A composite heating film for a new energy automobile battery pack and a preparation method thereof

Abstract

The application belongs to the technical field of battery thermal management, and particularly relates to a composite heating film for new energy automobile battery packs and a preparation method thereof. The composite heating film comprises a heating layer, and 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 dispersing agent, 0.5-1 part of defoaming agent, and 40-50 parts of solvent. In the composite heating film, the modified graphene and the epoxy triglyceride are matched to form a rich conductive crosslinking network, the surface energy is reduced, the thermal conversion efficiency is improved, the temperature can be quickly raised after power-on, the heating is uniform, the heating stability is good, the service life of the product is prolonged, the long-chain polysiloxane on the surface of the modified graphene can also improve the flexibility of the heating film, and the composite heating film can be applied to automobile auxiliary heating and new energy battery pack thermal management systems.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery thermal management, and particularly relates to a composite heating film for a new energy automobile battery pack and a preparation method thereof. BACKGROUND

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

[0003] At present, the preheating modules for power batteries on the market are mainly divided into metal electrothermal films and inorganic electrothermal films according to the heating materials, wherein the inorganic electrothermal 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 electrothermal films is relatively mature, and the temperature uniformity of the film heating is good, but its main disadvantage is that the production cost is high, in addition, the density of metal materials is large, which is contrary to the development demand of automobile lightweight. Under the current background of the new energy automobile industry, the inorganic electrothermal films such as graphene heating film, carbon fiber heating film, carbon nanotube heating film, etc. show certain advantages due to their lower cost and higher electro-thermal conversion efficiency.

[0004] Graphite-based materials are light and thin, which meet the conditions of automobile lightweight and internal narrow space arrangement of the battery pack. 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 application in the heating of the new energy automobile battery pack. SUMMARY

[0005] The first object of the present application is to provide a composite heating film for a new energy automobile battery pack. The composite heating film obtained by the present application has good heat conversion efficiency and thermal stability, and the heating is uniform, the temperature is uniform, the heating stability is good, and the working life of the product can be prolonged. It is of great significance to improve the performance and usability of electric vehicles in severe cold environments. In addition, it has good flexibility, which solves the technical problems of low electro-thermal conversion efficiency, slow heating time and poor flexibility of the current heating film.

[0006] The second object of the present application is to provide a preparation method of the composite heating film for new energy automobile battery pack, which is simple and efficient and has practical application value in industrial production.

[0007] In order to achieve the above object, the technical scheme adopted by the present application is:

[0008] A composite heating film for new energy automobile battery pack, comprising a heating layer, the heating layer comprising the following components by weight: epoxy resin 10-20 parts, modified graphene 2-5 parts, epoxy glyceride 3-7 parts, dispersing agent 0.5-1 part, defoaming agent 0.5-1 part, solvent 40-50 parts.

[0009] The preparation process of the modified graphene is as follows:

[0010] (1) Add graphene oxide to the solvent, then add 4-vinylphenylboric acid for heating reaction to obtain pretreated graphene oxide;

[0011] (2) Take hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, add them to the solvent, then add hexamethyldisiloxane, and add a catalyst under a nitrogen atmosphere to obtain vinyl polysiloxane by reaction;

[0012] (3) Add vinyl polysiloxane to the solvent, add pretreated graphene oxide and a catalyst for reaction, and collect the product after the reaction is completed to obtain modified graphene.

[0013] Further, in step (1), the amount ratio of the graphene oxide, 4-vinylphenylboric acid and solvent is 2-8g:1g:20-40mL, the solvent is toluene, the heating reaction temperature is 80-90℃, and the reaction time is 5-8h.

[0014] Further, 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.

[0015] Further, in step (2), the reaction temperature is 70-80℃, and the reaction time is 3-5h.

[0016] Further, in step (3), the mass ratio of the pretreated graphene oxide, the vinyl polysiloxane and the catalyst is 100:(10-15):(0.5-0.8); the use amount ratio of the vinyl polysiloxane and the solvent is 1g:10-15mL; the solvent is N,N-dimethylformamide; and the catalyst is azobisisobutyronitrile.

[0017] Further, in step (3), the reaction temperature is 90-100℃, and the reaction time is 3-5h.

[0018] Further, the composite heating film further comprises a base film layer and an insulation layer; the base film layer and the insulation layer are both polyimide films; the dispersant is HT-5027, and the defoaming agent is T-7511; and the solvent in the heating layer is dichloromethane or ethanol.

[0019] Further, the base film layer further comprises an electrode material; and the insulation layer is coated with EVA hot melt adhesive.

[0020] Further, the electrode material is conductive silver paste or copper paste.

[0021] The application provides a preparation method of a composite heating film for a new energy automobile battery pack, which comprises the following steps:

[0022] The epoxy resin, modified graphene, epoxy glyceride, dispersant, defoaming agent and solvent are uniformly mixed to obtain a mixed solution of the heating layer, the mixed solution is printed on the surface of the base film layer, and after solidification, the electrode material is printed on both ends of the printed base film layer, and then the base film layer is hot-pressed with the insulation layer coated with EVA hot melt adhesive, thereby obtaining the composite heating film.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] 1.The composite heating film for new energy automobile battery pack provided by the present application has good heat conversion efficiency and thermal stability, uniform heating, good heating stability, and can prolong the service life of the product, and has good flexibility, and overall solves the technical problems of low electric-thermal conversion efficiency, slow heating time and poor flexibility of the current heating film. Specifically, since the graphene oxide contains rich active groups, the present application introduces boronic acid groups by reacting the hydroxyl groups on the surface of graphene oxide with 4-vinylphenylboronic acid, and then grafts vinyl polysiloxane through double bonds, thereby improving the compatibility of graphene oxide and the resin matrix and reducing phase separation. The epoxy triglyceride has good diffusion activity and forms a rich conductive crosslinking network with modified graphene, reduces the surface energy, improves the heat conversion efficiency, can quickly heat up after being powered on, and has uniform and stable heating, prolongs the service life of the product, and the long-chain polysiloxane modified on the surface of the modified graphene can also improve the flexibility of the heating film; and can be applied to the new energy battery pack thermal management system.

[0025] 2.The preparation method of the composite heating film for new energy automobile battery pack provided by the present application is simple and efficient, and has practical application value in industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The electron microscope image of the modified graphene obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0027] The technical solutions of the present application are further described below in combination with specific embodiments. However, those skilled in the art should understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the present application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, such as those not specifically mentioned, are conventional products obtained through commercial channels.

[0028] The graphene oxide sheet diameter in the present application is 2-40 μm, and the thickness is 5-200 nm; the base film and the insulating layer are both polyimide films, and the thickness is both 13 μm; the thickness of the electrode material is 12 μm; and the epoxy resin is P01671-310.

[0029] Example 1

[0030] The composite heating film for new energy automobile battery pack comprises a base film layer (polyimide film), a heating layer and an insulating layer (polyimide film), wherein the heating layer comprises the following components in parts by weight: epoxy resin 15 parts, modified graphene 3 parts, epoxy glyceride 5 parts, dispersing agent (HT-5027) 0.8 parts, defoaming agent (T-7511) 0.8 parts, dichloromethane 45 parts.

[0031] The preparation process of the modified graphene is as follows:

[0032] (1) The graphene oxide is added into toluene, and then 4-vinylbenzene boronic acid is added, wherein the amount ratio of the graphene oxide, 4-vinylbenzene boronic acid and toluene is 5g:1g:30mL, and the reaction is carried out at 85℃ for 6h to obtain pretreated graphene oxide;

[0033] (2) Hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane are added into toluene, wherein the volume fraction of the hexamethylcyclotrisiloxane in toluene is 32%; then hexamethyldisiloxane is added, and tetramethylammonium hydroxide is added under nitrogen atmosphere, wherein the mass ratio of the hexamethylcyclotrisiloxane, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, hexamethyldisiloxane and tetramethylammonium hydroxide is 20:2:0.2:0.8; the reaction is carried out at 75℃ for 4h to obtain vinyl polysiloxane.

[0034] (3) The vinyl polysiloxane is added into N,N-dimethylformamide, wherein the amount ratio of the vinyl polysiloxane and N,N-dimethylformamide is 1g:13mL; the pretreated graphene oxide and azobisisobutyronitrile are added, wherein the mass ratio of the pretreated graphene oxide, vinyl polysiloxane and azobisisobutyronitrile is 100:12:0.7; the temperature is raised to 95℃, and the reaction is carried out for 4h to collect the product to obtain the modified graphene. Figure 1

[0035] The application provides a preparation method of the composite heating film for new energy automobile battery pack, which comprises the following steps:

[0036] According to the above parts by weight, the epoxy resin, modified graphene, epoxy glyceride, dispersing agent (HT-5027), defoaming agent (T-7511) and solvent (dichloromethane) are uniformly mixed to obtain a mixed solution of the heating layer, the solution is printed on the surface of the base film layer (polyimide film) by a screen printing machine, and the printing thickness is 50µm; after the film coating is cured, the conductive silver paste is printed on both ends of the printed base film layer, and then the insulating layer (polyimide film) coated with EVA hot melt adhesive is hot-pressed to obtain the composite heating film. ​

[0037] Example 2

[0038] A composite heating film for new energy automobile battery pack, comprising a base film layer (polyimide film), a heating layer and an insulating layer (polyimide film), the heating layer comprises the following components by weight: epoxy resin 10 parts, modified graphene 2 parts, epoxy triglyceride 3 parts, dispersing agent (HT-5027) 0.5 parts, defoaming agent (T-7511) 0.5 parts, ethanol 40 parts. Among them, the base film layer also includes electrode material (conductive silver paste); the insulating layer is coated with EVA hot melt adhesive.

[0039] The preparation process of the modified graphene is as follows:

[0040] (1) Add graphene oxide into toluene, then add 4-vinylbenzene boronic acid, the amount ratio of graphene oxide, 4-vinylbenzene boronic acid and toluene is 2g:1g:20mL, react at 80℃ for 8h to obtain pretreated graphene oxide;

[0041] (2) Take hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane into toluene, the volume fraction of hexamethylcyclotrisiloxane in toluene is 30%; then add hexamethyldisiloxane, and add tetramethylammonium hydroxide under nitrogen atmosphere, the mass ratio of hexamethylcyclotrisiloxane, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, hexamethyldisiloxane and tetramethylammonium hydroxide is 15:1:0.1:0.6; react at 70℃ for 5h to obtain vinyl polysiloxane.

[0042] (3) Add vinyl polysiloxane into N,N-dimethylformamide, the amount ratio of vinyl polysiloxane and N,N-dimethylformamide is 1g:10mL; add pretreated graphene oxide and azobisisobutyronitrile, the mass ratio of pretreated graphene oxide, vinyl polysiloxane and azobisisobutyronitrile is 100:10:0.5; heat to 90℃, react for 5h to collect the product to obtain modified graphene.

[0043] The application provides a preparation method of a composite heating film for new energy automobile battery pack, comprising the following steps:

[0044] According to the above weight parts, mix epoxy resin, modified graphene, epoxy triglyceride, dispersing agent (HT-5027), defoaming agent (T-7511) and solvent (ethanol) uniformly to obtain a heating layer mixed solution, print the solution onto the surface of the base film layer (polyimide film) through a screen printing machine, and the printing thickness is 40µm; after the film coating is cured, print conductive silver paste on both ends of the printed base film layer, and then adhere the insulating layer (polyimide film) coated with EVA hot melt adhesive through hot pressing to obtain the composite heating film.

[0045] Example 3

[0046] A composite heating film for new energy automobile battery pack, comprising a base film layer (polyimide film), a heating layer and an insulating layer (polyimide film), the heating layer comprises the following components by weight: epoxy resin 20 parts, modified graphene 5 parts, epoxy glyceride 7 parts, dispersing agent (HT-5027) 1 part, defoaming agent (T-7511) 1 part, dichloromethane 50 parts. Among them, the base film layer also includes electrode material (conductive copper paste); the insulating layer is coated with EVA hot melt adhesive.

[0047] The preparation process of the modified graphene is as follows:

[0048] (1) Add graphene oxide to toluene, then add 4-vinylbenzene boronic acid, the amount ratio of graphene oxide, 4-vinylbenzene boronic acid and toluene is 8g:1g:40mL, react at 90℃ for 5h to obtain pretreated graphene oxide;

[0049] (2) Take hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane and add them to toluene, the volume fraction of hexamethylcyclotrisiloxane in toluene is 35%; then add hexamethyldisiloxane, and add tetramethylammonium hydroxide under nitrogen atmosphere, the mass ratio of hexamethylcyclotrisiloxane, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane, hexamethyldisiloxane and tetramethylammonium hydroxide is 25:3:0.3:0.9; react at 80℃ for 3h to obtain vinyl polysiloxane.

[0050] (3) Add vinyl polysiloxane to N,N-dimethylformamide, the amount ratio of vinyl polysiloxane and N,N-dimethylformamide is 1g:15mL; add pretreated graphene oxide and azobisisobutyronitrile, the mass ratio of pretreated graphene oxide, vinyl polysiloxane and azobisisobutyronitrile is 100:15:0.5; heat to 100℃, react for 3h to collect the product to obtain modified graphene.

[0051] The present application provides a preparation method of a composite heating film for new energy automobile battery pack, comprising the following steps:

[0052] According to the above weight parts, mix epoxy resin, modified graphene, epoxy glyceride, dispersing agent (HT-5027), defoaming agent (T-7511) and solvent (dichloromethane) uniformly to obtain a mixed solution of the heating layer, print the solution onto the surface of the base film layer (polyimide film) through a screen printing machine, and the printing thickness is 60µm; after the film is cured, print conductive copper paste on both ends of the printed base film layer, and then adhere the insulating layer (polyimide film) coated with EVA hot melt adhesive through hot pressing to obtain the composite heating film.

[0053] Comparative Example 1

[0054] The difference between the present comparative example 1 and example 1 is only that the modified graphene is replaced by graphene oxide.

[0055] Comparative Example 2

[0056] The difference between the present comparative example 2 and example 1 is only that the modified graphene is replaced by pretreated graphene oxide.

[0057] Comparative Example 3

[0058] The difference between the present comparative example 3 and example 1 is only that the epoxy triglyceride is omitted.

[0059] Test Example 1

[0060] The products of the present application examples 1-3 and comparative examples 1-3 are tested for performance according to the national standard GB / T 7287-2008 “Test method for infrared radiation heater”, as follows: the working life of the heating film is detected according to the heater working life test method, and the electric-thermal radiation performance of the heating film is tested according to the measurement method of the electric-thermal radiation conversion efficiency of the heater. According to the measurement method of the heating time of the heater, the temperature is measured by a radiation thermometer, and the time required to rise from room temperature to 50℃ is recorded as the heating time; when the temperature is in a stable working state (50℃), the difference between the maximum temperature and the minimum temperature on the surface of the heating film is the temperature uniformity; the above test results are shown in Table 1.

[0061] Table 1

[0062]

[0063] As can be seen from Table 1, the composite heating films obtained in the present application examples 1-3 have long working life, high electric-thermal radiation conversion efficiency, fast heating time, small temperature difference, and good heating stability. Compared with example 1, in comparative example 1, the modified graphene is replaced by graphene oxide; in comparative example 2, the modified graphene is replaced by pretreated graphene oxide; and in comparative example 3, the epoxy triglyceride is omitted. The working life, heating time, temperature uniformity and electric-thermal radiation conversion efficiency of the three are all not as good as that of example 1, which shows that the use of modified graphene and epoxy triglyceride together can effectively improve the heat conversion efficiency and the heating stability, and can prolong the service life of the product.

[0064] Test Example 2

[0065] In order to test the performance of the products of the present application examples 1-3 and comparative examples 1-3, the following experiments are carried out:

[0066] The flexibility of the heat-generating film was tested according to the relevant method in GB / T1731-2020. The experimental results are shown in Table 2.

[0067] Table 2

[0068]

[0069] The heat-generating films of embodiments 1-3 of the present application have good flexibility, which is better than that of comparative examples 1-3, because the long-chain polysiloxane introduced into the modified graphene can also improve the flexibility of the heat-generating film. The above results show that the heat-generating film prepared by the present application has excellent flexibility, which can ensure that the heat-generating film still has good heating performance after being bent, and can be applied to automobile auxiliary heating and new energy battery packs.

[0070] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it. The basic principles and main features of the present application have been described above with specific embodiments, and some modifications or replacements can be made on the basis of the present application, but these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the present application.

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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