Electrolyte for magnesium ion battery and magnesium ion battery

Abstract

The invention provides an electrolyte for a magnesium ion battery and the magnesium ion battery. The electrolyte comprises magnesium electrolyte salt and an organic solvent, the organic solvent comprises an ether solvent and an alkyl nitrile cosolvent. According to the present invention, the specific type of the nitrile cosolvent and the ether solvent are compounded to be used in the electrolyte, such that the electrochemical window and the cycle efficiency of the electrolyte are improved, the polarization during the charge-discharge process is reduced, and the coulombic efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium ion batteries, and in particular relates to an electrolyte for a magnesium ion battery and a magnesium ion battery. Background Art

[0002] The continuous use of fossil energy has caused serious environmental pollution. In the context of global environmental governance, it is crucial to develop green, clean and efficient large-scale energy storage equipment. Lithium-ion batteries (LIBs) have high specific energy and low self-discharge rate and are widely used in electronic devices and electric vehicles. However, the limited distribution of lithium resources and the rising cost of raw materials have seriously hindered the development and utilization of lithium-ion batteries. It is imperative to find suitable lithium-ion battery alternative technologies.

[0003] Magnesium metal is abundant in reserves, low in cost, environmentally friendly, has relatively stable physical and chemical properties, is not prone to dendrite growth, and has a high theoretical volumetric capacity (3833 mA·h / cm 3 ), therefore, the magnesium-ion battery system with magnesium metal as the negative electrode material has the advantages of high energy density, low cost, and high safety, and will be one of the new energy storage systems with great development prospects.

[0004] However, due to the high charge density and low reduction potential of magnesium ions (-2.37V vs. SHE), most organic solvents and magnesium salts will react with magnesium metal, forming a passivation layer on the surface of magnesium metal that hinders the conduction of magnesium ions, which is not conducive to the operation of magnesium ion batteries. In addition, the surface of magnesium metal is easily affected by impurities (such as trace amounts of water, oxygen, carbon dioxide, etc.), which makes the interface between the electrode and the electrolyte unstable during long-term charging and discharging, making it impossible to effectively conduct magnesium ions, thereby causing large battery charge and discharge overpotential, uneven deposition-dissolution, and even short circuit problems, ultimately leading to the failure of the magnesium battery.

[0005] Currently, the organic solvents used in magnesium ion batteries are mainly ether solvents with strong solvation ability, good chemical stability, high boiling point and high dielectric constant. However, the strong interaction between divalent magnesium and ether solvents makes desolvation difficult, which hinders the further development of rechargeable magnesium ion batteries. Summary of the invention

[0006] Based on the above technical problems, the present invention provides an electrolyte for a magnesium ion battery and a magnesium ion battery, by compounding a specific type of nitrile co-solvent with an ether solvent for use in the electrolyte, thereby achieving an improvement in the electrochemical window and cycle efficiency of the electrolyte, reducing polarization during the charge and discharge process, and improving the coulombic efficiency.

[0007] The present invention provides an electrolyte for a magnesium ion battery, comprising a magnesium electrolyte salt and an organic solvent;

[0008] Wherein, the organic solvent includes an ether solvent and a nitrile cosolvent represented by general formula (I);

[0009]

[0010] R1 is a C1-C6 alkyl group or a substituted alkyl group.

[0011] In the present invention, after the alkyl nitrile co-solvent represented by the general formula (I) cooperates with the ether solvent, an electrolyte having a finely adjustable primary solvation sheath layer obtained by mixing a monomagnesium salt with a traditional ether solvent and a nitrile solvent can be obtained. This electrolyte not only improves the electrode / electrolyte interface properties, enhances the transport kinetics at the interface, and realizes highly reversible deposition and dissolution of magnesium, but also improves the conductivity of the electrode material, reduces the battery polarization, and improves the compatibility of the electrolyte and the electrode.

[0012] In the present invention, compared with aromatic nitrile co-solvents, the alkyl nitrile co-solvent represented by general formula (I) has a better coordination effect with ether solvents and is more helpful in improving the cycle stability performance of magnesium ion batteries.

[0013] Preferably, R1 is methyl, ethyl, propyl, butyl, pentyl or hexyl;

[0014] Preferably, the nitrile co-solvent is at least one of acetonitrile, propionitrile, butyronitrile, valeronitrile or capronitrile.

[0015] Preferably, the ether solvent is at least one of ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether or tetrahydrofuran.

[0016] Preferably, the volume ratio of the ether solvent to the nitrile co-solvent is 3-6:1.

[0017] Preferably, the magnesium electrolyte salt is at least one of magnesium chloride, magnesium fluoride, magnesium bromide, magnesium iodide, bis(hexamethyldisilazide)magnesium, bis(trifluoromethanesulfonyl)imide magnesium or a Grignard reagent.

[0018] Preferably, the molar concentration of the magnesium electrolyte salt in the electrolyte is 0.1-10 mol / L.

[0019] Preferably, the electrolyte further comprises a pyrrolidine ionic liquid represented by general formula (II);

[0020]

[0021] R2 is a C1-C6 fluoroalkyl group, X - It is at least one of a tetrafluoroborate anion, a hexafluorophosphate anion, a bistrifluoromethanesulfonyl imide anion, or a bisfluorosulfonyl imide anion.

[0022] In the present invention, compared with traditional pyrrolidine ionic liquids, when the pyrrolidine ionic liquid represented by general formula (II) is used as an electrolyte additive, ester bonds and CF bonds are introduced into the pyrrolidine ionic liquid, so that the performance of the ionic liquid is greatly enhanced. On the one hand, the complexing ability with magnesium ions is improved, and the electrochemical window and electrochemical stability of the ionic liquid are improved. On the other hand, the solubility of the pyrrolidine ionic liquid is increased, so as to realize the reversible electrochemical cycle of the magnesium metal negative electrode at a high current density.

[0023] Preferably, the pyrrolidine ionic liquid represented by general formula (II) is prepared by the following method:

[0024] After condensing a fluoroalkyl acyl halide and 2-bromoethanol into an ester, the ester is subjected to an electrophilic substitution reaction with N-methylpyrrolidine, and then an ion exchange reaction is carried out with an inorganic salt to obtain a pyrrolidine ionic liquid represented by the general formula (II);

[0025] The anion in the inorganic salt is at least one of a tetrafluoroborate anion, a hexafluorophosphate anion, a bistrifluoromethanesulfonyl imide anion or a bisfluorosulfonyl imide anion.

[0026] Preferably, the molar concentration of the pyrrolidine ionic liquid in the electrolyte is 0.05-5 mol / L.

[0027] The present invention also provides a magnesium ion battery, comprising the above electrolyte.

[0028] Compared with the prior art, the present invention has the following technical effects:

[0029] The first object of the present invention is to provide an electrolyte having a fine-tunable primary solvation sheath obtained by mixing a monomagnesium salt with a traditional ether solvent and a nitrile solvent. Another object of the present invention is to provide a stable solid electrolyte / electrode interface, enhance the transport kinetics at the interface, and achieve highly reversible deposition and dissolution. The third object of the present invention is to provide an electrolyte with reduced polarization during the charge and discharge process, good cycle stability, and low cost. Finally, the electrochemical window of the electrolyte of the present invention is greater than 5V, which effectively matches high-voltage positive electrode materials, significantly improves the energy density and cycle performance of secondary batteries, and is a very potential electrolyte. DETAILED DESCRIPTION

[0030] Hereinafter, the present invention will describe the technical solution in detail through specific embodiments, but it should be clearly stated that these embodiments are for illustration only and are not to be construed as limiting the scope of the present invention.

[0031] Example 1

[0032] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0033] In a glove box filled with argon, 8 mL of ethylene glycol diethyl ether, 2 mL of acetonitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion battery.

[0034] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0035] Example 2

[0036] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0037] In a glove box filled with argon, 8 mL of ethylene glycol diethyl ether, 2 mL of acetonitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion battery.

[0038] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, V2O5 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 1.5-2.8 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0039] Example 3

[0040] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0041] In a glove box filled with argon, 8 mL of ethylene glycol diethyl ether, 2 mL of propionitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion battery.

[0042] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0043] Example 4

[0044] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0045] In a glove box filled with argon, 8 mL of ethylene glycol diethyl ether, 2 mL of valeronitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion batteries.

[0046] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0047] Example 5

[0048] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0049] In a glove box filled with argon, 8 mL of diethylene glycol diethyl ether, 2 mL of acetonitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion battery.

[0050] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0051] Example 6

[0052] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0053] In a glove box filled with argon, 7.5 mL of ethylene glycol diethyl ether, 2.5 mL of acetonitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion battery.

[0054] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0055] Example 7

[0056] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0057] In a glove box filled with argon, 8.5 mL of ethylene glycol diethyl ether, 1.5 mL of acetonitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion batteries.

[0058] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0059] Example 8

[0060] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0061] In a glove box filled with argon, 8 mL of ethylene glycol diethyl ether, 2 mL of acetonitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly, and after stirring for 30 min, a transparent homogeneous phase was formed, and then 2 mmol of pyrrolidine ionic liquid was added, and after stirring for 10 min, the electrolyte for the magnesium ion battery was obtained;

[0062] The pyrrolidine ionic liquid is shown in the following structural formula:

[0063]

[0064] The preparation method of the pyrrolidine ionic liquid comprises:

[0065] 2-bromoethanol is dissolved in dichloromethane, and a dichloromethane solution containing an equimolar amount of fluoroacetyl chloride is added dropwise under an ice bath. After the addition is completed, the temperature is raised to room temperature, and the mixture is stirred for reaction for 2 hours. The mixture is then washed with deionized water until the pH value is neutral. After concentration, the obtained product and N-methylpyrrolidine are added to toluene at a molar ratio of 1.05:1. The mixture is heated to 80° C. under nitrogen protection, and stirred for reaction for 24 hours. After concentration, the obtained product is mixed with sodium tetrafluoroborate and deionized water at a molar ratio of 1:1:10. After stirring for reaction for 6 hours, dichloromethane is added for extraction. The obtained extract is washed with deionized water for multiple times until no precipitation is produced by titration with a silver nitrate solution. After concentration, the pyrrolidine ionic liquid is obtained.

[0066] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0067] Comparative Example 1

[0068] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0069] In a glove box filled with argon, 10 mL of ethylene glycol diethyl ether and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly, and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion batteries.

[0070] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0071] Comparative Example 2

[0072] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0073] In a glove box filled with argon, 10 mL of ethylene glycol diethyl ether and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly, and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion batteries.

[0074] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, V2O5 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 1.5-2.8 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0075] Comparative Example 3

[0076] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0077] In a glove box filled with argon, 10 mL of diethylene glycol diethyl ether and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly, and after stirring for 30 minutes, a transparent homogeneous phase was obtained, thereby obtaining the electrolyte for the magnesium ion battery.

[0078] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0079] Comparative Example 4

[0080] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0081] In a glove box filled with argon, 10 mL of acetonitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly, and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for the magnesium ion battery.

[0082] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0083] Comparative Example 5

[0084] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0085] In a glove box filled with argon, 8 mL of ethylene glycol diethyl ether, 2 mL of benzonitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly and stirred for 30 minutes to obtain a transparent homogeneous phase, thereby obtaining the electrolyte for magnesium ion battery.

[0086] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0087] Comparative Example 6

[0088] An electrolyte for a magnesium ion battery, the preparation method of which comprises:

[0089] In a glove box filled with argon, 8 mL of ethylene glycol diethyl ether, 2 mL of acetonitrile and 9 mmol of magnesium bis(trifluoromethanesulfonyl)imide were mixed evenly, and a transparent homogeneous phase was obtained after stirring for 30 min. Then, 2 mmol of N-butyl-N-methylpyrrolidine tetrafluoroborate was added, and the electrolyte for the magnesium ion battery was obtained after stirring for 10 min.

[0090] 0.12 mL of the above electrolyte was dropped into a magnesium ion battery with glass fiber as the support material, Mo6S8 as the positive electrode, and magnesium as the negative electrode, and allowed to stand at room temperature for 12 hours to allow it to be fully infiltrated. The obtained magnesium ion battery was subjected to a cycle test: the battery charge and discharge range was 0.2-2.5 V, the charge and discharge rate was 1C, the test temperature was room temperature, and the specific test results are shown in Table 1 below.

[0091] The cycle test results of the above magnesium ion battery are shown in Table 1 below:

[0092] Table 1 Performance comparison of magnesium ion batteries obtained in Examples and Comparative Examples

[0093]

[0094] It can be seen from the results in the above table that the electrolyte of the present invention has good compatibility with the two positive electrode materials Mo6S8 and V2O5. By controlling the ratio of ether solvents and nitrile solvents in the electrolyte, the charge and discharge polarization and capacity retention rate of the magnesium battery can be effectively regulated, and the electrochemical window is improved; at the same time, the solid electrolyte interface formed greatly accelerates the transmission kinetics of magnesium ions, effectively inhibiting the formation of the passivation layer and the generation of harmful substances.

[0095] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An electrolyte for a magnesium ion battery, characterized in that: comprising a magnesium electrolyte salt and an organic solvent; Wherein, the organic solvent includes an ether solvent and a nitrile cosolvent represented by general formula (I); R1 is a C1-C6 alkyl group or a substituted alkyl group.

2. The electrolyte for magnesium ion battery according to claim 1, characterized in that: R1 is methyl, ethyl, propyl, butyl, pentyl or hexyl; Preferably, the nitrile co-solvent is at least one of acetonitrile, propionitrile, butyronitrile, valeronitrile or capronitrile.

3. The electrolyte for magnesium ion battery according to claim 1 or 2, characterized in that: The ether solvent is at least one of ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether or tetrahydrofuran.

4. The electrolyte for magnesium ion battery according to any one of claims 1 to 3, characterized in that: The volume ratio of the ether solvent to the nitrile co-solvent is 3-6:

1.

5. The electrolyte for magnesium ion battery according to any one of claims 1 to 4, characterized in that: The magnesium electrolyte salt is at least one of magnesium chloride, magnesium fluoride, magnesium bromide, magnesium iodide, bis(hexamethyldisilazide)magnesium, bis(trifluoromethanesulfonyl)imide magnesium or a Grignard reagent.

6. The electrolyte for magnesium ion battery according to any one of claims 1 to 5, characterized in that: The molar concentration of the magnesium electrolyte salt in the electrolyte is 0.1-10 mol / L.

7. The electrolyte for magnesium ion battery according to any one of claims 1 to 6, characterized in that: The electrolyte further comprises a pyrrolidine ionic liquid represented by general formula (II); R2 is a C1-C6 fluoroalkyl group, X - It is at least one of a tetrafluoroborate anion, a hexafluorophosphate anion, a bistrifluoromethanesulfonyl imide anion, or a bisfluorosulfonyl imide anion.

8. The electrolyte for magnesium ion battery according to claim 7, characterized in that: The pyrrolidine ionic liquid represented by general formula (II) is prepared by the following method: After condensing a fluoroalkyl acyl halide and 2-bromoethanol into an ester, the ester is subjected to an electrophilic substitution reaction with N-methylpyrrolidine, and then an ion exchange reaction is carried out with an inorganic salt to obtain a pyrrolidine ionic liquid represented by the general formula (II); The anion in the inorganic salt is at least one of a tetrafluoroborate anion, a hexafluorophosphate anion, a bistrifluoromethanesulfonyl imide anion or a bisfluorosulfonyl imide anion.

9. The electrolyte for magnesium ion battery according to claim 7 or 8, characterized in that: The molar concentration of the pyrrolidine ionic liquid in the electrolyte is 0.05-5 mol / L.

10. A magnesium ion battery, characterized in that: The invention comprises the electrolyte according to any one of claims 1 to 9.

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