A compositionally tunable MoS2 with widened interlayer spacing x Se 2-x Nanosheets and their applications

Abstract

The application provides a component-regulatable MoS x Se 2‑x Nanosheet and application thereof, which uses carbon-based material as a carrier, inserts a nitrogen-doped amorphous carbon (NAC) monolayer between two adjacent MoS x Se 2‑x monolayers: it not only widens the interlayer spacing of MoS x Se 2‑x , facilitates fast sodium ion insertion / elimination, but also improves the electronic conductivity of the surface and interior of MoS x Se 2‑x , so as to fully accelerate the transmission of electrons; in addition, increasing the proportion of Se atoms in MoS x Se 2‑x will increase the conductivity, expand the interlayer spacing and enrich anion defect sites, and increasing the proportion of S atoms will increase the theoretical capacity. The product obtained by the application has a unique structure, a regular morphology, a uniform composition, no impurity phase and excellent electrochemical characteristics.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage, specifically relating to a MoS₂ with tunable composition and widened interlayer spacing. x Se 2-x Nanosheets and their application in sodium-ion batteries. Background Technology

[0002] Due to the requirements of sustainable development, the development of clean energy storage devices is an inevitable trend. As lithium resources become increasingly expensive, sodium-ion batteries are gradually coming into focus. Sodium and lithium share similar chemical properties, and sodium resources are far more abundant and cheaper than lithium, making sodium-ion batteries the most promising energy storage devices to replace lithium-ion batteries. The negative electrode is the key component determining the battery's sodium storage capacity. Layered transition metal dichalcogenides (LTMDs) are promising negative electrode materials for sodium-ion batteries because they have large interlayer spacing and excellent capacity. However, due to severe volume effects and poor conductivity, achieving long-term stable cycling and high-rate charge-discharge capabilities remains a key issue for the development of sodium-ion batteries. Molybdenum disulfide (MoS2) is another promising candidate due to its large interlayer space and high theoretical capacity (670 mAh g / g). –1 ), in Na + Storage has attracted considerable research interest. However, storing Na through embedding and substitution mechanisms... + MoS2 often suffers from key problems such as rapid capacity decay and poor rate performance due to its low electronic conductivity, high re-aggregation tendency, and large volume change during cycling. Therefore, two strategies are typically used to address the Na+ degradation in MoS2. + Related issues in storage. On the one hand, correlation performance can be improved by creating defects in 2D MoS2 nanosheets through heteroatom doping or substitution, which can alter the electronic structure of the surface and provide abundant active sites. Some reports have investigated how selenium (Se) doping affects correlation performance, as selenium itself has relatively high electrical conductivity (10⁻⁶). -4 S m -1 ) and larger radius Therefore, doping Se atoms into the MoS2 lattice forms S x Se 2-x Interlayer ligands will increase conductivity, widen interlayer spacing, and enrich anion defect sites, thereby enhancing Na+. + On the other hand, further widening the interlayer spacing of MoS2 can effectively improve sodium storage performance, but general interlayer modification using NH4+... + Inserting NH4 into the interlayer of a two-dimensional material, although the interlayer spacing changes significantly, under high-temperature heating conditions... +This will evaporate from the interlayer, restoring the interlayer spacing of the two-dimensional material to its original value; furthermore, typical conductivity enhancements only occur on the surface of MoS2, without significantly improving the conductivity within the MoS2 interlayers. Therefore, synthesizing stable MoS2 with widened interlayer spacing and enhanced internal conductivity is crucial. x Se 2-x Advanced composite materials can adapt to Na + The volume expansion during insertion maintains structural stability and improves electrical conductivity, thereby ensuring an extended service life. Summary of the Invention

[0003] The purpose of this invention is to provide a low-cost, simple-to-prepare MoS₂ with adjustable interlayer spacing that is suitable for mass production. x Se 2-x The preparation method of nanosheets and their application in sodium-ion batteries give them outstanding electrochemical sodium storage performance.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A compositionally tunable MoS2 with widened interlayer spacing x Se 2-x The preparation method of (0≤x≤2) nanosheets includes the following steps:

[0006] Step 1: Weigh 0-2.5 mmol of Se powder and NaBH4 and add them to 3-10 mL of ethanol solution. Then seal the beaker with sealing adhesive and stir for 1-20 minutes to obtain selenium ion solution A. The molar ratio of NaBH4 to Se powder is 2.5-3:1.

[0007] Step 2: Add 30-60 mg of carbon-based material to 15-30 mL of deionized water and sonicate for 0.1-5 hours, then stir for 0.1-2 hours. Continue by adding 0.1-0.2 mmol of (NH4)6Mo7O. 24 Stir with 4H2O for 1-30 minutes to obtain solution B;

[0008] Step 3: Add 1-6 mL of amino compound and 1-8 g of reducing sugar to solution B in sequence, stir for 1-15 minutes to obtain solution C;

[0009] Step 4: Weigh 0-5 mmol of CH4N2S and quickly transfer it to solution A. Seal the beaker with sealing adhesive and stir for 10-30 minutes. Transfer the resulting mixed solution to a reaction vessel and react at 160-220℃ for 12-24 hours to obtain the initial product.

[0010] Step 5: After centrifuging and washing the initial product, place it in a vacuum drying oven to dry and obtain the intermediate product;

[0011] Step 6: Place the intermediate product in a tube furnace, then heat it to 700-900℃ under vacuum, hold it at that temperature for 1-3 hours, and finally cool it to room temperature to obtain the target product, MoS₂ with broadened interlayer spacing. x Se 2-x Nanosheets. The MoS₂ with widened interlayer spacing. x Se 2-x Nanosheets are made by loading MoS2 onto the surface of a carbon-based material. x Se 2-x Nanosheets, and the MoS x Se 2-x Nanosheets are formed by two adjacent MoS2 nanosheets. x Se 2-x Nitrogen-doped amorphous carbon (NAC) monolayers are inserted between the monolayers, thereby enabling MoS2 to... x Se 2-x The interlayer spacing of the nanosheets is widened. By adjusting the ratio of Se powder to CH4N2S, the content of S and Se in the target product can be controlled.

[0012] Preferably, the carbon-based material is one of reduced graphene oxide, carbon nanotubes, carbon fibers, carbon nanowires, and carbon spheres.

[0013] Preferably, the amino compound is ethylenediamine.

[0014] Preferably, the reducing sugar is glucose.

[0015] Preferably, the cleaning in step 5 involves sequentially cleaning with deionized water and anhydrous ethanol.

[0016] The MoS2 with widened interlayer spacing prepared by this invention x Se 2-x Nanosheets can be used as negative electrode materials in sodium-ion batteries.

[0017] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0018] 1. This invention provides a monolayer of nitrogen-doped amorphous carbon (NAC) intercalated MoS₂ grown on a carbon-based material (such as rGO). x Se 2-x The method for preparing nanosheets yields products with unique structures, regular morphologies, uniform composition, and no impurity phases, as well as excellent electrochemical properties. Furthermore, the content ratio of S to Se can be flexibly adjusted to obtain electrode materials with even better performance.

[0019] 2. The monolayer NAC-intercalated MoS₂ prepared by this invention x Se 2-xThe sandwich structure is formed by two adjacent MoS� ... x Se 2-x Inserting nitrogen-doped amorphous carbon monolayers between MoS monolayers has a dual effect: it can not only broaden MoS2 but also... x Se 2-x The interlayer spacing facilitates rapid insertion / extraction of sodium ions; it can also improve the MoS2 interlayer spacing. x Se 2-x The surface and internal electronic conductivity of MoS₂ can be improved to fully accelerate electron transport. Furthermore, by enhancing the electronic conductivity of MoS₂... x Se 2-x The increased selenium (Se) atom ratio enhances conductivity, widens interlayer spacing, and enriches anion defect sites, while increasing the sulfur (S) atom ratio improves theoretical capacity. Therefore, regulating the sulfur-selenium ratio significantly improves electrode material performance. Furthermore, the unique nanostructure and the layered structure composed of a carbon-based conductive network (such as rGO) form a robust framework with excellent nanostructural stability.

[0020] 3. The rGO@MoS prepared by this invention x Se 2-x / NAC exhibits superior rate performance and excellent long-term cycle life at high current densities, and possesses leading sodium storage performance.

[0021] 4. This invention explores an economical and simple method for combining and modulating layered transition metal dichalcogenides (LTMDs) through interlayer regulation and nanoscale engineering to obtain advanced electrodes for high-performance rechargeable batteries. The preparation method of this invention is universally applicable to the synthesis of general LTMDs, providing an effective synthesis scheme for the practical application of advanced anode materials in sodium-ion batteries.

[0022] 5. The preparation process of this invention is simple, the preparation cost is low, and it is easy to synthesize and promote on a large scale. Attached Figure Description

[0023] Figure 1 These are SEM images of samples 1-4 prepared in Examples 1-4 of this invention. Figure 1 In the text, 'a' and 'b' correspond to sample 1 (rGO@MoSe2 / NAC) and sample 2 (rGO@MoS2), respectively. 0.6 Se 1.4 / NAC), Figure 1 c and d correspond to sample 3 (rGO@MoS) respectively. 0.8 Se 1.2 / NAC) and sample 4 (rGO@MoS 0.9 Se 1.1 / NAC).

[0024] Figure 2These are TEM images of samples 1-4 prepared in Examples 1-4 of the present invention. Figure 2 In the text, 'a' and 'b' correspond to sample 1 (rGO@MoSe2 / NAC) and sample 2 (rGO@MoS2), respectively. 0.6 Se 1.4 / NAC), Figure 2 c and d in the figure correspond to sample 3 (rGO@MoS) 0.8 Se 1.2 / NAC) and sample 4 (rGO@MoS 0.9 Se 1.1 / NAC).

[0025] Figure 3 In the figure, a and b correspond to the SEM and TEM images of sample 5 (rGO@MoS2 / NAC) prepared in Example 5 of this invention, respectively.

[0026] Figure 4 (rGO@MoS) prepared in Example 3 of this invention 0.8 Se 1.2 XPS plot of ( / NAC), where a, b, c, d, and e correspond to C1s, Mo 3d, Se 3d, Se 3p & S 2p and their full spectra, respectively.

[0027] Figure 5 Sample 3 (rGO@MoS) prepared for Example 3 of the present invention 0.8 Se 1.2 N1s of the XPS plot ( / NAC).

[0028] Figure 6 The XRD spectra of samples 1-5 prepared in Examples 1-5 of this invention are shown.

[0029] Figure 7 The Raman spectra of samples 1-5 prepared in Examples 1-5 of this invention are shown.

[0030] Figure 8 The variable rate performance curves are for the batteries assembled from Samples 1, 3 and 4 of this invention.

[0031] Figure 9 The variable rate performance curves are for the batteries assembled from Samples 2 and 5 of this invention.

[0032] Figure 10 The battery assembled for sample 3 of the present invention operates at current densities of 30 and 50 Ag. -1 The long-cycle performance curve is shown below.

[0033] Figure 11 The batteries assembled for samples 1 to 5 of this invention are at a current density of 10 Ag -1 The long-cycle performance curve is shown below. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0035] Unless otherwise specified, all process steps in the following embodiments are carried out at room temperature.

[0036] Example 1

[0037] This embodiment prepares rGO@MoSe2 / NAC according to the following steps:

[0038] Step 1: Weigh 2 mmol Se powder and 5 mmol NaBH4 and add them to 5 mL of ethanol solution. Immediately seal the mouth of the beaker with sealing tape and stir at room temperature for 10 minutes to obtain a clear solution A.

[0039] Step 2: Take 3.5 mL of solution with a concentration of 9.76 mg / mL. -1 The GO solution was sonicated in 20 mL of deionized water for 2 hours, then stirred for 1 hour, and 0.14 mmol of (NH4)6Mo7O was added. 24 Stir with 4H2O for 30 minutes to obtain solution B.

[0040] Step 3: Add 3 mL of C2H8N2 and 3 g of glucose to the above solution B in sequence, and stir for 10 minutes to obtain solution C.

[0041] Step 4: Quickly transfer the above solution C to solution A, then seal the beaker with sealant and stir for 10 minutes to obtain a mixed solution; transfer the mixed solution to a reaction vessel and react at 180°C for 20 hours to obtain the initial product.

[0042] Step 5: After centrifuging and washing the initial product, place it in a vacuum drying oven to dry and obtain the intermediate product.

[0043] Step 6: Place the intermediate product in a tube furnace, then heat it to 800°C under vacuum, hold it for 2 hours, and finally cool it to room temperature to obtain the target product rGO@MoSe2 / NAC, which is denoted as Sample 1.

[0044] Example 2

[0045] This embodiment prepares rGO@MoS according to the following steps. 0.6 Se 1.4 / NAC:

[0046] Step 1: Weigh 1 mmol Se powder and 2.5 mmol NaBH4 and add them to 5 mL of ethanol solution. Immediately seal the mouth of the beaker with sealing tape and stir at room temperature for 10 minutes to obtain a clear solution A.

[0047] Step 2: Take 3.5 mL of solution with a concentration of 9.76 mg / mL. -1 The GO solution was sonicated in 20 mL of deionized water for 2 hours, then stirred for 1 hour, and 0.14 mmol of (NH4)6Mo7O was added. 24 Stir with 4H2O for 30 minutes to obtain solution B.

[0048] Step 3: Add 3 mL of C2H8N2 and 3 g of glucose to the above solution B in sequence, and stir for 10 minutes to obtain solution C.

[0049] Step 4: Weigh 1.5 mmol of CH4N2S and the above solution C and quickly transfer them to solution A. Continue to seal the beaker with sealing adhesive and stir for 30 minutes to obtain a mixed solution. Transfer the mixed solution to a reaction vessel and react at 180°C for 20 hours to obtain the initial product.

[0050] Step 5: After centrifuging and washing the initial product, place it in a vacuum drying oven to dry and obtain the intermediate product.

[0051] Step 6: Place the intermediate product in a tube furnace, then heat it to 800°C under vacuum, hold it at that temperature for 2 hours, and finally cool it to room temperature to obtain the target product rGO@MoS. 0.6 Se 1.4 / NAC, denoted as sample 2.

[0052] Example 3

[0053] This embodiment prepares rGO@MoS according to the following steps. 0.8 Se 1.2 / NAC:

[0054] Step 1: Weigh 0.8 mmol Se powder and 2 mmol NaBH4 and add them to 5 mL of ethanol solution. Immediately seal the mouth of the beaker with sealing tape and stir at room temperature for 10 minutes to obtain a clear solution A.

[0055] Step 2: Take 3.5 mL of solution with a concentration of 9.76 mg / mL. -1 The GO solution was sonicated in 20 mL of deionized water for 2 hours, then stirred for 1 hour, and 0.14 mmol of (NH4)6Mo7O was added. 24 Stir with 4H2O for 30 minutes to obtain solution B.

[0056] Step 3: Add 3 mL of C2H8N2 and 3 g of glucose to the above solution B in sequence, and stir for 10 minutes to obtain solution C.

[0057] Step 4: Weigh 1.8 mmol of CH4N2S and the above solution C and quickly transfer them to solution A. Continue to seal the beaker with sealing tape and stir for 30 minutes to obtain a mixed solution. Transfer the mixed solution to a reaction vessel and react at 180°C for 20 hours to obtain the initial product.

[0058] Step 5: After centrifuging and washing the initial product, place it in a vacuum drying oven to dry and obtain the intermediate product.

[0059] Step 6: Place the intermediate product in a tube furnace, then heat it to 800°C under vacuum, hold it at that temperature for 2 hours, and finally cool it to room temperature to obtain the target product rGO@MoS. 0.8 Se 1.2 / NAC, denoted as sample 3.

[0060] Example 4

[0061] This embodiment prepares rGO@MoS according to the following steps. 0.9 Se 1.1 / NAC:

[0062] Step 1: Weigh 0.66 mmol Se powder and 1.65 mmol NaBH4 and add them to 5 mL of ethanol solution. Immediately seal the mouth of the beaker with sealing tape and stir at room temperature for 10 minutes to obtain a clear solution A.

[0063] Step 2: Take 3.5 mL of solution with a concentration of 9.76 mg / mL. -1 The GO solution was sonicated in 20 mL of deionized water for 2 hours, then stirred for 1 hour, and 0.14 mmol of (NH4)6Mo7O was added. 24 Stir with 4H2O for 30 minutes to obtain solution B.

[0064] Step 3: Add 3 mL of C2H8N2 and 3 g of glucose to the above solution B in sequence, and stir for 10 minutes to obtain solution C.

[0065] Step 4: Weigh 2.01 mmol CH4N2S and the above solution C and quickly transfer them to solution A. Continue to seal the beaker with sealing tape and stir for 30 minutes to obtain a mixed solution. Transfer the mixed solution to a reaction vessel and react at 180°C for 20 hours to obtain the initial product.

[0066] Step 5: After centrifuging and washing the initial product, place it in a vacuum drying oven to dry and obtain the intermediate product.

[0067] Step 6: Place the intermediate product in a tube furnace, then heat it to 800°C under vacuum, hold it at that temperature for 2 hours, and finally cool it to room temperature to obtain the target product rGO@MoS. 0.9 Se 1.1 / NAC, denoted as sample 4.

[0068] Example 5

[0069] This embodiment prepares rGO@MoS2 / NAC according to the following steps:

[0070] Step 1: Take 3.5 mL of solution with a concentration of 9.76 mg / mL. -1 The GO solution was sonicated in 25 mL of deionized water for 2 hours, then stirred for 1 hour, and 0.14 mmol of (NH4)6Mo7O was added. 24 Stir with 4H2O for 20 minutes to obtain solution B.

[0071] Step 2: Add 3 mL of C2H8N2 and 3 g of glucose to the above solution B in sequence, and continue stirring for 10 minutes to obtain solution C.

[0072] Step 3: Weigh 3 mmol of CH4N2S and add it to solution C. Seal the beaker with sealant and stir for 30 minutes to obtain a mixed solution. Transfer the mixed solution to a reaction vessel and react at 180°C for 20 hours to obtain the initial product.

[0073] Step 5: After centrifuging and washing the initial product, place it in a vacuum drying oven to dry and obtain the intermediate product.

[0074] Step 6: Place the intermediate product in a tube furnace, then heat it to 800°C under vacuum, hold it for 2 hours, and finally cool it to room temperature to obtain rGO@MoS2 / NAC, which is designated as sample 5.

[0075] Figure 1 The images are SEM images of the samples obtained in Examples 1-4. Figure 1 In the text, 'a' and 'b' correspond to sample 1 (rGO@MoSe2NAC) and sample 2 (rGO@MoS2NAC), respectively. 0.6 Se 1.4 / NAC), Figure 1 c and d in the figure correspond to sample 3 (rGO@MoS) 0.8 Se 1.2 / NAC) and sample 4 (rGO@MoS 0.9 Se 1.1 / NAC). In sample 1 (rGO@MoSe2 / NAC), MoSe2 nanosheets and NAC are alternately stacked and rolled into small spheres that are uniformly distributed on rGO, with a diameter of approximately 30-50 nm; in sample 2 (rGO@MoSe2 / NAC), MoSe2 nanosheets and NAC are rolled into small spheres that are uniformly distributed on rGO. 0.6 Se1.4 / NAC), Sample 3 (rGO@MoS) 0.8 Se 1.2 / NAC) and sample 4 (rGO@MoS 0.9 Se 1.1 MoS2 synthesized in / NAC) x Se 2-x Nanosheets grew uniformly on the surface of rGO without forming spheres.

[0076] Figure 2 These are TEM images of the samples obtained in Examples 1-4. Figure 2 In the text, 'a' and 'b' correspond to sample 1 (rGO@MoSe2 / NAC) and sample 2 (rGO@MoS2), respectively. 0.6 Se 1.4 / NAC), Figure 2 c and d in the sample correspond to sample 3 (rGO@MoS). 0.8 Se 1.2 / NAC) and sample 4 (rGO@MoS 0.9 Se 1.1 / NAC). In Sample 1 (rGO@MoSe2 / NAC), the ordered spheres on rGO are hollow spheres formed by rolling up MoSe2 nanosheets and NAC. Two adjacent MoSe2 monolayers are intercalated with an amorphous carbon monolayer, forming a superlattice shell structure of overlapping MoSe2 and NAC. The (002) crystal plane of MoSe2 is measured to extend to 1.12 nm. Sample 2 (rGO@MoSe2 / NAC) 0.6 Se 1.4 / NAC), Sample 3 (rGO@MoS) 0.8 Se 1.2 / NAC) and sample 4 (rGO@MoS 0.9 Se 1.1 ( / NAC) shows layered MoS2 grown on rGO as a support material. x Se 2-x Nanosheets, MoS2 grown on rGO x Se 2-x It is composed of stacked multilayer nanosheets with good crystallinity, and two adjacent MoS₂... x Se 2-x Intercalation of a single layer with an amorphous carbon monolayer forms MoS2. x Se 2-x The structure overlapped with NAC, and the MoS₂ content in samples 2, 3, and 4 was measured by TEM. x Se 2-x The interlayer spacings are 1.14 nm, 1.20 nm, and 1.09 nm, respectively.

[0077] Figure 3 The images are SEM and TEM images of sample 5 (rGO@MoS2 / NAC). Figure 3 a is a SEM image, which shows that the prepared MoS2 nanosheets are uniformly and vertically distributed on the surface of rGO. Figure 3 b is a TEM image, which shows that MoS2 / NAC nanosheets are ordered and vertically distributed on the rGO surface. The (002) crystal plane of MoS2 is measured to extend to 1.07 nm.

[0078] Figure 4 a, b, c, and d in the figure represent sample 3 (rGO@MoS). 0.8 Se 1.2 High-resolution XPS spectra of C1s, Mo 3d, Se 3d, Se 3p & S 2p from NAC. Figure 4 a is the high-resolution spectrum of C1s, with peaks at 282.8, 284.7, 285.7, 286.4, and 288.4 eV corresponding to Mo-C, C=C, CC, CN / CO, and C=O chemical bonds, respectively. Figure 4 The peaks at 229.0 and 232.1 eV in b correspond to Mo 3d5 / 2 and Mo 3d3 / 2, respectively, indicating that Mo is in the +4 valence state. Meanwhile, the weak peak at 230.3 eV represents the Mo-C bond signal, indicating that MoSxSe 2-x In-situ growth on rGO. The peak at 235.2 eV is due to Mo caused by slight surface oxidation. 6+ -O key. Figure 4 c is the high-resolution spectrum of Se 3d, with peaks at 54.6 and 55.4 eV corresponding to Se 3d5 / 2 and Se 3d3 / 2, respectively. 2- Price state. Figure 4 d represents the high-resolution spectrum of Se 3p & S 2p. The peaks at 166.7 and 161.0 eV correspond to Se 3p1 / 2 and Se 3p3 / 2, and the peaks at 163.4 and 162.2 eV correspond to S 2p1 / 2 and S2p3 / 2. Figure 4 e represents sample 3 (rGO@MoS) 0.8 Se 1.2 The full spectrum of / NAC shows the presence of N1s.

[0079] Figure 5 For sample 3 (rGO@MoS) 0.8 Se 1.2The high-resolution spectrum of N1s of N3P3C can be divided into three different nitrogen-containing peaks: pyridinic-N at 398.5 eV, pyrrolic-N at 400.9 eV, and graphitic-N at 403.2 eV. Among them, electrochemically active pyridinic-N and pyrrolic-N can provide abundant external defects and active sites. The doping of carbon with nitrogen further improves the electronic conductivity of carbon. In addition, the high intensity peak at 394.8 eV comes from Mo3p3 / 2.

[0080] Figure 6 The XRD patterns of the samples obtained in Examples 1-5 are shown. The X-ray diffraction peaks of sample 1 (rGO@MoSe2 / NAC) match well with those of 2H-MoSe2 (JCPDS 29-0914), with the most significant (002) diffraction peak shifting from 13.4° to 6.82°; Sample 2 (rGO@MoSe2 / NAC) shows a different XRD pattern. 0.6 Se 1.4 The (002) diffraction peak of sample 3 (rGO@MoS) shifted from 13.4° to 6.92°. 0.8 Se 1.2 The (002) diffraction peak of sample 4 (rGO@MoS) shifted from 13.4° to 7.58°. 0.9 Se 1.1 The (002) diffraction peak of sample 5 (rGO@MoS2 / NAC) shifted from 13.4° to 7.86°; the X-ray diffraction peaks of sample 5 (rGO@MoS2 / NAC) matched well with those of 2H-MoS2 (JCPDS 37-1492), with the most significant (002) diffraction peak shifting from 13.4° to 8.58°. This further demonstrates that adjusting the proportion of selenium atoms can alter the interlayer spacing.

[0081] Figure 7 The Raman spectra of the samples obtained in Examples 1-5 are shown. Sample 1 (rGO@MoSe2NAC), Sample 2 (rGO@MoS2NAC) 0.6 Se 1.4 / NAC), Sample 3 (rGO@MoS) 0.8 Se 1.2 / NAC), Sample 4 (rGO@MoS) 0.9 Se 1.1 / NAC) at 239cm -1 257cm -1 259cm -1 263cm -1 One peak corresponds to the out-of-plane vibration of the Mo-Se bond (A 1g) mode. Furthermore, due to the increased number of sulfur atoms, compared to sample 1 (rGO@MoSe2 / NAC), sample 2 (rGO@MoS)... 0.6 Se 1.4 / NAC), Sample 3 (rGO@MoS) 0.8 Se 1.2 / NAC) and sample 4 (rGO@MoS 0.9 Se 1.1 MoSe2 in / NAC) A 1g The peaks were weakened, shifted, and moved to higher wavenumbers. At 381 and 406 cm⁻¹... -1 The resonance peaks were assigned to the E values ​​of the Mo-S vibrations. 2g 1 and A 1g The pattern indicates that MoS2 was successfully prepared. x Se 2-x At 1350 and 1586cm -1 Two broadened peaks were also observed at 381 and 406 cm⁻¹, corresponding to the D and G bands of the carbon material, respectively, confirming the presence of surface rGO and amorphous carbon. Sample 5 (rGO@MoS₂ / NAC) showed peaks at 381 and 406 cm⁻¹. -1 The resonance peaks were assigned to the E values ​​of the Mo-S vibrations. 2g 1 and A 1g The pattern indicates that MoS2 was successfully prepared in sample 5.

[0082] Table 1 shows the atomic percentages of each element in the EDS of samples obtained in Examples 2-4. Table 1 can be used to obtain the atomic percentages of each element in sample 2 (rGO@MoS). 0.6 Se 1.4 The atomic distribution ratio of each element in / NAC was used to obtain S:Se≈0.6:1.4; this yielded sample 3 (rGO@MoS) 0.8 Se 1.2 The atomic distribution ratio of each element in / NAC was used to obtain S:Se≈0.8:1.2; this yielded sample 4 (rGO@MoS) 0.9 Se 1.1 The atomic distribution ratio of each element in the NAC (Neuro-NaCl) was calculated to yield S:Se ≈ 0.9:1.1. Further, it was demonstrated that by adjusting the ratio of selenium powder and thiourea, different proportions of MoS₂ could be obtained. x Se 2-x Nanosheets.

[0083] Table 1

[0084] element Sample 2 Sample 3 Sample 4 Mo 5.5％ 9％ 3.6％ S 3.1％ 6.4％ 3.0％ Se 7.0％ 9.9％ 3.5％ C 76.7％ 68.4％ 80.2％ N 7.7％ 6.3％ 9.7％

[0085] To characterize the electrochemical performance of the samples obtained in the above examples, the following tests were performed.

[0086] Step 1: Take the samples prepared in each example and grind them with acetylene black and sodium carboxymethyl cellulose in an agate mortar at a mass ratio of 6:2:2 to form a uniform slurry. Coat the slurry onto copper foil and then dry it in a vacuum drying oven at 80°C for 12 hours to make it into the working electrode of the battery.

[0087] Step 2: Assemble a CR2032 button cell using a sodium metal sheet as the counter electrode, glass microfiber filter paper (GF / D, Whatman) as the separator, and 1M NaClO4 in ethylene carbonate (EC) and propylene carbonate (PC) (1:1 v / v) with 5% fluoroethylene carbonate (FEC) as the electrolyte in an inflatable glove box (Etelux Lab 2000, O2 < 0.1 ppm, H2O < 0.1 ppm).

[0088] Step 3: Use a Neware CT-4008Tn 5V10 mA / 5V50 mA charge / discharge tester to perform charge / discharge tests on the assembled button batteries within a voltage window of 0.01-3V.

[0089] Figure 8 Sample 1 (rGO@MoSe2 / NAC) and Sample 3 (rGO@MoS) 0.8 Se 1.2 / NAC) and sample 4 (rGO@MoS 0.9 Se 1.1 Rate performance curves of button cells assembled with NAC. Figure 9 For sample 2 (rGO@MoS) 0.6 Se 1.4 Rate performance curves of coin cells assembled with sample 3 (rGO@MoS2 / NAC) and sample 4 (rGO@MoS2 / NAC). 0.8 Se 1.2 / NAC) exhibits superior sodium storage rate performance at current densities of 0.2, 0.5, 1, 2, 5, 10, 15 and 20 Ag. -1 The values ​​were 551, 526, 505, 469, 421, 381, 357, and 337 mAh g. -1 The capacity is in 30 and 50 Ag. -1 Even at ultra-high current densities, it can still maintain 304 and 264 mAh g. -1 Reversible high capacity. Sample 1 (rGO@MoSe2 / NAC) Sample 4 (rGO@MoS) 0.9 Se 1.1 / NAC), at 50Ag -1 Under ultra-high current density, it can maintain 1896 and 208 mAh g. -1Reversible capacity. Sample 2 (rGO@MoS) 0.6 Se 1.4 Sample 5 (rGO@MoS2 / NAC) and sample 6 (rGO@MoS2 / NAC) were tested at 50 Ag. -1 Under ultra-high current density, it can maintain 185 and 165 mAh g. -1 Reversible capacity.

[0090] Figure 10 For sample 3 (rGO@MoS) 0.8 Se 1.2 The long-cycle performance curve of the coin cell assembled by / NAC under high current was tested at 30Ag. -1 It exhibits excellent stability and maintains 195 mAh g after 14,000 cycles. -1 The capacity retention rate is 70%, and the calculated attenuation per revolution is only 0.0021%. Even at a higher current density of 50 Ag... -1 Below, sample 3 (rGO@MoS) 0.8 Se 1.2 The / NAC also exhibited excellent cycle stability. After 16,000 cycles, the battery maintained a stable performance at 50 Ag. -1 Maintain 172mAh g -1 The reversible capacity is equivalent to 71% capacity retention, with a capacity decay rate of 0.0017%. Furthermore, it exhibits good performance at 30 and 50 Ag. -1 The coulombic efficiency (CE) of the next cycle remains at approximately 100%, demonstrating excellent cycle stability.

[0091] Figure 11 Sample 1 (rGO@MoSe2 / NAC) and Sample 2 (rGO@MoS) 0.6 Se 1.4 / NAC), Sample 3 (rGO@MoS) 0.8 Se 1.2 / NAC), Sample 4 (rGO@MoS) 0.9 Se 1.1 The coin cell assembled with sample 5rGO@MoS2 / NAC and sample 5rGO@MoS2 / NAC was tested at a current density of 10 A g. -1 The following is a cycle curve. Sample 3 (rGO@MoS) 0.8 Se 1.2 The discharge capacity of / NAC) during the first cycle is 328 mAh g. -1 After 500 cycles, the capacity gradually increased to 386 mAh g. -1 It exhibits excellent stability. Sample 3 (rGO@MoS) 0.8 Se 1.2The rGO@MoSe2 / NAC sample significantly outperformed sample 1 (rGO@MoSe2 / NAC) and sample 5 (rGO@MoS2 / NAC) in terms of reversible capacity and stability. Meanwhile, sample 2 (rGO@MoS2 / NAC), which was also modulated, showed significantly better performance. 0.6 Se 1.4 / NAC) and sample 4 (rGO@MoS 0.9 Se 1.1 The rGO@MoSe2 / NAC was also superior to that of sample 1 (rGO@MoSe2 / NAC) and sample 5 (rGO@MoS2 / NAC).

[0092] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A compositionally tunable MoS₂ with broadened interlayer spacing x Se 2-x A method for preparing nanosheets, characterized in that, Includes the following steps: Step 1: Weigh 0-2.5 mmol of Se powder and NaBH4 and add them to 3-10 mL of ethanol solution. Then seal the beaker with sealing adhesive and stir for 1-20 minutes to obtain selenium ion solution A; wherein the molar ratio of NaBH4 to Se powder is 2.5-3:

1. Step 2: Add 30-60 mg of carbon-based material to 15-30 mL of deionized water and sonicate for 0.1-5 hours, then stir for 0.1-2 hours. Continue by adding 0.1-0.2 mmol of (NH4)6Mo7O. 24 Stir with 4H2O for 1-30 minutes to obtain solution B; Step 3: Add 1-6 mL of amino compound and 1-8 g of reducing sugar to solution B in sequence, stir for 1-15 minutes to obtain solution C; Step 4: Weigh 0-5 mmol CH4N2S and solution C and transfer them to solution A. Seal the beaker with sealing adhesive and stir for 10-30 minutes. Transfer the resulting mixed solution to a reaction vessel and react at 160-220℃ for 12-24 hours to obtain the initial product. Step 5: After centrifuging and washing the initial product, place it in a vacuum drying oven to dry and obtain the intermediate product; Step 6: Place the intermediate product in a tube furnace, then heat it to 700-900℃ under vacuum, hold it at that temperature for 1-3 hours, and finally cool it to room temperature to obtain the target product, MoS₂ with broadened interlayer spacing. x Se 2-x Nanosheets.

2. The preparation method according to claim 1, 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, characterized in that: The amino compound mentioned is ethylenediamine.

4. The preparation method according to claim 1, characterized in that: The reducing sugar mentioned is glucose.

5. The preparation method according to claim 1, characterized in that: The content of S and Se in the target product can be controlled by adjusting the ratio of Se powder to CH4N2S.

6. The preparation method according to claim 1, characterized in that: The cleaning described in step 5 involves sequentially cleaning with deionized water and anhydrous ethanol.

7. A MoS₂ with broadened interlayer spacing prepared by the preparation method according to any one of claims 1 to 6. x Se 2-x Nanosheets.

8. The MoS with widened interlayer spacing according to claim 7 x Se 2-x Nanosheets, characterized by: The widened interlayer spacing of MoS x Se 2-x Nanosheets are made by loading MoS2 onto the surface of a carbon-based material. x Se 2-x Nanosheets, and the MoS x Se 2-x Nanosheets are formed by two adjacent MoS2 nanosheets. x Se 2-x Nitrogen-doped amorphous carbon monolayers are inserted between the monolayers, thereby enabling MoS2 to... x Se 2-x The interlayer spacing of nanosheets is widened.

9. A MoS with widened interlayer spacing as described in claim 7 or 8 x Se 2-x Application of nanosheets as negative electrode materials in sodium-ion batteries.

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