An electrothermal paste and a method of making the same

Abstract

The application discloses an electrothermal paste and a preparation method thereof, and relates to the technical field of pastes. The application provides an electrothermal paste, which comprises the following components in parts by weight: 10-30 parts of a first bonding phase, 15-40 parts of a second bonding phase, 0.2-2 parts of a coupling agent, 3-15 parts of a dispersing agent, 0.2-2 parts of a leveling agent, 10-30 parts of graphene powder and 20-45 parts of spherical graphite powder. The first bonding phase is a mixture of a thermosetting resin and a latent curing agent, and the weight ratio of the thermosetting resin to the latent curing agent is thermosetting resin:latent curing agent = 100:(2-20). The second bonding phase is a mixture of a thermoplastic resin and a solvent, and the weight percentage of the thermoplastic resin in the second bonding phase is 10%-40%. The electrothermal paste prepared by the application uses the cooperation of graphene and spherical graphite to form a conductive network with synergistic effect, so that the solid content of the electrothermal paste is improved, and the resistance and film forming defects after curing of the paste are reduced.

Description

Technical Field

[0001] This invention relates to the field of slurry technology, and in particular to an electrothermal slurry and its preparation method. Background Technology

[0002] Electrothermal paste is a viscous fluid formed by uniformly mixing and dispersing conductive fillers, binder phases, solvents, and additives. It can be applied to a substrate using processes such as screen printing, gravure printing, blade coating, and plating, followed by drying and curing to form a film layer with electrothermal conversion function. Traditional conductive fillers include metal powders such as silver, copper, and nickel. Silver powder has excellent conductivity and chemical stability, but its cost is relatively high. Copper and nickel powders have good conductivity, but poor oxidation resistance. Furthermore, electrothermal pastes made from metal powders generally have high density and require high dosage per unit area. Electrothermal carbon paste, on the other hand, has good overall performance, stable resistance after curing, and high cost-effectiveness, and has already seen some development and application.

[0003] Graphene is a novel two-dimensional carbon nanomaterial composed of a single layer of carbon atoms. It possesses excellent electrical and thermal conductivity, corrosion resistance, and lightweight properties, with a room-temperature carrier mobility of 15,000 cm⁻¹. 2 / (V·s), with a thermal conductivity as high as 5300W / (m·K), and a theoretical electrical conductivity of 10. 8Graphene, when heated by electricity, produces far-infrared light with a wavelength of 6–16 μm, which is similar to the infrared wavelength emitted by the human body. This allows for better absorption by the body, resulting in therapeutic and health-promoting effects, making it an ideal carbon-based conductive filler. Graphene can be combined with other carbon-based conductive fillers such as carbon nanotubes, conductive carbon black, and graphite to form a spatial synergistic effect of "point-line-surface," thereby enhancing the conductivity of the electrothermal paste. For example, Chinese patent CN 108305704 A discloses a highly conductive carbon paste using graphene and conductive carbon black as conductive fillers and water-based resin as a binder; Chinese patent CN 104517664 B discloses a carbon-based electrothermal paste based on graphene clusters, which uses graphene clusters or a combination of graphene clusters and other carbon materials as conductive fillers; and Chinese patent CN 107682943 B discloses a multifunctional graphene electrothermal paste that uses physically modified or chemically modified graphene as a conductive filler. The electrothermal pastes prepared above all exhibited good electrical conductivity. However, graphene, conductive carbon black, and carbon nanotubes have large specific surface areas and oil absorption capacities, but poor dispersibility, resulting in low solid content in the prepared electrothermal pastes and a slow curing speed. Simultaneously, the film shrinkage during curing is significant, leading to poor film formation and the risk of dry film permeability, pinholes, or even cracking. Upon heating, localized hot spots may occur, potentially causing sparks or even burns, posing safety hazards and limiting the large-scale practical application of these electrothermal pastes. Graphite has a relatively low specific surface area and good dispersibility, but currently widely used expanded graphite and flake graphite are in flake form. During paste curing, they tend to lie parallel to the substrate, hindering the evaporation of solvents within the film layer and affecting the curing speed and completeness of the electrothermal paste, making it difficult to exhibit the expected performance.

[0004] In summary, further realizing the application of graphene in electrothermal pastes, improving its dispersion effect and paste solids content, reducing film-forming defects, and enhancing the curing efficiency of the paste are key issues that urgently need to be addressed in the field of electrothermal pastes. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to overcome the shortcomings of the prior art and provide an electrothermal paste and its preparation method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an electrothermal paste, comprising the following components in parts by weight: 10-30 parts of a first binder phase, 15-40 parts of a second binder phase, 0.2-2 parts of a coupling agent, 3-15 parts of a dispersant, 0.2-2 parts of a leveling agent, 10-30 parts of graphene powder, and 20-45 parts of spherical graphite powder; the first binder phase is a mixture of thermosetting resin and latent curing agent, wherein the weight ratio of the thermosetting resin to the latent curing agent is thermosetting resin:latent curing agent = 100:(2-20); the second binder phase is a mixture of thermoplastic resin and solvent, wherein the weight percentage of thermoplastic resin in the second binder phase is 10%-40%.

[0007] The first binder phase of this invention is a mixture of thermosetting resin and a latent curing agent. The thermosetting resin undergoes chemical cross-linking with the curing agent to form a rigid network structure, exhibiting advantages such as high strength, aging resistance, high dimensional stability, and strong adhesion, making it a suitable basic material for forming electrothermal paste films. The latent curing agent forms a single-component system with room-temperature storage stability with the thermosetting resin, rapidly reacting upon heating to achieve cross-linking and curing. The second binder phase is prepared by uniformly dissolving a thermoplastic resin in a solvent. Thermoplastic resins are linear or slightly branched polymers with good flexibility, effectively mitigating the brittleness caused by cross-linking and curing of thermosetting resins. The thermoplastic resin dissolved in the solvent forms a stable fluid with a certain viscosity, contributing to improved slurry leveling and film formation.

[0008] The spherical graphite powder used in this invention is dispersed between the sheet-like graphene powder in the slurry system, which plays a role in preventing the graphene powder from agglomerating and constructing a conductive network with synergistic effect with the graphene powder, so that the slurry has better conductivity and film quality.

[0009] Preferably, the electrothermal paste comprises the following components in parts by weight: 15-25 parts of a first binder phase, 18-35 parts of a second binder phase, 0.5-1.5 parts of a coupling agent, 5-10 parts of a dispersant, 0.5-1.5 parts of a leveling agent, 15-25 parts of graphene powder, and 25-38 parts of spherical graphite powder.

[0010] Preferably, the graphene powder is a mixture of graphene powder A and graphene powder B, and the weight ratio of graphene powder A to graphene powder B is (2-8):1; wherein, the number of layers of graphene powder A is 10-30, the average sheet diameter of graphene powder A is 8-20 μm, the number of layers of graphene powder B is 3-10, the average sheet diameter of graphene powder B is 0.5-3 μm; and the average particle size of the spherical graphite powder is 4-15 μm.

[0011] Through extensive research, the inventors discovered that combining graphene powders of different sizes allows smaller-diameter flakes to fill the gaps between larger-diameter flakes, resulting in a better conductive network. When the spherical graphene powder particles are small, less than 4 μm, they cannot effectively prevent the agglomeration of graphene powder, leading to poor conductivity and film quality after slurry curing. When the spherical graphene powder particles are large, greater than 15 μm, they excessively hinder the orderly stacking of graphene sheets during slurry curing, damaging the film's density and also negatively impacting conductivity and film quality.

[0012] More preferably, the weight ratio of graphene powder A to graphene powder B is graphene powder A: graphene powder B = (3.5-6):1.

[0013] Through extensive research, the inventors discovered that when the weight ratio of graphene powder A to graphene powder B is within the aforementioned range, the prepared electrothermal paste exhibits better performance.

[0014] Preferably, the electrothermal paste is at least one of the following (a)-(g):

[0015] (a) The thermosetting resin is a liquid epoxy resin; preferably, the liquid epoxy resin is at least one of bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin.

[0016] (b) The latent curing agent is an imidazole curing agent; preferably, the imidazole curing agent is at least one of 2-ethyl-4-methylimidazolium (2E4MZ), 1-cyanoethyl-2-ethyl-4-methylimidazolium (2E4MZ-CN), 2-undecylimidazolium (C11Z), 1-cyanoethyl-2-undecylimidazolium (C11Z-CN), 1-cyanoethyl-2-undecylimidazolium trimellitate (C11Z-CNS), and 1-benzyl-2-phenylimidazolium (1B2PZ);

[0017] (c) The thermoplastic resin is at least one of saturated polyester resin, saturated polyurethane resin, polyacrylic acid resin, polyvinyl butyral, and ethylene-vinyl acetate copolymer;

[0018] (d) The solvent is at least one of ketone solvents, ether solvents, and ester solvents;

[0019] (e) The coupling agent is at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, zirconate coupling agents, and bimetallic coupling agents;

[0020] (f) The dispersant is at least one of the following: amine salt type dispersant, block copolymer type dispersant, acrylate type dispersant, hyperbranched polyester type dispersant, and polycarboxylic acid ester type dispersant;

[0021] (g) The leveling agent is at least one of silicone leveling agent, acrylic leveling agent, and fluorocarbon leveling agent.

[0022] Preferably, the electrothermal paste is at least one of the following (a)-(f):

[0023] (a) The liquid epoxy resin is at least one of bisphenol A type epoxy resin E44, bisphenol A type epoxy resin E51, hydrogenated bisphenol A type epoxy resin 1510, bisphenol F type epoxy resin 862, phenolic epoxy resin F44, and phenolic epoxy resin F51.

[0024] (b) The thermoplastic resin is a saturated polyester resin with a relative molecular weight of 15,000-35,000;

[0025] (c) The solvent is at least one of cyclohexanone, diisobutyl ketone, isophorone, ethylene glycol butyl ether, dipropylene glycol methyl ether, diethylene glycol butyl ether, propylene glycol methyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, and DBE.

[0026] (d) The coupling agent is at least one of the following: silane coupling agent KH171, silane coupling agent KH550, silane coupling agent KH560, silane coupling agent KH570, silane coupling agent KH792, titanate coupling agent KR-TTS, titanate coupling agent KR-38S, and aluminate coupling agent LD-B-1;

[0027] (e) The dispersant is at least one of DISPERBYK-110, DISPERBYK-163, DISPERBYK-180, TEGO Dispers 610, and TEGO Dispers 671;

[0028] (f) The leveling agent is at least one of BYK-306, BYK-333, BYK-358N, EFKA-3740, and EFKA-3777.

[0029] Furthermore, the present invention provides a method for preparing the aforementioned electrothermal paste, comprising the following steps:

[0030] (1) Preparation of the first binder phase: Weigh the thermosetting resin and the latent curing agent according to the weight ratio, and mix them evenly to obtain the first binder phase;

[0031] (2) Preparation of the second binder phase: Weigh the thermoplastic resin and solvent by weight percentage, heat to dissolve, and cool to obtain the second binder phase;

[0032] (3) Weigh the first binder phase, the second binder phase, the coupling agent, the dispersant, and the leveling agent according to the weight ratio, and mix them evenly to obtain the slurry matrix;

[0033] (4) The slurry matrix, graphene powder and spherical graphite powder are mixed and ground, filtered and vacuum degassed to obtain the electrothermal slurry.

[0034] Preferably, in step (1), the mixing speed is 500-1500 rpm and the mixing time is 0.5-2 h; in step (2), the heating temperature is 50-90℃ and the heating time is 3-8 h, and then cooled to room temperature; in step (3), the mixing speed is 500-1500 rpm and the mixing time is 0.5-2 h.

[0035] Preferably, in step (4), the grinding is performed twice. The first grinding is to mix and grind the slurry matrix and graphene powder to obtain a mixture. The second grinding is to mix and grind the mixture and spherical graphite powder. The filtration is performed using a 50-200 mesh screen. Preferably, the rotation speed of the first grinding is 2000-3000 rpm and the grinding time is 3-6 hours. The rotation speed of the second grinding is 1500-2500 rpm and the grinding time is 1-2.5 hours.

[0036] Furthermore, the present invention provides the application of the described electrothermal paste in the field of ---.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The electrothermal paste prepared by the present invention uses the combination of graphene and spherical graphite to form a conductive network with synergistic effect. By blocking the aggregation tendency of graphene through spherical graphite, the conductive filler is easily dispersed in the paste matrix, which increases the solid content of the electrothermal paste and reduces the resistance and film defects after the paste is cured. At the same time, spherical graphite provides more evaporation channels for the solvent, reduces the obstruction of solvent evaporation by the flake powder, and greatly improves the curing efficiency of the paste. (2) The operation steps of the present invention are simple, no complex process flow is required, the stability of the product is improved, and it is suitable for industrial-scale production. Detailed Implementation

[0038] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0039] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0040] The raw materials used in the embodiments and comparative examples are described below, but are not limited to these materials:

[0041] Graphene powder A1: 10-30 layers, average sheet diameter 12μm;

[0042] Graphene powder B1: 3-10 layers, average sheet diameter 1.5μm;

[0043] Spherical graphite powder 1: average particle size is 5 μm;

[0044] Spherical graphite powder 2: average particle size is 10 μm;

[0045] Spherical graphite powder 3: average particle size is 15 μm;

[0046] Spherical graphite powder 4: average particle size is 2.5 μm;

[0047] Spherical graphite powder 5: average particle size is 17 μm;

[0048] Examples 1-8 and Comparative Examples 1-3

[0049] Example 1

[0050] This invention discloses an electrothermal paste, and the preparation method of the electrothermal paste includes the following steps:

[0051] (1) Preparation of the first binder phase: Weigh 100 parts of thermosetting resin (bisphenol A type epoxy resin E51) and 10 parts of latent curing agent (imidazolium curing agent 2E4MZ) according to the weight ratio, and mix them evenly to obtain the first binder phase; The mixing speed is 800 rpm and the mixing time is 1 h; Thermosetting resin: latent curing agent = 100:10;

[0052] (2) Preparation of the second binder phase: Weigh thermoplastic resin (25% saturated polyester resin, relative molecular weight 22000) and solvent (25% cyclohexanone and 50% ethylene glycol butyl ether acetate) by weight percentage, heat to dissolve, and cool to obtain the second binder phase; The heating temperature is 60℃, the heating time is 5h, and then cool to room temperature;

[0053] (3) Weigh out the first binder phase (20 parts), the second binder phase (20 parts), the coupling agent (0.5 parts silane coupling agent KH560, 0.3 parts titanate coupling agent KR-TTS), the dispersant (7 parts dispersant DISPERBYK-180), and the leveling agent (1 part leveling agent BYK-306) according to the weight ratio, and mix them evenly to obtain the slurry matrix; the mixing speed is 1200 rpm and the mixing time is 1 h;

[0054] (4) The slurry matrix, graphene powder (13.5 parts graphene powder A1, 3.2 parts graphene powder B1), and spherical graphite powder (34.5 parts, spherical graphite powder 1) prepared in step (3) are mixed and ground in two stages. The first grinding is to mix and grind the slurry matrix and graphene powder at a speed of 2500 rpm for 5 hours to obtain a mixture. The second grinding is to mix and grind the mixture and spherical graphite powder at a speed of 1800 rpm for 1.5 hours. The mixture is filtered through a 150-mesh screen and degassed under vacuum to obtain the electrothermal slurry.

[0055] Example 2

[0056] This invention discloses an electrothermal paste, and the preparation method of the electrothermal paste includes the following steps:

[0057] (1) Preparation of the first binder phase: Weigh the thermosetting resin (30 parts of hydrogenated bisphenol A type epoxy resin 1510 and 70 parts of bisphenol F type epoxy resin 862) and the latent curing agent (5 parts of imidazole curing agent 2E4MZ-CN) according to the weight ratio, and mix them evenly to obtain the first binder phase; the mixing speed is 700 rpm and the mixing time is 1 h; thermosetting resin: latent curing agent = 100: 5;

[0058] (2) Preparation of the second binder phase: Weigh thermoplastic resin (22% saturated polyester resin with a relative molecular weight of 30,000) and solvent (36% isophorone and 42% dipropylene glycol methyl ether) by weight percentage, heat to dissolve, and cool to obtain the second binder phase; The heating temperature is 80℃ and the heating time is 4h, and then cool to room temperature.

[0059] (3) Weigh out the first binder phase (18 parts), the second binder phase (25 parts), coupling agent (0.7 parts of silane coupling agent KH570 and 0.3 parts of aluminate coupling agent LD-B-1), dispersant (8 parts of dispersant DISPERBYK-110), and leveling agent (0.5 parts of leveling agent BYK-358N) according to the weight ratio, and mix them evenly to obtain the slurry matrix; the mixing speed is 1000 rpm and the mixing time is 1 h;

[0060] (4) The slurry matrix, graphene powder (16 parts graphene powder A1, 3 parts graphene powder B1), and spherical graphite powder (28.5 parts, spherical graphite powder 1) prepared in step (3) are mixed and ground in two stages. The first grinding is to mix and grind the slurry matrix and graphene powder at a speed of 2300 rpm for 4.5 h to obtain a mixture. The second grinding is to mix and grind the mixture and spherical graphite powder at a speed of 2000 rpm for 2 h. The mixture is filtered using a 150-mesh screen and degassed under vacuum to obtain the electrothermal slurry.

[0061] Example 3

[0062] This invention discloses an electrothermal paste, and the preparation method of the electrothermal paste includes the following steps:

[0063] (1) Preparation of the first binder phase: Weigh thermosetting resin (80 parts of bisphenol A type epoxy resin E51 and 20 parts of phenolic epoxy resin F51) and latent curing agent (7 parts of imidazole curing agent 1B2PZ) according to the weight ratio, and mix them evenly to obtain the first binder phase; the mixing speed is 1000 rpm and the mixing time is 1.5 h; thermosetting resin: latent curing agent = 100: 7;

[0064] (2) Preparation of the second binder phase: Weigh thermoplastic resin (27% saturated polyester resin with a relative molecular weight of 18000) and solvent (32% diethylene glycol ethyl ether acetate and 41% DBE) by weight percentage, heat to dissolve, and cool to obtain the second binder phase; The heating temperature is 80℃, the heating time is 6h, and then cool to room temperature;

[0065] (3) Weigh out the first binder phase (20 parts), the second binder phase (26 parts), the coupling agent (1 part silane coupling agent KH171), the dispersant (6 parts dispersant TEGO Dispers 671), and the leveling agent (0.7 parts EFKA-3740 and 0.5 parts EFKA-3777) according to the weight ratio, and mix them evenly to obtain the slurry matrix; the mixing speed is 1000 rpm and the mixing time is 1.5 h;

[0066] (4) The slurry matrix, graphene powder (14.2 parts graphene powder A1, 3.7 parts graphene powder B1), and spherical graphite powder (27.9 parts, spherical graphite powder 1) prepared in step (3) are mixed and ground in two stages. The first grinding is to mix and grind the slurry matrix and graphene powder at a speed of 2700 rpm for 5.5 h to obtain a mixture. The second grinding is to mix and grind the mixture and spherical graphite powder at a speed of 1800 rpm for 1.5 h. The mixture is filtered through a 150-mesh screen and degassed under vacuum to obtain the electrothermal slurry.

[0067] Example 4

[0068] Compared with Example 1, only the selection of spherical graphite powder in step (4) is different. Example 4 selects 34.5 parts of spherical graphite powder 2, and the other components, weight parts and preparation methods are exactly the same as those in Example 1.

[0069] Example 5

[0070] Compared with Example 1, only the selection of spherical graphite powder in step (4) is different. Example 5 selects 34.5 parts of spherical graphite powder 3, and the other components, weight parts and preparation methods are exactly the same as those in Example 1.

[0071] Example 6

[0072] Compared with Example 1, only the weight of graphene powder in step (4) is different. Example 6 uses 12 parts of graphene powder A1 and 4.7 parts of graphene powder B1. The other components, weights and preparation methods are exactly the same as in Example 1.

[0073] Example 7

[0074] Compared with Example 1, only the weight of graphene powder in step (4) is different. Example 7 uses 14.7 parts of graphene powder A1 and 2 parts of graphene powder B1. The other components, weights and preparation methods are exactly the same as in Example 1.

[0075] Example 8

[0076] Compared with Example 1, only the weight of graphene powder in step (4) is different. Example 8 uses 14 parts of graphene powder A1 and 2.7 parts of graphene powder B1. The other components, weights and preparation methods are exactly the same as in Example 1.

[0077] Comparative Example 1

[0078] Compared to Example 1, only step (4) differs. 30 parts of conductive carbon black with a particle size of 30 nm and 4.5 parts of carbon nanotube powder with a length range of 5-20 μm are used instead of spherical graphite powder. In the preparation steps of this comparative example, 11 parts of cyclohexanone and 22 parts of ethylene glycol butyl ether acetate are added to adjust the viscosity to suit the printing process. The remaining components, weight parts, and preparation methods are exactly the same as in Example 1.

[0079] Comparative Example 2

[0080] Compared with Example 1, only the selection of spherical graphite powder in step (4) is different. Example 4 selects 34.5 parts of spherical graphite powder 4, and the other components, weight parts and preparation methods are exactly the same as those in Example 1.

[0081] Comparative Example 3

[0082] Compared with Example 1, only the selection of spherical graphite powder in step (4) is different. Example 4 selects 34.5 parts of spherical graphite powder 5, and the other components, weight parts and preparation methods are exactly the same as those in Example 1.

[0083] Performance testing

[0084] Testing Procedure: Samples of the electrothermal pastes prepared in the examples and comparative examples were taken and printed into 10cm*10cm films using a 100-mesh screen with a thickness of 25μm. Viscosity, curing efficiency, solids content, adhesion, and film quality were tested respectively. The testing methods are as follows:

[0085] Viscosity: Measured using a Brookfield viscometer under the following conditions: CPA-51Z rotor, 100 rpm, 25°C.

[0086] Curing efficiency: Characterized by the change in sheet resistance of the paste at different curing times under a specified curing temperature. The sheet resistance of the electrothermal paste was tested at curing times of 15 min, 30 min, 45 min, and 60 min. Due to the different solvent systems, the curing temperature for Examples 1-2, Examples 4-8, and Comparative Examples 1-3 was specified as 120℃, and the curing temperature for Example 3 was specified as 130℃. The sheet resistance values ​​were measured using a four-probe tester.

[0087] Solid content: This is obtained by calculating the ratio of the dry film weight after curing at 150℃ for 90 minutes to the wet film weight before curing.

[0088] Adhesion: Tested according to GB / T 9286-2021 "Paints and Varnishes - Cross-cut Test";

[0089] Film quality: The film layer after the slurry has solidified is characterized by observing whether there are film defects such as cracks, voids, and pinholes using a backlight and microscope.

[0090] The test results are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] As shown in Table 1, the graphene / spherical graphite composite electrothermal paste of this invention, in addition to possessing advantages such as low resistance, moderate viscosity, and high adhesion, achieves a low sheet resistance within 15 minutes. The cured film is free of various defects, exhibiting characteristics of fast curing speed and high film quality. Compared with existing carbon-based electrothermal pastes, the graphene / spherical graphite composite electrothermal paste of this invention demonstrates significant advantages in terms of its own performance and process adaptability, effectively preventing the generation of local hot spots in the film layer, which is of great significance for improving the safety and quality of electrothermal products.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An electrothermal paste, characterized in that, The product comprises the following components in parts by weight: 15-25 parts of a first binder phase, 18-35 parts of a second binder phase, 0.5-1.5 parts of a coupling agent, 5-10 parts of a dispersant, 0.5-1.5 parts of a leveling agent, 15-25 parts of graphene powder, and 25-38 parts of spherical graphite powder; the first binder phase is a mixture of thermosetting resin and latent curing agent, wherein the weight ratio of the thermosetting resin to the latent curing agent is thermosetting resin:latent curing agent = 100:(2-20); the second binder phase is a mixture of thermoplastic resin and solvent, wherein the weight percentage of thermoplastic resin in the second binder phase is 10%-40%; and the average particle size of the spherical graphite powder is 4-15 μm. The graphene powder is a mixture of graphene powder A and graphene powder B, with a weight ratio of graphene powder A: graphene powder B = (3.5-6):1; wherein, graphene powder A has 10-30 layers and an average sheet diameter of 8-20 μm, and graphene powder B has 3-10 layers and an average sheet diameter of 0.5-3 μm.

2. The electrothermal paste as described in claim 1, characterized in that, At least one of the following (a)-(g): (a) The thermosetting resin is a liquid epoxy resin; (b) The latent curing agent is an imidazole curing agent; (c) The thermoplastic resin is at least one of saturated polyester resin, saturated polyurethane resin, polyacrylic acid resin, polyvinyl butyral, and ethylene-vinyl acetate copolymer; (d) The solvent is at least one of ketone solvents, ether solvents, and ester solvents; (e) The coupling agent is at least one of silane coupling agents, titanate coupling agents, aluminate coupling agents, zirconate coupling agents, and bimetallic coupling agents; (f) The dispersant is at least one of the following: amine salt type dispersant, block copolymer type dispersant, acrylate type dispersant, hyperbranched polyester type dispersant, and polycarboxylic acid ester type dispersant; (g) The leveling agent is at least one of silicone leveling agent, acrylic leveling agent, and fluorocarbon leveling agent.

3. The electrothermal paste as described in claim 2, characterized in that, At least one of the following (a)-(f): (a) The liquid epoxy resin is at least one of bisphenol A type epoxy resin E44, bisphenol A type epoxy resin E51, hydrogenated bisphenol A type epoxy resin 1510, bisphenol F type epoxy resin 862, phenolic epoxy resin F44, and phenolic epoxy resin F51. (b) The thermoplastic resin is a saturated polyester resin with a relative molecular weight of 15,000-35,000; (c) The solvent is at least one of cyclohexanone, diisobutyl ketone, isophorone, ethylene glycol butyl ether, dipropylene glycol methyl ether, diethylene glycol butyl ether, propylene glycol methyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, and DBE. (d) The coupling agent is at least one of the following: silane coupling agent KH171, silane coupling agent KH550, silane coupling agent KH560, silane coupling agent KH570, silane coupling agent KH792, titanate coupling agent KR-TTS, titanate coupling agent KR-38S, and aluminate coupling agent LD-B-1; (e) The dispersant is at least one of DISPERBYK-110, DISPERBYK-163, DISPERBYK-180, TEGO Dispers 610, and TEGO Dispers 671; (f) The leveling agent is at least one of BYK-306, BYK-333, BYK-358 N, EFKA-3740, and EFKA-3777.

4. A method for preparing an electrothermal paste as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Preparation of the first binder phase: Weigh the thermosetting resin and the latent curing agent according to the weight ratio, and mix them evenly to obtain the first binder phase; (2) Preparation of the second binder phase: Weigh the thermoplastic resin and solvent by weight percentage, heat to dissolve, and cool to obtain the second binder phase; (3) Weigh the first binder phase, the second binder phase, the coupling agent, the dispersant, and the leveling agent according to the weight ratio, and mix them evenly to obtain the slurry matrix; (4) The slurry matrix, graphene powder and spherical graphite powder are mixed and ground, filtered and vacuum degassed to obtain the electrothermal slurry.

5. The method for preparing the electrothermal paste as described in claim 4, characterized in that, In step (1), the mixing speed is 500-1500 rpm and the mixing time is 0.5-2h; in step (2), the heating temperature is 50-90℃ and the heating time is 3-8h, then cooled to room temperature; in step (3), the mixing speed is 500-1500 rpm and the mixing time is 0.5-2h.

6. The method for preparing the electrothermal paste as described in claim 4, characterized in that, In step (4), the grinding is carried out in two stages. The first grinding is to mix and grind the slurry matrix and graphene powder to obtain a mixture. The second grinding is to mix and grind the mixture and spherical graphite powder. The filtration is carried out using a 50-200 mesh screen.

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