A VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating, and its preparation method and application

Abstract

The present invention relates to the technical field of magnesium-based battery electrode materials, and specifically to a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating, a preparation method and application thereof, comprising the following steps: preparing a carbon nanotube film current collector by vacuum filtration; growing VSe2 flakes by atmospheric pressure chemical vapor deposition; and repeatedly alternating pulse injection deposition of EDOT monomer and oxidant on the surface of the prepared integrated electrode to obtain a VSe2 self-supporting structure integrated electrode coated with a PEDOT coating. The preparation method of the present invention is simple and controllable. There are no additional additives, and therefore no additional weight of inactive substances. The 1T phase VSe2 has metallic properties, and the electrical conductivity can reach 1000 S cm ‑1 It has strong electron transfer capability without the need for additional conductive agents. It has the characteristics of high conductivity and high specific capacity, and the PEDOT coating solves the problem of mechanical degradation caused by repeated ion insertion and de-insertion between layers.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium-based battery electrode materials, and in particular to a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating, a preparation method thereof, and applications thereof. Background Art

[0002] In recent years, the demand for lithium-ion batteries has been growing exponentially due to the growing markets for zero-emission electric vehicles, large-scale stationary storage for renewable energy production, and portable consumer electronics. This demand 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. Therefore, the development of new battery systems is crucial. Multivalent systems have shown potential as viable candidates that can 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 , with a specific capacity of 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 have advantages in production costs. Unlike lithium metal, magnesium has a very weak tendency to dendrite, and rechargeable magnesium batteries are inherently safer than lithium-ion batteries.

[0003] Despite the above advantages, the high charge density of Mg in rechargeable magnesium batteries 2+ The traditional intercalation method is a significant obstacle to magnesium batteries due to its heavy weight, and compatible cathode materials are also severely lacking. These issues are significant obstacles to practical application, prompting the development of a dual-ion strategy that introduces active Li ions into the system, leveraging the advantages of the Mg anode combined with the rapid transport properties of Li ions to form a magnesium-lithium hybrid battery. This "series" approach is a viable way to promote rapid cathode kinetics, opening up new possibilities for effectively pairing the Mg anode with more practical cathodes.

[0004] Transition metal chalcogenides are one of the most popular families of two-dimensional layered materials, with extensive research interest 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 chalcogenide 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 ), more than S(5×10 -28 S m -1Compared with transition metal sulfides, transition metal selenides (TMSes) exhibit excellent electrical conductivity, mechanical stability, thermal stability, and rich redox properties. 1T-VSe2 is a typical metallic member of the TMSes family. Its crystal structure is similar to that of layered graphite, with adjacent layers 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 cycling, making it a promising candidate for future large-scale practical energy storage applications.

[0005] However, layered VSe2 has some challenging problems when storing guest ions, including slow kinetics of ion diffusion and large strain due to volume changes and structural damage during the charge and discharge process, resulting in rapid capacity decay. In current technology, the preparation of layered VSe2 nanomaterials, especially VSe2 nanosheets, is a solution. However, due to the van der Waals interaction between adjacent nanosheets, VSe2 nanosheets are prone to aggregation, thereby extending the diffusion distance of Li ions and reducing the storage active sites on the surface or edge of the layered VSe2. And one thing that cannot be ignored is that its manufacturing steps are cumbersome and the cost is extremely high. Existing technology shows that coating the surface of the electrode material can effectively alleviate the problems of electrode mechanical failure and interface instability. Unfortunately, most coatings (carbon coatings, oxide coatings) have poor mechanical properties and it is impossible to achieve precise control of the coating thickness.

[0006] Therefore, it is crucial to develop a simple, fast and efficient method for preparing VSe2 electrodes and provide an electrode coating that can be precisely controlled to suppress mechanical failure. Summary of the Invention

[0007] One of the purposes of the present invention is to provide a method for preparing a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT (poly 3,4-ethylenedioxythiophene) coating, which is simple and controllable.

[0008] The second purpose of the present invention is to provide a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating, which has high conductivity and high specific capacity, and solves the mechanical degradation problem caused by repeated ion insertion and deintercalation through PEDOT coating, so that it is more suitable for the application of magnesium-lithium hybrid batteries.

[0009] A third object of the present invention is to provide an application of a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating.

[0010] The solution adopted by the present invention to achieve one of the objectives is: a method for preparing a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating, comprising the following steps:

[0011] S1: Preparation of carbon nanotube membrane current collector by vacuum filtration: Multi-walled carbon nanotubes are added to a solvent and ultrasonically treated to obtain a fully dispersed multi-walled carbon nanotube suspension. The carbon nanotube membrane is then vacuum filtered to obtain a carbon nanotube membrane sheet, which is then dried to obtain a carbon nanotube membrane current collector.

[0012] S2: VSe2 flakes grown by atmospheric pressure chemical vapor deposition: Using a two-zone tubular furnace with separate temperature control, Se powder is placed in the upstream temperature zone, VCl3 powder is placed between the upstream and downstream temperature zones, and the carbon nanotube film current collector is placed downstream of the VCl3 powder. In an inert atmosphere with a certain amount of carrier gas, the upstream and downstream temperature zones are heated to 350-370°C and 600-650°C respectively and maintained for a certain period of time, followed by natural cooling, and finally a VSe2 integrated electrode directly grown on the surface of the carbon nanotube film current collector is obtained.

[0013] S3: Molecular layer deposition of PEDOT coating: EDOT monomer and oxidant are repeatedly and alternately pulse-sprayed on the surface of the integrated electrode prepared in step S2 to obtain a VSe2 self-supporting structure integrated electrode coated with a PEDOT coating.

[0014] Preferably, in step S1, the solvent is at least one of N-methylpyrrolidone, water, and ethanol.

[0015] Preferably, in step S1, the concentration of the multi-walled carbon nanotubes in the solvent is 0.1-0.2 mg / mL.

[0016] Preferably, in step S1, the drying temperature is 80-120°C.

[0017] Preferably, in step S2, the mass ratio of VCl3 powder to Se powder is 1:5-10.

[0018] Preferably, in step S2, the carbon nanotube film current collector is placed 2-5 cm downstream of the VCl3 powder.

[0019] Preferably, step S2 further includes a chamber cleaning process, specifically comprising the following steps: before heating, using a mixed carrier gas purge of 95% N2+5% H2 at a flow rate of 200-300 sccm; at this time, raising the chamber dual temperature zone from room temperature to 120-150°C within 10 minutes, maintaining the temperature for 20-30 minutes, and then reducing the carrier gas flow rate to 50-60 sccm, and heating the reaction for a growth time of 10-30 minutes.

[0020] By controlling the amount of VCl3 and Se precursors and the growth time, the loading amount of the electrode active material can be directly regulated.

[0021] Preferably, in step S3, the oxidant is at least one of MoCl5, ReCl5, and SbCl5, the heating temperature of the oxidant is 180-200°C, the pulse pressure is 1-3 Pa, the heating temperature of the EDOT monomer is 100-120°C, the pulse pressure is 5-10 Pa., and the deposition temperature is 130-160°C.

[0022] Preferably, the deposition temperature is 150°C.

[0023] The amount of oxidant added is excessive.

[0024] The solution adopted by the present invention to achieve the second purpose is: a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating is prepared by the method described above.

[0025] The solution adopted by the present invention to achieve the third purpose is: the application of the VSe2 self-supporting structure electrode coated with the ultra-thin conformal PEDOT coating as the positive electrode material in the magnesium-lithium hybrid battery.

[0026] The specific steps of molecular layer deposition of PEDOT coating are as follows: transferring the grown integral electrode into a molecular layer deposition reaction chamber, heating it to the deposition temperature, and heating the source bottle containing the oxidant and EDOT monomer to obtain sufficient vapor pressure. Then, the EDOT monomer is first pulse-sprayed into the chamber, followed by purging with an inert carrier gas, and then the oxidant is pulse-sprayed again, followed by purging with an inert carrier gas again. This process is repeated alternately until the deposition is completed to obtain a VSe2 self-supporting integral electrode coated with a PEDOT coating. The inert carrier gas is nitrogen or argon. The heating temperatures of the oxidant and EDOT source bottle are 180-200°C and 100-120°C, respectively.

[0027] The present invention has the following advantages and beneficial effects:

[0028] The preparation method of the VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating of the present invention is simple and controllable, and only three steps are required from the current collector to the final electrode.

[0029] The preparation method of the present invention does not require any additional additives (conductive agents, binders), so there is no additional weight of inactive substances. The 1T phase VSe2 has metallic properties and the electrical conductivity can reach 1000 S cm -1 It has a strong electron transfer ability without the need for additional conductive agents. In addition, it avoids certain highly electronegative groups in the binder from irreversibly capturing intercalated ions, resulting in an increase in irreversible capacity.

[0030] The VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating of the present invention has the characteristics of high conductivity and high specific capacity, and the PEDOT coating solves the problem of mechanical degradation caused by repeated ion insertion and extraction between layers. The PEDOT coating has high electronic ionic conductivity and viscoelastic properties. Such mechanical properties can better adapt to the volume changes of VSe2 during repeated ion insertion and extraction, relieve stress, and achieve low molecular layer deposition temperature. Compared with the uneven coating and uncontrollable thickness of the commonly used solution coating method, the coating of the present invention is more uniform. The thickness of the coating can be controlled by the number of molecular layer deposition cycles, and its precision control can reach the angstrom level, which is conducive to achieving excellent electrochemical performance.

[0031] The VSe2 self-supporting structure electrode coated with the ultra-thin conformal PEDOT coating of the present invention can be applied to magnesium-lithium hybrid batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a scanning electron microscope image of the VSe2 self-supporting structure electrode prepared by the present invention in Example 1;

[0033] Figure 2 This is a scanning electron microscope image of the contact position between the bottom of the VSe2 nanosheet and the carbon nanotube film current collector in the VSe2 self-supporting structure electrode prepared by the present invention in Example 1;

[0034] Figure 3 is a scanning electron microscope image of the VSe2 self-supporting structure electrode prepared by the present invention in Example 1 after 10 cycles of molecular layer deposition;

[0035] Figure 4 is a transmission electron micrograph of the VSe2 nanosheets prepared by the present invention in Example 1 after 10 cycles of molecular layer deposition;

[0036] Figure 5 is a transmission electron micrograph of the uncoated VSe2 nanosheets prepared by the present invention in Example 1;

[0037] Figure 6 This is the elemental EDS-mapping of the VSe2 nanosheets prepared by the present invention after 10 cycles of molecular layer deposition in Example 1;

[0038] Figure 7 is the X-ray diffraction pattern of the VSe2 self-supporting structure electrode after 10 cycles of molecular layer deposition prepared by the present invention in Example 1 and the uncoated one;

[0039] Figure 8 10 cycles of molecular layer deposition prepared by the present invention in Example 1 and the uncoated VSe2 self-supporting structure electrode for magnesium-lithium hybrid batteries;

[0040] Figure 9 1 is a graph showing the long cycle performance of the VSe2 self-supporting structure electrode prepared by the present invention after 10 cycles of molecular layer deposition and an uncoated VSe2 self-supporting structure electrode at a current density of 1 A / g;

[0041] Figure 10 These are scanning electron microscope images of the molecular layer deposition electrode prepared by the present invention in Example 1 after 10 cycles and the uncoated VSe2 self-supporting structure electrode after 500 cycles at a current density of 1 A / g.

[0042] Figure 11 is a transmission electron micrograph of the VSe2 nanosheets prepared by the present invention after 20 cycles of molecular layer deposition in Example 2;

[0043] Figure 12 2 is a graph showing the short cycle performance of the VSe2 self-supporting structure electrode prepared by the present invention after 20 cycles of molecular layer deposition and an uncoated VSe2 self-supporting structure electrode at a current density of 200 mA / g;

[0044] Figure 13 The 5mg / cm 2 Short-cycle performance of the uncoated VSe2 free-standing structure electrode at a current density of 200 mA / g after 10 cycles of molecular layer deposition under high loading. DETAILED DESCRIPTION

[0045] 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.

[0046] Example 1

[0047] S1: Preparation of carbon nanotube membrane current collector by vacuum filtration: 35 mg of multi-walled carbon nanotubes were poured into 200 ml of N-methylpyrrolidone and ultrasonically treated for 6 h to obtain a fully dispersed multi-walled carbon nanotube suspension, and then vacuum filtered to obtain a carbon nanotube membrane sheet. Finally, the carbon nanotube membrane was placed in a forced air drying oven at 80°C and dried for 24 h to obtain a carbon nanotube membrane current collector.

[0048] S2: Atmospheric pressure chemical vapor deposition growth of VSe2 nanosheets: Using a two-zone tube furnace with independent temperature control, 0.1g of VCl3 powder, 0.5g of Se powder, and a carbon nanotube film 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 nanotube film current collector was placed ~2cm downstream of the VCl3. Before heating, a 95% N2 + 5% H2 mixed carrier gas was used for purging at a flow rate of 200-300sccm. At this time, the chamber's two temperature zones were raised from room temperature to 120°C within 10 minutes and maintained for 20 minutes to create an optimal growth atmosphere. Then 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 10 minutes. The furnace was then allowed to enter a natural cooling process, and finally a VSe2 integrated electrode directly grown on the carbon nanotube film current collector was obtained. Figure 1 As shown in the low-magnification scanning electron microscope (SEM) image of the vanadium diselenide nanosheet self-supporting electrode, the VSe2 nanosheets exhibit a tightly packed vertically arranged structure. This is because the dense carbon nanotubes are intertwined, providing a large specific surface area, increasing the VSe2 nucleation sites, and thus achieving the formation of a dense VSe2 nanosheet forest; further, through the local magnification SEM image of the nanosheet, it can be seen that the grown VSe2 nanosheets exhibit regular hexagonal or nearly hexagonal morphological features, indicating their high crystallinity and that the nanosheets are interconnected. By examining the connection between the VSe2 nanosheet and the carbon nanotube film current collector, it was found that the bottom of the VSe2 nanosheet was embedded in the VSe2 ( Figure 2 ), forming a firm fit and enhancing mechanical connection stability and electrical contact.

[0049] S3: Molecular layer deposition of PEDOT coating: The grown electrode is transferred to the molecular layer deposition reaction chamber, the chamber is heated to 150°C, MoCl5 powder is used as the oxidant, and EDOT is used as the reaction monomer. It is placed in a source bottle to supply the precursor. The two source bottles are maintained at 180°C and 100°C respectively, thereby maintaining the high vapor pressure of the two precursors to obtain a sufficient supply of precursors. The chamber's base pressure is ~600mtorr, using nitrogen as the carrier gas (150sccm). The cyclic process of molecular layer deposition of PEDOT includes ~1s EDOT pulse + ~100s nitrogen pulse + ~5s MoCl5 pulse + ~100s nitrogen pulse, and 10 cycles of deposition are performed. The morphology of the coated electrode was characterized by SEM ( Figure 3 ).and Figure 2In contrast, no significant morphological changes were observed after PEDOT deposition, demonstrating the remarkable super-conformality of the molecular layer deposition technique. To further confirm the presence and uniformity of PEDOT, transmission electron microscopy and energy dispersive X-ray spectroscopy (EDS) elemental mapping analysis were performed on the coated VSe2 nanosheets. Figure 4 A uniform amorphous layer with a thickness of ∼5 nm was confirmed along the edges of the nanosheets. For comparison, uncoated VSe2 nanosheets were also characterized by TEM ( Figure 5 ), where no coating was observed along the edges, Figure 6 EDS elemental mapping reveals the concentration distribution of V, Se, S, O, and C elements in the surface area of ​​the nanosheets, among which S, O, and C are characteristic elements of PEDOT. The presence of these elements and their uniform aggregation in the coating area confirm the deposition of PEDOT on the VSe2 nanosheets and further demonstrate the unparalleled superconformality exhibited by the MLD technology. Figure 7 The X-ray diffraction (XRD) analysis of the electrode is given. The XRD patterns of the electrode before and after coating have the same characteristics and the crystal structure does not change during the molecular layer deposition process, which is very consistent with the standard card PDF#89-1641 of VSe2.

[0050] S4: The VSe2 coated with 10 cycles of PEDOT obtained in S3 was directly used as the positive electrode, with an active material loading of 3 mg / cm 2 A magnesium-lithium double salt mixed electrolyte was prepared by dissolving 1M LiCl in a 0.4M tetrahydrofuran solution of PhMgCl-AlCl3. 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 and electrochemical performance tests were performed at a current density of 200mA / g. Figure 8 As shown. After 200 charge and discharge cycles, the uncoated electrode maintained a considerable capacity of 137 mAh / g, while after 10 cycles of coating, the retention capacity increased to 172.9 mAh / g, and the decay of the voltage curve was significantly suppressed. A long cycle test was then carried out, first activating it for three cycles with a current density of 50 mA / g, and then long cycling was carried out at a current density of 1 A / g, as shown. Figure 9 As shown in the figure, the uncoated electrode maintained a considerable capacity of 64.3 mAh / g after 3000 charge and discharge cycles, while the capacity was increased to 107.3 mAh / g after 10 cycles of coating, reflecting excellent cycle stability. Figure 10The SEM image of the electrode after the intermediate cycle showed that the surface of the uncoated VSe2 sheet had a large amount of peeling and severe cracking after 500 cycles at 1 A / g, confirming that it suffered relatively severe mechanical damage during the cycle. In contrast, the VSe2 sheet coated with 10 cycles of PEDOT maintained its structural integrity well and did not suffer from serious fractures and layer peeling, indicating that under the protection of the viscoelastic PEDOT coating, the stress of VSe2 was relieved during the cycle and it had enhanced mechanical properties, which is an important reason for the further improvement of electrochemical performance.

[0051] Example 2

[0052] S1: Preparation of carbon nanotube membrane current collector by vacuum filtration: 35 mg of multi-walled carbon nanotubes were poured into 200 ml of N-methylpyrrolidone and ultrasonically treated for 6 h to obtain a fully dispersed multi-walled carbon nanotube suspension, and then vacuum filtered to obtain a carbon nanotube membrane sheet. Finally, the carbon nanotube membrane was placed in a forced air drying oven at 80°C and dried for 24 h to obtain a carbon nanotube membrane current collector.

[0053] S2: Atmospheric pressure chemical vapor deposition growth of VSe2 nanosheets: Using a two-zone tube furnace with independent temperature control, 0.1g of VCl3 powder, 0.5g of Se powder, and a carbon nanotube film 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 nanotube film current collector was placed ~2cm downstream of the VCl3. Before heating, a 95% N2 + 5% H2 mixed carrier gas was used for purging at a flow rate of 200-300sccm. At this time, the chamber's two temperature zones were raised from room temperature to 120°C within 10 minutes and maintained for 20 minutes to create an optimal growth atmosphere. The carrier gas flow rate was then reduced to 50 sccm. At the same time, the upstream and downstream temperature zones were heated to 370°C and 600°C at heating rates 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 VSe2 integrated electrode directly grown on the carbon nanotube film current collector was obtained.

[0054] S3: Molecular layer deposition of PEDOT coating: The grown electrode is transferred to the molecular layer deposition reaction chamber, the chamber is heated to 150°C, MoCl5 powder is used as the oxidant, and EDOT is placed in a source bottle as a reaction monomer to supply the precursor. The two source bottles are maintained at 200°C and 120°C respectively, thereby maintaining high vapor pressure of the two precursors to obtain sufficient precursor supply. The chamber's base pressure is ~600mtorr, using nitrogen as the carrier gas (150sccm). The cyclic process of molecular layer deposition of PEDOT includes ~1s EDOT pulse + ~100s nitrogen pulse + ~5s MoCl5 pulse + ~100s nitrogen pulse, and 20 cycles of deposition are performed, through Figure 11 TEM images confirmed that a 10 nm coating layer was obtained.

[0055] S4: The VSe2 coated with 20 cycles of PEDOT obtained in S3 was directly used as an integrated electrode, with an active material loading of 3 mg / cm 2 A magnesium-lithium double salt mixed electrolyte was prepared by dissolving 1M LiCl in a 0.4M tetrahydrofuran solution of PhMgCl-AlCl3. 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 and electrochemical performance tests were performed at a current density of 200mA / g. Figure 12 After 20 cycles of coating, the storage capacity increased to 148.8 mAh / g, still showing improved cycle stability.

[0056] Example 3

[0057] S1: Preparation of carbon nanotube membrane current collector by vacuum filtration: 35 mg of multi-walled carbon nanotubes were poured into 200 ml of water and ultrasonically dispersed for 6 h to obtain a fully dispersed multi-walled carbon nanotube suspension. The carbon nanotube membrane was then vacuum filtered to obtain a carbon nanotube membrane sheet. The carbon nanotube membrane was finally placed in a forced air drying oven at 120°C and dried for 24 h to obtain a carbon nanotube membrane current collector.

[0058] S2: Atmospheric Pressure Chemical Vapor Deposition (APCVD) Growth of VSe2 Nanosheets: Using a two-zone tube furnace with independent temperature control, 0.2g of VCl3 powder, 2g of Se powder, and a carbon nanotube film 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 nanotube film current collector was placed ~5cm downstream of the VCl3. Before heating, a 95% N2 + 5% H2 carrier gas mixture was purged at a flow rate of 200sccm. The chamber's two temperature zones were then heated from room temperature to 120°C over 10 minutes and held for 30 minutes to create an optimal growth atmosphere. The carrier gas flow rate was then reduced to 60sccm. Simultaneously, the upstream and downstream temperature zones were heated at ramp rates of 5°C / min and 10°C / min to 370°C and 600°C, respectively, and held for 30 minutes. The furnace was then allowed to cool naturally, resulting in a VSe2 integrated electrode grown directly on the carbon nanotube film current collector.

[0059] S3: Molecular layer deposition (MLD) of PEDOT coating: The grown electrode is transferred to a MLD reaction chamber, which is heated to 150°C. MoCl5 powder is used as the oxidant, and EDOT is placed in source bottles to supply the precursors. The two source bottles are maintained at 180°C and 100°C, respectively, to maintain high vapor pressures of the two precursors and ensure sufficient precursor supply. The chamber's base pressure is ~600 mtorr, using nitrogen as the carrier gas (150 sccm). The MLD PEDOT cycle consists of a ~1s EDOT pulse followed by a ~100s nitrogen pulse, a ~5s MoCl5 pulse, and a ~100s nitrogen pulse. Ten cycles of this cycle produce a 5nm coating.

[0060] S4: The VSe2 coated with 10 cycles of PEDOT obtained in S3 was directly used as an integrated electrode with an active material loading of 5 mg / cm 2 A magnesium-lithium double salt mixed electrolyte was prepared by dissolving 1M LiCl in a 0.4M tetrahydrofuran solution of PhMgCl-AlCl3. 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 and electrochemical performance tests were performed at a current density of 200mA / g. Figure 13 After 10 cycles of coating, the retention capacity increased to 103.8 mAh / g, indicating that despite the high active material loading, the molecular layer deposited 5 nm PEDOT coating combined with the free-standing VSe2 electrode can still show significantly improved cycling stability.

[0061] The above description is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principles of the present invention. These improvements and changes are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating, characterized in that: The following steps are involved: S1: Preparation of carbon nanotube membrane current collector by vacuum filtration: Multi-walled carbon nanotubes are added to a solvent and ultrasonically treated to obtain a fully dispersed multi-walled carbon nanotube suspension. The carbon nanotube membrane is then vacuum filtered to obtain a carbon nanotube membrane sheet, which is then dried to obtain a carbon nanotube membrane current collector. S2: VSe2 flakes grown by atmospheric pressure chemical vapor deposition: Using a two-zone tubular furnace with separate temperature control, Se powder is placed in the upstream temperature zone, VCl3 powder is placed between the upstream and downstream temperature zones, and the carbon nanotube film current collector is placed downstream of the VCl3 powder. In an inert atmosphere with a certain amount of carrier gas, the upstream and downstream temperature zones are heated to 350-370°C and 600-650°C respectively and maintained for a certain period of time, followed by natural cooling, and finally a VSe2 integrated electrode directly grown on the surface of the carbon nanotube film current collector is obtained. S3: Molecular layer deposition of PEDOT coating: EDOT monomer and oxidant are repeatedly and alternately pulse-sprayed on the surface of the integrated electrode prepared in step S2 to obtain a VSe2 self-supporting structure integrated electrode coated with a PEDOT coating.

2. The method for preparing a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating according to claim 1, characterized in that: In step S1, the solvent is at least one of N-methylpyrrolidone, water, and ethanol.

3. The method for preparing a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating according to claim 1, characterized in that: In 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 VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating according to claim 1, characterized in that: In step S1, the drying temperature is 80-120°C.

5. The method for preparing a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating according to claim 1, characterized in that: In step S2, the mass ratio of VCl3 powder to Se powder is 1:5-10.

6. The method for preparing a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating 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 VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating according to claim 1, characterized in that: The step S2 also includes a cleaning process of the chamber, and the specific steps are as follows: 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 dual temperature zones of the chamber are raised from room temperature to 120-150°C within 10 minutes and maintained for 20-30 minutes. Subsequently, the carrier gas flow rate is reduced to 50-60 sccm, and the temperature is raised for reaction. The growth time is 10-30 minutes.

8. The method for preparing a VSe2 self-supporting structure electrode coated with an ultra-thin conformal PEDOT coating according to claim 1, characterized in that: In step S3, the oxidant is at least one of MoCl5, ReCl5, and SbCl5, the heating temperature of the oxidant is 180-200°C, the pulse pressure is 1-3 Pa, the heating temperature of the EDOT monomer is 100-120°C, the pulse pressure is 5-10 Pa, and the deposition temperature is 130-160°C.

9. A VSe2 self-supporting structure electrode coated with an ultrathin conformal PEDOT coating, characterized by: Prepared by the method according to any one of claims 1 to 8.

10. Use of the VSe2 self-supporting structure electrode coated with the ultra-thin conformal PEDOT coating as claimed in claim 9 as a positive electrode material in a magnesium-lithium hybrid battery.

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