(Fe (OH) 2) ((OH) 0.25 (H2O) 0.5) / W18O49 composite material as well as preparation method and application thereof

Abstract

The invention discloses a (Fe (OH) 2) ((OH) 0.25 (H2O) 0.5) / W18O49 composite material as well as a preparation method and application thereof, and belongs to the technical field of functional materials. The preparation method comprises the following steps: uniformly mixing and stirring cyclohexanol, acetylacetone and absolute ethyl alcohol, adding tungsten hexachloride, uniformly stirring at room temperature, then adding ferric trichloride, uniformly stirring at room temperature, carrying out hydrothermal reaction, washing and drying to obtain the (Fe (OH) 2) ((OH) 0.25 (H2O) 0.5) / W18O49 composite material. A mixed system of cyclohexanol, acetylacetone and absolute ethyl alcohol is utilized to synergistically solve the problems of advanced hydrolysis and agglomeration of metal ions; the oxygen vacancy of the W18O49 accelerates the conversion of the sodium polysulfide, and the Fe (OH) 2 derivative strengthens the chemical anchoring of the sodium polysulfide, thereby realizing the synergy of the anchoring and rapid conversion of the NaPSs. When being used as a sodium-sulfur battery positive electrode material catalyst, the catalyst shows excellent catalytic performance and rate capability, and still has the capacity of 420 mAh g <-1 > after circulating for 25000 circles under the large current density of 10 A g <-1 >. The strong adsorption characteristic of the hydroxylated iron-based component and the high catalytic activity of W18O49 are utilized to form a synergistic effect, and a new scheme is provided for breaking through the technical bottleneck of an RT Na-S battery.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, specifically relating to a (Fe(OH)2)((OH)2) 0.25 (H2O) 0.5 ) / W 18 O 49 Composite materials, their preparation methods, and applications. Background Technology

[0002] Against the backdrop of rapid iteration in new energy storage technologies, lithium-ion batteries, due to limited and unevenly distributed lithium resources leading to escalating costs, struggle to meet the long-term demands of large-scale energy storage. Room temperature sodium-sulfur (RT Na-S) batteries, however, benefit from high sodium abundance and a large theoretical specific capacity of the sulfur cathode (1675 mAh g⁻¹). -1 High theoretical energy density (760 Wh kg) -1 With its advantages such as [missing information], it has become a core candidate technology for next-generation low-cost energy storage systems, showing great application potential in areas such as grid peak shaving and renewable energy storage. However, the commercialization of RT Na-S batteries is limited by several inherent defects of sulfur cathodes. First, sulfur and its discharge products Na2S2 / Na2S are both insulating materials, leading to obstructed electron transport, low utilization of active materials, and slow reaction kinetics. Second, during charging and discharging, there is a volume expansion of up to 80% between sulfur and its products, which easily causes the electrode structure to pulverize and peel off, resulting in rapid capacity decay.

[0003] To address the aforementioned issues, existing technologies primarily employ three strategies to optimize sulfur cathode performance: physical confinement with carbon-based materials, chemisorption of polar components, and catalyst engineering. While carbon-based materials provide a conductive network and pore buffer, their chemical binding capacity for NaPSs is weak, and the shuttle effect remains significant at high rates. Single polar catalysts, such as cobalt-based metal compounds and tantalum-based metal nitrides, can enhance NaPS adsorption, but suffer from insufficient catalytic active sites and poor electronic conductivity, making it difficult to balance adsorption and conversion efficiency. Catalyst engineering has proven to be key to overcoming the kinetic bottleneck, with its core being the construction of active components possessing both strong chemisorption and rapid catalytic conversion capabilities. Studies have shown that oxygen-vacancy-rich metal oxides (such as W...) 18 O 49 Because the defect sites can modulate the electronic structure, they can effectively lower the reaction energy barrier and accelerate the conversion of NaPSs. However, W 18 O 49 Its adsorption capacity for NaPSs is limited.

[0004] Therefore, developing composite catalytic materials with high polarity adsorption capacity, excellent catalytic activity and good conductivity to achieve efficient anchoring and rapid conversion of NaPSs has become an urgent need to improve the cycle stability and rate performance of RT Na-S batteries. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a (Fe(OH)2)((OH)2) 0.25 (H2O) 0.5 ) / W 18 O 49 Composite materials, their preparation methods, and applications are used to address the capacity decay caused by the dissolution and shuttle effect of sodium polysulfides in existing sodium-sulfur batteries. 18 O 49 The technical problem of strong catalysis but weak adsorption of NaPSs.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a (Fe(OH)2)((OH)2) 0.25 (H2O) 0.5 ) / W 18 O 49 The preparation method of the composite material includes: mixing cyclohexanol, acetylacetone and anhydrous ethanol evenly, adding tungsten hexachloride, stirring evenly at room temperature, then adding ferric chloride, stirring evenly again at room temperature, and then undergoing hydrothermal reaction, washing and drying to obtain (Fe(OH)2)((OH)2). 0.25 (H2O) 0.5 ) / W 18 O 49 Composite materials.

[0007] Preferably, the volume ratio of cyclohexanol, acetylacetone and anhydrous ethanol is (10~20):(20~30):(10~20).

[0008] Preferably, the molar ratio of tungsten hexachloride to ferric chloride is 0.5 to 1.5.

[0009] Preferably, the temperature of the hydrothermal reaction is 170~200℃.

[0010] Preferably, the hydrothermal reaction time is 5-8 hours.

[0011] Preferably, the mixing time is 5-15 min; the stirring time at room temperature is 5-15 min; and the stirring time at room temperature again is 5-30 min.

[0012] Preferably, the drying temperature is 60-70 ℃.

[0013] Preferably, the drying time is 20-60 min.

[0014] This invention also discloses a (Fe(OH)2)((OH)2) 0.25 (H2O)0.5 ) / W 18 O 49 The composite material uses the aforementioned (Fe(OH)2)((OH)2) 0.25 (H2O) 0.5 ) / W 18 O 49 The composite material was prepared by a specific method.

[0015] The present invention also discloses the above-mentioned (Fe(OH)2)((OH)2). 0.25 (H2O) 0.5 ) / W 18 O 49 The method for preparing composite materials yields (Fe(OH)2)((OH)2). 0.25 (H2O) 0.5 ) / W 18 O 49 Application of composite materials in the preparation of room temperature sodium-sulfur batteries.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The (Fe(OH)2)((OH)2) disclosed in this invention 0.25 (H2O) 0.5 ) / W 18 O 49 The composite material was prepared by uniformly mixing cyclohexanol, acetylacetone, and anhydrous ethanol to construct a synergistic mixed system. Acetylacetone, acting as a bidentate chelating ligand, utilizes its keto-enol tautomerism to interact with Fe... 3+ and W 6+ The formation of stable complexes effectively avoids the problem of non-directional hydrolysis and precipitation of metal ions during the room temperature stirring stage. The addition of cyclohexanol further optimizes the dispersion of the precursor, preventing the local enrichment of Fe-based or W-based components in the subsequent composite material. Anhydrous ethanol, by reducing the viscosity of the mixture, increases the diffusion rate of tungsten hexachloride and ferric chloride in solution, ensuring that they can be uniformly mixed according to a specific molar ratio, providing a ratio guarantee for subsequent reactions. Through a specific mixing system and operation sequence, the problem of non-directional hydrolysis, precipitation, and agglomeration of metal ions during the preparation process is solved, achieving a uniform distribution of Fe-based and W-based components. Through the complexing effect of acetylacetone, the dispersing effect of cyclohexanol, and the viscosity regulation effect of anhydrous ethanol, a stable precursor solution environment is constructed, ensuring the uniform formation of composite materials in the subsequent hydrothermal reaction. First, tungsten hexachloride is added and stirred at room temperature. Tungsten hexachloride, as a tungsten source, preferentially forms complexes in the stable environment of acetylacetone, inhibiting the growth of W-based components. 6+The rapid hydrolysis tendency of the ferric chloride prevents premature precipitation of the tungsten-based components. Ferric chloride is then added and stirred again at room temperature. Ferric chloride is introduced into the system as an iron source, while acetylacetone reacts simultaneously with the Fe. 3+ Complexation is achieved to prevent hydrolysis. This stepwise addition sequence ensures the gradual stabilization of the two metal ions, avoiding the competitive aggregation problem that might occur with simultaneous addition. During the hydrothermal reaction, tungsten hexachloride gradually dissociates and is directionally converted into oxygen-rich vacancy W ions. 18 O 49 Ferric chloride preferentially hydrolyzes to Fe(OH)₂, and further combines with water molecules through hydroxyl groups to form (OH). 0.25 (H2O) 0.5 The derived structure contains a large number of -OH polar groups, which can enhance the chemical anchoring ability of sodium polysulfide, thereby effectively suppressing the "shuttle effect". After the hydrothermal reaction, the product is washed to remove residual impurities, and the nanostructure characteristics of the composite material are preserved by drying, finally yielding (Fe(OH)2)((OH)2). 0.25 (H2O) 0.5 ) / W 18 O 49 Composite materials. Through the synergistic effect of each step, W was achieved. 18 O 49 The uniform combination of catalytic active sites and the chemisorption capacity of Fe-based derivatives constructs a three-dimensional defense mechanism against sodium polysulfide, solving the problem of non-directional hydrolysis precipitation and agglomeration of metal ions. This ensures the uniform distribution of Fe-based and W-based components in the composite material, thereby achieving effective anchoring and rapid conversion of sodium polysulfide in sodium-sulfur batteries to suppress the shuttle effect.

[0017] Furthermore, the three solvents, when mixed in a specific ratio, form a dynamically balanced synergistic environment. Cyclohexanol ensures the uniform dispersion of metal ions in the solution through its moderate intermolecular forces; acetylacetone, as a key complexing agent, effectively inhibits the non-directional hydrolysis of metal ions by forming stable complex structures with iron and tungsten ions through its unique keto-enol tautomerism; and anhydrous ethanol optimizes the overall viscosity by adjusting the system polarity, promoting the uniform mixing of the precursor. This precise ratio design enables the three components to form a complementary mechanism in terms of complexation stability, dispersion optimization, and viscosity control, laying the foundation for constructing a uniform precursor solution in the subsequent hydrothermal reaction stage, thereby ensuring the uniform distribution of Fe-based and W-based components and the directional formation of oxygen vacancy structures in the composite material.

[0018] Furthermore, by controlling the molar ratio of tungsten hexachloride to ferric chloride between 0.5 and 1.5, the bidentate chelating effect of acetylacetone can be fully utilized, effectively preventing premature hydrolysis or aggregation of metal ions. When the molar ratio is below 0.5, the relative insufficiency of the tungsten source will lead to W 18O 49 The reduced amount of phase formation weakens the conversion ability of sodium polysulfide; and when the molar ratio is higher than 1.5, excessive iron source causes excessive aggregation of Fe(OH)2 derivatives, affecting the uniform distribution of hydroxylated structures. Therefore, this specific molar ratio range not only matches W 18 O 49 The catalytic activity of the Fe(OH)2 derivative and its adsorption activity also promote the uniform composite of the two components at the nanoscale, providing a fundamental guarantee for constructing a comprehensive mechanism of physical confinement, chemical adsorption and rapid catalysis, and ultimately achieving stable cycle performance and excellent rate characteristics of the sodium-sulfur battery cathode material.

[0019] Furthermore, by limiting the hydrothermal reaction temperature to the range of 170~200℃, tungsten hexachloride can be fully dissociated and recombined into W with a high oxygen vacancy density. 18 O 49 The crystalline phase, and ferric chloride can be stably hydrolyzed to form Fe(OH)₂ and its derived structures. This temperature window was rigorously verified: when the temperature is below 170℃, the reaction driving force is insufficient, leading to W... 18 O 49 Oxygen vacancy generation is limited, reducing the number of catalytically active sites; however, at temperatures above 200℃, the material is prone to over-sintering or lattice distortion, disrupting the morphological characteristics of one-dimensional nanowires and nanoparticles and weakening the physical confinement effect. Therefore, a temperature range of 170~200℃ not only ensures W 18 O 49 The uniform composite with Fe(OH)2-derived structures further achieves the optimal ratio of oxygen vacancy concentration to hydroxyl group stability through thermodynamic equilibrium.

[0020] Furthermore, the hydrothermal reaction time is 5–8 hours, ensuring that tungsten hexachloride can be directionally converted into W with abundant oxygen vacancies. 18 O 49 These oxygen vacancies are key catalytic sites for accelerating the conversion of sodium polysulfides. Simultaneously, ferric chloride can hydrolyze within this timeframe to form stable Fe(OH)₂ derivatives and maintain their hydroxylated structure, thereby enhancing the chemical anchoring ability to sodium polysulfides. If the time is too short, the reaction will be incomplete, resulting in insufficient oxygen vacancy formation and weakening the W phase. 18 O 49 The catalytic conversion ability of sodium polysulfide is demonstrated; however, excessively long conversion times may induce particle sintering or phase transformation, destroying the composite morphology of one-dimensional nanowires and nanoparticles, and reducing the physical confinement effect and chemical adsorption strength. Through the above technical solution, W in the composite material is achieved. 18 O 49 The effective combination of catalytic activity and the adsorption function of Fe(OH)2 derivatives lays the foundation for building a stable "anchoring-conversion" mechanism in sodium-sulfur batteries.

[0021] Furthermore, by precisely controlling the stirring time at each stage, the problem of premature hydrolysis and aggregation of metal ions during the preparation process was effectively solved. First, mixing and stirring for 5-15 min ensured the formation of a low-viscosity, homogeneous system of cyclohexanol, acetylacetone, and anhydrous ethanol, providing a foundation for the rapid diffusion of the subsequent metal salt. Based on this, stirring at room temperature for 5-15 min allowed acetylacetone to fully react with tungsten ions, forming a stable bidentate chelate complex, thus preventing premature dissociation and hydrolysis of tungsten ions at room temperature. Further, stirring at room temperature for another 5-30 min ensured sufficient complexation and uniform dispersion of iron ions and acetylacetone, avoiding competitive hydrolysis or localized enrichment of iron and tungsten ions. Through the above process, the synergistic distribution of the bimetallic components was achieved, providing a basis for the rapid diffusion of Fe(OH)₂)((OH)₂) in the hydrothermal reaction. 0.25 (H2O) 0.5 Derivative structures and W 18 O 49 The uniform composite structure laid the foundation and ultimately enhanced the material's ability to chemically anchor and catalytically convert sodium polysulfide.

[0022] Furthermore, by setting the drying temperature to 60-70℃, the residue remaining after washing can be gradually evaporated under mild conditions (Fe(OH)2)((OH)2). 0.25 (H2O) 0.5 ) / W 18 O 49 The moisture in the composite material is controlled to prevent material decomposition due to high temperatures or incomplete moisture removal due to low temperatures. This temperature has been optimized to protect Fe(OH)2)((OH)2. 0.25 (H2O) 0.5 The hydroxyl and water molecule structures in it are not destroyed, and W can be maintained. 18 O 49 The stability of oxygen vacancies is crucial for ensuring the adsorption and catalytic performance of the composite material. Precise control of the drying temperature helps maintain the integrity of the composite material's nanostructure and the stability of its chemical composition, which is significant for improving its long-term cycle performance and rate performance in sodium-sulfur batteries.

[0023] Furthermore, the drying time is 20-60 min, a time setting determined based on the material's dehydration kinetics. Under these conditions, residual components in the precursor solutions such as cyclohexanol, acetylacetone, and anhydrous ethanol can be effectively removed, avoiding side reactions that may be caused by residual moisture. Simultaneously, this duration effectively prevents lattice distortion problems caused by excessively long heat treatment, maintaining the Fe(OH)2 derivative and W... 18 O 49The interface integrity was ensured. By strictly controlling the drying time, not only was the functional stability of the oxygen vacancy catalytic sites and hydroxyl adsorption groups guaranteed, but also the rational utilization of energy was achieved, providing a reliable physicochemical basis for sodium-sulfur battery cathode materials.

[0024] The (Fe(OH)2)((OH)2) disclosed in this invention 0.25 (H2O) 0.5 ) / W 18 O 49 The composite material, by combining a mixture of cyclohexanol, acetylacetone, and anhydrous ethanol with the stepwise introduction of tungsten hexachloride and ferric chloride, solves the problem of non-directional hydrolysis precipitation and agglomeration of metal ions during preparation. Specifically, acetylacetone, as a bidentate chelating ligand, utilizes its keto-enol tautomerism to react with Fe... 3+ and W 6+ A stable complex is formed, preventing non-directional hydrolysis and precipitation of metal ions during the room-temperature stirring stage. Cyclohexanol further optimizes the dispersion of the precursor, preventing localized enrichment of Fe-based or W-based components in the subsequent composite material. Anhydrous ethanol, by reducing the viscosity of the mixture, increases the diffusion rate of tungsten hexachloride and ferric chloride in solution, ensuring that they can be uniformly mixed at a specific molar ratio, providing a ratio guarantee for subsequent reactions. This synergistic effect achieves the uniform distribution of Fe-based and W-based components, constructing a three-dimensional defense mechanism against sodium polysulfide, effectively suppressing the shuttle effect. This achieves the W... 18 O 49 The uniform combination of catalytic active sites and the chemisorption capacity of Fe-based derivatives constructs a three-dimensional defense mechanism against sodium polysulfide, solving the problem of non-directional hydrolysis precipitation and agglomeration of metal ions. This ensures the uniform distribution of Fe-based and W-based components in the composite material, thereby achieving effective anchoring and rapid conversion of sodium polysulfide in sodium-sulfur batteries to suppress the shuttle effect.

[0025] The (Fe(OH)2)((OH)2) disclosed in this invention 0.25 (H2O) 0.5 ) / W 18 O 49 The application of composite materials in the preparation of room-temperature sodium-sulfur batteries, utilizing (Fe(OH)2)((OH)2) 0.25 (H2O) 0.5 ) / W 18 O 49The synergistic effect of the composite material's structure and composition effectively inhibits the dissolution and diffusion of sodium polysulfide, thus solving the capacity decay problem. Due to the synergistic effect of cyclohexanol, acetylacetone, and anhydrous ethanol in the mixed system, acetylacetone, as a bidentate chelating ligand, prevents premature hydrolysis of the iron and tungsten sources at room temperature; cyclohexanol optimizes the dispersion of metal ions to avoid local enrichment of components; and anhydrous ethanol regulates the system viscosity to enhance the diffusion rate, ensuring uniform mixing of tungsten hexachloride and ferric chloride at a specific molar ratio. This, in turn, leads to the formation of a homogeneous Fe(OH)₂ derivative and W through a hydrothermal reaction. 18 O 49 Composite structure. This uniform composite structure enables the hydroxylated structure of the Fe(OH)₂ derivative (containing a large number of -OH polar groups) to enhance the chemical anchoring to sodium polysulfide, while W 18 O 49 The oxygen vacancies provide efficient catalytic sites to accelerate the conversion of sodium polysulfides, achieving a dynamic balance between adsorption and catalysis. This solves the problem of non-directional hydrolysis precipitation and aggregation of metal ions, ensuring the uniform distribution of Fe-based and W-based components in the composite material. This enables effective anchoring and rapid conversion of sodium polysulfides in sodium-sulfur batteries to suppress the shuttle effect. Attached Figure Description

[0026] Figure 1 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 XRD patterns of composite materials; Figure 2 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 XPS spectra of composite materials; Figure 3 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 SEM images of the composite material; Figure 4 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 Cyclic performance diagram of composite materials; Figure 5 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O)0.5 ) / W 18 O 49 Rate performance diagram of composite materials; Figure 6 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 Graph of long-cycle performance of composite materials under high current. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0029] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0030] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0031] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0032] In this invention, unless otherwise specified, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" indicates that all real numbers between "6~22" have been listed in this document, and "6~22" is simply a shortened representation of these numerical combinations.

[0033] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0034] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0035] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0036] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0037] This invention provides a (Fe(OH)2)((OH)2) 0.25 (H2O) 0.5 ) / W 18 O 49 The method for preparing composite materials includes the following steps: 1) Measure 10-20 mL of cyclohexanol, 20-30 mL of acetylacetone and 10-20 mL of anhydrous ethanol and add them to a beaker, then stir for 5-15 min. 2) Weigh 0.5~1g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 5-15 minutes; 3) Weigh out ferric chloride according to a molar ratio of tungsten hexachloride to ferric chloride of 0.5~1.5 and add it to the above solution. Stir at room temperature for 5-30 minutes. 4) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven. React at 170~200℃ for 5~8 hours. 5) After the reaction is complete, the product is washed with industrial alcohol by filtration, then dried in a vacuum oven at 60-70 ℃ for 20-60 min, and (Fe(OH)2)((OH)2) is collected. 0.25 (H2O) 0.5 ) / W 18 O 49 Composite material powder.

[0038] The scheme constructs a mixed system using "cyclohexanol + acetylacetone + anhydrous ethanol," and its core advantage lies in utilizing the synergistic effect of each component to address the problem of metal ions (Fe). 3+ W 6+ The problem of premature hydrolysis and aggregation: The stabilizing effect of acetylacetone: As a bidentate chelating ligand, acetylacetone can react with Fe through keto-enol tautomerism. 3+ W 6+ The formation of stable complexes prevents non-directional hydrolysis and precipitation of metal ions during the room temperature stirring stage, laying the foundation for uniform nucleation in the subsequent hydrothermal reaction; the dispersion and structure regulation of cyclohexanol: the interaction between cyclohexanol and metal ions can further optimize the dispersion of the precursor, avoiding the local enrichment of Fe-based or W-based components in the subsequent composite material; the viscosity regulation of anhydrous ethanol: anhydrous ethanol can reduce the viscosity of the mixed system, increase the diffusion rate of WCl6 and FeCl3 in the solution, and ensure that the two are uniformly mixed at a molar ratio of 0.5-1.5 (step 3), providing a ratio guarantee for the synergistic effect of the two components.

[0039] Using FeCl3 as the iron source, FeCl3 preferentially hydrolyzes to Fe(OH)2 under hydrothermal conditions, and further combines with water molecules through hydroxyl groups to form (OH). 0.25 (H2O) 0.5 The derived structure, with its hydroxylated structure (containing numerous -OH polar groups), enhances the chemical anchoring ability to sodium polysulfides (NaPSs) and suppresses the "shuttle effect." When WCl6 is used as a tungsten source, it readily dissociates under hydrothermal conditions, gradually transforming into tungsten-based oxides. A hydrothermal environment of 170-200℃ can promote the directional conversion of WCl6 into oxygen-rich vacancy W... 18 O 49 W 18 O 49 Oxygen vacancies are key catalytic sites for accelerating the conversion of sodium polysulfides. 18 O 49 The uniform combination of (catalytic activity) and Fe(OH)2 derivative (adsorption activity) can achieve the synergistic effect of "NaPSs anchoring-rapid conversion", solving the defects of single components that are "strong in adsorption but weak in catalysis" or "strong in catalysis but weak in adsorption".

[0040] Sodium polysulfides (NaPSs) dissolution and shuttle are the core reasons for capacity decay in sodium-sulfur batteries. The composite system constructs a "three-dimensional defense" mechanism through the physical confinement of one-dimensional nanowires and the synergistic effect of chemical adsorption-catalysis by nanoparticles. The porous structure or tubular cavity of the one-dimensional nanowires can act as "micro-containers," physically restricting NaPS diffusion; simultaneously, their surface defects (such as carbon vacancies and heteroatom doping) can assist in chemical anchoring. Transition metal-based nanoparticles, through their polar surfaces or d-orbital hybridization, achieve strong adsorption and rapid conversion of NaPSs.

[0041] The straight array W prepared in this invention 18 O4 material exhibits excellent catalytic performance as a cathode material in sodium-sulfur batteries. Within a voltage range of 0.2–3.0 V, 0.2 A g… -1 At current density, it exhibits approximately 900 mAh g after 300 cycles. -1 It has a high specific capacitance. It also exhibits excellent rate performance, with minimal capacitance difference at different current densities, maintaining stable capacitance, and retaining capacitance even at low current densities.

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0043] Example 1 A (Fe(OH)2)((OH) 0.25 (H2O) 0.5 ) / W 18 O 49 The method for preparing composite materials includes the following steps: 1) Measure 10 mL of cyclohexanol, 20 mL of acetylacetone and 20 mL of anhydrous ethanol and add them to a beaker, then stir for 5 min; 2) Weigh 0.5g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 5 minutes; 3) Weigh out ferric chloride according to a molar ratio of tungsten hexachloride to ferric chloride of 0.5 and add it to the above solution. Stir at room temperature for 10 minutes. 4) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven at 170°C for 8 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 30 min, and (Fe(OH)2)((OH)2) is collected. 0.25 (H2O) 0.5 ) / W 18 O 49 Composite material powder.

[0044] Example 2 A (Fe(OH)2)((OH) 0.25 (H2O) 0.5 ) / W 18 O 49 The method for preparing composite materials includes the following steps: 1) Measure 15 mL of cyclohexanol, 25 mL of acetylacetone and 15 mL of anhydrous ethanol and add them to a beaker, then stir for 10 min; 2) Weigh 0.7g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 10 minutes; 3) Weigh out ferric chloride according to a molar ratio of tungsten hexachloride to ferric chloride of 0.8 and add it to the above solution. Stir at room temperature for 10 minutes. 4) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven at 190°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 65 °C for 20 min, and (Fe(OH)2)((OH)2) is collected. 0.25 (H2O) 0.5 ) / W 18 O 49 Composite material powder.

[0045] Example 3 A (Fe(OH)2)((OH) 0.25 (H2O) 0.5 ) / W 18 O 49 The method for preparing composite materials includes the following steps: 1) Measure 14 mL of cyclohexanol, 26 mL of acetylacetone and 15 mL of anhydrous ethanol and add them to a beaker, then stir for 15 min; 2) Weigh 0.8g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 15 minutes; 3) Weigh out ferric chloride according to the molar ratio of tungsten hexachloride to ferric chloride of 1.1 and add it to the above solution. Stir at room temperature for 10 minutes. 4) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven at 180°C for 6 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 20 min, and (Fe(OH)2)((OH)2) is collected. 0.25 (H2O) 0.5 ) / W 18 O 49 Composite material powder.

[0046] The product obtained in Example 3 was analyzed, and the XRD pattern of the product is shown in the appendix. Figure 1 .

[0047] Figure 1 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 The XRD pattern of the composite material shows that the peak positions are consistent with the standard card, and no impurity peaks appear, indicating that (Fe(OH)2)((OH)2) was successfully prepared.0.25 (H2O) 0.5 ) / W 18 O 49 Composite materials.

[0048] Figure 2 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 XPS spectra of the composite material; the sample was observed under a scanning electron microscope. Figure 2 The fine XPS spectra show that the composite material contains three elements: W, O, and Fe. Among them, W... 4+ and W 5+ The existence of this proves the existence of aerobic vacancies.

[0049] Figure 3 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 SEM images of composite materials; from Figure 3 It can be seen that the product exhibits two morphologies: one-dimensional nanowires and nanoparticles, corresponding to two different phases.

[0050] The obtained product was used to prepare a button-type sodium-sulfur battery. The specific encapsulation steps are as follows: 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℃ 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 0.2-3.0V.

[0051] Figure 4 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 Cyclic performance diagram of composite materials; such as Figure 4 As shown, the battery is at 0.5 A g -1 The capacity is 980 mAh g after 150 cycles at the current density. -1 .

[0052] Figure 5 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W18 O 49 Ratio performance diagram of composite materials; its ratio performance is as follows: Figure 5 As shown, the capacity difference is small under different current densities, and the capacity remains stable. When returning to a low current density, the capacity can be maintained, indicating that its rate performance and stability are good.

[0053] Figure 6 This refers to (Fe(OH)2)((OH)2) disclosed in Example 3 of the present invention. 0.25 (H2O) 0.5 ) / W 18 O 49 Long-cycle performance diagram of composite material under high current; at 10 A g -1 After cycling 25,000 times at high current density, it still has 420 mAh g. -1 capacity.

[0054] Example 4 A (Fe(OH)2)((OH) 0.25 (H2O) 0.5 ) / W 18 O 49 The method for preparing composite materials includes the following steps: 1) Measure 18 mL of cyclohexanol, 24 mL of acetylacetone and 12 mL of anhydrous ethanol and add them to a beaker, then stir for 5 min; 2) Weigh 0.9g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 10 minutes; 3) Weigh out ferric chloride according to the molar ratio of tungsten hexachloride to ferric chloride of 1.3 and add it to the above solution. Stir at room temperature for 10 minutes. 4) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven at 170°C for 5 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 40 min, and (Fe(OH)2)((OH)2) is collected. 0.25 (H2O) 0.5 ) / W 18 O 49 Composite material powder.

[0055] Example 5 A (Fe(OH)2)((OH) 0.25 (H2O) 0.5 ) / W 18 O 49 The method for preparing composite materials includes the following steps: 1) Measure 20 mL of cyclohexanol, 25 mL of acetylacetone and 10 mL of anhydrous ethanol and add them to a beaker, then stir for 15 min; 2) Weigh 1g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 15 minutes; 3) Weigh out ferric chloride according to a molar ratio of tungsten hexachloride to ferric chloride of 1.5 and add it to the above solution. Stir at room temperature for 10 minutes. 4) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven at 170°C for 5 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 60 min, and (Fe(OH)2)((OH)2) is collected. 0.25 (H2O) 0.5 ) / W 18 O 49 Composite material powder.

[0056] Example 6 A (Fe(OH)2)((OH) 0.25 (H2O) 0.5 ) / W 18 O 49 The method for preparing composite materials includes the following steps: 1) Measure 15 mL of cyclohexanol, 25 mL of acetylacetone and 20 mL of anhydrous ethanol and add them to a beaker, then stir for 10 min. 2) Weigh 0.7g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 10 minutes; 3) Weigh out ferric chloride according to a molar ratio of tungsten hexachloride to ferric chloride of 1.0 and add it to the above solution. Stir at room temperature for 20 minutes. 4) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven at 200°C for 6 h; 5) After the reaction is complete, the product is washed with industrial alcohol by filtration, dried in a vacuum oven at 65 °C for 50 min, and (Fe(OH)2)((OH)2) is collected. 0.25 (H2O) 0.5 ) / W 18 O 49 Composite material powder.

[0057] Example 7 A (Fe(OH)2)((OH) 0.25 (H2O) 0.5 ) / W 18 O 49 The method for preparing composite materials includes the following steps: 1) Measure 12 mL of cyclohexanol, 22 mL of acetylacetone and 18 mL of anhydrous ethanol and add them to a beaker, then stir for 8 min; 2) Weigh 0.6g of tungsten hexachloride and add it to the above solution, then stir at room temperature for 8 minutes; 3) Weigh out ferric chloride according to a molar ratio of tungsten hexachloride to ferric chloride of 0.6 and add it to the above solution. Stir at room temperature for 30 minutes. 4) Transfer the mixed solution into a 100 mL reaction vessel, seal it, and place it in an oven at 185°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 62°C for 25 min, and (Fe(OH)2)((OH)2) is collected. 0.25 (H2O) 0.5 ) / W 18 O 49 Composite material powder.

[0058] In summary, the present invention provides a (Fe(OH)2)((OH)2) 0.25 (H2O) 0.5 ) / W 18 O 49 Composite materials, their preparation methods, and applications were discussed. A mixed system of "cyclohexanol + acetylacetone + anhydrous ethanol" was constructed as the basis for preparation. Among them, acetylacetone, with its bidentate chelating ligand properties, reacts with Fe through keto-enol tautomerism. 3+ W 6+ The formation of stable complexes effectively prevents non-directional hydrolysis and precipitation of metal ions during the room-temperature stirring stage, creating conditions for uniform nucleation in the subsequent hydrothermal reaction. Cyclohexanol optimizes the dispersion of the precursor, preventing local enrichment of Fe-based or W-based components. Anhydrous ethanol reduces the viscosity of the system, increases the diffusion rate of WCl6 and FeCl3, and ensures that the two are uniformly mixed at an appropriate molar ratio. In the hydrothermal reaction, FeCl3 is used as the iron source to generate Fe(OH)2-derived structures containing a large number of -OH polar groups, which enhances the chemical anchoring ability of sodium polysulfides (NaPSs) and suppresses the "shuttle effect". WCl6, as a tungsten source, is directionally converted into oxygen-rich WCl6 under a hydrothermal environment of 170~200℃. 18 O 49 The oxygen vacancies become key catalytic sites for accelerating the conversion of sodium polysulfides. The homogeneous composite of the two components achieves a synergistic effect of "NaPSs anchoring-rapid conversion," overcoming the shortcomings of single components that exhibit either "strong adsorption but weak catalysis" or "strong catalysis but weak adsorption." Simultaneously, the "stereoscopic defense" mechanism of one-dimensional nanowire physical confinement and nanoparticle chemisorption-catalysis synergy further enhances battery performance. When the final composite material is used as a cathode catalyst in sodium-sulfur batteries, it exhibits good performance within a voltage range of 0.2–3.0 V, with a yield of 0.2 A g. -1After 300 cycles at current density, it has approximately 900 mAh g. -1 Excellent specific capacity and rate performance; small capacity difference and stable capacity at different current densities; 10 A g -1 After 25,000 cycles at high current density, it still has 420 mAh g. -1 capacity.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A (Fe(OH)2)((OH) 0.25 (H2O) 0.5 ) / W 18 O 49 A method for preparing composite materials, characterized in that, include: Cyclohexanol, acetylacetone, and anhydrous ethanol were mixed and stirred until homogeneous. Tungsten hexachloride was added, and the mixture was stirred until homogeneous at room temperature. Then, ferric chloride was added, and the mixture was stirred until homogeneous again at room temperature. After hydrothermal reaction, washing, and drying, (Fe(OH)2)((OH)2) was obtained. 0.25 (H2O) 0.5 ) / W 18 O 49 Composite materials.

2. The (Fe(OH)2)((OH)2) according to claim 1 0.25 (H2O) 0.5 ) / W 18 O 49 A method for preparing composite materials, characterized in that, The volume ratio of cyclohexanol, acetylacetone and anhydrous ethanol is (10~20):(20~30):(10~20).

3. The (Fe(OH)₂)((OH)₂) according to claim 1 0.25 (H2O) 0.5 ) / W 18 O 49 A method for preparing composite materials, characterized in that, The molar ratio of tungsten hexachloride to ferric chloride is 0.5 to 1.

5.

4. The (Fe(OH)2)((OH)2) according to claim 1 0.25 (H2O) 0.5 ) / W 18 O 49 A method for preparing composite materials, characterized in that, The temperature of the hydrothermal reaction is 170~200℃.

5. The (Fe(OH)2)((OH) according to claim 1 0.25 (H2O) 0.5 ) / W 18 O 49 A method for preparing composite materials, characterized in that, The hydrothermal reaction takes 5-8 hours.

6. The (Fe(OH)₂)((OH)₂) according to claim 1 0.25 (H2O) 0.5 ) / W 18 O 49 A method for preparing composite materials, characterized in that, The mixing time is 5-15 min; the room temperature stirring time is 5-15 min; the room temperature stirring time is 5-30 min.

7. The (Fe(OH)₂)((OH)₂) according to claim 1 0.25 (H2O) 0.5 ) / W 18 O 49 A method for preparing composite materials, characterized in that, The drying temperature is 60-70 ℃.

8. The (Fe(OH)2)((OH) according to claim 1 0.25 (H2O) 0.5 ) / W 18 O 49 A method for preparing composite materials, characterized in that, The drying time is 20-60 minutes.

9. A (Fe(OH)2)((OH)2) 0.25 (H2O) 0.5 ) / W 18 O 49 Composite material, characterized in that, The (Fe(OH)2)((OH)2) as described in any one of claims 1 to 8 is used. 0.25 (H2O) 0.5 ) / W 18 O 49 The composite material was prepared by a specific method.

10. The (Fe(OH)₂)((OH)₂) as described in claim 9 0.25 (H2O) 0.5 ) / W 18 O 49 Application of composite materials in the preparation of room temperature sodium-sulfur batteries.

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