Thermal conductive silicone grease for new energy battery and preparation method thereof

Abstract

The present application relates to the field of thermal conductive materials, and specifically discloses a thermal conductive silicone grease for new energy batteries and a preparation method thereof, comprising the following raw materials in parts by weight: 20-40 parts of long alumina fiber grafted with low molecular weight silicone oil, 35-55 parts of short alumina fiber grafted with high molecular weight silicone oil, and 1-5 parts of microcapsules. The thermal conductive material in the present application has a relatively good long-term thermal conductive effect.

Description

Technical Field

[0001] The present application relates to the field of thermal conductive materials, and more specifically, to a thermal conductive silicone grease for new energy batteries and a preparation method thereof. Background Art

[0002] During the use of new energy batteries, especially new energy vehicle batteries, battery heat dissipation is a major issue related to the life safety of users. If the battery temperature rises sharply to 200°C, the electrolyte and the positive and negative electrodes will undergo a strong chemical reaction, releasing gas, forming internal high pressure and explosion. How to avoid excessive heat accumulation in the battery and causing battery loss of control is a problem that must be considered.

[0003] In addition to using air cooling, liquid cooling, and natural convection cooling, adding thermal conductive materials to the top and bottom of the electrode to allow the heat that is not easily dissipated at both ends to be transferred to the metal shell through the thermal conductive materials is a common means of battery heat dissipation. In addition, this thermal conductive material must also have insulation properties. The good thermal conductivity and insulation of silicone grease perfectly match these performance requirements. Silicone grease has a high thermal conductivity coefficient and is highly adaptable to the flatness of the application position. It can be used in conjunction with thermal conductive gaskets to further fill the gap between the battery and the radiator to improve thermal conductivity. However, the service life of silicone grease is short, and long-term use will cause problems such as silicone grease drying and oil leakage. How to provide a silicone grease with a long service life and good thermal conductivity is an urgent problem that needs to be solved. Summary of the invention

[0004] In order to solve the problem of insufficient thermal conductivity of silicone grease, the present application provides a thermal conductive silicone grease for new energy batteries and a preparation method thereof.

[0005] In the first aspect, the present application provides a thermal conductive silicone grease for new energy batteries, which adopts the following technical solution:

[0006] The thermal conductive silicone grease for new energy batteries contains the following raw materials in parts by weight: 20-40 parts of long alumina fiber grafted with low molecular weight silicone oil, 35-55 parts of short alumina fiber grafted with high molecular weight silicone oil, and 1-5 parts of microcapsules.

[0007] By adopting the above technical scheme, silicone oil has good insulation, good hydrophobicity and good chemical stability. As thermal grease, the thermal grease has good insulation and hydrophobicity. However, silicone oil is prone to migration after long-term use, causing the thermal grease to dry out and leak oil, and lose some of its thermal conductivity. Alumina is a commonly used thermal conductive material with good thermal conductivity, but it is not compatible with silicone oil as a thermal conductive filler. Due to the density difference, it tends to settle to the bottom after long-term use. The present application adopts alumina fiber as a thermal conductive filler, grafts the alumina fiber with silicone oil, so that the alumina fiber and silicone oil are stably present and evenly dispersed in the thermal grease system. By adding large molecular weight silicone oil and small molecular weight silicone oil, the viscosity of the thermal grease system and the permeability to the coated substrate are balanced, so that a thin and uniform silicone grease is easily formed. The good wettability with the substrate makes it closely connected with the substrate, and no residual air is left in the gaps at the bonding point between the substrate and the silicone grease, thereby fully reducing the contact thermal resistance and exerting the thermal conductivity of the thermal grease. By adding long alumina fibers and short alumina fibers, the viscosity and thermal conductivity effects are also balanced, and at the same time, it is more conducive to forming a thermal conductive network, further improving the thermal conductivity. In addition, the present application creatively grafts large molecular weight silicone oil with short alumina fibers, and grafts small molecular weight silicone oil with long alumina fibers to prepare thermal grease. Such molecular design makes it difficult for the silicone oil to migrate and volatilize to the surface, and the alumina fibers are not easy to deposit at the bottom. The thermal grease does not crack or dry out, and the thermal conductive path exists stably, thereby maintaining the long-term thermal conductivity of the thermal grease. The addition of microcapsules further increases the service life of the thermal grease of the present application.

[0008] In a specific embodiment, the weight average molecular weight of the high molecular weight silicone oil is 20000-30000 g / mol, and the weight average molecular weight of the low molecular weight silicone oil is 6000-9000 g / mol.

[0009] By adopting the above technical solution, the thermal grease has the advantages of being not easy to volatilize, and at the same time, the high molecular weight silicone oil and the low molecular weight silicone oil are interspersed with each other, so that the thermal grease has lower stress while ensuring a certain strength and is not easy to shrink, further ensuring the low contact thermal resistance of the thermal grease.

[0010] In a specific embodiment, the monofilament length of the long alumina fibers is 50-70 μm, and the monofilament length of the short alumina fibers is 10-30 μm.

[0011] By adopting the above technical solution, the relationship between the thickness, viscosity and thermal conductivity of the thermal grease is balanced, and at the same time, the thermal conductivity of the thermal grease is further improved by forming a thermal conductive network through the interlacing of long and short alumina fibers.

[0012] In a specific embodiment, the steps of preparing the long alumina fiber grafted with low molecular weight silicone oil include:

[0013] S1: Mix silane coupling agent, ethanol and pure water, stir evenly to obtain a mixed solution;

[0014] S2: adding the long alumina fiber into the mixed solution, stirring at 80-90° C. for 0.5-1.0 hour; filtering, drying, and obtaining the silane-modified long alumina fiber;

[0015] S3: putting the silane-modified long alumina fiber and low molecular weight silicone oil prepared in S2 into ethyl acetate, stirring for 2-5 hours, filtering, washing, and obtaining the long alumina fiber grafted with low molecular weight silicone oil;

[0016] The mass ratio of the silane coupling agent, ethanol, pure water, low molecular weight silicone oil and long alumina fiber is (2-4): (200-250): (20-30): (5-15): (100-150);

[0017] And / or, the preparation steps of the short alumina fiber grafted with high molecular weight silicone oil include:

[0018] S1: Mix silane coupling agent, ethanol and pure water, stir evenly to obtain a mixed solution;

[0019] S2: adding short alumina fibers into the mixed solution, stirring at 80-90° C. for 0.5-1.0 hours; filtering, drying, and obtaining silane-modified short alumina fibers;

[0020] S3: putting the silane-modified short alumina fiber and high molecular weight silicone oil prepared in S2 into ethyl acetate, stirring for 2-5 hours, filtering, washing, and obtaining short alumina fiber grafted with high molecular weight silicone oil;

[0021] The mass ratio of the silane coupling agent, ethanol, pure water, high molecular weight silicone oil and short alumina fiber is (2-4): (200-250): (20-30): (5-15): (100-150).

[0022] By adopting the above technical solution, alumina fiber is grafted with silicone oil. The grafting process is simple and convenient, does not require special processing conditions and processing equipment, and the grafting effect can meet the performance requirements.

[0023] In a specific embodiment, the wall material components of the microcapsules include: gelatin, silane-modified alumina powder, and the core material components of the microcapsules include: low molecular weight silicone oil.

[0024] By adopting the above technical scheme, gelatin is wrapped with small molecular weight silicone oil, and silane-modified alumina powder is distributed on the wall material of the microcapsule. Silane modification makes the alumina powder compatible with the system and evenly distributed. At the same time, the spherical microcapsules with modified alumina powder distributed on the outer wall are matched with long and short alumina fibers. The long and short alumina fibers are interspersed and fitted with each other. The long and short alumina fibers and the microcapsules form better heat conduction paths in different forms, so that the thermal conductive filler added to the thermal conductive silicone grease is reduced while still maintaining a good thermal conductive effect, further improving the thermal conductivity of the thermal conductive silicone grease and facilitating sizing. When the silicone grease is used in an environment As the temperature rises, the thermal conductivity decreases. When the system temperature exceeds the decomposition temperature of gelatin, the gelatin decomposes and takes away part of the heat, further ensuring that the heat source of the coated substrate is at a safe use temperature. The wall material of the microcapsule ruptures to release the coated silicone oil. The small molecular weight silicone oil can quickly migrate to fill the gap, allowing the thermal grease that has been used for a period of time to be re-moistened and mixed with the modified alumina powder in the system, further improving the long-term thermal conductivity of the thermal grease. The modified alumina powder dispersed in the system after the microcapsules are ruptured can also cooperate with alumina fibers to further form a point-line thermal conduction path to improve thermal conductivity.

[0025] In a specific embodiment, the particle size of the microcapsule is (0.1-0.8) mm.

[0026] By adopting the above technical solution, the microcapsules can effectively encapsulate small molecule silicone oil, and at the same time, the length of the alumina fibers is conducive to building a thermal conductive path to improve the thermal conductivity of the silicone grease.

[0027] In a specific embodiment, the preparation steps of the microcapsules include: adding small molecule silicone oil to a 10% gelatin aqueous solution, stirring for 30-45 minutes, stirring at a temperature of 25-40°C, and stirring at a rate of 300-450r / min, then adding a 10% glutaraldehyde aqueous solution, stirring for 20-30 minutes, filtering, washing, and low-temperature drying to obtain a microcapsule semi-finished product; adding silane-modified alumina powder to a 10% gelatin aqueous solution, stirring for 5-10 minutes, stirring at a temperature of 25-40°C, then adding the microcapsule semi-finished product, stirring for 10-15 minutes, then adding a 10% glutaraldehyde aqueous solution, stirring for 20-30 minutes, filtering, washing, and low-temperature drying to obtain microcapsule powder. The mass ratio of the gelatin aqueous solution, silane-modified alumina powder, and small molecule silicone oil used in the preparation process is (70-200): (3-7): (15-60).

[0028] By adopting the above technical scheme, the prepared microcapsule wall material modified alumina powder is evenly and stably distributed, effectively participating in the construction of the heat conduction path, the microcapsules stably wrap the small molecular weight silicone oil, and the gelatin wrapped outside the silicone oil has a moderate thickness and does not affect the thermal conductivity.

[0029] In a specific embodiment, the alumina powder used in the silane-modified alumina powder has a particle size of 1-3 μm.

[0030] By adopting the above technical solution, the alumina powder is not easy to agglomerate and is evenly distributed on the outer wall of the spherical microcapsule; the viscosity and hardness of the microcapsule are not increased, which is convenient for sizing; it is easy to construct a thermal conductive network with the alumina fiber, and the thermal conductive effect is good.

[0031] In the second aspect, the present application provides a method for preparing thermal conductive silicone grease for new energy batteries, which is characterized in that the preparation method comprises the following steps: short alumina fibers are grafted with high molecular weight silicone oil, long alumina fibers are grafted with low molecular weight silicone oil, and microcapsules are mixed, and vacuum stirred at a stirring temperature of 30-50°C to obtain thermal conductive silicone grease.

[0032] The thermally conductive silicone grease is prepared by adopting the above technical solution.

[0033] In a specific feasible implementation method, the steps of mixing short alumina fibers grafted with high molecular weight silicone oil, long alumina fibers grafted with low molecular weight silicone oil, and microcapsules include: adding microcapsules to the long alumina fibers grafted with low molecular weight silicone oil, stirring evenly in vacuum, and then adding short alumina fibers grafted with high molecular weight silicone oil, and stirring evenly in vacuum.

[0034] By adopting the above technical scheme, the adding process of the present application is to first add microcapsules to the long alumina fiber grafted with low molecular weight silicone oil, and then add the short alumina fiber grafted with high molecular weight silicone oil, so that the viscosity in the system is not large when the microcapsules are added, and the long alumina fiber constructs the framework of the basic heat conduction path, which is beneficial to the dispersion of the microcapsules and the construction of the heat conduction network between the long alumina fiber and the silane-modified alumina powder on the outer wall of the microcapsule.

[0035] This application has the following beneficial effects:

[0036] 1. Since the present application adopts long alumina fibers grafted with low molecular weight silicone oil and short alumina fibers grafted with high molecular weight silicone oil, the silicone oil in the grease system is not easy to migrate and volatilize, the thermal conductive filler alumina fibers are not easy to deposit and have good compatibility with the silicone oil in the system, the thermal conductive silicone grease has good thermal conductivity and a long effective thermal conductivity time; since the present application adds microcapsules, when the ambient temperature is high, the small molecule silicone oil encapsulated in the capsules migrates out, further extending the time for efficient thermal conductivity.

[0037] 2. In the present application, long alumina fibers, short alumina fibers, and microcapsules with silane-modified alumina powder dispersed on the outer wall are preferably used to construct a thermal conductive network. The sizes of the long alumina fibers, short alumina fibers, and alumina powder are limited to further enhance the thermal conductivity of the thermal grease, while also reducing the mass of the thermally conductive filler that needs to be added, further reducing the thermal resistance caused by the coating thickness of the thermal grease. DETAILED DESCRIPTION

[0038] The present application is further described in detail below in conjunction with the examples. The high molecular weight silicone oil in the preparation examples and examples of the present application refers to an epoxy silicone oil with a weight average molecular weight of 25000 g / mol, and the low molecular weight silicone oil in the preparation examples and examples of the present application refers to an epoxy silicone oil with a weight average molecular weight of 8000 g / mol. Unless otherwise specified, the raw materials in the preparation examples and examples of the present application are all from conventional commercial brands.

[0039] Preparation Example 1

[0040] Preparation of long alumina fiber grafted with low molecular weight silicone oil:

[0041] S1: Mix 3g of silane coupling agent KH-540, 225g of ethanol and 25g of pure water, stir evenly to obtain a mixed solution;

[0042] S2: 125 g of long alumina fibers with an average monofilament length of 60 μm were added to the mixed solution, and stirred at 80° C. for 1 hour; filtered and dried to obtain silane-modified long alumina fibers;

[0043] S3: Put the silane-modified long alumina fiber prepared in S2 and 15 g of low molecular weight silicone oil into ethyl acetate, stir for 5 hours, filter, and wash to obtain the long alumina fiber grafted with low molecular weight silicone oil;

[0044] Preparation of short alumina fibers grafted with high molecular weight silicone oil:

[0045] S1: Mix 3g of silane coupling agent KH-540, 225g of ethanol and 25g of pure water, stir evenly to obtain a mixed solution;

[0046] S2: 125 g of short alumina fibers with a monofilament length of 20 μm were added to the mixed solution, and stirred at 80° C. for 1 hour; filtered and dried to obtain silane-modified short alumina fibers;

[0047] S3: The silane-modified short alumina fibers prepared in S2 and 15 g of high molecular weight silicone oil were added to ethyl acetate, stirred for 5 hours, filtered, and washed to obtain short alumina fibers grafted with high molecular weight silicone oil.

[0048] Preparation Example 2

[0049] Preparation of long alumina fiber grafted with low molecular weight silicone oil:

[0050] S1: Mix 3g of silane coupling agent KH-540, 225g of ethanol and 25g of pure water, stir evenly to obtain a mixed solution;

[0051] S2: 150 g of alumina fiber with a monofilament length of 60 μm was added to the mixed solution, and stirred at 80° C. for 1 hour; filtered and dried to obtain silane-modified long alumina fiber;

[0052] S3: Put the silane-modified long alumina fiber prepared in S2 and 10 g of low molecular weight silicone oil into ethyl acetate, stir for 5 hours, filter, and wash to obtain the long alumina fiber grafted with low molecular weight silicone oil;

[0053] Preparation of short alumina fibers grafted with high molecular weight silicone oil:

[0054] S1: Mix 3g of silane coupling agent KH-540, 225g of ethanol and 25g of pure water, stir evenly to obtain a mixed solution;

[0055] S2: 150 g of short alumina fibers with a monofilament length of 20 μm were added to the mixed solution, and stirred at 80° C. for 1.0 hour; filtered and dried to obtain silane-modified short alumina fibers;

[0056] S3: The silane-modified short alumina fibers prepared in S2 and 10 g of high molecular weight silicone oil were added to ethyl acetate, stirred for 5 hours, filtered, and washed to obtain short alumina fibers grafted with high molecular weight silicone oil.

[0057] Preparation Example 3

[0058] Preparation of silane-modified alumina powder:

[0059] S1: Mix 3g of silane coupling agent KH-540, 225g of ethanol and 25g of pure water, stir evenly to obtain a mixed solution;

[0060] S2: 125 g of alumina powder with an average particle size of 2 μm was added to the mixed solution, stirred at 80° C. for 1.0 hour, filtered, and dried to obtain silane-modified alumina powder.

[0061] Preparation of microcapsules:

[0062] 30g of low molecular weight silicone oil is added into 100g of 10% gelatin aqueous solution, stirred for 30min, the stirring temperature is 25°C, the stirring rate is 300r / min, and then 2g of 10% glutaraldehyde aqueous solution is added, stirred for 20min, filtered, washed, and low-temperature dried to obtain a microcapsule semi-finished product; 5g of silane-modified alumina powder is added into 100g of 10% gelatin aqueous solution, stirred for 5min, the stirring temperature is 25°C, and then the microcapsule semi-finished product is added, stirred for 10 minutes, and then 2g of 10% glutaraldehyde aqueous solution is added, stirred for 20min, filtered, washed, and low-temperature dried to obtain a microcapsule powder.

[0063] Preparation Example 4

[0064] Preparation of microcapsules:

[0065] 30g of low molecular weight silicone oil is added into 100g of 10% gelatin aqueous solution, stirred for 30min, the stirring temperature is 25°C, the stirring rate is 300r / min, and then 2g of 10% glutaraldehyde aqueous solution is added, stirred for 20min, filtered, washed, and low-temperature dried to obtain a microcapsule semi-finished product; the microcapsule semi-finished product is added into 100g of 10% gelatin aqueous solution, stirred for 10min, the stirring temperature is 25°C, and then 2g of 10% glutaraldehyde aqueous solution is added, stirred for 20min, filtered, washed, and low-temperature dried to obtain a microcapsule powder.

[0066] Preparation Example 5

[0067] Preparation of short alumina fibers grafted with low molecular weight silicone oil:

[0068] S1: Mix 3g of silane coupling agent KH-540, 225g of ethanol and 25g of pure water, stir evenly to obtain a mixed solution;

[0069] S2: 125 g of short alumina fibers with an average monofilament length of 25 μm were added to the mixed solution, and stirred at 80° C. for 1 hour; filtered and dried to obtain silane-modified short alumina fibers;

[0070] S3: Put the silane-modified short alumina fiber prepared in S2 and 15 g of low molecular weight silicone oil into ethyl acetate, stir for 5 hours, filter, and wash to obtain short alumina fiber grafted with low molecular weight silicone oil;

[0071] Preparation of long alumina fibers grafted with high molecular weight silicone oil:

[0072] S1: Mix 3g of silane coupling agent KH-540, 225g of ethanol and 25g of pure water, stir evenly to obtain a mixed solution;

[0073] S2: 125 g of long alumina fiber with a monofilament length of 60 μm was added to the mixed solution, and stirred at 80° C. for 1 hour; filtered and dried to obtain silane-modified long alumina fiber;

[0074] S3: The silane-modified long alumina fiber prepared in S2 and 15 g of high molecular weight silicone oil are put into ethyl acetate, stirred for 5 hours, filtered, and washed to obtain long alumina fiber grafted with high molecular weight silicone oil. Example

[0075] Example 1

[0076] Add 3g of the microcapsules prepared in Preparation Example 4 to 20g of the long alumina fiber grafted with low molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum. Then add 55g of the short alumina fiber grafted with high molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum at a stirring temperature of 40°C to obtain thermal conductive silicone grease.

[0077] Example 2

[0078] Add 3g of the microcapsules prepared in Preparation Example 4 to 40g of the long alumina fiber grafted with low molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum. Then add 35g of the short alumina fiber grafted with high molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum at a stirring temperature of 40°C to obtain thermal conductive silicone grease.

[0079] Example 3

[0080] Add 3 g of the microcapsules prepared in Preparation Example 4 to 30 g of the long alumina fiber grafted with low molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum. Then add 45 g of the short alumina fiber grafted with high molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum at a stirring temperature of 40°C to obtain thermal conductive silicone grease.

[0081] Example 4

[0082] Add 3g of the microcapsules prepared in Preparation Example 4 to 30g of the short alumina fibers grafted with low molecular weight silicone oil prepared in Preparation Example 2, and stir evenly in vacuum. Then add 45g of the short alumina fibers grafted with high molecular weight silicone oil prepared in Preparation Example 2, and stir evenly in vacuum at a stirring temperature of 40°C to obtain thermal conductive silicone grease.

[0083] Example 5

[0084] Add 3 g of the microcapsules prepared in Preparation Example 3 to 30 g of the long alumina fiber grafted with low molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum. Then add 45 g of the short alumina fiber grafted with high molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum at a stirring temperature of 40°C to obtain thermal conductive silicone grease.

[0085] Comparative Example 1

[0086] 3 g of the microcapsules prepared in Preparation Example 4 were added to 75 g of the short alumina fiber grafted high molecular weight silicone oil prepared in Preparation Example 1, and stirred evenly in vacuum at a stirring temperature of 40° C. to obtain thermal conductive silicone grease.

[0087] Comparative Example 2

[0088] 3 g of the microcapsules prepared in Preparation Example 4 were added to 75 g of the long alumina fiber grafted low molecular weight silicone oil prepared in Preparation Example 1, and stirred evenly in vacuum at a stirring temperature of 40° C. to obtain thermal conductive silicone grease.

[0089] Comparative Example 3

[0090] Add 3g of the microcapsules prepared in Preparation Example 4 to 26.7g of long alumina fibers, then add 3.3g of low molecular weight silicone oil, stir evenly in vacuum, then add 40.05g of short alumina fibers and 4.95g of high molecular weight silicone oil in turn, stir evenly in vacuum at a stirring temperature of 40°C to obtain thermal grease.

[0091] Comparative Example 4

[0092] Add 30 g of the long alumina fiber grafted with low molecular weight silicone oil prepared in Preparation Example 1 to 45 g of the short alumina fiber grafted with high molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum at a stirring temperature of 40°C to obtain thermal conductive silicone grease.

[0093] Comparative Example 5

[0094] Add 3g of the microcapsules prepared in Preparation Example 4 to 20g of the long alumina fiber grafted high molecular weight silicone oil prepared in Preparation Example 5, and stir evenly in vacuum. Then add 55g of the short alumina fiber grafted high molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum at a stirring temperature of 40°C to obtain thermal conductive silicone grease.

[0095] Comparative Example 6

[0096] Add 3 g of the microcapsules prepared in Preparation Example 4 to 20 g of the long alumina fiber grafted low molecular weight silicone oil prepared in Preparation Example 1, and stir evenly in vacuum. Then add 55 g of the short alumina fiber grafted low molecular weight silicone oil prepared in Preparation Example 5, and stir evenly in vacuum at a stirring temperature of 40°C to obtain thermal conductive silicone grease.

[0097] Test 1: Use DRL-III thermal conductivity tester to test thermal conductivity. According to GB10297 standard, the test column size is 706.858mm 2 , tested with a thickness of 2mm.

[0098] Test 2: The test silicone grease was aged for 1000 hours under -40-150C thermal shock conditions, and then the thermal conductivity was tested using a DRL-III thermal conductivity tester. According to GB 10297 standard, the test column size was 706.858mm 2 , tested with a thickness of 2mm.

[0099] The test results are summarized in Table 1.

[0100] Table 1

[0101] Thermal conductivity1 (W / mK) Thermal conductivity2 (W / mK) Example 1 4.2 3.6 Example 2 4.4 3.9 Example 3 4.5 4.0 Example 4 4.6 4.0 Example 5 5.3 5.2 Comparative Example 1 3.6 2.8 Comparative Example 2 3.7 3.0 Comparative Example 3 3.9 3.2 Comparative Example 4 4.0 2.5 Comparative Example 5 3.4 2.7 Comparative Example 6 3.5 2.6

[0102] It can be seen from Examples 1 to 4 and Comparative Examples 1 to 3, Comparative Examples 5-6 and Table 1 that the present application grafts high molecular weight silicone oil with short alumina fibers, and low molecular weight silicone oil with long alumina fibers, so that the silicone oil does not migrate and the thermal conductive filler does not deposit during long-term use, and the thermal conductive silicone grease prepared has good thermal conductivity and long thermal conductive life.

[0103] It can be seen from Example 3, Example 5 and Comparative Example 4 and Table 1 that the present application further builds a thermal conductive network by adding gelatin containing modified alumina powder as the wall material, small molecular weight silicone oil as the core material of microcapsules, long and short alumina fibers, and the thermal conductive silicone grease made from the microcapsules. When the ambient temperature is high, the gelatin decomposes and releases new small molecular weight silicone oil to maintain the wettability of the thermal conductive silicone grease. The thermal conductive silicone grease obtained has good thermal conductive effect and long thermal conductive life.

[0104] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A thermal conductive silicone grease for new energy batteries, characterized in that: The thermal conductive silicone grease for new energy batteries comprises the following raw materials in parts by weight: 20-40 parts of long alumina fiber grafted with low molecular weight silicone oil, 35-55 parts of short alumina fiber grafted with high molecular weight silicone oil, and 1-5 parts of microcapsules; The preparation steps of the long alumina fiber grafted with low molecular weight silicone oil include: S1: Mix silane coupling agent, ethanol and pure water, stir evenly to obtain a mixed solution; S2: adding the long alumina fiber into the mixed solution of S1, stirring at 80-90° C. for 0.5-1.0 hour; filtering, drying, and obtaining the silane-modified long alumina fiber; S3: putting the silane-modified long alumina fiber and low molecular weight silicone oil prepared in S2 into ethyl acetate, stirring for 2-5 hours, filtering, washing, and obtaining the long alumina fiber grafted with low molecular weight silicone oil; The mass ratio of the silane coupling agent in S1, the ethanol in S1, the pure water in S1, the low molecular weight silicone oil and the long alumina fiber is (2-4): (200-250): (20-30): (5-15): (100-150); The preparation steps of the short alumina fiber grafted with high molecular weight silicone oil include: S11: mixing a silane coupling agent, ethanol and pure water, and stirring evenly to obtain a mixed solution; S12: adding the short alumina fiber into the mixed solution of S11, stirring at 80-90° C. for 0.5-1.0 hour; filtering, drying, and obtaining silane-modified short alumina fiber; S13: putting the silane-modified short alumina fiber and high molecular weight silicone oil prepared in S12 into ethyl acetate, stirring for 2-5 hours, filtering, washing, and obtaining short alumina fiber grafted with high molecular weight silicone oil; The mass ratio of the silane coupling agent in S11, the ethanol in S11, the pure water in S11, the high molecular weight silicone oil and the short alumina fiber is (2-4): (200-250): (20-30): (5-15): (100-150); The high molecular weight silicone oil is an epoxy silicone oil with a weight average molecular weight of 25000 g / mol, and the low molecular weight silicone oil is an epoxy silicone oil with a weight average molecular weight of 8000 g / mol; The monofilament length of the long alumina fiber is 50-70 μm, and the monofilament length of the short alumina fiber is 10-30 μm; The silane coupling agent in S1 and S11 is KH-540; The preparation steps of the microcapsules include: adding low molecular weight silicone oil into a gelatin aqueous solution with a mass fraction of 10%, stirring for 30-45 minutes, stirring at a temperature of 25-40°C, and stirring at a speed of 300-450r / min, then adding a glutaraldehyde aqueous solution with a mass fraction of 10%, stirring for 20-30 minutes, filtering, washing, and low-temperature drying to obtain a microcapsule semi-finished product; adding silane-modified alumina powder into a gelatin aqueous solution with a mass fraction of 10%, stirring for 5-10 minutes, stirring at a temperature of 25-40°C, then adding the microcapsule semi-finished product, stirring for 10-15 minutes, then adding a glutaraldehyde aqueous solution with a mass fraction of 10%, stirring for 20-30 minutes, filtering, washing, and low-temperature drying to obtain a microcapsule powder.

2. The thermal conductive silicone grease for new energy batteries according to claim 1, characterized in that: The particle size of the microcapsule is 0.1-0.8 mm.

3. The thermal conductive silicone grease for new energy batteries according to claim 1, characterized in that: The particle size of the alumina powder used in the silane-modified alumina powder is 1-3 μm.

4. A method for preparing the thermal conductive silicone grease for new energy batteries according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: short alumina fiber grafted with high molecular weight silicone oil, long alumina fiber grafted with low molecular weight silicone oil, and microcapsules are mixed, and vacuum stirred at a stirring temperature of 30-50 DEG C to obtain thermal conductive silicone grease.

5. The method for preparing thermally conductive silicone grease for new energy batteries according to claim 4, characterized in that: The steps of mixing short alumina fibers grafted with high molecular weight silicone oil, long alumina fibers grafted with low molecular weight silicone oil, and microcapsules include: adding microcapsules to the long alumina fibers grafted with low molecular weight silicone oil, stirring evenly in vacuum, and then adding short alumina fibers grafted with high molecular weight silicone oil, and stirring evenly in vacuum.