Composite heating film for new energy automobile battery pack and preparation method of composite heating film

Abstract

The invention belongs to the technical field of battery heat management, and particularly relates to a composite heating film for a new energy automobile battery pack and a preparation method thereof. The composite heating film comprises a heating layer, wherein the heating layer comprises the following components in parts by weight: 10-20 parts of epoxy resin, 2-5 parts of modified graphene, 3-7 parts of epoxy triglyceride, 0.5-1 part of a dispersing agent, 0.5-1 part of a defoaming agent and 40-50 parts of a solvent; the modified graphene and the epoxy triglyceride in the composite heating film are matched to form a rich conductive cross-linked network, so that the surface energy is reduced, the heat conversion efficiency is improved, the temperature can be quickly increased after electrification, the heating is uniform, the heating stability is good, the service life of the product is prolonged, and the production cost is reduced. The modified graphene surface modified long-chain polysiloxane can also improve the flexibility of the heating film; the method can be applied to automobile auxiliary heating and new energy battery pack heat management systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery thermal management, and specifically relates to a composite heating film for a new energy vehicle battery pack and a preparation method thereof. Background Art

[0002] The new energy vehicle industry is in a rapid growth phase, and the performance of its core component, the power battery, is crucial. However, lithium-ion automotive power batteries have significant performance degradation problems in low-temperature environments, which seriously restricts the application and promotion of electric vehicles in high-latitude cold regions. Specifically, low-temperature environments bring two key problems: first, the battery's discharge capacity drops sharply; second, charging under low-temperature conditions has been proven to be one of the fastest ways to accelerate the degradation of power battery life. To overcome this obstacle, it is crucial to develop an effective battery thermal management system, the goal of which is to safely and efficiently heat the battery from a low-temperature state to a suitable operating temperature range, thereby achieving full environmental adaptability of the battery. Among them, using an external heater to preheat the battery is a direct and efficient method.

[0003] Currently, the preheating modules for power batteries on the market are mainly divided into metal heating films and inorganic heating films according to the heating material. Inorganic heating films include graphene heating films, carbon fiber heating films, carbon nanotube heating films, carbon crystal heating films, etc. The production and processing technology of metal heating films is relatively mature, and the temperature uniformity of the heating of the diaphragm is good, but its main disadvantage is its high production cost. In addition, the density of metal materials is relatively high, which is contrary to the development demand of lightweight vehicles. In the current context of the new energy vehicle industry, inorganic heating films such as graphene heating films, carbon fiber heating films, and carbon nanotube heating films have shown certain advantages due to their lower cost and higher electric-to-heat conversion efficiency.

[0004] Graphite-based materials are light and thin, which meets the requirements of lightweight vehicles and small space layout inside battery packs. However, the current heating film still has problems such as poor thermal stability, temperature uniformity and heat conversion efficiency, and the flexibility of the heating film needs to be improved. Therefore, it is of great significance to improve the above problems and prepare a heating film with good comprehensive performance for use in heating battery packs of new energy vehicles. Summary of the Invention

[0005] The first objective of the present invention is to provide a composite heating film for new energy vehicle battery packs. The resulting composite heating film exhibits excellent heat conversion efficiency and thermal stability, and generates heat evenly, with uniform temperature and good thermal stability. This extends the product's operating life and is of great significance for improving the performance and usability of electric vehicles in severe cold environments. Furthermore, it exhibits good flexibility, resolving the technical issues of current heating films, such as low electro-thermal conversion efficiency, slow heat-up time, and poor flexibility.

[0006] The second purpose of the present invention is to provide a method for preparing a composite heating film for a new energy vehicle battery pack. The method is simple and efficient and has practical application value in industrial production.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: A composite heating film for a new energy vehicle battery pack, comprising a heating layer, wherein the heating layer comprises the following components in parts by weight: 10-20 parts of epoxy resin, 2-5 parts of modified graphene, 3-7 parts of epoxy triglyceride, 0.5-1 part of dispersant, 0.5-1 part of defoaming agent, and 40-50 parts of solvent; The preparation process of the modified graphene is as follows: (1) adding graphene oxide to a solvent, and then adding 4-vinylphenylboronic acid to carry out heating reaction to obtain pretreated graphene oxide; (2) Hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane are added to a solvent, and then hexamethyldisiloxane is added. A catalyst is added under a nitrogen atmosphere to react to obtain vinyl polysiloxane; (3) Adding vinyl polysiloxane to a solvent, adding pretreated graphene oxide and a catalyst to react, and after the reaction is completed, collecting the product to obtain modified graphene.

[0008] Furthermore, in step (1), the amount ratio of the graphene oxide, 4-vinylphenylboronic acid, and solvent is 2-8 g: 1 g: 20-40 mL, and the solvent is toluene; the temperature of the heating reaction is 80-90° C., and the time is 5-8 h.

[0009] Furthermore, in step (2), the mass ratio of hexamethylcyclotrisiloxane, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, hexamethyldisiloxane, and catalyst is (15-25): (1-3): (0.1-0.3): (0.6-0.9); the volume fraction of hexamethylcyclotrisiloxane in the solvent is 30-35%; the solvent is toluene, and the catalyst is tetramethylammonium hydroxide.

[0010] Furthermore, in step (2), the reaction temperature is 70-80°C and the reaction time is 3-5 hours.

[0011] Furthermore, in step (3), the mass ratio of the pretreated graphene oxide, vinyl polysiloxane, and catalyst is 100:(10-15):(0.5-0.8); the amount ratio of the vinyl polysiloxane to the solvent is 1 g:10-15 mL; the solvent is N,N-dimethylformamide; and the catalyst is azoisobutyronitrile.

[0012] Furthermore, in step (3), the reaction temperature is 90-100°C and the reaction time is 3-5h.

[0013] Furthermore, the composite heating film also includes a base film layer and an insulating layer; the base film layer and the insulating layer are both polyimide films; the dispersant is HT-5027, and the defoaming agent is T-7511; the solvent in the heating layer is dichloromethane or ethanol.

[0014] Furthermore, the base film layer also includes electrode material; and the insulating layer is coated with EVA hot melt adhesive.

[0015] Furthermore, the electrode material is conductive silver paste or copper paste.

[0016] The present invention provides a method for preparing a composite heating film for a new energy vehicle battery pack, comprising the following steps: Mix epoxy resin, modified graphene, epoxy triglyceride, dispersant, defoaming agent and solvent evenly to obtain a mixed solution of the heating layer, print the mixed solution onto the surface of the base film layer, and after curing, print electrode materials on both ends of the printed base film layer, and then hot-press with the insulating layer coated with EVA hot melt adhesive to obtain a composite heating film.

[0017] Compared with the prior art, the beneficial effects of the present invention are mainly: 1. The present invention provides a composite heating film for new energy vehicle battery packs. The resulting composite heating film has excellent thermal conversion efficiency and thermal stability, and exhibits uniform heat generation, temperature uniformity, and good thermal stability, extending the product's service life. Furthermore, it exhibits good flexibility, thereby addressing the current technical issues of low electrical-to-thermal conversion efficiency, slow temperature rise time, and poor flexibility in heating films. Specifically, because graphene oxide contains abundant active groups, the present invention utilizes the hydroxyl groups on the graphene oxide surface to react with 4-vinylphenylboronic acid to introduce boronic acid groups, and then uses double bonds to graft vinyl polysiloxane. This modification improves the compatibility of the graphene oxide with the resin matrix and reduces phase separation. Epoxy triglyceride has excellent diffusion activity and, when combined with the modified graphene, forms a rich conductive cross-linked network, reducing surface energy and improving thermal conversion efficiency. Upon application of power, the composite heating film can rapidly heat up, exhibits uniform heat generation, and exhibits good thermal stability, extending the product's service life. The long-chain polysiloxane modified on the surface of the modified graphene further enhances the flexibility of the heating film. The composite heating film can be applied to thermal management systems for new energy battery packs.

[0018] 2. The present invention provides a method for preparing a composite heating film for a new energy vehicle battery pack. The method is simple and efficient and has practical application value in industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1This is an electron microscope image of the modified graphene obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be further described below in conjunction with specific embodiments. However, it should be understood by those skilled in the art that the following examples are only intended to illustrate the present invention and should not be construed as limiting the present invention. Specific conditions not specified in the examples are to be followed according to conventional conditions or the conditions recommended by the manufacturer. All reagents or instruments used, unless otherwise specified, are conventional products obtained from commercial channels.

[0021] The graphene oxide sheet of the present invention has a diameter of 2-40 μm and a thickness of 5-200 nm; the base film and the insulating layer are both polyimide films, both with a thickness of 13 μm; the thickness of the electrode material is 12 μm; and the epoxy resin is P01671-310.

[0022] Example 1 A composite heating film for new energy vehicle battery packs includes a base film layer (polyimide film), a heating layer, and an insulating layer (polyimide film). The heating layer contains the following ingredients by weight: 15 parts epoxy resin, 3 parts modified graphene, 5 parts epoxy triglyceride, 0.8 parts dispersant (HT-5027), 0.8 parts defoaming agent (T-7511), and 45 parts dichloromethane. The base film layer also contains electrode material (conductive silver paste), and the insulating layer is coated with EVA hot-melt adhesive.

[0023] The preparation process of the modified graphene is as follows: (1) adding graphene oxide to toluene, and then adding 4-vinylbenzene boronic acid, wherein the amount ratio of graphene oxide, 4-vinylbenzene boronic acid, and toluene is 5 g:1 g:30 mL, and reacting at 85° C. for 6 h to obtain pretreated graphene oxide; (2) Hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane were added to toluene, wherein the volume fraction of the hexamethylcyclotrisiloxane in toluene was 32%. Hexamethyldisiloxane was then added, and tetramethylammonium hydroxide was added under a nitrogen atmosphere, wherein the mass ratio of hexamethylcyclotrisiloxane, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, hexamethyldisiloxane, and tetramethylammonium hydroxide was 20:2:0.2:0.8. The mixture was reacted at 75°C for 4 hours to obtain vinyl polysiloxane.

[0024] (3) Add vinyl polysiloxane to N,N-dimethylformamide, the amount ratio of vinyl polysiloxane to N,N-dimethylformamide is 1g:13mL; add pretreated graphene oxide and azoisobutyronitrile, the mass ratio of pretreated graphene oxide, vinyl polysiloxane and azoisobutyronitrile is 100:12:0.7; heat to 95℃, react for 4h, collect the product, and obtain modified graphene. The electron microscope image of modified graphene is shown below. Figure 1 shown.

[0025] The present invention provides a method for preparing a composite heating film for a new energy vehicle battery pack, comprising the following steps: According to the above weight parts, epoxy resin, modified graphene, epoxy triglyceride, dispersant (HT-5027), defoaming agent (T-7511) and solvent (dichloromethane) are mixed evenly to obtain a mixed solution of the heating layer, and the solution is printed onto the surface of the base film layer (polyimide film) by a screen printing machine with a printing thickness of 50µm; after the coating is cured, conductive silver paste is printed on both ends of the printed base film layer, and then it is hot-pressed with the insulating layer (polyimide film) coated with EVA hot melt adhesive to obtain a composite heating film.

[0026] Example 2 A composite heating film for new energy vehicle battery packs includes a base film layer (polyimide film), a heating layer, and an insulating layer (polyimide film). The heating layer contains the following ingredients by weight: 10 parts epoxy resin, 2 parts modified graphene, 3 parts epoxy triglyceride, 0.5 parts dispersant (HT-5027), 0.5 parts defoaming agent (T-7511), and 40 parts ethanol. The base film layer also contains electrode material (conductive silver paste), and the insulating layer is coated with EVA hot-melt adhesive.

[0027] The preparation process of the modified graphene is as follows: (1) adding graphene oxide to toluene, and then adding 4-vinylbenzene boronic acid, wherein the amount ratio of graphene oxide, 4-vinylbenzene boronic acid, and toluene is 2 g:1 g:20 mL, and reacting at 80° C. for 8 h to obtain pretreated graphene oxide; (2) Hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane were added to toluene, wherein the volume fraction of hexamethylcyclotrisiloxane in toluene was 30%. Hexamethyldisiloxane was then added, and tetramethylammonium hydroxide was added under a nitrogen atmosphere, wherein the mass ratio of hexamethylcyclotrisiloxane, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, hexamethyldisiloxane, and tetramethylammonium hydroxide was 15:1:0.1:0.6. The mixture was reacted at 70°C for 5 hours to obtain vinyl polysiloxane.

[0028] (3) Add vinyl polysiloxane to N,N-dimethylformamide, wherein the amount ratio of the vinyl polysiloxane to N,N-dimethylformamide is 1 g:10 mL; add pretreated graphene oxide and azoisobutyronitrile, wherein the mass ratio of the pretreated graphene oxide, vinyl polysiloxane and azoisobutyronitrile is 100:10:0.5; heat to 90°C, react for 5 hours, and collect the product to obtain modified graphene.

[0029] The present invention provides a method for preparing a composite heating film for a new energy vehicle battery pack, comprising the following steps: According to the above weight parts, epoxy resin, modified graphene, epoxy triglyceride, dispersant (HT-5027), defoaming agent (T-7511) and solvent (ethanol) are mixed evenly to obtain a heating layer mixed solution, and the solution is printed onto the surface of the base film layer (polyimide film) by a screen printing machine with a printing thickness of 40µm; after the coating is cured, conductive silver paste is printed on both ends of the printed base film layer, and then it is hot-pressed with the insulating layer (polyimide film) coated with EVA hot melt adhesive to obtain a composite heating film.

[0030] Example 3 A composite heating film for new energy vehicle battery packs includes a base film layer (polyimide film), a heating layer, and an insulating layer (polyimide film). The heating layer contains the following ingredients by weight: 20 parts epoxy resin, 5 parts modified graphene, 7 parts epoxy triglyceride, 1 part dispersant (HT-5027), 1 part defoamer (T-7511), and 50 parts dichloromethane. The base film layer also contains electrode material (conductive copper paste); the insulating layer is coated with EVA hot-melt adhesive.

[0031] The preparation process of the modified graphene is as follows: (1) adding graphene oxide to toluene, and then adding 4-vinylbenzene boronic acid, wherein the amount ratio of graphene oxide, 4-vinylbenzene boronic acid, and toluene is 8 g:1 g:40 mL, and reacting at 90° C. for 5 h to obtain pretreated graphene oxide; (2) Hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane were added to toluene, wherein the volume fraction of hexamethylcyclotrisiloxane in toluene was 35%. Hexamethyldisiloxane was then added, and tetramethylammonium hydroxide was added under a nitrogen atmosphere, wherein the mass ratio of hexamethylcyclotrisiloxane, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, hexamethyldisiloxane, and tetramethylammonium hydroxide was 25:3:0.3:0.9. The mixture was reacted at 80°C for 3 h to obtain vinyl polysiloxane.

[0032] (3) Add vinyl polysiloxane to N,N-dimethylformamide, wherein the amount ratio of the vinyl polysiloxane to N,N-dimethylformamide is 1 g:15 mL; add pretreated graphene oxide and azoisobutyronitrile, wherein the mass ratio of the pretreated graphene oxide, vinyl polysiloxane and azoisobutyronitrile is 100:15:0.5; raise the temperature to 100°C, react for 3 hours, and collect the product to obtain modified graphene.

[0033] The present invention provides a method for preparing a composite heating film for a new energy vehicle battery pack, comprising the following steps: According to the above weight parts, epoxy resin, modified graphene, epoxy triglyceride, dispersant (HT-5027), defoaming agent (T-7511) and solvent (dichloromethane) are evenly mixed to obtain a mixed solution of the heating layer, and the solution is printed onto the surface of the base film layer (polyimide film) by a screen printing machine with a printing thickness of 60µm; after the coating is cured, conductive copper paste is printed on both ends of the printed base film layer, and then it is hot-pressed with the insulating layer (polyimide film) coated with EVA hot melt adhesive to obtain a composite heating film.

[0034] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the modified graphene is replaced by graphene oxide.

[0035] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the modified graphene is replaced by pretreated graphene oxide.

[0036] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that epoxy triglyceride is omitted.

[0037] Test Example 1 Performance tests were conducted on the products of Examples 1-3 and Comparative Examples 1-3 of the present invention in accordance with the national standard GB / T 7287-2008, "Test Methods for Infrared Radiation Heaters." Specifically, the following tests were conducted: The operating life of the heating film was tested according to the heater operating life test method, and the electrothermal radiation performance of the heating film was tested according to the heater electric-to-thermal radiation conversion efficiency measurement method. The temperature was measured using a radiation thermometer according to the heater heating time measurement method, and the time required to rise from room temperature to 50°C was recorded as the heating time. When the temperature reached a stable operating state (50°C), the difference between the maximum and minimum temperatures on the heating film surface was used to determine the temperature uniformity. The test results are shown in Table 1.

[0038] Table 1 As can be seen from Table 1, the composite heating films obtained in Examples 1-3 of the present invention have a long working life, high electrothermal radiation conversion efficiency, fast heating time, small temperature difference, and good thermal stability. Compared with Example 1, Comparative Example 1 replaces the modified graphene with graphene oxide; Comparative Example 2 replaces the modified graphene with pretreated graphene oxide; and Comparative Example 3 omits epoxy triglyceride. The working life, heating time, temperature uniformity, and electrothermal radiation conversion efficiency of the three are all inferior to those of Example 1, indicating that the combination of modified graphene and epoxy triglyceride can effectively improve thermal conversion efficiency, achieve good thermal stability, and extend the service life of the product.

[0039] Test Example 2 In order to perform performance tests on the products of Examples 1-3 and Comparative Examples 1-3 of the present invention, the following experiments were conducted: The flexibility of the heating film was tested according to the relevant methods in GB / T1731-2020. The experimental results are shown in Table 2.

[0040] Table 2 The heating films of Examples 1-3 of the present invention exhibited excellent flexibility, surpassing those of Comparative Examples 1-3. This is because the long-chain polysiloxane introduced into the modified graphene further enhances the flexibility of the heating films. These results demonstrate that the heating films produced by the present invention possess excellent flexibility, ensuring that they maintain good heat generation performance even after bending, and are suitable for applications in automotive auxiliary heating and new energy battery packs.

[0041] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the same. The basic principles and main features of the present invention have been described above using specific implementation schemes. Modifications or substitutions may be made based on the present invention, but such modifications or substitutions do not detract from the essence of the corresponding technical solutions from the scope of protection claimed by the present invention.

Claims

1. A composite heating film for a new energy vehicle battery pack, characterized in that: The composite heating film includes a heating layer, which includes the following components in parts by weight: 10-20 parts of epoxy resin, 2-5 parts of modified graphene, 3-7 parts of epoxy triglyceride, 0.5-1 part of dispersant, 0.5-1 part of defoaming agent, and 40-50 parts of solvent; The preparation process of the modified graphene is as follows: (1) adding graphene oxide to a solvent, and then adding 4-vinylphenylboronic acid to carry out heating reaction to obtain pretreated graphene oxide; (2) Hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane are added to a solvent, and then hexamethyldisiloxane is added. A catalyst is added under a nitrogen atmosphere to react to obtain vinyl polysiloxane; (3) Vinyl polysiloxane is added to a solvent, and pretreated graphene oxide and a catalyst are added to react. After the reaction is completed, the product is collected to obtain modified graphene.

2. A composite heating film for a new energy vehicle battery pack according to claim 1, characterized in that: In step (1), the amount ratio of graphene oxide, 4-vinylphenylboronic acid, and solvent is 2-8 g:1 g:20-40 mL, and the solvent is toluene; the temperature of the heating reaction is 80-90° C., and the time is 5-8 h.

3. A composite heating film for a new energy vehicle battery pack according to claim 1, characterized in that: In step (2), the mass ratio of hexamethylcyclotrisiloxane, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, hexamethyldisiloxane, and catalyst is (15-25): (1-3): (0.1-0.3): (0.6-0.9); the volume fraction of hexamethylcyclotrisiloxane in the solvent is 30-35%; the solvent is toluene, and the catalyst is tetramethylammonium hydroxide.

4. The composite heating film for a new energy vehicle battery pack according to claim 1, characterized in that: In step (2), the reaction temperature is 70-80°C and the reaction time is 3-5 hours.

5. The composite heating film for a new energy vehicle battery pack according to claim 1, characterized in that: In step (3), the mass ratio of the pretreated graphene oxide, vinyl polysiloxane, and catalyst is 100:(10-15):(0.5-0.8); the amount ratio of the vinyl polysiloxane to the solvent is 1 g:10-15 mL; the solvent is N,N-dimethylformamide; and the catalyst is azoisobutyronitrile.

6. A composite heating film for a new energy vehicle battery pack according to claim 1, characterized in that: In step (3), the reaction temperature is 90-100°C and the reaction time is 3-5 hours.

7. A composite heating film for a new energy vehicle battery pack according to claim 1, characterized in that: The composite heating film also includes a base film layer and an insulating layer; the base film layer and the insulating layer are both polyimide films; the dispersant is HT-5027, and the defoaming agent is T-7511; the solvent in the heating layer is dichloromethane or ethanol.

8. A composite heating film for a new energy vehicle battery pack according to claim 7, characterized in that: The base film layer also includes electrode material; and the insulating layer is coated with EVA hot melt adhesive.

9. A composite heating film for a new energy vehicle battery pack according to claim 8, characterized in that: The electrode material is conductive silver paste or copper paste.

10. The method for preparing the composite heating film for new energy vehicle battery pack according to any one of claims 1 to 9, characterized in that: The steps include: Mix epoxy resin, modified graphene, epoxy triglyceride, dispersant, defoaming agent and solvent evenly to obtain a mixed solution of the heating layer, print the mixed solution onto the surface of the base film layer, and after curing, print electrode materials on both ends of the printed base film layer, and then hot-press with the insulating layer coated with EVA hot melt adhesive to obtain a composite heating film.

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