Preparation method and application of nitrogen-doped molybdenum diselenide hollow structure

Abstract

The present invention discloses a preparation method and application of a nitrogen-doped molybdenum diselenide hollow structure, which relates to the field of energy storage material preparation. The preparation process is as follows: first, in the absence of a template and a surfactant, selenium powder is dissolved in hydrazine hydrate, followed by sequentially adding an amide reagent and water, stirring evenly, adding a sodium molybdate solution, and stirring evenly to obtain a reaction precursor; then, the precursor is subjected to solvent thermal treatment to obtain the nitrogen-doped molybdenum diselenide hollow structure. The preparation method of the present invention is simple and easy, does not require a template, a surfactant, and complex equipment, and is low in cost; the prepared nitrogen-doped molybdenum diselenide has a hollow structure and is used as a lithium-ion battery material. The nitrogen-doped molybdenum diselenide hollow structure exhibits a large specific capacity, good rate performance, and excellent cycle stability, and is a lithium-ion battery negative electrode material with broad application prospects.

Description

Technical Field

[0001] The present invention relates to the field of energy storage material preparation, and in particular to a preparation method and application of a nitrogen-doped molybdenum diselenide hollow structure. Background Art

[0002] In recent years, with the rapid growth of energy demand and increasing environmental awareness, advanced energy storage devices have garnered increasing attention. Among these energy storage devices, lithium-ion batteries (Li-ion batteries) are highly favored due to their high energy density, long lifespan, superior safety, and wide operating temperature range. However, commercial Li-ion batteries primarily utilize graphite as their anode, which significantly limits their energy density. To achieve high-energy-density Li-ion batteries, high-performance anode materials have attracted significant attention.

[0003] Molybdenum diselenide is considered to be a promising negative electrode material for lithium-ion batteries due to its unique layered structure, stable Mo-Se bond, good catalytic performance, large specific surface area, higher conductivity than oxides and sulfides, larger dielectric constant, and multivalent oxidation states of transition metals.

[0004] Li Na et al. synthesized MoSe2 nanoparticles using a one-pot method, achieving a battery discharge capacity of 573.9 mAh / g after 200 cycles at a current density of 200 mA / g. Wu Yi-Chen et al. prepared ultrathin MoSe2 nanosheets using a jet cavitation process, achieving an initial discharge capacity of 538 mAh / g at a rate of 0.1C. Zhang Kai-Bo et al. synthesized three-dimensional flower-like MoSe2 using a hydrothermal method, achieving an initial discharge capacity of 642.6 mAh / g at a current density of 1000 mA / g. Zhang et al. synthesized MoSe2 nanoflowers using a simple solvothermal method, achieving a discharge capacity of 641.4 mAh / g after 200 continuous cycles at a current density of 0.1 A / g. Although MoSe2 exhibits promising properties for lithium-ion storage, further research is needed to address challenges such as long-term stability and cost-effectiveness.

[0005] In addition, optimizing the synthesis path and exploring new process methods are crucial to successfully promoting MoSe2 electrode materials into practical applications. An effective strategy is to construct a hollow structure with rich pores, which has the following advantages: 1) The rich pore structure is conducive to electrolyte wetting and lithium ion diffusion, thereby obtaining high specific capacity and excellent rate performance. 2) The cavity can act as a "storage" and buffer space, which can resist the stress during continuous charge and discharge, thereby improving the cycle stability. In addition, heteroatom doping can expose more active sites, further improving the specific capacity and electrochemical kinetics. Therefore, it is necessary to provide a preparation method and application of heteroatom-doped molybdenum diselenide hollow structure to solve the above problems. Summary of the Invention

[0006] To address the challenges of the existing technology, the present invention provides a method for preparing and applying nitrogen-doped hollow molybdenum diselenide structures. These hollow nitrogen-doped molybdenum diselenide spheres exhibit excellent energy storage performance as negative electrode materials for lithium-ion batteries. Compared to other two-dimensional layered materials, molybdenum diselenide has a smaller band gap and excellent mobility, as well as superior photoelectric properties. The hollow structure and nitrogen doping increase the contact area and electrochemically active sites, improving the storage capacity, rate capability, and cycling stability of the material as a negative electrode material for lithium-ion batteries.

[0007] A method for preparing a nitrogen-doped molybdenum diselenide hollow structure comprises the following steps:

[0008] (1) Dissolve selenium powder in hydrazine hydrate, then add amide reagent and water in sequence, and stir evenly to obtain selenization solution A;

[0009] (2) dissolving sodium molybdate dihydrate in water to obtain sodium molybdate solution B;

[0010] (3) Adding sodium molybdate solution B to selenide solution A and stirring evenly to obtain reaction precursor C;

[0011] (4) Transferring the precursor C into a sealed stainless steel reactor lined with PPL for solvothermal reaction;

[0012] (5) After the reaction is completed, the mixture is naturally cooled to room temperature, centrifuged, washed, and dried to obtain a nitrogen-doped molybdenum diselenide hollow structure.

[0013] In the above steps, the types, proportions, reaction temperature and time of the raw materials are key to forming the hollow structure and chemical composition of the material of the present invention.

[0014] In step 1, the amide reagent is one or both of formamide and N,N-dimethylformamide.

[0015] In step 1, the volume ratio of the amide reagent to water is 1:4 to 4:1.

[0016] In step 2, the solubility of the sodium molybdate solution is 10 mmol / L to 200 mmol / L.

[0017] In step 3, the molar ratio of selenium powder to sodium molybdate dihydrate is 2:1.

[0018] In step 4, the temperature of the solvent thermal reaction is 200° C. to 240° C., and the reaction time is 12 h to 24 h.

[0019] In step 5, the washing step is to wash with water and ethanol 3 to 5 times respectively.

[0020] In step 5, the drying temperature is 50°C to 70°C.

[0021] The present invention also discloses an application of a nitrogen-doped molybdenum diselenide hollow structure. The nitrogen-doped molybdenum diselenide hollow structure prepared by the above method is used to prepare an electrode sheet and assemble it into a button cell. The nitrogen-doped molybdenum diselenide hollow structure, super P, and PVDF are weighed in a mass ratio of 70:20:10, and NMP is added to form a slurry. The slurry is then coated on copper foil and dried in a vacuum drying oven. After drying, the foil is punched into a 12 mm diameter disc as a working electrode. A lithium sheet is then used as a counter electrode, and the battery is assembled into a 2016-inch button cell in an argon atmosphere.

[0022] Beneficial effects of the present invention:

[0023] 1. The nitrogen-doped molybdenum diselenide prepared by the present invention has a hollow structure and a high specific capacity, and can be applied to high-energy-density lithium-ion batteries;

[0024] 2. The nitrogen-doped molybdenum diselenide prepared by the present invention has a hollow structure and a rich pore structure, which is conducive to electrolyte wetting and lithium ion diffusion, thereby obtaining a high specific capacity and excellent rate performance.

[0025] 3. The nitrogen-doped molybdenum diselenide prepared by the present invention has a hollow structure, and the cavity can act as a "storage" and buffer space, which can resist the stress during continuous charge and discharge, thereby improving the cycle stability.

[0026] 4. The nitrogen-doped molybdenum diselenide hollow structure prepared by the present invention can expose more active sites and improve the specific capacity and electrochemical kinetics.

[0027] 5. The preparation process of the present invention is simple, the conditions are mild, the operation is easy, no surfactants, templates and complex equipment are required, the cost is low, the morphology of the product is controllable, and it is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the XRD pattern of the nitrogen-doped molybdenum diselenide hollow structure prepared in Example 1;

[0029] Figure 2 This is a TEM image of the nitrogen-doped molybdenum diselenide hollow structure prepared in Example 1;

[0030] Figure 3 CV graph of the nitrogen-doped molybdenum diselenide hollow structure battery prepared in Example 1;

[0031] Figure 4 The first GCD curves of the nitrogen-doped molybdenum diselenide hollow structure battery prepared in Example 1 at different current densities;

[0032] Figure 5 This is a rate performance diagram of the nitrogen-doped molybdenum diselenide hollow structure battery prepared in Example 1;

[0033] Figure 6 This is a cycle performance diagram of the nitrogen-doped molybdenum diselenide hollow structure battery prepared in Example 1. DETAILED DESCRIPTION

[0034] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0035] Example 1

[0036] Preparation method and application of nitrogen-doped molybdenum diselenide hollow structure:

[0037] (1) Weigh 0.158 g of selenium powder and dissolve it in 5.0 mL of hydrazine hydrate. Then, add 15.0 mL of formamide and 10.0 mL of water in sequence and stir for 15 min to obtain selenized solution A.

[0038] (2) dissolving 0.242 g of sodium molybdate dihydrate in 10.0 mL of water to obtain sodium molybdate solution B;

[0039] (3) Add sodium molybdate solution B to selenide solution A and stir for 30 minutes to obtain precursor C;

[0040] (4) Precursor C was transferred into a sealed stainless steel reactor with a PPL lining and reacted at 200 °C for 12 h;

[0041] (5) After the reaction is completed, the mixture is naturally cooled to room temperature, centrifuged, and the precipitate is washed with water and ethanol in sequence, and the precipitate is vacuum-dried at 60° C. to obtain nitrogen-doped molybdenum diselenide hollow structure powder;

[0042] XRD patterns of nitrogen-doped MoSe hollow structures Figure 1 shown.

[0043] TEM images of nitrogen-doped molybdenum diselenide hollow structures are shown in Figure 1. Figure 2 As shown in the figure, it can be seen that nitrogen-doped molybdenum diselenide has a hollow structure with rich pore structure, which is conducive to electrolyte wetting and lithium ion diffusion. The cavity can play the role of "storage" and buffer space, which can resist the stress during charging and discharging, thereby obtaining excellent lithium storage performance.

[0044] Example 2

[0045] The difference between Example 2 and Example 1 is that the formamide in step 1 is replaced by N,N-dimethylformamide, and the rest of the reaction process is the same.

[0046] Example 3

[0047] The difference between Example 3 and Example 1 is that the temperature of the solvent thermal reaction in step 4 is 240° C. The rest of the reaction process is the same.

[0048] Example 4

[0049] The difference between Example 4 and Example 1 is that the solvent thermal reaction time is 24 hours in step 4. The rest of the reaction process is the same.

[0050] Example 5

[0051] The difference between Example 5 and Example 1 is that in step 5, the precipitate is placed in a vacuum drying oven at 70° C. and dried for 12 hours. The rest of the reaction process is the same.

[0052] Electrochemical Performance Testing: The nitrogen-doped molybdenum diselenide hollow structure prepared in Example 1 was fabricated into a test electrode and assembled into a 2016-type button cell with a lithium sheet as the counter electrode. Lithium storage performance was tested over a voltage range of 0.01-300V. First, the nitrogen-doped molybdenum diselenide hollow structure, super P, and PVDF were weighed in a mass ratio of 70:20:10. NMP was added to form a slurry. The slurry was then coated onto copper foil and dried in a vacuum drying oven. After drying, the copper foil was punched into a 12 mm diameter disc as the working electrode. The lithium sheet was then used as the counter electrode and assembled into a 2016-type button cell in an argon atmosphere.

[0053] Figure 3 The CV curve of the nitrogen-doped MoSe hollow structure at 0.1mV / s. In the first scan, two obvious reduction peaks can be seen at 1.83V and 0.73V. The peak at 1.83V corresponds to the phase transition of MoSe from 2H to 1T and the Li + Ions are intercalated into nitrogen-doped MoSe2. The peak at 0.73 V is related to the formation of the SEI film and the reduction of MoSe2 to form Li2Se and metallic Mo. The small oxidation peak at 1.49 V can be attributed to the oxidation of Mo to MoSe2. The oxidation peak at 2.25 V corresponds to the oxidation of Li2Se to Se.

[0054] Figure 4 The first GCD curves of the nitrogen-doped MoSe hollow structure at different current densities are shown. When the current density is 100, 200, 500, and 1000 mA / g, the first cycle discharge specific capacity is 1837.3, 1558.1, 1369.5, and 1252.0 mAh / g, respectively.

[0055] Figure 5The figure shows the rate performance of nitrogen-doped molybdenum diselenide hollow structure batteries. At current densities of 0.1, 0.2, 0.5, 1.0, and 2.0 A / g, the average discharge specific capacities at each current density were 1168.4, 943.7, 823.7, 725.2, and 624.1 mAh / g, respectively. After a series of continuous cycles, when the current density returned to 0.1 A / g, the average discharge specific capacity reached 1028.1 mAh / g and subsequently stabilized, indicating that the nitrogen-doped molybdenum diselenide hollow structure has excellent rate performance and cycling stability.

[0056] Figure 6 The cycling performance of a nitrogen-doped molybdenum diselenide hollow structure battery is shown in Figure 2. At a current density of 100 mA / g, after 180 cycles of continuous charge and discharge, the battery's reversible specific capacity is 751.1 mAh / g, demonstrating that the nitrogen-doped molybdenum diselenide hollow structure battery has excellent cycling performance.

[0057] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

Claims

1. An application of a nitrogen-doped molybdenum diselenide hollow structure, characterized in that: It is used to prepare button-type lithium-ion batteries, including electrode preparation and performance testing. The method is as follows: First, nitrogen-doped molybdenum diselenide hollow structures, superP, and PVDF were weighed in a mass ratio of 70:20:10 and mixed with NMP to form a slurry. The slurry was then coated on copper foil and dried in a vacuum drying oven. After drying, the foil was punched into 12mm diameter discs as working electrodes. Then, a lithium sheet was used as the counter electrode and assembled into a 2016-type button cell in an argon atmosphere. The lithium storage performance of the battery was tested in the voltage range of 0.01 to 3.00V. The preparation of nitrogen-doped molybdenum diselenide hollow structures comprises the following steps: (1) Weigh 0.158 g of selenium powder and dissolve it in 5.0 mL of hydrazine hydrate. Then, add 15.0 mL of formamide and 10.0 mL of water in sequence and stir for 15 min to obtain selenized solution A. (2) dissolving 0.242 g of sodium molybdate dihydrate in 10.0 mL of water to obtain sodium molybdate solution B; (3) Add sodium molybdate solution B to selenide solution A and stir for 30 minutes to obtain precursor C; (4) Precursor C was transferred into a sealed stainless steel reactor with a PPL lining and reacted at 200 °C for 12 h; (5) After the reaction is completed, the mixture is naturally cooled to room temperature, centrifuged, and the precipitate is washed with water and ethanol in sequence. The precipitate is vacuum-dried at 60° C. to obtain nitrogen-doped molybdenum diselenide hollow structure powder.

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