Preparation method of high-performance sodium storage material based on sulfur vacancy engineering modified hollow zinc sulfide nanospheres

Abstract

The invention provides a preparation method of a high-performance sodium storage material based on sulfur vacancy engineering modified hollow zinc sulfide nanospheres, and belongs to the technical field of preparation of sodium ion battery negative electrode materials. Through the strategic design of introducing sulfur vacancies and constructing a hollow structure, a feasible solution is provided for improving the dynamic performance of zinc sulfide (ZnS) and relieving mechanical stress at the same time. The preparation method comprises the following steps: firstly, introducing polyvinylpyrrolidone (PVP) to enlarge the lattice spacing of zinc sulfide so as to reduce the formation energy of sulfur vacancies, and then carrying out annealing treatment in an argon atmosphere so as to form the vacancies in situ. The hollow structure effectively relieves the problem of volume expansion in the electrochemical cycle process. Meanwhile, the electronic structure of ZnS is modified by the introduced sulfur vacancy, so that the band gap is narrowed, and the intrinsic conductivity is remarkably improved. The improvement not only accelerates ion / electron transfer kinetics, but also increases the density of electrochemical active sites, thereby promoting excellent sodium storage performance.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery electrode material preparation technology, specifically relating to a method for preparing high-performance sodium storage materials based on sulfur vacancy engineering modified hollow zinc sulfide nanospheres. Background Technology

[0002] The rising global demand for sustainable energy storage systems has spurred in-depth research into sodium-ion batteries, which are gaining popularity due to their cost-effectiveness and abundant sodium reserves. However, sodium... + The large ionic radius brings inherent kinetic limitations and structural instabilities to traditional electrode materials, which poses a great challenge to the development of high-performance anode materials that can withstand repeated sodium insertion / extraction cycles.

[0003] Among various sodium storage materials, the transition metal chalcogenide ZnS stands out for its excellent theoretical capacity (approximately 550 mAh·g). -1 ZnS, with its abundant natural reserves and environmental friendliness, has become a highly attractive candidate material. However, the intrinsic low conductivity of ZnS stems from its wide-bandgap semiconductor characteristics, leading to poor electron transport efficiency. Furthermore, the large volume changes during repeated sodium-addition / de-sodiuming processes can trigger severe structural collapse. These intrinsic defects result in limitations commonly found in reported ZnS-based electrodes, including low reversible capacity, poor rate performance, and insufficient cycling stability. Notably, current research on ZnS-based sodium storage materials remains extremely limited, primarily because it is difficult to effectively overcome its inherent defects using traditional modification methods (such as carbon coating and heterostructure construction). Therefore, exploring innovative strategies to fundamentally overcome the intrinsic low conductivity of ZnS is imperative. In recent years, defect engineering (e.g., introducing anion vacancies) has been shown to significantly enhance ion diffusion, promote charge transfer, and increase active sites by modulating the electronic structure, thereby improving electrode performance. Summary of the Invention

[0004] This invention solves the problems of low intrinsic conductivity, slow ion / electron transfer kinetics, and structural instability caused by volume expansion during charge-discharge cycles when zinc sulfide (ZnS) is used as a negative electrode material for sodium-ion batteries through sulfur vacancy engineering and hollow structure design.

[0005] To achieve the above objectives, the present invention employs the following technical means:

[0006] A method for preparing a high-performance sodium storage material based on sulfur vacancy-engineered hollow zinc sulfide nanospheres includes the following steps:

[0007] Step 1: Dissolve 2.85g of thiourea in 25ml of deionized water, then add 0.22g of zinc acetate dihydrate. Stir the mixture for 30 minutes, then add 0-0.75g of PVP (K30) and continue stirring for another 30 minutes to ensure uniform dispersion.

[0008] Step 2: Transfer the solution obtained in Step 1 to a high-pressure reactor lined with polytetrafluoroethylene and carry out a hydrothermal synthesis reaction at 140°C for 5 hours.

[0009] Step 3: The reaction product obtained in Step 2 was centrifuged to obtain milky white hollow ZnS nanospheres, which were then washed three times each with deionized water and anhydrous ethanol to remove impurities. Subsequently, they were placed in an oven and dried at 60°C for 12 hours.

[0010] Step 4: Place the ZnS powder prepared in Step 3 into a ceramic boat and anneal it under an argon atmosphere. The temperature is increased from room temperature in increments of 1°C / min according to a pre-programmed sequence. -1 The heating rate was increased to 400-600℃, and then held at a constant temperature for 2 hours to obtain hollow ZnS nanospheres rich in sulfur vacancies.

[0011] Preferably, in the above technical solution, the PVP in step 1 is 0.75g.

[0012] In the above technical solution, the annealing temperature in step 4 is 400℃.

[0013] Because the present invention employs the above-mentioned technical means, it has the following beneficial effects:

[0014] 1. This invention successfully prepared hollow ZnS nanospheres with abundant sulfur vacancies (denoted as H-ZnS). 1-x This hollow structure design effectively buffers the volume expansion during sodium storage, enhancing structural stability. Simultaneously, the introduction of sulfur vacancies optimizes charge distribution, significantly improving the H-ZnS... 1-x Its intrinsic conductivity accelerates charge transfer kinetics and ion diffusion.

[0015] 2. The hollow ZnS nanospheres with abundant sulfur vacancies prepared in this invention exhibit excellent sodium storage performance when used as a sodium storage anode, at 5 A·g -1 After 1970 cycles at a current density, it still maintains 454 mAh·g. -1 The specific capacity was high, with a capacity retention of 90%. Furthermore, additional reversible sodium-storing active sites were generated at 1 A·g -1 and 2A·g -1 At current densities, they exhibited 621 mAh·g. -1 and 559mAh·g-1 Its excellent specific capacity exceeds the theoretical specific capacity of ZnS (approximately 550 mAh·g). -1 ). Attached Figure Description

[0016] Figure 1 These are the morphology, structure, and phase characterization diagrams of the sodium-ion battery electrode material of this invention;

[0017] Figure 2 The X-ray diffraction patterns are those of the precursors synthesized in Examples 1 and 2 of this invention.

[0018] Figure 3 These are SEM images of sodium-ion battery electrode materials synthesized at different annealing temperatures in Examples 3 and 4 of this invention.

[0019] Figure 4 This is a characterization diagram of sulfur vacancies in the sodium-ion battery electrode material of the present invention;

[0020] Figure 5 The electron paramagnetic resonance spectrum of the precursor synthesized in Example 1 of this invention;

[0021] Figure 6 The graph shows the electrochemical performance test results of the sodium-ion battery electrode material of this invention.

[0022] Figure 7 These are electrochemical performance test graphs of sodium-ion battery electrode materials synthesized at different annealing temperatures according to the present invention;

[0023] Figure 8 This is a kinetic analysis diagram of the sodium-ion battery electrode material of the present invention;

[0024] Figure 9 This is a density functional theory (DFT) analysis diagram of the sodium-ion battery electrode material of this invention. Detailed Implementation

[0025] The embodiments of the present invention will be described in detail below. Although the present invention will be described and illustrated in conjunction with some specific embodiments, it should be noted that the present invention is not limited to these embodiments. On the contrary, any modifications or equivalent substitutions made to the present invention should be covered within the scope of the claims of the present invention.

[0026] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art will understand that the present invention can be practiced without these specific details.

[0027] A method for preparing a sodium-ion battery material with excellent sodium storage performance includes the following steps:

[0028] Example 1

[0029] Step 1: Dissolve 2.85g of thiourea in 25ml of deionized water, then add 0.22g of zinc acetate dihydrate. Stir the mixture for 30 minutes, then add 0.75g of polyvinylpyrrolidone (PVP) (K30) and continue stirring for another 30 minutes to ensure uniform dispersion.

[0030] Step 2: Transfer the solution obtained in Step 1 to a high-pressure reactor lined with polytetrafluoroethylene and carry out a hydrothermal synthesis reaction at 140°C for 5 hours.

[0031] Step 3: The reaction product obtained in Step 2 was centrifuged to obtain milky white hollow ZnS nanospheres (denoted as H-ZnS@PVP), and washed three times each with deionized water and anhydrous ethanol to remove PVP and other impurities. Then, it was placed in an oven and dried at 60°C for 12 hours.

[0032] Step 4: Place the H-ZnS@PVP powder prepared in Step 3 into a ceramic boat and anneal it under an argon atmosphere. The temperature is increased from room temperature in increments of 1℃·min according to the set program. -1 The heating rate was increased to 400℃, and then held at that temperature for 2 hours to obtain hollow ZnS nanospheres rich in sulfur vacancies (denoted as H-ZnS). 1-x ).

[0033] Example 2

[0034] Step 1: Dissolve 2.85g of thiourea in 25ml of deionized water, then add 0.22g of zinc acetate dihydrate. Stir the mixture for 30 minutes, then add 0g of PVP (K30) and continue stirring for another 30 minutes to ensure uniform dispersion.

[0035] Step 2: Transfer the solution obtained in Step 1 to a high-pressure reactor lined with polytetrafluoroethylene and carry out a hydrothermal synthesis reaction at 140°C for 5 hours.

[0036] Step 3: The reaction product obtained in Step 2 was centrifuged to obtain milky white hollow ZnS nanospheres (denoted as H-ZnS@Free), and washed three times each with deionized water and anhydrous ethanol to remove impurities. Then, it was placed in an oven and dried at 60°C for 12 hours.

[0037] Step 4: Place the H-ZnS@Free powder prepared in Step 3 into a ceramic boat and anneal it under an argon atmosphere. The temperature is increased from room temperature in increments of 1℃·min according to the set program. -1 The heating rate was increased to 400℃, and then held at a constant temperature for 2 hours to obtain a hollow ZnS nanosphere structure without sulfur vacancies (denoted as H-ZnS).

[0038] Example 3

[0039] Step 1: Dissolve 2.85g of thiourea in 25ml of deionized water, then add 0.22g of zinc acetate dihydrate. Stir the mixture for 30 minutes, then add 0.75g of PVP (K30) and continue stirring for another 30 minutes to ensure uniform dispersion.

[0040] Step 2: Transfer the solution obtained in Step 1 to a high-pressure reactor lined with polytetrafluoroethylene and carry out a hydrothermal synthesis reaction at 140°C for 5 hours.

[0041] Step 3: The reaction product obtained in Step 2 was centrifuged to obtain milky white hollow ZnS nanospheres, which were then washed three times each with deionized water and anhydrous ethanol to remove impurities. Subsequently, they were placed in an oven and dried at 60°C for 12 hours.

[0042] Step 4: Place the H-ZnS@PVP powder prepared in Step 3 into a ceramic boat and anneal it under an argon atmosphere. The temperature is increased from room temperature in increments of 1℃·min according to the set program. -1 The heating rate was increased to 500°C, and then held at a constant temperature for 2 hours to obtain a hollow ZnS nanosphere structure rich in sulfur vacancies. Compared with Example 1, the annealing temperature was increased.

[0043] Example 4

[0044] Step 1: Dissolve 2.85g of thiourea in 25ml of deionized water, then add 0.22g of zinc acetate dihydrate. Stir the mixture for 30 minutes, then add 0.75g of PVP (K30) and continue stirring for another 30 minutes to ensure uniform dispersion.

[0045] Step 2: Transfer the solution obtained in Step 1 to a high-pressure reactor lined with polytetrafluoroethylene and carry out a hydrothermal synthesis reaction at 140°C for 5 hours.

[0046] Step 3: The reaction product obtained in Step 2 was centrifuged to obtain milky white hollow ZnS nanospheres, which were then washed three times each with deionized water and anhydrous ethanol to remove impurities. Subsequently, they were placed in an oven and dried at 60°C for 12 hours.

[0047] Step 4: Place the H-ZnS@PVP powder prepared in Step 3 into a ceramic boat and anneal it under an argon atmosphere. The temperature is increased from room temperature in increments of 1℃·min according to the set program. -1 The heating rate was increased to 600°C, and then held at a constant temperature for 2 hours to obtain a hollow ZnS nanosphere structure rich in sulfur vacancies. Compared with Example 1, the annealing temperature was increased.

[0048] Comparison table of examples:

[0049]

[0050] Figure 1 The images show the morphology, structure, and phase characterization of Examples 1 and 2. Figure 1 Table a illustrates the synthetic route of the implementation example. First, in Example 1, H-ZnS@PVP with expanded interlayer spacing was synthesized via a simple hydrothermal reaction by introducing PVP. Subsequently, annealing under an argon atmosphere resulted in the in-situ generation of H-ZnS rich in sulfur vacancies. 1-x Hollow nanospheres. In contrast, under the same synthesis conditions, Example 2, without the addition of PVP, yielded larger H-ZnS hollow nanospheres free of sulfur vacancies. Transmission electron microscopy (TEM) images show H-ZnS 1-x The nanospheres have a hollow structure and are assembled from numerous small crystallites. Figure 1 (b, c) Figure 1 The selected area electron diffraction (SAED) pattern shown in d reveals clear diffraction rings, which correspond to the ZnS crystal planes: (100), (002), (101), (110), and (112). Figure 1 As shown in Figure e, H-ZnS 1-x High-resolution transmission electron microscopy (HRTEM) images showed that its interplanar spacing was 0.349 nm, which corresponds to the (100) plane of ZnS. XRD was used to obtain H-ZnS... 1-x Phase information of H-ZnS ( Figure 1 (f, g). Clearly, all diffraction peaks correspond to the standard spectrum of hexagonal zinc sulfide (ICDD NO. 00-003-1093), confirming that a pure phase has been formed and no impurities were detected. It is noteworthy that from... Figure 1 A magnified view of the XRD pattern in medium g clearly shows that the sample H-ZnS 1-x The diffraction peaks of H-ZnS were significantly shifted towards smaller angles. This observation further demonstrates that, compared to H-ZnS, H-ZnS... 1-x The interplanar spacing increased. Furthermore, for H-ZnS... 1-x XRD analysis was performed on the precursor of H-ZnS. Figure 2 The results showed that the diffraction peaks of H-ZnS@PVP also shifted to a smaller angle, which can be attributed to the lattice expansion caused by the introduction of PVP during the hydrothermal synthesis process. Figure 3 The SEM images of Examples 3 and 4 show that increasing the annealing temperature has no significant effect on the particle morphology.

[0051] Figure 4This is a characterization diagram of sulfur vacancies in the material of this invention. The surface elemental composition and chemical state of the material were investigated using XPS. Figure 4 Figure a shows a high-resolution Zn 2p energy spectrum, where the characteristic peaks at 1046.0 eV and 1023.1 eV correspond to the H-ZnS synthesized in Example 1, respectively. 1-x 2p of Zn 1 / 2 and 2p 3 / 2 Orbit. Compared with H-ZnS (2pZn) synthesized in Example 2. 1 / 2 1046.3 eV, 2p of Zn 3 / 2 Compared to 1023.3 eV, these binding energies show a negative shift, which can be attributed to the excess electrons gained through sulfur vacancies in Zn. 2+ The density of the surrounding electron cloud increases. Similarly, Figure 4 High-resolution S 2p energy spectrum of H-ZnS indicates that... 1-x The middle corresponds to 2p of S 1 / 2 and 2p 3 / 2 The characteristic peaks of the orbitals are located at 163.9 eV and 163.1 eV, respectively. This is similar to the 2p phase of H-ZnS(S). 1 / 2 164.7 eV, 2p of S 3 / 2 Compared to 163.3 eV, the binding energies of these peaks showed a negative shift, which is due to the escape of sulfur atoms leading to the formation of low-coordinate sulfur species. EPR analysis further confirmed the presence of H-ZnS... 1-x There are a large number of sulfur vacancies in it. For example... Figure 4 As shown in c, H-ZnS 1-x A significant EPR signal was observed at a g-factor of 2.002, while the response of H-ZnS at this characteristic position was negligible. Sulfur vacancies were visualized using HAADF-STEM. Figure 4 As shown in Figure d, the HAADF-STEM image in bright-field (BF) imaging mode clearly reveals H-ZnS 1-x The periodic arrangement characteristics of the Zn-S atomic columns. For example... Figure 4 As shown in f, HAADF-STEM in dark field (DF) imaging mode ( Figure 4 Linear scanning analysis (e) revealed a significant intensity decay at the locations marked by the red dashed circles within the first and second layers of the sulfur atom column in the intensity distribution map, indicating a certain degree of sulfur atom deficiency. Furthermore, the formation mechanism of these sulfur vacancies was investigated. Figure 4 Figure g illustrates the generation of sulfur vacancies. During the hydrothermal process, a precursor H-ZnS@PVP with expanded interlayer spacing was synthesized by introducing PVP. Subsequent annealing under an argon atmosphere yielded the master sample H-ZnS containing sulfur defects. 1-xIt is worth noting that the EPR signal was not detected in the H-ZnS@PVP precursor. Figure 5 This indicates that sulfur vacancies are specifically generated during subsequent annealing. In contrast, the precursor H-ZnS@Free, which did not undergo interlayer spacing widening treatment, did not form sulfur vacancies under the same annealing conditions. DFT calculations show that sulfur vacancy formation in H-ZnS@PVP is significantly reduced compared to H-ZnS@Free. Figure 4 (h). This indicates that the increased interlayer spacing is conducive to the generation of sulfur vacancies in ZnS, thus making it easier for sulfur vacancies to form during annealing.

[0052] The H-ZnS synthesized in Example 1 was subsequently evaluated. 1-x Sodium storage performance of the electrode. First, CV curves were used to study H-ZnS. 1-x Sodium storage mechanism of electrodes ( Figure 6 (a) During the initial cathode scan, a characteristic peak observed at approximately 0.29 V can be attributed to the formation of the SEI film and the reduction conversion of ZnS to metallic Zn (ZnS + Na₂S). + +e - →Zn + NaS). Subsequently, the significant peak near 0.12 V corresponds to the further reduction of the intermediate NaS to form Na2S (NaS + Na). + +e - →Na2S). During the subsequent anodic scan, the oxidation peaks at 0.66 V and 0.88 V correspond to the desodiumation reaction of Na2S (Na2S→NaS+Na). + +e - And the regeneration process of ZnS (Zn + NaS → ZnS + Na) + +e - In the subsequent two scan cycles, the cyclic voltammetry curves almost overlapped, indicating that H-ZnS 1-x It exhibits excellent electrochemical reversibility. Figure 6 The image in section b shows H-ZnS 1-x The electrode is at 0.2 A·g -1 The electrode exhibits galvanostatic charge-discharge curves at a current density of 859 mAh·g⁻¹. It demonstrates a remarkable initial discharge / charge specific capacity of 859 mAh·g⁻¹. -1 and 663mAh·g -1 The initial coulombic efficiency reached 77.2%. This performance is significantly better than that of the H-ZnS electrode, which has an initial coulombic efficiency of only 67.1%. Furthermore, the capacity loss observed in the first cycle can be attributed to the formation of the SEI film and the occurrence of side reactions. Figure 6 The middle section shows H-ZnS 1-xRate performance of the electrode and the H-ZnS electrode. H-ZnS 1-x It exhibits a much higher reversible capacity than H-ZnS. At current densities of 0.2, 0.5, 1, 2, 3, and 5 A·g, it achieves this. -1 At that time, the specific capacities reached 537, 492, 449, 422, 389 and 349 mAh·g, respectively. -1 This superior rate performance can be attributed to the presence of sulfur vacancies, which enhance charge transfer efficiency and the diffusion rate of sodium ions. Notably, when the current density recovers to 0.2 A·g -1 At that time, H-ZnS 1-x The specific capacity of the electrode quickly recovered to 510 mAh·g. -1 And remained stable. In contrast, the specific capacity of the H-ZnS electrode decreased rapidly, possibly due to electrode structure degradation and pulverization at higher current densities. (The last part, "at 1 A·g", appears to be a separate, unrelated statement and is left as is.) -1 2A·g -1 and 5A·g -1 The cycling performance of these two electrodes was evaluated at a current density of H-ZnS. 1-x Electrode at 1 A·g -1 After 800 cycles at a current density, it exhibits a high capacity of 621 mAh·g. -1 The discharge specific capacity; at 2A·g -1 After 1500 cycles at a current density, the discharge specific capacity reaches as high as 559 mAh·g. -1 This far exceeds the theoretical capacity. Figure 6 (d, e). This performance improvement is mainly attributed to sulfur vacancies, which generate additional reversible redox sodium storage active sites. (This is in contrast to H-ZnS rich in sulfur vacancies.) 1-x Compared to the original H-ZnS electrode, the cycling stability of the original electrode is significantly worse, indicating that the introduction of sulfur vacancies plays a crucial role in enhancing the long-term cycling durability of metal sulfide anode materials. Furthermore, at 5 A·g... -1 H-ZnS under high current density 1-x The negative electrode exhibits excellent long-term cycling stability, maintaining 454 mAh·g after 1970 cycles. -1 Excellent reversible capacity, with a capacity retention rate of up to 90% ( Figure 6 (f). It maintains excellent capacity characteristics even under high current density conditions, mainly attributed to the significant improvement in kinetic performance induced by sulfur vacancies. The obtained performance surpasses all previously reported ZnS-based anode materials for sodium-ion batteries (f). Figure 6 (g). For example Figure 7As shown, the material properties of Examples 1, 3 and 4 at different annealing temperatures show that the material capacity increases with increasing annealing temperature, which may be due to the increase in sulfur vacancy concentration with increasing temperature. However, the cycle life is significantly lower than that of the material synthesized at the annealing temperature of Example 1.

[0053] To further investigate the H-ZnS synthesized in Example 1 1-x The kinetic characteristics of the H-ZnS electrode synthesized in Example 2 are as follows: from 0.2 to 1 mV·s -1 CV tests were performed at different scan rates. Figure 8 (a) The results show that with the increase of scan rate, H-ZnS 1-x The cyclic voltammetry curves of the electrode remain largely stable, demonstrating excellent reversibility. To elucidate the storage behavior of sodium, the value of b was determined using the following formula:

[0054] i = av b

[0055] log i = blog v + log a

[0056] In the formula, a and b are adjustable parameters. For example... Figure 8 As shown in b, H-ZnS 1-x The fitted b-value of the electrode is close to 1, indicating that H-ZnS 1-x The charge storage behavior is primarily dominated by pseudocapacitive behavior. Based on the following formulas, the pseudocapacitance (k1v) and diffusion (k2v) at different scan rates can be determined. 1 / 2 Contribution percentage:

[0057] i = k1v + k2v 1 / 2

[0058] At 1mV·s -1 At scan rates, H-ZnS 1-x The capacitance contribution of the electrode is 84.95%. Figure 8 c), which indicates that H-ZnS 1-x The electrode exhibits relatively rapid sodium storage kinetics. For example... Figure 8 As shown in Figure d, with the increase of scan rate, H-ZnS 1-x The pseudocapacitive contribution of the electrode increased from 71.62% to 84.95%. The introduction of sulfur vacancies generated additional reversible active sites, thereby significantly improving the pseudocapacitive storage capacity of the electrode. Furthermore, GITT (… Figure 8 The sodium ion diffusion coefficient (D) was determined using the following formula (e). Na+ ):

[0059]

[0060] In the formula, τ represents the relaxation time, m, V m M and A represent the mass, molar volume, and molar mass of the active material, respectively, A is the electrode area, and ΔE is the electrode surface area. s and ΔE τ This represents the voltage change caused by pulsed and constant-current charge / discharge cycles. Under most test conditions, especially during the charging phase, the calculated H-ZnS... 1-x D of the electrode Na+ The D value is significantly greater than that of the H-ZnS electrode. Na+ ( Figure 8 (f). This indicates that H-ZnS 1-x The electrode exhibits enhanced ion transport kinetics. Finally, regarding H-ZnS... 1-x Electrodes prior to H-ZnS cycling underwent in-situ ElS testing. Figure 8 (g). Through equivalent circuit curve fitting analysis, the H-ZnS was determined. 1-x Charge transfer resistance R of the electrode ct The charge transfer resistance is 3.97 Ω, significantly lower than that of the H-ZnS electrode (16.64 Ω), and compared with other recently reported metal sulfide anode materials. Figure 8 (h), H-ZnS 1-x R ct The value is smaller than that of most materials, which further indicates that H-ZnS 1-x The electrodes exhibit excellent charge transfer performance.

[0061] To fully understand the H-ZnS synthesized in Example 1 1-x The influence mechanism of sulfur vacancies on the electrochemical performance of ZnS was introduced, and systematic calculations were performed using density functional theory. Figure 9 Figures a and b respectively show H-ZnS 1-x Both H-ZnS structures adsorb Na + The model diagram. Figure 9 The data in section c shows that the calculated H-ZnS has a positive effect on Na. + The adsorption energy is -1.82 eV, while H-ZnS 1-x To Na + The adsorption energy is -2.35 eV, indicating that the introduction of sulfur vacancies significantly enhances the adsorption of Na. + The interaction between these elements allows for more effective anchoring of redox products and stabilization of the crystal structure. For example... Figure 9 As shown in d and e, the introduction of sulfur vacancies effectively reduced Na + The diffusion barrier within the structure confirms that these sulfur vacancies promote ion migration dynamics. Furthermore, Figure 9 The figures in the middle show H-ZnS and H-ZnS respectively. 1-xThe differences in charge density across the structure indicate that a significant redistribution of charge occurred near sulfur vacancies, which facilitates the charge transfer process. Figure 9 Zhongg and Figure 9 The total density of states (TDOS) and partial density of states (PDOS) analysis shown in Figure h indicates that sulfur vacancies reduce the band gap of this semiconductor material from 2.09 eV in H-ZnS to H-ZnS. 1-x The intrinsic conductivity is significantly increased to 1.17 eV. Therefore, a series of theoretical calculations confirm that the introduction of sulfur vacancies significantly improves sodium storage performance and electrochemical reactivity, while optimizing the reaction kinetics related to sodium storage.

[0062] In summary, this invention successfully constructed in situ a hollow nanomaterial H-ZnS with sulfur vacancies through a synergistic strategy of interlayer spacing control and argon annealing. 1-x This hollow structure design effectively buffers the volume expansion during sodium storage, enhancing structural stability. Simultaneously, the introduction of sulfur vacancies optimizes charge distribution, significantly improving the H-ZnS... 1-x The intrinsic conductivity is improved, thereby accelerating charge transfer kinetics and ion diffusion. Thanks to these excellent modifications, the material exhibits a high reversible capacity of 1 A·g⁻¹. -1 At a current density of up to 621 mAh.g -1 , in 2A·g -1 The current density can reach 559 mAh·g -1 It is worth noting that in 5A·g -1 After 1970 cycles at high current density, its capacity remained at 454 mAh·g. -1 The capacity retention rate is as high as 90%. Theoretical calculations further confirm the intrinsic influence of sulfur vacancies on the sodium storage mechanism and performance. This invention proposes a simple and direct method that retains the advantages of hollow nanostructures in sodium storage while enabling sulfur vacancy engineering to address the challenges of volume expansion and poor intrinsic conductivity faced by zinc sulfide in electrochemical applications.

[0063] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for preparing high-performance sodium storage materials based on sulfur vacancy-engineered hollow zinc sulfide nanospheres, characterized in that, Includes the following steps: Step 1: Dissolve 2.85g of thiourea in 25ml of deionized water, then add 0.22g of zinc acetate dihydrate, stir the mixture for 30min, then add 0.75g of polyvinylpyrrolidone, and continue stirring for 30min to form a uniform dispersion. Step 2: Transfer the solution obtained in Step 1 to a high-pressure reactor lined with polytetrafluoroethylene and hydrothermally react at 140°C for 5 hours. Step 3: Centrifuge the reaction product to obtain milky white hollow ZnS nanospheres, wash them three times with deionized water and anhydrous ethanol, and dry them at 60°C for 12 hours to obtain hollow zinc sulfide nanosphere precursors. Step 4: Place the precursor prepared in Step 3 in an argon atmosphere and incubate at 1℃·min -1 The temperature was increased to 400-600℃ and then held at a constant temperature for 2 hours to obtain hollow zinc sulfide nanospheres rich in sulfur vacancies.

2. The method for preparing a high-performance sodium storage material based on sulfur vacancy-engineered hollow zinc sulfide nanospheres according to claim 1, characterized in that, The PVP content is 0.75g.

3. The method for preparing a high-performance sodium storage material based on sulfur vacancy-engineered hollow zinc sulfide nanospheres according to claim 1, characterized in that, The annealing temperature is 400℃.

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