction under the action of hexamethylenetetramine, gradually forming a three-dimensional cross-linked network structure, transforming the system from a sol-state organic sol into a wet gel with a certain mechanical strength. This aging process promotes further cross-linking and structural homogenization of the gel network, improving the structural integrity and resistance to drying shrinkage of the wet gel.

[0102] It should be noted that when the composite gel is left to stand and age, it can be wrapped in plastic wrap to ensure a tight seal.

[0103] In some embodiments, the method for carbonizing the composite material described above includes: placing the composite material in an inert gas and maintaining it in the inert gas for a second preset time; the temperature of the inert gas is 600°C to 800°C, and the second preset time is 2 hours to 5 hours. For example, the temperature of the inert gas can be 600°C, 650°C, 700°C, 750°C, or 800°C; the second preset time can be 2 hours, 3 hours, 4 hours, or 5 hours. The inert gas may include at least one of argon, nitrogen, and helium.

[0104] It should be noted that when the temperature of the inert gas is too low (e.g., below 600℃), the organic sol cannot be fully carbonized, leaving behind a large amount of non-carbon elements (such as hydrogen, oxygen, and nitrogen), resulting in incomplete carbonization of the composite material. This leads to low graphitization, poor electrical and thermal conductivity, and weak mechanical strength. When the temperature of the inert gas is too high (e.g., above 800℃), it can easily cause structural collapse, microporous sintering, and a decrease in specific surface area. Simultaneously, high temperatures may cause Si-O-Si bond breakage, leading to defects in the graphite structure.

[0105] When the second preset time is too short (e.g., less than 2 hours), even if the reaction temperature reaches the set value, if the time held at that temperature is insufficient, the pyrolysis reaction inside the organic gel will not proceed fully. This will lead to incomplete carbonization of the composite material, leaving a large amount of volatile components and non-carbon elements (such as oxygen and hydrogen) in the composite material, resulting in problems such as low specific surface area, poor electrical and thermal conductivity, and weak structural stability. When the second preset time is too long (e.g., greater than 5 hours), it is easy to cause micropore sintering, pore wall thickening, or even collapse, leading to a decrease in specific surface area.

[0106] Therefore, by reacting the composite material in an inert gas at a temperature of 600℃~800℃ for a second preset time, the composite material can be pyrolyzed and carbonized, so that the organic sol in the composite material forms carbon aerogel 53, ensuring that the organic sol can be completely carbonized, and ensuring the specific surface area, thermal conductivity and structural stability of the formed carbon aerogel 53.

[0107] The aforementioned process of supercritical drying combined with pyrolysis carbonization under inert gas ensures the integrity of the microstructure and excellent thermal stability of the composite aerogel 5. Furthermore, the entire preparation process of the composite aerogel 5 does not require high temperature and high pressure, significantly improving safety and economic efficiency.

[0108] In some embodiments, the method for preparing the above-mentioned fiber gel includes: first, providing a silicon source, ethanol, water, an aluminum source, a pH adjuster, and a fiber matrix 52. For example, the ethanol can be anhydrous ethanol. Then, the silicon source, ethanol, water, and aluminum source are mixed to form a first mixture, and the pH adjuster is added to the first mixture to obtain a silica-alumina sol. Finally, the fiber matrix 52 is immersed in the silica-alumina sol to obtain the fiber gel. Ethanol, as a solvent and reaction medium, can adjust the viscosity of the organic sol and promote the uniform dispersion of the silica-alumina sol.

[0109] For example, after mixing silicon source, ethanol, water and aluminum source, stir for 1h to 3h (e.g. 1h, 2h or 3h) to make silicon source, ethanol, water and aluminum source mix evenly and react fully to obtain the first mixture.

[0110] The aforementioned pH adjuster can create an alkaline reaction environment, for example, by adjusting the pH of the first mixture to 6-7 (e.g., 6, 6.2, 6.4, 6.6, 6.8, or 7). Under this alkaline environment, on the one hand, it promotes further condensation reactions of the hydroxyl groups within the gel skeleton and facilitates the entry of Al into the Si-O-Si network, forming a denser and more complete Al-O-Si cross-linked network. On the other hand, the alkaline environment also promotes the condensation reaction between the monosilicic acid or disilicate generated by hydrolysis in the reaction system and the hydroxyl groups on the surface of the gel skeleton, forming a silicon shell structure in situ on the skeleton surface. This silicon shell structure helps enhance the structural stability and chemical resistance of the gel skeleton, improving the interfacial integrity and final product performance of the fibrous gel during subsequent processing.

[0111] In some embodiments, the silicon source includes at least one selected from tetraethyl orthosilicate, methyl orthosilicate, water glass, methyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, and phenyltriethoxysilane. The aluminum source includes at least one selected from aluminum nitrate, anhydrous aluminum chloride, aluminum chloride hexahydrate, polyaluminum chloride, aluminum isopropoxide, aluminum triethanolamine, and aluminum sulfate.

[0112] The aforementioned silicon and aluminum sources are prone to hydrolysis under the action of crosslinking agents. This facilitates the formation of an Al-O-Si crosslinked network and a silicon shell structure in the alkaline environment. Furthermore, the silicon source provides a SiO2 network framework, which determines the thermal stability and mechanical strength of the silicon-aluminum aerogel; the introduction of the aluminum source can improve the high-temperature resistance and chemical stability of the silicon-aluminum aerogel.

[0113] In some embodiments, the pH adjuster includes at least one selected from ammonia, sodium hydroxide, potassium hydroxide, triethanolamine, and urea. All of the above-mentioned pH adjusters can adjust the first mixture to an alkaline state, allowing the aluminum source and silicon source to react in an alkaline environment.

[0114] In some embodiments, the fiber matrix includes at least one selected from aluminosilicate fibers, glass fibers, mullite fibers, quartz fibers, pre-oxidized fiber mats, and basalt fiber mats. Using the above-mentioned materials as the fiber matrix of the fiber gel can provide a macroscopic support structure for the fiber gel, preventing the final fiber aerogel from becoming brittle and contributing to enhanced processability and compressive strength. Mullite fibers, in particular, possess high-temperature resistance, withstanding temperatures from 1400℃ to 1600℃. When combined with aerogel to form a fiber aerogel, it can reduce the thermal conductivity of the fiber aerogel, significantly inhibiting heat conduction.

[0115] In some embodiments, the molar ratio of silicon source, ethanol, water, and aluminum source is (50~160):(500~1250):(100~300):1. For example, the molar ratio of silicon source, ethanol, water, and aluminum source can be 150:1000:250:1, 100:1000:250:1, 100:1000:250:1, or 75:500:125:1.

[0116] It should be noted that a higher molar ratio of silicon to aluminum source in the first mixture indicates a higher molar concentration of silicon. Insufficient aluminum ion doping in the system causes the gelation process to tend towards the formation of isolated silicon-oxygen tetrahedra, resulting in a lower crosslinking density and a greater susceptibility to structural defects in the final silicon-aluminum aerogel. Conversely, a lower molar ratio of silicon to aluminum source in the first mixture indicates a higher molar concentration of aluminum, leading to higher crosslinking density, branching degree, and rigidity. However, the uniformity of the resulting Al-O-Si crosslinked network may decrease.

[0117] When the molar ratio of silicon source, ethanol, water and aluminum source is within a suitable range, aluminum moderately replaces silicon sites, which can maintain the stability of the Si-O-Si main chain, introduce charge imbalance through Si-O-Al bonds, enhance alkali-activated activity, promote the formation of dense network, and help reduce the thermal conductivity of silicon-aluminum aerosol.

[0118] In some embodiments, the method of immersing the fiber matrix 52 in a silica-alumina sol includes: rapidly pouring the silica-alumina sol into the fiber matrix 52, wherein the liquid level of the silica-alumina sol is slightly higher than the upper surface of the fiber matrix 52 to ensure that the internal pores of the fiber matrix 52 are completely filled by the silica-alumina sol, thereby obtaining a fiber gel. For example, the fiber matrix 52 can be a mullite fiber with an apparent density of 0.12 g / cm3 and dimensions of 150 mm × 150 mm × 2 mm.

[0119] It should be noted that after the silica-alumina sol is poured into the fiber matrix 52, it needs to be left to stand for no more than 5 hours (e.g., 1 hour, 2 hours, 4 hours or 5 hours) to ensure that the silica-alumina sol fills the gaps between the fibers of the fiber matrix 52 or covers the surface of the fibers.

[0120] In some embodiments, the method for preparing the above-mentioned organosol includes:

[0121] First, phenols, aldehydes, ethanol, and a crosslinking agent are provided; then, the phenols, aldehydes, and ethanol are mixed to form a second mixture, and the crosslinking agent is added to the second mixture to obtain an organosol. For example, the ethanol can be anhydrous ethanol.

[0122] The crosslinking agent slowly forms an alkaline environment under heating conditions. Phenols and aldehydes undergo aldehyde-phenol condensation reaction in the alkaline environment to form a three-dimensional crosslinked organosol network.

[0123] It should be noted that after the crosslinking agent is added to the second mixture, the entire mixture needs to react at 60℃~80℃ for 2h~5h. For example, the reaction temperature of the second mixture can be 60℃, 65℃, 70℃, 75℃ or 80℃, and the reaction time can be 2h, 3h, 4h or 5h.

[0124] It is understandable that when the reaction temperature is too low or the reaction time is too short, phenols and aldehydes cannot react fully, resulting in insufficient condensation. Consequently, the formed organic sol struggles to form a dense network during solidification, leading to low mechanical strength and easy cracking in the final carbon aerogel 53. When the reaction temperature is too high, the unreacted formaldehyde and moisture rapidly vaporize, forming bubbles or micropores within the organic sol. This can cause cracking and uneven shrinkage during subsequent drying into carbon aerogel 53. Excessive reaction time negatively impacts the preparation efficiency of the composite aerogel 5.

[0125] Therefore, by reacting the crosslinking agent and the second mixture at 60℃~80℃ for 2h~5h, the phenols and aldehydes can be fully reacted to form a dense organic gel network, ensuring the mechanical strength of the final carbon aerogel 53 and avoiding any impact on the preparation efficiency of the composite aerogel 5.

[0126] In some embodiments, phenols include at least one of phenol, resorcinol, catechol, and hydroquinone. Resorcinol has two hydroxyl groups in the meta position, resulting in less steric hindrance and making it readily react with formaldehyde through hydroxymethylation and condensation reactions; phenol is inexpensive and widely available; catechol's ortho-diol structure exhibits strong reducing and coordinating abilities, making it suitable for preparing conductive aerogels; hydroquinone possesses stable structural units, and its symmetrical structure facilitates the formation of a regular network, making it suitable for preparing thermally stable aerogels.

[0127] In some embodiments, the aldehydes include at least one selected from formaldehyde, furfural, glutaraldehyde, benzaldehyde, and acrolein. Formaldehyde can be synthesized with resorcinol to form resorcinol-formaldehyde aerogel, which is low-cost and has a mature process. Furfural has high reactivity, contains a furan ring and an aldehyde group, and can participate in condensation reactions to form furfural-phenolic carbon aerogel 53, which has high specific surface area, good electrical conductivity, and thermal stability. Glutaraldehyde has a dialdehyde structure with a relatively long interval between the two aldehyde groups, which can form a more flexible cross-linked network. The benzene ring in benzaldehyde can enhance the thermal stability and mechanical strength of the aerogel. Acrolein has high reactivity and can rapidly form a cross-linked network.

[0128] In some embodiments, the crosslinking agent includes at least one selected from hexamethylenetetramine, melamine, urea, sulfuric acid, hydrochloric acid, and sodium hydroxide. Hexamethylenetetramine is used under acidic conditions (such as H₂O₂). + Catalysis can decompose urea into formaldehyde and ammonia, providing formaldehyde for the phenol-aldehyde condensation reaction and acting as a curing agent to promote the formation of three-dimensional networks. Melamine contains three active amino groups and can react with formaldehyde to form hydroxymethyl melamine; urea has moderate reactivity with formaldehyde, which can buffer the intensity of the phenol-aldehyde condensation reaction, making the curing process more stable. Sulfuric acid, hydrochloric acid, and sodium hydroxide are mainly used to adjust the pH value of the reaction system to control the phenol-aldehyde condensation and crosslinking rates.

[0129] In some embodiments, the molar ratio of phenols, aldehydes, ethanol, and crosslinking agents is (10-16):(300-425):(100-150):1. For example, the molar ratio of phenols, aldehydes, ethanol, and crosslinking agents can be 10:300:100:1, 10:400:100:1, 15:400:150:1, or 16:425:150:1.

[0130] It should be noted that when the ratio of phenols to aldehydes is too high, i.e., too much phenol and too little aldehyde, linear or poorly cross-linked organic precursors are easily formed under acidic catalytic conditions. These precursors have a low degree of polymerization, and the molecular chain ends are mostly phenolic hydroxyl groups, making it difficult to spontaneously form a dense three-dimensional network. When the ratio of phenols to aldehydes is too low, i.e., too little phenol and too much aldehyde, the reaction is prone to violent reactions and local overheating, producing bubbles or heterogeneous networks and reducing pore order.

[0131] When the proportion of crosslinking agent is too small, it can easily lead to insufficient crosslinking and a loose network, affecting the strength and thermal stability of the final carbon aerogel 53. When the proportion of crosslinking agent is too large, it may cause localized rapid gelation, uneven structure, or even brittleness, thus destroying the uniformity of the pore structure.

[0132] Therefore, by controlling the molar ratio of phenols, aldehydes, ethanol and crosslinking agents within a suitable range, it is possible to ensure that phenols and aldehydes react fully to form a dense three-dimensional network, and also to ensure the structural stability and porosity of the final carbon aerogel 53.

[0133] Reference Figure 4 , Figure 4 This is a schematic diagram of the structure of a composite aerogel 5 provided in some embodiments of this application; this application also provides a composite aerogel 5, which includes a fiber aerogel 50 and a carbon aerogel 53. (Combined with...) Figure 6 , Figure 6 The image shows the microstructure of the composite aerogel 5 prepared in Example 1 under a scanning electron microscope; wherein, Figure 6 (b) shows the layered structure of carbon aerogel 53 and fiber aerogel 50. Figure 6 (a) shows the microstructure of fiber aerogel 50; Figure 6 Image (c) shows the microstructure of carbon aerogel 53. Fiber aerogel 50 includes a silicon-based aerogel and a fiber matrix 52. The silicon-based aerogel fills the gaps between the fibers of the fiber matrix; or, the silicon-based aerogel coats the fiber surface; or, the silicon-based aerogel both fills the gaps between the fibers of the fiber matrix 52 and coats the fiber surface.

[0134] For example, the silicon-based aerogel can be a silicon-aluminum aerogel. The introduction of aluminum into the silicon-aluminum aerogel can improve the high-temperature resistance and chemical stability of the composite aerogel 5.

[0135] Carbon aerogel 53 is disposed on at least one surface of the fiber aerogel 50 in the thickness direction. For example, carbon aerogel 53 is disposed on one surface of the fiber aerogel 50 in the thickness direction; or, carbon aerogel 53 is disposed on opposite two surfaces of the fiber aerogel 50 in the thickness direction. The composite aerogel 5 may be plate-shaped, with carbon aerogel 53 and fiber aerogel 50 stacked in the thickness direction.

[0136] Reference Figure 4 When carbon aerogel 53 is disposed on opposite sides of the fiber aerogel 50 in the thickness direction, carbon aerogel 53 can be two layers, with fiber aerogel 50 sandwiched between the two layers of carbon aerogel 53.

[0137] The composite aerogel 5 can be prepared by the preparation method of the composite aerogel 5 in any of the above embodiments. Of course, in some other embodiments, the composite aerogel 5 can also be prepared by other preparation methods.

[0138] It should be noted that, Figure 4 The dimensions of the composite aerogel 5 shown are only illustrative. The dimensions (including length, width and thickness) of the carbon aerogel 53 and the fiber aerogel 50 are designed according to actual needs. This application does not limit the dimensions of the composite aerogel 5.

[0139] In some embodiments, combined with Figure 2 The composite aerogel 5 can be combined with the cold plate 6 to construct a thermal management system 7. The composite aerogel 5 is disposed between two adjacent battery cells 10, and the carbon aerogel 53 in the composite aerogel 5 is thermally connected to the battery cell 10 (e.g., the carbon aerogel 53 conducts heat through contact with the battery cell 10). The heat emitted by the battery cell 10 can be transferred to the carbon aerogel 53. The composite aerogel 5 is arranged at an angle to the cold plate 6 (e.g., perpendicular), and the carbon aerogel 53 in the composite aerogel 5 is thermally connected to the cold plate 6. The heat on the carbon aerogel 53 can be transferred to the cold plate 6. The carbon aerogel 53 can achieve the function of heat conduction between the battery cell 10 and the cold plate 6, realizing heat dissipation for the battery cell 10 and reducing the risk of thermal runaway in the battery cell 10.

[0140] In addition, the composite aerogel 5 also has good thermal insulation performance. In particular, the fiber aerogel 50 in the composite aerogel 5 has a low thermal conductivity and good thermal insulation performance. It also has strong thermal stability and mechanical strength. Under extreme conditions such as thermal runaway, it can effectively block the spread of thermal runaway, that is, prevent the thermal runaway of a single battery cell 10 from spreading to other battery cells 10. This helps to suppress the spread of thermal runaway and has a fast thermal response speed, which can further ensure the thermal safety performance of the battery 100.

[0141] In some embodiments, the material of the cold plate 6 includes at least one of copper, aluminum, and stainless steel to ensure the thermal conductivity of the cold plate 6. The temperature of the cold plate 6 is 10°C to 25°C, which can effectively dissipate heat from the battery cell 10 and the carbon aerogel 53. For example, the temperature of the cold plate 6 can be 10°C, 12°C, 14°C, 16°C, 18°C, 20°C, 22°C, 24°C, or 25°C. The temperature of the cold plate 6 can be adjusted by controlling the temperature of the fluid inside the cold plate 6.

[0142] Therefore, coupling the composite aerogel 5 with the cold plate 6 to form the thermal management system 7 of the battery 100 can achieve excellent thermal safety performance in the battery 100. Furthermore, this thermal management system 7 possesses excellent thermal isolation and thermal conductivity regulation capabilities, effectively limiting temperature rise during 1C charge / discharge of the battery 100. For example, it can control the temperature of the battery 100 below 35°C, effectively preventing the spread of thermal runaway and ensuring the safe and stable operation of the battery 100. In addition, the synergistic design of the composite aerogel 5 and the cold plate 6 balances mechanical strength and heat dissipation performance, meeting the diverse operating requirements of the battery 100.

[0143] This application provides Example 1, which is one embodiment of the above-described method for preparing composite aerogel 5. The preparation steps are as follows:

[0144] First, a silica-alumina sol was prepared. Tetraethyl orthosilicate, anhydrous ethanol, water, and aluminum chloride hexahydrate were mixed in a molar ratio of 150:1000:250:1 to form the first mixture, which was then stirred for 60 minutes to promote hydrolysis. 0.5 mol / L ammonia was added to the first mixture to adjust the pH to 6-7, resulting in a uniform and transparent silica-alumina sol.

[0145] Then, the fiber matrix 52 is immersed in the silica-alumina sol. The silica-alumina sol obtained above is quickly poured into the mullite fiber body above, with the liquid level of the silica-alumina sol slightly higher than the upper surface of the mullite fiber body, to ensure that the internal pores of the mullite fiber body are completely filled by the silica-alumina sol, and the fiber gel body is obtained by impregnation.

[0146] Next, a composite gel was prepared. Resorcinol, furfural, anhydrous ethanol, and hexamethylenetetramine were mixed in a molar ratio of 10:300:100:1 to form a second mixture, which was stirred in a water bath at 70°C for 3-4 hours to form an organosol. The obtained organosol was then uniformly brushed onto both sides of the above-mentioned fiber gel in the thickness direction to form a composite gel.

[0147] Finally, the composite gel was left to stand for 24 hours to allow it to age. After aging, it was placed in a supercritical fluid generator for supercritical drying to obtain the composite material. The supercritical drying conditions can be referred to the conditions described above and will not be repeated here. The obtained composite material was then pyrolyzed at 600℃ under an argon atmosphere for 2 hours to obtain composite aerogel 5.

[0148] It should be noted that the preparation steps of the composite aerogel 5 in Example 1 are merely exemplary and do not represent a limitation of this application.

[0149] See Figure 5 , Figure 5 A photograph of the composite aerogel 5 prepared in Example 1; Figure 5Images (a) and (b) show composite aerogel 5 from different perspectives. Figure 5 As can be seen, the surface of composite aerogel 5 is relatively smooth, with a relatively obvious sandwich structure, high integrity, and no obvious defects.

[0150] See Figure 6 ,from Figure 6 As can be seen in (a), the silica-alumina aerogel is uniformly filled in the fiber matrix 52 (mullite fiber), which is beneficial for suppressing gaseous heat conduction. At the same time, the nano-sized silica-alumina aerogel is tightly bonded to the surface of the micron-sized mullite fiber, exhibiting good interfacial compatibility. This multi-scale structural composite strategy expands the stress absorption mechanism, thereby improving the mechanical properties of the composite aerogel 5.

[0151] See Figure 7 , Figure 7 This is a schematic diagram showing the thermal conductivity of the composite aerogel 5 prepared in Example 1 at different temperatures; the horizontal axis represents temperature in degrees Celsius (°C); the vertical axis represents thermal conductivity in W / m·K. Figure 7 As can be seen, the composite aerogel 5 has a thermal conductivity of 0.024 W / m·K at 100℃, exhibiting excellent thermal insulation performance.

[0152] Combination Figure 2 and Figure 4 The composite aerogel 5 is fabricated into two heat insulation plates 40. Each heat insulation plate 40 includes stacked carbon aerogel 53 and fiber aerogel 50, with the carbon aerogel 53 located on opposite sides of the fiber aerogel 50 in the thickness direction. The two heat insulation plates 40 are placed vertically on a copper-based cold plate 6 (e.g., a water-cooled plate), so that the carbon aerogel 53 is in contact with the cold plate 6, forming a thermal safety management system. For example, the heat insulation plate 40 has a length of 148 mm, a width of 96 mm, and a thickness of 2 mm.

[0153] The thermal safety management system is then applied to battery 100, as per [reference]. Figure 2 The battery 100 includes three battery cells 10, namely a first battery cell 101, a second battery cell 102, and a third battery cell 103. The outer casing 2 includes multiple side plates 21 and a bottom plate 22, with the side plates 21 connected to the bottom plate 22 and arranged circumferentially along the bottom plate 22. Thermal insulation material 3 is provided between the battery cells 10 and the side plates 21, and a cooling plate 6 is provided between the battery cells 10 and the bottom plate 22. Composite aerogel 5 is disposed between adjacent battery cells 10. The battery cell 10 is a power ternary lithium battery cell 10 with a capacity of 58 ampere-hours (Ah). For example, the battery 100 has a length of 204 mm, a width of 180 mm, and a thickness of 110 mm, with the three battery cells 10 arranged along the length of the battery 100.

[0154] The battery 100 was subjected to charge-discharge cycles and thermal runaway prevention tests. It should be noted that the thermal runaway prevention test is a key safety test to evaluate whether the thermal management system 7 of the battery 100 can effectively prevent the spread of heat and flame to adjacent battery cells 10 when thermal runaway occurs in a single battery cell 10.

[0155] See Figure 8 and combined Figure 2 and Figure 5 , Figure 8 Temperature-time curves of a battery 100 during charge-discharge cycles are shown in some embodiments of this application; wherein the thermal management system 7 in the battery 100 is formed by coupling the composite aerogel 5 prepared in Embodiment 1 with a cold plate 6. The temperature at three different points on the outer surface of the battery cell 10 of the battery 100 is measured. Figure 8 As can be seen, under constant current charging, constant voltage charging, constant current discharging, and static conditions, the temperatures at points T1, T2, and T3 are all controlled between 15℃ and 35℃. Therefore, it can be concluded that during multiple charge-discharge cycles of battery 100, the temperature of each battery cell 10 is controlled between 15℃ and 35℃, failing to reach the thermal runaway temperature, effectively reducing the risk of thermal runaway in battery 100. This thermal management system 7 exhibits superior heat dissipation and temperature control performance.

[0156] See Figure 9 and Figure 10 and combined Figure 2 , Figure 9 Temperature-time curves of battery 100 provided in some embodiments of this application during thermal runaway barrier tests Figure 1 ; Figure 10 The images show physical models of the battery 100 provided in some embodiments of this application after undergoing a thermal runaway barrier test; wherein, the thermal management system 7 in the battery 100 is formed by coupling the composite aerogel 5 prepared in Embodiment 1 with a cold plate 6. Temperature was measured at three points on each of the first battery cell 101, the second battery cell 102, and the third battery cell 103, i.e. Figure 9 The first battery cell 101 has three temperature-time curves, the second battery cell 102 has three temperature-time curves, and the third battery cell 103 has three temperature-time curves.

[0157] from Figure 9As can be seen, when the first battery cell 101 experiences thermal runaway (reaching a maximum temperature of 684.1℃), the temperature of the second battery cell 102 reaches 250℃, and then quickly decreases, indicating that the thermal management system 7 has a good heat dissipation and temperature control effect, preventing the second battery cell 102 from experiencing thermal runaway; the third battery cell 103 always maintains a low temperature, and its temperature is not affected by the thermal runaway of the first battery cell 101, indicating that the composite aerogel 5 has a significant heat insulation effect.

[0158] Figure 10 The middle section consists of a first battery cell 101, a second battery cell 102, a third battery cell 103, and two heat insulation plates 40 (made of the aforementioned composite aerogel 5). Figure 10 As can be seen, after the first battery cell 101 experiences thermal runaway, the impact on the second battery cell 102 is minimal, and the third battery cell 103 is unaffected. All of this demonstrates that the thermal management system 7 effectively blocks the propagation of thermal runaway.

[0159] See Figure 11 , Figure 11 This is a schematic diagram of the microstructure of the composite aerogel 5 prepared in Example 1 after undergoing one thermal runaway; from Figure 11 As can be seen from the data, the composite aerogel 5 still maintains a relatively obvious porous structure, which proves its excellent thermal stability.

[0160] This application also provides Example 2, which is prepared in a manner largely the same as that in Example 1, except that the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, water, and aluminum chloride hexahydrate is 75:500:125:1. The effects achieved by the preparation method in Example 2 and the beneficial effects of the resulting composite aerogel 5 are the same as those in Example 1, and will not be repeated here.

[0161] This application also provides Example 3, which is prepared in a manner similar to that in Example 1, except that: in Example 3, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, water and aluminum chloride hexahydrate is 75:500:125:1; and in Example 3, the fiber matrix 52 is glass fiber with an apparent density of 0.15 g / cm3 and a size of 150 mm × 150 mm × 2 mm.

[0162] The effects achieved by the preparation method in Example 3 and the beneficial effects of the resulting composite aerogel 5 are the same as those in Example 1, and will not be repeated here.

[0163] This application also provides a comparative example, which uses the same preparation method as in Example 1, except that the composite aerogel 5 in the comparative example is not coupled to the cold plate 6, that is, the thermal management system 7 of the battery 100 does not include the cold plate 6. The thermal management system 7 is applied to the battery 100, and the battery 100 is subjected to thermal runaway prevention tests.

[0164] Test results reference Figure 12 , Figure 12 Temperature-time curves of battery 100 provided in some embodiments of this application during thermal runaway barrier tests Figure 2 ;and Figure 9 Similarly, three temperature points were measured on each of the first battery cell 101, the second battery cell 102, and the third battery cell 103. The test results showed that when the first battery cell 101 experienced thermal runaway (reaching a maximum temperature of 914℃), the temperature of the second battery cell 102 was below 250℃, and the temperature of the third battery cell 103 was below 40℃. However, after a period of time, the second battery cell 102 also experienced thermal runaway (reaching a maximum temperature exceeding 700℃), and the temperature of the third battery cell 103 rose to above 350℃. After another period of time, the third battery cell 103 also experienced thermal runaway, reaching a maximum temperature of 800℃.

[0165] Therefore, placing the composite aerogel 5 between two adjacent battery cells 10 can delay the propagation of thermal runaway due to the excellent thermal insulation properties of the composite aerogel 5. However, since there is no cold plate 6 inside the battery 100 to dissipate heat from the battery cells 10, it does not block the propagation of thermal runaway within the battery 100.

[0166] In summary, the thermal management system 7 obtained by coupling the composite aerogel 5 and the cold plate 6 in the embodiments of this application has excellent heat dissipation performance, temperature control performance and thermal insulation performance. Under extreme conditions such as thermal runaway, it can effectively suppress the propagation of thermal runaway and improve the safety of the battery 100.

[0167] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a composite aerogel, characterized in that, include: A fiber gel and an organosol are provided, the fiber gel comprising an aluminosilicate gel and a fiber matrix, the aluminosilicate gel filling the voids between the fibers of the fiber matrix; and / or, the aluminosilicate gel coating the surface of the fiber. The organic sol is coated onto the outer surface of the fiber gel to obtain a composite gel. The composite gel is dried to form a silica-alumina aerogel, thus obtaining the composite material. The composite material is subjected to carbonization treatment to form a carbon aerogel from the organic sol, thereby obtaining the composite aerogel.

2. The method according to claim 1, characterized in that, The method for preparing the fibrous gel includes: It provides silicon sources, ethanol, water, aluminum sources, pH adjusters, and fiber matrices; The silicon source, ethanol, water and aluminum source are mixed to form a first mixture, and the pH adjuster is added to the first mixture to obtain a silica-alumina sol. The fiber matrix is ​​immersed in the silica-alumina sol to obtain the fiber gel. And / or, the method for preparing the organosol includes: It provides phenols, aldehydes, ethanol, and crosslinking agents; The phenols, aldehydes, and ethanol are mixed to form a second mixture, and the crosslinking agent is added to the second mixture to obtain the organosol.

3. The method according to claim 2, characterized in that, The silicon source, the aluminum source, the pH adjuster, and the fiber matrix satisfy at least one of the following conditions: (1) The silicon source includes at least one of tetraethyl orthosilicate, methyl orthosilicate, water glass, methyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane and phenyltriethoxysilane; (2) The aluminum source includes at least one of aluminum nitrate, anhydrous aluminum chloride, aluminum chloride hexahydrate, polyaluminum chloride, aluminum isopropoxide, aluminum triethanolamine, and aluminum sulfate; (3) The pH adjuster includes at least one of ammonia, sodium hydroxide, potassium hydroxide, triethanolamine and urea; (4) The fiber matrix includes at least one of aluminum silicate fiber, glass fiber, mullite fiber, quartz fiber, pre-oxidized fiber felt and basalt fiber felt.

4. The method according to claim 2, characterized in that, The molar ratio of the silicon source, ethanol, water and the aluminum source is (50~160):(500~1250):(100~300):

1.

5. The method according to claim 2, characterized in that, The phenols, the aldehydes, and the crosslinking agents satisfy at least one of the following conditions: (1) The phenols include at least one of phenol, resorcinol, catechol and hydroquinone; (2) The aldehydes include at least one of formaldehyde, furfural, glutaraldehyde, benzaldehyde and acrolein; (3) The crosslinking agent includes at least one of hexamethylenetetramine, melamine, and urea.

6. The method according to any one of claims 1-5, characterized in that, The method for drying the composite gel includes: The composite gel is placed in carbon dioxide and kept in the carbon dioxide for a first preset time; the temperature of the carbon dioxide is 31℃~70℃, the pressure of the carbon dioxide is 10MPa~12MPa, and the first preset time is 3h~8h. And / or, the method for carbonizing the composite material includes: The composite material is placed in an inert gas and kept in the inert gas for a second preset time; the temperature of the inert gas is 600℃~800℃, and the second preset time is 2h~5h.

7. A composite aerogel, characterized in that, include: A fiber aerogel, comprising aluminosilicate aerogel and a fiber matrix, wherein the aluminosilicate aerogel fills the voids between the fibers of the fiber matrix; And / or, the silica-alumina aerogel coats the fiber surface; Carbon aerogel, wherein the carbon aerogel is stacked on at least one side surface of the fiber aerogel in the thickness direction.

8. A thermal management system, characterized in that, include: The composite aerogel is prepared by the method for preparing the composite aerogel according to any one of claims 1-6; and / or, the composite aerogel is the composite aerogel according to claim 7. A cold plate, wherein the carbon aerogel is thermally connected to the cold plate.

9. A battery, characterized in that, include: The thermal management system is the thermal management system as described in claim 8; Multiple battery cells, wherein the composite aerogel is disposed between two adjacent battery cells.

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