Nitrogen-doped single-layer amorphous carbon intercalated MoX grown on carbon-based materials 2 Nanosheets and their applications

Abstract

The present invention provides nitrogen-doped monolayer amorphous carbon intercalated MoX grown on a carbon-based material 2 nanosheets and their applications. Taking the carbon-based material as a carrier, a monolayer of NAC is intercalated between two adjacent MoX 2 single molecular layers, which has a dual effect: it can not only widen the interlayer spacing of MoX 2 to facilitate rapid sodium ion insertion / extraction; but also improve the surface and internal electron conductivity of MoX 2 to fully accelerate the electron transport; in addition, the hierarchical structure composed of the unique nanostructure and the carbon-based material conductive network is a solid framework with excellent nanostructure stability. The product obtained by the present invention has a unique structure, regular morphology, uniform composition, no impurity phase, and excellent electrochemical properties.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical energy storage, and particularly relates to a MoX intercalated with nitrogen-doped single-layer amorphous carbon (abbreviated as NAC for nitrogen-doped amorphous carbon) grown on a carbon-based material 2 (X = Se, S) nanosheets and their application in sodium-ion batteries Background Art

[0002] With the successful commercialization of lithium-ion batteries, advanced energy storage battery technologies developed based on metallic lithium have advanced by leaps and bounds. However, the limited lithium resources on Earth and the continuous large consumption of lithium have forced us to search for a new type of battery. Sodium, which is in the same main group as lithium in the periodic table, has similar physical and chemical properties to lithium and has attracted the attention of researchers. However, sodium ions have a larger ionic radius and molar mass than lithium ions, resulting in slower reaction kinetics and more serious volume expansion, making the material electrodes suitable for lithium-ion batteries no longer applicable to sodium-ion batteries. Therefore, it has become urgent to develop an advanced anode material for sodium-ion batteries. Layered transition metal dichalcogenides (LTMDs) have attracted much attention in the fields of energy storage and catalysis due to their unique crystal structures and properties. MoX 2 (X = Se, S) has attracted considerable attention in sodium-ion batteries due to its large interlayer spacing, small bandgap, high theoretical specific capacity, and low production cost. Many researchers are committed to constructing advanced sodium-ion battery anodes based on MoX 2 , but MoX composites with long-cycle stability at high current are rarely reported. Due to the low electrical conductivity inside the layered MoX 2 nanosheet material and the van der Waals force between layers and high surface energy, which cause the nanosheets to stack and aggregate, resulting in problems such as slow reaction kinetics and volume expansion, MoX 2 exhibits poor rate performance and cycling performance when used as an anode for sodium-ion batteries. To overcome the deficiencies in the application performance of the material, in recent years, modification of MoX 2 has been carried out to obtain better and more stable performance. Research has shown that by widening the interlayer spacing of MoX 2 and improving the electrical conductivity of the MoX 2 material, the sodium storage performance can be effectively improved. However, in general, interlayer modification inserts NH 2 into the interlayer of two-dimensional materials. Although the interlayer spacing has changed significantly, NH 4 + will be discharged from the interlayer at high temperatures, causing the interlayer spacing of the two-dimensional material to return to its original initial value. In addition, general enhancement of electrical conductivity is only on the surface of MoX 4 + 2 2 ​​The conductivity inside the interlayer is not improved well. Therefore, synthesize stable interlayer broadening and enhanced internal conductivity of MoX 2 Advanced composite materials for rapid sodiation and desodiation of sodium ions have important research value and practical application significance. Summary of the Invention

[0003] To solve the problems of high cost, long cycle, and difficulty in mass production in the production of high-performance and ultra-stable anodes for sodium-ion batteries, the present invention provides a monolayer NAC intercalated MoX grown on a carbon-based material, which is inexpensive, has a simple preparation process, and is suitable for quantitative production 2 (X = Se, S) nanosheets and their application in sodium-ion batteries. The materials of the present invention have excellent sodium storage electrochemical performance.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for preparing a nitrogen-doped monolayer amorphous carbon intercalated MoX 2 (X = Se, S) nanosheets grown on a carbon-based material, comprising the following steps:

[0006] Step 1: Weigh 1.5 - 2.5 mmol of Se powder and 4 - 8 mmol of NaBH 4 Add them to 3 - 10 mL of ethanol solution, then seal the beaker with sealing tape and stir for 1 - 20 minutes to obtain a selenium ion solution;

[0007] Or: Weigh 2 - 5 mmol of CH 4 N 2 S and add it to 3 - 10 mL of deionized water, stir for 1 - 20 minutes to obtain a sulfur ion solution;

[0008] Use the selenium ion solution or the sulfur ion solution as solution A;

[0009] Step 2: Take 30 - 60 mg of carbon-based material and add it to 15 - 30 mL of deionized water, sonicate for 0.1 - 5 hours, then stir for 0.1 - 2 hours, and continue to add 0.1 - 0.2 mmol of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and stir for 1 - 30 minutes to obtain solution B;

[0010] Step 3: Add 1 - 6 mL of amino compound and 1 - 8 g of reducing sugar to solution B in sequence, and stir for 3 - 15 minutes to obtain solution C;

[0011] Step 4: Rapidly transfer the solution C into solution A, seal the beaker with sealing tape and stir for 1 - 8 minutes to obtain a mixed solution; transfer the mixed solution into a reaction kettle and react at 160 - 220 °C for 12 - 24 hours to obtain an initial product;

[0012] Step 5: Centrifuge and wash the initial product, then place it in a vacuum drying oven for drying to obtain an intermediate product;

[0013] Step 6: Place the intermediate product in a tubular furnace, then heat it to 700 - 900 °C in a vacuum environment, keep it warm for 1 - 3 hours, and finally cool it to room temperature to obtain a monolayer NAC - intercalated MoX 2 nanosheet grown on a carbon - based material; when a selenium ion solution is selected as solution A, MoSe 2 nanosheet is obtained; when a sulfur ion solution is selected as solution A, MoS 2 nanosheet is obtained.

[0014] Preferably, the amino compound is ethylenediamine.

[0015] Preferably, the reducing sugar is glucose.

[0016] Preferably, the carbon - based material is one of reduced graphene oxide, carbon nanotubes, carbon fibers, carbon nanowires and carbon spheres.

[0017] Preferably, in step 5, the washing is sequentially carried out with deionized water and absolute ethanol.

[0018] The nitrogen - doped monolayer amorphous carbon - intercalated MoX 2 nanosheets grown on a carbon - based material prepared by the present invention can be used as a negative electrode material in a sodium - ion battery.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. The present invention provides a preparation method of monolayer NAC - intercalated MoX 2 nanosheets grown on a carbon - based material (such as rGO). The obtained product has a unique structure, regular morphology, uniform composition, no impurity phase, and excellent electrochemical properties.

[0021] 2. The interlayer structure of the monolayer NAC - intercalated MoX 2 prepared by the present invention is that nitrogen - doped monolayer amorphous carbon is inserted between two adjacent MoX 2 single - molecular layers, which has a dual effect: it can not only widen the layer spacing of MoX 2 to facilitate the rapid insertion / extraction of sodium ions; but also improve MoX 2The electronic conductivity on the surface and inside is sufficient to accelerate the electron transport. Additionally, the hierarchical structure composed of unique nanostructures and the conductive network of carbon-based materials (such as rGO) is a robust framework with excellent nanostructure stability.

[0022] 3. The rGO@MoX 2 / NAC prepared by the present invention exhibits excellent rate performance and excellent long-term cycle life at high current density, and has leading sodium storage performance.

[0023] 4. The present invention explores an economical and simple method for combined modulation of layered transition metal dichalcogenides (LTMDs) through interlayer regulation and nanoscale engineering to obtain advanced electrodes for high-performance rechargeable batteries. The preparation method of the present invention has universality for the synthesis of general LTMDs, and provides an effective synthesis scheme for the practical application of advanced anode materials for sodium-ion batteries.

[0024] 5. The preparation process of the present invention is simple, the preparation cost is low, and it is easy to be synthesized and promoted in large quantities. Brief Description of the Drawings

[0025] Figure 1 It is the SEM diagram of Samples 1-3 prepared in Examples 1-3 of the present invention. a and b in the figure respectively correspond to Sample 1 (rGO@MoSe 2 ), and Sample 2 (MoSe 2 / C). c and d in the figure correspond to Sample 3 (rGO@MoSe 2 / NAC).

[0026] Figure 2 It is the TEM diagram of Samples 1-3 prepared in Examples 1-3 of the present invention. a and b in the figure respectively correspond to Sample 1 (rGO@MoSe 2 ), and Sample 2 (MoSe 2 / C). c and d in the figure correspond to Sample 3 (rGO@MoSe 2 / NAC).

[0027] Figure 3 It is the XPS diagram of rGO@MoSe 2 / NAC prepared in Example 3 of the present invention. a, b, c, and d in the figure respectively correspond to Mo 3d, Se 3d, C 1s, and N 1s.

[0028] Figure 4 It is the XRD spectrum of Samples 1-3 prepared in Examples 1-3 of the present invention.

[0029] Figure 5 It is the Raman spectrum of Samples 1-3 prepared in Examples 1-3 of the present invention.

[0030] Figure 6 SEM image of Sample 4 prepared in Example 4 of the present invention.

[0031] Figure 7 TEM image of Sample 4 prepared in Example 4 of the present invention.

[0032] Figure 8 XRD spectrum of Sample 4 prepared in Example 4 of the present invention ( Figure 8 a) and Raman spectrum ( Figure 8 b).

[0033] Figure 9 Variable rate performance curves of the batteries assembled with Samples 1-3 of the present invention;

[0034] Figure 10 Long cycle performance curves of the batteries assembled with Samples 1-3 of the present invention at a current density of 2 Ag -1 -.

[0035] Figure 11 Long cycle performance curves of the battery assembled with Sample 3 of the present invention at current densities of 20, 30, and 50 Ag -1 -.

[0036] Figure 12 Long cycle performance curves of the battery assembled with Sample 4 of the present invention at current densities of 20 and 30 Ag respectively -1 -. Detailed implementation manners

[0037] The present invention will be further described below in conjunction with embodiments. The examples are only for illustrating the implementation content of the present invention and are not limited to the present invention.

[0038] In each process step of the following examples, unless otherwise specified, they are all carried out at room temperature.

[0039] Example 1

[0040] In this example, rGO@MoSe is prepared according to the following steps 2 :

[0041] Step 1: Weigh 2 mmol of Se powder and 5 mmol of NaBH 4 and add them to 5 mL of ethanol solution. Then immediately seal the beaker mouth with sealing tape and stir at room temperature for 10 minutes to obtain a clear solution A.

[0042] Step 2: Take 4 mL of a GO solution with a concentration of 11.25 mgmL -1 in 20 mL of deionized water, ultrasonicate for 2 hours, then stir for 1 hour, and continue to add 0.14 mmol of (NH 4 ) 6 Mo7 O 24 ·4H 2 Stir for 20 minutes to obtain Solution B.

[0043] Step 3: Quickly transfer the above Solution B into Solution A, then continue to seal the beaker with sealing tape and stir for 5 minutes to obtain a mixed solution; transfer the obtained mixed solution into a reaction kettle and react at 180 °C for 20 hours to obtain an initial product.

[0044] Step 4: Centrifuge and wash the initial product, then place it in a vacuum drying oven for drying to obtain an intermediate product.

[0045] Step 5: Place the intermediate product in a tubular furnace, then heat it up to 800 °C under a vacuum environment, keep it warm for 2 hours, and finally cool it to room temperature to obtain the target product rGO@MoSe 2 , denoted as Sample 1.

[0046] Example 2

[0047] This example prepares MoSe 2 / C according to the following steps:

[0048] Step 1: Weigh 2 mmol of Se powder and 5 mmol of NaBH 4 Add them into 5 mL of ethanol solution, then immediately seal the beaker mouth with sealing tape and stir at room temperature for 10 minutes to obtain a clear solution A.

[0049] Step 2: Weigh 0.14 mmol of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and stir in 22 mL of deionized water for 10 minutes to obtain Solution B.

[0050] Step 3: Add 3 mL of C 2 H 8 N 2 and 3 g of glucose to the above Solution B in sequence, and continue to stir for 10 minutes to obtain Solution C.

[0051] Step 4: Quickly transfer the above Solution C into Solution A, then continue to seal the beaker with sealing tape and stir for 5 minutes to obtain a mixed solution; transfer the mixed solution into a reaction kettle and react at 180 °C for 20 hours to obtain an initial product.

[0052] Step 5: Centrifuge and wash the initial product, then place it in a vacuum drying oven for drying to obtain an intermediate product.

[0053] Step 6: Place the intermediate product in a tube furnace, then heat it to 800 °C under a vacuum environment, hold the temperature for 2 hours, and finally cool it to room temperature to obtain the target product MoSe 2 / C, denoted as Sample 2.

[0054] Example 3

[0055] In this example, rGO@MoSe 2 / NAC was prepared according to the following steps:

[0056] Step 1: Weigh 2 mmol of Se powder and 5 mmol of NaBH 4 and add them to 5 mL of ethanol solution. Then immediately seal the mouth of the beaker with sealing tape and stir at room temperature for 10 minutes to obtain a clear solution A.

[0057] Step 2: Take 4 mL of a GO solution with a concentration of 11.25 mg / mL -1 in 20 mL of deionized water, sonicate for 2 hours, then stir for 1 hour, and continue to add 0.14 mmol of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and stir for 20 minutes to obtain solution B.

[0058] Step 3: Add 3 mL of C 2 H 8 N 2 and 3 g of glucose to the above solution B in sequence, and stir for 10 minutes to obtain solution C.

[0059] Step 4: Quickly transfer the above solution C to solution A, then seal the beaker with sealing tape again and stir for 5 minutes to obtain a mixed solution; transfer the mixed solution to a reaction kettle and react at 180 °C for 20 hours to obtain the initial product.

[0060] Step 5: Centrifuge and wash the initial product, then place it in a vacuum drying oven for drying to obtain the intermediate product.

[0061] Step 6: Place the intermediate product in a tube furnace, then heat it to 800 °C under a vacuum environment, hold the temperature for 2 hours, and finally cool it to room temperature to obtain the target product rGO@MoSe 2 / NAC, denoted as Sample 3.

[0062] Figure 1 are the SEM images of the samples obtained in Examples 1 - 3. Figure 1 a and b in 2 correspond to Sample 1 (rGO@MoSe 2 ) and Sample 2 (MoSe Figure 1In samples 3 (rGO@MoSe 2 / NAC), c and d correspond to sample 3. In sample 1 (rGO@MoSe 2 ), the synthesized MoSe 2 nanoparticles are uniformly dispersed on the surface of rGO; in sample 2 (MoSe 2 / C), the prepared MoSe 2 nanosheets are piled up in a mass by the shrinkage and coating of carbon through the hydrothermal process; in sample 3 (rGO@MoSe 2 / NAC), the small balls formed by the alternating stacking and curling of MoSe 2 nanosheets and NAC are evenly distributed on rGO, and the diameter of the small balls is about 30 - 50 nm.

[0063] Figure 2 Figures a and b in Figure 2 correspond to sample 1 (rGO@MoSe 2 ) and sample 2 (MoSe 2 / C) respectively, Figure 2 and c, d in 2 correspond to sample 3 (rGO@MoSe 2 ). Sample 1 (rGO@MoSe 2 ) shows that layered MoSe 2 nanosheets grow on rGO as a support material. The MoSe 2 grown on rGO is composed of well-crystallized multi-layer nanosheets stacked together, and the measured interlayer spacing is 0.65 nm; sample 2 (MoSe 2 / C) shows MoSe 2 nanosheets that are exfoliated into few layers, and the MoSe 2 nanosheets are exfoliated and completely coated by amorphous carbon; in sample 3 (rGO@MoSe 2 / NAC), the small balls orderly distributed on rGO are hollow small balls formed by the curling of MoSe 2 nanosheets and NAC. Two adjacent MoSe 2 single layers are intercalated with a single layer of amorphous carbon molecules to form a superlattice shell structure with overlapping MoSe 2 and NAC, and the (002) crystal plane of MoSe

[0064] Figure 3 In 2 , a, b, c, and d are the XPS spectra of high-resolution Mo 3d, Se 3d, C 1s, and N 1s of sample 3 (rGO@MoSe Figure 3The peaks at 229.0 and 232.1 eV in a correspond to Mo 3d5 / 2 and Mo 3d3 / 2, indicating that Mo is in the +4 valence state. Meanwhile, the weak peak at 230.3 eV is the signal of the Mo-C bond, indicating MoSe 2 In-situ growth on rGO. The peak at 235.2 eV belongs to Mo 6+ -O bond caused by slight surface oxidation. Figure 3 b is the high-resolution spectrum of Se 3d. The peaks at 54.6 and 55.4 eV correspond to Se 3d5 / 2 and Se 3d3 / 2, corresponding to the Se 2- valence state. Figure 3 c is the high-resolution spectrum of C1s. The peaks appearing at 282.8, 284.7, 285.7, 286.4 and 288.4 eV correspond to Mo-C, C═C, C-C, C-N / C-O and C═O chemical bonds respectively. Figure 3 d is the high-resolution spectrum of N1s, which can be divided into peaks of three different nitrogen species, namely pyridinic-N at 398.5 eV, pyrrolic-N at 400.9 eV and graphitic-N at 403.2 eV. Among them, the electrochemically active pyridinic-N and pyrrolic-N can provide rich external defects and active sites. The doping of N element into carbon further improves the electronic conductivity of carbon. In addition, the high-intensity peak at 394.8 eV comes from Mo 3p3 / 2.

[0065] Figure 4 XRD patterns of the samples obtained in Examples 1 to 3. The X-ray diffraction peaks of Sample 1 (rGO@MoSe 2 ) can be well matched with the diffraction peaks of 2H-MoSe 2 (JCPDS 29-0914). The most prominent (002) diffraction peak is located at 13.4°, corresponding to a (002) interlayer spacing of 0.65 nm. For Sample 2 (MoSe 2 / C) and Sample 3 (rGO@MoSe 2 / NAC), the (002) diffraction peaks shift from 13.4° to 7.9°. By calculating with the Scherrer equation 2dsinθ = nλ, the (002) interlayer spacing of MoSe 2 extends to 1.12 nm.

[0066] Figure 5 Raman spectra of the samples obtained in Examples 1 to 3. The spectra of Sample 2 (MoSe 2 / C) and Sample 3 (rGO@MoSe 2 / NAC) both have a prominent peak at 238 cm -1 and a peak at 283 cm-1 There is a secondary peak corresponding to the out-of-plane vibration (A 1g ) mode and in-plane vibration (E 2g 1 ) mode of the Mo–Se bond. Compared with Sample 1 (rGO@MoSe 2 ), the A 2 and E 2 peaks of MoSe 2 in Sample 2 (MoSe 1g / C) and Sample 3 (rGO@MoSe 2g 1 / NAC) are weakened and shifted to lower wavenumbers. This indicates that the crystal size of MoSe 2 in Sample 2 (MoSe 2 / C) and Sample 3 (rGO@MoSe 2 ) is smaller, which is consistent with the Figure 2 observation results; there are also two broadened peaks at 1350 and 1586 cm -1 , corresponding to the D band and G band of the carbon material, respectively. The I 2 / I D ratio of Sample 1 (rGO@MoSe G ) is as high as 1.37, confirming the reduction of graphene oxide. The I 2 / I D of Sample 2 (MoSe G / C) is relatively low, 1.05, which is caused by amorphous carbon. Sample 3 (rGO@MoSe 2 / NAC) has a medium I D / I G ratio of 1.10, indicating the presence of surface rGO and amorphous carbon.

[0067] Example 4

[0068] rGO@MoS 2 / NAC was prepared according to the following steps:

[0069] Step 1: Weigh 3 mmol of thiourea and add it to 5 mL of deionized water, and stir at room temperature for 10 minutes to obtain Solution A.

[0070] Step 2: Take 4 mL of a GO solution with a concentration of 11.25 mg mL -1 and ultrasonicate it in 20 mL of deionized water for 2 hours, then stir for 1 hour. Then, add 0.14 mmol of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and stir for 20 minutes to obtain Solution B.

[0071] Step 3: Sequentially add 3 mL of C to the above solution B 2 H 8 N 2 and 3 g of glucose, and continue stirring for 10 minutes to obtain solution C.

[0072] Step 5: Transfer the above solution C to solution A and continue stirring for 5 minutes to obtain a mixed solution; transfer the mixed solution to a reaction kettle and react at 180 °C for 20 hours to obtain an initial product.

[0073] Step 6: Centrifuge and wash the initial product and then place it in a vacuum drying oven for drying to obtain an intermediate product.

[0074] Step 7: Place the intermediate product in a tube furnace, then heat it to 800 °C in a vacuum environment, hold for 2 hours, and finally cool it to room temperature to obtain rGO@MoS 2 / NAC, denoted as sample 4.

[0075] Figure 6 SEM image of sample 4 (rGO@MoS 2 / NAC). The prepared MoS 2 nanosheets are uniformly vertically distributed on the surface of rGO.

[0076] Figure 7 a and b in 2 are TEM images of sample 4 (rGO@MoS 2 / NAC). Few-layer MoS 2 / NAC nanosheets are orderly vertically distributed on the surface of rGO. It is measured that the (002) crystal plane of MoS

[0077] Figure 8 a and b in 2 are the XRD spectrum and Raman spectrum of sample 4 (rGO@MoS Figure 8 / NAC): In 2 a, by comparing with the standard card (JCPDS 17-0744), it can be known that the diffraction peak of the (002) crystal plane of the obtained product MoS 2 shifts from 14.5° to the left to 8.58°. Through calculation by the Scherrer equation 2dsinθ = nλ, the interlayer spacing of MoS Figure 8 b, the resonance peaks at 381 and 406 cm -1 are assigned to the E 2g 1 and A 1g modes of Mo-S vibration, indicating that MoS 2。

[0078] To characterize the electrochemical performance of the samples obtained in the above embodiments, the following tests were conducted.

[0079] Step 1: Respectively take the samples prepared in each embodiment, graphite, and sodium carboxymethylcellulose, and grind them into a uniform slurry in an agate mortar according to a mass ratio of 8:1:1, coat it on a copper foil, and then dry it in a vacuum drying oven at 80 °C for 12 hours to make the working electrode of the battery.

[0080] Step 2: Use a sodium metal sheet as the counter electrode, a glass microfiber filter paper (GF / D, Whatman) as the separator, and 1M NaClO 4 Add 5% fluoroethylene carbonate (FEC) to ethylene carbonate (EC) and propylene carbonate (PC) (1:1 v / v) as the electrolyte, and assemble a CR2032 coin battery in a glove box filled with inert gas (Etelux Lab 200, O 2 <0.1 ppm, H 2 O <0.1 ppm).

[0081] Step 3: Use the CT4008T 5V / 10mA / 50mA system of Neware Company to conduct charge-discharge tests on the assembled coin battery at a voltage window of 0.01 - 3V.

[0082] Figure 9 For the coin batteries assembled with Sample 1 (rGO@MoSe 2 ), Sample 2 (MoSe 2 / C), and Sample 3 (rGO@MoSe 2 / NAC), the variable magnification performance curves show that Sample 3 (rGO@MoSe 2 / NAC) exhibits excellent sodium storage magnification performance. At current densities of 0.2, 0.5, 1, 2, 5, 10, 15, and 20 A g -1 , it shows capacities of 405, 384, 353, 326, 297, 267, 246, and 233 mAh g -1 . At ultra-high current densities of 30 and 50 A g -1 , it can still maintain reversible high capacities of 218 and 194 mAh g -1 . At a current density of 50 A g -1 , the discharge capacity of Sample 2 (MoSe 2 / C) drops to 66 mAh g -1 , and the discharge capacity of Sample 1 (rGO@MoSe 2 ) drops to 18 mAh g -1 .

[0083] Figure 10For the coin cells assembled with Sample 1 (rGO@MoSe 2 ), Sample 2 (MoSe 2 / C), and Sample 3 (rGO@MoSe 2 / NAC) at a current density of 2 Ag -1 . The discharge capacity of Sample 3 (rGO@MoSe 2 / NAC) was 292 mAh g -1 during the first cycle and gradually increased to 388 mAh g -1 after 1000 cycles, showing excellent stability. Sample 3 (rGO@MoSe 2 / NAC) was significantly superior to Sample 1 (rGO@MoSe 2 ) and Sample 2 (MoSe 2 / C) in terms of reversible capacity and stability. Sample 1 (rGO@MoSe 2 ) and Sample 2 (MoSe 2 / C) maintained capacities of 52 mAh g -1 and 171 mAh g -1 respectively after 1000 cycles.

[0084] Figure 11 For the long cycle performance curve of the coin cell assembled with Sample 3 (rGO@MoSe 2 / NAC) tested at high currents, it showed superior stability at 20 Ag -1 and maintained a capacity of 202 mAh g -1 after 7000 cycles, with a capacity retention rate of 87%, and the calculated decay per cycle was only 0.0021%. Even at higher current densities of 30 and 50 Ag -1 , Sample 3 (rGO@MoSe 2 / NAC) also showed excellent cycling stability. After 9000 cycles, the battery maintained a reversible capacity of 159 mAh g -1 at 30 Ag -1 , and after 12000 cycles, the battery maintained a reversible capacity of 115 mAh g -1 at 50 Ag -1 , corresponding to 70% and 54% capacity retention, with capacity decay rates of 0.0033% and 0.0038% respectively. And the Coulombic efficiency (CE) during cycling at 20, 30, and 50 Ag -1 was basically maintained at 100%, showing outstanding cycling stability.

[0085] Figure 12 For Sample 4 (rGO@MoS 2The long cycle performance curves of the coin cells assembled with (NAC) at high currents. At a high current density of 20 Ag -1 After 9000 cycles, the capacity remained at 176 mAh g -1 ; while at a higher current density of 30 Ag -1 After 7000 cycles, it still maintained 159 mAh g -1 . At 20 and 30 Ag -1 , the average capacity decay rates were 0.0049% and 0.0052% respectively, and the Coulomb efficiency (CE) was basically maintained at 100%.

[0086] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. Preparation method of nitrogen-doped single-layer amorphous carbon intercalated MoX nanosheets grown on carbon-based materials, where X is Se or S 2 ​ It is characterized in that it includes the following steps: Step 1: Weigh 1.5 - 2.5 mmol of Se powder and 4 - 8 mmol of NaBH 4 Add them to 3 - 10 mL of ethanol solution, then seal the beaker with sealing tape and stir for 1 - 20 minutes to obtain a selenium ion solution; Or: Weigh 2 - 5 mmol of CH 4 N 2 S and add it to 3 - 10 mL of deionized water, stir for 1 - 20 minutes to obtain a sulfide ion solution; using the selenium ion solution or the sulfur ion solution as solution A; Step 2: Take 30 - 60 mg of carbon-based material and add it to 15 - 30 mL of deionized water, ultrasonicate for 0.1 - 5 hours, then stir for 0.1 - 2 hours. Then continue to add 0.1 - 0.2 mmol of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and stir for 1 - 30 minutes to obtain Solution B; Step 3: Sequentially add 1 - 6 mL of ethylenediamine and 1 - 8 g of glucose to the solution B, and stir for 1 - 15 minutes to obtain solution C; Step 4: Rapidly transfer the solution C to solution A, seal the beaker with sealing tape, stir for 1 - 8 minutes to obtain a mixed solution; transfer the mixed solution to a reaction kettle and react at 160 - 220 °C for 12 - 24 hours to obtain an initial product; Step 5: Centrifuge and wash the initial product and then place it in a vacuum drying oven for drying to obtain an intermediate product; Step 6: Place the intermediate product in a tubular furnace, then heat it to 700 - 900 °C under a vacuum environment, hold the temperature for 1 - 3 hours, and finally cool it to room temperature to obtain the target product, i.e., nitrogen-doped single-layer amorphous carbon intercalated MoX 2 nanosheets; when a selenium ion solution is used as solution A, MoSe 2 nanosheets are obtained; when a sulfur ion solution is used as solution A, MoS 2 nanosheets are obtained.

2. The preparation method according to claim 1, it is characterized in that: the carbon-based material is one of reduced graphene oxide, carbon nanotubes, carbon fibers, carbon nanowires, and carbon spheres.

3. The preparation method according to claim 1, it is characterized in that: in step 5, the washing is sequentially performed with deionized water and absolute ethanol.

4. MoX with nitrogen-doped single-layer amorphous carbon intercalation grown on a carbon-based material prepared by the preparation method according to any one of claims 1 to 3 2 nanosheets.

5. Use of the nitrogen-doped single-layer amorphous carbon intercalated MoX grown on a carbon-based material as described in claim 4 as an anode material in a sodium-ion battery. 2 ​

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