W18O49 / WS2 composite material, preparation method thereof and application of W18O49 / WS2 composite material in sodium-sulfur battery

Abstract

The invention discloses a W18O49 / WS2 composite material, a preparation method thereof and application of the W18O49 / WS2 composite material in a sodium-sulfur battery, and belongs to the field of electrochemical catalysis functional materials.The preparation method comprises the steps that 1, 10-20 mL of cyclohexanol is added into 20-30 mL of acetylacetone, and stirring is conducted to obtain a mixed solution A; 2) weighing 1-1.5 g of tungsten hexachloride, adding the tungsten hexachloride into the mixed solution A, and stirring to obtain a mixed solution B; (3) transferring the mixed solution B into a reaction kettle, sealing, putting into a drying oven, and reacting for 5-8 hours at 175-200 DEG C; 4) after the reaction is finished, performing suction filtration and washing on a product, drying in a vacuum oven, and collecting to obtain W18O49 powder; the preparation method comprises the following steps of 1, weighing W18O49 powder and thioacetamide according to a ratio of nW: nS of 0.125-0.5, and respectively placing the W18O49 powder and thioacetamide in a porcelain boat, and 6, simultaneously placing the porcelain boat in a tubular furnace, introducing an argon-hydrogen mixed gas, closing the gas, heating to 400-700 DEG C, carrying out heat preservation, and collecting to obtain W18O49 / WS2 powder.The preparation method solves the problems that an existing W18O49 / WS2 composite material is abnormal in electronic characteristics, the growth rate of a W18O49 core and the growth rate of a WS2 shell layer are not matched, deposition of WS2 on the surface of W18O49 is uneven, and active site distribution is unbalanced.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical catalytic functional materials, specifically relating to a W 18 O 49 / WS2 composite material, its preparation method, and its application in sodium-sulfur batteries. Background Technology

[0002] With the global trend of energy storage technology iterating towards low cost and high capacity, room temperature sodium-sulfur (RT Na-S) batteries have become a core candidate technology in fields such as grid peak shaving and renewable energy storage due to their high sodium resource abundance and excellent theoretical specific capacity (1675 mAh / g) and energy density (760 Wh / kg) of sulfur cathodes. However, their commercialization process has long been limited by the multiple inherent defects of sulfur cathodes, and the development of efficient catalytic materials to overcome technical bottlenecks has become an urgent need for the industry. The core bottlenecks of RT Na-S batteries are concentrated in two points: First, sulfur and the discharge product Na2S2 / Na2S are typical insulators, which leads to obstructed electron transport and slow reaction kinetics; second, the reaction intermediate sodium polysulfide (NaPSs) is easily soluble in ether-based electrolytes and shuttles to the negative electrode, causing loss of active materials, negative electrode corrosion, and a decrease in coulombic efficiency, forming the key problem of the "shuttle effect". Among them, the adsorption and catalytic conversion efficiency of NaPSs directly determines the cycle stability and rate performance of the battery, which is the core of catalytic material design.

[0003] In existing technologies, optimization strategies for catalytic materials mainly fall into three categories: physical confinement with carbon-based materials, chemical adsorption of single polar compounds, and catalyst engineering. While carbon-based materials can construct conductive networks and porous buffers, their chemical binding ability for NaPSs is weak, and the shuttle effect remains significant at high rates. Single transition metal oxides (such as W...) 18 O 49 Oxygen-rich vacancy characteristics can lower the reaction energy barrier and accelerate NaPSs conversion, but they lack strong polar adsorption sites, making it difficult to inhibit NaPSs dissolution at the source. Single transition metal sulfides (such as WS2) are two-dimensional layered materials with a wide interlayer spacing of 6.2 Å and a polar surface, which can anchor NaPSs through chemical action. However, the 2H phase of WS2 has poor inherent electronic conductivity, and the conversion reaction easily induces phase structure transformation and volume change, leading to a decline in catalytic activity.

[0004] In recent years, multi-component composite catalysts have become an important direction for overcoming the performance limitations of single materials. WS2, as a typical transition metal sulfide, provides ample adsorption sites due to its layered structure, but its shortcomings in conductivity and catalytic activity need to be compensated for by combining it with highly conductive oxides; while W... 18 O 49As an oxygen-rich vacancy tungsten-based oxide, it not only has excellent electron conduction properties, but its W sites can also participate in multi-electron transfer catalytic reactions. The combination of the two has natural performance complementarity potential and is expected to solve the core contradiction of existing catalytic materials that "adsorption and catalysis cannot be achieved at the same time".

[0005] Currently, there is already W. 18 O 49 Research on / WS2 composite materials has been conducted, but the following problems still exist: low-coordinate metal atoms easily form at the interface, generating localized states at the bottom of the WS2 conduction band, reducing electronic conduction efficiency and hindering carrier migration; W 18 O 49 The difference in lattice parameters between W and WS2 leads to non-uniform stress at the interface, forming a "wrinkling effect" and causing abnormal electronic properties; in the traditional vulcanization process, W 18 O 49 The mismatch between the growth rates of the core and the WS2 shell leads to deformation of the nanostructure, making it impossible to maintain the original W... 18 O 49 Its three-dimensional advantages; under conventional high-temperature vulcanization conditions (850-900℃), W 18 O 49 The core has been completely converted to WS2, losing W. 18 O 49 Unique electronic and structural properties; uneven distribution of sulfur source in traditional methods leads to WS2 in W 18 O 49 Uneven surface deposition, imbalance in the distribution of active sites, etc. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention aims to provide a W 18 O 49 / WS2 composite materials, their preparation methods, and their application in sodium-sulfur batteries: The polar surface and layered structure of WS2 enhance the adsorption and anchoring of NaPSs, utilizing W... 18 O 49 The oxygen-rich vacancies and high conductivity accelerate catalytic conversion, and the synergistic effect of the two is achieved through the construction of a heterogeneous interface, which solves the problem of existing W 18 O 49 / WS2 composite material has abnormal electronic properties, W 18 O 49 The mismatch between the growth rates of the core and the WS2 shell and the WS2 in W 18 O 49 The problem of uneven surface deposition and unbalanced distribution of active sites.

[0007] This invention is achieved through the following technical solution: A W 18 O 49The preparation method of / WS2 composite material includes the following steps: 1) Add 10-20 mL of cyclohexanol to 20-30 mL of acetylacetone and stir for 5-15 min to obtain mixed solution A; 2) Weigh 1-1.5 g of tungsten hexachloride and add it to the mixed solution A, stir for 15-30 min to obtain mixed solution B; 3) Transfer the mixed solution B into a reaction vessel, seal it, and place it in an oven. React at 175~200 ℃ for 5~8 hours. 4) After the reaction is complete, filter and wash the product obtained in step 3), dry it in a vacuum oven, and collect W. 18 O 49 Powder; 5) Press n W :n S =0.125~0.5 Weigh the W 18 O 49 The powder and thioacetamide were placed separately in porcelain boats; 6) Place the ceramic boat into a tube furnace, introduce an argon-hydrogen mixture, then seal the furnace. Heat the furnace to 400-700 °C at a rate of 10 °C / min, hold for 2 hours, and collect the W. 18 O 49 / WS2 powder.

[0008] Further, in step 4), the product is dried in a vacuum oven at 60-90 ℃ for 10-30 min.

[0009] Furthermore, in step 4), industrial alcohol is used for filtration and washing.

[0010] W obtained according to any one of the preparation methods described herein 18 O 49 / WS2 composite material.

[0011] Furthermore, WS2 is grown in the form of nanosheets on W 18 O 49 The surface forms a three-dimensional dispersed structure.

[0012] Furthermore, the thickness of the WS2 is less than 100 nm.

[0013] According to any one of the W 18 O 49 Application of / WS2 composite material in sodium-sulfur batteries.

[0014] Compared with existing technologies, the advantages of this invention are as follows: 1) The WS2 prepared in this invention is grown in the form of nanosheets (thickness ≤100nm) on W18 O 49 On the surface, a "three-dimensional dispersed" structure is formed, which significantly increases the specific surface area of ​​the material. This exposes the polar S sites of the WS2 layered structure (enhancing the chemisorption of sodium polysulfides (NaPSs)) on one hand, and highlights the W... 18 O 49 Oxygen-rich vacancy catalytic sites (accelerate NaPSs conversion). W 18 O 49 The heterojunction formed with WS2 is tightly coupled (without obvious phase separation). The WOS bond bridging at the interface can accelerate the transfer of electrons between the two phases, solving the problem of poor conductivity inherent in WS2. At the same time, the adsorption-catalytic synergistic enhancement of NaPSs is enhanced through the interface charge polarization effect.

[0015] 2) This invention uses cyclohexanol as a high-boiling-point polar solvent (boiling point 161℃), which can form a synergistic effect with acetylacetone (bidentate chelating ligand): acetylacetone reacts with W via keto-enol tautomerism. 6+ This forms a stable complex, preventing localized hydrolysis and precipitation of WCl6 during the room temperature stirring stage; cyclohexanol disperses the complex molecules through weak van der Waals forces, reducing the probability of particle aggregation, thus enabling WCl6 to form a stable complex. 6+ Uniform dissociation occurs during the hydrothermal reaction, facilitating subsequent W... 18 O 49 This ensures uniform growth and solves the problem of easy agglomeration of tungsten-based oxides in traditional hydrothermal methods.

[0016] 3) This invention uses thioacetamide (TAA) as the sulfur source, which can decompose into H2S (reducing sulfur species) at temperatures above 300℃. Compared with sulfur powder (which requires high-temperature melting and easily leads to uneven sulfidation), it can react more gently with W. 18 O 49 Reaction, control n W :n S =0.125-0.5 (i.e., S is in excess but not excessive), which can ensure a portion of W. 18 O 49 Convert to WS2 (retaining 10%–30% of W) 18 O 49 Instead of being completely vulcanized into WS2 (WS2 alone has poor conductivity), this proportioning design allows the composite material to retain W... 18 O 49 The high catalytic activity of WS2 and the strong adsorption capacity of WS2 resolve the contradiction of "strong catalysis but weak adsorption" or "strong adsorption but weak catalysis" of a single component.

[0017] 4) The H2 in the argon-hydrogen mixture (reducing atmosphere) of this invention can suppress W 6+ It is oxidized, while promoting W 18 O49 The S species reacts with the TAA decomposition to generate WS2, forming "W 18 O 49 The / WS2” heterostructure (with WOS bonds bridging the interface) allows for strong interfacial coupling, which accelerates electron transfer between the two phases, solves the problem of poor conductivity of WS2, and enhances the adsorption-catalytic synergy of sodium polysulfide through interfacial charge transfer effect.

[0018] 5) The straight array W prepared by this invention 18 O 49 / WS2 material exhibits excellent catalytic performance as a cathode catalyst in sodium-sulfur batteries, with a catalytic activity of 0.5 A g in the voltage range of 0.2-3.0 V. -1 At current density, it has approximately 960 mAh g after 300 cycles. -1 It exhibits high specific capacitance and excellent rate performance, with minimal capacitance difference at different current densities and stable capacitance. Even at low current densities, the capacitance remains consistent, maintaining its value at 10 A g. -1 After 20,000 cycles at high current density, it still has 440 Ah g. -1 Specific capacity. Attached Figure Description

[0019] Figure 1 The image shows the XRD pattern of the composite material prepared in Example 3 of this invention. Figure 2 SEM image of the composite material prepared in Example 3 of this invention; Figure 3 This is a graph showing the cycling performance of the composite material prepared in Example 3 of the present invention; Figure 4 This is a rate performance diagram of the composite material prepared in Example 3 of the present invention; Figure 5 This is a graph showing the long-cycle performance of the composite material prepared in Example 3 of the present invention under high current. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0021] Example 1 A W 18 O 49 The preparation method of / WS2 composite material includes the following steps: 1) Measure 10 mL of cyclohexanol and 20 mL of acetylacetone and add them to a beaker, then stir for 5 min; 2) Weigh 1g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 15 minutes; 3) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven at 175 °C for 8 h; 4) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 60 °C for 30 min, and W is collected. 18 O 49 Powder.

[0022] 5) Press n W :n S =0.125 means W is obtained 18 O 49 The powder and thioacetamide were placed in a large porcelain boat and a small porcelain boat, respectively.

[0023] 6) Place the porcelain boat in a tube furnace, introduce an argon-hydrogen mixture, then seal the furnace. Heat the furnace to 400 °C at a rate of 10 °C / min and hold for 2 h. Collect the W. 18 O 49 / WS2 powder.

[0024] Example 2 A W 18 O 49 The preparation method of / WS2 composite material includes the following steps: 1) Measure 15 mL of cyclohexanol and 25 mL of acetylacetone and add them to a beaker, then stir for 10 min; 2) Weigh 1.2g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 20 min; 3) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven. React at 180 °C for 7 h. 4) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 70 °C for 20 min, and W is collected. 18 O 49 Powder.

[0025] 5) Press n W :n S =0.2 means W is obtained 18 O 49 The powder and thioacetamide were placed in a large porcelain boat and a small porcelain boat, respectively.

[0026] 6) Place the ceramic boat in a tube furnace, introduce an argon-hydrogen mixture, then seal the furnace. Heat the furnace to 450 °C at a rate of 10 °C / min and hold for 2 h. Collect the W. 18 O 49 / WS2 powder.

[0027] Example 3 A W 18 O 49The preparation method of / WS2 composite material includes the following steps: 1) Measure 15 mL of cyclohexanol and 30 mL of acetylacetone and add them to a beaker, then stir for 15 min; 2) Weigh 1.3 g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 25 min; 3) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven. React at 190 °C for 6 h. 4) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 80 °C for 20 min, and W is collected. 18 O 49 Powder.

[0028] 5) Press n W :n S =0.25 means W is obtained 18 O 49 The powder and thioacetamide were placed in a large porcelain boat and a small porcelain boat, respectively.

[0029] 6) Place the ceramic boat in a tube furnace, introduce an argon-hydrogen mixture, then seal the furnace. Heat the furnace to 550 °C at a rate of 10 °C / min and hold for 2 hours. Collect the W. 18 O 49 / WS2 powder.

[0030] The product obtained in Example 3 was analyzed, and the XRD pattern of the product is shown in Figure 3. Figure 1 As shown, the peak position is consistent with the standard card, and no impurity peaks appear, indicating that W was successfully prepared. 18 O 49 / WS2 composite material. The sample was observed under a scanning electron microscope, from... Figure 2 It can be seen that the product exhibits two morphologies: nanosheets and nanowires, corresponding to two different phases. The nanosheet-like WS2 has a large specific surface area and abundant surface active sites. 18 O 49 The nanowires have high electron transport efficiency, and the combination of the two achieves synergistic optimization of adsorption and catalysis.

[0031] The product obtained in Example 3 was used to prepare a button-type sodium-sulfur battery. The specific packaging steps are as follows: the active powder, superconducting carbon black (Super P), carbon nanotubes, and binder (polyvinylidene fluoride PVDF) were ground evenly in a mass ratio of 7:1:1:1 to form a slurry. The slurry was then evenly coated onto copper foil using a coating machine and dried in a vacuum drying oven at 80°C for 24 hours. After that, the electrode sheets were assembled into a sodium-sulfur battery. The battery was subjected to constant current charge-discharge testing using a Blue Electric Electrochemical Workstation with a test voltage of 0.2–3.0V.

[0032] like Figure 3 As shown, the left vertical axis represents specific capacity, and the right vertical axis represents coulombic efficiency. The pink curve represents specific capacity, and the battery is at 0.5 A g. -1 The capacity is 960 mAh g after 300 cycles at the current density. -1 This indicates that it is at 0.5 Ag -1 At the specified current density, the battery exhibits good capacity retention after cycling. The yellow curve represents the coulombic efficiency, which remains close to 100% throughout the cycle. Coulombic efficiency is the ratio of discharge capacity to charge capacity during battery charging and discharging. A value close to 100% indicates that the battery experiences very few side reactions and has excellent reversibility during cycling.

[0033] like Figure 4 As shown, the battery capacity difference is small under different current densities. The specific capacity is high and the cycle stability is stable at low current densities. Although the specific capacity decreases at high current densities, it has good rate reversibility and the capacity can be recovered when returning to low current densities.

[0034] like Figure 5 As shown, at 10 A g -1 After cycling at high current density for 20,000 cycles, the capacity stabilized at 440mAh g. -1 This indicates that the button-type sodium-sulfur battery prepared using the product obtained in this invention has good rate performance and stability.

[0035] Example 4 A W 18 O 49 The preparation method of / WS2 composite material includes the following steps: 1) Measure 20 mL of cyclohexanol and 25 mL of acetylacetone and add them to a beaker, then stir for 15 min; 2) Weigh 1.4 g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 25 min; 3) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven at 195 °C for 6 h; 4) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 85 °C for 15 min, and W is collected. 18 O 49 Powder.

[0036] 5) Press n W :n S =0.4 means W is obtained 18 O 49 The powder and thioacetamide were placed in a large porcelain boat and a small porcelain boat, respectively.

[0037] 6) Place the ceramic boat in a tube furnace, introduce an argon-hydrogen mixture, then seal the furnace. Heat the furnace to 600 °C at a rate of 10 °C / min and hold for 2 h. Collect the W. 18 O 49 / WS2 powder.

[0038] Example 5 A W 18 O 49 The preparation method of / WS2 composite material includes the following steps: 1) Measure 20 mL of cyclohexanol and 30 mL of acetylacetone and add them to a beaker, then stir for 15 min; 2) Weigh 1.5g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 30 min; 3) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven. React at 200 °C for 5 h. 4) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 90 °C for 10 min, and W is collected. 18 O 49 Powder.

[0039] 5) Press n W :n S =0.5 means W is obtained 18 O 49 The powder and thioacetamide were placed in a large porcelain boat and a small porcelain boat, respectively.

[0040] 6) Place the ceramic boat in a tube furnace, introduce an argon-hydrogen mixture, then seal the furnace. Heat the furnace to 700 °C at a rate of 10 °C / min and hold for 2 h. Collect the W. 18 O 49 / WS2 powder.

Claims

1. A W 18 O 49 Method for the production of a WS2 composite material, characterized in that, The method comprises the following steps: 1) 10-20 mL of cyclohexanol is added to 20-30 mL of acetylacetone, and stirred for 5-15 min to obtain a mixed solution A; 2) 1-1.5 g of tungsten hexachloride is weighed and added to the mixed solution A, and stirred for 15-30 min to obtain a mixed solution B; 3) the mixed solution B is moved into a reaction kettle, sealed and placed in an oven, and reacted at 175-200 ℃ for 5-8 h; 4) After the reaction is completed, the product obtained in step 3) is collected by suction filtration and washed, and then dried in a vacuum oven to obtain W 18 O 49 powder; 5) by n W : n S = 0.125~0.5 weigh the W 18 O 49 powder and thioacetamide, and place them in a porcelain boat respectively; 6) The porcelain boat is put into the tube furnace at the same time, argon and hydrogen mixed gas is introduced, and the gas is closed after the temperature is raised to 400-700 ℃ at a rate of 10 ℃ / min and then the temperature is kept for 2 h, and W 18 O 49 / WS2 powder is collected.

2. A W 18 O 49 The method for preparing a WS2 composite material is characterized by, in the step 4), drying is performed at 60-90 ℃ in a vacuum oven for 10-30 min.

3. A W 18 O 49 The method for preparing a WS2 composite material is characterized by, in the step 4), industrial alcohol is used for filtration and washing.

4. W according to any one of claims 1 to 3, when prepared by the process 18 O 49 / WS2 composite material.

5. The W of claim 4, wherein the W is a W 18 O 49 / WS2 composite material, characterized in that, WS2grew in the form of nanosheets on W 18 O 49 surface, forming a three-dimensional dispersed structure.

6. The W of claim 4, wherein the W is a W 18 O 49 / WS2 composite material, characterized in that, the thickness of the WS2 is less than 100 nm.

7. The W of any one of claims 4-6 18 O 49 Use of WS2 composites in sodium-sulfur batteries.

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