Two-dimensional carbon plate loaded nanocrystalline composite material as well as preparation method and application thereof

Abstract

The invention discloses a two-dimensional carbon plate loaded nanocrystalline composite material and a preparation method and application thereof, and the preparation method comprises the following steps: S1, preparing a solution, dissolving a template agent, a carbon-containing anion agent and a metal salt in a solvent, and stirring to fully dissolve to obtain a mixed solution; s2, placing the mixed solution in a high-pressure reaction kettle by a one-pot method, converting a carbon-containing component in the solution into a two-dimensional carbon plate under a high-temperature condition, performing nucleation growth on metal ions and anions in the solution on the surface of the two-dimensional carbon plate, and after the reaction is finished, separating a solid to obtain a precursor; and S3, calcining: placing the precursor in an atmosphere furnace, adding an active substance into the atmosphere furnace or introducing active gas into the atmosphere furnace, and calcining in a protective gas atmosphere to obtain the two-dimensional carbon plate loaded nanocrystalline composite material. The two-dimensional carbon plate-loaded nanocrystalline composite material has a uniform nanoscale grain size, and has relatively high specific capacity when being used as a lithium ion battery negative electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of battery electrode materials, and particularly to a composite material of two-dimensional carbon sheets loaded with nanocrystals, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of portable electronic devices and electric vehicles, lithium-ion batteries based on graphite anodes with a low theoretical specific capacitance (372 mAh / g) are difficult to meet the demand. Therefore, it is imperative to develop lithium-ion batteries with both high specific capacitance and long cycle ability; anode materials with a two-dimensional layered morphology have various excellent properties. Their two-dimensional morphology can effectively release structural stress during charge and discharge, and their extremely thin thickness also reduces the ion migration path. In addition, the fully exposed active surfaces and edge sites also significantly increase the chemical reaction interface and improve reaction kinetics.

[0003] However, currently, only a few intrinsic layered crystal materials, such as molybdenum disulfide, are easily synthesized two-dimensional materials. Such materials are extremely prone to re-stacking and will undergo drastic volume changes and polysulfide dissolution during charge and discharge, resulting in a rapid decay of specific capacitance. Therefore, it is very important to develop a method for two-dimensionalizing various metal compounds.

[0004] There are also methods in the prior art for two-dimensionalizing metal compounds. For example, Chinese Patent Publication No. CN115312713A discloses a method for obtaining a similar product by loading nanocrystals on graphene. However, such methods have many problems, such as poor binding force between nanocrystals and graphene, easy aggregation of nanocrystals, uneven dispersion of the product, and high cost of graphene. Summary of the Invention

[0005] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a composite material of two-dimensional carbon sheets loaded with nanocrystals, a preparation method thereof, and an application thereof. By converting the carbon-containing components in the mixed solution into two-dimensional carbon sheets through a one-pot method, and enabling the nanocrystals to grow on the surface of the two-dimensional carbon sheets, and then obtaining the composite material of two-dimensional carbon sheets loaded with nanocrystals through calcination. The composite material of two-dimensional carbon sheets loaded with nanocrystals has a nanoscale uniform grain size and has a high specific capacity when used as an anode material for lithium-ion batteries.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a preparation method of a composite material of two-dimensional carbon sheets loaded with nanocrystals, comprising the following steps:

[0008] S1, preparing a solution by dissolving a template agent, a carbon-containing anion agent, and a metal salt in a solvent, and stirring to fully dissolve them to obtain a mixed solution;

[0009] S2. In the one-pot method, the mixed solution is placed in a high-pressure reactor. Under high-temperature conditions, the carbon-containing components in the solution are converted into two-dimensional carbon sheets, and metal ions and anions in the solution nucleate and grow on the surface of the two-dimensional carbon sheets. After the reaction ends, the solid is separated to obtain a precursor.

[0010] S3. Calcination: The precursor is placed in an atmosphere furnace, and an active substance is added to the atmosphere furnace or an active gas is introduced. Calcination is carried out under a protective gas atmosphere to obtain a composite material of two-dimensional carbon sheet-supported nanocrystals.

[0011] Preferably, in step S1:

[0012] The template agent is a surfactant, and the surfactant is selected from one of anionic surfactants, cationic surfactants, and non-ionic surfactants;

[0013] The carbon-containing anion agent is selected from one of polycarbonic acids or salts containing polycarbonate groups;

[0014] The metal salt is selected from one of soluble tin salts, copper salts, cobalt salts, iron salts, and nickel salts;

[0015] The solvent is a composite solvent containing water and / or ethanol.

[0016] Preferably, the non-ionic surfactant is a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer surfactant or a fatty alcohol polyoxyethylene ether; and / or

[0017] The carbon-containing anion agent is selected from one of citric acid, oleic acid, humic acid, citrates, oleates, humates, and citrates; and / or

[0018] The metal salt is selected from one of sodium molybdate, hydrated stannic chloride, copper chloride, hydrated cobalt nitrate, and hydrated ferric chloride; and / or

[0019] The composite solvent is selected from one or more of isopropanol, n-hexane, and cyclohexane, and the composite solvent contains an acid.

[0020] Preferably, in step S1, the mass ratio of the template agent, the carbon-containing component, and the metal salt is 2:1:1 to 1:3:3, and the volume ratio of the total mass of the template agent, the carbon-containing anion agent, and the metal salt to the solvent is 1:1 to 1:20.

[0021] Preferably, in step S2, the high-temperature condition is 120 to 270 °C, and the reaction time is 20 to 1440 min.

[0022] Preferably, the high-temperature condition is 150 to 220 °C, and the reaction time is 120 to 720 min.

[0023] Preferably, in step S2, after the reaction is completed, a filter membrane is used for suction filtration to separate the solid.

[0024] Preferably, in step S3:

[0025] The atmosphere furnace is one of a tube furnace, a box furnace or a vacuum atmosphere furnace; and / or

[0026] The active substance or active atmosphere is selected from one of NaH2PO2·H2O, sulfur, phosphorus, substances capable of releasing hydrogen sulfide or phosphine gas, or hydrogen sulfide, phosphine; and / or

[0027] The mass ratio of the precursor to the active substance is 10:1 to 1:10; and / or

[0028] During the calcination process, the calcination temperature is 300 - 1000 °C, the protective gas is nitrogen or an inert gas, and the calcination time is 0.5 - 12 h.

[0029] Preferably, in step S3, the calcination temperature is 350 - 800 °C.

[0030] The second aspect of the present invention provides a composite material of two-dimensional carbon sheet supported nanocrystals prepared by the preparation method of the composite material of two-dimensional carbon sheet supported nanocrystals as described in the first aspect of the present invention.

[0031] The third aspect of the present invention is the application of a composite material of two-dimensional carbon sheet supported nanocrystals as described in the second aspect of the present invention as a negative electrode material in a lithium-ion battery.

[0032] The beneficial effects of the present invention are as follows:

[0033] 1. The present invention converts the carbon-containing components in the mixed solution into two-dimensional carbon sheets by a one-pot method, enables the growth of nanocrystals on the surface of the two-dimensional carbon sheets, and then obtains a composite material of two-dimensional carbon sheet supported nanocrystals through calcination. The composite material of two-dimensional carbon sheet supported nanocrystals has a nanoscale uniform grain size and has a high specific capacity when used as a negative electrode material for lithium-ion batteries.

[0034] 2. The present invention induces the growth process of nanocrystal materials through a polymer template agent and uses a one-pot method to achieve the spreading and growth of nanocrystal materials on two-dimensional carbon sheets, which can be used to two-dimensionalize the grains of various metal compounds that are easy to grow in three dimensions;

[0035] 3. The composite material of two-dimensional carbon sheet supported nanocrystals prepared by the present invention has a nanoscale uniform grain size and tightly grows on the surface of the two-dimensional carbon sheet derived from carbon-containing components (carbon-containing anion agent, carbon-containing polymer in the solvent), greatly increasing the specific surface area of the grains. When it is used as an electrode material for lithium-ion batteries, it has a large contact area with the electrolyte, and the power performance is significantly improved.

[0036] 4. The preparation method of the present invention has controllable process, simple steps, and is convenient for process improvement and large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] By reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings, other features, objects and advantages of the present invention will become more apparent:

[0038] Figure 1 It is a process flow diagram of the preparation method of the composite material of two-dimensional carbon sheet supported nanocrystals of the present invention;

[0039] Figure 2 It is a scanning electron microscope (SEM) image of the composite material of two-dimensional carbon sheet supported nanocrystals prepared in Example 1 of the present invention;

[0040] Figure 3 It is a high-magnification SEM image of the composite material of two-dimensional carbon sheet supported nanocrystals prepared in Example 1 of the present invention;

[0041] Figure 4 It is a rate performance graph of the composite material of two-dimensional carbon sheet supported nanocrystals prepared in Example 1 of the present invention used as a negative electrode material for lithium-ion batteries. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form.

[0043] Combined with Figure 1 As shown, a preparation method of a composite material of two-dimensional carbon sheet supported nanocrystals provided by the present invention includes the following steps:

[0044] S1, prepare a solution by dissolving a template agent, a carbon-containing anion agent, and a metal salt in a solvent, and stir to fully dissolve them to obtain a mixed solution;

[0045] The templating agent can be common surfactants, such as anionic surfactants, cationic surfactants, and non-ionic surfactants; in a preferred embodiment, non-ionic surfactants can be used, such as poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer surfactants, fatty alcohol polyoxyethylene ethers, etc.; among them, the type of surfactant affects the morphology and composition of two-dimensional carbon sheets, so surfactants with long-chain polymer structures and surfactants with a high proportion of carbon atoms in the molecular chain are preferred. The role of this templating agent is to induce the growth process of nanomaterials.

[0046] The carbon-containing anion agent is selected from one of polycarboxylic acids or salts containing polycarboxylate groups, such as citric acid, oleic acid, humic acid, citric acid, citrate, oleate, humate, citrate, etc.; the role of the carbon-containing anion agent is to be converted into two-dimensional carbon sheets in the one-pot method.

[0047] The metal salt can be one of soluble tin salts, copper salts, cobalt salts, iron salts, nickel salts, such as sodium molybdate, hydrated stannous chloride, copper chloride, hydrated cobalt nitrate, hydrated ferric chloride, etc.; the role of the metal salt is to dissolve in the solvent and in the one-pot method, nucleate and grow on the surface of the two-dimensional carbon sheet into insoluble metal hydroxides or metal oxides corresponding to the metal ions contained in the metal salt.

[0048] The solvent can be an organic solvent containing water and / or ethanol, and the organic solvent can be one or more of isopropyl alcohol, n-hexane, cyclohexane; that is, the solvent can be one or more of water, ethanol, isopropyl alcohol, n-hexane, cyclohexane, but cannot be completely free of water or ethanol. The solvent also contains acids, such as hydrochloric acid, sulfuric acid, nitric acid, etc., and its role is to enable the metal salt to dissolve in the solvent; the role of the solvent: on the one hand, it dissolves the templating agent, the carbon-containing anion agent, and the metal salt, and on the other hand, the carbon-containing polymer in it is converted into two-dimensional carbon sheets in the one-pot method.

[0049] The mass ratio of the above-mentioned templating agent, carbon-containing anion agent, and metal salt is 2:1:1 to 1:3:3, and the volume ratio of the total mass of the templating agent, carbon-containing component, and metal salt to the solvent is 1:1 to 1:20.

[0050] Dissolve the templating agent, carbon-containing component, and metal salt in the solvent in proportion, and stir to completely dissolve them to obtain a mixed solution.

[0051] S2, One-pot method: Place the mixed solution in a high-pressure reactor. Under high-temperature conditions, the carbon-containing component in the solution is converted into two-dimensional carbon sheets, and metal ions and anions in the solution nucleate and grow on the surface of the two-dimensional carbon sheets. After the reaction ends, separate the solid to obtain the precursor;

[0052] This process uses a one-pot method to synthesize the precursor. The mixed solution prepared in S1 is placed in a high-pressure reactor. Under high-temperature conditions, the carbon-containing components in the solution (carbon-containing anion agents and carbon-containing polymers in the solvent) are derivatized and transformed into two-dimensional carbon sheets. Metal ions and anions in the solution nucleate and grow on the surface of the two-dimensional carbon sheets. After the reaction ends, wait for the high-pressure reaction furnace to cool down completely, and then separate the solid (the solid can be collected by filtration using a filter membrane, and then washed and dried) to obtain the precursor. In the above process, the high-pressure reactor can be a stainless-steel high-pressure reactor with a polytetrafluoroethylene inner liner; the high-temperature conditions are 120-270 °C, preferably 150-220 °C, the reaction time is 20-1440 min, preferably 120-720 min.

[0053] S3, calcination. Place the precursor in a muffle furnace, and add an active substance or introduce an active gas into the muffle furnace. After calcination under a protective gas atmosphere, a composite material of two-dimensional carbon sheets loaded with nanocrystals is obtained.

[0054] Specifically, place the precursor prepared in step S2 in a muffle furnace, add an active substance or introduce an active gas, and perform calcination under a protective gas atmosphere. During this process, the active gas (if an active substance is added, the active substance decomposes or sublimes to form an active gas during this process) reacts with the precursor to finally obtain a composite material of two-dimensional carbon sheets loaded with nanocrystals; in the above process, the muffle furnace can be one of a conventional tube furnace, box furnace or vacuum muffle furnace; the protective gas can be nitrogen or argon. The active substance can be NaH2PO2·H2O, sulfur, phosphorus, etc., and the active gas can be hydrogen sulfide, phosphine. The mass ratio of the precursor to the active substance is 10:1-1:10. During the calcination process, the calcination temperature is 300-1000 °C, preferably 350-800 °C, and the calcination time is 0.5-12 h.

[0055] The raw materials and reagents used in the preparation method of the present invention are all commercially available.

[0056] The composite material of two-dimensional carbon sheets loaded with nanocrystals prepared by using the above preparation method of the composite material of two-dimensional carbon sheets loaded with nanocrystals has typical two-dimensional nanomaterial characteristics, the material thickness is <50 nm, and the size of the nanocrystals loaded on the two-dimensional carbon sheets is <50 nm.

[0057] The above application of the composite material of two-dimensional carbon sheets loaded with nanocrystals as a negative electrode material in a lithium-ion battery has a specific capacity greater than 600 mAh / g at a current density of 0.1 A / g.

[0058] The following further introduces the composite material of two-dimensional carbon sheets loaded with nanocrystals of the present invention, its preparation method and application in combination with specific examples.

[0059] Example 1

[0060] The preparation method of the composite material of two-dimensional carbon sheet supported nanocrystals in this embodiment comprises the following steps:

[0061] (1) Prepare the solution: Dissolve 1.6 g of sodium oleate, 1.0 g of sodium molybdate, and 0.8 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer in a solvent containing 15 mL of water, 15 mL of ethanol, and 5 mL of hydrochloric acid (concentration 37%). After complete dissolution, a mixed solution is obtained.

[0062] (2) One-pot method: Transfer the mixed solution to a stainless-steel autoclave with a polytetrafluoroethylene inner liner. Seal the autoclave and place it in an electric furnace at 180 °C for 24 hours, then naturally cool it to room temperature. After that, use a filter membrane to filter and collect the precipitate, wash it with distilled water, and dry it to obtain the precursor.

[0063] (3) Calcination: Place 1 g of the obtained precursor in a tubular furnace filled with argon and calcine it at 650 °C for 2 hours. Place 1 g of NaH2PO2·H2O in the tubular furnace to decompose and release PH3. Finally, a composite material of two-dimensional carbon sheet supported molybdenum phosphide is obtained. The thickness of its two-dimensional nanosheets is about 10 nm, and the cauliflower-shaped molybdenum phosphide grains grown on the two-dimensional nanosheets are less than 50 nm.

[0064] Combined with Figure 2 the SEM image of the composite material of two-dimensional carbon sheet supported molybdenum phosphide shown in Figure 3 it can be seen that the composite material of two-dimensional carbon sheet supported molybdenum phosphide in this embodiment presents a typical flaky structure. Combined with

[0065] the high-magnification SEM image shown in Figure 4 it can be seen that the thickness of the flaky composite material of two-dimensional carbon sheet supported molybdenum phosphide is about 30 nm, and cauliflower-shaped fine protrusions of molybdenum phosphide grains are loaded on the sheet.

[0066] Example 2

[0067] The preparation method of the composite material of two-dimensional carbon sheet supported nanocrystals in this embodiment comprises the following steps:

[0068] (1) Preparation of solution: Dissolve 1.6 g of sodium oleate, 1.5 g of hydrated stannic chloride, and 0.8 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer in a solvent containing 15 mL of water, 15 mL of ethanol, and 5 mL of hydrochloric acid (concentration 37%) to obtain a mixed solution after complete dissolution;

[0069] (2) One-pot method: Transfer the mixed solution to a stainless-steel autoclave with a polytetrafluoroethylene inner liner. Seal the autoclave and place it in an electric furnace at 200 °C for 24 hours, then naturally cool it to room temperature. After that, use a filter membrane to filter and collect the precipitate, wash it with distilled water, and dry it to obtain the precursor.

[0070] (3) Calcination: Place 1 g of the obtained precursor in a tubular furnace filled with argon and calcine it at 800 °C for 2 hours. Place 1 g of sulfur (sublimed sulfur) in the tubular furnace to sublimate and release sulfur vapor, and finally obtain a composite material of tin sulfide supported on two-dimensional carbon sheets, with the thickness of the two-dimensional nanosheets less than 50 nm and the grains grown on the two-dimensional nanosheets less than 50 nm.

[0071] Example 3

[0072] The preparation method of the composite material of two-dimensional carbon sheets supported with nanocrystals in this example adopts the following steps:

[0073] (1) Preparation of solution: Dissolve 1.6 g of sodium oleate, 0.5 g of copper chloride, and 1.0 g of fatty alcohol polyoxyethylene ether in a solvent containing 15 mL of water, 15 mL of ethanol, and 5 mL of hydrochloric acid (concentration 37%) to obtain a mixed solution after complete dissolution;

[0074] (2) One-pot method: Transfer the mixed solution to a stainless-steel autoclave with a polytetrafluoroethylene inner liner. Seal the autoclave and place it in an electric furnace at 200 °C for 24 hours, then naturally cool it to room temperature. After that, use a filter membrane to filter and collect the precipitate, wash it with distilled water, and dry it to obtain the precursor.

[0075] (3) Calcination: Place 1 g of the obtained precursor in a tubular furnace filled with argon and calcine it at 800 °C for 2 hours. Place 1 g of sulfur (sublimed sulfur) in the tubular furnace to sublimate and release sulfur vapor, and finally obtain a composite material of copper sulfide supported on two-dimensional carbon sheets, with the thickness of the two-dimensional nanosheets less than 50 nm and the grains grown on the two-dimensional nanosheets less than 50 nm.

[0076] Example 4

[0077] The preparation method of the composite material of two-dimensional carbon sheets supported with nanocrystals in this example adopts the following steps:

[0078] (1) Preparation of solution: Dissolve 1.2 g of trisodium citrate, 1.0 g of cobalt nitrate hexahydrate, and 1.0 g of fatty alcohol polyoxyethylene ether in a solvent containing 15 mL of water, 15 mL of ethanol, and 5 mL of hydrochloric acid (concentration 37%). After complete dissolution, a mixed solution is obtained;

[0079] (2) One-pot method: Transfer the mixed solution to a stainless-steel autoclave with a polytetrafluoroethylene liner. Seal the autoclave and place it in an electric furnace at 200 °C for 24 hours, then naturally cool it to room temperature. After that, use a filter membrane to filter and collect the precipitate, wash it with distilled water, and dry it to obtain the precursor.

[0080] (3) Calcination: Place 1 g of the obtained precursor in a tubular furnace filled with argon and calcine it at 800 °C for 2 hours. Place 1 g of sulfur (sublimed sulfur) in the tubular furnace to sublimate and release sulfur vapor. Finally, a composite material of cobalt sulfide supported on two-dimensional carbon sheets is obtained, with the thickness of the two-dimensional nanosheets less than 50 nm and the grains grown on the two-dimensional nanosheets less than 50 nm.

[0081] Example 5

[0082] The preparation method of the composite material of two-dimensional carbon sheet supported with nanocrystals in this example adopts the following steps:

[0083] (1) Preparation of solution: Dissolve 2.2 g of humic acid (acid-soluble), 1.0 g of ferric chloride hexahydrate, and 0.8 g of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer in a solvent containing 15 mL of water, 15 mL of ethanol, and 5 mL of hydrochloric acid (concentration 37%). After complete dissolution, a mixed solution is obtained;

[0084] (2) One-pot method: Transfer the mixed solution to a stainless-steel autoclave with a polytetrafluoroethylene liner. Seal the autoclave and place it in an electric furnace at 200 °C for 24 hours, then naturally cool it to room temperature. After that, use a filter membrane to filter and collect the precipitate, wash it with distilled water, and dry it to obtain the precursor.

[0085] (3) Calcination: Place 1 g of the obtained precursor in a tubular furnace filled with argon and calcine it at 400 °C for 2 hours. Place 1 g of NaH2PO2·H2O in the tubular furnace to decompose and release PH3. Finally, a composite material of iron phosphide supported on two-dimensional carbon sheets is obtained, with the thickness of the two-dimensional nanosheets less than 50 nm and the grains grown on the two-dimensional nanosheets less than 50 nm.

[0086] Comparative Example

[0087] (1) Dissolve 1.0 g of sodium molybdate in a solvent containing 15 mL of water, 15 mL of ethanol, and 5 mL of hydrochloric acid (concentration 37%). After complete dissolution, a mixed solution is obtained;

[0088] (2) Transfer the mixed solution to a stainless-steel high-pressure reactor with a PTFE liner. After sealing the high-pressure reactor, place it in an electric furnace at 180 °C and react for 24 hours, then naturally cool it to room temperature. After that, use a filter membrane for suction filtration to collect the precipitate, wash it with distilled water, and dry it to obtain the precursor.

[0089] (3) Place 1 g of the obtained precursor in a tubular furnace filled with argon and calcine it at 650 °C for 2 hours. Place 1 g of NaH2PO2·H2O in the tubular furnace to decompose and release PH3. Finally, a bulk molybdenum phosphide material is obtained. It is a three-dimensional bulk material with dimensions greater than 1 micron in each dimension.

[0090] Fabricate the bulk molybdenum phosphide material of this comparative example into a negative electrode, use metallic lithium as the counter electrode, and use 1 mol / L LiPF6 / DMC + DEC + EC (volume ratio 1:1:1) as the electrolyte to fabricate a lithium-ion battery, and test its specific capacities at current densities of 0.1 A / g, 0.2 A / g, 0.5 A / g, 1.0 A / g, and 2.0 A / g, which are 460, 115, 30, 10, and 10 mAh / g respectively.

[0091] In summary, the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A preparation method of a composite material of two-dimensional carbon sheet supported nanocrystals, characterized in that, It includes the following steps: S1, Prepare a solution by dissolving a template agent, a carbon-containing anion agent, and a metal salt in a solvent, and stir to fully dissolve them to obtain a mixed solution; S2, One-pot method: Place the mixed solution in a high-pressure reactor. Under high-temperature conditions, the carbon-containing components in the solution are converted into two-dimensional carbon sheets, and metal ions and anions in the solution nucleate and grow on the surface of the two-dimensional carbon sheets. After the reaction ends, separate the solid to obtain a precursor; S3, Calcination: Place the precursor in an atmosphere furnace, add an active substance or introduce an active gas into the atmosphere furnace, and perform calcination under a protective gas atmosphere to obtain a composite material of two-dimensional carbon sheet-supported nanocrystals.

2. The preparation method of the composite material of nanocrystals supported on two-dimensional carbon sheets according to claim 1, characterized in that, In the step S1: The template agent uses a surfactant, and the surfactant is selected from one of an anionic surfactant, a cationic surfactant, and a nonionic surfactant; The carbon-containing anion agent is selected from one of polycarboxylic acids or salts containing polycarboxylate groups; The metal salt is selected from one of soluble tin salts, copper salts, cobalt salts, iron salts, and nickel salts; The solvent is a composite solvent containing water and / or ethanol.

3. The method for preparing a composite material of two-dimensional carbon sheet-supported nanocrystals according to claim 2, wherein: The nonionic surfactant uses a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer surfactant or a fatty alcohol polyoxyethylene ether; and / or The carbon-containing anion agent is selected from one of citric acid, oleic acid, humic acid, citrates, oleates, humates, and citrates; and / or The metal salt is selected from one of sodium molybdate, hydrated stannic chloride, copper chloride, hydrated cobalt nitrate, and hydrated ferric chloride; and / or The composite solvent is selected from one or more of isopropyl alcohol, n-hexane, and cyclohexane, and the composite solvent contains an acid.

4. The preparation method of the composite material of nanocrystals supported on two-dimensional carbon sheets according to claim 1, characterized in that, In the step S1, the mass ratio of the template agent, the carbon-containing component, and the metal salt is 2:1:1 to 1:3:3, and the volume ratio of the total mass of the template agent, the carbon-containing anion agent, and the metal salt to the solvent is 1:1 to 1:

20.

5. The preparation method of the composite material of nanocrystals supported on two-dimensional carbon sheets according to claim 1, characterized in that, In the step S2, the high-temperature condition is 120 - 270 °C, and the reaction time is 20 - 1440 min.

6. The preparation method of the composite material of nanocrystals supported on two-dimensional carbon sheets according to claim 5, characterized in that, The high-temperature condition is 150 - 220 °C, and the reaction time is 120 - 720 min.

7. The preparation method of the composite material of nanocrystals supported on two-dimensional carbon sheets according to claim 1, wherein, In the step S2, after the reaction ends, the solid is separated by the method of filtration with a filter membrane.

8. The preparation method of the composite material of nanocrystals supported on two-dimensional carbon sheets according to claim 1, characterized in that, In the step S3: The atmosphere furnace uses one of a tubular furnace, a box furnace, or a vacuum atmosphere furnace; and / or The active substance is selected from one of NaH2PO2·H2O, sulfur, and phosphorus; and / or The active gas is selected from one of phosphine and hydrogen sulfide; and / or The mass ratio of the precursor to the active substance is 10:1 to 1:10; and / or During the calcination process, the calcination temperature is 300 - 1000 °C, the protective gas is nitrogen or an inert gas, and the calcination time is 0.5 - 12 h.

9. The preparation method of the composite material of nanocrystals supported on two-dimensional carbon sheets according to claim 8, characterized in that, In the step S3, the calcination temperature is 350 - 800 °C.

10. A composite material of two-dimensional carbon sheet-supported nanocrystals prepared by using the method for preparing a composite material of two-dimensional carbon sheet-supported nanocrystals according to any one of claims 1 - 9.

11. Application of a composite material of two-dimensional carbon sheet supported nanocrystals as described in claim 10 as a negative electrode material in a lithium-ion battery.

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