A tungsten-doped VS2 / S composite material, its preparation method and application

Abstract

The invention discloses a tungsten-doped VS2 / S composite material and a preparation method and application thereof. The method comprises: completely dissolving a tungsten source in water; adding ammonium metavanadate into ammonia water and stirring until no precipitate is formed; mixing the solutions obtained above, adding a surfactant thereto, adding thioacetamide after mixing evenly to obtain a mixed solution, transferring the mixed solution to a polytetrafluoroethylene reactor, placing the reactor in a homogeneous reactor, reacting fully at 130-200° C. for 15-24 hours, cooling to room temperature with the furnace after the reaction is completed to obtain a reddish-brown mixed solution G, washing and drying to obtain a tungsten-doped VS2 / S powder; performing heat treatment in a tubular furnace to finally obtain a black powder, namely the tungsten-doped VS2 / S composite material; and successfully preparing a composite material in which a small-sized sulfur element is in situ grown on the surface of a lamellar VS2 and doped with tungsten by a simple one-step solvothermal method, the composite material has good sodium ion storage performance and exhibits excellent rate performance and stability as a SIBs electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, relates to energy storage materials, and particularly relates to a tungsten-doped VS2 / S composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Electrochemical energy storage is considered an efficient energy storage technology due to its high energy conversion efficiency, relatively compact volume, and fast response speed. Issues such as the low crustal abundance, geographical limitations, and high price of lithium metal have led to a significant increase in the manufacturing cost of LIBs, greatly hindering the large-scale application of LIBs.

[0003] Under the situation of continuously increasing energy storage demand and increasingly scarce lithium resources, sodium-ion batteries (SIBs) have shown strong competitiveness in the energy storage field due to their advantages such as rich resources, low cost, high energy conversion efficiency, and long cycle life, and thus have become the most promising alternatives. On the other hand, the large radius and heavy molar mass of sodium ions lead to slow reaction kinetics and significant volume changes in electrode materials, so SIBs have poor rate performance and high irreversible capacity loss. Therefore, it is imperative to develop electrode materials suitable for SIBs.

[0004] Two-dimensional transition metal dichalcogenides (TMDs) have unique single-layer or multi-layer nanosheets similar to graphite, and their interlayer spacing is larger than that of graphite. Such structural features can provide channels of appropriate size for the insertion and extraction processes of Na + without obvious structural deformation. Vanadium disulfide (VS2), as a kind of transition metal dichalcogenide, has a hexagonal structure with the P-3m1 space group. The VS2 lattice is formed by stacking S-V-S monolayers through weak van der Waals interactions to form a layered structure with an interlayer distance of . The large interlayer spacing is conducive to the insertion and extraction of sodium ions. Moreover, vanadium disulfide has a large electron state at the Fermi level, demonstrating the metallic state characteristics of vanadium disulfide and revealing the good electrical conductivity of VS2. Although vanadium disulfide has many advantages as a sodium-ion battery, there are also deficiencies, such as slow charge transfer leading to poor rate behavior, and problems such as poor stability caused by pulverization and structural damage during the reaction process. The three-dimensional self-assembled structure can solve the above problems due to its unique structural advantages, and the high pseudocapacitance storage mechanism can explain the source of excellent rate performance. The theoretical specific capacity of sulfur is 1675 mAh / g. By compounding vanadium disulfide with sulfur, the capacity of vanadium disulfide as a sodium-ion battery negative electrode material can be further improved through the structural synergistic effect of the two. Tungsten has an atomic radius similar to that of vanadium . For tungsten doping of vanadium disulfide, it is easier to replace the vanadium sites for doping. The tungsten-doped VS2 / S composite material is expected to become an excellent SIBs electrode material. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a tungsten-doped VS2 / S composite material, its preparation method and application. A composite material in which small-sized sulfur is in-situ grown on the surface of lamellar VS2 and doped with tungsten is successfully prepared by a simple one-step solvothermal method. This composite material has good sodium ion storage performance and exhibits excellent rate performance and stability as an SIBs electrode material.

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

[0007] A preparation method of a tungsten-doped VS2 / S composite material, comprising the following steps:

[0008] Step 1: Add 0.033 g to 1.1 g of tungsten source into 5 to 10 mL of water, and stir until completely dissolved to obtain solution A;

[0009] Step 2: Measure 15 to 35 mL of water and pour it into a beaker, then add 3 to 18 mL of ammonia water with a mass fraction of 25% to 28% to obtain solution B. Weigh 0.5 g to 3.8 g of ammonium metavanadate and add it to solution B, stir well until there is no precipitate at the bottom of the beaker to obtain solution C. Mix solution A and solution C evenly to obtain solution D, add 0.01 g to 2.5 g of surfactant to it, and stir well until evenly mixed to obtain solution E;

[0010] Step 3: Weigh 2 g to 9 g of thioacetamide and add it to solution E, stir until completely dissolved to obtain solution F;

[0011] Step 4: Transfer solution F to a polytetrafluoroethylene reaction kettle, then place the reaction kettle in a homogeneous reactor, react at 130 to 200 °C for 15 to 24 h, after the reaction is completed, cool it to room temperature with the furnace, obtain a reddish-brown mixed solution G, wash and dry to obtain tungsten-doped VS2 / S powder;

[0012] Step 5: Grind the powder collected in Step 4 until the particles are uniform, then transfer it to a tube furnace. In an argon atmosphere, set the tube furnace to heat up to 300 to 900 °C at a rate of 5 °C / min, keep it warm for 2 to 5 h, then cool it to 100 to 300 °C at a rate of 5 °C / min, and then naturally cool it to room temperature. Finally, obtain black powder, which is the tungsten-doped VS2 / S composite material. -1 of the rate, and then cool it to 100 to 300 °C at a rate of 5 °C / min -1 of the rate, and then naturally cool it to room temperature. Finally, obtain black powder, which is the tungsten-doped VS2 / S composite material.

[0013] Preferably, the tungsten source described in Step 1 includes any one of WCl6 and Na2WO4.

[0014] Preferably, the stirring described in Step 1 is to stir with a magnetic stirrer for 10 to 50 min.

[0015] Preferably, the surfactant in step 2 is any one of sodium dodecylbenzene sulfonate, polyvinyl pyrrolidone or hexadecyltrimethylammonium bromide.

[0016] Preferably, the sufficient stirring in step 2 is stirring in a magnetic stirrer for 30 to 90 minutes.

[0017] Preferably, the stirring in step 3 is carried out using a magnetic stirrer for 60 to 180 minutes.

[0018] Preferably, the cleaning in step 4 is performed by filtering and cleaning with ethanol and water respectively for 3 to 5 times.

[0019] Preferably, the drying in step 4 is freeze drying for 8 to 12 hours.

[0020] The present invention also protects a tungsten-doped VS2 / S composite material prepared by the method as described above and its application in the negative electrode of a sodium ion battery. The material is a lamellar self-assembled structure with a lamellar size of about 2 μm, and nanoparticles exist on the lamellar structure.

[0021] Compared with the prior art, the present invention has the following technical effects:

[0022] The present invention adopts a simple solvent thermal method to prepare a tungsten-doped VS2 / S composite material with a nano-flower-like structure composed of lamellar components. Small particles of zero-dimensional size are generated on the three-dimensional nano-flower-like structure. The small particles are sulfur. VS2 is an intercalation mechanism in sodium ion batteries, and sulfur reacts with sodium ions to form a conversion reaction. Compared with pure phase VS2, the composite material has two mechanisms to synergistically improve the electrochemical performance of sodium ion batteries; the lamellar structure is conducive to the intercalation and deintercalation of sodium ions between layers, and after heat treatment, VS2 will produce a phase change and defects will also be generated in the lattice; after tungsten doping of the VS2 / S composite material, on the one hand, tungsten ions will enter the lattice to occupy a part of V vacancies, so that the composite material has defects, thereby increasing the active sites for sodium ion embedding, so that it has better sodium ion storage performance, and on the other hand, tungsten doping reduces the size of VS2 / S. During the heat treatment process, W 6+ Replace V 4+ The ion concentration can be further increased, which is beneficial to further improve the electrochemical performance of sodium ion batteries;

[0023] The preparation method of the present invention is simple, and by controlling the content of each precursor, the content of the additive, the reaction temperature, the reaction time, etc., the morphology of the product can be well regulated, so that the product has better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1is the X-ray diffraction (XRD) pattern of the composite prepared in Example 1 of the present invention;

[0025] Figure 2 is the scanning electron microscope (SEM) photograph (10 μm) of the composite prepared in Example 1 of the present invention;

[0026] Figure 3 is the scanning electron microscope (SEM) photograph (1 μm) of the composite prepared in Example 1 of the present invention;

[0027] Figure 4 is the cycling performance graph of the composite prepared in Example 1 of the present invention. Detailed implementation manners

[0028] The following further elaborates on the specific content of the present invention in conjunction with examples.

[0029] The polyvinylpyrrolidone is K88-96 with an average molecular weight of 1,300,000.

[0030] Example 1:

[0031] This example provides a preparation method for tungsten-doped VS2 / S composite material, which specifically includes the following steps:

[0032] Step 1: Add 0.033 g of WCl6 into 5 mL of water, and stir in a magnetic stirrer for 10 min until completely dissolved to obtain solution A;

[0033] Step 2: Measure 15 mL of water and pour it into a beaker, then add 3 mL of ammonia water with a mass fraction of 25% to obtain solution B. Weigh 0.5 g of ammonium metavanadate and add it to solution B, stir in a magnetic stirrer for 30 min until there is no precipitate at the bottom of the beaker to obtain solution C. Mix solution A and solution C evenly to obtain solution D, and then add 0.01 g of polyvinylpyrrolidone to it, stir in a magnetic stirrer for 30 min until evenly mixed to obtain solution E;

[0034] Step 3: Weigh 2 g of thioacetamide and add it to solution E, stir on a magnetic stirrer for 60 min until completely dissolved to obtain solution F;

[0035] Step 4: Transfer the mixed solution F to a polytetrafluoroethylene reaction kettle, then place the reaction kettle in a homogeneous reactor, react at 130 °C for 15 h. After the reaction, cool it to room temperature with the furnace. Obtain a reddish-brown mixed solution G; Filter the mixed solution G 3 times with ethanol and water, and then freeze-dry it for 8 h. Collect the freeze-dried powder to obtain the tungsten-doped VS2 / S composite material;

[0036] Step 5: Grind the powder collected in Step 4 until the particles are uniform, then transfer it to a tubular furnace. In an argon atmosphere, set the tubular furnace to heat up to 600 °C at a rate of 5 °C / min -1 , hold the temperature for 3 h, and then cool down to 200 °C at a rate of 5 °C / min -1 . Then cool it naturally to room temperature. Finally, the black powder obtained is the tungsten-doped VS2 / S composite material.

[0037] The samples (tungsten-doped VS2 / S composite materials) were analyzed using a Rigaku D / max2000PC X-ray diffractometer. The results are shown in Figure 1 , and it was found that the samples were consistent with the VS2 structure with a JCPDS number of 89-1640, indicating that VS2 nanoparticles were prepared. The samples were observed using a field emission scanning electron microscope (FESEM). The results are shown in Figure 2 and Figure 3 . It can be seen that the samples have a lamellar structure and there are small particles on the flakes. The cyclic performance of the samples was tested as shown in Figure 4 . It can be seen that the capacity is about 900 mAh / g after 400 cycles at a current density of 1 A / g.

[0038] Example 2:

[0039] A preparation method of a tungsten-doped VS2 / S composite material is given in this example, which specifically includes the following steps:

[0040] Step 1: Add 0.1 g of Na2WO4 to 7 mL of water, and stir in a magnetic stirrer for 20 min until completely dissolved to obtain solution A;

[0041] Step 2: Measure 20 mL of water and pour it into a beaker, then add 7 mL of 28% ammonia water to obtain solution B. Weigh 1.2 g of ammonium metavanadate and add it to solution B. Stir in a magnetic stirrer for 50 min until there is no precipitate at the bottom of the beaker to obtain solution C. Mix solution A and solution C evenly to obtain solution D, and then add 0.2 g of sodium dodecylbenzenesulfonate to it. Stir in a magnetic stirrer for 80 min until evenly mixed to obtain solution E;

[0042] Step 3: Weigh 5 g of thioacetamide and add it to solution E, and stir on a magnetic stirrer for 90 min until completely dissolved to obtain solution F;

[0043] Step 4: Transfer the mixed solution F to a polytetrafluoroethylene reaction kettle, then place the reaction kettle in a homogeneous reactor, and react at 150 °C for 18 h. After the reaction, cool it to room temperature with the furnace. Obtain a reddish-brown mixed solution G; Filter the mixed solution G 5 times with ethanol and water, and then perform freeze-drying for 12 h. Collect the freeze-dried powder to obtain the tungsten-doped VS2 / S composite material;

[0044] Step Five: Grind the powder collected in Step Four until the particles are uniform, then transfer it to a tube furnace. In an argon atmosphere, set the tube furnace to heat up to 300 °C at a rate of 5 °C / min -1 , hold for 5 h, and then cool down to 100 °C at a rate of 5 °C / min -1 . Then cool it naturally to room temperature. Finally, the black powder obtained is the tungsten-doped VS2 / S composite material.

[0045] Example 3:

[0046] This example provides a method for preparing a tungsten-doped VS2 / S composite material, which specifically includes the following steps:

[0047] Step One: Add 0.5 g of Na2WO4 to 8 mL of water, and stir in a magnetic stirrer for 45 min until completely dissolved to obtain Solution A;

[0048] Step Two: Measure 30 mL of water and pour it into a beaker, then add 10 mL of ammonia water with a mass fraction of 26% to obtain Solution B. Weigh 2.4 g of ammonium metavanadate and add it to Solution B. Stir in a magnetic stirrer for 75 min until there is no precipitate at the bottom of the beaker to obtain Solution C. Mix Solution A and Solution C evenly to obtain Solution D, and then add 0.5 g of sodium dodecylbenzenesulfonate to it. Stir in a magnetic stirrer for 60 min until evenly mixed to obtain Solution E;

[0049] Step Three: Weigh 8 g of thioacetamide and add it to Solution E, and stir on a magnetic stirrer for 150 min until completely dissolved to obtain Solution F;

[0050] Step Four: Transfer the mixed solution F to a polytetrafluoroethylene reaction kettle, then place the reaction kettle in a homogeneous reactor, and react at 160 °C for 20 h. After the reaction is completed, cool it to room temperature with the furnace. Obtain a reddish-brown mixed solution G; Filter the mixed solution G 4 times with ethanol and water, and then perform freeze-drying on it for 10 h. Collect the freeze-dried powder to obtain the tungsten-doped VS2 / S composite material;

[0051] Step Five: Grind the powder collected in Step Four until the particles are uniform, then transfer it to a tube furnace. In an argon atmosphere, set the tube furnace to heat up to 900 °C at a rate of 5 °C / min -1 , hold for 2 h, and then cool down to 300 °C at a rate of 5 °C / min -1 . Then cool it naturally to room temperature. Finally, the black powder obtained is the tungsten-doped VS2 / S composite material.

[0052] Example 4:

[0053] This embodiment provides a method for preparing tungsten-doped VS2 / S composite material, which specifically includes the following steps:

[0054] Step 1: Add 1.1 g of Na2WO4 to 10 mL of water, and stir in a magnetic stirrer for 50 min until completely dissolved to obtain solution A;

[0055] Step 2: Measure 35 mL of water and pour it into a beaker, then add 18 mL of ammonia water with a mass fraction of 27% to obtain solution B. Weigh 3.8 g of ammonium metavanadate and add it to solution B, stir in a magnetic stirrer for 90 min until there is no precipitate at the bottom of the beaker to obtain solution C. Mix solution A and solution C evenly to obtain solution D, then add 2.5 g of cetyltrimethylammonium bromide to it, and stir in a magnetic stirrer for 90 min until evenly mixed to obtain solution E;

[0056] Step 3: Weigh 9 g of thioacetamide and add it to solution E, stir on a magnetic stirrer for 180 min until completely dissolved to obtain solution F;

[0057] Step 4: Transfer the mixed solution F to a polytetrafluoroethylene reaction kettle, then place the reaction kettle in a homogeneous reactor, react at 200 °C for 24 h, after the reaction is completed, cool it to room temperature with the furnace to obtain a reddish-brown mixed solution G; Filter the mixed solution G 4 times with ethanol and water, then perform freeze-drying on it for 10 h, and collect the freeze-dried powder to obtain the tungsten-doped VS2 / S composite material;

[0058] Step 5: Grind the powder collected in Step 4 until the particles are uniform, then transfer it to a tube furnace. In an argon atmosphere, set the tube furnace to heat up to 900 °C at a rate of 5 °C / min, keep it warm for 4 h, then cool it down to 300 °C at a rate of 5 °C / min, and then naturally cool it to room temperature. Finally, obtain the black powder, which is the tungsten-doped VS2 / S composite material. -1 of the rate, and then cool it down to 300 °C at a rate of 5 °C / min, and then naturally cool it to room temperature. Finally, obtain the black powder, which is the tungsten-doped VS2 / S composite material. -1 of the rate, and then cool it down to 300 °C at a rate of 5 °C / min, and then naturally cool it to room temperature. Finally, obtain the black powder, which is the tungsten-doped VS2 / S composite material.

[0059] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of tungsten-doped VS2 / S composite material, characterized in that, The following steps are involved: Step 1: Add 0.033 g to 1.1 g of tungsten source into 5 to 10 mL of water and stir until completely dissolved to obtain solution A. Step 2, measure 15 ~ 35 mL of water into a beaker, then add 3 ~ 18 mL of 25% ~ 28% ammonia water to obtain solution B, weigh 0.5 g ~ 3.8 g of ammonium metavanadate and add it to solution B, stir until there is no sediment at the bottom of the beaker to obtain solution C, mix solution A and solution C to obtain solution D, add 0.01 g ~ 2.5 g of surfactant thereto, stir until mixed to obtain solution E; Step 3, weigh 2 g to 9 g of thioacetamide, add it to solution E, and stir until it is completely dissolved to obtain solution F; Step 4: Transfer solution F to a polytetrafluoroethylene reactor, and then place the reactor in a homogeneous reactor to fully react at 130-200 °C for 15-24 h. After the reaction is completed, cool the furnace to room temperature to obtain a reddish-brown mixed solution G, which is then washed and dried to obtain tungsten-doped VS2 / S powder; Step 5: Grind the powder collected in Step 4 until the particles are uniform, and then transfer it to a tube furnace. In an argon atmosphere, set the tube furnace to heat up to 300 - 900 °C at a rate of 5 °C / min -1 , hold the temperature for 2 - 5 h, and then cool down to 100 - 300 °C at a rate of 5 °C / min -1 . Then cool it naturally to room temperature. Finally, the obtained black powder is the tungsten-doped VS2 / S composite material; The surfactant described in step 2 is any one of sodium dodecylbenzene sulfonate, polyvinyl pyrrolidone or hexadecyltrimethylammonium bromide.

2. The preparation method of the tungsten-doped VS2 / S composite material according to claim 1, characterized in that, The tungsten source described in step 1 includes any one of WCl6 and Na2WO4.

3. The preparation method of the tungsten-doped VS2 / S composite material according to claim 1, wherein, The stirring described in step 1 is stirring with a magnetic stirrer for 10 to 50 min.

4. The preparation method of the tungsten-doped VS2 / S composite material according to claim 1, wherein, The sufficient stirring described in step 2 is stirring in a magnetic stirrer for 30 to 90 minutes.

5. The preparation method of the tungsten-doped VS2 / S composite material according to claim 1, characterized in that, The stirring described in step 3 is stirring using a magnetic stirrer for 60 to 180 min.

6. The preparation method of the tungsten-doped VS2 / S composite material according to claim 1, characterized in that, The cleaning described in step 4 is to use ethanol and water to filter and clean 3 to 5 times respectively.

7. The preparation method of the tungsten-doped VS2 / S composite material according to claim 1, wherein, The drying described in step 4 is freeze drying for 8 to 12 hours.

8. A tungsten-doped VS2 / S composite material prepared by the method according to any one of claims 1 to 7, characterized in that, The material is a lamellar self-assembled structure with a flake size of about 2 μm and sulfur nanoparticles present on the flake structure.

9. Use of the tungsten-doped VS2 / S composite material as claimed in claim 8 in the negative electrode of a sodium ion battery.

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