Water-resistant electrolyte for magnesium metal battery as well as preparation method and application of water-resistant electrolyte

Abstract

The invention belongs to the technical field of new energy batteries, and particularly relates to a magnesium metal battery water-resistant electrolyte as well as a preparation method and application thereof. The magnesium metal battery water-resistant electrolyte is prepared from the following raw materials: magnesium salt, metal or non-metal halide, an organic ether solvent and a boric acid ester additive. According to the water-resistant electrolyte for the magnesium metal battery, boric acid ester additives react with water molecules, the content of free water or coordinated water is reduced, meanwhile, components of an electrode / electrolyte interface are improved through preferential decomposition, and a more stable SEI / CEI (solid electrolyte interface film / positive electrode electrolyte interface film) is formed, so that the water resistance of the battery is remarkably improved, and the service life of the battery is prolonged. And after water (especially water content of 0-50000 ppm) is added, stable circulation can still be realized, and the preparation cost, drying cost and environmental requirements of the magnesium metal battery can be greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of new energy battery technology, specifically relating to a water-resistant electrolyte for magnesium metal batteries, its preparation method, and its application. Background Technology

[0002] Rechargeable magnesium batteries (RMBs) are a core candidate for next-generation energy storage technology, boasting abundant magnesium resources and a high theoretical volumetric capacity (3833 mAh·cm³). -3 The significant advantages of RMBs, such as uniform magnesium deposition behavior, ensure the safety of negative electrode operation. Combined with sustainable resource sources and good economic feasibility, RMBs have attracted considerable attention in the field of large-scale energy storage. The electrolyte is a key component of RMBs, serving both ion transport functions and determining the magnesium deposition rate. 2+ Diffusion dynamics at the electrode interface directly affect the cycle stability and energy efficiency of the battery.

[0003] However, the commercialization of RMBs is limited by the extreme sensitivity of traditional electrolytes to moisture: even trace amounts of residual moisture can trigger irreversible side reactions on the magnesium anode surface, forming an electrically insulating MgO / Mg(OH)2 layer, severely reducing the coulombic efficiency and cycle stability of magnesium deposition / dissolution. Simultaneously, the high sensitivity of both the electrolyte and the magnesium anode to trace amounts of moisture significantly increases drying costs during battery production. From a molecular mechanism perspective, water, due to its high dielectric constant and donor number, readily competes with solvent molecules and anions for coordination into Mg. 2+ The first solvation shell, enriched and reacted on the negative electrode surface, weakens the reversibility of deposition / dissolution; in addition, the hydrolysis reaction of the anion-water coordination compound consumes active anions and releases free protons (H). + This leads to accelerated electrolyte degradation and parasitic side reactions.

[0004] To address the aforementioned issues, existing research has attempted to improve water resistance by introducing additives. For example, in the Mg(TFSI)₂ system, AlCl₃-based additives can remove water through coordination water capture, but this consumes active ionic species in the electrolyte. While some additives (such as dibutylmagnesium, isobutylamine, and 2-methoxyethylamine) can improve the reversibility of the magnesium anode and remove water impurities, their water resistance is limited, tolerating only 5300 ppm of impurity water, and their improvement on coulombic efficiency is also limited. Therefore, developing a highly efficient water-resistant electrolyte is crucial for realizing a reversible, water-resistant magnesium battery prototype and significantly reducing manufacturing costs. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide a water-resistant electrolyte for magnesium metal batteries, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention can adopt the following technical solutions: This invention provides a water-resistant electrolyte for magnesium metal batteries, the raw materials for which include: magnesium salts, metal or non-metal halides, organic ether solvents and borate ester additives.

[0007] Preferably, in the above-mentioned water-resistant electrolyte for magnesium metal batteries, Magnesium salts are selected from one or more combinations of magnesium chloride, magnesium hexafluoroisopropoxide, magnesium bis(trifluoromethanesulfonyl)imide, and magnesium trifluoromethanesulfonate; and / or The metal or nonmetal halide is selected from one or more combinations of aluminum chloride, boron trichloride, titanium trichloride, titanium tetrachloride, phosphorus pentachloride, copper chloride, indium chloride, aluminum bromide, indium bromide, aluminum iodide, and indium iodide; and / or Organic ether solvents are selected from one or more combinations of 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, diethyl cellosolve, 1,3-dimethoxypropane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; and / or The borate ester additives are selected from one or more combinations of trimethyl borate, triethyl borate, triisopropyl borate, tri(2,2,2-trifluoroethyl) borate and tri(hexafluoroisopropyl) borate.

[0008] More preferably, in the above-mentioned water-resistant electrolyte for magnesium metal batteries, the magnesium salt is magnesium trifluoromethanesulfonate, the metal or non-metal halide is aluminum chloride, the organic ether solvent is ethylene glycol dimethyl ether, and the borate ester additive is tris(2,2,2-trifluoroethyl) borate.

[0009] Preferably, in the above preparation method, the molar ratio of magnesium salt to metal or non-metal halide is 1:(1.0 to 2.0); and / or the molar ratio of magnesium salt to borate ester additive is 1:(0.5 to 2.5).

[0010] Preferably, in the above-mentioned water-resistant electrolyte for magnesium metal batteries, the water content of the water-resistant electrolyte for magnesium metal batteries is ≤50000ppm.

[0011] Another aspect of the present invention provides a method for preparing the above-mentioned water-resistant electrolyte for magnesium metal batteries. The preparation method includes: mixing magnesium salt, metal or non-metal halide, organic ether solvent and borate ester additive to obtain the water-resistant electrolyte for magnesium metal batteries.

[0012] Preferably, the above preparation method includes: (1) mixing magnesium salt, metal or non-metal halide and organic ether solvent to obtain magnesium salt solution; (2) mixing magnesium salt solution with borate ester additive to obtain water-resistant electrolyte for magnesium metal battery.

[0013] In another aspect, the present invention provides a magnesium metal battery comprising the above-mentioned magnesium metal battery water-resistant electrolyte.

[0014] Preferably, in the above-mentioned magnesium metal battery, the magnesium metal battery is a Mg||SS battery, a Mg||Mg symmetric battery, a Mg||Mo asymmetric battery, or a Mg||Mo6S8 battery.

[0015] The beneficial effects of this invention include at least the following: the water-resistant electrolyte for magnesium metal batteries provided by this invention uses borate ester additives to optimize the composition of the electrode / electrolyte interface, forming a more stable SEI / CEI (solid electrolyte interface film / positive electrode electrolyte interface film), thereby significantly improving the water resistance of the battery. It can still cycle stably after adding water (especially ≤50000ppm water content), which can greatly reduce the drying cost of magnesium battery industrialization. Attached Figure Description

[0016] Figure 1 Near-infrared spectroscopy results of the water-resistant electrolyte for magnesium metal batteries prepared in Example 1, the electrolytes with added 5000 ppm and 10000 ppm water respectively, and the electrolyte prepared in Comparative Example 1. Figure 2 The specific chemical reaction pathway for Experiment Example 1; Figure 3 The cyclic voltammetry (CV) curves of the Mg||SS battery assembled with the water-resistant electrolyte of the magnesium metal battery prepared in Example 1 and the electrolyte prepared in Comparative Example 1 are compared at 25°C. Figure 4 Comparison of cyclic voltammetry (CV) curves of Mg||SS batteries assembled after adding 10000ppm of water to the water-resistant electrolyte of magnesium metal batteries prepared in Example 1 and Comparative Example 1; Figure 5 Linear sweep voltammetry (LSV) curves of different current collectors assembled after adding 5000 ppm and 10000 ppm of water to the water-resistant electrolyte of the magnesium metal battery prepared in Example 1. Figure 6 The Mg||Mg symmetric cells assembled after adding 5000 ppm and 10000 ppm of water to the water-resistant electrolyte of the magnesium metal battery prepared in Example 1, respectively, were tested at 0.1 mA·cm⁻¹. -2 Cyclic performance test results at current density; Figure 7 The Mg||Mg symmetric batteries assembled after adding 5000 ppm and 10000 ppm of water to the water-resistant electrolyte of the magnesium metal battery prepared in Example 1, respectively, achieved a performance of 0.5 mAh·cm⁻¹. -2 Rate performance test results at specific capacity; Figure 8The Mg||Mo asymmetric cells assembled after adding 5000 ppm and 10000 ppm of water to the water-resistant electrolyte of the magnesium metal battery prepared in Example 1 were tested at 0.1 mA·cm⁻¹. -2 Long-cycle performance test results at current density; Figure 9 The specific capacity-voltage curves of Mg||Mo6S8 batteries assembled by adding 5000ppm and 10000ppm water to the water-resistant electrolyte of the magnesium metal battery prepared in Example 1 are shown. Figure 10 The long-cycle performance and coulombic efficiency of Mg||Mo6S8 batteries assembled by adding 5000ppm and 10000ppm of water to the water-resistant electrolyte of the magnesium metal battery prepared in Example 1 were investigated. Detailed Implementation

[0017] The illustrated embodiments are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the illustrated embodiments. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description of the invention still fall within the protection scope of the present invention.

[0018] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” “including,” are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials, or combinations thereof. The terminology of the invention is disclosed in the specification and is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations thereof may be present or added. As used herein, “ / ” may be interpreted as “and” or “or,” depending on the context.

[0019] In a first aspect, embodiments of the present invention provide a water-resistant electrolyte for magnesium metal batteries, the raw materials for which include: magnesium salts, metal or non-metal halides, organic ether solvents and borate ester additives.

[0020] It should be noted that the magnesium salt in this invention undergoes a Lewis acid-base reaction with metal or non-metal halides to form active anions and cations, thereby maintaining the reversible deposition and dissolution process of the electrolyte, and the borate esters, as additives, impart water resistance to the electrolyte. Specifically, the borate ester additives can pre-protonate water molecules, eliminating water impurities in the electrolyte and side reactions at the interface. Simultaneously, the borate esters and their derivatives participate in the interfacial phase reaction, forming a more stable electrode / electrolyte interface film, improving the stability of the battery's electrochemical reaction, significantly enhancing battery performance, and giving the electrolyte a certain degree of water resistance. It can maintain stable cycling in the range of 0-50000 ppm, significantly reducing the cost of constructing expensive drying chambers, and providing a promising direction for the future design of high-performance, cost-effective magnesium metal battery electrolytes.

[0021] In some specific examples, the magnesium salt in the water-resistant electrolyte of the above-mentioned magnesium metal battery is selected from one or more combinations of magnesium chloride (MgCl2), magnesium hexafluoroisopropoxide (Mg(HFIP)2), magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2), and magnesium trifluoromethanesulfonate (Mg(OTf)2).

[0022] It should be noted that the magnesium salts used in this invention are known in the art, including but not limited to the magnesium salts listed above.

[0023] In some specific examples, the metal or non-metal halide in the water-resistant electrolyte of the above-mentioned magnesium metal battery is selected from one or more combinations of aluminum chloride (AlCl3), boron trichloride (BCl3), titanium trichloride (TiCl3), titanium tetrachloride (TiCl4), phosphorus pentachloride (PCl5), copper chloride (CuCl2), indium chloride (InCl3), aluminum bromide (AlCl3), indium bromide (InBr3), aluminum iodide (AlI3), and indium iodide (InI3).

[0024] It should be noted that the metal or non-metal halides in this invention are known in the art, including but not limited to the metal or non-metal halides listed above.

[0025] In some specific examples, the organic ether solvent in the water-resistant electrolyte of the above-mentioned magnesium metal battery is selected from one or more combinations of 1,3-dioxolane (DOL), 1,3-dioxane (1,3-DOX), 1,4-dioxane (1,4-DOX), tetrahydrofuran (THF), ethylene glycol dimethyl ether (DME), diethyl cellosolve (DEE), 1,3-dimethoxypropane (DMP), diethylene glycol dimethyl ether (G2), triethylene glycol dimethyl ether (G3), and tetraethylene glycol dimethyl ether (G4).

[0026] It should be noted that the organic ether solvents used in this invention are known in the art, including but not limited to the organic ether solvents listed above.

[0027] In some specific examples, the borate ester additives in the above-mentioned water-resistant electrolyte for magnesium metal batteries are selected from one or more combinations of trimethyl borate (B(TM)3), triethyl borate (B(TE)3), triisopropyl borate (B(TIP)3), tri(2,2,2-trifluoroethyl) borate (B(TFE)3) and tri(hexafluoroisopropyl) borate (B(HFIP)3).

[0028] It should be noted that the borate ester additives in this invention are known in the art, including but not limited to the borate ester additives listed above.

[0029] In some specific examples, the magnesium salt in the water-resistant electrolyte of the above-mentioned magnesium metal battery is magnesium trifluoromethanesulfonate, the metal or non-metal halide is aluminum chloride, the organic ether solvent is ethylene glycol dimethyl ether, and the borate ester additive is tris(2,2,2-trifluoroethyl) borate.

[0030] It should be noted that the water-resistant electrolyte for magnesium metal batteries in this invention can preferably include magnesium trifluoromethanesulfonate, aluminum chloride, ethylene glycol dimethyl ether, and tri(2,2,2-trifluoroethyl) borate.

[0031] In some specific examples, the molar ratio of magnesium salt to metal or non-metal halide in the above preparation method is 1:(1.0 to 2.0).

[0032] It should be noted that the molar ratio of magnesium salt to metal or non-metal halide in this invention can be 1:(1.0 to 2.0), such as 1:1.3, 1:1.5 or 1:1.7, etc.

[0033] In some specific examples, the molar ratio of magnesium salt and borate ester additives in the above preparation method is 1:(0.5 to 2.5).

[0034] It should be noted that the molar ratio of magnesium salt and borate ester additives in this invention can be 1:(0.5 to 2.5), such as 1:1, 1:1.5 or 1:1.7, etc.

[0035] In some specific examples, the water content of the water-resistant electrolyte for magnesium metal batteries is ≤50000ppm.

[0036] It should be noted that the water-resistant electrolyte for magnesium metal batteries in this invention has excellent water resistance and still exhibits excellent electrochemical performance and stability even when water is present. In particular, when the water content is ≤50000ppm, there is no significant difference in electrochemical performance between the water-resistant electrolyte for magnesium metal batteries in this invention and the water-resistant electrolyte for magnesium metal batteries without water.

[0037] Secondly, embodiments of the present invention provide a method for preparing the above-mentioned water-resistant electrolyte for magnesium metal batteries. The preparation method includes: mixing magnesium salt, metal or non-metal halide, organic ether solvent and borate ester additive to obtain the water-resistant electrolyte for magnesium metal batteries.

[0038] It should be noted that the preparation method of the water-resistant electrolyte for magnesium metal batteries in this invention is simple, the reaction conditions are mild, and it can be obtained by simply mixing the various reaction raw materials, making it easy to carry out large-scale industrial production.

[0039] In some specific examples, the above preparation method includes: (1) mixing magnesium salt, metal or non-metal halide and organic ether solvent to obtain magnesium salt solution; (2) mixing magnesium salt solution with borate ester additive to obtain water-resistant electrolyte for magnesium metal battery.

[0040] It should be noted that, in the preparation process of the water-resistant electrolyte for magnesium metal batteries in this invention, it is preferable to first mix magnesium salt, metal or non-metal halide, organic ether solvent and magnesium salt solution, and then add borate ester additives to react and obtain the water-resistant electrolyte for magnesium metal batteries, which can make the reaction more complete.

[0041] Thirdly, embodiments of the present invention provide a magnesium metal battery, which includes the above-mentioned magnesium metal battery water-resistant electrolyte.

[0042] It should be noted that, based on the excellent electrochemical performance of the water-resistant electrolyte in the magnesium metal battery of the present invention, it can be assembled into a magnesium metal battery by combining it with a positive electrode, a negative electrode and a separator; wherein, the positive electrode, a negative electrode and the separator are all known in the art and can be selected according to the specific battery.

[0043] In some specific examples, the magnesium metal batteries mentioned above are Mg||SS batteries, Mg||Mg symmetric batteries, Mg||Mo asymmetric batteries, or Mg||Mo6S8 batteries.

[0044] It should be noted that the magnesium metal battery in this invention includes, but is not limited to, the types of batteries listed above, and the water-resistant electrolyte in the magnesium metal battery of this invention is applicable to all magnesium metal batteries known in the art.

[0045] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.

[0046] Preparation Examples and Comparative Examples Example 1 This invention provides a water-resistant electrolyte for magnesium metal batteries, the preparation method of which includes the following steps: (1) Add 0.8061g Mg(OTf)2 (magnesium trifluoromethanesulfonate) and 0.3334g AlCl3 (aluminum chloride) to 10mL LDME (ethylene glycol dimethyl ether) and mix well to obtain a magnesium salt solution; wherein the magnesium salt concentration in the magnesium salt solution is 0.25mol / L; (2) Add 1.54g of B(TFE)3 (tri(2,2,2-trifluoroethyl) borate) to the magnesium salt solution in (1), mix well and obtain a water-resistant electrolyte for magnesium metal batteries.

[0047] Example 2 Example 2 is largely the same as Example 1, except that B(HFIP)3 (tris(hexafluoroisopropyl) borate) is used in Example 2 instead of B(TFE)3 in Example 1. Otherwise, the same as Example 1 is used to prepare a water-resistant electrolyte for magnesium metal batteries.

[0048] Example 3 Example 3 is largely the same as Example 1, except that Mg(HFIP)2 (magnesium hexafluoroisopropoxide) is used in Example 3 instead of Mg(OTf)2 in Example 1. Otherwise, the same as Example 1 is used to prepare a water-resistant electrolyte for magnesium metal batteries.

[0049] Example 4 Example 4 is largely the same as Example 1, except that Mg(TFSI)2 (bis(trifluoromethanesulfonyl)imide magnesium) is used instead of Mg(OTf)2 in Example 1 in Example 4. Otherwise, the same as in Example 1 is used to prepare a water-resistant electrolyte for magnesium metal batteries.

[0050] Example 5 Example 5 is largely the same as Example 1, except that BCl3 (boron trichloride) is used in Example 5 instead of AlCl3 in Example 1. Otherwise, the same as Example 1 is used to prepare a water-resistant electrolyte for magnesium metal batteries.

[0051] Comparative Example 1 0.8061 g of Mg(OTf)2 (magnesium trifluoromethanesulfonate) and 0.3334 g of AlCl3 (aluminum chloride) were added to 10 mL of LDME (dimethyl ether) and mixed thoroughly to obtain an electrolyte; wherein the magnesium salt concentration in the electrolyte was 0.25 mol / L.

[0052] Comparative Example 2 Comparative Example 2 is largely the same as Comparative Example 1, except that bis(trifluoromethanesulfonyl)imide magnesium (Mg(TFSI)2) is used in Comparative Example 2 to replace Mg(OTf)2 in Comparative Example 1. Otherwise, the electrolyte is prepared in the same way as Comparative Example 1.

[0053] Characterization test Near-infrared spectroscopy was performed on the magnesium salt (Mg(OTf)2), solvent (DME), water-resistant electrolyte for magnesium metal batteries in Example 1, and the electrolytes prepared with 5000 ppm and 10000 ppm water respectively, as well as the electrolyte prepared in Comparative Example 1. The results are as follows: Figure 1 As shown, the results indicate that the electrolyte prepared in Comparative Example 1 contains 3480 cm⁻¹ -1 The peaks containing OH bonds were detected. The peaks of the magnesium metal battery water-resistant electrolyte prepared in Example 1, after adding 5000 ppm and 10000 ppm respectively, were very weak, indicating that the borate ester additive in Example 1 absorbed water. Meanwhile, the stretching vibration peak of Example 1 was consistent in both aqueous and anhydrous conditions, also indicating that due to the presence of borate esters, water does not change the active anionic and cation species and chemical environment of the electrolyte, demonstrating that the magnesium metal battery water-resistant electrolyte prepared in Example 1 has strong water resistance. Specifically, the chemical reaction equation for the electrolyte reaction is as follows: Figure 2 As shown, magnesium salts first undergo a Lewis acid-base reaction with metal or non-metal halides to form complex magnesium cations and anions, which dissolve in ether solvents. Then, the introduced borate esters can react with impurity water to form hydroxyl-containing borate esters and fluorinated alcohols, preventing water molecules from coordinating with magnesium ions and reacting on the surface of the magnesium anode to form a large number of passivation layers.

[0054] Performance testing All batteries were assembled in a glove box. The CR-2032 button cell casings used were ultrasonically treated three times with alternating cycles of anhydrous ethanol and grade III pure water, and then dried in a forced-air drying oven for more than 48 hours before being assembled as follows: Processing of negative electrode magnesium foil: Magnesium foil (thickness of 0.1mm) is polished with sandpaper of 240 grit, 400 grit, 800 grit, 1200 grit and 1500 grit in sequence, the dust on the surface is wiped off with lint-free paper, and then cut into magnesium foil with a diameter of 12mm for later use. The assembly process of the Mg||SS, Mg||Mg, Mg||Mo or Mo6S8 batteries used in the following tests is as follows: The negative electrode shell, spring, gasket (0.5 mm thick), 12 mm diameter magnesium sheet, 45 μL electrolyte, 17 mm diameter glass fiber separator (GF / A), 45 μL electrolyte, different positive electrodes (16 mm diameter SS (stainless steel), 12 mm diameter magnesium, 16 mm diameter Mo or 10 mm diameter Mo6S8), gasket (0.5 mm thick) and positive electrode shell are assembled, and then sealed under 5 MPa hydraulic pressure to obtain Mg||SS battery, Mg||Mg symmetric battery, Mg||Mo asymmetric battery and Mg||Mo6S8 battery respectively.

[0055] (1) Performance testing was conducted after assembling the Mg||SS battery. The water-resistant magnesium metal battery electrolyte prepared in Example 1 and the electrolyte prepared in Comparative Example 1 were assembled into Mg||SS batteries according to the above method. Cyclic voltammetry (CV) curves were then tested at 25°C. The scan rate was set to 25 mV / s, and the scan voltage range was -1 V to 2 V. The results are as follows: Figure 3 As shown, the results indicate that... Figure 3 (a) and Figure 3 The redox peaks in curve (b) clearly show that the polarization of Example 1 is significantly reduced and the current density is increased, which is superior to the reversible magnesium deposition / dissolution performance of Comparative Example 1.

[0056] The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 and the electrolyte prepared in Comparative Example 1 were added to 10,000 ppm of water, and then assembled into Mg||SS batteries according to the above method. Cyclic voltammetry (CV) curves were then tested at 25°C. The scan rate was set to 25 mV / s, and the scan voltage range was -1V to 2V. The results are as follows: Figure 4 As shown, the results indicate that the magnesium metal battery water-resistant electrolyte prepared in Example 1 maintained the same reversible magnesium deposition / dissolution process at a scan rate of 25 mV / s after the addition of 10,000 ppm of water, and its polarization potential and current density remained unchanged; while the electrolyte prepared in Comparative Example 1 could not undergo deposition / dissolution after the addition of 10,000 ppm of water. These results indicate that the introduction of borate ester additive B(TFE)3 (Example 1) gave the electrolyte (Comparative Example 1) strong water resistance.

[0057] The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 was added to 5000 ppm and 10000 ppm of water, respectively, and then assembled into asymmetric batteries using different positive electrodes (Cu, SS, Mo, and GF (graphite felt)) according to the above method. The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 without added water (0 ppm) was used as a control. The linear sweep voltammetry (LSV) curves at 25°C were then tested. The scan rate was set to 25 mV / s, and the scan voltage range was OCP (open circuit voltage) - 3.5 V. The results are as follows: Figure 5 As shown, the results indicate that the electrochemical window of the coin cells assembled with different current collectors based on the water-resistant electrolyte of the magnesium metal battery prepared in Example 1 is basically the same before and after the addition of water.

[0058] The magnesium metal battery water-resistant electrolytes prepared in Examples 2 to 5, as well as the electrolytes prepared in Comparative Examples 1 and 2, were added to 10,000 ppm of water and assembled into Mg||SS batteries according to the above method. Then, the cyclic voltammetry (CV) curves at 25°C were tested to observe the changes in polarization potential and current density after adding 10,000 ppm of water. The scan rate was set to 25 mV / s and the scan voltage range was -1V to 2V. The test results are shown in Table 1 below.

[0059] Table 1. Changes in electrochemical performance of the electrolytes prepared in the examples and comparative examples after adding 10,000 ppm water.

[0060] As can be seen from Table 1 above, the Mg||SS batteries assembled based on the water-resistant electrolytes of magnesium metal batteries prepared in Examples 1 to 5, after adding 10,000 ppm of water, still have excellent electrochemical performance, while the electrolytes prepared in Comparative Examples 1 and 2 fail after adding 10,000 ppm of water and do not produce electrochemical performance.

[0061] (2) Performance testing was conducted after assembling the Mg||Mg symmetric cell. The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 was added to 5000 ppm and 10000 ppm of water, respectively, and then assembled into different Mg||Mg symmetric batteries according to the above method. The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 without the addition of water (0 ppm) was used as a control. Then, at 25°C, 0.1 mA·cm -2 Cyclic testing was performed at current density, and the results are as follows: Figure 6 As shown in the figure, the results indicate that the water-resistant electrolyte for magnesium metal batteries prepared in Example 1 can maintain stable cycling for 1500h, 2000h, and 2500h at water contents of 0ppm, 5000ppm, and 10000ppm, respectively. Furthermore, the enlarged view shows that the polarization voltage of the water-resistant electrolyte for magnesium metal batteries in Example 1 remains stable at 80mV under different water contents. These data demonstrate that the water-resistant electrolyte for magnesium metal batteries prepared in Example 1 has excellent chemical compatibility with Mg.

[0062] The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 was added to 5000 ppm and 10000 ppm of water, respectively, and then assembled into different Mg||Mg symmetric batteries according to the above method. The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 without added water (0 ppm) was used as a control. Then, at 25°C, 0.5 mAh·cm⁻¹… -2 Rate performance was tested at specific capacity, and the results are as follows: Figure 7 As shown, the results indicate that the water-resistant electrolyte for magnesium metal batteries prepared in Example 1 can withstand 6 mA·cm⁻¹ in both aqueous and non-aqueous environments.-1 The high current density is maintained while maintaining a low magnesium deposition / dissolution polarization potential of <0.3V; at the same time, the water-resistant electrolyte of the magnesium metal battery prepared in Example 1 maintains the same electrochemical polarization as the anhydrous case at a water content of 10000ppm.

[0063] (3) Performance testing was conducted after assembling the Mg||Mo asymmetric cell. The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 was added to 5000 ppm and 10000 ppm of water, respectively, and then assembled into different Mg||Mo asymmetric batteries according to the above method. The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 without added water (0 ppm) was used as a control. Then, at 0.1 mA·cm... -2 Long-cycle performance tests were conducted at current density, and the results are as follows: Figure 8 As shown, the initial coulombic efficiencies of the water-resistant magnesium metal battery electrolyte prepared in Example 1 were 83.99%, 81.95%, and 77.47%, respectively. With increasing water content, the initial electrochemical efficiency of the electrolyte decreased slightly, possibly due to the formation of trace Mg-H2O species at the magnesium anode. However, the cyclic coulombic efficiencies of these electrolytes gradually showed the opposite trend: after 500 cycles, they were 97.5%, 97.1%, and 98.4%, respectively, while after 1000 cycles, they increased to 98.3%, 98.5%, and 99.2%, and could then maintain a stable cycle life of over 2500 cycles.

[0064] (4) Performance testing was conducted after assembling the Mg||Mo6S8 battery. The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 was added to 5000 ppm and 10000 ppm of water, respectively, and then assembled into different Mg||Mo6S8 batteries according to the above method. The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 without added water (0 ppm) was used as a control. The specific capacity-voltage curves were then tested at 25°C, and the results are as follows: Figure 9 As shown, the results indicate that at 1C, the energy content remains at 65.4 mAh·g. -1 77.3mAh·g -1 and 72.8mAh·g -1 Meanwhile, the battery also exhibited low polarization voltages of 0.32V, 0.25V, and 0.26V, respectively. The above data indicate that the addition of water to the water-resistant electrolyte of the magnesium metal battery prepared in Example 1 has almost no effect on the battery's capacity and polarization.

[0065] The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 was added to 5000 ppm and 10000 ppm of water, respectively, and then assembled into different Mg||Mo6S8 full cells according to the above method. The water-resistant electrolyte for magnesium metal batteries prepared in Example 1 without added water (0 ppm) was used as a control. The long-cycle curves of the batteries were then tested at 25°C, and the results are as follows: Figure 10 As shown, the results indicate that the Mg||Mo6S8 battery assembled with the water-resistant electrolyte prepared in Example 1 can maintain stable cycling for 460 cycles. The batteries with added 5000 ppm and 10000 ppm water exhibit even better cycling stability due to the interaction between the borate ester additives and water. Specifically, the battery assembled with the electrolyte containing 5000 ppm water maintains stable cycling for over 1600 cycles, while the battery assembled with the electrolyte containing 10000 ppm water maintains stable cycling for 1300 cycles, with no significant decrease in specific capacity. These data indicate that the electrolyte acquires water resistance after the addition of borate ester additives. This is because the B(TFE)3 in the water-resistant electrolyte prepared in Example 1 reacts with water, and the resulting substance increases the insertion and extraction reactions of positive electrode active ions and contributes to the stability of the magnesium anode interface.

[0066] In summary, the water-resistant electrolyte for magnesium metal batteries prepared in the examples exhibits significantly better overall performance than the electrolyte prepared in the comparative examples. In particular, it demonstrates stable cycling performance, low overpotential, high coulombic efficiency, and excellent full-cell performance in high water content environments. This outstanding water resistance can significantly reduce experimental costs and facilitate the commercialization of magnesium batteries.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A water-resistant electrolyte for magnesium metal batteries, characterized in that, Its raw materials include: magnesium salts, metal or non-metal halides, organic ether solvents and borate ester additives.

2. The water-resistant electrolyte for magnesium metal batteries according to claim 1, characterized in that, Magnesium salts are selected from one or more combinations of magnesium chloride, magnesium hexafluoroisopropoxide, magnesium bis(trifluoromethanesulfonyl)imide, and magnesium trifluoromethanesulfonate; and / or The metal or nonmetal halide is selected from one or more combinations of aluminum chloride, boron trichloride, titanium trichloride, titanium tetrachloride, phosphorus pentachloride, copper chloride, indium chloride, aluminum bromide, indium bromide, aluminum iodide, and indium iodide; and / or Organic ether solvents are selected from one or more combinations of 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, diethyl cellosolve, 1,3-dimethoxypropane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; and / or The borate ester additives are selected from one or more combinations of trimethyl borate, triethyl borate, triisopropyl borate, tri(2,2,2-trifluoroethyl) borate, and tri(hexafluoroisopropyl) borate.

3. The water-resistant electrolyte for magnesium metal batteries according to claim 2, characterized in that, The magnesium salt is magnesium trifluoromethanesulfonate, the metal or non-metal halide is aluminum chloride, the organic ether solvent is ethylene glycol dimethyl ether, and the borate ester additive is tris(2,2,2-trifluoroethyl) borate.

4. The water-resistant electrolyte for magnesium metal batteries according to any one of claims 1 to 3, characterized in that, The molar ratio of magnesium salt to metallic or nonmetallic halide is 1:(1.0–2.0); and / or The molar ratio of magnesium salts to borate esters is 1:(0.5 to 2.5).

5. The water-resistant electrolyte for magnesium metal batteries according to any one of claims 1 to 3, characterized in that, Magnesium metal batteries have a water-resistant electrolyte with a water content ≤50000ppm.

6. The method for preparing the water-resistant electrolyte for magnesium metal batteries according to any one of claims 1 to 5, characterized in that, The preparation method includes: mixing magnesium salt, metal or non-metal halide, organic ether solvent and borate ester additive to obtain a water-resistant electrolyte for magnesium metal batteries.

7. The preparation method according to claim 6, characterized in that, Preparation methods include: (1) A magnesium salt solution is obtained by mixing a magnesium salt, a metal or non-metal halide, and an organic ether solvent; (2) The magnesium salt solution is mixed with borate ester additives to obtain a water-resistant electrolyte for magnesium metal batteries.

8. A magnesium metal battery, characterized in that, Includes the water-resistant electrolyte for magnesium metal batteries as described in any one of claims 1 to 5.

9. The magnesium metal battery according to claim 8, characterized in that, Magnesium metal batteries are Mg||SS batteries, Mg||Mg symmetric batteries, Mg||Mo asymmetric batteries, or Mg||Mo6S8 batteries.

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