A low-volatility high-thermal-conductivity insulating silica gel composite material suitable for power batteries

Abstract

The application discloses a low-volatility high-thermal-conductivity insulating silica gel composite material suitable for power batteries, characterized by comprising the following components in mass parts: 3-10 parts of vinyl silicone oil, 8-20 parts of liquid acrylic ester rubber, 95-105 parts of compounded thermal conductive powder, 0.3-0.5 parts of hydrogen-containing silicone oil, 0.02-0.04 parts of platinum catalyst, 0.02-0.05 parts of acetylenic alcohol inhibitor and 0.8-2.0 parts of silane modifier. The low-volatility high-thermal-conductivity insulating silica gel composite material adopts low-volatility vinyl silicone oil and liquid acrylic ester rubber as a composite matrix, can effectively coat the vinyl silicone oil at a very low content and the compounded thermal conductive powder at a high content, avoids problems such as sharp increase of dispersion resistance and particle agglomeration in the modification and subsequent mixing process of the thermal conductive powder, and can stabilize the thermal conductivity coefficient at more than 6.5 W / (m*K), the volatilization amount is less than 90 ppm, and can be used in the range of -40 DEG C to 200 DEG C.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive silicone technology, and in particular to a low-volatility, high-thermal-conductivity insulating silicone composite material suitable for power batteries. Background Technology

[0002] With the development of new energy vehicles, the density of power batteries has increased significantly. For their long-term safe and reliable operation, thermal pads must balance thermal conductivity, insulation performance, low volatility, and no oil leakage. In conventional high thermal conductivity silicone formulations, the amount of vinyl silicone oil matrix added is generally ≥20 parts. While a large amount of flexible silicone oil can improve processability and resilience, it also has problems such as high content of small molecule cyclosiloxanes and easy volatilization and oil leakage at high temperatures. Long-term use can contaminate battery cells, circuit boards, and liquid cooling pipelines, leading to insulation failure and device corrosion. Simply reducing the proportion of silicone oil or increasing the amount of thermally conductive powder to improve thermal conductivity easily results in fatal defects such as severe powder agglomeration, inability of the matrix to wet the filler, brittle and inelastic materials, incomplete cross-linking reaction, soaring interfacial thermal resistance, molding difficulties, and easy cracking and powder shedding. Summary of the Invention

[0003] To address the above shortcomings, the present invention adopts the following technical solution: A low-volatile, high-thermal-conductivity insulating silicone composite material suitable for power batteries, comprising the following components by weight: Vinyl silicone oil: 3-10 parts; Liquid acrylate rubber: 8-20 parts; Composite thermally conductive powder: 95-105 parts; Hydrogen-containing silicone oil: 0.3–0.5 parts; Platinum catalyst: 0.02–0.04 parts; Alkyne alcohol inhibitors: 0.02–0.05 parts; Silane modifier: 0.8-2.0 parts.

[0004] The mechanism of this scheme is that a composite matrix liquid of vinyl silicone oil and liquid acrylate rubber is compatiblely blended, and the vinyl silicone oil wets the surface of the thermally conductive powder, reducing the interfacial tension and forming a uniform wetting film. An elastic entanglement layer is formed outside the wetting film, which synergistically coats the composite thermally conductive powder to form an ultrathin layer. At the same time, the two construct a tight elastic cross-linked network, which helps to reduce the escape of small molecules, effectively inhibits silicone oil seepage, and avoids high-filling embrittlement. The composite thermally conductive powder forms a densely packed skeleton, and the modified wettability is enhanced. The organic phase occupies only the gaps and does not block the heat conduction path. The dual matrix and hydrogen-containing silicone oil are cross-linked under platinum catalysis, which further anchors the vinyl silicone oil and liquid acrylate rubber in the entire composite material system network, synergistically inhibiting the migration of small molecules and oil seepage. Meanwhile, alkynyl alcohol inhibitors can effectively extend the mixing operation time and prevent the ultra-high filling system from premature gelation and curing.

[0005] In a preferred embodiment, the vinyl silicone oil has a volatile content of <0.1%, a volatilization amount at room temperature of ≤100ppm, and a viscosity of 30-150mPa·s.

[0006] In a preferred embodiment, the molecular weight Mn of the liquid acrylate rubber is 10,000-30,000.

[0007] Low-viscosity, low-volatility vinyl silicone oil is selected, which has strong wetting and reactive crosslinking properties, and is conducive to the formation of a primary ultrathin layer on the powder surface. Liquid acrylate rubber is completely compatible with vinyl silicone oil and can participate in hydrosilylation crosslinking, solving the problems of high-filler embrittlement and compression set.

[0008] In a preferred embodiment, the composite thermally conductive and insulating powder is an inorganic composite powder with different particle sizes.

[0009] In a preferred embodiment, the total amount of the compounded thermally conductive and insulating powder is 95-100 parts, and the thermally conductive and insulating powder is composed of 60-75 parts of spherical alumina with a particle size of 5-40 μm, 15-25 parts of aluminum nitride with a particle size of 0.5-5 μm, and 5-10 parts of nano-magnesium oxide with a particle size of 20-200 nm.

[0010] A ternary graded compound system of large-particle alumina, medium-particle aluminum nitride, and nano-magnesium oxide is employed. Compared to traditional systems using a single alumina compound of different particle sizes, this system leverages the ultra-high intrinsic thermal conductivity of aluminum nitride to construct a three-dimensional thermally conductive network, significantly reducing interfacial thermal resistance and ensuring a stable thermal conductivity of the composite material exceeding 6.5 W / (m·K). Nano-magnesium oxide optimizes the inorganic-organic interfacial bonding of the entire thermally conductive silicone composite system, adapting to ultra-thin coating systems with low-addition vinyl silicone oil and liquid acrylate rubber. This enhances the material's compression resilience and structural integrity, and synergistically improves overall temperature resistance, electrical insulation, and thermal aging stability with alumina, enabling long-term stable use under high pressure, wide temperature, and vibration conditions. Furthermore, this three-level particle size gradient close packing not only improves thermal conductivity but also completely seals powder packing voids, reducing the space occupied by small-molecule silicone oil. Combined with the low-volatility vinyl silicone oil system, this enhances low volatility and oil-resistant properties.

[0011] In a preferred embodiment, the hydrogen-containing silicone oil is a side-chain hydrogen-containing silicone oil with a hydrogen content of 0.5–0.7 wt% and a viscosity of 100–200 mPa·s. A low-volatility, low-viscosity hydrogen-containing silicone oil is selected, and it is cross-linked with a low-addition amount of low-volatility vinyl silicone oil and a double-bond liquid acrylate rubber to achieve precise functional group ratios. This avoids defects such as excessive cross-linking leading to embrittlement or insufficient cross-linking causing oil seepage, constructing a high-strength, high-resilience, and dense three-dimensional silicone cross-linked network. This synergistically reduces the precipitation of small molecules and high-temperature volatilization in the system, making it suitable for long-term stable use in ultra-high thermal conductivity powder-filled systems.

[0012] The silane modifier is a compound of vinylsilane and epoxysilane in a mass ratio of 1:1 to 1:2. This compound specifically coats the surface of the thermally conductive powder, reducing powder agglomeration. It can bind to the hydroxyl groups of inorganic powders and is compatible with the silicone oil crosslinking system, improving the interfacial bonding force between inorganic powders and the organic matrix, eliminating interfacial voids, reducing interfacial thermal resistance, and simultaneously improving material toughness, preventing the material from hardening, becoming brittle, and losing its resilience under high filling conditions. The vinylsilane is preferably vinyltrimethoxysilane, and the epoxysilane is preferably 3-glycidoxypropyltrimethoxysilane.

[0013] The alkynyl alcohol inhibitor is one or more of 3-methyl-1-butyn-3-ol, 1-ethynylcyclohexanol, 3-propyl-1-butyn-3-ol, and 3-octyl-1-butyn-3-ol, preferably 1-ethynylcyclohexanol.

[0014] The preparation method of the above-mentioned low-volatility, high-thermal-conductivity, insulating silicone composite material includes the following steps: S1 involves adding the compounded thermally conductive and insulating powder into a hot air oven at 120–140°C for 2–4 hours to remove adsorbed water, free impurities, and weakly bound hydroxyl groups from the powder surface. After cooling to 40–60°C, the powder is added together with a silane modifier into a high-speed stirring device and sheared and dispersed at 1200–1800 r / min for 20–35 minutes. Then, it is allowed to stand and mature for 30 minutes under a vacuum of -0.090–-0.095 MPa to ensure that silane molecules are firmly grafted onto the surface of the inorganic powder, thereby reducing the surface energy of the powder and preventing agglomeration. This lays the foundation for subsequent uniform ultrathin coating of trace organic phases. S2 is prepared by mixing vinyl silicone oil and liquid acrylate rubber in a vacuum mixing vessel according to the specified ratio. The mixture is heated to 50-60℃ and the vacuum degree is -0.090 to -0.095MPa. The mixture is stirred at 300-500 r / min for 20-30 min to achieve molecular-level compatibility between the vinyl silicone oil and the liquid acrylate elastomer, forming a low-volatility, high-wetting, and high-elasticity composite matrix liquid. This solves the problem of powder being difficult to wet under low resin dosage. The modified thermally conductive and insulating powder in S1 is slowly added to the dual-matrix mixture in 3-5 batches to avoid agglomeration from a single addition. The mixture is heated to 60-75℃ and stirred at 400-600 r / min under vacuum for 40-60 min. Relying on the low surface tension of the dual matrix, a continuous and uniform nano-scale ultrathin coating layer is formed on the surface of the multi-graded powder particles, filling the microscopic gaps in the powder, reducing the storage space of small molecules, and achieving a low-volatility and oil-proof basic structure. S3: Reduce the temperature inside the vacuum stirrer to below 35℃, add alkynyl alcohol inhibitors, and stir at 300-500 r / min for 5-10 min to disperse evenly. Then add platinum catalyst and continue stirring for 10-15 min to disperse evenly, ensuring uniform distribution of the catalytic system, extending the operational life, and adapting to ultra-high filler system processing. Next, slowly and evenly drip in hydrogen-containing silicone oil, and continue stirring under vacuum for 20-30 min to allow trace amounts of silanium groups to uniformly contact the vinyl and acrylate double bonds in the bimatrix system. This results in a low-density, high-elasticity, dense network cross-linked structure formed between the low-added amount of side-added hydrogen-containing silicone oil and the bimatrix, further preventing excessive cross-linking and brittleness in the high-filler system, while also preventing insufficient cross-linking, stickiness, and oil seepage. S4 maintains high vacuum degassing for 15-25 minutes to completely remove trapped air from the system, reduce interfacial voids and lower thermal resistance, resulting in a paste-like material. The paste-like material is then pressed into sheet blanks of a set thickness using molding or precision calendering equipment, ensuring a smooth surface and uniform thickness. The sheets are then fed into a tunnel oven for segmented curing. First, they are kept at 70-85℃ for 20-30 minutes to fix and lock in small molecules, preventing their migration and precipitation in the early stages of high temperature. Then, they are kept at 100-120℃ for 40-60 minutes to complete full hydrosilylation crosslinking. Finally, they are allowed to cool naturally to room temperature and cut to obtain low-volatility, high-thermal-conductivity insulating silicone gaskets.

[0015] The effective effects of this invention are as follows: 1. The low-volatility, high-thermal-conductivity, insulating silicone composite material of this invention breaks through the conventional formulation logic. It adopts ultra-high filling of thermally conductive inorganic powder and introduces liquid acrylate rubber to form a compound dual matrix liquid with extremely low addition of vinyl silicone oil. Under the premise of minimal organic matrix, it takes into account powder wetting and dispersion, material flexibility and resilience, low volatility and oil seepage resistance, high thermal conductivity and high insulation. It is perfectly adapted to the long-life, low-exudation, high-reliability and harsh working conditions of power batteries. The system composition is simple and does not require a large number of flexible additives.

[0016] 2. The low-volatility, high-thermal-conductivity insulating silicone composite material of this invention utilizes a multi-level, multi-graded inorganic thermally conductive powder gradation and silane coating modification. It employs a ternary gradation system of large-particle alumina, medium-particle aluminum nitride, and nano-magnesium oxide. Compared to traditional formulations that use high-addition alumina as the thermally conductive powder and struggle to exceed 5 W / (m·K), this system leverages the ultra-high intrinsic thermal conductivity of aluminum nitride to construct a three-dimensional thermally conductive network, significantly reducing interfacial thermal resistance and ensuring a stable thermal conductivity of over 6.5 W / (m·K). Nano-magnesium oxide optimizes the inorganic-organic interfacial bonding of the entire thermally conductive silicone composite material system, adapting to ultra-thin coating systems of low-addition vinyl silicone oil and liquid acrylate rubber. This enhances the material's compression resilience and structural integrity, and synergistically improves overall temperature resistance, electrical insulation, and thermal aging stability with alumina, making the material suitable for long-term stable use under high pressure, wide temperature, and vibration conditions. Detailed Implementation

[0017] The present invention will be further illustrated below with reference to the embodiments, the purpose of which is to better understand the content of the present invention and to demonstrate the essential features of the present invention. Therefore, the examples given should not be regarded as a limitation on the scope of protection of the present invention.

[0018] All components used in the following examples and comparative examples are derived from commercially available products, wherein: Vinyl silicone oil, CAS No.: 26710-23-6, purchased from Zhejiang Rongli High-Tech Materials Co., Ltd. Liquid acrylic rubber (ACM), purchased from Dongguan Nabaichuan Plastics Co., Ltd., was found to have a Mn content of 20056. The spherical alumina had a D50 (measured by an LS-POP(9) laser particle size analyzer) of 7.895 μm. Aluminum nitride, D50 (measured by LS-POP(9) laser particle size analyzer) was 1.362 μm; Nano magnesium oxide, CAS No.: 1309-48-4, D50 (measured by LS-POP(9) laser particle size analyzer) is 0.114μm; Side-containing hydrogen silicone oil, CAS No.: 68037-59-2; Platinum catalyst, 3000 ppm, purchased from Dongguan Maiteng Rubber & Plastic Materials Co., Ltd. 1-Ethynylcyclohexanol, CAS No.: 78-27-3; 3-Glycidyl etheroxypropyltrimethoxysilane (KH-560), CAS No.: 2530-83-8; Vinyltrimethoxysilane (KH-171), CAS No.: 2768-02-7.

[0019] The component allocation of Examples 1-3 and Comparative Examples 1-2 is as follows: Table 1. Distribution ratio of each sample group

[0020] The main steps of the preparation method for the above samples are briefly described below: S1 The thermally conductive powder is added to a hot air oven in a certain proportion and dried at 120-140℃ for 2-4 hours to remove adsorbed water, free impurities and weakly bound hydroxyl groups on the powder surface. Then it is cooled to 40-60℃ and added to a high-speed mixer together with a silane modifier. It is sheared and dispersed at 1500r / min for 30min. Then it is allowed to stand and mature in a vacuum (-0.085 to -0.095Mpa) for 30min to obtain silane molecules firmly grafted onto the surface of inorganic powder, thus obtaining modified thermally conductive powder, reducing the surface energy of the powder and avoiding agglomeration. S2: Vinyl silicone oil and liquid acrylate rubber are added to a vacuum mixer according to the specified ratio. The mixture is heated to 60 °C, with a vacuum degree of -0.095 MPa, and stirred at 500 r / min for 20–30 min to achieve molecular-level compatibility between the vinyl silicone oil and the liquid acrylate elastomer, forming a low-volatility, high-wetting, and high-elasticity composite matrix liquid. This solves the problem of powder being difficult to wet with low resin dosage. Then, the modified thermally conductive powder is slowly added to the composite matrix liquid in 3–5 batches to avoid agglomeration from a single addition. The mixture is heated to 75 °C and dispersed under vacuum at 50 r / min for 40–60 min. This process relies on the low surface tension of the composite matrix to form a continuous, uniform, nano-scale ultrathin coating layer on the surface of the multi-graded powder particles, filling the microscopic gaps in the powder, reducing the storage space for small molecules, and achieving a low-volatility, oil-proof basic structure. S3. Reduce the temperature inside the vacuum stirring device to below 35°C, add alkynyl alcohol inhibitors, disperse evenly, add platinum catalyst and continue to disperse until uniform, then slowly and evenly drip in hydrogen-containing silicone oil, and continue to stir evenly under vacuum conditions. After stirring at S4 is stopped, vacuum is maintained to degas the material and obtain a paste. The paste is then pressed into a sheet of a preset thickness using a calender. The sheet is then sent into a tunnel oven for segmented curing. First, it is pre-cured at 70-85℃ for 20-30 minutes, and then heated to 100-120℃ for 40-60 minutes for deep curing. After natural cooling to room temperature, it is cut to obtain a low-volatility, high-thermal-conductivity insulating silicone pad.

[0021] The preparation processes of Examples 1-3 and Comparative Examples 1-2, prepared according to the above preparation method, and the obtained silicone pads were observed. The obtained silicone pads were then subjected to the following tests: 1) Thermal conductivity was tested using a DRL-3 thermal conductivity tester according to ASTM D5470 standard; 2) Test the volatilization amount at 105℃ for 2 hours according to GB / T 2793; 3) Test volume resistivity according to GB / T 1410; 4) Test the compression set at 100℃ for 4 hours according to GB / T 7759.1-2015.

[0022] Table 2 Test results for each sample

[0023] As shown in Table 2, the low-volatility, high-thermal-conductivity insulating silicone composite materials of Examples 1-3, using low-volatility vinyl silicone oil and liquid acrylate rubber as the composite matrix, can effectively coat the materials even with low vinyl silicone oil content and high thermal conductive powder content, avoiding problems such as increased dispersion resistance and particle agglomeration during thermal conductive powder modification and subsequent mixing. Their thermal conductivity is stable at 6.5 W / (m·K), and the volatile content is <90 ppm. Example 1 shows a 40% increase in thermal conductivity compared to using spherical alumina alone as the thermal conductive powder (Comparative Example 2), and also exhibits good resilience and insulation properties. A comparison between Comparative Example 1 and Example 1 shows that the addition of liquid acrylate rubber effectively forms a tight cross-linked network, significantly reducing the escape of small molecules and effectively inhibiting silicone oil seepage. Long-term use in power batteries can prevent contamination of battery components.

[0024] The inventors also conducted wide-temperature stability tests on the silicone gaskets of Examples 1-3 through high and low temperature environment tests. The test results are as follows: The cold resistance test was conducted at -40℃ according to GB / T 1682.1 standard. The sample did not show any brittleness, hardening or rebound failure under low temperature environment. Accelerated aging tests were conducted in hot air at 200℃ according to GB / T 3512 standard. The material showed no cracking, oil seepage, pulverization, or significant performance degradation at high temperatures. According to the temperature cycling test in GB / T 2423.22, after 300 cycles of high and low temperature alternation from -40℃ to 200℃, the product structure, insulation performance, thermal conductivity and mechanical resilience remain stable. This shows that the composite material can work stably for a long time in a wide temperature range of -40℃ to 200℃.

[0025] Through extreme temperature testing, the material may be able to withstand even lower and higher instantaneous temperatures in the short term, thus further expanding its applicable temperature range.

[0026] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0027] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A low-volatility, high-thermal-conductivity, insulating silicone composite material suitable for power batteries, characterized in that, Based on parts by weight, it includes the following components: Vinyl silicone oil: 3-10 parts; Liquid acrylate rubber: 8-20 parts; Composite thermally conductive powder: 95-105 parts; Hydrogen-containing silicone oil: 0.3–0.5 parts; Platinum catalyst: 0.02–0.04 parts; Alkyne alcohol inhibitors: 0.02–0.05 parts; Silane modifier: 0.8-2.0 parts.

2. The low-volatility, high-thermal-conductivity, insulating silicone composite material according to claim 1 for power batteries, characterized in that, The vinyl silicone oil has a volatile content of <0.1%, a volatilization amount of ≤100ppm at room temperature, and a viscosity of 30-150 mPa·s.

3. The low-volatility, high-thermal-conductivity, insulating silicone composite material according to claim 2 for power batteries, characterized in that, The molecular weight (Mn) of the liquid acrylate rubber is 10,000-30,000.

4. The low-volatility, high-thermal-conductivity, insulating silicone composite material according to claim 1 for power batteries, characterized in that, The composite thermally conductive and insulating powder is an inorganic composite powder with different particle sizes.

5. The low-volatility, high-thermal-conductivity, insulating silicone composite material according to claim 4 for power batteries, characterized in that, The total amount of the compounded thermally conductive and insulating powder added is 95-100 parts. The thermally conductive and insulating powder is composed of 60-75 parts of spherical alumina with a particle size of 5-40 μm, 15-25 parts of aluminum nitride with a particle size of 0.5-5 μm, and 5-10 parts of nano-magnesium oxide with a particle size of 20-200 nm.

6. The low-volatility, high-thermal-conductivity, insulating silicone composite material according to claim 1 for power batteries, characterized in that, The hydrogen-containing silicone oil is a side-chain hydrogen-containing silicone oil with a hydrogen content of 0.5 to 0.7 wt% and a viscosity of 100 to 200 mPa·s.

7. The low-volatility, high-thermal-conductivity, insulating silicone composite material according to claim 1 for power batteries, characterized in that, The silane modifier is a compound of vinyl silane and epoxy silane in a mass ratio of 1:1 to 1:

2.

8. The low-volatility, high-thermal-conductivity, insulating silicone composite material suitable for power batteries as described in any one of claims 1 to 7, characterized in that, The preparation method includes the following steps: S1 The thermally conductive and insulating powder is dried and activated at 120-140℃ and then cooled to 40-60℃. It is then added together with the silane modifier into a high-speed mixer for shearing and dispersion. After standing for 30 minutes to mature, the modified thermally conductive and insulating powder is obtained. S2. Vinyl silicone oil and liquid acrylate rubber are added to a vacuum stirring device according to the formula. The mixture is heated and stirred in a vacuum environment to obtain a composite matrix liquid. The modified thermally conductive and insulating powder is slowly added to the composite matrix liquid in batches and stirred to disperse evenly. S3 lowers the temperature inside the vacuum stirring device to below 35°C, adds alkynyl alcohol inhibitors, disperses them evenly, adds platinum catalyst and continues to disperse until uniform, then slowly and evenly drips in hydrogen-containing silicone oil, and continues to stir evenly under vacuum conditions. After stirring stops at S4, vacuum is maintained to degas the material and obtain a paste. The paste is then pressed into a sheet of a preset thickness using a calender. The sheet is then sent into a tunnel oven for segmented curing and naturally cooled to room temperature. It is then cut to obtain a low-volatility, high-thermal-conductivity insulating silicone pad.

9. The low-volatility, high-thermal-conductivity, insulating silicone composite material for power batteries according to claim 8, characterized in that, In the preparation method, the vacuum degree of S2 is controlled at -0.092 to -0.098 MPa; the vacuum degree of S3 and S4 is controlled at -0.090 to -0.095 MPa.

10. The low-volatility, high-thermal-conductivity, insulating silicone composite material for power batteries according to claim 8, characterized in that, In the preparation method, the segmented curing of S4 includes the following operations: first, pre-curing is carried out at 70-85℃ for 20-30 minutes, and then the temperature is raised to 100-120℃ and held for 40-60 minutes for deep curing.

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