A molybdenum cobalt telluride heterostructure material, a preparation method and application thereof

Abstract

The application belongs to the technical field of inorganic nanometer material synthesis, and relates to a molybdenum cobalt telluride heterostructure material and a preparation method and application thereof. A divalent cobalt salt, a hexavalent molybdenum salt and glycerol are co-precipitated in isopropyl alcohol at a temperature of 160-200 DEG C to synthesize molybdenum cobalt glycerate precursor nanospheres; the molybdenum cobalt glycerate precursor nanospheres are heated to 500-600 DEG C in an air atmosphere for annealing and oxidation treatment to obtain molybdenum cobalt oxide; the molybdenum cobalt oxide and a tellurium source are heated to 550-650 DEG C in a mixed atmosphere of inert and reducing gas for annealing and tellurization treatment, and the molybdenum cobalt telluride heterostructure material is obtained. The molybdenum cobalt telluride heterostructure material provided by the application has a kind of strawberry-like structure formed by cross-linking of nanometer particles, and the molybdenum cobalt telluride heterostructure material with the structure has excellent reversibility and fast sodium storage kinetics and exhibits excellent sodium storage performance.

Description

Technical Field

[0001] This invention belongs to the field of inorganic nanomaterial synthesis technology, and relates to a molybdenum cobalt telluride heterostructure material, its preparation method and application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Due to the large radius of sodium ions, sodium-ion batteries face higher requirements. Currently, the volume expansion of electrode materials during sodium ion insertion / extraction and the slow sodium storage kinetics are problems that urgently need to be addressed. Compared to transition metal sulfides and transition metal selenides, transition metal tellurides have higher intrinsic conductivity and density, and weaker metal-tellurium bonds, which are conducive to the rapid transfer of sodium ions. Therefore, metal tellurides have high volumetric capacity and good rate performance.

[0004] According to the inventor's research, molybdenum ditelluride has a unique layered structure and a high theoretical specific capacity, but it has the defect that the electrode is easily pulverized when sodium ions are inserted / extracted, resulting in poor cycle stability and rate performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a molybdenum-cobalt telluride heterostructure material, its preparation method, and its application. The molybdenum-cobalt telluride heterostructure material provided by the present invention has a passion fruit-like structure formed by cross-linking of nanoparticles. This structured molybdenum-cobalt telluride heterostructure material exhibits excellent reversibility and rapid sodium storage kinetics, demonstrating superior sodium storage performance.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] On the one hand, a method for preparing a molybdenum-cobalt telluride heterostructure material includes the following steps:

[0008] Molybdenum cobalt glycerate precursor nanospheres were synthesized by co-precipitation of divalent cobalt salt, hexavalent molybdenum salt and glycerol in isopropanol at a temperature of 160-200℃ using a solvothermal method.

[0009] In an air atmosphere, the molybdenum cobalt glycerate precursor nanospheres were annealed and oxidized at 500–600 °C to obtain molybdenum cobalt oxide.

[0010] Under a mixed atmosphere of inertness and reduction, molybdenum cobalt oxide and a tellurium source are heated to 550–650 °C for annealing and tellurization treatment to obtain the product.

[0011] This invention utilizes a solvothermal method to control the particle size of molybdenum cobalt glycerate nanospheres through co-precipitation. Synergistic annealing treatment yields a cross-linked, passion fruit-like structure of molybdenum cobalt telluride heterostructure material. This material exhibits a stable heterostructure interface formed by the coupling between the two metal tellurides, and the cross-linking of multiple nanoparticles buffers volume changes during sodium ion insertion / extraction, maintaining the structural stability of the electrode material. Furthermore, the unique electronic structure and abundant active sites at the heterostructure interface result in a faster charge migration rate, enhanced conductivity, and a lower ion diffusion barrier, thus demonstrating excellent reversibility and rapid sodium storage kinetics. Therefore, the heterostructure material prepared in this invention combines these advantages and exhibits superior sodium storage performance.

[0012] On the other hand, a molybdenum-cobalt telluride heterostructure material is obtained by the above preparation method.

[0013] Thirdly, the above-mentioned molybdenum-cobalt telluride heterostructure material is used as a negative electrode in sodium-ion batteries.

[0014] When the molybdenum-cobalt telluride heterostructure material provided by this invention is applied to the anode material of sodium-ion batteries, it exhibits excellent electrochemical performance.

[0015] Fourthly, a sodium-ion battery, wherein the active material in the negative electrode of the sodium-ion battery is the aforementioned molybdenum-cobalt telluride heterostructure material.

[0016] The beneficial effects of this invention are as follows:

[0017] This invention utilizes divalent cobalt salt, hexavalent molybdenum salt, and glycerol to prepare precursor nanospheres via a solvothermal method. Then, through annealing oxidation and annealing tellurization, a MoTe2 / CoTe heterostructure material with a passion fruit-like structure is prepared. The coupling between the two tellurides can form a stable heterostructure interface, which provides abundant redox reaction sites, improves the overall conductivity of the material, and lowers the sodium ion diffusion barrier. The passion fruit-like cross-linked nanoparticle structure can effectively alleviate volume expansion and inhibit structural collapse, which is beneficial to the stability of the electrode material structure. When applied to sodium-ion battery anode materials, it exhibits excellent sodium storage performance. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 This is a scanning electron microscope image of the molybdenum cobalt glycerate nanosphere precursor prepared in Example 1 of the present invention;

[0020] Figure 2This is a transmission electron microscope (TEM) image of the molybdenum cobalt glycerate nanosphere precursor prepared in Example 1 of this invention.

[0021] Figure 3 This is an X-ray powder diffraction pattern of the passion fruit-like MoTe2 / CoTe heterostructure material prepared in Example 2 of the present invention;

[0022] Figure 4 This is a transmission electron microscope (TEM) image of the passion fruit-like MoTe2 / CoTe heterostructure material prepared in Example 2 of this invention.

[0023] Figure 5 The passion fruit-like MoTe2 / CoTe heterostructure material prepared in Example 2 of this invention, when applied to a sodium-ion battery, achieves a yield of 0.5 A g. -1 Capacity-voltage plot at current density;

[0024] Figure 6 This is a scanning electron microscope image of the MoTe2 / CoTe heterostructure material prepared in Example 3 of the present invention. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] As described in the background section, existing technologies suffer from drawbacks such as complex preparation methods, easy structural collapse, and poor sodium storage performance. To address these technical problems, this invention proposes a molybdenum-cobalt telluride heterostructure material, its preparation method, and its applications.

[0028] A typical embodiment of the present invention provides a method for preparing a molybdenum-cobalt telluride heterostructure material, comprising the following steps:

[0029] Molybdenum cobalt glycerate precursor nanospheres were synthesized by co-precipitation of divalent cobalt salt, hexavalent molybdenum salt and glycerol in isopropanol at a temperature of 160-200℃ using a solvothermal method.

[0030] In an air atmosphere, the molybdenum cobalt glycerate precursor nanospheres were annealed and oxidized at 500–600 °C to obtain molybdenum cobalt oxide.

[0031] Under a mixed atmosphere of inertness and reduction, molybdenum cobalt oxide and a tellurium source are heated to 550–650 °C for annealing and tellurization treatment to obtain the product.

[0032] This invention controls the particle size of molybdenum cobalt glycerate nanospheres through a solvothermal method for co-precipitation synthesis. Synergistic annealing treatment yields a passion fruit-like cross-linked molybdenum cobalt telluride heterostructure material. This heterostructure stabilizes the electrode structure while enhancing conductivity, accelerating sodium storage reaction kinetics, and improving sodium storage performance.

[0033] The divalent cobalt salts described in this invention are compounds containing divalent cobalt ions, such as cobalt dichloride, cobalt nitrate, cobalt sulfate, cobalt acetate, etc.

[0034] The hexavalent molybdenum salts described in this invention are compounds containing hexavalent molybdenum ions, such as ammonium molybdate, molybdenum acetylacetonate, sodium molybdate, etc.

[0035] The solvothermal method described in this invention is a reaction method that uses alcohol as a solvent in a closed container and generates high temperature and high pressure conditions after heating.

[0036] In some embodiments, the molar ratio of divalent cobalt salt to hexavalent molybdenum salt is 1:0.9 to 1.1.

[0037] In some embodiments, the reaction time for the solvothermal method is 6 to 14 hours.

[0038] In some embodiments, the mass ratio of molybdenum cobalt oxide to tellurium powder is 1.0:2.0 to 5.0.

[0039] When the above conditions are met simultaneously, obtaining molybdenum cobalt glycerate nanosphere precursors can better prepare passion fruit-like molybdenum cobalt telluride heterostructure materials. The effect is particularly good when the mass ratio of molybdenum cobalt oxide to tellurium powder is 1.0–2.0:4.0 and the stirring time is 15–17 h.

[0040] In some embodiments, the volume fraction of the reducing gas in the mixed atmosphere is 5-10%. The reducing gas is hydrogen, CO, etc. When hydrogen is used as the reducing gas, the obtained material properties are better.

[0041] The annealing process refers to a heat treatment process in which the temperature is heated to a set temperature at a certain rate, held at that temperature, and then cooled down at a certain rate.

[0042] In some embodiments, the annealing oxidation treatment is performed at a temperature of 540–560°C.

[0043] In some embodiments, the annealing and tellurization treatment is performed at a temperature of 590–610°C.

[0044] In some embodiments, the heating rate during annealing is 1–5 °C / min, preferably 2.5–3.5 °C / min.

[0045] In some embodiments, the annealing time is 2 to 6 hours, preferably 2.5 to 3.5 hours. The annealing time described in this invention refers to the time spent holding the material at the set temperature, excluding the heating and cooling times.

[0046] Another embodiment of the present invention provides a molybdenum cobalt telluride heterostructure material obtained by the above preparation method.

[0047] A third embodiment of the present invention provides an application of the above-mentioned molybdenum cobalt telluride heterostructure material as a negative electrode in a sodium-ion battery.

[0048] Specifically, the negative electrode of a sodium-ion battery is generally obtained by mixing an active material, a conductive material (such as acetylene black, graphene, etc.), and a binder material (such as polyvinylidene fluoride, carboxymethyl cellulose, etc.) with a solvent to form a slurry, which is then coated onto a current collector and dried. In this case, by replacing the active material with the aforementioned molybdenum-cobalt telluride heterostructure material, a sodium-ion battery negative electrode can be obtained.

[0049] A fourth embodiment of the present invention provides a sodium-ion battery, wherein the active material in the negative electrode of the sodium-ion battery is the above-mentioned molybdenum-cobalt-telluride heterostructure material.

[0050] A sodium-ion battery consists of a positive electrode, a separator, an electrolyte, and a negative electrode. The positive electrode is a sodium sheet, and the electrolyte is an electrolyte containing sodium ions (such as NaPF6, NaClO4, etc.).

[0051] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0052] Example 1

[0053] The preparation of molybdenum cobalt glycerate nanospheres includes the following process steps:

[0054] Molybdenum cobalt glycerate nanospheres were synthesized via a solvothermal coprecipitation method. Cobalt nitrate hexahydrate and molybdenum acetylacetonate were used as the cobalt and molybdenum sources, respectively, in a molar ratio of 1:1 (0.20 mol each). The solvents were 15 mL of glycerol and 50 mL of isopropanol. The solvothermal reaction was carried out in a polytetrafluoroethylene reactor at 180 °C for 12 h. After washing three times with anhydrous ethanol, the nanospheres were dried in a vacuum drying oven at 65 °C for 3 h to obtain the molybdenum cobalt glycerate nanospheres. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that the molybdenum cobalt glycerate nanospheres had a uniform size of approximately 400–450 nm. Figure 1 and Figure 2 .

[0055] Example 2

[0056] The preparation of passion fruit-like molybdenum-cobalt-telluride heterostructure materials includes the following process steps:

[0057] (1) Take about 50 mg of molybdenum cobalt glycerate nanosphere precursor, calcine it in air at a temperature of 550 °C, a heating rate of 2 °C / min, an oxidation annealing time of 3 h, and a cooling rate of 5 °C / min to prepare molybdenum cobalt oxide heterostructure material.

[0058] (2) Approximately 50 mg of the above-mentioned molybdenum-cobalt oxide heterostructure material and approximately 150 mg of tellurium powder were placed at both ends of a magnetic boat. After three vacuum cycles in a tube furnace, the material was calcined at 600 °C under an Ar / H2 (95%:5% volume fraction) atmosphere at a heating rate of 2 °C / min, with a tellurization annealing time of 3 h and a cooling rate of 5 °C / min, to prepare a passion fruit-like molybdenum-cobalt telluride heterostructure material. The passion fruit-like MoTe2 / CoTe heterostructure material was characterized, and its X-ray powder diffraction pattern is shown in the figure. Figure 3 It can be concluded that the main components of the MoTe2 / CoTe material are MoTe2 and CoTe. Transmission electron microscopy (TEM) images show that the MoTe2 / CoTe material is composed of nanospheres with a diameter of approximately 400-500 nm, and the cross-linked nanoparticles have a size of approximately 20-30 nm. Figure 4 .

[0059] Electrochemical performance testing:

[0060] The passion fruit-like MoTe2 / CoTe heterostructure material obtained in this embodiment is used as a negative electrode material for sodium-ion batteries. The negative electrode material is added to secondary water with acetylene black and sodium carboxymethyl cellulose at a mass ratio of 7:2:1 and ball-milled for 3-6 hours. Then it is coated on copper foil, vacuum dried, and cut into negative electrode sheets with a diameter of 12 mm.

[0061] The sodium-ion battery was assembled using a self-made sodium sheet as the positive electrode, glass fiber (Whatman GF / F) as the separator, and NaClO4 as the main electrolyte component. (0.5 Ag) -1 The capacity-voltage plot at current density shows that the charge-discharge specific capacities in the first three cycles are as high as 258.17 / 298.41, 236.59 / 251.99, and 215.01 / 226.81 mAh g. -1 ,See Figure 5 .

[0062] Example 3

[0063] The preparation of molybdenum cobalt glycerate nanospheres includes the following process steps:

[0064] Molybdenum cobalt glycerate nanospheres were synthesized by solvothermal coprecipitation, wherein the solvent was 15 mL of glycerol and 50 mL of ethanol, and other process steps were the same as in Example 1 above.

[0065] The preparation process of the molybdenum-cobalt telluride heterostructure material is the same as in Example 2 above. The MoTe2 / CoTe heterostructure material was characterized. Scanning electron microscopy revealed that the MoTe2 / CoTe material is composed of stacked nanoparticles with a size of approximately 300 nm. No passion fruit-like spherical structures were observed. Figure 6 .

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a molybdenum-cobalt telluride heterostructure material, characterized in that, Includes the following steps: Molybdenum cobalt glycerate precursor nanospheres were synthesized by co-precipitation of divalent cobalt salt, hexavalent molybdenum salt, and glycerol in isopropanol at a temperature of 160–200 °C; the molar ratio of divalent cobalt salt to hexavalent molybdenum salt was 1:0.9–1.

1. In an air atmosphere, the molybdenum cobalt glycerate precursor nanospheres were annealed and oxidized to 500-600 °C to obtain molybdenum cobalt oxide. Under a mixed atmosphere of inertness and reduction, molybdenum cobalt oxide and a tellurium source are heated to 550~650 °C for annealing and tellurization treatment to obtain the product. The mass ratio of molybdenum cobalt oxide to tellurium powder is 1.0:2.0~5.0; the volume fraction of reducing gas in the mixed atmosphere is 5~10%.

2. The method for preparing the molybdenum-cobalt telluride heterostructure material as described in claim 1, characterized in that, The reaction time for the solvothermal method is 6–14 h.

3. The method for preparing the molybdenum-cobalt telluride heterostructure material as described in claim 1, characterized in that, The reducing gas is hydrogen.

4. The method for preparing the molybdenum-cobalt telluride heterostructure material as described in claim 1, characterized in that, The annealing and oxidation treatment temperature is 540~560 °C.

5. The method for preparing the molybdenum-cobalt telluride heterostructure material as described in claim 4, characterized in that, The annealing and tellurization treatment temperature is 590~610 °C.

6. The method for preparing the molybdenum-cobalt telluride heterostructure material as described in claim 1, characterized in that, During annealing, the heating rate is 1~5 °C / min.

7. The method for preparing the molybdenum-cobalt telluride heterostructure material as described in claim 6, characterized in that, During annealing, the heating rate is 2.5~3.5 °C / min.

8. The method for preparing the molybdenum-cobalt telluride heterostructure material as described in claim 1, characterized in that, The annealing process takes 2 to 6 hours.

9. The method for preparing the molybdenum-cobalt telluride heterostructure material as described in claim 8, characterized in that, The annealing time is 2.5~3.5 h.

10. A molybdenum-cobalt telluride heterostructure material, characterized in that, Obtained by the preparation method according to any one of claims 1 to 9.

11. The application of the molybdenum-cobalt telluride heterostructure material of claim 10 as a negative electrode in a sodium-ion battery.

12. A sodium-ion battery, characterized in that, The active material in the negative electrode of the sodium-ion battery is the molybdenum-cobalt telluride heterostructure material as described in claim 10.

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