A vanadium oxide-based cathode material, a preparation method thereof, and a secondary magnesium ion battery

Abstract

The present invention provides a method for preparing a vanadium oxide-based cathode material, comprising the following steps: mixing a composite additive material, vanadium oxide and a hydrogen peroxide solution, and performing heat treatment to obtain the vanadium oxide-based cathode material; the composite additive material includes a solution additive and a carbon-based additive; the solution additive contains a transition metal salt compound and / or a selenium compound. Compared with the prior art, the vanadium oxide-based cathode material provided by the present invention can effectively improve the microstructure of the vanadium oxide material, promote the stripping of magnesium ions and solvent ions, realize the desolvation of magnesium ions, effectively improve the diffusion rate of magnesium ions, and enable the obtained magnesium ion battery to have high reversible cycle performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary magnesium ion batteries, and particularly relates to a vanadium oxide-based cathode material, a preparation method thereof, and a secondary magnesium ion battery. Background Art

[0002] Secondary magnesium batteries are regarded as the most promising large-scale energy storage and conversion technologies in the post-lithium ion battery era. Magnesium has advantages such as high energy density, relatively low reduction potential (2.37 V), large volumetric specific capacity (3833 mAh cm -3 ), large storage capacity, rich resources, and low cost. More importantly, different from lithium metal, magnesium metal does not form dendrites during the reversible electrochemical deposition / dissolution process, so magnesium batteries do not pose serious safety hazards. Thus, the development and design of secondary magnesium batteries have potential advantages for large-scale power battery systems.

[0003] However, the sluggish kinetic behavior and charge screening effect of divalent Mg 2+ provide obstacles for the intercalation of Mg 2+ , restricting the performance of most cathode materials. During the process of ion insertion and extraction, it also has a strong Coulomb interaction with the host, severely restricting the diffusion kinetics of magnesium ions. Most critically, during the intercalation process of Mg 2+ , it combines with the solvent to form a solvated complex ion, and the solvated ion has a large radius, greatly reducing the electrochemical reaction kinetics and seriously affecting the performance of the battery. Therefore, selecting a suitable cathode material has become the key to the development of magnesium ion batteries. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a vanadium oxide-based cathode material, a preparation method thereof, and a secondary magnesium ion battery. The vanadium oxide-based cathode material has a catalytic desolvation effect, can realize the deintercalation and intercalation of single Mg 2+ in the cathode material, solve the problems such as difficult embedding of magnesium ions in the cathode material, poor battery cycle performance, and low capacity, and achieve rapid deintercalation and intercalation and rapid kinetic behavior of Mg 2+ in the electrode material.

[0005] The present invention provides a preparation method of a vanadium oxide-based cathode material, comprising the following steps:

[0006] Mix a composite additive material, vanadium oxide, and a hydrogen peroxide solution, and perform heat treatment to obtain a vanadium oxide-based cathode material;

[0007] The composite additive material includes a solution additive and a carbon-based additive; the solution additive contains a transition metal salt compound and / or a selenium-based compound.

[0008] Preferably, the mass of the transition metal salt compound and / or selenium compound in the solution additive is 0.5% to 5% of the mass of vanadium oxide;

[0009] The mass of the carbon-based additive is 5% to 25% of the mass of vanadium oxide.

[0010] Preferably, the metal ions in the transition metal salt compound are selected from one or more of cobalt ions, zinc ions, iron ions, molybdenum ions, ferrous ions, nickel ions and manganese ions.

[0011] Preferably, the solution additive includes any one or more of cobalt chloride, selenium chloride, zinc chloride, iron chloride, cobalt sulfate, molybdenum sulfate, ferrous sulfate, nickel sulfate, manganese sulfate, cobalt sulfide, molybdenum sulfide, nickel sulfide, molybdenum nitrate, iron nitrate, manganese nitrate, zinc nitrate.

[0012] Preferably, the carbon-based additive is selected from one or more of carbon nanotubes, activated carbon, graphite, hard carbon, soft carbon and graphene.

[0013] Preferably, the concentration of the transition metal salt compound and / or selenium compound in the solution additive is 0.2 to 4 mol / L;

[0014] The solvent in the solution additive is selected from one or more of methanol, ethanol, ethylene glycol, acetonitrile, carbon tetrachloride, benzene and water;

[0015] The concentration of the hydrogen peroxide solution is 20 to 40 wt.%; the mass of the hydrogen peroxide solution is 5 to 20 times the mass of vanadium oxide.

[0016] Preferably, the temperature of the heat treatment is 150 °C to 200 °C; the time of the heat treatment is 12 to 24 h.

[0017] The present invention also provides a vanadium oxide-based cathode material, which is obtained by heat treatment of a composite additive material, vanadium oxide and a hydrogen peroxide solution;

[0018] The composite additive material includes a solution additive and a carbon-based additive; the solution additive includes a transition metal salt compound and / or a selenium compound.

[0019] The present invention also provides a vanadium oxide-based cathode, including a current collector and a cathode active layer composite on the surface of the current collector; the cathode active layer includes the above vanadium oxide-based cathode material, a conductive additive and a binder.

[0020] The present invention also provides a secondary magnesium ion battery, including the above vanadium oxide-based cathode material or vanadium oxide-based cathode.

[0021] The present invention provides a method for preparing a vanadium oxide-based cathode material, comprising the following steps: mixing a composite additive material, vanadium oxide and a hydrogen peroxide solution, and performing a heat treatment to obtain the vanadium oxide-based cathode material; the composite additive material includes a solution additive and a carbon-based additive; the solution additive contains a transition metal salt compound and / or a selenium-based compound. Compared with the prior art, the vanadium oxide-based cathode material provided by the present invention can effectively improve the microstructure of the vanadium oxide material, promote the stripping of magnesium ions and solvent ions, realize the desolvation of magnesium ions, effectively improve the diffusion rate of magnesium ions, and enable the obtained magnesium ion battery to have a high reversible cycle performance.

[0022] Experimental data show that the secondary magnesium ion battery assembled with this cathode material has a high charge / discharge specific capacity, a stable Coulomb efficiency, and excellent cycle performance. More importantly, the design of this cathode material enables the battery system to have fast magnesium ion intercalation kinetics and a high energy density. The material synthesis method is simple and low-cost, and has high commercial potential. Description of the Drawings

[0023] Figure 1 is the Coulomb efficiency diagram of the battery assembled with the cathode material in Example 1 of the present invention at a current density of 50 mA g -1 ;

[0024] Figure 2 is the charge-discharge curve diagram of the first cycle of the battery assembled with the cathode material in Example 1 of the present invention at a current density of 50 mA g -1 ;

[0025] Figure 3 is the charge-discharge curve diagram of the first cycle of the battery assembled with the cathode material without the solution additive in Example 1 of the present invention at a current density of 50 mA g -1 ;

[0026] Figure 4 is the charge-discharge curve diagram of the first cycle of the battery assembled with the cathode material without the carbon-based additive in Example 1 of the present invention at a current density of 50 mA g -1 ;

[0027] Figure 5 is the electrochemical impedance diagram of the battery assembled with the cathode material in Example 1 of the present invention;

[0028] Figure 6 is the charge-discharge curve diagram of the 100th cycle of the battery assembled with the cathode material in Example 2 of the present invention at a current density of 50 mA g -1 ;

[0029] Figure 7 is the charge-discharge curve diagram of the battery assembled with the cathode material in Example 2 of the present invention at 500 mA g-1 Coulomb efficiency graph at a current density;

[0030] Figure 8 For the battery assembled with the cathode material in Example 3 of the present invention at 200 mA g -1 Coulomb efficiency graph at a current density;

[0031] Figure 9 For the battery assembled with the cathode material in Example 4 of the present invention at a current density of 50 mA g -1 Charge-discharge curve graph of the 3rd cycle;

[0032] Figure 10 For the battery assembled with the cathode material in Example 4 of the present invention at a current density of 100 mA g -1 Coulomb efficiency graph. Detailed implementation manners

[0033] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0034] The present invention provides a preparation method of a vanadium oxide-based cathode material, comprising the following steps: mixing a composite additive material, vanadium oxide and a hydrogen peroxide solution, and performing heat treatment to obtain the vanadium oxide-based cathode material; the composite additive material includes a solution additive and a carbon-based additive; the solution additive contains a transition metal salt compound and / or a selenium-based compound.

[0035] Among them, the present invention does not have special limitations on the sources of all raw materials, and they can be commercially available.

[0036] In the present invention, the composite additive material includes a solution additive and a carbon-based additive; the solution additive contains a transition metal salt compound and / or a selenium compound; the metal ion in the transition metal salt compound is preferably one or more of cobalt ion, zinc ion, iron ion, molybdenum ion, ferrous ion, nickel ion and manganese ion; the transition metal salt compound is preferably one or more of chloride, sulfate, sulfide and nitrate; the selenium compound is preferably selenium chloride; in the present invention, more preferably, the solution additive contains any one or more of cobalt chloride, selenium chloride, zinc chloride, iron chloride, cobalt sulfate, molybdenum sulfate, ferrous sulfate, nickel sulfate, manganese sulfate, cobalt sulfide, molybdenum sulfide, nickel sulfide, molybdenum nitrate, iron nitrate, manganese nitrate and zinc nitrate; the concentration of the transition metal salt compound and / or the selenium compound in the solution additive is 0.2 to 4 mol / L; the solvent in the solution additive is preferably one or more of methanol, ethanol, ethylene glycol, acetonitrile, carbon tetrachloride, benzene and water; in the vanadium oxide-based cathode material, the solution additive, first, has a catalytic effect, which can catalyze the rapid occurrence of an electrochemical reaction and promote the migration of Mg 2+ and further enhance the kinetics of the Mg 2+ intercalation reaction; second, it can improve the ionic conductivity of the vanadium oxide material; the carbon-based additive is preferably one or more of carbon nanotubes, activated carbon, graphite, hard carbon, soft carbon and graphene; in the vanadium oxide-based cathode material, the solution additive, first, serves as a carrier of the solution additive A and participates in the reaction of the battery system together; second, it enhances the electronic conductivity of the cathode material, and thus the prepared cathode has high ionic and electronic conductivity; the mass ratio of the transition metal salt compound and / or the selenium compound to the carbon-based additive in the solution additive is preferably (0.5 to 5):(5 to 25); in the examples provided by the present invention, the mass ratio of the transition metal salt compound and / or the selenium compound to the carbon-based additive is specifically 5:25, 3.5:15, 2:20 or 0.5:20; in the present invention, it is preferred to first mix the solution additive and the carbon-based additive to obtain the composite additive material; the mixing method can be the method well known to those skilled in the art and there is no special limitation. In the present invention, stirring and / or ultrasonic treatment are preferred; the power of the ultrasonic treatment is preferably 500 to 1500 W, more preferably 800 to 1200 W, and still more preferably 1000 W; the mixing time is preferably 10 to 60 min, more preferably 20 to 40 min; in the examples provided by the present invention, the mixing time is specifically 20 min, 25 min, 30 min, 35 min or 40 min, or it can also be a range value with any of the above values as the upper or lower limit; in the present invention, too long or too low stirring or ultrasonic mixing time will affect the additive effect. Too short a time is not conducive to the uniform dispersion of the additive, and too long a time will cause the additive to react with oxygen to generate by-products.

[0037] Mix the composite additive material, vanadium oxide and hydrogen peroxide solution, and perform heat treatment to obtain a vanadium oxide-based cathode material; the mass of the transition metal salt compound and / or selenium compound in the solution additive of the composite additive material is preferably 0.5% to 5% of the mass of vanadium oxide; in the examples provided by the present invention, the mass of the transition metal salt compound and / or selenium compound is specifically 5%, 3.5%, 2.0% or 0.5% of the mass of vanadium oxide; the mass of the carbon-based additive is preferably 5% to 25% of the mass of the vanadium oxide-based cathode material; in the examples provided by the present invention, the mass of the carbon-based additive is specifically 20%, 15% or 25% of the mass of vanadium oxide; the concentration of the hydrogen peroxide solution is preferably 20 to 40 wt.%, more preferably 25 to 35 wt.%, and still more preferably 30 wt.%; the mass of the hydrogen peroxide solution is preferably 5 to 20 times the mass of vanadium oxide, more preferably 10 to 20 times, and still more preferably 15 to 20 times; the temperature of the heat treatment is 150°C to 200°C; the time of the heat treatment is 12 to 24 h.

[0038] The vanadium oxide-based cathode material provided by the present invention can effectively improve the microstructure of the vanadium oxide material, promote the stripping of magnesium ions and solvent ions, realize the desolvation of magnesium ions, effectively improve the diffusion rate of magnesium ions, and enable the obtained magnesium ion battery to have high reversible cycle performance. Experimental data show that the secondary magnesium ion battery assembled with this cathode material has high charge / discharge specific capacity, stable Coulomb efficiency, and excellent cycle performance. More importantly, the design of this cathode material enables the battery system to have fast magnesium ion intercalation kinetics behavior and high energy density. The material synthesis method is simple, the cost is low, and it has high commercialization potential.

[0039] The present invention also provides a vanadium oxide-based cathode material as described above, which is obtained by heat treatment of a composite additive material, vanadium oxide and hydrogen peroxide solution; the composite additive material includes a solution additive and a carbon-based additive; the solution additive contains a transition metal salt compound and / or a selenium compound.

[0040] Among them, the solution additive, the carbon-based additive and the hydrogen peroxide solution are the same as those described above, and will not be elaborated here.

[0041] The present invention also provides a vanadium oxide-based cathode, which includes a current collector and a cathode active layer composite on the surface of the current collector; the cathode active layer includes the above-mentioned vanadium oxide-based cathode material, a conductive additive and a binder.

[0042] In the present invention, the current collector can be a current collector well-known to those skilled in the art without special limitation. In the present invention, it is preferably one or more of copper foil, aluminum foil, stainless steel foil, carbon paper and carbon cloth.

[0043] The surface of the current collector is compounded with a positive electrode active layer; the thickness of the positive electrode active layer is preferably 20-100 μm; the positive electrode active layer includes a vanadium oxide-based positive electrode material, a conductive additive and a binder; the vanadium oxide-based positive electrode material is as described above and will not be elaborated here; the conductive additive can be any conductive additive well-known to those skilled in the art without special limitations, and in the present invention, it is preferably one or more of KS-6, KS-15, SFG-6, SFG-15, Super-P, acetylene black and Ketjen black.

[0044] The present invention also provides a method for preparing the above vanadium oxide positive electrode, including: mixing the above vanadium oxide-based positive electrode material, conductive additive and binder to obtain a positive electrode material slurry; coating the positive electrode slurry on a current collector and drying to obtain a vanadium oxide-based positive electrode.

[0045] Mix the above vanadium oxide-based positive electrode material, conductive additive and binder to obtain a positive electrode material slurry; the vanadium oxide positive electrode material, conductive additive and binder are all as described above and will not be elaborated here; the mass of the conductive additive is preferably 8%-15% of the mass of the vanadium oxide-based positive electrode material, more preferably 10%-15%, and still more preferably 12.5%; the mass of the binder is preferably 8%-15% of the mass of the vanadium oxide-based positive electrode material, more preferably 10%-15%, and still more preferably 12.5%.

[0046] Coat the positive electrode slurry on a current collector and dry to obtain a vanadium oxide-based positive electrode.

[0047] The present invention also provides a secondary magnesium ion battery, including the above vanadium oxide-based positive electrode material or the above vanadium oxide-based positive electrode.

[0048] The secondary magnesium ion battery provided by the present invention includes, but is not limited to, one or more of a metal negative electrode secondary magnesium ion battery, an alloy negative electrode secondary magnesium ion battery, a composite material negative electrode secondary magnesium ion battery, and a non-metal negative electrode secondary magnesium ion battery.

[0049] In order to further illustrate the present invention, the following examples are used to describe in detail a vanadium oxide-based positive electrode material, its preparation method and a secondary magnesium ion battery provided by the present invention.

[0050] All the reagents used in the following examples are commercially available; the nano-molybdenum sulfide solution used in the examples is a 2 mol / L aqueous nano-molybdenum sulfide solution.

[0051] Example 1

[0052] Mix the nano-molybdenum sulfide solution with carbon nanotubes (below 30 nm), and perform ultrasonic treatment for 30 min with an ultrasonic power of 1000 W to obtain a composite additive.

[0053] Mix the above composite additive (in the composite additive, the mass of molybdenum disulfide is 5.0% of that of vanadium oxide, and the mass of carbon nanotubes is 25% of that of vanadium oxide) with vanadium oxide powder and 30 wt.% hydrogen peroxide solution (the mass ratio of vanadium oxide powder to hydrogen peroxide solution is 1:20), and heat-treat at 200 °C for 24 h to obtain a cathode material for a vanadium oxide-based secondary magnesium ion battery.

[0054] Mix the cathode material, conductive additive Super-P, and binder PVDF in a ratio of 8:1:1 to obtain a cathode material slurry, coat it on a current collector with a thickness of 0.01 mm, with a coating thickness of 50 μm, and dry at 80 °C for 12 h to obtain a cathode for a vanadium oxide-based secondary magnesium ion battery.

[0055] Place the cathode for the vanadium oxide-based secondary magnesium ion battery in a glove box, use activated carbon as the anode, and assemble a composite cathode / / 0.5M Mg(TFSI)2 / / AC full battery. The electrolyte solvent is ethylene glycol dimethyl ether (DME), and evaluate its cycling performance and interfacial impedance performance.

[0056] Figure 1 This is the Coulombic efficiency graph of the battery assembled with the cathode for the vanadium oxide-based secondary magnesium ion battery in Example 1 of the present invention at a current density of 50 mA g -1 -1. Figure 2 This is the charge-discharge curve graph of the battery assembled with the cathode for the vanadium oxide-based secondary magnesium ion battery in Example 1 of the present invention at a current density of 50 mA g -1 -1. Figure 3 This is the electrochemical impedance graph of the battery assembled with the cathode for the vanadium oxide-based secondary magnesium ion battery in Example 1 of the present invention.

[0057] From Figure 1 it can be seen that the assembled composite cathode / / Mg(TFSI)2 / / AC full battery still maintains a Coulombic efficiency of more than 99.9% after cycling 200 times at a current density of 50 mA g -1 -1, demonstrating the good cycling performance of this material.

[0058] From Figure 2 it can be seen that the composite cathode / / Mg(TFSI)2 / / AC full battery (single Mg 2+ intercalation) reached a high charge specific capacity and discharge specific capacity of 380 mAh g -1 -1 in the first cycle, demonstrating that the introduction of the solution additive and the carbon-based additive can promote the diffusion of ions, improve the reaction kinetics, and thus increase the battery specific capacity. Comparative experiments (solvated magnesium ion intercalation), that is, Figure 3 without introducing the solution additive, and Figure 4 without introducing the carbon-based additive, only obtained about 75 mAh g -1and about 145mAhg -1 The discharge specific capacity is significantly different from that of the composite positive electrode introduced with solution additives and carbon-based additives.

[0059] from Figure 5 It can be seen that the composite cathode / / Mg(TFSI)2 / / AC full battery has a very small interface resistance of only 2Ωcm 2 This proves the excellent performance of the positive electrode material.

[0060] Example 2

[0061] The nano-molybdenum sulfide solution was mixed with carbon nanotubes (less than 30 nm), and subjected to ultrasonic treatment for 20 minutes with an ultrasonic power of 1000 W to obtain a composite additive.

[0062] The composite additive (the mass of molybdenum sulfide in the composite additive is 3.5% of the mass of vanadium oxide, and the mass of carbon nanotubes is 15% of the mass of vanadium oxide) is mixed with vanadium oxide powder and 30wt.% hydrogen peroxide solution (the mass ratio of vanadium oxide powder to hydrogen peroxide solution is 1:20), and heated at 200°C for 24h to obtain a vanadium oxide-based secondary magnesium ion battery positive electrode material.

[0063] The positive electrode material, the conductive additive Super-P and the binder PVDF are mixed in a ratio of 8:1:1 to obtain a positive electrode material slurry, which is coated on a 0.01 mm thick current collector with a coating thickness of 50 μm. After drying at 80° C. for 12 hours, a vanadium oxide-based secondary magnesium ion battery positive electrode is obtained.

[0064] The vanadium oxide-based secondary magnesium ion battery positive electrode was placed in a glove box, and activated carbon was used as the negative electrode to assemble a composite positive electrode / / 0.5M Mg(TFSI)2 / / AC full cell. The electrolyte solvent was ethylene glycol dimethyl ether (DME), and its cyclability and interfacial impedance performance were evaluated.

[0065] Figure 6 The battery assembled with the positive electrode material in Example 2 of the present invention is subjected to a current density of 50 mA g -1 The charge and discharge curves of the third cycle are shown below. Figure 6 It can be seen that the composite cathode / / Mg(TFSI)2 / / AC full battery (single Mg 2+ Intercalation) The third cycle can reach 300mAh g -1 The high charge specific capacity and discharge specific capacity prove that the introduction of solution additives and carbon-based additives can promote the diffusion of ions, improve reaction kinetics, and thus increase the battery specific capacity.

[0066] Figure 7 The battery assembled with the vanadium oxide-based secondary magnesium ion battery positive electrode in Example 2 of the present invention is subjected to 500 mA g-1 Coulomb efficiency graph during cycling at a current density. Starting from Figure 7 As can be seen, the assembled composite cathode / / Mg(TFSI)2 / / AC full cell still maintains a Coulomb efficiency of over 99.7% after cycling 300 times at a current density of 500 mA g -1 which is similar to Example 1.

[0067] Example 3

[0068] Mix the molybdenum sulfide nanosolution with carbon nanotubes (below 30 nm), and perform ultrasonic treatment for 20 min with an ultrasonic power of 1000 W to obtain a composite additive.

[0069] Mix the above composite additive (the mass of molybdenum sulfide in the composite additive is 2.0% of that of vanadium oxide, and the mass of carbon nanotubes is 20% of the mass of vanadium oxide) with vanadium oxide powder and 30 wt.% hydrogen peroxide solution (the mass ratio of vanadium oxide powder to hydrogen peroxide solution is 1:20), and perform heat treatment at 200 °C for 24 h to obtain a cathode material for a secondary magnesium-ion battery based on vanadium oxide.

[0070] Mix the cathode material with a conductive additive Super-P and a binder PVDF in a ratio of 8:1:1, and coat the resulting cathode material slurry on a current collector with a thickness of 0.01 mm and a coating thickness of 50 μm, and dry it at 80 °C for 12 h to obtain a cathode for a secondary magnesium-ion battery based on vanadium oxide.

[0071] Place the cathode for a secondary magnesium-ion battery based on vanadium oxide in a glove box, use activated carbon as the anode, and assemble a composite cathode / / 0.5M Mg(TFSI)2 / / AC full cell. The electrolyte solvent is ethylene glycol dimethyl ether (DME), and evaluate its cycling performance and interfacial impedance performance.

[0072] Figure 8 This is the Coulomb efficiency graph during cycling at a current density of 200 mA g for the battery assembled with the cathode for a secondary magnesium-ion battery based on vanadium oxide in Example 3 of the present invention. Starting from -1 As can be seen, the assembled composite cathode / / 0.5M Mg(TFSI)2 / / AC full cell still maintains a Coulomb efficiency of over 90% after cycling 400 times at a current density of 200 mA g Figure 8 which is similar to Example 1. -1

[0073] Example 4

[0074] Mix the molybdenum sulfide nanosolution with carbon nanotubes (below 30 nm), and perform ultrasonic treatment for 35 min with an ultrasonic power of 1000 W to obtain a composite additive.

[0075] Mix the above composite additive (in the composite additive, the mass of molybdenum sulfide is 0.5% of that of vanadium oxide, and the mass of carbon nanotubes is 20% of that of vanadium oxide) with vanadium oxide powder and 30 wt.% hydrogen peroxide solution (the mass ratio of vanadium oxide powder to hydrogen peroxide solution is 1:20), and heat-treat at 200 °C for 24 h to obtain the cathode material for a secondary magnesium ion battery based on vanadium oxide.

[0076] Mix the cathode material, conductive additive Super-P, and binder PVDF in a ratio of 8:1:1 to obtain a cathode material slurry, coat it on a current collector with a thickness of 0.1 mm with a coating thickness of 50 μm, and dry at 80 °C for 12 h to obtain the cathode for a secondary magnesium ion battery based on vanadium oxide.

[0077] Place the cathode for a secondary magnesium ion battery based on vanadium oxide in a glove box, use activated carbon as the anode, and assemble a composite cathode / / 0.5M Mg(TFSI)2 / / AC full battery. The electrolyte solvent is ethylene glycol dimethyl ether (DME), and evaluate its cycling performance and interfacial impedance performance.

[0078] Figure 9 The charge-discharge curve of the battery assembled with the cathode material in Example 4 of the present invention at a current density of 50 mA g -1 at the 3rd cycle. From Figure 9 it can be seen that the composite cathode / / Mg(TFSI)2 / / AC full battery (single Mg 2+ intercalation) still maintained a charge specific capacity and a discharge specific capacity of up to 180 mAh g -1 at the 3rd cycle.

[0079] Figure 10 The Coulomb efficiency graph of the battery assembled with the cathode for a secondary magnesium ion battery based on vanadium oxide in Example 4 of the present invention at a current density of 100 mA g -1 current density. From Figure 10 it can be seen that the assembled composite cathode / / 0.5M Mg(TFSI)2 / / AC full battery still maintained a Coulomb efficiency of more than 99% after cycling 800 times at a current density of 100 mA g -1 current density, similar to Example 1.

[0080] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a vanadium oxide-based cathode material, characterized in that, Comprising the following steps: Mix a composite additive material, vanadium oxide and a hydrogen peroxide solution, and perform heat treatment to obtain a vanadium oxide-based cathode material; The composite additive material includes a solution additive and a carbon-based additive; the solution additive contains molybdenum sulfide; The mass of molybdenum sulfide in the solution additive is 0.5% - 5% of the mass of vanadium oxide; The mass of the carbon-based additive is 5% - 25% of the mass of vanadium oxide.

2. The preparation method according to claim 1, characterized in that, The carbon-based additive is selected from one or more of carbon nanotubes, activated carbon, graphite, hard carbon, soft carbon and graphene.

3. The preparation method according to claim 1, characterized in that, The concentration of molybdenum sulfide in the solution additive is 0.2 - 4 mol / L; The solvent in the solution additive is selected from one or more of methanol, ethanol, ethylene glycol, acetonitrile, carbon tetrachloride, benzene and water; The concentration of the hydrogen peroxide solution is 20 - 40 wt.%; the mass of the hydrogen peroxide solution is 5 - 20 times the mass of vanadium oxide.

4. The preparation method according to claim 1, characterized in that, The temperature of the heat treatment is 150°C - 200°C; the time of the heat treatment is 12 - 24 h.

5. The vanadium oxide-based cathode material prepared by the preparation method according to claim 1, characterized in that Obtained by heat treatment of a composite additive material, vanadium oxide and a hydrogen peroxide solution; The composite additive material includes a solution additive and a carbon-based additive; the solution additive contains molybdenum sulfide.

6. A vanadium oxide-based positive electrode, characterized in that, Comprising a current collector and a cathode active layer composite on the surface of the current collector; the cathode active layer includes the vanadium oxide-based cathode material prepared by the preparation method according to any one of claims 1 - 4 or the vanadium oxide-based cathode material according to claim 5, a conductive additive and a binder.

7. A secondary magnesium ion battery, characterized in that, Including the vanadium oxide-based cathode material prepared by the preparation method according to any one of claims 1 - 4, the vanadium oxide-based cathode material according to claim 5 or the vanadium oxide-based cathode according to claim 6.

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