Lithium metal-vanadium-based oxide secondary battery and preparation method thereof
By adopting a lithium-vanadium-based oxide secondary battery, utilizing a vanadium-based oxide cathode, a lithium metal anode, and a LiFSI-KFSI molten salt electrolyte, the low energy density of lithium-ion batteries and the safety issues of high-temperature molten salt batteries are solved, achieving high specific capacity, long cycle stability, and low-cost battery performance, suitable for large-scale energy storage and power supply in special environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-04-07
AI Technical Summary
Existing lithium-ion batteries have low energy density, and traditional high-temperature molten salt batteries operate at excessively high temperatures and pose safety risks, making it difficult to meet the needs of large-scale energy storage applications.
A lithium-vanadium oxide secondary battery is adopted, using vanadium oxide as the positive electrode material, lithium metal as the negative electrode, and a molten salt system of LiFSI and KFSI as the electrolyte. The operating temperature is between 70-200℃. The membrane material is optimized by combining appropriate conductive agents and binders.
It achieves battery performance with high specific capacity, long cycle stability, high energy density, low cost and high safety, and is suitable for large-scale energy storage and power supply scenarios in special environments.
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Abstract
Description
Technical Field
[0001] This invention relates to energy storage batteries, and more specifically to a lithium-vanadium-based oxide secondary battery and its preparation method, which is particularly suitable for large-scale electrochemical energy storage, new energy supporting energy storage, and power supply scenarios under special environments. Background Technology
[0002] With the large-scale application of renewable energy sources such as wind and solar power becoming a core direction of energy transformation, efficient and stable large-scale energy storage systems are key to solving the intermittency and volatility issues of renewable energy. Electrochemical energy storage technology converts electrical energy into chemical energy for storage through electrochemical reactions. Due to its advantages such as high energy density, fast response speed, and flexible installation, it has been widely used in power system peak shaving, new energy vehicles, portable electronic devices, and other fields. Its main forms include lithium-ion batteries, sodium-ion batteries, flow batteries, and high-temperature molten salt batteries. For example, lithium-ion batteries have been widely used in portable electronic devices, electric vehicles, and large-scale energy storage due to their excellent electrochemical performance.
[0003] However, existing electrochemical energy storage technologies still face many bottlenecks that urgently need to be addressed. In the field of lithium-ion batteries, the theoretical specific capacity of traditional cathode materials (such as lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and ternary materials) is generally below 200 mAh / g, severely limiting further improvements in battery energy density. Furthermore, their high cost and insufficient safety also constrain large-scale energy storage applications. While sodium-ion batteries have potential advantages in terms of cost, their safety still needs further verification. Flow batteries, on the other hand, face the problem of persistently high costs, making it difficult to meet the demands of large-scale deployment.
[0004] To overcome energy density limitations, researchers have turned their attention to vanadium-based oxides (including V₂O₅, V₂O₄, V₂O₃, and VO). Vanadium possesses multiple variable valences, allowing it to theoretically achieve reversible capacities exceeding 350 mAh / g when used as a cathode material in lithium-ion batteries, far surpassing traditional cathode materials. However, in traditional liquid electrolyte systems, vanadium-based oxides suffer from slow electrochemical reaction kinetics, significant volume expansion, and unstable electrode-electrolyte interfaces, resulting in limited actual discharge capacity, low discharge voltage, and poor cycle stability, severely restricting their large-scale application. For example, the V₂O₅ thin-film electrode reported by Samuel A. Hevia et al. only achieved a reversible capacity of 271 mAh / g at 0.5C. Similarly, the layered nanofiber V₂O₅ developed by Lijie Song et al. only achieved a reversible capacity of 311.6 mAh / g at a current density of 0.1 A / g, failing to fully realize the high capacity potential of vanadium-based oxides.
[0005] Previous studies have explored battery systems using molten salts as electrolytes, but all have significant drawbacks. The liquid metal battery developed by the MIT Sadoway team employs a three-layer liquid composition, naturally separating due to density differences. The top layer (negative electrode) is a low-density liquid metal (such as lithium or magnesium), the middle layer is a molten salt electrolyte (such as LiCl-KCl or Lii-Ki), and the bottom layer (positive electrode) is a high-density liquid metal alloy (such as lead-antimony or bismuth-tin). To ensure that the molten salt electrolyte has sufficiently high ionic conductivity, its operating temperature needs to reach above 400°C. High-temperature sodium-sulfur (Na-S) batteries use molten liquid sodium (Na) as the negative electrode and liquid sulfur (S) as the positive electrode. The electrolyte is solid β-alumina ceramic (Na⁺ ion conductor). They are mainly used in grid-scale energy storage (such as products from NGK Corporation of Japan) and have been applied in demonstration projects in the United States, Japan, France and other countries. In order to maintain the molten state of the electrodes, the operating temperature is around 300-350℃. This not only poses a safety risk of high-temperature fire caused by the reaction of liquid sodium and sulfur after the electrolyte membrane is damaged, but also an explosion risk when exposed to water. In addition, the need for complex anti-corrosion and heat insulation design leads to high cost and difficult maintenance. The principle of high-temperature sodium-nickel chloride batteries (Na-NiCl2 / ZEBRA batteries) is similar to that of Na-S batteries, but the cathode material uses a mixture of solid NiCl2 and NaCl, the electrolyte uses β"-alumina ceramic, and a molten NaAlCl4 secondary electrolyte is used to enhance electrochemical performance and safety. Its operating temperature is above 300℃. Even with some low-temperature improvements, such as liquid metal batteries incorporating rubidium or cesium salts, the operating temperature is still above 270℃, failing to completely solve the technical challenges posed by high temperatures. Summary of the Invention
[0006] To address the problems of low energy density in existing lithium-ion batteries and excessively high operating temperatures in traditional high-temperature molten salt batteries, this invention aims to provide a lithium-vanadium-based oxide secondary battery and its preparation method, achieving a balance between high specific capacity, high energy density, high safety, mild operating temperature, and low cost.
[0007] The lithium-vanadium-based oxide secondary battery according to the present invention comprises a positive electrode, a negative electrode, and an electrolyte, wherein the active material of the positive electrode is a vanadium-based oxide, which is vanadium pentoxide, V2O4, V2O3, VO, carbon-coated vanadium pentoxide, or vanadium pentoxide doped with a heterogeneous element, wherein the heterogeneous element is one or more of Ti, Al, Cr, K, Na, or Zn; the negative electrode is a lithium metal-based material; and the electrolyte is a molten salt system of LiFSI and KFSI.
[0008] In a preferred embodiment, the LiFSI and KFSI are mixed in a molar ratio of 56:44.
[0009] In a preferred embodiment, the electrolyte contains 10% by mass of CsFSI as an additive.
[0010] In a preferred embodiment, the positive electrode is made by mixing the vanadium-based oxide, a conductive agent, and a binder.
[0011] In a preferred embodiment, the conductive agent is Super P, the binder is PVDF, and the vanadium-based oxide, conductive agent, and binder are mixed in a mass ratio of 90:5:5.
[0012] In a preferred embodiment, the active material of the positive electrode is micron-sized vanadium pentoxide.
[0013] In a preferred embodiment, the lithium metal-based material is a Li-M alloy material, where M is Mg, Al, In, Sb, or Sn. In a preferred embodiment, the negative electrode is a lithium metal foil or a lithium-based composite foil, where the lithium-based composite foil is a Li-Al alloy foil or a Li-In alloy foil.
[0014] In a preferred embodiment, the lithium-vanadium oxide secondary battery includes a separator, which is a glass fiber separator, a PP separator, a modified PP separator, a PE separator, or a polyimide separator.
[0015] In a preferred embodiment, the operating temperature of the lithium-vanadium-based oxide secondary battery is 70-200°C.
[0016] The method for preparing a lithium-vanadium-based oxide secondary battery according to the present invention includes the following steps: S1, preparing a positive electrode using vanadium-based oxide, providing a negative electrode using lithium metal, and providing an electrolyte through a molten salt system of LiFSI and KFSI; S2, completing battery encapsulation at 70-90°C in a glove box with a water and oxygen content of less than 0.5 ppm.
[0017] The lithium-vanadium-based oxide secondary battery and its preparation method according to the present invention have advantages such as specific capacity greater than 350 mAh / g, energy density higher than 900 Wh / kg, excellent cycle stability, high safety, and low cost, and can be widely used in large-scale energy storage, power supply in special high-temperature environments and other scenarios. Detailed Implementation
[0018] The lithium-vanadium-based oxide secondary battery according to the present invention includes a positive electrode, a negative electrode, an electrolyte, and a separator.
[0019] The positive electrode is prepared by mixing an active material, a conductive agent, and a binder. The active material is a vanadium-based oxide, which can provide high specific capacity and high energy density compared with traditional ion battery positive electrode materials. The vanadium-based oxide is vanadium pentoxide (V₂O₅), V₂O₄, V₂O₃, VO, carbon-coated vanadium pentoxide, or vanadium pentoxide doped with a heteroelement, wherein the heteroelement is one or more of Ti, Al, Cr, K, Na, or Zn. In a preferred embodiment, the vanadium-based oxide is inexpensive micron-sized vanadium pentoxide, which has a significant cost advantage. In a preferred embodiment, the conductive agent is Super P. In a preferred embodiment, the binder is PVDF. In a preferred embodiment, the active material, conductive agent, and binder are mixed in a mass ratio of 90:5:5.
[0020] The negative electrode is prepared using lithium metal foil or lithium-based composite foil (including Li-Al alloy foil, Li-In alloy foil, etc.). Lithium metal is used as the negative electrode material because it is abundant in reserves and inexpensive to produce, thus offering a significant cost advantage. Furthermore, the theoretical specific capacity of the lithium metal negative electrode is extremely high (3860 mAh / g), with an electrode potential of only -3.04 V vs. a standard hydrogen electrode (SHE) and a density of only 0.534 g / cm³. 3 .
[0021] The electrolyte is a molten salt system consisting of lithium bisfluorosulfonylimide (LiFSI, chemical formula F2NLiO4S2) and potassium bisfluorosulfonylimide (KFSI, chemical formula KN(SO2F)2) mixed in a molar ratio of 56:44. Compared to organic liquid electrolytes, this molten salt system does not use organic solvents, resulting in significantly improved safety; compared to solid electrolytes, it eliminates interface problems and exhibits high ionic conductivity. At room temperature, this molten salt system is solid, becoming liquid at 60°C, and provides sufficiently high ionic conductivity at, for example, 80°C. In particular, this molten salt system has excellent compatibility with vanadium-based oxides, which exhibit superior electrochemical performance and cycle stability within this system. In a preferred embodiment, 10% by mass of cesium bisfluorosulfonylimide (CsFSI) can be added to the molten salt system as an additive to lower the melting point and improve performance.
[0022] The diaphragm is selected from one of the following: glass fiber diaphragm, PP diaphragm, modified PP diaphragm, PE diaphragm or polyimide diaphragm.
[0023] The operating temperature is between 70℃ and 200℃. The operating temperature of the lithium-vanadium oxide secondary battery can be less than 200℃, far lower than existing high-temperature Na-S batteries and liquid metal batteries. In a preferred embodiment, the operating temperature is 80℃.
[0024] The lithium-vanadium-based oxide secondary battery obtained by this invention exhibits excellent electrochemical performance, including advantages such as high specific capacity, long cycle life, high energy density, high efficiency, high safety, high temperature characteristics, and good cycle stability. The average operating voltage is 2.4-2.8V, and it exhibits a reversible capacity of more than 350mAh / g, with an energy density of more than 900Wh / kg.
[0025] Preferred embodiments of the present invention are given below and described in detail.
[0026] Example 1: Lithium metal anode || LiFSI + KFSI molten salt electrolyte || Vanadium pentoxide cathode
[0027] The positive electrode active material (vanadium pentoxide), conductive agent Super P, and binder PVDF are mixed at a mass ratio of 90:5:5 to prepare a uniform slurry. The slurry is coated on the surface of Al current collector, and after drying, rolling, cutting, and weighing, the finished positive electrode sheet is obtained.
[0028] Commercially available Li foil was selected as the negative electrode material to obtain the negative electrode sheet.
[0029] Prepare a mixed molten salt electrolyte with a LiFSI to KFSI molar ratio of 56:44, and accurately weigh 70 mg as the electrolyte.
[0030] Inside a glove box (with water and oxygen levels less than 0.5 ppm), the positive electrode, glass fiber separator, and negative electrode are stacked in sequence, and the weighed mixed molten salt electrolyte is injected to assemble a complete battery. During the assembly process, the temperature inside the glove box is kept at 80°C (the assembly temperature can be adjusted within the range of 70-90°C).
[0031] After the battery is assembled, an electrochemical cycle test is conducted at 80℃ (the operating temperature can be adjusted within the range of 70-200℃).
[0032] Tests showed that the battery in this embodiment had an average operating voltage of 2.6V, a specific capacity of 380mAh / g, an energy density of 988Wh / kg, and a capacity retention rate of 81% after 100 cycles, demonstrating excellent basic electrochemical performance.
[0033] Example 2: Lithium metal anode || LiFSI + KFSI molten salt electrolyte || Carbon-coated vanadium pentoxide cathode
[0034] The positive electrode active material (carbon-coated vanadium pentoxide), conductive agent Super P, and binder PVDF are mixed at a mass ratio of 90:5:5 to prepare a uniform slurry. The slurry is coated on the surface of the Al current collector, and after drying, rolling, cutting, and weighing, the finished positive electrode sheet is obtained.
[0035] Commercially available Li foil was selected as the negative electrode material to obtain the negative electrode sheet.
[0036] Prepare a mixed molten salt electrolyte with a LiFSI to KFSI molar ratio of 56:44, and accurately weigh 70 mg as the electrolyte.
[0037] Inside a glove box (with water and oxygen levels less than 0.5 ppm), the positive electrode, glass fiber separator, and negative electrode are stacked in sequence, and a weighed mixed molten salt electrolyte is injected to assemble a complete battery. During the assembly process, the temperature inside the glove box is maintained at 80°C.
[0038] After the battery is assembled, an electrochemical cycle test is conducted at 80°C.
[0039] Tests showed that the battery in this embodiment had an average operating voltage of 2.6V, a specific capacity of 382mAh / g, and a capacity retention rate of 90% after 100 cycles. The carbon coating modification effectively improved the cycle stability of the battery.
[0040] Example 3: Lithium metal anode || LiFSI + KFSI molten salt electrolyte || Zn-doped vanadium pentoxide cathode
[0041] The positive electrode active material (Zn-doped vanadium pentoxide), conductive agent Super P, and binder PVDF are mixed at a mass ratio of 90:5:5 to prepare a uniform slurry. The slurry is coated on the surface of the Al current collector, and after drying, rolling, cutting, and weighing, the finished positive electrode sheet is obtained.
[0042] Commercially available Li foil was selected as the negative electrode material to obtain the negative electrode sheet.
[0043] Prepare a mixed molten salt electrolyte with a LiFSI to KFSI molar ratio of 56:44, and accurately weigh 70 mg as the electrolyte.
[0044] Inside a glove box (with water and oxygen levels less than 0.5 ppm), the positive electrode, glass fiber separator, and negative electrode are stacked in sequence, and a weighed mixed molten salt electrolyte is injected to assemble a complete battery. During the assembly process, the temperature inside the glove box is maintained at 80°C.
[0045] After the battery is assembled, an electrochemical cycle test is conducted at 80°C.
[0046] Tests showed that the battery in this embodiment had an average operating voltage of 2.6V, a specific capacity of 378mAh / g, and a capacity retention rate of 89% after 100 cycles. Zn doping modification achieved a balance between capacity and cycle stability.
[0047] Example 4: Lithium metal anode || LiFSI + KFSI + 10% wt. CsFSI molten salt electrolyte || Vanadium pentoxide cathode
[0048] The positive electrode active material (vanadium pentoxide), conductive agent Super P, and binder PVDF are mixed at a mass ratio of 90:5:5 to prepare a uniform slurry. The slurry is coated on the surface of Al current collector, and after drying, rolling, cutting, and weighing, the finished positive electrode sheet is obtained.
[0049] Commercially available Li foil was selected as the negative electrode material to obtain the negative electrode sheet.
[0050] In a mixed molten salt of LiFSI and KFSI with a molar ratio of 56:44, 10% by mass of CsFSI was added as an additive, stirred evenly, and 70 mg was accurately weighed as the electrolyte.
[0051] Inside a glove box (with water and oxygen levels less than 0.5 ppm), the positive electrode, glass fiber separator, and negative electrode are stacked in sequence, and a weighed mixed molten salt electrolyte is injected to assemble a complete battery. During the assembly process, the temperature inside the glove box is maintained at 80°C.
[0052] After the battery is assembled, an electrochemical cycle test is conducted at 80°C.
[0053] According to the test, the battery in this embodiment has an average operating voltage of 2.6V, a specific capacity of 395mAh / g, and a capacity retention rate of 94% after 100 cycles. CsFSI improves capacity and cycle stability.
[0054] Example 5: Lithium-aluminum composite negative electrode || LiFSI+KFSI molten salt electrolyte || Vanadium pentoxide positive electrode
[0055] The positive electrode active material (vanadium pentoxide), conductive agent Super P, and binder PVDF are mixed at a mass ratio of 90:5:5 to prepare a uniform slurry. The slurry is coated on the surface of Al current collector, and after drying, rolling, cutting, and weighing, the finished positive electrode sheet is obtained.
[0056] Commercial lithium-aluminum composite foil was selected as the negative electrode material to obtain the negative electrode sheet.
[0057] Prepare a mixed molten salt electrolyte with a LiFSI to KFSI molar ratio of 56:44, and accurately weigh 70 mg as the electrolyte.
[0058] Inside a glove box (with water and oxygen levels less than 0.5 ppm), the positive electrode, glass fiber separator, and negative electrode are stacked in sequence, and a weighed mixed molten salt electrolyte is injected to assemble a complete battery. During the assembly process, the temperature inside the glove box is maintained at 80°C.
[0059] After the battery is assembled, an electrochemical cycle test is conducted at 80°C.
[0060] Tests showed that the battery in this embodiment had an average operating voltage of 2.4V, a specific capacity of 382mAh / g, and a capacity retention rate of up to 96% after 100 cycles. The lithium-aluminum composite anode significantly improved the cycle stability of the battery.
[0061] Example 6: Lithium-aluminum composite negative electrode || LiFSI+KFSI molten salt electrolyte || Vanadium pentoxide positive electrode
[0062] The positive electrode active material (vanadium pentoxide), conductive agent Super P, and binder PVDF are mixed at a mass ratio of 90:5:5 to prepare a uniform slurry. The slurry is coated on the surface of Al current collector, and after drying, rolling, cutting, and weighing, the finished positive electrode sheet is obtained.
[0063] Commercial lithium-aluminum composite foil was selected as the negative electrode material to obtain the negative electrode sheet.
[0064] Prepare a mixed molten salt electrolyte with a LiFSI to KFSI molar ratio of 56:44, and accurately weigh 70 mg as the electrolyte.
[0065] Inside a glove box (with water and oxygen levels less than 0.5 ppm), the positive electrode, high-temperature resistant PP separator, and negative electrode are stacked in sequence, and the weighed mixed molten salt electrolyte is injected to assemble a complete battery. During the assembly process, the temperature inside the glove box is maintained at 80°C.
[0066] After the battery is assembled, an electrochemical cycle test is conducted at 80°C.
[0067] Tests showed that the battery in this embodiment had an average operating voltage of 2.6V, a specific capacity of 375mAh / g, and a capacity retention rate of 83% after 100 cycles, demonstrating good compatibility with the high-temperature resistant PP separator.
[0068] Example 7: Lithium metal anode || LiFSI + KFSI molten salt electrolyte || Vanadium pentoxide cathode
[0069] The positive electrode active material (vanadium pentoxide), conductive agent Super P, and binder PVDF are mixed at a mass ratio of 90:5:5 to prepare a uniform slurry. The slurry is coated on the surface of Al current collector, and after drying, rolling, cutting, and weighing, the finished positive electrode sheet is obtained.
[0070] Commercially available Li foil was selected as the negative electrode material to obtain the negative electrode sheet.
[0071] Prepare a mixed molten salt electrolyte with a LiFSI to KFSI molar ratio of 56:44, and accurately weigh 70 mg as the electrolyte.
[0072] Inside a glove box (with water and oxygen levels less than 0.5 ppm), the positive electrode, glass fiber separator, and negative electrode are stacked in sequence, and a weighed mixed molten salt electrolyte is injected to assemble a complete battery. During the assembly process, the temperature inside the glove box is maintained at 80°C.
[0073] After the battery is assembled, an electrochemical cycle test is conducted at 100°C.
[0074] According to the test, the battery in this embodiment has an average operating voltage of 2.8V, a specific capacity of 401mAh / g, and a capacity retention rate of 90% after 100 cycles. The higher operating temperature further improves the specific capacity of the battery.
[0075] The relevant parameters in the above embodiments can be found in Table 1 below.
[0076] Table 1
[0077]
[0078] In summary, the positive electrode of this invention uses vanadium-based oxide, exhibiting excellent electrochemical performance in molten salt electrolytes, providing a reversible capacity exceeding 350 mAh / g and a battery energy density as high as 900 Wh / kg, far surpassing traditional lithium-ion batteries (generally less than 200 mAh / g). Even with micron-sized materials (diameters selectable between 1 and 20 micrometers), it maintains good cycle stability. Moreover, the electrolyte of this invention has a low melting point of 60°C, requiring a battery operating temperature of only 70-200°C, far lower than traditional high-temperature molten salt batteries (above 300°C), reducing the difficulty of heat preservation and corrosion prevention design. Furthermore, the electrolyte of this invention uses a LiFSI-KFSI mixed molten salt, which does not contain flammable and explosive organic solvents and is free of high-risk materials such as liquid sodium, avoiding the risks of fire and explosion; at the same time, the electrolyte has good compatibility with the positive and negative electrodes and excellent interface stability. In addition, the electrode material of the present invention is a commercial product, the electrolyte is a low-cost molten salt system, the preparation process is simple and does not require complex processes, making it suitable for large-scale production. By modifying the positive electrode (carbon coating, element doping), adding additives to the electrolyte, changing the type of negative electrode or the separator material, the battery cycle stability, specific capacity and other performance can be further optimized.
[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims. All aspects not described in detail in this invention are conventional technical content.
Claims
1. A lithium-vanadium-based oxide secondary battery, characterized in that, The lithium-vanadium-based oxide secondary battery includes a positive electrode, a negative electrode, and an electrolyte. The active material of the positive electrode is a vanadium-based oxide, which is vanadium pentoxide, V2O4, V2O3, VO, carbon-coated vanadium pentoxide, or vanadium pentoxide doped with a heteroelement. The heteroelement is one or more of Ti, Al, Cr, K, Na, or Zn. The negative electrode is a lithium metal-based material, and the electrolyte is a molten salt system of LiFSI and KFSI.
2. The lithium-vanadium-based oxide secondary battery according to claim 1, characterized in that, The LiFSI and KFSI are mixed at a molar ratio of 56:
44.
3. The lithium-vanadium-based oxide secondary battery according to claim 2, characterized in that, The electrolyte contains 10% by mass of CsFSI as an additive.
4. The lithium-vanadium-based oxide secondary battery according to claim 1, characterized in that, The positive electrode is made by mixing the vanadium-based oxide, conductive agent and binder.
5. The lithium-vanadium-based oxide secondary battery according to claim 4, characterized in that, The conductive agent is SuperP, the binder is PVDF, and the vanadium-based oxide, conductive agent and binder are mixed in a mass ratio of 90:5:
5.
6. The lithium-vanadium-based oxide secondary battery according to claim 1, characterized in that, The active material of the positive electrode is micron-sized vanadium pentoxide.
7. The lithium-vanadium-based oxide secondary battery according to claim 1, characterized in that, The lithium metal-based material is a Li-M alloy material, where M is Mg, Al, In, Sb, or Sn.
8. The lithium-vanadium-based oxide secondary battery according to claim 1, characterized in that, The lithium-vanadium-based oxide secondary battery includes a separator, which is a glass fiber separator, a PP separator, a modified PP separator, a PE separator, or a polyimide separator.
9. The lithium-vanadium-based oxide secondary battery according to claim 1, characterized in that, The operating temperature of this lithium-vanadium-based oxide secondary battery is 70-200℃.
10. The method for preparing a lithium-vanadium-based oxide secondary battery according to claims 1-9, characterized in that, The preparation method includes the following steps: S1 uses vanadium-based oxide to prepare the positive electrode, lithium metal to provide the negative electrode, and a molten salt system of mixed LiFSI and KFSI to provide the electrolyte; S2, battery encapsulation is completed in a glove box with a water and oxygen content of less than 0.5 ppm at 70-90°C.