CN111547710B - 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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CN111547710B
CN111547710B CN202010261182.3A CN202010261182A CN111547710B CN 111547710 B CN111547710 B CN 111547710B CN 202010261182 A CN202010261182 A CN 202010261182A CN 111547710 B CN111547710 B CN 111547710B
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graphene
manganese
based composite
temperature
composite material
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CN111547710A (en
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刘芳芳
高学森
张勃
李建刚
刘婷婷
李金来
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Inner Mongolia Xinminhui Nanotechnology Co ltd
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Enn Inner Mongolia Graphene Materials Co ltd
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
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    • H01—ELECTRIC ELEMENTS
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    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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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 manganese salt, urea and diethylene glycol containing PVP to obtain a mixed solution, supplying the mixed solution into a reaction kettle for hydrothermal reaction, and sequentially filtering, washing, drying and calcining the obtained reaction product to obtain a manganese-based oxide; (2) placing the manganese-based oxide 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 reaches a first preset temperature so as to obtain a manganese oxide template; (3) and placing the manganese oxide template in a high-temperature reactor, continuously heating, introducing the protective gas, introducing a 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 after the temperature reaches a second preset temperature, so that the manganese oxide template is deposited to form graphene or nitrogen-doped graphene, and the graphene-based composite material is obtained.

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
As a new national strategic industry, the graphene industry has a huge application prospect in the fields of new energy, chemical industry, electronic information, biomedicine and the like, and plays an important role in the revolution of new industry and innovation-driven development in China. The graphene has the excellent characteristics of high electron mobility, high strength, good electrical conductivity/thermal conductivity, high light transmittance, small mass and the like, and is expected to initiate the revolution of related industries in the traditional fields and emerging fields of new energy, petrochemical industry, electronic information, composite materials, biomedicine, wearable equipment, energy conservation, environmental protection and the like.
The existing graphene-based composite material has the following problems:
(1) graphene oxide functional group defects: in most methods for preparing graphene composite materials, the used graphene is obtained by reducing graphene oxide, some oxygen-containing functional groups are inevitably introduced, the reaction temperature in some composite material synthesis methods is low, the oxygen-containing functional groups are difficult to decompose, and the residual oxygen-containing functional groups react with electrolyte in the battery circulation process, so that the first effect of the battery is reduced, the battery circulation life is influenced, and potential safety hazards are brought.
(2) Insufficient transition metal oxide properties: 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.
(3) Preparing graphene in 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.
Therefore, the existing technology for preparing graphene-based composite materials is in need of improvement.
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 manganese salt, urea and diethylene glycol containing PVP, supplying the mixture to a hydrothermal reaction kettle, and sequentially filtering, washing, drying and calcining the obtained reaction product to obtain manganese-based oxide;
(2) placing the manganese-based oxide 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 reaches a first preset temperature so as to obtain a manganese oxide template;
(3) and placing the manganese oxide template in a high-temperature reactor, continuously heating, introducing the protective gas, introducing a 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 after the temperature reaches a second preset temperature, so that the manganese oxide template is deposited to form graphene or nitrogen-doped graphene, and the graphene-based composite material is obtained.
According to the method for preparing the graphene-based composite material, manganese salt, urea and diethylene glycol containing PVP are mixed and then are supplied to a hydrothermal reaction kettle for hydrothermal reaction, manganese-based oxide particles with a regular structure, high crystallinity and high surface activity can be prepared, then the manganese-based oxide particles are placed in a high-temperature reactor for reduction reaction in a first gas atmosphere containing protective gas and hydrogen, the obtained manganese oxide template not only has excellent graphene catalytic activity, but also has good electrochemical activity, the manganese oxide can also improve the tap density of the subsequent graphene-based composite material, finally the manganese oxide template is placed in a high-temperature reactor for deposition reaction in a second gas atmosphere containing protective gas and carbon source or protective gas, carbon source and nitrogen source, and graphene or nitrogen-doped graphene is deposited on the surface of the manganese oxide template, the graphene in the graphene-based composite material can improve the conductivity of the material and has better elasticity, the graphene in the negative electrode material prepared by 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, meanwhile, because the graphene-based composite material is porous, the negative electrode material prepared by the graphene-based composite material is assembled into a battery, the porous structure of the graphene-based composite 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, and in addition, when the composite material is applied as the negative electrode material, the manganese oxide does not need to be removed through the steps of acid washing and the like, so that the prepared negative electrode material simultaneously plays the advantages of high oxide capacity and good conductivity of the graphene, and avoids the defects of a single material structure, the electrochemical performance is improved through the synergistic effect of the graphene and the graphene, the cost performance is extremely high, 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 present invention may further have the following additional technical features:
in some embodiments of the invention, in the step (1), the concentration of manganese ions in the mixed solution is 0.01-0.5 mol/L.
In some embodiments of the invention, in step (1), the manganese salt comprises at least one of manganese acetate, manganese nitrate, manganese chloride, and manganese bromide.
In some embodiments of the invention, in the step (1), the concentration of urea in the mixed solution is 0.01-0.5 mol/L.
In some embodiments of the invention, in step (1), the PVP has a molecular weight of 40000-65000.
In some embodiments of the invention, in step (1), the concentration of the PVP-containing diethylene glycol is 0.01-0.3 g/mL.
In some embodiments of the invention, in step (1), the mass ratio of the manganese salt, the urea and the PVP is (1-5):1 (1-15).
In some embodiments of the present invention, in the step (1), the temperature of the hydrothermal reaction is 150 to 250 ℃, the pressure is 0.5 to 3MPa, the rotation speed is 0 to 300rpm, and the reaction time is 1 to 40 hours.
In some embodiments of the invention, the temperature rise rate in the calcination process is 3-15 ℃ per minute, the calcination temperature is 400-900 ℃ and the time is 1-8 hours.
In some embodiments of the present invention, in the step (2), the temperature rise rate is 5 to 15 degrees Celsius/min.
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 800 degrees celsius, and the reaction is performed at the first predetermined temperature for 0.5 to 5 hours.
In some embodiments of the present 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 to 1).
In some embodiments of the present invention, in the step (3), the temperature rise rate is 5 to 15 degrees Celsius/min.
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 600 to 1200 degrees celsius, and the reaction is performed at the second predetermined temperature for 5 to 60 minutes.
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 carbon source is 0.3-10L/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, the carbon source and the nitrogen source is 0.3-10L/min, and the volume ratio of the protective gas to the carbon source to the nitrogen source is 1: (0.05-1): (0.03-1);
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 invention, in step (3), the nitrogen source comprises at least one of triethanolamine, diethanolamine, hexamethylenetetramine, aniline, N-dimethylformamide, ammonia, melamine, acetonitrile, propionitrile, butyronitrile, ammonia, 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 graphene in the composite material can not only improve the conductivity of the material, but also has better elasticity, the negative electrode material prepared by the graphene-based composite material can buffer an electrode in the charging and discharging process, so as to improve the cycle performance and the rate capability of the negative electrode material, meanwhile, because the graphene-based composite material is porous, the negative electrode material prepared by the graphene-based composite material is assembled into a battery, the porous structure of the battery is not only beneficial to the insertion and the separation of lithium ions, but also can buffer the stress generated in the reaction process, in addition, when the composite material is applied as the negative electrode material, the manganese oxide is not required to be removed through the steps of acid washing and the like, so that the prepared negative electrode material simultaneously exerts the advantages of high oxide capacity and good conductivity of the graphene, the structural defect of a single material is avoided, and the electrochemical performance is improved through the synergistic effect of the two, the method has extremely high cost performance, and is favorable for realizing low-cost large-scale preparation of high-quality graphene.
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.
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, graphene in the composite material can improve the conductivity of the negative electrode material and has good elasticity, and the graphene can play a buffering role on an electrode in the charging and discharging process of the negative electrode material, so that the cycle performance and the rate capability of the negative electrode material are improved.
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 (5-95): (1-10): (0-10).
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 graphene in the negative electrode 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.
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 manganese-based oxide particles obtained in example 1;
FIG. 3 is an SEM photograph of manganese-based oxide particles obtained in example 4;
fig. 4 is an SEM image of the graphene-based composite material obtained in example 1;
fig. 5 is an SEM image of the graphene-based composite material obtained in example 4;
fig. 6 is a raman chart of the graphene-based composite obtained in example 3;
fig. 7 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 drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In one aspect of the present invention, a method of preparing a graphene-based composite is presented. Referring to fig. 1, the method according to an embodiment of the present invention includes:
s100: mixing manganese salt, urea and diethylene glycol containing PVP, supplying the mixture into a hydrothermal reaction kettle, and sequentially filtering, washing, drying and calcining the obtained reaction product
In this step, PVP is first added to diethylene glycol and uniformly mixed to obtain diethylene glycol containing PVP, manganese salt is then added to diethylene glycol containing PVP and uniformly mixed, urea is then added to the solution with stirring and uniformly mixed, the obtained mixed solution is transferred to a reaction kettle to undergo a hydrothermal reaction, after the reaction is completed, the obtained reaction product is filtered, a solid is collected, the separated solid is washed with a washing solution (for example, water and ethanol as a washing agent), and the washed solid is then sequentially dried and calcined to obtain a manganese-based oxide. Wherein the concentration of manganese ions in the mixed 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 urea in the mixed solution is 0.01-0.5 mol/L; the molecular weight of PVP is 40000-65000, and the concentration of diethylene glycol containing PVP is 0.01-0.3 g/mL; the mass ratio of the manganese salt to the urea to the PVP is (1-5) to 1 (1-15). The inventors found that this mixing ratio not only facilitates the formation of the precipitated particles, but also the resultant manganese-based oxide particles have a dense structure. Further, the temperature of the hydrothermal reaction is 150-250 ℃, the pressure is 0.5-3 MPa, the rotating speed is 0-300 rpm, the reaction time is 1-40 hours, the drying temperature is 50-100 ℃, the drying time is 1-24 hours, the heating rate of the calcining process is 3-15 ℃ per minute, in addition, the equipment for calcining comprises at least one of a microwave high-temperature furnace, a high-temperature carbonization furnace, a medium-frequency induction high-temperature furnace and a muffle furnace, the calcining temperature is 400-900 ℃, and the time is 1-8 hours. The inventors have found that if the temperature increase rate is too high, the manganese-based oxide surface particle size becomes too large and the structure collapses, and if the temperature increase rate is too low, the production cycle is prolonged and the yield is lowered.
S200: putting the manganese-based oxide into a high-temperature reactor, continuously heating, introducing protective gas, introducing first gas containing protective gas and hydrogen into the high-temperature reactor after the temperature reaches a first preset temperature
In the step, the obtained manganese-based oxide 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 protective gas and hydrogen is introduced into the high-temperature reactor, and the manganese-based oxide is reduced to obtain a manganese oxide template. The inventors found that by placing the manganese-based oxide in a high-temperature reactor to perform a reduction reaction in a first gas atmosphere containing a protective gas and hydrogen, the obtained manganese oxide template not only has excellent graphene catalytic activity, but also has good electrochemical activity, and the manganese oxide can also improve the tap density of a subsequent graphene-based composite material. Further, the temperature rise rate of the high temperature reactor is 5-15 degrees centigrade per minute, such as 5 degrees centigrade per minute, 6 degrees centigrade per minute … … 14 degrees centigrade per minute, 15 degrees centigrade per minute, and the inventors found that if the temperature rise rate is too fast, the defects of the manganese oxide particle structure increase, and if the temperature rise rate is too low, the yield decreases. The adopted protective gas is nitrogen, argon or helium, the first preset temperature is 400-800 ℃, such as 400 ℃, 410 ℃, … … 790 ℃ and 800 ℃, the reaction is carried out for 0.5-5 hours at the first preset temperature, the flow of the protective gas in the first gas containing the protective gas and hydrogen is 0.3-10L/min, such as 0.3L/min, 0.4L/min … … 9.9.9L/min and 10L/min, and the volume ratio of the protective gas to the hydrogen is 1: (0.03 to 1), for example, 1: (0.03, 0.04 … … 0.99.99, 1). The inventors have found that if the first predetermined temperature is too low and the volume ratio of the shielding gas and hydrogen is too low, incomplete reduction may result, and if the first predetermined temperature is too high, melting of the manganese oxide particles may result.
S300: putting the manganese oxide template in a high-temperature reactor for continuous heating, simultaneously introducing protective gas, and after reaching a second preset temperature, introducing second gas containing protective gas and carbon source or containing protective gas, carbon source and nitrogen source into the high-temperature reactor
In the step, the obtained manganese oxide template 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, a carbon source and a nitrogen source is introduced into the high-temperature reactor so as to deposit on the manganese oxide template to form graphene or nitrogen-doped graphene, 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 through deposition, so that the graphene-based composite material of graphene-coated manganese oxide is obtained, the graphene in the composite material can not only improve the conductivity of the material, but also has better elasticity, the graphene in the negative electrode material prepared by the graphene-based composite material can play a role in buffering an electrode in the charging and discharging processes, so that the cycle performance and the rate capability of the negative electrode are improved, meanwhile, because the graphene-based composite material is porous, the negative electrode material prepared by the graphene-based composite material is assembled into a battery, the porous structure of the negative electrode material is not only favorable for the insertion and the extraction of lithium ions, but also can buffer stress generated in the reaction process, and in addition, when the composite material is used as the negative electrode material, the manganese oxide does not need to be removed through steps of acid washing and the like, so that the prepared negative electrode material can simultaneously play the advantages of high oxide capacity and good graphene conductivity, the defect of a single material structure is avoided, the electrochemical performance is improved through the synergistic effect of the two materials, the cost performance is extremely high, and the low-cost large-scale preparation of high-quality graphene is facilitated. Further, the temperature rise rate of the high-temperature reactor in this step is 5-15 degrees centigrade per minute, for example, 5 degrees centigrade per minute, 6 degrees centigrade per minute … … 14 degrees centigrade per minute, 15 degrees centigrade per minute, and the inventors found that if the temperature rise rate is too fast, the defects of the manganese oxide particle structure increase, and if the temperature rise rate is too low, the yield decreases. The adopted protective gas is nitrogen, argon or helium, the second preset temperature is 600-1200 ℃, for example 600 ℃, 610 ℃, … … 1190, 1190 ℃ and 1200 ℃, and the reaction is carried out for 5-60 minutes at the second preset temperature. The inventors found that if the second predetermined temperature is too high, the manganese oxide structure is damaged, a melting phenomenon occurs, and thus the graphene defect is large, and if the second predetermined temperature is too low, the reaction rate is too slow, and the yield is reduced. Meanwhile, the second gas contains protective gas and a carbon source, the flow rate of the protective gas is 0.3-10L/min, such as 0.3L/min, 0.4L/min … … 9.9.9L/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 … … 0.99.99, 1), and if the second gas contains a shielding gas, a carbon source and a nitrogen source, the flow rate of the shielding gas is 0.3-10L/min, such as 0.3L/min, 0.4L/min … … 9.9.9L/min, 10L/min, and the volume ratio of the shielding gas to the carbon source to the nitrogen source is 1: (0.05-1): (0.03 to 1). The inventor finds that if the volume ratio of the protective gas to the carbon source or the protective gas to the carbon source and the nitrogen source is too high, manganese oxide particles are fused, and the quality of deposited graphene is low, and if the volume ratio of the protective gas to the carbon source or the protective gas to the nitrogen source is too low, carbon is deposited too much in the initial stage, the activity of manganese oxide is affected, and the defects of the obtained negative electrode material are increased.
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 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, manganese salt, urea and diethylene glycol containing PVP are mixed and then are supplied to a hydrothermal reaction kettle for hydrothermal reaction, manganese-based oxide particles with regular structure, high crystallinity and high surface activity can be prepared, then the manganese-based oxide particles are placed in a high-temperature reactor for reduction reaction in a first gas atmosphere containing protective gas and hydrogen, the obtained manganese oxide template not only has excellent graphene catalytic activity, but also has good electrochemical activity, the tap density of the subsequent graphene-based composite material can be improved by the manganese oxide, finally the manganese oxide template is placed in a high-temperature reactor for deposition reaction in a second gas atmosphere containing protective gas and carbon source or protective gas, carbon source and nitrogen source, graphene or nitrogen-doped graphene is formed on the surface of the manganese oxide template through deposition, the graphene in the graphene-based composite material can improve the conductivity of the material and has better elasticity, the graphene in the negative electrode material prepared by 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, meanwhile, because the graphene-based composite material is porous, the negative electrode material prepared by the graphene-based composite material is assembled into a battery, the porous structure of the graphene-based composite 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, and in addition, when the composite material is applied as the negative electrode material, the manganese oxide does not need to be removed through the steps of acid washing and the like, so that the prepared negative electrode material simultaneously plays the advantages of high oxide capacity and good conductivity of the graphene, and avoids the defects of a single material structure, the electrochemical performance is improved through the synergistic effect of the graphene and the graphene, the cost performance is extremely high, 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 graphene in the composite material can not only improve the conductivity of the material, but also has better elasticity, the negative electrode material prepared by the graphene-based composite material can buffer an electrode in the charging and discharging process, so as to improve the cycle performance and the rate capability of the negative electrode material, meanwhile, because the graphene-based composite material is porous, the negative electrode material prepared by the graphene-based composite material is assembled into a battery, the porous structure of the battery is not only beneficial to the insertion and the separation of lithium ions, but also can buffer the stress generated in the reaction process, in addition, when the composite material is applied as the negative electrode material, the manganese oxide is not required to be removed through the steps of acid washing and the like, so that the prepared negative electrode material simultaneously exerts the advantages of high oxide capacity and good conductivity of the graphene, the structural defect of a single material is avoided, and the electrochemical performance is improved through the synergistic effect of the two, the method has extremely high cost performance, and is favorable for realizing low-cost large-scale preparation of high-quality graphene. 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 provided. According to an embodiment of the invention, the method comprises: mixing the graphene-based composite material with a binder, graphite 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 graphene-based composite material with good conductivity and high capacity is mixed with the binder, the graphite and the conductive agent to prepare the negative electrode material, the graphene in the composite material can improve the conductivity of the negative electrode material and has good elasticity, and the graphene in the negative electrode material can play a role in buffering an electrode in the charging and discharging process, so that the cycle performance and the rate capability of the negative electrode material are improved, and meanwhile, the porous structure of the graphene-based composite material is favorable for the insertion and the extraction of lithium ions and can also buffer stress generated in the reaction process.
Further, the binder comprises at least one of polyvinylidene fluoride, sodium carboxymethylcellulose and polyacrylic acid, the graphite comprises artificial high-purity graphite or natural high-purity graphite, the particle size of the used graphite is 2-20 microns, 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 to the binder to the graphite to the conductive agent is (5-95): (1-10): (0-85): (0-10).
The test result shows that the mass specific capacity of the negative electrode material assembled into the lithium battery reaches 750-950 mAh/g, and the tap density reaches 2.5-3.5 g/cm3The compaction density reaches 3.5 to 4.5g/cm3The volume energy density is as high as 1810 to 2880mAh/cm3Much higher than commercial graphite (mass specific capacity 310-370 mAh/g, volume specific capacity 248-360 mAh/cm)3) The specific mass capacity of the silicon-carbon anode material is 580-950 mAh/g, and the specific volume capacity is 348-638 mAh/cm3). 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 graphene in the negative electrode 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. 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 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. 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 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) preparation of manganese-based oxide: slowly adding 2g of PVP K-30 (with the molecular weight of 44000-54000) into 80mL of diethylene glycol, and stirring until the PVP K-30 is completely dissolved to obtain diethylene glycol containing PVP; adding 0.003mol of magnesium acetate tetrahydrate into diethylene glycol containing PVP, and uniformly mixing; finally, adding 0.003mol of urea and uniformly stirring to obtain a mixed solution; transferring the mixed solution into a high-temperature high-pressure hydrothermal reaction kettle, reacting for 24h under the conditions of 200 ℃, 0.5MPa and the stirring speed of 120rmp, filtering a reaction product, washing for 5 times by using water and ethanol, then drying for 14h under vacuum at 60 ℃, and finally heating to 600 ℃ at the speed of 5 ℃/min and calcining for 2h to obtain a manganese-based oxide;
(2) reduction of manganese-based oxide: putting the manganese-based oxide into a high-temperature reaction furnace, heating at a heating rate of 5 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 600 ℃, preserving heat, simultaneously uniformly introducing hydrogen at a flow rate of 0.1L/min, uniformly introducing argon at a flow rate of 1L/min, and reacting for 4 hours to obtain a MnO template;
(3) preparing graphene: and (2) placing the MnO template in a high-temperature reaction furnace, heating at a heating rate of 5 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 900 ℃, preserving heat, uniformly introducing methane at a flow rate of 0.5L/min, uniformly introducing argon at a flow rate of 1L/min, and reacting for 25min 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 the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 80:10:10 to form paste, and coating the paste on a copper foil to obtain the negative electrode material.
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 substance, mixing the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 90:5:5 to form paste, and coating the paste on a copper foil to obtain the negative electrode material.
Example 3
The method for preparing the graphene-based composite material comprises the following steps:
(1) preparation of manganese-based oxide: slowly adding 1.5g of PVP (molecular weight is 55000) into 70mL of diethylene glycol, and stirring until the PVP is completely dissolved to obtain the diethylene glycol containing the PVP; adding 0.004mol of magnesium acetate tetrahydrate into diethylene glycol containing PVP, and uniformly mixing; finally, adding 0.004mol of urea and stirring uniformly to obtain a mixed solution; transferring the mixed solution into a high-temperature high-pressure hydrothermal reaction kettle, reacting for 30h under the conditions of 180 ℃, 0.6MPa and the stirring speed of 100rmp, filtering the reaction product, washing with water and ethanol for 5 times, then drying in vacuum at 80 ℃ for 12h, and finally heating to 400 ℃ at the speed of 5 ℃/min and calcining for 3h to obtain manganese-based oxide;
(2) Reduction of manganese-based oxides: putting the manganese-based oxide into a high-temperature reaction furnace, heating at a heating rate of 5 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 500 ℃, preserving heat, simultaneously uniformly introducing hydrogen at a flow rate of 0.1L/min, uniformly introducing argon at a flow rate of 1L/min, and reacting for 5 hours to obtain a MnO template;
(3) preparing graphene: and (2) placing the MnO template in a high-temperature reaction furnace, heating at a heating rate of 10 ℃/min, uniformly introducing argon at a flow rate of 1.5L/min in the heating process, heating to a reaction temperature of 1000 ℃, preserving heat, uniformly introducing methane at a flow rate of 0.8L/min, uniformly introducing argon at a flow rate of 1.5L/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 the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 80:10:10 to form paste, and coating the paste on a copper foil to obtain the negative electrode material.
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 substance, mixing the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 90:5:5 to form paste, and coating the paste on a copper foil to obtain the negative electrode material.
Example 5
The method for preparing the graphene-based composite material comprises the following steps:
(1) preparation of manganese-based oxide: slowly adding 2.5g of PVP K-30 (molecular weight is 44000-54000) into 60mL of diglycol, and stirring until the PVP K-30 is completely dissolved to obtain the diglycol containing PVP; adding 0.003mol of magnesium acetate tetrahydrate into diethylene glycol containing PVP, and uniformly mixing; finally, adding 0.004mol of urea and stirring uniformly to obtain a mixed solution; transferring the mixed solution into a high-temperature high-pressure hydrothermal reaction kettle, reacting for 24h under the conditions of 180 ℃, 0.6MPa and the stirring speed of 150rmp, filtering the reaction product, washing with water and ethanol for 5 times, then drying in vacuum at 80 ℃ for 12h, and finally heating to 600 ℃ at the speed of 5 ℃/min and calcining for 2h to obtain manganese-based oxide;
(2) reduction of manganese-based oxide: putting the manganese-based oxide into a high-temperature reaction furnace, heating at a heating rate of 5 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 600 ℃, preserving heat, simultaneously uniformly introducing hydrogen at a flow rate of 0.1L/min, uniformly introducing argon at a flow rate of 1L/min, and reacting for 3 hours to obtain a MnO template;
(3) preparing graphene: and (2) placing the MnO template in a high-temperature reaction furnace, heating at a heating rate of 15 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 900 ℃, preserving heat, uniformly introducing ethylene at a flow rate of 1L/min, uniformly introducing argon at a flow rate of 2L/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 substance, mixing the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 80:10:10 to form 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 5;
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 the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 90:5:5 to form paste, and coating the paste on a copper foil to obtain the negative electrode material.
Example 7
The method for preparing the graphene-based composite material comprises the following steps:
(1) preparation of manganese-based oxide: slowly adding 5g of PVP K-30 (molecular weight is 44000-54000) into 100mL of diglycol, and stirring until the PVP K-30 is completely dissolved to obtain the diglycol containing PVP; adding 0.009mol of magnesium acetate tetrahydrate into diethylene glycol containing PVP, and mixing uniformly; finally, adding 0.004mol of urea and stirring uniformly to obtain a mixed solution; transferring the mixed solution into a high-temperature high-pressure hydrothermal reaction kettle, reacting for 20h under the conditions of 200 ℃, 0.5MPa and the stirring speed of 150rmp, filtering the reaction product, washing with water and ethanol for 5 times, then drying in vacuum at 80 ℃ for 12h, and finally heating to 500 ℃ at the speed of 8 ℃/min and calcining for 3h to obtain manganese-based oxide;
(2) Reduction of manganese-based oxides: putting the manganese-based oxide into a high-temperature reaction furnace, heating at a heating rate of 7 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 550 ℃, preserving heat, simultaneously uniformly introducing hydrogen at a flow rate of 0.2L/min, uniformly introducing argon at a flow rate of 2L/min, and reacting for 2.5 hours to obtain an MnO template;
(3) preparing graphene: and (2) placing the MnO template in a high-temperature reaction furnace, heating at a heating rate of 10 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 800 ℃, preserving heat, simultaneously uniformly introducing ethylene at a flow rate of 0.5L/min, uniformly introducing argon at a flow rate of 1L/min, and uniformly introducing ammonia at a flow rate of 0.5L/min to react for 40min 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 the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 80:10:10 to form paste, and coating the paste on a copper foil to obtain the negative electrode material.
Example 8
The method of preparing the graphene-based composite material was the same as in example 7;
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 the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 90:5:5 to form paste, and coating the paste on a copper foil to obtain the negative electrode material.
Example 9
The method for preparing the graphene-based composite material comprises the following steps:
(1) preparation of manganese-based oxide: slowly adding 5g of PVP K-30 (molecular weight is 44000-54000) into 120mL of diethylene glycol, and stirring until the PVP K-30 is completely dissolved to obtain diethylene glycol containing PVP; adding 0.012mol of magnesium acetate tetrahydrate into diethylene glycol containing PVP, and uniformly mixing; finally, adding 0.003mol of urea and uniformly stirring to obtain a mixed solution; transferring the mixed solution into a high-temperature high-pressure hydrothermal reaction kettle, reacting for 20h under the conditions of 210 ℃, 0.6MPa and the stirring speed of 150rmp, filtering the reaction product, washing with water and ethanol for 5 times, then drying in vacuum at 60 ℃ for 20h, and finally heating to 550 ℃ at the rate of 5 ℃/min and calcining for 2h to obtain manganese-based oxide;
(2) reduction of manganese-based oxide: putting the manganese-based oxide into a high-temperature reaction furnace, heating at a heating rate of 5 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 500 ℃, preserving heat, simultaneously uniformly introducing hydrogen at a flow rate of 0.5L/min, uniformly introducing argon at a flow rate of 1L/min, and reacting for 3 hours to obtain a MnO template;
(3) preparing graphene: and (2) placing the MnO template in a high-temperature reaction furnace, heating at a heating rate of 12 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 900 ℃, preserving heat, uniformly introducing ethylene at a flow rate of 0.5L/min, uniformly introducing argon at a flow rate of 1L/min, and uniformly introducing pyridine at a flow rate of 0.5L/min to react for 10min 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 the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 80:10:10 to form paste, and coating the paste on a copper foil to obtain the negative electrode material.
Example 10
The method of preparing the graphene-based composite material was the same as in example 9;
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 the active substance with conductive carbon black and polyvinylidene fluoride in a mass ratio of 90:5:5 to form paste, and coating the paste on a copper foil to obtain the negative electrode material.
Comparative example 1
The method for preparing the graphene-based composite material is the same as that in the example 1, the difference is that in the step (2), the temperature is raised at the rate of 4 ℃/min, argon is uniformly introduced at the flow rate of 1L/min in the temperature raising process, the temperature is kept after the temperature is raised to the reaction temperature of 600 ℃, hydrogen is uniformly introduced at the flow rate of 0.02L/min, and argon is uniformly introduced at the flow rate of 1L/min.
The method of preparing the anode material was the same as in example 1.
Comparative example 2
The method for preparing the graphene-based composite material is the same as that in example 1, the difference is that in the heating process in the step (3), the heating rate is 16 ℃/min, argon is uniformly introduced at the flow rate of 1L/min in the heating process, the temperature is kept after the temperature is raised to the reaction temperature of 900 ℃, methane is uniformly introduced at the flow rate of 1.1L/min, and argon is uniformly introduced at the flow rate of 1L/min.
The method of preparing the anode material was the same as in example 1.
Comparative example 3
The method for preparing the graphene-based composite material is the same as that in the example 1, the difference is that in the heating process in the step (2), the heating rate is 16 ℃/min, argon is uniformly introduced at the flow rate of 1L/min in the heating process, the temperature is kept after the temperature is raised to the reaction temperature of 600 ℃, hydrogen is uniformly introduced at the flow rate of 1.2L/min, and argon is uniformly introduced at the flow rate of 1L/min; and (3) heating at a heating rate of 4 ℃/min, uniformly introducing argon at a flow rate of 1L/min in the heating process, heating to a reaction temperature of 900 ℃, preserving heat, uniformly introducing methane at a flow rate of 1.1L/min, and uniformly introducing argon at a flow rate of 1L/min.
The method of preparing the anode material was the same as in example 1.
Comparative example 4
The method for preparing the graphene-based composite material is the same as that in example 10, the difference is that in the heating process in the step (2), the heating rate is 9 ℃/min, argon is uniformly introduced at the flow rate of 1L/min in the heating process, the temperature is kept after the temperature is raised to the reaction temperature of 600 ℃, hydrogen is uniformly introduced at the flow rate of 0.1L/min, and argon is uniformly introduced at the flow rate of 1L/min; and (3) uniformly introducing argon at the flow rate of 1L/min in the heating process, heating to the reaction temperature of 900 ℃, preserving the temperature, simultaneously uniformly introducing ethylene at the flow rate of 0.04L/min, uniformly introducing argon at the flow rate of 1L/min, and uniformly introducing thiourea at the flow rate of 0.02L/min for reacting for 25min to obtain the graphene-based composite material.
The method of preparing the anode material was the same as in example 1.
Evaluation:
1. respectively representing the surface morphology and the structure of the manganese-based oxide, the manganese oxide template and the graphene-based composite material obtained in the examples 1-10 and the comparative examples 1-4 and the electrochemical performance of the button cell prepared by the manganese-based oxide, the manganese oxide template and the graphene-based composite material;
2. the test method comprises the following steps:
and (3) morphology observation: observing the surface morphology of the manganese-based oxide and graphene-based composite material by a scanning electron microscope (S-4800, Hitachi, Japan);
structural characterization: the chemical structure of the graphene-based composite was characterized by raman spectroscopy (model XploRA PLUS, HORIBA Scientific, japan) and XRD;
electrochemical performance: and (3) carrying out vacuum drying on the copper foil coated with the slurry for 8-15 h at 100 ℃, rolling and shearing to prepare the negative plate. A button cell (CR2025) was assembled in a glove box filled with argon gas, using LiPF6 (dimethyl carbonate (DMC): Ethylene Carbonate (EC): 1, volume ratio) with an electrolyte of 1mol/L, a diaphragm being Celgard2400 monolayer polypropylene membrane (PP), and a metallic lithium sheet as a counter electrode. And (3) carrying out charge-discharge cycle performance and rate performance tests on the button cell by using a cell test system (LAND CT2100A 5V/10mA), wherein the voltage is 0.01-3V. Electrochemical performances of button cells assembled by the anode materials of examples 1-10 and comparative examples 1-4 are shown in Table 1:
TABLE 1 electrochemical performance of button cells assembled with negative electrode materials of examples 1-10 and comparative examples 1-4
Figure GDA0003510538120000141
Figure GDA0003510538120000151
Morphological and structural experimental analysis: FIG. 2 is an SEM photograph of manganese-based oxide particles obtained in example 1, and FIG. 3 is an SEM photograph of manganese-based oxide particles obtained in example 4; as can be seen from fig. 2 and 3, the manganese-based oxide particles in flower form obtained in examples 1 and 4 have compact platelet stacking, uniform platelet thickness and uniform particle size distribution, and the manganese-based oxide particles in flower form having compact platelet stacking, uniform platelet thickness and uniform particle size distribution can be seen from SEM images of the manganese-based oxide particles obtained in examples 5 to 10, indicating that the manganese-based oxide particles with regular structure and high crystallinity can be prepared by the "hydrothermal reaction" technique of the present application; fig. 4 is an SEM image of the graphene-based composite material obtained in example 1, and fig. 5 is an SEM image of the graphene-based composite material obtained in example 4; as can be seen from fig. 4 to 5, the graphene-based composite materials obtained in example 1 and example 4 maintained the particle integrity structure and were porous materials, fig. 6 is a raman chart of the graphene-based composite material obtained in example 3, from which a G peak and a 2D peak were detected, indicating the presence of a large amount of graphite crystallite structures, and I was calculated from the raman charts of the graphene-based composite materials obtained in examples 1 to 10 and comparative examples 1 to 4 D/IGAs shown in Table 2, it can be seen from the data in Table 2 that the graphene-based composite materials I obtained in examples 1 to 10D/IGThe ratio is not higher than 1, which proves that the graphene structure on the surface of the graphene-based composite material formed by the method has high regularity, and the graphene-based composite materials I obtained by the comparative examples 1-4D/IGThe ratio is more than 1, which indicates that the graphene obtained in the comparative examples 1-4 has high defect and low structural regularity, and simultaneously confirms the high catalytic activity of the MnO template obtained by the method.
Table 2 in raman spectra of graphene-based composite materials obtained in examples 1 to 10 and comparative examples 1 to 4ID/IGRatio of
Figure GDA0003510538120000152
Figure GDA0003510538120000161
And (3) analyzing electrochemical properties: fig. 7 is a charge/discharge graph of the lithium ion battery assembled with the negative electrode material obtained in example 2, showing a significant plateau, confirming that lithium ions are sufficiently intercalated into the three-dimensional graphene and can stably and rapidly migrate, and showing a significant plateau in the charge/discharge graph of the lithium ion battery assembled with the negative electrode material obtained in examples 1, 3 to 10. Table 1 shows the specific mass capacity and the specific volume capacity of the negative electrode materials obtained in examples 1-10 and comparative examples 1-4, and the specific mass capacity and the specific volume capacity of the lithium battery assembled by the negative electrode materials obtained in examples 1-10 are far higher than those of commercial graphite (the specific mass capacity is 310-370 mAh/g, and the specific volume capacity is 248-360 mAh/cm) 3) The specific mass capacity of the silicon-carbon anode material is 580-950 mAh/g, and the specific volume capacity is 348-638 mAh/cm3). The graphene in the negative electrode material can prevent volume expansion of metal oxide and agglomeration of nano particles in the charging and discharging processes, and can improve the conductivity between an electrode and a current collector, so that the capacity of the metal oxide is maintained. Meanwhile, the metal oxide nanoparticles can prevent the graphene layer from being accumulated, and the high surface area of the graphene is kept. The storage capacity and the cycle performance of lithium are improved simultaneously through the synergistic effect of the two components, and the graphene-based electrode material with high quality, adjustable structure and excellent electrochemical performance is obtained. The battery buckling volume specific capacity and the mass specific capacity of the negative electrode material assembly obtained in the examples 1 to 10 are higher than those of the negative electrode material assembled in the comparative examples 1 to 4, and meanwhile, the method provided by the application can be used for obtaining the negative electrode material with excellent electrochemical performance.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean 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 is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, 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 (10)

1. A method of preparing a graphene-based composite, comprising:
(1) mixing manganese salt, urea and diethylene glycol containing PVP to obtain a mixed solution, supplying the mixed solution into a reaction kettle for hydrothermal reaction, and sequentially filtering, washing, drying and calcining the obtained reaction product to obtain a manganese-based oxide;
(2) placing the manganese-based oxide 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 reaches a first preset temperature so as to obtain a manganese oxide template;
(3) placing the manganese oxide template 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, the carbon source and a nitrogen source into the high-temperature reactor after reaching a second preset temperature so as to deposit and form graphene or nitrogen-doped graphene on the manganese oxide template to obtain the graphene-based composite material,
In the step (1), the concentration of manganese ions in the mixed solution is 0.01-0.5 mol/L, the concentration of urea in the mixed solution is 0.01-0.5 mol/L, the molecular weight of PVP is 40000-65000, the concentration of diethylene glycol containing PVP is 0.01-0.3 g/mL, the mass ratio of manganese salt, urea and PVP is (1-5): 1-15), the temperature of the hydrothermal reaction is 150-250 ℃, the pressure is 0.5-3 MPa, the rotating speed is 0-300 rpm, the reaction time is 1-40 hours, the heating rate in the calcining process is 3-15 ℃ per minute, the calcining temperature is 400-900 ℃, and the time is 1-8 hours;
in the step (2), the temperature rise rate is 5-15 ℃ per minute, the flow of the protective gas in the first gas containing the protective gas and the hydrogen is 0.3-10L/min, and the volume ratio of the protective gas to the hydrogen is 1: (0.03-1);
in the step (3), the heating rate is 5-15 ℃ per minute, the second preset temperature is 600-1200 ℃, and the reaction is carried out for 5-60 minutes at the second preset temperature.
2. The method of claim 1, wherein in step (1), the manganese salt comprises at least one of manganese acetate, manganese nitrate, manganese chloride, and manganese bromide.
3. The method according to claim 1 or 2, wherein in step (2), the shielding gas is nitrogen, argon or helium;
optionally, in the step (2), the first predetermined temperature is 400 to 800 ℃, and the reaction is carried out at the first predetermined temperature for 0.5 to 5 hours.
4. The method according to claim 1, wherein in step (3), the shielding gas is nitrogen, argon or helium;
optionally, in the step (3), in the second gas containing the protective gas and the carbon source, the flow rate of the protective gas is 0.3-10L/min, and the volume ratio of the protective gas to the carbon source is 1: (0.05-1);
optionally, in the step (3), in the second gas containing a shielding gas, a carbon source and a nitrogen source, the flow rate of the shielding gas is 0.3-10L/min, and the volume ratio of the shielding gas to the carbon source to the nitrogen source is 1: (0.05-1): (0.03-1);
optionally, 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;
optionally, in step (3), the nitrogen source comprises at least one of triethanolamine, diethanolamine, hexamethylenetetramine, aniline, N-dimethylformamide, ammonia, melamine, acetonitrile, propionitrile, butyronitrile, ammonia, pyridine, pyrrole, and thiourea.
5. A graphene-based composite material, wherein the graphene-based composite material is prepared by the method of any one of claims 1-4.
6. A method for preparing a negative electrode material is characterized in that a graphene-based composite material is mixed with a binder and a conductive agent, and then paste is coated on copper foil, wherein the graphene-based composite material is obtained by the method of any one of claims 1 to 4 or the graphene-based composite material of claim 5.
7. The method of claim 6, wherein the binder comprises at least one of polyvinylidene fluoride, sodium carboxymethylcellulose, and polyacrylic acid;
optionally, the conductive agent comprises at least one of carbon nanotubes, acetylene black, and conductive carbon black;
optionally, the mass ratio of the graphene-based composite material to the binder to the conductive agent is (5-95): (1-10): (0-10).
8. A negative electrode material, characterized in that the negative electrode material is prepared by the method of claim 6 or 7.
9. A lithium battery having the negative electrode material obtained by the method of claim 6 or 7 or the negative electrode material of claim 8.
10. An automobile, characterized in that it has a lithium battery as claimed in claim 9.
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