Spraying paint for increasing convective heat exchange coefficient of soft package lithium battery and preparation method thereof

Abstract

The application provides a spraying coating for increasing the convection heat exchange coefficient of a soft package lithium battery and a preparation method thereof, which comprises the following raw materials in parts by weight: 45-65 parts of silicone resin, 10-15 parts of modified silicon nitride, 5-10 parts of carbon material, 2-5 parts of silane coupling agent, 1-3 parts of heat-conducting metal powder, 1-2 parts of aluminum oxide, 1-2 parts of cerium oxide, 1-2 parts of antimony oxide, 1-3 parts of modified dispersing agent, 1-3 parts of leveling agent, 0.5-2 parts of defoaming agent, 0.5-1.5 parts of anti-settling agent and 50-85 parts of solvent. The spraying coating can effectively increase the convection heat exchange coefficient and improve the heat dissipation efficiency, and has the properties of hydrophobicity, dust prevention, energy saving, environmental protection, good flame retardancy, corrosion resistance and high hardness, and is suitable for the application of the soft package lithium battery in a new energy automobile, and has a good market prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spraying coating, and particularly relates to a spraying coating for soft-packaged lithium batteries and capable of increasing the convective heat transfer coefficient and a preparation method thereof. BACKGROUND

[0002] With the increasing requirements of consumers for travel comfort and convenience, the overall new energy vehicle industry chain has entered a high-speed development track. According to statistics, the market share of new energy vehicles in China reached 25.6% in 2022, and the domestic retail sales of new energy vehicles reached 7.736 million in 2023, increasing by 36.2% over 2022. New energy vehicles powered by lithium-ion batteries are the fastest developing new energy vehicle type in China at present.

[0003] Lithium-ion batteries supply energy through chemical reactions, which inevitably generates a certain amount of heat. When the heat continues to increase and cannot be effectively dissipated, the activity of electrochemical substances will be stronger. If the activity continues to increase, the lithium-ion battery may catch fire or explode. Therefore, technical personnel soft-pack the lithium-ion battery and use spraying coating to increase the convective heat transfer coefficient of the soft-packaged lithium battery to solve the problem of safety hazards.

[0004] Patent No. 201811543268.4 relates to an anti-corrosion coating for the surface of a lithium battery and a preparation method thereof, which comprises the following raw materials: nano-aluminum oxide, nano-titanium dioxide, sodium hypochlorite, glycerol, perfluoroethyl propylene, and toluene. The anti-corrosion coating prepared by the invention has excellent anti-corrosion performance and can meet market demand. However, this patent focuses on preventing corrosion of lithium batteries during use and cannot effectively increase the convective heat transfer coefficient. Patent No. 201611174386.3 relates to a heat-conducting anti-corrosion coating for the surface of a lithium battery and a preparation method thereof. The components include nano-aluminum oxide, silicone-modified acrylic resin, perfluoroethyl propylene, and toluene. The preparation includes the following steps: a) acid washing nano-aluminum oxide, and b) grinding and mixing. The heat-conducting anti-corrosion coating of the invention can be applied to the surface of a lithium battery to prevent corrosion of the lithium battery tube during use, thereby prolonging the service life of the lithium battery. However, this patent can obtain a better convective heat transfer coefficient to some extent by increasing the thermal conductivity, but the solvent used is toluene, which is highly toxic and poses potential hazards.

[0005] Therefore, there is an urgent need for a spraying coating for soft-packaged lithium batteries that can increase the convective heat transfer coefficient, so that the coating meets the performance requirements of good heat dissipation, hydrophobicity and dust resistance, energy saving and emission reduction, flame retardation, and corrosion resistance. SUMMARY

[0006] In view of the existing technical problems, the present application aims to provide a spraying coating for increasing the convective heat transfer coefficient of soft package lithium battery and a preparation method thereof.The spraying coating provided by the present application can effectively increase the convective heat transfer coefficient and improve the heat dissipation efficiency, and has the properties of hydrophobicity, dust prevention, energy saving, environmental protection, good flame retardancy, corrosion resistance and high hardness, and is suitable for the application of soft package lithium battery in new energy vehicles, and has good market prospect.

[0007] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] The present application provides a spraying coating for increasing the convective heat transfer coefficient of soft package lithium battery, which comprises the following raw materials in parts by weight: 45-65 parts of silicon resin, 10-15 parts of modified silicon nitride, 5-10 parts of carbon material, 2-5 parts of silane coupling agent, 1-3 parts of heat-conducting metal powder, 1-2 parts of aluminum oxide, 1-2 parts of cerium oxide, 1-2 parts of antimony oxide, 1-3 parts of modified dispersing agent, 1-3 parts of leveling agent, 0.5-2 parts of defoaming agent, 0.5-1.5 parts of anti-settling agent and 50-85 parts of solvent.

[0009] The reaction mechanism and action of the present application are as follows:

[0010] 1.The silicon resin is a kind of thermosetting polysiloxane system with Si-O-Si repeating units and highly cross-linked structure, which has the advantages of low-temperature flexibility, high thermal stability, weather resistance, hydrophobicity and low dielectricity.However, the silicon resin also has many shortcomings, such as poor adhesion caused by low surface energy, poor tear resistance, impact resistance and mechanical properties caused by low intermolecular force, which greatly limits its application range.The silicon resin of the present application is composed of epoxy modified silicon resin and phenyl silicon resin in a specific proportion.The combination of epoxy resin and silicon resin can make up for the shortcomings of the above properties, and obtain high-performance epoxy modified silicon resin.The phenyl silicon resin has high heat resistance, chemical resistance and oxidation resistance, which further enhances the stability and durability of the coating, prolongs the service life, and achieves the effect of energy saving and environmental protection.

[0011] 2.The present application uses tetraethyl orthosilicate and polyethylene glycol to preliminarily modify silicon nitride, which can graft active functional groups of hydroxyl groups on the surface of silicon nitride, which is beneficial to the smooth grafting of dichlorodimethylsilane on silicon nitride, and then methyl methacrylate and organic solvent are used to modify the intermediate of modified silicon nitride by secondary ball milling, so that acrylic acid is grafted onto the surface of silicon nitride, and the finally formed modified silicon nitride particles are uniform in size, have space steric hindrance effect and no agglomeration phenomenon, which is beneficial to its dispersion in the system, and the grafted ester group, silane and hydroxyl group make it have stronger heat resistance, chemical stability, corrosion resistance and hardness.

[0012] 3. The modified dispersant is made of allyl polyoxyethylene ether, acrylic acid, 2-methylenyl butyrolactone and 2-propenamide-2-methylpropane sulfonic acid, and introduces multiple functional groups. On the one hand, the dispersant can be combined with the silicone resin and cured to participate in the curing process of the silicone resin in the form of chemical reaction, thereby improving the interaction between the dispersant and the film-forming matrix. On the other hand, the suitable molecular weight can make the dispersant fully stretch and attach the anchoring group to the surface of the powder, thereby improving the dispersion efficiency of the raw material.

[0013] In some embodiments, the silicone resin is an epoxy-modified silicone resin and a phenyl silicone resin, and the mass ratio of the two is 1:(0.5-1).

[0014] In some embodiments, the preparation method of the modified silicon nitride comprises the following steps:

[0015] (1) Silicon nitride, ethanol and water are added to a reaction kettle, stirred for 10-30 min, tetraethyl orthosilicate is added, the pH is adjusted to 7.5-8.5 by using an acid-base regulator, heated to 45-55℃, stirred for 1-3 h, centrifuged, washed and dried to obtain tetraethyl orthosilicate-modified silicon nitride;

[0016] (2) The tetraethyl orthosilicate-modified silicon nitride prepared in step (1), ethanol and water are added to a reaction kettle, stirred for 10-30 min, polyethylene glycol is added, heated to 50-60℃, stirred for 2-5 h, centrifuged, washed and dried to obtain a modified powder;

[0017] (3) The modified powder prepared in step (2), dichlorodimethylsilane and an organic solvent are placed in a ball mill tank, sealed and ball-milled for 5-10 h to obtain an intermediate of the modified silicon nitride;

[0018] (4) The intermediate of the modified silicon nitride prepared in step (3), ethyl methacrylate and an organic solvent are placed in a ball mill tank, sealed and ball-milled for 10-15 h to obtain the modified silicon nitride.

[0019] In some embodiments, the mass ratio of the silicon nitride to the tetraethyl orthosilicate in step (1) is 1:(1-1.5).

[0020] In some embodiments, the number average molecular weight of the polyvinyl alcohol in step (2) is 200-4000, and the mass ratio of the polyvinyl alcohol to the tetraethyl orthosilicate-modified silicon nitride is 1:(10-20).

[0021] Preferably, the number average molecular weight of the polyvinyl alcohol in step (2) is 400-2000, and the mass ratio of the polyvinyl alcohol to the tetraethyl orthosilicate-modified silicon nitride is 1:15.

[0022] In some embodiments, the preparation method of the modified dispersant comprises the following steps:

[0023] S1. Dissolve the allyl polyoxyethylene ether in water and stir until uniform to obtain solution A; dissolve the acrylic acid, 2-methylenebutyrolactone and 2-acrylamide-2-methylpropane sulfonic acid in water and stir until uniform to obtain solution B;

[0024] S2. Mix solution A and solution B and add to a reaction kettle, heat to 70-75°C, add a chain transfer agent, drop in an initiator under an inert gas protective atmosphere, heat to 80-85°C, react for 2-4 hours under 100-250 kPa to obtain a reaction solution;

[0025] S3. When the reaction solution is cooled to 30-40°C, adjust the pH to 7.5-8.5 with an acid-base adjusting agent to obtain the modified dispersant.

[0026] In some embodiments, the molar ratio of the allyl polyoxyethylene ether, the acrylic acid, the 2-methylenebutyrolactone and the 2-acrylamide-2-methylpropane sulfonic acid is 1:(4-8):(3-5):(2-4).

[0027] In some embodiments, the number average molecular weight of the allyl polyoxyethylene ether is 2000-3000.

[0028] In some embodiments, the chain transfer agent is sodium hypophosphite, and the molar amount of the chain transfer agent is 1-5% of the total molar amount of the allyl polyoxyethylene ether, the acrylic acid, the 2-methylenebutyrolactone and the 2-acrylamide-2-methylpropane sulfonic acid.

[0029] In some embodiments, the initiator is a mixture of ammonium persulfate and sodium bisulfite, and the molar amount of the initiator is 2-6% of the total molar amount of the allyl polyoxyethylene ether, the acrylic acid, the 2-methylenebutyrolactone and the 2-acrylamide-2-methylpropane sulfonic acid.

[0030] In some embodiments, the carbon material is any one or more of carbon nanotubes, carbon spheres and carbon fibers; the silane coupling agent is any one or more of KH-550, KH-560 and KH-570; the thermally conductive metal powder is any one or more of silver powder, copper powder and aluminum powder, and the particle size is 1-20 μm; the leveling agent is a silicone leveling agent; the defoaming agent is a silicone defoaming agent; the anti-settling agent is any one or more of bentonite, polyethylene wax and polyamide wax; and the solvent is any one or more of ethyl acetate, butyl acetate and propylene glycol methyl ether acetate.

[0031] Another aspect of the present application provides a preparation method of a sprayed coating for increasing the convective heat transfer coefficient of a soft package lithium battery, comprising the following steps:

[0032] One, mix modified silicon nitride, carbon material, silane coupling agent, heat-conducting metal powder, aluminum oxide, cerium oxide, antimony oxide, modified dispersant, leveling agent, defoaming agent, anti-settling agent and part of solvent, stir uniformly at a rotating speed of 700-1000 r / min, to obtain a first mixed material;

[0033] Two, mix the silicone resin and the remaining solvent, then add to the first mixed material obtained in step one, heat to 60-70 DEG C, grind and disperse, stir uniformly at a rotating speed of 700-1000 r / min, then move to a grinding machine for grinding, to obtain a spray coating.

[0034] Compared with the prior art, the spray coating has the advantages that:

[0035] 1. The spray coating can effectively increase the convective heat transfer coefficient, improve the heat dissipation efficiency, and has the properties of hydrophobicity, dust prevention, energy saving, environmental protection, good flame retardancy, corrosion resistance and high hardness, and is suitable for application of soft package lithium battery in new energy vehicles, and has good market prospect.

[0036] 2. The silicone resin is composed of epoxy modified silicone resin and phenyl silicone resin in a specific proportion. The use of the two can avoid the problems of poor adhesion, poor impact resistance and poor mechanical properties, and enhance the heat resistance, oxidation resistance, stability and durability of the coating, thereby prolonging the service life and achieving the effect of energy saving and environmental protection.

[0037] 3. The modified silicon nitride is preliminarily modified by tetraethyl orthosilicate and polyethylene glycol, and then the intermediate of the modified silicon nitride is modified twice by dichlorodimethylsilane, ethyl methacrylate and organic solvent, so that the modified silicon nitride has good dispersibility, and the grafted ester group, silane and hydroxyl group make it have stronger heat resistance, chemical stability, corrosion resistance and hardness.

[0038] 4. The modified dispersant prepared in the application introduces a variety of functional groups. On the one hand, the dispersant can be combined and solidified with the silicone resin; on the other hand, the suitable molecular weight can make the dispersant fully expand and improve the dispersion efficiency of the raw materials.

[0039] 5. The coating can prolong the service life of the material and reduce the maintenance cost, and can maintain the environmental temperature by nano heat dissipation during use, thereby saving power consumption and achieving the performance of energy saving and environmental protection. DETAILED DESCRIPTION

[0040] The application will be described below in connection with specific embodiments. It should be noted that the following examples are illustrative of specific embodiments of the application and are not intended to limit the scope of the application. Other combinations and sub-combinations of the disclosed features and elements, and other modifications, variations, and uses will be apparent to those skilled in the art.

[0041] Each spray coating was prepared according to the ratio of each raw material and the preparation method as specified in the following examples and comparative examples.

[0042] In order to facilitate the implementation of the application by those skilled in the art, the manufacturers of some raw materials of the examples and comparative examples are described as follows:

[0043] Epoxy-modified silicone resin: purchased from Hubei Xingdongcheng Chemical Co., Ltd.;

[0044] Phenyl silicone resin: purchased from Shandong Changyao New Material Co., Ltd., model CY-D2;

[0045] Polyethylene glycol PEG-600: purchased from Haian Petrochemical Factory in Jiangsu Province;

[0046] Allyl polyoxyethylene ether APEG-1000: purchased from Haian Petrochemical Factory in Jiangsu Province;

[0047] Polyurethane dispersant: purchased from Dongguan Hongrui Chemical Co., Ltd., model 4138;

[0048] Silicone defoamer: purchased from Shandong Qimin Chemical Technology Co., Ltd., model BYK-310;

[0049] Other raw materials are not specially mentioned and can be purchased from the market.

[0050] Preparation Example 1

[0051] The preparation method of modified silicon nitride A comprises the following steps:

[0052] (1) 10 g of silicon nitride, 50 ml of ethanol, and 50 ml of water were added to a reaction kettle, stirred for 20 min, 12 g of tetraethyl orthosilicate was added, the pH was adjusted to 8.0 with ammonia water, heated to 50°C, stirred for 2 h, centrifuged, and the solid-phase product 1 obtained by centrifugal separation was washed with deionized water to neutral, and dried at 105°C for 8 h to obtain tetraethyl orthosilicate-modified silicon nitride;

[0053] (2) 15 g of the tetraethyl orthosilicate-modified silicon nitride prepared in step (1), 25 ml of ethanol, and 25 ml of water were added to a reaction kettle, stirred for 20 min, 1 g of polyethylene glycol was added, heated to 55°C, stirred for 3.5 h, centrifuged, and the solid-phase product 2 obtained by centrifugal separation was washed with deionized water to neutral, and dried at 105°C for 8 h to obtain a modified powder;

[0054] (3) Take 10 g of the modified powder prepared in step (2), 20 g of dichlorodimethylsilane, and 45 ml of dichloromethane in a ball mill tank, seal it, and ball mill for 8 h to obtain an intermediate of modified silicon nitride;

[0055] (4) Take 15 g of the intermediate of modified silicon nitride prepared in step (3), 30 g of ethyl methacrylate, and 68 ml of dichloromethane in a ball mill tank, seal it, and ball mill for 12 h to obtain modified silicon nitride A.

[0056] Preparation Example 2

[0057] The preparation method of modified silicon nitride B comprises the following steps:

[0058] (1) Take 10 g of silicon nitride, 20 g of dichlorodimethylsilane, and 45 ml of dichloromethane in a ball mill tank, seal it, and ball mill for 8 h to obtain an intermediate of modified silicon nitride;

[0059] (2) Take 15 g of the intermediate of modified silicon nitride prepared in step (2), 30 g of ethyl methacrylate, and 68 ml of dichloromethane in a ball mill tank, seal it, and ball mill for 12 h to obtain modified silicon nitride B.

[0060] Preparation Example 3

[0061] The preparation method of modified dispersant A comprises the following steps:

[0062] S1. Dissolve 1.2 mol of allyl polyoxyethylene ether in 200 ml of water, stir uniformly to obtain solution A; dissolve 7.2 mol of acrylic acid, 4.8 mol of 2-methylenebutyrolactone, and 3.6 mol of 2-acrylamide-2-methylpropane sulfonic acid in 300 ml of water, stir uniformly to obtain solution B;

[0063] S2. Mix solution A and solution B and add to a reaction kettle, heat to 70°C, add 0.5 mol of sodium hypophosphite, under a nitrogen protective atmosphere, drop 0.34 mol of a mixed solution of ammonium persulfate and sodium bisulfite, heat to 85°C, react for 3 h under 150 kPa to obtain a reaction solution;

[0064] S3. When the reaction solution is cooled to 40°C, adjust the pH to 8 with a 40 wt% sodium hydroxide aqueous solution to obtain modified dispersant A.

[0065] Preparation Example 4

[0066] The preparation method of modified dispersant B comprises the following steps:

[0067] S1. Dissolve 1.2 mol of allyl polyoxyethylene ether in 200 ml of water, stir until uniform to obtain solution A; dissolve 2.4 mol of acrylic acid, 2.4 mol of 2-methylenebutyrolactone, 2.4 mol of 2-acrylamido-2-methylpropane sulfonic acid in 300 ml of water, stir until uniform to obtain solution B;

[0068] S2. Mix solution A and solution B and add to a reaction kettle, heat to 70℃, add 0.25 mol of sodium hypophosphite, under a nitrogen protective atmosphere, drop in a mixed solution of 0.168 mol of ammonium persulfate and 0.168 mol of sodium bisulfite, heat to 85℃, react for 3 h under 150 kPa to obtain a reaction solution;

[0069] S3. When the reaction solution is cooled to 40℃, adjust the pH to 8 with a 40 wt% aqueous sodium hydroxide solution to obtain modified dispersant B.

[0070] Example 1

[0071] A spraying paint for increasing the convective heat transfer coefficient of a soft package lithium battery, comprising the following raw materials in parts by weight: epoxy modified silicone resin 30 parts, phenyl silicone resin 25 parts, modified silicon nitride A 12.5 parts, carbon nanotube 7.5 parts, silane coupling agent KH-570 3.5 parts, silver powder 2 parts, aluminum oxide 1.5 parts, cerium oxide 1.5 parts, antimony oxide 1.5 parts, modified dispersant A 2 parts, leveling agent BYK-370 2 parts, silicone defoamer 1.2 parts, bentonite 1 part, and ethyl acetate 68 parts.

[0072] The preparation method of the spraying paint for increasing the convective heat transfer coefficient of a soft package lithium battery of the present embodiment comprises the following steps:

[0073] I. Mix modified silicon nitride A, carbon nanotube, silane coupling agent KH-570, silver powder, aluminum oxide, cerium oxide, antimony oxide, modified dispersant A, leveling agent BYK-370, silicone defoamer, bentonite, and ethyl acetate (70 wt% of the solvent amount) at a stirring speed of 850 r / min until uniform to obtain a first mixture;

[0074] II. Mix epoxy modified silicone resin, phenyl silicone resin, and ethyl acetate (30 wt% of the solvent amount), add to the first mixture obtained in step I, heat to 70℃, grind and disperse, stir at a speed of 850 r / min until uniform, then move to a grinding machine for grinding to obtain the spraying paint.

[0075] Example 2

[0076] A spraying coating for increasing the convective heat transfer coefficient of a soft package lithium battery, comprising the following raw materials in parts by weight: epoxy modified silicone resin 30 parts, phenyl silicone resin 15 parts, modified silicon nitride A 10 parts, carbon nanotube 5 parts, silane coupling agent KH-570 2 parts, silver powder 1 part, aluminum oxide 1 part, cerium oxide 1 part, antimony oxide 1 part, modified dispersant A 1 part, leveling agent BYK-370 1 part, silicone defoaming agent 0.5 parts, bentonite 0.5 parts, and ethyl acetate 50 parts.

[0077] The preparation method of the spraying coating for increasing the convective heat transfer coefficient of a soft package lithium battery in the embodiment is the same as that in embodiment 1.

[0078] Example 3

[0079] A spraying coating for increasing the convective heat transfer coefficient of a soft package lithium battery, comprising the following raw materials in parts by weight: epoxy modified silicone resin 32.5 parts, phenyl silicone resin 32.5 parts, modified silicon nitride A 15 parts, carbon nanotube 10 parts, silane coupling agent KH-570 5 parts, silver powder 3 parts, aluminum oxide 2 parts, cerium oxide 2 parts, antimony oxide 2 parts, modified dispersant A 3 parts, leveling agent BYK-370 2 parts, silicone defoaming agent 2 parts, bentonite 1.5 parts, and ethyl acetate 85 parts.

[0080] The preparation method of the spraying coating for increasing the convective heat transfer coefficient of a soft package lithium battery in the embodiment is the same as that in embodiment 1.

[0081] Example 4

[0082] A spraying coating for increasing the convective heat transfer coefficient of a soft package lithium battery and a preparation method thereof, the specific implementation manner is the same as that in embodiment 1, and the difference lies in that epoxy modified silicone resin 55 parts are used to replace epoxy modified silicone resin 30 parts and phenyl silicone resin 25.

[0083] Example 5

[0084] A spraying coating for increasing the convective heat transfer coefficient of a soft package lithium battery and a preparation method thereof, the specific implementation manner is the same as that in embodiment 1, and the difference lies in that equal amount of modified silicon nitride B is used to replace modified silicon nitride A.

[0085] Example 6

[0086] A spraying coating for increasing the convective heat transfer coefficient of a soft package lithium battery and a preparation method thereof, the specific implementation manner is the same as that in embodiment 1, and the difference lies in that equal amount of modified dispersant B is used to replace modified dispersant A.

[0087] Comparative Example 1

[0088] A spraying coating for increasing the convective heat transfer coefficient of a soft package lithium battery and a preparation method thereof, the specific implementation manner is the same as that of example 1, the difference is that an equal amount of commercially available silicon nitride is used to replace modified silicon nitride A.

[0089] Comparative Example 2

[0090] A spraying coating for increasing the convective heat transfer coefficient of a soft package lithium battery and a preparation method thereof, the specific implementation manner is the same as that of example 1, the difference is that an equal amount of commercially available polyurethane dispersant is used to replace modified dispersant A.

[0091] Effect evaluation:

[0092] The spraying coatings prepared in the above examples 1-6 and comparative examples 1-2 are tested and analyzed, and the specific results are shown in Table 1.

[0093] Performance test:

[0094] (1) Corrosion resistance test:

[0095] Select a titanium alloy plate, polish the surface of the titanium alloy with sandpaper, clean it with ethanol and water, and then spray it with an air-powered spray gun, with a spraying thickness of 30 μm, a spray gun pressure of 0.45 MPa, and a spray gun-sample angle of 45°. A CHI660D electrochemical workstation is used to test and analyze the polarization curve of the sample, with the corrosion current density Icorr as the corrosion resistance performance index.

[0096] (2) Heat dissipation test:

[0097] The prepared spraying coating is sprayed on the heat sink, with a spraying thickness of 30 μm. Under the same standard conditions of heat source type and heat source input power (20 W), each heat sink sample is heated, and the temperature of each heat sink sample is detected in real time by an Agilent temperature recorder.

[0098] Table 1 Performance test

[0099] No. [Icorr / μA·cm -2 ]] Temperature of heat source after reaching thermal equilibrium Example 1 0.34 64 Example 2 0.39 68 Example 3 0.32 62 Example 4 0.51 71 Example 5 0.45 73 Example 6 0.48 75 Comparative Example 1 0.52 76 Comparative Example 2 0.57 79

[0100] From the results in Table 1, it can be seen that the spraying coatings of examples 1-3 have good heat dissipation and strong corrosion resistance.

[0101] Example 4 only uses one kind of silicone resin epoxy modified silicone resin, without adding phenyl silicone resin, which reduces the heat resistance, chemical resistance and oxidation resistance of the coating. Example 5 uses an equal amount of modified silicon nitride B to replace modified silicon nitride A, which reduces the number of groups grafted on the surface of silicon nitride; Comparative Example 1 uses an equal amount of commercially available silicon nitride to replace modified silicon nitride A, which makes the silicon nitride disperse unevenly, thereby affecting the heat resistance, chemical stability, corrosion resistance and hardness. Example 6 uses an equal amount of modified dispersant B to replace modified dispersant A, and Comparative Example 2 uses an equal amount of commercially available polyurethane dispersant to replace modified dispersant A, which lacks multiple functional groups, reduces the dispersibility of each raw material, and further reduces the corrosion resistance and heat dissipation performance of the sprayed coating.

[0102] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application is disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and such changes or modifications are equivalent to equivalent embodiments. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, as long as it does not deviate from the technical solution of the present application, is still within the scope of the technical solution.

Claims

1. A spray coating for increasing the convective heat transfer coefficient of a soft-pack lithium battery, characterized in that, By weight, it contains the following raw materials: 45-65 parts silicone resin, 10-15 parts modified silicon nitride, 5-10 parts carbon material, 2-5 parts silane coupling agent, 1-3 parts thermally conductive metal powder, 1-2 parts alumina, 1-2 parts cerium oxide, 1-2 parts antimony oxide, 1-3 parts modified dispersant, 1-3 parts leveling agent, 0.5-2 parts defoamer, 0.5-1.5 parts anti-settling agent, and 50-85 parts solvent; The silicone resin is an epoxy-modified silicone resin and a phenyl silicone resin, with a mass ratio of 1:(0.5-1). The method for preparing the modified silicon nitride includes the following steps: (1) Add silicon nitride, ethanol and water to the reaction vessel, stir for 10-30 min, add tetraethyl orthosilicate, adjust the pH to 7.5-8.5 with acid-base adjuster, heat to 45-55℃, stir for 1-3 h, centrifuge, wash and dry to obtain tetraethyl orthosilicate modified silicon nitride; (2) Take the tetraethyl orthosilicate-modified silicon nitride, ethanol and water prepared in step (1) and add them to the reaction vessel. Stir for 10-30 min, add polyethylene glycol, heat to 50-60℃, stir for 2-5 h, centrifuge, wash and dry to obtain modified powder. (3) Take the modified powder prepared in step (2), dichlorodimethylsilane, and organic solvent into a ball mill jar, seal it, and ball mill for 5-10 hours to obtain the intermediate of modified silicon nitride; (4) Take the intermediate of modified silicon nitride prepared in step (3), ethyl methacrylate, and organic solvent into a ball mill jar, seal it, and ball mill for 10-15 hours to obtain modified silicon nitride. The preparation method of the modified dispersant includes the following steps: S1. Dissolve allyl polyoxyethylene ether in water and stir until homogeneous to obtain solution A; dissolve acrylic acid, 2-methylbutyrolactone, and 2-acrylamide-2-methylpropanesulfonic acid in water and stir until homogeneous to obtain solution B; S2. Mix solution A and solution B and add them to the reaction vessel. Heat to 70-75℃, add chain transfer agent, and add initiator dropwise under an inert gas protective atmosphere. Heat to 80-85℃ and react at 100-250kPa for 2-4 hours to obtain the reaction solution. S3. After the reaction solution is cooled to 30-40℃, adjust the pH to 7.5-8.5 with an acid-base regulator to obtain the modified dispersant.

2. The spray coating for increasing the convective heat transfer coefficient of a soft-pack lithium battery according to claim 1, characterized in that, The mass ratio of silicon nitride to tetraethyl orthosilicate in step (1) is 1:(1-1.5).

3. The spray coating for increasing the convective heat transfer coefficient for soft-pack lithium batteries according to claim 1, characterized in that, The number average molecular weight of the polyethylene glycol in step (2) is 200-4000, and the mass ratio of the polyethylene glycol to the tetraethyl orthosilicate-modified silicon nitride is 1:(10-20).

4. The spray coating for increasing the convective heat transfer coefficient for soft-pack lithium batteries according to claim 1, characterized in that, The molar ratio of allyl polyoxyethylene ether, acrylic acid, 2-methylbutyrolactone and 2-acrylamide-2-methylpropanesulfonic acid is 1:(4-8):(3-5):(2-4).

5. A spray coating for increasing the convective heat transfer coefficient for soft-pack lithium batteries according to claim 1, characterized in that, The number average molecular weight of the allyl polyoxyethylene ether is 2000-3000.

6. The spray coating for increasing the convective heat transfer coefficient of a soft-pack lithium battery according to claim 1, characterized in that, The chain transfer agent is sodium hypophosphite, and the molar amount of the chain transfer agent is 1-5% of the total molar amount of allyl polyoxyethylene ether, acrylic acid, 2-methylbutyrolactone and 2-acrylamide-2-methylpropanesulfonic acid.

7. A method for preparing a spray coating for increasing the convective heat transfer coefficient for a soft-pack lithium battery according to any one of claims 1-6, characterized in that, It includes the following steps:

1. Mix modified silicon nitride, carbon materials, silane coupling agent, thermally conductive metal powder, alumina, cerium oxide, antimony oxide, modified dispersant, leveling agent, defoamer, antisettling agent and part of the solvent, and stir evenly at a speed of 700-1000 r / min to obtain the first mixture.

2. Mix the silicone resin and the remaining solvent and add them to the first mixture obtained in step 1. Heat to 60-70℃, grind and disperse, stir evenly at a speed of 700-1000r / min, and then transfer to a grinder for grinding to obtain the spray coating.