A battery thermal insulation material with multi-level micropore synergistic regulation, its preparation method and its application

Abstract

This invention belongs to the field of thermal protection technology, and relates to a battery thermal insulation material with multi-level microporous synergistic regulation, its preparation method, and its application. The preparation method includes: dispersing modified active fibers in an aqueous slurry containing nano-ceramic powder to obtain nano-ceramic-coated reinforcing fibers; mixing the nano-ceramic-coated reinforcing fibers with large-size aerogel microspheres, micron-sized hollow microspheres, and an infrared shielding agent at low speed in a planetary mixer; then adding small-size aerogel microspheres and a binder solution, and mixing at high speed to form a paste-like mixture; transferring the paste-like mixture to a mold for multi-level molding; and after demolding, undergoing a secondary curing treatment by heating. This invention constructs a multi-level structure through multi-level aerogel gradient mixing and gradient molding processes, achieving integrated performance of ultra-low thermal conductivity, wide temperature range high temperature resistance, high compression resilience, and impact resistance in the thermal insulation material.

Description

Technical Field

[0001] This invention belongs to the field of thermal protection technology, and relates to a battery thermal insulation material with multi-level micropore synergistic regulation, its preparation method and its application. Background Technology

[0002] As the energy density requirements of electric vehicles and energy storage power stations continue to increase, the thermal safety issues of lithium-ion power batteries are becoming increasingly prominent. When a battery cell experiences thermal runaway due to overcharging, short circuits, or mechanical abuse, it releases a large amount of heat in a very short time, forming high-temperature jet flames and shock waves with temperatures exceeding 1000°C, which rapidly spread to adjacent cells, triggering a catastrophic chain reaction. GB38031-2025 sets stringent requirements for battery systems to be "non-flammable and non-explosive," posing unprecedented challenges to passive protection materials for thermal runaway.

[0003] Current mainstream battery thermal insulation solutions typically consist of a combination of materials, including mica sheets, aerogel felt, fire-retardant foam, and fire-retardant coatings. However, this combination approach has the following drawbacks: 1. Limited functionality and bloated system: While mica sheets are heat-resistant, their high density and brittleness make them prone to breakage under vibration or impact; foam, while able to cushion cell expansion, has poor temperature resistance (typically <350℃) and is prone to decomposition and failure at high temperatures; aerogel felt, while having low thermal conductivity, has low mechanical strength and is prone to powder shedding and collapse, making it unsuitable as a standalone structural support. The combination of multiple materials results in a bulky and heavy protection system, encroaching on battery mounting space and reducing system energy density.

[0004] 2. Limited ability to suppress thermal runaway: In real-world thermal runaway scenarios, the joints and performance weaknesses of traditional composite materials are highly susceptible to becoming entry points for heat and flames. Experiments show that existing composite protection solutions typically only suppress the spread of thermal runaway for a few seconds to a dozen seconds, far from sufficient to trigger an active fire suppression system or provide occupants with escape time.

[0005] 3. Poor process compatibility: The multi-material assembly process is complex and has a low degree of automation, which increases the manufacturing cost and quality control difficulty of battery packs.

[0006] In recent years, aerogel-based composite materials have attracted much attention due to their excellent thermal insulation potential. For example, Chinese patent CN202410054315.8 provides a buffer space by creating cavities in the aerogel layer; CN202010962539.0 solves the dust shedding problem by generating aerogel in situ in fiber felt using the sol-gel method and coating it with an encapsulation coating. However, existing technologies generally focus on optimizing single properties (such as thermal conductivity or dust shedding rate), failing to address how materials can achieve controllable compression to absorb cell expansion stress and maintain structural integrity against high-temperature jet impacts while maintaining ultra-low thermal conductivity and ultra-high temperature resistance under extreme thermo-coupling conditions. The core scientific problem behind this is that traditional preparation processes struggle to precisely control the "multi-level micropore-multiphase interface" structure between the fiber skeleton, aerogel nanopores, and micron-scale functional fillers at the micro-nano scale, resulting in a lack of synergistic balance between lightweight, thermal insulation, mechanical properties, and temperature resistance.

[0007] Therefore, developing a new type of heat insulation material that can overcome the above-mentioned performance barriers and achieve "multi-effect of one material" is of great significance for improving the safety and energy density of power battery systems. Summary of the Invention

[0008] To address the aforementioned problems in the prior art, the present invention aims to provide a battery thermal insulation material with multi-level micropore synergistic control, its preparation method, and its application, thereby overcoming the shortcomings of the prior art.

[0009] The present invention employs the following technical solutions to achieve its objective: The first aspect of this invention provides a method for preparing a battery thermal insulation material with multi-level micropore synergistic regulation, comprising the following steps: S1. The fiber is subjected to plasma activation and surface grafting of silane coupling agent to obtain modified active fiber; S2. The modified active fiber is dispersed in an aqueous slurry containing nano-ceramic powder, and the reaction is carried out to obtain nano-ceramic coated reinforcing fiber. S3. The nano-ceramic-coated reinforcing fibers are mixed with large-sized aerogel microspheres, micron-sized hollow microspheres, and infrared opacifiers at low speed in a planetary mixer. The revolution speed of the low-speed mixing is 10-20 rpm and the rotation speed is 100-300 rpm. Then, small-sized aerogel microspheres and binder solution are added and mixed at high speed. The revolution speed of the high-speed mixing is 30-50 rpm and the rotation speed is 800-1500 rpm, forming a paste-like mixture. S4. Transfer the paste mixture to the mold and perform multi-stage molding, which includes three molding stages. S5. After demolding, heat for secondary curing. The small-sized aerogel microspheres have a D50 particle size of 5~30μm, and the large-sized aerogel microspheres have a D50 particle size of 50~200μm.

[0010] The D50 particle size was determined using laser diffraction with a Malvern MS2000 laser particle size analyzer, in accordance with ISO 13320 standards. After testing, the instrument generates a complete cumulative particle size distribution curve. The particle size on the x-axis corresponding to 50% of the cumulative distribution on the curve is the D50 particle size.

[0011] This invention employs a composite of small-sized and large-sized aerogel microspheres, forming a flexible "nanoporous-porous" contact between the large and small spheres. Each time heat flows across the interface, it undergoes a transformation from a high-density aerogel framework to air and back to that framework, generating significant contact thermal resistance (similar to a series thermal resistance circuit). The large spheres form the main framework, with the small spheres filling the gaps, creating a chain-like high-resistance heat flow path of "large-small-large". The large aerogel spheres produce Mie scattering (directional scattering) of infrared light, while the small spheres produce Rayleigh scattering (isotropic scattering). After composite application, light undergoes long-range scattering between the large spheres and is randomly redirected by the small spheres, forming a three-dimensional light trap, significantly extending the radiation path and effectively increasing the concentration of the light-blocking agent. Stacking single-sized aerogel microspheres creates micron-sized macropores, allowing air to flow freely. However, when microspheres one to two orders of magnitude smaller are added, the smaller microspheres are precisely embedded in the gaps between the larger microspheres, dividing the macropores into nano-sized (<50nm) pores. When the pores are smaller than the mean free path of air molecules (~70nm), the air molecules are "trapped," and thermal convection almost completely stops, producing the classic Knudsen effect.

[0012] However, using micron-sized hollow microspheres or infrared shading agents cannot achieve the same heat insulation gain. This is due to the uniqueness of aerogel microspheres in terms of nanopore structure and optical scattering properties, which is an effect that single-sized aerogel powder cannot achieve.

[0013] Furthermore, during the preparation process, large-sized aerogel microspheres are first mixed at low speed to build a large particle framework network, and then small microspheres are uniformly filled into the pores at high speed, thereby ensuring the uniformity of the multi-level porous structure.

[0014] Preferably, the raw materials for preparing the battery heat insulation material, by weight, include: Fiber: 5-25 parts; Silane coupling agent: 0.5-5 parts; Nano-ceramic powder: 5-20 parts; Small-sized aerogel microspheres: 15-30 parts Large-sized aerogel microspheres: 15-30 parts; Micron-sized hollow microspheres: 5-15 parts; Infrared shielding agent: 3-10 parts; Adhesive solution, based on solid content: 1 to 8 parts.

[0015] The total weight of the above components is not limited to 100 parts; each component should be weighed and used according to the actual proportions.

[0016] Preferably, the fiber is a high-temperature resistant fiber, selected from one or more of the following: high-silica fibers with SiO2 content ≥96%, alumina fibers, zirconium oxide fibers, silicon carbide fibers, mullite fibers, aluminum silicate fibers, potassium hexatitanate fibers, silicon nitride fibers, hexagonal boron nitride fibers, carbon fibers, basalt fibers, and boron fibers.

[0017] Preferably, the fiber has a diameter of 3~15μm and an aspect ratio of 100~1500.

[0018] Preferably, the nano-ceramic powder is one or more of nano-zirconia, nano-titanium oxide, nano-zirconia silicate, and nano-alumina, and its D50 particle size is 20~100nm.

[0019] Preferably, the small-sized aerogel microspheres and the large-sized aerogel microspheres are each independently selected from one or more of silica aerogel, alumina aerogel, titanium dioxide aerogel, zirconium dioxide aerogel, and titanium dioxide-silica composite aerogel.

[0020] Preferably, the mass ratio of the small-sized aerogel microspheres to the large-sized aerogel microspheres is 1:0.5 to 1:2.

[0021] Preferably, the micron-sized hollow microspheres are hollow glass microspheres or hollow ceramic microspheres, with a D50 particle size of 10~50μm and a true density of 0.15~0.40g / cm³. 3 .

[0022] Preferably, the infrared shielding agent is one or more of silicon carbide, potassium hexatitanate whiskers, and rutile titanium dioxide, with a D50 particle size of 1~20μm.

[0023] Preferably, the adhesive solution is an inorganic adhesive and / or an organic adhesive, wherein the inorganic adhesive is silica sol and / or aluminum sol, and the organic adhesive is an aqueous polyurethane emulsion and / or an aqueous acrylic emulsion. More preferably, the adhesive solution is a compound of an inorganic adhesive and an organic adhesive, wherein the weight ratio of the solid component in the inorganic adhesive to the solid component in the organic adhesive is 3:1 to 1:1.

[0024] Inorganic binders exhibit good high-temperature stability and, after curing, can form ceramic phase bonding points, ensuring that the structure does not collapse at high temperatures. Organic binders possess excellent flexibility and bonding strength, which can improve the material's room-temperature mechanical toughness and impact resistance. A compounding ratio of 3:1 to 1:1 can effectively combine the advantages of both inorganic and organic binders.

[0025] Further preferred, the inorganic binder has a solid content of 20-50 wt%, and the organic binder has a solid content of 40-60 wt%.

[0026] Fiber surface modification includes plasma activation and surface grafting of silane coupling agents. Plasma activation can etch the fiber surface with high-energy particles, introducing active polar groups such as hydroxyl and carboxyl groups, while increasing surface roughness and enhancing the activity and interfacial bonding of subsequent grafting reactions. Surface grafting can introduce reactive functional groups into the fiber surface, achieving chemical bonding with nano-ceramic powders. The combination of these two methods can synergistically enhance the fiber surface activity. Then, the nano-ceramic powders are adsorbed onto the modified fiber surface in slurry form. Through the dual effects of chemical bonding and physical adsorption, the nano-ceramic powders can form a dense, strong, high-temperature resistant "armor" on the fiber surface, making the ceramic coating layer denser and more firmly bonded.

[0027] Preferably, the plasma activation includes: placing the fiber in a plasma treatment device and treating it at a power of 50-200W for 5-20 minutes in an oxygen or air atmosphere. More preferably, the plasma activation uses atmospheric pressure dielectric barrier discharge (DBD) plasma with a treatment power of 80-120W and a treatment time of 10-15 minutes.

[0028] Preferably, the surface-grafted silane coupling agent comprises: impregnating plasma-activated fibers in a silane coupling agent solution and reacting at 40-80°C for 1-3 hours. The silane coupling agent solution is formed by dissolving the silane coupling agent in a solvent, and the concentration of the silane coupling agent is 0.5-5 wt%. The solvent is one or more of ethanol, isopropanol, n-propanol, and water.

[0029] Preferably, the silane coupling agent is one or more of aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, and methacrylate-type silane coupling agents, and can be listed as one or more of KH-540, KH-550, KH-560, KH-570, KH-580, KH-792, KH-562, KH-602, KH-902, and KH-573.

[0030] Preferably, the aqueous slurry containing nano-ceramic powder is formed by dispersing nano-ceramic powder in water, and the concentration of nano-ceramic powder is 3~15wt%.

[0031] Preferably, the reaction in step S2 is carried out at 60~90°C for 2~5 hours.

[0032] Preferably, the low-speed mixing time in step S3 is 5 to 20 minutes, and the high-speed mixing time is 25 to 60 minutes.

[0033] Preferably, the three molding stages include: First stage: Molding temperature is 10~40℃, pressure is maintained at 5~10MPa for 1~5 minutes; Second stage: Temperature rises to 42~60℃, pressure rises to 12~20MPa, and pressure is maintained for 5~15 minutes; Third stage: The temperature rises to 70~90℃, the pressure rises to 25~40MPa, and the pressure is maintained for 10~30 minutes.

[0034] Three-stage gradient molding enables the gradual shaping and precise control of the microporous structure: The first stage, held at room temperature and low pressure, primarily removes most of the air from the mixture, preventing bubble defects after molding, and simultaneously allows the particles to initially contact and stack; the second stage, held at medium temperature and medium pressure, allows the organic binder to initially cross-link and solidify, "locking" the initially formed multi-level skeleton structure and preventing structural collapse under subsequent high pressure; the third stage, held at high temperature and high pressure, allows the inorganic binder to undergo a condensation reaction and fully solidify, ultimately shaping the material structure and ensuring the material's strength and dimensional stability. Staged heating and pressurization avoids problems such as gas retention, uneven binder curing, and internal stress concentration caused by a single high-pressure, high-temperature process.

[0035] More preferably, during the multi-stage compression molding process, the heating rate is controlled at 2~5℃ / min, and the pressure rate is controlled at 1~3MPa / min.

[0036] Preferably, the secondary curing process in step S5 includes curing at 100~120℃ for 2~4 hours.

[0037] The second aspect of the present invention provides a battery thermal insulation material with multi-level micropore synergistic control, wherein the battery thermal insulation material is prepared by the preparation method of the first aspect, and the thickness of the battery thermal insulation material is 1~10mm.

[0038] A third aspect of the present invention provides an application of a battery thermal insulation material with multi-level micropore synergistic regulation as a thermal insulation material in a battery.

[0039] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention introduces an aerogel microsphere system with a dual particle size distribution, achieving a balance between the low thermal conductivity of nanopores and the high compressibility of micropores. Small-sized aerogel microspheres ensure a large number of pores smaller than the mean free path of air (~70 nm) within the material, thereby reducing the thermal conductivity at 25°C to a low level of 0.014–0.019 W / (m·K); large-sized aerogel microspheres and hollow microspheres form a reversible elastic deformation space. This "nano-micro synergy" pore-forming strategy is impossible to achieve by traditional methods relying solely on nano-aerogel powder filling.

[0040] 2. In the preparation process of this invention, large-sized aerogel microspheres are first mixed at low speed to build a large particle skeleton network, and then small microspheres are uniformly filled into the pores at high speed, thereby ensuring the uniformity of the multi-level pore structure.

[0041] 3. This invention employs a three-step method of "plasma activation - surface grafting - nano-ceramic coating" to modify the surface of fibers, rather than simple physical mixing. Plasma treatment, without damaging the fiber's inherent strength, uniformly and efficiently creates numerous active sites on the fiber surface, laying a solid foundation for subsequent chemical grafting and dense ceramic layer coating. The coated nano-ceramic layer (such as ZrO2) possesses an extremely high melting point (>2700℃) and excellent thermal shock resistance. Under a flame impact at 1200℃, it effectively protects the internal high-silica fibers (softening point approximately 1000℃) from rapid melting and fracture, thereby maintaining the integrity of the elastic network skeleton to dissipate impact energy, achieving a balance between temperature resistance and impact resistance. Experiments have shown that the 3.3mm thick thermal insulation sheet of this invention can withstand continuous ablation at 1200℃ for 30 minutes, with the back surface temperature consistently below 200℃, and it was not broken down during a battery cell thermal runaway explosion test.

[0042] 4. This invention constructs a composite structure through multi-stage powder gradient mixing and gradient molding processes: a fibrous skeleton provides basic elastic support, micron-sized hollow microspheres and large-sized aerogel microspheres act as "reinforced elastic air cushions," generating reversible deformation space under pressure, which is filled by nano-aerogel. This structure endows the material with excellent compression resilience, with a compressive strain of 45%–60% under 2.0 MPa pressure, and a high deformation recovery rate after unloading. It can effectively and continuously absorb the "breathing" expansion stress generated by the battery cell during charge-discharge cycles, extending the battery pack's lifespan.

[0043] 5. Overall, this invention constructs a unique multi-level microporous structure through specific component selection and gradation design. High-temperature resistant fibers, activated by plasma and coated with nano-ceramics, form an elastic three-dimensional network framework, providing mechanical support and energy dissipation channels. Aerogel microspheres with dual particle size distribution and micron-sized hollow microspheres form a multi-level filling system. Large-sized aerogel microspheres and hollow microspheres construct micron-sized "cavities" to enhance compression resilience, while small-sized aerogel microspheres fill the gaps between fibers and large particles, maintaining nanoscale pores to block gas molecule heat conduction. Infrared shielding agents are uniformly dispersed in the network, effectively scattering and reflecting high-temperature infrared radiation. The composite binder forms a "rivet" structure between the phase interfaces, enhancing interfacial bonding and preventing interfacial debonding failure under stress or high temperature. The prepared composite thermal insulation material achieves breakthroughs in ultra-low thermal conductivity, wide-temperature-range high-temperature resistance, high compression resilience, and impact resistance, meeting the stringent requirements of next-generation high-safety power batteries for thermal runaway protection materials, and possesses extremely high industrial application value and market prospects.

[0044] 6. The preparation method of this invention uses an aqueous slurry and aqueous binder system, avoiding the use of organic solvents and making it environmentally friendly. The plasma activation process replaces traditional strong acid etching, which is safer, more environmentally friendly, and more efficient. The multi-stage molding process achieves one-step molding, eliminating the need for complex post-processing or multi-layer composites, simplifying the process flow and facilitating continuous and automated production. Attached Figure Description

[0045] Figure 1 This is a BET pore size distribution diagram of the thermal insulation material prepared in Example 1 of the present invention.

[0046] Figure 2 The bar chart shows the thermal conductivity at 25°C for Example 1 and Comparative Example 1.

[0047] Figure 3 The graph shows the back temperature curve of the insulation material of Example 1 under flame erosion at 1200°C.

[0048] Figure 4 The temperature change curves and thermal propagation suppression time of the battery module equipped with the thermal insulation material of Example 1 after the single cell thermal runaway is triggered.

[0049] Figure 5 This is a schematic diagram of the thermal insulation material and cell assembly for testing the thermal runaway of a battery module. Detailed Implementation

[0050] In the description of this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, and includes both a and b. "Multiple" includes two or more types, and can be two, three, four, five, or more.

[0051] In some embodiments of the present invention, the preparation method of the battery thermal insulation material with multi-level micropore synergistic regulation specifically includes the following steps: S1. Plasma activation and surface grafting of fibers: High-temperature resistant fibers are placed in a low-temperature plasma treatment device and treated for 50-200W for 5-20 minutes in an oxygen or air atmosphere to generate active free radicals and hydrophilic groups on their surface. Subsequently, the treated fibers are immersed in a silane coupling agent solution (silane coupling agent concentration of 0.5-5wt%) and reacted at 40-80℃ for 1-3 hours. After removal, they are vacuum dried at 40-70℃ to obtain modified active fibers.

[0052] S2. Liquid-phase coating of nano-ceramic powder: The modified active fiber obtained in step S1 is dispersed in an aqueous slurry containing nano-ceramic powder (the concentration of nano-ceramic powder is 3~15wt%), and reacted at 60~90℃ with continuous stirring for 2~5 hours, so that the nano-ceramic powder is firmly coated on the fiber surface through chemical bonding and physical adsorption. After filtration, washing and drying, nano-ceramic coated reinforcing fiber is obtained.

[0053] S3. Gradient mixing of multi-stage powders: A vacuum planetary mixer with multi-stage variable speed stirring function is used, and the vacuum gauge pressure is evacuated to -0.05~-0.098MPa. First, the reinforcing fibers obtained in step S2 are mixed with large-sized aerogel microspheres, micron-sized hollow microspheres, and infrared opacifier in the planetary mixer at low speed (10~20 rpm revolution speed, 100~300 rpm rotation speed) for 5~20 minutes to construct a preliminary micron-sized skeleton network. Then, small-sized aerogel microspheres and binder solution are added and mixed at high speed (30~50 rpm revolution speed, 800~1500 rpm rotation speed) for 25~60 minutes. High-speed shearing is used to make the small-sized aerogel microspheres and binder uniformly fill and adhere to the pores of the skeleton network to form a uniform paste mixture.

[0054] S4. Multi-stage molding and micropore shaping: Transfer the mixture obtained in step S3 to the mold of a precision molding machine, and perform molding using a gradient pressure and gradient temperature process. The heating rate is controlled at 2~5℃ / min, and the pressure rate is controlled at 1~3MPa / min. First stage: Hold pressure at 10~40℃ and 5~10MPa for 1~5 minutes; Second stage: Raise the temperature to 42~60℃ and the pressure to 12~20MPa, and hold pressure for 5~15 minutes; Third stage: Raise the temperature to 70~90℃ and the pressure to 25~40MPa, and hold pressure for 10~30 minutes.

[0055] S5. Post-processing and finishing: After demolding, place the material in an oven and perform a secondary curing treatment at 100~120℃ for 2~4 hours. After cooling, process it into the required size heat insulation sheet by laser cutting or die cutting.

[0056] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the specific scope of the present invention. Furthermore, the accompanying drawings used herein are merely for better illustrating the content disclosed in the present invention and do not limit the scope of protection. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used in the art, and the methods used in the embodiments are all conventional methods in the art.

[0057] The following are the sources of raw materials used in the examples and comparative examples: High-silica fiber: purchased from Linyi Haoquan Silicon Industry Technology Co., Ltd., with SiO2 content ≥96%, fiber diameter 9±1μm, and length 6mm.

[0058] Basalt fiber: 13μm in diameter and 9mm in length, purchased from Sichuan Aerospace Tuoxin Basalt Industry Co., Ltd.

[0059] KH-550 solution: Take silane coupling agent KH-550: isopropanol: deionized water in a mass ratio of 1:15:3, slowly add glacial acetic acid to adjust the pH of the system to 9.0, stir at 1500 rpm for 25 minutes at room temperature, and let stand for 20 minutes until the solution is completely clear and transparent to obtain KH-550 solution.

[0060] Nano-zirconia powder: D50=50nm, purchased from Xuancheng Jingrui New Materials Co., Ltd.

[0061] Nano-alumina: D50=30nm, purchased from Xuancheng Jingrui New Materials Co., Ltd.

[0062] Nano-zirconium silicate powder: D50=60nm, purchased from Zibo Yishun Ceramic Glaze Co., Ltd.

[0063] Silica aerogel microspheres: D50=10μm, D50=15μm, D50=100μm, D50=150μm, Jiangsu Jiayun New Materials Co., Ltd.

[0064] Hollow glass microspheres: D50=30μm, true density 0.25g / cm³ 3 Purchased from Zhengzhou Shenglait Hollow Microsphere New Material Co., Ltd.

[0065] Hollow ceramic microspheres: D50=40μm, true density 0.30g / cm³ 3Zhengzhou Shenglait Hollow Microsphere New Material Co., Ltd.

[0066] Silicon carbide: D50=5μm, purchased from Shandong Jinmeng New Material Co., Ltd.

[0067] Potassium hexatite whiskers: aspect ratio 20, diameter 2μm, purchased from Shanghai Kaiyin Chemical Co., Ltd.

[0068] Silica sol: solid content 30wt%, purchased from Hubei Jinwei New Materials Co., Ltd.

[0069] Waterborne polyurethane emulsion: solid content 50wt%, purchased from Guangdong Xidun New Material Technology Co., Ltd.

[0070] Aluminum sol: solid content 30wt%, purchased from Hangzhou Jikang New Materials Co., Ltd.

[0071] Example 1

[0072] The raw materials for preparing the thermal insulation material in this embodiment are: High-silica fiber: 12 parts; silane coupling agent: KH-550 solution, 0.8 parts based on the effective component KH-550; nano-zirconia powder: 12 parts; large-size silica aerogel microspheres (D50=100μm): 20 parts; small-size silica aerogel microspheres (D50=10μm): 20 parts; hollow glass microspheres: 8 parts; silicon carbide: 5 parts; composite binder solution 1: silica sol and waterborne polyurethane emulsion are compounded at a solid component weight ratio of 2:1, with a total solid content of 4 parts.

[0073] The preparation method of thermal insulation material is as follows: S1. The high-silica fibers are evenly spread on the conveyor belt of the atmospheric pressure DBD plasma treatment equipment and treated for 12 minutes in an air atmosphere at 100W power. After removal, they are immediately immersed in a 2wt% KH-550 solution at 60℃, stirred and reacted for 2 hours, filtered, washed with deionized water, and vacuum dried at 60℃ to obtain surface-grafted active fibers.

[0074] S2. Disperse the nano-zirconia powder in deionized water and sonicate for 30 minutes to prepare a uniform slurry (concentration 10wt%). Add the active fibers obtained in step S1 to the slurry, stir and react in an 80℃ water bath for 3 hours, filter, wash, and dry at 80℃ to obtain nano-zirconia-coated reinforcing fibers.

[0075] S3. Using a planetary mixer, evacuate to a vacuum gauge pressure of -0.08 MPa. First, add the reinforcing fibers, large-sized silica aerogel microspheres, hollow glass microspheres, and silicon carbide from step S2. Set the mixer to 15 rpm for revolution and 200 rpm for rotation, and mix for 15 minutes. Then, add the small-sized silica aerogel microspheres and composite binder solution 1. Set the mixer to 40 rpm for revolution and 1200 rpm for rotation, and mix at high speed for 45 minutes to obtain a uniform paste mixture.

[0076] S4. Transfer the mixture into the precision molding die, set the thickness to 3.3mm, and execute the gradient molding program: First stage: room temperature (25℃), pressure 8MPa (rate 2MPa / min), hold pressure for 3 minutes.

[0077] Second stage: Heat to 50℃ (rate 3℃ / min), pressurize to 15MPa (rate 2MPa / min), and hold pressure for 10 minutes.

[0078] Third stage: Heat to 80℃ (rate 3℃ / min), pressurize to 30MPa (rate 2MPa / min), and hold pressure for 20 minutes.

[0079] S5. After demolding, place the blank in a 110℃ oven for secondary curing for 3 hours. After cooling, use a laser cutting machine to process it into a heat insulation sheet with a thickness of 3.3mm and a size of 150mm×100mm, which is the finished product.

[0080] Example 2

[0081] The raw materials for preparing the thermal insulation material in Example 2 are: High-silica fiber: 12 parts; silane coupling agent: KH-550 solution, 1.0 part based on the effective ingredient KH-550; nano-zirconium silicate powder: 15 parts; large-size silica aerogel microspheres (D50=150μm) 27 parts, small-size silica aerogel microspheres (D50=15μm): 18 parts; hollow ceramic microspheres: 10 parts; potassium hexatitanate whiskers: 6 parts; composite binder solution 2: aluminum sol and waterborne polyurethane emulsion are compounded at a solid component weight ratio of 1.5:1, with a total solid content of 5 parts.

[0082] The preparation method is the same as in Example 1.

[0083] Example 3

[0084] This embodiment is basically the same as Embodiment 1, except that basalt fiber is used instead of high-silica fiber, and the plasma treatment parameters (power 150W, time 15 minutes) and nano-ceramic powder (nano-alumina, 15 parts) are adjusted accordingly. Other raw materials and steps are the same as in Embodiment 1.

[0085] Example 4

[0086] This embodiment is basically the same as Embodiment 1, except that in the mixing process of step S3, the low-speed mixing time is 20 minutes and the high-speed mixing time is 60 minutes, in order to examine the effect of more thorough shear mixing on performance. Other raw materials and steps are the same as in Embodiment 1.

[0087] Example 5

[0088] The raw materials for Example 5 are basically the same as those for Example 1, except that the binder solution in Example 5 is silica sol, with a total solids content of 4 parts.

[0089] Example 6

[0090] The raw materials of Example 6 are basically the same as those of Example 1, except that the adhesive solution of Example 6 is an aqueous polyurethane emulsion with a total solids content of 4 parts.

[0091] Comparative Example 1 A commercially available pre-oxygenated fiber-based aerogel felt (nominal thickness 3.0 mm, thermal conductivity 0.022 W / (m·K)) from a mainstream brand was selected as a control.

[0092] Comparative Example 2 The raw material ratio of Comparative Example 2 is basically the same as that of Example 1, except that the aerogel microspheres with dual particle size distribution are replaced with an equal weight of aerogel powder with a single particle size, specifically: 40 parts of small-sized silica aerogel powder (D50=10μm).

[0093] Step S3 of the preparation method is as follows: Using a planetary mixer, evacuate to a vacuum gauge pressure of -0.08 MPa. First, add reinforcing fibers, 20 parts of small-sized silica aerogel microspheres, hollow glass microspheres, and silicon carbide. Set the mixer to 15 rpm for revolution and 200 rpm for rotation, and mix for 15 minutes. Then, add 20 parts of small-sized silica aerogel microspheres and composite binder solution 1. Set the mixer to 40 rpm for revolution and 1200 rpm for rotation, and mix at high speed for 45 minutes to obtain a uniform paste mixture.

[0094] The other steps are the same as in Example 1.

[0095] Comparative Example 3 The raw material ratio of Comparative Example 3 is basically the same as that of Example 1, except that the dual-size aerogel microspheres are replaced with an equal weight of single-size aerogel powder, specifically: 40 parts of large-size silica aerogel powder (D50=100μm).

[0096] Step S3 of the preparation method is as follows: Using a planetary mixer, evacuate to a vacuum gauge pressure of -0.08 MPa. First, add reinforcing fibers, 20 parts of large-sized silica aerogel microspheres, hollow glass microspheres, and silicon carbide. Set the mixer to 15 rpm for revolution and 200 rpm for rotation, and mix for 15 minutes. Then, add 20 parts of large-sized silica aerogel microspheres and composite binder solution 1. Set the mixer to 40 rpm for revolution and 1200 rpm for rotation, and mix at high speed for 45 minutes to obtain a uniform paste mixture.

[0097] The other steps are the same as in Example 1.

[0098] Comparative Example 4 The raw material ratio of Comparative Example 4 is exactly the same as that of Example 1.

[0099] Step S3 of the preparation method is as follows: Using a planetary mixer, evacuate to a vacuum gauge pressure of -0.08 MPa, add reinforcing fibers, large-sized silica aerogel microspheres, hollow glass microspheres, silicon carbide, small-sized silica aerogel microspheres, and composite binder solution 1, and mix for 60 minutes at a revolution speed of 30 rpm and a rotation speed of 800 rpm to obtain a uniform paste mixture.

[0100] The other steps are the same as in Example 1.

[0101] Comparative Example 5 The raw material ratio of Comparative Example 5 is exactly the same as that of Example 1.

[0102] In the preparation method, Comparative Example 5 did not have step S2. In a planetary mixer, nano-zirconia powder was mixed at low speed together with reinforcing fibers, large-sized silica aerogel microspheres, hollow glass microspheres and silicon carbide.

[0103] The other steps are the same as in Example 1.

[0104] Comparative Example 6 The raw material ratio of Comparative Example 6 is exactly the same as that of Example 1.

[0105] The gradient molding procedure in step S4 of the preparation method was replaced with conventional isothermal and isobaric molding: a single pressurization at 60°C and 25 MPa for 30 minutes. Other steps were the same as in Example 1. This comparative example was used to verify the unique role of gradient molding in controlling microporous structure and internal stress.

[0106] Comparative Example 7 The raw material ratio of Comparative Example 7 is basically the same as that of Example 1, except that no composite binder was added to Comparative Example 7.

[0107] The other steps are the same as in Example 1.

[0108] Application Example 1 A 3.3 mm thick, 150 mm × 100 mm heat insulation sheet prepared in Example 1 was assembled between 73 Ah ternary lithium battery cells to form a 5-parallel, 1-string battery module. The heat insulation sheet was placed between the large surfaces of adjacent cells, tightly adhering to the cell surfaces. The module was placed in a 25°C ambient temperature-controlled chamber, and one of the cells was heated to the point of triggering thermal runaway using a heating element. The surface temperature changes of adjacent cells were recorded in real time using thermocouples and a data acquisition system, and a high-speed camera was used to record whether the heat insulation sheet was broken down by the high-temperature jet at the moment of thermal runaway.

[0109] Figure 5 This is a schematic diagram of the thermal insulation material and cell assembly for a battery module thermal runaway test. Figure 4 The temperature change curves of adjacent cells in a battery module equipped with the thermal insulation material of Embodiment 1 after the thermal runaway of a single cell are shown. It can be seen that the thermal insulation sheet of Embodiment 1 of the present invention exhibits excellent thermal propagation suppression capability, increasing the temperature rise delay time of adjacent cells to 1589 seconds.

[0110] The thermal insulation materials prepared in the above embodiments and comparative examples (Comparative Example 1 is a commercially available finished product) were subjected to the following performance tests, and the test results are summarized in Table 1.

[0111] Density test: The bulk density of the material is measured in accordance with GB / T5480-2017 standard.

[0112] Thermal conductivity test: According to GB / T10295-2008 standard, the thermal conductivity is measured at 25℃ using a heat flow meter thermal conductivity meter; according to YB / T4130-2005 standard, the thermal conductivity is measured at 800℃ using a water flow plate thermal conductivity meter.

[0113] High-temperature ablation test: Fix a 3.3 mm thick sample in a fixture, and use a butane torch (flame temperature of about 1200℃) to vertically burn the central area of ​​the sample. Attach a thermocouple to the center of the back of the sample, record the back temperature change over 20 minutes, and observe whether the sample is burned through or develops through cracks.

[0114] Compression mechanical properties test: According to GB / T13480-2014 standard, the compressive strain (%) of the sample under 2.0MPa compressive stress was tested using a universal testing machine.

[0115] Impact resistance test (thermal runaway simulation): The sample is placed between two 73Ah ternary lithium battery cells. One of the cells is overcharged or heated until thermal runaway is triggered. High-speed camera is used to observe whether the heat insulation sheet is broken down by the high-temperature jet at the moment of thermal runaway. The temperature change of adjacent cells is recorded by thermocouples, and the thermal runaway propagation suppression time is calculated.

[0116] Table 1 Comparison of performance test results of thermal insulation materials in each embodiment and the comparative example

[0117] Combination Figure 1 As can be seen from the BET pore size distribution, Example 1 of this invention successfully constructed the expected multi-level micro / nanoporous structure. Large-sized aerogel microspheres and hollow microspheres are embedded in the fiber network, forming obvious micron-sized cavities, which are then tightly filled by small-sized aerogel microspheres, decomposing into nano-cavities. More than half of the nanopore sizes are between 20 and 70 nm, exhibiting a significant Knudsen effect. This effect results in a thermal conductivity as low as 0.01524 W / (m·K) in Example 1, far lower than that of the traditional aerogel felt in Comparative Example 1 (0.02250 W / (m·K)). Figure 2 As shown. Similarly, the thermal conductivity at 25℃ for Examples 2-6 is also ≤0.01951W / (m·K), which is much lower than that of Comparative Examples 1-7 (0.022~0.030W / (m·K). Comparative Example 2, due to the use of only a single small-sized aerogel powder, although rich in nanopores, is prone to agglomeration during molding, failing to form an effective micron-level "air cushion" structure, resulting in limited increase in interparticle contact thermal resistance, and a thermal conductivity (0.02501W / (m·K)) higher than that of Example 1. Example 4, by extending the high-speed mixing time, makes the distribution of small-sized aerogel microspheres and binder more uniform, further optimizing the interfacial bonding and pore uniformity, thereby obtaining the lowest thermal conductivity (0.01493W / (m·K)). At a high temperature of 800℃, the thermal conductivity of Examples 1-4 remained at a low level (0.02292-0.02514 W / (m·K)). This is because the uniformly dispersed infrared shading agent effectively suppressed radiative heat transfer, while the complete fiber skeleton prevented the structure from collapsing at high temperatures.

[0118] In the 1200℃ ablation test, all examples passed the 30-minute ablation test, with the back temperature consistently below 200℃ (e.g., Figure 3 As shown in the figure, the comparative examples all exceeded 195°C and exhibited burn-through or cracking. Under a pressure of 2.0 MPa, the compressive strain of Example 1 reached 52.5%, and the compressive strain of Example 2 was further increased to 58.7% by increasing the hollow microspheres and optimizing the fiber content. In the final thermal runaway simulation test, the thermal insulation sheet of Example 1 of this invention showed excellent thermal propagation suppression capability, increasing the temperature rise delay time of adjacent cells to 1589 seconds (>26 minutes). Example 4 used a longer mixing time, which is beneficial to improving the thermal runaway propagation suppression time. In stark contrast, the conventional solution of Comparative Example 1 transferred heat to adjacent cells almost instantly (4 seconds) during thermal runaway, and the thermal runaway propagation suppression time of the thermal insulation materials in other comparative examples was also greatly reduced.

[0119] Comparing Example 1 and Comparative Examples 2-4, it is evident that the combined use of large-size and small-size silica aerogels, employing low-speed and high-speed stepwise mixing processes respectively, facilitates the formation of a hierarchical porous structure and ensures its uniformity, thereby comprehensively improving the overall performance of the thermal insulation material. Comparative Example 5, which uses direct mixing of nanoparticles, yielded the sample with the highest thermal conductivity and the most severe cracking, demonstrating the necessity of the gradient fiber modification process.

[0120] Comparative Example 6 employed constant temperature and pressure molding. A comparison of data from Example 1 and Comparative Example 6 reveals that constant temperature and pressure molding may lead to excessively rapid cross-linking of the organic binder and insufficient curing of the inorganic binder. The resulting microporous structure exhibits lower uniformity and elastic recovery compared to gradient molding, resulting in reduced compressive and thermal insulation performance. In contrast, gradient molding, through gradual heating and pressurization, provides a buffer time for the binder's reaction and gas expulsion, allowing the fiber skeleton, large particles, and small particles to be "locked" in their ideal positions at their respective optimal stages. The resulting multi-level microporous structure exhibits higher elastic efficiency and fatigue resistance.

[0121] The comparison between Example 1 and Comparative Example 7 shows that the overall performance of the sample without binder is significantly deteriorated, and the thermal runaway propagation inhibition time is only 14s, which verifies the key supporting role of binder in the material structure and performance.

[0122] In summary, this invention successfully solves the problem of traditional thermal insulation materials' inability to achieve synergistic performance improvements through innovative material formulation design, unique plasma activation and nano-coating processes, mixing of aerogel microspheres of varying sizes at different speeds, and precise multi-level gradient molding technology. The prepared composite thermal insulation material achieves breakthroughs in ultra-low thermal conductivity, wide-temperature-range high-temperature resistance, high compression resilience, and impact resistance, integrating ultra-low thermal conductivity, high-temperature structural stability, and efficient energy dissipation (compression energy absorption). Under extreme conditions of thermal runaway in power battery cells, this material can construct a three-in-one protective barrier of "thermal insulation, impact resistance, and buffering," buying crucial time for personnel to escape safely. It meets the requirements of next-generation high-safety power batteries for thermal runaway protection materials, possessing industrial application value and broad market prospects.

[0123] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0124] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0125] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for preparing a battery thermal insulation material with multi-level micropore synergistic regulation, characterized in that, Includes the following steps: S1. The fiber is subjected to plasma activation and surface grafting of silane coupling agent to obtain modified active fiber; S2. The modified active fiber is dispersed in an aqueous slurry containing nano-ceramic powder, and the reaction is carried out to obtain nano-ceramic coated reinforcing fiber. S3. The nano-ceramic-coated reinforcing fibers are mixed with large-sized aerogel microspheres, micron-sized hollow microspheres, and infrared opacifiers at low speed in a planetary mixer. The revolution speed of the low-speed mixing is 10-20 rpm and the rotation speed is 100-300 rpm. Then, small-sized aerogel microspheres and binder solution are added and mixed at high speed. The revolution speed of the high-speed mixing is 30-50 rpm and the rotation speed is 800-1500 rpm, forming a paste-like mixture. S4. Transfer the paste mixture to the mold and perform multi-stage molding, which includes three molding stages. S5. After demolding, heat for secondary curing. The small-sized aerogel microspheres have a D50 particle size of 5~30μm, and the large-sized aerogel microspheres have a D50 particle size of 50~200μm.

2. The preparation method according to claim 1, characterized in that, The raw materials for preparing the battery heat insulation material, by weight, include: Fiber: 5-25 parts; Silane coupling agent: 0.5~5 parts; Nano-ceramic powder: 5-20 parts; Small-sized aerogel microspheres: 15-30 parts; Large-sized aerogel microspheres: 15-30 parts; Micron-sized hollow microspheres: 5-15 parts; Infrared shielding agent: 3-10 parts; Adhesive solution, based on solid content: 1 to 8 parts.

3. The preparation method according to claim 1 or 2, characterized in that, The fiber is a high-temperature resistant fiber, selected from one or more of the following: high-silica fibers with SiO2 content ≥96%, alumina fibers, zirconium oxide fibers, silicon carbide fibers, mullite fibers, aluminum silicate fibers, potassium hexatitanate fibers, silicon nitride fibers, hexagonal boron nitride fibers, carbon fibers, basalt fibers, and boron fibers. And / or, the fiber has a diameter of 3~15μm and an aspect ratio of 100~1500.

4. The preparation method according to claim 1 or 2, characterized in that, The nano-ceramic powder is one or more of nano-zirconia, nano-titanium oxide, nano-zirconia silicate, and nano-alumina, and its D50 particle size is 20~100nm. And / or, the aqueous slurry containing nano-ceramic powder is formed by dispersing nano-ceramic powder in water, with the concentration of nano-ceramic powder being 3~15wt%; And / or, the small-sized aerogel microspheres and the large-sized aerogel microspheres are each independently selected from one or more of silica aerogel, alumina aerogel, titanium dioxide aerogel, zirconium dioxide aerogel, and titanium dioxide-silica composite aerogel; And / or, the mass ratio of the small-sized aerogel microspheres to the large-sized aerogel microspheres is 1:0.5 to 1:2; And / or, the micron-sized hollow microspheres are hollow glass microspheres or hollow ceramic microspheres, with a D50 particle size of 10~50μm and a true density of 0.15~0.40g / cm³. 3 ; And / or, the infrared shielding agent is one or more of silicon carbide, potassium hexatitanate whiskers, and rutile titanium dioxide, with a D50 particle size of 1~20μm.

5. The preparation method according to claim 1 or 2, characterized in that, The adhesive solution is composed of inorganic and organic adhesives. The inorganic adhesive is silica sol and / or aluminum sol, and the organic adhesive is waterborne polyurethane emulsion and / or waterborne acrylic emulsion. The weight ratio of the solid components in the inorganic adhesive to the solid components in the organic adhesive is 3:1 to 1:

1.

6. The preparation method according to claim 1, characterized in that, The plasma activation includes: placing the fiber in a plasma treatment device and treating it for 5 to 20 minutes at a power of 50 to 200W in an oxygen or air atmosphere; The surface-grafted silane coupling agent comprises: impregnating plasma-activated fibers in a silane coupling agent solution and reacting at 40~80°C for 1~3 hours; The silane coupling agent solution is formed by dissolving the silane coupling agent in a solvent, and the concentration of the silane coupling agent is 0.5~5wt%.

7. The preparation method according to claim 1, characterized in that, The reaction in step S2 is carried out at 60~90℃ for 2~5 hours; And / or, the low-speed mixing time in step S3 is 5-20 minutes, and the high-speed mixing time is 25-60 minutes; And / or, the secondary curing treatment in step S5 includes curing at 100~120℃ for 2~4 hours.

8. The preparation method according to claim 1, characterized in that, The three molding stages include: First stage: Molding temperature is 10~40℃, pressure is maintained at 5~10MPa for 1~5 minutes; Second stage: Temperature rises to 42~60℃, pressure rises to 12~20MPa, and pressure is maintained for 5~15 minutes; Third stage: Temperature rises to 70~90℃, pressure rises to 25~40MPa, and pressure is maintained for 10~30 minutes; During the multi-stage compression molding process, the heating rate is controlled at 2~5℃ / min, and the pressure rate is controlled at 1~3MPa / min.

9. A battery thermal insulation material with multi-level micropore synergistic regulation, characterized in that, It is prepared by the preparation method described in claim 1, wherein the thickness of the battery heat insulation material is 1~10mm.

10. The application of the multi-level micropore synergistic control battery thermal insulation material as described in claim 9 as a thermal insulation material in a battery.

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