Graphene composite conductive paste and preparation method thereof

Abstract

The invention discloses graphene composite conductive paste and a preparation method thereof, and belongs to the technical field of batteries. The preparation method of the graphene composite conductive paste comprises the following steps: S1, mixing and stirring modified graphene, carbon nanotube coated aminated silicon dioxide microspheres, humic acid, deionized water and sodium hydroxide for 1-2 hours to obtain a mixed solution; s2, lignin is added into the mixed solution to be mixed and stirred for 2-3 h, and the graphene composite conductive paste is obtained. The modified graphene is hydrophilic modified graphene, the prepared graphene composite conductive paste is good in dispersity and stability and good in conductivity when being applied to a battery, and the obtained battery has good rate capability, cycle performance and thermal stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a graphene composite conductive paste and a preparation method thereof. Background Art

[0002] With the rapid development of electronic devices, electric vehicles, and renewable energy, the demand for high-performance batteries is increasing day by day. Traditional lithium-ion batteries have approached their limits in terms of energy density, power density, and cycle life, and it is difficult to meet future requirements. Therefore, developing new electrode materials and conductive pastes has become the key to improving battery performance.

[0003] Graphene is considered an ideal choice for next-generation battery materials due to its excellent electrical conductivity, high specific surface area, and outstanding mechanical properties. However, graphene is prone to agglomeration in practical applications, which affects the performance of graphene. In addition, the adhesion and structural stability of single graphene materials in electrodes are insufficient, limiting their applications.

[0004] To overcome these problems, researchers have developed graphene composite conductive pastes. Currently, the research on graphene composite conductive pastes is still in its infancy, and there are problems such as poor conductivity caused by poor dispersion and stability of graphene composite conductive pastes, thus affecting the performance of batteries. Summary of the Invention

[0005] The purpose of the present invention is to provide a graphene composite conductive paste and a preparation method thereof to solve the problem of poor conductivity of graphene composite conductive pastes due to poor dispersion and stability.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] In the first aspect, the present invention provides a graphene composite conductive paste, comprising the following raw materials in parts by weight:

[0008] 1 - 10 parts of modified graphene, 0.5 - 5 parts of carbon nanotube-coated amino-functionalized silica microspheres, 0.1 - 2 parts of humic acid, 0.5 - 5 parts of lignin, 0.1 - 1 part of sodium hydroxide, and 80 - 95 parts of deionized water.

[0009] In the second aspect, the present invention provides a preparation method of a graphene composite conductive paste, comprising the following steps:

[0010] S1. Mix and stir modified graphene, carbon nanotube-coated amino-functionalized silica microspheres, humic acid, deionized water, and sodium hydroxide for 1 - 2 h to obtain a mixed solution;

[0011] S2. Add lignin to the mixed solution and stir for 2 - 3 h to obtain a graphene composite conductive paste.

[0012] Further, the modified graphene is hydrophilic modified graphene, which is prepared by the following steps:

[0013] Add graphene into H 2 SO 4 solution, heat and react for 1 - 2 h, then wash the sulfuric acid on the surface of graphene with deionized water until the solution is neutral, and dry to obtain hydrophilic modified graphene.

[0014] Further, the mass concentration of the H 2 SO 4 solution is 65 - 75%.

[0015] Further, the mass ratio of the graphene to the H 2 SO 4 solution is 1 - 3:10.

[0016] Further, the temperature of the heating reaction is 50 - 60 °C.

[0017] Further, the carbon nanotube-coated amino-functionalized silica microspheres are prepared by the following steps:

[0018] Add the amino-functionalized silica microspheres into the ethanol dispersion of carbon nanotubes, stir, then let it stand, filter, wash, and dry to obtain the carbon nanotube-coated silica microspheres.

[0019] Further, the mass ratio of the amino-functionalized silica microspheres to the carbon nanotubes is 3 - 5:1.

[0020] Further, the amino-functionalized silica microspheres are prepared by the following steps:

[0021] Add the silica microspheres into the KH550 solution, ultrasonicate for 0.5 - 1 h, then heat to 70 - 80 °C and react for 8 - 10 h, filter by suction, and dry to obtain the amino-functionalized silica microspheres.

[0022] Further, the size of the silica microspheres is 1 - 5 μm; the dosage of KH550 is 3 - 5% of the mass of the silica microspheres.

[0023] Advantages of the present invention:

[0024] (1) When preparing the graphene composite conductive paste in the present invention, the solvent used is deionized water, which is very friendly to the environment compared with organic solvents; the graphene is hydrophilically modified, so that the graphene and deionized water have good compatibility, and thus the graphene has good dispersibility when made into a paste.

[0025] (2) When preparing the graphene composite conductive paste of the present invention, an amino-functionalized silica microsphere coated with carbon nanotubes is added. The amino-functionalized silica microsphere coated with carbon nanotubes imparts good conductivity to the silica microsphere. The silica microsphere can promote the dispersion of graphene and improve the heat resistance of the battery paste, thereby improving the thermal stability of the battery.

[0026] (3) When preparing the graphene composite conductive paste of the present invention, graphene and an amino-functionalized silica microsphere coated with carbon nanotubes are used simultaneously. Since the molecules of the amino-functionalized silica microsphere coated with carbon nanotubes are rich in amino groups, they carry a positive charge, while the surface of graphene carries a negative charge. There is an interaction force between the charges of the two, which helps the mutual attraction between the amino-functionalized silica microsphere coated with carbon nanotubes and graphene, increasing the steric hindrance of graphene and the repulsive force between graphene sheets, thus improving the dispersibility; and the amino-functionalized silica microsphere coated with carbon nanotubes has rich functional groups such as amino and hydroxyl groups, which can form hydrogen bonds or van der Waals interactions with the solvent, thereby synergistically dispersing graphene and making the graphene composite conductive paste more stable; the improvement of the dispersibility and stability of the graphene composite conductive paste is beneficial to improving the rate performance and cycling performance of the battery. Detailed implementation mode

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0028] Embodiment 1

[0029] This embodiment provides a graphene composite conductive paste, including the following raw materials in parts by weight:

[0030] 5 parts of modified graphene, 3 parts of amino-functionalized silica microsphere coated with carbon nanotubes, 1 part of humic acid, 3 parts of lignin, 0.5 part of sodium hydroxide, and 90 parts of deionized water.

[0031] It is prepared by the following steps:

[0032] (1) Prepare modified graphene, that is, hydrophilic modified graphene:

[0033] By weight, add 3 parts of graphene to 10 parts of H 2 SO 4 solution with a mass fraction of 70%, heat to 55 °C and react for 1 h, then wash the sulfuric acid on the surface of graphene with deionized water until the solution is neutral, and dry to obtain hydrophilic modified graphene;

[0034] (2) Preparation of carbon nanotube-coated amino-functionalized silica microspheres:

[0035] 1) Add silica microspheres with a size of 1 - 5 μm to the KH550 solution. The dosage of KH550 is 3% of the mass of the silica microspheres. After ultrasonic treatment for 0.5 h, heat to 75 °C and react for 9 h, then filter by suction and dry to obtain amino-functionalized silica microspheres;

[0036] 2) Add the amino-functionalized silica microspheres to the ethanol dispersion of carbon nanotubes. The mass ratio of the amino-functionalized silica microspheres to the carbon nanotubes is 5:1. After stirring, let it stand, filter, wash, and dry to obtain carbon nanotube-coated silica microspheres;

[0037] (3) Mix and stir the modified graphene, carbon nanotube-coated amino-functionalized silica microspheres, humic acid, deionized water, and sodium hydroxide for 2 h to obtain a mixed solution;

[0038] (4) Add lignin to the mixed solution and stir for 2 h to obtain the graphene composite conductive paste.

[0039] Example 2

[0040] This example provides a graphene composite conductive paste, which includes the following raw materials in parts by weight:

[0041] 5 parts of modified graphene, 3 parts of carbon nanotube-coated amino-functionalized silica microspheres, 1 part of humic acid, 3 parts of lignin, 0.5 part of sodium hydroxide, and 90 parts of deionized water.

[0042] It is prepared through the following steps:

[0043] (1) Preparation of modified graphene, i.e., hydrophilic modified graphene:

[0044] By weight, add 2 parts of graphene to 10 parts of an H 2 SO 4 solution with a mass fraction of 70%. Heat to 55 °C and react for 1 h, then wash the sulfuric acid on the surface of the graphene with deionized water until the solution is neutral, and dry to obtain hydrophilic modified graphene;

[0045] (2) Preparation of carbon nanotube-coated amino-functionalized silica microspheres:

[0046] 1) Add silica microspheres with a size of 1 - 5 μm to the KH550 solution. The dosage of KH550 is 3% of the mass of the silica microspheres. After ultrasonic treatment for 0.5 h, heat to 75 °C and react for 9 h, then filter by suction and dry to obtain amino-functionalized silica microspheres;

[0047] (2) Add the aminated silica microspheres to the ethanol dispersion of carbon nanotubes. The mass ratio of the aminated silica microspheres to the carbon nanotubes is 5:1. After stirring, let it stand, filter, wash, and dry to obtain silica microspheres coated with carbon nanotubes;

[0048] (3) Mix and stir the modified graphene, silica microspheres coated with carbon nanotubes, humic acid, deionized water, and sodium hydroxide for 2 h to obtain a mixed solution;

[0049] (4) Add lignin to the mixed solution and stir for 2 h to obtain the graphene composite conductive paste.

[0050] Example 3

[0051] This example provides a graphene composite conductive paste, which includes the following raw materials in parts by weight:

[0052] 5 parts of modified graphene, 3 parts of silica microspheres coated with carbon nanotubes, 1 part of humic acid, 3 parts of lignin, 0.5 part of sodium hydroxide, and 90 parts of deionized water.

[0053] It is prepared through the following steps:

[0054] (1) Prepare modified graphene, that is, hydrophilic modified graphene:

[0055] By weight, add 1 part of graphene to 10 parts of an H 2 SO 4 solution with a mass fraction of 70%. Heat to 55 °C and react for 1 h. Then wash the sulfuric acid on the surface of the graphene with deionized water until the solution is neutral. After drying, obtain hydrophilic modified graphene;

[0056] (2) Prepare silica microspheres coated with carbon nanotubes:

[0057] 1) Add silica microspheres with a size of 1 - 5 μm to the KH550 solution. The dosage of KH550 is 3% of the mass of the silica microspheres. After ultrasonic treatment for 0.5 h, heat to 75 °C and react for 9 h, filter by suction, and dry to obtain aminated silica microspheres;

[0058] 2) Add the aminated silica microspheres to the ethanol dispersion of carbon nanotubes. The mass ratio of the aminated silica microspheres to the carbon nanotubes is 5:1. After stirring, let it stand, filter, wash, and dry to obtain silica microspheres coated with carbon nanotubes;

[0059] (3) Mix and stir the modified graphene, silica microspheres coated with carbon nanotubes, humic acid, deionized water, and sodium hydroxide for 2 h to obtain a mixed solution;

[0060] (4) Add lignin to the mixed solution and stir for 2 h to obtain the graphene composite conductive paste.

[0061] Example 4

[0062] This example provides a graphene composite conductive paste, which comprises the following raw materials in parts by weight:

[0063] 5 parts of modified graphene, 3 parts of carbon nanotube-coated amino-functionalized silica microspheres, 1 part of humic acid, 3 parts of lignin, 0.5 part of sodium hydroxide, and 90 parts of deionized water.

[0064] It is prepared through the following steps:

[0065] (1) Prepare modified graphene, i.e., hydrophilic modified graphene:

[0066] By weight, add 1 part of graphene to 10 parts of an H 2 SO 4 solution with a mass fraction of 70%, heat to 55 °C and react for 1 h, then wash the sulfuric acid on the surface of the graphene with deionized water until the solution is neutral, and dry to obtain hydrophilic modified graphene;

[0067] (2) Prepare carbon nanotube-coated amino-functionalized silica microspheres:

[0068] 1) Add silica microspheres with a size of 1 - 5 μm to the KH550 solution, and the dosage of KH550 is 4% of the mass of the silica microspheres. After ultrasonic treatment for 0.5 h, heat to 75 °C, react for 9 h, filter by suction, and dry to obtain amino-functionalized silica microspheres;

[0069] 2) Add the amino-functionalized silica microspheres to the ethanol dispersion of carbon nanotubes, and the mass ratio of the amino-functionalized silica microspheres to the carbon nanotubes is 5:1. After stirring, let it stand, filter, wash, and dry to obtain carbon nanotube-coated silica microspheres;

[0070] (3) Mix and stir the modified graphene, carbon nanotube-coated amino-functionalized silica microspheres, humic acid, deionized water, and sodium hydroxide for 2 h to obtain a mixed solution;

[0071] (4) Add lignin to the mixed solution and stir for 2 h to obtain the graphene composite conductive paste.

[0072] Example 5

[0073] This example provides a graphene composite conductive paste, which comprises the following raw materials in parts by weight:

[0074] 5 parts of modified graphene, 3 parts of carbon nanotube-coated amino-functionalized silica microspheres, 1 part of humic acid, 3 parts of lignin, 0.5 part of sodium hydroxide, and 90 parts of deionized water.

[0075] It is prepared through the following steps:

[0076] (1) Preparation of modified graphene, namely hydrophilic modified graphene:

[0077] By weight, add 1 part of graphene into 10 parts of H 2 SO 4 solution with a mass fraction of 70%, heat to 55°C and react for 1 h, then wash the sulfuric acid on the surface of graphene with deionized water until the solution is neutral, and obtain hydrophilic modified graphene after drying;

[0078] (2) Preparation of carbon nanotube-coated amino-functionalized silica microspheres:

[0079] 1) Add silica microspheres with a size of 1 - 5 μm into the KH550 solution, and the dosage of KH550 is 5% of the mass of silica microspheres. After ultrasonic treatment for 0.5 h, heat to 75°C and react for 9 h, filter by suction, and dry to obtain amino-functionalized silica microspheres;

[0080] 2) Add the amino-functionalized silica microspheres into the ethanol dispersion of carbon nanotubes. The mass ratio of amino-functionalized silica microspheres to carbon nanotubes is 5:1. After stirring, let it stand, filter, wash, and dry to obtain carbon nanotube-coated silica microspheres;

[0081] (3) Mix and stir the modified graphene, carbon nanotube-coated amino-functionalized silica microspheres, humic acid, deionized water, and sodium hydroxide for 2 h to obtain a mixed solution;

[0082] (4) Add lignin to the mixed solution and stir for 2 h to obtain graphene composite conductive paste.

[0083] Example 6

[0084] This example provides a graphene composite conductive paste, which includes the following raw materials by weight:

[0085] 5 parts of modified graphene, 3 parts of carbon nanotube-coated amino-functionalized silica microspheres, 1 part of humic acid, 3 parts of lignin, 0.5 part of sodium hydroxide, and 90 parts of deionized water.

[0086] Prepared by the following steps:

[0087] (1) Preparation of modified graphene, namely hydrophilic modified graphene:

[0088] By weight, add 1 part of graphene into 10 parts of H 2 SO 4 solution with a mass fraction of 70%, heat to 55°C and react for 1 h, then wash the sulfuric acid on the surface of graphene with deionized water until the solution is neutral, and obtain hydrophilic modified graphene after drying;

[0089] (2) Preparation of carbon nanotube-coated amino-functionalized silica microspheres:

[0090] 1) Add silica microspheres with a size of 1 - 5 μm to the KH550 solution. The dosage of KH550 is 5% of the mass of the silica microspheres. After ultrasonic treatment for 0.5 h, heat to 75 °C and react for 9 h, then filter and dry to obtain amino-functionalized silica microspheres;

[0091] 2) Add the amino-functionalized silica microspheres to the ethanol dispersion of carbon nanotubes. The mass ratio of the amino-functionalized silica microspheres to the carbon nanotubes is 4:1. After stirring, let it stand, filter, wash, and dry to obtain carbon nanotube-coated silica microspheres;

[0092] (3) Mix and stir the modified graphene, carbon nanotube-coated amino-functionalized silica microspheres, humic acid, deionized water, and sodium hydroxide for 2 h to obtain a mixed solution;

[0093] (4) Add lignin to the mixed solution and stir for 2 h to obtain the graphene composite conductive paste.

[0094] Example 7

[0095] This example provides a graphene composite conductive paste, which includes the following raw materials in parts by weight:

[0096] 5 parts of modified graphene, 3 parts of carbon nanotube-coated amino-functionalized silica microspheres, 1 part of humic acid, 3 parts of lignin, 0.5 part of sodium hydroxide, and 90 parts of deionized water.

[0097] It is prepared through the following steps:

[0098] (1) Prepare modified graphene, that is, hydrophilic modified graphene:

[0099] By weight, add 1 part of graphene to 10 parts of an H 2 SO 4 solution with a mass fraction of 70%. Heat to 55 °C and react for 1 h, then wash the sulfuric acid on the surface of the graphene with deionized water until the solution is neutral, and dry to obtain hydrophilic modified graphene;

[0100] (2) Prepare carbon nanotube-coated amino-functionalized silica microspheres:

[0101] 1) Add silica microspheres with a size of 1 - 5 μm to the KH550 solution. The dosage of KH550 is 5% of the mass of the silica microspheres. After ultrasonic treatment for 0.5 h, heat to 75 °C and react for 9 h, then filter and dry to obtain amino-functionalized silica microspheres;

[0102] 2) Add the amino-functionalized silica microspheres to the ethanol dispersion of carbon nanotubes. The mass ratio of the amino-functionalized silica microspheres to the carbon nanotubes is 3:1. After stirring, let it stand, filter, wash, and dry to obtain carbon nanotube-coated silica microspheres;

[0103] (3) Mix the modified graphene, carbon nanotube-coated amino-functionalized silica microspheres, humic acid, deionized water, and sodium hydroxide and stir for 2 h to obtain a mixed solution;

[0104] (4) Add lignin to the mixed solution and stir for 2 h to obtain the graphene composite conductive paste.

[0105] Comparative Example 1

[0106] This comparative example provides a graphene composite conductive paste, comprising the following raw materials in parts by weight:

[0107] 5 parts of graphene, 3 parts of carbon nanotube-coated amino-functionalized silica microspheres, 1 part of humic acid, 3 parts of lignin, 0.5 part of sodium hydroxide, and 90 parts of deionized water.

[0108] It is prepared by the following steps:

[0109] (1) Prepare carbon nanotube-coated amino-functionalized silica microspheres:

[0110] 1) Add silica microspheres with a size of 1 - 5 μm to the KH550 solution. The dosage of KH550 is 3% of the mass of the silica microspheres. After ultrasonic treatment for 0.5 h, heat to 75 °C, react for 9 h, filter by suction, and dry to obtain amino-functionalized silica microspheres;

[0111] 2) Add the amino-functionalized silica microspheres to the ethanol dispersion of carbon nanotubes. The mass ratio of the amino-functionalized silica microspheres to the carbon nanotubes is 5:1. After stirring, let stand, filter, wash, and dry to obtain carbon nanotube-coated silica microspheres;

[0112] (2) Mix the graphene, carbon nanotube-coated amino-functionalized silica microspheres, humic acid, deionized water, and sodium hydroxide and stir for 2 h to obtain a mixed solution;

[0113] (3) Add lignin to the mixed solution and stir for 2 h to obtain the graphene composite conductive paste.

[0114] Comparative Example 2

[0115] This comparative example provides a graphene composite conductive paste, comprising the following raw materials in parts by weight:

[0116] 5 parts of modified graphene, 3 parts of silica microspheres, 1 part of humic acid, 3 parts of lignin, 0.5 part of sodium hydroxide, and 90 parts of deionized water.

[0117] It is prepared by the following steps:

[0118] (1) Prepare modified graphene, i.e., hydrophilic modified graphene:

[0119] By weight, add 3 parts of graphene into 10 parts of an H 2 SO 4 solution with a mass fraction of 70%, heat to 55 °C and react for 1 h, then wash the graphene surface with sulfuric acid with deionized water until the solution is neutral, and obtain hydrophilic modified graphene after drying;

[0120] (2) Mix and stir the modified graphene, silica microspheres, humic acid, deionized water and sodium hydroxide for 2 h to obtain a mixed solution;

[0121] (3) Add lignin to the mixed solution and stir for 2 h to obtain a graphene composite conductive paste.

[0122] Mix the graphene composite conductive paste prepared in Examples 1 - 7 and Comparative Examples 1 - 2 with lithium iron phosphate in a mass ratio of 85:15, and make a positive electrode sheet through processes such as coating, rolling, slitting, and sheet making; the negative electrode is made of graphite, carbon black, a thickening agent (sodium carboxymethyl cellulose) and a binder (styrene-butadiene rubber) mixed in a mass ratio of 95:1:1:3 to make a negative electrode paste, and the negative electrode sheet is made by the same process; a 16-μm thick porous polyethylene film is used as the separator; 1 mol / L lithium hexafluorophosphate is used as the electrolyte; assemble the positive electrode sheet, negative electrode sheet, separator and electrolyte into a battery for performance testing.

[0123] At 25 °C and within a voltage range of 2.0 - 3.8 V, test the discharge capacity of the battery at different rates, and the results are shown in Table 1;

[0124] Conduct charge and discharge cycle tests on the battery at 25 °C and 50 °C respectively within a voltage range of 2.0 - 3.8 V, test the discharge capacity of the battery when cycling 100 times at a 1C rate, and calculate the capacity retention rate. The results are shown in Table 2:

[0125] Table 1

[0126] Discharge capacity (mAh / g) 0.5C 1C 2C 5C 10C Example 1 154.4 145.2 133.1 118.2 107.4 Example 2 155.3 146.2 134.0 119.1 108.3 Example 3 156.5 147.3 135.2 120.3 109.5 Example 4 158.4 149.3 137.1 122.2 111.4 Example 5 160.5 151.4 139.2 124.3 113.5 Example 6 163.3 154.1 142.0 127.1 116.3 Example 7 166.5 157.4 145.2 130.3 119.5 Comparative Example 1 144.2 135.1 122.9 108.0 97.2 Comparative Example 2 140.1 131.0 118.8 103.9 93.3

[0127] Table 2

[0128] Capacity retention rate (%) 100 cycles at 1C at 25°C 100 cycles at 1C at 50°C Example 1 94.3 93.6 Example 2 94.4 94.0 Example 3 95.5 95.1 Example 4 95.6 95.2 Example 5 95.8 95.3 Example 6 96.0 95.5 Example 7 96.4 95.9 Comparative Example 1 84.2 83.3 Comparative Example 2 79.1 78.7

[0129] It can be seen from Table 1 and Table 2 that when the graphene composite conductive paste prepared in Examples 1 - 7 is applied to the battery, the obtained battery has good rate performance, cycle performance, and good thermal stability.

[0130] Compared with Example 1, in Comparative Example 1, graphene was used instead of hydrophilically modified graphene, resulting in poorer rate performance and cycling performance of the battery; compared with Example 1, in Comparative Example 2, silica microspheres were used instead of amino-functionalized silica microspheres coated with carbon nanotubes, resulting in poorer rate performance and cycling performance of the battery, and also poorer thermal stability.

[0131] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0132] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A graphene composite conductive slurry, characterized in that: The invention comprises the following raw materials in parts by weight: 1-10 parts of modified graphene, 0.5-5 parts of amino-modified silicon dioxide microspheres coated with carbon nanotubes, 0.1-2 parts of humic acid, 0.5-5 parts of lignin, 0.1-1 parts of sodium hydroxide, and 80-95 parts of deionized water.

2. The method for preparing a graphene composite conductive slurry according to claim 1, characterized in that: The following steps are involved: S1, mixing the modified graphene, the carbon nanotube-coated aminated silica microspheres, humic acid, deionized water and sodium hydroxide for 1-2 hours to obtain a mixed solution; S2. Add lignin to the mixed solution and stir for 2-3 hours to obtain a graphene composite conductive slurry.

3. The method for preparing a graphene composite conductive slurry according to claim 2, characterized in that: The modified graphene is hydrophilic modified graphene, which is prepared by the following steps: Graphene is added to a H2SO4 solution and heated to react for 1-2 hours, and then the sulfuric acid on the surface of the graphene is washed with deionized water until the solution is neutral, and then dried to obtain hydrophilic modified graphene.

4. The method for preparing a graphene composite conductive slurry according to claim 3, characterized in that: The mass concentration of the H2SO4 solution is 65-75%.

5. The method for preparing a graphene composite conductive slurry according to claim 3, characterized in that: The mass ratio of the graphene to the H2SO4 solution is 1-3:

10.

6. The method for preparing a graphene composite conductive slurry according to claim 3, characterized in that: The temperature of the heating reaction is 50-60°C.

7. The method for preparing a graphene composite conductive slurry according to claim 2, characterized in that: The carbon nanotube-coated aminated silica microspheres are prepared by the following steps: The aminated silica microspheres are added into the ethanol dispersion of carbon nanotubes, stirred, allowed to stand, filtered, washed and dried to obtain the silica microspheres coated with carbon nanotubes.

8. The method for preparing a graphene composite conductive slurry according to claim 7, characterized in that: The mass ratio of the amino-modified silica microspheres to the carbon nanotubes is 3-5:

1.

9. The method for preparing a graphene composite conductive slurry according to claim 7, characterized in that: The amination silica microspheres are prepared by the following steps: Add silica microspheres to the KH550 solution, sonicate for 0.5-1 h, heat to 70-80° C., react for 8-10 h, filter, and dry to obtain amino silica microspheres.

10. The method for preparing a graphene composite conductive slurry according to claim 9, characterized in that: The size of the silica microspheres is 1-5 μm; the amount of KH550 used is 3-5% of the mass of the silica microspheres.