CN109904397B - Molybdenum disulfide/C/graphene composite material - Google Patents
Molybdenum disulfide/C/graphene composite material Download PDFInfo
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Abstract
A molybdenum disulfide/C/graphene composite material is prepared by the following steps: firstly, preparing a thio-metal salt precursor by using molybdenum salt, ammonia water and quaternary ammonium salt as raw materials; mixing and grinding the oxidized graphene and the precursor of the thio-metal salt, placing the mixture in a microwave reaction cavity, and heating the mixture for 1 to 15 minutes at the microwave power of 300-1000W to obtain the molybdenum disulfide/C/graphene composite material. According to the invention, the composite material is prepared by a solvent-free microwave heating method, the solvent-free mode omits the post-treatment processes of washing, separation, drying and the like of the product, the molybdenum disulfide nanosheets are uniformly dispersed on the surface of the graphene, the amorphous carbon effectively relieves the problem that the graphene is stacked again in the compounding process, and the obtained product can be directly used; due to the fact that microwave heating speed is high, heating is uniform, graphene is reduced thoroughly, aggregation and accumulation of nanoparticles, graphene and MoS in the long-term heat treatment process can be effectively relieved2The combination is firm. The material has good stability, is not easy to denature in air and is easy to store; the specific surface area is large, and the lithium ion battery cathode material provides a good channel for lithium ion transmission, and shows a large specific capacity and a good cycling stability performance.
Description
Technical Field
The invention relates to a molybdenum disulfide/C/graphene hierarchical structure lithium battery cathode material and provides a preparation method thereof, belonging to the technical field of nano composite materials and application thereof.
Background
Lithium ion batteries are widely used in modern electrical energy storage systems such as mobile phones and electric vehicles due to their high energy density, high operating voltage and long service life. The electrochemical properties of the negative electrode material directly affect the overall performance of the lithium ion battery. Graphite has the advantages of high coulombic efficiency, good cycle stability, abundant natural reserves and the like, and is widely applied to lithium ion battery cathode materials. However, its lower specific capacity (372 mAh g)-1) And the poor rate performance cannot meet the requirements of future portable equipment and electric automobiles, so that the development of a novel high-performance lithium battery cathode material is urgently required.
Transition metal chalcogenides are an important component in the field of materials, have attracted a great deal of attention and intense research interest due to their specific physical and chemical properties and potential application values in various fields, and increasingly exhibit many unique properties, such as optoelectronic properties, magnetic properties and superconducting properties. Some transition metal chalcogenides have a unique layered structure and other alkali metals or other atoms may be introduced between layers. Wherein, MoS2As a typical transition metal chalcogenide, has a graphene-like layered structure and a high theoretical capacity (670 mAh g)-1) And the material is low in price and good in stability, so that the material attracts wide attention as a potential high-performance lithium battery cathode material.
However, MoS2The defects of poor conductivity, poor cycling stability and the like hinder the large-scale application of the conductive material. The graphene with the two-dimensional structure has high specific surface area, excellent conductivity and good electrochemical stability, so that MoS is obtained2The/graphene nano composite material becomes a research hotspot.
CN106207171A provides a method for preparing MoS2The method for preparing the graphene nano composite material mainly comprises the steps of carrying out a hydrothermal compounding process, and washing and drying a hydrothermal product to obtain MoS2Graphene nanocomposite and MoS obtained therefrom2Application of graphene nanocomposite material in lithium batteryIn the cathode material, the electrochemical performance is excellent. However, the hydrothermal and solvothermal composite process has some problems, for example, the reaction time is long, the reaction time is often more than 20 hours, the graphene oxide is difficult to be completely reduced in the reaction process, and MoS2The combination with graphene is unstable, electrodes are easily damaged in the charging and discharging processes, and products obtained by hydrothermal treatment need to be washed, separated, dried and the like, so that graphene is easily re-accumulated to influence the transmission of lithium ions in graphene, and further influence MoS2The electrochemical performance of the graphene nanocomposite material.
Disclosure of Invention
Aiming at solving the problems that in the prior art, a hydrothermal method is mostly adopted for the molybdenum disulfide/graphene nano composite material, or a solvent is needed in the synthesis process, the reaction time is generally longer, the product needs a complex separation post-treatment process, and MoS in the synthetic material2The invention provides a method for synthesizing a molybdenum disulfide/C/graphene composite material by a solvent-free method, and the obtained product can be directly used as a lithium battery cathode material without washing, separating, drying and other processes and has good application performance.
In order to achieve the technical purpose, the invention provides a preparation method of a molybdenum disulfide/C/graphene composite material, which comprises the following steps:
(1) preparation of a Thiometallate precursor: mixing molybdenum salt and ammonia water, heating to 40-70 ℃, adding ammonium sulfide, reacting for 0.5-2h, adding quaternary ammonium salt into the solution to generate a precipitate, cooling, standing until crystals are separated out, washing and drying to obtain a thio-metal salt precursor;
(2) preparing a composite material: mixing graphene oxide and the precursor of the thio-metal salt prepared in the step (1), and placing the mixture in a ball mill for grinding; and placing the ball-milled material in a microwave reaction cavity, and heating for 1-15min at the microwave power of 300-1000W to obtain the molybdenum disulfide/C/graphene composite material.
In the above preparation method, the molybdenum salt is selected from ammonium molybdate and/or sodium molybdate.
In the above preparation method, the quaternary ammonium salt is an ammonium halide having 4 to 30 carbons, preferably an ammonium halide having a carbon chain length of 4 to 25 carbons, and as a more specific embodiment, the quaternary ammonium salt is at least one selected from the group consisting of tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride and octadecyltrimethylammonium bromide.
In the above production method, the mixing molar ratio of the molybdenum salt, ammonium sulfide and alkylammonium salt is 1:1-20:0.1-5, and the ammonia water is added in an amount such that the molybdenum salt is completely dissolved and the pH of the mixed solution is maintained at 7.5-11, preferably 8-10.
In the preparation method, the mixing mass ratio of the graphene oxide and the thio-metal salt precursor in the step (2) is 1: 1-20.
In the preparation method, the feeding mass ratio of the grinding balls and the mixture in the ball mill during grinding is 1-20:1, the rotating speed is 300-. The grinding ball and the feeding ratio is more than 1, which is beneficial to the full contact of the feeding and the grinding ball, and the grinding effect is better.
In the above preparation method, the milling is carried out under an inert atmosphere.
In the preparation method, the microwave reaction in the step (2) is preferably heated at 500-1000W for 3-10 min.
In the preparation method, the microwave reaction cavity is purged by nitrogen or inert gas before and during the microwave reaction, and preferably, argon is used for purging.
In the above preparation method, the graphene oxide is selected from among graphene oxides having the following properties: the area of the sheet layer is 100 mu m2The conductivity is 3500S/m or more.
In the above preparation method, the graphene oxide is obtained by oxidizing graphite, and the graphene oxide of the present invention is synthesized by Hummers method, and as a more specific embodiment, the present invention discloses a specific preparation method of the graphite oxide as follows: adding natural crystalline flake graphite into ice-bath concentrated sulfuric acid under stirring, cooling to 0-10 ℃, adding sodium nitrate and potassium permanganate, stirring for reaction, adding deionized water, heating to 50-100 ℃, reacting at constant temperature until the reaction solution turns to bright yellow, adding hydrogen peroxide, stirring for reaction, cooling, washing, drying to obtain graphene oxide, and grinding into powder for later use.
The specification of the natural crystalline flake graphite is 100-500 meshes. After the reaction is finished, repeatedly settling with deionized water during post-treatment to remove unreacted graphite particles, centrifuging with hydrochloric acid, cleaning, removing Cl ions in the reaction solution, washing with deionized water until the pH value is close to neutral, drying, and grinding.
The stripping efficiency of the Hummers method is more than 93%, the yield is more than 90%, the structural integrity of the obtained graphene oxide sheet layer is high, and the crystal lattice is complete after thermal reduction.
The technical purpose of the second aspect of the invention is to provide the molybdenum disulfide/C/graphene composite material prepared by the method, wherein the material is MoS generated by pyrolyzing a precursor of a thio-metal salt under the solvent-free microwave heating condition2The nanosheets directly grow on the surface of the graphene in situ, and meanwhile, amorphous carbon generated by alkyl pyrolysis in the thio-metal salt precursor can effectively relieve the heavy stacking of the graphene in the compounding process, so that the stability of the composite material is further enhanced. Because the microwave heating speed is high and the heating is uniform, the MoS is enabled2The combination of the nano sheets and the graphene is firm, particles are not easy to accumulate, the time for synthesizing the material is greatly shortened, and the graphene and MoS are relieved2Agglomeration under long-term heating.
The technical purpose of the third aspect of the invention is to provide an application of the molybdenum disulfide/C/graphene composite material, wherein the material can be used as a lithium ion battery cathode material and shows good cycle stability and rate capability.
Compared with the prior art, the invention has the following advantages:
the method adopts a solvent-free microwave heating method to prepare the molybdenum disulfide/C/graphene composite material, the solvent-free treatment mode omits the post-treatment processes of washing, separation, drying and the like of the product, and the molybdenum disulfide nanosheetThe graphene is uniformly dispersed on the surface of the graphene, the amorphous carbon effectively relieves the phenomenon that the graphene is stacked again in the compounding process, and the obtained product can be directly used; in addition, as the microwave heating speed is high, the heating is uniform, the graphene reduction is thorough, the aggregation and accumulation of nano particles, graphene and MoS in the long-term heat treatment process can be effectively relieved2The bonding is firm and no obvious aggregation occurs, and the molybdenum disulfide nanosheets are uniformly dispersed on the surface of the graphene. The material has good stability, is not easy to denature in air and is easy to store; the specific surface area is large, and the lithium ion battery cathode material provides a good channel for lithium ion transmission, and shows a large specific capacity and a good cycling stability performance.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
Fig. 1 is an XRD pattern of graphene oxide prepared in example 1;
FIG. 2 shows the current density of 100 mA-g for the molybdenum disulfide/C/graphene composite material in example 12-1Time charge and discharge cycle curve.
Detailed Description
The following non-limiting examples are presented to enable those of ordinary skill in the art to more fully understand the present invention and are not intended to limit the invention in any way.
Example 1
(1) Preparing graphene oxide, namely, slowly adding 100m L98% concentrated sulfuric acid into a 500m L dry three-necked bottle, placing the three-necked bottle on a magnetic stirrer for ice bath cooling, adding 2.0g of natural crystalline flake graphite (180 meshes) under rapid stirring, slowly adding 4.0g of sodium nitrate when the temperature of a reaction solution is reduced to about 0 ℃, continuously stirring for 2 hours, slowly adding 10g of potassium permanganate in batches within 1 hour, continuously stirring for 2 hours, controlling the reaction temperature to be below 10 ℃, then transferring the three-necked bottle into a 40 ℃ water bath, continuously stirring for reaction for 2 hours, then slowly adding 200m L ℃ deionized water, keeping the temperature of the reaction solution within 100 ℃, reacting at constant temperature and 98 ℃ until the reaction solution becomes bright yellow, adding 20m L30% hydrogen peroxide into the reaction solution, continuously stirring to fully react, cooling, and then coolingAnd replacing deionized water for repeated sedimentation of the obtained solution, removing unreacted graphite particles, centrifugally cleaning with hydrochloric acid to remove Cl ions in the reaction solution, and washing with deionized water until the pH value is close to neutral. And finally, vacuum drying for 12h at 80 ℃ to obtain graphene oxide, and grinding the graphene oxide into powder for later use. Its XRD pattern is shown in FIG. 1 and is located at 11oTo the left and right is the typical 001 diffraction peak of graphene oxide, which is mainly due to the intercalation of a large number of oxygen-containing functional groups between graphene sheets. The distance between graphite oxide sheets can be calculated to be 0.7nm through the Sherle formula, and is obviously larger than the interlayer spacing 0.3254nm of graphite. The increased interlayer spacing is primarily due to oxygen-containing functional groups intercalated between graphene sheets.
(2) Preparation of tetramethylammonium tetrathiomolybdate by mixing 1.00g ammonium molybdate with 30m L concentrated aqueous ammonia (NH)3·H2O) was added to the three-necked flask. Heated with stirring and 8g ammonium sulfide ((NH) added when the temperature rises to 60 deg.C4)2S), and reacting for 0.5h under the condition of magnetic stirring. Tetramethyl ammonium bromide is then added to the solution, and a precipitate is formed as the reaction continues. And then standing for 2 hours in an ice bath, gradually precipitating crystals, filtering the reaction solution, washing with absolute ethyl alcohol and deionized water, and drying to obtain the tetramethyl ammonium tetrathiomolybdate.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing tetramethylammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 1:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of balls to materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after carrying out ball milling for 1h, collecting a product, placing the ball-milled material into a reaction tube, then placing the reaction tube into a microwave reaction cavity, purging for 1h by using 100m L/min of argon, carrying out microwave heating for 3min by using 600W of power, and cooling to room temperature under the Ar atmosphere to obtain the molybdenum disulfide/C/graphene nano composite material.
Example 2
(1) The preparation method of graphene oxide is the same as example 1.
(2) The preparation of tetramethylammonium tetrathiomolybdate was carried out in the same manner as in example 1.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing tetramethylammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 2:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of balls to materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after carrying out ball milling for 1h, collecting a product, placing the ball-milled material into a reaction tube, then placing the reaction tube into a microwave reaction cavity, purging for 1h by using 100m L/min of argon, carrying out microwave heating for 5min by using 600W of power, and cooling to room temperature under the Ar atmosphere to obtain the molybdenum disulfide/C/graphene nano composite material.
Example 3
(1) The preparation method of graphene oxide is the same as example 1.
(2) The preparation of tetramethylammonium tetrathiomolybdate was carried out in the same manner as in example 1.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing tetramethylammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 2:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of ball materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after ball milling for 1h, collecting products, placing the ball-milled materials into a reaction tube, then placing the reaction tube into a microwave reaction cavity, purging for 1h by using 100m L/min argon, carrying out microwave heating for 10min by using 1000W power, cooling to room temperature under the Ar atmosphere, and obtaining MoS2A/C/graphene nanocomposite material.
Example 4
(1) The preparation method of graphene oxide is the same as example 1.
(2) Preparation of tetraethylammonium tetrathiomolybdate 1.00g ammonium molybdate and 30m L concentrated ammonia (NH)3·H2O) was added to the three-necked flask. Heated with stirring and 8g ammonium sulfide ((NH) added when the temperature rises to 60 deg.C4)2S), and reacting for 0.5h under the condition of magnetic stirring. Tetraethylammonium bromide was then added to the solution and a precipitate formed as the reaction continued. And then standing for 2 hours in an ice bath, gradually precipitating crystals, filtering the reaction solution, washing with absolute ethyl alcohol and deionized water, and drying to obtain tetraethylammonium tetrathiomolybdate.
(3) And (3) preparing the molybdenum disulfide/C/graphene composite material, namely mixing tetraethylammonium tetrathiomolybdate in the step (2) with graphene oxide according to the mass ratio of 1:1, placing the mixture into an agate tank filled with nitrogen, ball-milling the mixture by using a ball mill at the ball-material mass ratio of 3:1 and the rotation speed of 400rpm, naturally cooling the mixture to room temperature after ball-milling for 1h, collecting a product, putting the ball-milled material into a reaction tube, then placing the reaction tube into a microwave reaction cavity, purging the reaction tube for 1h by using 100m L/min argon, carrying out microwave heating for 5min by using 600W power, and cooling the mixture to room temperature under the Ar atmosphere to obtain the molybdenum disulfide/C/graphene nanocomposite material.
Example 5
(1) The preparation method of graphene oxide is the same as example 1.
(2) Tetraethylammonium tetrathiomolybdate was prepared as in example 4.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing tetraethylammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 2:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of balls to materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after ball milling for 1h, collecting a product, placing the ball-milled material into a fluidized reaction tube, then placing the reaction tube into a microwave reaction cavity, purging with 100m L/min of argon gas for 1h, carrying out microwave heating with 600W power for 8min, and cooling to room temperature under the Ar atmosphere to obtain the molybdenum disulfide/C/graphene nanocomposite material.
Example 6
(1) The preparation method of graphene oxide is the same as example 1.
(2) Tetraethylammonium tetrathiomolybdate was prepared as in example 4.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing tetraethylammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 2:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of balls to materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after ball milling for 1h, collecting a product, placing the ball-milled material into a fluidized reaction tube, then placing the reaction tube into a microwave reaction cavity, purging with argon gas of 100m L/min for 1h, carrying out microwave heating with the power of 1000W for 10min, and cooling to room temperature under the Ar atmosphere to obtain the molybdenum disulfide/C/graphene nanocomposite material.
Example 7
(1) The preparation method of graphene oxide is the same as example 1.
(2) Preparation of tetrabutylammonium tetrathiomolybdate 1.00g ammonium molybdate and 30m L conc ammonia (NH)3·H2O) was added to the three-necked flask. Heated with stirring and 8g ammonium sulfide ((NH) added when the temperature rises to 60 deg.C4)2S), and reacting for 0.5h under the condition of magnetic stirring. Tetrabutylammonium bromide is then added to the solution, and a precipitate forms as the reaction continues. And then standing for 2 hours in an ice bath, gradually precipitating crystals, filtering the reaction solution, washing with absolute ethyl alcohol and deionized water, and drying to obtain tetraethylammonium tetrathiomolybdate.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing tetrabutylammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 1:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of balls to materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after carrying out ball milling for 1h, collecting a product, placing the ball-milled material into a reaction tube, then placing the reaction tube into a microwave reaction cavity, purging for 1h by using argon gas of 100m L/min, carrying out microwave heating for 3min by using the power of 600W, and cooling to room temperature under the Ar atmosphere to obtain the molybdenum disulfide/C/graphene nanocomposite material.
Example 8
(1) The preparation method of graphene oxide is the same as example 1.
(2) Tetrabutylammonium tetrathiomolybdate was prepared as in example 7.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing tetrabutylammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 2:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of balls to materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after carrying out ball milling for 1h, collecting a product, placing the ball-milled materials into a reaction tube, then placing the reaction tube into a microwave reaction cavity, and stirring at 100m L ^ Cmin argon purge for 1 h. Microwave heating with 600W power for 5 min. Cooling to room temperature under Ar atmosphere to obtain MoS2A/C/graphene nanocomposite material.
Example 9
(1) The preparation method of graphene oxide is the same as example 1.
(2) Tetrabutylammonium tetrathiomolybdate was prepared as in example 7.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing tetraethylammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 2:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of balls to materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after ball milling for 1h, collecting a product, placing the ball-milled material into a reaction tube, then placing the reaction tube into a microwave reaction cavity, purging for 1h by using argon gas of 100m L/min, carrying out microwave heating for 10min by using the power of 1000W, and cooling to room temperature under the Ar atmosphere to obtain the MoS2A/C/graphene nanocomposite material.
Example 10
(1) The preparation method of graphene oxide is the same as example 1.
(2) Preparation of hexadecyltrimethyl ammonium tetrathiomolybdate by taking 1.00g ammonium molybdate and 30m L strong ammonia (NH)3·H2O) was added to the three-necked flask. Heated with stirring and 8g ammonium sulfide ((NH) added when the temperature rises to 60 deg.C4)2S), and reacting for 0.5h under the condition of magnetic stirring. Cetyl trimethylammonium bromide was then added to the solution, and a precipitate formed as the reaction continued. And then standing for 2 hours in an ice bath, gradually precipitating crystals, filtering the reaction solution, washing with absolute ethyl alcohol and deionized water, and drying to obtain tetraethylammonium tetrathiomolybdate.
(3) And (3) preparing the molybdenum disulfide/C/graphene composite material, namely mixing the hexadecyl trimethyl ammonium tetrathiomolybdate obtained in the step (2) with graphene oxide according to the mass ratio of 1:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of ball materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after carrying out ball milling for 1h, collecting a product, putting the ball-milled material into a reaction tube, then placing the reaction tube into a microwave reaction cavity, purging with 100m L/min of argon for 1h, carrying out microwave heating for 3min by using 600W of power, and cooling to room temperature under Ar atmosphere to obtain the molybdenum disulfide/C/graphene nano composite material.
Example 11
(1) The preparation method of graphene oxide is the same as example 1.
(2) Hexadecyltrimethylammonium tetrathiomolybdate was prepared as in example 10.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing hexadecyl trimethyl ammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 2:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of ball materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after carrying out ball milling for 1h, collecting a product, placing the ball-milled material into a reaction tube, then placing the reaction tube into a microwave reaction cavity, purging for 1h by using argon gas of 100m L/min, carrying out microwave heating for 5min by using power of 600W, and cooling to room temperature under the Ar atmosphere to obtain the molybdenum disulfide/C/graphene nanocomposite material.
Example 12
(1) The preparation method of graphene oxide is the same as example 1.
(2) Hexadecyltrimethylammonium tetrathiomolybdate was prepared as in example 10.
(3) The preparation method of the molybdenum disulfide/C/graphene composite material comprises the steps of mixing hexadecyl trimethyl ammonium tetrathiomolybdate and graphene oxide according to the mass ratio of 2:1, placing the mixture into an agate tank filled with nitrogen, carrying out ball milling by using a ball mill, wherein the mass ratio of ball materials is 3:1, the rotating speed is 400rpm, naturally cooling to room temperature after carrying out ball milling for 1h, collecting a product, placing the ball-milled material into a reaction tube, then placing the reaction tube into a microwave reaction cavity, purging for 1h by using argon gas of 100m L/min, carrying out microwave heating for 10min by using 1000W power, and cooling to room temperature under the Ar atmosphere to obtain the molybdenum disulfide/C/graphene composite material.
The molybdenum disulfide/C/graphene composite material obtained in the embodiment 1-12 is used as a lithium ion battery cathode material. Selecting synthesized molybdenum disulfide/C/graphene as an active componentUsing 2016 type battery case, lithium metal sheet (phi 16mm × 1mm), 1.0M L iPF6The mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1) is used as electrolyte, and Celgard2300 microporous polypropylene coal membrane is used as battery diaphragm. The materials are assembled into a button cell in a glove box filled with Ar gas, and the test is carried out after the working electrode is fully soaked by the electrolyte. The method comprises the following five steps:
(1) size mixing
The material used has a large specific surface and is easy to adsorb moisture in the air, so the material for preparing the electrode is firstly dried fully in a vacuum drying oven at 120 ℃ to remove the surface moisture. Then adding an active substance, a conductive additive (acetylene black) and a binder (PVDF) into the dispersant according to the mass percentage of 80:10:10N-methylpyrrolidone (NMP) mixed grinding, resulting in uniform mixing of the materials, making a viscous slurry.
(2) Coating film
The resulting viscous paste was uniformly coated on a copper foil (thickness of about 100 μm). The specific operation is as follows: 1) the copper foil of moderate size is cut and laid flat on a table top. 2) Removing stains on the surface of the copper foil. 3) The slurry was dispersed on a copper foil and uniformly spread on the copper foil using a die. 4) The copper foil coated with the slurry was dried in a vacuum drying oven at 120 ℃ for 12 hours.
(3) Roller compaction
After the completion of drying, the copper foil coated with the slurry was rolled with a small-sized rolling machine to prevent the electrode material from falling off from the surface of the copper foil.
(4) Tabletting
And cutting the rolled film into a plurality of circular electrode slices with the diameter of 12mm by using a manual slicer. In order to prevent the coating film from falling off during charge and discharge cycles, it was pressed into a sheet by an oil press. And taking out and weighing after drying, and waiting for battery loading.
(5) Assembled battery
The process of assembling the button cells was carried out in a glove box filled with Ar gas. The battery is assembled according to the sequence of negative battery shell/electrolyte/working electrode plate/electrolyte/diaphragm/lithium plate/positive battery shell. And standing for 24 hours, and carrying out electrochemical test after the electrolyte is fully soaked.
And carrying out charge and discharge tests on the assembled button type simulation battery. The material of example 12 was used at a voltage in the range of 0.01 to 3.0V and at a current of 100mA · g-1The results of the cycle stability test at the current density of (a) are shown in fig. 2. The first charge/discharge capacity and the discharge capacity after 100 charge/discharge tests of examples 1 to 12 are shown in Table 1.
TABLE 1
Comparative example 1
The same preparation method as in example 12 was employed except that microwave heating was not used and baking was carried out in a conventional muffle furnace at 800 ℃ for 10 min. The result shows that ammonium paramolybdate is not completely reacted, so that the yield of molybdenum disulfide/C/graphene is low, and the initial discharge capacity of the obtained material used for a lithium battery anode material is only 405.6 mAh.g-1。
Claims (15)
1. A preparation method of a molybdenum disulfide/C/graphene composite material comprises the following steps:
(1) preparation of a Thiometallate precursor: mixing molybdenum salt and ammonia water, heating to 40-70 ℃, adding ammonium sulfide, reacting for 0.5-2h, adding quaternary ammonium salt into the solution to generate a precipitate, cooling, standing until crystals are separated out, washing and drying to obtain a thio-metal salt precursor;
(2) preparing a composite material: mixing graphene oxide and the precursor of the thio-metal salt prepared in the step (1), and placing the mixture in a ball mill for grinding; and placing the ball-milled material in a microwave reaction cavity, and heating for 1-15min at the microwave power of 300-1000W to obtain the molybdenum disulfide/C/graphene composite material.
2. The method of claim 1, wherein the molybdenum salt is selected from ammonium molybdate and/or sodium molybdate.
3. The method according to claim 1, wherein the quaternary ammonium salt is an ammonium halide containing 4 to 30 carbons.
4. The method according to claim 3, wherein the quaternary ammonium salt is an ammonium halide having 4 to 25 carbons.
5. The method according to claim 3, wherein the quaternary ammonium salt is at least one selected from the group consisting of tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, octadecyltrimethylammonium chloride and octadecyltrimethylammonium bromide.
6. The method according to claim 1, wherein the molybdenum salt, the ammonium sulfide and the quaternary ammonium salt are mixed in a molar ratio of 1:1 to 20:0.1 to 5.
7. The method according to claim 1, wherein the aqueous ammonia is added in an amount to completely dissolve the molybdenum salt and maintain the pH of the mixed solution at 7.5 to 11.
8. The method according to claim 7, wherein the aqueous ammonia is added in an amount such that the pH of the mixed solution is 8 to 10.
9. The preparation method according to claim 1, wherein the mixing mass ratio of the graphene oxide and the thiometalate precursor in the step (2) is 1:1 to 20.
10. The preparation method of claim 1, wherein the mass ratio of the grinding balls to the mixed material in the ball mill during grinding is 1-20:1, and the grinding time is 0.5-3 h.
11. The method according to claim 1, wherein the graphene oxide is selected from the group consisting ofThe graphene oxide of (a): the area of the sheet layer is 100 mu m2The conductivity is 3500S/m or more.
12. The preparation method according to claim 1, wherein the graphene oxide is obtained by oxidizing graphite.
13. The preparation method according to claim 11, wherein the graphene oxide is synthesized by a Hummers method, and the preparation method comprises the following steps: adding natural crystalline flake graphite into ice-bath concentrated sulfuric acid under stirring, cooling to 0-10 ℃, adding sodium nitrate and potassium permanganate, stirring for reaction, adding deionized water, heating to 50-100 ℃, reacting at constant temperature until the reaction solution turns to bright yellow, adding hydrogen peroxide, stirring for reaction, cooling, washing, drying to obtain graphene oxide, and grinding into powder for later use.
14. The molybdenum disulfide/C/graphene composite material prepared by the method of any one of claims 1 to 12.
15. Use of the molybdenum disulfide/C/graphene composite material of claim 14 as a negative electrode material for a lithium ion battery.
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