阅读说明：本技术 碳包覆石墨烯/金属氧化物复合材料及其制备方法 (Carbon-coated graphene/metal oxide composite material and preparation method thereof ) 是由 何承恩 郭超 郭晓丽 于 2021-08-23 设计创作，主要内容包括：本发明提供了一种碳包覆石墨烯/金属氧化物复合材料的制备方法,所述碳包覆石墨烯/金属氧化物复合材料是将石墨粉在高速剪切乳化作用下剥离形成石墨烯,同时加入稳定剂、金属盐和助剂提高剥离效率和分散稳定性,进而同步进行砂磨处理,在石墨烯表面发生机械化学反应生成金属氧化物前驱体,最后热退火得到碳包覆石墨烯/金属氧化物复合材料。该方法工艺简单、成本低廉、无污染,且所制备的复合材料中石墨烯片层薄、结构缺陷少、导电性好,金属氧化物粒径小、有效比表面积大、电化学活性高,多孔碳包覆提高了石墨烯与金属氧化物之间的界面作用,作为超级电容器电极材料,可提升其能量密度、功率密度和循环寿命。(The invention provides a preparation method of a carbon-coated graphene/metal oxide composite material, wherein graphite powder is stripped under the action of high-speed shearing emulsification to form graphene, meanwhile, a stabilizer, metal salt and an auxiliary agent are added to improve stripping efficiency and dispersion stability, sanding treatment is further carried out synchronously, a mechanochemical reaction is carried out on the surface of the graphene to generate a metal oxide precursor, and finally, thermal annealing is carried out to obtain the carbon-coated graphene/metal oxide composite material. The method is simple in process, low in cost and free of pollution, the graphene in the prepared composite material is thin in sheet layer, few in structural defects, good in conductivity, small in metal oxide particle size, large in effective specific surface area and high in electrochemical activity, the interface effect between graphene and the metal oxide is improved by coating porous carbon, and the graphene can be used as a super capacitor electrode material, so that the energy density, the power density and the cycle life of the super capacitor electrode material can be improved.)

1. A preparation method of a carbon-coated graphene/metal oxide composite material is characterized by comprising the following steps:

step 1, dispersing graphite powder and a stabilizer in a solvent, and then carrying out high-speed shearing emulsification treatment for 10-30 minutes by using a high-speed shearing emulsifier to obtain a mixed solution;

step 2, adding metal salt and an auxiliary agent into the mixed solution, and continuing to perform high-speed shearing emulsification for 10-30 minutes to obtain a dispersion liquid;

step 3, placing a sand mill feeding pipe into the dispersion liquid, carrying out continuous sanding treatment while carrying out high-speed shearing and emulsification for 30-60 minutes, and then carrying out suction filtration and drying to obtain graphene/metal oxide precursor powder;

and 4, carrying out thermal annealing treatment on the graphene/metal oxide precursor powder to obtain the carbon-coated graphene/metal oxide composite material.

2. The method for preparing a carbon-coated graphene/metal oxide composite material according to claim 1, wherein:

in step 1, the graphite powder includes at least one of flake graphene, expanded graphite, graphite fluoride and thermal cracking graphite.

3. The method for preparing a carbon-coated graphene/metal oxide composite material according to claim 1, wherein:

wherein, in step 1, the stabilizer comprises at least one of urea, glucose, melamine, procyanidins, tannic acid, methylimidazole, tetrakis (4-aminophenyl) methane, bis (1H-pyrrol-2-yl) methane, tribenzoate, biphenyl-4, 4' -dicarboxylic acid, fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene alkylamine and F127.

4. The method for preparing a carbon-coated graphene/metal oxide composite material according to claim 1, wherein:

wherein, in step 1, the solvent comprises at least one of deionized water, ethanol, methanol, N-Dimethylformamide (DMF), N-methylpyrrolidone (NMP) and dibasic ester mixture (DBE).

5. The method for preparing a carbon-coated graphene/metal oxide composite material according to claim 1, wherein:

in step 2, the metal salt includes at least one of nickel nitrate, manganese sulfate, cobalt acetate, ferric chloride, titanium normal sulfate and zinc chloride.

6. The method for preparing a carbon-coated graphene/metal oxide composite material according to claim 1, wherein:

in step 2, the auxiliary agent comprises at least one of ammonium carbonate, ammonium bicarbonate, sodium hydroxide, ammonium chloride, ammonia water and sodium carbonate.

7. The method for preparing a carbon-coated graphene/metal oxide composite material according to claim 1, wherein:

wherein the concentration of graphite powder in the solvent is 0.2-5 g/L, the mass ratio of graphite to the stabilizer is 1: 0.5-1: 5, the mass ratio of graphite to the metal salt is 1: 0.2-1: 10, and the mass ratio of the metal salt to the auxiliary agent is 1: 0.5-1: 2.

8. The method for preparing a carbon-coated graphene/metal oxide composite material according to claim 1, wherein:

wherein the high-speed shearing and emulsifying speed is 5000-30000 r/min, the temperature is 20-70 ℃, the ball mill is a horizontal sand mill or a vertical sand mill, the grinding beads are at least one of glass beads, zirconium silicate beads or zirconium oxide beads, the size of the grinding beads is 0.4-3.0 mm, the mass ratio of the grinding medium to the formula material is 1: 0.5-1: 2, and the grinding rotating speed is 300-1000 r/min.

9. The method for preparing a carbon-coated graphene/metal oxide composite material according to claim 1, wherein:

wherein the thermal annealing temperature in the step 4 is 200-600 ℃, the thermal annealing atmosphere is at least one of air atmosphere and nitrogen atmosphere, and the thermal annealing time is 0.5-6 hours.

10. A carbon-coated graphene/metal oxide composite material, characterized by being prepared by the preparation method of any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of energy materials, and particularly relates to a carbon-coated graphene/transition metal compound composite material and a preparation method thereof.

Background

The graphene/metal oxide composite material can be used as an electrode material of energy storage devices such as lithium ion batteries or super capacitors, can combine the excellent conductivity of graphene and the high energy density of transition metal oxide, exerts the synergistic effect of the two components, and improves the energy density, power density, rate capability, cycle life and the like of the energy storage devices.

Since the discovery of graphene in 2004, graphene has shown great application prospects in various fields such as new materials and electronic information. The preparation method of the graphene mainly comprises the following steps: chemical redox, chemical vapor deposition, mechanical lift-off, and the like. The chemical oxidation-reduction method comprises the steps of treating natural graphite by sulfuric acid and potassium permanganate, carrying out ultrasonic stripping to obtain graphene oxide, and finally reducing by using reducing agents such as hydrazine hydrate and the like to obtain graphene, wherein the method is beneficial to grafting modification of the graphene, but easily causes environmental pollution; the chemical vapor deposition method can obtain few-layer graphene with a complete structure, but the yield is low, the cost is high, and the method is only suitable for high-end application fields such as photoelectrons; the graphene with a complete lattice structure can be obtained by adopting a mechanical stripping method, has low requirements on equipment, can be prepared in a large scale, and can meet the requirements of energy and composite material industries. For example: few-layer (<10) graphene can be obtained by stripping graphite by means of ultrasound, ball milling and the like, but the energy utilization efficiency and the graphene yield of the ultrasonic stripping method are low. For example, the yield of single-layer graphene obtained by an ultrasonic stripping method in nat, nanotechnol, 2008,3(9):563 is 1 wt%, and the yield after repeated ultrasonic stripping is expected to reach 7-12 wt%, but the method consumes time and energy, and is low in efficiency. The ball-milling stripping method has long preparation time and difficult control of the quality of graphene sheets, such as: the chinese invention patent CN105084374A proposes that a surfactant assists in ball milling graphite, a first supernatant is obtained after a grinding fluid is allowed to stand, a second supernatant is obtained after the first supernatant is centrifuged, and graphene is obtained after the second supernatant is filtered and dried. In addition, the graphene sheet layer is subjected to not only van der waals forces but also hydrophobic effects and the like, and thus easily forms an agglomerate, resulting in poor stability of graphene prepared by the exfoliation method, and also difficulty in functionalization or compounding with other materials.

At present, graphene oxide is mostly used as a precursor for preparing a graphene/metal oxide composite material, and is mixed with a transition metal compound, then the transition metal oxide is generated in situ on the surface of the graphene oxide by methods such as coprecipitation, hydrothermal method, solvothermal method and the like, and finally the graphene/metal oxide composite material is obtained by thermal annealing treatment or chemical reduction (for example, chinese patent CN 104701035A, CN 106829927A, CN 102757041A, CN102185144 and the like). However, the above method has complex process, high cost and easy environmental problem; meanwhile, the graphene oxide is difficult to reduce by 100%, and the obtained graphene has low conductivity, so that the improvement on the power density and the rate capability of the device is limited; in addition, the method is more suitable for preparing the composite material in a laboratory, and industrial mass production is difficult, so that the commercial application of the graphene is restricted.

Disclosure of Invention

The present invention is made to solve the above problems, and aims to provide a method for preparing a carbon-coated graphene/metal oxide composite material by a high-speed shearing assisted continuous sanding method. According to the invention, a high-speed shearing emulsifying machine is adopted to pre-strip graphite, and meanwhile, a stabilizing agent and metal salt are added into a reaction system, so that the graphite stripping efficiency and the dispersion stability are improved; further placing a feeding pipe of a sand mill in the reaction system for synchronous grinding treatment to initiate a mechanochemical reaction to obtain a graphene/metal oxide precursor; and finally, carrying out thermal annealing treatment to obtain the carbon-coated graphene/metal oxide composite material. The method organically combines the graphene preparation by high-speed shearing and stripping of graphite, the sand grinding treatment for promoting the mechanochemical reaction to generate the metal oxide precursor and the thermal annealing for generating the carbon coating, can realize continuous production and processing, has low production cost, does not cause the problem of environmental pollution, and has complete structure and excellent electrochemical performance of the graphene.

In order to achieve the purpose, the invention adopts the following scheme:

< preparation method >

The invention provides a preparation method of a carbon-coated graphene/metal oxide composite material, which is characterized by comprising the following steps of: step 1, dispersing graphite powder and a stabilizer in a solvent, and then carrying out high-speed shearing emulsification treatment for 10-30 minutes by using a high-speed shearing emulsifier; step 2, adding metal salt and an auxiliary agent into the mixed solution obtained in the step 1, and continuing to perform high-speed shearing emulsification treatment for 10-30 minutes; step 3, placing a feeding pipe of a sand mill into the dispersion liquid obtained in the step 2, carrying out continuous sanding treatment while carrying out high-speed shearing and emulsification for 30-60 minutes, and then carrying out suction filtration and drying to obtain graphene/metal oxide precursor powder; and 4, carrying out thermal annealing treatment on the powder sample obtained in the step 3 to obtain the carbon-coated graphene/metal oxide composite material.

Preferably, the graphite powder comprises at least one of flake graphene, expanded graphite, graphite fluoride and thermal cracking graphite.

Preferably, the stabilizer includes at least one of urea, glucose, melamine, procyanidin, tannic acid, methylimidazole, tetrakis (4-aminophenyl) methane, bis (1H-pyrrol-2-yl) methane, tribenzoate, biphenyl-4, 4' -dicarboxylic acid, fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene alkylamine, polyoxyethylene-polyoxypropylene ether triblock copolymer (F127).

Preferably, the solvent comprises at least one of deionized water, ethanol, methanol, N-Dimethylformamide (DMF), N-methylpyrrolidone (NMP), dibasic ester mixture (DBE).

Preferably, the metal salt comprises at least one of nickel nitrate, manganese sulfate, cobalt acetate, ferric chloride, titanium normal sulfate and zinc chloride.

Preferably, the auxiliary agent comprises at least one of ammonium carbonate, ammonium bicarbonate, sodium hydroxide, ammonium chloride, ammonia water and sodium carbonate.

Preferably, the concentration of the graphite powder in the solvent is 0.2-5 g/L, the mass ratio of the graphite to the stabilizer is 1: 0.5-1: 5, the mass ratio of the graphite to the metal salt is 1: 0.2-1: 10, and the mass ratio of the metal salt to the auxiliary agent is 1: 0.5-1: 2.

Preferably, the speed of the high-speed shearing emulsification is 5000-30000 r/min, and the temperature is 20-70 ℃.

Preferably, the ball mill is a horizontal sand mill or a vertical sand mill, the grinding beads are at least one of glass beads, zirconium silicate beads or zirconium oxide beads, the size of the grinding beads is 0.4-3.0 mm, the mass ratio of the grinding medium to the formula material is 1: 0.5-1: 2, and the grinding rotating speed is 300-1000 r/min.

Preferably, the thermal annealing temperature in the step 4 is 200-600 ℃, the thermal annealing atmosphere is at least one of air atmosphere and nitrogen atmosphere, and the thermal annealing time is 0.5-6 hours.

< carbon-coated graphene/Metal oxide composite >

Further, the present invention also provides a carbon-coated graphene/metal oxide composite material prepared by the method described in the above < preparation method >.

< application >

Further, the invention also provides an active electrode material using the carbon-coated graphene/metal oxide composite material as a super capacitor, a lithium ion battery and a sodium ion battery.

Action and Effect of the invention

Compared with the prior art, the carbon-coated graphene/metal oxide composite material and the preparation method thereof have the following outstanding characteristics and excellent effects:

1. according to the invention, the graphene sheet layer is obtained by pre-stripping graphite by a high-speed shearing emulsification method, and the stabilizer is adsorbed on the surface of the newly generated graphene sheet layer to prevent the graphene sheet layer from self-aggregation, so that the graphite stripping efficiency is greatly improved, the integrity of a graphene lattice structure is also ensured, and the conductivity and the electrochemical performance are favorably improved.

2. On one hand, the metal salt and the auxiliary agent can be used as an ion intercalation agent, and intercalation is carried out between graphite layers in the high-speed shearing emulsification process to increase the interlayer spacing and improve the graphite stripping efficiency; on the other hand, a mechanochemical reaction is generated in the grinding process of the sand mill to generate a metal oxide precursor which is loaded on the surface of the graphene sheet layer.

3. The high-speed shearing pre-stripping and sanding grinding stripping are combined, the efficiency of stripping graphite into graphene is improved, the efficiency of converting graphite into graphene can reach more than 80 wt%, which is far higher than 7-12 wt% of the traditional ultrasonic stripping method (nat. nanotechnol.,2008,3(9):563), and the efficiency is also obviously superior to a small amount of graphene in secondary supernatant of a ball milling-centrifugation method (Chinese patent CN 105084374A).

4. The method uses a continuous sanding treatment method, can realize continuous production operation, simultaneously directly obtains the graphene/metal oxide precursor, and obtains the carbon-coated graphene/metal oxide composite material after thermal annealing treatment.

5. According to the method provided by the invention, the stabilizer is converted into porous carbon to be coated on the surface of the graphene/metal oxide in the thermal annealing process, so that the interface bonding force between the graphene and the metal oxide nanoparticles is enhanced, the conductivity and the structural stability are improved, and the porous carbon can be used as an electrode material of a super capacitor or a lithium ion battery to improve the energy density and the power density and prolong the service life.

Drawings

Fig. 1 is a transmission electron microscope photograph of a carbon-coated graphene/manganese dioxide composite material prepared in example one;

fig. 2 is a high-resolution tem photograph of the carbon-coated graphene/manganese dioxide composite prepared in the first example;

fig. 3 is a cyclic voltammetry curve of the carbon-coated graphene/manganese dioxide composite prepared in the first example;

fig. 4 is a constant current charge and discharge curve of the nitrogen-doped porous carbon-coated graphene/cobaltosic oxide composite material prepared in example two.

Detailed Description

Specific embodiments of the carbon-coated graphene/metal oxide composite material and the method for preparing the same according to the present invention will be described in detail below with reference to the accompanying drawings.

< example one >

In this embodiment, graphite is peeled off by a high-speed shearing assisted continuous sand milling method, and then a carbon-coated graphene/manganese dioxide composite material is obtained by thermal annealing treatment.

The preparation method comprises the following steps:

(1) weighing 1000mg of expanded graphite, 600mg of F127 and 1000mg of tannic acid, adding the expanded graphite, the F127 and the tannic acid into 1000mL of deionized water/ethanol (volume ratio is 4:1) mixed solvent, and treating for 20 minutes by using a high-speed shearing emulsifying machine, wherein the stirring speed is 20000 revolutions per minute;

(2) 3200mg of manganese sulfate and 2000mg of ammonium carbonate are weighed and added into the dispersion liquid in the step 1, and high-speed shearing emulsification treatment is continued for 20 minutes;

(3) putting a feeding pipe of a sand mill into the dispersion liquid in the step (2), using grinding beads (0.5mm and 1.0mm) with two diameters in a mass ratio of 2:1 as a sanding medium, adjusting the grinding speed to be 500 rpm, continuously performing sanding grinding for 60 minutes while maintaining high-speed shearing emulsification, and during the process, shearing and thinning the graphene sheet layer, and simultaneously performing mechanochemical reaction on the metal salt, the auxiliary agent and the stabilizing agent to grow a manganese dioxide precursor (manganese carbonate) in situ on the surface of the graphene sheet layer. And finally, filtering, washing and drying the product to obtain graphene/metal oxide precursor powder, and weighing the graphene/metal oxide precursor powder to obtain the graphene/metal oxide precursor powder with the yield of 82 wt% and the efficiency far higher than that of a traditional ultrasonic stripping method (nat. nanotechnol.,2008,3(9):563) and a direct ball milling-centrifugation method (Chinese patent CN 105084374A).

(4) And (4) transferring the powder sample obtained in the step (3) to an atmosphere furnace, and annealing for 4 hours at 450 ℃ in a nitrogen atmosphere. In the process, manganese carbonate is converted into manganese dioxide, and F127 and tannic acid are converted into porous carbon, so that the carbon-coated graphene/manganese dioxide composite material is obtained.

And (3) performance characterization:

carbon-coated graphene/manganese dioxide composite material

The obtained carbon bagThe appearance of the graphene/manganese dioxide-coated composite material is shown in fig. 1, and the material can be observed to contain a two-dimensional lamellar structure, and the lamellar thickness of the graphene/manganese dioxide-coated composite material is very thin, the graphene/manganese dioxide-coated composite material is few layers of graphene sheets, and a large number of granular structures are loaded on the surface of the graphene/manganese dioxide-coated composite material. Further observation by high resolution transmission electron microscopy in FIG. 2 shows that the material exhibits three different crystalline states, each representing MnO₂Crystalline, amorphous porous carbon, regular graphene lamellae. The above results confirm the successful preparation of carbon-coated graphene/manganese dioxide composite material in example 1, in which MnO is₂The crystal size is about 10nm, and the crystal is coated by porous carbon and uniformly loaded on the surface of few-layer graphene.

Further, the carbon-coated graphene/manganese dioxide composite material is used as an electrode of a supercapacitor, the electrochemical performance of the supercapacitor is tested, the cyclic voltammetry curve of the supercapacitor is shown in fig. 3, the energy storage device shows the typical electrochemical characteristics of manganese dioxide, the specific capacitance under 5mV/s and 100mV/s is respectively up to 338F/g and 242F/g, and the capacitance retention rate reaches 71.6% after the scanning speed is increased by 20 times, which shows that the energy storage device has excellent specific capacitance and rate capability, and the performance is obviously superior to that of the graphene/manganese dioxide composite material prepared by other methods, such as: the literature Electrochimica Acta,2016,222, 1393-; documents Composites Part B,2019,161, 37-43 (5 mV/s-292.9F/g, 100 mV/s-156.1F/g, 53.3%); the literature Energy environ. Sci.,2014,7,3709-3719(10 mV/s-215F/g, 100 mV/s-106F/g, 49.3%).

The excellent electrochemical performance comes from the structure of a carbon-coated graphene/manganese dioxide composite material, and MnO is coated by porous carbon₂Nano crystal loaded on the surface of less-layer graphene, MnO₂The nano crystal particles have small size and large specific surface area, which is beneficial to the diffusion of electrolyte ions and improves the utilization efficiency of active materials, thereby improving the specific capacitance of the active materials; meanwhile, few-layer graphene has a regular graphitized structure, and MnO is coated by porous carbon₂The nano crystal enhances the interface interaction between the nano crystal and graphene sheets, and is beneficial to the conduction of electrons, thereby improving the multiplying power of the nano crystalEnergy is saved; in addition, the coating with porous carbon can also suppress MnO₂And the dissociation of the nano crystals in the electrochemical reaction process ensures that the super capacitor has long service life.

The method has the advantages of simple process, cheap raw materials, continuous generation, macro-preparation, low cost, no pollution, high conductivity and high quality of the obtained product, is very suitable for the requirement of industrial generation, and is far superior to the conventional method in specific capacitance and rate capability as the electrode material of the super capacitor.

< example two >

In this embodiment, graphite is stripped by a high-speed shearing assisted continuous sanding method, and then a nitrogen-doped porous carbon-coated graphene/cobaltosic oxide composite material is obtained by thermal annealing treatment.

The preparation method comprises the following steps:

(1) weighing 2000mg of expanded graphite and 1500mg of N-methylimidazole, adding the expanded graphite and the N-methylimidazole into 1000mL of deionized water/methanol (volume ratio is 1:9) mixed solvent, and treating for 20 minutes by using a high-speed shearing emulsifying machine, wherein the stirring speed is 30000 r/min;

(2) weighing 1000mg of cobalt nitrate, adding the cobalt nitrate into the dispersion liquid obtained in the step 1, and continuing high-speed shearing emulsification for 10 minutes;

(3) and (3) putting a feeding pipe of a sand mill into the dispersion liquid in the step (2), using grinding beads with three diameters (0.5mm, 1.0mm and 2.0mm) in a mass ratio of 1:1:1 as a grinding medium, adjusting the grinding rotating speed to be 800 r/min, continuously carrying out grinding for 30 min while maintaining high-speed shearing emulsification, and in the process, carrying out coordination interaction on cobalt ions and N-methylimidazole to grow a cobalt-based organic covalent polymer (MOF: ZIF-67) on the surface of the graphene sheet layer in situ. And finally, filtering, washing and drying the product to obtain precursor powder.

(4) Transferring the powder sample obtained in the step (3) into an atmosphere furnace, annealing for 2 hours in a nitrogen atmosphere at 600 ℃, and converting the organic ligand into porous carbon; and then, reducing the temperature to 250 ℃, and carrying out heat treatment in an air atmosphere for 2 hours to generate cobaltosic oxide in the process, thereby obtaining the nitrogen-doped porous carbon-coated graphene/cobaltosic oxide composite material.

And (3) performance characterization:

the nitrogen-doped porous carbon-coated graphene/cobaltosic oxide composite material is used as an electrode of a super capacitor, the electrochemical performance of the super capacitor is tested, the constant-current charging and discharging curve is shown in fig. 4, the energy storage device shows typical pseudocapacitance electrochemical characteristics, the specific capacitance under 1A/g and 8A/g is respectively up to 1025F/g and 800F/g, and the retention rate reaches 78% after the scanning speed is increased by 8 times, so that the energy storage device has excellent specific capacitance and multiplying power performance.

< example three >

In the embodiment, graphite is stripped through a high-speed shearing auxiliary continuous sand grinding method of the tee joint, and then the porous carbon coated graphene/NiCo is obtained through thermal annealing treatment₂O₄A composite material.

The preparation method comprises the following steps:

(1) weighing 1000mg of expanded graphite and 1000mg of biphenyl-4, 4' -dicarboxylic acid (stabilizer) to be added into 1000mL of N-methylpyrrolidone solvent, and treating for 30 minutes by using a high-speed shearing emulsifying machine, wherein the stirring speed is 10000 r/min;

(2) 728mg of cobalt nitrate, 352mg of nickel acetate and 240mg of sodium hydroxide are weighed and added into the dispersion liquid in the step 1, and high-speed shearing emulsification treatment is continued for 30 minutes;

(3) and (3) placing a feeding pipe of a sand mill into the dispersion liquid in the step (2), using grinding beads with the diameter of 0.5mm as a sanding medium, adjusting the grinding speed to 300 revolutions per minute, continuously performing sanding grinding for 60 minutes while maintaining high-speed shearing emulsification, performing mechanochemical reaction on cobalt and nickel ions and an auxiliary agent in the process, growing cobalt/nickel hydroxide on the surface of the graphene sheet layer in situ, and filtering, washing and drying the product to obtain precursor powder.

(4) Transferring the powder sample obtained in the step (3) into an atmosphere furnace, annealing for 1 hour in a nitrogen atmosphere at 500 ℃, and converting the stabilizer into porous carbon; the temperature was then lowered to 280 ℃ and heat treated in an air atmosphere for 2 hours, during which the cobalt/nickel hydroxide was converted to NiCo₂O₄Further obtaining the graphene/NiCo coated by the porous carbon₂O₄Composite materialAnd (5) feeding.

And (3) performance characterization:

graphene/NiCo coated with porous carbon₂O₄The composite material is an electrode material of the lithium ion battery, the electrochemical performance of the lithium ion battery is tested, the specific capacities under 0.1C and 2C are respectively 1225mAh/g and 800mAh/g, and the capacity retention rate after 500 cycles of charge-discharge circulation under 0.5C can reach 82%, which indicates that the energy storage device has excellent specific capacity, rate capability and cycle service life.

The above embodiments are merely illustrative of the technical solutions of the present invention. The carbon-coated graphene/metal oxide composite material, the preparation method and the application thereof according to the present invention are not limited to the contents described in the above embodiments, but are subject to the scope defined by the claims. Any modification or supplement or equivalent replacement made by a person skilled in the art on the basis of this embodiment is within the scope of the invention as claimed in the claims.