Solvent Composition, Electrolyte and Rechargeable Magnesium Battery

Abstract

The present application discloses a solvent composition, an electrolyte, and a rechargeable magnesium battery. The composition comprises a fluorinated ether and a non-aqueous solvent in a volume ratio of 1:0.15 to 4, and the non-aqueous solvent comprises an ionic liquid and / or an organic solvent selected from imidazole compounds substituted with C1-C4 alkyl groups, sulfoxide or sulfone compounds with C2-C6, cyclic carbonate compounds with C3-C5, carboxylic ester compounds with C2-C6, pyridine or alkylbenzene aromatic compounds substituted with methyl, chlorine, amino groups or unsubstituted, C1-C4 amide compounds, acetonitrile compounds substituted with chlorine, pyridine or unsubstituted, and an ether compound selected from cyclic monoethers or diethers with C3-C4 or an ether compound satisfying the general formula H3CO(C2H4O) n CH3, where n ranges from 1 to 8, or a combination thereof. The composition utilizes the property that fluorinated ether molecules are relatively easy to obtain electrons to form a stable electrode-electrolyte interface, regulates the solvation structure of the chlorine-containing electrolyte, improves the ionic conductivity, and realizes the reversible electrochemical cycle of the magnesium metal negative electrode at a high current density.

Description

Technical Field

[0001] This application belongs to the field of rechargeable battery technology, and particularly relates to a solvent composition, an electrolyte containing the solvent composition, and a rechargeable magnesium battery. Background Technology

[0002] The development of rechargeable batteries is key to solving the problem of renewable energy storage. Magnesium is abundant, inexpensive, environmentally friendly, and has relatively stable physicochemical properties, possessing a high theoretical volumetric capacity (3833 mA·h / cm³). 3 Magnesium battery systems, which use metallic magnesium as the negative electrode material, have advantages such as high energy density, low cost, and high safety, and are one of the new energy storage systems with great development potential.

[0003] Since the first rechargeable magnesium battery prototype was reported, numerous researchers have conducted extensive work on the design and synthesis of rechargeable magnesium battery electrolytes over the past two decades, resulting in the development of various types of magnesium battery electrolyte systems. However, existing magnesium battery electrolytes generally suffer from one or more problems, such as low ionic conductivity, unstable electrochemical performance, and interface passivation. These problems seriously hinder the development of practical rechargeable magnesium batteries. Summary of the Invention

[0004] This application provides a solvent composition that, by adding a set proportion of fluorinated ether to a non-aqueous solvent, can regulate the solvation structure of the electrolyte, improve ionic conductivity, realize reversible electrochemical cycling of the magnesium metal anode under high current density, and promote the practical development of rechargeable magnesium batteries.

[0005] In a first aspect, embodiments of this application provide a solvent composition comprising a fluorinated ether and a non-aqueous solvent, wherein the non-aqueous solvent comprises an ionic liquid and / or an organic solvent; the organic solvent is selected from imidazole compounds substituted with C1-C4 alkyl groups, sulfoxide or sulfone compounds substituted with C2-C6 groups, cyclic carbonate compounds substituted with C3-C5 groups or carboxylic acid ester compounds substituted with C2-C6 groups, pyridine or alkylbenzene aromatic compounds substituted with or unsubstituted with methyl, chlorine, amino, or unsubstituted, C1-C4 amide compounds, acetonitrile compounds substituted with or unsubstituted with chlorine, pyridine, or unsubstituted, ether compounds selected from one or a combination thereof of cyclic monoethers or diethers substituted with C3-C4 groups or ether compounds satisfying general formula (I);

[0006] H3CO(C2H4O)nCH3(I), where n takes values ​​from 1 to 8;

[0007] The volume ratio of fluorinated ether to non-aqueous solvent is 1:0.15 to 4.

[0008] Secondly, this application provides an electrolyte comprising the above-described solvent composition and a halogen electrolyte salt; the halogen electrolyte salt includes a magnesium halogen salt.

[0009] Thirdly, embodiments of this application provide a method for preparing the above-mentioned electrolyte, comprising:

[0010] S1. Preparation of halogen-containing electrolyte: In an environment with oxygen and water content below 1 ppm and filled with nitrogen, halogen electrolyte salts are added to an organic solvent and stirred to react, thus obtaining a halogen-containing electrolyte.

[0011] S2. Introduction of fluorinated ether: Fluorinated ether is added to a halogen-containing electrolyte in a predetermined volume, and a magnesium battery electrolyte containing fluorinated ether is prepared by reaction.

[0012] Fourthly, embodiments of this application provide a rechargeable magnesium battery, comprising the electrolyte described above. The positive electrode material of the rechargeable magnesium battery is selected from one or a combination of transition metal sulfides, transition metal oxides, transition metal borides, and polyanionic phosphates.

[0013] The solvent composition of this application embodiment, by adding fluorinated ether to the solvent composition, utilizes the characteristic that the fluorinated ether cosolvent molecules have low unoccupied molecular orbitals (LUMO) energy levels, which make it easier to gain electrons for reduction and decomposition to form a stable electrode-electrolyte interface. This enables the magnesium battery to effectively control the solvation structure of various chlorine-containing electrolytes, improve ionic conductivity, and realize reversible electrochemical cycling of the magnesium metal anode under high current density. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a comparison diagram of the effect of fluorinated ethers on the chemical shift of the NMR spectrum of mixed solvents, provided in the embodiments of this application.

[0016] Figure 2a This is a radial distribution function diagram of hydrogen (H) and chlorine (Cl) in a magnesium lithium chloride complex (MLCC)-tetrahydrofuran (THF) electrolyte system without fluorinated ether, generated by molecular dynamics simulation. The electrolyte salt ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0017] Figure 2bThis is a radial distribution function diagram of hydrogen (H) and chlorine (Cl) in a magnesium lithium chloride complex (MLCC)-tetrahydrofuran (THF) electrolyte system containing fluorinated ether, as simulated by molecular dynamics. The electrolyte is a 1:1 volume ratio of MLCC-THF:BTFE, and the electrolyte salt ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0018] Figure 3a This is an impedance diagram of the electrolyte of the solvent magnesium lithium chloride complex (MLCC) without fluorinated ether provided in the embodiments of this application, with the electrolyte salt ratio being 0.3 mol / L MgCl2 + 0.3 mol / L LiCl;

[0019] Figure 3b This is an impedance diagram of the electrolyte containing a fluorinated ether-containing solvent magnesium lithium chloride complex (MLCC) provided in the embodiments of this application. The electrolyte is a MLCC-THF:BTFE electrolyte with a volume ratio of 1:1, and the electrolyte salt dosage ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0020] Figure 4 a is a scanning electron microscope image of the morphology of the magnesium metal anode after electrochemical cycling with the solvent without fluorinated ether provided in the embodiments of this application. The electrolyte salt ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0021] Figure 4 b is a scanning electron microscope image of the morphology of the magnesium metal anode after electrochemical cycling in the solvent containing fluorinated ether provided in the embodiments of this application. The electrolyte is a MLCC-THF:BTFE electrolyte with a volume ratio of 1:1 and the electrolyte salt ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0022] Figure 5a This is a graph showing the current change during rate and long-cycle performance testing of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a magnesium lithium chloride complex (MLCC) electrolyte system without fluorinated ether. The electrolyte salt ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0023] Figure 5b This is a voltage change graph of the Mg / / Mg symmetric half-cell provided in the embodiments of this application during rate and long-cycle performance testing in a magnesium lithium chloride complex (MLCC) electrolyte system without fluorinated ether. The electrolyte salt dosage ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0024] Figure 5cThis is a graph showing the current change during rate and long-cycle performance testing of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a magnesium lithium chloride complex (MLCC) electrolyte system containing fluorinated ether. The electrolyte is a MLCC-THF:BTFE electrolyte with a volume ratio of 1:1, and the electrolyte salt ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0025] Figure 5d This is a voltage change graph of the Mg / / Mg symmetric half-cell provided in the embodiments of this application during rate and long-cycle performance testing in a magnesium lithium chloride complex (MLCC) electrolyte system containing fluorinated ether. The electrolyte is a MLCC-THF:BTFE electrolyte with a volume ratio of 1:1 and an electrolyte salt ratio of 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0026] Figure 6a This is a graph showing the relationship between the number of cycles, specific capacity, and coulombic efficiency of the Mg / CuS full cell provided in the embodiments of this application during long-cycle performance testing in a magnesium lithium chloride complex (MLCC) electrolyte system without fluorinated ether. The electrolyte salt ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0027] Figure 6b This is a graph showing the relationship between the number of cycles, specific capacity, and voltage of the Mg / CuS full cell provided in the embodiments of this application during long-cycle performance testing in a magnesium lithium chloride complex (MLCC) electrolyte system without fluorinated ether. The electrolyte salt ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0028] Figure 6c This is a graph showing the relationship between the number of cycles, specific capacity, and coulombic efficiency of the Mg / CuS full cell provided in the embodiments of this application during long-cycle performance testing in a magnesium lithium chloride complex (MLCC) electrolyte system containing fluorinated ether. The electrolyte is a MLCC-THF:BTFE electrolyte with a volume ratio of 1:1, and the electrolyte salt dosage is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0029] Figure 6d This is a graph showing the relationship between the number of cycles, specific capacity, and voltage of the Mg / CuS full cell provided in the embodiments of this application during long-cycle performance testing in a magnesium lithium chloride complex (MLCC) electrolyte system containing fluorinated ether. The electrolyte is a MLCC-THF:BTFE electrolyte with a volume ratio of 1:1, and the electrolyte salt dosage ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0030] Figure 7This is a comparison graph showing the relationship between the number of cycles, specific capacity, and voltage of the Mg / / Mo6S8 full cell provided in the embodiments of this application in a magnesium lithium chloride complex (MLCC) electrolyte system with / without fluorinated ether solvent. The electrolyte salt dosage ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0031] Figure 8a This is a time-voltage relationship diagram of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a simple salt MgCl2-based electrolyte system without fluorinated ether, wherein the electrolyte is MgCl2-THF electrolyte, and the electrolyte salt ratio in the MgCl2-based electrolyte is 0.15mol / L MgCl2;

[0032] Figure 8b This is a time-voltage relationship graph of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a simple salt MgCl2-based electrolyte system containing fluorinated ether. The electrolyte is a MgCl2-THF:BTFF electrolyte with a volume ratio of 1:1, and the electrolyte salt content in the MgCl2-based electrolyte is 0.15 mol / L MgCl2.

[0033] Figure 9a This is a time-voltage comparison graph of the long-cycle performance test of the Mg / / Mg symmetric half cell and (b) Mg / / Mo6S8 full cell provided in the embodiments of this application in magnesium aluminum chloride complex (MgCl2+AlCl3) electrolyte systems with and without fluorinated ethers. In the magnesium aluminum chloride complex (MACC) electrolyte system containing fluorinated ethers, MACC-THF:BTFE = 1:4, and the electrolyte salt ratio is 0.06mol / L MgCl2+0.03mol / L AlCl3.

[0034] Figure 9b This is a time-voltage comparison graph of the Mg / / Mg symmetric half-cell and (b) Mg / / Mo6S8 full cell provided in the embodiments of this application during long-cycle performance testing in a magnesium aluminum chloride complex (MgCl2+AlCl3) electrolyte system containing fluorinated ether solvent. The electrolyte is a MACC-THF:BTFE = 1:4 electrolyte, and the electrolyte salt ratio is 0.06 mol / L MgCl2 + 0.03 mol / L AlCl3.

[0035] Figure 10aThis is a time-voltage relationship graph of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a magnesium aluminum chloride complex (MACC) electrolyte system without fluorinated ether, wherein the electrolyte is MACC-THF electrolyte and the electrolyte salt ratio is 0.06mol / L MgCl2+0.03mol / L AlCl3;

[0036] Figure 10b This is a time-voltage relationship diagram of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a magnesium aluminum chloride complex (MACC) electrolyte system containing fluorinated ether, wherein the electrolyte is a MACC-THF:BTFE = 1:1 electrolyte, and the electrolyte salt ratio is 0.06 mol / L MgCl2 + 0.03 mol / L AlCl3;

[0037] Figure 10c This is a time-voltage relationship diagram of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a magnesium aluminum chloride complex (MACC) electrolyte system containing fluorinated ether, wherein the electrolyte is a MACC-THF:BTFE = 1:2 electrolyte, and the electrolyte salt ratio is 0.06 mol / L MgCl2 + 0.03 mol / L AlCl3;

[0038] Figure 10d This is a time-voltage relationship diagram of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a magnesium aluminum chloride complex (MACC) electrolyte system containing fluorinated ether, wherein the electrolyte is a MACC-THF:BTFE = 1:4 electrolyte, and the electrolyte salt ratio is 0.06 mol / L MgCl2 + 0.03 mol / L AlCl3;

[0039] Figure 10e This is a time-voltage relationship diagram of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a magnesium aluminum chloride complex (MACC) electrolyte system containing fluorinated ether, wherein the electrolyte is a MACC-THF:BTFE = 1:6 electrolyte, and the electrolyte salt ratio is 0.06mol / L MgCl2 + 0.03mol / L AlCl3;

[0040] Figure 11aThis is a time-voltage relationship diagram of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a MgCl2-based ethylene glycol dimethyl ether (DME) electrolyte system without fluorinated ether, wherein the electrolyte is a MgCl2-based DME electrolyte, and the electrolyte salt ratio is 0.6 mol / L MgCl2 + 0.3 mol / L MgTFSI2;

[0041] Figure 11b This is a time-voltage relationship diagram of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a MgCl2-based ethylene glycol dimethyl ether electrolyte system containing fluorinated ether. The electrolyte is a MgCl2-based DME:BTFE = 4:1 electrolyte, and the electrolyte salt ratio is 0.6 mol / L MgCl2 + 0.3 mol / L MgTFSI2.

[0042] Figure 11c This is a time-voltage relationship diagram of the deposition-dissolution behavior test of the Mg / / Mg symmetric half-cell provided in the embodiments of this application in a MgCl2-based ethylene glycol dimethyl ether electrolyte system containing fluorinated ether. The electrolyte is a MgCl2-based DME:BTFE = 2:1 electrolyte, and the electrolyte salt ratio is 0.6 mol / L MgCl2 + 0.3 mol / L MgTFSI2.

[0043] For example, MLCC-THF:BTFE = 1:1 refers to the volume ratio of tetrahydrofuran (THF) to trifluoroethyl ether (2,2,2-trifluoroethyl ether, BTFE) in the electrolyte; in other figures (including the MACC electrolyte system), such ratios also refer only to the volume ratio of THF or DME to BTFE.

[0044] In the appendix Figures 1 to 7 In the MLCC electrolyte system, the electrolyte salt ratio is 0.3 mol / L MgCl2 + 0.3 mol / L LiCl. Detailed Implementation

[0045] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0046] Magnesium battery electrolytes are still in the early stages of development. Currently available magnesium battery electrolytes mainly include Grignard reagent systems, hexamethyldisilazide (HMDS) systems, trifluoromethanesulfonylimide (TFSI) systems, and boron-based systems. However, these electrolytes generally suffer from one or more problems such as expensive raw materials, complex synthesis processes, and unstable electrochemical performance, which are not conducive to the development of practical magnesium batteries.

[0047] Inorganic salt electrolytes based on magnesium chloride (MgCl2) are promising magnesium battery electrolyte systems due to their low raw material cost and simple synthesis. However, due to the strong interaction between Mg and Cl, MgCl2 has extremely low solubility in most organic solvents compatible with magnesium metal anodes, mainly forming a large number of electrically neutral clusters in the form of Mg-Cl bridging. Therefore, the ionic conductivity of MgCl2-based electrolytes cannot meet the requirements for future practical applications.

[0048] While magnesium ions possess the advantages mentioned in the background section, they also have several drawbacks. On one hand, due to their high charge density and strong electrostatic interactions, the solubility of many magnesium salts is limited, and ion transport is hindered, significantly limiting the ionic conductivity of the electrolyte and resulting in low ionic conductivity. On the other hand, due to magnesium's low reduction potential (-2.37V, measured at a standard hydrogen electrode), most organic solvents and magnesium salts react with metallic magnesium, forming an interfacial passivation layer that cannot effectively conduct magnesium ions, as well as uneven deposition and dissolution on the magnesium metal surface. This hinders the stable operation of rechargeable magnesium batteries, easily inducing large charge / discharge overpotentials, or even short circuits, ultimately leading to battery failure.

[0049] Therefore, it is necessary to further optimize the ionic conductivity and electrode-electrolyte interface stability of the rechargeable magnesium battery electrolyte to improve the electrochemical performance of the electrolyte under high current density and high capacity density conditions for future practical applications.

[0050] To address the problems existing in the prior art, this application provides a solvent composition. The solvent composition provided in this application is described below.

[0051] A solvent composition comprising a fluorinated ether and a non-aqueous solvent, wherein the non-aqueous solvent comprises an ionic liquid and / or an organic solvent; the organic solvent is selected from imidazole compounds substituted with C1-C4 alkyl groups, sulfoxide or sulfone compounds substituted with C2-C6 groups, cyclic carbonate compounds substituted with C3-C5 groups or carboxylic acid ester compounds substituted with C2-C6 groups, pyridine or alkylbenzene aromatic compounds substituted with or unsubstituted with methyl, chlorine, amino, or unsubstituted, C1-C4 amide compounds, acetonitrile compounds substituted with or unsubstituted with chlorine, pyridine, or unsubstituted, ether compounds selected from one or a combination of cyclic monoethers or diethers substituted with C3-C4 groups or ether compounds satisfying general formula (I);

[0052] H3CO(C2H4O)nCH3(I), where n takes values ​​from 1 to 8;

[0053] The volume ratio of the fluorinated ether to the non-aqueous solvent is 1:0.2 to 3.

[0054] The solvent composition of this application embodiment, by adding fluorinated ether as a co-solvent to the solvent composition, increases the electrolyte in the electrolyte while taking advantage of the characteristic that the fluorinated ether co-solvent molecules have low unoccupied molecular orbitals (LUMO) energy levels, which make it easier to gain electrons for reduction and decomposition to form a stable electrode-electrolyte interface. This allows the magnesium battery to effectively control the solvation structure of various chlorine-containing electrolytes, improve ionic conductivity, and realize reversible electrochemical cycling of the magnesium metal anode under high current density.

[0055] In the embodiments of this application, the fluorinated ether has weak polarity and does not easily interact with magnesium ions. Besides gaining electrons and undergoing reduction decomposition to form a stable electrode-electrolyte interface, the main function of the fluorinated ether is also to improve the wettability of the electrolyte due to its low viscosity.

[0056] In one embodiment, the volume ratio of fluorinated ether to non-aqueous solvent is 1:0.25.

[0057] In one embodiment, the fluorinated ether is selected from one or a combination of 2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1-(1,1,2,2-tetrafluoroethoxy)propane, and 2-methyl-1-(1,1,2,2-tetrafluoroethoxy)propane.

[0058] In one embodiment, the ether compound is selected from one or a combination of tetrahydrofuran, dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or polyethylene glycol dimethyl ether with n taking the value of 5 to 8.

[0059] In the embodiments of this application, cyclic ethers (such as tetrahydrofuran and dioxolane) and short-chain ethers (such as ethylene glycol dimethyl ether) generally have low viscosity but poor ability to chelate and coordinate magnesium ions. Long-chain ethers (such as triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or polyethylene glycol dimethyl ether with n values ​​of 5 to 8) generally have high viscosity but strong ability to chelate and coordinate magnesium ions. This application uses a mixed solvent of long-chain and short-chain ethers to ensure the surface hardness and high dissociation degree of the electrolyte, achieving better ionic conductivity.

[0060] In one embodiment, the imidazole compound is selected from one or a combination of 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole, and 1-butylimidazole.

[0061] In one embodiment, the sulfoxide or sulfone compound is selected from one or a combination of dimethyl sulfoxide, sulfolane, dipropyl sulfone.

[0062] In one embodiment, the cyclic carbonate compound or carboxylic acid ester compound is selected from one or a combination of ethylene carbonate, propylene carbonate, butene carbonate, 1,2-dimethylethylene carbonate, methyl formate, ethyl formate, methyl acetate, ethyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0063] In one embodiment, the pyridine or alkylbenzene aromatic compound is selected from one or a combination of pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, 2-aminopyridine, toluene, and xylene.

[0064] In one embodiment, the amide compound is selected from one or a combination of dimethylamine, 1-methoxy-2-propylamine, 2-methoxyethylamine, and methoxyamine.

[0065] In one embodiment, the nitrile compound is selected from one or a combination of acetonitrile, trichloroacetonitrile, 3-cyanopyridine.

[0066] In some embodiments, the ionic liquid is selected from one or a combination of imidazole ionic liquids, piperidine ionic liquids, or pyrrole ionic liquids.

[0067] In one embodiment, the imidazole ionic liquid is selected from one or a combination of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1-ethyl-3-methylimidazolium hexafluorophosphate; the pyrrole ionic liquid is N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imine salt; and the piperidine ionic liquid is N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imine salt.

[0068] In the embodiments of this application, imidazole compounds, sulfoxide or sulfone compounds, and amide compounds generally have high polarity (i.e., high dielectric constant). Strongly polar solvents can effectively dissociate the electrolyte magnesium salt, that is, form effective coordination with magnesium ions, thereby improving the ionic conductivity of the electrolyte.

[0069] According to the solvent composition of the embodiments of this application, the fluorinated ether is 2,2,2-trifluoroethyl ether, the ionic liquid is 1-ethyl-3-methylimidazolium tetrafluoroborate, and the organic solvent is tetrahydrofuran.

[0070] According to the solvent composition of the embodiments of this application, the fluorinated ether is 2,2,2-trifluoroethyl ether, and the organic solvent includes ethylene glycol dimethyl ether.

[0071] Secondly, embodiments of this application provide an electrolyte comprising the solvent composition described above, and a halogen electrolyte salt.

[0072] In some embodiments, the halogen electrolyte salt includes a magnesium halogen salt, which is selected from magnesium chloride, magnesium fluoride, magnesium bromide, and magnesium iodide.

[0073] In some embodiments, the halogen electrolyte salt of the electrolyte in this application further includes a metal halide salt, wherein the metal halide salt satisfies MX n M is a metallic element, X is a halogen element, and n is any integer from 1 to 4; the molar ratio of magnesium halide salt to metal halide salt is 1:0 to 5.

[0074] In one embodiment, the metal halide salt is selected from one or a combination of metal chloride salts, metal fluoride salts, metal bromide salts, and metal iodide salts.

[0075] In one embodiment, the metal chloride salt is selected from one or a combination of aluminum trichloride, lithium chloride, gallium trichloride, and indium trichloride; and / or

[0076] The metal fluoride salt is selected from one or a combination of aluminum trifluoride, gallium trifluoride, indium trifluoride, sodium fluoride, potassium fluoride, and calcium difluoride; and / or

[0077] Metal bromide salts are selected from lithium bromide, indium tribromide, or combinations thereof; and / or

[0078] The metal iodide salt is selected from one or a combination of aluminum triiodide, lithium iodide, gallium triiodide, and indium triiodide.

[0079] In one embodiment, the concentration of the magnesium halogen salt is 0.01 mol / L to 0.6 mol / L.

[0080] In one embodiment, the magnesium halide salt is magnesium chloride, and the metal chloride salt is selected from one or a combination of aluminum trichloride, lithium chloride, gallium trichloride, and indium trichloride.

[0081] In one embodiment, the magnesium halide salt is magnesium chloride, and the metal chloride salt is a mixture of aluminum trichloride and gallium trichloride, with a molar ratio of magnesium chloride to metal chloride of 1:0.5.

[0082] In one embodiment, the magnesium halide salt is magnesium chloride, the metal chloride salt is lithium chloride, and the molar ratio of magnesium chloride to lithium chloride is 1:0.8.

[0083] In one embodiment, the magnesium halogen salt is magnesium chloride, the metal chloride salt is aluminum trichloride, and the molar ratio of magnesium chloride to aluminum trichloride is 1:0.5.

[0084] In one embodiment, the magnesium halogen salt is magnesium fluoride, and the metal chloride salt is a mixture of lithium chloride and aluminum trichloride, with a molar ratio of magnesium fluoride to metal chloride of 1:2.

[0085] In one embodiment, the electrolyte comprises trifluoroethyl ether and tetrahydrofuran in a volume ratio of 2 to 6:1.

[0086] In one embodiment, the electrolyte comprises trifluoroethyl ether and ethylene glycol dimethyl ether in a volume ratio of 1:2 to 4.

[0087] The fluorinated ether cosolvent molecules added to the electrolyte in this application embodiment have the characteristic of having a low unoccupied molecular orbital (LUMO) energy level, which makes it easier to gain electrons and decompose to form a stable electrode-electrolyte interface. This allows for the in-situ construction of a stable electrode-electrolyte interface on the surface of the magnesium metal anode, thereby achieving the stability of the magnesium metal battery under long-term reversible deposition-dissolution cycles at ultra-high current densities. This will develop and promote a low-cost, high-rate, and high-capacity rechargeable magnesium battery system with magnesium metal as the anode, and realize its practical application.

[0088] Thirdly, embodiments of this application provide a method for preparing an electrolyte, comprising:

[0089] S1. Preparation of halogen-containing electrolyte: In an environment with oxygen and water content below 1 ppm and filled with argon, magnesium halogen salts are added to an organic solvent and stirred to react, thereby obtaining a halogen-containing electrolyte.

[0090] S2. Introduction of fluorinated ether: Fluorinated ether is added to a halogen-containing electrolyte according to a predetermined volume, and a magnesium battery electrolyte with fluorinated ether co-dissolved with BTFE is obtained through reaction.

[0091] In one embodiment, step S1 of preparing a halogen-containing electrolyte further includes adding an ionic liquid to an organic solvent.

[0092] In one embodiment, the temperature of the solvent composition in step S1 is 0°C to 200°C, and the stirring reaction time is 6 hours to 72 hours.

[0093] In one embodiment, when the fluorinated ether is added to the halogen-containing electrolyte in step S2, the temperature of the electrolyte is 0°C to 60°C, and the reaction time is 3 hours to 48 hours.

[0094] By introducing fluorinated ethers as co-solvents into magnesium battery electrolytes, the solvation structure of various chlorine-containing electrolytes and the electrode-electrolyte interface are controlled, enabling long-term stable electrochemical cycling of magnesium metal anodes under ultra-high current densities.

[0095] In one embodiment, the application of magnesium battery electrolyte in a rechargeable magnesium battery involves: assembling a magnesium symmetrical half-cell and testing the high-rate and long-cycle performance and interface properties of the magnesium metal anode; assembling a full cell with magnesium metal as the anode and testing the charge-discharge performance of the full cell.

[0096] Fourthly, embodiments of this application provide a rechargeable magnesium battery, including the electrolyte described above.

[0097] According to embodiments of the present invention, the positive electrode of a rechargeable magnesium battery is a deintercalation and conversion material.

[0098] In one embodiment, the cathode material is selected from one or a combination of transition metal sulfides, transition metal oxides, transition metal borides, and polyanionic phosphates.

[0099] As an example, the transition metal sulfide is selected from TiS2, MoS2, WS2, VS2, HfS2, ZrS2, NbS3, VS4, and Mg. a One or a combination of Mo3S4 (0 < a < 2), Mo6S8, CuS, and Cu2S.

[0100] As an example, the transition metal oxide is selected from V2O5 and V6O. 13 One or a combination of MnO2, Mn2O3, MoO3, and WO3.

[0101] As an example, the transition metal boride is selected from one or a combination of TiB2, MoB2, and ZrB2.

[0102] Fifthly, this application provides the use of a cosolvent composition containing fluorinated ethers in a chlorine-containing electrolyte or a rechargeable magnesium battery.

[0103] The advantages and benefits of the technical solution in this application will be demonstrated through specific experiments below.

[0104] 1. Effect of fluorinated ether cosolvent on the electrochemical performance of magnesium battery electrolyte

[0105] To illustrate the effect of the fluorinated ether BTFE (trifluoroethyl ether) cosolvent proposed in this application on the electrochemical performance of magnesium battery electrolytes, we investigated the solvation structure and its impact on electrochemical performance of magnesium-lithium-chloride complex electrolytes (i.e., MLCC electrolytes, with MgCl2+LiCl as the electrolyte salt).

[0106] Five solutions were selected for NMR spectroscopy analysis: a solvent containing only tetrahydrofuran (THF), a solvent containing only trifluoroethyl ether (BTFE), a mixed solvent containing tetrahydrofuran and trifluoroethyl ether (THF+BTFE), a magnesium-lithium chloride complex (MLCC+THF) electrolyte without fluorinated ether, and a magnesium-lithium chloride complex (MLCC+THF+BTFE) electrolyte with fluorinated ether co-solvent. The MLCC-THF:BTFE solution indicated a THF:BTFE volume ratio of 1:1. The component ratios of the other four solutions were not limited. The electrolyte salt ratio was 0.3 mol / L MgCl2 + 0.3 mol / L LiCl.

[0107] Figure 1 This is a comparison diagram showing the effect of fluorinated ethers on the chemical shifts of the NMR spectra of mixed solvents, as provided in the embodiments of this application. Figure 1 The dashed line in the figure represents the position of the highest peak in the quartet, indicating the hydrogen content (H₂O) in the tetrahydrofuran (THF) solvent. 1 The NMR spectrum chemical shifts were at 1.83 and 3.64 ppm; in the electrolyte of the fluorine-free magnesium lithium chloride complex (MLCC-THF), it contained only trifluoroethyl ether (BTFE) and no obvious hydrogen (H) 1 H) Nuclear magnetic resonance spectrum chemical shift, corresponding to hydrogen atoms in trifluoroethyl ether (BTFE) solvent. 1 The chemical shift in the H) NMR spectrum is at 3.99 ppm. When trifluoroethyl ether and tetrahydrofuran (THF) are mixed, the hydrogen ( 1 The chemical shift in the H NMR spectrum shifted to 4.09 ppm, indicating an interaction between hydrogen (H) in the trifluoroethyl ether (BTFE) molecule and tetrahydrofuran (THF) molecule. Furthermore, in a magnesium-lithium-hydrogen complex electrolyte (MLCC-THF:BTFE = 1:1) containing a fluorinated ether (BTFE) co-solvent, the chemical shift corresponding to the dashed line shifted even further to 4.14 ppm. This suggests a weak H···C interaction between hydrogen (H) in the trifluoroethyl ether (BTFE) molecule and chlorine (Cl) in the electrolyte, leading to the shift in the chemical environment.

[0108] Molecular dynamics simulations can further confirm this conclusion; the radial distribution function reflects the interactions between elements, and the presence of a distinct peak indicates the existence of interactions. Figure 2a As shown, in the magnesium-lithium chloride complex electrolyte (MLCC-THF) without fluorinated ether, the radial distribution function peak of hydrogen (H) in the solvent tetrahydrofuran (THF) and chlorine (Cl) in the electrolyte is very weak; while in the magnesium-lithium chloride complex electrolyte (MLCC-THF:BTFE = 1:1) containing fluorinated ether (trifluoroethyl ether, BTFE) as a co-solvent, such as Figure 2bAs shown, the radial distribution function of hydrogen (H) in fluorinated ether, i.e. trifluoroethyl ether (BTFE), and chlorine (Cl) in the electrolyte exhibits a significant interaction peak at 0.31 nm, with the radial distribution function peak reaching 1.6. Figure 2a and Figure 2b The comparison results show that there is a significant interaction between the hydrogen atoms (H) in the trifluoroethyl ether (BTFE) molecule and the chlorine (Cl) in the electrolyte, which is consistent with... Figure 1 The results from the nuclear magnetic resonance (NMR) spectra corroborate each other, showing an H···Cl interaction distance of approximately 0.31 nm. In summary, the introduction of the fluorinated ether co-solvent (trifluoroethyl ether BTFE) enables it to interact with chlorine (Cl) in the magnesium-lithium-chlorine complex electrolyte system.

[0109] 2. Effect of fluorinated ethers on conductivity

[0110] The conductivity of the magnesium-lithium chloride complex electrolyte without fluorinated ether and the complex electrolyte containing fluorinated ether were tested using a Mettler F3 ion conductivity meter. The organic solvent for the magnesium-lithium chloride complex electrolyte without fluorinated ether (MLCC-THF) was THF, and the electrolyte salt was 0.3 mol / L MgCl₂ + 0.3 mol / L LiCl. The electrolyte salt for the complex electrolyte containing fluorinated ether (MLCC-THF:BTFE = 1:1) was THF + BTFE (volume ratio 1:1), and the electrolyte salt was 0.3 mol / L MgCl₂ + 0.3 mol / L LiCl.

[0111] The ionic conductivity of the electrolyte containing fluorinated ether was tested using an ionic conductivity meter. It was found that the introduction of trifluoroethyl ether (BTFE) co-solvent effectively improved the ionic conductivity of the electrolyte. The ionic conductivity increased from 355 μS / cm without fluorinated ether (BTFE) to 1929 μS / cm with fluorinated ether (BTFE), an increase of 443%.

[0112] 3. Compare the interfacial properties of Mg / / Mg symmetric half-cells assembled with fluorinated ethers in a magnesium-lithium chloride complex electrolyte (MLCC)-THF system.

[0113] The effect of fluorinated ethers on the battery interface was compared using electrochemical impedance spectroscopy. The interfacial impedance of the symmetric battery assembled with a magnesium-lithium chloride complex electrolyte (MLCC-THF) without fluorinated ethers was approximately 10 ohms, as shown in the attached figure. Figure 3a As shown; after the introduction of trifluoroethyl ether, the interfacial impedance decreased to 8 ohms, as shown in the attached figure. Figure 3b As shown, this illustrates that fluorinated ether co-solvents help improve interfacial impedance, thereby enhancing battery stability and cycle life.

[0114] The effects of scanning electron microscopy on the interface of fluorinated ether batteries were compared, such as... Figure 4As shown in Figure a, the magnesium anode surface morphology of the lithium magnesium chloride complex electrolyte without fluorinated ether is relatively rough, with obvious plate-like protrusions and depressions; as shown in the attached figure. Figure 4 As shown in b, compared to lithium magnesium chloride complex electrolytes without fluorinated ethers, the magnesium metal surface morphology of the lithium magnesium chloride complex electrolyte (MLCC-THF:BTFE = 1:1) undergoing electrochemical cycling using a fluorinated ether (trifluoroethyl ether, BTFE) co-solvent is more uniform, dense, and smooth. Figure 4 a and Figure 4 The morphology comparison of b also shows that the trifluoroethyl ether co-solvent is beneficial to the deposition-dissolution reaction of the magnesium anode, avoids the formation of the interfacial passivation layer, and thus improves the electrochemical cycle life of the anode.

[0115] 4. The effect of fluorinated ethers on battery current and cycle life

[0116] Furthermore, the effectiveness of the fluorinated ether trifluoroethyl ether (BTFE) co-solvent in providing high current and long cycling performance for the magnesium metal anode was verified using a Mg / / Mg symmetric half-cell.

[0117] like Figure 5a As shown, when tetrahydrofuran (THF) is used as the sole solvent, the Mg / / Mg symmetric half-cell operates at a current density of 12.0 mA / cm². 2 A short circuit occurred; such as Figure 5c As shown, magnesium-lithium chloride complex electrolytes containing trifluoroethyl ether (BTFE) co-solvent can withstand even ultra-high current densities (20.0 mA / cm²). 2 Magnesium can still be reversibly deposited and dissolved under these conditions.

[0118] Comparing the deposition-dissolution overpotential reveals that the magnesium-lithium chloride complex electrolyte (MLCC-THF:BTFE = 1:1) containing fluorinated ether (trifluoroethyl ether BTFE) exhibits a lower overpotential at the same current density. For example, as... Figure 5b The data shows that at 10 mA / cm 2 At a given current, the overpotential of the electrolyte without fluorinated ether co-solvent (MLCC-THF) reached as high as 390mV–400mV, and after 230 hours of electrochemical cycling, a sharp drop in overpotential occurred, indicating a short circuit in the magnesium battery; Figure 5d As shown, the overpotential decreased to 230 mV after introducing trifluoroethyl ether (BTFE) as a co-solvent. This is attributed to the significant increase in ionic conductivity caused by the interaction between trifluoroethyl ether (BTFE) and chlorine (Cl) in the electrolyte. The Mg / / Mg symmetric half-cell was tested at 5.0 mA / cm². 2 Long-term deposition-dissolution tests were conducted at current densities. Figure 5dThe data shows that the magnesium-lithium chloride complex MLCC electrolyte with fluorinated ether (BTFE) co-dissolved (MLCC-THF:BTFE = 1:1) achieves superior long-cycle stability and lower deposition-dissolution overpotential. The electrolyte can stably cycle for 1200 hours, with a dissolution overpotential as low as -280mV. The above comparison demonstrates that the electrolyte of this application can reduce charge-discharge overpotential and operate stably under high current density conditions.

[0119] 5. The effect of fluorinated ethers on charge-discharge performance

[0120] To demonstrate the application potential of BTFE co-dissolved MLCC electrolyte (MLCC-THF:BTFE = 1:1 electrolyte) in full cells with magnesium metal as the negative electrode, two types of full cells, Mg / / CuS and Mg / / Mo6S8, were assembled using copper sulfide (CuS, theoretical specific capacity 560 mAh / g) and molybdenum octasulfide (Mo6S8, theoretical specific capacity 128.8 mAh / g) as positive electrode materials and metallic magnesium as the negative electrode material. Their charge-discharge performance was then tested. Figures 6a to 6d The graphs show the cycle number-discharge specific capacity / coulombic efficiency and charge / discharge specific capacity-voltage of the Mg / / CuS full cell.

[0121] In an electrolyte without a fluorinated ether co-solvent (MLCC-THF), the Mg / / CuS full cell can achieve a high discharge specific capacity in the early stages of electrochemical cycling, such as... Figure 6a and Figure 6b As shown, a high discharge specific capacity of 277 mAh / g can be achieved after the 10th charge-discharge cycle; however, the capacity decays drastically after prolonged electrochemical cycling, such as... Figure 6a and Figure 6b As shown, after 800 cycles, the discharge specific capacity decreased from 280 mAh / g at the beginning to only 68 mAh / g, a decrease of 75.71%.

[0122] After introducing a fluorinated ether (BTFE) co-solvent, the Mg / / CuS full cell at a charge / discharge rate of 0.5C (1C = 560 mA / g) shows the following performance: Figure 6c and Figure 6d As shown, it can still maintain a high discharge specific capacity of 160mAh / g after 800 cycles, with a specific capacity decay of only 42.85%. The coulombic efficiency is close to 100% and the capacity retention rate is high, which shows great application potential in the development of high energy density energy storage systems.

[0123] Figure 7The graph shows the cycle number-discharge specific capacity / coulombic efficiency of Mg / / Mo6S8 full cells. Mg / / Mo6S8 cells assembled using a fluorinated ether co-solvent electrolyte (MLCC-THF) exhibit almost no capacity release at an ultra-high current of 80C (1C = 128.8 mA / g) due to the very high overpotential. Conversely, MLCC electrolytes with BTFE co-solution (MLCC-THF:BTFE = 1:1 electrolyte) can achieve capacity release at 80C (positive electrode active material loading of 1.1 mg / cm³). 2 The current density is approximately 11.3 mA / cm². 2 It can operate stably for 10,000 cycles at ultra-high charge and discharge rates, with a discharge specific capacity of about 80 mAh / g and an average coulombic efficiency of nearly 100%, showing great promise for future applications in fast charging and discharging of magnesium secondary batteries.

[0124] 6. Effects of fluorinated ethers on magnesium chloride and other metal chlorides

[0125] To further verify the universality of the fluorinated ether trifluoroethyl ether (BTFE) co-solvent in various magnesium battery electrolytes, the fluorinated ether (BTFE) co-solvent was introduced into a simple salt magnesium chloride (MgCl2 as the electrolyte salt) electrolyte and a magnesium aluminum chloride complex (MACC, MgCl2 and AlCl3 as electrolyte salts) electrolyte, respectively, to prepare a magnesium chloride electrolyte containing fluorinated ether (MgCl2-THF:BTFE = 1:1) and a magnesium aluminum chloride complex electrolyte containing fluorinated ether (MACC-THF:BTFE = 1:4).

[0126] In a simple magnesium chloride electrolyte, a Mg / / Mg symmetric half-cell is formed, such as... Figure 8a As shown, the magnesium chloride electrolyte (MgCl2-THF) without fluorinated ethers performs well even at 0.2 mA / cm². 2 At low current densities, the deposition-dissolution overpotential of magnesium remains very high, gradually increasing to 1.8V after 1000 hours of cycling. However, using a magnesium chloride electrolyte containing fluorinated ether (MgCl2-THF:BTFE = 1:1) significantly reduces the deposition-dissolution overpotential of the magnesium metal anode; even after 1000 hours of electrochemical cycling, the overpotential remains stable below 120mV. Figure 8b As shown, the contrast is quite striking.

[0127] In MACC electrolyte, such as Figure 9a As shown, the overpotential of a Mg / / Mg symmetric cell assembled using a magnesium aluminum chloride complex electrolyte (MACC-THF) without fluorinated ethers gradually increased after 50 hours of deposition-dissolution reaction, and the cell eventually failed after 180 hours; Figure 9bAs shown, the Mg / / Mo6S8 full cell also exhibited drastic capacity decay, with the specific capacity decreasing to near 0 mAh / g after 60 cycles. The addition of the fluorinated ether BTFE co-solvent also effectively improved the electrochemical performance of the magnesium-aluminum-chloride complex electrolyte, such as... Figure 9a As shown, a Mg / / Mg symmetric half-cell assembled using a magnesium aluminum chloride complex electrolyte containing fluorinated ether (MACC-THF:BTFE = 1:4) operates at 1.0 mA / cm². 2 It can operate stably for over 800 hours at current densities without significant increase in overpotential, which remains below 200mV; Figure 9b As shown, the assembled Mg / / Mo6S8 full cell still retains a discharge specific capacity of 60 mAh / g after 2000 charge-discharge cycles, with a coulombic efficiency of up to 100%. Compared to the magnesium aluminum chloride complex electrolyte (MACC-THF) without fluorinated ether, the trifluoroethyl ether (BTFE) cosolvent achieves higher discharge specific capacity, better cycle stability, and higher capacity retention.

[0128] 7. Effects of fluorinated ether content and other solvent compositions on battery performance

[0129] To further verify the content of the fluorinated ether, namely trifluoroethyl ether (BTFE), and its electrochemical performance in other solvent compositions, electrolytes with different volume ratios were first prepared in a magnesium aluminum chloride complex (MACC) electrolyte, and Mg / / Mg symmetric half-cells were assembled to test the deposition-dissolution performance. Figure 10a As shown, the battery using a non-fluorinated ether electrolyte rapidly short-circuited after 5 hours of cycling; the battery using a fluorinated ether-containing MACC-THF:BTFE = 1:1 electrolyte maintained stable long-term cycling, but the deposition-dissolution overpotential was relatively large, such as... Figure 10b As shown, by gradually increasing the content of fluorinated ether (MACC-THF:BTFE = 1:2 and MACC-THF:BTFE = 1:4), the symmetrical cell exhibits a gradually decreasing overpotential, as shown in the figure. Figure 10c and Figure 10d As shown. However, excessive fluorinated ether (MACC-THF:BTFE = 1:6) can lead to the precipitation of a small amount of electrolyte salt, which in turn slightly increases the overpotential, such as... Figure 10e As shown. Next, the universality of fluorinated ethers combined with other non-aqueous solvents was verified. In the MgCl2-based ethylene glycol dimethyl ether (DME) electrolyte system without fluorinated ether BTFE, the symmetrical cell also exhibited short-circuit failure, as shown. Figure 11aAs shown, electrolytes containing a combination of fluorinated ether (BTFE) and dimethyl ethylene glycol (DME) (MgCl2-based-DME:BTFE = 4:1 or MgCl2-based-DME:BTFE = 2:1) can achieve stable deposition-dissolution behavior, such as... Figure 11b and Figure 11c As shown.

[0130] The above performance experiments demonstrate that the electrolyte containing fluorinated ether cosolvent of this application, through the added fluorinated ether cosolvent molecules having the characteristic of easily gaining electron reduction and decomposition to form a stable electrode-electrolyte interface by dissipating unoccupied molecular orbitals (LUMO) energy levels, can construct a stable electrode-electrolyte interface in situ on the surface of the magnesium metal anode, thereby achieving the stability of the magnesium metal battery under long-term reversible deposition-dissolution cycle at ultra-high current density, developing and promoting a low-cost, high-rate, high-capacity rechargeable magnesium battery system with magnesium metal as the anode, and realizing its practical application.

[0131] It should also be noted that the exemplary embodiments mentioned in this application describe methods or systems based on a series of steps or apparatus. However, this application is not limited to the order of the above steps; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0132] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. An electrolyte, characterized in that, Includes solvent compositions and magnesium halogen salts; The magnesium halogen salt is selected from one of magnesium chloride, magnesium fluoride, magnesium bromide, and magnesium iodide; The solvent composition includes fluorinated ethers and non-aqueous solvents, wherein the non-aqueous solvents include ionic liquids and / or organic solvents; The organic solvent is selected from imidazole compounds with C1-C4 alkyl substituted, sulfoxide or sulfone compounds with C2-C6, cyclic carbonate compounds with C3-C5 or carboxylic acid ester compounds with C2-C6, pyridine or alkylbenzene aromatic compounds with methyl, chlorine, amino or unsubstituted, C1-C4 amide compounds, acetonitrile compounds with chlorine, pyridine or unsubstituted, cyclic monoethers or diethers with C3-C4 or ethers satisfying general formula (I), or combinations thereof. H3CO(C2H4O)nCH3(I), where n takes values ​​from 1 to 8; The volume ratio of the fluorinated ether to the non-aqueous solvent is 1:0.15 to 4.

2. The electrolyte according to claim 1, characterized in that, Electrolyte salts also include metal halide salts, which satisfy MX n M is a metallic element, X is a halogen element, and n is any integer from 1 to 4; the molar ratio of the magnesium halide salt to the metal halide salt is 1:0 to 5.

3. The electrolyte according to claim 2, characterized in that, The metal halide salt is selected from one or a combination of metal chloride salts, metal fluoride salts, metal bromide salts, and metal iodide salts.

4. The electrolyte according to claim 3, characterized in that, The metal chloride salt is selected from one or a combination of aluminum trichloride, lithium chloride, gallium trichloride, and indium trichloride; and / or The metal fluoride salt is selected from one or a combination of aluminum trifluoride, gallium trifluoride, indium trifluoride, sodium fluoride, potassium fluoride, and calcium difluoride; and / or The metal bromide salt is selected from lithium bromide, indium tribromide, or a combination thereof; and / or The metal iodide salt is selected from one or a combination of aluminum triiodide, lithium iodide, gallium triiodide, and indium triiodide.

5. The electrolyte according to claim 1, characterized in that, The concentration of the magnesium halogen salt is 0.01 mol / L to 0.6 mol / L.

6. The electrolyte according to claim 3, characterized in that, The halogenated magnesium salt is magnesium chloride, and the metal chloride salt is selected from one or a combination of aluminum trichloride, lithium chloride, gallium trichloride, and indium trichloride.

7. The electrolyte according to claim 3, characterized in that, The halogenated magnesium salt is magnesium chloride, and the metal chloride salt is aluminum trichloride, with a molar ratio of magnesium chloride to aluminum trichloride of 1:0.5; or the halogenated magnesium salt is magnesium fluoride, and the metal chloride salt is a mixture of aluminum trichloride and lithium chloride, with a molar ratio of magnesium fluoride to the metal chloride salt of 1:

2.

8. The electrolyte according to claim 1, characterized in that, This includes tetrahydrofuran and trifluoroethyl ether in a volume ratio of 1:2 to 6, or trifluoroethyl ether and ethylene glycol dimethyl ether in a volume ratio of 1:2 to 4.

9. The method for preparing the electrolyte according to any one of claims 1-8, characterized in that, include: S1. Preparation of halogen-containing electrolyte: In an environment with oxygen and water content below 1 ppm and filled with nitrogen, halogen electrolyte salts are added to the organic solvent and stirred to react, thereby obtaining a halogen-containing electrolyte. S2. Introduction of fluorinated ether: Fluorinated ether is added to a halogen-containing electrolyte in a predetermined volume, and a magnesium battery electrolyte containing fluorinated ether is prepared by reaction.

10. The method for preparing the electrolyte according to claim 9, characterized in that, Step S1 of preparing the halogen-containing electrolyte further includes adding an ionic liquid to the organic solvent.

11. A rechargeable magnesium battery, characterized in that, Includes the electrolyte as described in any one of claims 1-8.

12. The rechargeable magnesium battery according to claim 11, characterized in that, The positive electrode material of the rechargeable magnesium battery is selected from one or a combination of transition metal sulfides, transition metal oxides, transition metal borides, and polyanionic phosphates.

13. The rechargeable magnesium battery according to claim 12, characterized in that, The transition metal sulfides are selected from TiS2, MoS2, WS2, VS2, HfS2, ZrS2, NbS3, VS4, and Mg. a Mo3S4 (0 < a < 2), Mo6S8, CuS, Cu2S, or a combination thereof; the transition metal oxide is selected from V2O5, V6O 13 The transition metal boride is selected from one or a combination of MnO2, Mn2O3, MoO3, and WO3; the transition metal boride is selected from one or a combination of TiB2, MoB2, and ZrB2.

14. The electrolyte according to claim 1, characterized in that, The fluorinated ether is selected from one or a combination of 2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1-(1,1,2,2-tetrafluoroethoxy)propane, and 2-methyl-1-(1,1,2,2-tetrafluoroethoxy)propane.

15. The electrolyte according to claim 1, characterized in that, The ether compound is selected from one or a combination of tetrahydrofuran, dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or polyethylene glycol dimethyl ether with n values ​​of 5 to 8. The imidazole compound is selected from one or a combination of 1-methylimidazolium, 1-ethylimidazolium, 1-propylimidazolium, and 1-butylimidazolium; The sulfoxide or sulfone compound is selected from one or a combination of dimethyl sulfoxide, sulfolane, and dipropyl sulfone. The cyclic carbonate or carboxylic acid ester compound is selected from one or a combination of ethylene carbonate, propylene carbonate, butene carbonate, 1,2-dimethylethylene carbonate, methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate. The pyridine or alkylbenzene aromatic compounds are selected from one or a combination of pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, 2-aminopyridine, toluene, and xylene. The amide compound is selected from one or a combination of dimethylamine, 1-methoxy-2-propylamine, 2-methoxyethylamine, and methoxyamine. The nitrile compound is selected from one or a combination of acetonitrile, trichloroacetonitrile, and 3-cyanopyridine.

16. The electrolyte according to claim 1, characterized in that, The ionic liquid is selected from one or a combination of imidazole ionic liquids, piperidine ionic liquids, or pyrrole ionic liquids.

17. The electrolyte according to claim 16, characterized in that, The imidazole ionic liquid is selected from one or a combination of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine salt, 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1-ethyl-3-methylimidazolium hexafluorophosphate; the pyrrole ionic liquid is N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imine salt; and the piperidine ionic liquid is N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imine salt.

18. The electrolyte according to claim 1, characterized in that, The fluorinated ether is 2,2,2-trifluoroethyl ether, the ionic liquid is 1-ethyl-3-methylimidazolium tetrafluoroborate, and the organic solvent is tetrahydrofuran; or the fluorinated ether is 2,2,2-trifluoroethyl ether, and the organic solvent includes ethylene glycol dimethyl ether.

19. The electrolyte according to claim 1, characterized in that, The volume ratio of the fluorinated ether to the non-aqueous solvent is 1:0.25.

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