Magnesium battery electrolyte based on highly fluorinated asymmetric anions as well as preparation method and application of magnesium battery electrolyte

Abstract

The invention belongs to the technical field of organic magnesium ion batteries, and particularly relates to a magnesium battery electrolyte based on highly fluorinated asymmetric anions as well as a preparation method and application of the magnesium battery electrolyte. According to the invention, perfluorobutane sulfonic acid anions are adopted to construct the novel magnesium salt electrolyte, and the asymmetric structure can disperse local charges, promote formation of anion-enriched double electric layers and improve magnesium deposition uniformity. The perfluorination characteristic of anions endows the electrolyte with strong electron-withdrawing capability, and the electrolyte can be preferentially reduced and decomposed on an electrode interface to form a solid electrolyte interface film which is rich in inorganic components and is compact and stable. The anions can be specifically adsorbed to the crystal face (002) of the magnesium negative electrode, magnesium is induced to horizontally and epitaxially grow along the crystal face, and dendritic crystal formation is inhibited. The obtained electrolyte has high coulombic efficiency (99.1%) and ultra-long cycle life (gt; 1800 h). The magnesium salt is simple in synthesis process, high in yield, good in thermal stability and suitable for large-scale preparation, and a reliable solution is provided for development of high-energy-density and high-safety magnesium batteries.

Description

Technical Field

[0001] This invention belongs to the field of organic magnesium-ion battery technology, specifically relating to a magnesium battery electrolyte based on highly fluorinated asymmetric anions, its preparation method, and its application. Background Technology

[0002] Among various metal-ion-based rechargeable battery energy storage systems, rechargeable magnesium batteries (RMBs) have attracted much attention due to their high safety, superior electrochemical performance, and broad application prospects. Compared to lithium, metallic magnesium has a lower electrode potential (-2.37V vs SHE) and a higher theoretical volumetric capacity (3833 mAh cm⁻¹). −3 Meanwhile, magnesium resources are abundant, inexpensive, environmentally friendly, and highly safe to use, making magnesium batteries one of the most promising electrochemical energy storage systems after lithium-ion batteries.

[0003] However, the commercial application of rechargeable magnesium batteries still faces many challenges, particularly at the magnesium metal anode interface. Magnesium has high reactivity and readily undergoes side reactions with traditional electrolytes, forming ion-insulating passivation layers (such as MgO, Mg(OH)2, etc.), which hinder the absorption of magnesium. 2+ The migration and reversible electrochemical reactions of magnesium lead to large voltage polarization and low coulombic efficiency. Furthermore, studies have found that under various typical electrolyte systems (such as Grignard reagents, Mg(TFSI)2-based electrolytes, etc.) or high current density conditions, magnesium anodes are prone to uneven deposition, forming dendritic-like structures. This structure can not only penetrate the separator and cause internal short circuits, but also form electrochemically deactivated "dead magnesium" due to mechanical fracture during the stripping process, further leading to capacity decay and shortened cycle life, severely affecting battery performance. It is noteworthy that magnesium deposition / stripping behavior is closely related to its solvation structure, interfacial double layer composition, and substrate properties, making it a complex electrochemical problem involving multiple scales and processes. Its kinetics are influenced by Mg... 2+ The magnesium anode is constrained by various factors, including the desolvation energy barrier, interfacial ion migration rate, and nucleation overpotential. Therefore, achieving precise control of the interfacial reaction of the magnesium anode, suppressing side reactions, and guiding uniform magnesium deposition have become core issues that urgently need to be addressed for the practical application of magnesium batteries.

[0004] To address the aforementioned challenges, numerous strategies have been proposed to improve the electrochemical performance of RMBs by resolving interface issues. These mainly include (1) introducing electrolyte additives. This involves modifying the Mg... 2+(1) Use solvation structures to suppress passivation layer formation and promote the construction of rapid magnesium ion transport interface channels. (2) Construct artificial SEI films to suppress side reactions at the interface and promote the desolvation of magnesium ion solvation clusters to achieve highly reversible uniform deposition. (3) Design three-dimensional composite electrodes. By designing good structures and high surface area negative electrode materials, the local current density can be effectively reduced to slow down the formation of passivation films and guide uniform Mg deposition. Nevertheless, most existing strategies have not explored in depth the direct influence of magnesium salt anions on the deposition morphology in the interfacial adsorption behavior, especially the regulatory role of anion structure on the composition of the electric double layer (EDL), the SEI formation mechanism and magnesium crystal orientation. Therefore, developing a new magnesium salt that can reconstruct the electrode / electrolyte interface through anion design and induce uniform magnesium deposition has become an urgent need to improve the performance of RMBs. Summary of the Invention

[0005] The purpose of this invention is to provide a magnesium battery electrolyte based on highly fluorinated asymmetric anions, its preparation method, and its application. This electrolyte can significantly improve the stability of the anode / electrolyte interface of magnesium-ion batteries and ensure the long cycle life of magnesium-ion batteries.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0007] In a first aspect, the present invention provides a highly fluorinated asymmetric anionic magnesium electrolyte salt, the structural formula of which is shown in (1).

[0008] (1).

[0009] Secondly, the present invention provides a method for highly fluorinated asymmetric anionic magnesium electrolyte salt, comprising the following steps:

[0010] (1) Mix perfluoro-1-butylsulfonic acid (PFBS) with magnesium oxide in anhydrous ethanol, stir at a certain temperature, and maintain the pH value of the solution;

[0011] (2) Remove excess MgO powder by filtration to obtain a clear solution;

[0012] (3) The solution obtained by evaporation and crystallization in the crucible is dried under vacuum to obtain anhydrous Mg(PFBS)2 powder.

[0013] Preferably, using a molar ratio meter, n PFBS :n MgO =2.05:1, where n PFBS n is the amount of PFBS. MgO This represents the amount of MgO.

[0014] Preferably, the synthesis reaction temperature is controlled to be maintained at 30°C to 60°C.

[0015] More preferably, the synthesis reaction temperature is controlled to be maintained at 40°C.

[0016] Preferably, the pH of the reaction solution should be tested with pH test paper and should be close to neutral (pH 6-7). If pH < 5, a trace amount of MgO should be added to continue the reaction.

[0017] Preferably, the product is dried in a vacuum oven at 80°C for 24 hours.

[0018] Thirdly, the present invention provides a highly fluorinated asymmetric anionic magnesium salt prepared by the above method as an electrolyte for magnesium-ion batteries. It includes the following steps:

[0019] (1) Under an inert atmosphere, magnesium salt is added to an organic solvent, wherein the concentration of magnesium salt in the electrolyte is 0.1~0.5 mol / L;

[0020] (2) Stir evenly until the magnesium salt is completely dissolved to obtain the magnesium battery electrolyte.

[0021] Preferred inert atmosphere conditions include: water and oxygen content both below 0.1 ppm.

[0022] Preferably, the organic solvent is trimethoxypropylamine (S2).

[0023] Preferably, the concentration of magnesium salt in the trimethoxypropylamine solution is 0.1~0.3 mol / L.

[0024] More preferably, the concentration of the magnesium salt in the trimethoxypropylamine solution is 0.2 mol / L.

[0025] Ideally, the speed should be set to 350 rpm and the stirring time to 24 hours.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. This invention constructs a novel magnesium salt electrolyte by introducing perfluorobutane sulfonic acid anions. Its asymmetric framework structure effectively disperses the local negative charge of the anion coordinating groups, inducing the formation of an anion-enriched double-layer structure, thereby significantly improving the uniformity of magnesium deposition. Simultaneously, PFBS... – The perfluorinated structure generates a strong electron-withdrawing effect to promote the complete decomposition of anions and the formation of a stable SEI layer.

[0028] 2. This invention can significantly accelerate the diffusion kinetics of magnesium ions. PFBS – Anions preferentially adsorb onto the negative electrode surface, forming an anion-rich interface layer, effectively reducing Mg content. 2+ The desolvation energy barrier promotes nucleation and growth. Furthermore, this electrolyte system has a high Mg content.2+ Migration number helps alleviate concentration polarization, making the magnesium deposition process more uniform and stable.

[0029] 3. This invention enables selective deposition of magnesium metal across crystal planes, suppressing dendrite growth. PFBS – Anions can specifically adsorb onto the (002) crystal plane of magnesium metal. By inhibiting the growth rate of this crystal plane, magnesium is induced to grow horizontally along the (002) crystal plane, ultimately forming a dense and flat magnesium metal deposition layer. This effectively avoids dendrite formation, thereby achieving long-term stability of the magnesium anode. Electrochemical test results show that the magnesium battery based on this electrolyte achieves a stability of 0.1 mA cm⁻¹. −2 Stable cycling for up to 1800 hours can be achieved at current densities, far superior to the traditional Mg(TFSI)2 system. Furthermore, the Mg(PFBS)2 / S2 electrolyte at 0.1 mAcm⁻¹... −2 0.1 mAh cm −2 Under certain conditions, the average coulombic efficiency reaches 99.1%, and it can operate stably for more than 800 cycles, demonstrating excellent cycle life and electrochemical reversibility. Attached Figure Description

[0030] Figure 1 This is a comparison chart of the electrostatic potential distribution (ESP) and molecular polarity index (MPI) of electrolyte anions in Example 2 and Comparative Example 1 of the present invention.

[0031] Figure 2 The figures show the test results of the electric double layer capacitance (EDLC) of the Mg||Mg symmetric cells assembled in Example 2 and Comparative Example 1 of the present invention. Among them, (a) CV curves of Mg(TFSI)2 / S2 electrolyte at different scan rates, (b) CV curves of Mg(PFBS)2 / S2 electrolyte at different scan rates, and (c) comparison of EDLC values ​​of the two electrolytes.

[0032] Figure 3 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the Mg anode in the electrolyte system prepared in Example 2 of this invention after 100 constant current charge-discharge cycles of the Mg||Mg symmetric battery.

[0033] Figure 4 The diagram shows a comparison of the desolvation activation energy (Ea) of the electrolyte systems prepared in Example 2 and Comparative Example 1 of this invention. In the diagram, a: electrochemical impedance spectroscopy (EIS) of Mg(PFBS)2 / S2 and Mg(TFSI)2 / S2 at different temperatures during the charge transfer process at the negative electrode interface; b: Ea fitting results based on the Arrhenius equation.

[0034] Figure 5The figures show the current-time curves of the electrolyte systems prepared in Example 2 and Comparative Example 1 of this invention under constant potential (50 mV) polarization. Wherein, a: Mg(TFSI)2 / S2; b: Mg(PFBS)2 / S2.

[0035] Figure 6 PFBS in Embodiment 2 of the present invention – A comparison of adsorption energies on different Mg crystal planes.

[0036] Figure 7 The X-ray diffraction (XRD) spectra of the Mg anode after 20 cycles of the electrolyte systems prepared in Example 2 and Comparative Example 1 of this invention.

[0037] Figure 8 This is a grazing incidence wide-angle X-ray scattering (GIWAXS) image of the Mg anode after 20 cycles of the electrolyte system prepared in Example 2 and Comparative Example 1 of this invention.

[0038] Figure 9 This is a scanning electron microscope (SEM) image of the Mg anode in the electrolyte system prepared in Example 2 of the present invention after 100 constant current charge-discharge cycles of the Mg||Mg symmetric battery.

[0039] Figure 10 This is a scanning electron microscope (SEM) image of the Mg anode in the electrolyte system prepared in Comparative Example 1 of this invention after 100 constant current charge-discharge cycles.

[0040] Figure 11 The images are atomic force microscopy (AFM) images of the Mg anode in the electrolyte systems prepared in Example 2 and Comparative Example 1 of this invention after 100 constant current charge-discharge cycles.

[0041] Figure 12 The Mg||Mg symmetric cells in the electrolyte systems prepared in Examples 1, 2, 3, 4, and 5 of this invention are at 0.1 mAcm⁻¹ −2 0.05 mAh cm −2 A constant current charge-discharge cycle diagram under certain conditions.

[0042] Figure 13 The Mg||Mg symmetric cells in the electrolyte systems prepared in Example 2 and Comparative Examples 1, 2, and 3 of this invention operate at 0.1 mA cm⁻¹. −2 0.05 mAh cm −2 A constant current charge-discharge cycle diagram under certain conditions.

[0043] Figure 14 The Mg||SS asymmetric cells in the electrolyte systems prepared in Example 2 and Comparative Example 1 of this invention achieve a current of 0.1 mA cm⁻¹. −20.05 mAh cm −2 Coulomb efficiency diagram under the given conditions. Detailed Implementation

[0044] The present application will be further described below with reference to specific embodiments.

[0045] It should be noted that terms such as "upper", "lower", "left", "right", and "middle" used in this specification are only for clarity of description and are not intended to limit the scope of implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of this application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0047] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0048] As used herein, the term “about” is used to provide for the flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[0049] Example 1:

[0050] 1. Mix 5.457 mL of perfluoro-1-butylsulfonic acid and 0.6474 g of magnesium oxide in 50 mL of anhydrous ethanol and stir.

[0051] 2. Remove excess MgO powder by filtration to obtain a clear solution;

[0052] 3. The solution obtained by crucible evaporation and crystallization was dried under vacuum at 80°C for 24 hours to obtain anhydrous Mg(PFBS)2 powder;

[0053] IV. Under conditions where the water and oxygen content are both below 0.1 ppm, 0.1245 g of anhydrous Mg(PFBS)2 powder is added to 2 mL of organic solvent S2 and stirred for 24 hours. After the magnesium salt is completely dissolved, a 0.1 mol / L magnesium battery electrolyte is obtained.

[0054] Example 2:

[0055] The other processes are the same as in Example 1, except that the amount of Mg(PFBS)2 added is changed to 0.249 g, resulting in an electrolyte of 0.2 mol / L Mg(PFBS)2.

[0056] Example 3:

[0057] The other processes are the same as in Example 1, except that the amount of Mg(PFBS)2 added is changed to 0.3735 g, resulting in an electrolyte of 0.3 mol / L Mg(PFBS)2.

[0058] Example 4:

[0059] The other processes are the same as in Example 1, except that the amount of Mg(PFBS)2 added is changed to 0.498 g, resulting in an electrolyte of 0.4 mol / L Mg(PFBS)2.

[0060] Example 5:

[0061] The other processes are the same as in Example 1, except that the amount of Mg(PFBS)2 added is changed to 0.6225 g, resulting in an electrolyte of 0.5 mol / L Mg(PFBS)2.

[0062] Comparative Example 1:

[0063] In an environment where the water and oxygen content are both below 0.1 ppm, 0.234 g of anhydrous Mg(TFSI)2 powder is added to 2 mL of organic solvent S2 and stirred for 24 hours. After the magnesium salt is completely dissolved, a 0.2 mol / L magnesium battery electrolyte is obtained.

[0064] Comparative Example 2:

[0065] The other processes were the same as in Comparative Example 1, except that the amount of Mg(TFSI)2 added was changed to 0.351 g, resulting in an electrolyte of 0.3 mol / L Mg(TFSI)2.

[0066] Comparative Example 3:

[0067] In an environment where the water and oxygen content are both below 0.1 ppm, 0.322 g of anhydrous Mg(OTf)2 powder was added to 2 mL of organic solvent S2 and stirred for 24 h. After the magnesium salt was completely dissolved, a 0.2 mol / L magnesium battery electrolyte was obtained.

[0068] Application Example 1

[0069] The electrolytes obtained in the above embodiments and comparative examples were used as electrolytes to prepare magnesium-ion symmetric batteries. The process is as follows:

[0070] Step 1: Prepare the electrolyte according to the above proportions;

[0071] Step 2: In a glove box where the water and oxygen content are both below 0.1 ppm, assemble the prepared magnesium-ion battery components into a button cell in the following order: negative electrode shell, spring, gasket, negative magnesium electrode, glass fiber separator, electrolyte, positive magnesium electrode, gasket, and positive electrode shell. The battery shell model used is CR2032.

[0072] Step 3: Place the button battery assembled in Step 2 into a sealed test bottle and let it stand in the sealed bottle for 2 hours;

[0073] Step 4: The battery test conditions in Step 3 are: rest for 1 hour - constant current discharge (cut off at 0.5 hours) - rest for 10 seconds - constant current charging (cut off at 0.5 hours) - rest for 10 seconds - cycle 4000 times - stop.

[0074] Figure 1 The corresponding ESP and MPI of the electrolytes in Example 2 and Comparative Example 1 are shown. Compared to the anionic TFSI of the electrolyte in Comparative Example 1... – Example 1 Electrolyte PFBS – PFBS possesses an asymmetric framework that delocalizes a large amount of charge to reduce the local negative charge of the anionic coordinating groups. – The MPI of the anion decreased to 85.13 kcal / mol. –1 .

[0075] Figure 2 The EDCLs of Example 2 and Comparative Example 1 are shown, wherein the EDCL of Mg(TFSI)2 / S2 is 165.5 μF cm⁻¹. –2 The ratio is higher than that of Mg(PFBS)2 / S2 (70.5 μF cm). –2 This indicates that it has a specific adsorption preference at the Janus interface, forming an anion-rich EDL structure. This suppresses local excess charge, minimizes surface charge fluctuations, and thus ensures the uniformity and orientation of the deposited magnesium morphology.

[0076] Figure 3 The XPS spectrum of the magnesium sheet is shown after 100 hours of cycling in the electrolyte of Example 2. PFBS – Complete fluorination of the anion has a strong electron-withdrawing effect, making PFBS... – Electrons are more readily gained during deposition, making it easier to reduce and form SEI from the Mg anode surface. Organic species such as RNO and CN were detected on the Mg anode surface. MgF2, a classic inorganic species with a large band gap, showed a significant peak at 684.9 eV, while other inorganic species, including MgCO3 (290.1 ​​eV) and MgS (161.7 eV), also showed significant peaks in PFBS. −Detected in the induced SEI component. SEI is a conductive Mg... 2+ And a dense layer that blocks electrons. Multi-component surface SEI layers have a low stacking factor, which is beneficial for Mg. 2+ It offers fast transmission and high mechanical strength.

[0077] Figure 4 This demonstrates how to calculate Mg by fitting the impedance at different temperatures. 2+ The Ea values ​​in the electrolytes of Example 2 and Comparative Example 1 were calculated using the Arrhenius equation. The Ea value for the electrolyte in Example 2 was 38.54 kJ / mol, while the Ea value for the electrolyte in Comparative Example 1 decreased to 15.18 kJ / mol. This indicates that Mg... 2+ The desolvation energy barrier is lowered, making nucleation easier.

[0078] Figure 5 The changes in impedance of the Mg||Mg symmetric cells before and after polarization in Example 2 and Comparative Example 1 are shown to be calculated. 2+ The migration number was 0.64 in the electrolyte of Example 2, while it was 0.29 in the electrolyte of Comparative Example 1. PFBS – Anions increased Mg 2+ The migration number accelerates Mg 2+ Migration is beneficial to Mg 2+ Uniform deposition on the Mg anode surface improves Mg 2+ Reversible properties of deposition / stripping.

[0079] Figure 6 PFBS in Example 2 is shown – Comparison of adsorption energies on different Mg crystal planes, PFBS – The adsorption energies on the Mg(002), (100), and (101) crystal planes are -5.19, -4.28, and -4.35 eV, respectively. PFBS – The absolute value of the adsorption energy on the Mg(002) crystal plane is higher than that on the (100) and (101) crystal planes. Therefore, PFBS... – The difference in adsorption behavior on the three crystal planes results in a faster growth rate on the (100) and (101) crystal planes than on the (002) crystal plane, leading to the eventual exposure of the (002) crystal plane. This makes Mg more likely to be deposited at a small angle, which helps to achieve uniform horizontal magnesium metal deposition and alleviates the problem of irreversible magnesium plating / stripping.

[0080] Figure 7The XRD patterns of Mg||Mg symmetric batteries prepared with the electrolyte systems of Example 2 and Comparative Example 1 after 20 constant current charge-discharge cycles are shown to investigate the crystal orientation of the magnesium anode after cycling. The I(002) / I(101) peak intensity of the electrode after cycling with the electrolyte of Example 2 is significantly larger than that of Comparative Example 1.

[0081] Figure 8 The GIWAXS plots of Mg||Mg symmetric batteries prepared with the electrolyte systems of Example 2 and Comparative Example 1 after the same number of constant current charge-discharge cycles are shown. The (002) diffraction peak intensity of the electrode after cycling with the electrolyte of Example 1 is higher than that of Example 2. These indicate that in the Mg(PFBS)2 / S2 electrolyte, Mg... 2+ Horizontally oriented on the (002) crystal plane. Adsorbed PFBS – It can adjust Mg 2+ The deposition behavior is induced and horizontal extension along the (002) crystal plane of Mg is induced, which promotes uniform Mg deposition.

[0082] Figure 9 and Figure 10 The images show scanning electron microscope (SEM) images of the Mg anode in the electrolyte systems prepared in Example 2 and Comparative Example 1 after 100 constant current charge-discharge cycles. In contrast, the electrolyte cycle surface of Example 2 shows a completely uniform coverage by magnesium grains of similar size, which grow in a flattened epitaxial manner, while the electrolyte cycle surface of Comparative Example 1 shows dendritic growth and surface fragmentation.

[0083] Figure 11 Atomic force microscopy (AFM) images of the Mg anode in the electrolyte systems prepared in Example 2 and Comparative Example 1 after 100 constant current charge-discharge cycles of the Mg||Mg symmetric cells are shown. It can be seen that magnesium is uniformly deposited in the electrolyte of Example 2. In the Mg(TFSI)2 / S2 electrolyte, the magnesium deposits form irregular wavy ridges with a height of up to 80 nm, while the magnesium deposits in the Mg(PFBS)2 / S2 electrolyte exhibit a distinctly regular morphology with a thickness of approximately 50 nm.

[0084] Figure 12 The images show Mg||Mg symmetric cells prepared using the electrolyte systems described in Examples 1, 2, 3, 4, and 5, operating at 0.1 mA cm⁻¹. −2 Current density, battery capacity is 0.05 mAh cm⁻¹ −2 The results of long-cycle stability tests show that 0.2 mol / L Mg(PFBS)2 / S2 in Example 2 can provide stable cycling for more than 1800 hours and is considered the optimal addition amount.

[0085] Figure 13The Mg||Mg symmetric cells prepared using the electrolyte systems of Example 2 and Comparative Examples 1, 2, and 3 are shown to operate at 0.1 mA cm⁻¹. −2 Current density, battery capacity is 0.05 mAh cm⁻¹ −2 The results of long-term cycle stability tests show that the cycle life of both Mg(TFSI)2 and Mg(OTf)2 electrolytes under charge-discharge conditions is less than 650 hours.

[0086] Figure 14 The coulombic efficiency of the electrolyte systems prepared in Example 2 and Comparative Example 1, assembled into a Mg||SS asymmetric battery, is shown. The electrolyte in Example 2 at 0.1 mAh cm⁻¹... −2 At the specified current density, the average coulombic efficiency (CE) is 99.1%, and it can maintain this efficiency for over 1000 cycles. In contrast, the battery using the electrolyte in Comparative Example 1 only experienced an efficiency decrease after 150 cycles. Coulombic efficiency (CE) is an important indicator for evaluating the reversibility of deposition / stripping on the surface of magnesium anodes. These results confirm that PFBS... − Anions have a significant positive effect on magnesium deposition / stripping.

[0087] The above embodiments are merely preferred embodiments of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, or combinations made without departing from the spirit and principle of the present invention, such as various combinations of the solutions in the embodiments, should be considered equivalent replacements and are all within the protection scope of the present invention.

Claims

1. A highly fluorinated asymmetric anionic magnesium electrolyte salt, characterized in that, The anion of the electrolyte salt is perfluorobutane sulfonate (PFBS). – Its chemical formula is Mg(PFBS)2, and its structural formula is shown in (1). （1）。 2. A method for preparing a highly fluorinated asymmetric anionic magnesium electrolyte salt, characterized in that, Includes the following steps: (1) Mix perfluoro-1-butylsulfonic acid (PFBS) with magnesium oxide in anhydrous ethanol and stir at 30°C to 60°C, keeping the pH of the solution at 6-7. (2) Remove excess MgO powder by filtration to obtain a clear solution; (3) The solution obtained by evaporation and crystallization was dried under vacuum at 80°C for 24 hours to obtain anhydrous Mg(PFBS)2 powder.

3. A method for preparing a magnesium-ion battery electrolyte, characterized in that, Includes the following steps: (1) Under an inert atmosphere, the magnesium salt of claim 1 is added to an organic solvent; (2) Stir evenly until the magnesium salt is completely dissolved to obtain the magnesium battery electrolyte.

4. The preparation method according to claim 3, characterized in that, The conditions for an inert atmosphere include: water and oxygen content both below 0.1 ppm.

5. The preparation method according to claim 3, characterized in that, The organic solvent is trimethoxypropylamine.

6. The preparation method according to claim 5, characterized in that, The concentration of magnesium salt in organic solvents is 0.1~0.5 mol / L.

7. The preparation method according to claim 5, characterized in that, The concentration of magnesium salt in organic solvents is 0.1~0.3 mol / L.

8. The preparation method according to claim 5, characterized in that, The concentration of magnesium salt in the organic solvent is 0.2 mol / L.

9. A magnesium-ion battery electrolyte, characterized in that, The magnesium-ion battery electrolyte is prepared according to any one of claims 2-8.

10. The application of the magnesium-ion battery electrolyte as described in claim 9 in organic magnesium-ion batteries.

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