CN110322986B - Preparation method of high-fluidity graphene conductive paste - Google Patents
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- CN110322986B CN110322986B CN201810272675.XA CN201810272675A CN110322986B CN 110322986 B CN110322986 B CN 110322986B CN 201810272675 A CN201810272675 A CN 201810272675A CN 110322986 B CN110322986 B CN 110322986B
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- H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon
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Abstract
The invention provides a preparation method of graphene conductive slurry, which comprises the following steps of firstly stripping a graphite dispersion liquid under an ultrasonic condition, and then separating to obtain graphene nanosheets; then mixing the graphene nanosheets obtained in the previous step, a dispersing agent and a solvent to obtain pre-slurry; and finally, carrying out sanding pulping on the pre-slurry obtained in the step to obtain the graphene conductive slurry. According to the invention, a low-temperature normal-pressure liquid phase stripping method is selected, a graphite-solvent mixing-ultrasonic dispersion-wet sanding method is adopted, graphene nanosheets are prepared firstly, and then flowing graphene conductive slurry is prepared, so that graphene can be prepared rapidly and at low cost under mild conditions. The graphene prepared by the method has a complete lamellar structure, is not subjected to surface modification, maintains the intrinsic characteristics of a two-dimensional lamellar layer, has the characteristics of high conductivity and high fluidity, and can be used as a conductive additive in the fields of lithium batteries, supercapacitors, conductive coatings and the like.
Description
Technical Field
The invention belongs to the technical field of graphene, relates to a preparation method of graphene conductive paste, and particularly relates to a preparation method of high-fluidity graphene conductive paste.
Background
The graphene is a two-dimensional crystal material formed by hexagonal close packing of single-layer carbon atoms, the thickness of the graphene is about 0.335 nm, the graphene has a perfect crystal structure and super-strong conductivity, the graphene is the material with the best conductivity at present, the theoretical electron mobility of the graphene is 200000cm2/V.S, and the theoretical thermal conductivity of the graphene is 5000W/m.K. Graphene draws attention to people because of its excellent properties such as conductivity, ultrahigh specific surface area, unique two-dimensional network structure, high strength and high electron mobility, and further promotes the rapid development of graphene preparation technology. Due to the excellent physicochemical properties, the material is widely applied to energy storage materials, environmental engineering and sensitive sensing, is called as 'black gold' or 'king of new materials', has a wide potential application prospect, and has become a focus and a research hotspot all over the world at present.
To realize such applications of graphene, a preparation method capable of preparing graphene having excellent properties becomes an essential task. However, in practical applications, the preparation of graphene is a major obstacle that restricts the practical application and development of graphene. Although researchers have developed numerous methods for preparing graphene to date. Among the more popular methods, there are graphite oxide reduction, epitaxial growth, and Chemical Vapor Deposition (CVD). The graphene oxide reduction method is one of the best methods for preparing graphene at present, and is to react natural graphite with strong acid and strong oxidizing substances to generate graphite oxide, prepare graphene oxide (single-layer graphite oxide) through ultrasonic dispersion, and add a reducing agent to remove oxygen-containing groups, such as carboxyl, epoxy and hydroxyl, on the surface of the graphite oxide to obtain the graphene. The method is simple to operate and low in preparation cost, and can be used for preparing the graphene on a large scale, but the lattice structure of the graphene is inevitably damaged due to the introduction of strong oxidant concentrated sulfuric acid or potassium permanganate and the like in the preparation process, and a large number of defects are introduced, so that the intrinsic performance of the graphene is seriously lost.
Chemical Vapor Deposition (CVD) is a process technique in which a reaction substance is chemically reacted in a gaseous state to generate a solid substance, and the solid substance is deposited on the surface of a heated solid substrate to obtain a solid material. Although the graphene with complete crystal lattice and few defects and high quality and large area can be obtained by the epitaxial growth method and the chemical vapor deposition method, the preparation cost is high, the yield is low, the preparation process requirement is strict, and the commercial requirement of large-scale production cannot be met. Therefore, the above-mentioned preparation methods cannot meet the requirements for the industrialization of high-quality graphene.
The solvent stripping method is proposed in recent two years, and the principle is that a small amount of graphite is dispersed in a solvent to form a low-concentration dispersion liquid, intercalation reaction is carried out at high temperature and high pressure to destroy van der waals force between graphite layers, and the solvent can be inserted between the graphite layers to carry out layer-by-layer stripping to prepare the graphene. The method does not damage the structure of the graphene like an oxidation-reduction method, and can prepare high-quality graphene. However, the method has the problems of high requirements on equipment, high reaction risk, high cost and the like, and also has the problem of chemical reagent pollution.
More importantly, the graphene prepared by any method is lack of fluidity, and the inherent defect that the graphene is easy to agglomerate cannot be overcome, so that the graphene is lack of fluidity during application.
Therefore, how to obtain a more environment-friendly method for preparing high-quality graphene in order to better realize commercial application of graphene, and meanwhile, the defect that graphene is easy to agglomerate is overcome, and the fluidity of graphene is improved, is one of the key challenges and the problems to be solved urgently faced by various research and development enterprises in the field.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a method for preparing a graphene conductive paste, and in particular, a method for preparing a high-fluidity graphene conductive paste at a low temperature, the method for preparing a high-fluidity graphene conductive paste at a normal temperature by liquid phase exfoliation provided by the present invention can rapidly obtain graphene with better conductive performance at a low cost under a mild condition, and the high-fluidity graphene conductive paste can be used as a conductive additive in the fields of lithium batteries, super capacitors, and the like by being matched with an auxiliary agent.
The invention provides a preparation method of graphene conductive slurry, which comprises the following steps:
1) stripping the graphite dispersion liquid under the ultrasonic condition, and then separating to obtain graphene nanosheets;
2) mixing the graphene nanosheets obtained in the previous step, a dispersing agent and a solvent to obtain pre-slurry;
3) and (3) carrying out sanding pulping on the pre-slurry obtained in the step to obtain the graphene conductive slurry.
Preferably, the graphite in the graphite dispersion liquid comprises one or more of graphite powder, crystalline flake graphite, artificial graphite, expandable graphite and expanded graphite;
the mass concentration of graphite in the graphite dispersion liquid is 0.5-5%;
the solvent in the graphite dispersion liquid comprises water and an organic solvent which is mutually soluble with water.
Preferably, the water-miscible organic solvent comprises one or more of methanol, ethanol, ethylene glycol, glycerol, acetone, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and dimethylsulfoxide;
the mass concentration of the organic solvent which is mutually soluble with water in the graphite dispersion liquid is 30-70%;
the power of the ultrasonic wave is 600-3000W; the ultrasonic time is 1-20 h;
the method also comprises a drying step after the separation.
Preferably, the stripping means comprises one or more of stirring, shearing, ball milling and sanding;
the carbon content of the graphene nanosheet is greater than or equal to 98%;
the thickness of the graphene nanosheet is less than or equal to 5 nm;
the sheet diameter of the graphene nanosheet is 1-20 microns.
Preferably, the dispersant comprises one or more of polyvinylpyrrolidone, polyvinylidene chloride, polypropylene, cetyl trimethyl ammonium bromide and sodium dodecyl benzene sulfonate;
the solvent comprises one or more of water, ethanol, acetone, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide;
in the pre-slurry, the mass concentration of the dispersant is 0.2-10%;
in the pre-slurry, the mass concentration of the graphene nanosheets is 1-10%.
Preferably, the sanding is wet sanding;
the size of the sanding medium for sanding is 0.1-2 mm;
the conductivity of the graphene conductive paste is greater than or equal to 40000S/m.
Preferably, the wet sanding is wet superfine sanding;
the sanding medium comprises one or more of zirconium silicate beads, zirconium oxide beads, glass beads and steel beads;
the sanding frequency is 2-50 times.
Preferably, the graphite is pretreated graphite;
the pretreatment steps are as follows:
A) reacting graphite with a small molecular intercalation agent to obtain intercalated graphite;
B) and (3) performing high-temperature expansion on the intercalated graphite obtained in the step to obtain the treated graphite.
Preferably, the granularity of the graphite is 50-10000 meshes;
the carbon content of the graphite is more than or equal to 70 percent;
the micromolecular intercalation agent comprises micromolecular high-temperature decomposable compounds;
the reaction time is 10-30 hours; the reaction temperature is 0-40 ℃.
Preferably, the small molecule intercalation agent comprises one or more of sulfuric acid, nitric acid, urea, sodium bicarbonate, sodium dihydrogen carbonate, disodium hydrogen carbonate, oxalic acid, phosphoric acid, perchloric acid, periodic acid and trifluoromethanesulfonic acid;
the mass ratio of the graphite to the micromolecular intercalator is 1: (1-5);
the temperature of the high-temperature expansion is 500-1200 ℃;
the time of high-temperature expansion is 5-60 seconds.
The invention provides a preparation method of graphene conductive slurry, which comprises the following steps of firstly stripping a graphite dispersion liquid under an ultrasonic condition, and then separating to obtain graphene nanosheets; then mixing the graphene nanosheets obtained in the previous step, a dispersing agent and a solvent to obtain pre-slurry; and finally, carrying out sanding pulping on the pre-slurry obtained in the step to obtain the graphene conductive slurry. Compared with the prior art, the method can be used for preparing high-quality graphene by aiming at the existing micromechanical stripping method, but has the defects of low yield and high cost, does not meet the requirements of industrialization and large-scale production, and can only be used for small-scale preparation in a laboratory at present. The chemical vapor deposition method can prepare high-quality large-area graphene, but the price of the ideal substrate material, namely the single crystal nickel, is too expensive, so that the industrial production of the graphene is greatly limited, the cost is higher, and the process is complex. The oxidation-reduction method may result in loss of electrical properties of a portion of graphene, so that the application of graphene is limited. The conventional solvent stripping method has the defects of high temperature and high pressure and low yield. According to the invention, a low-temperature normal-pressure liquid phase stripping method is selected, a graphite-solvent mixing-ultrasonic dispersion-wet sanding method is creatively adopted, graphene nanosheets are prepared firstly, and then flowing graphene conductive slurry is prepared, so that graphene can be prepared rapidly and at low cost under mild conditions. The graphene prepared by the method has a complete lamellar structure, is not subjected to surface modification, and keeps the intrinsic characteristics of a two-dimensional lamellar. The graphene conductive slurry prepared by the invention has the characteristics of high conductivity and high fluidity, and can be used as a conductive additive in the fields of lithium batteries, supercapacitors, conductive coatings and the like.
Experimental results show that the high-conductivity graphene slurry prepared by the invention has the carbon content of more than or equal to 99.5 percent and the conductivity of more than 50000S/m, and can reach 70000S/m and 10S-1The viscosity is less than 1500 mPas.
Drawings
Fig. 1 is a graph of rheological test data of highly conductive graphene prepared in comparative example 1 of the present invention;
fig. 2 is a graph of rheological test data of the highly conductive graphene prepared in example 1 of the present invention;
fig. 3 is a graph of rheological test data of the highly conductive graphene prepared in example 2 of the present invention;
fig. 4 is a graph of rheological test data of the highly conductive graphene prepared in example 3 of the present invention.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All the raw materials of the invention are not particularly limited in purity, and the invention preferably adopts the purity requirements of analytical purity or the purity requirements of the conventional graphene preparation field.
All the raw materials, the marks and the acronyms thereof belong to the conventional marks and acronyms in the field, each mark and acronym is clear and definite in the field of related application, and the raw materials can be purchased from the market or prepared by a conventional method by the technical staff in the field according to the marks, the acronyms and the corresponding application.
The invention provides a preparation method of graphene conductive slurry, which comprises the following steps:
1) stripping the graphite dispersion liquid under the ultrasonic condition, and then separating to obtain graphene nanosheets;
2) mixing the graphene nanosheets obtained in the previous step, a dispersing agent and a solvent to obtain pre-slurry;
3) and (3) carrying out sanding pulping on the pre-slurry obtained in the step to obtain the graphene conductive slurry.
According to the method, firstly, the graphite dispersion liquid is stripped under the ultrasonic condition and then separated, so that the graphene nanosheet is obtained.
The selection of the graphite in the graphite dispersion liquid is not particularly limited by the present invention, and the graphite material well known to those skilled in the art can be selected and adjusted by those skilled in the art according to the actual production situation, the product requirement and the quality requirement, and the graphite of the present invention preferably includes one or more of graphite powder, flake graphite, artificial graphite, expandable graphite and expanded graphite, and more preferably includes graphite powder, flake graphite, artificial graphite, expandable graphite or expanded graphite.
The particle size of the graphite in the graphite dispersion liquid is not particularly limited, and the particle size of the graphite powder known by the skilled person in the art can be selected and adjusted by the skilled person in the art according to the actual production situation, the product requirements and the quality requirements, the graphite dispersion liquid is preferably the graphite powder dispersion liquid, and the particle size of the graphite is preferably 50-10000 meshes, more preferably 100-5000 meshes, more preferably 500-3000 meshes, and most preferably 1000-2000 meshes.
The carbon content of the graphite in the graphite dispersion liquid is not particularly limited in the present invention, and may be the carbon content of graphite powder known to those skilled in the art, and those skilled in the art can select and adjust the carbon content according to actual production conditions, product requirements and quality requirements, and the carbon content of the graphite in the present invention is preferably equal to or greater than 70%, more preferably equal to or greater than 80%, most preferably equal to or greater than 90%, specifically, 70% to 95%, and may also be 75% to 90%, or 78% to 93%.
The concentration of graphite in the graphite dispersion liquid is not particularly limited by the invention, and can be a conventional concentration well known by those skilled in the art, and those skilled in the art can select and adjust the concentration according to the actual production condition, the product requirement and the quality requirement, and in order to improve the performance of the subsequent product and the uniformity of the graphite dispersion liquid, the mass concentration of graphite in the graphite dispersion liquid is preferably 0.5-5%, more preferably 1.5-4%, and more preferably 2.5-3%.
The solvent in the graphite dispersion liquid is not particularly limited by the invention, and a conventional solvent which is well known to a person skilled in the art can be used, and the person skilled in the art can select and adjust the solvent according to the actual production situation, the product requirement and the quality requirement. The water-miscible organic solvent according to the present invention preferably includes one or more of methanol, ethanol, ethylene glycol, glycerol, acetone, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and dimethylsulfoxide, and more preferably methanol, ethanol, ethylene glycol, glycerol, acetone, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, or dimethylsulfoxide.
The specific composition ratio of the solvent in the graphite dispersion liquid is not particularly limited, and the solvent can be prepared according to conventional mixing ratios well known to those skilled in the art, and can be selected and adjusted by those skilled in the art according to actual production conditions, product requirements and quality requirements.
The stripping manner is not particularly limited by the present invention, and may be selected and adjusted by those skilled in the art according to the actual production situation, product requirements and quality requirements, and in order to improve the performance of the final product, the stripping manner is preferably mechanical stripping, that is, stripping is performed by a combination of mechanical stripping and ultrasound, specifically, one or more of stirring, shearing, ball milling and sanding are preferably performed, and ultrasound is performed simultaneously.
The stripping temperature is not particularly limited, and the stripping temperature known to those skilled in the art can be selected and adjusted according to actual production conditions, product requirements and quality requirements, and is preferably room temperature, i.e., preferably 0 to 40 ℃, more preferably 5 to 35 ℃, more preferably 10 to 30 ℃, and more preferably 15 to 25 ℃ in order to improve the performance of the final product and the advantages of a liquid phase separation method.
The ultrasonic conditions are not particularly limited, and conventional conditions known by the skilled in the art can be adopted, and the skilled in the art can select and adjust the ultrasonic conditions according to actual production conditions, product requirements and quality requirements, in order to improve the performance of subsequent products and improve the uniformity of the graphite dispersion liquid, the ultrasonic power is preferably 600-3000W, more preferably 1100-2500W, and even more preferably 1600-2000W. The ultrasonic time, namely the stripping time, is preferably 1-20 h, more preferably 5-16 h, more preferably 9-12 h, and specifically may be 1h, 2h, 8h or 20 h.
The separation method is not particularly limited in the present invention, and may be a conventional separation method well known to those skilled in the art, and those skilled in the art can select and adjust the separation method according to actual production conditions, product requirements and quality requirements, and the separation method is preferably filtration separation, and more particularly preferably comprises suction filtration. The present invention preferably further comprises a drying step after the separation. The specific manner and conditions of drying are not particularly limited in the present invention, and may be selected and adjusted by those skilled in the art according to actual production conditions, product requirements and quality requirements by using conventional drying manners and conditions well known to those skilled in the art.
In order to further improve the conductivity of subsequent products and improve the uniformity of the graphite dispersion liquid, the graphite in the graphite dispersion liquid is preferably pretreated graphite. The invention particularly preferably comprises the following steps of pretreatment:
A) reacting graphite with a small molecular intercalation agent to obtain intercalated graphite;
B) and (3) performing high-temperature expansion on the intercalated graphite obtained in the step to obtain the treated graphite.
The selection and requirements of graphite in the above steps and the corresponding preferred principle of the present invention may correspond to the selection and requirements of raw materials corresponding to the preparation method of the graphene conductive paste and the corresponding preferred principle, and are not described in detail herein.
The invention firstly reacts graphite with a micromolecular intercalation agent to obtain the intercalation graphite.
The small molecule intercalator is selected without any particular limitation, and can be selected and adjusted by those skilled in the art according to actual production conditions, product requirements and quality requirements, and is preferably a small molecule high temperature decomposable compound, more preferably one or more of sulfuric acid, nitric acid, urea, sodium bicarbonate, sodium dihydrogen carbonate, disodium hydrogen carbonate, oxalic acid, phosphoric acid, perchloric acid, periodic acid and trifluoromethanesulfonic acid, and more preferably sulfuric acid, nitric acid, urea, sodium hydrogen carbonate, sodium dihydrogen carbonate, disodium hydrogen carbonate, oxalic acid, phosphoric acid, perchloric acid, periodic acid or trifluoromethanesulfonic acid, in order to improve the performance of the final product. More preferably sulfuric acid, nitric acid, urea, sodium bicarbonate, sodium dihydrogen carbonate, disodium hydrogen carbonate, oxalic acid or phosphoric acid.
The invention has no special limitation on the dosage of the small molecule intercalation agent, and a person skilled in the art can select and adjust the dosage according to the actual production condition, the product requirement and the quality requirement, and in order to improve the performance of the final product, the mass ratio of the graphite to the small molecule intercalation agent is preferably 1: (1-5), more preferably 1: (1.5 to 4.5), more preferably 1: (2-4), most preferably 1: (2.5-3.5).
The reaction temperature is not particularly limited, and can be selected and adjusted by a person skilled in the art according to actual production conditions, product requirements and quality requirements, and in order to improve the performance of a final product and the advantages of a liquid phase separation method, the reaction temperature is particularly maintained at room temperature, namely the reaction temperature is preferably 0-40 ℃, more preferably 5-35 ℃, more preferably 10-30 ℃, and more preferably 15-25 ℃.
The reaction time is not particularly limited in the present invention, and the conventional intercalation reaction time of a liquid phase separation method known to those skilled in the art may be used, and those skilled in the art may select and adjust the reaction time according to the actual production situation, product requirements and quality requirements, and the reaction time in the present invention is preferably 10 to 30 hours, more preferably 12 to 28 hours, more preferably 15 to 25 hours, more preferably 17 to 24 hours, and specifically may be 10 hours, 15 hours, 20 hours or 30 hours.
According to the invention, the graphite is intercalated by adopting the micromolecular high-temperature decomposable intercalation agent, and micromolecular high-temperature decomposable compounds can realize that micromolecules enter the interlayer, so that the graphite reaction is reduced, and the complete structure of a graphite sheet layer is maintained; and the reaction condition of high temperature and high pressure is avoided, the temperature of intercalation reaction is further reduced, effective intercalation of graphite can be realized under the moderate conditions of lower temperature and common room temperature, a graphite intercalation compound is obtained, the loss and energy consumption in the preparation process are reduced, and the preparation method is green and environment-friendly.
In order to improve the practicability of the preparation method and complete the process route, the method preferably further comprises a post-treatment step after the reaction. The present invention does not specifically limit the specific steps of the post-treatment, and the post-treatment steps known to those skilled in the art can be selected and adjusted according to the actual production situation, the product requirements and the quality requirements, and the post-treatment of the present invention preferably includes water washing and separation, more preferably water washing to neutrality and centrifugal separation.
The invention then expands the intercalated graphite obtained in the above steps at high temperature to obtain expanded graphite.
The temperature of the high-temperature expansion is not particularly limited, the temperature of the high-temperature expansion is selected and adjusted by the temperature of the expansion known by the technical personnel in the field, and the technical personnel in the field can select and adjust the temperature according to the actual production condition, the product requirement and the quality requirement, and in order to improve the performance of the final product and the advantages of a liquid phase separation method, the temperature of the high-temperature expansion is preferably 500-1200 ℃, more preferably 600-1100 ℃, more preferably 700-1000 ℃, and more preferably 800-900 ℃.
The time of the high-temperature expansion is not particularly limited, and the time of the high-temperature expansion known to those skilled in the art can be selected and adjusted by those skilled in the art according to actual production conditions, product requirements and quality requirements, and the time of the high-temperature expansion is preferably 5 to 60 seconds, more preferably 10 to 55 seconds, more preferably 15 to 50 seconds, more preferably 25 to 40 seconds, and particularly may be 5 seconds, 10 seconds, 30 seconds or 60 seconds.
The graphene nanosheet is obtained through the steps. The specific performance parameters of the graphene nanoplatelets are not particularly limited, and the graphene nanoplatelets with the specific performance can be obtained by referring to the above method by those skilled in the art, and the carbon content of the graphene nanoplatelets of the present invention is preferably greater than or equal to 98%, more preferably greater than or equal to 98.5%, and still more preferably greater than or equal to 99%, which can be selected and adjusted by those skilled in the art according to the actual production situation, the product requirements and the quality requirements. The thickness of the graphene nanoplatelets is preferably 5nm or less, more preferably 4nm or less, and even more preferably 3nm or less. The sheet diameter of the graphene nanosheet is preferably 1-20 μm, more preferably 5-16 μm, and more preferably 9-12 μm.
According to the invention, the graphene nanosheet obtained in the above step, a dispersant and a solvent are mixed to obtain a pre-slurry.
The specific choice of the dispersant is not particularly limited by the present invention, and may be conventional dispersants well known to those skilled in the art, and those skilled in the art can select and adjust the dispersant according to actual production conditions, product requirements and quality requirements, and in order to improve the performance of subsequent products and the homogeneity of the pre-slurry, the dispersant preferably includes one or more of polyvinylpyrrolidone, polyvinylidene chloride, polypropylene, cetyltrimethylammonium bromide and sodium dodecylbenzenesulfonate, and more preferably, the dispersant includes one or more of polyvinylpyrrolidone, polyvinylidene chloride, polypropylene, cetyltrimethylammonium bromide or sodium dodecylbenzenesulfonate.
The amount of the dispersant used in the present invention is not particularly limited, and may be any conventional amount known to those skilled in the art, and those skilled in the art may select and adjust the amount according to actual production conditions, product requirements, and quality requirements, and in order to improve the performance of subsequent products and the uniformity of the pre-slurry, the mass concentration of the dispersant in the pre-slurry is preferably 0.2% to 10%, more preferably 0.7% to 9%, more preferably 2% to 8%, and more preferably 4% to 6%.
The specific choice of the solvent is not particularly limited in the present invention, and may be a conventional solvent well known to those skilled in the art, and those skilled in the art can select and adjust the solvent according to actual production conditions, product requirements and quality requirements, and in the present invention, in order to improve the performance of subsequent products and the homogeneity of the pre-slurry, the solvent preferably includes one or more of water, ethanol, acetone, dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide, and more preferably, water, ethanol, acetone, dimethylformamide, dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.
The amount of the solvent used in the present invention is not particularly limited, and may be a conventional amount of the solvent known to those skilled in the art, and those skilled in the art may select and adjust the solvent according to actual production conditions, product requirements, and quality requirements, and in order to improve the performance of subsequent products and improve the uniformity of the pre-slurry, the mass concentration of the graphene nanoplatelets in the pre-slurry is preferably 1% to 10%, more preferably 2% to 9%, more preferably 3% to 8%, and more preferably 4% to 7%.
The mixing method is not particularly limited in the present invention, and may be a mixing method known to those skilled in the art, and those skilled in the art can select and adjust the mixing method according to the actual production situation, the product requirement and the quality requirement, and the mixing method of the present invention is preferably stirring mixing.
Finally, carrying out sanding pulping on the pre-slurry obtained in the step to obtain the graphene conductive slurry.
In order to improve the performance of the final product and provide the fluidity and the conductivity of the graphene conductive slurry, the method is particularly preferably used for pulping by adopting a sanding mode. The specific sanding mode of the present invention is not particularly limited, and can be selected and adjusted by those skilled in the art according to the actual production situation, the product requirement and the quality requirement, and the sanding mode of the present invention is preferably wet sanding, more preferably wet superfine sanding, i.e. sanding with a wet superfine sanding machine, and the specific type can be a rod pin type nanometer sanding machine.
The sanding medium for sanding according to the present invention is not particularly limited, and may be any one known to those skilled in the art, and may be selected and adjusted by those skilled in the art according to actual production conditions, product requirements, and quality requirements, and preferably includes one or more of zirconium silicate beads, zirconium oxide beads, glass beads, and steel beads, more preferably zirconium silicate beads, zirconium oxide beads, glass beads, or steel beads, and still more preferably zirconium silicate beads or zirconium oxide beads. The size of the sanding medium for sanding is preferably 0.1-2 mm, more preferably 0.5-1.5 mm, and more preferably 0.8-1.2 mm.
The sanding frequency is not particularly limited, and can be selected and adjusted by a person skilled in the art according to actual production conditions, product requirements and quality requirements, and the sanding frequency is preferably 2-50 times, more preferably 5-35 times, more preferably 10-30 times, and more preferably 15-25 times.
The other conditions of the sanding are not particularly limited by the invention, and the sanding conditions known by the skilled in the art can be selected and adjusted by the skilled in the art according to the actual production condition, the product requirement and the quality requirement, and the power of the sanding is preferably 2-15 KW, more preferably 5-12 KW, and more preferably 7-10 KW. The processing amount of the sanding is preferably 1-100L/h, more preferably 10-90L/h, more preferably 30-70L/h, and more preferably 40-60L/h.
The graphene conductive paste obtained through the steps is a high-conductivity graphene conductive paste, the performance and the structure of the high-conductivity graphene are not particularly limited, and the performance and the structure of the high-conductivity graphene known to those skilled in the art can be obtained, and the performance and the structure of the graphene in the high-conductivity graphene conductive paste can be obtained by those skilled in the art according to the preparation method. The thickness of the graphene is the average thickness of 20 randomly selected sheets measured by an atomic force microscope.
According to the high-conductivity graphene disclosed by the invention, the carbon content is measured by element analysis, and the carbon content is preferably more than or equal to 99.5%.
The conductivity of the high-conductivity graphene is measured by a four-probe conductivity test method, and is preferably greater than 40000S/m, more preferably greater than or equal to 45000S/m, more preferably greater than or equal to 50000S/m, and more preferably can reach 70000S/m.
The steps of the invention provide a conductive slurry containing high-conductivity graphene, a low-temperature normal-pressure liquid phase stripping method is selected, a graphite-solvent mixing-ultrasonic dispersion-ultrahigh-pressure homogenization method is creatively adopted, a small-molecule intercalation-high-temperature expansion graphite pretreatment mode is further preferably adopted, graphene nanosheets are prepared firstly, then flowing graphene conductive slurry is prepared, and graphene can be prepared quickly and at low cost under mild conditions. The graphene prepared by the method has a complete lamellar structure, is not subjected to surface modification, and keeps the intrinsic characteristics of a two-dimensional lamellar. The graphene conductive paste prepared by the method has the characteristics of high conductivity and high fluidity, and the excellent conductivity of graphene is utilized through the research on the insufficient performance of the conventional commercial conductive agent, so that the graphene conductive paste is prepared by the method and is applied to the positive electrode material of the lithium battery, and the rate capability, the cycle life and the like of the lithium battery are obviously improved. The conductive paste disclosed by the invention is excellent in conductivity, uniform in dispersion, good in fluidity, simple in process, easy to realize and suitable for being prepared into the graphene conductive paste on a large scale.
Experimental results show that the high-conductivity graphene slurry prepared by the invention has the carbon content of more than or equal to 99.5 percent and the conductivity of more than 50000S/m, and can reach 70000S/m and 10S-1The viscosity is less than 1500 mPas.
For further illustration of the present invention, the following will describe in detail a method for preparing a graphene conductive paste according to the present invention with reference to examples, but it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific procedures are given, which are only for further illustration of the features and advantages of the present invention, but not for limitation of the claims of the present invention, and the scope of protection of the present invention is not limited to the following examples.
Comparative example 1
The raw material is 1000 mesh natural graphite (Qingdao Dongkai graphite Co., Ltd.). Mixing 10g of graphite and 50g of sodium bicarbonate, dispersing the mixture in 100g of water, mechanically stirring the mixed solution, reacting for 20 hours at room temperature, adding 400g of water for dilution, and centrifuging to obtain the intercalated graphite. The intercalated graphite was placed in a muffle furnace at 1000 ℃ and expanded for 30 s. Dispersing 5g of expanded graphite in 5 mLN-methyl pyrrolidone, ultrasonically stripping at 800W for 8h, and ball-milling at 300rmp for 2h to obtain the high-conductivity graphene.
Rheological viscosity characterization is carried out on the high-conductivity graphene prepared in comparative example 1 of the invention.
The test method comprises the following steps: the rheological viscosity test of the graphene sample is carried out by an antopa MCR302 rheometer.
Referring to fig. 1, fig. 1 is a graph of rheological test data of highly conductive graphene prepared in comparative example 1 of the present invention.
As can be seen from FIG. 1, the highly conductive graphene prepared in comparative example 1 of the present invention was used for 10s-1The viscosity was 2353 mPas under the shear rate condition (2), and the apparent fluidity was poor.
Elemental analysis of the highly conductive graphene prepared in comparative example 1 of the present invention showed that the carbon content of the highly conductive graphene prepared in comparative example 1 of the present invention was 99.414%.
The high-conductivity graphene prepared in comparative example 1 of the present invention was measured for conductivity using a four-probe conductivity test method.
The test method comprises the following steps: the conductivity of the graphene samples was measured by pressing the samples into wafers of 10mm diameter, using a suzhou lattice four-probe conductivity tester.
The conductivity of the highly conductive graphene prepared in comparative example 1 of the present invention was 51000S/m.
The stability of the highly conductive graphene prepared in comparative example 1 of the present invention was tested.
The test method comprises the following steps: and (3) introducing the graphene sample into a sealed transparent sample bottle, placing the sealed transparent sample bottle in an oven at 60 ℃, and performing rheometer again to test the viscosity of the graphene sample after 24 hours.
After 24 hours, the highly conductive graphene prepared in comparative example 1 delaminates significantly, and the rheological data shows that it is greater than about 3000mPa · s.
Example 1
Preparing 1.5L of aqueous solution from 8g of graphite powder and 1L of ethanol, mechanically stirring the aqueous solution at 600r/min for 30min, performing ultrasonic treatment at 1000W for 12h, performing suction filtration and drying to obtain graphene nanosheets, mixing 3g of nanosheets, 2g of polyvinylpyrrolidone and 95g of ethanol, mechanically stirring at 600r/min for 10min, and performing ultrasonic treatment at 800W for 20min to obtain mixed solution. And circularly pulping for 120min by using a sand mill with 0.3mm of zirconia beads to obtain the graphene conductive slurry with good fluidity.
Rheological viscosity characterization is carried out on the high-conductivity graphene prepared in the embodiment 1 of the invention.
The test method comprises the following steps: the rheological viscosity test of the graphene sample is carried out by an antopa MCR302 rheometer.
Referring to fig. 2, fig. 2 is a graph of rheological test data of the highly conductive graphene prepared in example 1 of the present invention.
As can be seen from fig. 2, the highly conductive graphene prepared in example 1 of the present invention is within 10s-1The viscosity of the resulting polymer was 788 mPas under the shear rate conditions of (1), and the apparent fluidity was good.
Elemental analysis is performed on the high-conductivity graphene prepared in the embodiment 1 of the present invention, and the carbon content of the high-conductivity graphene prepared in the embodiment 1 of the present invention reaches 99.621%.
The high-conductivity graphene prepared in example 1 of the present invention was measured for conductivity using a four-probe conductivity test method.
The test method comprises the following steps: the conductivity of the graphene samples was measured by pressing the samples into wafers of 10mm diameter, using a suzhou lattice four-probe conductivity tester.
The conductivity of the high-conductivity graphene prepared in the embodiment 1 of the invention reaches 57000S/m.
The stability of the highly conductive graphene prepared in example 1 of the present invention was tested.
The test method comprises the following steps: and (3) introducing the graphene sample into a sealed transparent sample bottle, placing the sealed transparent sample bottle in an oven at 60 ℃, and performing rheometer again to test the viscosity of the graphene sample after 24 hours.
After 24 hours, the highly conductive graphene prepared in example 1 was not delaminated, and rheological data showed about 810mPa · s, which was good in fluidity.
Example 2
Preparing 1.5L of aqueous solution from 15g of graphite powder and 1L of ethanol, mechanically stirring the aqueous solution at 400r/min for 30min, carrying out ultrasonic treatment at 2000W for 3h, carrying out suction filtration and drying to obtain graphene nanosheets, mixing 7g of nanosheets, 3g of polyvinylidene chloride and 90g of dimethylacetamide, mechanically stirring at 700r/min for 20min, and carrying out ultrasonic treatment at 1000W for 30min to obtain mixed solution. And circularly pulping for 20min by using a sand mill with 0.8mm zirconium silicate beads to obtain the graphene conductive slurry with good fluidity.
Rheological viscosity characterization is carried out on the high-conductivity graphene prepared in the embodiment 2 of the invention.
The test method comprises the following steps: the rheological viscosity test of the graphene sample is carried out by an antopa MCR302 rheometer.
Referring to fig. 3, fig. 3 is a graph of rheological test data of the highly conductive graphene prepared in example 2 of the present invention.
As can be seen from fig. 3, the highly conductive graphene prepared in example 2 of the present invention is within 10s-1Under the shear rate condition of (3), the viscosity is 774 mPas, and the apparent fluidity is good.
Elemental analysis is performed on the high-conductivity graphene prepared in embodiment 2 of the present invention, and the carbon content of the high-conductivity graphene prepared in embodiment 2 of the present invention reaches 99.58%.
The high-conductivity graphene prepared in example 2 of the present invention was measured for conductivity using a four-probe conductivity test method.
The test method comprises the following steps: the conductivity of the graphene samples was measured by pressing the samples into wafers of 10mm diameter, using a suzhou lattice four-probe conductivity tester.
The conductivity of the high-conductivity graphene prepared in the embodiment 2 of the invention reaches 59000S/m.
The stability of the highly conductive graphene prepared in example 2 of the present invention was tested.
The test method comprises the following steps: and (3) introducing the graphene sample into a sealed transparent sample bottle, placing the sealed transparent sample bottle in an oven at 60 ℃, and performing rheometer again to test the viscosity of the graphene sample after 24 hours.
After 24 hours, the highly conductive graphene prepared in example 2 has no delamination, and rheological data show that the highly conductive graphene is about 790mPa · s, and the highly conductive graphene has good fluidity.
Example 3
Preparing 1.5L of aqueous solution from 20g of graphite powder and 1L of ethanol, mechanically stirring the aqueous solution at 600r/min for 20min, carrying out ultrasonic treatment at 3000W for 6h, carrying out suction filtration and drying to obtain graphene nanosheets, mixing 4g of nanosheets, 4g of sodium dodecyl benzene sulfonate and 92g of N-methyl pyrrolidone, mechanically stirring at 600r/min for 20min, and carrying out ultrasonic treatment at 1000W for 20min to obtain mixed solution. And then circularly pulping for 240min by using a sand mill with 1.0mm of zirconium silicate beads to obtain the graphene conductive slurry with good fluidity.
Rheological viscosity characterization is carried out on the high-conductivity graphene prepared in the embodiment 3 of the invention.
The test method comprises the following steps: the rheological viscosity test of the graphene sample is carried out by an antopa MCR302 rheometer.
Referring to fig. 4, fig. 4 is a graph of rheological test data of the highly conductive graphene prepared in example 3 of the present invention.
As can be seen from fig. 4, the highly conductive graphene prepared in example 3 of the present invention is within 10s-1The viscosity was 872 mPas under the shear rate conditions of (1), and the apparent fluidity was good.
Elemental analysis is performed on the high-conductivity graphene prepared in embodiment 3 of the present invention, and the carbon content of the high-conductivity graphene prepared in embodiment 3 of the present invention reaches 99.462%.
The high-conductivity graphene prepared in example 3 of the present invention was measured for conductivity using a four-probe conductivity test method.
The test method comprises the following steps: the conductivity of the graphene samples was measured by pressing the samples into wafers of 10mm diameter, using a suzhou lattice four-probe conductivity tester.
The conductivity of the high-conductivity graphene prepared in embodiment 3 of the invention reaches 62000S/m.
The stability of the highly conductive graphene prepared in example 3 of the present invention was tested.
The test method comprises the following steps: and (3) introducing the graphene sample into a sealed transparent sample bottle, placing the sealed transparent sample bottle in an oven at 60 ℃, and performing rheometer again to test the viscosity of the graphene sample after 24 hours.
After 24 hours, the highly conductive graphene prepared in example 3 has no delamination, and rheological data show that the graphene is about 920mPa · s, and the graphene has good fluidity.
The above detailed description of the method for preparing a high-fluidity graphene conductive paste according to the present invention is provided, and the principles and embodiments of the present invention are described herein with reference to specific examples, which are provided only to help understand the method and the core concept of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention, including making and using any devices or systems and performing any combination of the methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Claims (9)
1. A preparation method of graphene conductive paste with high fluidity is characterized by comprising the following steps:
1) stripping the graphite dispersion liquid under the ultrasonic condition, and then separating to obtain graphene nanosheets;
the graphite is pretreated graphite;
the pretreatment steps are as follows:
A) reacting graphite with a small molecular intercalation agent to obtain intercalated graphite;
B) performing high-temperature expansion on the intercalated graphite obtained in the step to obtain treated graphite;
the power of the ultrasonic wave is 600-3000W;
the solvent in the graphite dispersion liquid is water and an organic solvent mutually soluble with water;
the water-miscible organic solvent comprises one or more of methanol, ethanol, glycol, glycerol, acetone, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide;
the graphite dispersion liquid does not contain a dispersing agent;
the sheet diameter of the graphene nanosheet is 1-20 microns;
2) stirring and mixing the graphene nanosheets obtained in the previous step, a dispersing agent and a solvent to obtain a pre-slurry;
the carbon content of the graphene nanosheet is greater than or equal to 98%;
in the pre-slurry, the mass concentration of the graphene nanosheets is 1% -10%;
3) carrying out sanding pulping on the pre-slurry obtained in the step to obtain graphene conductive slurry;
the conductivity of the graphene conductive slurry is greater than or equal to 40000S/m;
10s of the graphene conductive paste-1The viscosity is less than 1500 mPas.
2. The production method according to claim 1, wherein the graphite in the graphite dispersion liquid includes one or more of graphite powder, flake graphite, artificial graphite, expandable graphite, and expanded graphite;
the mass concentration of graphite in the graphite dispersion liquid is 0.5-5%.
3. The preparation method according to claim 2, wherein the mass concentration of the water-miscible organic solvent in the graphite dispersion is 30-70%;
the ultrasonic time is 1-20 h;
the method also comprises a drying step after the separation.
4. The method of claim 1, wherein the stripping comprises one or more of stirring, shearing, ball milling, and sanding;
the thickness of the graphene nanosheet is less than or equal to 5 nm.
5. The method of claim 1, wherein the dispersant comprises one or more of polyvinylpyrrolidone, polyvinylidene chloride, polypropylene, cetyltrimethylammonium bromide, and sodium dodecylbenzenesulfonate;
the solvent comprises one or more of water, ethanol, acetone, dimethylformamide, dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide;
in the pre-slurry, the mass concentration of the dispersing agent is 0.2-10%.
6. The method of manufacturing according to claim 1, wherein the sanding is wet sanding;
the size of the sanding medium for sanding is 0.1-2 mm.
7. The method of manufacturing according to claim 6, wherein the wet sanding is wet ultra-fine sanding;
the sanding medium comprises one or more of zirconium silicate beads, zirconium oxide beads, glass beads and steel beads;
the sanding frequency is 2-50 times.
8. The method according to claim 1, wherein the graphite has a particle size of 50 to 10000 mesh;
the carbon content of the graphite is more than or equal to 70 percent;
the micromolecular intercalation agent comprises micromolecular high-temperature decomposable compounds;
the reaction time is 10-30 hours; the reaction temperature is 0-40 ℃.
9. The method of claim 8, wherein the small molecule intercalant comprises one or more of sulfuric acid, nitric acid, urea, sodium bicarbonate, sodium dihydrogen carbonate, disodium hydrogen carbonate, oxalic acid, phosphoric acid, perchloric acid, periodic acid, and trifluoromethanesulfonic acid;
the mass ratio of the graphite to the micromolecular intercalator is 1: (1-5);
the temperature of the high-temperature expansion is 500-1200 ℃;
the time of high-temperature expansion is 5-60 seconds.
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| CN104966837A (en) * | 2015-04-24 | 2015-10-07 | 深圳市德方纳米科技股份有限公司 | Graphene conductive liquid as well as preparation method and application thereof |
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