Vertically oriented vanadium diselenide nanosheet self-supporting electrode as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electrode materials, in particular to a vertically-oriented vanadium diselenide nanosheet self-supporting electrode and a preparation method and application thereof.The preparation method comprises the steps that a carbon nanotube film current collector is prepared through a vacuum filtration method; a two-zone tube furnace with independent temperature control is used, Se powder is placed in an upstream temperature zone, VCl3 powder is placed between the upstream temperature zone and a downstream temperature zone, a carbon nano tube film current collector is placed in the downstream position of the VCl3 powder, the upstream temperature zone and the downstream temperature zone are heated to 350-370 DEG C and 600-650 DEG C respectively in an inert atmosphere with a certain gas carrying capacity and kept for a certain time, then natural cooling is conducted, and the Se / VCl3 / carbon nano tube film composite material is obtained. And finally, the vertically-oriented vanadium diselenide nanosheet self-supporting electrode directly grown on the surface of the carbon nanotube film current collector is obtained. The preparation method is simple, efficient and controllable. The prepared self-supporting electrode has the characteristics of high conductivity and high specific capacity, and realizes excellent capacity, rate capability and cycling stability in the application of a magnesium-lithium hybrid battery.

Description

Technical Field

[0001] The invention relates to the technical field of electrode materials, and in particular to a vertically oriented vanadium diselenide nanosheet self-supporting electrode, a preparation method and application thereof. Background Art

[0002] The demand for lithium-ion batteries has increased exponentially in recent years, driven by the growing markets for zero-emission electric vehicles, large-scale stationary storage for renewable energy production, and portable consumer electronics, and is expected to continue for at least the next few decades. However, the low natural abundance of lithium leads to an eventual shortage of lithium, and more seriously, safety concerns caused by lithium dendrites, so the development of new battery systems is crucial. Multivalent systems have shown potential as viable candidates to supplement future energy needs by adopting relatively safe metal anodes. Magnesium metal has a low reduction potential (-2.356 V vs. SHE) and a volumetric capacity of 3833 mAh cm -3 , the specific capacity is 2205mAh g -1 In particular, the natural abundance of magnesium in the earth's crust is as high as 2.3%, which makes rechargeable magnesium batteries advantageous in terms of production cost, and unlike lithium metal, magnesium has a weak tendency to dendrite, making rechargeable magnesium batteries inherently safer than lithium-ion batteries.

[0003] Despite the above advantages, the high charge density of Mg in rechargeable magnesium batteries 2+ It is very "bulky", so the traditional embedding method will become an obstacle to magnesium batteries, and there is also a serious lack of compatible positive electrode materials. These problems are huge obstacles on the road to practicality, which has prompted people to develop a dual-ion strategy, introducing active Li ions into the system. The advantages of the Mg negative electrode combined with the characteristics of rapid Li ion transmission form a magnesium-lithium hybrid battery. This "series" method is a feasible way to promote the rapid kinetics of the positive electrode, bringing more possibilities for the effective matching of the Mg negative electrode with more practical positive electrodes.

[0004] Transition metal chalcogenides are one of the most popular families of two-dimensional layered materials with extensive research interests in electrochemical energy-related fields due to their fascinating properties. The metal atoms in each monolayer are sandwiched between two chalcogenides, resulting in a stoichiometric MX2, where M is a transition metal element and X is a chalcogen such as S, Se, or Te. Se belongs to the same family as S and has some similarities with S in some properties. However, Se exhibits better metallic and intrinsic electrical properties than S. Se has a higher electrical conductivity (10 -3 S m -1 ), exceeding S(5×10 -28 S m -1). Compared with transition metal sulfides, transition metal selenides (TMSes) exhibit excellent electrical conductivity, mechanical stability, thermal stability, and rich redox properties. 1T phase vanadium diselenide is a typical metallic member of the TMSes family. Its crystal structure is similar to layered graphite, and adjacent layers are stacked together through weak van der Waals interlayer interactions along the c-axis. Because it has a large interlayer spacing (~0.61nm), it is sufficient to achieve alkali metal ion intercalation; its high conductivity (≈1000S cm -1 ) can quickly transfer electrons during circulation, making it a powerful choice for large-scale practical energy storage applications in the future. In current technology, solution methods (hydrothermal method, sol method) are more often used to synthesize vanadium selenide powder. However, this method has two disadvantages: first, the vanadium diselenide synthesized by the solution method has complex reaction steps, high solvent toxicity, and relatively low growth temperature (150-200°C), and the particles have poor crystallinity, which cannot give full play to the advantages of high conductivity; second, the powdered material needs to be mixed with additives (conductive agent, binder) to prepare electrodes, and then go through the coating and drying process before it can be used as a positive / negative electrode. The process is complicated and inefficient.

[0005] Therefore, it is particularly important to provide a fast, simple and efficient method for preparing 1T phase vanadium diselenide electrodes and achieve excellent capacity, rate capability and cycle stability. Summary of the invention

[0006] One of the purposes of the present invention is to provide a method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode, so as to quickly, simply and efficiently prepare a vanadium diselenide nanosheet self-supporting positive electrode material with high conductivity and high specific capacity.

[0007] The second object of the present invention is to provide a vertically oriented vanadium diselenide nanosheet self-supporting electrode with high conductivity and high specific capacity, which can achieve excellent capacity, rate capability and cycle stability in the application of magnesium-lithium hybrid batteries.

[0008] The third object of the present invention is to provide an application of a vertically oriented vanadium diselenide nanosheet self-supporting electrode.

[0009] The solution adopted by the present invention to achieve one of the purposes is: a method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode, comprising the following steps:

[0010] S1: Preparation of carbon nanotube film current collector by vacuum filtration method: Multi-walled carbon nanotubes are added to a solvent and ultrasonically treated to obtain a fully dispersed multi-walled carbon nanotube suspension, and then vacuum filtered to obtain a carbon nanotube film sheet, which is then dried to obtain a carbon nanotube film current collector;

[0011] S2: Growth of vanadium diselenide nanosheets by atmospheric pressure chemical vapor deposition: Use a two-zone tubular furnace with separate temperature control, place Se powder in the upstream temperature zone, place VCl3 powder between the upstream and downstream temperature zones, place the carbon nanotube film current collector downstream of the VCl3 powder, and heat the upstream and downstream temperature zones to 350-370°C and 600-650°C respectively under an inert atmosphere with a certain amount of carrier gas and maintain for a certain period of time, followed by natural cooling, to finally obtain a vertically oriented vanadium diselenide nanosheet self-supporting electrode directly grown on the surface of the carbon nanotube film current collector.

[0012] Preferably, in step S1, the solvent is at least one of N-methylpyrrolidone, water and ethanol.

[0013] Preferably, in step S1, the concentration of the multi-walled carbon nanotubes in the solvent is 0.1-0.2 mg / mL.

[0014] Preferably, in step S1, the drying temperature is 80-120°C.

[0015] Preferably, in step S2, the mass ratio of VCl3 powder to Se powder is 1:5-10.

[0016] Preferably, in step S2, the carbon nanotube film current collector is placed 2-5 cm downstream of the VCl3 powder.

[0017] Preferably, step S2 also includes a cleaning process of the chamber, and the specific steps are: before heating, a mixed carrier gas of 95% N2+5% H2 with a flow rate of 200-300sccm is used for purging. At this time, the double temperature zone of the chamber is raised from room temperature to 120-150°C within 10 minutes, and maintained for 20-30 minutes. Then, the carrier gas flow rate is reduced to 50-60sccm, and the temperature is raised for reaction. The growth time is 10-30 minutes.

[0018] By controlling the dosage of VCl3 and Se precursors and the growth time, the loading amount of the electrode active material can be directly regulated.

[0019] ~5% H2 is doped into the carrier gas in the reaction chamber to generate more active species (such as VCl - 、VCl 2- ), which increases the nucleation site density and growth rate of vanadium diselenide nanosheets.

[0020] Preferably, in step S2, the heating rates of the upstream temperature zone and the downstream temperature zone are 5-10°C / min and 10-20°C / min respectively, and the insulation time is 10-30 minutes.

[0021] The solution adopted by the present invention to achieve the second purpose is: a vertically oriented vanadium diselenide nanosheet self-supporting electrode is prepared by the method described.

[0022] The solution adopted by the present invention to achieve the third purpose is: the vertically oriented vanadium diselenide nanosheet self-supporting electrode is used as a positive electrode material in a magnesium-lithium hybrid battery.

[0023] Since metal halide precursors often provide better growth regulation and reproducibility than metal oxides, the present invention selects vanadium trichloride powder and selenium powder as precursors for atmospheric pressure chemical vapor deposition growth. Further, a simply filtered carbon nanotube film is selected as a growth substrate / current collector to directly grow 3D vertical 1T phase vanadium diselenide nanosheets. The carbon nanotube film current collector is composed of a multi-directional nanotube interwoven network, showing a unique fabric-type structure. This structure is characterized by many nanopores interwoven with undulating nanotubes, providing a significantly larger surface area than traditional 2D planar substrates, and therefore, can provide abundant nucleation sites during the growth process. And the bottom of the vanadium diselenide nanosheet is embedded in the carbon nanotube film current collector, forming a firm mosaic, which enhances the mechanical connection stability and electrical contact. In summary, metallic 1T phase vanadium diselenide is directly grown vertically on a highly conductive carbon nanotube film current collector by atmospheric pressure chemical vapor deposition. The two highly conductive materials are combined without the need for a high content of conductive carbon additives, and the self-supporting and substrate interlocking structure does not require the use of adhesives. Because they are inactive materials, they are beneficial for fully exposing active sites to the electrolyte, accelerating the lithiation / magnesiation process, and thus facilitating the realization of excellent electrochemical performance in magnesium-lithium hybrid batteries.

[0024] The present invention has the following advantages and beneficial effects:

[0025] The preparation method of the vertically oriented vanadium diselenide nanosheet self-supporting electrode of the present invention is simple, efficient and controllable, and only two steps are required from the current collector to the final electrode.

[0026] The preparation method of the vertically oriented vanadium diselenide nanosheet self-supporting electrode of the present invention has no additional added components (conductive agent, binder), and therefore no additional weight caused by inactive substances. The 1T phase vanadium diselenide prepared based on chemical vapor deposition technology has strong crystallinity, metallic properties, and strong electron transfer ability without the need to add additional conductive agents. In addition, the self-supporting structure avoids certain high electronegative groups present in the adhesive from irreversibly capturing intercalated ions, resulting in an increase in irreversible capacity.

[0027] The vertically oriented vanadium diselenide nanosheet self-supporting electrode prepared by the present invention has the characteristics of high conductivity and high specific capacity, and achieves excellent capacity, rate capability and cycle stability in the application of magnesium-lithium hybrid batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is an X-ray diffraction pattern of the vertically oriented vanadium diselenide nanosheet self-supporting electrode obtained in Example 1;

[0029] Figure 2 is a low-magnification scanning electron microscope image of the vanadium diselenide nanosheet self-supporting electrode obtained in Example 1;

[0030] Figure 3 is a high-magnification scanning electron microscope image of the vanadium diselenide nanosheet self-supporting electrode obtained in Example 1;

[0031] Figure 4 Atomic force microscopy characterization and thickness measurement of the vanadium diselenide nanosheets in the vanadium diselenide nanosheet self-supporting electrode obtained in Example 1;

[0032] Figure 5 It is the element EDS-mapping of the vanadium diselenide nanosheets in the vanadium diselenide nanosheet self-supporting electrode obtained in Example 1;

[0033] Figure 6 is a scanning electron microscope image of the connection between the bottom of the nanosheet and the carbon nanotube film current collector in the vanadium diselenide nanosheet self-supporting electrode obtained in Example 1;

[0034] Figure 7 This is a rate performance diagram of the vanadium diselenide nanosheet self-supporting electrode used in a magnesium-lithium hybrid battery in Example 1;

[0035] Figure 8 This is the short cycle performance diagram of vanadium diselenide nanosheet self-supporting electrode for magnesium-lithium hybrid battery at 200mA / g;

[0036] Fig. 9 This is a constant current charge and discharge curve diagram of the vanadium diselenide nanosheet self-supporting electrode used in a magnesium-lithium hybrid battery at 200 mA / g in Example 1;

[0037] Fig.10 This is a long cycle performance diagram of the vanadium diselenide nanosheet self-supporting electrode used in a magnesium-lithium hybrid battery at 1000 mA / g in Example 1;

[0038] Fig.11 5mg / cm in Example 2 2 High-loaded vanadium diselenide nanosheet self-supporting electrode for magnesium-lithium hybrid battery long cycle performance at 200mA / g;

[0039] Fig.12 These are low-magnification and high-magnification scanning electron microscope images showing the morphology of the vanadium diselenide nanosheet self-supporting electrode using carbon cloth as the current collector in Example 3. DETAILED DESCRIPTION

[0040] For a better understanding of the present invention, the following examples are provided to further illustrate the present invention, but the present invention is not limited to the following examples.

[0041] Example 1

[0042] S1: Preparation of carbon nanotube membrane current collector by vacuum filtration method: Pour 35 mg of multi-walled carbon nanotubes into 200 ml of N-methylpyrrolidone and ultrasonically treat for 6 hours to obtain a fully dispersed multi-walled carbon nanotube suspension, then vacuum filter to obtain a carbon nanotube membrane sheet, and finally put it in a forced air drying oven at 80°C and dry it for 24 hours to obtain a carbon nanotube membrane current collector.

[0043] S2: Growth of vanadium diselenide nanosheets by atmospheric pressure chemical vapor deposition: Using a two-zone tubular furnace with separate temperature control, 0.1g of VCl3 powder, 0.5g of Se powder, and a carbon nanotube film current collector are placed on a quartz plate (boat). The Se powder is placed in the middle of the upstream temperature zone, the VCl3 powder is placed between the upstream and downstream temperature zones, and the carbon nanotube film current collector is placed ~2cm downstream of the VCl3. Before heating, a 95% N2+5% H2 mixed carrier gas is used for purging with a flow rate of 200sccm. At this time, the chamber double temperature zone is raised from room temperature to 120°C within 10 minutes and maintained for 20 minutes to create a preferred growth atmosphere. Then the carrier gas flow rate was reduced to 50 sccm. At the same time, the upstream temperature zone and the downstream temperature zone were heated to 370°C and 600°C at a heating rate of 5°C / min and 10°C / min respectively and maintained for 10 minutes. The furnace was then allowed to enter a natural cooling process, and finally a self-supporting electrode of vanadium diselenide nanosheets directly grown on the carbon nanotube film current collector was obtained.

[0044] Figure 1 The peak position of the X-ray diffraction spectrum of the electrode prepared in the experiment matches the diffraction peak position of vanadium diselenide, which confirms the successful preparation of vanadium diselenide and its good crystallinity. The morphology of the vanadium diselenide nanosheet self-supporting electrode is characterized as follows: Figure 2 This is a low-magnification scanning electron microscope image of a vanadium diselenide nanosheet self-supporting electrode, showing the dense vertical arrangement of vanadium diselenide nanosheets. This is because the densely interwoven carbon nanotubes provide a large specific surface area, increasing the nucleation sites of vanadium diselenide, thereby achieving the formation of a dense vanadium diselenide nanosheet forest; further, by Figure 3 The local magnified scanning electron microscope image of the vanadium diselenide nanosheets shows that the grown vanadium diselenide nanosheets have regular hexagonal or nearly hexagonal morphology, indicating their high crystallinity and that the nanosheets are interconnected. Figure 4 Atomic force microscopy shows that the thickness of a single sheet is about 150nm. Figure 5EDS detection of the nanosheets revealed that the distribution of V and Se elements was consistent with the shape of the nanosheets, further confirming the composition of vanadium diselenide. By examining the connection between the vanadium diselenide nanosheets and the carbon nanotube film current collector, it was found that the bottom of the vanadium diselenide nanosheets was embedded in the vanadium diselenide ( Figure 6 ), forming a firm fit, enhancing mechanical connection stability and electrical contact.

[0045] S3: The vanadium diselenide self-supporting nanosheets obtained in step S2 are directly used as the positive electrode, and the active material loading is 3 mg / cm 2 A magnesium-lithium dual salt mixed electrolyte was prepared by dissolving 1 M LiCl in a 0.4 M PhMgCl-AlCl3 tetrahydrofuran solution. A glass fiber membrane (Whatman, GF / D) was used as a separator and a polished magnesium disc was used as the negative electrode. Button cells were assembled in an argon-filled glove box. Figure 7 The rate test in the experiment showed that at a high current density of 2000mA / g, the reversible capacity of the vanadium diselenide self-supporting nanosheet electrode was 66.3mAh / g, and after undergoing a high current test, it showed good recovery at 50mA / g, indicating that the vanadium diselenide self-supporting nanosheet electrode benefited from the excellent electronic conductivity of the vanadium diselenide nanosheet itself and the close interlocking contact with the current collector, thus showing excellent rate capability. Then, the electrochemical performance test was carried out at a current density of 200mA / g. Figure 8 The test results show that the vanadium diselenide self-supporting nanosheet electrode still retains a considerable capacity of 137mAh / g after 200 charge and discharge cycles. Fig. 9 The charge-discharge curves at different cycle numbers in the graph show that the curves still show similar profiles after a short cycle, maintaining two pairs of charge-discharge platforms, and the voltage curves at each cycle number match well, which means that the vanadium diselenide self-supporting nanosheet electrode has excellent cycle stability at low current density. Fig.10 As shown in the figure, a long cycle test was carried out. First, it was activated for three cycles with a current density of 50mA / g, and then a long cycle was carried out at a current density of 1A / g. After 3000 charge and discharge cycles, the vanadium diselenide self-supporting nanosheet electrode still maintained a reversible capacity of 64.3mAh / g, reflecting excellent long-term cycle stability.

[0046] Example 2

[0047] S1: Preparation of carbon nanotube membrane current collector by vacuum filtration method: Pour 35 mg of multi-walled carbon nanotubes into 200 ml of water and ultrasonically disperse for 6 hours to obtain a fully dispersed multi-walled carbon nanotube suspension, then vacuum filter to obtain a carbon nanotube membrane sheet, and finally put it into a forced air drying oven at 120°C and dry it for 24 hours to obtain a carbon nanotube membrane current collector.

[0048] S2: Growth of vanadium diselenide nanosheets by atmospheric pressure chemical vapor deposition: Using a two-zone tubular furnace with separate temperature control, 0.2g of VCl3 powder, 2g of Se powder, and a carbon nanotube film current collector are placed on a quartz plate (boat). The Se powder is placed in the middle of the upstream temperature zone, the VCl3 powder is placed between the upstream and downstream temperature zones, and the carbon nanotube film current collector is placed ~5cm downstream of the VCl3. Before heating, a 95% N2+5% H2 mixed carrier gas is used for purging with a flow rate of 200sccm. At this time, the chamber double temperature zone is raised from room temperature to 120°C within 10 minutes and maintained for 30 minutes to create a preferred growth atmosphere. The carrier gas flow rate was then reduced to 60 sccm. At the same time, the upstream temperature zone and the downstream temperature zone were heated to 370°C and 600°C at a heating rate of 5°C / min and 10°C / min, respectively, and maintained for 30 minutes. The furnace was then allowed to enter a natural cooling process, and finally a self-supporting electrode of vanadium diselenide nanosheets directly grown on the carbon nanotube film current collector was obtained.

[0049] S3: The vanadium diselenide self-supporting nanosheet obtained in step S2 is directly used as the positive electrode, and the active material loading is 5 mg / cm 2 . A magnesium-lithium dual salt mixed electrolyte was prepared by dissolving 1M LiCl in a 0.4M PhMgCl-AlCl3 tetrahydrofuran solution. A glass fiber membrane (Whatman, GF / D) was used as a separator and a polished magnesium disc was used as the negative electrode. Button cells were assembled in an argon-filled glove box. The electrochemical performance was tested at a current density of 200mA / g. Fig.11 The results show that the electrode can still retain a reversible capacity of 67.1 mAh / g after 500 cycles, indicating that the vanadium diselenide self-supporting nanosheet electrode can still exhibit excellent cycle stability even under such a high loading condition.

[0050] Example 3

[0051] S1: Cut a piece of carbon cloth (2*5cm), clean it with ultrasonic in acetone, anhydrous ethanol and deionized water for 5 minutes respectively, and then dry it in a forced air drying oven at 80℃ for 12h

[0052] S2: Growth of vanadium diselenide nanosheets by atmospheric pressure chemical vapor deposition: Using a two-zone tubular furnace with separate temperature control, 0.1g of VCl3 powder, 0.75g of Se powder, and a carbon cloth current collector were placed on a quartz plate (boat). The Se powder was placed in the middle of the upstream temperature zone, the VCl3 powder was placed between the upstream and downstream temperature zones, and the carbon cloth current collector was placed 2cm downstream of the VCl3. Before heating, a 95% N2+5% H2 mixed carrier gas was used for purging with a flow rate of 200sccm. At this time, the chamber double temperature zones were raised from room temperature to 120°C within 10 minutes and maintained for 20 minutes to create a preferred growth atmosphere. Subsequently, the carrier gas flow rate was reduced to 50 sccm. At the same time, the upstream and downstream temperature zones were heated to 370°C and 600°C at a heating rate of 5°C / min and 10°C / min, respectively, and maintained for 20 minutes. The furnace was then allowed to enter a natural cooling process, and finally a vanadium diselenide nanosheet self-supporting electrode directly grown on a carbon cloth current collector was obtained. The high- and low-magnification morphological characterizations of the scanning electron microscope are shown in Fig.12 middle.

[0053] S3: The vanadium diselenide self-supporting nanosheets obtained in step S2 are directly used as an integrated electrode, and the active material loading is 2 mg / cm 2 The magnesium-lithium dual salt mixed electrolyte was prepared by dissolving 1M LiCl in 0.4M PhMgCl-AlCl3 in tetrahydrofuran. A glass fiber membrane (Whatman, GF / D) was used as a separator and a polished magnesium disc was used as a negative electrode. The button cell was assembled in an argon-filled glove box and the electrochemical performance was tested.

[0054] Obviously, it is easy for a person skilled in the art to make other different forms of changes based on the above description, and it is not necessary and impossible to list all the embodiments here. The raw materials and reagents used in the present invention are all commercially available, and various changes or modifications to the material composition and dosage, process time, etc. in these embodiments belong to the protection scope of the present invention.

Claims

1. A method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode, characterized in that: The following steps are involved: S1: Preparation of carbon nanotube film current collector by vacuum filtration method: Multi-walled carbon nanotubes are added to a solvent and ultrasonically treated to obtain a fully dispersed multi-walled carbon nanotube suspension, and then vacuum filtered to obtain a carbon nanotube film sheet, which is then dried to obtain a carbon nanotube film current collector; S2: Growth of vanadium diselenide nanosheets by atmospheric pressure chemical vapor deposition: Use a two-zone tubular furnace with separate temperature control, place Se powder in the upstream temperature zone, place VCl3 powder between the upstream and downstream temperature zones, place the carbon nanotube film current collector downstream of the VCl3 powder, and heat the upstream and downstream temperature zones to 350-370°C and 600-650°C respectively under an inert atmosphere with a certain amount of carrier gas and maintain them for a certain period of time, followed by natural cooling, to finally obtain a vertically oriented vanadium diselenide nanosheet self-supporting electrode directly grown on the surface of the carbon nanotube film current collector.

2. The method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode according to claim 1, characterized in that: In the step S1, the solvent is at least one of N-methylpyrrolidone, water and ethanol.

3. The method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode according to claim 1, characterized in that: In the step S1, the concentration of the multi-walled carbon nanotubes in the solvent is 0.1-0.2 mg / mL.

4. The method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode according to claim 1, characterized in that: In the step S1, the drying temperature is 80-120°C.

5. The method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode according to claim 1, characterized in that: In the step S2, the mass ratio of VCl3 powder to Se powder is 1:5-10.

6. The method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode according to claim 1, characterized in that: In the step S2, the carbon nanotube film current collector is placed 2-5 cm downstream of the VCl3 powder.

7. The method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode according to claim 1, characterized in that: The step S2 also includes a cleaning process of the chamber, and the specific steps are: before heating, a mixed carrier gas of 95% N2+5% H2 with a flow rate of 200-300 sccm is used for purging. At this time, the double temperature zone of the chamber is raised from room temperature to 120-150°C within 10 minutes, maintained for 20-30 minutes, and then the carrier gas flow rate is reduced to 50-60 sccm, and the temperature is raised for reaction.

8. The method for preparing a vertically oriented vanadium diselenide nanosheet self-supporting electrode according to claim 1, characterized in that: In the step S2, the heating rates of the upstream temperature zone and the downstream temperature zone are 5-10°C / min and 10-20°C / min respectively, and the insulation time is 10-30 minutes.

9. A vertically oriented vanadium diselenide nanosheet self-supporting electrode, characterized in that: The method according to any one of claims 1 to 8 is adopted to prepare the present invention.

10. Use of the vertically oriented vanadium diselenide nanosheet self-supporting electrode according to claim 9 as a positive electrode material in a magnesium-lithium hybrid battery.

Images