Magnesium / alkali metal hybrid battery containing layered MnO2 positive electrode material and preparation method of magnesium / alkali metal hybrid battery

Abstract

The invention discloses a magnesium / alkali metal hybrid battery containing a layered MnO2 positive electrode material, which comprises a positive pole piece, a negative pole piece and a magnesium / alkali metal double-salt electrolyte, the positive pole piece comprises the layered MnO2 positive electrode material, the negative pole piece comprises the layered MnO2 positive electrode material, and the magnesium / alkali metal double-salt electrolyte comprises the layered MnO2 negative electrode material. The negative pole piece is pure magnesium metal, and the electrolyte is magnesium / alkali metal double-salt electrolyte. The invention also provides a preparation method of the magnesium / alkali metal hybrid battery containing the layered MnO2 positive electrode material. The high-magnesium / alkali metal hybrid battery provided by the invention has a high voltage window; compared with the prior art, the layered manganese dioxide positive electrode material has the advantages that dendritic crystals are not easily generated on the magnesium negative electrode side, meanwhile, the advantage of high ion migration rate of alkali metal ions in the positive electrode material is achieved, the electrochemical performance of the layered manganese dioxide positive electrode material in a high-voltage magnesium-based hybrid battery is improved, and the layered manganese dioxide positive electrode material is a low-cost and high-safety novel secondary battery system.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel high-voltage magnesium-based hybrid battery materials, and specifically relates to a novel high-voltage magnesium-based hybrid battery material containing layered MnO 2 A magnesium / alkali metal hybrid battery with positive electrode material and a method for preparing the same. Background Art

[0002] At a time when the demand for energy storage is rising, battery technology is developing in a diversified way. In addition to the most widely used lithium-ion batteries, emerging battery systems based on abundant and low-cost magnesium and sodium are also experiencing unprecedented development momentum in the field of electrochemical research and application. Since magnesium is abundant in the earth's crust, has low cost, and is only 1 / 25-1 / 50 of the price of lithium, magnesium negative electrodes are not prone to dendrite growth during the electrochemical process, have high volume energy density, and are environmentally friendly and highly safe. Rechargeable magnesium-based hybrid batteries can complement lithium-ion batteries (LIBs). In order to fully tap the application potential of magnesium-based energy storage batteries, the selection of suitable cathode materials is crucial to the overall electrochemical performance of magnesium-ion battery systems.

[0003] Transition metal oxide cathode materials have high theoretical capacity, simple synthesis process and low cost. Taking manganese dioxide cathode materials as an example, manganese dioxide cathodes have been widely studied in lithium, sodium and other secondary ion batteries. They have the advantages of low cost, large specific capacity and good cycle performance. However, in magnesium batteries, due to the interaction between divalent magnesium ions and the anion framework (O 2- ) have a strong Coulomb force between each other, which makes it difficult for magnesium ions to be quickly and reversibly deintercalated in the crystal structure, affecting the electrochemical properties of the positive electrode material.

[0004] Given the limited selection of magnesium storage cathode materials and their poor performance, in order to overcome the limitations of magnesium battery cathode materials, a feasible and effective solution for constructing a rechargeable magnesium-based hybrid battery is to match the traditional alkali metal embedded cathode with the magnesium metal anode, and combine it with a magnesium / alkali metal double salt electrolyte to construct a magnesium / alkali metal hybrid battery system. During discharge, the alkali metal ions / magnesium ions are embedded in the cathode, and the magnesium ions are electrochemically dissolved on the magnesium metal anode side and enter the electrolyte. During charging, the alkali metal ions / magnesium ions are deintercalated from the cathode crystal structure and enter the electrolyte, and the magnesium ions are electrochemically deposited on the anode surface. Since the redox potential of magnesium metal (-2.37V vs SHE) is higher than that of alkali metal (Li / Na), it can be ensured that only magnesium ions are reduced on the magnesium metal anode, and dendrites are not easily generated on the anode side, so that safety is guaranteed. Rechargeable magnesium-based hybrid batteries have the advantages of both alkali metal ion batteries and magnesium ion batteries, and are a new type of secondary battery system with good prospects. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the main purpose of the present invention is to provide a layered MnO 2 The magnesium / alkali metal hybrid battery with positive electrode material is used to solve the problem that the discharge capacity of manganese dioxide positive electrode material is low and the energy density is not high enough in the charging and discharging process of traditional magnesium battery. 2+ Problems include slow diffusion kinetics and poor rate performance.

[0006] The magnesium / alkali metal hybrid battery of the present invention uses layered δ-phase manganese dioxide as the positive electrode material, combines with magnesium / alkali metal double salt electrolyte, and constructs a high-voltage magnesium / alkali metal hybrid battery system, thereby improving the electrochemical performance of the layered δ-phase manganese dioxide positive electrode material in the magnesium-based hybrid battery system; and because the prepared layered δ-MnO 2 Compared with the tunnel-type structure, manganese dioxide has a wider interlayer spacing, and it is easier to insert magnesium / alkali metal ions during the charge and discharge process, thereby obtaining higher electrochemical performance; in addition, the magnesium / alkali metal double salt electrolyte provided by the present invention can not only achieve a high voltage window, but also match the traditional magnesium metal negative electrode, thereby obtaining a high-voltage magnesium-based hybrid battery.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A layered MnO 2 A magnesium / alkali metal hybrid battery with positive electrode materials comprises a positive electrode plate, a negative electrode plate and a magnesium / alkali metal double salt electrolyte, wherein the positive electrode plate comprises a layered manganese dioxide positive electrode material, the negative electrode plate is pure magnesium metal, and the electrolyte is a magnesium / alkali metal double salt electrolyte.

[0009] In some specific embodiments, the positive electrode plate further includes a current collector, a positive electrode material layer coated on the current collector, and the positive electrode material layer includes a layered manganese dioxide positive electrode material, a conductive additive and a binder.

[0010] In some specific embodiments, the alkali metal in the magnesium / alkali metal double salt electrolyte is one of Li, Na, and K.

[0011] In certain specific embodiments, it is characterized in that in the magnesium / alkali metal double salt electrolyte, the molar ratio of Mg and alkali metal atoms is (0.1-2):1.

[0012] In some specific embodiments, the layered manganese dioxide positive electrode material is prepared by the following method, specifically: dissolving carbon nanotubes, manganese sulfate and potassium permanganate in deionized water in a certain proportion, stirring to form a uniform solution, and transferring the solution to a constant temperature oven for hydrothermal growth to obtain a layered manganese dioxide positive electrode material.

[0013] In some specific embodiments, the mass ratio of the carbon nanotubes, manganese sulfate and potassium permanganate is (0.02-0.06) g: (0.1-0.2) g: (0.5-1.5) g, and the process conditions of the hydrothermal growth are: maintaining at 120-180° C. for 8-12 hours.

[0014] In certain specific embodiments, the magnesium / alkali metal double salt electrolyte is prepared by the following method, specifically: under an inert atmosphere, magnesium bis(trifluoromethylsulfonyl imide) and lithium / sodium bis(trifluoromethylsulfonyl imide) are dissolved in ethylene glycol dimethyl ether in different proportions to form a uniform clear solution;

[0015] Add dioxymethylethylamine solution as a stabilizing additive to the clear solution, stir until a uniform clear solution is formed, and finally obtain a magnesium / alkali metal / double salt electrolyte.

[0016] In certain specific embodiments, the layered MnO 2 A magnesium / alkali metal hybrid battery with positive electrode material, characterized in that the molar ratio of magnesium bistrifluoromethylsulfonyl imide to lithium / sodium bistrifluoromethylsulfonyl imide is 1:(0.5-3).

[0017] The present invention also provides a kind of layered MnO 2 A method for preparing a magnesium / alkali metal hybrid battery of a positive electrode material, characterized in that it comprises the following steps:

[0018] 1) Preparation of positive electrode

[0019] The layered manganese dioxide positive electrode material, the conductive additive and the binder are mixed into a slurry, uniformly coated on the current collector, and dried to obtain a positive electrode sheet;

[0020] 2) Preparation of magnesium / alkali metal hybrid batteries

[0021] Under an inert atmosphere, the positive electrode sheet prepared in step 1) is used, pure magnesium metal is used as the negative electrode sheet, and a magnesium / alkali metal double salt solution is used as the electrolyte to assemble a high-voltage magnesium / alkali metal hybrid battery.

[0022] The mass ratio of the layered manganese dioxide, the conductive agent and the binder is 7:2:1; the current collector is Al foil; the conductive additive is Super P; and the binder is polyvinylidene fluoride (PVDF).

[0023] Compared with the prior art, the present invention has at least the following advantages:

[0024] 1) The present invention provides a layered MnO 2The magnesium / alkali metal hybrid battery of the positive electrode material; while taking advantage of the inherent advantages of magnesium batteries, it also has the advantages of the rapid ion migration rate of lithium (sodium) ions in the positive electrode material, with a higher discharge voltage platform, higher first-cycle charge and discharge specific capacity and cycle stability. Therefore, combining layered manganese dioxide positive electrode materials with magnesium / alkali metal double salt electrolytes to construct high-voltage magnesium / alkali metal hybrid batteries is an effective way for new secondary battery systems to become practical;

[0025] 2) The layered MnO provided by the present invention 2 The preparation method of the positive electrode material has simple and easy steps, abundant raw material resources, low cost, small batch difference, and conventional equipment used in the process, which is easy to apply in large-scale production;

[0026] 3) The magnesium / alkali metal double salt electrolyte provided by the present invention can ensure that only magnesium ions are reduced on the magnesium metal negative electrode, and dendrites are not easily generated on the negative electrode side, thereby improving the intrinsic safety of the battery; the double salt electrolyte can alleviate the Mg(TFSI) 2 The base electrolyte is passivated on the magnesium metal negative electrode, and at the same time has a high voltage window that is difficult to achieve in traditional magnesium-based hybrid batteries. The assembled high-voltage magnesium / alkali metal hybrid battery also has excellent electrochemical properties and is a new type of secondary battery system with good prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention, the drawings required for use in the specific embodiments or the description of the prior art will be briefly introduced below.

[0028] Figure 1 The layered MnO provided in Example 1 of the present invention 2 XRD pattern of positive electrode material;

[0029] Figure 2 The layered MnO provided in Example 1-1 of the present invention 2 SEM images of cathode materials;

[0030] Figure 3 The charge and discharge curve of the magnesium metal battery provided in Example 2 of the present invention;

[0031] Figure 4 The charge and discharge curves of the high voltage magnesium / lithium metal hybrid battery provided in Example 3 of the present invention;

[0032] Figure 5 The charge and discharge curves of the high voltage magnesium / lithium metal hybrid battery provided in Example 4 of the present invention;

[0033] Figure 6The charge and discharge curves of the high voltage magnesium / sodium metal hybrid battery provided in Example 5 of the present invention;

[0034] Figure 7 This is the charge and discharge curve of the high voltage magnesium / sodium metal hybrid battery provided in Example 6 of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following embodiments are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0036] When a certain amount, concentration or other value or parameter is expressed in the form of a range, a preferred range, or a preferred upper and lower numerical limit, it should be understood that it is equivalent to specifically revealing any range by combining any pair of upper range limits or preferred numerical values ​​with any lower range limit or preferred numerical value, regardless of whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values ​​listed herein include the endpoints of the range, and all integers and fractions within the range.

[0037] Unless otherwise stated, all percentages, parts, ratios, etc. herein are by weight. The materials, methods, and examples herein are exemplary and should not be construed as limiting unless otherwise stated. The raw materials, equipment or devices used in the production and testing processes used herein, unless otherwise stated, can be purchased through commercial channels or obtained by conventional preparation methods in the art.

[0038] The layered manganese dioxide positive electrode material in the present application can be prepared by the following preparation method: potassium permanganate, a manganese source and / or a carbon nanotube dispersion are uniformly mixed to obtain a precursor, and the precursor is hydrothermally grown in a constant temperature oven to synthesize the layered manganese dioxide positive electrode material;

[0039] The manganese source includes one or more of manganese acetate, manganese sulfate, manganese chloride, and manganese nitrate;

[0040] A high voltage magnesium / alkali metal hybrid battery comprises a positive electrode sheet, a negative electrode sheet and a magnesium / alkali metal double salt electrolyte. The positive electrode sheet comprises a current collector, a positive electrode material layer coated on the current collector, and the positive electrode material layer comprises the aforementioned layered manganese dioxide positive electrode material, a conductive additive and a binder.

[0041] Wherein, the negative electrode plate is pure magnesium

[0042] Wherein, the alkali metal in the magnesium alkali metal double salt electrolyte may be one of Li, Na, and K;

[0043] Wherein, the molar ratio of Mg to alkali metal atoms (Li, Na, K) in the magnesium alkali metal double salt electrolyte is (0.1-2):1.

[0044] Example 1

[0045] This embodiment provides a layered MnO 2 A method for preparing a positive electrode material comprises the following steps:

[0046] 1) 40 mg of carbon nanotubes (single-wall, purity > 95 wt%, specific surface area > 380 m 2 / g) as raw material, 30ml of deionized water as solvent, and ultrasonic dispersion to obtain solution A;

[0047] 2) 0.168 g of manganese sulfate monohydrate and 0.948 g of potassium permanganate were used as reaction raw materials and 40 ml of deionized water was used as solvent, and solution B was obtained by stirring and dispersing.

[0048] 3) gradually adding the solution A in step 1 to the solution B in step 2 under stirring to obtain a uniform solution, and after further stirring at room temperature, transferring the solution into a 100 ml polytetrafluoroethylene reactor, hydrothermally heating at 160° C. for 10 h, centrifugally washing, and drying to obtain a layered manganese dioxide positive electrode material;

[0049] Among them, the present application is about the layered MnO prepared in this embodiment 2 The positive electrode material was tested for appearance and morphology, and its XRD pattern is shown in Figure 1 , from the XRD spectrum, its crystal structure is a δ-phase layered oxide; Figure 2 This is a scanning electron microscope (SEM) image of the positive electrode material. It can be seen from the image that its particle size distribution is mainly 1 to 5 μm and is flower-shaped.

[0050] Example 2

[0051] This embodiment provides a layered MnO 2 A method for preparing a magnesium / alkali metal hybrid battery of a positive electrode material comprises the following steps:

[0052] 1) Preparation of positive electrode: 0.14 g of layered MnO 2 The positive electrode material, 0.04g Super P and 0.02g PVDF binder were ground in a mortar and then 700ul N-methylpyrrolidone solvent was added to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on an aluminum foil using a scraper, and then the aluminum foil was transferred to a vacuum oven at 80°C and dried for 12h. The dried aluminum foil was then cut into a circular electrode sheet with a diameter of 12mm.

[0053] 2) Preparation of magnesium monosalt electrolyte: In a glove box filled with argon atmosphere, dissolve magnesium bis(trifluoromethylsulfonylimide) in ethylene glycol dimethyl ether (DME) solvent to prepare 0.25M Mg(TFSI) 2solution, adding dioxymethylethylamine to the solution at a mass ratio of ethylene glycol dimethyl ether to dioxymethylethylamine of 4.7:1 to obtain a magnesium monosalt electrolyte;

[0054] 3) Preparation of high voltage magnesium metal battery: The circular electrode sheet prepared in step 1) is used as the positive electrode, the Mg metal disc with a diameter of 14 mm and a thickness of 0.2 mm is used as the negative electrode, the glass fiber with a diameter of 17 mm and a thickness of 1 mm is used as the separator, and the magnesium monosalt electrolyte prepared in step 2) is used as the electrolyte, and a button battery is assembled in a CR2032 battery shell.

[0055] The button cell in this embodiment is 50 mA g -1 The constant current charge and discharge test was carried out under the current density. The test results were as follows under the conditions of discharge cut-off voltage of 0.4V and charge cut-off voltage of 2.7V. Figure 3 As shown, the battery’s first cycle discharge capacity is 163.3 mAh g - 1. After 30 cycles, the discharge capacity is only 13.8 mAh g -1 .

[0056] Example 3

[0057] This embodiment provides a layered MnO 2 A method for preparing a magnesium / alkali metal hybrid battery of a positive electrode material comprises the following steps:

[0058] 1) Preparation of positive electrode sheet: The preparation method of the positive electrode sheet in this embodiment is the same as that in Example 2;

[0059] 2) Preparation of magnesium / alkali metal double salt electrolyte: In a glove box filled with argon atmosphere, magnesium bis(trifluoromethylsulfonyl imide) and lithium trifluoromethylsulfonyl imide were dissolved in ethylene glycol dimethyl ether (DME) solvent at a molar ratio of 1:1 to obtain 0.25 M Mg(TFSI) 2 / 0.25M LiTFSI solution, adding dioxymethylethylamine to the solution at a mass ratio of ethylene glycol dimethyl ether to dioxymethylethylamine of 4.7:1, and finally obtaining a magnesium / lithium double salt electrolyte;

[0060] 3) Preparation of high voltage magnesium / alkali metal hybrid battery: The circular electrode sheet prepared in step 1) is used as the positive electrode, the Mg metal disc with a diameter of 14 mm and a thickness of 0.2 mm is used as the negative electrode, the glass fiber with a diameter of 17 mm and a thickness of 1 mm is used as the separator, and the magnesium / lithium dual salt electrolyte prepared in step 2) is used as the electrolyte, and assembled into a button battery in a CR2032 battery shell.

[0061] The button cell in this embodiment is 50 mA g -1The constant current charge and discharge test was carried out under the current density. The test results were as follows under the conditions of discharge cut-off voltage of 0.4V and charge cut-off voltage of 2.7V. Figure 4 As shown, the battery’s first cycle discharge capacity is 174.1 mAh g -1 After 30 cycles, the discharge capacity is 54.1 mAh g -1 .

[0062] Example 4

[0063] This embodiment provides a layered MnO 2 A method for preparing a magnesium / alkali metal hybrid battery of a positive electrode material comprises the following steps:

[0064] 1) Preparation of positive electrode sheet: The preparation method of the positive electrode sheet in this embodiment is the same as that in Example 2;

[0065] 2) Preparation of magnesium / alkali metal double salt electrolyte: In a glove box filled with argon atmosphere, magnesium bis(trifluoromethylsulfonyl imide) and lithium trifluoromethylsulfonyl imide were dissolved in ethylene glycol dimethyl ether (DME) solvent at a molar ratio of 1:2 to obtain 0.25M Mg(TFSI) 2 / 0.25M LiTFSI solution, adding dioxymethylethylamine to the solution at a mass ratio of ethylene glycol dimethyl ether to dioxymethylethylamine of 4.7:1, and finally obtaining a magnesium / lithium double salt electrolyte;

[0066] 3) Preparation of high voltage magnesium / alkali metal hybrid battery: The circular electrode sheet prepared in step 1) is used as the positive electrode, the Mg metal disc with a diameter of 14 mm and a thickness of 0.2 mm is used as the negative electrode, the glass fiber with a diameter of 17 mm and a thickness of 1 mm is used as the separator, and the magnesium / lithium dual salt electrolyte prepared in step 2) is used as the electrolyte, and assembled into a button battery in a CR2032 battery shell.

[0067] The button cell in this embodiment is 50mA g -1 The constant current charge and discharge test was carried out under the current density. The test results were as follows under the conditions of discharge cut-off voltage of 0.4V and charge cut-off voltage of 2.7V. Figure 5 As shown, the battery’s first cycle discharge capacity is 172.1 mAh g -1 After 30 cycles, the discharge capacity is 66.8 mAh g -1 .

[0068] Example 5

[0069] This embodiment provides a layered MnO 2 A method for preparing a magnesium / alkali metal hybrid battery of a positive electrode material comprises the following steps:

[0070] 1) Preparation of positive electrode sheet: Preparation of positive electrode sheet: The preparation method of the positive electrode sheet in this embodiment is the same as that in Example 2;

[0071] 2) Preparation of magnesium / alkali metal double salt electrolyte: In a glove box filled with argon atmosphere, magnesium bis(trifluoromethylsulfonyl imide) and sodium trifluoromethylsulfonyl imide were dissolved in ethylene glycol dimethyl ether (DME) solvent at a molar ratio of 1:1 to obtain 0.25M Mg(TFSI) 2 / 0.25M NaTFSI solution, adding dioxymethylethylamine to the solution at a mass ratio of ethylene glycol dimethyl ether to dioxymethylethylamine of 4.7:1, and finally obtaining a magnesium / sodium double salt electrolyte;

[0072] 3) Preparation of high voltage magnesium / alkali metal hybrid battery: The circular electrode sheet prepared in step 1) is used as the positive electrode, the Mg metal disc with a diameter of 14 mm and a thickness of 0.2 mm is used as the negative electrode, the glass fiber with a diameter of 17 mm and a thickness of 1 mm is used as the separator, and the magnesium / sodium double salt electrolyte prepared in step 2) is used as the electrolyte, and assembled into a button battery in a CR2032 battery shell.

[0073] The button cell in this embodiment is 50 mA g -1 The constant current charge and discharge test was carried out under the current density. The test results were as follows under the conditions of discharge cut-off voltage of 0.4V and charge cut-off voltage of 2.7V. Figure 6 As shown, the battery’s first cycle discharge capacity is 175.1 mAh g -1 After 30 cycles, the discharge capacity is 57.5 mAh g -1 .

[0074] Example 6

[0075] This embodiment provides a layered MnO 2 A method for preparing a magnesium / alkali metal hybrid battery of a positive electrode material comprises the following steps:

[0076] 1) Preparation of positive electrode sheet: The preparation method of the electrode sheet in this embodiment is the same as that in embodiment 2-1

[0077] 2) Preparation of magnesium / alkali metal double salt electrolyte: In a glove box filled with argon atmosphere, magnesium bis(trifluoromethylsulfonyl imide) and sodium trifluoromethylsulfonyl imide were dissolved in ethylene glycol dimethyl ether (DME) solvent at a molar ratio of 1:2 to obtain 0.25M Mg(TFSI) 2 / 0.5M NaTFSI solution, dioxymethylethylamine was added to the solution at a mass ratio of ethylene glycol dimethyl ether / dioxymethylethylamine of 4.7:1, and finally a magnesium / sodium double salt electrolyte was obtained.

[0078] 3) Preparation of high voltage magnesium / alkali metal hybrid battery: The circular electrode sheet prepared in step 1) is used as the positive electrode, the Mg metal disc with a diameter of 14 mm and a thickness of 0.2 mm is used as the negative electrode, the glass fiber with a diameter of 17 mm and a thickness of 1 mm is used as the separator, and the magnesium / sodium double salt electrolyte prepared in step 2) is used as the electrolyte, and assembled into a button battery in a CR2032 battery shell.

[0079] The button cell in this embodiment is 50mA g -1 The constant current charge and discharge test was carried out under the current density. The test results were as follows under the conditions of discharge cut-off voltage of 0.4V and charge cut-off voltage of 2.7V. Figure 7 As shown in the figure, the battery has a discharge capacity of 178.3 mAh g-1 in the first cycle and a discharge capacity of 61.4 mAh g-1 after 30 cycles. -1 .

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A magnesium / alkali metal hybrid battery containing a layered MnO2 positive electrode material, characterized in that: It comprises a positive electrode sheet, a negative electrode sheet and a magnesium / alkali metal double salt electrolyte, wherein the positive electrode sheet comprises a layered manganese dioxide positive electrode material, the negative electrode sheet is pure magnesium metal, and the electrolyte is a magnesium / alkali metal double salt electrolyte.

2. The magnesium / alkali metal hybrid battery containing layered MnO2 positive electrode material according to claim 1, characterized in that: The positive electrode plate further comprises a current collector and a positive electrode material layer coated on the current collector, wherein the positive electrode material layer comprises a layered manganese dioxide positive electrode material, a conductive additive and a binder.

3. The magnesium / alkali metal hybrid battery containing layered MnO2 positive electrode material according to claim 1, characterized in that: The alkali metal in the magnesium / alkali metal double salt electrolyte is one of Li, Na and K.

4. The magnesium / alkali metal hybrid battery containing layered MnO2 positive electrode material according to claim 1, characterized in that: In the magnesium / alkali metal double salt electrolyte, the molar ratio of Mg to alkali metal atoms is (0.1-2):

1.

5. The magnesium / alkali metal hybrid battery containing layered MnO2 positive electrode material according to claim 1, characterized in that: The layered manganese dioxide positive electrode material is prepared by the following method, specifically: dissolving carbon nanotubes, manganese sulfate and potassium permanganate in deionized water in a certain proportion, stirring to form a uniform solution, and transferring the solution to a constant temperature oven for hydrothermal growth to obtain the layered manganese dioxide positive electrode material.

6. The magnesium / alkali metal hybrid battery containing layered MnO2 positive electrode material according to claim 1, characterized in that: The mass ratio of the carbon nanotubes, manganese sulfate and potassium permanganate is (0.02-0.06) g: (0.1-0.2) g: (0.5-1.5) g, and the process conditions of the hydrothermal growth are: maintaining at 120-180° C. for 8-12 hours.

7. The magnesium / alkali metal hybrid battery containing layered MnO2 positive electrode material according to claim 1, characterized in that: The magnesium / alkali metal double salt electrolyte is prepared by the following method, specifically: dissolving magnesium bis(trifluoromethylsulfonyl imide) and lithium / sodium bis(trifluoromethylsulfonyl imide) in ethylene glycol dimethyl ether under an inert atmosphere to form a uniform clear solution; Add a dioxymethylethylamine solution as a stabilizing additive to the clear solution, stir until a uniform clear solution is formed, and finally obtain a magnesium / alkali metal double salt electrolyte.

8. The magnesium / alkali metal hybrid battery containing layered MnO2 positive electrode material according to claim 1, characterized in that: The molar ratio of the magnesium bis(trifluoromethylsulfonyl)imide to the lithium / sodium bis(trifluoromethylsulfonyl)imide is 1:(0.5-3).

9. A method for preparing a magnesium / alkali metal hybrid battery containing a layered MnO2 positive electrode material as claimed in any one of claims 1 to 8, characterized in that: It includes the following steps: 1) Preparation of positive electrode The layered manganese dioxide positive electrode material, the conductive additive and the binder are mixed into a slurry, uniformly coated on the current collector, and dried to obtain a positive electrode sheet; 2) Preparation of magnesium / alkali metal hybrid batteries Under an inert atmosphere, the positive electrode sheet prepared in step 1) is used, pure magnesium metal is used as the negative electrode sheet, and a magnesium / alkali metal double salt solution is used as the electrolyte to assemble a high-voltage magnesium / alkali metal hybrid battery.

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