Preparation method and application of graphene / carbon nanotube composite conductive agent

Abstract

The invention discloses a preparation method and application of a graphene / carbon nanotube composite conductive agent, and the preparation steps are as follows: step S1, mixing graphene powder with a metal salt solution, drying and calcining in an oxygen-containing atmosphere to obtain graphene powder intercalated with metal oxides; step S2, treating the graphene powder intercalated with metal oxides in a reducing atmosphere to obtain graphene powder intercalated with metal particles; step S3, mixing the graphene powder intercalated with metal particles with volatile organic matter, calcining at 600-900°C, and then heat-insulating at 1400-1800°C to obtain graphene / carbon nanotube composite powder; step S4, mixing iron graphene / carbon nanotube composite powder, dispersant and solvent. The preparation method of the invention is simple, suitable for large-scale production, and the obtained graphene / carbon nanotube composite conductive agent has low resistivity.

Description

Technical Field

[0001] The invention relates to the technical field of graphene materials, and in particular to a preparation method and application of a graphene / carbon nanotube composite conductive agent. Background Art

[0002] Graphene is a single layer of sp 2 A new type of carbon nanomaterial in which carbon atoms are stacked into a two-dimensional honeycomb structure, it can form an effective conductive network in the active material particles through the "surface-point" contact mode, thereby improving the performance of lithium batteries. However, while graphene's unique two-dimensional planar structure brings extremely high conductivity, it also produces a steric effect on lithium ions, such as agglomeration and polarization in practical applications, which affects the performance of the battery to a certain extent.

[0003] In the related art, carbon nanotubes are a material with a special one-dimensional structure. They are in point-line contact with active materials, and can form a large number of conductive contact sites between active material particles, thereby reducing the contact impedance between electrode material particles. Related studies have shown that the combination of graphene and carbon nanotubes can improve their conductivity to a certain extent, but there is still a technical problem of insufficient conductivity in actual applications.

[0004] Therefore, it is necessary to provide a method for preparing a graphene / carbon nanotube composite conductive agent, which has a simple production process, is suitable for large-scale production, and the obtained graphene / carbon nanotube composite conductive agent has low resistivity. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a preparation method and application of a graphene / carbon nanotube composite conductive agent. The preparation method of the graphene / carbon nanotube composite conductive agent of the present invention is simple, suitable for large-scale production, and the obtained graphene / carbon nanotube composite conductive agent has low resistivity.

[0006] The invention also provides a graphene / carbon nanotube composite conductive agent.

[0007] The present invention also proposes an application of a graphene / carbon nanotube composite conductive agent in the preparation of a battery.

[0008] The first aspect of the present invention provides a method for preparing a graphene / carbon nanotube composite conductive agent, comprising the following preparation steps:

[0009] Step S1, mixing graphene powder with a metal salt solution, drying and calcining in an oxygen-containing atmosphere to obtain metal oxide intercalated graphene powder;

[0010] Step S2, treating the graphene powder intercalated with metal oxides in a reducing atmosphere to obtain graphene powder intercalated with metal particles;

[0011] Step S3, mixing the graphene powder intercalated with the metal particles with volatile organic matter, calcining at 600-900° C., and then keeping the mixture at 1400-1800° C. to obtain a graphene / carbon nanotube composite powder;

[0012] Step S4: mixing the graphene / carbon nanotube composite powder, dispersant and solvent to obtain a graphene / carbon nanotube composite conductive agent.

[0013] The preparation method of the graphene / carbon nanotube composite conductive agent according to the embodiment of the present invention has at least the following beneficial effects: the present invention adopts a supporting method to prepare graphene powder with metal particles intercalated, and then uses an in-situ generation method to prepare a graphene / carbon nanotube composite powder, and finally the graphene / carbon nanotube composite powder is compounded with a dispersant and a solvent to obtain a graphene / carbon nanotube composite conductive agent. The preparation method of the graphene / carbon nanotube composite conductive agent of the present invention is simple and suitable for large-scale production.

[0014] Secondly, since the carbonization rate of volatile organic matter is too fast at 600-900°C, which is not conducive to forming a uniform doping form, the present invention first mixes the graphene powder intercalated with metal particles with the volatile organic matter, allowing the volatile organic matter to penetrate into the interior and then carbonize, which effectively solves the technical problem of uneven carbonization in the prior art.

[0015] According to some embodiments of the present invention, in step S1, the metal in the metal salt solution is selected from at least one of nickel, cobalt and iron.

[0016] According to some embodiments of the present invention, the molar concentration of the metal in the metal salt solution is 1 to 5 mol / L;

[0017] Preferably, the solid-liquid volume ratio (g / mL) of the graphene powder to the metal salt solution is 1:4-8.

[0018] According to some embodiments of the present invention, in step S1, the calcination temperature is 150°C to 180°C;

[0019] Preferably, the calcination temperature is 160°C to 180°C;

[0020] More preferably, the calcination temperature is 160°C.

[0021] According to some embodiments of the present invention, in step S1, the oxygen-containing atmosphere is air.

[0022] According to some embodiments of the present invention, in step S2, the reducing atmosphere is a mixed gas of CO and hydrogen.

[0023] According to some embodiments of the present invention, in step S2, the treatment temperature is 500-600°C.

[0024] According to some embodiments of the present invention, in step S2, the treatment temperature is 550-600°C.

[0025] According to some embodiments of the present invention, in step S2, the treatment time is 6 to 8 hours.

[0026] According to some embodiments of the present invention, in step S2, the processing time is 6 hours.

[0027] According to some embodiments of the present invention, in step S3, an inert gas is introduced during the calcination process;

[0028] Preferably, the inert gas comprises hydrogen.

[0029] According to some embodiments of the present invention, the volatile organic compound is at least one of ethane, propane, ethylene, propylene, ethanol and acetone.

[0030] According to some embodiments of the present invention, the solid-liquid mass ratio of the metal particle intercalated graphene powder to the volatile organic matter is 1:2-4.

[0031] According to some embodiments of the present invention, in step S3, the calcination time is 24 to 36 hours.

[0032] According to some embodiments of the present invention, in step S3, the insulation time is 12 to 48 hours.

[0033] According to some embodiments of the present invention, in step S4, the mass ratio of the graphene / carbon nanotube composite powder, the dispersant and the solvent is 1:0.5 to 2:10 to 20.

[0034] According to some embodiments of the present invention, the dispersant is selected from one of polyvinylidene fluoride, polyethylene glycol, and polyvinyl pyrrolidone.

[0035] According to some embodiments of the present invention, the solvent is N-methylpyrrolidone or water.

[0036] The second aspect of the present invention provides a graphene / carbon nanotube composite conductive agent prepared by the above preparation method.

[0037] The graphene / carbon nanotube composite conductive agent according to the embodiment of the present invention has at least the following beneficial effects: the graphene / carbon nanotube composite conductive agent prepared by the preparation method of the present invention has low resistivity and good cycle performance.

[0038] The third aspect of the present invention provides a use of the above-mentioned graphene / carbon nanotube composite conductive agent in the preparation of a battery.

[0039] According to the application of the embodiment of the present invention, there are at least the following beneficial effects: applying the graphene / carbon nanotube composite conductive agent prepared by the present invention to battery preparation is conducive to improving the recycling performance of the battery.

[0040] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0042] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0043] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased from the market.

[0044] Example 1

[0045] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0046] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0047] Step S2, immersing 20 g of graphene powder in the above-mentioned nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain a nickel oxide intercalated graphite powder, and finally placing the nickel oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal nickel intercalated graphite powder;

[0048] Step S3, adding three times the volume of ethylene to the graphite powder intercalated with metal nickel, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 800° C. at a rate of 30° C. / min, keeping the temperature for 1 hour, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001 Pa, and then heating it to 1500° C. at a rate of 15° C. / min, and keeping the temperature for 36 hours to obtain a graphene / carbon nanotube composite powder;

[0049] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0050] Example 2

[0051] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0052] Step S1, dissolving 80 g of cobalt chloride in 100 mL of deionized water to obtain a cobalt chloride solution;

[0053] Step S2, immersing 20 g of graphene powder in the above cobalt chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain a cobalt oxide intercalated graphite powder, and finally placing the cobalt oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal cobalt intercalated graphite powder;

[0054] Step S3, adding three times the volume of ethylene to the graphite powder with metal cobalt intercalation, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 800° C. at a rate of 30° C. / min, keeping the temperature for 1 hour, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001 Pa, and then heating it to 1500° C. at a rate of 15° C. / min, and keeping the temperature for 36 hours to obtain a graphene / carbon nanotube composite powder;

[0055] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0056] Example 3

[0057] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0058] Step S1, dissolving 80 g of ferric chloride in 100 mL of deionized water to obtain a ferric chloride solution;

[0059] Step S2, immersing 20 g of graphene powder in the above-mentioned ferric chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain iron oxide intercalated graphite powder, and finally placing the iron oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain metallic iron intercalated graphite powder;

[0060] Step S3, adding three times the volume of ethylene to the graphite powder intercalated with metallic iron, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 800° C. at a rate of 30° C. / min, keeping the temperature for 1 hour, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001 Pa, and then heating it to 1500° C. at a rate of 15° C. / min, and keeping the temperature for 36 hours to obtain a graphene / carbon nanotube composite powder;

[0061] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0062] Example 4

[0063] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0064] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0065] Step S2, immersing 20 g of graphene powder in the above-mentioned nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain a nickel oxide intercalated graphite powder, and finally placing the nickel oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal nickel intercalated graphite powder;

[0066] Step S3, adding three times the volume of ethanol to the graphite powder intercalated with metal nickel, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 800° C. at a rate of 30° C. / min, keeping the temperature for 1 hour, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001 Pa, and then heating it to 1500° C. at a rate of 15° C. / min, and keeping the temperature for 36 hours to obtain a graphene / carbon nanotube composite powder;

[0067] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0068] Example 5

[0069] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0070] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0071] Step S2, immersing 20 g of graphene powder in the above-mentioned nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain a nickel oxide intercalated graphite powder, and finally placing the nickel oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal nickel intercalated graphite powder;

[0072] Step S3, adding three times the volume of ethane to the graphite powder intercalated with metal nickel, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 800° C. at a rate of 30° C. / min, keeping the temperature for 1 hour, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001 Pa, and then heating it to 1500° C. at a rate of 15° C. / min, and keeping the temperature for 36 hours to obtain a graphene / carbon nanotube composite powder;

[0073] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0074] Example 6

[0075] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0076] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0077] Step S2, immersing 20 g of graphene powder in the above-mentioned nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 150° C. in an air atmosphere for 6 hours to obtain a nickel oxide intercalated graphite powder, and finally placing the nickel oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal nickel intercalated graphite powder;

[0078] Step S3, adding three times the volume of ethylene to the graphite powder intercalated with metal nickel, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 800° C. at a rate of 30° C. / min, keeping the temperature for 1 hour, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001 Pa, and then heating it to 1500° C. at a rate of 15° C. / min, and keeping the temperature for 36 hours to obtain a graphene / carbon nanotube composite powder;

[0079] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0080] Example 7

[0081] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0082] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0083] Step S2, immersing 20 g of graphene powder in the above-mentioned nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain a nickel oxide intercalated graphite powder, and finally placing the nickel oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal nickel intercalated graphite powder;

[0084] Step S3, adding three times the volume of ethylene to the graphite powder intercalated with metal nickel, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 700° C. at a rate of 30° C. / min, keeping the temperature for 1 hour, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001 Pa, and then heating it to 1500° C. at a rate of 15° C. / min, and keeping the temperature for 36 hours to obtain a graphene / carbon nanotube composite powder;

[0085] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0086] Example 8

[0087] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0088] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0089] Step S2, immersing 20 g of graphene powder in the above-mentioned nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain a nickel oxide intercalated graphite powder, and finally placing the nickel oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal nickel intercalated graphite powder;

[0090] Step S3, adding three times the volume of ethylene to the graphite powder intercalated with metal nickel, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 800° C. at a rate of 30° C. / min, keeping the temperature for 1 hour, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001 Pa, and then heating it to 1800° C. at a rate of 15° C. / min, and keeping the temperature for 36 hours to obtain a graphene / carbon nanotube composite powder;

[0091] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0092] Comparative Example 1

[0093] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0094] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0095] Step S2, immersing 20 g of graphene powder in the above-mentioned nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain a nickel oxide intercalated graphite powder, and finally placing the nickel oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal nickel intercalated graphite powder;

[0096] Step S3, adding three times the volume of ethylene to the graphite powder intercalated with metal nickel, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 1500° C. at a rate of 15° C. / min, keeping the temperature for 36 hours, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and obtaining a graphene / carbon nanotube composite powder;

[0097] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0098] Comparative Example 2

[0099] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0100] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0101] Step S2, immersing 20 g of graphene powder in the above-mentioned nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain a nickel oxide intercalated graphite powder, and finally placing the nickel oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal nickel intercalated graphite powder;

[0102] Step S3, adding three times the volume of ethylene to the graphite powder intercalated with metal nickel, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 800° C. at a rate of 30° C. / min, keeping the temperature for 36 hours, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and obtaining a graphene / carbon nanotube composite powder;

[0103] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0104] Comparative Example 3

[0105] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0106] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0107] Step S2, immersing 20 g of graphene powder in the above nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then heat-treating at 550° C. in a nitrogen atmosphere for 12 h to obtain nickel chloride intercalated graphite powder;

[0108] Step S3, adding three times the volume of ethylene to the graphite powder intercalated with metal nickel, mixing evenly, and then putting it into a quartz boat, placing the quartz boat in a tube furnace, heating the tube furnace to 800° C. at a rate of 30° C. / min, keeping the temperature for 1 hour, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001 Pa, and then heating it to 1500° C. at a rate of 15° C. / min, and keeping the temperature for 36 hours to obtain a graphene / carbon nanotube composite powder;

[0109] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0110] Comparative Example 4

[0111] A method for preparing a graphene / carbon nanotube composite conductive agent, specifically comprising the following steps:

[0112] Step S1, dissolving 80 g of nickel chloride in 100 mL of deionized water to obtain a nickel chloride solution;

[0113] Step S2, immersing 20 g of graphene powder in the above-mentioned nickel chloride solution, stirring evenly and heating to 60° C. to remove the solvent, and then calcining at 180° C. in an air atmosphere for 6 hours to obtain a nickel oxide intercalated graphite powder, and finally placing the nickel oxide intercalated graphite powder in a reaction furnace, and heat-treating at 550° C. in a mixed atmosphere of CO and hydrogen (volume ratio of 2:1) for 12 hours to obtain a metal nickel intercalated graphite powder;

[0114] Step S3, putting the graphite powder with metal nickel intercalation into a quartz boat, placing the quartz boat in a tube furnace, and introducing ethylene gas with a gas flow rate of 0.4L / min, heating the tube furnace to 800°C at a rate of 30°C / min, keeping the temperature for 1h, and then closing the tube furnace, taking out the powder in the furnace after the tube furnace is cooled, and placing it in a graphite crucible, and then placing it in a carbonization furnace, evacuating to a vacuum degree of 0.001Pa, and then heating to 1500°C at a rate of 15°C / min, keeping the temperature for 36h, to obtain a graphene / carbon nanotube composite powder;

[0115] Step S4, mixing the graphene / carbon nanotube composite powder, polyvinylidene fluoride and N-methylpyrrolidone in a mass ratio of 1:1:20 to obtain a graphene / carbon nanotube composite conductive agent.

[0116] Test example

[0117] The resistivity of the graphene / carbon nanotube composite conductive agents prepared in the above Examples 1 to 8 and Comparative Examples 1 to 4 was tested respectively, and the test results are shown in Table 1.

[0118] Table 1

[0119] - Resistivity (Ω·cm) Example 1 3.624 Example 2 3.748 Example 3 3.941 Example 4 3.674 Example 5 3.925 Example 6 3.774 Example 7 3.862 Example 8 3.691 Comparative Example 1 4.572 Comparative Example 2 5.741 Comparative Example 3 6.421 Comparative Example 4 5.845

[0120] As can be seen from Table 1, the resistivity of the graphene / carbon nanotube composite conductive agent prepared by the preparation method of the present invention is low, all lower than 4Ω·cm, as shown in Examples 1 to 8. Comparative Example 1 Compared with Example 1, the graphene powder intercalated with metal particles in the in-situ generation process of carbon nanotubes was not calcined at 600 to 900°C. The results show that the resistivity of the graphene / carbon nanotube composite conductive agent obtained without calcination at 600 to 900°C is significantly higher, which may be due to the rapid carbonization of volatile organic matter by direct high-temperature treatment, which leads to uneven carbonization. Comparative Example 2 Compared with Example 1, the graphene powder intercalated with metal particles was calcined in a carbon-containing atmosphere at 600 to 900°C without being subjected to a 1500°C heat preservation carbonization treatment. It can be seen from the test results that it is not conducive to reducing the resistivity. Compared with Example 1, in Comparative Example 3, the graphene powder intercalated with metal chloride is not subjected to redox treatment after being formed. From the test results, it can be seen that after the metal chloride is subjected to redox treatment, it is helpful to improve its catalytic activity and obtain a graphene / carbon nanotube composite material with high conductivity. Compared with Example 1, in Comparative Example 4, the volatile organic matter is introduced in the form of gas during the calcination process. From the test results, it can be seen that it is not conducive to a relatively higher resistivity. This may be because when the organic matter is introduced in the form of gas, the carbonization speed is too fast, which is not conducive to forming a uniform doping form, thereby resulting in a high resistivity.

[0121] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for preparing a graphene / carbon nanotube composite conductive agent, characterized in that: The method comprises the following preparation steps: Step S1, mixing graphene powder with a metal salt solution, drying and calcining in an oxygen-containing atmosphere to obtain metal oxide intercalated graphene powder; wherein the molar concentration of the metal in the metal salt solution is 1-5 mol / L, and the solid-liquid volume ratio of the graphene powder to the metal salt solution is 1 g:4-8 mL; Step S2, placing the metal oxide intercalated graphene powder in a reducing atmosphere at 500-600° C. for 6-8 hours to obtain metal particle intercalated graphene powder, wherein the reducing atmosphere is a mixed gas of CO and hydrogen; Step S3, mixing the graphene powder intercalated with the metal particles with volatile organic matter, allowing the volatile organic matter to penetrate into the interior of the graphene powder intercalated with the metal particles, calcining at 600-900° C. for 24-36 hours, and then keeping it at 1500° C. for 12-48 hours to obtain a graphene / carbon nanotube composite powder, wherein the volatile organic matter is at least one of ethane, propane, ethylene, propylene, ethanol, and acetone; Step S4: mixing the graphene / carbon nanotube composite powder, dispersant and solvent to obtain a graphene / carbon nanotube composite conductive agent.

2. The preparation method according to claim 1, characterized in that: In step S1, the metal in the metal salt solution is selected from at least one of nickel, cobalt and iron.

3. The preparation method according to claim 1 or 2, characterized in that: In step S4, the mass ratio of the graphene / carbon nanotube composite powder, the dispersant and the solvent is 1:0.5-2:10-20.

4. The preparation method according to claim 3, characterized in that: In step S4, the dispersant is selected from one of polyvinylidene fluoride, polyethylene glycol, and polyvinyl pyrrolidone.

5. The preparation method according to claim 3, characterized in that: In step S4, the solvent is N-methylpyrrolidone or water.

6. A graphene / carbon nanotube composite conductive agent, prepared by the preparation method of the graphene / carbon nanotube composite conductive agent according to any one of claims 1 to 5.

7. Use of the graphene / carbon nanotube composite conductive agent as claimed in claim 6 in preparing a battery.