CN112201484A - Two-dimensional ultrathin carbon nanosheet and preparation method and application thereof - Google Patents

Two-dimensional ultrathin carbon nanosheet and preparation method and application thereof Download PDF

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CN112201484A
CN112201484A CN202010856506.8A CN202010856506A CN112201484A CN 112201484 A CN112201484 A CN 112201484A CN 202010856506 A CN202010856506 A CN 202010856506A CN 112201484 A CN112201484 A CN 112201484A
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ultrathin carbon
dimensional ultrathin
dimensional
sulfur
carbon
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邹艳文
杨斌
林倩
陈锡安
郭大营
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Wenzhou University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/44—Raw materials therefor, e.g. resins or coal
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors

Abstract

The invention discloses a two-dimensional ultrathin carbon nano-sheet, a preparation method and application thereof, wherein the thickness of the two-dimensional ultrathin carbon nano-sheet is between 4 and 29nm, the average thickness is about 12nm, the two-dimensional ultrathin carbon nano-sheet has rich micro-mesoporous structure and 494-doped 640m specific surface area2g‑1. In particular toA cheap and easily-obtained high-molecular polymer material sodium polyacrylate with strong water absorbability is used as a carbon precursor, water is used as a regulator, a freeze drying technology is combined, and the template-free method is used for preparing the ultrathin carbon nanosheet by controlling the using amount of the water. The method has the advantages of simple and easy operation, high controllability, cheap and easily obtained raw materials, and environmental protection. The prepared ultrathin carbon nanosheet is used as a supercapacitor electrode material or can be used as a lithium-sulfur battery anode to load sulfur, and the characteristics of ultrathin porous structure, rich oxygen atoms in a carbon skeleton and the like are utilized to accelerate the diffusion of electrolyte ions, strengthen the binding to polysulfide ions and improve the performances of a capacitor and the lithium-sulfur battery.

Description

Two-dimensional ultrathin carbon nanosheet and preparation method and application thereof
Technical Field
The invention belongs to the field of nano materials and electrochemical energy storage, and particularly relates to a two-dimensional ultrathin carbon nanosheet and a preparation method and application thereof.
Background
With the ever increasing demand for energy storage for portable electronics, vehicle electrification and grid-scale stationary storage, electrochemical storage devices with high energy and power densities have rapidly developed. Therefore, there is an urgent need to find suitable electrode materials for the preparation of high-performance electrochemical energy storage devices, such as supercapacitors and lithium-sulfur batteries. The carbon-based compound has the excellent characteristics of low cost, easy acquisition, no toxicity, environmental friendliness, good stability and the like, and is widely concerned in recent years. Various carbon materials such as hard carbon, soft carbon, porous carbon, modified graphite and the like are developed, and the carbon materials show good application prospects in super capacitors and lithium-sulfur batteries. Designing a special morphology with stable nanostructures and hierarchical porosity is an effective method to improve the electrochemical performance of carbon-based materials.
The carbon nanosheet is used as a novel two-dimensional carbon nanomaterial with a graphene-like structure, and has a high specific surface area, so that the mass transfer distance is reduced, and the overall conductivity of the electrode is improved. And the ultrathin nanosheets shorten the electron transfer distance, are favorable for the permeation of electrolyte and the like, and can be used as ideal electrode materials of lithium-sulfur batteries and super capacitors.
At present, carbon nano-sheets are generally prepared by a template method, and are generally synthesized under the synergistic action of a plurality of templates. For example, Qiu et al (adv.Funct.Mater.1/2016) use gelatin as a carbon and nitrogen precursor, and boric acid as a boron source and a two-dimensional template to prepare a carbon nanosheet for application in a supercapacitor.
In addition, chinese patent application publication No. CN106025239A discloses a preparation method of a two-dimensional nitrogen-doped hierarchical porous carbon nanosheet, comprising the following steps: carbonizing an organic metal framework containing nitrogen at a carbonization temperature of 910-2000 ℃ in a gas atmosphere, and cooling to obtain a two-dimensional nitrogen-doped hierarchical porous carbon nanosheet; the metal ions in the nitrogen-containing metal organic framework are zinc ions, although the method can prepare the two-dimensional porous nitrogen-doped carbon nanosheet without a template. However, the synthesis method is subjected to two steps of carbonization and activation, the process is complex, and the precursor source is not easy to obtain.
Chinese patent application publication No. CN110577207A discloses a nitrogen-phosphorus co-doped carbon nanosheet, which adopts p-phenylenediamine, terephthalaldehyde and DOPO as raw materials, and adopts an organic reagent to pollute the environment, which is not favorable for large-scale production.
In conclusion, due to the defects of the prior art, how to simply and effectively prepare the ultrathin carbon nanosheet still has very important significance.
Disclosure of Invention
In order to solve the problems and the defects in the prior art, the first purpose of the invention is to provide a preparation method of a two-dimensional ultrathin carbon nanosheet, the preparation method has the advantages of no need of a template, cheap and easily available raw materials and adjustable thickness, and the preparation of the ultrathin carbon nanosheet can be realized.
The invention also provides an application of the two-dimensional ultrathin carbon nanosheet material in a lithium-sulfur battery anode and a supercapacitor electrode.
In order to realize the first purpose of the invention, the technical proposal is that sodium polyacrylate and water are mixed and stirred vigorously to obtain a jelly-shaped precursor, then the solvent in the precursor is removed by a freeze drying mode, and then the high-temperature annealing treatment is carried out under the atmosphere of inert gas; and then washing the annealing product by using a hydrochloric acid aqueous solution to remove a sodium compound, performing suction filtration, and drying to obtain the two-dimensional carbon nanosheet.
The ratio of the sodium polyacrylate to the water is further set to be 1:50-1: 250.
Further setting the annealing temperature to 700-1000 ℃ and the heating rate to 1-5 ℃ for min in the annealing treatment-1And keeping the temperature for 1-3 h.
Further setting the standing time of freeze drying to be 36-45 h.
The thickness of the two-dimensional ultrathin carbon nano-sheet is between 4 and 29nm, the appearance, the structure and the size are uniform, the two-dimensional ultrathin carbon nano-sheet has a large number of micropores and mesoporous structures, and the specific surface area is 494-2 g-1。
The invention also provides an application method of the two-dimensional ultrathin carbon nanosheet, which is characterized by comprising the following steps: the two-dimensional ultrathin carbon nanosheet can be loaded with sulfur and applied to the positive electrode of a lithium-sulfur battery.
In the above application method, the preparation method of the positive electrode of the lithium-sulfur battery comprises the following steps:
1) grinding and mixing the two-dimensional ultrathin carbon nanosheet and elemental sulfur according to the mass ratio of 1:3-2:3, then placing the mixture into a reaction oven, heating the mixture to 165 ℃, reacting for 12 hours, and cooling the mixture to room temperature after the reaction is finished to obtain the two-dimensional ultrathin carbon nanosheet/sulfur composite material.
2) Uniformly mixing the two-dimensional ultrathin carbon nanosheet/sulfur composite material, conductive carbon and polyvinylidene fluoride according to the mass ratio of 8:1:1, coating the mixture on an aluminum foil current collector, drying the aluminum foil current collector in vacuum at the temperature of 60 ℃, and then rolling and slicing the aluminum foil current collector to obtain the lithium-sulfur battery anode. Then the negative electrode is a lithium sheet, and the electrolyte is a mixed solution of lithium bistrifluoromethylsulfonate imide, lithium nitrate, ethylene glycol dimethyl ether and 1, 3-dioxane.
3) The weighed positive plate, the diaphragm, the button battery shell, the lithium plate, the electrolyte and other accessories required by the assembled battery are led into a glove box filled with argon gas to be assembled to test the performance of the assembled battery, and the specific capacity of the battery is 1245mAh g when the battery is discharged at 0.2C-1。
The invention also provides an application of the two-dimensional ultrathin carbon nanosheet as a working electrode of a supercapacitor. The two-dimensional microporous ultrathin carbon nanosheet is used as an electrode material of a supercapacitorThe electrochemical performance of the carbon nano-chip is evaluated by using a conventional three-electrode system, a platinum sheet is used as a counter electrode, saturated calomel is used as a reference electrode, the electrolyte is 6M KOH, and the carbon nano-chip base electrode has the current density of 0.5A g-1Specific capacitance reaches 260F g during discharge-1Increasing the current density to 100A g-1The discharge specific capacitance can still reach 137F g-1。
The invention has the following beneficial effects:
1. the method takes a cheap and easily-obtained high polymer material (PAAS) with strong water absorption as a carbon precursor, utilizes water as a regulator, combines a freeze drying technology, and realizes the template-free method for preparing the ultrathin carbon nanosheet by controlling the using amount of solvent water.
2. The prepared ultrathin carbon nanosheet has a rich microporous structure and a uniform structural height. Using water as regulator, the specific surface area is 297m2 g-1Increased to 639m2 g-1. The ultrathin nanosheets form a two-dimensional conductive network, so that the mass transfer distance is reduced, and the overall conductivity of the electrode is improved. The ultrathin nanosheets shorten the electron transfer distance, and are beneficial to the permeation of electrolyte, so that the ultrathin nanosheets have excellent performance when being applied to lithium-sulfur batteries and super capacitors.
3. The method has the advantages of simple process, easy operation, high controllability, cheap and easily obtained raw materials, and environmental protection.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is within the scope of the present invention for a person skilled in the art to obtain other drawings based on the drawings without inventive exercise.
FIG. 1 is an SEM image of a sample obtained in examples 1 and 2 of the present invention;
FIG. 2 is an AFM image of a sample obtained in example 2 of the present invention;
FIG. 3 is a graph showing a nitrogen adsorption/desorption curve and a pore size distribution of samples obtained in examples 1 to 4 of the present invention;
FIG. 4 is a TG plot of samples obtained in examples 1 and 2 of the present invention;
FIG. 5 is a graph showing discharge capacities at different rates of charge and discharge when samples obtained in examples 1 to 4 according to the present invention were used as positive electrodes of lithium sulfur batteries;
FIG. 6 is a graph showing the charge-discharge cycle stability and coulombic efficiency of the samples obtained in examples 1 and 2 of the present invention as the positive electrode of a lithium-sulfur battery;
FIG. 7 is a graph showing capacity comparison of samples obtained in examples 1 and 2 of the present invention as electrode materials of a supercapacitor at different current densities;
FIG. 8 is a graph showing the cycle performance of the sample obtained in example 2 of the present invention as an electrode material for a supercapacitor.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
Example 1 as a comparative example
2g of sodium polyacrylate is annealed at a high temperature in an argon atmosphere and at a temperature of 5 ℃ for min-1Heating to 800 ℃, preserving heat for 2h, naturally cooling, washing with 1M HCl to remove sodium compounds, filtering, and drying to obtain the Carbon Nanosheet (CNS). (see FIG. 1a)
And (3) knotting: sodium polyacrylate direct annealing as a comparative sample, the average thickness of the carbon nanosheets was 151. + -. 7.40 (see FIGS. 1c, e), and the specific surface area was 297m2 g-1The pore volume is 0.2328cm3 g-1(see FIG. 3).
Example 2
250mL of deionized water was first added to a round bottom flask, 2g of sodium Polyacrylate (PAAS) was uniformly dispersed in the water with slow stirring, and stirred rapidly for 2h to form a uniform jelly-like solution. Freezing and coagulating the uniformly dispersed mixed solution in a refrigerator, freeze-drying the frozen solution in a freeze dryer, annealing the freeze-dried solution at a high temperature under argon atmosphere for 5 min-1Raising the temperature to 800 ℃, preserving the temperature for 2 hours, and then naturally coolingAnd washing with 1M HCl to remove sodium compounds, filtering, and drying to obtain the carbon nanosheet (U-PCNS 2). (see FIG. 1b)
And (3) knotting: the size of the carbon nano-sheet is between 4 and 29nm (see figures 1 and 2), the average thickness is 12.57 +/-1.18 (see figures 1d and e), and the specific surface area is 639m2 g-1The pore volume is 0.5223cm3 g-1(see FIG. 3).
Example 3
100mL of deionized water was first added to a round bottom flask, 2g of sodium Polyacrylate (PAAS) was uniformly dispersed in the water with slow stirring, and stirred rapidly for 2h to form a uniform jelly-like solution. Freezing and coagulating the uniformly dispersed mixed solution in a refrigerator, freeze-drying in a freeze dryer, treating at high temperature under argon atmosphere, and cooling at 5 deg.C for 5 min-1Heating to 800 ℃, preserving heat for 2h, naturally cooling, washing with 1M HCl to remove sodium compounds, filtering, and drying to obtain the carbon nano sheet (U-PCNS 1).
And (3) knotting: the specific surface area is 494m2 g-1The pore volume is 0.4123cm3 g-1(see FIG. 3).
Example 4
500mL of deionized water was first added to a round bottom flask, 2g of sodium Polyacrylate (PAAS) was uniformly dispersed in the water with slow stirring, and stirred rapidly for 2h to form a uniform jelly-like solution. Freezing and coagulating the uniformly dispersed mixed solution in a refrigerator, freeze-drying the frozen solution in a freeze dryer, annealing the freeze-dried solution at a high temperature under argon atmosphere for 5 min-1Heating to 800 ℃, preserving heat for 2h, naturally cooling, washing with 1M HCl to remove sodium compounds, filtering, and drying to obtain the carbon nano sheet (U-PCNS 3).
And (3) knotting: the specific surface area is 509m2 g-1The pore volume is 0.4387cm3 g-1(see FIG. 3).
Example 5
Step one, preparation of two-dimensional carbon nanosheet/sulfur composite material
Taking 0.08g of the two-dimensional carbon nanosheet material in examples 1, 2, 3 and 4, placing the two-dimensional carbon nanosheet material in an agate mortar, mixing 0.187g of sulfur powder, placing the mixture in an oven at 165 ℃ for heating, cooling after 12h, taking out the mixture to obtain two-dimensional carbon nanosheets/sulfur (CNS @ S and U-PCNS @ S), and analyzing the two-dimensional carbon nanosheets/sulfur by a thermogravimetric diagram (FIG. 4), wherein the sulfur content is 70 wt%.
Step two, preparation of lithium-sulfur battery positive electrode and battery assembly
Dissolving the two-dimensional carbon nanosheet/sulfur composite material, conductive carbon and PVDF in a mass ratio of 8:1:1 in pyrrolidone, stirring for 24 hours to form slurry, coating the slurry on an aluminum foil on a coating machine, drying in vacuum at 60 ℃ for 12 hours, taking out, cutting into round pieces with the diameter of 1.5cm to obtain a self-made lithium-sulfur battery anode, and assembling the battery according to a conventional lithium battery assembling method, wherein an electrolyte is a mixed solution of 1mol/L bis (trifluoromethyl) sulfonic acid imide lithium, 1% ethylene glycol dimethyl ether of lithium nitrate and 1, 3-dioxane.
Step three, testing the performance of the battery conventionally
All the examples were tested for charge and discharge at different current densities using the LAND test system, with the voltage range of charge and discharge being 1.5-3V, and the electrochemical performance was evaluated at different rates (0.2-5C). It follows that the initial capacity of the U-PCNS2@ S battery can reach 1245mAh g at 0.2C-1. At 5C, the capacity of the battery can reach 628mAh g-1. The initial capacity of the CNS @ S battery can reach 1019mAh g-1. At 5C, the capacity of the battery can reach 476mAh g-1(see FIG. 5). Meanwhile, the carbon nano sheet has excellent cycle performance, and the U-PCNS2@ S still has 496mAh g after 1000 cycles under the multiplying power of 1C-1The capacity of (a), the capacity fade rate of 0.046% and the coulombic efficiency close to 100% (see fig. 6), is superior to CNS @ S cells.
Example 6
The two-dimensional carbon nanosheet material (CNS and U-PCNS2) is used as an electrode material of a supercapacitor, the electrochemical performance of the supercapacitor is evaluated in a conventional three-electrode system, a platinum sheet is used as a counter electrode, saturated calomel is used as a reference electrode, and an electrolyte is 6M KOH. Active substance (80 wt%), acetylene black (10 wt%) and polytetrafluoroethylene (10 wt%) were mixed. The mixture was pressed into a sheet and then into a nickel foam (1 x 1 cm) current collector for use in a working electrode. Putting the foamed nickel into an oven at 100 DEG CAnd drying for 12h, taking out the foamed nickel, and pressing into a sheet to obtain the electrode plate. The electrode pieces were then immediately weighed and the label recorded. Before testing, the electrode plate is soaked in electrolyte for 5h, so that the electrolyte is fully contacted with the electrode material. Various electrochemical properties were measured in a three-electrode system, with red sandwiched counter electrode, green sandwiched working electrode, and white sandwiched reference electrode. The two-dimensional carbon nanosheet materials in examples 1 and 2 were subjected to charge and discharge tests at different current densities, wherein the voltage range of charge and discharge was-1-0V, and the charge and discharge voltage ranges from 0.5 to 100A g at different current densities-1) The electrochemical properties were evaluated as follows. At a current density of 0.5A g-1When the specific capacity of the U-PCNS2 electrode reaches 255F g-1The CNS specific capacity reaches 137.3F g-1(see FIG. 7). Increasing the current density to 100A g-1The specific capacitance of the electrode of the U-PCNS2 still reaches 139F g-1Whereas the specific capacitance of the CNS electrode is only 48F g-1The result shows that the ultrathin structure has a good effect of improving the rate capability. Meanwhile, the carbon nano sheet has excellent cycle performance, and the cycle performance is 5A g-1At a current density of 97% of the initial capacity after 10000 cycles (see fig. 8).
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.

Claims (8)

1. A preparation method of a two-dimensional ultrathin carbon nanosheet comprises the following specific steps: mixing sodium polyacrylate and water, stirring vigorously to obtain a jelly-like precursor, removing a solvent in the precursor in a freeze drying mode, and performing high-temperature annealing treatment in an inert gas atmosphere; and then washing the annealing product by using a hydrochloric acid aqueous solution to remove a sodium compound, performing suction filtration, and drying to obtain the carbon nanosheet.
2. A method for preparing two-dimensional ultrathin carbon nanosheets as recited in claim 1, wherein: the ratio of the sodium polyacrylate to the water amount is 1:50-1: 250.
3. A method for preparing two-dimensional ultrathin carbon nanosheets as recited in claim 1, wherein: in the annealing treatment, the annealing temperature is 700-1000 ℃, and the heating rate is 1-5 ℃ for min-1And keeping the temperature for 1-3 h.
4. A method for preparing two-dimensional ultrathin carbon nanosheets as recited in claim 1, wherein: the standing time for freeze drying is 36-45 h.
5. Two-dimensional ultrathin carbon nanosheets produced by the method of any one of claims 1 to 4, wherein: the two-dimensional ultrathin carbon nano-sheet has the thickness of 4-29nm, rich micro-mesoporous structures and the specific surface area of 494-2g-1。
6. A method of using the two-dimensional ultrathin carbon nanoplates of claim 5, wherein: the two-dimensional ultrathin carbon nanosheet can be loaded with sulfur and applied to the positive electrode of a lithium-sulfur battery.
7. A preparation method of a lithium-sulfur battery positive electrode is characterized by comprising the following steps:
1) grinding and mixing the two-dimensional ultrathin carbon nanosheet and elemental sulfur according to the mass ratio of 1:3-2:3, then placing the mixture into a reaction oven, heating the mixture to 165 ℃, reacting for 12 hours, and cooling the mixture to room temperature after the reaction is finished to obtain a two-dimensional ultrathin carbon nanosheet/sulfur composite material;
2) uniformly mixing the two-dimensional ultrathin carbon nanosheet/sulfur composite material, conductive carbon and polyvinylidene fluoride according to the mass ratio of 8:1:1, coating the mixture on an aluminum foil current collector, drying the aluminum foil current collector in vacuum at the temperature of 60 ℃, and then rolling and slicing the aluminum foil current collector to obtain the lithium-sulfur battery anode.
8. The application of the two-dimensional ultrathin carbon nanosheets prepared by the preparation method as claimed in any one of claims 1 to 4, wherein the two-dimensional ultrathin carbon nanosheets are used as electrode materials of a supercapacitor.
CN202010856506.8A 2020-08-24 2020-08-24 Two-dimensional ultrathin carbon nanosheet and preparation method and application thereof Pending CN112201484A (en)

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CN112838215A (en) * 2021-03-04 2021-05-25 桂林电子科技大学 Three-dimensional porous carbon nanosheet-sulfur material and preparation method and application thereof

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