CN113428851A - Graphene-carbon nanotube composite material, preparation method thereof and prepared graphene-carbon nanotube composite slurry - Google Patents
Graphene-carbon nanotube composite material, preparation method thereof and prepared graphene-carbon nanotube composite slurry Download PDFInfo
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Abstract
The application relates to the field of carbon nanotube materials, in particular to a graphene-carbon nanotube composite material, a preparation method thereof and prepared graphene-carbon nanotube composite slurry. The preparation method of the graphene-carbon nanotube composite material comprises the steps of adding the completely oxidized graphene oxide into a dilute acid solution, and uniformly stirring to obtain a component A; adding carbon nanotube powder into the component A, stirring uniformly, and then filtering to obtain a graphene oxide/carbon nanotube filter material; and (2) pickling the graphene oxide/carbon nano tube filter material for at least three times by using a dilute acid solution, finally extruding, granulating and drying the graphene oxide/carbon nano tube filter material, and carrying out thermal reduction to obtain the graphene-carbon nano tube composite material. According to the method, the graphene oxide acid pickling purification process and the carbon nano tube acid pickling purification process are combined, one-step acid purification is performed, the acid purification process and the waste liquid amount are reduced, the acid pickling cost is reduced, the pollution is reduced, and the composite material has excellent conductivity.
Description
Technical Field
The application relates to the field of carbon nanotube materials, in particular to a graphene-carbon nanotube composite material, a preparation method thereof and prepared graphene-carbon nanotube composite slurry.
Background
The graphene has good electrical conductivity and thermal conductivity, large specific surface area, excellent mechanical property and good chemical stability, and can be used as a conductive additive to be applied to a lithium ion battery to improve the electrical conductivity of an electrode material; the functional additive can also be applied to composite materials as a functional additive, improves the electric and thermal conductivity and mechanical properties of the composite materials, and has wide application. However, due to the special two-dimensional structure, graphene is easy to agglomerate in practical application, so that the dispersion is not uniform, and the application performance is limited.
The carbon nano tube can be used as a support between graphene sheets as a one-dimensional nano material to prevent the aggregation between the graphene sheets and realize the coordination between one-dimensional and two-dimensional carbon materials. At present, related documents report methods for preparing graphene/carbon nanotube composite materials, but the preparation methods in the related documents all realize the compounding of graphene and carbon nanotubes by using a simple mechanical mixing mode (for example, directly mixing and stirring graphene and carbon nanotubes), and have the defect of uneven dispersion of graphene and carbon nanotubes.
In contrast, there are related inventions that introduce a method for preparing graphene/carbon nanotube composite material by adding carbon nanotubes to the graphene preparation process, such as chinese patent application CN106861617B and chinese patent application CN109994733A, in which carbon nanotube powder is added to the oxidation process of graphite, and finally graphene/carbon nanotube composite material is obtained. Although the graphene/carbon nanotube composite material prepared by the method has better dispersion uniformity than the composite material prepared by direct mechanical mixing, the carbon nanotube is oxidized to a certain degree in the graphite oxidation process, the integrity of the carbon nanotube is damaged, and the conductivity of the carbon nanotube is reduced.
Disclosure of Invention
In order to solve the problems of dispersion uniformity and balance of conductivity of the graphene/carbon nanotube composite material, the application provides a graphene-carbon nanotube composite material, a preparation method thereof and prepared graphene-carbon nanotube composite slurry.
In a first aspect, the present application provides a method for preparing a graphene-carbon nanotube composite material, which adopts the following technical scheme:
a preparation method of a graphene-carbon nanotube composite material comprises the following steps:
adding the completely oxidized graphene oxide material into a dilute acid solution, and uniformly stirring to obtain a component A;
adding carbon nanotube powder into the component A, stirring uniformly, and then filtering to obtain a graphene oxide/carbon nanotube filter material;
adding the graphene oxide/carbon nano tube filter material into a dilute acid solution, uniformly stirring, filtering, completing one-time acid washing operation, repeating the acid washing operation at least three times, extruding, granulating and drying the graphene oxide/carbon nano tube filter material to obtain a graphene oxide/carbon nano tube material, and performing thermal reduction to obtain the graphene-carbon nano tube composite material.
Preferably, the carbon nanotube powder is a carbon nanotube powder that has not been subjected to purification treatment.
The existing preparation method of graphene mainly comprises a physical stripping method and a chemical oxidation method, wherein the chemical oxidation method is a common method for industrially preparing graphene with higher specific surface area at present. In the traditional process of preparing graphene by adopting a chemical oxidation method, graphite is oxidized to prepare graphene oxide, then the graphene oxide is directly subjected to acid cleaning and purification for many times, and finally the graphene oxide is prepared and molded by reduction. According to the method, the graphene oxide intermediate product prepared after complete oxidation in the graphene preparation process and the carbon nano tube are subjected to acid washing and purification, so that the subsequent post-treatment process of the graphene oxide is saved, and the graphene-carbon nano tube composite material is prepared; and compared with a mode that the carbon nano tube is added into the graphite and is oxidized together, the method has the advantages that the carbon nano tube is added into the completely oxidized graphene oxide, and the carbon nano tube is purified by one-step acid washing, so that the carbon nano tube can be prevented from being oxidized in the graphite oxidation process to influence the conductivity of the carbon nano tube, and the prepared graphene-carbon nano tube composite material has excellent conductivity.
The method preferably adopts a Hummers method, a Brodie method, a staudenmaeer method or an electrochemical oxidation method to prepare graphene, for example, in the Hummers method to prepare graphene, the completely oxidized graphene oxide material refers to a graphene oxide material prepared by oxidizing graphite to prepare graphene oxide in the graphene preparation process, and the graphene oxide material is not subjected to acid washing purification and filtration; for the preparation of graphene by the Brodie method, the staudenmier method or the electrochemical oxidation method, the completely oxidized graphene oxide material is designated, and the completely oxidized graphene oxide material is mixed with the carbon nano tube, purified by acid pickling together, and reduced to prepare the graphene-carbon nano tube composite material with excellent conductivity.
In addition, transition metals (Fe, Co, Ni, etc.) or compounds thereof are generally required as catalysts in industrial production of carbon nanotubes, and the prepared carbon nanotubes contain a large amount of transition metals, and in order to remove these transition metals, purification treatment with an acid solution such as a dilute hydrochloric acid solution is generally required. At present, in the preparation of the graphene-carbon nanotube composite material, graphene prepared by acid washing, filtering and reduction treatment and acid-washed and purified carbon nanotubes are directly mixed, wherein acid washing is to carry out acid washing on oxidized graphene completely oxidized for multiple times, namely, multiple acid washing treatments are carried out in the process of preparing the graphene, and multiple acid washing treatments are also required for purifying the carbon nanotubes, and both the multiple acid washing processes of the oxidized graphene and the multiple acid washing and purification processes of the carbon nanotubes cause the generation of a large amount of acid washing waste liquid, thereby causing environmental pollution.
The carbon nanotube added into the component A is preferably the carbon nanotube which is not subjected to acidification and purification treatment, the two processes of carbon nanotube purification and completely oxidized graphene oxide material acid pickling and purification are synchronously completed through one-step acid pickling, the acid pickling and purification process of the carbon nanotube independently is reduced, the generation of waste liquid in the acid pickling process is reduced, the preparation cost is reduced, the pollution is low, and the dispersibility of the carbon nanotube and the graphene oxide is improved through the combined acid pickling process.
And finally, carrying out acid washing for multiple times, filtering, extruding, granulating, drying and carrying out thermal reduction to obtain the graphene-carbon nanotube composite material. The extrusion granulation is normal-temperature extrusion granulation to prepare a granular material, the thermal reduction is performed to reduce the graphene oxide into graphene, the high-temperature thermal reduction is performed in a hydrogen atmosphere or an inert atmosphere, the graphene is thermally expanded in the thermal reduction process, the dispersion of the carbon nano tubes is promoted, and the dispersion uniformity of the carbon nano tubes and the graphene is improved.
Preferably, the carbon nanotube is one or a combination of several of a single-walled carbon nanotube, a double-walled carbon nanotube and a multi-walled carbon nanotube.
The method combines the two processes of acid cleaning and purification of the graphene oxide filter cake and the acid cleaning and purification of the carbon nano tube, can be suitable for single-walled carbon nano tubes, double-walled carbon nano tubes and multi-walled carbon nano tubes, is easy to disperse uniformly with graphene oxide, improves the material dispersion uniformity and conductivity of the graphene-carbon nano tube composite material, and is high in stability.
Preferably, the dilute acid solution is a hydrochloric acid solution with the mass fraction of 1-5 wt%.
By adopting the dilute acid solution with the concentration, the environmental pollution is less, the unpurified carbon nano tube and the unpurified graphene oxide can be subjected to acid pickling purification together, the carbon nano tube is fully purified, the graphene oxide is fully subjected to acid pickling, the respective acid pickling purification processes are saved, and the generation of acid pickling waste liquid is reduced.
Preferably, the thermal reduction is to reduce the graphene oxide at 2500 ℃ in a hydrogen atmosphere or an inert atmosphere.
By controlling the thermal reduction temperature, the graphene oxide can be fully reduced into graphene, so that the stable graphene-carbon nanotube composite material is prepared, and the conductivity is excellent.
In a second aspect, the present application provides a graphene-carbon nanotube composite material, which adopts the following technical scheme:
the graphene-carbon nanotube composite material is prepared by the preparation method of the graphene-carbon nanotube composite material, and the prepared graphene-carbon nanotube composite material is formed by mixing graphene and carbon nanotubes in a weight ratio of (10-99.9) to (0.1-90).
By controlling the mixing ratio of the graphene and the carbon nano tube and combining the preparation method, the prepared graphene-carbon nano tube composite material has excellent dispersibility and conductivity, can be used as a functional additive of other polymer composite materials, and improves the physical and chemical properties of the polymer composite material.
In a third aspect, the present application provides a graphene-carbon nanotube composite slurry, which adopts the following technical scheme:
the graphene-carbon nanotube composite slurry is prepared from the following raw materials in percentage by weight:
0.2 to 15 percent of graphene-carbon nanotube composite material
0.1 to 3 percent of dispersant
82-99.7% of solvent;
the graphene-carbon nanotube composite material is the graphene-carbon nanotube composite material prepared by the preparation method of the first aspect or the graphene-carbon nanotube composite material of the second aspect.
The graphene-carbon nanotube composite material, the dispersing agent and the solvent are mixed and dispersed uniformly, so that the prepared graphene-carbon nanotube composite slurry has excellent conductivity, uniform material dispersion and high stability, and can be applied to the field of batteries as a conductive slurry.
Preferably, the dispersant is one or more of polyvinylpyrrolidone, polyvinyl alcohol, silane coupling agent, polyacrylic acid, polyoxyethylene ether, carboxymethyl cellulose salt, ethyl cellulose, nitrile rubber, graphene oxide, hydroxypropyl cellulose, chitosan and polyamide dispersant; the solvent is one or more of water, NMP, DMF, THF, DMSO, alcohol solvent and benzene solvent.
By adopting the dispersing agent, the graphene-carbon nanotube composite material can be uniformly dispersed to form a stable graphene-carbon nanotube composite slurry system, so that the graphene-carbon nanotube composite slurry system can be conveniently applied to the field of batteries, and can be used for preparing water-based conductive slurry or solvent-based conductive slurry and applied to a ternary material system or a lithium iron phosphate material system as required.
In a fourth aspect, the present application provides a method for preparing graphene-carbon nanotube composite slurry, which adopts the following technical scheme:
a preparation method of graphene-carbon nanotube composite slurry comprises the following steps:
dividing the solvent into a first part of solvent and a second part of solvent according to the weight ratio of 0.5-1.5: 1;
dissolving a dispersant in a first solvent, and uniformly dispersing to obtain a first component;
adding the graphene-carbon nanotube composite material into a second solvent, and uniformly dispersing to obtain a second component;
and adding the first component into the second component under the condition of stirring the second component, and uniformly dispersing to obtain the graphene-carbon nanotube composite slurry.
By adopting the technical scheme, the graphene-carbon nanotube composite material can be uniformly dispersed in the slurry system, the stability is high, and the slurry system is improved to be further applied to the preparation of a battery product as a conductive slurry; the dispersing agent is uniformly dispersed by adopting a part of solvent, the graphene-carbon nanotube composite material is dispersed by adopting the rest solvent, and meanwhile, the dispersing agent solution is added into the graphene-carbon nanotube composite material dispersion system, so that the dispersion uniformity of the graphene-carbon nanotube composite material can be effectively improved.
Preferably, the uniform dispersion mode is stirring dispersion, ultrasonic dispersion, sand mill dispersion, ball milling dispersion, colloid mill dispersion, high-pressure micro-jet or high-pressure homogeneous dispersion.
The dispersion mode of the dispersant and the first part of solvent, the dispersion mode of the graphene-carbon nanotube composite material and the second part of solvent and the dispersion mode of the first component and the second component can adopt any one of the dispersion modes listed above, and the three dispersion steps can adopt the same dispersion mode or different dispersion modes and can uniformly disperse materials so as to prepare the graphene-carbon nanotube composite slurry with stable system.
Preferably, the dispersion time of the dispersant after being dissolved in the first solvent is 10-120min, the dispersion time of the graphene-carbon nanotube composite material after being added to the second solvent is 30-180min, and the dispersion time of the first component after being added to the second component is 30-180 min.
By controlling the dispersion time of the three dispersion steps, the dispersing agent, the graphene-carbon nanotube composite material and the solvent can be uniformly dispersed to form a stable graphene-carbon nanotube composite slurry system, so that the conductive slurry of the battery can be further conveniently prepared, and the conductivity is excellent.
In summary, the present application has the following beneficial effects:
1. according to the method, a graphene oxide intermediate product prepared in the graphene preparation process and the carbon nano tube are subjected to acid pickling and purification together, the process flow of the acid pickling and purification of the carbon nano tube independently is reduced, the waste liquid amount of the acid pickling and purification is reduced, the acid pickling cost is reduced, the pollution of waste acid liquid is reduced, and finally the graphene-carbon nano tube composite material is prepared through multiple acid pickling, filtering, extrusion granulation, drying and thermal reduction.
2. In the process of preparing the graphene-carbon nanotube composite slurry, the solvent is divided into two parts, the two parts are uniformly dispersed with the dispersing agent and the graphene-carbon nanotube composite material respectively, and then the two parts are mixed and dispersed, so that the graphene-carbon nanotube composite material can be uniformly dispersed in a system, and the dispersion stability of the graphene-carbon nanotube composite slurry is improved.
Drawings
Fig. 1 is a flow chart of a method of preparing a graphene-carbon nanotube composite material according to the present application;
fig. 2 is a flowchart of a method of preparing a graphene-carbon nanotube composite slurry according to the present application;
fig. 3 is an SEM image of the graphene-carbon nanotube composite material prepared in example 1 of the present application.
Detailed Description
The present application is described in further detail below with reference to the accompanying fig. 1-3 and preparation examples, and application examples.
Preparation example
The method for preparing the completely oxidized graphene oxide material by using a Hummer's method comprises the following specific steps:
step one, adding 5g of graphite powder into 115 mL of concentrated sulfuric acid, and stirring for 15min in an ice-water bath to obtain a material A;
step two, slowly adding 15g of KMnO4(the temperature is lower than 20 ℃), and stirring is continued in an ice-water bath for 30min to prepare a material B;
step three, heating the material B prepared in the step two to 35 ℃, and reacting for 120min to prepare a material C;
step four, adding 230mL of water into the reaction system of the material C at a temperature lower than 90 ℃, and reacting for 30min to obtain a material D;
step five, adding H into the material D prepared in the step four2O2(the temperature at this time is 90 ℃) until the color of the system becomes bright yellow, and then filtering is carried out while the system is hot to prepare a completely oxidized graphene oxide material.
In the step of preparing the graphene oxide material, the concentrated sulfuric acid in the step one provides a reaction medium for graphite powder, and the KMnO in the step two4As oxidant, it can oxidize graphite powder, and in step five, H2O2Mainly to remove unreacted KMnO4So as to prepare the graphene oxide material with stable performance.
Examples
Example 1
A graphene-carbon nanotube composite material is prepared by the following steps:
(1) adding the graphene oxide material prepared in the preparation example into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt%, and stirring for 15min to obtain a component A;
(2) adding 2g of unpurified multi-wall carbon nanotube powder into the component A, stirring for 30min, filtering, and removing filter residues to obtain a graphene oxide/carbon nanotube filter material;
(3) adding the graphene oxide/carbon nano tube filter material into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt% for acid pickling, uniformly stirring, and filtering;
(4) and (4) repeating the acid washing process in the step (3) for 3 times, then extruding and granulating the graphene oxide/carbon nano tube filter material at normal temperature, drying at 60 ℃, and carrying out thermal reduction at 800 ℃ to obtain the graphene-carbon nano tube composite material.
Example 2
A graphene-carbon nanotube composite material is prepared by the following steps:
(1) adding the graphene oxide material prepared in the preparation example into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt%, and stirring for 15min to obtain a component A;
(2) adding 2g of unpurified multi-wall carbon nanotube powder into the component A, stirring for 30min, filtering, and removing filter residues to obtain a graphene oxide/carbon nanotube filter material;
(3) adding the graphene oxide/carbon nano tube filter material into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt% for acid pickling, uniformly stirring, and filtering;
(4) and (4) repeating the acid washing process in the step (3) for 4 times, then extruding and granulating the graphene oxide/carbon nano tube filter material at normal temperature, drying at 60 ℃, and carrying out thermal reduction at 1000 ℃ to obtain the graphene-carbon nano tube composite material.
Example 3
A graphene-carbon nanotube composite material is prepared by the following steps:
(1) adding the graphene oxide material prepared in the preparation example into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt%, and stirring for 15min to obtain a component A;
(2) adding 2g of unpurified single-walled carbon nanotube powder into the component A, stirring for 30min, filtering, and removing filter residues to obtain a graphene oxide/carbon nanotube filter material;
(3) adding the graphene oxide/carbon nano tube filter material into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt% for acid pickling, uniformly stirring, and filtering;
(4) and (4) repeating the acid washing process in the step (3) for 4 times, then extruding and granulating the graphene oxide/carbon nano tube filter material at normal temperature, drying at 60 ℃, and carrying out thermal reduction at 1000 ℃ to obtain the graphene-carbon nano tube composite material.
Example 4
A graphene-carbon nanotube composite material is prepared by the following steps:
(1) adding the graphene oxide material prepared in the preparation example into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt%, and stirring for 15min to obtain a component A;
(2) adding 2g of unpurified single-walled carbon nanotube powder into the component A, stirring for 30min, filtering, and removing filter residues to obtain a graphene oxide/carbon nanotube filter material;
(3) adding the graphene oxide/carbon nano tube filter material into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt% for acid pickling, uniformly stirring, and filtering;
(4) and (4) repeating the acid washing process in the step (3) for 4 times, then extruding and granulating the graphene oxide/carbon nano tube filter material at normal temperature, drying at 60 ℃, and carrying out thermal reduction at 500 ℃ to obtain the graphene-carbon nano tube composite material.
Example 5
A graphene-carbon nanotube composite material is prepared by the following steps:
(1) adding the graphene oxide material prepared in the preparation example into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt%, and stirring for 15min to obtain a component A;
(2) adding 2g of unpurified multi-wall carbon nanotube powder into the component A, stirring for 30min, filtering, and removing filter residues to obtain a graphene oxide/carbon nanotube filter material;
(3) adding the graphene oxide/carbon nano tube filter material into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt% for acid pickling, uniformly stirring, and filtering;
(4) and (4) repeating the acid washing process in the step (3) for 4 times, then extruding and granulating the graphene oxide/carbon nano tube filter material at normal temperature, drying at 60 ℃, and carrying out thermal reduction at 2500 ℃ to obtain the graphene-carbon nano tube composite material.
Comparative example
Comparative example 1
This comparative example differs from example 1 in that: adding 2g of unpurified multi-walled carbon nanotube powder into graphene oxide, specifically, in the first step of the preparation example, mixing 5g of graphite powder and 2g of unpurified multi-walled carbon nanotube powder together, adding concentrated sulfuric acid and 230mL of water, and reacting for 30 min; then step five is to add H into the material D prepared in step four2O2(the temperature at this time is 90 ℃) until the color of the system becomes bright yellow, and then filtering is carried out while the system is hot to prepare the graphene oxide-carbon nanotube material.
In the preparation steps of the graphene-carbon nanotube composite material:
(1) adding the prepared graphene oxide-carbon nanotube material into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt%, stirring for 30min, and filtering;
(2) and (2) repeating the acid washing process in the step (1) for 3 times, removing filter residues to obtain the graphene oxide/carbon nano tube filter material, then extruding and granulating the graphene oxide/carbon nano tube filter material at normal temperature, drying at 60 ℃, and carrying out thermal reduction at 800 ℃ to obtain the graphene-carbon nano tube composite material.
Comparative example 2
A graphene-carbon nanotube composite material is prepared by the following steps:
adding the graphene oxide material prepared in the preparation example into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt%, stirring for 15min, filtering, completing one pickling operation, repeating the pickling operation for 4 times, and drying to prepare pickled graphene oxide;
adding 2g of unpurified multi-walled carbon nanotube powder into 80mL of dilute hydrochloric acid solution with the mass fraction of 3wt%, stirring for 30min, filtering, completing one pickling purification operation, repeating the pickling purification operation for 4 times, and drying to obtain the purified multi-walled carbon nanotube;
and mixing the graphene oxide after acid washing with the purified carbon nano tube filter material, and performing thermal reduction at 1000 ℃ to obtain the graphene-carbon nano tube composite material.
Application example
Application example 1
The graphene-carbon nanotube composite slurry is prepared by the following steps:
A. dissolving 5g of polyvinylpyrrolidone in 300g of NMP, and dispersing for 20min by using a sand mill to obtain polyvinylpyrrolidone dispersion liquid;
B. taking 25g of the graphene/carbon nanotube composite material prepared in the embodiment 1, dispersing the graphene/carbon nanotube composite material in 300g of NMP solution by using a sand mill for 30min to obtain graphene/carbon nanotube solution;
C. and C, slowly adding the polyvinylpyrrolidone dispersion liquid prepared in the step A into the graphene/carbon nano tube solution prepared in the step B, and dispersing for 120min by using a sand mill to obtain the graphene/carbon nano tube composite slurry.
Application example 2
The graphene-carbon nanotube composite slurry is prepared by the following steps:
A. dissolving 5g of polyvinylpyrrolidone in 200g of NMP, and dispersing for 20min by using a sand mill to obtain polyvinylpyrrolidone dispersion liquid;
B. taking 25g of the graphene/carbon nanotube composite material prepared in the embodiment 2, dispersing the graphene/carbon nanotube composite material in 400g of NMP solution by using a sand mill for 30min to obtain graphene/carbon nanotube solution;
C. and C, slowly adding the polyvinylpyrrolidone dispersion liquid prepared in the step A into the graphene/carbon nano tube solution prepared in the step B, and dispersing for 120min by using a sand mill to obtain the graphene/carbon nano tube composite slurry.
Application example 3
The graphene-carbon nanotube composite slurry is prepared by the following steps:
A. dissolving 5g of polyvinylpyrrolidone in 300g of NMP, and dispersing for 20min by using a sand mill to obtain polyvinylpyrrolidone dispersion liquid;
B. taking 25g of the graphene/carbon nanotube composite material prepared in the embodiment 3, dispersing the graphene/carbon nanotube composite material in 300g of NMP solution by using a sand mill for 50min to obtain graphene/carbon nanotube solution;
C. and C, slowly adding the polyvinylpyrrolidone dispersion liquid prepared in the step A into the graphene/carbon nano tube solution prepared in the step B, and dispersing for 120min by using a sand mill to obtain the graphene/carbon nano tube composite slurry.
Application example 4
The graphene-carbon nanotube composite slurry is prepared by the following steps:
A. dissolving 5g of polyvinylpyrrolidone in 300g of NMP, and dispersing for 20min by using a sand mill to obtain polyvinylpyrrolidone dispersion liquid;
B. taking 25g of the graphene/carbon nanotube composite material prepared in the embodiment 4, dispersing the graphene/carbon nanotube composite material in 300g of NMP solution by using a sand mill for 50min to obtain graphene/carbon nanotube solution;
C. and C, slowly adding the polyvinylpyrrolidone dispersion liquid prepared in the step A into the graphene/carbon nano tube solution prepared in the step B, and dispersing for 120min by using a sand mill to obtain the graphene/carbon nano tube composite slurry.
Application example 5
The graphene-carbon nanotube composite slurry is prepared by the following steps:
A. dissolving 5g of polyvinylpyrrolidone in 200g of NMP, and dispersing for 20min by using a sand mill to obtain polyvinylpyrrolidone dispersion liquid;
B. taking 25g of the graphene/carbon nanotube composite material prepared in the embodiment 5, dispersing the graphene/carbon nanotube composite material in 150g of NMP solution by using a sand mill for 30min to obtain graphene/carbon nanotube solution;
C. and C, slowly adding the polyvinylpyrrolidone dispersion liquid prepared in the step A into the graphene/carbon nano tube solution prepared in the step B, and dispersing for 120min by using a sand mill to obtain the graphene/carbon nano tube composite slurry.
Application comparative example 1
The comparative example of the application is different from the application example 1 in that: and step B, adding 25g of the graphene/carbon nanotube composite material prepared in the comparative example 1.
Comparative application example 2
The comparative example of the application is different from the application example 2 in that: in step B, 25g of the graphene/carbon nanotube composite material prepared in comparative example 2 was added.
Performance test
The graphene/carbon nanotube composite slurry prepared in the application examples 1-5 and the application comparative examples 1-2 is subjected to a conductivity test, and the test method comprises the following steps:
the graphene/carbon nanotube composite slurry is prepared by taking a nickel-cobalt-manganese ternary active material (NCM 523) as a main material, PVDF as a binder and a conductive agent as application examples 1-5 and application comparative examples 1-2, wherein the main material is used in an amount of 98%, the binder is used in an amount of 1% and the conductive agent is used in an amount of 1%. And respectively carrying out anode slurry mixing according to the formula, coating the anode slurry on a PET film, drying, and testing the body resistivity by using a four-probe body resistivity tester, wherein the test results are shown in Table 1.
Table 1 raw material formula and conductivity data table of slurry
From the data, the application examples 1 to 5 are all graphene-carbon nanotube composite materials prepared by adopting a completely oxidized graphene oxide material and a carbon nanotube which are subjected to acid washing together, extrusion granulation and thermal reduction, and the prepared slurry has low resistivity and high conductivity; the thermal reduction temperature affects the conductivity of graphene, and the conductivity of the single-walled carbon nanotube is superior to that of a multi-walled carbon nanotube, so that the resistivity of the prepared slurry is lower and the conductivity is higher when the single-walled carbon nanotube is added in the preparation process of the graphene-carbon nanotube composite material and thermally reduced at a higher temperature (application example 3).
The graphene-carbon nanotube composite material of the comparative example 1 is adopted in the application comparative example 1, the multi-walled carbon nanotube is added into the preparation process of the graphene oxide (namely the oxidation reaction process of the graphite) in the comparative example 1, the resistivity of the graphene-carbon nanotube composite slurry prepared by adopting the graphene-carbon nanotube composite material is obviously increased, and the conductivity is reduced, mainly because the multi-walled carbon nanotube is easily oxidized in the oxidation process of the graphite, the conductivity of the multi-walled carbon nanotube composite slurry is further influenced, and the conductivity of the graphene-carbon nanotube composite slurry is further influenced.
The application comparative example 2 adopts the graphene-carbon nanotube composite material of the comparative example 2, and the comparative example 2 is that the graphene oxide and the multi-walled carbon nanotube are respectively subjected to acid pickling purification and then mixed and extruded for granulation, so that the resistivity of the prepared graphene-carbon nanotube composite slurry is increased compared with that of the application example 2, which shows that the graphene oxide and the multi-walled carbon nanotube are subjected to acid pickling purification together by adopting a one-step method, on one hand, the acid pickling process is saved, the use of acid solution is reduced, on the other hand, the reduced graphene is subjected to thermal expansion in a thermal reduction system and can be uniformly dispersed with the multi-walled carbon nanotube, so that the prepared graphene-carbon nanotube composite material is uniform in material and good in conductivity.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (10)
1. A preparation method of a graphene-carbon nanotube composite material is characterized by comprising the following steps: the method comprises the following steps:
adding the completely oxidized graphene oxide material into a dilute acid solution, and uniformly stirring to obtain a component A;
adding carbon nanotube powder into the component A, uniformly stirring, filtering, and taking filter residues to obtain a graphene oxide/carbon nanotube filter material;
adding the graphene oxide/carbon nano tube filter material into a dilute acid solution, uniformly stirring, filtering, completing one-time acid washing operation, repeating the acid washing operation at least three times, extruding, granulating and drying the graphene oxide/carbon nano tube filter material to obtain a graphene oxide/carbon nano tube material, and performing thermal reduction to obtain the graphene-carbon nano tube composite material.
2. The method for preparing a graphene-carbon nanotube composite material according to claim 1, wherein: the carbon nanotube powder is not subjected to acid cleaning and purification treatment.
3. The method for preparing a graphene-carbon nanotube composite material according to claim 2, wherein: the carbon nano tube is one or a combination of several of a single-wall carbon nano tube, a double-wall carbon nano tube and a multi-wall carbon nano tube.
4. The method for preparing a graphene-carbon nanotube composite material according to claim 1, wherein: the dilute acid solution is a hydrochloric acid solution with the mass fraction of 1-5 wt%.
5. The method for preparing a graphene-carbon nanotube composite material according to claim 1, wherein: the thermal reduction is to reduce the graphene oxide in a hydrogen atmosphere or an inert atmosphere at the temperature of 500-2500 ℃.
6. A graphene-carbon nanotube composite material produced by the method for producing a graphene-carbon nanotube composite material according to any one of claims 1 to 5, wherein: is prepared by mixing graphene and carbon nano tubes according to the weight ratio of (10-99.9) to (0.1-90).
7. The graphene-carbon nanotube composite slurry is characterized in that: the composite material consists of the following raw materials in percentage by weight:
0.2 to 15 percent of graphene-carbon nanotube composite material
0.1 to 3 percent of dispersant
82-99.7% of solvent;
the graphene-carbon nanotube composite material is the graphene-carbon nanotube composite material prepared by the preparation method of any one of claims 1 to 5 or the graphene-carbon nanotube composite material of claim 6.
8. The graphene-carbon nanotube composite paste according to claim 7, wherein: the dispersing agent is one or a combination of more of polyvinylpyrrolidone, polyvinyl alcohol, a silane coupling agent, polyacrylic acid, polyoxyethylene ether, carboxymethyl cellulose salt, ethyl cellulose, nitrile rubber, graphene oxide, hydroxypropyl cellulose, chitosan and a polyamide dispersing agent; the solvent is one or more of water, NMP, DMF, THF, DMSO, alcohol solvent and benzene solvent.
9. A method for preparing the graphene-carbon nanotube composite slurry according to claim 7 or 8, wherein: the method comprises the following steps:
dividing the solvent into a first part of solvent and a second part of solvent according to the weight ratio of 0.5-1.5: 1;
dissolving a dispersant in a first solvent, and uniformly dispersing to obtain a first component;
adding the graphene-carbon nanotube composite material into a second solvent, and uniformly dispersing to obtain a second component;
and adding the first component into the second component under the condition of stirring the second component, and uniformly dispersing to obtain the graphene-carbon nanotube composite slurry.
10. The method for preparing graphene-carbon nanotube composite slurry according to claim 9, wherein: the dispersion time of the dispersant after being dissolved in the first solvent is 10-120min, the dispersion time of the graphene-carbon nanotube composite material after being added into the second solvent is 30-180min, and the dispersion time of the first component after being added into the second component is 30-180 min.
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