Molybdenum diselenide hollow microspheres, and preparation method and application thereof

Abstract

This invention relates to a hollow molybdenum diselenide microsphere and its preparation method. The product is prepared by the following steps: ammonium molybdate is weighed and dissolved in deionized water, stirred until completely dissolved; dopamine hydrochloride is then added to the resulting solution and stirred until homogeneous; anhydrous ethanol is added to the resulting solution and stirred until homogeneous; ammonia is added dropwise to the resulting solution; the resulting solution is allowed to stand at room temperature for a period of time, washed, and dried to obtain a precursor; the obtained precursor and selenium powder are placed in an inert atmosphere and calcined in a sealed environment, then naturally cooled to room temperature to obtain the hollow molybdenum diselenide microsphere. The beneficial effects of this invention are: it can suppress the shuttle effect of polysulfides through strong electronic interactions with polysulfides, promoting the catalytic conversion process of polysulfides, making it an ideal high-efficiency electrocatalyst; simultaneously, the hollow structure can physically confine polysulfides, thereby effectively suppressing the shuttle effect of polysulfides.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and electrochemical technology, specifically relating to a hollow molybdenum diselenide microsphere and its preparation method. This material can be used as an electrocatalyst for high-capacity, high-cycle-life room-temperature sodium-sulfur batteries. Background Technology

[0002] Electrochemical energy storage technology plays an increasingly important role in our lives. Among various energy storage technologies, rechargeable green chemical storage devices—alkali metal sulfur batteries—have excellent performance and abundant sulfur resources, offering broad application prospects. They are widely used in mobile electronic devices and have now expanded to electric vehicles and large-scale energy storage systems. Compared to lithium resources, sodium and sulfur are widely available and inexpensive. This has led to increasing attention being paid to sodium-sulfur batteries. Traditional high-temperature sodium-sulfur batteries operate at 300-350℃ and consist of molten electrodes and a solid inorganic β-alumina electrolyte, but they pose certain safety risks. Room-temperature sodium-sulfur batteries, in principle, allow sulfur to undergo a two-electron redox reaction, thus possessing a higher theoretical energy of 1273 Wh / kg. −1 It is also safer and more reliable.

[0003] The key role of sulfur-loaded cathode materials in room-temperature sodium-sulfur batteries is to adsorb polysulfides and catalytically convert them into Na₂S. Therefore, they are also considered electrocatalyst materials. Traditional sulfur-loaded cathodes suffer from an imbalance between the adsorption and catalytic abilities of polysulfides, leading to the easy dissolution of polysulfides in the electrolyte. Under the influence of the concentration gradient, these polysulfides migrate to the negative electrode, exhibiting a "shuttle effect," which reduces the utilization rate of the sulfur cathode and consequently results in poor battery cycle stability. Therefore, it is necessary to develop electrocatalysts with high catalytic activity.

[0004] This invention is supported by the National Undergraduate Innovation and Entrepreneurship Training Program S202210497052. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a hollow molybdenum diselenide microsphere and its preparation method. The synthesis process is simple, and the resulting sulfur-loaded molybdenum diselenide hollow microsphere cathode exhibits excellent electrochemical performance in room-temperature sodium-sulfur batteries.

[0006] The technical solution of this invention to solve the above problems is: hollow molybdenum diselenide microspheres; hollow microspheres composed of nanosheets, the thickness of the nanosheets being 5~10 nm, and the diameter of the hollow microspheres being 300~500 nm.

[0007] It is a product prepared by the following method, including the following steps:

[0008] 1) Weigh out ammonium molybdate and dissolve it in deionized water, stirring until completely dissolved;

[0009] 2) Add dopamine hydrochloride to the solution obtained in step 1) and stir until homogeneous;

[0010] 3) Add anhydrous ethanol to the solution obtained in step 2) and stir until homogeneous;

[0011] 4) Add ammonia water dropwise to the solution obtained in step 3);

[0012] 5) After the solution obtained in step 4) is left to stand at room temperature for a period of time, it is washed and dried to obtain the precursor;

[0013] 6) Place the precursor and selenium powder obtained in step 5) in an inert atmosphere and calcine them in a sealed environment. After naturally cooling to room temperature, take them out to obtain molybdenum diselenide hollow microspheres.

[0014] According to the above scheme, in step 1), the mass of ammonium molybdate is 100~500 mg, the amount of deionized water is 50~100 mL, in step 2), the amount of dopamine hydrochloride is 200~400 mg, in step 3), the amount of anhydrous ethanol is 100~300 mL, and in step 4), the amount of ammonia water is 0.2~1 mL.

[0015] According to the above scheme, the settling time in step 5) is 8~20 h.

[0016] According to the above scheme, the mass ratio of precursor and selenium powder in step 6) is 0.2~1.

[0017] According to the above scheme, the calcination temperature in step 6) is 500~700℃ and the time is 0.5~3 h.

[0018] The aforementioned molybdenum diselenide hollow microspheres can be used as electrocatalysts for room-temperature sodium-sulfur batteries.

[0019] The formation mechanism of hollow microspheres during the hydrothermal process in this invention is the Kirkendall effect, which yields molybdenum diselenide hollow microspheres through anion exchange during calcination. This method can be applied to the preparation of hollow microspheres of molybdenum nitride, molybdenum carbide, and molybdenum sulfide.

[0020] The beneficial effects of this invention are as follows: The hollow molybdenum diselenide microsphere structure not only physically confines polysulfides but also accelerates their conversion process, thereby achieving high-rate and long-cycle stable room-temperature sodium-sulfur battery performance. Because the hollow molybdenum diselenide microspheres can suppress the shuttle effect of polysulfides through strong electron interactions with them, promoting the catalytic conversion process, they are an ideal high-efficiency electrocatalyst. Simultaneously, the hollow structure physically confines the polysulfides, effectively suppressing their shuttle effect. The synthesis of high-performance molybdenum diselenide hollow microsphere sulfur-supported cathodes using a simple, convenient, and low-cost method for room-temperature sodium-sulfur batteries will be of great significance. Attached Figure Description

[0021] Figure 1 This is the X-ray diffraction pattern of the hollow molybdenum diselenide microspheres of Embodiment 1 of the present invention;

[0022] Figure 2 This is a transmission electron microscope image of the hollow molybdenum diselenide microspheres of Embodiment 1 of the present invention;

[0023] Figure 3 This is a rate performance graph of the molybdenum diselenide hollow microsphere sulfur-loaded cathode of Example 1 of the present invention at current densities of 100, 200, 500, 1000, 2000, 4000, and 6000 mA / g.

[0024] Figure 4 This is a graph showing the cycling performance of the molybdenum diselenide hollow microsphere sulfur-loaded cathode of Example 1 of the present invention at a current density of 1000 mA / g. Detailed Implementation

[0025] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0026] Example 1:

[0027] The method for preparing molybdenum diselenide hollow microspheres includes the following steps:

[0028] 1) Weigh 100 mg of ammonium molybdate and dissolve it in 50 mL of deionized water, stirring until completely dissolved;

[0029] 2) Add 200 mg of dopamine hydrochloride to the solution obtained in step 1) and stir until the solution turns a clear wine-red color;

[0030] 3) Add 100 mL of anhydrous ethanol to the solution obtained in step 2) and stir until the solution turns orange-yellow;

[0031] 4) Add 0.2 mL of ammonia water dropwise to the solution obtained in step 3) using a pipette until the solution turns reddish-brown;

[0032] 5) After the solution obtained in step 4) is allowed to stand at room temperature for 8 h, it is washed with water and alcohol and dried to obtain the precursor;

[0033] 6) The precursor and selenium powder obtained in step 5) are placed in an argon atmosphere and calcined in a sealed environment. The mass ratio of the precursor to the selenium powder is 0.2. The calcination temperature and time are 500℃ and 0.5 h, respectively. After naturally cooling to room temperature, the molybdenum diselenide hollow microspheres are obtained.

[0034] Taking the hollow molybdenum diselenide microspheres of this example as an example, their structure was determined by X-ray diffraction (XRD) patterns. Figure 1As shown, the characteristic peaks of the hollow molybdenum diselenide microspheres can be well matched with the molybdenum diselenide crystalline phase (JCPDS: 01-017-0887), proving that pure phase molybdenum diselenide has been obtained. Figure 2 The images show transmission electron microscopy (TEM) images of hollow molybdenum diselenide microspheres, confirming that the material consists of hollow microspheres composed of nanosheets with a thickness of 5–10 nm and a diameter of 300–500 nm. The sulfur-loaded molybdenum diselenide hollow microsphere cathode prepared in this example serves as the active material for a room-temperature sodium-sulfur battery. The assembly method for the sodium-sulfur battery is the same as the usual preparation method. Figure 3 The rate performance diagram of the molybdenum diselenide hollow microspheres is shown, which can achieve a discharge specific capacity of 452 mAh / g at a high current density of 6000 mA / g. Figure 4 This study demonstrates that the sulfur-loaded cathode with hollow molybdenum diselenide microspheres achieves an initial capacity of 607 mAh / g at a current density of 1000 mA / g, and a capacity of 514 mAh / g after 100 cycles. These results indicate that the sulfur-loaded cathode with hollow molybdenum diselenide microspheres possesses excellent high capacity and high rate performance, making it a potential material for room-temperature sodium-sulfur batteries.

[0035] Example 2:

[0036] The method for preparing molybdenum diselenide hollow microspheres includes the following steps:

[0037] 1) Weigh 150 mg of ammonium molybdate and dissolve it in 70 mL of deionized water, stirring until completely dissolved;

[0038] 2) Add 250 mg of dopamine hydrochloride to the solution obtained in step 1) and stir until the solution turns a clear wine-red color;

[0039] 3) Add 150 mL of anhydrous ethanol to the solution obtained in step 2) and stir until the solution turns orange-yellow;

[0040] 4) Add 0.2 mL of ammonia water dropwise to the solution obtained in step 3) using a pipette until the solution turns reddish-brown;

[0041] 5) After the solution obtained in step 4) is allowed to stand at room temperature for 8 h, it is washed with water and alcohol and dried to obtain the precursor;

[0042] 6) The precursor and selenium powder obtained in step 5) are placed in an argon atmosphere and calcined in a sealed environment. The mass ratio of the precursor to the selenium powder is 0.5. The calcination temperature and time are 600℃ and 0.5 h, respectively. After naturally cooling to room temperature, the molybdenum diselenide hollow microspheres are obtained.

[0043] The molybdenum diselenide hollow microsphere sulfur-supported cathode prepared in this example, used as the positive electrode active material for a room-temperature sodium-sulfur battery, achieved an initial capacity of 590 mAh / g at a current density of 1000 mA / g, and a capacity of 495 mAh / g after 100 cycles. At a high current density of 6000 mA / g, a discharge specific capacity of 425 mAh / g was achieved.

[0044] Example 3:

[0045] The method for preparing molybdenum diselenide hollow microspheres includes the following steps:

[0046] 1) Weigh 300 mg of ammonium molybdate and dissolve it in 80 mL of deionized water, stirring until completely dissolved;

[0047] 2) Add 300 mg of dopamine hydrochloride to the solution obtained in step 1) and stir until the solution turns a clear wine-red color;

[0048] 3) Add 200 mL of anhydrous ethanol to the solution obtained in step 2) and stir until the solution turns orange-yellow;

[0049] 4) Add 0.5 mL of ammonia water dropwise to the solution obtained in step 3) using a pipette until the solution turns reddish-brown;

[0050] 5) After the solution obtained in step 4) is allowed to stand at room temperature for 14 h, it is washed with water and alcohol and dried to obtain the precursor;

[0051] 6) The precursor and selenium powder obtained in step 5) are placed in an argon atmosphere and calcined in a sealed environment. The mass ratio of the precursor to the selenium powder is 0.5. The calcination temperature and time are 700℃ and 2 h, respectively. After naturally cooling to room temperature, the molybdenum diselenide hollow microspheres are obtained.

[0052] The molybdenum diselenide hollow microsphere sulfur-supported cathode prepared in this example, used as the positive electrode active material for a room-temperature sodium-sulfur battery, achieved an initial capacity of 550 mAh / g at a current density of 1000 mA / g, and a capacity of 431 mAh / g after 100 cycles. At a high current density of 6000 mA / g, a discharge specific capacity of 411 mAh / g was achieved.

[0053] Example 4:

[0054] The method for preparing molybdenum diselenide hollow microspheres includes the following steps:

[0055] 1) Weigh 400 mg of ammonium molybdate and dissolve it in 90 mL of deionized water, stirring until completely dissolved;

[0056] 2) Add 350 mg of dopamine hydrochloride to the solution obtained in step 1) and stir until the solution turns a clear wine-red color;

[0057] 3) Add 250 mL of anhydrous ethanol to the solution obtained in step 2) and stir until the solution turns orange-yellow;

[0058] 4) Add 0.7 mL of ammonia water dropwise to the solution obtained in step 3) using a pipette until the solution turns reddish-brown;

[0059] 5) After the solution obtained in step 4) is allowed to stand at room temperature for 16 h, it is washed with water and alcohol and dried to obtain the precursor;

[0060] 6) The precursor and selenium powder obtained in step 5) were placed in an argon atmosphere and calcined in a sealed environment. The mass ratio of the precursor to the selenium powder was 0.7. The calcination temperature and time were 600℃ and 2.5 h, respectively. After naturally cooling to room temperature, the molybdenum diselenide hollow microspheres were obtained.

[0061] The molybdenum diselenide hollow microsphere sulfur-supported cathode prepared in this example, used as the positive electrode active material for a room-temperature sodium-sulfur battery, achieved an initial capacity of 560 mAh / g at a current density of 1000 mA / g, and a capacity of 466 mAh / g after 100 cycles. At a high current density of 6000 mA / g, a discharge specific capacity of 414 mAh / g was achieved.

[0062] Example 5:

[0063] The method for preparing molybdenum diselenide hollow microspheres includes the following steps:

[0064] 1) Weigh 400 mg of ammonium molybdate and dissolve it in 100 mL of deionized water, stirring until completely dissolved;

[0065] 2) Add 400 mg of dopamine hydrochloride to the solution obtained in step 1) and stir until the solution turns a clear wine-red color;

[0066] 3) Add 300 mL of anhydrous ethanol to the solution obtained in step 2) and stir until the solution turns orange-yellow;

[0067] 4) Add 1 mL of ammonia water dropwise to the solution obtained in step 3) using a pipette until the solution turns reddish-brown;

[0068] 5) After the solution obtained in step 4) is allowed to stand at room temperature for 20 h, it is washed with water and alcohol and dried to obtain the precursor;

[0069] 6) The precursor and selenium powder obtained in step 5) are placed in an argon atmosphere and calcined in a sealed environment. The mass ratio of the precursor to the selenium powder is 1:1. The calcination temperature and time are 700℃ and 3 h, respectively. After naturally cooling to room temperature, the molybdenum diselenide hollow microspheres are obtained.

[0070] The molybdenum diselenide hollow microsphere sulfur-supported cathode prepared in this example, used as the positive electrode active material for a room-temperature sodium-sulfur battery, achieved an initial capacity of 620 mAh / g at a current density of 1000 mA / g, and a capacity of 535 mAh / g after 100 cycles. At a high current density of 6000 mA / g, a discharge specific capacity of 467 mAh / g was achieved.

Claims

1. The application of molybdenum diselenide hollow microspheres as electrocatalysts for room-temperature sodium-sulfur batteries, characterized in that, The molybdenum diselenide hollow microspheres are hollow microspheres composed of nanosheets with a thickness of 5-10 nm and a diameter of 300-500 nm. The preparation method of the molybdenum diselenide hollow microspheres includes the following steps: 1) Weigh out ammonium molybdate and dissolve it in deionized water, stirring until completely dissolved; 2) Add dopamine hydrochloride to the solution obtained in step 1) and stir until homogeneous; 3) Add anhydrous ethanol to the solution obtained in step 2) and stir until homogeneous; 4) Add ammonia water dropwise to the solution obtained in step 3); 5) After the solution obtained in step 4) is left to stand at room temperature for a period of time, it is washed and dried to obtain the precursor; 6) Place the precursor and selenium powder obtained in step 5) in an inert atmosphere and calcine in a sealed environment. After naturally cooling to room temperature, take them out to obtain molybdenum diselenide hollow microspheres.

2. The application according to claim 1, characterized in that... Step 1) The mass of ammonium molybdate is 100~500 mg, and the amount of deionized water is 50~100 mL. Step 2) The amount of dopamine hydrochloride is 200~400 mg. Step 3) The amount of anhydrous ethanol is 100~300 mL. Step 4) The amount of ammonia water is 0.2~1 mL.

3. The application according to claim 1, characterized in that... The settling time in step 5) is 8~20 h.

4. The application according to claim 1, characterized in that... In step 6), the mass ratio of the precursor to selenium powder is 0.2~1.

5. The application according to claim 1, characterized in that... In step 6), the calcination temperature is 500~700℃ and the time is 0.5~3 h.

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