Sodium ion battery electrode material, electrode sheet, preparation method thereof, and battery

Abstract

The present invention discloses a sodium ion battery electrode material, an electrode sheet, a preparation method thereof, and a battery. The preparation steps of the sodium ion battery electrode material include: reacting raw materials with a sulfur hydride at a predetermined temperature to obtain the obtained material; the sulfur hydride includes: one or more of H2S, H2Se, or H2Te; the raw materials are selected from at least one of MAX phase materials, MXene materials, or transition metal sulfur compounds MY2, wherein M in MY2 represents a transition metal element, and Y represents one of sulfur, selenium, or tellurium.

Description

[0001] This application is a divisional application, and its parent application is an invention patent application with an application date of April 18, 2022, application number "202210404234.7", and invention name "A transition metal sulfur compound, its preparation method, use and energy storage device". Technical Field

[0002] The present invention belongs to the field of new materials and batteries, and in particular relates to a sodium ion battery electrode material, an electrode sheet, a preparation method thereof, and a battery. Background Art

[0003] Two-dimensional nanocrystals such as graphene, hexagonal boron nitride (h-BN), and transition metal chalcogenides (TMCs) have attracted widespread attention due to their exceptionally high anisotropy. In particular, 2D TMCs, composed of transition metals (M = V, Nb, Ta, Mo, W, etc.) and chalcogenides (X = S, Se, Te), possess diverse chemical functionalities and exhibit tunable electrical properties ranging from semiconductors to semimetals and metals, holding great promise in electronics, optoelectronics, and energy storage and conversion. Currently, the most widely studied 2D TMC nanocrystals are typically van der Waals (vdW) layers, such as MoS2 and WS2, which can be readily prepared via top-down approaches through mechanical, liquid-phase, and electrochemical exfoliation of their layered counterparts. During the exfoliation process, bulk layered TMC compounds, with weak interlayer van der Waals forces, can be cleaved by external forces (such as adhesion, shear, and ultrasound), resulting in the formation of monolayers and small amounts of 2D TMC nanocrystals. Compared with van der Waals TMC layers, 2D non-van der Waals TMCs are more difficult to prepare because these compounds exist in a three-dimensional bonded network without the presence of interlayer van der Waals forces, making them difficult to cut by common exfoliation methods and greatly hindering their further development and widespread application.

[0004] Non-van der Waals TMCs can exist in a variety of crystal structures, such as cubic pyrite and NiAs-type structures, which consist of metal atoms surrounded by six sulfur atoms in an octahedral configuration. These unique structural features, with their anisotropic in-plane and out-of-plane bonding, coupled with the tunable d-orbital electrons of specific transition metals, give non-van der Waals TMC nanocrystals excellent electrical properties. For example, non-van der Waals vanadium sulfides, such as V5S8, consist of VS2 layers with V atoms embedded in VS6 octahedral coordination. The embedded V atoms and other V atoms have localized and mobile 3d electrons, respectively, resulting in a charge transfer rate of approximately 500 S cm -1The metallic properties of the highly conductive non-van der Waals TMCs are evident. More strikingly, by isolating a large number of non-van der Waals TMCs to the 2D limit, fully exposed metal, abundant dangling bonds, and unsaturated coordination emerge – features absent in 2D van der Waals TMCs, which can provide numerous electrochemically active sites. Unfortunately, the preparation of 2D non-van der Waals TMC nanocrystals remains a significant challenge due to their three-dimensional bonding structure. Summary of the Invention

[0005] The present invention provides a novel electrochemically active electrode material for sodium ion batteries, namely a class of transition metal sulfide compounds. The preparation method of the electrode material comprises: reacting a raw material with a sulfide hydride at a predetermined temperature to obtain the electrode material; the sulfide hydride comprises: one or more of H2S, H2Se or H2Te; the raw material is selected from at least one of a MAX phase material, a MXene material or a transition metal sulfide compound MY2, wherein M in MY2 represents a transition metal element; and Y represents one of sulfur, selenium or tellurium.

[0006] In some embodiments, the sodium ion battery electrode material has an expanded body morphology of two-dimensional sheet stacking.

[0007] In some embodiments, the sodium ion battery electrode material has a two-dimensional sheet morphology.

[0008] In some embodiments, the thickness of the two-dimensional sheet is between 2 nm and 10 nm.

[0009] In some embodiments, the two-dimensional sheet contains metal M vacancies.

[0010] In some embodiments, the two-dimensional sheet has a monoclinic crystal structure or a hexagonal crystal structure.

[0011] In some embodiments, the chemical formula of the sodium ion battery electrode material is represented by M a Y 2a-2 , 3≤ a ≤5, wherein M represents one or more transition metal elements.

[0012] In some embodiments, the M is selected from one or more of vanadium, titanium, chromium, molybdenum, tungsten or niobium.

[0013] In some embodiments, the predetermined temperature in the above preparation method is between 600°C and 800°C.

[0014] In some embodiments, the predetermined temperature is preferably 700°C.

[0015] The present invention also provides a sodium ion battery positive electrode sheet, comprising the above-mentioned sodium ion battery positive electrode material; as well as a conductive agent and a current collector.

[0016] In some embodiments, the conductive agent includes Ketjen black;

[0017] In some embodiments, the current collector is a metal titanium foil.

[0018] The present invention also provides a method for preparing the above-mentioned sodium ion battery positive electrode sheet, which comprises the following steps: mixing the above-mentioned sodium ion battery positive electrode material and the above-mentioned conductive agent to form a slurry; coating the slurry on the above-mentioned current collector and drying it to obtain a slurry.

[0019] The present invention also provides a sodium ion battery, which includes the above-mentioned sodium ion battery electrode material, or the above-mentioned sodium ion battery electrode sheet.

[0020] This invention provides a novel technical approach for the preparation of 2D non-van der Waals transition metal sulfides, resulting in a novel structural class of transition metal dichalcogenide materials characterized by ultrathin two-dimensional properties, a highly exposed surface, high conductivity, and a unique vacancy structure. Based on these structural features, the invention also provides applications for ion storage, including as electrode materials for batteries or supercapacitors. In particular, the 2D non-van der Waals transition metal dichalcogenides of the invention provide novel electrode materials for the development of novel non-lithium ion energy storage devices targeting ions with larger ionic radii, such as zinc, sodium, and aluminum. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the process of converting MAX-V2GeC into 2D Non-vdW V3S4 during heat treatment in Example 1 of the present invention (a); XRD pattern (b) and XPS measurement spectrum (c) of the obtained 2D Non-vdW V3S4;

[0022] Figure 2 This is the SEM image of 2D Non-vdW V3S4 in Example 1 of the present invention;

[0023] Figure 3 Figure 1 shows the morphology of 2D Non-vdW V3S4 in Example 1 of the present invention, including: cross-sectional TEM images (a) and (b) of 2D Non-vdW V3S4; cross-sectional HRTEM images (c-d) of 2D Non-vdW V3S4; AFM image (e) and corresponding thickness analysis (f) of 2D Non-vdW V3S4.

[0024] Figure 4This is an SEM image of the precursor MAX-V2GeC in Example 1 of the present invention;

[0025] Figure 5 The structural and electrical properties of 2D Non-vdW V3S4 in Example 1 of the present invention include: an SEM image of 2D Non-vdW V3S4 (a), showing ultrathin transparent nanosheets; an HRTEM image of 2D Non-vdW V3S4 and the corresponding FFT pattern (inset), showing the regular atomic arrangement and single crystal characteristics of the hexagonal crystal (b); an HRTEM image of 2D Non-vdW V3S4 (c), in which many V vacancies are circled; an atomic model of monoclinic V3S4 in a top view, in which V vacancies are highlighted with dotted circles (d); a Raman spectrum of 2D Non-vdW V3S4 (e), showing the typical peaks of the VS bond vibration mode; 2D Non-vdW V3S4 and MXene V2CT x The current-voltage curve (f) reveals the metallic characteristics of V3S4 nanocrystals;

[0026] Figure 6 High-resolution V 2p XPS spectra (a) and high-resolution S 2p XPS spectra (b) of 2D Non-vdW V3S4 nanocrystals in Example 1 of the present invention, indicating the presence of VS bonds and VO bonds;

[0027] Figure 7 The X-ray absorption near-edge structure (XANES) spectrum of the VK edge of 2D Non-vdW V3S4 nanocrystals (a) and the Fourier transform of the EXAFS spectra of V3S4, V2O5 and V foil (b) in Example 1 of the present invention are shown.

[0028] Figure 8 In Example 2 of the present invention, at a high temperature of 600°C, the XRD patterns of vdW VS2 and Non-vdW V3S4 (a) show significantly different diffraction peaks, indicating that vdW VS2 will be transformed into Non-vdW V3S4 after heat treatment. The SEM image of the transformed Non-vdW V3S4 (b) does not show obvious layered morphology;

[0029] Figure 9 The electrochemical performance of 2D Non-vdW V3S4 for zinc storage in aqueous electrolyte in Example 4 of the present invention includes: 50 mA g obtained from the 1st, 2nd and 5th cycles -1The constant current discharge-charge curves (a) show the high reversible capacity during the discharge-charge process; Non-vdW V3S4-600, Non-vdW V3S4-700 and Non-vdW V3S4-800 at 50 mA g -1 Cycling performance (b) and rate performance (c) of Non-vdW V3S4-7000 at 5000 mA g -1 Cycling performance under (d);

[0030] Figure 10 In Example 4 of the present invention, the precursor V2GeC is -1 Cycling performance at current density of ;

[0031] Figure 11 The material characterization of 2D Non-vdW V3S4 nanocrystals during zinc storage discharge-charge cycles in Example 4 of the present invention includes: 2D contour map (a) of the in-situ XRD measurement of 2D Non-vdW V3S4 nanocrystals during the discharge-charge process, and 50 mA g -1 The corresponding discharge-charge curves (b) are shown below; Zn storage using V vacancies on the 2D Non-vdW V3S4 basal plane 2+ Schematic diagram (c); HRTEM image of 2D Non-vdW V3S4 nanocrystals after discharge (d), showing good crystallinity; elemental mapping images of V (e), S (f) and Zn (g) species of 2D Non-vdW V3S4 nanocrystals in the discharged state;

[0032] Figure 12 The electrochemical impedance spectroscopy (EIS) spectrum of the zinc ion battery in Example 4 of the present invention is as follows;

[0033] Figure 13 In Example 4 of the present invention, the cycle performance of the assembled battery in 0.05 M potassium hydrogen phthalate electrolyte was measured with a voltage range of 0.3 to 1.6 V and a current density of 50 mA g -1 ;

[0034] Figure 14 In Example 4 of the present invention, 2D Non-vdW V3S4 is subjected to a scanning rate of 0.01 to 50 mV s -1 CV curves (a) and logarithmic relationships between the anodic and cathodic peak currents and scan rates (b) show the hybrid pseudocapacitive behavior during the discharge-charge cycle.

[0035] Figure 15The electrochemical performance of 2D Non-vdW V3S4 sodium storage in Example 5 of the present invention includes: 2D Non-vdW V3S4 at 50 mA g -1 Constant current discharge-charge curves under current density (a); Non-vdW V3S4-600, Non-vdW V3S4-700, Non-vdW V3S4-800, and V2GeC at 50 mA g -1 Cycling performance at current density (b); Rate performance of Non-vdW V3S4 nanocrystals (c); Non-vdW V3S4-700 at 2 A g -1 Cycling performance under current density (d);

[0036] Figure 16 The XRD patterns of 2D Non-vdW Ti5S8 and its precursor Ti2SnC in Example 6 of the present invention are as follows;

[0037] Figure 17 The SEM image (a), TEM image (b), HRTEM image (c) and FFT spectrum (d) of 2D Non-vdW Ti5S8 in Example 6 of the present invention;

[0038] Figure 18 STEM image (a) of 2D Non-vdW Ti5S8, and element distribution diagrams of Ti (b) and S (c) in Example 6 of the present invention. DETAILED DESCRIPTION

[0039] The technical solutions of the present invention are described below by means of specific embodiments. It should be understood that one or more steps mentioned in the present invention do not exclude the presence of other methods and steps before and after the combination step, or other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Unless otherwise specified, the numbering of each method step is only for the purpose of identifying each method step, and does not limit the order of arrangement of each method or the scope of implementation of the present invention. Changes or adjustments in their relative relationships can also be regarded as the scope of implementation of the present invention without substantial changes in the technical content.

[0040] The sources of the raw materials and instruments used in the examples are not particularly limited and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0041] The technical solution of the present invention includes: using MAX phase material as a precursor and subjecting it to high temperature heat treatment in a chalcogenide atmosphere. We found that during this heat treatment process, on the one hand, the chalcogenide can etch the A component; on the other hand, the chalcogenide element can replace the X element to form MS2; on the other hand, the vanadium atoms in the van der Waals gap of the MS2 layer are self-intercalated to form M 1+x The S2 layer eventually forms 2D non-van der Waals M3S4 or M5S8 nanocrystals. This 2D non-van der Waals transition metal chalcogenide compound has a unique two-dimensional layer stacking expansion structure, and ultra-thin layers of 2D non-van der Waals transition metal chalcogenide compounds can be obtained through simple treatment (such as ultrasound).

[0042] In the present invention, the MAX phase material is replaced with a MXene material. That is, after the A component in the MAX phase material is etched in advance, the product MXene material is reacted with a chalcogenide hydride at a certain temperature, and 2D non-van der Waals transition metal chalcogenide compound sheets can also be obtained.

[0043] The present invention also found that by replacing the raw material with a van der Waals transition metal disulfide compound MY2 and reacting it with a sulfide hydride at a certain temperature, the transition metal disulfide compound MY2 can be converted to produce a non-van der Waals transition metal disulfide compound.

[0044] It should be noted that the chalcogenides in the present invention include sulfur (S), selenium (Se), and tellurium (Te). The above embodiments are described using sulfur in the chalcogenides as an example. Since Se and Te are in the same family as S and have similar chemical and physical properties, 2D non-van der Waals transition metal chalcogenide compound (such as V3Se4, V3Te4, Ti5Se8, Ti5Te8, etc.) nanocrystals can also be obtained by adjusting the experimental conditions.

[0045] Example 1

[0046] To better illustrate the technical features of the present invention, this embodiment provides a two-dimensional non-van der Waals vanadium-based sulfide compound V3S4 and a preparation method thereof, comprising the following steps:

[0047] 1) Preparation of MAX phase material: Vanadium powder (V, 99.9%, 100-200 mesh, Aladdin Reagent), germanium powder (Ge, 99.999%, 100 mesh, Alfa Aesar), and graphite (C, 99.9%, 10 mesh, Alfa Aesar) were sealed in an agate container with agate balls and milled at 600 rpm for 20 h. The molar ratio of V / Ge / C was 2:1.05:1. The powder mixture was then transferred to a tube furnace and heated at 3°C ​​min-1 for 10 min-1. -1 The mixture was heated at 1400 °C at a heating rate of 0.05. The mixture was kept at this temperature for 4 hours to obtain the MAX phase material, which was labeled as MAX-V2GeC;

[0048] 2) Preparation of 2D non-van der Waals V3S4 nanocrystals: 10 °C min-1 under Ar flow -1 The V2GeC prepared in step 1 (300 mg) was heated at a heating rate of 100°C. A mixture of H2S / Ar (10 vol.% H2S) was then introduced at different temperatures (600, 700, and 800°C). This temperature was maintained for 2 hours to yield 2D non-van der Waals V3S4 nanocrystals. The resulting product was then sonicated in IPA solvent and labeled as non-vdW V3S4-X (where X represents the reaction temperature).

[0049] Figure 1 a shows a schematic diagram of the process of converting MAX phase material (MAX-V2GeC) into 2D non-van der Waals vanadium-based chalcogenide (V3S4). At high temperature (600 to 800°C), the germanium layer in MAX-V2GeC first reacts with hydrogen sulfide to form germanium sulfide (GeS) at a temperature above 600°C. Since the GeS intermediate is gaseous in this temperature range, it can be easily removed from the reaction system to obtain high-purity V3S4. At the same time, the vanadium atoms in the van der Waals gap of the VS2 layer are self-intercalated to form V 1+x S2 layer, and finally gradually formed a 2D non-van der Waals V3S4 layer.

[0050] Figure 1 b shows the XRD pattern of the obtained non-van der Waals V3S4. It can be seen that a series of strong peaks at 15.3°, 17.0°, 28.0°, 31.0°, 34.6°, 44.5° and 45.1° are detected on the (002), (101), (011), (110), (1-12), (1-14) and (204) planes of non-van der Waals V3S4, respectively, while the main peak at 41.1° of MAX-V2GeC is invisible; it can also be seen that there are no other impurities in non-van der Waals V3S4, indicating that MAX-V2GeC has undergone complete transformation during our synthesis process. X-ray photoelectron spectroscopy (XPS) measurement spectrum ( Figure 1 c and inset) further show that the obtained product displays S and V species without any Ge element, indicating that the Ge layer is completely removed from V2GeC in our conversion reaction.

[0051] The morphology and microstructure of 2D non-van der Waals TMC-V3S4 were characterized by scanning electron microscopy (SEM). Figure 2 As shown in Figure 2, the prepared sample has an expanded accordion layered structure, which is similar to the morphology of reported accordion MXenes. The morphology and microstructure of 2D non-van der Waals TMC-V3S4 were characterized by transmission electron microscopy (TEM), as shown in Figure 2. Figure 3As shown in a and b, the prepared samples have a highly expanded structure, similar to the accordion-shaped MXenes, which is different from the morphology of the precursor V2GeC bulk (such as Figure 4 The highly expanded 2D non-van der Waals TMC-V3S4 can be peeled off to obtain ultra-thin two-dimensional sheets after simple ultrasound. To further evaluate the thickness of the generated 2D layer, an ultra-thin sectioning experiment was conducted. The cross-sectional HRTEM image is shown in Figure 1. Figure 3 As shown in c and d, there are many thin nanosheets with thickness ranging from 2.0 to 4.0 nm. Atomic force microscopy (AFM) images ( Figure 3 e) further reveals the presence of ultrathin nanosheets with an average thickness of 3.2 nm ( Figure 3 f), and cross-sectional HRTEM observation results ( Figure 3 Of course, in some embodiments, the thickness of the ultra-thin nanosheets of the present invention can be between 2 nm and 10 nm.

[0052] The crystal structure of the as-prepared 2D non-van der Waals V3S4 layers can be further investigated by scanning electron microscopy (SEM) and high-resolution TEM (HRTEM) measurements. Figure 5 As shown in a and b, atoms are regularly arranged in a hexagonal system in the ultrathin layer, showing high crystallinity. Figure 5 c The measurement clearly shows that the spacing between the lattice fringes is 0.29 nm, which is consistent with the interplanar spacing between the monoclinic V3S4 (200) planes ( Figure 5 d) Correlation. The good crystallinity of these 2D V3S4 nanocrystals can also be seen from the hexagonal diffraction spots in the fast Fourier transform (FFT) pattern ( Figure 5 b). In the above HRTEM analysis, the calculated spacing between (2-02) and (202-) points agrees well with the interplanar spacing of the (2-02) plane. More notably, in the HRTEM image ( Figure 5 A large number of V vacancies are observed in Figure c), which is likely the result of the migration of V atoms during the self-intercalation process at high temperature. This is further supported by the relatively low V / S atomic ratio of 0.7:1 in the non-van der Waals TMC-V3S4 planes as determined by electron dispersion spectroscopy (EDS).

[0053] To determine the chemical structure of the prepared 2D non-van der Waals V3S4 nanocrystals, Raman measurements were performed. Figure 5 As shown in e, there are four main peaks at 276.2, 401.1, 682.5, and 984.5 cm -1 The rocking and stretching vibration modes of the VS bond can be seen by high-resolution XPS spectroscopy ( Figure 6a and b) and VK-edge extended X-ray absorption fine structure spectroscopy (EXAFS, Figure 7 a and b) further prove the existence of VS bond. Figure 5 f It can be seen that the 2D non-van der Waals TMC-V3S4 nanocrystals of the present invention show a linear current-voltage relationship and a low resistance of 3.2 kΩ□ -1 , only MXene V2CT x (16.6 kΩ -1 ), which is one-fifth of that of metallic 1T TMDs, demonstrating the high conductivity of 2D non-van der Waals V3S4 nanocrystals.

[0054] Example 2

[0055] This example provides another method for preparing a two-dimensional non-van der Waals vanadium-based sulfide compound, namely, an implementation method for converting VS2 to V3S4. The specific implementation steps include:

[0056] 1) Hydrothermal synthesis of VS2: Using NH4VO3 and TAA as precursors, a simple hydrothermal method was used to synthesize two-dimensional van der Waals VS2 (vdW VS2). For more detailed implementation, please refer to Nature 2020, 577, 647.;

[0057] 2) Thermal treatment to transform vdW VS2 into non-van der Waals V3S4 nanocrystals (Non-vdW V3S4): Two-dimensional Non-vdW V3S4 was obtained by thermal annealing at 600°C for 1h under a flow rate of H2S / Ar (10vol%H2S).

[0058] Figure 8 Figure a shows the XRD patterns of vdW VS2 and Non-vdW V3S4. It can be seen that the characteristic peaks of Non-vdWV3S4 after heat treatment are significantly different from those of vdW VS2, indicating that heat treatment of vdW VS2 in an atmosphere containing hydrogen sulfide can promote the transformation of vdW VS2 into Non-vdW V3S4. However, the Non-vdW V3S4 prepared in the comparative example obviously does not have the characteristics of a layered expansion body and a two-dimensional morphology, as shown in Figure 4. Figure 8 As shown in b, it can be seen that the 2D TMC prepared using MAX phase material as a precursor has significantly different structural morphology characteristics.

[0059] Example 3

[0060] This embodiment provides another method for preparing a two-dimensional non-van der Waals vanadium-based chalcogenide compound, which is obtained by using a MXenes material containing the V element as a precursor and performing a high-temperature conversion reaction in a chalcogen hydride atmosphere.

[0061] Taking the preparation of 2D non-van der Waals V3S4 nanocrystals as an example, the specific implementation steps include: x The powder was placed in a high temperature reactor and heated at 10°C min -1 The mixture was heated at a heating rate of 100 ℃ and a H2S / Ar (10 vol.% H2S) mixture was introduced at different temperatures (600-1200℃). The temperature was maintained for 2 hours to obtain 2D non-van der Waals V3S4 nanocrystals.

[0062] Among them, MXenes material V2CT x The MAX phase material V2AlC is obtained by etching Al therein. Different etchants can be selected, such as hydrofluoric acid solution, a mixture of halogen metal salt and acid solution, or molten metal salt, etc. In this embodiment, more specifically, the V2AlC is placed in an HF acid solution and etched at 80°C for 24 hours to obtain the MAX phase material V2AlC.

[0063] Example 4

[0064] From the above examples, it can be seen that the 2D non-van der Waals vanadium-based sulfur compounds prepared by the present invention have two-dimensional ultra-thin features, highly exposed surfaces, high conductivity and unique vacancy structures. We believe that they can be used for ion storage (such as lithium ions, sodium ions, zinc ions, aluminum ions, etc.) as battery electrode materials or supercapacitor electrode materials.

[0065] In this embodiment, we provide a method for using the 2D non-van der Waals vanadium-based sulfide compound of the present invention for zinc ions with larger ionic radius in aqueous electrolytes, that is, a zinc ion battery is provided, wherein the 2D non-van der Waals vanadium-based sulfide compound of the present invention is used as an electrode material to prepare a working electrode, and then zinc foil is used as a counter electrode, glass fiber is used as a separator, and the electrolyte is 3 mol L in deionized water. -1 Zinc trifluoromethanesulfonate (Zn(CF3SO3)2) was assembled into a button-type zinc ion battery to test the electrochemical performance. The working electrode was prepared by mixing 80wt.% 2D V3S4, 10wt.% Ketjen black, and 10wt.% PVDF in NMP, uniformly coating it on Ti foil, and vacuum drying it at 120°C for 12 h. Constant current discharge / charge tests were carried out on a Bluetron system (CT2001A) in the voltage range of 0.3-1.6 V (relative to Zn / Zn 2+ ).

[0066] like Figure 9 As shown in a and b, 2D non-van der Waals V3S4 (Non-vdW V3S4-700) converted from V2GeC at 700 °C was subjected to 50 mA g -1 A current density of 341 mAh g -1The high stable capacity is much higher than that of the V2GeC precursor (18 mAh g -1 , please see Figure 10 ), 2D TMC-V3S4 produced at other temperatures (200~300 mAh g -1 ) and the transition metal chalcogenides reported so far. More importantly, 2DNon-vdW V3S4-700 exhibits a high performance in the range of 50 to 10000 mA g -1 shows high rate performance at different current densities ( Figure 9 c). Even at 10000 mA g -1 At a high current density of 1.5 Å, the reversible capacity of 2DNon-vdW V3S4-700 remains at 162 mAh g -1 , which should be attributed to the rapid diffusion of zinc ions in vacancy-enriched 2D V3S4 nanocrystals. In addition, at 5000 mA g -1 After 1200 cycles, 152 mA g -1 The stable capacity is maintained at 71% capacity retention rate ( Figure 9 d), indicating that 22DNon-vdW V3S4 is a promising ion storage electrode material.

[0067] In order to clarify the Zn 2+ The discharge-charge mechanism in 2D Non-vdW V3S4 nanocrystals was further investigated by in-situ XRD and TEM measurements during the constant current discharge-charge process. Figure 11 In a), the characteristic peaks of the (002), (101), (011), (110), (1-12), (1-14), and (204) planes of 2D Non-vdW V3S4 at 15.3°, 17.0°, 28.0°, 31.0°, 34.6°, 44.5°, and 45.1° remain unchanged during the discharge and charge processes ( Figure 11 b). This indicates that 2DNon-vdW V3S4 nanocrystals have a strong affinity for Zn 2+ The good structural stability after intercalation and deintercalation is in good agreement with the ex situ XRD measurements. This can be attributed to the highly exposed surface and the large number of V vacancies in the basal plane, which not only facilitate access to the electrolyte but also help Zn 2+ Rapid transfer ( Figure 11 c). This can be further verified by the reduced semicircle diameter in the electrochemical impedance spectroscopy (EIS) spectrum ( Figure 12 ). Therefore, after repeated cycles, the 2D Non-vdW V3S4 nanocrystals still maintain their original structure and good crystallinity, as shown in the HRTEM images ( Figure 11d). Elemental mapping image of the 2D Non-vdW V3S4 layer in the discharge state ( Figure 11 e~g) show the uniform distribution of V, S and Zn species.

[0068] In order to verify the electrochemical performance of the 2D Non-vdW V3S4 electrode material of the present invention, a button cell was assembled in a similar manner to Example 3, except that the electrolyte was replaced with a Zn-free 2+ The 2D Non-vdW V3S4 nanocrystals exhibited a negligible capacity of 6 mAh g during charge and discharge. -1 ( Figure 13 ), which confirms that the electrochemical behavior of 2D Non-vdW V3S4 is entirely due to the Zn 2+ Furthermore, the hybrid pseudocapacitive behavior of 2D Non-vdW V3S4 nanocrystals can be demonstrated by cyclic voltammograms (CVs) from 0.3 to 1.6 V in the range of 0.1 to 50 mV s -1 The scan rate proves that ( Figure 14 a). The fitting results of the b value (according to the relationship: i=aνb) show that the b values ​​of the anodic peak and the cathodic peak are 0.88 and 0.85 respectively ( Figure 14 b) Hybrid pseudocapacitive behavior corresponding to Zn storage, which can be attributed to the presence of highly exposed surfaces of 2D Non-vdW V3S4.

[0069] Example 5

[0070] This embodiment provides an embodiment of using the 2D non-van der Waals vanadium-based sulfide compound prepared by the present invention for sodium ion storage. More specifically, 2D Non-vdW V3S4 is used as a sodium ion battery electrode material to prepare a working electrode, metallic sodium is used as a counter electrode, a polypropylene porous separator, and an electrolyte is a 1M NaPF6 organic solution. A button-type sodium ion battery is assembled to test the electrochemical performance; the working electrode is prepared by mixing 80wt.% 2D V3S4, 10wt.% Ketjen black, and 10wt.% PVDF in NMP, uniformly coating the mixture on Cu foil, and vacuum drying the mixture at 120°C for 12 h; constant current discharge / charge tests are carried out on a blue electric system (CT2001A) in a voltage range of 0.05-3.0V (relative to Na / Na + ).

[0071] like Figure 15 As shown in a and b, 2D non-van der Waals V3S4 (Non-vdW V3S4-700) converted from V2GeC at 700 °C was subjected to 50 mA g -1A current density of ~500 mAh g -1 The high stable capacity is much higher than that of the V2GeC precursor (20 mAh g -1 ), 2D TMC-V3S4 produced at other temperatures (230~350 mAh g -1 ). 2DNon-vdW V3S4-700 at 50 to 5000 mA g -1 shows high rate performance at different current densities ( Figure 15 c). Even at 2A g -1 At a high current density of 1.5 Å, the reversible capacity of 2DNon-vdW V3S4-700 remains at ~360 mAh g -1 ( Figure 15 d), which can also be attributed to the rapid diffusion of sodium ions in vacancy-enriched 2D V3S4 nanocrystals, further indicating that 2DNon-vdW V3S4 is a promising ion storage electrode material.

[0072] Example 6

[0073] This embodiment provides a two-dimensional non-van der Waals titanium-based chalcogenide compound Ti5S8 and a preparation method thereof, the steps comprising:

[0074] 1) Preparation of MAX phase material: Titanium powder (Ti, 99.99%, 300 mesh, Aladdin reagent), tin powder (Sn, 99.95%, 100 mesh, Aladdin reagent), and graphite (C, 99.9%, 10 mesh, Alfa Aesar) were sealed in an agate container with agate balls and ball milled at 600 rpm for 20 h. The molar ratio of Ti / Sn / C was 2:1.5:1. The powder mixture was then transferred to a tube furnace and heated at 3°C ​​min-1 for 20 h. -1 The mixture was heated at 1300 °C at a heating rate of 0.05. The mixture was kept at this temperature for 2 h to obtain a MAX phase material, which was labeled as MAX-Ti2SnC;

[0075] 2) Preparation of 2D non-van der Waals Ti5S8 nanocrystals: 10 °C min-1 under Ar flow -1The Ti2SnC (300 mg) prepared in step 1 was heated at a heating rate of , and then a mixture of H2S / Ar (10 vol.% H2S) was introduced when different temperatures (800, 900 and 1000 °C) were reached. The temperature was maintained for 2 hours to obtain the product 2D non-van der Waals Ti5S8 nanocrystals, which were then ultrasonically treated in IPA solvent. The obtained product was labeled as non-vdW Ti5S8-X (X represents the reaction temperature). At high temperatures (800 to 1200 °C), the tin layer in MAX-Ti2SnC first reacted with hydrogen sulfide to form tin sulfide (SnS) at temperatures above 700 °C. Since the SnS intermediate is in a gaseous state in this temperature range, it can be easily removed from the reaction system to obtain high-purity Ti5S8. At the same time, TiS2 is formed by self-intercalation of vanadium atoms in the van der Waals gap of the TiS2 layer. 1+x S2 layer, and finally gradually formed a 2D non-van der Waals Ti5S8 layer.

[0076] Figure 16 The XRD pattern of the obtained non-van der Waals Ti5S8 is given. It can be seen that the diffraction peaks corresponding to the (002), (101), (102), (103), (104), (006), (105), (110), (112), (106), (202) and (008) crystal planes appear at 15.5°, 31.1°, 34.0°, 38.4°, 43.9°, 47.6°, 50.3°, 53.5°, 56.0°, 57.4°, 64.9° and 65.1° of the non-van der Waals Ti5S8, while the main diffraction peaks of MAX-Ti2SnC disappear. It can also be seen that there are no other impurities in the XRD diffraction pattern of non-van der Waals Ti5S8, indicating that MAX-Ti2SnC has undergone a complete transformation during our synthesis process.

[0077] The morphology and microstructure of 2D non-van der Waals TMC-Ti5S8 were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 17 As shown in a, the prepared sample has a highly expanded structure, similar to the accordion-shaped MXenes, which is significantly different from the bulk morphology of the MAX phase. After simple ultrasound, the highly expanded 2D non-van der Waals TMC-Ti5S8 can be peeled off to obtain ultra-thin two-dimensional layers ( Figure 17 b). In the high-resolution TEM (HRTEM) image ( Figure 17 In c), atoms are regularly arranged in a hexagonal system in the ultrathin layer, showing high crystallinity, with a 0.28 nm interplanar spacing corresponding to the (100) crystal plane. Hexagonal diffraction spots in the fast Fourier transform (FFT) pattern ( Figure 17d) to further demonstrate that the prepared Ti5S8 single crystal structure is good. TEM element surface scanning analysis results ( Figure 18 ) shows the uniform presence of Ti and S elements, indicating that the non-van der Waals two-dimensional material Ti5S8 was prepared by converting Ti2SnC.

[0078] In summary, the present invention provides a novel technical approach for the preparation of 2D non-van der Waals transition metal sulfides, resulting in a novel class of transition metal dichalcogenide materials with ultrathin, highly exposed surfaces, high conductivity, and a unique vacancy structure. Based on these structural features, the present invention also provides applications for ion storage, such as as electrode materials for batteries or supercapacitors. In particular, the 2D non-van der Waals transition metal dichalcogenides of the present invention offer novel electrode materials for the development of novel non-lithium ion energy storage devices targeting ions with larger ionic radii, such as zinc, sodium, and aluminum.

[0079] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A sodium ion battery electrode material, characterized in that The preparation steps of the sodium ion battery electrode material include: reacting raw materials with sulfur hydrides at a predetermined temperature; the sulfur hydrides include: one or more of H2S, H2Se or H2Te; the raw materials are selected from at least one of MAX phase materials, MXene materials or transition metal sulfur compounds MY2, wherein M in MY2 represents a transition metal element and Y represents one of sulfur, selenium or tellurium; the sodium ion battery electrode material has an expanded body morphology of two-dimensional sheet stacking, or a two-dimensional sheet morphology; the two-dimensional sheet contains metal M vacancies.

2. The sodium ion battery electrode material according to claim 1, wherein The thickness of the two-dimensional sheet is between 2 nm and 10 nm.

3. The sodium ion battery electrode material according to claim 2, wherein The two-dimensional sheet has a monoclinic crystal structure or a hexagonal crystal structure.

4. The sodium ion battery electrode material according to claim 1, wherein The chemical formula of the sodium ion battery electrode material is expressed as M a Y 2a-2 , 3≤ a ≤5, wherein M represents one or more transition metal elements.

5. The sodium ion battery electrode material according to claim 4, wherein The M is selected from one or more elements selected from vanadium, titanium, chromium, molybdenum, tungsten or niobium.

6. The sodium ion battery electrode material according to any one of claims 1 to 5, wherein The predetermined temperature is between 600°C and 800°C.

7. The sodium ion battery electrode material according to claim 6, wherein The predetermined temperature is 700°C.

8. A sodium ion battery electrode sheet, characterized in that: include: The sodium ion battery electrode material according to any one of claims 1 to 7; and, a conductive agent and a current collector.

9. The sodium ion battery electrode sheet according to claim 8, wherein: The conductive agent includes Ketjen black; And / or, the current collector is metal copper foil.

10. A method for preparing a sodium ion battery electrode sheet according to claim 8 or 9, characterized in that the steps include: Mixing the sodium ion battery electrode material and the conductive agent to form a slurry; The slurry is coated on the current collector and dried to obtain the slurry.

11. A sodium ion battery, characterized in that: include: The sodium ion battery electrode material according to any one of claims 1 to 7; Or, the sodium ion battery electrode sheet according to claim 8 or 9; Or, a sodium ion battery electrode sheet obtained by the preparation method according to claim 10.

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