CN111348685B - Graphene-based composite material and preparation method and application thereof - Google Patents

Graphene-based composite material and preparation method and application thereof Download PDF

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CN111348685B
CN111348685B CN202010136221.7A CN202010136221A CN111348685B CN 111348685 B CN111348685 B CN 111348685B CN 202010136221 A CN202010136221 A CN 202010136221A CN 111348685 B CN111348685 B CN 111348685B
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graphene
gas
based composite
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manganese
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CN111348685A (en
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刘东海
高学森
张勃
刘芳芳
李金来
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Xinao Group Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G45/00—Compounds of manganese
    • C01G45/02—Oxides; Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/182—Graphene
    • C01B32/184—Preparation
    • C01B32/186—Preparation by chemical vapour deposition [CVD]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a graphene-based composite material and a preparation method and application thereof, wherein the method comprises the following steps: (1) Mixing a manganese salt solution, a hydroxide solution and a solution containing a conductive carbon material to obtain a mixed slurry, carrying out suction filtration and washing on the mixed slurry, dispersing the mixed slurry in water, and carrying out spray drying on the dispersion to obtain a precursor containing manganese hydroxide and the conductive carbon material; (2) Placing the precursor in a high-temperature reactor, continuously heating, introducing protective gas, and after the temperature reaches a first preset temperature, introducing first gas containing the protective gas and hydrogen into the high-temperature reactor to obtain manganese oxide containing a conductive carbon material; (3) And (3) placing the manganese oxide containing the conductive carbon material in a high-temperature reactor, continuously heating, introducing protective gas, and after reaching a second preset temperature, introducing second gas containing the protective gas and a carbon source or containing the protective gas, the carbon source and a nitrogen source into the high-temperature reactor to obtain graphene or nitrogen-doped graphene deposited on the manganese oxide containing the conductive carbon material.

Description

Graphene-based composite material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of carbon materials, and particularly relates to a graphene-based composite material as well as a preparation method and application thereof.
Background
The rapid development of the information industry in the current society brings a huge market scale for the application of lithium ion batteries, but with the continuous progress of the society, the society has a higher desire for a battery system with high energy density, high volume energy density, high safety and low cost. The existing lithium ion battery obviously cannot meet the requirements, so that the development of the lithium ion battery with stronger performance becomes an important target of the majority of scientific researchers.
The manganese oxide cathode material has the advantages of high energy density, excellent cycle stability, low material cost and the like, and becomes a hot cathode material of current researchers. The graphene has high electron mobility (2 x 10) 5 cm 2 V.s), high strength (130 GPa), high thermal conductivity (5300W/m.K), and high surface activity (2630 m) 2 The material has excellent characteristics of/g) and the like, can effectively improve the electron and ion transmission process dynamics of the electrode material in the charging and discharging process, and enhances the cycle stability of the battery, and the design of the microstructure and the chemical property of the graphene is the key for realizing the high-performance electrode material.
The existing graphene-based composite material has the following problems:
(1) Graphene is difficult to prepare on a large scale: the traditional oxidation-reduction method is limited by the problems of long production period, large amount of waste acid and waste liquid generation and safety and environmental protection, while the reaction condition of the epitaxial growth method is harsh, the cost of the single crystal silicon carbide substrate is too high, the graphene is difficult to separate from the substrate, the graphene material is difficult to prepare on a large scale, and the prospect of industrial production is not great.
(2) The graphene structure is difficult to regulate and control: the quality of the currently widely used graphene (mainly based on a chemical oxidation-reduction method) is not high, which is obviously reflected in that most graphene products are extremely non-uniform in size and not high in conductivity. The defects are generated in the graphene structure due to the limitation of the preparation method, and the controllability of the number of layers, the size and the like of the graphene is poor. Although many graphene preparation methods have been developed over the last decade, mechanical exfoliation, chemical Vapor Deposition (CVD), graphite oxidation-reduction, direct liquid phase exfoliation, and other chemical synthesis techniques have been developed. However, these methods still have scientific bottlenecks in terms of macro-scale preparation, graphene layer number and lateral dimension control, and structural integrity.
(3) Insufficient transition metal oxide performance: although the theoretical capacity is high, the problems of poor conductivity, high irreversible capacity, obvious volume effect in the charging and discharging process, pulverization of electrode materials, poor cycle stability, fast capacity attenuation and the like of the transition metal oxide are solved, and the industrial application of the transition metal oxide is restricted.
(4) The processing technology of the graphene composite material is immature: for the development of graphene composite materials, well-defined and controllable manipulation techniques are crucial for optimizing the performance of the composite material system in detail. For example, the current technology of coating the electrode material with graphene only adopts a simple random physical mixing method, and the disordered structure of the coating sometimes blocks the transmission of ions.
Therefore, the existing technology for preparing graphene-based composite materials needs to be improved.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, one object of the present invention is to provide a graphene-based composite material, and a preparation method and an application thereof, wherein the graphene-based composite material prepared by the method has excellent electrical conductivity and good elasticity, and graphene in the negative electrode material prepared from the graphene-based composite material can buffer an electrode during charging and discharging processes, so as to improve cycle performance and rate capability of the negative electrode material.
In one aspect of the present invention, a method of preparing a graphene-based composite is presented. According to an embodiment of the invention, the method comprises:
(1) Mixing a manganese salt solution, a hydroxide solution and a solution containing a conductive carbon material to obtain a mixed slurry, carrying out suction filtration and washing on the mixed slurry, dispersing the washed mixed slurry in water, and then carrying out spray drying on the dispersion liquid to obtain a precursor containing manganese hydroxide and the conductive carbon material;
(2) Placing the precursor in a high-temperature reactor, continuously heating, introducing protective gas, and after reaching a first preset temperature, introducing first gas containing the protective gas and hydrogen into the high-temperature reactor so as to obtain manganese oxide containing a conductive carbon material;
(3) And placing the manganese oxide containing the conductive carbon material in a high-temperature reactor, continuously heating, introducing the protective gas, and introducing a second gas containing the protective gas and a carbon source or containing the protective gas and a nitrogen-containing carbon source into the high-temperature reactor after reaching a second preset temperature so as to obtain graphene or nitrogen-doped graphene deposited on the manganese oxide containing the conductive carbon material, thereby obtaining the graphene-based composite material.
According to the method for preparing the graphene-based composite material, the manganese salt solution, the hydroxide solution and the solution containing the conductive carbon material are mixed to obtain mixed slurry, the mixed slurry is subjected to suction filtration and washing and then is dispersed in water, then the dispersion liquid is subjected to spray drying, the conductive carbon material forms a three-dimensional network structure among manganese hydroxide particles, and good contact among the manganese hydroxide particles is realized, so that the defects of poor conductivity and the like of an electrode material caused by introducing a transition metal oxide as a negative electrode material are reduced on the premise of realizing high load of subsequent manganese oxide and graphene composite particles, the defects are used as electron and ion transmission channels in the charging and discharging process to improve the rate capability of the electrode material, then the obtained precursor containing the manganese hydroxide and the conductive carbon material is placed in a high-temperature reactor to perform reduction reaction in a first gas atmosphere containing protective gas and hydrogen, the obtained manganese oxide containing the conductive carbon material has excellent graphene catalytic activity, so that graphene with a complete structure is formed in the subsequent deposition process, the manganese oxide has good electrochemical activity, and finally the manganese oxide template containing the conductive material is placed in a high-temperature reactor to perform deposition reaction in a second gas atmosphere containing protective gas and a carbon source or containing protective gas, a carbon source and a nitrogen source, and graphene or nitrogen-doped graphene is deposited on the surface of the manganese oxide template to obtain the graphene-based composite material coated with the manganese oxide by the graphene, wherein the graphene in the composite material can improve the conductivity of the material and has good elasticity, and the graphene can play a role in buffering the electrode in the charge and discharge process of a negative electrode material prepared by adopting the graphene-based composite material, the graphene-based composite material is porous, so that a battery is assembled by adopting the prepared negative electrode material, the porous structure of the graphene-based composite material is favorable for the insertion and the separation of lithium ions, and the stress generated in the reaction process can be buffered. When the composite material is applied as a negative electrode material, steps such as acid washing and the like are not needed to remove manganese oxide, so that the prepared negative electrode material simultaneously exerts the advantages of high oxide capacity and good graphene conductivity, the structural defect of a single material is avoided, the electrochemical performance is improved through the synergistic effect of the two, the composite material has extremely high cost performance, and the low-cost large-scale preparation of high-quality graphene is facilitated.
In addition, the method for preparing the graphene-based composite material according to the above embodiment of the invention may further have the following additional technical features:
in some embodiments of the present invention, in the step (1), the manganese ion concentration in the manganese salt solution is 0.01 to 0.5mol/L.
In some embodiments of the invention, in step (1), the manganese salt solution comprises at least one of manganese acetate, manganese nitrate, manganese chloride, and manganese bromide.
In some embodiments of the present invention, in step (1), the concentration of hydroxide ions in the hydroxide solution is 0.01 to 0.5mol/L.
In some embodiments of the invention, in step (1), the hydroxide solution contains at least one of sodium hydroxide and potassium hydroxide.
In some embodiments of the invention, in step (1), the solution containing conductive carbon material comprises at least one of conductive carbon black, carbon nanotubes, graphene, conductive activated carbon, conductive graphite, and carbon nanofibers.
In some embodiments of the present invention, in step (1), the concentration of the solution containing the conductive carbon material is 0.01 to 0.5g/L.
In some embodiments of the present invention, in step (1), the mass ratio of the conductive carbon material in the precursor is 0.5-20%.
In some embodiments of the present invention, in step (1), the concentration of the dispersion is 0.01 to 1mol/L.
In some embodiments of the present invention, in step (1), the feeding speed of the spray drying process is 3 to 30mL/min, the inlet air temperature is 200 to 300 ℃, and the outlet air temperature is 90 to 160 ℃.
In some embodiments of the invention, in step (2), the ramp rate is 5 to 20 degrees celsius per minute.
In some embodiments of the invention, in step (2), the shielding gas is nitrogen, argon or helium.
In some embodiments of the present invention, in the step (2), the first predetermined temperature is 400 to 700 degrees celsius, and the reaction is performed at the first predetermined temperature for 0.5 to 3 hours.
In some embodiments of the invention, in the step (2), the flow rate of the shielding gas in the first gas containing the shielding gas and hydrogen is 0.3 to 10L/min, and the volume ratio of the shielding gas to the hydrogen is 1: (0.03-1).
In some embodiments of the invention, in step (3), the ramp rate is 5 to 20 degrees celsius per minute.
In some embodiments of the invention, in step (3), the shielding gas is nitrogen, argon or helium.
In some embodiments of the present invention, in the step (3), the second predetermined temperature is 700 to 1000 degrees celsius, and the reaction is performed at the second predetermined temperature for 5 to 60 minutes.
In some embodiments of the present invention, in the step (3), the flow rate of the protective gas and the carbon source is 0.3 to 10L/min, and the volume ratio of the protective gas to the carbon source is 1: (0.05-1).
In some embodiments of the invention, in the step (3), the flow rate of the protective gas in the second gas containing the protective gas and the nitrogen-containing carbon source is 0.3 to 10L/min, and the volume ratio of the protective gas to the nitrogen-containing carbon source is 1: (0.05-1).
In some embodiments of the invention, in step (3), the carbon source comprises at least one of methane, ethane, propane, butane, ethylene, acetylene, propylene, urea, methanol, ethanol, propylene, acetic acid, and acetone.
In some embodiments of the present invention, in step (3), the nitrogen-containing carbon source comprises at least one of triethanolamine, diethanolamine, hexamethylenetetramine, aniline, N-dimethylformamide, ammonia gas, melamine, acetonitrile, propionitrile, butyronitrile, ammonia gas, pyridine, pyrrole, and thiourea.
In yet another aspect of the present invention, a graphene-based composite is provided. According to the embodiment of the invention, the graphene-based composite material is prepared by the method. Therefore, the three-dimensional network structure constructed by the carbon material in the composite material can be used as an electron and ion transmission channel in the charge and discharge process, the multiplying power performance of an electrode material is improved, the graphene can improve the conductivity of the material and has better elasticity, the negative electrode material prepared by the graphene-based composite material can buffer the electrode in the charge and discharge process, so that the cycle performance and the multiplying power performance of the negative electrode material are improved, meanwhile, the porous structure of the negative electrode material is favorable for the insertion and the separation of lithium ions, and the stress generated in the reaction process can be buffered.
In a third aspect of the invention, a method of making an anode material is provided. According to an embodiment of the invention, the method comprises: mixing the graphene-based composite material with a binder and a conductive agent, and then coating paste on copper foil, wherein the graphene-based composite material is the graphene-based composite material obtained by the method or the graphene-based composite material.
According to the method for preparing the negative electrode material, the graphene-based composite material with good conductivity and high capacity is mixed with the binder and the conductive agent to prepare the negative electrode material, the three-dimensional network structure constructed by the carbon material in the composite material can be used as an electron and ion transmission channel in the charge and discharge process, the rate capability of the electrode material is improved, the graphene can improve the conductivity of the negative electrode material and has good elasticity, and in the charge and discharge process of the negative electrode material, the graphene can play a role in buffering the electrode, so that the cycle performance and the rate capability of the negative electrode material are improved, and meanwhile, the graphene-based composite material is porous, so that the negative electrode material is adopted to assemble a battery, the porous structure of the negative electrode material is not only beneficial to the insertion and the extraction of lithium ions, but also can buffer the stress generated in the reaction process.
In addition, the method for preparing the anode material according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, the binder comprises at least one of polyvinylidene fluoride, sodium carboxymethylcellulose, and polyacrylic acid.
In some embodiments of the present invention, the conductive agent comprises at least one of carbon nanotubes, acetylene black, and conductive carbon black.
In some embodiments of the present invention, the mass ratio of the graphene-based composite material, the binder, and the conductive agent is (80 to 95): (2-10): (3-10).
In a fourth aspect of the invention, an anode material is provided. According to the embodiment of the invention, the negative electrode material is prepared by the method. Therefore, the negative electrode material has excellent conductivity and good elasticity, and in the charging and discharging process of the negative electrode material, the three-dimensional net structure constructed by the carbon material can be used as an electron and ion transmission channel in the charging and discharging process, the multiplying power performance of the electrode material is improved, and meanwhile, the graphene can play a buffering role on an electrode, so that the cycle performance and the multiplying power performance of the electrode material are improved.
In a fifth aspect of the present invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery has the negative electrode material obtained by the method described above or the negative electrode material described above. Therefore, the lithium battery has long cycle life on the basis of high volume specific capacity.
In a sixth aspect of the present invention, an automobile is provided. According to an embodiment of the present invention, the automobile has the lithium battery described above. Therefore, the vehicle loaded with the lithium battery with high volume specific capacity and long cycle life has excellent cruising ability, thereby meeting the use requirements of consumers.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic flow diagram of a method of preparing a graphene-based composite according to one embodiment of the present invention;
FIG. 2 is an SEM photograph of a precursor containing manganese hydroxide and a conductive carbon material obtained in example 1;
fig. 3 is a charge/discharge graph of a lithium ion battery assembled with the negative electrode material obtained in example 2.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative and intended to explain the present invention and should not be construed as limiting the present invention.
In one aspect of the present invention, a method of preparing a graphene-based composite material is presented. Referring to fig. 1, the method according to an embodiment of the present invention includes:
s100: mixing manganese salt solution, hydroxide solution and solution containing conductive carbon material to obtain mixed slurry, suction filtering, washing, dispersing in water, and spray drying
Dissolving manganese salt in deionized water to obtain a manganese salt solution, dissolving hydroxide in deionized water to obtain a hydroxide solution, dispersing a conductive carbon material in a solvent to obtain a solution containing the conductive carbon material, slowly introducing the hydroxide solution into the rapidly-stirred manganese salt solution, rapidly adding the solution containing the conductive carbon material into the solution, uniformly mixing to obtain a mixed slurry, rapidly performing suction filtration on the mixed slurry, collecting a solid, washing the separated solid with a washing solution (for example, the washing solution is water and ethanol), dispersing the washed solid in water to form a dispersion liquid, performing spray drying on the dispersion liquid, and collecting a precursor containing manganese hydroxide and the conductive carbon material. The inventor finds that a mixed slurry obtained by mixing a manganese salt solution, a hydroxide solution and a solution containing a conductive carbon material is dispersed in water after suction filtration and washing, then the dispersion liquid is subjected to spray drying, the conductive carbon material forms a three-dimensional network structure among manganese hydroxide particles, and good contact among the manganese hydroxide particles is realized, so that the defects of poor conductivity and the like of an electrode material caused by introducing a transition metal oxide as a negative electrode material are reduced on the premise of realizing high load of subsequent manganese oxide and graphene composite particles, and the obtained electrode material is used as an electron and ion transmission channel in the charging and discharging process, and the rate capability of the electrode material is improved. Wherein, the manganese ion concentration in the manganese salt solution is 0.01-0.5 mol/L, and the manganese salt comprises at least one of manganese acetate, manganese nitrate, manganese chloride and manganese bromide; the concentration of the hydroxide solution is 0.01-0.5 mol/L; hydroxides include sodium hydroxide and potassium hydroxide; the conductive carbon material in the solution containing the conductive carbon material comprises at least one of conductive carbon black, carbon nano tubes, graphene, conductive activated carbon, conductive graphite and carbon nano fibers, the solvent for dispersing the conductive carbon material is at least one of water, ethanol, N-methyl pyrrolidone, dimethyl sulfoxide and isopropanol, and the concentration of the solution containing the conductive carbon material is 0.01-0.5g/L. Furthermore, the mass ratio of the conductive carbon material in the conductive carbon/manganese hydroxide precursor material is 0.5-20%. The inventor finds that the introduction of the carbon material can effectively construct a conductive three-dimensional network structure and further promote the close contact between manganese hydroxide particles, but an excessively high proportion of the carbon material can result in excessively low tap density of a final material and affect the volume energy density of a final battery, and an excessively low proportion of the carbon material can cause electron transport obstacle and affect the capacity exertion of the battery, and the preferable proportion is 3% -10%.
Meanwhile, the concentration of the dispersion liquid is 0.01-1 mol/L, and the spray drying method of the application is a two-fluid spray drying method, atomized slurry shrinks into a sphere by the surface tension of the atomized slurry, water in the slurry is quickly volatilized by hot air, and the fog drops are dried to form spherical powder; wherein the feeding speed is 3-30mL/min, the air inlet temperature of spray drying is 200-300 ℃, the air outlet temperature is controlled at 90-160 ℃, the temperature is adjusted to limit the full drying of the powder, and then the dried agglomerated powder is pumped into a cyclone separator for collection by air draft.
S200: placing the precursor in a high-temperature reactor, continuously heating, introducing protective gas, introducing first gas containing protective gas and hydrogen into the high-temperature reactor after the first preset temperature is reached
In the step, the obtained precursor is placed in a high-temperature reactor to be continuously heated, meanwhile, protective gas is introduced, after the first preset temperature is reached, first gas containing the protective gas and hydrogen is introduced into the high-temperature reactor, and high-valence manganese oxide prepared by side reaction in the precursor preparation process is fully reduced under the action of hydrogen reduction gas, so that manganese oxide containing a conductive carbon material is obtained. The inventor finds that the manganese oxide containing the conductive carbon material obtained by placing the precursor in a high-temperature reactor to perform a reduction reaction in a first gas atmosphere containing a protective gas and hydrogen has excellent graphene catalytic activity, so that graphene with a complete structure is formed in a subsequent deposition process, and the manganese oxide has good electrochemical activity. Further, the temperature rise rate of the high-temperature reactor is 5-20 ℃ per minute, such as 5 ℃ per minute, 6 ℃ per minute 8230, 823019 ℃ per minute and 20 ℃ per minute, and the inventors found that an excessively high temperature rise rate can cause incomplete dehydration of moisture in the carbon-containing precursor material, and an excessively low temperature rise rate can increase the preparation cost of the material, preferably 10-15 ℃ per minute. The adopted protective gas is nitrogen, argon or helium, the first preset temperature is 400-700 ℃, such as 400 ℃, 410 ℃, 8230, 690 ℃, 700 ℃ and the reaction is carried out for 0.5-3 hours at the first preset temperature. The inventors have found that too low a preset temperature may lead to incomplete removal of moisture from the carbonaceous precursor material, and too high a preset temperature may increase the cost of manufacturing the material, preferably 450-500 degrees celsius. In the first gas simultaneously containing the protective gas and the hydrogen, the flow rate of the protective gas is 0.3-10L/min, such as 0.3L/min, 0.4L/min, 8230, 9.9L/min and 10L/min, and the volume ratio of the protective gas to the hydrogen is 1: (0.03-1), for example, 1: (0.03, 0.04 \8230; 0.99, 1). The inventor finds that the volume ratio is too high to realize complete reduction of high-valence manganese oxide, and too low to waste reduction hydrogen and increase material preparation cost, and preferably 1: (0.1-0.3).
S300: putting the manganese oxide containing the conductive carbon material into a high-temperature reactor, continuously heating, introducing protective gas, and introducing second gas containing the protective gas and a carbon source or containing the protective gas and a nitrogen-containing carbon source into the high-temperature reactor after the temperature reaches a second preset temperature
In the step, manganese oxide containing a conductive carbon material is placed in a high-temperature reactor to be continuously heated, meanwhile, protective gas is introduced, and after a second preset temperature is reached, second gas containing protective gas and a carbon source or containing protective gas and a nitrogen-containing carbon source is introduced into the high-temperature reactor, so that graphene or nitrogen-doped graphene is formed on the manganese oxide containing the conductive carbon material through deposition, and the graphene-based composite material is obtained. The inventor finds that graphene or nitrogen-doped graphene is formed on the surface of the manganese oxide template containing the conductive carbon material through deposition, and the graphene-coated manganese oxide graphene-based composite material is obtained, the graphene in the composite material can improve the conductivity of the material and has better elasticity, and the graphene in the negative electrode material prepared from the graphene-based composite material can buffer an electrode in the charging and discharging process, so that the cycle performance and the rate capability of the negative electrode material are improved. Furthermore, the temperature rise rate of the high-temperature reactor in the step is 5-20 ℃ per minute, such as 5 ℃, 6 ℃, 8230; 823019 ℃, 20 ℃ per minute. The adopted protective gas is nitrogen, argon or helium, and the second preset temperature is 700-1000 ℃, such as 700 ℃, 710 ℃, 823080 \8230990 ℃, 990 ℃, 1000 ℃, and the reaction is carried out for 5-60 minutes at the second preset temperature. The inventor finds that too low temperature can lead to insufficient cracking of reaction gas, while too high reaction temperature can lead to insufficient arrangement of cracked carbon atoms on the surface of manganese oxide to form defective graphene, and in addition, high reaction temperature can lead to melting of manganese oxide material to destroy the morphology of the material, preferably 750-900 ℃. Meanwhile, if the second gas contains the protective gas and the carbon source, the flow rate of the protective gas is 0.3-10L/min, such as 0.3L/min, 0.4L/min, 8230, 9.9L/min and 10L/min, and the volume ratio of the protective gas to the carbon source is 1: (0.05 to 1), for example, 1: (0.05, 0.06 \8230; 0.99, 1). The inventor finds that too high proportion can lead to insufficient cracked carbon atoms and can not form high-quality graphene, and too low proportion can lead to the generation of a large amount of cracked carbon atoms in a short time, disturbs the sedimentation of the carbon atoms on the surface of manganese oxide, forms defects, causes the waste of an air source, increases the cost, and the optimized proportion is 1: (0.2-0.8), if the second gas contains the protective gas and the nitrogen-containing carbon source, the flow rate of the protective gas is 0.3-10L/min, such as 0.3L/min, 0.4L/min \8230 \ 8230, 9.9L/min, 10L/min, and the volume ratio of the protective gas to the nitrogen-containing carbon source is 1: (0.05 to 1), for example, 1: (0.05, 0.06 \8230; 0.99, 1). The inventor finds that too high a proportion can lead to insufficient cracked carbon atoms, can't form high quality graphite alkene, and too low a proportion can lead to a large amount of cracked carbon atoms in the short time to generate, disturbs the settlement of carbon atoms on the manganese oxide surface, forms the defect, causes the air supply extravagant simultaneously, increases the cost, and the optimization proportion is 1: (0.2-0.8).
Preferably, the carbon source includes at least one of methane, ethane, propane, butane, ethylene, acetylene, propylene, urea, methanol, ethanol, propylene, acetic acid, and acetone, and the nitrogen-containing carbon source includes at least one of triethanolamine, diethanolamine, hexamethylenetetramine, aniline, N-dimethylformamide, ammonia, melamine, acetonitrile, propionitrile, butyronitrile, ammonia, pyridine, pyrrole, and thiourea.
According to the method for preparing the graphene-based composite material, disclosed by the embodiment of the invention, a mixed slurry obtained by mixing a manganese salt solution, a hydroxide solution and a solution containing a conductive carbon material is subjected to suction filtration and washing, and then is dispersed in water, then the dispersion liquid is subjected to spray drying, the conductive carbon material forms a three-dimensional network structure among manganese hydroxide particles, so that good contact among the manganese hydroxide particles is realized, on the premise of realizing high load of subsequent manganese oxide and graphene composite particles, the defects of poor conductivity and the like of an electrode material caused by introducing a transition metal oxide as a negative electrode material are reduced, the defects are taken as an electron and ion transmission channel in the charging and discharging process, the rate performance of the electrode material is improved, then the obtained precursor containing the manganese hydroxide and the conductive carbon material is placed in a high-temperature reactor to carry out a reduction reaction in a first gas atmosphere containing protective gas and hydrogen, the obtained manganese oxide containing the conductive carbon material has excellent graphene catalytic activity, so that the graphene with a complete structure is formed in the subsequent deposition process, the manganese oxide has good electrochemical activity, and finally the manganese oxide template is placed in a high-temperature reactor to perform a carbon source-containing reaction in a carbon source and protective gas-containing graphene deposition reaction, and a graphene-containing buffer carbon source and a graphene-containing composite material can be formed in the subsequent deposition process, and the graphene-doped graphene composite material can be used for preparing the composite material, and capable of preparing the graphene material with the carbon-containing carbon source and the graphene. The graphene-based composite material is porous, and a battery is assembled by adopting the negative electrode material prepared from the graphene-based composite material, so that the porous structure of the graphene-based composite material is beneficial to the insertion and the separation of lithium ions, and the stress generated in the reaction process can be buffered. When the composite material is applied as a negative electrode material, steps such as acid washing and the like are not needed to remove manganese oxide, so that the prepared negative electrode material simultaneously exerts the advantages of high oxide capacity and good graphene conductivity, the structural defect of a single material is avoided, the electrochemical performance is improved through the synergistic effect of the two, the composite material has extremely high cost performance, and the low-cost large-scale preparation of high-quality graphene is facilitated.
In yet another aspect of the present invention, a graphene-based composite is provided. According to the embodiment of the invention, the graphene-based composite material is prepared by the method. Therefore, the three-dimensional network structure constructed by the carbon material in the composite material can be used as an electron and ion transmission channel in the charge-discharge process, the multiplying power performance of the electrode material is improved, the graphene can improve the conductivity of the material and has better elasticity, the negative electrode material prepared by the graphene-based composite material can buffer the electrode in the charge-discharge process, so that the cycle performance and the multiplying power performance of the negative electrode material are improved, meanwhile, the negative electrode material prepared by the graphene-based composite material is porous, and the porous structure of the negative electrode material is favorable for the embedding and the separation of lithium ions and can buffer the stress generated in the reaction process. It should be noted that the features and advantages described above for the method for preparing the graphene-based composite material are also applicable to the graphene-based composite material, and are not described herein again.
In a third aspect of the invention, a method of making an anode material is presented. According to an embodiment of the invention, the method comprises: mixing the graphene-based composite material with a binder and a conductive agent, and then coating the paste on a copper foil, wherein the graphene-based composite material is the graphene-based composite material obtained by the method or the graphene-based composite material. The inventor finds that the negative electrode material is prepared by mixing the graphene-based composite material with good conductivity and high capacity with a binder, graphite and a conductive agent, a three-dimensional network structure constructed by the carbon material in the composite material can be used as an electron and ion transmission channel in the charge and discharge process, the multiplying power performance of the electrode material is improved, graphene not only can improve the conductivity of the negative electrode material, but also has good elasticity, and the negative electrode material is in the charge and discharge process, wherein the graphene can buffer an electrode, so that the cycle performance and the multiplying power performance of the negative electrode material are improved, and meanwhile, the graphene-based composite material is porous, so that the negative electrode material is adopted to assemble a battery, and the porous structure of the negative electrode material is not only beneficial to the insertion and extraction of lithium ions, but also can buffer stress generated in the reaction process.
Further, the binder comprises at least one of polyvinylidene fluoride, sodium carboxymethylcellulose and polyacrylic acid, the conductive agent comprises at least one of carbon nanotubes, acetylene black and conductive carbon black, and preferably, the mass ratio of the graphene-based composite material, the binder, the graphite and the conductive agent is (80-95): (2-10): (3-10).
The test results show that the negative electrode material is assembled into a lithium battery, the specific mass capacity of the lithium battery reaches 500-750 mAh/g, and the compaction density of a pole piece reaches 2.5-3.2 g/cm 3 The volume energy density is as high as 1200-2000mAh/cm 3 Much higher than commercial graphite (mass specific capacity 310-370 mAh/g, volume specific capacity 248-360 mAh/cm) 3 ) Compared with commercial silicon carbon cathode materials (the specific mass capacity is 580-950 mAh/g, and the specific volume capacity is 348-638 mAh/cm) 3 ). The higher the volumetric capacity, the smaller the battery size. The material has great advantages and competitiveness in the development of small-volume and high-capacity battery application.
It should be noted that the features and advantages described above for the graphene-based composite material and the preparation method thereof are also applicable to the method for preparing the anode material, and are not described herein again.
In a fourth aspect of the invention, an anode material is provided. According to the embodiment of the invention, the negative electrode material is prepared by the method. Therefore, the negative electrode material has excellent conductivity and good elasticity, and in the charging and discharging process of the negative electrode material, the three-dimensional net structure constructed by the carbon material can be used as an electron and ion transmission channel in the charging and discharging process, so that the multiplying power performance of the electrode material is improved, and meanwhile, the graphene can play a buffering role on an electrode, so that the cycle performance and the multiplying power performance of the negative electrode material are improved. It should be noted that the features and advantages described above for the method of preparing the anode material are also applicable to the anode material, and are not described herein again.
In a fifth aspect of the invention, a lithium battery is provided. According to an embodiment of the present invention, the lithium battery has the negative electrode material obtained by the method described above or the negative electrode material described above. Therefore, the lithium battery has long cycle life on the basis of high volume specific capacity. It should be noted that the features and advantages described above for the negative electrode material and the preparation method thereof are also applicable to the lithium battery, and are not described herein again.
In a sixth aspect of the present invention, an automobile is provided. According to an embodiment of the present invention, the automobile has the lithium battery described above. Therefore, the vehicle loaded with the lithium battery with high volume specific capacity and long cycle life has excellent cruising ability, thereby meeting the use requirements of consumers. It should be noted that the features and advantages described above for the lithium battery are also applicable to the vehicle and will not be described in detail here.
The following embodiments of the present invention are described in detail, and it should be noted that the following embodiments are exemplary only, and are not to be construed as limiting the present invention. In addition, all reagents used in the following examples are commercially available or can be synthesized according to methods herein or known, and are readily available to those skilled in the art for reaction conditions not listed, if not explicitly stated.
Example 1
The method for preparing the graphene-based composite material comprises the following steps:
(1) Preparing a precursor: dissolving 9.85g of manganous chloride tetrahydrate in 40mL of deionized water, and uniformly mixing to obtain a manganese salt solution; dissolving 4g of sodium hydroxide in 40mL of deionized water, and uniformly mixing to obtain a sodium hydroxide solution; dispersing 100mg of multi-walled carbon nanotubes in 20mL of isopropanol to form an isopropanol solution containing the multi-walled carbon nanotubes; slowly and uniformly adding a sodium hydroxide solution into a rapidly-stirred manganese salt solution, rapidly adding an isopropanol solution containing multi-walled carbon nanotubes into the mixed solution, and uniformly mixing to obtain a khaki mixed slurry; quickly performing suction filtration and washing on the mixed slurry, collecting the precipitate, and dispersing the precipitate in 100mL of deionized water; after uniform dispersion, carrying out spray drying, wherein the feeding speed is 5mL/min, the air inlet temperature of the spray drying is 260 ℃, the air outlet temperature is controlled at 105 ℃, and then, pumping the dried agglomerated powder into a cyclone separator through air draft for collection;
(2) Reduction of the precursor: placing the obtained precursor in a high-temperature reaction furnace (Hunan morning Xin high-frequency equipment Co., ltd.), heating at a heating rate of 10 ℃/min, uniformly introducing argon gas at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 500 ℃, preserving heat, uniformly introducing hydrogen gas at a flow rate of 0.1L/min, uniformly introducing argon gas at a flow rate of 0.5L/min, and reacting for 2 hours to obtain manganese oxide containing a conductive carbon material;
(3) Preparing graphene: putting manganese oxide containing conductive carbon material in a high temperature reaction furnace (Hunan Xin high frequency equipment Co., ltd.), heating at a heating rate of 10 ℃/min, uniformly introducing argon gas at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 850 ℃, preserving heat, uniformly introducing methane at a flow rate of 0.2L/min, uniformly introducing argon gas at a flow rate of 0.5L/min, and reacting for 30min to obtain the graphene-based composite material.
The method for preparing the anode material comprises the following steps:
and (3) taking the graphene-based composite material obtained in the step (3) as an active substance, mixing conductive carbon black and polyvinylidene fluoride into paste according to a mass ratio of 80.
Example 2
The method of preparing the graphene-based composite material was the same as in example 1;
the method for preparing the anode material comprises the following steps:
and (3) taking the graphene-based composite material obtained in the step (3) as an active material, mixing the active material with conductive carbon black and polyvinylidene fluoride into paste according to a mass ratio of 90.
Example 3
A method of preparing a graphene-based composite;
the steps (1) and (2) are the same as in example 1.
Preparing graphene in step (3): putting manganese oxide containing conductive carbon material in a high temperature reaction furnace (Hunan Xin high frequency equipment Co., ltd.), heating at a heating rate of 10 ℃/min, uniformly introducing argon gas at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 850 ℃, preserving heat, uniformly introducing acetonitrile at a flow rate of 0.2L/min, uniformly introducing argon gas at a flow rate of 0.5L/min, and reacting for 30min to obtain the graphene-based composite material.
The method of preparing the negative electrode material was the same as in example 1.
Example 4
The method of preparing the graphene-based composite material was the same as in example 3.
The method for preparing the anode material comprises the following steps:
and (3) taking the graphene-based composite material obtained in the step (3) as an active material, mixing the active material with conductive carbon black and polyvinylidene fluoride into paste according to a mass ratio of 90.
Example 5
The method for preparing the graphene-based composite material comprises the following steps:
(1) Preparing a precursor: dissolving 3.94g of manganous chloride tetrahydrate in 50mL of deionized water, and uniformly mixing to obtain a manganese salt solution; dissolving 1.6g of sodium hydroxide in 50mL of deionized water, and uniformly mixing to obtain a sodium hydroxide solution; dispersing 50mg of multi-walled carbon nanotubes and 50mg of graphene in 20mL of isopropanol to form an isopropanol solution containing the multi-walled carbon nanotubes and the graphene; slowly and uniformly adding a sodium hydroxide solution into a rapidly-stirred manganese salt solution, rapidly adding an isopropanol solution containing multi-walled carbon nanotubes and graphene into the mixed solution, and uniformly mixing to obtain a mixed slurry; rapidly carrying out suction filtration and washing on the mixed slurry, collecting the precipitate, and dispersing the precipitate in 40mL of deionized water; after uniform dispersion, carrying out spray drying, wherein the feeding speed is 2mL/min, the air inlet temperature of the spray drying is 280 ℃, the air outlet temperature is controlled at 120 ℃, and then sucking the dried agglomerated powder into a cyclone separator through air draft for collection;
(2) Reduction of the precursor: placing the precursor in a high-temperature reaction furnace (Hunan morning central high-frequency equipment Co., ltd.), heating at a heating rate of 10 ℃/min, uniformly introducing argon gas at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 600 ℃, preserving the temperature, uniformly introducing hydrogen gas at a flow rate of 0.2L/min, uniformly introducing argon gas at a flow rate of 0.5L/min, and reacting for 2 hours to obtain manganese oxide containing a conductive carbon material;
(3) Preparing graphene: putting manganese oxide containing conductive carbon material in a high temperature reaction furnace (Hunan Xin high frequency equipment Co., ltd.), heating at a heating rate of 10 ℃/min, uniformly introducing argon gas at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 850 ℃, preserving heat, uniformly introducing methane at a flow rate of 0.4L/min, uniformly introducing argon gas at a flow rate of 0.5L/min, and reacting for 15min to obtain the graphene-based composite material.
The method for preparing the anode material comprises the following steps:
taking the graphene-based composite material obtained in the step (3) as an active substance, and mixing the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 80:10:10, mixing the mixture into paste, and coating the paste on a copper foil to obtain the negative electrode material.
Example 6
The method of preparing the graphene-based composite material was the same as in example 1;
the method for preparing the anode material comprises the following steps:
and (4) taking the graphene-based composite material obtained in the step (3) as an active material, mixing the active material with conductive carbon black and polyvinylidene fluoride into paste according to the mass ratio of 90.
Example 7
The method for preparing the graphene-based composite material comprises the following steps:
(1) Preparing a precursor: dissolving 3.84g of manganous chloride tetrahydrate in 50mL of deionized water, and uniformly mixing to obtain a manganese salt solution; dissolving 1.6g of sodium hydroxide in 50mL of deionized water, and uniformly mixing to obtain a sodium hydroxide solution; dispersing 30mg of multi-walled carbon nanotubes and 20mg of graphene in 20mL of isopropanol to form an isopropanol solution containing the multi-walled carbon nanotubes and the graphene; slowly and uniformly adding a sodium hydroxide solution into a rapidly-stirred manganese salt solution, rapidly adding an isopropanol solution containing multi-walled carbon nanotubes and graphene into the mixed solution, and uniformly mixing to obtain a mixed slurry; rapidly carrying out suction filtration and washing on the mixed slurry, collecting the precipitate, and dispersing the precipitate in 40mL of deionized water; after uniform dispersion, carrying out spray drying, wherein the feeding speed is 2mL/min, the air inlet temperature of the spray drying is 280 ℃, the air outlet temperature is controlled at 120 ℃, and then, pumping the dried agglomerated powder into a cyclone separator through air draft for collection;
(2) Reduction of the precursor: placing the obtained precursor in a high-temperature reaction furnace (Hunan morning Xin high-frequency equipment Co., ltd.), heating at a heating rate of 5 ℃/min, uniformly introducing argon gas at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 600 ℃, preserving heat, uniformly introducing hydrogen gas at a flow rate of 0.2L/min, uniformly introducing argon gas at a flow rate of 0.5L/min, and reacting for 2 hours to obtain manganese oxide containing a conductive carbon material;
(3) Preparing graphene: putting manganese oxide containing conductive carbon material in a high temperature reaction furnace (Hunan Xin high frequency equipment Co., ltd.), heating at a heating rate of 20 ℃/min, uniformly introducing argon gas at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 850 ℃, preserving heat, uniformly introducing acetonitrile at a flow rate of 0.5L/min, uniformly introducing argon gas at a flow rate of 0.5L/min, and reacting for 15min to obtain the graphene-based composite material.
The method for preparing the anode material comprises the following steps:
and (4) taking the graphene-based composite material obtained in the step (3) as an active substance, mixing acetylene black and polyvinylidene fluoride into paste according to the mass ratio of 80.
Example 8
The method for preparing the graphene-based composite material comprises the following steps:
(1) Preparing a precursor: dissolving 7.88g of manganous chloride tetrahydrate in 50mL of deionized water, and uniformly mixing to obtain a manganese salt solution; dissolving 3.2g of sodium hydroxide in 70mL of deionized water, and uniformly mixing to obtain a sodium hydroxide solution; dispersing 60mg of multi-walled carbon nanotubes and 60mg of graphene in 20mL of isopropanol to form an isopropanol solution containing the multi-walled carbon nanotubes and the graphene; slowly and uniformly adding a sodium hydroxide solution into a rapidly-stirred manganese salt solution, rapidly adding an isopropanol solution containing multi-walled carbon nanotubes and graphene into the mixed solution, and uniformly mixing to obtain a mixed slurry; quickly performing suction filtration and washing on the mixed slurry, collecting the precipitate, and dispersing the precipitate in 40mL of deionized water; after uniform dispersion, carrying out spray drying, wherein the feeding speed is 2mL/min, the air inlet temperature of the spray drying is 260 ℃, the air outlet temperature is controlled at 120 ℃, and then sucking the dried agglomerated powder into a cyclone separator through air draft for collection;
(2) Reduction of the precursor: placing the obtained precursor in a high-temperature reaction furnace (Hunan morning Xin high-frequency equipment Co., ltd.), heating at a heating rate of 10 ℃/min, uniformly introducing argon at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 600 ℃, preserving heat, uniformly introducing hydrogen at a flow rate of 0.2L/min, uniformly introducing argon at a flow rate of 0.5L/min, and reacting for 2 hours to obtain manganese oxide containing a conductive carbon material;
(3) Preparing graphene: the manganese oxide containing the conductive carbon material is placed in a high temperature reaction furnace (Hunan Xin high frequency equipment Co., ltd.), the temperature is raised at the rate of 5 ℃/min, meanwhile, argon gas is uniformly introduced at the flow rate of 0.5L/min in the temperature raising process, the temperature is kept after the temperature is raised to the reaction temperature of 900 ℃, simultaneously, methane is uniformly introduced at the flow rate of 0.5L/min, argon gas is uniformly introduced at the flow rate of 0.5L/min, and the graphene-based composite material is obtained after the reaction is carried out for 15 min.
The method for preparing the anode material comprises the following steps:
and (4) taking the graphene-based composite material obtained in the step (3) as an active substance, mixing the active substance with acetylene black and polyvinylidene fluoride into paste according to the mass ratio of 80.
Example 9
The method for preparing the graphene-based composite material comprises the following steps:
(1) Preparing a precursor: dissolving 3.94g of manganous chloride tetrahydrate in 50mL of deionized water, and uniformly mixing to obtain a manganese salt solution; dissolving 1.6g of sodium hydroxide in 50mL of deionized water, and uniformly mixing to obtain a sodium hydroxide solution; dispersing 50mg of multi-walled carbon nanotubes and 50mg of graphene in 20mL of isopropanol to form an isopropanol solution containing the multi-walled carbon nanotubes and the graphene; slowly and uniformly adding a sodium hydroxide solution into a rapidly-stirred manganese salt solution, rapidly adding an isopropanol solution containing multi-walled carbon nanotubes and graphene into the mixed solution, and uniformly mixing to obtain a mixed slurry; rapidly carrying out suction filtration and washing on the mixed slurry, collecting the precipitate, and dispersing the precipitate in 40mL of deionized water; after uniform dispersion, carrying out spray drying, wherein the feeding speed is 2mL/min, the air inlet temperature of the spray drying is 280 ℃, the air outlet temperature is controlled at 120 ℃, and then sucking the dried agglomerated powder into a cyclone separator through air draft for collection;
(2) Reduction of the precursor: placing the obtained precursor in a high-temperature reaction furnace (Hunan morning Xin high-frequency equipment Co., ltd.), heating at a heating rate of 8 ℃/min, uniformly introducing argon gas at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 600 ℃, preserving heat, uniformly introducing hydrogen gas at a flow rate of 0.2L/min, uniformly introducing argon gas at a flow rate of 0.5L/min, and reacting for 2 hours to obtain manganese oxide containing a conductive carbon material;
(3) Preparing graphene: putting manganese oxide containing conductive carbon material in a high temperature reaction furnace (Hunan Xin high frequency equipment Co., ltd.), heating at a heating rate of 11 ℃/min, uniformly introducing argon gas at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 1000 ℃, preserving heat, uniformly introducing argon gas at a flow rate of 0.5L/min, uniformly introducing acetonitrile at a flow rate of 0.3L/min, and reacting for 15min to obtain the graphene-based composite material.
The method for preparing the anode material comprises the following steps:
and (3) taking the graphene-based composite material obtained in the step (3) as an active material, mixing the active material with acetylene black and polyvinylidene fluoride into paste according to a mass ratio of 80.
Example 10
The method for preparing the graphene-based composite material comprises the following steps:
(1) Preparing a precursor: dissolving 3.94g of manganous chloride tetrahydrate in 50mL of deionized water, and uniformly mixing to obtain a manganese salt solution; dissolving 1.6g of sodium hydroxide in 50mL of deionized water, and uniformly mixing to obtain a sodium hydroxide solution; dispersing 40mg of multi-walled carbon nanotubes and 40mg of graphene in 20mL of isopropanol to form an isopropanol solution containing the multi-walled carbon nanotubes and the graphene; slowly and uniformly adding a sodium hydroxide solution into a rapidly-stirred manganese salt solution, rapidly adding an isopropanol solution containing multi-walled carbon nanotubes and graphene into the mixed solution, and uniformly mixing to obtain a mixed slurry; quickly performing suction filtration and washing on the mixed slurry, collecting the precipitate, and dispersing the precipitate in 40mL of deionized water; after uniform dispersion, carrying out spray drying, wherein the feeding speed is 2mL/min, the air inlet temperature of the spray drying is 280 ℃, the air outlet temperature is controlled at 120 ℃, and then sucking the dried agglomerated powder into a cyclone separator through air draft for collection;
(2) Reduction of the precursor: placing the obtained precursor in a high-temperature reaction furnace (Hunan morning Xin high-frequency equipment Co., ltd.), heating at a heating rate of 8 ℃/min, uniformly introducing argon gas at a flow rate of 0.5L/min in the heating process, heating to a reaction temperature of 600 ℃, preserving heat, uniformly introducing hydrogen gas at a flow rate of 0.2L/min, uniformly introducing argon gas at a flow rate of 0.5L/min, and reacting for 2 hours to obtain manganese oxide containing a conductive carbon material;
(3) Preparing graphene: the manganese oxide containing the conductive carbon material is placed in a high temperature reaction furnace (Hunan Xin high frequency equipment Co., ltd.), the temperature is raised at the rate of 11 ℃/min, meanwhile, argon gas is uniformly introduced at the flow rate of 0.5L/min in the temperature raising process, the temperature is kept after the temperature is raised to the reaction temperature of 900 ℃, the argon gas is uniformly introduced at the flow rate of 0.5L/min, pyridine is uniformly introduced at the flow rate of 0.4L/min, and the graphene-based composite material is obtained after the reaction is carried out for 10 min.
The method for preparing the anode material comprises the following steps:
and (3) taking the graphene-based composite material obtained in the step (3) as an active material, mixing the active material with acetylene black and polyvinylidene fluoride into paste according to a mass ratio of 80.
Comparative example 1
The method for preparing the graphene-based composite material is the same as in example 1, except that the precursor is prepared in step (1): dissolving 9.85g of manganous chloride tetrahydrate in 40mL of deionized water, and uniformly mixing to obtain a manganese salt solution; dissolving 4g of sodium hydroxide in 40mL of deionized water, and uniformly mixing to obtain a sodium hydroxide solution; slowly and uniformly adding a sodium hydroxide solution into a rapidly stirred manganese salt solution, and uniformly mixing to obtain a khaki mixed slurry; quickly performing suction filtration and washing on the mixed slurry, collecting the precipitate, and dispersing the precipitate in 100mL of deionized water; after uniform dispersion, carrying out spray drying, wherein the feeding speed is 5mL/min, the air inlet temperature of the spray drying is 260 ℃, the air outlet temperature is controlled at 105 ℃, and then, pumping the dried agglomerated powder into a cyclone separator through air draft for collection;
the method of preparing the anode material was the same as in example 1.
Comparative example 2
The method of preparing the graphene-based composite material is the same as example 1 except for removing step (3).
The method of preparing the anode material was the same as in example 1.
The method for preparing the anode material comprises the following steps: the same as in example 10.
Evaluation:
1. respectively representing the surface morphology and the structure of the precursor containing the manganese hydroxide and the conductive carbon material, the manganese oxide containing the conductive carbon material and the graphene-based composite material obtained in the examples 1-10 and the comparative examples 1-2 and the electrochemical performance of the button cell prepared by the precursor;
2. the test method comprises the following steps:
and (3) morphological observation: observing the surface morphology of the precursor containing the manganese hydroxide and the conductive carbon material and the graphene-based composite material by a scanning electron microscope (S-4800, hitachi, japan);
electrochemical performance: and (3) carrying out vacuum drying on the copper foil coated with the slurry for 8-15 h at 100 ℃, and carrying out rolling compaction and sheet shearing to prepare the negative plate. A button cell was assembled in an argon-filled glove box with 1mol/L electrolyte of LiPF6 (dimethyl carbonate (DMC): ethylene Carbonate (EC) =1, volume ratio), a diaphragm of Celgard2400 monolayer polypropylene film (PP), and a metallic lithium sheet as a counter electrode (CR 2025). And (3) using a battery test system (LAND CT2100A 5V/10 mA) to test the charge-discharge cycle performance and the multiplying power performance of the button battery, wherein the voltage is 0.01-3V. Electrochemical performances of button cells assembled by the negative electrode materials of examples 1-10 and comparative examples 1-4 are shown in table 1:
TABLE 1 electrochemical performance of assembled button cells assembled from examples 1-10 and comparative examples 1-4 negative electrode materials
Figure BDA0002397413670000161
Figure BDA0002397413670000171
Morphological and structural experimental analysis: fig. 2 is an SEM image of the precursor containing manganese hydroxide and the conductive carbon material obtained in example 1, and it can be seen from fig. 2 that the precursor particles obtained in example 1 have complete morphology and uniform particle size distribution, and the precursor particles having complete morphology and uniform particle size distribution can also be seen from the SEM images of the precursors containing manganese hydroxide and the conductive carbon material obtained in examples 3 to 10, which indicates that the "spray drying" technique of the present application can prepare precursor particles having complete morphology and uniform particle size distribution; and SEM images of the graphene-based composite materials obtained in examples 1 to 10 can see that the graphene-based composite materials maintain the particle integrity and are porous materials.
And (3) analyzing electrochemical properties: FIG. 3 is a charge-discharge curve diagram of a lithium ion battery assembled with the negative electrode material obtained in example 1, table 1 shows data of specific mass capacity and specific volume capacity of the negative electrode materials obtained in examples 1-10 and comparative examples 1-2, and the specific mass capacity and specific volume capacity of the lithium battery assembled with the negative electrode materials obtained in examples 1-10 are much higher than those of commercial graphite (specific mass capacity of 310-370 mAh/g, and specific volume capacity of 248-360 mAh/cm) 3 ) Compared with commercial silicon carbon cathode materials (the specific mass capacity is 580-950 mAh/g, and the specific volume capacity is 348-638 mAh/cm) 3 ). Compared with the battery with the same energy density, the battery using the graphene-based composite material as the negative electrode can be greatly reduced in volume. The preparation technology of the graphene-based composite material is beneficial to promoting the development of the lithium battery industry, has quite strong competitiveness in developing small-volume and high-capacity batteries, is simple and safe in preparation process, is green and pollution-free, can promote the industrialization of the graphene-based negative electrode material, and brings considerable economic benefits. Meanwhile, the volume specific capacity and the mass specific capacity of the lithium battery assembled by the negative electrode materials obtained in the examples 1 to 10 are higher than those of the lithium batteries corresponding to the negative electrode materials of the comparative examples 1 to 4, which shows that the negative electrode materials with excellent electrochemical performance can be obtained by adopting the method.
In the description of the specification, reference to the description of "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are exemplary and not to be construed as limiting the present invention, and that changes, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (25)

1. A method of preparing a graphene-based composite, comprising:
(1) Mixing a manganese salt solution, a hydroxide solution and a solution containing a conductive carbon material to obtain a mixed slurry, carrying out suction filtration and washing on the mixed slurry, dispersing the washed mixed slurry in water, and then carrying out spray drying on the dispersion liquid to obtain a precursor containing manganese hydroxide and the conductive carbon material;
(2) Placing the precursor in a high-temperature reactor, continuously heating, introducing protective gas, and introducing first gas containing protective gas and hydrogen into the high-temperature reactor after the temperature of the precursor reaches a first preset temperature so as to obtain manganese oxide containing a conductive carbon material;
(3) Placing the manganese oxide containing the conductive carbon material in a high-temperature reactor, continuously heating, simultaneously introducing the protective gas, introducing a second gas containing the protective gas and a carbon source or containing the protective gas and a nitrogen-containing carbon source into the high-temperature reactor after reaching a second preset temperature so as to obtain graphene or nitrogen-doped graphene deposited on the manganese oxide containing the conductive carbon material to obtain the graphene-based composite material,
in the step (1), the mass ratio of the conductive carbon material in the precursor is 0.5-20%;
in the step (2), the heating rate is 5-20 ℃ per minute;
in the step (2), the first preset temperature is 400-700 ℃;
in the step (2), in the first gas containing the shielding gas and the hydrogen, the volume ratio of the shielding gas to the hydrogen is 1: (0.03-1);
in the step (3), the second preset temperature is 700-1000 ℃;
in the step (3), the second gas contains a protective gas and a carbon source, and the volume ratio of the protective gas to the carbon source is 1: (0.05-1);
in the step (3), the second gas contains a protective gas and a nitrogen-containing carbon source, and the volume ratio of the protective gas to the nitrogen-containing carbon source is 1: (0.05-1);
in step (3), the carbon source comprises at least one of methane, ethane, propane, butane, ethylene, acetylene, methanol, ethanol, propylene, acetic acid, and acetone;
in the step (3), the nitrogen-containing carbon source includes at least one of triethanolamine, diethanolamine, hexamethylenetetramine, aniline, N-dimethylformamide, melamine, acetonitrile, propionitrile, butyronitrile, pyridine, pyrrole, and thiourea.
2. The method according to claim 1, wherein in the step (1), the manganese ion concentration in the manganese salt solution is 0.01 to 0.5mol/L.
3. The method of claim 2, wherein in step (1), the manganese salt solution comprises at least one of manganese acetate, manganese nitrate, manganese chloride, and manganese bromide.
4. The method according to claim 1, wherein in the step (1), the concentration of hydroxide ions in the hydroxide solution is 0.01 to 1.0mol/L.
5. The method according to claim 4, wherein in the step (1), the hydroxide solution contains at least one of sodium hydroxide and potassium hydroxide.
6. The method of claim 1, wherein in step (1), the solution containing conductive carbon material comprises at least one of conductive carbon black, carbon nanotubes, graphene, conductive activated carbon, conductive graphite, and carbon nanofibers.
7. The method according to claim 6, wherein in the step (1), the concentration of the solution containing the conductive carbon material is 0.01 to 0.5g/L.
8. The method according to claim 1, wherein in the step (1), the concentration of the dispersion is 0.01 to 1mol/L.
9. The method according to claim 1, wherein in the step (1), the feeding speed of the spray drying process is 3-30mL/min, the inlet air temperature is 200-300 ℃, and the outlet air temperature is 90-160 ℃.
10. The method according to claim 1 or 2, wherein in step (2), the shielding gas is nitrogen, argon or helium.
11. The method according to claim 1, wherein in the step (2), the first predetermined temperature is reacted for 0.5 to 3 hours.
12. The method according to claim 1, wherein in the step (2), the flow rate of the shielding gas in the first gas containing the shielding gas and hydrogen is 0.3 to 10L/min.
13. The method according to claim 1, wherein in the step (3), the temperature increase rate is 5 to 20 degrees Celsius per minute.
14. The method of claim 1, wherein in step (3), the shielding gas is nitrogen, argon or helium.
15. The method according to claim 1, wherein in step (3), the reaction is carried out at the second predetermined temperature for 5 to 60 minutes.
16. The method according to claim 1, wherein in the step (3), the second gas contains a shielding gas and a carbon source, and the flow rate of the shielding gas is 0.3 to 10L/min.
17. The method according to claim 1, wherein in the step (3), the second gas contains a protective gas and a nitrogen-containing carbon source, and the flow rate of the protective gas is 0.3 to 10L/min.
18. A graphene-based composite material, wherein the graphene-based composite material is prepared by the method of any one of claims 1-17.
19. A method for preparing a negative electrode material, characterized by mixing a graphene-based composite material with a binder and a conductive agent, and then coating a paste on a copper foil, wherein the graphene-based composite material is the graphene-based composite material obtained by the method according to any one of claims 1 to 17 or the graphene-based composite material according to claim 18.
20. The method of claim 19, wherein the binder comprises at least one of polyvinylidene fluoride, sodium carboxymethylcellulose, and polyacrylic acid.
21. The method of claim 19, wherein the conductive agent comprises at least one of carbon nanotubes, acetylene black, and conductive carbon black.
22. The method according to claim 19, wherein the mass ratio of the graphene-based composite material to the binder to the conductive agent is (80-95): (2-10): (3-10).
23. A negative electrode material, characterized in that it is prepared by the method of any one of claims 19 to 22.
24. A lithium battery having the negative electrode material obtained by the method of any one of claims 19 to 22 or using the negative electrode material of claim 23.
25. An automobile having the lithium battery of claim 24.
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