An alkaline earth metal Ca-doped W 18 O 49 Catalysts, their preparation methods and applications

Abstract

This invention discloses an alkaline earth metal Ca-doped W 18 O 49 This invention relates to a catalyst, its preparation method, and its application, belonging to the field of functional materials. The method includes: 1) mixing 40-50 mL of anhydrous ethanol and 10-20 mL of acetone and stirring to obtain mixed solution A; 2) weighing 0.001-0.003 mol of tungsten hexachloride and adding it to mixed solution A, and stirring to obtain mixed solution B; 3) weighing CaCl2 according to nCa:nW = 0.01-0.05 and adding it to mixed solution B, and stirring to obtain mixed solution C; 4) transferring mixed solution C to a reaction vessel, sealing it, and placing it in an oven, reacting at 190-210℃ for 6-12 h; 5) after the reaction is complete, washing the product with industrial alcohol by filtration, drying it in a vacuum oven at 50-80℃ for 10-30 min, and collecting the product. This invention solves the problem of single W 18 O 49 Catalysts often suffer from insufficient electronic conductivity, limited utilization of active sites, and poor stability. This invention increases the number of oxygen vacancies and the density of active sites, while simultaneously improving the ion transport channels of the material and enhancing its adsorption and anchoring ability for polar polysulfides.

Description

Technical Field

[0001] This invention belongs to the field of functional materials, specifically relating to an alkaline earth metal Ca-doped W 18 O 49 Catalysts, their preparation methods, and applications. Background Technology

[0002] The large-scale application of renewable energy sources such as wind and solar power urgently requires the support of low-cost, long-life, large-scale energy storage technologies. Room-temperature sodium-sulfur (RT Na-S) batteries, using sodium and sulfur as core active materials, combine the advantages of low cost with ultra-high theoretical energy density (1275 Wh·kg⁻¹). -1 It has become a core candidate direction for the next generation of large-scale energy storage technology. Compared with traditional high-temperature sodium-sulfur batteries, its room-temperature operation characteristics greatly reduce safety hazards and energy loss, and its application scenarios are more extensive.

[0003] However, the commercialization of room-temperature sodium-sulfur batteries is still limited by three core technological bottlenecks in sulfur cathodes, which severely restrict the overall performance of the batteries: First, sulfur and its discharge products have extremely low intrinsic conductivity, making it difficult for electrochemical reactions to proceed efficiently and resulting in low sulfur utilization. Second, soluble long-chain sodium polysulfides generated during charging and discharging are easily dissolved in the electrolyte and migrate through the separator to the sodium anode, causing a severe shuttle effect, resulting in irreversible loss of active materials, leading to rapid capacity decay and reduced coulombic efficiency. Third, the reaction energy barrier for the conversion of solid polysulfides Na2S2 / Na2S is high, the reaction kinetics are slow, and the deposition of solid products easily leads to increased electrode polarization and increased impedance, further deteriorating the cycle stability of the battery.

[0004] Introducing catalysts into sulfur cathodes has proven to be a key strategy for simultaneously addressing the shuttle effect and kinetic sluggishness, becoming a focus of research in the field. Transition metal oxides, due to their polar surfaces and abundant active sites, exhibit unique advantages in the adsorption and catalytic conversion of polysulfides. Among them, W... 18 O 49 As a typical substoichiometric tungsten oxide, it possesses a unique layered structure and abundant oxygen vacancies. These oxygen vacancies can serve as active sites for the efficient adsorption of polysulfides and the promotion of electron transfer, while the layered structure provides channels for ion transport. Therefore, it is considered a highly promising precursor material for sulfur cathode catalysts in sodium-sulfur batteries. However, a single W... 18 O 49 Significant limitations remain: insufficient electronic conductivity makes it difficult to construct an efficient electron transport network; the number and distribution of oxygen vacancies are difficult to control precisely, resulting in limited utilization of active sites; and during charge-discharge cycles, the layered structure is prone to stacking, resulting in poor stability and the inability to achieve long-term efficient catalysis. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention proposes an alkaline earth metal Ca-doped W... 18 O 49 Catalysts, their preparation methods, and applications have solved the problem of single W 18 O 49 The catalyst suffers from problems such as insufficient electronic conductivity, limited utilization of active sites, and poor stability.

[0006] This invention is achieved through the following technical solution: An alkaline earth metal Ca-doped W 18 O 49 The method for preparing the catalyst includes the following steps: 1) Mix 40-50 mL of anhydrous ethanol and 20-10 mL of acetone and stir to obtain mixed solution A; 2) Weigh 0.001~0.003 mol of tungsten hexachloride and add it to the mixed solution A, then stir to obtain mixed solution B; 3) Weigh CaCl2 according to nCa:nW = 0.01~0.05 and add it to the mixed solution B, then stir to obtain mixed solution C; 4) Transfer the mixed solution C to a reaction vessel, seal it, and place it in an oven. React at 190~210℃ for 6~12 hours. 5) After the reaction is complete, the product is washed with industrial alcohol by filtration, then dried in a vacuum oven at 50-80℃ for 10-30 min to obtain Ca-W. 18 O 49 Powder.

[0007] Furthermore, in step 1), the mixture is stirred at room temperature for 5 to 15 minutes.

[0008] Furthermore, in step 2), the mixture is stirred at room temperature for 5 to 15 minutes.

[0009] Furthermore, in step 3), the mixture is stirred at room temperature for 5 to 15 minutes.

[0010] A Ca-doped W obtained according to the preparation method 18 O 49 catalyst.

[0011] A Ca-doped W 18 O 49 The catalyst is a self-assembled nanorod with a mace-like morphology.

[0012] A Ca-doped W 18 O 49 Application of catalysts in sodium-sulfur batteries.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: Alkaline earth metal Ca possesses characteristics such as moderate ionic radius, stable electronic structure, and high abundance in the Earth's crust, demonstrating unique advantages in the doping and modification of catalytic materials. This invention utilizes alkaline earth metal Ca for W... 18 O 49 Doping can not only reduce the cost of material preparation, but also optimize W through charge regulation. 18 O 49 The electronic structure further increases the number of oxygen vacancies and the density of active sites. Simultaneously, its unique ionic properties improve the ion transport channels of the material, enhancing its adsorption and anchoring ability for polar polysulfides. This provides key technological support for the commercialization of room-temperature sodium-sulfur batteries, aligning with the development needs of large-scale energy storage technologies for low cost, high safety, and long lifespan.

[0014] (1) This invention uses a mixed system of anhydrous ethanol and acetone, which combines the reducing power of alcohols with the polarity regulation characteristics of ketones. Compared with a single ethanol solvent, it can more precisely control the hydrolysis rate of tungsten hexachloride and avoid the formation of impurity phases caused by local over-hydrolysis. At the same time, acetone can optimize the dielectric constant of the reaction system and promote the reaction of Ca. 2+ The uniform complexation with the tungsten precursor lays the foundation for the uniformity of subsequent doping and solves the problem of easy agglomeration of metal ions in single solvent systems.

[0015] (2) This invention utilizes a charge compensation mechanism (Ca) 2+ Replace W 6+ ) induce W 18 O 49 The oxygen vacancy concentration in the crystal lattice is significantly increased compared to undoped W. 18 O 49 The increased number of oxygen vacancies creates high-density polysulfide adsorption-catalytic active sites. Appropriate Ca doping also avoids lattice distortion and structural collapse caused by overdoping, maintaining W... 18 O 49 The unique layered structure provides an efficient channel for sodium ion transport while maintaining the material's stability. Furthermore, the Ca-OW bonding structure formed at this ratio enhances the material's polarity, strengthening its anchoring ability to polar polysulfides through strong Lewis acid-base interactions and suppressing the shuttle effect.

[0016] (3) The ionic radius of alkaline earth metal Ca and W 6+ The difference in electron density creates a moderate lattice distortion, promoting electron localization and improving the material's conductivity. Furthermore, the high electronegativity of Ca enhances the conductivity of W. 18 O 49 Electron enrichment on the surface accelerates the redox kinetics of polysulfides.

[0017] (4) Industrial alcohol washing effectively removes Cl. -The removal of impurity ions prevents residual ions from triggering side reactions during battery cycling, thereby improving battery coulombic efficiency. Compared to water washing, this process reduces the formation of surface hydroxyl groups and preserves the catalytically active sites of the material.

[0018] (5) Ca-doped W prepared in this invention 18 O 49 The catalyst is used as a sulfur cathode catalyst, Ca-W 18 O 49 Make the battery at 1 Ag -1 After 280 cycles at a current density, the capacity is approximately 1250 mAh g. -1 Excellent catalytic kinetics performance enables the battery to operate at 20 A g. -1 It still maintains 1180 mAh g at high rates -1 The above capacity significantly improves the rate performance of room temperature sodium-sulfur batteries.

[0019] (6) The low-cost preparation characteristics of the material (the Ca source is cheap and readily available, and the solvothermal process has low energy consumption) reduce the production cost of room temperature sodium-sulfur batteries and promote their large-scale application. Attached Figure Description

[0020] Figure 1 Ca-W prepared in Example 3 18 O 49 XRD pattern of the material.

[0021] Figure 2 Ca-W prepared in Example 3 18 O 49 Fine XPS spectrum of Ca in the material.

[0022] Figure 3 Ca-W prepared in Example 3 18 O 49 SEM images of the material.

[0023] Figure 4 Ca-W prepared in Example 3 18 O 49 Cyclic performance diagram of the material.

[0024] Figure 5 Ca-W prepared in Example 3 18 O 49 Ratio performance diagram of the material. Detailed Implementation

[0025] 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.

[0026] Example 1: An alkaline earth metal Ca-doped W18 O 49 The method for preparing the catalyst includes the following steps: 1) Measure 50 mL of anhydrous ethanol and 20 mL of acetone and add them to a beaker, then stir for 5 min; 2) Weigh 0.001 mol of tungsten hexachloride and add it to the above solution, then stir at room temperature for 5 min; 3) Weigh CaCl2 according to nCa:nW = 0.01 and add it to the solution described in step 2), and stir at room temperature for 5 min; 4) Transfer the mixed solution obtained in step 3) into a 100 mL reaction vessel, seal it and place it in an oven, and react at 190°C for 12 h; 5) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 80°C for 10 min, and Ca-W is collected. 18 O 49 Powder.

[0027] Example 2: An alkaline earth metal Ca-doped W 18 O 49 The method for preparing the catalyst includes the following steps: 1) Measure 45 mL of anhydrous ethanol and 15 mL of acetone and add them to a beaker, then stir for 10 min; 2) Weigh 0.0015 mol of tungsten hexachloride and add it to the above solution, then stir at room temperature for 10 min; 3) Weigh CaCl2 according to nCa:nW=0.02 and add it to the solution described in step 2), and stir at room temperature for 10 min; 4) Transfer the mixed solution obtained in step 3) into a 100 mL reaction vessel, seal it and place it in an oven, and react at 195°C for 7 h; 5) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 60°C for 20 min, and Ca-W is collected. 18 O 49 Powder.

[0028] Example 3: An alkaline earth metal Ca-doped W 18 O 49 The method for preparing the catalyst includes the following steps: 1) Measure 45 mL of anhydrous ethanol and 10 mL of acetone and add them to a beaker, then stir for 8 min; 2) Weigh 0.002 mol of tungsten hexachloride and add it to the above solution, then stir at room temperature for 8 min; 3) Weigh CaCl2 according to nCa:nW = 0.03 and add it to the solution described in step 2), and stir at room temperature for 8 min; 4) Transfer the mixed solution obtained in step 3) into a 100 mL reaction vessel, seal it and place it in an oven, and react at 200℃ for 9 h; 5) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 55°C for 25 min, and Ca-W is collected. 18 O 49 Powder.

[0029] Example 4: An alkaline earth metal Ca-doped W 18 O 49 The method for preparing the catalyst includes the following steps: 1) Measure 40 mL of anhydrous ethanol and 16 mL of acetone and add them to a beaker, then stir for 12 min; 2) Weigh 0.0025 mol of tungsten hexachloride and add it to the above solution, then stir at room temperature for 12 min; 3) Weigh CaCl2 according to nCa:nW=0.04 and add it to the solution described in step 2), and stir at room temperature for 12 min; 4) Transfer the mixed solution obtained in step 3) into a 100 mL reaction vessel, seal it and place it in an oven, and react at 205℃ for 11 h; 5) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 70°C for 15 min, and Ca-W is collected. 18 O 49 Powder.

[0030] Example 5: An alkaline earth metal Ca-doped W 18 O 49 The method for preparing the catalyst includes the following steps: 1) Measure 40 mL of anhydrous ethanol and 10 mL of acetone and add them to a beaker, then stir for 15 min; 2) Weigh 0.003 mol of tungsten hexachloride and add it to the above solution, then stir at room temperature for 15 min; 3) Weigh CaCl2 according to nCa:nW=0.05 and add it to the solution described in step 2), and stir at room temperature for 15 min; 4) Transfer the mixed solution obtained in step 3) into a 100 mL reaction vessel, seal it and place it in an oven, and react at 210℃ for 6 h; 5) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 50°C for 30 min, and Ca-W is collected. 18 O49 Powder.

[0031] The product obtained in Example 3 was analyzed, and the XRD pattern of the product is shown in the appendix. Figure 1 Peak position and W 18 O 49 The presence of no impurity peaks, consistent with the standard card, indicates successful preparation of Ca-W. 18 O 49 The strong XRD diffraction peaks indicate that the material has good crystallinity, which is beneficial for electron transport.

[0032] like Figure 2 As shown, the diffraction peaks of Ca indicate that Ca has been successfully incorporated into the material.

[0033] The sample was observed under a scanning electron microscope. Figure 3 As can be seen, the product exhibits a mahogany morphology resulting from the self-assembly of nanorods. This morphology has a large specific surface area and exposes numerous catalytically active sites, which is beneficial for improving reaction efficiency.

[0034] The obtained product was used to prepare a button-type sodium-sulfur battery. The specific encapsulation steps are as follows: Active powder, Ketjen black, 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℃ for 24 hours. Afterwards, the electrode sheets were assembled into a sodium-sulfur battery. A constant current charge-discharge test was performed on the battery using a Blue Electric electrochemical workstation, with a test voltage of 0.3-3.0V.

[0035] like Figure 4 As shown, the battery at 1 A g -1 After 280 cycles at a current density, the capacity is approximately 1250 mAh g. -1 Its rate performance is as follows: Figure 5 As shown, the capacitance difference is small under different current densities, and the capacitance remains stable. Even at lower current densities, the capacitance remains consistent, indicating good rate performance and stability. At 20 A g... -1 It still maintains 1180 mAh g at high rates -1 The above capacity.

Claims

1. An alkaline earth metal Ca-doped W 18 O 49 A method for preparing a catalyst, characterized in that, Includes the following steps: 1) Mix 40-50 mL of anhydrous ethanol and 10-20 mL of acetone and stir to obtain mixed solution A; 2) Weigh 0.001~0.003 mol of tungsten hexachloride and add it to the mixed solution A, then stir to obtain mixed solution B; 3) Weigh CaCl2 according to nCa:nW = 0.01~0.05 and add it to the mixed solution B, then stir to obtain mixed solution C; 4) Transfer the mixed solution C to a reaction vessel, seal it, and place it in an oven. React at 190~210℃ for 6~12 h. 5) After the reaction is complete, the product is washed with industrial alcohol by filtration, then dried in a vacuum oven at 50-80℃ for 10-30 min to obtain Ca-W. 18 O 49 Powder.

2. The alkaline earth metal Ca-doped W according to claim 1 18 O 49 A method for preparing a catalyst, characterized in that, In step 1), stir at room temperature for 5-15 minutes.

3. The alkaline earth metal Ca-doped W according to claim 1 18 O 49 A method for preparing a catalyst, characterized in that, In step 2), stir at room temperature for 5-15 minutes.

4. The alkaline earth metal Ca-doped W according to claim 1 18 O 49 A method for preparing a catalyst, characterized in that, In step 3), stir at room temperature for 5-15 minutes.

5. Ca-doped W obtained by the preparation method according to any one of claims 1-4 18 O 49 catalyst.

6. The Ca-doped W according to claim 5 18 O 49 Catalyst, characterized in that, The catalyst has a mace-like morphology formed by the self-assembly of nanorods.

7. The Ca-doped W according to any one of claims 5-6 18 O 49 Application of catalysts in sodium-sulfur batteries.

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